The following tables work well for PV applications. We also have an inverter calculator which can help you decide what size wiring to use in a 12 volt system. It is located at http://www.skingcompany.com/portable_power/calc.htm
Wiring Reference Guide
When additional wiring is needed refer to the following charts to determine correct sizing. Selecting the correct size and type of wire will enhance the performance and reliability of your PV system. The size of the wire must be large enough to carry the maximum current expected without undue voltage losses. All wire has a certain amount of resistance to the flow of current. This resistance causes a drop in the voltage from the source to the load. Voltage drops cause inefficiencies, especially in low voltage systems (12V or less). There are several different types of wire available depending on how and where it will be used. For example, there are wire types designed for resistance to sunlight exposure, high temperatures and direct burial. Specify wiring that will withstand the worst conditions.
The wire sizing guide below provides the minimum wire size needed to limit voltage drops to 5% at a given distance in a 12V or 24V system. If you want to limit your losses to 2% simply divide the distance by 2.5. For a 48V system multiply the distance taken from the 24V chart by 2. The dashes represent currents which cannot be handled by the wire size.
How charts work
1. On the left, locate the current you will be dealing with (either array or load current.) 2. Move across to locate distance to be traveled. 3. Move up to locate size of wire to be used.
Wire Sizing Chart 12 Volt System
Maximum one-way distance (feet) for 5% voltage loss in 12 volt systems. Wire Size (AWG)
Wire Sizing Chart 24 Volt System
Maximum one-way distance (feet) for 5% voltage loss in 24 volt systems. Wire Size (AWG)
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