1. What is the Wire Size Formula?

The wire size formula calculates the minimum cross-sectional area of a conductor needed to maintain a specified voltage drop over a given distance. It's essential for proper electrical system design to ensure adequate voltage at the load.

2. How Does the Calculator Work?

The calculator uses the wire size formula:

Where:

• \( A \) — Cross-sectional area of wire (m²)
• \( I \) — Current (Amperes)
• \( L \) — Length of wire (meters)
• \( \rho \) — Resistivity of conductor material (Ω·m)
• \( V_{drop} \) — Maximum allowable voltage drop (Volts)

Explanation: The formula accounts for the resistance of the wire over distance and the current it must carry while maintaining acceptable voltage levels.

3. Importance of Proper Wire Sizing

Details: Correct wire sizing prevents excessive voltage drop (which can cause equipment malfunction), reduces energy loss, and minimizes fire hazards from overheating.

4. Using the Calculator

Tips: Enter current in amperes, length in meters, resistivity in Ω·m (1.68×10⁻⁸ for copper), and desired maximum voltage drop. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why multiply by 2 in the formula?
A: The factor of 2 accounts for the round-trip length of the circuit (both hot and neutral wires in single-phase systems).

Q2: What's a typical acceptable voltage drop?
A: For most applications, 3% is recommended for branch circuits and 5% for feeder circuits.

Q3: What resistivity value should I use?
A: 1.68×10⁻⁸ Ω·m for copper at 20°C. For aluminum, use 2.65×10⁻⁸ Ω·m.

Q4: Does this account for temperature effects?
A: No, this is a basic calculation. For high-temperature environments, additional derating factors may be needed.

Q5: How do I convert mm² to AWG?
A: Use an AWG conversion chart. For example, 2.5 mm² ≈ AWG 13, 4 mm² ≈ AWG 11, etc.