[RE-wrenches] fronius IG Plus practical engineering WAA???

[Phil Undercuffler]

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_solar at 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 <solarphil at gmail.com> wrote:
>
> > From: Phil Undercuffler <solarphil at gmail.com>
> > Subject: Re: [RE-wrenches] fronius IG Plus practical engineering WAA???
> > To: "RE-wrenches" <re-wrenches at 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_solar at 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 <solarphil at gmail.com>
> > wrote:
> >
> >
> >
> > > From: Phil Undercuffler <solarphil at 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
> >
> > >
> >
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