Generally all protectors attentuate signals. In earlier days, I
always wondered why center core connection was not performed. Some
experienced professionals in the rec.radio.amateur.antenna newsgroup
confirmed what I had been told. Leakage from the center conductor to a
well earthed outer conductor provides sufficient protection. A
capacitive protector on center core would only attentuate signals;
provide little protection advantage. But then some legendary
manufacturers do make protectors that include that center core.
You are not earthing a 200,000 amp direct strike - which you probably
will never see in your lifetime. Using a ground block to earth the
outer braid is a massive protection improvement. If you still need
better, then visit some expensive and superior protector manufacturers
such as www.polyphaser.com .
Nothing 'stops transients on the ... conductor'. Anything that
stops or blocks such transients is not effective. Effective protection
is diverting. Destructive transients seek earth. Therefore the sooner
that transient is diverted / earthed (meaning a shorter connection to
earth and farther from transistors), then the better that protection.
Tom like to make an argument out of everything, including symantics.
Most reasonable folks would agree that if a protective device shunts a
surge to ground, that it has in fact stopped the transient, because the
destructive transient does not make it to the protected equipment.
Granted it is a minor point. But the point is made because many
assume a plug-in protectors sitting between a transistor and a surge
will somehow stop or block what three miles of sky could not.
Effective protectors 'shunt'. Those protectors that don't have earth
ground hope one assumes it will instead 'stop' or 'absorb' a surge to
promote a myth. Even shunt mode plug-in protectors only shunt - divert
- a transient. To be effective, it must shunt to earth and not divert
into the appliance. A 'semantic' that can otherwise create confusion
- promote an ineffective product.
This is the only place I dissagree with W-Tom.
He is 100% right about the importance of a single point ground,
bonding of all point of entry protection plus the importance of solid
grounding electrodes and connections. You should try to stop the
surge at the service entrance but where I dissagree is I still think a
plug in protector has value to catch the things his point of entry
system didn't stop. These will usually be a very low order tranient if
the POE system was working but still enough to hurt you. It is better
to heat up a shunt wired MOV than to let this into a MOSFET.
Good point of use protectors also have a large ferro resonant
componant that will eat some heat too.
It still needs a good ground path back to your grounding electrode
system, just to stabilize the reference levels. He is right that it
does little good to clamp the transient if the resulting "zero" is 40v
above the ground reference of the interface lines.
You can't have too many layers of protection if you live in a
lightning area. I just like to add another layer to his system.
When I was doing physical planning for a large corporation that sold
business machines internationally we had a lot of lightning experience
is South Florrida. Layers of protection works for people who can't
turn off their system and unplug it every afternoon in the summer.
I agree. Tom starts off with good advice, but then goes down the path
of "If the whole house surge protection didn't work, then you did
something wrong and point of use protectors are useless." I and many
others have had experiences where it was pretty clear that plug-in
surge protectors did work. He's right, that a short ground path with
a service protector is clearly better, but that doesn't mean the
plug-in protectors are totally useless. A lot, for example, depends on
the rise time of the surge. The slower the rise time, the less
impedance there will be.
Also, for many folks, eg, those living in apartments, a whole house AC
protector is just not possible.
The cable shield was grounded via a grounding block, a 4' piece of #10
bare copper wire, and a separate grounding rod of unknown length, all
installed by the cable company. They have since rerouted the ground to
the service entrance ground.
The modem was damaged from the incoming phone line. The computer was
switched off. The modem's impedance matching transformers were blown
along with the input/output stage. By the way, the phone line is all
underground for miles so it was a ground induced surge. But that is
Plug-in surge suppressors for cable TV need to have a port to include
both the power and cable TV. The multi-port surge suppressor will clamp
all voltages on power and signal wires to the common ground at the
suppressor. The IEEE guide at
explains this quite well. It says the cable center conductor can be 4000
volts with respect to the shield. A plug-in suppressor will clamp this,
likely with a gas discharge tube. A bigger problem is if the cable
entrance ground block is not near, and connected with a short wire, to
the power service earthing conductor. That is also protected by a
multi-port plug-in surge suppressor and is illustrated in the IEEE guide.
Similarly, a plug-in suppressor for a computer with phone connection has
to have ports for both power and phone line.
Plug-in protector has no effective earth ground. No earth ground
means no effective protection. Therefore Bud's article shows a plug-in
protector putting two TVs at 8000 volts. Will those TVs at 8000 volts
not be damaged - not leak currents in destructive paths? No. Those TVs
may be damaged because they are at 8000 volts. Bud's citation even
demonstrates why plug-in protectors can contribute to damage.
Other papers he forgets to cite note how plug-in protectors can even
contribute to damage of that adjacent appliance - TVs:
Martzloff and Key in 1994 wrote in "Surging the Upside-Down House:
into Upsetting Reference Voltages" :
But then that is what the mikeholt.com paper also demonstrates on
page 33/34 in figures 8 and 9. TVs put at 8000 volts because a plug-in
protector is too far from earth ground; therefore is not properly
earthed. Earthing is essential to effective protection.
The paper on page 22 says:
Of course. A protector is only as effective as its earth ground.
That protector adjacent to TVs put those TVs at 8000 volts -
ineffective protection. Effective protection must make a low impedance
connection to a good earth ground. That again means a protector
located 'less than 10 feet' from earth. Even Bud's paper demonstrates
how "objectionable ... voltages ... occur even when or perhaps because
surge protective devices are present at the point of connection of
appliances". The adjacent protector can even contribute to damage of
The IEEE guide clearly describes the action of a multi-port plug-in
surge suppressor as clamping all wires to the common ground at the surge
suppressor, with earthing being secondary. Why does chapter 6 of the
IEEE guide "SPECIFIC PROTECTION EXAMPLES" use multi-port plug-in surge
suppressors in both examples??
I agree with <wfretwell>. that a service panel surge suppressor and a
single point ground are both a very good ideas. The question is whether
plug-in surge suppressors are effective. To anyone who can read, the
IEEE and NIST guides clearly say they are.
You have proviced no reputable links saying plug-in surge suppressors
are not effective.
Where are your supporting links??
have 3 surge protectors running in my home.<<
I had a surge once (caused by nearby lightning strike) while I had 3 five
outlet strips connected together in one room. The surge protectors were
destroyed and the carpet they were sitting on was scorched/burned but
nothing that was connected to them was damaged which included a
computer a police scanner , shortwave radio and a couple of other small
During the same incident in an adjacent room another surge protector
was destroyed along with a VCR but a TV that was connected to the
same protector was spared. RM~
PS, The surge protectors in use had well constructed metal housings. I
suspect we would have had a fire if they were of the plastic type.
I had a similar experience, where my PC and Fax machine, which were
connected to the strip type surge protectors including phone line
protection were undamaged. During the same event my Tivo, which did
not have a surge protector on the phone line, had the telephone/modem
interface blown out. Of course, Tom has told me that this happened
by the surge coming in the AC line, getting through the AC surge
protector, going through the Tivo, and then blowing the modem on the
way out the phone line. I think the rest of us have a pretty good
idea of how it happened.
For "have a pretty good idea of how it happened", than what also
protected those other undamaged electronic appliances? What protected
those kitchen and bathroom GFCIs? What protected the smoke detector?
What protected the dishwasher? How did those appliances without
plug-in protectors not suffer damage? Invisible surge protectors?
You are using same logic process that somehow proved childhood
leukemia from AC electric wires. Selectively ignoring other data such
as that undamaged microwave oven and furnace controls. Meanwhile,
demonstrated was how a plug-in protector simply provided lightning with
a destructive path through a network of computers. Shunt mode
protectors require earthing. No earth ground asks how does that surge
get shunted into earth? Via adjacent appliance. Or maybe another
appliance acts as a surge protector - shunts the surge to earth
destructively. IOW you only assume that protection works and
completely ignore that air conditioner control electronics that was not
A method of making a kludge 'whole house' protector for apartment
dwellers was defined. Take a plug-in protector of maximum joules. Cut
its six foot power cord down to near zero feet. Plug it into the wall
receptacle that is closest to earth ground (and breaker box). It
becomes a 'poor mans' whole house protector. Best you can do if an
apartment owner will not install your 'whole house' protector.
But again, what makes that kludge solution into better protection?
Shorter power cord. Closer to earth ground. Increased distance from
appliance to be protected. What does a shunt mode protector do? It
shunts. Either it shunts a transient into earth (safely), or it shunts
a transient to earth, destructively, via the adjacent appliance. Or it
does nothing because the Tivo did that shunting.
Meanwhile: "getting through the AC surge protector" ? Do you think
some magical blocking device exists inside a shunt mode protector?
Incoming protector wire and outgoing receptacles are direct electrical
connections. Nothing 'blocks' inside that protector. Wall receptacle
connects directly to appliance plugged into that protector - a direct
wire connection. In fact, if a protector provides protection to its
receptacles, then protector also provides protection to anything
plugged into other side of same duplex wall receptacle and to other
wall receptacles on same circuit.
Nothing inside a shunt mode protector stops or blocks surges.
Protection is about diverting surges before surges gets to the
appliance. Protector is designed with transients "getting through the
AC surge protector". That direct connection is what wire inside the
Last time I checked, none of the devices on your list above gets
connected to the telephone line. The PC, FAX, and Tivo were connected
to the telephone line. The PC and FAX were connected through a strip
type surge protector and survived a surge caused by a thunderstorm.
The Tivo was not connected The Tivo had the modem section blown out,
while the rest of the Tivo was still functional.
Based on that, it seems very reasonable to conclude that the surge
likely came in on the phone line and that the surge protector for the
PC and Fax very likely saved them. However I know you will argue
Again, the furnace and microwave were not connected to the phone line.
Hmmm, is your air conditioner connected to the phone line?
Rant on Tom. Others have provided links to credible sources, like the
IEEE, that clearly state that plug in surge protectors can be effective
and part of a tiered protection system. They even clearly show a
diagram in chapter 6 of exactly the settup that saved my PC and FAX,
while the unprotected Tivo got whacked. Now, who should we believe,
you or the IEEE?
So how did a surge enter on phone line, ignore the telephone line
'whole house' protector, destroy Tivo ... and then stop? What kind of
electricity does trader4 have that crashed on a Tivo like a wave on the
beach? That can decide to ignore a phone line protector but is somehow
miraculously stopped by a plug-in protector.
Trader4 knows how damaged happened only because he had damage and
then made assumptions. It must have been incoming on phone line
because only Tivo was damaged. What about other phones? What about
portable phone base station? He has no other phones - or just forgets
to mention that they too have no surge protector and yet were not
A warning about how phone line items (Tivo. portable phone base
stations, modems, etc) are easily damaged when a 'whole house' AC
electric protector is not installed. Incoming on AC electric (that has
no protection) AND outgoing to earth via phone line is typically how
phone appliances are damaged. Phone line already has a 'whole house'
protector provided free by the telco. But somehow trader4 suffered
Tivo damage from a surge protected phone line. Somehow his surges
ignore earthed surge protectors - of they really enter on AC electric
that has no 'whole house' protector.
Somehow AC electric that even protects phone lines from lightning,
that is more often struck, then enters without any earthed protector,
and connects to most every household appliance including Tivo - somehow
AC electric did have any surge? Somehow lightning never struck AC
electric AND somehow a surge completely ignored the telephone line
protector? In reality, surge was on AC electric and other appliances
protected themselves. Lightning strikes AC electric wires - the most
exposed - most often. AC electric is the most common source of damage
even to phone line appliances. And then there is the telephone line
protector that somehow a surge will completely ignore to damage Tivo.
He must have treacherously smart surges.
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