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The "Wire Size" charts are provided for easy selection of wire sizes. (The
charts, however, neglect losses due to connections or switches.)
To use the chart:
A) Determine the total wire length from the power source to the most
distant point in the circuit.
B) Determine the total electrical load on the circuit.
C) Find the load along one edge of the chart (6V or 12V) depending
on the vehicle voltage in question, taking the nest
higher load if
the indicated load falls between two points on the chart.
D) Find the cable length required on the top of the chart, taking the
next higher length (if exact length is not
cited).
E) At the intersection of the length and load column, read the minimum
size wire required for that particular circuit.
See below for a detailed example
12V
(AMP) |
6V
(AMP) |
10' |
20' |
30' |
40' |
50' |
60' |
70' |
80' |
90' |
100' |
|
|
Gauge |
Gauge |
Gauge |
Gauge |
Gauge |
Gauge |
Gauge |
Gauge |
Gauge |
Gauge |
| 1.0 |
.5 |
18 |
18 |
18 |
18 |
18 |
18 |
18 |
18 |
18 |
18 |
| 1.5 |
.75 |
18 |
18 |
18 |
18 |
18 |
18 |
18 |
18 |
18 |
18 |
| 2.0 |
1.0 |
18 |
18 |
18 |
18 |
18 |
18 |
18 |
16 |
16 |
16 |
| 3.0 |
1.5 |
18 |
18 |
18 |
18 |
18 |
16 |
16 |
16 |
14 |
14 |
| 4.0 |
2.0 |
18 |
18 |
18 |
16 |
16 |
16 |
14 |
14 |
14 |
12 |
| 5.0 |
2.5 |
18 |
18 |
18 |
16 |
14 |
14 |
14 |
12 |
12 |
12 |
| 6.0 |
3.0 |
18 |
18 |
16 |
16 |
14 |
14 |
12 |
12 |
12 |
10 |
| 7.0 |
3.5 |
18 |
18 |
16 |
14 |
14 |
12 |
12 |
12 |
12 |
10 |
| 8.0 |
4.0 |
18 |
16 |
16 |
14 |
12 |
12 |
12 |
10 |
10 |
10 |
| 10.0 |
5.0 |
18 |
16 |
14 |
12 |
12 |
12 |
10 |
10 |
10 |
10 |
| 11.0 |
5.5 |
18 |
16 |
14 |
12 |
12 |
10 |
10 |
10 |
10 |
8 |
| 12.0 |
6.0 |
18 |
16 |
14 |
12 |
12 |
10 |
10 |
10 |
8 |
8 |
| 15.0 |
7.5 |
18 |
14 |
12 |
12 |
10 |
10 |
10 |
8 |
8 |
8 |
| 18.0 |
9.0 |
16 |
14 |
12 |
10 |
10 |
8 |
8 |
8 |
8 |
8 |
| 20.0 |
10.0 |
16 |
12 |
12 |
10 |
10 |
8 |
8 |
8 |
8 |
6 |
EXAMPLE
Determine: Wire size required for the clearance light circuit having eleven
lights with No. 97 bulbs
SOLUTION:
A) Find total ampere load in the circuit. There are 11 lights - No. 97
bulbs.
Each bulb has an ampere rating of .69 amps.
TOTAL AMP LOAD = .69 x
11 = 7.59 amps
B) Find the distance from the power source to the 
most distant light. Total distance
= 3 + 45 + 8 + 4 = 60 feet.
C) Find the wire size in the
above chart. Find the length along
the top - 60'. Find the ampere
load in the 12V column then 8
amps is the next higher load
above 7.69 amps. At the
instersection of these two lines a 12 gauge wire is
indicated.
This is the WIRE SIZE TO BE USED.
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