Thermostat wiring color codes
Description Color Terminal Code
24VAC Return Red R or RC RH
Call For Heat White W or W1 W2
Force Fan On Green G
Compressor/Call For Cool Yellow Y or Y1 Y2
Description Color Terminal Code 24VAC Return Red R or RC RH Call For Auxiliary Heat White W or W1 W2
Force Fan On Green G
Compressor Yellow Y or Y1
Changeover Orange C/O or O or B for brown
the orange and brown wires only appear in seven conductor thermostat wire which is used to wire heat pump systems.
Description Color Terminal Code
24VAC Return Red RF
Call For Auxiliary Heat White W1
Force Fan On Green GT
Compressor Stage 1 Yellow Y1
Compressor Stage 2 Not standardized, use Blue Y2
Changeover Orange C/O or O or B for brown
A multi-stage heat pump system brings one more facet to the control equation: The second stage compressor control. Multi-stage heat pump systems either have a dual-speed compressor or they have two compressors. The thermostat can cause the compressor to run at either a low or high setting. So the HVAC system can cool at two rates, and heat at three rates (remember the auxiliary heat).
Terminal name color function
R Red hot side of transformer
C Black, Blue, Brown Common side of transformer
Y Yellow Compressor activity (cooling or cooling & heating on a heat pump
Y2 Blue or Pink second compressor stage
W or W1 White Heat" (gas burner, oil burner , electric heat, (auxiliary heat on a heat pump including defrost output from the outdoor unit to activate electric heat and turn on the AUX. heat lamp).some thermostats require a jumper from "W" to "Y" for heat pump operation.
W2 Pink or other second stage of heat
G Green furnace blower fan
O Orange Energize to cool (used for reversing valve on heat pumps)
B Blue or Orange Energize to heat
(B) or (X) Blue, brown or Black common side of transformer. Needed on some electronic thermostats or if you have indicator lamps. Do not confuse with (B) Reversing valve (energize to heat) above. York and Trane like to use (B) as common
E blue, pink, gray or tan emergency heat relay on a heat pump.
Active all the time when selected, usually not used
T Tan or Gray outdoor anticipator reset.
Used on GE/Trane/American Standard and some Carrier Products.
L Blue, brown, tan or gray service indicator lamp.
