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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>All,<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'>Transformerless inverters are simply a subset of ungrounded or
resistively grounded PV systems covered by the NEC in 690.35 since the 2005
code cycle. Power-One has been marketing their ungrounded inverter in the U.S.
for several years now. It was listed by CSA. The requirements for ungrounded
systems in 690.35 are as follows:<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 style='margin-left:.5in;text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;color:#1F497D'><span style='mso-list:Ignore'>•<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'>“Photovoltaic power systems shall be permitted to operate
with ungrounded photovoltaic source and output circuits where the system
complies with 690.35(A) through 690.35(G).<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.0in;text-indent:-.25in;mso-list:l0 level2 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Trebuchet MS","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>−<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><b><span style='font-size:11.0pt;font-family:
"Calibri","sans-serif";color:#1F497D'>(A) Disconnects. </span></b><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>All
photovoltaic source and output circuit conductors shall have disconnects
complying with 690, Part III.<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.0in;text-indent:-.25in;mso-list:l0 level2 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Trebuchet MS","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>−<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><b><span style='font-size:11.0pt;font-family:
"Calibri","sans-serif";color:#1F497D'>(B) Overcurrent Protection. </span></b><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>All
photovoltaic source and output circuit conductors shall have overcurrent protection
complying with 690.9.<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.0in;text-indent:-.25in;mso-list:l0 level2 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Trebuchet MS","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>−<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><b><span style='font-size:11.0pt;font-family:
"Calibri","sans-serif";color:#1F497D'>(C) Ground-Fault Protection. </span></b><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>All
photovoltaic source and output circuits shall be provided with a ground-fault
protection device or system that complies with (1) through (3):<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.5in;text-indent:-.25in;mso-list:l0 level3 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;color:#1F497D'><span style='mso-list:Ignore'>•<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'>(1) Detects a ground fault.<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.5in;text-indent:-.25in;mso-list:l0 level3 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;color:#1F497D'><span style='mso-list:Ignore'>•<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'>(2) Indicates that a ground fault has occurred<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.5in;text-indent:-.25in;mso-list:l0 level3 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;color:#1F497D'><span style='mso-list:Ignore'>•<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'>(3) Automatically disconnects all conductors or causes the
inverter or charge controller connected to the faulted circuit to automatically
cease supplying power to output circuits.<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.0in;text-indent:-.25in;mso-list:l2 level2 lfo2'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Trebuchet MS","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>−<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><b><span style='font-size:11.0pt;font-family:
"Calibri","sans-serif";color:#1F497D'>(D) </span></b><span style='font-size:
11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The photovoltaic
source and output conductors shall consist of the following:<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.0in;text-indent:-.25in;mso-list:l2 level2 lfo2'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Trebuchet MS","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>−<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'>(1) Nonmetallic jacketed multiconductor cables<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.0in;text-indent:-.25in;mso-list:l2 level2 lfo2'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Trebuchet MS","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>−<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'>(2) Conductors installed in raceways, or<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.0in;text-indent:-.25in;mso-list:l2 level2 lfo2'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Trebuchet MS","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>−<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'>(3) Conductors listed and identified as Photovoltaic (PV) Wire
installed as exposed, single conductors.<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.0in;text-indent:-.25in;mso-list:l2 level2 lfo2'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Trebuchet MS","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>−<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><b><span style='font-size:11.0pt;font-family:
"Calibri","sans-serif";color:#1F497D'>(E) </span></b><span style='font-size:
11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The photovoltaic power
system direct-current circuits shall be permitted to be used with ungrounded
battery systems complying with 690.71(G).<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.0in;text-indent:-.25in;mso-list:l2 level2 lfo2'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Trebuchet MS","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>−<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><b><span style='font-size:11.0pt;font-family:
"Calibri","sans-serif";color:#1F497D'>(F) </span></b><span style='font-size:
11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The photovoltaic power
source shall be labeled with the following warning at each junction box,
combiner box, disconnect, and device where the ungrounded circuits may be
exposed during service:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>WARNING<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>ELECTRIC SHOCK HAZARD<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>THE DC CIRCUIT CONDUCTORS OF THIS<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>PHOTOVOLTAIC POWER SYSTEM ARE<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>UNGROUNDED AND MAY BE ENERGIZED<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>WITH RESPECT TO GROUND DUE TO<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>LEAKAGE PATHS AND/OR GROUND FAULTS.<o:p></o:p></span></p>
<p class=MsoNormal style='margin-left:1.0in;text-indent:-.25in;mso-list:l1 level2 lfo3'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Trebuchet MS","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>−<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><b><span style='font-size:11.0pt;font-family:
"Calibri","sans-serif";color:#1F497D'>(G) </span></b><span style='font-size:
11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The inverters or
charge controllers used in systems with ungrounded photovoltaic source and
output circuits shall be listed for the purpose.<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 now have several products newly on the market to include on
the list such as the SMA and Exeltech products. Ungrounding the array requires
additional fusing and disconnects, but the most significant difference is that
the module wiring and all external cable must be PV Wire/Cable. Therefore only
modules with PV Wire/Cable can be used in these systems. You must confirm from
the manufacturer that they have made the switch. Hopefully all manufacturers
will be installing PV Wire/Cable soon so that this will not be a problem
anymore.<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'>It is a good call to use up your USE-2 and order PV Wire/Cable
from now on.<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>Exeltech<br>
<b>Sent:</b> Friday, October 01, 2010 6:39 AM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] Tranformless inverter<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0>
<tr>
<td valign=top style='padding:0in 0in 0in 0in'>
<p class=MsoNormal>Transformerless grid-tie inverters are permitted under the
National Electric Code as of 2008. The Nationally Recognized Testing
Laboratories (UL, ETL/Intertek, CSA, etc.) took a while to develop the
testing procedures for testing to UL1741, which was the basis for most of the
delay.<br>
<br>
SMA isn't the only company with transformerless grid-tie inverters. I
know of one American manufacturer with transformerless models on the market
as well.<br>
<br>
Transformerless inverters are smaller, much lighter, and tend to be more
efficient than transformer-based units. No transformer also means lower
product cost, and less shipping expense. Win-win-win.<br>
<br>
<br>
Dan<br>
<br>
<br>
--- On <b>Fri, 10/1/10, Drake <i><drake.chamberlin@redwoodalliance.org></i></b>
wrote:<o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><br>
From: Drake <drake.chamberlin@redwoodalliance.org><br>
Subject: Re: [RE-wrenches] Tranformless inverter<br>
To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org><br>
Date: Friday, October 1, 2010, 6:58 AM<o:p></o:p></p>
<div id=yiv831815003>
<p class=MsoNormal>I also received this advertisement. Previously I had
investigated the smaller SMA transformerless inverters, and was told that
this type would not be allowed in the US until the 2011 code. Has the
ban been lifted?<br>
<br>
<br>
<br>
At 12:52 AM 9/29/2010, you wrote:<br>
<br>
<o:p></o:p></p>
<p class=MsoNormal>Wrenches:<br>
<br>
I received an advertisement from a distributor that SMA is now shipping 8, 9
and 10 KW transformerless inverters. Don't these require double
insulated PV wiring and no connection to ground on the AC side? It's
been too long since this subject last crossed my desk and I want to refresh
my memory on the specifics.<br>
<br>
William Miller<br>
<br>
<br>
<u>Please note new e-mail address and domain:<br>
<br>
</u>William Miller <br>
Miller Solar<br>
Voice :805-438-5600<br>
email: william@millersolar.com<br>
<a href="http://millersolar.com/" target="_blank">http://millersolar.com</a><br>
License No. C-10-773985<o:p></o:p></p>
</div>
</td>
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</table>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
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