Outdoor Lightning Protection System Designs

Outdoor Lightning Protection System Design Specifications & Details
- Aluminum lightning protection system components
- Outdoor connectors and details for lightning protection systems
Questions & Answers about outdoor lighning protection system design
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This lightning protection system article describes common Outdoor Lightning Protection System Design Specifications & Details using aluminum components - 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. Page top photo courtesy of Bud Schoch, PE.

Design Details for Outdoor Lightning Protection Systems Using Aluminum Components

Example Lightning Protection System Installation Details for Outdoor Systems

Photographs of lightning protection system components

[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) wherever feasible.

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
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 11' long, and driven into the ground 10', leaving 1' of the ground rod exposed above ground and 10' below ground [this is the UL standard]. 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. UL requires that at least two ground rods shall be installed.
Metal components on the building such as antennas, weather vanes, and metal gutters are connected to the roof or down conductor
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.
Surge protection devices are installed at receptacles on for circuits serving electronic equipment like computers, TV's, or other electronics. Surge protection may also be installed at the electrical panel to protect the circuit serving a well or well pump, or to protect equipment from strikes drawn to steel well casings protruding above ground as well as to protect building appliances.
Lightning protection systems for commercial buildings have similar requirements and add additional air terminals and a "mid roof" conductor at 50' intervals (or less) on larger and flat roof buildings.

[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.]

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

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]
For more details on how lightning protection systems work, see Lightning Protection from Pacific Electric and Gas Company, and Electrical System Grounding and Lightning Protection, Engineering Technical Letter 90-6, Department of the Air Force, HQ USAF.
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

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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"
Electrical EINET
Lightning Protection for Facilities, Dr. Bruce Gabrielson, Robert B. Marcus, Published and presented: EMCEXPO92, Washington D.C.
MIT's Electrical Safety Files
Lightning Protection for Workers What to Do if You're Outside in a Lightning Storm - Center to Protect Workers' Rights (PDF)
1998 and Current Lightning Protection Conferences & Exhibitions
Lightning Risk and Hazard Analysis Measurement from the National Lightning Safety Institute (NLSI).
"Lightning Fatalities, Injuries, and Damage Reports in the United States from 1959-1994", E. Brian Curran, Ronald L. Holle, Raul E. Lopez, NOAA Technical Memorandum NWS SR-193 October 1997
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.)
* Safety Hazards and Safe Inspection Procedures for Electrical and Home Inspectors at Residential Electric Panels
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
Lightning Strike Risk Assessment, Protection Systems & Services
Multi-wire branch circuit inspection and defects
Rust and Corrosion in Electrical Panels, A Study and Report on Frequency and Cause for Electrical and Home Inspectors at Residential Electric Panels
Directory of Home Inspectors accessible via internet
Electrical System & Wiring Hazard Inspection, Detection, Cause, Remedy, Prevention - Main Electrical Page
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