MOCP Calculator - HVAC Calculator Toolbox

About this calculator This calculator determines the Maximum Overcurrent Protection (MOCP) per NEC Article 440. MOCP is the largest standard fuse or breaker size that may be used to protect the circuit. Use it when selecting circuit breakers or fuses for HVAC equipment to provide short-circuit and ground-fault protection while allowing motor starting inrush.

Use when You need to determine the maximum breaker or fuse size for equipment protection.

Formula MOCP = FLA × 2.25

Variables

FLA Full load amps from equipment nameplate

Full Load Amps (FLA)

Full load amps from motor nameplate

MOCP (Amps) —

Standard Breaker —

What is Maximum Overcurrent Protection (MOCP)?

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 Article 440, MOCP is calculated as 225% of the largest motor's full-load amperage plus all other connected loads: MOCP = (Largest Motor FLA × 2.25) + Other Loads. The result is rounded down to the next standard breaker or fuse size. 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.

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