When using multiple ground rods, they should be spaced apart at least farther than what measurement?

When using multiple ground rods, ensuring proper spacing between them is essential for effective electrical grounding. The correct measurement for spacing is at least twice the length of their immersion. This guideline is based on the principle that each ground rod should operate independently to provide an effective grounding system.

If the rods are placed too closely together—specifically within a distance that is less than twice their immersion length—they may interfere with each other's ability to dissipate fault currents into the ground effectively. This can lead to reduced grounding effectiveness, which is critical in preventing electrical surges from causing damage to equipment or posing safety risks.

In contrast, the other suggested measurements do not provide adequate separation to ensure that each rod can function optimally without interacting in a way that would diminish their overall grounding performance. For example, spacing them a distance equal to half the length of their immersion or the diameter of each rod may not provide sufficient distance to prevent interference. The total depth of immersion is also not a practical measurement for spacing, as it does not directly relate to the rods' performance in a grounding system. Thus, maintaining at least double the immersed length of each rod sets a standard that promotes the best operational performance for each grounded element.