They are called shunt mode protectors. They work by earthing a
destructive transient such as a direct lighting strike and then remain
functional. If a 'whole house' protector could not earth that
transient, then what good willl a plug-in protector do trying to earth
to the same ground?

So instead some assume plug-in protectors sit between the surge and
an appliance to block or stop surges. Bull. Will that silly little
less than one inch component stop what 3 miles of sky could not?
Effective protection was never about stopping or absorbing surges.
Effective protection is about diverting - shunting - a destructive
transient to earth. Divert - not stop or absorb.

Protector amperage is additive IF all protectors have a same 'low
impedance' connection. And that is the problem. Things such as sharp
wire bends, long distances, splices, etc all increase that wire
impedance. Now a plug-in protector has too much impedance. Instead of
seeking earth via safety ground wire, that transient may seek earth
through an adjacent appliance and phone line. This is how modems are
so easily damaged. Incoming on AC electric. Through an adjacent
protector. Into comptuer motherboard and modem. Out to earth ground
via phone line. Notice where most modem destructive transients come
from.

Having learned this by tracing destructive surges, then what is a
most typically damaged component? The path through adjacent protector,
through modem (its DAA section), is often via a transistor that drives
an off-hook relay. The failure message is "No Dialtone Detected".
Incoming on AC. Through that transistor and off-hook relay. To earth,
destructively, via phone line and phone line surge protector.

Why did damage result? A transient was not earthed BEFORE it could
enter the building.

A surge protector basically shunts - connects all wires together
during a transient. If that wire makes a low impedance connection to
earth, then the transient is earthed. No damage. But plug-in
protectors don't have a good earthing connection. Above is one
example; demonstrated by tracing surges and replacing transistor. A
protector too close to transistors and too far from earth ground can
even contribute to damage of the adjacent (and powered off) appliance.
An effective protector makes a 'less than 10 foot' connection to the
building's earth ground.

Ineffective protectors (power strip and UPS) are easily identified.
1) No dedicated earthing wire. 2) Manufacturer does not even discuss
earthing. Look at your protector. Does it meet these criteria for
ineffective protector?

What does a telephone company do to protect their $multimillion
switching computer? Its computer connects to overhead wires everywhere
in town. Why do they not provide service for a whole week while
replacing that computer? Because the telco installs 'whole house' type
protectors on every single wire of every cable that enters the
building. Tehcnology even discussed in an Oct 1960 Bell System
Technical Journal article - because the technology is that old and that
well proven. An effective protector is ideally 50 meters from
transistors AND as close as possible to earth ground. That 50 meter
separation adds to protection. But most important is what makes that
'whole house' type protectors effective. A low impedance - meaning
short - connection to a building's single point *earth ground*. Not
only is the connection short. Every protector is earthed to a same
ground - the single point earth ground.

For residential protection, manufacturers with responsible brand
names provide effective 'whole house' protectors. Siemens,
Cutler-Hammer, Square D, Leviton, Intermatic, and GE all sell 'whole
house' protectors that are available in Home Depot, Lowes, and
electrical supply houses. These protectors have a dedicated earthing
wire. These protectors costs tens of times less money per protected
appliance. And these protectors are properly sized.

Why properly sized? Many plug-in protectors are so grossly
undersized (MOVs undersized; too few joules) as to vaporize during a
surge. Vaporized MOV provided ineffective protection. But its smoke
promotes more sales. Effective protectors, instead, earth direct
lightning strikes and remain functional. A human never knows that when
a properly sized protector is doing protection. Grossly undersized
plug-in protectors that vaporize and smoke will be recommended by the
naive. So many plug-in protectors are undersized - to promote sales
rather than provide effective protection.

Earthing - at minimum, the building must conform to post 1990
National Electrical Code earthing. Enhanced earthing means a protector
will be even more effective. And so we say, "a protector is only as
effective as its earth ground." What do those plug-in power strip and
UPS protectors manufacturers not even discuss? Earthing. Where is
that dedicated earthing wire? Did they just forget? Or do they hope
you never learn why earthing is so essential?

Some incoming wires are earthed using a protector. Telco provides a
'whole house' protector where their wire enters your building. But
again, that protector will only be as effective as its earth ground.
Did you (or your builder) provide that essential earthing connection?
Cable needs no protector. Its ground block must connect directly to
the same earth ground - a 'less than 10 foot' connection. Every
incoming wire must be earthed directly or through a 'whole house'
protectors to the single point earth ground.

Ineffective protector manufactures and those who promote them hope
you never learn what a shunt mode protector does: makes a low impedance
connection to earth. No earth ground means no effective protection.
So where is that earthing connection in a plug-in UPS? Notice that
their own numerical specifications don't even define protection? How's
that for a damning overlooked fact.

Appliances already contain internal protection. Protection that can
be overwhelmed if destructive transients are not earthed where wires
enter the building. Earthing is why 'whole house' protectors are so
effective. No earth ground (such as with plug-in protectors) means no
effective protection.

If you don't earth incoming transients such as the direct lighting
strike, then protection inside that appliance can be overwhelmed;
appliance damaged. Plug-in protectors can even provide more
destructive paths through an adjacent appliance.

Pete C. wrote:
" wrote:
...
A WHOLE HOUSE surge protector is better, and probably more reliiable
and costs less than a bunch strewn all around the house

The clamping capacity (Amps) of the surge suppressers will be additive
(no, not perfectly additive, but still increasing protection) so more
will be able to clamp bigger surges. A surge suppresser at the main
panel is best since it can clamp a surge before it gets further into the
homes wiring. Additional surge suppressers further down the line,
whether the little blocks or power strips with suppressers built in will
just add an additional line of defense.

The surge suppressers that install at the service entrance panel are
generally higher quality and capacity and more likely to use multiple
technologies like MOVs and gas discharge arrestors. Nearly all the small
plug in suppressers just use inexpensive MOVs.

A decent UPS is a must for computers and any other expensive items like
big plasma / LCD TVs, etc. UPSes used to be expensive, but they are now
quite reasonably priced for decent units. One thing to watch out for is
surge suppressers on the output of a UPS. Since suppressers work by
creating a short circuit across the line (briefly) they can damage a
UPSes inverter if a surge gets through and they clamp. Some cheaper
UPSes may generate small HV spikes that could trigger the suppresser as
well and again damage the UPS output.

Nothing will protect against a direct strike on the power line near your
house, so if that happens you'll have a big insurance claim no matter
what. The suppressers might help clamp things enough to lessen the
damage though.

Inductive pickup of nearby lightning strikes is also an issue and long
wires like phone, network and CATV lines can pickup significant surges
that way. Good suppressers on those lines along with good grounds will
help.

Pete C.