[RE-wrenches] Shell SM110-12P Pvs

[Nick Soleil]

Perhaps the inverter is too hot, and derating its power for temperature.  Have 
you installed a fan (such as a SunnyFan on the heat sink, to help it cool.

 Nick Soleil
Project Manager
Advanced Alternative Energy Solutions, LLC
PO Box 657
Petaluma, CA 94953
Cell:   707-321-2937
Office: 707-789-9537
Fax:    707-769-9037




________________________________
From: frenergy <frenergy at psln.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Tue, August 24, 2010 6:27:13 PM
Subject: [RE-wrenches] Shell SM110-12P Pvs

  
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


      
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