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When manufacturers build devices that exceed the listing requirements, they outline these advanced capabilities in a document called a Protocol Implementation Conformance Statement (PICS). The PICS gives facility managers an additional tool and detailed information for making educated decisions about specifying BACnet devices, either in a new system or as a replacement for existing products, says Steve Tom, director of technical information at Automated Logic Corp.
"The BTL tests the devices to make sure they do indeed fulfill all the claims made in the PICS, and if the device passes the test, they include it in their listing online," Tom says. "The BTL guarantees interoperability — the ability to exchange data and support services required by a particular device — not interchangeability," Tom adds. "However, even in situations where additional information is needed, checking the BTL listing is an important first step to guarantee the device actually has been tested in a BACnet system and behaves the way it is supposed to behave."
To further ensure interoperability in a real-life setting, Brian Dutt, vice president of sales and marketing at Delta Controls, suggests facility managers work with their consulting engineers to conduct a "plug-fest."
"This essentially is a live demo between multiple, local system integrators who represent a BTL-listed, BACnet product," he explains. "This plug-fest would require each system integrator to show up at the engineer's office with a sample of the product, connect it to a simple network, similar to typical building controls network architecture or one suitable for a particular product design, and to begin doing some basic interoperability verification."
This process helps to ensure that systems do interoperate as specified and also provides a quick sense of the particular system integrators and their respective products' capability to network successfully with other systems.
One additional litmus test of BACnet manufacturer interoperability is to check to see if they have worked successfully together in the past and have project documentation or case studies to prove it, says Michael R. Wilson, OEMCtrl and marketing chair of BACnet International. One resource for facility managers and engineers is BACnet International's "BACnet Success Stories." Here, users can read about successful BACnet implementations in a mini-case study format and find out specific BACnet manufacturers involved in the projects. (See "Litmus Tests for Interoperability" on page 68.)
Designing a truly interoperable building automation system opens the door to selecting what Terry Hoffman, director of BAS marketing at Johnson Controls, calls "best of breed" technology.
"Every major manufacturer of lighting, electrical and mechanical equipment has a BACnet interface available. Most do not require the use of gateways or translators," Hoffman says.
As BACnet becomes even more widely accepted now that it has a decade's track record, more and more organizations have begun to turn to interoperability as a means to increase building efficiency and improve operations. In fact, a quick search of published articles will reveal numerous examples of how BACnet has successfully integrated systems and equipment into a unified system, Tom says.
"The recent ASHRAE headquarters renovation integrated equipment made by multiple, often competing, manufacturers into a LEED Platinum facility," Tom says. "The Mississauga City Centre project integrated multiple vendors' HVAC, lighting, fire and security controls in multiple buildings and was certified as a 'Go Green' system. And Rowan University in New Jersey has successfully used BACnet to unify buildings across its campus and to get competitive bidding on all new work."
Interoperability can mean different things to different users in the building, the facility department or even in different buildings throughout an organization.
"Typical customers want to have systems that provide flexible interoperability with other facility systems and also the ability to cost-effectively upgrade and migrate the solution over time to minimize life-cycle costs and maximize investment," Hollinger says. "They also want the ability to provide cost-effective, add-on systems to grow the facility system as the facility grows."
Hollinger further says that daily users want systems that work reliably while providing an easy-to-use, access-anywhere Web interface that also provides troubleshooting parameters. Facility management wants effective reporting tools and information to assist in decision-making. Purchasing wants cost efficiency and low life-cycle costs.
Consequently, no two BACnet-based BAS will be the same. That's where knowledgeable engineers, suppliers and BACnet consultants become important parts of any facility manager's team.
BACnet President Andy McMillan urges facility executives to seek outside help in designing a truly interoperable BAS, including the advice of a consulting engineer. "A consulting engineer can offer them the appropriate knowledge and skills to effectively employ BACnet as an important interoperability tool," says McMillan, president of Teletrol, a Philips company.
Another important team player in a successful interoperability initiative is the controls system integrator, says Zaban of Reliable Controls. "The local controls contractor has an important partnering role by helping the client decide what equipment to buy and how to maximize the interoperability capabilities and benefits," he says.
"In the long run, a facility manager will be best served by looking for BACnet suppliers they can partner with in a common effort to achieve interoperable systems," he says. "It's easier to do that than to look for a guarantee that all devices from one supplier will seamlessly interoperate with all devices from any other supplier."
About BACnet International
BACnet International encourages the successful use of BACnet in building automation and control systems through interoperability testing, educational programs and promotional activities. Members include companies involved in the design, manufacturing, installation, and commissioning of equipment that uses BACnet.
BACnet International endeavors to support BACnet conformance certification based on ASHRAE standards, as well as sustain and fund the BACnet Testing Laboratories (BTL) to support compliance and interoperability testing. A product with the BTL mark has been tested to ensure that it correctly implements BACnet features claimed in its listing. The organization maintains a single Web site displaying all BTL-listed products.
Verifying and Customizing Interoperability