SQ D HU 362 A Ratings? [RE-wrenches]

[Mark Frye]

During my time in solar, I have consistently seen the HU used to 
disconnect multiple strings leading to a single inverter.  The bulletin 
uses the term string and inverter interchangeable.  However, strictly 
speaking, Diagram 2 does not show multiple strings.

As far as the backfeed current, I am pretty sure that any UL1714 listed 
inverter will not backfeed DC current during a fault.

There is a white paper from SMA that talks about the need for fusing on 
multiple string inverters, but their site has been re-built and I can't 
yet find the document.

I personally use a UL 1714 inverter (not the one starting with an X)that 
has an integrated DC disconnect and use a fused combiner box whenever I 
have more than two strings.

Clear as mud as usual.






Robert wrote:
> 
> Hello All
> 
> Thanks Mark for that link.
> 
> Now that I've studied the bulletin, I have a lingering question.
> The diagram shows that you can connect 3 separate
> inverters to the 3 poles of a disconnect, and the text confirms
> that "One inverter may be connected to each pole of the
> switch", as long as the PV current is no higher than the
> maximums listed in Table 1.
> 
> Fine, but are there cases in which we can connect 2 or 3 of
> those strings to a single inverter?
> 
> The bulletin tells us "If a non-fusible disconnect is used, the
> inverter must not be capable of backfeeding currents into a
> short circuit or fault in the photovoltaic array or string."
> This suggests that unless the inverter has internal fusing on
> each string input (or other circuitry to explicitly handle the
> issue), then we'd have to use a fused disconnect for this
> method, otherwise the current from one string could feed
> back through another pole to a short circuit in another string,
> violating the requirement.
> 
> Still, I'm hoping that some inverters can handle this situation,
> or that it would be allowed with fused disconnects.
> 
> Thanks much,
> Robert
> 
> 
> Mark Frye wrote:
> 
> >
> > For those who may like to review the Bulletin, the link is as follows:
> >  http://ecatalog.squared.com/pubs/Electrical%20Distribution/Safety% 
> > 20Switches/Heavy%20Duty/3110DB0401.pdf
> >
> >
> > Ryan Mayfield wrote:
> >>
> >> Jeff,
> >>
> >> Square D has an updated bulletin for the 30, 60 and 100 A HU
> >> disconnects. The HU362 can take an array up to 38A Isc per pole  
> >> (the 100
> >> can take up to 64A Isc) . I'll forward the new bulletin to you  
> >> directly.
> >>
> >> Ryan
> >>
> >>> Jeff C. wrote:
> >>>
> >>> Hi Folks,
> >>>
> >>> I have a copy of the Listing Information letter for the Square D
> >>> HU361 (30A)  from Square D.
> >>>
> >>> Is there an equivalent letter for the HU 362 (60 Amp model?)  Or  
> >>> does
> >>> anyone know the ratings for the various wiring schemes?  The 30 Amp
> >>> model can carry 30 amps when using one pole wired in series to the
> >>> far pole (2 poles per inverter)  and 18 amps (max A) when using one
> >>> pole per inverter.
> >>>
> >>> Anyone know the corresponding amperage rating for the 362?
> >>>
> >>> Thanks!
> >>>
> >>> Jeff C.



Berkeley Solar Electric Systems


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