Heating/cooling changeover - 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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The universal RMU7x0B controllers are programmed with the new "H/C changeover" function block, which is used for changeover of the specified "Heating" or "Cooling" mode in 2-pipe systems.

The specified "Heating" or "Cooling" mode can be generated in the controller itself, or received as a "Heating/cooling changeover signal" over the KNX bus.

The following methods of changeover can be programmed for the specified "Heating/Cooling" mode:

  • Changeover via digital input, e.g. with manual switch or with a changeover thermostat in the flow (already an option with RMU7x0).

  • Changeover vie analog input, e.g. based on outside air temperature or flow temperature.

  • Changeover based on the calendar (date): Configured in the "H/C Changeover" function block (calendar symbol selected).

  • Changeover with operating mode selector: Configured in the "H/C Changeover" function block ("Hand" symbol selected).

Effect of specified mode

The "Heating/Cooling" mode is not affected by the type of changeover.

If several types of changeover are selected, the required operating mode is determined in the following order of priority:

  1. Operating mode selector

  2. H/C changeover input

  3. Heating/cooling by calendar

The required "Heating/Cooling" mode is transmitted by the "changeover controller" to all other controllers in the heating distribution and refrigeration distribution zones.

In a hydraulic circuit, the "Heating/Cooling" mode can be defined in one location only. If several H/C changeover signals in the same distribution zone are distributed over the KNX bus, a fault message is generated.


If possible, the required "Heating/Cooling" changeover command should be activated in the primary controller or generator.

Activate function

The "H/C changeover" function is activated by setting the operating line "2-pipe system heating/cooling" to "Yes".


Main menu > Commissioning > Extra configuration > Heating/cooling ch'over

Operating line Range Factory setting
2-pipe heating/cooling system No, yes. No