NEC 700.32 / 701.27

NEC 645.5 / NEC 300.22

This fails code. When the space under a raised floor is used as an air-handling plenum — which is the standard cooling configuration in data centers — NEC 300.22 and NEC 645.5 restrict the types of wiring methods permitted. Standard NM-B cable is not rated for plenum use because its PVC jacket produces toxic smoke and fumes when exposed to fire. Only plenum-rated cables (such as Type DP), wiring enclosed in metal conduit, or other listed wiring methods specifically approved for plenum spaces are permitted. This requirement exists because toxic smoke spread through the air distribution plenum could rapidly contaminate the entire data center and endanger personnel.

NEC 645.5(E)(2)(5)

The deciding fact is the fire suppression system, not the airflow. NEC 645.5(E)(2)(4) PERMITS Types CL2, CL3, CM and CMG under a raised floor where the air space is protected by an automatic fire suppression system — the normal condition in a modern data hall. Only where that space is NOT protected does 645.5(E)(2)(5) narrow the allowance to substitute Type CMP. Article 645 exists precisely to relax the ordinary plenum-cable rule inside a qualifying IT equipment room, so reaching for the general rule here gets it backwards.

NEC 700.10(B)(1)

NEC 700.10(B)(1) requires emergency circuit wiring to be kept entirely independent of all other wiring and equipment. Routing emergency and normal power in the same raceway means a single fire or physical damage event can disable both systems simultaneously, eliminating the redundancy that emergency power provides.

NEC 708.22

This fails code. NEC Article 708 (Critical Operations Power Systems) Section 708.22 (Capacity of Power Sources) requires the alternate power source to be sized for a minimum of 72 hours (3 days) of full-load operation of the Designated Critical Operations Area. The 24-hour supply provides only about 33% of the required minimum run time. The 72-hour requirement exists because during major disasters such as hurricanes, earthquakes, or ice storms, fuel delivery infrastructure can be disrupted for days or even weeks. A COPS facility must be capable of sustaining critical operations independently during extended emergencies, regardless of assumptions about local fuel delivery availability. Management convenience or cost considerations do not override this code requirement.

NEC 725.136

Low-voltage thermostat wire must maintain separation from line-voltage wiring. Running parallel causes electromagnetic interference that can damage the thermostat or cause erratic operation.

NEC 760.49 / IBC 909.11

NEC 760.49 and IBC 909.11 require fire alarm circuits serving smoke control functions to use fire-rated wiring (2-hour rated CI cable or wiring in 2-hour rated enclosures). Standard fire alarm cable that burns through in the first minutes of a fire will disable smoke damper control precisely when it is needed most.