RCDD · Question #36
You are designing a horizontal pathway system where you will provide 100 mm (4 in) conduit and pull boxes. The building architectural elements will only allow for a single layer of conduits (not…
The correct answer is C. 1220 mm (48 in). Pull box sizing follows the standard formula based on NEC 314.28 and BICSI guidelines. For a straight pull configuration, the minimum box dimension in the pull direction is 8× the diameter of the largest conduit. When multiple conduits enter the same wall in a single row, the…
Question
You are designing a horizontal pathway system where you will provide 100 mm (4 in) conduit and pull boxes. The building architectural elements will only allow for a single layer of conduits (not stacked). The main horizontal pathway system consists of five 100 mm (4 in) conduits. Large single sheath copper cables are not expected to be placed. Which of the following is the MINIMUM width pull box that is to be provided?
Options
- A600 mm (24 in)
- B900 mm (36 in)
- C1220 mm (48 in)
- D1520 mm (60 in)
- E1830 mm (72 in)
How the community answered
(33 responses)- A3% (1)
- B6% (2)
- C79% (26)
- D9% (3)
- E3% (1)
Explanation
Pull box sizing follows the standard formula based on NEC 314.28 and BICSI guidelines. For a straight pull configuration, the minimum box dimension in the pull direction is 8× the diameter of the largest conduit. When multiple conduits enter the same wall in a single row, the additional conduits each add one conduit diameter to that dimension. Calculation: 8 × 100 mm (for the largest/first conduit) + (5 - 1) × 100 mm (for the four additional conduits) = 800 mm + 400 mm = 1200 mm. Converted to the nearest standard size, this equals 48 in (1219 mm ≈ 1220 mm). Smaller options (600 mm, 900 mm) are insufficient; larger options (1520 mm, 1830 mm) exceed the minimum required.
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