BACnet: Beyond HVAC
OTHER PARTS OF THIS ARTICLEPt. 1: Specifying BACnetPt. 2: This PagePt. 3: Pieces of the Green Puzzle
It’s not surprising that many facility executives think that BACnet is strictly for HVAC applications. After all, it was developed by ASHRAE — the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. And, in reality, most of the early applications of BACnet were HVAC-related. But things have changed since those early days.
“The idea that BACnet is only suitable for HVAC control applications is definitely more myth or urban legend than reality,” says Bernhard Isler, senior system architect at Siemens Building Technologies. Today, there are BACnet applications in many areas beyond HVAC, including lighting, fire/life safety and security. “All of these other initiatives have the common intent to achieve cross-discipline interoperability and interactions, as well as to facilitate simplified workstations to manage all building systems based on a single protocol,” says Isler.
The intent to do just that has guided BACnet since the very beginning. When BACnet was under development, the vision of its founders was to create a protocol that would enable the integration of building automation and control products from any manufacturer and for any building automation application.
“For practical reasons, the original focus was on HVAC applications with the intent of creating an extensible protocol that could evolve with technology and adapt to new applications,” says Steven T. Bushby, leader of the mechanical systems and controls group at the Building and Fire Research Laboratory for the National Institute of Standards and Technology. “A standing committee was created immediately upon publication of the standard and has been making extensions to BACnet ever since.”
Additions have been adopted or are in process for a range of non-HVAC applications, including lighting control, access control, life-safety systems, and vertical and horizontal transportation, among others — areas that are overseen by 11 different BACnet Standing Standard Project Committee Working Groups, which research and propose extensions to the BACnet standard to support various non-HVAC control and automation requirements.
“The areas for which BACnet makes the most sense have jumped on it right away,” says Chris Hollinger, product manager at Siemens Building Technologies. “You have to have someone taking the lead in the competitive landscape to raise the bar. It prompts everyone else to start making changes. Having a standalone product is not nearly as valuable as having an innovative, comprehensive solution.”
Fire and Life Safety
In the late 1990s, work commenced on integrating fire, life safety and intrusion detection into the BACnet standard through two new object types, the Life Safety Point and Life Safety Zone. These extensions were approved in 2001 as Addendum C to BACnet 1995. These extensions were among the first non-HVAC applications considered and were handled in collaboration with the National Fire Protection Association and the Signaling, Protection and Communication Committee of the National Electrical Manufacturing Association.
“The target domain of these additions was fire and intrusion detection panels, but they may also be used for any other type of life safety panels,” Isler says. “One of the fundamental functions of these new object types is the concept of latching an alarm state until reset by a human operator. Also, these objects have properties for switching the mode of operation of the functions represented by these objects. Examples are switching on or off a fire detector and changing a life safety zone to manned or unmanned operation.”
Soon after approval of the life safety extensions as an ANSI and ASHRAE standard in 2001, the first gateway products that provided a BACnet interface to proprietary fire systems began to appear in the marketplace. Today, several manufacturers provide gateways to proprietary fire systems or have fire panels with a built-in BACnet interface.
“Most BACnet systems that integrate life safety applications with other building systems do so through a gateway,” Bushby says. “This is not because of protocol limitations. It has to do with building code requirements and liability issues with installation and maintenance of life safety systems. The listing and maintenance requirements for life safety systems are expensive so there is reluctance to impose them on the entire building automation system. A gateway approach protects the integrity of the life safety system but still permits information exchange with other building systems.”
Lighting control is one area that has received recent and escalating attention in the building automation industry.
“Like all the technologies it enables, BACnet is an ever-evolving communication standard that is constantly being expanded and improved by the BACnet Lighting Applications Working Group (LA-WG), which works in cooperation with the National Electrical Manufacturers Association Lighting Control Council and the Illuminating Engineering Society Controls Committee,” says Michael R. Wilson, business development and strategic planning manager for Lumisys. “Evidence of the success of BACnet in lighting control can be ascertained from the fact that the majority of integrated lighting controls manufacturers support the BACnet protocol.”
The lighting controls industry, says Eddie Hickerson, staff product specialist with the installation systems and control group of Schneider Electric, is using BACnet to enable facility executives to meet their specific needs.
The core extension for supporting lighting applications is the proposed Lighting Output object type, which incorporates various features used in lighting applications, such as blink warning, continuous analog control, ramping, fading or incremental stepping of lighting levels. It also allows for a clear mapping of DALI-based lighting systems functions.
The new object type went through its second public review in the spring of 2008 as part of an addendum to BACnet 2004. A draft addendum is now in the works for the next public review. There is also work on additional lighting application topics, including color lighting support and efficient control of lighting groups.
“In the last several years, I have noticed a heightened interest in lighting controls by most of the building controls companies. It seems that each one is scrambling to find ways to accommodate lighting control into the scope of their systems,” says Pete Baselici, senior product line manager for Watt Stopper/Legrand. “With a few exceptions, BACnet is chosen as the enabling technology. Interest in lighting control is not surprising because it is often seen as low-hanging fruit when it comes to extracting energy savings from a building.”
Consider this scenario, which combines interoperability between HVAC and lighting, yielding efficient energy management:
“Spaces having schedule-based lighting controls are usually required by code to have a way for occupants to override the schedule, turning the lights on when they otherwise would be off. With a BACnet-enabled lighting control solution, an override initiated from a keypad button-press to turn on lights can also be shared with the building control system,” Hickerson says. “In response, the building controller commands the HVAC system to heat or cool the area when the lights are on.”
In 2003, the BACnet Life Safety and Security Working Group began work on extensions for physical access control systems. The effort resulted in the definition of a new, sophisticated and comprehensive set of object types and an alarm algorithm for the functionality of access control systems. The group identified three distinct application parts — the access door interface, the credential reader interface and the authentication and authorization interface.
According to Isler, the access-door-interface object type became standard with Addendum F to BACnet 2004. The definitions for the latter two interfaces are included into Addendum J to BACnet 2004. This recently underwent its fourth public review and is expected to be finalized and approved in 2009.
“We can anticipate to proceed with the new standard at ASHRAE’s winter meeting,” says Rob Zivney, vice president of marketing for Hirsch Electronics. “Many federal agencies using BACnet already are eager for access control to come along.”
Isler says a white paper that outlines and describes the overall concepts and details of the BACnet extensions for physical access control systems can be found in the bibliography section of the BACnet International Website (www.bacnet.org).
“This paper was specifically written for non-BACnet experts in the security industry,” he says.
To complete BACnet coverage of electronic security, the Life-Safety and Security Working Group (LSS-WG) has started work on video surveillance systems.
“Right from the beginning, it was clear that the scope should include transmission and streaming of video data itself, including the control of cameras, streams, video recorders and displays,” Isler says. “It also became clear that a more powerful modeling of streams to be controlled would allow incorporation of audio surveillance, which is an upcoming discipline in electronic security.”
To have a name that would cover both video and audio, the workgroup coined the term, “Multimedia Security System.” The LSS-WG now is seeking participation in this work by a larger range of video manufacturers, integrators and end users. Zivney says relationship-building and exploration with these organizations and individuals is underway.
“Digital video is hot, and it’s driving the need for standards – much more than analog video,” Zivney says.
Operators of large elevator systems in Asia recently have expressed the desire to use BACnet to facilitate central monitoring and control of “people-moving systems,” including elevators, escalators and passenger conveyors.
As a result, the BACnet Objects and Services Working Group is now considering a proposal that defines a set of new object types for modeling elevator functionality, as well as new BACnet services. The current draft includes object types for the representation of buildings, floors, rooms, elevator groups, elevator cars, escalators and more, says Bill Swan, buildings standards initiatives leader for Alerton, Trend Control Systems, and Honeywell.Swan, BACnet committee past chair, drafted the proposal with assistance from a Chinese university.
“The basic idea is to have a box built into every elevator that can issue an alarm if a problem occurs with the elevator,” Swan says. “These alarms would come to a common point with other systems in the building across an already installed BACnet network.” The draft was reviewed last September and will be reviewed again in the spring.
The scope of BACnet has become vast. From its HVAC roots dating back more than 20 years ago to a widely accepted open protocol for building communications and integration, BACnet now touches just about every system that is commonly part of a building. Those in the control industry don’t see the standard losing momentum any time soon.
“I really don’t see an end to this trend now that BACnet is firmly established as the standard for building automation,” Baselici says.