SYSTEM FOR CONTROL OF SUPERHEAT SETPOINT FOR HVAC SYSTEM

BACKGROUND

The disclosure relates generally to heating, ventilation, and air conditioning (HVAC) systems, and specifically, to controlling operation parameter setpoints of HVAC systems.

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.

Environmental control systems are utilized in residential, commercial, and industrial environments to control environmental properties, such as temperature and humidity, for occupants of the respective environments. The environmental control system may control the environmental properties through control of an airflow delivered to and ventilated from the environment. For example, an HVAC system may transfer heat between the airflow and refrigerant flowing through the system. The HVAC system may flow the refrigerant through a circuit that includes certain target property setpoints for the refrigerant. The HVAC system may also operate at a certain capacity indicative of the heating and/or cooling ability or capacity of the HVAC system based on components of the HVAC system. In some HVAC systems, the heating and/or cooling capacity may vary during operation.

SUMMARY

A summary of certain embodiments disclosed herein is set forth below. It should be understood 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 one embodiment, a refrigeration system includes a variable capacity compressor system configured to pressurize refrigerant within a refrigerant circuit and a controller configured to receive data indicative of an operating capacity of the variable capacity compressor system and configured to adjust a superheat target setpoint of the refrigerant within the refrigerant circuit based on the data.

In one embodiment, a control system is configured to control operation of a vapor compression system, where the control system comprises a memory device and a processor, and where the memory device includes instructions. The instructions, when executed by the processor, cause the processor to adjust an operating capacity of a variable capacity compressor system disposed along a refrigerant circuit of the vapor compression system and cause the processor to adjust a superheat target setpoint of a refrigerant flowing through the refrigerant circuit based on the operating capacity.

In one embodiment, a vapor compression system includes a condenser disposed along a refrigerant circuit and configured to condense a refrigerant flowing through the refrigerant circuit, a variable capacity compressor system disposed along the refrigerant circuit and configured to pressurize the refrigerant supplied to the condenser, and a controller configured to adjust a superheat target setpoint of the refrigerant based on an operating capacity of the variable capacity compressor system.

DRAWINGS

Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which:

FIG. 1 is a schematic of an environmental control for building environmental management that may employ one or more HVAC units, in accordance with an aspect of the present disclosure;

FIG. 2 is a perspective view of an embodiment of an HVAC unit that may be used in the environmental control system of FIG. 1, in accordance with an aspect of the present disclosure;

FIG. 3 is a schematic of a residential heating and cooling system, in accordance with an aspect of the present disclosure;

FIG. 4 is a schematic of an embodiment of a vapor compression system that can be used in any of the systems of FIGS. 1-3, in accordance with an aspect of the present disclosure;

FIG. 5 is a schematic of an embodiment of an HVAC system configured to adjust an operating capacity of the HVAC system via a variable capacity compressor system, in accordance with an aspect of the present disclosure;

FIG. 6 is a diagram depicting properties of a refrigerant during operation of an embodiment of an HVAC system, in accordance with an aspect of the present disclosure; and

FIG. 7 is a block diagram of an embodiment of a method for adjusting operations of an HVAC system based on an operating capacity, in accordance with an aspect of the present disclosure.

DETAILED DESCRIPTION

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.

The present disclosure is directed to heating, ventilation, and air conditioning (HVAC) systems that use a refrigerant circuit to transfer heat between a refrigerant and an airflow. For example, the refrigerant circuit includes an evaporator configured to transfer heat to the refrigerant, a condenser configured to remove heat from the refrigerant, and a compressor configured to pressurize the refrigerant. As used herein, a refrigerant circuit may include any path that refrigerant may flow therethrough, including a loop and/or a conduit. There may be target setpoints for certain operating parameters of the HVAC system, such as parameters related to properties of the refrigerant flowing through the refrigerant circuit. Operation of components of the HVAC system may be based on values of the target setpoints for certain operating parameters.

As will be appreciated, the components of the HVAC system may include a certain operating capacity. The operating capacity for a component may be indicative of a capability, such as a power, to heat and/or cool a refrigerant or an airflow. In some embodiments, the HVAC system may vary the heating and/or cooling capacity of the system by adjusting the operation of certain components, such as a compressor system. Variation of component operating capacity may be based on airflow conditions, such as a desired rate or a desired temperature of the airflow. For example, when a difference between a desired temperature of the airflow and a current temperature of the airflow is small and/or when a desired rate of conditioned airflow is low, decreasing an operating capacity of an HVAC system component, such as the compressor, may result in an increase in efficiency of the HVAC system. However, in certain existing systems, some operating parameter target setpoint values in the refrigerant circuit are fixed regardless of the operational mode of the HVAC system. It is now recognized that maintaining the same target setpoint values while varying the operating capacity of the HVAC system may affect the efficiency of the HVAC system.

Thus, in accordance with certain embodiments of the present disclosure, it is presently recognized that adjusting certain operating parameter target setpoint values based on the operating capacity of the HVAC system may enable the HVAC system to operate more efficiently. Specifically, adjusting the target setpoints for certain operational parameters may result in an adjustment in the operation of certain components of the HVAC system to further accommodate to the change in operational settings and improve operating efficiency of the HVAC system. For example, a target setpoint value for refrigerant temperature, such as a superheat value, may be established for a particular section or location of the refrigerant circuit. The HVAC system is configured to measure and monitor the temperature of the refrigerant at the particular section of the refrigerant circuit and compare the measured temperature to the target setpoint value. Operation of a component of the HVAC system, such as a condenser, heat exchanger, and/or compressor, may be adjusted to achieve and/or maintain the refrigerant temperature at the target setpoint value. The adjustment of the component operation may improve operating efficiency of the HVAC system.

Turning now to the drawings, FIG. 1 illustrates a heating, ventilating, and air conditioning (HVAC) system for building environmental management that may employ one or more HVAC units. In the illustrated embodiment, a building 10 is air conditioned by a system that includes an HVAC unit 12. The building 10 may be a commercial structure or a residential structure. As shown, the HVAC unit 12 is disposed on the roof of the building 10; however, the HVAC unit 12 may be located in other equipment rooms or areas adjacent the building 10. The HVAC unit 12 may be a single packaged unit containing other equipment, such as a blower, integrated air handler, and/or auxiliary heating unit. In other embodiments, the HVAC unit 12 may be part of a split HVAC system, such as the system shown in FIG. 3, which includes an outdoor HVAC unit 58 and an indoor HVAC unit 56.

The HVAC unit 12 is an air cooled device that implements a refrigeration cycle to provide conditioned air to the building 10. Specifically, the HVAC unit 12 may 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 unit 12 is a rooftop unit (RTU) that conditions a supply air stream, such as environmental air and/or a return air flow from the building 10. After the HVAC unit 12 conditions the air, the air is supplied to the building 10 via ductwork 14 extending throughout the building 10 from the HVAC unit 12. For example, the ductwork 14 may extend to various individual floors or other sections of the building 10. In certain embodiments, the HVAC unit 12 may 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 unit 12 may include one or more refrigeration circuits for cooling an air stream and a furnace for heating the air stream.

A control device 16, one type of which may be a thermostat, may be used to designate the temperature of the conditioned air. The control device 16 also may be used to control the flow of air through the ductwork 14. For example, the control device 16 may be used to regulate operation of one or more components of the HVAC unit 12 or other components, such as dampers and fans, within the building 10 that may control flow of air through and/or from the ductwork 14. 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 device 16 may 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 10.

FIG. 2 is a perspective view of an embodiment of the HVAC unit 12. In the illustrated embodiment, the HVAC unit 12 is a single package unit that may include one or more independent refrigeration circuits and components that are tested, charged, wired, piped, and ready for installation. The HVAC unit 12 may 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 unit 12 may directly cool and/or heat an air stream provided to the building 10 to condition a space in the building 10.

As shown in the illustrated embodiment of FIG. 2, a cabinet 24 encloses the HVAC unit 12 and provides structural support and protection to the internal components from environmental and other contaminants. In some embodiments, the cabinet 24 may be constructed of galvanized steel and insulated with aluminum foil faced insulation. Rails 26 may be joined to the bottom perimeter of the cabinet 24 and provide a foundation for the HVAC unit 12. In certain embodiments, the rails 26 may provide access for a forklift and/or overhead rigging to facilitate installation and/or removal of the HVAC unit 12. In some embodiments, the rails 26 may fit into “curbs” on the roof to enable the HVAC unit 12 to provide air to the ductwork 14 from the bottom of the HVAC unit 12 while blocking elements such as rain from leaking into the building 10.

The HVAC unit 12 includes heat exchangers 28 and 30 in fluid communication with one or more refrigeration circuits. Tubes within the heat exchangers 28 and 30 may circulate refrigerant, such as R-410A, through the heat exchangers 28 and 30. The tubes may be of various types, such as multichannel tubes, conventional copper or aluminum tubing, and so forth. Together, the heat exchangers 28 and 30 may implement a thermal cycle in which the refrigerant undergoes phase changes and/or temperature changes as it flows through the heat exchangers 28 and 30 to produce heated and/or cooled air. For example, the heat exchanger 28 may function as a condenser where heat is released from the refrigerant to ambient air, and the heat exchanger 30 may function as an evaporator where the refrigerant absorbs heat to cool an air stream. In other embodiments, the HVAC unit 12 may operate in a heat pump mode where the roles of the heat exchangers 28 and 30 may be reversed. That is, the heat exchanger 28 may function as an evaporator and the heat exchanger 30 may function as a condenser. In further embodiments, the HVAC unit 12 may include a furnace for heating the air stream that is supplied to the building 10. While the illustrated embodiment of FIG. 2 shows the HVAC unit 12 having two of the heat exchangers 28 and 30, in other embodiments, the HVAC unit 12 may include one heat exchanger or more than two heat exchangers.

The heat exchanger 30 is located within a compartment 31 that separates the heat exchanger 30 from the heat exchanger 28. Fans 32 draw air from the environment through the heat exchanger 28. Air may be heated and/or cooled as the air flows through the heat exchanger 28 before being released back to the environment surrounding the rooftop unit 12. A blower assembly 34, powered by a motor 36, draws air through the heat exchanger 30 to heat or cool the air. The heated or cooled air may be directed to the building 10 by the ductwork 14, which may be connected to the HVAC unit 12. Before flowing through the heat exchanger 30, the conditioned air flows through one or more filters 38 that may remove particulates and contaminants from the air. In certain embodiments, the filters 38 may be disposed on the air intake side of the heat exchanger 30 to prevent contaminants from contacting the heat exchanger 30.

The HVAC unit 12 also may include other equipment for implementing the thermal cycle. Compressors 42 increase the pressure and temperature of the refrigerant before the refrigerant enters the heat exchanger 28. The compressors 42 may be any suitable type of compressors, such as scroll compressors, rotary compressors, screw compressors, or reciprocating compressors. In some embodiments, the compressors 42 may include a pair of hermetic direct drive compressors arranged in a dual stage configuration 44. However, in other embodiments, any number of the compressors 42 may 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 12, 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 unit 12 may receive power through a terminal block 46. For example, a high voltage power source may be connected to the terminal block 46 to power the equipment. The operation of the HVAC unit 12 may be governed or regulated by a control board 48. The control board 48 may 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 16. The control circuitry may be configured to control operation of the equipment, provide alarms, and monitor safety switches. Wiring 49 may connect the control board 48 and the terminal block 46 to the equipment of the HVAC unit 12.

FIG. 3 illustrates a residential heating and cooling system 50, also in accordance with present techniques. The residential heating and cooling system 50 may 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 system 50 is a split HVAC system. In general, a residence 52 conditioned by a split HVAC system may include refrigerant conduits 54 that operatively couple the indoor unit 56 to the outdoor unit 58. The indoor unit 56 may be positioned in a utility room, an attic, a basement, and so forth. The outdoor unit 58 is typically situated adjacent to a side of residence 52 and is covered by a shroud to protect the system components and to prevent leaves and other debris or contaminants from entering the unit. The refrigerant conduits 54 transfer refrigerant between the indoor unit 56 and the outdoor unit 58, typically transferring primarily liquid refrigerant in one direction and primarily vaporized refrigerant in an opposite direction.

When the system shown in FIG. 3 is operating as an air conditioner, a heat exchanger 60 in the outdoor unit 58 serves as a condenser for re-condensing vaporized refrigerant flowing from the indoor unit 56 to the outdoor unit 58 via one of the refrigerant conduits 54. In these applications, a heat exchanger 62 of the indoor unit functions as an evaporator. Specifically, the heat exchanger 62 receives liquid refrigerant, which may be expanded by an expansion device, and evaporates the refrigerant before returning it to the outdoor unit 58.

The outdoor unit 58 draws environmental air through the heat exchanger 60 using a fan 64 and expels the air above the outdoor unit 58. When operating as an air conditioner, the air is heated by the heat exchanger 60 within the outdoor unit 58 and exits the unit at a temperature higher than it entered. The indoor unit 56 includes a blower or fan 66 that directs air through or across the indoor heat exchanger 62, where the air is cooled when the system is operating in air conditioning mode. Thereafter, the air is passed through ductwork 68 that directs the air to the residence 52. The overall system operates to maintain a desired temperature as set by a system controller. When the temperature sensed inside the residence 52 is higher than the set point on the thermostat, or the set point plus a small amount, the residential heating and cooling system 50 may become operative to refrigerate additional air for circulation through the residence 52. When the temperature reaches the set point, or the set point minus a small amount, the residential heating and cooling system 50 may stop the refrigeration cycle temporarily.

The residential heating and cooling system 50 may also operate as a heat pump. When operating as a heat pump, the roles of heat exchangers 60 and 62 are reversed. That is, the heat exchanger 60 of the outdoor unit 58 will serve as an evaporator to evaporate refrigerant and thereby cool air entering the outdoor unit 58 as the air passes over the outdoor heat exchanger 60. The indoor heat exchanger 62 will receive a stream of air blown over it and will heat the air by condensing the refrigerant.

In some embodiments, the indoor unit 56 may include a furnace system 70. For example, the indoor unit 56 may include the furnace system 70 when the residential heating and cooling system 50 is not configured to operate as a heat pump. The furnace system 70 may include a burner assembly and heat exchanger, among other components, inside the indoor unit 56. Fuel is provided to the burner assembly of the furnace 70 where 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 62, such that air directed by the blower 66 passes over the tubes or pipes and extracts heat from the combustion products. The heated air may then be routed from the furnace system 70 to the ductwork 68 for heating the residence 52.

FIG. 4 is an embodiment of a vapor compression system 72 that can be used in any of the systems described above. The vapor compression system 72 may circulate a refrigerant through a circuit starting with a compressor 74. The circuit may also include a condenser 76, an expansion valve(s) or device(s) 78, and an evaporator 80. The vapor compression system 72 may further include a control panel 82 that has an analog to digital (A/D) converter 84, a microprocessor 86, a non-volatile memory 88, and/or an interface board 90. The control panel 82 and its components may function to regulate operation of the vapor compression system 72 based on feedback from an operator, from sensors of the vapor compression system 72 that detect operating conditions, and so forth.

In some embodiments, the vapor compression system 72 may use one or more of a variable speed drive (VSDs) 92, a motor 94, the compressor 74, the condenser 76, the expansion valve or device 78, and/or the evaporator 80. The motor 94 may drive the compressor 74 and may be powered by the variable speed drive (VSD) 92. The VSD 92 receives 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 94. In other embodiments, the motor 94 may be powered directly from an AC or direct current (DC) power source. The motor 94 may 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 compressor 74 compresses a refrigerant vapor and delivers the vapor to the condenser 76 through a discharge passage. In some embodiments, the compressor 74 may be a centrifugal compressor. The refrigerant vapor delivered by the compressor 74 to the condenser 76 may transfer heat to a fluid passing across the condenser 76, such as ambient or environmental air 96. The refrigerant vapor may condense to a refrigerant liquid in the condenser 76 as a result of thermal heat transfer with the environmental air 96. The liquid refrigerant from the condenser 76 may flow through the expansion device 78 to the evaporator 80.

The liquid refrigerant delivered to the evaporator 80 may absorb heat from another air stream, such as a supply air stream 98 provided to the building 10 or the residence 52. For example, the supply air stream 98 may include ambient or environmental air, return air from a building, or a combination of the two. The liquid refrigerant in the evaporator 80 may undergo a phase change from the liquid refrigerant to a refrigerant vapor. In this manner, the evaporator 38 may reduce the temperature of the supply air stream 98 via thermal heat transfer with the refrigerant. Thereafter, the vapor refrigerant exits the evaporator 80 and returns to the compressor 74 by a suction line to complete the cycle.

In some embodiments, the vapor compression system 72 may further include a reheat coil in addition to the evaporator 80. For example, the reheat coil may be positioned downstream of the evaporator relative to the supply air stream 98 and may reheat the supply air stream 98 when the supply air stream 98 is overcooled to remove humidity from the supply air stream 98 before the supply air stream 98 is directed to the building 10 or the residence 52.

It should be appreciated that any of the features described herein may be incorporated with the HVAC unit 12, the residential heating and cooling system 50, 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.

As discussed above, an HVAC system may have a capacity indicative of a capability of the HVAC system to heat and/or cool an airflow or other fluid. The capacity is based on the operation of components of the HVAC system, such as a compressor. In other words, operation of components of the HVAC system, such as compressors, may be adjusted to adjust the capacity of the HVAC system. Additionally, the HVAC system may use target property setpoints for a refrigerant flowing through a refrigerant circuit in the HVAC system to control operation of the HVAC system. That is, at different sections or locations along the refrigerant circuit, target values of certain properties for the refrigerant may be used and/or referenced, and operation of the HVAC system be adjusted or otherwise controlled such that measured properties of the refrigerant approach or achieve the respective target values. As discussed in detail below, such target property setpoints may be adjusted based on a current operational capacity of the HVAC system.

As an example, the HVAC system may set a superheat target setpoint, such as a temperature, for the refrigerant between an outlet of an evaporator and an inlet of a compressor and may adjust operation of certain components of the HVAC system to cause the refrigerant between the outlet of the evaporator and the inlet of the compressor to approach or achieve the superheat target setpoint. In certain embodiments, the superheat target setpoint may be a target refrigerant temperature or a target amount of refrigerant superheat. The superheat target setpoint may be used or referenced to control operation of the HVAC system to achieve a desired suction temperature of the refrigerant, which is the temperature of the refrigerant when entering the compressor. If the suction temperature is outside of a certain range of temperatures, an efficiency or a performance of the compressor may be affected. As such, adjusting operation of the HVAC system based on the superheat target setpoint may result in a desirable suction temperature of the refrigerant to maintain a desirable performance of the compressor. Furthermore, based on the superheat target setpoint, operation of other components of the HVAC system, such as condenser fans, may be modified to improve an efficiency of the HVAC system.

Although this disclosure primarily discusses adjustment of the superheat target setpoint of the refrigerant based on an operational capacity of the HVAC system, it should be appreciated that adjustments of other setpoints along the refrigeration circuit may be based on the capacity of the HVAC system. For example, target setpoints related to refrigerant temperature downstream of the condenser and upstream of the expansion device, target setpoints related to refrigerant at a compressor discharge, target setpoints related to a position of the expansion valve, another property setpoint, or any combination thereof may be adjusted based on an operational capacity of the HVAC system. As used herein, “based on” includes embodiments where the adjustment of a setpoint is based at least on a current operating capacity of the HVAC system. As should be understood, embodiments of this disclosure may be implemented for packaged systems, split HVAC systems, or any other suitable heating and cooling systems.

FIG. 5 is a schematic of an HVAC system 150 that includes a variable capacity compressor system 152. The HVAC system 150 is configured to adjust a setpoint, such as a superheat target setpoint, based on an operational capacity of the HVAC system 150. As illustrated in FIG. 5, the variable capacity compressor system 152 includes a first compressor 154, a second compressor 156, and a third compressor 158, where each compressor 154, 156, and 158 is configured to pressurize vapor refrigerant flowing through the HVAC system 150 at a particular capacity. During operation, the HVAC system 150 may operate the first, second, and third compressors 154, 156, and 158 individually or in any combination to operate the variable capacity compressor system 152 at a desired capacity. That is, the HVAC system 150 may operate any number of the compressors 154, 156, and 158, and the capacity of the variable capacity compressor system 152 is adjusted based on which compressors 154, 156, and 158 are operating. For example, the capacity of the HVAC system 150 when all three compressors 154, 156, and 158 are operating is the sum of the respective capacities of the three compressors 154, 156, and 158. It should be appreciated that each of the three compressors 154, 156, and 158 may have different capacities or a same respective capacity.

After pressurization via the variable capacity compressor system 152, the saturation temperature of the refrigerant, or a temperature at which the refrigerant changes between a vapor and a liquid state, is increased. Additionally, as a result of the pressurization of the refrigerant, the temperature of the refrigerant is increased. The refrigerant then flows to a condenser 160 configured to cool the refrigerant. By way of example, the condenser 160 uses fans 162 to force air, such as ambient air, across the condenser 160 to cool the refrigerant via convectional heat transfer. That is, heat from the refrigerant is rejected to the air forced across the condenser 160, which cools and condenses the refrigerant. When the refrigerant exits the condenser 160, the refrigerant may be a saturated liquid. In certain embodiments, the refrigerant may exit the condenser as a subcooled liquid at a subcooled temperature or a temperature below the saturation temperature. The refrigerant then enters an expansion valve 164 configured to decrease the pressure of the refrigerant. The temperature of the refrigerant may be further reduced as a result of the decrease in pressure. The refrigerant then enters an evaporator 166 configured to exchange heat between the refrigerant and an airflow 168 flowing across the evaporator 166. As the airflow 168 is warmer than the refrigerant, heat transfers from the airflow 168 to the refrigerant. Therefore, the airflow 168 is cooled, and the refrigerant is heated. The cooled airflow 168 may then exit the evaporator 166 to cool areas conditioned by the HVAC system 150, such as the building 10. Meanwhile, the refrigerant may be heated to a saturated vapor. In some embodiments, the refrigerant may exit the evaporator 166 as a superheated vapor at a temperature above the saturation temperature of the refrigerant. The superheated refrigerant returns to the variable capacity compressor system 152 to become pressurized again and recirculate within the refrigerant circuit.

As mentioned, a suction temperature of the refrigerant returning to the variable capacity compressor system 152 may affect performance of the variable capacity compressor system 152. For example, there may be a range of suction temperatures at which the refrigerant may enter the variable capacity compressor system 152 to achieve a desirable efficiency or performance. In certain embodiments, it may be desirable for the refrigerant to enter the variable capacity compressor system 152 above a certain temperature, such as a minimum suction temperature in a range of suction temperatures, such that the refrigerant is a superheated vapor. This ensures that no liquid enters the variable capacity compressor system 152, as liquid may affect a performance of the variable capacity compressor system 152. Additionally, it may be desirable for the refrigerant to enter the variable capacity compressor system 152 below a certain temperature, such as a maximum suction temperature in a range of suction temperatures, to ensure the variable capacity compressor system 152 performs as desired to compress the refrigerant. To this end, a superheat target setpoint, or a target superheated temperature of the refrigerant, may be set to obtain a desired superheated temperature of the refrigerant that is within the range of desirable suction temperatures in order to improve and/or optimize performance of the HVAC system 150.

While the temperature at which the refrigerant exits the evaporator 166 is affected by the heat exchanged between the airflow 168 and the refrigerant within the evaporator 166, the amount of heat exchanged in the evaporator 166 may be based primarily on a desired temperature of the airflow 168 exiting the evaporator 166, and provided to a conditioned space, instead of a desired temperature of the refrigerant entering the variable capacity compressor system 152. Accordingly, the temperature of the refrigerant entering the evaporator 166 may be adjusted to affect the temperature of the refrigerant exiting the evaporator 166 after the refrigerant exchanges heat with the airflow 168 in the evaporator 166.

In order to modify the temperature of the refrigerant entering the evaporator 166, operation of one or more components of the HVAC system 150 may be adjusted. For example, an operation of the condenser 160 may be adjusted. The condenser 160 may include coils through which the superheated refrigerant flows. The fans 162 of the condenser 160 force or draw air across the coils to remove heat from the refrigerant. The fans 162 may be operated in various stages. For example, one or more of the fans 162 may be operational, while one or more of the fans 162 may be non-operational. Similarly, one or more of the fans 162 may be variable speed fans. As will be appreciated, adjustment of the staging of the fans adjusts a rate of airflow directed across the coils and therefore adjusts an amount of heat removed from the refrigerant in the condenser 160 to cool the refrigerant. In this way, operation of the condenser 160 and the fans 162 can be modified to achieve a desired temperature of the refrigerant as the refrigerant exits the condenser 160. For example, operation of the condenser 160 and the fans 162 may be modified to achieve a target or desired amount of subcooling in the refrigerant exiting the condenser 160. In adjusting the temperature of the refrigerant leaving the condenser 160, the temperature of the refrigerant entering the evaporator 166 and leaving the evaporator 166 may be ultimately adjusted and controlled.

It should be appreciated that, in certain embodiments, operations of other components of the HVAC system 150 may be adjusted to effectuate a change in the refrigerant temperature at different stages or locations along the refrigerant circuit. By way of example, a position of the expansion valve 164 may be adjusted to modify the temperature of the refrigerant entering the evaporator 166 and/or leaving the evaporator 166.

As will be appreciated, adjusting the operation of the variable capacity compressor system 152, and thus the capacity of the HVAC system 150, may cause a change in the saturation temperature of the refrigerant and/or a discharge temperature of the refrigerant exiting the variable capacity compressor system 152. For example, when operation of the variable capacity compressor system 152 is adjusted from a low capacity to a high capacity, the pressure of the refrigerant exiting the variable capacity compressor system 152 and entering the condenser 160 increases. Accordingly, a saturated condensing temperature of the refrigerant also increases. The increase in saturated condensing temperature may further result in a higher temperature of the refrigerant exiting the condenser 160. Therefore, in the manner described above, the temperature of the refrigerant entering and exiting the evaporator 166 may be ultimately affected by the change in refrigerant properties at the condenser 160 that are caused by the change in operating capacity of the variable capacity compressor system 152.

The increase in saturated condensing temperature of the refrigerant may also result in a different amount of cooling utilized to condense the refrigerant into a saturated or subcooled liquid in the condenser 160. As described in detail below, due to the refrigerant property changes effectuated by a change in the operating capacity of the variable capacity compressor system 152, one or more target setpoints of the HVAC system 150 may be adjusted. Additionally, one or more components of the HVAC system 150 may correspondingly be adjusted to improve an efficiency of the HVAC system 150.

To control the operation of the components, the HVAC system 150 may include and/or be in communication with a controller 170. The controller 170, which may be similar to the control panel 82, may include a memory 172 and a processor 174. The memory 172 may be a mass storage device, a flash memory device, removable memory, or any other non-transitory computer-readable medium that includes instructions regarding control of the HVAC system 150. The memory 172 may also include volatile memory such as randomly accessible memory (RAM) and/or non-volatile memory such as hard disc memory, flash memory, and/or other suitable memory formats. The processor 174 may execute the instructions stored in the memory 172, such as instructions to adjust operation of the variable capacity compressor system 152, the condenser 160, the fans 162, the expansion valve 164, or any other component of the HVAC system 150.

The controller 170 may be in communication with multiple sensors. For example, in the illustrated embodiment, a first sensor 176 is configured to measure the suction temperature of the refrigerant, a second sensor 178 is configured to measure the discharge temperature and/or pressure of the refrigerant exiting the variable capacity compressor system 152, and a third sensor 180 is configured to measure the temperature of the refrigerant exiting the condenser 160. In some embodiments, the HVAC system 150 also includes a fourth sensor 182 configured to measure the temperature and/or pressure of the refrigerant downstream of the expansion valve 164 and upstream of the evaporator 166. The controller 170 may use the sensors 176-182 to determine operational adjustments to components of the HVAC system 150. The operational adjustments to components of the HVAC system 150 may also be based an adjustment to the superheat target setpoint that is modified based on the operational capacity of the HVAC system 150.

For example, the controller 170 may use the first sensor 176 to monitor the suction temperature of the refrigerant to determine if the refrigerant entering the variable capacity compressor system 152 is at the superheat target setpoint and/or whether operation of any components of the HVAC system 150 should be modified. In some embodiments, the first sensor 176 may be used to detect a pressure of the refrigerant entering the variable capacity compressor system 152, which may be used to determine the saturation temperature of the refrigerant.

The controller 170 may use the second sensor 178 to determine the temperature of the refrigerant prior to entering the condenser 160 to determine a desired amount of cooling to be performed via the condenser 160. For example, the controller 170 may compare a measured temperature of the refrigerant received from the second sensor 178 with the saturated condensing temperature of the refrigerant to determine the amount of cooling desired for the refrigerant. The controller 170 may use the third sensor 180 to detect the temperature of the refrigerant exiting the condenser 160. The measurement of the third sensor 180 may be further used by the controller 170 to determine whether operational adjustment of the condenser 160 is desired to adjust the temperature of the refrigerant exiting the condenser 160.

The controller 170 may use the fourth sensor 182 to detect the temperature entering the evaporator 166. The measurement of the fourth sensor 182 may be further used by the controller 170 to adjust operation of the expansion valve 164 to achieve a desired temperature of the refrigerant upstream of the evaporator 166. It should be appreciated that the HVAC system 150 may include additional sensors, and any sensor of the HVAC system 150 may measure any appropriate parameter of the HVAC system 150 to determine whether adjustment in the operation of any components of the HVAC system 150 is desirable.

Although FIG. 5 illustrates the variable capacity compressor system 152 as including three compressors 154, 156, and 158, there may be any suitable number of compressors in the HVAC system 150. Additionally, in certain embodiments, the variable capacity compressor system 152 includes a number of variable capacity compressors, which are each configured to adjust an individual capacity during operation. In this manner, the variable capacity compressor system 152 may include one variable capacity compressor capable of adjusting the capacity of the HVAC system 150. Additionally, it should be appreciated that the HVAC system 150 may include several refrigerant circuits, each with separate evaporator and/or condenser coils, and one or more compressors. As such, the capacity of the HVAC system 150 may be based on the operation of the respective refrigerant circuits. Additionally, separate superheat target setpoints may be set for each respective refrigerant circuit. To this end, operational adjustments for the respective components of each refrigerant circuit may be individually controlled.

FIG. 6 illustrates properties of a refrigerant during operation of the HVAC system 150. Specifically, the illustrated embodiment includes a first scale 250 of a first performance parameter of the HVAC system 150 and a second scale 252 of a second performance parameter of the HVAC system 150. The first scale 250 illustrates performance parameter values of the refrigerant during operation of the HVAC system 150 at a first capacity or first compressor capacity. The second scale 252 illustrates performance parameter values of the refrigerant during operation of the HVAC system 150 at a second capacity or compressor capacity that is greater than the first capacity represented with the first scale 250. Comparison of the first and second scales 250 and 252 illustrates differences in the operation of the HVAC system 150 and refrigerant properties at different operating capacities of the HVAC system 150. In particular, the discussion below is focused on refrigerant temperature within the HVAC system 150 at different operating capacities of the HVAC system 150 and the associated operation of the HVAC system 150. In other words, the first and second scales 250 and 252 described below represent variations in refrigerant temperature at first and second operating capacities, respectively, of the HVAC system 150.

The first scale 250 represents refrigerant temperature at different points along the refrigerant circuit of the HVAC system 150 during operation of the HVAC system 150 at a first capacity. For example, the first scale 250 shows a first saturated vapor temperature 254 indicative of a temperature of the refrigerant at which the refrigerant is completely vaporized, where an increase in pressure and/or a decrease in temperature of the refrigerant will cause at least a portion of the refrigerant to change from a vapor to a liquid. In certain embodiments, the saturated vapor temperature of the refrigerant is based on a capacity or compressor capacity of the HVAC system 150. Indeed, increasing the first capacity or first compressor capacity of the HVAC system 150 may increase the first saturated vapor temperature 254 of the refrigerant within the HVAC system 150. Since the variable capacity compressor system 152 is configured to increase pressure of the refrigerant, it may be desirable for the refrigerant to enter the variable capacity compressor system 152 at a first superheated temperature 256, which is a temperature greater than the first saturated vapor temperature 254, to ensure that liquid is not formed after the variable capacity compressor system 152 has increased the pressure of the refrigerant. For example, the first superheated temperature 256 may be greater than the first saturated vapor temperature 254 by a first superheat amount 258, such as 10° C. In some embodiments, an adjustment to the first saturated vapor temperature 254, such as via a change in operational capacity of the HVAC system 150, may result in a similar adjustment to the first superheated temperature 256 to maintain a desired or target magnitude of the first superheat amount 258.

There may be a first range of superheated temperatures 260 at which the refrigerant may enter the variable capacity compressor system 152 for effective and/or efficient operation. The first range of superheated temperatures 260 may include a first minimum superheated temperature 262 and/or a first maximum superheated temperature 264, which may be determined based on capabilities of the variable capacity compressor system 152. Therefore, the first superheated temperature 256 may be within in first range of superheated temperatures 260. In other words, the first superheated temperature 256 may be between the first minimum superheated temperature 262 and the first maximum superheated temperature 264. It should be appreciated that, although a selected superheated target setpoint may be between the minimum superheated temperature 262 and the maximum superheated temperature 264, the superheated target setpoint may not be in the exact average of the minimum superheated temperature 262 and the maximum superheated temperature 264. For example, it may be more desirable to achieve a lower superheated temperature of the refrigerant and thus, the superheated target setpoint may be more proximate to the minimum superheated temperature 262 than the maximum superheated temperature 264.

The temperature of the refrigerant may approach or achieve the first superheated temperature 256 when heat is added to the refrigerant in the evaporator 166. Specifically, the refrigerant may enter the evaporator 166 at a first chilled temperature 266 and may absorb heat from the airflow 168. The heat from the airflow 168 may raise the temperature of the refrigerant by a first heating amount 268. As will be appreciated, the HVAC system 150 is configured to operate to enable the refrigerant to reach the first superheated temperature 256 when the first heating amount 268 is added to the refrigerant within the evaporator 166.

It should be understood the first heating amount 268 may be based on a desired temperature of the airflow 168. For example, the first heating amount 268 may be determined via building occupancy setpoints of desired temperatures for areas conditioned by the HVAC system 150. In other words, a magnitude of the first heating amount 268 applied to the refrigerant, and therefore removed from the airflow 168, may be based a desired temperature of the airflow 168 cooled by the evaporator 166, which may be based on a target temperature of a conditioned space serviced by the HVAC system 150. Thus, the first heating amount 268 may not directly depend on target temperature setpoints of the refrigerant itself.

Therefore, to achieve the first superheated temperature 256, a desired or targeted value of the first chilled temperature 266 entering the evaporator 166 may be determined based on an expected value of the first heating amount 268. In particular, a targeted value of the first chilled temperature 266 of the refrigerant may be selected that will enable the refrigerant to achieve the first superheated temperature 256 upon application of the first heating amount 268 to the refrigerant in the evaporator 166. In certain embodiments, the magnitude of the first chilled temperature 266 entering the evaporator 166 may be adjusted by adjusting operation of other components of the HVAC system 150. For example, the magnitude of the first chilled temperature 266 may be adjusted by adjusting an amount that the refrigerant is cooled by the condenser 160 and/or by the expansion valve 164. Thus, to adjust the value of the first chilled temperature 266, operation of the condenser 160 and/or the expansion valve 164 may be adjusted accordingly. For example, the fans 162 of the condenser 160 may be operated at a different speed and/or the expansion valve 164 may be set at a different position in order cause the refrigerant to approach or reach a different value of the first chilled temperature 266 upon entering the evaporator 166. In other words, adjusting operation of the condenser 160 and/or the expansion valve 164 effectuates an adjustment to the first chilled temperature 266 of the refrigerant entering the evaporator 166.

If the first heating amount 268 is unchanged, then adding the first heating amount 268 to the adjusted value of the first chilled temperature 266 generates an adjusted value for the first superheated temperature 256. In this manner, the operation of the condenser 160 and/or the expansion valve 164 may be adjusted in order to ultimately adjust the superheated temperature of refrigerant entering the variable capacity compressor system 152.

In certain embodiments, the first heating amount 268 may change. For example, based on an adjusted thermostat set point for a conditioned spaced served by the HVAC system 150, a desired temperature of the airflow 168 cooled by the evaporator 166 may change. As a result, the first heating amount 268 transferred from the airflow 168 to the refrigerant in the evaporator 166 may change. If the first heating amount 268 is changed, operation of the HVAC system 150 may still be adjusted, in the manners described above, in order to achieve a particular value of the first chilled temperature 266 of the refrigerant entering the evaporator 166 that will enable the refrigerant to approach or attain the first superheated temperature 256 upon application of the adjusted first heating amount 268 to the refrigerant.

As mentioned above, the second scale 252 represents refrigerant temperatures at various points along the refrigerant circuit when the HVAC system 150 is operating at a second operational capacity that is greater than the first operational capacity. An increase in the compressor capacity of the HVAC system 150 causes the saturation temperature of the refrigerant to increase. For example, the compressor capacity of the HVAC system 150 may be increased such that the first saturated vapor temperature 254 increases by a first amount 270 to a second saturated vapor temperature 272. Due to the increase in the refrigerant saturation temperature to the second saturated vapor temperature 272, it may be desirable to increase the first superheated temperature 256, or superheat target temperature, by a second amount 274 to a second superheated temperature 276. In other words, it may be desirable to provide the refrigerant to the variable capacity compressor system 152 with a second superheat amount 278 above the second saturated vapor temperature 272 to ensure that no liquid refrigerant enters and is compressed by the variable capacity compressor system 152. In some embodiments, the second superheat amount 278 is approximately the same as the first superheat amount 258. In other words, the amount of superheat that it is desirable for the refrigerant to have as the refrigerant enters the variable capacity compressor system 152 may be constant for multiple different operating capacities of the HVAC system 150. In other embodiments, the amount of superheat targeted for the refrigerant entering the variable capacity compressor system 152 may vary as the operating compressor capacity of the HVAC system 150 varies.

The second superheated temperature 276 may be in a second range of superheated temperatures 280 that includes a second minimum superheated temperature 282 and a second maximum superheated temperature 284. In some embodiments, the range of superheated temperatures may be adjusted based on a change to the saturated vapor temperature caused by variation in operational or compressor capacity of the HVAC system 150.

At the second operational capacity or compressor capacity of the HVAC system 150, a second heating amount 286 may be added to the refrigerant as the refrigerant passes through the evaporator 166. As similarly discussed above, the magnitude of the second heating amount 286 may be based on a desired temperature of the airflow 168. If an expected value of the second heating amount 286 is known, calculated, or otherwise determined, the temperature of the refrigerant entering the evaporator 166 may be adjusted accordingly to cause the refrigerant to approach or attain the second superheated temperature 276 when the second heating amount 286 is added to the refrigerant in the evaporator 166.

As the value of the second superheated temperature 276, or target superheat temperature setpoint, increases for the second operational capacity represented by scale 252, a target temperature value of the refrigerant entering the evaporator 166 may correspondingly be increased. For example, the value of the first chilled temperature 266 shown in the first scale 250 may be increased by a third amount 288 to a second chilled temperature 290 value. In some embodiments, operation of the condenser 160 and/or the expansion valve 164 may be adjusted such that refrigerant approaches or reaches the second chilled temperature 290 at the refrigerant enters the evaporator 166. For example, the fans 162 of the condenser 160 may be operated at lower speeds to effectuate less cooling of the refrigerant at the condenser 160. The reduced cooling of the refrigerant at the condenser 160 may enable the refrigerant to enter the evaporator 166 at the second chilled temperature 290 instead of, for example, the lower first chilled temperature 266. In this manner, operation of the HVAC system 150 may be more efficient. Specifically, the amount of power consumed by the fans during operation of the condenser 160 may be decreased when the operational capacity or compressor capacity of the HVAC system 150 is increased, while still superheating the refrigerant entering the variable capacity compressor system 152 by a desired amount.

It should be appreciated that, in certain embodiments, the first amount 270, the second amount 274, and the third amount 288 may be approximately the same. In other words, the superheated temperature of refrigerant entering the compressor and the chilled temperature of refrigerant entering the evaporator may be adjusted by an amount that is approximately the same as an amount that the saturation temperature of the refrigerant is adjusted by virtue of the increase in compressor capacity. In additional or alternative embodiments, the superheated temperature target setpoint and/or the chilled temperature target setpoint may be adjusted by an amount different from the amount by which the saturation temperature of the refrigerant is adjusted. For example, the superheated temperature target setpoint and/or the chilled temperature target setpoint may be adjusted by a multiple of or an offset of the amount by which the saturation temperature is adjusted.

It should also be understood that, in certain embodiments, the superheated temperature, such as the second superheated temperature 276, may be a target setpoint that is based on the operational capacity or compressor capacity of the HVAC system 150. That is, when the operational capacity or compressor capacity of the HVAC system 150 is adjusted, the target temperature of the refrigerant exiting the evaporator 166 is also adjusted. In additional or alternative embodiments, the superheat amount, such as the second superheat amount 278, may be a target setpoint value that is based on the operational capacity or compressor capacity. In other words, when the operational capacity or compressor capacity of the HVAC system 150 is adjusted, the target amount by which the refrigerant is heated above the saturation temperature when exiting the evaporator 166 may be adjusted.

To illustrate adjustment in the operation of the HVAC system 150 in accordance with present techniques, FIG. 7 is a block diagram of an embodiment of a method 350 for adjusting operating parameter setpoints, such as superheat temperature or superheat amount setpoints, based on a capacity of the HVAC system 150. At block 352, a change of operation of the HVAC system 150 is detected. For example, an adjustment to the operation of a particular component, such as the variable capacity compressor system 152, may be monitored and detected. In one embodiment, operation of the variable capacity compressor system 152 may be adjusted in response to a change in desired temperature of an airflow supplied by the HVAC system 150 and/or in response to a change in ambient temperature.

The change in operation of the particular component, such as the variable capacity compressor system 152, may result in the HVAC system 150 operating at a different operational capacity or compressor capacity. At block 354, the new capacity is determined. As discussed above, the capacity may depend on desired operations of components of the HVAC system 150. In some embodiments, the variable capacity compressor system 152 may operate at different capacities. The determination of the new operating capacity may include a determination of the operational mode, stage, or other operating parameter of the variable capacity compressor system 152. In additional or alternative embodiments, operations of additional components of the HVAC system 150 may also be monitored to determine the total operating capacity of the HVAC system 150.

At block 356, an operational parameter setpoint value is adjusted. More specifically, the operational parameter setpoint value is adjusted based on the new capacity of HVAC system 150 operation determined in block 354. As discussed in detail above, the operational parameter setpoint may be a superheat temperature target setpoint or a superheat amount target setpoint. However, it should be appreciated that the operational parameter setpoint may be indicative of or related to another suitable operational parameter, such as a target suction temperature of refrigerant, a target subcooled temperature of refrigerant, or any other target refrigerant temperature at any suitable location along the refrigerant circuit of the HVAC system 150.

In the manner described above, adjustment of a particular refrigerant temperature setpoint value, and subsequent, consequential HVAC system 150 operation, may ultimately result in an adjustment of other refrigerant temperatures within the HVAC system 150. In particular, adjustment of a particular refrigerant temperature setpoint value may enable control of an amount of superheat or a superheat temperature of refrigerant exiting the evaporator 166.

The temperature setpoint value may be adjusted based at least on the newly determined capacity of the HVAC system 150. For example, the particular refrigerant temperature setpoint value may be proportionally adjusted based on the change in operating capacity of the HVAC system 150. In other embodiments, the adjustment to the refrigerant temperature setpoint value may be based on a percentage of the newly-determined operating capacity relative to a maximum operating capacity of the HVAC system 150. In another embodiment, the adjustment to the refrigerant temperature setpoint value may be based on an algorithm, a lookup table of capacities and setpoints, and/or other factors in addition to a change in operating capacity of the HVAC system 150.

Based on the adjustment to the operational parameter setpoint value, the operation of the HVAC system 150 is further adjusted to achieve the new operational parameter setpoint, as shown at block 358. For example, based on an adjustment to a target superheat temperature of refrigerant exiting the evaporator 166, operation of the HVAC system 150 may be modified to cause the refrigerant exiting the evaporator 166 to approach or achieve the new target superheat temperature. As previously discussed, components of the HVAC system 150, such as the condenser 160, fans of the condenser 160, the expansion valve 164, the variable capacity compressor system 152, another suitable component, or any combination thereof, may be adjusted to cause the refrigerant to approach or reach the new target superheat temperature. As discussed above, certain adjustments to the operation of the HVAC system 150, such as a decrease in condenser 160 fan speed or power based on an increase in the capacity of the variable capacity compressor system 152 or HVAC system 150 may result in more efficient operation of the HVAC system 150.

After the operation of the HVAC system 150 is adjusted, the steps of blocks 352 and 354 may be repeated to determine if the HVAC system 150 operation adjustment results in a new operational capacity of the HVAC system 150. As such, the steps of the method 350 may be repeated to iteratively achieve a target operational value corresponding to a particular operational capacity.

In some embodiments, the steps of the method 350 are adjusted via the controller 170. Moreover, it should be appreciated that the steps described in the method 350 are not exclusive. Indeed, additional steps may be performed in the method 350, such as after block 358 or in between any of the blocks 352-358 of the method 350. Furthermore, in certain embodiments, some of the aforementioned steps may not be performed during execution of the method 350.

As set forth above, embodiments of the present disclosure may provide one or more technical effects useful in the operation of HVAC systems. For example, an operational parameter setpoint value, such as a temperature setpoint of refrigerant, may be adjusted based on an operating capacity of an HVAC system. Based on the adjustment in the operational parameter setpoint value, operation of the HVAC system is further adjusted. The additional adjustment in operation of the HVAC system may result in more efficient operation of the HVAC system 150. For example, the disclosed embodiments include an HVAC system configured to adjust a refrigerant temperature setpoint value, such as a superheat temperature or superheat amount, based on a change in operational capacity of a variable capacity compressor system of the HVAC system 150. In response to the refrigerant temperature setpoint value adjustment, components of the HVAC system, such as condenser fans, may also adjust operation to cause the refrigerant to approach or achieve the new temperature setpoint value. As discussed above, such adjustment to the operation of HVAC system components improves operation the HVAC system and increases efficiency of HVAC system operation. The technical effects and technical problems in the specification are examples and are not limiting. It should be noted that the embodiments described in the specification may have other technical effects and can solve other technical problems.

While only certain features and embodiments of the disclosure have been illustrated and described, many modifications and changes may occur to those skilled in the art, such as variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, and the like, without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described, such as those unrelated to the presently contemplated best mode of carrying out the disclosed embodiments, or those unrelated to enabling the claimed embodiments. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. 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, without undue experimentation.

SYSTEM FOR CONTROL OF SUPERHEAT SETPOINT FOR HVAC SYSTEM

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