250 kcmil Voltage Drop at 480V 3-Phase
This page provides detailed voltage drop analysis for 250 kcmil conductors operating at 480V 3-Phase (three-phase). The 250 kcmil copper conductor has a resistance of 0.0515 ohms per 1000 feet and an ampacity of 255 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 250 kcmil wire while staying within the NEC recommended voltage drop limits.
Maximum Distance for 250 kcmil at 480V 3-Phase
The table below shows the maximum one-way distance you can run 250 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 | 32287 ft | 53812 ft | 14.4 V |
| 10A | 16143 ft | 26906 ft | 14.4 V |
| 15A | 10762 ft | 17937 ft | 14.4 V |
| 20A | 8071 ft | 13453 ft | 14.4 V |
| 25A | 6457 ft | 10762 ft | 14.4 V |
| 30A | 5381 ft | 8968 ft | 14.4 V |
| 40A | 4035 ft | 6726 ft | 14.4 V |
| 50A | 3228 ft | 5381 ft | 14.4 V |
| 60A | 2690 ft | 4484 ft | 14.4 V |
| 80A | 2017 ft | 3363 ft | 14.4 V |
| 100A | 1614 ft | 2690 ft | 14.4 V |
Voltage Drop Table — 250 kcmil Copper at 480V 3-Phase
Complete voltage drop matrix for 250 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 0.0515 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% | 0.1V 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% |
| 50 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 0.1% | 0.3V 0.1% | 0.4V 0.1% | 0.5V 0.1% |
| 75 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% | 0.5V 0.1% | 0.7V 0.1% |
| 100 ft | 0.0V 0.0% | 0.1V 0.0% | 0.1V 0.0% | 0.2V 0.0% | 0.2V 0.1% | 0.3V 0.1% | 0.4V 0.1% | 0.5V 0.1% | 0.5V 0.1% | 0.7V 0.1% | 0.9V 0.2% |
| 125 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% | 0.5V 0.1% | 0.6V 0.1% | 0.7V 0.1% | 0.9V 0.2% | 1.1V 0.2% |
| 150 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% | 0.5V 0.1% | 0.7V 0.1% | 0.8V 0.2% | 1.1V 0.2% | 1.3V 0.3% |
| 200 ft | 0.1V 0.0% | 0.2V 0.0% | 0.3V 0.1% | 0.4V 0.1% | 0.5V 0.1% | 0.5V 0.1% | 0.7V 0.1% | 0.9V 0.2% | 1.1V 0.2% | 1.4V 0.3% | 1.8V 0.4% |
| 250 ft | 0.1V 0.0% | 0.2V 0.1% | 0.3V 0.1% | 0.5V 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% |
| 300 ft | 0.1V 0.0% | 0.3V 0.1% | 0.4V 0.1% | 0.5V 0.1% | 0.7V 0.1% | 0.8V 0.2% | 1.1V 0.2% | 1.3V 0.3% | 1.6V 0.3% | 2.1V 0.5% | 2.7V 0.6% |
| 400 ft | 0.2V 0.0% | 0.4V 0.1% | 0.5V 0.1% | 0.7V 0.1% | 0.9V 0.2% | 1.1V 0.2% | 1.4V 0.3% | 1.8V 0.4% | 2.1V 0.5% | 2.9V 0.6% | 3.6V 0.7% |
| 500 ft | 0.2V 0.1% | 0.5V 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% | 2.7V 0.6% | 3.6V 0.7% | 4.5V 0.9% |
When to Use 250 kcmil at 480V 3-Phase
250 kcmil wire at 480V 3-Phase is appropriate for circuits where the amperage does not exceed 255 amps (copper, 75 degrees C) and the voltage drop at the planned distance stays within NEC recommendations. At short distances under 50 feet, 250 kcmil handles 204-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 250 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, 250 kcmil has an ampacity of 204 amps at 75 degrees C and a resistance of 0.0847 ohms per 1000 feet. The higher resistance means aluminum requires approximately 64% 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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