Always Start With the Nameplate
Unlike a standard receptacle circuit, an HVAC or mini split circuit is sized from the unit data plate rather than a fixed rule. The outdoor condenser or heat pump lists two numbers that control everything: the minimum circuit ampacity, or MCA, and the maximum overcurrent protection, or MOCP. The MCA tells you the smallest wire ampacity allowed, and the MOCP tells you the largest breaker you may use.
Typical Mini Split Wire Sizes
Single-zone mini splits vary widely by capacity, so these are general starting points only. Confirm against the nameplate before you buy wire.
| Mini Split Size | Typical Circuit | Typical Copper Wire |
|---|---|---|
| 9,000 to 12,000 BTU | 15 amps | 14 AWG |
| 12,000 to 18,000 BTU | 20 amps | 12 AWG |
| 18,000 to 24,000 BTU | 20 to 30 amps | 12 to 10 AWG |
The Power Circuit
Most mini splits run on a dedicated 240-volt circuit using two hots and a ground, with no neutral needed. The power conductors are typically NM-B Romex for an interior run to the disconnect, or THHN in conduit for an outdoor run to the condenser. Size the wire to meet or exceed the MCA on the nameplate.
The Control or Communication Cable
Mini splits also need a low-current control cable that carries signals between the indoor air handler and the outdoor unit. This is usually a 14 AWG four-conductor stranded cable, and the manufacturer instructions specify the exact conductor count and gauge. This cable is separate from the power circuit.
Disconnect at the Outdoor Unit
A disconnecting means is required within sight of the outdoor condenser so the unit can be safely serviced. This is standard for all outdoor HVAC equipment, not just mini splits.
Code and Safety Note
HVAC circuits must match the equipment nameplate and the manufacturer installation manual exactly, and refrigerant work is a licensed trade. Follow the National Electrical Code and local amendments, confirm with your authority having jurisdiction, and use a licensed electrician and HVAC technician for the installation.
IB Lighting carries Southwire NM-B, THHN, and control cable for HVAC circuits in our electrical wire and cable collection, with free freight plus free freight insurance on every order. Call (800) 674-9019 with your unit MCA and we will match the wire.