Two switch control of Bathroom Fan

rsattelJanuary 11, 2010

I'm installing a replacement fan in the kid's bathroom. There are two wall switches in the present setup. One for lights (not in the fan) and the other for the fan. My kids often "forget" to turn on the fan when using the bathroom. I want to wire the fan to the light switch as well as to a timer switch right next to it. That way when the lights go on or off so does the fan, unless we turn on the timer to vent the room after taking a shower (lights could be off in that case). I was thinking of jumpering the downstream wires from one switch to the other, but now am thinking that would make both switches control both lights and fan...Any suggestions?

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Ron Natalie

The biggest issue with what you are doing (unless the fan requires something special with regard to circuits, but that's usually only an issue with those with heaters) is that in addition to the light switch turning on the fan, the fan timer will also turn the lights on. Of course, given my kids, I'd use one those intermatic timers that turns off the lights and the fan after some time (15-30-45-1hr) after they were turned on.

    Bookmark   January 11, 2010 at 1:35PM
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Thanks. That's kind of what I figured. Is there any safety downside to doing it that way (having both switches running both fan and lights)? If not, would it be ok to just jumper the outputs together? I'm thinking that I don't want the lights to stay on for 5 to 60 minutes after a midnight pee run, so the switch would be best in that situation. When bathing, the 60 minute option with lights on too would be ok...

    Bookmark   January 11, 2010 at 1:45PM
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You could solve the lighting problem with an occupancy sensor. The fan is a bit more complicated. You don't need it at all for the midnight potty run. A short run would be beneficial for some potty functions. A 10-15 minute run after the end of a shower would best to clear moisture from the room. Short of water flow sensors on the shower line and noxious gas sensors in the toilet, I don't think they make a fan timer that anticipates run time.

I think an ordinary light switch and some kind of timer for the fan would work best. We occasionally forgot to turn of lights when we were kids and Dad helped use remember with a little smack in the back of the head. After the first smack, our memories were pretty good for at least a month. Now I know current parenting wisdom eschews smacking so trying taking away the cell phone, iPod, etc. instead.

    Bookmark   January 11, 2010 at 4:24PM
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Lights being left on aren't really an issue (in the bathroom, at any rate). The bigger issue is not running the fan while taking a shower ("it's too cold") which allows the room to steam up, dampens the ceiling and presto! Mold! Turning the fan on after the shower and letting it run doesn't help much at that point. I want to make sure that when lights are on, fan is on (of course, they could always shower in the dark too I guess). Guess I'll try tying the outputs from the switch and the timer together. I can live with lights on for a while while timer runs down. Thanks for your input, folks.

If anyone sees a potential hazard to my work around, please let me know!!

    Bookmark   January 12, 2010 at 12:08PM
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your compilcation comes from wanting the fan on and lights off..not easy...

an on/off switch for the light..parallel with a timer..but this means the fan and lights are one together..

what about a motion detector with a time delay for the fan, but not the light..ok so during the midnight pee run the fan the fan quite?


    Bookmark   January 12, 2010 at 3:34PM
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I like the idea of a motion detector with a time delay for the fan. It is pretty quiet. I didn't know such an animal existed. Now to start looking for one.

Thanks for the suggestion.

    Bookmark   January 13, 2010 at 7:45AM
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