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Too few panels on solar string ?.

  • 21-01-2022 8:40pm
    Registered Users Posts: 47

    Hello all,

    I was recently in touch with the manufacturers support team for my solar inverter.After helping me with a problem I was having, they questioned me about the number of panels on each of the two strings, and their respective orientation.I have 9 panels on pv1 ,facing 250 degrees.The other string has 3 panels on pv2 facing 160 degrees.The following is a direct quote "There are too few panels in series with PV2,which will cause the PV2 to have a very low open circuit voltage, which will cause PV2 to never work properly.You can also see this on the Solarman app"

    Imagine my surprise at this information .The support team would appear to have hit the nail on the head,Icannot see any production from PV2 historically .

    The panels are 450w JINKO .VOC is 41.18 volts

    The inverter

    has a max pv input power of 4800 watts.Max PV input voltage 580 volts.MPPT range of 120v-550v.There are 2 MPPT on inverter.

    The system was installed 6 months ago,There is not enough room on the roof to add another panel to PV2.I could possibly move all the panels from PV2,to the same roof as PV1, and also add a few more panels, and make a new PV2.

    I would appreciate any and all help and suggestions from the knowledgeable people on this forum.

    Many Thanks



  • Moderators, Education Moderators, Home & Garden Moderators Posts: 8,095 Mod ✭✭✭✭Jonathan

    Installer should really have foreseen this. I'd be contacting them looking to do a deal to rectify.

    I'm assuming from the aspects provided that the two roofs are adjacent. How about adding 2-3 additional panels to 250° roof and adding them to string PV2. You'll need to add to optimisers new panels and to three existing ones on 160° roof. That should get you up over the start up voltage for MPPT2.

  • Registered Users Posts: 47 prf

    Jonathan,Thanks for the fast reply, my initial thinking is to relocate the 3 panels from PV2 to the 260 roof,and maybe add a couple of extra ones to create a totally new PV2.The other idea is to take a few panels from PV1 string and add these to the relocated panels to bring up the starting voltage. Your idea of just adding a few new panels to the 260 roof,and joining them to the same string (pv2) while leaving the existing 3 panels on the other roof sounds good.Just to clarify, do I need optimisers on the existing 3 panels or on all panels in PV2?. Also, do you think the inverter would be overloaded by the additional 2 or 3 panels?.

    Thanks again,


  • Moderators, Education Moderators, Home & Garden Moderators Posts: 8,095 Mod ✭✭✭✭Jonathan

    What model of inverter do you have? I don't think overloading the DC will be an issue. Sure as things currently stand you have 5.4kWp on a 4.8kW(?) inverter. You'd need to check panel and inverter datasheets to be sure though.

    Ordinarily optimisers are only required on panels with shading, however, if a string has multiple aspects, optimisers are required on all panels on that string.

  • Moderators, Sports Moderators Posts: 18,644 Mod ✭✭✭✭slave1

    You are dealing with Installer issue, they are the experts, take the information provided (which we totally get) and back to them, see what they say and then back to us

  • Registered Users Posts: 47 prf

    I will contact installer and see,that's going to be fun,don't hold out much hope. Thanks for all help.

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  • Registered Users Posts: 47 prf

    hello all, just to update on this issue, the installer was here yesterday and managed to fit one panel to the roof that had 3 fitted, so these 4 panels are now on PV2 string, it is now producing power.They also put 2 extra on the other roof ,happy days.I am eager to see the quantity of the increased production.

    Thanks again for all the help and suggestions