Thread: Intermittent GFCI Tripping

I was called upon to inspect a GFCI in a bathroom that intermittently trips. It is in a 3-gang plastic box that contains the GFCI, a dimmer switch to a light, and a switch to the ceiling fan. The only time that the GFCI trips is when the ceiling fan is turned off (not turned on, but off.) There is one 20 amp feed coming into the box. The GFCI and both the switches are pigtailed off of the feed. The GFCI is definitely fed to the Line side. I replaced both switches but not the GFCI (didn't have one with me), but that did not solve the problem. I am at the point in the process of elimination where I will have to pull the fan unit, but I would prefer not to if someone has a better idea.

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I'd change the GFI out just so you can eliminate it but it's pretty unlikely that it's the problem (assuming it's relatively modern). I'd also check the box(s) where the lights/fans that the switches contol for neutrals touching grounds or other problems. Also, maybe try taking the dimmer off the circuit (temporarily anyway) just to see if it's causing a problem. The part about it only tripping when the fan is turned off is strange.

I spent the better part of my Saturday trying to chase down a short/fault when updating my kitchen counter top outlets with a GFI. I isolated the problem to a run of wire that fed two j-boxes (abandoned floor outlets) and one other outlet but couldn't see anything wrong. I ended up just pulling a new cable (3 holes in the wall later) and all is well. My point is that GFIs can be quite picky.

Terry

Are there any other connections to the gfci other than the incoming power hot and neutral to its line terminals??

Saying intermittent means that it does not happen every time you turn of the fan switch. If there are no connections of neutral or hot wires for the fan and light to the gfci then that leaves you with a bad gfci....maybe. Is this a leviton gfci? Try tapping the gfci or trim cover with the back of your screwdriver and see if the slight impact causes it to trip.

If U change out the fart-fan, the problem will most likely go away.
We're all assuming that the fan & light are not on the load side of the gfci.
Very seldom have I encountered a gfci so irritable, that small shade-pole motors (such as the fan) make them trip with a line-side connection.
Anythings possible however.
Bob Smit, County EI

Well, it turned out to be the GFCI although I really don't understand why since the fan was not on the load side. Regardless, it's fixed.

If I understood and am remembering correctly you described a three-gang PLASTIC box containing a switch, a dimmer switch, and a combination GFCI/duplex receptacle.

You don't know why you had a touchy GFCI receptacle.

I'd say you likely have a heat problem - thus premature aging, etc.

Your plastic 3-gang box can't put off the heat unlike a metal box, to fit at least one if not both fins off the dimmer, and your combo GFCI/duplex receptacle is large.

This is why often a larger box is used with a reducing trim ring. Unknown depth of box but between leads, pigtails, wire nuts, a likely mushy snap switch for the FAN, and derating for the dimmer stuffed into a three-gang plastic box (likely non-metalic face plate, but is it?) in a bathroom - it all adds up. Throw on some extra heat running say a 1500-1800 hair drier just after a shower (add more heat, humidity and condensation to the environment of the "plastic box" and the GFCI receptacle trips when the likely mushy switch for the fan is cut off.

Specifics weren't offered. You might just be treating the symptoms and not the real problem is the point.

Gotta say that I didn't consider ambient temperature. Thing is that I have basically the same set-up in two other bathrooms at that house and no problems.

Originally Posted by Terry Fitzgerald

Gotta say that I didn't consider ambient temperature. Thing is that I have basically the same set-up in two other bathrooms at that house and no problems.

Derating for the heat generated by the dimmer, you've removed fins both sides to cram it in to your three-gang with two other devices - therefore its rating must be reduced otherwise it will produce excessive heat which with no way effectively to "put off" the heat contained in the plastic box, will overheat the other devices in the box and the wiring, thus exceeding the temperature insulation limits along the way, and the GFCI.

Originally Posted by Terry Fitzgerald

I was called upon to inspect a GFCI in a bathroom that intermittently trips. It is in a 3-gang plastic box that contains the GFCI, a dimmer switch to a light, and a switch to the ceiling fan. The only time that the GFCI trips is when the ceiling fan is turned off (not turned on, but off.) There is one 20 amp feed coming into the box. The GFCI and both the switches are pigtailed off of the feed. The GFCI is definitely fed to the Line side. I replaced both switches but not the GFCI (didn't have one with me), but that did not solve the problem. I am at the point in the process of elimination where I will have to pull the fan unit, but I would prefer not to if someone has a better idea.

Hmmm. DIYer, Handyman, HI, or what? What's your story? and why are you performing electrical work in the residences of others?