What size pull box do three 2 inch conduits need for a straight pull?

At least 16 inches in the direction of the pull. NEC 314.28(A)(1) requires the length to be not less than 8 times the trade size of the largest raceway, which is 8 times 2 inches.

When does 314.28 apply instead of 314.16?

NEC 314.28 applies to pull and junction boxes where any conductor is 4 AWG or larger. If every conductor is smaller than 4 AWG, size the box by volume using the box fill rules in 314.16.

If I am connecting three 2 inch conduits, what size junction box do I need?

Q: How do you size an angle pull box in the NEC?

NEC 314.28(A)(2) requires 6 times the trade size of the largest raceway plus the sum of the trade sizes of the other raceways in the same row on that wall. For three 2 inch raceways in one row that is 16 inches.

Two different rules can apply, and the first thing to determine is the size of the conductors inside. Section 314.28 of the 2023 NEC governs pull and junction boxes where any conductor is 4 AWG or larger. Below that, you size the box by volume using 314.16 instead. Most jobs pulling 2 inch raceway are running conductors well above 4 AWG, so 314.28 is normally the one you need.

Straight pulls

Section 314.28(A)(1) requires the length of the box to be not less than 8 times the trade size of the largest raceway. With 2 inch conduit that is 16 inches measured in the direction of the pull. The width and depth are not fixed by that rule, but they must be enough to satisfy 314.28(A)(3), which requires the box to have adequate space to accommodate all conductors, and to leave room for the locknuts and bushings.

Angle and U pulls

Section 314.28(A)(2) is the one that catches people. The distance between each raceway entry inside the box and the opposite wall shall be not less than 6 times the trade size of the largest raceway, plus the sum of the trade sizes of the other raceways in the same row on the same wall.

If all three 2 inch raceways enter the same wall in the same row on an angle pull, the math is 6 times 2 inches, which is 12 inches, plus 2 inches plus 2 inches for the other two raceways, for a total of 16 inches. If only one raceway enters that wall, the requirement drops to 12 inches. Spreading the entries across different walls and rows is how you keep the box smaller.

The same section adds a second requirement that gets missed. The distance between raceway entries enclosing the same conductor shall not be less than 6 times the trade size of the larger raceway, so 12 inches between the entry and the exit for a 2 inch conduit. That is a center to center measurement between the two entries carrying the same conductor.

Worked example

Three 2 inch conduits, all conductors 4 AWG or larger, entering one wall in a row and turning 90 degrees. The wall the raceways enter needs 16 inches to the opposite wall. If the exits are on an adjacent wall, that wall gets its own calculation based on the raceways entering it. The entry to exit spacing for any given conductor set is at least 12 inches. A 24 by 24 by 8 inch pull box is the common off the shelf answer for this arrangement, because it satisfies both dimensions with room to work.

Section 314.28(A)(3) permits a smaller box where it is permanently marked with the maximum number and maximum size of conductors, and the marking is based on calculations by a qualified person. Section 314.28(B) requires a removable cover with adequate access, and 314.29 requires the box to remain accessible without removing part of the building.

Field takeaway

For 2 inch raceway, remember 16 and 12. Sixteen inches for a straight pull, 12 inches for a single raceway angle pull, and add the trade sizes of the other raceways in the same row. Keep 12 inches between the entry and exit for the same conductors, and use 314.16 volume calculations only when every conductor is smaller than 4 AWG.