Site Preparation Guide, Second Edition - HP Integrity cx2620 Server

Main Building Electrical Ground The main electrical service entrance equipment should have
an earth ground connection, as required by applicable codes. Connections such as a grounding
rod, building steel, or a conductive type cold water service pipe provide an earth ground.
Electrical Conduit Ground All electrical conduits should be made of rigid metallic conduit that
is securely connected together or bonded to panels and electrical boxes, so as to provide a
continuous grounding system.
Power Panel Ground Ground each power panel to the electrical service entrance with green
(green/yellow) wire ground conductors. Size the green (green/yellow) wire ground conductors
per applicable codes (based on circuit-over-current device ratings).
NOTE: The green wire ground conductor mentioned above may be a black wire marked with
green tape (LAHJ).
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).
Dual Power Source Grounding When using dual power sources, measure voltage potentials
with a high impedence digital multi-meter (DMM). The use of dual power might create an
electrical potential that can be hazardous to personnel and might cause performance issues for
the equipment.
Dual power sources might originate from two different transformers or two different UPS devices.
Voltage potentials from ground pin to ground pin of these sources should be measured and
verified to be at or near 0.0 volts. Voltage levels that deviate or are measured above 3.0 volts
should be further investigated. Increased voltages might be hazardous to personnel, and should
be further investigated.
Cabinet Performance Grounding (High Frequency Ground)
In some cases power distribution system green (green/yellow) wire ground conductors are too
long and inductive to provide adequate high frequency ground return paths. Therefore, a ground
strap (customer-supplied) should be used for connecting the system cabinet to the site grounding
grid (customer-supplied). When connecting this ground, ensure that the raised floor is properly
grounded for high frequency.
WARNING! Do not use cabinet-to-floor ground strap in place of a properly installed safety
(50–60Hz) grounding system, nor in place of a properly installed Signal Reference Grid. An
improperly installed grounding system can present a shock hazard to personnel.
Connect power panels ground buses and transformers XO bond in close proximity to the computer
equipment to the site grounding grid as well. Methods of achieving a sufficiently high-frequency
ground grid are described in the next sections.
Raised Floor “High Frequency Noise” Grounding
If a raised floor system is used, install a complete signal grounding grid for maintaining equal
potential over a broad band of frequencies. The grounding grid should be connected to the
equipment cabinet and electrical service entrance ground at multiple connection points using a
minimum #6 AWG (16mm2) wire ground conductor. The following figure illustrates a metallic
strip grounding system.
Electrical Factors 27