Search

The article discusses the importance of selective coordination of circuit protection for emergency circuits and legally-required standby systems. According to the author, the point of selective coordination is to isolate the faulted portion of the circuit while maintaining power to the rest of the electrical system. The author also discusses fuse limitation, current-limiting benefits, load comparisons and coordinating circuit protection.

The article discusses the need to understand the difference between short-circuit current rating (SCCR) and interrupting rating (IR). It notes that specifiers using the terms interchangeably without understanding their difference could lead to under-protection or death. To obtain protection and compliance with the National Electrical Code (NEC), the circuit designer must calculate available fault current. Moreover, NEC Article 409 demands the SCCR to be displayed on industrial control panels.