Chapter 5
Site Preparation
Electrical and Environmental Guidelines
135
NOTE The green wire ground conductor mentioned above may be a black wire marked with green tape.
Computer Safety Ground Ground all computer equipment with the green (green/yellow) wire included in the branch
circuitry. The green (green/yellow) wire ground conductors should be connected to the appropriate power panel and should
be sized per applicable codes (based on circuit over current device ratings).
Superdome was approved by regulatory agencies around the world, and therefore requires a ground/protective earth.
there are no exclusions to this regulatory approval.
High-frequency grounding between IOX and Superdome is provided by the cabinet-to-cabinet signal cabling. Whenever
an IOX is connected to a Superdome cabinet, low-frequency grounding between these two cabinets is provided by a ground
strap. This ground strap is shipped with each IOX. Refer to the I/O Expansion Cabinet Guide for more detail.
Newtwork-connected Equipment Ground The installation must provide a ground connection for the network
equipment. This statement is translated into the following two languages as required:
WARNING Sweden: Apparaten skall anslutas till jordat uttag, när den ansluts till ett nätverk.
WARNING Denmark: Før tilslutning af de øvrige ledere, se medfølgende installationsvejledning.
Raised Flooring, Signal Reference Grids, and High Frequency Grounding
If a raised floor system is used, install a complete signal reference grid (SRG) for maintaining equal potential
over a broad range of frequencies. The grid should be connected to power source X0 and cabinet grounds as
well as to other electrical service grounds. Flat braid offers superior frequency controls to round wire. Figure
5-1 on page 136 illustrates a metallic strip grounding system.
NOTE Regardless of the grounding connection method used, the raised floor should be grounded as an
absolute safety minimum. For more information regarding raised computer floors, see NEC
section 645-15.
HP recommends the following approaches:
• Excellent—Add a grounding grid to the subfloor. The grounding grid should be made of flat braid copper
strips in a 2 ft. by 2 ft. manner mounted to the subfloor. The strips should be 0.032 in. (0.08 cm) thick and
a minimum of 3.0 in. (8.0 cm) wide. Connect each pedestal to four strips using 1/4-in (6.0-mm) bolts
tightened to the manufacturer’s torque recommendation.
• Better—A grounded #6 or #4 AWG 2 ft. by 2 ft. copper wire grid mechanically clamped to floor pedestals
and properly bonded to the building or site ground.
• Good—Use the raised floor structure as a ground grid. In this case, the floor must be designed as a ground
grid with bolted down stringers and corrosion resistive plating (to provide low resistance and attachment
points for connection to service entrance ground and HP computer equipment). The use of conductive floor
tiles with this style of grid further enhances ground performance.
NOTE The structure needs to meet all applicable safety codes and be mechanically bonded to known
good grounding points.
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