HVAC MCA / MOP Calculator

Air conditioning and heat pump nameplates list MCA (Minimum Circuit Ampacity) and MOP (Maximum Overcurrent Protection) rather than a single FLA value, because these units combine a compressor with fan motors. NEC 440.22 and 440.32 define the standard multipliers used to size the conductors and breaker/fuse. This tool applies those multipliers to a compressor RLA and any additional motor FLA.

Tip: On a real nameplate, always use the MCA/MOP printed by the manufacturer — this tool reproduces the standard NEC 440 formula for practice, not equipment-specific engineering data.

The largest motor-compressor in the circuit.
Sum of full-load amps for any other motors on the same circuit. Enter 0 if none.
MCA (Amps)
MOP (Amps)
NEC 440.32: MCA = 1.25 × compressor RLA + other motor FLA — used to size the conductors.
NEC 440.22(A): MOP = 175% of compressor RLA + other motor FLA (the standard default), rounded to the nearest standard fuse/breaker size (NEC 240.6(A)) — used to size the branch-circuit protective device. If 175% isn't enough to handle starting current, the code permits going up to 225%, but never higher.