Introduction to Data Centre Design

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Introduction toData Centre Design
Barry Elliott
BSc RCDD MBA CEng
Earthing, grounding and bonding
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Earthing whats the point

• Safety from electrical hazards
• Reliable signal reference within the entire
  information technology installation
• Satisfactory electromagnetic performance of the
  entire information technology installation

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Applicable Standards

• UK
• BS 6701 Telecommunication cabling and equipment
  installations
• BS 7671 Requirements for electrical
  installations IEE wiring regulations 16th
  Edition
• Europe
• EN 50310 Application of equipotential bonding
  and earthing in buildings with information
  technology equipment
• EN 50174-2 Information technology Cabling
  installation Part 2 installation and planning
  practices inside buildings

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Applicable Standards

• World
• IEC 60364-1 Electrical installations of
  buildings, various sections including Part
  5-548 Earthing arrangements and equipotential
  bonding for information technology equipment
• ISO 118012002 Information technology cabling
  for customer premises
• USA
• ANSI/TIA/EIA-J-STD-607 Commercial building
  grounding and bonding requirements for
  telecommunications
• IEEE STD 1100-2005 Powering and Grounding
  Sensitive Electronic Equipment

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Applicable Standards and.

• ETS 300 253 Equipment engineering earthing
  and bonding of telecommunications equipment in
  telecommunication centres
• ITU-T K.27 Bonding configurations and earthing
  inside a telecommunications building
• ITU-T K.31 Bonding configurations and earthing of
  telecommunications installations inside a
  subscribers building

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Terminology

• Earthing
• The connection of the exposed conductive parts of
  an installation to the main earthing terminal of
  that installation (BS 7671)
• Equipotential bonding
• The electrical connection putting various exposed
  conductive parts and extraneous conductive parts
  at a substantially equal potential (EN 50174-2)
• Grounding (American)
• A conducting connection, whether intentional or
  accidental, between an electrical circuit and the
  earth. (TIA/EIA-607)

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Bolting it all together the equipotential
bonding system

• In an installation, main equipotential bonding
  conductors shall connect to the main earthing
  terminal extraneous conductive parts of that
  installation including the following
• Water service pipes
• Gas service pipes
• Other service pipes and ducting
• Central heating and air conditioning systems
• Exposed metallic structural parts of the building
• The lightning protective system
• The metallic sheath of any telecommunications
  cable

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EN 50310 Application of equipotential bonding
and earthing in buildings with information
technology equipment
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The frame ground grid shall be installed with a
maximum cell size of 2 metres in each horizontal
direction. The minimum cross-sectional area of
the conductors that create the frame ground grid
shall be 10 mm² min. The frame ground grid shall
be connected to the earthing network at multiple
points, where available. If the raised floor is
installed with a surface that is intended to
provide protection against electrostatic
discharge, the DC resistance between the raised
floor surface and the earthing grid shall be in
the range 1 MO to 10 MO
EN 50310
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TIA 607
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6.3 mm thick 101 mm high
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Examples of Clean Earth Bar
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Earth everything!
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Earth everything!
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Additionally, every sixth metallic raised floor
pedestal needs to be bonded (to the SRG). This
helps to bleed off static charges built up from
the raised floor system. EN 50174-2 suggest
every 2 or 3 pedestals earthed with a 10 sq mm
wire
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Earthing system for computer room and entrance
room
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Underfloor TGB serving a row of racks
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TGB in Entrance Room
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Signal Reference Grid - Purpose
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Signal reference grid

• G.5.1.6 TIA 942 Data center grounding
  infrastructure.
• IEEE Standard 1100 provides recommendations for
  the electrical design of bonding and grounding.
  Consideration should be given to installing a
  common bonding network (CBN) such as a signal
  reference structure as described in IEEE Standard
  1100 for the bonding of telecommunications and
  computer equipment.
• If the system is on raised flooring, use a
  2-foot x 2-foot (61-cm x 61-cm) grounding grid.
  (HP) Site preparation guide

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SRG - Do we need one?

• Access (raised) flooring systems that utilize
  bolted stringer construction can be used to
  provide a simple SRG. Floor systems that have
  either no stringer or snap-in stringers do not
  provide for an effective SRG, and other methods
  for installing an SRG should be used. (IBM)
• system reference potential plane (SRPP)
  conductive solid plane, as an ideal goal in
  potential equalising, is approached in practice
  by horizontal or vertical meshes. The mesh width
  thereof is adapted to the frequency range to be
  considered. Horizontal and vertical meshes may be
  interconnected to form a grid structure
  approximating to a Faraday cage, EN 50310

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• The high operating frequencies of modern computer
  equipment require that computer room products be
  supported both by a good equipment-grounding
  system and an effective signal reference grid.
  Compaq/HP
• A signal reference grid should be designed for
  the computer room. This provides an equal
  potential plane of reference over a broad band of
  frequencies through the use of a network of
  low-impedance conductors installed throughout the
  facility. SUN

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ETSI EN 300 253

• 4.2 Signal reference
• Reliable signal reference shall be provided by a
  SRPP dedicated at least to a functional unit or a
  system block. To avoid undue functional
  distortion or risk of component failure, the SRPP
  shall provide sufficiently low impedance up to
  the highest frequency to be regarded by using a
  metal plane or a meshed configuration having
  adequate mesh dimensions, e.g. a bonding mat. The
  frequency band to be covered shall include the
  spectral components of transients caused by
  switching, short circuits and atmospheric
  discharges.

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• Critical equipment should be located and bonded
  to the SRG at more than 6 feet away from the
  building steel or other potential lightning
  paths.
• All interconnecting communications, data and
  power cables should lay on or very close to the
  SRG
• Bond the signal reference grid to each piece of
  electronic equipment and to any other electrical
  or mechanical equipment located on the signal
  reference grid.
• Bonding connections to the signal reference grid
  should be as short as practical with no sharp
  folds or bends. Flexible straps are preferred to
  the use of round conductors.

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IEEE 1100