How many current carrying conductors necessitate derating factors in a wireway?

The correct answer is based on the National Electrical Code (NEC) provisions concerning conductor derating in wireways and raceways. According to NEC guidelines, when the number of current-carrying conductors in a wireway exceeds a certain threshold, derating factors must be applied to prevent overheating and ensure safe operation.

When there are more than 20 current-carrying conductors present, the NEC specifies that the allowable ampacity of the conductors must be adjusted, or "derated," to account for the increased thermal conditions created by the proximity of the conductors.

By recognizing that the derating process kicks in with this number, the choice highlighting 30 as a critical threshold reflects this understanding, as it emphasizes correct energy management and safety protocols in electrical installations. The need for derating ensures that the conductors can operate effectively within their designed thermal limits, thereby preventing potential fire hazards or equipment failure.

This rationale clarifies why the selected answer specifically addresses industry standards and safety measures related to wireways and raceways.