Noisy SquareD main breaker

[Codyboy]

In my new shop is a new 200 amp square d panel.

The main breaker has a constant weird noise while AC is running.
At first I thought it was the 15 A that feeds a bank of five LED lights.
But using a high tech stethoscope (pvc pipe) it is the main.
I can turn off the AC and it stops the noise. AC breakers make no noise.
Turn off LEDs no change.

Voltage under load is good at 122.5, 122.5, 245 steady
Hz 59.96 and steady.

I can hear it without the pipe if I get close to the panel. Used the pipe to pin point where it was coming from.

ETA
Square D QO

 

[Bert_]

Could do a millivolt drop test. All it is measuring is voltage lost in the breaker. I'm not super familiar with it but a search will show some information

 

[mm08822]

Cycle the main cb. make sure everything is tight....field wire terminations in the panel and incoming to the main cb.

Do you have access to an IR camera?

 

[Chuckster in NJ]

Take the loads off then turn the breaker on and off about 8-10 times while tapping it with a screw driver (handle end) and see if the noise changes once you load it up. Maybe doing this will put everything back in alignment or dislodge something…….. It’s worth a try.

You can also take a meter and go line to load (same phase) across the breaker and see if you are reading any voltage….. The reading should be zero volts.

 

[Codyboy]

Ok I'll cycle the breaker a few times and check the voltage drop across it.

It sounds more like vibration than electrical , if that makes sense.

Also while thinking about it, I have another SqD QO 200a at home and when the AC kicks on it "grunts"
Been doing it since it was new 20 years ago.
Never feels warm or anything.

 

[PCustoms]

Ok I'll cycle the breaker a few times and check the voltage drop across it.

It sounds more like vibration than electrical , if that makes sense.

Probably vibrating around 60Hz...

 

[wyliesdiesels]

something is loose and vibrating....

 

[wyliesdiesels]

Ok I'll cycle the breaker a few times and check the voltage drop across it.

It sounds more like vibration than electrical , if that makes sense.

Also while thinking about it, I have another SqD QO 200a at home and when the AC kicks on it "grunts"
Been doing it since it was new 20 years ago.
Never feels warm or anything.

Ive seen breakers for elevator hydraulic pump motors do that.... its completely normal due to the high magnetic flux of the large in-rush current pulled by the motor. Also have heard (and seen) conductors jumping in conduit that are powering pump motors for elevators, compressors, etc... its pretty wild...