400 kcmil Voltage Drop at 480V 3-Phase
This page provides detailed voltage drop analysis for 400 kcmil conductors operating at 480V 3-Phase (three-phase). The 400 kcmil copper conductor has a resistance of 0.0321 ohms per 1000 feet and an ampacity of 335 amps at 75 degrees C per NEC Table 310.16. Use the tables below to determine the voltage drop at any distance and amperage combination, or to find the maximum distance you can run 400 kcmil wire while staying within the NEC recommended voltage drop limits.
Maximum Distance for 400 kcmil at 480V 3-Phase
The table below shows the maximum one-way distance you can run 400 kcmil copper conductor at 480V 3-Phase for each amperage level while maintaining voltage drop at or below 3% (branch circuit) and 5% (feeder + branch combined). If your planned run exceeds these distances, you must use a larger wire gauge. These values assume three-phase power with a 1.732 multiplier in the voltage drop formula.
| Amperage | Max Distance (3%) | Max Distance (5%) | 3% Drop = 14.4V |
|---|---|---|---|
| 5A | 51801 ft | 86335 ft | 14.4 V |
| 10A | 25900 ft | 43167 ft | 14.4 V |
| 15A | 17267 ft | 28778 ft | 14.4 V |
| 20A | 12950 ft | 21583 ft | 14.4 V |
| 25A | 10360 ft | 17267 ft | 14.4 V |
| 30A | 8633 ft | 14389 ft | 14.4 V |
| 40A | 6475 ft | 10791 ft | 14.4 V |
| 50A | 5180 ft | 8633 ft | 14.4 V |
| 60A | 4316 ft | 7194 ft | 14.4 V |
| 80A | 3237 ft | 5395 ft | 14.4 V |
| 100A | 2590 ft | 4316 ft | 14.4 V |
Voltage Drop Table — 400 kcmil Copper at 480V 3-Phase
Complete voltage drop matrix for 400 kcmil copper conductor at 480V 3-Phase. Each cell shows the voltage drop in volts and percentage. Cells in red exceed the 3% NEC recommendation for branch circuits. Cells within the green range are NEC compliant. This table uses the three-phase voltage drop formula with a conductor resistance of 0.0321 ohms per 1000 feet.
| Distance | 5A | 10A | 15A | 20A | 25A | 30A | 40A | 50A | 60A | 80A | 100A |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 25 ft | 0.0V 0.0% | 0.0V 0.0% | 0.0V 0.0% | 0.0V 0.0% | 0.0V 0.0% | 0.0V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.1V 0.0% |
| 50 ft | 0.0V 0.0% | 0.0V 0.0% | 0.0V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.2V 0.0% | 0.2V 0.1% | 0.3V 0.1% |
| 75 ft | 0.0V 0.0% | 0.0V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.2V 0.0% | 0.2V 0.0% | 0.3V 0.1% | 0.3V 0.1% | 0.4V 0.1% |
| 100 ft | 0.0V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.2V 0.0% | 0.2V 0.1% | 0.3V 0.1% | 0.3V 0.1% | 0.4V 0.1% | 0.6V 0.1% |
| 125 ft | 0.0V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.2V 0.0% | 0.2V 0.0% | 0.3V 0.1% | 0.3V 0.1% | 0.4V 0.1% | 0.6V 0.1% | 0.7V 0.1% |
| 150 ft | 0.0V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.2V 0.0% | 0.2V 0.0% | 0.3V 0.1% | 0.3V 0.1% | 0.4V 0.1% | 0.5V 0.1% | 0.7V 0.1% | 0.8V 0.2% |
| 200 ft | 0.1V 0.0% | 0.1V 0.0% | 0.2V 0.0% | 0.2V 0.1% | 0.3V 0.1% | 0.3V 0.1% | 0.4V 0.1% | 0.6V 0.1% | 0.7V 0.1% | 0.9V 0.2% | 1.1V 0.2% |
| 250 ft | 0.1V 0.0% | 0.1V 0.0% | 0.2V 0.0% | 0.3V 0.1% | 0.3V 0.1% | 0.4V 0.1% | 0.6V 0.1% | 0.7V 0.1% | 0.8V 0.2% | 1.1V 0.2% | 1.4V 0.3% |
| 300 ft | 0.1V 0.0% | 0.2V 0.0% | 0.3V 0.1% | 0.3V 0.1% | 0.4V 0.1% | 0.5V 0.1% | 0.7V 0.1% | 0.8V 0.2% | 1.0V 0.2% | 1.3V 0.3% | 1.7V 0.3% |
| 400 ft | 0.1V 0.0% | 0.2V 0.1% | 0.3V 0.1% | 0.4V 0.1% | 0.6V 0.1% | 0.7V 0.1% | 0.9V 0.2% | 1.1V 0.2% | 1.3V 0.3% | 1.8V 0.4% | 2.2V 0.5% |
| 500 ft | 0.1V 0.0% | 0.3V 0.1% | 0.4V 0.1% | 0.6V 0.1% | 0.7V 0.1% | 0.8V 0.2% | 1.1V 0.2% | 1.4V 0.3% | 1.7V 0.3% | 2.2V 0.5% | 2.8V 0.6% |
When to Use 400 kcmil at 480V 3-Phase
400 kcmil wire at 480V 3-Phase is appropriate for circuits where the amperage does not exceed 335 amps (copper, 75 degrees C) and the voltage drop at the planned distance stays within NEC recommendations. At short distances under 50 feet, 400 kcmil handles 268-amp loads with comfortable voltage drop margin. As the distance increases, the voltage drop grows proportionally, and at some point a larger gauge becomes necessary.
If 400 kcmil does not provide adequate voltage drop performance for your run distance, consider the next larger gauge. Each step up in wire size roughly doubles the maximum distance for the same voltage drop percentage. Alternatively, if the circuit operates at 120 volts and the distance is problematic, consider whether the load can be served by a 240-volt circuit instead, which halves the percentage voltage drop and doubles the effective run distance for the same wire gauge.
For aluminum conductors, 400 kcmil has an ampacity of 268 amps at 75 degrees C and a resistance of 0.0529 ohms per 1000 feet. The higher resistance means aluminum requires approximately 65% more distance correction compared to copper, often requiring an increase of one or two gauge sizes to match copper's voltage drop performance at the same distance.
Related Wire Sizes at 480V 3-Phase
Compare voltage drop performance across different wire gauges at 480V 3-Phase. Larger gauges have lower resistance and can run longer distances with less voltage drop.
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