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  • Only generating power in the morning and sometimes evening

    My mom recently purchased a home that already had a solar installation installed in it -
    Inverter: SMA Sunny Boy 10000TLUS-12
    Panels: MAXPOWER2 CS6U-340M (30 panels arranged in 3 strings)
    Array: Azimuth 180 degrees, Elevation 18 degrees, portrait orientation, 2 rows of 15
    Location: Terrestrial mount in San Diego, CA

    The system is doing something very strange. Example - On June 16th, there was power produced consistently throughout the day mostly about 1 kwatt, but it was a very low rate. The peak power was at 11:15am, at which point it produced 1.83 kwatts. The weather history for this day was cloudy all day. On June 13th, power was only produced in the morning, and peaked at 1.46 kwatts, but power stopped being produced for the day by 10am. The weather history for this day reports a sunny and hot day, with temperatures reaching the 90s. Daily generation is about 2 to 3.5kwh. This is WAY below what the array should be generating. (see attached)

    There is minimal shading in the morning, but by noon there is no shading. During full sun and no shading, the inverter has a green flashing light (about 1hz), the manual is ambiguous in it's description of this indicator. It either means waiting for grid or waiting for panels. It does very clearly state that no power is being generated (Pac=0). I have measured the AC and DC voltage during both times when it is operational and non-operational. The two legs of AC are at 123volts each (246 total), and the DC array voltage is 365 in both scenarios. The inverter reported values are the same or really close to the values I measured with a multimeter.

    The installer (selected by the previous owner) appears to be a crook. The owner says this was a new installation (indeed the array is not in google maps yet). It is not known if the array was fully operational before my mom bought it. The installer mentioned that the previous owner "took" the internet interface of the box, and she had to purchase a new one to figure out what was going on with the array. Now that the stats are being monitored, he recognized the power output stops early morning, and said it was due to shading issues. He said a new inverter should be purchased. Never mind the fact that this new installation has an inverter that was discontinued a long time ago. The previous owner of the home is not being very cooperative.

    Anyways, I am not really looking for advise on how to deal with the installer or previous owner. I'm curious if any of you guys have seen something like this before, and have any insight as to what might be technically wrong with the installation, or have any direction on what additional investigation or tests I can perform.

    Thanks in advance!!


    Attached Files

  • #2
    Someone needs to be there to get a more definitive look for what's going on. It could be simple or involved.

    I'd be persistent with the installer. In most situations, most recently installed systems are still under warranty. That's part of the cost and expectation of a turnkey system.

    If you can verify that the install is still under warranty, and the installer still balks, go to small claims court. If the repair turns out to be more costly, retain legal counsel.

    I'm aware of a lot/most of the installers in/around San Diego. Who did the install ?
    Last edited by J.P.M.; 06-20-2018, 10:47 AM.

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    • #3
      Thanks for your input J.P.M...

      Further trouble shooting led me to determine that the panels installed are not the ones that sunnyportal/sunnyexplorer is reporting.

      The panels are Q.PEAK BLK-G4.1 290. The voltage on these panels is less than the ones that the inverter is programmed with.

      I was incorrect in my previous assertion that the DC voltage was the same during the morning and afternoon. During the day the voltage actually dropped to ~345. I went and sprayed water on the panels to cool them down. Boom! Once the DC voltage got up to 350, the inverter started outputting power. Once they heated back up, the voltage dropped, and power output stopped.

      My mom contacted the solar company with these new findings, and they said they would get back to her... but surprise surprise, have not heard back from them...

      So now I am convinced the idiot installers set an incorrect lower DC threshold for the inverter. Maybe they did it maliciously, I don't know. Either way my mom wants nothing to do with them going forward.

      The question now is how do i modify the minimum DC threshold? The installer changed the inverter installer password (the default didn't work). Any recommendations? Can another installer reset the installer code?




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      • #4
        If it really is low DC voltage, a test is disconnect a panel from a string (disabling it) and connect
        the panel in series with another string for a total of 11. However my inverters are much more
        flexible about input voltage, no programming required. Bruce Roe

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        • #5
          Originally posted by ekay View Post
          Thanks for your input J.P.M...

          Further trouble shooting led me to determine that the panels installed are not the ones that sunnyportal/sunnyexplorer is reporting.

          The panels are Q.PEAK BLK-G4.1 290. The voltage on these panels is less than the ones that the inverter is programmed with.

          I was incorrect in my previous assertion that the DC voltage was the same during the morning and afternoon. During the day the voltage actually dropped to ~345. I went and sprayed water on the panels to cool them down. Boom! Once the DC voltage got up to 350, the inverter started outputting power. Once they heated back up, the voltage dropped, and power output stopped.

          My mom contacted the solar company with these new findings, and they said they would get back to her... but surprise surprise, have not heard back from them...

          So now I am convinced the idiot installers set an incorrect lower DC threshold for the inverter. Maybe they did it maliciously, I don't know. Either way my mom wants nothing to do with them going forward.

          The question now is how do i modify the minimum DC threshold? The installer changed the inverter installer password (the default didn't work). Any recommendations? Can another installer reset the installer code?



          BE CAREFUL !

          Spraying water on PV panels whose temp. is probably a lot different (higher) than the water can break the panel glazing. Not a wise move. If you do that, and some glazing breakage results, among other things, any hope of solution to your system problem(s) will be much more difficult. Reason: You voided the warranty by damaging the panels.

          From what you write, it looks like, at this time, the installer isn't going to meet their responsibilities without you resorting to the legal system. Or, you could begin by calling the installer yourself - persistently. Usually, the squeaky wheel gets the grease.

          Any work by another installer, good or bad, will also probably void the warranty, or at least and quite likely make things more difficult and/or slow down any resolution. .

          If what you write is correct, or mostly correct with respect to the vendor's actions, it's too bad you're reluctant to name that vendor. Folks around San Diego considering PV and visiting this forum might benefit from the information. On the other hand, there's usually at least 2 sides to every story.

          As for the equipment actually installed, first, and before you call the installer, check the contract that was signed and determine if what's installed matches what was sold. If so, and the inverter thinks it's working to a different panel, relate that to the installer.

          That the installer is uncommunicative is common and usual these days. Welcome to life in 21st century America.

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          • #6
            Originally posted by ekay View Post
            So now I am convinced the idiot installers set an incorrect lower DC threshold for the inverter. Maybe they did it maliciously, I don't know. Either way my mom wants nothing to do with them going forward.
            He didn't set it. The low voltage threshold on that inverter is 345 volts. You can't set it lower than that. (For more info download the data sheet; a Google search will get it for you.)

            (BTW those inverters are somewhat annoying to work with because their MPPT range is 345-480 volts, which means there are fewer string configurations that work well.)
            The question now is how do i modify the minimum DC threshold?
            You can't. There's no way to make it work to a lower voltage than it is rated for.

            Your options are:

            1) Legal action (as others have pointed out)
            2) Restring the system to bring the voltage up (i.e. go to 2 strings - but you will have to idle some panels)
            3) Add 1 identical panel to the end of each string to bring the voltage up (i.e. add 3 panels) (note - even this is marginal when it's hot out)
            4) Replace the inverter.

            For replacement you'd be looking at something like the SB7.7-US, which has a range of 270-480 volts.
            Last edited by jflorey2; 07-12-2018, 01:40 PM.

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            • #7
              I think you might be able to restring them for 2 strings of either 14 or 15 panels. With 15 panels there's no waste; you still get full power. However you are very close to the absolute limit of the inverter with 15 panel. You'd get an OCV of 588 volts (max is 600) with almost no temperature margin. Your operating voltage would be around 480 volts, again very close to the limit.

              With 14 panels per string, you have an OCV of 548 volts and operating voltage of 447 volts, which gives you some margin. You'd have to get the weather data for your area for absolute lowest temperature and do the OCV calculation for that. That would require you to idle only 2 panels, so it might be worth it.
              Last edited by jflorey2; 07-12-2018, 01:42 PM.

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