Wire SizeĬhart developed by John Davey and Windy Dankoff. What if this system was 24-volt? The modules would be wired in series so each pair of modules would produce 4.4 amps. Looking at our chart, a VDI of 29 means we’d better use #2 wire in copper, or #0 wire in aluminum. These modules are rated at 4.4 amps x 4 modules = 17.6 amps maximum. This is actual wiring distance, up pole mounts, around obstacles, etc. Wire gauge, or the measurement of a wires diameter, is an extremely important measurement for your determining your projects choice of wire. (This is not usually a problem in low-voltage circuits).Įxample: Your PV array consisting of four 75W modules is 60 feet from your 12-volt battery. Be sure that your circuit amperage does not exceed the figure in the Ampacity column for that wire size.For motors, it is recommended to multiply the nameplate FLA by 1.25 for wire sizing. Amperes - Enter the maximum current in amps that will flow through the circuit. Single-phase voltages are usually 115V or 120V, while three-phase voltages are typically 208V, 230V or 480V. Take the VDI number you just calculated and find the nearest number in the VDI column, then read to the left for AWG wire gauge size. Calculate Reset Voltage - Enter the voltage at the source of the circuit.Determine the appropriate wire size from the chart below. % Volt Drop = Percentage of voltage drop acceptable for this circuit (typically 2% to 5%)Ģ.VDI = AMPS x FEET ÷ (% VOLT DROP x VOLTAGE) Calculate the Voltage Drop Index (VDI) using the following formula: Note: This formula doesn’t directly yield a wire gauge size, but rather a “VDI” number, which is then compared to the nearest number in the VDI column, and then read across to the wire gauge size column.ġ. There’s no sense using your expensive PV wattage to heat wires. For most DC circuits, particularly between the PV modules and the batteries, we try to keep the voltage drop to 3% or less. This chart is useful for finding the correct wire size for any voltage, length, or amperage flow in any AC or DC circuit.
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