On 5/20/2016 10:39 AM, email@example.com wrote:
From an expert investigation - maximum energy at a plug-in protector
was 35 joules, and almost all cases under 1 joule, with a power line
surge including those caused by a 100,000A lightning strike to the
primary wire at an adjacent utility pole. The maximum energy wasn't even
from the worst surge.
When the voltage at service panel busbars reaches about 6,000V there is
arc-over to the enclosure. The voltage of the established arc is
hundreds of volts. Since the enclosure is connected to the earthing
system that dumps most of the surge energy to earth. Since the "ground"
and neutral are also connected to the enclosure, the exposure beyond the
panel if far less than imagined.
A strong surge will drive the voltage on the busbars to 6,000V and
arc-over. With a weaker surge, a plug-in protector on a short branch
circuit may keep the service panel voltage below arc-over. The 35 joule
energy in the investigation was with one of those weaker surges.
I don't suggest that people use plug-in protectors. I suggest they make
decisions based on science.
Discussion centers on plug-in protectors because of the misinformation
posted by westom (and other misinformation that has been posted).
On 05/19/2016 12:05 PM, firstname.lastname@example.org wrote:
Many years the utility pole directly behind my house got a direct
lightning hit. I was in the kitchen and almost lost it when I observed
the simultaneous lightning and thunder!
My answering machine was on the closest run to the outdoor wiring and
was taken out...but nothing else in the house was damaged.
As a kid, I used to play the "5 second game" (flash-to-sound) during
Tstorms. One evening, the house "shook" as I saw the flash. I.e.,
too startled to even think of "counting". Of course, had I tried
to count, I wouldn't have made it past "0"! :>
Next morning, noticed lots of bark on the ground beneath one of the
walnut trees adjacent to the living room. "That's odd". Looked up
to see the bark peeled off one side of the tree all the way to the
"Ah! That must have been what shook the house!"
We had a "nearby" strike when living in Denver (no idea how close it was as
I was at work at the time). It took out the protection network in one of
our (cheap) "electronic" telephones -- resulting in a perpetual off-hook
indication (annoying cuz every time I tried to call home, the line was
"busy"!). Also magnetized the screen in our TV. Took many weeks of
the built-in degausser operating to restore color purity!
We get plenty of thunderstorm practice here in Florida. There is a
thunderstorm just about every day for 6-7 months of the year. We call
that thing "Flash/bang" lightning when they both occur at the same
Usually when a tree is hit, you will see little sticks everywhere,
burning on both ends.
was dwarfed by a HUGE Oak tree, about 3 times as tall as the house and
some 18 feet in circumference at chest height. They had both a well
and a cistern on the "back porch" - opposite side of the house from
the oak, and a big bank barn on the other side of the tree - house and
barn both festooned with lightning rods. All rhis perched on the top
of a hill, no-less.
Several times the cystern pump or well pump were struck, and on at
least one occaision the ligtning jumped from the pump, through the
back door,to the aluminum edging on the kitchen counter, to the wood
cookstove, to the water pump on the kitchen sink - on one occaision
going through an enamelled steel dipper and blowing off the enamel on
the earth side about the size of a silver dollar. The oak was struck
numerous times, and fire-balls flying around the yard during a
thunderstorm were not at all uncommon. Who knows how many times either
the house or barn took a direct hit - and never a fire, although it
did blow part of the roof off the barn at least once.
Forward ahead 50 years or so, and friends who also live at the top of
a hill on a farm were having problems keeping electric fence chargers
functioning, because with about 2 miles of fence connected, a
lightning strike anywhere within 3 or 4 miles would induce such a
charge on the fence that it would kill the charger. We ended up
installinf an air-core choke and spark-gap lightning arrester on the
fence and in a storm you could see the spark jump the gap to ground
and the fence-charger l;ived another day.
I was in my driveway with a Mexican concrete guy when my garage
mounted weather station was hit *the second time). Very exciting
stuff. The shock wave felt like getting hit in the face with a wet
towel. Everything was blue for a second. I am not sure if it was
really blue or that was just an electrical shock to the optic nerve.
It's a good thing the GDO was still working or my buddy Poncho would
have made a roadrunner style hole in the door.
On 05/19/2016 02:05 PM, email@example.com wrote:
I was in the Army with a guy who one day in casual conversation
mentioned that he had once been struck indirectly by lightning.
(We sometimes called him "old man Robbie: because he was 24 years old.)
It was not much of a story and I don't think he told it to anyone else.
Then, a few months later word spread through the barracks that Robbie
had been hit (indirectly) by lightning while he was on guard duty.
When I got the word, everyone in my unit freaked out when all I said was:
Then they learned about his previous encounter.
Any, once they replaced his eardrum he was OK
On Friday, May 20, 2016 at 4:08:59 AM UTC-4, Gz wrote:
Phone line must already have been protection installed for free. Unfortuna
tely that protector is only as effective as an earth ground that you provid
e and are responsible for maintaining.
Most common incoming surge path is AC electric. Once inside, it hunts for
earth destructively via household appliances. Damage means both an incomin
g and an outgoing path must exist. Damaged are appliances that make a best
outgoing connection to earth.
Incoming on AC mains into an answering machine. Outgoing to earth via the
telco 'installed for free' protector. Damage is often on the outgoing path
You assumed the outgoing path was an incoming path. Why would a surge ente
r on a protected wire. And not enter on the most commonly unprotected wire
- AC electric. You had damage because a surge was all but invited inside.
It more likely found an excellent outgoing path to earth destructively via
the answering machine and phone line.
Modems were the first things we determined would benefit from a point
of use protector and with thousands of them installed, we had lots of
chance to test the theory. The telco protection was designed to keep
an old style Western Electric phone from catching on fire, not to
protect CMOS. On a recording volt meter we saw alarming transients
getting past their "gas" protectors. If you still had the carbon rods,
you might as well just tie a knot in the cord.
Certainly you need to be sure the Telco protector is bonded to the GES
on the service but that is not all you need. The longer the phone
wires are on the customer side of the Dmark, the less protection you
Do you disagree that the risk with underground is lower?
If yes, then why do you say it doesn't matter which it is? This kind
of clever phrasing is what politicians use to make a point that sounds
stronger than it should. But I see it a lot from regular folk.
Here the statement should have skipped half of the first sentence and
been "Risk from surges () remains whether the AC service is overhead
or underground." That's all you are saying, but for some reason** you
want to say O vs. U doesn't matter, even though, if the risk is lower,
of course it matters.
**It may just be a habit people pick up from listening to others who
speak in the same way. But IMVSO it's a bad habit.
Now I"m just quibbing but you must mean major appliances. I've taken
toasters, table radios, etc. apart and there was no surge protection.
Most of these things are fairly immune to transients. A toaster will
just get momentarily and imperceptibly hotter for a few microseconds.
This stuff really did not become a huge issue until we started using
CMOS and that is everywhere now.
Microwaves and washing machines would still be fine if they did not
have that little circuit board. Usually the bad part is the clock.
We had a real nice "lightning damaged" microwave in our shop. I
drilled a hole through that touch panel and put in a spring wound
timer. It worked great.
On Fri, 20 May 2016 12:35:07 -0400, firstname.lastname@example.org wrote:
The problem is that the "clock" (and that circuit board) is on all the
time. The actual cooking part is only on if you are cooking. The ones
that use relays are very well isolated when it is "off".
The same will be true of the new washing machines that started this
thread. That $400 circuit board is always on.
On Friday, May 20, 2016 at 12:47:26 PM UTC-4, email@example.com wrote:
Obviously a millimeters gap in a relay does not block what three miles of s
ky cannot. Appliances contain robust protection from a type of surge that
a power strip might protect from. Concern is for a completely different ty
pe of surge that actually does damage - will even blow through a millimeter
s gap inside a relay.
That means that surge must be connected low impedance to earth BEFORE enter
ing a building - so that it does not blow through millimeter relay gaps and
other robust protection that already exists inside each appliance.
On Friday, May 20, 2016 at 2:39:51 PM UTC-4, westom wrote:
Obviously only a tiny part of the energy of a lightning bolt traveling through 3 miles of sky is going to make it to an appliance in a house.
Yes, and it almost always uses MOVs as I showed you with the Littlefuse
reference, app notes, etc. You deny that MOVs are used in appliances
period. So, we're all still waiting to hear exactly how this "robust" protection
is accomplished in your world?
Poor W Tom. Supposed to be an expert on surge protection, but doesn't
know what's in an appliance power circuit.
Concern is for a completely different type of surge that actually does damage - will even blow through a millimeters gap inside a relay.
That "robust" protection inside the appliance has no low impedance path
to ground. So, how can it possibly work? And note that you rant on about
impedance in one direction only and ignore it in the other direction.
The same wiring impedance also limits the surge that can reach an appliance.
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