1. What is the Southwire Wire Size Calculator?

The Southwire Wire Size Calculator determines the appropriate wire cross-sectional area based on length, current, resistivity, and allowable voltage drop. It ensures electrical systems operate efficiently and safely by preventing excessive voltage drops.

2. How Does the Calculator Work?

The calculator uses the Southwire equation:

Where:

• \( A \) — Wire cross-sectional area (mm²)
• \( L \) — Length of the wire (m)
• \( I \) — Current flowing through the wire (A)
• \( \rho \) — Resistivity of the wire material (ohm m)
• \( Vd \) — Allowable voltage drop (V)

Explanation: The equation calculates the minimum wire size needed to maintain voltage drop within acceptable limits for a given current and length.

3. Importance of Wire Size Calculation

Details: Proper wire sizing is crucial for electrical safety, efficiency, and compliance with electrical codes. It prevents overheating, energy loss, and ensures equipment operates correctly.

4. Using the Calculator

Tips: Enter length in meters, current in amperes, resistivity in ohm meters, and voltage drop in volts. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is typical resistivity for copper wire?
A: Copper has a resistivity of approximately 1.68 × 10⁻⁸ ohm m at 20°C.

Q2: What is an acceptable voltage drop?
A: Generally, voltage drop should not exceed 3% for branch circuits and 5% for feeder and branch circuits combined.

Q3: Why multiply by 2 in the formula?
A: The factor of 2 accounts for the round trip path of the current (out and back) in single-phase systems.

Q4: Does temperature affect resistivity?
A: Yes, resistivity increases with temperature. The calculator uses resistivity at standard temperature unless specified.

Q5: Can this be used for AC and DC systems?
A: The basic formula works for DC systems. For AC systems, additional factors like power factor and skin effect may need consideration.