The sum of the cross-sectional area of individual conductors cannot exceed what percentage of the cross-sectional area of the wireway?

In wiring and conduit applications, it's crucial to maintain proper allowances for conductors within a wireway to ensure safety, reduce the risk of overheating, and comply with code requirements. When it is stated that the sum of the cross-sectional areas of individual conductors cannot exceed a certain percentage of the cross-sectional area of the wireway, this refers to ensuring an adequate amount of space is available for air circulation and to prevent crowding.

The correct answer indicates that the total area taken up by the conductors should not exceed 50% of the wireway's cross-sectional area. This rule helps to provide room for any thermal expansion, mechanical stresses, and the potential for heat dissipation that could lead to overheating if conductors are tightly packed together. Adhering to this guideline maintains both performance and safety standards within electrical installations.

In contrast, other choices would not provide enough space, increasing risks associated with heat buildup, potential short circuits, or even equipment failure. Therefore, maintaining a restriction at 50% is a balanced approach, promoting safety and functionality in electrical wiring.