Lightning Protection Systems Information and Sources of Lightning Protection Systems
InspectAPedia® -
What is lightning, where and why does lightning strike?
Example of lightning and lightning-related fire damage to a home
What are lightning protection systems ?
How do lightning rods work?
Design specifications for lightning protection systems (basic)
How to inspect lightning protection systems
Where to buy lightning protection systems & equipment
What is the chance of being struck by lightning? What happens?
How to avoid being struck by lightning
Lightning Strikes Small Boat on Rappahannock River - photos
This lightning protection system website describes common lightning protection systems, certification, installation, and lightning protection system inspection.
We provide information about lightning strikes, lightning hazards, related equipment, sources of lightning protection system installers, and lightning strike risk assessment. The photograph at page top was taken by the author from an aircraft.
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.
What is Lightning, What makes lightning strike? Which way does lightning move?
Example of lightning-related damage to a home: This house fire in Georgia was caused by a lightning strike in April, 2008.
According to UL, "lightning is the visible discharge of static electricity within a cloud, between clouds, or between the earth and a cloud".
Thunderstorms occur when warm and cold air masses meet.
Charges of electrical energy build up within the air masses and periodically discharge as energy flows from one area to another. Upwards-moving air in the churning caused where the cold and warm fronts meet causes a separation and movement of positively-charged ions or particles to the top of clouds, leaving negative charges at the bottom of clouds.
Lightning bolts may pass vertically or horizontally between clouds or may move between the air and the ground where energy is finally dissipated.
As lightning moves towards the earth (in the form of downwards flowing negatively charged electrical energy called a "pilot leader"),
positive "lightning bolts" actually move upwards from vertical features on the earth such as the edges of buildings, chimneys or trees,
reaching towards along an ionized path in the air towards the downwards-moving negative energy.
[It's interesting that UL says the energy moves in discrete 150' steps, ionizing a pathway in the air.]
Types of Building Damage Caused by Lightning Strikes
The photo at left shows the extent of fire damage to the same house as the fire photo above. Damage to a home subject to a lightning strike and subsequent major fire could be expected to include:
Lightning strike damage to the home - damage caused by the lightning strike itself
Fire damage to the home, caused by the subsequent fire resulting from the lightning strike
Water damage to the home, damage to the structure caused by water used to extinguish the fire. In this instance water contacting bricks heated by the fire may have caused additional losses.
Mold contamination: risk of damage to the structure from mold growth resulting from wet conditions in any wall, ceiling, or floor cavities or surfaces which were wet during the extinguishment of the fire, if these areas were not also promptly opened, wet materials removed, and the building dried quickly.
Our photographs of house fires caused by lightning strikes (above) were contributed by website readers.
UL adds that "Scientists still do not
fully understand what causes lightning but most experts believe that different kinds of ice interact in a cloud.
Updrafts in the cloud separate charges so
that positive charges end up at the top of the cloud while negative flow to the
bottom."
Our photograph of multiple lightning arrestor masts (left) shows a lightning protection system for an electrical power substation on the Hudson River.
[Our photograph of lightning shown at page top was of strikes moving between high clouds and was taken by the author from an airplane over northern Minnesota.]
When the negative charge moves down, a pilot leader forms. This lightning strike leader rushes toward the earth in 150 discrete steps, ionizing a path in the air. The
final breakdown generally occurs to a high object and the major part of the lightning discharge is then carried in the return stroke which flows along the
ionized path.
What is the Amount of Energy in Lightning Strikes? What Causes Thunder?
A lightning bolt that strikes the ground, "groundstroke lightning, is producing a tremendous electrical current, around 100,000 amps. (By contrast
a typical home electrical panel supports 100 to 200 amps of current to operate everything in the home).
The energy in a 100,000 amp lightning
strike can in turn produce very high temperatures, up to 50,000 deg. F (this is five times hotter than the surface of the sun!). It's the rapid
heating (expansion) and then cooling (contraction) of air around a lightning strike that produces the shock wave (air movement) which is heard
as a thunderclap during lightning storms. Incidentally, while lightning is normally associated with thunderstorms, lightning strikes can also
be caused by erupting volcanoes, hurricanes, forest fires, and (let's hope not) nuclear explosions.
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. [Quotations are from UL publication 200-128C 25M/9/93]
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Portions of this information are based on UL publication 200-81 11/87 and other local service company information about lightning protection systems and lightning strike hazards.
Special thanks to Associated Lightning Rod Company, Cooper Road Box 329A, Millerton NY who has been contributing technical content in presentations
to NY ASHI home inspectors since 1996. Some of that information [on lightning system material and installation details] was edited for clarity. ALRCi can be reached at 518-789-4603, 845-373-8309, 860-364-1498 and will inspect your lightning protection
system at no charge. [We have no financial nor any other business relationship with any company or product discussed at this website--DF]
Lightning strike risk assessment: for the full body of this excellent article which summarizes recent opinions about lightning
strike risk assessment and safe practices for individuals or groups needing to avoid being struck by lightning, see Updated Recommendations for Lightning Safety - 1998 Ronald L. Holle and Raul E. Lopez from National Severe Storms Laboratory,
NOAA and Norman, Oklahoma, Christoph Zimmermann Global Atmospherics, Inc. Tucson, Arizona
As we indicated in an original version of this article, a lightning strike risk assessment guide can be found in Appendix I of the
National Fire Protection Association's Lightning Protection Code, NFPA #780.
The guide considers type of structure, type
of construction, structure location, topography, occupancy, contents and lightning frequency. Contact NFPA, Batterymarch
Park, Quincy, MA 02269 617-770-3000.
Lightning Protection Institute, 3365 N. Arlington Heights Rd., Suite J., Arlington Heights IL 60004
Underwriters Laboratory Standard UL96A. These requirements cover the installation of lightning protection systems on all types of structures other than structures used for the production, handling, or storage of ammunition, explosives, flammable liquids or gases, and other explosive ingredients including dust. These requirements apply to lightning protection systems that are complete and cover all parts of a structure. Partial systems are not covered by this standard. These requirements do not cover the installation of lightning protection systems for electrical generating, distribution, or transmission systems. These requirements do not cover lightning protection components, which are covered by the Standard for Lightning Protection Components, UL 96.
Underwriters Laboratory Standard UL96: These requirements cover lightning protection components for use in the installation of complete systems of lightning protection on buildings and structures. These requirements do not cover the installation of lightning protection components. Products of this type are covered by the Standard for Installation Requirements for Lightning Protection Systems, UL 96A.
"Lightning Awareness," Gerry Schulte, BMW ON magazine, June 2007 pp. 58-60, provided some technical details about lightning, and refers readers to www.lightningsafety.noaa.gov/outdoors.htm
What Are Lightning Protection Systems?
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. But lightning protection systems have a confusing history.
The earliest lightning rod design, by Ben Franklin, ended in a sharp pointed trident which may have actually created an electrical field
around the tip which invited strikes. You'll notice that modern lightning rods have a short blunt tip and that they are connected to earth
by heavy metal cables, often using braided copper. Having a properly-designed lightning protection system is very important if you're going
to have one at all, since an improperly designed or installed system might actually increase the chances of a building being damaged by
a lightning hit. Lightning strikes at buildings and other sudden electrical currents (such as a tree touching a high tension power line)
produce very high voltages which can take surprising routes at a property such as following underground tree roots, metal porch railings,
and copper or steel building water pipes.
How do Lightning Protection Systems Work?
Lightning protection systems control electrical discharges
by directing them through a low-resistance path to the ground, avoiding passage
through parts of a structure and reducing risk of fire or other damage.
Air terminals (rods - the sketch here is of a rod tip) are fastened to the building to intercept electric discharges which
might otherwise strike a building component itself, such as a chimney or metal roof.
Electrical discharges striking the air terminal are directed through
heavy duty metal conductors to a grounding system (rods driven into the soil) and thence into the
earth. The lightning protection system was first invented by Ben Franklin in 1752.
Example of a Damaged Lightning Protection System
We took these photographs of a damaged lightning protection system on an 1865 house in Orange County, New York. The
air terminal and conductor were bent down away from the top of the home leaving the chimney and roof (a metal one in an
area of frequent lightning strikes) unprotected.
This is an example of what can happen when someone who is not qualified works on the system. The lightning protection
system for this home was dangerously compromised when the maintenance crew simply bent components down out of their way.
[The photographs of details of an old lightning protection system shown here were NOT the work of any of the
companies or sources described at this website.]
Lightning Protection System Certification
Lightning protection systems are examined and certified by Underwriters
Laboratories, Inc. Be sure your installer is listed by UL and that a
Master Label application is submitted to UL for your installation.
There are other listing and certifying agencies as well, including the Lightning Protection Institute (LPI)
and the National Fire Protection Association (NFPA).
Verify that your Lightning Protection System Installer is UL-Listed
To verify that an installer is Listed or to obtain further information
call the Follow-Up Services Department at UL, 1285 Walt Whitman Road, Melville,
NY 11747 516/271-6200. UL has other offices in Northbrook, IL, Santa Clara,
CA, and Research Triangle Park, NC.
Design Details for Outdoor Lightning Protection Systems Using Aluminum Components
Example Lightning Protection System Installation Details for Outdoor Systems
[The photographs of details of an old lightning protection system shown here were NOT the work of any of the
companies or sources described at this website.]
As with any good construction project, the contract will include a statement that "All equipment shall be installed in a neat workmanlike manner by an experienced installer.
That last part, "experienced installer" is very important in this case since sloppy or improper details can increase rather than reduce the
hazards of lightning damage.
All components and work shall meet or exceed all national safety and electrical codes including the Lightning Protection Institute (LPI)
and the National Fire Protection Association (NFPA), and all components used shall be approved and listed for that purpose by
the Underwriters Laboratories (UL).
All lightning protection system cabling shall be installed along the side of the main, highest ridge of the building or building-section
being protected, along the rake or gable-end boards, and shall continue down to ground level along building corners at inconspicuous
locations such as near downspouts or trim wherever feasible.
All lightning protection system cabling shall be installed in a horizontal or downward direction and shall not contain U or V-shaped
sections or pockets.
The source of all materials is usually listed in order to assure that they are accountable and code-compliant. These lightning protection system specifications and details were provided to us during presentations on lightning
protection systems provided to NY ASHI home inspectors and conducted by Associated Lightning Rod Co..
Example Lighting Protection System Materials for Outdoor Installations
Building chimneys shall be protected with an air terminal to be placed no more than 2' from any outside corner.
Lightning protection system air terminals shall be pointed, solid round aluminum of 1/2" diameter or greater and shall project no less than
10" above the building component or object to be protected from lightning. Air terminals shall be located and spaced according to UL and LPI
code requirements, including placement of terminals within 2' of outside corners and at intervals no greater than 20 horizontal feet (along the
ridge line).
Air terminal bases shall be aluminum, using bolted or crimped cable connectors and shall be securely mounted with stainless
steel screws, nails, or bolts. [By contrast, note the older, rusted and loose components in the lightning protection system photographs shown above. -DF]
Lightning protection system cabling shall be Class I conductors, 24-strand 14-gauge aluminum cable, (102#/1000Ft., 98k circular mils or equivalent)
Cable support fasteners shall be 1/2" wide aluminum strips spaced no greater than at 3' intervals.
Grounding locations shall be properly connected to copper [where rods extend below ground level] using a 3 1/2" x 3/4" hexagonal
bimetallic 4-bolt splice connector located 18" above grade.
Ground rods shall be at least 1/2" in diameter and 9' long, and driven into the ground leaving 12" of the ground rod
above ground and 8' below ground. Ground rods shall be connected to the lightning protection system using a two-bolt
bronze clamp of at least 1.5" long and using stainless steel cap screws.
Other bonding devices cable splices, and other miscellaneous connectors shall be aluminum with bolt pressure or crimp connections to
stainless steel.
Other hardware such as miscellaneous bolts, nuts, nails, screws, shall be stainless steel.
Building water piping shall be bonded to the lightning protection system with a full-sized copper conductor
and a lead-coated water pipe clamp.
[The photographs of details of an old lightning protection system shown here were NOT the work of any of the
companies or sources described at this website.]
Design Details for Hidden Lightning Protection Systems Using Copper Components
Example Hidden Lightning Protection System Installation Details
Workmanship: As with any good construction project, the contract will include a statement that "All equipment shall be installed in a neat workmanlike manner by an experienced installer.
That last part, "experienced installer" is very important in this case since sloppy or improper details can increase rather than reduce the
hazards of lightning damage.
Lightning Protection System Cabling details: All lightning protection system cables shall be concealed within the building, running along the ridge board, down rafters, down wall studs,
and shall exit the building as close to the ground as possible. If construction is incomplete and a chimney has not been extended above
the roof line at the time of installation of the lightning protection system, the lightning protection system cables can be concealed
within the masonry.
Lightning Protection System Code Compliance: All components and work shall meet or exceed all national safety and electrical codes including the Lightning Protection Institute (LPI)
and the National Fire Protection Association (NFPA), and all components used shall be approved and listed for that purpose by
the Underwriters Laboratories (UL).
Use of properly-rated materials in the lightning protection system: The source of all materials is usually listed in order to assure that they are accountable and code-compliant. These lightning protection system specifications and details were provided to us during presentations on lightning
protection systems provided to NY ASHI home inspectors and conducted by Associated Lightning Rod Co..
Example Hidden Lighting Protection System Materials
Building chimneys shall be protected with an air terminal to be placed no more than 2' from any outside corner.
Lightning protection system air terminals shall be solid copper, round, pointed, 3/8" or larger in diameter,
project at least 10" above the object or building section to be protected, and shall comply with UL and LPI requirements for lightning protection systems
and shall be located within 2' of outside corners and at intervals no greater than 20 horizontal feet (along the
ridge line).
Air terminal bases shall be made of cast bronze and shall be securely mounted using pressure-bolt or crimp connectors
and stainless steel screws, nails, or bolts.
Lightning Protection System Cabling shall all be 28-strand 16 gauge copper (230#/1000', 72,258 mils or equivalent).
Corrosion protection shall be provided by lead coating on metal components (air terminals, terminal bases, cable connectors,
strapping,) where located within 2' of the chimney top.
Cable fasteners shall be made of 1/2" wide 20 ga. copper strips and shall be spaced at 2' intervals (exceeding the UL and LPI requirements).
Ground rods shall be 9' long x 1/2" diameter, driven to at leave exposed no more than 1' of rod length above ground, and shall
be connected to the lightning protection system by two-bolt cast-bronze clamps at least 1.5" long and using stainless steel cap screws.
Building ground-devices such as water piping, electrical systems, telephone, cable, internet systems, and metal waste piping shall be grounded
in common and bonded to the lightning protection system using full-sized grounding conductors.
Other hardware such as miscellaneous bolts, nuts, nails, screws, shall be stainless steel.
Lightning Strike Risk Assessment
"The magnitude of the cloud-to-ground lightning hazard is understood better today than had been the case due in
large part to data collected by the U.S. National Lightning Detection Network TM (NLDN) described by Holle and Lopez
(1994) and Cummins et al. (1998). From 1992 to 1995, the NLDN identified an average of 21,746,000 cloud-to-ground
flashes per year (Orville and Silver 1997).
Lightning occurs in the U.S. every day in summer, and nearly every day
during the rest of the year. Since lightning strikes the ground in such large numbers and is so widespread, it is not
possible to warn each person for every flash. For this reason, lightning can be considered the most dangerous weather
hazard that many people encounter each year. Lightning-specific warnings have proven effective in some unique
applications, such as at the Kennedy Space Center and during major golf tournaments."
"Although the scientific
understanding of lightning has advanced significantly in the last few decades (Krider 1996), a consistent match between
basic science and applications to safety had not been made. For example, NOAA (1992) said to squat on the balls of your
feet and minimize contact with the ground, while NOAA (1985) recommended dropping to the knees during the lightning
threat, and NOAA (1970) suggested dropping to the ground.
Concerning when to reach a safe location, NOAA (1992)
recommended going to a safe location at the first sound of thunder, NOAA (1985) was not specific about when to go to a
safe place, and NOAA (1970) made no mention of this decision process. Similar variations can be found in these and many
other publications regarding additional issues such as medical and first aid approaches to lightning victims."
-- Quotation - see Holle/Lopez.
Portions of this information are based on UL publication 200-81 11/87 and other local service company information about lightning protection systems and lightning strike hazards.
Special thanks to Associated Lightning Rod Company, Cooper Road Box 329A, Millerton NY who has been contributing technical content in presentations
to NY ASHI home inspectors since 1996. Some of that information [on lightning system material and installation details] was edited for clarity. ALRCi can be reached at 518-789-4603, 845-373-8309, 860-364-1498 and will inspect your lightning protection
system at no charge. [We have no financial nor any other business relationship with any company or product discussed at this website--DF]
Lightning strike risk assessment: for the full body of this excellent article which summarizes recent opinions about lightning
strike risk assessment and safe practices for individuals or groups needing to avoid being struck by lightning, see Updated Recommendations for Lightning Safety - 1998 Ronald L. Holle and Raul E. Lopez from National Severe Storms Laboratory,
NOAA and Norman, Oklahoma, Christoph Zimmermann Global Atmospherics, Inc. Tucson, Arizona
As we indicated in an original version of this article, a lightning strike risk assessment guide can be found in Appendix I of the
National Fire Protection Association's Lightning Protection Code, NFPA #780.
The guide considers type of structure, type
of construction, structure location, topography, occupancy, contents and lightning frequency. Contact NFPA, Batterymarch
Park, Quincy, MA 02269 617-770-3000.
Lightning Protection Institute, 3365 N. Arlington Heights Rd., Suite J., Arlington Heights IL 60004 http://www.lightning.org/
Underwriters Laboratory Standard UL96A. These requirements cover the installation of lightning protection systems on all types of structures other than structures used for the production, handling, or storage of ammunition, explosives, flammable liquids or gases, and other explosive ingredients including dust. These requirements apply to lightning protection systems that are complete and cover all parts of a structure. Partial systems are not covered by this standard. These requirements do not cover the installation of lightning protection systems for electrical generating, distribution, or transmission systems. These requirements do not cover lightning protection components, which are covered by the Standard for Lightning Protection Components, UL 96.
Underwriters Laboratory Standard UL96: These requirements cover lightning protection components for use in the installation of complete systems of lightning protection on buildings and structures. These requirements do not cover the installation of lightning protection components. Products of this type are covered by the Standard for Installation Requirements for Lightning Protection Systems, UL 96A.
"Lightning Awareness," Gerry Schulte, BMW ON magazine, June 2007 pp. 58-60, provided some technical details about lightning, and refers readers to www.lightningsafety.noaa.gov/outdoors.htm
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Armor Lightning Protection Inc Manchester Center, VT, 802-375-0266
state-of-the-art lightning protection and surge protection for residential and commercial buildings in Vermont, New England, and throughout the Northeast
Associated Lightning Rod Company, Inc., Box 329A, Cooper Road, Millerton, NY 12546 914/373-8309 518/789-4603
A-C Lightning Security, Inc., 2100 East First St., PO Box 329, Maryville MO 64468 816-582-8115 800-821-5575 816-562-2932. In New York, Hudson Valley, contact Christensen Electrical Power Systems, Richard G. Christensen, 518-537-4128.
Lightning Eliminators & Consultants 6687 Arapahoe Road Boulder, CO 80303 (303) 447-2828. "Engineering Solutions For Lightning, Grounding and Surge Protection Worldwide Since 1971"
UL - Underwriters Labs Lightning equipment certification program.
"Underwriters Laboratories Inc. (UL) has been testing and certifying lightning protection equipment since 1908. UL issues certificates of conformance for systems, inspecting system components and checking completed installations. Installations are required to comply with UL's internationally recognized Standards for lightning protection systems. Manufacturers, suppliers and installers demonstrate their commitment to safety by building,
selling and installing only those lightning protection products that pass UL's rigorous testing." -- (Op.Cit.)
Aluminum Wiring Information Website Aluminum Electrical Wiring Hazards and Repairs: in-depth authoritative info, photos, documents including selection of proper vs. ineffective repair methods. E.g.: Ideal 65 "Twister" purple connector fails in field and lab testing with aluminum wire.
Electrical Panels, How to Inspect in buildings, safety for electrical inspectors, electrical panel, fusing, wiring defects, defective products. Inspection Class Presentation
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