How to Hook Up a Home Thermostat - If you need to install a new thermostat then you have found the right place to learn. Below we will describe to you how to hook up a new digital thermostat. Whether the old thermostat is bad or not if you simply want to replace your old one and hook up a new one. First of all, the first thing you need to take into consideration is to select the right replacement thermostat.
To select the correct replacement you need to know what kind of HVAC equipment you have in your home. Or where you want to hook up the new thermostat. There are numerous types of air conditioner and heating combinations. Therefore, to simplify things, we will cover a basic gas furnace and air conditioner split system HVAC system. For hooking up a new thermostat similar systems to the air conditioner/gas furnace combination would be:
How to Hook Up a Home Thermostat
If you do not know what kind of unit you have to take a look at the paperwork from the last time the unit was serviced. Perhaps it will show the type of equipment on the service ticket where the unit had maintenance. It is assumed that most people will know what kind of unit they have so that they can select the proper thermostat.
- Air conditioner/oil furnace combination (4 to 5 wires)
- AC (stand-alone with no heat source) (2 to 4 wires)
- An air conditioner with electric heat combination (4 to 5 wires)
- Gas furnace Stand-alone (2 to 4 wires)
- Electric furnace Stand-alone (2 to 4 wires)
- Oil furnace Stand-alone (2 to 4 wires)
- Boilers with AC systems controlled by a single thermostat (5 to 6 wires)
*It is possible to have more wires than noted here depending on the complexity of the system. This article assumes you have a basic single-stage air conditioner/single-stage gas furnace system.
How to Hook Up a Home Thermostat – Location of New Thermostat Installation
Now that you have selected the proper thermostat you want to install the new thermostat in place of the old thermostat. It is best to place the thermostat in the same location as the old thermostat.
Moving the thermostat to a new location is not recommended unless you hire an HVAC professional to relocate the thermostat first. Thermostats need to be located in a strategic area of the home to be effective and work properly. Besides, you would have to pull a new thermostat wire through the wall to relocate the thermostat. Finally, that is a big job for anyone.
Tools Needed | How to Hook Up a Home Thermostat
You will need:
- a small flat head screwdriver, possibly a Phillips head screwdriver
- pair of electrical stripping and cutting pliers for #18 thermostat wire
- pen and paper or your cell phone to snap a few reference photos
- some small labels to label the existing wires hooked to the existing thermostat
- Finally, a small drop cloth or paper can also be used to place on the floor below the thermostat to catch dust, debris, and other stuff that can fall on the floor.
Step by Step
How to Install a Home Thermostat – Step by step list with details below the list:
- Turn Off the power
- Remove old thermostat*
- Make note of wires (take a picture)
- Remove old sub-base
- Mount the new sub-base
- Attach wires to new sub-base
- Install new thermostat on new sub-base
- Finally, restore power and set up a new thermostat following manufacturers instructions
Power if Off? How to Install a Home Thermostat
1Turn off the power to the air conditioner or furnace. Preferably at the electrical panel where the circuit breakers are located. For most split systems you will have two circuit breakers for the air conditioning and heating system. Lastly, make sure you flip both of these breakers to the off position.
Out with the Old - How to Hook Up a Home Thermostat
2Remove the old thermostat – sometimes the old thermostat will have screws holding it to the sub-base. Other times it will not have screws but with a little force will pop right off from the sub-base. If you do not see any screws give the thermostat a little tug and it should pop right off. If you have the original instructions for the old thermostat take a quick look at the installation instructions.
This can tell you how the old thermostat disassembles. Be careful not to pull the sub-base from the wall when taking the thermostat apart. Lastly, once you get the thermostat separated from the sub-base go to the next step of hooking up a thermostat.
Make Notes (or Better, Take a Picture) - How to Hook Up a Home Thermostat
3Now that you have the main thermostat separated from the sub-base you will see the wires hooked up to the terminals on the thermostat. You can reference the thermostat color code chart to see what the thermostat wires are for or what the thermostat wires control. That will give you an idea of how to install the new thermostat.
Take the piece of paper and pen or pencil and write down where each thermostat wire is landed on the terminal board. Finally, take the labels and label each wire for the terminal where the thermostat wire was landed, and note the color to the terminal for the wires you will soon disconnect. Alternatively, you can snap a picture with your cell phone to cover this step.
Again, before touching any wires make sure the power is off. For the standard basic air conditioner/gas furnace combination you should have either 4 or 5 wires.* Red wire to red on the thermostat terminal strip (this can also be an RC – RH terminal with a jumper between the two terminals). Yellow wire to Y on the thermostat terminal strip for air conditioning. White wire to the thermostat terminal strip for the gas furnace. A green wire to the G on the thermostat terminal board for manual blower fan operation. Finally, an optional blue wire hooked to the common terminal or C terminal on the thermostat terminal board. Detailed thermostat wiring color codes can be found here.
Old Sub-base Removal - How to Install a Home Thermostat
4Now after making sure the power is off and you have written down where the thermostat wires go and have labeled them you can disconnect the wires from the old thermostat and remove the old sub-base from the wall. Be careful not to let the wire fall into the wall. Finally, you can use a pen or pencil and wrap one of the wires around the pen or pencil so the thermostat wire will not slip and fall into the hole in the wall.
Mount the New Sub-base
5Mount the new thermostat sub-base using the same holes the old thermostat sub-base was mounted to and tighten it down until it is secure. Finally, the old holes should match up to the holes in the new thermostat sub-base so you will likely not need any new screws or anchors.
Wiring Time - How to Install a Home Thermostat
6Attached the thermostat wires to the designated terminals as noted in your notes and how the wires are labeled. This should be cut and dry as the old thermostat terminals should match up to the new thermostat terminal connections. Furthermore, see the installation guide that came with the new thermostat for further instructions if anything is different.
Install New Thermostat
7Next, install the new thermostat onto the sub-base as per manufacturer instructions. Cautiously, a little care may be taken here to make sure the pins line up from the sub-base to the thermostat base as the pins can easily be bent if not properly aligned.
Restore Power and Set Up the New Thermostat | How to Hook Up a Home Thermostat
8Restore power and test the system for proper operation. A proper test would include testing the furnace for heating, testing the air conditioner for cooling, and testing the fan for manual operation. Make sure each unit cycles on and off, as usual, taking into account there are built-in time delays possible in both the thermostat and the HVAC system. Lastly, if something doesn’t start right away don’t freak out as most systems have time delays to protect the equipment.
Conclusion - How to Install a Home Thermostat
High Performance HVAC hopes this “How to Hook Up a Thermostat” article helps you when you have to hook up a new thermostat. Finally, see our other articles about thermostat installation. And don’t forget to bookmark us and give a nod or two with Facebook and the Twitter button.
How to Hook Up a Thermostat
Video | How to Hook Up a Home Thermostat
Finally, see a video about the common mistakes when installing a new home thermostat.
Ok. I want to hookup my Nest Learning Thermostat to my air conditioner/heater ‘fan control’. I have the wire all the way to the Kenmore unit in the basement and I have located what I am quite sure is the fan control terminal in the furnace circuit board. It is labeled fan on the diagram. Everything is working fine, just want to add this to be able to run the fan by itself from the app. I am concerned that I might be missing something, that is all. I am prepared to go ahead and hook it up, but don’t wNt to fry anything if you know what i mean
It’s difficult to tell what is what when you say air conditioner/heater. However, if it’s a conventional system the fan should work through app when you want it to work. In most systems, that is controlled by the green wire which is hooked to your thermostat. That wire runs to the heater/furnace/air handler (whatever you have). That controls the fan in most systems.
Thanks this helped me change my thermostat. My wife bet I couldn’t do it but with your help and reading the instructions that came with the thermostat (which admittedly I usually never do and is one of the reasons why my wife bet I couldn’t do it) I accomplished the job successfully in a about an hour and a half. Thanks again!!