Patent ID: 7228692
Filing Date: 2007-06-12
Classification: F25B

Abstract:
1. A heat pump cycle comprising: a compressor for compressing a refrigerant; a heat exchanger downstream of said compressor; a main expansion device downstream of said heat exchanger; an evaporator downstream of said main expansion device, and a refrigerant flowing from said compressor to said heat exchanger, to said expansion device, to said evaporator, and returning to said compressor; a control for said cycle, said control being operable to control components and initiate a defrost mode at which refrigerant from a discharge side of said compressor is cycled into said evaporator at a relatively hot temperature to defrost said evaporator, said control being operable to initiate said defrost mode based upon an algorithm developed to maximize heat transfer from said heat pump to an environment to be heated: said environment to be heated is a hot water supply, and a water pump drives cooler water through said heat exchanger to be heated by said refrigerant, with said water pump being stopped during defrost mode; said control operating to minimize the likelihood of water being heated unduly by hot refrigerant in said heat exchanger during defrost mode, said water pump being actuated intermittently to minimize said likelihood; and said water pump being stopped during defrost mode, but said water pump does not stop until said control has determined that a discharge temperature of said refrigerant has dropped below a predetermined maximum to minimize said likelihood.