Vertical air rods (finials) strike plates
should mounted above the roof and connected
to the conductor system beneath.
—
03 Effect the
height the
reference plane on
the protection angle
—
04 Concealed air
termination network
—
05 Determination the
protective angle (IEC/
BS 62305-3 Table 2)
Concealed
conductor
Vertical air
termination
Down conductor
—
05
Note Not applicable beyond the values marked with
Only rolling sphere and mesh methods apply these cases
Note the height air-termination above the reference
plane the area protected
Note The angle will not change for values below 2m
h (m)
Class LPS
I III IV
α°
80
60
40
20
0
2 60
111
TECHNICAL REFERENCE IEC/BS 62305-3 PHYSICAL DAMAGE STRUCTURES LIFE HAZARD
.—
03
—
04
The mesh method
IEC/BS 62305 lists four different air
termination mesh sizes that are defined and
correspond the relevant class LPS.
The IEC/BS 62305 Standard permits the use
of conductors (whether they fortuitous
metalwork dedicated conductors) under the
roof.
This method suitable where plain surfaces
require protection the following conditions
are met:
• Air termination conductors must positioned at
roof edges, roof overhangs and the ridges
of roof with pitch excess (5.7°)
• metal installation protrudes above the
air termination system
Modern research lightning inflicted damage
has shown that the edges and corners roofs
are most susceptible damage. all
structures particularly with flat roofs, perimeter
conductors should installed close the
outer edges the roof practicable.
The air rods should spaced not more than m
apart and strike plates are used an
alternative, these should strategically placed
over the roof area not more than apart
