HP Management LAN Blade for bh7800 Site Preparation Guide, Second Edition - HP - Page 24

General System and Facility Guidelines Electrical Load Requirements (Circuit Breaker Sizing) Electrical Load Requirements (Circuit Breaker Sizing) Appendix A summarizes electrical power load (KVA input) requirements for this HP server but additional capacity should be added for equipment upgrading or expansion. It is good practice to derate power distribution systems for one or more of the following reasons: • To avoid nuisance tripping from load shifts or power transients, circuit protection devices should never be run above 80% of their DC current ratings. • Safety agencies derate most power connectors to 80% of their DC current ratings. Power Quality HP equipment is designed to operate over a wide range of voltages. However, damage can occur if this range is exceeded. Severe electrical disturbances can exceed the design specifications of the equipment. Sources of Voltage Fluctuations Voltage fluctuations, sometimes called glitches, affect the quality of electrical power. Common sources of these fluctuations are: • Fluctuations occurring within the facility's distribution system • Utility service low-voltage conditions (such as sags or brownouts) • 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 Computer systems 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 out the effects of undesirable transmissions • Lightning arresters on power cables to protect equipment against electrical storms 24 Chapter 2