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690.47(C) applies to almost all our solar work (anything with an inverter). The whole point is: where does the equipment grounding conductor EGC become the grounded electrode conductor GEC? At that point and down, 250.166 applies as well. IMHO, once the separate modules are bonded to a center grounding point at or very near the array framing, then the conductor to the required supplementary electrode is the GEC. (which can be the framing, if 250.52 is followed.) <div>A separate EGC sized by 250.122 connects this center array grounding point back along with the power conductors to the AC ground buss , which is bonded to the house's GEC to a separate electrode.</div><div>These electrodes are connected through the EGC, and therefore satisfy 250.54 and ultimately 250.4. </div><div><br></div><div>They should not be connected by a 2nd pathway, as this creates a ground loop.</div><div>Connecting the various electrodes through EGC system alone satisfies both the requirements of the NEC, and good lightning protection practice of a single connection point grounding system with no loops.</div><div>Lightning strikes are conducted directly to earth at multiple points in the system by their separate large GECs while decoupling parts of the system somewhat from surges (via the reduced size EGC), but still bonded, insuring that no potential exists in different parts of the ground system normally.</div><div><br></div><div>Ok I'm going home<br><div> <span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><div>R. Walters</div><div>Solarray.com<span class="Apple-tab-span" style="white-space:pre"></span></div><div>NABCEP # 04170442<span class="Apple-tab-span" style="white-space:pre"><span class="Apple-style-span" style="white-space: pre; "> </span></span></div><div><br class="khtml-block-placeholder"></div><br class="Apple-interchange-newline"></span> </div><br><div><div>On Jun 19, 2009, at 12:22 PM, Peter Parrish wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"> <div class="Section1"><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">Thanks. One last thing: 690.47(C) has its own set of grounding requirements (C)(1)-(8). So we need to follow those as apposed to 250-166?</span></font></p><div><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"> </span></font><br class="khtml-block-placeholder"></div><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">- Peter</span></font></p><div><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"> </span></font><br class="khtml-block-placeholder"></div> <div><div><font size="3" color="navy" face="Times New Roman"><span style="font-size:12.0pt;color:navy"> </span></font><br class="khtml-block-placeholder"></div> <br clear="ALL"><div><font size="2" color="navy" face="Arial"><span style="font-size:10.0pt"> </span></font><br class="khtml-block-placeholder"></div><p class="MsoNormal"><span><image002.gif></span><font size="1" color="navy"><span style="font-size:9.0pt;color:navy">Peter T. Parrish, Ph.D., President<br> California Solar Engineering, Inc.<br> 820 Cynthia Ave., Los Angeles, CA 90065<br> CA Lic. 854779, NABCEP Cert. 031806-26<br> <a href="mailto:peter.parrish@calsolareng.com">peter.parrish@calsolareng.com</a> <br> Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 </span></font></p><div><font size="2" color="navy" face="Arial"><span style="font-size:10.0pt"> </span></font><br class="khtml-block-placeholder"></div> </div> <div> <div class="MsoNormal" align="center" style="text-align:center"><font size="3" face="Times New Roman"><span style="font-size:12.0pt"> <hr size="2" width="100%" align="center" tabindex="-1"> </span></font></div><p class="MsoNormal"><b><font size="2" face="Tahoma"><span style="font-size:10.0pt; font-family:Tahoma;font-weight:bold">From:</span></font></b><font size="2" face="Tahoma"><span style="font-size:10.0pt;font-family:Tahoma"> re-wrenches-bounces@lists.re-wrenches.org [<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <b><span style="font-weight: bold">On Behalf Of </span></b>R. Walters<br> <b><span style="font-weight:bold">Sent:</span></b> Friday, June 19, 2009 10:50 AM<br> <b><span style="font-weight:bold">To:</span></b> RE-wrenches<br> <b><span style="font-weight:bold">Subject:</span></b> Re: [RE-wrenches] What is a "direct-current system"?</span></font></p> </div><div><font size="3" face="Times New Roman"><span style="font-size: 12.0pt"> </span></font><br class="khtml-block-placeholder"></div><p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size: 12.0pt">I just sort of hit this in a previous post: </span></font></p> <div><p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size: 12.0pt">check 690.47C(3). Your system falls under (C) AC & DC grounding requirements.....</span></font></p> </div> <div><p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size: 12.0pt">This just shouldn't be that hard with the inspectors....</span></font></p> </div> <div><div><font size="3" face="Times New Roman"><span style="font-size: 12.0pt"> </span></font><br class="khtml-block-placeholder"></div> <div><span style="border-spacing: 0px 0px;text-align:auto;-khtml-text-decorations-in-effect: none; -apple-text-size-adjust: auto;orphans: 2;widows: 2;word-spacing:0px"> <div><p class="MsoNormal"><font size="1" color="black" face="Helvetica"><span style="font-size:6.0pt;font-family:Helvetica;color:black">R. Walters</span></font></p> </div> <div><p class="MsoNormal"><font size="1" color="black" face="Helvetica"><span style="font-size:6.0pt;font-family:Helvetica;color:black">Solarray.com</span></font></p> </div> <div><p class="MsoNormal"><font size="1" color="black" face="Helvetica"><span style="font-size:6.0pt;font-family:Helvetica;color:black">NABCEP # 04170442<span class="apple-style-span"> </span></span></font></p> </div> <div><div><font size="1" color="black" face="Helvetica"><span style="font-size:6.0pt;font-family:Helvetica;color:black"> </span></font><br class="khtml-block-placeholder"></div> </div><p class="MsoNormal"><font size="1" color="black" face="Helvetica"><span style="font-size:6.0pt;font-family:Helvetica;color:black"><br> <br> </span></font></p> </span></div><div><font size="3" face="Times New Roman"><span style="font-size: 12.0pt"> </span></font><br class="khtml-block-placeholder"></div> <div> <div><p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size: 12.0pt">On Jun 19, 2009, at 10:55 AM, Peter Parrish wrote:</span></font></p> </div><p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size: 12.0pt"><br> <br> </span></font></p> <div><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">I have a LA Dept. of B&S inspector cite Article 690.47(B) “Direct-Current Systems” and its consequent grounding requirements (250.166(A)(B)) in connection with a very straightforward grid tied PV system (i.e. no batteries, just PV and a Xantrex GT inverter).</span></font></p> <div><div><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"> </span></font><br class="khtml-block-placeholder"></div> </div><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">He said that since there is a DC circuit as well as an AC circuit, 690.47(B) applies. I countered that all PV systems have a DC circuit, so to separately call out a “Direct-Current System” must apply to something other than the DC PV circuit inherent in all PV systems.</span></font></p> <div><div><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"> </span></font><br class="khtml-block-placeholder"></div> </div><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">Am I missing something here? Is “Direct-Current System” defined in Article 690? We are working off NEC 2008.</span></font></p> <div><div><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"> </span></font><br class="khtml-block-placeholder"></div> </div><p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy">Thanks in advance for your help.</span></font></p> <div><div><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"> </span></font><br class="khtml-block-placeholder"></div> </div> <div><p class="MsoNormal" style="margin-left:.5in;text-indent:-.25in"><font size="2" face="Times New Roman"><span style="font-size:10.0pt">-</span></font><font size="1"><span style="font-size:7.0pt"> </span></font><font size="2" face="Arial"><span style="font-size:10.0pt;font-family: Arial">Peter</span></font></p> <div><div><font size="2" color="navy" face="Arial"><span style="font-size: 10.0pt;font-family:Arial;color:navy"> </span></font><br class="khtml-block-placeholder"></div> </div><p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size: 12.0pt"><image003.gif></span></font><font size="2" color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;color:navy">Peter T. 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