SMA Combi-Switch questions about UL rating [RE-wrenches]

[Phil Undercuffler]

If SMA had just "packaged" the HU361RB with fuseholders, then yes the
11.5A (18/1.56) limitation would still apply.  However, since SMA took
the extra step (and expense) to submit the product to a Nationally
Recognized Testing Lab (NRTL) and received a listing on it, then the new
specifications (40A max, 32A max continuous, 10a per pole) applies.

I believe the bottom line on the Combi-Switch is that SMA makes a
product designed to fill a certain niche, using an off the shelf
disconnect (the HU361RB) for the core.  They, as the new manufacturer,
got that product Listed by a NRTL to a certain performance
specification.  The Listing is held by SMA, and they (not SqD) are
responsible for it.  As long as you install the Combi-Switch within the
limits of its design and according to the manual, it should be
acceptable.

And yes, you can use the HU361RB for more than 11.5 amps -- you just
wire it old school, with two poles in series (drawing B on the following
doc:
http://ecatalog.squared.com/techlib/docdetail.cfm?oid=09008926800f998d )
That will allow you to run 24A ISC through that switch to a single
inverter, as the non-fusible switches are rated at 100% continuous.  

However, you can usually stuff more wattage through the switch by using
the recommended wiring for PV systems: 11.5A per pole x 3 poles = 34.5A
ISC total.  


------------------------------------------------------------

Phil Undercuffler
Technical Services Manager
Conergy, Inc.
1730 Camino Carlos Rey Suite 103
Santa Fe NM 87507 USA
Office | 505.473.3800 x4841
Fax | 505.473.3830
www.conergy.us

------------------------------------------------------------


-----Original Message-----
From: Larry Crutcher, Starlight Solar [mailto:larry at starlightsolar.com] 
Sent: Friday, December 14, 2007 4:51 PM
To: RE-wrenches at topica.com
Subject: RE: SMA Combi-Switch questions about UL rating [RE-wrenches]



> Larry, the way I understand it Sq D makes this switch for SMA (both 
> German companies).  Why would they agree to do this if it can't be
used 
> for anything?  I mean if you can't put 4 strings on it what is it?
> 
> It happens we have used it only with the Sharp 170 so far.  Isc is 5.5

> so 2 strings on 1 pole is 11 amps.  Its rated for 11.5 amps short 
> circuit.  Maximum current is 18 amps per pole.  I think this is the 
> intended use and also that Sq D and SMA make good products and have
good 
> 
> engineering.  But I may be all wet. You know - like the time I thought
I 
> 
> was wrong but it turned out I was right after all?

That's the point of my question, why did (could) they do this? If the 
switch was originally de-rated by Sq D to 11.5 amp per disconnect, not 
per pole, to receive a UL listing, bla, bla...

If it will not cause arcing or be a fire hazard, that's a good thing.  
Sorry for being anal-retentive here but it is still illogical to me. 
Thanks for all the suggestions.

Larry Crutcher
Starlight Solar
Yuma, AZ
Renewable Energy Products Powered by STARLIGHT


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