Final answer:
Derating factors must be applied when the number of current-carrying conductors in a wireway exceeds 30 to prevent overheating and potential electrical hazards.
Step-by-step explanation:
Derating factors should be applied when the number of current-carrying conductors in a wireway exceeds 30. Derating is important because it ensures that the wires do not overheat due to an excessive number of conductors, which could otherwise increase the resistance and cause power losses. The heat generated by the conductors needs to be dissipated effectively to prevent damage to the insulation and potential electrical fires.
In many electrical codes, there are specific guidelines provided for the maximum number of conductors before derating is necessary, and these guidelines must be followed to ensure safe and efficient operation of electrical systems. While these numbers can vary based on a particular code or set of regulations, the common threshold after which derating factors become applicable is often at 30 or more.