From building automation to enterprise systems
In 2013 the OPC Foundation and BACnet Interest Group Europe started a common working group to specify a mapping document. Both organizations identified a need to share information between building automation installations and industry automation or enterprise systems. For the BACnet community the collaboration with the OPC Foundation is highly appreciated. Since the first release in 1995 BACnet has become a global standard for building automation supported by more than 842 registered vendors. BACnet is standardized in the ISO standards 16484-5 and 16484-6. The integration of building and industry automation into homogeneous systems requires standard procedures how to interface the data. The main purpose of this mapping document is to describe an interface to specify observation, operation and engineering.
TYPICAL USE-CASES INCLUDE
- Observation: Providing energy information like consumption, operating-hours or maintenance intervals to enterprise systems.
- Operating: Commanding building automation systems by writing data like temperature setpoints, operatingmodes or acknowledge alarms.
- Engineering: Specifying operating modes or schedule programs, configuration of alarm-detection.
- Advantages: Using this mapping profile vendors in building automation find ready-to-use methods to provide building or energy data while manufacturers of SCADA-systems or enterprise connectivity directly access the required data without the need for interpretations or conversions.
The current mapping specifies the data flow from BACnet to OPCUA. In a future revision of this mapping document OPC-UA data may be connected to BACnet as well.
Both OPC UA and BACnet specify objects to model application data. Unlike in other standards or more simple communication protocols not only the values are provided. Extra information like the name of an object, a description text, the engineering-unit, alarm-limits, operating-hours or change-of-state count, etc. is provided. The mapping document describes a gateway interface between the two object models. The methods how to retrieve the data (polling, Change-of-Value) and the network media to be used is a local matter and not part of the mapping profile. The following picture shows an example of a BACnet Analog-Input object (left hand box) represented as OPC UA Analog Input Object (middle and right boxes).
MAPPING BACNET ➞ OPC UA
- BACnet Objects / Properties ➞ OPC UA Object Types
- BACnet Events ➞ OPC UA Alarms & Conditions
- BACnet Logging ➞ OPC UA Historical Access
- BACnet Data Structures ➞ OPC UA Structure Data Types
- BACnet Units ➞ OPC UA Engineering Units
While BACnet uses a flat model (structured objects providing their properties) OPC UA allows for inheritance. Wherever possible the mapping combines functional items in re-usable groups. E.g. alarm parameters are collected as a group of properties and can be used for different object types.
➞ Supporting organizations:
The BACnet standard was developed and is still maintained by the ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers in the SSPC-135 (Standing Standard Project Committee aka the BACnetCommittee). ASHRAE granted use of the BACnet standard and greatly supported the process of developing this mapping document. BACnet International (BI) and the BACnet Interest Group Europe (BIG-EU) are the two largest organizations promoting BACnet world-wide. Members of both organizations volunteered in this working group. In many face-to-face meetings and teleconferences finally the first version got approved and was presented to the public. The working group awaits feedback by early adopters or companies prototyping the mapping in their products.
- BECKHOFF Automation
- TU Wien
- Specification: The mapping document is ready and awaiting prototyping.
The current version can be downloaded from the BIG-EU website: Get PDF
- 3 min video “Quick overview BACnet & OPC UA Collaboration”
- 12 min video “Introduction BACnet & OPC UA Collaboration”
Contact working group
- Matthias Damm (OPCF) Matthias.Damm@ascolab.com
- Frank Schubert (BACnet) F.Schubert@beckhoff.de
- Working group: email@example.com
BACnet is an open and neutral communication protocol for networks in building automation and control networks under continuous maintenance and development by ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers). BACnet is a world-wide standard published in DIN EN ISO16484-5 and 16484-6. The BACnet Interest Group Europe (BIG-EU), founded in 1998 as an association under German law, meanwhile represents BACnet activities all over Europe and has more than 115 members: vendors, project designer, system integrators and end-users of BACnet systems.