What Size Cable Do You Need for an Air Conditioning Unit?
For a typical residential split system AC (2.5-5kW), use 2.5mm² cable on a 16-20A circuit. For larger commercial units (7-14kW), use 4-6mm² cable. Always size from the manufacturer's MCA (Minimum Circuit Ampacity) on the nameplate, not the cooling capacity in kW.
Quick Reference: Cable Size for Air Conditioning Unit by Standard
| Standard | Cable Size | Conditions | Reference |
|---|---|---|---|
| BS 7671 | 2.5mm² to 6mm² | Depends on unit capacity, dedicated circuit | Table 4D1A |
| NEC | 12 AWG to 8 AWG | Per nameplate MCA, NEC 440 | Table 310.16 |
| AS/NZS 3008 | 2.5mm² to 6mm² | Per unit rating, AS/NZS 3000 | Table 13 |
| IEC 60364 | 2.5mm² to 6mm² | Per compressor FLA | Table B.52.4 |
Values shown are for copper conductors in typical domestic/commercial conditions. Actual size depends on installation method, ambient temperature, and cable length. Use our free cable sizing calculator for your exact scenario.
Typical Applications for a Air Conditioning Unit
- Split system AC
- Multi-split system
- Window AC unit
- Portable AC
Calculate Your Exact Cable Size
These are general guidelines. Your specific installation needs exact calculation accounting for cable route length, installation method, ambient temperature, and cable grouping.
Frequently Asked Questions
What size cable for a 5kW split system?▼
A 5kW split system typically draws 8-12A. Use 2.5mm² cable on a 16A or 20A circuit. Check the outdoor unit nameplate for the exact MCA and MOCP values.
Does an AC unit need a dedicated circuit?▼
Yes. Air conditioning units with compressors should have dedicated circuits due to starting current surges and continuous operation. This prevents nuisance tripping of shared circuits.
What breaker type for air conditioning?▼
Use a Type C MCB for air conditioning units. Type C handles the 5-10x starting current surge from the compressor motor without nuisance tripping. Type B MCBs may trip on compressor start.
Can I run AC from a 13A socket?▼
Only portable AC units under 3kW. Fixed split systems must have a dedicated circuit with an isolator switch visible from the outdoor unit, as required by BS 7671 and manufacturer installation guides.
What is MCA on an AC nameplate?▼
MCA (Minimum Circuit Ampacity) is the minimum current rating the circuit conductors must have. It accounts for compressor full load current plus fan motor current, typically 125% of the largest motor plus sum of other loads.
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