October 2009


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BACnet Triple Play

Three ways to win with BACnet Integration


Andy McMillanAndy McMillan
President and CEO
Teletrol Systems Inc.

now a part of Phillips

BACnet International
Contributing Editor

It’s October, a month when minds turn to baseball and people start to think about strategies their favorite team might use to win the World Series. So, maybe this is a good time look at how to win with BACnet, too. In particular, let’s look at the BACnet integration triple play with device, functional and application integration.

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In the early days of BACnet development the integration vision consisted of controls from multiple suppliers on a single network with one PC running a shared controls user interface program. That vision was very forward-looking at the time, but the world has evolved beyond it. In our current world we find controls are nodes on a vast cloud of connections where the other nodes may be IT devices (e.g. firewalls) or even virtual devices (e.g. enterprise applications). The world has even evolved beyond the concept of a PC running a shared controls user interface. Current generation systems use server-based interfaces where the controls information and interaction happen through a web browser or even better, where control system information and interactions are embedded in standard office applications (e.g. Excel) or enterprise information dashboards. The good news is that the BACnet specification continues to evolve along with the world so users can still hit a home run with BACnet.

The First Out

One obstacle to a winning integration project is a lack of direct connectivity between BAS devices that need to interact. For example, many HVAC applications include a boiler providing hot water, a chiller providing cold water and an air handler using both to provide conditioned air to a series of locally controlled zone dampers serving different rooms in a building. In this application, each device could usefully communicate with other devices to optimize energy use and occupant comfort in real-time. Because all of these devices are building automation specific, BACnet defines everything needed to accomplish device integration including:

• Physical interconnection options
• Network routing options
• Data representation options
• Data exchange options
• Action-Requests/Response options
• Capability options

For each of these communication elements BACnet provides a variety of options so the solution can be tailored to the requirements of the application. Used appropriately, BACnet device integration eliminates one major obstacle to a winning project, but there are two more integration obstacles consider.

The Second Out

The second obstacle to a winning integration project is functional subsystems that can’t communicate, even though there is value in sharing some high-level information. For example, access control subsystems may have information that could be useful in HVAC and lighting control subsystems. When someone enters a building the access control system may “know” who it is and may also “know” where in the building they typically work. By providing that information to a supervisory function in the HVAC and lighting control systems, the building could “respond” to the person’s entry by lighting a path to their work area, setting their work area to the preferred lighting scene and changing the HVAC setpoints in their work area to their preferred values. Like device integration, functional integration involves data sharing among intelligent network nodes, but it differs from device integration in a number of ways. Typically, functional integration:

1. operates at a higher level of control hierarchy;
2. involves equipment that is more geographically dispersed;
3. has a less demanding real-time requirement;
4. and is less mission critical.

Functional integration could involve subsystems that do not share a common physical connection to a network but merely have a means to exchange information at a higher level. Even so, functional integration can rely on BACnet to define the elements of communication that are required, including:

• Data representation options
• Data exchange options
• Action-Requests/Response options
• Capability options

[an error occurred while processing this directive] Effective functional integration allows building systems to act together in a seamless and intelligent fashion to ensure positive occupant experience, reduce the use of energy and maximize facility staff productivity. Even so, a winning project requires more than just device and functional integration. There is one more obstacle to deal with.

The Third Out

The third obstacle to a winning integration project is building equipment and operational information that is trapped in a BAS database where enterprise applications cannot take advantage of it. The solution to this problem is application integration. One example of a value proposition for application integration is the use of an asset management program to track maintenance and repair records for HVAC mechanical equipment. Most BACnet-enabled equipment can provide manufacturer, model and serial number information to the BAS system. Current generation BAS systems can also recognize and record a variety of equipment failures. This information is useful in a BAS but its value is even greater when incorporated in an enterprise-wide asset management system. Like most enterprise applications, asset management programs are not BAS-specific so they do not have any knowledge of BACnet, per se. BACnet addresses that issue by including a web services definition that details the required communications elements for application integration, including:

• Data representation;
• Data exchange.

Since web services is a standard mechanism for application integration in many domains, BACnet web services is a natural way to pull together the final piece of the BACnet triple play.

Wrap Up

The vision for system integration has evolved a lot since the conception of BACnet in the late 1980’s. The BACnet specification has grown with the industry and now supports effective integration at all levels of system hierarchy, from devices, through subsystems all the way to applications. A key part of the power of BACnet is its ability to provide comprehensive integration solutions through its definition of the required elements of communication at each level. As a result, BACnet’s integration triple play is a platform for more and more winning projects.

As always, the views expressed in this column are mine and do not necessarily reflect the position of BACnet International, Teletrol Systems, Philips, ASHRAE, or any other organization. If you want to send comments to me directly, feel free to email me at andysview@arborcoast.com.



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