Lighting Protection system for 23 m or 75 ft height exceeding building

General Information

Class II Materials:

Lighting Conductors, air terminals, grounding electrodes and other associated fittings required for the protection of structures exceeding 23m (75 ft) in height.

Reference: NFPA 4.1.1.1 (B)

Table 4.1.1.1 (B) NFPA 780

Factory Details
Height of the building	80ft or 24.386m m
Roof perimeter	358 m

NFPA 780 General Requirements:

1. Air terminals are places at the locations indicated, not more than 2’-0” from the edges of ridges, outside corners, or outside edges of main roofs and must extend a minimum of 24” above object to be protected.

2. Air terminals are spaced at 50’-0” O.C. Maximum spacing.

3. All structural steel, rebar, framing and miscellaneous steel are made electrically continuous through construction.

4. Air terminals 24” and over are spaced 25 feet maximum.

5. One down conductor are provided for every 100 feet perimeter.

6. Resistance value of earth pit will be measured at any pit below 10 ohm.

Grounds Rods:

a. Ground rods shall not be less than 12.7 mm (1/2 inch) in diameter and 2.4 m (8 ft ) long.

b. Ground rods shall be free of paint or other nonconductive coatings.

Material Specification (Class II) For Factory Building
Type of Conductor	Parameter	Copper (Cu)
Type of Conductor	Parameter	SI Units	U.S. Units
Air Te4rminal, Solid	Diameter	12.7 mm	½ in.
Main Conductor, Solid Strip	Width	20 mm	0.787 in.
	Thickness	3 mm	0.118 in.
	Cross-section area	60 mm²	115,000cir.mills
Bonding Conductor Solid strip	Thickness	1.30 mm	0.051 in.
Bonding Conductor Solid strip	Width	12.7 mm	½ in.

Lighting Risk Index Calculation
Index	Description	Type		Index Number
Index A	Use of Structure	Medium Size Factory		6
Index B	Type of Construction	Reinforced concrete with nonmetal roof		2
Index C	Contents or Consequential Effects	Industrial and agricultural building with especially susceptible contents.		5
Index D	Degree of Isolation	Structure located in an area with a few other structures or trees of similar height.		5
Index E	Type of Terrain	Flat terrain at any level		2
Index F	Height of Structure	24-30 m (24.386m)		11
Index G	Lighting Prevalence	Number of thunderstorm days per year: over 21		21
Building risk Index			51
Marginal Risk index 40
Remarks: Lighting Protection is required

Comments

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