Event Horizon Solar & Wind Inc
Providing Solar and Wind power for 15 years.
Retail, Wholesale Solar and Wind products.
616-389-3172 9am to 5pm eastern.
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Voltage Drop Table
To achieve maximum efficiency from your power system you do not want to under-size your wire between various components. If in doubt use a larger wire size than the charts below suggest. We will generally size the wire to maintain no more than a 2 - 3 percent voltage drop regardless of the system voltage, however this factor is more critical on low voltages. For 120/240 volts a maximum of five percent loss is acceptable unless specific equipment dictates otherwise.
The difference in cost of the next larger-size wire is usually insignificant
to the overall
costs where performance may be affected over the life of the components.
In addition, improperly sized wire can shorten the life of your components.
Before using these tables, some calculations must first be performed by the system designer to insure accurate current ratings and safety factors are used. For solar modules, the UL-1703 standard requires the short circuit current (lsc) rating of the PV module be multiplied by 125% before other factors are applied. This is because the PV module electrical performance can increase above the factory rating due to the combination of increased operating temperatures and enhanced irradiances over 1000W/M2 (such as edge-of-cloud effect).
NOTE: The "edge-of-cloud effect" is also a consideration when sizing a charge/voltage controller for solar modules. Use the short-circuit current rating to determine the controller.
The NEC requires the short circuit current ratings of the PV module or array be multiplied by 125% before calculating ampacities of any cable or over current device. This is in addition to the UL required 125%! This yields a multiplier of (125%x125%=156%) or 1.56. Although this may seem redundant, good design practice dictates both factors should be used when determining wire size from the solar array to the battery.
For larger batteries and inverters (battery to inverter cable
a minimum 4/0 cable is recommended.
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|Maximum Ampacity for Copper and Aluminum Wire|
NEC allows rounding up cable ampacity to next standard fuse or breaker.
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