SAB Pick:

Thermostat wiring explained

Your step-by-step, DIY guide to thermostat wiring. Although, when it comes to electrical units, we highly suggest hiring a professional. Safety first!

  • Do you like this article?

Quality Services

Where do you need services?

Where do you need services?

Featured in

Thermostat wiring visual by Mukumbura on Flickr.If you own a home, it is likely that you are eventually going to have to replace your AC thermostat. Thermostat installation and thermostat wiring can be challenging, particularly if this is your first time taking on this type of task.

It is highly recommended that you hire a contractor with experience in thermostat wiring, thermostat replacement and other HVAC specialties. Reply! can help you find a contractor in your area who can replace your thermostat or give you an HVAC estimate if you need a new thermostat.

According to Energy Star, it is possible to save almost $200 in energy costs each year by simply adding a thermostat to your central home cooling system.

Ask contractors for thermstat wiring and installation estimates!

Correct wiring is one of the ways to make sure that you're getting the most out of any temperature control unit. How you wire your system will depend on the type of system you have. If you install an air conditioner that also has heating capabilities, connecting this system to a thermostat will require you to deal with more wires then you would if you installed an AC that is only designed for cooling.

However, most manufacturers have universal thermostats that can be used with any type of system.

Step No. 1: Don't electrocute yourself

The first thing you need to do before wiring or rewiring your thermostat is to shut off your circuit breaker. If you keep it on while doing this task, you run the risk of getting electrocuted.

Next, remove the cover of your thermostat unit.

Step No. 2: Organize wired colors

If your system is already wired, you will instantly notice that each wire has a different color. In thermostat units, each wire is generally connected to a specific letter. It is important for you to make sure that you write down the letter that each colored wire connects to before detaching them. If you don't make sure that you place the correct color wires back in the proper place when you reinstall them, your thermostat may not work.

After writing down where each wire should connect, detach each of the colored wires. If your system is not wired, you must refer to your thermostat's guide to determine where each wire should be placed.

Step No. 3: Cut new wires

After detaching each of the colored wires, cut your new wires. Make sure that they are the exact length of the wires you just detached from your thermostat.

If the wire is not exposed, cut the very top of the wiring cover using a wire-stripping tool, and make sure that no more than one-half inch of wire is exposed on each end. The exposed wire will go into the slot that you just removed the used wires from.

Step No. 4: Secure your wires

Your last step is to make sure that each wire is secure, which is generally done by using a small screwdriver to tighten the wiring screws.

Backup step No. 5: Hire a contractor

If you have never rewired a thermostat before, ask your contractor about wiring your thermostat for you. You can also talk to him about air conditioner prices and getting a new thermostat with a warranty. 

Thermostat wiring and rewiring can be tricky and dangerous if you do not know what you are doing. Although this process may sound easy to some, it is always a good idea to get help from someone with experience before working with electrical units.

Get your 3 HVAC estimates! 

Photo credit: Mukumbura via Compfight CC.