I have a thermostat that I have used in the past with an external power supply on a system that did not have a C wire at all. But now I'm trying to connect it to a system that does have a C wire, but the voltage is too high. The thermostat is designed to work on 12-24 AC or DC.
If I understand it right, the C terminal on the thermostat is the "ground". So if I were to use a DC external power supply, would (-) go to C and (+) to ..... where?
If I understand it right, the C terminal on the thermostat is the "ground". So if I were to use a DC external power supply, would (-) go to C and (+) to ..... where?