Wire Size and Ampacity
Even the experts have to check occasionally on the correct gauge and ampacity (maximum amount of electrical current a conductor can carry) of wire for a given marine DC load. The simplest method we’ve found uses the charts below.
Select either the 10% (Marine Wire 1)or 3% (Marine Wire 2) voltage drop chart, based on the type of load you are running.
Next, find the current consumption of the load on the vertical axis of the chart.
Find the length of the circuit on the horizontal axis of the chart, noting that the length is the “round trip” distance from the panel or battery to the load and back.
The color of the graph at the intersection (Marine Wire 3) denotes the gauge of wire to use.
Of particular interest is the equation:
Voltage Drop = Current x Length x Ohms per foot
This simple equation allows you to calculate the voltage drop for a circuit of any length and any current flow, if you know the resistance of the wire.
Finally, note that the amp capacity of the wire curtails using very short lengths of wire for large current flows, as show by the “flat tops” of the 10% chart areas.
Marine Wire Marine Wire
Wire Gauge Color Code
Colors in above charts correspond to AWG wire sizes below:
These simple, proprietary graphs assume:
2007 Chevy 2500HD Classic LBZ Duramax/Allison (Stock)
2005 Bigfoot 1500C8.2 AWESOME