HVAC Equipment Circuit (MCA / MOCP)
The minimum circuit ampacity and maximum overcurrent device for a condenser or heat pump per NEC 440.33 / 440.22 -- MCA is 125% of the compressor RLA plus the other loads, MOCP is 175% to the next standard size down (225% to start) -- with a check of the installed breaker against the nameplate maximum.
Formula and source
MCA = 1.25 x largest motor RLA + sum of the other loads (NEC 440.33). MOCP = 1.75 x largest RLA + others, taken to the next NEC 240.6(A) standard size DOWN (NEC 440.22(A)); the 225% value is the ceiling allowed only where the 175% size will not start the equipment.
NEC 2023 (NFPA 70). Section 440.33 (MCA), 440.22(A) (MOCP), and 240.6(A) (standard device sizes).
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