I should have clarified which derate I was applying. If using the SqD heavy duty unfused disconnects with two poles series connected, it is rated at 100% continuous, so only the "sunlight can be brighter than STC" derate need be applied (30 / 1.25 = 24). If using the fusible disconnect, then you'd need to apply a second derate for the fuses (30 / 1.25 / 1.25 = 19.2 amps).
If you want to run a subarray through a single pole per the special listing, then the 1.56 derate would apply, whether it's fusible or non-fusible. In addition, the maximum current per pole (the number you work back from) would be *18*/60/100 amps -- due to arc clearance issues, apparently, they were not able to obtain the full 30 amps on the smallest disconnect. Again, it's great to have options, and Square D should be commended for upping the ante and expanding the listings for their equipment to aid the solar installer. Phil Undercuffler -------- On Sat, Jun 27, 2009 at 10:01 PM, Darryl Thayer <daryl_so...@yahoo.com>wrote: > > If I use the Hu361 (unfused) it has the 30 amp rating, the 80% reduction > only applies if I use fuses per the continuous operation derating for > overcurrent devices. The switch is not a conductor or overcurrent device. > If I use the H361 (fused) then the 80% derate applies, (24 amps) and if I > use the double break I am limited to 18 amps in all cases. > > Darryl > Correct? > > --- On Sat, 6/27/09, Phil Undercuffler <solarp...@gmail.com> wrote: > > > From: Phil Undercuffler <solarp...@gmail.com> > > Subject: Re: [RE-wrenches] fronius IG Plus practical engineering WAA??? > > To: "RE-wrenches" <re-wrenches@lists.re-wrenches.org> > > Date: Saturday, June 27, 2009, 10:47 PM > > They added a special listing, where > > they were able to expand the range of their heavy duty > > switch when used in PV direct applications. The special PV > > listing doesn't void the standard wiring methods, > > however. You can still run the full 30 amps (24 * 1.25) > > through two poles series connected, or you can bring > > multiple subarrays through each of the poles, each with a > > lower individual Isc limit but with an aggregate higher > > current capacity. > > > > This really becomes handy on the larger 60 and > > 100A disconnects. Suddenly, a 3 pole 100A disconnect can > > be used for three large subarrays to a central inverter, > > which saves considerably on BOS costs. Also, be aware that > > (the last I looked) the special listing doesn't apply to > > their 200A and larger disconnects. > > > > > > > > Phil Undercuffler > > > > -------- > > > > > > > > > > > > On Sat, Jun 27, 2009 at 9:22 PM, > > Darryl Thayer <daryl_so...@yahoo.com> > > wrote: > > > > > > > > Again this is FMI for my information, Did not Square D > > change there rating for PV systems? > > > > Darryl > > > > > > > > --- On Fri, 6/26/09, Phil Undercuffler <solarp...@gmail.com> > > wrote: > > > > > > > > > From: Phil Undercuffler <solarp...@gmail.com> > > > > > Subject: Re: [RE-wrenches] fronius IG Plus practical > > engineering WAA??? > > > > <snip> > > > > > > > > > > This confirmed my understanding > > > > > that the limiting factor > > > > > on the 30A switch > > > > > > > > > > in a photovoltaic applications is > > > > > not 30A * 0.8. The limiting factor > > > > > is 18A > > > > > > > > > > per pole or 11.5A Isc per pole. > > > > > > > > > > <unsnip> > > > > > > > > > > > > > > > > > > > > To clarify – the 18A per pole / > > > > > 11.5A Isc per pole only > > > > > applies if you are using the limited listing for PV > > > > > applications, with one > > > > > string or subarray per pole. If you > > > > > wire > > > > > the HU361RB disconnect with two poles connected in > > series, > > > > > then you may run the > > > > > switch at 100% of its rating. > > > > > > > > > > > > > > > > > > > > Therefore, you can stuff up to 24 > > > > > amps Isc (24 * 1.25 = > > > > > 30) through a single disconnect if the poles are wired > > in > > > > > series, or you can > > > > > run 3 subarrays each with no more than 11.5A per pole > > if > > > > > wired in > > > > > parallel. > > > > > > > > > > > > > > > > > > > > Sometimes it’s good to have > > > > > options. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Phil Undercuffler > > > > > > > > > > Director, Battery-based and > > > > > Off-grid > > > > > > > > > > Distribution Sales Group > > > > > > > > > > Conergy > > > > > > > > > > Our World Is Full of Energy > > > > > > > > > > 1730 > > > > > Camino Carlos Rey Suite 103 > > > > > > > > > > Santa > > > > > Fe, NM 87507 > > > > > > > > > > p.undercuff...@conergy.us > > > > > > > > > > Direct > > > > > | > > > > > 505.216.3841 > > > > > > > > > > Toll Free | 888.396.6611 x4841 > > > > > > > > > > Fax | 505.473.3830 > > > > > > > > > > www.conergy.us > > > > > > > > > > > > > > > > > > > > -----Inline Attachment Follows----- > > > > > > > > > > _______________________________________________ > > > > > 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 > > > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > 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 > > > > > > > > > > > > > > -----Inline Attachment Follows----- > > > > _______________________________________________ > > 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 > > > > > > > > _______________________________________________ > 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 > >
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