What is the minimum size of bare conductor allowed as a concrete-encased electrode?

The minimum size of bare conductor allowed as a concrete-encased electrode is defined by electrical codes and standards to ensure adequate conductivity and safety. A No. 4 copper conductor meets these requirements because it has sufficient cross-sectional area to handle the fault currents that could occur in an electrical system. This size helps ensure that the connection to the grounding system is reliable and can dissipate current effectively during a fault condition.

Using a conductor that is too small, such as No. 6 or No. 8 copper, does not provide the same level of conductivity and could potentially lead to overheating or failure to adequately ground the system. Therefore, selecting No. 4 copper as the minimum size ensures compliance with safety standards and effective grounding practices, making it the correct answer.