On May 6, 10:54 am, Jitt wrote:
I suppose I phrased the question badly. I wonder why a surge
would wander around looking for ground, when its available
in the box!

If all grounds are same, then connect lightning rods into a
motherboard ground. That would be perfect building protection because
a lightning rod is grounded?

Ground inside a stereo is different from ground inside a TV is
different from ground on the computer case is different from ground on
a wall receptacle is different from ground inside a cell phone is
different from a ground inside a breaker box is different from ground
in earth. Most all those grounds are interconnected and are still not
the same ground.

Electricity is different at both ends of a wire. That 100 amp surge
seeking earth from a wall receptacle may leave the wall receptacles at
12,000 volts - again, due to wire impedance. That plug-in protector
on Page 42 Figure 8 was so far from earth ground (via AC electric
wire) as to be 8000 volts - a destructive path via an adjacent TV to
earth.

The EE Times article entitled "Protecting Electrical Devices from
Lightning Transients" defines why a ground in a box is not a ground to
surges. Why electricity at both ends of a wire is always different.
Why that difference during a surge is so important that an effective
protection makes a 'less than 10 foot' connection to earth. Only
relevant 'ground' is the one that is ground to a surge. That is not
an 'inside the box' ground.

Typically destructive surges are an electrical connection from a
cloud to earthborne charges maybe miles away - the relevant ground.
If any part of that connection is via an appliance, then the appliance
may be damaged. Surge protection has always been about diverting a
connection from cloud to earthborne charges so that current need not
pass inside the building.

A protector is only as effective as its earth ground so that surges
need not enter a building. No earth ground means no effective
protection; means a surge creates connections to earth destructively
inside a building. Any facility that installs effective protection
does earthing connected, very short, via a 'whole house' type
protector.

Polyphaser makes a protector that has NO earth ground connection.
Earthing is so critical that their protector mounts directly ON the
earthing electrode - zero feet from earth ground. Distance to earth
ground is critical for effective protection. Which ground? Earth
ground is not found and not provide in three wire AC wall
receptacles. That is a safety ground.