<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:x="urn:schemas-microsoft-com:office:excel" xmlns:p="urn:schemas-microsoft-com:office:powerpoint" xmlns:a="urn:schemas-microsoft-com:office:access" xmlns:dt="uuid:C2F41010-65B3-11d1-A29F-00AA00C14882" xmlns:s="uuid:BDC6E3F0-6DA3-11d1-A2A3-00AA00C14882" xmlns:rs="urn:schemas-microsoft-com:rowset" xmlns:z="#RowsetSchema" xmlns:b="urn:schemas-microsoft-com:office:publisher" xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet" xmlns:c="urn:schemas-microsoft-com:office:component:spreadsheet" xmlns:odc="urn:schemas-microsoft-com:office:odc" xmlns:oa="urn:schemas-microsoft-com:office:activation" xmlns:html="http://www.w3.org/TR/REC-html40" xmlns:q="http://schemas.xmlsoap.org/soap/envelope/" xmlns:rtc="http://microsoft.com/officenet/conferencing" xmlns:D="DAV:" xmlns:Repl="http://schemas.microsoft.com/repl/" xmlns:mt="http://schemas.microsoft.com/sharepoint/soap/meetings/" xmlns:x2="http://schemas.microsoft.com/office/excel/2003/xml" xmlns:ppda="http://www.passport.com/NameSpace.xsd" xmlns:ois="http://schemas.microsoft.com/sharepoint/soap/ois/" xmlns:dir="http://schemas.microsoft.com/sharepoint/soap/directory/" xmlns:ds="http://www.w3.org/2000/09/xmldsig#" xmlns:dsp="http://schemas.microsoft.com/sharepoint/dsp" xmlns:udc="http://schemas.microsoft.com/data/udc" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:sub="http://schemas.microsoft.com/sharepoint/soap/2002/1/alerts/" xmlns:ec="http://www.w3.org/2001/04/xmlenc#" xmlns:sp="http://schemas.microsoft.com/sharepoint/" xmlns:sps="http://schemas.microsoft.com/sharepoint/soap/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:udcs="http://schemas.microsoft.com/data/udc/soap" xmlns:udcxf="http://schemas.microsoft.com/data/udc/xmlfile" xmlns:udcp2p="http://schemas.microsoft.com/data/udc/parttopart" xmlns:wf="http://schemas.microsoft.com/sharepoint/soap/workflow/" xmlns:dsss="http://schemas.microsoft.com/office/2006/digsig-setup" xmlns:dssi="http://schemas.microsoft.com/office/2006/digsig" xmlns:mdssi="http://schemas.openxmlformats.org/package/2006/digital-signature" xmlns:mver="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns:mrels="http://schemas.openxmlformats.org/package/2006/relationships" xmlns:spwp="http://microsoft.com/sharepoint/webpartpages" xmlns:ex12t="http://schemas.microsoft.com/exchange/services/2006/types" xmlns:ex12m="http://schemas.microsoft.com/exchange/services/2006/messages" xmlns:pptsl="http://schemas.microsoft.com/sharepoint/soap/SlideLibrary/" xmlns:spsl="http://microsoft.com/webservices/SharePointPortalServer/PublishedLinksService" xmlns:Z="urn:schemas-microsoft-com:" xmlns:st="" 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)">
<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:Tahoma;
panose-1:2 11 6 4 3 5 4 4 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";}
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;}
span.EmailStyle17
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.Section1
{page:Section1;}
-->
</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=Section1>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The serving transformer is also an issue. I’ve seen 800-amp
service conductors on a 25kVA transformer. Just because you have wires large enough
for a 400-amp service, does not mean you have a transformer capable of
delivering 400-amps continuous. That is why you have to work with the serving
utility with larger systems.<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>
<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>Scott
McCalmont<br>
<b>Sent:</b> Thursday, March 04, 2010 3:30 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] Supply Side Interconnections - Maximum
Backfeed<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Going all the way up to the rating of the service might not
be such a good idea. The utility may use smaller wires for the service drop
than you would expect based on the ampacity tables in the NEC. Considering the
example of a 400 A service:<o:p></o:p></p>
<div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
<div>
<p class=MsoNormal>- PG&E (local utility) requires 350 kcmil Aluminum
conductors.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>- Table 310.17 rates 350 kcmil Aluminum for 395 amps before
temperature correction.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
<div>
<p class=MsoNormal>With load diversity the smaller wires will be fine, but the
output of a PV system is continuous. Running the output of a system sized at
400 amps through the wires on a hot summer day could overload them.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
<div>
<p class=MsoNormal>So... it depends.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
<div>
<p class=MsoNormal>Scott<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
<div>
<p class=MsoNormal>Scott McCalmont, P.E.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>McCalmont Engineering<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>San Jose, CA<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>(408) 204-0318<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal style='margin-bottom:12.0pt'><o:p> </o:p></p>
<div>
<p class=MsoNormal>On Thu, Mar 4, 2010 at 3:02 PM, Michael Kelly <<a
href="mailto:mike@solarflair.com">mike@solarflair.com</a>> wrote:<o:p></o:p></p>
<div>
<p class=MsoNormal>Kirpal,<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><br>
That was always my interpretation as well. So in the case of a 400A
service, I can backfeed 400A when utilizing a supply side connection.
Others have thoughts on this?<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>- Mike<o:p></o:p></p>
<div>
<p class=MsoNormal style='margin-bottom:12.0pt'><br clear=all>
--<br>
Michael Kelly<br>
Project Manager / Project Engineer<br>
NABCEP Certified Solar PV Installer ™<br>
<br>
SolarFlair Energy, Inc.<br>
11 Mayhew Street<br>
Framingham, MA 01702<br>
Direct Mobile: 617-899-9840<br>
Main Phone: 508-293-4293<br>
Main Fax: 508-293-4003<br>
<a href="mailto:mike@solarflair.com" target="_blank">mike@solarflair.com</a><br>
<br>
<o:p></o:p></p>
</div>
</div>
<div>
<div>
<div>
<p class=MsoNormal>On Thu, Mar 4, 2010 at 4:16 PM, Kirpal Khalsa <<a
href="mailto:solarworks@gmail.com" target="_blank">solarworks@gmail.com</a>>
wrote:<o:p></o:p></p>
<p class=MsoNormal>Mike.....i may be wrong....but I think i am right....you are
limited by the wire size feeding the supply and/or the transformer size
which supplies the service.....depending on the physical location of the tap
you may be limited by the enclosure and the enclosure ratings as well<br>
would love to hear any other ideas...<br>
Cheers,<br>
-- <br>
Sunny Regards,<br>
Kirpal Khalsa <o:p></o:p></p>
<div>
<p class=MsoNormal><br>
NABCEP Certified Solar PV Installer<o:p></o:p></p>
</div>
<p class=MsoNormal style='margin-bottom:12.0pt'>Renewable Energy Systems<br>
<a href="http://www.oregonsolarworks.com/" target="_blank">www.oregonsolarworks.com</a><br>
541-218-0201 m<br>
541-592-3958 o<br>
<br>
<o:p></o:p></p>
<div>
<div>
<div>
<p class=MsoNormal>On Thu, Mar 4, 2010 at 12:50 PM, Michael Kelly <<a
href="mailto:mike@solarflair.com" target="_blank">mike@solarflair.com</a>>
wrote:<o:p></o:p></p>
</div>
</div>
<blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;
margin-left:4.8pt;margin-right:0in'>
<div>
<div>
<div>
<p class=MsoNormal>Hi All,<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>Next to grounding, I find the calculation of the maximum
amount of backfeed current allowed in a supply side connection to be the most
vague issue in Article 690. Let's assume we have a 400A, 480/277 service
in a commercial building, a 400A main service disconnect, and the jurisdiction
is under NEC 2008. What is the maximum backfeed current allowed in a
supply side connection? The only place the code points you to is
230.82(6), which is no help, or to Article 705, which is no help either.
I know that in the draft version of NEC 2011, there is an expansion of
705.12(A) which states "<b><span style='font-size:10.0pt'> </span></b>Supply
Side. An electric power production source shall be permitted to be
connected to the supply side of the service disconnecting means as permitted in
230.82(6). The sum of the ratings of all overcurrent devices connected to power
production sources shall not exceed the rating of the service." That
is a helpful sentence from the Code, but as it is in draft form, what do we do
under NEC 2008? What have you used as a maximum backfeed current for
supply side connections?<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal> <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>Thanks,<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>Mike<br clear=all>
--<br>
Michael Kelly<br>
Project Manager / Project Engineer<br>
NABCEP Certified Solar PV Installer ™<br>
<br>
SolarFlair Energy, Inc.<br>
11 Mayhew Street<br>
Framingham, MA 01702<br>
Direct Mobile: 617-899-9840<br>
Main Phone: 508-293-4293<br>
Main Fax: 508-293-4003<br>
<a href="mailto:mike@solarflair.com" target="_blank">mike@solarflair.com</a><o:p></o:p></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
</div>
<p class=MsoNormal style='margin-bottom:12.0pt'>_______________________________________________<br>
List sponsored by Home Power magazine<br>
<br>
List Address: <a href="mailto:RE-wrenches@lists.re-wrenches.org" target="_blank">RE-wrenches@lists.re-wrenches.org</a><br>
<br>
Options & settings:<br>
<a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org"
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"
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" target="_blank">www.re-wrenches.org/etiquette.htm</a><br>
<br>
Check out participant bios:<br>
<a href="http://www.members.re-wrenches.org/" target="_blank">www.members.re-wrenches.org</a><br>
<br>
<o:p></o:p></p>
</blockquote>
</div>
<p class=MsoNormal style='margin-bottom:12.0pt'><br>
<br>
<br>
_______________________________________________<br>
List sponsored by Home Power magazine<br>
<br>
List Address: <a href="mailto:RE-wrenches@lists.re-wrenches.org" target="_blank">RE-wrenches@lists.re-wrenches.org</a><br>
<br>
Options & settings:<br>
<a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org"
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"
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" target="_blank">www.re-wrenches.org/etiquette.htm</a><br>
<br>
Check out participant bios:<br>
<a href="http://www.members.re-wrenches.org/" target="_blank">www.members.re-wrenches.org</a><br>
<br>
<o:p></o:p></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
</div>
<p class=MsoNormal style='margin-bottom:12.0pt'><br>
_______________________________________________<br>
List sponsored by Home Power magazine<br>
<br>
List Address: <a href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a><br>
<br>
Options & settings:<br>
<a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org"
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"
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" target="_blank">www.re-wrenches.org/etiquette.htm</a><br>
<br>
Check out participant bios:<br>
<a href="http://www.members.re-wrenches.org" target="_blank">www.members.re-wrenches.org</a><br>
<br>
<o:p></o:p></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
</div>
</div>
</body>
</html>