Copyright (C) 1994, 1995 L.F. Polk

           Surge protector secrets
        you're not supposed to know...

     Everyone knows that a surge protector is
necessary.  It's sort of an afterthought when buying
a computer, stereo, industrial control panel, or any
other expensive electronics.

     Most give little thought to it's purchase,
simply buying whatever the salesman happens to be
pushing.  Many times it's only $20.  Other times you
are steered to a $129 protector.  And you see all
kinds of "connected-equipment" guarantees.  And all
kinds of claims about surge and spike performance.

     What's really going on?   Sit back and buckle
up.

     You're not going to believe what a scam most of
these products are. Virtually all of them are
designed incorrectly.  That's right.  I said
designed incorrectly.

     But first you need to understand that spikes,
those very brief voltages that may go up into the
hundreds or thousands of volts will slowly degrade
all the solid state devices they hit.  If they're
strong enough they can destroy solid state devices.
Weaker ones degrade the junctions within
semiconductors.  And these spikes can contaminate
your data.  They frequently cause unexplained
problems that no one can figure out.  They're
especially hard on networks.

     There are two completely different schools of
thought on power protection.

             Parallel vs. Series

     Parallel just means that the protection devices
are placed across the wires.  They're connected hot
to neutral, hot to ground, and neutral to ground.
If there is a spike over a couple of hundred volts,
these devices divert it to ground where they claim
it does no harm.

     Ground means some point on the ground circuit.
This is where the problem begins.

     Many people erroneously think that ground is
ground.  It is if you're talking about DC or 60 Hz
AC.  But it isn't to a spike.  Spikes contain high
frequency components which can create voltage
differences on a ground wire.  In other words, the
spike can travel through the ground wire and enter
your electronic equipment.

     Why are surge protectors designed this way?
Simple.  It's cheap.  The most common item used in a
parallel type surge protector is an MOV.  That
stands for Metal Oxide Varistor.  These essentially
act as a short to high voltages.

     They are connected as mentioned above.  Across
the wires.  So if you get a spike in the hot wire,
the MOV conducts and dumps it onto the ground wire
where it travels unimpeded into your electronics.
They didn't tell you this, did they?

     There are other parallel devices that act
similarly such as the gas discharge tube,
transzorbs, and others.  Same story.  The spike gets
dumped onto the ground wire and travels directly
into your electronics.

     Wait, there's more.  All parallel type devices
have a delay time before they act.  That's not good.

     Still more:  MOV's, the most common parallel
device used in these surge protectors, degrade
fairly quickly.  Each spike they dump to ground
degrades them.  After a while they don't do anything
except possibly catch on fire. That's right, there
are many cases of MOV's catching on fire and
destroying themselves.  And in some cases MOV's
explode and destroy the whole surge protector unit.

     Many of the higher priced parallel type surge
protectors do contain small coils that are, in fact,
in series with the hot wire.  But these do virtually
nothing to slow down a spike.  Their primary
function is to block radio frequency interference
from coming into your electronics via the hot wire.
They do this nicely, but do virtually nothing to
attenuate a spike. So don't be confused if you look
inside one of these parallel type surge suppressors
and see some small coils.

     Same with any capacitors you may see.  They're
in there for radio frequency interference
suppression, not spike suppression.

     It gets even worse if you have a network.
Networks usually use ground as a voltage reference
for a 5 volt signal.  These parallel type surge
suppressors dump a several hundred to several
thousand volt spike onto your network voltage
reference.  Can you imagine what this does to your
data?

             What should you do?

     Don't buy a parallel type surge suppressor.

     How do you find out?  Just ask if it contains
MOV's.  If the salesman doesn't know, look inside.
They are disks about an inch in diameter, about an
1/8 inch thick, with 2 wires sticking out the bottom
of the disk.  You can't miss them.

     MOV's cost about 25 cents at the Original
Equipment Manufacturer level. No wonder they love
them.

                "But they have a
          connected-equipment guarantee."

     So what.  You have to let your computer be
destroyed to collect on their guarantee.  What does
down-time cost you?  Do they compensate you for
down-time?  Of course not.  So a $129 surge
protector with a connected-equipment guarantee could
end up costing you thousands in downtime.

     Even if it's a home computer, the time and data
you can lose will cost you far more than the cost of
a properly designed surge protector.

             So what's the solution.

     The best solution would be to stop the spikes
before they get into your equipment.  You certainly
don't want to dump them onto the ground which is
hard-wired to your equipment (as required by code).

     This is where series type devices come in.

     What is a series type device?  It works
oppositely from the parallel type devices.  Remember
that parallel type devices go across the wires. From
hot to ground, for example.

     Series type devices are inserted "between" the
hot wire coming from the wall outlet and the hot
wire going into your electronics.  In other words,
the electricity has to travel "through" the series
type device to get to the computer.

     The oldest series protection device is the
ferro-resonant transformer. It's been around for
years and does a wonderful job stopping spikes and
radio frequency interference.

     Ferro-resonant transformers work.  But they
have a few drawbacks.  They are quite expensive.
You're looking at $hundreds to over a $thousand for
the sizes that would handle a computer to one that
would handle a computer with a laser printer.  They
generate a lot of heat which also means they waste
electricity.  They have an audible hum which is
quite annoying.  (Sort of like a noisy fluorescent
light.)  And lastly, they have a fairly high output
impedance which computer switch-mode power supplies
don't particularly like.

     What about the surge protection built into
uninterruptible power supplies?  I'm talking about
the common standby type that kick on the inverter
within milliseconds after a power failure.  This is
the most common type of UPS used on small computers.
As long as there is power coming from the wall
outlet, these standby UPS' are off.  When they are
off, they are functionally equivalent to a parallel
surge protector.

     So we've still got the same problem with almost
every standby UPS on the market.  The same 25 cent
MOV's are used.   The few that don't use MOV's use
ferro-resonant transformers and are expensive and
have all the ferro-resonant transformer drawbacks.

              So what do you do?

     Luckily, a few years back, a small company
developed a series type surge protector that's light
weight, small, quiet, cool, and priced not much
higher than the better parallel type surge
protectors but lower than the expensive
ferroresonant transformers.

     It contains no MOV's or other parallel devices.

     So there is nothing to degrade in it.

     And there's nothing in it that could dump the
spike onto the ground where it could zip right into
your equipment.

     But how did it's designers handle the spike?
This is the most interesting part:  The unit absorbs
the spike.  Then it very slowly and harmlessly
bleeds the energy from the spike into the neutral
wire, not the ground wire.

     Slowly bleeding the energy into the neutral
wire was a stroke of genius. The neutral goes into
your computer's power supply and the power supply
doesn't even flinch from this small bleed of energy.

     Let me give you an analogy.

     Let's say you have a vegetable garden with a
number of small plants in it.  You're watering the
plants with a hose with light water flow.  All of a
sudden the is a tremendous surge of high pressure
water through the hose and it destroys your small
vegetable plants.  Knocks them right out of the
ground.

     That's a spike.  The high pressure burst of
water is analogous to a high voltage spike.

     Now put a bucket between the plants and the
hose.  The bucket has a small hole in it.  You put
water into the bucket at any flow rate you want but
the water hitting the plants is controlled by the
small hole.  The bucket is in series with the water
flow.  The water has to go "through" the bucket to
get to the plants.  If there is a water surge in the
hose, the plants won't know it.  It will just
temporarily raise the water level in the bucket.
This will temporarily increase the water flow to the
plants through the small hole, but barely
noticeably.

     No damage whatsoever to the small plants.

     No damage whatsoever to your electronics.

                   Common Mode

     What we've just looked at is called Normal Mode
protection.  Normal mode is a spike that occurs
between the hot and neutral. It's called Normal mode
because this is the normal way spikes appear --
between the hot and neutral.

                 But what about
             Common Mode protection?

     Common-mode spikes are "created" by parallel-
type surge protectors.  Common mode spikes are
different.

     Common mode is a spike between the neutral and
ground -- the white and green (or bare) wires.  This
is called common mode because the neutral and ground
have a common point.  This common point is where
they are physically tied together at the breaker
panel.

     Normal mode is the only way a spike can get
into your building from the outside.

     Outside your building, neutral and ground are
the same wire.  And the ground/neutral outside the
building is grounded to the earth both at the pole
and at your building.  If you have overhead wires
from the pole, it's the bare wire.

     The further from the breaker panel, the more
impedance in the ground and neutral wires.  Thus the
further you get from the breaker panel, the higher
the voltage spike that can be generated between the
neutral and ground.

     They're supposed to be at the same potential,
but the further from the breaker panel, the easier
it is to impress a voltage spike between neutral and
ground.

     The closer to the breaker panel, the more
difficult it would be to generate a spike between
the neutral and ground.  Remember, neutral and
ground are physically tied together at the breaker
panel.  A spike between neutral and ground is a
common mode spike.  Common because the two wires
have the "common" point at the breaker panel.

     Again, normal mode spikes are between hot and
neutral.  This is the only way a spike can get into
the building from the outside.

     A common mode spike is between neutral and
ground.  Since neutral and ground are the same wire
outside the building, a common mode spike cannot be
generated outside the building.  All common mode
spikes have to be "created" inside the building.

     So you only have to protect for normal mode
spikes unless "you" do something inside the building
to put a spike between the neutral and ground at
some point downstream from the breaker panel.  A
voltage spike between the neutral and ground is
called a common mode spike.  Remember, common mode
spikes have to be created inside the building.

     Common mode spikes are caused by parallel type
surge protectors.  That's right!  The MOV's, gas
discharge tubes, transzorbs, and other parallel
surge protector devices in all parallel surge
suppressors actually cause common mode spikes.
That's why some feel it's better to have no surge
suppressor than to have any surge suppressor with
parallel devices.  Unbelievable, but true.

     The branch circuit from the breaker panel that
feeds a computer should contain absolutely no
parallel type surge devices as these can create
common mode spikes.

     One more point about common mode spikes.
Computers are inherently capable of handling common
mode spikes of moderate intensity.  So not only is
this not a real-world problem, but even if there
were a modest common mode spike, the computer would
handle it by itself without problems.

                     UPS
         (Uninterruptible Power Supply)

     If you use a UPS, it should be in the circuit
downstream from the series type surge protector.
Some even feel that its parallel devices (MOV's,
etc.) should be physically removed.

            Telephone Line Protectors

     What about telephone line protectors?  The
phone line is inherently a high impedance circuit to
spikes and is protected at the interface box to 300
volts.  Phone line protectors that plug into a wall
outlet either directly or with a cord are parallel
type protectors.  These put spikes onto the ground
where they travel right into your computer or they
upset the ground reference on a network.  In other
words, grounded telephone line protectors create
common mode spikes.

              Conventional Wisdom

     I'm sorry if I'm upsetting the conventional
wisdom apple cart, but this is reality. The sales
departments of the parallel type surge suppressor
manufacturers have no knowledge of this (based on
our discussions with them). And they don't want to.
Why would they want to learn something which if
implemented would decrease their profitability?

             Advertising Half-Truths

     At least one of the parallel (shunt) type
manufacturers has resorted to calling their units
dual-mode, implying that they have series and
parallel protection.

     There are two problems with this.  The first is
that they don't have true series protection and the
second is that you don't want parallel protection.

     In other words, you don't want dual-mode.  You
want single mode -- series.

     What they do have is EMI and RFI filters.  Some
of the components of these EMI RFI filters are in
series.  But this is not series mode spike
protection.  Don't be fooled by these tactics.

     Another misleading sales pitch is 3-modes-of-
protection.  This is nothing but three 25 cent MOVs
across the 3 sets of wires. Hot to Ground, Hot to
Common, and Common to Ground.  Sure does sound
impressive though.

                   Confusion

     After reading all the literature from all the
surge protection manufacturers, it's easy to get
confused.  The most likely result is for one to give
up and simply buy a protection device based upon
price alone and say, "Oh, I just have one computer
and I'm sure this is good enough for me."  This is
exactly what their advertising gimmicks are designed
to do.  Don't fall for it.

                 Don't Rely on
               "Consumer Reports"

     Consumer Reports said, "And computer hard
drives sometimes sustained damage from a spike
reaching them via an apparently undamaged
suppressor."

     They were referring to parallel surge
protectors.  They offered no explanation.  The
explanation is obvious:  The spike used the parallel
protection device such as an MOV to contaminate the
ground.  So the spike easily entered the computer
via the ground wire.

     Consumer Reports also said, "Most suppressors
have circuitry to absorb surges between any pair of
the three wires in an electrical circuit -- the
ground wire, the "hot" or line wire, and the neutral
wire, which can be paired three ways."

     Consumer Reports is parroting the old disproven
theory that 3 MOVs should be used.  We now know that
this approach is the cause of surges entering your
equipment.

     The parallel devices don't absorb much of a
large surge. They can't. They're physically too
small.  Sure, they absorb what they can.  But if the
energy surge exceeds their capacity, then they get
hot rather quickly.  We have photographs of burnt
and exploded MOVs.  While this is happening, much of
the energy is passed through to the other conductor
and into your equipment.


          "Surges are only 2% of the problem.
            You need a UPS. And it comes with
              built-in surge protection at
                 no extra charge and at a
                   cost less than surge
                     protection alone."

     This is a very crafty marketing technique used
by some manufacturers.  What they are really doing
is trying to minimize the importance of surge
protection in your mind since their surge protection
is inferior (25 cent MOVs).

     But it's the surges, not power failures, that
destroy equipment.

     If you need a UPS due to an unreliable power
company, then buy an inexpensive UPS and put it in
the circuit after a high quality series-mode surge
protector. This way, both the UPS and your equipment
will be protected from surges.


                      Think RF

     Anytime you're thinking about spikes or
lightning, you have to think in terms of radio
frequencies, not DC.  Ham radio operators fully
understand that at radio frequencies, what you think
is ground isn't necessarily ground.


           More Information Available

     If you'd like some information, just send me
your postal mailing address and I'll have some info
mailed to you by postal mail.

America Online: LF Polk
Internet: LFPolk@aol.com

Copyright (C) 1994, 1995 L.F. Polk
