Have a contractor requesting to use a #6AL equipment ground for a 125A feeder. Phase conductors will be 2/0 aluminium (not my sizing). I dont see a problem with it initially but table 250.122 does not list a size for 125A MOCP. Not sure if im just drawing a blank here but what would be the required minimum Al EG size for 125A being that it isnt listed in 250.122.
125A MOCP, Aluminum Equipment Ground
- Thread starter Npstewart
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He would need a #4 Al (or a #6 Cu.)
Note that T250.122 says...Rating or setting of OCPD in circuit ahead of equipment, Not Exceeding (Amperes).
I never mentioned it was a he...
Thanks guys, much appreciated. I dont ever use AL equipment grounds and I missed that.
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Look at the heading of the first column, especially the words "not exceeding".
Does 125 exceed 100? Yes, so you cannot use that row of the table.
Does 125 exceed 200? No, so that is the row you need to use.
Use #4 Al (or larger at your option.)
This is not a table where you interpolate to find intermediate values.
ADD: My but the fish are in a feeding frenzy on this one!
PS: However, if the feeder wires have been upsized compared to the required size because of voltage drop concerns, you may even be forced to use a larger EGC than the table requires.
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