For a feeder circuit with a continuous load of 10A and a noncontinuous load of 5A, what should the overcurrent protective device be sized at?

To properly size the overcurrent protective device for a feeder circuit, both the continuous load and the noncontinuous load must be considered. The National Electrical Code (NEC) specifies that continuous loads should be calculated at 125% of their rating, while noncontinuous loads can be calculated at their full value.

In this scenario, the continuous load is 10A. When calculating for a continuous load, it should be multiplied by 125%, which results in:

10A * 1.25 = 12.5A

The noncontinuous load is simply 5A, so it remains as is.

Now, to find the total required capacity for the overcurrent protective device, you add the adjusted value of the continuous load to the noncontinuous load:

12.5A (from the continuous load) + 5A (from the noncontinuous load) = 17.5A

This total of 17.5A determines the minimum rating for the overcurrent protective device. Therefore, an overcurrent protective device sized at 17.5A is appropriate, as it effectively protects the circuit without being undersized or oversized. This selection helps to avoid nuisance tripping while ensuring adequate protection against overcurrents.