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High availability and energy
efficiency make data centers
unique facilities when, if not
properly designed, these robust
systems can result in undesirable
complexity and increased safety
hazard. Several articles in the
NEC deal directly with mission
critical data centers, including
Article 645 Information
Technology Equipment, Article
646 Modular Data Centers and
Article 708 Critical Operations
Power Systems. Some of the
changes with the most impact:
1. Article 645 – Information
Technology Equipment (ITE) has
eliminated the electrical code
requirement for smoke detection
below the raised access floor.
The NEC now permits the critical
cooling to remain functional
during an underfloor smoke
event. This will minimize the
opportunity for false shutdowns
of the ITE cooling systems.
2. New Article 646 Modular Data
Centers (MDC) regulates the
increasing popular offsite
constructed data center (modular
or containerized). This, along
with UL 2755 for Modular Data
Centers, will provide structure
and regulation to this form of
data center deployment.
3. The revised more strict
definition of Selective
Coordination will pose new
challenges for critical operations
data centers and will require
detailed engineering to specify
equipment and more expensive
overcurrent protective devices to
meet the new requirements.
4. To increase safety by reducing
arc flash energy exposure all
circuit breakers rated 1200A and
above are required to have an
approved method for speeding
up device operation. This change
may increase equipment costs
and complexity within the data
center. Engineering will be
needed to determine the
appropriate features and
sequence of operations.
The eliminaTion of The neC requiremenT for smoke deTeCTion under The raised floor, wiTh
The requiremenT To shuT down air CirCulaTionwhen smoke is deTeCTed, is a signifiCanT and
long desired Change. This and oTher Changes are ConTained in The new naTional fire
PrevenTion assoCiaTion (nfPa) issued 2014 ediTion of nfPa 70, naTional eleCTriC Code (neC).
By Dennis R. Julian PE, ATD, DCEP
