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Short Circuit Current Rating (SCCR)

Short Circuit Current Rating (SCCR) is a protection rating required by the National Electrical Code for industrial control systems.  NEC 2005 recognizes UL508A as an approved method for determining panel SCCR.   

The glossary of UL508A defines SCCR as the prospective fault current to which a system can be connected without sustaining damage.  All power circuits are required to have a SCCR with the exception of Power Transformers and Reactors, because voltage does not flow thru without restriction (UL508A SB4.2).    

For a power transformer where the SCCR of all components in the secondary circuit are not less than 5kA, the SCCR of the primary over current protective device is able to be assigned to the line side of the power transformer circuit (UL508A SB4.3). So the transformer assumes the SCCR of the fuses above it and has no specific SCCR of it’s own.   

In regard to MARCIE Transformer Disconnects, several SCCR ratings are available.  Our standard product line has a rating of 5kA.  By adding the suffix -65K a 65kA SCCR rating is available, and suffix -200K allows a 200kA rating.  Each rating is achieved with the proper switch and fusing. 
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