[RE-wrenches] Square D DC disconnects

[David Brearley]

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.brearley at solarprofessional.com


On 1/9/10 4:14 PM, "Kirpal Khalsa" <solarworks at 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/
>> 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?
>  
>  




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