Multiple simultaneous faults’ impacts on air-conditioner behavior and performance of a charge diagnostic method

Abstract

• Experiments on split air conditioner with two, three, four simultaneous faults. • Triple faults reduced COP up to 39% and reduced cooling capacity up to 42%. • Triple faults increased refrigerant superheat up to 21 °C. • Simultaneous fault impacts of this study were compared with a previous study. • An existing virtual refrigerant charge sensor was tested with simultaneous faults. Although there have been several studies that have focused on the effects of faults on the performance and on the characteristic features that could be used to detect faults, almost none of the research has studied the effects of multiple simultaneous faults. Existing fault detection and diagnosis approaches that have been developed based on single faults may struggle with simultaneous faults. This paper is part of a series that present a methodology and comprehensive measurement data from a battery of laboratory tests on an air-conditioner with combinations of common faults (refrigerant charge, evaporator airflow, non-condensable gas, and liquid line restrictions) imposed, to show how the indicator variables and overall performance are impacted. The system has a microtube condenser and a fixed-orifice (FXO) expansion device, which are found to affect the features’ fault sensitivity. This experiment is the first to test these combined faults in an FXO-equipped system, so comparisons are made to a previously studied thermostatic expansion valve-equipped system. Finally, a promising charge diagnostic technology is assessed, to see how it is impacted by other faults. The faults reduced capacity by up to 42%, and efficiency by up to 39%. The charge diagnostic performed well, even with multiple faults present.