Not a problem. I assume that each is for a separate circuit, such as a
computer, hi-fi, misc. electronics, etc.
The only problem that I've had is knowing that they have been "hit," as
many of them are a "one shot" thing, and must be replace (varistor
type), if a real nasty surge hits them.
I have such devices, in the form of outlet strips, on both computers in
The clamping capacity (Amps) of the surge suppressers will be additive
(no, not perfectly additive, but still increasing protection) so more
will be able to clamp bigger surges. A surge suppresser at the main
panel is best since it can clamp a surge before it gets further into the
homes wiring. Additional surge suppressers further down the line,
whether the little blocks or power strips with suppressers built in will
just add an additional line of defense.
The surge suppressers that install at the service entrance panel are
generally higher quality and capacity and more likely to use multiple
technologies like MOVs and gas discharge arrestors. Nearly all the small
plug in suppressers just use inexpensive MOVs.
A decent UPS is a must for computers and any other expensive items like
big plasma / LCD TVs, etc. UPSes used to be expensive, but they are now
quite reasonably priced for decent units. One thing to watch out for is
surge suppressers on the output of a UPS. Since suppressers work by
creating a short circuit across the line (briefly) they can damage a
UPSes inverter if a surge gets through and they clamp. Some cheaper
UPSes may generate small HV spikes that could trigger the suppresser as
well and again damage the UPS output.
Nothing will protect against a direct strike on the power line near your
house, so if that happens you'll have a big insurance claim no matter
what. The suppressers might help clamp things enough to lessen the
Inductive pickup of nearby lightning strikes is also an issue and long
wires like phone, network and CATV lines can pickup significant surges
that way. Good suppressers on those lines along with good grounds will
They are called shunt mode protectors. They work by earthing a
destructive transient such as a direct lighting strike and then remain
functional. If a 'whole house' protector could not earth that
transient, then what good willl a plug-in protector do trying to earth
to the same ground?
So instead some assume plug-in protectors sit between the surge and
an appliance to block or stop surges. Bull. Will that silly little
less than one inch component stop what 3 miles of sky could not?
Effective protection was never about stopping or absorbing surges.
Effective protection is about diverting - shunting - a destructive
transient to earth. Divert - not stop or absorb.
Protector amperage is additive IF all protectors have a same 'low
impedance' connection. And that is the problem. Things such as sharp
wire bends, long distances, splices, etc all increase that wire
impedance. Now a plug-in protector has too much impedance. Instead of
seeking earth via safety ground wire, that transient may seek earth
through an adjacent appliance and phone line. This is how modems are
so easily damaged. Incoming on AC electric. Through an adjacent
protector. Into comptuer motherboard and modem. Out to earth ground
via phone line. Notice where most modem destructive transients come
Having learned this by tracing destructive surges, then what is a
most typically damaged component? The path through adjacent protector,
through modem (its DAA section), is often via a transistor that drives
an off-hook relay. The failure message is "No Dialtone Detected".
Incoming on AC. Through that transistor and off-hook relay. To earth,
destructively, via phone line and phone line surge protector.
Why did damage result? A transient was not earthed BEFORE it could
enter the building.
A surge protector basically shunts - connects all wires together
during a transient. If that wire makes a low impedance connection to
earth, then the transient is earthed. No damage. But plug-in
protectors don't have a good earthing connection. Above is one
example; demonstrated by tracing surges and replacing transistor. A
protector too close to transistors and too far from earth ground can
even contribute to damage of the adjacent (and powered off) appliance.
An effective protector makes a 'less than 10 foot' connection to the
building's earth ground.
Ineffective protectors (power strip and UPS) are easily identified.
1) No dedicated earthing wire. 2) Manufacturer does not even discuss
earthing. Look at your protector. Does it meet these criteria for
What does a telephone company do to protect their $multimillion
switching computer? Its computer connects to overhead wires everywhere
in town. Why do they not provide service for a whole week while
replacing that computer? Because the telco installs 'whole house' type
protectors on every single wire of every cable that enters the
building. Tehcnology even discussed in an Oct 1960 Bell System
Technical Journal article - because the technology is that old and that
well proven. An effective protector is ideally 50 meters from
transistors AND as close as possible to earth ground. That 50 meter
separation adds to protection. But most important is what makes that
'whole house' type protectors effective. A low impedance - meaning
short - connection to a building's single point *earth ground*. Not
only is the connection short. Every protector is earthed to a same
ground - the single point earth ground.
For residential protection, manufacturers with responsible brand
names provide effective 'whole house' protectors. Siemens,
Cutler-Hammer, Square D, Leviton, Intermatic, and GE all sell 'whole
house' protectors that are available in Home Depot, Lowes, and
electrical supply houses. These protectors have a dedicated earthing
wire. These protectors costs tens of times less money per protected
appliance. And these protectors are properly sized.
Why properly sized? Many plug-in protectors are so grossly
undersized (MOVs undersized; too few joules) as to vaporize during a
surge. Vaporized MOV provided ineffective protection. But its smoke
promotes more sales. Effective protectors, instead, earth direct
lightning strikes and remain functional. A human never knows that when
a properly sized protector is doing protection. Grossly undersized
plug-in protectors that vaporize and smoke will be recommended by the
naive. So many plug-in protectors are undersized - to promote sales
rather than provide effective protection.
Earthing - at minimum, the building must conform to post 1990
National Electrical Code earthing. Enhanced earthing means a protector
will be even more effective. And so we say, "a protector is only as
effective as its earth ground." What do those plug-in power strip and
UPS protectors manufacturers not even discuss? Earthing. Where is
that dedicated earthing wire? Did they just forget? Or do they hope
you never learn why earthing is so essential?
Some incoming wires are earthed using a protector. Telco provides a
'whole house' protector where their wire enters your building. But
again, that protector will only be as effective as its earth ground.
Did you (or your builder) provide that essential earthing connection?
Cable needs no protector. Its ground block must connect directly to
the same earth ground - a 'less than 10 foot' connection. Every
incoming wire must be earthed directly or through a 'whole house'
protectors to the single point earth ground.
Ineffective protector manufactures and those who promote them hope
you never learn what a shunt mode protector does: makes a low impedance
connection to earth. No earth ground means no effective protection.
So where is that earthing connection in a plug-in UPS? Notice that
their own numerical specifications don't even define protection? How's
that for a damning overlooked fact.
Appliances already contain internal protection. Protection that can
be overwhelmed if destructive transients are not earthed where wires
enter the building. Earthing is why 'whole house' protectors are so
effective. No earth ground (such as with plug-in protectors) means no
If you don't earth incoming transients such as the direct lighting
strike, then protection inside that appliance can be overwhelmed;
appliance damaged. Plug-in protectors can even provide more
destructive paths through an adjacent appliance.
Pete C. wrote:
The fact that they will operate in parallel. The transient will rise to
the trigger point of all the suppresser devices and all will clamp the
line. If there is sufficient clamping capacity the differential voltage
will be substantially reduced.
As I noted, nothing is going to stop a direct strike. Most strikes
aren't direct however and are primarily inductive pickup from a nearby
strike and therefore reduced to a much more manageable level.
Again for a direct hit. For a surge of the level of the much more common
inductively coupled strike that does not apply.
The MOVs that are located adjacent to the phone line connector on a
quality modem should clamp the surge. The drive to the off hook relay is
also not electrically connected to the line, nor is most of the rest of
the modem. The DAA transformer, ring detect optoisolator and hook switch
relay are about all that is connected to the line.
There is absolutely nothing magic about the building. The building wall
is no different than the wall of an electrical panel, or the case of a
One thing you do buy by clamping the surge as far out as possible is to
keep the current path of the clamped surge further away from other wires
which helps limit further inductive coupling.
Again, reducing the current path and the potential for further inductive
As I noted, every suppresser on the line adds some level of protection.
Suppressers at the electric service entrance panel, the CATV and telco
demarcs all with short connections to a proper grounding electrode are
the first line of defense.
Any suppressers downstream provide further protection against
inductively coupled surges which don't have to come through the service
entrance conductors and residual surges past what the primary
suppressers were able to clamp. Also for #1, that third pin on the power
plug *is* a dedicated earthing wire.
Yes, the closer you can locate the suppressers to the grounding
electrode the more effective they can be. Those grounding electrodes are
also rarely a single point ground particularly in a utility application.
More commonly they will be a multipoint electrode array bonded together
with quite heavy conductors, often with exothermic welded connections.
The telco is also a good example since it employs multiple stages of
protection from the primary suppressers at the drop entrance to the
suppressers on the SLIC cards, the suppressers on the power system, etc.
More is better for the most part.
Again these should be the first line of defense along with quality
suppressers at the telco and CATV demarcs. This does not mean that
additional suppressers are of no value as lightning can induce surges in
the building wiring inside the house just as easily as outside.
I've never seen a vaporized MOV of any size. I have seen a few that have
failed and cracked after being subjected to substantial surges. If you
review the joule ratings of the various MOVs and gas discharge arrestors
you find in typical small suppressers you'll see that their ratings are
not at all far behind those of the common whole house suppressers. Some
of the quite expensive service entrance suppressers intended for
commercial services have higher ratings, but not the common ones.
Refer you to the dedicated grounding (earthing) conductor provided to
every electrical device in a residence. The dedicated third pin on a
NEMA 5-15 (or 5-20 or 5-xx, 6-xx, etc.) receptacle.
Cable is not required by any code to have anything but the ground block
at the demarc, however this only grounds (earths) the shield of the
coax. The coax center conductor still can and often does convey
significant surges into the premises. A quality coax surge suppresser
will clamp surges on the center conductor to ground as well.
Again, every single one of those suppressers has an earth ground
connection. They wouldn't pass code and UL listing requirements if they
The grounding pin of the NEMA 5-15 plug on the UPS.
The specifications for my UPS indicate the clamping voltage and joule
rating of the suppresser devices.
Some appliances do, many do not. Don't recall the last time I saw any
suppression devices in a toaster or a blender.
Again you are 100% incorrect, any plug in suppresser with a three prong
plug *does* have an earth ground. What the heck do you think NEC article
250 is all about? NEC articles 280 and 285 relate to surge arrestors and
transient voltage surge suppressers BTW.
If you have a direct lightning strike on your service entrance drop or
service feeder on the poles, your glorious whole house suppresser will
be in pieces along with your entire service panel.
I work as a communications wireman whenever the electrical service
industry gets too slow. I have built alternative powered and utility
powered radio equipment shelters in remote places from Alaska to the
Argentine pampas. These room sized buildings are struck quite regularly
by lightning without loosing a single circuit. The inevitability of
damage secondary to a direct strike is a myth. If you are willing to
invest the necessary effort damage can be averted. Most home owners
will not find it cost effective to install fully effective lightning
"This alternating current stuff is just a fad. It is much too dangerous
Numerous points that make assumptions based in a world where
impedance does not exist - where only resistance exists.
First, nothing will stop a direct strike. But direct strikes
routinely do no damage when they are diverted. Major difference
between stopping (which plug-in protectors hope you will assume) and
diverting which is standard where direct lightning strikes do not
damage. Again, 25 direct strikes annually to electronics atop the
Empire State Building; 40 annually to the WTC - and electronics not
damaged. It is routine to earth direct strikes without damage -
because we don't stop a direct strike. We divert it to earth.
Inductive transients? Well put some numbers to them. I assume
this is about a nearby lightning strike to a long wire antenna. Well
that nearby strike may induce a few thousand volts onto that antenna.
Then we connect an NE-2 (neon glow lamp) from that antenna to earth.
Because that neon glow lamp conducts only milliamps, then that
thousands volts on antenna is now less than 60 volts. IOW induced
transients are that trivial. So trivial as to be made irrelevant by
protection inside all appliances. And yet, even industry standards of
30+ years ago (i.e. CBEMA) defined protection that was inside all
electronic appliances even that long ago. It takes so little to make
induced transients irrelevant. But it is the direct strike that causes
You did not see protector devices inside the blender? You were not
looking like an engineer? Why do you think wire was heavier gauge than
necessary? You are making a classic mistake. You have assumed
protector is as specific device. Protection is not necessary achieved
by a protector. Protection is something in the engineering. You are
instead looking for a specific device rather than first learning the
design. Meanwhile, we were discussing electronics appliances - not
blenders that have no electronics.
Is "drive to the off hook relay ... also not electrically connected
to the line, nor is most of the rest of the modem"? First go to data
sheets. That coil inside a modem off hook relay does electrically
connect to its wiper as those datasheets demonstrate. Not at 100
volts. But then even floors and wall paints become conductive during
these transients. Datasheet for that off-hook relay even states what
voltage causes a coil to connect to relay wiper. That is how modems
are so often damaged - as we also demonstrated when constructing
massive relay switching drawers in test equipment to connect and
disconnect those voltages. How are modems damaged? Get those
datasheets. Even optocouplers have breakdown voltages. When that
off-hook relay coil breakdown voltage is exceeded, then a destructive
transient passes through PNP transistor, through relay, and to earth
ground via phone line. Everything has a breakdown voltage. What we
assume is not conductive at trivial low voltages become a perfect
conductor at higher voltage.
Defined was how a modem is damaged when an AC electric line surge
finds earth ground via modems DAA section, phone line, and earthed
'whole house' protector.
Try to make two ends of a fluorescent lamp conduct with an ohm meter.
No connection. Then why do so few volts conduct current across that
tube when tube is glowing? Same principle. That relay coil and relay
wiper are electrically connected during a surge which is why we so
routinely repaired modems by replacing a surge damaged PNP driver
transistor. Surge incoming on AC lines and outgoing on phone line. To
be damage, electronics must have both an incoming and outgoing path.
Surges do not enter on phone line, ignore phone line 'whole house'
protector, crash on a modem, and stop. Electricity just does not work
As described in another post is wire impedance. Using Bud's
citations that demonstrate how plug-in protectors can fail to provide
protection: two TVs sharing a plug-in protector are at 8000 volts.
How can this be when those plug-in protectors are grounded by three
prong electrical connection to breaker box? Because one end of that
safety ground wire is at near zero volts and the other end is at 8000
volts - wire impedance. How can one end of a wire be at 8000 volts and
the other end at near zero volts? Welcome to a basic electrical
principle that also explains why different parts of a transmitting
antenna wire are at different voltages.
A 50 foot AC electric ground wire is maybe 0.2 ohms resistance. But
that same ground wire is maybe 120 ohms impedance to a surge. A
trivial 100 amp surge enters wall receptacle. 120 ohms times 100 amps
is a voltage somewhere below 12,000 volts. Same reason why those two
TVs can be at 8000 volts during a surge. Same reason why earthing must
be 'less than 10 feet' to single point earth ground. But then this is
old and well proven concepts - wire impedance.
More reasons why that 50 foot AC electric wire has even higher
impedance and creates other surge related problems. Sharp bends.
Splices. Bundled with other wires thereby induced transients on those
other wires. Wall receptacle is not an earth ground. Wall receptacle
is a safety ground. Wire impedance is why that wall receptacle is not
sufficient for earthing.
Yes appliances do have internal protection as required by industry
standards. Once some appliances (ie Apple II) installed those
protectors. No longer. MOVs inside the computer were as not effective
as they would be on its power cord - for so many reasons - including
too far from earth ground.
You have not seen MOVs vaporize? Get 30+ years experience with this
technology to see it. Some vaporized MOVs looked ominously ghostly.
Only left were two leads. Nothing left of its carbon material or red
Meanwhile, learn what joules really mean in a plug-in protector.
1000 joules in a plug-in protector is maybe equivalent to a 333 joule
'whole house' protector. And that assumes none of those joules are
used on other ports such as telephone or cable. Furthermore, as
joules increase, then protector life expectancy increases
exponentially. To be equivalent to a minimal 1000 joule 'whole house'
protector, the plug-in protector must be at least 3000 joules. Too
often, UPSes and power strips were only 345 or 900 joules - grossly
undersized. Only recently have some plug-in protectors sold 'still
too small' 2000 joules products.
You have never seen a grossly undersized protector vaporize? View
what was too unacceptably common with so many plug-in protectors:
Imagine what these would do in dust balls on a rug behind the table or
on a desktop covered in papers. Does not matter if your desktop does
not have papers. Other's do which is but another reason why plug-in
protectors can also cause human safety problems.
But again, some principles to grasp before understanding surge
protection. Ever touch a doorknob to cause a static discharge? What
was the electrical connection from that finger to charges below your
shoes? Notice how many of those items are normally not considered
conductive. And yet electricity flowed from that finger tip, through
door, through floor to bottom of your shoes. Welcome to surge
protection where concrete and linoleum become excellent conductors of
electricity. Where a coil and wiper inside a relay become electrically
connected. Just more examples of why surges cannot be stopped - and
therefore why effective protection has always been about diverting
before a surge can enter a building. Diverting via low impedance - not
just low resistance - connections to a single point electrode.
One final point. Single point need not be a single ground rod.
Single point can also be a halo or ufer ground completely enclosing a
building's perimeter. But single point earthing and low impedance
connections are essential to effective protection.
Pete C. wrote:
You sure do like to babble, too bad 99.9% of what you say is either
total nonsense, pseudo-science, or hopelessly misapplied scientific
principles. Your links to claimed "vaporized" MOVs show no such thing
You don't understand wire impedance. You insist that industry
professional papers are lies. Those burning power strip protectors due
to failing MOVs somehow are not fire threats? Meanwhile others who
want effective protection learn why properly earthed and properly sized
'whole house' protectors from responsible manufacturers such as Square
D, GE, Siemens, Polyphaser, Cuter-Hammer, Intermatic, and Leviton make
that short connection to earth; therefore provide effective
Reasons why such protectors sold in Home Depot and Lowes are long;
assume the reader understands basic electrical concepts such as wire
impedance. To make such problems such as wire impedance irrelevant, we
install an effective protector with a 'less than 10 foot' connection to
earth. Apparently concepts such as wire impedance and MOVs vaporizing
is completely new information to Pete C. Others are encouraged to learn
why above manufacturers of 'whole house' protectors are considered so
responsible; provide effective protection. In the case of Polyphaser,
that protection is considered legendary.
I understand wire impedance, you apparently do not and misapply the
concept. You haven't provided reference to any industry papers that
support your assertions.
Failing MOVs in an old poorly designed power strip / surge suppresser
combo that doesn't meet current standards could well be a fire threat,
however they have not been "vaporized" by a surge as you have claimed.
I have effective protection and it's multi level distributed protection
as good engineering practice dictates.
It starts with a Square D suppresser on the Square D QO series panel,
Leviton coax suppressers adjacent to the ground blocks at the CATV
demarc, the integral suppressers in the telco demarc and solid heavy
gauge ground leads to the adjacent 8' grounding electrode which is
solidly bonded to the secondary 8' electrode about 10' away.
It does not however end at this point in a "hope for the best" strategy,
the protection continues further with reasonable quality suppresser /
power strips (that have status indicators and thermal fuses), a large
quality UPS on the server rack, and additional suppressers on internal
phone / data / CATV lines.
Apparently folks like you latch onto technical terms like "wire
impedance" without bothering to get an understanding of what it really
means and how it is not the same as the wires DC resistance. You have
also not provided a single link to your claimed "vaporizing" MOVs.
The answer to the OP's original question "It is dangerous to have more
than one surge protectors in you home I
have 3 surge protectors running in my home." is clearly "no", it is not
And as myself and others have indicated a quality "whole house"
suppresser is very beneficial, but it does not obsolete secondary
suppressers further down the line, nor does it obsolete suppressers on
non power lines like CATV, phone and data.
They are all called shunt mode protectors. Typically destructive
transient seeks earth ground. Each layer of protection is defined by
its single point earthing. Primary protection is provided by a utility
and requires homeowner inspection:
Secondary protection is the 'whole house' protector, et al - also
defined by its single point earth ground as demonstrated by:
In each case, wire impedance must be kept low as repeatedly cited in
professional papers - which means short distance, no sharp bends, no
splices, not inside metallic conduit, etc.
When Orange County FL emergency response system suffered damage from
lightning, then reasons for system protector failure were repaired.
They fixed the earthing system:
Why? Each protector is defined by what it connects to. Earth
ground. Those interior protectors claim to protect from what type of
surge? Well plug-in protectors don't even define protection for each
type of transient. Why let a consumer know it protects only from a
transient that is typically not destructive and that is made irrelevant
by protection already inside equipment.
Many plug-in protectors are undersized because that MOV vaporization
even promotes protectors to the naive. Meanwhile, if better protection
is required, did Orange County install plug-in protectors? Of course
not. They enhanced earth so that effective protectors would perform
What does that protector inside a plug-in UPS do? Where in numerical
specs does it even claim protection? Is dBs filtering considered
protection? No. Do standard numbers such as C62.xx or UL1449 define
protection? No. It does not list protection from every type of
transient because you might notice a glaring anomaly. With no low
impedance connection to earth ground, it does not claim to protection
from surges that cause damage. They forget to define protection from
each type of transient so that a consumer might assume it. And then we
have this layer of protection - forgetting to mention what defines each
layer: earth ground.
Pete C. has a problem with low impedance wiring requirement when
virtually every responsible installation requires 'a low impedance
connection'. His own Square D 'whole house' protector is reported
earthed by 10 feet. Of course that protector could be made better if
earthing wire was shorter, no sharp bends, separated from other wires,
etc. Each protector is defined by quality of and connection to its
single point earth ground. As one industry professional defined it
for every building owner and operator:
They are called shunt mode protectors. They don't magically stop
surges. As wire impedance increases, then surges find other
(destructive) paths to earth. Wire impedance defined by an equation
where wire impedance increases proportional to wire length multiplied
by a factor that includes the Log of 4 times wire length divided by
wire diameter. Wire length increases wire impedance twice over which
is why low impedance means a shorter connection. A fact demonstrated as
relevant by Thottappillil in "Electromagnetic Pulse Environment of
Cloud to Ground Lightning for EMC Studies":
Of course, higher impedance means higher maximum overvoltage when we
want voltage to earth to be as low as possible. So we carefully lower
that wire impedance connection to earth.
As wire gets longer, impedance increases unacceptably. Polyphaser
notes in TD1023: Multiple I/O port protection, Single Point Ground
So what does that plug-in protector adjacent to two TVs do? Leaves
both TVs at 8000 volts. Why? Wire impedance to earth ground is too
large causing TVs to sit at 8000 volts during a surge. Where is the
protection? Demonstrates how a plug-in protector - without a low
impedance connection to earth - does nothing useful.
Some hype a myth about layered protection and forget to mention what
defines that layer - earth ground. Why would supplemental protectors
with excessively high impedance somehow earth to a point that the surge
ignored when entering a building? If that earthing was made superior,
then a surge is better earthed by the 'whole house' protector. And if
earthing is not sufficient, then why is a supplemental (plug-in)
protector going to earth to that same insufficient earth ground?
Rather than waste money on plug-in protectors, what did they do in
Orange County FL? They repaired reasons for lightning damage -
insufficient earthing. Plug-in protectors are in the same protection
layer as a 'whole house' protector. If 'whole house' protector's
earthing is not sufficient, then a plug-in protector - with excessive
wire impedance - will somehow earth to same ground? Nonsense. And yet
that is what plug-in shunt mode protectors must do.
BTW, another solution called series mode protectors; beyond scope of
As has been repeatedly demonstrated, even in a paper from Martzloff,
Each layer of protection is defined by the and most essential system
component - earth ground. Primary protection layer is earthed at the
utility pole. Secondary protection layer is properly earthed adjacent
to 'whole house' protector. Since plug-in protectors don't even claim
such protection in numerical specs, then such protectors neither have a
dedicated wire for earthing nor do they even discuss earthing. A shunt
mode protector earths. No earth ground - such as with plug-in
protectors - means no effective protection. Better is to put money
into enhancing the earthing system.
Lower wire impedance connection to earth. Enhance the earthing
electrodes. Establish a single point earth ground to be used by all
incoming utilities. Money wasted on plug-in protectors is better spent
here. Effective protection is defined by its most essential 'system'
component - single point earth ground.
Pete C. wrote:
The same old Bull.
The best information I have seen on surge protection is at
It is a guide that was published by the Institute of Electrical and
Electronic Engineers in 2005. You provided the link to this guide.
Another good source is
published by the US government - National Institute of Standards and
Both guides were intended for wide distribution to the general public to
explain where surges come from and how to protect against them. The IEEE
guide was targeted at people who have some (not much) technical
background. The NIST guide is intended for everyone.
Both the IEEE and the NIST say that plug-in surge suppressors ARE
EFFECTIVE. Perhaps you are smarter than they are.
Note that if equipment, like a computer, has connections in addition to
the power line, particularly phone but also possibly LAN or other, that
wiring also needs to go through the plug-in surge suppressor. That also
applies to equipment with power and cable TV connections. This is
described in both guides.
Plug-in surge suppressors work primarily by clamping the voltage on all
wires (power and signal) to the common ground at the surge suppressor.
That includes the cable TV coax center conductor, as described by Pete C.
Any protector that was one shot protection was grossly undersized -
ineffective. When it vaporizes, then it promotes more sales to the
naive. Effective protectors do their job without vaporizing; human
never knows when it is working. But effective protectors are not
promoted by the naive.
Active component in a protector is the MOV. A datasheet from an MOV
manufacturer provides a ballpark idea how many times a properly sized
protector should work - without failing:
Does that sound like a one shot protector device? Of course not.
Ineffective protectors are also grossly undersize to be promoted by the
naive. Smoke rather than facts promote ineffetive plug-in protectors.
Effective 'whole house' protectors are manufactured by names
recognized as responsible: Square D, Cutler-Hammer, Leviton,
Intermatic, Square D, and GE. They are sold in Home Depot, Lowes, and
electrical supply houses. They are not sold in Radio Shack, Sears, and
grocery stores. Essential for any effective protector is earthing. A
protector is not protection. Protection is what the protector connects
'less than 10 feet' to: earthing.
Meanwhile, let's look at what some grossly undersized plug-in
protectors have done:
Think about it. Would you put a protector in dust balls behind a
table or atop a desk of papers? There are overhyped, so called 'one
shot' protectors. Properly earthed and sufficiently sized 'whole
house' protectors are available. And then we have this fact
demonstrated in commercial broadcasting stations and telephone
switching centers everywhere in the world. The protector is nothing
more than a connection to protection. That protection is a good earth
ground. An effective protector is only as effective as its earth
ground which is why effective protectors have a dedicated earthing
If you mean the kind that plug into the wall (may be called power strips)
and they are installed in seperate outlets, you can not have too many in
The only thing is if you have too many things using too much current plugged
in to them. Then a fuse or breaker should blow or trip.
I have 4 or 5 in use right now. One on each of the TV sets, computers and
my ham radio gear.
In a house I lived in before I moved , having 3 in use probably saved me a
bunch of equipment. A surge during a lightning storm took out 3 of the
protectors but did not get any of the electronic gear except an unprotected
telephone and an internal surge supressor saved most of the electronics in
the oven control.
I have a whole house "protector" at the electrical panel and several
smaller units scattered throught the house. I have had several
lightning hits in the near vicinity and have never had electrical
damage. But I have lost 4 TV's from lightning coming in on the cable -
all damaged in the tuner sections rather than power sections. And I
have had computer modems fry from surges on the telephone line. So
from that, I deduce the whole house unit is doing it's job, but the
others are questionable.
Was cable earthed before entering a building? If not, then yes,
cable may be an incoming source of electricity called a surge. Cable
must drop down and make a 'less than 10 foot' connection to a same
earth ground used by AC electric and telephone. If cable enters house
without dropping down and connecting to earth, then yes, cable can be
the incoming path of a surge that was seeking earth ground
destructively through tuners.
No protector is required to earth coax cable surges. But the most
important component of a protector - earth ground - must connect to
that cable. Connected so that a surge finds earth at the building
entrance instead of via TV tuners.
Actually we don't know that any protectors were doing their job. You
suffered damage. If, for example, the telephone line 'whole house'
protector and AC electric 'whole house' protector were not using a same
earth ground, then damage could still occur. Protection starts with
and is defined by earthing - not by some protector. The effective
protector makes a 'less than 10 foot' connection to same earth ground
used by all other protectors.
What makes problems more complex is that plug-in protectors have a
history of offering surges more destructive paths through household
Forget that protectors are protection. What was the earth ground?
Earth ground is the protection. How were those protectors earthed?
Don't assume a modem was damaged by a surge from phone line. Don't
think of surges as a wave crashing on a beach. Surges just don't work
that way. First electricity flows in everything in a path through that
modem. Everything is conducting the same electricity. Long afterwards
(microseconds later), something in that path is destroyed. That path
could be incoming on phone line. Or a destructive path through modem
can be incoming on AC electric or cable; outgoing on phone line.
Notice - first there must be both an incoming and outgoing path.
Notice, the cable is not directly connected to computer. Since
numerous household items may be conductors, then even a cable surge
could have found a path to earth via that computer modem.
Any incoming utility could have been an incoming surge path into the
computer. However most modems are damaged by surges incoming on AC
electric; outgoing to earth via phone lines. No 'wave crashing on a
beach'. An incoming path and an outgoing path to earth must exist to
You don't know if phone line was incoming or outgoing path based upon
what was posted. You only know a modem was in a destructive path from
cloud to earth. And that path existed because something was not
properly earthed where it enters the building. How do you learn from
and fix the problem? Start with earth ground. Is it the best earthing
on the property? Does every utility make a 'less than 10 foot'
connection to that one earthing electrode? IOW do all utilities enter
at a same location or is that earth ground expanded to connect to all
incoming utilities? We don't yet know whether cable or TV wire was the
incoming source or outgoing path to earth. Analysis must start by
identifying both incoming and outgoing path through that modem and
those TV tuners.
How did lightning from a cloud find earth ground through those tuners
and modem? Until we can answer that question, then it is only a guess
why something was damaged and no idea yet how to fix this human created
You cannot deduce the 'whole house' protector is doing anything
effective until the most essential part of a protection system - earth
ground - is verified. Did a surge enter on phone line if telco had
installed a 'whole house' protector -for free? Well again, what is
that protector earthed to. Protection is defined mostly by the quality
Meanwhile, what did those plug-in protectors have for a 'less than 10
foot' connection to earth? No less than 10 foot connection? Then of
course they were not effective.
I've looked rather closely at my coax entrance -- only the outer
conductor is grounded. The center conductor is not. (Shouldn't be too
surprising, if you shorted them both to ground, it would attenuate the
signal a bit, no?)
What, other than a surge protector, stops transients on the center
conductor of cable TV?
firstname.lastname@example.org is Joshua Putnam
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