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    Walmart PV Roof fires with Tesla PV systems

    Walmart is suing Tesla alleging breach of contract after fires on the roofs of at least seven stores. A few photos have surfaced (https://www.businessinsider.com/wal-...mistake-2019-8 ), but no technical details.
    Do any forum members have further information on the causes of these fires?

    #2
    Originally posted by BillK-AZ View Post
    Walmart is suing Tesla alleging breach of contract after fires on the roofs of at least seven stores. A few photos have surfaced (https://www.businessinsider.com/wal-...mistake-2019-8 ), but no technical details.
    Do any forum members have further information on the causes of these fires?
    Wow, 7 roofs with fires. Hadnt heard about this. Very interested to hear what the causes were.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

    Comment


      #3
      I was hoping for more details here. I can’t imagine the lawyer costs involved.
      Tom
      TBLO

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        #4
        Here is a link to the complaint. Lot's of allegations with details and photos. https://assets.documentcloud.org/doc...la-Walmart.pdf

        Comment


          #5
          Originally posted by pv_n00b View Post
          Here is a link to the complaint. Lot's of allegations with details and photos. https://assets.documentcloud.org/doc...la-Walmart.pdf
          Skimmed thru some of it mostly looking at pictures. Taken from page 42. Note 93. "….Improper grounding can cause an electric system to trip (i.e., to stop conducting electricity)…."

          I'll have to think about that for a bit.
          Tom
          TBLO

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            #6
            There's quite a lot going on here.

            It would seem that the different fires did not all have the same cause. What I find most notable though is the evidence that points to manufacturing defects ( or possibly misuse of modules above their rates voltage). I wonder how much of these modules were SolarCity brand vs. other manufacturers. It's clear that the lawyers don't really understand what's going on. It's also a bit presumptuous to claim that there must be a clear cause in all cases. (Sometimes the cause of a fire may just get too burned up, especially if something like internal module failure.) But it's also clear that SolarCity had serious installation shortcomings.

            I could be wrong but it appears that none of these systems had optimizers and that as a result there was no room for error on things like ground faults. I wonder what the typical DC voltage was.
            Last edited by jaggedben; 08-23-19, 03:41 PM.

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              #7
              This is the roof of the Indio store. Must be some complex wiring involved.
              Click image for larger version

Name:	Walmart-Tesla fire Indio roof.jpg
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                #8
                Originally posted by BillK-AZ View Post
                This is the roof of the Indio store. Must be some complex wiring involved.
                Click image for larger version

Name:	Walmart-Tesla fire Indio roof.jpg
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                Wow what a nightmare. I worked on about 8 large rooftop arrays like that (not sprawl marts, the red one) and there were far fewer array breaks. Cant imagine stringing that one up.
                Ethan Brush - East West Electric. NY, WA. MA

                "You can't generalize"

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                  #9
                  Originally posted by electrofelon View Post

                  Wow what a nightmare. I worked on about 8 large rooftop arrays like that (not sprawl marts, the red one) and there were far fewer array breaks. Cant imagine stringing that one up.
                  I see a huge number of potential points of failure.

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                    #10
                    Originally posted by ggunn View Post

                    I see a huge number of potential points of failure.
                    Physical or mental failure?

                    Comment


                      #11
                      Originally posted by pv_n00b View Post
                      Here is a link to the complaint. Lot's of allegations with details and photos. https://assets.documentcloud.org/doc...la-Walmart.pdf
                      As a matter of professional curiosity, regarding the photo on page 28 labeled "Module Junction Box at Indio Site (Likely Source of Fire)": Does anyone see anything in this photo that indicates to you something this was a likely source of ignition? I know next to nothing about fire forensics.

                      Comment


                        #12
                        Looks like the two power cables are still attached to their terminals in the J-box, but I see only two bypass diodes and there would be thee for 60-cell modules. Could be that cracked cell(s) resulted in operation of the bypass diode and it failed. The series fuses for module strings are basically to protect the bypass diodes. Incorrect series fuses can cause bypass diodes to fail. I have seen many 'failed' 12-volt modules that RV owners connected backwards to a battery, One even blew the J-box apart.

                        In this system with varying number of modules in an area it would be easy for installers in a rush to parallel strings with different numbers of modules in series. This was likely a 600V max inverter and not micro-inverters.

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                          #13
                          Originally posted by BillK-AZ View Post


                          In this system with varying number of modules in an area it would be easy for installers in a rush to parallel strings with different numbers of modules in series. This was likely a 600V max inverter and not micro-inverters.
                          I'll agree that it was most likely not microinverters; I don't see how a fire like this could even happen with micros.

                          I'd check to see if the same crew installed all the systems that caught fire and if so I'd shut down any other systems they installed and disconnect all the home run cabling. I'll wager that Wal*Mart has already shut down PV systems on all their stores.
                          Last edited by ggunn; 08-25-19, 10:35 AM.

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                            #14
                            Originally posted by ggunn View Post
                            ...

                            I'd check to see if the same crew installed all the systems that caught fire and if so I'd shut down any other systems they installed and disconnect all the home run cabling. I'll wager that Wal*Mart has already shut down PV systems on all their stores.
                            These are all over the country and almost certainly installed by many, many different people. That's allegedly part of the problem, I think. (i.e lack of training and standards)

                            Your point about home run wiring is apt. It appears that Tesla agreed to 'de-energize' the systems but did not take the meaning of that word seriously when it comes to the exposed DC cables on the roof which might be having ground faults. If you have a string double-faulting to racking then turning off the inverter not only doesn't fix the danger but it theoretically it makes it some amount worse.


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                              #15
                              What are these systems used for? Are they partly powering the stores equipment? Are they just selling energy back to the POCO?
                              If you aim at nothing, you will hit it every time!

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