...
So, it is a good idea to check your home's existing grounding,
and a common/"whole house" surge protecting "breaker" may
be worth while. You should also check that any other lines
entering your home are properly grounded as well. But, if
your home meets the common building codes, the plug-in
protection devices are a valid and useful option/ additional
protection.
Wall receptacle ground is not earth ground. Specific references
defined earthing: 'less than 10 foot' connection, no sharp bends, no
splices, not bundled with other wires, etc. All necessary because
surge currents are high frequency. For example, a 50 foot wire from
wall receptacle to breaker box may be less than 0.2 ohms resistance.
That same wire to a trivial 100 amp surge might be 130 ohms
impedance. 130 ohms times 100 amps puts the wall receptacle ground
as something less than 13,000 volts. Will all surge current take the
13,000 volts path to earth ground? Of course not. Wire too long, too
many sharp bends, too many splices, .... Remember all those
requirements? IOW excessive wire impedance. Surge may find other
paths to earth such as destructively through an adjacent TV.
Bud follows me everywhere to promote for the plug-in manufacturers.
He hopes you don't read what his citation Page 42 Figure 8
demonstrates a plug-in protector too far from earth ground and too
close to TVs puts a TV at 8000 volts. Surge currents through an
adjacent protector to earth ground take what path? An 8000 volt path,
destructively, via the TV because a protector (using wall receptacle
safety ground) is too far away from earth ground.
Page 42 Figure 8 demonstrates why high reliability facilities don't
use grossly overpriced protectors. They need protection - as has been
well proven for the past 100 years. Not just any connection to
earth. A short connections to protection. As Page 42 Figure 8
demonstrates, a protector is too far from earth ground. Therefore
protector may earth a surge destructively through adjacent appliances.
Another of Bud's citations, an IEEE paper, even defined the problem
in it conclusion:
1) ... objectionable difference in reference voltages ... occur
even when or perhaps because, surge protective devices are
present at the point of connection of appliances.
Yes, a plug-in protector (costing tens of times more money per
protected appliance), being too far from earth, may simply earth
destructively via household appliances.
Wire impedance is why a connection from protector to earth must be
short (less than 10 feet) and why a wall receptacle safety (equipment)
ground is not earth ground. Phone companies prefer that separation
between protector and switching computer to be up to 50 meters. That
separation contributes to protection. Earthing wire impedance so
critical that even sharp wire bends can adversely affect protection.
Ground wires from AC wall receptacles have far too many sharp bends.
Meanwhile, what happens if a plug-in protector attempts to earth via
safety ground wire. That ground wire is bundled with all other
wires. A surge is now induces on all other wires. Just another
reason why a plug-in protector is not effective. Again, what is
required of that earthing connection? It must be separated from other
non-earthing wires. Why? So that a surge on the earthing wire will
not induce surges on all other wires. Just another reason why AC wall
receptacle safety grounds will not act as earthing for surges.
Each protector will only be as effective as its earth ground. A
protector 'less than 10 foot' to earth can be extremely effective.
The plug-in protector is so far from earth (via wires inside the wall)
as to even earth a surge destructively through adjacent appliances -
as demonstrated on Page 42 Figure 8.
Industry professionals discuss wire impedance - not wire
resistance. Things like long wires, sharp bends, etc increase
impedance - adversely compromise connection to earth. 'Whole house'
protector is effective because it has a short connection to earth.
BTW it is not surge protecting breakers. A breaker would open
circuit - try to stop a surge. Is that silly little breaker going to
stop what three miles of sky could not? Of course not. Again,
protector acts like a switch that closes.
Meanwhile earthing only according to code is insufficient. As
stated before, earthing must meet and exceed post 1990 code. That
means 'less than 10 feet', separated from other non-earthing wires, no
sharp bends, etc. A home that meets code still may not meet those
requirements. For example, a breaker box earthing wire should not
travel up over a foundation and then down to a ground rod. Too long.
Too many sharp bends. Better protection means through a foundation
and down to ground rods. Earthing - not the protector - defines
protection. That shorter path with fewer 90 degree turns means
enhanced protection - earthing that meets and *exceeds* code
requirements.
