HP 9000 Superdome SX2000 Generic Site Preparation Guide - Edition 6 - Page 8

• Electrical infrastructure is rated for maximum load. • The distance from a receptacle to power source X0 is less than 75 feet (23 m). • There are no daisy-chained receptacles or hot, neutral, or ground wires. • The system is sourced from higher distribution voltages. AC Power Quality Devices HP products have a wide range of voltage tolerances. In general, approximately 10% of the nominal voltage is sufficient for the marked electrical-rated voltage. The best operating margin is in the middle of this range but your business needs will dictate the risk you can withstand. Although utility-fed AC power is usually error free, your particular building or area might be subject to local problems. Use uninterruptible power supplies (UPSs), backup generators, auto transfer devices, floor-mounted distribution transformers (less than 75-foot distances), and other alternatives for critical systems and applications demanding high availability. To ensure sufficient power quality, keep in mind: • The best voltage operating margin is in the middle of the distribution range. • High availability equipment should have UPS sourcing and dedicated breakers. • A few large UPSs provide more protection than numerous smaller cabinet UPSs. UPS Recommendations Use online versus offline UPSs for the highest availability environment. HP does not recommend the practice of sourcing a cabinet UPS from a room UPS as this can result in increased costs without providing more system availability. Indeed, this practice can introduce more system downtime than just a room-level or system-level UPS. UPSs that are compatible with present-day technology generally use pulse width modulation (PWM) and have ratings that are appropriate for a nonlinear load. UPS loading is based on type and manufacture: • Selective Catalytic Reduction (SCR)-based should be no greater than 80%. • Transistorized-based at 100%. Power Consumption Safety and regulatory labels on computer equipment list the ratings for maximum power consumption conditions. Even though you will not normally reach maximum conditions, size all electrical distribution infrastructures to meet maximum conditions. It is better to rate up rather than down. For example, if the marked electrical voltage is 15 amperes (A) on a product, depending on your local electrical code, the electrical infrastructure should include 20A receptacles, 20A sized wiring, and 20A breakers. Undersizing the wiring might save costs in the beginning, but it will cause problems as infrastructure grows. Average-sized wiring can be used with power quality devices, such as UPSs, but not with the electrical infrastructure. In determining the power requirements: • Size electrical infrastructure for maximum-rated consumption. • Size air-conditioning and UPSs with typical ratings, but realize that overloading might take place with additional growth of the infrastructure. 8 General Site Preparation Guidelines