[RE-wrenches] Voltage Degradation with Uni-Solar laminate

[Luke Christy]

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 <larry at starlightsolar.com> wrote:

> Sorry...I meant to type 17.75V (71V).
> 
> 
> 
> On Jun 1, 2015, at 11:21 AM, Starlight Solar Power Systems <larry at 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
> 
>