Overcurrent Protection Device (OCPD)

An Overcurrent Protection Device (OCPD) is any device designed to interrupt the flow of electrical current when it exceeds a safe level, protecting wiring, equipment, and people from damage or fire. Common OCPDs include circuit breakers and fuses.

In solar installations, overcurrent protection is required at multiple points in the system per the National Electrical Code (NEC). Fuses in the combiner box protect individual panel strings, a breaker at the inverter output protects the AC circuit, and a dedicated solar breaker in the main service panel protects the connection to your home’s electrical system. The NEC’s “120% rule” for bus bar ratings and proper OCPD sizing are critical design considerations that your solar installer must calculate correctly. Undersized OCPDs can trip nuisance faults and reduce system uptime, while oversized OCPDs fail to provide adequate protection. All OCPDs in a solar installation must be rated for the specific voltage and current type (AC or DC) they protect — DC-rated breakers and fuses are required on the panel side of the system since DC arcs are harder to extinguish than AC arcs.