Minuteman
Senior Member
- Location
- The Sooner Nation
A while back, I was hired to upgrade a outdoor 1200 amp, 120/240 Single phase MDP to a 1600 amp, 120/240 Delta 3 phase.
They had six 200 amp, single phase subpanel mains in the old MDP and added three 125 amp, 3 phase A/C units.
We re-used the two 5" Schedule 80 PVC underground (and under slab)conduits that ran from the CT can to the new MDP, and pulled paralleled 800 kcmil. That would be 8 total conductors per conduit. No problem... I thought.
I had to get an EE to stamp a drawing before I could pull the permit (only new construction requires a permit before the work begins). The facility has a Engineering Group that they use, who says that I have to derate the current carrying conductors per 310.15(B)(2)(a) because there are 8 current carrying conductors. No stamp!
I sited 310.4 and 310.15(B)(4)(c) as my support for not derating. We are still using the 2002 NEC
What saith thou?
edited to correct code reference
[ December 29, 2005, 12:26 AM: Message edited by: Minuteman ]
They had six 200 amp, single phase subpanel mains in the old MDP and added three 125 amp, 3 phase A/C units.
We re-used the two 5" Schedule 80 PVC underground (and under slab)conduits that ran from the CT can to the new MDP, and pulled paralleled 800 kcmil. That would be 8 total conductors per conduit. No problem... I thought.
I had to get an EE to stamp a drawing before I could pull the permit (only new construction requires a permit before the work begins). The facility has a Engineering Group that they use, who says that I have to derate the current carrying conductors per 310.15(B)(2)(a) because there are 8 current carrying conductors. No stamp!
I sited 310.4 and 310.15(B)(4)(c) as my support for not derating. We are still using the 2002 NEC
What saith thou?
edited to correct code reference
[ December 29, 2005, 12:26 AM: Message edited by: Minuteman ]