NEC 645.10
What it means on the job
This satisfies NEC 645.10. Article 645 is an optional set of alternate rules for an IT equipment room, and one of the conditions for using it is a disconnecting means that will remove power from all electronic equipment in the room and shut down the dedicated HVAC serving it, with the controls grouped, identified, and readily accessible at the principal exit doors. The logic is a firefighter's: someone should be able to kill the load and the air moving through it on the way out, without hunting through a dark room full of energized cabinets.
Tested in 2 CraftIQ puzzles
- code-checkNEC 645 — IT Room Disconnecting Means
- code-checkIT Room Disconnecting Means
Related NEC sections
NEC 590.4(D) / high-rise office Specification
The high-rise commercial office specification requires all panels and breakers used for temporary lighting to be clearly labeled. Unlabeled temporary power creates confusion about which circuits are temporary vs. permanent and risks leaving construction power live during turnover.
NEC 590.6(A) / high-rise office Specification
This temporary power installation is code-compliant. NEC 590.6(A) requires GFCI protection for all 125V, 15A and 20A receptacle outlets used for temporary power during construction. The high-rise office specification additionally requires clear labeling of all temporary panels and breakers. Properly labeled temporary power ensures systematic removal at project completion and prevents confusion with permanent circuits during final inspection. The contractor must remove all temporary stringers, lamps, outlets, breakers, and fusing at completion per high-rise office specifications.
NEC 620.37 / IMC 602.2
NEC 620.37 and IMC 602.2 prohibit using elevator machine rooms as supply, return, or exhaust air plenums for other building spaces. Ductwork from adjacent spaces introduces contaminants, fire risk, and smoke migration paths into the machine room. The machine room must have its own dedicated ventilation system.
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.
CraftIQ explanations are original educational commentary written in trade language and verified against the cited standards. Always confirm requirements against the code edition adopted by your jurisdiction — this is training material, not a substitute for the code book or your AHJ.