Quizzes on the Code

Sept. 1, 2000
Sizing Pull Boxes Art. 370 Choose the best answer. (Assume all conductors pulled through the conduits in Questions 1-5 are No. 4 and larger.) 1. What is the minimum length pull box required for a straight pull having a run of 2-in. conduit entering and leaving opposite walls of the box? (a) 12 in. (c) 16 in. (b) 14 in. (d) 18 in. 2. What is the minimum size pull box required for a straight pull having

Sizing Pull Boxes — Art. 370

Choose the best answer. (Assume all conductors pulled through the conduits in Questions 1-5 are No. 4 and larger.)

1. What is the minimum length pull box required for a straight pull having a run of 2-in. conduit entering and leaving opposite walls of the box?

(a) 12 in.
(c) 16 in.
(b) 14 in.
(d) 18 in.

2. What is the minimum size pull box required for a straight pull having parallel runs of 2½-in., 2-in., and 1½-in. conduit entering and leaving opposite walls of the box?

(a) 14 in.
(c) 18 in.
(b) 16 in.
(d) 20 in.

3. What is the minimum size pull box required for an angle pull with a run of 2-in. conduit that enters the top left wall and leaves the bottom right wall of the box?

(a) 8 in. x 8 in.
(b) 12 in. x 12 in.
(c) 14 in. x 14 in.
(d) 16 in. x 16 in.

4. What is the minimum size pull box required for an angle pull with runs of 4-in., 3-in., and 2-in. conduit entering and leaving the box?

(a) 29 in. x 29 in.
(b) 30 in. x 30 in.
(c) 32 in. x 32 in.
(d) 36 in. x 36 in.

5. What is the minimum size pull box required for a U-pull having a run of 2-in. conduit?

(a) 10 in. x 10 in.
(b) 12 in. x 12 in.
(c) 14 in. x 14 in.
(d) 16 in. x 16 in.

Answers and Discussion

1. (c). When sizing a pull box for a straight pull (conduits on opposite walls), multiply the dimension of the largest size conduit entering and leaving the box by a specified multiplier.

Step 1: Find the appropriate multiplier in Sec. 370-28(a)(1).

Multiplier = 8

Step 2: Calculate the required length.

2 in. x 8 = 16 in.

Solution: The minimum length of the pull box is 16 in.

Stallcup’s Code Loop: Sec. 370-28(a) and 370-28(a)(1).

2. (d). Junction boxes with more than two conduits connected to their sides (to form a straight pull) are sized by multiplying the trade diameter of the largest raceway by a specified multiplier. The dimensions of the remaining conduits do not factor into this calculation.

Step 1: Find the appropriate multiplier in Sec. 370-28(a)(1).

Multiplier = 8

Step 2: Calculate the required length.

2½ in. x 8 = 20 in.

Solution: The minimum length of the pull box is 20 in.

Stallcup’s Code Loop: Sec. 370-28(a) and 370-28(a)(1).

3. (b). When sizing a pull box for an angle pull, multiply the trade diameter of the largest conduit entering and leaving by a specified multiplier.

Step 1: Find the appropriate multiplier in Sec. 370-28(a)(2).

Multiplier = 6

Step 2: Calculate the required length.

2 in. x 6 = 12 in.

Solution: The minimum dimension of the pull box is 12 in. x 12 in.

Stallcup’s Code Loop: Sec. 370-28 and 370-28(a)(2).

4. (a). Junction boxes with more than one run of conduit connected to their walls to form an angle pull are sized by multiplying the trade diameter of the largest conduit by a specified multiplier and adding the dimensions of the remaining conduits to this value.

Step 1: Find the appropriate multiplier in Sec. 370-28(a)(2).

Multiplier = 6

Step 2: Calculate the required length.

4 in. x 6 = 24 in.

Step 3: Now add the diameters of the remaining conduits.

24 in. + 3 in. + 2 in. = 29 in.

Solution: The minimum dimension of the pull box is 29 in. x 29 in.

Stallcup’s Code Loop: Sec. 370-28 and 370-28(a)(2)

5. (b). Junction boxes with more than one run of conduit connected to their walls to form a U-pull are sized by multiplying the trade diameter of the largest conduit by a specified multiplier and adding the dimensions of the remaining conduits to this value.

Step 1: Find the appropriate multiplier in Sec. 370-28(a)(2).

Multiplier = 6

Step 2: Calculate the required length.

2 in. x 6 = 12 in.

Solution: The minimum dimension of the pull box is 12 in. x 12 in.

Stallcup’s Code Loop: Sec. 370-28(a) and 370-28(a)(2).

About the Author

James Gray Stallcup | CEO

James Gray Stallcup is CEO of Grayboy, Inc. He's a National Electrical Code (NEC) and OSHA expert, as well as being designated as having the qualifications to be classified as a Safety Engineer.

Voice your opinion!

To join the conversation, and become an exclusive member of EC&M, create an account today!

Sponsored Recommendations

Electrical Conduit Comparison Chart

CHAMPION FIBERGLASS electrical conduit is a lightweight, durable option that provides lasting savings when compared to other materials. Compare electrical conduit types including...

Fiberglass Electrical Conduit Chemical Resistance Chart

This information is provided solely as a guide since it is impossible to anticipate all individual site conditions. For specific applications which are not covered in this guide...

Considerations for Direct Burial Conduit

Installation type plays a key role in the type of conduit selected for electrical systems in industrial construction projects. Above ground, below ground, direct buried, encased...

How to Calculate Labor Costs

Most important to accurately estimating labor costs is knowing the approximate hours required for project completion. Learn how to calculate electrical labor cost.