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Mixing Panels

  • 09-06-2023 03:02PM
    #1
    Registered Users, Registered Users 2 Posts: 441 ✭✭


    What are people's thoughts on mixing panels?

    I have 16 X 380 Peimar panels installed as part of a grant. I can squeeze in another 4 panels on the same West facing roof space. The original supplier wants to charge €2500 to supply and do this work, but I can probably knock €1200 off of that by purchasing the materials and having my carpenter do the install (I don't want to venture onto the 2 storey roof).

    Question is should I try source 380w panels or can I purchasing 410 longi and connect them to the existing string?



Comments

  • Registered Users, Registered Users 2, Paid Member Posts: 9,237 ✭✭✭10-10-20


    Hi, a few techy questions to start:

    What inverter do you have and what output capacity?

    How many MPPT strings does your inverter support and how many are in use, and what is the max DC voltage allowed at the inverter; and then what would the max voltage be at Voc for all of the existing panels and then again with all of the new panels?



  • Registered Users, Registered Users 2 Posts: 623 ✭✭✭idc


    At that price I'd be asking is this just 4 panels added to your existing strings - or adding a second inverter plus any electrical work to connect it all up? As that could potentially involve separate staff - one for fitting panels and then electrician for inverter and cabling. but just 4 panels added to existing strings seems very expensive



  • Registered Users, Registered Users 2 Posts: 59,758 ✭✭✭✭unkel


    We need more details as @10-10-20 has asked. But in the meantime, I'd gamble an answer. That your setup is with 2 strings of 8 panels and with a 6kW inverter?

    If so, you can add those 4 panels to one of the 8 panel strings, but the output of the entire string will be limited down to the the max of the voltage / current settings of the lowest panel. Also, you will already have clipping as your max output already is more than 6kW (16 * 380wp = 6.08kwp), not that clipping is very relevant, particularly not on anything except pure south facing orientations.

    Hope that helps!



  • Registered Users, Registered Users 2 Posts: 441 ✭✭jasgrif11


    My inverter is the Solis S5-EH1P5K-l. I have two MPPT strings.

    String 1: 9 x 380w South facing

    String 2: 7 x 380w West facing

    The south-facing roof is maxed out on space. I was planning to add 4 panels on west side therefore extending the string to 11 panels. Given the price the installer quoted I'm just assuming they don't want to do it.

    Should I try to source the same make and size (wp) panels?



  • Moderators, Home & Garden Moderators Posts: 7,102 Mod ✭✭✭✭graememk


    Ideally the same model of the same wattage or higher



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  • Registered Users, Registered Users 2, Paid Member Posts: 9,237 ✭✭✭10-10-20


    I would try source the same panel initially. If not then I believe (don't quote me on this) that the trick is to match the panel current (Imp) so that it is equal or slightly greater than the existing panels and also ensure that the overall string voltage does not then exceed the allowed input voltage into the inverter.

    So in a string of 7 x 380w panels, if the panel current was 11A at Ipm (then the voltage would be 34.5Vmp), you would look for a 380W panel or slightly greater with an Imp of 11A or greater. The reason being that your new panel can only pass it's rated current, so if you installed a 550W panel, you would only get ~380W of current through the panel and it would underperform.




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