Re: MOVs and surge suppressors

w_tom wrote:

On Aug 30, 9:16 pm, craigm <n...@xxxxxxxxxxxxxx> wrote:
If the device has a 2 wire cord, no ground, and no other connections, is
a earth ground really necessary for protection of that device? A point of
use surge protector will limit the voltage going to the device. (The key
is that there are no other electrical connections to the device.)
Relative to ground, the device may see a large change, but since nothing
on the device is referenced to ground, the device see no destructive
voltages. (Any capacitative coupling is taken as insignificant in this
case.)

Ben Franklin's lightning was also finding earth ground via
something non-conductive - wooden church steeple. That same problem
exists inside a home. Things such as some wall paints, and linoleum
and concrete floors are even better conductors.

Why can a static electric discharge occur? Electric path is down an
arm, through something on the table top, and somehow into the rug to
charges beneath feet. How many of those items are wires? The house
is chock full of conductive items when we discuss surges.

Once permitted inside a building, then the surge will find numerous
paths to earth. Those many paths also explain why one appliance is
damaged while an adjacent appliance is unharmed.

Do we locate every conductive path in a room and conductive
materials inside walls? No. To create equipotential in one room, then
carefully integrate walls, floors, air ducts, and pipes all into the
protection system. No one will or is expected to do all that -
especially when one 'whole house' protector makes all that work for
every room unnecessary.

Make everything in the building equipotential. Create equipotential
by using earth beneath the building. Now all conductive materials in
the building are at near same voltages - no surge currents flow. Now
protection inside all appliances is not overwhelmed.

Yes, devices with multiple utility connections (portable phone base
station, cable modem, answering machine, dishwasher) are at greater
risk. Makes no difference if power cord is two wire or three wire (or
only one wire because switch is open). Anything that would protect on
that power cord is already inside those appliances. So that
protection inside all appliances is not overwhelmed, spend less money
for significantly superior protection. Earth one 'whole house'
protector, or earth cable TV and satellite dish wires using no
protector. Significantly better protection for tens of times less
money per appliance.

A surge approaching on a black wire is distributed to white and
green wires by an adjacent plug-in protector. Surge on all (two or
three) wires is still seeking earth ground. Incoming on AC electric
black wire, given more paths into stereo on black and white wires by
an adjacent protector, then out to earth ground via speaker wire
touching baseboard heater. Another example of damage because the
surge was permitted inside a building. The adjacent protector simply
gave that surge more wires to find earth ground via the stereo.


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.

Point of use protectors also have value where a whole house protector is
being used.




.

Relevant Pages

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  • Re: Whole house phoneline surge protection
    ... I'd have to install quite a few surge ... "How to protect your house and its contents from lightning: IEEE guide for surge protection of equipment connected to AC power and communication circuits" published by the IEEE in 2005. ... Your symptoms sound like high voltage between phone wires and the power system ground. ... Wall warts generally are more immune to voltage from phone wires to power/ground wires - might point to a phone entrance protector. ...
    (alt.home.repair)
  • Re: MOVs and surge suppressors
    ... surge protector will limit the voltage going to the device. ... Ben Franklin's lightning was also finding earth ground via ... How many of those items are wires? ... then the surge will find numerous ...
    (sci.electronics.basics)
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