Grounding in a Parallel Installation with a twists

[1972Grady]

250 KCMIL AL is rated for 205A in the 75C column. I have 2 sets of them so that puts me at 410 amps which is greater than the 10% rule in 240.21(B)(1)(4)

Sorry. I didn't read what I posted for #2. Correct. The smallest OCP you could feed from a 4000A busway protected at 4000A would be 400A. There is only 1 Grady. It depends which computer I log in with as to which name populates.

 

[infinity]

250 KCMIL AL is rated for 205A in the 75C column. I have 2 sets of them so that puts me at 410 amps which is greater than the 10% rule in 240.21(B)(1)(4)

My response about the 10'/10% tap rule was to your initial statement about one set of 250's.

Question #2
Say I have a 4000A busway rising up the building fed from a 4000A OCP. Im tapping off the busway to a 200A MCB panel less than 10' away. I'm using (1) set of 250 KCMIL AL to feed the 200A panel. Would a 250 KCMIL AL ground be large enough or would i need a 750 KCMIL ground?

 

[GoldDigger]

There is only 1 Grady. It depends which computer I log in with as to which name populates.

There is only one of you but you managed to create two accounts, not one account with two names.
Pick the one you want to keep and an Admin can probably merge the two.

In the meantime log out of the other account on one computer and log in again with the account you want to keep.

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