# Humidity-sensing switch for bathroom fan...does it exist?



## gregzoll (Dec 25, 2006)

Yes, it is called wiring it up, so that when you turn on the light, the fan comes on. That is how ours is wired.


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## secutanudu (Mar 15, 2009)

I'd rather not have the fan come on every time I go into the bathroom, if possible. That's why I was looking for the sensor. Wiring the light and fan together would be my fallback.


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## Michael Thomas (Jan 27, 2008)

One problem with the wiring the fan to the light switch is that you are exhausting a lot of conditioned air – often unnecessarily – if you do it this way you might want to consider an “intelligent” timer switch such as the *AireTrak* controller.
 
On a more fundamental level one issue with conventional “humidity controlled” bathroom fans is that they have to be set to a very high relative humidity level (higher than is ideal), otherwise they would be activated by naturally occurring high summer humidity in hot, humid climates.

The solution used in some commercial controls is to locate a separate sensor _outside_ the bathroom – you can then set the trigger humidity lower because you are not only controlling based on bathroom relative humidity but also on the _difference_ between the humidity within the bath and outside it, for example you could set it to activate at 70% RH - as long as that a few percent higher than outside the bathroom .

There is a company that makes these for around $240 – probably more than most people want to pay for a residential installation, but well worth it my rental units, where tenants often don’t understand and/or care why they should turn on the fan but I only want it running when necessary,


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## Scuba_Dave (Jan 16, 2009)

They do have humidity sensing fans, not sure about switches:

http://lmgtfy.com/?q=humidity+sensor+fan


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## secutanudu (Mar 15, 2009)

Thanks - I guess I can also just try and remember to turn on the fan when I shower.

Any thoughts on my second (unrelated, I know) question?


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## 47_47 (Sep 11, 2007)

Either way is fine. My opinion, use the GFCI outlet and connect the line terminals to the light and fan, if allowed by manufacturer.


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## secutanudu (Mar 15, 2009)

I believe most light/fans can be non-gfci unless they are installed over the shower/tub.


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## adave (Nov 20, 2007)

Try changing your fan switch with a timer. Once you have finished your shower, turn on the timer and the fan will shut off automatically.


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## secutanudu (Mar 15, 2009)

Timer is a good idea. Then I can just hit it as I leave, or just before I get in the shower. Thanks.

I wonder if the humidity-sensing fans will turn on in the summer on a humid day, while I'm not home (a/c would be off).


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## 47_47 (Sep 11, 2007)

Yes, most do not require GFCI, but still verify. Murphys law.


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## Thurman (Feb 9, 2009)

I had recently posted about a delay-timer switch I had installed in both of my baths in my home, and I like these. I, as others, had a problem with either turning the bath fan off too early and not removing enough humidity, or leaving it running way too long, removing conditioned air. I didn't like the rotary timers which I found for this application. I finally found a timed switch which looks much like a normal toggle switch, the toggle is just a little different, and the timer setting is behind the faceplate when installed. Now when I turn on the bath fan/light unit, then take a shower (and I like them hot), after the shower I just flip the switch "OFF" and leave. This activates the timer, which is now set for 10 minutes after many trial runs. All moisture is removed from the bath area and the fan/light turns off by itself, it has not failed to do so yet. I plan on separating the fan and light, which will require another switch, but that is later. I think it is alright to state that this unit is made by "Mark Time", which is known for rotary timers. I had to find an online supplier to buy from as none of the local electrical suppliers carried them. They all thought it was a good idea, but they just didn't sell them. Just another option, David


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## plummen (Jan 10, 2010)

check heating/cooling supply house :thumbsup:


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## secutanudu (Mar 15, 2009)

A thought I just had would be a switch that can detect a quick change in humidity, then turn on for a specified amount of time. This would account for humid days in the summer, where the increase would be more gradual.


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## Michael Thomas (Jan 27, 2008)

AFAIK it's OK to post a link to a product we are discussing, as long as the poster is not selling or marketing it, at least I do it frequently, and no one has complained so far...

One source for the switch above:

http://www.energyfederation.org/consumer/default.php/cPath/39_766_3058


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## secutanudu (Mar 15, 2009)

That switch is kind of interesting. Only thing is - wouldn't you also want the fan on while in the shower?


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## High Gear (Nov 30, 2009)

I use this type of timer http://www.intermatic.com/products/timers/in-wall%20timers/decorator%20spring%20wound%20timers.aspx.

I have a heat lamp outside the walk in shower and a fan inside connected to it also.

I turn it on right before entering the shower( shower time + 10 minutes).

The heat lamp is warming the ceramic tile just outside the shower( and warming me later).

As I leave the shower and step on the bath mat invariably some moisture gets on the tile.

My theory is that the air getting sucked under the bathroom door across 

the warmed tile to the shower would help dry the floor better.

Probably cost me a whole 5 cents extra a day to do it this way.


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## icicicles (Feb 6, 2011)

I too like you forget to turn on the fan when I shower.
To great options.
1. purches a wireless switch and mount it next to the shower, takes a 9volt to run it.
2. This is my favorite. Wire in a clap on switch around from the timer switch so you can still use them both.
The next time you forget---clap on!
Good luck!


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## rprice113 (Feb 13, 2011)

*Humidity Sensing Switch for Bathroom Fan*

I found a company called Dewstop that makes a humidity sensing switch that I used for my laundry room fan switch.


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## Michael Thomas (Jan 27, 2008)

In my experience, there are two problems with retro-fitting humidistats in bathrooms:

1) Typically, they are replacing a switch by the entry door, and don't start the fan even if there is substantial condensation at the ceiling until/unless the humidity rises at the humidistat location. 

2) They have to be set to a high trip level to avoid unwanted activation in humid weather (see comment # 4 above).


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## Mike in Arkansas (Dec 29, 2008)

Is there somewhere you could mount a motion detector sensor that would only detect when someone was in the shower? Maybe shield it so it won't trigger from motion in other areas? Just a thought


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## handy andy (Feb 25, 2011)

*yes*

Humidity sensing switches are available. About $20.00 at Home depot in Canada. I have installed several. They come with a sticker that suggest humidity settings depending on outside tempurature. 

I have also installed timer switches with several buttons where you can set the on time for 10, 20 or 30 minutes. I think these were somewhere between $20-30.


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## maxwellpj (Mar 2, 2012)

handy andy said:


> Humidity sensing switches are available. About $20.00 at Home depot in Canada. I have installed several. They come with a sticker that suggest humidity settings depending on outside tempurature.
> 
> I have also installed timer switches with several buttons where you can set the on time for 10, 20 or 30 minutes. I think these were somewhere between $20-30.


 
Handy is correct. I am going through the same thought that many of you are as well. I called my brother (a master electrician) and was told to go to the following link and check these switches out. I just thought I would share it as it is the easiest option to turn the fan on and off automatically and installs in the existing switchbox. I imagine other manufacturers sell them as well although I have not looked personally. 
http://www.bathroomfanexperts.com/product.php?p=panasonic_fv-wccs1-w&product=176968&category=3924

Recommend you search the net for humidity sensing switch for bathroom...

Hope it helps!
Mad Maxx


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## silversport (Feb 4, 2012)

my full baths have two light fixtures, one over the vanity and one over the shower, on separate switches. The shower light switch is also connected to the exhaust fan, the vanity light switch is not. May be a simple solution to forgetting to turn on the fan.


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## JRigby (Feb 17, 2012)

Motion sensor in the shower, with an off delay would be sweet. Hmmm...


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## Canucker (May 5, 2011)

I have a fan with the sensor in it. I thought about just getting the switch but it seemed i would need way more humidity to trigger the switch sensor than I would having it in the fan. I did end up using a motion sensor for the lights because the women in my house don't seem to understand that the switch can also return to the off position. lol


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## maxwellpj (Mar 2, 2012)

maxwellpj said:


> Handy is correct. I am going through the same thought that many of you are as well. I called my brother (a master electrician) and was told to go to the following link and check these switches out. I just thought I would share it as it is the easiest option to turn the fan on and off automatically and installs in the existing switchbox. I imagine other manufacturers sell them as well although I have not looked personally.
> http://www.bathroomfanexperts.com/product.php?p=panasonic_fv-wccs1-w&product=176968&category=3924
> 
> Recommend you search the net for humidity sensing switch for bathroom...
> ...


Update: I had my brother order one of these switches and I love it. We installed it and no longer have any problems. The one we ordered is a "dewstop - model FS-100" made by GTR Technologies. To test it, all you have to do is breathe into it like you are trying to fog up a mirror. It comes on about 2 minutes after we turn the shower on and keeps sensing the whole time we are in there. Once it no longer senses humidity, it sets the internal timer to run an additional 1/2 hour to clear out all the condensation up by the ceiling. A large part of the reason that we love it is to ensure the fan gets turned on while our kids (9 and 6) are showering. They like it because they do not get yelled at and I love it because I no longer get water streeks on the wall from the hot showers going for so long. It solved my issues with the fan. I hope it will solve yours too.

Maxx :thumbup:


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