The grounded conductor for feeders shall be permitted to be sized by adding ___ percent of the continuous load and ___ percent of the noncontinuous load.

• A. 125,100
• B. 100,125
• C. 100,100
• D. 100,80

Answer: (C)

The main idea is that the grounded conductor (the neutral) must be sized to carry the maximum possible return current from all loads on the feeder. Since both continuous and noncontinuous loads can contribute current through the neutral, the sizing rule uses the full value of each type of load. That’s why you add 100% of the continuous load and 100% of the noncontinuous load to determine the neutral size.

For example, if you have 20 A of continuous load and 30 A of noncontinuous load on the feeder, size the grounded conductor to handle 50 A (20 + 30). The neutral is not reduced by any factor here, so both portions are taken at full value.

Other percentage combinations would imply applying reductions or extra allowances to one type of load, which isn’t how this sizing rule is applied for the grounded conductor in feeders.