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Thread: Wire Gauge Question

  1. #1
    Junior Member
    Join Date
    Oct 2011

    Question Wire Gauge Question

    I'm new to solar and I'm having trouble determining what gauge of wire I need to go from the combiner box to the controller I have Sun Electronics panels - 200w, 33.2V Open circuit, and 7.28A. I'm wiring them in 2 series of 3. So the voltage will be 99.6 and the amperage will be at 14.56. The distance from the combiner box to the Outback FM60 is about 120 feet. I'm thinking I'll need either 4, 5, or 6 gauge. Also, this will show my ignorance but, will stranded wire work or does it need to be solid?

    While I'm at it, I should back up. How should I get the pv cables to the combiner box? I was planning on putting the combiner box inside which means putting it about 30 ft from the panels. First off, is that pointless? If not, should I run four separate pv cables (two positive and two negative) and connect them at the combiner box? Or should I reduce to two at the panels and run two to the combiner box?


  2. #2
    Super Moderator
    Join Date
    Feb 2011
    Annapolis Md


    Google voltage drop calculator. follow the instructions there and keep the voltage drop to less than 2%

    NABCEP certified Technical Sales Professional


    http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)


  3. #3

  4. #4
    Join Date
    May 2009
    off grid retirement in Northern Calif


    And in my .sig is another wire gauge designed for solar PV applications. Just a free reg to download.
    Since the dawn of time it has been mankind's dream to blot out the sun.
    Montgomery Burns

    "Always listen to experts. They'll tell you what can't be done and why. Then do it."

    spreadsheet based voltage drop calculator:


    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,
    battery lugs http://tinyurl.com/LMR-BigLug
    Setting up batteries http://tinyurl.com/LMR-NiFe

    gear :
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||

    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||

    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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