If the modules test out to spec., Are there any mystery junction boxes where there may be a corroded connection [i.e. - split bolt or butt splice] and are all the connections tight?
Seen this on several occasions. Thanks, Dana Orzel Great Solar Works, Inc E - [email protected] V - 970.626.5253 F - 970.626.4140 C - 970.209.4076 web - www.solarwork.com Responsible Technologies for Responsible People since 1988" From: [email protected] [mailto:[email protected]] On Behalf Of Allan Sindelar Sent: Friday, June 25, 2010 12:50 PM To: RE-wrenches Subject: [RE-wrenches] Unisolar US64 problem We have an off-grid customer whose PV arrays seem to be under performing and we're not sure why. The customer has 16 Unisolar US64 modules, which have a peak output of 3.88 amps, but which were only putting out from 2 to 2.4 amps each. He has a C40 charge controller, so they were operating off the peak of the I-V curve (they were operating at 13.6 volts each at the time of the system inspection, instead of the peak, which is up around 17 volts), but still the amps that they were putting out were lower than they should be. He used to get 30+ amps (at 24 volts) from his array, but now he's only getting a little more than 20 amps (611 watts from a 1024 watt array is what my tech saw when he was there a week ago). The C40 was still in its bulk cycle, not having reached the absorption set-point. The sunshine was strong (there was no shading all day), there was no haze in the sky, it was solar noon (1pm MDT), in the mid to high 70's with a breeze, the arrays are on tilt-up racks, and there was no more than a little dust on the modules. His arrays are at a year round setting (~latitude), so not optimal for this time of year, but not that far off. Half of the modules are 12 years old and half are 10 years old, but it was only last year that he had 30+ amps coming in, so they couldn't have deteriorated/aged that much in one year. Since there is no combiner box (we didn't design or install this system), each pair (string) was checked with a clamp-on meter and was putting out only 2 to 2.4 amps. When the C40 was bypassed, there was no increase in current coming in, so the controller doesn't appear to be at fault. The customer's measurement of the performance of his system is the LED on the C40. He has a meter face on his C40, but he mostly just looks at the LED. He says that the LED used to go solid green by noon, and now he doesn't get more than two or three blinks all day. Any idea why all his modules might be under performing? Thanks Russell Mueller Positive Energy 211-M Cruz Alta Rd. Taos, NM 87571 575-737-9553 No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.830 / Virus Database: 271.1.1/2961 - Release Date: 06/25/10 00:35:00
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