Uncertainty analysis Model uncertainty Model structure Measurement uncertainty Fault detection Condition monitoring Air-conditioning Heat exchanger Physical modelling Sensors HVAC Information poor systems
BUSWELL, R.A. and WRIGHT, J.A., 2002. Uncertainty in model based condition monitoring. IN: Proceedings of the 6th International Conference on System Simulation in Buildings, University of Liege, Belgium, 15-18 December 2002.
Model based techniques for automated condition monitoring of HVAC systems have been
under development for some years. The generation of false alarms has been identified as a
principal factor affecting the potential usefulness of condition monitoring in HVAC applications.
Results from the application of these methods to systems installed in real buildings
have highlighted the difficulty in selecting good alarm thresholds that balance robustness (lack
of false alarms) and sensitivity (early detection). This paper demonstrates that this balance
can be met in a transparent and analytical manner, through the application of uncertainty
analysis. The paper discusses the sources of uncertainty associated with component models
and system measurements. A Condition Monitoring scheme applied to a typical HVAC cooling
coil subsystem installed in a real building is presented. Faults are artificially introduced
into the system and are used in conjunction with fault-free operation to demonstrate the
sensitivity and robustness of the scheme. The principle conclusions drawn by the paper consider
the likely minimum magnitudes of faults that can be detected in typical HVAC systems,
without false alarm generation. More broadly however, the paper demonstrates that the issue
of uncertainty affects all aspects of system monitoring, modelling and control.