Voltage Loss Calculator
Calculate the voltage drop and percentage loss in your electrical circuit to ensure efficient and safe operation.
Understanding Voltage Loss
Voltage loss, also known as voltage drop, is the reduction in electrical potential along the length of a conductor carrying current. It's a natural phenomenon in any electrical circuit due to the resistance of the wire. While some voltage drop is unavoidable, excessive loss can lead to several problems, including:
- Reduced efficiency of electrical appliances and motors.
- Dimming lights.
- Overheating of conductors.
- Malfunction or premature failure of sensitive electronic equipment.
The National Electrical Code (NEC) generally recommends a maximum voltage drop of 3% for feeders and branch circuits to the farthest outlet, and a total maximum of 5% for the combined feeder and branch circuit. Adhering to these guidelines ensures optimal performance and safety of your electrical system.
How Voltage Loss is Calculated
Our calculator uses a standard formula based on the conductor's material, size, length, and the current flowing through it. The primary factors influencing voltage loss are:
- Current (Amps): Higher current leads to greater voltage drop.
- Wire Length (Feet): Longer wires have more resistance, resulting in increased voltage loss.
- Wire Gauge (AWG): Thicker wires (smaller AWG numbers) have lower resistance and thus less voltage drop.
- Conductor Material: Copper has lower resistivity than aluminum, meaning it will have less voltage drop for the same gauge and length.
- System Type: Single-phase/DC and three-phase AC systems use slightly different constants in their voltage drop calculations.
The general formula for voltage drop (Vd) is:
For DC or Single-Phase AC: Vd = (2 * K * I * L) / CMA
For Three-Phase AC: Vd = (√3 * K * I * L) / CMA
Where:
Vd= Voltage Drop in VoltsK= Resistivity constant of the conductor material (e.g., 12.9 for Copper, 21.2 for Aluminum at 75°C)I= Current in AmperesL= One-way length of the circuit in feetCMA= Circular Mil Area of the conductor (derived from AWG)
Using the Calculator
To use the Voltage Loss Calculator, simply input the required values:
- Current (Amps): Enter the expected current draw of your circuit.
- One-Way Wire Length (Feet): Input the distance from the power source to the load.
- Source Voltage (Volts): Provide the nominal voltage of your power supply.
- Wire Gauge (AWG): Select the American Wire Gauge of your conductor from the dropdown.
- Conductor Material: Choose between Copper and Aluminum.
- System Type: Specify if your system is Single-Phase AC/DC or Three-Phase AC.
Click "Calculate Voltage Loss" to see the voltage drop in volts and as a percentage of your source voltage.
Example Calculation
Let's say you have a circuit with the following parameters:
- Current: 15 Amps
- One-Way Wire Length: 100 Feet
- Source Voltage: 120 Volts
- Wire Gauge: 12 AWG
- Conductor Material: Copper
- System Type: Single-Phase AC
Using the calculator:
First, we find the CMA for 12 AWG copper, which is 6530 CM. The K-factor for copper is 12.9.
Vd = (2 * 12.9 * 15 Amps * 100 Feet) / 6530 CM
Vd = (38700) / 6530
Vd ≈ 5.93 Volts
Percentage Voltage Drop:
Percentage Vd = (5.93 Volts / 120 Volts) * 100 ≈ 4.94%
In this example, a 4.94% voltage drop is higher than the recommended 3% for branch circuits, suggesting that a larger wire gauge (e.g., 10 AWG) or a shorter run might be necessary to meet NEC guidelines and ensure optimal performance.