Kirpal,
I have two older versions of this bulletin. The 2005 version mentions
a limited UL listing (E2875) for switching three 600-volt dc circuits.
It is interesting that the 2007 version does not mention a UL listing
for that use, but otherwise it looks like the same document. So this
change may have happened some time ago without anyone being aware of
it. With the 2009 bulletin, you probably couldn't get a system wired
that way in Oregon to pass inspection. At least you couldn't if the
inspector knows that there is no 3rd party certification. On the other
had, at least SQ D is still certifying that it is suitable for that
purpose. Manufacturer certification for non-standard uses is not
uncommon. I'm suspicious that back in 2005 Some Manufacturer Asked for
the special listing and perhaps even paid for it.
Kent Osterberg
Blue Mountain Solar, Inc
Kirpal Khalsa wrote:
Hi All......
I recently came across a revised technical
bulletin from square D ( http://ecatalog.squared.com/pubs/Electrical%20Distribution/Safety%20Switches/Heavy%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?
--
Sunny Regards,
Kirpal Khalsa
NABCEP Certified Solar PV Installer
Renewable Energy Systems
www.oregonsolarworks.com
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