Christopher There are some level of micro fractures that are always present in cells and not visible to the naked eye. Some of these will produce visible fractures over time from loading and flexing of the module from weather and temperature changes. The micro fractures can be an issue with performance, but may not show up until later, they are not necessarily an issue with safety. If the encapsulation is intact and the there is not a specific internal fault caused by the separation the only issue would be loss of conducting surface between the broken piece and the internal string wiring resulting in a loss of performance. Bottom line as long as there is not a fault, your AHJ does not have much to say about performance, the NEC says nothing about performance, only if the installation is safe. All modules are flash tested and sorted for performance and checked for faults ( insulation resistance tested at a voltage significantly higher than the operational rating, 2x max voltage + 1000V). This is required before a module manufacturer can place a UL sticker on it. IMHO as long as the damage and is not causing leakage current during an insulation resistance test at the factory the AHJ really cannot say anything about it legally, he is not an inspector for UL and really only needs to be able to read the UL sticker and certify it is being used according to the listing.
That being said some module manufacturers do add an additional Electroluminescence test that does detect micro cracks by placing a small reverse current through the module that causes the active material to act as a Light Emitting Diode in the near infrared spectrum that it is possible to detect with a special camera calibrated for that light spectrum. Usually done in a lab, although there are expensive field units available now. These test will show micro-cracks, bad print screening and bad spots on the cells from the doping process. I have done tests were we purposely damage cells in a module and we have been able to detect micro cracks that did not necessarily result in a reduced flash test at the factory. Over time I assume that will not be the case and reduced output may be the. So IMHO your AHJ does not have the equipment nor does he have the expertise to perform these tests, nor does the NEC or UL1703 require it! Good Luck with the inspector, but I think he is way out of his league on this one, until it becomes a safety issue, even a visible crack in a cell is not an issue of his concern. Bill On Sat, Oct 4, 2014 at 8:20 AM, Christopher Warfel < cwar...@entech-engineering.com> wrote: > Recently a inspector raised the issue of microfractures in pv modules, and > that the existence of such fractures would require replacement of the > modules and a failing of the system inspection. I found information from > NREL confirming the existence of microfractures in poly crystalline. > However, I have not seen any information on how to detect them (ie, what > they look like). Does anyone have a reference that shows this, and is this > a valid concern for the industry? Thank you, Chris > > > > > > > -- > Christopher Warfel, President > ENTECH Engineering, Inc. > PO Box 871, Block Island, RI 02807 > 401-466-8978 > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches. > org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > -- William Hoffer 161 SE Fourth Ave P.O. Box 1823 White Salmon, WA 98672-1823 suneng...@gmail.com <bhof...@sunergyengineeringservices.com>
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