Larry, Thanks. This is helpful. I think it's pretty clear that this system should have been designed with at least 5 or 6 modules in series to keep the VOC higher, but that wasn't very feasible with the original controller when the system was installed 15 years ago. Still, it has worked pretty well for a decade and a half, and I've never noticed the array voltage that low before. I fear I'm in for a hot attic crawl to do some more testing and checking for faults.
-Luke On Jun 1, 2015, at 12:30 PM, Starlight Solar Power Systems <la...@starlightsolar.com> wrote: > Sorry...I meant to type 17.75V (71V). > > > > On Jun 1, 2015, at 11:21 AM, Starlight Solar Power Systems > <la...@starlightsolar.com> wrote: > > Luke, > > For reference, we sold/installed many hundreds of Uni-Solar products since > 2002. I have never seen anywhere near that much Voc loss. > > Since the PVL-68 has an open circuit of 23.1V (92.4V) but you only see 14.2V > (71V), a loss of 25%, I do not believe degradation is the culprit even at 15 > years. The rated degradation is 0.73% per year. That should put you at 82.3 > Voc. But, Uni-Solar consistantly outputs at least 10% more than rated power, > even with age it should be higher than 82 volts. > > Proper Uni-Solar installation required 2 screws into the roof up near the > top. A misplaced screw and time or an open seam may be causing a ground > fault, pulling down the voltage of the array. Start by using a Megger at the > combiner to check for leakage. No one likes crawling in a hot attic but I > think you may need to. > > > Larry Crutcher > > _______________________________________________ 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
