| Lightning
is the visible discharge of static electricity within
a cloud, between clouds, or between the earth and
a cloud. Scientists still do not fully understand
what causes lightning, but most experts believe that
water droplets and ice crystals interact within the
cloud. Updrafts in the cloud separate charges so that
positive charges (ice crystals) end up at the top
of the cloud while negative charges (water droplets)
concentrate in the bottom. When the negative charge
moves down, a "pilot leader" forms. This
leader rushes toward the earth in discrete steps,
approximately 150' in length, ionizing a path in the
air. The final breakdown occurs when the path to earth,
or an object on the earth is completed and the major
part of the lightning discharge current is then carried
upward in the return stroke following along the ionized
path. The average flash of lightning carries an electrical
charge of about 100 million volts! |
|
A lightning
protection system provides a means by which
this discharge may enter or leave the earth without passing
through and damaging conducting parts of a structure,
such as those made of wood, brick, tile or concrete. A
lightning protection system does not prevent lightning
from striking; it provides a means for controlling it
and preventing damage by providing a low resistance path
for the discharge of lightning energy. Don't
be one of the many who have suffered a lightning disaster!
MAIN
COMPONENTS OF A LIGHTNING PROTECTION SYSTEM:
 |
Air
Terminals - Also known as lightning
rods, must be installed on roof ridges, dormers,
chimneys, ventilators, and other structures as
required. |
 |
Main
Conductors - Cables which interconnect
the air terminals to grounds. |
 |
Ground
Terminations - These are typically
copper or copper-clad rods driven into the earth
a minimum of 10 feet in depth. |
 |
Bonding
Connections - These are made to equalize
the potential between grounded metal objects. |
 |
Lightning
Arresters - These protect wiring from
lightning induced damage. |
 |
Surge
Suppressors - These may be added to
further protect valuable electronic equipment. |
LIGHTNING
PROTECTION FREQUENTLY ASKED QUESTIONS:
Q.
Don't
lightning rods actually attract lightning?
A. No; they
neither attract nor repel lightning. In the event
of a strike, a protection system simply creates a pre-determined
path of low resistance to ground, facilitating a harmless
discharge of the lightning strike.
Q.
Our
home is grounded; doesn't that protect us?
A.
No; a house may be grounded to assure electrical
safety; however, grounding is not intended to prevent
lightning damage.
Q.
Our antenna is grounded; doesn't that protect us?
A.
No; an antenna is not designed to handle a lightning strike
and, instead, allows dangerous current to enter the home.
Q.
Don't our trees protect our home?
A.
No; many times after trees are struck, the lightning
is side-flashed to the house.
Q.
Can't we install our own lightning protection?
A.
No; an improperly-installed system may be dangerous.
Lightning protection is a very specialized industry requiring
trained technicians. A proper system takes into
account your home's design, construction, electrical components,
soil condition, location and more.
Q.
Won't it ruin the aesthetics of our home?
A.
No; the system can be concealed within the walls during
the construction stage. For existing homes, conductors
can be semi-concealed.
To
verify that your installer is UL Listed, call the Follow-Up
Services department at UL's office:
333
Pfingsten Road, Northbrook, IL 60062
(847) 272-8800.
