NEC Pull and Junction Box Sizing
The minimum pull or junction box dimension for large raceways under NEC 314.28.
Example
You enter
- Pull type straight
- Largest raceway (trade size, in) 3
You get
- Minimum box dimension 24.0 in (straight pull)
- Straight-pull minimum (8x) 24.0 in
- Angle/U-pull minimum (6x + others) 18.0 in
- Between same-conductor entries (6x) 18.0 in
Checked against published worked examples from: EC&M (Mike Holt).
Details, formula, and sources
Scope8x the largest raceway for a straight pull, 6x plus the same-row others for an angle or U pull, and the 6x between-entries rule. box-fill is the separate 314.16 conductor-volume fill.
Formula or tableStraight pull: min = 8 x largest raceway. Angle/U pull: min = 6 x largest raceway + sum of same-row others. Between same-conductor entries: >= 6 x larger raceway.
Source and editionNEC (NFPA 70) 314.28(A)(1) and (A)(2) (by name).
Free accessNFPA 70 free read-only at nfpa.org (registration); the multipliers are stated, not reproduced.
What governsEstimate. AHJ and licensed professional govern.
API field namespull_type, largest_raceway_in, governing, straight_min, angle_min, between
- Straight-pull multiplier 8x the largest raceway trade size (NEC 314.28(A)(1))NEC 314.28(A)(1)
- Angle/U-pull multiplier 6x the largest raceway + the sum of the other same-row raceways (NEC 314.28(A)(2))NEC 314.28(A)(2)
- Minimums only the box's listed dimensions, conductor bending space, and the AHJ governNEC 314.28