Abstract: A refrigerator has a refrigeration system including a variable speed compressor, a condenser, a condenser fan, an evaporator, a variable speed evaporator fan. The refrigerator further includes multiple temperature sensors that communicate with an electronic microprocessor-based control system that in turn controls the operation of the refrigerator system based on the information provided by the multiple temperature sensors.

Abstract: A compressor is controlled by generating and storing a compressor operation log. In addition, a compressor operation is selected from the compressor operation log in response to a sensor failure. Furthermore, the compressor is modulated according to the selected compressor operation in response to the sensor failure.

Abstract: A heat pump, and in particular a heat pump for heating a hot water supply is provided with an improved defrost mode. The defrost mode is actuated to remove frost from an outdoor evaporator that may accumulate during cold weather operation. An algorithm for operation of the defrost mode is developed experimentally by seeking to maximize the heat transfer provided by the refrigerant. A heating system condition is experimentally related to the heat transfer capacity. One then maximizes the average heat transfer capacity to determine the optimum initiation point for the defrost mode. Further, protections are included into the defrost mode. When the heat pump is utilized to heat hot water, methods are provided to prevent the water that remains in the heat exchanger from becoming unduly heated. In one method, the water pump may be periodically operated to move the water.

Abstract: The present invention discloses a defrost operating method for a refrigerator which performs a defrost operation by controlling operations of a compressor and a fan on the basis of a continuous operation time of the compressor and surface temperatures of evaporators to prevent frost from being formed on the evaporators, when cool air is generated in a freezing chamber and a refrigerating chamber by circulating refrigerants through a refrigeration cycle built in a refrigerator main body and forcibly circulated bX rotating the fan. The defrost operating method for the refrigerator can omit a general defrosting heater by performing the defrost operation by using the compressor and the fan. In addition, the defrost operating method for the refrigerator improves heat exchange efficiency and reduces power consumption by efficiently performing the defrost operation.

Abstract: A method includes sensing an exposure of a refrigerated compartment of a vending machine to ambient air and, in response, sensing an initial temperature of the refrigerated compartment. The method also includes, responsive to sensing the exposure to ambient air, selecting a procedure from a plurality of procedures according to the sensed initial temperature, and controlling a refrigeration system of the vending machine using the selected procedure during an initial period. The method may include sensing a current temperature of the vending machine and, once the refrigerated compartment reaches a second predetermined temperature, controlling the refrigeration system according to the sensed current temperature, monitoring an operational characteristic of a compressor of the refrigeration system, and performing a defrost procedure according to the monitored operational characteristic.

Abstract: A method for controlling the defrost of an evaporator in a refrigeration appliance provided with a compressor and in which a temperature sensor (TP) is used for detecting the temperature inside a cell of the appliance, comprises the steps of estimating the temperature of the evaporator on the basis of the cell temperature (TP) and of a mathematical model of the refrigeration appliance, and controlling the compressor on the basis of the estimated temperature of the evaporator.

Abstract: An object of the present invention is to provide a control system, an integrated control apparatus, and a control program that are capable of well maintaining freshness and quality of food articles, by reducing time for performing a recovery operation following a frost removing operation of cooling devices. In response to a start of the frost removing operation of a first showcase, an integrated control apparatus provides a second device controller (device control unit) with a “lower limit cooling instruction (increase instruction)” to increase the refrigerant supplied to a second showcase to an amount larger than that before the frost removing operation starts. In response to the “lower limit cooling instruction (increase instruction),” the second device controller (device control unit) increases the amount of the refrigerant supplied to the second showcase.

Abstract: A refrigerating air conditioning system is provided with a refrigerant circuit which includes a compressor 3, an indoor heat exchanger 6, a first pressure reducing device 10, an outdoor heat exchanger 11, and a switching device 4 for switching a direction of a refrigerant flow between heating and cooling modes for supplying heat from the indoor heat exchanger 6. In the system, a refrigerant temperature detection sensor 14c of the outdoor heat exchanger 11 and an outdoor air temperature detection sensor 14d are provided for determining a state of a frost formed on the outdoor heat exchanger 11. Two types of defrosting inhibition time values ?1 and ?3 are allowed to be set in accordance with a previous defrosting time ?2 for continuously performing heating operation.

Abstract: A refrigeration unit (40) having a defroster (30) has a refrigeration compartment (44), an evaporator coil (26) having an amount of crystallized water being aggregated thereon from air and a thermo-electric module (32, 46, 48, 50) having a semiconductor material. The thermo-electric module (32, 46, 48, 50) provides heating from a first location of the thermoelectric module (32, 46, 48, 50) and cooling from a second location of the thermo-electric module (32, 46, 48, 50) based on a Peltier effect when a current from a power supply is traversed through the thermo-electric module (32, 46, 48, 50). The heating from a first location heats the evaporator coil (26) to defrost the aggregated amount of crystallized water thereon. The cooling from the second location is communicated to the refrigeration compartment (44).

Abstract: A defrost heater relay control circuit having reduced power consumption during a de-energized mode of operation is provided. The relay drive circuit utilizes a series connected capacitor to introduce a phase shift in the AC current waveform such that the amount of real power dissipated in the circuit during periods when the defrost heater control relay is de-energized is greatly reduced. This effectively shorts out the relay drive voltage without generating heat due to real power dissipation through the switched circuitry that disables the relay.

Abstract: An equipment control system for equipment such as a refrigeration device, its control device, and its control program are provided in which present-round defrosting operation start time can be changed appropriately. The integrated controller 10 controls a defrosting operation to remove frost adhered to showcases 53, 54, and 55 . . . , in which the defrosting operation is started at a fixed or varying time interval. The integrated controller 10 stores past record data based on required time for past defrosting operations for different environmental conditions.

Abstract: In a controller for a refrigerating system including refrigerating machines and showcases, a showcase that is about to execute a defrost operation is detected on the basis of a defrost operation indicating information. When the controller receives a notification indicating start of the defrost operation from the showcase concerned or on the basis of a comparison result between a pre-stored defrost-operation start time and the present time, at least one of the refrigerating machines is instructed to reduce the output power thereof. When the showcase finishes the defrost operation, the at least one of the refrigerating machines is instructed to increase the output power thereof so that the output power of the refrigerating machine is set to stationary output power.

Abstract: A system and method for refrigeration timer control having an energy efficient defrost cycle are provided. The system and method provide a delay time after the refrigeration cycle and prior to the defrost cycle. During this delay period the evaporator fan may run. The fan circulation and the heat from the fan coil provide a pre-warm cycle to the evaporator prior to the defrost cycle. To further enhance energy efficiency, the system and method may also provide a pre-refrigeration cycle after the defrost cycle. During this pre-refrigeration cycle only the compressor is energized. This prevents warm moist air from being circulated until the evaporator coils are cooled.

Abstract: A method of controlling a refrigerated merchandiser. The method includes providing a case that defines a product display area and an air passage that has an inlet and an outlet, positioning an evaporator in the air passage to refrigerate the air, positioning a fan in the air passage to move the air through the passage, and logging a first temperature value during frost-free operation of the evaporator. The method also includes logging a second temperature value during frosted operation of the evaporator, calculating a difference of the first and second temperature values, and defrosting the evaporator when the difference exceeds a pre-determined value. Each of the first temperature value and the second temperature value is independently associated with at least one of the air entering the inlet of the air passage, the air exiting the outlet of the air passage, and saturated evaporator temperature.

Abstract: A timer is provided. The timer includes a rotatable electrically non-conducting ratchet gear, an electrically conducting pawl mechanism, and an electronic drive circuit. The ratchet gear has a plurality of teeth. The electrically conducting pawl mechanism includes a pawl configured to engage one of the plurality of teeth on the ratchet gear. The an electronic drive circuit is electrically coupled to the pawl mechanism. The electronic drive circuit passes a current through the pawl mechanism such that the pawl advances the ratchet gear by one tooth pitch.

Abstract: An adaptive defrost control for a frozen product machine implements an algorithm that utilizes various operating parameters of the machine to adaptively adjust the time interval between successive defrost cycles in a manner such that defrost cycles occur only on an as-needed basis. The adaptive defrost control minimizes the time during which the machine is in a defrost cycle, thereby maximizing the uptime of the machine during which frozen can be prepared.

Abstract: Methods, systems and computer readable code for controlling a defrost cycle of a refrigeration device are disclosed. According to some embodiments, a defrost command is issued to a defrost heater at a time determined at least in part by a total wasted energy parameter of the compressor for at least one time interval. In some embodiments, time interval includes a plurality of runtimes, and the total wasted energy parameter of a runtime is measured relative to a chosen reference runtime such as a minimum energy runtime after a defrost or an early runtime after a defrost. Optionally, a sequence of wasted energy parameters of the compressor for a sequence of time intervals is analyzed, and then a correction is performed on at least one wasted energy parameter.

Abstract: A heat pump is provided with an improvement while switching from heating/cooling mode to a defrost mode. Prior to initiation of a defrost mode, an electronic expansion device is moved to an open position such that refrigerant can migrate between the indoor-outdoor heat exchangers. When the operation of the defrost cycle is initiated, there is a lower likelihood and severity of flooded starts, as the refrigerant, under existing pressure differential at system shutdown, will move to the heat exchanger that will be downstream of the compressor in the defrost mode. Thus, no flooded start will occur on the subsequent compressor start-up. After completion of the defrost cycle, the electronic expansion device is again opened prior to return to operation in the conventional heating/cooling mode. In case subsequent starts are in an identical mode of operation, the electronic expansion valve is kept closed during shutdown to minimize cyclic performance losses.

Abstract: A freezer includes a refrigeration surface that can be frozen, such as an evaporator surface, a heating device for heating the refrigeration surface, and a control circuit for controlling the operation of the heating device in accordance with a timer. The control circuit is configured to block the operation of the heating device for a time period that is defined by the timer. The timer is used to ensure that the refrigeration surface is only heated to defrost the freezer, if the refrigeration power requirement of the latter is low.

Abstract: A defrost system for a temperature controlled storage unit includes an enclosure providing a space for storage of products. A refrigeration system has a supply line and a return line coupled to a cooling element to circulate a refrigerant through the cooling element to provide cooling to the space. A control module initiates a plurality of defrost modes on a predetermined frequency and for a predetermined duration by reducing a flow rate of the refrigerant through the cooling element so that a superheat temperature of the refrigerant in the cooling coil is increased to a predetermined range.

Abstract: A defrosting method of an air conditioner is disclosed. The air conditioner has an indoor unit having an indoor heat-exchanger, an indoor blower fan, an auxiliary heater, an outdoor unit having an outdoor heat-exchanger, a compressor, an expansion device, and an outdoor blower fan, and a four-way valve to selectively switch a circulation direction of a refrigerant between the indoor unit and the outdoor unit such that the air conditioner is operated in a heating cycle when the four-way valve is turned off and the air conditioner is operated in a refrigerating cycle when the four-way valve is turned on. The defrosting method is selectively determined according to the number of the heating cycles of the air conditioner.

Abstract: A heat pump, and in particular a heat pump for heating a hot water supply is provided with an improved defrost mode. The defrost mode is actuated to remove frost from an outdoor evaporator that may accumulate during cold weather operation. An algorithm for operation of the defrost mode is developed experimentally by seeking to maximize the heat transfer provided by the refrigerant. A heating system condition is experimentally related to the heat transfer capacity. One then maximizes the average heat transfer capacity to determine the optimum initiation point for the defrost mode. Further, protections are included into the defrost mode. When the heat pump is utilized to heat hot water, methods are provided to prevent the water that remains in the heat exchanger from becoming unduly heated. In one method, the water pump may be periodically operated to move the water.

Abstract: A refrigerator includes a plurality of walls forming a refrigeration compartment, an evaporator is positioned proximate at least one of the walls, a thermal insulator is positioned proximate the evaporator, and an airflow duct is positioned proximate the thermal insulator such that the thermal insulator is between the evaporator and the airflow duct.

Abstract: A damper apparatus for controlling airflow between compartments in a two compartment refrigerator having a door includes a controller for controlling opening and closing of a damper; and a door sensor connected to the controller for detecting when the door is open. If the controller determines that the door has remained closed for a set period, the controller maintains the damper in the closed position. A method for cleaning a damper in a refrigerator includes a steps of defrosting a refrigeration apparatus of the refrigerator, at least partially opening the damper, followed by waiting for a set period and then at least partially closing the damper. The steps of at least partially opening and waiting are repeated a set number of times and then a cooling operation of the refrigeration apparatus is commenced.

Abstract: A refrigerator and a defrosting method thereof which are capable of achieving an appropriate defrosting operation even when a part of constituent elements included in a defrosting system fails. The defrosting method includes the steps of determining whether or not a predetermined first defrosting completion condition is usable, if the predetermined first defrosting completion condition is usable, executing a first defrosting mode, which uses the predetermined first defrosting completion condition, and if the predetermined first defrosting completion condition is not usable, executing a second defrosting mode, which uses a predetermined second defrosting completion condition different from the predetermined first defrosting completion condition, and a defrosting execution determination condition different from that of the first defrosting mode.

Abstract: A refrigerant cycling device is provided, wherein a compressor comprises an electric motor element, a first and a second rotary compression elements in a sealed container. The first and the second rotary compression elements are driven by the electric motor element. The refrigerant compressed and discharged by the first rotary compression element is compressed by absorbing into the second rotary compression element, and is discharged to the gas cooler.

Abstract: An improvement in defrosting an air-to-air heat pump system when in the heating mode. A bypass loop transfers refrigerant at a higher temperature and pressure than is normally cycled through the outdoor unit to an outdoor coil to defrost ice on the outdoor coil, The bypass loop includes a valve movable between closed and open positions. A sensor monitors a preselected condition indicative of outdoor coil performance. A controller communicates with the valve and the sensor. Once the controller determines that a preselected set point of a preselected condition indicative of deteriorating performance has been reached, based on received sensor signals, the controller sends a signal to open the valve, allowing warm refrigerant to bypass expansion valves and flow to the outdoor unit to defrost the outdoor unit. Once defrosting is accomplished, the valve can be moved to a closed position to resume normal operation of the heat pump unit.

Abstract: A refrigerator includes a refrigeration compartment having an upper region and a lower region, a first evaporator positioned in the upper region, a second evaporator, positioned in the lower region, and a fan disposed between the first and second evaporators. The fan is configured, such that air flows past first and second evaporators and is discharged into said upper and lower regions when said fan is energized.

Abstract: A refrigeration system for objects is disclosed. The system includes a refrigeration device and a defrost system. The refrigeration device provides a case or container defining a space for the objects, a first heat exchanger associated with the container for cooling a fluid communicating with the space to cool the objects and a second heat exchanger to receive a heat supply from an air source for warming the fluid. A system for cooling articles is also disclosed. The system includes a space configured to contain the articles, a first element to provide cooling of the articles within the space, a first coolant source to refrigerate the space by cooling the first element in a first state, and a second coolant source to elevate a temperature of the first element in a second state.

Abstract: A refrigerant cycle is provided with a transient mode for moving from a defrost cycle back to steady state operation. In particular, some default position of the expansion device is selected when defrost cycle ends. The evaporator is hot at the end of defrost cycle, and might otherwise suggest an increased flow of refrigerant through the expansion device, which could be undesirable. Thus, a control for the inventive system moves the expansion device to a defrost transient position, with the defrost transient position restricting the flow of refrigerant to a value that would be less than that dictated by the high temperature of the evaporator. At some period of time after the end of the defrost mode, the refrigerant cycle can be returned to state steady operation.

Abstract: In drying the interior of an indoor unit, room humidity (Rh) is detected by a humidity sensor, and a drying operation cycle, in which after first heating operation, which is weak heating operation in which a compressor included in a refrigerating cycle is operated at a low rotational speed, has been performed for a predetermined period of time, second heating operation, which is heating operation close to air blowing operation in which the compressor is stopped, is performed for a predetermined period of time, is repeated a predetermined number of times according to the room humidity (Rh). Thus, the indoor unit's interior can be dried properly without occurrence of dew condensation therein.

Abstract: A compressor is controlled by generating and storing a compressor operation log. In addition, a compressor operation is selected from the compressor operation log in response to a sensor failure. Furthermore, the compressor is modulated according to the selected compressor operation in response to the sensor failure.

Abstract: An integrated refrigeration control (IRC) module is disclosed which combines both thermal and electrical protection to the main components of a refrigerator and uses sensor inputs to control the compressor. The IRC module employs triacs (Q2, Q4, Q6, Q8, Q10) to control power to the start and run windings of the compressor motor, evaporator and compressor fans and the defrost heater. The module adaptively controls the refrigerator defrost cycle using pervious defrost cycle run times to determine new cumulative compressor run times. Also disclosed is the use of preventive defrost periods performed for brief periods at intervals between portions of the cumulative compressor run time.

Abstract: A method for defrosting a household refrigeration appliance including a compressor and a defrost heater. After a controller indicates that it is time for a defrost cycle, the compressor is operated if the temperature of the appliance is greater than a set temperature. The compressor is stopped when a temperature of the appliance is equal to or less than the set temperature. After the step of stopping, the temperature of the appliance is raised while the defrost heater is inactivated. After the temperature is raised, the defrost heater is energized. The controller pauses for a drip time after deenergizing the defrost heater before allowing the compressor to run.

Abstract: An integrated refrigeration control (IRC) module is disclosed which combines both thermal and electrical protection to the main components of a refrigerator and uses sensor inputs to control the compressor. The IRC module employs triacs (Q2, Q4, Q6, Q8, Q10) to control power to the start and run windings of the compressor motor, evaporator and compressor fans and the defrost heater. The module adaptively controls the refrigerator defrost cycle using previous defrost cycle run times to determine new cumulative compressor run times. Also disclosed is the use of preventive defrost periods performed for brief periods at intervals between portions of the cumulative compressor run time.

Abstract: An apparatus and method for defrosting an evaporator of a refrigeration sealed system is described. The system includes a controller operatively coupled to an evaporator fan, a condenser fan and a defrost heater, and the method includes operating the sealed system until a selected time till defrost interval expires, initiating a defrost cycle when the time till defrost interval expires, and selectively operating the sealed system to raise a temperature of the evaporator while the defrost heater is inactivated.

Abstract: A compressor is controlled by generating and storing a compressor operation log. In addition, a compressor operation is selected from the compressor operation log in response to a sensor failure. Furthermore, the compressor is modulated according to the selected compressor operation in response to the sensor failure.

Abstract: The present invention relates to a device and method for operating a refrigeration cycle without icing of the evaporative surface of the device.

Abstract: An adaptive defrost control includes a microcomputer for controlling the initiation and termination of a defrost operation based, at least in part, on opening of the fresh food door and the freezer door. The control monitors the compressor run time and the fresh food and freezer door open times and adjusts the time until defrost accordingly. A pre-chill operation cools the freezer prior to defrosting the evaporator coils so that the defrost heat will have less of an affect on the maximum temperature after defrost, and enables the freezer compartment to be maintained at a temperature a few degrees higher than with known refrigerators, providing energy savings.

Abstract: A defrost control system for a refrigerator having freezer and fresh food compartments includes a plurality of temperature sensors, a plurality of door sensors to provide signals indicative of the occurrence of a door opening condition, a memory to store the signals in a plurality of usage blocks, and a CPU or controller to categorize the usage blocks into periods of high and low usage. When a defrost cycle is required, the control system establishes the cycle at an upcoming period designated as one of low usage. Additionally, prior to activating the system, the controller lowers the temperature of at least the freezer compartment to below a set point. The controller establishes the defrost cycle for a period based upon the time duration of previously completed cycles.

Abstract: In general the present invention provides a refrigeration system and a method of controlling the refrigeration system. The system includes a coolant circuit having in series a compressor, a metering device, an evaporator coil, and sensors for determining the coolant temperature and pressure within the circuit. The system also includes a defrost system that includes a fan and/or a resistive heating element. The present invention also provides a method of operating the refrigeration system to protect the individual components such as the compressor from damage from flooding with liquid coolant. Additionally, the operating method provides a more efficient operation by using a self-adaptive defrost sequence and rapid startup sequences after the defrost periods.

Abstract: A device and method is provided for sensing or predicting when condensation having a given physical state is present or imminent and for suppressing such condensation from a surface, such as a vehicle windscreen, eyewear, goggles, helmet visor, computer monitor screen, window, electronic equipment, etc, by preventing or removing it. A first thermal sensor is in thermally conductive contact with the surface. A second thermal sensor is in an environment separated from the surface. A humidity sensor is in the environment of the second thermal sensor. A circuit causes a condensation suppression mechanism to be activated for preventing or removing condensation having the given physical state from the surface when a temperature sensed by the first thermal sensor, a temperature sensed by the second thermal sensor, and a humidity sensed by the humidity sensor indicate that a condensation condition is either present or imminent and requires prevention or removal at the surface.

Abstract: A refrigeration system includes a first refrigeration chamber, a second refrigeration chamber in flow communication with said the first refrigeration chamber, a sealed system for producing desired temperature conditions in the first refrigeration chamber and the second refrigeration chamber, and a controller operatively coupled to the sealed system. The controller is configured to accept a plurality of user-selected inputs including at least a first refrigeration chamber temperature and a second refrigeration chamber temperature, and to execute a plurality of algorithms to selectively control the first refrigeration chamber at a temperature above the second refrigeration chamber and at a temperature below the second chamber. Various control algorithms are provided for maintaining desired temperature conditions in the refrigeration chambers.

Abstract: A device and method for automatically defrosting a refrigeration system only during times of non-peak energy demand. The device is a defrost delay module that plugs into the current defrost timer supplied with frost-free refrigerators. The defrost delay module includes a microprocessor that utilizes a clock to define peak power consumption periods. If the defrost cycle will occur during a peak power period, the delay module interrupts the normal operation and prevents defrosting of a refrigerator or freezer until the peak power periods has passed. The delay module is able to learn the operating characteristics of the defrost timer such that the delay module can be retrofit to existing appliances.

Abstract: A system and a method of automatic defrost for a refrigeration appliance, including a hermetic compressor driven by an electric motor (1); a control unit (2); a thermal switch means (10) having a first and a second turn on condition and a turn off condition and another turn off condition of the electric motor (1); a timer (20), which measures the periods of time in the turn on and turn off conditions of the electric motor (1); a switch means (40), which selectively interrupts the energization of the electric motor (1), by instruction of the control unit (2); and a cycle counting means (30), which counts each first and second turn on conditions of the electric motor (1), the control unit (2) selectively activating the thermal switch means (10) to operate in determined turn on and turn off conditions of the electric motor (1).

Abstract: An adjustable angle display device for holding and displaying objects includes a base portion, a display portion coupled to the base portion and adapted to pivot about a pivot point, and a positioning device having a first end coupled to the base portion and a second end coupled to the display portion, the positioning device adapted to adjustably position the display portion in a first position and a second position relative to the base. A method of providing an adjustable angle display device includes pivotally coupling a first end of a display portion to a base portion, providing a positioning device to selectively raise and lower a second end of the display device relative to the base portion, coupling the positioning device in operable engagement with the base portion and the display portion, and operating the positioning device to selectively adjust a display angle of the display device.

Abstract: A refrigeration system and method for controlling defrost includes a refrigeration case, an evaporator disposed in the refrigeration case, and a condenser and compressor coupled in fluid communication with the evaporator. The condenser is disposed on the refrigeration case and the compressor is a pulse width modulated variable capacity compressor. The system also includes a controller responsive to a load sensor disposed in the refrigeration case and is coupled to the compressor for providing a variable duty cycle control signal to the compressor, wherein the compressor is modulated between a first capacity and a second capacity while operating to adjust the operating capacity of the refrigeration system. The system further includes a module for periodically defrosting the refrigeration system as a function of duty cycle.

Abstract: A method and apparatus for defrosting an evaporator of a refrigeration system including a defrost heater and a controller operatively connected to the evaporator and a defrost heater is provided. The method comprises initiating a defrost cycle to energize the defrost heater to defrost the evaporator, monitoring a temperature of the evaporator, terminating the defrost cycle by de-energizing the defrost heater when a low temperature termination point of the evaporator is reached when in a low temperature defrost cycle, and terminating the defrost cycle by de-energizing the defrost heater when a high temperature termination point of the evaporator is reached when in a high temperature defrost cycle.

Abstract: The invention is a method and a defroster control circuit to sequentially defrost a series of refrigerated display cases. The method begins by operating the series of refrigerated display cases during a normal refrigeration mode. At the beginning of the refrigeration mode, a refrigeration time is set to zero and an elapsed refrigeration time is subsequently monitored. When the refrigeration time equals an activation time, a defrost mode begins and a defrost cycle for the first case starts. The defrost mode for the first case terminates based either on a defrost time criterion or a defrost temperature criterion. After the first refrigerated display case is defrosted, a refrigeration mode is restarted for the first case. After the first refrigerated display case is defrosted, the other refrigerated display cases in the series of refrigerated display cases are then sequentially defrosted.

Abstract: An apparatus and method for defrosting an evaporator of a refrigeration sealed system is described. The system includes a controller operatively coupled to an evaporator fan, a condenser fan and a defrost heater, and the method includes operating the sealed system until a selected time till defrost interval expires, initiating a defrost cycle when the time till defrost interval expires, and selectively operating the sealed system to raise a temperature of the evaporator while the defrost heater is inactivated.