residential panel humming, buzzing

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For how long does it last?

Does it happen in random or when a load turns ON?
 
magnetic/thermal or just thermal breakers?

High current loads on a wire against cabinet with just the right loop for 'springiness" and the mag field from the wire to cabinet can cause movement and 'buzz'. It will also eventually wear thru the wire insulation and arc.

Best you take the panel off and inspect - look for shiny paint spot of cabinet or worn thru paint.. flat spot on adjacent wire.
 
Stevenfyeager said:
I think it happens when a load turns on.
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Then it might be loose connection within the breaker or the breaker is loose on the buss. Check ALL of the connections in the panel. It could be loose conduit fitting as well. Also what "junkhood" suggested earlier.
 
60 cycle magnetic effects on components within specific breaker(s). Starting of motor loads is likely the worst offending conditions.

These effects have been there all along, as the thing ages some pieces may have become looser fitting as they have worn off material that secures them in place and now they have more range of possible movement, which makes the noise they make when they do move even louder.
 
something rattles at whatever freq you hear, and the amplitude of such rattle must be big enough to create the sound wave, but sometimes it could be in resonance, hence a small amplitude source suddenly becomes louder.
 
The steel body of a panel can act as a magnetic sounding board when heavy starting loads come on line.

From experience, I was in one of our switchrooms when two of the 150HP exhaust fans started DOL. The main incoming panel was making horrendous noises due to the magnetic effect of the load, you could hear the change in frequency as the motors accelerated.
 
For DOL starting I can see the hum amplitude changing as motor ramped up, but am at a loss to explain why the frequency would change unless it were from direct motor vibration instead of magnetic effects.
 
If the hum is at the meter panel, it's not unusual for the older electro-mechanical meters to buzz. Don't ever say I said this, but if you give the meter a pretty stout smack on the side, it'll sometimes fix the problem. I had an elderly lady at an assisted living center who used to call us every other week to say her meter was humming and it was "melting her brain". I went out several times and found nothing. Finally, one of our meter readers was there when she came out complaining again. The employee went inside to see where she was hearing the hum, and it turned out, when she turned off the lady's TV, the sound disappeared. Has nothing to do with this thread, but a story that kind of makes you smile....which is a good thing!:)
 
Have you tried turning off all breakers and turning them (and associated load) one at a time. I would begin at the larger loads A/c, WH, Ranges/cooktops, etc. and work down to the smaller branch circuits. Try to isolate the noise to a specific breaker. If you find a specific breaker, you could try replacing them (or swap with another similar breaker temporarily to test) and see if that solves your problem.

Please let us know if you get a solution.

Thank you.
 
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