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Discussion Starter · #1 ·
I need an (off)-on or an (off)-on-(off) "push-to-break" switch for residential use

I have a humidity sensing exhaust fan in my bathroom. When the fan has power and senses humidity, it will run the fan until the humidity is removed. If you want to turn the fan on manually (in a stinky situation) you can switch the power off momentarily and then back on and it will run for a pre determined amount of time.

In order to make the fan dummy-proof and to prevent mold from growing, I do not want to give users the ability to turn off power to the fan. I could just eliminate the switch and the humidity sensor would take care of the rest, but then the user would not have the ability to momentarily cycle the power to run the fan manually when there is stink but no humidity.

So what I need is a switch that always springs back to the on position. I have found this type of switch in different physical styles that won't neatly work with a wall plate. I need it to be a typical residential/commercial rocker or toggle switch.

The closest I have come to such a thing is the Leviton 1256 but it's center-off instead of center-on. Is it possible to reverse the function of the switch? Or is there another switch out there that would work better? Or is there another more elegant solution all together that I haven't though of?
 

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A "Handy Husband"
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Re: I need an (off)-on or an (off)-on-(off) "push-to-break" switch for residential us

Google a single pole normally closed switch. They come as a push button style that you can drill and mount in a blank switch cover plate.

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Re: I need an (off)-on or an (off)-on-(off) "push-to-break" switch for residential us

Have you considered an occupancy sensor?
It will turn the circuit on when someone enters the room and keep it on for a pre-determined time.
Wired in parallel it will allow fan control without over-riding the humidity control.
If you don't want it to be automatic a simple toggle switch will work. You just have to make sure it doesn't break the power to the humidity sensor.
You would be adding a second switch to the circuit, only one needs to be on at a time and neither will over-ride the other.
 

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Discussion Starter · #4 ·
Re: I need an (off)-on or an (off)-on-(off) "push-to-break" switch for residential us

Thanks for the replies! I am probably going to try out a push button switch with normally closed contacts. I'm planning to drill a hole in a blank wall plate to mount it next to the light switch.
 

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Re: I need an (off)-on or an (off)-on-(off) "push-to-break" switch for residential us

You need a SPST NC Momentary Contact switch.
Single Pole, Single Throw, Normally Closed, Momentary Contact.
These are readily available in industrial push button and toggle.
I haven't seen one in a residential rocker or toggle grade.
How Many switches are in that wall plate?
 

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Re: I need an (off)-on or an (off)-on-(off) "push-to-break" switch for residential us

Maybe I'm missing something . Why not use a regular 3 way switch ? Up would turn the fan on , down would power the humidity sensor .
 

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A "Handy Husband"
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Re: I need an (off)-on or an (off)-on-(off) "push-to-break" switch for residential us

Maybe I'm missing something . Why not use a regular 3 way switch ? Up would turn the fan on , down would power the humidity sensor .
That would require additional wiring from the switch to the fan. But IMO it is the best solution.

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