I need help making sure that I am calculating the minimum dimensions for a field installed
junction box. This box seems huge, so I know I am doing something wrong.
Assumptions: Field installed junction box with 5 kV multiconductor cables (cable OD = 1.35") entering from Right and Exiting at LEFT of box.
Size of Box based on type of Pull
The box width required per NEC 314.71 for straight through pulls is a minimum of 32
times the OD of the MC cable (32 x 1.35?) or 43.2? .
Size of Box based on LIVE part spacing
The minimum air separation between bare live parts (Phase to Phase ? Outdoors) per
NEC 490-24 is 7?. Similarly the minimum air separation between bare live parts (Phase
to Ground ? Outdoors) per NEC 490-24 is 6?. Therefore the minimum width is 33? (7?
+ 7? + 7? = 21? for phase to phase) + (6? + 6? = 12? for phase to ground ? top to bottom).
The minimum depth of the enclosure would be 12? (6? + 6? - front & back)
junction box. This box seems huge, so I know I am doing something wrong.
Assumptions: Field installed junction box with 5 kV multiconductor cables (cable OD = 1.35") entering from Right and Exiting at LEFT of box.
Size of Box based on type of Pull
The box width required per NEC 314.71 for straight through pulls is a minimum of 32
times the OD of the MC cable (32 x 1.35?) or 43.2? .
Size of Box based on LIVE part spacing
The minimum air separation between bare live parts (Phase to Phase ? Outdoors) per
NEC 490-24 is 7?. Similarly the minimum air separation between bare live parts (Phase
to Ground ? Outdoors) per NEC 490-24 is 6?. Therefore the minimum width is 33? (7?
+ 7? + 7? = 21? for phase to phase) + (6? + 6? = 12? for phase to ground ? top to bottom).
The minimum depth of the enclosure would be 12? (6? + 6? - front & back)