HP Integrity rx7620 Site Preparation Guide, Fourth Editon - HP Integrity rx762 - Page 46

General Site Preparation Guidelines Electrical Factors • Wide and rapid variations in input power frequency • Electrical storms • Large inductive sources (such as motors and welders) • Faults in the distribution system wiring (such as loose connections) • Microwave, radar, radio, or cell phone transmissions Power System Protection The server can be protected from the sources of many of these electrical disturbances by using: • A dedicated power distribution system • Power conditioning equipment • Over- and under-voltage detection and protection circuits • Screening to cancel the effects of undesirable transmissions • Lightning arresters on power cables to protect equipment from electrical storms 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. Refer to qualified contractors or consultants for each situation. 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) 32 Appendix B