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Content preview: Your free subscription is supported by today's sponsor: ------------------------------------------------------------------- You could save Hundreds on your Car insurance We track down the best Car Insurance rates for you Click here if you are in the ma Content analysis details: (6.06 points, 6.00 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.1 CLICK_BELOW Asks you to click below 2.8 SAVE_ON_INSURANCE Trying to sell insurance online 3.0 FORGED_MUA_OUTLOOK Forged mail pretending to be from MS Outlook 0.2 MR_NOT_ATTRIBUTED_IP Beta rule: an non-attributed IPv4 found in headers 0.0 NO_RDNS2 Sending MTA has no reverse DNS Received: from out009.topica-platinum-y.com ([66.227.60.29]) by mail.homepower.com (Merak 8.3.8) with SMTP id FWY40740 for ; Sat, 1 Apr 2006 10:49:40 -0800 Return-Path: Received: (qmail 17774 invoked by uid 0); 1 Apr 2006 18:49:22 -0000 Received: from unknown (HELO smtp103.sbc.mail.mud.yahoo.com) (68.142.198.202) by inmta010.topica.com with SMTP; 1 Apr 2006 18:49:22 -0000 Received: (qmail 65138 invoked from network); 1 Apr 2006 18:49:22 -0000 Received: from unknown (HELO BILLNOTEBOOK) (billbrooks7@71.131.55.162 with login) by smtp103.sbc.mail.mud.yahoo.com with SMTP; 1 Apr 2006 18:49:21 -0000 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: <6.0.1.1.2.20060331231541.02fd3a18@mpandc.com> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 To: 'William Miller' , 'Mark Edmunds' , RE-wrenches@topica.com From: Bill Brooks Subject: RE: String sizing: Are the web tools accurate? [RE-wrenches] Date: Sat, 1 Apr 2006 10:48:55 -0800 Message-ID: <1757220824-1463747838-1143917370@boing.topica.com> Errors-To: Reply-To: RE-wrenches@topica.com X-Topica-Id: <1143917363.inmta010.24737.1693591> List-Help: List-Unsubscribe: Your free subscription is supported by today's sponsor: ------------------------------------------------------------------- You could save Hundreds on your Car insurance We track down the best Car Insurance rates for you Click here if you are in the market for Car insurance http://click.topica.com/caaeE3lbz8Qcsbz9JC9a/Firstand10.com ------------------------------------------------------------------- William and Mark, Unless the code official is willing to make and exception, or doesn't know to ask, table in 690.7 trumps manufacturer's data on single and multi-crystal silicon modules. This is exactly the problem that Fronius ran into with their 450 max Voc--in their case almost no module configuration would work to "optimize" their voltage performance so they had to go to a 500 Vdc max. If the product is anything other than single or multi-crystalline silicon, you can use the manufacturer's data. I would always ask the local building official to approve this situation first, but if they say "no", you are out of luck. Fronius puts a note in their string sizing chart that says something to the effect that a certain configuration exceeds the 690.7 table limit. Bill. -----Original Message----- From: William Miller [mailto:wrmiller@mpandc.com] Sent: Friday, March 31, 2006 11:26 PM To: Mark Edmunds; RE-wrenches@topica.com Cc: Bill Brooks Subject: RE: String sizing: Are the web tools accurate? Mark: Thanks for your speedy reply. I imagine your phone support was quite busy today. I think we are talking about two different calculations: Below you have performed the calculation to derive what the predicted max OC voltage would be. As an installer who has to satisfy local building officials, I am also obligated to conform to the National Electrical Code. The NEC section 690.7 (attached) has a much simpler formula that, unfortunately, arrives at a value over 600 VDC. Would you be so kind as to review the attached citation and see if I am interpreting this correctly. I will also ask Bill Brooks, a very knowledgeable and generous expert in the field to look at this. I presume you know Bill, but if not, I highly recommend his acquaintance. If indeed the OCV of a 12 module string exceeds 600 VDC, then I might suggest that your web site be configured to indicate this. No installer in a zone that gets below 32deg. F can use this string quantity legally (assuming I have interpreted the code section correctly). Thanks again for your quick response. This dialog has reassured me that whatever is determined, we can arrive at an answer in a timely manner. Sincerely, William Miller At 04:23 PM 3/31/2006, you wrote: Hi again, Just checked the data from the Shell specs, which shows: Voc at 25C = 44.6V Temp coef. of Vmp = -145mV/C So converting 14F to Celsius gives -10C, which is 35C below 25C rating, so Voc(14F) = (44.6+35*.145)*12 = 596.1 So our sizing tool calc. looks right. I did notice however that Shell gives a less stringent temperature coefficient for Voc, of -129mV/C, using that Voc(14F) = (44.6+35*.129)*12 = 589.38 This implies you have more margin than we show with the tool. It uses the Vmp number as a generalization, and to be somewhat conservative. Hope this helps! Thanks Mark _____ From: William Miller [mailto:wrmiller@mpandc.com] Sent: Friday, March 31, 2006 10:40 AM To: RE-wrenches@topica.com Cc: Mark Edmunds Subject: String sizing: Are the web tools accurate? Friends: I tried to ask this question directly of Xantrex but they are not answering any of their phone numbers today: I need to match 12 Shell SQ-175 PC modules to a GT2.5. The Xantrex web-based string sizing tool shows that, at 14 Deg F., the Max OC voltage is 596.1. My understanding of section NEC 690.7 requires that you calculate the max VOC thusly: Module OC voltage X Qty of modules in string X correction factor. The correction factor at 14 D F is 1.13. Therefore: 44.6*12*1.13= 604.776 There is a difference of results between what I calculate and the Xantrex sizing software that would put me over the 600 volt ceiling. How does Xantrex derive their value of 596.1? Mark, can you shed some light? William Miller [Non-text portions of this message have been removed] Your free subscription is supported by today's sponsor: ------------------------------------------------------------------- Unlimited International Calls to Certain Counties with Packet8. Our International VoIP Plans offer subscribers a easier way to save on overseas calls. 1-877-868-1135 http://click.topica.com/caaeE3sbz8Qcsbz9JC9f/ TMONE ------------------------------------------------------------------- - - - - To send a message: RE-wrenches@topica.com Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read List rules & how to change your email address: www.mrsharkey.com/wrenches/etiquette.php Check out participant bios: www.mrsharkey.com/wrenches/ Hosted by Home Power magazine Moderator: michael.welch@homepower.com --^---------------------------------------------------------------- This email was sent to: michael.welch@homepower.com EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl Or send an email to: RE-wrenches-unsubscribe@topica.com For Topica's complete suite of email marketing solutions visit: http://www.topica.com/?p=TEXFOOTER --^----------------------------------------------------------------