Method of operating an electronic expansion valve in an air conditioning unit

Abstract

An air conditioning unit includes a refrigeration circuit including a condenser and an evaporator, a compressor to circulate refrigerant, and an electronic expansion valve. A controller monitors operating superheat of the refrigerant passing through the evaporator, identifies an overheat fault condition based on at least one of the operating superheat, a target valve position of the electronic expansion valve, or a compressor speed, stops the compressor in response to identifying the overheat fault condition, and initiates a calibration process of the electronic expansion valve.

Description

Technical Field

[0001] The present disclosure relates generally to air conditioning units, and more particularly to a method of operating an electronic expansion valve in an air conditioning unit. Background Art

[0002] Air conditioning units are conventionally used to regulate the temperature of a room (e.g., within a structure such as a residence or office building). Such units typically include a closed refrigeration circuit that heats or cools the indoor air. Typically, the indoor air is recirculated while being heated or cooled. Various sizes and configurations are available for such air conditioning units. For example, some units may have a portion that is installed indoors that is connected to another portion located outdoors, for example, by a pipe or tube that carries a refrigerant. These types of units are typically used to regulate the air in larger spaces.

[0003] Another type of air conditioning unit, often called a single-package vertical unit (SPVU) or package terminal air conditioner (PTAC), can be used to regulate the temperature in a single room or a group of rooms in a building, for example. These units typically operate like split-system heat pump systems, except that the indoor and outdoor sections are defined by a partition and all system components are housed in a single package mounted in a wall casing positioned within an opening in the building's exterior wall.

[0004] When a conventional PTAC is operated in cooling or heating mode, the compressor circulates the refrigerant within the sealed system, while the indoor and outdoor fans push the air flow through the indoor and outdoor heat exchangers, respectively. For example, when operating these air conditioning units to heat or cool a room under various ambient conditions or compressor speeds, an expansion device (such as an electronic expansion valve or "EEV") is used to expand the refrigerant and allow a phase change from liquid to vapor within the evaporator before passing the refrigerant back to the compressor.

[0005] To determine the absolute position of the EEV, a homing or calibration process may be performed by driving the EEV to a fully closed position so that the software position (e.g., where the controller believes the EEV is) equals the absolute position (e.g., the EEV's actual physical position). However, after performing this calibration, the EEV may lose steps over time, causing the software position to not equal the absolute position. Eventually, so many steps may be lost that the controller believes the EEV is fully closed when it is not. In this case, the controller will be unable to generate superheat, thereby sending liquid into the compressor and potentially damaging it.

[0006] Therefore, improved air conditioning units and operating methods would be useful. More specifically, a heat pump air conditioning unit that regulates an electronic expansion valve to improve operational safety and system performance would be particularly beneficial. Summary of the Invention

[0007] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0008] In one exemplary embodiment, an air conditioning unit is provided, comprising: a refrigeration circuit including a condenser and an evaporator; a compressor operatively coupled to the refrigeration circuit and configured to force refrigerant through the refrigeration circuit; an electronic expansion valve fluidly coupled to the refrigeration circuit; and a controller operatively coupled to the compressor and the electronic expansion valve. The controller is configured to monitor an operational superheat of the refrigerant passing through the evaporator, identify an overheat fault condition based on at least one of the operational superheat, a target valve position of the electronic expansion valve, or a compressor speed, stop the compressor in response to identifying the overheat fault condition, and initiate a calibration procedure for the electronic expansion valve.

[0009] In another exemplary embodiment, a method of operating an air conditioning unit is provided. The air conditioning unit includes a refrigeration circuit including a condenser and an evaporator; a compressor operably coupled to the refrigeration circuit and configured to force refrigerant through the refrigeration circuit; and an electronic expansion valve fluidly coupled to the refrigeration circuit. The method includes monitoring an operational superheat of the refrigerant passing through the evaporator, identifying an overheat fault condition based on at least one of the operational superheat, a target valve position of the electronic expansion valve, or a compressor speed, stopping the compressor in response to identifying the overheat fault condition, and initiating a calibration process for the electronic expansion valve.

[0010] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] A full and enabling disclosure of the invention, including the best mode thereof, to one skilled in the art is set forth in the specification, which refers to the accompanying drawings.

[0012] Figure 1 A perspective view of an air conditioning unit according to an exemplary embodiment of the present disclosure is provided, wherein a portion of an indoor portion is exploded from the rest of the air conditioning unit for illustrative purposes.

[0013] Figure 2 yes Figure 1 Another perspective view of components of the indoor portion of an exemplary air conditioning unit.

[0014] Figure 3 is a schematic diagram of a refrigeration circuit according to one embodiment of the present disclosure.

[0015] Figure 4 yes Figure 1 A rear perspective view of an outdoor portion of an exemplary air conditioning unit illustrating vent apertures in a bulkhead according to one embodiment of the present disclosure.

[0016] Figure 5 According to one embodiment of the present disclosure Figure 4 A front perspective view of an exemplary diaphragm of FIG. 1 , wherein the vent door is illustrated in an open position.

[0017] Figure 6 A fan assembly for providing supplemental air according to one embodiment of the present disclosure Figure 4 Rear perspective view of an exemplary air conditioning unit and partition.

[0018] Figure 7 yes Figure 1 A side cross-sectional view of an exemplary air conditioning unit.

[0019] Figure 8 A method for operating an air conditioning unit according to one embodiment of the present disclosure is illustrated.

[0020] Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. DETAILED DESCRIPTION

[0021] Reference will now be made in detail to embodiments of the present invention, one or more examples of which are shown in the accompanying drawings. Each example is provided in an illustrative manner and does not limit the present invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the scope or spirit of the present invention. For example, features illustrated or described as part of one embodiment can be used in another embodiment, thereby producing yet another embodiment. Thus, it is intended that the present invention covers these modifications and variations that fall within the scope of the appended claims and their equivalents.

[0022] Now refer to Figure 1 and Figure 2, an air conditioning unit 10 is provided. The air conditioning unit 10 is a unitary air conditioner, also conventionally referred to as a room air conditioner or a packaged terminal air conditioner (PTAC). The unit 10 includes an indoor portion 12 and an outdoor portion 14, and generally defines a vertical direction V, a lateral direction L, and a transverse direction T. The directions V, L, and T are perpendicular to each other so as to generally define an orthogonal coordinate system. Although various aspects of the present subject matter are described with reference to the PTAC unit 10, it should be understood that various aspects of the present subject matter may be equally applicable to other air conditioning unit types and configurations, such as single packaged vertical units (SPVUs) and split heat pump systems.

[0023] The housing 20 of the unit 10 can house various other components of the unit 10. The housing 20 can include, for example, a rear grille 22 and a room front 24, which can be separated along a transverse direction T by a wall casing 26. The rear grille 22 can be part of the outdoor portion 14, and the room front 24 can be part of the indoor portion 12. Components of the outdoor portion 14, such as an outdoor heat exchanger 30, an outdoor fan 32, and a compressor 34, can be housed within the wall casing 26. A fan shroud 36 can additionally surround the outdoor fan 32, as shown.

[0024] The indoor portion 12 may include, for example, an indoor heat exchanger 40, a blower or indoor fan 42, and a heating unit 44. These components may be housed, for example, behind the room front portion 24. Additionally, a partition 46 may generally support and / or house various other components of the indoor portion 12, or portions thereof, such as the indoor fan 42 and the heating unit 44. The partition 46 may generally separate and define the indoor portion 12 and the outdoor portion 14.

[0025] The outdoor heat exchanger 30 and the indoor heat exchanger 40 may be components of a sealed system or refrigeration circuit 48, which is Figure 3 Schematically illustrated in FIG. The refrigeration circuit 48 may further include, for example, a compressor 34 and an expansion device 50. As illustrated, the compressor 34 and the expansion device 50 may be in fluid communication with the outdoor heat exchanger 30 and the indoor heat exchanger 40, allowing refrigerant to flow therethrough, as is generally understood. More specifically, the refrigeration circuit 48 may include various lines for flowing refrigerant between the various components of the refrigeration circuit 48, thereby providing fluid communication therebetween. Refrigerant may thus flow through these lines from the indoor heat exchanger 40 to the compressor 34, from the compressor 34 to the outdoor heat exchanger 30, from the outdoor heat exchanger 30 to the expansion device 50, and from the expansion device 50 to the indoor heat exchanger 40. As is generally understood, the refrigerant may typically undergo phase changes associated with a refrigeration cycle as it flows to and through these various components. Suitable refrigerants for the refrigeration circuit 48 may include pentafluoroethane, difluoromethane, or mixtures such as R410a, but it should be understood that the present disclosure is not limited to these examples and that any suitable refrigerant may be utilized.

[0026] As is understood in the art, the refrigeration circuit 48 can alternately operate as a refrigeration component (and thereby perform a refrigeration cycle) or a heat pump (and thereby perform a heat pump cycle). Figure 3 As shown, when the refrigeration circuit 48 operates in cooling mode and thereby performs a refrigeration cycle, the indoor heat exchanger 40 acts as an evaporator, while the outdoor heat exchanger 30 acts as a condenser. Alternatively, when the assembly operates in heating mode and thereby performs a heat pump cycle, the indoor heat exchanger 40 acts as a condenser, while the outdoor heat exchanger 30 acts as an evaporator. As is generally understood, the outdoor heat exchanger 30 and the indoor heat exchanger 40 can each include a coil through which a refrigerant can flow for heat exchange purposes.

[0027] According to an exemplary embodiment, the compressor 34 can be a variable speed compressor. In this regard, the compressor 34 can operate at various speeds depending on the current air conditioning needs of the room and the demand from the refrigeration circuit 48. For example, according to an exemplary embodiment, the compressor 34 can be configured to operate at any speed between a minimum speed of, for example, 1500 revolutions per minute (RPM) to a maximum rated speed of, for example, 3500 RPM. In particular, the use of a variable speed compressor 34 enables the refrigeration circuit 48 (and thus the air conditioning unit 10) to operate efficiently, minimizes unnecessary noise when the compressor 34 does not need to operate at full speed, and ensures a comfortable environment in the room.

[0028] Specifically, according to an exemplary embodiment, the compressor 34 can be an inverter compressor. In this regard, the compressor 34 can include a power inverter, power electronics, a rectifier, or other control electronics suitable for converting an alternating current (AC) power input into a direct current (DC) power supply for the compressor. The inverter electronics can adjust the DC power output to any suitable DC voltage corresponding to a specific operating speed of the compressor. In this way, the compressor 34 can be adjusted to any suitable operating speed, for example, 0% to 100% of the full rated power and / or speed of the compressor. This can help the compressor operate accurately at the desired operating power and speed, thereby meeting system needs while maximizing efficiency and minimizing unnecessary system cycling, energy use, and noise.

[0029] In the exemplary embodiment illustrated in the figures, an expansion device 50 may be disposed in the outdoor portion 14 between the indoor heat exchanger 40 and the outdoor heat exchanger 30. According to an exemplary embodiment, the expansion device 50 may be an electronic expansion valve ("EEV") that enables controlled expansion of the refrigerant, as is known in the art. According to alternative embodiments, the expansion device 50 may be a capillary tube or another suitable expansion device configured for use in a thermodynamic cycle.

[0030] More specifically, according to an exemplary embodiment, the electronic expansion device 50 can be configured to precisely control the expansion of the refrigerant to maintain a desired temperature differential of the refrigerant across, for example, the evaporator (i.e., the outdoor heat exchanger 30 in heat pump mode). In other words, the electronic expansion device 50 throttles the flow of refrigerant based on the reaction of the temperature differential across the evaporator or the amount of superheat temperature differential, thereby ensuring that the refrigerant entering the compressor 34 is in a gaseous state.

[0031] In general, the terms "superheat," "operating superheat," and the like are generally intended to refer to the increase in temperature of the refrigerant above the fully saturated vapor temperature in the evaporator. In this regard, for example, superheat can be quantified in degrees Fahrenheit, such that 1°F superheat means the refrigerant exiting the evaporator is 1°F above the saturated vapor temperature. It should be understood that the operating superheat can be measured and monitored by the controller 64 in any suitable manner. For example, the controller can be operably coupled to a pressure sensor for measuring the pressure of the refrigerant exiting the evaporator, can convert this pressure to a saturated vapor temperature, and can subtract this temperature from the measured refrigerant temperature at the evaporator outlet to determine the superheat.

[0032] According to an exemplary embodiment, the expansion device or electronic expansion valve 50 can be driven by a stepper motor or other drive mechanism to any desired position between a fully closed position (e.g., when no refrigerant is passing through the EEV 50) and a fully open position (e.g., when there is little or no restriction through the EEV 50). For example, the controller 64 can be operably coupled to the EEV 50 and can adjust the position of the EEV 50 via a control signal to achieve a target superheat, target restriction / expansion, etc.

[0033] More specifically, the control signal transmitted from the controller 64 may specify the number of control steps (or simply "steps") and the corresponding direction (e.g., counterclockwise toward the closed position or clockwise toward the open position). Each EEV 50 may have a physical travel span equal to the difference between the fully open position and the fully closed position. Additionally, the EEV 50 may include a step range or control step range corresponding to the number of adjustment steps the EEV 50 takes to travel from the fully closed position to the fully open position.

[0034] Each "step" may refer to a predetermined rotation of a drive mechanism (e.g., such as a stepper motor), which in turn may move the EEV 50 a fixed linear distance toward an open or closed position (depending on the commanded step direction). For example, according to an exemplary embodiment, the EEV 50 may have a step range of 500 steps, where 0 steps corresponds to fully closed and 500 steps corresponds to fully open. However, it should be understood that according to alternative embodiments, any given electronic expansion valve may include a different number of control steps, and the absolute step adjustments described herein may be modified accordingly.

[0035] Additionally, as used herein, the position of the EEV 50 may be expressed as a percentage, for example, where 0% corresponds to a fully closed position and 100% corresponds to a fully open position. According to an exemplary embodiment, the percentage representation may also refer to a percentage of the total control steps taken from the closed position, for example, where 10% refers to 50 steps (e.g., 10% of a total of 500 steps) and 80% refers to 400 steps (e.g., 80% of a total of 500 steps).

[0036] According to the illustrated exemplary embodiment, the outdoor fan 32 is an axial flow fan, and the indoor fan 42 is a centrifugal fan. However, it should be understood that, according to alternative embodiments, the outdoor fan 32 and the indoor fan 42 can be any suitable fan type. In addition, according to an exemplary embodiment, the outdoor fan 32 and the indoor fan 42 are variable speed fans, for example, similar to the variable speed compressor 34. For example, the outdoor fan 32 and the indoor fan 42 can rotate at different rotational speeds, thereby generating different air flow rates. It may be desirable to operate the fans 32, 42 at a speed less than their maximum rated speed to ensure that the refrigeration circuit 48 operates safely and appropriately at a speed less than its maximum rated speed, for example, to reduce noise when full speed operation is not required. In addition, according to alternative embodiments, the fans 32, 42 can be operated to push make-up air into the room.

[0037] According to the illustrated embodiment, the indoor fan 42 can operate as an evaporator fan in the refrigeration circuit 48 to promote the flow of air through the indoor heat exchanger 40. Therefore, the indoor fan 42 can be positioned downstream of the indoor heat exchanger 40 along the flow direction of the indoor air and downstream of the heating unit 44. Alternatively, the indoor fan 42 can be positioned upstream of the indoor heat exchanger 40 along the flow direction of the indoor air and can be operated to push air through the indoor heat exchanger 40.

[0038] In the exemplary embodiment, the heating unit 44 includes one or more heater groups 60. Each heater group 60 can be operated as needed to generate heat. In some embodiments, as shown, three heater groups 60 can be utilized. However, alternatively, any suitable number of heater groups 60 can be utilized. Each heater group 60 can also include at least one heater coil or coil channel 62, such as two heater coils or coil channels 62 in the exemplary embodiment. Alternatively, other suitable heating elements can be utilized.

[0039] The operation of the air conditioning unit 10, including the compressor 34 (and typically the refrigeration circuit 48), the indoor fan 42, the outdoor fan 32, the heating unit 44, the expansion device 50, and other components of the refrigeration circuit 48, can be controlled by a processing device such as a controller 64. The controller 64 can communicate with these components of the air conditioning unit 10 (e.g., via a suitable wired or wireless connection). The controller 64 may include a memory and one or more processing devices, such as a microprocessor, CPU, etc., such as a general-purpose or special-purpose microprocessor, which is operable to execute programmed instructions or microcontrol code associated with the operation of the unit 10. The memory may represent a random access memory such as DRAM or a read-only memory such as ROM or FLASH. In one embodiment, the processor executes the programmed instructions stored in the memory. The memory may be a component separate from the processor, or may be included on board within the processor.

[0040] The runner 10 may further include a control panel 66 and one or more user inputs 68 that may be included in the control panel 66. The user inputs 68 may be in communication with the controller 64. A user of the runner 10 may interact with the user inputs 68 to operate the runner 10, and user commands may be transmitted between the user inputs 68 and the controller 64 to facilitate operation of the runner 10 based on such user commands. A display 70 may further be provided in the control panel 66 and may be in communication with the controller 64. The display 70 may be, for example, a touch screen or other text-readable display screen, or alternatively may simply be a light that can be activated and deactivated as needed to provide, for example, an indication of an event or setting of the runner 10.

[0041] Brief reference Figure 4 In one embodiment, a vent aperture 80 may be defined in the partition 46 for providing fluid communication between the indoor portion 12 and the outdoor portion 14. The vent aperture 80 may be used in an installed air conditioning unit 10 to allow outdoor air to flow into the room through the indoor portion 12. In this regard, in some circumstances, it may be desirable to allow outside air (i.e., "make-up air") to flow into the room in order to, for example, meet government regulations, compensate for negative pressure created within the room, etc. Thus, according to an exemplary embodiment, make-up air may be provided to the room through the vent aperture 80 when desired.

[0042] like Figure 5 As shown, the vent door 82 can be pivotally mounted to the partition 46 near the vent aperture 80 to open and close the vent aperture 80. More specifically, as shown in the figure, the vent door 82 is pivotally mounted to the indoor-facing surface of the indoor portion 12. The vent door 82 can be configured to pivot between a first closed position and a second open position. In the first closed position, the vent door 82 prevents air from flowing between the outdoor portion 14 and the indoor portion 12. In the second open position, the vent door 82 is in an open position (e.g., Figure 5According to the illustrated embodiment, the vent door 82 can be pivoted between an open position and a closed position by an electric motor 84 controlled by the controller 64 or by any other suitable method.

[0043] In some cases, it may be desirable to treat or condition the make-up air flowing through the vent aperture 80 before it is blown into the room. For example, outdoor air with a relatively high humidity level may require treatment before entering the room. Additionally, if the outdoor air is cool, it may be desirable to heat the air before blowing it into the room. Therefore, according to an exemplary embodiment of the present subject matter, the unit 10 may further include a secondary seal system positioned above the vent aperture 80 for conditioning the make-up air. The secondary seal system may be a miniature seal system that functions similarly to the refrigeration circuit 48 but only conditions the air flowing through the vent aperture 80. According to alternative embodiments, such as those described herein, the make-up air may be pushed through the vent aperture 80 without the assistance of a secondary seal system. Instead, the make-up air pushed through the vent aperture 80 may be at least partially conditioned by the refrigeration circuit 48 (e.g., by passing through the indoor heat exchanger 40). Furthermore, the make-up air may be conditioned immediately upon entering through the vent aperture 80, or sequentially after combining with the air flow introduced through the indoor heat exchanger 40.

[0044] Now refer to Figure 6 , the fan assembly 100 will be described according to an exemplary embodiment of the present subject matter. According to the illustrated embodiment, the fan assembly 100 is generally configured to propel a flow of supplemental air through the vent aperture 80 and into the conditioned room without the assistance of a secondary seal system. However, it should be understood that the fan assembly 100 can be used in conjunction with a supplemental air module that includes a secondary seal system for conditioning the supplemental air flow. As illustrated, the fan assembly 100 includes an auxiliary fan 102 for propeling a flow of supplemental air through a fan duct 104 and through the vent aperture 80 into the room portion 12.

[0045] According to the illustrated embodiment, the auxiliary fan 102 is an axial flow fan positioned at the inlet of the fan duct 104 (e.g., upstream of the vent opening 80). However, it should be understood that according to alternative embodiments, any other suitable number, type, and configuration of fans or blowers may be used to propel the supplemental air flow. In addition, the auxiliary fan 102 may be positioned at any other suitable location within the air conditioning unit 10, and the auxiliary fan 102 may be positioned at any other suitable location within the fan duct 104 or be in fluid communication therewith. The embodiments described herein are exemplary only and are not intended to limit the scope of the present subject matter.

[0046] Now refer to Figure 7, the operation of the unit 10 will be described in accordance with an exemplary embodiment. More specifically, the operation of the components within the indoor portion 12 during the cooling operation or cooling cycle of the unit 10 will be described. To simplify the discussion, the operation of the auxiliary fan 102 for providing make-up air through the vent aperture 80 will be omitted, for example, as if the vent door 82 is closed. Although the cooling cycle will be described, it will be understood that according to alternative embodiments, the indoor heat exchanger 40 and / or the heating unit 44 are used to heat the indoor air. Moreover, although the operation of the unit 10 is described below with respect to an exemplary complete terminal air conditioning unit, it will be understood that aspects of the present subject matter may be used with any other suitable air conditioning unit, such as a heat pump or split unit system.

[0047] As illustrated, the front portion 24 of the room of the unit 10 generally defines an air inlet 110 and an exhaust vent 112 for circulating an air flow (indicated by arrow 114) throughout the room. In this regard, the indoor fan 42 is generally configured to draw air 114 through the air inlet 110 and force the air flow through the indoor heat exchanger 40 before exhausting the air 114 out of the exhaust vent 112. According to the illustrated embodiment, the air inlet 110 is located near the bottom of the unit 10, and the exhaust vent 112 is located near the top of the unit 10. However, it should be understood that according to alternative embodiments, the air inlet 110 and the exhaust vent 112 may have any other suitable size, shape, location, or configuration.

[0048] During the cooling cycle, the refrigeration circuit 48 is generally configured to push cold refrigerant through the indoor heat exchanger 40 to reduce the temperature of the air flow 114 before discharging it back into the room. Specifically, during cooling operation, the controller 64 can be provided with a target temperature, for example, as set by a user for a desired room temperature. Generally, the components of the refrigeration circuit 48, the outdoor fan 32, the indoor fan 42, and other components of the unit 10 operate to continuously cool the air flow.

[0049] To facilitate operation of the refrigeration circuit 48 and other components of the unit 10, the unit 10 may include various sensors for detecting conditions inside and outside the unit 10. These conditions may be fed to the controller 64, which may make decisions regarding the operation of the unit 10 to correct undesirable conditions or otherwise adjust the air flow 114 into the room. For example, Figure 7 As best illustrated, the unit 10 may include an indoor temperature sensor 120 positioned and configured to measure the indoor temperature of the room. Additionally, the unit 10 may include an indoor humidity sensor 122 positioned and configured to measure the indoor humidity of the room. Thus, the unit 10 may be configured to regulate the air flow 114 entering the room until the measured indoor temperature reaches a desired target temperature and / or humidity level.

[0050] As used herein, "temperature sensor" or equivalents are intended to refer to any suitable type of temperature measurement system or device disposed at any suitable location for measuring a desired temperature. Thus, for example, temperature sensors 120 may each be any suitable type of temperature sensor, such as a thermistor, a thermocouple, a resistance temperature detector, a semiconductor-based integrated circuit temperature sensor, or the like. Additionally, temperature sensors 120 may be positioned at any suitable location and may output a signal, such as a voltage, to a controller that is proportional to and / or indicative of the measured temperature. Although exemplary positioning of temperature sensors is described herein, it should be understood that, according to alternative embodiments, unit 10 may include any other suitable number, type, and location of temperature and / or other sensors.

[0051] As used herein, the term "humidity sensor" or equivalents may be intended to refer to any suitable type of humidity measurement system or device positioned at any suitable location for measuring a desired humidity. Thus, for example, humidity sensor 122 may refer to any suitable type of humidity sensor, such as a capacitive digital sensor, a resistive sensor, and a thermal conductivity humidity sensor. Additionally, humidity sensor 122 may be positioned at any suitable location and may output a signal, such as a voltage, to a controller that is proportional to and / or indicative of the measured humidity. Although exemplary positioning of the humidity sensors is described herein, it should be understood that, according to alternative embodiments, unit 10 may include any other suitable number, type, and location of humidity sensors.

[0052] Now that the configuration of the air conditioning unit 10 and the configuration of the controller 64 according to an exemplary embodiment have been presented, an exemplary method 200 for operating a packaged terminal air conditioning unit will be described. Although the following discussion relates to the exemplary method 200 for operating the air conditioning unit 10, those skilled in the art will appreciate that the exemplary method 200 is applicable to operating various other air conditioning appliances. In an exemplary embodiment, the various method steps disclosed herein can be performed by the controller 64 or a separate dedicated controller.

[0053] Now refer to Figure 8, method 200 includes, at step 210, monitoring the operational superheat of the refrigerant passing through the evaporator of the air conditioning unit. In this regard, continuing with the example above, the controller 64 can continuously or periodically determine the superheat within the refrigeration circuit 48. More specifically, for example, when the air conditioning unit 10 is operating in a heat pump mode such that the outdoor heat exchanger 30 acts as an evaporator, the air conditioning unit 10 can monitor the superheat within the outdoor heat exchanger 30. As explained above, the superheat can be determined or measured in any suitable manner. For example, as understood in the art, the operational superheat can be obtained by subtracting the saturated vapor temperature (e.g., as determined by the measured evaporator pressure) from the measured refrigerant temperature leaving the evaporator. Other suitable methods for determining superheat are possible and are within the scope of the present subject matter.

[0054] Step 220 generally includes identifying an overheat fault condition based on at least one of an operating superheat (e.g., as measured in step 210), a target valve position for the electronic expansion valve, or a compressor speed. In this regard, when these parameters fall within a predetermined range or outside of a target range, this may indicate an overheat fault, such as a problem with the expansion device 50 (e.g., an EEV). Failure to adjust the operation of the air conditioning unit 10 to correct the overheat fault condition may result in inefficiency of the air conditioning unit 10 or damage to the air conditioning unit 10. For example, if the overheat fault condition is associated with a superheat that is too low, the refrigerant may enter the compressor 34 as a liquid, thereby causing damage. Conversely, if the overheat fault condition is associated with a superheat that is too high, the heat extraction and efficiency of the system may be low.

[0055] An exemplary manner of identifying an overheat fault condition will be described below. However, it should be understood that other methods of identifying an overheat fault condition may be used while remaining within the scope of the present subject matter. For example, one manner of identifying an overheat fault condition may involve an undesirable low superheat condition. In this regard, identifying an overheat fault condition may include determining that the operating superheat (e.g., measured at step 210) is less than a predetermined lower preheat threshold, and that the target valve position is less than the lower valve position for a predetermined period of time, and further determining that the compressor speed exceeds a compressor speed threshold. According to an exemplary embodiment, if all of these conditions are met, an overheat fault condition should be triggered.

[0056] It should be understood that the predetermined lower preheat threshold, lower valve position, predetermined time period, and compressor speed threshold may be determined in any manner and may vary depending on unit design, ambient conditions, target room conditions, etc. For example, the predetermined lower preheat threshold may be between approximately 0° F. and 4° F., between approximately 0.5° F. and 2° F., or approximately 1° F. According to an exemplary embodiment, the target valve position may be a desired position of the EEV 50 determined by the controller 64, for example, to maintain a desired superheat across the evaporator.

[0057] Additionally, the lower valve position may be any quantitative data representing the position of the EEV 50. For example, the lower valve position may be expressed as a percentage of the EEV 50 being open. In this regard, 0% may refer to the valve being fully closed, while 100% may refer to the valve being fully open. The lower valve position may also refer to the linear position of the valve along its stroke length or the area of ​​the valve opening relative to its maximum area when in the fully open position. According to exemplary embodiments, the lower valve position may be between approximately 2% and 20% open, between approximately 6% and 15% open, or approximately 10% open.

[0058] Additionally, the lower valve position can be quantified by reference to the number of steps the valve has moved within the valve step range. In this regard, as described above, the EEV 50 can move approximately 500 steps between the fully closed position and the fully open position. Thus, a lower number of steps can generally refer to fewer rotations of the stepper motor within the EEV 50, less translation of the valve plunger, and a greater closure of the EEV 50. According to exemplary embodiments, the lower valve position can be between approximately 10 and 150 steps, between approximately 25 and 100 steps, between approximately 40 and 60 steps, or at approximately 50 steps.

[0059] According to exemplary embodiments, the compressor speed threshold may be between approximately 1000 rpm and 3000 rpm, between approximately 1500 rpm and 2500 rpm, or at approximately 2000 rpm. As described above, when these conditions exist, this may indicate a low superheat fault condition. However, to avoid constant triggering during transient operation of the air conditioning unit 10, a predetermined time period may be used to ensure that the condition persists long enough to indicate that a problem actually exists. For example, according to exemplary embodiments, the predetermined time period may be between approximately 30 seconds and 10 minutes, between approximately 1 minute and 5 minutes, between approximately 2 minutes and 4 minutes, or approximately 3 minutes.

[0060] According to another exemplary embodiment, another way to identify an overheat fault condition may involve an undesirable high superheat condition. In this regard, identifying an overheat fault condition may include determining that the operating superheat (e.g., as determined in step 210) is greater than a predetermined upper preheat threshold and that the target valve position is greater than the upper valve position for a predetermined period of time. Generally, the predetermined upper preheat threshold and upper valve position may be similar to the thresholds described above, but applied to a high superheat condition. In this regard, for example, the predetermined upper preheat threshold may be between approximately 5°F and 15°F, approximately 7°F and 13°F, or approximately 10°F. Furthermore, the upper valve position may be between approximately 50% and 95% open, approximately 70% and 90% open, or approximately 80% open. Additionally or alternatively, the upper valve position may be between approximately 300 steps and 450 steps, approximately 350 steps and 425 steps, approximately 375 steps and 410 steps, or at approximately 400 steps. The predetermined time period may be the same as or similar to the time period described above for the low superheat condition.

[0061] According to other embodiments, another way to identify an overheat fault condition may involve identifying a significant difference between the target valve position and then an empirically determined linear position. For example, as described above, the target valve position relates to the position of the EEV 50 that the controller deems necessary to maintain a desired superheat across the evaporator. Generally, the empirically determined linear position of the EEV 50 refers to the expected position of the EEV 50 based on compressor speed, ambient temperature conditions, and empirically determined constants. For example, the empirically determined linear position may be determined using the following equation:

[0062] EEV position = A·ω Comp +B·(T Outdoor -T Indoor )+C

[0063] Among them, the EEV position is the empirically determined linear position;

[0064] A, B, and C are empirically determined constants;

[0065] ω Comp is the compressor speed;

[0066] T Outdoor is the outdoor ambient temperature; and

[0067] T Indoor is the indoor ambient temperature.

[0068] Under normal operating conditions, the target valve position and the empirically determined linear position should be relatively similar. Thus, if the magnitude of the difference between these two values ​​remains greater than an offset threshold for a predetermined amount of time, this may indicate an overheat fault condition. It will be appreciated that the offset threshold may be based on the difference in absolute valve position, the difference in number of steps between the target valve position and the empirically determined linear position, or as a percentage difference relative to a total step range.

[0069] For example, the offset threshold may be between approximately 5% and 40%, between approximately 10% and 30%, or approximately 20% of the step range of the electronic expansion valve. Thus, for example, if the target valve position is 300 steps and the empirically determined linear position is 150 steps, the difference is 150 steps, which is 30% of the total step range. If this 30% offset persists for a predetermined amount of time (e.g., similar to the time period described above), and the offset threshold is 20%, this may trigger an overheat fault condition.

[0070] When an overheat fault condition is identified in step 220, step 230 may include stopping the compressor in response to identifying the overheat fault condition. This may prevent potentially damaging operation of the air conditioning unit 10. Additionally, step 240 may include initiating a calibration or homing process for the electronic expansion valve. Thus, the overheat fault condition may indicate that the controller software position of the electronic expansion valve does not correspond to the actual position of the electronic expansion valve. The calibration process performed in step 240 may be intended to synchronize the software position with the actual position.

[0071] For example, the calibration process may include operating the controller 64 to move the EEV 50 to a fully closed software position and then proceeding to close the EEV 50. In this way, by driving the electronic expansion valve beyond what the software believes to be a closed position, the controller 64 may infer that the electronic expansion valve is actually fully closed. The controller 64 may then set the step position to zero so that the software position and the actual position are reset to zero / closed. In other words, when the physical position is known to be zero (i.e., or fully closed), the software position may be set to zero. According to an exemplary embodiment, a time delay (e.g., 2 minutes) may be implemented after stopping the compressor and before performing the calibration / homing process, for example to allow pressure equalization within the refrigeration circuit. According to other embodiments, an additional time delay may be implemented after calibration before the operating cycle is allowed to be restarted.

[0072] In particular, if the calibration process is successful and there are no other hardware faults within the air conditioning unit 10, subsequent operating cycles of the air conditioning unit 10 will result in no triggering of the overheat fault state. However, repeated and continued triggering of the overheat fault state may indicate a system error other than poor calibration of the electronic expansion valve. Therefore, the controller 64 can be programmed to analyze the faults to determine whether they are repeating at an unexpected rate. For example, when the overheat fault state is identified, the controller can implement a fault counter, but when a successful operating cycle is completed, the fault counter can be cleared. If the fault counter exceeds a predetermined count threshold (e.g., such as a count of 5), the controller 64 can permanently lock the air conditioning unit 10, for example until maintenance is performed or other corrective action is taken.

[0073] According to an alternative embodiment, a fault counter can be used that tracks the number of EEV faults and starts at a predetermined maximum value (such as a count of 5). Each time a cycle in proportional-integral ("PI") control is successfully completed without an EEV fault, or when 24 hours have passed, the counter is incremented by 1 (unless it is at its maximum value). If an EEV overheat fault occurs, the counter can be decremented by 1. If the counter reaches 0, the EEV PI control is locked, and empirically determined linear control is used until the counter is incremented (i.e., 24 hours have passed and the fault counter is incremented by 1).

[0074] Figure 8 The steps are depicted as being performed in a particular order for purposes of illustration and discussion. Using the disclosure provided herein, one of ordinary skill in the art will appreciate that the steps of any method described herein may be adapted, rearranged, expanded, omitted, or modified in various ways without departing from the scope of the present disclosure. Furthermore, while various aspects of method 200 are explained using unit 10 as an example, it should be understood that the method may be applied to operate any suitable air conditioning unit.

[0075] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. If such other examples include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims, then such other examples are intended to be within the scope of the claims.

Claims

1. An air conditioning unit, comprising: a refrigeration circuit comprising a condenser and an evaporator; a compressor operatively coupled to the refrigeration circuit and configured to force refrigerant through the refrigeration circuit; an electronic expansion valve fluidly coupled to the refrigeration circuit; as well as a controller operably coupled to the compressor and the electronic expansion valve, the controller being configured to: monitoring an operational superheat of the refrigerant passing through the evaporator; identifying an overheat fault condition based on at least one of the operational superheat, a target valve position of the electronic expansion valve, or a compressor speed; stopping the compressor in response to identifying the overheat fault condition; as well as Initiating a calibration process of the electronic expansion valve; Wherein, identifying the overheating fault state includes any of the following methods: determining that the operating superheat is less than a predetermined lower preheat threshold and the target valve position is less than a lower valve position for a predetermined period of time; determining that the operational superheat is greater than a predetermined upper preheat threshold and the target valve position is greater than an upper valve position for a predetermined period of time; or It is determined that a magnitude of a difference between the target valve position and an empirically determined linear position of the electronic expansion valve is greater than an offset threshold for a predetermined period of time.

2. The air conditioning unit according to claim 1, wherein: Identifying the overheat fault state further includes: The compressor speed is determined to exceed a compressor speed threshold in addition to determining that the operating superheat is less than a predetermined lower preheat threshold and the target valve position is less than a lower valve position for a predetermined period of time.

3. The air conditioning unit according to claim 1, wherein: The predetermined lower preheat threshold is 1 degree Fahrenheit.

4. The air conditioning unit according to claim 1, wherein: The lower valve position is a 10% open position.

5. The air conditioning unit according to claim 1, wherein: When the step range of the electronic expansion valve extends from 0 steps at the fully closed position to 500 steps at the fully open position, the lower valve position is 50 steps.

6. The air conditioning unit according to claim 2, wherein: The compressor speed threshold is between 1500 rpm and 2500 rpm.

7. The air conditioning unit according to claim 1, wherein: The predetermined time period is between 2 minutes and 4 minutes.

8. The air conditioning unit according to claim 1, wherein: The predetermined upper preheat threshold is 10 degrees Fahrenheit.

9. The air conditioning unit according to claim 1, wherein: The upper valve position is an 80% open position.

10. The air conditioning unit according to claim 1, wherein: When the step range of the electronic expansion valve extends from 0 steps at the fully closed position to 500 steps at the fully open position, the upper valve position is 400 steps.

11. The air conditioning unit according to claim 1, wherein: The offset threshold is 20% of the step range of the electronic expansion valve.

12. The air conditioning unit according to claim 1, wherein: Initiating the calibration process of the electronic expansion valve includes: driving the electronic expansion valve beyond a closed position; and Set the step position to zero.

13. The air conditioning unit according to claim 1, wherein: The controller is further configured to: When the overheat fault condition is identified, incrementing a fault counter; clearing the fault counter upon completion of a successful operation cycle; as well as If the fault counter exceeds a count threshold, the air conditioning unit is locked or an empirically determined linear control mode is initiated.

14. A method of operating an air conditioning unit, the air conditioning unit comprising: a refrigeration circuit comprising a condenser and an evaporator; a compressor operatively coupled to the refrigeration circuit and configured to force refrigerant through the refrigeration circuit; and an electronic expansion valve fluidly coupled to the refrigeration circuit, the method comprising: monitoring an operational superheat of the refrigerant passing through the evaporator; identifying an overheat fault condition based on at least one of the operational superheat, a target valve position of the electronic expansion valve, or a compressor speed; stopping the compressor in response to identifying the overheat fault condition; and Initiating a calibration process of the electronic expansion valve; Wherein, identifying the overheating fault state includes any of the following methods: determining that the operating superheat is less than a predetermined lower preheat threshold and the target valve position is less than a lower valve position for a predetermined period of time; determining that the operational superheat is greater than a predetermined upper preheat threshold and the target valve position is greater than an upper valve position for a predetermined period of time; or It is determined that a magnitude of a difference between the target valve position and an empirically determined linear position of the electronic expansion valve is greater than an offset threshold for a predetermined period of time.

15. The method according to claim 14, wherein Identifying the overheat fault state further includes: The compressor speed is determined to exceed a compressor speed threshold in addition to determining that the operating superheat is less than a predetermined lower preheat threshold and the target valve position is less than a lower valve position for a predetermined period of time.

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