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Honeywell CHRONOTHERM T8621A User Manual

Fuel saver thermostats
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The T8621A,C,D Chronotherm III Program-
mable Fuel Saver Thermostats provide auto-
matic control of single or multistage heating/
cooling systems and offer users the highest
standard of comfort and convenience available
with energy savings.
Full seven-day program capability; different sched-
ules may be selected for every day.
Can be programmed in hand (with batteries in-
stalled) or on wall to provide up to four temperature
settings per day.
Large digital clock (liquid crystal display) indi-
cates continuous time, day, current period and
room temperature.
Adaptive Intelligent Recovery™ brings room
temperature to programmed temperature at pro-
grammed time, maximizing comfort and energy
savings.
Temperature control program maintains tempera-
ture within 1 F of setpoint.
Temporary program override available by using-
-W ARMER and COOLER keys
-SKIP next period key
-CHANGE to last period key
HOLD TEMP key provided for indefinite pro-
gram override (vacation/holiday).
Installer self-test and time delay override save
installation time.
SYSTEM light-emitting diode (LED) indicates
system is energized.
Chronotherm™ III Fuel
Saver Thermostats
C. H. • Rev. 8-92 • ©Honeywell Inc. 1992 • Form Number 68-0058-1
T8621A,C,D
Models available with automatic or manual heat/
cool changeover.
Batteries included provide power to maintain
clock and memory during power failures.
Switching subbase with wiring terminals included.
Powered directly from control transformer, requir-
ing an extra (24V) wire to thermostat.
Fan operation switch included on back of SUPER
TRADELINE models to select either indepen-
dent or direct thermostat control of fan in heating.
Models available with separate sensor for remote
mounting.
CONTENTS
Specifications ............................................... 2
Ordering Information ................................... 2
Selection/Application ................................... 5
Installation ................................................... 7
Checkout ..................................................... 17
Programming the Thermostat .................... 19
Operating the Thermostat .......................... 25
Operation ................................................... 28
Troubleshooting ......................................... 29
Glossary ..................................................... 30
Table of Contents ....................................... 31
1
68-0058-1

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  Summary of Contents for Honeywell CHRONOTHERM T8621A

  • Page 1: Table Of Contents

    Checkout ... 17 Programming the Thermostat ... 19 Operating the Thermostat ... 25 Operation ... 28 Troubleshooting ... 29 Glossary ... 30 Table of Contents ... 31 C. H. • Rev. 8-92 • ©Honeywell Inc. 1992 • Form Number 68-0058—1 68-0058—1...
  • Page 2: Specifications

    If you have additional questions, need further information or would like to comment on our products or services, please write or phone: 1. Your local Honeywell Home and Building Control Sales Office (check white pages of your phone directory). 2. Home and Building Control Customer Satisfaction Honeywell Inc., 1885 Douglas Drive North...
  • Page 3 40 F to 110 F [4 C to 43 C]. SETPOINT RANGE: 45 F to 88 F [7 C to 31 C]. CALIBRATION: Self-calibrating thermostat and ther- mometer to 1 F. SHIPPING TEMPERATURE: -20 F to +120 F [-29 C to +49 C].
  • Page 4: Selection/Application

    T8621A,C,D SPECIFICATIONS • SELECTION/APPLICATION Fig. 2—202905AA Remote Temperature Sensor dimensions in in. [mm]. FRONT Fig. 3—Typical thermostat keypad. PROGRAM PRESENT DAY/TIME HOLD TEMP HEAT/COOL HEAT SIDE [50] [104] MIDDAY COPY PERIOD FROM CANCEL COPY PERIOD COOL BACK [51] [50] 64 [16] [35] DIA.
  • Page 10: Installation

    T8621A,C,D INSTALLATION Fig. 9—T8621C 2-stage heat/1-stage cool thermostat with HEAT-AUTO-COOL-OFF system and AUTO-ON fan switching. THERMOSTAT LOGIC CIRCUIT POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FOR SINGLE TRANSFORMER SYSTEM JUMPER R AND RC. HIGH LIMIT POWER SUPPLY...
  • Page 11 Fig. 10—T8621D 2-stage heat/2-stage cool thermostat with HEAT-AUTO-COOL-OFF system and AUTO-ON fan switching. THERMOSTAT LOGIC CIRCUIT POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. FOR SINGLE TRANSFORMER SYSTEM JUMPER R AND RC. NOMINAL 24 Vac POWER MUST BE PRESENT BETWEEN R AND C FOR THERMOSTAT OPERATION.
  • Page 12 T8621A,C,D INSTALLATION Fig. 11—T8621D 2-stage heat/2-stage cool thermostat with HEAT-OFF-COOL system and AUTO-ON fan switching; auto fan on heat and cool; convertible to auto fan on cool only. THERMOSTAT LOGIC CIRCUIT POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
  • Page 13 SWITCH SUBBASE AUTO LOGIC/ CONTROL CIRCUIT T8621D ONLY. DENOTES THERMOSTAT TO SUBBASE CONNECTIONS. NOTE: SET CYCLE RATE TO HOT WATER SETTING (3 cph). THERMOSTAT DOES NOT PROVIDE MINIMUM OFF TIME IN HEATING. T8621A,C,D INSTALLATION (HOT) SYSTEM TRANSFORMER HEATING CHANGEOVER COMPRESSOR...
  • Page 14 200 ft. [61 m] MAXIMUM LENGTH. ROUTE INTERCONNECT CABLE AWAY FROM SOURCES OF ELECTRICAL NOISE. T8621D ONLY. DENOTES THERMOSTAT TO SUBBASE INTERCONNECTION. NOTE: SET CYCLE RATE TO HOT WATER SETTING (3 cph). THERMOSTAT DOES NOT PROVIDE MINIMUM OFF TIME IN HEATING. (HOT) SYSTEM...
  • Page 15: Adjusting Cycle Rate

    ADJUSTING CYCLE RATE To customize the thermostat cycling performance to various types of heating equipment, cycle rate adjustment screws are provided on the back of the thermostat to provide optimum room temperature control. NOTE: Most applications will not require a change in...
  • Page 17: Checkout

    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 thermostat call for cooling and also with the thermostat call for heating. T8621A,C,D INSTALLATION •...
  • Page 18: Installer Self-Test

    2. Five-minute time delay on cooling does not function 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.
  • Page 19: Programming The Thermostat

    ENTER THE DAY AND TIME This thermostat can be programmed either on wall or in hand. See page 8 to find out how to remove the thermostat from the subbase. Always press the keys with fingertip or similar blunt tool. Sharp instruments like a pen or pencil point can damage the keyboard.
  • Page 20: Set The Program Times And Temperatures For One Day

    If the display flashes while holding down TEMPERATURE WARMER or COOLER, the setting limit has been reached. If thermostat is an auto- changeover model, the heating tempera- ture must be at least 3 degrees below the air conditioning temperature. For ex- ample, if the cooling setting is 75 F, the maximum heating setting is 72 F.
  • Page 21 If the display blinks while holding down TEMPERATURE WARMER or COOLER, the setting limit has been reached. If thermostat can switch auto- matically between heating and cooling, the heating temperature must be at least 3 degrees F below the air conditioning temperature.
  • Page 22: Copy The Program To The Desired Days

    T8621A,C,D PROGRAMMING THE THERMOSTAT STEP 3 COPY THE PROGRAM TO THE DESIRED DAYS It is possible to copy the program for one day to any other day or combination of days. The new program will replace any program already set in the day se- lected.
  • Page 23: Set The Schedules And Temperatures For The Remaining Days

    NOTE: The display will show 32 F instead of the current temperature until the thermostat is mounted on the subbase and the system is pow- ered. STEP 4 SET THE SCHEDULES AND TEMPERATURES FOR THE REMAINING DAYS Use the procedures described in Steps 2 and 3 and summarized in this step to program the remaining days.
  • Page 25: Operating The Thermostat

    Now, read on to learn about the operating flexibility that makes this thermostat the smart choice. TEMPORARILY CHANGING THE PROGRAM These features allow customizing the program for those times when someone comes home early, is working late or planning to be out for the evening.
  • Page 26: Holding A Temperature For Extended Absence

    It does not cancel the program. CANCELING PROGRAM SETTINGS The thermostat requires time and tem- perature settings in the MORNING time period for each day, but any of the others can be canceled. Each time pe- riod for each day must be canceled separately.
  • Page 27: Checking The Program Times And Temperatures

    During recovery from energy savings, the setting displayed will not match the programmed setting. This is because the thermostat gradually changes the temperature setting during recovery to provide maximum comfort combined with most efficient use of the heating or cooling equipment.
  • Page 28: Operation

    T8621A,C,D OPERATION ADAPTIVE INTELLIGENT RECOVERY™ OPERATION Adaptive Intelligent Recovery™ is the Honeywell trade- mark for the way the T8621 controls the heating and cooling equipment during recovery from an energy sav- ings setting to a comfort setting. During recovery, the control point changes gradually rather than jumping from the energy savings setting to the comfort setting all at once.
  • Page 29: Troubleshooting

    –CHECK WIRING DIAGRAM CONDUCT SELF-TEST; SEE CHECKOUT. ADJUST TEMPERATURE BY PUSHING WARMER/ COOLER KEYS. RESET THERMOSTAT SYSTEM SWITCH. WAIT 5 -10 MIN. OR USE SELF-TEST IN THERMOSTAT. SEE CHECKOUT. CHECK CIRCUIT DIAGRAM. CONSULT FURNACE OR AIR CONDITIONER INSTRUCTIONS. REPLACE THERMOSTAT.
  • Page 30: Glossary

    Also called the setback (heating) or setup (cooling) temperature. Preprogrammed schedule This is the schedule programmed into the thermostat at the factory. It sets a night program that provides energy savings when owner sets no program, or if personal program is lost for any reason.
  • Page 31: Table Of Contents

    Adjusting Cycle Rate ... 15 Time/Temperature Conversion ... 15 Fan Operation Option Switch ... 16 Installing Batteries ... 16 Power Outages ... 16 Mounting the Thermostat ... 16 Setting Day and Time ... 16 Checkout ... 17 Heating ... 17 Cooling ... 17 Fan ...
  • Page 32 Home and Building Control Home and Building Control Honeywell Inc. Honeywell Limited—Honeywell Limitée 1985 Douglas Drive North 740 Ellesmere Road Golden Valley, MN 55422 Scarborough, Ontario M1P 2V9 Printed in U.S.A.