HP Integrity rx7620 Server - User Service Guide, Sixth Edition

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 to provide a continuous grounding system.
Power Panel Ground
Each power panel should be grounded to the electrical service entrance with green (green/yellow)
wire ground conductors. The green (green/yellow) wire ground conductors should be sized per
applicable codes (based on circuit over current device ratings).
NOTE: The green wire ground conductor can 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 dual power sources are utilized, strong consideration should be given to measure voltage
potentials. 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 for 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)
Signal interconnects between system cabinets require high-frequency ground return paths.
Connect all cabinets to site ground.
NOTE: 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,
the server is shipped with a ground strap for connecting the system cabinet to the site grounding
grid (customer-supplied). When connecting this ground, ensure that the raised floor is properly
grounded.
Power panels located in close proximity to the computer equipment should also be connected
to the site grounding grid. Methods of providing 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 reference grid for maintaining equal
potential over a broad band of frequencies. The grid should be connected to the equipment
cabinet and electrical service entrance ground at multiple connection points using a minimum
#6 AWG (16 mm) wire ground conductor. The following figure illustrates a metallic strip gounding
system.
184 General Site Preparation Guidelines