Lightning Protection Systems Lesson 1 Introduction Lightning Protection

Lightning Protection Systems Lesson 1 Introduction

Lightning Protection Systems are designed and installed based on the NFPA 780 Standard. This standard defines a lightning protection systems as: A complete system of strike determination devices, conductors (which could include conductive structural members), grounding electrodes, interconnecting conductors, surge protective devices and other connectors and fittings required to complete the system

Lightning Protection Systems A lightning Protection System can be broken into four main parts: Part 1: Intercept the lightning strike via the strike termination devices also known as air terminals and lightning rods. Part 2: Conduct the strike safely down the building which includes the bonding of all metallic bodies to the lightning protection system conductors in an attempt to keep all components at an equal potential during the lightning strike event.

Lightning Protection Systems Part 3: Disperse the lightning strike safely into the earth. This includes ground rod electrodes, ground rings, and radials. Part 4: The utilization of surge suppression devices to dispose of any unwanted electrical currents attempting to enter the building through conductive wiring.

Lightning Protection Systems There are two types or classes of lightning protection system materials. Class I materials are used on structures which do not exceed 75’ in height. Class I materials are the smaller class of materials. Class II materials are used on any structure that exceeds 75’ in height. These are generally larger or heavier materials than the Class I materials.

Lightning Protection Systems If you have a structure that has two differing heights with one portion under 75’ and the other portion over 75’ you can use a combination of the two classes of materials. Class II materials would need to be used on the upper structure and continued completely to the ground. The lower portion, which could utilize Class I materials, is simply connected to the Class II downleads.

Lightning Protection Systems When a product is labeled, it means that there is some sort of a symbol or identifying mark from an organization that is acceptable to the AHJ (Authority Having Jurisdiction). This also means that the product has been evaluated and tested and that the manufacturer of this product has periodic inspections from this organization, such as Underwriters Laboratory, to ensure that the manufacturer stays in compliance.

Lightning Protection Systems A product or service is considered listed when it is on a list published by an organization that is acceptable to the AHJ, as long as it has been tested and inspected for that specific purpose. Being listed for “that specified purpose” is very important. It is very possible that a component listed for grounding purposes would not meet the requirements for a lightning protection system.

Lightning Protection Systems All materials used in a lightning protection system must be resistant to corrosion. Most systems are either copper or aluminum or they can be a combination of both materials. Copper materials are made from the same grade of copper as the ones used for commercial electrical work; these are generally designed to be 95% conductive when annealed. Copper materials must not be installed on any aluminum surfaces such as aluminum roofing, siding, etc. Copper also cannot be installed on any steel or galvanized surfaces

Lightning Protection Systems Aluminum materials cannot be installed on copper roofing materials or other copper materials or be exposed to runoff from copper surfaces. They also must not be attached to a surface with an alkaline-based paint or embedded in concrete or masonry. Lastly, aluminum materials cannot be installed in locations subject to excessive moisture or come in direct contact with the earth.

Lightning Protection Systems Whenever transitioning from aluminum to copper, all fittings must be of the bi-metallic type. These bi-metallic transition connectors cannot be placed closer than 18” of the earth’s surface.

Lightning Protection Systems If any part of the lightning protection system is subject to mechanical damage it must be protected by some form of a protective mold or covering, such as conduit or cable guard. If a metal raceway is utilized it must be bonded to the cable at each end. Using PVC raceway is an acceptable alternative to the need of bonding of the cable and raceway