cable tray

[acid75070]

I have a run that is about 250 feet long its going on a 1200 amp frame breaker that is 1000 amp feed to a screw compressor. The engineer ask for 2- 3 phase runs of 500 kcm and a 2/0 ground in each conduit. My question is the grounding. If I ran a open air cable tray for this Houston cable has a tray rated cable that has 3-500 kcm and a number 2 ground in it. Can i derated the cable scent it is in open air and does the grounding still have to be sized by the nec 250-122 table.

 

[tom baker]

Yes the ground conductor has to be sized per 250.122, there is an exception for cable fed from a ground fault protected feeder. See 250.122 (F)(2)

 

[bob]

conduit. If I ran a open air cable tray for this Houston cable has a tray rated cable that has 3-500 kcm and a number 2 ground in it. Can i derated the cable scent it is in open air and does the grounding still have to be sized by the nec 250-122 table.

You say "if I ran open air cable tray". Is there a question that you might use
conduit instead?