I hooked up a new hot water heater 23 amps. When the hot water heater is on, there is the faintest hum coming from the panel box. By faintest I mean I have to put my ear up against the panel and only then can I hear a faint hum. You definitely can not hear it without pressing you ear up against the panel. I know its the hot water heater as its in a sub panel with only one other circuit and if I flip that breaker the noise stops.

I'm inclined to think this is normal for a high load. Opinions?

 

if I had to guess, the breaker needs to be replaced.

The last breaker I had to change was on a dryer. Same thing. Buzzing.

 

Does the breaker fit tightly? Any sign of pitting on the bus bars? Is the breaker warm to touch when in use? What size breaker.

 

The breaker is brand new as well as the circuit panel. Its a 30 amp breaker. No it is not warm.

 

It is probably normal. Circuit breakers use two technologies to cause them to "trip"; one is thermal for long time period minor overloads and the other is magnetic for quick action in the case of short circuits. The magnetic uses an electromagnet and a faint buzzing is indicative of the laminations in the magnetic core vibrating.