The PQR050 is a high-performance, surge protective device (SPD), protecting your electrical equipment from damaging electrical power surges due to lightning; utility power generation/distribution systems; and inductive load switching equipment. Intended for service entrance / load center, sub panels, and large equipment (e.g., air conditioners, heat pumps). 

The PQR050 standard series is UL Type 1 listed (automatically suitable for UL type 2) and can be installed before or after the service equipment overcurrent device, with or without a dedicated circuit breaker for the SPD.