[RE-wrenches] Shell SM110-12P Pvs

[frenergy]

Wrenches,

        I installed a grid tied system 6 years ago consisting of 24, Shell 110 watt, 12V PVs ( Vmp = 17.5V, 6.9 amps short circuit),  running through an SMA2500U inverter, one string, very short DC run ala 10 ga. USE-2 wire. 

        At installation I documented a solar noon output of 1900 watts, a hair low of SMA's estimated inverter output for that temp. However, over the years, the customer and myself have seen the output gradually drop to lately about 1250 watts under the same conditions, panels clean.  It's kinda a long story, but let's just say I know the inverter is not the problem (recently changed-out to a factory rebuilt job with no change in output....different issue).

        I clamped the DC pos before the inverter and got 4.7 amps (about 11AM, array faces 180 degrees, 6:12 pitch, clean PVs, 80 degrees, F.), DC neg was about 4.3 amps (hmmm).  SMA display and my meter reading  for Vmp for the array about 300 volts, pretty low it seems (Green light steady on the inverter, GFI fuse not failing, SMA display power about 1250 watts.  I guess I should have clamped the inverter output... I didn't.  It looked to me like a failed  PV.

        So, I removed (as in unbolted, unwired, removed) all 24 PVs to find that all Voc and Isc with a Fluke 87 were "good", meaning 6.2 amps short circuit (I never seem to get the full rated output on any new or old PV for Isc).  That was fun.  Before I finish here a note, the panels have the Procharger, J box, which means 2 Jboxes (pos and neg) per panel, SS screws to secure your USE-2 wire.  So, PVs check out, it's the wiring??  I saw no chaffing, wearing, cracks, etc in the wiring.  I will remount the PVs and diligently resecure the wiring.

        I'm looking for comments about these PVs (I tried calling Arco-Siemens-Shell- now Solarworld today, after 4 tries got a human being who told me the guy that may know about any issues with these PVs is on vacation till next week).   Or, anything else that may help me find the loss of power here.  Should I spray on some contact cleaner then use silicone grease on the wire/terminal connection?

        Thanks in advance,

Bill Battagin
Feather River Solar Electric
4291 Nelson St.
Taylorsville, CA  95983
530-284-7849/6544 fax
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20100824/af7cc4f5/attachment-0003.html>