In alt.tv.tech.hdtv bud-- wrote:

| According to NIST guide, US insurance information indicates equipment
| most frequently damaged by lightning is
| computers with a modem connection
| TVs, VCRs and similar equipment (presumably with cable TV
| connections).
| All can be damaged by high voltages between power and signal wires.

And this is new information how?


| This suppressor includes, in the unit, ports for cable and phone. That
| limits the voltages at the entrance point. You can still get problems
| downstream. One possibility is a very near strike producing direct
| induction with wiring acting as a long wire or loop antenna.

Of course. And this is new info?


| A rather common recommendation is to use a power service suppressor to
| provide gross limitation and a plug-in suppressor at "sensitive
| electronics" particularly with signal and power connections.

I would add to that, to protect ALL metallic wiring coming in to the
building at one place. That way you keep all at the same potential
and using a single point of earthing. You can get substantial voltage
difference between different points of earthing even when no lightning
happens to strike anywhere near at all. A ground charge builds up
under a storm, with the opposite polarity of the lower layer of the
cloud base. Now as the storm moves along, what do you think happens
to that ground charge? It moves along, too. But, it actually lags
behind the storm a bit, varying depending on ground conditions, speed
of storm movement, etc. This is one reason why you can often see a
lightning strike jump from the backside of a storm and go laterally
for even as far as several miles, and then hit ground. I have seen
such lightning strikes (a 5 mile one) and seen the damage from ground
currents (melted a wire between two electrodes placed about 1/4 mile
apart along a storm track direction).


| | For the next best suppressor - QO2175SB and HOM2175SB
| | - The connected equipment warranty $ does not include "electronic
| | devices such as: microwave ovens, audio and stereo components, video
| | equipment, televisions, and computers."
| |
| | It appears none of w_'s companies has a high reputation.
|
| Or maybe it's a different type of suppressor. Did you even look?
|
| The differences have absolutely no relevance for the response to w_.
|
| But this one is a plug-onto-the-bus unit with suppression only for power
| wires.
|
| A service panel suppressor does not limit the voltage between power and
| signal wires. To do that you need a short ground wire from the signal
| entrance protector to the ground at the power service (or the combined
| suppressor above). SquareD has no idea what is in your house.

Or a combined entrance suppressor. I don't know if anyone makes one.
I would just ground everything on a board with a big sheet of copper as
grounded backing.


| There are other possible sources of damage a power-service-only
| suppressor does nothing about, including high voltage between conductor
| and shield in cable wire, which is not limited by the cable entrance
| ground block.

It can be limited to some degree by the grounding block by having an arc
crossover inside. If the voltage exceeds the arc breakdown, you then have
a much lower impedance for center conductor surges to get to ground.


| Maybe you should look at the Eaton-Cutler-Hammer devices.
|
| Maybe you should look at CH. I don't really care.

If you want to see options beyond what SQD has, then do look at CH.
I have downloaded the SQD and CH catalogs, so I can look (but I will
for myself, not for you).


| The only sources you are looking at simply give a generic list of what kinds
| of things you might use. There are no scientific explanations to help you
| figure out what is needed in your particular situation for you to achieve the
| level of protection you want. OTOH, I have my doubts about your ability to
| understand the science, so that may explain why they limited things to a few
| simplistic illustrations in what is really just a "to do" guide that does not
| cover all situations or all levels of protection.
|
| I have read a lot of sources, including many technical papers on surges
| and surge suppression. You should have figured that out from references
| provided previously, which included several technical papers. But you
| seem to do minimal reading of reading of what others write.

Given your long diatribes, and your fixation on how you respond to others
in an accusatory manner, a lot of your posts go unread even by me.

Maybe what you could do is start a blog. bud-vs-surges.blogspot.com maybe?
Then you can have a collection of links all together in one place where its
easy to refer to them all at once. Or just make a web page.


| You have read little on surges and have said you base your beliefs on
| your experience. Experience shows astrology works.

I've read enough. I've also talked with experts in the field who hold
jobs as college professors in EE departments.


| You suggest experts in the field "missed a lot of reality" and "flubbed
| the experiment".

I propose that as one explanation as to why these guides come up short on
the explanations.


| You discount the IEEE guide. It comes from the IEEE Surge Protection
| Devices Committee, was peer reviewed in the IEEE, and is aimed at
| technical people including electrical engineers. If you ever read it you
| would find "scientific explanations". You might also find "scientific
| explanations" in the technical papers I have referenced, which you
| probably have not read.

The guide I read that you pointed me to simply did not cover the whole topic.
It left out lots of things. Maybe what it covered was all technically correct.
But it was not a useful guide for the purpose of determing what solution is
needed for all situations.

And look carefully at the name "IEEE Surge Protection Devices Committee".
This is about DEVICES. Proper surge protection involves MORE than just
devices. If you are in the business of designing a DEVICE, then sure, go
with their advice. If you need to select a DEVICE to fit into an overall
plan of surge protection, then sure, use their information about devices.
But when the issue has a broader scope than just devices, you may need to
recognize that you won't get all your information from one place.


| But what could -you- learn by reading what others write. There
| apparently is no expert but you.

I'm not claiming to be an expert. But when people talk about things with
even less knowledge than I have, and especially when what they say contradicts
actual observations, then I know _they_ cannot be an expert (or else there is
some misinformation and the situations are not really a match).

For example, consider the high frequency issue. High frequency energy is
less common than low frequency energy. Partly this is because the chance
of a closer lightning strike is less than a more distant one. A strike
within 100 meters is only 1/8 as like as a strike outside of 100 meters
but within 300 meters. Some people then feel that they can dismiss high
frequency energy issues entirely. It's really a matter of degree. But
there are low cost solutions that can still justify addressing these less
frequent events. For example, a simple small inductor on the power wires
just immediately after the point where the neutral is bonded to ground
and the hot conductors can be clamped to ground under high voltages (MOVs
and/or arc gaps) can force more of the high frequency energy to divert to
ground instead of continuing on to the vulnerable devices.

Right now, all of my computers are wired on a single power outlet and there
is no long term alternate metallic path. Broadband is wireless to another
room where a sacrificial wireless router is attached to the cable modem.
When I add DSL, that will go on another wireless router and a 2nd wireless
bridge will be added to the computer room LAN, on the same power strips,
to access it.

Unfortunately, I'm getting close to the circuit limit. I need another
power circuit. That can create issues. So my current plan is to add a
240 volt circuit. That will be fed through a separate protector, probably
a CH one, next to the panel, and fed to the computer room to a single NEMA
14-20 outlet. I'm looking for a plug-in suppressor to supplement at that
location. I may have to make one from CH or SQD components, since this is
still a 240 volt point. Once that exists, then I can split the circuit to
separate 120 volt strips at short distances.


| You have never provided a source that agrees with you on disputed issues.

Nor do I need to. This is not an issue about trying to get people to agree
with me. It's about knowing a broad enough scope of science to be able to
determine a solution in a _wide_ range of possibilities, and to know when a
given situation really does _not_ match one that a known solution applies to.

--
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| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |