Non-intrusive performance monitoring method for air conditioners

A novel technique that relies solely on cost-effective and non-intrusive instrumentation for monitoring the performance of air conditioning installations in buildings was developed and experimentally tested. The proposed method addresses the challenges of field measurements in air-to-air units by using thermocouples and strain gauges placed strategically on the refrigerant pipeline of the outdoor unit to estimate the cycle COP. The tests demonstrated the feasibility of estimating refrigerant temperature and pressure without cutting the refrigerant pipeline. Real-time cycle COP deviations could be limited to 3 % with proper calibration of the strain signal and the use of refrigerant properties. Additionally, compressor speed is identified through the frequency spectrum of the strain signal. Therefore, the refrigerant flow rate can be estimated using a compressor curve method that relies exclusively on simple instrumentation. Widespread adoption of this method could help close the knowledge gap between catalogue and field-operating performance of the numerous air conditioning installations.