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<TITLE>Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?</TITLE>
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<FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>In the same issue of SolarPro as the “Optimal PV-to-Inverter” Sizing Ratio” article (April/May 2010), the lead article is “Production Modeling for Grid-Tied PV Systems” by Tarn Yates and Bradley Hibberd at Borrego Solar:<BR>
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<a href="http://solarprofessional.com/article/?file=SP3_3_pg30_Yates">http://solarprofessional.com/article/?file=SP3_3_pg30_Yates</a><BR>
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While your question below can’t be answered using PVWatts, it can be answered using the Solar Advisor Model (SAM), which was developed by NREL and Sandia w/ DOE funding. SAM is available for free download here:<BR>
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www.nrel.gov/analysis/sam/<BR>
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David Brearley, Senior Technical Editor<BR>
<I>SolarPro</I> magazine <BR>
NABCEP Certified PV Installer ™<BR>
<a href="david.brearley@solarprofessional.com">david.brearley@solarprofessional.com</a><BR>
Direct: 541.261.6545<BR>
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On 4/19/10 6:40 PM, "Jim MacDonald" <<a href="jmac@solaresystems.com">jmac@solaresystems.com</a>> wrote:<BR>
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</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'><FONT COLOR="#1F497D">SB8000US only good for 480 Vac, we’re tying in at 208.<BR>
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11 strings has been calc’d to be OK (<600vdc) for record low -4 fahrenheit (-20 celsius).<BR>
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I think the big concern as mentioned is getting the Voc high early in the AM to wake the inverter up, also maintaining the Vmp later in the day to keep it running for as long as possible into the late afternoon/ evening.<BR>
Will those extra kWh gleaned in the early AM/ late PM over the course of 365 days be more than the kWh clipped during peak production times with the 9.075 kWdc?<BR>
NYC average summer highs between 79 and 84 fahrenheit early june-late august.? Sunlink rack @ 10</FONT></SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>° </SPAN></FONT><FONT COLOR="#1F497D"><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>on a silver-painted built-up roof.<BR>
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Time-of-use utility $ peak-shaving is not an issue here.<BR>
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Thank you<BR>
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</SPAN></FONT><FONT SIZE="2"><FONT FACE="Tahoma, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:10pt'><B>From:</B> <a href="re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a> [<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <B>On Behalf Of </B>Darryl Thayer<BR>
<B>Sent:</B> Monday, April 19, 2010 5:58 PM<BR>
<B>To:</B> RE-wrenches<BR>
<B>Subject:</B> Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?<BR>
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</SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>The temperature correction is the concern. I have heard lots of stories of inverters dieing when it gets to cold. Look in the code book 690.7 at the temperature correction table. Go to weather.com and find your record low temperature. Find you Tc factor and will your senerios work? I have heard from a sunny boy rep that it is OK to over power by 1.25% </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
</SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>darryl<BR>
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--- On <B>Mon, 4/19/10, Dana <I><<a href="dana@solarwork.com">dana@solarwork.com</a>></I></B> wrote:</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
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</SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> From: Dana <<a href="dana@solarwork.com">dana@solarwork.com</a>><BR>
Subject: Re: [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?<BR>
To: "'RE-wrenches'" <<a href="re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>><BR>
Date: Monday, April 19, 2010, 4:31 PM</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT SIZE="4"><FONT FACE="Arial"><SPAN STYLE='font-size:14pt'>Many times we switch to another module manufacturer as one will not fit or another inverter manufacturer. </SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
</SPAN></FONT><FONT SIZE="4"><FONT FACE="Arial"><SPAN STYLE='font-size:14pt'>PVPowered has a more relaxed window and we have had fine success with them when SMA does not fit. </SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
</SPAN></FONT><FONT SIZE="4"><FONT FACE="Arial"><SPAN STYLE='font-size:14pt'>Cold is the dictator and the 600 VDC threshold.</SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
</SPAN></FONT></BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT SIZE="4"><FONT FACE="Arial"><SPAN STYLE='font-size:14pt'> </SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT SIZE="4"><FONT FACE="Arial"><SPAN STYLE='font-size:14pt'> </SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:12pt'>Thanks, Dana Orzel</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
</SPAN></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:12pt'>Great Solar Works, Inc</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:12pt'>web - www.solarwork.com</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:12pt'>E - <a href="dana@solarwork.com">dana@solarwork.com</a></SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:12pt'>V - 970.626.5253</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:12pt'>F - 970.626.4140</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:12pt'>C - 970.209.4076</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:12pt'>"We have been slow to give up on the myth of the Earth's generosity.</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:12pt'>Rather grandly, we have overdrawn our accounts."</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Arial"><SPAN STYLE='font-size:12pt'>Barbara Kingsolver - Water is life.</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT SIZE="4"><FONT FACE="Arial"><SPAN STYLE='font-size:14pt'> </SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT SIZE="2"><FONT FACE="Arial"><SPAN STYLE='font-size:10pt'><B>From:</B> <a href="re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a> [<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <B>On Behalf Of </B>Jim MacDonald<BR>
<B>Sent:</B> Monday, April 19, 2010 2:37 PM<BR>
<B>To:</B> <a href="RE-wrenches@lists.re-wrenches.org">RE-wrenches@lists.re-wrenches.org</a><BR>
<B>Subject:</B> [RE-wrenches] overfeed 7kW gridtie inverter or drop a mod per string?</SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
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</SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>For a straight grid-tie system@ 10 degree tilt, 180 azimuth, zero/little shade, NYC avg 4.29 kWh/m²/day.</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>Feed an SMA7000 with (3) strings of 11 Suntech STP275’s [9.075 kWdc]</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>Or</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>Do strings of 10, so itd be 8.250 kWdc into the 7 kWac inverter.</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>Strings of 11= 491.7 Voc; 386 Vmp</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>Strings of 10= 447 Voc; 351 Vmp </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>The tradeoff would be power clipping at/around noon in the sunny months in the 9.075 kW scenario;</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>Inverter sleeping late every morning and retiring early in the evenings in the lowered voltage scenario.</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>Trying to figure out which would yield more kWh at the end of the year.</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>Any ideas appreciated,</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'>thanks</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT COLOR="#002060"><FONT SIZE="2"><FONT FACE="Arial"><SPAN STYLE='font-size:10pt'><B>Jim MacDonald</B></SPAN></FONT></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT COLOR="#002060"><FONT SIZE="2"><FONT FACE="Arial"><SPAN STYLE='font-size:10pt'>Solar Energy Systems, LLC</SPAN></FONT></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT COLOR="#002060"><FONT SIZE="2"><FONT FACE="Arial"><SPAN STYLE='font-size:10pt'>Brooklyn, NY 11222</SPAN></FONT></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT COLOR="#0000FF"><FONT SIZE="2"><FONT FACE="Arial"><SPAN STYLE='font-size:10pt'><U>www.solarEsystems.com</U></SPAN></FONT></FONT></FONT><FONT SIZE="2"><FONT FACE="Arial"><SPAN STYLE='font-size:10pt'><FONT COLOR="#1F497D"> <<a href="http://www.solaresystems.com/">http://www.solaresystems.com/</a>> </FONT></SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> </SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> </SPAN></FONT><FONT SIZE="2"><FONT FACE="Arial"><SPAN STYLE='font-size:10pt'>No virus found in this incoming message.<BR>
Checked by AVG - www.avg.com<BR>
Version: 9.0.801 / Virus Database: 271.1.1/2819 - Release Date: 04/19/10 00:31:00</SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
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