Honeywell CT3451 User Manual

Programmable Thermostat

T S

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.

Programmable Heat and/or Cool

CT3451

OWNER’S GUIDE

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.

SCREWDRIVER

WIRE CUTTER/STRIPPER IF NEEDED TO STRIP WIRES

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

YPICAL LOCATION OF A MERCURY WITCH IN A THERMOSTAT

MERCUR SWITCH

M10614

LEVEL, IF NEEDED TO LEVEL THERMOSTAT FOR APPEARANCE

Fig. 1. Required installation tools/supplies.

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M20551

CT3451 PROGRAMMABLE THERMOSTAT

2 REMOVE OLD THERMOSTAT

❑ Test to be sure your heating and air conditioning

systems (where applicable) are working correctly. If not, contact your local heating/air conditioning dealer. To avoid compressor damage, do not operate the

Table 1. Compatibility Chart.

System Type Compatible With CT3451

Gas—standing pilot Yes

Gas—electronic ignition Yes

Gas-fired boilers

Gas—750 millivolt Yes

Oil-fired boilers

Oil-fired furnace Yes

Electric furnace Yes

Electric air conditioning Yes

Single stage heat pumps (no backup or auxiliary heat) Yes

Baseboard electric (120/240 line volt) No

Multistage heat pumps/multistage equipment No

Not compatible with any 120/240 volt circuit.

Compatible with 2-wire Honeywell zone valves. Isolating relay required for zone valves that have a 3-wire thermostat

connection.

cooling system when outdoor temperature is below 50°F (10°C).

Yes

Replacing Clock WIth C or C1 Clock

CAUTION

Equipment Damage Hazard. Handling wires during installation can damage equipment.

Disconnect power at furnace or main breaker/ fuse box before beginning installation.

❑ Carefully unpack your new thermostat and wallplate

and save package of screws, instructions and receipt.

❑ Remove the cover from the old thermostat. If it does

not snap off when pulled firmly from the bottom, check for screw that locks on the cover.

❑ Loosen screws holding thermostat to subbase,

wallplate or wall and lift away.

❑ Disconnect wires from old thermostat or subbase. As

you disconnect each wire, use the wiring labels (enclosed) to label each wire with the old terminal designation. If there are only two wires, they do not require labeling. Wrap wires around a pencil to keep them from falling back into the wall as shown in Fig. 2.

WIRES THROUG WALL OPENING

Terminals

If you are replacing a Honeywell Chronotherm® Thermostat, you may find one or two wires that go to 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 Thermostat Wires

If there are six or more wires connected to the thermostat (excluding clock wires attached to terminals), you probably have a variation of a multistage heat pump or other multistage system. The thermostat is not compatible with these systems, so return the product to your retailer. If you want information about which programmable thermostats work with your system, visit our Web site at www.honeywell.com/yourhome or call the customer information line at 1-800-468-1502.

M5136

Fig. 2. Wrapping wires around pencil.

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Three Thermostat Wires

If you have three wires for heating only and can operate the fan using the Fan On switch, this thermostat works with your system. However, some hot water (zoned) heating systems have three thermostat wires. The thermostat works only if a contractor installs an isolating relay on these systems. For details, contact a local heating/cooling contractor.

CT3451 PROGRAMMABLE THERMOSTAT

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3 MOUNT WALLPLATE

IMPORTANT

Level for appearance only. The thermostat functions normally even when not mounted level.

❑ Position the wallplate on the wall. Level the wallplate

for appearance, if desired. Use a pencil to mark the two mounting holes that best fit the application. See Fig. 3.

WALL

MOUNTING SCREWS (2)

WHEN USING WALL ANCHORS, DRILL 3/16 INCH HOLES FOR DRYWALL, 7/32 INCH HOLES FOR PLASTER OR WOOD.

Fig. 3. Mounting wallplate to wall.

❑ Remove the wallplate from the wall and drill two 3/16-

in. holes in the wall (if drywall). For firmer wall material such as plaster or wood, drill 7/32-in. holes. Gently tap provided anchors into the drilled holes until flush with the wall.

❑ Reposition the wallplate, pulling wires through the

wiring opening. Loosely insert the mounting screws into the holes.

❑ Level for appearance only; the thermostat functions

correctly even when not level. Tighten the mounting screws.

WALL ANCHORS (2)

WALLPLATE

M12202A

ERMINAL CREW

FOR STRAIGHT INSERTION STRIP 5/16 IN. (8 MM)

FOR WRAPAROUND STRIP 7/16 IN. (11 MM

Fig. 4. Connecting wiring.

NOTE: To ensure correct mounting of thermostat,

restrict all wiring to the shaded area in the center of the terminals.

❑ Loosen the terminal screws and slip each wire

beneath its matching terminal. The shape of the terminals permit insertion of straight or wraparound connections. See Fig. 5. Tighten the terminals.

M12559A

FOR WRAPAROUND, STRIP 7/16 IN. (11 mm)

FOR STRAIGHT INSERTION STRIP 5/16 IN. (8 mm)

4 WIRE WALLPLATE TERMINALS

All wiring must comply with local electrical codes and ordinances. If unsure about household wiring procedures, call your local heating and air conditioning contractor.

Refer to 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.

M1253

Fig. 5. CT3451 methods for wiring connection.

❑ Plug the hole in the wall with insulation to help prevent

drafts from adversely affecting thermostat operation.

The CT3451 Thermostat is powered with 3AA alkaline batteries and is adaptable to most 18 to 30 Vac heatingcooling systems. Refer to Fig. 6 through 10 for typical system wiring diagrams.

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CT3451 PROGRAMMABLE THERMOSTAT

THERMOSTAT

)

THERMOSTAT

HEAT RELAY

L1 (HOT)

TRANSFORMER

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

CAN BE USED FOR CHANGEOVER VALVE ON SINGLE-STAGE HEAT

PUMP SYSTEMS.

JUMPER R TO Rc.

Fig. 6. Typical heat-cool system hookup with single

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

Fig. 7. Typical heat system hookup with 2-wire, heat-

FAN RELAY

COMPRESSOR CONTACTOR

transformer.

B O

HEATING RELAY AND FAN COIL

24V

only system.

B O

COOL DAMPER

M20536

HEAT DAMPER

M20510

Fig. 8. Typical cool system hookup with 3-wire,

L1 (HOT)

COOLING TRANSFORMER

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

REMOVE RC TO R JUMPER WHEN INSTALLED ON A TWO TRANSFORMER SYSTEM.

CAN BE USED FOR CHANGEOVER VALVE ON SINGLE-STAGE HEAT PUMP SYSTEMS.

Fig. 9. Typical heat-cool system hookup with two

B O

COOLIING

24V

CONTRACTOR COIL

1 L1 (HOT)

POWER SUPPLY. PROVIDE DISCONNECT MEAN AND OVERLOAD PROTECTION AS REQUIRED.

cool-only system.

W Y

FAN

COOL

RELAY

DAMPER

COMPRESSOR CONTACTOR

HEAT RELAY

transformers.

B O

HEAT DAMPER

FAN COIL

M2053

HEATING TRANSFORMER

L1 (HOT

M20511

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