Building Automation Systems – the protocols that are important now, and for the future?

By Neil Cameron of Johnson Controls System & Service Africa

Four decades ago, building automation comprised of simple control panels with switches and timers. By 2003, industry standards were being established. More than 10 such standards, each supporting different aspects of building automation (lighting, electrical metering, etc.), have been widely adopted. With the recent evolution of these technologies, however, organisations are revisiting strategic decisions about the communication protocols they want to continue to invest in. BACnet is currently leading the race.

BACnet stands for Building Automation Control network. It is a data communication protocol developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to help standardise communications between building automation devices from different manufacturers, allowing data to be shared and equipment to work together easily.

While BACnet will never be the only standard it is certainly the most popular at present, and with good reason. Building automation systems are increasing in sophistication — they no longer just control the air conditioning systems, wiggling valves and actuators; they incorporate sophisticated algorithms to tap into multiple systems to manage organisations’ UPS’, generators, pumps, lighting, access control, CCTV and emergency systems, as well as heating ventilation and air conditioning systems. This is helping to drive greater value from these systems, cut energy consumption, improve building efficiency and the productivity of occupants. BACnet, because it is open ended with multiple interfaces, is ideal for the job.

BACnet has since 2003 been adopted as an American national standard, a European standard, a national standard in more than 30 countries, and an ISO global standard. With more vendors incorporating BACnet standards natively into their equipment, greater interoperation is occurring and users have greater choice – they are no longer tied into proprietary brands.

Another big advantage of BACnet is that the data link or physical layers over which BACnet can communicate includes not just Ethernet, MSTP, and others but UDP and IP.. BACnet over Zigby, a wireless mesh protocol, also enables wireless communications. This fits right into the current trend of convergence between information technology and plant control data.

That said, many organisations still employ equipment using older or other communication protocols. LONworks, a traditional favourite seems to be declining in popularity. This is partly due to the cost associated with using it (it is not free) and the fact that it is more suited to smaller limited systems. Similarly, Modbus, strong in industry controls is suited to smaller systems with simpler centralised control, is expected to lose traction.

Compared to use of these protocols, with BACnet there are less hurdles to overcome and a lot of functionality that can be leveraged.

A recent BAS communication trends survey puts BACnet/IP and BACnet MS/TP (the master-slave/token-passing network) ahead of DALI (Digital Addressable Lighting Interface), EnOcean (wireless sensor and switch solutions) and KNX (for home and building automation) as protocols important to organisations today. Protocols voted most important for the market in the future see a similar line-up appear.

While Johnson Controls has a vested interest in BACnet, having built native support for the protocol into its building management systems, access control and HVAC equipment, it is not alone – BACnet is supported by an increasing line-up of equipment manufacturers and solution providers.

Some of the principal benefits of BACnet? It offers, notes BACnet International:

• Practical interoperability between building automation and controls systems from multiple vendors
• Real choices for scalability between cost, performance and size
• Systems based on a single unified ANSI and international standard and Testing standard
• Endorsement and adoption by nearly every major building automation and controls vendor in North America and in many other countries
• Capability for integration with and use of existing LANs and LAN infrastructure
• Highest performance and Lowest cost
• Robust internetworking including multiple LAN types and dial-up
• Easy and robust scalability from very small to enormous system sizes
• Unrestricted growth and the ability to add new innovations and new features anytime
• An open, transparent, no fee, consensus process for ongoing use and maintenance of the standard where every interested party has a voice


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Building Automation Systems – the protocols that are important now, and for the future?