What causes the buzzing or humming sound that comes from my electrical panel? There was no problem originally, but now the panel hums from time to time -which can be quite annoying, since it is in my kitchen.  I have a 125 Amp main breaker and the house is wired up to capacity but not over capacity for a 125 Amp main.  Although it is difficult to tell, I believe it is the main breaker that hums, and it does this even when the electrical load is relatively light.  For example, in the summer, there is no electric heat on, but the clothes dryer, or range – or sometimes even the fridge or toaster - will start the music happening.

Although uncommon, main electric panels have been known to break into full Broadway chorus renditions of “Cats”. Thankfully, your panel is still limited to an occasional hum. And, fortunately, there are some possible causes and solutions that you may consider.

The least likely source may be a small low voltage transformer attached to or near your main panel. The most common of these would be a doorbell transformer. Look for a small metal box with light gauge wiring running from and to it. These transformers often hum, but this is not the most probable source of the annoyance.

A more likely source of the problem is a loose breaker. Often, the contact point between a main or circuit breaker and one of the power supply buss bars will loosen and a small gap will occur between the two contact points. The gap or loose contact point will hum when electricity flows across the contact points. There is a possible simple cure for the problem. Open the panel door when you hear the humming. Do not remove the main panel cover. You will be looking at the main and circuit breakers. With your finger on a breaker, press each breaker in turn pushing it toward the back of the panel. If the humming stops when you press a particular breaker, you have found the loose contact point.

However, if the humming continues after you release pressure on the breaker, the contact points on the breaker or the harness that holds the breaker is worn to the extent that new a breaker, breaker harness or buss bar(s) may be required. If the humming cannot be eliminated by simply pressing on the breaker, I suggest that you contact a qualified electrical contractor for any further investigation because loose contact points and loose wires attached to breakers can cause short circuits and electrical fires.