Page 214 - Basic Course

KNX BASIC COURSE

Figure 50: Division of lines in a medium-sized project

10 Bus hierarchy

10.1 General considerations
Before you finally start the actual ETS project design work, you should have made a
rough draft for the later assignment of the bus devices. Assignment means: area and line
addressing. Moreover, it is about translating project requirements put forward by the client
into the functional scope of the available bus devices. For instance, a requirement could
be: “Emergency function for lighting and blinds must be guaranteed in the event of a bus
failure”. In this case, the corresponding actuators must be selected under these
prerequisites. Devices without manual operation are hence excluded right from the
beginning. We will deal with this issue later.
If higher data throughput is to be expected, one should contemplate to create TP lines as
islands, connected to an Ethernet network via TP/IP routers, which has a significantly
higher transmission rate.

10.2 Taking the building structure into account

In order to maintain a clear overview, also during later extensions and servicing work, the
division of the KNX system into lines and areas should be optimally adapted to the real
building structure. The easiest way would be that a building could represent an area and
the floors could represent the lines.
If however the number of bus devices that are placed in these individual segments
deviates significantly from the requirements regarding cost efficiency, you need to modify
the structure accordingly, resulting in the most cost-effective but nevertheless convenient
solution.

Home and Building Management Systems KNX Association
KNX Project Design with ETS: Advanced ETS4_Planning complex_E0411c 38/59