Ductless Mini Split Breaker & Wire Size
Free online tool • 2026 NEC Compliant
Unlike most appliances, ductless mini split breaker size is not calculated from BTU rating alone — NEC 440.22 requires sizing based on the Minimum Circuit Ampacity (MCA) and Maximum Overcurrent Protection (MOCP) values printed on the outdoor condenser's nameplate. A small single-zone 9,000–12,000 BTU unit typically needs a 15A or 20A circuit, while larger single-zone and multi-zone systems often require 20A–30A at 208/240V.
Recommended Sizing
NEC Standard SizeBreaker Type: Standard Inverse-Time
NEC Reference Note: 125% multiplier applied for continuous loads per NEC 210.20(A).
How to Use This Calculator
Find the outdoor unit nameplate
Locate the MCA and MOCP values on the condenser's data plate — never estimate from BTU rating alone.
Select a breaker at or below MOCP
Choose the largest standard breaker size that does not exceed the MOCP rating.
Select wire meeting or exceeding MCA
Wire ampacity must be equal to or greater than the MCA value.
Confirm dedicated circuit and disconnect
Verify a dedicated circuit and a disconnect located within sight of the outdoor unit per NEC 440.14.
Frequently Asked Questions
What size breaker does a mini split need?
It depends on the unit. Small single-zone systems (9k–12k BTU) commonly use a 15A or 20A breaker at 115–230V. Larger single-zone and multi-zone systems (18k–36k+ BTU) often require 20A–30A double-pole breakers at 208/240V. Always use the MCA/MOCP values on the outdoor unit's nameplate rather than estimating from BTU.
Do mini splits need a dedicated circuit?
Yes. Mini split condensers require a dedicated branch circuit sized to the manufacturer's nameplate rating, per NEC Article 440. A disconnect within sight of the outdoor unit is also required.
What is MCA and MOCP on a mini split nameplate?
MCA (Minimum Circuit Ampacity) is the minimum wire ampacity required for the circuit. MOCP (Maximum Overcurrent Protection) is the largest breaker size permitted. The installed breaker must be at or below the MOCP value and the wire must meet or exceed the MCA value.
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