Buzzing circuit breaker box - electrical question

paul · Feb 12, 2015

Walked into my machine shed today and the electrical box was buzzing, or humming. What would cause that?

4-5 years old, professional wiring job, 200 amp service/ box, almost nothing turned on or plugged in. Nothing new on the whole place electrical wise.

Cold over night, below zero, but nothing we haven't had the past 2 years.

I'm familiar with a transformer doing this, but the Square D circuit box, not sure what to think? Kinda went away in 10 minutes, just don't want to ignore something I'm not familiar with.

Paul

glennster · Feb 12, 2015

could be a bad breaker , or carbon arcing where the breaker snaps into the box. or a loose connection.

dr sportster · Feb 12, 2015

Well I know the answer to "Why does the transformer hum" Answer:" because it doesn't know the words".

BradyW · Feb 12, 2015

(GFI) Ground Fault Interrupters sometimes make a buzzing sound ?? Reset it.

Bob Bancroft · Feb 12, 2015

This doesn't help, but reminds me- The all new 200 amp service was installed here in 1988, on the side of a new stir/drying grain bin. I did the work, supervised by an electrician. It had been inspected, and electric company had powered it up. I double checked everything(off), then flipped on the main. The thing growled at me! It was more than a hum. My hand was still on the breaker and I immediately shut it off. I stood there not knowing what to do. I rechecked everything, worked up my nerve, and tried it again. Nothing. Has worked fine ever since. There are now four sub feeds off that panel, besides the equipment in that bin itself.

Dave H (MI) · Feb 12, 2015

I generally poke at things with a screw driver...try to see if I can find out where the noise is coming from. Probably not the best idea in this case though...

RJKeith · Feb 12, 2015

The Buzzing is 60 cycle hum. Something, a screw, a wire, something has worked loose over time, and as the magnetic field changes polarity 60 (actually 120 times) per second what ever is loose is buzzing. Turn off the power and start tightening things, or if you do not feel comfortable around electricity, get an electrician to do it. But get it checked out. Just because you think electrical equipment doesn't move, and therefore doesn't need maintenance, doesn't mean its true.

Keith Molden · Feb 12, 2015

It could be one of the incomming wires loose in their breaker. Check all of them, it can cause a lot of heat to generate in the box. Kinda hard to determine from the information given. Just my thoughts, Keith

Bob · Feb 12, 2015

I've noticed breakers doing the same thing.

Sure wouldn't be a bad idea to have a "pro" check it out, but I'm gonna guess they won't find anything specific that needs attention.

If you have an infra-red temp gun, you could check to see if any of the breakers or connections are warmer than the others.

Also, if you have a mechanic's stethoscope with a non-metallic probe end, you could listen and identify which component is making the noise.

paul · Feb 12, 2015

I know, just not sure what info to say, this kinda surprised me at the moment. Was a very light buzz, very similar to the controller box transformer on my furnace, the furnace controller has hummed a couple times a year for couple decades, give it a tap and good for another 6 months, furnace guy never worried about that one. Just not sure what to think of a breaker box doing....

I understand on the loose screw deal. Lovely day to have to check things.....

Normal breakers in a Square D box, a few regular incandescent bulbs on 2 switches, an unused 220v outlet, and 5 120v GFIC outlets with a fencer, tiny water bowl, and a boot heater mat (both very very low watt) the only loads on the outlets.

I'll have to go check stuff, unplug/reset stuff, look for heat and be careful of course.

Paul

buickanddeere · Feb 12, 2015

One breaker off at a time may isolate the offender. Wear safety glasses and good thermal gloves when switching a potential dud breaker . Good practice with just about any breaker in particular if it's large or is high voltage .

FBH44 · Feb 12, 2015

I think many electricians sometimes fail to exactly tighten every last screw correctly. Happens. You might take a couple feet of garden hose, listen like a sthesoscope, isolate the offending loose item or loose screw, THEN TURN OFF ALL POWER, AND USE A MULTI-METER-TESTER TO VERIFY NO POWER, and tighten up.

glennster · Feb 12, 2015

if you have a non contact laser thermometer, that will pinpoint a bad connection right away.

Steve@Advance · Feb 12, 2015

I suspect the newer breakers are more than just thermal overloads as they were in the past.

The larger breakers have electronic circuitry in them, not sure what it does, some have adjustments to fine tune the amperage and delay times. Possibly there may be something inside one of the breakers that was humming. If all is working, nothing loose, I would leave it until the problem can be found. Call out an electrician, and it's not doing anything, he can't diagnose it either, but bet he can charge for a service call!

Side note: Couple of years ago I was installing a 200a Square D I line breaker. It was a used one from Ebay, but still cost about $200. When I went to stab it in the switch gear, as soon as it made contact something hissed and gave a puff of smoke!

That was an interesting half-second to make a decision... Do I drop the breaker and run away? Or wait a second more and see if this blows my hand off? Then I thought if it's gonna blow it would have done it faster than I could run anyway, so I just pried it on in... It never gave anymore problem, still working, still don't know what happened.

JML755 · Feb 12, 2015

I'd just go through the box and tighten all connections on breakers AND the neutral bus bar. If it happens again, I'd suspect a breaker. I've seen breakers that were flipped frequently (used as switches for the lights on that circuit :roll: )start to arc where they snap onto the panel bus. Would buzz and you could see an arc in the dark. As others have said, buzzing/arcing is not good. That's how fires start.

Guess it could be condensation as well. Was listening to the power lines hum yesterday.

oneshot · Feb 12, 2015

FBH is on the right track, once you determine the origin of the sound the problem is identified and well on the way to being repaired.

Make sure all the breakers are seated properly and check all the connections including the line side wires, with the power of course. Let us know what you find.

Dick2 · Feb 12, 2015

Had an empoyee of the electric company tell me this one once.

"Do you know why that transformer is humming?

It's because it doesn't know the words."

buickanddeere · Feb 12, 2015

(quoted from post at 17:33:36 02/12/15) I'd just go through the box and tighten all connections on breakers AND the neutral bus bar. If it happens again, I'd suspect a breaker. I've seen breakers that were flipped frequently (used as switches for the lights on that circuit :roll: )start to arc where they snap onto the panel bus. Would buzz and you could see an arc in the dark. As others have said, buzzing/arcing is not good. That's how fires start.

Guess it could be condensation as well. Was listening to the power lines hum yesterday.

As you alluded about using thermal overload/Instantaneous short circuit protection,GFI or Arc Fault breakers as a switch. The Jackleg electrician who is doing this needs a serious "tuning up" and the proper light switch installed.

john *.?-!.* cub owner · Feb 12, 2015

If your mtere is immediately outside the breaker panel check it. If you have areal drop, it may be the wind causing it to vibrate.

Steve@Advance · Feb 12, 2015

Another thought, don't know what size the service is, but it might have a "CT" meter. (Think the CT stands for control transformer) The current doesn't pass directly through the meter, but uses a transformer to drive the meter. Could be the transformer buzzing.

JDBRIDER · Feb 12, 2015

Do any of the breakers feel hot?

Frank 41 · Feb 12, 2015

Any magnetic starters close? Like said above, could be your meter.

David G · Feb 12, 2015

CT Current Transformer, usually used over 320 amps, converts down 0-5 amps for meter.

PT Potential transformer usually used over 480 volts, converts down 0-120 volts for meter.

Buzzing circuit breaker box - electrical question

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