According to the National Electrical Code® (NEC), what is the recommended maximum ground resistance for a ground rod?

The recommended maximum ground resistance for a ground rod, as specified by the National Electrical Code® (NEC), is 25 ohms. This standard is set to ensure that the grounding system is effective and can adequately dissipate electrical faults and surges, thereby protecting both equipment and personnel.

A resistance of 25 ohms is deemed sufficient to ensure that any fault currents can flow into the ground effectively, minimizing the risk of electrical shock and preventing damage to electrical systems. Ground resistance that exceeds this limit may indicate inadequacies in the grounding system, which could lead to increased risks during electrical faults.

The other values listed are not considered optimal for grounding effectiveness according to NEC standards. Values higher than 25 ohms may not provide the necessary safety and performance for electrical systems in various environments. The NEC sets these standards based on extensive research and industry practices to protect both property and lives.