I have 12 sharp 72 cell and that only 444 voc so that should not be an issue, yes l know he has SW but they are very close Jerry On Jun 21, 2016 10:31 AM, "Brian Teitelbaum" <[email protected]> wrote:
> Hi Ash, > > > > Are you sure that there are 12 of the SolarWorld 175’s on a single string? > > > > Those were 72-cell modules, and I would think that having 12 in series in > CO would see open-circuit voltages over 600 VDC at least on some occasions. > That’s 864 cells in series, with would be about equal to having 14.4 > typical 60-cell modules in series. That sounds too high to me for CO. > > > > One option would be to reduce the number of 175’s to 10 (720 cells in > series) and match them with 12 of the 60-cell modules (also 720 cells in > series). The older modules are 5” cells, so their amperage would be lower, > but as long as you get the voltage as close as possible it should be fine. > Of course, this doesn’t account for degradation, so you may want to do some > actual voltage measurements on the old modules. > > > > One thing though – since twelve 280W modules is about 3360W, and you have > a 3kW inverter, there really isn’t enough room to add. The older Sunny Boys > had a much narrower MPPT voltage range, so I doubt that you could use > strings shorter than nine 60-cell modules. I don’t see how you would be > able to add much to the old inverter anyway. Adding a second inverter > system may be your only option, unless you can find some used 175’s. 18 or > 20 of the 175’s, in two strings, should work fine on the 3kW Sunny Boy. > > > > Brian Teitelbaum > > AEE Solar > > > > > > *From:* RE-wrenches [mailto:[email protected]] *On > Behalf Of *Ash Bowersock > *Sent:* Tuesday, June 21, 2016 12:48 PM > *To:* [email protected] > *Subject:* [RE-wrenches] Add-On to DGT, string inverter, w/Different > Modules on 2nd string > > > > Good day RE Wrench crew, > > I’ve got a client whom installed a 2kW array with a 3kW SunnyBoy inverter > a number of years back. Due to the age of the system I assume it is single > MPPT. The client oversized his inverter in the hopes of using it for this > future expansion (and unfortunately his installer went along with it). The > original modules were 12 SolarWorld 175’s I believe, and we would be > looking at adding SolarWorld 280’s more than likely. To me it is clear that > this is poor design practice and not something I am willing to do. My > recommendation is a micro-inverter system that we tie in w/his existing > using an AC Combiner. But the client wants to know exactly why we don’t > want to just add a second string of 12 SolarWorld 280’s to his 6 year old > SunnyBoy inverter. > > Can someone please give me a technical reason why mixed modules on a > string inverter is “poor design practice”? > > The more technical and dry an explanation, the better ;) > > If you can’t convince them, bore them to tears with the details. > > > > Ash Bowersock > Senior System Designer > > [image: RGS Energy] <http://www.rgsenergy.com/> > > 833 W. South Boulder Road | Louisville, CO 80027 > tel 303.222.8387 > > *RGSEnergy.com* <http://www.rgsenergy.com/> > > *Confidentiality Note: *This e-mail message may contain confidential or > legally privileged information and is intended only for the use of the > intended recipient(s). Any unauthorized disclosure, dissemination, > distribution, copying or the taking of any action in reliance on the > information herein is prohibited. E-mails are not secure and cannot be > guaranteed to be error free as they can be intercepted, amended, or contain > viruses. Anyone who communicates with us by e-mail is deemed to have > accepted these risks. RGS Energy is not responsible for errors or omissions > in this message and denies any responsibility for any damage arising from > the use of e-mail. Any opinion and other statement contained in this > message and any attachment are solely those of the author and do not > necessarily represent those of the company. > > > > > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/[email protected]/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > >
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