Low voltage calculations - 21 March 2007
A look at low valtage cable installation to the gate way.
a: Cable size and capacity
b: Voltage drop in volts and percent
c: Maximum length of run
d: Fuse size
e: Working Temperature
Cable Sizing Chart
This chart indicates the sizes of cable required to carry a given amount of power over various distances.
12v Systems Minimum cable size to keep voltage drop to less than about 5%
| Watts up to : |
Current up to: |
Absolute Minimum |
| Cable length in metres. |
|
3m |
10m |
30m |
100m |
| 36 W |
3A |
0.5 |
0.75 |
2.5 |
6 25 |
| 72 W |
6A |
0.75 |
1.5 |
4 |
10 35 |
| 120 W |
10A |
1 |
2.5 |
6 |
16 50 |
| 192 W |
16A |
1.5 |
2.5 |
10 |
25 -- |
| 288 W |
24A |
2.5 |
4 |
16 |
35 -- |
| 384 W |
32A |
4 |
6 |
16 |
50 -- |
| 480 W |
40A |
6 |
6 |
25 |
50 -- |
24v Systems Minimum cable size to keep voltage drop to less than about 5%
| Watts up to : |
Current up to: |
Absolute Minimum |
| Cable length in metres. |
|
3m |
10m |
30m |
100m |
| 72 W |
3A |
0.5 |
0.5 |
0.75 |
2.5 10 |
| 144 W |
6A |
0.75 |
0.75 |
1.5 |
4 16 |
| 240 W |
10A |
1 |
1 |
2.5 |
10 25 |
| 384 W |
16A |
1.5 |
1.5 |
4 |
16 50 |
| 576 W |
24A |
2.5 |
2.5 |
6 |
25 -- |
| 768 W |
32A |
4 |
4 |
10 |
25 -- |
| 960 W |
40A |
6 |
6 |
10 |
35 -- |
the above is for your guidance only and it is important to check the lenght of the run to obtain the correct cable size
Example: 24v 180 w underground automation motor with a current absorption of 15 amps will require a 1.5 mm cable for a length of run upto 20 m & a 2.5 mm cable for lengths not longer than 30 m.