Electrical Pull Box Size Calculator

Pull Box Size Calculation:

\[ \text{Size} = \max(\text{straight pull}, \text{angle pull}) \text{ per NEC} \]

Required Pull Box Size:

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1. What is Electrical Pull Box Size?

The Electrical Pull Box Size calculation determines the minimum required size for junction boxes and conduit bodies per National Electrical Code (NEC) requirements. Proper sizing ensures safe conductor bending space and pulling access.

2. How Does the Calculator Work?

The calculator uses the NEC formula:

\[ \text{Size} = \max(\text{straight pull}, \text{angle pull}) \]

Where:

Straight Pull — Sum of diameters of all conduits on one wall multiplied by 8 (or largest conduit multiplied by 6 for certain conditions)
Angle Pull — Sum of diameters of conduits entering the adjacent walls multiplied by 6

Explanation: The calculator takes the larger of the two calculated dimensions to ensure compliance with NEC requirements.

3. Importance of Proper Pull Box Sizing

Details: Correct pull box sizing prevents conductor damage during installation, provides adequate working space, and ensures compliance with electrical codes for safety and functionality.

4. Using the Calculator

Tips: Enter both straight pull and angle pull dimensions in inches. The calculator will determine which value governs and provide the required minimum size.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between straight pull and angle pull?
A: Straight pull applies when conductors enter and leave opposite walls. Angle pull applies when conductors enter and leave adjacent walls.

Q2: Are there additional NEC requirements for pull boxes?
A: Yes, NEC also specifies minimum depth requirements and other dimensional considerations based on conduit size and arrangement.

Q3: How does U-pull factor into sizing?
A: U-pulls (conductors entering and leaving the same wall) have different calculation methods not covered by this basic calculator.

Q4: What about multiple conduits?
A: For multiple conduits, the calculation considers the sum of diameters for straight pulls or the row with the largest sum for angle pulls.

Q5: Does this apply to all conduit types?
A: The calculation applies to metallic and nonmetallic conduits alike, though some special conditions may apply for very large conduits.