What is the correct treatment of neutrals and grounds in a subpanel?

• A. Neutrals must be bonded to grounds in a subpanel.
• B. Grounds must be isolated from neutrals in a subpanel.
• C. Neutrals must be isolated from grounds in a subpanel.
• D. Grounds and neutrals can be bonded at any point in a subpanel

Answer: (C)

Separating neutral and ground paths in a subpanel is essential to keep normal return current on the neutral conductor and prevent it from traveling on the equipment grounding conductor. In a subpanel, the neutral bus must be isolated from the panel enclosure and from any grounding conductors; there is no bond between neutral and ground at this point. The grounding conductor from the feeder, along with all branch-circuit grounds, lands on a grounding bus that is bonded to the panel enclosure. Bonding neutral to ground is reserved for the main service disconnect, not the subpanel. This arrangement avoids stray currents on metal enclosures and ensures fault currents are safely carried back to the source, improving safety and proper operation of protective devices.