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Add 4 panels in parallel to 1 panel in my solar array?

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  • Add 4 panels in parallel to 1 panel in my solar array?

    I have a solar array of 20 230w 24v panels for on grid use. There are 2 groups in series to make 240vdc. I also had 4 of the same panels powering my barn. But, due to various machines using more power, I can no longer power my barn with those 4 panels. I was wondering if I can splice these 4 panels into my 20 panel array. The only way I think I could do it would be to splice all 4 24v panels in parallel to one panel in the array. But, that would mean one of my 240v groups would be the same 240v, but would produce about 1000 watts more than the other. Can I do this? Or, is there a better way to add in the panels? Any constructive input is appreciated. Thanks!

  • #2
    in a brief - NO

    Adding or changing a GT system needs a new permit, new agreement with the power company and for just 4 panels, I would not do it.
    Powerfab top of pole PV mount (2) | 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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • #3
      Any technical reason why it can't be done?

      Comment


      • #4
        Originally posted by bbells View Post
        Any technical reason why it can't be done?
        yes, The string voltages of the panels feeding into the Inverter, have to fall within a specific window, accounting for high voltage in cold weather . If the Voc limit in cold weather is exceeded, your inverter gets fried. Not knowing your inverter, panel voltages, I'll assume it's a working system and I would not mess with it for just 4 panels.
        Powerfab top of pole PV mount (2) | 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

        solar: http://tinyurl.com/LMR-Solar
        gen: http://tinyurl.com/LMR-Lister

        Comment


        • #5
          Originally posted by Mike90250 View Post

          yes, The string voltages of the panels feeding into the Inverter, have to fall within a specific window, accounting for high voltage in cold weather . If the Voc limit in cold weather is exceeded, your inverter gets fried. Not knowing your inverter, panel voltages, I'll assume it's a working system and I would not mess with it for just 4 panels.
          Fortunately, the voltage would not change since the panels would be in parallel.

          Comment


          • #6
            Other than permitting etc. Like Mike says the voltage and the amps (essentially total watts would also have to fall within the parameters specified for each string of the inverter and the totals specified for the inverter then Decrease the inverter rating about 25% to allow for overirradiance and cold weather etc. I would presume if the system was designed to use the most panels in each string that met the inverters specs then you probably cannot add 4 more panels to one string almost certainly. Its more probable that you might be able to add 2 more panels to each string but still doubtful and even then if you could it would come closer to being possible to connect 2 pairs of 2 parallel panels on each string rather than 2 panels to 1 existing panel since that might not exceed the current limitations of present wire for the wire its connected in parallel to. In other words , its much more likely that a single panel could be added to a single existing panel in parallel than it is for 2 or 3 or 4 to be added to a single panel.Again probobly not worth the permitting process etc and most likely won't fall within the inverter parameters. Maybe if the inverter provides for more than 2 strings and has less total wattage attached now than 25% less than its rating . Three strings of 8 might work. Note: reading about this type of thing is easily confusing even to the composer.

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            • #7
              What is the panel configuration? The way you described it, I'm imagining two paralleled strings of ten panels. What do you mean by "24V" panel, do you mean 72 cell panels? In a grid tie system these are not 24V panels.

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              • #8
                It is clear I need to make the question simpler. Is there any problem having 2 banks of solar panels with one having 40% more watts?

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                • #9
                  Answer my questions please.

                  Comment


                  • #10
                    Originally posted by sdold View Post
                    Answer my questions please.
                    Read the original post.

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                    • #11
                      Originally posted by bbells View Post
                      It is clear I need to make the question simpler. Is there any problem having 2 banks of solar panels with one having 40% more watts?
                      Based on the information you provided, you cannot do this.

                      Comment


                      • #12
                        Originally posted by sdold View Post

                        Based on the information you provided, you cannot do this.
                        I know I can do it. It is done all the time. I was just wondering if there are any negative repercussions of having 2 banks with differing watts.

                        Comment


                        • #13
                          Originally posted by bbells View Post
                          I know I can do it. It is done all the time. I was just wondering if there are any negative repercussions of having 2 banks with differing watts.
                          Generally, the bank with the lower voltage, will drag the higher bank down to it's level. But read the manual for your inverter, you've not given us enough info to give a knowledgeable reply.

                          I don't understand how you can have a Grid tie inverter, with 10 panels in parallel ( x2 ). Generally, GT inverters use a high voltage string of 30V panels in series (total of 300-500VDC). I've not heard of a GT inverter using parallel wired panels.
                          Powerfab top of pole PV mount (2) | 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

                          solar: http://tinyurl.com/LMR-Solar
                          gen: http://tinyurl.com/LMR-Lister

                          Comment


                          • #14
                            The string you added 4 extra panels, in parallel will probably act like the other string being that the current of the 5 paralleled panels will get nullified by the fact that current doesn't add in a series configuration, voltage does. The current of the 5x paralleled will be driven down to the current of a single panel, or string of panels. That's why you can't do it. You can but will gain nothing and will likely put a lot of stress on the 5 paralleled panels. Something like that.
                            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                            Comment


                            • #15
                              Originally posted by Mike90250 View Post
                              I don't understand how you can have a Grid tie inverter, with 10 panels in parallel ( x2 ). Generally, GT inverters use a high voltage string of 30V panels in series (total of 300-500VDC). I've not heard of a GT inverter using parallel wired panels.
                              Just a wild guess based on his first post, it sounds like he has 72 cell panels that he's been told are "24V" panels, and he's wired ten of them in series for what he thinks is 240V, and has paralleled two such strings. Now he plans to put four more panels in parallel and put those across one of the panels, thinking that will increase the wattage of that string. If he'd answer the questions we could make sense of this, but his refusal leaves too many unknowns and nothing to go on to guide him toward a better solution.

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