What causes a light, switch, or breaker box to hum?
Some dimmer switches will cause light fixtures to hum. At the breaker panel, the 60 cycles per second of your alternating current can set up a vibration or slight buzz or hum in some components. Fluorescent lights, transformers, and an electric water heater can also hum. All these are fairly normal, but if the hum is loud, it may mean that the component is loose or close to failing. If a circuit breaker gets wet, it can cause a buzzing sound as the moisture is boiled off. A loud buzzing at a breaker could indicate that the breaker overloading without tripping as it should.
