Electrical Pull Box Size Calculator

Pull Box Sizing Formulas:

\[ \text{Straight Pull: } L = 8 \times \text{Largest Conduit} \] \[ \text{Angle/U Pull: } L = (6 \times \text{Largest Conduit}) + \sum \text{Other Conduits} \]

Pull Type:

Largest Conduit Size:

inches

Sum of Other Conduits:

inches

Minimum Box Size:

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1. What is an Electrical Pull Box Size Calculator?

Definition: This calculator determines the minimum required size for electrical pull boxes based on conduit sizes and NEC (National Electrical Code) rules.

Purpose: It helps electricians and electrical engineers properly size pull boxes to meet code requirements and ensure safe wire pulling.

2. How Does the Calculator Work?

The calculator uses NEC formulas:

\[ \text{Straight Pull: } L = 8 \times \text{Largest Conduit} \] \[ \text{Angle/U Pull: } L = (6 \times \text{Largest Conduit}) + \sum \text{Other Conduits} \]

Where:

\( L \) — Minimum box length (inches)
Largest Conduit — Diameter of largest conduit entering the box
Other Conduits — Sum of diameters of all other conduits on same wall

Explanation: The formulas ensure sufficient space for conductors to bend without damage during installation.

3. Importance of Proper Pull Box Sizing

Details: Correct sizing prevents conductor damage, meets electrical codes, and facilitates easier wire pulling.

4. Using the Calculator

Tips: Select pull type (straight or angle/U), enter largest conduit size, and for angle pulls, enter sum of other conduit sizes on the same wall.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between straight and angle pulls?
A: Straight pulls have conduits entering opposite walls in a straight line. Angle/U pulls have conduits entering at angles (90° or 180° turns).

Q2: Does this calculator cover all NEC pull box requirements?
A: This covers basic sizing. NEC 314.28 has additional rules for complex installations.

Q3: How do I measure conduit size?
A: Use the trade size (e.g., 1", 2") not the actual outer diameter.

Q4: What about box depth?
A: Depth must be at least equal to the largest conduit size.

Q5: When would I need a larger box than calculated?
A: For very large conductors, multiple bends, or when specified by manufacturer.