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For building owners and consulting engineers alike, interoperability of controls systems is an attractive concept. However, the ability of equipment, regardless of manufacturer, to coexist on the same network and share data coherently is often an elusive goal.

A number of factors have driven development of standard and open protocols for building control systems. Firstly, building owners want the freedom to choose the best product for each system element at a competitive price. Increased flexibility is also an incentive with high churn rates in offices often requiring hvac and lighting controls to be reconfigured. Clients also want lower installation costs due to less wiring and fewer components; forward compatibility with any future developments; and reduced labour and training costs.

Many open protocols have been developed by national and international bodies, and manufacturers.

Setting standards
The European Committee for standardisation has classified the communications within a building into three levels: field, automation and management. This allows for the assorted types of transport media and varying numbers of devices at each level. The lowest level, the field network, connects devices such as sensors and actuators. The automation layer operates at the level of controllers and user interfaces, while the management network allows data to be collected for say energy reporting and is also used to connect complete systems together.

Although the Committee sought to recognise one protocol per layer, conflicts and national interest led to a number of protocols being selected for each of the three levels. For the field level these include: EIBus, EHS, Batibus and LONtalk. For the automation level there is BACnet, FIP and Profibus. The management level has BACnet and FND. There are other commonly used open standards that are not recognised, but are still used for integrated systems.

Gateways, aren't open systems but they allow communication between dissimilar protocols, but they have are drawbacks. They are difficult and expensive to develop and are often short-lived because of the inevitable upgrades manufacturers make to their systems. Complete translation is not always achievable and there can be a loss of some of the systems functions.

Open protocol providers
There are numerous open systems on the market today although their origins vary greatly.

BACnet is a standard protocol governed by ASHRAE. Development of the protocol began in 1987 when ASHRAE established a committee of manufacturers, consultants and end-users.

BACnet is essentially hardware independent and has been implemented in software on a variety of platforms by different vendors. It was designed to work on a number of communications media. BACnet local area networks can be interconnected using tunnelling routers or native BACnet/IP devices may communicate directly.

The protocol took eight years to develop and was released as an ASHRAE standard in July 1995 and an American National Standard in December 1995.

At around the same time that BACnet was being developed, Apple Computers founder, Mike Markkula, was busy developing LonWorks – an open system protocol for control networks in buildings, homes, industrial and transportation applications.

Developed by Echelon Corporation, LonWorks is hardware dependent. At its heart is the Neuron chip, manufactured by Cypress and Toshiba, which is embedded with the LonTalk communications protocol.

The LonMark Interoperability Association was formed to manage the evolution of both the interoperability model and the certification of products that conform to the interoperability standard. It also promotes LonMark products and systems. The Association is funded by its members which include manufacturers, end-users and system integrators.

LonWorks is capable of utilising several different communication media within the same network by the application of routers. The application of fully interoperable LonWorks systems however is limited by the range of functional profiles which have been defined and their incorporation into products.

Developed in 1988 under the leadership of Merlin Gerin in France, Batibus was primarily designed to interconnect field level devices within commercial, institutional and industrial buildings. The Batibus Club International (BCI) was founded in 1989 to administer the protocol.

European Installation Bus was developed by a group of companies led by Siemens who up until the end of 1995 held the exclusive rights for the bus installation interface implementation. It is controlled by the European Installation Bus Association (EIBA) and is widely used in Germany especially for lighting and blind control.

European Home Systems (EHS) is a home communication system developed by European industries with funding from the European Commission. In 1999 BCI, EIBA and the EHS Association converged under the Konnex association to promote the common field bus standard KNX.

BACnet are currently working with representatives of EIBA on an interface specification between BACnet and EIB. This specification is likely become an annex to the ISO BACnet standard. Thereafter it may also be added to the ANSI/ASHRAE version of BACnet.

The above are only a few of the open systems available, others include MODBUS, PROcess Field BUS (PROFIBUS), FIP and FirmenNeutrales Datenubertragungsprotokoll (FND).

The future
For a good example of a truly de facto standard look no further than Microsoft's operating system which, for better or worse, can be found on the vast majority of pcs. Such domination is clearly not the case for any of the protocols currently on offer in the building controls sector.

"The systems integration industry is currently seeing phenomenal growth," says Paul Price from North Communications. This is testament to the fact that there has not been uptake of one particular protocol.

One of the reasons for this is the way in which buildings are designed and built in the UK where, for example, the lighting, ventilation and lifts services are let as separate packages each developed as a segregated technology. It's has only been in the last decade that those involved have looked at ways to bring them together.

"Certain sectors of the building controls market place have never even heard of LONworks or BACnet. They are grappling with a completely different set of interoperability standards" adds Price.

The end user view
A lot of the incentive for development of open systems came from end-users, but it often seems of less importance in commercial buildings, where the route to market is mainly through contractors, than it does for industrial complexes. "In industrial buildings the processes must link together on a continually changing production facility so the new technology must interface with the old, upgrading must therefore be easy with interoperable controls being utilised," explains Kevin Doyle of Siemens plc.

  "This should still be the case with commercial projects taking into account the 'churn factor', but maybe with changing tenants the importance is overlooked," adds Doyle. This effects life cycle costs but as he explains: "Convincing a contractor of this, unless they are tied to the long-term maintenance of the building, is not possible". So should end-users take more responsibility in their approach?

Contractually, total building services controls integration can be difficult because of the route by which the works are let. For example, the hvac controls may fall under the mechanical package and the lighting under the electrical. This can be overcome if controls are considered at the earliest stage of the project and clients and architects made aware, but it is very difficult to tackle in the later stages. However there is still a lot of nervousness about connecting access, security and fire systems to the same network. It is still common practice for separate networks to be installed to handle these systems.

What's more some control system companies offer both proprietary and open systems which can lead to conflicts. It has been known for the proprietary tender to undercut the open system thereby securing any maintenance and upgrade work. What is also concerning end-users and consultants alike is the policy of some companies who have developed open systems but who are delaying their launch until market demand makes it unavoidable.

To some extent government also plays a role in the open systems market. FND was developed by the German government who specify its use on public projects. Further installation of these systems is expected to be limited to the extension of existing systems in Germany.

Net benefits
The Internet is also being used to connect remote networks and provide remote access to building systems.

The original standard of BACnet's Transmission Control Protocol/ Internet Protocol (TCP/IP) incorporated the concept of IP tunnelling (using internet technology to connect BACnet local area networks). An addendum published in 1999 established BACnet/IP which defines how BACnet devices can be resided directly on the Internet. As Michael Newman, former chairman of the BACnet committee states: "BACnet/IP is now rapidly becoming the favoured way of tying together multiple BACnet local area networks." Similar capabilities are also available for other open systems.

The Internet protocol suite is supported by many manufacturers and there are numerous products on the market with embedded IP capabilities. Many of these can generate their own web pages, resulting in the use of standard IT technologies being used to manage buildings.

The likelihood of a single protocol or network solution being adopted by the industry is slim. Market domination isn't guaranteed despite the huge marketing effort that lies behind some of the technologies. Many believe over the next ten years the market is liable to become much more product, rather than systems, orientated. As Paul Price says: "Probably the biggest threat to the industry is the IT companies who are currently involved in systems at the management layer. They have both the technological and financial muscle to potentially move into all levels of the building controls market and edge out the likes of BACnet and LONworks".