Nest’s connector can accept only one of these wires:
W3, E, HUM or DEHUM
According to our online compatibility checker, Nest works with 95% of 24V heating and cooling systems, including gas, electric, forced air, heat pump, radiant, oil, hot water, solar, and geothermal
The Nest Learning Thermostat is designed to work even if your home doesn’t have a common “C” wire, but installing a new C wire may be required in rare cases.
If you have dual fuel or a whole-home humidifier/