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  1. #1
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    Default Faulty humidistat, or did I break it?

    I've run into this twice this month, an old house with a fan switch in the bathroom. The exhaust fan comes on, no problem, turn it off. There is a humidistat in the hallway, probably wired to the same exhaust fan. It is invariably turned all the way to the off position.

    I turn the dial to a low % humidity and nothing happens, no response at the fan. Turn the humidistat back to off or high %.
    Now the exhaust fan in the bathroom no longer works, and the home owners say I've broken it.

    The humidistat is somehow keeping the fan circuit open. Can somebody explain why this happens and is there a simple fix? Not replacement, that is beyond the scope of my inspection, eh? A sharp blow with a hammer, maybe?

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  2. #2
    Norman Ellis's Avatar
    Norman Ellis Guest

    Talking Re: Faulty humidistat, or did I break it?

    Quote Originally Posted by John Kogel View Post
    I've run into this twice this month, an old house with a fan switch in the bathroom. The exhaust fan comes on, no problem, turn it off. There is a humidistat in the hallway, probably wired to the same exhaust fan. It is invariably turned all the way to the off position.

    I turn the dial to a low % humidity and nothing happens, no response at the fan. Turn the humidistat back to off or high %.
    Now the exhaust fan in the bathroom no longer works, and the home owners say I've broken it.

    The humidistat is somehow keeping the fan circuit open. Can somebody explain why this happens and is there a simple fix? Not replacement, that is beyond the scope of my inspection, eh? A sharp blow with a hammer, maybe?
    humidistats/tempstats usually are installed in basements or close to attics to operate exhaust fans, not bathroom exhaust. but my question would be have you tested the air moisture level? the stat was off this would place the contactors in normally open or normally closed position (pending its setting), they could be stuck in the normally open position from you turming the knob, the moisture level could be too low to close the contactor or maybe the spring is week? it could have lost contact to power or neutral? try a non flammable lube on the contactors, if that doesn't work I would not fight it, keeping your customer happy would be cheaper than a stain on your record. old items break if was never altered in position by them how would they know it was working?
    on the other hand if you do any of these tasks you take responsability! how are you with public relations?


  3. #3

    Wink Re: Faulty humidistat, or did I break it?

    Quote Originally Posted by John Kogel View Post
    I've run into this twice this month, an old house with a fan switch in the bathroom. The exhaust fan comes on, no problem, turn it off. There is a humidistat in the hallway, probably wired to the same exhaust fan. It is invariably turned all the way to the off position.

    I turn the dial to a low % humidity and nothing happens, no response at the fan. Turn the humidistat back to off or high %.
    Now the exhaust fan in the bathroom no longer works, and the home owners say I've broken it.

    The humidistat is somehow keeping the fan circuit open. Can somebody explain why this happens and is there a simple fix? Not replacement, that is beyond the scope of my inspection, eh? A sharp blow with a hammer, maybe?
    Hi John,

    A marrette should fix that...


  4. #4
    James Duffin's Avatar
    James Duffin Guest

    Default Re: Faulty humidistat, or did I break it?

    Quote Originally Posted by John Kogel View Post
    I've run into this twice this month, an old house with a fan switch in the bathroom. The exhaust fan comes on, no problem, turn it off. There is a humidistat in the hallway, probably wired to the same exhaust fan. It is invariably turned all the way to the off position.

    I turn the dial to a low % humidity and nothing happens, no response at the fan. Turn the humidistat back to off or high %.
    Now the exhaust fan in the bathroom no longer works, and the home owners say I've broken it.

    The humidistat is somehow keeping the fan circuit open. Can somebody explain why this happens and is there a simple fix? Not replacement, that is beyond the scope of my inspection, eh? A sharp blow with a hammer, maybe?
    Take out the humidistat and bypass the switch. It will tell you if that is the problem with the fan and if it is then the fan will work. If the fan still does not work you have other problems. Could the fan be on a GFCI protected circuit and the GFCI is tripped?


  5. #5
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    Default Re: Faulty humidistat, or did I break it?

    Ppresumtion of interconnection to simple bathroom "exhaust fan" is questionable. Suppose series parallel override or relay at fan is possible and 'off' position caused relays to fall open, again no specifics offered.

    Ventillator, exchanger, etc. perhaps. Otherwise and esp. location outside the bathroom (hall, IIRC) suggests other. Humidifier, dehumidifer, air conditioning system, heat pump, HRV, air-to-air, etc.

    Safety, interactive board, back at the tsf (usually LV, 24vac common), board or relay, w/o specifics unknown. If older rheostat or pot. interface might have spun out, loosened retention nut, lock washer or retention clip.

    If tied into a pad humidifier at furnace with fouled valve or shut off might have popped secondary protection at LV power supply, look for reset, check operation, presence of evap pad, etc. If dehumidier function float, drain, etc. or primary system off or in 'other' mode. If was indeed simple exhaust fan interface may have been jumped or disabled.

    Last edited by H.G. Watson, Sr.; 09-30-2011 at 09:03 AM.

  6. #6
    Michael Avis's Avatar
    Michael Avis Guest

    Default Re: Faulty humidistat, or did I break it?

    All the technical mumbo jumbo aside... You turned dials that were meant to be turned. You operated switches that were meant to be operated. You may have inadvertently broken it but you are in no way responsible for the coincidental failure of a system that occurs during normal operation.

    If you flushed a toilet at the moment a soil line decides to fail are you responsible? I think your clients, perhaps through ignorance of the system are unfairly blaming you.


  7. #7
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    Default Re: Faulty humidistat, or did I break it?

    John, I've got to go with J.P.'s standard "Failed during test". Recommend further investigation by licensed electrician.

    The beatings will continue until morale has improved. mgt.

  8. #8
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    Default Re: Faulty humidistat, or did I break it?

    Quote Originally Posted by Marcel Gratton View Post
    Hi John,

    A marrette should fix that...
    OK, I'll try hitting it with a Marrette. A Canadian wire nut. Good point, as it could simply be a loose connection but I would not fix it myself. Not my house, eh?

    So far, it has never come to anything more than "Have a qualified electrician repair the faulty exhaust fan".

    It is common practice in my area to install a humidistat switch in a hallway and use it to operate an exhaust vent fan in a nearby bathroom.

    I suspect the wiring to two switches would need to be in parallel, so am not understanding how a faulty humidistat is preventing the bathroom wall switch from working, but only after I turn the humidistat?

    I was wondering if anyone has had similar experience with older seldom used humidistats?

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    Last edited by John Kogel; 09-30-2011 at 09:40 AM.
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  9. #9
    Ken Bates's Avatar
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    Default Re: Faulty humidistat, or did I break it?

    Post Hoc Ergo Propter Hoc.

    That which follows must have been caused by the proceeding.

    People of limited intelligence adhere to this false logic as it is simple and simple minded.

    I keep several copies of this with me and when assaulted as you were I just hand it to the cretins.

    Some humidistats use animal hairs as sensors and they have a short life.

    But that may not relate to this issue

    Don't cave on this one.

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    Last edited by Ken Bates; 09-30-2011 at 09:37 AM. Reason: typo add url

  10. #10
    Ted Menelly's Avatar
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    Default Re: Faulty humidistat, or did I break it?

    Quote Originally Posted by John Kogel View Post
    I've run into this twice this month, an old house with a fan switch in the bathroom. The exhaust fan comes on, no problem, turn it off. There is a humidistat in the hallway, probably wired to the same exhaust fan. It is invariably turned all the way to the off position.

    I turn the dial to a low % humidity and nothing happens, no response at the fan. Turn the humidistat back to off or high %.
    Now the exhaust fan in the bathroom no longer works, and the home owners say I've broken it.

    The humidistat is somehow keeping the fan circuit open. Can somebody explain why this happens and is there a simple fix? Not replacement, that is beyond the scope of my inspection, eh? A sharp blow with a hammer, maybe?

    That is the same as checking the garage door manually and then after that check hitting the button for the door opener and the darn thing jams and crumples before your eyes.

    Folks tend to be upset at first at the repair being in the hundreds but most and I mean almost everyone of them will understand "I hit the button after visually and physically checking the door out and then I hit the button and it jammed and crumpled to the floor"

    After they take a breath it is always something like "Yeah, that darn thing did hang up from time to time" or something along those lines

    You turned a knob and flicked a switch. Oh well, I guess it is time for them to fix it.


  11. #11
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    Default Re: Faulty humidistat, or did I break it?

    Let's try this again.

    Forget the homeowners, can we?
    I need an intelligent, informed reason WHY the humidistat is able to disable the fan switch.
    So I can tell my client the buyer "the fan which was functional no longer functions because when I turned the humidistat control, which appears to be nonfunctional, it disabled the wall switch somehow."

    Does anyone know why?

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  12. #12
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    Default Re: Faulty humidistat, or did I break it?

    Quote Originally Posted by John Kogel View Post
    Let's try this again.

    Forget the homeowners, can we?
    I need an intelligent, informed reason WHY the humidistat is able to disable the fan switch.
    So I can tell my client the buyer "the fan which was functional no longer functions because when I turned the humidistat control, which appears to be nonfunctional, it disabled the wall switch somehow."

    Does anyone know why?
    I thought someone already addressed that by pointing out that the humidistat may be connected in series with the fan switch. If the humidistat is off, or fails in the off position ...

    ... then ain't nothin' gonna work!

    Jerry Peck, Construction / Litigation Consultant
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  13. #13
    Ted Menelly's Avatar
    Ted Menelly Guest

    Default Re: Faulty humidistat, or did I break it?

    Quote Originally Posted by John Kogel View Post
    Let's try this again.

    Forget the homeowners, can we?
    I need an intelligent, informed reason WHY the humidistat is able to disable the fan switch.
    So I can tell my client the buyer "the fan which was functional no longer functions because when I turned the humidistat control, which appears to be nonfunctional, it disabled the wall switch somehow."

    Does anyone know why?
    Without being there and testing no one will really know.

    My best guess is that someone cut into the power that goes to the bath fan/switch and when one went the other went of course. Until you or an electrician investigates deeper , that is all you could come up with for possibilities.

    That is the only intelligent answer you could possibly guess at until further evaluation. Uh oh, that is another whole thread.


  14. #14
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    Default Re: Faulty humidistat, or did I break it?

    Quote Originally Posted by Jerry Peck View Post
    I thought someone already addressed that by pointing out that the humidistat may be connected in series with the fan switch. If the humidistat is off, or fails in the off position ...

    ... then ain't nothin' gonna work!
    The humidistat is off, the wall switch works. The fan must come on for the wall switch, regardless of the humidity or the humidistat setting. Same for the humidistat. So they must be in parallel. If they were correctly wired that is.

    After trying the humidistat, the wall switch no longer works, regardless of whether the humidistat is turned up or down.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  15. #15
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    Default Re: Faulty humidistat, or did I break it?

    Quote Originally Posted by John Kogel View Post
    I've run into this twice this month, an old house with a fan switch in the bathroom. The exhaust fan comes on, no problem, turn it off. There is a humidistat in the hallway, probably wired to the same exhaust fan. It is invariably turned all the way to the off position.

    I turn the dial to a low % humidity and nothing happens, no response at the fan. Turn the humidistat back to off or high %.
    Now the exhaust fan in the bathroom no longer works, and the home owners say I've broken it.

    The humidistat is somehow keeping the fan circuit open. Can somebody explain why this happens and is there a simple fix? Not replacement, that is beyond the scope of my inspection, eh? A sharp blow with a hammer, maybe?

    Some bathroom fans that come on auto due to high humidity can only be turned on manually by knowing the exact switch sequence that is published in the instructions. Typically you have to flip the wall switch from off to on then right back off and back on fairly quickly or with one second intervals.

    Bruce King, B.A. King Home Inspections, LLC
    www.BAKingHomeInspections.com
    Certified Master Inspector, Independent Inspectorwww.IndependentInspectors.org

  16. #16
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    Default Re: Faulty humidistat, or did I break it?

    Quote Originally Posted by Bruce King View Post
    Some bathroom fans that come on auto due to high humidity can only be turned on manually by knowing the exact switch sequence that is published in the instructions. Typically you have to flip the wall switch from off to on then right back off and back on fairly quickly or with one second intervals.
    Thanks, Bruce. That is something to try, and I appreciate the info.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  17. #17
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    Default Re: Faulty humidistat, or did I break it?

    Today's "low maintenance humidifier"...

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    Michael Thomas
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