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February 2011 -
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BACnet offers a practical, user-friendly and cost effective way to connect any system that needs to be monitored or automated within a facility.
"BACnet connectivity and interoperability has added much value over the years," Hollinger says. "While building systems are still complex, in many ways due to the nature of control, harvesting relevant mechanical and electrical system information continues to get easier. With fewer hurdles in the way related to connectivity, customers can more simply generate reports on system performance on a daily, weekly or yearly basis. This allows facility managers to spend more time actively and productively managing their facilities, while producing value-added information to their customers. This saves time and money."
An emerging area in which BACnet controls are playing a role in efficiency and indoor air quality is natural ventilation, which Todd Cowles, sales director for the Americas at Trend, calls "one of the most interesting new focuses in the area of energy efficiency, IAQ and sustainability."
With natural ventilation, a building's indoor climate is controlled by fresh air through the façade or roof windows that open and close automatically at set points for indoor air temperature and carbon dioxide levels. Within the control sequences, consideration is given to measured outside air temperature and humidity, as well as rain and the influence of wind on the building.
"Interoperability is essential when incorporating natural ventilation," Cowles says. "The control system ties directly into the natural ventilation system, working smoothly to ensure comfort, IAQ and avoiding wasted energy from conditioning extra fresh air."
Another area of importance is using controls to provide fault detection and diagnostics to contribute to a building's long-term efficiency, says Steve Tom, director of Technical Information for Automated Logic. Ideally, all equipment and control systems will be installed properly and commissioned during construction. A new building then will operate at peak efficiency on Day 1. Entropy then takes its toll, causing the building's efficiency to decline over time. Regular maintenance, such as changing filters, greasing bearings, cleaning coils, can slow this decline but will not catch everything that might be deteriorating.
"Well-designed control applications can spot many of these problems and alert the system operator," Tom says, who says that there are many well-documented case histories where building owners have cut their energy costs by thousands of dollars a year by recommissioning a building — going through all of its systems to fix problems and recalibrate the controls.
"A much more effective strategy, but one whose savings are not so easily documented, is to maintain energy efficiency and sustainability by fixing these problems as they occur and not letting them drag down a building's performance to the point where recommissioning is needed," Tom says.
One of the quickest ways to assess the health of controls, and ultimately the building, is to review the quantity of items that are "overridden in the system," says Eugene Shedivy, controls product management leader at Trane.
"Although it may be necessary to temporarily override a control system parameter or output, the override should only accommodate a unique, temporary condition," Shedivy says. "If you discover that multiple items are overridden, you most likely are losing a substantial element of efficiency with your control system. Overrides often are entered in lieu of actually troubleshooting and resolving a control issue. A building management system, such as BACnet, can assist with continuous commissioning to help facility managers validate and sustain performance, as well as identify and correct issues."
BACnet is growing in popularity for multiple reasons. Some reasons are simple to understand, like the fact that the range of BACnet product options has increased. Other reasons are more technical — for example, the baud rate that makes BACnet faster than many other forms of serial communication, says Joseph Koepke, building automation application engineer for Yaskawa America.
But whether the benefits are technical or not, one thing is clear: BACnet-based systems have proven themselves in the field. What's more, facility managers are farther along on the learning curve about all the ways that BACnet can be used. VFDs are a good example. "The word is out about VFD usage in BACnet," says Koepke. But individual products aren't the whole story. "VFDs are another piece of the larger puzzle that BACnet communicates with," says Koepke. "It's easier to tie more of the building together and centrally monitor and control the building with BACnet."
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