HP Integrity rx7620 Server - User Service Guide, Sixth Edition

Every precaution has been taken during power distribution system design to provide immunity
to power outages of less than one cycle. However, testing cannot conclusively rule out loss of
service. Therefore, adherence to the following guidelines provides the best possible performance
of power distribution systems for server equipment:
• A dedicated power source isolates the server power distribution system from other circuits
in the facility.
• Missing-phase and low-voltage detectors automatically shuts equipment down when a
severe power disruption occurs. For peripheral equipment, these devices are recommended
but optional.
• An online uninterruptible power supply (UPS) keeps input voltage to devices constant and
should be considered if outages of one-half cycle or more are common. For each situation,
enlist the assistance of a qualified contractor or consultant.
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 because 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 loosen, overheat, and fail.
Raceway Systems (Electrical Conduits)
Raceways (electrical conduits) form part of the protective ground path for personnel and
equipment. Raceways protect the wiring from accidental damage and provide a heatsink for the
wires.
Any of the following types can be used:
• Electrical Metallic Tubing (EMT) thin-wall tubing
• Rigid (metal) conduit
• Liquidtight with RFI strain relief (most commonly used with 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.
Power Routing
Power drops and interface cables from the equipment are routed down from the power panel,
through a grommet-protected opening (beneath the floor level), and under the floor panels.
Grounding Systems
The 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 computer room personnel might
touch protects them against shock hazard from current leakage and fault conditions.
Power distribution systems consist of several parts. HP recommends that these parts be solidly
interconnected to provide an equipotential ground to all points.
Electrical Factors 183