What is the minimum size of a copper bonding jumper connecting from the ground bar to the bushings in a 400-amp service?

In a 400-amp service, the minimum size of a copper bonding jumper connecting the ground bar to the bushings is determined by the National Electrical Code (NEC). According to NEC guidelines, the minimum sizing for bonding jumpers is based on the ampacity of the service and the size of the equipment being bonded.

For a service of this size, a bonding jumper must have sufficient capacity to ensure that in the event of a fault, the system can properly ground and clear any faults, maintaining safety and functionality in the electrical system. The requirements stipulate that a #2 copper bonding jumper is suitable for 400-amp services, as it provides the necessary conductivity, allowing effective operation of overcurrent protective devices when a fault occurs.

Thus, a #2 copper bonding jumper satisfies the code requirements and ensures safety and reliability in the electrical service setup.