How to Comply with NEC 700.27 and 701.18 and Selectively Coordinate Emergency and Standby Systems

Mr. Robert E. Fuhr, PE will be presenting this topic at Portland & Southern California Facilities Expo

Portland - May 10th,  10:05 – 11:05AM  (See us at Booth #606)

Anaheim, CA June 7th, 10:00 - 11:00 AM

The 2005 NEC has new sections that require Emergency, Standby, and Essential Systems to be selectively coordinated.  This requirement will radically affect the way engineers and electricians design these systems.  Today’s systems use fuses and circuit breakers to provide protection to the cables, transformers, panelboards, switchboards, and other equipment.  Fuses are relatively easy to selectively coordinate in the system.  However, fused lighting and distribution panels are not always desired by the owner. 

 Most circuit breakers have an instantaneous trip unit or trip function that makes selective coordination difficult to achieve.  However, with proper design and equipment selection, selective coordination can be achieved for protective devices and also meet the requirements of the NEC. 

 There are various NEC sections referenced below that require selective coordination:

 Article 100 Coordination (Selective) - Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the choice of overcurrent protective devices and their ratings or settings.

 Article 700.27 Coordination - Emergency system(s) overcurrent devices shall be selectively coordinated with all supply side overcurrent protective devices.

 Article 701.18.  Coordination - Legally required standby system(s) overcurrent devices shall be selectively coordinated with all supply side overcurrent protective devices.

 Article 517 Health Care Facilities Essential Electrical Systems - Essential electrical systems must meet the requirements of Article 700 except as amended in Article 517.  However, Article 517 does not contain any amended sections pertaining to selective coordination.  Therefore, essential systems must be selectively coordinated.

 Selective coordination is a term to describe devices tripping in sequence.  This means that the upstream protective device nearest the fault must trip first and before the next upstream device operates.  Another way to look at selective coordination is to view the time current characteristic curves for the protective devices.  The device time current curves must not touch or overlap.  If the device curves overlap, then the devices are not selectively coordinate.  Both the normal and alternate energy sources must be coordinated for standby and emergency systems.

 The seminar will discuss selective coordination and equipment short circuit ratings.  We will view device time current curves and examples of selective coordination.  The seminar will also compare how electrical equipment is tested and rated for short circuit current.  And finally, the instructor will provide tools and methods to help engineers and electricians select and specify equipment that will be selectively coordinated.  This will help the attendees meet these new important NEC requirements.

 About the Author

    Bob Fuhr graduated with a B.S.E.E. from the University of Wisconsin in 1980.  Before graduating, Mr. Fuhr worked for Madison Gas and Electric in Madison, WI and Tennessee Valley Authority in Knoxville, TN. 

 After graduation, he worked for General Electric Company from 1980 to 1986 as a Field Engineer performing commissioning and start up tests on a multitude of power distribution equipment. 

 From 1986 to 1989 he worked as a Senior Facilities Engineer at the University of Washington.  There he re-commissioned the electrical power distribution system for University Hospital. 

 In 1986, he established Power Systems Engineering, a consulting firm that specializes in power systems studies, power quality services, and commissioning services.  He also teaches classes in electrical safety, short circuit calculation, protective device coordination, arc flash hazard assessment, power factor correction, harmonics and filter design. 

 Mr. Fuhr is a Professional Engineer registered in Alaska, Arizona, California, Colorado, Nevada, Oregon, and Washington.

 Bob has been involved in IEEE and the Industrial Applications Society since 1986.  He has served as an officer for IAS from 1988 to 1992.  He was the 1991-92 Chairperson of IAS.  He was a Member-at-large for the Seattle Section of IEEE for 1992-93.  He is an IEEE Senior Member.  He is also member of the Electric League of the Pacific Northwest.