I have a newly constructed ADU and the AFCI breaker for the plug my AV system is in keeps tripping. We've replaced the breaker twice with no change and checked all the internal wiring. I had a Denon AVR plugged into the wall which sometimes makes a popping sound when it turns on. I removed the unit and now the AFCI never trips. So I see two possible issues: (1) the Denon AVR itself is arcing or (2) one or more speaker wires was loose and arcing. Is #2 even possible -- would a loose speaker wire cause an AFCI breaker to trip? I can't find an answer anywhere online.

  • I don't see how speaker wires could cause that. They're not connected to the AC mains electrical system, and the amplifier better be isolating them fully! – Harper - Reinstate Monica Feb 4 at 20:08
  • I agree with Harper here; any properly functioning amplifier will fully isolate the speaker outputs from the power inputs, so speaker wire arcing (which should be hard tbh; the voltage isn't that high) should not be able to trip an AFCI in general. – Nate S. Feb 4 at 20:29
  • @harper an arc on a power supply even low voltage is still a non Linear load it will be reflected through the transformer in high end gear and with switching gear is more directly connected, a pop from things in the unit charging up it looks like a short so the AFCI thinks this is an arc. I have seen it repeated on some equipment after ~3 minutes of being turned off. – Ed Beal Feb 4 at 20:30
  • Does the AFCI trip happen immediately when you plug the AVR in, or does it happen some time later? And if it's later, is it when you're using it, or when it's just sitting there? And finally, does this plug into a two prong or three prong outlet? – Nate S. Feb 4 at 20:30
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    @EdBeal, yeah, that makes sense -- dimmers definitely do put out tons of nasty harmonics. In fact, a lot of times if you plug a cheap audio amplifier into the same circuit as a dimmer, you can hear those harmonics in the audio output. That situation comes up a lot at concerts, which was my former career before becoming an EE. I think our only point of disagreement is whether an audio amplifier can cause significant harmonic distortion on the power input like dimmers do. – Nate S. Feb 4 at 23:19

A properly functioning audio/video amplifier should not cause AFCI trips

AFCIs work by monitoring the waveform of the AC power signal and looking for a particular type of distortion that is indicative of an electrical arc, and cutting power if that is seen. This doesn't play well with every device -- some devices, such as brushed motors, have small electric arcs inside as part of their normal usage, and others such as dimmers, consume power in such a weird and inconsistent way that they can fool the detector.

However, none of these concerns apply to typical audio/video systems like you have. In fact, audio amplifiers have quite a lot of filtering in the power supply section, to make sure that noisy incoming power won't be heard in the speaker output. This same filtering means that the way audio amplifiers draw power is also very clean, and won't make any unusual noise on the AC line. The video section of the unit is all digital electronics, and isn't any more likely to trip an AFCI than a regular computer.

Most likely, something is wrong with your AVR unit

The fact that the trip sometimes happens right away, and sometimes happens after a while makes me think it's likely your AVR does indeed have an intermittent fault internally. My guess would be an insulation breakdown in the transformer somewhere. Since devices this complex sometimes have several transformer windings for independent power supply rails, such a fault might not even cause the amplifier to stop functioning completely, but it is a real problem that the AFCI might detect.

Double check your grounding

This is a little more esoteric and less likely to be your problem, but for completeness I'll include it as well. While most electrical equipment uses the ground wire only for safety purposes, audio equipment frequently also uses it for shielding of audio signals. Often, the shells of all the HDMI and RCA plugs on the back are connected directly to the earth ground coming from the wall plug. This then gives lots of opportunities for unusual signals to couple to the ground wire.

How does this affect AFCI? If everything is wired correctly, it doesn't at all -- the AFCI doesn't look at the ground wire. But if your outlet was wired with a bootleg ground, i.e. where the ground terminal is also connected to the neutral wire, then the AFCI will be able to see that ground noise, and it could interpret it as an arc.

  • Thank you! The ground is definitely properly wired so I'll start looking for a new AVR. – Michael Feb 4 at 23:58

The popping noise you hear on start up was probably the surge charging the electronics up and that confused the AFCI. AFCI’s monitor the load and a non Linear current draw the pop on startup could be the issue. I have seen this in audio gear plugged into different circuits the first piece of equipment cross connected to the mixer tripped the circuit, leave things plugged in and reset the breaker and everything is fine I told them an arc is an arc they wanted the protection in there studio and because of the nuance tripping with that and some of the sound effects generators causing trips they had me go to GFCI receptacles at each outlet and no AFCI and that solved there problems and they felt safe.

  • Is that going to be all AVRs or is this older one just a problem then? Denon AVR-1913. – Michael Feb 4 at 21:07
  • Michael with the popping noise when turned on it could be completely disconnected from power thus when turned on it could be the issue. The intermittent issue after start up could be that with the multiple loads having different types of power supplies could cause the problem when something like a heavy audio or white screen there can be different reasons, I might try plugging it in with an extension cord to a different circuit to see if it’s the total load and this is pushing it over the limit, if the extension cord works then swap the AVR and something else to prove, avr or total load issue. – Ed Beal Feb 4 at 21:25
  • Ed, thanks. I'm pretty sure there is no total load issue because there is almost nothing on the Circuit: LED TV, a BluRay player, a Nintendo Wii, an ethernet switch, and a Eero access point (plus the AVR which is now not in use). The electrician measured the load at the AFCI (not an engineer so I may have that terminology wrong) and said we are way under the limit. He also thought it was the Denon AVR. The Circuit is just for the plugs in that room (no lights or dimmers) and none of the other plugs have anything in them. – Michael Feb 4 at 21:55
  • Sounds like maybe I just need a new AVR unit. – Michael Feb 4 at 21:55
  • Michael maybe you do but do the extension cord test 6 different power supplies who knows. – Ed Beal Feb 4 at 23:05

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