Voltkit US · NEC 2023
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NEC 2023NEC 314.28

Pull Box Calculator

Pick the pull type and the largest raceway (and, for an angle or U pull, the other raceways in the same row) to get the minimum box dimension.

Straight pull · min MIN
24in
Angle/U
20 in
Largest
3"
Row spacing
18 in

NEC 314.28(A) · NEC 2023

Values checked against the printed NEC 2023 tables, using the same engine as the Voltkit app.

Show calculation
  1. Straight pull8 × 3"24 in
  2. Angle / U pull6 × 3" + 2"20 in
  3. Between entries6 × 3" (same conductor)18 in

NEC 314.28(A)(1) & (A)(2)

Pull

Applies to conductors 4 AWG and larger. For smaller conductors, size the box by box fill.

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How pull boxes are sized

NEC 314.28(A) sizes a pull or junction box from the trade sizes of the raceways, not from the conductors' volume:

  • Straight pull (A)(1): length at least 8 × the largest raceway trade size.
  • Angle or U pull (A)(2): from each entry to the opposite wall, at least 6 × the largest raceway plus the other raceways in the same row on that wall.
  • Entry spacing (A)(2): raceways enclosing the same conductor at least 6 × the larger raceway apart.

The box has to work in every direction a conductor is pulled, so check each wall with entries on it. If any dimension of the box is over 6 ft, 314.28(B) also requires the conductors inside to be cabled or racked.

Worked examples

  1. Straight pull with 2" conduit. The box must be at least 16 in long.
  2. Angle pull: a 3" conduit and two 2" conduits on the same wall. 6 × 3" plus 2" + 2" gives 22 in to the opposite wall (it would be 18 in with the 3" alone). Entries carrying the same conductors must be at least 18 in apart.

This page cites the code but doesn't reproduce NEC text or tables. Use your copy of the NEC 2023 for the exact wording.

Worked examples on this page are computed by the same engine as the Voltkit app. The page cites NEC 2023 sections but doesn't reproduce NFPA text or tables; use your copy of the code for the exact wording.

Worked examples

Frequently asked questions

When do the pull box rules apply?

NEC 314.28 applies to pull and junction boxes on raceways containing conductors of 4 AWG or larger that are required to be insulated. For 6 AWG and smaller, size the box by volume with 314.16 box fill instead.

Is it the trade size or the actual outside diameter?

The trade size. 314.28(A) multiplies the metric designator or trade size of the raceway, so a 2" EMT counts as 2 in even though its outside diameter is larger. The calculator works in trade sizes for that reason.

How far apart do the raceway entries need to be?

For an angle or U pull, entries enclosing the same conductor must be at least 6 times the trade size of the larger raceway apart, measured between the nearest edges of the entries.

What if there are several rows of raceways?

Work out each row on its own and use the row that gives the largest dimension. Do it for each wall that has entries. The calculator handles one row at a time: enter the largest raceway in the row and the others in that same row.

Can a box be smaller than these dimensions?

Only if it is listed and permanently marked for the maximum number and size of conductors, and the raceways are filled less than Chapter 9 allows (314.28(A)(3)). Otherwise the 8× and 6× rules set the minimum.

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