What is the maximum allowable sum of cross-sectional areas for conductors in a nonmetallic auxiliary gutter?

In the context of nonmetallic auxiliary gutters, the regulations are established to ensure safety and adequate performance of electrical installations. The maximum allowable sum of cross-sectional areas for conductors refers to the proportion of the gutter's inner cross-section that can be occupied by the combined cross-sectional areas of the conductors within.

The correct answer indicates that only 20% of the gutter's total area is permitted to be filled with conductor cross-sectional areas. This standard is laid out to prevent overcrowding, which can lead to overheating and possible electrical failures. By limiting the conductor area to 20%, it allows adequate space for heat dissipation and maintenance of safe operating conditions.

Additionally, the guideline is rooted in electrical code requirements, which aim to ensure safety and reliability in electrical installations. This limitation helps avoid excessive accumulation of heat, thereby enhancing the overall safety of electrical distribution systems.

While the other options suggest larger percentages, choosing a lower percentage aligns with safety standards that prioritize effective heat management and the physical integrity of the gutter's supporting structure.