This Siemens 20 A rated GFCI 1-pole circuit breaker features a self-test function. If the breaker detects that it has been compromised, it trips itself and locks in this position so that it can't be reset. It also features ground-fault protection. The breaker is CSA licensed for HACR-type equipment (Heating, Air Conditioning & Refrigeration). The breaker provides overload and short circuit protection (120 V AC).