Honeywell Q674B User's Manual
Contents
1. HEAT RELAY 2 Exh SYSTEM HEAT RELAY 3 SWITCH l RESET HEATER HEAT CHANGEOVER VALVE C1 ANTICIPATOR 7 47r A7 FAN RELAY o o C2 ANTICIPATOR COOL CHANGEOVER VALVE 4 COMPRESSOR CONTACTOR 2 I POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED COMPRESSOR CONTACTOR 1 4 Fig 7 T874W Q674B with outdoor reset in heating and cooling system 69 0087 6 4 THERMOSTAT a 7874H Q W MULTISTAGE THERMOSTATS AND Q674B C G L SUBBASES SUBBASE i H1 ANTICIPATOR il H2 ANTICIPATOR H3 ANTICIPATOR AUXILIARY HEAT LED GREEN SYSTEM COMPONENTS L1 A IL C815A OD THERMISTOR AUX HEAT RELAY m gt gt FAN SWITCH AUTO yj RESET EMERGENCY HEAT LED RED 8 FAN RELAY Eve EM HEAT RELAY A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED AA connect CHANGEOVER RELAY TO O TERMINAL FOR CHANGEOVER IN COOLING OR TO B TERMINAL FOR CHANGEOVER IN HEATING CONTACTOR 2 A COMPRESSOR D MONITOR CHECKLED Y RED 02 SYSTEM SWITCH 8 T A CHANGEOVER RELAY HEAT CHANGEOVER RELAY COOL vs Y COMPRESSOR CONTACTOR 1 9 COMPRESSOR oo M156A Fig 8 T874W Q674L for three stage heat and two stage cool with outdoor reset a2. between W2 and R Move the system switch to AUTO if applicable Q After one minute read the ammeter and record the reading After mounting the thermostat set the adjustable heat anticipator s to match the respective reading s measured in step Temperature Setting Move the heating and cooling levers to the desired positions The minimum differential between the heating and cooling setpoints is 3 F 1 7 C which means the setting levers cannot be set closer together than 3 F 1 7 C 6 F 2 8 C for T874W Subbase Setting System switching positions control thermostat operation as follows OFF Both the heating and cooling systems are off If the fan switch is in the AUTO position the cooling fan is also off AUTO Thermostat automatically changes between the heat and cool modes depending on the indoor temperature HEAT Heating system is controlled by the thermostat Cooling system is off EM HT Emergency heat relay is energized The cooling system is off When the compressor has failed and the heat pump is not operating switch to the EM HT position Fan switching positions control fan operation as follows Q674B C or L ON Fan operates continuously AUTO Fan operates with cooling equipment as controlled by the thermostat or with the heating equipment as controlled by the plenum switch To switch positions use thumb and index finger to slide the lever to the desired position The switch leve
3. electrical shock or equipment damage 2 Run the wires as close as possible to the subbase To prevent interference with the thermostat linkage keep the wire length to a minimum Push the excess wire back into the hole and plug the hole to prevent drafts from affecting the thermostat operation 3 Do not tighten the thermostat captive mount ing screws to the point of damaging the subbase threads 4 short across the coil terminals on the relay This can burn out the heat anticipator 5 Never install more than one wire per terminal unless a factory supplied jumper with a spade terminal is used IMPORTANT These thermostats are calibrated at the factory by using subbases mounted at true level Inaccurate subbase leveling causes thermostat control deviation Location Install the thermostat about 5 ft 1 5m above the floor in an area with good air circulation at average temperature Do not install the thermostat where it can be affected by drafts or dead spots behind doors and in corners hotor cold air from ducts radiant heat from sun or appliances concealed pipes and chimneys unheated uncooled areas behind the thermostat Such as an outside wall Mounting and Wiring the Subbase Mount the subbase on a wall or horizontal outlet box If you mount it on a vertical outlet box order Honeywell part no 193121A Adapter Assembly which includes an adapter ring with two screws and a cover pl
4. ERMOSTAT THERMOSTAT UP TO 12 M927 Fig 2 Leveling subbase Connect the system wires to the subbase See Fig 4 through 9 A letter code for identification is located near each terminal The terminal barrier permits straight or conventional wraparound wiring connections See Fig 3 Either method is accept able Run the wires as close as possible to the subbase keeping the wire length to a minimum Push the excess wire back into the hole Plug the hole to prevent drafts IMPORTANT An incorrectly leveled subbase causes the temperature control to deviate from the setpoint 7874H Q W MULTISTAGE THERMOSTATS AND Q674B C G L SUBBASES Mounting C815A Thermistor T874W only INSERTIONS FOR WRAPAROUND The T874W is used with the C815A Thermistor mounted in STRIP 5 16 in 8 mm STRIP 7 48 in R1 mm the outdoor section Locate it in an area where it can measure the true outdoor ambient temperature Avoid mounting the C815A in an area where it is exposed to high temperatures or direct sunlight Refer to heat pump equipment instructions for proper mounting BARRIER SUBBASE TERMINAL SCREW M928 Fig 3 Wiring connections SYSTEM COMPONENTS THERMOSTAT SUBBASE RN COOL CHANGEOVER VALVE FALL FAN SWITCH FAN RELAY sf SYSTEM SWITCH C
5. Honeywell T8 4H Q W Multistage Thermostats and Q674B C G L Subbases APPLICATION The T874H Q W Multistage Thermostats provide 24 to 30 Vac control for heating and cooling systems as listed in Table 1 Table 1 Heating and Cooling Stages itor Moet we eo Cocina Sages 1 2 Plus a changeover stage that operates with cooling The Q674B C G L Subbases provide wiring terminals system and fan switching and mounting bases for T874 Multistage Thermostats as listed in Table 2 Table 2 Switching Positions Q674 Switch Positions E Rm s haoc Amos Pe orm wwe G OPERATION On a two stage or three stage heat thermostat the stages of heat zake sequentially as the temperature drops Make refers to the mercury switch initiating a call for heat or cool There are about 2 F 1 C between the stages so that the Second stage makes only when the first stage can not handle the load About one degree later the third stage makes T874W only This degree difference is called the interstage differential Select models include LEDs light emitting diodes The LED lights to indicate a problem with the system refer to the system manufacturer instructions Copyright 1996 Honeywell Inc All Rights Reserved INSTALLATION INSTRUCTIONS When an LED lights refer to this list for the meaning FILTER clogged filter needs replacement EM HT emergency heat is o
6. OMPRESSOR Fs 4 CONTACTOR RISE ANTICIPATOR Je 10 L1 12 MF RISE C1 DENON TE COMPRESSOR ZA POWER SUPPLY PROVIDE DISCONNECT MEANS FAULT AND OVERLOAD PROTECTION AS REQUIRED AA SERVICE LED ON SELECT MODELS M3680A Fig 4 T874H Q674C in heating cooling system THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR Hi FAN switch wae OFOMER Q Q LE AUTO OY ME 3 9 12 FAN RELAY Li COMPRESSOR Hon CONTACTOR F RISE SYSTEM SWITCH SERVICE C1 ANTICIPATOR GF 88 YELLOW 10 FN AUTO _ ci RISE G 24 VAC A POWER SUPPLY PROVIDE DISCONNECT MEANS FILTER LED RED AND OVERLOAD PROTECTION AS REQUIRED Lg M5902 Fig 5 T874H Q674C in heating cooling system with SERVICE LED and FILTER LED 69 0087 6 7874H Q W MULTISTAGE THERMOSTATS AND Q674B C G L SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR W1 A NO FAN SWITCH CHANGEOVER RELAY H2 ANTICIPATOR FAN RELAY SYSTEM swicHO O OFF 10 COMPRESSOR A CONTACTOR 12 AUTO 8 L1 POWER SUPPLY PROVIDE DISCONNECT MEANS AND Hon OVERLOAD PROTECTION AS REQUIRED M6008A FS C1 ANTICIPATOR RISE AAN 8 Fig 6 T874Q Q674G for heating only system SYSTEM COMPONENTS O A C815A THERMISTOR THERMOSTAT SUBBASE L1 HOT FAN SWITCH HEAT RELAY 1 H3 ANTICIPATOR
7. about 10 F 6 C below room temperature The heating equipment shuts off and the fan runs for a short time and then shuts off Cooling Move the system switch on the Q674 Subbase to COOL or AUTO Move the cooling lever on the T874 Thermostat about 10 F 6 C below room temperature The cooling equipment and fan start Move the cooling lever about 10 F 6 C above room temperature The cooling equip ment and fan stop Emergency Heat Move the system switch to EM HT The EM HT LED comes on Move the heating lever about 10 F 6 C above room temperature The electric strip heater s comes on Move the heating lever about 10 F 6 C below room temperature The electric strip heater de energizes The EM HT LED remains on until the system switch is moved to another postion 69 0087 6 7874H Q W MULTISTAGE THERMOSTATS AND Q674B C G L SUBBASES Fan Select Models Move the subbase system switch to OFF and the fan Switch to ON The fan runs continuously When the fan switch is in the AUTO position the fan operation is controlled by the heating or cooling system CALIBRATION Thermostat T874 Thermostats are accurately calibrated at the factory They do not have provision for field calibration Thermometer Remove the thermostat cover by pulling up from the bottom of the cover until it clears the locking springs Set the cover on a table near an accurate thermom eter After allowing 10 or 15 minutes for s
8. ate to cover the marks on the wall All wiring must comply with local electrical codes and ordinances Follow the equipment manufacturer wiring instructions when available To install the subbase Prepare a hole for the thermostat wires at the chosen location Run wires to the location Pull about 6 in 152 mm of wire through the hole IMPORTANT Use 18 gauge color coded thermostat cable for proper wiring When mounting the subbase on a vertical outlet box install an adapter ring with the two screws provided with the adapter assembly See Fig 1 Pull the wires through the cover plate if used and the subbase wire opening Secure the cover plate and subbase with the two screws provided but do not fully tighten Q The subbase mounting slots provide for minor out of level adjustments Level the subbase by using a spirit level and tightening the subbase mounting screws See Fig 2 69 0087 6 OUTLET MOUNTING SCREWS 2 COVER J PLATE A ADAPTER G A HORIZONTAL OUTLET BOX THERMOSTAT COVER E SUBBASE MOUNTING SCREWS 2 CAPTIVE A MOUNTING SCREWS 2 INCLUDED WITH UNIT A accessory PARTS AVAILABLE 1931214 M6009 Fig 1 Installation on vertical or horizontal outlet box TOP MOUNTING HOLES 2 WIRING TERMINAL THERMOSTAT CABLE OPENING 2 SPIRIT LEVEL MOUNTING POST 2 FOR TO SPRING FINGER HOLES 2 MOUNTING CONTACTS ON THE TH
9. nd compressor monitor 69 0087 6 7874H Q W MULTISTAGE THERMOSTATS AND Q674B C G L SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS M NM M FALL H1 ANTICIPATOR il A2 C815A OUTDOOR 1 H2 2 ANTICIPATOR ES al FALE 5 AUX HT RELAY FAN SWITCH AUX HEAT NA Q LED GREEN H3 ANTICIPATOR FAN RELAY EM HEAT L1 gt l PN SYSTEM SWITCH EM HT U ALAH 4 FH LED RED A EM HT RELAY CHECK LED YELLOW XS CHANGEOVER RELAY HEAT 9 CHANGEOVER RELAY COOL compressor CONTACTOR 1 RISE COMPRESSOR CONTACTOR 2 ce 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 M6999 Fig 9 T874W Q674L for three stage heat and two stage cool with outdoor reset Mounting the Thermostat Remove the thermostat cover by pulling the bottom edge of the cover upward 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 Carefully remove and discard the polys
10. perating The compressor has failed and the heat pump is not operating The LED lights when the homeowner places the system switch in the EM HT position AUX HT auxiliary heat is operating because the weather is so cold that the heat pump alone cannot handle the load SERVICE or CHECK system needs to be checked See heating system instructions for specific meaning LEDs are not field addable or replaceable RECYCLING NOTICE This control contains mercury in a sealed tube Do not place the 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 your old control in the trash Contact your local waste management authority for instructions regarding the recycling and the proper disposal of this control or of an old control containing mercury in a sealed tube INSTALLATION When Installing this Product Read these instructions carefully Failure to follow them could damage the product or cause a hazard ous condition Check the ratings given in the instructions and on the product to make sure the product is suitable for your application Q Installer must be a trained experienced service technician After installation is complete check out product operation as provided in these instructions 69 0087 6 7874H Q W MULTISTAGE THERMOSTATS AND Q674B C G L SUBBASES A CAUTION Disconnect the power supply to prevent
11. r must stop in detent over the desired function indicator mark for proper circuit operation C815 Outdoor Reset Thermistor T874W only The T874W is used with a C815 Thermistor mounted in the outdoor section The thermistor must be used if not thermostat performance will deviate radically from proper operation C815A THERMISTOR RESISTANCE T 3800 R 400 ohms 10 AT 77 F 25 C T 20 0 20 40 60 80 100 120 140 TEMPERATURE OF THERMISTOR M1590A Fig 10 Thermistor resistance chart The proper thermistor operation must be verified to assure the correct operation of the thermostat Check the thermistor operation as follows Disconnect the T wire on the subbase Use an ohmmeter to measure resistance between the 7wire and the transformer common Q Take the outdoor temperature at thermistor location and find the correct thermistor resistance on the chart in Fig 10 If the resistance measured in step and the calculated resistance in step vary by more than 15 percent the thermistor requires replacement Contact the installing dealer for the packaged replacement outdoor thermistor CHECKOUT Heating Move the system switch on the Q674 Subbase to HEAT or AUTO Move the heating lever on the T874 about 10 F 6 C above room temperature Both stages of heating start and the fan runs after a short delay Move the heating lever
12. tabilization compare the readings If they are the same replace the cover and put the system into operation If they are different recalibrate the thermostat thermom eter see step Insert a small screwdriver into the thermometer shaft and turn it until the thermometers read the same See Fig 11 When the thermometer is calibrated replace the cover and place the system into operation NOTE Hand heat offsets the thermometer reading After making each adjustment wait 10 or 15 minutes for the thermometer to stabilize before comparing B Pe M5070 Fig 11 Thermometer calibration Honeywell Automation and Control Solutions Honeywell Internationl Inc Honeywell Limited Honeywell Limit e 1985 Douglas Drive North 35 Dynamic Drive Golden Valley MN 55422 Scarborough Ontario MIV 4Z9 69 0087 6 Rev 9 96 Printed in U S A on recycled paper containing at least 10 post consumer paper fibers www honeywell com
13. tyrene packing insert that protects the mercury switches during shipment Tum over the thermostat base and note the spring fingers that engage the subbase contacts Make sure the spring fingers are 7ofbent flat preventing proper electrical contact with the subbase 69 0087 6 o e T874Q only Set the heat anticipator indicators to the respective current setting for each stage See Setting the Heat Anticipator section T874H and T874W have fixed anticipation the settings are preselected and cannot be adjusted Note the tabs along the top inside edge of the thermostat base The tabs fit into the subbase notches Mount the thermostat base on the subbase and tighten the captive mounting screws See Fig 1 Place the upper edge of the thermostat cover on the thermostat base and swing the cover downward until it engages with the cover clip on the base 7874H Q W MULTISTAGE THERMOSTATS AND Q674B G L SUBBASES SETTING Setting the Heat Anticipator T874Q Only Set each heat anticipator to match its primary control current draw If the primary control nameplate has no rating or if further adjustment is necessary use the following procedure to determine the current draw of each stage Measure the current draw of each heating stage with the thermostat removed and the power on Connect an ac ammeter of appropriate range between the heating terminals of the subbase as follows Stage 1 between W1 and RH or R Stage 2
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