wire size-panels to charge controller

ldiorio
ldiorio Solar Expert Posts: 48 ✭✭
in PV Installers Forum - NEC, Wiring, Installation #1
hi all,
am in the process of installing 6- 255 watt panels for a 48 volt system(vmp=30.4v,imp-8.4a.voc=37.6v,isc=9.1a)--
about 15 feet from the panels to the combiner w/AWG10 extender cable--then 40-45 feet from the combiner to the charge controller

some say i i could use 10AWG the entire length of the loop--but i ran a voltage loss calc and it says i need 6AWG for a min of 3% voltage drop

pls need opinions on this -i want to reduce the loss as much as i can-i already have 1" PVC run from the combiner to the CC

thanks
lou
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Comments

  • Imurphy
    Imurphy Registered Users Posts: 16 ✭✭
    #2
    Assuming you will be putting 3 panels in series for 2 strings. You would be running ~90VMP. 90 volts DC at 18 amps for the string.
    45' of
    4 AWG at 90 volts and 18 amps will be 0.44% drop or a loss of 0.4 Volt DC.
    6 AWG will be 0.71% or 0.64 Volt DC drop.
    10 AWG gives you 1.8% drop or 1.62 Volt DC.

    Do you have any plans or hopes/ ideas of expanding this system at some time? If the definitive answer is no than you can use 6AWG. But if the answer is anything other then a solid no. go bigger. If this were my set up I would be using 2 AWG as I design for 0.25% or less loss when ever I can. I play by telco rules. no more then 1v drop from the source to the load. And we don't consider batteries to be a load. You can beat the numbers for 2 AWG by running 2 conductors per phase of 4 AWG. Depending on the price of wire this may be cheaper than a single run of #2. Or you may be happy with a single run of #4. These are the numbers, you can make up your own mind.
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  • ldiorio
    ldiorio Solar Expert Posts: 48 ✭✭
    #3
    i figured #10 would not do it

    can i run a #10 insul ground

    tks
    lou
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