When I tested a murray 20amp AFCI breaker it started to humm…
To me this is no good just wondering if anyone has encountered it?
When the breaker is in the on position it is quiet. When turned off or tested with button it humms?

Its a Murray 20amp AFCI breaker AB5666

Humming may or may not be significant. Really hard to say, for sure. Most humming sounds from breakers are just annoying, and not particularly significant, but some are symptomatic of a bigger problem. There’s no way to tell the two apart by the hum alone, without further investigation. I would add that in my personal opinion, Murray is a trash brand, so I’d suspect poor design rather than a real problem. Just hard to say without more effort put into it, however. You might also consider the possibility that the breaker was just bored by being tripped off, so it decided to hum.

Hmmmmm, hmmmm so I see. :mrgreen:

It just doesn’t know the words.

Did it actually disconnect the load when you tested it, or did the load remain energized during the ‘humming’? Maybe it is a built-in signal:mrgreen:

the load was disconnected when terminated & thats when it hummmmsssss, when activated its nice and quiet. strange.
thanks for the input.