Circuit Panel Buzzes when starting DC

[Dennis Lopeman]

I saw someone asking electric questions, which made me think of my issue.

The circuit panel for the house is in my shop. Convenient for if/when I trip it!

But, on to the subject. When I start my DC, I hear the circuit panel do this load BUZZZZ sound while it gets up to speed. Maybe lasts a second or 3.

What is the problem? I haven't started any fires, yet...

[Matt Meiser]

My parents had something like this when their window AC was running. Theirs was a bad breaker and replacing it resolved the problem.

[Dennis Lopeman]

Hmmmm. But it doesn't buzz when starting everything else in the shop (RAS, TS, Jointer, MiterSaw, Compressor, ShopSmith...)

Could be pulling too much power? I don't know the right terminology here! Too many amps - maybe the wire gauge - may the 15amp breaker???

I suppose I could try changing the break... should be easy, right?

[Ken Gardiner]

The start-up current of the DC is very close to the trip current limit of the circuit breaker. When this is the case the breaker is on the verge of tripping and that causes a humming sound. Once the DC is up and running it requires less current so the humming stops. Not a dangerous situation but not a good one either and you really should have a higher current rated breaker; assuming the wiring is of sufficient gauge to support more amperage.

[Rod Sheridan]

Occasionally, the clearances in the magnetic trip actuator of cheap breakers are excessive, and the breaker makes a buzzing noise at high current values.

You can change the breaker if you want, with the same size if the noise is bothering you.

Regards, Rod.

[Dennis Lopeman]

huh - magneto trip actuator McGismo thingie???

LOL - I'm outa my league here!

The noise isn't bothering me, per se... asside from the thought that I might be causing damage somewhere. I was actually thinking that the circuit was ABOUT to pop... but never does. As a habit, I start my DC first, then the tool. they are on the same circuit.

I'll need to check the gauge. I printed out a chart, but just haven't taken the op to check it.

[Rod Sheridan]

Dennis, how many amperes is the breaker, and what are the ampere ratings on the tools and dust collector?

Regards, Rod.

[Mark Bosse]

Turn off the power to the subpanel. That means going to the main panel and shutting off the double breaker labeled for the subpanel feeding your shop.

Locate the white wire from the buzzing circuit.

Tighten the screw on the bar that connects the white wire to the panel box. It is normally in a bar sort of device called a neutral bus. It should be set up above the back of the panel on little black plastic thingoids. Those thingoids are called isolators. Look for a white wire screwed into a metal bar thing sitting above the back of the panel box. Obvioulsy it is the white wire that goes with the black wire which feeds the buzzing circuit.

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Most of the time, the buzzing is due to a floating neutral. The neutral is the return side of the power conductor. It should be colored white. Be sure the screw that connects it is good and tight. If it is loose, it is called a floating neutral.

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If a floating neutral is not the problem, replace the breaker. If that does not work, call a qualified service provider.

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I hope some of this helped you.

[Dennis Lopeman]

That is a helpful guide! Thanks. I will try all that.

This panel is the panel for the house... so I would have to turn off the whole house (outside near the meter)?? It's ok, if so.

[Mark Bosse]

Dennis,

If it is your main panel (the one directly connected to the service), be very careful.

Go to the meter. Find the "main" breaker. It will be labeled "main" or "disconnect" or "service disconnect" or some such thing. It will be a 2 pole breaker (having two handles tied together somehow). It will be marked as "100" or "200" or whatever your service rating is. Turn the "main" off.

Typically, you will have either of two situations:

(a) A "main" breaker inside your main panel.
(b) A metered "main" where there is a breaker at the meter base itself.

Choice B is very safe. Just flip it and you should be safe to work at your panel.

Choice A is a little scary. If you have a meter, with no breaker actually on the same box as the meter, and you have a "main" breaker (typically at the top) of you main panel, be very, very careful.

See, situation B means that the "service conductors" which run between the meter and the big-ass double pole "main" breaker are in the same enclosure (read that panel box) as your "main" breaker. That also means that when you flip the "main" off, the service conductors are still live.

Where I live, there is really nothing between a non-metered main (i.e. those live service conductors) and a really, realy, really big dam and power house. True that there are 12.5 KV fuses on the power pole. I have seen a car melt from a live service conductor in an auto shop before those 12.5 KV fuses blew.

If you have live service conductors in your main panel (i.e. you don't have a metered main), please watch your parts. Screwdrivers, pliers, you name it. I actually bought Cementex Cat IV gloves to protect me when I am in those boxes running test equipment. They cost me about $50. Read up on Cat III and Cat IV electrical arc flash risks. The stuff is all over the net.

OK - I know - as always from me, more than you wanted when you posted. But here is the real deal - be as careful as you can around live service conductors. It is your life. So they did tell you that you don't take your shop with you when you go right? Like an old song from the '70s.

Seriously, you can't work wood today without being OK with electricity. But for God's sake, be careful.

If you find a loose neutral screw, better check every single one on all your panels. Loose and floating neutrals cause the wierd lights dimming thing when you turn something on. They also cause buzzing, arcing, ground faults, and fires. Be careful but check every single one. Not a bad idea to check all the hots (wires coming from breakers - we call those live conductor terminals) and all the equipment grounds (bare or green wires).

Please post when you check this stuff so I don't worry about you.

Mark

[Dennis Lopeman]

Well - I put it off this long! Maybe, in light of the latest information, put it off longer!!

Thanks Mark. If I do try it, I'll let you know. You would happen to be near Atlanta, GA, would you?? LOL (I'll look at your profile in a minute)