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| OCPD Rating (Amps) | Copper EGC Size (AWG) | Copper EGC Size (mm²)* | |--------------------|-----------------------|------------------------| | 15 | 14 AWG | 2.1 | | 20 | 12 AWG | 3.3 | | 30 | 10 AWG | 5.3 | | 40–60 | 10 AWG | 5.3 | | 100 | 8 AWG | 8.4 | | 200 | 6 AWG | 13.3 | | 300 | 4 AWG | 21.2 | | 400 | 3 AWG | 26.7 | | 500 | 2 AWG | 33.6 | | 600 | 1 AWG | 42.4 | | 800 | 1/0 AWG | 53.5 | | 1000 | 2/0 AWG | 67.4 |
*Approximate mm² conversion for reference only – use AWG for NEC compliance. earth cable size chart
| Phase Conductor Size (mm²) | Min. Earth Conductor Size (mm²) – Copper | |----------------------------|-------------------------------------------| | ≤ 16 | Same as phase conductor | | 25 | 16 | | 35 | 16 | | 50 | 25 | | 70 | 35 | | 95 | 50 | | 120 | 70 | | 150 | 70 | | 185 | 95 | | 240 | 120 | | 300 | 150 | If using aluminum for earthing, multiply the copper size by 1.5–2.0 (but aluminum is rarely used for earth conductors). Example: A 10 mm² phase conductor → use 10 mm² earth. A 50 mm² phase → use 25 mm² earth. B. NEC (USA & other countries using NFPA 70) Method: Equipment grounding conductor (EGC) size is based on the rating of the overcurrent protective device (OCPD) – not directly on phase conductor size. | OCPD Rating (Amps) | Copper EGC Size