All metallic distribution boxes and cabinets must be grounded to ensure safety and compliance with NEC standards, while non-metallic enclosures generally do not require grounding unless they contain metallic components.

Why Grounding is Necessary

Grounding provides a safe path for fault currents and prevents electric shock. If a metallic enclosure or cabinet is not grounded, any accidental contact with live wires inside can energize the cabinet, posing a serious risk to anyone touching it. Grounding also helps dissipate static charges that can accumulate on metal surfaces, which is particularly important in high-voltage or industrial environments .

NEC Requirements

• NEC 250.148 mandates that all metallic parts of electrical boxes, including cabinet doors, must be bonded to ground using a designated grounding screw or clip .
• NEC 314.28 requires that metal boxes be reliably grounded and bonded to maintain electrical continuity and safety .
• NEC 110.26 ensures that workers can safely access equipment doors without obstruction, which indirectly supports proper grounding practices . Non-metallic boxes, such as PVC or composite enclosures, typically do not require grounding unless they have metallic frames, hinges, or other conductive parts .

Practical Installation Guidelines

• Use a dedicated green grounding screw or bonding clip for metallic doors and panels; do not rely on mounting bolts alone .
• Ensure the grounding path is continuous and connected to the building's main grounding system, with resistance ideally below 25 ohms for effective fault dissipation .
• Verify that all metallic components inside the enclosure, including racks, panels, and doors, are bonded to the ground bar to prevent accidental energization .

Summary

All metallic distribution boxes and cabinets, including doors and internal metallic parts, must be grounded to comply with NEC standards and ensure safety. Non-metallic enclosures generally do not require grounding unless they contain conductive components. Proper grounding prevents electric shock, protects equipment, and ensures compliance with electrical codes .