Do I add 125 percent to a mini split's nameplate amps?

No. The Minimum Circuit Ampacity on the nameplate already includes the 125 percent factor per NEC 440.33. Size conductors to at least the MCA and choose the breaker from the marked MOCP.

Can the breaker be bigger than the wire ampacity on a mini split?

Yes. Under NEC 440.22 the maximum overcurrent protection is set for compressor starting and may exceed the MCA. The equipment's overload protection guards the conductors, so a 25 amp MCA with a 40 amp max breaker is compliant.

25 Amp Mini Split: What Breaker, and Do You Add 125 Percent?

A user asked the app about a single phase mini split showing 25 amps: what breaker does it need, and does the 125 percent factor get added on top? The key insight is that the manufacturer already did the 125 percent math for you. Your job is to read two numbers off the nameplate and obey both.

MCA: the wire number

Air conditioning equipment is governed by Article 440 in NEC 2023 because it uses a hermetic refrigerant motor compressor. The nameplate lists Minimum Circuit Ampacity, and 440.4 requires it to be marked. MCA is calculated by the manufacturer as 125 percent of the largest motor load plus the sum of the other loads, per the method in 440.33. If the 25 amps on this unit is the MCA, the branch circuit conductors simply need an ampacity of at least 25, which is 10 AWG copper at 75 degrees. Adding another 125 percent on top would be doubling a factor the nameplate already contains, and 440.33 does not ask for that.

MOCP: the breaker number

The second nameplate number is Maximum Overcurrent Protection, often marked Max Fuse or Max Breaker. Under 440.22 the manufacturer sets this to let the compressor start without nuisance tripping, and it is frequently larger than the MCA; a unit with a 25 amp MCA might list a 40 amp MOCP. That mismatch is legal and normal for motor loads: the conductors are protected against overload by the equipment itself, and the breaker only handles short circuits and ground faults. Install any breaker at or below the MOCP that is above the load, commonly a 30 or the listed maximum. Never exceed the MOCP, and if the nameplate says fuses only, HACR breakers do not satisfy it.

The rest of the circuit

Outdoor units need a disconnecting means within sight per 440.14, and the common non fused pull out satisfies it. If the disconnect is fused and the nameplate lists fuse sizes, match them. A 115 or 120 volt receptacle for servicing is required within 25 feet of the equipment by 210.63, GFCI protected outdoors under 210.8(A)(3) or 210.8(B) as applicable. Wire type matters too: the minimum conductor is sized from MCA, but long runs to a backyard condenser deserve a voltage drop check before the trench closes.

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