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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#000000" vlink="#000000"><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Jamie,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The 6kVA imbalance limit, as you point out, is for 120V/240 split phase services, not 3-phase. It comes from California’s Rule 21 interconnection rules adopted by each California utility. As the technical facilitator of the development of Rule 21, I had a lot to do with the 6kVA number. It was based on the largest 120-Volt inverter that could be placed on the smallest available service. It JUST happened to coincide with the size of my Trace Engineering SW5500 inverter—funny how that works out.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Bill.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","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-bounces@lists.re-wrenches.org [mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Jamie Johnson<br><b>Sent:</b> Friday, December 10, 2010 12:14 PM<br><b>To:</b> RE-wrenches<br><b>Subject:</b> Re: [RE-wrenches] feed-in imbalance<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>Marco,<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'> <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>I believe some of the discussions in the past had to do with the old 6kW imbalance limit that is used by several utilities on a 120/240 small residential single phase transformer. (don't remember the CA utility that came up with this)<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>I had this discussion with our local utility (FPL) recently and they look at it on a case by case basis due to the many variables involved with 3 phase power distribution, such as the size and type of transformer(s), 3 phase loads on the premises, the harmonic distortion if any on a shared 3 phase transformer, core saturation, load balancing, etc.<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'> <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>If you install a system in the FPL service area that is not balanced and either the harmonics or voltage is out of spec as a result (yes, they do test them), then you basically have 2 choices, balance the system or pay to upgrade the service drop and transformer.<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'> <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>There has been talk of testing various 3 phase transformer(s) to determine the maximum/safe out of balance configuration by our local utility, however, again there are a lot of variables, so it would be difficult to cover every scenario. And this usually is only an issue on small 3 phase transformer(s).<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'> <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>I think that the 8,9,10TL 208v inverter has a load limiting ability that is incorporated in the inverter when you install 2 or more inverters, and it is programmable to limit the output of a single inverter to 6kW. I believe you have to purchase the additional communication cables from SMA (cables available after the first of the year? or so I have been told). Also, the design parameters seem a bit limited on the TL's.<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'> <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>Jamie<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal><b><span style='font-size:8.0pt;font-family:"Verdana","sans-serif";color:blue'><img width=226 height=210 id="_x0000_i1025" src="cid:image001.jpg@01CB9880.3B4B0840"></span></b><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'> <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'> <o:p></o:p></span></p></div><blockquote style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 6.0pt;margin-left:6.0pt;margin-top:5.0pt;margin-bottom:5.0pt' id=replyBlockquote><div id=wmQuoteWrapper><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>-------- Original Message --------<br>Subject: [RE-wrenches] feed-in imbalance<br>From: "Marco Mangelsdorf" <<a href="mailto:marco@pvthawaii.com"><span style='color:windowtext'>marco@pvthawaii.com</span></a>><br>Date: Fri, December 10, 2010 2:00 pm<br>To: "'RE-wrenches'" <<a href="mailto:re-wrenches@lists.re-wrenches.org"><span style='color:windowtext'>re-wrenches@lists.re-wrenches.org</span></a>><o:p></o:p></span></p><div><div><p class=MsoNormal><span style='font-family:"Verdana","sans-serif";color:black'>Now that SMA has come up with their new 8, 9 and 10 kW transformerless line of single-phase 120/208V inverters, it brings up the question once again about how practical and wise it is to have one or two of these inverters feed into a three-phase service. That is, is such an unbalanced feed much, if any, of a big deal?<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Verdana","sans-serif";color:black'> <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Verdana","sans-serif";color:black'>I spoke to my consulting E.E. about this and he said that the large majority of utility-provided transformers are so large these days that an unbalanced feed of, say, a 10 kW inverter that only has output power through L1 and L2 should not present a problem.<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Verdana","sans-serif";color:black'> <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Verdana","sans-serif";color:black'>Any other thoughts out there on this matter?<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Verdana","sans-serif";color:black'> <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Verdana","sans-serif";color:black'>Thanks,<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Verdana","sans-serif";color:black'>marco <o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Verdana","sans-serif";color:black'> <o:p></o:p></span></p></div></div><div class=MsoNormal align=center style='text-align:center'><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><hr size=2 width="100%" align=center></span></div><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>_______________________________________________<br>List sponsored by Home Power magazine<br><br>List Address: <a href="mailto:RE-wrenches@lists.re-wrenches.org"><u><span style='color:blue'>RE-wrenches@lists.re-wrenches.org</span></u></a><br><br>Options & settings:<br><a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org"><u><span style='color:blue'>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</span></u></a><br><br>List-Archive: <a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org"><u><span style='color:blue'>http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</span></u></a><br><br>List rules & etiquette:<br><a href="http://www.re-wrenches.org/etiquette.htm"><u><span style='color:blue'>www.re-wrenches.org/etiquette.htm</span></u></a><br><br>Check out participant bios:<br><a href="http://www.members.re-wrenches.org"><u><span style='color:blue'>www.members.re-wrenches.org</span></u></a><o:p></o:p></span></p></div></blockquote></div></body></html>