Which article governs the grounding and neutrals in service equipment and subpanels?

• A. Article 260
• B. Article 250
• C. Article 540
• D. Article 720

Answer: (B)

Grounding and bonding rules, including how neutrals are treated at service equipment versus subpanels, are defined in Article 250. This article lays out the equipment grounding conductors that provide a safe path for fault currents and the bonding requirements that connect enclosures and conductive parts to the grounding system. A central rule is that the neutral is bonded to the grounding system at the service equipment only, creating the fault-current return path and ensuring proper operation of overcurrent protection. In service equipment, the neutral is bonded to the enclosure and grounding conductor as part of the service disconnect. In subpanels, the neutral must be isolated from the grounding conductor and the enclosure, with a separate grounding conductor connecting back to the service equipment or grounding-electrode system. This separation prevents stray currents on the grounding path from traveling on the neutral, which helps avoid shock hazards and unwanted energization of metal parts. Other articles cover different topics and do not address grounding and neutral relationships in service equipment and subpanels, so Article 250 is the governing reference.