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Bryant Thermostat Q674 User's Manual

1. Model Fig Q674 Trade Number No Description Replacement Remarks Q674A System HEAT AUTO COOL Fan AUTO ON A1001 71 Standard OEM Q674A1019 A1019 71 TRADELINEQG model used with T874A D Q674A1019 A1035 71 Obsolete Trane part no BAS 0435 used with T874A D Q674A1019 A1043 71 Honeywelllogo TRADELINE model Q674A1019 A1050 71 Obsolete Standard OEM Q674A1043 Q674B System HEAT OFF COOL Fan AUTO ON B1000 45 Standard OEM used with T874C1570 C1695 C1703 Q674B1034 D1843 used 594 1363 B1018 44 Standard OEM used with T874B1035 01082 used Q674B1018 Y594B1026 D1016 B1026 45 Obsolete System HEAT OFF RESET COOL Q674B1034 B1034 45 TRADELINE Q674B1034 B1042 47 Obsolete Used with T874R1004 R1509 used in Y594R1243 Wiring differences old new Y594R1029 R1334 W12Wa2 B1059 45 Obsolete Factory installed RC RH jumper used with Q674B1034 Field wire RC RH T874C1059 used in Y594C1256 B1075 46 Auto fan in heating and cooling mode used with Q674B1075 T874B1035 C1000 D1082 used in Y594D1040 B1083 51 Obsolete Carrier part no HH93AZ178 factory Q674B1075 system transformer only installed RC RH jumper B1091 45 Obsolete Carrier part no HH93AZ184 factory Q674B1034 installed RC RH jumper B1109 47 Obsolete Addison heat pump used with T874R1012 Y594R1243 Wiring differences old new W1 W2 B1117 44 Obsolet
2. Model Fig Trade Model Number No Description Replacement Remarks Y594A A1001 46 Obsolete Amana part no D68535 11 contains T874A1036 T874A1077 Q674B1075 Q674B1075 A1019 82 Obsolete Amana part no P68535 12 contains T874A1036 T874A1077 Q674E1056 Q674E1049 A1035 44 Obsolete Trane part no 268 0187 1 contains T874A1036 T874A1085 Q674B1018 Q674B1018 A1043 46 Obsolete Trane part no 268 0201 5 contains T874A1036 T874A1085 Q674B1075 Q674B1075 A1050 55 66 Obsolete Trane part no 268 0201 3 contains T874A1036 T874A1085 Q674D1008 Q674D1040 A1068 82 Obsolete Sears part no 42 9144 contains T874A1036 T874A1119 Q674E1007 Q674E1049 A1126 64 Contains T874A1291 067401012 None A1159 91 Obsolete Contains T874A1440 Q674G1005 T874A1150 Q674G1070 A1167 184 California Economizer Premier White color T874A1036 Replacement is beige color contains T874A1580 and Q674G1161 Q674G1070 1175 55 Obsolete York logo part no 2 4703224 T874A1010 contains T874A1622 Q674D1180 Q674D1040 A1191 46 Obsolete Amana logo part no P6853524R T874A1036 contains T874A1002 Q674B1075 Q674B1075 Y594B B1026 44 Trane part BAYSTAT012 contains T874B1035 T874B1019 Q674B1018 Q674B1018 B1034 46 Obsolete Trane part no 163 552 1 contains T874B1019 T874B1035 Q674B1075 Q674B1075 B1042 88 Obsolete Goodman part no CHTS36 60 con
3. Model Fig Q674 Trade Number No Description Replacement Remarks L1850 120 York Canada gray color includes one LED used with Y594R1672 T874R1970 used in Y594R1789 L1868 125 TRADELINE includes two LEDs used with Y594R1797 T874R1988 used in Y594R1797 direct replacement for Evcon Coleman Y594R1235 T874R1368 Q674L1421 Coleman part no 3600 368 L1876 245 Obsolete Amana part no 10573902 includes two Y594R1797 Wiring differences old new LEDs used with T874R2002 used in Y594R1805 11884 245 Obsolete Amana part no 10573904 includes two Y594R1797 Wiring differences old new LEDs used with T874R2010 used in Y594R1813 C X X W3 W2 L1892 103 Obsolete TRADELINE System SUPL Y594G1674 Replacement has auto OFF COOL includes one LED used with T874G2004 changeover used in Y594G1666 direct replacement for Carrier Y507J1011 T874G1055 Q674L 1041 Carrier part no HH07AT171 HH93AZ175 L1900 241 Obsolete TRADELINE System SUPL HT HEAT Y594J1019 Replacement has auto OFF COOL includes SUPL HT LED used with changeover T874J1069 used Y594J1001 direct replacement for Carrier T874J1028 Q674J1068 Carrier part no HH07AT165 HH93AZ183 Carrier T874J1002 Q674J1068 Carrier part no HHO7AT175 HH93AZ183 L1918 125 Obsolete York logo part no 2TH11703424A includes Y594R17972 two LEDs used with T874R2028 in Y594R1821 L1934 123 Obsole
4. Model Fig Trade Model Number No Description Replacement Remarks A1200 51 53 Obsolete Carrier logo part no HHO7AT164 T874A1036 1 heat anticipator for scaleplate includes Allen wrench and screws to lock total current draw of fan and cover used with Q674B stage 1 heat primary replacement has F scaleplate A1226 44 Honeywell logo Honeywell Canada TRADELINE model 874 1036 Replacement has F C scaleplate includes Allen wrench and screws to lock scaleplate cover A1234 44 Qbsolete Friedrich Climate Master logo heat T874A1036 anticipator factory set 1 2A A1242 44 Qbsolete Friedrich Climate Master logo T874A1036 A1259 44 Obsolete Wesco logo heat anticipator set at 0 8A T874A1036 A1267 59 Obsolete McQuay logo used with 067401004 T874A1036 A1275 44 J Obsolete Lennox logo part no 13F0101 meets DoD T874A1176 specifications A1283 75 McQuay Air Conditioning logo part no 03005047 used T874A1036 Replacement does have with Q674C1132 and thermistor to display outdoor ability to display external temperature temperature or momentary system switch position A1291 64 three speed fan one setpoint lever for heat and T874A1036 Replacement has two levers cool setpoints used with 067401012 used in Q674B1075 1 speed fan Y594A1126 A1309 44 J Obsolete Arcoaire Air Conditioning and Heating logo T874A
5. HEAT CHANGEOVER NOTE Model Heating Cool ing I COOL CHANGEOVER Bulbs Bulbs QS T874A H1 C1 VALVE A C ANTICIPATOR T874B Hi C1 C2 ix SYSTEM OHA T874C H1 H2 C1 8 LP i 18740 H1 H2 1 22 Ales 779 S Fe TE74D HE 2 Lor Ko 2 55 HA CONTACTOR 2 C2 ANTICIPATOR 3 Ao C2 PROTECTION AS REQUIRED A JUMPER RH RC FOR SINGLE TRANSFORMER A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD COMPRESSOR CONTACTOR 1 Fig 44 Schematic and hookup of T874A B C D E F with Q674B Used in standard applications SUBBASE SYSTEM COMPONENTS THERMOSTAT 4 UT is Dun FALL Q AUTO H1 ANTICIPATOR C 1 HOT 7 d HEAT RELAY 1 AG Br 2 2 i HEAT CHANGEOVER VALVE H2 4 PUTES O 8 FALL H2 ANTICIPATOR SYSTEM SWITCH C1 ANTICIPATOR C2 ANTICIPATOR 1 PAGD c2 POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A JUMPER RH RC FOR SINGLE TRANSFORMER COMPRESSOR CONTACTOR 2 COMPRESSOR L2 CONTACTOR 1 A OPTIONAL LED ON SOME MODELS M933C Fig 45 Schematic and hookup of T874C D with Q674B Used in standard applications 60 2485 8 96 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HE
6. Model Fig Trade Model Number No Description Replacement Remarks R1319 191 Obsolete Carrier part no 42QH400083 used with See OEM for Q674B1281 on two speed fan applications replacement R1327 120 Qbsolete Borg Warner multi logo part no Y594R1672 6TH11702224A used with Q674L1272 used in Y594R1193 R1335 106 Obsolete multi logo part no HH641501 H2 Y594R1243 anticipator factory set 1 2A used with 067411405 used in Y594R1201 R1343 133 Qbsolete Fedders multi logo part no Y594R1425 Wiring differences old new THTX 120 HEHC 88 58 0056 001 used with K E CzX1 Z L remove Q674L1413 used in Y594R1219 Y1 W1 jumper R1350 113 Qbsolete Honeywell logo used with Q674L 1181 Y594R1243 Wiring differences old new X1 X R1368 125 Obsolete Coleman logo part no 3600 368 used with Y594R1797 Q674L1421 used in Y594R1235 R1376 115 Honeywell logo scaleplate used with 067411207 T874R1152 R1384 131 Obsolete Carrier Heat Pump System Control logo part Y594G1243 Wiring differences old new 185 HH07AQ170 used with Q674L HH93AZ187 06741 HH93AZ197 06741 HH93AZ198 R1392 128 QObsolete Williamson logo used with Q674L1447 used Y594R1425 Wiring differences old new in Y594R1250 A L R1400 113 Obsolete LSI part no 104710001 used with See subbase description for Q674L1181 L1462 replacement information R1426 136 Obsolete Trane Weathertron Heat Pump l
7. 5 6 COOL E 4 FA VALVE Eon ANTICIPATOR oO Omm Lej A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR Nazis CONTACTOR A FACTORY INSTALLED JUMPER BETWEEN TERMINALS W1 AND Y1 Fig 238 Schematic and hookup of T874C with Q674F Used in heat pump applications 217 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR COMPRESSOR MONITOR OUTDOOR SENSOR SYSTEM SWITCH COOL CHANGEOVER VALVE OUTDOOR 4 a THERMOSTAT o Loo L___ CONTACTOR CONTACTOR Ee POWER SUPPLY PROVIDE DISCONNECT MEANS 7744 AND OVERLOAD PROTECTION AS REQUIRED Aren FIEMOVAGEE JUMPER Fig 239 Schematic and hookup of T874R with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS Hi ANTICIPATOR SYSTEM Q Q L2 L1 K2 K2 K2 Co ANTICIPATOR 3 SPEED FAN SCHEMATIC POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR M7745 FAN CONTINUOUS IN ON POSITION CONTACTOR Fig 240 Schematic and hookup of T874A with Q674W Used in standard applications 60 2485 8 218 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH Q COMPRESSOR CONTACTOR CHANGEOVER VALVE NO 1 SYSTEM SWITCH HEAT Q CHANGEOVER CH
8. THERMOSTAT SUBBASE SYSTEM COMPONENTS O PS HEAT RELAY 1 COMPRESSOR SWITCH CONTACTOR 1 H1 ANTICIPATOR AUTO 4 2 ise uen 0 1 oe ME J 2 ANTICIPATOR FALL SYSTEM FN SWITCH RISE OFF HA rA TS HEAT F4 FW 25160 1 SYSTEM L1 5 me A FAULT CONTACT C1 ANTICIPATOR C OMPRESSOR 10 LOCKOUT LED CONTACTOR 2 C2 ANTICIPATOR RED D ENS A FIELDWIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER Fig 87 Schematic and hookup of T874D with Q674E Used in standard applications THERMOSTAT SUBBASE POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M4668 SYSTEM COMPONENTS SYSTEM SWITCH E a 62 RISE wy 4 HEAT I HA 5 55 AUTO FH HU L1 5 m HOT COOL 5 4 9 Q HIGH LED RED oE n COMPRESSOR CONTACTOR 2 A POWER SUPPLY PROVIDE DISCONNECT LOW LED GREEN COMPRESSOR MEANS AND OVERLOAD CONTACTOR 1 PROTECTION AS REQUIRED 7 E Fig 88 Schematic and hookup of T874B D with Q674E Used standard applications 60 2485 8 118 M4669 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS EA 8 HEAT nana H1 ANTICIPATOR C RELAY 1 HEAT CHANGEOVER VALVE on ees pay AUTOL_ 4 J COMPRESSOR gt CONTACTOR 1 SYSTEM SWITCH oN 4 0 T aka OHR or 4 Hil 2A
9. SYSTEM MONITOR 1 EUN Q HOT M2852A AND OVERLOAD PROTECTION AS REQUIRED A TWO TRANSFORMER SYSTEM Fig 150 Schematic and hookup of T874G with Q674F Used in heat pump applications 161 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE n S SYSTEM COMPONENTS EM HT RELAY L1 12 CONTACT 1 ANTICIPATOR FAN T6031 REFRIGERATON SWITCH TEMPERATURE CONTROLLER AUTO ON SYSTEM ANTICIPATOR SWITCH COMPRESSOR CONTACTOR SEQUENTIAL ANTICIPATOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Ci RISE L1 L REVERSING FAN A OPTIONAL FIELD WIRE JUMPER TO CYCLE W2 WITH H1 IN EM HT HOT SOLENOID FASTER RESPONSE M4710 Fig 151 Schematic and hookup of T874G with Q674F Used in heat pump applications 60 2485 8 162 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS Li L2 HOT HEAT RELAY COMPRESSOR CONTRACTOR 1 FAN SWITCH H2 ANTICIPATOR 6 SYSTEM SWITCH Q RISE or fe Ute 5 ci EM HTH 4 HJA 1 0 OX HEAT Q Q O Wey A LED RED 5 AUTOL 4 HH RISE Q7 9 9 i C1 ANTICIPATOR FX HI x2 5 C2 C2 ANTICIPATOR 3 COMPRESSOR CONTRACTOR 2 22 umm POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A FACTORY SUP
10. N FAN RELAY B Ee Le 1 B C2 ANTICIPATOR COMPRESSOR CONTACTOR 2 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD COMPRESSOR PROTECTION AS REQUIRED CONTACTOR 1 M2980 Fig 202 Schematic and hookup of T874D with Q674G Used in standard applications 60 2485 8 194 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COMPRESSOR HOT CONTACTOR P FAN SWITCH SYSTEM SWITCH Q Q X FH O O COMPRESSOR C1 ANTICIPATOR M2981 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 203 Schematic and hookup of T874L with Q674C Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 HEAT RELAY 1 jn T 1 FAN wi V 97 A LU SWITCH HEAT RELAY 2 AUTO Are O O D eNe H1 ANTICIPATOR E zy 0 og J L ANTICIPATOR SYSTEM swTCHO Q Q OFF H F4 K Uc RISE F 4 F 4 COMPRESSOR Q 6 OCS AUTO Q COMPRESSOR CONTACTOR 1 C1 ANTICIPATOR C2 ANTICIPATOR FOS c2 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A LED IS NOT LABELED JUMPER W2 TO X FOR AUXILIARY HEAT INDICATION JUMPER E TO X FOR EMERGENCY HEAT INDICATION CONNECT SYSTEM MONITOR TO X TO IDENTIFY WHEN SYSTEM M2982A NEEDS TO BE CHECKED Fig 204 Schemati
11. AUX HT RELAY M COMPRESSOR EM HT LED FAILURE RED C1 ANTICIPATOR AUTO FAFA 20 OQ 73 AUX HT LED GREEN C1 o o lt gy COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS A B TERMINAL ON SELECT MODELS AND OVERLOAD PROTECTION AS REQUIRED M5721 Fig 158 Schematic and hookup of T874G with Q674F Used in heat pump applications 167 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE H1 ANTICIPATOR HEAT RELAY CONTACT OUTDOOR THERMOSTAT HEAT RELAY HT CONTACT RELAY COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5722 Fig 159 Schematic and hookup of T874G with Q674J Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH AUX HT RELAY i RISE EY system i gt SWITCH i co p EM HT RELAY EM HT E EM HT 5 O CH LED RED auto 6 s F4 E COMPRESSOR C1 ANTICIPATOR O CONTACTOR O Exe gt C1 STA POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5723 Fig 160 Schematic and hookup of T874G with Q674J Used in heat pump applications 60 2485 8 168 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS S d COOL CHANGEOVER VALVE
12. H1 P ANTICIPATOR FALL Q5 Q H2 ANTICIPATOR FAN RELAY C1 ANTICIPATOR 9 POWER SUPPLY PROVIDE DISCONNECT MEANS COMPRESSOR AND OVERLOAD PROTECTION AS REQUIRED CONTACTOR 1 M3957 COMPRESSOR CONTACTOR 2 Fig 232 Schematic and hookup of T874D with Q674G Used in standard applications 60 2485 8 214 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS MM H1 ANTICIPATOR Hoge NE 4 ANTICIPATOR E FALL Joc D e H3 5 PF T FALL H2 F Q 88 C1 ANTICIPATOR Ke Rise ANTICIPATOR C2 W89 HEAT PUMP CONTROL PANEL COMPRESSOR LOW SPEED OUTDOOR RESET RESET M3952 Fig 233 Schematic and hookup of T874W with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS F COMPRESSOR FALL H1 H1 ANTICIPATOR CONTACTOR FAN SWITCH H2 ANTICIPATOR SYSTEM SWITCH AUX HEAT LED RED CHANGEOVER VALVE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M3961 Fig 234 Schematic and hookup of T874G with Q674B Used in heat pump applications 215 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR SWITCH AUX HT
13. Other terminal designations can be used that are not listed on this table Refer to the hookup drawing and internal schematic for exact connections W3 controls the auxiliary heat like W2 and allows adding additional stages of auxiliary heat with outdoor thermostats while maintaining the proper second stage anticipation Outdoor Disconnect The National Electrical Code requires the installation of a disconnect switch within sight of the outdoor unit of an air conditioner or heat pump The switch is for the safety of any technician working on the unit The technician can assure that the unit remains unpowered Install and Adjust Stop Brackets The stop brackets should be installed only if there is a need to restrict the adjustable range of the heating and cooling temperature setpoint levers If adjustable lever stops are desired order 4074ECK Envelope Assembly which contains two adjustable lever stop brackets one brass insert one HOLES FOR INSULATED LOCKING LEVER SCREWS COOL LEVER HOLE WITH BRASS INSERT BRACKET TABS HEAT LEVER ADJUSTABLE LEVER STOP BRACKETS 7 MOUNTING BRACKET SCREW SLOTS ADJUSTABLE STOPS mounting screw and two locking screws with insulated heads When installed the stop brackets limit the movement of the T874 HEAT and COOL levers TO INSTALL 1 Remove the thermostat cover by pulling the bottom edge of the cover upward until it snaps
14. Y2 Y R none L R setback used with Q674C1389 C1397 jumper required no night setback T8611G1004 Includes night setback programmable G1717 175 QObsolete Carrier Heat Pump System Control logo part Y594G1252 Wiring differences old new no HHO7AT102N used with Q674J1167 used in C X D L replacement has Y507J1201 AUX HEAT and EM HEAT LEDs G1741 227 Honeywell logo TRADELINE model includes factory Y594G1476 set range stops at 68 F max heat and 78 F min cool Premier White color used with Q674F1477 used in Y594G1476 G1758 211 by Honeywell logo Premier White color None See Trol A Temp for changeover is provided by Trol A Temp zone panel replacement used with Q674F1485 used in Y594G1492 G1774 216 Obsolete Comfortmaker logo part 1505756 used Y594G1252 Wiring differences old new with Q674J1175 used in Y594G1500 E W2 W1 W3 G1782 216 Obsolete Arcoaire logo part no 1506756 used with Y594G1252 Wiring differences old new Q674J1175 used in Y594G1518 E W2 W1 W3 X E G1790 161 Obsolete Carrier logo Premier White color Y594G1252 Wiring differences old new scaleplate includes Allen wrench and screws to lock CzX replacement has F cover used with Q674J1191 scaleplate G1816 163 Climate Master logo part no AT5716 F C scaleplate Y594G1393 No momentary reset switch 10 F differential between H1 and H2 and momentar
15. Y594R1664 Replacement is beige L1785 103 Obsolete Carrier part no HH93AZ175 W Canada gray color System Supl Ht Heat Off Cool includes one LED Y594G1476 Wiring differences old new CzX Y1 W1 jumper required L1793 124 Obsolete Carrier Canada part no HH93AZ186 W gray color Fan Auto On System Supl Ht Heat Off Cool includes one LED Y594J10192 L1801 197 American Standard Trane part no THT1225 includes two LEDs used with T874R1939 used Y594R1748 Y594R1763 L1819 168 Obsolete Inter City Products part no HQ1149407HW includes three LEDs used with T874R1947 used in Y594R1755 Y594R1425 L1827 197 TRADELINE includes two LEDs used with T874R1954 used in Y594R1763 direct replacement for Trane American Standard Y594R1748 T874R1939 Q674L1801 Trane part no ASYSTAT 631A Y594R1136 T874R1053 Q674L 1140 Y594R1763 L1835 140 Obsolete Inter City Products includes three LEDs used in Y594W1030 T8611M2025 programmable Includes night setback L1843 115 Obsolete Consolidated Industries part no 9036100 gray color includes two LEDs used with T874R1962 used in Y594R1771 Y594R1680 Includes CHECK LED Both the thermostat and subbase must be replaced 85 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 9 Q674 Subbase Cross Reference
16. G1501 195 Obsolete Coleman logo part no 3600 375 changeover Y594G1252 Wiring differences old new in cooling mode used with Q674F1378 L1 L changeover in cooling only G1535 163 Obsolete AAF Snyder General logo 4ELN7839 F C Y594G13932 night setback or scaleplate 10 F differential between H1 and H2 for night momentary reset switch RESET system switch position T8611G1004 Includes night setback usea wi i programmable G1543 194 Obsolete Addison logo Weather King part no 8403 Y594G1252 Wiring differences old new 197 used with Q674F1345 used in Y594G1328 1 0 W1 Y X L G1568 160 Obsolete Luxaire logo part 026 00068 000 Y594G13672 Replacement has F scaleplate used with Q674J1126 used Y594G1351 scaleplate G1576 169 Obsolete Coleman logo part no 3600 373 changeover Y594G16332 in heating and cooling mode used with Q674F1402 used in Y594G1377 G1584 73 Obsolete No logo Friedrich part no AT5784 8 F Y594H1012 Wiring differences old new 4 4 C differential between H1 and H2 used with 1 2 L R R none Q674C1223 L R jumper required no night setback T8611G1004 Includes night setback programmable G1592 155 QObsolete Arcoaire logo used with Q674F1212 used in T874G1246 or Y594G1385 Y594G12528 G1600 199 Obsolete Honeywell logo meets DoD specifications Y594G1419 Wiring differences old new used with Q674F1
17. TRADELINE package with cross reference label and special instruction sheet T874A C model available with factory stops for DoD applications T874A C model available with adjustable temperature locking stops Q674 SUBBASE Q674 switching subbases provide system and fan switching See Table 2 Table 2 System and Fan Switching Q674 System Fan A Heat Auto Cool Auto On B Heat Off Cool Auto On C Off Auto Auto On D None None E Off Heat Auto Cool Auto On F Em Ht Off Heat Auto Cool Auto On G Off Auto None J Em Ht Auto Off Auto On L Em Ht Heat Off Cool Auto On TRADELINE FEATURE TRADELINE package with cross reference label and special instruction sheet Q674A E G are standard non heat pump models Q674F J L are heat pump models When purchasing replacement and modernization products from your TRADELINE wholesaler or distributor refer to the TRADELINE Catalog or price sheets for complete ordering number If you have additional questions need further information or would like to comment on our products or services please write or phone 1 Yourlocal Home and Building Control Sales Office check white pages of your phone directory 2 Home and Building Control Customer Relations Honeywell 1885 Douglas Drive North Minneapolis Minnesota 55422 4386 800 328 5111 In Canada Honeywell Limited Honeywell Limit e 35 Dynamic Drive Scarborough Ontario M1V
18. 115 Obsolete Econar contains T874R1921 and Q674L1207 Y594R1243 R1748 197 American Standard Trane part no ASYSTAT651A contains T874R1939 and Q674L1801 Y594R1763 R1755 168 Obsolete Inter City Products part no HQ1149376HW contains T874R1947 and Q674L1819 Y594R1425 R1763 197 TRADELINE contains T874R1954 and Q674L1827 direct replacement for Y594R1136 T874R1053 Q674L 1140 Y594R1748 T874R1939 Q674L1801 Trane part no ASYSTAT651A Y594R1444 T874R1657 067411611 Trane part no ASYSTAT651 Y594R1763 R1771 115 Obsolete Consolidated Industries part no 9036100 contains T874R1962 and Q674L1843 Y594R1680 Includes CHECK LED 1789 120 York Canada part no 2TH11701524 contains T874R1970 and Q674L1850 Y594R1672 Replacement has F scaleplate a Both the thermostat and subbase must be replaced 60 2485 8 94 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10 Y594 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks R1797 125 TRADELINE contains T874R1988 Y594R1797 06741 1868 direct replacement for Y594R1235 T874R1368 Q674L1421 Evcon Coleman part no 3600 368 R1805 245 Obsolete Amana part no 10636702 contains Y594R1797 Wiring differences old new T874R2002 and Q674L1876 1813 245 Obsolete Amana
19. 134 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS RESET HEATER H1 ANTICIPATOR H2 ANTICIPATOR C2 RISE C2 ANTICIPATOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED FAN SWITCH AUTO SYSTEMO SWITCH A REMOVE FACTORY INSTALLED V VR JUMPER WHEN CONNECTING A TWO TRANSFORMER SYSTEM Ene EH Q OUTDOOR THERMOSTAT HIGH SPEED COMPRESSOR CONTACTOR E FAN LOW SPEED RELAY COMPRESSOR CONTACTOR DE 7 OUTDOOR THERMOSTAT SUPPL ELEC HT RELAY SERVICE LED RED SUPPL ELEC HT RELAY M2853 Fig 114 Schematic and hookup of T874D with Q674L Used in heat pump applications 135 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HOT L1 12 H1 C1 ANTICIPATOR SYSTEM SWITCH COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5072A A AUXILIARY HEAT LED AVAILABLE ON SOME MODELS Fig 115 Schematic and hookup of T874R with Q674L Used in heat pump applications 60 2485 8 136 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH ANTICIPATOR LED RED AUX HT RELAY H2 ANTICIPATO
20. A H2 HAS 10jF FIXED SETBACK FROM H1 ON T874G1485 0 12jF ADJUSTABLE T874G1535 RESET IN MOMENTARY POSITION SPRING RETURN TO OFF UPON SWITCH RELEASE M1820C Fig 163 Schematic and hookup of T874G with Q674C Used in standard applications 171 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR COOL CHANGEOVER VALVE COMPRESSOR CONTACTOR FAN RELAY HEAT CHANGEOVER MALFUNCTION SWITCH POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED R L JUMPER SUPPLIED BY HONEYWELL M5726 Fig 164 Schematic and hookup of T874H with Q674C Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS ao O A L2 p 2 GG EN 1 1 AUX HT RELAY 1 COMPRESSOR R1 N C 1 CONTACTOR SYSTEM SWITCH OFF C A POWER SUPPLY PROVIDE DISCONNECT MEANS A FIELD REMOVABLE JUMPER M5727 AND OVERLOAD PROTECTION AS REQUIRED H1 AND C1 ARE DPST SWITCHES Fig 165 Schematic and hookup of T874L with Q674C Used in heat pump applications 60 2485 8 172 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS MM 12 AUX HT LED HEAT RELAY 1 GREEN EM HT LED RED ci HEAT RELAY 2 SYSTEM H2 ANTICIPATOR SWIT
21. Indicator LEDs OFF COOL Q674C Standard and TRADELINE Q672C Standard OFF AUTO AUTO ON T874A H W Indicator LEDs Heat Pump OVERRIDE AUTO AUTO ON T874K L N OFF T874P Q674D Standard and TRADELINE Q672D Standard None None T874A F For use when subbase switching is not required 5 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Q674E Standard and TRADELINE Q672bE Standard OFF HEAT AUTO AUTO ON T874A D COOL Q674F Two LED models Q672F Heat Pump OFF EM HT HEAT AUTO ON T874C D G N S EM HT light AUTO COOL Provision for AUTO fan operation in OFF COOL AUTO AUTO ON EM HT HEAT EM HT Q674G O and B terminals Q672G Standard OFF AUTO None T874A F Q674J Provision for AUTO fan operation Q672J Heat Pump EM HT AUTO OFF AUTO ON T874A D G J in EM HT EM HT ON OFF AUTO ON Provision for outdoor thermistor SUPL HT ON OFF AUTO ON Q674K Standard Q672K Standard OFF HEAT AUTO None T874F COOL OFF WOOD WOOD None OIL OIL Q674L Provision for AUTO fan operation in 06721 Heat Pump EM HT HEAT OFF AUTO ON T874R W EM HT COOL Indicator LEDs SUPL HT HEAT AUTO ON OFF COOL Q674N Standard Q672N Evaporative EVAP COOL OFF AUTO ON T874C Cooler HEAT Q674P Standard Q672P Heat Pump SUPL HT HEAT AUTO ON T874G COOL Q674Q Standard None Fan Coil HEAT OFF COOL LO MED HI T874A ON Q674R Standard None Fan Coil OFF COOL
22. T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 HOT L2 H1 WA FAN SWITCH A SYSTEM SWITCH LED ie HEAT CHANGEOVER COOL CHANGEOVER RELAY Pe A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR M2977 CONTACTOR Fig 199 Schematic and hookup of T874G with Q674F Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS OUTDOOR THERMOSTAT EOD US SERVICE LED YELLOW C1 ANTICIPATOR SYSTEM SWITCH COMPRESSOR CONTACTOR Fig 200 Schematic and hookup of T874R with Q674L Used in heat pump applications 193 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 C815A OUTDOOR THERMISTOR 48 H2 ANTICIPATOR OUTDOOR THERMOSTAT SEQ2 FAN SWITCH AUTO OUTDOOR THERMOSTAT SERVICE LED YELLOW H1 ANTICIPATOR HEAT CHANGEOVER VALVE Tpu A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 201 Schematic and hookup of T874R with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS o bo L1 FALL LED RED GE H1 ANTICIPATOR SERVICE LED RED NO FAN SWITCH e FALL ANTICIPATOR
23. T874R1202 and Q674L 1264 W2zW X B Z no connection 1 R1193 120 Qbsolete York part 6TH11702224 contains Y594R1664 T874R1327 and Q674L1272 R1201 106 Qbsolete BDP part HH641501 contains Y594R1243 T874R1335 and Q674L1405 1219 133 Obsolete Fedders 88 58 00560 001 Y594R1425 Wiring differences old new contains T874R1343 and Q674L1413 K E 2 remove factory installed jumper R1235 125 Qbsolete Coleman part no 3600 368 contains Y594R1797 T874R1368 and Q674L1421 R1243 115 TRADELINE contains 874 1152 067411207 Y594R1243 R1250 128 QObsolete Williamson part no 75 191 contains Y594R1425 Wiring differences old new T874R1392 and Q674L1447 A L R1284 136 Obsolete Trane part no BAYSTAT339 contains Y594R1763 a Both the thermostat and subbase must be replaced 60 2485 8 92 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10 Y594 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks R1292 108 Contains T874R1467 and Q674L1512 replaces Y594R1292 Y594R1110 T874R1137 Q674L 1132 R1300 123 Contains T874R1475 and Q674L1520 Y594R1300 R1318 130 Obsolete Comfortmaker part no 1505721 contains Y594R1763 Wiring differences old new T874R1483 Q674L1538 and C815A1005 W1 W 2 X F R1326 137 Qbsolete SUPER TRADELINE contai
24. nan CHANGEOVER 6 VALVE NO 1 LS FALL ete ANTICIPATOR SYSTEM CHANGEOVER CHANGEOVER SWITCH VALVENO 1 VALVE NO 2 qs 10 SUPLHT4 Q HEAT kalka HEAT oN o 5 6 BR CHANGEOVER CHANGEOVER VALVE NO 2 VALVE NO 3 OFF A r4 oN o gum o On JN P co 9 X RELAY E RISE mae 12 ECT P RELAY O O 9 CooL CHANGEOVER POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD VALVE M7743 PROTECTION AS REQUIRED Fig 244 Schematic and hookup of T874J with Q674J Used in heat pump applications 60 2485 8 220 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES SYSTEM COMPONENTS SUBBASE THERMOSTAT FAN SWITCH H1 C1 ANTICIPATOR SYSTEM SWITCH AUX HT LED GREEN AUX HT RELAY POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A COMPRESSOR M7718 TERMINAL LABELED C X ON SOME MODELS CONTACTOR Fig 245 Schematic and hookup of T874R with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR NO FAN SWITCH SYSTEM H2 ANTICIPATOR SWITCH COOL CHANGEOVER 1 3 VALVE M7717 POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 246 Schematic and hookup of T874C with Q674G Used in standard applications 221 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUB
25. 8 112 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS RESET LED RED HEAT CHANGEOVER VALVE H1 ANTICIPATOR HEAT RELAY 2 HEAT RELAY 1 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A JUMPER RH AND RC FOR SINGLE TRANSFORMER SYSTEM COMPRESSOR CONTACTOR M4729 Fig 77 Schematic and hookup of T874K with Q674C Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS COMPRESSOR CONTACTOR H1 ANTICIPATOR SETBACK CONTACT SYSTEM SWITCH O OVERRIDE Q FA Fd F4 Fd o JUMPER AX J REVERSING VALVE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M7026 A JUMPER HONEYWELL SUPPLIED FIELD INSTALLED Fig 78 Schematic and hookup of T874P with Q674C Used in heat pump applications 113 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH RESET LED RED H1 ANTICIPATOR SETBACK CONTACT CHANGEOVER VALVE SYSTEM SWITCH COMPRESSOR CONTACTOR ANTICIPATOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A SETBACK CONTACT ON Q674C1124 A H2 ON T874G M7027 Fig 79 Schematic and hookup of T874G H with Q674C Used in standard app
26. Contains T874F1031 and 40003440 001 T874F1015 wallplate with installed diode F1048 72 Obsolete Reznor part no 93436 contains T874F1015 T874F1130 Q674C1009 Q674C1058 F1063 91 Obsolete Reznor part no 93435 contains T874F1015 T874F1130 Q674G1005 Q674G1070 Y594G G1013 160 Qbsolete York part 2TH11702424 contains Y594G1567 T874G1170 Q674J1027 G1138 160 Qbsolete York part no 025 22286 contains Y594G1567 T874G1196 Q674J1027 G1153 154 Obsolete Crispaire part no HP10 51 contains Y594G1252 Wiring differences old new T874G1089 Q674F1204 A L G1161 162 Contains T874G1204 Q674J1043 Y594G1161 G1195 155 Obsolete Heil Quaker part no HQ521387HW Y594G1252 contains T874G1246 Q674F1212 G1229 160 York part 6TH11702424 contains Y594G1567 T874G1428 Q674J1027 G1245 155 Obsolete part no HH641502 contains Y594G1252 T874G1451 Q674F1212 G1252 155 TRADELINE contains T874G1246 Q674F1212 Y594G1252 a Both the thermostat and subbase must be replaced 89 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10 Y594 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks G1294 79 Qbsolete LSI contains T874G1378 Q674C1124 See for 2 is night setback replacement G1328 194 Qbsolete Addison part no 8403 197 conta
27. D68535 03 used with T874D1165 Q674B1075 used in Y594D1149 D1330 44 Obsolete Trane logo part no 13080242 scaleplate 787401165 Replacement has F scaleplate D1355 44 Obsolete Climate Control special part no 02005942 T874D1165 Replacement has 2 F C scaleplate 6 C 11 F differential between H1 and differential between H1 and H2 H2 D1363 44 J Obsolete McQuay logo part no 02005943 12 F T874D1165 Replacement has 2 F 6 6 C differential between H1 and H2 6 F 3 3 C differential between H1 and differential between C1 and C2 H2 2 F differential between C1 and C2 D1405 44 Obsolete Trane logo part no 02005952 12 F 6 6 C T874D1165 Replacement has 2 F differential between H1 and H2 6 F 3 3 C differential differential between H1 and between C1 and C2 H2 2 F differential between C1 and C2 D1413 44 Trane logo part no 02005956 12 F 6 6 C T874D1165 Replacement has 2 F differential between H1 and H2 differential between H1 and H2 D1421 44 Obsolete Climate Control special part no 02005938 T874D1165 Replacement has F scaleplate scaleplate D1439 90 McQuay logo part no 02005935 used with T874D1165 Q674G1096 D1447 90 Obsolete Climate Control special part no 02005940 T874D1165 Replacement has F scaleplate used with Q674G1096 scaleplate D1454 51 53 Obsolete Carrier logo T874D11652 Set H1 anticipator for current draw
28. GREEN H1 C1 ANTICIPATOR EM HT LED RED COMPRESSOR FAILURE OUTDOOR THERMOSTAT SYSTEM Q SWITCH COOL OUTDOOR CHANGEOVER THERMISTOR VALVE POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR Fig 109 Schematic and hookup of T874R with Q674L Used in heat pump applications 130 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS RESET INTERNAL THERMOSTAT COMPRESSOR CONTACTOR OVERLOAD SWITCH FAN SWITCH 2 OUTDOOR SUPL ELEC THERMOSTAT TIME DELAY FAN RELAY EM HT RELAY CONTACT SYSTEM SWITCH C1 ANTICIPATOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A REMOVE FACTORY INSTALLED S Y JUMPER TO DISABLE SERVICE LIGHT A REMOVE FACTORY INSTALLED V VR JUMPER WHEN m2854 CONNECTING A TWO TRANSFORMER SYSTEM Fig 110 Schematic and hookup of T87C R with Q674L Used in heat pump applications 131 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR COMPRESSOR INTERNAL CONTACTOR THERMOSTAT FAN SWITCH OVERLOAD HIGH SWITCH PRESSURE SWITCH SERVICE FAN RELAY SERVICE LED RED OUTDOOR EM HT THERMOSTAT SUPPL ELEC RELAY RELAY
29. HEAT L2 45 48 AUTO CF 4 4 L 5 x SERVICE A cooL C T 4 4 LED RED lf a Lo fo COMPRESSOR C1 ANTICIPATOR O O O CONTACTOR 2 L ann COOL CHANGEOVER lt C2 ANTICIPATOR VALVE SO Qt POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD M7023 PROTECTION AS REQUIRED Fig 89 Schematic and hookup of T874D with Q674E Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS FILTER LED YEL A SERVICE LED RED H1 ANTICIPATOR Q NO FAN SWITCH H2 ANTICIPATOR COMPRESSOR CONTACTOR 2 CO 2 RISE CONTACTOR 1 9 COMPRESSOR O A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD M7022 PROTECTION AS REQUIRED Fig 90 Schematic and hookup of T874D with Q674G Used in standard applications 119 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR NO FAN SWITCH SYSTEM SWITCH COMPRESSOR CONTACTOR 2 C1 ANTICIPATOR C2 ANTICIPATOR COMPRESSOR CONTACTOR 1 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD HOT PROTECTION AS REQUIRED A A JUMPER RH RC FOR SINGLE TRANSFORMER M3201B Fig 91 Schematic and hookup of T874A F Q with Q674G Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR NO FAN SWITCH CHANGEOVER RELAY H2 ANTICIPATOR SYSTEM
30. Obsolete Used with T874G1618 Y594H1012 Wiring differences old new 1 Y2 Y L R R none R L jumper required no night setback T8600D2028 Wiring differences old new programmable L R WzO W Y jumper required night setback C1264 165 Obsolete Carrier part no HH93AZ193 used with See OEM for T874L1018 HHO7AT178 replacement C1280 181 Qbsolete McQuay heat pump part no 60687401 T8600D2028 See thermostat description for 203 COMP FAULT LED used with T874K1019 L1034 replacement information C1298 76 Obsolete McQuay part no 60684801 SERVICE LED See OEM for 225 used with T874A1523 A1549 01918 replacement C1306 75 Obsolete McQuay part no 60685001 SERVICE LED See OEM for spring return momentary system switch position used replacement with T874A1325 C1314 72 Obsolete Trane part no BAS 0429 used with T874A F Q674C1058 C1322 173 Obsolete Carrier part no HH93AZ199 FAULT and CK Y594H1012 Wiring differences old new FILTER LEDs used with T874H1070 HHO7AT166 2 T874H1088 7 167 or T874H1153 7 167 used Y594H1053 C1330 177 Obsolete LSI Mammoth part no 71115201 RESET Y594H1012 Wiring differences old new LED used on systems with night setback contacts R1 R R2 L used with T874G1659 H1096 used in Y594G1427 H1020 C1355 74 Friedrich part no AQ355 SERVICE LED used with Y594H1012 Wiring differences old new T874H1112 1 Y2zY L R jumper
31. The difference between the two temperatures is the interstage differential which should match the number set on the scale with the tension screw CHECKOUT Heating Move the system switch on the Q674 Subbase to HEAT or AUTO Move the heat lever on the T874 about 10 F 6 C above room temperature See Fig 12 Heating system should start and the fan should run after a short delay Move the heat lever about 10 F 6 C below room temperature The heating equipment should shut off and the fan should run for a short time then shut off In heat pump applications sometimes time delays are involved before the compressor and auxiliary heat are activated This is due to a minimum off timer which prevents the compressor from restarting for five minutes from when the thermostat last turned off the compressor or from when the system first received power Cooling N CAUTION Equipment Damage Hazard Do not operate cooling if outdoor temperature is below 50 F 10 C Refer to manufacturer recommendations 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Move the system switch on the Q674 Subbase to COOL or AUTO Move the cool setting lever on the T874 Multistage Thermostat about 10 F 6 below room temperature See Fig 12 The cooling equipment and fan should start If the system has two stages of cooling both stages should start Move the cool lever about 10 F 6 C above room temperature The cooling equipm
32. W1 W2 R1020 102 Qbsolete Lennox logo part no 24F5401 F C Y594R1243 Wiring differences old new scaleplate H1 and C1 anticipators are fixed auxiliary M Y F G V VR R Y W2 heat circuit powered by separate transformer used with R O replacement has F Q674L1025 scaleplate R1038 102 Lennox logo C scaleplate H1 and C1 Y594R1243 Wiring differences old new anticipators are fixed auxiliary heat circuit powered by M Y F G V VR R Y W2 separate transformer used with Q674L1025 R O replacement has F scaleplate R1046 120 Obsolete York logo part no 2TH11702224A H2 Y594R1664 101 anticipator is fixed used with Q674L1272 in Y594R1011 or with Q674L 1094 R1053 109 Qbsolete Honeywell logo H2 anticipator is fixed used Y594R1763 Designed for use on Trane with Q674L1140 used Y594R1136 heat pumps R1061 104 Obsolete Honeywell logo H2 anticipator is field Y594R1243 Replacement has auto fan in adjustable changeover in cooling used with Q674L1082 Emergency Heat mode aBoth the thermostat and subbase must be replaced 65 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 8 T874 Cross Reference with Q674L1181 used in Y594R1417 Model Fig Trade Model Number No Description Replacement Remarks R1079 123 Obsolete Ruud logo part no UXMT C
33. _ OFF 205 E HT RELAY o o nO 5 N Fd LED EM Hr ELECTRIC o GREEN LED YELLOW HT RELAY C1 ANTICIPATOR HEAT MN ON Q 5 10 COOL 4 EA C815A OUTDOOR Q 9 RISE AUTOU T A 5 O A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COOL CHANGEOVER M3264 A REMOVABLE JUMPER INSTALLED VALVE Fig 229 Schematic and hookup of T874G with Q674F Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS oo E oo W3 RELAY ANTICIPATOR CHECK LED RED COMPRESSOR MONITOR FAN RELAY FAN SWITCH C ANTICIPATO SYSTEM SWITCH Q COMPRESSOR RELAY A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5068 Fig 230 Schematic and hookup of T874R with Q674L Used in heat pump applications 213 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 COOL ANTICIPATOR CHANGEOVER VALVE H2 AN a F SYSTEM SWITCH C1 COMPRESSOR RELAY A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED RISE A ONLY TERMINAL B OR O TO BE USED 0 8A MAX Fig 231 Schematic hookup of T874G with Q674F Used heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 1
34. cooling includes locking cover and field adjustable differential in heating and locking levers cooling D2064 53 Obsolete Carrier Weathermaker part no HHO7AT209 T874D1165 Setstage 1 heat anticipator for stage 1 and 2 heat anticipator factory set 0 1A taupe total current draw of fan and color used with Q674E1445 used in Y594D1412 stage 1 heat primary Replacement is beige D2072 53 Obsolete Carrier Zone Perfect part no HHO7AT208 T874D1165 Setstage 1 heat anticipator for taupe color used with Q674E1445 used in Y594D1420 total current draw of fan and stage 1 heat primary Replacement is beige D2080 139 Obsolete Hydroheat logo T874D1165 Replacement system switch Q674B1018 HEAT OFF COOL no LEDs D2098 44 Obsolete Honeywell logo F scaleplate one setpoint T874D1165 Replacement has F lever used with Q674D1008 used in Y594D1438 scaleplate and two setpoint levers D2106 44 Obsolete Honeywell logo C scaleplate one setpoint T874D1165 Replacement has F lever used with Q674D1008 used in Y594D1446 scaleplate and two setpoint levers D2114 44 Obsolete Bard logo scaleplate T874D1165 Replacement has F scaleplate D2122 224 Obsolete McQuay T874D2023 Replacement has 225 scaleplate T874D1165 Replacement has F scaleplate D2130 226 Obsolete McQuay See OEM for replacement D2148 44 Obsolete Dry Aire Systems logo scaleplate T874D1165 D2155 139 Hydroheat lo
35. differential between H1 and H2 T874D1165 D1417 Fedders logo T874D1165 D1425 Climatrol logo T874D1165 D1433 Singer logo 02005785 8 F 4 4 C differential 87401165 between H1 and H2 D1441 American Air Filter T874D1165 D1474 Carrier no 7 072 03 Celsius scale T874D1165 T872bE 2 stage cool E1002 Standard OEM T874E1016 E1010 TRADELINE T874E1016 E1028 Westinghouse logo T874E1016 When replacing a T872 Thermostat and Q672 Subbase always replace both the thermostat and the subbase 33 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 6 T872 T874 Thermostat Cross Reference T874 Trade Model Number Description Replacement Remarks E1036 American Standard logo T874E1016 E1044 York logo locking cover T874E1016 E1051 ITT logo T874E1016 E1069 Climatrol logo T874E1016 E1077 Airtemp Chrysler logo T874E1016 E1085 Lennox logo T874E1016 E1093 Trane logo T874E1016 E1101 Dunham Bush logo T874E1016 E1119 Fedders logo T874E1016 E1127 Climatrol logo T874E1016 E1135 General Electric logo no AY28X108 T874E1016 E1143 Lennox logo Celsius scale T874E1016 E1150 Celsius scale T874E1016 E1168 Airtemp logo T874E1016 T872F 2 stage heat F1001 Standard OEM T874F1015 F1019 TRADELINE T874F1015 F1027 Lennox logo fast cycle heat anticipator T874C1018 F1035 Luxaire logo
36. o ba FAN RELAY 1 DEFROST ax 1 ENTHALPY 1 CONTROL 7 a Ho 1 1 1 1 OUTDOOR FAN RELAY 3 OUTDOOR FAN RELAY 2 15 STAGE LOW PRESSURE LIMIT 1ST STAGE SHORT CYCLE ECONOMISER CONTROL RELAY 1 TIME DELAY SYSTEM SWITCH TIME DELAY C1 ANTICIPATOR 2ND STAGE C2 ANTICIPATOR SHORT CYCLE 2ND STAGE LOW CONTROL PRESSURE LIMIT OFF COOL DEFROST AUXILIARY RELAY CONTACT HEAT RELAY DEFROST RELAY COOL CHANGEOVER CONTACT VALVE AUX HEAT LED GREEN RESET HEATER EMERGENCY HEAT RELAY A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED C815 OUTDOOR A OPTIONAL ECONOMIZER HOOKUP DOTTED LINES THERMISTOR Fig 118 Schematic and hookup of T874W with Q674L Used in heat pump applications 139 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 4 S L1 L2 NS 815 RESET OUTDOOR HEATER THERMISTOR H2 ANTICIPATOR FAN SWITCH AUTO EU on 9 O O AUX RELAY 0 _ o 4 NE NNI SERVICE LED YELLOW CES 1 SYSTEM FALL 5 SWITCH Q SERVICE HTL 5 Q Eo OFF F oN o s COOL CONTACTOR 5 5 o
37. oN o POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD 9 muda Seats PROTECTION AS REQUIRED Fig 94 Schematic and hookup of T874D with Q674G Used in standard applications 121 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTATS SUBBASE SYSTEM COMPONENTS L1 SWITCH H1 ANTICIPATOR OIL RELAY SYSTEM SWITCH OIL LED RED WOOD LED H2 ANTICIPATOR GREEN WOOD RELAY A POWER SUPPLY PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5984 Fig 95 Schematic and hookup of T874F with Q674K Used in wood oil applications THERMOSTAT SUBBASE SYSTEM COMPONENTS TT FS a D Q FAN SWITCH R L vo FALE mU amp 1 HEAT RELAY ON 1 HEAT RELAY 4 KE ER L2 Uc Ho PP ANTICIPATOR SYSTEM SWITCH L1 Uf QQ A c OFF H4 AUTO 3 O BR COOL DAMPER NO 1 COMPRESSOR 000 C1 ANTICIPATOR CONTACTOR 9 EN ONLED YELLOW c SERVICE L2 LED RED M A A POWER SUPPLY PROVIDE DISCONNECT HOT MEANS AND OVERLOAD PROTECTION AS REQUIRED M104A Fig 96 Schematic and hookup of T874C with Q674C Used in standard applications 60 2485 8 122 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS ENS COMPRESSOR CONTACTOR CLOSED DAY OPEN NITE OVERRIDE LED RED SERVICE LED RED COMPRESSURE FAILURE cer JUMPE
38. required C1363 99 Obsolete McQuay part no 61202601 SERVICE LED T874C1125 Replacement has HEAT OFF auto fan in heat and cool mode used with T874C 0674810752 COOL 219 Obsolete Used with T874C See OEM for replacement 220 Obsolete Used with T874W See OEM for replacement 100 Obsolete Used with T874W T8611M2025 Includes night setback programmable C1371 72 American Standard part no ASYSTAT616 Q674C1058 a Both the thermostat and subbase must be replaced 60 2485 8 74 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9 Q674 Subbase Cross Reference Model Fig Q674 Trade Number No Description Replacement Remarks C1389 205 Obsolete Command Aire part P1099 0021 two None See thermostat description for 176 LEDs used with T874G H replacement information C1397 205 Obsolete Command Aire part no P1099 0023 used None See thermostat description for 171 with T874G H replacement information C1413 213 Obsolete Carrier part no HH93AZ204 Fan Lo Med See OEM for High On used with T874L1059 replacement C1439 217 Obsolete Bard part no 8404 016 used with See OEM for T874N1024 replacement C1454 163 Obsolete Climate Master part no AQ5354 two LEDs Y594G1393 momentary reset switch spring return momentary system switch position C1462 25 Climate Master Special Q674C1058 Replacement has
39. used in Y594R1490 None See Trol A Temp L1686 209 Trol A Temp by Honeywell used with T874R1715 used in Y594R1508 None See Trol A Temp L1702 132 Obsolete Snyder General heat pump part no 654958 07 used with T874R1723 and C815A1005 used in Y594R1516 Y594R1672 Wiring differences old new C B W1 W X X2 L1710 230 Used with T874R1822 used in Y594R1615 Y594R1615 L1728 228 Obsolete Lennox gray color used with T874R1855 used in Y594R1714 Y594R1763 Wiring differences old new Y1zY L F W1 W 2 C B L1736 120 Designed to replace Y594R1011 York part no 2TH11702224 used with T874R1871 used in Y594R1664 Y594R1664 Designed to replace Y594R1151 York part no 2TH11702324 Y594R1193 York part no 6TH11702224 and York part no 2TH11704024 used with T874R1889 and C815A1054 used in Y594R1672 Y594R1672 L1751 230 Gray color used with T874R1897 used in Y594R1680 Y594R1680 L1769 124 Obsolete Nordyne part no 9132260 used with T874J See OEM for replacement L1777 120 Obsolete Gray color designed to replace Y594R1151 York part no 2TH11702324 Y594R1193 York part no 6TH11702224 and York part no 2TH11704024 used with T874R1905 and C815A1059 used in Y594R1698 Y594R1672 Replacement is beige Designed to replace Y594R1011 York part no 2TH11702224 used with T874R1913 used in Y594R1706
40. 2000 1800 1600 1400 1200 1000 800 600 400 200 0 720 0 20 40 60 80 100 120 140 TEMPERATURE THERMISTOR 815 THERMISTOR RESISTANCE 400 ohms 10 AT 77 F 25 1590 Fig 29 Thermistor resistance chart Features Two of the features of the T874 Q674 include LED indicators and restricted setpoint LED Indicators The light emitting diodes LED indicators on the subbase light on command when something specific happens in the system See Fig 30 Up to four different LEDs are available The thermostat has a clear lens window for viewing each LED On TRADELINE models a small insert is used so the LED function desired can be selected This must be done during installation A blank insert is factory installed in some T874 models To remove it push both temperature setting levers to the far ends of the thermostat Use index fingernail to gently pull out the scaleplate a fraction of an inch Turn thermostat upside down and the blank insert falls out 60 2485 8 22 A strip of four inserts is included with TRADELINE T874 Drop a strip into the recessed area behind the scaleplate so selected LEDs show Make sure insert is completely seated in recessed area Let scaleplate pop back then set levers to desired position FILTER LED lights when the filter is clogged and needs replacement CHECK LED lights when something needs to be checked or done to maintain efficient op
41. A o r H1 ANTICIPATOR HOT FAN L2 SWITCH OUTDOOR im l THERMOSTAT EM HT RELAY 1 m i 2 m gt lt 2 SYSTEM SWITCH Fi RELAY EM HT CONTACT 2 RELAY 3 19 C1 ANTICIPATOR 5 SUPL HT LED RED COMPRESSOR CONTACTOR 1 Uc 10 A POWER SUPPLY PROVIDE DISCONNECT MEANS A N O SWITCH INSTALLER ADDED TO LIGHT EM HT LED AND OVERLOAD PROTECTION AS REQUIRED WHEN COMPRESSOR OPERATION IS NOT NORMAL M5724 i Fig 161 Schematic and hookup of T874G with Q674J Used in heat pump applications 169 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THEROMSTAT SUBBASE SYSTEM COMPONENTS re C815A OUTDOOR 2 HoN o THERMISTOR FAN SWITCH O CHANGEOVER VALVE OUTDOOR THERMOSTAT LED RED COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5725 Fig 162 Schematic and hookup of T874G with Q674J Used in heat pump applications 60 2485 8 170 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT DAMPER RESET CIRCUIT H1 ANTICIPATOR FAN SWITCH SYSTEM SWITCH AUTO COOL CHANAGEOVER VALVE ANTICIPATOR SERVICE LED RED COMPRESSOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD RELAY PROTECTION AS REQUIRED
42. ANTICIPATOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED FACTORY INSTALLED JUMPER LED COMPRESSOR FAILURE C815A OUTDOOR THERMISTOR C SYSTEM COMPRESSOR CONTACTOR Fig 130 Schematic and hookup of T874R with Q674L Used in heat pump applications 148 M1628A T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS le EE e ifi 1 1 ANTICIPATOR FAN AUTO 1 1 ALL FN HCR 1 HEATER a ODT SYSTEM SWITCH SUPL HT uu LED RED H2 ANTICIPATOR FALL POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR VN FOR Q674L1454 5 OFF M Ey CR 1 HCR2 M4723 I Fig 131 Schematic and hookup of T874R with Q674L Used in heat pump applications 149 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS o E FAN COOL CHANGEOVER 47 H1 C1 ON ANTICIPATOR SYSTEM SWITCH UIs FALL H2 ANTICIPATOR SYSTEM LED OUTDOOR GREEN THERMISTOR RESET A A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED 4R M1858 A REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS Fig 132 Schematic and hookup
43. AS REQUIRED HOT M4666 Fig 84 Schematic and hookup of T874G with Q674E Used in heat pump applications 60 2485 8 116 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR H2 ANTICIPATOR FAN SWITCH ON AUTO HEAT RELAY 1 zi COMPRESSOR CONTACTOR 1 1 FAN RELAY SYSTEM O SWITCH Q OFF AUTO M 4 ANTICIPATOR COOL Le _ COMPRESSOR C2 ANTICIPATOR CONTACTOR 2 macs Q c2 A POWER SUPPLY PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5983 Fig 85 Schematic and hookup of T874A D with Q674E Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR H2 ANTICIPATOR 3 UA FN H2 lt FALL 8 C1 ANTICIPATOR Uc 5 D c dra mec SYSTEM SWITCH Q Q OFF F4 FA CO Q Q Q AUTO _F Q Q cooL JA POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED 09 CHANGEOVER DEFROST DEFROST SWITCH HIGH PRESSURE SWITCH COMPRESSOR CONTACTOR DEFROST RELAY AUX HT RELAY CONTACT L2 1 7 HOT Fig 86 Schematic and hookup of T874G with Q674E Used in heat pump applications 117 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
44. B L1348 115 Obsolete Williamson heat pump used with Q674L1207 T874R1236 L1355 111 Obsolete Lennox part no 31F3201 V VR jumper Y594R1763 Wiring differences old new 190 used with T874C1448 R1178 and C815A1015 V VR R M Y F G X B Y W 2 11363 129 Obsolete York heat pump HEAT LED used with Y594R1425 Wiring differences old new T874G1402 W W2 jumper Y wi L1371 124 Obsolete BDP heat pump part no 34427DP125 Y594J1001 Wiring differences old new P272 1878 EM HEAT LED used with T874J1010 W1 W2 F L L1389 114 Obsolete Lennox part no 41F6501 V VR jumper T8611M2025 Wiring differences old new used with T874D1207 programmable V VR R Y W3 R O M Y M2 Y2 W2 F G jumper Y2 W2 no outdoor reset needed use only one system transformer Both the thermostat and subbase must be replaced 83 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 9 Q674 Subbase Cross Reference WY28X235 used with T874R1657 used in Y594R1441 Model Fig Q674 Trade Number No Description Replacement Remarks L1397 103 Obsolete Carrier part no HH93AZ185A SUPL HEAT Y594G1393 Wiring differences old new LED 11405 106 Obsolete heat pump part no HH641501 used Y594R1243 with T874R1335 used in Y594R1201 L1413 133 Ob
45. Contact your local waste management authority for instructions regarding recycling and the proper disposal of this control or of an old control containing mercury in a sealed tube If you have questions call the Honeywell Customer Response Center at 1 800 468 1502 INSTALLATION en Installing this Product Read these instructions carefully Failure to follow them could damage the product or cause a hazardous condi tion 2 Checkthe ratings given on the product to make sure the product is suitable for your application 3 Installer must be a trained experienced service techni cian 4 After installation is complete check out product opera tion as provided in these instructions N CAUTION Hazardous Voltage Can damage heating cooling system 1 Disconnect power supply before beginning instal lation to prevent electrical shock or equipment damage 2 Do not short across coil terminals on relay This can burn out thermostat heat anticipator 3 To prevent interference with the thermostat link age keep wire length to a minimum and run wires as close as possible to the subbase 4 Do not overtighten thermostat captive mounting screws because damage to subbase threads result IMPORTANT An incorrectly leveled thermostat will cause the tem perature control to deviate from setpoint It is not a calibration problem Location Install the thermostat about 5 ft 1 5m above the floor in an area with good air c
46. DISCONNECT 11 MEANS AND OVERLOAD PROTECTION AS REQUIRED CHANGEOVER VALVE SERVICE eas COMPRESSOR CONTACTOR JE Fig 122 Schematic and hookup of T874R with Q674L Used in heat pump applications 60 2485 8 142 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIAPTOR EM HT CH RED COMPRESSOR MONITOR ANTICIPATOR CHANGEOVER VALVE POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED CONNECT CHANGEOVER RELAY TO B FOR HEAT CHANGEOVER TO O FOR COMPRESSOR COOL CHANGEOVER CONTACTOR HEAT CHANGEOVER VALVE M1030A Fig 123 Schematic and hookup of T874R with Q674L Used in heat pump applications 143 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 L2 HOT A TS T S E T Toho H1 FAN RELAY HEAT RELAY 1 ANTICIPATOR H2 ANTICIPATOR EM HT OR SUPL HT LED RED OUTDOOR THERMOSTAT gt 2 m ne cc HEAT RELAY HEAT RELAY 2 CONTACT 1 SYSTEM SWITCH Q Q EM HT OR SUPL HT 5 5 PB HEAT RELAY CONTACT 2 PF NRISE gt C1 ANTICIPA HEAT RELAY 3 HEAT O OFF C 4 H4 0 O A95 p P RELAY UNSA Rise Doa ES
47. Ex oN o cox o o 12 CHANGEOVER VALVE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED 18002 A ON MODELS INCLUDING EXTERNAL JUMPER W2 W1 AND L F Fig 124 Schematic and hookup of T874J with Q674L Used in heat pump applications 60 2485 8 144 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT rN SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR AUX HT LED GRN RELAY ANTICIPATOR SYSTEM SWITCH COMPRESSOR CONTACTOR B RELAY A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A TERMINAL LABELED C X ON SOME MODELS M3683A A W3 TERMINAL AVAILABLE ON SOME MODELS ONLY Fig 125 Schematic and hookup of T874R with Q674L Used in heat pump applications 145 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE fF SYSTEM COMPONENTS COOL CHANGEOVER VALVE H1 ANTICIPATOR FAN SWITCH Q 1 OUTDOOR e H THERMOSTAT HEAT RELAY 1 amp t o Lo 2 1 o No 1 Fuuumuumum Fuuumuuuuu HEAT RELAY HEAT RELAY 2 CONTACT 1 ARE LOR SE SYSTEM SWITCH Fuuuumuum HEAT RELAY HEAT RELAY 3 gt O mur Q 2 SUPL HT Hj 5 43 10 A Saat SUPL HT COOL F d a LED RED o A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIR
48. H1039 79 Obsolete Mammoth logo F C scaleplate used with Y594H1012 Wiring differences old new Q674C1124 used in Y594H1004 R1 R R2 L H1054 74 Obsolete No logo Friedrich part no AT5854 used with Y594H1012 Wiring differences old new Q674C1041 1 Y2 Y L R jumper required H1062 164 logo used with Q674C1249 used in Y594H1012 Y594H1012 H1070 172 Obsolete Carrier Heat Pump System Control logo part None See subbase description for 173 HHO7AT166 C scaleplate used with Q674B1406 replacement information HH93AZ200 or Q674C1322 HH93AZ199 H1088 172 Obsolete Carrier Heat Pump System Control logo part None See subbase description for 173 HHO7AT167 used with Q674B1406 HH93AZ200 replacement information or Q674C1322 HH93AZ199 H1096 177 Qbsolete Mammoth Water Source Heat Pump logo F Y594H10122 Wiring differences old new C scaleplate changeover stage 0 8A maximum used B R1 R R2 L L R jumper or O terminal used with Q674C1330 required H1112 74 Nologo Friedrich part no AT5812 used with Y594H1012 Wiring differences old new Q674C1355 1 Y2 Y L R jumper required H1120 205 Obsolete Command Aire logo part no P1013 0055 Y594H1012 Wiring differences old new used with Q674C1389 C1397 1 Y2 Y H1138 221 Qbsolete Climate Master logo part no AT5838 used Y594H1012 Wiring differences old new with Q674C1470 1 0 Y2 Y replacement
49. HT RELAY SWITCH EM HT LED i5 EM HT YELLOW C815A FALL OUTDOOR THERMISTOR H2 ANTICIPATOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND A REMOVE FACTORY INSTALLED V VR JUMPER WHEN OVERLOAD PROTECTION AS REQUIRED CONNECTING A TWO TRANSFORMER SYSTEM m2851 Fig 111 Schematic and hookup of T874R with Q674L Used in heat pump applications 60 2485 8 132 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS a COOL CHANGEOVER FAN SWITCH H1 C1 ANTICIPATOR COMPRESSOR FAILURE EM HT LED AUX HT LED GREEN AUX HT RELAY COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 112 Schematic and hookup of T874R with Q674L Used in heat pump applications 133 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60 2485 8 THERMOSTAT SUBBASE SYSTEM COMPONENTS HOT HEAT 12 HT RELAY CONTRACTOR 3 AN H1 C1 ANTICIPATOR HIGH LIMIT FAN SWITCH REVERSING CHECK LED GREEN SYSTEM H2 ANTICIPATOR SWITCHO EM HT EM HT RELAY LED RED FAN RELAY COMPRESSOR HIGH CONTACTOR PRESSURE SWITCH POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED LOW AMBIENT COOL CHANGEOVER CUTOFF VALVE Fig 113 Schematic and hookup of T874R with Q674L Used in heat pump applications
50. LED GRN ANTICIPATOR H2 SYSTEM SWITCH b4 Lo GES CHANGEOVER VALVE ch ses RELAY COMPRESSOR 5v CONTACTOR LACO CHP 9 2 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD M7064 PROTECTION AS REQUIRED Fig 235 Schematic and hookup of T874G and Q674F Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS CONTROL MODULE COMPRESSOR COMPRESSOR RELAY 2 SERVICE C2 Uc LED RED A A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M7570 Fig 236 Schematic and hookup of T874A D with Q674C Used in standard applications 60 2485 8 216 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR SYSTEM SWITCH COMPRESSOR C1 ANTICIPATOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED 716 Fig 237 Schematic and hookup of T874C with Q674B Used standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS Hi Q FAN SWITCH CHECK Q9 Eee ANTICIPATOR LED RED AUTO 2 Em em FA de ESL Sears HOT T oN o SYSTEM SWITCH D RUE 0 N97 Q HT AUX HT A y RELAY o O Oo N o HT PUMP A 5 5 AUX HT 5 2 STAGE HT LED RED oO HEAT PUMP RELAY I i A COOL CHANGEOVER
51. MODELS M3680A Fig 74 Schematic and hookup of T874H with Q674C Used in heat pump applications 111 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS s ANTICIPATOR SYSTEM SWITCH HEAT RELAY YELLOW A Q FILTER LED SERVICE LED RED FAN SWITCH Ai H4 FH FEB C1 ANTICIPATOR MOMENTARY CIRCUIT 9 OO COMPRESSOR CONTACTOR EXTERNAL THERMISTOR TEMP READOUT POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED MOMENTARY POSITION SPRING RETURN TO ON UPON SWITCH RELEASE FILTER LED ON SELECT MODELS M5731 Fig 75 Schematic and hookup of T874A with Q674C Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 2 H1 ANTICIPATOR SWITCH HEAT RELAY 1 F HEAT CHANGEOVER Ei C FAL VALVE ETE LIEN 9 E M Op H2 ANTICIPATOR T C HOT COOL CHANGEOVER VALVE SYSTEM nae SWITCH Q OO 00000000 COMPRESSOR COMPRESSOR CONTACTOR 1 RISE CONTACTOR 2 ze C2 FILTER m TSS C2 ANTICIPATOR LED YEL Lo fo A A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD SERVICE amp PROTECTION AS REQUIRED LED REDJI O es gt Lo A FOR T874C DELETE C2 A FILTER LED ON SELECT MODELS M7025 Fig 76 Schematic and hookup of T874A D with Q674C Used in standard applications 60 2485
52. Premier White color None See Trol A Temp H1 and H2 heat anticipators set at 0 10A used with Q674B1471 D1123 D1843 45 J Obsolete Janitrol logo Goodman part no CHT 90 120 787401165 used with Q674B1000 used in Y594D1321 D1850 44 Honeywell logo Carrier part no HH621606 T874D1165 D1868 44 logo part no 8405 031 H1 and H2 heat T874D1165 Replacement has 2 F fixed anticipators factory set at 0 25A 5 F interstage interstage differential between differential between H1 and H2 and between C1 and C2 H1 and H2 and between C1 includes Allen wrench and screws to lock cover field and C2 adjustable range stops D1876 44 Qbsolete AAF Snyder General logo part no T874D1165 Replacement has F 4ELN69814 F C scaleplate scaleplate D1892 44 Obsolete Climate Tel logo T874D1165 D1918 224 Obsolete AAF Snyder General logo F C scaleplate See OEM for 225 cooling anticipation used with Q674E1312 C1298 replacement 66804407 D1926 226 Obsolete AAF Snyder General logo F C scaleplate See OEM for no cooling anticipation used with Q674G1120 replacement 66804406 D1934 44 Bardlogo T874D1165 D1942 82 Honeywell logo TRADELINE model used with Y594D1347 Q674E1403 used in Y594D1347 designed to replace York part no 2TH04701024 D1959 44 part no 41 21444 01 T874D1165 D1967 44 Obsolete Desert Aire logo T874D1165 D1975 224 Obsolete McQuay part no 066816603 F C
53. Q672C System OFF AUTO Fan AUTO ON C1003 Standard OEM Q674C1058 C1011 Westinghouse RC RH jumper Q674C1058 RC RH jumper required C1029 W1 Y2 jumper for heat pump used with Q674E1049 Replacement has heat cool system T872D1136 switching C1037 Chrysler Airtemp System COOL OFF AUTO Q674C1058 C1045 Westinghouse heat pump used with T874C1018 Wiring differences old new T87281005 Q674C1058 V RC RH F G C Y1 Z B H2 W2 W1 Y1 jumper required C1052 Isolated stage 2 heat circuit for dc electric heat Recontrol Use T874G1246 Q674F1212 which relay adds HEAT COOL EM HT system switch C1060 Fedders special Q674C1058 C1078 General Electric no AY28X109 Q674C1058 C1086 Command Aire heat pump used with Y594H1012 T872H1009 C1102 TRADELINE Q674C1058 Q672D System None Fan None D1002 Standard OEM used with T872F 1126 Q674D1040 D1010 Lennox special None D1028 Carrier RC RH jumper None D1036 Carrier no HH93AZ070 RC RH jumper Q674D1040 RC RH jumper required D1044 General Electric no AY 28X100 None D1069 Square D no HCB 4 None D1077 York used with T872G1364 None D1085 TRADELINE Q674D1040 Q672E System OFF HEAT AUTO COOL Fan AUTO ON E1001 Standard OEM Q674E1049 E1019 Lennox no P 8 8892 heat pump cool mode T874D1165 changeover used with T872G1026 Q674B1075 E1027 Heat pump circuit W1 Y2 jumper cool mode Y594G1393 Wiring differences old new Y1 O changeover used with T872G1018 Y2 Y E1035 Heat pump circuit W1
54. R1271 Westinghouse logo used with Q672L1375 and Y594R1664 W89 R1297 York Celsius scale used with Q672L1011 None R1305 Used with Q672L1235 and W89 None R1321 Duotherm logo used with Q672L1409 W89 R1339 Williamson used with Q672L1391 Y594R1243 T872S Heat pump model 2 stage heat plus changeover 1 stage cool S1005 Westinghouse logo adjustable anticipator stage 1 T874C1018 Wiring differences old new and 2 heat fixed anticipator stage 1 heat Q674C1058 V RC RH F G C Y1 Z B changeover with heating used with Q672C 1045 H2 W2 W1 Y1 jumper required T872T 1 heat stage 1 vent and 2 cool stages T1004 Trane logo used with Q672B1129 None T872W 3 heat stages 2 cool stages manual changeover W1019 Lennox logo no 52C7501 used with Q672L1342 and C815A1013 W1027 Westinghouse logo used with Q672L1268 and None C815A1021 W1035 TRADELINE used with C815A1043 and Y594W1014 Q672B1251 When replacing a T872 Thermostat and Q672 Subbase always replace both the thermostat and the subbase 60 2485 8 38 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7 0672 0674 Subbase Cross Reference Model Number Description Q674 Trade Replacement Remarks Q672A System HEAT AUTO COOL Fan AUTO ON A1005 Standard OEM Q674A1019 A1013 TRADELINE Q674A1019 A1021 RC RH j
55. R1590 R1640 R1921 used in 067411207 or Y594R1243 R1706 Y594R1243 L1215 116 Obsolete Crispaire heat pump used with T874R1111 Y594R1243 Replacement has auto fan in used in Y594R1128 emergency heat mode Wiring differences old new AzL set anticipator to 1 2 L1223 117 Obsolete Westinghouse special See OEM for replacement L1231 182 Obsolete Used with T874R1186 and W89 None L1249 115 Obsolete Used with T874R1194 and W89 Y594R1243 L1256 118 Obsolete Westinghouse special used with T8611M2025 Includes night setback T874W1007 programmable L1264 119 Obsolete Intertherm heat pump EM HEAT and SERV Y594R16722or Wiring differences old new LEDs used with T874R1202 R1608 R1699 used in Y594R1763 W2zW Z no Y594R1185 R1409 R1482 connection K X W1 H L1272 120 Obsolete York part no 025 22290 used with Y594R1672 T874R1046 R1145 used in Y594R1011 R1102 used with T874R1228 R1251 R1327 and C815A1039 used in Y594R1144 R1151 R1193 L1280 233 Obsolete Lennox no 52C7601 used with T874W1023 Y594W1014 W89 L1298 182 Singer heat pump used with T874R1160 See OEM for W89 replacement L1314 115 Obsolete Westinghouse heat pump used with Q674L1207 or T874R1244 and W89 Y594R1243 L1322 127 Obsolete EM HEAT and AUX HEAT LEDs used with Y594R1243 T874C1455 L1330 120 Obsolete York heat pump used with T874R 594 16642 Wiring differences old new L X X
56. SWITCH CHANGEOVER VALVE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR M5841 Fig 19 Tracing the heat 1 and anticipation circuit 17 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 F ANTICIPATOR FALL 2 prr E CESS 3 FAN SWITCH AUTO 4 9 5 ONU FD H2 O ANTICIPATOR SYSTEM SYSTEM LED RED MONITOR SWITCH olo j 4 e A HEAT 7 OFF F4 O OQ A POWER SUPPLY PROVIDE CooL 4 DISCONNECT MEANS AND Y O 9 OVERLOAD PROTECTION AS REQUIRED R A 8 COMPRESSOR CONTACTOR Mad Fig 20 Tracing the heat 1 anticipation circuit THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR FAN SWITCH SYSTEM MONITOR SYSTEM SWITCH LED RED EN CHANGEOVER A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR M5843 Fig 21 Tracing the heat 2 anticipation and AUX HT LED circuit 60 2485 8 18 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR FAN SWITCH EM HT SYSTEM LED RED MONITOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR M5844 Fig 22 Tracing the emer
57. THERMOSTAT SUBBASE SYSTEM COMPONENTS 1 COOL CHANGEOVER H1 e m FAN SWIT CH FALL NO 2 AUTO H2 Aas sy O D T H2 P ANTICIPATOR SYSTEM H C R 1 H C R 2 SWITCH sepes eve H C R 2 H C R 3 C1 ANTICIPATOR 5 SUPL HT COMPRESSOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD CONTACTOR M2975 PROTECTION AS REQUIRED Fig 196 Schematic and hookup of T874G with Q674J Used in heat pump applications 191 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS AUX HEATER COMPRESSOR MONITOR FAN SWITCH SYSTEM SWITCH OUTDOOR THERMISTOR OUTDOOR THERMOSTAT POWER SUPPLY PROVIDE DISCONNECT MEANS AND VALVE OVERLOAD PROTECTION AS REQUIRED M2970 A FIELD REMOVABLE JUMPER Fig 197 Schematic and hookup of T874R with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 STAGE 1 HEAT RELAY HOT 9 Or o N o FSS FALL COMPRESSOR CONTACTOR H1 ANTICIPATOR STAGE 2 HEAT RELAY SYSTEM SWITCH HEAT H4 AUTO FAX o 6 C2 ANTICIPATOR 2 22 2 2976 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 198 Schematic and hookup of T874L with Q674E Used in standard applications 60 2485 8 192
58. Y2 jumper cool mode Y594G1393 Wiring differences old new 1 changeover Y2 Y E1043 Heat pump circuit heat mode changeover Q674E1049 Wiring differences old new W1 B W2 W1 W1 Y1 jumper When replacing a T872 Thermostat and Q672 Subbase always replace both the thermostat and subbase 60 2485 8 40 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7 0672 0674 Subbase Cross Reference Q674 Trade Model Number Description Replacement Remarks E1050 TRADELINE Q674E1049 E1068 RC RH jumper used with T872C1699 Q674E1049 RC RH jumper required E1076 RC RH internal jumper EM HT LED Q674E1049 RC RH jumper required E1084 Carrier no HH93AZ076 RC RH jumper Q674E1049 RC RH jumper required E1092 Carrier no HH93AZ082 RC RH jumper B Q674E1049 terminal isolated G terminal E1100 General Electric no AY28X099 Q674E1049 E1118 Airtemp heat pump used with T872D1169 T874D1165 Wiring differences old new Q674E1049 A W1 set H1 anticipator to 1 2A E1126 Common R terminal Q674E1049 RC RH jumper required E1134 ITT Nesbitt RC RH jumper and B terminals Q674E1049 isolated G terminal E1142 Lennox no P 8 11224 heat pump Y594G1252 Wiring differences old new V VR jumper cool mode changeover used with V VR R Y W2 R O M Y F G 787261067 1159 Carrier no HH93AZ077 RC RH jumper Q674E1
59. Y594H1012 Wiring differences old new 787491352 1 Y2 Y L R R L jumper required no night setback T8600D2028 Wiring differences old new programmable 1 Y2 Y L R W Y jumper required night setback C1074 81 Obsolete Used with T874C1018 Q674C1058 W2 Y1 and RH RC C1090 77 Obsolete LSI Mammoth heat pump used with Y594R1419 Wiring differences old new T874K1001 RH RC R W1 B W3 W2 W2 W1 remove 1 1 jumper C1108 143 Obsolete Northrup special AUX HEAT LED used with Y594R1243 Wiring differences old new 787401139 1 W1 W2 1116 76 Obsolete McQuay part 02005959 two LEDs used 067461058 Replacement has no LEDs with T874D1116 C1124 79 Obsolete LSI Mammoth heat pump RESET LED Y594G1294 used with T874G H used in Y594G H T8600D2028 C1132 75 Obsolete McQuay part no 03005049 spring return See OEM for momentary system switch position used with replacement T874A1283 C1140 78 Obsolete McQuay 860 442728B 00 System 7860002028 Wiring differences old new OVERRIDE AUTO OFF used with T874P1006 programmable L R W O W Y jumper required night setback C1157 72 Obsolete York part no 27 04700124 Q674C1058 C1165 192 Obsolete McQuay part no 03005050 spring return See OEM for momentary system switch position replacement 1173 96 American Air Filter part no 4ELN 8787 Q674C1058 Replacement has no
60. a T872 Thermostat and Q672 Subbase always replace both the thermostat and subbase 43 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 7 0672 0674 Subbase Cross Reference Q674 Trade Model Number Description Replacement Remarks L1052 Carrier no HH93AZ075 heat pump HT Y594R1615 Wiring differences old new LED cool mode changeover compressor lockout in EM HT used with T872G1075 G1182 G1273 G1307 L1060 Dunham Bush EM HT LED used with Y594R1243 T872R1099 L1078 Tappan no B13708 58 heat pump EM HT None LED cool mode changeover compressor lockout in EM HT EM HT relay provides fan operation in EM HT used with T872G1190 L1086 Friedrich heat mode changeover HT LED Y594R1243 Wiring differences old new X2 E used T872R1115 with L terminal 11094 Crispaire W2 H jumper LED used Y594R1243 Replacement has auto fan in with T872R1065 R1156 Emergency Heat mode L1102 Fedders heat mode changeover EM HT LED 59491425 Wiring differences old new K E used with T872C1509 C1517 C1541 CzX remove Y W1 jumper L1110 Westinghouse EM HT LED used with Y594R1243 Wiring differences old new T872R1149 W W2 L1128 Westinghouse EM HT LED used with Y594R1243 Wiring differences old new T872R1149 W W2 L1136 Rheem no 41 20796 07 cool mode Y594R1243 changeo
61. has MALFUNCTION LED only H1146 205 Trane logo part no X13510598010 Y594H1012 Wiring differences old new 1 Y2 Y H1153 173 Qbsolete Carrier Heat Pump System Control logo part None See subbase description for no HH07AT167 scaleplate used with replacement information Q674C1322 used in Y594H1053 H1161 74 Obsolete Carrier Heat Pump System Control logo part Y594H1012 Wiring differences old new no HHO7AT203 scaleplate used with 1 Y2 Y L R jumper Q674C1496 used in Y594H1038 required T874J Heat pump model 2 stage heat 1 stage cool J1002 124 Obsolete Carrier Heat Pump System Control logo part None See subbase description for 144 no HHO7AT175 used with Q674J1068 HH93AZ183 replacement information 206 Q674J1159 HH93AZ196 Q674L1074 HH93AZ186 207 6741 1637 HH93AZ195 J1010 124 Obsolete BDP multi logo part no 34427DP124 P272 None See subbase description for 171 2471 used with Q674J1084 L1371 replacement information J1028 124 Obsolete Carrier Heat Pump System Control logo part None See subbase description for 144 no HHO7AT165 C scaleplate used with Q674J1068 replacement information 206 HH93AZ183 Q674J1159 HH93AZ196 067411074 207 HH93AZ186 067411637 HH93AZ195 J1036 124 Obsolete Miller logo part no 9132230 used with T8511G1021 171 Q674J1217 J1044 124 Obsolete Intertherm logo part no 9132240 used with T8511G1021 171 Q674J121
62. logo part no Y594R1797 Wiring differences old new 10574104 C X X W3 W2 R2028 209 Obsolete York logo part no 2TH11703424A used with Y594R1797 Q674L1918 in Y594R1821 R2036 134 Ruud logo scaleplate used with 067411504 See OEM for replacement T874S 2 stage heat 3 stage cool 51001 223 Obsolete Carrier Synergy 2000 Heat Pump System T8611M2025 Includes night setback Control logo used with Q674F1501 programmable or see OEM for direct replacement T874V 1 stage cool V1008 69 Obsolete No logo Carrier part no HHO7AT177 used T874A1036 with Q674R1003 aBoth the thermostat and subbase must be replaced 69 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks T874W 3 stage heat 2 stage cool manual changeover W1007 118 Obsolete Honeywell logo Westinghouse special used T8611M2025 Includes night setback with Q674L1256 programmable W1015 54 Honeywell logo used with Q674B1216 and C815A1005 T874W1015 used in Y594W1014 W1023 233 Obsolete Lennox Advanced Heat Pump System logo T874W1015 used with Q674L1280 and W89 W1031 140 Qbsolete No logo Rheem part no 41 20797 20 used T8611M2025 _ Includes night setback with 067411546 and C815A1005 used in Y594W1022 programmable W1049 100 Obsolete M
63. one LED Y594G1674 Replacement is beige color J1266 160 York Canada gray color includes EM HT LED used in Y594G1625 Y594G1567 J1274 161 TRADELINE System SUPL HT ON OFF includes one LED used with T874G2004 used in Y594G1674 Y594G1674 J1282 244 Obsolete TRADELINE System SUPL HT ON OFF includes SUPL HT LED used with T874J1069 used in Y594J1019 Recontrol T8511G1021 a Both the thermostat and subbase must be replaced 81 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 9 Q674 Subbase Cross Reference Model Fig Q674 Trade Number No Description Replacement Remarks Q674K System OFF HEAT AUTO COOL Fan None K1000 93 Obsolete Carrier part no HH93AZ172 RC RH jumper Q674E1049 switch is not operational K1018 95 Obsolete Oneida Heater part no 3040284 02 Q674K1026 System OFF WOOD WOOD OIL OIL used with T874F1106 K1026 95 System OFF WOOD WOOD OIL OIL used with Q674K1026 T874F1155 K1034 93 Obsolete Snyder General part no 4ELN 7920 Q674E1049 switch is not operational K1042 93 Obsolete Carrier part no HH93AZ172 W gray color Q674E1049 Fan switch is not operational includes removable jumper between RC and RH terminals Q674L System EM HT HEAT OFF COOL Fan ON AUTO L1017 101 Obsolete York hea
64. pump EM HEAT and Y594G1674 Both the thermostat and subbase must be replaced 60 2485 8 80 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9 Q674 Subbase Cross Reference Model Number Fig No Description Q674 Trade Replacement J1068 144 Obsolete Carrier heat pump part no HH93AZ183 used with T874J1002 HHO7AT175 T874J1028 HHO7AT165 Y594J1019 Remarks J1076 180 Obsolete McQuay part no 02005964 two LEDs used with T874A D Q674F1022 Replacement has no LEDs J1084 171 Obsolete BDP heat pump part no 34427DP126 P272 1879 EM HEAT LED used with T874J1010 Y594J1019 Wiring differences old new W12We F L J1118 196 Obsolete Carrier heat pump part no HH93AZ188 SUPL HEAT LED System SUPL HT ON OFF used with T874G1055 HHO7AT171 Y594G1674 Wiring differences old new C X Y1 W1 jumper required no auto fan in emergency heat J1126 160 Obsolete Luxaire no 026 00068 000 EM HEAT LED used with T874G1568 used in Y594G1351 Y594G1567 J1142 174 Obsolete American Standard part no WY28X0250 AUX HEAT and EM HEAT LEDs used with T874G1675 used Y594G1443 Y594G1161 J1159 206 Obsolete Carrier heat pump part no HH93AZ196 used with T874J1002 HHO7AT175 T874J1028 HHO7AT165 Y594J1019 J1167 175 Obsolete Carrier heat pump MANUAL AUTO HEAT
65. range The anticipator is a small resistive heater in the thermostat that heats when the system is on heat mode or off cool mode The heat produced by the anticipator raises the internal bimetal temperature slightly faster than the surrounding room temperature The thermostat anticipates the need to shut off the heating system sooner than it would if affected by room temperature only There are two types of heat anticipation adjustable and fixed Adjustable anticipation is also called current anticipation See Fig 26 The heater is in series with the mercury switch and heating primary The pointer is adjusted to match the current draw of the primary control and the correct amount of heat is added for proper cycle rates L1 L2 HOT H1 ANTICIPATOR FALL STAGE 1 HEAT RELAY M5823 Fig 26 Adjustable anticipation heater in series with load Fixed anticipation is also called voltage anticipation See Fig 27 The heater is in parallel with the primary control and is not affected by the current draw of the primary It establishes the proper cycle rate for any application L1 L2 HOT STAGE 1 HEAT RELAY H1 ANTICIPATOR Fig 27 Fixed anticipation heater in parallel with load M5824 21 Heat anticipators add heat during the call for heat Cooling anticipators are activated while the air conditioner is off See Fig 28 This heater makes the thermostat think it is warmer than it really is and brings
66. range scaleplate stops set at 23 max heat and min cool 73 F C1034 44 Lennox logo part no 13F0401 F C scaleplate T874C1018 Replacement has F scaleplate C1042 44 J Obsolete Westinghouse logo H1 anticipator factory set T874C1018 at 75A H2 anticipator factory set at 1 2A used with Q674A E G C1059 44 142 Obsolete Amana Air Conditioning logo part no T874C1018 D68535 2 H1 anticipator factory set at 1 2A used with Q674E1056 Q674B1059 Q674F1022 used in Y594C1009 Y594C1017 Y594C1256 Y594C1330 C1067 44 Obsolete Sears logo part no 42 9297 F C T874C1018 Replacement has F scaleplate scaleplate C1075 51 53 Carrier logo part no HHO7AT170 used with Y594C1421 or When using the T874C1018 Q674B1166 T874C1018 set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary C1083 44 Obsolete Trane logo used with Q674E1007 used in T874C1018 Y594C1082 C1117 44 Honeywell logo scaleplate T874C1018 Replacement has F scaleplate C1125 60 61 Obsolete Honeywell logo 12 F 6 7 C differential T8611M2025 92 between stage 1 heat and stage 2 heat used with 067401047 1133 96 Obsolete AAF Snyder General logo part no T874C1018 Must have H1 anticipator set 4ELN7546 no H1 heat anticipation used with Q674A to maximum value G N and Q674C1173 C1141 44 J Obsolete Honeywell logo meets DoD specs includes T874C1141 Allen wrench and screws to lock cover no
67. swircHO Q F 4 r4 COMPRESSOR CONTACTOR HL A POWER SUPPLY PROVIDE DISCONNECT MEANS AND HOT OVERLOAD PROTECTION AS REQUIRED M6008A L2 Fig 92 Schematic and hookup of T874C with Q674G Used in heat pump applications 60 2485 8 120 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS gt FALL HEAT FAN RELAY S 1 H1 ANTICIPATOR NO FAN SWITCH 4 HEAT RELAY poo H2 L1 SYSTEM _ RH HOT SWITCH Q Qo 12 OFF F4 4 UIs HEAT 9 9 COMPRESSOR Q 1 AUTO H4 rA 5 OO REESE 4 C1 ANTICIPATOR 11524 L1 g HOT L2 C2 ANTICIPATOR RISE 1 B Ae Uc COMPRESSOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD CONTACTOR 2 PROTECTION AS REQUIRED M4664 Fig 93 Schematic and hookup of T874D with Q674K Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR f NO FAN SWITCH HEAT CHANGEOVER VALVE oE n P H2 ANTICIPATOR wey S 3 FILTER LED YELLOW L2 AN b EE SYSTEM SWITCH A o COMPRESSOR SEL ce ee CONTACTOR 1 O 5 RED AUTO oN O 2 COMPRESSOR pz C1 ANTICIPATOR CONTACTOR 2 EE pEi 11 COOL CHANGEOVER Ci Lw VALVE QA C2 ANTICIPATOR N o dis T RELAY
68. temperature at which to permit each additional unit of electric heat to be operated by the second stage of the room thermostat 27 The disadvantage of this system is that it can require several outdoor thermostats Also since the unit is operating most often at nearly full capacity the thermostat is on longer which results in more droop with a little more offset from the thermostat setpoint In addition the capacity is tied to theoretical load based on heat loss calculations Normally this is very close to the actual load but there are times where the second stage is switched on too soon no harm done or too late the building gets cold The T874 Thermostat produces time modulated control which is the on time of the thermostat changing during each cycle as the load changes The on time of the heating system is directly proportional to the heating load of the building As an example of the quality of time modulated control consider the typical gas furnace It can have a capacity of 100 000 Btu 293 kW which is controlled On Off The output is 100 000 Btu 293 kW or nothing A quality thermostat controls so closely that the occupants rarely detect changes in room temperature The same is true with 50 000 or 60 000 Btu 146 5 or 178 8 kW of heat pump auxiliary electric heat The T874 can provide the same high quality control This scheme also eliminates the need for outdoor thermostats and thus offers the manufacturer an oppo
69. thermostat and a sensor tell the economizer damper to open to let in cool air from the outside When enthalpy is high the thermostat and sensor tell the damper to close No more outside air comes in so the air conditioner is used instead Heat Pump Application A heat pump system operates much like an air conditioner However the heat pump is capable of moving heat in two directions from inside the home to outdoors for cooling or from outdoors to inside for heating The heat pump can be controlled by separate relay contactor components which are energized or de energized by the T874 Changeover between heating and cooling for heat pump circuits can be accomplished either manually or automatically Manual changeover control requires a system switch movement to change the mode The reversing valve is activated by moving the system switch to COOL for cooling or to HEAT for heating operation Automatic changeover is accomplished by one of the mercury bulb switches in the thermostat On a system with automatic changeover on cooling the changeover valve is energized by a mercury switch that makes on a temperature rise On heating the changeover valve is energized by a mercury switch that makes on a temperature fall A description of the methods used to control heat pumps follows Space Temperature Sensing Low Voltage Controls Control systems for heat pumps usually utilize low voltage control circuits The variety of control fun
70. to a higher current rating but not more than one half divi sion at a time and recheck the cycle rate Most con ventional two stage heating equipment is designed to operate at three cycles per hour per stage and one stage heating equipment at six cycles per hour at 50 percent load conditions When using the T874 Thermostat in heat pump systems set the heat 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES anticipator at 140 percent of the actual primary con trol current draw to reduce the cycling rate See Fig 11 Most heat pump systems should cycle 2 1 2 to 3 times per hour 4 Hang the upper edge of the thermostat cover on top of the thermostat base and swing the cover downward until it engages with the cover clip STAGE ONE ANTICIPATOR HEATING CONTROL STAGE TWO ANTICIPATOR HEATING CONTROL MOVE INDICATOR TO MATCH CURRENT RATING OF PRIMARY CONTROL Fig 11 Adjustable heat anticipator scales Temperature Setting Move the heating and cooling levers to the desired comfort positions See Fig 12 On some models with two stages of heating or cooling the same lever controls both stages The minimum differential between heating and cooling setpoints is F 2 C 5 F 3 C on T874W If model has optional screws to lock temperature control levers loosen these screws before making temperature adjustment tighten the screws when levers are set at desired position STAGE 1 HEATI
71. with T874D1116 replacement G1120 202 Obsolete McQuay part no 60684701 two SERVICE See OEM for 226 LEDs no fan switching used with 787401694 G1926 replacement G1138 91 Obsolete Trane part no BAS 0433 used with T874A F 067461070 91153 184 Obsolete Carrier part no HH93AZ212 used Q674G1070 Y594D1396 G1161 184 Gray color Q674G1070 Replacement is beige color G1179 202 Obsolete McQuay logo part no 073319601 includes Q674G1161 Replacement has no LEDs two LEDs Q674J System EM HT AUTO OFF Fan AUTO ON J1001 180 Obsolete Singer heat pump part 02005964 See OEM for HEAT LED changeover heat mode replacement J1019 159 Obsolete Westinghouse heat pump EM HT LED Y594G1252 Wiring differences old new System EM HT ON OFF used with T874G1048 W W2 J1027 160 Obsolete York part no 025 22291 EM HEAT LED Y594G15672 auto fan in emergency heat mode changeover in cool mode used with T874G1170 G1196 G1428 G1345 G1444 used in Y594G1013 G1138 G1229 J1035 161 Carrier heat pump part no HH93AZ173 System Y594G1674 SUPL HT ON OFF SUPL HEAT LED used with T874G1055 HHO7AT171 J1043 162 TRADELINE heat pump model designed for use on Q674J1043 or Designed for use Trane Trane heat pumps AUX HT and EM HT LEDs auto fan Y594G1161 heat pumps in emergency heat changeover in cooling mode used with T874G1204 and C815A1008 used in Y594G1161 J1050 183 Obsolete Westinghouse heat
72. with T874G1097 G1212 G1220 G1238 F1246 156 Obsolete Westinghouse heat pump EM HEAT and Y594G12522 AUX HEAT LEDs auto fan in emergency heat mode changeover in cooling mode F1253 157 Obsolete Wesco Addison heat pump used with Y594G1252 Wiring differences old new T874G1261 G1279 G1287 1 0 C X W1 Y X L F1261 179 Includes two LEDs used with T874N1024 used in Y594G1419 Wiring differences old new Y594N L X2 Y Y1 F1279 158 Obsolete Westinghouse heat pump two LEDs used Y594G1252 Wiring differences old new with T874G L1 L F1295 147 Obsolete Keeprite Westinghouse heat pump Y594G1252 Wiring differences old new SERVICE AUX HEAT and EM HEAT LEDs used with S L replacement does not T874G1188 include A or T terminals F1311 155 York heat pump AUX HEAT and EM HEAT LEDs used Y594G1252 with T874G1410 F1329 142 Obsolete Heil Quaker part no HQ712005HW one Q674F1022 LED and field selectable inserts F1337 166 Obsolete WeatherKing heat pump two LEDs and field Q674F1022 Wiring differences old new R RC RH replacement has no LEDs Both the thermostat and subbase must be replaced 60 2485 8 78 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9 Q674 Subbase Cross Reference Model Fig Q674 Trade Number No Description Replacement Remarks F1345 194 Obsolete Addison heat pump EM HEA
73. with T874R1137 Y594R1292 R1673 R1731 R1749 R1814 used in Y594R1110 1466 R1524 R1532 R1607 L1140 109 Obsolete Includes EM HEAT and AUX HEAT LEDs Y594R1763 Designed for use on Trane used with T874R1053 used in Y594G1136 heat pumps L1157 115 Obsolete Rheem part no 41 20796 14 EM HEAT and 0674112072 AUX HEAT LEDs used with T874R 121 Obsolete Used with T874C Y594C1322 123 Obsolete Used with T874R Y594R1243 L1165 110 Obsolete Lennox no 24F5901 factory installed V VR Y594R1763 Wiring differences old new jumper EM HEAT and SERVICE LEDs stage 2 heat is V VR R M Y F G X B isolated used with T874C 1448 R1178 and Y W A T R O E X2 C815A1013 L1173 112 Obsolete Westinghouse AUX HEAT and EM HEAT Y594R1243 LEDs Both the thermostat and subbase must be replaced 60 2485 8 82 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9 Q674 Subbase Cross Reference Model Fig Q674 Trade Number No Description Replacement Remarks L1181 113 Used with T874R1129 used in Y594R Y594R1243 Wiring differences old new 1 11199 114 Obsolete Lennox no 24F6001 used with 787401207 T8611M2025 Wiring differences old new and C815A1013 programmable V VR R Y2W3 R O MzY M2zY2 W2 jumper Y2 W2 no outdoor reset needed use only one System transformer L1207 115 Used with T874R1152
74. 0 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS SYSTEM SWITCH IGNITION RELAY C1 ANTICIPATOR COMPRESSOR CONTACTOR 1 C2 ANTICIPATOR COMPRESSOR CONTACTOR 2 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M3954 Fig 185 Schematic and hookup of T874D with Q674E Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS 4 NO FAN gt 5 SWITCH HOT TS FALL ANTICIPATOR H ev o SYSTEM 7 SWITCH Q Q Q y OFF FA RIS 8 C ci 10 Lt HOT RISE 11 QS c2 COMPRESSOR CONTACTOR 2 LA A POWER SUPPLY PROVIDE DISCONNECT MEANS COMPRESSOR AND OVERLOAD PROTECTION AS REQUIRED CONTACTOR 1 M3955 Fig 186 Schematic and hookup of T874D with Q674G Used in standard applications 60 2485 8 186 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 2 FAN H1 ANTICIPATOR H2 ANTICIPATOR SYSTEM HEAT RELAY 1 LO SPEED FAN RELAY COOL CONTACTOR HI SPEED FAN RELAY LOCKOUT RELAY HIGH PRESSURE TEMP SWITCH HIGH SWITCH SWITCH Q HEAT L1 HOT OFF HJA E RD C1 ANTICIPATOR COOL e O O POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROT
75. 049 RC RH jumper required no LED in LOCKOUT LED indicates activation of TRADELINE model compressor lockout switch E1167 Square D no HCB 2 Chek Lite Q674E1049 E1183 Square D no HCB 3 Q674E1049 E1191 Lennox HIGH and LOW LEDs used with Q674E1049 No LEDs on replacement T872D1045 Q672F System EM HT HEAT AUTO COOL OFF Fan AUTO ON F1000 With EM HT LED used with T872C 1699 Q674F 1022 Remove W3 X2 jumper to E X2 F1018 Heat pump heat mode changeover Chek Lite Y594G1252 Wiring differences old new used with T872G1000 W W2 1 F1026 Chek Lite W2 X2 jumper Q674F1022 F1034 Airtemp EM HT LED RC RH and X2 E Q674F1022 If RC RH jumper removed on jumpers Q672F 1034 Q674F1022 does not replace F1042 W2 X2 jumper Chek Lite Q674F1022 F1059 Carrier no HH93AZ074 EM HT LED Q674F1022 Remove W2 X2 jumper to E X2 X terminal same as C F1067 Lennox heat pump cool mode changeover None EM HT LED used with T872G1026 F1075 Heat pump circuit EM HT LED 2 terminal RC None RH jumper F1083 Lennox no P 8 11225 heat pump None V VR jumper cool mode changeover EM HT LED used with T872G1067 F1091 Westinghouse heat pump EM HT LED cool Y594G1252 Wiring differences old new mode changeover compressor lockout in W W2 EM HT used with T872G1034 F1109 Airtemp no 3778567ACC R X2 jumper Q674F1022 R X2 jumper required EM HT LED F1117 Tappan no 080 13708 53 heat pump EM HT Y594G1252 W
76. 1 and C2 replacement has scaleplate D1561 44 Obsolete General Electric logo used with Q674 A G T874D1165 D1587 44 Obsolete Stiles Four Seasons logo T874D1165 D1595 139 Obsolete logo used with Q674F1394 T874D1165 Replacement has HEAT OFF Q674B1018 COOL system switching no LEDs D1603 44 Obsolete Arcoaire logo T874D1165 D1611 44 Obsolete No logo Friedrich part AT5411 F C T874D1165 Replacement has F scaleplate scaleplate D1629 82 Qbsolete Reznor logo F C scaleplate used with T874D1165 Replacement has F Q674E1007 used in Y594D1248 scaleplate D1678 44 Obsolete Honeywell logo Saudi Oger special C T874D1165 Replacement has F scaleplate one setpoint lever used with Q674A K scaleplate separate heating and cooling setpoint levers D1686 98 Obsolete McQuay logo part no 60685501 8 F 4 4 C T874D1165 Replacement has 2 F differential between H1 and H2 6 F 3 3 C differential differential between H1 and between C1 and C2 used with Q674E1312 H2 2 F differential between C1 and C2 D1694 202 Obsolete McQuay logo part no 60685201 used with See OEM for Q674G1120 replacement D1702 44 Obsolete McQuay logo part no 60685101 T874D1165 D1710 44 Trane logo T874D1165 D1728 44 York Miraco logo T874D1165 D1744 44 American Standard logo heat anticipator factory set at T874D1165 0 4A D1751 44 Obsolete Goettl logo part no 372080 range stops set T874
77. 1 and H2 heat differential between H1 and H2 heat C1265 44 Obsolete Singer special C scaleplate 5 C 8 F T874C1125 Replacement has 12 F differential between H1 and H2 heat differential between H1 and H2 heat replacement has F scaleplate C1273 44 Honeywell logo scaleplate includes Allen wrench T874C1018 Replacement has F and screws to lock cover non adjustable range stops scaleplate factory set at 23 max heat and min cool 73 F C1281 44 Qbsolete Heat Wave special T874C1018 C1307 44 Obsolete Friedrich Climate Master logo T874C1018 C1315 44 Obsolete Wesco logo heat anticipator factory set at T874C1018 0 8A C1323 44 Obsolete Le Chauffage Urbain special C scaleplate T874C1018 Replacement has F scaleplate C1331 82 141 Obsolete Duotherm logo used with Q674E or Q674F T874C1018 C1349 61 Obsolete Sigler logo used with Q674N1023 T874C1018 C1372 52 Obsolete Honeywell logo used with Q674B1190 T874C1018 For systems requiring Q674B1034 automatic fan in cooling mode only T874C1018 For systems requiring Q674B1075 automatic fan in heating and cooling C1398 105 Obsolete Fedders logo F C scaleplate used with Y594R1425 Wiring differences old new 6741 1090 K E C X replacement has F scaleplate C1406 105 Obsolete Climatrol logo F C scaleplate used with Y594R1425 Wiring differences old new Q674L1090 replacement has F scaleplate C1414
78. 1036 part no AO2076 includes Allen wrench and screws to lock cover A1317 44 Qbsolete McQuay logo part 60685301 no T874A1036 scaleplate used with Q674A E G A1325 75 Obsolete McQuay logo part no 60685401 no T874A1036 Replacement does not have scaleplate used with Q674C1306 and outdoor ability to display external thermistor to display outdoor temperature temperature or momentary system switch position A1341 44 Obsolete Trane logo part no THT 0577 meets DoD T874A1176 specifications A1358 44 logo T874A1036 A1366 51 53 Obsolete Multi logo part no HHO7AT182 T874A1036 Set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary A1374 44 American Standard logo part no ASYSTAT610 heat T874A1036 anticipator factory set at 0 4A A1390 44 Obsolete Climate Control logo part no 654958804 F T874A1036 Replacement has F scaleplate scaleplate A1416 44 J Obsolete Reznor logo part no 654758803 F C T874A1036 Replacement has F scaleplate scaleplate A1424 214 Obsolete Carrier Olympia Series Split System logo part See OEM for HHO7AT194 used with Q674B1455 HH93AZ208 replacement A1440 91 Simplex System 2000 logo heat anticipator 874 1036 factory set at 1 2A used with 067491005 used Y594A A1465 212 Honeywell Trol A Temp logo Premier White color None See Trol A Temp for h
79. 105 Obsolete Airtemp logo F C scaleplate used with Y594R1425 Wiring differences old new Q674L1090 K E C X replacement has F scaleplate C1422 187 Obsolete Honeywell logo used with Q674B1208 None C1430 49 Obsolete Lennox Zone Master Two Speed logo part T874C1018 no 25F7201 used with Q674B1224 C1448 110 Obsolete Lennox logo part no 24F5101 meets DoD Y594R1763 Wiring differences new old 190 specifications requires outdoor reset used with R V VR G F B X Q674L1165 L1355 WzY O R X2 E Emergency Heat becomes stage 1 heat source C1455 127 Qbsolete Williamson logo used with Q674L1322 Y594R1243 C1463 82 Qbsolete AAF logo scaleplate T874C1018 Replacement has F scaleplate C1471 56 Obsolete Mammoth logo part no 71120102 used with T874C1018 Both the thermostat and subbase must be replaced 60 2485 8 50 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks C1489 121 Honeywell logo non adjustable range stops Y594C1322 set at 75 F max heat and min cool 24 C used with Q674L1157 C1497 121 Qbsolete Honeywell logo meets DoD specifications Y594C1322 used with Q674L1157 C1513 44 Obsolete Borg Warner multi logo part no T874C1018 6 11703124 1562 44
80. 1202 Carrier logo T874C1018 C1210 Carrier logo Celsius scale T874C1018 C1228 0 4A heat anticipator setting T874C1018 C1236 Carrier logo no HHO7ATO70 T874C1018 C1244 Fraser Johnson logo T874C1018 C1251 Trane logo T874C1018 C1269 Fedders logo T874C1018 C1277 Climatrol special T874C1018 C1285 Autogas logo T874C1018 C1293 Fedders logo T874C1018 C1301 Climatrol logo T874C1018 C1319 Command Aire logo T874C1018 C1327 Melco logo lock cover and levers T874C1018 C1335 Singer logo Carteret T874C1018 C1343 Singer logo no 050240 04 T874C1018 C1350 Celsius scale T874C1018 C1368 12 F 67 C differential between heat 1 and T874C1125 heat 2 C1376 AAF logo locking cover 72 78 F 22 26 stop T874C1018 C1384 Servel logo T874C1018 C1392 TRADELINE fast cycle performance on both heat T874C1018 Adjust anticipator faster for correct stages performance C1400 72 78 22 26 stop locking cover no T874C1141 thermometer meets DoD specs C1418 Solaron logo T874C1018 C1426 Lennox logo no 42C04 four LEDs None C1434 Carrier logo no HHO7ATO70C Celsius scale T874C1018 C1442 Goettl logo T874C1018 C1459 Goettl logo used with Q672N1001 N1019 None C1467 Lennox logo Celsius scale T874C1018 C1475 Tappan logo no 080 13708 37 T874C1018 C1483 Fasco logo no 1230 8161 T874C1018 C1491 Lennox logo no 6440501 locking cover no T874C1141 thermometer meets DoD specs When replacing a T872 Thermostat and Q672 Subbase always replace both the
81. 1225 used in Y594G1575 G1881 167 Rheem part no 41 20797 18 Y594G1526 G1899 169 Obsolete Amana part no 10574101 used with Y594G1633 Q674F1550 used Y594G1591 G1915 155 Econar logo used with Q674F1212 used Y594G12523 Y594G1609 170 Used with Q674F1410 Y594G1393 G1923 176 Trane logo part no X13510599010 H2 make 12 F Y594H1012 Wiring differences old new below H1 make 1 Y2 Y R none L R jumper required no night setback T8611G1004 Includes night setback programmable G1931 155 Obsolete Honeywell logo Premier White color C None See subbase description for 170 5 used with Q674F 1568 replacement information G1949 73 Obsolete Carrier Heat Pump System Control logo part Y594H1012 Wiring differences old new no HHO7AT204 F C scaleplate H2 make 8 F below 1 Y2 Y L R R H1 make used in Y594 L jumper required no night setback T8600D1004 Wiring differences old new programmable 1 Y2zY L RH RC RH jumper required includes night setback G1956 30 103 Obsolete Carrier logo Canada Premier White color Y594G1476 Replacement has F 126 C scaleplate includes locking cover scaleplate 183 G1964 160 York logo Canada Premier White color C scaleplate Y594G1575 Replacement has F used in Y594G1625 scaleplate G1972 169 Honeywell logo TRADELINE model used with Y594G1633 Q674F1584 used in Y594G1633 G1980 1
82. 138 Obsolete Carrier part no HH93AZ192 used with See OEM for T874L1018 HHO7AT178 replacement B1372 44 Obsolete Trane part no BAS 0427 used with T874A D Q674B1018 B1380 46 Obsolete Trane part no BAS 0426 used with T874A D Q674B1075 B1398 48 Obsolete Trane part BAS 0431 FILTER LED Q674B1034 Replacement has no LEDs used with T874A D B1406 172 Obsolete Carrier part no HH93AZ200 FAULT and T874A1150 Wiring differences old new CHECK FILTER LEDs used with T874H1070 Q674B1075 YzY1 jumper W1 Y1 HHO7AT166 T874H1088 HHO7AT167 or replacement has no LEDs T874H1153 HHO7AT167 used in Y594H1046 B1414 51 American Standard Trane part no ASYSTAT1617 Q674B1075 B1448 215 Obsolete Carrier part no HH93A2202 Fan Lo Med See OEM for High On used with 787411059 replacement B1455 214 Obsolete Carrier part no HH93AZ208 Fan Lo Med See OEM for High On used with T874A1424 HHO7AT194 replacement B1463 45 Trol A Temp used with 787401801 None See Trol A Temp B1471 45 Trol A Temp used with 787401827 None See Trol A Temp B1513 53 Qbsolete TRADELINE exact replacement for 067481075 Jumper RC RH replacement Q674B1125 York part no 2TB04700324 has no LOCKOUT LED B1521 53 Obsolete Carrier Canada part no HH93AZ179 W Q674B1075 Jumper RC RH replacement gray color includes LOCKOUT LED and removable has no LOCKOUT LED beige jumpers between RC and RH terminals color B1539 45 Obsolete Carrie
83. 196 N1015 179 Qbsolete Contains T874N1040 and Q674F 1261 Y594G1419 Wiring differences old new L X2 Y Y1 N1023 178 Qbsolete Intertherm part no 9111882 contains T874N1016 T874N1057 and Q674F 1220 Q674F 1220 N1031 178 Obsolete Nordyne Miller part no 9122240 T874N1016 contains T874N1065 and Q674F1220 Q674F 1220 Y594P P1005 97 Obsolete Carrier 50QE90021101 contains 7860002028 Wiring differences old new T874P1055 and Q674C1512 YzY1 1 1 jumper required Y594R R1011 120 Qbsolete York part no 2TH11702224 contains Y594R1664 T874R1046 and Q674L1272 R1029 47 Obsolete Bryant contains T874R1004 and Y594R1243 Wiring differences old new Q674B1042 W1 W2 R1037 122 Qbsolete Fedders part no 88 58 00540 001 Y594R1615 Wiring differences old new contains T874R1269 and Q674L1066 K E W1 B 2 R1102 120 Qbsolete York part 025 22285 000 contains Y594R1664 T874R1145 and Q674L1272 R1110 108 Qbsolete Heil Quaker part no HQ712004HW Y594R1292 contains T874R1137 and Q674L1132 R1128 116 Obsolete Crispaire part no HP9 51 contains Y594R1243 Wiring differences old new T874R1111 and Q674L 1215 A L R1136 109 Qbsolete Contains T874R1053 and 067411140 Y594R1763 R1151 120 Obsolete York part no 2TH11702324 contains Y594R1672 T874R1251 Q674L1272 and C815A1039 1185 201 Intertherm part no 9111871 contains Y594R1672 Wiring differences old new
84. 221 Schematic and hookup of T874H with Q674C Used in heat pump applications 60 2485 8 206 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HOT H1 ANTICIPATOR L2 SYSTEM A MONITOR FAN SWITCH SYSTEM Les REDS HEAT RELAY SWITCH HIGH SPEED LED YELLOW C1 ANTICIPATOR COMPRESSOR CONTACTOR 1 C2 ANTICIPATOR COMPRESSOR CONTACTOR 2 RISE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5920 Fig 222 Schematic and hookup of T874B with Q674E Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH AUX HT LED RED EM HT RELAY MALFUNCTION SYSTEM LED RED SWITCH HIGH SPEED LED YELLOW LOW SPEED COMPRESSOR ANTICIPATOR LED GREEN CONTACTOR 1 C2 ANTICIPATOR COMPRESSOR CONTACTOR 2 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED CHANGEOVER VALVE M5923 Fig 223 Schematic and hookup of T874S with Q674F Used in heat pump applications 207 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60 2485 8 THERMOSTAT SUBBASE SYSTEM COMPONENTS F CONTROL MODULE FALL 7 HEAT CHANGEOVER VALVE CO H1 ANTICIPATOR FAN SWITCH Q AUTO 4 H2 ANTICIPATOR SYSTEM SWITCH SERVICE LED RED Q co RISE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVE
85. 4 See subbase description for replacement information G1190 Tappan no B13708 57 used with Q672L1078 for 8 and 10 ton heat pumps with 2 compressors None When replacing a T872 Thermostat and Q672 Subbase always replace both the thermostat and the subbase 35 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6 T872 T874 Thermostat Cross Reference T874 Trade Model Number Description Replacement Remarks G1208 Marvair logo special for Crispaire used with Y594G1393 Q672F1166 F1323 G1216 Janitrol logo no 26G05 stage 2 heat anticipator Y594G1252 Wiring differences old new set at 1 2A used with Q672F1117 G1224 TRADELINE adjustable anticipator stage 2 heat Y594G1419 fixed anticipator stage 1 heat and cool changeover in cool used with Q672F1208 G1232 Heat Wave Southwest Mfg logo stage 2 heat anticipator set at 1 2A used with Q672F1224 G1240 Lennox fast cycle anticipator stage 2 heat used None with Q672F1240 G1257 Carrier logo no 07 073 used with None Q672L1169 HH93AZO071 G1265 Addison logo used with Q672F1265 Y594G1252 Wiring differences old new G1273 Carrier logo DoD model 68 F 20 C maximum See subbase description for heating 78 F 26 minimum cooling used with replacement information Q672L1052 J1054 G1281 Wesco logo us
86. 4 86 150 Obsolete Lennox logo part no 24F5801 F C Y594G1252 Wiring differences old new scaleplate H2 anticipator factory set at 0 25A for fast M Y F G Y W2 cycle performance changeover in cooling mode V VR R must use single independent heating and cooling circuits used with transformer Q674E1148 F1113 G1022 86 150 Obsolete Lennox logo part no 24F5701 F C Y594G1252 Wiring differences old new scaleplate H2 anticipator factory set at 0 25A for fast M Y F G Y W2 cycle performance changeover in cooling mode V VR R must use single independent heating and cooling circuits used with transformer Q674E1148 F1113 G1048 153 Obsolete Westinghouse logo H2 anticipator factory set Y594G1252 Wiring differences when 159 at 1 2A used with Q674F1121 J1019 replacing T874G Q674J1019 old new W W2 G1055 161 Carrier Heat Pump System Control logo part no None See subbase description for HH07AT171 H2 anticipator factory set at 0 8A replacement information changeover in cooling mode used with Q674J1035 HH93AZ173 G1071 50 103 Obsolete Carrier Heat Pump System Control logo Y594G1419 Wiring differences old new 126 meets DoD specifications H2 anticipator factory set at CzX jumper Y1 W1 183 0 8 used with Q674P1005 HH93AZ169 11041 HH93AZ175 B1158 or J1050 G1089 154 Obsolete Marvair logo special for Crispaire H2 Y594G1393 Wiring differences old new anticipato
87. 4 Thermostats are accurately calibrated at the factory They do not have provision for field calibration 60 2485 8 14 Thermometer The thermometer in your thermostat has been accurately calibrated at the factory The thermometer should only need adjustment if it has been dropped or shifted due to mishandling If the setpoint lever and the thermometer reading do not agree use the following procedure 1 Remove the thermostat cover by pulling up from the bottom edge of the cover away from the base until it snaps free of the cover clip 2 Setthe thermostat cover on a table near an accurate thermometer 3 Allow ten minutes for cover thermometer to sense area temperature compare the readings Be careful not to touch thermometer or breathe on it 4 Ifthe readings are the same replace cover and put the System into operation 5 Ifthe readings are different insert a small screwdriver in the thermometer slot and turn it until the thermometers have the same reading See Fig 15 6 Replace thermostat cover and put the system into oper ation Be M5070 Fig 15 Thermometer calibration UNDERSTANDING CIRCUITS To understand wiring diagrams it is important to know what all the symbols mean and how to trace the path of the circuits from the transformer See Fig 16 through 25 Circuit descriptions and terminology are defined as follows For standard heating cooling circuits Auto changeover refers to the presence of an
88. 403 F C scaleplate H1 anticipator set at CzX W B A L jumper 0 83A 8 F interstage differential between H1 and H2 for E W2 no night setback night setback used with Q674C1280 T8611G1004 Wiring differences old new programmable W B A X2 jumper X2 R remove external time clock includes night setback T874L Heat pump model 2 stage heat 1 stage cool changeover in cool L1000 198 Qbsolete Carrier logo part no HHO7AT176 used with Y594G1419 E W2 jumper required Q674E1270 HH93AZ189 L1018 138 Obsolete Carrier Multiplex System logo part See OEM for 165 HHO7AT178 used with Q674B1356 HH93AZ192 or replacement Q674C1264 HH93AZ193 L1026 198 Obsolete Honeywell logo BDP part no 272 2786 Y594G14192 E W2 jumper required used with Q674E1304 L1034 203 Obsolete McQuay logo part no 60687201 F C Y594G1419 Wiring differences old new scaleplate H1 anticipator factory set at 0 83A used with YzY1 W B AzX1 remove Q674C1280 Y1 W1 jumper L1059 215 Obsolete Carrier logo part no HHO7AT192 used with See OEM for 213 0674 1448 HH93A2202 Q674C1413 replacement HH93AZ204 L1067 203 Obsolete AAF Snyder General logo part no Y594G1419 Wiring differences old new 066804402 H1 anticipator factory set at 0 83A used YzY1 W B A X1 remove with Q674C 1280 Y1 W1 jumper L1075 203 Obsolete McQuay logo part no 073318601 Premier See OEM for White color F C sc
89. 428 used in Y594G1401 jumper W1 Y1 G1618 73 Obsolete Honeywell logo 12 F differential between H1 Y594H1012 Wiring differences old new and H2 for night setback used with Q674C1256 1 2 L R R none L R jumper required no night setback T8600C1162 Wiring differences old new programmable L R W O W Y jumper required includes night setback G1626 167 Honeywell logo used with Q674F1436 used in None Y594G1526 G1642 227 Honeywell logo TRADELINE model meets DoD Y594G14192 specifications used with Q674F 1444 used in Y594G1419 Both the thermostat and subbase must be replaced 60 2485 8 60 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks G1659 177 Obsolete Mammoth logo 0 8A maximum current Y594H1012 Wiring differences old new through B or O terminal 12 F differential between H1 R2 L R1 none L R jumper and H2 for night setback used with Q674C 1330 used in required no night setback 59401427 T8611G1004 Includes night setback programmable G1675 174 Qbsolete American Standard logo part no Y594G11612 ASYSTAT650 used with Q674J1142 used in Y594G1443 G1691 176 Qbsolete Command Aire logo part no P1013 0060 Y594H1012 Wiring differences old new 12 F 6 6 C differential between H1 and H2 for night 1
90. 4G1824 Q674F1477 G1542 231 Qbsolete Intertherm part no 9129290 contains Y594G1252 Cooling changeover only T874G1832 Q674F1519 G1559 231 Qbsolete Miller part no 9129310 contains Y594G1252 Cooling changeover only T874G1840 Q674F1519 G1567 160 TRADELINE contains T874G1865 Q674J1209 Y594G1567 G1575 160 Obsolete TRADELINE same as Y594G1567 Y594G1567 Replacement is beige except Premier White color contains T874G1873 Q674J1225 direct replacement for York 2TH11702424 Y594G1013 contains T874G1170 Q674J1027 and 6TH11702424 Y594G1229 contains T874G1428 Q674J1027 G1583 229 Obsolete Lennox Canada part no 97E78 contains Y594G1161 Wiring differences old new T874G1857 Q674F 1535 E X2 C B L F G1591 243 Obsolete Amana part no 10636701 contains Y594G1633 T874G1899 and 0674 1550 G1609 155 Obsolete Econar contains T874G1915 and Y594G1252 Q674F1212 a Both the thermostat and subbase must be replaced 60 2485 8 90 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10 Y594 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks G1617 73 Qbsolete Carrier part no 50QE90020101 contains Y594H1012 Wiring differences old new T874G1949 and Q674C1504 1 2 L R R none R L jumper required night setback T8600D2028 Wiring differences old new programmable 1 2 L R
91. 4Z9 International Sales and Service Offices in all principal cities of the world Manufacturing in Australia Canada Finland France Germany Japan Mexico Netherlands Spain Taiwan United Kingdom U S A 60 2485 8 2 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Standard Models T874 THERMOSTATS Models See Table 3 Electrical Rating 24 to 30 Vac Switching Coiled bimetal elements operate mercury Switches Temperature Adjustment Heating and cooling setting levers with separate scales located on top of thermostat base Common lever for heating and cooling on T874R one cooling lever on T874E V and one heating lever on T874F Q Dimensions See Fig 1 Temperature Scale Range 42 to 88 F 6 to 31 C stan dard optional ranges available THERMOSTAT MOUNTED ON SUBBASE FRONT SIDE 50 60 70 80 NW TI L IL IIl Honeywell FAN H AUTO ON OFF EM HT o AUTO COOL lt 1 7 8 48 a 2 3 16 56 gt 3 1 2 89 Thermometer Range 42 to 88 F 6 to 31 C Changeover Differential 4 F 2 C minimum between heat ing and cooling 5 F 3 C T874W Levers can be set apart for greater separation Interstage Differential Standard Models Mechanical differential is 1 F 0 6 C between heating or cooling stages operating differential is approximately 1 9 F 1 C between stages in heating or cooling Special Models See Table 3 Finish
92. 52 Wiring differences old new special H2 anticipator factory set 1 2A scaleplate S L changeover in cooling mode used with Q674F 1295 G1196 160 Obsolete York logo C scaleplate changeover in Y594G15672 Both the thermostat and subbase must be replaced 60 2485 8 58 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks G1204 162 Honeywell logo designed for use on Trane heat pumps Y594G1161 Designed for use on Trane no H2 anticipation changeover in cooling mode used heat pumps with Q674J1043 and C815A1005 used in Y594G1161 G1212 155 Obsolete Honeywell logo H2 anticipator factory set at Y594G1252 0 2A changeover in cooling mode includes shunt to bypass H2 anticipator with W3 heat relays used with Q674F1238 G1220 235 Obsolete Rheem logo part no RXMT C71 changeover Y594G1252 in cooling mode used with Q674F1238 G1238 155 Obsolete Ruud logo part no UXMT C71 changeover Y594G1252 in cooling mode used with Q674F1238 G1246 Obsolete Honeywell logo changeover in cooling mode 155 Used with Q674F1212 used in Y594G1195 91252 Y594G1252 G1369 170 Used with Q674F1410 used Y594G1393 Y594G13934 G1261 58 157 Obsolete Borg Warner used with 067401032 F1253 None See subbase description for replacement inform
93. 672 Subbase always replace both the thermostat and subbase 60 2485 8 42 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 7 0672 0674 Subbase Cross Reference Model Number G1074 Description Singer no 02005754 X1 and X terminals for field added indicator lights used with T872D1375 Q674 Trade Replacement None G1082 Singer no 02005792 X1 and X terminals for field added indicator lights used with T872D1375 None G1090 TRADELINE B and O terminals Q674G1070 Q672H System OFF ON Fan NIGHT INT DAY CONT H1008 Used with T872 None Q672J System EM HT AUTO OFF Fan AUTO ON J1005 With EM HT LED used with T872C or D None J1013 Westinghouse heat pump EM HT LED cool mode changeover compressor lockout in EM HT used with T872G1034 Y594G1252 J1021 York heat pump EM HT LED cool mode changeover compressor lockout and auto fan in EM HT E W jumper used with T872G1042 G1331 G1398 Y594G1567 Remarks J1039 Heat pump EM HT and AUX HEAT LEDs cool mode changeover compressor lockout and auto fan in EM HT used with T872G1059 Y594G1161 Designed for use on General Electric heat pumps J1047 Singer no 02005699 heat pump EM HT LED heat mode changeover Q674F1022 J1054 Carrier HH93AZ073A heat pump EM LED cool mode changeover compressor lockout
94. 674 SUBBASES THERMOSTAT HEAT 2 HEAT 1 COMPRESSOR CONTROLS CONTRACTOR AT 65 F 18 AUXILIARY CONTROLS HEAT RELAY AT 63 F 17 M5836 Fig 39 Auxiliary heat in two stage thermostat This method keeps the auxiliary heat off until the heating load is large enough to demand 100 percent heat pump operation That demand is measured by the thermostat and is the actual heat requirement of the space The two stage thermostat requires about a 2 F 1 1 C room temperature drop to bring on the second stage Stage or Time Modulated Control There are two different ways to control auxiliary heat staged or time modulated control Outdoor thermostats are used to switch additional increments of electric heat into the thermostat circuit as the outdoor temperature gets lower All increments of auxiliary heat are still controlled by stage two of the thermostat but only if the outdoor temperature requires the additional capacity See Fig 40 THERMOSTAT eere nme COMPRESSOR CONTACTOR AUXILIARY HEAT RELAY 1 AUXILIARY HEAT RELAY 2 AUXILIARY HEAT RELAY 3 Fig 40 Outdoor thermostats for auxiliary heat 20 7 OUTDOOR THERMOSTATS 5 15 T 5834 The rationale for this system is that it very closely matches the system capacity to the heating load of the building By calculating the heat loss of a building the installing contractor can pick the theoretical outdoor
95. 674 SUBBASES e OFF HEAT AUTO COOL M5828 Fig 31 System switching for automatic changeover Automatic changeover is frequently used in areas where there are large temperature differences in 24 hours Some uses for the automatic changeover feature are in the southern states cool in the morning and hot in the afternoon and in commercial applications Manual changeover requires a system switch movement to change the mode See Fig 32 Most manual changeover switches consist of HEAT OFF COOL choices For heating switch to HEAT For cooling switch to COOL It is not automatic Manual changeover is often used in areas where the temperature is relatively stable between day and night e e OFF EM HT HEAT COOL M5829 Fig 32 System switching for manual changeover Commercial Rooftop Application The T874 can be used as part of a commercial rooftop application to run mechanical cooling An economizer is often used as part of a rooftop application to save on air conditioning See Fig 33 OUTDOOR AIR H205 OR H705 2 N RETURN DISCHARGE AIR SENSOR ENTHALPY AIR DOWNSTREAM FROM THE CONTROL EVAPORATOR COIL M5827A Fig 33 Typical commercial rooftop economizer application Enthalpy is the temperature and humidity of the air A more accurate analysis of the suitability for free cooling can be made by monitoring the enthalpy 23 When enthalpy is low enough the
96. 69 Obsolete Amana logo part no 10574103 used with Y594G1633 Wiring differences old new Q674F1600 used Y594G1641 W3 W2 G1998 155 Obsolete Tempstar logo Inter City Products used in Y594G1252 Y594G1658 used with Q674F1212 G2004 103 Honeywell logo TRADELINE model used with Q674L Y594G1666 used in Y594G 161 Used with Q674J1274 used in Y594G1674 Y594G1674 G2046 155 WaterFurnace logo part no TA21H03 Premier White Y594G1716 170 color F C scaleplate used with Q674F 1667 used in Y594G1716 T874H Heat pump model 1 stage heat 1 stage cool 1 stage changeover in cool H1005 74 Obsolete Command Aire logo used with Q674C1041 Y594H1012 Wiring differences old new 1 Y2 Y L R jumper required H1013 74 Obsolete Friedrich part no AT5813 C scaleplate used Y594H1012 Wiring differences old new with Q674C1041 1 2 L R jumper required replacement has scaleplate Both the thermostat and subbase must be replaced 60 2485 8 62 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks H1021 74 Obsolete Friedrich Climate Master logo part no Y594H1012 Wiring differences old new 5821 scaleplate used with Q674C1041 1 Y2 Y L R jumper required replacement has scaleplate
97. 7 J1051 124 Obsolete Carrier logo part no HHO7AT165 W Premier None See subbase description for 144 White color C scaleplate replacement information Both the thermostat and subbase must be replaced 63 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks J1069 124 Obsolete Honeywell logo TRADELINE model used T8511G1021 144 with Q674J1282 used in Y594J1019 206 207 J1077 124 Obsolete Nordyne logo part no 9148300 F C T8511G1021 171 scaleplate T874K Heat pump model 2 stage heat 1 stage cool automatic changeover in heat K1001 77 Obsolete LSI Mammoth logo used with Q674C1090 Y594G1419 Wiring differences old new RH RC R W1 B W3 W2 W2 W1 remove Y1 W1 jumper K1019 181 Qbsolete McQuay Snyder General logo part no Y594G1252 Wiring differences old new 60687301 scaleplate H1 anticipator set at 0 83A W B A L jumper 8 F interstage differential between H1 and H2 for night E W2 no night setback setback used with Q674C1280 T8611G1004 Wiring differences old new programmable W B A X2 jumper X2 R remove external time clock includes night setback K1027 181 Obsolete AAF Snyder General logo part no Y594G1252 Wiring differences old new 066804
98. 70 used with Y594R1243 Q674L1157 R1087 120 Obsolete Honeywell logo Special for Dunham Bush Y594R1664 use with Q674L R1095 123 Obsolete Rheem logo part no RXMT C70 used with T874R1152 Q674L1157 Y594R1243 R1103 104 Obsolete Westinghouse logo used with Q674L Y594R1243 R1111 116 Obsolete Marvair logo H2 anticipator factory set at Y594R1243 has auto fan in 104 1 2A used with Q674L1215 11082 used in Emergency Heat mode Y594R1128 R1129 113 Bard logo used with Q674L1181 Y594R1243 Wiring differences old new X1 X R1137 108 Qbsolete Honeywell logo Heil Quaker part no Y594R1292 125 HQ711597HW used with 067411132 used Y594R1110 R1145 120 Obsolete York logo scaleplate H2 anticipator is Y594R1664 fixed used with Q674L1272 used in Y594R1102 R1152 115 Honeywell logo used with Q674L1207 11033 used in Y594R1243 Y594R1243 1160 182 Obsolete Honeywell Advanced Heat Pump System None logo used with Q674L1298 and W89 R1178 110 Obsolete Lennox logo part no 24F5601 F C 594 17632 Wiring differences old new 111 scaleplate auxiliary heat circuit powered by separate V VR R M Y F G X B transformer fast cycle stage H2 anticipator requires YzW 2 outdoor reset and independent circuits used with Q674L1165 L1355 R1186 182 Obsolete Honeywell Advanced Heat Pump System None logo used with 067411231 and W89 R1194 115 Obsolete Am
99. 74B1075 D1156 48 Obsolete Trane part no BAYSTAT013 contains T874D1165 Replacement has no FILTER T874D1082 Q674B1133 Q674B1018 D1180 82 York part no 025 23321 000 contains T874D1504 T874D1165 Q674E1007 Q674E1049 D1222 166 Qbsolete WeatherKing contains T874D1009 T874D1165 Wiring differences old new Q674F1337 Q674F1022 R RH jumper RC RH replacement has no EM HT or AUX HT LEDs D1248 82 Obsolete Reznor part no 93437 contains T874D1165 T874D1629 Q674E1007 Q674E1049 D1297 82 Obsolete ArcoAire part no 1506753 contains T874D1165 T874D1769 Q674E1346 Q674E1049 D1305 82 Obsolete Comfortmaker part no 1505753 contains T874D1165 T874D1785 Q674E1346 Q674E1049 D1321 45 Obsolete Goodman part no CHT 90 120 contains T874D1165 T874D1843 Q674B1000 Q674B1034 D1339 82 Obsolete Nordyne part no 5471180 contains T874D1165 T874D1009 Q674E1007 Q674E1049 a Both the thermostat and subbase must be replaced 60 2485 8 88 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10 Y594 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks D1347 82 TRADELINE contains T874D1942 Q674E1403 Y594D1347 D1354 82 SUPER TRADELINE contains T874D2031 no Y594D1354 cover Q674E1049 and TG504A with two keys D1370 45 ObDsolete Carrier part 50QE90022101 contains
100. 74D1165 anticipator setting D1169 Airtemp Chrysler logo used with Q672E1118 T874D1165 Wiring differences old new Q674E1049 1 set H1 anticipator to 1 2A D1177 Trane logo T874D1165 D1185 Dunham Bush logo T874D1165 D1193 Fedders logo T874D1165 D1201 Climatrol logo T874D1165 D1219 Command Aire logo T874D1165 D1227 Singer logo no 02005522 Celsius scale T874D1165 D1235 Singer logo Carteret T874D1165 D1243 Friedrich logo T874D1165 D1250 Singer logo no 050240 02 T874D1165 D1268 Airtemp logo T874D1165 D1276 Celsius scale T874D1165 D1284 Solaron T874D1165 D1292 Tokyo Carrier logo no HHO7ATO72C Celsius T874D1165 scale D1300 SUPER TRADELINE T874D1165 D1318 General Electric logo no 28 098 fan current T874D1165 shunt for auto fan in heating Q674B1075 D1326 General Electric logo locking cover 72 78 F T874D1165 22 26 C stop fan current shunt for auto fan in heating D1334 Lennox logo Celsius scale T874D1165 D1342 Tappan logo no 080 13708 32 T874D1165 D1359 Singer logo no 02005740 Celsius scale 6 6 87401165 Only 2 F 1 C differential between differential between H1 and H2 H1 and H2 D1367 Friedrich logo no 600 580 23 T874D1165 D1375 Singer logo no 02005713 Celsius scale controls None 2 separate heat cool circuits used with Q674G1017 D1383 TRADELINE Celsius scale T874D1165 D1391 Singer logo no 02005712 controls two separate None heat cool circuits used with Q674G1017 D1409 12 F 7 C
101. 74F1015 Set H1 and H2 anticipators to an 839 lowest settings F1106 95 Obsolete Oneida logo part no 30A0287 02 used with T874F1155 Q674K1018 on combination wood and oil applications F1114 44 Honeywell logo Honeywell Canada TRADELINE model T874F1015 Replacement has F C scaleplate includes Allen wrench and screws to lock scaleplate cover field adjustable locking levers F1122 62 Obsolete Honeywell logo two heat setpoint levers T874F1015 Replacement has LED used with Q674B1307 Q674D1040 F1130 72 91 Obsolete Reznor logo F C scaleplate used with T874F1015 Replacement has F Q674C D or G used with Q674C1009 G1005 used in scaleplate Y594F1048 F1148 44 Obsolete Trane logo part no 0584 T874F1015 F1155 95 Honeywell logo used with Q674K1026 on combination T874F1155 wood and oil applications T874G Heat pump models 2 stage heat 1 stage cool 1 stage changeover G1006 84 155 Obsolete Honeywell logo used with Q674E1015 Y594G12522 Wiring differences old new F G V R Y W2 E W2 jumper required Both the thermostat and subbase must be replaced 57 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 8 T874 Cross Reference cooling mode used with Q674J1027 used in Y594G1138 Model Fig Trade Model Number No Description Replacement Remarks G101
102. 87 Fig 181 Schematic and hookup of T874K with Q674C Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS OUTDOOR RESET H1 C ANTICIPATOR H2 ANTICIPATOR SYSTEM W89 SWITCH HEAT Q PUMP CONTROL PANEL EM HT LIGHT SERVICE LED RED SERVICE LIGHT COMPRESSOR M3951 Fig 182 Schematic and hookup of T874R with Q674L Used in heat pump applications 60 2485 8 184 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS EN COOL CHANGEOVER VALVE H1 FALL ANTICIPATOR O CO 2 4 COMPRESSOR FAILURE SYSTEM F RISE 8 SWITCH 5 alo EM HT O Cc AUX HT LED GREEN ura W Ee da zal gt 50 zi Q T E OB COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS A AND OVERLOAD PROTECTION AS REQUIRED 11 12 HOT M3950 Fig 183 Schematic and hookup of T874G with Q674J Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 1 H1 ANTICIPATOR L2 L1 HOT L1 HOT L2 COMPRESSOR CONTACTOR 1 C1 ANTICIPATOR C2 ANTICIPATOR COMPRESSOR A POWER SUPPLY PROVIDE DISCONNECT MEANS CONTACTOR 2 AND OVERLOAD PROTECTION AS REQUIRED M3953 Fig 184 Schematic and hookup of T874A F with Q674G Used in standard applications 185 6
103. 872G1224 F1216 TRADELINE heat mode changeover EM 874 1016 LED used with T872N1028 Q674F1220 F1224 Heatwave Southwest Mfg compressor Y594G1252 lockout in EM HT EM HT LED used with T872G1232 F1232 Rheem cool mode changeover EM HT and Y594G1252 AUX HEAT LEDs compressor lockout in EM HT used with T872G1133 F1240 Lennox cool mode changeover EM HT and None SERVICE LEDs used with T872G1240 F1257 Westinghouse cool mode changeover Y594G1252 Wiring differences old new EM HT and AUX HEAT LEDs auto fan in W W2 EM HT used with T872G1034 F1265 Wesco Addison Chek and EM HT LEDs used Y594G1252 Wiring differences old new C X with T872G1281 G1265 F1273 Southwest special no 0361 136 W2 X2 None jumper F1281 Luxaire special used with T872G1315 Y594G1252 F1299 Bard special used with T872N1036 N1044 T874N1016 Q674F1220 F1315 Williamson special used with T872N1010 T874N1016 Q674F1220 F1323 Crispaire special used with T872G1208 Y594G1252 Q672G System OFF AUTO Fan None G1009 Standard OEM Q674G1070 G1017 Singer O B jumper used with T872D1375 Q674G1070 G1025 Includes O and B terminals Q674G1070 G1033 General Electric no AY28X102 Q674G1070 G1041 Singer no 02005649 French wording O B Q674G1070 Less French wording jumper G1066 SLI Mammoth heat pump heat mode Q674G1070 Connect fan G wire to Y1 terminal B O and RC RH jumpers When replacing a T872 Thermostat and Q
104. 913 120 Qbsolete Honeywell logo Premier White color Y594R1664 Replacement is beige designed to replace Y594R1011 York part no 2TH11702224 used with Q674L1777 used in Y594R1706 R1921 115 Obsolete Econar logo used with Q674L1207 used in Y594R1243 Y594R1722 R1939 197 American Standard logo Trane part no Y594R1763 ASYSTAT651A includes outdoor reset used with Q7674L1801 used in Y594R1748 R1947 168 Qbsolete Inter City Products logo part no Y594R1425 HQ1149406HW used with Q674L1819 used in Y594R1755 R1954 197 Honeywell logo TRADELINE model includes outdoor Y594R1763 Direct replacement for reset used with Q674L1827 used in Y594R1763 Y594R1748 T874R1939 Q674L1801 American Standard logo ASYSTAT 651A and Y594R1136 T874R1053 Q674L 1140 R1962 115 Obsolete Consolidated Industries logo part no Y594R1680 Includes CHECK LED 9036100 Premier White color used with 067411843 used in Y594R1771 R1970 120 York logo Canada Premier White color scaleplate Y594R1672 Replacement has F used in Y594R1789 used with C815A1039 scaleplate R1988 125 Honeywell logo TRADELINE model used with Y594R1797 Direct replacement for Q674L1868 used in Y594R1797 Y594R1235 T874R1368 Q674L1421 Evcon Coleman part no 3600 368 R2002 245 Obsolete Amana Air Conditioning logo part no Y594R1797 Wiring differences old new 10574102 used in Y594R1805 C X X R2010 245 Obsolete Amana Air Conditioning
105. 99 McQuay logo part no 073320001 includes one LED See OEM for 100 replacement C1595 72 Obsolete Standard OEM Q674C1058 Q674D System None Fan None D1008 55 66 Obsolete Used with T874D1082 F1056 used in Q674D1040 Y594D1057 D1016 55 Obsolete Carrier part no HH93AZ170 RC RH Q674D1040 RC RH jumper required D1032 58 Obsolete Borg Warner used with T874G T874D1165 Wiring differences old new 0674010402 2 OzY1 W W2 jumper 1 2 required D1040 55 TRADELINE Q674D1040 D1057 55 66 Obsolete York part no 2TB04700424A Q674D1040 a Both the thermostat and subbase must be replaced 75 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 9 Q674 Subbase Cross Reference Model Fig Q674 Trade Number No Description Replacement Remarks D1065 63 Obsolete Includes two LEDs used with T874F1122 T874F1015 has LEDs Q674D1040 D1099 55 66 Obsolete Trane part no BAS 0430 used with T874A F Q674D1040 D1107 55 66 Obsolete Snyder General part nos 654958801 Q674F1040 1520503 4ELN30070 D1115 208 Trol A Temp used with 787401801 None See Trol A Temp D1123 208 Trol A Temp gray color used with T874D1827 None See Trol A Temp D1156 55 Obsolete Gray color includes removable jumper Q674D1040 Replacement is beige c
106. ACTOR SWITCH THERMOSTAT SWITCH FLoxro dl NM O O ee ne os ps ncn HESS ANTICIPATOR FAN FALL a 2 AUTO e FAN RELAY Z CASS Crt e NOD OUTDOOR SUPPL ELEC 4 THERMOSTAT HT RELAY 1 1 H2 ANTICIPATOR SYSTEM 5 7 o AS REQUIRED OFFO 4 4 2 EM HT Hj HA EM LED RED POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION C A FIELD WIRE JUMPER TO ALLOW SINGLE 9 COOL SYSTEM TRANSFORMER COOL CHANGEOVER VALVE Pupu mane D L1 12 L1 12 4726 HOT 7 Fig 102 Schematic and hookup of T874J R with Q674L Used in heat pump applications 60 2485 8 126 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS M N _Ch YL COOL CHANGEOVER VALVE A H1 ANTICIPATOR FAN SWITCH FAN RELAY F OUTDOOR LC H THERMOSTAT HEAT RELAY 1 egeta ED Ld CICS H2 ANTICIPATOR i Dou ERO HEAT RELAY 2 SYSTEM 9 rra SWITCH j 9 pron E i Lo uv mim EAT RELAY HEAT RELAY 3 CONTACT 2 1 0 COMPRESSOR L 4 FAULT COMPRESSOR CONTACTOR 1 C1 RISE A POWER SUPPLY PROVIDE DISCONNECT MEANS A N O SWITCH INSTALLER ADDED TO LIGHT SUPL HT LED AND OVERLOAD PROTECTION AS REQUIRED WHEN COMPRESSOR OPERATION IS NOT NOR
107. AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH SYSTEM SWITCH LED GREEN COMPRESSOR FAULT C1 ANTICIPATOR COMPRESSOR M2989 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED CONTACTOR Fig 211 Schematic and hookup of T874G with Q674F Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 1 FAN FALL SWITCH H1 ANTICIPATOR SYSTEM SWITCH OFF COMPRESSOR HEAT b CONTACTOR 2 AUTO DN Fr 4 H4 COMPRESSOR L1 5 5 CONTACTOR 1 HOT C1 ANTICIPATOR Lo C2 ANTICIPATOR D POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED AFAQIN RH REMOVABLE JUMPER WHEN SPECIFIED acu rise CO C Fig 212 Schematic and hookup of T874A with Q674E Used in standard applications 199 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS SYSTEM UTS H1 ANTICIPATOR SWITCH OFF 4 COMPRESSOR S1 O CONTACTOR RELAY N C H2 F Uc H2 ANTICIPATOR FALL 2 C1 ANTICIPATOR FAN SWITCH REMOVABLE JUMPER COMPRESSOR CONTACTOR G LED RED N POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 213 Schematic and hookup of T874L with Q674C Used in heat pump application
108. ANGEOVER VALVE NO 1 VALVE NO 2 CHANGEOVER CHANGEOVER VALVE NO 2 VALVE NO 3 P RELAY COOL CHANGEOVER POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD VALVE M7742 PROTECTION AS REQUIRED Fig 241 Schematic and hookup of T874J with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR FAN SWITCH SYSTEM SWITCH OFF OVERRIDE CIRCUIT CHANGEOVER VALVE AUTO OVERRIDE OVERRIDE CIRCUIT POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED OVERRIDE IS MOMENTARY POSITION SPRING RETURN TO OFF UPON SWITCH RELEASE M7212 Fig 242 Schematic and hookup of T874G with Q674C Used in standard applications 219 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH H1 ANTICIPATOR SYSTEM SWITCH AUX HEAT LED GREEN AUX HEAT RELAY COMPRESSOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND CONTACTOR OVERLOAD PROTECTION AS REQUIRED M7715 A TERMINAL LABELED C X ON SOME MODELS Fig 243 Schematic and hookup of T874G with Q674F Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 2 i H1 T ANTICIPATOR FAN SiTe 2 Uc O AUTO R ENS COMPRESSOR FAN RELAY CONTACTOR FALL ON Lo Ao ANTICIPATOR y 5
109. AT RELAY 1 FAN SWITCH FALL H1 ANTICIPATOR 1 HOT 12 SYSTEM SWITCH 0 0 HEAT CHANGEOVER ODO OFF HA O 5 cooLC HA 4 5 5 65 CONTACTOR 2 C2 ANTICIPATOR A rem POV RISE COMPRESSOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD CONTACTOR 1 M2904 PROTECTION AS REQUIRED Fig 46 Schematic and hookup of T874A B D with Q674B Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH COOL CHANGEOVER VALVE H1 C1 ANTICIPATOR SYSTEM SWITCH POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR 2906 Fig 47 Schematic and hookup of T874R with Q674B Used in heat pump applications 97 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS ARN suu L2 1 Oe maka A FALL DOQ H1 ANTICIPATOR EXTERNAL FAN SWITCH HEAT CHANGEOVER VALVE SWITCH T amp i Q Q OFF F4 FA 2 60 6 COOLU F Md FA o 0 ge FILTER LED RED COOL CHANGEOVER COMPRESSOR CONTACTOR 1 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED va oN o A CLOGGED FILTER SERVICE SWITCH COMPRESSOR sie CONTACTOR 2 Fig 48 Schematic and hookup of T874D with Q674B Used in standard application
110. AUTO position in the system switching EX Q674E with OFF HEAT AUTO COOL switching The thermostat auto matically changes between heat and cool modes as indoor temperature changes Manual changeover requires a system switch movement to change mode EX Q674B with HEAT OFF COOL switching T874D Multistage Thermostats with 2 heat or 2 cool switches are shown on most standard circuits Most standard TRADELINE subbases Q674A E G can be used with T874A F standard or TRADELINE T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES thermostats The schematics can be field modified as required EX if T874C is being used eliminate second stage of heat For heat pump circuits Cool changeover valve operates on cooling The revers ing valve or relay is activated either by moving the sys tem switch to COOL manual changeover or by a mercury switch that makes on a temperature rise auto changeover Heat changeover valve operates on heating The revers ing valve or relay is activated either by moving the sys tem switch to HEAT manual changeover or by a mercury switch that makes on a temperature fall auto changeover System monitor relay optional equipment on some heat pumps includes an R4222P1065 or equivalent This system monitor relay detects a malfunction in the com pressor and indicates the malfunction by activating the EMERGENCY HEAT LED on the Q674 Switching Sub base The system monitor relay is usually wired into
111. Allen wrench and screws to T874A1010 lock cover non adjustable range stops set at 72 F max heat and 78 F min cool 22 26 field adjustable locking levers A1028 44 Honeywell logo heat anticipator factory set at 0 4A T874A1036 A1036 44 Honeywell logo TRADELINE model includes Allen T874A1036 wrench and screws to lock cover field adjustable locking levers A1044 44 J Obsolete AAF Snyder General logo part no 4ELN T874A1036 Replacement has F 3006C scaleplate scaleplate A1051 44 1 logo part no 12F9901 F C scaleplate heat T874A1036 Replacement has F anticipator set at 0 45A scaleplate A1069 44 Obsolete Westinghouse logo used with Q674A E G T874A1036 A1077 46 82 Obsolete Amana Air Conditioning logo part no 874 1036 D68535 1 heat anticipator factory set at 1 2A used with Q674B1075 E1056 used in 594 1001 A1019 A1085 44 46 Obsolete Trane logo part no 13510451 used with 874 1036 55 66 0674 1018 1075 01008 A1093 44 Obsolete McQuay logo part no 02005935 F C T874A1036 Replacement has F C scaleplate scaleplate A1101 51 53 Carrier logo part no 07 174 used with Q674B Y594C1421 or When using the T874C1036 T874A1036 set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary A1119 82 Obsolete Sears logo part no 541 91441 49 9144 F T874A1036 Replacement has F scaleplate used
112. BAS 0434 Q674E1049 E1338 88 Goodman part no CHTS36 60 HIGH and Q674E1049 Replacement has no LEDs LOW LEDs used with T874B1100 used in Y594B1042 E1346 82 Qbsolete Snyder General part nos 1505753 1506753 Q674E1049 654958B02 used with T874D1769 used in Y594D1297 E1353 210 Obsolete Mammoth used with T874Y 1005 used in T8611M2025 Y594Y 1004 E1379 212 Trol A Temp by Honeywell used with T874A1465 None See Trol A Temp E1395 222 Obsolete Carrier part no HH93AZ209 used with T874B1019 Wiring differences old new T874B1134 HHO7AT199 Q674E1049 W1 W RC RH jumper required replacement has no LEDs E1403 82 TRADELINE designed to replace York 27 04701024 Y594D1347 used with T874D1942 used in Y594D1347 E1411 82 Obpsolete Carrier Canada part no HH93AZ176 W Q674E1049 RC RH jumper required gray color removable jumper between RC and RH Replacement is beige color terminals E1429 87 Carrier Canada part no HH93AZ177 W gray color Q674E1049 RC RH jumper required includes LOCKOUT LED removable jumper between Replacement has no LOCK RC and RH terminals OUT LED and is beige color E1445 82 Obpsolete Carrier part no HH93AZ217 W gray color Q674E1049 RC RH jumper required removable jumper between RC and RH terminals Replacement is beige color E1460 224 McQuay logo part no 073319801 includes one LED E1478 82 Obsolete Armstrong logo part no 03299A19 Q674E1049 RC R ju
113. BASE SYSTEM COMPONENTS C815A OUTDOOR THERMISTOR AUX HEAT LED GREEN HOT EM HEAT LED RED EM HT RELAY CHECK LED YELLOW CHANGEOVER RELAY HEAT RELAY COOL Porro 0 COMPRESSOR CONTACTOR 1 OFF COOL N POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A CONNECT CHANGEOVER RELAY TO O TERMINAL FOR CHANGEOVER IN COOLING OR TO B TERMINAL FOR CHANGEOVER IN HEATING M6999 Fig 247 Schematic and hookup of T874W with Q674L Used in heat pump applications 60 2485 8 222 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR L1 9 FAN SWITCH 8 12 Q Q 5 FAN RELAY ae EM HT RELAY LED RED MALFUNCTION De SYSTEM LED RED SWITCH 6 HIGH SPEED LED YELLOW LOW SPEED COMPRESSOR ANTICIPATOR LED GREEN CONTACTOR 1 o fr COMPRESSOR CONTACTOR 2 RISE 9 a A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED CHANGEOVER VALVE M5923 Fig 248 Schematic hookup of T874Y with Q674F Used in heat pump applications 223 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 1 D Pre FAN FAN RELAY SWITCH AUTO UA H2 ANT
114. Beige or Premier White finish Mounting Means T874 Multistage Thermostat mounts on Q674 Subbase Subbase mounts horizontally on wall or outlet box Mounts on vertical outlet box with optional 193121A Adapter Plate Assembly SUBBASE lt 3 9 32 83 gt 5 1 8 130 5849 Fig 1 7874 Thermostat 0674 Subbase dimensions mm Optional Specifications 7874 Only Temperature scale ranges are 40 to 75 F 4 to 24 C heat ing and 75 to 90 F 24 to 32 C cooling with stop 44 to 68 F 7 to 20 C heating 80 to 86 F 27 to 30 C cool ing 6 to 29 C 43 to 85 F Celsius scale 3 to 22 C 38 to 72 F and 26 to 32 C 78 to 90 F cooling with stop Nonadjustable factory added stop limits heating setpoint to 72 F 22 C maximum and cooling setpoint to 78 F 26 C minimum OEM customer personalization Locking cover and locking lever see Thermostat Accesso ries Thermostat cover without thermometer Adjustable locking temperature stops Voltage heat anticipation for first or second stage heat or both See Table 3 Fast cycling on heating stage s for electric heat applications C815A Outdoor Thermistor for improved performance on specified models Thermostat Accessories Locking Cover and Locking Lever Assembly Part no 194559R with thermometer 194559S without thermome ter See Fig 2 Includes cover screws and Allen wrench for loc
115. CH COOL CHANGEOVER SYSTEM SWITCH LED RED LED GREEN AUX HT RELAY POWER SUPPLY PROVIDE DISCONNECT MEANS AND CONTACTOR COMPRESSOR OVERLOAD PROTECTION AS REQUIRED A TERMINAL LABELED C X ON SOME MODELS A W3 TERMINAL ON SOME MODELS ONLY M5986A Fig 169 Schematic and hookup of T874G with Q674F Used in heat pump applications 60 2485 8 176 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH SYSTEM SWITCH LED GREEN EM HT LED RED COMPRESSOR CONTACTOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A ON SOME MODELS Y TERMINAL MAY BE LABELED Y1 A EMERGENCY HEAT RUNS CONTINUOUSLY WHEN SWITCH IN IN EM HT POSITION M5987A Fig 170 Schematic and hookup of T874G with Q674F Used in heat pump applications 177 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS SYSTEM SWITCH X RELAY P RELAY COOL CHANGEOVER A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED VALVE EXTERNAL JUMPER SUPPLIED BY HONEYWELL M5729 Fig 171 Schematic and hookup of T874J with Q674J Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN RELAY COOL CHANGEOVER VALVE SYSTEM SWITCH HEAT COMPRESSOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND CON
116. CH Q ore CD 43 42 Q Q SYSTEM HT MONITOR EM HT RELAY 6 Q 2 Q C est C1 ANTICIPATOR D C2 ANTICIPATOR 9 RISE Ds A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 166 Schematic and hookup of T874D with Q674F Used in standard applications 173 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR ANTICIPATOR AUX HT LED GREEN SYSTEM SWITCH s RED COMPRESSOR FAILURE CHANGEOVER VALVE COMPRESSOR CONTACTOR SNT Ci RISE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M1592A Fig 167 Schematic and hookup of T874G with Q674F Used in heat pump applications 60 2485 8 174 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS MM COOL CHANGEOVER VALVE COMPRESSOR MONITOR FAN H1 ANTICIPATOR SWITCH HOT SYSTEM SWITCH Q CHANGEOVER VALVE W1 RELAY NPowER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD Iw uS PROTECTION AS REQUIRED REMOVE JUMPER WHEN W1 RELAY IS USED COMPRESSOR RELAY M5067 A FACTORY INSTALLED JUMPER Fig 168 Schematic and hookup of T874R with Q674L Used in heat pump applications 175 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWIT
117. CHECK Q674E1049 Replacement has LED LED E1148 86 Obsolete Lennox heat pump used with T874G1014 Y594G1252 Wiring differences old new G1022 R O M Y F G Y W2 V VR R must use single transformer E1155 88 Obsolete Lennox part 91C7501 HIGH and LOW Q674E1049 Replacement has no LEDs LEDs used with T874B1076 D1017 E1197 89 Obsolete McQuay part no 02005961 two LEDs used Q674E1049 Wiring differences old new with T874D1116 replacement has no LEDs E1205 80 Obsolete Fedders special SERVICE LED used with Q674E1049 Replacement has no LEDs T874D1462 E1213 82 York part no 2TB04700224A Q674E1403 E1221 82 Quaker part no HQ712003HW Q674E1049 a Both the thermostat and subbase must be replaced 60 2485 8 76 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9 Q674 Subbase Cross Reference Model Fig Q674 Trade Number No Description Replacement Remarks E1262 82 Lennox part no 13F1701 Q674E1049 E1270 198 Obsolete Carrier part no HH93AZ189 used with Y594G1419 E W2 jumper required T874L1000 HHO7AT176 E1304 82 Obsolete BDP part P272 1887 used with Y594G14192 E W2 jumper required T874L1026 E1312 224 Obsolete McQuay part no 60684901 LED used Q674E1049 Replacement has no LEDs with T874A1523 A1549 01686 01918 E1320 82 Qbsolete Trane part no
118. CONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED oo M4724 Fig 106 Schematic and hookup of T874R with Q674L Used in heat pump applications 60 2485 8 128 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE FAN SWITCH Q FAN RELAY AUTO ANTICIPATOR a Fa oN o AoH ON 0 0 OUTDOOR SUPPL HT THERMSTAT EM HT RELAY CONTACT COMPRESSOR CONTACTOR 2 SYSTEM 9 comp EM HT RELAY Q 8 i SWITCH EM HT FAILURE EMHT Fx ELA LED RED HEAT Q orFC FX rud coo tH d i AN ENS A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR hare CONTACTOR 1 XX 0Q 0 o Fig 107 Schematic and hookup of T874D with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR FAN SWITCH SYSTEM SWITCH Fig 108 Schematic and hookup of T874R with Q674L Used in heat pump applications H2 ANTICIPATOR COOL CHANGEOVER VALVE POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION COMPRESSOR AS REQUIRED CONTACTOR M4725 129 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60 2485 8 THERMOSTAT SUBBASE SYSTEM COMPONENTS AUX HT RELAY AUX HT CE igp
119. CONTACTOR CONTROLLED BY OUTDOOR DEFROST RELAY EAN MOTOR 5839 Fig 37 Outdoor fan with defrost control AUXILIARY HEAT DURING DEFROST Most pump manufacturers bring on some auxiliary heat during defrost although this is not a universal practice Some rely on the second stage of the thermostat to call for auxiliary heat as needed Since the heat pump is operating in the cooling mode to defrost it is delivering cold air to the living space Auxiliary heat is used to offset this cooling It requires another normally open contact on the defrost relay See Fig 38 60 2485 8 26 L1 L2 HOT DEFROST TRANSFORMER f RELAY CONTACT THERMOSTAT HEAT 2 HEAT 1 AUXILIARY HEAT RELAY Fig 38 Auxiliary heat with defrost control M5835 WHEN TO DEFROST Timely defrosting is an essential component of effective heat pump operation Failure to defrost often enough permits too much ice to accumulate on the coil At the very least this hurts efficiency at worst it results in compressor damage Insufficient defrosting is a condition the heat pump manufacturer wants very much to avoid A 50 percent reduction in outdoor airflow is the maximum that would be tolerated So the designer of a heat pump would select a control point that puts the system into defrost when airflow through the outdoor coil approaches half its normal level Restricted airflow causes a greater load on the compressor the outdoor coil run
120. D1165 at 68 F max heating and 78 F min cooling D1769 82 Qbsolete Arcoaire logo part 1506753 F C T874D1165 Replacement has F scaleplate used with Q674E1346 used in Y594D1297 scaleplate D1777 44 Obsolete Climate Control logo part no 65495806 F T874D1165 Replacement has F scaleplate scaleplate D1785 82 Obsolete Comfortmaker logo part no 1505753 F C T874D1165 Replacement has F scaleplate used with Q674E1346 used in Y594D1305 scaleplate D1793 44 Qbsolete McQuay logo part no 65495805 F C T874D1165 Replacement has F scaleplate scaleplate aBoth the thermostat and subbase must be replaced 60 2485 8 54 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks D1801 45 208 Trol A Temp by Honeywell logo H1 and H2 anticipators None See Trol A Temp for set at 0 10A used with 0674 1463 D1115 replacement D1819 44 Marv Air Com Stat logo part no 50059 adjustable T874D1165 Replacement has a 2 F fixed interstage between H1 and H2 and between C1 and C2 interstage differential between includes Allen wrench and screws to lock cover field H1 and H2 and between C1 adjustable range stops F C scaleplate and C2 replacement has F scaleplate D1827 45 208 Trol A Temp by Honeywell logo
121. E THERMOSTATS AND Q674 SUBBASES Table 7 0672 0674 Subbase Cross Reference Model Number Description Q674 Trade Replacement Remarks L1342 Lennox no 52C7601 used with T872W1019 None and C815A1013 L1375 Westinghouse used with T872R1271 W89 None L1383 Dunham Bush used with T872R1099 Y594R1243 L1391 Williamson used with T872R1339 Y594R1243 L1409 Duotherm special used with T872R1321 W89 None Q672N System OFF HEAT COOL EVAP N1001 Goettl heat pump heat mode changeover None evaporative cooler circuit Fan AUTO ON System AUTO used with T872C1459 N1019 Goettl heat pump heat mode changeover None evaporative cooler circuit W1 Y1 jumper used with T872C1459 N1027 Siegler special used with T872C1707 None Q672P System EM HT HEAT COOL P1009 Carrier special no HH93AZ069 used with Y594R1243 Replacement has OFF system T872G1075 HHO7ATO71 switch position When replacing a T872 Thermostat and Q672 Subbase always replace both the thermostat and subbase 45 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks T874A 1 stage heat 1 stage cool A1002 44 65 Honeywell logo Standard OEM used with Q674B1331 T874A1036 A1010 44 Honeywell logo includes
122. EANS AND OVERLOAD PROTECTION BN C2 AS REQUIRED RISE A JUMPER RC RH FOR SINGLE TRANSFORMER A O AND B TERMINALS ON SELECTED MODELS COMPRESSOR CONTACTOR 2 COMPRESSOR CONTACTOR 1 M934 Fig 82 Schematic and hookup of T874A C D with Q674E Used in standard applications 115 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR Ue F H1 COMPRESSOR CONTACTOR 1 H2 ANTICIPATOR 8 O JJ Q Q OFF X r CHECK LED RED HEAT gt x1 ali BR Q COMPRESSOR C1 ANTICIPATOR D AUTO F4 hA CONTACTOR 2 Oo CKO v2 C2 ANTICIPATOR 5 A POWER SUPPLY PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 83 Schematic and hookup of T874G with Q674C Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR COOL CHANGEOVER VALVE OUTDOOR O FAN RELAY FAN IAN SWITCH Q AUTO 4 ON HIGH PRESSURE COMPRESSOR SWITCH CONTACTOR H2 ANTICIPATOR tar 9 FAN RELAY H2 RELAY SYSTEM C1 ANTICIPATOR ds OFF O O DEFROST AUx HT HEAT RELAY RELAY Oj 515 D AUTO CHA 4 Y oo O O F COOL t Jo RISE Ili 2 AN A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD 1 PROTECTION
123. EAT C1 ANTICIPATOR FILTER LED RED M SERVICE LED Q YELLow A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5976 Fig 65 Schematic and hookup of T874A with Q674B Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 1 Sig Sales NO FAN SWITCH HEAT RELAY 2 JS FALL oN o UE 5 6 fes L2 A H2 ANTICIPATOR L1 m amp GO POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD M7011 PROTECTION AS REQUIRED Fig 66 Schematic and hookup of T874A D F with Q674D Used in standard applications 107 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN RELAY FAN SWITCH HEAT CHANGEOVER VALVE SYSTEM SWITCH AUX HT RELAY COMPRESSOR CONTACTOR N POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5998 Fig 67 Schematic and hookup of T874R with Q674B Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS i COMPRESSOR CONTACTOR H1 UIS ANTICIPATOR FN gt OO CLOSED DAY OPEN NITE F RISE 7 ES H1 t LED RED a Se FN RISE S COMPRESSOR C1 ANTICIPATOR JUMPER A i power SUPPLY PROVIDE DISCONNECT 4 MEANS AND OVERLOAD PROTECTION P COOL CHANGEOVER VA
124. ECT MEANS AND OVERLOAD VALVE M2985 PROTECTION AS REQUIRED Fig 207 Schematic and hookup of T874J with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS FN FALL CU H1 ANTICIPATOR NO FAN SWITCH ANTICIPATOR 4 JN H2 UIN H2 FALL lt 9 COMPRESSOR CONTACTOR 2 L1 ifi HOT L2 NO COMPRESSOR SYSTEM CONTACTOR 1 SWITCH A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED C2 ANTICIPATOR A RC RH REMOVABLE JUMPER WHEN SPECIFIED icone ve Fig 208 Schematic and hookup of T874D with Q674D Used in standard applications 197 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED FALL 60 2485 8 THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR AUX HT LED GREEN SYSTE 2 CHANGEOVER SWITCH COMPRESSOR CONTACTOR M2987 Fig 209 Schematic and hookup of T874R with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR CHANGEOVER VALVE HEAT CHANGEOVER FILTER SYSTEM LED SWITCH Q Q YELLOW A OFF 4 COMPRESSOR CONTACTOR 1 COMPRESSOR CONTACTOR 2 M2988 Fig 210 Schematic and hookup of T874Y with Q674E Used in heat pump applications 198 T874 MULTISTAGE THERMOSTATS
125. ECTION AS REQUIRED M3956 Fig 187 Schematic and hookup of T874C with Q674B Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS Hi ANTICIPATOR MEAT HELAY 1 FALL H1 H2 ANTICIPATOR L2 ANTICIPATOR dE A GG 9 9 OO RISE C2 C2 ANTICIPATOR COMPRESSOR CONTACTOR 2 OAc A POWER SUPPLY PROVIDE DISCONNECT MEANS COMPRESSOR M3958 AND OVERLOAD PROTECTION AS REQUIRED CONTACTOR 1 Fig 188 Schematic and hookup of T874D with Q674G Used in standard applications 187 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS NO FAN SWITCH SYSTEM SWITCH 2 M3960 Fig 189 Schematic and hookup of T874F with Q674D Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS RESET 9 D IN STAT H1 j GEN HE FALL COMPRESSOR 7 USJ CONTACTOR lt H1 ce PR L1 TI Is H2 ANTICIPATOR SERVICE H2 LED RED FALL 6 M A svsttM O RISE SWITCH EM HT LED ELEC HT RELAY 8 O rid en 2 HA PA ANTICIPATOR e 4 10 AN p ae 5 C815A COOL r 2 OUTDOOR THERMISTOR Po A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED VE oe A OPTIONAL REMOVABLE JUMPER TO ALLOW SINGLE SYSTEM TRA
126. ED COMPRESSOR A N O SWITCH INSTALLER ADDED TO LIGHT EM HT LED WHEN COMPRESSOR OPERATION IS NOT NORMAL CONTACTOR 1 M4722 Fig 126 Schematic and hookup of T874G with Q674P Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS AUX HT LED GREEN EM HT COMPRESSOR LED RED FAILURE COMPRESSOR C1 ANTICIPATOR CONTACTOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5652A Fig 127 Schematic and hookup of T874C with Q674L Used in heat pump applications 60 2485 8 146 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 K ANTICIPATOR FAN SWITCH SYSTEM MONITOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION COOL CHANGEOVER AS REQUIRED VALVE COMPRESSOR CONTACTOR Fig 128 Schematic and hookup of T874R with Q674L Used in heat pump applications M5653A SYSTEM COMPONENTS THERMOSTAT SUBBASE FAN RELAY COOL CHANGEOVER VALVE COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M102A Fig 129 Schematic and hookup of T874G with Q674L Used in heat pump applications 147 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES gt 60 2485 8 THERMOSTAT FAN SWITCH SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR SYSTEM SWITCH H2
127. EM SWITCH Q Q OFF HA A 2 EM HT LED RED A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A W3 TERMINAL ON SELECT MODELS Fig 155 Schematic and hookup of T874G with Q674F Used in heat pump applications 165 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 HOT COOL H1 CHANGEOVER VALVE ANTICIPATOR OUTDOOR AUX HT THERMOSTAT RELAY EM HT CONTACT RELAY COMPRESSOR EM HT LED FAILURE RED EM HT LED GREEN AUX HT RELAY A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5720 Fig 156 Schematic and hookup of T874G with Q674F Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE FAN SWITCH CHECK LED TIME DELAY GREEN RELAY 2 TIME DELAY SYSTEM RELAY SWITCH LOCKOUT RELAY HI PRESSURE COMPRESSOR CEN SWITCH CONTACTOR RISE M2860 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 157 Schematic and hookup of T874G with Q674F Used in heat pump applications 60 2485 8 166 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS re FT OF HOT L2 A COOL CHANGEOVER VALVE i H1 ANTICIPATOR FAN SWITCH AUTO _ F 4_ 5 5 m M HEAT CHANGEOVER VALVE
128. ENCY HEAT RELAY FIXED ANTICIPATOR HIGH RESISTANCE RTD TIME DELAY RELAY RD DEFROST RELAY ADJUSTABLE ANTICIPATOR pricssunE LOW RESISTANCE LACO TYPICALLY 0 TO 5 OHMS LOW AMBIENT CUTOFF M5848 TYPICALLY 5 KILOHMS Fig 16 Key to hookup symbols 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HOT L1 L2 A H1 C1 ANTICIPATOR FAN SWITCH SYSTEM SWITCH COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5072A A AUXILIARY HEAT LED AVAILABLE ON SOME MODELS Fig 17 Internal schematic and typical hookup of a T874R Thermostat and Q674L Subbase in a heat pump application The thermostat provides two stage heating and one stage cooling manual changeover operates on cooling 60 2485 8 16 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR FAN SWITCH AUX HT LED GREEN EM HT SYSTEM LED RED SWITCH SYSTEM MONITOR CHANGEOVER VALVE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR M5840 Fig 18 Tracing the changeover relay circuit THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR FAN SWITCH H2 ANTICIPATOR EM HT SYSTEM LED RED MONITOR SYSTEM
129. ERLOAD PROTECTION AS REQUIRED A TERMINAL LABELED ON SOME MODELS M3683A A W3 TERMINAL AVAILABLE ON SOME MODELS ONLY Fig 218 Schematic and hookup of T874R with Q674L Used in heat pump applications 204 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS CONTROL MODULE H1 ANTICIPATOR HEAT RELAY 2 SYSTEM SWITCH Q SERVICE LED RED FAN SWITCH AUTO A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A MOMENTARY POSITION SPRING RETURN TO ON UPON SWITCH RELEASE A H2 OFFSET 12 F FROM H1 M5901 Fig 219 Schematic and hookup of T874C with Q674C Used in standard applications 205 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS CONTROL MODULE HEAT RELAY 1 SYSTEM SWITCH OFF H1 ANTICIPATOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A MOMENTARY POSITION SPRING RETURN TO ON UPON SWITCH RELEASE M5929 Fig 220 Schematic and hookup of T874W with Q674C Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH Q HH AUTO COMPRESSOR CONTACTOR SYSEMO SWITCH SERVICE OFF l Ba LED YELLOW 10 5 3 F AUTO 4 C1 RISE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5902 Fig
130. ESSOR CONTACTOR 1 M3674 Fig 54 Schematic and hookup of T874W with Q674B Used in standard applications 101 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS NO FAN SWITCH COMPRESSOR NO CONTACTOR 2 SYSTEM SWITCH COMPRESSOR CONTACTOR 1 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED JUMPER RC RH FOR SINGLE TRANSFORMER A B AND 5 TERMINALS AVAILABLE ON SOME MODELS M3667A Fig 55 Schematic and hookup of T874A D F with Q674D Used in standard applications SUBBASE SYSTEM COMPONENTS FAN SWITCH LED RED COMPRESSOR CONTACTOR 1 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5975 Fig 56 Schematic and hookup of T874C with Q674B Used in standard applications 60 2485 8 102 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH COMPRESSOR FAN RELAY CONTACTOR CLOSED DAY OPEN NITE BRELAY SYSTEM SWITCH COOL CHANGEOVER VALVE A POWERSUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A JUMPER HONEYWELL SUPPLIED FIELD INSTALLED M8004 Fig 57 Schematic and hookup of T874P with Q674B Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS ECONOMIZER PACKAGE NO SYSTEM SWITCH CONTROL C1 PANEL M3722 Fig 58 Sche
131. Economizer logo Premier White color heat 187441036 anticipator factory set at 1 2A A1598 224 McQuay logo part 073319001 Premier White See OEM for 225 color F C scaleplate includes Allen wrench screws to replacement lock cover and AAF insert A1614 44 Honeywell logo TRADELINE model scaleplate T874A1036 Replacement has F Premier White color includes Allen wrench and scaleplate replacement is screws to lock cover used with Q674B beige A1622 44 Obsolete York logo part no 2TH047032244A includes T874A1010 Allen wrench and screws to lock cover and non adjustable range stops set at 72 F max heat and 78 F min cool T874B 1 stage heat 2 stage cool B1001 44 Obsolete Honeywell logo T874B1019 B1019 44 Honeywell logo TRADELINE model includes Allen T874B1019 wrench and screws to lock cover B1027 44 Obsolete Westinghouse logo T874B1019 B1035 44 46 Obsolete Trane logo used with Q674B1018 B1075 T874B1019 used in Y594B1026 B1034 B1043 44 Obsolete Honeywell logo C scaleplate T874B1019 Replacement has F scaleplate B1050 44 Lennox logo part no 13F0201 F C scaleplate T874B1019 Replacement has F scaleplate B1068 44 Honeywelllogo Honeywell Canada TRADELINE model T874B1019 Replacement has F scaleplate includes Allen wrench and screws to lock scaleplate cover B1076 88 Obsolete Lennox Power Saver Two Speed logo part T874B1019 Rep
132. G RETURN TO ON UPON SWITCH RELEASE AA THERMISTOR INTERNAL TO THERMOSTAT M531 A H1 AND C1 ARE DPST SWITCHES Fig 99 Schematic and hookup of T874C with Q674C Used in standard applications 60 2485 8 124 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR HEAT RELAY 1 SYSTEM OFF gt 47 SWITCH C COMPRESSOR CONTACTOR 2 SERVICE LED RED FAN SWITCH AUTO ONU FA AS 4 MOMENTARY CIRCUIT EXTERNAL TEMP READOUT A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED H3 OFFSET 12 F FROM H2 FOR NIGHT SETBACK A MOMENTARY POSITION SPRING RETURN TO ON UPON SWITCH RELEASE A THERMISTOR INTERNAL TO THERMOSTAT M532 A H1 AND C1 ARE DPST SWITCHES Fig 100 Schematic and hookup of T874W with Q674C Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE SYSTEM SWITCH H2 FALL ANTICIPATOR COMPRESSOR CONTACTOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M3718A Fig 101 Schematic and hookup of T874R with Q674L Used in heat pump applications 125 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES EM HT TIME DELAY RELAY CONTACT FAN RELAY THERMOSTAT SUBBASE SYSTEM COMPONENTS 4 7 HIGH COMPRESSOR OVERLOAD INTERNAL PRESSURE CONT
133. Honeywell T874 Multistage Thermostats ENSE APPLICATION These thermostats and subbases provide low voltage control of multistage heating and cooling systems including heat pump systems U S Registered Trademark Copyright 2001 Honeywell All Rights Reserved and Q674 Subbases PRODUCT DATA FEATURES T874 Thermostat has silent dust free mercury switches operated by coiled bimetal elements Heatanticipator s are adjustable or fixed cooling anticipator s are fixed Individual heat and cool levers and scales most models for temperature setting located on top of thermostat case Cover thermometer on most T874 Multistage Thermostat models Locking cover and locking lever screws available for T874 Multistage Thermostats Versaguard Thermostat Guard or custom key lock thermostat guards available for T874 Multistage Thermostats T874 Thermostat requires a Q674 Subbase 0674 Subbase provides system and fan switching wiring terminals and mounting base for T874 Multistage Thermostat Adapter plate available for mounting Q674 on wall or horizontal outlet box Light emitting diodes LEDs located on subbase for easy reference Upto three stages each of heating and cooling control possible Models with setpoint restrictions and locking cover with no thermometer available for Department of Defense DoD and other special applications Outdoor reset used on som
134. ICIPATOR CyH2 SERVICE LED RED SYSTEM SWITCH olo FA EA 5 OFF 47 47 O COOL OH a Xx HEAT 9 C1 ANTICIPATOR Q9 C2 ANTICIPATOR UTS c A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER M18622 Fig 249 Schematic and hookup of T874C with Q674B Used in heat pump applications Honeywell Home and Building Control Home and Building Control Honeywell Honeywell Limited Honeywell Limit e 1985 Douglas Drive North 35 Dynamic Drive Golden Valley MN 55422 Scarborough Ontario MIV 479 Printed in U S A on recycled 60 2485 8 J H Rev 3 01 paper containing at least 10 www honeywell com post consumer paper fibers
135. INGLE TRANSFORMER Fig 193 Schematic and hookup of T874D with Q674E Used in stand THERMOSTAT SUBBASE A CHANGEOVER RELAY HEAT ORS CHANGEOVER RELAY COOL Om Ee FAN RELAY COMPRESSOR CONTACTOR 2 Ofc COMPRESSOR X69 CONTACTOR 1 A L2 L1 HOT M3203B ard applications SYSTEM COMPONENTS gene 9 Q D son LN A AUTO C E Fo FAN RELAY CHANGEOVER VALVE ANTICIPATOR 5 2 9 5 ES CHECK SWITCH CHE 4 GREEN H2 9 macs SYSTEM 1 SWITCH 5 OFF ChA 4 9 c EM HT p 4 NC EM HT 4 2 ay LED RED COMPRESSOR HEAT 4 NC CONTACTOR NS AUTO wj IN POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 194 Schematic and hookup of T874G with Q674F Used in heat pump applications 190 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES FALL FALL ANTICIPATOR F RISE RISE CO GD THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE E E B RELAY EE H1 ANTICIPATOR H1 FAN SWITCH H2 SYSTEM SWITCH UIJ C1 GO F Jci COMPRESSOR BISE POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD CONTACTOR ies PROTECTION AS REQUIRED Fig 195 Schematic and hookup of T874G with Q674F Used in heat pump applications
136. IRED A FIELD REMOVABLE JUMPER SYSTEM SWITCH COMPRESSOR CONTACTOR Q REVERSING R1 RELAY M103A Fig 138 Schematic and hookup of T874L with Q674B Used in heat pump applications THERMOSTAT H1 ANTICIPATOR H2 ANTICIPATOR C1 ANTICIPATOR C2 ANTICIPATOR C2 RISE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED SWITCH SUBBASE SYSTEM COMPONENTS SYSTEM SWITCH COMPRESSOR HEAT PUMP RELAY LED GREEN AUX HT RELAY OFF LED RED COOL COMPRESSOR CONTACTOR 1 COMPRESSOR CONTACTOR 2 Fig 139 Schematic and hookup of T874D with Q674F Used in heat pump applications 60 2485 8 154 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS AUX HT RELAY unt HT LED GREEN vs FAN RELAY EM HT LED RED COMPRESSOR EM HT RELAY MONITOR AED LED SYSTEM SWITCH A HEAT CHANGEOVER RELAY S CHANGEOVER CONTACTOR 1 O pre COMPRESSOR CONTACTOR 2 va O A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A CONNECT CHANGEOVER RELAY TO O TERMINAL FOR CHANGEOVER IN COOLING OR TO B TERMINAL FOR CHANGEOVER IN HEATING M156A Fig 140 Schematic and hookup of T874W with Q674L Used in heat pump applications 155 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 S
137. IRED A A JUMPER RH RC FOR SINGLE TRANSFORMER A OPTIONAL LED ON SOME MODELS Fig 71 Schematic and hookup of T874A D with Q674A Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 H1 ANTICIPATOR SYSTEM SWITCH Q COMPRESSOR CONTACTOR 2 C2 ANTICIPATOR 9 RISE NPowER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR 1 12 1 TERMINALS RC RH FOR SINGLE SYSTEM TRANSFORMER ONLY M5122A TERMINALS SOME MODELS Fig 72 Schematic and hookup of T874D E F with Q674C Used in standard applications 60 2485 8 110 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H ANTICIPATOR REVERSING VALVE RELAY COMPRESSOR CONTACTOR SETBACK FAN RELAY SYSTEM SWITCH OPEN NIGHT CLOSED DAY SETBACK RELAY A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M7008 Fig 73 Schematic and hookup of T874G with Q674C Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS to COOL CHANGEOVER VALVE FAN SWITCH FAN RELAY SYSTEM SWITCH Q Q OFF COMPRESSOR CONTACTOR A SERVICE LED YELLOW COMPRESSOR FAULT A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A SERVICE LED ON SELECT
138. J Obsolete Honeywell logo Heil Quaker part no T874C1018 HQ712001HW C1570 45 Obsolete Williamson logo used with Q674B1000 used T874C1018 in Y594C1280 C1638 121 Obsolete Honeywell logo meets DoD specifications Y594C1322 includes Allen wrench and screws to lock cover no thermometer non adjustable range stops set at 72 F max heat and 78 F min cool 22 26 field adjustable locking levers used with Q674L1561 used in Y594C1322 C1653 70 Obsolete Fiberglas Canada C scaleplate no H1 H2 See OEM for or C1 anticipation used with 067451000 used in replacement Y594C1348 C1661 99 Obsolete McQuay logo part no 61202401 F C T874C1125 Replacement has HEAT OFF scaleplate includes momentary system switch position Q674B1075 COOL system switching no with spring release used with 0674 1363 momentary system switch position no LEDs C1695 45 Obsolete Miller logo used with Q674B1000 used in T874C1018 Y594C1355 C1703 45 Qbsolete Intertherm logo used with Q674B1000 used T874C1018 in Y594C1363 C1737 44 Obsolete Honeywell logo Carrier part no HH621603 T874C1018 C1745 44 Qbsolete AAF Snyder General logo part no T874C1018 4ELN7919 C1752 219 Obsolete McQuay Snyder General logo part no T8611M2025 061202402 12 F offset between H1 and H2 F C scaleplate no C1 anticipation used with Q674C1363 C1760 44 Bard logo T874C1018 C1778 219 Obsolete AAF Snyder General logo par
139. LEDs used with T874C1133 C1181 76 Obsolete California heat pump used with T874C1000 Q674C1058 C1199 163 Obsolete American Air Filter part no 4ELN 8788 two T8600D2028 momentary reset switch LEDs spring return momentary system switch position used with T874G1485 G1535 a Both the thermostat and subbase must be replaced 73 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 9 Q674 Subbase Cross Reference Model Fig Q674 Trade Number No Description Replacement Remarks C1207 78 Obsolete Friedrich System OVERRIDE AUTO OFF T8600D2028 Wiring differences old new used with T874P1014 programmable L R WzO W Y jumper required night setback C1215 97 Obsolete Friedrich part no AQ5315 System T8600D2028 Wiring differences old new OVERRIDE AUTO OFF OVERRIDE and SERVICE programmable L R WzO W Y jumper LEDs used with T874P1022 P1030 required night setback C1223 73 Obsolete Friedrich part no AQ5323 used on systems Y594H1012 Wiring differences old new requiring night setback contacts used with 1 Y2 Y L R R none R T874G1584 L jumper required no night setback T8600D2028 Wiring differences old new programmable L R WzO W Y jumper required night setback C1249 164 Includes MALFUNCTION LED used with T874H1062 Y594H1012 used in Y594H1012 C1256 73
140. LO HI T874V International symbols CONT Q674S Indicator LED None Standard HEAT COOL None T874C Optional Specifications Q674 Only Models available with up to four LEDs for example LEDs can show EM HT AUX HT SERVICE CHECK FILTER and LOCKOUT See Fig 3 System switching marked HEAT OFF RESET COOL for sys tems requiring impedance relay reset Available on Q674B only G terminal isolated on heating to provide fan relay operation from external low voltage fan switch Q674B only Auto fan operation on both heat and cool L terminal is used for system monitoring devices Common R terminal for heating cooling Changeover in cool or heat mode for heat pumps Auto fan in EM HT for heat pumps Subbase Accessory 193121A Adapter Plate Assembly for mounting on vertical outlet box Assembly includes adapter ring and cover plate Use to cover wall marks from replaced thermostat T874 Thermostat with One Setpoint Lever T874 Thermostat with Separate Q674 Subbase with Four LEDs Heatina and Cooling Levers Fig 3 Heating cooling levers and system LED indicators 60 2485 8 6 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES MERCURY NOTICE This control contains mercury in a sealed tube Do not place control in the trash at the end of its useful life If this control is replacing a control that contains mercury in a sealed tube do not place your old control in the trash
141. LVE AS REQUIRED PF oho A JUMPER HONEYWELL SUPPLIED FIELD INSTALLED 7 A H2 MAKE OFFEST 8 F BELOW 1 MAKE M101A Fig 68 Schematic and hookup of T874P with Q674B Used in heat pump applications 60 2485 8 108 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT a FAN SWITCH AUTO C1 ANTICIPATOR SUBBASE SYSTEM SWITCH Q OFF SYSTEM COMPONENTS A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED THERMOSTAT SUBBASE UIN SWITCH H2 F SYSTEM FALL SWITCH Q Q Q 8 HEAT Q Q CooL LFA FAJ 5 CO NH A POWER SUPPLY PROVIDE DISCONNECT FALL MEANS AND OVERLOAD PROTECTION AS REQUIRED FAN RELAY L1 HOT MA COOL RELAY M107A Fig 69 Schematic and hookup of T874V with Q674R Used in fan coil applications M SERVICE LED RED SYSTEM COMPONENTS COMPRESSOR FAULT AUX RELAY 8 OES COMPRESSOR CONTACTOR A L2 Wings HOT M1402A Fig 70 Schematic and hookup of T874C with Q674S Used in heat pump applications 109 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH H1 A woe SYSTEM SWITCH COMPRESSOR CONTACTOR 2 COMPRESSOR L2 CONTACTOR 1 POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD HOT PROTECTION AS REQU
142. M HT selector switch on the thermostat subbase The compressor is prevented from running The electric heaters are cycled as they normally would be by the second stage of 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES the thermostat A set of contacts on the emergency heat relay is used to bypass each outdoor thermostat so that all electric heat is under immediate thermostat stage two control So the emergency heat relay simply bypasses the outdoor thermostats See Fig 41 In the second method the emergency heat relay is cycled directly by the thermostat mercury bulb In this hookup the relay is controlled by the thermostat first stage The emergency heat relay energizes all of the auxiliary heat relays on a call for heat See Fig 42 So the emergency heat is controlled by the first stage of the thermostat The emergency heat relay energizes all of the electric strip heaters so the heat and the indoor fan come on together as soon as the first stage calls for heat With the first method the fan remains on being controlled by the first stage of the thermostat and the electric heaters cycle on and off with the second stage In either case a subbase indicator light is turned on whenever the function switch is in the emergency heat position THERMOSTAT FUNCTION HEAT 1 SWITCH ibd bei COMPRESSOR AUXILIARY HEAT RELAY 1 AUXILIARY HEAT RELAY 2 EMERGENCY HEAT RELAY
143. MAL M4665 Fig 103 Schematic and hookup of T874G with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS EM HT LED FAN SWITCH ANTICIPATOR COMPRESSOR CONTACTOR H2 ANTICIPATOR SYSTEM SWITCH POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED OPTIONAL FIELD WIRE JUMPER TO CYCLE AUXILIARY HEAT RELAY H1 INSTEAD OF H2 FASTER RESPONSE ELEC HT RELAY Fig 104 Schematic and hookup of T874R with Q674L Used in heat pump applications 127 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR FAN SWITCH FAN RELAY Wa SYSTEM OQ SYSTEM 6 SWITCH MONITOR F A SWITCH FALL EM HT _ H2 ANTICIPATOR 9 HEAT H2 Q 8 OFF HJ EA O15 COMPRESSOR COOL _ uw 4 CONTRACTOR C1 ANTICIPATOR v LS POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD 73 HEAT RELAY f PROTECTION AS REQUIRED A L1 L2 M8384 HOT Fig 105 Schematic and hookup of T874C with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER Ed S FAN SWITCH 5 1 1 Q Q FAN RELAY C1 ANTICIPATOR AUTO ON Fd 9 5 SYSTEM SWITCH JN H2 FALL H2 ANTICIPATOR COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DIS
144. MP STAGE 1 COMP STAGE2 OUTDOOR THERMOSTAT AUXILIARY HEAT M5838 Fig 35 Two stage heat pump with two stage thermostat The outdoor thermostat is set at the balance point with both heat pump stages running So if the heat pump can control the heating load down to 20 7 C the auxiliary heat comes on with the second stage of the compressor In effect this control strategy changes the heat input of the second stage depending on the amount of heat needed Additional stages of auxiliary heat can be added with or without the control of more outdoor thermostats See Auxiliary Heat section Another way to control a two stage heat pump is with a three stage thermostat The T874W is designed for this application as well as others See Fig 36 The advantage of this system is that no auxiliary heat is used until there is an actual demand from the controlled space THERMOSTAT rj HEAT 3 HEAT 2 HEAT 1 COMP STAGE 1 COMP STAGE 2 AUXILIARY HEAT Fig 36 Two stage heat pump with three stage thermostat M5837 Two speed Heat Pump One way to control capacity is to use a two speed compressor The compressor runs at low speed for stage one heating and cooling The compressor runs at the low speed instead of cycling the heat pump on and off under some light load conditions The high speed is stage two cooling The compressor runs on high speed when loads increase so the low spe
145. N SWITCH A L1 HOT SYSTEM SWITCH SETBACK RELAY OFF RISE ANTICIPATOR LED c A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A SETBACK STAGE OFFSET 12 F 7 C FROM H1 STAGE A LEDS ON SOME MODELS M5730 Fig 176 Schematic and hookup of T874G with Q674C Used in standard applications 60 2485 8 180 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR Jc LOCKOUT RESET RELAY ae eee ee REN 7 HEAT CHANGEOVER VALVE COOL CHANGEOVER VALVE C1 ANTICIPATOR COMPRESSOR CONTACTOR 72 RISE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A USE EITHER B OR O ONLY FOR SYSTEM CHANGEOVER 0 8A AT 30 VAC MAXIMUM LOAD CURRENT A SECOND STAGE HEAT MAKES 12 F 7 C AFTER FIRST STAGE HEAT TO PROVIDE SETBACK M114C Fig 177 Schematic and hookup of T874G H with Q674C Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS CHANGEOVER RELAY H1 ANTICIPATOR SWITCH SERVICE SYSTEM LED RED SWITCH OFF EM HT LED YELLOW FAN RELAY COMPRESSOR RELAY A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M18623 Fig 178 Schematic and hookup of T874N with Q674F Used in heat pump applications 181 60 2485 8 T874 MULTISTAGE THERMOSTA
146. N o Ta 10 5 12 FA HE H1 ANTICIPATOR EM HT LED RED 1 ANTICIPATOR T HT RELAY HEAT CHANGEOVER RELAY A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5955 Fig 119 Schematic and hookup of T874R with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 HOT FAN SWITCH FAN RELAY H1 C1 ANTICIPATOR H2 ANTICIPATOR C815A1039 THERMISTOR RESET HEATER COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M3173B Fig 120 Schematic and hookup of T874R with Q674L Used in heat pump applications 60 2485 8 140 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FN L1 2 H1 ANTICIPATOR FAN COMPRESSOR 12 5 SWITCH FAILURE Q o Lo Eam E COMPRESSOR CONTACTOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD M7012 PROTECTION AS REQUIRED Fig 121 Schematic and hookup of T874C with Q674L Used in heat pump applications 141 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN RELAY FAN SWITCH Q Q AUTO 2 0 0 ON _F d ANTICIPATOR EM HT LED YELLOW SERVICE H2 ANTICIPATOR 6 5 LED RED A POWER SUPPLY PROVIDE
147. NG STAGE 3 HEATING LEVER COOLING STAGE 1 COOLING e STAGE2 HEATING STAGE 2 CAPTIVE COOLING MOUNTING SCREWS 2 M7625 Fig 12 Internal view of T874W three stages of heating two stages of cooling 60 2485 8 12 Subbase Setting The subbase switching positions control the system operation as described below SYSTEM SWITCH see subbase for positions OFF both the heating and cooling systems are off If the fan switch is at the AUTO position the cooling fan is also off HEAT heating system is automatically controlled by the thermostat Cooling system is off AUTO thermostat automatically changes between heat ing and cooling system operation depending on the indoor temperature COOL cooling system is automatically controlled by the thermostat Heating system is off EM HT emergency heat relay is automatically controlled by the thermostat Cooling system is off Compressor is de energized SUPL HT supplemental heat relay is energized Cooling system is off Compressor is de energized WOOD heating system is operating with only the wood burning stage OlL heating system is operating with only the oil burning stage WOOD OIL wood and oil stages operate sequentially first the WOOD stage operates then the OIL stage operates if the WOOD stage cannot handle the load EVAP controls cooling system by water evaporation see equipment instructions for further information
148. NSFORMER A WIRE JUMPER FOR SERVICE LIGHT M3978 Fig 190 Schematic and hookup of T874C with Q674L Used in heat pump applications 60 2485 8 188 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS i COOL CHANGE OVER VALVE i H2 HOT ANTICIPATOR SYSTEM SWITCH A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M3965 Fig 191 Schematic and hookup of T874R with Q674B Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 HEAT RELAY 1 P ANTICIPATOR 6 C n Q SYSTEM OFF 7 SWITCH H2 ANTICIPATOR FILTER YELLOW c x o HoH SERVICE LED RED L2 L1 HOT C1 ANTICIPATOR COMPRESSOR CONTACTOR 1 C2 ANTICIPATOR COMPRESSOR c2 A POWER SUPPLY PROVIDE DISCONNECT MEANS CONTACTOR 2 AND OVERLOAD PROTECTION AS REQUIRED A MOMENTARY POSITION SPRING RETURN TO ON UPON SWITCH RELEASE M3959 Fig 192 Schematic and hookup of T874D with Q674C Used in standard applications 189 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60 2485 8 THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH H1 ANTICIPATOR SYSTEM SWITCH OFF HEAT AUTO Q COOLU Fd Fd POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A JUMPER RH RC FOR S
149. OUTDOOR THERMOSTAT J EMERGENCY HEAT RELAY CONTACT M5833 Fig 41 Emergency heat relay that bypasses the outdoor thermostats THERMOSTAT FUNCTION HEAT 1 SWITCH BEAT EMERGENCY HEAT RELAY CONTACT COMPRESSOR AUXILIARY 1 HEAT RELAY EMERGENCY HEAT RELAY Fig 42 Emergency heat relay that energizes all of the auxiliary heat relays on a call for heat M5832 60 2485 8 28 Crankcase Heat In any mechanical refrigeration system refrigerant tends to migrate to the coldest part of the equipment and condense there In a heat pump this coldest spot could be the compressor because it is usually outdoors In addition the oil in the com pressor crankcase is capable of absorbing a high concentration of refrigerant On compressor startup there are two risks 1 the liquid refrigerant which is noncompressible can be drawn into the cylinder and 2 considerable oil can be entrained in the refrigerant and swept out of the crankcase through the changeover valve and dispersed in the piping and coils So the migration of refrigerant to the crankcase is undesirable because it can interfere with system lubrication and because the liquid refrigerant must be kept from going through the compressor Adding a crankcase heater creates enough temperature differential to prevent this migration because the compressor is no longer the coldest part of the system so refrigerant does not migrate
150. OVER VALVE systmQ O SWITCH Q EM HT FI4 PN o LO Y AUTO A Q x RO 0 6 lt SYSTEM LED GREEN HPS 4R D COMPRESSOR 4R POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED CONTACTOR VN REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS 1629 Fig 216 Schematic and hookup of T874G with Q674J Used heat pump applications THERMOSTAT SUBBASE N SYSTEM COMPONENTS HEAT CHANGEOVER VALVE Ep HEAT CONTACTOR 2 HEAT CONTACTOR ES A CHECK LED HO FALL ANTICIPATOR FAN SWITCH O Q AUTO S Q Q H2 S ON CH ray ANTICIPATOR 5 05 BN H2 FALL SYSTEM SWITCH 0 OFF GREEN 5 UO s AUTO me O p C1 ANTICIPATOR D FAN RELAY HEAT CONTACTOR 1 OPTIONAL COMPRESSOR FAILURE i COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5900 Fig 217 Schematic and hookup of T874N with Q674C Used in heat pump applications 203 HOT 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 60 2485 8 THERMOSTAT MM SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR AUX HT LED GRN RELAY ANTICIPATOR SYSTEM SWITCH COMPRESSOR CONTACTOR B RELAY A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OV
151. OVERRIDE night setback is disabled ON heating system is controlled by the thermostat EM HT or SUPL HT relay is not energized FAN SWITCH positions control fan operation as follows ON or CONT fan operates continuously AUTO fan operates as controlled by the thermostat in heat pump systems or conventional cooling mode fan operates as controlled by the plenum switch in conven tional heating mode LO fan operates constantly at low speed MED fan operates constantly at medium speed HI fan operates constantly at high speed To move the subbase switches to the desired control positions use thumb and index finger to slide the lever The lever must stop over desired function indicator position for proper circuit operation Spring return momentary position switching feature is available on selected subbase models On these models the fan switch is positioned to the right of the system switch By moving the fan switch to the far right and releasing it the ON position circuit makes The lever springs back on release This position is not marked on the subbase Setting the Adjustable Differential The adjustable interstage differential feature on a selected T874D model only can be identified by the scale and tension screw near the heating and cooling mercury switches See Fig 13 On this model the number of degrees between the making of the first and second stage mercury bulbs is adjustable This feature is especial
152. PLIED FIELD INSTALLED JUMPER TO E X2 FOR CONSTANT POWER TO EM HT LIGHT IN EM HT POSITION A Li L2 A OPTIONAL FIELDWARE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER HOT M8377 Fig 152 Schematic and hookup of T874D with Q674F Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE H1 ANTICIPATOR OUTDOOR THERMOSTAT H2 ANTICIPATOR AUX HT RELAY EM HT CONTACT RELAY C1 ANTICIPATOR COMPRESSOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED CONTACTOR M8381 Fig 153 Schematic and hookup of T874G with Q674F Used in heat pump applications 163 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS EM HT RELAY 4 4 CONTACT 1 H1 ANTICIPATOR Li L2 HOT 031 REFRIGERATION TEMPERATURE CONTROLLER H2 ANTICIPATOR SYSTEM SWITCH COMP FAULT LED YELLOW A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED OPTIONAL FIELD WIRE JUMPER TO CYCLE W2 WITH H1 IN EM HEAT FASTER RESPONSE REVERSING SOLENOID Fig 154 Schematic and hookup of T874G with Q674F Used in heat pump applications 60 2485 8 164 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR FAN 2 5 SWITCH TO FALL ON t_ HJA CS Law 5 FALL AUX HT LED GRN SYST
153. PONENTS H1 ANTICIPATOR HEAT RELAY 2 H2 ANTICIPATOR SYSTEM SWITCH COMPRESSOR CONTACTOR C1 ANTICIPATOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A OPTIONAL FIELD WIRE JUMPER W3 AND F TO BE JUMPERED EXCEPT FOR TWO STAGE GAS APPLICATION A FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER M5999 Fig 52 Schematic and hookup of T874C with Q674B Used in standard applications 60 2485 8 100 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS O HEAT RELAY 1 ANTICIPATOR FAN SWITCH Q H2 FALL lt H2 ANTICIPATOR 9 8 A 5 5 EE 1 4 A OFF rx 4 D CooL 47 S pe e 5 RELAY COMPRESSOR O A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD COMPRESSOR PROTECTION AS REQUIRED CONTACTOR 1 M3202A Fig 53 Schematic and hookup of T874D with Q674B Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS A L1 HOT gt H1 ANTICIPATOR AK XO FALL H1 H2 ANTICIPATOR TA SYSTEM HEAT RELAY 3 SWITCH 8 mw qeu F HEAT CHANGEOVER VALVE OFF HA FA c oN o UES 2 9 9 CQ C1 ANTICIPATOR 5 E 5 Q COOL CHANGEOVER VALVE HIRE 3 9 v9 Jo COMPRESSOR CONTACTOR 2 A POWER SUPPLY PROVIDE DISCONNECT v oN o MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPR
154. PUMP and DEFROST LEDs System SUPL HEAT ON OFF used with T874G1717 used in Y507J1201 Y594G1252 Wiring differences old new C X D L replacement has AUX HEAT and EM HEAT LEDs J1175 216 Obsolete Snyder General part nos 1505756 1506756 CHECK AUX HEAT and SYSTEM LEDs used with T874G1774 G1782 used in Y594G1500 G1518 Y594G1252 Wiring differences old new E W2 W1 W3 X E J1191 161 Obsolete Carrier heat pump gray color used with 787401790 Y594G1252 Wiring differences old new C X replacement has F scaleplate J1209 160 TRADELINE designed to replace Y594G1013 York part no 2TH11702424 Y594G1229 York part no 6TH11702424 and York part no 2TH11704124 used with T874G1865 used in Y594G1567 Y594G1567 J1217 171 Obsolete Nordyne part no 9132250 used with T874J1036 J1044 Y594J1019 Wiring differences old new F L J1225 160 Obsolete TRADELINE gray color designed to replace Y594G1013 York part no 2TH11702424 Y594G1229 York part no 6TH11702424 and York part no 2TH11704124 used with T874G1873 used in Y594G1575 Y594G1567 Replacement is beige J1241 144 Obsolete Carrier Canada part no HH93AZ183 W gray color System SUPL HT ON OFF includes one LED See OEM for replacement J1258 161 Obsolete Carrier Canada part no HH93AZ173 W gray color System SUPL HT ON OFF includes
155. R COMPRESSOR CONTACTOR H2 FALL COMP FAULT LED YELLOW A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A OPTIONAL FIELD WIRE JUMPER TO CYCLE AUXILIARY HEAT RELAY WITH H1 INSTEAD OF H2 FASTER RESPONSE ELEC HT RELAY Fig 116 Schematic and hookup of T874R with Q674L Used in heat pump applications 137 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 ANTICIPATOR H2 ANTICIPATOR C2 ANTICIPATOR PROTECTION AS REQUIRED SUBBASE ENTHALPY CONTROL RELAY HEAT RELAY CONTACT 1 FAN SWITCH DEFROST SWITCH ENTHALPY CONTROL A ENTHALPY CONTROL 1 1 1 RELAY 2 p OUTDOOR FAN RELAY 2 1ST STAGE LOW PRESSURE LIMIT ENTHALPY CONTROL RELAY 1 TIME DELAY HEATER TIME DELAY 2ND STAGE LOW PRESSURE LIMIT DEFROST RELAY SYSTEM SWITCH OUTDOOR SYSTEM COMPONENTS OUTDOOR OUTDOOR FAN RELAY 3 1ST STAGE SHORT CYCLE CONTROL 2ND STAGE SHORT CYCLE CONTROL THERMOSTAT DEFROST RELAY A OPTIONAL ECONOMIZER HOOKUP DOTTED LINES 60 2485 8 COOL CHANGEOVER VALVE Fig 117 Schematic and hookup of T874D with Q674L Used in heat pump applications 138 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY CONTACT 1 m ECONOMIZER RELAY SWITCH PA DEFROST 101 SWITCH OUTDOOR
156. R FOR LARGER DIFFERENTIAL MARK THE SCALE REPRESENTS 1 F 0 6 C M937 Fig 13 Set adjustable interstage differential 13 N CAUTION Equipment Damage Hazard When the thermostat is used to control a two stage heating or cooling system the second stage mercury bulb must never make before the first stage bulb or severe equipment damage could result To prevent this problem provide at least 2 F 1 C differential between stage one and stage two make points Example in heating if stage one makes at 70 F 21 C stage two should make at 68 F 20 or lower Verify the Adjustment Heating Start with the heating setpoint lever all the way to the left Slowly move the lever to the right just until the first stage bulb makes mercury rolls to the right side of the bulb Note the setting on the temperature scale Slowly move the lever to the right until the second stage bulb makes Note the setting on the temperature scale The difference between the two temperatures is the interstage differential which should match the number set on the scale with the tension screw Cooling Start with the cooling setpoint lever all the way to the right Slowly move the lever to the left just until the first stage bulb makes mercury rolls to the left side of the bulb Note the setting on the temperature scale Slowly move the lever to the left until the second stage bulb makes Note the setting on the temperature scale
157. R A C1 ANTICIPATOR COOL CHANGEOVER VALVE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A JUMPER HONEYWELL SUPPLIED FIELD INSTALLED A H2 MAKE OFFEST 8 F BELOW H1 MAKE Fig 97 Schematic and hookup of T874P with Q674C Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS service i pol bo LED RED SYSTEM MONITOR E E H1 ANTICIPATOR SWITCH HEAT RELAY 1 EAT RELAY 2 a CHANGEOVER RELAY ENS L2 HOT L1 HOT CHANGEOVER i SYSTEM SWITCH 12 gt 1 RELAY nwa AN Page 2 S 00 79 FAN RELAY oN oH eye COMPRESSOR COMPRESSOR CONTACTOR 1 CONTACTOR 2 ES RISE C2 C2 ANTICIPATOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5106A A T874A IS SINGLE STAGE NO W2 OR Y2 Fig 98 Schematic and hookup of T874D with Q674E Used in standard applications 123 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR HEAT RELAY 1 SYSTEM Q Q OFF SWITCH SERVICE LED RED FAN SWITCH AUTO MOMENTARY CIRCUIT THERMISTER EXTERNAL TEMP READOUT A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED H3 OFFSET 12 F FROM H2 FOR NIGHT SETBACK A MOMENTARY POSITION SPRIN
158. R1466 108 Quaker part no 1060321 model no Y594R1292 HAXBOO4TWO 1 contains T874R1673 and 06741 1132 R1482 119 Qbsolete Nordyne Miller part no 9122230 Y594R1763 Wiring differences old new contains T874R1699 and 067411264 W2 W Z F K X2 W1 0 R1490 209 Trol A Temp contains T874R1707 067411678 None See Trol A Temp for replacement R1508 209 Trol A Temp contains T874R1715 067411686 None See Trol A Temp for replacement R1516 132 Obsolete Snyder General part no 654958B07 Y594R1763 Wiring differences old new contains T874R1723 Q674L1702 and C815A1005 W1 W 2 R1524 108 Obsolete Inter City Products part no Y594R1292 HQ1147925HW contains T874R1731 and Q674L1132 R1532 108 Quaker part no 1060322 model Y594R1292 004 01 contains T874R1749 06741 1132 R1607 108 Obsolete Keeprite THPC contains T874R1814 and Y594R1292 Q674L 1132 a Both the thermostat and subbase must be replaced 93 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 10 Y594 Cross Reference Model Number 1615 Fig No 230 Description TRADELINE contains T874R1822 and Q674L1710 replaces Y594R1326 T874R1491 Q674L 1553 Trade Model Replacement Y594R1615 R1623 134 Obsolete Rheem Universal Parts part no 41 20796 46 contains T874R1558 and Q674L1504 Y594R1300 R1631 134 Rheem
159. RLOAD PROTECTION AS REQUIRED M5927 Fig 224 Schematic and hookup of T874A D with Q674E Used in standard applications 208 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS MM S FN FALL 1 CONTROL MODULE HEAT RELAY 1 H1 ANTICIPATOR SWITCH Q AUTO 4 Q L1 HOT AN L2 L2 L1 HOT COOL DAMPER v v D H2 ANTICIPATOR SYSTEM SWITCH UTES A C1 RISE 9 F c2 RISE SERVICE LED RED A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5928 Fig 225 Schematic and hookup of T874D with Q674C Used in standard applications 209 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS CONTROL MODULE SYSTEM MONITOR F FALL SERVICE C LED RED E NO FAN SERVICE H1 SWITCH LED RED ANTICIPATOR d gt D FALL ANTICIPATOR C1 RISE IA RISE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5930 Fig 226 Schematic and hookup of T874G with Q674G Used in standard applications 60 2485 8 210 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COMPRESSOR FAULT COOL CHANGEOVER RELAY HEAT CHANGEOVER W1 RELAY RELAY COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNEC
160. STEM COMPONENTS te Orr OOOO FAN SWITCH FAN RELAY H2 ANTICIPATOR SYSTEM SWITCH COMPRESSOR CONTACTOR H1 ANTICIPATOR EXTERNAL COOLING THERMOSTAT SUCH AS T87 F POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED m Fig 62 Schematic and hookup of T874F with Q674B Used in wood coal applications 105 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED H1 THERMOSTAT SUBBASE SYSTEM COMPONENTS NO FAN AUX HT RELAY SWITCH UI po CO H2 ANTICIPATOR HOT NO L2 SYSTEM SWITCH HEAT COOL SWITCH WOOD COAL RELAY H1 ANTICIPATOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M3725 Fig 63 Schematic and hookup of T874F with Q674D Used in wood coal applications THERMOSTAT SUBBASE SYSTEM COMPONENT ANTICIPATOR SYSTEM SWITCH HEAT OFF 1 HOT L2 L1 K1 K1 K2 K2 K2 9 MED A SINGLE SETPOINT LEVER AND BIMETAL FAN SCHEMATIC 60 2485 8 M8005 Fig 64 Schematic and hookup of T874A with Q674Q Used in fan coil applications 106 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR L1 FT L2 CT E HOT SYSTEM SWITCH H
161. See OEM for 225 5 no cooling anticipation replacement D1983 226 Obsolete McQuay part no 066816602 F C See OEM for scaleplate no cooling anticipation used with replacement 067461120 D1991 51 53 Carrier logo Premier White color C scaleplate T874D1165 Set H1 anticipator for total current draw of fan and stage 1 primary replacement has F scaleplate D2007 44 Ultra Zone logo T874D1165 D2023 44 Honeywell logo TRADELINE model Premier White T874D1165 Replacement has F color scaleplate includes locking cover used with scaleplate and is beige Q674A K D2031 82 Qbsolete Honeywell logo no cover used with T874D1165 or Q674E1049 and TG504A1025 used in Y594D1354 Y594D1354 D2049 45 72 Obsolete Carrier Heat Pump System Control logo part T874D1165 Replacement has F 55 66 HHO7AT236 F C scaleplate used with Q674B D scaleplate 184 067406 used in Y594D the thermostat and subbase must be replaced 55 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 8 T874 Cross Reference Y594E1015 Model Fig Trade Model Number No Description Replacement Remarks D2056 44 Obsolete ComStat logo part no 50056 F C T874D1165 Replacement has F scaleplate adjustable interstage on both heating and scaleplate and 2 F fixed
162. T MEANS AND OVERLOAD PROTECTION AS REQUIRED A W1 Y1 JUMPER IS Y TERMINAL REMOVE JUMPER WHEN W1 RELAY IS USED M1230B Fig 227 Schematic and hookup of T874G with Q674F Used in heat pump applications 211 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 4 S L1 L2 HOT Lond FAN SWITCH H1 C1 ANTICIPATOR COMP RELAY O L IN STAT HI PRO E FAN RE SENSOR LED RED H2 ANTICIPATOR FN FALL EM HT ELECTRIC HEAT RELAY M HT ELECTRIC SYSTEM SWITCH Q Q HEAT RELAY EM HT FA Q HEAT O Q C815A OUTDOOR Dna THERMISTOR zm L 12 COOL CHANGEOVER VALVE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A REMOVABLE JUMPER INSTALLED aes Fig 228 Schematic and hookup of T874R with Q674L Used in heat pump applications 60 2485 8 212 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS M TL Oo 0 A L2 H1 ANTICIPATOR FAN COMP RELAY OL IN STAT HI PRO SWITCH 1 AUTO Y 1 TEST ES S TES Q Q H2 ANTICIPATOR ON FH PEPE O O Cj FAN RELAY SERVICE H1 ra D Pore 5 SERVICE RESET s QC SYSTEM FN SWITCH Q Q EM HT ELECTRIC RISE 8
163. T and CHECK Y594G1252 Wiring differences old new LEDs used with T874G used in Y594G Y12O W1 Y X L F1360 167 Obsolete Rheem part 41 20797 17 AUX HEAT Y594G1526 EM HEAT LEDs used with T874G1493 F1378 195 Obsolete Includes EM HEAT and AUX HEAT LEDs Y594G1252 Wiring differences old new used with T874G1501 L1 L changeover in cooling only F1394 139 Obsolete Nepco heat pump HEAT PUMP and AUX T874D1165 Replacement has HEAT OFF HEAT LEDs System AUX HEAT HEAT PUMP 2 Q674B1018 COOL system switching and STAGE HEAT OFF COOL used with T874D1595 no LEDs F1402 169 Obsolete Coleman heat pump two LEDs used with Y594G1633 T874G1576 used in Y594G1377 F1410 170 Used with T874G1246 G1915 used in Y594G1393 Y594G1393 F1428 199 Obsolete Used with T874G1600 used in Y594G1401 Y594G1419 Wiring differences old new jumper W1 Y1 F1436 167 Includes AUX HEAT and EM HEAT LEDs changeover None in heating mode used with T874G1626 used in Y594G1526 F1444 227 Includes AUX HEAT EM HEAT and CHECK LEDs Y594G1419 used with T874G1642 used Y594G1419 F1451 204 Obsolete York part no 27 047700524 one LED and Q674F1012 Wiring differences old new field selectable inserts X2 X X1 B F1477 227 TRADELINE gray color used with T874G1741 Y594G1476 G1824 used in Y594G1476 G1534 F1485 211 Trol A Temp by Honeywell changeover is provided by None See Trol A Temp Trol A
164. T874D1165 Replacement has T874D2049 and Q674B1539 Q674B1034 scaleplate D1388 72 Obsolete Carrier part no 50QE90023101 contains T874D1165 Replacement has F T874D2049 and Q674C1520 Q674C1058 scaleplate D1396 184 Obsolete Carrier part no 50QE90025101 contains T874D1165 Replacement has F T874D2049 and Q674G1153 067491070 01404 55 66 Obsolete Carrier part 50QE90024101 contains T874D1165 Replacement has F T874D2049 and Q674D1164 Q674D1040 scaleplate D1412 82 Obsolete Carrier Weathermaker part no T874D1165 Replacement is beige color 7 209 taupe color contains T874D2064 and Q674E1049 Q674E1445 D1420 82 Obsolete Carrier Zone Perfect part no T874D1165 Replacement is beige color 7 208 taupe color contains T874D2072 and Q674E1049 Q674E1445 D1438 55 66 Obsolete Contains T874D2098 and Q674D1008 T874D1165 Replacement has 2 setpoint Q674D1040 evers D1446 55 66 Obsolete Contains T874D2106 and Q674D1008 T874D1165 Replacement has F Q674D1040 scaleplate and 2 setpoint levers D1453 208 Amana logo part no P1217501F T874D1165 contains T874D2163 and Q674D1172 Q674D1040 D1461 45 Obsolete Amana logo part no P1217701F T874D1942 contains T874D2171 and Q674B1562 Q674B1034 Y594E E1015 72 Obsolete Trane part no 5 015 contains T874B1019 T874E1040 Q674C1009 Q674C1058 Y594F F1022 44 Obsolete
165. T874G1246 or no 6TH117030244A used with Q674F1311 Y594G12522 G1428 160 Obsolete Borg Warner multi logo part no Y594G15672 6 11702424 used with Q674J1027 used in Y594G1229 G1436 58 Obsolete Borg Warner multi logo part no T874D1165 Wiring differences old new 6TH11702724A Q674D1040 Y Y2 O Y1 W W2 jumper W1 Y2 Both the thermostat and subbase must be replaced 59 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks G1444 160 Obsolete ROCA logo scaleplate used with Y594G1567 Replacement has F Q674J1027 scaleplate G1451 155 Obsolete multi logo part no HH641502 used with T874G1246 or Q674F 1212 used in Y594G1245 V594G1252 G1469 194 Obsolete No logo Addison special used with Y594G1252 Wiring differences old new Q674F1345 used Y594G1344 1 W1 Y1 X L G1485 163 Obsolete AAF logo part no 4ELN 7839 F C Y594G13932 night setback or scaleplate 10 F differential between H1 and H2 for night momentary reset switch EAE IUE RESET system switch position 78611G1004 Includes night setback no programmable momentary reset switch G1493 167 Qbsolete Honeywell logo Rheem part no 41 20797 Y594G1526 18 used with Q674F1360
166. TACTOR OVERLOAD PROTECTION AS REQUIRED Fig 172 Schematic and hookup of T874H with Q674B Used in heat pump applications 60 2485 8 178 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH FAN RELAY COOL CHANGEOVER VALVE SYSTEM SWITCH FILTER LED YELLOW COMPRESSOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND CONTACTOR OVERLOAD PROTECTION AS REQUIRED Fig 173 Schematic and hookup of T874H with Q674C Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS HA FAN SWITCH 3 FAN RELAY SYSTEM SWITCH EM HT D D m y LED GREEN COOL CHANGEOVER VALVE RISE 9 Eel A POWER SUPPLY PROVIDE DISCONNECT MEANS AND V9 compressor OVERLOAD PROTECTION AS REQUIRED CONTACTOR A REMOVABLE JUMPER Y HoN o M1403 Fig 174 Schematic and hookup of T874G with Q674J Used in heat pump applications 179 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR COO CHANGEOVER VALVE H2 SYSTEM SWITCH SUPL HT COMPRESSOR CONTACTOR POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD TET PROTECTION AS REQUIRED Fig 175 Schematic and hookup of T874G with Q674J Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS COMPRESSOR CONTACTOR FAN RELAY OPEN NIGHT CLOSED DAY L2 FA
167. THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS EMR4 2R 1 i FALL H1 1R H1 ANTICIPATOR THERMAL SWITCHES FOR HEATING ELEMENTS FAN HTR 1 SWITCH C1 ANTICIPATOR C2 ANTICIPATOR EM HT LED SYSTEM 11 SWITCH o o OFF HJA A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED EM HT 4 LA e A FIELD WIRE JUMPER TO ALLOW HEAT 2 SINGLE SYSTEM TRANSFORMER O LO CO RH HON AUTO C F 4 F 4 A FoR Q674F1048 DELETE C2 STAGE B N E cooLt 4 4 6561516 E RES 12 A 11 12 4 T 3 Fig 149 Schematic and hookup of T874C with Q674F Used in heat pump applications 60 2485 8 160 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 ANTICIPATOR FALL gt H1 H2 ANTICIPATOR C1 ANTICIPATOR Q9 POWER SUPPLY PROVIDE DISCONNECT MEANS A REMOVE FACTORY INSTALLED V VR JUMPER WHEN CONNECTING SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE Ae INTERNAL THERMOSTAT OVERLOAD HI PRESSURE FAN SWITCH SWITCH SWITCH 0 0 AUTO X 5 0 ON 4 LN 9 9 OUTDOOR SUPL ELEC THERMOSTAT HT RELAY 6 957 Eo TIME DELAY FAN RELAY EM HT RELAY CONTACT SYSTEM SWITCH TIME DELAY FAN RELAY OFF EM HEAT LED RED
168. TS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS OUTDOOR DEFROST THERMOSTAT REVERSING RELAY VALVE H1 ANTICIPATOR EM HT RELAY HEAT CONTACT RELAY 2 EM HT RELAY CONTACT OPTIONAL COMPRESSOR FAILURE DEVICE COMPRESSOR CONTACTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M3686 Fig 179 Schematic and hookup of T874N with Q674F Used in heat pump applications 60 2485 8 182 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS L0 12 HOT FAN DELAY A L RELAY lt R 11 R 11 CHANGEOVER VALVE ELEC HT Fr Le RELAY STG 1 O COMPRESSOR R 8 CONTACTOR R 6 OVERLOAD H1 ANTICIPATOR La IN C1 ANTICIPATOR RISE C2 ANTICIPATOR o HEAT PUMP OPERATION R 10 RANDOM START BIOLERLESS R 8 OPERATION R 11 6 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5957 A FILTER LED ON SOME MODELS Fig 180 Schematic and hookup of T874A D with Q674J Used in heat pump applications 183 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENT L1 L2 F FALL HOT FAN SWITCH AUTO REVERSING VALVE COMPRESSOR C1 A FAULT LED RED COMPRESSOR ANTICIPATOR FAUL O A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M185
169. Temp zone panel used with T874G1758 used in Y594G1492 F1501 223 Obsolete Carrier two speed compressor heat pump T8611M2025 Includes night setback used with 87451001 programmable F1519 231 Obsolete Nordyne used with T874G1832 G1840 Y594G12522 Replacement has auto used in Y594G1542 G1559 changeover in cooling mode only F1535 229 Obsolete Lennox heat pump gray color used with Y594G11612 Wiring differences old new 787491857 used Y594G1583 E X2 C B L F F1543 204 Obsolete TRADELINE Q674F1022 Wiring differences old new X2 X X1 B F1550 243 Obsolete Amana part no 10573901 includes two Y594G1633 LEDs used with T874G1899 used in Y594G1591 F1568 155 Obsolete Gray color includes two LEDs used with Y594G1476 1 1 jumper required only T874G1931 F1584 169 TRADELINE includes two LEDs used with Y594G1633 T874G1972 used in Y594G1633 Direct replacement for Coleman Evcon Y594G1377 T874G1576 Q674D1402 Coleman part no 3600 373 F1592 238 Heat Controller Fan AUTO ON System AUX HEAT Y594R1425 E W2 jumper required system HEAT PUMP 2 STAGE HEAT OFF COOL includes switch EM HT HEAT OFF two LEDs used with T874C1844 used in Y594C1413 COOL F1600 169 Obsolete Amana part no 10573903 includes two Y594G1633 Wiring differences old new LEDs used with T874G1980 used in Y594G1641 W3 W2 F1634 139 Standard OEM System AUX HEAT HEAT PUMP Y594G1716 2 STG HEAT OFF COOL in
170. UBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH H1 ANTICIPATOR COMPRESSOR CONTACTOR 2 C1 ANTICIPATOR COMPRESSOR CONTACTOR 1 C2 ANTICIPATOR PowER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 141 Schematic and hookup of T874C with Q674F Used in standard applications THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 2 SYSTEM SWITCH LED RED OFF HA FA VISE 5 Pe gt Q AUTO _F 4 Fd COOL HA FA 0 5 lt COMPRESSOR CONTACTOR 2 zi CONTACTOR 1 JN M5985 RISE A POWER SUPPLY PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 142 Schematic and hookup of T874C D with Q674F Used in standard applications 60 2485 8 156 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL H1 ANTICIPATOR FAN Hi 3 SWITCH COMPRESSOR CONTACTOR FAN RELAY Q AUTO ON 4 J 0 9 1 6 TO SYSTEM A SWITCH H2 Q ANTICIPATOR orr k AK C 5 G ao 2 RISE O O AUX HT RELAY diy A 9 AUX HT LED C1 RED ANTICIPATOR re ae 10 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND COOL 1 OVERLOAD PROTECTION AS REQUIRED CHANGEOVEH VALVE QUS RISE M8378 Fig 143 Schematic and hookup of T874G
171. W Y jumper required night setback G1625 160 York Canada part no 2TH11702524 contains Y594G15672 Replacement has F T874G1964 and Q674J1266 scaleplate G1633 169 TRADELINE contains T874G1972 and Y594G16334 Q674F 1584 direct replacement for Y594G1377 T874G1576 Q674F 1402 Evcon Coleman part no 3600 373 G1641 169 Obsolete Amana part no 10636703 contains Y594G1633 Wiring differences old new T874G1980 and 0674 1600 W3 WA2 G1658 155 Obsolete Tempstar Inter City Products part no Y594G1252 1149910 contains T874G1998 and Q674F1212 G1666 103 Obsolete TRADELINE manual changeover Y594G1674 Replacement has auto contains T874G2004 067411892 direct changeover replacement for Y507J1011 T874G1055 6741 1041 Carrier part no 997290041106 07 171 93421750 G1674 161 TRADELINE automatic changeover contains Y594G1674 T874G2004 and Q674J1274 direct replacement Y507J1003 T874G1055 Q674J1035 Carrier part 997290040106 HHO7AT171 HH93AZ173 61716 155 WaterFurnace logo part TA21H03 contains Y594G1716 T874G2046 and Q674F1667 Y594H H1004 79 Obsolete LSI part no 73033901 contains T8600D2028 H2 is night setback T874H1039 and Q674C1124 H1012 164 Contains T874H1062 and Q674C1249 replaces Y594H1012 T874H1005 Q674C1041 H1020 177 Qbsolete Mammoth part no 71117101 contains Y594H1012 Wiring differences old new T874H1096 and Q674C1330 R1 R R2 L use jumper provided H1038 74 O
172. Y594R1243 Wiring differences old new Y594R1383 R1391 CzX X L W W2 L1546 140 Obsolete Rheem part no 41 20797 21 three LEDs T8611M2025 Includes night setback used with T874W1031 and C815A1005 used in programmable Y594W1022 11553 137 Obsolete Includes three LEDs used with T874R1491 Y594R1615 used in Y594R1326 L1561 121 Obsolete Used with T874C1638 used Y594C1322 Y594C1322 Use Y594C1322 when T874C is used 123 Obsolete Used with T874R Y594R1243 Use Y594R1243 when T874R is used L1579 135 Obsolete Carrier heat pump part no HH93AZ198 Y594R1243 Wiring differences old new SUPL HEAT LED used with T874R1384 HH07AQ170 L1587 168 Used with T874R1616 used in Y594R1425 Y594R1425 L1595 200 Obsolete Miller heat pump used with T874R1624 or Y594R1243 or 201 874 1202 used in 594 1433 Y594R1763 11603 134 Obsolete Used with T874R1632 Y594R1243 L1611 136 Obsolete American Standard heat pump part no Y594R1763 a Both the thermostat and subbase must be replaced 60 2485 8 84 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9 Q674 Subbase Cross Reference Model Number Fig No Description Q674 Trade Replacement L1637 207 Obsolete Carrier heat pump part no HH93AZ195 used with T874J1002 HHO7AT175 or T874J1010 HHO7AT165 Y594J1001 Remarks L1678 209 Trol A Temp by Honeywell gray color used with T874R1707
173. acement has fan switching and HEAT OFF COOL system switching C1355 45 Obsolete Nordyne Miller part no 9122250 T874C1018 contains T874C1695 Q674B1000 Q674B1034 C1363 45 Obsolete Nordyne Intertherm part no 911100001 T874C1018 Wiring differences old new contains T874C1703 Q674B1000 Q674B1075 YzY1 jumper RC RH Y1 W replacement has no SERVICE LED C1371 184 Qbsolete California Economizer contains T874C1018 T874C1802 and Q674G1005 Q674G1070 C1389 237 Qbsolete TRADELINE Premier White color Y594C1389 contains T874C1810 and Q674B1547 C1413 238 Controller Energy Night logo contains Y594R1425 E W2 jumper required system T874C1844 and Q674F1592 EM HT Heat Off Cool C1421 249 Obsolete TRADELINE contains T874C1877 and Y594D1347 Replacement has auto Q674B1554 changeover jumper RH RC C1439 T874C1869 and Q674C1579 None Y594D D1016 44 Obsolete Trane part no 268 0201 2 contains T874D1165 T874D1082 Q674B1018 Q674B1018 D1024 72 part no BAYSTATO10 contains T874D1082 T874D1165 Q674C1009 Q674C1058 D1032 91 Obsolete Trane part no BAYSTATO11 contains T874D1165 T874D1082 067401021 Q674G1070 D1040 46 Amana part no P68535 19R contains T874D1082 T874D1165 Q674B1075 Q674B1075 D1057 55 66 Obsolete Trane part no 5 007 contains T874D1165 T874D1082 Q674D1008 Q674D1040 D1149 46 Obsolete Amana part P68535 20C contains T874D1165 T874D1322 Q674B1075 Q6
174. aleplate includes AAF insert replacement T874N Heat pump model 2 stage heat 1 stage cool plus changeover changeover in heat mode N1008 178 QObsolete Williamson logo used with Q674F1196 used T874N1016 in Y594N1007 N1016 178 Honeywell Heat Pump Thermostat logo used with T874N1016 Q674F 1220 N1024 179 Bard logo H1 and C1 anticipation fixed used with None See subbase description for 217 0674 1261 replacement information Both the thermostat and subbase must be replaced 60 2485 8 64 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks N1040 179 Obsolete Honeywell logo H1 and C1 anticipation fixed None used with Q674F1261 used in Y594N1015 N1057 178 Obsolete Intertherm logo part no 9111882 used with T874N1016 Q674F1220 used in Y594N1023 N1065 178 Obsolete Miller logo Nordyne part no 9122240 used T874N1016 with Q674F1220 used in Y594N1031 T874P Heat pump model 2 stage heat 1 stage cool automatic in cool P1006 57 78 Obsolete McQuay logo part no 860 442725B 00 8 F None See subbase description for 4 4 C interstage differential between H1 and H2 used replacement information with Q674B1273 C1140 P1014 78 Obsolete Friedrich Climate Master logo F C T8600D2028 Wiring differences
175. ana logo used with Q674L1249 and W89 Y594R1243 R1202 201 Qbsolete Intertherm logo part no 9111871 used with Y594R1672 Wiring differences old new Q674L1264 or 067411595 used in Y594R1185 W2 W Z no connection K X W G W1 H X B R1210 101 Obsolete Roca logo C scaleplate used with Y594R1243 Wiring differences old new Q674L1017 W W2 X L R1228 120 Obsolete York logo part no 2TH11702524A C Y594R1672 scaleplate used with Q674L1272 and C815A1005 used in Y594R1144 R1236 115 Obsolete Williamson logo includes Allen wrench and T874R1152 screws to lock cover used with Q674L1348 R1244 115 Obsolete Westinghouse logo used with 067411314 T874R1152 and W89 Y594R1243 R1251 120 Obsolete York logo part no 2TH11702324A H2 Y594R1672 anticipator is fixed used with Q674L1272 and C815A1039 R1269 122 Obsolete Fedders multi logo part no Y594R1615 Wiring differences old new THTX 120 HEHB 88 58 00540 001 used with K E C X W1 B 7 Q674L1066 used in Y594R1037 R1285 123 Obsolete Honeywell logo Rheem part no 41 20796 Y594R1243 15 used with 067411157 R1301 113 Obsolete Comfortmaker logo part no 1505 714 used Y594R1243 Wiring differences old new 1 Both the thermostat and subbase must be replaced 60 2485 8 66 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference
176. ard Terminal Alternate Designations or Designation Customer Specials Typical Connection B Heating damper motor changeover valve E K Emergency heat relay G F Fan relay coil L System monitor R Cooling damper motor changeover valve R V Power connection to transformer internally connected for heating and cooling RC Power connection to cooling transformer RH Power connection to heating transformer W1 H1 R3 Stage 1 heating control W2 H2 Y R4 Stage 2 heating control W3 Stage 3 heating control Y1 C1 M Stage 1 cooling control Y2 C2 Stage 2 cooling control Y3 Stage 3 cooling control X X1 X2 C Clogged filter switch or common connection T A Outdoor thermistor L C H HSII control panel P Defrost Momentary circuit changeover A 1 2 2 C L LEDs Other terminal designations can be used that are not listed on this table Refer to the hookup drawing and internal schematic for exact connections 5 W3 controls the auxiliary heat like W2 and allows adding additional stages of auxiliary heat with outdoor thermostats while maintaining the proper second stage anticipation 9 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 5 Terminal Designations Standard Terminal Alternate Designations or Designation Customer Specials Typical Connection T External temperature readout T relay R1 R2 LO and HI speed fan relays RS Cooling contactor Y M Compressor contactor
177. as F scaleplate D1157 51 53 Carrier logo part no HHO7AT172 C scaleplate used T874D1165 Replacement has F 146 with Q674B or Q674F1030 F1063 scaleplate set H1 anticipator for current draw of fan and stage 1 heat primary D1165 82 Honeywell logo SUPER TRADELINE model includes 787401165 Allen wrench and screws to lock cover field adjustable range stops field adjustable locking levers D1173 51 53 Trane logo part no BAY28X183 heat anticipator factory 7874011652 Set H1 anticipator for current set at 0 4A draw of fan and stage 1 heat primary D1181 51 53 Obsolete General Electric logo locking cover includes 87401165 Set H1 anticipator for current Allen wrench and screws to lock cover and range stops draw of fan and stage 1 heat set at 72 F max heat and 78 F min cool primary D1199 44 Obsolete Lennox logo part no 13F0701 C scaleplate 787401165 Replacement has F scaleplate D1207 114 Qbsolete Lennox logo part no 24F5201 used with T8611M2025 Wiring differences old new V VR R Y W3 R O MzY M2 Y2 W2 F G jumper Y2 W2 no outdoor reset needed use only one system transformer Both the thermostat and subbase must be replaced 60 2485 8 52 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replac
178. ation G1279 58 157 Obsolete Bryant logo used with Q674D1032 F1253 None See subbase description for replacement information G1287 58 157 Obsolete Wesco logo used with 067401032 F1253 None See subbase description for replacement information G1295 58 Obsolete York logo part no 2TH11702724A used with T874D1165 Wiring differences old new Q674D1032 Q674D1040 2 OzY1 W W2 jumper W1 Y2 G1345 160 Qbsolete York logo part no 2TH11702624A C Y594G1575 scaleplate used with Q674J1027 G1352 73 Obsolete Command Aire logo 12 F differential Y594H10122 Wiring differences old new between H1 and H2 for night setback used with 1 Y2 Y L R R none R Q674C1066 L jumper required no night setback T8600D1004 Wiring differences old new programmable Y2 Y L RH RC RH jumper required includes night setback G1378 79 Obsolete Mammoth logo H2 anticipator factory set at Y594H1012 Wiring differences old new 0 8A 12 F differential between H1 and H2 for night R1 none R2 L R L jumper setback F C scaleplate used with Q674C1124 used required no night setback in Y594G1294 T8090A1007 Includes night setback W Y Q682A10382 jumper required programmable G1402 129 Qbsolete York part no 2TH11702824A meets DoD Y594R14252 Wiring differences old new specifications used with Q674L1363 W W2 X E B X jumper Y W1 G1410 155 Qbsolete Borg Warner multi logo part
179. ator for operation in heat and cool combined load of heat relay and fan relay B1202 Lennox no P 8 11223 heat pump circuit used Y594R1243 Wiring differences old new with T872R1040 V VR R M Y Y W2 F G R O B1210 None B1228 General Electric no BAY28X137 isolated Q674B1018 G terminal B1236 Carrier no HH 93AZ079 RC RH jumper Q674B1034 RC RH jumper LED cannot be LOCKOUT LED indicates compressor lockout provided in TRADELINE model Switch activated B1244 Friedrich heat mode changeover used with T874C1018 Wiring differences old new T872R1115 Q674B1034 connection RC RH and W1 Y1 jumpers required B1251 Used with T872W1035 and C815A1043 Y594W1014 a When replacing a T872 Thermostat and 0672 Subbase always replace both the thermostat and subbase 39 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 7 0672 0674 Subbase Cross Reference Q674 Trade Model Number Description Replacement Remarks B1269 Whalen Hi Lo fan switch constant fan in heat None and cool system switch positions used with T872C1574 B1277 Square D no HCB 5 Q674B1034 B1285 Wards RC RH and F W3 jumpers used with Gas Furnace T872C1673 T874C1018 Q674B1034 Electric Furnace Adjust anticipator faster for correct T874C1018 performance Q674B1075 B1293 Lennox no 41C96 used with T872C1673 Same as Q672B1285
180. ator set at 0 4A T874C1018 C1020 72 78 22 26 stop locking cover no T874C1141 Use T874C1141 for Dept of thermometer 42 88 F 6 31 C setpoint range Defense DoD application C1038 TRADELINE T874C1018 C1046 American Standard logo T874C1018 C1053 Friedrich logo T874C1018 C1061 Lennox logo no P 8 8896 T874C1018 C1079 Westinghouse logo stage 1 heat anticipator set at T874C1018 0 75A stage 2 anticipator set at 1 2A C1087 Fast cycle performance on both heat stages T874C1018 Adjust anticipator faster for correct anticipator range 0 12 0 6A performance C1095 Payne logo no 0 1 0 175 T874C1018 When replacing a T872 Thermostat and Q672 Subbase always replace both the thermostat and the subbase 60 2485 8 30 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6 T872 T874 Thermostat Cross Reference T874 Trade Model Number Description Replacement Remarks C1103 Amana logo anticipator set at 1 2A T874C1018 C1111 Airtemp Chrysler logo T874C1018 C1129 Day and Night logo no 0 1 0 174 T874C1018 C1137 Fast cycle performance on both heat stages T874C1018 Adjust anticipator faster for correct performance C1145 Rheem logo T874C1018 C1152 Ruud logo T874C1018 C1160 Climatrol logo T874C1018 C1178 Wesco logo T874C1018 C1186 Sears logo T874C1018 C1194 First Co logo T874C1018 C
181. ays used with Q672F 1158 Y594G1252 G1091 Lennox logo same as T872G1026 except meets DoD specs See subbase description for replacement information G1109 Tappan logo no 080 13708 52 adjustable anticipator stage 1 heat and cool changeover with cooling used with Q672F 1117 Y594G1252 Wiring differences old new C X G1117 Changeover used with Q672F 1125 Y594G1252 Wiring differences old new C X G1125 Lennox logo no 63A0401 Celsius scale isolated auxiliary heat power circuit fast cycle anticipator stage 2 heat None G1133 Rheem logo no RXMT B71 adjustable anticipator stage 2 heat fixed anticipator stage 1 heat and cool changeover with cooling includes shunt to bypass stage 2 anticipator with auxiliary heat relays used with Q672F 1158 F1232 Y594G1252 G1141 Ruud logo adjustable anticipator stage 2 heat fixed anticipator stage 1 heat and cool changeover with cooling includes shunt to bypass stage 2 anticipator with auxiliary heat relays used with Q672F1158 Y594G1252 G1158 Carrier logo same as T872G1075 Except DoD styling See subbase description for replacement information G1166 BDP used with Q672F1125 Y594G1252 Wiring differences old new G1174 BDP used with Q672F1125 Y594G1252 Wiring differences old new G1182 Carrier no HHO7AT071C Celsius scale used with Q672L 1052 J105
182. bsolete Carrier part no 50QE90019101 contains Y594H1012 Wiring differences old new T874H1161 and Q674C1496 X120 Y2 Y L R jumper required H1046 172 Obsolete Carrier part no 50QE90026101 contains T874A1130 Wiring differences old new T874H1153 and Q674B1406 0674810752 YzY1 Wh1 Y1 jumper required replacement has no LEDs H1053 173 Obsolete Carrier part no 50QE90027101 contains Y594H1012 Wiring differences old new T874H1153 and Q674C1322 2 Y594J J1001 241 Obsolete TRADELINE manual changeover Recontrol contains T874J1069 and Q674L1900 direct replacement for T874J1002 or 874 1028 used with Q674L1074 Q674L1637 HHO7AT175 or 7 165 used with HH93AZ186 or HH93AZ195 T8511G1021 a Both the thermostat and subbase must be replaced 91 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10 Y594 Cross Reference T874R1426 and Q674L1496 Model Fig Trade Model Number No Description Replacement Remarks J1019 244 Obsolete TRADELINE automatic changeover Recontrol contains T874J1069 and Q674J1282 direct T8511G1021 replacement for T874J1002 or T874J1028 used with Q674J1068 or Q674J1159 HHO7AT175 or HH07AT165 used with HH93AZ183 or HH93AZ196 Y594N N1007 178 Qbsolete Williamson part no 75 189 contains T874N1016 T874N1008 Q674F 1196 Q674F 1
183. c and hookup of T874D with Q674F Used in standard applications 195 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER H1 ANTICIPATOR ro H1 F gt COMPRESSOR FALL CONTACTOR FAN SWITCH v3 oN o Q O AUTO Ft O 8 SYSTEM SWITCH RISE TS 90 Q OFF FH 4 5 5 9 9 C1 ANTICIPATOR 9 FS A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M2983 A LEDS ON SOME MODELS Fig 205 Schematic and hookup of T874H with Q674C Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS COMPRESSOR CONTACTOR FAN SWITCH grs H SO b H1 ANTICIPATOR H ANTICIPATOR d SUPL HT LED RED SYSTEM SWITCH C1 ANTICIPATOR OFF FA FX o O amp F IN COOL RISE co A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD we M2984 PROTECTION AS REQUIRED Fig 206 Schematic and hookup of T874J with Q674J Used in heat pump applications 60 2485 8 196 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS B NND FAN SWITCH CES H1 ANTICIPATOR O O COMPRESSOR CONTACTOR OO SUPL HT LED RED SYSTEM SWITCH COOL CHANGEOVER Ci co A POWER SUPPLY PROVIDE DISCONN
184. cQuay logo part no 61202501 12 F T8611M2025 Includes night setback interstage differential between H2 and H3 for night programmable setback used with Q674C1363 W1056 220 Obsolete McQuay Snyder General logo part no See OEM for 1202501 12 differential between H2 and H3 for night replacement setback used with Q674C1363 61202502 W1064 220 Obsolete AAF Snyder General logo part no See OEM for 066804408 12 F differential between H2 and H3 for replacement night setback used with Q674C1363 66804408 W1072 140 Qbsolete Honeywell logo Inter City Products used T8611M2025 night setback Y594W1030 programmable W1080 220 McQuay logo part 073318901 Premier White None color 12 F differential between H2 and H3 for night setback W1106 247 Obsolete Addison logo part no 843 277 F C T8611M2025 scaleplate used with Q674L1934 in Y594W1055 T874Y Heat pump model 2 stage heat 2 stage cool heat or cool auto changeover Y1005 210 Obsolete Mammoth Water Source Heat Pump logo See OEM for used with Q674E1353 used in Y594Y1004 replacement Y1013 248 Obsolete WaterFurnace logo part no TA21H03 See OEM for Premier White color F C scaleplate used with replacement Q674F1675 32003081 Both the thermostat and subbase must be replaced 60 2485 8 70 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9 Q674 Subbase Cross Reference
185. cement Remarks E1081 44 logo part no 28 186 scaleplate T874E1016 Replacement has F scaleplate E1099 44 Obsolete Lennox logo part no 13F1001 C scaleplate T874E1016 Replacement has F scaleplate E1107 44 Honeywell logo scaleplate T874E1016 Replacement has F scaleplate E1123 44 J Obsolete Amana logo part no D68535 4 T874E1016 E1149 44 Obsolete York logo part no 27 04701724 T874E1016 E1156 44 Obsolete Borg Warner multi logo part no T874E1016 6 04701724 1164 44 Obsolete E Juffali amp Bros logo T874E1016 E1206 44 Obsolete Trane logo T874E1016 E1230 44 Obsolete Climar logo T874E1016 T874F 2 stage heat O stage cool F1007 44 Honeywell logo T874F1015 F1015 44 Honeywell logo TRADELINE model includes Allen T874F1015 wrench and screws to lock cover field adjustable locking levers F1023 44 J Obsolete Lennox logo part no 13F1101 T874F1015 F1031 44 J Obsolete Honeywell logo C scaleplate used with T874F1015 Replacement has F 40003440 001 wallplate used in Y594F1022 scaleplate F1049 44 Obsolete Lennox logo scaleplate T874F1015 Replacement has F scaleplate F1056 55 ObDsolete Honeywell logo stages 1 and 2 heat None 66 electrically isolated used with Q674D1008 F1072 44 Qbsolete Wesco logo heat anticipator factory set at T874F1015 0 8A F1098 189 Lennox logo used with Q674D1008 to control T8
186. ckets Short circuit and potential equipment damage can result Mount Thermostat 1 Remove the thermostat cover by pulling the bottom edge of the cover away from the base until it snaps free of the cover clip NOTE The cover is hinged at the top and must be removed by pulling up at the bottom 2 Carefully remove and discard the polystyrene packing insert that protects the mercury switches during ship ment 3 If LED indication EM HT CHECK etc is to be used with the Q674 Subbase install the preprinted insert under the thermostat setpoint scale To install push both thermostat setpoint levers to the far ends of the thermostat Use index finger to gently pull out the plastic setpoint scale about 1 4 in 6 mm Position the desired preprinted insert in the space above the LED lights Reposition setpoint levers 4 Turn over the thermostat base and note the spring fin gers that engage the subbase contacts Make sure the spring fingers are not bent flat preventing proper elec trical contact with the subbase 5 Setthe heat anticipator indicator s to the respective current setting of each stage See Set The Heat Antici pator section 6 If the thermostat provides optional locking cover assem bly start the Allen locking screws in the cover with the wrench provided See Fig 10 7T Note the two tabs along the top inside edge of the ther mostat base The tabs fit into corresponding slots on top of the subbase Mount the t
187. cludes two LEDs used with T874D2155 Both the thermostat and subbase must be replaced 79 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 9 Q674 Subbase Cross Reference AUX HEAT LEDs used with T874G1071 Model Fig Q674 Trade Number No Description Replacement Remarks F1667 155 WaterFurnace logo part no TA21H03 System OFF Y594G1716 AUTO HEAT EM HT includes two LEDs used with T874G2046 F1675 248 Obsolete WaterFurnace logo part no TA21H03 See OEM for includes four LEDs replacement Q674G System OFF AUTO Fan None G1005 184 Obsolete Used in Y594F1063 Q674G1070 G1013 186 Obsolete Climate Control used with 787401298 See OEM for replacement G1021 91 Obsolete Includes O and B terminals used with Q674G1070 T874A F Q T874D1082 used Y594D1032 G1047 92 Obsolete Used with T874C1018 C1125 T8611 G1054 188 Obsolete Singer part 0200 5963 used with See OEM for T874D1298 replacement G1062 232 Obsolete Singer used with 787401298 See OEM for replacement G1070 91 TRADELINE Q674G1070 G1088 92 Obsolete LSI Mammoth part no 71120201 used with See OEM for T874C replacement G1096 90 Obsolete Climate Control part no 02005958 used See OEM for with T874D1439 D1447 replacement G1104 94 Obsolete McQuay part no 0200 5963 two LEDs See OEM for used
188. cription Replacement Remarks B1240 234 Obsolete Northrup heat pump AUX HEAT LED used Y594G1252 Wiring differences old new with T874G1139 1 2 W1 W2 EM HT system switch position is not operational B1257 56 Obsolete LSI Mammoth RESET LED automatic fan Q674B1075 Replacement has no LED operation in heat and cool modes used with 874 1471 used in Y594C1314 B1273 57 Obsolete McQuay part no 860 442727B 00 System T874A1036 Wiring differences old new OVERRIDE HEAT OFF COOL used with 874 1006 Q674B1075 Y Y1 L R W O jumper Y1 W1 no night setback T8600D2028 Wiring differences old new programmable L R WzO W Y jumper required night setback B1281 191 Obsolete Carrier 42QH400103 System HEAT See OEM for OFF COOL Fan LOW HI CONT international replacement symbols on switches used with T874R1319 B1299 46 Obsolete Heil Quaker part no HQ521714HW Q674B1075 B1307 62 Obsolete Includes two LEDs used with T874F1122 T874F1015 Replacement has LEDs Q674D1040 B1315 68 Obsolete Friedrich part no AQ5215 OVERRIDE and T8600D2028 Wiring differences old new SERVICE LEDs used with T874P1022 P1030 programmable L R WzO W Y jumper required set dual fuel switch to electric heat night setback B1331 65 Obsolete Includes two LEDs used with 874 1002 Q674B1034 Replacement has no LEDs B1349 67 Obsolete Goettl part no 372072 used with Y594R1300 T874R1541 B1356
189. ctions required and the relative complexity require a versatile and economical method of control There are several interlocks and indication functions that would be more difficult and expensive to wire in line voltage circuits Low voltage controls have the precision and flexibility needed The thermostat used is a low voltage device that has good temperature sensitivity and several manual and automatic switching capabilities Two Stage Thermostat In most installations the heat pump itself requires auxiliary heat usually in the form of electric strip heaters to carry the building heating load at design conditions Since the heat pump is usually more efficient the control strategy is to run the heat pump whenever possible and the auxiliary heat only when necessary during very cold weather or if the heat pump fails Usually the auxiliary heat is used only below the balance point temperature at which the heat pump cannot handle heating load by itself A two stage thermostat makes this possible The two stages make sequentially as the temperature drops There is a degree or two between stages so that the second stage the 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES one controlling the auxiliary heat makes only when the heat pump alone cannot handle the load That is how the strategy of using the most economical heat first is implemented Cycling Rate Normally thermostat anticipation is set to cycle a fossi
190. d with Q674L1504 used in Y594R1623 R1566 130 Obsolete Honeywell logo used with 067411538 and Y594R1763 Wiring differences old new C815A1005 used in Y594R1375 W1 W 2 X F C B Both the thermostat and subbase must be replaced 67 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks R1574 132 Obsolete Comfortmaker logo part no 1505739 used Y594R1243 Wiring differences old new with 067411538 used in Y594R1383 C X X L W W2 R1582 132 Obsolete Arcoaire logo part no 150739 used with Y594R1243 Wiring differences old new Q674L1538 used in Y594R1391 C X X L W W2 R1590 115 Obsolete Refac logo used with 067411207 T874R1152 has F Y594R1243 scaleplate R1608 119 Obsolete Honeywell logo Intertherm heat pump used 594 17632 Wiring differences old new with Q674L1264 used in Y594R1409 W2 W Z F K X2 W1 0 R1616 168 Honeywell logo SUPER TRADELINE model used Y594R1425 with Q674L1587 used in Y594R1425 R1624 200 Obsolete Honeywell logo used with 067411595 used Y594R1243 Wiring differences old new in Y594R1433 X B Z F W2 W K X2 W1 0 R1632 134 Obsolete Honeywell logo used with 067411603 Y594R1243 R1640 115 Ob
191. diagram A letter code is located near each terminal for identification Typical terminal desig nation and wiring connections are listed in Table 5 The terminal barrier permits straight or wraparound wiring connection See Fig 7 The subbase can require one or more jumpers that may or may not be factory supplied See Fig 8 and the wiring diagrams for specific terminals to be jumpered FOR STRAIGHT INSERTION STRIP 5 16 IN 8 MM FOR WRAPAROUND STRIP 7 16 IN 11 MM BARRIER 7 SUBBASE TERMINAL SCREW M928 Fig 7 Barrier configuration CAUTION Equipment Damage Hazard Never install more than one wire per terminal unless using factory supplied jumper with spade terminal 2 Firmly tighten each terminal screw 3 Fit wires as close as possible to the subbase Push excess wire back into the hole 4 Plug hole with nonflammable insulation to prevent drafts from affecting the thermostat T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES JUMPER WIRE SUPPLIED WITH SOME MODELS NTwo ADJACENT TERMINALS SHOWN JUMPERED ARE FOR EXAMPLE ONLY COMPARE WIRING DIAGRAM AND SUBBASE TO IDENTIFY TERMINALS TO BE JUMPERED M5899 Fig 8 Jumper adjacent terminals for special system hookup using stripped wire 3 4 in 19 mm For nonadjacent terminals and using jumper wire supplied with subbase Table 5 Terminal Designations Stand
192. e Carrier part no HH93AZ180 factory Q674B1018 installed RC RH jumper B1125 53 Obpsolete York part no 2 04700324 used with Q674B1075 Jumper RC RH replacement T874D1041 has no LOCKOUT LED B1133 48 Obsolete Includes FILTER LED used with Q674B1018 T874D1082 used in Y594D1156 B1141 51 part no BAY28X185 automatic fan operation in Q674B1075 Set T874 H1 anticipator for heat and cool mode combined load of heat relay and fan relay B1158 50 Obsolete Used with T874G1071 T874C1018 W1 Y1 and RH RC jumpers Q674B1018 required B1166 249 Carrier part no HH93AZ179 factory installed RC RH Y594C1421 or Replacement only requires jumper LOCKOUT LED used with T874C1075 0674810752 transformer and has no 7 170 LOCKOUT LED B1190 52 Obsolete Wards special factory installed RH RC and Gas Furnace F W3 jumpers used with T874C1372 Q674B1034 Electric Furnace Q674B1075 B1208 187 Obsolete Used with T874C1422 None B1216 54 Used with T874W1015 and C815A1005 used in Q674B1216 Y594W1014 B1224 49 Obsolete Lennox part no 25F7301 four LEDs used Q674B1034 Replacement has LEDs with T874C1430 Both the thermostat and subbase must be replaced 71 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 9 Q674 Subbase Cross Reference Model Fig Q674 Trade Number No Des
193. e Charts refer to the following instructions 1 Locate and identify the existing thermostat and subbase model 2 Refer to the Model Number column to find the model that matches the existing thermostat and subbase 3 The Description column identifies certain characteristics of the existing device 4 The Trade Replacement column identifies the correct replacement device 5 The Remarks column lists any characteristics or adjust ments to be made on the Trade replacement model 6 TheFig No column lists the wiring hookup used for the specific model number The wiring diagrams follow the Cross Reference section 7 Referto the circuit illustration that corresponds with the appropriate number This figure illustrates the internal electric circuit for the desired model number Table 6 T872 T874 Thermostat Cross Reference T874 Trade Model Number Description Replacement Remarks T872A 1 stage heat 1 stage cool A1006 Standard OEM T874A1036 A1014 72 78 F 22 26 stop locking cover no T874A1010 Use T874A1176 for Dept of thermometer Defense DoD application A1022 Heat anticipator set at 0 45A T874A1036 A1030 0 4A heat anticipator setting T874A1036 A1048 TRADELINE T874A1036 A1055 AAF logo locking cover T874A1036 A1063 Climatrol logo T874A1036 A1071 Lennox logo 0 5A heat anticipator setting T874A1036 A1089 Melco logo T874A1036 A1097 Wes
194. e models to improve thermal performance Contents Applications eno OR inia i 1 Featur S wor ERR Cac 1 Specifications 2 Ordering Information 2 Installation 7 Settings ee 11 Checkout ES 13 Calibration 2 222 22 4 smaa tomite 14 Understanding 14 Operation lt I ge 21 Cross Reference 29 Wiring Diagrams 96 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES SPECIFICATIONS IMPORTANT The specifications given in this publication do not include normal manufacturing tolerances Therefore this unit may not exactly match the listed specifica tions This product is tested and calibrated under closely controlled conditions and some minor differ ences in performance can be expected if those con ditions are changed Super Tradeline Tradeline Models SUPER TRADELINE controls offer features not available on TRADELINE or standard models and are designed to replace a wide range of Honeywell and competitive controls TRADELINE models are selected and packaged to provide ease of stocking ease of handling and maximum replacement value Specifications of SUPER TRADELINE and TRADELINE contr
195. eat anticipator factory set at 0 10A used with Q674E1379 replacement aBoth the thermostat and subbase must be replaced 47 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 8 T874 Cross Reference Q674A E Model Fig Trade Model Number No Description Replacement Remarks A1481 44 Obsolete Honeywell logo Carrier part no HH621602 T874A1036 includes locking cover and non adjustable range stops set at 72 F max heat and 78 F min cool A1507 44 Obsolete Climate Tel logo includes Allen wrench and T874A1176 screws to lock cover and non adjustable range stops set at 72 F max heat and 78 F min cool A1523 224 Obsolete AAF Snyder General logo part no See OEM for 225 066804404 F C scaleplate no cooling anticipation replacement used with Q674E1312 C1298 A1549 224 Obsolete McQuay logo part no 066816601 no cooling See OEM for 225 anticipation used with Q674E1312 C1298 replacement A1556 51 53 Carrier logo part no HHO7AT164 W C scaleplate T874A1036 Replacement has F Premier White color includes Allen wrench and scaleplate replacement is screws to lock cover used with Q674B beige A1572 224 Obsolete McQuay logo part no 066816611 Premier See OEM for 225 White color F C scaleplate no cooling anticipation replacement A1580 91 California
196. ed can no longer handle the cooling load This reduces cycling rate and improves capacity 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Defrost Control In some regions during half or more of the heating season the outdoor coil operates below 32 F 0 C Frost or ice builds up on the outdoor coil of a heat pump similarly to the frost buildup in a household refrigerator Eventually this accumulation of ice interferes with efficient heat transfer from the outdoor air to the coil and refrigerant Defrosting is occasionally required to remove this ice and restore the heat pump ability to absorb heat from the air Defrosting A heat pump defrosts its outdoor coil by temporarily switching to the cooling mode which causes hot gas from the compressor to be directed to the outdoor coil instead of to the indoor coil so the heat pump is taking heat from the home to warm up the outdoor coil Defrosting is the greatest detriment to heat pump efficiency Defrost Control Functions Besides changing over to the cooling mode defrosting requires several more control initiated actions that follow OUTDOOR FAN When defrosting has begun it is standard practice to turn off the outdoor fan to speed up the melting process A separate defrost relay is required to control that fan See Fig 37 Other contacts can be needed on the defrost relay to power the changeover valve or power part of the auxiliary heat COMPRESSOR MOTOR
197. ed with 0672 1265 Y594G1252 Wiring differences old new C X G1299 York logo meets DoD specs used with Y594G1567 Q672L1177 G1307 Carrier no 38EQ1900 Celsius used with See subbase description for Q672J1054 L1052 replacement information G1315 Luxaire special stage 2 heat anticipator set to Y594G1252 1 2A used with Q672F 1281 G1323 Lennox special used with Q672L1201 and None C815A1013 G1331 York used with Q672J1021 Y594G1567 Wiring differences old new X X1 L X2 W E Y1 W1 and Y2 W2 jumpers required G1356 Westinghouse used with Q672L1219 T874D1165 Wiring differences old new Q674F 1022 X X1 L X2 W E Y1 W1 and Y2 W2 jumpers required G1364 York used with Q672D1077 None G1372 Tappan Janitrol logo no B 13708 521 Y594G1252 Wiring differences old new C X used with Q672F 1117 G1398 York logo no 025 21454C used with Q672J1021 Y594G1567 T872H Heat pump model 1 stage heat 1 stage cool 1 stage changeover H1009 logo fixed anticipator stage 1 heat 594 1012 and cool changeover with cooling used with Q672C1086 H1017 Friedrich logo Y594H1012 H1025 Friedrich logo Celsius Y594H1012 T872M 1 stage heat 1 stage cool with stage 2 heat factory set at 60 F 16 C M1003 Standard OEM used with Q672D and external T874C1125 T874C1125 has 12 F 6 7 C switching means differential between stage 1 and stage 2 heat T872N Heat pump model 2 stage heat 1 stage cool plus changeover c
198. ement Remarks D1215 44 Qbsolete Friedrich Climate Master logo part no T874D1165 Replacement has F AT5415 scaleplate scaleplate D1223 44 Honeywell logo Honeywell Canada TRADELINE model 787401165 Replacement has F Celsius scale scaleplate D1231 44 Obsolete Honeywell logo 12 F 7 C differential T874D1165 Replacement has 2 F between H1 and H2 differential between H1 and H2 D1249 44 Qbsolete Fedders special T874D1165 D1256 44 Obsolete Climatrol special T874D1165 D1264 107 Qbsolete Carrier Heat Pump System Control logo part See OEM for HH07AT173 used with Q674L1116 HH93AZ171 replacement D1272 51 53 Obsolete Carrier logo part no HHO7AT162 03 7874011652 Replacement thermostat has scaleplate used with Q674B F scaleplate set H1 anticipator for current draw of fan and stage 1 heat primary D1280 44 Obsolete Command Aire logo T874D1165 D1298 90 232 Obsolete Singer special scaleplate controls two See OEM for separate heat cool circuits used with Q674D or replacement 067461054 91062 01306 90 186 Obsolete Trane special part no 02005949 controls See OEM for two separate heat cool circuits used with Q674G1013 replacement D1314 44 J Obsolete McQuay logo part no 02005941 12 F T874D1165 Replacement has F 6 6 C differential between H1 and H2 scaleplate 2 F differential between H1 and H2 D1322 46 Obsolete Amana logo part no
199. energized with cooling or with heating a heat pump system can be controlled by the appropriate T874 Multistage Thermostat T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Low Temperature Lockouts Some manufacturers of heat pumps have previously controlled their units so the compressor was locked out below a specified outdoor temperature This was done because of the stress placed on the compressor by the very cold temperatures and the fact that efficiency drops off at low temperatures Other manufacturers say that although efficiency is low at cold temperatures the problem of starting the cold compressor is the most critical point It is more important to keep the compressor running than to shut it off and try to restart it when the temperature warms up to 10 F 12 C Also the crankcase heater which can run only when the compressor is off compensates for the lower compressor efficiency So it is equitable to let the heat pump run even with a coefficient of performance COP slightly less than one rather than to turn it off and have to run the crankcase heater NOTE To determine the COP of a heat pump use the fol lowing formula COP Btu Out Btu we pay for or Btuh Capacity Unit Wattage x 3 413 Btu Watt Another factor favoring this control strategy is that newer heat pump designs maintain a level of efficiency even at outdoor temperatures well below zero Some brands do not reach 1 0 COP until 25 F 32 C Virt
200. ent and fan should stop Fan Move the system switch to COOL OFF or AUTO If necessary position both temperature setting levers so that the heating and cooling equipment are off Move the fan switch to ON or CONT The fan should run continuously When the fan Switch is in AUTO LO MED or HI position fan operation is controlled by the heating or cooling system Outdoor Reset Thermistor Where Applicable If the system is supplied with a thermistor it must be used if not used thermostat performance deviates radically from proper operation The proper thermistor operation must be verified to ensure the correct operation of the thermostat Check thermistor operations as follows 1 Disconnect the T wire on the subbase 2 Use an ohmmeter to measure resistance between the T wire and the A subbase terminal 3 Take outdoor temperature at thermistor location and find the correct thermistor resistance on the Fig 14 chart 4 Ifthe resistance measured in step 2 and the calculated resistance in step 3 vary by more than 15 percent the thermistor requires replacement Contact Honeywell or installing dealer for replacement packaged outdoor ther mistor part no C815A1005 X4 C815A THERMISTOR RESISTANCE 400 ohms 10 AT 77 F 25 1 20 0 20 40 60 80 100 120 140 TEMPERATURE OF THERMISTOR M1590A Fig 14 Thermistor resistance chart CALIBRATION Thermostat T87
201. eration of system See heating system instructions for CHECK LED meaning e EM HT LED lights when the emergency heat is operating e SUPL HT LED lights when the supplemental heat is operating LOCKOUT LED lights when the system is shut down and needs maintenance AUXILIARY HEAT LED lights when the auxiliary heat is operating SERVICE or MALFUNCTION LED can have several meanings Consult heating system instructions LEDs cannot be replaced or added in the field EM AU HEAT FILTER SERV HEAT M5830 Fig 30 T874 Q674 LED location Restricted Setpoint DoD The Department of Defense DoD models are equipped with a restricted setpoint feature for fuel efficiency Fixed stops are factory set so setpoint levers cannot be set above 72 F 22 on heating or below 78 F 26 on cooling Applications The T874 Q674 can be applied to standard residential systems for automatic or manual changeover to commercial rooftop applications or to heat pump applications Changeover on Standard Residential Systems In a standard residential heating cooling circuit changeover between heating and cooling can be done either automatically or manually Automatic changeover is done by an AUTO position on the subbase system switch See Fig 31 When the switch is in the AUTO position the thermostat automatically changes between heat and cool modes depending on the indoor temperature T874 MULTISTAGE THERMOSTATS AND Q
202. fast cycle performance on both heat T874C1018 M839 draws 0 724 set adjustable stages heat anticipator to setting of 0 9A for proper cycle rate F1043 York logo locking cover used with M839 T874C1018 F1050 Raehco logo T874F1015 F1068 Fast cycle performance on both heat stages T874C1018 F1076 Wesco logo T874F1015 F1084 Lennox logo T874F1015 F1092 Auto Gas logo T874F1015 F1100 Celsius scale T874F1015 F1118 Lennox logo Celsius scale T874F1015 F1126 Stages 1 and 2 heat electrically isolated used with None Q672D1002 F1134 Square D logo HCD 4 T874F1015 F1159 Wesco logo heat anticipator set at 0 8A T874F1015 F1167 York logo T874F1015 F1175 Oneida Heater logo no 30A0287 01 used with 1874F1015 Q672K1012 Q674K1026 T872G Heat pump models 2 stage heat 1 stage cool 1 stage changeover G1000 Fast cycle performance stage 2 heat fixed Y594G1252 Wiring differences old new anticipator stage 1 heat and cool changeover with WzW2 1 cooling used with Q672F1018 G1018 Adjustable anticipator stage 2 heat fixed Y594G1393 Wiring differences old new anticipator stage 1 heat and cool changeover with 1 Y2 Y cooling used with 0672 1027 When replacing a T872 Thermostat and Q672 Subbase always replace both the thermostat and the subbase 60 2485 8 34 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6 T872 T874 Thermostat Cross Reference Model Number G1026 Description Le
203. free of the mounting slots 2 Turn to the back of the T874 Thermostat Locate the hole for the brass insert in the plastic base below the LED window Push the brass insert into the hole with finger Turn to the front of the T874 Thermostat Place the two stop brackets in position with the tabs in the slot between the HEAT and COOL levers See Fig 9 NONADJUSTABLE STOPS WITH LOCKING LEVER SCREWS 75 F 24 MAX HEAT 75 F 24 C MIN COOL NONADJUSTABLE D O D STOPS 72 F 22 C MAX HEAT 78 26 MIN COOL Fig 9 Range limiting and lever locking methods 6 Insert the mounting screw into the two slots in the stop brackets and attach to the brass insert Tighten the Screw to pull the brass insert into the back of the ther 60 2485 8 10 mostat 7 Loosen the mounting screw enough to free the stop brackets for adjustment T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES 8 Move the HEAT and COOL levers to the maximum tem perature desired 9 Slide the stop brackets until one rests against the HEAT lever and the other against the COOL lever 10 Firmly tighten the mounting screw 11 If the HEAT and COOL levers are to be locked in place at a specific temperature use the two insulated head screws supplied instead of the two adjustable lever stop brackets N CAUTION Equipment Damage Hazard Do not use standard screws that provide metal to metal contact with the stop bra
204. g Fixed T874A Standard and TRADELINE 72 F 78 F 22 C 26 C setpoint stops with locking cover Adjustable anticipator set 0 4A Adjustable locking temperature stops TRADELINEG 72 F 78 F 22 C 26 C setpoint stops with locking cover no thermometer for DoD T872A Standard Heat 1 Cool 1 Other Stage 1 0 1 1 2A Stage 2 Stage 1 0 1 5A Stage 2 T874B Standard and TRADELINE T872B Standard 0 1 1 2A 0 1 2A 0 1 0A T874C Standard and TRADELINE 72 F 78 F 22 C 26 C set stops with locking cover no thermometer for DoD 12 7 C differential between H1 and H2 stages T874C1125 Fast cycling T872C Standard 0 1 1 2A 0 1 1 2A 0 1 5A 0 12 0 6A 0 12 0 6A T874D Standard and SUPER TRADELINE Adjustable locking temperature stops SUPER TRADELINE T872D Standard 0 1 1 2A 0 1 1 2A 0 1 2A 0 1 0A T874E Standard and TRADELINE T872bE 2 Stage Cool 0 1 2A 0 1 0A T874F Standard and TRADELINE Locking cover Department of Defense gt Changeover stage operates with heating Fixed voltage type anticipation T872F 2 Stage Heat 4 Changeover stage operates with heating a secondary changeover is provided in cooling switch e Provides night setback used with standard T874 and timer operated remote switching f Ma
205. g Standard Department of Defense Changeover stage operates with heating Fixed voltage type anticipation 4 Changeover stage operates with heating a secondary changeover is provided in cooling switch Provides night setback used with standard T874 and timer operated remote switching f Manual changeover stage use Q674B L subbase 9 Changeover stage operates with cooling Q674 Subbases Models See Table 4 Mounting Designed to mount horizontally on an outlet box or the wall Adapter plate assembly available for mounting on a vertical outlet box see Subbase Accessory Electrical Ratings Switch Contacts 2 5A at 30 Vac 7 5A inrush LED Lights Optional 30 Vac Finish Dark brown or gray Dimensions in in mm 3 1 2 89 height 5 5 8 143 width Switches Two slide switches one switch on Q674G and 5 16 8 depth See Fig 1 no switches on Q674D operated by levers Switch position is shown on scaleplate Table 4 Q674 Subbase Specifications Switch Positions Models and Options Replaces Application System Fan Use With Q674A Standard and TRADELINE Q672A Standard HEAT AUTO COOL AUTO ON T874A D Indicator LEDs Q674B Standard and TRADELINE Q672B Standard HEAT OFF COOL AUTO ON T874A D Provision for fan relay operation from Heat Pump T874G H L R external fan switch isolate G terminal OVERRIDE HEAT AUTO ON T874P
206. ge heat 2 stage cool D1009 166 82 Obsolete Honeywell logo used with Q674F 1337 T874D1165 E1007 used in Y594D1222 D1339 D1017 44 88 Obsolete Honeywell logo TRADELINE model includes T874D1165 Allen wrench and screws to lock cover used with Q674A G and Q674E1155 D1025 44 Obsolete Westinghouse logo H1 anticipator factory set 787401165 at 0 75A H2 anticipator factory set at 1 2A D1033 44 J Lennox logo part no 13F0601 F C scaleplate T874D1165 Replacement has F scaleplate D1041 53 Yorklogo part no 2TH04701524A used with T874D1165 Q674B1125 D1058 44 Obsolete Shiger special T874D1165 D1066 44 Obsolete ITT logo T874D1165 D1074 51 53 Carrier logo part no HHO7AT172 used with T874D1165 Set H1 anticipator for current 146 Q674F1030 HH93AZ174 F1063 HH93AZ181 or draw of fan and stage 1 heat Q674B primary D1082 44 46 logo used with Q674B1018 C1009 1075 T874D1165 48 72 B1133 used Y594D1024 01040 D1090 44 J Obsolete Dunham Bush logo T874D1165 D1108 44 Obsolete Westinghouse logo T874D1165 D1116 176 89 Obsolete Comfortmaker logo part no 1505 682 F C T874D1165 Replacement has F 94 scaleplate used with Q674C1116 E1197 G1104 scaleplate D1124 44 Obsolete Airtemp special T874D1165 D1132 44 Honeywell logo scaleplate T874D1165 Replacement has F scaleplate D1140 44 Obsolete Solaron special T874D1165 Replacement h
207. gency heat and EM HT LED circuit THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR FAN SWITCH ANTICIPATOR EM HT SYSTEM LED RED MONITOR SYSTEM SWITCH A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR M5845 Fig 23 Tracing the cooling circuit 19 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR FAN SWITCH H2 ANTICIPATOR AUX HT LED GREEN EM HT SYSTEM LED RED MONITOR SYSTEM SWITCH A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR M5846 Fig 24 Tracing the auto fan circuit THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 C1 ANTICIPATOR FAN SWITCH H2 ANTICIPATOR SYSTEM MONITOR SYSTEM SWITCH LED RED A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR M5847 Fig 25 Tracing the fan on circuit 60 2485 8 20 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES OPERATION Heat Anticipation Cool Anticipation When controlling a heating unit with a thermostat the temperature does not remain exactly at the thermostat setpoint but varies within a certain temperature range Heat anticipation is added to the thermostat to reduce this
208. go Premier White color F C scaleplate T874D1165 Replacement system switch used with Q674F 1634 0674810182 HEAT OFF COOL no LEDs D2163 208 Obsolete Amana logo part no P1217501F F C T874D1165 scaleplate D2171 44 Obsolete Amana logo part no P1217701F F C T874D1942 scaleplate D2189 44 Armstrong logo part no 01142A024 scaleplate T874D1165 includes Air Ease insert D2197 44 Liebert logo part 138968P3 F C scaleplate T874D1165 interstage differential between H1 and H2 and between C1 and C2 includes Allen wrench and screws to lock cover field adjustable locking levers D2205 44 J Aaon logo Premier White color F C scaleplate T874D1165 T874E O stage heat 2 stage cool E1008 44 Obsolete Honeywell logo T874E1016 E1016 44 Honeywell logo TRADELINE model includes Allen T874E1016 wrench and screws to lock cover field adjustable locking levers E1024 44 Obsolete Westinghouse logo T874E1016 E1032 44 1 logo part no 13F0901 F C scaleplate T874E1016 Replacement has F scaleplate E1040 72 Obsolete Trane logo used with Q674C1009 used in T874E1016 Both the thermostat and subbase must be replaced 60 2485 8 56 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Repla
209. h Q672B1285 B1293 Gas systems T874C1018 Q674B1034 Electric systems Adjust anticipator faster for correct T874C1018 performance Q674B1075 C1681 Lechauffage Urbain logo Celsius scale T874C1018 C1699 Duotherm logo used with Q672E1068 or T874C1018 See subbase description for Q672F1000 replacement information C1707 Sigler logo used with Q672N1027 None C1715 Westinghouse logo T874C1018 T872D 2 stage heat 2 stage cool D1003 Standard OEM T874D1165 D1011 TRADELINE T874D1165 D1029 Westinghouse logo T874D1165 D1037 Climatrol logo T874D1165 D1045 Lennox logo no P 8 8897 used with 0672 1191 T874D1165 D1052 York logo T874D1165 D1060 Singer logo no 02005385 T874D1165 D1078 Rheem logo T874D1165 D1086 Rudd logo T874D1165 D1094 York logo locking cover T874D1165 D1102 American Standard logo T874D1165 D1110 ITT logo T874D1165 D1128 Carrier logo T874D1165 D1136 No anticipator on stage 1 cool used with T874D1165 Q672C1029 When replacing a T872 Thermostat and Q672 Subbase always replace both the thermostat and the subbase 60 2485 8 32 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6 T872 T874 Thermostat Cross Reference T874 Trade Model Number Description Replacement Remarks D1144 Carrier logo no 7 72 T874D1165 D1151 General Electric logo no AY28X098 0 4 heat T8
210. h Y594HR1615 Q674L1710 used in Y594R1615 R1830 134 Obsolete Addison logo WeatherKing part 41 Y594R1300 20796 61 used with Q674L1504 used in 594 1656 R1855 228 Obsolete Lennox logo Premier White color Y594R1763 Wiring differences old new scaleplate outdoor reset required use C815A1005 Y1 Y L F W1 W 2 used with Q674L1728 used in Y594R1714 C B replacement has F scaleplate R1871 120 Honeywell logo designed to replace Y594R1011 York Y594R1664 part no 2TH11702224 used with Q674L1736 used in Y594R1664 Both the thermostat and subbase must be replaced 60 2485 8 68 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks R1889 120 Honeywell logo designed to replace Y594R1151 York Y594R1672 part no 2TH11702324 Y594R1193 York part no 6TH11702224 and York part no 2TH11704024 used with 067411736 and 815 1054 used Y594R1672 R1897 230 Honeywell logo Premier White color used with Y594R1680 Q674L1751 used in Y594R1680 R1905 120 Qbsolete Honeywell logo Premier White color 594 1672 Replacement is beige designed to replace Y594R1151 York part no 2TH11702324 Y594R1193 York part no 6TH11702224 and York part no 2TH11704024 used with Q674L1777 and C815A1054 used Y594R1698 R1
211. hangeover in heat mode N1002 None a When replacing T872 Thermostat and 0672 Subbase always replace both the thermostat and the subbase 60 2485 8 36 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 6 T872 T874 Thermostat Cross Reference T874 Trade Model Number Description Replacement Remarks N1010 Williamson logo adjustable anticipator stage 1 T874N1016 and 2 heat fixed anticipator stage 1 cool used Q674F 1220 with Q672F1133 or F1315 N1028 TRADELINE heat mode changeover used with T874N1016 Q672F 1216 N1036 Bard used with Q672F 1299 T874N1016 Q674F 1220 N1044 Thermotron logo 1st stage changeover heat T874N1016 mode used with Q672F 1299 Q674F 1220 T872Q 1 stage heat used with another T872 for heating setback Q1009 Standard OEM T874C1125 Q1017 York logo T874C1125 Replacement only good for 1 stage heat and 1 stage cool applications Q1025 ITT logo None Q1033 Lennox logo no P 8 8899 None Q1041 Lennox logo no 63A6401 None T872R Heat pump model 2 stage heat 1 stage cool manual changeover R1008 Fixed anticipator stage 1 heat and cool no Y594R1425 Wiring differences old new anticipator stage 2 heat changeover with cooling W W2 W1 Y1 jumper required used with Q672B1046 R1016 Addison same as T872R1008 used with Y594R1425 Wiring differences old new Q672B1103 W W2 W1 Y1 jumper required R1024 Lenn
212. hermostat on the subbase 8 Align the two captive mounting screws in the thermostat base with the posts on the subbase Tighten both screws Do not overtighten screws or damage to sub base posts can result ALLEN RETAINING SCREWS 2 M956 Fig 10 Installation of locking cover assembly SETTINGS N CAUTION Equipment Damage Hazard On systems using a gas valve never apply a jumper across the valve coil terminals even temporarily This can burn out thermostat heat anticipator s Set the Heat Anticipator Move the indicator to match the primary control current draw When using a T874 Thermostat with two stages of heating set each heat anticipator to match its respective primary control current draw If you cannot find the current rating on the primary control or if further adjustment is necessary see NOTE and use the following procedure to determine the current draw of each stage The current draw of each heating stage must be measured with the thermostat removed and power on to the heating system 1 Connect an ac ammeter of appropriate range between the heating terminals of the subbase a Stage 1 between W1 and RH or b Stage 2 between W2 and RH or R c Stage 3 between W3 and RH or R 2 Move the system switch to HEAT or AUTO 3 After one minute read the ammeter and record the reading a Stage 1 A b Stage 2 A c Stage3 NOTE If equipment cycles too fast set the indicator
213. in EM HT used with T872G1075 G1182 G1307 Y594G1252 Wiring differences old new J1062 Westinghouse EM HT and AUX HEAT LEDs used with T872G1034 Y594G1252 Wiring differences old new W W2 Q672K System OFF HEAT AUTO COOL Fan None K1004 Carrier no HH93AZ072 Q674E1049 Fan switch does not function K1012 Oneida Heater no 30A0288 01 System OFF WOOD WOOD OIL OIL used with T872F 1175 T874F1155 Q674K1026 Q672L System EM HT HEAT OFF COOL Fan ON AUTO L1003 Lennox heat pump EM HT LED cool mode changeover used with T872R1024 Y594R1425 L1011 York heat pump EM HT LED cool mode changeover compressor lockout and auto fan in EM HT used with T872R1032 R1180 R1297 Y594R1664 L1029 Lennox no P 8 11226 heat pump EM HT LED V VR jumper cool mode changeover compressor lockout in EM HT used with T872R1040 Y594R1425 Wiring differences old new V VR R M Y Y W2 F G R O L1037 Heat pump EM HT and AUX HT LEDs cool mode changeover compressor lockout and auto fan in EM HT used with T872R1057 Y594R1763 Wiring differences old new A T designed for used on General Electric heat pumps L1045 Rheem heat pump EM LED cool mode changeover compressor lockout in EM HT auto fan in EM HT used with T872R1065 R1081 R1107 Y594R1243 When replacing
214. ins Y594G1252 Wiring differences old new T874G1543 Q674F1345 1 X L 61344 194 Qbsolete Heat Controller part 7601 110B Y594G1252 Wiring differences old new contains T874G1469 Q674F1345 1 X L W1 Y 91351 160 Qbsolete Luxaire part 026 00068 000 contains Y594G1567 T874G1568 Q674J1126 G1369 155 Qbsolete Contains T874G1246 Q674F 1212 Y594G1252 G1377 169 Qbsolete Coleman part no 3600 373 contains Y594G1633 T874G1576 Q674F 1402 G1385 155 Qbsolete ArcoAire contains T874G1592 Y594G1252 Q674F1212 G1393 170 Qbsolete Contains T874R1393 Q674L1454 Y594G1393 G1419 227 TRADELINE contains T874G1642 Q674F 1444 Y594G1419 G1427 177 Qbsolete Mammoth part no 73034101 contains See OEM for H2 is night setback T874G1659 Q674C1330 replacement G1443 174 Qbsolete American Standard Trane part no Y594G1161 ASYSTAT650 contains T874G1675 Q674J1142 G1476 227 TRADELINE same as Y594G1419 except Premier Y594G1476 White color contains T874G1741 Q674F 1477 G1492 211 Trol A Temp contains T874G1758 Q674F 1485 None See Trol A Temp for replacement G1500 216 Obsolete Comfortmaker part 1505756 contains See OEM for T874G1774 Q674J1175 replacement G1518 216 Obsolete ArcoAire part no 1506756 contains See OEM for T874G1782 Q674J1175 replacement G1526 167 TRADELINE contains T874G1626 Q674F1436 None G1534 227 TRADELINE C white Australia contains None T87
215. ions THERMOSTAT SUBBASE SYSTEM COMPONENTS C1 ANTICIPATOR AUX HEAT AUX HT RELAY LED GRN FAN SWITCH H1 ANTICIPATOR EM HT LED RED FAILURE SWITCH C815A OUTDOOR THERMISTOR COOL CHANGEOVER COMPRESSOR CONTACTOR A FIELD REMOVABLE JUMPER A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD M2012 PROTECTION AS REQUIRED Fig 136 Schematic and hookup of T874R with Q674L Used in heat pump applications 60 2485 8 152 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS ANTICIPATOR H2 ANTICIPATOR _ i FALL B SYSTEM SWITCH Q Q Q e Q Q COOL t 17 4_ LACO AUX HT LED GREEN eG CHECK LED RED CHANGEOVER VALVE HEAT COMPRESSOR CONTACTOR F gt 2 fol m lt gt POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED 9 ZR ayo 105 Fig 137 Schematic and hookup of T874R with 06741 Used heat pump applications 153 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS MM M 0 M M M T H1 ANTICIPATOR H2 ANTICIPATOR ire C1 ANTICIPATOR D A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQU
216. irculation at average temperature Do not mount the thermostat where it can be affected by drafts or dead spots behind doors in corners or under cabinets hot or cold air from ducts radiant heat from the sun fireplace or appliances concealed pipes and chimneys unheated uncooled areas such as an outside wall behind the thermostat Mount Subbase The subbase can be mounted on a vertical outlet box horizontal outlet box or directly on the wall 1 If the subbase is mounted on a vertical outlet box order Honeywell part no 193121A Adapter Assembly See Fig 4 The assembly includes an adapter ring two screws and a cover plate to cover marks on the wall Install the ring and cover plate on the vertical outlet box NOTE For a wall installation hold subbase in position and mark holes for anchors See Fig 5 Wall anchors must be obtained from local hardware store Be careful that the wires do not fall back into the wall opening Set aside subbase Drill four 3 16 in 4 8 mm holes and gently tap anchors into the holes until flush with the wall 2 Pull wires through the cover plate if used and subbase cable opening See Fig 6 3 Secure the cover plate if used and subbase with the screws provided Do not fully tighten the subbase screws Level the subbase using a spirit level see Fig 7 and firmly tighten subbase mounting screws The subbase mounting holes provide for minor out of level ad
217. iring differences old new C X LED cool mode changeover compressor lockout and auto fan in EM HT used with T872G1109 G1216 G1372 a When replacing T872 Thermostat and 0672 Subbase always replace both the thermostat and subbase 41 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 7 0672 0674 Subbase Cross Reference changeover Q674 Trade Model Number Description Replacement Remarks F1125 BDP no 3442DP90 used with T872G1117 Y594G1252 Wiring differences old new C X G1166 G1174 F1133 Williamson heat pump EM HT LED heat T874N1016 mode changeover compressor lockout in Q674F1220 EM HT used with T872N1010 F1141 Westinghouse EM HT LED auto fan in Y594G1252 Wiring differences old new EM HT used with T872G1034 W W2 F1158 Rheem Ruud heat pump EM HT LED cool Y594G1252 mode changeover compressor lockout in EM HT used with T872G1083 G1133 G1141 auto fan in EM HT F1166 Crispaire HT LED used with T872G1208 59401252 F1174 Carrier no HH93AZ081 EM HT LED Q674F1022 F1182 Square D no HCB 1 Chek Lite R X2 jumper Q674F1022 R X2 jumper add monitor switch System Aux Heat replaces EM HT between X1 and low side of power F1190 EM HT LED X2 E and RC RH jumpers None F1208 TRADELINE cool mode changeover EM HT Y594G1419 LED used with T
218. it on sooner than the bimetal alone would L1 L2 HOT STAGE 1 COOL RELAY C1 ANTICIPATOR M5825 Fig 28 Internal cooling anticipation schematic Interstage Differential The mercury switch of each stage of heat makes at a slightly different temperature that is the mercury makes the contacts of the first stage bulb at one temperature and the second stage bulb at another temperature The difference between these two temperatures is the interstage differential Interstage differential is the difference between the two make points when the bulbs are controlled by the heating of the bimetal and the action of the heat anticipator The interstage differential is 1 9 F 1 C between the stages of heating or the stages of cooling for most models Mechanical differential is the difference between the make and break points of each switch The mechanical differential for the T874 is 1 F 0 6 C between the stages of heating or between the stages of cooling for most models Droop The addition of anticipator heat to the bimetal causes a control factor called droop As the weather grows colder the heating appliance must operate longer and more frequently More heat must be added to the bimetal The bimetal now thinks it is warmer than it really is and actual room temperature is controlled at a lower temperature than the setpoint indicates At 100 percent heat load this droop can be significant The C815A Outdoor Reset Thermi
219. justments VERTICAL OUTLET BOX A MOUNTING SCREWS 2 COVER PLATE HORIZONTAL OUTLET THERMOSTAT COVER BOX p SR A e E THERMOSTAT Ld 2 VA LZ v 2 SUBBASE MOUNTING SCREWS 2 CAPTIVE MOUNTING SCREWS 2 NOT INCLUDED WITH UNIT A ACCESSORY PART AVAILABLE 1931214 M6009 Fig 4 Installing Q674 Subbase on outlet box 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES WIRES THROUGH WALL OPENING ANCHORS MOUNTING 2 HOLES 4 R MOUNTING M926 SUBBASE SCREWS 2 Fig 5 Installing Q674 Subbase on wall WIRING TERMINAL THERMOSTAT CABLE OPENING SPIRIT LEVEL MOUNTING POST FOR TO SPRING FINGER MOUNTING HOLES 4 CONTACTS ON THERMOSTAT 2 THE THERMOSTAT UP TO 12 M927 Fig 6 Subbase components and leveling procedure Wire Subbase Disconnect power supply before beginning installation to prevent electrical shock or equipment damage 60 2485 8 8 All wiring must comply with local electrical codes and ordinances IMPORTANT Use 18 gauge solid conductor wire whenever possi ble If using 18 gauge stranded wire no more than 10 wires can be used Do not use larger than 18 gauge wire Follow equipment manufacturer wiring instructions when available To wire subbase proceed as follows 1 Connect the system wires to the subbase as shown in the applicable
220. king cover The screws must be used to assure proper operation Adjustable Lever Stop Part no 4074ECK includes lever stop and screws Universal Versaguard Thermostat Guard Includes wall plate ring base guard cover tumbler lock two keys and optional Honeywell logo insert Double wall construction provides extra measure of tamper resistance Tamper resistant lock key cannot be removed without being in locked position Vents in guard base allow airflow for opti mum thermostat performance See form 68 0104 for more information TG511A1000 Clear cover 7951181008 Opaque cover 7951101004 Painted steel off white cover See Fig 2 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Key Lock Cover Part no TG504A replaces existing T874 cover Mounts on T874 base and covers thermostat set tling levers and subbase switches Includes LED window and two keys Should not be used with 193121A Adapter Plate 50 60 70 80 194559R Locking Cover with Thermometer Allen Wrench TG504A1025 Blank face internal thermometer TG504A1033 External thermometer See Fig 2 TG504A1033 Key Lock Cover with External Thermometer Fig 2 T874 Thermostat accessories Table 3 T874 Thermostat Specifications TG511D1004 Includes Painted Steel Cover Opaque Base and Wallplate Models and Options Replaces Applications System Stages Anticipation Heating Adj Coolin
221. l fuel furnace about five or six times an hour at 50 percent load This provides a reasonable balance between comfort stability and economy A heat pump being a mechanical refrigeration system should be cycled at a rate of 2 1 2 to 3 times an hour With a T874 this is accomplished by setting the anticipator at the total current draw of the controlled device the contactor and possibly the changeover relay or valve Most likely the compressor operates from the first stage of the thermostat The second stage normally controls the auxiliary heaters This heat anticipator can be set for the current draw of the electric heat primary and produces good control Voltage Anticipation Although not a specific requirement for heat pumps several models of the T874 have voltage heat anticipation instead of current anticipation With voltage anticipation the amount of heat added to the thermostat is constant no matter which load is connected to it The anticipator realizes a constant voltage and produces a constant amount of heat during the ON cycle This allows the cycling rate to be designed into the thermostat The heat pump manufacturer is assured of correct performance independent of later thermostat adjustments Outdoor Reset Outdoor reset which a C815A Outdoor Thermistor makes possible is sometimes applied in heat pump systems to help minimize the effect of the differential between stages It takes 2 F 1 1 C change in temperat
222. lacement has F no 91C7401 scaleplate used with Q674E1155 scaleplate B1084 44 Obsolete Lennox Two Speed logo part no 13F0301 T874B1019 Replacement has F scaleplate scaleplate B1092 44 Obsolete Honeywell logo Heil Quaker part no T874B1019 HQ521389HW B1100 88 Obsolete Janitrol logo part no CHTS36 60 F C T874B1019 Replacement has F scaleplate used with Q674E1338 used in Y594B1042 scaleplate B1118 44 Honeywell logo scaleplate used with T874B1019 Replacement has F scaleplate Both the thermostat and subbase must be replaced 60 2485 8 48 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks B1134 222 Obsolete Carrier Synergy 2000 logo part no T874B1019 Wiring differences old new 074 7199 scaleplate used with Q674E1395 Q674E1049 W1 W RC RH jumper HH93AZ209 required replacement has no LEDs T874C 2 stage heat 1 stage cool C1000 44 76 Honeywell logo used with Q674B1075 C1181 used in T874C1018 Y594C1058 C1018 60 61 Honeywell logo TRADELINE model includes Allen T874C1018 81 92 wrench and screws to lock cover used with Q674C1074 C1026 44 Qbsolete AAF logo C scaleplate includes Allen T874C1018 Replacement has F wrench and screws to lock cover non adjustable
223. lications THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 1 CONTACTOR COMPRESSOR 1 Lo o AUTO H1 ANTICIPATOR ON youl t FAN RELAY H2 ANTICIPATOR HEAT RELAY 2 MS 9 SYSTEM Q Q 4 e T SWITCH 5 5 Don HEAT E i O N AUTO M SERVICE LED RED 0000 j COMPRESSOR FAULT COMPRESSOR C2 ANTICIPATOR CONTACTOR 2 E amp v POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5997 OPTIONAL FIELDWIRE JUMPER ALLOW SINGLE SYSTEM TRANSFORMER Fig 80 Schematic and hookup of T874D with Q674E Used in standard applications 60 2485 8 114 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE FALL Ue FAN SWITCH o AUTO e H2 ANTICIPATOR ON 5 SYSTEM SWITCH C1 ANTICIPATOR 0 A POWER SUPPLY PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED 9 SYSTEM COMPONENTS CHANGEOVER RELAY COMPRESSOR CONTACTOR L1 L2 M5981 HOT Fig 81 Schematic and hookup of T874C with Q674C Used in heat pump applications THERMOSTAT gt FALL Ue H1 ANTICIPATOR SUBBASE SYSTEM COMPONENTS H2 ANTICIPATOR SYSTEM SWITCH C1 ANTICIPATOR 5 9 C2 ANTICIPATOR UIN A POWER SUPPLY PROVIDE DISCONNECT M
224. ly useful if the first stage controls the comfort temperature and the second stage controls the energy savings temperature Timers such as the 56005 for insertion between the first and second stage control points must be ordered separately T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Each mark on the scale represents 1 F 0 6 C differential is factory set at 2 F 1 C the differential can be set as high as 12 F 7 C To set the adjustable interstage differential loosen the tension screw See Fig 13 Slide the adjustable scale to align with the number of degrees desired between stages Use the lower edge of the tension screw bracket as a guide for alignment In heating slide the lever wider apart for a larger differential or closer together for a smaller differential In cooling slide the lever closertogether for a larger differential or wider apart for a smaller differential While supporting the scale with hand tighten the tension screw IMPORTANT Support the scale with hand while tightening tension screw See Fig 13 Failure to do so can result in twisting and damaging bimetal coil HEATING SET POINT LEVER AMANS LILIO 11 1 50 60 FIRST STAGE SWITCH SECOND STAGE ADJUSTABLE SWITCH HEATING TENSION SCREW ALIGN LOWER EDGE WITH SLIDE LEVER WIDER APART FOR LARGER DIFFERENTIAL COOLING TENSION SCREW ALIGN LOWER EDGE WITH SLIDE LEVER CLOSER TOGETHE
225. matic and hookup of T874G with Q674D Used in standard applications 103 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS SYSTEM SWITCH H1 ANTICIPATOR C1 ANTICIPATOR A POWER SUPPLY PROVIDE DISCONNECT MEANS COMPRESSOR AND OVERLOAD PROTECTION AS REQUIRED CONTACTOR M3729 Fig 59 Schematic and hookup of T874A with Q674Q Used in fan coil applications THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 HOT L2 A H1 ANTICIPATOR D FAN SWITCH COOL RELAY Ll CONTACT FAN RELAY o Ee Hees ELEC HT RELAY SWITCH SYSTEM H2 ANTICIPATOR CDe CHANGEOVER VALVE OFF 9 HEAT COMPRESSOR CONTACTOR Uia C1 ANTICIPATOR EVAPORATOR RELAY power SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD v2 oN o PROTECTION AS REQUIRED M2863 Fig 60 Schematic and hookup of T874C with Q674N Used in evaporative cooler applications 60 2485 8 104 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS MM COMPRESSOR CONTACTOR FAN SWITCH H1 ANTICIPATOR SYSTEM EVAPORATOR SWITCH CHANGEOVER HEAT C1 ANTICIPATOR M2862 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 61 Schematic and hookup of T874C with Q674N Used in evaporative cooler applications THERMOSTAT SUBBASE SY
226. mper required Replacement is beige color E1486 82 Obsolete Standard OEM Q674E1049 RC R jumper required Replacement is beige color Q674F System EM HT HEAT AUTO COOL OFF Fan AUTO ON F1006 141 Obsolete Includes EM HEAT LED used with Q674F1022 Jumper E X2 T874C1331 F1022 142 Includes LED and field selectable inserts used with Q674F 1022 T874C1059 used in Y594C1017 C1330 F1030 146 Carrier part no HH93AZ174 SUPL HEAT LED used Q674F1022 Wiring differences old new with T874D1074 HHO7AT172 C X1 X X2 F1048 149 Obsolete Includes EM HEAT LED and auxiliary power Q674F1022 Replacement does not include terminal Z Z terminal and only requires one transformer F1063 146 Obsolete Carrier part no HH93AZ181 SUPL HEAT Q674F1022 Wiring differences old new LED used with T874D1074 7 172 C X1 X X2 F1071 142 Obsolete Square D part no 63600 002 11 CHECK Q674F1022 LED a Both the thermostat and subbase must be replaced 77 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 9 Q674 Subbase Cross Reference selectable inserts used with T874D1009 used in Y594D1222 Model Fig Q674 Trade Number No Description Replacement Remarks F1089 152 Obsolete Includes EM HEAT LED 2 and RC RH Q674F1022 jumpers F1097 142 Obsolete Southwest special W2 X2 jum
227. nnox logo fast cycle performance stage 2 heat fixed anticipator stage 1 heat and cool changeover with cooling used with Q672E1019 F1067 T874 Trade Replacement None Remarks See subbase description for replacement information G1034 Westinghouse logo adjustable anticipator stage 2 heat fixed anticipator stage 1 heat and cool changeover with cooling used with Q672F1091 F1141 F1257 or Q672J1013 J1062 Y594G1252 Wiring differences old new W W2 G1042 York logo fixed anticipator on all stages heat and cool changeover with cooling used with Q672J1021 Y594G1567 G1059 TRADELINE no anticipator stage 2 heat fixed anticipator stage 1 heat and cool changeover with cooling used with Q672J1039 outdoor reset Y594G1161 Designed for use on General Electric heat pumps G1067 Lennox logo no P 8 11222 fast cycle performance stage 2 heat fixed anticipator stage 1 heat and cool changeover with cooling used with Q672E1142 F1083 See subbase description for replacement information G1075 Carrier logo adjustable anticipator stage 2 heat fixed anticipator stage 1 heat and cool changeover with cooling used with Q672J1054 L1052 See subbase description for replacement information G1083 Adjustable anticipator stage 2 heat fixed anticipator stage 1 heat and cool changeover with cooling includes shunt to bypass stage 2 anticipator with auxiliary heat rel
228. no LEDs C1470 221 Obsolete Climate Master part no RQ5370 used with Y594H10122 Wiring differences old new T874H1138 1 Y2 Y replacement has MALFUNCTION LED only C1496 74 Obsolete Carrier part no HH93AZ213 includes Y594H1012 Wiring differences old new SERVICE LED used with T874H1161 used in 1 2 L R jumper Y594H1038 required C1504 83 Obsolete Carrier part no HH93AZ214 used in Y594 Y594H1012 Wiring differences old new 1 Y2 Y L R R none R L jumper required no night setback T8600D2028 Wiring differences old new programmable 1 Y2 Y L R W Y jumper required night setback C1512 97 Obsolete Carrier part no HH93AZ216 System T8600D2028 Wiring differences old new Override Auto Off includes two LEDs used Y594 programmable L R W O W Y jumper required night setback C1520 72 Obsolete Carrier part no HH93AZ210 used with Q674C1058 T874D2049 used in 59401388 C1538 163 Climate Master part no AQ5354 System Off Auto Y594G1393 No momentary reset switch Override includes two LEDs and momentary spring position C1546 76 Obsolete McQuay part no 060684802 gray color Q674C1058 Replacement has LEDs 225 includes LED beige color C1553 181 Obsolete McQuay logo part no 073319901 includes Q674C1058 Replacement is beige 203 LED 1561 76 McQuay logo part no 073319701 includes one LED See OEM for replacement C1579
229. ns Y594R1615 T874R1491 and Q674L1553 R1334 47 Obsolete Slant Fin contains T874R1509 and Y594R1243 Wiring differences old new Q674B1042 W1 W2 R1342 130 Obsolete ArcoAire part no 1506721 contains Y594R1763 Wiring differences old new T874R1517 Q674L1538 and C815A1005 W1 W E X2 X F C B R1359 113 Qbsolete ArcoAire part no A02074 contains Y594R1243 Wiring differences old new T874R1525 and Q674L1181 1 R1375 130 Obsolete Contains T874R1566 067411538 and Y594R1763 Wiring differences old new C815A1005 W1 W E X2 X F C B R1383 132 Obsolete Comfortmaker part no 1505739 contains Y594R1243 Wiring differences old new T874R1574 and Q674L1538 W W2 X L R1391 132 Obsolete ArcoAire part no 1506739 contains Y594R1243 Wiring differences old new T874R1582 and Q674L1538 W W2 X L R1409 119 Qbsolete Intertherm part no 6244630 contains Y594R1763 Wiring differences old new T874R1608 and Q674L1264 W2 W Z F K X2 W1 0 R1417 113 Qbsolete Comfortmaker part no 1505 735 Y594R1243 Wiring differences old new contains T874R1301 and 067411181 1 R1425 168 SUPER TRADELINE contains T874R1616 and Y594R1425 Q674L1587 R1433 200 Obsolete Miller part no 9115900 contains Y594R1243 Wiring differences old new T874R1624 and 067411595 W2 W X B Z F K X2 W1 0 R1441 136 Obsolete American Standard Trane part no Y594R1763 ASYSTAT651 contains T874R1657 and Q674L1611
230. nual changeover stage use Q674B L subbase 9 Changeover stage operates with cooling Q674 Subbases 60 2485 8 0 1 1 2A 0 1 1 2A T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Fast cycling Electric Heat 0 12 0 12 0 6A 0 6A T874G Heat pump cool T872G HeatPumpor 2 1 10 0 1 0 2 0 1 1 2A 0 1 0A changeover with fast cycling Standard Fixed anticipator for H2 0 1 1 5A Fast cycling 0 12 0 6A T874H Use with Q674C T872H 1 1 10 0 1 0A 0 1 0A Standard T874J Heat pump None Heat Pump 2 1 2d 9 1 0A 0 1 5A 0 1 0 2 T874K Heat pump None Heat Pump 2 1 1 0 1 1 2 0 1 5 0 1 5A T874L Heat pump None Heat Pump 2 1 0 1 1 2 0 1 1 2 0 1 5A T874N Heat pump heat T872N Heat Pump 2 1 1 0 1 1 2 0 1 1 2A 0 1 0A changeover T874P Heat pump None Heat Pump 2 1 0 1 1 2 0 1 1 2 0 1 5A T874Q Night setback heating T872Q Standard 16 0 1 1 2A T874R Heat pump T872R Heat Pump 2 1 0 1 5A 0 1 1 2A 0 1 5A mE T874S Two speed compressor heat None Heat Pump 2 2 19 0 1 2A 0 1 2A 0 1 2A 0 1 0A pump T874V Standard None Standard 1 0 1 5A T874W Heat pump and standard T872W HeatPumpor 3 2 0 1 2A 0 1 2A 89 0 1 2A 0 1 0 Night setback heatin
231. of T874R with Q674L Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH H1 C1 ANTICIPATOR SYSTEM SWITCH COMPRESSOR CONTACTOR M2018 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 133 Schematic and hookup of T874R with Q674L Used in heat pump applications 60 2485 8 150 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS ANTICIPATOR FAN SWITCH SYSTEM SWITCH 2 8 HT 4 HEAT Q OFF C 4 HA 9 COMPRESSOR Fd CONTACTOR LACO 5 CHANGEOVER VALVE HEAT o Xx F gt 2 fol m lt gt al LI SSeS BE A POWER SUPPLY PROVIDE DISCONNECT MEANS RE AND OVERLOAD PROTECTION AS REQUIRED Fig 134 Schematic hookup of T874R with Q674L Used in heat pump applications 151 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FAN SWITCH O SUPL HT RESET LED RED HEATER SYSTEM O SWITCH Q FAN RELAY COOL CHANGEOVER VALVE COMPRESSOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD CONTACTOR M2017 PROTECTION AS REQUIRED Fig 135 Schematic and hookup of T874R with Q674L Used in heat pump applicat
232. of fan and stage 1 heat primary D1462 80 Obsolete Fedders multi logo THTX 220 AOHB 787401165 88 58 00550 001 used with Q674E1205 Both the thermostat and subbase must be replaced 53 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks D1470 44 Obsolete York logo part no 27 04701624 includes T874D1165 Replacement has F Allen wrench and screws to lock cover scaleplate scaleplate D1488 44 Obsolete Risco special T874D1165 D1496 44 Obsolete Borg Warner multi logo part no T874D1165 6TH047015244A includes Allen wrench and screws to lock cover D1504 82 York logo part no 025 23321 000 scaleplate used T874D1165 Replacement has F with Q674E1007 used in Y594D1180 scaleplate D1512 44 Honeywell logo Heil Quaker part no HQ712002HW T874D1165 D1520 44 Obsolete Bard logo adjustable lever stops set 68 F T874D1165 max heat and 78 F min cool D1538 44 Obsolete McQuay logo part no 02005937 T874D1165 D1553 44 Obsolete Climate Control special part 02005944 T874D1165 Replacement has 2 F scaleplate 6 C differential between H1 and H2 3 C differential between H1 and differential between C1 and C2 H2 2 F differential between C
233. ogo part Y594R1763 BAYSTAT339 WY28X0112 F C scaleplate used with 067411496 used in Y594R1284 R1434 134 Ruud logo part no 41 20796 32 used with 067411504 Y594R1300 used in Y594R1649 R1442 134 Rheem logo part no 41 20796 28 used with Y594R1300 Q674L1504 used in Y594R1631 R1459 134 Obsolete Honeywell logo Rheem part no 41 20796 Y594R1300 25 used with Q674L1504 R1467 108 Honeywell logo used with Q674L1512 used in Y594R1292 Y594R1292 R1475 123 logo scale range 42 F to 88 F used with Y594R1300 Q674L1520 used in Y594R1300 R1483 130 Obsolete Comfortmaker logo F C scaleplate used Y594R1763 Wiring differences old new with 067411538 and 815 1005 used in Y594R1318 W1 W 2 X F C B R1491 137 Obsolete Honeywell logo TRADELINE model used Y594R1615 with Q674L1553 used in 594 1326 R1509 47 J Obsolete Slant Fin logo used with Q674B1042 usedin Y594R1243 Wiring differences old new Y594R1334 W1 W2 R1517 130 Obsolete Arcoaire logo part no 150671 used with Y594R17632 Wiring differences old new Q674L1538 and 815 1005 used Y594R1342 W1 W E X2 X F C B R1525 113 Qbsolete Arcoaire logo used with 067411181 used in Y594R12432 Wiring differences old new Y594R1359 X1 X R1541 67 Obsolete Goettl logo part no 372071 used with Y594R1300 Q674B1349 R1558 134 Obsolete Universal Parts logo part no 41 20796 45 Y594R1300 use
234. okup of T874D with Q674F Used in heat pump applications 60 2485 8 158 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS MODE SIGNAL H1 2 1 H1 ANTICIPATOR CO SWITCH 2 AUTO o Nco 0 0 ON FAN RELAY 5 0 0 d AN N OA ANTICIPATOR SERVIGE LED RED 2 nwa HEAT RELAY 1 HEAT RELAY 2 SYSTEM o SWITCH AUX HT 9 v9 LED GRN Q COOL 1 CHANGEOVER VALVE G E COMPRESSOR CONTACTOR EH EM HT RELAY UT C1 ul e ANTICIPATOR E oye C1 MODE SIGNAL POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A JUMPER FACTORY INSTALLED mE CONNECT TO Y OR W TERMINAL WITH FACTORY INSTALLED JUMPER Fig 147 Schematic and hookup of T874G with Q674F Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER we H1 ANTICIPATOR DEFROST BLOWER SPEED RELAY RELAY SWITCH 2 Q Q BLOWER RELAY c3 AUTO Co 21 A ONC O O T 12 A FALL DEFROST RELAY AUX HT RELAY He pev EM HT RELAY LOCKOUT COOL THERMOSTAT CONTRACTOR C1 ANTICIPATOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 148 Schematic and hookup of T874G with Q674F Used in heat pump applications 159 60 2485 8 T874 MULTISTAGE
235. old new scaleplate 8 F 4 4 C differential between H1 and H2 programmable L R W O W Y jumper for night setback used with Q674C1207 required includes night setback P1022 97 Obsolete Friedrich Climate Master logo part no None See subbase description for AT5922 scaleplate 8 F 4 4 differential replacement information between H1 and H2 for night setback used with Q674C1215 P1030 97 Obsolete No logo Friedrich part no AT5930 8 F None See subbase description for 4 4 C differential between H1 and H2 for night setback replacement information used with Q674C1215 P1055 68 97 Obsolete Carrier Heat Pump System Control logo part None See subbase description for no HHO7AT205 F C scaleplate heat interstage replacement information differential 8 4 4 C T874Q 1 stage heat used with another T874 for night setback Q1005 44 Honeywell logo T874A1036 Q1013 44 Obsolete Lennox logo part 13F1201 F C T874A1036 Replacement has F scaleplate scaleplate Q1021 44 Obsolete Lennox logo part no 13F1301 scaleplate 874 1036 Replacement has F scaleplate T874R Heat pump model 2 stage heat 1 stage cool manual changeover R1004 47 J Obsolete Honeywell logo used with Q674B1042 used Y594R1243 Wiring differences old new in Y594R1029 W12W2 R1012 47 J Obsolete Honeywell logo Addison heat pump used Y594R1243 Wiring differences old new with Q674B1109
236. olor between RC and RH terminals D1164 66 Obsolete Carrier part no HH93AZ211 used in Q674D1040 Y594D1440 D1172 208 Obsolete Amana logo part no P121501F removable Q674D1040 jumpers between RC and RH terminals D1180 55 Obsolete York logo part no 2TH04703224A Q674D1040 D1198 55 66 Obsolete Standard OEM T874D1165 Replacement is beige color Q674D1040 Q674E System OFF HEAT AUTO COOL Fan AUTO ON E1007 82 with T874D1504 used Y594D1180 Q674E1049 E1015 84 Obsolete Lennox heat pump used with T874G1006 Y594G12522 Wiring differences old new G1154 M Y F G V R Y W2 E W2 jumper required E1049 193 TRADELINE used with T874D2031 and TG504A1025 Q674E1049 used in Y594D1354 E1056 82 Obsolete Amana part no D68535 7 used with Q674E1049 RC RH jumper required T874C1059 C1331 used in Y594C1009 E1064 83 Obsolete RC RH jumpered internally EM HEAT LED Q674E1049 E1072 82 Carrier part no HH93AZ176 RC RH jumpered Q674E1049 RC RH jumper required internally E1080 82 Trane part no BAY28X184 Q674E1049 E1098 85 Obsolete Used with T874A D Q674E1049 RC RH jumper required E1106 185 Obsolete ITT Nesbitt See OEM for replacement E1114 87 Carrier part no HH93AZ177 RC RH jumper Q674E1049 RC RH jumper required LOCKOUT LED to indicate compressor lockout used replacement has no LED with HHO7AT series thermostats E1122 83 Obsolete Square D part no 63600 002 10
237. ols are the same as those of standard models except as noted below Super Tradeline Models T874 THERMOSTAT T874D Thermostat Provides two stages of heating and two stages of cooling Use with Q674A F Subbases Y594D T874D Q674E TG504A Thermostat Subbase key lock cover package Provides two stages of heating and two stages of cooling Includes a key lock cover for set point protection Y594G T874G Q674F Thermostat Subbase package for heat pump Provides two stages of heating and one stage of cooling Automatic changeover in heat or cool mode Available in beige or Premier White color Y594R T874R Q674L Thermostat Subbase package for heat pump Provides two stages of heating and one stage of cooling Manual changeover in heat or cool mode Avail able in beige or Premier White color SUPER TRADELINE FEATURES SUPER TRADELINE package with cross reference label and special instruction sheet e SUPER TRADELINE model supplied with locking lever and locking cover accessories Includes adjustable temperature locking stops T874D replaces T874A F TRADELINE or standard models ORDERING INFORMATION Tradeline Models T874 THERMOSTAT T874 TRADELINE models provide staged heat and or cool operation See Table 1 Table 1 Heating and Cooling Stages Models A B D E F Heating Stages 1 1 2 2 2 Cooling Stages 1 2 1 2 2 e T874A F are standard models TRADELINE FEATURES
238. on is represented by a zig zag line and adjustable anticipation is a zigzag with an arrow The resistance of the fixed anticipator is so large it limits current so that a system relay cannot be pulled in from a circuit path going through the fixed anticipator The relay can be pulled in through an adjustable antici pator because its resistance is generally 0 to 5 ohms 5 The center portion the subbase contains the switches The fan switch is above the system switch The small circles on the switch represent the maximum possible contacts available on the Q674 Subbase The larger cir cles represent the switch positions available on this par ticular Q674 with the solid circle representing where it is actually switched on the diagram NOTE Solid circles are not interconnected electrically At the right the relays and contactors are shown attached to the proper terminals The terminals are represented by large circles with terminal designations in capital letters See Table 3 for the meaning of each lettered terminal Sometimes power for a fixed anticipator is brought through an off system relay like the changeover relay shown in Fig 20 This current is kept low by the high resistance of the fixed anticipator so that relay does not pull in KEY TO HOOKUP SYMBOLS 05 Eu RELAY CONTACTOR CONTACTS TRANSFORMER 24 VAC SECONDARY RELAY OR CONTACTOR COIL LED MERCURY SWITCH OUTDOOR THERMOSTAT EHR NA V EMERG
239. ox logo fast cycle stage 2 heat fixed See subbase description for anticipator stage 1 heat and cool changeover with replacement information cooling used with Q672B1160 and Q672L1003 R1032 York logo fixed anticipator stage 1 and 2 heat and Y594R1664 stage 1 cool changeover with cooling used with Q672L1011 R1040 Lennox logo fast cycle stage 2 heat fixed See subbase description for anticipator stage 1 heat and cool isolated stage 2 replacement information heat switch changeover with cooling used with Q672B1202 no P 8 11221 Q672L1029 R1057 TRADELINE fixed anticipator stage 1 heat Y594R1763 Designed for use on General cool no anticipator stage 2 heat changeover on Electric heat pumps Wiring cooling used with Q672L1037 outdoor reset differences old new R1065 Adjustable anticipator stage 2 heat fixed Y594R1243 anticipator stage 1 heat and cool changeover on cooling used with Q672L1045 R1073 Lennox logo no 63A0301 Celsius scale None separate auxiliary heat power circuit fast cycle stage 2 heat antic R1081 Ruud logo same circuit as T872R1065 used with Y594R1243 Q672L1045 L1136 R1099 Dunham Bush special used with Q672L1060 Y594R1243 L1383 R1107 Rheem no RXMT B70 used with Q672L1045 59491243 L1136 R1115 Friedrich logo fixed anticipator used with See subbase description for Q672B1244 L1086 replacement information When replacing a T872 Thermostat and Q672 S
240. part 10636704 contains Y594R1797 Wiring differences old new T874R2010 067411884 C X X W3 W2 R1821 125 Qbsolete York logo part no 2TH11703424A Y594R1797 contains T874R2028 and Q674L1918 R1839 134 Rudd logo part no 41 20796 48 contains See OEM for T874R2036 and Q674L1504 replacement R1854 123 Obsolete Rheem logo part no 41 20796 47 Y594R1300 contains T874R1996 and 067411504 Y594W W1014 54 Contains T874W1015 0674 1216 Y594W1014 C815A1005 W1022 140 Obsolete Rheem part no 41 20797 19 contains T8611M2025 T874W1031 Q674L1546 and C815A1005 W1030 68 Obsolete Inter City Products part no 1072350 T8611M2025 Includes night setback contains T874W1072 Q674L1835 and C815A1005 programmable Outdoor Thermistor W1055 247 Obsolete Addison logo part no 843 277 contains T8611M2025 T874W1106 067411934 and 815 1005 Y594Y Y1004 210 Obsolete Mammoth part no 71117301 contains See OEM for T874Y1005 and Q674E1353 replacement Y1012 248 Obsolete WaterFurnace logo part no TA21H03 contains T874Y1013 and Q674F1675 Both the thermostat and subbase must be replaced 95 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES WIRING DIAGRAMS THERMOSTAT SUBBASE SYSTEM COMPONENTS L1 RH HOT HEAT RELAY 1 2 a US SWITCH FALL H1 ANTICIPATOR DE 2 t I 1 HEAT RELAY 2 1 1 1 1
241. part no 41 20796 29 contains T874R1442 and Q674L1504 Y594R1300 R1649 134 Ruud part no 41 20796 33 contains T874R1434 and Q674L1504 Y594R1300 R1656 134 Obsolete WeatherKing part no 41 20796 64 contains T874R1830 and Q674L1504 Y594R1300 R1664 120 TRADELINE contains T874R1871 and Q674L1736 direct replacement for York 2TH11702224 Y594R1011 contains T874R1046 Q674L1272 Y594R1664 R1672 120 TRADELINE contains T874R1889 Q674L1736 and C815A1054 direct replacement for York 2TH11702324 Y594R1151 contains T874R1251 Q674L1272 C815A1039 and 6TH11702224 Y594R1193 contains T874R1327 Q674L 1272 Y594R1672 R1680 230 TRADELINE same as Y594R1615 except Premier White color contains T874R1897 and Q674L1751 direct replacement for Y594R1326 T874R1491 Q674L1553 Y594R1680 Remarks R1698 120 Obsolete TRADELINE Premier White color contains T874R1905 Q674L1777 and C815A1054 Y594R1672 Replacement is beige R1706 120 Obsolete TRADELINE same as Y594R1664 except Premier White color contains T874R1913 and Q674L1777 direct replacement for Y594R1011 T874R1046 Q674L1272 York part no 2TH11702224 Y594R1664 Replacement is beige R1714 228 Obsolete Lennox part no 97E79 Canada Premier White color contains T874R1855 and Q674L1728 Y594R1763 Wiring differences old new Y1 Y L F W1 W E W2 C B R1722
242. per Q674F1022 F1105 145 Obsolete Lennox heat pump EM HEAT LED used Y594G12522 Wiring differences old new with T874G1154 V R Y W2 F G X2 X R O M Y L E jumper required F1113 150 Obsolete Lennox heat pump part no 24F6201 V VR Y59461252 Wiring differences old new jumper EM HEAT LED changeover in cooling used M Y F G Y WC with T874G1014 G1022 V VR R must use single transformer F1121 153 Obsolete Westinghouse heat pump EM HEAT LED Y594G12522 used with T874G1048 F1139 148 Obsolete Tappan heat pump EM HEAT LED auto fan Y594G1252 Wiring differences old new in emergency heat mode used with T874G1147 F1162 151 Obsolete Crispaire heat pump EM HEAT LED used Y594G1393 with T874G F1170 153 Obsolete Heatwave Southwest Mfg heat pump EM Y594G12522 HT LED used with T874G1105 F1188 153 Obsolete Luxaire heat pump Y594G12522 F1196 178 Obsolete Williamson EM HEAT and SERVICE LEDs Q674F1220 used with T874N1008 used in Y594N1007 F1204 154 Obsolete Special for Crispaire EM HEAT and COMP Y594G1393 Wiring differences old new FAULT LEDs used with T874G1089 used in A L Y594G1153 F1212 155 Includes AUX HEAT and EM HEAT LEDs used with Q674F1212 or T874G1246 G1451 G1592 G1915 used in Y594G12522 Y594G1252 F1220 178 Used with T874N1016 used in Y594N Q674F 1220 F1238 155 Obsolete Rheem part no 41 20797 14 AUX HEAT Y594G12522 and EM HEAT LEDs used
243. r factory set at 1 2A used with Q674F1204 A L used in Y594G1153 G1097 155 Obsolete Honeywell logo Rheem part no ZXMT B79 Y594G12522 used with Q674F 1238 41 20797 14 G1105 153 Obsolete Heat Wave Southwest Mfg logo H2 Y594G1252 anticipator factory set at 1 2A used with Q674F1170 G1113 103 Obsolete Carrier Heat Pump System Control logo Y594G1419 Wiring differences old new meets DoD specifications H2 anticipator factory set at CzX jumper Y1 W1 0 8A used with 067411041 G1121 103 Obsolete Carrier Heat Pump System Control logo part Y594G1419 Wiring differences old new no 7 161 scaleplate H2 anticipator factory CzX jumper Y1 W1 set at 0 8A includes Allen wrench and screws to lock cover G1139 143 Obsolete Honeywell logo used with Q674B1240 None See subbase description for 234 1108 replacement information G1147 148 Obsolete Honeywell logo changeover in cooling mode Y594G1252 Wiring differences old new used with Q674F1139 61154 84 139 Obsolete Lennox logo used with Q674E1015 F1105 Y594G1252 5 subbase description for replacement information G1162 155 Obsolete Lennox logo meets DoD specifications used Y594G1419 1 1 jumper required with Q674F G1170 160 Obsolete York logo part no 2TH11702424A H2 Y594G15672 anticipator is fixed used with Q674J1027 used in Y594G1013 G1188 147 Qbsolete Honeywell logo Keeprite Westinghouse Y594G12
244. r part no HH93AZ139 used with Q674B1034 T874D2049 used in Y594D1370 B1547 237 Obsolete TRADELINE gray color used with Y594C1389 T874C1810 used in Y594C1389 a Both the thermostat and subbase must be replaced 60 2485 8 72 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 9 Q674 Subbase Cross Reference Model Fig Q674 Trade Number No Description Replacement Remarks B1554 82 TRADELINE includes LOCKOUT LED and Y594D1347 Jumper RH RC system removable jumpers between RC and RH terminals switch Off HEAT AUTO used with T874C1877 used in Y594C1421 COOL B1562 45 Obsolete Amana logo part no P1217701F Q674B1034 removable jumpers between RC and RH terminals B1570 45 Armstrong logo part no 03299418 Q674B1034 Replacement is beige B1588 45 Obsolete Standard OEM Q674B1034 Replacement is beige Q674C System OFF AUTO Fan AUTO ON C1009 72 Standard OEM used with T874D1082 used in Q674C1058 Y594D1024 C1017 Obsolete Includes factory installed RC RH jumper Q674C1058 used with T874A F Q C1033 72 part no BAY28X187 Q674C1058 1041 74 Obsolete Command Aire heat pump used with Y594H1012 Wiring differences old new T874H1005 H1054 1 Y2 Y W Y jumper required C1058 72 TRADELINE Q674C1058 C1066 73 Obsolete Command Aire heat pump used with
245. rature See Fig 34 In warm weather the thermistor has very low resistance permitting a large current flow in the heater which generates a relatively large amount of heat in the thermostat In cold weather the outdoor sensor has high resistance which results in low current flow and little or no heat being added to the thermostat This raises the control point overcoming the effects of droop and interstage differential L1 L2 HOT C815A OUTDOOR THERMISTOR SENSOR M5826 Fig 34 Location of thermistor Changeover Changeover between heating and cooing can be accomplished either automatically or manually depending on the application Changeover can occur in heating or cooling The changeover valve is energized as long as the subbase function switch is in the appropriate position when manual changeover is used If a system manually changes over on cooling the valve energizes whenever the subbase switch is in the cooling mode One of the mercury bulb switches is used for control when the thermostat has automatic changeover When the automatic changeover is in cooling the changeover valve is energized when the first stage cooling switch makes The second stage Switch turns on the compressor It is more common with new equipment to find that changeover occurs with cooling that is the changeover valve is energized to produce cooling Whether automatic or manual changeover is used and whether the reversing valve is
246. rmometer Defense DoD application A1287 General Electric no AY28X097A fan current T874A1036 Set thermostat stage 1 heat shunt for auto fan in heating heat anticipator set at Q674B1018 anticipator for total of fan and stage 0 4A 1 primary control current draw A1295 Lennox Celsius scale T874A1036 A1303 Lennox logo no 6440601 meets DoD specs T874A1176 A1311 Envirotron special Celsius scale T874A1010 A1329 Carrier logo Celsius scale no HH07ATO74C T874A1036 A1337 Square D no HCD 3 heat anticipator set at 0 2A 874 1036 A1345 TRADELINE Celsius scale T874A1010 A1352 Heat anticipator set 1 2A T874A1036 A1360 Friedrich logo heat anticipator set at 0 2A T874A1036 A1378 Wesco logo heat anticipator set at 0 8A T874A1036 T872B 1 stage heat 2 stage cool B1005 Standard OEM T874B1019 B1013 0 4A heat anticipator setting T874B1019 B1021 TRADELINE T874B1019 B1039 Westinghouse logo T874B1019 B1047 American Standard logo T874B1019 B1054 Climatrol logo T874B1019 B1062 Carrier logo T874B1019 B1070 Trane logo T874B1019 B1088 Fedders logo T874B1019 B1096 Climatrol logo T874B1019 B1104 Carteret logo T874B1019 B1112 Singer logo no 050240 03 T874B1019 B1120 Celsius scale T874B1019 B1138 Singer logo no 02005711 locking cover and T874B1019 lever B1146 Lennox logo no P 8 8895 T874B1019 B1153 Lennox logo Celsius scale T874B1019 T872C 2 stage heat 1 stage cool C1004 Standard OEM T874C1018 C1012 Heat anticip
247. rtunity to reduce unit cost One disadvantage is that a thermostat jiggler can be demanding more kW of strip heat when chilly The method any particular manufacturer selects depends on which arguments it finds persuasive and the opinions of its distributors and dealers Three Stage Thermostat A definite improvement in quality of control and economy can be achieved with a three stage thermostat T874W which is especially true with heat pumps using dual compressors Three stage control permits both the heat pump and the auxiliary heat to be tied directly to the demand of the controlled space With a two stage compressor maximum 100 percent heat pump operation is required before auxiliary heat is brought on Emergency Heat Some provision is generally required to back up the compressor in the event of a failure during the heating season In fact it is quite common to find that local building codes or electric utilities require that a specified percent of the building heating requirements be available from emergency heat a source other than the heat pump compressor Almost universally the source is electric resistance heaters Typically the requirement is for 70 or 80 percent of the building heating needs Switching to Emergency Heat Conventional heat pump control thermostat logic usually includes a manual subbase switch to bring on the emergency heat In one control strategy the emergency heat relay is turned on by the E
248. s 60 2485 8 200 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS FALL SYSTEM SWITCH HEAT H1 ANTICIPATOR C1 ANTICIPATOR COOL CHANGEOVER VALVE FAN SWITCH COMPRESSOR CONTACTOR CHECK LED RED A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 214 Schematic and hookup of T874A with Q674B Used in standard applications 201 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS 2 SYSTEM SWITCH H1 ANTICIPATOR b COMPRESSOR 61 CONTACTOR RELAY N C PS H2 7 HRANTICIPATOR p 8 E pr 7 2 ai REMOVABLE FAN Pp o 1 SWITCH JUMPER 2 LOU F 4 HHA 5 xy 5 MED 4 WK CHECK COMPRESSOR C LED RED CONTACTOR HIGH s 9 C1 ANTICIPATOR ONC FX COOL CHANGEOVER VALVE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED K2 RELAY ENS 9 2 M2993 Fig 215 Schematic and hookup of T874L with Q674B Used in heat pump applications 60 2485 8 202 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT H1 ANTICIPATOR JN FALL FAN AUTO SWITCH ON SUBBASE N H2 ANTICIPATOR ANTIGIFATOR SYSTEM COMPONENTS COOL CHANGE
249. s 60 2485 8 98 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR H2 ANTICIPATOR SYSTEM SWITCH FAN SWITCH POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED HEAT RELAY 1 HEAT LED RED L1 HOT COOL LED YELLOW COMPRESSOR CONTACTOR LO SPEED LED GREEN HI SPEED LED GREEN L1 HOT L2 M5945 Fig 49 Schematic and hookup of T874C with Q674B Used in standard applications THERMOSTAT H1 ANTICIPATOR FALL H2 ANTICIPATOR C1 ANTICIPATOR SYSTEM SWITCH SUBBASE SYSTEM COMPONENTS COOL CHANGEOVER VALVE COMPRESSOR CONTRACTOR AUX HT RELAY FAN RELAY 8000 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED Fig 50 Schematic and hookup of T874G with Q674B Used in heat pump applications 99 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HEAT RELAY 1 FAN SWITCH H1 ANTICIPATOR SYSTEM SWITCH C2 A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER L1 L2 HOT A B O TERMINALS ON SOME MODELS M5944 Fig 51 Schematic and hookup of T874D with Q674B Used in standard applications THERMOSTAT SUBBASE SYSTEM COM
250. s colder suction pressure is lower and the motor runs hotter At the other end of the scale defrosting too often hurts the overall energy efficiency of the system Consider that in terms of heating the building defrosting is a big loss Not only does the system stop heating but it actually moves heat out of the building If electric strip heat is used it is a further waste because its COP is 1 0 and not the 2 0 or more COP realized if the heat is provided by the heat pump So concern for equipment safety suggests fairly frequent defrosting while economy of operation argues for fewer defrost cycles Since the equipment manufacturer chooses the balance is usually tipped in favor of more frequent defrosting to avoid the possibility of damaging the compressor Auxiliary Heat Except in warm climates all air to air heat pump installations require auxiliary heat capability Electric resistance heaters can provide this auxiliary heat The electric heaters sometimes called strip heaters usually are supplied in 5 kW units or strips about 17 000 Btu The indoor unit of the heat pump is designed to accommodate various electric heat units so it can be used in variously sized buildings in different parts of the country Two Stage Thermostat The most common heat pump control strategy is for the thermostat first stage to switch the compressor and the second stage to switch the auxiliary heat See Fig 39 T874 MULTISTAGE THERMOSTATS AND Q
251. solete Fedders heat pump used with T874R1343 Y594R1425 Wiring differences old new used in Y594R1219 K E 7 remove W1 Y jumper L1421 125 Obsolete Coleman heat pump used with T874R1368 Y594R1797 used in Y594R1235 L1439 131 Obsolete Carrier part no HH93AZ187 SUPL HEAT Q674L1207 or Wiring differences old new LED System SUPL HT HEAT COOL used with Y594G1393 T874R1384 HH07AQ1 70 L1447 128 Obsolete Williamson heat pump three LEDs used Y594R1425 Wiring differences old new with T874R1392 used in Y594R1250 A L L1454 131 Obsolete Carrier part no HH93AZ197 SUPL HEAT Y594R13934 Wiring differences old new LED used with T874R1384 HHO7AQ170 11462 113 Obsolete LSI heat pump part no 104710002 used Y594R12434 Wiring differences old new with T874R1400 1 11496 136 Obsolete Trane heat pump used with 874 1426 Y594R1763 used in Y594R1284 L1504 134 Rheem part no 41 20796 24 used with T874R1442 Y594R1300 R1434 R1459 used in Y594R1631 R1649 R1854 L1512 108 ncludes two LEDs used with T874R1467 used in Y594R1292 Y594R1292 L1520 123 Includes EM HEAT and AUX HEAT LEDs used with Y594R1300 T874R1475 used in Y594R1300 L1538 130 Obsolete Snyder General heat pump used with Y594R1763 Wiring differences old new T874R1483 R1517 R1566 and C815A1005 used in C B W1 W 2 X F Y594R1318 R1342 R1375 132 Obsolete Used with T874R1574 R1582 used in
252. solete Hitecsa logo scaleplate H2 anticipator Y594R1243 Replacement has F factory set at 1 2A used with Q674L 1207 scaleplate R1657 136 Obsolete American Standard logo part no Y594R1763 ASYSTAT651 requires outdoor reset used with Q674L1611 used in Y594R1441 R1673 108 Heil logo part no 1060321 004 01 used with Y594R1292 Q674L1132 used in Y594R1466 R1699 119 Obsolete Miller logo used with Q674L 1264 used in Y594R1763 Wiring differences old new Y594R 1482 W2 W X B Z F K X2 W1 0 R1707 209 Trol A Temp by Honeywell logo Premier White color None See Trol A Temp for used with Q674L1678 used in Y594R1490 replacement R1715 209 Trol A Temp by Honeywell logo used with 067411186 None See Trol A Temp for used in Y594R1508 replacement R1723 218 Obsolete No logo Snyder General part no 654958 07 Y594R1672 Wiring differences old new scaleplate used with Q674L1702 and W1 W 2 C B C815A1005 used in Y594R1516 R1731 108 QObsolete Inter City Products logo part no Y594R1292 HQ11477909HW used with Q674L1132 used in Y594R1524 R1749 108 Tempstar logo part no 1060322 004 01 used Y594R1292 with Q674L1132 used in Y594R1532 R1814 108 Obsolete Honeywell logo Keeprite part no THPC Y594R1292 Replacement has F scaleplate used with Q674L1132 used in Y594R1607 scaleplate R1822 230 Honeywell logo TRADELINE model used wit
253. stor is used in heat pump systems to minimize droop Without some method of countering this situation the occupant could notice the temperature offset Outdoor Reset Some T874 Q674 models are intended for use with the C815A Outdoor Thermistor The outdoor thermistor provides significantly improved thermostat performance when compared to conventional multistage thermostats The C815A is usually located in the heat pump condensing unit outdoors 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES N CAUTION Equipment Damage Hazard Due to calibration techniques used for T874 Thermostats with outdoor reset the C815A Thermistor must be wired into the system at all times Failure to do so will result in serious degradation of performance Service and Replacement of C815A Outdoor Thermistor To check and verify thermistor operation perform the following steps 1 Disconnect wire from T terminal on subbase 2 Measure resistance with ohmmeter across the T sub base wire and X subbase terminal 3 Take outdoor temperature measurement at thermistor location and find correct thermistor resistance on the chart in Fig 29 4 Compare resistance on the chart with measured resis tance Replace C815A if resistance varies more than 15 percent Contact installing dealer for packaged replace ment outdoor thermistor 4600 4400 z 4200 4000 5 3800 3600 3400 amp 3200 5 3000 2800 2600 2400 2200 2
254. t no See OEM for 066804405 12 F offset between H1 and H2 F C replacement scaleplate no C1 anticipation used with Q674C1363 C1794 53 Obsolete Carrier logo Canada part no HHO7AT160 W T874C1018 Setstage 1 heat anticipator for Premier White color C scaleplate includes locking total current draw of fan and cover stage 1 heat primary C1802 246 Obsolete California Economizer logo F C scaleplate 787461018 used with Q674G1005 used in Y594C 1371 C1810 237 Obsolete Honeywell logo TRADELINE model Premier Y594C1389 White color used with Q674B1547 used in Y594C19389 C1844 238 Energy Night logo used with Q674F1592 used in Y594R1425 E W2 system switch Y594C1413 EM HT HEAT OFF COOL C1851 60 Obsolete Whalen logo T874C1018 C1869 219 McQuay logo part no 0073318801 Premier White See OEM for color scaleplate replacement Both the thermostat and subbase must be replaced 51 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 8 T874 Cross Reference Q674L1199 and C815A1013 067411389 programmable Model Fig Trade Model Number No Description Replacement Remarks C1877 53 Obsolete Honeywell logo TRADELINE model used Y594D1347 Jumper RC RH system with Q674B1554 used in Y594C1421 switch OFF HEAT AUTO COOL T874D 2 sta
255. t pump EM HEAT LED cooling Y594R1243 Wiring differences old new mode changeover compressor lockout auto fan in W W2 X L EM HT used with T874R1046 L1025 102 Obsolete Lennox heat pump part no 24F6101 EM Y594R1243 Wiring differences old new HEAT LED V VR jumper used with T874R1020 M Y F G V VR VR Y2W2 J1038 R O L1033 115 Obsolete Rheem heat pump EM HEAT LED used Y594R1243 with T874R1152 L1041 103 Obsolete Carrier heat pump part no HH93AZ175 Y594G1419 Wiring differences old new SUPL HEAT LED used with T874G1055 C X jumper Y1 W1 HHO7AT171 G1071 HH93AZ175 G1113 L1066 122 Obsolete Fedders heat pump used with T874R1269 Y594R1615 Wiring differences old new used in Y594R1037 K E C X W1 B 7 L1074 124 Obsolete Carrier heat pump part no HH93AZ186 Y594J1001 SUPL HT LED used with T874J1002 HHO7AT175 or T874J1028 HHO7AT165 L1082 104 Obsolete Crispaire heat pump W2 H jumper EM Y594R1243 Replacement has auto fan in HEAT LED used with T874R1061 R1111 emergency heat mode L1090 105 Obsolete Fedders heat pump EM HEAT LED Y594R1425 Wiring differences old new changeover in heat mode used with T874C1398 K E C X C1406 C1414 L1108 106 Obsolete Westinghouse EM HEAT LED Y594R1243 L1116 107 Obsolete Carrier part no HH93AZ171 SUPL HEAT See OEM for LED used with T874D1264 HHO7AT173 replacement L1132 108 Quaker part no HQ711598 used
256. tains T874B1019 No LEDs on replacement T874B1100 Q674E1338 Q674E1049 Y594C C1009 82 Obsolete Amana part no D68535 9 contains T874C1018 Jumper RC RH T874C1059 Q674E1056 Q674E1049 C1017 142 Qbsolete Amana part no D68535 10 contains T874C1018 T874C1059 Q674F1022 Q674F1022 C1058 46 Contains T874C1000 Q674B1075 T874C1018 Q674B1075 C1082 82 Obsolete Trane part no 166 162 1 contains T874C1018 T874C1083 Q674E1007 Q674E1049 C1256 45 Obsolete Amana part no D68535 16 contains T874C1018 Jumper RC RH T874C1059 Q674B1059 Q674B1034 C1280 45 Obsolete Williamson contains T874C1570 T874C1018 Q674B1000 Q674B1034 C1314 56 Obsolete LSI contains T874C1471 0674 1257 T874C1018 Jumper RC RH no RESET 067481018 LED on replacement C1322 121 Obsolete Contains T874C1638 067411561 Y594C1322 C1330 142 Qbsolete Amana part no D68535 21 contains T874C1018 T874C1059 Q674F1022 Q674F1022 Both the thermostat and subbase must be replaced 87 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10 Y594 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks C1348 70 Obsolete Fiberglas contains T874C1653 T874C1000 Wiring differences old new Q67481000 Q674B1075 YzY1 jumper RC RH and Y1 W1 replacement has no SERVICE LED repl
257. te Addison logo part no 843 277 includes T8611M2025 three LEDs used with T874W1106 in Y594W1055 Q674N System OFF HEAT COOL EVAP Fan AUTO ON N1015 60 Obsolete Goettl heat pump changeover in heat mode See OEM for evaporative cooler circuit used with T874C1182 replacement N1023 61 Obsolete Sigler heat pump evaporative cooler circuit See OEM for used with T874C1349 replacement Q674P System SUPL HT HEAT COOL Fan AUTO ON P1005 126 Obsolete Carrier heat pump part no HH93AZ169 Y594G1419 Wiring differences old new used with T874G1071 HHO7AT171 CzX jumper Y1 W1 replacement has OFF EM HT HEAT AUTO COOL system switching 06740 System HEAT OFF COOL Fan LOW MED HI ON Q1004 59 Obsolete McQuay special used with T874A1267 See OEM for replacement Q1012 64 Used with T874A1291 None Q674R System OFF COOL Fan LO HI CONT R1003 69 Obsolete Carrier part no HH93AZ190 international See OEM for symbols on fan and switches used with T874V1008 replacement HHO7AT177 Q674S System HEAT COOL Fan None 1000 70 QObsolete Fiberglas Canada SERVICE LED used See OEM for with T874C1653 used in Y594C1348 replacement Q674W System OFF ON Fan LO MED HI W1006 240 Obsolete Snyder General part no 044271801 See OEM for replacement Both the thermostat and subbase must be replaced 60 2485 8 86 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 10 Y594 Cross Reference
258. the L terminal on the Q674 Each mercury switch is identified by function H1 Stage 1 Heating H2 Stage 2 Heating H3 Stage 3 Heating C1 Stage 1 Cooling C2 Stage 2 Cooling C3 Stage 3 Cooling C O Changeover heat pumps Each anticipator is identified and each switch affected is named EX H1 anticipator C1 anticipator All T874 Multistage Thermostats use mercury switches Each schematic indicates switch operation by being drawn in the open position with an arrow indicating operation with a temperature RISE or FALL One circuit has been selected that is typical of various models used with heat pumps This circuit has been traced to illustrate the functions performed by these control systems Tracing Method 1 Always begin at the system transformer or R terminal You may want to draw the switch contacts in each switch position to aid in tracing Colored pencils are helpful when only one copy of the circuit is available See Fig 16 for a description of the hookup symbols and Fig 17 through 25 for typical hookups 2 Completely trace only one circuit at a time for example heat or cool 3 Connections are indicated by small dots at the point of intersection If there is no dot there is no connection 4 The left portion of the circuit the thermostat contains the mercury switches The heat switches make on a temperature fall and the cool switches make on a tem 15 perature rise Fixed anticipati
259. thermometer non adjustable range stops set at 72 F max heat and 78 min cool 22 26 field adjustable locking levers C1158 44 Obsolete Solaron special T874C1018 C1166 51 53 Obsolete Carrier logo part no HHO7AT160 T874C10182 Replacement has F scaleplate includes Allen wrench and screws to lock scaleplate set stage 1 heat cover used with Q674B anticipator for total current draw of fan and stage 1 heat primary C1174 44 Obsolete Goettl logo T874C1018 C1182 60 Obsolete Goettl logo H1 anticipator factory set at 0 8A T874C1018 used with Q674N1015 C1190 44 Obsolete Lennox logo part no 13F0501 scaleplate T874C1018 Replacement has F scaleplate aBoth the thermostat and subbase must be replaced 49 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 8 T874 Cross Reference Q674B1257 used in Y594C1314 Model Fig Trade Model Number No Description Replacement Remarks C1216 44 Obsolete Fasco part no 1230 8197 T874C1018 C1224 105 Qbsolete Square D logo T874C1018 C1240 44 Honeywelllogo Honeywell Canada TRADELINE model 787461018 Replacement has F scaleplate includes Allen wrench and screws to lock scaleplate cover C1257 44 Obsolete Singer part no 0200 5931 8 F 4 4 C T874C1125 Replacement has 12 F differential between H
260. thermostat and the subbase 31 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 6 T872 T874 Thermostat Cross Reference T874 Trade Model Number Description Replacement Remarks C1509 Fedders logo used with Q672L1102 Y594R1425 Wiring differences old new K E remove Y W1 jumper C1517 Climatrol logo used with Q672L1102 Y594R1425 Wiring differences old new K E remove Y W1 jumper C1525 Square D logo no HCD 2 T874C1018 C1533 Airtemp logo T874C1018 C1541 Airtemp logo used with 067211102 Y594R1425 Wiring differences old new K E remove Y W1 jumper C1566 TRADELINE Celsius scale T874C1018 Replacement has F scaleplate C1574 Whalen special used with Q672B1269 None C1582 Lennox meets DoD None C1590 Singer 8 F 4 4 C differential between stage T874C1125 Replacement has 2 1 C 1 and stage 2 differential between H1 and H2 C1608 Singer logo no 02005784 8 F 4 4 C differential T874C1125 Replacement has 2 F 1 C between stage 1 and stage 2 differential between H1 and H2 C1616 Celsius scale stop set at 23 None Add 4074ECK adjustable stop C1624 Heat Wave logo no 0360 116 T874C1018 C1632 York logo heat anticipator set at 0 2A T874C1018 C1640 Heat anticipator set at 0 4A T874C1018 C1665 Wesco logo heat anticipator set at 0 8A T874C1018 C1673 Wards logo used wit
261. tinghouse logo T874A1036 A1105 Amana logo 1 2A heat anticipator setting T874A1036 A1113 Trane logo T874A1036 A1121 Airtemp Chrysler logo T874A1036 A1139 Singer logo no 02005384 T874A1036 A1147 American Standard logo T874A1036 A1154 Carrier logo and color no HHO7AT074 T874A1036 A1162 General Electric logo no AY28X097 T874A1036 A1170 Sears logo no 4291441 T874A1036 A1188 Command Aire logo T874A1036 A1196 Singer logo Celsius scale no 02005521 T874A1036 A1204 Carteret logo T874A1036 A1212 General Electric AY28X114 72 78 F T874A1010 Use T874A1176 for Dept of 22 26 C stop Defense DoD application A1220 Singer logo no 050240 01 T874A1036 1238 Celsius scale T874A1036 A1246 TRADELINE locking cover and adjustable locking 874 1150 lever stops A1253 Trane Comfort Corp T874A1036 A1261 TRADELINE 72 78 F 22 26 stop locking T874A1176 cover no thermometer meets DoD specs When replacing T872 Thermostat 0672 Subbase always replace both the thermostat and the subbase 29 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 6 T872 T874 Thermostat Cross Reference T874 Trade Model Number Description Replacement Remarks A1279 General Electric logo AY28X114A 75 F stop 874 1010 Use T874A1176 for Dept of locking cover no the
262. to it Compressor Fault Relay Another very simple method of detecting a compressor failure has been developed It uses the voltage developed across the capacitor in a permanent split capacitor compressor motor The principle involved is that virtually all serious problems reduce the voltage across the motor capacitor By carefully selecting the correct coil voltage the normally closed relay does not pull in unless the proper voltage builds up across the capacitor which brings on the SERVICE LED See Fig 43 Here is how it works Onacall for cooling the thermostat makes R to Y the contactor coil is powered and the compressor motor turns on Atthe same time the indicator light is energized Asthe motor gets up to speed about one second the fault relay sees enough voltage to pull in Its normally closed contact opens and the indicator light goes out Anything that prevents the motor from running prevents the fault relay from pulling in COMPRESSOR MOTOR FAULT RELAY HOT CONTACTOR THERMOSTAT SUBBASE M5831 Fig 43 Compressor fault relay schematic T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES CROSS REFERENCE The following section lists the current T874 Trade replace ments for T872 and T874 Multistage Thermostats It also lists the Q674 Trade replacements for Q672 and Q674 Subbases All thermostats listed carry the Honeywell logo unless otherwise noted When using the Cross Referenc
263. ually all manufacturers now let the heat pump run continuously rather than lock it out at cold temperatures Heat Pumps with Dual Compressors Staging residential sized heat pumps is a requirement that developed from the need to make heat pumps as efficient as possible One of the methods used to improve overall seasonal efficiency is to reduce the amount of time the machine is operating in a transitional mode Transitional mode is starting and stopping in addition to recovering from defrost Under light loads when the heat pump is cycling on and off this can be a significant amount of time and can result in a significant efficiency reduction Capacity control is one way to reduce the cycling rate and improve the efficiency Additional capacity control methods used on other refrigeration systems unloading multiple compressors are not as likely to be seen on residential heat pumps With a single stage heat pump the compressor is normally controlled by the first stage and the auxiliary heat by the second stage The T874G N and R Thermostats are used for this purpose With a two stage compressor the two thermostat switches control the individual compressor stages Auxiliary heat is controlled along with the compressor stage two by the thermostat second stage It comes on with the compressor high speed if an outdoor thermostat wired in series with it is made See Fig 35 25 THERMOSTAT NE HEAT 2 HEAT 1 CO
264. ubbase always replace both the thermostat and the subbase 37 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 6 T872 T874 Thermostat Cross Reference T874 Trade Model Number Description Replacement Remarks R1123 York logo no 025 21453C Celsius scale Y594R1664 R1131 Lennox logo separate auxiliary heat power circuit None fast cycle stage 2 heat anticipator outdoor reset used with Q672L1144 C815A1013 R1149 Westinghouse logo adjustable stage 2 heat Y594R1243 Wiring differences old new anticipator cooling changeover fixed anticipator W W2 stage 1 heat and cool used with Q672L1110 L1128 L1151 R1156 Marvair logo used with Q672L1094 L1250 Y594R1243 Replacement has auto fan in Emergency Heat mode R1164 Bard used with Q672L1185 Y594R1243 R1172 Heil Quaker used with Q672L1193 Y594R1243 Wiring differences old new B X W W2 R1180 York Celsius used with Q672L1011 Y594R1664 R1198 TRADELINE used with Q672L1227 Y594R1243 R1206 For use with W89 used with Q672L1235 None R1214 Intertherm logo used with Q672L1276 Y594R1300 Wiring differences old new W1 B Z L K E R1222 York logo used with C815A1039 adjustable Y594R1672 anticipator stage 2 heat used with Q672L1284 R1230 Amana logo no C62397 1 used with None Q672L1300 W89 R1255 Singer logo used with Q672L1326 and W89 None
265. umper Q674A1019 RC RH jumper required A1039 RC RH jumper Chek Lite Q674A1019 RC RH jumper required Q672B System HEAT OFF COOL Fan AUTO ON B1004 Standard OEM Q674B1034 B1012 Isolated G terminal Q674B1018 B1020 System HEAT OFF RESET COOL Q674B1034 Used system off as reset position B1038 TRADELINE Q674B1034 B1046 Heat pump circuit used with T872R1008 Y594R1425 Wiring differences old new W1 Y1 W W2 B1053 RC RH jumper Q674B1034 RC RH jumper required B1061 Chek Lite Q674B1034 B1079 Auto fan operation in heat and cool Q674B1075 B1087 Carrier no HH93AZ078 RC RH jumper Q674B1075 B1095 Carrier no HH93AZ084 RC RH jumper Q674B1034 B1103 Addison heat pump circuit used with Y594R1425 Wiring differences old new T872R1016 W W2 W1 Y1 jumper required B1111 Carrier no HH93AZ080 isolated terminal Q674B1018 B1129 Trane special circuit used with T872T1004 None B1137 RC RH jumper isolated G terminal Q674B1018 RC RH jumper required B1145 Fedders special Q674B1034 RC RH jumper required B1152 Fedders special auto fan operation in heat Q674B1075 and cool B1160 Lennox heat pump circuit used with Y594R1243 Wiring differences old new T872R1024 includes compressor lockout in V VR R M Y Y W2 F G R O EM HT B1178 General Electric no AY28X107 auto fan Q674B1075 operation in heat and cool B1186 Trane isolated G terminal Filter LED Q674B1018 B1194 General Electric no AY28X124 auto fan Q674B1075 Set T874 stage 1 anticip
266. ure to bring on the second stage and full heating Added to a certain amount of droop under high loads there can be a large offset between the setpoint and room temperature Without some method to counteract this situation the temperature offset from the setpoint could be as much as 6 F 3 3 C under high load conditions It is not likely that the occupants accept this variation without making frequent thermostat setting changes Outdoor reset has the effect of raising the setpoint at cold outdoor temperatures Then even with a few degrees droop the space temperature stays near the desired setting This is done by calibrating the thermostat high by 5 F 3 the amount of expected offset This offset compensates for differential and droop at high load factors so the thermostat switches at the setpoint At warm temperatures heat is added to the thermostat to compensate for this offset at cold temperatures the extra heat is automatically removed The effect is the same as raising the setpoint as the outdoor temperature goes down 60 2485 8 24 This is particularly important on the 3 stage T874 The additional stage means that more droop is introduced when the system is in operation That is the reason the TRADELINE T874W is sold in a package with the outdoor sensor and the correct subbase Outdoor Reset How it Works The heater in the thermostat is connected in series with a thermistor sensor that measures outdoor tempe
267. ver EM HT and AUX HT LEDs used with T872R1081 T872R1107 L1144 Lennox V VR jumper HT and SERVICE None LEDs isolated stage 2 heat used with T872R1131 C815A1013 L1151 Westinghouse AUX HT and EM HT LEDs Y594R1243 Wiring differences old new used with T872R1149 W W2 L1169 Carrier no HH93AZ071 EM HT LED used None with T872G1257 7 073 L1177 York DoD EM HT LED used with T872G1299 Y594G1567 L1185 Bard used with T872R1164 Y594R1243 L1193 Heil Quaker 001 501 used with Y594R1243 Wiring differences old new T872R1172 W W2 L1201 Lennox special no 1485701 used with None T872G1323 L1219 Westinghouse special used with 787261356 87401165 Wiring differences old new X X1 Q674F1022 L X2 W E Y1 W1 and Y2 W2 jumpers required L1227 Heat pump used with T872R1198 Y594R1243 L1235 Intertherm used with T872R1206 R1305 None L1250 Crispaire special used with T872R1156 and Y594R1243 C815A1021 L1268 Westinghouse special used with T872W1027 and C815A1021 L1276 Intertherm special used with T872R1214 Y594R1300 Wiring differences old new W1 B Z L K E L1284 York special used with T872R1222 Y594R1672 L1300 Amana special no C62345 1 used with None T872R1230 L1326 Singer used with T872R1255 None When replacing a T872 Thermostat and Q672 Subbase always replace both the thermostat and subbase 60 2485 8 44 T874 MULTISTAG
268. with Q674B Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS EMIT HOT COMPRESSOR CONTACTOR FAN SWITCH H1 ANTICIPATOR OUTDOOR THERMOSTAT H2 ANTICIPATOR SUPP HT M LED RED HEAT RELAY HEAT RELAY 2 CONTACT 1 HEAT RELAY HEAT RELAY 3 CONTACT 2 COOL CHANGEOVER VALVE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M5956 Fig 144 Schematic and hookup of T874J with Q674J Used in heat pump applications 157 60 2485 8 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS HOT L1 12 FAN Hi SWITCH 9 SUP ELEC ANTICIPATOR HT RELAY OUTDOOR THERMOSTAT TIME DELAY EM HT RELAY FAN RELAY SYSTEM SWITCH H2 ANTICIPATOR LED RED COOL CHANGEOVER C1 ANTICIPATOR COMPRESSOR INTERNAL CONTACTOR THERMOSTAT RISE A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD HIGH C1 OVERLOAD PROTECTION AS REQUIRED PRESSURE SWITCH M8375 Fig 145 Schematic and hookup of T874G with Q674F Used in heat pump applications THERMOSTAT SUBBASE SYSTEM COMPONENTS REVERSING RELAY COMPRESSOR CONTACTOR 1 FAN SWITCH SYSTEM SWITCH HEAT RELAY 1 HEAT RELAY 3 COMPRESSOR CONTACTOR 2 POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD 7010 PROTECTION AS REQUIRED Fig 146 Schematic and ho
269. with Q674E1007 used in scaleplate Y594A1068 A1127 44 Obsolete Climate Control logo part no 02005936 C T874A1036 Replacement has F scaleplate scaleplate A1135 44 Fedders multi logo part no THTX 110 WCHA T874A1036 88 58 00500 001 A1143 44 Honeywell logo scaleplate T874A1036 Replacement has F scaleplate A1150 44 Honeywell logo TRADELINE model includes Allen T874A1150 wrench and screws to lock cover field adjustable locking levers 68 F max heat 78 F min cool A1168 44 Obsolete Trane Comfort Corps logo 874 1036 1176 44 Honeywell logo meets DoD specs includes Allen T874A1176 wrench and screws to lock cover no thermometer non adjustable range stops set at 72 F max heat and 78 F min cool 22 26 field adjustable locking levers A1184 51 53 Trane logo part no BAY28X182 F C scaleplate T874A1036 When used with Q674E1080 automatic fan in heating and cooling modes heat set stage 1 heat anticipator for anticipator set at 0 4A used with Q674B1141 E1080 total current draw of fan and stage 1 heat primary replacement has F scaleplate A1192 44 Obsolete Lennox logo part no 13F0001 C scaleplate 874 1036 Replacement has F heat anticipator factory set at 458A scaleplate Both the thermostat and subbase must be replaced 60 2485 8 46 T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES Table 8 T874 Cross Reference
270. y RESET system switch position G1824 227 Honeywell logo Australian TRADELINE model Premier Y594G1476 White color scaleplate used with Q674F1477 used in Y594G1534 G1832 231 Obsolete Intertherm logo used with Q674F1519 used Y594G1252 Replacement has auto in Y594G1542 changeover in cooling mode only G1840 231 Obsolete Miller logo used with Q674F1519 used Y594G1252 Replacement has auto Y594G1559 changeover in cooling mode only G1857 229 Obsolete Lennox logo C scaleplate Premier White Y594G1161 Wiring differences old new color used with Q674F1535 used in Y594G1583 2 C B L F G1865 160 logo TRADELINE model designed to Y594G1567 replace Y594G1013 York part no 2TH11702424 Y594G1229 York part no 6TH11702424 and York part no 2TH117704124 used with Q674J1209 used in Y594G1567 aBoth the thermostat and subbase must be replaced 61 60 2485 8 T874 MULTISTAGE THERMOSTATS AND 674 SUBBASES Table 8 T874 Cross Reference Model Fig Trade Model Number No Description Replacement Remarks G1873 160 Obsolete Honeywell logo TRADELINE model Premier Y594G1567 Replacement is beige White color designed to replace Y594G1013 York part no 2TH11702424 Y594G1229 York part no 6TH11702424 and York part no 2TH117704124 used with Q674J

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