8
Replacing Old Thermostat
Note: Do not operate the cooling system when outside temperature is below 10ºC (50ºF) to avoid damaging the
compressor.
• Test the system to make sure that your heating and cooling are working properly before installation. If either
does not work, contact your local heating/air-conditioning dealer to fix the problem before installation.
• TURN OFF POWER to system at the furnace, or at the fuse/circuit breaker panel.
• Carefully unpack your new thermostat and mounting plate; save packaging 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 secure the cover.
• Loosen screws holding thermostat to the wall and lift away the thermostat.
• Disconnect wires from old thermostat or sub-base. As you disconnect each wire, use masking tape to label them
with the old terminal designation. If there are only two wires, they don’t need to be labeled.
• If there is an extra wire that is not connected to your old thermostat, then you won’t need to connect it to the
new thermostat.
• Take care not to let the wires fall back into the wall or let the ends of the wires touch one another.
• The wires are usually designated 'W', 'Y', 'G', 'RH', 'RC', 'O', 'B', 'H1', 'H2'.
Installation
