When applying derating factors for conductors in a raceway, the neutral conductor that carries only unbalanced current is required to be counted.

The assertion is that the neutral conductor carrying only unbalanced current is not required to be counted when applying derating factors for conductors in a raceway. This is correct because in practical electrical installations, the neutral conductor can indeed be treated differently when it only carries the unbalanced load of the phase conductors. Derating factors typically apply to the conductors carrying the full load currents that are subjected to heating due to those currents.

In cases where a neutral conductor is carrying only the unbalanced loads, it is often permissible to exclude it from the count when determining the number of conductors in a raceway for the purpose of applying derating factors. This allows for a more accurate assessment of the thermal effects and load conditions within the raceway system.

The reasoning behind this is grounded in safety and efficiency; it allows for a more effective management of the current-carrying capacities of conductors, ensuring that the system operates within safe temperature limits while not unduly penalizing installations that may have well-designed neutral configurations.