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For internal use only
Siemens
KNX bus communications
CE1P3127en
Building Technologies
Appendix
2013-04-08
Variant 2 with surge arresters
With Alternative 2, the bus cable is protected with surge arresters and routed in a
metal conduit or duct which is part of the equipotential bonding system.
The minimum cross-section of the conduit or duct must be sufficient to allow a
substantial part of the lightning current to pass across it (min. cross-section: Cu 16
mm
2
, Al 25 mm
2
, Fe 50 mm
2
).
230/400 V
PE
A
C
2
3
0
V
External
lightning protection
Bus
device
Surge arrester
(secondary protection)
Lightning arrester
(primary protection)
3
1
2
7
Z
1
4
e
n
Equipotential bonding rail
Metal pipe / - duct
Piping (water)
(room unit)
Bus
device
(controller)
With Variants 1 and 2, a surge arrester must be installed as secondary on the bus
device closest to the entry to the building. In relation to the bus cable length, the
bus device should be installed some meters away from the lightning arrester, so
that the surge arrester is not also partly responsible for primary protection.
Routing cables
between buildings
Note
