On-site fault experiment and diagnosis research of the carbon dioxide transcritical heat pump system for energy saving

Carbon dioxide transcritical heat pump air conditioning has an excellent performance in heating conditions, and is a very potential heating alternative, which will help to improve the energy saving level of buildings. The occurrence of the fault will lead to an increase of energy consumption, damage of system components and other consequences. However, the current research focuses on the heat pump system with Freon as refrigerant, and the experimental research on the fault of the carbon dioxide transcritical heat pump system has not been studied. Therefore, this research carried out the operation experiment of the carbon dioxide heat pump with eight fault types under the actual conditions in winter. The operation characteristics under different fault conditions are analyzed. Based on the fault characteristics, a causality table is proposed, which can quickly identify the fault type when there are at least 6 characteristic variables. Besides, it is concluded that after the fault occurs, the energy consumption will increase directly or indirectly. Most of the faults will directly cause the decrease of system heating capacity and reduce indoor thermal comfort. The research results will contribute to the early identification of carbon dioxide system faults and the improvement of building energy efficiency.