20A load, 120V, 100ft run, 12 AWG copper wire
Calculation: VD = 2 × 0.017241 × 20 × 30.48 / 3.31
Result: 6.4V drop (5.3%)
Status: Exceeds 3% recommendation
Solution: Use 10 AWG wire for 3.2V drop (2.7%)
100A load, 208V, 200ft run, 1 AWG copper wire
Calculation: VD = √3 × 0.129 × 100 × 60.96 / 83.69
Result: 9.4V drop (4.5%)
Status: Exceeds 3% feeder recommendation
Solution: Use 1/0 AWG wire for 7.5V drop (3.6%)
50A motor starting current, 480V, 150ft run, 6 AWG copper wire
Calculation: VD = √3 × 0.491 × 50 × 45.72 / 26.24
Result: 42.6V drop (8.9%)
Status: Excessive for motor starting (max 15%)
Solution: Use 2 AWG wire for 21.3V drop (4.4%)
25A DC current, 12V system, 50ft run, 10 AWG copper wire
Calculation: VD = 2 × 1.018 × 25 × 15.24 / 5.26
Result: 1.5V drop (12.5%)
Status: Too high for low voltage DC (max 2%)
Solution: Use 6 AWG wire for 0.6V drop (5%)
12A load, 120V, 75ft run through wet location, 12 AWG copper wire
Calculation: VD = 2 × 2.0 × 12 × 22.86 / 3.31
Result: 3.3V drop (2.8%)
Status: Within 3% recommendation
Note: Higher resistance due to wet conditions considered
8A LED load, 277V, 300ft run, 14 AWG copper wire
Calculation: VD = 2 × 2.57 × 8 × 91.44 / 2.08
Result: 9.0V drop (3.2%)
Status: Slightly exceeds 3% recommendation
Solution: Use 12 AWG wire for 5.7V drop (2.1%)
VD = 2 × R × I × L / A
VD = √3 × R × I × L / A
Where: VD = Voltage Drop, R = Resistance (Ω·m), I = Current (A), L = Length (m), A = Cross-sectional Area (mm²)
3% Maximum
Outlets, receptacles, lighting
3% Maximum
Panel to panel connections
5% Maximum
Feeder + branch circuit