Wiring up your house thermostat
These instructions are for a forced air furnace, with a single-speed fan.
If you have other
than a single-speed fan, a boiler or are unsure about anything, you will need to consult
an HVAC technician.
Most existing thermostats have a fan switch that you can set to ON or AUTO. Simply
remove the thermostat cover and you will see a wire running to that switch, usually
marked as terminal G.
Disconnect the wire that runs to the G terminal on your existing thermostat.
Purchase a simple, 2-wire thermostat (a simple ON/OFF switch). Usually less than $15.
If you have a simple 2-wire thermostat, just use those 2 wires to connect to Terminal G
and the wire you just removed.
If you are using a thermostat with more than 2 wires, find the two wires that run to the
mercury switch shown below (or bi-metal switch or thermistor on a digital thermostat)
that make a connection when you turn the thermostat up. Those 2 wires are wired into
the fan switch wire(s) above at to Terminal G and the wire you just removed.
on the existing thermostat.
(The two wires are shown below (next page), as tan and blue on a 3 terminal mercury
switch)
Never assume that a wire color (or letter code) is correct for the function
it should perform
; check it out first
Assemble the new thermostat on the wall and turn the fan switch on the existing
thermostat to ON. That’s it! You’re done!
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