Patent ID: 7958737
Filing Date: 2011-06-14
Classification: F25B

Abstract:
1. A heat pump comprising: a compressor, a valving system for selectively directing refrigerant from a discharge of said compressor to one of an indoor heat exchanger and an outdoor heat exchanger, and for moving refrigerant from the other of said indoor and outdoor heat exchanger back to a suction of said compressor, said valving system being operable to direct refrigerant from said compressor discharge line to said indoor heat exchanger when in a heating mode, and to direct refrigerant from said compressor discharge to said outdoor heat exchanger when in a cooling mode; an expansion device intermediate of said indoor and outdoor heat exchangers, said expansion device being an electronic expansion device that can operate in both said cooling mode and said heating mode; and a control for operating said refrigerant system, said control being operable to operate said refrigerant system in one of said heating mode and said cooling mode and determine that a defrost mode is required, said control being operable to stop operation of the heat pump and leave said expansion device in an open position for a period of time such that refrigerant can communicate between said indoor and outdoor heat exchangers, said control then being operable to move said valving system such that refrigerant flows in a manner consistent with the other of said heating mode and said cooling mode for a period of time sufficient to at least partially defrost one of said indoor and outdoor heat exchangers; and said expansion device being moved to a position that is more open than a position for one of said cooling mode and said heating mode when said system is shut down prior to switching into said defrost mode.