The minimum size circuit conductors for a 115/230-V 1Ø 5 hp motor using a 1-pole breaker are what size?

To determine the minimum size circuit conductors for a 115/230-V single-phase 5 hp motor, it is essential to consider the full-load current rating of the motor. The National Electrical Code (NEC) provides guidelines and tables for calculating the appropriate wire size based on the motor's horsepower and voltage.

For a 5 hp motor operating at 230 volts, the full-load current typically is around 25 amps according to NEC standards. When sizing conductors, it is necessary to consider not only the full-load current but also factors like the length of the run, the ambient temperature, and any potential derating due to the installation environment.

The appropriate conductor size is then determined based on these calculations. Following standard practices, a number 10 AWG copper wire is typically sufficient to handle the load safely, accounting for any derating factors that may apply in specific installations. Therefore, a number 10 conductor is the minimum size recommended for this application, ensuring sufficient current-carrying capacity while adhering to code requirements for safety and efficiency. This is why the correct answer is number 10.