Thread: Solar Swing-Set
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Old 08-24-13, 09:37 AM   #10
where2
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Quote:
Originally Posted by greif View Post
Low voltage needs big wire, been a long time since I took the solar classes. Just like you have big cables on your 48 v citicar
My thoughts exactly. So, I put Ben's scenario into a DC voltage drop calculator I found through Google search. I would definitely look for larger wire Ben. Voltage drop calculations yielded the following results:

Voltage drop: 4.04
Voltage drop percentage: 8.42%
Voltage at the end: 43.96volts

I used the following inputs:
Copper Conductors
AWG: 14
Voltage:48
AC/DC: DC
# of conductors: single set
Distance: 100'
Load Current: 8A

I presumed 50 feet out to the load, and 50 feet back to the panel, thus I have 100' of wire for the moving electrons to traverse.

Idealy, something #6AWG or larger would yield results like this:
Voltage drop: 0.63
Voltage drop percentage: 1.31%
Voltage at the end: 47.37

Usually, you want to keep your voltage drop under 2%, because it's just wasting energy. Again, my numbers are all relative to a 100 ft wire run. I don't know what your run distance really will be from the panel, through the conduit to your load and back to the panel.

The reason you can run 15A through #14AWG in a house is because you are running Alternating Current. Direct Current is much worse about voltage drop. That was actually one of the motivating factors in my use of micro-inverters: short DC run, then converted to 240V AC to get from the roof to the service entrance panel.

Last edited by where2; 08-24-13 at 09:45 AM..
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