diskMAGazine (Sep 1991) : SurgeSupressors

Surge Suppressors:  Worse than Useless? 
by Andy Baird

This article originally appeared in the June 1990 issue of the Princeton
Macintosh Users' Group newsletter, and is copyright 1990 by Andy Baird.  It
may be reprinted in substantially unedited form by other nonprofit
publications provided this notice remains intact.  I found it in the July
1991 issue of NAG RAG, newsletter of the Northwest Amiga Group of Oregon.

Jolted out of my early morning sleep by the deafening buzz of an electrical
arc, I knew at once something was badly wrong.  I lunged toward the sound,
which came from beneath my computer desk, taking in the ominous blue-white
glare from my surge suppressor, and the cloud of black soot staining the
wall behind it.  As I ripped the computer's plug from the outlet, the arc
died and an evil smell filled the room.
    After my heart had stopped pounding, I examined the remains of my surge
suppressor.  Looking at the charred interior of the case, I shuddered.  If
it had been made of plastic instead of steel, there probably would have
been a fire.  The MOVs (Metal Oxide Varistors) had been literally blown
apart by the force of the surge; then, like a welder's rod, had arced
across the bare wire leads.
    I thanked by lucky stars that the MOVs had done their job and saved my
computer, while wondering whether there wasn't a better way to protect
equipment -- a way that did not involve an explosive failure of the
components that did the protecting.
    I thought about a couple of years back, when my Hayes SmartModem had
died during a thunderstorm along with a couple of chips on my computer's
motherboard.  I had surge protection on the computer, but none on the
telephone line.  [The phone companies generally place lightning arrestors
every quarter-mile along their line.  They do not eliminate all of the
surge, however.]  When lightening struck nearby, a spike came up the phone
line, fried the modem, then continued up the serial cable to kill the line
driver chips in my computer.  After that experience, I added a surge
suppressor on my phone line, so I was completely protected.

Or So I Thought at the Time
Now I know that I was wrong. In fact, I now realize that the modem was
probably killed by the surge suppressor.  The MOVs which were supposed to
protect my computer, had done their job by shunting an incoming power line
surge onto the ground conductor -- the same ground used by the modem as a
signal ground reference.  The result was a few thousand volts across the
modem's inputs -- and a dead modem.

Everything that You Know is Wrong
I want to make three points.  First, if your surge suppressor is more than
a year old, it is probably not protecting your equipment.  The MOVs have
degraded to the point of uselessness and there is no practical way you can
test them.  Second, even if it is brand new or uses expensive TransZorb
devices instead of MOVs, it is designed to dump surge energy to the ground
connector used as a reference by your modem, network connector, or other
serial device.  Thus your peripherals or other networked computers are
endangered, even if your own computer is protected.  Third, there is a new
device which will protect yor equipment from ten to twenty yreas without
endangering it.  Before I tackle these points and try to convince you that
the conventional wisdom about surge suppressors is wrong, let me tell you
where I am getting my information.

NIST Studies
The National Institute of Standards and Technology (NIST), Washington, DC,
has a section devoted to the study of power line surges.  The head of this
group, Francois Martzloff, has been studying surges and other transient
electrical phenomena for many years, resulting in ANSI/IEEE standards
(C632.41-1980) defining commonly encountered spikes and surges.  Recently,
surges were artificially induced into the power wiring of an industrial
building and got an unexpected result:  Suppressor unprotected computers
were undamaged but serial printers connected to them were damaged by surges
on the data input lines -- not the power lines.
    Where did the surges come from?  Martzloff and his colleagues finally
concluded that the data line spikes had been created when the computers'
surge suppressors shunted the excess electrical energy to the common ground
conductor.  The printers had been killed by the surge suppressors

MOVs Are Not the Answer
Interestingly, the NIST team was not the first to arrive at this
conclusion.  A small New Jersey company, Zero Surge, Inc., was founded not
long before by two engineers who set out to build a power conditioning
device which would not dump excess energy to ground.  We'll talk about this
later but back to my three main points.
    First, a look at GE's MOV Design Manual discloses some interesting
facts.  One, MOVs do not respond to a voltage spike for 10 to 40
nanoseconds (a nanosecond is one-billionth of a second.)  That may sound
fast but according to the IEEE standard, the typical spike has a rise time
of five nanoseconds.  This means that the MOVs cannot react fast enough to
stop the most common electrical spikes.  The IEEE standard says that these
can be expected many times a week in an average building!
    Second, MOVs wear out.  Every little jolt shortens the lifetime of a
MOV.  Finally, it fails to provide any protection.  Those little jolts
include the "many times a week" spikes described in the IEEE standard.  The
industry journal LAN Times (May 1990) says: "If your surge protectors have
been in use for a while (six months is reasonable), the MOVs may be
incapable of proper performance.  Moreover, as it ages, the MOV's clamping
voltage decreases and it may begin a process called thermal runaway, which
has resulted in fire."  (Remember, I spent a long time scrubbing soot off
my walls after the surge suppressor burned.)  A dead MOV or one which has
deteriorated to the point where it offers no protection can only be
detected with expensive, sophisticated test gear.  That ten cent LED which
glows so reassuringly on your surge suppressor may make a good night light,
but it tells little or nothing about whether your MOVs are doing their job.
 I've been shown several commercial surge suppressors (a Kensington
MasterPiece included) which appeared fully functional but provided no
protection whatsoever!
    In short, MOVs provide inadequate protection; they wear out; and they
fail without warning; and they can pose a fire hazard.

What About TransZorbs
I've always figured that I was extra safe, because my computer was plugged
into an expensive power strip using TransZorbs instead of MOVs.  TransZorbs
(avalanche diodes) are semiconductor devices which respond faster than MOVs
and don't degrade with time.  However, I've discovered that they have
another problem: when a really big surge hits, they fail "open", so they
can't divert the surge voltage just when they're needed most.
    But that's minor.  The real problem is this: Just about all presently
available surge suppressors, whether they use MOVs or TransZorbs, are wired
to divert, or shunt, energy to ground.  As the NIST researchers found, this
almost guarantees contamination of data lines, resulting in garbled data at
best and fried equipment at worst....

But I have a UPS
Some people may think they are protected by use of UPS (uninterruptable
power supply) equipment, which by definition is a 100% battery fed system.
[Most UPS systems swithch in the battery only after loss of primary power.
 This switch can cause another spike in the computer's power supply
voltage]  But not only are UPS's quite expensive, their inputs are
protected by the same fifteen-cent MOVs the average surge suppressor uses.
(The single exception, Abacus Controls, use licensed technology from Zero

Zero Surge
So how can you protect your expensive computer equipment?  The LAN Times
has this to say: "The ideal surge protector would be a circuit that
presents a high impedance to the surge and a low impedance to the normal
power wave, while protecting the integrity of the ground circuit.  It
should also contain no degrading components like MOVs." such exist; they
are made by Zero Surge, Inc.
    If I tell you that the Zero Surge units appear to by the only ones on
the market which work properly, you have a right to be skeptical.  After
all, the power conditioning business is full of snake oil salesmen, each
claiming that he has the only product worth buying.
    Well, I don't blame you.  I was certainly skeptical, but after reading
articles in LAN Times, PC Week, and Power Quality magazines and talking
with electrical engineers, I believe the Zero Surge protectors are the only
ones which 1) will adequately protect equipment and 2) won't contaminate
data lines by dumping surges onto the ground circuit ....
    Zero Surge makes two sizes of surge interceptors, a 7.5 Amp model (list
$149.00), which is right for those of us who don't have laser printers; and
a 15 Amp model (list $199.00) for those who do.  The 15 Amp unit is offered
at $169.00 to user group members.  [It is unclear what user group is meant
here -ed.]  (You won't be surprised to hear that I bought one.)  Their
phone number is 201 766-4220 [FAX 201 766-4144].  Don't hesitate to call
President Wendell Laidley if you have questions.