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--></style></head><body lang="EN-US" link="blue" vlink="purple"><div class="WordSection1"><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Colleagues:</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">I have an interesting project. I am working for a family that lives part time in a planned community built some years ago. The HOA owns the 12 KV distribution and it is old and undersized. This client shares a 25 kVA transformer with a neighbor. This calculates out to 50 amps per home at 240 VAC.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">The client has more stuff to power than they have power. To make it possible to power their loads, I am imagining a pseudo off-grid installation. We have grid power, but precious little of it, so we have to stand-alone, at least to some degree.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">I am thinking that we can provide a battery inverter system that can be programmed to limit the draw from the grid. All the loads will be connected to the AC output of the inverter system. If the load increases over that programmed limit, a smart inverter system should be able to synchronize to the grid input and assist with inverted power (like gen support on the grid input). I believe the Radian inverters can do this.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">If occasionally the batteries get low, a generator can run intermittently and top off the batteries.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">There is an 8kW grid-tied system on site. This should be able to help power on-site loads or charge the batteries during day-light hours. I will specify a contactor to kill the GT feed if the grid goes out and the batteries are fully charged. </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">We can add another 11 kW of GT solar. However, I am concerned that we might be over-feeding the transformer on sunny days. The neighbor has about 8 kW of GT solar. If you add all of the GT solar into this one 25 kVA transformer, you arrive at 27 kVA. This is too much. Our additional GT solar might be with a Solar Edge HD-Wave SE10000-US. This inverter has an external box that can monitor net back-feed and limit the output of the SE inverter to a programmed level.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Anyway, this is a lot of detail that maybe you don\u2019t need to know. My question is this: How would you design a system to take 12 kVA from a grid source and turn it in to 60, or more?</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Any input is appreciated.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">William Miller</span></p></div></body></html>