Overvoltage Protection - Siemens Synco 700 Series Basic Documentation

Overvoltage protection,

secondary protection
AC 230/400 V mains
network
KNX network
Effect of surge
protectors
Note
Surge arresters in bus
terminal technology
Building Technologies
HVAC Products
9.7.2 Overvoltage protection
Overvoltage protection acts as secondary protection. Surge protectors are installed
in the AC 230/400 V mains network and in the KNX network.
Surge arrester (Class B) for the AC 230/400 V mains network:
• Nominal discharge capacity of at least 5 kA (8/20 µs)
• Protection level < 2 kV
• If varistors are used, they must be thermally monitored, and provided with an
insulating arrangement
Surge arresters for the KNX network
• Nominal discharge capacity of at least 5 kA (8/20 µs)
• Protection level < 2 kV
• The surge arrester must be matched to the KNX (TP1) levels.
The surge protector protects the bus devices from overvoltages (transient surge
voltages) which can be picked up by the bus cables. If the protective effect is
damaged (e.g. by exceeding the permitted number of surge arresters), this results
in a bus fault (bus low resistance). Note that no message is generated by this bus
fault. Faulty surge arresters must be replaced immediately.
The use of surge arresters can improve the interference immunity of a KNX (TP1)
network regardless of any precautions for overvoltage protection in conjunction with
lightning protection.
Surge arresters normally have the same dimensions as bus connection terminals.
However, the surge arresters can be distinguished by their color (blue) and the
additional earth conductor. Where surge arresters are used instead of bus terminals,
they must be connected to the nearest grounding point (e.g. protective conductor).
Surge arresters (manufacturer: Dehn) are available from Siemens as off-the-shelf
components in bus terminal format.
• Overvoltage protection Order no.
Ensure in the design engineering phase, that surge arresters can be installed, and
that there is a connection point for them.
Basic documentation: Communication via the KNX bus
Appendix
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CE1P3127en
30.08.2007