What is the size of the grounding electrode conductor connected to the steel building structure from the BCES main service?

The size of the grounding electrode conductor (GEC) connected to a steel building structure from the main service is typically determined based on the size of the service conductors and the specific requirements outlined in the National Electrical Code (NEC). According to NEC guidelines, the grounding electrode conductor must be properly sized to ensure effective grounding of the electrical system.

A conductor size of 250 kcmil is applicable for larger services where the main service conductors exceed a certain ampacity threshold. This corresponds to the requirement for larger buildings or systems with significant power demands, necessitating a robust grounding system to enhance safety and minimize the risk of electrical hazards.

In contrast, the other sizes mentioned, such as 3/0, 4, and 1/0, are appropriate for smaller services and may not meet the necessary criteria for larger installations that rely on steel building structures. This makes the 250 kcmil size the most suitable choice for ensuring a reliable and compliant grounding system for such installations.