What Size Cable Do You Need for a 32 Amp Circuit?
For a 32 amp radial circuit, use 4mm² copper cable (BS 7671, IEC, AS/NZS) or 10 AWG (NEC). For a BS 7671 ring final circuit, 2.5mm² is standard as the ring topology effectively halves the current per conductor. Always verify voltage drop for runs over 20m.
Quick Reference: Cable Size for 32 Amp Circuit by Standard
| Standard | Cable Size | Conditions | Reference |
|---|---|---|---|
| BS 7671 | 4mm² (radial) or 2.5mm² (ring) | Method C clipped direct | Table 4D1A |
| NEC | 10 AWG | THWN-2, 30A breaker (NEC rounds up) | Table 310.16 |
| AS/NZS 3008 | 4mm² | Enclosed in conduit, 30°C ambient | Table 13 |
| IEC 60364 | 4mm² | Reference method C, PVC 70°C | 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 32 Amp Circuit
- Ring final circuit
- Electric shower
- Single-phase EV charger
- Cooker circuit
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
Can I use 2.5mm² for a 32 amp circuit?▼
Only in a ring final circuit configuration under BS 7671, where the ring topology divides the current between two paths. For a radial circuit, 2.5mm² is NOT adequate for 32A — use 4mm² minimum.
What size cable for an electric shower at 32 amps?▼
A 10kW electric shower draws approximately 43A at 230V, requiring a 45A circuit with 10mm² cable. An 8.5kW shower draws 37A, needing 6mm² minimum. Only low-power showers (7.2kW, 31A) suit a 32A circuit with 4mm² cable.
What size cable for a 32 amp EV charger?▼
A 7.4kW single-phase EV charger at 32A requires 6mm² cable for most runs under 25m. For longer runs or grouped cables, upgrade to 10mm². A dedicated 32A Type A RCBO is required.
Is 6mm² overkill for 32 amps?▼
No. While 4mm² is the minimum for a 32A radial, 6mm² provides better voltage drop performance on longer runs and future-proofs the circuit. The extra cost is typically under 20% for domestic runs.
What is the voltage drop limit for a 32 amp circuit?▼
BS 7671 allows 5% voltage drop for power circuits (11.5V on a 230V supply). At 32A on 4mm² cable, the maximum run length before exceeding 5% is approximately 18m. Use 6mm² for runs up to 30m.
Related Cable Sizing Guides
🔌
What Size Cable Do You Need for a 25 Amp Circuit?4.0mm² (BS 7671)
🔌What Size Cable Do You Need for a 40 Amp Circuit?6mm² (BS 7671)
🔌What Size Cable Do You Need for an Electric Shower?6mm² (8.5kW) or 10mm² (10.5kW) (BS 7671)
🔌What Size Cable Do You Need for an EV Charger?6mm² (7.4kW) or 10mm² (long runs) (BS 7671)
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