Thermostat Center

Reviews and General Information on Programmable Thermostats

Thermostat Wiring for Dummies

Heck, now I’m not calling anyone a dummy! Even the most seasoned people who enjoy DIY may come across problems with wiring a thermostat. The main trouble is dealing with those different colored wires, knowing which one does what and if that wasn’t enough, you also have numbers and letters to deal with.

One of the biggest complaints, or rather, reasons for confusion I have come across is down to the fact that many thermostats on the market don’t work if your system isn’t equipped with a ‘C’ (common) wire. I will explain that in a little more detail further down this page.

Wiring Set-Up Explained

What I would like you to know is the information detailed below is based on the industry standard, yet not all thermostats will work this way simply because letters and numbers are used as well as color. Plus, I’m anything but a technician so what I have detailed below is here purely as a guideline.

Colored WiresSo, this is what you might expect to see in terms of colored wires and what they mean:

  • White – The white wire is what connects to the (auxiliary) heat on your system.
  • Yellow – The yellow wire connects to your compressor.
  • Green – The green wire connects to the fan.
  • Orange – This wire connects to your heat pump (if you have one).
  • Red – Now, there can be two separate wires for this. One is for cool and the other is for heat, hence the abbreviation “RH” and “RC”.
  • Blue – This is your common or “C” wire.

You may also have up to two black wires as well but these are used for various heating systems in the North or for outdoor purposes, so for most of you these won’t need any attention.
If you’re still a little confused (and I can understand why you would be), I have added a thermostat wiring made simple video for you to look at which isn’t very long but is one of the best explanations I have come across. AND it has been recorded by a professional in the industry.

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