Isolated ground receptacles are only permitted to be used with equipment grounding conductors of branch circuits that are isolated and installed to meet the provisions of which NEC section?

• A. NEC 210.8
• B. NEC 250.146(D)
• C. NEC 300.5
• D. NEC 240.6

Answer: (B)

Isolated ground receptacles rely on an equipment grounding conductor that is kept separate from all other grounding paths and run back to the main grounding system, so the grounding path remains noise-free for sensitive equipment. The NEC provision that specifies how this isolated grounding conductor must be installed is NEC 250.146(D), which lays out the requirements for isolated grounding receptacles and the need for the grounding conductor to be isolated from other grounding conductors and connected back to the service equipment’s grounding system. This is why this option is the correct choice. Other sections address different topics such as GFCI protection, general wiring rules, or overcurrent protection, which do not govern isolated grounding conductors.