Electrician's Licensing Practice Exam

For 400-amp services, how far apart must the ground rods be placed?

1. 4 feet

2. 6 feet

3. 8 feet

4. 10 feet

The correct answer is: 6 feet

For a 400-amp service, ground rods must be spaced at least 6 feet apart to ensure effective grounding. This distance helps prevent interference between the grounding systems of each rod, as the purpose of multiple ground rods is to enhance the overall grounding effectiveness by providing additional paths for fault currents to dissipate into the earth. The spacing is critical because if the rods are too close together, they could potentially "see" the same fault current, which diminishes the effectiveness of the grounding system. By adhering to the specified distance, electrical systems can achieve better performance in terms of safety and reliability. Other options suggest distances that do not meet the minimum requirement set by code, thus potentially compromising grounding effectiveness.