Configurable Desigo room automation system
DXR2 room automation stations are perfectly suited to exclusively automate heating, ventilation, and A/C plants.
Further, the DXR2 can be extended by adding devices with KNX PL-Link and lighting and shading functions. The configurable Desigo room automation stations offer solutions with a high level of functionality and flexibility that operate plants optimized to energy use without sacrificing Comfort.
Figure: Overview of configurable Desigo room automation system with BACnet IP
The DXR2 can automate heating, ventilation, A/C, lighting, and shading in the room.
Depending on the model, communication among the stations or to other system components takes place over BACnet/IP (DXR2.E…) or BACnet MS/TP (DXR2.M...).
Figure: Overview of configurable Desigo room automation system with BACnet MS/TP
Room automation stations have a fixed number of I/O data points for connecting field devices as well as an interface to KNX. Automation stations are supplied with preloaded applications that only need be configured. A comprehensive library with tested, standardized applications is available that can be used instead of the preloaded applications. Buttons, sensors, and actuators for lighting and shading are connected to the room automation station via the KNX PL-Link.
Both preloaded as well as tested standardized applications in the library are configured in ABT Site and offer a high degree of flexibility, since, in addition to the functions, even inputs and outputs on the DXR2… can be configured.
DXR2
The DXR2..
- assumes the control functions for a room.
- communicates with each other or other system components via BACnet/IP or MS/TP. Scope and functionality of supported BACnet objects are matched to the requirements of room automation.
- provides a 2-port Ethernet interface for cost-effective cabling via line topology.
- receives bus power for the KNX PL-Link. Internal bus power can be extended as needed with an external supply module.
KNX PL-Link
The KNX PL-Link (Peripheral Link) connects communicating room and field devices (room devices, sensors, actuators) to the DXR2.
Plug&play allows for connecting selected Siemens field devices to the KNX PL-Link using plug and play.
KNX PL-Link is not suitable for KNX subsystem integration, as communication is not directly between field devices but field devices and room automation station.
The DXR2 has its own KNX PL-Link has bus-internal supply allowing for cost-effective installation without requiring additional wiring. The 2-wire bus allows for connecting up to 64 devices.
DXR2 applications include an optimum set of preconfigured devices. They support simple engineering.
KNX PL-Link provides extended functionality and additional diagnostic functions compared to direct connected field devices.
Groups
In Desigo room automation, numerous system elements and system data are grouped by means of grouping functions.
- Groups allow structuring and central control of system elements and data.
- Groups support data exchange between central control functions and individual system elements.
System elements and data can be grouped by either geographical, functional, or discipline-specific criteria.
Typical reasons for exchanging data within a group:
- Distributing common group data by central function.
- Collecting data from individual group elements.
- Calculating resulting group data via central function.
- Merging room segments to multiple DXR2s into one large room
Room
DXR2 can control one room. One segment also belongs to the room in each DXR2. The DXR2 includes the control function for the room as well as control function for the associated room segment.
Room segment
Each DXR2 includes, in addition to the control for the room, control for the associated room segment. A room segment is the smallest indivisible element in the building.
Application types
An application type includes all possible versions of an application. The application type forms the starting point for configuring a DXR2. Functions for the associated application functions are enabled or disabled by selecting or clearing the function.
Figure: HVAC depiction of VAV application type
There are four application types on configurable Desigo room automations:
- VAV including radiators and ceiling heating/chilled ceilings
- Fan coil including radiators and ceiling heating/chilled ceilings
- Fan-powered box including radiators and ceiling heating/chilled ceilings
- Central functions
Management platform
The Desigo CC management platform graphics library supports the most important DXR2 application data points.
Figure: Fan Coil application on the Desigo CC management platform
Alarms
BACnet distinguishes for alarming between Intrinsic Reporting and Algorithmic Change Reporting. Desigo room automation uses Algorithmic Change Reporting.
The BACnet object is not alarm capable on its own. Alarms and events (notifications) are generated via an additional Event Enrollment object.
The event enrollment object references a value (property) for monitoring from another BACnet object, e.g. analog input, analog value, or in the form of a binary or multistate signal.
Details on monitoring are defined using the following event algorithms within the event enrollment object.
Event algorithms | Function |
|---|---|
Change of Value | Monitoring for change of value of an analog value. The change of value can be individually set. |
Change-Of-State | Monitoring for a definable state, such as program state, system state, load shedding state, silenced, door state, security level, binary value, etc. |
Change of Value | Monitoring a bitstring value for a specific state such as In Alarm, or fault. |
Out of range | Monitor Real value for a high/low limit value including delay time and neutral zone. |
Command failure | Feedback monitoring: Monitors, via two references, whether a feedback to a switching command occurs within a defined period. |
Floating Limit | Floating limits: Can monitor, via two references, whether the actual value is located with an adjustable range around the setpoint. |
You can still define prioritization, alarming (acknowledge and reset) as well as response (alarm or event notification) on the event enrollment object (similar to intrinsic reporting). In other words, all required properties are available on the object and can be edited specific to the application during engineering as well as from a BACnet client.
Standard BACnet object for alarms
Standard BACnet objects are compiled from a series of properties.
The functional response and state are displayed from these properties. BACnet uses the following properties:
Property | State | Description |
|---|---|---|
State flag | In alarm | True process alarm, e.g. high limit is exceeded or low limit breached for an analog input of value object. |
In Alarm, fault | System alarm for no sensor, short circuit, interrupt, etc. | |
Out of service | When the object is placed out of service. | |
Overridden. | Local override on an I/O module. | |
Reliability | No error. |
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