3 Determine if your system has a 24 VAC common wire which is required to power the thermostat.
•If your system is a heat pump, skip to step 4.
a.If your existing thermostat has a terminal named C, COM, X, or B with a wire connected to it, skip to step 4.
b.If your thermostat does not have that terminal, or does not have a wire connected to it, go to step 3a.
3A Connect a 24 VAC common wire to power the thermostat.
a.Locate all unused (disconnected) wires from the thermostat wire bundle and write down the colors.
•i24V Common wire is typically (not always) colored blue
Thermostat wire bundle
Unused wires
b.Go to your HVAC unit and remove the cover(s) to access the 24 VAC furnace wire terminals.
24VAC Furnace
wire 
terminals 
Furnace
cover
c.Find the 24 VAC common terminal identified with the letter C, X, B, or COM.
•This terminal may already have a wire connected to it but it may not be a wire that goes to the thermostat
| W |
24 VAC common | R |
| |
terminal | C |
(C, X, B, or COM) |
|
d.Locate the thermostat wire bundle inside the furnace panel.
•This wire bundle is routed from the thermostat, through the walls, and into the furnace panel.
•This bundle can be identified at the furnace by checking the wire colors connected and not connected and comparing to the wire bundle at the thermostat.
|
| Thermostat |
W | Unused | wire bundle |
|
| |
R | wires |
|
|
| |
C |
|
|
e.Find a wire from the thermostat bundle that is unused at the thermostat and at the furnace.
•It is possible that one of the unused wires at the thermostat will already be connected to the 24 VAC common terminal at the furnace. If so, go to step 4.
W |
|
R |
|
C | Unused |
| wire |
f.Connect the unused wire to the 24 VAC terminal, then replace the furnace cover.
•The 24 VAC common wire is typically (but not always) blue in color. If the blue wire has been unused, it is recommended that you use the blue wire.
W |
| |
R |
| |
C | Connect | |
wire | ||
|
If you are unsure about connecting this wire or you do not have any unused wires at the thermostat, contact Customer Service at
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