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IAEI
News>Issue Listing>January/February 2001 >Installations and Inspections of Information Technology Equipment
| Installations and Inspections of Information Technology Equipment |
This article looks at the requirements in the NEC relative to information technology equipment and the correct use of Article 645. |
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Computer Rooms
In the 1996 National Electrical Code the title of
Article 645 was changed from Computer/Data Processing
Equipment to Information Technology Equipment (ITE). This
change reflects the fact that computer rooms are more than
just for housing computers. In many cases they are the
heartbeat of organizations. They serve multiple functions such
as data processing, telecommunications, and data storage. The
primary function of the computer room is still to house the
information technology equipment, the computers. This article
will look at the requirements in the National Electrical
Code relative to information technology equipment and the
correct use of Article 645.
NEC Arrangement
The Code, in review, is arranged into nine chapters and
an introduction. Section 90-3 states that the rules in
chapters 1 through 4 apply generally, and chapters 5, 6, and 7
apply to special occupancies, special equipment, or other
special conditions—modifying or amending the general rules
in chapters 1 through 4. Chapters 1 through 4 apply to all
installations except as amended by chapters 5, 6, and 7 for
the particular conditions. Chapter 8 of the NEC is
independent of all other chapters unless referenced therein.
Scope
Article 645 "covers equipment, power supply wiring,
equipment interconnecting wiring and cables, and grounding of
information technology equipment and systems, including
terminal units, in an information technology equipment
room." 1
The Room
What qualifies as an Information Technology Equipment (ITE)
room? Section 645-2 sets the stage for whether or not the
rules in Article 645 may be used for a computer room, or if
the room and all electrical equipment associated with it must
follow the requirements of chapters 1 through 4 of the Code.
A close look at Article 645 reveals that several things must
be considered. Article 645 offers alternatives to the some of
the requirements of chapters 1 through 4, but several items
must be in place to qualify for their application. Section
645-2 specifically states that Article 645 is applicable if
"all of the following conditions" exist. This
statement makes it clear that unless all of the items in
Section 645-2 are complied with, Article 645 is not permitted
to be used and the basic chapters 1 through 4 are the
applicable rules for the installation.
Requirements for a
Computer Room
Six items must be in place before the computer room is
permitted to be wired in accordance with the rest of Article
645.
The first requirement in Section 645-2(a)
is that a disconnecting means complying with Section 645-10 be
provided. Section 645-10 requires a means be provided for
disconnecting all electronic equipment in the information
technology room. The HVAC system dedicated to serving the room
must also be provided with a means of disconnect and any
required fire/smoke dampers must close when this disconnect is
thrown to the off position. The control for these
disconnecting means is required to be grouped, identified, and
readily accessible at the principle exits of the room. A
single means that will disconnect both simultaneously shall be
permitted. A mushroom-type button, often called a panic
button, is usually installed at the principle exit doors of
the computer room (see photo
1a, photo 1b,
and photo 1c).
The button usually is connected to a control circuit to
actuate a shunt trip device for simultaneous disconnection of
these loads. Any uninterruptible power supply (UPS) systems
installed in the information technology room are also required
to comply with the disconnecting means requirements of Article
645-10.
The second requirement in Section 645-2(b)
is that a dedicated HVAC system be provided specifically for
the information technology equipment (see photo
2). Any such HVAC system that serves other occupancies
shall be permitted to also serve the information technology
equipment room if fire/smoke dampers are provided at the point
of penetration of the room boundary (see photo
3). These dampers are required to close upon operation of
the disconnecting means installed to comply with Section
645-10 and upon activation of smoke detectors in the room (see photo 4).
The third requirement in Section 645-2(c)
is that listed information technology equipment is installed.
This equipment often bears a label that indicates suitability
for use in an information technology room that meets the
requirements of Article 645 of the NEC. Equipment that
is marked in this manner must only be installed and operated
in rooms that are set up in accordance with Section 645-2.
The fourth requirement in Section 645-2(d)
is that the only personnel occupying the room are those needed
for the functional operation and maintenance of the installed
information technology equipment.
The fifth requirement in Section 645-2(e)
is that the room is separated from other occupancies by
fire-resistant/fire-rated walls, floors, and ceilings with
protected openings (see photo
5). The minimum fire rating for an information technology
room shall be 1-hour. This fire rating is not stated directly
in Article 645, but four fine print notes (FPN) refer to NFPA
75, Standard for Protection for Electronic Computer/Data
Processing Equipment, which requires the minimum 1-hour fire
rating.
The sixth requirement in Section 645-2(f)
is that building construction, rooms, or areas and occupancy
comply with the applicable building code. With all of these
requirements in Section 645-2 complied with, the wiring for
the information technology equipment room shall be permitted
to follow the rules in Article 645 that amend the basic
requirements of chapters 1 through 4. Remember that unless
specifically amended by Article 645, all of the requirements
in chapters 1 through 4 are still applicable. This is often a
point of confusion in the design of a computer room or
information technology room. Sometimes a building design will
call for a raised floor assembly in the computer room for a
convenient way to interconnect the computers. This method is
allowed and the installation is clean in appearance when
completed. Problems start when the raised floor is set up to
be used as a space for transporting the air-conditioning for
the equipment and the room. Remember, if the room or space is
not constructed to meet the minimum requirements of Section
645-2 then it would be required to comply with the
requirements for wiring installed in spaces used for air
handling purposes. In that case, all of the installed wiring
and cabling, etc., would need to meet the requirements of
Section 300-22.
Supply Circuits
and Interconnecting Cables
Section 645-5 sets up requirements for the branch-circuit
conductors, connecting cables, interconnecting cables, and the
guidelines for the area under raised floors. The
branch-circuit conductors are required to have an ampacity of
not less than 125 percent of the total connected loads. These
are continuous loads most of the time. In Section 645-5(b)
"the data processing equipment is permitted to be
connected by any of the following three methods listed for the
purpose (see photo
6).
(1) Computer/data processing cable and
attachment cap
(2) Flexible cord and attachment plug
cap
(3) Cord set assemblies. If run on the
surface of a floor, they are to be protected from physical
damage.
"Separate data processing units are
permitted to be interconnected by means of cables and cable
assemblies listed for the purpose. They also must be protected
from physical damage where run on the surface of the floor.
"Power cables, interconnecting cables,
connecting cables, and receptacles associated within the
information technology equipment shall be permitted under a
raised floor under the following conditions.
(1) The floor is of suitable
construction and is accessible.
(2) Branch circuit supply conductors to
receptacles or field-wired equipment are installed in
rigid metal conduit, rigid nonmetallic conduit,
intermediate metal conduit, electrical metallic tubing,
metal wireways, surface metal raceways with metal covers,
flexible metal conduit, liquidtight flexible metal or
nonmetallic conduit, MI cable, MC cable, or AC cable
assemblies. These wiring methods must be installed to meet
the securing and supporting requirements specified in
Section 300-11.
(3) The ventilation in the under-floor
area is for the information technology equipment only.
(4) Openings are such that the cables
and cords passing through them are protected from
abrasion, and are of a design that minimizes debris from
accumulating beneath the raised floor (see photo
6a).
(5) Cables other than those mentioned
in item 2 above are listed as Type "DP" having
adequate fire-resistance characteristics suitable for use
under raised floors of an information technology equipment
room (see photo
7):
a. Interconnecting cables enclosed in a
raceway
b. Interconnecting cables listed with
equipment manufactured prior to July 1, 1994, and
installed with that equipment
c. Cable type designations TC, CL2,
CL3, PLTC, NPFL, FPL, OFC, OFN, CM, MP, and type CATV.
These designations shall be permitted to have an
additional letter P, R, or G in their designation. Green
insulated single conductor cables, No. 4 and larger,
marked "for use in cable trays" or "for CT
use" shall be permitted for equipment
grounding." 2
"Power cables, communication cables,
interconnecting cables and associated boxes, connectors,
plugs, and receptacles that are listed as part of the
information technology equipment shall not be required to be
secured in place" 3 (see photo
8 through 8b). This allows
flexibility for expansion and reconfiguring of the computer
room. This is one area where relief from the basic support and
securing requirements of chapter 3 is permitted. Any cables
that extend beyond the information technology room are subject
to all of the requirements in the code, even if they originate
in the computer room. Any penetration of the fire-resistant
room boundary must be have the appropriate fire seals at those
penetrations in accordance with the rules in Section 300-21
(see photo 9 ).
Uninterruptible
Power Supplies
UPS systems can come in a variety of types and sizes, and are
often utilized in information technology equipment rooms. UPS
systems installed within the information technology room and
any output circuits must comply with the disconnecting means
rules in Section 645-10. This includes the output of battery
UPS systems. The output of the batteries must also be
disconnected from its load. There are some alternative
requirements for integrated electrical systems installation in
accordance with Article 685. This would allow means of
disconnect to be in the form of orderly shut down to ensure
safe operation. Specific conditions outlined in Section
685-1(1)(2) and (3) must be complied with. This is a case
where the rules of Article 645 are further modified by a later
article in chapter 6 (Article 685), if certain rules are
complied with. Small UPS unit equipment capable of supplying
loads of 750 VA or less are not required to be disconnected
from the source if the requirements of Section 645-11 are met.
Grounding
Requirements
The grounding requirements for information technology
equipment rooms are found in Section 645-15. "All exposed
noncurrent-carrying metals parts of an information technology
system shall be grounded in accordance with Article 250 or
shall be double insulated. Power systems derived within listed
information technology equipment that supply information
technology systems through receptacles or cable assemblies
supplied as part of the equipment shall not be considered
separately derived for the purpose of applying Section
250-20(d)" (see photo
12).
Some alternative requirements are here
also, but remember the first sentence of Section 645-15. The
power distribution unit (PDU) may contain a separately derived
system and even a line conditioner, but may not be required to
have a grounding electrode conductor run to the electrode
system of the structure. Equipment grounding conductors are
always required on the primary and secondary sides of such
PDUs. Installation instructions and wiring diagrams supplied
with the PDU are key at this point in the inspection or
installation. Bonding and grounding requirements in the
product standards governing this type of listed equipment or
systems ensure that the requirements of Article 250 are met.
Isolated grounding type receptacles must comply with the
requirements of Sections 250-146(d), 384-20 Exception, and
410-56(c) [see figure
11]. The earth shall not be used as an equipment grounding
conductor. These isolated equipment grounding conductors are
permitted to pass through one or more panelboards so as to
terminate at the system grounding point, either at the source
of a separately derived system or at the service (see figure
12). Remember, these equipment grounding conductors are
required to be installed in the same raceway, cable or trench
as the ungrounded (hot) conductors and the grounded (usually
the neutral) conductors of the circuit [see Sections
250-134(b)]. Supplemental grounding electrodes are permitted
for information technology equipment and equipment rooms, but
they must be bonded to the building grounding electrode
system.
Signal Reference
Grid Systems
Signal reference grids are often installed in information
technology equipment rooms. This is a method of keeping the
shields of cables and chassis (frames) of information
technology equipment at the same zero potential as the derived
system (see figure
13 figure 14, figure 15,
and figure 16).
These signal reference grids, usually installed under the
raised floor in the information technology room (see photo
13), must be bonded to the equipment grounding system
provided for the information technology equipment. This simply
means there will be two grounding conductor connections at the
equipment: the required equipment grounding conductor, and the
supplemental reference grounding conductor. Sometimes there
might even be a third grounding conductor connected to a
supplemental grounding electrode. The important point here is
that the safety equipment grounding conductor always remains
connected. Isolated grounding conductors and systems do
not mean isolated from connection to the grounding point of
the supply system or service. This is extremely important for
personnel safety, which has to come first.
Markings on
Information Technology Equipment
Information technology equipment is required to be marked with
a manufacturer’s nameplate which shall include the input
power requirements for voltage, frequency, and maximum rated
load amperes. This information technology equipment is usually
listed by a qualified electrical testing laboratory, and will
bear the appropriate listing markings. Listed equipment is
required to be installed and used in accordance with any
instructions included in the listing or labeling [see Section
110-3(b) of the NEC].
Summary
The NEC has a specific article designated
for information technology equipment and covers the
requirements of information technology equipment rooms. There
are some alternatives to the requirements of the basic rules
in chapters 1 through 4 of the Code, if Article 645 is
adhered to. Equal and effective safety is maintained if all of
the conditions specified in Section 645-2 are met. As
previously noted, unless modified or amended by the
requirements of Article 645, the rules in Chapters 1 through 4
must be followed. We hope that this writing will assist
readers in understanding these basic requirements and clarify
the rules for information technology equipment and ITE rooms.
NFPA Standard 75, The Standard for Computer/Data Processing
Equipment, contains other details and information regarding
information technology equipment and rooms. As always, one
should consult the local authority having jurisdiction to
ensure compliance with the NEC and any local amendments
or ordinances.
1 National Electrical
Code, NFPA 70-1998 (Quincy, MA: National Fire Protection
Association, 1998) Article 645-1, Scope, p. 70-463.
2 National Electrical
Code, NFPA 70-1998 (Quincy, MA: National Fire Protection
Association, 1998) Article 645-5(b) through 645(5)(c), p.
70-463-464.
3 National Electrical
Code, NFPA 70-1998 (Quincy, MA: National Fire Protection
Association, 1998) Article 645-5(e), p. 70-464.
Michael J. Johnston is IAEI’s
director of education, technical editor and an IAEI
principal member on CMP-5. Johnston was formerly
employed as an electrical field inspections supervisor
for the city of Phoenix, Arizona. He is a member of the
IBEW. Additionally, he holds all IAEI certifications. He
also holds ICC Electrical Inspections Certification. He
is a member of the UL Electrical Council.
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