Ram & Reason: The UPS
By Rob Rice March 2005
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A few years ago a computer’s need for safe and clean power became apparent to me in a rather expensive way. While in the process of writing an important paper one summer day I suddenly heard a loud “BOOM!” outside and below my open second story window. This was accompanied by the unmistakable sound of electricity running rampant. My computer’s monitor started acting erratically with wild wavy lines and sickly looking colors. I reached for the power switch and killed the power to the computer. Next – I got the heck out of the building!
The power box on the side of my apartment building had exploded. A huge stream of white sparks was shooting from the box. The fire department was only a block away and arrived within minutes. The fact that this was a dangerous and unnerving situation was not lost upon the firepersons who were attacking this spectacle by creeping up on it with long fiberglass poles with their arms shielding their faces. The power company finally ended the show by killing power to the box.
Once the apartment complex finally repaired the power box (with duct tape, but that is another story) power was eventually restored. I held my breath as I turned on my computer. To my amazement it booted without a hitch and I had only lost the last two paragraphs of my paper. It seems that my 1150-joule rated surge suppressor had done its job. Even on-board testing suggested all was well.
However, several weeks later it became obvious that something was wrong. The computer began to reboot on its own. Spontaneous reboots evolved into spontaneous black screens. However, enough time had elapsed from the exploding power box to the erratic behavior that I did not immediately recognize it as the culprit. I replaced power supplies, video cards, hard drives, sound cards, CPU, CPU fans and even the BIOS chip. Nothing worked. While clearing the CMOS would usually restore it, it was obvious something was wrong with the motherboard – and it was only five months old. A careful examination with a magnifying glass at first revealed nothing. I had checked each capacitor to see if it showed any signs of leaking. But there were no bulging or exploded tops, no brown ooze leaking from the bottom or the top of the little cylinders. Finally I decided to take a last look this time in direct sunlight. Suddenly there it was, in the corner of the motherboard was a single capacitor that had at one time two wires going into it but now one of those wires was broken. The power box explosion had probably damaged it and the wire separated over a period of time. Trying to repair the damage did not work so I trashed the motherboard and the surge suppressor reasoning that it also was probably hiding damage as well.
While my experience may be rather extreme the importance of having good clean power cannot be understated. So-called “dirty power” is electricity that is experiencing fluctuating voltages and cycles. Surges, brownouts and spikes are examples of dirty power. It is believed that power quality will erode as power deregulation allows municipalities to buy power from hundreds and even thousands of miles away.
As a result computer monitors, printers, or any expensive electronics equipment should never be plugged straight into a wall socket. At the very least it should be plugged into a surge suppressor but preferably it should be plugged into an Uninterruptible Power Supply (UPS).
The UPS The UPS is typically a rechargeable battery and some associated circuitry that you plug your computer and monitor into and in turn, plug it into the wall. The UPS keeps a constant charge so that in the event of a power failure the circuitry of the UPS switches from power supplied from the wall outlet to power supplied from the battery. This allows for enough time to save work and gracefully shut down the computer or allow it to remain running until power is restored (Never recommended).
The simplest type of UPS for home and office is the Standby Power System. This type, which switches to battery during a power loss is described above.
The Line-interactive UPS is very similar but it also has Automatic Voltage Regulation (AVR) and monitors power consistency. The AVR cleans up dirty power that is flowing through the utility lines by switching to battery power even when low voltages occur and not just blackouts. This keeps the power at an almost constant state and minimizing or eliminating damage.
A third type is the On-line UPS system. It provides the most protection by constantly supplying power from its own inverter. This avoids those few milliseconds of switching from AC power to battery power. This type is often much more expensive and is used in critical systems such as found in medicine or on critical network servers.
Isn’t a surge protector enough?
Most people will have a surge protector to protect their computer equipment from damage as a result of a power surge. These are rated by joules, the higher the number the more resistant it is to power surges, or so common thought goes. Somewhere around 800 joules or more is typically recommended today. However, a surge protector cannot protect against power under-voltages and may not survive erratic power cycles. These can damage equipment as well. Power sags, dropouts and transient voltages account for the majority of power problems and can either damage your equipment in a matter of minutes or slowly over a period of months.
Symptoms of a power problem
Shopping for a UPS
In addition to the three types mentioned earlier, the UPS that is typically found in stores these days has Automatic Voltage Regulation. The box should say so and will typically have a rating measured in volt-amps (VA). The most popular UPS suppliers have guides on their Web site to help you select the proper size of UPS for your computer and monitor. For example, at Tripp-Lite’s site (http://www.tripplite.com) we find that a desktop computer with a 17-inch monitor, Athlon XP processor, DSL modem, ink-jet printer, a writable CD-ROM and powered speakers will have an estimated draw of 315VA. In order to have an estimated 10 minutes of battery power to save your work and shut down in the event of a blackout, a product with a rating of 500VA would probably be about right. A 325VA UPS would be too small with the battery not being able to keep enough charge to supply power. Also one should note that typically printers are not put on the UPS, especially a laser printer, which draws too much power. At the time of this writing a 500VA UPS typically costs $40 to $70 and at times $30 on sale.
Most of the more-advanced models come with software that will detect that the computer has reverted to battery power and will shut the system down gracefully. Batteries can also be replaced by the consumer and will have status lights and surge protection built in. Still, the UPS manufacturers are businesses and many have resorted to offering inexpensive UPS devices by sacrificing surge protection. You may find that 500VA UPS for a cheap price but check the surge protection rating on it. It may be only 325 joules, which is not much protection. You may have to go to the model’s website to get the information as manufacturers with low joule ratings typically don’t brag about it.
While we have been talking about using a UPS for computers you may wish to consider putting one on your television or expensive stereo equipment as well. A 350VA UPS (no software would be needed) can handle a 32-inch television, VCR and DVD player without much trouble. As expensive as these big screen televisions are it’s not a bad idea to maximize protection. Not to mention that they weigh a ton and any trip to the shop for repairs would be an ordeal.
A simple formula can tell you the correct size of UPS: Multiply the number of amps your equipment uses (see the label or owners manual) by 120. If your equipment is rated in watts, multiply the number by 1.67. So if your monitor uses 3 amps and your computer uses 100 watts, you would need 360 (3 x 120) amps plus 167 (100 x 1.67) watts for a total of 567 (360 + 167) volt-amps.
Other items to consider when buying a UPS:
If a UPS is just too bulky or expensive, a line conditioner performs some of the same functions as a UPS but without battery backup.
Predications are that electrical power will continue to see a decrease in quality and that the potential for your PC or electronics to have an equipment failure will only increase. A UPS can be insurance against damage and data loss.
A few popular brands in alphabetical order:
APC – http://www.apc.com Belkin - http://www.belkin.com/ CyberPower - http://www.cyberpowersystems.com/ Opti-UPS - http://www.opti-ups.com/ Powercom - http://www.powercom-usa.com/ Tripplite - http://www.tripplite.com/
More information about the UPS: http://businessweek.buyerzone.com/computers/upss/buyers_guide1.html http://www.pcguide.com/ref/power/ext/ups/
Rob Rice is a computer specialist working in Anchorage, Alaska. Rob can be contacted at articles@isp.com
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