Peter,
The fact that the cut sheet does not have that information should be an indicator to you. EPV has never manufactured modules much above 42 watts-that's what is currently listed. 8 in parallel sounds very suspect. They would have to have a series fuse rating of about 35 amps to pull that off. Remember that the parallel module currents must be subtracted from the fuse size to determine the final fuse size when paralleling strings before going to a fuse. Lots of folks are claiming to start production on a-Si arrays, and few people have a clue on how to design arrays for them-least of which are most of the manufacturers. Minimum fuse size for 8 strings in parallel: Isc = 1.49 A Imax = 1.49 A x 1.25 = 1.86 A Minimum fuse size for parallel strings = 8 x 1.86A x 1.25 = 18.6 A (20A next available size) Fault analysis: 7 strings (n-1) plus series fuse = total current into faulted string 7 x 1.86 = 13.02 A Total current in fault condition = 13.02A +20 A = 33.02 A (35A next available size) I sincerely doubt they are going to come out with a 35A max series fuse rating for their module. Many PV module manufacturers have done the fault analysis wrong and only included the fuse as the source of current. I would expect them manufacturer to say that their max series fuse rating is 20 A and that 8 strings can be paralleled. That is clearly wrong. From the previous analysis, it is clear that much fewer than 8 in parallel would be allowed (maybe 3 or 4 would work-you do the math). To answer your original question, SMA makes a 52-string combiner box with a max series fuse of 8 amps. This would be an ideal box for an a-Si array. The other issue that is often not understood is that most glass a-Si modules should have blocking diodes for each series string. Broken modules produce high currents that become pyrovoltaic without diodes. Bill. Bill Brooks, PE Brooks Engineering 873 Kells Circle Vacaville, CA 95688 Office and Mobile: 707-332-0761 Office Fax: 707-451-7739 email: b...@brooksolar.com www.BrookSolar.com From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Peter Parrish Sent: Tuesday, July 21, 2009 5:52 PM To: 'RE-wrenches' Subject: Re: [RE-wrenches] String Combiners for a-Si modules EPV Solar EVP-54 The Isc is 1.49 A The cut sheet does not list a series fuse rating for the module. But it does say something about being able to use up to 8 in parallel without external protection. I am in the hunt for installation instructions. - Peter Peter T. Parrish, Ph.D., President California Solar Engineering, Inc. 820 Cynthia Ave., Los Angeles, CA 90065 CA Lic. 854779, NABCEP Cert. 031806-26 peter.parr...@calsolareng.com Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 _____ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Kirpal Khalsa Sent: Tuesday, July 21, 2009 3:11 PM To: RE-wrenches Subject: Re: [RE-wrenches] String Combiners for a-Si modules Peter...depending on the series fuse rating you might be able to get away with more strings in parallel before series fusing is required........what panels are they and what is the series fuse rating of the modules? Fronius has a white paper explaining when series fusing is required and when you can get by without.......it all relates to series fuse rating and Isc......the higher the series fuse rating and the lower the Isc the more strings you can parallel with out adding series fusing........ -- Sunny Regards, Kirpal Khalsa NABCEP Certified Solar PV Installer Renewable Energy Systems www.oregonsolarworks.com 541-218-0201 m 541-592-3958 o On Tue, Jul 21, 2009 at 2:44 PM, Peter Parrish <peter.parr...@calsolareng.com> wrote: We are doing an engineering design for a large scale PV ground mount system based on a-Si modules. Since the Isc of the modules is 1.5 A, instead of 7-8 A of typical c-Si modules, are there special low-current combiners out there? Does each string need an overcurrent protection device? Any help with a-Si based system design would be greatly appreciated. Peter T. Parrish, Ph.D., President California Solar Engineering, Inc. 820 Cynthia Ave., Los Angeles, CA 90065 CA Lic. 854779, NABCEP Cert. 031806-26 peter.parr...@calsolareng.com Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 _______________________________________________ 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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