January
1998, Issue 90
Ground
Zero:
A
Real World Look at Lightning
by
Steve Ciarcia & Jeff Bachiochi
Living
on a granite hill during a thunderstorm gives you
a whole new respect for Mother Nature. To guard against
paranoia, Jeff and Steve figure out how to automatically
unhook their appliances before they become toast.
I
know that some day I’ll regret telling so many
people this, but you see, we’ve had this little
problem with thunderstorms. I know, you think I’m
kidding. Isn’t tornado alley in Oklahoma? Out west
maybe, but Connecticut?
While
storms are frequently predicted on hot summer afternoons
around here, the reality is that there are very few
severe storms and only one or two tornado warnings a
year. That’s the good news.
When
a big thunderstorm occurs in Texas or Oklahoma, three
vultures and a mountain goat might be the only ones
who see the furious lightning display or even know it’s
happening. When it drops a 200-MPH tornado funnel, a
few prairie dogs are often the only ones who have to
rebuild their homes.
The
bad news is that Connecticut is very small. Two traffic
helicopters on opposite ends of the state have to be
careful not to run into each other.
When
a severe thunderstorm happens around here, everyone
knows about it. When lightning strikes, it invariably
hits something valuable. And, when a tornado funnel
drops in a densely populated area, it doesn’t miss.
Contrary
to the paranoid description, however, my problem is
not tornadoes. The infrequency and narrow path of a
tornado make the odds of getting hit by one about the
same as a 747 landing in the driveway.
My
problem is lightning. And, location has everything to
do with it. I live in one of the higher areas of Connecticut.
By Colorado standards, it’s barely a gopher mound,
but 1000' is high around here.
Unfortunately,
underneath everything in this part of the state is probably
the biggest slab of granite ledge east of the Mississippi.
You can guess a few obvious consequences. For example,
when my wife suggests I dig a hole, I don’t even
think about using a shovel. Short of dynamite, the only
solution is the backhoe!
All
that rock has an insidious consequence—earth grounding.
More correctly, it’s the lack of an effective earth
ground that’s the problem. Zap! Here’s comes
the lightning bolt, and where does it go? You guessed
it—everywhere but down!
As
you might expect, rock is a lousy electrical conductor.
On my street, the earth-neutral grounding point at the
electrical-service entrance is about as functional as
the ground rod the electric company tries to drive into
solid rock.
Prior
to my all-out assault on the problem, I had a half-dozen
lightning hits and over $20,000 in damages. My neighbor
has had an electric blanket burned off his clothes line
(it wasn’t plugged in), seen flames coming from
his power outlets, and had appliances blown off his
counter. I’ve had TVs barbecued, computer equipment
incinerated, and satellite systems destroyed.
The
final straw was a few years back. While my wife and
I were sitting on the front deck, we could hear a storm
in the distance. Just as I said it would probably miss
us, there was a brilliant flash and a deafening KAPOW!
A
lightning bolt slammed into something right next to
us. "Next to us" turned out to be my 15' C-band
satellite dish. I jumped up in time to see a cloud of
steam rising from the recently melted LNA and what looked
like smoke billowing from the garage. I grabbed a fire
extinguisher and headed to the rescue.
Much
to the EPA’s chagrin, I’m sure, the smoke
turned out to be freon. The lightning hit on the LNA
had fed underground to the garage. Where the coax and
control cables entered the house, the path of least
resistance was out of the cable and into the central
air conditioning lines.
As
you might expect with all that power, it burned through
the cables and copper tubing. Pow! Instant smog.
It
was only because of the 2² packed fiberglass insulation
that I wasn’t at a redwood-house–fueled wienie
roast. When I saw how close we came to having everything
torched, I got religion.
