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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