MOCP Calculator

Maximum Overcurrent Protection (MOCP) is the largest standard fuse or circuit breaker size permitted to protect the branch circuit serving a piece of HVAC equipment. Per NEC 440.22(A) and the UL 1995 nameplate convention, MOCP is a maximum of 225% of the largest motor's full-load amperage plus all other connected loads: MOCP = (Largest Motor FLA × 2.25) + Other Loads. The standard breaker or fuse is that value rounded down to the next standard size, but never below the first standard size above the MCA. The 225% factor allows the overcurrent device to withstand motor starting inrush current (typically 5–7 times the full-load amps) without nuisance tripping, while still providing short-circuit and ground-fault protection. MOCP determines the maximum breaker or fuse size—the actual device selected may be smaller if the circuit conductor ampacity requires it. Equipment manufacturers list MOCP on the unit nameplate alongside MCA to define the complete electrical requirements for the installation.