Refrigerant charge management in a heat pump water heater

Abstract

Heat pumps that heat or cool a space and that also heat water, refrigerant management systems for such heat pumps, and methods of managing refrigerant charge. Various embodiments remove idle refrigerant from a heat exchanger that is not needed for transferring heat by opening a refrigerant recovery valve and delivering the idle refrigerant from the heat exchanger to an inlet port on the compressor. The heat exchanger can be isolated by closing an electronic expansion valve, actuating a refrigerant management valve, or both. Refrigerant charge can be controlled by controlling how much refrigerant is drawn from the heat exchanger, by letting some refrigerant back into the heat exchanger, or both. Heat pumps can be operated in different modes of operation, and various components can be interconnected with refrigerant conduit. Some embodiments deliver refrigerant gas to the heat exchanger and drive liquid refrigerant out prior to isolating the heat exchanger.

What is claimed is: 
     
         1 . A heat pump that heats or cools a space and also heats water, the heat pump comprising:
 an outdoor heat exchanger that transfers heat between refrigerant and outdoor air or a heat source/sink;   an indoor heat exchanger that transfers heat between the refrigerant and indoor air;   a water heat exchanger that transfers heat from the refrigerant to water;   a compressor;   an outdoor expansion device;   an indoor expansion device;   a refrigerant management valve;   a reversing valve;   a first refrigerant conduit connecting the outdoor heat exchanger to the outdoor expansion device;   a second refrigerant conduit connecting the indoor heat exchanger to the indoor expansion device;   a third refrigerant conduit connecting the outdoor expansion device to the indoor expansion device;   a fourth refrigerant conduit connecting a discharge port on the compressor to the water heat exchanger;   a fifth refrigerant conduit connecting the water heat exchanger to the refrigerant management valve;   a sixth refrigerant conduit connecting the refrigerant management valve to the reversing valve;   a seventh refrigerant conduit connecting the reversing valve to the outdoor heat exchanger;   an eighth refrigerant conduit connecting the reversing valve to the indoor heat exchanger;   a ninth refrigerant conduit connecting the refrigerant management valve to the third refrigerant conduit; and   a tenth refrigerant conduit connecting the reversing valve to an inlet port on the compressor.