SYSTEM AND METHOD FOR CONTROLLING OPERATION OF A HEAT PUMP

Abstract

Described herein is a system and a method for controlling operation of a heat pump. The system comprises an electronic expansion valve (EXV) configured to fluidically connect an indoor unit of the heat pump with an outdoor unit of the heat pump, and a controller operatively connected to the EXV, where the controller is configured to issue a first control signal, during a first defrost mode, to at least partially close the EXV to increase discharge pressure in an outdoor coil of the outdoor unit to facilitate defrosting of the outdoor coil.

Claims

1. A system for controlling operation of a heat pump, the system comprising: an electronic expansion valve (EXV) configured to fluidically connect an indoor unit of the heat pump with an outdoor unit of the heat pump; and a controller operatively connected to the EXV, the controller configured to: issue a first control signal, during a first defrost mode, to at least partially close the EXV to increase discharge pressure in an outdoor coil of the outdoor unit to facilitate defrosting of the outdoor coil.

2. The system of claim 1, wherein a closing percentage of the EXV is based on temperature and/or flow rate of outdoor air flowing across the outdoor coil.

3. The system of claim 1, wherein during the first defrost mode, responsive to the discharge pressure in the outdoor coil reaching a ceiling discharge pressure, the controller is configured to issue a first actuation signal to completely open the EXV to keep the discharge pressure in the outdoor coil below the ceiling discharge pressure.

4. The system of claim 1, wherein responsive to substantially zero flow of air across the outdoor coil during the first defrost mode, the controller is configured to issue a second actuation signal to open the EXV at 100% to keep the discharge pressure in the outdoor coil below a tipping point discharge pressure.

5. The system of claim 1, wherein the controller is further configured to issue a second control signal, during a second defrost mode, to enable and control flow of hot or warm refrigerant from a compressor associated with the heat pump to the outdoor coil, to facilitate defrosting of the outdoor coil.

6. The system of claim 5, wherein responsive to the second control signal during the second defrost mode, the controller is configured to completely close the EXV for a period of time to retain the hot or warm refrigerant within the outdoor coil for the period of time to facilitate defrosting of the outdoor coil.

7. A method for controlling operation of a heat pump, the heat pump comprising an electronic expansion valve (EXV) fluidically connecting an indoor unit of the heat pump with an outdoor unit of the heat pump and a controller operatively connected to the EXV, the method comprising the steps of: issuing, by the controller, a first control signal, during a first defrost mode, to at least partially close the EXV to increase discharge pressure in an outdoor coil of the outdoor unit to facilitate defrosting of the outdoor coil.

8. The method of claim 7, wherein a closing percentage of the EXV is based on temperature and/or flow rate of outdoor air flowing across the outdoor coil.

9. The method of claim 7, wherein responsive to the discharge pressure in the outdoor coil reaching a ceiling discharge pressure during the first defrost mode, the method comprises the step of issuing, by the controller, a first actuation signal to completely open the EXV to keep the discharge pressure in the outdoor coil below the ceiling discharge pressure.

10. The method of claim 7, wherein responsive to substantially zero flow of air across the outdoor coil during the first defrost mode, the method comprises the step of issuing, by the controller, a second actuation signal to open the EXV at 100% to keep the discharge pressure in the outdoor coil below a tipping point discharge pressure.

11. The method of claim 7, wherein during a second defrost mode, the method comprises the step of issuing, by the controller, a second control signal to enable and control flow of hot or warm refrigerant from a compressor associated with the heat pump to the outdoor coil, to facilitate defrosting of the outdoor coil.

12. The method of claim 11, wherein responsive to the second control signal during the second defrost mode, the method comprises the step of completely closing the EXV for a period of time to retain the hot or warm refrigerant within the outdoor coil for the period of time to facilitate defrosting of the outdoor coil.

13. A heat pump comprising: an indoor unit fluidically connected to an outdoor unit via a compressor and an electronic expansion valve (EXV); a controller connected to the compressor and the EXV, wherein the controller is configured to: issue a first control signal, during a first defrost mode, to at least partially close the EXV to increase discharge pressure in an outdoor coil of the outdoor unit to facilitate defrosting of the outdoor coil.

14. The heat pump of claim 13, wherein a closing percentage of the EXV is based on temperature and/or flow rate of outdoor air flowing across the outdoor coil.

15. The heat pump of claim 13, wherein responsive to the discharge pressure in the outdoor coil reaching a ceiling discharge pressure during the first defrost mode, the controller is configured to issue a first actuation signal to completely open the EXV to keep the discharge pressure in the outdoor coil below the ceiling discharge pressure.

16. The heat pump of claim 13, wherein responsive to substantially zero flow of air across the outdoor coil during the first defrost mode, the controller is configured to issue a second actuation signal to open the EXV at 100% to keep the discharge pressure in the outdoor coil below a tipping point discharge pressure.

17. The heat pump of claim 13, wherein the controller is further configured to issue a second control signal, during a second defrost mode, to enable and control flow of hot or warm refrigerant from the compressor to the outdoor coil, to facilitate defrosting of the outdoor coil.

18. The heat pump of claim 17, wherein responsive to the second control signal during the second defrost mode, the controller is configured to completely close the EXV for a period of time to retain the hot or warm refrigerant within the outdoor coil for the period of time to facilitate defrosting of the outdoor coil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are included to provide a further understanding of the subject disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the subject disclosure and, together with the description, serve to explain the principles of the subject disclosure.

[0017] In the drawings, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

[0018] FIG. 1 illustrates an exemplary schematic representation of a system implemented in a heat pump for controlling operation of the heat pump in accordance with one or more embodiments of the subject disclosure.

[0019] FIG. 2 illustrates exemplary steps involved in a method for controlling the operation of the heat pump in accordance with one or more embodiments of the subject disclosure.

[0020] FIG. 3A illustrates an exemplary representation of FIG. 1 depicting the operation of the heat pump during a first defrost mode, in accordance with one or more embodiments of the subject disclosure.

[0021] FIG. 3B illustrates an exemplary representation of FIG. 1 depicting the operation of the heat pump during a second defrost mode, in accordance with one or more embodiments of the subject disclosure.

DETAILED DESCRIPTION

[0022] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject disclosure as defined by the appended claims.

[0023] Various terms are used herein. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[0024] In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the subject disclosure, the components of this disclosure described herein may be positioned in any desired orientation. Thus, the use of terms such as above, below, upper, lower, first, second or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components.

[0025] Heat pumps are widely used for heating and cooling applications due to their efficiency and environmental benefits. Among these, large coil heat pumps may be prevalent in both residential and commercial settings. However, these systems may experience performance issues during the defrost cycle, particularly in windy conditions.

[0026] Wind may carry heat away from the outdoor coils associated with the heat pump, which may reduce the discharge pressure and saturation temperature of the refrigerant in the outdoor coil of the heat pump, thereby reducing the effectiveness of the defrost process, and leading to the accumulation of ice. This may not only hamper the heat pump's efficiency but may also increase wear and tear on the heat pump, shortening its lifespan.

[0027] In an effort to mitigate these issues, some heat pump systems involve electric resistance heaters to assist with the defrost process. While this may be effective in melting accumulated ice, it may introduce several drawbacks. For instance, the use of electric resistance heat may inherently be less efficient than the heat pump's primary operation mode, leading to increased energy consumption and higher operating costs. In addition, the reliance on electric heat for defrosting may not comply with increasingly stringent regulatory standards aimed at reducing energy usage and promoting sustainability, as regulatory bodies are pushing for solutions that limit or eliminate the need for electric resistance heating during defrost cycles.

[0028] Further, using heat extracted from indoor spaces to facilitate defrosting is another common approach. However, this method may lead to a temporary reduction in indoor comfort levels, as the heat intended for maintaining a comfortable indoor environment is diverted to defrost the outdoor coils. This practice may be problematic in regions with extreme weather conditions, where maintaining indoor warmth may be the priority.

[0029] Given these challenges, there is a need for an efficient and effective solution that improves the defrost performance of heat pumps, particularly in windy conditions, without relying on electric resistance heating or compromising indoor comfort.

[0030] Referring to FIG. 1, a system 100 for controlling operation of a heat pump 100A is disclosed. Although the term heat pump is employed herein, those of skill in the art will appreciate that the term is inclusive of air conditioning systems as well. In addition, the teachings of the subject disclosure may be implemented in large coil heat pumps as well as other heat pumps without any limitation. In one or more embodiments, the heat pump 100A may include an outdoor unit 104 connected to an indoor unit 102 by a refrigeration circuit, where the indoor unit 102 may be used to condition air within a space or an area of interest (AOI) (not shown) such as but not limited to a space or room associated with a building and/or a storage space associated with a container or a cargo truck. The indoor unit 102 and the outdoor unit 104 may include heat exchangers that may function as a condenser as well as an evaporator (respectively or vice-versa), based on the mode of operation of the heat pump 100A. In one or more embodiments, the heat pump 100A or refrigeration circuit may include, but not limited to, a compressor 106, an electronic expansion valve (EXV) 108 configured to fluidically connect the indoor unit 102 with the outdoor unit 104, a thermostatic expansion valve (TXV) 110, a reversing valve 112, an accumulator 114, a discharge muffler 116, and an oil separator 118.

[0031] In one or more embodiments, the system 100 may include an outdoor air temperature (OAT) sensor 122 positioned outside the outdoor unit 104 to monitor the temperature of the air outside the outdoor unit 104 or around an outdoor coil 104-1 of the outdoor unit 104, and an outdoor coil temperature (OCT) sensor 124 configured with the outdoor coil 104-1 to monitor the temperature of the refrigerant in the outdoor coil 104-1 or temperature of the outdoor coil 104-1. In addition, the system 100 may include a suction pressure (SP) sensor 126 configured on the suction side of the compressor 106 to monitor the suction pressure of the refrigerant. Further, the system 100 may include a differential pressure sensor or differential pressure transmitter (DPT) 128 configured on the discharge side of the compressor 106 to monitor discharge pressure of the refrigerant discharged from the compressor 106, and a safety device 120 that may be configured to shut off the compressor 106 if the discharge pressure is too high.

[0032] In one or more embodiments, the OAT sensor 122 may be configured to generate ambient temperature data, which the controller 130 may use to determine a potential need for a defrost cycle. For instance, when the ambient temperature data indicates a temperature below a frost threshold, the controller 130 may begin monitoring other system parameters for signs of frost accumulation.

[0033] In some embodiments, the OCT sensor 124 may be a thermistor attached to the outdoor coil 104-1, configured to generate coil temperature data. The coil temperature data may indicate instances of frosting at the outdoor unit 104. The controller 130 may be configured to use the coil temperature data as a primary trigger for initiating a defrost mode, where a coil temperature below freezing during operation signals frost buildup. Further, during a defrost mode, the controller 130 may monitor the coil temperature data to determine completion of the defrost process, terminating the cycle once the temperature rises above a defrost-complete threshold.

[0034] In one or more embodiments, the DPT 128 may include a pressure transducer. The DPT 128 may be configured to generate a signal proportional to the discharge pressure of the refrigerant leaving the compressor 106 (i.e. the discharge pressure). The controller 130 may be configured to modulate the EXV 108 during the first defrost mode based on the discharge pressure, allowing for active management of the discharge pressure relative to target setpoints.

[0035] In one or more embodiments, the system 100 may further include a means for determining the rate of airflow across the outdoor coil 104-1. In one or more embodiments, an airflow sensor (not shown) may be positioned in the air stream of a fan or a blower of the outdoor unit 104, and generate an airflow velocity signal for the controller 130. In other embodiments, the controller 130 may be configured to determine the airflow rate indirectly. For instance, the controller 130 may be configured to determine the airflow rate based on power consumption of the fan, and/or physical design parameters of the fan. In further embodiments, the controller 130 may be configured to determine the airflow rate through a thermodynamic model stored in the memory 130-2. The model may use inputs from any one or a combination of the OAT sensor 122, the OCT sensor 124, and the DPT 128 to determine an expected heat rejection rate. Deviations between the expected and actual performance (determined from sensor data from the sensors 122 to 128) may be used to infer the effect of wind, thereby determining the airflow rate without a dedicated physical sensor.

[0036] In some embodiments, the safety device 120 may include a cutout switch mechanically and electrically integrated into the heat pump 100A. The switch may be positioned along the refrigerant circuit downstream of the compressor 106. In operation, if the discharge pressure exceeds a safety threshold limit (which may be greater than a ceiling discharge pressure), the switch may be configured to open an electrical circuit that supplies power to the compressor 106, thereby halting its operation to prevent over-pressurization damage. As an alternative or as a redundant safety layer, the controller 130 may be configured to execute a software-based safety routine that uses the pressure data from the DPT 128, and command the controller 130 to shut down the compressor 106 if the measured discharge pressure reaches or exceeds the safety threshold limit.

[0037] The system 100 may further include a controller 130 in communication with the EXV 108, and a drive (motor) associated with the compressor 106. The controller 130 may be in further communication with the OAT sensor 122, the OCT sensor 124, the SP sensor 126, the DPT 128, and the safety device 120. In one or more embodiments, the controller 130 may comprise one or more processors 130-1 coupled to a memory 130-2 storing instructions executable by the processors 130-1, which may enable the controller 130 to perform one or more designated operations.

[0038] The one or more processor(s) 130-1 may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, graphical processing units, logic circuitries, and/or any devices that manipulate data based on operational instructions. Among other capabilities, the one or more processor(s) 130-1 may be configured to fetch and execute computer-readable instructions stored in the memory 130-2. The memory 130-2 may store the computer-readable instructions or routines, which may be fetched and executed to create or share the data units to other elements of the controller 130. The memory 130-2 may include any non-transitory storage device including, for example, volatile memory such as Random Access Memory (RAM), or non-volatile memory such as an Erasable Programmable Read-Only Memory (EPROM), flash memory, and the like.

[0039] Referring to FIG. 3A, in one or more embodiments, during a first defrost mode, the controller 130 may be configured to issue a first control signal to the EXV 108, causing the EXV 108 to at least partially close its opening (or outlet) to increase (or build up) the discharge pressure within the outdoor unit 104, which may correspondingly increase the temperature of refrigerant supplied into the outdoor coil 104-1. As a result, the refrigerant (with increased temperature) within the outdoor unit 104 may facilitate in defrosting of the outdoor coil 104-1. In such embodiments, a closing percentage of the EXV 108 may be selected based on the temperature and/or flow rate of outdoor air (wind) flowing across the outdoor coil 104-1. The closing percentage corresponds to amount of the refrigerant allowed to flow through the EXV 108.

[0040] In one or more embodiments, the closing percentage of the opening (outlet) of the EXV 108 during the first defrost mode may be selected between 20 to 90% of the maximum opening size of the EXV 108 but is not limited to the like. In a non-limiting example, when flow rate of wind is moderate, the EXV 108 may be opened up to 70% of the maximum opening size of the EXV 108. Further, when the flow rate of wind is high, the EXV 108 may be opened up to 25% of the maximum opening size of the EXV 108. In such instances, the discharge pressure may increase.

[0041] In one or more embodiments, during the first defrost mode, responsive to the discharge pressure in the outdoor coil 104-1 reaching a ceiling discharge pressure, the controller 130 may be configured to issue a first actuation signal to the EXV 108, which may cause the EXV 108 to completely open the opening (outlet) (at 100%), thereby keeping the discharge pressure in the outdoor coil 104-1 below the ceiling discharge pressure. This may prevent the refrigeration circuit and the outdoor coil 104-1 from over-pressurization or overheating (which may otherwise cause damage to the refrigerant circuit).

[0042] Further, in one or more embodiments, during the first defrost mode, responsive to substantially zero flow of air across the outdoor coil 104-1, the controller 130 may be configured to issue a second actuation signal to the EXV 108 which may cause the EXV 108 to open at 100% (fully open) to keep the discharge pressure in the outdoor coil 104-1 below the tipping point discharge pressure, thereby keeping the outdoor coil 104-1 temperature and pressure within safer limit, as the outside air may not lead to any additional defrosting. In one or more embodiments, the ceiling discharge pressure and the tipping point discharge pressure may be different. For instance, the ceiling discharge pressure may be greater than the tipping point discharge pressure.

[0043] In one or more embodiments, the ceiling discharge pressure and the tipping point discharge pressure may be predetermined values stored in the memory 130-2 of the controller 130. The ceiling discharge pressure and/or the tipping point discharge pressure may be identified based on the mechanical pressure limits of the system components, such as the compressor 106 and the outdoor coil 104-1, and/or the thermodynamic properties of the refrigerant. The ceiling discharge pressure and/or the tipping point discharge pressure may be established during the design and testing phase of the heat pump 100A to ensure safe and reliable operation. In some embodiments, the safety discharge pressure may be a fixed or may be dynamically selected from a lookup table based on inputs, such as the ambient temperature from the OAT sensor 122, the coil temperature from the OCT sensor 124, discharge pressure based on DPT 128, and so on. In one or more embodiments, the ceiling discharge pressure and/or the tipping point discharge pressure may be determined by processing data from any one or a combination of sensors 122 to 128 through a machine learning model.

[0044] Referring to FIG. 3B, in one or more embodiments, during a second defrost mode, the controller 130 may be configured to issue a second control signal to the compressor 106 that may enable and control the flow of hot or warm refrigerant (i.e., refrigerant having temperature greater than a threshold) from the compressor 106 to the outdoor coil 104-1, to facilitate defrosting of the outdoor coil 104-1. Additionally, responsive to the issue of the second control signal, the controller 130 may be configured to completely close the EXV 108 for a period of time to retain the hot or warm refrigerant within the outdoor coil 104-1 for the period of time to facilitate defrosting of the outdoor coil 104-1. As a result, the hot or warm refrigerant available at the compressor 106 may facilitate in defrosting of the outdoor coil 104-1 without retrieving any heat from the indoor unit 102 or the AOI/space (where the indoor unit 102 is present), thereby keeping the indoor condition unaffected from the defrost operation.

[0045] In one or more embodiments, during a heating mode of operation, the reversing valve 112 may be configured such that the refrigerant may flow from a discharge end of the compressor 106, through the reversing valve 112 to an indoor coil 102-1 associated with the indoor unit 102. The indoor unit 102, in this mode of operation, may function as a condenser. The refrigerant may then continue flowing through the piping of the refrigeration circuit through the TXV 110 and EXV 108. Further, the refrigerant may flow into and through the outdoor coil 104-1 associated with the outdoor unit 104, which may function as an evaporator. The refrigerant may then complete the circuit by flowing through the reversing valve 112 to a suction end of the compressor 106.

[0046] In one or more embodiments, during a cooling mode of operation, the reversing valve 112 may be configured so that the refrigerant may flow from the discharge end of the compressor 106 through the reversing valve 112 to the outdoor unit 104. In this mode of operation, the outdoor unit 104 may function as a condenser. The refrigerant may then continue flowing through the EXV 108 and TXV 110 and into and through the indoor unit 102. In this mode of operation, the indoor unit 102 may function as an evaporator. The refrigeration may then complete the circuit by flowing into and through the reversing valve 112 and to the suction end of the compressor 106.

[0047] In one or more embodiments, the controller 130 may be configured to operate the heat pump 100A in either the first or second defrost modes based on a plurality of operational parameters. In one or more embodiments, the controller 130 may be configured to operate the heat pump 100A in the first defrost mode when the operational parameters (such as OAT) are less than a first threshold, and in the second defrost mode when the operational parameters are less than a second threshold. The first threshold may be greater than the second threshold. In one or more embodiments, the controller 130 may be configured to determine the defrost mode based on a temperature differential between the ambient air (from OAT sensor 122) and the refrigerant in the outdoor coil 104-1 (from OCT sensor 124). For example, if this differential is less than a threshold, indicating reduced heat transfer due to frost, the controller 130 may initiate the first defrost mode. The controller 130 may escalate to the second defrost mode if the temperature difference exceeds a differential threshold.

[0048] In one or more embodiments, the compressor 106 may be a fixed-speed compressor 106 or a variable-speed compressor 106, which may be driven by a motor that may operate the compressor 106 at a fixed speed or over a wide range of speeds. The operational characteristics of the motor-driven compressor 106 may enable the compressor 106 to operate or function as a variable capacity heating or cooling system 100. This enables the heat pump 100A to condition a space over a wide range of load conditions while utilizing minimum energy usage.

[0049] During the heating mode, the indoor unit 102 may function as a condenser and the outdoor unit 104 may function as an evaporator. In such embodiments, the compressor 106 may supply high-temperature, high-pressure refrigerant vapor to the indoor unit 102 that may release heat through the coil of the indoor unit 102 and transition the refrigerant to a high-pressure liquid/two-phase mixture and further supply the refrigerant to the EXV 108. The pressure of the refrigerant may then reduce as the refrigerant passes through the EXV 108. The low-pressure refrigerant may then flow into the outdoor coil 104-1 of the outdoor unit 104 (evaporator) where the refrigerant may absorb heat from the outside environment and transition to a low-pressure gas. This low-pressure, hot vapor may then flow to the compressor 106 through the piping after passing through the reversing valve 112 and the accumulator 114 to complete a single cycle.

[0050] During the cooling mode, the indoor unit 102 may function as an evaporator and the outdoor unit 104 may function as a condenser. In such embodiments, the compressor 106 may supply high-temperature, high-pressure refrigerant vapor to the outdoor unit 104. The outdoor unit 104 may then release heat through its outdoor coil 104-1, transitioning the refrigerant to a high-pressure liquid/two-phase mixture, and then supplying it to the EXV 108. The pressure of the refrigerant may reduce as it passes through the EXV 108. The low-pressure refrigerant may then flow into the indoor coil 102-1 of the indoor unit 102 (evaporator) where the indoor coil 102-1 may absorb heat from the indoor environment or space and transition it to a low-pressure gas. This low-pressure, hot vapor refrigerant may then flow back to the compressor 106 through the piping after passing through the reversing valve 112 and the accumulator 114, completing the cooling cycle.

[0051] In one or more embodiments, the accumulator 114 may be configured to store excessive fluid (refrigerant) flowing through the circuit to protect the compressor 106 from flooding. Further, the discharge muffler 116 may be configured to reduce pulsation and noise from the discharge side of the compressor 106. Furthermore, in one or more embodiments, the oil separator 118 may be configured to separate oil from the refrigerant and return it to the compressor 106.

[0052] In one or more embodiments, the controller 130, the drive associated with the compressor 106, the one or more sensors 122-128, and other components of the heat pump 100A may include a transceiver or a communication module to communicatively connect the controller 130 to one or more components of the heat pump 100A through a network via wired and/or wireless media.

[0053] Referring to FIG. 2, method 200 for controlling the operation of a heat pump is disclosed. Method 200 may involve the controller and other components associated with the heat pump and system of FIG. 1.

[0054] Method 200 may include step 202 of issuing, by a controller operatively connected to the EXV and the EXV fluidically connecting an indoor unit with an outdoor unit of the heat pump, a first control signal during a first defrost mode to at least partially close the EXV. As a result, the at least partially closed EXV may increase the discharge pressure and temperature of refrigerant supplied into the outdoor coil of the outdoor unit, thereby facilitating defrosting of the outdoor coil. In one or more embodiments, the closing percentage of the EXV may be selected based on the temperature and/or flow rate of outdoor air flowing across the outdoor coil. In a non-limiting example, the closing percentage of the EXV during the first defrost mode may be selected between 20 to 90% of the maximum opening of the EXV.

[0055] Further, in one or more embodiments, responsive to the discharge pressure in the outdoor coil reaching a ceiling discharge pressure during the first defrost mode, method 200 may include the steps of issuing, by the controller, a first actuation signal to completely open the EXV to keep the discharge pressure in the outdoor coil below the ceiling discharge pressure. This may prevent the refrigeration circuit and the outdoor coil from over-pressurization or overheating.

[0056] Furthermore, in one or more embodiments, responsive to substantially zero flow of air across the outdoor coil during the first defrost mode, method 200 may include the steps of issuing, by the controller, a second actuation signal to open the EXV at 100% to keep the discharge pressure in the outdoor coil below the tipping point discharge pressure, thereby keeping the outdoor coil temperature and pressure within a safer limit, as the outside air may not lead to any additional defrosting.

[0057] In one or more embodiments, during a second defrost mode, method 200 may include step 204 of issuing, by the controller, a second control signal to enable and control the flow of hot or warm refrigerant from a compressor associated with the heat pump to the outdoor coil, to facilitate defrosting of the outdoor coil. Additionally, responsive to the issue of the second control signal during the second defrost mode, method 200 may include the steps of completely closing the EXV for a period of time to retain the hot or warm refrigerant within the outdoor coil for the period of time to facilitate defrosting of the outdoor coil, As a result, the hot or warm refrigerant available at the compressor may facilitate in defrosting of the outdoor coil without retrieving any heat from the indoor unit or the AOI/space, thereby keeping the indoor condition unaffected from the defrost operation.

[0058] In one or more embodiments, during a heating mode of operation of the heat pump, method 200 may include the steps of configuring the reversing valve so that the refrigerant may flow from a discharge end of the compressor, through the reversing valve to the indoor coil associated with the indoor unit (functioning as a condenser). During the heating mode, method 200 may further include the steps of enabling the flow of the refrigerant through the piping of the refrigeration circuit through the TXV and EXV, and further enabling its flow into and through an outdoor coil associated with the outdoor unit (functioning as an evaporator), where the refrigerant may then complete the circuit by flowing through the reversing valve to a suction end of the compressor.

[0059] In one or more embodiments, during a cooling mode of operation of the heat pump, method 200 may include the steps of configuring the reversing valve so that the refrigerant may flow from the discharge end of the compressor through the reversing valve to the outdoor unit (functioning as a condenser). During the cooling mode, method 200 may further include the steps of enabling the flow of the refrigerant through the EXV and TXV and further into and through the indoor unit (functioning as an evaporator), where the refrigeration may then complete the circuit by flowing into and through the reversing valve and to the suction end of the compressor.

[0060] Thus, this disclosure (system and method) addresses the limitations associated with existing defrosting operations implemented in heat pumps, by providing. an efficient and effective solution that may improve the defrost performance of heat pumps, particularly in windy conditions, without relying on electric resistance heating or compromising indoor comfort.

[0061] While the subject disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the subject disclosure as defined by the appended claims. Modifications may be made to adapt a particular situation or material to the teachings of the subject disclosure without departing from the scope thereof. Therefore, it is intended that the subject disclosure not be limited to the particular embodiment disclosed, but that the subject disclosure includes all embodiments falling within the scope of the subject disclosure as defined by the appended claims.

[0062] In interpreting the specification, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms comprises and comprising should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refer to at least one of something selected from the group consisting of A, B, C . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.