Junction Box Design (NEC 314.71)
Junction Box Design (NEC 314.71)
(OP)
I'm trying to design a junction 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 a single 3-conductor 5kV shielded cable into and out of the junction box. The O.D. of the cable is 2", the O.D. of the sheath over each conductor is 0.703”. So do I need to make the box 48*2=96” long or 48*0.703=34” long. Any insight into this would be greatly appreciated.






RE: Junction Box Design (NEC 314.71)
RE: Junction Box Design (NEC 314.71)
Here's my dilemma:
Extending 2 sets of 3#350kcil, 1#1G, 3½"C. via Junction Box (and compression fittings); straight through, no bends.
Handbook NEC 314.28(A)(1) states that 314.28(A)(2) applies if splicing in a straight pull; thus allowing 6x91mm (3½" = 91mm [trade size]) between entry and opposite wall. 6x91mm = 546mm ÷ 25.4 (mm/inches) = 21.496". This gives me the distance from conduit entry to opposite wall, but where are the requirements for volume allowances of the 6#350kcmil & 2#1 conductors; minimum width & depth of the junction box? Row-spacing of the 3½" conduits?? I know the answer is buried in the NEC somewhere, just can't find it...
RE: Junction Box Design (NEC 314.71)
As far as the row spacing, there is no rule...just the practical one that requires you to have enough room to install the required locknuts and bushings.
Don
RE: Junction Box Design (NEC 314.71)
Thanks again.
RE: Junction Box Design (NEC 314.71)
Insight appreciated.
RE: Junction Box Design (NEC 314.71)
RE: Junction Box Design (NEC 314.71)