HEAT PUMP SYSTEM AND HEAT PUMP TYPE WATER HEATER

摘要

PROBLEM TO BE SOLVED: To provide a two-stage compression type heat pump system that can easily maintain amounts of refrigerating machine oil in two compressors equally.SOLUTION: A heat pump system includes: a compression mechanism 10 that has a low stage side compressor 10a and a high stage side compressor 10b for compressing and discharging a refrigerant; a water-refrigerant heat exchanger 11 for exchanging heat between the refrigerant compressed by the compression mechanism 10 and a heat exchange target; an expansion valve 12 for decompressing and expanding the refrigerant flowing out from the water-refrigerant heat exchanger 11; a heat source side air heat exchanger 13 for exchanging heat between the refrigerant decompressed and expanded by the expansion valve 12 and the heat exchange target; an oil equalizing mechanism 20 that interconnects the low stage side compressor 10a and the high stage side compressor 10b for making refrigerant machine oil flow; and a four-way changeover valve 14 for selectively switching between a two-stage compression route for making the refrigerant flow in the low stage side compressor 10a and the high stage side compressor 10b in this order and a single-stage compression route for making the refrigerant flow in only one of the low stage side compressor 10a and the high stage side compressor 10b.