GFCI Tripping Repeatedly?

We recently remodeled my in-laws bathroom and, as per code, the entire 20 amp bathroom circuit is protected by a 20A GFCI outlet. Everything was inspected and functions as it should.

Unfortunately, the GFCI is tripping occasionally when the bathroom vent fan is turned "off". It never trips when turning on the fan, only when turning it off. And, it may go a few weeks before it trips, and then suddenly trip three times in a row. Then it'll work fine again for a few weeks.

I suspected a bad GFCI, so I replaced it with a new one, and also replaced the switch that controls the fan. It doesn't seem to trip as often now, but it tripped for me again last night when we were visiting.

The only remaining item seems to be the fan itself, but I'm curious if there's some other possible cause I might be overlooking? The fan has been installed for a few months now, so I probably can't return it at this point.

I thought maybe condensation from moisture draining back through the vent pipe (it had to be routed up over a beam to get out through the side wall). But, the tripping doesn't really seem to be related to when the shower was used recently.

Thoughts?

Anthony

Reply to
HerHusband
Loading thread data ...

Hi, Probably motor body and fan enclosure does not have or have poor ground?

Reply to
Tony Hwang

I have had trouble with motor loads tripping GFI's.

The fact that it trips when the fan is turned "off" leads me to believe what you're seeing is not a true ground fault (current leakage to ground) but "merely" a difference between the instantaneous currents on the hot & neutral wires.

I'm an ME but I did study some motor & circuit stuff in school.......here's my best attempt at an explanation, when the fan is turned off, the magnetic field of the windings of the motor collapses & induces a current back thru the neutral (since the hot lead is switched & therefore open).

The GFI senses this slight current as mismatch between hot & neutral currents & trios.

cheers Bob

Reply to
BobK207

Hi Bob,

If this is the story, what is the proper way to deal with this? Is there a type of motor that can be specified and which would minimize this effect? Would it be acceptable practice to switch both the neutral and hot to the motor? If so do double pole switches break both connections sufficiently close to simultaneously to avoid the induced current imbalance?

Thanks, Wayne

Reply to
Wayne Whitney

The fan isn't required to be on a GFI protected circuit unless it is in the shower/tub space. I'm not sure what could be causing your problem. Maybe try installing a two pole switch so that the hot and the neutral are being disconnected at the same time.

Reply to
John Grabowski

Why connect the fan to the GFI at all? Is it a requirement in your locality?

Reply to
J.A. Michel

The field collapses 60 times a second when running...

Reply to
HeyBub

Wayne-

Sorry for the short post (the potential cause & no solution)...... I was off to the airport to pickup one of my NorCal sons

Your questions are all good ones (I had / have them as well but don't really have any answers)

If the fan location requires GFI maybe one just has to deal with the nuisance trips?

Per John's post (& I agree), fans may or may not need GFI protection depending on their location relative to the bath or shower.

I just re-did my bath & didn't GFI protect the fan or the light I was going to but it wasn't required; even though I wanted to for curiosity & extra safety.

I also was going to suggest a double pole to switch the hot & the neutral...... but in all my electrical experience.....switching the neutral is a major no-no.

cheers Bob

Reply to
BobK207

Incorrect. Switching *only* the neutral is a major no-no. There's nothing wrong with switching both the neutral and the hot.

Reply to
Doug Miller

This is not an uncommon anomaly. As others have said, the NEC doesn't require GFCI protection for the fan unless it's located over the tub, and the manufacturer requires it

Reply to
RBM

I had this same problem a while back with my bath fan. The problem was a minor leak from the roof vent. Fixed leak. Haven't had this problem since.

Reply to
Roger W

yeah but BOTH the hot & the neutral are still connected when the fan is running.....

I believe it is the "collapse" with the hot open & the neutral still connected that causes the problem for the GFI current sensing circuit.

My comments were meant to provide a plausible reason for the behavior "GFI trip on fan shutdown"

& your theory is?

Sounds like Doug's comment that its ok to switch both should solve the issue.

OP-

Is the fan / switch wiring such that you can easily install a DPST switch and switch the hot & the neutral to the fan?

cheers Bob

Reply to
BobK207

I was afraid of something like that. At this point, there's not much I can do to rewire the fan to be off the GFCI.

Yes, I could install a DPST, but I can't say I've seen them in stores? Then again, I've never really been looking for them.

Anthony

Reply to
HerHusband

Well, good to know, but a little too late. It had been my understanding that the entire bathroom circuit needed to be protected by the GFCI. But the inspector mentioned a couple of things that didn't need to be on it also. Oh well, no harm done, except for the fan nuisance.

The DPST switch idea sounds like my best option if I can find one.

Anthony

Reply to
HerHusband

Roger,

My in-laws just had a new roof installed, so I didn't want to cut any holes and risk causing a leak. So we routed the duct out through a sidewall. Except for a short bump up over a beam, the 8' duct slopes mostly towards the outside wall vent.

So, there's no chance of a leak, other than maybe condensation working it's way back. However, the tripping doesn't seem to be related to shower usage, which makes me doubtful of a moisture related cause.

Anthony

Reply to
HerHusband

Anthony-

If you have a Home Depot near by, they probably have the DPST

here's a link to listing of the Leviton double pole products (white), HD (at least in my area) stocks Leviton products

formatting link
the 1202-2W switch looks to be the one you'd want.

The DPST solution will only work IF the neutral to the fan comes from the switch box & can be safely broken there.

cheers Bob

Reply to
BobK207

Bob,

Thanks for the info!

We have a couple of HD's and a Lowes nearby. I'll have a look next time I'm there. I've never had a need for them before, so I've probably looked over them and didn't know it.

Yep, the power comes into the 3-gang switch box, then separate cables run to the fans and lights. It'll be no problem switching to the DPST switch.

I'll have to wait and see if changing the switch will prevent the GFCI from tripping when the fan is turned off, but it's a relatively simple and inexpensive thing to try. Thanks for the tip.

Anthony

Reply to
HerHusband

An easy "try this" will be to swap out the washroom fan with a new one or one from another bathroom. The puzzling thing is the exhaust fan motor draws so little power that even stopping the motor by hand should not cause any circuit hiccups (and will not cause the motor to overheat.)

Reply to
PaPaPeng

If the GFCI is in the same three gang box as the switch for the fan and lights you should be able to reconfigure the wiring to eliminate the light and fan from the GFCI protection.

Reply to
John Grabowski

I am skeptical that a properly working fan should trip a properly working GFCI when the fan is turned off. If there is no ground fault in the fan or switch, there can be no imbalance of currents (conservation of electrons). A double pole switch should not make a difference. I might suggest an intermittent ground fault in the fan or switch when the fan is turned off.

Please let us know what the problem is/was when/if you figure it out.

Reply to
M Q

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.