<div dir="ltr">Hi William, <div><br></div><div>Thanks for sharing. I like your interlocking system, especially for when you need to run a load panel that is >100A. Have you ever had an inspector give you a hard time about making your own interlock, rather than using something listed?</div><div><br></div><div>For 100A load panels or less, I have found something like the GE TC10323R to be well enough priced. Most hybrid inverters have load breakers, so I'll just bug those together in the gutter if there is more than one inverter. However, as you mentioned, the 200A versions of these double throw transfer switches are quite pricey.</div><div><br></div><div>Cheers, </div><div>Dave</div></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Tue, Oct 14, 2025 at 1:55\u202fAM William Miller via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="msg6214010999814048119"><div lang="EN-US"><div class="m_6214010999814048119WordSection1"><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">Friends:</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">For many years I had committed to the Outback product line. The decline of Outback forced me to branch out. </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">I just completed my first install of Fortress Envy inverters. Not long ago I installed a Sol-Ark 12K in my shop. Both experiences were mostly positive.</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">What is interesting is the Envy and Soul-ark inverters do not come with BOS equipment. </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">Now, if you want a PV disconnect, you need to add one manufactured by a third party. This can be accomplished with a 600 volt safety switch.</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">If you want AC disconnecting means or distribution, you need to provide outboard equipment. This is easily provided with off-the-shelf circuit breaker panels. </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">Since my second Radian install I have avoided putting AC breakers in the GSLC because wiring them was beyond tedious. Instead I ran my AC leads right through the GSLC and straight to one of two breaker panels: A generator-fed panel and in inverter-fed panel. Therefore I am not inconvenienced by lack of AC BOS with the new generation inverters.</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">There is one other function that is missing with the lack of BOS cabinets: Bypass switching. I think it is imperative that bypass capabilities be provided. Inverters can fail and occasionally need service and a bypass makes these scenarios much easier to handle. As a matter of policy I will not support a batter-inverter client if they do not have a bypass.</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">The Fortress and Sol-Ark manuals recommend use of an outboard double throw switch for bypass. These are expensive and bulky.</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">Over the years I have developed circuit breaker interlocks that can be fitted in a standard breaker panel and take care of the bypassing function cheaply and efficiently. </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">For a long time I have been meaning to write an article on the subject of transfer switches and bypass options. I finally got around to it and it can be found <a href="https://millersolar.com/MillerSolar/practices/Technical_Procedures/Interlock/Interlock.html" target="_blank">here</a>. I hope my efforts writing this might provide some insight on the subject.</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">I think I have fine-tuned my interlock design to a final iteration, as described in the article. If any of you are interested in trying out my Universal Bypass Interlock I am willing to send one for you to try at no cost. Contact me off list if you are interested.</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">Sincerely,</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif"">William Miller</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Arial,"sans-serif"">Miller Solar</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Arial,"sans-serif"">17395 Oak Road, Atascadero, CA 93422</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Arial,"sans-serif"">805-438-5600</span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Arial,"sans-serif""><a href="http://www.millersolar.com/" target="_blank">www.millersolar.com</a></span></p><p class="MsoNormal"><span style="font-size:12pt;font-family:Arial,"sans-serif"">CA Lic. 773985</span></p><p class="MsoNormal"> </p><p class="MsoNormal"> </p></div></div>
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