PC Hardware

Power-Protection Devices

Surge suppressors are devices used to filter out the effects of voltage spikes and surges that are present in commercial power sources and smooth out power variations. They are available from local computer dealers and superstores. A good surge suppressor will protect your system from most problems, but if you purchase an economy model, it might not work when you need it most. Keep in mind that almost nothing will shield your hardware from a very close lightning strike.

Most power strips with surge protection have a red indicator light. If the light goes out, this means that the unit is not providing protection. Most power strip/surge protectors should be replaced every year or so. If the light starts flashing before then, the power strip is failing and should be replaced.

When evaluating the quality of surge suppressors, look for performance certification. At a minimum, it should have an Underwriters Laboratory (UL) listing and power ratings. A high-quality unit will also provide protection for phone/fax/modem and network connections. These units protect up to a point; however, for complete protection from power fluctuations and outages, the uninterruptible power supply (UPS) is recommended.

A UPS is an inline battery backup. When properly installed between a computer and the wall outlet, a UPS device protects the computer from surges and acts as a battery when the power dips or fails. It also provides a warning that the power is out of specification (above or below acceptable levels). Many models can also interact with the computer and initiate a safe shutdown in the event of a complete power failure. They do this by means of software that runs in the background and is set in action by a signal through one of the computer's COM ports when the power goes down.

The amount of time that a UPS device can keep a system running is determined by battery capacity and the power demands of the equipment connected to it. A more powerful UPS device will need its own line and circuit breaker. One of the principal power drains is the monitor. To keep a system online as long as possible during a power failure, turn off the monitor immediately after the failure commences.

When recommending a UPS, take into consideration how much protection is needed as well as the importance of peace of mind to the user. The VA rating (voltage x amps = watts) must be sufficient to supply the computer and all its peripherals with power for long enough to safely shut down the system. The easiest way to calculate this number is to total the power rating (watts) for all pieces of equipment that are to be connected to the UPS, as shown in the following table.

Device Power Rating (Watts) Connected to UPS Power Required
Computer 200-350 Yes 250
Monitor 80-100 Yes 80
External modem 5.5 No 0
External backup drive 50 Yes 50
Total 330-500 - 380
Never plug a laser printer into a UPS unless the UPS is specifically rated to support that type of device. Laser printers can easily require more power than an underspecified UPS is able to provide; the printer, the UPS, and the computer could all be endangered if the printer is connected to the UPS power source.