ECN Forum Forums General Topics of the Trade General Discussion Area humming panel

went out on a service call today and swapped out a couple of bad breakers.in the process i heard a humming sound coming from inside the panel. any suggestions on what may be causing the humming sound...

OK, I've had a REAL bad day.
1) Something is loose, usually a breaker, could even be inside a breaker. Take the insulated end of your screwdriver and GENTLY put pressure on each breaker, when the humming stops, you found it. Could also be the buss bar, however.

Like I said, I had a real bad day. Went to work at 5 am, it's about 10:40pm, and I just got home, and we did not accomplish what we wanted to........so I gotta be the first.

2) IT DON'T KNOW THE WORDS.

what do u mean it dont know the words

Smokey,
Think about it a few minutes....it'll come to 'ya.

GJ

Even brandy new installs seem to buzz with a motor load starting.
I imagine this is 60Hz vibrating the innards of breakers, as all else is new/tight?

If nothin's hot, and it doesn't change by pressing on the breakers, I would say it's the nature of the panel, sometimes what it's mounted to makes it sound louder than it is, like the big board in the back of a piano. However if it's a buzz, or a fuzz sound rather than a hum
The other thing is, what was on? The water heater, dryer, a/c, some other heavy load?
Things like this keep a person up at night.
trainwire

Smokey:
Just a random thought...could it possibly be a mechanical noise from another piece of equipment or machinery being coupled to the panel through a conduit? I have also seen (aka heard) circuit breakers buzz when loaded pretty close to their ampacity.

George; sometimes I don't know the words either...HMMM, HMMM, HMMM...

Mike (mamills)

Is the doorbell transformer in one of the knockouts on the side of the panel? A really cheap one will have core laminations that flap in the wind.

This is a real shot in the dark...and hopefully is not going to cause you more work for naught.

Maybe the cause of the humming is power harmonics?

There's a PDF file at http://www.fluke.com/ElectricalPower/elec.asp (go to Application Notes, which is on the left menu, third up from the bottom).

The PDF is entitled "In Tune With Power Harmonics" and on page 4 mentions humming panels.