This page has some really good information on heating system wiring in America. One thing I can't tell from it though, is what exactly the 24VAC call-for-heat and call-for-cool signals drive.

Presumably they don't supply the actual power for heating or cooling (24VAC wouldn't get you far), so I guess it is some kind of control signal, but what is the load? Does it drive a relay? If so what is the coil resistance, etc.?

In other words, what exactly is in the question marks here?

us thermostat wiring


Yes, the thermostat contacts control the current to relays within the heating/cooling system. I believe the current is on the order of 100 mA.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.