I recently got this unit tested for annual inspection and it passed the test. But all in a sudden, it is making this loud humming sound. Needless to say, it is driving me crazy.
Is there some sort of reset button I can restart the panel? Or I should just shut the main switch and flip it back on…
Looks like an older panel, the loud hum could be the transformer that powers it. You can try powering it off (via the main switch) and back on, but it’s possible the power supply is showing its age. Usually, a very loud transformer is a sign of a problem.
That’s usually due to the magnetostriction in the transformer’s core caused by the coil’s magnetic fields.
Usually it’s not very audible, but as the transformer ages, the E-shaped plates that constitutes its core can delaminate, and when they do, they can slightly (not enough to be visible, but enough so they can vibrate due to the magnetostriction). The more plates are shifting around, the louder the “hum” will be.
It can be due to age (and in this case, I wouldn’t worry too much about that) but as Nicholas said, this could also be indicative of a bigger problem.
As others said, the transformer is likely to blame for the noise. To add to it though, it’s not too uncommon for this kind of issue to pop up after an inspection. With a panel of that age, a day of testing could cause extra strain on the transformer. Unfortunately if the noise continues, you may need your service company to come back out and figure out why.
Yep, the xfrm.
Try tightening down the xfrm mounts. Try tightening down everything around it. It going to hum but if its loud its probably rattling on the chassis or something else
