Southwire Voltage Drop Calculator Wire Size

Southwire Voltage Drop Formula:

\[ V_{drop} = I \times \left( \frac{2 \times L \times \rho}{A} \right) \]

Current (I):

Amps

Length (L):

feet

Resistivity (ρ):

ohm-ft

Cross-Sectional Area (A):

circular mils

Voltage Drop (V_drop):

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1. What is the Southwire Voltage Drop Formula?

The Southwire voltage drop formula calculates the voltage loss in an electrical circuit due to the resistance of the wire. It's essential for determining proper wire sizing in electrical installations to ensure adequate voltage at the load end.

2. How Does the Calculator Work?

The calculator uses the Southwire voltage drop formula:

\[ V_{drop} = I \times \left( \frac{2 \times L \times \rho}{A} \right) \]

Where:

\( I \) — Current in amperes (A)
\( L \) — Length of the wire in feet (ft)
\( \rho \) — Resistivity of the wire material in ohm-feet (Ω·ft)
\( A \) — Cross-sectional area of the wire in circular mils

Explanation: The formula accounts for the resistance of both the hot and neutral conductors (hence the factor of 2), the inherent resistivity of the wire material, and the cross-sectional area which determines the wire's current-carrying capacity.

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation is crucial for ensuring electrical equipment operates efficiently and safely. Excessive voltage drop can lead to equipment malfunction, reduced efficiency, and potential safety hazards.

4. Using the Calculator

Tips: Enter current in amperes, length in feet, resistivity in ohm-feet (copper is typically 0.0000104 Ω·ft, aluminum is 0.0000168 Ω·ft), and cross-sectional area in circular mils. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a circular mil?
A: A circular mil is a unit of area used for wire cross-sections, equal to the area of a circle with a diameter of one mil (1/1000 inch).

Q2: Why is there a factor of 2 in the formula?
A: The factor of 2 accounts for the total length of both the hot and neutral conductors in a single-phase circuit.

Q3: What is considered an acceptable voltage drop?
A: Generally, a voltage drop of less than 3% for branch circuits and less than 5% for feeder circuits is considered acceptable for most applications.

Q4: How does temperature affect resistivity?
A: Resistivity increases with temperature. The calculator uses room temperature values; for high-temperature applications, adjusted resistivity values should be used.

Q5: Can this calculator be used for DC circuits?
A: Yes, the formula works for both AC and DC circuits, though for AC circuits, additional factors like power factor and skin effect may need consideration.