What is acceptable voltage drop on a 415V circuit?

Most engineers target 3% or less on branch circuits. Over 5% total (feeder plus branch) is generally considered poor practice. Check your local authority having jurisdiction.

What wire size should I use for a 415V circuit?

Wire size depends on load current, run length, and acceptable voltage drop. Use the voltage drop calculator linked above to find the right gauge for your specific run.

Voltage Drop at 415V (Three-Phase AC)

415V three-phase is common in international commercial and industrial power systems.

Open 415V Voltage Drop Calculator with Example Values →

Why 415V Systems Need Attention

At 415V, voltage drop matters less on short runs but becomes significant over long feeders in large buildings or industrial plants.

Example Calculation

For a 415V Three-Phase AC circuit at 80 A over 180 ft using 4 AWG copper:

Voltage drop = 1.732 x I x R = 1.732 x 80 x (ohms per ft for 4 AWG x 180 ft)

Run this example in the calculator →

Common Applications at 415V

International industrial motors
Process equipment
Factory distribution

Common Questions

What is the acceptable voltage drop for a 415V circuit?

Most engineers target 3% or less on branch circuits and 5% total (feeder plus branch). These are general guidelines, not hard NEC requirements. Check your local code.

What wire gauge should I use for a 415V circuit?

It depends on load current and run length. Use the voltage drop calculator with your specific values. A longer run or heavier load requires a larger gauge.

Does voltage drop affect safety?

Excessive voltage drop can cause motors to overheat, breakers to nuisance-trip, and equipment to malfunction. It is not just an efficiency issue.

Can I use aluminum wire on a 415V circuit?

Aluminum is commonly used for larger feeders (service entrances, subpanel feeds). For small branch circuits, copper is generally required. Aluminum has higher resistance than copper for the same gauge, so voltage drop is worse for the same wire size.