Abstract: A hydraulic cartridge valve including a housing with an interior, first and second ports that pass through the housing, a poppet in the housing interior, and an activation sensor. The poppet moves between a closed position that blocks flow through the housing interior between the first and second ports, and an open position that allows flow through the housing interior between the first and second ports. The activation sensor senses poppet position, and generate a valve open signal when the poppet is in the open position. The activation sensor can be a contact or contactless sensor, and can be located in an opening through the housing blocked by a diaphragm. A pushrod pushed by the poppet can activate the sensor, such that when the poppet blocks flow the pushrod is separated from the diaphragm, and when the poppet allows flow the pushrod is pushed towards the diaphragm.

Abstract: A refrigerator includes a cabinet configured to form a first storage chamber and a second storage chamber, a first evaporator configured to cool the first storage chamber, a first fan configured to circulate air in the first storage chamber to the first evaporator and the first storage chamber, a second evaporator configured to cool the second storage chamber, a compressor configured to be connected to the first evaporator and the second evaporator, a second fan configured to circulate air in the second storage chamber to the second evaporator and the second storage chamber; a refrigerant valve configured to guide refrigerant to the first evaporator or the second evaporator, and a controller configured to perform a plurality of modes sequentially to defrost the second evaporator.

Abstract: A transportation refrigeration unit is provided. The transportation refrigeration unit comprising: a compressor configured to compress a refrigerant; a compressor motor configured to drive the compressor; an evaporator heat exchanger operatively coupled to the compressor; an energy storage device for providing power to the compressor motor; and an evaporator fan configured to provide return airflow from a return air intake and flow the return airflow over the evaporator heat exchanger, wherein the return airflow thermodynamically adjusts a temperature of the energy storage device.

Abstract: The present disclosure relates to a heating, ventilation, and/or air conditioning (HVAC) unit having a refrigerant circuit including a heat exchanger, an expansion valve, and a compressor. The heat exchanger includes a first coil and a second coil packaged in a common support structure. The HVAC unit further has a flow control system configured to direct refrigerant flow to the first coil from the expansion valve in a cooling mode of the HVAC unit and to the first coil from the compressor in a reheat mode of the HVAC unit, and configured to direct refrigerant flow to the second coil from the expansion valve in both the cooling mode and the reheat mode of the HVAC unit.

Abstract: A motor vehicle chiller with several evaporators of different cooling capacity, has a refrigerant circulation with at least one refrigerant compressor, at least one condenser, at least one expansion element as well as at least two evaporators disposed in parallel of different cooling capacity. A refrigerant collector is disposed downstream of the expansion element and upstream of the evaporator of lesser cooling capacity to separate liquid refrigerant. Between the refrigerant collector and the evaporator a refrigerant pump is disposed to convey the liquid refrigerant to the evaporator of lesser cooling capacity. The refrigerant vapor can be guided from the evaporator across the refrigerant collector functioning as a separator and be drawn in by the refrigerant compressor.

Abstract: A refrigerated display case includes a housing surrounding multiple shelves. An air return passage is defined below the shelves. A fan is disposed at a downstream end of the air return passage. An air distribution gap is connected to an outlet of the fan and disposed behind the shelves and a top passage is disposed above the shelves. At least one microchannel heat exchanger connects the air distribution gap to the shelves.

Abstract: A refrigerator includes a storage chamber, an evaporator configured to cool the storage chamber, and an air passage through which cold air generated by the evaporator flows. The air passage includes a blower fan configured to blow the cold air to the storage chamber, and a trap part in which warm air generated by a defrosting operation stays, such that warm air generated by the defrosting operation is prevented from being introduced into the inner space of the refrigerator through the air passage. The refrigerator reduces the defrosting operation time, efficiently prevents increase of the inner temperature of the refrigerator due to warm air during the defrosting operation, reduces a temperature difference in inner temperature of the refrigerator, and prevents food stored in the refrigerator from being rotten due to a temperature change.

Abstract: A refrigeration system includes a first circulation fan electrically coupled to a power source via a first load wire. A relay is electrically coupled to the first circulation fan via a second load wire and to the power source. In an open position, the relay interrupts electrical voltage from the relay to the first circulation fan via the second load wire causing the first circulation fan to operate in a low-speed mode. In a closed position, the relay supplies electrical voltage to the first circulation fan via the second load wire causing the first circulation fan to operate in a high-speed mode. Operation of the first circulation fan in the high-speed mode reduces a defrost cycle time associated with the refrigeration system relative to operation of the first circulation fan in low-speed mode.

Abstract: A controller switches between and performs a first simultaneous heating and defrosting operation of supplying part of refrigerant discharged from a compressor is supplied to one or some parallel heat exchangers among a plurality of parallel heat exchangers through a defrosting circuit and allowing the other one or more parallel heat exchangers to operate as evaporators, and a second simultaneous heating and defrosting operation of, in one or some heat source units among a plurality of heat source units, supplying the refrigerant discharged from the compressor is supplied to all the plurality of parallel heat exchangers through the defrosting circuit, and in the other one or more heat source units, continuing heating by allowing all the plurality of parallel heat exchangers to operate as evaporators.

Abstract: A refrigerated merchandiser includes a case having a lower wall, an upper wall, a rear wall, and a rear panel. A product support area is at least partially defined by the lower wall, the upper wall, and the rear panel. A first air passageway is formed in the case for supplying refrigerated air to the product support area. A fan is positioned in the first air passageway for creating airflow. An evaporator coil is disposed in the air passageway to condition the airflow. A duct is coupled to the rear panel to create a second air passageway.

Abstract: In various implementations, a heat pump may include heating operations and defrost operations. The heat pump may monitor cycle time(s) for one or more of the operations. Defrost operation(s) in the heat pump may be automatically adjusted based at least partially on cycle times.

Abstract: In various implementations, a heat pump may include heating operations and defrost operations. The heat pump may monitor cycle time(s) for one or more of the operations. Defrost operation(s) in the heat pump may be automatically adjusted based at least partially on cycle times.

Abstract: A refrigerator having an insulated interior which is formed, at least in part, by a drawer with a bottom boundary wall, a front boundary wall, two lateral boundary walls and a rear boundary wall. Included at an upper portion of the drawer is an inner drawer, of which the height is smaller than the height of the drawer. According to the invention, the height of the rear boundary wall of the drawer is reduced at least to the extent where the inner drawer can have its base wall displaced, at least in part, beyond the rear boundary wall of the drawer.

Abstract: A system and method for controlling automatic defrost of a refrigerator device adaptively moves the defrost cycle to a time period of comparatively low compressor activity based on an evaluation of compressor usage over a cyclically recurring time interval. An adaptive defrost controller (ADC) analyzes stored data to develop a profile for compressor activity vs. time. From this profile, high compressor activity times of the time interval are distinguished from low compressor activity times in the time interval and a defrost cycle is scheduled based on the results of the analyzed data.

Abstract: A method and system is provided which receives a desired humidity level from a user for the refrigeration compartment of a refrigerator, determines the current humidity level, and then activates an atomizer in the refrigeration compartment to increase the humidity level if needed. The humidity in the refrigeration compartment may be determined based at least in part on the temperature of the refrigeration compartment, the defrost timer, the door opening times, and the compressor timer.

Abstract: A heat pump system is configured to have a defrost cycle operable during a heating mode of operation. The system uses: larger than conventionally sized capillary tubes at the liquid refrigerant entry end of an exterior air-source heat exchanger; a special amount of additional refrigerant charge; a supplemental hot gas refrigerant transport line extending from the compressor; a special valve in the new supplemental hot gas refrigerant transport line; and another special valve controlling a restriction to the refrigerant flow in the common consolidated vapor refrigerant transport line exiting the exterior heat exchanger. A controller opens the valve in the new supplemental hot gas refrigerant transport line and to simultaneously engages, for a special period of time, the valve controlling the specially sized restriction to the refrigerant flow in the common consolidated vapor refrigerant transport line exiting the exterior heat exchanger at periodic intervals during potential frost conditions.

Abstract: Heat pumps with improved defrost cycles and methods of defrosting heat exchangers, for example, having microchannel outdoor heat exchangers. A heat exchanger has three types of connection points that are used during a defrost cycle. Two connection points are used to deliver hot refrigerant gas to the heat exchanger and one connection point is where refrigerant exits the heat exchanger. Two of the connection points are at the same header and during at least part of the defrost cycle, at least part of the hot refrigerant gas is passed through that header without passing through any cross tubes of the heat exchanger. A defrost valve in a refrigerant conduit opens during the defrost cycle to deliver hot refrigerant gas to the connection point on the header. In a number of embodiments, the defrost valve is open only during a portion of the defrost cycle.

Abstract: A heat pump apparatus includes a refrigerant circuit in which a compressor, a condenser, expansion means, and an evaporator are serially connected. Condensation temperature detection means that detects a saturation temperature of the condenser, and evaporation temperature detection means that detects the saturation temperature of the evaporator are provided. Operation efficiency is estimated by a value obtained by dividing heating ability estimated from a detection value of the condensation temperature detection means by a difference between a detection value of condensation temperature detection means and that of evaporation temperature detection means or dissipation power estimated by the difference.

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: An apparatus for managing operation of refrigerating machines controls defrosting of evaporators of refrigeration cycles. Each of the refrigeration cycles uses a compressor, a condenser, a decompressor, and the evaporator, and is formed for a corresponding one of cooling/heating devices installed in a single store. The apparatus obtains a total estimated power consumption in a case of a pull-down operation using power consumptions necessary for the pull-down operation performed for the cooling/heating devices after defrosting is performed and using a power consumption of the store that includes at least the power consumptions of the refrigeration cycles and that is estimated for each of predetermined time periods. The apparatus changes defrosting start times or defrosting end times of the cooling/heating devices so that the total estimated power consumption does not exceed an upper limit value of a power consumption set in advance by the store.

Abstract: A refrigerator is provided that includes a chilled interior and a cooling circuit for a coolant, the cooling circuit being provided with an evaporator, a compressor, and a condenser. The refrigerator further includes a controller as well as a fan for cooling the condenser and the compressor. The controller controls the fan to operate during an idle phase of the compressor.

Abstract: A heat pump system includes a controller and a closed system that includes a condensing heat exchanger coil, an evaporating heat exchanger coil, a refrigerant and a compressor. The compressor is configured to compress the refrigerant, thereby causing the refrigerant to have a greater pressure in the condensing heat exchanger coil than in the evaporating heat exchanger coil. The controller is configured to perform a passive defrost of the evaporating heat exchanger coil. The passive defrost includes disabling the compressor and providing a bypass path between the condensing and evaporating heat exchanger coils that bypasses the compressor. The bypass path allows the refrigerant to flow from the condensing heat exchanger coil to the evaporating heat exchanger coil while the compressor is disabled.

Abstract: The defrost timer is typically provided to remove frost on an evaporator in a refrigerator. The defrost timer includes a circuit board, a first terminal, a second terminal, a third terminal, a fourth terminal, a switching unit, a first AC line, a second AC line, a third AC line and a fourth AC line. The first AC line is provided on the circuit board and connects the first terminal and the switching unit. The second AC line is provided on the circuit board and connects the second terminal and the switching unit. The third AC line is provided on the circuit board and connects the third terminal and the switching unit. The fourth AC line is provided on the circuit board and connects the fourth terminal and the switching unit. Distance between the third AC line and the fourth AC line is at least 5 mm.

Abstract: A method and system for liquid purification and defrosting a freezing unit harvests energy released as heat from a condenser. Liquid received from a source into a first liquid storage container is heated using heat collected from the condenser using at least one heat conducting rod. A second liquid storage container connected to the first liquid storage container is maintained at a lower temperature than the first liquid storage container. As a first portion of heated liquid is transferred from the first liquid storage container to the second liquid storage container, bacteria in the first portion of heated liquid is denatured as a result of the temperature change, and the liquid is purified. Filters may also be used to improve purification. A second portion of heated liquid is transferred between the first liquid storage container and a freezing unit via at least one heat conducting pipe causing defrosting of the freezing unit.

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: A refrigerator and a control method of the same are disclosed. A refrigerator includes a plurality of evaporators and a refrigerant path conversion device connected with the plurality of the evaporates, the refrigerant path conversion device controlling a path of refrigerant to perform defrosting operations for predetermined evaporators and cooling operations for the other evaporators.

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: 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: An equipment control system includes a control device, and a control program in which present-round defrosting operation start time can be changed appropriately. An integrated controller controls a defrosting operation to remove frost adhered to showcases, in which the defrosting operation is started at a fixed or varying time interval. The integrated controller stores past record data based on required time for past defrosting operations for different environmental conditions. The integrated controller includes an environmental condition acquisition unit for obtaining present environmental conditions; a database control unit for obtaining required time for a present-round defrosting operation based on the past record data corresponding to the present environmental conditions from among the stored past record data; and a start time changing unit for changing start time of the present-round defrosting operation based on the obtained required time from the scheduled start time.

Abstract: A transport unit including a container defining a cargo space. The transport unit includes position detection apparatus coupled to the container, and adapted to determine a geographic location of the container and to generate a signal indicative of the geographic location. The transport unit also includes a refrigeration system in communication with the cargo space, and a control system including route data that defines a plurality of potential destinations of the container. The control system is programmed to predict a container route defined by at least two potential destinations of the container based on the geographic location and the route data, and to determine a proximity of the container relative to at least one potential destination of the route. The control system is in communication with the refrigeration system to control the refrigeration system based on the proximity of the container relative to the at least one potential destination.

Abstract: Controllers for controlling heating, ventilating, air conditioning, and cooling (HVAC) systems are provided. The controllers include graphical user interfaces for user adjustment of system settings. The controllers also include communication interfaces for receiving climate data. In certain embodiments, the controllers govern operation of the HVAC systems based at least in part on the climate data. Further, the controllers may display information and alerts related to the climate data. The controllers also may govern operation of air treatment devices within the HVAC systems.

Abstract: The present invention relates to a no-frost refrigerator unit and/or freezer unit comprising a fan for the generation of an airflow in a compartment of the unit to be cooled, wherein the unit comprises detection means for the detection of at least one parameter as well as a control or regulation unit which is made such that it varies the speed of the fan in dependence on the at least one measured parameter.

Abstract: A method of defrosting a eutectic plate of a refrigeration system involves activating a defrost system when a power source is connected to the refrigeration system. The defrost system is operated for all or a portion of a defrost cycle and is then deactivated. The initiation of a subsequent defrost cycle is prevented until the power source has been disconnected from the refrigeration system for at least a selected amount of time. A defrost system may include a controller programmed to carry out the method and automatically initiate a series of defrost cycles.

Abstract: A heat pump defrost system for efficiently defrosting an outdoor coil while simultaneously operating the heat pump in a normal heating manner. The heat pump defrost system generally includes a primary flow circuit including an indoor heat exchanger, an outdoor heat exchanger, a compressor connected thereto and a reverse valve for toggling a direction of refrigerant flow therethrough, and an auxiliary flow circuit for deicing the outdoor heat exchanger. The auxiliary flow circuit includes a valve for connecting the auxiliary flow circuit to the primary flow circuit, a heat sink in line with the auxiliary flow circuit, wherein the heat sink stores defrost fluid within the auxiliary flow circuit, at least one thermostat to read an outdoor ambient temperature and a control unit for operatively engaging the valve to direct the hot gas from the compressor of the primary circuit within the auxiliary flow circuit and the heat pump according to the outdoor ambient temperature for deicing the outdoor heat exchanger.

Abstract: A transport unit including a container defining a cargo space. The transport unit includes position detection apparatus coupled to the container, and adapted to determine a geographic location of the container and to generate a signal indicative of the geographic location. The transport unit also includes a refrigeration system in communication with the cargo space, and a control system including route data that defines a plurality of potential destinations of the container. The control system is programmed to predict a container route defined by at least two potential destinations of the container based on the geographic location and the route data, and to determine a proximity of the container relative to at least one potential destination of the route. The control system is in communication with the refrigeration system to control the refrigeration system based on the proximity of the container relative to the at least one potential destination.

Abstract: An environment control unit including an environment control system, a reactive oxygen species (ROS) generator, and a controller. The refrigeration system and the ROS generator positioned within a housing of the environment control unit and providing conditioned air to the interior of a cargo space to clean and condition air and surfaces within the cargo space.

Abstract: Disclosed herein are a refrigerator and a defrost control method thereof that are capable of sensing an amount of frost formed on an evaporator based on a change amount of absolute humidity in the refrigerator to control a defrost operation. A defrost control method of a refrigerator including a storage chamber and an evaporator to cool the storage chamber, includes sensing absolute humidity in the storage chamber, determining an estimated amount of frost formed on the evaporator using time segments in which the absolute humidity in the storage chamber decreases, and controlling a defrost operation based on the estimated amount of frost. According to the present embodiments, it is possible to perform the defrost operation at the point of time for optimum defrost, thereby maximizing energy efficiency and cooling efficiency.

Abstract: A defrost indicator is configured such that the process of freezing and defrosting the defrost indicator places the defrost indicator into a state that is not completely reversed by refreezing, so that one can detect whether the defrost indicator defrosted and refroze or never defrosted by observing its current state. In an embodiment, the defrost indicator is initially placed in a first state before being frozen (e.g., upside down with fluid in an upper chamber). Freezing the defrost indicator places it in a second state (e.g., with the fluid frozen in the upper chamber). Then when the defrost indicator is defrosted, the defrost indicator is placed into a third state that is different than the first state (e.g., right-side-up with liquid fluid in the lower chamber). If the defrost indicator is again frozen, the defrost indicator is placed into a fourth state (e.g., the fluid frozen in the lower chamber).

Abstract: Disclosed is a high speed defrosting heat pump having a closed refrigerant circulation loop including a four-way valve so as to conduct cooling and heating operations by switching a refrigerant-circulating direction by means of the four-way valve. A three-way valve is disposed on a refrigerant pipe connected between a compressor and the four-way valve, and a bypass pipe is branched off from the three-way valve in such a manner as to be connected to a refrigerant pipe connected between an expansion valve and a exterior heat exchanger, such that the hot gas discharged from the compressor is introduced to the exterior heat exchanger via the bypass tube by the control of the three-way valve.

Abstract: A system for desuperheating hot gaseous refrigerant using both a heat exchanger and a dispersed Venturi-driven injection of liquid refrigerant is disclosed. Further, a system, relating to cooling at least one compressed superheated refrigerant fluid prior to condensing, relating to extending the life of at least one condenser is disclosed.

Abstract: An air includes: a compressor for compressing a refrigerant; an indoor heat exchanger for cooling or heating indoor with a refrigerant; an outdoor heat exchanger for exchanging heat of a refrigerant and outdoor air; an outdoor fan for ventilating outdoor air with the outdoor heat exchanger; a cooling/heating switching valve for switching cooling/heating; a first expansion device installed between the indoor heat exchanger and the outdoor heat exchanger; a CNT heater module installed between the outdoor heat exchanger and the cooling/heating switching valve to evaporate a refrigerant; a second expansion device installed between the outdoor heat exchanger and the CNT heater module; and a controller for sustaining a heating mode of the cooling/heating switching valve.

Abstract: A method for defrosting an evaporator of a refrigeration sealed system, the system including at least one refrigeration compartment and a controller operatively coupled to a compressor, an evaporator, an evaporator fan and a condenser fan, wherein the method includes initiating a defrost cycle, operating the sealed system to prechill the refrigeration compartment, and selectively operating the evaporator fan and the condenser fan to raise a 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 system and method for controlling automatic defrost of a refrigerator device are provided. The system adaptively moves the defrost cycle to low usage times based on an evaluation of compressor usage in a daily cycle.

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: The defrost timer is typically provided to remove frost on an evaporator in a refrigerator. The defrost timer includes a circuit board, a first terminal, a second terminal, a third terminal, a fourth terminal, a switching unit, a first AC line, a second AC line, a third AC line and a fourth AC line. The first AC line is provided on the circuit board and connects the first terminal and the switching unit. The second AC line is provided on the circuit board and connects the second terminal and the switching unit. The third AC line is provided on the circuit board and connects the third terminal and the switching unit. The fourth AC line is provided on the circuit board and connects the fourth terminal and the switching unit. Distance between the third AC line and the fourth AC line is at least 5 mm.

Abstract: A defrosting assembly, a refrigerator having the same, and a method of controlling the same are provided. The refrigerator may include a food defrosting chamber, which may be divided from a food storage chamber that cools or freezes food, a defrosting device, which may be positioned in and may be removable from the food defrosting chamber, and a thermoelectric module, which may be positioned in the food defrosting chamber to heat an inside of the defrosting device and to cool an outside of the defrosting device. In a defrosting mode, frozen food may be rapidly defrosted by using the defrosting device, while in a general or a rapid cooling mode, the defrosting device may be used for food storage.

Abstract: An appliance includes a compression stage, a condensation stage, and an evaporation stage. The evaporation stage includes a first evaporator for a first refrigerated enclosure and a second evaporator for a second refrigerated enclosure. A first valve in a condensation stage bypass line is openable to allow a supply of refrigerant to bypass the condensation stage during a defrost mode, where a condensation stage bypass line is positioned between an output of the compression stage and the second evaporator. A second valve is positioned in a line from the second evaporator to the input to the compression stage and is closeable to block a supply of refrigerant from the second evaporator to the compression stage during the defrost mode. An additional line positioned between the second evaporator and the first evaporator carries the supply of refrigerant from the second evaporator to the first evaporator in the defrost mode.

Abstract: An assembly for installation in a refrigerator provides an enclosure for conducting service lines therethrough and an air filter unit mounted to the enclosure. The air filter unit includes an air filter housing that contains an air filter and includes openings for the ingress of air from the refrigerator which, after passing through the air filter, is discharged to the refrigerator interior through discharge openings in the air filter housing. Means such as a fan is provided to establish a flow of air through the air filter housing. The air filter unit has utility separately from the enclosure for conducting service lines in which case the air filter housing includes first and second portions that are pivotally connected to one another. The air filter within the air filter housing is supported by one of the first and second portions of the air filter housing.

Abstract: A method to detect and respond to a coil condition in an HVAC system. The method includes calculating an initial airflow restriction value and a current airflow restriction value, which are compared. If the current airflow restriction value is greater than a first sum including the initial airflow restriction value and a first restriction factor, then a coil condition is preliminarily determined to be freezing and cooling in the HVAC system is stopped.