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<TITLE>Re: [RE-wrenches] Square D DC disconnects</TITLE>
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<FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>Thanks for the clarification, Bill. If they add this to UL1741, I hope they will do so in a manner that recognizes the unique characteristics of PV applications. Definitely easier to interrupt a 10A source than a 10,000A one.<BR>
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On 1/11/10 6:43 PM, "Bill Brooks" <<a href="billbrooks7@yahoo.com">billbrooks7@yahoo.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">David,<BR>
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The state by the Eaton guy at SPI shows that person’s lack of understanding. The person I talked to was adamant that all disconnects had to be tested to the disconnect standard that assumes a high (10,000-amp) current source behind any fault. Switch openings are also tested based on the inductance in the circuit since that has a major impact on the size and duration of the arc—especially in ac systems.<BR>
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Square D did an evaluation based on the limited fault currents and inductance in PV system circuit that has no batteries. I believe their evaluation is valid. The issue is that there is no specific test at UL yet—that’s why UL did not list it (I’m pretty sure they were involved at some level, but that is impossible to prove). It will probably be added to UL1741. Perhaps that was what the Eaton rep was referring—we’ll give him the benefit of the doubt.<BR>
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I still use my basic rule similar to the rule for politicians—how do you know if a marketing guy is lying?== his lips are moving.<BR>
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Bill.<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>David Brearley<BR>
<B>Sent:</B> Monday, January 11, 2010 3:41 PM<BR>
<B>To:</B> RE-wrenches<BR>
<B>Cc:</B> 'Tim Townsend'<BR>
<B>Subject:</B> Re: [RE-wrenches] Square D DC disconnects<BR>
</SPAN></FONT></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'> <BR>
</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>Thanks, Bill.<BR>
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Glad to hear you think the HU series is still a good option.<BR>
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When I was making the rounds at SPI, I stopped by the Eaton booth and got the sense that they were gunning for Square D. They made light of Square D’s self-certification of the HU series discos. The rep also made a statement about the new Eaton dc discos being the only ones designed to meet UL1741 requirements. When I got home, the first thing I looked up was 690.4(D). This doesn’t say anything about dc disconnects needing to be listed to some special PV standard. <BR>
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Is there a movement in this direction? Is there a UL1741 standard for dc discos that is somehow different that the standard used for other dc disconnects?<BR>
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Best,<BR>
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David <BR>
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On 1/11/10 5:28 PM, "Bill Brooks" <<a href="billbrooks7@yahoo.com">billbrooks7@yahoo.com</a>> wrote:<BR>
<FONT COLOR="#1F497D">David and Kirpal,<BR>
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It is ultimately up to the AHJ whether or not they accept the Schneider/Square D self certification. That is a judgment call the installer needs to clear with the AHJ. That being said, having Square D behind the rating of a switch is a whole lot more than any one of the smaller companies making equipment for the PV industry. <BR>
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I will continue to use the 30, 60, and 100-amp versions in the way recommended by the manufacturer because it is a huge saving in cost and they are well made switches. I will also check with the local AHJ before installing them in case they are not going to pass it. You have to remember you are working with one of the largest electrical suppliers in the world. They have a huge reputation with local jurisdictions.<BR>
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Eaton has been in the process of trying to make a big deal out of this issue since they want a piece of the market. Fortunately, they are starting to build products specifically for the PV industry, which I applaud. However, they need to be given a hard time for the way they have tried to imply that all Square D switches are not properly listed. They won’t admit to that because they would end up in a legal battle, but that is essentially what they have been doing. Square D still has the largest selection of dc-rated equipment on the market. Eaton has a long way to go. <BR>
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In a recent project that I reviewed, the engineer pulled the Square D 400-amp disconnect and replaced it with an Eaton disconnect at the insistence of the Eaton rep. The Eaton product was not properly rated or listed for the voltage while the Square D product was. This is the insanity that needs to stop.<BR>
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Bill.<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>David Brearley<BR>
<B>Sent:</B> Monday, January 11, 2010 11:39 AM<BR>
<B>To:</B> RE-wrenches<BR>
<B>Subject:</B> Re: [RE-wrenches] Square D DC disconnects<BR>
</SPAN></FONT></FONT><FONT FACE="Times New Roman"><SPAN STYLE='font-size:12pt'><BR>
</SPAN></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>Kirpal,<BR>
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Have you checked out the SolarBOS disconnecting combiners? Their 28A version might be ideal for large resi or small commercial applications. For larger projects, Blue Oak PV Products and AMtec Solar also have disconnecting combiners.<BR>
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Thanks for sharing the updated Square D tech note. I had no idea that the Square D HU Series disconnects were not UL-listed when used as described in the older tech notes. The fact that this is not a UL-listed use of the heavy duty safety switch, pretty much means that it is not an option for integrators. As far as I know, there is no other product that is listed for this use. <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>
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On 1/9/10 4:14 PM, "Kirpal Khalsa" <<a href="solarworks@gmail.com">solarworks@gmail.com</a>> wrote:<BR>
Hi All......<BR>
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I recently came across a revised technical bulletin from square D ( <a href="http://ecatalog.squared.com/pubs/Electrical%20Distribution/Safety%20Switches/Heavy%20Duty/3110DB0401.pdf">http://ecatalog.squared.com/pubs/Electrical%20Distribution/Safety%20Switches/Heavy%20Duty/3110DB0401.pdf</a> )......we have for years been using the Square D DC Disconnect of various amperages (30, 60, 100) as disconnects leading upto the inverter from the array.....we have frequently wired one string to each of the three poles of the disconnect......we have had this configuration inspected by inspectors regularly with approval everytime......this new revision of the document from Square D shows this is no longer a UL listed method.....they are now stating in this document that they are "self certifying" this technique.......have any of you come across this or know why Square D has back tracked? <BR>
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Something else I noticed is that they have raised the amperage rating on the 30A disconncect per pole by 2 amps from 18 to 20 which is good especially when using higher amperage modules like Evergreen ES-A series which would not have ben allowed to use the 30A disconnect as the short circuit current rating was too high for the derated poles. <BR>
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This is not a huge concern as more and more of the inverters we are using these days have an appropriate disconnect included with the inverter negating the need for an additional stand alone disconnect. <BR>
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On a side note............Are there any other manufacturers making <U>listed</U> muiti pole DC disconnects in which each pole can handle one string? Also there is definately a need for roof mounted multi string (1-4 strings) combiner boxes with integrated DC disconnects for residential applications that have a reasonable price.......any one know if any?<BR>
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</SPAN></FONT></FONT><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>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>
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