1.1 This Outline of Investigation covers Modular Data Centers (MDC). The Modular Data Centers covered
by these requirements are pre-fabricated units consisting of an outer enclosure housing ITE and various
support equipment such as electrical service and distribution equipment, HVAC systems and the like.
Some configurations may have the support equipment housed in a separate enclosure. A typical
construction may use a standard ISO shipping container or other structure as the outer enclosure, racks
or cabinets of ITE, NEC compliant service entrance equipment and power distribution components, power
storage such as a UPS and an air or liquid cooling system.
1.2 These factory-built modules incorporate pre-installed materials and equipment which, after
installation, may be concealed and may not be accessible for inspection at the final installation site.
1.3 The modular data centers covered by these requirements are intended for fixed installation either
indoors or outdoors based on their construction and resistance to environmental conditions. MDCs
intended for outdoor use shall be identified with a NEMA environmental class rating.
1.4 These requirements are intended to demonstrate compliance with the National Electrical Code (NEC),
NFPA 70 and other national Codes such as Building, Fire, Plumbing, Mechanical, and the like. Where
state or local codes differ from the national codes anticipated by these requirements, determining
compliance with these codes is the responsibility of the local authority having jurisdiction.
1.5 When these requirements do not cover a specific technology or construction feature, the applicable
requirements of the National Codes shall be used.
1.6 This Outline of Investigation assumes that the final installation of the MDC will be performed by
qualified service personnel in accordance with the applicable installation instructions, installation practices
and national installation codes. These MDCs are intended for installation subject to approval by the
Authority Having Jurisdiction.
UL SUBJECT 2755-2011 history
2018UL SUBJECT 2755-2018 UL Standard for Safety Outline of Investigation for Modular Data Centers (Issue 2)
2011UL SUBJECT 2755-2011 UL Standard for Safety Outline of Investigation for Modular Data Centers (Issue 1)