At what minimum depth can a rod or pipe electrode be buried horizontally in a trench where rock bottom is encountered?

The minimum depth at which a rod or pipe electrode can be buried horizontally in a trench when rock bottom is encountered is defined to ensure proper grounding and safety standards. A depth of 30 inches is significant because it complies with the National Electrical Code (NEC) requirements, which aim to provide adequate burial depth to protect the electrode from physical damage and ensure effective electrical conductivity with the earth.

When rock bottom is hit, it becomes impractical to bury the electrode much deeper, so the NEC establishes a minimum requirement to ensure that grounding systems are effective while also being achievable given the conditions. A depth of 30 inches strikes a balance between functionality and practicality, making it the correct answer to this question.

This understanding of electrode installation is crucial for ensuring safe and effective electrical grounding in residential and commercial buildings. It helps to mitigate risks associated with electrical faults, protecting both the equipment and the occupants.