Get our free book (in Spanish or English) on rainwater now - To Catch the Rain.

Wire length tables

Introduction

Describe wire length, voltage loss, etc. here.

Tables

The following table shows the American Wire Gauge (AWG) size for several different round trip (RT) wire lengths based on maximum current (A) for a 12V DC system (assuming 3% maximum wire loss):

Table 1. Wire Sizes
RT length 5A 10A 15A 20A 25A 30A 40A 50A
15 ft 16 12 10 10 8 8 6 6
20 ft 14 12 10 8 8 6 6 4
25 ft 14 10 8 8 6 6 4 4
30 ft 12 10 8 6 6 4 4 2
40 ft 12 8 6 6 4 4 2 2
50 ft 10 8 6 4 4 2 2 1
60 ft 10 6 4 4 2 2 1 1/0
70 ft 8 6 4 2 2 2 1/0 2/0
80 ft 8 6 4 2 2 1 1/0 2/0
90 ft 8 4 2 2 1 1/0 2/0 3/0

This table was adapted from Engineering Toolbox [1] .

Calculating Wire Sizes

1. copper wire resistivity = 11.2 [2]
2. 3% loss from wires
3. allowable voltage drop = 0.36V
• 12V system, 3% (0.03) wire loss -> 12V x 0.03 = 0.36V

Variable Declarations:

• An: circular mil area
• n: AWG
• m: AWG
• Conductor resistivity: constant, 11.2
• Current: current through wire in Amps, acquired from table
• Roundtrip (RT) wire length: complete length of wire, ft, acquired from table
• Allowable voltage drop: voltage drop through wires, V
Table 2. Calculating Wire Sizes
Eqn. # Equation Step/Explanation
#1 $A_n=(5*92^\frac{36-n}{39})^2$ Eqn. 1 was used, rearranged, and iterated on to produce Table 1. [3].
#2 $n=36-\frac{39*log\sqrt{\frac{A_n}{5}}}{log(92)}$ Algebraically rearrange Eqn. 1 to solve for n. The resulting equation is Eqn. 2 to the left.
#3 $n=1-m$ If n<0, replace n with 1-m in Eqn. 1 [4] .
#4 $A_n=(5*92^\frac{36-(1-m)}{39})^2$ Substituting n equals 1-m into Eqn. 1 yields this equation (Eqn. 3). Use Eqn. 3 if n<0.
#5 $m=\frac{39*log\frac{\sqrt{A_n}}{5}}{log(92)}-35$ Solve Eqn. 3 for m, the resulting equation (Eqn. 4) is to the left.
#6 $A_n=\frac{(conductor-resistivity)*(current[A])*)roundtrip-wire-length[ft])}{allowable-voltage-drop[V]}$ Eqn. 3 is also a rearrangement of Eqn. 1. Use Eqn. 4 to solve for A_n

See Help:Tables.

Use help:references to see how to use the reference format.[1]

Use Help:Images on how to upload the graph image(s). Please remember to use a very descriptive name for the file.

References

1. It is quite easy and just relies on ref and /ref in between less than and greater than symbols.