by: Jack Colton
Customer Question: Is "buzzing" in the RV circuit breaker panel normal?
Buzzing is normal with magnetic circuit breakers; basically they are made of a coiled wire that pulls on a ferrite strip that trips the breaker to open the circuit when the magnetic field gets too strong. When the current is less than the trip level, the parts rattle because of MSW. The rattle becomes louder as more current is drawn through the coil. Pure Sine AC will not cause a rattle.
Most circuit breakers are thermal and heat dissimilar bimetal strips. The heat is proportional to the current drawn. When excessive current is drawn, the heat causes the bimetal strip to bend and trip the breaker.
I advise changing the circuit breakers to thermal type and look over the AC loads and the charging system. This customer is using a windmill to charge golf cart batteries. In this case with their relatively light load, they could directly plug into the inverter and bypass the breaker panel to avoid the buzzing noise.