Asked by: Lisbel Bernhoeft
home and garden smart home

What is the purpose of the C wire on a thermostat?

Last Updated: 8th June, 2020

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.

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In this manner, what color is the C wire?

Here are common uses for wire colors: Blue or Black – C – Common wire, may be unused by your existing thermostat. Enables continuous power flow from the Red wire. Red – R – 24VAC power from the furnace's transformer.

does Honeywell thermostat need C wire? C-Wires are required on most Honeywell Wi-Fi thermostats, with the exception of the Smart Round Thermostat (formerly known as the Lyric Round). How do I check if my thermostat is using a C-Wire? To protect your equipment, turn off the power at the breaker box or switch that controls your furnace or heating equipment.

what if there is no C wire for thermostat?

If your current thermostat didn't need a C-wire, it (or a wire that can be used as a C-wire) might be rolled up inside the wall. This is more likely to be true if you see all the other color wires present.

Is the C wire a ground?

The C wire is the common wire ground wire. You already have 24v ac going to the red wire. If you have an extra wire connect it to the C at the thermostat and ground it at the transformer box in the AC unit.

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