Number of bus devices per line, area and network - Basic Documentation - RMK770-1

Communication via the KNX bus

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Air conditioning controller
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Basic Documentation
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64 bus devices
on one line

Up to 64 bus devices can be installed on one line (including a main line and area line 0). There are no restrictions relating to the type mix.


The Synco 700 type RMZ78x expansion modules, the RMZ790 and RMZ791 operator units and the room units connected (via PPS2) to the RXB/RXL room controllers do not have a KNX interface and can be omitted from the design total.

In installations incorporating Synco bus devices (plus the OCI700.1 service tool, if connected) and third-party devices, the number of Synco bus devices is reduced in accordance with the number of third-party devices.

960 bus devices
in one area

Based on 64 bus devices per line and 15 lines per area, up to 960 bus devices can be installed in an area. The network addresses for Area 1 are:

  • Area couplers: 1.0.0

  • Line couplers: 1.1.0…1.15.0

  • Bus devices: 1.1.1…1.15.254


With KNX TP1 only 64 bus devices are permitted in device address range 1…254.

16,320 bus devices
in a network

Theoretically, a total of 16,320 bus devices could be installed in a full KNX TP1 (wired) network. In practice the number is approximately 12,000 bus devices.

Based on 960 bus devices per area, and a full-scale network comprising 15 areas, up to 14,400 bus devices can be installed in one network.

Main lines 1…15

64 bus devices can be connected to each of the 15 main lines, giving a further 960 bus devices in addition to the 14,400 calculated above, which makes a total of 15,360 bus devices.

Area line 0

Another 64 bus devices can be installed in each of the 15 lines branching off from area line 0, now giving a total of 15,260 bus devices. Normally, however, no line couplers are installed in area line 0.

Notional Line 2

Note: The preset addresses, area address 0 and line address 2 relate to a "fictitious line 2" branching from area line 0. The network addresses for this line are 0.2.1 to 0.2.254.

The term "fictitious line 2" indicates that there is no need to install a line coupler 0.2.0. See the illustration in Section 1.3, Full-scale KNX network