Honeywell T8621D User's Manual
Contents
1. BATTERY PLACEMENT NOTE CORRECT PLUS AND MINUS DIRECTION 372A Fig 11 Battery placement 69 0330 3 When the batteries are low the display will flash REPL BAT The building owner will have 20 30 seconds to install new batteries after removing old batteries from thermostat After 20 30 seconds it will be necessary to reprogram REPL BAT indication will disappear when ther mostat is mounted back on the subbase If batteries are completely dead the display will go blank After replacing the battery in this case reprogram ming will be necessary POWER OUTAGES Backup batteries will hold the programming and keep the display on during most power outages Once the power is restored the system will resume normal operation If the display goes off when power is lost either the backup batteries need to be replaced or are not installed When power is restored the display will flash 1 00 PM to remind you to reprogram MOUNTING THE THERMOSTAT Hang the thermostat on the tabs at the top of the base Fig 12a Swing down and press on lower edge until thermostat snaps in place Fig 12b Open cover and tighten the captive mounting screws Fig 12c Fig 12 Mounting thermostat on subbase SETTING DAY AND TIME Restore 24 V power to the thermostat When2. FAN OPERATION OPTION SWITCH The SUPER TRADELINE model includes a fan opera tion option switch on the subbase visible before the ther mostat is mounted on the subbase The switch should be in electric heat position for electric heating systems that do not have independent fan control INSTALLING BATTERIES Three AAA alkaline batteries are provided as backup to prevent program loss in case of power outage Batteries are included with thermostat Install batteries in back of thermo stat as shown in Fig 11 Without battery backup the program will remain about 30 seconds in event of power loss IMPORTANT When batteries are first installed the display will flash 1 00 PM and 32 or 0 The temperature display will stay at 32 or 0 until the thermostat is powered from the system wiring CYCLES TIME TEMP SYSTEM PERHOUR DisPLAY GRAVITY OUT 1 2 OUT 1 2 AIR WATER TO 1 TURN TO 1 TURN 24HR HOT OUT 1 2 IN WATER TO 1 TURN 12HR GAS OIL IN IN WARM AIR FACTORY SETTING OUT 1 2 TO 1 TURN ELECTRIC IN OUT 1 2 OUT 1 2 WARM AIR TO 1 TURN TO 1 TURN A SCREWS 2A 2B ONLY AVAILABLE ON SOME MODELS M311A Fig 10 Cycle rate adjustment
3. power is applied to the thermostat the display will read 1 00 PM and room temperature It will go off for a few seconds then begin to flash on and off Set present day and time to set the current day Each press of the DAY key advances the display one day Press TIME or to setthe currenttime If the display will not come on check mounting of thermostat to subbase If loose or misaligned remove thermostat and reinstall on the subbase making sure it is firmly attached check to see that heat or cool system power is on check voltage between R and C should be 24 to 30 Vac CHECKOUT HEATING NOTE When heating setting is changed thermostat will wait up to 5 minutes before turning on the heating equipment This delay protects the compressor Move the system switch to HEAT and the fan switch to AUTO Press WARMER key until the setting is about 10 F 6 C above room temperature Heating should start both stages if multistage and the fan should run may be a short delay on gas or oil forced air systems Press COOLER key until the setting is about 10 F 6 C below room tempera ture The heating equipment should shut off followed by the fan NOTE On an AUTO changeover thermostat the cooling temperature must be set at least 3 F 2 C above the heating temperature or display will flash COOLING CAUTION Do not operate cooling if outdoor temperature is below 50 F 10 C Refer to ma
4. EEP WIRING BELOW THIS SURFACE CROSS SECTIONAL VIEW OF TERMINAL AREA Fig 3 Restrict wiring to recessed area surrounding terminals WIRING All wiring must comply with local electrical codes and ordinances Disconnect power before wiring to prevent electrical shock or equipment damage The shape of the terminal barrier permits insertion of straight or conventional wraparound wiring connections Either method is acceptable Push excess wire back into the hole and plug hole with nonhardening caulk putty or insulation to prevent drafts from affecting thermostat operation Refer to Figs 4 9 for typical hookups of subbase thermo stat NOTE Restrict all wiring to recessed area surrounding terminals Fig 3 to assure thermostat subbase contact ADJUSTING CYCLE RATE To custom tailor the thermostat s cycling performance to different types of heating equipment cycle rate adjust ment screws are provided on the back of the thermostat Correct setting of these screws will provide optimum room temperature control NOTE MOST APPLICATIONS WILL NOT REQUIRE A CHANGE IN CYCLE RATE HEATING TRANSFORMER HEAT RELAY FAN COOLING SWITCH CONTACTOR ovo FAN RELAY L1 HOT L2 A COOLING TRANSFORMER A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A FOR SINGLE TRANSFORMER SYSTEM JUMPER R AND RC A NOMINAL 24 Vac POWER MUST BE PRESENT BETWEE
5. N R AND C FOR THERMOSTAT OPERATION M1574 Fig 4 T8621A 1 stage heat 1 stage cool thermostat with HEAT AUTO COOL OFF system and AUTO ON fan switching HEATING TRANSFORMER N L1 AV HOT A Cc L2 HEAT RELAY 1 HEAT RELAY 2 Eee COOLING CONTACTOR 2 ovo COOLING CONTACTOR 1 AUTO N FAN RELAY COOLING TRANSFORMER A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A FOR SINGLE TRANSFORMER SYSTEM JUMPER R AND RC A NOMINAL 24 Vac POWER MUST BE PRESENT BETWEEN R AND C FOR THERMOSTAT OPERATION M1573 Fig 5 T8621C D 2 stage heat 2 stage cool thermostat with HEAT AUTO COOL OFF system and AUTO ON fan switching For T8621C delete second cooling stage SYSTEM TRANSFORMER Q POWER SUPPLY Hove i us cooune CHANGE SYSTEM a Ns SWITCH TITEL HEAT AUTO COMPRESSOR COOL CONTACTOR OFF FAN RELAY Lovo E POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED ADD RELAY SPDT TO ACCOMMODATE COOLING CHANGEOVER T8621D ONLY NOTE SET CYCLE RATE TO HOT WATER SETTING 3 cph THERMOSTAT DOES NOT PROVIDE MINIMUM OFF TIME IN HEATING M1575 Fig 6 T8621C D single stage heat pump thermostats with cooling changeover HEAT AUTO COOL OFF system and AUTO ON fan switching 69 0330 3 L1 A HEATING T
6. PETE TU rl am fec ET Ie DA AENA V PM es t 0 ROOM SUN MON TUE WED THU FRI SAT TEMPORARY ourooon MORNING MIDDAY EVENING NIGHT COOL ON HEAT ON Fig 13 All segments on display 2 Set system switch to OFF Press AHEAD and BACK and PRESENT SETTING keys at the same time to enter self test 3 Press each key as listed below and look for response listed as key is held down and released SYSTEM PRESS LOOK FOR THIS RESPONSE SWITCH THIS KEY KEY POSITION KEY DOWN RELEASED OFF CHANGE 03 Blank PERIOD Ea 07 Blank NEXT PERIOD 15 Blank SETTING COOL or 15 1st stage cooling AUTO with fan and SYSTEM fan in AUTO LED on 15 2nd stage cooling SEEING also on 15 2nd stage cooling off SETTING 15 1st stage cooling fan Sou and SYSTEMLED off NOTE If single stage cooling system press key twice instead of 4 times once to turn cooling fan and SYS TEM LED on second time to turn off OFF 06 Blank Sz 02 Blank 05 Blank 04 Blank 01 Blank FROM 00 Blank TO CHECK 12 See note EACH e POSITION Blank PERIOD Microprocessor mask DAY no and revision no 09 Blank HEAT COOL B PRESENT DAY TIME HEAT or SET 14 AUTO DAYTIME e m n Blank 1st stage heating and ME SYSTEM LED on ET yr 14 2nd stage heating DAY TIME also on SET 14 2nd stage heating off PRESENT DAY TIME SET 14 1st stage heating and SYS
7. RANSFORMER SYSTEM 2 CHER FAN ou OPERATION EE Anne Ez EECR STAGE 1 HEAT RELAY won AN ELECTRIC O Ho HEATING CHANGEOVER SYSTEM STAGE 2 HEAT RELAY SH SYSTEM SWITCH COMPRESSOR CONTACTOR HEATING DAMPER OR HEAT CHANGEOVER RELAY AUTO COOLING DAMPER OR CHANGEOVER RELAY COOL OFF STAGE 2 COOLING RELAY E11 STAGE 1 COOLING RELAY FAN FAN SWITCH AUTO FAN RELAY SWITCH FAN RELAY ON AUTO A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD COOLING PROTECTION AS REQUIRED TRANSFORMER T8621D ONLY A NOTE SET CYCLE RATE TO HOT WATER SETTING 3 cph ON L1 L2 THERMOSTAT DOES NOT PROVIDE MINIMUM OFF TIME A POWER SUPPLY PROVIDE DISCONNECT MEANS HOT IN HEATING M1576 AND OVERLOAD PROTECTION AS REQUIRED A FOR GAS OR OIL APPLICATIONS OR ELECTRIC HEAT APPLICATIONS WHERE THE FAN OPERATION IS CONTROLLED INDEPENDENTLY OF THE THERMOSTAT AUTO FAN OPERATES WITH Y1 ONLY TWO TRANSFORMERS MAY BE USED SET SWITCH TO NONELECTRIC POSITION FOR ELECTRIC HEAT APPLICATIONS AUTO FAN OPERATES WITH W1 AND Y1 USE ONLY ONE TRANSFORMER JUMPER R AND RC SET SWITCH TO ELECTRIC POSITION A NOMINAL 24 VAC POWER MUST BE PRESENT BETWEEN R AND C FOR THERMOSTAT OPERATION M13444 Fig 7 T8621C D single stage heat pump thermostats Fig 8 T8621D 2 stage heat 2 stage cool manual with heating changeover HEAT AUTO COOL changeover
8. TEM LED off NOTE If single stage heating system press key twice instead of 4 times once to turn heating and SYSTEM LED on second time to turn off OFF HOLD 10 TEMP Blank 11 Normal operating display 7 For electric heat fan operation The fan will operate with the heating system when fan switch is in AUTO HEAT displayed when system switch is in HEAT COOL when in COOL HEAT and COOL when in AUTO neither when in OFF Also a four digit code is displayed with each digit explained below PROGRAM D 2 z 69 0330 3 CYCLE RATE SETTING SYSTEM CPH at 50 on time for THIRD MANUAL OR AUTO SWITCH FIRST stage 1 on 1 heat models DIGIT CHANGEOVER POSITION DIGIT stage 2 on 2 heat models 0 Manual HEAT or OFF 0 1 1 Auto HEAT or OFF 1 3 3 Auto AUTO 2 9 4 Manual COOL 3 6 5 Auto COOL It Ft A t Ch M13443 SECOND STAGES OF SYSTEM DIGIT HEAT COOL FOURTH CLOCK SWITCH 0 2 1 DIGIT DEGREES HRS POSITION 1 2 2 0 F 12 COOL AUTO 2 1 1 or OFF 3 1 2 1 F 24 COOL AUTO 4 0 2 or OFF 5 1 o 2 F 12 HEA 6 2 0 3 F 24 HEAT 4 C 12 COOL AUTO or OFF 5 C 24 COOL AUTO or OFF 6 C 12 HEAT 7 C 24 HEAT This equipment is a Class B digital apparatus which complies with Canadian Radio Interference Regulations CRC c 1374 Honeywell Inc International Sales Offices in all principal cities of the world Manuf
9. TRADELINE T8621A C D CHRONOTHERM III FUEL SAVER THERMOSTATS APPLICATION These thermostats provide energy saving control for a 24 Vac heating cooling system as indicated in Table 1 and are powered direct from the control transformer As long as thermostat is continuously powered the thermostat will be compatible with any control system These models include a SYSTEM LED which is on whenthe thermostatis signaling for heating or cooling Heat necessary Cycle rates are adjustable for highest stage of heating Fan operation option switch is included on SUPER TRADELINE model to select fan operation for electric heat application 12 24 hour clock conversion and C F conversion is available on some models only and cool anticipation is fixed in all models no adjustment is TABLE 1 THERMOSTAT MODELS STAGES SWITCHING THERMOSTAT HEAT COOL SYSTEM FAN APPLICATION T8621A 1 1 HEAT AUTO COOL OFF ON AUTO Single Stage T8621C 2 1 HEAT AUTO COOL OFF ON AUTO Multistage T8621D 2 2 HEAT AUTO COOL OFF ON AUTO Multistage T8621D8 2 2 HEAT OFF COOL ON AUTO Multistage 8SUPER TRADELINE model INSTALLATION WHEN INSTALLING THIS PRODUCT 1 Read these instructions carefully Failure to follow them could damage the product or cause a hazardous condition 2 Check the ratings on the product to make sure the product is suitable for your application 3 Installer must be a trained experienced service te
10. acturing in U S A 1885 Douglas Drive N Australia Canada Finland France Germany Japan Mexico Netherlands Golden Valley MN 55422 4386 Spain Taiwan United Kingdom U S A Q K CANADA 740 Ellesmere Road Scarborough Ontario M1P 2V9 PRINTED IN TAIWAN R O C QUALITY IS KEY
11. ble with one conductor for each wiring terminal is recommended Good service prac tice recommends selecting cable with one or two more conductors than the immediate application requires MOUNTING SUBBASE IMPORTANT The T8621 requires an additional conductor to transformer common to provide continuous 24 V power for thermostat operation Set the system switch in the OFF position before mounting the subbase The subbase does not require leveling for proper opera tion but for appearance only Remove thermostat from subbase Fig 1 The subbase mounts directly onto the wall with the screws and anchors included in the package If drywall construction plastic anchors must be used use the sub base as a template and with a pencil mark the two mounting screw positions Fig 2 Use 3 16 in bit to drill holes for anchors Gently tap anchors into holes until they are flush to the wall surface Thread wires through the center opening of the subbase Then mount the subbase using two screws provided Gently tighten screws level top surface of subbase then securely tighten screws Fig 1 Removing thermostat from subbase Form Number 69 0330 3 Honeywell Inc 1990 MOUNTING SCREWS 2 M846 Fig 2 Mounting subbase on wall FOR STRAIGHT INSERTION STRIP 5 16 in 8 mm FOR WRAPAROUND RESTRICT STRIP 7 16 in 11 mm WIRING TO THIS AREA FRONT VIEW OF TERMINAL AREA TOP SURFACE OF SUBBASE K
12. ch nician 4 Allow thermostat to warm to room temperature before operating 5 After installation is complete check out product op eration as provided in these instructions CAUTION Disconnect power supply to prevent electrical shock or equipment damage IMPORTANT After wiring is complete push excess wire back into the hole and plug hole with nonhardening caulk putty or insulation to prevent drafts from affecting thermostat operation LOCATION Install thermostat and subbase about 5 ft 1 5 m above the floor in an area with good air circulation at room temperature Do not install the thermostat where it may be affected by drafts or dead spots behind doors in corners or under cabinets hot or 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 IF REPLACING AN EXISTING THERMOSTAT Turn power to thermostat off at furnace or boiler A two transformer system may require turning off two switches or disconnects Remove any existing wallplate or subbase from wall Label or write down each wire color with the letter or number on the wiring terminal as the wire is removed to avoid miswiring later C H Rev 12 90 IF NEW INSTALLATION Run cable to a hole at the selected wall location and pull about 3 in 76 mm of wire through the opening Color coded 18 gauge thermostat ca
13. nufacturer s recom mendations NOTE When cooling setting is changed thermostat will wait up to 5 minutes before turning on the cooling equipment This delay protects the compressor Move the system switch to COOL and the fan switch to AUTO Press COOLER key until the setting is about 10 F 6 C below room temperature The cooling equipment and fan should start Press WARMER key until the setting is about 10 F 6 C above room temperature The cooling equipment and fan should stop NOTE On an AUTO changeover thermostat the heating temperature must be set at least 3 F 2 C below the cooling temperature or display will flash FAN Move the system switch to OFF and the fan switch to ON The fan should run continuously When the fan switch is in the AUTO position fan operates directly with the cooling system and also with heating system on some models INSTALLER SELF TEST optional IMPORTANT AC power must be present on thermostat to con duct self test Relays will nottoggle codes will not be present and thermostat will not manually exit self test without ac power Five minute time delay on cooling does not func tion during self test Perform the following test as a check of all thermostat functions If thermostat does not respond as indicated thermostat must be replaced 1 Press AHEAD and BACK keys at the same time While holding keys down all segments ofthe display should be on Fig 13
14. thermostat with auto fan on heat OFF system and AUTO ON fan switching and cool convertible to auto fan on cool only HEAT OFF COOL system and AUTO ON fan switching SYSTEM TRANSFORMER HIGH LIMIT FAN OPERATION NON ELECTRIC O SYSTEM HEATING SWITCH CHANGEOVER RELAY Et COOLING CHANGEOVER RELAY COMPRESSOR CONTACTOR FAN RELAY ON RC AN POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED FAN SWITCH A FAN OPERATION SWITCH MAY BE IN EITHER POSITION A NOMINAL 24 VAC POWER MUST BE PRESENT BETWEEN R AND C FOR THERMOSTAT OPERATION VM edo Fig 9 T8621D single stage manual changeover heat pump thermostat HEAT OFF COOL system and AUTO ON fan switching The room air temperature will normally vary slightly from the comfort temperature setting with the cycling of the furnace or air conditioner The heating cycle rate of this thermostat is factory set for gas oil warm air heating The cooling cycle rate cannot be adjusted The heating cycle rate can be adjusted by turning one or both cycle rate adjustment screws located on the back of the thermostat In multistage heat systems the cycle rate adjustment applies to stage 2 only stage 1 is fixed See Fig 10 TIME TEMPERATURE CONVERSION SOME MODELS The display readout may be converted between 12 and 24 hour clock or C and F using screws 2A and 2B as indicated in Fig 10
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