Power Protection Devices; Surge Protectors; Line Conditioners; Uninterruptible Power Supplies - Dell PowerEdge 350 User Manual

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The system basic input/output system (BIOS) detects the presence of external
devices when you boot or reboot your system. When you connect external devices to
your system, follow these guidelines:
•
Check the documentation that accompanied the device for specific installation
and configuration instructions.
•
Always attach external devices while your system is turned off. Turn on any exter-
nal devices before turning on the system unless the documentation for the
device specifies otherwise. (If the system does not seem to recognize the
device, try turning on the system before turning on the device.)

Power Protection Devices

A number of devices are available that protect your system against power problems
such as power surges, transients, and power failures. The following subsections
describe some of these devices.

Surge Protectors

Surge protectors are available in a variety of types and usually provide a level of pro-
tection commensurate with the cost of the device. Surge protectors prevent voltage
spikes, such as those caused during an electrical storm, from entering a system
through the electrical outlet. Surge protectors, however, do not offer protection
against brownouts, which occur when the voltage drops more than 20 percent below
the normal AC line voltage level.

Line Conditioners

Line conditioners go beyond the overvoltage protection of surge protectors. Line con-
ditioners keep a system's AC power source voltage at a fairly constant level and,
therefore, can handle brownouts. Because of this added protection, line conditioners
cost more than surge protectors—up to several hundred dollars. However, these
devices cannot protect against a complete loss of power.

Uninterruptible Power Supplies

Uninterruptible power supply (UPS) systems offer the most complete protection
against variations in power because they use battery power to keep the system running
when AC power is lost. The battery is charged by the AC power while it is available, so
once AC power is lost, the battery can provide power to the system for a limited amount
of time—from 15 minutes to an hour or so—depending on the UPS system.
UPS systems range in price from a few hundred dollars to several thousand dollars,
with the more expensive units allowing you to run larger systems for a longer period
of time when AC power is lost. UPS systems that provide only 5 minutes of battery
power let you conduct an orderly shutdown of the system, but are not intended to
provide continued operation. Surge protectors should be used with all UPS systems,
and the UPS system should be Underwriters Laboratories (UL) safety-approved.
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