8.4 Pull Boxes, Junction Boxes & Conduit Bodies

Why Pull Box Sizing Is Tested Differently

Article 314.28 governs pull boxes, junction boxes, and conduit bodies containing conductors 4 AWG or larger. If all conductors are 6 AWG or smaller, 314.16 (covered in the previous section) applies. The exam will state the conductor size explicitly — read carefully, because the sizing rules differ dramatically between the two articles. Mix them up and you will calculate the wrong minimum dimension.

When 314.28 Applies

314.28 applies to pull boxes, junction boxes, and conduit bodies that:

• Contain conductors 4 AWG or larger, AND
• Have raceways entering and leaving the enclosure.

If conductors are all 6 AWG or smaller, 314.16 governs (volume-based fill). The 314.28 rules are dimension-based — they set minimum distances, not volumes. This is the fundamental distinction.

Straight Pulls [314.28(A)(1)]

A straight pull occurs when raceways enter one wall and leave through the opposite wall in the same direction. The minimum distance from the raceway entry to the opposite wall is:

Minimum distance = 8 × trade size of the largest raceway

Example: A 3-inch conduit enters the left wall and leaves the right wall → minimum box width = 8 × 3 in. = 24 inches.

Both horizontal and vertical dimensions must be calculated independently if raceways enter and leave in both directions. Calculate each direction separately and use the largest result for each dimension.

Angle Pulls [314.28(A)(2)]

An angle pull occurs when raceways enter a wall and leave through a wall at 90 degrees to the entry wall. The distance from the raceway entry to the opposite wall must be at least:

Minimum distance = (6 × largest raceway trade size) + (sum of all other raceway trade sizes on the same wall and row)

The "same wall and row" addition is critical — you only add the trade sizes of other raceways that share the same wall and the same horizontal or vertical row as the largest raceway. Raceways on the opposite wall or a different row are not added.

U-Pulls [314.28(A)(2)]

A U-pull occurs when a raceway enters and leaves from the same wall — the conductor makes a 180-degree turn. The sizing formula is identical to the angle pull:

Minimum distance = (6 × largest raceway) + (sum of other raceways on the same wall and row)

Distance Between Raceway Entries [314.28(A)(2)]

When multiple raceways on the same wall carry the same conductors, the distance between their entries must be at least:

Minimum separation = 6 × largest raceway trade size

This distance is measured from the nearest edge to nearest edge of the raceways — not from locknuts, bushings, or connectors. This rule prevents conductor damage from excessive bending at the entry points.

Conduit Bodies (Condulets)

Conduit bodies like LB, LL, LR, and T condulets are common on the exam. Key rules:

1. Conduit bodies may be used as splice points only if they are marked with their volume in cubic inches per 314.16(C)(2). Unmarked conduit bodies cannot contain splices — they may only serve as pull points.
2. When splices are made in a conduit body, it must be sized per 314.16(C) — the same box-fill method from the previous section, using Table 314.16(B) allowances. The volume of the conduit body must be greater than or equal to the total fill.
3. If the conduit body does not contain splices and only provides a pull point for conductors 4 AWG or larger, the 314.28 dimension rules apply.
4. Covers must be accessible after installation (314.72).

Worked Example: Angle Pull Box

Given: A pull box has a 3-inch and a 2-inch raceway on the left wall (same row). The 3-inch raceway makes an angle pull to the top wall. The 2-inch raceway makes a straight pull to the right wall. All conductors are 4 AWG or larger, so 314.28 applies.

Horizontal dimension — calculate all paths and use the largest:

The angle pull path gives 20 in. because the 3-inch raceway is the largest (6 × 3 = 18) and the 2-inch raceway shares the same wall and row (+ 2 = 20).

Horizontal minimum = 20 inches

Vertical dimension:

Vertical minimum = 18 inches

Distance between raceways: If the 3-inch raceways on the left and top walls carry the same conductors, the minimum separation between their entries = 6 × 3 = 18 inches, measured nearest edge to nearest edge.

Answer: Minimum box size = 20 in. × 18 in.

Exam Traps

• 314.16 vs 314.28: If the question says "4 AWG or larger," use 314.28 dimensions. If it says "6 AWG or smaller," use 314.16 volume fill. Mixing these is the #1 pull-box error.
• Same wall and row: In angle pulls, only add raceway sizes on the same wall and same row as the largest raceway. Raceways on the opposite wall or a different row are not added.
• Calculate both directions: For each dimension (horizontal and vertical), calculate both the straight-pull and angle-pull paths and use the largest result.
• Unmarked conduit bodies: An unmarked conduit body cannot be used as a splice point — it can only serve as a pull point.
• Nearest edge to nearest edge: The distance between raceway entries is measured from the nearest edges of the raceways, not from locknuts, bushings, or connectors.
• Splice vs no splice in conduit bodies: A conduit body with splices uses 314.16(C) volume rules; a conduit body without splices (pull point only) with conductors 4 AWG+ uses 314.28 dimension rules. The exam may ask you to identify which rule applies.