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STEP 2 Remove Old Thermostat
□ Test to make certain that your heating
and cooling systems are working properly. If
either 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 system at the
furnace, or at the fuse/circuit breaker panel.
□ Carefully unpack your new thermostat and
mounting plate; save the package of screws,
instructions and receipt.
□ Remove cover from old thermostat. If it
does not snap off when pulled firmly from the
bottom, check for a screw used to lock 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
masking tape to label it with the old terminal
designation. If there are only two wires, they
do not need to be labeled. If there is an extra
wire that is not connected to your old thermo¬
stat, you will also not be connecting it to your
new thermostat. Keep the wires from falling
back into the wall by wrapping them around a
pencil as shown.
Replacing a Clock Thermostat that has C
or Cl Clock Terminals?
If you are replacing a Honeywell
Chronotherm® Thermostat, you may find one
or two wires that go to the C or Cl clock
terminals on the Chronotherm Thermostat
wiring wallplate. Do not allow them to touch,
or you may damage your transformer.
Disconnect the wires and wrap them sepa¬
rately, 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.
Six or more wires?
If there are six or more wires (excluding
clock wires attached to terminals), you
most likely have a variation of a heat pump
or multistage system. The thermostat is
not compatible with such systems so return
the product to the place of purchase. If you
would like information about which program¬
mable thermostats will work with your system,
call Honeywell Customer Assistance at
1-800-468-1502.
Three thermostat wires?
If you have three wires for heating only and
can operate the fan using the fan ON switch,
this thermostat will work with your system.
However, some hot water (zoned) heating
systems have three thermostat wires. The
thermostat will not work without installing an
isolating relay on these systems. For details,
call Honeywell Customer Assistance at 1-800-
468-1502.
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