Electrical Cable Size May 2026

[ R = \rho \fracLA ]

[ A = \frac\sqrtI_sc^2 \times tk ]

: 120V single-phase, 20A load, 150 ft one-way, copper, target VD <3% (3.6V). electrical cable size

#10 AWG: 3.9 ohms/1000 ft → R = 2×150/1000×3.9 = 1.17 ohms → VD = 23.4V (19.5%) still too high. [ R = \rho \fracLA ] [ A

Example: 90°C wire in 50°C ambient → factor 0.71. NEC 310.15(C)(1): More than 3 current-carrying conductors in a raceway or cable. 150 ft one-way

#6 AWG: 2.4 ohms/1000 ft → R = 0.72 ohms → VD = 14.4V (12%) – still high.

[ VD = \sqrt3 \times K \times I \times L / A ]