What is the minimum length of a ground rod?

The minimum length of a ground rod is defined by electrical codes and standards to ensure that the grounding system is effective in providing a stable reference ground for electrical installations. The correct answer, which states that the minimum length is 8 feet, aligns with the National Electrical Code (NEC) requirements.

A ground rod of this length is considered adequate because it must penetrate the earth to a depth that allows it to achieve low resistance to ground, which is essential for safety. A ground rod that is too short may not provide sufficient grounding, potentially exposing the electrical system to the risk of ground faults or surges.

This standard ensures that the grounding system can dissipate fault currents effectively and maintain safety for both people and property. The other lengths listed, while they may be used in specific contexts or jurisdictions, do not meet the standard minimum length required for general grounding applications under the current NEC specifications.