Ductless Mini-Split: Complete Wiring Guide
Bill of materials
Ductless mini-splits are one of the most common residential electrical additions. Most single-zone units (9-18k BTU) run on a 15A or 20A/240V circuit. Multi-zone units may require 25-30A. Always check the nameplate MCA and MOCP - these override generic sizing charts.
Mini-splits require a dedicated circuit with a disconnect within sight of the outdoor unit per 440.14. Most 9-12k BTU units specify 14 AWG on 15A. The communication wire between indoor and outdoor units is typically 14/4 stranded (4-conductor, 14 AWG) but check the installation manual. Run the communication wire alongside the refrigerant lines but not inside the same conduit as the power wires.
9,000 BTU mini-split (15A)
| Component | Specification | NEC basis |
|---|---|---|
| Wire (copper) | 14 AWG THHN | Table 310.16, 110.14(C) |
| Breaker | 15A double-pole | 240.4 |
| Voltage | 240V single-phase | |
| Conduit (EMT) | 1/2" EMT | Chapter 9 Table 4 |
| Max distance (3% VD) | 163 ft at 240V copper | 210.19(A) Note 4 |
12,000 BTU mini-split (15A)
| Component | Specification | NEC basis |
|---|---|---|
| Wire (copper) | 14 AWG THHN | Table 310.16, 110.14(C) |
| Breaker | 15A double-pole | 240.4 |
| Voltage | 240V single-phase | |
| Conduit (EMT) | 1/2" EMT | Chapter 9 Table 4 |
| Max distance (3% VD) | 114 ft at 240V copper | 210.19(A) Note 4 |
24,000 BTU mini-split (25A)
| Component | Specification | NEC basis |
|---|---|---|
| Wire (copper) | 10 AWG THHN | Table 310.16, 110.14(C) |
| Wire (aluminum alt.) | 8 AWG THHN | Table 310.16, 110.14(C) |
| Breaker | 25A double-pole | 240.4 |
| Voltage | 240V single-phase | |
| Conduit (EMT) | 1/2" EMT | Chapter 9 Table 4 |
| Max distance (3% VD) | 181 ft at 240V copper | 210.19(A) Note 4 |
36,000 BTU multi-zone (30A)
| Component | Specification | NEC basis |
|---|---|---|
| Wire (copper) | 10 AWG THHN | Table 310.16, 110.14(C) |
| Wire (aluminum alt.) | 8 AWG THHN | Table 310.16, 110.14(C) |
| Breaker | 30A double-pole | 240.4 |
| Voltage | 240V single-phase | |
| Conduit (EMT) | 1/2" EMT | Chapter 9 Table 4 |
| Max distance (3% VD) | 132 ft at 240V copper | 210.19(A) Note 4 |
Installation notes
GFCI is not specifically required for this application by NEC, though local amendments may differ. Check with your local building department before starting work.
For the wire run, you have two options: NM-B cable (Romex) for interior runs through framing, or individual THHN conductors in conduit for exposed runs, outdoor installations, or runs through unfinished spaces. NM-B is faster to install but cannot be used outdoors or in conduit. For conduit, use EMT (metallic) or PVC Schedule 40.
Run length matters: every foot of wire adds voltage drop, reducing power to your equipment. The table below shows the exact voltage drop at common distances. If your run exceeds the 3% threshold, upsize one gauge.
Voltage drop by distance
Percentage voltage drop at common run lengths. NEC recommends 3% maximum for branch circuits and 5% for combined feeder plus branch.
| Distance | 14 AWG Co | 12 AWG Co |
|---|---|---|
| 25 ft | 0.5% | 0.3% |
| 50 ft | 0.9% | 0.6% |
| 75 ft | 1.4% | 0.9% |
| 100 ft | 1.8% | 1.2% |
| 150 ft | 2.8% | 1.7% |
| 200 ft | 3.7% | 2.3% |
Common products for 14 AWG Copper circuits
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Related wire data
Detailed ampacity: 14 AWG copper. Wire size lookup: 15A circuit. Calculators: voltage drop · panel load calculator.
Frequently asked questions
What wire size do I need for ductless mini-split?
Use 14 AWG copper or 14 AWG aluminum on a 15A breaker at 240V. This is based on NEC 2023 Table 310.16 ampacity with 110.14(C) termination limits and 125% continuous load sizing per 210.19(A)(1).
Does ductless mini-split require GFCI?
No. GFCI is not required for this application.
NEC 2023 references verified April 2026