What is the minimum size for the bonding jumper for a metal water piping system served by a separately derived system with 4/0 AWG copper conductors?

In the context of bonding jumpers for metal water piping systems connected to a separately derived system, it is crucial to select the proper size to ensure safety and effective grounding. The minimum size for a bonding jumper is determined by the size of the conductors in the system.

When dealing with a separately derived system that uses conductors of 4/0 AWG copper, the National Electrical Code (NEC) provides guidelines for selecting the appropriate size of bonding jumpers. According to NEC standards, the bonding jumper size for copper conductors is typically a fraction of the size of the conductors it is meant to bond. For a 4/0 AWG copper system, the smallest bonding jumper that is compliant is 2 AWG.

This choice ensures that there is adequate conductivity and minimizes the risk of potential faults, which could lead to dangerous voltage levels on the piping system. A bonding jumper that is too small would be ineffective in carrying the fault current, posing safety risks, while a larger size than necessary can increase costs unnecessarily without adding protective benefits. Hence, choosing 2 AWG aligns with the code requirements and provides adequate protection in this scenario.