Cable Ampacity Derating
Calculate derated ampacity based on NEC 310.15 correction factors.
NEC 310.15 Derating
Final ampacity = Base x Temp Factor x Fill Factor
For continuous loads, conductor must be sized for 125% of load (or use 80% of ampacity).
NEC 310.15(B)(1) - Conduit Fill Adjustment Factors
| Conductors in Raceway | Adjustment Factor |
|---|---|
| 1-3 | 100% |
| 4-6 | 80% |
| 7-9 | 70% |
| 10-20 | 50% |
| 21-30 | 45% |
| 31-40 | 40% |
| 41+ | 35% |
Note: Only current-carrying conductors count. Equipment grounding and neutral conductors (under certain conditions) may not count.