If a 100A load is connected, how should the neutral conductor be sized?

The correct approach to sizing the neutral conductor when a load is connected is by considering the need to balance the total loads. When dealing with a 100A load, it's important to recognize that the neutral conductor is responsible for carrying the unbalanced current of the system. In many cases, especially in multi-wire branch circuits, the current on the neutral will vary depending on the loads on each phase and the overall balance between them.

Proper sizing of the neutral is crucial because if the neutral is undersized, it can overheat due to carrying excess current, potentially leading to safety hazards, such as electrical fires. Balancing the total loads ensures that the neutral conductor can adequately handle the return current without being overloaded, providing safety and compliance with electrical codes.

In contrast, choosing a size based on the load's amperage, selecting a standard size, or sizing it based on the circuit breaker would not take into account the actual operating conditions and may lead to improper sizing in scenarios where unbalanced loads are present. Hence, factor D emphasizes the importance of balancing the loads for optimal neutral conductor sizing.