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Results from Field Testing of Embedded Air Handling Unit and Variable Air Volume Box Fault Detection Tools



J Schein


Fault detection and diagnostic (FDD) methods that can detect common mechanical faults and control errors in air-handling units (AHUs) and variable-air-volume (VAV) boxes were developed and commercialized. The tools are sufficiently simple that they can be embedded in commercial building automation and control systems and rely only upon the sensor data and control signals that are commonly available in these systems. AHU Performance Assessment Rules (APAR) is a diagnostic tool that uses a set of expert rules derived from mass and energy balances to detect faults in air-handling units. VAV box Performance Assessment Control Charts (VPACC) is a diagnostic tool that uses statistical quality control measures to detect faults or control problems in VAV boxes.This report describes the transfer of the FDD methods from research to commercial use. An interface between the FDD tools and the building operator is introduced. Results are presented from a multiple site field demonstration in which APAR and VPACC were embedded in commercial AHU and VAV box controllers. Robust FDD parameters are tabulated for both APAR and VPACC. The parameters, which eliminate the need for site-specific configuration, were developed based on experience from the field demonstration.
Journal of Research (NIST JRES) - 7365
Report Number


BACnet, building automation and control, direct digital control, energy management systems, fault detection and diagnostics


Schein, J. (2006), Results from Field Testing of Embedded Air Handling Unit and Variable Air Volume Box Fault Detection Tools, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed April 16, 2024)
Created October 30, 2006, Updated February 19, 2017