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I have been dealing with a phantom AFCI breaker trigger for the better part of a year. The circuit controls bathroom fans and lights for part of my home. For the last year, at some random interval, the AFCI breaker would trigger. I had no idea what was going on, and had tried various things to fix it.

I did try swapping the breaker to a new Siemens AFCI 15-amp breaker. The problem remained.

Today, I spent some time on a different issue. I defrosted an area of my fridge, which required me to turn it off for about 2-3 hours. Once I turned it back on, guess what, the AFCI in a separate circuit triggered!

My guess is that whenever the fridge draws more power, somehow it triggers the AFCI on my bathroom light circuit. This would explain why it was so random throughout the year, since most of the time it wouldn't need to draw that much power. Maybe it was associated with grocery shopping or something...

In anycase, the refrigerator is on its own circuit with a non-afci breaker. The bathroom lights are on a circuit with a 15-amp afci breaker. I did some light reading, and saw that it is possible for an afci breaker to trigger from another circuit. This one is very consistent now - as in I can replicate the issue.

Now, once the fridge reaches the desired temperature, I believe the problem will go back to it's sporatic nature. My question is, are there some simple things I can do to fix this?

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  • What make and model is the fridge in question? Nov 5, 2023 at 5:24
  • It’s a thermador freedom thermador.com/us/products-list/T36BB920SS
    – Coffee123
    Nov 5, 2023 at 8:39
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    What do the diagnostic LEDs indicate the trip reason to be? See the link below the image in my answer or your instructions to learn how to interpret them.
    – Ecnerwal
    Nov 6, 2023 at 2:58
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    @Coffee123 yeah, my thought is to see if the fridge can trip an AFCI that's directly powering it Nov 6, 2023 at 3:44
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    So a ground fault, with or without arc. I'd continute to be on high alert for improper neutral connections, either between circuits or to ground.
    – Ecnerwal
    Nov 6, 2023 at 18:50

1 Answer 1

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The QFGA2 is a combination GFCI & AFCI device.

You comment that "the neutrals go directly into the neutral bar."

That's a problem. The QFGA2 neutral pigtail (B) should go to the neutral bar, the circuit neutral (D) should go directly into the proper port (H) on the QFGA2.

Breaker instructions illustration.

Image Source https://assets.new.siemens.com/siemens/assets/api/uuid:99290277-3237-45e3-a03b-0496fc5586fe/sie-is-dualfunctionafci-gfci.pdf

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  • Thanks for looking this up! I should clarify the coiled neutral cable is what I meant when I said the neutral goes into the neutral bar (as in the picture). I will double check that the load neutral (D) and the load power (E) are not flipped.
    – Coffee123
    Nov 6, 2023 at 17:35

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