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A friend of mine had a receptacle on an outdoor circuit clearly arcing whenever he put a load (pressure washer) on a downstream receptacle of that circuit, to the point that you could visually see a flash every time he turned on the pressure washer.

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I think that GFCI receptacle was probably wired badly to cause the arc, and should be easy to replace and wire correctly. But my bigger question is why didn't the AFCI breaker trip here?

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A local electrician said something along the lines of "AFCI breaker doesn't work here because the arc is on a neutral", but this doesn't make any sense to me since, IIUC, an AFCI breaker is supposed to monitor the circuit between both hot and neutral and look for weird waves.

Is there something I don't understand about AFCIs, or is this a simple case of a bad breaker that need to be replaced?

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  • Maybe an AFCI breaker can't see arcing on the load side of a GFCI outlet? I don't know this, just a guess.
    – jay613
    Jun 17, 2023 at 21:16
  • I would be concerned about that breaker. From I have read they listen for sparks on the circuit with a lot of electronics inside. If possible I would have that breaker tested and at least a few of the others tested also. Might gotten a bad batch. Your insurance should be interested in checking the breaker for you.
    – crip659
    Jun 17, 2023 at 21:16
  • FWIW -- Asking ChatGPT (via Bing) "Can an AFCI breaker see arcing on the load side of a GFCI outlet" produces a good example of ChatGPT making sh*t up, with an enthusiastic "Yes" based on absolutely nothing.
    – jay613
    Jun 17, 2023 at 21:23
  • @jay613 What on earth are you on about? A GFCI is just a normally-closed switch that opens when a ground fault occurs. There is absolutely no reason why an upstream AFCI shouldn't be able to detect arcs on the load side. A GFCI is not an isolation transformer.
    – nobody
    Jun 18, 2023 at 1:33
  • And while ChatGPT is indeed a steaming pile of junk in general, it appears to have come up with the correct answer in this case. You shouldn't be trying to bash it if you don't understand the subject material. Leave that to people who do understand.
    – nobody
    Jun 18, 2023 at 1:47

1 Answer 1

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But my bigger question is why didn't the AFCI breaker trip here?

A white-buttoned Square D combination AFCI breaker should detect neutral series arcs. A CAFCI detects five things:

  • Series arcing on the hot wire (in series with a load)
  • Series arcing on the neutral wire
  • Parallel (short) arcing hot-neutral
  • Parallel arcing hot-ground (this is also a ground fault)
  • Parallel arcing neutral-ground (ditto)

The "also a ground fault" is why the breaker includes weak GFCI protection called GFPE.

It may be a faulty breaker.

I think that GFCI receptacle was probably wired badly to cause the arc, and should be easy to replace and wire correctly.

In NEC 2014 a requirement was added to torque to spec all connections which state a torque. This is why. And yeah, we owe aluminum wire an apology, because nobody was doing that on small branch circuits back in 1973. (aluminum has always been reliable on large feeders, but then, electricians have always torqued those).

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    OP is wondering why the AFCI breaker did "not" trip. I imagine non of the others did not trip either.
    – crip659
    Jun 17, 2023 at 21:40
  • @crop659 good catch, don't know why I went there! Jun 17, 2023 at 21:45
  • I think you're tripping over crop659 instead of @crip659 .. :-)
    – JACK
    Jun 17, 2023 at 23:25

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