1. What is the Underground Service Wire Size Calculation?

The Underground Service Wire Size calculation determines the appropriate cross-sectional area of wire needed to minimize voltage drop over a specified distance while carrying a given current. This is crucial for safe and efficient electrical installations.

2. How Does the Calculator Work?

The calculator uses the wire size formula:

Where:

• \( A \) — Wire cross-sectional area (mm²)
• \( I \) — Current (Amperes)
• \( L \) — Length of wire run (Meters)
• \( \rho \) — Resistivity of copper (1.68 × 10^-8 Ω·m)
• \( V_{drop} \) — Maximum allowable voltage drop (Volts)

Explanation: The formula calculates the minimum wire size needed to maintain voltage within acceptable limits over the specified distance.

3. Importance of Proper Wire Sizing

Details: Proper wire sizing prevents excessive voltage drop, reduces energy loss, minimizes heat generation, and ensures electrical safety and equipment performance.

4. Using the Calculator

Tips: Enter current in amperes, length in meters, resistivity (default is 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 path of the current (both the "hot" and "neutral" wires in AC systems).

Q2: What's a typical acceptable voltage drop?
A: For branch circuits, 3% is common; for feeders, 2% is often recommended (NEC suggests 5% total for both).

Q3: Does this work for aluminum wire?
A: For aluminum, use resistivity of 2.65 × 10^-8 Ω·m instead of copper's 1.68 × 10^-8 Ω·m.

Q4: How does temperature affect the calculation?
A: Higher temperatures increase resistivity. For precise calculations, temperature correction factors should be applied.

Q5: Should I round up the calculated wire size?
A: Yes, always round up to the next standard wire size available in your area.