What is the minimum contact with the earth required for a concrete-encased grounding electrode's orientation?

The minimum contact with the earth required for a concrete-encased grounding electrode is designed to ensure adequate grounding effectiveness and stability. A grounding electrode system, including one that is encased in concrete, must have sufficient length and depth to maintain a reliable electrical connection to the earth.

The answer of 20 feet aligns with established grounding requirements that provide a balance between safety and functionality. This distance allows the grounding electrode to dissipate fault currents safely into the earth, reducing the risk of electrical shock and fire. The specific dimension reflects standardized practices in grounding that take into account soil conditions, moisture levels, and the physical properties of concrete.

In contrast, the other answer choices of 10 feet, 15 feet, and 25 feet do not meet the common standards that have been recognized in grounding and bonding provisions. A measurement that is too short may not effectively fulfill the grounding requirements, while one that is excessively long could introduce unnecessary material costs without significant benefit. Thus, 20 feet is a well-established minimum to ensure safety and compliance with the necessary electrical codes.