Grounding of the meter inside the secondary distribution box

The meter inside a secondary distribution box should be grounded at a single point, typically at the meter base, with a properly sized grounding conductor connected to the grounding electrode system.

Single-Point Grounding

For safety and compliance, grounding must be done at a single point to prevent objectionable currents and ensure proper fault clearing. In systems with a single meter base and service box, the grounding connection can be made either at the meter base or the service box, but not at multiple points on the supply side of the distribution system . In multi-gang meter bases, grounding must be at the meter base, with bonding conductors connecting each service box to maintain continuity .

Grounding Conductor and Electrode

The grounding conductor (also called the Grounding Electrode Conductor, GEC) connects the meter box to the grounding electrode, such as a ground rod or Ufer ground. The conductor must be mechanically secure, corrosion-resistant, and sized according to the largest ungrounded service conductors . The grounding electrode should be installed near the meter box, with at least 8 feet of its length in continuous contact with the earth, and the top flush with or below ground level .

Bonding and Metal Parts

All metal parts of the distribution box, including the enclosure and any service panels, must be bonded to the grounding system to maintain equal electrical potential and prevent shock hazards . Bonding ensures that if a live conductor contacts a metal part, the fault current flows through the low-impedance path, tripping the breaker and de-energizing the system . In industrial or specialized equipment, additional bonding may be required between mounting plates and connected components to maintain resistance below 0.1 ohm .

Compliance and Safety

Grounding must comply with local electrical codes, such as the Ontario Electrical Safety Code (OESC) or the National Electrical Code (NEC), depending on jurisdiction. Key rules include:

• Grounding at a single point only on the supply side .
• Using separate conduits for grounding if the meter base is ahead of the utility ownership demarcation .
• Properly sizing bonding conductors between service boxes and the meter base .
• Ensuring all connections are secure and capable of carrying fault currents safely . By following these guidelines, the meter inside a secondary distribution box will be safely grounded, minimizing the risk of electrical shock, equipment damage, and ensuring proper operation of overcurrent protection devices.