Is a neutral conductor carrying only unbalanced current counted when determining ampacity?

The reasoning for disregarding the neutral conductor carrying only unbalanced current when determining ampacity is rooted in the principles of electrical circuits, particularly in how currents flow and interact in multi-phase systems. In a balanced three-phase system, the current expected in the neutral should ideally be zero, as the phases cancel each other out. Therefore, the neutral only carries current when there's an imbalance in the system.

When assessing ampacity, it is generally concerned with the overall current that contributes to heat generation within conductors due to resistance. In instances where the neutral conductor is solely carrying unbalanced current from the other phases, it does not contribute to the total current load that is typically used in ampacity calculations for the purpose of heat management.

This approach simplifies the process of determining the allowable load and protects the conductor integrity by ensuring it is not overloaded. Even though unbalanced current can flow through the neutral under certain circumstances, the determination of ampacity focuses on ensuring that the primary conductors carrying the actual load are calculated for their thermal limits, rather than adding the uncertainty that a variable neutral current might introduce.

The other options introduce conditions that either unnecessarily complicate the calculation of ampacity using grounded or specific configurations of the neutral, but the standard practice simplifies it by not