Occupancy Sensor to Turn off Dehumidifier

[Charles P. Wright]

I have a dehumidifier in my basement shop. I would like to have an occupancy sensor that would cut power to a receptacle while I'm in there, to avoid the noise. I tried searching, but couldn't find anything that turns the power off when you're in the room (instead of on). Does anyone have any suggestions on how to get what I'm looking for?

[Harry Hagan]

I’m thinking it’s no problem turning the unit off—but remembering to turn it back on is what you’re wanting to avoid. Having a sensor that turns the unit off/on intermittently when it doesn’t detect your presence might harm the dehumidifier. Also, you’ll need a unit that will come back on after a “power outage”. Perhaps something to remind you to turn it back on would be better for your dehumidifier.

[Mel Fulks]

Don't think you would want something that would trigger with each pass through the door since stuff with a compressor is not supposed to be quickly cycled on and off. String and magnet, or clip, connected to the FULL float?

[Von Bickley]

You could do it with a motion detector and a relay that has a normally close contact.

[Don Jarvie]

Don't most of them has an intermittent switch so it switches on when it senses moisture?

[Curt Harms]

The 'short cycling' seems like it might not be real good for the compressor. If you wanted to get fancy, you could maybe go with Von's idea of a relay and add to it a time delay so that once off, it wouldn't turn back on until after a period of no traffic.

[Alex Mielko]

Wouldn't be easier to tie it to the light switch (off when lights on)? Sort of like the switch controlled wall outlets in rooms?

[sean meltvedt]

Charles-you will have to build it-but Von has the right idea. Get a motion sensor light switch with an adjustable delay. Use it to power the coil on a relay with a normally closed contact. Then power the humidifier through the normally closed contacts in the relay. This way when the switch is active (you are in the room) the humidifier power is off, and after you leave and the delay has expired, the humidifier is back online. This could fit in a large double gang box with a cord pigtail so you could use it without any modification to your house or the humidifier.
Have fun!

[Charles P. Wright]

I think Von has nailed it. Get a motion sensor and a NC relay. I can set it up with a 30 minute delay or so to avoid short cycling the compressor.

[Bill Dufour]

I think you could replace the light switch with a three way switch. Wire it so in one position the lights are on and in the other the power goes to the dehumidifier. Probably a good idea to add a "delay on" relay so flicking on the lights for a minute does not short cycle the pump.

[Jerome Stanek]

I have a 2 relays that kicks my air compressor on and opens an air valve when I turn the lights on. When I leave I shut the lights off and all air is shut down