How to connect panels in the junction box, parallel or serial?

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  • astroprojector
    Member
    • Aug 2016
    • 40

    How to connect panels in the junction box, parallel or serial?

    Hello

    I want to install an additional set panels. I have an existing junction box to which I can connect the panels.






    If I want to connect the panels to this connection, do I connect them in parallel ( Black to Black and Red to Red) or serial, (break the red connection and connect each wire coming from the new panels to the end of each wire)?


    Here is an example. The existing panels are on the same string.


    Thank you


  • SunEagle
    Super Moderator
    • Oct 2012
    • 15126

    #2
    Originally posted by astroprojector
    Hello

    I want to install an additional set panels. I have an existing junction box to which I can connect the panels.






    If I want to connect the panels to this connection, do I connect them in parallel ( Black to Black and Red to Red) or serial, (break the red connection and connect each wire coming from the new panels to the end of each wire)?


    Here is an example. The existing panels are on the same string.


    Thank you

    It sounds like you currently have a series wired string of panels. Depending on what your inverter is rated should direct you to how additional panels are wired to it.

    While I do not believe the new panels should be wired in parallel I really need more information about your equipment such as how many existing panels, the panel Voc, the inverter max DC voltage input and the specs of your additional panels.

    Comment

    • astroprojector
      Member
      • Aug 2016
      • 40

      #3
      I have SolarEdge SE10000A-US. The system rate to 10.2kW. Currently I have two strings 39 panels

      String 1.1: 17 panels @ 300w
      String 1.2: 17 panels @ 300w, 2 @ 285w and 3 @250w

      The max kW I am reaching now is about 8.5. The image below is about at the max

      2020-05-04_12-23-41.png

      Here is the view of the entire system. Disregard the 5 new panels, (these were added recently to string 2 - 2 @ 285w and 3 @250w).

      solarpanellayout_wires.jpg

      I want to add 5 more 300w panels to string 1.1 and connect them to the junction box located next to the panel 1.1.5.

      Since the max I produce now is 8.5kW, I should be OK adding another 5 or even 6 panels. The panels will never reach the max wastage. The best placed 300w panels I have now produce reach about 270w.

      Per Solar edge the string may contain 25 panels the most for single phase inverter (https://www.solaredge.com/sites/defa..._sizing_na.pdf).

      If I get the 300w panels the Voc is 39.76, if I get the 305w panels the Voc is 40.05.

      Comment

      • SunEagle
        Super Moderator
        • Oct 2012
        • 15126

        #4
        Based on that drawing it looks like there are 19 panels on String 1.1 and 20 panels on String 1.2 so I presume the drawing is not up to date based on what you posted.

        I am also assuming the String 1.2 with the 22 panels (that you mention) does not exceed the inverter input maximum. So I would say you can add the 5 (300w - 305w) panels wired in series to the existing 17 panels on String 1.1 to get 22 panels.

        Again if the 22 panels wired in series does not exceed the max input voltage for a string then you should be ok.

        Comment

        • astroprojector
          Member
          • Aug 2016
          • 40

          #5
          Here is the update image.

          2020-05-04_14-57-45.png

          So, if I connect the new panels in series, do I connect it to the red or the black wire? Also does polarity matter?

          Comment

          • SunEagle
            Super Moderator
            • Oct 2012
            • 15126

            #6
            Yes polarity matters.

            How you add the panels depends on how the existing ones are wired. I am not sure how you added the 5 panels on string 1.2 but you will have to similarly wire the 5 new panels in series and then somehow break the existing string 1.1 wiring so the new ones are in series with the existing ones.

            Comment

            • astroprojector
              Member
              • Aug 2016
              • 40

              #7
              The 5 panels that were added to the string 1.2 are connected to panel 1.2.20. I unplugged one of the wire that were coming from the optimizer on panel 1.2.20 and connected the leading wires from the 5 panels.

              Comment

              • SunEagle
                Super Moderator
                • Oct 2012
                • 15126

                #8
                Originally posted by astroprojector
                The 5 panels that were added to the string 1.2 are connected to panel 1.2.20. I unplugged one of the wire that were coming from the optimizer on panel 1.2.20 and connected the leading wires from the 5 panels.
                Somehow find the positive wire at the end of the string and connect it to the negative wire of the 5 new panels. Then connect the negative wire from the existing string and connect it to the positive wire of the 5 new panels.

                Comment

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