Engineering and commissioning - Basic Documentation - RMK770-1

Communication via the KNX bus

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Air conditioning controller
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Technical Documentation > Basic Documentation
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Large plants

In large projects, observe the following points during the engineering and commissioning.

Distances and line lengths

For all lines, observe the distances and line lengths (see Section 2.3.1). If the topology exceeds the prescribed limits, use area/line couplers.

Number of bus devices

Max. 64 bus devices may be installed on one line. In plants with more than 64 bus devices, the bus devices must be distributed to different lines and/or areas (see Section 2.1.2).

Area/line couplers

When structuring large plants, LTE-compatible area/line couplers are required (see Section 1.4).

IP routers

For the "KNX to IP network" connection, LTE-compatible IP routers are required (see Section 1.4).

Predefined filter table

The area/line couplers and IP routers must contain the predefined LTE filter table (see Section 8.2).

Alarm sinks

Alarm sinks should be on the same line or the next higher line in the hierarchy (see Section 8.1.1, example 2). Alarm sinks:

  • OZW771 central communication unit

  • OZW775 central communication unit

  • OZW772 web server

  • RM… controllers with enabled fault relay.

Devices with
room functions

Devices with room functions should be located on the same line as the devices with which they exchange data via KNX in LTE-Mode, i.e.:

  • Synco QAW740 room unit ⬄ Synco RM… controllers

  • RXB/RXL room controllers ⬄ Synco RMB795B central control unit

  • Room thermostats RDG/RDF/RDU ⬄ Synco central control unit RMB795B

  • Synco RM… controllers for room control combinations (see Section 9.3)

Clock time master

Only one bus device in the network may be configured as the time master (see "Time synchronization" in Section 6.1.2).

ACS790 software

A search via ACS for devices in all areas and lines only works with correctly addressed area/line couplers.

Design rules for zone addressing

Observe the following rules when addressing zones:

  • The zone addresses, which can be filtered, are permanently predefined in the LTE filter table (see Section 8.2). For this reason, both the assignment of devices to areas and lines, and the addressing of the zones must be planned with extreme care.

  • Keep data traffic to the minimum by creating "communication islands" (see Section 1.4).

  • There is a limit to the number of LTE telegrams that can be transmitted via area/line coupler and IP router (see Section 8.2.4).