Check this against the Code
These results come from NEC Table 310.16, 240.4(D) and the standard voltage-drop formula, and they assume no more than three current-carrying conductors in a raceway at 30 degC ambient. Bundling, heat, solar gain and local amendments all change the answer. This is a reference tool, not a design, and it is not a substitute for a licensed electrician or the current printed Code.
Where the numbers come from
- Ampacity: NFPA 70 (National Electrical Code), Table 310.15(B)(16), formerly 310.16 - copper, no more than three current-carrying conductors in a raceway, 30 degC ambient.
- Overcurrent limits on 14, 12 and 10 AWG: NEC 240.4(D).
- Continuous loads sized at 125%: NEC 210.19(A) and 210.20(A).
- Standard breaker ratings: NEC 240.6(A).
- Conductor geometry and resistance: the AWG definition, d(n) = 0.005 in x 92^((36-n)/39).
- Voltage drop: V = 2 x L x R x I, the round trip on a single-phase run.
© 2026 Sarmate Tools · Checked 2026-10-28