HP 9000 rp5400 Servers - Manual (Page 145)

Distribution Hardware
This section describes wire selection and the types of raceways (electrical conduits) used in the
distribution system.
Wire Selection
Use copper conductors instead of aluminum, as aluminum's coefficient of expansion differs
significantly from that of other metals used in power hardware. Because of this difference,
aluminum conductors can cause connector hardware to work loose, overheat, and fail.
Raceway Systems (electrical conduits) [LAHJ]
Raceways (electrical conduits) form part of the protective ground path for personnel and
equipment. Raceways protect the wiring from accidental damage and also provide a heatsink
for the wires.
Any of the following types may be used:
•
Electrical metallic tubing (EMT) thin-wall tubing
• Rigid (metal) conduit
• Liquidtight with RFI shield grounded (most commonly used under raised floors)
Building Distribution
All building feeders and branch circuitry should be in rigid metallic conduit with proper
connectors (to provide ground continuity) Conduit that is exposed and subject to damage should
be constructed of rigid galvanized steel.
Grounding Systems
An hp server requires two methods of grounding:
•
Power distribution safety grounding
• High frequency intercabinet grounding
Power Distribution Safety Grounding [LAHJ]
The power distribution safety grounding system consists of connecting various points in the
power distribution system to earth ground using green (green/yellow) wire ground conductors.
Having these ground connections tied to metal chassis parts that may be touched by computer
room personnel protects them against shock hazard from current leakage and fault conditions.
Power distribution systems consist of several parts. Hewlett-Packard recommends that these
parts be solidly interconnected to provide an equipotential ground to all points.
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
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).
Electrical Factors 145