Abstract: Embodiments are directed to determining, by a controller comprising a processor, that a coil associated with a heat pump is subjected to a defrost cycle, determining, by the controller, that at least one of: a conditioned space is occupied, and a thermostat associated with the conditioned space indicates that an energy saving mode is not in use, and enabling, by the controller, an auxiliary heat source based on the determination that the coil is subject to the defrost cycle and the determination that the conditioned space is occupied or the thermostat indicates that the energy saving mode is not in use.

Abstract: A method for controlling a refrigerant distribution in a vapour compression system, such as a refrigeration system, e.g. an air condition system, comprising at least two evaporators. The refrigerant distribution determines the distribution of the available amount of refrigerant among the evaporators. While monitoring a superheat, SH, at a common outlet for the evaporators, the distribution of refrigerant is modified in such a manner that a mass flow of refrigerant to a first evaporator is altered in a controlled manner. The impact on the monitored SH is then observed, and this is used for deriving information relating to the behaviour of the first evaporator, in the form of a control parameter. This is repeated for each evaporator, and the refrigerant distribution is adjusted on the basis of the control parameters. The impact may be in the form of a significant change in SH.

Abstract: The invention relates to a method for controlling a refrigeration system by establishing a defrost period during an initial defrost period. One or more compressors of the refrigeration system are monitored to establish if the one or more compressors are running, and a parameter representative of the one or more compressors running is monitored. The monitoring establishes at least one parameter limit value representative of whether a defrost period or a non-defrost period is to be initiated. The invention also relates to a method for controlling a refrigeration system subsequent to an electrical power interruption. The invention also relates to control units for applying one or both of the methods according to the invention, and to a refrigeration system having one or more control units controlling the refrigeration system according to one or both of the methods.

Abstract: A method for controlling evaporator defrost in a refrigeration appliance having a cooling circuit with a variable cooling capacity compressor is disclosed. The method includes assessing the cooling capacity of the cooling circuit and calculating the defrost time on the basis of such cooling capacity. Defrost time is preferably assessed on the basis of the inverter frequency driving the compressor and/or the percentage of insertion of the compressor.

Abstract: An order in which parts of a heat source side heat exchanger are defrosted is determined on the basis of the heat exchanger capacity of the parts of the heat source side heat exchanger, the necessary heating capacity of the parts of the heat source side heat exchanger, and the arrangement of the parts of the heat source side heat exchanger, the opening and closing of first flow switching valves, second flow switching valves, and third flow switching valves are controlled accordingly, and a defrosting operation in which a refrigerant discharged from a compressor is caused to flow through the heat source side heat exchanger is performed.

Abstract: A refrigerator including an evaporator to carry out heat exchange, a frost sensing unit to sense an amount of frost formed on the frost sensing unit, and a heater to be operated for removing the frost from the frost sensing unit is provided. The heater is operated in at least a portion of a defrosting section. Methods for operating the refrigerator are also provided.

Abstract: Frost may accumulate on a heat pump. In various implementations, a primary defrost operation and/or a secondary defrost operation may be utilized to remove at least a portion of the frost from the heat pump.

Abstract: In various implementations, frost in a vapor compression system may be controlled. A property of a fan may be determined. A determination may be made whether a frost event and/or a nonfrost event has occurred based at least partially on the determined fan property.

Abstract: In various implementations, an ice sensor may include heater(s), ice accumulation surface(s), and/or temperature sensor(s). During operation, heat from a heater may be provided to an ice accumulation surface and a temperature sensor(s) may determine temperature(s) of the ice accumulation surface. A determination of whether ice is present on the ice sensor may be based at least partially on the determined temperature(s).

Abstract: Adaptable evaporator defrost logic is employed in a refrigeration system to detect a build-up of ice on the evaporator. In response to the detected build-up of ice, a defrost operation is initiated that includes decreasing the speed of the compressor. At the end of the defrost operation, the adaptable evaporator defrost logic determines whether the defrost operation was a success. If the defrost operation was a success, then normal operation is resumed. If the defrost operation was not a success, then the defrost operation is modified by turning the compressor off and extending a duration of the defrost operation.

Abstract: A method of refrigeration control through a refrigeration system of a refrigerated transport container includes performing a defrost cycle on the refrigeration system by activating a heat source; and restarting the refrigeration system after the defrost cycle has completed, wherein restarting the refrigeration system includes performing a liquid slugging avoidance process including: initiating a compressor of the refrigeration system at a speed; opening a pressure equalization valve in parallel with the compressor in response to the initiating; opening a liquid valve in series between a condenser and an evaporator after opening of the pressure equalization valve; and closing the pressure equalization valve after a period of time.

Abstract: A method for operating a refrigerator appliance during a defrost cycle of the refrigerator appliance is provided. The method includes deactivating a compressor of the refrigerator appliance at a beginning or commencement of the defrost cycle until a predetermined period of time elapses or a chilled chamber of the refrigerator appliance rises to a preselected temperature. The method can improve an energy efficiency of the refrigerator appliance.

Abstract: A method of defrosting a heat exchanger while the heat exchanger continues to cool air passing through the heat exchanger. The heat exchanger includes liquid passages for carrying cold liquid between an inlet and an outlet and air passages in thermal communication with the liquid passages for cooling air passing through the air passages. The method includes introducing warmer liquid to a first selected section of the heat exchanger liquid passage while continuing to provide cold liquid to the liquid passages of the heat exchanger.

Abstract: A heat exchanger door system includes a heat exchanger and a first rotatable member, proximate to the heat exchanger, that rotates about an axis of rotation. The system includes a first door member rolled around the rotatable member and movable from a rolled position to an unrolled position in which the first door member covers more of the heat exchanger than when the door member is in the rolled position.

Abstract: A merchandiser system includes a case that has a door and a door heater. The system includes a low temperature refrigeration unit sized to fit within a case compartment and to operably couple to the case to maintain food product within a low temperature range. The system also includes a medium temperature refrigeration unit sized to fit within the compartment and operably couple to the case to maintain food product within a medium temperature range. The system includes a controller in communication with the door heater and is programmed to activate the door heater only in response to the low temperature modular refrigeration unit positioned within the compartment. One of the low temperature refrigeration unit and the medium temperature refrigeration unit is removably coupled to the case within the compartment, and is replaceable by the other refrigeration unit to change the temperature range of the product display area.

Abstract: A refrigerated merchandiser including a case, a refrigeration system, a sensor, and a controller. The refrigeration system is operable in a defrost mode defrosting the evaporator, and a refrigeration mode discharging a refrigerated airflow into the product storage area to refrigerate the product and to maintain the product within a predetermined temperature range without freezing the product, and to receive the refrigerated airflow along a return passageway. The sensor senses one or more defrost conditions of the case. The controller controls the refrigeration system in the refrigeration mode and in the defrost mode, and includes an algorithm for calculating when to initiate the defrost mode and for calculating a duration of the defrost mode. The controller is programmed to vary the refrigeration system between the refrigeration mode and the defrost mode based on the signals indicative of the defrost conditions and the calculations by the algorithm.

Abstract: Systems, methods, and apparatuses are provided for preventing condensation in refrigerated display cases. A display case can be provided with one or more heater circuits and one or more sensors communicably coupled thereto. The sensor can sense ambient humidity levels, ambient temperature levels, and surface temperature levels. In certain embodiments, dewpoint temperatures may be calculated based on the ambient humidity and temperature levels provided by the sensor. The sensed ambient humidity level, temperature level, surface temperature, or calculated dewpoint can be compared to preset trigger levels and at least one of the heater circuits can be activated if the preset trigger level is violated. Activation of the heater circuit can be for a predetermined amount or percentage of time or at a predetermined voltage level based on the sensed or calculated level or the amount the sensed or calculated level is over the preset trigger level.

Abstract: A cooling apparatus includes a storage compartment, an evaporator to cool air in the storage compartment by evaporating a refrigerant, a compressor to compress the refrigerant evaporated by the evaporator, an air blower to supply the air cooled by the evaporator to the storage compartment and to remove frost formed on the evaporator, a storage temperature sensor to sense a temperature of the storage compartment, a driving unit to drive the compressor and the air blower, and a controller to perform a defrosting operation of operating the air blower to remove frost formed on the evaporator when a cooling operation of cooling the storage compartment is terminated and to perform the cooling operation, wherein the controller defers, when the defrosting operation is being performed, operation of the compressor, even if the temperature of the storage compartment is greater than or equal to the storage upper limit temperature.

Abstract: Systems and methods are disclosed for water collection from atmospheric moisture in large quantities in uncontrolled outdoor environments where the temperature may be cold and humidity levels low. To extract water from air when the dew point is low, a heat exchanger cools to a point where water vapor is deposited on its surface as ice. The heat exchanger then cycles through a heating phase to melt the ice and generate liquid water. The accumulation of frost is advantageous. Frost accumulation enables water collection when the dew point is low. Disclosed variations enhance efficiency and environmental tolerance.

Abstract: Disclosed herein are a cooling apparatus and a control method thereof. The cooling apparatus using latent heat of a refrigerant includes evaporators evaporating the refrigerant, a compressor compressing the evaporated refrigerant to a high pressure, defrosting heaters removing frost accumulated on the evaporators, a driving unit providing driving current selectively to the compressor or the defrosting heaters, and a control unit controlling the driving unit to provide driving current to the compressor in a cooling operation mode and controlling the driving unit to provide driving current to the defrosting heaters in a defrosting operation mode. The cooling apparatus controls the defrosting heaters using a driving circuit controlling the compressor, and thus lowers the manufacturing costs of a refrigerator operated at DC power.

Abstract: A climate control system for the interior cabin of an automotive vehicle. The climate control system includes a mode selection device configured for selecting a defrost mode. When the system is in the defrost mode, a controller receives a signal from a humidity sensor indicative of the measured humidity level in the vicinity of the window. The controller compares this measured humidity level with a threshold humidity level and, if the humidity is below the threshold humidity level, the controller stops operation of a compressor being used to dehumidify the air being provided to defrost the window, thereby minimizing possible fogging of the window and increasing the efficiency of the vehicle.

Abstract: A refrigerated merchandiser including a case defining a product display area supporting product and an evaporator disposed in an air passageway in fluid communication with the product display area via an outlet to direct a refrigerated airflow into the product display area. The merchandiser also includes a control system in communication with and programmed to control the refrigeration system so that the product display area is maintained within a predetermined temperature range. The control system also varies the temperature of the refrigerated airflow through the outlet above an airflow temperature threshold between about 35 degrees Fahrenheit and 41 degrees Fahrenheit at least once during a predetermined time period to avoid formation of frost on the evaporator while maintaining the product display area within the predetermined temperature range.

Abstract: A refrigeration machine for a domestic refrigerator includes a compressor, a condenser and an evaporator, which are connected to form a refrigerant circuit, wherein a stop valve is arranged in a refrigerant path from the condenser to the evaporator.

Abstract: A refrigeration cycle apparatus 100 includes a first compressor 101, a second compressor 102 provided in parallel with the first compressor 101, a radiator 103 for cooling a refrigerant compressed by the compressors 101 and 102, an expander 104 for recovering power while expanding the refrigerant cooled by the radiator 103, an evaporator 105 for evaporating the refrigerant expanded by the expander 104, a rotation shaft 123 connecting the first compressor 101 to the expander 104 so that the first compressor 101 uses the power recovered by the expander 104, a controller 112 for executing a control including a step of increasing a flow rate of the refrigerant gradually during a defrosting operation in which frost formed on the evaporator 105 is melted by allowing the refrigerant having a high temperature to flow through the evaporator 105.

Abstract: An icephobic coating is disposed on at least a cold side of a condenser in an environmental control system (ECS) of an aircraft. By applying the icephobic coatings to the condenser, the adhesive strength of the ice can be significantly reduced. As a result, it is difficult for ice to stick on the condenser. The vibration in the system and the force of the air flow can then knock the ice particles off of the condenser, resulting in reduced ice buildup.

Abstract: An energy saving defrost control system for reducing power consumption of an electromechanically controlled refrigerator is provided. The system includes a defrost timer configured to control a compressor according to an established run time, a defrost heater control operatively connected to the defrost timer and configured to activate a defrost heater in response to a timeout by the defrost timer, a DSM module responsive to demand state signals from an associated utility indicative of at least a peak demand and off peak demand state, and a time delay latching relay comprising a timer and configured to switch to one of a low position and a high position based on the demand state signal.

Abstract: An automated, ultra-low temperature freezer having multiple structural features that reduce heat transfer into the freezer, protect its internal mechanical devices against low temperature mechanical binding of their movements, allow defrosting and autoclaving as a result of only minimal changes to the conventional CO2 emergency backup system. A group of freezers are arranged so they can simultaneously provide an HVAC function. A vial management system allows biological samples or vials to be automatically placed in and recovered from the freezer and associates the temperature history with each sample or vial that it was subjected to during its storage.

Abstract: A method for controlling the operation of a transport refrigeration system to limit current drawn by a compressor powered by AC electric current includes the steps of: (a) determining whether an ambient temperature in which the refrigeration unit is operating has been greater than a set point ambient temperature for a first time period; (b) determining whether the refrigeration unit has been operating in a temperature pulldown mode; (c) determining whether the AC electric current is equal to or exceeds a preset maximum current limit; (d) determining whether a time period between a last defrost cycle and a next previous defrost cycle is less than fifteen minutes; and (e) if the determination is YES in both of step (a) and step (b) and is also YES in at least one of step (c) and step (d), reducing the preset maximum current limit to a reset maximum current limit.

Abstract: An air conditioner and a method for controlling the same for securing reliability and increasing efficiency are provided. The air conditioner and the method of controlling the same detect freezing occurring in the heat exchanger of the outdoor unit, determine a time of the defrosting operation according to a freezing degree such that the defrosting operation is performed, thereby preventing cooling/heating operation efficiency and capability due to a frequent defrosting operation from being deteriorated. The air conditioner and the method of controlling the same according to the present invention provide comfort of a predetermined level to the user to solve deterioration of convenience, and remove freezing due to a defrosting operation to thereby improve efficiency during cooling/heating operations.

Abstract: Disclosed therein are a heat pump system for a vehicle and a method of controlling the heat pump system, which determines that frosting begins on an exterior heat exchanger and carries out a defrosting control if a difference value between outdoor temperature and refrigerant temperature of an outlet side of the exterior heat exchanger is above a frosting decision temperature in a heat pump mode, thereby increasing frost-prevention and defrosting effects and enhancing heating performance and stability of the system because the system recognizes the beginning of frosting on the exterior heat exchanger at a proper time so as to carry out the defrosting control.

Abstract: A method for defrost control of a refrigerator having a refrigeration and defrost system that includes a compressor, an evaporator, an evaporator fan and a heater. The refrigerator also has a control system to control the operation of the refrigerator. The method includes stopping the compressor operation; starting a defrost process; starting the heater; maintaining a start state over a preset period of time; closing off the heater; and starting the compressor. After starting the compressor and before the evaporator fan is started to perform the refrigeration operation, the evaporator fan is operated at least once briefly and intermittently.

Abstract: An icing protection system comprises a fuel cell, an evaporative cooling system, a thermal deicing device, a control unit and a device for measuring the pressure in the evaporative cooling system. The evaporative cooling system is in thermal contact with the fuel cell and with the thermal deicing device in order to conduct heat from the fuel cell to the thermal deicing device. The control unit controls the electrical power demanded from the evaporatively cooled fuel cell in dependence on a deviation of the pressure measured by the pressure measuring device from a predetermined NOMINAL pressure. In this way, an energetically very efficient and very well controllable icing protection system is made available that can be operated without bleed air supplied by engines or electrical energy provided by engine generators.

Abstract: A refrigerator according to the present invention includes a compressor compressing a coolant, a condenser condensing the coolant compressed in the compressor, an expander through which the coolant condensed in the condenser passes, an evaporator evaporating the coolant expanded in the expander and cooling an inside of the refrigerator, a defroster defrosting the evaporator, a coolant adjusting valve adjusting the coolant flowing from the condenser to the evaporator, and a controller driving the compressor and turning on the defroster after closing the coolant adjusting valve. The refrigerator may minimize power consumed for defrosting and the defrosting time.

Abstract: A method is provided for controlling a heating and air conditioning system in a vehicle. The evaporator of the air conditioner is switched off below a predefined external temperature threshold in order to prevent the risk of icing. The external temperature threshold for switching off the evaporator as a function of the external temperature, is also defined, preferably variably, below the freezing point.

Abstract: An apparatus comprising a cooling chamber comprising a cooling unit for cooling uranium hexafluoride in the chamber; and a heater comprising a first region inside the cooling chamber arranged to defrost the cooling unit; and a second region outside the cooling chamber arranged to receive heating fluid cooled in the first region and to heat the received fluid. A method of defrosting a cooling unit is also described.

Abstract: An air conditioner may include a plurality of indoor units and a plurality of outdoor units connected to the plurality of indoor units. Each of the plurality of outdoor units may include a plurality of outdoor heat exchangers. Each of the outdoor heat exchangers may include a plurality of heat exchanger parts. When a defrosting operation condition is satisfied during a heating operation, indicating that a defrosting operation should be performed the plurality of heat exchanger parts of the plurality of outdoor heat exchangers may successively perform the defrosting operation.

Abstract: A high performance refrigerator includes a cabinet with a refrigerated interior, a refrigeration fluid circuit having an evaporator located within an insulated evaporator compartment outside the cabinet, and at least one damper that opens to permit air circulation from the refrigerated interior through the evaporator compartment. The refrigerator also includes a eutectic member configured to melt at an operating temperature of the refrigerator. The evaporator cools the refrigerated interior to a temperature below the operating temperature so that the eutectic member melts to cool the refrigerated interior or the evaporator compartment during a defrost cycle. The insulated evaporator cover limits heat transfer into the refrigerated interior during the defrost cycle to avoid temperature spikes in the refrigerated interior.

Abstract: A high performance refrigerator includes a cabinet with a refrigerated interior, an insulating cover separating a portion of the cabinet from the refrigerated interior, and a refrigeration fluid circuit having an evaporator located within the portion of the cabinet separated by the insulating cover from the refrigerated interior. The refrigerator also includes a controller that commands the refrigerator to perform a defrosting cycle when the evaporator coil requires defrosting. This defrosting cycle includes closing dampers in the insulating cover during the defrosting of the evaporator coil, thereby keeping the refrigerated interior thermally isolated from the evaporator during the defrost cycle. The controller is also operable to stop operation of a defrost heater when the evaporator reaches a first target temperature above the freezing point of water, and to re-open the dampers when the evaporator reaches a second target temperature above the freezing point of water.

Abstract: A method is disclosed for controlling initiation of a defrost cycle of an evaporator heat exchanger of a refrigeration system operatively associated with a refrigerated transport cargo box. The method includes the steps of establishing an return air-saturation temperature differential equal to the difference of a sensed air temperature of an air flow returning from the cargo box to pass over the heat exchange surface of the evaporator heat exchanger minus a refrigerant saturation temperature of a flow of refrigerant passing through the evaporator heat exchanger, comparing the return air-saturation temperature differential to a set point threshold defrost temperature differential, and if the return air-saturation temperature differential exceeds the set point threshold defrost temperature differential, initiating a defrost cycle for defrosting the evaporator heat exchanger.

Abstract: A refrigerator includes a low-temperature storage compartment damper to control supply of cool air to a low-temperature storage compartment, a high-temperature storage compartment damper to control supply of hot air to a high-temperature storage compartment, and a controller to control the low-temperature storage compartment damper to be opened and the high-temperature storage compartment damper to be closed while controlling a compressor and blowing fan to be driven so that the temperature of the low-temperature storage compartment reaches a low set temperature, to control the driving of the compressor and blowing fan to be stopped and the low-temperature storage compartment damper to be closed when the temperature of the low-temperature storage compartment reaches the low set temperature, and to control a defrosting heater and the blowing fan to be driven and the high-temperature storage compartment damper to be opened when the supply of cool air is stopped.

Abstract: A system and a method are provided for monitoring a condition and selectively executing a certification defrost algorithm for a heating, ventilation, and air conditioning (HVAC) system in response to the status of the monitored condition. A system and a method are provided for selectively operating a certification defrost algorithm in parallel to a field defrost algorithm. A system and a method are also provided for causing a controller to execute a first algorithm and for causing the controller to selectively execute a second algorithm while also executing the first algorithm where each of the first algorithm and the second algorithm are configured to selectively cause the HVAC system to operate in a defrost mode.

Abstract: An intelligent defrosting control for an air conditioner is disclosed, which comprises the following steps: setting a standard air pressure value; placing a high-pressure sensor on the exhaust pipe of the compressor of the air conditioner to measure the air pressure; When the air pressure measured by the high-pressure sensor is lower than the standard air pressure value, said air conditioner begins to come into the defrosting mode; otherwise, said air conditioner working in previous mode.

Abstract: The refrigerator of the present invention comprises: a refrigeration cycle composed of a compressor, a condenser and an expansion unit; an evaporator for evaporating a refrigerant which passes through the expansion unit; a heating unit for providing the heat for defrosting the evaporator; and a frost sensor unit which is provided at one side of the evaporator for sensing the amount of frost on the evaporator, and is characterized in that an operation of the frost sensor unit is started on the basis of whether operation conditions of the frost sensor unit are recognized and the heating unit selectively generates the heat according to the sensed result of the frost sensor unit. According to one embodiment of the present invention, the amount of frost on the evaporator is easily determined by the operation of the frost sensor unit and the evaporator is effectively defrosted according to the amount of frost determined thereby.

Abstract: A heat exchanging apparatus and an associated method are provided so as to permit a heat exchanger to be defrosted without being taken out of service. A defrostable heat exchanging apparatus includes a heat exchanger configured to cool gas flowing there through by heating a liquid also passing there through. The defrostable heat exchanging apparatus also includes a blockage positionable upstream of the heat exchanger with respect to the liquid so as to reduce flow of the liquid through a portion of the heat exchanger aligned with the blockage relative to the flow of the liquid through other portions of the heat exchanger. The defrostable heat exchanging apparatus may also include a positioning mechanism for moving the blockage relative to the heat exchanger.

Abstract: The present invention provides an energy efficient air conditioner that can provide a continuous supply of air at dew point that is several degrees Celsius below zero, without requiring a defrost cycle. The air conditioner in accordance to present invention comprises a plurality of cooling coils with interconnecting refrigerant piping, refrigeration circuit consisting of compressor and condenser coils, control circuit and one or more electric motor driven centrifugal fan. The present invention uses two cooling systems. The first cooling system having single coil cools the air to a temperature just above zero deg. C., say four deg. C. so that the second stage gets a steady supply of cold air. The second stage has two coils, each being half the size of the first stage coil, thus taking half the air from it so that all the air from stage 1 passes through stage 2. In operation, only one coil of the second stage is active arid chills the air going through it to say minus 14 Deg. C.

Abstract: A refrigerator and a method of operating a refrigerator to determine the time at which to initiate a defrost cycle is provided. Changes in the voltage provided to an evaporator fan are used to determine and/or predict when to initiate a defrost cycle. Adjustments to the timing of the defrost cycle can be made based on known periods of peak energy demand and/or the increased costs associated with operating the defrost cycle during such peak energy demand periods.

Abstract: A door for a refrigerated merchandiser including a case that defines a product display area. The door includes a frame and a first glass pane coupled to the frame. The first glass pane has heat-absorbing glass and is configured to be positioned adjacent an ambient environment surrounding the refrigerated merchandiser to absorb radiation from the ambient environment. The door also includes a second glass pane coupled to the frame and configured to be positioned adjacent the product display area. The second glass pane includes a conductive coating. The door further includes a third glass pane positioned between and spaced from the first glass pane and the second glass pane, and has a low emissivity coating.

Abstract: Disclosed is a system for and a method of reducing and/or avoiding ice formation inside a cooling space (41) of a refrigerated transport container (1) comprising at least a cooling unit (40) and an evaporator (16) located in the cooling space (41), where the cooling unit (40) comprises at least an intermittently operated compressor (6) operated between a first active state and a second less active state, and wherein the method comprises: reducing and/or avoiding ice formation inside the cooling space (41), when the system is operated at a temperature setpoint where a potential risk of ice build-up on the external surface of the evaporator exists, by altering a cycling of the compressor (6) between the first active state and the second less active state such that the number of melting-refreezing cycles at an external surface of the evaporator is reduced.

Abstract: Embodiments of apparatus, transport refrigeration units, and methods for operating the same can control defrost operations for a refrigerant vapor compression system. Embodiments can provide control for transitioning a refrigerant vapor compression system into and out of a defrost mode.

Abstract: An auxiliary heater control device can be readily attached to a hot water heating system configured with a simple water circuit without a hot water storage tank, and is capable of preventing freezing of circulating water such that use of an auxiliary heater is minimized. When a sensed temperature tS sensed by a temperature sensor is in a range, a control device increases a rotational speed of a circulation pump. When the sensed temperature tS is in a range, the control device increases the rotational speed of the circulation pump and lowers an operating frequency of a compressor. When the sensed temperature tS is in a range, the control device increases the rotational speed of the circulation pump, lowers the operating frequency of the compressor, and activates an auxiliary heater.