What is Short Circuit Current Rating (SCCR)?
NEC Article 409 provides minimum requirements to facilitate the safe installation and inspection of industrial control panels for general use that operate at a voltage of 600V or less.
This change to NEC addresses the fact that if an over-current situation arises, the energy level may be higher than the lowest level SCCR on a component within the panel. When ratings on components are less than the available fault current, the safe performance of the panel comes into question. Further analysis of the panel and component combinations may be necessary to ensure a safe electrical installation.
Article 409 recognizes that industrial control panels may be constructed and installed for use in applications covered by other articles in the NEC. Examples can be found in Article 440 for air-conditioning and refrigeration equipment, Article 610 for cranes and hoists and Article 670 for industrial machinery.
No Standard Way to Appropriately Identify the Short Circuit Current Rating
Article 409 impacts control panel equipment design and construction so that the entire panel and all its components inside meet a defined Short Circuit Current Rating (SCCR) and that the panel is appropriately labeled with the SCCR. Before now, industrial control panels could have been installed based upon general electrical requirements from several different articles in the NEC. Previous standards allowed the practice of listing a panel according to the AIR rating of its main over-current protective device. The new standards include the entire combined power circuit in requirements for the SCCR.