Conventional heating, air conditioning and heat pump thermostat wiring labels, wire color codes and the corresponding function description:
| Terminal Designation |
Wire Color |
Function Description |
| Rh | Red | 24 Volt Hot for Heating |
| Rc | Red | 24 Volt Hot for Cooling |
| Y1 | Yellow | First Stage Cooling |
| Y2 | Blue | Second Stage Cooling |
| G | Green Grey * |
Energizes Indoor Fan |
| W1 | White | Energizes First Stage Heat |
| W2 | Black | Energizes Second Stage Heat |
| O | Orange | Heat Pump Reversing Valve Energized In Cooling |
| B | Brown | Heat Pump Reversing Valve Energized In Heating |
| C | Brown** | 24 Volt Neutral (Common) leg |
* Found in some Carrier furnaces
** The brown is often the first choice to use for the 24 volt common leg but white, black and blue are also frequently used.
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