Which wiring method is NOT permitted by the NEC for underground service conductors?

Which wiring method is NOT permitted by the NEC for underground service conductors?

• A. RMC Conduit
• B. HDPE Conduit
• C. Type USE Cable
• D. Type SER Cable

Answer: (D)

Underground service conductors must be installed in a way that provides moisture and physical protection. The NEC allows using raceways like RMC or HDPE conduit, and also cables that are listed for direct burial in wet locations, such as Type USE, for underground service conductors. Type USE Cable is designed for direct burial in soil or in a buried conduit environment, making it suitable for underground service installations. Type SER Cable, however, is not rated for direct burial or underground service conductors; it’s intended for indoor or exposed outdoor installations and isn’t listed for burial. For that reason, the wiring method not permitted is SER Cable.

Underground service conductors must be installed in a way that provides moisture and physical protection. The NEC allows using raceways like RMC or HDPE conduit, and also cables that are listed for direct burial in wet locations, such as Type USE, for underground service conductors. Type USE Cable is designed for direct burial in soil or in a buried conduit environment, making it suitable for underground service installations. Type SER Cable, however, is not rated for direct burial or underground service conductors; it’s intended for indoor or exposed outdoor installations and isn’t listed for burial. For that reason, the wiring method not permitted is SER Cable.