<div>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).</div>
<div><br></div><div>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 <b>18</b>/60/100 amps -- due to arc clearance issues, apparently, they were not able to obtain the full 30 amps on the smallest disconnect.</div>
<div><br></div><div>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.</div><div><br></div><br clear="all">
Phil Undercuffler<br><br>--------<br><br><br>
<br><br><div class="gmail_quote">On Sat, Jun 27, 2009 at 10:01 PM, Darryl Thayer <span dir="ltr"><<a href="mailto:daryl_solar@yahoo.com" target="_blank">daryl_solar@yahoo.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
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.<br>
<br>
Darryl<br>
Correct?<br>
<div><br>
--- On Sat, 6/27/09, Phil Undercuffler <<a href="mailto:solarphil@gmail.com" target="_blank">solarphil@gmail.com</a>> wrote:<br>
<br>
> From: Phil Undercuffler <<a href="mailto:solarphil@gmail.com" target="_blank">solarphil@gmail.com</a>><br>
> Subject: Re: [RE-wrenches] fronius IG Plus practical engineering WAA???<br>
</div>> To: "RE-wrenches" <<a href="mailto:re-wrenches@lists.re-wrenches.org" target="_blank">re-wrenches@lists.re-wrenches.org</a>><br>
> Date: Saturday, June 27, 2009, 10:47 PM<br>
<div><div></div><div>> They added a special listing, where<br>
> they were able to expand the range of their heavy duty<br>
> switch when used in PV direct applications.The special PV<br>
> listing doesn't void the standard wiring methods,<br>
> however. You can still run the full 30 amps (24 * 1.25)<br>
> through two poles series connected, or you can bring<br>
> multiple subarrays through each of the poles, each with a<br>
> lower individual Isc limit but with an aggregate higher<br>
> current capacity. <br>
><br>
> This really becomes handy on the larger 60 and<br>
> 100A disconnects. Suddenly, a 3 pole 100A disconnect can<br>
> be used for three large subarrays to a central inverter,<br>
> which saves considerably on BOS costs. Also, be aware that<br>
> (the last I looked) the special listing doesn't apply to<br>
> their 200A and larger disconnects.<br>
><br>
><br>
><br>
> Phil Undercuffler<br>
><br>
> --------<br>
><br>
><br>
><br>
><br>
><br>
> On Sat, Jun 27, 2009 at 9:22 PM,<br>
> Darryl Thayer <<a href="mailto:daryl_solar@yahoo.com" target="_blank">daryl_solar@yahoo.com</a>><br>
> wrote:<br>
><br>
><br>
><br>
> Again this is FMI for my information, Did not Square D<br>
> change there rating for PV systems?<br>
><br>
> Darryl<br>
><br>
><br>
><br>
> --- On Fri, 6/26/09, Phil Undercuffler <<a href="mailto:solarphil@gmail.com" target="_blank">solarphil@gmail.com</a>><br>
> wrote:<br>
><br>
><br>
><br>
> > From: Phil Undercuffler <<a href="mailto:solarphil@gmail.com" target="_blank">solarphil@gmail.com</a>><br>
><br>
> > Subject: Re: [RE-wrenches] fronius IG Plus practical<br>
> engineering WAA???<br>
><br>
> <snip><br>
><br>
> ><br>
><br>
> > This confirmed my understanding<br>
><br>
> > that the limiting factor<br>
><br>
> > on the 30A switch<br>
><br>
> ><br>
><br>
> > in a photovoltaic applications is<br>
><br>
> > not 30A * 0.8. The limiting factor<br>
><br>
> > is 18A<br>
><br>
> ><br>
><br>
> > per pole or 11.5A Isc per pole.<br>
><br>
> ><br>
><br>
> > <unsnip><br>
><br>
> ><br>
><br>
> > <br>
><br>
> ><br>
><br>
> > To clarify the 18A per pole /<br>
><br>
> > 11.5A Isc per pole only<br>
><br>
> > applies if you are using the limited listing for PV<br>
><br>
> > applications, with one<br>
><br>
> > string or subarray per pole. If you<br>
><br>
> > wire<br>
><br>
> > the HU361RB disconnect with two poles connected in<br>
> series,<br>
><br>
> > then you may run the<br>
><br>
> > switch at 100% of its rating.<br>
><br>
> ><br>
><br>
> > <br>
><br>
> ><br>
><br>
> > Therefore, you can stuff up to 24<br>
><br>
> > amps Isc (24 * 1.25 =<br>
><br>
> > 30) through a single disconnect if the poles are wired<br>
> in<br>
><br>
> > series, or you can<br>
><br>
> > run 3 subarrays each with no more than 11.5A per pole<br>
> if<br>
><br>
> > wired in<br>
><br>
> > parallel.<br>
><br>
> ><br>
><br>
> > <br>
><br>
> ><br>
><br>
> > Sometimes its good to have<br>
><br>
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