Most thermostats have a note right on them which color wire goes to which terminal. If you don’t have this, 4-wire color codes go as following:
|R||Red||Power (24-volt hot wire)|
- Green wire – goes to Green Terminal (G)
- White wire – goes to White Terminal (Y)
- Yellow wire – goes to the Yellow Terminal (Y)
- Red wire – goes to Red Terminal (R)
If you have an older thermostat wiring, it will have a blue wire instead of a yellow. Attach the blue wire to:
Yellow terminal (Y)
If you happen to have a bunch of wires hiding behind the wall and have both yellow and blue (common in newer thermostat wiring), the blue one is most likely to be a Common (C) 24VAC wire.
Even though in our example Common Wire (C) is NOT included, here is a great visual breakdown of thermostat wires (with schematics):
Green terminal and wire (G)
If you just want air to be moving around your house without being heating or cooled down, G-wire (or green wire) is responsible for that.
White terminal and wire (W)
Once your thermostat will go into the Heating Mode, 24-volt power will be sent back to the control board and the furnace will start working.
Yellow terminal and wire (Y)
In older wiring setups, this wire could be a blue color. Yellow wire activates your outside air conditioning unit and a fan at the control panel (or board).
Red wire to Terminal (R)
The red wire is a 24-volt hot wire that triggers either the heating or cooling mode of your thermostat (fan as well). It starts from the control board (which is equipped with a transformer that changes the voltage to 24-volts) and goes all the way to the thermostat, where appropriate wires will be triggered upon your selection of a setting.
Here is a video on how to connect a thermostat with 4 wires:
** Very Important! Before starting to work on your thermostat wiring, make sure you turned all the power OFF. If you are not sure what you are doing, consult a professional.
Attention! This article is for informational purposes ONLY and is NOT a replacement for a professional advice! You will need to visit school's website for details and updates, as well as consult your local HVAC specialist for appropriate solution to your problem.
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