According to the NEC, what should a ground rod's resistance not exceed?

The National Electrical Code (NEC) stipulates that the resistance of a ground rod should not exceed 25 ohms. This standard is set to ensure that the grounding system is effective in providing a low-resistance path for electric currents, especially during fault conditions. A lower resistance ensures that the ground system can effectively dissipate electrical surges or faults, minimizing the risk of electrical shock and enhancing overall safety.

In practical applications, keeping the ground resistance at or below 25 ohms improves the functionality of electrical systems by allowing for quicker fault current detection and response. This standard is crucial for maintaining the performance and safety of electrical installations, particularly in areas prone to lightning strikes or electrical surges.