What off-the-shelf plug-in devices are available to prevent inductive kickback from reaching the mains circuit?


I have a plug-in Air Conditioner unit (rated 10.8A) on a 20A panel-protected AFCI that works fine, but when the compressor (not the blower) turns off, it trips a 20A GFCI panel breaker on a separate circuit. To repeat, the A/C unit is not on the GFCI circuit, it is on a separate AFCI circuit.

I suspect that inductive kickback into the mains from the compressor turning off is creating enough of a voltage spike on the mains to exceed the breakdown voltage of the NM cable insulation and be detected as a ground fault on the separate GFCI circuit. I believe if I can prevent any inductive kickback from reaching the mains, I think I can prevent this nuisance trip.

Typically, inductive kickback is prevented by putting an RC snubber network in parallel with the switch , but I really need something I can plug in between the A/C unit and the mains to do this. Would a simple surge suppressor do the job , or do I need something more specialized.

  • I never knew electric panels can essentially suffer from water-hammer. Learn something new every day on this site!
    – MonkeyZeus
    Commented Jul 2, 2021 at 17:54
  • I have had limited success with surge suppressors in the main panel. Part of the issue is because of kickback. Making sure to get a model with low enough voltage threshold but high enough wattage that it won’t be wiped out in a short time. I have connected a small whole house unit at the disconnect that was one fix that did work but the next time I tried that is only improved or reduced the tripping not eliminated.
    – Ed Beal
    Commented Jul 2, 2021 at 18:38
  • See discussion here. Commented Jul 2, 2021 at 21:42

2 Answers 2


Try a newer breaker, some of the older ones displayed that problem. Also be sure it is not an AFCI. The problem could be caused by too high an impedance on the supply lines (wire to small for the starting inrush).


If you want something to plug in, a filter will probably work better than a suppressor.

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