If a single grounding electrode has a resistance to earth of 25 ohms or less, what is required?

When a single grounding electrode has a resistance to earth of 25 ohms or less, it meets the acceptable standards for grounding systems. In this case, it is not necessary to install a supplemental electrode because the primary grounding electrode can effectively dissipate fault currents into the earth.

A grounding electrode with a resistance of 25 ohms or less indicates that it provides a low-resistance path for electrical currents, which is crucial for safety and compliance with electrical codes. The presence of a low-resistance ground helps to protect against electrical shocks and ensures that protective devices, like circuit breakers, operate effectively during fault conditions.

In situations where the resistance exceeds 25 ohms, supplemental grounding electrodes might be needed to lower the overall grounding resistance. The lack of requirement for additional electrodes under these conditions reinforces the importance of effective grounding in electrical systems.