Option 1: Add a C Wire to Your Furnace

Remove the access panel from the furnace and locate the thermostat wires and terminals. Connect an 18 AWG wire to the C terminal at the furnace. Next, remove the thermostat face plate. Now, run the new C wire from the furnace to the back of the new thermostat.

Where do you connect the C wire on an old furnace?





Quote from the video:
Quote from Youtube video: The common terminal is going to be right here so if you're installing. Something you would stick the wire. Into this screw terminal from the bottom.

What do I do if I dont have C wire?

Quote from the video:
Quote from Youtube video: Terminal. If there's already a wire attached to the C terminal. Just leave it be and attach a new wire next to it go ahead and push all the wires back into the wall. And close the backplate.

How do I install a new C wire?

Quote from the video:
Quote from Youtube video: So here in my old wiring you can see that i have the y1. Gw1 rh and the c-space is missing that c wire. So here i definitely could use the c wire now that we have determined we need to add the c wire.

How do you put a common wire in a thermostat?

Option 1: Add a C Wire to Your Furnace





Remove the access panel from the furnace and locate the thermostat wires and terminals. Connect an 18 AWG wire to the C terminal at the furnace. Next, remove the thermostat face plate. Now, run the new C wire from the furnace to the back of the new thermostat.

Can I use the G wire for the 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.

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 install Nest thermostat without C wire?

According to the Nest website, your Nest thermostat will work without a C-wire but specialists still recommend using an adapter if you can’t get a C-wire installed. If your Best thermostat will not receive a constant flow of power, it might not work properly and it runs out of power it will not work at all.

Does Nest E work without C wire?



In a system with a C-wire, the Nest charges itself from the C-wire’s current and all is fine. In a system without a C-wire, though, Nest recharges its battery when the heating or cooling runs.

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.

How do you install a common wire on a furnace?

Quote from the video:
Quote from Youtube video: Basically take the the plate here take your transformer. You're gonna make your connections. For everything just like they were on the thermostat that you took off with the exception of two.

Can I jump R to C wire?



C is a common neutral wire. You can’t jump it from Rh as that is a 24v wire. You need a third wire, C, to return to the unit and hook to the common side of the transformer. For ease of thought, think of R as “hot” and C as “ground”.

Is RC the same 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.

How much does it cost to install a common wire?

The cost to install a C-wire will range from $120 to $200. A professional electrician will run the “common” wire from your furnace to your new smart thermostat. This requires fishing the new wires through your existing walls and making the connection at both ends.

Do you need a common wire for Nest?

Nest thermostats are designed to use very little power, and in many cases they can use your system’s heating and cooling wires to get enough consistent power. But sometimes, you may need to connect a common wire (C wire) or power accessory, like the Nest Power Connector, to make your system compatible.

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.

How do I know if C wire is live?

Quote from the video:
Quote from Youtube video: Begin by putting one probe whichever probe you want on the rh wire and test every other wire with the other probe. One of the wires will show up is 24 volts and that is your c wire.

Do I need a jumper from R to RC?

If you just have one wire, regardless if it’s labeled RC, it will go into the R terminal, and the jumper connecting terminals R and RC will be in place. Some thermostats have a jumper switch, some have a metal staple, others may have a plug, and the jumper may also just be a wire connecting the two terminals.

What does the common wire do?

A C-wire, or a common wire, runs from your low voltage heating system (24v) and carries continuous power to your thermostat. In today’s electric market, most newer heating and cooling systems have C-wires, which guarantees compatibility for the installation of all smart thermostats.

Does the common wire carry current?



Yes, the neutral wire carries current. The neutral wire is a return path for any circuit. The neutral wire completes the electrical circuit and is an automatic return path for the hot wire. It serves as a balance for the current flowing in the circuit.

Is neutral and common wire the same?

The common wire is normally the white wire, at least in the United States, and is often called the neutral wire. It’s also called common because all circuits in the house typically have the white wires tied together, which means every circuit has that wire in common.