35 mm² copper is rated about 138 A installed per Method C (clipped direct, 70 °C thermoplastic) and drops 1.3 mV/A/m (single-phase figure, matching BS 7671 Appendix 4 within rounding). The chart shows how far it runs before the drop exceeds the limits.
| Load | 230 V @ 3% | 230 V @ 5% | 400 V 3Ø @ 5% |
|---|---|---|---|
| 6 A | 894 m | 1491 m | 2994 m |
| 10 A | 537 m | 894 m | 1796 m |
| 16 A | 335 m | 559 m | 1123 m |
| 20 A | 268 m | 447 m | 898 m |
| 32 A | 168 m | 280 m | 561 m |
| 40 A | 134 m | 224 m | 449 m |
| 63 A | 85 m | 142 m | 285 m |
Computed with ρ ≈ 0.0225 Ω·mm²/m (copper at operating temperature), matching BS 7671 Appendix 4 mV/A/m values within rounding. Grouping, insulation type and installation method change the amp rating — treat 138 A as the Method C reference figure.
The nearest equal-or-larger AWG size is 1 AWG — see the gauge converter for exact areas.
About 138 A for copper clipped direct (Method C). Enclosed in conduit in insulation it derates substantially — always check the installation method column in BS 7671 Appendix 4.