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Basic Thermostat Wiring Colors - Air Conditioner Systems - Always remember when changing a thermostat for a new thermostat to take a photo of the colors and where they go on the old thermostat or get a pencil and paper and write it down. It is better to take a good up-close photo of the old thermostat and what terminals the colored wiring are terminated. Nearly everyone has a camera on their cell phone.
Basic Thermostat Wiring Colors - Air Conditioner Systems
See the important notes below for further instructions – Thermostat Wiring Colors
Basic Thermostat Wiring Colors – AC Systems Control Diagram
| Thermostat Terminal | Wire Color | What is Does |
|---|---|---|
| R | Red | 24 Volts AC/Heat Single Transformer |
| RC | Red | 24 Volts for Dual Transformer – AC♦ |
| RH | Red | 24 Volts for Dual Transformer – Heat♦ |
| G | Green | Blower Fan Control |
| Y1 | Yellow | Cooling Terminal – Condenser Control |
| Y2 | Light Blue but Varies♣ | Cooling Second Stage |
| W1 | White | Heating Control |
| W2 | Brown or Black but Varies♣ | 2nd Stage for Heat |
| C | Dark Blue but Varies♣ | Common |
See our other thermostat installation advice articles.
Notes on Thermostat Wiring Colors:
♦Some HVAC systems will have two transformers set up. A 24 Volt transformer for the air conditioner and one for the boiler or furnace. If you have a dual transformer system then you need to use terminals RC and RH. RC is for the air conditioner and RH is for the heating system.
♣The thermostat wire colors for these terminals will vary depending on the installer of the HVAC system and if they used conventionally accepted colors for that terminal. This is why it is good to take a photo so you get it right the first time. You don’t know who wired the old thermostat and if they used conventional colors.
For additional wiring for air conditioners, you can visit our other articles in the thermostat category.
Basic Thermostat Wiring Colors - Air Conditioner Systems
The more I read these the more confused I get.
First, determine what type of system you have eg a heat pump, an air conditioner with a gas furnace (or whatever type of system you have), and follow the instructions. Each type of system is wired differently.