Nec Pull Box Size Calculator

NEC 314.28 Rules:

\[ \text{Size} = \text{per NEC 314.28 rules} \]

Minimum Pull Box Size:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is NEC 314.28?

NEC 314.28 specifies the minimum size requirements for pull and junction boxes in electrical installations. Proper sizing ensures conductors can be installed without damage and allows for proper bending space.

2. How Does the Calculator Work?

The calculator uses NEC 314.28 rules:

\[ \text{Straight Pull} = 8 \times \text{Largest Conduit Size} \] \[ \text{Angle Pull} = (6 \times \text{Largest Conduit Size}) + (0.5 \times \text{Number of Conductors}) \]

Where:

All dimensions are in inches
Measurements are based on the largest conduit entering the box
Angle pulls include additional space for conductor bending

3. Importance of Proper Pull Box Sizing

Details: Proper sizing prevents conductor insulation damage, makes installation easier, and ensures compliance with electrical codes. Undersized boxes can lead to failed inspections and safety hazards.

4. Using the Calculator

Tips: Enter the largest conduit size in inches, select the angle of pull (180° for straight pulls, 90° for angle pulls), and the number of conductors. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What if multiple conduits enter the box?
A: The calculation is always based on the largest conduit size entering the box.

Q2: Are there exceptions to these rules?
A: Yes, for very large conductors or special installations, consult the complete NEC 314.28 text.

Q3: How does conductor size affect the calculation?
A: The calculation is based on conduit size, but larger conductors may require additional space.

Q4: What about boxes with multiple angle pulls?
A: Size the box based on the most restrictive dimension (usually the largest angle pull).

Q5: Does this apply to all types of boxes?
A: These rules apply to standard pull and junction boxes. Special boxes may have different requirements.