The bridge to more building efficiency
Lifts have long since ceased to be considered to be the concern of an isolated building trade, but instead as part of successful facility management need to be thought of in the context of the building as a whole.
Lighting and shade, lift, heating and ventilation – if the various building trades are coordinated with each other, the building can be operated with much greater energy efficiency. Additional options, such as monitoring and alarms, emerge if the individual components are interlinked with a high degree of integration. At the same time trend log records open up new potential for building automation.
Communicative connection using data protocols
Where more complex control parameters or functions are involved, exchanging analogue and digital control signals in a classic connection by hardware contacts is often not enough. Here communicative connection using data protocols provides advantages, which arise from coordinated interaction of the individual building trades.
Apart from the know-how required for this, the interoperability of the various manufacturers is the greatest challenge in this respect. The network protocol BACnet (building automation and control networks) establishes the bridges required. As the leading international standard (ISO 16484-5), BACnet overcomes manufacturer limits and in this way creates the basis for standardising data exchange between the devices used.
Internationally leading standard
Information acquired is provided as standardised objects; an object can have various properties. The visualisation and analysis software BACeye facilitates easy access to the BACnet devices and their objects and properties. Over 50 objects constitute analogue, binary or multilevel factors.
They represent time sequence programmes, alarm classes, fire or burglar alarms, access control systems or trend logs and in future are also to include lifts and escalators. Over 40 defined services facilitate simple services like reading/writing, management access to devices and the exchange of routing information or authentications.
Technical and organisational system integration
Communicative interlinking of the various components poses a whole series of questions. There are not only the devices affected and the goals to be achieved through integration, but also the communication protocols and tools employed, user authorisations and the maintenance of the network.
In organisational terms the standardised use of texts and characters, the responsibilities for individual building trades, coordination with the IT department and connection to the Internet, etc. have to be borne in mind.
Connections to various levels
As a rule, conveyance equipment like lifts and escalators is not equipped with a BACnet interface. Gateways like the universal gateway UWG can be used as interpreters here. In addition, they assume more complex tasks such as specifications for time sequence programmes, alarm transmission and trend log records.
DDC or SPS controllers usually access the sensors and actuators of the field level, which provide the data as servers, as clients. If both fail to use the same network medium, a BACnet router can connect them like a media converter. If both devices use different communication protocols, gateways can be used as interpreters and assume more complex tasks like the specifications for time sequence programmes, alarm transmission and trend log records if the field device does not provide these functionalities.
Gateways ensure that all devices are integrated functionally as a homogeneous BACnet composite. Here BACnet regulates the standardised data exchange as part of the building automation. Today more information – such as unit, description texts, etc. – can be provided with BACnet. As a result, additional functionalities can be provided at the management level, such as alarm recognition.
All systems in view
System integration with BACnet would not be perfect if an overview of the different devices and functionalities were missing. For this purpose the standard provides eight device profiles. There are five profiles for mapping the individual field and automation devices.
This makes the scalability clear that the BACnet provides for building automation. BACnet will continue to strengthen its position as internationally leading standard in building automation.
Nils-Gunnar Fritz, Thomas Reimann