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HVAC Monitor: Intelligent Condition-based Maintenance
Steven B. Leeb

Air conditioning accounts for a substantial portion of the the total energy consumed by an average building in the US and approximately 27% of total electricity use in the US. One estimate of the cost required to bring building air within an acceptable temperature range is 30 to 60% of the total yearly energy cost for a building. We are developing a nonintrusive monitor as a diagnostic tool for RTUs (roof-top air conditioning units). Diagnostic procedures are being investigated and developed for the most common causes of RTU energy inefficiency and or failure.

Examples include liquid slugging, air-side blockage, incorrect refrigerant load, malfunctining electrical controls.

Fig. 14. Preparing a refrigerant compressor for slugging tests in the laboratory.

Dual-Use Electronics: Intelligent Metering
Steven B. Leeb

Power system monitoring is an exciting approach for creating an inexpensive, highly capable "black-box" for monitoring the performance of critical electrical components and for energy score-keeping and conservation initiatives. We are developing nonintrusive diagnostic and energy monitors that make measurements of voltage and current solely at the utility service entry of a building, automobile, ship, aircraft, or any other system using electrical power distribution. The nonintrusive monitor characterizes individual loads by their unique signatures of power drawn from the mains. A transient detection algorithm can identify when each load turns on and off, even when several do so nearly simultaneously. The nonintrusive monitor analyzes observed waveforms to develop diagnostic and prognostic metrics that presage failures and indicate inefficient energy utilization.

Fig. 15. Intelligent power system monitoring is used here to sense impending coupling failure on a US Coast Guard warship. See graph right.