What is the minimum size copper bonding jumper for a metal water piping system supplied by a 400-ampere feeder with a 600 kcmil copper conductor?

To determine the minimum size copper bonding jumper for a metal water piping system supplied by a 400-ampere feeder with a 600 kcmil copper conductor, we need to refer to the relevant electrical codes and standards, such as those set by the National Electrical Code (NEC).

In this scenario, the code specifies that the bonding jumper must be sized based on the largest ungrounded conductor supplying the system. For conductors that are larger than 250 kcmil, the NEC provides specific guidelines for sizing the bonding jumper. According to NEC Table 250.102(C)(1), for a feeder that has a conductor size of 600 kcmil, the bonding jumper size should be based on the conductor size and the size of the equipment being bonded.

The table also indicates that for a 400-ampere feeder size (larger than 250 kcmil), the minimum size bonding jumper should be at least 3 AWG copper. This choice ensures that the bonding jumper can adequately handle potential fault currents and properly ground the metal water piping system, providing necessary safety and compliance.

Thus, the minimum size of the copper bonding jumper required in this case is indeed 3 AWG, which is why it is the correct