I recently bought a condominium in a large building, built in 2005. It has a single thermostat, and the thermostat works fine. But right next to the thermostat, there is a switch. It looks like an ordinary light switch, and it is positioned where one might find an ordinary light switch. But it governs the thermostat: when it is switched to the "off" position, I get neither hot nor cool air, no matter how I set the thermostat.

The switch is a three-way switch, not a single-pole switch. Every unit in the building has such a switch, and my switch doesn't seem to affect any other units in the building. Here are pictures of the switch and the junction box:

switch junction box photo 1 junction box photo 2

At the switch:

  • two black wires on one side
  • two red wires on the other side
  • nothing connected to the ground screw

In the box:

  • one red wire going up from the switch, and one red wire going down from the switch
  • one black wire going up from the switch, and one black wire going down from the switch
  • one wire that passes through the box without ever being connected to the switch

It is a small condominium, and there is a direct line of sight between the switch and the circuit breaker. At a slow pace, you can walk the distance between the circuit breaker and the switch in under six seconds.

I don't think that I will ever want my switch to be in the "off" position. The thermostat itself has a switch with an "off" position, and I would rather just use that. Can I simply remove the switch, use a wire connector to connect the two wires that are now affixed to the switch, and then cover the opening with a blank faceplate?

  • Does the furnace/air handler still have electrical power when the switch is shut off? – ThreePhaseEel May 12 '19 at 3:36
  • You CANNOT "patch the hole in the drywall" if, in fact you can remove this switch. You must use a blank junction box cover so the junction box it's mounted to remains accessible. Patching over (hiding) junction boxes is absolutely not OK, for very good reasons. – Ecnerwal May 12 '19 at 3:40
  • @ThreePhaseEel: yes, the furnace/air handler for the building does still have power when the switch is shut off. It's a large and fairly new building (built in 2005), and every unit in the building has such a switch. – user697473 May 12 '19 at 3:51
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    All electrical junction boxes must have their cover plates be accessible without tools, forever. To remove a coverplate aesthetically, you must remove 100% of the length of any cables going to that box, and then remove the box, and then drywall it over. You could then fit new cables between other boxes which perform the function of the cables you removed. Also builders are cheap. You can't get them to install ceiling lamps, they certainly wouldn't install that switch unless it was absolutely required by law. So it is. – Harper - Reinstate Monica May 12 '19 at 17:28
  • Can you open up the junction box the switch is in and post a photo of the back of the box with the wires still attached to the switch? – ThreePhaseEel May 15 '19 at 4:17

This might be the furnace emergency shut-off switch. That switch plate should look like the illustration below, and be mounted much higher on the wall than a regular light switch.

Switch plate for furnace

Check with the condo management... It would likely be a fire code violation to remove it, in that case!

However, it might be a "vacation" switch, which could be removed... But again, check with the condo management, since they surely have rules about what is allowed.

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  • Thank you. The condominium is in a large building, built in 2005. The switch is at ordinary light-switch height. It is not shutting off the furnace, and it doesn't seem to be affecting any other units in the building. – user697473 May 12 '19 at 3:48
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    It's still an "ask condo management" thing, because condo builders are cheap and do not install useless things like that unless the government holds a gun to their head. They are also holding a gun to your head. Given that it disables the furnace functions, it definitely powers the furnace transformer which makes 24V power. It may power other stuff. Just because parts of the furnace are still energized does not mean the switch doesn't control it. Again, consult with condo management to find why they spent the $ to put it there. And pull a permit for this work. – Harper - Reinstate Monica May 12 '19 at 17:40
  • @Harper -- I think the switch cuts out either the R wire or the W wire going to the thermostat (so, basically, the "vacation switch" theory) – ThreePhaseEel May 12 '19 at 22:48
  • Or it may cut AC power to the transformer. – Harper - Reinstate Monica May 12 '19 at 22:57

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