Plug in protectors claim to protect from one type of surge.
Do some punching. As one arm swings out, the other
withdrawals. That 1-2 punching is an example of a surge that
typically does not do damage. Now instead punch with both
left and right arms simultaneously. That is the common mode
surge that typically damages electronics.

Lightning seeks earth ground. It comes down any and all
'arms', passes through punching bag, and exits out other side
of punching bag. The plug-in protector does not stop, block,
or absorb such destructive surges. IOW it does not sit
between surge and the electronics - even though they hope you
will assume that. And effective protector connects earlier
where wires enter the building so that the 'surge down all
wires simultaneously' all find the same earth ground.

Lightning in 1752 found earth ground destructively via a
church steeple. Franklin simply gave lightning a better path
to earth. Lightning is the 'all arms moving forward at the
same time" type of surge. You don't stop, block, or filter
what miles of sky could not even stop. You 'shunt' lightning
to earth ground. That is also what the 'whole house'
protector does. It provides lightning with a short path to
earth ground.

You are surprised how small the Cutler Hammer unit is. It
need not be large because it does not stop, block, or absorb
the energy. Wire is also not massive because it too carry
massive electrical energy and does not try to stop or block
it. A surge protector is nothing more than a wire. A wire
that conducts only during the rare and short transient. It
can be small because the transient is only in microseconds.

In a parallel example, try to push a common nail into wood.
You cannot. It takes the force of a backhoe to drive that
nail. However, we hit that nail with only a 20 oz hammer.
Does the human arm have same energy as the backhoe? Of course
not. People often confuse energy with power. The hammer has
low energy but high power. Lightning has low energy but high
power. The protector need not be monstrous because 1) it does
not stop or absorb the energy, and 2) the energy is not as
massive as urban myths portray. Too many only 'feel' that a
lightning strike is high energy.

The electrical circuit is best demonstrated by an NIST
figure used in an example from:
http://www.epri-peac.com/tutorials/sol01tut.html
They demonstrate why a fax machine was damaged. Notice that
the phone line was not 'earthed' less than 10 feet to the same
single point ground as AC electric. Telephone line protector
is inside the box labeled NID.

The 'whole house' protector is located where 'Arrestor' is
labeled. Notice that the destructive surge goes through
Arrestor, then to earth ground. Since it need not pass
through fax machine to get earth ground, then an AC electric
surge does not damage fax machine.

All electronic appliances contain effective protection.
Anything that is going to work on the end of a power cord
(those grossly overpriced plug-in protectors) is already
inside electronics - as even required by industry standards.
But we worry that internal electronics protection might be
overwhelmed. So we install a 'whole house' protector on every
incoming utility wire - to same earth ground.

Demonstrated in various posts is the AC electric 'whole
house' protector (such as the Cutler Hammer), the telco
provided protector, and a ground block for cable wire (no
protector required). All are only as effective as that earth
ground.

Now about earthing. Engineered discussed this in two
discussions in the newsgroup misc.rural entitled:
Storm and Lightning damage in the country 28 Jul 2002
Lightning Nightmares!! 10 Aug 2002
http://tinyurl.com/ghgv and http://tinyurl.com/ghgm

Depending on the problem with transients, the earth ground
may need be enhanced. Important is the neighborhood history.
Also important is the geology. Does the ground tend to
attract more CG lightning? For example, mid-west storms may
be spectacular, but most of the lightning remains sky to sky.
WV is a region with high numbers of CG (cloud to ground)
strikes per thunderstorm.

Those discussions also mention equipotential which is why
Ufer grounds and halo grounds make the protector even more
effective.

Also is earth conductive or is it sand. I believe that
previous discussion also tells a story of a house struck
multiple times - and lightning rods did not work. Why?
Lightning rods were earthed poorly in non-conductive sand.
Bottom line - a surge protector is only as effective as its
earth ground. In most locations, a single ground rod may
provide massive increase in protection. A house that does not
at least meet post 1990 National Electrical Code earthing
requirements does not have the necessary earth ground.

Also in that misc.rural discussion would be how wire must be
routed. For example, no sharp bends and no splices. A ground
wire bundled with other wires may only induce more surges on
that other wire (which is but another reason why plug-in
protectors have no effective earth ground).

There is much to read. Come back with questions. The
simple earthing of surges is surprisingly not intuitively
obvious. In discussing this, I was amazed how many don't even
know what a Ben Franklin air terminal (lightning rod) does -
AND yet would recommend surge protectors. Many even argue
pointed verse blunt lighting rods - when earth ground defines
the effectiveness of that rod. A surge protector is only as
effective as its earth ground.

Milleron wrote:
tom,
I read your referenced thread with great interest. The principles were
clearly explained but some of the stuff about different types of
surges was over my head (I'm a physician whose use and knowledge of
electricity is pretty much limited to dc defibrillators).
At my newly constructed home, I employed an electrician whose business
is limited to surge protection to provide and install the whole-house
suppressor. He put in an Eaton/Cutler Hammer CHSP Ultra that comes
with a $100,000 warranty. He says he's never in his career seen a
claim against Cutler Hammer for damage occurring in spite of this
unit. I have faith in this electrician and his recommendations, but
the whole-house suppressor was MUCH smaller than what I expected from
my minuscule knowledge of electricity.
Here's my question: This unit is mounted on the side of the
circuit-breaker box, so where is it's connection to ground? It is
very clearly within ten feet of the external earthing rod, but does it
connect to this through the inside of the breaker box? Can you give
me a brief explanation, of how this thing is wired to protect all the
circuits in the house? Also, in one of your posts, you mentioned that
phones and cable do not require separate protection because they have
built-in surge suppression, and, yet, my guy installed a companion
module (on the whole-house suppressor) for cable (not phone)
connections. Is that superfluous?

Thanks for all the time you take to provide us with these
explanations. They're great.