DC wire run length in parallel?

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freedj
freedj Registered Users Posts: 15 ✭✭
in Solar Beginners Corner #1
I currently have a 40' length of 10awg wire connecting my charge controller to my PV array. My array is 20' from my charge controller. Obviously i want to shorten the run, but I have enough wire that I could run 2 lengths in parallel.

10awg is to small for my application. I am probably loosing between %5 and %10 over the length of my current run. I am trying to find some cheap 6awg, but If i can gain most of the same benefit from using a parallel link between the array and the charge controller using the materials i have on hand, that's even better.

I couldn't quite find the right search terms to learn more.

How would 2 parallel runs of 10awg compair to a single 6awg or 8awg wire?
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #2
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    Re: DC wire run length in parallel?
    freedj wrote: »
    I currently have a 40' length of 10awg wire connecting my charge controller to my PV array. My array is 20' from my charge controller. Obviously i want to shorten the run, but I have enough wire that I could run 2 lengths in parallel.

    10awg is to small for my application. I am probably loosing between %5 and %10 over the length of my current run. I am trying to find some cheap 6awg, but If i can gain most of the same benefit from using a parallel link between the array and the charge controller using the materials i have on hand, that's even better.

    I couldn't quite find the right search terms to learn more.

    How would 2 parallel runs of 10awg compare to a single 6awg or 8awg wire?

    Excellent thought. Someone can correct me if I'm wrong but I believe two parallel runs of #10 is very close in resistance to one single run of # 7.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #3
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    Re: DC wire run length in parallel?

    What are the array specs? Twenty feet isn't very far; you should not be experiencing huge Voltage drop on that distance unless the array Voltage is low (12 V nominal) and the current is high (more than 16 Amps).

    Using those minimal numbers, 10 AWG would be about 5% drop, 8 AWG about 3%, 6 AWG about 2%.
    If you double the 10 AWG it's like halving the current, so each run would take 8 Amps and have about 2.5% Voltage drop (nearly the same as a single run of 6 AWG).
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,443 admin
    #4
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    Re: DC wire run length in parallel?

    Wayne is correct... 3 AWG increase in size is a doubling of the diameter. There still may be the issue of surface area/insulation/cooling which would be srt(2) larger.

    NEC, as I remember, does not "allow" paralleling of smaller conductor cables (when you get the big stuff-something like 1/O or heavier(?), then they do allow paralleling).

    As long as the one wire carries rated load, then you should be OK even if the other parallel path gets "broken"--the remaining wire will not overheat.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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