what is the c wire on a thermostat

The C wire, also known as the common wire, is a wire that runs from your low-voltage heating system (24v) and carries continuous power to your thermostat. It provides a constant source of power to your thermostat, allowing it to function properly. Unlike other wires connected to your thermostat, a C wire doesnt control heating or cooling functions. Most newer heating and cooling systems have C-wires, which guarantees compatibility for the installation of all smart thermostats. If youre installing a new thermostat, but your existing one is missing a C-wire, you have a few options. You can check if there is an unused wire that can be used as a C wire, or you can use a C wire adapter. If youre unsure whether your system has a C wire, you can turn off the power supply and check the wiring behind your thermostat to see if there is a wire connected to the terminal C.