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LIGHTING, EXTERIOR GUIDE
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LIGHTNING PROTECTION SYSTEMS
LOW VOLTAGE BUILDING WIRING
LOW VOLTAGE TRANSFORMER TEST
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MOISTURE SOURCES in PANELS
MURRAY SIEMENS Recall
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PUSHMATIC - BULLDOG PANELS
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THERMAL EXPANSION of HOT WATER
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WIND ENERGY SYSTEMS
ZINSCO SYLVANIA ELECTRICAL PANELS
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.
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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.
[Click to enlarge any image]
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
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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Frequently Asked Questions (FAQs)
Reader Question: (July 26, 2012) Deji@Imon wireless said: Good day to you. Please we are a Vsat solutions provider. and our operations is majorly in a terrain with high Ionic Content which brings us under serious lightning and thunder attacks. Please, i would greatly appreciate if you could advice us on what to do and if you have products that could help us, we would appreciate if you could avail us the necessary details.
Reply: Deji, Best would be for you to search InspectApedia for "lightning protection" and you'll find all of our information there.
Check the FAQs just above, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
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.]
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.
Example Lightning Protection System Installation Details for Outdoor Systems
Example Lighting Protection System Materials for Outdoor Installations
Example Hidden Lightning Protection System Installation Details
Example Hidden Lighting Protection System Materials
"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.