Special Conditions
What to master
Articles 700 through 770 cover systems defined by how critical they are and by how their circuits are classified. Article 700 emergency systems must supply power within 10 seconds for life safety; Article 701 legally required standby has 60 seconds; Article 702 optional standby has no Code-mandated time. Article 705 governs interconnections with sources such as PV, 708 covers critical operations power systems, and 760 covers fire alarm circuits. Article 725 separates Class 1, Class 2, and Class 3 remote-control and signal circuits by power and voltage limits, which matters because Class 2 and 3 cables cannot be mixed with power conductors in the same raceway without a barrier.
Traps
Treating emergency and standby as synonyms; assuming a generator automatically satisfies Article 700 without the required separation and transfer equipment; applying Class 1 wiring rules to a Class 2 thermostat cable; and forgetting that 700.10(B) requires emergency wiring to be physically separated from other circuits.
Worked example
A hospital asks for a standby generator to keep operating rooms running. Because the load is life safety and critical, Article 517 and Article 700 govern, not Article 702. The designer must separate emergency circuits, provide the correct transfer time, and ensure the emergency source and its feeders are protected from fire or physical damage as 700.10 requires.