String Sizing: Need Help

solarpower2009solarpower2009 Registered Users Posts: 7
I am new to Solar power. I want to install 1kw system with 10 100w 12v panels. I am trying to see how to maximize the output from my panels.

I have a flexmax80 and an outback gvfx3524.

I tried using the outback string sizing tool, but was not successful.

Here are my specifications for the panels.
Isc. 5.4 voc. 24.8 Imp. 4.81 vmp. 20.8 vtoc. -.38 vtmp. -.47

Are 5 arrays of 2 panels in series a good option.
are 2 arrays of 5 panels in series a better option.

Any help in this regard is appreciated as I am about to install them on my roof.


  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: String Sizing: Need Help

    give the Outback tool another try.

    I had to go to one of the stock panels first, seems to be veeeerrrry slow to load. then you can click on OWN and enter the panel details. Just cant print it off...

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    West Chilcotin, BC, Canada
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: String Sizing: Need Help

    i think 5 arrays of 2 in series would be better as the higher voltages become less efficient the farther from the output voltage they are. i think it'll work if i'm not overlooking something here. btw, with a 2 string by 5 series pv arrangement during colder weather it could go far higher in voltage and around the controller's maximum voltage specs. you will need to fuse and combine these strings being more than 2.
  • solarpower2009solarpower2009 Registered Users Posts: 7
    Re: String Sizing: Need Help

    Westbranch and Niel,

    Thanks for your quick replies.

    I revisited the string sizing tool and was able to input my values for the first time.

    I am not sure how to interpret the results for a 5 strings of 2 arrangement. (Picture below)

    With highest and lowest temperatures in the DC area the 2 strings of 5 arrangement shows all green squares for a 12 volt system along with 1000watts output. attachment 1

    The same arrangement for a 24 volt system shows a row of lavender squares.attachement 2

    What do different colors of these squares tell you? Do lavender squares tell you that you are at the limit or something?

    Looking forward to your comments.
  • audredgeraudredger Solar Expert Posts: 272 ✭✭
    Re: String Sizing: Need Help

    You want to stay in the green... lavender does show either over voltage or over current condition, no doubt due to weather / temp conditions. With a gvfx3524 you should be looking at 24v system.

    I just ran it using 98 f for a high temp and 23 f for a low. Note: the high temp may be to low and the low temp may be to high!

    24 panels max; 6 parellel strings of 5 in series, 8 parellel strings of 3 in series or, 12 strings of 2 in series.

    Providing 23 f is the record low, I would recomend 6 strings of 4 series. If your low is colder than 23 f then, 8 strings of 3 in series. ( thats good for -23 f)
  • solarpower2009solarpower2009 Registered Users Posts: 7
    Re: String Sizing: Need Help

    Hello Audredger,

    Thank you for your suggestions. I think I will go with the 12 string arrangement since we hit temps lower than 20 this Winter. This has been very helpful.
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