I just bought a house, and I'm trying to save some money by doing simple projects, on my own. I just purchased a smart thermostat and I am trying to follow the directions, for installation. The problem I am encountering, though, is that I can't seem to shut the power to the thermostat.

I removed the batteries from the current thermostat, turned off all the breakers in my breaker panel, but power is still getting to my thermostat. I went to look at my central air unit, and saw that it appears that the wiring from the thermostats is wired directly into the unit. Is this correct? Here are some images:

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I also see that there is a small box, on the side. I am not sure what it is, and therefore I'm reluctant to polk around. I took the lid off, and there was another cover.

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Anyway, my questions are: First, is it normal to just have the wiring directly into the central air unit, or should there be a breaker somewhere between? Second, if all this is fine, how do I turn off the power to the thermostat?


  • 1
    Are you sure there isn't another breaker panel somewhere? Also, have you tried turning off the disconnect for the air conditioner that's visible in the 2nd photo? Oct 31, 2017 at 22:29
  • 1
    1. yes, it's normal. 2. try the big gray box on the side. it also won't kill you to wire hot, it's low voltage.
    – dandavis
    Oct 31, 2017 at 23:01
  • Can you post a photo of what you see when you lift the lid on the grey disconnect box? Nov 1, 2017 at 11:44
  • Thanks, I ended up shutting the whole main breaker off, and it shut it down. When I was going through each breaker, individually, I must have missed the correct one. Anyway, I got it working. But, I see two responses, about if the first photos wiring is correct. One person wrote that it was fine, while someone else wrote it was not. Any clarification on that would be great.
    – jason
    Nov 1, 2017 at 14:59
  • 1
    @Jeff: how's that possible? the thermostat literally shorts the wires on purpose to turn the thing on...
    – dandavis
    Nov 1, 2017 at 23:29

1 Answer 1


No it is not normal. There is normally a disconnect between the power supping the condenser and the condenser itself. It should be near the condenser. (the condenser is the outdoor portion of the A/C side of your system. I am certain that the disconnect you need is the box shown in the second picture. Open the front and pull out the plug. This should kill the power to the transformer. Also you could find the breaker in the house panel that supplies the furnace and secure the power there.

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