NEC Article 215.2(A)(1) Informational Note 2Worked ExampleElectrical
Three-Phase 480V Feeder Voltage Drop: 500ft 100A
Calculate 3-phase line-to-line voltage drop and percentage loss over 500 feet for a 100A 480V industrial feeder under NEC recommendations.
Direct Answer
13.34 V Drop (2.78% Loss - Compliant with NEC 3% Feeder Recommendation)
Calculated strictly in accordance with NEC Article 215.2(A)(1) Informational Note 2.
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Launch Full InstrumentGiven Scenario Parameters
distance500
wire Gauge1 AWG
current100
voltage480
phase3
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Circuit Parameters & Electrical Load
Calculate wire gauge, voltage drop, and NEC 310.16 ampacity for single-phase, 3-phase, and DC circuits.
Circuit System:
AC Presets:
Standard Breaker Sizes:
Verified NEC Code Proof Available (NEC 215.2(A)(1) & Chapter 9 Table 9)Configuration matches: 500ft 480V 3-Phase 100A Commercial Feeder Proof
Recommended Conductor & Voltage Drop Sizing
Recommended Minimum Conductor Size (COPPER):
1 AWGCOPPER (83,690 CM)
Delivers 466.65V at load terminal with 2.78% voltage drop (-13.35V drop).
Actual Voltage Drop13.35V (2.78%)
Voltage at Load466.65V delivered
NEC Base Ampacity130A (130A derated)
Max 3% Distance539.4 ft limit
Copper vs. Aluminum Conductor ComparisonAt 500 ft run
Copper (Cu) Recommendation1 AWG
2.78% DropHigher conductivity
Aluminum (Al) Recommendation2/0 AWG
2.87% DropLower material weight/cost
Educational and reference calculator only. Conductor sizing must comply with the National Electrical Code (NEC Table 310.16), local AHJ amendments, equipment terminal temperature ratings (60°C/75°C), and short-circuit withstand ratings. Always consult a licensed electrical contractor.
Target ≤ 3% • K = 12.9 Ω·cmil/ft
Circuit Voltage Drop & Conductor Schematic
PASS (< 3%)3-Phase AC
Conductor Size1 AWG (copper)
Voltage at Load466.65 Volts (-13.35V)
Voltage Drop %2.78% (Target ≤ 3%)
Max Distance (3%)539.4 ft limit
Conductor Candidate Sizing & Voltage Drop Comparison Table
COPPER Conductors| Conductor Size | Circular Mils | Base / Derated Ampacity | Voltage Drop | Voltage at Load | Max 3% Distance | Status |
|---|---|---|---|---|---|---|
| 14 AWG | 4,110 CM | 20A / 20A | 271.82V (56.63%) | 208.18V | 26.5 ft | FAIL |
| 12 AWG | 6,530 CM | 25A / 25A | 171.08V (35.64%) | 308.92V | 42.1 ft | FAIL |
| 10 AWG | 10,380 CM | 35A / 35A | 107.63V (22.42%) | 372.37V | 66.9 ft | FAIL |
| 8 AWG | 16,510 CM | 50A / 50A | 67.67V (14.1%) | 412.33V | 106.4 ft | FAIL |
| 6 AWG | 26,240 CM | 65A / 65A | 42.58V (8.87%) | 437.42V | 169.1 ft | FAIL |
| 4 AWG | 41,740 CM | 85A / 85A | 26.77V (5.58%) | 453.23V | 269 ft | FAIL |
| 3 AWG | 52,620 CM | 100A / 100A | 21.23V (4.42%) | 458.77V | 339.1 ft | WARNING |
| 2 AWG | 66,360 CM | 115A / 115A | 16.84V (3.51%) | 463.16V | 427.7 ft | WARNING |
| 1 AWGRecommended | 83,690 CM | 130A / 130A | 13.35V (2.78%) | 466.65V | 539.4 ft | RECOMMENDED |
| 1/0 AWG | 105,600 CM | 150A / 150A | 10.58V (2.2%) | 469.42V | 680.6 ft | PASS |
| 2/0 AWG | 133,100 CM | 175A / 175A | 8.39V (1.75%) | 471.61V | 857.8 ft | PASS |
| 3/0 AWG | 167,800 CM | 200A / 200A | 6.66V (1.39%) | 473.34V | 1081.4 ft | PASS |
| 4/0 AWG | 211,600 CM | 230A / 230A | 5.28V (1.1%) | 474.72V | 1363.7 ft | PASS |
| 250 kcmil | 250,000 CM | 255A / 255A | 4.47V (0.93%) | 475.53V | 1611.2 ft | PASS |
| 300 kcmil | 300,000 CM | 285A / 285A | 3.72V (0.78%) | 476.28V | 1933.5 ft | PASS |
| 350 kcmil | 350,000 CM | 310A / 310A | 3.19V (0.66%) | 476.81V | 2255.7 ft | PASS |
| 400 kcmil | 400,000 CM | 335A / 335A | 2.79V (0.58%) | 477.21V | 2577.9 ft | PASS |
| 500 kcmil | 500,000 CM | 380A / 380A | 2.23V (0.46%) | 477.77V | 3222.4 ft | PASS |
| 600 kcmil | 600,000 CM | 420A / 420A | 1.86V (0.39%) | 478.14V | 3866.9 ft | PASS |
| 750 kcmil | 750,000 CM | 475A / 475A | 1.49V (0.31%) | 478.51V | 4833.6 ft | PASS |
| 1000 kcmil | 1,000,000 CM | 545A / 545A | 1.12V (0.23%) | 478.88V | 6444.8 ft | PASS |
NEC Electrical Code & Safety Disclaimer: This calculation is for design and reference estimation only. Final conductor sizing must comply with the National Electrical Code (NEC Article 310, Table 310.16), local electrical amendments, terminal temperature ratings (typically 75°C), and equipment manufacturer specifications. High-voltage and feeder installations should be verified by a licensed electrical contractor.
Calculation Methodology & Mathematical Steps
1.Calculate Voltage Drop for Recommended 1 AWG (COPPER): (√3 (1.732) × 12.9 × 100A × 500 ft) ÷ 83690 CM
= 13.35V (2.78% drop, 466.65V at load)
2.Determine Maximum Distance for 3% Voltage Drop: (0.03 × 480V × 83690) ÷ (√3 (1.732) × 12.9 × 100A)
= 539.4 ft maximum one-way length
Step-by-Step Solution
Formal engineering derivation citing applicable National Electrical Code articles.
Governing Code Equation
VD = (1.732 * K * L * I) / CM
Citing NEC Article 215.2(A)(1) Informational Note 21
Select 1 AWG copper conductor (CM = 83,690) with copper constant K = 12.9.
2
Apply 3-phase formula: (1.732 * 12.9 * 500 * 100) / 83,690 = 13.34 Volts drop.
3
Calculate percentage drop: (13.34 / 480) * 100 = 2.78%.
4
Compare against code limits: 2.78% is within the NEC recommended 3% feeder limit.
Conclusion: 13.34 V Drop (2.78% Loss - Compliant with NEC 3% Feeder Recommendation)
NEC Article 215.2(A)(1) Informational Note 2