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Even the experts have to check occasionally on the correct gauge of wire for a given marine DC load. The simplest method we’ve found uses the charts below.
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Select either the 10% or 3% voltage drop chart,
based on the type of load you are running.
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Next, find the current consumption of the load on
the vertical axis of the chart.
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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.
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The color of the graph at the intersection denotes
the gauge of wire to use.
We've
included copper wire specifications which comply with the AWG
standards at the bottom.
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.
Wire Gauge Color Code Colors in above charts correspond to AWG wire sizes.
These simple, proprietary graphs assume:
1.105ºC insulation rating: All Ancor wire uses 105ºC insulation rating. Lower temperature insulation cannot handle as much current (the flat tops on the 10% graph would be lower than shown)
2. AWG wire sizes: Not SAE All
Ancor wire uses AWG wire sizes. SAE wire sizes are 6%-12% smaller,
carry proportionally less
current, and have greater resistance
3. Wires are not run in engine spaces: Maximum
current is 15% less in engine spaces, which are assumed to be 20¼C
hotter than nonengine
spaces (50¼C vs. 30¼C).
4. Conductors are not bundled: If
three conductors are bundled, reduce maximum amperage by 30%. If
4-6 conductors are
bundled, reduce maximum amperage by 40%. If 7-24 conductors are
bundled, reduce amperage
by 50%.
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AWG Wire Specs
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| Wire Size (AWG) |
Nominal OD |
Weight per 1000' |
Cir.Mil. Area |
Square mm |
Ohms per 1000' |
Max Amps |
| 18 |
7/64" |
12# |
1,600 |
0.823 |
6.48 |
20 |
| 16 |
1/8" |
16# |
2,600 |
1.31 |
4.00 |
25 |
| 14 |
9/64" |
23# |
4,100 |
2.08 |
2.5 |
35 |
| 12 |
5/32" |
31# |
6,500 |
3.31 |
1.75 |
45 |
| 10 |
7/32" |
44# |
10,500 |
5.26 |
0.98 |
60 |
| 8 |
5/16" |
86# |
16,800 |
8.37 |
0.62 |
80 |
| 6 |
11/32" |
18# |
26,600 |
13.30 |
0.40 |
120 |
| 4 |
13/32" |
178# |
42,000 |
21.15 |
0.24 |
160 |
| 2 |
15/32" |
277# |
66,500 |
33.62 |
0.157 |
210 |
| 1 |
17/32" |
350# |
83,690 |
44.21 |
0.127 |
245 |
| 1/0 |
9/16" |
437# |
105,600 |
53.49 |
0.099 |
285 |
| 2/0 |
5/8" |
549# |
133,000 |
67.43 |
0.077 |
330 |
| 3/0 |
11/16" |
675# |
167,800 |
85.01 |
0.062 |
385 |
| 4/0 |
13/16" |
837# |
211,600 |
107.20 |
0.049 |
445 |
To complete your project, don’t forget:
- Heat Shrink tubing
- Wire-strippers, cutters, and crimpers
- Terminals: ring, spade or butt connectors
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