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This has been going on for awhile, but it is intermittent - about every 3 - 8 times the fluorescent light in a closet off the bathroom are turned off, one of the two GFCI outlets in the bathroom will trip. 95% of the time, it is one particular of the two GFCI outlets in the bathroom. The fluorescent light will still turn on with the GFCI tripped. This will also happen - about every 3 - 4 times - with fluorescent lights in my garage. The lights there will also still work with the GFCI tripped.

The bathroom GFCIs seem easily tripped by what I am 99% certain are non-faulty appliances (hair trimmers, electric tooth brush, etc...)

Ideas? Thx!

  • Do these lights use magnetic or electronic ballasts? Are they on the same circuit as the GFCIs in question? – ThreePhaseEel Aug 5 '17 at 23:43
  • How many GFCIs are on that circuit? How are they wired? – Harper Aug 6 '17 at 1:32
  • Hi, There are 2 GFCI's on the circuit - do not know how they are wired. When I open the breaker in the garage for the master bedroom (a 20 amp breaker), all the bathroom lights go out, the fluorescents in the master closet go out (the ones that trip the GFCIs), and the GFCI green lights go out. So, the fluoresecents and the GFCIs appear to be on the same circuit. – Ken Aug 6 '17 at 2:41
  • I am not certain of the ballasts - the fixtures are roughly 11 years old and appear pretty cheap. – Ken Aug 6 '17 at 2:41
  • Can you get us photos of the culprit ballasts? – ThreePhaseEel Aug 6 '17 at 5:44
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Anytime a thing on circuit 1 trips a thing on circuit 2, you have a crossed neutral. That's bad wiring. On ground wires, it is ok to just twist all the grounds together (if they're all from the same panel) even if they are different circuits. Some people think they can do the same with neutrals. That was always bad... and with GFCIs, it does not work.

Another sign of sloppy work is two GFCI receptacles on the same circuit. Occasionally a wiring topology makes this semi-necessary, but usually it means the installer does not understand how to install GFCI's.

What's happening with the crossed neutrals is that current to an appliance, now returning to source, has a choice of two directions: directly on circuit A's neutral, or through a GFCI device on circuit B's. Actually, it follows all routes at once, in proportion to their conductivity (1/resistance). That conductivity is influenced by loop effects and eddy current heating, because those occur at the cost of conductivity: in short, it prefers to go back the way it came. That still means some current is going the wrong way, and that will still tend to trip a GFCI.

So you need to untangle those neutrals.

  • Hi, Thanks for the response... Since this started some years after the home was built, where/how would the neutrals have become crossed? Most likely place - at the receptacle itself? They have never been messed with so far. Thanks: Ken – Ken Sep 16 '17 at 16:59
  • Sigmund Freud was once asked whether everything is a sexual metaphor. He replied "sometimes, a cigar is just a cigar." Ground fault trips are like that too... Sometimes they actually are a ground fault. What I wonder if maybe the ground for the faulting device is crossed onto the neutral of the circuit that is tripping. Such a cross could be in any junction box or behind any outlet. – Harper Sep 16 '17 at 20:34
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On the first part of your question the fluorescent. Turning off the light is probably causing some sort of inequality between the neutral and the ground and that is being sensed by the GFCI. Perhaps in a situation where you have a shared neutral somewhere. The bad news is that it whatever is causing this problem could be many different reasons. A bad ballast, a broken neutral, neutral and ground tied together, or neutrals from different circuits tied together.

This might have something in common with your second problem with your bathroom GFCI or you just might have faulty equipment.

Though it is rare GFCI's do go bad meaning it could be a bad GFCI. Just remember GFCI's are there to protect you from electrical shock and they are very sensitive. So if it senses that there might be any reason for shock it will trip even if it is a nuisance trip.

You might be thinking this doesn't answer your question but it does. I am thinking you have a wiring problem brought about by a poor installation technique. This could take a service electrician some time to track down. so it wouldn't hurt to try and disconnecting the fluorescent and see if that stops the tripping. Try replacing the ballast and try replacing the GFCI. Then if it still occurs you need to have someone come in and begin tracing out the circuits.

  • Thanks - because I have a similar issue with the garage GFCI and fluorescents out there, I am "hoping" it involves the fluorescents only... Although the bathroom GFCI does occasionally trip when something is plugged into it - sometimes just an extension cord with nothing else on it. So, perhaps I'll change out the closet fluorescents for LEDs (something we were considering anyway) and see if that makes a difference. – Ken Aug 6 '17 at 14:28
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    @Ken rather than blindly stab at the dark like this, it would be better to examine how the GFCIs are wired. Just the very fact that there are two GFCIs in the same circuit guarantees there is at least one wiring blunder. How many more are there? – Harper Aug 6 '17 at 17:38
  • Actually. I do NOT believe the two GFCIs ARE on the same circuit - they are on the same BREAKER... However, when I test one GFCI to trip it, the other one does not shut down. Neither does the second one shut off when the first trips dues to the fluorescent lights being turned off. – Ken Aug 6 '17 at 19:39
  • As Harper suggests more than 1 GFCI on a circuit breaker can be the problem even if they are in separate rooms. – Ed Beal Sep 12 '17 at 22:59
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The florescence lights are not on same circuit as the GFI Outlets. When a GFI trips it kills the entire circuit - nothing connected to that circuit works. Something else is tripping the GFI.

Next time it trips, try to figure out what is on that circuit. Probably only outlets. If only outlets, is anything plugged into those outlets?

I had a GFI circuit outside than tripped whenever it rained.

A GFI outlet works my monitoring the voltage entering and leaving the outlet. When the variation between those two measurments exceeds a certain threshold, it trips.

  • -1 because you have wrongly stated what a GFCI measures. – Michael Karas Aug 6 '17 at 7:40
  • I cannot find anything other than outlets that go dead when a GFCI trips. Nothing is plugged into any of those outlets. – Ken Aug 6 '17 at 14:31
  • @MichaelKaras not Webster perfect, but outside of 10k+ rep luminaries like ThreePhaseEel, the best description I've seen here. – Harper Sep 12 '17 at 21:55

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