Which means is NOT permitted for identifying an equipment grounding conductor?

Identifying an equipment grounding conductor requires adherence to specific Color Code standards established in electrical codes. The primary purpose of the equipment grounding conductor is to ensure safety by providing a path to ground in the event of a fault, and thus must be easily recognizable.

Green insulation is permitted and clearly indicates grounding conductors. White insulation is typically reserved for neutral conductors, while black insulation often designates hot conductors in AC systems.

Gray insulation can sometimes be ambiguous, but it is not an acceptable designation for an equipment grounding conductor. By using gray insulation, there could be confusion in identifying the wire's purpose, which is why it is not permitted for this application. Ensuring that equipment grounding conductors are easily identifiable through standardized color coding is crucial for maintaining safety in electrical installations.