Thread: Quirky bathroom exhaust fan

Ran into a master bathroom exhaust fan that did not run with the wall switch turned on. The switch was already in the on position when I walked into the room. Jotted a note to self and kept on checking the bath. Turned on the shower and started to fill the hydro-massage tub and so on.

Within a moment the exhaust fan kicked on. I tried the wall switch and it turned off and on reliably. I let it run to see if it would shut off again and was thinking that perhaps the drive motor had overheated.

The fan ran fine while I was working in the area. Later when I was about finished in the bath area the fan shut off again. I thought, "There it goes. It’s overheated again". I turned the switch off and went on to inspect in other areas of the house.

At the end of the inspection I came back to the bath thinking it would have cooled off by then. No good...was dead when I turned on the wall switch. Meanwhile my client came in and asked me to show her how the shower worked. It was one of those new "modern" showers with multiple delivery heads spraying in all conceivable directions.

I started to put the shower through its paces again for her benefit and the exhaust fan kicks on again! After I shut the shower down I began to explain to her how the exhaust fan has been acting up. As we were talking the fan shut down again on its own.

I was pretty much done with that fan's behavior at that point and was ready to just call it "malfunctioning" with a "repair or replace" comment. But...something just did not "feel" right about they way it was behaving.
I went to get a stepladder to get a closer look at the guts expecting to find a drive motor too hot to touch but determined to verify it anyway. By the time I got back with a ladder my client is playing with the shower controls herself and the fan is running again!

Down comes the cover face off the fan and what did I find? A humidistat controller installed inline between the wall switch and the motor not so neatly tucked into the fan housing. Well that explained the fan's operational quirks and it seemed to work really well.

I confess that I was somewhat reluctant when I wrote it up anyway as a potential problem. The controller was not designed to be installed inside the UL Listed exhaust fan unit and was in fact a humidistat that was designed to be installed over a j-box as the intended wall switch.

Great idea though to operate the fan based on humidity rising up to the ceiling mounted fan housing. First time I have actually seen that in the field.

The other down side was that the fan could not be forced to turn on unless the humidity was high at the ceiling. Operation purely for odor removal was therefore not possible the way it was configured.

Similar Threads:

• Condensate leak at furnace exhaust
• White "powder" at furnace exhaust tube
• bath fans, exhaust to exterior
• Gas Dryer in Bathroom
• That dread Exhaust Vent - Texas gang

Originally Posted by Phillip Stojanik

Ran into a master bathroom exhaust fan that did not run with the wall switch turned on. The switch was already in the on position when I walked into the room. Jotted a note to self and kept on checking the bath. Turned on the shower and started to fill the hydro-massage tub and so on.

Within a moment the exhaust fan kicked on. I tried the wall switch and it turned off and on reliably. I let it run to see if it would shut off again and was thinking that perhaps the drive motor had overheated.

The fan ran fine while I was working in the area. Later when I was about finished in the bath area the fan shut off again. I thought, "There it goes. It’s overheated again". I turned the switch off and went on to inspect in other areas of the house.

At the end of the inspection I came back to the bath thinking it would have cooled off by then. No good...was dead when I turned on the wall switch. Meanwhile my client came in and asked me to show her how the shower worked. It was one of those new "modern" showers with multiple delivery heads spraying in all conceivable directions.

I started to put the shower through its paces again for her benefit and the exhaust fan kicks on again! After I shut the shower down I began to explain to her how the exhaust fan has been acting up. As we were talking the fan shut down again on its own.

I was pretty much done with that fan's behavior at that point and was ready to just call it "malfunctioning" with a "repair or replace" comment. But...something just did not "feel" right about they way it was behaving.
I went to get a stepladder to get a closer look at the guts expecting to find a drive motor too hot to touch but determined to verify it anyway. By the time I got back with a ladder my client is playing with the shower controls herself and the fan is running again!

Down comes the cover face off the fan and what did I find? A humidistat controller installed inline between the wall switch and the motor not so neatly tucked into the fan housing. Well that explained the fan's operational quirks and it seemed to work really well.

I confess that I was somewhat reluctant when I wrote it up anyway as a potential problem. The controller was not designed to be installed inside the UL Listed exhaust fan unit and was in fact a humidistat that was designed to be installed over a j-box as the intended wall switch.

Great idea though to operate the fan based on humidity rising up to the ceiling mounted fan housing. First time I have actually seen that in the field.

The other down side was that the fan could not be forced to turn on unless the humidity was high at the ceiling. Operation purely for odor removal was therefore not possible the way it was configured.

The problem with the humidisat in a bath is that it is doing no drawing until the misture level reaches xxx. You want the fan on the entire time any water is running to be drawing the moisture out before it has opportunity to get in to the walls and such. By then the dead is done. Not to mention the odor part. It sounds like someone did not like hearing the fan running all the time and figured they would just have it run to remove the excess moiture from the air and had no concerns with odor or the moiture getting into and staying in the walls.

Originally Posted by Ted Menelly

Not to mention the odor part. It sounds like someone did not like hearing the fan running all the time and figured they would just have it run to remove the excess moiture from the air and had no concerns with odor or the moiture getting into and staying in the walls.

Unless the occupant of the bathroom had severly wet farts!

The problem with the humidisat in a bath is that it is doing no drawing until the misture level reaches xxx. You want the fan on the entire time any water is running to be drawing the moisture out before it has opportunity to get in to the walls and such.

Mr. Mennely: Convection currents cause moisture laden air to rise to the ceiling in a bathroom. A humidistatically-controlled fan is an excellent idea, provided that it also has an on/off switch for odor control, as does this one:

http://www.broan.com/ImageLibrary/br...s/99043591.pdf

Read more here: Product Detail

And here: HVI Publications

Originally Posted by Elliot Franson

Mr. Mennely: Convection currents cause moisture laden air to rise to the ceiling in a bathroom. A humidistatically-controlled fan is an excellent idea, provided that it also has an on/off switch for odor control, as does this one:

http://www.broan.com/ImageLibrary/br...s/99043591.pdf

Read more here: Product Detail

And here: HVI Publications

OK then

The way it is hooked up is all wet........................

The air in the room that the moisture is in slowly rises to the top. The humidistat eventually picks up on it, turns the fan on and sucks it out until it reads a certain level in the air. All the air has to get x saturated slowly working its way to the ceiling and fan before the moisture is getting sucked out and it is not winding up in the walls. Good theory but a little wet Just a little pun there. The only thing I do like about it is that if the air gets x saturated it does kick on and will do a somewhat decent job in removing the moisture before it shuts off. Some folks just never turn the fan on and this is where it comes in handy if it were hooked up right. But of course in this case you are not relying on just the humidistat working but someone actually turning the power on for it to work...Again...all wet. I can keep going but I am sure you are getting my point. I rather like the idea of hit the switch for the light and the fan turns on as well...instantly... and will not shut off until you are done. Either that or set it up so it comes on anytime the humidity is x in the air around it and also be able to turn it on instantly if you wish.

It is wired up wrong.

An occupancy sensor or other type of sensor (such as in this case) is fine, but there should be a manual override that allows for forced operation when desired.

In this case the sensor and fan have been wired from the switch, which does not allow for a manual override operation, but instead shuts down the entire operation when not left in an "on" postion.

Someone DIY-botched its installation.

Write it up as deficient as in cannot operate by indicating switch without delay, and recommend it be properly evaluated and remediated by a licensed electrical contractor or electrician.

I would also doubt if the fan's location is over the shower that it is properly GFIC protected since its control/power wiring already and obviously has been botched.

Very glad to see that someone like Broam is actually making a model that incorporates humidistat technology. What I saw was definitely home brewed and broke some rules (as previously discussed by others) but I was impressed with the general concept of having the exhaust fan operation tied to a humidity constraint.

Might be a good thing if the humidistat was on a parallel circuit with the manual switch. Kind of like the On/Auto switch on a central A/C. If the humidistat can override the manual switch it would help in places where folks don't run the fan or run it long enough.
I have not seen the factory jobs.

Sounds like its in series. When he flipped the switch to off it instantly cut off was the way I read the first post. Parallel NG, no override. Needs a relay or logic circuit.