Vibrating panel

G

Gadi

Member
Location
Baltimore
Occupation
Electrician
Troubleshooting a panel for a loud hum/vibration noise.

Checked that everything was tight.
Corrected bonding and grounding issues.
Check for over amping, it’s a 200 amp panel 120/240 3 wire, and it’s only drawing 56 amps.

The issues still persists.
Found that when I put a magnet within 3 inches of the panel or the service wires the magnet shakes intensely. I assume that this is some sort of electromagnetic field that is out of balance. Has anybody run into something like this? What are the next troubleshooting steps.
 
Put your amp clamp on the GEC ('ground wire' to any grounding electrodes) and see if you get any large current flow.

If you have a large enough amp clamp, see if you can go around _all_ service conductors at once, and see if you get any large net current flow.

Heavily loaded breakers can hum pretty noticeably, especially if they are feeding non-linear loads. (I just discovered this on a 50A breaker feeding 15A to a well pump VFD. 15A isn't too bad on a 50A breaker, but when the well pump is running continuously.....)

-Jon
 
I checked the grounding, there was about 4 A returning on the (GEC) grounding conductor, pretty typical in Baltimore since they have such crappy utility neutrals.

The panel will moderately hum when there is the regular receptacles and lighting loads (12 amp) on. It will start humming very noticeably when the heat pump and auxiliary heat loads kick (56 amp) on.

That being said, the breakers are not vibrating, the wires are making an electromagnetic force that is causing the panel and panel cover to vibrate.

Again, if I take a magnet and hold it 3 inches away from the panel, not touching anything, just holding it in my hand, the magnet vibrates.
 
This is a new owner, they just renovated the house and its a real mess. Looks like it was done with no permits and in the middle of the night.

that being said I don't know how long its been vibrating..

What would make a magnet vibrate, when the magnet is not touching the wires or panel.

I suggested to the owner to call the utility to have them check the transformer.. but I'm not very hopeful that that's the issue.

panel has good voltage...
 
Gadi said:
What would make a magnet vibrate, when the magnet is not touching the wires or panel.
Click to expand...

You already have an idea in your first post:
Gadi said:
I assume that this is some sort of electromagnetic field that is out of balance. Has anybody run into something like this? What are the next troubleshooting steps.
Click to expand...

When current in a conductor, it creates a magnetic field around the wire. If you have alternating current, then the magnetic field will also be alternating, and could make a magnet vibrate.

With a proper installation, all current flowing in one circuit conductor will be balanced by current flowing in the other conductors in the same cable or conduit. Because the _net_ current of all of the circuit conductors taken together will be zero, the net magnetic field will be very close to zero; you only get some magnetic field because the wires are slightly separated from each other.

Your vibrating magnet suggests that current is not flowing in a balanced fashion on the cables. For example you could have current entering via one of the service entrance 'hot' conductors, an then leaving via a metal piping.

Measuring 'net' current on entire circuits is a great way to chase this sort of imbalance. You use some sort of current clamp wrapped around the entire cable to probe if there is imbalanced current flow on that cable.

-Jonathan
 
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