<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";
color:black;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
pre
{mso-style-priority:99;
mso-style-link:"HTML Preformatted Char";
margin:0in;
margin-bottom:.0001pt;
font-size:10.0pt;
font-family:"Courier New";
color:black;}
span.HTMLPreformattedChar
{mso-style-name:"HTML Preformatted Char";
mso-style-priority:99;
mso-style-link:"HTML Preformatted";
font-family:Consolas;
color:black;}
span.EmailStyle19
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dave, Gary, and Charlie,<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'>First, the directions from the manufacturer should be the guide as to whether a GEC is required or not. Just because a GEC terminal is located on the equipment, does not mean that one is required. Case in point—Enphase’s new IG product does not require a GEC, yet it has a grounding terminal for AHJs that might insist on one. This terminal is not intended for a GEC, but it is intended for an extra EGC if the AHJ requires it (LOL on all the abbreviations). <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 2014 NEC makes it very clear that ungrounded PV systems do NOT require an GEC on the dc side and that the ac EGC is sufficient to provide a ground reference for the required dc EGC.<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'>“690.47(B) <b><i>Direct-Current Systems.</i></b> …</span><i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:red'>An ac equipment grounding system shall be permitted to be used for equipment grounding of inverters and other equipment and for the ground-fault detection reference for ungrounded PV systems.</span></i><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><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>“690.47(C)(3) <b><i>Combined Direct-Current Grounding Electrode Conductor and Alternating-Current Equipment<o:p></o:p></i></b></span></p><p class=MsoNormal><b><i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Grounding Conductor.</span></i></b><i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> An unspliced, or irreversibly spliced, combined grounding conductor shall be run from<o:p></o:p></span></i></p><p class=MsoNormal><i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>the marked dc grounding electrode conductor connection point along with the ac circuit conductors to the grounding<o:p></o:p></span></i></p><p class=MsoNormal><i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>busbar in the associated ac equipment. This combined grounding conductor shall be the larger of the sizes specified<o:p></o:p></span></i></p><p class=MsoNormal><i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>by 250.122 or 250.166 and shall be installed in accordance with 250.64(E).</span></i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> </span><i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:red'>For ungrounded systems, this conductor shall be sized in accordance with 250.122 and shall not be required to be larger than the largest ungrounded phase conductor.</span></i><i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>”<o:p></o:p></span></i></p><p class=MsoNormal><i><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></i></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Red letters not Jesus’ words. This is the new language of the 2014 NEC. It is now in print.<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 very practical reason that a 6AWG is only required with a single ground rod has to do with the current carrying capacity of a 5/8”, 8’ ground rod in soils of low resistivity—nothing more.<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'>Bill.<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'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext'>From:</span></b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:windowtext'> re-wrenches-bounces@lists.re-wrenches.org [mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Dave Click<br><b>Sent:</b> Wednesday, September 18, 2013 5:38 AM<br><b>To:</b> re-wrenches@lists.re-wrenches.org<br><b>Subject:</b> Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system with microinverters<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='margin-bottom:12.0pt'>I think Gary may be overthinking this. If the micro-inverters have a GEC lug then you'll need to run a GEC.<br><br>If you run your GEC to a ground rod, then you don't need to use one larger than #6 per 250.166(C). (note also (D) and (E) but they're less useful to you here)<br><i><br>Commentary:</i><br>It makes no sense to me why the NEC can require a 0.9in diameter, #600mcm GEC for some systems (not this one) per 250.166(B) and then say "oh wait, you installed a single ground rod? Then a #6 is all you need!" in 250.166(C). But it certainly makes our lives easier.<br><br>If the building GE is not a ground rod, you could still run your #6 GEC to that new ground rod, and then bond that rod to the existing electrode using whatever size jumper is required per 250.53 (which I believe would also be a #6). This lets you keep that 300' run as a #6 rather than a #4 or #2 that may be required otherwise.<br><br>DKC<o:p></o:p></p><div><p class=MsoNormal>On 2013/9/17 23:56, Gary Willett wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal>Charlie:<br><br>The answer depends on whether the "system" (modules and micro-inverters) is "grounded" or "ungrounded". I think you are describing a "grounded" system, but it's not totally clear based on your issue description.<br><br>If the micro-inverter is "transformer-less" the conductors are not isolated between the DC-in and the AC-out. This requires the micro-inverter to have no DC-side system ground. The micro-inverter AC-side always requires an EGC.<br><br>I am assuming that the PV modules are in close proximity to the micro-inverters, and the 300' home-run is for the AC outputs of the micro-inverters.<br><br>Is either DC bus (PV+ or PV-) a grounded conductor, or are both busses ungrounded? If the DC-side combiners and re-combiners have OCPDs and disconnecting means for both PV+ and PV-, then your system is considered to be "floating" or "ungrounded".<br><br>If the system is "ungrounded", a GEC is not required on the DC-side of the micro-inverter, and only an AC-EGC sized per NEC 690.45 is required.<br><br>If the DC-side combiners and re-combiners have OCPDs and disconnecting means for only one conductor (PV+ or PV-), then your PV system is considered to be "grounded". If the system is "grounded", the combined DC-GEC and AC-EGC sizing requirements in NEC 690.47(C)(3) apply. The larger of the EGC (Table 250.122) and GEC [250.166(B)] sizes will be required.<br><br>More specifics on the PV module Vmpp and micro-inverter you're dealing with would be helpful.<br><br>Regards,<br><br>Gary Willett<br>Icarus Solar<br><br><br>On 9/17/13 8:37 PM, Aladdin Solar wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>We will be installing a 40KW grid-tied PV system that uses PV modules wired in parallel as per the module manufacturer -- so it's a high amperage, low voltage system on the DC side. 2 branches of about 3KW of parallel wired modules each come together onto a DC bus. The DC branch conductors are sized as 2AWG.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>The inverter system provided by the manufacturer consists of a number of UL1741 single phase microinverters that all are powered off of the low voltage DC bus. So there's a bunch of microinverters in parallel, combined output is single phase power.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Those microinverters have a ground lug labeled "GEC". You know where this is going...</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Assuming we are following NEC 690.47(C)(3), we'll be treating this ground as GEC and following all the GEC rules. My understanding is that because the DC conductors within the array are 2AWG (NEC 250.166(B), we will need to connect all 12 branches and 6 DC buses with continuous 2AWG and bring it all the way back 300' to where the AC GEC bond is located. We're getting a lot of pushback from the electrical sub and even some disagreement from the module manufacturer on this--no one's ever seen a grounding conductor of this size being required for this application.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Please don't get too bogged down with understanding the low voltage, parallel module spec and the massive number of microinverters involved. What I'm looking for is confirmation that I am properly understanding how the NEC GEC requirements apply, especially to the GEC size.</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Charlie Pickard<br>NABCEP Certified PV Installation Professional ™<br>Aladdin Solar, LLC</span><o:p></o:p></p></div><p class=MsoNormal><br><br>__________ Information from ESET NOD32 Antivirus, version of virus signature database 8813 (20130917) __________<br><br>The message was checked by ESET NOD32 Antivirus.<br><br><a href="http://www.eset.com">http://www.eset.com</a><br><br><br><br><o:p></o:p></p><pre>_______________________________________________<o:p></o:p></pre><pre>List sponsored by Home Power magazine<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>List Address: <a href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Change email address & settings:<o:p></o:p></pre><pre><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><o:p></o:p></pre><pre><o:p> </o:p></pre><pre>List-Archive: <a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre>List rules & etiquette:<o:p></o:p></pre><pre><a href="http://www.re-wrenches.org/etiquette.htm">www.re-wrenches.org/etiquette.htm</a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Check out participant bios:<o:p></o:p></pre><pre><a href="http://www.members.re-wrenches.org">www.members.re-wrenches.org</a><o:p></o:p></pre><pre><o:p> </o:p></pre></blockquote><p class=MsoNormal><br><br><br><br><o:p></o:p></p><pre>_______________________________________________<o:p></o:p></pre><pre>List sponsored by Home Power magazine<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>List Address: <a href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Change email address & settings:<o:p></o:p></pre><pre><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><o:p></o:p></pre><pre><o:p> </o:p></pre><pre>List-Archive: <a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre>List rules & etiquette:<o:p></o:p></pre><pre><a href="http://www.re-wrenches.org/etiquette.htm">www.re-wrenches.org/etiquette.htm</a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre>Check out participant bios:<o:p></o:p></pre><pre><a href="http://www.members.re-wrenches.org">www.members.re-wrenches.org</a><o:p></o:p></pre><pre><o:p> </o:p></pre></blockquote><p class=MsoNormal><o:p> </o:p></p></div></body></html>