If your system has a C-wire, it might be in use or just tucked away behind your current thermostat. If your system doesn’t have a C-wire, you’ll need to run a new cable from your furnace to your thermostat to install most of the modern smart thermostat models.

How do you wire a C wire to a furnace?

Quote from the video:
Quote from Youtube video: One of these is gonna be Diggs wires they go to the thermostat. One of these is gonna be the wires that go to the AC compressor. And they come in through the top here.

What is the C wire connected to?





WHAT IS A C-WIRE? 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.

Can I connect C wire to ground?

Wiring to the ground @ any outlet would potentially work, but is not good practice,as many things could go wrong and possibly short or overload the circuits in your furnace controls, not good! Happy trails. Hello, and welcome to Home Improvement. Thanks for the answer; keep ’em coming.

Does C wire connect to air handler?

Older wires will have only 2 or 4 strands but the 5 strand will provide that extra wire known as the c wire. When connected inside the air handler, it provides that needed 24vac power for the smart thermostat.

How many wires can be connected to the C terminal at the furnace?

Two wires per terminal in HVAC work is common (though not usually correct), while 3 or more will tend to use a pigtail.

How do I know if my C wire is working?





Easiest way to check is pull any batteries out of the old thermostat and look for a wire (normally blue) is connected to the C spot. If the old unit supports being powered by the common wire, then the unit will turn on without batteries.

Where does the C wire connect to a transformer?

A C wire transformer has two output wires; connect one wire to Rc terminal and the other wire to the C terminal of your thermostat. Once you finish this connection, plug the transformer into your mains power outlet.

Is RC and C wire the same?

Hi there! The C and Rc wires are not the same. To install this thermostat you should follow the exact same wiring of the previous thermostat.

What color is C wire for thermostat?

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.

Where does the C wire go to in the air handler?

If there’s a C terminal on your board (can’t tell from picture), use that. If you have an air conditioner, it will have two wires that connect back to the thermostat (usually via the furnace): so long as one is going to R , the other will be C and you can splice into the same spot.

Is C wire 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 I know if my C wire is connected to my furnace?



If there is a wire connected to the C terminal at the HVAC control board:

  1. Note its color.
  2. Check if there are any wires tucked behind the back of the thermostat with the same color.
  3. If there is a matching wire, that should be your C wire.