Why is a circuit breaker required in series with a parallel surge protector?
A circuit breaker used in series with a surge protector for the same reason a circuit breaker is used to protect a branch circuit, to prevent a fire. A circuit breaker is invisible to a transient or surge so it will not open during most transient events. But should the surge protector start to draw large amounts of AC current (which is not normal operation of parallel AC surge protector), the breaker will open and disconnect the protector from the AC line. Fuses may also be used in series with the surge protector to achieve the same level of safety, but we find that circuit breakers have better transient withstand capacity.
