What is the smallest bonding jumper you can run in each of the sections of flexible conduit when feeding a 600-A panel board from a 225 KVA transformer?

When determining the smallest bonding jumper required when feeding a 600-A panel board from a 225 KVA transformer, it is important to consider the requirements set forth in the National Electric Code (NEC). The bonding jumper is crucial in ensuring that all conductive parts of the system are at the same electrical potential, which enhances safety and reduces the risk of electric shock.

To calculate the appropriate size of the bonding jumper, you would typically reference NEC Table 250.122, which outlines the size of bonding jumpers according to the rating of the overcurrent protection devices (OCPD). For a 600-A service, the table indicates that the minimum size for equipment bonding jumpers should correspond to a specific minimum ampacity, which is adjusted according to the size and type of conduit.

In this scenario, the size 6 AWG copper bonding jumper is satisfactory for grounding a 600-A service, particularly when considering the flexible conduit method and the associated bonding requirements. Copper is generally more efficient than aluminum in grounding applications and follows a different sizing paradigm. A 6 AWG copper bonding jumper provides adequate capacity to handle fault currents that may occur in the system without failing or increasing the resistance, helping to ensure that any fault currents are safely redirected.

Therefore