Siemens Synco 700 Series Basic Documentation page 112

Routing cables between
buildings
Note
112/120
Building Technologies
HVAC Products
Alternative 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 (minimum cross-section:
2 2
Cu 16 mm , Al 25 mm , Fe 50 mm
Surge arrester
(secondary protection)
Lightning arrester
(primary protection)
Bus
device
(room unit)
Piping (water)
Equipotential bonding rail
With Alternatives 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.
Basic documentation: Communication via the KNX bus
Appendix
2
).
External
lightning protection
Bus
PE
device
(controller)
Metal pipe / - duct
230/400 V
CE1P3127en
30.08.2007