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Home / Code Guides / Mini-Split Circuits

Mini-Split Electrical Requirements — MCA, MOCP & Disconnects

Mini-splits are wired differently than most appliances: you don’t size the circuit from a generic table, you size it from two numbers stamped on the unit’s nameplate — Minimum Circuit Ampacity (MCA) and Maximum Overcurrent Protection (MOCP). Get those two right, add a disconnect within sight of the outdoor unit, and most of Article 440 falls into place.

RequirementModel Code StandardSection
Conductor sizingBranch-circuit conductors must have an ampacity at least equal to the MCA on the unit’s nameplate — the manufacturer has already done the 125% compressor math for youNEC 440.4, 440.32
Breaker/fuse sizingThe overcurrent device must not exceed the nameplate MOCP (sometimes labeled “max fuse/breaker”), and if the nameplate specifies fuses or HACR-type breakers, that requirement is part of the listingNEC 440.4(B), 440.22
Disconnect locationA disconnecting means is required within sight of the outdoor unit and readily accessible — a locked breaker across the yard doesn’t qualifyNEC 440.14
Working spaceThe disconnect and equipment likely to need servicing while energized require clear working space — generally 30 inches wide and 36 inches deep in front of the disconnectNEC 110.26(A)
Indoor head powerMost residential mini-splits power the indoor head from the outdoor unit over the interconnect cable specified by the manufacturer — a separate branch circuit to the head is only used where the installation manual calls for itNEC 110.3(B), 440.4
Outdoor wiringThe whip between disconnect and unit must be a wet-location wiring method (liquidtight flexible conduit is typical), and conductors must be rated for the environmentNEC 300.9, 350.10

Worth knowing

  • MCA and MOCP often look odd together — an MCA of 19A with an MOCP of 30A is normal. Wire for 19A (12 AWG typically qualifies), breaker at up to 30A. The compressor’s overload protection is inside the unit; the breaker only handles faults.
  • GFCI protection for outdoor HVAC outlets has been a moving target: the requirement in 210.8(F) has been delayed by code action for mini-splits and similar equipment until September 1, 2026, and some states amended it out entirely — ask your local inspector what’s enforced.
  • The manufacturer-specified interconnect cable (often 14 AWG, 4-conductor stranded) is part of the listing — substituting random cable is a 110.3(B) violation and a common warranty denial.
  • Mount the disconnect beside the unit, not behind it — inspectors read “readily accessible” to mean you can reach it without moving the condenser or squeezing behind refrigerant lines.
Sections cite the 2021 International Residential Code and 2023 National Electrical Code as model standards. This is BuildSpec’s own summary — not ICC or NFPA text; read the authoritative language at codes.iccsafe.org. Your state may be on a different edition with amendments — check your jurisdiction page or get an Address Report.
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