Maybe Marv can help out here. I¹ve talked with tech support at Enphase and am under the impression that you can center tap their branch circuits to reduce voltage drop. This technique was used on a project that we profiled in SolarPro:
http://solarprofessional.com/article/?file=SP3_2_pg92_Projects_1&search= David Brearley, Senior Technical Editor SolarPro magazine On 6/11/10 2:50 PM, "Nick Soleil" <nicksoleilso...@yahoo.com> wrote: > Did you notice that in my calculation I divided the total amperage by 2 to get > the average ampacity across the string. This seems to be the best way to deal > with that. Otherwise the loss would have been over 2.8% > > 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: "ma...@berkeleysolar.com" <ma...@berkeleysolar.com> > To: RE-wrenches <re-wrenches@lists.re-wrenches.org> > Sent: Fri, June 11, 2010 7:02:00 AM > Subject: Re: [RE-wrenches] AC wiring loss on micro-inverters > > Nick, > > Good to see other wrenches looking at this issue. However, remember that > in the interconnect cable between the last and the second to last Enphase, > the current is small. If you really want to see how the loss is adding up > you need a more detailed analysis that averages the voltage drop for the > entire system of interconnect cables. > > Mark Frye > Berkeley solar Electric Systems > >> > Hello wrenches and Marv: >> > How many Enphase inverters do you put on a single parallel string? >> > The Enphase manual allows for up to 15, but I have found that a single >> > string of 15 can have very high voltage rise on the AC wiring. Up to >> > 1.5% loss just on the Enphase cables, and that does not take into >> > account resistance at the plug connectors or any home-run wiring. >> > 15 inverters x 190 watts = 2850 watts >> > 2850 watts / 240 Volts = 11.875 Amps (however at the beginning of the >> > string it is 0 Amps) >> > Average Amps on the Enphase cables is 11.875 / 2 = 5.9375 Amps >> > length of contacts + internal wiring = ~6' >> > Total Enphase cabling length (6' x 15 inverters) = ~90' >> > 5.9375 Amps @ 240 V running 90' on #14 AWG CU = 1.4% loss >> > It is pretty hard to design for 1.5% voltage drop if you have to size for >> > 0% loss on your wiring! I hope Enphase will increase the size of the wire >> > in their cables soon. Have you experienced issues with micro-inverters >> > shutting off due to high AC voltages? >> > >> > 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: i2p <i...@aol.com> >> > To: RE-wrenches <re-wrenches@lists.re-wrenches.org> >> > Sent: Thu, June 10, 2010 4:50:47 PM >> > Subject: Re: [RE-wrenches] Real world PV production >> > >> > >> > >> > On Jun 10, 2010, at 7:57:53 AM, "Kelly Keilwitz, Whidbey Sun & Wind" >> > <ke...@whidbeysunwind.com> wrote: >> > >> > PV Watts VASTLY underestimate PV production >>> >> in our area. >> > PV Watts underestimates in Central Ca too. >> > >> > Don >> > >> > >> > _______________________________________________ >> > 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 >> <http://www.re-wrenches.org/etiquette.htm> >> > >> > Check out participant bios: >> > www.members.re-wrenches.org <http://www.members.re-wrenches.org> >> > >> > > > > _______________________________________________ > 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 <http://www.members.re-wrenches.org> > > > > > _______________________________________________ > 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 >
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