The grounding of a distribution box should be connected to a dedicated grounding electrode, typically via the equipment grounding conductor to a ground rod or grounding system, and in main panels, bonded to the neutral.

Main Panel Grounding

In a main service panel, the grounding electrode conductor (GEC) must be connected to the neutral busbar at the service disconnect or main panel, which is also bonded to the equipment grounding system. This ensures that fault currents have a low-resistance path to earth, allowing overcurrent protective devices to operate correctly and safely remove dangerous voltages from the system (NEC Sec. 250.24(A)), . The connection can be made at the meter socket or within the main panel, depending on local utility requirements .

Subpanel Grounding

For a subpanel or remote distribution box, the neutral and ground must remain separate. The grounding terminal bar in the subpanel should be connected to a ground rod or grounding electrode using a properly sized equipment grounding conductor. The neutral busbar in the subpanel should not be bonded to the ground, preventing neutral currents from flowing on metal parts and reducing shock hazards . If the subpanel is in a separate building, an additional ground rod is required.

Grounding Electrode Considerations

• Use copper-bonded steel rods or other NEC-approved electrodes for durability and low resistance .
• Test the grounding system to ensure resistance is below 25 ohms; if not, install multiple rods connected with a continuous conductor .
• All metal parts of the distribution box, including the enclosure, should be bonded to the grounding system to maintain continuity and safety .

Summary

• Main panel: Grounding electrode conductor connects to neutral busbar and ground rod.
• Subpanel: Grounding bar connects to ground rod; neutral remains isolated.
• All panels: Ensure low-resistance path, proper bonding, and compliance with NEC standards. Proper grounding protects personnel, equipment, and ensures safe operation of overcurrent devices while preventing dangerous voltages on conductive surfaces .