How to Install a Wi-Fi Thermostat Without C Wire

wifi thermostat without c wire
Honeywell RTH9580WF Wi-Fi Thermostat

Wi-Fi thermostats are great devices. They help you limit your energy use and gain precise control over the temperature and humidity levels in your home. But, in order for these devices to work, they need to connect to your central heating/cooling system using a c-wire.

What if you do not have a c-wire? How can you install a Wi-Fi thermostat without a c-wire? Take a look at the following details to find out.

What is a C-Wire?

First, you should know more about the c-wire. Also referred to as a common wire, the c-wire delivers low voltage power to your Wi-Fi thermostat. Basically, the c-wire is used to power the Wi-Fi thermostat.

The other power wires that run from your furnace do not provide continuous power. They only deliver power as needed. For an electronic device, such as the Wi-Fi thermostat, to work on demand, it needs a continuous flow of power. This is the purpose of a c-wire, which can be found connected to most furnaces. Though, this is not always the case.

Identify the Wires for Your Thermostat

You will need to identify the wires that are used for your thermostat. Detach your existing thermostat and look at the wires that are connected to it. If you see a wire that is connected to a screw labeled “C”, then you probably have a c-wire. The wire will typically be blue or black. Though, this can vary.

If you do not see a wire connected to the screw labeled “C”, you may still have a c-wire hidden in the wall. When installing the existing thermostat, if the c-wire was not required, then the installer may have simply stuffed it into the wall.

Another option is to check your furnace. First, turn off the power to your furnace. Then, remove the cover. Look at the circuit board and try to find a row of screws connected to wires running from your furnace. You should see a row of screws labeled as follows:

• R
• C
• W
• W2
• G
• Y/Y2

The c-wire will be connected to the screw labeled “C”. If you do not see any wires connected to this screw, then you do not have a c-wire. You have several options for adding a Wi-Fi thermostat.

What Should You Do if You Do Not Have a C-Wire?

If you do not have a c-wire, you have three primary options. Consider each of the following before you purchase a Wi-Fi thermostat:

Install New Wires

You could run new wires from your furnace to your thermostat. Depending on the location of the thermostat and your furnace, this may not be a major project. Though, it will require some research and technical knowledge.

Installing new wires is something that you can hire a professional to handle. You could contact a local HVAC company and ask about the installation of a c-wire. The cost should be minimal, as it is a relatively simple process. Though, you should be prepared to hear a sales pitch for upgrading your HVAC system.

Use a Wire Adapter

Another option is to use a wire adapter. You can add a 5th wire to your furnace without any complicated steps. This may be more suitable for homeowners that do not have any experience handling electrical wiring. The adapter has the added benefit of not requiring you to run the wire through your home.

You can simply connect the adapter to your furnace and the wiring behind your thermostat. This will require a few basic steps, but it is not a complicated process. You will need a Philips head screwdriver, electrical tape, needle nose pliers, a drill and drill bit, and the wire adapter.

Purchase a Wi-Fi Thermostat Without C-Wire

The final option is to purchase a Wi-Fi thermostat that does not require a c-wire. There are two popular models that can work without a c-wire. This includes the ecobee3 and the Emerson Sensi thermostat. The ecobee3 includes an adapter for systems that do not have a c-wire, while the Emerson Sensi does not need a c-wire at all.

Nest that owned by Google also have a model that does not requires a c wire to work properly.

See: Nest Learning Thermostat

Nest Learning Thermostat (wifi thermostat without c wire)
Nest Learning Thermostat, 3rd Generation, Works with Alexa

Increase the Energy Efficiency of Your Home

Adding a Wi-Fi thermostat will help increase the energy efficiency of your home. You can control the temperature from your phone or tablet and use presets to easily adjust the temperature. Overall, the average homeowner will reduce their energy bill by 10 to 30% after installing a Wi-Fi thermostat.

These modern thermostats are not the only thermostats that require a c-wire. The old mercury thermostats are outdated and no longer in production. Even if you do not purchase a Wi-Fi thermostat, any electronic thermostat that you purchase will likely require a c-wire.

For this reason, adding a c-wire or an adapter is a good way to future proof your home. If you are not planning on purchasing a new thermostat, the next thermostat that you buy will probably need a c-wire.

Use these tips to set up your Wi-Fi thermostat. Remember, if you need help with any of these steps or if you feel uncomfortable working with electrical wiring, then you should contact a professional.

Some people claim that there are workarounds for not having a c-wire. This includes using the fan wire as the power wire for your thermostat. This method is not recommended. You will no longer be able to manually turn the fan on.

The bottom line is that, in most cases, you will not be able to install a Wi-Fi thermostat without a c-wire. You will need to come up with a solution for correcting the problem. You can either add a c-wire, use an adapter, or purchase a Wi-Fi thermostat that does not require a c-wire.

If you do not have a c-wire, then you should definitely consider adding a c-wire or purchase the adapter. These are really the only viable options at the moment.


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