It is important to review previous articles that dealt with magnetic motor starters, input and output devices, and ladder logic as they provide some necessary background for PLC operation.
Selective coordination of the emergency system is intended to provide a high level of reliability and continuance of supply needed for systems providing emergency functions.
The scope of this article covers the requirements for branch circuits and feeders running on or between buildings, structure, or poles on the premises, which would also include the wiring for the supply of utilization equipment that is located on or attached to the outside of buildings, structures or poles.