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) | 240V Drop | % Drop | Verdict |
|---|---|---|---|
| 50 ft | 1.7V | 0.7% | OK |
| 75 ft | 2.6V | 1.1% | OK |
| 100 ft | 3.5V | 1.4% | OK |
| 150 ft | 5.2V | 2.2% | OK |
| 200 ft | 7.0V | 2.9% | OK |
| 250 ft | 8.7V | 3.6% | Caution |
| 300 ft | 10.4V | 4.3% | Caution |
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NEC 2023 references verified April 2026