I've managed to get my hands on a really nice window unit AC that can cool my entire living space (about 900 sq ft), but the downside of it being so powerful is that I either have to

  • leave it running on max, which gets the house too cold and uses too much electricity,

  • use its thermostat, which causes it to switch to just fan after the air gets cool enough, thereby re-humidifying the house. (This is problematic as the temperature setting needed to get the humidity to an acceptable level varies greatly by time-of-day and weather, and aside from eliminating extreme heat, removing humidity is my main reason for having an AC.) or,

  • keep manually switching it on and off based on temperature and humidity

What I'd like is to find or make a sensor-based switch I could put between the outlet and the plug to turn the unit fully on or off (not on or fan-only, where the latter actually makes the climate worse by re-introducing moisture) based on the humidity, rather than the temperature. Is there a product to do this, preferably something purely mechanical rather than over-priced electronics? I would think such a switching device would be a standard component in dehumidifiers, but I don't know what it's called or how to search for it.

Edit: Before commenting that this won't work, please be aware that the AC unit does not itself have any electronic controls that would misbehave when power is cut and restored. The control system is purely mechanical switches.

1 Answer 1



assuming it is rated for the draw on your A/C unit, the very first hit is this item:


I didn't look any further than that first hit.

  • All of those look like they're for the range where condensation is happening, near 100% humidity. I couldn't tell if they're adjustable to a more reasonable target like 30-40% or even lower (since the sample is to be taken at the dryest point, near the unit, it's conceivable I'd want to set it much lower than the normal comfort level). Jul 4, 2013 at 18:44
  • It would depend on your 'big picture' of course, and I don't know what that is obviously, but why not let the A/C remain thermostatically driven, and buy a dehumidifier? it'd be plug-n-play, have resale value, and maybe result in a lower the electricity bill compared to the conversion approach.
    – mike
    Jul 4, 2013 at 18:56
  • I have a dehumidifier (unused, sitting in the basement), but I'd rather not use it since it takes up space, makes more noise, and requires regular emptying or a place to run a drain hose. Jul 4, 2013 at 19:20
  • I guess I could always do like in my car (where this is not wasteful, unlike in a house) and just run both AC and heat to keep it dry but not too cold... ;-) Jul 4, 2013 at 19:27
  • Then i'd just put it wherever and keep a remote control near the entryway to turn the dehumidifier on whenever I left. Otherwise, google.
    – mike
    Jul 4, 2013 at 20:21

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