C-6 Dell PowerEdge 6100/200 System User’s GuidePower Protection DevicesA number of devices are available that protect againstpower problems, such as power surges, transients, andpower failures. The following subsections describe someof these devices.Surge ProtectorsSurge protectors are available in a variety of types andusually provide a level of protection commensurate withthe cost of the device. Surge protectors prevent voltagespikes, such as those caused during an electrical storm,from entering a system through the AC power source.Surge protectors, however, do not offer protection againstbrownouts, which occur when the voltage drops morethan 20 percent below the normal AC line voltage level.Line ConditionersLine conditioners go beyond the overvoltage protectionof surge protectors. Line conditioners keep a computer’sAC power source voltage at a fairly constant level and,therefore, can handle brownouts. Because of this addedprotection, line conditioners cost more than surge protec-tors—up to several hundred dollars. However, thesedevices cannot protect against a complete loss of power.Uninterruptible Power SupplyA UPS offers the most complete protection against varia-tions in power because it uses battery power to keep thesystem running when AC power is lost. The battery ischarged by the AC power while it is available, so onceAC power is lost, the battery can provide power to thesystem for a limited amount of time—from 15 minutes toan hour or so—depending on the UPS system.UPS systems range in price from a few hundred dollars toseveral thousand dollars, with the more expensive unitsallowing you to run larger systems for a longer period oftime when AC power is lost. UPS systems that provideonly 5 minutes of battery power let you conduct anorderly shutdown of the system, but are not intended toprovide continued operation. Surge protectors should beused with all UPS systems, and the UPS system shouldbe Underwriters Laboratory (UL) safety-approved.If you are using the optional redundant power suppliesinstalled in your PowerEdge 6100 system, connect thetwo power supplies to different circuits, if possible.
