Design engineering procedure - Basic Documentation - RMK770-1

Communication via the KNX bus

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For engineering see also the information in data sheet N3127.

Design engineering
flow chart

Project data

Step Activity Objective

Assess the situation.

  • Accurate plan of plant with location of buildings and room layout.

  • Overview of hydraulic system.

2 Draft proposed solutions and establish how to implement them.
  • Clear project definition.

3 Include plans for possible expansion zones for extensions.
  • Advance planning of the scope to expand the plant.

Devices, bus devices

Step Activity Objective

Determine device types and quantity.

  • Table of device types.

  • Number of devices per line and
    area, within the permitted limits.


Define the installation of the devices in accordance with technical functions.

  • Entry on plant diagram.

  • List of applications.


Step Activity Objective
6 Define cable routing and cable lengths.
  • Entry on plant diagram.

  • Network size within allowed limits.


Determine type of bus power supply.

  • Distributed bus power.

  • Central bus power supply.


Check limits.

  • Number of bus devices per line and area.

  • Size of network.

  • Adequate bus power (with reserve for later expansion).

9 Create network structure and wiring diagram.
  • Complete installation and commissioning documents.

Special criteria

When structuring a network, special attention should be paid to certain criteria:

  • The number of bus devices in a line, in an area and in the network.

  • The type of bus power supply in relation to the number and properties of the bus devices.

  • The total length of all the bus cables in one line and in the network.

  • The distances between the bus devices.

  • The distance between the bus devices and the nearest bus power supply.

Large plants

See the special notes in Section 8 on design engineering for "large plants".

Lightning and overvoltage protection, and EMC

Note special criteria in relation to lightning and overvoltage protection and EMC. For details see the discussion in Section 9.7.