1. What is the Wire Size Calculation?

The wire size calculation determines the minimum cross-sectional area of a conductor needed to carry 100 amps over a specified distance while maintaining acceptable voltage drop. Proper sizing ensures safety and efficiency in electrical systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( A \) — Wire cross-sectional area (mm²)
• \( L \) — Length of wire (meters)
• \( \rho \) — Resistivity of copper (1.68 × 10⁻⁸ Ω·m)
• \( V_{drop} \) — Acceptable voltage drop (volts)
• 2 — Accounts for both supply and return paths

Explanation: The equation calculates the minimum wire size needed to maintain the specified voltage drop for a 100 amp current over the given distance.

3. Importance of Proper Wire Sizing

Details: Correct wire sizing prevents excessive voltage drop, reduces heat generation, and ensures electrical safety. Undersized wires can cause fires, while oversized wires are unnecessarily expensive.

4. Using the Calculator

Tips: Enter wire length in meters, acceptable voltage drop in volts, and resistivity (default is copper). Typical voltage drop limits are 3% of circuit voltage for branch circuits.

5. Frequently Asked Questions (FAQ)

Q1: Why is resistivity important?
A: Different materials have different resistivities. Copper (1.68 × 10⁻⁸ Ω·m) is most common, but aluminum (2.65 × 10⁻⁸ Ω·m) is also used.

Q2: What's a typical voltage drop allowance?
A: For 120V circuits, 3.6V (3%); for 240V circuits, 7.2V (3%). Critical circuits may require 1% or less.

Q3: Does this account for temperature?
A: No, this uses standard resistivity values. For high-temperature environments, consult NEC tables.

Q4: How does wire length affect sizing?
A: Longer runs require larger wire sizes to maintain the same voltage drop.

Q5: Is this calculator for AC or DC?
A: This calculation works for both, but AC systems may need additional considerations for skin effect at high frequencies.