The National Electrical Code (NEC) rules for the aforementioned are in Sec. 314.28. But don’t confuse them with outlet boxes [314.27(A) through (E)].
The rules for pull boxes, junction boxes, and outlet boxes cover five areas. In summary:
- Minimum size [314.28(A)]. These requirements constitute most of Sec. 314.28. One key point is that on straight pulls the box or conduit body length must be at least eight times the trade size of the raceway. For angle pulls, U pulls, and splices, the distance between each raceway box entry must be at least six times the trade size of the largest raceway in a row.
- Conductors in pull or junction boxes [314.28(B)]. If any dimension exceeds 6 ft, cable or rack the conductors in an approved manner.
- Covers [314.28(C)]. Use a compatible cover that is suitable for the conditions of use.
- Permanent barriers [314.28(D)]. If you install these, consider each section a separate box.
- Power distribution blocks [314.28(E)]. There are limits on where you can use these. A key requirement is through conductors that don’t terminate on these blocks can’t obstruct the blocks.
