Patent ID: 8733118

Claim:
A heat pump water heater outdoor unit, comprising: a compressor, a water heat exchanger for heat exchange between a refrigerant and water flowing through the water heat exchanger, a first decompression device, and an air exchanger for heat exchange between air and the refrigerant are connected with piping, the piping supplying heat absorbed from the air by the refrigerant flowing through the air heat exchanger to the water flowing through the water heat exchanger by the refrigerant flowing through the water heat exchanger; a first internal heat exchanger provided between the water heat exchanger and the first decompression device for heat exchange between the refrigerant flowing between the water heat exchanger and the first decompression device and the refrigerant flowing between the air heat exchanger and the compressor; an injection circuit branching off at a point between the first internal heat exchanger and the first decompression device to inject the refrigerant into the compressor through a second decompression device; a second internal heat exchanger for heat exchange between the refrigerant flowing between the first internal heat exchanger and the first decompression device and the refrigerant flowing between the second decompression device and the compressor in the injection circuit; a pressure sensor arranged for detecting a compressor discharge refrigerant pressure of the refrigerant discharged from the compressor; a discharge refrigerant temperature sensor for detecting a discharge refrigerant temperature of the refrigerant discharged from the compressor; an ambient temperature sensor for detecting an ambient temperature; and an inflow water temperature sensor for detecting an inflow water temperature of the water flowing into the water heat exchanger; and a controller configured to control an opening degree of the second decompression device based on at least one condition, wherein the controller is further configured to start an injection control using the second decompression device, after the second decompression device is set to initial value and a predetermined time elapses and when the at least one condition is satisfied, the at least one condition being: (a) the ambient temperature, measured with the ambient temperature sensor, falls below a first predetermined value; or (b) the inflow water temperature, measured with the inflow water temperature sensor, exceeds a second predetermined value and; in addition, after one of condition (a) or condition (b) is met, the controller is configured to perform controlling the opening degree of the second decompression device based on the comparison of a target temperature difference with a temperature difference between the temperature calculated form the discharged refrigerant pressure of the compressor detected by the pressure sensor and the discharged refrigerant temperature detected by the discharged refrigerant temperature sensor.