What type of installation is permitted for luminaires identified for through-wiring?

The correct choice for the type of installation permitted for luminaires identified for through-wiring is when they are configured as a conductor raceway. In this context, luminaires that are designed for through-wiring allow electrical conductors to pass through them, enabling connection of multiple fixtures in a series. This setup is advantageous because it minimizes the number of junction boxes needed and maintains a cleaner installation.

Using luminaires as conductor raceways complies with the National Electrical Code, which specifies that certain types of lighting fixtures can serve as pathways for electrical conductors. This capability is particularly useful in installations where multiple lights are required, as it simplifies the task of wiring them while ensuring that all connections are secure and compliant with safety standards.

The other options do not align with the NEC guidelines for luminaires designed for through-wiring. Directly connecting the luminaires to the main circuit could potentially bypass the specifications meant for through-wiring, while requiring a disconnecting means introduces an unnecessary complication for fixtures primarily designed for seamless electrical flow. Employing only flexible cords may also violate the more stringent installation requirements outlined in the NEC for permanent wiring solutions.