The IT factor

IT networks are today a standard part of the infrastructure of most non-domestic buildings. Virtually all are based on the Ethernet network and most employ Transmission Control Protocol/Internet Protocol (TCP/IP) as the communications procedure for data transportation. As the use of Ethernet has become more widespread, its cost has fallen dramatically. Moreover, its installation is now simple, whereas once it required a very high degree of skill.

BEMS/IT integration dates back to the mid 1990s. Now as then it basically involves having Ethernet take over the role of the building management system's communications backbone. Importantly, the Windows-based supervisory software packages that provide operator access, can be connected directly to this. The bems' distributed controllers are still linked to local area networks (lans), but it is Ethernet that joins the lans together (see figure 1).

Fast, flexible and cost saving
Two key benefits of the arrangement described are that it enables the bems to take advantage of the IT system's flexibility and high speed.

A system supervisor can be placed wherever there is a data port, which effectively means almost anywhere in a building. This feature is especially useful when office layouts are changed and people moved around, which in many modern buildings is a frequent occurrence. It is also increasingly valuable because of the growing number of individuals who expect access to bems monitored data. It is no longer just technical staff who want this information but others such as financial and facilities management personnel.

The high data transmission speed provided by Ethernet/TCP/IP is many times greater than for a normal bems network. This is especially significant where the system has an extensive monitoring and logging role, which more and more do, and data traffic to the supervisors can thus reach high levels.

Over Ethernet, downloading a 1000 point data log would take a fraction of a second. Even if hundreds of system alarms were generated simultaneously, which might occur if there were a power failure, it could easily handle the resultant traffic.

An additional advantage of having an IT network serve as a bems' communications backbone is that infrastructure costs are reduced, a saving that is likely to be appreciable on large sites with many buildings. There may also be no need to invest in separate communication links in those situations where a number of sites are remotely monitored from a central supervisor, which is typically done via modem over leased telephone lines. It is probable that the necessary links already exist as part of the IT network, possibly in the form of integrated services digital network (isdn), though increasingly it is a permanent internet connection that is fulfilling this role.

A bems can of course incorporate Ethernet without actually being linked to the IT system and there are some buildings in which each has its own completely separate Ethernet network, possibly running side by side within structured cabling. This obviously offers fewer benefits than are gained through integration, particularly with regard to flexibility.

Also, it is sometimes just the bems' supervisors that share the same network as the IT system. The controller lans are on their own Ethernet segment, the two parts being linked by a router. With this halfway house approach, flexibility over supervisor siting is retained.

It should be stressed that the normal operation of an IT network is in no way affected by its use for bems traffic. Nor does integration compromise the functionality or essential features of the building management system.

Today, the merging of bems and IT is a straightforward operation. Devices have been developed which allow a much more plug-and-play approach when connecting a controller lan to Ethernet. Supervisors are easier to connect too and it is also now possible for a bems to run across IT routers, which has eliminated a major limitation.

New spur to integration
To date, integration has been driven by a desire to cut costs and improve bems performance and user access. However, with the emergence of new building control products, there are now further powerful reasons why it makes sense.

Some of the latest bems supervisors and other operator interfaces found inside buildings are able to display data on hypertext mark-up language (html) pages, which can be viewed using just a web browser. Consequently, data from say the bems, fire and security systems could all be shown on a common head-end, though the information from each would appear on separate displays. This represents a first, small step towards using IT networks for integrating different building services.

Far more significant is the recent development of bems controllers that can connect directly to Ethernet. This means more than simply being able to run the whole system, or at least most of it, over the IT network. It is an advance that ultimately will have its biggest impact in the area of data sharing and inter-communication between systems.

At present, bems use Ethernet/TCP/IP as little more than a medium for carrying their own protocols. The new generation of controllers will be able to exploit their Ethernet connectivity to support multiple formats and protocols. For instance, as well as being able to serve up html pages, they will be able to create files in Extensible Mark-up Language (XML), which is a new data format that can be read by any IT application. This would allow controller logged data such as utility meter readings to be directly transferred over a company's Intranet into say a spreadsheet or billing package – where it could potentially be combined with XML data from other systems.

Using XML, it would also be possible to have a common head-end on which data and control settings for different systems would be accessible on the same displays. For example, a floor plan schematic could be created which showed both temperature levels and fire alarm status.

Need for a standard approach
While XML is eminently suitable for use at system management level, it is not designed for communicating data directly between controllers or smaller devices. For performing this function there are various proprietary and open protocols.

The quest for a common communications standard for building controls, which began over ten years ago, has in fact produced several competing open protocols. Currently there are three principle contenders vying for business: BacNet, LonTalk and Konnex (previously EIB). In the UK their use has been more limited than elsewhere, partly because contractors here see open systems technology as a risk and also because of the dearth of impartial sources of advice available to specifiers. It hardly helps of course that there are three standards rather than one – with several more on the horizon.

If two systems that use different protocols (whether open or proprietary) are to interact at anything but the most basic level it is generally necessary to connect them via an intelligent gateway. Often this is a complex device that is difficult and expensive to engineer. Gateway products could be greatly simplified if bems and other protocols were to adopt a common way of representing system functions, using a set of standard objects. This would also make head-end integration easier to accomplish. Figure 2 illustrates how standard objects would complete an Ethernet-based model of integration.

Many believe that the objects used within the BacNet protocol represent a good basis for developing a standard structure, though they would first need to be simplified. Co-ordinating this important work could be done by the international standardisation committees that have been dealing with building controls.

There is no doubt that Ethernet could provide an excellent platform for building services integration, particularly as it is continuing to penetrate ever deeper into buildings. Owing to its attractive and improving price to performance ratio it is being incorporated in smaller and smaller devices. Little wonder that its use is growing at a faster rate than any other communications system used in non-domestic buildings.