<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>Not sure about the rest but under ground conductors are considered a wet location. <br><br><div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);">Jesse Dahl</span></div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);"><br></span></div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);">NABCEP PV Installation Professional</span></div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);">IBEW Local 292 - Electrician </span></div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);">Electrical/Solar PV Instructor - HCC</span></div></div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);"><br></span></div>Sent from my iPhone</div><div><br>On Jun 23, 2016, at 3:41 PM, Peter Parrish <<a href="mailto:peter.parrish@calsolareng.com">peter.parrish@calsolareng.com</a>> wrote:<br><br></div><blockquote type="cite"><div><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="Generator" content="Microsoft Word 12 (filtered medium)"><style><!--
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</o:shapelayout></xml><![endif]--><div class="WordSection1"><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I am working with a customer who is doing a complete remodel, and upgrading to PV and Smart Energy Storage. The house was broken down to floor joists, open studded walls and open roof rafters.<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 client wanted a 8 kW/16 kWh Smart Energy Storage system and a 10 kW-ac PV system. The Main panel, the Critical Load sub-panel, the Energy Storage system and the PV inverters will all be either in a detached garage or hung on the west facing exterior wall of the detached garage.<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">We have been given a number of 1-1/2” PVC conduits, buried a minimum of 18”, that run between the main house and the detached garage, so we have to convey 2/3rds of the PV source circuits and all of the critical load branch circuits using this conduit. This raises a number of questions/confirmations:<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="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><span style="mso-list:Ignore">(1)<span style="font:7.0pt "Times New Roman""> </span></span></span><!--[endif]--><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">We cannot mix PV source circuits and critical load branch circuits in the same conduit. Pretty obvious.<br><br><o:p></o:p></span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><span style="mso-list:Ignore">(2)<span style="font:7.0pt "Times New Roman""> </span></span></span><!--[endif]--><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">What ambient temperature should I use in my ampacity calculations? I assumed something less than 30°C, such as 20°C. But I read somewhere that one has to be careful when the conduit exists the ground, in that one has only 18” of conduit above ground before one has to use the full maximum ambient temperature which in our case is 45°. The argument says that for the first 18”, the portion of the copper conductors in the ground will cool the portion of the conductors above ground via thermal conduction. I can’t find any citation to confirm this argument. Does anyone have any sources of information on the subject? Even if there is a sound engineering basis for the argument, soon after exiting the ground, one would need a vault to splice in a higher ampacity conductors and continue on to either the critical load sub-panel or the inverters, you have to calculate the ampacity at 45°C. These buried conduit runs are approximately 50 feet in length.<br><br><o:p></o:p></span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><span style="mso-list:Ignore">(3)<span style="font:7.0pt "Times New Roman""> </span></span></span><!--[endif]--><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">One end of the conduit run is supposed to come out of the ground inside the building envelope, so we could derate using 30°C or so for air conditioned space. We cannot count on the garage being air conditioned however.<br><br><o:p></o:p></span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><!--[if !supportLists]--><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><span style="mso-list:Ignore">(4)<span style="font:7.0pt "Times New Roman""> </span></span></span><!--[endif]--><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Can we use THHN as opposed to THWN-2? I am assuming the forces of nature or human stupidity will eventually cause the PVC to crack and the extra expense of THWN-2 (or another wet rated 90°C conductor) will be a better choice.<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">This job is the same one where the electrician claimed that neutrals on a 120V branch circuit don’t count as current carry conductors in conduit for the purposes of de-rating ampacity. He’s gone, but his replacement may not be any more careful in his ampacity calculations.<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">Faithfully yours,<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">Peter T. Parrish, Ph.D.<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">NABCEP™ Solar Professional #031806-26<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">President, SolarGnosis<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">1107 Fair Oaks Ave.<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Suite 351<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">South Pasadena, CA 91030<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">(323) 839-6108<o:p></o:p></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><a href="mailto:petertor@pobox.com">petertor@pobox.com</a></span><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"><o:p> </o:p></span></p></div></div></blockquote><blockquote type="cite"><div><span>_______________________________________________</span><br><span>List sponsored by Redwood Alliance</span><br><span></span><br><span>List Address: <a href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a></span><br><span></span><br><span>Change listserver email address & settings:</span><br><span><a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a></span><br><span></span><br><span>List-Archive: <a href="http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html">http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html</a></span><br><span></span><br><span>List rules & etiquette:</span><br><span><a href="http://www.re-wrenches.org/etiquette.htm">www.re-wrenches.org/etiquette.htm</a></span><br><span></span><br><span>Check out or update participant bios:</span><br><span><a href="http://www.members.re-wrenches.org">www.members.re-wrenches.org</a></span><br><span></span><br></div></blockquote></body></html>