Walmart PV Roof fires with Tesla PV systems

electrofelon

Senior Member

jaggedben

Senior Member
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.
 
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electrofelon

Senior Member
This is the roof of the Indio store. Must be some complex wiring involved.
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.
 

ggunn

PE (Electrical), NABCEP certified
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.
 

jaggedben

Senior Member

BillK-AZ

Senior Member
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.
 

ggunn

PE (Electrical), NABCEP certified
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.
 
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jaggedben

Senior Member
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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.
 

jaggedben

Senior Member
They are utility-interactive and supply electricity to the premises and the grid or perhaps just to the grid. Most are presumably net-metered, some may be some kind of feed-in tarrif. The rate and tarrif details will vary from state to state.
 

ggunn

PE (Electrical), NABCEP certified
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.
Yep, that's what happened in the infamous Bakersfield Fire and why I said they should disconnect the home run conductors for all the similarly installed systems that have not burnt up yet. BTW, those conductors should be disconnected at the modules, not at the DC combiners.
 

five.five-six

Senior Member
The walmart by my house appears to be starting a ground mount installation. Looks like the are starting with a cinderblock structure in the middle of the parking lot about 100 yards from the building. The carport style ground mount PV installations are becoming rather popular out here. I just wonder how much it costs to erect the steel mounts.


I will say that the installs I have seen have been absolute garbage, PV wire free to air held in place by zip ties and lots of slack and self tapper that are 1-2” longer than they need to be just sticking out into space
 
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