Multiple mechanical and electrical installations (referred to as technical installations in this chapter) come together in one room. These typically are HVAC, lighting, and blinds. Each technical installation is automated and operated optimally from its perspective. For Desigo room automation, coordination of the individual technical installations must be optimized while considering that the same type of installation may exist several times in one room.

Room featuring:

  1. HVAC zone (blue)
  2. Lighting zones (yellow)
  3. Shading/blinds zones (green)

HVAC zone

The room typically is considered 1 HVAC zone influenced via a common automation and control strategy regardless of number and type of installed HVAC plant components (e.g., radiator, chilled ceiling, fan coil unit).

Lighting zone

All lamps operated/automated together are grouped into a lighting zone regardless of number and type of the installed lamps. A room typically has one or several lighting zones.

Shading zone

All shading products (blinds) operated/automated together are grouped into a shading zone regardless of number and type of the installed shading products. A room typically has one or several shading zones.

Desigo room automation and room coordination

Application function structure

Specific functionality is set up for each zone of each technical installation: The application functions. For Desigo room automation, this is supplemented by a room-wide function coordination called room coordination.

Room coordination basically has two application functions:

  • Cross-technical installation coordination to ensure smooth functional interplay of the various installations
  • Centralized, room-wide access point to operate and monitor a room

Cross-technical installation coordination

The application functions of the individual technical installations contain functionality required for technical installation-specific control. Additional functionality assuming coordination with other technical installations is part of room coordination. As a result, project-specific Desigo room automation requests and changes can be carried out without changes to technical installation-specific application functions.

Examples for coordination functions are coordination of HVAC and shading functions and coordination of shading and lighting functions.

Centralized, room-wide access point

Room coordination offers a centralized, room-wide access point to operate and monitor a room. This allows users to enter common data for several technical installations only once and retrieve them as a group.


  • Predefinition of the room operating mode (across all technical installations)
  • Predefinition of a scene for the entire room
  • Queries for general occupancy
  • Common alarm for system alarms

The room coordination default solution influences the following functions:

Room operating mode

Various sources influence and determine the room operating mode:

  • Centralized commands from scheduler programs or manual intervention
  • Local commands from presence detectors or scheduler program override

Room coordination offers a centralized, room-wide access point to operate and monitor a room operating mode. The individual technical installations separately acquire all relevant information.


Scenes are defined to command several or all technical installations in a room via one single command, e.g., brightness of a lighting zone, or blinds positions in each shading zone can be defined for each scene. Room coordination:

  • Controls a scene as per the predefined values
  • Changes the predefined values

Both are carried out by the room user.

Thermal room load analysis

Room coordination supports room temperature control via blinds control. The various HVAC data is analyzed to determine the thermal room load and the associated signal definition for blinds control:

  • Load if energy must be supplied to the room via the blinds position
  • Unload if no additional energy must be supplied to the room via the blinds position

Blinds control determines the optimal blinds position in dependence of room occupancy and solar position (thermal radiation and glare).

Green Leaf (RoomOptiControl)

Manual room user manipulations (e.g., manual lighting and shading commands, or manual changes to the room temperature setpoint) can result in inefficient energy operation. Each zone and each technical installation is checked for inefficient definitions to be pointed out to the room user. Room coordination then summarizes the results and visualizes them on the room operator unit. The room user can then reset all manual entries (which lead to inefficient plant operation) by one single pressure of a button.

Room common alarm

One common alarm is set up for each room to keep down the number of set up system alarms. To this end, room coordination acquires status information (normal/alarm) for each zone and each technical installation, and determines the room-wide alarm state as a common alarm.

HVAC room control

HVAC plants and their HVAC devices in the room influence the climate in closed rooms.

HVAC plants in rooms are used to:

  • Maintain a temperature range suitable for building occupancy
  • Control other control variables such as humidity and air quality
  • Efficiently operate HVAC plants in the room

HVAC plants in the room are grouped into plant families, radiators (right), Fan coil units (center), VAV (left), differentiated by mechanical design and functioning:

The members of the related HVAC family differ only marginally:

HVAC supply chain requirements

HVAC plants in a room consume energy. The supply chains outside the room supply air, water, or electricity to the room. Linked existing energy sources and consumers are called supply chain. An air supply chain or a water supply chain thus is an HVAC system with a supply/consumer relationship to the HVAC plant in the room.

The supply equipment typically supplies more than one room, and the HVAC plant in the room often is a consumer of multiple supply chains.

HVAC control basically has the same objectives as the entire HVAC plant:

  • Maintain the room temperature in the selected comfort range
  • Adapt the room temperature range to room user needs
  • Supply, extract, and recirculated air to satisfy air quality and comfort needs
  • Adapt the air flows to room user needs

Energy saving requirements:

  • Devices for sequential control of a heating and cooling sequence and thus:
    • Preventing sequence overlap (simultaneous heating and cooling)
    • Using the most efficient energy source
  • Reducing the temperature as soon as comfort mode no longer is needed
  • Reducing ventilation as soon as it is no longer needed

Coordination of the HVAC supply chain:

  • Operation of supply chain equipment as per user demand
  • Optimization of operating levels (temperature, pressure) of the supply plant
  • Prevention of damages to HVAC equipment

HVAC control structure

An HVAC control application in the room is connected to the following:

  • HVAC plant in the room via sensors and actuators
  • Room coordination application
  • Centralized coordination application for HVAC supply chain(s)
  • Building operator via BAC workstations
  • Building automation and control functions for scheduling
  • Room user

The HVAC control application in the room consists of two parts:

  • Application function for user requirements
  • Application function for HVAC plant control

The HVAC plant control contains a control module (CFC) that implements the control functions associated with the HVAC device.

Control concepts

The physical room conditions are controlled by a combination of control methods (setpoints by operating mode).

Sequence control

Algorithms for room temperature sequence control operate the heating and cooling equipment within applicable limits. The algorithm for one single heating element is as follows (e.g., radiator):

Below is an illustration of the temperature control sequence for a more complex HVAC plant in the room. The charts show the segregation of heating and cooling control sequences and associated setpoints and sequencing of heat convection by fan air flow or associated switching stages.

Individual temperature sequence controllers are assigned to each heating and cooling element. They intercommunicate to achieve required sequencing.

Open-loop control

Additional interactions between HVAC devices implemented via open-loop control functions are required in an HVAC plant in the room. The open-loop control functions feature two basic interactions:

  • Support: Heating coil and cooling coil require the fan to run on the stage/speed required for their operation.
  • Lock: The electric heating coil is locked to ensure that it cannot be operated without air flow.

Open-loop control and sequence controller are used together to implement the above, typical control sequence.

The following image shows the connection between controller and actuating devices (this does not correspond to the actual program structure).

Operating modes

The HVAC plants in the room adapt to the room's comfort requirements, e.g., ventilation is:

Active while the room is occupied

Off, as soon as the room no longer is occupied

The following illustrations show sequence control for an HVAC plant in the room for operating modes Comfort and Economy. Sequence control acts on heating and cooling equipment and a multi-speed fan.

Control sequences in the Comfort operating mode:

Control sequences in the Economy operating mode:

The available operating modes determine both operation and basic control strategy in the automation and control system at three different levels:

  • The room operating modes determine the operation of HVAC equipment in a room in terms of current use by the user. The room operating modes defined for the room are available in all HVAC control applications in the room.
  • The HVAC plant operating modes determine the operation the HVAC plant in the room with regard to existing, physical plant processes. The HVAC plant operating modes are defined specifically for 1 HVAC plant in the room.
  • The device operating modes determine the operation of the HVAC devices in a room by predefining their tasks and implementation method. The device operating modes are defined specifically for each individual HVAC device.

Plant and device operating modes of a plant with heating coil, cooling coil, and fan

Project-specific adaptations of both plant and device operating modes can be implemented by adapting the operating mode table.

Plant operating mode

Fan operating mode

Heating coil operating mode

Cooling coil operating mode





















Heat up




Cool down




In addition, setpoints and setpoint limits define room and device operating modes. They can vary depending on the selected HVAC plant operating mode. Four different setpoints are provided for heating and cooling in the room.

The HVAC control applications in the room dynamically enable and disable the setpoints to achieve the desired combination of energy-saving Economy and demand-based Comfort operating mode.

Command priorities

An HVAC control application simultaneously achieves several goals. Functions with different objects may conflict when they are implemented. In this case, the command priority determines which command value has priority in the priority array of the BACnet objects.

HVAC control applications in a room are programmed to accept commands at many different levels, including operating mode variable level. As a result, HVAC control applications control the controlled output objects at a priority commensurate with the active priority of the operating mode variable. The following figure shows how commands and priorities are passed in the application.

The BACnet objects in the system support 16 priority levels. The HVAC control applications apply these levels as follows:


Purpose assigned to the level

Use in HVAC library

Emergency mode 1

Manual commands related personal safety


Emergency mode 2

Automatic commands related to personal safety

Propagated response to Emergency mode commands

Emergency mode 3

Unassigned - additional level for commands related to personal safety


Protection mode 4

Manual commands to avoid damage to equipment


Protection mode 5

Automatic commands to avoid damage to equipment

Programmed response to equipment safety conditions

Minimum On/Off 6

Commands to avoid damage by short cycling equipment


Manual operating 7

Manual commands through switches on equipment


Manual operating 8

Manual commands through BAS workstation


Automatic control 9

Unassigned - commands for comfort and energy conservation


Automatic control 10

Unassigned - commands for comfort and energy conservation


Automatic control 11

Unassigned - commands for comfort and energy conservation


Automatic control 12

Unassigned - commands for comfort and energy conservation


Manual operating 13

Manual commands through room unit

Programmed response to inputs from occupants

Automatic control 14

Unassigned - commands for comfort and energy conservation


Automatic control 15

Typical automatic commands for comfort and energy conservation

Typical automatic commands

Automatic control 16

Unassigned - commands for comfort and energy conservation


Adaptation to another HVAC plant

An HVAC control application comprises several different members of an HVAC room family. It contains application-specific components (CFC) matching existing HVAC devices in the room. Components no longer matching existing HVAC devices in the room are either added, removed, or replaced to control a slightly different HVAC plant with different HVAC devices.

Often, more must be done than merely adding or removing components (CFCs). If, an HVAC device, e.g., is to be added, the following must be added or removed:

  • Information in the operating mode table
  • Corresponding BACnet objects to operate the new device

Shading control

Products and requirements

Suitable façade products and intelligent control allow for optimum satisfaction of various requirements for shading.

Façade products and their control required to protect against environmental influences or to make use of the same are the primary issue:

  • Shading to protect against glare
  • Using daylight
  • Using solar energy for heating
  • Shading to protect against overheating
  • Protection against rain

Other requirements may be:

  • Intrusion protection
  • Protection of privacy

Façade product control in addition must protect persons and equipment against the façade products themselves. Examples:

  • Drive up blinds in case of fire to open an escape route
  • Protect against collision (e.g., in the event of outward-opening doors)

Façade control protects the façade products and their functionality against environmental damages caused, e.g., by rain, wind, or frost.

The market knows many different façade products such as roller shutters, blinds, awnings, etc. to satisfy the various requirements. The different properties of the products are included in the respective control functions. The following figure shows a few typical façade products (from left to right):

  • Horizontal blinds
  • Roller shutter
  • Vertical blinds
  • Drop-arm awning
  • Vertical awning
  • Sliding-arm awning

Influences on blinds control

Blinds control requires much information on environmental influences and user interactions to be able to best satisfy requirements.

The blinds control can be influenced by, e.g.:

  • Smoke, fire alarm
  • Maintenance switch
  • Wind, rain, humidity, temperature
  • Intrusion alarm
  • Date/Time
  • Solar radiation
  • Geographical position
  • Horizon limitation
  • Presence detector
  • Local operator
  • Saving and retrieving scenes
  • Central operation (operation, scenes, override)
  • Desigo CC
  • Commissioning/Test

Blinds position on a building, room purpose, and allocation of rooms to an organizational unit determine the type of information acting on blinds control. Example:

  • Wind speed monitoring acts on all blinds of a building or building wing
  • Automatic shading acts on all blinds of façade or part of a facade
  • A scheduler program acts on all rooms of a renter
  • Local manual operation acts on all blinds of a room, or on a single blind