Diagnostics for Packaged HVAC Units
According to the Energy Information Administration (EIA), packaged cooling equipment is used in 42% (4.7 million) of all commercial buildings, serving over 54% (36.5 billion sf) of the commercial building floor space in the U.S. These units consume a 230 trillion Btus of energy annually but are some of the most neglected of building systems. During commissioning and re-tuning, they are often found with inoperable dampers, dirty/clogged filters and coils, incorrect refrigerant charges, failing compressors, failed fans, missing enclosure panels, incorrectly implemented controls, and other problems. Service contracts alone are not likely the solution to this problem. A study in the 1990s showed that package units in California under maintenance contracts were in no better condition than units not under service contracts.
These units are often run until a catastrophic failure occurs, such as complete loss of cooling caused by a failed compressor, failed condenser fan, failed supply fan, or significant loss of refrigerant. Upon complete failure, the owner, operator, or building occupant calls a service company to repair the unit. Complete failure, though, is often preventable. Avoiding failures by properly maintaining the equipment would reduce repair costs, increase operating efficiency, extend equipment life, and ensure comfortable conditions, but this would require awareness of equipment condition and when the equipment needs servicing. With increasing pressure to reduce operation and maintenance (O&M) costs and with the reduced number of operation staff in today’s facilities, regular visual inspection by staff is out of the question. Without a lower cost solution, package units are likely to continue to be maintained poorly and operated inefficiently.
A low-cost wireless infrastructure for monitoring, diagnosing, and controlling building systems and equipment.
To address this problem, the U.S. Department of Energy’s Building Technologies Program and a team led by NorthWrite Inc., which includes Pacific Northwest National Laboratory, is working to develop a low-cost wireless infrastructure for monitoring, diagnosing, and controlling building systems and equipment. This technology will monitor, detect and diagnose problems with the air side and refrigerant side systems and overall efficiency of packaged rooftop HVAC units. The system will use wireless communications for: 1) collecting data centrally on site from many wireless sensors installed on building equipment, 2) transmitting control signals to actuators and 3) transmitting data to an off-site network operations center where it will be processed and made available to clients on the Web (see Figure below). End users obtain information via the world wide web and need only a web browser and Internet connection.
For background information and the economics of wireless condition monitoring, see the paper titled, “Wireless Condition Monitoring and Maintenance for Rooftop Packaged Heating, Ventilating and Air-Conditioning.”