What is the minimum size copper wire required for a 230-volt, single-phase circuit supplying a 65-ampere load over a distance of 250 feet?

To determine the minimum size of copper wire required for a 230-volt, single-phase circuit supplying a 65-ampere load over a distance of 250 feet, it’s important to consider both the wire's current-carrying capacity (ampacity) and voltage drop.

For a 65-ampere load, you would typically refer to the National Electrical Code (NEC) tables which provide the ampacity for different wire sizes. In general, a 2 AWG copper wire is rated for a current of approximately 95 amperes at a temperature rating of 60-75°C, making it adequate for carrying a 65-ampere load safely.

Moreover, voltage drop is a significant consideration for longer distances. The NEC suggests that a voltage drop of 3% is acceptable for branch circuits. Calculating the voltage drop for a 250-foot run with a 65-amp load using the resistance of copper wire, a 2 AWG wire will keep the voltage drop within acceptable limits while still carrying the required current. In fact, using smaller wire sizes, such as 3 AWG or 4 AWG, may result in a voltage drop that exceeds acceptable standards over that distance, which can lead to ineff