NEC has several articles requiring selective coordination: Art. 700 - Emergency Systems,
Art. 701 - Legally Required Standby Systems, Art. 708 - Critical Operations Power Systems,
Art. 517 - Healthcare Facility, Art, Art. 620 - Elevators
NFPA 99 - Health Care Facilities Code, also requires selective coordination of overcurrent protective
devices (OCPDs) within the essential electrical system (EES).
Industrial facilities and other organizations often have internal procedures regarding coordination strategy
to prevent outages and production delays, and to protect equipment from damage.
The initial settings and characteristics of overcurrent protective devices installed in series and
considered for evaluation are documented in the field and used to develop time-current curves (TCCs).
Based on the objective (whether coordination has never been evaluated, needs improvement, or requires
no action) TCCs can be adjusted to achieve acceptable coordination levels. The results can then be
reviewed graphically and included in the final printed analysis.
Circuit breaker settings can be adjusted in the field to match the time-current curves (TCCs), or replacements
may be recommended where practical.
