Re: MOVs and surge suppressors

w_tom wrote:

On Aug 31, 1:57 pm, craigm <n...@xxxxxxxxxxxxxx> wrote:
A lot of words, but none respond to my comments. Sure, a whole house
protector is a good idea, but that is not viable for everyone. (Think
about apartment dwellers or those who rent their home.)

For some folks, point of use protectors may be sufficient.

Where does a 'point of use' protector make that short connection to
earth? If a plug-in protector is protection, then your post makes
sense. However the protector is not protection. It is only a
connecting device to protection. Lots of word repeatedly demonstrate
why plug-in protectors would appear to be a complete solution but
don't even claim to be protection. It only claims to be a protector..

You sure can have fun with words and say nothing.

A MOV works by limiting the voltage between two nodes of a circuit. It does
nothing else. It does not know about 'ground' or 'earth'. Devices
connected to the nodes are protected from surges greater than the
specifications of the MOV. If the device connects to 2,3, 4, or 5 nodes in
the circuit, and all nodes are protected, then the device is protected.
(Within the limitations of the protection device, of course.)



In an apartment, modify a plug-in protector to act more like an
effective 'whole house' protector. First, cut its power cord as short
as possible. Every foot on that power cord means diminished
protection. Find a wall receptacle that is electrically closest to
the breaker box - minimum number of splices, shortest distance, etc..
Plug that 'short power cord' protector into that receptacle.

This does not provide useful protection as the protected nodes are where the
protector is. Any wiring between the node to be protected and the protector
defeats the protection. (As you appear to know.)

Hopefully a breaker box earth ground exists. What makes a protector
better? Increased distance between the protector and electronics.

Absolutely false. Disctance between the protector and the protected device
allows charge to be coupled into the connecting wire. What you suggest only
applies to surgest that come from the supply side of the {house, breaker
box, whatever].

This kind of a statement needs to be qualified w.r.t. the source of the
surge for it to have meaning.


Decrease a connection length to earth ground.

A protector without earth ground does nothing sufficient. It is
only a protector - a connecting device to protection. A protector
without connection to protection does nothing useful.

"Earth" is not protection. Numerous lightening victims connected to earth
were not protected.

Protection is keeping the voltages seen by the protected device to a
minimum.

"Earth" or "ground" becomes something else in the presense of a
surge. "Ground" does not revpresen an infinite volume of zero-voltage
space. Any grounding system is limited by the impedance to some arbitrary
reference point. If lightening hits the power lines entering a structure
ground potential can rise significantly inside the structure. However is
all the devices inside the structure only see the potentials the
protections devices allow to pass, damage is minimized.

A simple analogy is ESD packaging. Devices inside a sealed ESD bag are
protected from ESD as they can not see what goes on outside the bag. A
connection to "ground" is not required for this protection.





If a 'magic box' was sufficient, then it would claim such protection
in spec sheets. Why no such claim? Why is a 'magic box' that does
not even claim to provide protection also called sufficient?

For fun with words. Cute but meaningless.

The plug-
in protector without earthing is not sufficient for anyone. The
protector is only as effective as its earth ground. Or do we know it
is protection only because it is called a protector?

.

Quantcast