Mini Split Wire Size & Circuit Breaker Sizing Chart
Statutory branch circuit sizing table under NEC Article 440, Table 310.16, and NEC 250.122 for standard residential installations up to 50 feet.
| Capacity | Voltage | MCA / MOP | Conductor | Breaker (HACR) | Disconnect | Min Conduit | Equipment Ground | Torque Rating |
|---|---|---|---|---|---|---|---|---|
| 9,000 BTU (115V) → | 115V | 12A / 15A | 14 AWG Copper | 15A Single-Pole | 30A Non-Fused | 1/2" Liquid-Tight or EMT | 14 AWG Copper | 10.6–13.3 in-lbs |
| 12,000 BTU (115V) → | 115V | 16A / 20A | 12 AWG Copper | 20A Single-Pole | 30A Non-Fused | 1/2" Liquid-Tight or EMT | 12 AWG Copper | 10.6–13.3 in-lbs |
| 12,000 BTU (208/230V) → | 230V | 9A / 15A | 14 AWG Copper | 15A Double-Pole | 30A Non-Fused | 1/2" Liquid-Tight or EMT | 14 AWG Copper | 10.6–13.3 in-lbs |
| 18,000 BTU (208/230V) → | 230V | 16A / 20A | 12 AWG Copper | 20A Double-Pole | 30A Non-Fused | 1/2" Liquid-Tight or EMT | 12 AWG Copper | 13.3–15.0 in-lbs |
| 24,000 BTU (208/230V) → | 230V | 21A / 30A | 10 AWG Copper | 30A Double-Pole | 30A Non-Fused | 3/4" Liquid-Tight or EMT | 10 AWG Copper | 15.0–18.0 in-lbs |
| 30,000 BTU (208/230V) → | 230V | 26A / 35A | 10 AWG Copper | 35A Double-Pole | 60A Non-Fused | 3/4" Liquid-Tight or EMT | 10 AWG Copper | 15.0–18.0 in-lbs |
| 36,000 BTU (208/230V) → | 230V | 32A / 45A | 8 AWG Copper | 45A Double-Pole | 60A Non-Fused | 3/4" or 1" EMT | 10 AWG Copper | 18.0–20.0 in-lbs |
Engineering Standards & Conductor Ampacity Rules
Ductless heat pumps cannot be sized with standard residential 15A/20A lighting circuit assumptions (NEC 240.4(D)). Conductor gauge and overcurrent protection must be calculated independently:
- Conductor Gauge (Sized to MCA): Pursuant to NEC 440.6, branch supply wires are sized to the Minimum Circuit Ampacity rating at 60°C insulation column (NEC Table 310.16). Built-in solid-state thermal overloads safeguard the wire against running overcurrent.
- Circuit Breaker (Sized to MOP): Pursuant to NEC 440.22, the breaker is sized up to the Maximum Overcurrent Protection rating to absorb locked-rotor inrush current during DC inverter startup without tripping.
- Equipment Grounding Conductor (EGC): Sized under NEC Table 250.122 based on the upstream circuit breaker rating (14 AWG copper for 15A circuits, 12 AWG for 20A, 10 AWG for 30A to 60A circuits).
- Terminal Screw Torque (NEC 110.14(D)): Electrical terminations must be tightened with a calibrated torque tool to manufacturer ratings to avoid arcing and circuit board failures.