What size overcurrent protective device should be selected for a 120V feeder with a continuous load at 20A and a noncontinuous load at 25A?

To determine the appropriate size of the overcurrent protective device for a feeder that has both continuous and noncontinuous loads, it is important to follow the guidelines set by the National Electrical Code (NEC).

In this scenario, you have a continuous load of 20A and a noncontinuous load of 25A. Continuous loads are defined as those that run for three hours or more, and the NEC requires that these loads must be multiplied by 125% to ensure that the overcurrent device can handle the load without tripping.

So for the continuous load calculation:

• 125% of 20A = 25A (which is the current rating that should be used for the continuous load).

Now, for the noncontinuous load of 25A, no adjustment is necessary, so we take it as is.

Next, add the adjusted continuous load to the noncontinuous load:

• Total = 25A (from the continuous load) + 25A (from the noncontinuous load) = 50A.

The selected overcurrent protective device should be rated at least this total load. Therefore, the proper overcurrent protection in this case would be 50A. It is important to choose the next standard size above this calculated load