For a feeder supplying household cooking equipment and electric clothes dryers, the maximum unbalanced load on the neutral conductor shall be considered as ___ of the load on the ungrounded conductors.

For a feeder supplying household cooking equipment and electric clothes dryers, the maximum unbalanced load on the neutral conductor shall be considered as ___ of the load on the ungrounded conductors.

• A. 40%
• B. 50%
• C. 70%
• D. 80%

Answer: (C)

In a feeder that has two hot (ungrounded) conductors sharing a neutral, the neutral current is the unbalanced portion of the currents on those hot legs. To size the neutral safely for typical household loads (like cooking equipment and a clothes dryer), a conservative code-based assumption is that the neutral may carry up to 70% of the total load on the ungrounded conductors. So the maximum neutral load is 0.7 times the sum of the currents on the hot conductors. This accounts for potential imbalance between the two legs while keeping the neutral adequately protected. For example, if the two hot legs together carry 100 A, you’d size the neutral for up to 70 A. The other percentages aren’t the standard design value used in this scenario.

In a feeder that has two hot (ungrounded) conductors sharing a neutral, the neutral current is the unbalanced portion of the currents on those hot legs. To size the neutral safely for typical household loads (like cooking equipment and a clothes dryer), a conservative code-based assumption is that the neutral may carry up to 70% of the total load on the ungrounded conductors. So the maximum neutral load is 0.7 times the sum of the currents on the hot conductors. This accounts for potential imbalance between the two legs while keeping the neutral adequately protected. For example, if the two hot legs together carry 100 A, you’d size the neutral for up to 70 A. The other percentages aren’t the standard design value used in this scenario.