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motor wind / rain sensor
24 V d.c. < 4 A

smoke detector
No. Surge protective device Part No.
DG M TN 275 (TN-S system) 952 200
DG M TT 2 P 275 (TT system) 952 110
fire control
panel 3* BXT ML4 BE 24 920 324
2* + BXT BAS 920 300
4*
2 x BXT ML4 BE 24 920 324
230 V / 50 Hz + 2 x BXT BAS 920 300
BXT ML4 BE 36 (1.8 A) 920 336
+ BXT BAS or 920 300
6* 4* (6*) 2 x BVT ALD 36 (4 A) 918 408
BXT ML2 BE S 24 920 224
SDS VS + BXT BAS 920 300
=

6* 4* (6*)
Alternative
SDS VS TL2 10DA CC 907 991
DRL 10 B 180 FSD 907 401
EF 10 DRL 907 498
8 x DRL RE 24 907 422
* Minimum number of required cores
(observe manufacturers’ instructions)
Figure 9.27.3 Domelight located in the protected volume of an air-termination rod on a metal roof of a structure equipped with conventional
arresters

B. The walls consist of non-conductive material (bricks, A structure with a metal roof and conventional down con-
wood, etc.) and the down conductors are connected to ductors is considered to be critical (Figure 9.27.3). In case
the earth-termination system at the intervals required by of a lightning strike, the lightning current will be evenly dis-
the class of LPS. tributed between the down conductors. Nevertheless, the
structure is still at risk and the relevant separation distance
Different combinations of air-termination systems (see 1., 2., must be maintained. Air-termination systems must also be
3.) and down conductors (see A., B.) can be used. Ignitable installed to prevent direct lightning strikes to this type of
sparkover does not occur in structures with air-termination structure, however, the domelight is not located in LPZ 0 B .
systems and down conductors in the combinations 1.+ A., Since partial lightning currents may flow into the structure
via the cable for the drive of the smoke and heat extraction
2.+ A. or 3.+ A. Air-termination systems must be installed to system, a lightning current arrester must be installed. Due to
prevent lightning strikes to the domelights. Thus, the dome- their size, structures with domelights typically have several
lights are protected against direct lightning strikes, however, down conductors which prevent overload of the lightning
they are not located in LPZ 0 B since the air-termination sys- current arrester.
tems directly conduct the lightning current to the metal roof,
thus spreading the lightning current over a large area. In Structure without external lightning protection
view of the fact that lightning may also strike in the vicinity system
of the domelights, it is recommended to install a lightning No distinction has to be made between metal or non-metal
current arrester (Figure 9.27.2). roofs since every direct lightning strike to the structure pre-

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