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Our shower exhaust fan is tripping the GFCI when turned on. When I disconnect the FAN (there is a molex plug in the fan) the GFCI does not trip when the switch is turned on or off.

Looking for troubleshooting suggestions?

I was thinking about diving into the switch box and looking for loose connections and neutrals. Replacing the GFCI outlet, which incidentally, is all the way in the garage and also does our outdoor outlets, it's strange the way it was wired. Especially since there already is a GFCI outlet in the bathroom for the outlets.

Finally, I was going to clean out the fan. It's filled with dust and I'm thinking maybe some of the "wet" dust might be causing a bit of leakage to the ground?

It seems to happen more in the cold months where there is more condensation which leads me to think its more a problem with the FAN than an issue with the switch box or a weak GFCI itself.

I just don't want to replace the fan only to find out it was something else.

Also -- the Fan is actually on ceiling 10' feet above the shower and outside of the sunken in the shower area. So technically it likely does even need to be GFCI protected. I'd need an 8' ladder to touch it while in the shower.

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    Wet dust can definitely provide enough of a current path to ground to trip a GFCI. If you can vacuum and wipe the dust away, the tripping might stop.
    – Jim Stewart
    Jan 31, 2019 at 13:26
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    You already did competent, scientific troubleshooting to certain conclusion. And you are not the first to disbelieve the results because GFCI is involved. We get that a lot :)
    – Harper - Reinstate Monica
    Jan 31, 2019 at 16:35

3 Answers 3

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First try to stop the nuisance tripping by cleaning out the dust from the fan motor and connection block.

You don't need to have the ceiling fan GFCI protected. You said you have a GFCI receptacle in bathroom so that satisfies the requirement.

You could change the connections of the wires to the GFCI receptacle in the garage so you don't use the load terminals. If this means that some outside receptacles are no longer GFCI protected, then you would have to replace the existing receptacles with GFCI ones.

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  • Thanks, Jim. That will be my plan. It is just strange to me that they pulled it from that outside circuit. The switch is in a box with another lighting circuit used for the bathroom. So I could see what else is on that circuit and maybe swing it over there. I suspect that it failed inspection and they just humored inspector by finding another GFCI circuit and tied it into that. I'll pull down the fan and blow it all out and see what happens. I think that if it was in the switch box or something else it would trip always and not upon activation of the fan.
    – jr.
    Jan 31, 2019 at 16:00
  • I'd be the first to say "don't GFCI everything", but defeating GFCI protection by adding a bunch of separate GFCI receptacles does seem like "the hard way". Fans don't need to be on GFCI but it shouldn't hurt either.
    – Harper - Reinstate Monica
    Jan 31, 2019 at 16:33
  • @Harper I would do some measurements/fixture counts and move it over to the other lighting circuit in that switch box (fed by a non-GFCI breaker or outlet) before I did swap out all those outlets to individual GFCIs. The way it is just doesn't make any sense. They had to grab the outdoor GFCI because it was close.
    – jr.
    Jan 31, 2019 at 20:16
  • I took the fan assembly out and blew it all out with compressed air and put it back together and was fine, but first shower this morning it tripped again. I am going to replace the GFCI outlet this morning. If that still trips it, I'll look into replacing the motor assembly in the fan or just moving it to a non GFCI circuit.
    – jr.
    Feb 1, 2019 at 11:37
  • What about the wall switch for the fan? Could it be that when it is switched on it is leaking current to ground? Pull out the switch and temporarily connect the two wires of the switch loop? Does it trip the GFCI? (It would be sufficient to disconnect the switched hot and touch it to the screw for the line hot. You know the line hot cannot be leaking.
    – Jim Stewart
    Feb 1, 2019 at 13:20
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Just a reminder .... Make sure the circuit giving power to your bathroom fan is not an 'AFCI' protected circuit. Sometimes people confuse a 'GFCI' with an 'AFCI' protected circuit. An AFCI circuit will usually trip if a motor is connected to it, like a power drill or a hair dryer or a fan motor. That is what an AFCI is designed to do; trip if it detects any arcing in the line. And most motors produce an arc (sparks) when they run.

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  • Understood. We have AFCI breakers for all the bedrooms.
    – jr.
    Jan 31, 2019 at 20:15
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The fan motor is producing back EMF when turned on and off. This back EMF will cause a momentary current imbalance on the hot and neutral and the GFCI interprets this as a ground fault. To eliminate the nuisance tripping of the GFCI, simply install an RC surge suppressor in parallel with the fan motor leads and connect it physically by the fan motor. An Electrocube RG1986-8-5 will solve the issue. This is a two lead device containing a 0.5 uf 600 volt capacitor connected in series with a 220 ohm 1/2 watt resistor.

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