What is the required ampacity for branch circuit conductors supplying a single motor in continuous duty?

The required ampacity for branch circuit conductors supplying a single motor in continuous duty is determined by the National Electrical Code (NEC) provisions, which specify that branch circuit conductors must have an ampacity that is at least 125% of the motor's full-load current. This requirement is in place to ensure that the conductors can handle the continuous load of the motor without overheating.

By calculating the ampacity at 125% of the full-load current, you are accounting for potential increases in current that may occur during operation, as well as any ambient temperature effects that could further challenge the conductors' ability to carry current safely. This provides a safety margin, reducing the risk of overheating and ensuring reliable operation over time.

In this context, other options such as 100%, 110%, or 150% of full-load current do not meet the necessary standards for continuous duty motors. The NEC has intentionally defined the 125% rule to promote safety and efficiency, making it the correct choice in this scenario.