<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;"><DIV>I never thought I would disagree with William, I have the highest admiration for him, <BR>But the transformerless inverter has no seperation between grid and array, no problem if everything is fused. </DIV>
<DIV>Darryl<BR>--- On <B>Sat, 11/13/10, William Miller <I><william@millersolar.com></I></B> wrote:<BR></DIV>
<BLOCKQUOTE style="BORDER-LEFT: rgb(16,16,255) 2px solid; PADDING-LEFT: 5px; MARGIN-LEFT: 5px"><BR>From: William Miller <william@millersolar.com><BR>Subject: Re: [RE-wrenches] Head Spinning..(Con) fused.<BR>To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org><BR>Date: Saturday, November 13, 2010, 11:26 PM<BR><BR>
<DIV id=yiv1641626777><FONT size=3>Eric:<BR><BR>The best resource I have found on this subject is the white paper that John <SPAN>Berdner</SPAN> wrote. I have a copy on my web site: millersolar.com under Resources.<BR><BR>The general rule is no system with two strings combined needs fuses. Run the calcs as presented in the white paper for verification.<BR><BR>Just because circuits share a J-box or conduit is not a reason to fuse. Actual connection into an inverter is required before the number of strings is tabulated.<BR><BR>William Miller<BR><BR><BR><BR><BR>At 08:40 PM 11/13/2010, you wrote:<BR>
<BLOCKQUOTE class=yiv1641626777cite cite="" type="cite">Wrenches,<BR><BR>Can anyone shed guidance on the following for me? Should these strings be fused:<BR><BR>Total Modules: 44<BR>Total Strings: 4 strings of 11 <BR>Total Inverters: 2<BR><BR>Modules: Silicon Energy 195 Watt @ 8A<BR>Each string feeding an independent MPPT input on an Aurora PVI 4.2kW Inverter (there are 2 / Aurora)<BR>Inverter is transformerless (READ 690.35 (B))<BR><BR>Each strings passes through a shared SolaDeck jbox, no combining, and head directly to their own dedicated GE THN2261RDC DC Disconnect before entering a dedicated MPPT input on the inverter.<BR><BR>My big question is 690.9 (A) exception (b) which states I don't need ocpd as long as "The short circuit currents from all sources do not exceed the ampacity of the conductors."<BR><BR>Because all four strings pass through the same jboxs and conduit before reaching their disconnect and could potentially short together, should I
fuse each string? <BR><BR>Or am I just up too late reading code....?<BR><BR>Thanks for being a resource.<BR><BR>-- <BR>Eric Thomas<BR>Solar Epiphany LLC<BR>(206) 919-3014<BR><A href="http://www.solarepiphany.com/" rel=nofollow target=_blank>www.solarepiphany.com</A><BR><BR>_______________________________________________<BR>List sponsored by Home Power magazine<BR><BR>List Address: RE-wrenches@lists.re-wrenches.org<BR><BR>Options & settings:<BR><A href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org" rel=nofollow target=_blank>http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</A><BR><BR>List-Archive: <A href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org" rel=nofollow target=_blank>http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</A><BR><BR>List rules & etiquette:<BR><A href="http://www.re-wrenches.org/etiquette.htm" rel=nofollow
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<DIV><U>Please note new e-mail address and domain:<BR><BR></U>William Miller <BR>Miller Solar<BR>Voice :805-438-5600<BR>email: william@millersolar.com<BR><A href="http://millersolar.com/" rel=nofollow target=_blank>http://millersolar.com<BR></A>License No. C-10-773985<BR></FONT></DIV></DIV><BR>-----Inline Attachment Follows-----<BR><BR>
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