Step 2. Remove Old Thermostat - Honeywell CT3550 Owner's Manual

STEP 2. REMOVE OLD THERMOSTAT

Test your heating and cooling systems to make sure they work properly. If either system does not work, contact
your local heating/air-conditioning dealer. To avoid compressor damage, do not operate the cooling system when
outdoor temperature is below 50°F (10°C).
Turn off power to the system at the furnace or the fuse/circuit breaker panel.
Carefully unpack your new thermostat and wallplate. Save package of screws, instructions, and receipt.
Remove the cover from the old thermostat. If the cover does not snap off when pulled firmly from the bottom, check
for a screw or screws used to lock on the cover.
Loosen the screw or screws holding the thermostat to the wallplate and lift the thermostat away.
Disconnect the wires from the old thermostat. As you disconnect each wire, attach the enclosed labels with the old
terminal designation. If there are only two wires, they do not need to be labeled. Wrap the wires around a pencil as
shown to keep them from falling back into the wall.
Special Installations
Read this section if you are replacing:
• Clock thermostat with separate wires for the clock.
• Thermostat with six or more wires connected to it.
• Thermostat in a heating only system with three wires.
Replacing a Clock Thermostat that has C or C1 Clock Terminals
If you are replacing a Honeywell Chronotherm® Thermostat, you may find one or two wires going to the C or C1 clock
terminals on the Chronotherm wiring wallplate. Do not allow them to touch, or you can damage the transformer.
Disconnect the wires and wrap them separately using electrical tape. Do not wrap them together. Place the wires
where they will not interfere with the operation of the new thermostat. Record the colors and terminal designation
labels of the remaining wires.
Replacing a Thermostat that has Six or More Wires
If there are six or more wires (excluding clock wires attached to terminals), you probably have a variation of a
multistage heat pump or other multistage system. This thermostat is not compatible with multistage systems, so return
the product to the place of purchase. For information about which programmable thermostats will work with your
system, call Honeywell Customer Relations Center, at 1-800-468-1502.
69-1284—2 6
WIRES THROUGH
WALL OPENING
M5136