Chris......Less than 2 years.......
On Wed, Nov 12, 2008 at 7:59 PM, Chris @ the Oasis <[EMAIL PROTECTED]>wrote: > Hello Kirpal: > > What is the relative age of these modules? For starters.... Just curious. > > Chris Daum > Oasis Montana Inc. > 406-777-4309 local line > 406-777-0830 fax > > > ------------------------------ > *From:* [EMAIL PROTECTED] [mailto: > [EMAIL PROTECTED] *On Behalf Of *Kirpal Khalsa > *Sent:* Wednesday, November 12, 2008 8:33 PM > *To:* RE-wrenches > *Subject:* Re: [RE-wrenches] Trouble Shooting Bad Diode > > Bill and all.......So we were at the site today and these were our > findings: > We covered each solar panel with cardboard 1 at a time.....we continued to > see the same lower voltage on string #2. String #1 had an expected Voc. > String 1 had a Voc of 368, String 2 had Voc of 312. > We decided to disconnect the entire string. Luckily the interconnects were > accessible without physically removing the modules.......I love array's that > are only 2 rows deep with service aisles all around..... > The system was 2 strings of 9 BP SX170's connected to a PVP2800XV. > Module nameplate Voc was 44V. Cell temp of the modules at time of > measurement was roughly 85-90 degrees F. > all modules were in the 40.1-8 range....except module # 3 from the positive > homerun side was 38.8V, module 6 was 36.6V and module 8 was 10V. > We had no trouble determining that module # 8 was defective......In these > modules I believe that the entire 72 cells are in a series.string...(am i > right?roughly .5+V per cell.). > Covering 1 module at a time did not give us any indication as to which > panel was defective. The Voc with 1 module covered ranged from a low of > 299VV to a high of 304V. This did not make sense to me as to reducing the > string Voc from 312 to 304 by covering 1 module......... > > Anyhow........the 2 modules that had reduced voltages......1 with ~38V and > 1 with ~36V......would you consider those defective? Worthy of trying to > get BP to warranty those? > We will be filing a warranty claim on the single panel that is obviously > defective....... > Thanks for your advice and input..... > Cheers, > > Kirpal Khalsa > Renewable Energy Systems > > > On Fri, Oct 31, 2008 at 10:33 AM, Bill Brooks <[EMAIL PROTECTED]>wrote: > >> Kirpal, >> >> >> >> When you parallel, your voltages have to be the same, so you are correct >> in that assumption. >> >> >> >> Your assumption about the diodes is not correct. Diodes don't work like >> that. You could have a shorted module (all three diodes shorted) which would >> lower the Voc by one module. It looks like you have nearly two modules worth >> of problems. It could be a total of 5 bad diodes, but that would be weird. >> It could be you have a ground fault, and haven't tripped the GFP yet because >> of lower sunlight levels—(it has to be very low sun to stay under 1 amp). >> You also could have a wiring mistake, either because the factory reversed >> wired a module (rare, but it happens)—that would be 2 modules low; or, you >> could have skipped two modules somehow. >> >> >> >> It does seem like a quarter of the bad string is out. Your assumption >> about bad diodes could be correct, but it only affects the groups of cells >> its connected to. Each diode protects 24 cells—it looks like you have 5 >> diodes worth of loss. It could be in 2 modules, or up to 5 modules. >> >> >> >> The shading test is the best way to find bad diodes. Disconnect the bad >> string from the good one and take a piece of cardboard the dimension of the >> module. With your meter testing Voc on the back string, completely cover >> each module, one at a time. When the Voc is not affected by complete shading >> of a module, that module is completely bad. If the shaded module only loses >> a portion of one module's Voc, then you have one or two, of the three >> diodes, bad. >> >> >> >> This is a great opportunity to learn how to troubleshoot a PV array. Take >> the time, and the effort, to run through it carefully, learn the problems, >> and report back with your findings. It's a beautiful thing to learn >> something new. >> >> >> >> Bill. >> >> >> >> *From:* [EMAIL PROTECTED] [mailto: >> [EMAIL PROTECTED] *On Behalf Of *Kirpal Khalsa >> *Sent:* Friday, October 31, 2008 10:43 AM >> *To:* RE-wrenches >> *Subject:* [RE-wrenches] Trouble Shooting Bad Diode >> >> >> >> Greetings all......I was hoping i could have someone help me confirm a >> troubled series string on a system we have installed..... >> System consists of 16 BP 170 W 24V nominal modules......2 strings of 8 >> modules.....Vmp of each module is roughly 34V and Voc of each module is >> roughly 41V. One string is under-producing......String 1 Voc is 346V and >> String 2 Voc is 272V. String 1 Vmp under load is 270V and String 2 Vmp >> underload is 270V. I am hypothesizing that String 2 has a bad diode on the >> 3rd panel in and is reducing the Voc of that string by th 2 panels ahead of >> it in the string. I am hoping to figure this out without removing the >> entire string and checking each panel if possible..... >> I think the Vmp is equal due to the fact that both strings are paralleled >> in the inverter and the 1st string is being pulled to the same level V as >> the 2nd string under load......Is my logic good? >> Thanks for the help and advice..... >> Cheers, >> >> >> _______________________________________________ >> List sponsored by Home Power magazine >> >> List Address: RE-wrenches@lists.re-wrenches.org >> >> Options & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> List-Archive: >> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >> >> List rules & etiquette: >> www.re-wrenches.org/etiquette.htm >> >> Check out participant bios: >> www.members.re-wrenches.org >> >> >> > > > -- > Sunny Regards, > Kirpal Khalsa > NABCEP Certified Solar PV Installer > Renewable Energy Systems > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > > > -- Sunny Regards, Kirpal Khalsa NABCEP Certified Solar PV Installer Renewable Energy Systems
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