4
5
Remove Old Thermostat
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. Call Honey-
well Customer Assistance at 1-800-468-1502
for details.
■
■
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 10
°
C [50
°
F].
■
■
TURN OFF POWER to system at the
furnace, or at the fuse/circuit breaker panel.
■
■
Carefully unpack your new thermostat and
mounting plate; save 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. Keep the wires from
falling back into the wall by wrapping them
around a pencil, as shown.
STEP 2
WIRES THROUGH
WALL OPENING
M5136
One or two extra wires?
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 may damage your transformer. Discon-
nect 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.
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
