On Fri, 08 Oct 2004 05:35:32 +0000, NSM wrote:


"James Sweet" wrote in message
news:jcp9d.5644$eq1.2343@trnddc08...

| Lightning can cause some very bizarre failures indeed. I had a USR modem
| years ago that failed after a nearby lightning strike (rare here) and the
| problem turned out to be a 10 ohm surface mount resistor with a crater in
| it. Replaced it with a normal resistor and it worked fine until it was
| retired years later.

What most people think is caused by lightning is really caused by induction.
A direct lightning strike will turn your computer etc. into a pile of
bubbling slag. A strike near the phone line causing induction elsewhere will
zap things in very odd ways.

Not really. Most of the lightning damage is caused by ground currents
going where you don't want them to go. A strike on a tree in the back
yard can fry all electronics in the house ifthe grounds aren't done
right. There should only be *one* ground (floating boats theory) and if
there must be more they must all be bonded together with some serious
conductors (see: floating boats).

--
Keith

"keith" wrote in message
news | On Fri, 08 Oct 2004 05:35:32 +0000, NSM wrote:
....
| What most people think is caused by lightning is really caused by
induction.
| A direct lightning strike will turn your computer etc. into a pile of
| bubbling slag. A strike near the phone line causing induction elsewhere
will
| zap things in very odd ways.
|
| Not really. Most of the lightning damage is caused by ground currents
| going where you don't want them to go. A strike on a tree in the back
| yard can fry all electronics in the house ifthe grounds aren't done
| right. There should only be *one* ground (floating boats theory) and if
| there must be more they must all be bonded together with some serious
| conductors (see: floating boats).

Yes. Induction.

N

On Sat, 09 Oct 2004 02:34:47 +0000, NSM wrote:


"keith" wrote in message
news | On Fri, 08 Oct 2004 05:35:32 +0000, NSM wrote:
...
| What most people think is caused by lightning is really caused by
induction.
| A direct lightning strike will turn your computer etc. into a pile of
| bubbling slag. A strike near the phone line causing induction elsewhere
will
| zap things in very odd ways.
|
| Not really. Most of the lightning damage is caused by ground currents
| going where you don't want them to go. A strike on a tree in the back
| yard can fry all electronics in the house ifthe grounds aren't done
| right. There should only be *one* ground (floating boats theory) and if
| there must be more they must all be bonded together with some serious
| conductors (see: floating boats).

Yes. Induction.

No, *NOT* induction! It's simple resistance. You simply don't want to
be in the middle. The idea is to float, like a boat.

--
Keith

keith wrote:


No, *NOT* induction! It's simple resistance. You simply don't want to
be in the middle. The idea is to float, like a boat.



Brings to mind an interesting question. Out here in well and septic
country, the code authorities make us ground the electrical system with
a UFER ground (copper wire buried in concrete, buried in the ground).
But they also make us ground our well pumps to the steel well casing.

Which gives us.... competing grounds with different ground potentials.

I wonder how much trouble that causes with lightning?

-Chuck

"Chuck Harris" wrote in message
...

| Brings to mind an interesting question. Out here in well and septic
| country, the code authorities make us ground the electrical system with
| a UFER ground (copper wire buried in concrete, buried in the ground).
| But they also make us ground our well pumps to the steel well casing.
|
| Which gives us.... competing grounds with different ground potentials.
|
| I wonder how much trouble that causes with lightning?

I'd certainly want to bond the well to the UFER ground system. IME any
system with different grounds allowing potential differences is dangerous.

N

NSM wrote:
"Chuck Harris" wrote in message
...

| Brings to mind an interesting question. Out here in well and septic
| country, the code authorities make us ground the electrical system with
| a UFER ground (copper wire buried in concrete, buried in the ground).
| But they also make us ground our well pumps to the steel well casing.
|
| Which gives us.... competing grounds with different ground potentials.
|
| I wonder how much trouble that causes with lightning?

I'd certainly want to bond the well to the UFER ground system. IME any
system with different grounds allowing potential differences is dangerous.

It is bonded back at the service panel with a #10ga copper wire. The pipe
to the well is plastic.

The last time we got a direct hit by lightning, the water changed its tint
for several days. It went from grey, to yellow/orange. We lost a chunk of
terracotta flue liner on that one, and several appliances.

-Chuck

In comp.sys.ibm.pc.hardware.chips Chuck Harris wrote:
It is bonded back at the service panel with a #10ga copper
wire. The pipe to the well is plastic.

#10 is good, #00 is better~!

The last time we got a direct hit by lightning, the water
changed its tint for several days. It went from grey,
to yellow/orange. We lost a chunk of terracotta flue liner
on that one, and several appliances.

Perhaps you should install a whole-house surge protector on
the panel (~$50). You lose two-wire appiances through ground
vs power surges. Your pole transformer and it's ground is
probably a ways away.

-- Robert

Robert Redelmeier wrote:
In comp.sys.ibm.pc.hardware.chips Chuck Harris wrote:

It is bonded back at the service panel with a #10ga copper
wire. The pipe to the well is plastic.


#10 is good, #00 is better~!


The last time we got a direct hit by lightning, the water
changed its tint for several days. It went from grey,
to yellow/orange. We lost a chunk of terracotta flue liner
on that one, and several appliances.


Perhaps you should install a whole-house surge protector on
the panel (~$50). You lose two-wire appiances through ground
vs power surges. Your pole transformer and it's ground is
probably a ways away.

-- Robert

The lightning hit the chimney cap, went down the brickwork of the
chimney, and entered the bond system by way of an outdoor flood
light that is mounted next to the chimney. The current zapped
a 3 wire treadmill (7 ft from floodlight), and flipped the breaker
on the circuit that had the flood light. No damage through the power
to any other devices. However, the induced surge in the security
wire/telephone wires that pass through the house blew two modems and
a phone answering machine. But not a cordless phone, or any other
telephones. One modem carried its surge into the RS232 line, and
toasted the drivers and uart on a Dell motherboard. I lost a
HPJetDirect card too... a failure in the 10baseT driver circuits.

Our power is buried, and the transformer is one of those steel
enclosed boxes about 70 feet from the house.

Fun!

One thing I have never been able to determine is whether we would
be safer with a lightning rod system, or without. My insurance
company is silent on this issue... you pay the same rates either
way. In our area, there have been several houses and barns that
have burned down,due to lightning strikes, and they had lightning
rod systems. Anecdotal evidence, to be sure.

-Chuck Harris

In comp.sys.ibm.pc.hardware.chips Chuck Harris wrote:
The lightning hit the chimney cap, went down the brickwork of the

All bets are off in a direct strike. Common grounding only
reduces the damage from a nearby strike.

to any other devices. However, the induced surge in the
security wire/telephone wires that pass through the house
blew two modems and a phone answering machine. But not a
cordless phone, or any other telephones. One modem carried

I still doubt this was induced _unless_ 1) Phone was
run parallel to the floodlight circuit for some distance
and 2) Phone and power were on the same groundstake.

Most likely, phone was on it's own groundstake, so anything
bonded to power ground would get fried by the ground
differential between power and ground.

Our power is buried, and the transformer is one of those
steel enclosed boxes about 70 feet from the house.

Good!

One thing I have never been able to determine is whether
we would be safer with a lightning rod system, or without.

Hard to say. A lightening rod system could be dangerous
if the insulation was insufficiently heat-resistant.

-- Robert

"Chuck Harris" wrote in message
...
.....
| One thing I have never been able to determine is whether we would
| be safer with a lightning rod system, or without. My insurance
| company is silent on this issue... you pay the same rates either
| way. In our area, there have been several houses and barns that
| have burned down,due to lightning strikes, and they had lightning
| rod systems. Anecdotal evidence, to be sure.

Lightning strikes up from the best point on the ground. IMO, the safest way
is to install a lightning rod away from the house (separately guyed) but
close enough to protect your property. Just don't stick your tongue on it
when it's stormy out!

N

Robert Redelmeier wrote:

All bets are off in a direct strike. Common grounding only
reduces the damage from a nearby strike.

....
I still doubt this was induced _unless_ 1) Phone was
run parallel to the floodlight circuit for some distance
and 2) Phone and power were on the same groundstake.

When I built my house, I wanted some wiring to be available
in all rooms, so I ran loops of 25 pair CAT3 telephone cable
around the outside perimeter of each floor in the house. The
loops end at punch down (66) blocks in the basement. There
are no sections of the loops that run parallel to the power wiring
separated closer than 1 foot. There is only one area where the
loops run perpendicular to the power wiring, and that is where the
power cables drop to the service panel. At these points, the loops
are a couple of inches away from the power cables.

One of the damaged modems was connected to the loop that ran
nearest to the lightning strike. It was a zoom modem ISA bus
modem, and its protection circuitry shorted out. No damage
was done to the computer.

The other damaged modem was a $15 Centdyne. It had a chip inductor
in series with one side of the line that was completely blown away.
The MOV that was across the line was still OK. The current that entered
this modem would have had to pass through about 100 feet of
#24 gauge wire, yet it still had enough zap to burn that inductor
off of the board (and destroy the modem's chip set, and the computer's
RS232 drivers and uart)

Most likely, phone was on it's own groundstake, so anything
bonded to power ground would get fried by the ground
differential between power and ground.

Since I did the power and telephone work, they are both grounded
to the UFER ground at the service panel, which is where they enter
the house. The nearest power pole is 600 feet away. So there is
no point in the power grid within 600 feet where lightning could
enter the system... other than my house.

One thing I have never been able to determine is whether
we would be safer with a lightning rod system, or without.


Hard to say. A lightening rod system could be dangerous
if the insulation was insufficiently heat-resistant.

What seems to happen, anecdotally, is the rods conduct the
bolt, and burn the roof where the ground wires run along
the ridge... even though the ground wires for the rods typically
are held 1 foot above the roof.

What I am thinking of doing is adding a lightning rod to the
masonry chimney structure. It is the highest point on the house,
and in the vicinity. I will give it a decent UFER ground
of its own, a few dozen feet from the house. My hope is this
will protect the chimney, but will not endanger the rest of
the house.

-Chuck Harris

NSM wrote:

Lightning strikes up from the best point on the ground. IMO, the safest way
is to install a lightning rod away from the house (separately guyed) but
close enough to protect your property. Just don't stick your tongue on it
when it's stormy out!

N



It is my understanding that a lightning rod provides a statistical cone of
protection that is approximately the same diameter at the base as the rod
is high. To protect my 65 foot long house would require a rod that is
around 150 feet high, and right next to the chimney. Or perhaps 2 rods
100 feet high on either end of the house.

"Honey, I have to put up a 200 foot ham tower to protect our house from
lightning!"

-Chuck Harris

On Sun, 10 Oct 2004 12:18:20 -0400, Chuck Harris
wrote:

It is my understanding that a lightning rod provides a statistical cone of
protection that is approximately the same diameter at the base as the rod
is high. To protect my 65 foot long house would require a rod that is
around 150 feet high, and right next to the chimney. Or perhaps 2 rods
100 feet high on either end of the house.

Hmm i read in the newspaper once that some university expert says it
was a 30 degrees cone, so that would make it even taller no? pPp

--
L.Angel: I'm looking for web design work.
If you need basic to med complexity webpages at affordable rates, email me
Standard HTML, SHTML, MySQL + PHP or ASP, Javascript.
If you really want, FrontPage & DreamWeaver too.
But keep in mind you pay extra bandwidth for their bloated code

The little lost angel wrote:

It is my understanding that a lightning rod provides a statistical cone of
protection that is approximately the same diameter at the base as the rod
is high. To protect my 65 foot long house would require a rod that is
around 150 feet high, and right next to the chimney. Or perhaps 2 rods
100 feet high on either end of the house.


Hmm i read in the newspaper once that some university expert says it
was a 30 degrees cone, so that would make it even taller no? pPp


Could be, but I would suppose it depends on where you set your probability
threshold. 50%? 80%? 90%?...

The only place where there is a 100% probability of protection is inside
the ground wire, which would correspond to a zero degree cone. My point is
that just having a lightning rod up high somewhere, doesn't necessarily mean
you should expect it will protect your house.

The Navy found that the best protection was afforded by having a horizontal
ground wire over the top of the building to be protected. But again, you
had to put the wire up high enough so it gave you a "tent" with a comfortable
probability of protection from a strike.

I don't think I can talk my wife into allowing such a system.

-Chuck Harris

On Mon, 11 Oct 2004 00:07:48 -0400, Chuck Harris wrote:

The little lost angel wrote:

It is my understanding that a lightning rod provides a statistical cone of
protection that is approximately the same diameter at the base as the rod
is high. To protect my 65 foot long house would require a rod that is
around 150 feet high, and right next to the chimney. Or perhaps 2 rods
100 feet high on either end of the house.


Hmm i read in the newspaper once that some university expert says it
was a 30 degrees cone, so that would make it even taller no? pPp


Could be, but I would suppose it depends on where you set your probability
threshold. 50%? 80%? 90%?...

The only place where there is a 100% probability of protection is inside
the ground wire, which would correspond to a zero degree cone. My point is
that just having a lightning rod up high somewhere, doesn't necessarily mean
you should expect it will protect your house.

The Navy found that the best protection was afforded by having a horizontal
ground wire over the top of the building to be protected. But again, you
had to put the wire up high enough so it gave you a "tent" with a comfortable
probability of protection from a strike.

I don't think I can talk my wife into allowing such a system.


Chuck, Chuck, Chuck, you obviously haven't tried hard enough. L'Angel is
giving you the ammunition. Tell SWMBO that another of her half agrees
with you. Build that 400' tow^h^h^hlightning arrestor; her life may
depend on it! ...but watch the blinkin' lights. ;-)

-Chuck Harris

On Mon, 11 Oct 2004 22:05:08 -0400, keith wrote:

I don't think I can talk my wife into allowing such a system.


Chuck, Chuck, Chuck, you obviously haven't tried hard enough. L'Angel is
giving you the ammunition. Tell SWMBO that another of her half agrees
with you. Build that 400' tow^h^h^hlightning arrestor; her life may
depend on it! ...but watch the blinkin' lights. ;-)

I din say I agreed with having some ugly monstrousity hanging over
anybody's house!!! I was only sharing something I read! But of course
if he could find a way to make a 200ft lightning rod look pretty...
PpPpPpP

--
L.Angel: I'm looking for web design work.
If you need basic to med complexity webpages at affordable rates, email me
Standard HTML, SHTML, MySQL + PHP or ASP, Javascript.
If you really want, FrontPage & DreamWeaver too.
But keep in mind you pay extra bandwidth for their bloated code

On Thu, 14 Oct 2004 01:02:19 +0000, The little lost angel wrote:

On Mon, 11 Oct 2004 22:05:08 -0400, keith wrote:

I don't think I can talk my wife into allowing such a system.


Chuck, Chuck, Chuck, you obviously haven't tried hard enough. L'Angel is
giving you the ammunition. Tell SWMBO that another of her half agrees
with you. Build that 400' tow^h^h^hlightning arrestor; her life may
depend on it! ...but watch the blinkin' lights. ;-)

I din say I agreed with having some ugly monstrousity hanging over
anybody's house!!! I was only sharing something I read! But of course
if he could find a way to make a 200ft lightning rod look pretty...
PpPpPpP

LOL, but Ham antennnas *are* pretty! I even like the look of cell towers.
....business ...money ...good!

--
Keith