Which type of ground does the NEC allow to be used as a grounding electrode?

The National Electrical Code (NEC) specifies certain types of grounding electrodes that are permitted for use in electrical installations to ensure safety and proper grounding. The correct answer identifies metal underground water pipes, concrete-encased electrodes, and ground rods as acceptable grounding electrodes.

Metal underground water pipes provide a direct connection to the earth and are often utilized because they have a significant surface area in contact with the ground, enhancing the grounding effectiveness. Concrete-encased electrodes also serve a vital role as they are typically made from rebar or other conductive materials embedded in concrete, providing an excellent grounding path. Ground rods are specifically designed for grounding purposes, driven into the earth, and serve to dissipate electrical energy safely.

Using these types of electrodes helps establish a low-resistance path for fault currents, which is fundamental in protecting both people and equipment from electrical surges and faults. Each of these grounding methods ensures compliance with safety standards mandated by the NEC, contributing to the overall reliability of electrical systems.