jmbelectrical said:
First of all, why would a manufacturer be unable to provide controllers with SCCRs above 5,000A?
Unable? There is no reason. It is
"unwilling". The 5kA is a "courtesy" rating that UL allows for people who put zero effort into it. I can get a 5kA SCCR on a bathtub if I want to. Attaining a higher SCCR is simply a matter of selecting components that have been tested and listed TOGETHER by the manufacturer at higher levels. Virtually every major manufacturer of electrical power components has a table of parts that state what can be used in series with what else and what the attainable SCCR level will be, it is NOT that difficult. The thing is, if I have a Siemens contactor and Siemens Overload, it might be series listed at a higher SCCR with a SIEMENS circuit breaker, but not with a SCHNEIDER circuit breaker. The Series Listing process for the component manufacturer is an expensive destructive test, so why would Siemens test with someone else' circuit breaker? So that panel builder has elected to forego even that simple process of opening up a spreadsheet and possibly changing what brand of contactor or overload relay they use, rather than just shopping for the CHEAPEST thing they can get. It's an indication that they care more about saving a dollar on their component cost than they do about making it possible for an end user to actually install something legally.
Second, it is my understanding that, with a UL508 control panel, you cannot legally attain a higher SCCR by depending on upstream fusing. (Is my understanding of this correct?)
Sort of. End users cannot
themselves ATTAIN a higher level on their own
in the field, that's true. But the panel manufacturer can, again, get a
Series Listing of their panel with fuses, because MOST (if not all) power components will be
already be series listed by the manufacturers with specific fuse classes and/or types. So as long as you use them in your panel (in accordance with the aforementioned component
series listing table), you are good to go. Alternatively the panel manufacturer can LIST those fuse details in an installation manual and place the burden on the end user to provide those fuses, but in that case it generally must have very SPECIFIC fuse data, such as manufacturers and exact part numbers of compatible products.
Again, getting a higher SCCR is not rocket surgery... it just takes slightly more than doing absolutely nothing! So in my opinion, suppliers who choose to do nothing are the ones to avoid. Better yet, talk to YOUR procurement people about ADDING the requirement for a reasonable SCCR to your tender specifications. That way the lazy vendors don't even bother to bid.
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden 
