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How does a home thermostat system work?

I always thought that the thermostat display box, was wired through the wall and connected to the furnace.

I didn't know you can just buy the display thing, attach it to the wall and have it run your furnace and AC and whatnot.

So how exactly does it work? I mean, how is it able to control the furnace and AC?

Thanks.
  • Answers
  • It still has control wires connected to thermostat and out to furnace. The thermostat sends signals to tell Furnace Aircon what you want.
    D C · 0 2
  • a thermostat is a sensor with many function
    harry · 0 1
  • if it isn't wired, it's using some sort of short range radio control -- that requires installing a receiver on or near the control board and running its antenna through a small hole in the air return plenum
    Spock (rhp) · 0 0
  • There is a relay in the thermostat, the old style ones had a mercury bulb switch on a bimetal coil spring.
    I think you are referring to the new WiFi models, they still need a WiFi receiver box to emulate contacts.
    You replace the hard wire Tstat with a master and then the remotes communicate via your home WiFi.
    Rolomatic · 1 0