122 remains the definitive reference for equipment grounding conductor sizing, while Table 250. This guide explains both tables with practical applications. Here we will cover details for the ground size chart and other features. So let's get started with What Size. The National Electrical Code (NEC) specifies minimum ground wire sizes based on the circuit being protected, and understanding these requirements is essential for safe, code-compliant installations. It ensures safe fault current paths, compliance with NEC codes, and reliable protection for residential, commercial, and industrial installations. Grounding and Bonding and the NEC 250 Training.