What is the minimum required size for the main bonding jumper as specified in the NEC®?

The minimum required size for the main bonding jumper, according to the National Electrical Code (NEC), is determined based on the size of the largest ungrounded service conductors that supply the service. For services with conductors sized at 250 kcmil or smaller, the NEC specifies that the main bonding jumper must be at least 2/0 AWG copper or equivalent. This ensures a robust fault path that can carry potential fault currents safely back to the source, thus offering reliable protection against electrical hazards.

In this context, the selection of 2/0 AWG as the minimum size for the main bonding jumper aligns with the NEC's guidelines, emphasizing the importance of creating a safe and effective grounding and bonding system within electrical installations. A smaller size would not adequately handle the fault conditions, while larger sizes, although acceptable, exceed the minimum requirement established by the Code.