Unlike a fuse rating, a circuit breaker rating indicates the maximum current the circuit breaker will consistently maintain at an ambient room temperature. Thus, a 10A circuit breaker will maintain a 10A current without nuisance tripping. In fact, a typical 4A circuit breaker with a slow trip profile will tolerate a temporary 10A current surge without nuisance tripping. Oftentimes, nuisance tripping is caused by in-rush currents associated with certain electrical components – primarily motors, transformers, solenoids, and large capacitors. In such cases, the designer needs to specify a circuit breaker with a delay. Thermal circuit breakers have a natural delay, and magnetic circuit breakers can have added hydraulic delays. When designing equipment with high in-rush currents, match the delay to the duration of the expected in-rush current.