Heat Pump Protection Against High Pressure Trips in Defrost Cycle

This application claims priority from and the benefit of India Provisional Patent Application No. 202421045310, entitled “HEAT PUMP PROTECTION AGAINST HIGH PRESSURE TRIPS IN DEFROST CYCLE,” filed Jun. 12, 2024, which is herein incorporated by reference in its entirety for all purposes.

This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

Embodiments of the present disclosure are generally directed to a heat pump of a heating, ventilation, and/or air conditioning (HVAC) system, and, more specifically, to features of the heat pump that are configured to reduce, negate, or mitigate adverse effects associated with tripping (e.g., compressor tripping of the heat pump).

An HVAC system provides proper ventilation and maintains air quality in a confined space, such as a commercial or household building. For example, the HVAC system circulates a refrigerant through a closed circuit (e.g., a refrigerant loop or circuit, vapor compression loop or circuit) including a compressor, a condenser, an expansion device, and an evaporator. During operation, the system components are subject to various pressure, temperature, and load conditions that may fluctuate depending on ambient temperature, system demand, and operating mode. Certain operating conditions, such as excessively high working fluid pressure, may trigger tripping. While necessary for equipment safety, such tripping may interrupt operation and reduce overall system efficiency and reliability. Accordingly, it is now recognized that improved HVAC systems and/or associated control methods are desired.

A summary of certain embodiments disclosed herein is set forth below. It should be noted that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.

In an embodiment, a heat pump configured to selectively circulate a working fluid includes an outdoor heat exchanger, an indoor heat exchanger, a compressor, a reversing valve configured to direct the working fluid from the compressor to the outdoor heat exchanger or to the indoor heat exchanger, and a controller. The controller is configured to determine whether a pressure of the working fluid exiting the compressor exceeds a pressure threshold, and, in response to determining that the pressure of the working fluid exiting the compressor exceeds the pressure threshold, control the reversing valve to block the working fluid from flowing from the compressor through the reversing valve to the outdoor heat exchanger.

In another embodiment, a method of operating a heat pump includes determining that a pressure of a working fluid exiting a compressor of the heat pump exceeds a pressure threshold, and, in response to determining that the pressure of the working fluid exiting the compressor exceeds the pressure threshold, controlling the reversing valve to block the working fluid from flowing from the compressor through the reversing valve to the outdoor heat exchanger.

In a further embodiment, a heating, ventilation, and air conditioning (HVAC) system includes a heat pump configured to circulate a working fluid through two or more circuits. The heat pump includes a first outdoor heat exchanger in a first circuit, a second outdoor heat exchanger in a second circuit, an indoor heat exchanger, a compressor, a pressure sensor disposed downstream of the compressor to measure a pressure of the working fluid exiting the compressor, a first temperature sensor configured to measure a first temperature of the working fluid within the first outdoor heat exchanger, a reversing valve configured to direct the working fluid from the compressor to the first outdoor heat exchanger, the second outdoor heat exchanger, or the indoor heat exchanger, and a controller. The controller configured to determine whether the pressure exceeds a pressure threshold, determine whether the first temperature exceeds a temperature threshold, and, in response to determining that the pressure exceeds the pressure threshold or the first temperature exceeds the temperature threshold, control the reversing valve to direct the working fluid to flow from the compressor through the reversing valve to the indoor heat exchanger.

One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” “having,” and “based on” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent, however, to one skilled in the art that embodiments of the present disclosure may be practiced without some of these specific details.

As briefly discussed above, a heating, ventilation, and/or air conditioning (HVAC) system may be used to thermally regulate a space within a building, home, or other suitable structure. For example, the HVAC system may include a vapor compression system that transfers thermal energy between a working fluid, such as a refrigerant, and a fluid to be conditioned, such as air. The vapor compression system includes heat exchangers, such as a condenser and an evaporator, which are fluidly coupled to one another via one or more conduits of a working fluid (e.g., a refrigerant) loop or circuit. A compressor may be used to circulate the working fluid through the conduits and other components of the working fluid circuit (e.g., an expansion device) and, thus, enable the transfer of thermal energy between components of the working fluid circuit (e.g., between the condenser and the evaporator) and one or more thermal loads (e.g., an environmental air flow, a supply air flow).

Generally, the compressor receives low-pressure working fluid vapor from the evaporator and compresses it before delivering high-pressure vapor to the condenser, thereby enabling thermal energy transfer for heating or cooling a confined space. Specifically, in a heat pump system, the indoor and outdoor heat exchangers therein alternate between functioning as an evaporator and a condenser depending on the operation mode (e.g., heating mode, cooling mode, and defrost mode). The system may include a reversing valve that operates to reverse the flow of working fluid within the system to facilitate these mode-dependent role changes. In heating mode, the outdoor heat exchanger functions as the evaporator, absorbing heat from the ambient air, while the indoor heat exchanger functions as the condenser, releasing heat to condition the confined space. Conversely, in cooling mode, the roles are reversed: the indoor heat exchanger acts as the evaporator, absorbing heat from the confined space, and the outdoor heat exchanger acts as the condenser, rejecting heat to the ambient environment. During defrost mode, which is typically initiated during heating operation to remove accumulated frost from the outdoor heat exchanger, the system temporarily reverses the working fluid flow from its heating mode configuration, causing the outdoor heat exchanger to operate as a condenser instead of an evaporator. This reversal of the working fluid flow allows the outdoor coil to be heated, thereby melting the accumulated frost and restoring heat transfer efficiency.

However, such reversal may cause an elevated discharge pressure of the working fluid exiting the compressor, potentially triggering high-pressure tripping. While tripping is a protective function initiated by safety controls to prevent damage to the compressor or other system components, frequent or premature tripping can interrupt system operation and reduce overall efficiency. For example, because termination of the defrost mode typically requires the compressor to be operating, a compressor trip during defrost may prevent the heat pump from exiting the defrost mode. As a result, the system may continue operating in defrost mode unintentionally when the compressor subsequently restarts. Accordingly, improvements in heat pump systems and associated control methods are desirable to reduce the occurrence of premature tripping and its adverse effects on system performance.

Present embodiments may monitor the discharge pressure of the working fluid exiting the compressor and terminate the defrost mode operation upon detecting that the discharge pressure exceeds a predetermined pressure threshold. The predetermined pressure threshold is set below the discharge pressure level at which the compressor may trip. In accordance with the present disclosure, a heat pump system includes a controller configured to determine whether the discharge pressure of the working fluid exiting the compressor exceeds the predetermined pressure threshold. When the discharge pressure is equal to or exceeds the predetermined threshold, the controller may terminate defrost mode operation by blocking the working fluid flow from flowing from the compressor to the outdoor heat exchanger. In some embodiments, the controller may be further configured to monitor additional operating conditions (e.g., temperature of the working fluid in the outdoor heat exchanger) and determine whether those operation conditions warrant termination of the defrost mode (e.g., a temperature exceeds a predetermined temperature threshold). In some embodiments, the controller may terminate the defrost mode by controlling operation of the reversing valve. In some embodiments, the controller may further control the reversing valve to operate the heat pump in the heating mode. In some embodiments, the controller may continue with the heating mode operation until frosting is detected at the outdoor heat exchanger. These and other aspects of the present disclosure are described in greater detail below with reference to the drawings.

Turning now to the drawings,illustrates an embodiment of a heating, ventilation, and/or air conditioning (HVAC) system for environmental management that employs one or more HVAC units in accordance with the present disclosure. As used herein, an HVAC system includes any number of components configured to enable regulation of parameters related to climate characteristics, such as temperature, humidity, air flow, pressure, air quality, and so forth. For example, an “HVAC system” as used herein is defined as conventionally understood and as further described herein. Components or parts of an “HVAC system” may include, but are not limited to, all, some of, or individual parts such as a heat exchanger, a heater, an air flow control device, such as a fan, a sensor configured to detect a climate characteristic or operating parameter, a filter, a control device configured to regulate operation of an HVAC system component, a component configured to enable regulation of climate characteristics, or a combination thereof. An “HVAC system” is a system configured to provide such functions as heating, cooling, ventilation, dehumidification, pressurization, refrigeration, filtration, or any combination thereof. The embodiments described herein may be utilized in a variety of applications to control climate characteristics, such as residential, commercial, industrial, transportation, or other applications where climate control is desired.

In the illustrated embodiment, a buildingis air conditioned by a system that includes an HVAC unit. The buildingmay be a commercial structure or a residential structure. As shown, the HVAC unitis disposed on the roof of the building; however, the HVAC unitmay be located in other equipment rooms or areas adjacent the building. The HVAC unitmay be a single package unit containing other equipment, such as a blower, integrated air handler, and/or auxiliary heating unit. In other embodiments, the HVAC unitmay be part of a split HVAC system, such as the system shown in, which includes an outdoor HVAC unitand an indoor HVAC unit.

The HVAC unitis an air-cooled device that implements a refrigeration cycle to provide conditioned air to the building. Specifically, the HVAC unitmay include one or more heat exchangers across which an air flow is passed to condition the air flow before the air flow is supplied to the building. In the illustrated embodiment, the HVAC unitis a rooftop unit (RTU) that conditions a supply air stream, such as environmental air and/or a return air flow from the building. After the HVAC unitconditions the air, the air is supplied to the buildingvia ductworkextending throughout the buildingfrom the HVAC unit. For example, the ductworkmay extend to various individual floors or other sections of the building. In certain embodiments, the HVAC unitmay be a heat pump that provides both heating and cooling to the building with one refrigeration circuit configured to operate in different modes. In other embodiments, the HVAC unitmay include one or more refrigeration circuits for cooling an air stream and a furnace for heating the air stream.

A control device, one type of which may be a thermostat, may be used to designate the temperature of the conditioned air. The control devicealso may be used to control the flow of air through the ductwork. For example, the control devicemay be used to regulate operation of one or more components of the HVAC unitor other components, such as dampers and fans, within the buildingthat may control flow of air through and/or from the ductwork. In some embodiments, other devices may be included in the system, such as pressure and/or temperature transducers or switches that sense the temperatures and pressures of the supply air, return air, and so forth. Moreover, the control devicemay include computer systems that are integrated with or separate from other building control or monitoring systems, and even systems that are remote from the building.

is a perspective view of an embodiment of the HVAC unit. In the illustrated embodiment, the HVAC unitis a single package unit that may include one or more independent vapor compression circuits and components that are tested, charged, wired, piped, and ready for installation. The HVAC unitmay provide a variety of heating and/or cooling functions, such as cooling only, heating only, cooling with electric heat, cooling with dehumidification, cooling with gas heat, or cooling with a heat pump. As described above, the HVAC unitmay directly cool and/or heat an air stream provided to the buildingto condition a space in the building.

As shown in the illustrated embodiment of, a cabinetencloses the HVAC unitand provides structural support and protection to the internal components from environmental and other contaminants. In some embodiments, the cabinetmay be constructed of galvanized steel and insulated with aluminum foil faced insulation. Railsmay be joined to the bottom perimeter of the cabinetand provide a foundation for the HVAC unit. In certain embodiments, the railsmay provide access for a forklift and/or overhead rigging to facilitate installation and/or removal of the HVAC unit. In some embodiments, the railsmay fit into “curbs” on the roof to enable the HVAC unitto provide air to the ductworkfrom the bottom of the HVAC unitwhile blocking elements such as rain from leaking into the building.

The HVAC unitincludes heat exchangersandin fluid communication with one or more vapor compression circuits. Tubes within the heat exchangersandmay circulate a working fluid (e.g., a refrigerant), such as R-410A, R-407, R-134a, R-1234ze, R1233zd, R-32, hydrofluoro olefin (HFO), “natural” refrigerants like ammonia (NH3), R-717, carbon dioxide (CO2), R-744, or hydrocarbon based refrigerants, water vapor, or any other suitable working fluid through the heat exchangersand. As will be appreciated, different working fluid may include different saturation properties depending on chemical composition and mixture composition. The tubes may be of various types, such as multichannel tubes, conventional copper or aluminum tubing, and so forth. Together, the heat exchangersandmay implement a thermal cycle in which the working fluid undergoes phase changes and/or temperature changes as it flows through the heat exchangersandto produce heated and/or cooled air. For example, the heat exchangermay function as a condenser where heat is released from the working fluid to ambient air, and the heat exchangermay function as an evaporator where the working fluid absorbs heat to cool an air stream. In other embodiments, the HVAC unitmay operate in a heat pump mode where the roles of the heat exchangersandmay be reversed. That is, the heat exchangermay function as an evaporator and the heat exchangermay function as a condenser. In further embodiments, the HVAC unitmay include a furnace for heating the air stream that is supplied to the building. While the illustrated embodiment ofshows the HVAC unithaving two of the heat exchangersand, in other embodiments, the HVAC unitmay include one heat exchanger or more than two heat exchangers.

The heat exchangeris located within a compartmentthat separates the heat exchangerfrom the heat exchanger. Fansdraw air from the environment through the heat exchanger. Air may be heated and/or cooled as the air flows through the heat exchangerbefore being released back to the environment surrounding the HVAC unit. A blower assembly, powered by a motor, draws air through the heat exchangerto heat or cool the air. The heated or cooled air may be directed to the buildingby the ductwork, which may be connected to the HVAC unit. Before flowing through the heat exchanger, the conditioned air flows through one or more filtersthat may remove particulates and contaminants from the air. In certain embodiments, the filtersmay be disposed on the air intake side of the heat exchangerto prevent contaminants from contacting the heat exchanger.

The HVAC unitalso may include other equipment for implementing the thermal cycle. Compressorsincrease the pressure and temperature of the working fluid before the working fluid enters the heat exchanger. The compressorsmay be any suitable type of compressors, such as scroll compressors, rotary compressors, screw compressors, or reciprocating compressors. In some embodiments, the compressorsmay include a pair of hermetic direct drive compressors arranged in a dual stage configuration. However, in other embodiments, any number of the compressorsmay be provided to achieve various stages of heating and/or cooling. As may be appreciated, additional equipment and devices may be included in the HVAC unit, such as a solid-core filter drier, a drain pan, a disconnect switch, an economizer, pressure switches, phase monitors, and humidity sensors, among other things.

The HVAC unitmay receive power through a terminal block. For example, a high voltage power source may be connected to the terminal blockto power the equipment. The operation of the HVAC unitmay be governed or regulated by a control board. The control boardmay include control circuitry connected to a thermostat, sensors, and alarms. One or more of these components may be referred to herein separately or collectively as the control device. The control circuitry may be configured to control operation of the equipment, provide alarms, and monitor safety switches. Wiringmay connect the control boardand the terminal blockto the equipment of the HVAC unit.

illustrates a residential heating and cooling system, also in accordance with present techniques. The residential heating and cooling systemmay provide heated and cooled air to a residential structure, as well as provide outside air for ventilation and provide improved indoor air quality (IAQ) through devices such as ultraviolet lights and air filters. In the illustrated embodiment, the residential heating and cooling systemis a split HVAC system. In general, a residenceconditioned by a split HVAC system may include working fluid conduitsthat operatively couple the indoor unitto the outdoor unit. The indoor unitmay be positioned in a utility room, an attic, a basement, and so forth. The outdoor unitis typically situated adjacent to a side of residenceand is covered by a shroud to protect the system components and to prevent leaves and other debris or contaminants from entering the unit. The working fluid conduitstransfer working fluid between the indoor unitand the outdoor unit, typically transferring primarily liquid working fluid in one direction and primarily vaporized working fluid in an opposite direction.

When the system shown inis operating as an air conditioner, a heat exchangerin the outdoor unitserves as a condenser for re-condensing vaporized working fluid flowing from the indoor unitto the outdoor unitvia one of the working fluid conduits. In these applications, a heat exchangerof the indoor unit functions as an evaporator. Specifically, the heat exchangerreceives liquid working fluid, which may be expanded by an expansion device, and evaporates the working fluid before returning it to the outdoor unit.

The outdoor unitdraws environmental air through the heat exchangerusing a fanand expels the air above the outdoor unit. When operating as an air conditioner, the air is heated by the heat exchangerwithin the outdoor unitand exits the unit at a temperature higher than it entered. The indoor unitincludes a blower or fanthat directs air through or across the indoor heat exchanger, where the air is cooled when the system is operating in air conditioning mode. Thereafter, the air is passed through ductworkthat directs the air to the residence. The overall system operates to maintain a desired temperature as set by a system controller. When the temperature sensed inside the residenceis higher than the set point on the thermostat, or the set point plus a small amount, the residential heating and cooling systemmay become operative to refrigerate additional air for circulation through the residence. When the temperature reaches the set point, or the set point minus a small amount, the residential heating and cooling systemmay stop the refrigeration cycle temporarily.

The residential heating and cooling systemmay also operate as a heat pump. When operating as a heat pump, the roles of heat exchangersandare reversed. That is, the heat exchangerof the outdoor unitwill serve as an evaporator to evaporate working fluid and thereby cool air entering the outdoor unitas the air passes over the outdoor heat exchanger. The indoor heat exchangerwill receive a stream of air blown over it and will heat the air by condensing the working fluid.

In some embodiments, the indoor unitmay include a furnace system. For example, the indoor unitmay include the furnace systemwhen the residential heating and cooling systemis not configured to operate as a heat pump. The furnace systemmay include a burner assembly and heat exchanger, among other components, inside the indoor unit. Fuel is provided to the burner assembly of the furnacewhere it is mixed with air and combusted to form combustion products. The combustion products may pass through tubes or piping in a heat exchanger, separate from heat exchanger, such that air directed by the blower or fanpasses over the tubes or pipes and extracts heat from the combustion products. The heated air may then be routed from the furnace systemto the ductworkfor heating the residence.

is an embodiment of a vapor compression systemthat can be used in any of the systems described above. The vapor compression systemmay circulate a working fluid through a circuit starting with a compressor. The circuit may also include a condenser, an expansion valve(s) or device(s), and an evaporator. The vapor compression systemmay further include a control panelthat has an analog to digital (A/D) converter, a microprocessor, a non-volatile memory, and/or an interface board. The control paneland its components may function to regulate operation of the vapor compression systembased on feedback from an operator, from sensors of the vapor compression systemthat detect operating conditions, and so forth.

In some embodiments, the vapor compression systemmay use one or more of a variable speed drive (VSDs), a motor, the compressor, the condenser, the expansion valve or device, and/or the evaporator. The motormay drive the compressorand may be powered by the variable speed drive (VSD). The VSDreceives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor. In other embodiments, the motormay be powered directly from an AC or direct current (DC) power source. The motormay include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor.

The compressorcompresses a working fluid vapor and delivers the vapor to the condenserthrough a discharge passage. In some embodiments, the compressormay be a centrifugal compressor. The working fluid vapor delivered by the compressorto the condensermay transfer heat to a fluid passing across the condenser, such as ambient or environmental air. The working fluid vapor may condense to a working fluid liquid in the condenseras a result of thermal heat transfer with the environmental air. The liquid working fluid from the condensermay flow through the expansion deviceto the evaporator.

The liquid working fluid delivered to the evaporatormay absorb heat from another air stream, such as a supply air streamprovided to the buildingor the residence. For example, the supply air streammay include ambient or environmental air, return air from a building, or a combination of the two. The liquid working fluid in the evaporatormay undergo a phase change from the liquid working fluid to a working fluid vapor. In this manner, the evaporatormay reduce the temperature of the supply air streamvia thermal heat transfer with the working fluid. Thereafter, the vapor working fluid exits the evaporatorand returns to the compressorby a suction line to complete the cycle.

In some embodiments, the vapor compression systemmay further include a reheat coil. In the illustrated embodiment, the reheat coil is represented as part of the evaporator. The reheat coil is positioned downstream of the evaporator heat exchanger relative to the supply air streamand may reheat the supply air streamwhen the supply air streamis overcooled to remove humidity from the supply air streambefore the supply air streamis directed to the buildingor the residence.

It should be appreciated that any of the features described herein may be incorporated with the HVAC unit, the residential heating and cooling system, or other HVAC systems. Additionally, while the features disclosed herein are described in the context of embodiments that directly heat and cool a supply air stream provided to a building or other load, embodiments of the present disclosure may be applicable to other HVAC systems as well. For example, the features described herein may be applied to mechanical cooling systems, free cooling systems, chiller systems, or other heat pump or refrigeration applications. Further, a heat pump in any of the HVAC systems illustrated inand/or any other suitable HVAC system may include, as described in greater detail with reference to later drawings below, a controller configured to block tripping (e.g., tripping caused by elevated working fluid pressure) during defrost mode by terminating the defrost mode upon detecting certain operating conditions of the heat pump. For example, the controller may be configured to monitor, via a pressure sensor, the discharge pressure of the working fluid exiting the compressor and terminate, via control of a reversing valve, the defrost mode operation upon detecting that the discharge pressure exceeds a predetermined pressure threshold. Detailed aspects of the heat exchanger, including detailed aspects of the controller, the pressure sensor, and the reversing valve, are described below with reference to later drawings.

is a block diagram of an embodiment of a portion of an HVAC systemincluding a heat pump, in accordance with an aspect of the present disclosure. A vapor compression system(e.g., vapor compression systemof) is incorporated into the heat pumpto circulate a working fluid through a circuit starting with a compressor(e.g., compressorofand compressorof). The circuit may also include a reversing valve, an outdoor heat exchanger(e.g., outdoor heat exchanger), an expansion device (e.g., expansion valve), and an indoor heat exchanger(e.g., indoor heat exchanger).

In some embodiments, the compressor, the reversing valve, the outdoor heat exchanger, and the expansion devicemay be housed in an outdoor unit (e.g., outdoor unitof) disposed outside the building (e.g., buildingof) that contains the space conditioned by the heat pump. A piping system may be provided between the components within the outdoor unit to facilitate the flow of the working fluid. In some embodiments, the outdoor unit may include one or more outdoor fans (e.g., fanof) configured to generate airflow across the outdoor heat exchanger.

The indoor heat exchangermay be housed within an indoor unit (e.g., indoor unit) located inside of the building, such as in a utility room, an attic, a basement, and so forth. The indoor unit may include an indoor fan (e.g., fanof) configured to direct supply air across the heat exchanger coils of the indoor heat exchanger, thereby heating or cooling the air depending on the operating mode. The conditioned supply air may then be distributed to the interior space of the building through a ductwork system (e.g., ductworkofand ductworkof) or other air distribution system. The indoor unit and the outdoor unit may be fluidly coupled via one or more working fluid conduits (e.g., working fluid conduitsof) to form a working fluid circuit (e.g., loop).

The outdoor heat exchangermay be configured to facilitate thermal exchange between the working fluid and ambient air, and the indoor heat exchangermay be configured to facilitate thermal exchange between the working fluid and the air within the conditioned space. The outdoor heat exchangerand the indoor heat exchangermay, respectively, include one or more heat exchanger coils for circulating the working fluid. As such, the heat pumpmay operate to heat or cool the space by selectively transferring thermal energy between the indoor air and the ambient air.

To heat the space, thermal energy may be absorbed from the ambient air by the outdoor heat exchangerand transferred via the working fluid to the indoor heat exchangerfor delivery into the conditioned space. Conversely, to cool the space, thermal energy may be absorbed from the indoor air by the indoor heat exchangerand transferred via the working fluid to the outdoor heat exchangerfor discharge to the ambient air. The direction of heat transfer may be controlled by the reversing valve, and the expansion devicemay facilitate pressure and temperature regulation of the working fluid to support efficient heating or cooling operations.

The heat pumpmay be configured to switch among multiple operating modes, such as heating mode, cooling mode, and defrost mode, by using the reversing valveto control the direction of working fluid flow within the vapor compression circuit. In heating mode, the reversing valvedirects high-pressure working fluid from the compressorto the indoor heat exchanger. In cooling mode, the reversing valvereverses the flow, routing the high-pressure working fluid from the compressorto the outdoor heat exchanger. In defrost mode, which typically initiates from the heating mode during cold weather conditions, the heat pumpmay temporarily operate in a cooling configuration to melt frost that has accumulated on the outdoor heat exchanger. During defrost mode, the reversing valveredirects the heated working fluid to the outdoor heat exchanger, raising its temperature and causing the frost to melt. In some embodiment, the systemmay disable the indoor fan (e.g., fanof) and/or activate auxiliary heating elements during the defrost cycle to maintain comfort within the conditioned space. Once the outdoor heat exchangerhas been sufficiently defrosted, the heat pumpmay automatically return to heating mode and resume normal operation.

Specifically, the reversing valvemay selectively route the discharge of the compressorto either the outdoor heat exchangeror the indoor heat exchanger, while routing the return flow from the other heat exchanger back to the compressorto complete the circuit. For example, in heating mode, the reversing valvemay route the high-pressure discharge from the compressorto the indoor heat exchangerand route the low-pressure return flow from the outdoor heat exchangerback to the compressor. Conversely, in cooling mode, the reversing valvemay route the discharge from the compressorto the outdoor heat exchangerand route the return flow from the indoor heat exchangerback to the compressor.

In some embodiments, the reversing valvemay have a first portin fluid communication with a discharge portof the compressorand a second portin fluid communication with an inlet portof the compressor. Further, the reversing valvemay have a third portin fluid communication with the outdoor heat exchanger(e.g., an inlet portthereof) and a fourth portin fluid communication with the indoor heat exchanger(e.g., an inlet portthereof). The reversing valveselectively establishes communication between the ports,,, anddepending upon mode of operation of the heat pump.

For example, referring to, a block diagram of an embodiment of the portion of the HVAC systeminwhere the heat pumpis operating in heating mode is illustrated, in accordance with an aspect of the present disclosure. In heating mode, the outdoor heat exchangerfunctions as an evaporator and the indoor heat exchangerfunctions as a condenser. The reversing valveconnects the first portto the fourth port, thereby routing the high-pressure discharge from the compressorto the indoor heat exchanger(e.g., via the inlet port). Simultaneously, the reversing valveconnects the third portto the second port, thereby routing the low-pressure return flow from the outdoor heat exchangerback to the compressor(e.g., via the inlet port).

Thus, in heating mode, the vapor compression circuit may operate as follows: low-pressure, low-temperature working fluid enters the compressor, where it is compressed into a high-pressure, high-temperature working fluid (e.g., vapor). The high-pressure, high-temperature working fluid is then discharged from the compressorand directed by the reversing valveto the indoor heat exchanger, which functions as a condenser and exchanges heat with an environment (e.g., a building interior). Within the indoor heat exchanger, the working fluid releases thermal energy to the indoor air and condenses into a high-pressure liquid. The condensed working fluid then flows through the expansion device, where the working fluid is depressurized. The resulting low-pressure working fluid flows into the outdoor heat exchanger, which functions as an evaporator. There, the working fluid absorbs heat from the ambient air and evaporates into a low-pressure vapor, which then returns to the compressorto complete the cycle.

As another example, referring to, a block diagram of an embodiment of the portion of the HVAC systeminwhere the heat pumpis operating in cooling mode or defrost mode is illustrated, in accordance with an aspect of the present disclosure. In cooling mode or defrost mode, the indoor heat exchangerfunctions as an evaporator and the outdoor heat exchangerfunctions as a condenser. The reversing valveconnects the first portto the third port, thereby routing the high-pressure discharge from the compressorto the outdoor heat exchanger(e.g., via the inlet port). Simultaneously, the reversing valveconnects the fourth portto the second port, thereby routing the low-pressure return flow from the indoor heat exchangerback to the compressor(e.g., via the inlet port).

Thus, in cooling mode, the vapor compression circuit may operate as follows: low-pressure, low-temperature working fluid enters the compressor, where it is compressed into a high-pressure, high-temperature working fluid (e.g., vapor). The high-pressure, high-temperature working fluid is then discharged from the compressorand directed by the reversing valveto the outdoor heat exchanger, which functions as a condenser and exchanges heat with an outdoor environment. Within the outdoor heat exchanger, the working fluid releases thermal energy to the ambient air and condenses into a high-pressure liquid. The condensed working fluid then flows through the expansion device, where the working fluid is depressurized. The resulting low-pressure working fluid flows into indoor heat exchanger, which functions as an evaporator. There, the working fluid absorbs heat from the indoor air, cooling the conditioned space, and evaporates into a low-pressure vapor, which then returns to the compressorto complete the cycle.

Similarly, in defrost mode, the heat pumpmay temporarily operate in a configuration similar to cooling mode in order to remove frost or ice accumulation on the outdoor heat exchanger. The reversing valvemay redirect the high-pressure, high-temperature working fluid from the compressorto the outdoor heat exchanger, which functions as a condenser. As such, thermal energy may be released to the outdoor coil to melt any accumulated frost.

Returning to, the heat pumpmay further include a controller(e.g., an automation control system, a programmable logic controller) configured to manage operation of the vapor compression circuit. The controllermay include processing circuitry(e.g., a processor system including one or more processors). The processing circuitrymay include multiple microprocessors, one or more “general-purpose” microprocessors, one or more special-purpose microprocessors, and/or one or more application specific integrated circuits (ASICS), or some combination thereof. For example, the processing circuitrymay include one or more reduced instruction set (RISC) processors.