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  • Advice Needed!! Am I being robbed in proper materials

    Received the engineering plans today and I'm not sure I understand this correctly so if someone can clarify I'd appreciate it. We are getting a 11.5 kW (36 LG320 neon 2 gen 4) system installed. Original plans said we'd get SE15k-AUS inverter and P400 Solar edge power optimizers. Looking at the engineering plans today, I see we are getting SE10000A-US inverter and P320 power optimizers. Doing some research online, my understanding is that the inverter is undersized and capped at 10kW vs the 11.5kW we need for the system. Am I wrong? Thanks in advance

    This is the response I received from the company: "Remember a 10kw inverter is AC current and that equals 11.7kw in DC which is totally fine for your system size"


    Is this true? and if it is then why did they write the SE15k inverter and p400 power optimizers and then later change them to lower sizes? Thank you
    Last edited by Techm7; 10-12-2017, 08:07 PM.

  • #2
    Originally posted by Techm7 View Post
    Received the engineering plans today and I'm not sure I understand this correctly so if someone can clarify I'd appreciate it. We are getting a 11.5 kW (36 LG320 neon 2 gen 4) system installed. Original plans said we'd get SE15k-AUS inverter and P400 Solar edge power optimizers. Looking at the engineering plans today, I see we are getting SE10000A-US inverter and P320 power optimizers. Doing some research online, my understanding is that the inverter is undersized and capped at 10kW vs the 11.5kW we need for the system. Am I wrong? Thanks in advance

    This is the response I received from the company: "Remember a 10kw inverter is AC current and that equals 11.7kw in DC which is totally fine for your system size"


    Is this true? and if it is then why did they write the SE15k inverter and p400 power optimizers and then later change them to lower sizes? Thank you
    I don't know why they included the 15k originally, but the 10k is fine with 11.5 kW of panels.... they would only very rarely ever be capable of producing more than 10 kW even if optimally oriented. You mentioned in a previous thread you are in Miami and have a flat roof... what array orientation did the plans settle on?
    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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    • #3
      Originally posted by sensij View Post

      I don't know why they included the 15k originally, but the 10k is fine with 11.5 kW of panels.... they would only very rarely ever be capable of producing more than 10 kW even if optimally oriented. You mentioned in a previous thread you are in Miami and have a flat roof... what array orientation did the plans settle on?
      Thanks for your reply Sensji. Greatly appreciate it. That's a relief. Yes we are in Miami. We had some hurdles trying to get the contractors to angle the panels because they said they would put them completely flat and that we didn't pay for the hardware to have them angled. Long story short we got them to agree installing at 23 degrees and 180 degrees south.

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      • #4
        Originally posted by Techm7 View Post

        Thanks for your reply Sensji. Greatly appreciate it. That's a relief. Yes we are in Miami. We had some hurdles trying to get the contractors to angle the panels because they said they would put them completely flatland that we didn't pay for the hardware to have them angled. Long story short we got them to agree installing at 23 degrees and 180 degrees south.
        Are the panels all in one row? If not, are they leaving enough distance between rows to minimize self-shading?
        CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

        Comment


        • #5

          Screen Shot 2017-10-12 at 8.48.07 PM.png
          Originally posted by sensij View Post

          Are the panels all in one row? If not, are they leaving enough distance between rows to minimize self-shading?
          It seems they are 4 ft apart in 9x4 layout. Let me attach a pic of the plans. Let me know what you think? Thank you!!
          Attached Files

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          • #6
            The way I read the picture they are quite a bit less than 4' apart - the rails are 4' apart...

            Maybe 96" - Panel Length x cos(23 degrees) or something like that.

            I have a feeling this is not going to work out well.
            Last edited by AzRoute66; 10-12-2017, 10:29 PM.

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            • #7
              Did they design for No Shadowing between 9AM-3PM on Dec 21st ?
              It would be best to have that, or whatever their "No Shadow" spec is, in writing.

              I believe ...
              The Sun will be at 25 Degrees above horizon at 9AM & 3PM on Dec 21st
              and at 45 Degree azimuth
              The Panels are inclined 23 Degrees

              Height of Panels ...
              25" = 64.6" x sin(23)

              Spacing Initial ...
              54" = 25" / tan(25)

              Spacing Final between Rows = Slight shading 9am-3pm DEC 21st
              38" (minimum) = 54" x cos(45)


              Edit:
              Changed the Panel Length from 5 feet to 64.6 inches (more accurate & longer)
              Recalculated ...
              Spacing between rows increased from 36" to 38"
              Row spacing should be 98" = 60" + 38", not 96"

              So, row spacing at 96" and 23 Degree Tilt is ~2" too close to prevent "No Self Shading" 9am-3pm Dec 31st
              But it is within 97% of peak power.
              Last edited by NEOH; 10-15-2017, 12:26 PM.

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              • #8
                I think he will have no shading between 11:49 AM and 12:49 PM on December 21. But, that is while watching both Thursday Night Football and Cubs/Nats elimination game...

                Edit: Naw, not quite that bad. Stupid calculator wouldn't let me change the pole spacing...

                Found a different calculator - it thinks he'll be just fine. Someone better check me, only 6th inning ....
                Last edited by AzRoute66; 10-12-2017, 11:06 PM.

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                • #9
                  Originally posted by AzRoute66 View Post
                  The way I read the picture they are quite a bit less than 4' apart - the rails are 4' apart...

                  Maybe 96" - Panel Length x cos(23 degrees) or something like that.

                  I have a feeling this is not going to work out well.
                  Oh boy, should I be worried? Ask the contractor to do something different?

                  Comment


                  • #10
                    Using proposed array dimensions and tilts, and something called the solar profile angle will allow a reasonable estimate determination of whether or not, and also when an array will undergo self shading from the more southerly panels. Or, if familiar with its use, SAM will do a pretty fair job as well.

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                    • #11
                      Originally posted by AzRoute66 View Post
                      I think he will have no shading between 11:49 AM and 12:49 PM on December 21. But, that is while watching both Thursday Night Football and Cubs/Nats elimination game...

                      Edit: Naw, not quite that bad. Stupid calculator wouldn't let me change the pole spacing...

                      Found a different calculator - it thinks he'll be just fine. Someone better check me, only 6th inning ....
                      LG320's are 64.57 in long.

                      Drawing shows rafters 24" OC, so 8 ft for the row pitch.

                      64.57/96 = 0.672 ground cover ratio.

                      PVwatts doesn't calculate self-shading for a fixed array, will have to check SAM later.

                      CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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                      • #12
                        sensij
                        see mesg #7 for spacing calc

                        Comment


                        • #13
                          I just used this website and put all the proper info and it seems the measurements point to having inter-row spacing of 29.806 inches. I think the plans reflect something very close to that. http://www.rbisolar.com/solar-shading-calc/



                          Btw: love this community. So helpful and informative. #Appreciation

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                          • #14
                            Originally posted by Techm7 View Post
                            I just used this website and put all the proper info and it seems the measurements point to having inter-row spacing of 29.806 inches. I think the plans reflect something very close to that. http://www.rbisolar.com/solar-shading-calc/ Btw: love this community. So helpful and informative. #Appreciation
                            I think I used that tool once, then read the fine print and it says that spacing is to ensure there is no solar shading at noon on Dec. 21 - not very helpful.

                            I am pretty sure my calculations were right and you will have no trouble from 9:00 AM - 4:00 PM, but definitely try to get more votes. This is worth double checking (or more).
                            Last edited by AzRoute66; 10-13-2017, 12:36 AM.

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                            • #15
                              Originally posted by NEOH View Post
                              sensij
                              see mesg #7 for spacing calc
                              Yeah... I was calculating GCR, because it will be the same no matter the tilt angle. That feeds a parametric run in SAM nicely: shading.JPG




                              By this analysis, 13 deg tilt looks like the best choice for that particular layout (8 ft pitch).

                              Also, back to the original question, here is what it looks like with an 11.4 kW inverter instead of 10 kW... the extra 20-30 kWh is less than $5 / year difference in production.
                              shading2.JPG
                              Last edited by sensij; 10-13-2017, 01:01 AM.
                              CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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