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Do-it-Yourself Thermostat Replacement

Replacing a thermostat most times is pretty simple. Thermostats run on 24V low voltage, so there isn’t any chance of electrocution, although you can get a jolt if you don’t turn the power off. Replacing a Thermostat is a good Do it Yourself (DIY) project if you are mechanically inclined or a handyman can do it. For more complicated heating and cooling jobs: new installation, recharging freon, replacing a compressor, etc I recommend calling an HVAC contractor, but for simple things like replacing the air filters, or replacing a thermostat- a handyman is fine. With that said, calling an HVAC company is always fine if you don’t want to deal with it, they just might be a little more expensive. 

What is a thermostat?

The thermostat is an “ON” and “OFF” switch for your HVAC. Thermostats come in a wide variety of shapes and sizes and with different functions. They range in price from as little as $30 for the most basic thermostat that has just an on/off button and a temperature control (the landlord’s favorite) to wifi controlled, touch screen, 7 day a week programmable thermostats, like Nest that can cost $250-$300.

How much does it cost to install a New Thermostat?

The Price of installation will depend on the cost of the thermostat, but figure $100-$150 for labor (thirty minutes to 1 hr HVAC Contractor) and $50-$100 for parts. I would expect a new thermostat to cost $250 on average if you hire someone to install it for you.

How do I install a thermostat?

If you want to install the thermostat yourself or supervise your handyman, here are the basics of installation. Thermostats come with installation instructions. You can usually get by with some basic tools (screw driver, camera from your phone), patience, and following the directions.

Step #1: Remove the old Thermostat to reveal the wiring.

Most thermostats snap in and out of place, so if you tug on it firmly it will come off, but some of the older ones are screwed in.

Step #2 Take a picture of the wiring.

For replacing a thermostat, you can usually just copy the wiring configuration from your old thermostat to your new one and it will work. If you have an extra wire(s), or you tried to install the thermostat with the same wiring configuration as the old thermostat and it didn’t work, it is probably time to call an HVAC professional.

Step #3 Turn off the Power

Anytime you work with electrical, it is a good idea to turn off the power so you don’t shock yourself. You can turn off the power at your homes electric panel. Most of the time electric panel breakers are labeled so you can figure out which one is for the AC. I personally just like to turn off everything with the “Main Service Disconnect” or flipping all the breakers to “OFF” because that why you don’t risk zapping yourself or blowing a fuse. If the power is on when you are rewiring in step #5, if two hot wires touch they could cause a power surge which could damage an HVAC component or blow a fuse and then you will need to call an HVAC contractor to come to help you.

Step #4 Attach the new Thermostat Case to the wall

If you hold the Thermostat Case to where you want it to be on the wall and take a pencil or screwdriver and mark pilot holes, then remove the case and drill, that makes it easier to line up the case. You can also just punch a normal screwdriver through the wall, which is about the same diameter as the drywall anchors. Put the drywall anchors in the hole, if they are stubborn, you can gently tap with a hammer. Then place the case back over them and screw the case into the wall. Make sure while you are fiddling with the case that the Thermostat wires don’t fall back into the wall. It is a real pain to fish them out!

Step #5 Rewire

Thermostat Wiring is color coded. Thermostat Wires can range from 4 wires to 8 wires depending on the type of system. The most common is 5 wires. It is important to note that sometimes the wires are not appropriately color coded, so refer back to the picture you took in Step #2, and place each color wire into the corresponding terminal Code based on your picture.  

If you are trying to figure out what the wires do, it is probably time to call a professional. The Red Wire is supposed to go in R terminal and it brings in 24V that powers the thermostat. The Yellow wire is supposed to go in Y terminal and is for cooling. The White Wire goes into W terminal and is suppose to be heat. the Green wire goes into Green terminal and is suppose to control the Fan blower. The Blue Wire is the ground and is supposed to go into C terminal. 

Thermostats usually have two different terminal sides- one for “conventional” and one for “heat pump”. When you are putting in the wires make sure you put them into the correct terminal side based on your system. Again just copy from the picture you took in Step #2.

Step #6 Install the Thermostat

One the wiring is done, you should be able to snap the thermostat on to the case.

Step #7 Turn on the Power

Step #8 Test and Program the thermostat.

Thermostat not Working?

Some thermostats are Battery Operated. If your thermostat isn’t working try to snap it off and Replace the AA batteries. 

You can also check if you blew a fuse. Fuses are in the furnace. 



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