I installed an attic fan with a thermostat. However, there are times when I just want the thing to turn on and stay on no matter what the temperature is.

I could just add another switch, run two wires from both terminals of the thermostat gauge (both switches on would bypass the thermostat; switch 1 only would be thermostat-dependent; switch 2 would do nothing on its own). I know of how I could do this, but I'm wondering what is considered the best practice here.

  • I would probably do the same as you plan. you might check and see if there is a spare wire going to the fan in the existing cable if there is you could take the spare to the other side of the thermostat and use the hot from the existing switch to power the 2nd switch. If there is a spare a single gang double switch would fit in the existing box and you would have the same control that you plan. (by spare wire if they ran 12-3 or 14-3 instead of the normal 12-2 or 14-2) you might get lucky. – Ed Beal Oct 12 '16 at 22:45
  • Yeah, I'd like to use a double pole, double-throw rocker switch (i.e., push to the first click for thermostat; push to the second click for always-on), but I don't seem to be able to find any decor models (only big, ugly industrial versions) so I think I'll probably go with one of those sideways twofer switches. – Network Effects Oct 12 '16 at 22:56
  • Here is a switch I think you will like you only need a single pole double throw. The common would be the hot one side would go before the thermostat and 1 after. Center position would be off – Ed Beal Oct 12 '16 at 23:03
  • Can you post a photo of the thermostat wiring? – ThreePhaseEel Oct 13 '16 at 0:14

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