Surge / Ground / Lightning

[w_tom]

On May 6, 10:54 am, Jitt <tser...@yahoo.com> wrote:

I suppose I phrased the question badly. I wonder why a surge
would wander around looking for ground, when its available
in the box!

If all grounds are same, then connect lightning rods into a
motherboard ground. That would be perfect building protection because
a lightning rod is grounded?

Ground inside a stereo is different from ground inside a TV is
different from ground on the computer case is different from ground on
a wall receptacle is different from ground inside a cell phone is
different from a ground inside a breaker box is different from ground
in earth. Most all those grounds are interconnected and are still not
the same ground.

Electricity is different at both ends of a wire. That 100 amp surge
seeking earth from a wall receptacle may leave the wall receptacles at
12,000 volts - again, due to wire impedance. That plug-in protector
on Page 42 Figure 8 was so far from earth ground (via AC electric
wire) as to be >8000 volts - a destructive path via an adjacent TV to
earth.

The EE Times article entitled "Protecting Electrical Devices from
Lightning Transients" defines why a ground in a box is not a ground to
surges. Why electricity at both ends of a wire is always different.
Why that difference during a surge is so important that an effective
protection makes a 'less than 10 foot' connection to earth. Only
relevant 'ground' is the one that is ground to a surge. That is not
an 'inside the box' ground.

Typically destructive surges are an electrical connection from a
cloud to earthborne charges maybe miles away - the relevant ground.
If any part of that connection is via an appliance, then the appliance
may be damaged. Surge protection has always been about diverting a
connection from cloud to earthborne charges so that current need not
pass inside the building.

A protector is only as effective as its earth ground so that surges
need not enter a building. No earth ground means no effective
protection; means a surge creates connections to earth destructively
inside a building. Any facility that installs effective protection
does earthing connected, very short, via a 'whole house' type
protector.

Polyphaser makes a protector that has NO earth ground connection.
Earthing is so critical that their protector mounts directly ON the
earthing electrode - zero feet from earth ground. Distance to earth
ground is critical for effective protection. Which ground? Earth
ground is not found and not provide in three wire AC wall
receptacles. That is a safety ground.

 

[w_tom]

On May 6, 12:08 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:

Where did I say HOW was protected? It was my second week at that
station, and the chief engineer took off on a long overdue vacation. If
you would learn to read, rather than just do mindless rants you wouldn't
look so stupid. At that time the building had a UFER ground, and a
three phase protection system at the meter CTs. That didn't prevent the
damage, as you claim it should.

Lightning created damage. Since Michael Terrell says it had an Ufer
ground, that means grounding was properly installed and not
corrupted? Therefore the resulting damage proves, "Woe is me.
Nothing can protect from lightning."? Nonsense.

Damage was created by a surge. A responsible human locates the
defect in that protection system. Michael Terrell was defeatist. He
'knew' nothing can earthing lightning without damage.

Then Michael posts nonsense about other protectors so he need not
admit this fact: MOVs are not used on telephone lines. Why discuss
fuses? Fuses obviously are not for surge protection - when one has
basic electrical knowledge. Effective protectors (even gas discharge
tubes - GDTs) earth direct lightning strikes and remain functional.

So why is Michael now discussing GDTs and fuses? Michael has again
been caught posting in error. MOVs are not used for telephone line
surge protection due to excessive capacitance. This has long been
common knowledge among those who post facts - not insults. Nnoted and
finally admitted by Michael is a reasons why so little lightning in
the UK creates so much damage. Master sockets are not even earthed as
the equivlant NID is, routinely, in all North America.

Responsible people who suffer surge damage immediately search for
the human failure that made damage possible. Search typically begins
by looking for defects in the single point earth ground system. Those
who promote magic box plug-in protectors would not do this and must
assume lightning damage cannot be avoided - a defeatist attitude.

 

[w_tom]

On May 6, 3:08 pm, trad...@optonline.net wrote:

W_ denies MOVs are commonly used in typical electonics or modern
appliances too. He had to, because he can't answer the obvious
question of how MOVs can be used effectively in these applications,
yet they can't work in plug-in protectors and the only way to get any
protection is to have a nearby direct earth ground. Faced with the
problem of MOVs providing protection in electronics/appliance without
an earthground, he simply denies MOVs are used in electronics and
appliances. ...

Using trader's reasoning, all appliances contain MOVs. Therefore
plug-in protectors need not be purchased AND all appliances never
suffer surge damage. Conclusions directly from trader's post.

Reality: all appliances contain protection using numerous techniques
such as galvanic isolation. Protection that means all but a rare and
typically destructive surge is made irrelevant. Internal appliance
protection is dependent on a properly earthed 'whole house'
protector. The typically destructive surge must be earthed to not
overwhelm protection inside all appliances.

 

[w_tom]

On May 6, 10:22 am, Eric <m...@nomail.com> wrote:

I can attest to vhf/uhf content in lightning strikes. I worked for a
communications outfit. We owned and maintained a number of comm sites
with towers and antennas. One strike on an antenna destroyed the LDF rf
cable all the way to the polyphaser at the bottom of the tower.

Eric notes damage only up to the earthed Polyphaser protector.
Polyphaser is legendary among professionals who install effective
protection. Polyphaser is blunt about what provides protection - why
their products are so effective. Polyphaser protectors are earthed.
Polyphaser application notes repeatedly discuss what their products
must connect to; what provides protection: earth ground:
http://www.polyphaser.com/technical_notes.aspx

 

[Mike Tomlinson]

In article <d905d997-1802-48c8-9298-fc348411f154@59g2000hsb.googlegroups
..com>, w_tom <w_tom1@usa.net> writes

[snip w_'s usual lies and bald statements with no citations or proof to
back them up and his boilerplate messianic statement of religious
belief]

Same technique used by Rush Limbaugh to prove Saddam
had WMDs.

ROTFL!! You've really lost it this time, w_twat.
I hereby invoke Godwin's law.

--
(\__/) Bunny says NO to Windows Vista!
(='.'=) http://www.cs.auckland.ac.nz/~pgut001/pubs/vista_cost.html
(")_(") http://www.cypherpunks.to/~peter/vista.pdf

 

On May 7, 12:36 am, Mike Tomlinson <m...@jasper.org.uk> wrote:

In article <d905d997-1802-48c8-9298-fc348411f...@59g2000hsb.googlegroups
.com>, w_tom <w_t...@usa.net> writes

[snip w_'s usual lies and bald statements with no citations or proof to
back them up and his boilerplate messianic statement of religious
belief]

Same technique used by Rush Limbaugh to prove Saddam
had WMDs.

ROTFL!!  You've really lost it this time, w_twat.  
I hereby invoke Godwin's law.

And as usual, W_'s statement taken at face value is wrong and/or
misleading. A simple check of history shows Saddam did in fact have
WMDs for years, because they were used in war and against his own
people. The UN weapons inspectors had spent a decade of hide and seek
locating and destroying most of them. Just prior to the start of
the Iraq war, not only did US intelligence believe he still had some
of them and was trying to reconstruct the weapons programs, but so did
British, Israeli and Russian intelligence.

--
(\__/)   Bunny says NO to Windows Vista!
(='.'=)  http://www.cs.auckland.ac.nz/~pgut001/pubs/vista_cost.html
(")_(")  http://www.cypherpunks.to/~peter/vista.pdf

 

On May 6, 2:42 am, w_tom <w_t...@usa.net> wrote:

   This will address some of your questions only in summary.  Details
are provided in other posts.

  First, much of this stuff was learned by earliest 20th century
hams.  They would disconnect their antenna, put the lead inside a
mason jar, and still suffer radio damage. Even mason jars could not
stop or block lightning.

I'd love to see a reference for this. In that time frame, lightning
was already fairly well understood. I find it hard to believe any ham
would try to use a mason jar in this way. Sounds more like some urban
legend to me.



But then the antenna was earthed, then damage

stopped.  It's just like Franklin's lightning rod (air terminal).
Protection has always been about diverting "it to ground, where it can
do no harm".  Disconnecting did not provide sufficient protection.
That wire had to be earthed.

  Protection for the TV, computer, and all other appliances is same.
Computers contain some of the most robust protection.  Computer grade
UPSes can output electricity so dirty (when in battery backup mode) as
to even harm some small electric motors.  But computers are so robust
as to make even that 'dirty' electricity irrelevant.  Do not assume
computers have less internal protection.  Intel ATX standards require
computers to be more robust than what is standard for other
appliances.

And guess what component is used as part of that robust protection?
MOVs, which W_ denies are used in electronics/appliances. Once again,
I'll ask the same question W_ refuses to answer. How is it that MOVs
or any other component can offer protection when used in a PC power
supply, but are useless in a plug-in surge protector? According to
W_, surge protection is impossible unless there is a direct and short
connection to earth ground. Does the PC power supply come with a
built-in earth ground?

 

On May 6, 9:52 pm, w_tom <w_t...@usa.net> wrote:

On May 6, 3:08 pm, trad...@optonline.net wrote:

W_  denies MOVs are commonly used in typical electonics or modern
appliances too.   He had to, because he can't answer the obvious
question of how MOVs can be used effectively in these applications,
yet they can't work in plug-in protectors and the only way to get any
protection is to have a nearby direct earth ground.   Faced with the
problem of MOVs providing protection in electronics/appliance without
an earthground, he simply denies MOVs are used in electronics and
appliances.  ...

  Using trader's reasoning, all appliances contain MOVs.  Therefore
plug-in protectors need not be purchased AND all appliances never
suffer surge damage. Conclusions directly from trader's post.

LOL. You're a real riot. YOU are the one that in previous and
similar long threads has stated that manufacturers of appliances and
electronic equipment put surge protection in them and that it works,
and used that as an argument as to why a plug-in surge protector is
useless.

I never stated that all appliances contain MOVs. I only stated that
they frequently or commonly do. You, on the other hand, denied that
MOVs are used in that kind of application. At which point, I
provided you references to a couple of articles in Appliance Magazine
that discuss how MOV are in fact commonly used in those applications:
A poster just told you his microwave has them. Another told you the
phone system sitting in front of him has them.

So, once again, stop lying about what I stated and answer the simple
question:

How is it that MOVs can work as surge protection inside the appliance,
but not in a plug-in surge protector? Where is that essential direct
earth ground? Does that microwave come with a built-in earth
ground? If not, then just like the plug-in surge protector, there is
no direct earth ground, so how can the MOV be helping protect the
microwave?

And it would help if you just answer that question, not start with a
long rant.

  Reality: all appliances contain protection using numerous techniques
such as galvanic isolation.  Protection that means all but a rare and
typically destructive surge is made irrelevant.  Internal appliance
protection is dependent on a properly earthed 'whole house'
protector.  The typically destructive surge must be earthed to not
overwhelm protection inside all appliances.

 

[bud--]

Mike Tomlinson wrote:

In article <8fa76$482087fc$4213ea45$31115@DIALUPUSA.NET>, bud--
remove.budnews@isp.com> writes

Last I heard UK phone entry protectors did not clamp the voltage to
earth.

You're quite correct. It's a practice that the GPO (forerunner to
British Telecom) abandoned in the 1960s, showing how up to date w_'s
"knowledge" is.

Phone wires were clamped to ground before the 1960s?

--
bud--

 

On May 6, 3:29 am, phil-news-nos...@ipal.net wrote:

In alt.engineering.electrical Don Kelly <d...@shaw.ca> wrote:

| Now - is this all germane to household protection? You say not and I agree
| with you- because household equipment can ride through - at worst- doubling
| of the clamped voltage for a very short time even though the clamped voltage
| is relatively small compared to the peak of the incoming surge. --

What if the surge is an extreme case (e.g. direct strike very near) and it is
arriving at protection devices in common mode (same polarity on all three
wires).  Bud's assertion _seems_ to be that no surge could ever be of the
type with substantial energy at high frequencies.  My belief is that they
can, and will at times.  Lightning strokes have that energy, or else you
would not receive them on UHF.  If the stroke is strong _and_ close (e.g..
less line inductance between the point of strike and where it is being
considered), then more of that UHF energy will arrive.

I have seen damage patterns in electronics that strongly suggests that there
were specific paths involved based on minor levels of reactance in the circuit.
A resistor would be melted along one path, but not so along another which had
a small inductor (3 turns in air) in the way.  And this device (a VCR) was on
a surge protector along with a TV that was unharmed.

If Bud is just arguing about the _typical_ (median?) surge level, then maybe
we are arguing apples and oranges.  I certainly don't intent to protect against
50% of surges.  My target is better than 99%.  I want to feel comfortable
sleeping through a severe thunderstorm while my computers and media center
remain plugged in.

I do agree that things can survive at the clamping voltage.  But there has to
be a clamping situation.  It's too easy for a surge to come in as a common
mode surge where the voltage difference across the MOVs would be (nearly) zero.
Then all we have is a propogating wavefront.  And if it is strong and/or close
then we have very fast rise times.  And it passes by the MOVs "laterally".

There's probably a big difference of opinion about just how much protection is
worth it.  But one thing I do see in at least part of this thread is that Bud
focuses on quoting things other people say, and does very little to express
things in his own words.  That suggests he reads but does not fully understand.
And that means I can't ask questions of what is said in the thread.  Since Bud
can't (or won't) defend what he's saying in his own words based on his own
knowledge, it's not really a two way street.  His "experts" are not involved
in the debate; they can neither defend their position nor be questioned about
it to get more details.

I find Bud's use of actual references interesting and think they add
to his credibility. Trying to suggest that someone using references
such as the IEEE to support their position detracts from their
credibility is preposterous. And trying to impugn him in this fashion
only detracts from your credibility.

It also has brought some other comments from people who are either anti-social
insulting types, or those that just don't understand what is said (apparently
having never dealt with transmission line propogation), or both.  But at least
I know who not to trust any technical opinions from when I have question to
ask about things I want to learn more about.

--
|WARNING: Due to extreme spam, I no longer see any articles originating from  |
|         Google Groups. If you want your postings to be seen by more readers |
|         you will need to find a different place to post on Usenet.          |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

 

[bud--]

VWWall wrote:

trader4@optonline.net wrote:

"New thermally enhanced MOVs help protect a wide variety of low-power
systems against damage caused by over-current, over-temperature and
over-voltage faults, including lightning strikes, electrostatic
discharge (ESD) surges, loss of neutral, incorrect input voltage and
power induction.

I had a microwave oven that had a MOV across the 120V line ahead of the
power switch. The other side of the 120/240 20A circuit supplied a
refrigerator. The loss of the neutral applied a good part of the 240V
across the MOV when the refrigerator attempted to start.

The MOV didn't last long! It would probably have been OK on the load
side of the switch.

Using a MOV to protect against loss of neutral (in the article) is
rather futile. Sustained overvoltage will rapidly kill them. Although if
the protected load was across the MOV and a fuse was ahead of both
protection may work. Would be interesting why the MOV was ahead of the
switch.

I know that refrigerators should be alone on a "home run" circuit, and
neutrals shouldn't be connected with wire nuts, but that wasn't how it was!

My only complaint with some plug-in protectors is that the MOVs are
often much too small. I've also seen some with only a line-line MOV.

I would only buy one with fairly high ratings (which are readily
available).

UL, as far as I know, requires MOVs to be L-N, L-G, N-G. I thought that
was the standard since the start, which w_ said was 1985.

--
bud--

 

[bud--]

phil-news-nospam@ipal.net wrote:

In alt.engineering.electrical bud-- <remove.budnews@isp.com> wrote:
| phil-news-nospam@ipal.net wrote:
|> In alt.engineering.electrical bud-- <remove.budnews@isp.com> wrote:
|> | phil-news-nospam@ipal.net wrote:
|> |> In alt.tv.tech.hdtv bud-- <remove.budnews@isp.com> wrote:
|
|> |> | w_' professional engineer source says 8 micoseconds with most of the
|> |> | spectrum under 100kHz.
|> |
|> |> Even with 1 nanosecond rise time, most of the energy will be present in
|> |> the spectrum below 100 kHz. That means nothing when the surge is strong
|> |> enough to have energy above some frequency that is relevant to the whole
|> |> system involved that can do damage. That frequency might be 100 Mhz for
|> |> some thing, and 1 GHz for other things.
|> |
|> | Still missing - your source. Nanosecond risetime. 100MHz spectrum.
|
|> Observation. Of course this is a concept you cannot understand.
|
| Observation proves flying saucers and magic.
|
| Without supporting sources it is Phil's Phantasy Physics.
| Where is a source that supports your belief in nanosecond risetimes and
| 100MHz spectrum?

There is no point in spending the effort to find some quotable source because
you wouldn't know what to do with it.

In other words - it is Phil’s Phantasy Physics, so no supporting link
exists.

--
bud--

 

[bud--]

trader4@optonline.net wrote:

On May 5, 2:20 pm, phil-news-nos...@ipal.net wrote:
In alt.engineering.electrical trad...@optonline.net wrote:

| On May 5, 1:44?am, phil-news-nos...@ipal.net wrote:
|> In alt.tv.tech.hdtv bud-- <remove.budn...@isp.com> wrote:| phil-news-nos...@ipal.net wrote:
|
|> |> In alt.engineering.electrical Leonard Caillouet <nos...@noway.com> wrote:|> | <phil-news-nos...@ipal.net> wrote in message
|
|> |> |news:fvjhvk016vr@news5.newsguy.com...
|> |> |> In alt.tv.tech.hdtv Franc Zabkar <fzab...@iinternode.on.net> wrote:
|> |> |
|> |> |
|> |> |> The MOVs will act like conductors when they are clamping. ?The surge will
|> |> |> take both paths ... the path through the MOVs, and the path going past the
|> |> |> MOVs. ?In general, about 50% will go each way. ?That can vary at higher
|> |> |> frequencies.
|> |> |
|> |> | Why would you assume that 50% will go each way when you don't know the
|> |> | impedance of each direction? ?When conducting, or at failure, the MOV has a
|> |> | very low impedance.
|> |
|> |> There is a distinction between "go each way" and "what comes back" due to
|> |> the impedance. ?It will be about 50% that goes each way _because_ the power
|> |> itself does not (yet) know the impedance (at a distance), until it gets
|> |> there.
|> |
|> | Another installment of Phil's Phantasy Physics using transmission line
|> | theory.
|
|> Not understanding it is your loss.
|
|
| I have to agree that this is Phantasy Physics. We're supposed to
| believe that a surge reaching a MOV is going to split 50-50, with half
| of it going to the MOV path and half moving on down the line,
| reagrdless of the impedance of the two paths? That would render all
| surge protection about 50% effective.

You did not read very carefully. The reference to 50-50 split is about the
contribution of the MOVs themselves. That is an essential understanding of
the components so the whole system can be figured out. The impedance down
the paths is another separate component, which also has to be figured in
when determining the whole picture.

You have confused a component with the entire system. You need to read more
carefully. Or you need to understand the distinction of individual components
as they apply to the whole system

The whole wiring system is extrememly complex. It cannot be understood
properly without first understanding the components. And that includes
understanding that MOVs, when they conduct, do look to the propogating
energy as two paths to go down, and it will (initially) go both ways in
about an equal amount.

Maybe you should review what you actually stated in the context of
current surge supression discussion:
"
"The MOVs will act like conductors when they are clamping. The surge
will
|> |> take both paths ... the path through the MOVs, and the path
going past the
|> |> MOVs. In general, about 50% will go each way. That can vary at
higher
|> |> frequencies. "

That sure sounds like 50% of the surge is going through the MOV and
the other 50% is going on past it to the protected equipment.

And that I would have to agree with Bud on, it's phantasy physics,
because if it were true, no type of surge protection would work,
because it would only be 50% effective.

He is using transmission line effects which Martzloff investigated and
said do not come into play unless the circuit is 200m long. Phil claims
high frequencies.

Still missing - a source that supports nanosecond risetimes and 100MHz
spectrum.

--
bud--

 

[bud--]

w_tom wrote:

On May 6, 1:00 pm, bud-- <remove.budn...@isp.com> wrote:

w_ can't understand his own hanford link. It is about "some older
model" power strips and says overheating was fixed with a revision to
UL1449 that required thermal disconnects. That was 1998.

Bud will only challenge the hanford link because he cannot challenge
those 'scary pictures'.

w_ only provides those ‘scary pictures’ because he has no valid
technical arguments.

Still missing - a link to any source that says UL listed plug-in
suppressors made after 1998 are a problem.

Another is a fire marshal describing
why plug-in protectors can create house fires.

The fire marshal said: "More modern surge suppressors are manufactured
with a Thermal Cut Out mounted near, or in contact with, the MOV that is
intended shut the unit down overheating occurs.[sic]"

And then Bud posts a half fact. UL1449 was created on 28 Aug 1985 -
not in 1998 as Bud claims.

It is really hard to understand how someone could be stupid enough to
not know the difference between a creation date and a revision date.

From w_'s hanford link:
"Underwriters Laboratories Standard UL 1449, 2nd Edition, Standard For
Safety For Transient Voltage Surge Suppressors, now requires thermal
protection in power strips. This protection is provided by a thermal
fuse located next to the MOV."

The fire marshal says the same thing (above)

If w_ had any knowledge of the field he would know UL 1449, 2nd Ed was
effective in 1998.

Bud refuses to post a
specification for one simple reason.

Posted often and ignored. Another of w_'s favorite lies.

In reply, this is
what Bud is really promoting - these 'scary pictures':
http://www.hanford.gov/rl/?page=556&parent=554

The lie repeated. But w_ is a fan of Josef Goebbels and thinks if you
repeat a lie often enough, people will believe it.


Still missing - a link to another lunatic that says plug-in suppressors
are NOT effective.

Still missing – answers to embarrassing questions:
- Why do the only 2 examples of surge suppression in the IEEE guide use
plug-in suppressors?
- Why does the NIST guide says plug-in suppressors are "the easiest
solution"?
- Why do all but one of w's "responsible manufacturers" make plug-in
suppressors?
- Why does SquareD say in addition to their "whole house" suppressors
"electronic equipment may need additional protection" from plug-in
suppressors.
- Why aren't airplanes crashing daily when they get hit by lightning (or
do they drag an earthing chain)?

–-
bud--

 

[bud--]

phil-news-nospam@ipal.net wrote:

In alt.engineering.electrical bud-- <remove.budnews@isp.com> wrote:
| phil-news-nospam@ipal.net wrote:
|> In alt.engineering.electrical Don Kelly <dhky@shaw.ca> wrote:
|
|> | Now - is this all germane to household protection? You say not and I agree
|> | with you- because household equipment can ride through - at worst- doubling
|> | of the clamped voltage for a very short time even though the clamped voltage
|> | is relatively small compared to the peak of the incoming surge. --
|
|> My belief is that they
|> can, and will at times.
|
| People believe in flying saucers.
| Where is a source that supports your belief?

My observations support my belief.

Observations support belief in astrology, reflexology, homeopathy,
dowsing, healing touch, Feng Shui, Sylvia Brown, ....

|> I do agree that things can survive at the clamping voltage. But there has to
|> be a clamping situation. It's too easy for a surge to come in as a common
|> mode surge where the voltage difference across the MOVs would be (nearly) zero.
|> Then all we have is a propogating wavefront. And if it is strong and/or close
|> then we have very fast rise times. And it passes by the MOVs "laterally".
|
| Where is a source that supports your belief in nanosecond risetimes and
| 100MHz spectrum?

Another poster followed up to my post you just followed up to that also has
experienced the same thing.

I am not interested in direct lightning strikes to my house. Protection
requires lightning rods.

I am interested in surge protection. That is surges coming in on utility
wires, direct induction, ground potential rise, ....

Martzloff says transmission line effects require 200m branch circuits.

You disagree with Martzloff (and have said "he flubbed the experiment")
but provide no sources that agree with your belief.

|> But one thing I do see in at least part of this thread is that Bud
|> focuses on quoting things other people say, and does very little to express
|> things in his own words.
|
| I focus on the real world. You focus on your beliefs.

You focus on citing and quoting things you do not understand well enough to
just talking about them in technical terms.

In other words, it is Phil’s Phantasy Physics.

Where is a source that supports your belief in nanosecond risetimes and
100MHz spectrum?
There should be plenty of sources.

--
bud--

 

[VWWall]

bud-- wrote:

VWWall wrote:
trader4@optonline.net wrote:

"New thermally enhanced MOVs help protect a wide variety of low-power
systems against damage caused by over-current, over-temperature and
over-voltage faults, including lightning strikes, electrostatic
discharge (ESD) surges, loss of neutral, incorrect input voltage and
power induction.

I had a microwave oven that had a MOV across the 120V line ahead of
the power switch. The other side of the 120/240 20A circuit supplied
a refrigerator. The loss of the neutral applied a good part of the
240V across the MOV when the refrigerator attempted to start.

The MOV didn't last long! It would probably have been OK on the load
side of the switch.

Using a MOV to protect against loss of neutral (in the article) is
rather futile. Sustained overvoltage will rapidly kill them. Although if
the protected load was across the MOV and a fuse was ahead of both
protection may work. Would be interesting why the MOV was ahead of the
switch.

Good question. In the MW oven case, the switch was a relay controlled
by the timer circuit. It was probably easier to locate the MOV at the
line input.

I have seen cases with a "blown" MOV and the circuit protector tripped.
The MOV, if it tripped the protector, may have saved the following
circuits from the over-voltage condition for a longer period of time. I
haven't tried to calculate the conditions under which this would work.

I know that refrigerators should be alone on a "home run" circuit, and
neutrals shouldn't be connected with wire nuts, but that wasn't how it
was!

My only complaint with some plug-in protectors is that the MOVs are
often much too small. I've also seen some with only a line-line MOV.

As you know, MOVs lose their capacity each time a "spike" causes them to
conduct. This reduces the remaining capability to handle "surges".

I would only buy one with fairly high ratings (which are readily
available).

True, but some are marketed as "surge protected" with minimal capacity.
I've replaced the MOVs in several cheap multiple socket strips with
higher rated MOVs from Radio Shack.

UL, as far as I know, requires MOVs to be L-N, L-G, N-G. I thought that
was the standard since the start, which w_ said was 1985.

I think the UL requires only that the MOVs don't start a fire when
exposed to conditions which cause their break-down. They don't rate
their ability to function as "surge protectors".

--
Virg Wall, P.E.

 

[VWWall]

fl_fly_boy@yahoo.com wrote:

I think the UL requires only that the MOVs don't start a fire when
exposed to conditions which cause their break-down. They don't rate
their ability to function as "surge protectors".


UL evaluates surge suppressors for fire, electric shock and personal
injury hazards, and also measures and categorizes the devices for how
much voltage they can "clamp," thus preventing excess voltage from
passing through to electronic equipment. UL refers to this as a
"suppressed voltage rating," with ranges from 330V (volts) to 4000V.
Believe it or not, the lower the rating, the better the protection.

How can one find this rating for a particular device?

Whatever surge suppression protection you're looking for, make sure
the surge suppressor has been tested and Listed to the stringent
requirements of UL 1449, the Standard for Transient Voltage Surge
Suppressors.

http://www.ul.com/consumers/surge.html

"The unpredictable nature of surges makes it difficult to suppress them;
you never know when, how long or how powerful they will be. In some
cases, a surge may have a higher energy level than the device can
handle. When this happens, the surge suppressor may be damaged and lose
its ability to provide protection against future surges."

I'm happy to see that UL agrees! They don't seem to put any evaluation
of this parameter, unless the "suppressed voltage rating" includes the
Jules rating of the MOVs.

http://ulstandardsinfonet.ul.com/tocs/tocs.asp?doc=s&fn=1449.toc

Thanks for the reference.

--
Virg Wall, P.E.

 

[VWWall]

VWWall wrote:
<see original post>

http://www.ul.com/consumers/surge.html

"The unpredictable nature of surges makes it difficult to suppress them;
you never know when, how long or how powerful they will be. In some
cases, a surge may have a higher energy level than the device can
handle. When this happens, the surge suppressor may be damaged and lose
its ability to provide protection against future surges."

I'm happy to see that UL agrees! They don't seem to put any evaluation
of this parameter, unless the "suppressed voltage rating" includes the
Jules rating of the MOVs.

This should read "Joules". See:

http://en.wikipedia.org/wiki/Varistor

for some useful information.

--
Virg Wall, P.E.

 

I think the UL requires only that the MOVs don't start a fire when
exposed to conditions which cause their break-down.  They don't rate
their ability to function as "surge protectors".

UL evaluates surge suppressors for fire, electric shock and personal
injury hazards, and also measures and categorizes the devices for how
much voltage they can "clamp," thus preventing excess voltage from
passing through to electronic equipment. UL refers to this as a
"suppressed voltage rating," with ranges from 330V (volts) to 4000V.
Believe it or not, the lower the rating, the better the protection.

Whatever surge suppression protection you're looking for, make sure
the surge suppressor has been tested and Listed to the stringent
requirements of UL 1449, the Standard for Transient Voltage Surge
Suppressors.

http://www.ul.com/consumers/surge.html

http://ulstandardsinfonet.ul.com/tocs/tocs.asp?doc=s&fn=1449.toc

 

[flyboy]

On May 7, 2:37 pm, VWWall <vw...@large.invalid> wrote:

fl_fly_...@yahoo.com wrote:
I think the UL requires only that the MOVs don't start a fire when
exposed to conditions which cause their break-down.  They don't rate
their ability to function as "surgeprotectors".

UL evaluatessurgesuppressors for fire, electric shock and personal
injury hazards, and also measures and categorizes the devices for how
much voltage they can "clamp," thus preventing excess voltage from
passing through to electronic equipment. UL refers to this as a
"suppressed voltage rating," with ranges from 330V (volts) to 4000V.
Believe it or not, the lower the rating, the better the protection.

How can one find this rating for a particular device?

Look for ul1449 330v or 400 for example, or surge voltage rating SVR
330v or Clamping Category 330v

Whateversurgesuppression protection you're looking for, make sure
thesurgesuppressor has been tested and Listed to the stringent
requirements of UL 1449, the Standard for Transient VoltageSurge
Suppressors.

http://www.ul.com/consumers/surge.html

"The unpredictable nature of surges makes it difficult to suppress them;
you never know when, how long or how powerful they will be. In some
cases, asurgemay have a higher energy level than the device can
handle. When this happens, thesurgesuppressor may be damaged and lose
its ability to provide protection against future surges."

MOV’s and surge protectors are like tires on your car, the more you
use them the shorter useful life, mistreat them, the shorter the
useful life, too small or light weight the shorter the useful life.
Ul 1449 certification take care of the too small or light weight.
Proper selection for problem locations is the key to protection.

I'm happy to see that UL agrees!  They don't seem to put any evaluation
of this parameter, unless the "suppressed voltage rating" includes the
Jules rating of the MOVs.

Don’t pay attention to joules on surge protectors, no standard to
measure, a better and recommended rating is “Peak Surge Current” the
higher the better.

http://ulstandardsinfonet.ul.com/tocs/tocs.asp?doc=s&fn=1449.toc

Thanks for the reference.

--
Virg Wall, P.E.