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Wrenches, We have been hired to serve as independent consultants on a large Sunny Boy/Sunny Island off grid project. The array and the battery bank (of unknown type and capacity at this time) have proven inadequate for the loads and the owners want outside review of the proposed upgrade, which we have agreed to provide. In reviewing project information, I have learned that each Sunny Boy inverter is serving 32 260W modules in three parallel strings. Two of the strings have eleven modules and one has ten. This is to us a fundamental violation of good design practice, such that we have never tried it to learn the results. That's my question: what will be the output of this array of mismatched strings? We figure that the inverter will find a MPPT "sweet spot" that is pulled down below the MPP of the two eleven-module strings, to where the ten-module string's contribution is close enough to its MPP to maximize the output of the three strings together. This would result in slightly more than 30 modules' worth of wattage output from the 32-module array. We have not yet been to the installation or seen photos of it. My verbal understanding is that the 96 modules are on eight pole-top racks. It would be fun to figure out the array wiring on this one. Has anyone encountered this mismatch situation? What did you learn? Thank you, Allan --
Allan Sindelar [email protected] NABCEP Certified Photovoltaic Installer NABCEP Certified Technical Sales Professional New Mexico EE98J Journeyman Electrician Founder and Chief Technology Officer Positive Energy, Inc. 3209 Richards Lane (note new address) Santa Fe, New Mexico 87507 505 424-1112 www.positiveenergysolar.com
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