<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">I think the 100% rating exception is an interpretation issue. I consider the assembly to be defined as the breaker mounted in its listed enclosure.<div>I agree that the AFIs would add cost, but they might actually offer some protection too. (possibly one AFI unit could offer protection for multiple circuits?)</div><div>I've never had a PV circuit breaker actually trip, except some nuisance tripping due to faulty breakers.</div><div>PV breakers seem to only offer protection for very limited situations ie, a short in a PV wire being backfed by enough other PV circuits to trip the breaker.</div><div>It could happen, but I've never actually seen it. Even completely shattered modules still have enough internal resistance to limit the short circuit current to</div><div>a value below the breaker trip point.<br><div><br><div>
<span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><div>Ray</div></span></div><br><div><div>On Apr 4, 2010, at 11:47 PM, Kent Osterberg wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
<div bgcolor="#ffffff" text="#000000">
Ray,<br>
<br>
The exception in 690.8(B)(1) reads: Circuits containing an assembly,
together with its overcurrent device(s), that is listed for continuous
operation at 100% of its rating shall be permitted to be utilized at
100% of it rating. The field installed cable used to connect a
breaker is not part of an "assembly that is listed for continuous
operation at 100% of its rating" and as such the cable still has to be
sized to carry 156% of Isc.<br>
<br>
I agree with you about the need for DC arc fault protection. I believe
the 2011 code is going to require it for circuits over 80 volts. But
it seems unlikely that such a device will exist for a while. It will
have to have embedded electronics for detection that operates the
contacts. And at present we resort to 600 volt fuses because "simple"
breakers rated for 600 volts dc are excessively expensive. When dc
AFCIs are available, they are sure to be expensive and are likely to
add $100s to the cost of a combiner box.<br>
<br>
Kent Osterberg<br>
Blue Mountain Solar, Inc.<br>
<br>
<br>
<br>
R Ray Walters wrote:
<blockquote cite="mid:5FE1A816-7D91-42D2-8A1F-900D49055C41@solarray.com" type="cite">And just to be clear, when using these 100% duty rated
breakers, you only have to oversize the cable by 125%, not 156%.
<div><br>
</div>
<div>Also, as William mentioned, even correctly sized wiring can have
problems; we just recently had a short circuit that caused quite some
damage in a junction box, and the breaker never tripped.</div>
<div>The 156% rule has its downsides too, as you end up with a
breaker so oversized that array current will never trip it, even if you
wish it could.</div>
<div>I'm now advocating for DC Arc Fault protection, as I have seen
several cases of dangerous DC arcs that sustained for several minutes,
but never drew enough current to trip a breaker.( but did create heat
over 2000 degree F )</div>
<div>The standard thinking for safety in electrical systems assumes
an infinite current supply that will trip a breaker, as soon as
something goes wrong. (true for grid power, and battery systems) But on
the PV source circuit, many bad things can happen that will not be
stopped by the breakers. Also, high voltage DC has much more Arc
potential than AC, so AFI protection is even more important.</div>
<div>Now, we just need somebody to make a reasonably priced UL listed
DC AFI unit.</div>
<div><br>
<div><span class="Apple-style-span" style="border-collapse: separate; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-indent: 0px; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; ">
<div>R. Walters</div>
<div><a moz-do-not-send="true" href="mailto:ray@solarray.com">ray@solarray.com</a></div>
<div>Solar Engineer</div>
<div><br class="khtml-block-placeholder">
</div>
<div><br class="khtml-block-placeholder">
</div>
<br class="Apple-interchange-newline">
</span></div>
<br>
<div>
<div>On Apr 2, 2010, at 4:35 PM, Allan Sindelar wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">
<div bgcolor="#ffffff" text="#000000">Yes, they are 100% duty
rated. Also, a little-known fact about the CBI
breakers used by Midnite and Outback, gleaned from conversations with
Robin Gudgel: because of this hydraulic/magnetic construction, all are
capable of controlling both AC and DC, even if not listed as both. <br>
<br>
<div class="moz-signature">
<link rel="File-List" href="x-msg://260/signature_files/filelist.xml">
<!--[if gte mso 9]><xml>
<o:DocumentProperties>
<o:Author>pe</o:Author>
<o:LastAuthor>pe</o:LastAuthor>
<o:Revision>2</o:Revision>
<o:TotalTime>1</o:TotalTime>
<o:Created>2009-12-09T22:29:00Z</o:Created>
<o:LastSaved>2009-12-09T22:30:00Z</o:LastSaved>
<o:Pages>1</o:Pages>
<o:Words>52</o:Words>
<o:Characters>298</o:Characters>
<o:Company>pe</o:Company>
<o:Lines>2</o:Lines>
<o:Paragraphs>1</o:Paragraphs>
<o:CharactersWithSpaces>349</o:CharactersWithSpaces>
<o:Version>11.9999</o:Version>
</o:DocumentProperties>
</xml><![endif]--><!--[if gte mso 9]><xml>
<w:WordDocument>
<w:SpellingState>Clean</w:SpellingState>
<w:GrammarState>Clean</w:GrammarState>
<w:ValidateAgainstSchemas/>
<w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid>
<w:IgnoreMixedContent>false</w:IgnoreMixedContent>
<w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText>
<w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel>
</w:WordDocument>
</xml><![endif]--><x ml="">
<w:latentstyles deflockedstate="false" latentstylecount="156"> </w:latentstyles>
<style>
<!--
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{mso-style-parent:"";
margin:0in;
margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:12.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";
color:black;}
a:link, span.MsoHyperlink
{color:blue;}
a:visited, span.MsoHyperlinkFollowed
{color:blue;}
<a href="<a href="http://span.il">http://span.il</a>">span.il</a>
{mso-style-name:il;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.25in 1.0in 1.25in;
mso-header-margin:.5in;
mso-footer-margin:.5in;
mso-paper-source:0;}
div.Section1
{page:Section1;}
-->
</style><!--[if gte mso 10]>
<style>
/* Style Definitions */
table.MsoNormalTable
{mso-style-name:"Table Normal";
mso-tstyle-rowband-size:0;
mso-tstyle-colband-size:0;
mso-style-noshow:yes;
mso-style-parent:"";
mso-padding-alt:0in 5.4pt 0in 5.4pt;
mso-para-margin:0in;
mso-para-margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:10.0pt;
font-family:"Times New Roman";
mso-ansi-language:#0400;
mso-fareast-language:#0400;
mso-bidi-language:#0400;}
</style>
<![endif]--><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="2050"/>
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1"/>
</o:shapelayout></xml><![endif]-->
<div class="Section1"><p class="MsoNormal" style=""><span class="il"><b style="">Allan</b></span><b style=""> Sindelar</b><span style="font-size: 10pt;"><br>
<a moz-do-not-send="true" href="mailto:Allan@positiveenergysolar.com" target="_blank"><span class="il">Allan</span>@positiveenergysolar.com</a><br>
NABCEP Certified Photovoltaic Installer<br>
EE98J Journeyman Electrician<br>
<b style="">Positive Energy, Inc.</b><br>
3201 Calle Marie<br>
Santa Fe, New Mexico 87507<br>
<b style="">505 424-1112</b><br>
<a moz-do-not-send="true" href="http://www.positiveenergysolar.com/" target="_blank">www.positiveenergysolar.com</a></span></p>
</div>
</x></div>
<br>
<br>
robert ellison wrote:
<blockquote cite="mid:o2udae2914c1004021517z98e6800es4043c8d3291c46e6@mail.gmail.com" type="cite">
<div>I believe that the breakers from CBI, Midnite and Outback
are
hydraulic / magnetic and may be operated at 100% While the derating
applies to all others that are Thermal / magnetic,</div>
<div> </div>
<div>Bob<br>
<br>
</div>
<div class="gmail_quote">On Fri, Apr 2, 2010 at 11:14 AM, Kent
Osterberg <span dir="ltr"><<a moz-do-not-send="true" href="mailto:kent@coveoregon.com">kent@coveoregon.com</a>></span>
wrote:<br>
<blockquote style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;" class="gmail_quote">
<div text="#000000" bgcolor="#ffffff">Erika,<br>
<br>
You should refer to NEC 690.8 this information. There are two issues
that contribute to the 1.56 factor. First is that the maximum current
from the PV array is considered the short circuit current multiplied by
1.25 to account for higher than standard irradiance such as cloud edge
effect, high altitude, and high operating temperature. The second
multiplier of 1.25 is because PV current is considered to be
continuous. All conductors (and breakers) operating continuously (over
three hours I believe) that are subject to NEC rules are limited to 80%
of the ampacity in Table 310.16. The two 1.25 factors equals 1.56.<br>
<br>
For normal operation, wires selected under this criteria are
conservatively rated. But it is also the objective of the NEC to
design power systems in a manner that they will remain safe under
abnormal circumstances.<br>
<font color="#888888"><br>
Kent Osterberg<br>
Blue Mountain Solar, Inc.</font>
<div>
<div class="h5"><br>
<br>
<br>
<br>
Erika M. Weliczko wrote:
<blockquote type="cite">
<div><p class="MsoNormal"><font face="Century Gothic" size="2"><span style="font-family: 'Century Gothic'; font-size: 10pt;">To my
understanding the 156% on PV source and output circuits is related to
the ability of PV to deliver more than rated and be continuous.</span></font></p><p class="MsoNormal"><font face="Century Gothic" size="2"><span style="font-family: 'Century Gothic'; font-size: 10pt;">Therefore, the
wire has to be able to carry this current, so now the temperature and
fill corrections are applied to find the wire capable of the 156%.</span></font></p>
<div><font face="Century Gothic" size="2"><span style="font-family: 'Century Gothic'; font-size: 10pt;"> </span></font><br class="webkit-block-placeholder">
</div><p class="MsoNormal"><font face="Century Gothic" size="2"><span style="font-family: 'Century Gothic'; font-size: 10pt;">I am in a
debate where the question is why correct for temp and fill on 156% of
ISC and spend all that extra money when the normal operating is at Imp.
Or why correct the 156% but why not correct the Isc or Imp.</span></font></p>
<div><font face="Century Gothic" size="2"><span style="font-family: 'Century Gothic'; font-size: 10pt;"> </span></font><br class="webkit-block-placeholder">
</div><p class="MsoNormal"><font face="Century Gothic" size="2"><span style="font-family: 'Century Gothic'; font-size: 10pt;">I am going to
stick to the fact that the circuit has to carry the 156% under all
conditions…</span></font></p><p class="MsoNormal"><font face="Century Gothic" size="2"><span style="font-family: 'Century Gothic'; font-size: 10pt;">Thoughts? </span></font></p>
<div><font face="Century Gothic" size="2"><span style="font-family: 'Century Gothic'; font-size: 10pt;"> </span></font><br class="webkit-block-placeholder">
</div><p class="MsoNormal"><font face="Century Gothic" size="2"><span style="font-family: 'Century Gothic'; font-size: 10pt;">Erika</span></font></p>
</div>
<br>
</blockquote>
</div>
</div>
</div>
<br>
_______________________________________________<br>
List sponsored by Home Power magazine<br>
<br>
List Address: <a moz-do-not-send="true" href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a><br>
<br>
Options & settings:<br>
<a moz-do-not-send="true" 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 moz-do-not-send="true" 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 moz-do-not-send="true" 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 moz-do-not-send="true" href="http://www.members.re-wrenches.org/" target="_blank">www.members.re-wrenches.org</a><br>
<br>
<br>
</blockquote>
</div>
<br>
<pre wrap=""><hr size="4" width="90%">
_______________________________________________
List sponsored by Home Power magazine
List Address: <a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a>
Options & settings:
<a moz-do-not-send="true" class="moz-txt-link-freetext" 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>
List-Archive: <a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a>
List rules & etiquette:
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="http://www.re-wrenches.org/etiquette.htm">www.re-wrenches.org/etiquette.htm</a>
Check out participant bios:
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="http://www.members.re-wrenches.org/">www.members.re-wrenches.org</a>
</pre>
</blockquote>
</div>
_______________________________________________<br>
List sponsored by Home Power magazine<br>
<br>
List Address: <a moz-do-not-send="true" href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a><br>
<br>
Options & settings:<br>
<a moz-do-not-send="true" 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><br>
<br>
List-Archive:
<a class="moz-txt-link-freetext" href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><br>
<br>
List rules & etiquette:<br>
<a class="moz-txt-link-abbreviated" href="http://www.re-wrenches.org/etiquette.htm">www.re-wrenches.org/etiquette.htm</a><br>
<br>
Check out participant bios:<br>
<a class="moz-txt-link-abbreviated" href="http://www.members.re-wrenches.org/">www.members.re-wrenches.org</a><br>
<br>
</blockquote>
</div>
<br>
</div>
<pre wrap=""><hr size="4" width="90%">
_______________________________________________
List sponsored by Home Power magazine
List Address: <a class="moz-txt-link-abbreviated" href="mailto:RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a>
Options & settings:
<a class="moz-txt-link-freetext" 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>
List-Archive: <a class="moz-txt-link-freetext" href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a>
List rules & etiquette:
<a class="moz-txt-link-abbreviated" href="http://www.re-wrenches.org/etiquette.htm">www.re-wrenches.org/etiquette.htm</a>
Check out participant bios:
<a class="moz-txt-link-abbreviated" href="http://www.members.re-wrenches.org/">www.members.re-wrenches.org</a>
</pre>
<pre wrap=""><hr size="4" width="90%">
No virus found in this incoming message.
Checked by AVG - <a class="moz-txt-link-abbreviated" href="http://www.avg.com/">www.avg.com</a>
Version: 9.0.800 / Virus Database: 271.1.1/2790 - Release Date: 04/04/10 06:31:00
</pre>
</blockquote>
</div>
_______________________________________________<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">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a><br><br>List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org<br><br>List rules & etiquette:<br>www.re-wrenches.org/etiquette.htm<br><br>Check out participant bios:<br>www.members.re-wrenches.org<br><br></blockquote></div><br></div></div></body></html>