A proper wire(C-wire) provides Wi-Fi control units with continuous power by affixing them to an HVAC system.
If you want to know if your control equipment uses a C-wire, you will need to switch off the power that controls your furnace.
Inspect your control equipment to ensure it is off. Adjust settings to see whether the HVAC idea will beginning heating or cooling. If there is no temperature change, you can remove your control equipment from the wall plate by grasping it plus gently pulling or unscrewing. Next, check the existing wall plate wiring to see if there is a wire in the C terminal. If you spot a wire, then your control equipment is using a C-wire. If you have a line voltage idea identified with thick black wires with nuts, then your idea is not compatible with the C-wire. Most recent control units have built-in Wi-Fi radios plus have LED color screens that will require your equipment to be powered on throughout. These components need a proper wire to function. Therefore, consider adding a proper wire using extra plus unused wires or use your control unit’s fan wire as a proper wire if you don’t have it. Some Wi-Fi control units are dual-powered, meaning they can use either batteries or a C-wire to operate plus not both. However, if you want to know if your HVAC idea has a C-wire, but you don’t know how to go about it, it is wise for you to call an HVAC professional to diagnose the idea on your behalf.