<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 12 (filtered medium)">
<!--[if !mso]>
<style>
v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style>
<![endif]-->
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
@font-face
{font-family:Verdana;
panose-1:2 11 6 4 3 5 4 4 2 4;}
@font-face
{font-family:"Monotype Corsiva";
panose-1:3 1 1 1 1 2 1 1 1 1;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
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;}
p
{mso-style-priority:99;
mso-margin-top-alt:auto;
margin-right:0in;
mso-margin-bottom-alt:auto;
margin-left:0in;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
{mso-style-priority:34;
margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:.5in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
span.EmailStyle18
{mso-style-type:personal;
font-family:"Calibri","sans-serif";
color:windowtext;}
span.EmailStyle21
{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 lang=EN-US link=blue vlink=purple>
<div class=WordSection1>
<p class=MsoNormal><span style='color:#1F497D'>Matt,<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Thanks for the reply. I should
have clarified, but I am talking about a standard grid-tied, non-backup system.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>I’m still not quite sure I
have any solid code sections to back up my assumption that it is OK to tie the
inverter GEC to the nearest steel, rather than running all the way back to the
water main (where the utility service entrance GEC is tied). <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>If we have an inverter mounted
on a roof, are you saying we can or cannot go to the closest building steel
with the GEC? 690.47(C)(6) sounds like we have to go back to the water main. While
690.47(D) sounds like we are supposed to tie to the nearest building steel (“Grounding
electrodes shall be installed… as close as practicable to the location of
roof-mounted photovoltaic arrays”).<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>Thanks for any clarifications,<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<p class=MsoNormal><b><span style='font-size:12.0pt;color:#244061'>Jason M.
Szrom, PE<o:p></o:p></span></b></p>
<p class=MsoNormal><span style='font-size:12.0pt;color:#244061'>Engineer<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#244061'>Solar Energy Systems, LLC<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#244061'>718-389-1545 x13<o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Matt
Lafferty<br>
<b>Sent:</b> Thursday, August 19, 2010 2:01 PM<br>
<b>To:</b> 'RE-wrenches'<br>
<b>Subject:</b> Re: [RE-wrenches] PV GEC to the same point as the utility
service GEC?<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>Good questions, Jason. </span><span style='font-size:12.0pt;
font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>No. Yes (2008 NEC 690.47(C) & (D)).</span><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>Alternative considerations that might result in a
"maybe": Does the system in question have storage (i.e. batteries)?
Is your POCC on a Delta system? (your hi-rise example says Wye... But if it is
directly tied to a Delta system, you might gotta run back to basement.)</span><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>If you are talking about a standard, grid-tied, non-backup system,
and the AC distribution between your tie-in and the utility is suitably sized
for the PV, you should hit the GE system where your AC
system is getting it's neutral bond. (Closest steel OK for PV grounding
electrode.) Equipment ground, same thing. Be sure to run an equipment grounding conductor
from the inverter to the array (i.e. don't just bond the rack to building
steel). </span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>Regarding your Additional Info items:</span><span style='font-size:
12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>1. Yep.</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>2. Some people on this list and in the AHJ
community would argue that the AC side of the inverter in this case IS a
separately derived system in all cases (I'm not among that bunch). Either
way, the output of your entire system is going thru the building's
AC distribution system. ESPECIALLY if you are on the secondary of a WYE
xfrmer, you can and SHOULD source your PV GEC where the xfrmer neutral
is bonded. </span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>3. You are right. The various provisions of 690.47(C)
allow/require this. In particular, (C)5 & 6.</span><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>The underlying principle that counts here is, "Get your GEC
where your AC source gets its system ground." </span><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><strong><i><span style='font-size:12.0pt;font-family:"Monotype Corsiva"'>Matt "I'm
no building inspector" Lafferty</span></i></strong><span style='font-size:
12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p>
<div class=MsoNormal align=center style='text-align:center'><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'>
<hr size=2 width="100%" align=center>
</span></div>
<p class=MsoNormal style='margin-bottom:12.0pt'><b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Jason
Szrom<br>
<b>Sent:</b> Thursday, August 19, 2010 7:38 AM<br>
<b>To:</b> re-wrenches@lists.re-wrenches.org<br>
<b>Subject:</b> [RE-wrenches] PV GEC to the same point as the utility service
GEC?</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal>Wrenches,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Questions: Does the PV GEC have to be bonded to the
ground electrode system at the same point as the utility service equipment GEC?
Is there a code section to back this up?<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Additional info:<o:p></o:p></p>
<p class=MsoListParagraph style='text-indent:-.25in'>1.<span style='font-size:
7.0pt;font-family:"Times New Roman","serif"'>
</span>The DC side of the inverter is a separately derived system and therefore
needs a GEC to a ground electrode.<o:p></o:p></p>
<p class=MsoListParagraph style='text-indent:-.25in'>2.<span style='font-size:
7.0pt;font-family:"Times New Roman","serif"'>
</span>The AC side of the inverter is not a separately derived system therefore
250.30(A)(7) does not apply. This section states that AC separately derived
systems should be grounded to the nearest ground electrode (building steel in
many cases) and therefore does not need to be bonded to the same point as the
utility service GEC.<o:p></o:p></p>
<p class=MsoListParagraph style='text-indent:-.25in'>3.<span style='font-size:
7.0pt;font-family:"Times New Roman","serif"'>
</span>My thought process is this: The PV GEC can be bonded to the
nearest ground electrode as long as this electrode is tied to the same ground
electrode as the utility service electrode, forming one complete ‘ground
electrode system’. My opinion is that this setup is analogous to this
example which is regularly seen in the field. High rise building with
structural steel bonded to water main with utility service GEC bonded as well.
Delta-wye step-down transformer on an upper level with the derived neutral on
the secondary bonded to closest building steel. Yet there is still an equipment
grounding connection to both the primary and secondary sides of the
transformer. This implies that it is OK and even preferable to tie the PV GEC
to the nearest ground electrode, but I can’t find any evidence or
section in the code that confirms or denies this.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Thanks for any input,<o:p></o:p></p>
<p class=MsoNormal>Jason<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><b><span style='font-size:12.0pt;color:#244061'>Jason M.
Szrom, PE<o:p></o:p></span></b></p>
<p class=MsoNormal><span style='font-size:12.0pt;color:#244061'>Engineer<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;color:#244061'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#244061'>Solar Energy Systems, LLC<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#244061'>1205 Manhattan Ave<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#244061'>Suite 1210<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#244061'>Brooklyn, NY 11222<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#244061'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#244061'>718-389-1545 x13<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:#244061'><a href="http://www.solaresystems.com/"><span style='color:#244061'>www.solarEsystems.com</span></a></span><span
style='font-size:10.0pt;color:#244061'><o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>No virus
found in this incoming message.<br>
Checked by AVG - www.avg.com<br>
Version: 9.0.851 / Virus Database: 271.1.1/3089 - Release Date: 08/23/10
02:35:00</span><o:p></o:p></p>
</div>
</body>
</html>