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Again Thanks Bill and David;<br>
<br>
Continued excellent information. <br>
I just jumped on Solectria'a string sizing online tool, and what are
they using for the Vmpp coefficent? just a tiny bit higher than the
Voc coefficient. SMAs new design tool just lists the Voc coeff. I
think some manus might need to be following this thread as well, and
tweak their sizing tools appropriately.<br>
<br>
Ray<br>
<br>
On 12/1/2011 5:54 PM, Bill Brooks wrote:
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<p class="MsoNormal"><span style="color:#1F497D">Ray,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">There is an
explanation on the <a moz-do-not-send="true"
href="http://www.solarabcs.org/permitting">www.solarabcs.org/permitting</a>
webpage for the interactive solar map. The 2% ASHRAE data
represents 14 hours in a month—meaning temperature will be
at or above that value for 14 hours in a typical month. This
is likely to correspond to at least one 3-hour timeframe
which is considered “continuous” in the NEC. The Copper
Development Association has chosen this number for ambient
temperature calculations in the NEC. The NEC Handbook (not
the NEC) uses this number in their example problems.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">The 0.4% ASHRAE
date represents 3 hours in a month. It is much more
conservative number. I put it in the data to provide a
context for the 2% number and it allows engineers to
consider a more conservative number.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Of course, the
mean extreme minimum drybulb temperature is also on that
website for 690.7 max system voltage calculations. Enjoy—its
free thanks to SolarABCs.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Bill.<o:p></o:p></span></p>
<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"
style="margin-bottom:0in;margin-bottom:.0001pt;line-height:normal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">
<a class="moz-txt-link-abbreviated" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a class="moz-txt-link-freetext" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On
Behalf Of </b>Ray Walters<br>
<b>Sent:</b> Thursday, December 01, 2011 3:58 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] calculating low string
voltage<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Fantastic Info everyone, I think I've got a
full grasp on this topic now, from using the correct
coefficient to the correct weather data, to the adders for
installation type, and a nice link to the applicable data
without spending $180 for the ASHRAE book. <br>
<br>
I'm guessing the 2% number is 2% of the time year round 24/7,
not 2% of the time the sun is shining, so losses could be
higher than 2% of production? Sorry to keep asking questions,
but I know my class will probably ask the same thing.<br>
<br>
Ray<br>
<br>
On 12/1/2011 2:57 PM, Gary Willett wrote: <o:p></o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span
style="font-size:13.5pt;line-height:115%">RAY:<br>
<br>
This "Solar Reference Guide Map" web site is also linked to
on the SolarABCs site and provides the ASHRAE 0.4% & 2%
high temperatures, as well as the PV module max temp based
on distance above the roof (0.5, 3.5, and 12").<br>
<br>
<a moz-do-not-send="true"
href="http://www.solarabcs.org/about/publications/reports/expedited-permit/map/index.html">http://www.solarabcs.org/about/publications/reports/expedited-permit/map/index.html</a></span><o:p></o:p></p>
<div>
<p class="MsoNormal"
style="margin-bottom:0in;margin-bottom:.0001pt;line-height:normal">Regards,<br>
<br>
Gary Willett, PE<o:p></o:p></p>
</div>
<p class="MsoNormal"
style="margin-bottom:0in;margin-bottom:.0001pt;line-height:normal"><span
style="font-size:12.0pt;font-family:"Times New
Roman","serif""><br>
On 12/1/2011 14:56, Gary Willett wrote: <o:p></o:p></span></p>
<p class="MsoNormal"
style="margin-bottom:12.0pt;line-height:normal"><span
style="font-size:13.5pt;font-family:"Times New
Roman","serif"">Ray: <br>
<br>
Look at Appendix F in the Expedited Permit Process for PV
Systems - A Standardized Process for the Review of
Small-Scale PV Systems Prepared by Bill Brooks, P.E. Brooks
Engineering<br>
<br>
This document provides the ASHRE temperatures for a lot of
locations around the USA.<br>
<br>
<a moz-do-not-send="true"
href="http://www.solarabcs.org/about/publications/reports/expedited-permit/pdfs/Expermitprocess.pdf">http://www.solarabcs.org/about/publications/reports/expedited-permit/pdfs/Expermitprocess.pdf</a><br>
<br>
</span><span style="font-size:12.0pt;font-family:"Times
New Roman","serif""><o:p></o:p></span></p>
<div>
<p class="MsoNormal"
style="margin-bottom:0in;margin-bottom:.0001pt;line-height:normal">Regards,<br>
<br>
<br>
Gary Willett, PE<o:p></o:p></p>
</div>
<pre><o:p> </o:p></pre>
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