Wire Size

Wire sizes become important at low voltages. At 12 volts DC a loss of more than 10% in voltage across the length of the wire can mean the difference between the inverter running or not running. The currents can get high and any voltage drop becomes significant. In general at 12 Volts DC one should run the inverter close to the battery and then pipe the 120 Volts AC to the point of use on smaller wire.

The general rule is at low voltages pay attention to voltage drop and at high voltages pay attention to maximum current caring capacity for the size of wire.

Properly sized wire can make the difference between inadequate and full charging of a battery system, between dim and bright lights, and between feeble and full performance of tools and appliances. Designers of low voltage power circuits are often unaware of the implications of voltage drop and wire size. In conventional home electrical systems (120/240 volts ac), wire is sized primarily for safe amperage carrying capacity (ampacity). The overriding concern is fire safety.

In low voltage systems (12, 24, 48VDC) the overriding concern is power loss. Wire must not be sized merely for the ampacity, because there is less tolerance for voltage drop (except for very short runs). For example, a 1V drop from 12V causes 10 times the power loss of 1V drop from 120V.

Use the charts on this PDF file as your primary tool in solving wire sizing problems.

Offered by Mike.