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.
On 1/11/10 6:43 PM, "Bill Brooks" <billbroo...@yahoo.com> wrote: > David, > > The state by the Eaton guy at SPI shows that person¹s 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 > arcespecially in ac systems. > > 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 yetthat¹s why UL did > not list it (I¹m 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 referringwe¹ll give him the benefit of the doubt. > > I still use my basic rule similar to the rule for politicianshow do you know > if a marketing guy is lying?== his lips are moving. > > Bill. > > > From: re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of David Brearley > Sent: Monday, January 11, 2010 3:41 PM > To: RE-wrenches > Cc: 'Tim Townsend' > Subject: Re: [RE-wrenches] Square D DC disconnects > > Thanks, Bill. > > Glad to hear you think the HU series is still a good option. > > 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 D¹s > 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 > doesn¹t say anything about dc disconnects needing to be listed to some special > PV standard. > > 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? > > Best, > > David > > On 1/11/10 5:28 PM, "Bill Brooks" <billbroo...@yahoo.com> wrote: > David and Kirpal, > > 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. > > 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. > > 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 won¹t 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. > > 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. > > Bill. > > > > From: re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of David Brearley > Sent: Monday, January 11, 2010 11:39 AM > To: RE-wrenches > Subject: Re: [RE-wrenches] Square D DC disconnects > > Kirpal, > > 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. > > 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. > > David Brearley, Senior Technical Editor > SolarPro magazine > NABCEP Certified PV Installer > david.brear...@solarprofessional.com > > > On 1/9/10 4:14 PM, "Kirpal Khalsa" <solarwo...@gmail.com> wrote: > Hi All...... > > I recently came across a revised technical bulletin from square D ( > http://ecatalog.squared.com/pubs/Electrical%20Distribution/Safety%20Switches/H > eavy%20Duty/3110DB0401.pdf )......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? > > 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. > > 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. > > On a side note............Are there any other manufacturers making listed > 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? > > > > > > > > > > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > David Brearley, Senior Technical Editor SolarPro magazine NABCEP Certified PV Installer david.brear...@solarprofessional.com Direct: 541.261.6545 Fax: 541.512.0343 Visit our Web site at solarprofessional.com (Sample copy available for download at: solarprofessional.com/sample)
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