We asked an expert to explain all the problems that can cause tripped circuits, how to check your circuit breaker, and when to call a professional.

Each wire powers one “bus” (copper vertical leg) inside the main service panel. That’s why you usually see two columns of circuit breakers (or fuses) when you open your service panel door.

An MCB (miniature circuit breaker) can be reset and uses an electromagnet to open a switch if the current goes above a certain value. MCBs switch off the current faster than a fuse. An RCCB ...