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Copyright © 2003 Honeywell •   

 •All Rights Reserved 

OWNER’S GUIDE

69-1620-1

CT3451

Programmable Thermostat

Programmable Heat and/or Cool

Low Voltage (20 to 30 Vac) Thermostat and Wallplate

Congratulations on the purchase of your new thermostat! 
More than 100 years of Honeywell engineering produced 
this thermostat that can provide you with a more 
comfortable and convenient living environment.

Your new thermostat automatically controls the 
temperature in your home, keeping you comfortable 
while saving energy when programmed according to 
these instructions.

Direct questions about this thermostat to our Web site at 
www.honeywell.com/yourhome or call the customer 
information line at 1-800-468-1502.

MERCURY NOTICE

If this control is replacing a control that contains 
mercury in a sealed tube, do not place your old 
control in the trash. Dispose of it properly.

Contact your local waste management authority 
for instructions regarding recycling and the 
proper disposal of an old control. 

1 PREPARE FOR INSTALLATION 

Check Table 1 to make sure this thermostat is 
compatible with your system. If not, return it to the 
retailer.

Acquire tools and items, as needed. See Fig. 1.

Fig. 1. Required installation tools/supplies.

M10614

MERCURY
SWITCH

TYPICAL LOCATION OF A MERCURY 
SWITCH IN A THERMOSTAT

M20551

SCREWDRIVER

HAND OR POWER
DRILL WITH 3/16 INCH
DRILL BIT, IF NEEDED TO
DRILL HOLES IN WALL

WIRE CUTTER/STRIPPER IF NEEDED TO STRIP WIRES

LEVEL, IF NEEDED TO LEVEL
THERMOSTAT FOR APPEARANCE

Summary of Contents for CT3451

Page 1: ...ll com yourhome or call the customer information line at 1 800 468 1502 MERCURY NOTICE If this control is replacing a control that contains mercury in a sealed tube do not place your old control in the trash Dispose of it properly Contact your local waste management authority for instructions regarding recycling and the proper disposal of an old control 1 PREPARE FOR INSTALLATION Check Table 1 to ...

Page 2: ...the C or C1 clock terminals on the Chronotherm Thermostat wiring wallplate Do not allow them to touch or you can damage your transformer Disconnect the wires and wrap them separately using electrical tape do not wrap them together Do not place the wires where they can interfere with the new thermostat operation Record the colors and terminal designation labels of the remaining wires Six or More Th...

Page 3: ...the labels you placed on wires when you removed your old thermostat Match the letter of your old thermostat wire with the terminal of the corresponding letter on your new thermostat Refer to Fig 4 Fig 4 Connecting wiring NOTE To ensure correct mounting of thermostat restrict all wiring to the shaded area in the cen ter of the terminals Loosen the terminal screws and slip each wire beneath its matc...

Page 4: ...2 2 2 1 Y G Rc W 3 R B O HEAT RELAY HEAT DAMPER 3 1 1 HEATING RELAY AND FAN COIL 24V POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M20536 THERMOSTAT Y G Rc W R B O L1 HOT L2 1 FAN COIL COOLIING CONTRACTOR COIL 24V POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED M20537 THERMOSTAT Y G Rc W R B O 1 Y G Rc W 2 R B O M20511 L1 HOT L2 FAN RELAY HEAT ...

Page 5: ...tteries to operate Remove the battery door located on the right side of the thermostat by pulling outward from the bottom See Fig 13 Insert three AA alkaline batteries as shown in Fig 13 NOTE The thermostat shows a bAtLo message on the digital display to alert the homeowner one to two months before the batteries run out com pletely IMPORTANT Homeowner should replace the batteries once a year to pr...

Page 6: ...keys to display the three digit soft ware revision code Information displayed varies by model Press the key FC factory configuration dis plays A typical example is shown but informa tion displayed varies by model This information is for factory use only Setting C or F Press the key again to display the current setting Press the key to change the C or F indication Setting Heat Cycle Rate see Table ...

Page 7: ...ure while you are sleeping IMPORTANT Always press the keys with your fingertip or sim ilar blunt tool Sharp instruments like pens and pencil points can damage the keyboard Setting Current Time and Day 1 To set current time press Select twice Press or key to set current time NOTE While setting the current time the word SET is displayed 2 To set day of week press Select again Press or key to set cur...

Page 8: ...Sleep temperature Setting Saturday and Sunday Programs To set the Saturday program 1 Wake a Press Select Press or key to set Wake time b Press Select Press or key to set Wake temperature 2 Leave a Press Select Press or key to set Leave time b Press Select Press or key to set Leave temperature 3 Return a Press Select Press or key to set Return time b Press Select Press or key to set Return temperat...

Page 9: ...ou to indefinitely hold a temperature When Hold is active the letters Hld are displayed continuously Hold can be canceled by pressing the Hold key again Press Hold Press or key to set indefinite temperature setting 11 SET FAN AND SYSTEM SWITCHES Manually control Fan and System settings using the switches located at the bottom of the thermostat case See Fig 14 for switch locations Fig 14 Time tempe...

Page 10: ...temperature to start the heating equipment When using the thermostat with the Fuel switch set to the E position for electric heat the fan starts immediately Press the key to lower the temperature setting below the room temperature The heating equipment should shut down Cooling System CAUTION Compressor Damage Hazard Operating at too low of an outdoor temperature can cause compressor damage Do not ...

Page 11: ...s blank or says bAtLo install fresh batteries The thermostat has a built in time delay on cooling Allow five to ten minutes after changing the setting before the air conditioner starts If the temperature setting is lower than the current room temperature and the snowflake is displaying the thermostat is operating correctly Contact an air conditioning contractor for assistance The furnace cycles to...

Page 12: ...ct was in the possession of a consumer Honeywell s sole responsibility shall be to repair or replace the product within the terms stated above HONEYWELL SHALL NOT BE LIABLE FOR ANY LOSS OR DAMAGE OF ANY KIND INCLUDING ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES RESULTING DIRECTLY OR INDIRECTLY FROM ANY BREACH OF ANY WARRANTY EXPRESS OR IMPLIED OR ANY OTHER FAILURE OF THIS PRODUCT Some states do not al...

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