How deep must ground rods be driven into the ground?

The requirement for grounding rods is to ensure they provide a stable and effective grounding system to protect both people and equipment. The National Electrical Code (NEC) specifies that a ground rod must be a minimum of 8 feet in length when properly installed in the earth. This length is crucial because it allows the grounding system to make adequate contact with the surrounding soil, which is essential for dissipating electrical surges and providing an effective path for fault currents.

Driving the ground rod at least 8 feet deep helps ensure that it reaches soil that is moist enough to provide low resistance, which enhances the effectiveness of the grounding system. A ground rod that is too short may not achieve proper grounding, potentially leading to safety hazards or equipment damage.

In contrast, the other options either exceed the requirement or do not specify a standard depth that aligns with NEC guidelines. Thus, the requirement of 8 feet is both a standard practice and a necessary criterion for electrical safety and compliance.