Keeping Up With the Protocols
Much has been said recently about control-system interoperability by the guardians of the interoperable control languages...
Much has been said recently about control-system interoperability by the guardians of the interoperable control languages and the manufacturers that have staked some portion of their future profits on one technology or another. Much as parents might protect an only child, these protocol architects dote on their progeny, vehemently defending them from any critical mention. It is no surprise then that specifying engineers-and their clients-until now have met these purveyors of building controls with a healthy measure of skepticism.
Amid all the discussion, very little has been written about interoperability benefits that can be empirically proven to building owners. Even less has been penned that documents actual buildings realizing these benefits, outside of a small number of showcase projects that provide little real value to engineers-who know that nearly anything can be done if time and money are not an issue. Unfortunately, for every commercial project, time and money are two of the key issues.
Show me the buildings
On inspection, it seems understandable that there exists a lack of documented benefit and detail of interoperability-control systems are technical and complex. To add to the confusion, there are conflicting definitions among manufacturers of what the term "interoperability" actually means. Subtle differences in these definitions, the products available and even the implementation of a technology can have ramifications for a building's future interoperability. The level of integration, cost effectiveness, increased reliability and added benefits-for real buildings-are what should be scrutinized in any "interoperable" system.
Only projects specified by independent engineers that receive bid responses from at least three vendors can be considered real examples. They should be void of gateways and consist of communicating control products from multiple vendors on the same control network. Projects cannot be truly tested or even considered interoperable if they consist of products from only a single vendor. After all, isn't "multivendor" what interoperability is all about?
While heating, ventilation and air-conditioning (HVAC) controls are at the forefront of building interoperability, other systems are no less important: lighting controls, security systems, access controls and fire- and life-safety systems. In the past, most of these subsystems have been installed on completely separate communication infrastructures, duplicating the network cost of each subsystem (see Figure, opposite) and adding to training and maintenance expenditures.
Both BACnet and LonWorks (see "A Brief History of Building-Automation Interoperability," below) incorporate plans for interoperability at the device level. BACnet, however, includes many different architectures, so two manufacturers of native BACnet systems may or may not have terminal-control devices that can interoperate on the same set of wires. Other BACnet systems require some sort of media converter or gateway to connect disparate systems (see Figure, page 34). Each of these hardware devices requires considerable computing power and therefore adds significant cost to the system while simultaneously creating a single point of failure. The majority of BACnet systems installed today use this system-to-system approach.
Contrary to BACnet's "islands of intelligence" methodology, products from LonWorks manufacturers are designed to interoperate on the same set of wires (see Figure, page 35), and LonWorks media converters are relatively inexpensive, on the order of several hundred dollars.
For this reason, LonWorks has been found to be suitable for device-level integration. While the LonWorks protocol is network-independent and can use network transceivers for optical fiber, radio frequency, infrared light, Ethernet and power-line carrier, it is most widely used in buildings on twisted pair using a transceiver known as FTT-10. This has proven to be an inexpensive and popular execution of the LonTalk protocol-very competitive with proprietary technologies and offered by the largest building control-system manufacturers, although not all in the United States.
Benefits of interoperability
That being said, what are the functions that specifiers and owners seek in "open system," and what nontechnical attributes are sought?
Competitive bidding of multiple projects. Historically, one of the driving forces behind interoperability has been the competitive bidding of projects across different vendors. As long as new bids are for separate buildings and not tenant improvements or other additions to an existing building, the only requirement necessary to fulfill this need is the ability to operate and manipulate the system from a common "host" computer. On the surface, both BACnet and LonWorks platforms seem capable of providing this "one-seat host."
Competitive bidding is fine for new construction, but what about changes for new tenants, or work and maintenance performed after the original sale? End-users and owners may be captive when dealing with proprietary systems.
Sharing of control-network infrastructure between subsystems. Control systems have been using a separate wire for so long now that some owners and engineers actually fear using a common infrastructure. Imagine creating different networks for accounting, sales and operations data. The cost and maintenance benefits of sharing a network are difficult to ignore, so engineers are now beginning to incorporate multiple subsystems on the control network.
Energy profiling and usage reduction. With energy costs again on the rise, owners and engineers must again understand and mitigate energy usage. Deregulation in many areas is raising the stakes, and knowledge of energy usage can be the only remedy for higher bills.
Integration of new product innovations. Automation requirements today can change in the blink of an eye as the usage of a building can be altered from industrial to commercial and from typical to the highly complex. Owners need the ability to add specialized functions to systems that are not necessarily available from the original vendor.
Risk reduction, or "future-proofing." With the usage of facilities changing rapidly and products becoming obsolete at a frightening rate, owners are now at greater risk of owning an obsolete system. Owners need to be able to introduce new products to the network regardless of manufacturer, evolving the system one device at a time, if necessary, and effectively giving it an infinite life.
Bringing interoperability to life
As interoperable controls become prevalent, engineers must be comfortable specifying systems that share not only the same infrastructure, but also common operational sequences. Energy and product savings can come from integrating best-of-breed products on common networks to create building-wide sequences of operations, as a few recent projects show.
St. John's Medical Center. In 1998, St. John's Medical Center in southern Washington initiated plans to construct a new building and retrofit several structures at their low-rise campus. Hospital staff determined operational needs for the projects, and specifications were written and placed for traditional public bid by separate sections.
Meanwhile, the hospital design staff was coming to a startling realization: the number of networked systems in their hospital had swelled to over 36 parallel networks. Installing traditional systems would require a wire bundle approximately 12 inches in diameter between buildings set well apart. Before final decisions were made, the team sent out requests to potential vendors to submit proposals that would share a common standard-fiber network.
One submission proposed placing all major building systems-HVAC, lighting, security and card access-on a single building network and directly connecting each building to a shared Ethernet network. The proposed design would use LonWorks technology and products from multiple manufacturers.
An opportunity to test the technology presented itself in an accelerated HVAC retrofit of an emergency ward, where LonMark variable-air-volume (VAV) boxes were installed. Two years later, the new building is in operation, five others have been retrofitted and a single pair of optical fibers connects all buildings-and products from five different manufacturers.
Coeur Defense Facility. At almost 4 million square feet, the Coeur Defense Facility in Paris has been called the largest mixed-use tower in Europe. Designed with a "configurable workspace" concept, entire work areas can be reconfigured in a "cookie cutter" fashion dealing not only with HVAC, but also with lighting control. With retail space, museums, restaurants and a myriad of other service-related businesses, the project had diverse needs and tenants, so products from different manufacturers were needed to fit their unique requirements. This-along with the owner's desire to have HVAC, lighting and other system data available in a single location-all but mandated interoperability. Another concern was the tight schedule and coordination of 5 million hours of work when all the tenants were in.
The project team and French-based system integrator Exprimm chose to install a LonWorks-based system with lighting and HVAC controllers from several vendors. The scalability and flexibility of the "peer-to-peer" system met their requirements for functionality and project synchronization. The owner is able to add devices on the network anywhere without running into limits to the number of devices that can occur with hierarchical, or area-controller, systems.
With the core project nearing completion, the owners and engineers are discussing the addition of other tenant systems to the network backbone.
Tiffany Park Elementary School. When Renton School District No. 403 needed to build five new schools, they hired independent consultant Robert Shives, C.E.M., from Seattle, to investigate such options as choosing interoperable controls. The district had hoped to monitor and control as many systems as possible from a central facility-and lower operations, maintenance and training costs in the process.
Shives investigated the available options to ensure that at least three competitive bids would be available for any system chosen. The district elected to create a single control network in each school to lower installation costs and to ensure that as many systems as possible could be accessed. A specification was created that put HVAC, lighting and security on a LonWorks network. The projects were placed for public bid and received bids from at least three contractors.
To date, two different contractors have been selected, and the first school-Tiffany Park Elementary-has been created using products from six manufacturers. The system will be monitored locally and from the facility-maintenance center over the district local-area network.
LonMark occupancy sensors now serve double duty, controlling lighting during the day and functioning as part of the security system during off hours. When the security system senses an intruder, in addition to sirens wailing, the area is illuminated by the lighting controls. When the security system is armed, all systems automatically operate in an unoccupied mode. In addition, these facilities are ideally prepared for the addition of card-access systems in the future.
Dealing with change
In physics, it is said that a body will remain in motion and on the same course in the absence of resistance. Similarly, building technology will tend to remain the same unless engineers convince their clients of the benefits of interoperability.
Realizing the practical benefits of interoperability requires all parties involved to modify their thinking. Risk management and human nature do not, however, favor change. If logical skepticism is a requirement of successful engineering, then knowledge is the antidote to complacency. Interoperable technologies clearly offer added functionality and lowered costs-but those benefits are largely determined by the resolve and demand of engineers and owners.