350 kcmil THHN Copper Ampacity
350 kcmil copper THHN: 350A base at 90°C, 310A usable after 110.14(C) termination limit.
Base350A
Usable310A
NEC Table310.16
Full derating calculation
Applications
350 kcmil copper is commonly used for large commercial feeders (260-310A) and industrial motor feeders.
Voltage drop by distance
| Distance (ft) | Verdict | 240V Drop | % Drop |
|---|---|---|---|
| 50 ft | OK | 1.1V | 0.5% |
| 75 ft | OK | 1.7V | 0.7% |
| 100 ft | OK | 2.3V | 0.9% |
| 150 ft | OK | 3.4V | 1.4% |
| 200 ft | OK | 4.5V | 1.9% |
| 250 ft | OK | 5.7V | 2.4% |
| 300 ft | OK | 6.8V | 2.8% |
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NEC 2023 references verified February 2026