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

Larry Crutcher, Starlight Solar larry at starlightsolar.com
Fri Dec 14 15:51:00 PST 2007



> 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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