In underground circuit conductors, where must the overcurrent protective device be located?

• A. At the point where the conductors receive their supply
• B. At the service disconnect
• C. On the branch circuit panel near the outlets
• D. At the transformer only

Answer: (B)

Overcurrent protection should be placed at the point where the circuit originates from the source. For underground feeders, that means the service disconnect. Positioning the protective device there ensures the entire underground run and any downstream equipment are protected and can be quickly de-energized if a fault occurs. If protection were moved downstream (for example, only at a branch panel near outlets), faults on the underground portion could leave unprotected length of conductors, increasing fire and shock risk and delaying a proper shutdown. Placing protection only at the transformer wouldn’t provide a single, reliable disconnect for the building’s circuits or proper coordination with the service equipment. Therefore, the protective device belongs at the service disconnect.