Control System for Hvac System

This application claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 63/650,335, entitled “CONTROL SYSTEM FOR HVAC SYSTEM,” filed May 21, 2024, which is incorporated herein 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 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.

Heating, ventilation, and/or air conditioning (HVAC) systems are utilized in residential, commercial, and industrial environments to control environmental properties, such as temperature and humidity, for occupants of the respective environments. An HVAC system may control environmental properties by controlling a supply air flow delivered to the environment. For example, the HVAC system may place the supply air flow in a heat exchange relationship with a refrigerant of a vapor compression circuit to condition the supply air flow. Some thermostats (e.g., communicating thermostats) may provide command data to enable variable operation of certain components of the HVAC system. Other thermostats (e.g., non-communicating thermostats) may provide a simple switching command to the components instead. Thus, operation and/or performance of the HVAC system may be limited when certain thermostats are utilized with the HVAC system.

In an embodiment, a heating, ventilation, and/or air conditioning (HVAC) system includes a thermostat configured to generate a thermostat signal to control a vapor compression system based on a difference between a temperature setpoint and a measured temperature. The HVAC system further includes control circuitry configured to receive the thermostat signal and to determine a target evaporator temperature based on the thermostat signal. Further, the control circuitry is configured to adjust a compressor speed of a compressor based on a difference between the target evaporator temperature and a measured evaporator temperature.

In another embodiment, a method of controlling a heating, ventilation, and/or air conditioning (HVAC) system includes receiving, via control circuitry, a thermostat signal from a thermostat indicative of an instruction to operate a vapor compression system. Additionally, the method includes determining, via the control circuitry, a target evaporator temperature based on the thermostat signal. Furthermore, the method includes generating, via the control circuitry, a control signal to control a compressor speed of a compressor based on a difference between the target evaporator temperature and a measured evaporator temperature.

In another embodiment, a heating, ventilation, and/or air conditioning (HVAC) system includes control circuitry configured to operate in a first mode when connected to a communicating thermostat and configured to operate in a second mode when connected to a non-communicating thermostat. In the first mode, the control circuitry is configured to receive digital communication from the communicating thermostat, determine a target evaporator temperature based on the digital communication, and adjust a compressor speed of a compressor based on the target evaporator temperature. In the second mode, the control circuitry is configured to receive an activation signal from the non-communicating thermostat, set the target evaporator temperature to a predetermined value associated with the activation signal, and adjust the compressor speed of the compressor based on the target evaporator temperature.

One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be 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,” and “having” 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.

As used herein, the terms “approximately,” “generally,” and “substantially,” and so forth, are intended to convey that the property value being described may be within a relatively small range of the property value, as those of ordinary skill would understand. For example, when a property value is described as being “approximately” equal to (or, for example, “substantially similar” to) a given value, this is intended to mean that the property value may be within +/−5%, within +/−4%, within +/−3%, within +/−2%, within +/−1%, or even closer, of the given value. Similarly, when a given feature is described as being “substantially parallel” to another feature, “generally perpendicular” to another feature, and so forth, this is intended to mean that the given feature is within +/−5%, within +/−4%, within +/−3%, within +/−2%, within +/−1%, or even closer, to having the described nature, such as being parallel to another feature, being perpendicular to another feature, and so forth. Further, it should be understood that mathematical terms, such as “planar,” “slope,” “perpendicular,” “parallel,” and so forth are intended to encompass features of surfaces or elements as understood to one of ordinary skill in the relevant art, and should not be rigidly interpreted as might be understood in the mathematical arts. For example, a “planar” surface is intended to encompass a surface that is machined, molded, or otherwise formed to be substantially flat or smooth (within related tolerances) using techniques and tools available to one of ordinary skill in the art. Similarly, a surface having a “slope” is intended to encompass a surface that is machined, molded, or otherwise formed to be oriented at an angle (e.g., incline) with respect to a point of reference using techniques and tools available to one of ordinary skill in the art.

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 loop or circuit (e.g., refrigerant 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). Additionally or alternatively, the HVAC system may include a heat pump (e.g., a heat pump system) having a first heat exchanger (e.g., a heating and/or cooling coil, an indoor coil, the evaporator) positioned within the space to be conditioned, a second heat exchanger (e.g., a heating and/or cooling coil, an outdoor coil, the condenser) positioned in or otherwise fluidly coupled to an ambient environment (e.g., the atmosphere), and a pump (e.g., the compressor) configured to circulate the working fluid (e.g., refrigerant) between the first and second heat exchangers to enable heat transfer between the thermal load (e.g., an air flow to be conditioned) and the ambient environment, for example. The heat pump system is operable to provide both cooling and heating to the space to be conditioned (e.g., a room, zone, or other region within a building) by adjusting a flow of the working fluid through the working fluid circuit. Thus, the heat pump may not include a dedicated heating system, such as a furnace or burner configured to combust a fuel, to enable operation of the HVAC system in the heating mode.

The HVAC system may be configured to operate in various operating modes to condition a supply air flow and to deliver the supply air flow to a space to condition the space. For example, the HVAC system may have a compressor (e.g., in an outdoor unit) that can operate at different (e.g., variable) capacities or stages. Additionally or alternatively, the HVAC system may include a furnace (e.g., a modulating furnace) that can operate at different (e.g., variable) stages or modes. A control system (e.g., a primary control system, a primary control board, primary control circuitry) of the HVAC system may select or adjust the operating mode of the HVAC system to condition the supply air flow more efficiently or effectively, such as based on various operating parameters (e.g., a set point temperature) associated with the HVAC system.

In existing HVAC systems, the control system may be configured to operate the HVAC system in the various operating modes based on signals received from a thermostat. The signals may be indicative of operating parameters used for selecting or adjusting the operating mode of the HVAC system. However, certain thermostats (e.g., non-communicating thermostats) may not provide a portion of the signals typically utilized to adjust variable operation of the HVAC system. As a result, the control system may be unable to operate the HVAC system in various operating modes based on the signals received from such thermostats. For this reason, operation and/or performance of the HVAC system may be limited when certain thermostats are utilized with the HVAC system.

Thus, it is presently recognized that enabling the control system to operate the HVAC system in various operating modes based on signals provided by a conventional or traditional thermostat (e.g., a switching thermostat) may improve operation of the HVAC system. Accordingly, embodiments of the present disclosure are directed to control circuitry (e.g., additional control circuitry, secondary control circuitry) that enables the control system to operate in various operating modes using signals (e.g., electrical signals) transmitted by a traditional or conventional thermostat (e.g., non-communicating thermostat). For example, the control circuitry may provide a predetermined value to be used as a set point for a variable capacity operating parameter. As discussed in further detail below, the value or predetermined value of the operating parameter may be utilized by the control system as a substitute for data that would typically be provided by a communicating (e.g., non-conventional) thermostat. As a result, the control circuitry enables operation of the HVAC system in the various operating modes using signals from conventional, non-communicating thermostats, thereby improving performance of the HVAC system.

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 unitin accordance with present embodiments. 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 and/or integrated air handler. 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 flow, 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.

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 working fluid 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 dehumidification, heating with a heat pump, and/or cooling with a heat pump. As described above, the HVAC unitmay directly cool and/or heat an air flow 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 working fluid circuits. Tubes within the heat exchangersandmay circulate a working fluid (e.g., refrigerant), such as R-454B and/or R32, through the heat exchangersand. 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 flow. In some 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. 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 components.

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 conduits(e.g., refrigerant conduits) that 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.

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, a scroll compressor, a screw compressor, a rotary compressor, or any other suitable type of 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 flow, such as a supply air flowprovided to the buildingor the residence. For example, the supply air flowmay 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 flowvia 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 flowand may reheat the supply air flowwhen the supply air flowis overcooled to remove humidity from the supply air flowbefore the supply air flowis 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 flow 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.

To provide context for the following discussion,is a schematic of an embodiment of a portion of an HVAC systemthat includes a heat pump(e.g., a heat pump system, a reverse-cycle heat pump, an energy efficient heat pump) in accordance with present embodiments. The heat pumpmay include one or more components of the vapor compression systemdiscussed above and/or may be included in any of the systems described above (e.g., the HVAC unit, the heating and cooling system). The heat pumpincludes a first heat exchangerand a second heat exchangerthat are fluidly coupled to one another via a working fluid circuitor working fluid loop (e.g., one or more conduits, refrigerant circuit). The first heat exchangermay be in thermal communication with (e.g., fluidly coupled to) a thermal load(e.g., a room, space, and/or device) serviced by the heat pump, and the second heat exchangermay be in thermal communication with an ambient environment(e.g., the atmosphere, outdoor environment) surrounding the HVAC system.

In some embodiments, a first fan(e.g., blower) may direct a first air flow across the first heat exchangerto facilitate heat exchange between working fluid within the first heat exchangerand the thermal load, while a second fanmay direct a second air flow across the second heat exchangerto facilitate heat exchange between working fluid within the second heat exchangerand the ambient environment. Thus, the heat pumpmay be an air-source heat pump. One or more electronic expansion valves (EEV)(e.g., a bi-directional expansion valve) may be disposed along the working fluid circuitbetween the first heat exchangerand the second heat exchangerand may be configured to regulate (e.g., throttle) a flow of working fluid and/or a working fluid pressure differential between the first and second heat exchangers,.

The heat pumpalso includes a compressor(e.g., compressor system, positive displacement compressor) disposed along the working fluid circuit. The compressoris configured to direct working fluid flow through the first heat exchanger, the second heat exchanger, and remaining components (e.g., the EEV(s)) that may be fluidly coupled to the working fluid circuit. Although one compressoris shown in the illustrated embodiment, the heat pumpmay include any suitable quantity of compressors, such as two, three, four, five, six, or more than six compressors. The compressormay be a fixed speed compressor, a multi-stage (e.g., two stage) compressor, and/or a variable speed compressor. Additionally, the compressormay be a rotary compressor, a scroll compressor, a screw compressor, or any other suitable type of compressor (e.g., high-side shell compressor, positive displacement compressor).

The compressoris configured to receive working fluid (e.g., a primary flow of working fluid) via a suction conduitfluidly coupled to a suction portof the compressorand to discharge working fluid (e.g., compressed working fluid) via a discharge conduitfluidly coupled to a discharge portof the compressor. Further, the compressoris also configured to receive an injected flow of working fluid (e.g., a secondary flow of working fluid) via one or more injection portsof the compressor, as described in further detail below. As shown, the one or more injection portsmay be configured to direct the injected flow of working fluid into the compressorat an intermediate location between the suction portand the discharge portof the compressor. That is, the one or more injection portsare configured to direct the injected flow of working fluid into the compressordownstream of the suction portand upstream of the discharge port, relative to a flow direction of working fluid through the compressor. In some embodiments, the compressormay include multiple injection portspositioned at different intermediate locations along the compressor(e.g., along a working fluid flow path of the compressorfrom the suction portto the discharge port).

The compressormay be fluidly coupled to a remainder of the working fluid circuitvia a reversing valve(e.g., a switch-over valve). In the illustrated embodiment, the reversing valveincludes a first portthat is fluidly coupled to the suction conduit, a second portthat is fluidly coupled to the discharge conduit, a third portthat is fluidly coupled to a first conduit portionof the working fluid circuitextending to the first heat exchanger, and a fourth portthat is fluidly coupled to a second conduit portionof the working fluid circuitextending to the second heat exchanger.

The reversing valveis configured to transition between a first configuration, in which the reversing valvefluidly couples the first portand the fourth portand fluidly couples the second portand the third port, and a second configuration(), in which the reversing valvefluidly couples the first portand the third portand fluidly couples the second portand the fourth port. Accordingly, in the first configuration, the reversing valveenables the compressorto receive a flow of working fluid (e.g., via the suction port) from the second heat exchangerand to discharge a flow of working fluid (e.g., via the discharge port) to the first heat exchanger. Conversely, in the second configuration, the reversing valveenables the compressorto receive a flow of working fluid (e.g., via the suction port) from the first heat exchangerand to discharge a flow of working fluid (e.g., via the discharge port) to the second heat exchanger. In this way, while in the first configuration, the reversing valveenables the heat pumpto operate in a heating mode, in which the first heat exchangerrejects thermal energy to the thermal loadto heat the thermal load and the second heat exchangerabsorbs thermal energy from the ambient environment. Further, while in the second configuration, the reversing valveenables the heat pumpto operate in a cooling mode, in which the first heat exchangerabsorbs thermal energy from the thermal loadto cool the thermal load and the second heat exchangerrejects the absorbed thermal energy (e.g., absorbed from the thermal load) to the ambient environment. As such, while the reversing valveis in the first configuration, the compressormay direct a working fluid flow along at least a portion of the working fluid circuitin a first flow direction. While the reversing valveis in the second configuration, the compressormay direct a working fluid flow along at least a portion of the working fluid circuitin a second flow direction, opposite the first flow direction. For clarity, the heat pump(e.g., energy efficient heat pump) is shown configured for operation in a heating mode in the illustrated embodiment of. Moreover,is a schematic of an embodiment of a portion of the HVAC systemillustrating the heat pump(e.g., energy efficient heat pump) configured for operation in a cooling mode.

The present discussion continues with reference to. The heat pumpmay also include additional components, such as an accumulatorand/or a compensator. The accumulatoris generally configured to enable control of an amount of liquid working fluid circulating in the working fluid circuit. For example, the accumulatormay enable adjustment in the amount of liquid working fluid circulating in the working fluid circuitin low ambient conditions (e.g., cold temperatures in the ambient environment). The compensatormay also be configured to enable control of an amount of working fluid circulating in the working fluid circuit. For example, the compensatormay be configured to retain a portion of working fluid therein during the heating mode of the heat pump, such that the portion of retained working fluid does not circulate through the working fluid circuit(e.g., in the first flow direction), to improve operation of the heat pumpin the heating mode.

As mentioned above, the heat pumpis also configured to enable injection of working fluid into the compressor. Specifically, present embodiments include the heat pumpconfigured to divert a portion of working fluid within the working fluid circuitand to inject the portion of working fluid into the compressorvia the injection portof the compressor. To this end, the heat pump(e.g., the working fluid circuit) includes an injection conduitextending from a liquid conduit portion(e.g., a third conduit portion) of the working fluid circuitto the injection portof the compressor. As shown, the liquid conduit portionextends between the first heat exchangerand the second heat exchanger. Thus, working fluid directed through the liquid conduit portionmay be in a liquid phase in both the heating mode and cooling mode of the heat pump. For example, in the heating mode, the working fluid may flow along the working fluid circuitthrough (e.g., sequentially through) the first conduit portion, the first heat exchanger, the liquid conduit portion, the second heat exchanger, and the second conduit portion.

In the heating mode, liquid working fluid may be directed along the liquid conduit portion(e.g., in the first flow direction) from the first heat exchangertoward the second heat exchanger. As indicated by arrow, a portion the working fluid within the liquid conduit portionmay be diverted to the injection conduitfor injection into the compressorvia the injection port. The working fluid may be provided to the injection portas a vapor working fluid or as a liquid-vapor mixture of working fluid. To this end, the heat pumpincludes an injection electronic expansion valve (EEV)disposed along the injection conduit. For example, the injection EEVmay be an electronic expansion valve (EEV), a modulating valve, a solenoid valve, a fixed orifice, a capillary tube, or a combination thereof. Thus, the injection EEVmay operate to reduce a pressure and/or a temperature of (e.g., “flash”) the portion of the working fluid directed from the liquid conduit portionto the injection conduit, which may cause the working fluid within the injection conduitto vaporize or partially vaporize. The injection EEVmay also be controlled to enable adjustment of the flow of working fluid directed along the injection conduitto the injection portof the compressor, as discussed further below.

The HVAC systemmay also include a controller(e.g., a control system, a thermostat, a control panel, control circuitry, automation controller) that is communicatively coupled to one or more components of the heat pumpand is configured to monitor, adjust, and/or otherwise control operation of one or more components of the heat pump. For example, one or more control transfer devices, such as wires, cables, wireless communication devices, and the like, may communicatively couple the compressor, the EEV(s), the first and/or second fans,, the control device(e.g., a thermostat), and/or any other suitable components of the HVAC systemto the controller. That is, the compressor, the EEV(s), the first and/or second fans,, and/or the control devicemay each have one or more communication components that facilitate wired or wireless (e.g., via a network) communication with the controller. In some embodiments, the communication components may include a network interface that enables the components of the HVAC systemto communicate via various protocols such as EtherNet/IP, ControlNet, DeviceNet, or any other communication network protocol. Alternatively, the communication components may enable the components of the HVAC systemto communicate via mobile telecommunications technology, Bluetooth®, near-field communications technology, and the like. As such, the controller, the compressor, the EEV(s), the first and/or second fans,, and/or the control devicemay wirelessly communicate data between each other. In other embodiments, operational control of certain components of the heat pumpmay be regulated by one or more relays or switches (e.g., a 24 volt alternating current [VAC] relay).

In some embodiments, the controllermay be a component of or may include the control panel. In other embodiments, the controllermay be a standalone controller, a dedicated controller, or another suitable controller included in the HVAC system. In any case, the controlleris configured to control components of the HVAC systemin accordance with the techniques discussed herein. The controllerincludes processing circuitry, such as a microprocessor, which may execute software for controlling the components of the HVAC system. 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.

The controllermay also include a memory device(e.g., a memory) that may store information, such as instructions, control software, look up tables, configuration data, etc. The memory devicemay include a volatile memory, such as random access memory (RAM), and/or a nonvolatile memory, such as read-only memory (ROM). The memory devicemay store a variety of information and may be used for various purposes. For example, the memory devicemay store processor-executable instructions including firmware or software for the processing circuitryexecute, such as instructions for controlling components of the HVAC system(e.g., the heat pump). In some embodiments, the memory deviceis a tangible, non-transitory, machine-readable-medium that may store machine-readable instructions for the processing circuitryto execute. The memory devicemay include ROM, flash memory, a hard drive, or any other suitable optical, magnetic, or solid-state storage medium, or a combination thereof. The memory devicemay store data, instructions, and any other suitable data.

In accordance with present techniques, the controllermay also be configured to control operation of the injection EEVdisposed along the injection conduit. In particular, the controllermay regulate operation of the injection EEVto control flow of the working fluid through the injection conduitto the injection port. Indeed, the injection EEVmay be controlled to adjust one or more properties of the working fluid injected into the compressor(e.g., via the injection port), such as a flow rate, a temperature, a pressure, a phase, or other attribute of the working fluid. The controllermay also regulate operation of the injection EEVto achieve other operating parameters (e.g., target operating parameters) of the heat pump. For example, the heat pumpmay include one or more sensorsconfigured to detect one or more operating parameters of the heat pump, and the controllermay control operation of the injection EEV(e.g., adjust a position of the injection EEV) based on feedback received from the one or more sensors. The one or more sensorsmay be configured to detect any suitable operating parameter associated with the heat pump, such as temperature, pressure, flow rate, and so forth.

In some embodiments, one or more of the sensorsmay be disposed along the discharge conduitand may be configured to detect a temperature and/or a pressure (e.g., operating parameter) of working fluid discharged by the compressor. In such embodiments, the controllermay control operation of the injection EEVto adjust flow of working fluid injected into the compressorvia the injection portto achieve a desired temperature and/or pressure of the working fluid (e.g., desired superheat, desired discharge temperature, desired operating parameter value) discharged by the compressor. In some embodiments, the controllermay control operation of the expansion valvebased on other parameters, such as a speed of the compressor, a stage of the compressor, an operating mode of the heat pump, a set point temperature of a space conditioned by the heat pump, a detected temperature of the space conditioned by the heat pump, a temperature of the ambient environment, and so forth. For example, the controllermay be configured to operate the injection EEVto enable injection of working fluid into the compressorvia the injection portduring operation of the compressorat an upper speed limit (e.g., highest speed, full capacity).

The working fluid within the injection conduitmay be injected into the compressorvia the injection portto enable improved operation of the heat pump. For example, present embodiments may enable improved operation of the heat pumpin cold climate conditions (e.g., cold temperatures of the ambient environment) that may also coincide with increased demands for heating by the heat pump(e.g., increase demand of the thermal load). As will be appreciated, in cold climate conditions, a discharge temperature and/or discharge superheat of the working fluid discharged by the compressormay be greater than desired (e.g., in the heating mode of the heat pump) Accordingly, the heat pumpmay operate to direct vapor working fluid and/or a vapor-liquid mixture of working fluid into the compressorvia the injection conduitand injection port, which may cause cooling of working fluid within the compressorand reduce the discharge temperature and/or superheat of the working fluid discharged by the compressor. The injected working fluid may also cause cooling of the compressor. In this way, the present techniques may enable improved operation of the heat pumpin cold climate conditions. For example, present embodiments enable improved operation of the heat pumpduring periods of compressoroperation at greater pressure ratios.

In some embodiments, the disclosed techniques may enable an increase in operating efficiency of the compressorand the heat pump. As will be appreciated, operation of the compressorwith greater efficiency may enable operation of the heat pumpwith reduced energy consumption. Indeed, as discussed above, the controllermay adjust operation of the injection EEVbased on feedback from one or more of the sensors, whereby the feedback is indicative of the superheat or discharge temperature of the discharged working fluid. In some embodiments, the one or more sensorsmay include a pressure transducer and a temperature sensor disposed along the discharge conduit, feedback from the pressure transducer and the temperature sensor may be received by the controller, and the controllermay determine a discharge temperature and/or superheat of the working fluid discharged by the compressor.

The controllermay control the injection EEVsuch that the discharged working fluid achieves a particular discharge superheat or temperature (e.g., set point, set point value) and/or does not exceed a particular discharge superheat or discharge temperature (e.g., set point, set point value). A set point of the desired discharge superheat or discharge temperature may be based on a particular embodiment of the heat pump, a particular embodiment or type of the compressor, or other suitable parameter. In some embodiments, the set point of the desired discharge superheat or discharge temperature may be stored in the memory device. The controllermay be configured to receive feedback from one of the sensorsindicative of the discharge superheat or discharge temperature of the working fluid, compare the feedback to the set point (e.g., set point value) stored in the memory device, and adjust operation of the injection EEVto cause the measured discharge superheat or discharge temperature to approach the set point discharge superheat or discharge temperature.