Calculate The Cable Size Link

For 230 V circuits, if the load exceeds ~15 A or length exceeds 30 m, voltage drop often dictates the size, not ampacity.

The Critical Engineering of Conductor Sizing: Balancing Safety, Efficiency, and Economics calculate the cable size

Formula for single-phase (approximate): [ V_drop = \frac2 \times L \times I \times R_cable1000 ] Where: ( L ) = one-way length (m), ( I ) = actual load current (A), ( R_cable ) = resistance per km (from cable data, e.g., 7.98 Ω/km for 2.5 mm² copper). For 230 V circuits, if the load exceeds

Three-phase drop formula: ( V_drop = \frac\sqrt3 \times L \times I \times R1000 ) → (1.732 × 80 × 13.6 × 4.95)/1000 = 9.3 V. 9.3/415 = 2.2% – excellent. For 230 V circuits

| Load Current (A) | Cable Length (m) | Voltage Drop (%) | Cable Size (mm²) | | --- | --- | --- | --- | | 25 | 50 | 5 | 6 | | 50 | 100 | 3 | 16 | | 100 | 200 | 5 | 35 |

For our 21.7 A load, 2.5 mm² might be borderline. If derating factors apply (e.g., 0.8 total), we need 21.7 / 0.8 = 27.1 A design current → step up to 4 mm².