Siemens NEC Article 409 - Introduction

Short-circuit current rating (SCCR) of industrial control panels
Reference Manual, 06/2013, A5E31896849002A/RS-AA/001
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Introduction
1
Article 409 on Industrial Control Panels was added to the NEC (National Electrical Code) in
its 2005 edition. This Article requires all Industrial Control Panels to be marked with a short-
circuit current rating. The short-circuit current rating (SCCR) requirements for UL 508A came
into force in April 2006. These changes impact control panel builders, OEMs and end users
in a number of different ways:
● The correct choice of power circuit components of a control panel
● Specification of preferred device manufacturers
● Design and marking of panels
● Correct installation and modification of control panels
Siemens is committed to supplying best-in-class products and services to our customers.
Siemens provides extensive product documentation to enable its customers to comply with
NEC Article 409 and the UL 508A standard.
Guide
This document includes the following information:
● Overview of NEC Article 409
● Overview of Supplement SB of the UL 508A standard with relevant examples
● Process flow charts
– Calculating the SCCR value of a component
– Calculating the SCCR with current-limiting feeder components
– Calculation of the SCCR of a control panel
Further information about UL / NFPA
Underwriters Laboratories UL (http://www.ul.com)
UL online certifications directory (http://www.ul.com/database)
National Fire Protection Association NFPA (http://www.nfpa.org)