large JB/pull box sizing

[Ty Irvin]

I have a rack of (18) 2" EMT conduits in a horizontal run that need to transition to a vertical rack. Or plan is to fabricate a box 90" wide x 24" tall 6" deep metal box with a removal cover on the 24x90 face. Typically each concuit will have up to 9 current carying conductors in it for a total of 140 current carying conductors within the box ranginge between #10 and 1/0. Within this box the we will be sorting and directing three phase equipemt circuts to relocated equipment ie. the concutors entering in the first conduit will not necessary exit in the corresponding first concuit. Due to the shear size of this is does not seam like a typical JB/pull box but more as a receway so with that said do our conductors need to be derated per 314.15(B)(2)(a)? We currently have the wire ampicity derated to 70% assuming 9 current carying conductors in a condut, if this is not correct and we need to detrate to 35% our current plan of adapting and utilizing exising condut/wire will not be pheasible and will require extensive conduit rework any thoughts?

 

[infinity]

I don't see where the conductors in a box require derating unless they were possibly all bundled together, but even if it were required 310.15(A)(2)Exception would probably apply.

 

[Strathead]

I have a rack of (18) 2" EMT conduits in a horizontal run that need to transition to a vertical rack. Or plan is to fabricate a box 90" wide x 24" tall 6" deep metal box with a removal cover on the 24x90 face. Typically each concuit will have up to 9 current carying conductors in it for a total of 140 current carying conductors within the box ranginge between #10 and 1/0. Within this box the we will be sorting and directing three phase equipemt circuts to relocated equipment ie. the concutors entering in the first conduit will not necessary exit in the corresponding first concuit. Due to the shear size of this is does not seam like a typical JB/pull box but more as a receway so with that said do our conductors need to be derated per 314.15(B)(2)(a)? We currently have the wire ampicity derated to 70% assuming 9 current carying conductors in a condut, if this is not correct and we need to detrate to 35% our current plan of adapting and utilizing exising condut/wire will not be pheasible and will require extensive conduit rework any thoughts?

Why so big?

 

[Ty Irvin]

thanks for your thoughts, the with of the box was set from the spacing of the existing conduits