For branch-circuit conductors supplying a continuous load, what is the required ampacity?

The required ampacity for branch-circuit conductors supplying a continuous load is correctly defined as 125% of the continuous load plus 100% of any noncontinuous load. This is outlined in the National Electrical Code to ensure that conductors can safely handle the demand placed on them over extended periods.

Continuous loads are defined as loads that are expected to run for three hours or more, and they require additional capacity to account for the heating effects that occur with prolonged use. By specifying 125% of the continuous load, the code provides a safety margin to prevent overheating and potential failures. The inclusion of 100% of any noncontinuous load recognizes that these loads do not operate for extended time periods, which allows them to be calculated at their full ampacity without the additional margin.

This approach ensures that the electrical system is both safe and reliable, accommodating different types of loads effectively. Therefore, the correct answer incorporates both the necessary safety factor for continuous loads and the full capacity for noncontinuous loads to provide a complete solution to conductor sizing.