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I moved into a house last year that has some 2-wire receptacles, and some 3-wire receptacles. I have been adding GFCIs and AFCIs where required. I recently removed the conductors and old receptacles from a circuit and replaced them with a 12 gauge two wire with ground. The first receptacle from the breaker panel is a GFCI/AFCI. I have one receptacle wired from the load side of the GFCI/AFCI receptacle, and then one wired from the 2nd receptacle. I have been noticing that the GFCI/AFCI will be tripped when I check on it. The GFCI trip light is on when it trips. I'll reset it, go to bed, and it'll be tripped the next day. There are no loads connected to this circuit.

The other day I turned on the lights in the basement (florescent) and as soon as they turned on, the GFCI trips. It only happened once and I haven't been able to repeat it.

To troubleshoot, I have tried the following:

  • Replaced GFCI/AFCI

  • Replaced all of the wire

  • Disconnected the wire on the load side of the receptacle

So, here's the summary of problem:

  • Changing receptacles 2-wire to 3-wire

  • Wiring and receptacles on this circuit are new

  • Using existing circuit breaker

  • GFCI trips on GFCI/AFCI receptacle with no loads on it

  • I have replaced the GFCI/AFCI and still have the same problem

  • Wiring and work was checked

Any ideas what could be the problem?

Pictures:

Circuit Wiring

Panel Connections

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  • You could change the GFCI/AFCI to only GFCI and see if it trips. You could change them one by one or all at once. I will say that if you somehow connect the neutral and the ground of a GFCI protected receptacle, then it will trip. This must be due to a slight potential difference between neural and ground sufficient to cause a current of a few milliamps. I have not done this on circuits with all loads definitely disconnected.
    – Jim Stewart
    Apr 19, 2018 at 20:14
  • I have observed an unloaded GFCI/AFCI breaker trip due to a Neutral/Ground short...
    – brhans
    Apr 19, 2018 at 20:17
  • I think I will try switching it to GFCI only just to see what happens. Another thing to add is that the wire from the breaker panel to the AFCI/GFCI is only 10 feet long, and it's completely visible with no breaks or splices.
    – EEKeefe
    Apr 19, 2018 at 20:17
  • I checked the wiring on the receptacle and I know there's no short from neutral or line to ground. I taped the exposed screws on the receptacle with electrical tape to insulate it.
    – EEKeefe
    Apr 19, 2018 at 20:18
  • 1
    This may be a total red-herring and I just wonder, are the neutrals and grounds bonded in the panel? Is there a bond in the panel from a ground bar to a neutral bar or is there only one bar in the panel and both neutrals and grounds are connected there?
    – Jim Stewart
    Apr 19, 2018 at 21:09

1 Answer 1

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AFCIs and GFCIs operate on totally different principles.

You may recall the wiring rule that all wires must be grouped together. This is so magnetic fields cancel each other out, since currents are equal. Likewise if 2 wires together are wound around a relay, and currents are equal in the two wires, then they would cancel each other out and the relay would not pick up. This is essentially what a GFCI is.

Submarines detect enemy submarines using passive sonar - they listen to sea noises and use signal processing on powerful computers to pick out artificial noises. If you've ever hooked up old fashioned speakers with speaker wire, you may have heard the crunchy sound of a loose speaker wire. If you washed out the normal 60 cycle hum, that is what arcing sounds like. An AFCI has a digital signal processor listening for that sound.

If a GFCI trips with no loads attached

Then the GFCI is defective. That shouldn't be happening/possible.

If an AFCI trips with no loads attached

Then the AFCI is hearing the sound of arcing. Because of the way wires are all interconnected at the panel, it's possible the AFCI hears arcing that is occurring on a completely different circuit. Sometimes it hears arcing that is intentional or not really arcing - I could see it being caused by an old-style fluorescent light that uses a starter, since its action is intentional arcing. For that matter a fluorescent light starts by striking its arc, but a modern electronic or even old magnetic ballast will buffer that "sound".

Silencing a warning device isn't really solving a problem, so I would focus on the root cause of the arc fault, if any.

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  • Thank you for your detailed response. As someone who has evaluated, tested, and listed GFCI's in a previous job, I understand their operation. I replaced the AFCI/GFCI already and still have the problem. It baffles me that this is happening because as you said, it shouldn't be happening. Like I said in the original post, the GFCI part is tripping, not the AFCI. There are indicator lights on the receptacle that state what the fault is. The AFCI/GFCI I replaced it with is the same model, so I'm going to buy a different model to see if that helps.
    – EEKeefe
    Apr 20, 2018 at 11:56
  • Well you're the expert... why are you asking us? Seriously though, what you say simply does not add up. With nothing on the LOAD terminals, a GFCI can't trip unless it's defective. You know the adage, when the impossible is eliminated, what remains, however improbable, must be the truth. Now you know why I don't like combo AFCI-GFCI.
    – Harper - Reinstate Monica
    Apr 20, 2018 at 16:27
  • I replaced the receptacle with one from a different manufacturer and it worked. Not sure why the other one had so many problems, but the new one works. Thank you to everyone that helped!
    – EEKeefe
    Apr 23, 2018 at 12:11

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