Yes, all metallic distribution cabinets and boxes must be grounded to ensure safety and comply with electrical codes.

Why Grounding is Required

Metallic distribution cabinets and boxes can become electrically live if a fault occurs, such as a loose wire contacting the enclosure. Grounding provides a low-resistance path for fault currents, preventing electric shock and reducing fire risk. Even if the cabinet body is grounded, metal doors and removable panels must also be bonded to the grounding system to prevent static discharge or accidental shock when touched .

Applicable Standards

• NEC 250.148: Requires all metallic parts of electrical boxes, including doors, to be bonded to ground using a designated grounding screw or clip .
• NEC 314.28: Mandates that metal boxes must be reliably grounded and bonded .
• OSHA 1926.405: Specifies that metal covers for pull boxes, junction boxes, and fittings must be grounded .
• NFPA Section 250.4: Emphasizes electrical equipment grounding and bonding to create an effective ground-fault current path .

Grounding Methods

• Metallic boxes: Use a dedicated green grounding screw, bonding clip, or listed bonding device to connect the enclosure to the grounding conductor. Mechanical connections like mounting bolts alone are not sufficient .
• Non-metallic boxes: Typically do not require grounding unless they have metallic frames, hinges, or conductive components .
• Raceways and service conductors: Metal raceways containing service conductors must be bonded to the enclosure using approved methods such as bonding-type locknuts, bushings, or jumpers sized according to NEC Table 250.102(C)(1), .

Practical Considerations

• Ensure all metallic parts, including doors, panels, and covers, are bonded to the grounding system.
• Remove non-conductive coatings like paint at bonding points to ensure a reliable connection, or use fittings designed to maintain conductivity through coatings .
• Verify that grounding conductors are properly sized according to NEC tables to safely carry potential fault currents .
• Maintain accessibility of boxes and covers for inspection and maintenance, as required by NEC 110.26 and OSHA standards . Conclusion: Grounding is mandatory for all metallic distribution cabinets and boxes, including doors and covers, to ensure safety and code compliance. Non-metallic enclosures generally do not require grounding unless they contain conductive components. Proper bonding and grounding prevent electric shock, facilitate fault current flow, and are essential for safe electrical installations.