1. What is the Southwire Voltage Drop Formula?

The Southwire voltage drop formula calculates the voltage drop in an electrical circuit based on the conductor material, current, length of the run, and wire size. It's essential for proper circuit design to ensure adequate voltage at the load.

2. How Does the Calculator Work?

The calculator uses the Southwire formula:

Where:

• \( V_{drop} \) — Voltage drop (volts)
• \( K \) — Material constant (12.9 for copper, 21.2 for aluminum)
• \( I \) — Current (amps)
• \( L \) — One-way length of wire (feet)
• \( CM \) — Circular mils of conductor

Explanation: The formula accounts for the resistance of the conductor material and the distance the current must travel.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation ensures electrical devices receive adequate voltage to operate correctly and prevents excessive power loss in wiring.

4. Using the Calculator

Tips: Enter the material constant (K), current in amps, one-way length in feet, and conductor size in circular mils. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the maximum acceptable voltage drop?
A: For branch circuits, the National Electrical Code recommends no more than 3% drop for branch circuits and 5% total drop for feeder and branch circuits combined.

Q2: How do I find the circular mils for my wire?
A: Refer to wire gauge tables - common values are 16,530 CM for #6 AWG copper, 41,740 CM for #2 AWG copper, etc.

Q3: Why multiply length by 2 in the formula?
A: The formula accounts for the round-trip distance of current flow (hot and neutral conductors).

Q4: Does this work for both AC and DC circuits?
A: Yes, though for AC circuits at higher frequencies, additional factors like skin effect may need consideration.

Q5: How does temperature affect voltage drop?
A: Higher temperatures increase conductor resistance, which increases voltage drop. The K value changes with temperature.