Stop Power Woes
Author: Donald Dalley
Email: ddalley@idirect.com
(c) Copyright 1996, Donald Dalley
Are you willing to gamble thousands of dollars worth of computer
equipment on a $5 powerbar? We can all relate to seeing LED
clocks and the VCR blinking at us because of a power disturbance,
which barely hints at what actually occurred. If you have
seen lights dim or flicker as your air-conditioner starts running,
it is giving you a clue that lots of power has quickly drained from
the system. Similar events can happen at any time and,
without protection of the proper type, you are powerless to do
anything about electrical damage. How common are these
disturbances? A US study covering nearly 40 years quantified
what happened electrically at a "typical" location. There
were 443 disruptive or destructive power disturbances; 15 outages,
36 spikes, 128 surges and 264 sags, causing a variety of errors or
failures. There were 3 times as many power outages in
1991 as in 1972.
Do you feel safe with your computer now? Just how bad is
it for electronics, especially your computer equipment? Do
you need an uninteruptable power supply (UPS)? From my
experience, yes, and here is why. You just can not predict
when or with what force power problems will occur. After two
previous experiences with power related damage done to motherboards
of a printer and a Commodore 64, I didn't want any power problems
to affect my Amigas. I now use a standby power supply (SPS)
for an Amiga 2000, a UPS for the A4000 station, and surge
protectors for the C=64, modem and laser printer. Seriously
consider getting appropriate protection, since computer hardware is
expensive to repair and down-time could be disastrous. Amiga
stuff may be rare or nearly impossible to replace and your data
could be priceless!
Power Absolutely Corrupts
Using a UPS is better than buying insurance because the situation
is not could your computer be hit, it's how often or how severely
has it already been hit! If a circuit is near capacity, you
may be subjecting it to many under-voltages, the most frequent
problem, which could invisibly corrupt data. Over-voltages
can take their toll over time; a spike can kill your computer
immediately. These all could be from something as powerful as
a lightning strike, a motor turning on, or as innocuous as warming
up a laser printer. Many problems, except long-term power
failure, are local to your building, not from outside. I
often watch a small nearby light dim in rhythm with the heatlamp
doing its job inside the printer! So, depending on what was
just turned on, you can see the voltage drop, but chances are these
attacks will go unnoticed. The damage done may not be
apparent until later when chips, components, disks or tiny
motherboard traces finally fail.
The location of your computer has a great effect on
reliability. If you live near parks, ravines or wooded areas,
animals on overhead powerlines can be a big problem.
Industrial areas or certain floors in a big building can have
widely variable fluctuations. Power fluctuations in rural
areas are known to be more severe than the ones in cities,
too. With computer
chips using lower voltages and operating at much faster speeds,
they are increasingly more sensitive to changes in electricity.
A UPS/SPS is a battery-backed and filtered power source that
protects against various power anomalies; spikes, surges, sags
(brown-outs) and RF noise, among others, including outright power
failure (blackouts). Sags and surges can be caused by a
sudden change in demand from a device being turned on or off.
Lightning, solar radiation, or changes made by a power
utility are more reasons. The lowly surge is more dangerous
the longer or more frequent it is, not necessarily by its
magnitude, by accumulating undetected damage. Superior
SPS/UPS models have meaningful surge protection (pass ing ANSI,
IEEE and CSA/UL Category A and B tests) to dampen the size of any
over-voltage or spike to very small amounts. Figures to look for
regarding suppression are the lowest pass-through on over-voltages,
and the higher joules number. The unrated power bar you may
be using probably has little or no ability to handle spikes, let
alone typical over-voltages. Cheap powerbars may not even
have an overload reset button (similar to a fuse) or isolation
between its outlets. Only higher quality UPSes have brownout
protection, preventing some problems such as disk read/write
errors.
Another less common power problem is an outright power
loss. This could last for hours, but more than likely it will
happen only briefly. While older analog power supplies can't
handle any loss in power, most computer power supplies today have
the ability to bridge a gap of a relatively lengthy time.
Depending on quality, most standby power supplies have a power
break time of 2-10ms; an uninteruptable power supply has no break
at all and is more expensive than an SPS as a result. Total
loss of power (longer than about 10ms) not only loses your data
since the last save, but, if writing data to a disk at the time of
failure, would cause data corruption and potentially hurt the hard
drive media, or worse. Disk file systems become corrupted if
the power failure interrupts a write-to-disk operation. This
means the hard drive or floppy probably won't be recognised when
power returns. The UPS has saved me in this circumstance,
too. At the same time, as power comes back into the system,
your equipment could also be hit with a line spike!
Numbers
When buying a UPS, get one with a large enough power capacity to
keep your primary equipment (CPU, monitor and external drives)
working until you power down, which should potentially be no more
than a few minutes. An Amiga 4000 could draw 5.0 Amps
(depending upon boards, hard drives or extra RAM) when initially
turned on. This is the in-rush current, but most of
the time it will idle much lower, around 1 Amp for a 150W computer
box. An EnergyStar monitor could draw .6 Amp, to well over 2
Amps for coal- fired ones, with a 1084 drawing 1A. Then you
have to consider power used by any other externals and how long you
want to run under battery power.
Here is how you calculate your needs:
- List all equipment you need to connect to the UPS with their
Ampere and Volt ratings found on the back or bottom. You may as
well get the Watt ratings, if they are listed, too.
- Multiply the Volts (120 in North America) by the total Amp
figure to get the V-A requirements for all devices. For example, a
system with a draw of 3.3 Amps x 120 Volts = 396 V-A. If you use
220-240 Volts, cut the V-A time in half. If the power consumption
is in Watts, simply multiply Watts by 1.43 to get V-A. The V-A
duration is the main figure for choosing a UPS.
- Catalogues will list battery capacity as V-A or KV-A (1000 V-A)
with full-load and half-load durations. Half-loads will usually
extend the full-load duration by about 3 times. If you can't find
this number, UPS cases have an output (don't confuse with the input
rating) Amp and Watt rating on the back. You can compare the total
Amps or Watts to see if your estimate is
reasonable. Pick a model that has at least a 25% increase in
capability over the total V-A load. This allows longer run times
and future increased loads.
- Costs vary for battery capacity, component quality, design and
features, and customer support. Expect to pay between $120-400 for
popular models (from 200 to 650 V-A) from APC, Best, OPTI-UPS or
TRIPP-Lite brands.
Save your #%% (CPU)
In real use even small SPSes can handle more than a minimal
computer set-up, such as my A2000, 8Mb RAM card, network board, a
hardcard controlling two SCSI devices, and a 1084 monitor.
The American Power Corporation's Back-UPS 400 supports a large
inefficient monitor and my A4000 with lots of RAM, two hard drives
and a network board by supplying
only 3.3 Amps. Although this is close to its recommended
limit, the in-rush does not set off the alarm. Some laser
printer power supplies now have their own MOVs to protect against
power surges and don't need to be attached to a suppressor or
standby. My printers, external speakers and modem do not, but
they are connected through a powerbar to a separate integrated
phone/power surge protector and can recycle when the power returns.
When a dangerous power situation exists, the UPS will warn you
with an alarm. I have been using my computer for months at a
time with no indication that anything is wrong. Then, more
than once and for no obvious reason, the alarm has gone off 3-9
times within a few minutes! Damage and data loss could have
occurred with the first hit, as these were more than likely caused
by sags or surges. The lights did not flicker and neither
were any clocks blinking at me. Without the alarm, I would
never have
known there was a hit!
My computers have never been powered by a cell for an extended
time to know just how long my set-up would run on battery power,
nor do I want to be in this position. Both supplies should be
enough to keep things running for less than 10 minutes, which is a
long time to be without power.
Tips
Although a UPS can be bought in computer and chain stores, there
are specialists who can help you accurately assess your needs and
sell you power supplies that are not available from
discounters. Commonly, an SPS is mistakenly called a UPS, so
make sure you know what you are buying. Any good SPS, UPS or
surge suppressor comes with a computer equipment
replacement guarantee of some sort - higher values are better, of
course. Read and keep this guarantee! Also, find out if the
model you want allows user replacement of the battery. The
sealed battery is protected from being drained too deeply (below 10
volts), but don't leave it in a discharged state. There is
PC, Mac and UNIX (no Amiga) software for some models to
automatically shut the system down so that you don't lose data if
the battery runs out of power.
Don't tempt fate by using computers during a local electrical
storm. If power does go off, turn the power On/Off switch off
so that equipment will not be affected by a blast when the power
returns. Be careful if you plug a big monitor or laser
printer into the power outlet of the computer; you may be taxing a
low wattage computer power supply. If you transport your
computer to a different location, such as a business demo or
computer club meeting, take your protection with you! Don't
forget that there is a back-door into the computer through any
telephone or network connection; integrated phoneline surge
suppressors are readily available.
With the summer storm and air-conditioner season soon upon us,
some shocks are coming your way, but by now you know how to keep
the computer safe and protected with clean, continuous power.
Inform yourself about your purchases - use this info at your own
risk. Don't hold me responsible if you make a wrong choice
and your computer disintegrates in a cloud of
smoke.
Thanks go to Best Power Technology, Inc. of Canada
(800-356-5794), Rolf Stiefel of Power Control in King City
(905-933-4327) and North York Hydro for information and their kind
assistance. Prices and phone numbers
are Canadian.
This text may be freely reprinted only in other e-zines or computer
club newsletters. If you do so, please send me a copy of your
newsletter.
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