Understanding NEC Article 409 and the Short Circuit Current Rating (SCCR):
What it means, how to comply, and why. Attend a FREE Brady webinar to learn more.
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The Short Circuit Current Rating, or SCCR, of an electrical panel represents the maximum fault current that the panel can withstand in the event of a short circuit, or overcurrent situation. Until recently, there were no standardized guidelines for determining or labeling the SCCR of a panel, leading to inaccuracies, confusion during installation and inspection, and an increased potential for user injury from electric shock. The National Electric Code (NEC) article 409 addresses the need for a standard measurement of SCCR, as well as the need for clear, consistent control panel labeling. |
Prior to the development of NEC article 409, the SCCR of an industrial control panel was generally determined based on the rating of the primary electrical component in the panel - a method that could prove inaccurate if other components in the panel are not equally rated. Additionally, because there were no specific guidelines for determining and labeling SCCR, panels were built and installed based on several different requirements from various articles within the NEC.
Article 409 covers Industrial Control Panels for general use at 600V or less. The standard covers two areas: Those who are most affected by the standard are equipment manufacturers, who must determine the SCCR rating and label the panel. End users are also affected, because they must specify an appropriate SCCR rating for any industrial control panels they have installed in their facility. This means that they must rate the potential fault current for their location.
As a result of NEC article 409, equipment builders have had to re-evaluate the design of their panels. Instead of basing the SCCR on the main component in the panel, the rating must be determined based on the "weakest link" in the panel, to get an accurate estimate of the maximum available fault current the panel can withstand.
According to Jay Tamblingson, an Applications Manager of the OEM Engagement Team at Rockwell Automation, a clear consistent standard has advantages for both manufacturers and end users beyond the obvious need for increased plant safety: "The NEC article 409 standard makes it easy for a customer to know if they're ordering the right panel for their facility, and it avoids problems, delays, or confusion during installation."
Prior to the enactment of the standard, industrial control panels were not labeled consistently, often leading to confusion and potential danger to end users. Now, installers, inspectors, and end users all know what information to look for, in what location. For manufacturers of industrial control panels, Brady offers many solutions for fast, easy, cost-effective labeling that is NEC article 409 compliant, including the BradyprinterTM 300 MVP Plus Thermal Transfer Printer, the Brady TagusTM T300 Thermal Transfer Printer, LabelMarkTM Label Design Software, and BradySoftTM Label Design Software, plus industrial labels (including labels with pre-printed headers) that are designed to meet the requirements of the standard.
For many manufacturers and end users, the new standard presents some challenges, including how to determine a panels SCCR, what to do if a location's fault current is increased, and how to be certain of specifying the correct SCCR for the intended application and fault current. Tamblingson points out that there are resources available, including materials provided by industry experts like Rockwell and Brady, and training courses offered by UL and the NEC.
To help our customers better understand NEC article 409 and SCCR issues, Brady is offering a FREE Short Circuit Current Rating Webinar on Tuesday, June 12, 2007, at 1pm CDT (GMT -05:00, Chicago). The webinar will feature experts from Rockwell Automation and Brady Corporation - don't miss this chance to get your questions answered! To register, visit www.bradyid.com/webinars.
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