EITHER/OR switch instead of ON/OFF


Old 08-06-04, 12:20 PM
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Join Date: Jul 2001
Location: SW Alabama
Posts: 164
EITHER/OR switch instead of ON/OFF

Howdy y'all!

Again, I tried the search but to no avail--it always brings up a blank page for me. I think it has to do with the security and restrictions on our work network server. Anyway...

Is there an AC switch that acts as what I'll call (don't know if there's a technical term) an EITHER/OR switch rather than an ON/OFF switch like your standard single-pole does? I'm wondering if I could use one 3-way switch for this since it seems like what it does, but I'll explain what I'm trying to do if someone (or someones) could point me in the right direction.

I am remodeling a bathroom. I am installing a ceiling exhaust fan (properly vented to the outside). Problem is my wife always forgets to turn it on when she showers, so I am installing a humidity sensor to automatically switch the fan on when the humidity gets so high.

So far so good.

On the sensor, I can manually turn the 'dehumidifying device' off, but I can't turn it to constantly on. I would like to have that option, though, so I was hoping to install a switch that would fit in a single gang box (and that hopefully has more of a residential decorative look than a commercial look like a metal toggle switch) that would either:
  1. Send constant power directly to the exhaust fan
  2. Send power to the humidity sensor which would then control the exhaust fan
I don't need a switch that would 'cut off' power, as I could always direct the power to the sensor and use the off switch there, or just turn off the breaker.

Fire away!
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Old 08-06-04, 01:23 PM
Join Date: Sep 2003
Location: Central New York State
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Just use a three way switch. The incoming power goes into the switch. Connect one outgoing line to the sensor and the other directly to the fan.
Old 08-06-04, 05:30 PM
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& an RC Cola
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Location: SW Alabama
Posts: 164
Thumbs up

Thanks racraft!

As I mentioned in the original post, I theoretically thought (hoped) that would work. But you know theory & practice don't always meet eye-to-eye, so I wanted to hear what a pro had to say.

Now I've got a plan for the weekend. Oh joy, huh?

Last edited by Moonpie; 08-06-04 at 05:31 PM. Reason: Tpyo
Old 08-06-04, 09:01 PM
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Yep, a three way switch is exactly what you need. If you want to continue your web research, try searching for "single pole, double throw" switch (which is what a three way switch is.
Old 08-09-04, 07:08 AM
Join Date: Sep 2002
Location: welland ontario
Posts: 5,663
Just use a regular switch and wire it in parallel with the humidity sensor. That way if the sensor want to turn on the fan is can at any time. If you want to turn on the fan you can with the switch. Both will need to be off for the fan to stop. Either one can turn on the fan at any time.

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