A common wire (C-Wire) provides Wi-Fi thermostats continuous power by connecting it to a heating and cooling system (e.g. furnace). C-Wires are required on most Honeywell Wi-Fi thermostats, with the exception of the Smart Round Thermostat (formerly known as the Lyric Round).

What can I use instead of C wire?

If there is no hidden C-wire, you can use a G-wire instead. However, you will not be able to use your fan independently when the heating or cooling isn’t running. Also, many HVAC systems are incompatible with this solution, including: HVAC systems using electric heat.

Do I need the C wire on a thermostat?





Yes, you should install a C-wire if you are upgrading your thermostat. Nearly all modern thermostats, smart or not, require a power source, and that doesn’t look likely to change any time soon.

Can I install smart thermostat without C wire?

No C Wire—No Problem



Buying a smart thermostat that doesn’t require a C wire for installation doesn’t mean you’re in for a poor experience. In fact, some of the most advanced and popular smart thermostats like the Google Nest Learning Thermostat are among those that can be installed without a C wire.

How do I connect my Nest thermostat without C wire?


Quote from Youtube video: For the common wire. So what you would do is go to your nest thermostat. Take off the G wire. Usually. It's going to be the green wire going to G. So you press on it you pull it out and before.

Can I use RC wire as C wire?

No the Rc is the red wire. You need 5 wires or more for this to run with all the functions. You can use one of the other wires but you have to drop control of the fan. It will only come on when furnace comes on.

Can I use ecobee without C wire?





If you’re lacking a C wire and have at least four wires at your thermostat to work with (refer to this article if you only have two wires), you’ll want to install the Power Extender Kit (PEK).

How do I bypass the C wire on my thermostat?

Quote from the video:
Quote from Youtube video: Connect the extra wire to the C terminal of Union thermostat trace the extra unused wire from the thermostat to the furnace board make sure it's connected to the C.

Is the blue wire the C wire?

Blue wires are also called C wires because they are the Common wire. C wires are necessary for any smart thermostat that needs to be connected to a power source 24/7, regardless of your heat pump type.

How does C wire adapter work?

A C wire adapter (common wire adapter) is basically a small electronic device, which re-purposes the existing wiring between your thermostat and the furnace, to add a new wire to the system. This new wire will serve as the C wire or common wire to provide the necessary power to the thermostat.

Can I use a Nest Thermostat with only 2 wires?



The Nest Thermostat is compatible with 2 wire low voltage HVAC systems that are either heat only systems or cooling only systems.

What color is the C wire?

Blue wires

Blue wires are also called “C” wires because they are the Common wire. C wires are necessary for any “smart” thermostat that needs to be connected to a power source 24/7, regardless of your heat pump type.

Does Nest e need C wire?



The Nest Thermostat E is designed to work even if your home doesn’t have a common (C) wire, but installing a new C wire may be required. If you have a dual fuel system, we strongly recommend professional installation.

How do you put a common wire in a thermostat?

Quote from the video:
Quote from Youtube video: Run actual thermostat wire in the all and connect. It to the existing thermostat wire if you've got an extra wire or if you want to fish some new ones in the wall. Not a big deal there.

What is a common wire for Nest Thermostat?

Quote from the video:
Quote from Youtube video: So that the thermostat the nest thermostat can charge itself with the C wire.

How do you hook up a C wire to a furnace?

Quote from the video:
Quote from Youtube video: You would just look where the c wire goes or where the wire from the air conditioner goes to the c. And that is going to be your 24 volt. Common.

Is com 24V the same as C wire?



The c wire is an extra wire that can be used to provide a return path for continuous 24V power for any application. It’s normally used to provide a return path to power the thermostat. The “c” stands for common. It is often labeled as “c” on thermostat backplates.

Does C wire have voltage?

The C wire, a.k.a. the “common wire”, allows a constant flow of 24 VAC (volts AC) power to a smart thermostat. However, the C wire doesn’t provide the actual source of power to the thermostat. The wires that provide the source of power are the R wires (or hot wires).

Is the C wire a ground?

No way! A “return” is not the same thing as a “ground”. In certain situations it is, but not here. The C wire (together with “the other half of the circuit”) forms a circuit through the secondary of the 24V transformer.

Is C wire same as neutral?

The C wire is more like a neutral wire (in electrical terms) and it completes the electrical circuit between the furnace (or any heating system) and the thermostat, thus ensuring a flawless power supply to thermostat even when the furnace is OFF.

How do you identify C wire?



Quote from the video:
Quote from Youtube video: Likely there is gonna be a fifth wire tucked into the wall I'm thinking that's going to be our C wire most likely because as you can see we have a green a yellow a white in a red.