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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>Hi
All,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>I
agree with Ray with the exception that I use Imp*1.25 in my calculations.
I developed a simple spreadsheet for either fixed conductor size or for fixed
voltage drop. You can feel free to use it by downloading here: <a
href="http://www.mechanicalmike.com/solar/DC_Voltage_Drop_Calculations_Template_04_20_2010.xltx">http://www.mechanicalmike.com/solar/DC_Voltage_Drop_Calculations_Template_04_20_2010.xltx</a>.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>-
Mike<o:p></o:p></span></p>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>---<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>Michael
Kelly<br>
Applications Engineer<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>NABCEP
Certified Solar PV Installer ™<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'><img
border=0 width=150 height=36 id="Picture_x0020_1"
src="cid:image001.jpg@01CB29B6.7012AD50" alt=toplogo><br>
Solectria Renewables, LLC<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>360
Merrimack St.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>Building
9, Floor 2<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>Lawrence,
MA 01843<br>
Phone: 978-683-9700 ext. 167<br>
Fax: 978-683-9702<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'><a
href="mailto:mike@solren.com">mike@solren.com</a><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'><a
href="http://www.solren.com/">www.solren.com</a><o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'><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>R Ray
Walters<br>
<b>Sent:</b> Thursday, July 22, 2010 3:45 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] calculating DC voltage drop<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I use actual operating current, without multipliers. I also
use actual temperatures, not the worst case temperatures that many use.<o:p></o:p></p>
<div>
<p class=MsoNormal>I created a spread sheet that uses the NEC adjustments for
wire temperature, (see NEC chapter 9, table 8, FPN 2)<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>It makes quite a difference!<o:p></o:p></p>
<div>
<p class=MsoNormal>Volt drop and the accompanying loss of energy production
needs to be looked at realistically under normal operating conditions. Adding
worst case multipliers is necessary for sizing cables and breakers for safety,
but it isn't appropriate when calculating energy losses. We shouldn't do an
energy loss analysis for a situation that might never occur, or for only a very
small % of the time. <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>A correct analysis will reflect actual losses over the
lifetime of the system, so that an informed economic decision can be made.
Especially on larger systems with long runs, its worth it to you and the client
to use real world numbers, not blind over sizing.<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal>I got into this over a decade ago, when I noticed that
actual measured volt drop was much less than calculated, now my calculations
match real measurements. <o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><o:p> </o:p></p>
<div>
<div>
<p class=MsoNormal><span style='font-size:9.0pt;font-family:"Helvetica","sans-serif";
color:black'>R. Walters<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:9.0pt;font-family:"Helvetica","sans-serif";
color:black'><a href="mailto:ray@solarray.com">ray@solarray.com</a><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:9.0pt;font-family:"Helvetica","sans-serif";
color:black'>Solar Engineer<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:9.0pt;font-family:"Helvetica","sans-serif";
color:black'><o:p> </o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:9.0pt;font-family:"Helvetica","sans-serif";
color:black'><o:p> </o:p></span></p>
</div>
<p class=MsoNormal><span style='font-size:9.0pt;font-family:"Helvetica","sans-serif";
color:black'><br>
<br>
</span><o:p></o:p></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<div>
<div>
<p class=MsoNormal>On Jul 22, 2010, at 1:22 PM, Marco Mangelsdorf wrote:<o:p></o:p></p>
</div>
<p class=MsoNormal><br>
<br>
<o:p></o:p></p>
<div>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>When
calculating the voltage drop from a PV array to the inverter, what’s the
most common accepted practice? To use the Isc X 1.25 or 1.56 as the
multiplier?<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>Thanks,<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>marco<o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'> <o:p></o:p></span></p>
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