M. Darr, R. Douglass, V. Saporita - New solutions for overcurrent protective device discrimination requirements

Matt Darr, Robert Douglass and Vince Saporita

Cooper Bussmann, P.O. Box 14460, St. Louis, MO 63178 USA

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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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