1. What is the Straight Pull Box Size Calculation?

The Straight Pull Box Size calculation determines the minimum length required for a pull box when conduits enter one side and exit the opposite side without any angle pulls or U-shaped pulls. This is based on the National Electrical Code (NEC) requirements.

2. How Does the Calculator Work?

The calculator uses the NEC straight pull box formula:

Where:

• Length — Minimum required box length in inches
• Largest Conduit Diameter — Diameter of the largest conduit entering the box in inches

Explanation: The NEC requires that for straight pulls, the length of the box must be at least eight times the trade diameter of the largest conduit.

3. Importance of Proper Box Sizing

Details: Proper pull box sizing is critical for safe wire pulling, preventing conductor damage, and complying with electrical codes. Undersized boxes can make wire pulling difficult and may damage insulation.

4. Using the Calculator

Tips: Measure the diameter of the largest conduit that will enter the pull box. Enter this value in inches. The calculator will determine the minimum required box length for a straight pull configuration.

5. Frequently Asked Questions (FAQ)

Q1: Does this calculation apply to angle or U pulls?
A: No, this is specifically for straight pulls. Angle and U pulls have different calculation methods.

Q2: What if multiple conduits enter the box?
A: The calculation is based on the largest conduit diameter, regardless of how many conduits enter the box.

Q3: Are there additional requirements for box depth?
A: Yes, the box must also be deep enough to allow proper installation of locknuts and bushings.

Q4: Does this apply to both metal and nonmetallic boxes?
A: Yes, the sizing requirements apply to all types of pull boxes.

Q5: What NEC article covers this requirement?
A: This is covered in NEC Article 314.28(A)(1) for straight pulls.