“What came first — the distribution equipment or the coordination study?” is the electrical equivalent of the timeless chicken-or-egg dilemma, according to an article on the Electrical Construction & Maintenance website.
A selectively coordinated system means that each overcurrent protective device (OCPD) in an electrical distribution system does its job in the correct order.
Selective coordination has been required for emergency systems in healthcare facilities since 1985.
The discussion starts: How can I submit equipment for you to review if I don’t know if it coordinates? The reply is typically: How do you know it coordinates if you don’t submit equipment for the coordination study?
According to the article, the answer to the question, “What came first . . . ” is they walked across the street together.