Abstract: A refrigerator includes a compressor, an evaporator fan, a condensor fan and a defrost heater which are controlled by a defrost control system. The control senses the number and duration of freezer and fresh food compartment openings, the duration of the previous defrost operation, and the total accumulated compressor run time since the previous defrosting operation. A stored count is decremented by weighting functions which are adaptably varied in accordance with the number and duration of compartment door openings and the duration of the previous defrosting operation. When the stored count is decremented to zero, the defrosting operation may be initiated, unless inhibited. The defrosting operation is inhibited if the total accumulated compressor run time is less than a predetermined amount. The control is reset to a point just short of a defrosting operation if a power outage occurs.

Abstract: An energy efficient refrigeration system having a valve in series with a fixed flow restrictor between the condenser and evaporator of the system. The valve is controlled to permit fluid flow whenever the compressor is running, and when the compressor is not running, only in the event the pressure at the outlet of the compressor is above a preselected pressure. The preselected pressure is a high pressure, such as would prevent starting of the compressor, which, in the illustrated embodiment, is a rotary compressor. The pressure sensing structure, in the illustrated embodiment, utilizes an analog of the pressure of the liquid refrigerant within the condenser and, more specifically, utilizes a temperature condition which corresponds to the liquid pressure therein. Alternatively, the temperature sensing may be of the condenser or of the ambient space in which the condenser is housed.