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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Arial","sans-serif";color:#1F497D'>Garrison:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Arial","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Arial","sans-serif";color:#1F497D'>Are you sure you need a transformer to connect directly to the 3 phase? I believe the system you refer to is an open-delta. We’ve installed the old SB2500 units on open-delta before. This was before the neutral sensing requirements, however. Many inverters have provisions for disabling the neutral sense, if that would help. I’d verify there is actually a need for a transformer.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Arial","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Arial","sans-serif";color:#1F497D'>William<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Arial","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Arial","sans-serif";color:#1F497D'>PS: I do remember that I incorrectly ordered 208 inverters for the open-delta installation referred to above. It was actually a 240 volt three phase. The SB2500s had to be specified for the correct voltage. I had to eat a lot of freight to get 5 inverters reconfigured….<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Arial","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Arial","sans-serif";color:#1F497D'>Wm<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Arial","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Arial","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'><img width=64 height=28 id="Picture_x0020_1" src="cid:image003.jpg@01CFFFFC.CEC7B630" alt="Gradient Cap_mini"><br>Lic 773985<br><a href="http://www.millersolar.com/"><span style='color:blue'>millersolar.com</span></a><br>805-438-5600<o:p></o:p></span></p></div><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Arial","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> RE-wrenches [mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Garrison Riegel<br><b>Sent:</b> Friday, November 14, 2014 7:51 AM<br><b>To:</b> re-wrenches@lists.re-wrenches.org<br><b>Subject:</b> [RE-wrenches] Preventing 24/7 Transformer Losses<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Hello Wrenches,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>In my area we end up installing a lot of systems on 240V 3Ph high leg services. To allow for more inverter options (like TL that require a neutral) it seems like using a transformer would a good idea, but it is hard to justify the losses under load and especially 24/7 losses required to keep the core magnetized.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>In a recent post on this same subject by Greg Smith from SMA he wrote, “If you specify a transformer specifically for solar PV designs then the losses are negligible.” The transformer tech people at the manufacturers I spoken with have no idea what this means. I emailed Greg for clarification but have not yet had a reply. On a recent project that needed a 30KVA transformer the 24/7 losses were 200-300W depending on manufacturer, which is not negligible, and in my area would require about 2kW of PV to offset. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Does anyone know what Greg might be referring to?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>What are folks doing to mitigate these losses? Some kind of DC actuated switch on the utility side of the transformer maybe?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Anything else to keep in mind when specifying a PV specific transformer?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thank you for your thoughts.<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>Garrison<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='color:#44546A'>Garrison Riegel<o:p></o:p></span></p><p class=MsoNormal><span style='color:#44546A'>Project Manager | </span><a href="http://www.solarserviceinc.com/"><i><span style='color:#222A35'>Solar Service Inc</span></i></a><span style='color:#44546A'><o:p></o:p></span></p><p class=MsoNormal><span style='color:#44546A'>[p] 847-677-0950 | </span><a href="mailto:garrison@solarserviceinc.com"><span style='color:#44546A;text-decoration:none'>garrison@solarserviceinc.com</span></a><span style='color:#44546A'><o:p></o:p></span></p><p class=MsoNormal><span style='color:#44546A'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#44546A'>NABCEP Certified PV Installation Professional™<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>