Matt Darr, Robert Douglass and Vince Saporita
Cooper Bussmann, P.O. Box 14460, St. Louis, MO 63178 USA
Abstract
The US National Electrical Code® (NEC®) has initiated requirements for discrimination (selective coordination) in emergency, legally required, and critical operations power systems. While this required discrimination increases the reliability of critical, life-safety-related loads, it has been a challenge to design and install systems that discriminate with currently available fusible and circuit breaker equipment. Challenges included equipment footprint (size), interrupting rating, short-circuit current rating, and cost. Solutions led to a new UL Class fuse, a new load-break disconnect switch with the footprint of an MCCB, and a new MCCB-sized panelboard , all specifically designed to meet the discrimination requirements.
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