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.
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)
|
|
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.
|
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
|
||||
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