4 Wire Ampacity & Specifications
NEC ampacity, resistance and typical uses for 4 copper and aluminum wire.
Calculations are built on the 2023 National Electrical Code (NEC) and cross-checked against the published code tables. How we verify. Last reviewed June 2026.
Copper 75°C
85A
Copper 90°C
95A
Aluminum 75°C
65A
Typical breaker
80A
4 Wire Specifications
| Ampacity — Copper (60 / 75 / 90°C) | 70 / 85 / 95 A |
| Ampacity — Aluminum (60 / 75 / 90°C) | 55 / 65 / 75 A |
| Cross-section | 41,740 circular mils |
| DC resistance — Copper | 0.308 Ω / 1000 ft |
| DC resistance — Aluminum | 0.508 Ω / 1000 ft |
| Typical voltage drop (240V) | 1.0% at 50 ft · 2.1% at 100 ft (at 80A) |
Common Uses for 4 Wire
- 70–85A feeders and large appliance circuits
- Sub-panel feeders (70–85A)
Ampacities are from NEC Table 310.16. 14, 12 and 10 AWG are limited to 15A, 20A and 30A overcurrent protection (240.4(D)). Terminations rated 60°C or 75°C usually cap the usable ampacity below the 90°C value.
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