Sizing the grounded conductor for feeders can involve adding percentages of loads. Which combination is permitted?

Sizing the grounded conductor for feeders can involve adding percentages of loads. Which combination is permitted?

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

Answer: (A)

Grounded conductor (neutral) sizing for feeders is about carrying the unbalanced current from all the circuits on the feeder. When you determine how large the neutral must be, you take the full load present for each category and do not apply extra multipliers to the neutral calculation. The 125% or other percentages are used for sizing the ungrounded conductors for continuous loads, not for the neutral itself. So the neutral should reflect the actual sum of the loads without increasing one of them by 125% or decreasing it, which is why using both loads at 100% is appropriate. The option with 100% for both loads represents the correct approach, while the other choices would misrepresent or over/under-size the neutral.

Grounded conductor (neutral) sizing for feeders is about carrying the unbalanced current from all the circuits on the feeder. When you determine how large the neutral must be, you take the full load present for each category and do not apply extra multipliers to the neutral calculation. The 125% or other percentages are used for sizing the ungrounded conductors for continuous loads, not for the neutral itself. So the neutral should reflect the actual sum of the loads without increasing one of them by 125% or decreasing it, which is why using both loads at 100% is appropriate. The option with 100% for both loads represents the correct approach, while the other choices would misrepresent or over/under-size the neutral.