# Pull box sizing (NEC 314.28)

> Pull box sizing under NEC 314.28 applies to conductors 4 AWG and larger. A straight pull needs a box 8 times the trade size of the largest raceway; an angle or U pull needs 6 times the largest raceway in a row plus the trade sizes of the other raceways in that row.

Exams: Journeyman Electrician, Master Electrician. Boxes and raceways.

## Formula

    Straight pull: Length (in.) ≥ 8 × largest trade size
    Angle or U pull: Distance to opposite wall (in.) ≥ 6 × largest trade size in the row + sum of the other trade sizes in that row
    Same conductor: Distance between entries (in.) ≥ 6 × larger trade size

## Variables

- **Trade size**: Raceway trade size used as a number of inches (2-1/2 = 2.5) (in.)
- **Largest**: Largest trade size entering the wall or row you are sizing (in.)

## Open your 2026 NEC to

- 314.28(A)(1): Straight pulls: 8 times the largest raceway
- 314.28(A)(2): Angle pulls, U pulls and splices: 6 times the largest plus the others in the row, and spacing between entries of the same conductor

Large conductors need room to bend. If a pull box is too small, the insulation gets crushed against the box or the conductors cannot be pulled at all. NEC 314.28 sets minimum box dimensions from the raceway trade sizes, and it applies when the conductors are 4 AWG or larger.

There are two kinds of pull. In a straight pull the conductors go in one end and out the opposite end, so the box length must be at least 8 times the trade size of the largest raceway. In an angle pull or a U pull the conductors turn. Then the distance from each wall with raceways to the opposite wall must be at least 6 times the largest raceway in a row, plus the trade sizes of every other raceway in that same row.

Angle and U pulls have a second check. Two raceway entries that carry the same conductors must be at least 6 times the trade size of the larger raceway apart. Each wall and each row is figured separately, and the largest result sets the box size. The trade size is used as a plain number: a trade size 2-1/2 conduit counts as 2.5 in.

## Worked example

Two conduits, trade sizes 4 and 1-1/2, enter each end of a pull box. The 1/0 AWG conductors run straight through the box from one end to the other. Using NEC 314.28(A)(1), what is the minimum length of the box in inches?

1. The conductors are 4 AWG or larger, so 314.28 applies.
2. A straight pull needs a box at least 8 times the trade size of the largest raceway.
3. Largest raceway: trade size 4, which counts as 4.00 in.
4. Minimum length: 8 × 4.00 = 32 in.

**Answer: 32 in.**

## How to solve it on the exam

1. Check that the conductors are 4 AWG or larger. If they are smaller, 314.28 does not set the size.
2. Decide if the pull is straight (in one end, out the other) or an angle or U pull (the conductors turn).
3. Straight pull: multiply the largest trade size entering the box by 8.
4. Angle or U pull: for each wall, take the row with the largest result: 6 × the largest trade size in the row plus the other trade sizes in that row.
5. For angle pulls, also check the spacing between entries carrying the same conductors: 6 × the larger trade size.

## Common mistakes

- Using 6 times for a straight pull or 8 times for an angle pull.
- Multiplying every raceway by 6 instead of only the largest one.
- Forgetting to add the other raceways in the row for an angle or U pull.
- Adding the other raceways in a straight pull, where only the largest counts.
- Using the actual outside diameter of the conduit instead of the trade size number.

## Exam tips

- Sketch the box and write the trade sizes on each wall. Most mistakes come from mixing up which raceways are in the same row.
- Write trade sizes as decimals before you multiply: 1-1/4 = 1.25, 2-1/2 = 2.5, 3-1/2 = 3.5.

## Questions people ask

### How do you size a pull box for a straight pull?

Multiply the trade size of the largest raceway by 8. That is the minimum length of the box in inches for conductors 4 AWG and larger, under NEC 314.28(A)(1).

### How do you size a pull box for an angle pull?

Multiply the largest trade size in the row by 6 and add the trade sizes of the other raceways in the same row on that wall. Do this for each wall to get the box width and length.

### Is a U pull sized like an angle pull?

Yes. NEC 314.28(A)(2) treats angle pulls, U pulls and splices the same way: 6 times the largest raceway in the row plus the other raceways in that row.

### Does 314.28 apply to 6 AWG conductors?

No. The pull box sizing rules in 314.28(A) apply to conductors 4 AWG and larger. Smaller conductors are sized by box fill under 314.16.

## Sources

- [TDLR: Electrician examination information](https://www.tdlr.texas.gov/electricians/elecexam.htm)
- [PSI: Texas electrician candidate information bulletin](https://test-takers.psiexams.com/api/content/bulletin/1682)

Interactive practice: https://texaselectricianexam.com/calculations/pull-box-sizing/