all
structures particularly with flat roofs, perimeter
conductors should installed close the
outer edges the roof practicable.—
03
—
04
The mesh method
IEC/BS 62305 lists four different air
termination mesh sizes that are defined and
correspond the relevant class LPS.
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.
—
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
. Vertical air rods (finials) strike plates
should mounted above the roof and connected
to the conductor system beneath.
The IEC/BS 62305 Standard permits the use
of conductors (whether they fortuitous
metalwork dedicated conductors) under the
roof.
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.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
