<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">HI Ash,<div class=""><br class=""></div><div class="">Backwoods solar sells 190 watt 72 cell modules that might give you some options.</div><div class=""><br class=""></div><div class="">jay</div><div class=""><br class=""></div><div class="">Peltz power<br class=""><div><blockquote type="cite" class=""><div class="">On Jun 21, 2016, at 8:31 PM, Brian Teitelbaum <<a href="mailto:bteitelbaum@aeesolar.com" class="">bteitelbaum@aeesolar.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="WordSection1" style="page: WordSection1; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">Hi Ash,</span></div><p class="MsoNormal" style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;"><span style="color: rgb(31, 73, 125);" class=""> </span></p><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">Are you sure that there are 12 of the SolarWorld 175’s on a single string?</span></div><p class="MsoNormal" style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;"><span style="color: rgb(31, 73, 125);" class=""> </span></p><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">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.</span></div><p class="MsoNormal" style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;"><span style="color: rgb(31, 73, 125);" class=""> </span></p><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">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.</span></div><p class="MsoNormal" style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;"><span style="color: rgb(31, 73, 125);" class=""> </span></p><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">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.</span></div><p class="MsoNormal" style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;"><span style="color: rgb(31, 73, 125);" class=""> </span></p><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">Brian Teitelbaum</span></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">AEE Solar</span></div><p class="MsoNormal" style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;"><span style="color: rgb(31, 73, 125);" class=""> </span></p><p class="MsoNormal" style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;"><span style="color: rgb(31, 73, 125);" class=""> </span></p><div class=""><div style="border-style: solid none none; border-top-color: rgb(181, 196, 223); border-top-width: 1pt; padding: 3pt 0in 0in;" class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><b class=""><span style="font-size: 10pt; font-family: Tahoma, sans-serif;" class="">From:</span></b><span style="font-size: 10pt; font-family: Tahoma, sans-serif;" class=""><span class="Apple-converted-space"> </span>RE-wrenches [mailto:<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" style="color: rgb(149, 79, 114); text-decoration: underline;" class="">re-wrenches-bounces@lists.re-wrenches.org</a>]<span class="Apple-converted-space"> </span><b class="">On Behalf Of<span class="Apple-converted-space"> </span></b>Ash Bowersock<br class=""><b class="">Sent:</b><span class="Apple-converted-space"> </span>Tuesday, June 21, 2016 12:48 PM<br class=""><b class="">To:</b><span class="Apple-converted-space"> </span><a href="mailto:re-wrenches@lists.re-wrenches.org" style="color: rgb(149, 79, 114); text-decoration: underline;" class="">re-wrenches@lists.re-wrenches.org</a><br class=""><b class="">Subject:</b><span class="Apple-converted-space"> </span>[RE-wrenches] Add-On to DGT, string inverter, w/Different Modules on 2nd string</span></div></div></div><p class="MsoNormal" style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;"> </p><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Good day RE Wrench crew,</div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">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.<span class="Apple-converted-space"> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">Can someone please give me a technical reason why mixed modules on a string inverter is “poor design practice”?</div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">The more technical and dry an explanation, the better ;)<span class="Apple-converted-space"> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">If you can’t convince them, bore them to tears with the details.<span class="Apple-converted-space"> </span></div><p class="MsoNormal" style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;"> </p><table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0" style="background-color: white;"><tbody class=""><tr class=""><td valign="top" style="padding: 0in;" class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 14pt; font-family: 'Baskerville Old Face', serif; color: rgb(153, 153, 153);" class="">Ash Bowersock</span><span style="color: rgb(31, 73, 125);" class=""><br class=""></span><span style="font-size: 9pt; font-family: Arial, sans-serif; color: rgb(153, 153, 153);" class="">Senior System Designer</span></div><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><a href="http://www.rgsenergy.com/" style="color: rgb(149, 79, 114); text-decoration: underline;" class=""><span style="font-family: '.HelveticaNeueInterface-M3'; color: blue; text-decoration: none;" class=""><img border="0" width="349" height="83" id="_x0000_i1025" src="http://rgsenergy.com/images/new_rgs_energy-cpbs.png" alt="RGS Energy" class=""></span></a><span style="font-size: 9pt; font-family: Arial, sans-serif; color: rgb(153, 153, 153);" class=""></span></div></td></tr><tr class=""><td valign="top" style="padding: 5.25pt 0in 3pt;" class=""></td></tr><tr class=""><td valign="top" style="padding: 0in;" class=""><div style="margin: 0in 0in 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 9pt; font-family: Arial, sans-serif; color: rgb(153, 153, 153);" class="">833 W. 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