richwaskowitz
Senior Member
- Location
- Shelby Twp. MI, near Detroit
I would like your opinions on an application where the customer (Ford Motor Co., our beloved benefactor) is calling for supplying 480 volt 3 phase power to various distributed control panels in a conveyor system using 3 conductor tray cables in a metallic tray system for the 3 phase conductors and running separate equipment grounding conductors, not part of that cable. They call for a ground loop of bare copper that runs around the system and each panel is provided with its only EGC by tapping off this loop. The loop originates at the power distribution panel. The question is, does 300.0 (B) require that the EGC be part of the 3 conductor feeder cable and cannot be run separate from it, even if it does run in the same cable tray.
OR, IF it is intended that the tray IS the EGC (392.3(C)), would this practice be permitted? In that case, would this ground loop be considered supplemental and simply additional bonding?
I guess what would really surprise me would be if anyone would ever use the tray as the only means of providing the EGC. Although permitted, it does not seem like a very good design in my opinion.
Sorry if this seems to ramble.
OR, IF it is intended that the tray IS the EGC (392.3(C)), would this practice be permitted? In that case, would this ground loop be considered supplemental and simply additional bonding?
I guess what would really surprise me would be if anyone would ever use the tray as the only means of providing the EGC. Although permitted, it does not seem like a very good design in my opinion.
Sorry if this seems to ramble.