how to properly ground equipment when 480v buss bar has no ground

[Bmxer883]

I haven't seen it personally but was told by coworker our 480v buss has no ground. In the past I just add a ground lug to buss switch and hope the encloser is grounded where power feeds buss. He just has 3 wires coming from buss and was trying to figure out how to ground it. The guy who used to be electrical supervisor and has now moved up said they just always grounded to the steel beams in the shop. I do not feel that is correct cause you dont know how good connections are. Looking for others input or any reference to codes. Thanks

 

[tom baker]

Bear with us as we need more information. Is the system voltage 480/277 3 of 4 wire, 480 corner grounded or 480 ungrounded delta?
In grounding terminology is critical.Ground in the NEC is defined as the earth. What the NEC requires is an equipment grounding conductor, ie green wire or conduit to the service or source if a SDS. At the service or SDS is a bonding jumper to the neutral and earth
Connection to structural metal is required as a bonding connection
Grounding can be confusing as many of us were taught wrong. Thanks for asking so we can all learn.

 

[jim dungar]

Many, especially older, bus duct systems use the enclosure for grounding and do not include a dedicated ground bar. Look at the manufacturers UL listing.

Adding a dedicated ground bus would be similar to adding a grounding wire inside of EMT. It is usually a design decision.

 

[jaggedben]

If the bus raceway is being used as the equipment ground then equipment grounding connections should be made to that raceway. Not building steel.