From TNPC issue #4.02...

Electricity, Rolling Blackouts, and Computers

by T.J. Lee
January 25, 2001

California is in the grip of record power shortages and Stage Three crisis warnings. Lee Hudspeth and I are both carrying extra Micro-Lights around with us and have insisted our kids and spouses have one handy at all times in case the lights suddenly go out! Usually we talk about electrical problems and computers in the spring here in the Northern Hemisphere since that is when we experience electrical storms around the U.S., but since the rolling blackouts have us all thinking about power let's cover the basics in this issue.

You have to protect your system from three power conditions. The first is too much power coming out of the wall (i.e., power surges). The second is too little power, known as a "sag." We don't often think about low power but a sag can make your computer suddenly reboot itself, making you think there's a ghost in the machine. The lights may not flicker and the radio keeps playing but a sag can cause a spontaneous reboot. Last is line noise. The solution to these three power condition risks is: the right hardware.

For most home users the first line of electrical defense is a "surge protector." This is usually a power strip into which you plug a CPU, monitor, printer, speakers, and maybe a desk lamp. Someone in this scenario typically sets up the system, plugs everything in, and promptly forgets about it until an electrical problem arises.

Two problems right off the bat with this approach. First is the practice of plugging in as many pieces of equipment as there are outlets on the strip. This almost always places too much load on the wattage rating of the strip, which is drawing all its power from a single outlet, which means a single circuit in your house. The second problem is that surge strips use metal-oxide varistors (MOVs) to connect the hot side of the circuit to the ground side. At normal voltages MOVs don't conduct electricity but when a surge of power hits them they conduct and shunt the load to the ground. This method of protection assumes your outlet is properly grounded. It's not a bad idea to examine the plugs you use for your electronic equipment--computers, stereo, big screen TV, etc.--and make sure they're properly grounded. The problem with MOV technology is that not only are they only good against relatively low power spikes (in the 5-6 kiloamp range), MOVs deteriorate over time due to the minor fluctuations in day to day power coming out of the wall. There's no way to look at a surge suppressor and tell if the MOVs are working. Even if the MOVs are working they won't do anything to protect you from sags or line noise.

Your best bet to deal with surges, sags, and line noise is to hook your equipment up to an uninterruptible power supply (UPS).

Most people think that a UPS is primarily used as a power backup to keep your computer running when the lights go out. That's a nice feature but really secondary to its power conditioning abilities. The battery will only run your system for a short time, usually measured in minutes, just enough time to save your files and shut down your system.

A UPS takes the power coming out of your wall and uses it to keep an internal battery charged. The battery provides the electricity that actually powers your computer. This ensures a steady, even flow of electricity filtering out line noise and providing protection from surges and sags. UPS devices can protect against surges in the 50-500 kiloamp range (which is what you can get if lightning strikes a power pole near you).

A nice benefit of the higher end models is that they come with software that will monitor your Windows computer and in the event that the power goes out and no one is at the keyboard it tells Windows to Shut Down. Lee reviewed several UPS models in TNPC #2.24:
http://www.TheNakedPC.com/t/402/tr.cgi?roll1

Like the power strip it's important to get a UPS with enough umph to power the equipment you'll be plugging into it. If you have our book T.J. Lee and Lee Hudspeth's Absolute Beginner's Guide to PC Upgrades check chapter 10, "Adding Power Protection," for a discussion on how to calculate your requirements and the steps for installing a UPS on your system.

If you're concerned about the power going out due to electrical storms, planned rolling blackouts as we're having in California, or other causes don't just rely on your UPS and go merrily on your way. If there's a good possibility that your power will go out be sure to shut down your computer and turn it off. Shut the UPS down as well and as an added precaution unplug the UPS from the wall outlet. If you're working on your computer and the power suddenly goes out an alarm on the UPS will sound and you should close your programs, shut down your computer, shut down the UPS, then unplug the UPS from the outlet.

Unplugging is important because when power is restored the power company boosts the amperage because of the load on the grid caused by all the appliances that were left on when the power stopped. It takes a boost to get them all running again so they spike the power. While your UPS can protect your equipment from a surge, the spike will not do your UPS any good and since you know it's coming so you should unplug it. Research any UPS you may purchase carefully. A UPS may have seven outlets but it's better than even money that some of those outlets will not be conditioned power from the battery but only protected via MOVs. For example, on my main UPS there are 7 outlets but only 4 offer battery power. The other 3 are MOV surge protected only.

Finally, be aware of all the entry points into your computer. You can unplug your computer from the wall only to have your motherboard get fried because of a lightning strike to your telephone line, right into your modem and into your motherboard. You can get surge suppressors for your phone lines as well and it's well worth considering (many UPS models include this as a built-in feature). If you have more than one computer connected by a network be mindful that a surge hitting one unprotected machine can conceivably run through your network and affect other systems. Be wary of any entry point where a conductive cable is plugged into your computer.

You can reach T.J. Lee at:
mailto:tj_lee@TheNakedPC.com

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