NEMA AB 4-2009 describes the necessary procedures and precautions for maintainers of molded case circuit breakers


Sep 21, 2009

The National Electrical Manufacturers Association (NEMA) has published NEMA AB 4-2009 Guidelines for Inspection and Preventive Maintenance of Molded Case Circuit Breakers Used in Commercial and Industrial Applications. The standard was last revised in 2003.

NEMA AB 4 presents procedures for identifying molded case circuit breakers requiring maintenance or replacement. It contains instructions for non-destructive tests for verifying specific operating characteristics, and discusses safety procedures and operation of accessory devices. This revision features updates to the test equipment mentioned to reflect changes in technology and a revised definition of “qualified person.”

NEMA AB 4 may downloaded at

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