According to the NEC, which of the following would provide the best earth ground for an electrical installation?

The best earth ground for an electrical installation, according to the National Electrical Code (NEC), is provided by a metal underground water pipe and a connection to a driven electrode. This approach is optimal for several reasons.

A metal underground water pipe is usually in contact with the earth along its entire length, providing a reliable path for grounding. Since water pipes are typically buried and can extend over long distances, they can establish a significant surface contact area with the ground, enhancing grounding effectiveness. Additionally, when connected to a driven electrode, like a ground rod, this system minimizes ground resistance and provides a strong and stable electrical grounding point, which is crucial for electrical safety and system performance.

The use of a ground rod alone or other configurations can be less effective due to factors like soil conductivity, depth of the grounding, and electrical continuity. While concrete building foundations and ground wires connected to a steel frame can provide grounding, they do not offer the same level of direct earth contact and conductivity that a water pipe connection combined with a driven electrode does. Thus, the combination of a metal underground water pipe and a driven electrode is the most effective option for ensuring the installation is grounded properly and safely.