AFCI breakers

Does anyone know if AFCI breakers normally make a buzzing noise or would this be a defective breaker?
I haven’t noticed this buzzing on other afci breakers but this homeowner insists that an electrician told him “that this was normal”.


Yeah, some are worse than others, but they all generally have an audible hum. I wouldn’t really characterize any that I’ve heard as a buzz, but if you’re in a quiet area, you can notice that most of them hum to some degree.

Not sure…I have 16 of them in my panel at my house and I dont hear them humming.

Turn up your Belltones?

Maybe the voices in your head are drowning out the hum?

Ok sparky pants, what causes the hum?

Humming noises are generally the result of vibrations.

sounds like maybe from a bad mechanical connection to the panel, unless we are talking internal dynamics.

Seriously, though, I suspect Paul has CH breakers in his panel, which are among the quietest of all the AFCI’s. Murray’s have been reported to be among the loudest. The breaker contains a small resonant circuit as part of the AFCI electronics. This could be the cause of the buzz. Local coincident magnetic fields acting upon internal components (Eddy Currents) give a similar (barely) audible hum.

OK ,guess physical connection is out of the equation.
If resonance is the problem might a different make have a different tune sorta speak.?

No, not completely, but that’s not really the first thing that pops in to my mind with regard to AFCI’s.

You got it. The connected load may also attenuate the sound to one extreme or the other as well. I’ve noticed that a few times.

Makes sense as the ac has its own resonance and another model might not vibrate at the same frequency as this one.
Common sense even us cavemen might understand.

Even the same model, but a different batch from a different day.

I have already put in a bunch of identical fluorescent lights, for instance, and had a couple with ballasts that hum notably more than the rest of the batch of lights.

I think the odd humming AFCI isn’t really someting to get too excited over. They all hum if you put your ear near them or if you’re in a quiet home. Naturally, if there’s little or no load on them, I don’t suspect you’d hear much of anything. This is probably most normally the case when you’re inspecting homes, I might guess.

Funny you bring up flourecent lights since when the ballast starts humming it was taught to me as an indication it was going on the fritz.

Not all the floursecent luminaires will buzz before they will fritzed up.

most electronic ballast useally are very quiet they run in very high frequecty range not like convental maganatic ballast they buzz at 60 HZ.

some cheap ballast will buzz like sonavagunner but more common with slimline with mag. ballast and HO’s high output] mag ballast do it.

with the electronic verison it kinda very quiet you dont heard them running at all.

Merci, Marc

The first time I installed AFCI’s I was with an electrician in his 50’s. I heard buzzing, he didn’t. Over time, I’ve seen a pattern, many people loose their hearing in ‘areas’, not total.

So if an AFCI buzzes and the electrician doesn’t hear it, does it really matter? :wink:


Thanks for the info Marc as my experiance was from the old days.
(no electronic)
I had been working high rises and learned that when they start humming they always went out several days later.
Sure enough I would find my self upon a ladder bringing in the ballast.