How should outdoor or detached structures be wired from the main building?

• A. With underground trenching only.
• B. With appropriate feeders or branch circuits run in approved raceways, protected from damage, and with separate ground-fault/arc-fault protection as required.
• C. With loose cords and no protection as long as in the shade.
• D. With only lighting circuits.

Answer: (B)

Outdoor or detached structures must be supplied from the main building using feeders or branch circuits that travel in approved raceways. This keeps the conductors protected from moisture, physical damage, and the elements, which is essential for safe outdoor wiring. The circuits also need proper overcurrent protection and, where required by the code, ground-fault and arc-fault protection to reduce shock risk and fire danger in outdoor locations. That means using appropriate protective devices (GFCI where required for outdoor/wet locations and AFCI where required for dwelling circuits) and ensuring the wiring is installed in a way that prevents damage and deterioration.

This approach is safer and more compliant than relying on underground trenching alone, loose cords, or wiring only for lighting, which either neglects other loads, lacks protection, or creates exposure to damage. It’s also standard to run a grounding conductor with the feeder and install a grounding-electrode system at the detached structure, with a means to disconnect as required.