Q. What are the Code requirements for bonding bushings on 277V or 480V branch and feeder and circuits?

A.Metal raceways or cables containing 277V and/or 480V branch or feeder circuits terminating at ringed knockouts must be bonded to the metal enclosure with a bonding jumper sized in accordance with 250.122, based on the rating of the circuit overcurrent device [250.102(D)]. A bonding jumper isn’t required where ringed knockouts aren’t encountered or where the box is listed to provide a reliable bonding connection as in a typical 4 square outlet box [250.97].