It is safe when installed to code with AL-rated terminals. Power companies use it because it is cheaper than copper and lighter in weight, even though a larger size must be used. ![]() More Techniques for Cost ReductionĪLUMINUM WIRE may be more economical than copper for some main lines. Consult the wind system’s instruction manual. That loss will only occur occasionally, when energy is most abundant. If wire sized for low loss is large and very expensive, you may consider sizing for a voltage drop as high as 10% at the rated current. WIND GENERATOR CIRCUITS: At most locations, a wind generator produces its full rated current only during occasional windstorms or gusts. Your customer will appreciate that when it comes time to add to the array. If you think that the PV array may be expanded in the future, size the wire for future expansion. Our general recommendation here is to size for a 2-3% voltage drop. A voltage drop greater than 5% will reduce this necessary voltage difference, and can reduce charge current to the battery by a much greater percentage. That’s why most PV modules are made for 16-18V peak power point. To charge a battery, a generating device must apply a higher voltage than already exists within the battery. PV BATTERY CHARGING CIRCUITS are critical because voltage drop can cause a disproportionate loss of charge current. Without a battery to hold the voltage down, the working voltage will be around the peak power point voltage of the PV array. 24V) but for the actual working voltage (in that case approximately 34V). PV-DIRECT SOLAR WATER PUMP circuits should be sized not for the nominal voltage (i.e. In the case of a well pump, follow the manufacturer’s instructions. Significant voltage drop in these circuits may cause failure to start and possible motor damage. ![]() They exhibit very high surge demands when starting. Voltage drop during the starting surge simply results in a “soft start”.ĪC INDUCTION MOTORS are commonly found in large power tools, appliances and well pumps. DC motors do NOT have excessive power surge demands when starting, unlike AC induction motors. They operate at 10-50% higher efficiencies than AC motors, and eliminate the costs and losses associated with inverters. Buzz, flicker and poor color rendition are eliminated in most of today’s compact fluorescents, electronic ballasts and warm or full spectrum tubes.ĭC MOTORS may be used in renewable energy systems, especially for water pumps. ![]() We advocate use of quality fluorescent lights. Fluorescents use 1/2 to 1/3 the current of incandescent or QH bulbs for the same light output, so they can use smaller wire. LIGHTING CIRCUITS, FLUORESCENT: Voltage drop causes a nearly proportional drop in light output. This is because the bulb not only receives less power, but the cooler filament drops from white-hot towards red-hot, emitting much less visible light. LIGHTING CIRCUITS, INCANDESCENT AND QUARTZ HALOGEN (QH): Don’t cheat on these! A 5% voltage drop causes an approximate 10% loss in light output. Different electrical circuits have different tolerances for voltage drop. When that turns out to be very expensive, consider some of the following advice. ![]() For other conditions, refer to National Electric Code or an engineering handbook.ĭid you know altE offers free solar system design consulting? Call us at 87 or tell us about your desired system using our free quote tool.įREE QUOTE Determining Tolerable Voltage Drop for Various Electrical LoadsĪ general rule is to size the wire for approximately 2-3% drop at typical load. Ampacity is based on the National Electrical Code (USA) for 30☌ (85☏) ambient air temperature, for no more than three insulated conductors in raceway in free air of cable types AC, NM, NMC and SE and conductor insulation types TA, TBS, SA, AVB, SIS, RHH, THHN and XHHW. Ampacity rating of wire size must be at least 125% of the continuous current passing through it.Īvailable sizes: 1 1.5 2.5 4 6 10 16 25 35 50 70 95 120 mm 2Ģ0-amp load at 24V over a distance of 100 feet with 3% max voltage drop Compare your calculated VDI with VDI in the chart to determine the closest wire size. Step 2 – Determine appropriate wire size from the chart below. %VOLT DROP = Your choice of acceptable voltage drop (example: use 3 for 3%) VDI = Voltage Drop Index (a reference number based on resistance of wire)įEET = ONE-WAY wiring distance (1 meter = 3.28 feet) Step 1 – Calculate the following: VDI = (AMPS x FEET)/(%VOLT DROP x VOLTAGE) It applies to typical DC circuits and to some simple AC circuits (single-phase AC with resistive loads, not motor loads, power factor = 1.0, line reactance negligible). This chart works for any voltage or voltage drop, American (AWG) or metric (mm2) sizing.
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