I'm trying to design a pull box and I am having difficulty interpreting NEC 314.71 for the sizing requirements. I have a straight pull through the junction box and it states that the length of the box needs to be 48 times the outside diameter, over sheath, of the largest shielded conductor or cable. I am running (3)750kcmil & (1) #2awg 15kV shielded cables into and out of the junction box. The O.D. of the 750kmcil cable is 1.75", the O.D. of the #2awg cable is 1.0”.
So do I need to make the box 48x1.75=84” long or 48x1.75+(2x1.75)+1=88.5” long? Any insight into this would be greatly appreciated.
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