1. What is NEC Voltage Drop Calculator Southwire?

Definition: This calculator estimates voltage drop in electrical circuits according to NEC standards using Southwire's methodology.

Purpose: It helps electricians and engineers ensure proper voltage levels in electrical installations.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( VD \) — Voltage drop (volts)
• \( I \) — Current (amps)
• \( L \) — Length of conductor (meters)
• \( R \) — Resistance (millivolts per amp per meter)

Explanation: The formula accounts for the round-trip distance (hence the 2) and converts millivolts to volts (hence the 1000 divisor).

3. Importance of Voltage Drop Calculation

Details: Proper voltage drop calculation ensures electrical equipment receives adequate voltage for optimal performance and safety.

4. Using the Calculator

Tips: Enter the circuit current in amps, conductor length in meters, and resistance in mV/A/m. All values must be > 0.

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 (out to the load and back).

Q2: Where can I find resistance values?
A: Consult Southwire's conductor specifications or NEC tables for standard resistance values.

Q3: What's an acceptable voltage drop?
A: NEC recommends no more than 3% voltage drop for branch circuits and 5% for feeder and branch circuits combined.

Q4: Does this work for both AC and DC circuits?
A: This simplified formula works for DC and AC resistive loads. For AC inductive loads, impedance should be used instead of resistance.

Q5: How does conductor size affect the calculation?
A: Larger conductors have lower resistance values (R), resulting in less voltage drop for the same current and distance.