According to the NEC, what is the minimum size at which conductors must be stranded in raceways?

The minimum size at which conductors must be stranded in raceways is established by the National Electrical Code (NEC) to ensure flexibility, workability, and reduce the risk of damage during installation. Stranded conductors are typically required in larger sizes because they provide more flexibility compared to solid conductors, making them easier to route and maneuver through raceways.

The correct choice reflects NEC guidelines which state that conductors of size 8 AWG and larger must be stranded to accommodate bending and installation in confined spaces. This requirement helps to prevent issues such as conductor breakage or fatigue that can occur with solid conductors when manipulated in tight areas.

Understanding this standard is crucial for ensuring the physical integrity and reliability of electrical installations. This context reinforces why stranded conductors are preferentially required in raceways for larger sizes, which promotes safety and compliance in electrical engineering practices.