Special permission must be obtained to allow conductors larger than what gauge to be installed in a cellular metal floor raceway?

The correct choice reflects the standards outlined in the National Electrical Code (NEC), which governs the installation of wiring and electrical components. Specifically, for cellular metal floor raceways, there are restrictions regarding the size of conductors that can be installed without special permission. Conductors larger than 1/0 AWG require special permission to ensure safety and compliance with electrical codes.

This requirement exists because larger conductors generate more heat and may necessitate more robust installation methods to maintain safe operating conditions. The NEC aims to prevent potential hazards such as overheating or fire risks that could arise from improper installations in confined spaces like raceways.

Therefore, in the context of ensuring safety and adherence to established electrical practices, special permission is mandated for conductors exceeding the 1/0 AWG size in cellular metal floor raceways.