250 kcmil THHN Aluminum Ampacity
250 kcmil aluminum THHN: 230A base at 90°C, 205A usable after 110.14(C) termination limit.
Base230A
Usable205A
NEC Table310.16
Full derating calculation
Applications
250 kcmil aluminum is commonly used for commercial service feeders, large subpanels (200-225A), and industrial branch circuits.
Voltage drop by distance
| Distance (ft) | Verdict | 240V Drop | % Drop |
|---|---|---|---|
| 50 ft | OK | 1.7V | 0.7% |
| 75 ft | OK | 2.6V | 1.1% |
| 100 ft | OK | 3.5V | 1.4% |
| 150 ft | OK | 5.2V | 2.2% |
| 200 ft | OK | 7.0V | 2.9% |
| 250 ft | Caution | 8.7V | 3.6% |
| 300 ft | Caution | 10.4V | 4.3% |
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NEC 2023 references verified February 2026