UL 96A:2016 pdf free download – STANDARD FOR SAFETY Installation Requirements for Lightning Protection Systems.
8.2.3.2 A protected building protects lower building sections that lie within its zone of protection described in 8.2.3. An example is shown in Figure 8.7 where two higher protected sections of the building protect a lower section.
8.2.3.3 A protected building that is more than 150 feet (45.7 m) high provides protection for lower roof areas starting at 150 feet (45.7 m) and below when the lower area is located under an arc that has a 150 foot (45.7 m) radius and that is tangent to the side of the protected building and to the earth. See Figure
8.4.
8.2.4 Protective angle
8.2.4.1 A strike termination device that is not more than 25 feet (7.6 m) above earth protects lower areas in a one-to-two zone of protection.
8.2.4.2 A strike termination device that is more than 25 feet (7.6 m) but not more than 50 feet (15.2 m) above earth protects lower areas in a one-to-one zone of protection.
8.3 Dormers
8.3.1 Dormers that are as high or higher than the main roof shall be protected with air terminals, cable, down conductors, and grounds as normally specified in 8.2. Dormers and projections below the main ridge shall have air terminals on all areas extending outside a zone of protection as defined in 8.2. See Figure 9.2.
8.4 Intermediate ridges
8.4.1 A roof with a series of parallel ridges shall have air terminals along the end ridges at intervals not exceeding 20 feet (6 m) for air terminals 10 inches (254 mm) in height; or at intervals not exceeding 25 feet (7.6 m) for air terminals 24 inches (610 mm) in height. See 8.2.2.1. The intermediate area between ridges shall be protected according to the requirements for flat roofs in 8.2.2.2. Any intermediate ridge higher than an end ridge shall be protected in a manner similar to the end ridges. See Figure 8.8.
8.4.2 An air terminal shall be placed within 2 feet (610 mm) of the end of each intermediate ridge. See Figure 8.8.
8.5 Irregular roof lines
8.5.1 The edge of irregular roofs, which also applies to curved buildings, shall be a continuous line of air terminals that are located within 2 feet (610 mm) of the outermost projections of the roof edge at intervals in accordance with 8.2.2.1. See Figure 8.9.
8.6 Open areas
8.6.1 The perimeter of an open area (such as an open court yard) located within a large flat roofed structure shall be protected if the perimeter exceeds 300 feet (91.44 m) and both rectangular dimensions exceed 50 feet (15.24 m).
8.7 Domed or curved roofs
8.7.1 On curved or domed roofs, an air terminal shall be located at the center of the curve or dome with additional air terminals as required to provide a zone of protection determined in accordance with Zone of protection, 8.2.
8.8 Chimneys, vents and roof top metal bodies
8.8.1 Air terminals shall be placed on all chimneys, vents, and roof top metal bodies, including prefabricated metal chimneys, vents, and roof top metal bodies with metal thickness less than 3/16 inch (4.8 mm) — when such chimneys, vents, or roof top metal bodies are not within a zone of protection determined in accordance with zone of protection, 8.2.
Exception: Metal handrails or guardrails, including metal cables, outside a zone of protection that are 1/8 in (3 mm) thick or more shall not require air terminals when the installation of the air terminals may result in a casualty risk. The handrail or guardrail shall be bonded at each end as specified in 8.1.1. When the handrail exceeds 100 ft (30.5 m) in length it shall be bonded every 100 ft (30.5 m) or fraction thereof with main size conductor and clamps to the lightning protection system. The average distance between bonds shall not exceed 100 ft (30.5 m).