Wiring Connections; Data Communications Cables; Computer Safety Ground; Environment - HP Cluster Platform Introduction v2010 Introduction Manual

C.1.3.4 Wiring Connections
Expansion and contraction rates vary among different metals. Therefore, the integrity of an
electrical connection depends on the restraining force applied. Connections that are too tight can
compress or deform the hardware and causes it to weaken. This usually leads to high impedance,
which can cause circuit breakers to trip.
Caution:
Connections that are too loose have a high resistance that causes serious problems, such as erratic
equipment operation. A high resistance connection overheats and sometimes causes fire or high
temperatures that can destroy hard-to-replace components, such as distribution panels or system
bus bars.
Wiring connections must be properly torqued. Many equipment manufacturers specify the proper
connection torque values for their hardware. Use a torque driver or wrench to tighten all
connections to the correct torque. Make ground connections only on conductive, nonpainted
surfaces. Use locking nuts and washers on all connections to prevent connection hardware from
loosening.
C.1.3.5 Data Communications Cables
Power transformers and heavy foot traffic create high energy fields. Route data communications
cables away from these areas. Use shielded data communications cables that meet approved
industry standards to reduce the effects of external fields. Data cables that are run externally to
a metal fire enclosure must have a minimum fire rating of VW-1 or VW-4 or better.
C.1.4 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 according to applicable codes (based on circuit over current
device ratings).
High-frequency grounding between cabinets is provided by the cabinet-to-cabinet signal cabling.
Low-frequency grounding between these two cabinets is provided by a ground strap. The
installation must provide a ground connection for the network equipment.
C.2 Environment
The following guidelines are recommended when preparing a computer room for a cluster.
C.2.1 Computer Room
The following guidelines are recommended when preparing a computer room:
• Locate the computer room away from the exterior walls of the building to avoid the heat
gain from windows and exterior wall surfaces.
• When exterior windows are unavoidable, use windows that are double- or triple-glazed
and shaded to prevent direct sunlight from entering the computer room.
• Maintain the computer room at a positive pressure relative to surrounding spaces.
• Use a vapor barrier installed around the entire computer room envelope to restrain moisture
migration.
• Caulk and vapor seal all pipes and cables that penetrate the envelope.
• Use at least a 12-inch raised floor system for the most favorable room air distribution system
(underfloor distribution).
• Ensure a minimum ceiling height of 12 inches between the top of the server and the ceiling.
Ensure all ceiling clips are in place.
C.2 Environment 53