Electrician's Licensing Practice Exam

For a 400-amp service, how many ground rods are required?

1. One ground rod

2. Two ground rods

3. Three ground rods

4. Four ground rods

The correct answer is: Two ground rods

For a 400-amp service, the National Electrical Code (NEC) typically mandates the installation of two ground rods. This requirement is in place to ensure a more effective grounding system that reduces the potential for electrical shock and enhances the overall safety of the electrical installation. Ground rods help to provide a low-resistance path for electrical fault currents and help to dissipate surge currents, such as those from lightning strikes, safely into the ground. Having two ground rods, spaced adequately apart, not only improves the grounding effectiveness but also complies with local codes and standards, which often adopt this requirement based on the NEC. While there are exceptions and specific conditions that might lead to different grounding requirements—such as the type of soil or existing grounding systems—the general rule for a service rated at 400 amps is to utilize two ground rods for optimal safety and reliability.