Short Circuit Current Ratings (SCCR) for UL508A and NEC

Code and Standard requirements

Significant changes were made to the National Electric Code (NEC), made effective in 2006, in how to determine the Short Circuit Current Ratings (SCCR).


Guidelines on the Short Circuit Current Rating for Industrial Control Panels

Download the Technical Paper for Practical Applications now

Guideline for practical implementation of the SCCR requirements in Industrial control panels

The following guideline may provide assistance in calculating the SCCR for an industrial control panels, applying the requirements of the UL508A, Supplement SB, with general notes and practical flow charts.


SINAMICS G-120 PM240-2: Information about Branch Circuit Protection and SCCR according to UL and IEC


High capacity short circuit current ratings

High capacity short circuit current ratings for Siemens IEC based industrial control equipment and accessories

High capacity short circuit current ratings for Siemens NEMA Contactors & Overload Relays

High capacity short circuit current ratings for Siemens solid state soft starters  


Ip (Peak-let-through current) curves for Siemens current limiting Circuit Breakers

Siemens Current Limiting Circuit Breakers offer additional advantages when trying to maximize the SCCR for your control panel. However Circuit Breakers are only considered as current limiting if they are:

  • Applied in the ‘feeder circuit’

  • Marked as “current limiting”

Please open and review the SCCR White Paper for more details how to apply and to use them.

The file below provides the Peak let-through p) Curves for the following Current Limiting Circuit Breakers: CED6, CFD6, CJD6, CLD6, CMD6, CND6, CPD6, SCJD6, SCLD6, SCMD6, SCND6.

Siemens Current Limiting Circuit Breakers Peak let-through curves

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