HVAC CONTROL SYSTEM FOR ELECTRIC HEATING SYSTEM

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. Provisional Application No. 63/555,830, entitled “HEATER CONTROL THROUGH AIR FLOW DETECTION IN HEATING, VENTILATION AND/OR AIR CONDITIONING SYSTEM,” filed Feb. 20, 2024, which is hereby incorporated by reference in its entirety for all purposes.

BACKGROUND

This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure and 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 noted that these statements are to be read in this light, and not as admissions of prior art.

Heating, ventilation, and air conditioning (HVAC) systems are utilized to control environmental properties, such as temperature and humidity, for occupants of residential, commercial, and industrial environments. The HVAC systems may control the environmental properties through control of an air flow delivered to the environment. For example, an HVAC system may include one or more blowers configured to generate an air flow and to direct the air flow across one or more heat exchangers configured to transfer heat to and/or from the air flow. Unfortunately, in existing HVAC systems, heat exchangers may be oriented and/or arranged in a manner that causes uneven transfer of heat between the air flow and the heat exchangers. In some instances, heat exchangers may be susceptible to overheating, which may render the HVAC system vulnerable to operational interruptions and/or other inefficiencies. Accordingly, it is now recognized that improved control systems for HVAC systems are desired.

SUMMARY

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

In one embodiment, a heating, ventilation, and air conditioning (HVAC) system includes a housing defining a chamber configured to receive an air flow and a heating system disposed within the housing. The heating system includes a heating coil disposed within the chamber and configured to transfer heat to the air flow within the chamber and a power supply control system configured to control supply of an electric current to the heating coil. The power supply control system includes power supply control circuitry disposed at least partially external to the chamber and a switch disposed along the power supply control circuitry. The switch is configured to open to interrupt supply of the electric current to the heating coil and to close to enable supply of the electric current to the heating coil based on an operating parameter indicative of the air flow within the chamber.

In another embodiment, a heating system for a heating, ventilation, and air conditioning (HVAC) system includes an electric heating coil configured to transfer heat to an air flow directed through the HVAC system and a power supply control system configured to control supply of a first voltage to the electric heating coil. The power supply control system includes an electrical contactor configured to transmit the first voltage from a power source to the electric heating coil and a relay including a coil and a set of relay contacts. The set of relay contacts is configured to transmit a signal indicative of a call for heating from a control system of the HVAC system to the electrical contactor in a closed configuration of the set of relay contacts, and the coil is configured to transition the set of relay contacts from a normally open configuration to the closed configuration in response to receipt of a second voltage. The power supply control system further includes a switch configured to transmit the second voltage to the coil of the relay in a closed configuration of the switch and configured to interrupt transmission of the second voltage to the coil of the relay in an open configuration of the switch. The switch is also configured to transition between the open configuration and the closed configuration based on a detected parameter indicative of the air flow directed through the HVAC system.

In a further embodiment, a heating, ventilation, and air conditioning (HVAC) system includes a housing defining a blower section, a supply air section, and a power component section, a blower disposed within the blower section and configured to direct an air flow into the supply air section, an electric heating coil disposed within the supply air section and configured to transfer heat to the air flow, a partition disposed within the housing and extending between the supply air section and the power component section, and a power supply control system configured to control supply of a first voltage to the electric heating coil. The power supply control system includes an electrical contactor configured to transmit the first voltage from a power source to the electric heating coil in response to receipt of a call for heating from a control system of the HVAC system, a relay configured to electrically couple the control system of the HVAC system and the electrical contactor in response to receipt of a second voltage, and an air proving switch configured to transition from an open configuration to a closed configuration to enable transmission of the second voltage to the relay in response to detection of a pressure differential between the supply air section and the power component section greater than a threshold value.

BRIEF DESCRIPTION OF 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 perspective view of a building having an embodiment of a heating, ventilation, and air conditioning (HVAC) system for environmental management in a commercial setting, in accordance with an aspect of the present disclosure;

FIG. 2 is a perspective view of an embodiment of a packaged HVAC unit, in accordance with an aspect of the present disclosure;

FIG. 3 is a cutaway perspective view of an embodiment of a residential, split HVAC system, in accordance with an aspect of the present disclosure;

FIG. 4 is a schematic illustration of an embodiment of a vapor compression system that may be used in an HVAC system, in accordance with an aspect of the present disclosure;

FIG. 5 is a perspective view of a portion of an embodiment of an HVAC system including a heating system and a power supply control system, in accordance with an aspect of the present disclosure;

FIG. 6 is a cross-sectional, schematic side view of a portion of an embodiment of an HVAC system including a heating system and a power supply control system, in accordance with an aspect of the present disclosure;

FIG. 7 is a schematic diagram of a portion of an embodiment of an HVAC system including a heating system and a power supply control system, in accordance with an aspect of the present disclosure;

FIG. 8 is a schematic diagram of an embodiment of a power supply control system for a heating system of an HVAC system, in accordance with an aspect of the present disclosure; and

FIG. 9 is a perspective view schematic of a portion of an embodiment of a heating system and a power supply control system of an HVAC system, 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 noted 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 noted 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 noted 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.

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

In many applications, HVAC systems also include a heating system configured to transfer heat to an air flow directed through the HVAC system. For example, the heating system may be configured to heat the air flow as the air flow is directed across heating coils of the heating system. In some embodiments, the heating coils may be arranged in a packaged outdoor unit or a rooftop unit configured to both heat and cool the air flow, such as a supply air flow that is conditioned and directed to a conditioned space (e.g., a building). For example, the heating coils may be electric heating coils configured to convert electrical energy passing therethrough into thermal energy. Indeed, the HVAC system may include multiple heating coils configured to exchange heat with one or more air flows directed through the HVAC system. The HVAC system may also include one or more blowers configured to direct the air flow across the heating coils, thereby placing the air flow in a heat exchange relationship with the heating coils. As the air flow is directed across the heating coils, the air flow may be heated and a temperature (e.g., surface temperature) of the heating coils may be reduced via transfer of heat from the heating coils to the air flow.

As will be appreciated, it may be desirable to utilize certain working fluids (e.g., refrigerants) with HVAC systems, such as working fluids having a low global warming potential (GWP). Traditional refrigerants, while effective to transfer heat between components of HVAC systems and/or between other fluids, may have a high GWP. Therefore, more environmentally-friendly working fluids, such as A2L refrigerants or other low GWP refrigerants, may be utilized as a working fluid of the HVAC system to reduce potential impact on an environment surrounding the HVAC system. However, some low GWP refrigerants may be reactive (e.g., mildly flammable), such as when exposed to certain elevated temperatures.

In some instances, working fluid (e.g., refrigerant) may inadvertently escape from the HVAC system (e.g., working fluid circuit). For example, working fluid may escape from a coupling or joint between components of a heat exchanger, from tubing of the heat exchanger, from conduits of the working fluid circuit, from another portion of the heat exchanger, and/or from other components of the working fluid circuit. In some circumstances, the escaped (e.g., leaked) working fluid may mix with the air flow and/or other fluids circulating through the HVAC system. For HVAC systems that utilize a low GWP refrigerant as a working fluid of the working fluid circuit, it is desirable to ensure escaped (e.g., leaked) working fluid is not exposed to certain elevated temperatures (e.g., within the HVAC system) that may otherwise induce a reaction of the working fluid (e.g., low GWP refrigerant).

Existing approaches that modify operation of HVAC systems to avoid undesired exposure of escaped working fluid to other components of the HVAC system are susceptible to various drawbacks. For example, certain existing systems may incorporate a refrigerant detection sensor (RDS) configured to detect the presence of working fluid that has escaped from the working fluid circuit and is external to the working fluid circuit. In response to a detection of escaped working fluid and/or a working fluid leak via the refrigerant detection sensor, operation of the HVAC system may be modified (e.g., suspended, shut down). Unfortunately, utilization of refrigerant detection sensors may present challenges, for example, due to variations in positioning of the refrigerant detection sensors within the HVAC system, reliance on complicated control schemes, increased manufacturing and/or operating costs, and so forth.

Accordingly, present embodiments are directed to improved HVAC systems configured to enable utilization of low GWP refrigerants as a working fluid, while also avoiding exposure of the working fluid (e.g., inadvertently escaped working fluid) to elevated temperatures that may otherwise render the working fluid susceptible to undesired reactions. More specifically, the present techniques enable utilization of low GWP refrigerants as a working fluid of a working fluid circuit in an HVAC system having an electric heating system while also avoiding, blocking, mitigating, and/or preventing exposure of the working fluid to components of the electric heating system that may produce elevated temperatures during operation. As discussed in further detail below, the HVAC system may include a power supply control system configured to selectively enable and disable supply of power to the electric heating system based on one or more detected parameters indicative of an air flow directed across heating coils of the electric heating system. The power supply control system may include a switch, such as an air proving switch and/or a pressure switch, configured to enable supply of power to heating coils of the electric heating system in response to detection of adequate (e.g., suitable, sufficient) air flow across the heating coils and to disable supply of power to the heating coils in response to detection of inadequate (e.g., unsuitable, insufficient). In this way, the present techniques advantageously avert exposure of the working fluid to the heating coils during instances in which a temperature of the heating coils may approach certain elevated temperatures. Indeed, present embodiments may provide the benefits described herein with increased reliability, reduced costs, and reduced complexity, as compared to certain existing systems. It should also be appreciated that the present techniques may be incorporated with HVAC systems to satisfy and comply with one or more regulatory standards.

Turning now to the drawings, FIG. 1 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 building 10 is air conditioned by a system that includes an HVAC unit 12 in accordance with present embodiments. 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 package unit containing other equipment, such as a blower and/or integrated air handler. 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 flow, 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.

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 working fluid circuits (e.g., refrigerant circuits). Tubes within the heat exchangers 28 and 30 may circulate a working fluid (e.g., refrigerant), such as R-454B and/or R32, 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 working fluid 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 working fluid to ambient air, and the heat exchanger 30 may function as an evaporator where the working fluid absorbs heat to cool an air flow. In some 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. 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 HVAC 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 working fluid before the working fluid 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 components.

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 working fluid conduits 54 (e.g., refrigerant conduits) that operatively couple the indoor HVAC unit 56 to the outdoor HVAC unit 58. The indoor HVAC unit 56 may be positioned in a utility room, an attic, a basement, and so forth. The outdoor HVAC unit 58 is typically situated adjacent to a side of the 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 working fluid conduits 54 transfer working fluid between the indoor HVAC unit 56 and the outdoor HVAC unit 58, typically transferring primarily liquid working fluid in one direction and primarily vaporized working fluid in an opposite direction.

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

The outdoor HVAC unit 58 draws environmental air through the heat exchanger 60 using a fan 64 and expels the air above the outdoor HVAC unit 58. When operating as an air conditioner, the air is heated by the heat exchanger 60 within the outdoor HVAC unit 58 and exits the unit at a temperature higher than it entered. The indoor HVAC unit 56 includes a blower or fan 66 that directs air through or across the 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.

In some embodiments, the residential heating and cooling system 50 may also be configured to 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 working fluid and thereby cool air entering the outdoor HVAC unit 58 as the air passes over the heat exchanger 60. The heat exchanger 62 will receive a stream of air blown over it and will heat the air by condensing the working fluid.

In some embodiments, the indoor HVAC unit 56 may include a heating system 70. For example, the indoor HVAC unit 56 may include the heating system 70 when the residential heating and cooling system 50 is not configured to operate as a heat pump. Alternatively, embodiments of the residential heating and cooling system 50 configured to operate as a heat pump may also include the heating system 70 to provide supplemental heating of an air flow supplied to the residence 52. The heating system 70 may include one or more heating coils (e.g., electric heating coils), among other components, inside the indoor HVAC unit 56. As air is directed across and/or through the heating system 70 (e.g., across heating coils) by the blower or fan 66, heat may be transferred from the heating coils to the air, and the heated air may then be routed from the heating 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 working fluid through a circuit (e.g., working fluid 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 working fluid vapor and delivers the vapor to the condenser 76 through a discharge passage. In some embodiments, the compressor 74 may 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 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 working fluid vapor may condense to a working fluid liquid in the condenser 76 as a result of thermal heat transfer with the environmental air 96. The liquid working fluid from the condenser 76 may flow through the expansion device 78 to the evaporator 80.

The working fluid delivered to the evaporator 80 may absorb heat from another air flow, such as a supply air flow 98 provided to the building 10 or the residence 52. For example, the supply air flow 98 may include ambient or environmental air, return air from a building, or a combination of the two. The liquid working fluid in the evaporator 80 may undergo a phase change from the liquid working fluid to a working fluid vapor. In this manner, the evaporator 80 may reduce the temperature of the supply air flow 98 via thermal heat transfer with the working fluid. Thereafter, the vapor working fluid 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 80 relative to the supply air flow 98 and may reheat the supply air flow 98 when the supply air flow 98 is overcooled to remove humidity from the supply air flow 98 before the supply air flow 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 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.

As briefly discussed above, present embodiments are directed to improved HVAC systems configured to enable utilization of low GWP refrigerants as a working fluid of a working fluid circuit, while also avoiding exposure of the working fluid (e.g., working fluid inadvertently released from the work-in fluid circuit) to elevated temperatures that may otherwise render the working fluid susceptible to undesired reactions. In accordance with the present techniques, the HVAC system includes a heating system (e.g., electric heating system) having one or more heating coils configured to transfer heat to an air flow directed across the heating coils. During operation of the heating system, the air flow directed across the heating coil may cause a reduction in a temperature of the heating coils (e.g., a surface of the heating coils). However, in some circumstances, an amount (e.g., flow rate) of air flow directed across the heating coils may be insufficient to absorb heat output by the heating coils and thereby reduce the temperature of the heating coils. In such instances, the temperature of the heating coils may be greater than desired. For example, the temperature of the heating coils may rise to approach a temperature value (e.g., threshold value) at which the working fluid may be more susceptible to reaction. Accordingly, present embodiments include a power supply control system of the heating system that is configured to selectively enable and disable supply of power (e.g., voltage, electric current) to the heating coils based on an operating parameter (e.g., detected operating parameter) indicative of the air flow directed across the heating coils. More specifically, the power supply control system may be configured to interrupt, suspend, or otherwise inhibit supply of power to the heating coils based on a detection and/or a determination that an amount (e.g., flow rate) of air flow directed across the heating coils is insufficient, less than desired, and/or otherwise incompatible with operation of the HVAC system incorporating a working fluid, such as a low GWP refrigerant.

With this in mind, FIG. 5 is a perspective view of an embodiment of an HVAC system 100 (e.g., rooftop unit, air handling unit, HVAC unit) includes one or more of the features disclosed herein. The HVAC system 100 may be or include any suitable HVAC system and/or HVAC system components, such as the HVAC unit 12, the residential heating and cooling system 50, and/or any of the components described above. In the illustrated embodiment, the HVAC system 100 includes various components enclosed within an internal volume of a housing 102 of the HVAC system 100. The HVAC system 100 may be configured to circulate air through the housing 102 via operation of a blower assembly 104 having a first blower 106 and a second blower 108 disposed within a blower section 110 of the housing 102. That is, the blower assembly 104 may be configured to direct (e.g., force, draw) an air flow 112 along an air flow path 114 through the housing 102 of the HVAC system 100. For example, the housing 102 of the HVAC system 100 may include a return air section 116 configured to receive an air flow, such as a return air flow from the building 10 of FIG. 1, and a supply air section 118 (e.g., discharge section, heating section, chamber) configured to output or discharge a supply air flow 120 conditioned by the HVAC system 100. In the illustrated embodiment, the housing 102 includes a discharge outlet 122 (e.g., supply air outlet) formed in a lateral side 124 of the housing 102 to enable discharge of the supply air flow 120 from the supply air section 118. Thus, the configuration of the HVAC system 100 (e.g., housing 102) may be described as a side flow or side discharge configuration. However, it should be appreciated that, in other embodiments, the discharge outlet 122 may be formed in a base 126 of the housing 102 and may therefore be configured in a downflow or downward discharge configuration.

During operation, the blower assembly 104 may draw an air flow (e.g., air flow 112) into the return air section 116 of the housing 102 and direct the air flow into the supply air section 118, from which the air flow may be discharged as the supply air flow 120 toward a conditioned space. In other words, the air flow path 114 of the HVAC system 100 may be defined at least partially by the return air section 116, the blower section 110, and the supply air section 118. As an example, the HVAC system 100 (e.g., housing 102) may be installed in an outdoor or ambient environment, such as on a rooftop of a building, and may be fluidly coupled to ductwork that directs air to and/or from rooms or other areas within the building. Ductwork may be fluidly coupled to the return air section 116 to direct a return air flow into the housing 102, and ductwork may be fluidly coupled to the supply air section 118 to receive the supply air flow 120 from the housing 102. In this manner, the blower assembly 104 may circulate air through the HVAC system 100 and a conditioned space. It should be appreciated that the HVAC system 100 may additionally or alternatively be configured to receive and/or discharge other air flows. For example, the HVAC system 100 may be configured to receive an air flow from an outdoor environment (e.g., an ambient air flow), to discharge an air flow to the outdoor embodiment (e.g., discharge return air flow as an exhaust air flow), and so forth. In some embodiments, the HVAC system 100 may receive and combine a return air flow and an ambient air flow to generate the supply air flow 120. Accordingly, the air flow 112 illustrated in FIG. 5 may include a return air flow, an ambient air flow, or a combination thereof.

In addition to circulating air through the housing 102, the HVAC system 100 may be configured to adjust one or more operating parameters of the one or more air flows (e.g., air flow 112) directed therethrough. For example, the HVAC system 100 may be configured to adjust a temperature, pressure, humidity, particle content, or other operating parameter of the air flow 112 directed therethrough. Indeed, the HVAC system 100 may operate in multiple different operating modes, such as a cooling mode, a heating mode, a dehumidification mode, and so forth. In some embodiments, the HVAC system 100 may include a working fluid circuit (e.g., vapor compression system 72, refrigerant circuit) configured to circulate a working fluid therethrough, and one or more components of the working fluid circuit may be placed in thermal communication with one or more of the air flows directed through the HVAC system 100. In particular, the working fluid circuit may include one or more heat exchangers configured to place the working fluid in thermal communication with one or more of the air flows to adjust an operating parameter of supply air flow 120.

The illustrated embodiment of the HVAC system 100 includes an evaporator coil 128 (e.g., cooling coil) configured to circulate the working fluid therethrough to absorb heat from one or more air flows directed across the evaporator coil 128, thereby reducing a temperature of the one or more air flows, in a cooling mode of the HVAC system 100. Thus, the working fluid within the evaporator coil 128 may be heated as the one or more air flows are directed across the evaporator coil 128. In the illustrated embodiment, the evaporator coil 128 is positioned downstream of the return air section 116 and upstream of the blower section 110 relative to a direction of the air flow 112 along the air flow path 114. Accordingly, the blower assembly 104 may operate to draw an air flow from the return air section 116 and across the evaporator coil 128 and may force the air flow through the blower section 110 and into the supply air section 118.

The HVAC system 100 may also be configured to increase a temperature of one or more air flows directed through the housing 102 in a heating operating mode of the HVAC system 100. Thus, the supply air flow 120 may be discharged from the housing 102 and directed toward a condition space to 100 to heat the conditioned space. To this end, the HVAC system 100 includes a heating system 130 (e.g., electric heating system, heating assembly) including heating coils 132 (e.g., heaters, electric heating coils) configured to transfer thermal energy to the air flow 112 directed through the housing 102 via the blower assembly 104. In some embodiments, the heating coils 132 may be electric heating coils coupled to a power source and configured to convert electrical energy to thermal energy. In the illustrated embodiment, the heating coils 132 of the heating system 130 are disposed within the supply air section 118 of the HVAC system 100. Thus, during a heating mode of the HVAC system 100, the blower assembly 104 (e.g., first blower 106, second blower 108) may direct one or more air flows into the supply air section 118, and the one or more air flows may be directed across or through one or more of the heating coils 132. While the heating system 130 is shown as including four heating coils 132, it should be appreciated that the heating system 130 may include any suitable number of heating coils 132 and implement the present techniques to achieve the benefits described herein.

As mentioned above, the HVAC system 100 may be configured to utilized a low GWP refrigerant, such as R-454B, as a working fluid circulated through a working fluid circuit of the HVAC system 100. The low GWP refrigerant may therefore be circulated through the evaporator coil 128 disposed within the air flow path 114 extending through the housing 102. For example, during operation of the HVAC system 100 in a cooling mode, the low GWP refrigerant may absorb heat from the air flow 112 to cool the air flow 112 before the air flow 112 is discharged from the housing 102 as the supply air flow 120. During non-operation of the HVAC system 100 and/or during operation of the HVAC system 100 in a heating mode (e.g., operation of the heating system 130 to heat the air flow 112), at least a portion of the low GWP refrigerant may remain within the evaporator coil 128. In some instances, the working fluid (e.g., low GWP refrigerant) may inadvertently escape from the working fluid circuit, such as at or proximate to the evaporator coil 128. For example, low GWP refrigerant may escape from a coupling or joint between components of the evaporator coil 128, from tubing of the evaporator coil 128, from conduits of the working fluid circuit, from another portion of the evaporator coil 128, and/or from other components of the working fluid circuit. Therefore, a potential exists for escaped low GWP refrigerant to enter the air flow path 114. Operation of the blower assembly 104 may cause escaped low GWP refrigerant within the air flow path 114 to mix (e.g., become entrained) with the air flow 112. During operation of the heating system 130 (e.g., in a heating mode of the HVAC system 100), escaped low GWP refrigerant within the air flow path 114 may therefore be directed with the air flow 112 across the heating coils 132, for example, due to the positioning of the heating coils 132 within the supply air section 118 downstream of the blower section 110 and the evaporator coil 128 (e.g., relative to a flow direction of the air flow 112 along the air flow path 114).

It is desirable to ensure that any escaped low GWP refrigerant, which may be reactive upon exposure to certain elevated temperatures, does not contact surfaces, components, and/or other features that may approach certain elevated temperatures (e.g., 700 degrees Centigrade, 1292 degrees Fahrenheit) in order to avoid inadvertent reaction of the low GWP refrigerant. During operation of the heating system 130, surfaces 134 of the heating coils 132 (e.g., surfaces of heating elements) are increased in order to enable heat transfer to the air flow 112 directed across the heating coils 132. As mentioned above, flow of the air flow 112 across the heating coils 132 (e.g., via operation of the blower assembly 104), and the resulting transfer of heat from the heating coils 132 to the air flow 112, may inhibit the surfaces 134 of the heating coils 132 from approaching or reaching certain elevated temperatures at which the low GWP refrigerant may be susceptible to reaction. However, operation of the heating coils 132 without adequate and/or sufficient flow of the air flow 112 across the heating coils 132 may render the heating coils 132 more susceptible to approaching or reaching certain elevated temperatures at which the low GWP refrigerant may be susceptible to reaction. In order to avoid such occurrences, present embodiments include a power supply control system 136 of the heating system 130 that is configured to block operation of the heating coils 132 in response to a detection and/or a determination indicative of a characteristic of the air flow 112 across the heating coils 132. In particular, the power supply control system 136 is configured to block supply of power (e.g., electrical power, electric current, voltage) to the heating coils 132, and thereby inhibit operation of the heating coils 132, in response to a detection and/or a determination indicative of insufficient, inadequate, and/or undesired flow of the air flow 112 across the heating coils 132.

As shown in the illustrated embodiment, the power supply control system 136 (e.g., at least a subset of components of the power supply control system 136) may be disposed within the housing 102. In particular, the components of the power supply control system 136 may be disposed within a power component section 138 defined within the housing 102. The power component section 138 may be disposed adjacent to the supply air section 118 (e.g., heating section) and may be separated from the supply air section 118 by a partition 140 (e.g., wall, panel, divider) extending between the power component section 138 and the supply air section 118 (e.g., from the blower section 110 to the base 126 of the housing 102). The partition 140 may generally fluidly separate the power component section 138 from the supply air section 118 (e.g., to block flow of the air flow 112 into the power component section 138). In some embodiments, components of the heating system 130, such as one or more of the components of the power supply control system 136, the partition 140, and the heating coils 132 may be assembled together to form a heating system assembly 142 configured to be collectively installed within the housing 102 and/or removed from the housing 102, such as via translational (e.g., sliding) actuation. Details of the power supply control system 136 are described further below.

FIG. 6 is a cross-sectional, schematic side view of a portion of an embodiment of the HVAC system 100 including the heating system 130 having the power supply control system 136, in accordance with the present techniques. The illustrated embodiment includes certain elements and element numbers similar to those discussed above with reference to FIG. 5, including the blower assembly 104, the heating coils 132 (e.g., electric heating coils, electric heaters) disposed within the supply air section 118, components of the power supply control system 136 disposed within the power component section 138, the partition 140 separating the supply air section 118 and the power component section 138, and so forth. The illustrated embodiment is intended to focus on certain features that enable the functionalities and benefits of the presently disclosed techniques, but it should be appreciated that the HVAC system 100 and/or the heating system 130 may include additional features, such as one or more of the components described above with reference to FIGS. 1-5.

As shown, the HVAC system 100 may include a control system 150 (e.g., controller, automation controller, control circuitry) configured to enable operation of the HVAC system 100 and the components thereof. For example, the control system 150 may include an embodiment of the control board 48 described above, an embodiment of the control panel 82 described above, one or more controllers of a rooftop HVAC unit, an air handler, an indoor HVAC unit, and/or an outdoor HVAC unit, a thermostat, a system controller, a dedicated controller, a standalone controller, another suitable control device or component, or any combination thereof. For example, the control system 150 may be configured to operate the HVAC system 100 in a particular operating mode (e.g., heating mode, cooling mode) to satisfy a call for conditioning (e.g., call for heating, call for cooling). To this end, the control system 150 may be communicatively coupled to one or more sensors configured to provide data indicative of one or more operating parameter of the HVAC system 100 and may be communicatively coupled to components of the HVAC system 100, such as one or more of the components described above.

One or more control transfer devices, such as wires, cables, wireless communication devices, and the like, may communicatively couple the blower assembly 104, the heating system 130, the control device 16 (e.g., thermostat), and/or any other suitable components of the HVAC system 100 to the control system 150. That is, one or more components of the HVAC system 100 may each have one or more communication components that facilitate wired or wireless (e.g., via a network) communication with the control system 150. In some embodiments, the communication components may include a network interface that enables the components of the HVAC system 100 to 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 system 100 to communicate via mobile telecommunications technology, Bluetooth®, near-field communications technology, and the like. In other embodiments, operational control of certain components of the HVAC system 100 may be regulated by one or more relays or switches (e.g., a 24 volt alternating current [VAC] relay).

The control system 150 includes processing circuitry 152, such as a microprocessor, which may execute software for controlling components of the HVAC system 100. The processing circuitry 152 may 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 circuitry 152 may include one or more reduced instruction set (RISC) processors. The control system 150 may also include a memory 154 (e.g., memory device) that may store information, such as instructions, control software, look up tables, configuration data, etc. The memory 154 may include a volatile memory, such as random access memory (RAM), and/or a nonvolatile memory, such as read-only memory (ROM). The memory 154 may store a variety of information and may be used for various purposes. For example, the memory 154 may store processor-executable instructions including firmware or software for the processing circuitry 152 to execute, such as instructions for controlling components of the HVAC system 100. In some embodiments, the memory 154 is a tangible, non-transitory, machine-readable-medium that may store machine-readable instructions for the processing circuitry 152 to execute. The memory 154 may include ROM, flash memory, a hard drive, or any other suitable optical, magnetic, or solid-state storage medium, or a combination thereof. The memory 154 may store data, instructions, and any other suitable data.

The HVAC system 100 is configured to receive power (e.g., electrical power, voltage, electric current) from a power source 156 (e.g., power supply). The power source 156 may be a utility grid, a battery, a generator, a solar panel, another suitable source of electrical power, or any combination thereof. The power source 156 may be configured to supply electrical power having any suitable type of electrical power, such as 240 volt alternating current (VAC), 220 VAC, 208 VAC, 120 VAC, or any other suitable type of electrical power. In some embodiments, the HVAC system 100 may also include a transformer 158 configured to modify a voltage of alternating current provided by the power source 156. For example, the transformer 158 may decrease (e.g., step down) the voltage (e.g., from 240 VAC, 220 VAC, 208 VAC, 120 VAC) to 24 VAC. In some embodiments, the reduced voltage (e.g., 24 VAC) may be provided from the transformer 158 to the control system 150, such as to a thermostat of the control system 150. The control system 150 may direct a signal 160 (e.g., electrical signal, current, voltage), such as a 24 volt (V) signal, to the power supply control system 136, in accordance with the present techniques. Additionally, one or more components of the power supply control system 136 may be configured to receive electrical power 162 (e.g., electric current, voltage, 240 VAC, 220 VAC, 208 VAC, 120 VAC) from the power source 156. The electrical power 162 output by the power source 156 and received by the power supply control system 136 may be suitable for use by the heating coils 132 to generate heat for transfer to the air flow 112. In the manner described below, the power supply control system 136 is configured to regulate supply of the electrical power 162 to the heating coils 132, and thereby control operation of the heating coils 132, based on a detection and/or a determination indicative of a quality, quantity, and/or characteristic of the air flow 112 directed through the supply air section 118 (e.g., across the heating coils 132).

The illustrated embodiment also shows certain components of the power supply control system 136 that may be incorporated in accordance with the present techniques. For example, the power supply control system 136 includes power circuitry 164 (e.g., power supply control circuitry, power management circuitry, electrical circuit, electrical path, power supply path) configured to control supply of the electrical power 162 to the heating coils 132. The power circuitry 164 may include a variety of components (e.g., electrical components) disposed along an electrical path that are configured to enable and/or disable flow of the electrical power 162 to the heating coils 132. In particular, the power supply control system 136 includes a switch 166 incorporated with the power circuitry 164. As described further below, the switch 166 is configured to selectively enable and disable flow of the electrical power 162 to the heating coils 132 based on a detected parameter associated with the air flow 112 directed through the supply air section 118 and across the heating coils 132.

The detected parameter may be a pressure differential between the supply air section 118 (e.g., high pressure region, high pressure section) and the power component section 138 (e.g., low pressure region, low pressure section), and the switch 166 may be an air proving switch and/or a pressure switch (e.g., differential pressure switch) configured to enable and disable flow of the electrical power 162 to the heating coils 132 based on the pressure differential relative to a threshold value. To this end, in some embodiments, the switch 166 may be fluidly coupled to the supply air section 118 and the power component section 138. For example, as shown, the switch 166 may be disposed within the power component section 138 and may be exposed (e.g., fluidly coupled) to a pressure (e.g., first pressure, low pressure) within the power component section 138. Additionally, the switch 166 may be fluidly coupled to the supply air section 118, such as via a conduit system 168, to expose (e.g., fluidly couple) the switch 166 to a pressure (e.g., first pressure, high pressure) within the supply air section 118. Accordingly, based on the pressure within the power component section 138 and the pressure within the supply air section 118, the switch 166 may be configured to detect a pressure differential between the supply air section 118 and the power component section 138.

As will be appreciated, the switch 166 may be configured to open and/or close based on a value of the pressure differential detected by the switch 166 relative to a threshold value. The threshold value (e.g., threshold differential pressure value) may be indicative of and/or associated with a lower limit (e.g., minimum, baseline, lower threshold amount) of the air flow 112 directed through the supply air section 118, such as to enable sufficient heat transfer from the heating coils 132 to the air flow 112 to maintain a temperature (e.g., surface temperature) of the heating coils 132 at or below a desired value (e.g., threshold temperature value, sufficiently below a particularly elevated temperature at which a low GWP refrigerant may be more susceptible to reaction, below a temperature value associated with a regulatory standard). During normal, expected, intended, and/or adequate operation of the blower assembly 104, the air flow 112 directed through the supply air section 118 and may cause the pressure within the supply air section 118 to increase, whereas the pressure within the power component section 138 may not rise during operation of the blower assembly 104, because the power component section 138 is generally fluidly separated from the supply air section 118 via the partition. Accordingly, during normal, expected, intended, and/or adequate operation of the blower assembly 104, the pressure differential between the supply air section 118 and the power component section 138 detected by the switch 166 may be equal to or greater than the threshold value. In such instances, the switch 166 may remain in and/or may transition to a closed configuration that enables supply of the electrical power 162 to the heating coils 132.

However, in some instances, the blower assembly 104 may not operate as intended and/or another operational interruption (e.g., blockage, obstruction) may cause the air flow 112 to flow through the supply air section 118 at a reduced and/or insufficient rate (e.g., that may render the heating coils 132 more susceptible to greater increases in temperature). For example, the blower assembly 104 may not operate properly (e.g., may not receive power, may operate deficiently, may malfunction) and may not direct the air flow 112 through the supply air section 118 at an intended flow rate and/or at or above a lower limit flow rate determined to enable sufficient heat transfer from the heating coils 132 to the air flow 112. In such instances, the pressure differential between the supply air section 118 and the power component section 138 detected by the switch 166 may be less than the threshold value. As a result, the switch 166 may remain in and/or may transition to an open configuration that interrupts and/or disables supply of the electrical power 162 to the heating coils 132. In this way, the heating coils 132 may not be operated under circumstances that may otherwise result in elevated temperatures (e.g., temperatures at or undesirably approaching a threshold temperature value) of the heating coils 132, and exposure of low GWP refrigerant (e.g., inadvertently escaped from a working fluid circuit of the HVAC system 100) to surfaces that may have a temperature at or undesirably approaching a threshold temperature value (e.g., 600 degrees Centigrade, 650 degrees Centigrade, 700 degrees Centigrade) may be effectively avoided.

As shown, the power supply control system 136 further includes a plurality of electrical contactors 170 (e.g., contactors) disposed within the power component section 138. The electrical contactors 170 may also be disposed along and/or incorporated with the power circuitry 164. As will be appreciated, the electrical contactors 170 may be configured to receive the electrical power 162 from the power source 156 and, upon activation and/or actuation of the electrical contactors 170, may be configured to supply the electrical power 162 to the heating coils 132 to enable operation of the heating coils 132 (e.g., generation of heat via the electrical power 162). One or more of the electrical contactors 170 may be actuated (e.g., energized) in response to receipt of a signal (e.g., 24V signal, indicative of a call for heating) from the control system 150. As described further below, the switch 166 may operate to interrupt transmission of a signal (e.g., energizing signal) from the control system 150 (e.g., thermostat) to one or more of the electrical contactors 170 in an open configuration of the switch 166 (e.g., based on a pressure differential between the supply air section 118 and the power component section 138 being less than a threshold value, which may be indicative of insufficient flow of the air flow 112 across the heating coils 132).

FIG. 7 is a schematic diagram of a portion of an embodiment of the HVAC system 100 including the heating system 130, the control system 150, and the blower assembly 104. The illustrated embodiment includes certain elements and element numbers similar to those discussed above with reference to FIGS. 5 and 6, such as the blower assembly 104, the heating system 130, and the control system 150. As described above, the control system 150 may include the processing circuitry 152 and the memory 154. The control system 150 may also include a communication bus 180, an input/output (I/O) interface 182, and a network interface 184, in some embodiments. The communication bus 180 may be a communication system (e.g., data transmission system) that may enable communication between various components of the processing circuitry 152 and/or other components of the control system 150. For example, the communication bus 180 may include a bridge, a message queue, a multi-core message-passing scheme, another suitable communication architecture (e.g., wires, fibers, traces, etc.). In some embodiments, the communication bus 180 may include multiple buses, such as a data bus, an address bus, and/or a control bus.

The I/O interface 182 may include an interface configured to enable communicatively coupling between the control system 150 (e.g., processing circuitry 152) and one or more components of the HVAC system 100, such as any or multiple of the components described herein. For example, the I/O interface 182 may include one or more pins, sockets, I/O devices, ports, I/O devices (e.g., touchscreen, slider, scroll wheel, keypad, etc.), another suitable feature to enable communication with the control system 150 and/or one or more components of the HVAC system 100, or any combination thereof. The network interface 184 may include wired and/or wireless interfaces (e.g., jacks, antennas, transmitters, receivers, transceivers, wire terminals, etc.) configured to transmit data communications with various external systems, devices, and/or networks. For example, the network interface 184 may include an Ethernet card and port for sending and receiving data via an Ethernet-based communications network and/or a Wi-Fi transceiver for communicating via a wireless communications network. The network interface 184 may be configured to communicate via local area networks or wide area networks (e.g., the Internet, a building WAN, etc.) and may use a variety of communication protocols (e.g., BACnet, IP, LON, IDNAC, Modbus, etc.). The network interface 184 may be a communication interface configured to facilitate electronic data communication between the processing circuitry 152 (e.g., control system 150) and various internal and external systems or devices.

The HVAC system 100 further includes a user interface 186 communicatively coupled to the control system 150. The user interface 186 may be associated with an electronic device of a user (e.g., system administrator, technician, installer, authorized personnel). The user interface 186 may be a smart phone, a mobile device, a desktop computer, a laptop, a tablet computing device, a digital media device, a personal digital assistant (PDA), a wearable device (e.g., optical head mounted display, smartwatch, etc.), a thermostat, another device having communication capabilities and/or processing capabilities, or any combination thereof.

As similarly described above, the blower assembly 104 includes a blower 188 (e.g., first blower 106, second blower 108) configured to force a flow of air (e.g., air flow 112) through the HVAC system 100 and across the heating coils 132 of the heating system 130. The blower 188 may be driven (e.g., rotated) by a motor 190 operatively coupled to the blower 188. For example, the motor 190 may drive rotation of the blower 188 at various speeds to generate and/or induce the air flow 112 directed through the HVAC system 100 (e.g., housing 102). In some embodiments, the motor 190 may be an electronically commutated motor (ECM). In some embodiments, the motor 190 may be a three-phase, brushless alternating current motor. As shown, operation of the motor 190 may be controlled by a motor controller 192. The motor controller 192 may be configured to regulate one or more inputs to the motor 190 (e.g., electrical input, control signals) to control a speed and/or rotation direction of the blower 188. As will be appreciated, operation of the blower assembly 104 may be controlled by the processing circuitry 152 (e.g., control system 150). For example, the processing circuitry 152 may regulate operations of the motor 190 and therefore the blower 188, for example, by providing speed settings and/or rotation settings to the motor controller 192.

Operation of the heating system 130 (e.g., heating coils 132) may also be regulated by the control system 150. For example, the processing circuitry 152 may be configured to output one or more signals (e.g., 24V signals, one or more voltages, control signals) toward the heating system 130 to enable actuation of one or more of the heating coils 132. In some embodiments, the processing circuitry 152 may output one or more signals to the heating system 130 based on data received by the control system 150, such data indicative of a temperature (e.g., detected by a sensor) of a conditioned space and/or a set point temperature of the conditioned space (e.g., received via a thermostat). The processing circuitry 152 may determine one or more signals to output to the heating system 130 based on a comparison of the data indicative of the temperature of the conditioned space and the set point temperature of the conditioned space. Some embodiments of the control system 150 and/or the heating system 130 may be configured to enable multi-stage operation of the heating system 130. For example, the heating system 130 may be configured for two-stage operation and, in response to a determination that a temperature differential between the temperature of the conditioned space and the set point temperature of the conditioned space is less than a threshold value (e.g., threshold temperature differential value), the control system 150 may output a first control signal to the heating system 130 to enable first stage operation of the heating system 130 (e.g., operate a subset of the heating coils 132). In response to a determination that the temperature differential between the temperature of the conditioned space and the set point temperature of the conditioned space is greater than the threshold value, the control system 150 may output a second control signal or multiple control signals to the heating system 130 to enable second stage operation of the heating system 130 (e.g., operation of all heating coils 132).

In any case, the heating system 130 includes an embodiment of the switch 166 (e.g., air proving switch), which is configured to enable and disable operation of the hating coils 132 (e.g., supply of the electrical power 162 to the heating coils 132) based on a detected parameter indicative of an air flow (e.g., air flow 112) directed across the heating coils 132, such as via operation of the blower 188. In response to a detection of a parameter (e.g., parameter value) indicative of the air flow 112 being sufficient (e.g., equal to or above a threshold value) to absorb heat from the heating coils 132 and inhibit an increase in temperature of surfaces of the heating coils 132 to and/or beyond a particular threshold (e.g., threshold temperature value, elevated temperature threshold value), the switch 166 may transition to and/or remain in a closed configuration (e.g., closed state). In the closed configuration, the switch 166 may enable supply of the electrical power 162 to the heating coils 132. However, in response to a detection of the parameter indicative of the air flow 112 being insufficient (e.g., below a threshold value) to absorb heat from the heating coils 132 and inhibit an increase in temperature of surfaces of the heating coils 132 to and/or beyond the particular threshold, the switch 166 may transition to and/or remain in an open configuration (e.g., open state), which may block supply of the electrical power 162 to the heating coils 132. In this way, the switch 166 blocks generation of undesired temperatures (e.g., surface temperatures, elevated temperatures) of the heating coils 132 that may otherwise render any inadvertently escaped low GWP refrigerant within the air flow path 114 from reacting upon exposure to the undesired temperatures and/or surfaces of the heating coils 132.

It should be appreciated that the detected parameter indicative of the air flow (e.g., air flow 112) directed across the heating coils 132 may be any suitable parameter value, such as a differential pressure value between the supply air section 118 (e.g., high pressure section) and the power component section 138 (e.g., low pressure section) of the heating system 130. Alternatively, the detected parameter may be a single value detected by the switch 166, such as a pressure value within the supply air section 118, and air flow rate of the air flow 112 directed across the heating coils 132, or another suitable value. Based on a particular parameter detected by the switch 166, a corresponding threshold value may be determined (e.g., via testing, via experimental data) that is indicative of an adequate amount of the air flow 112 directed across the heating coils 132 to block a temperature (e.g., surface temperature) of the heating coils 132 approaching and/or reaching a particular temperature threshold value (e.g., upper limit value).

The threshold value (e.g., differential pressure threshold value, actuation value, transition value, threshold pressure value) to which the detected parameter value indicative of the air flow (e.g., detected by the switch 166) is compared to determine whether the switch 166 is in the closed configuration or the open configuration may be a fixed value. In such embodiments, the threshold value may be based on a capacity (e.g., heating capacity) of the heating coils 132, a capacity (e.g., air flow capacity) of the blower assembly 104, a tonnage of the HVAC system 100 (e.g., HVAC unit), a physical arrangement and/or layout of components of the HVAC system 100 (e.g., blower assembly 104, heating system 130), another suitable parameter or characteristic of the HVAC system 100, or any combination thereof. In other embodiments, the threshold value may be an adjustable value. For example, the threshold value (e.g., switch 166 actuation value, switch 166 transition value) may be adjusted via modification of a physical configuration and/or component of the switch 166.

FIG. 8 is a schematic diagram of an embodiment of a portion of the HVAC system 100 including the power supply control system 136 for the heating system 130, in accordance with aspects of the present disclosure. The illustrated embodiment also includes embodiments of the control system 150, the transformer 158, and the power source 156 described above, which may operate in a similar manner as that previously described.

The HVAC system 100 further includes a thermostat 200 (e.g., control device) configured to receive electrical power (e.g., 24V signal, voltage, electric current) from the transformer 158. In some implementations, the thermostat 200 may be considered a component of the control system 150. The thermostat 200 (e.g., user interface, controller) may be disposed within a conditioned space serviced by the HVAC system 100. As briefly discussed above, the thermostat 200 may be configured to receive a user input indicative of a set point temperature (e.g., a desired temperature) for the conditioned space. The thermostat 200 may also be configured to receive data or feedback indicative of a measured temperature associated with the conditioned space. In particular, the thermostat 200 may be communicatively coupled to a sensor 202 configured to detect the measured temperature. In some embodiments, the sensor 202 may be positioned within the conditioned space and be configured to detect a temperature (e.g., air temperature) within the conditioned space. In other embodiments, the sensor 202 may be positioned within ductwork or within the HVAC system 100 and be configured to detect a temperature of return air received by the HVAC system 100 from the conditioned space.

In operation, the thermostat 200 may compare the set point temperature (e.g., received via user input) and the measured temperature detected by the sensor 202. Based on a determination that the measured temperature deviates from (e.g., is less than) the set point temperature (e.g., by a threshold percentage, by a threshold amount), the thermostat 200 may output a signal 204 (e.g., electrical signal, 24V signal, voltage, call for conditioning signal, call for heating signal) indicative of a call for conditioning (e.g., a call for heating). The signal 204 may be directed to one or more components of the HVAC system 100 communicatively coupled to the thermostat 200 to enable operation of the HVAC system 100 to provide a supply air flow (e.g., supply air flow 120) to the conditioned space and cause the measured temperature to approach the set point temperature. In some embodiments, the signal 204 output by the thermostat 200 may be directed to the control system 150 (e.g., control board 48, control panel 82, HVAC unit control board) and/or to another component of the HVAC system 100, such as the transformer 158, which may output the signal 204 and/or another signal (e.g., 24V signal) to the control system 150 (e.g., HVAC unit control board). Additionally or alternatively, the thermostat 200 may output the signal 204 to a relay of the HVAC system 100 (e.g., power supply control system 136), an electrical contactor of the HVAC system 100, another suitable component, or any combination thereof. In any case, the signal 204 may be received by the control system 150 and, in response, the control system 150 may output the signal 160 (e.g., 24V signal) to the power supply control system 136.

As described above, present embodiments of the power supply control system 136 include the power circuitry 164 (e.g., power supply control circuitry) configured to enable and disable supply of the electrical power 162 to the heating coils 132. More specifically, the illustrated embodiment of the power circuitry 164 includes a power supply control circuit 206 (e.g., power supply path, electrical path, electrical circuit) configured to enable the functionalities and achieve the benefits described herein. The power supply control circuit 206 includes various components (e.g., electrical components) disposed along the power supply control circuit 206, such as the switch 166 (e.g., pressure switch, air proving switch, pressure differential switch, vane switch, sail switch, paddle switch, flow switch, etc.), limit switches 208, and a heating system relay 210 (e.g., relay, heater relay, heating coil relay).

As shown, the limit switches 208, the switch 166, and the heating system relay 210 may be arranged in series along the power supply control circuit 206. For example, relative to a direction of an electrical signal along the power supply control circuit 206, the limit switches 208, the switch 166, and the heating system relay 210 may be sequentially arranged (e.g., in series) along the power supply control circuit 206. However, other embodiments of the power supply control circuit 206 may include an alternative arrangement of the components described herein that enables supply of the electrical power 162 to the heating coils 132 in response a detection of the air flow 112 directed across the heating coils 132 being sufficient, as described herein, and disables supply of the electrical power 162 to the heating coils 132 in response a detection of the air flow 112 directed across the heating coils 132 being insufficient, as described herein. It should also be appreciated that the power circuitry 164 and the power supply control circuit 206 may include additional or alternative components different from those shown in the illustrated embodiment and nevertheless provide the functionalities and benefits described herein.

The signal 160 (e.g., 24V signal, supply voltage, first voltage) may be directed from the control system 150 to the power supply control circuit 206 via an input node 212 of the power supply control circuit 206. The signal 160 may flow along the power supply control circuit 206 from the input node 212 to the limit switches 208, which are arranged in series along the power supply control circuit 206 (e.g., between the input node 212 and the switch 166). The limit switches 208 may be configured to detect undesirable (e.g., unexpected, abnormal) operating conditions associated with operation of the heating system 130. Upon detection of an operating parameter value (e.g., temperature value, air temperature value) that deviates from an expected operating parameter value range and/or from an expected operating parameter value (e.g., exceeds a threshold value, exceeds a predetermined limit), one or more of the limit switches 208 may be tripped (e.g., transition to an open configuration or open state) to block flow of the signal 160 along the power supply control circuit 206 and inhibit operation of the heating coils 132 (e.g., inhibit supply of the electrical power 162 to the heating coils 132). In some embodiments, one or more of the limit switches 208 may include a bimetallic strip configured to deform in response to differential expansion of two metals in the bimetallic strip. The deformation may result in the limit switch 208 transitioning to an open configuration or open state to interrupt transmissions of the signal 160 along the power supply control circuit 206.

For example, the limit switches 208 include a first set of limit switches 214 including a first limit switch 216 and a second limit switch 218. The first limit switch 216 and the second limit switch 218 may each be configured to detect a temperature of air, such as a temperature of the air flow 112 within the supply air section 118, a temperature of the supply air flow 120, an air temperature within a duct (e.g., ductwork) of the HVAC system 100, or any other suitable temperature. To this end, the first limit switch 216 and the second limit switch 218 may be arranged in any suitable location to enable detection of a particular temperature within and/or associated with the HVAC system 100. For example, the first limit switch 216, the second limit switch 218, or both may be positioned within the supply air section 118 (e.g., heating section) adjacent or near the heating coils 132. Indeed, installed locations of the first set of limit switches 214 may vary in different embodiments of the HVAC system 100. In response to detection of an air temperature greater than a first threshold value (e.g., first threshold temperature value, 200 degrees Fahrenheit), one or more of the first set of limit switches 214 may be tripped and may transition to a respective open position, thereby blocking further transmission of the signal 160 along the power supply control circuit 206 (e.g., to the switch 166, to the heating system relay 210). To this end, the first limit switch 216 and the second limit switch 218 may be arranged in any suitable location to enable detection of a particular temperature within and/or associated with the HVAC system 100.

With the first limit switch 216 and the second limit switch 218 in respective closed configurations, the signal 160 may be transmitted along the power supply control circuit 206 to a second set of limit switches 220, which include a third limit switch 222 and a fourth limit switch 224. In some respects, the third limit switch 222 and the fourth limit switch 224 may be similar to the first limit switch 216 and the second limit switch 218. For example, the third limit switch 222 and the fourth limit switch 224 may also be configured to detect a temperature of air within the HVAC system 100 and/or associated with the HVAC system 100, as similarly described above. In response to detection of an air temperature greater than a second threshold value (e.g., second threshold temperature value, 160 degrees Fahrenheit), different from the first threshold value associated with the first set of limit switches 214, one or more of the second set of limit switches 220 may be tripped and may transition to a respective open position, thereby blocking further transmission of the signal 160 along the power supply control circuit 206 (e.g., to the switch 166, to the heating system relay 210).

In some embodiments, the second set of limit switches 220 may be implemented (e.g., function, operate) as primary limit switches, while the first set of limit switches 214 may be implemented (e.g., function, operate) as backup limit switches. Accordingly, the second set of limit switches 220 may be positioned along the power supply control circuit 206 between (e.g., in series with) the first set of limit switches 214 and the switch 166, and the first set of limit switches 214 may be positioned along the power supply control circuit 206 between (e.g., in series with) the input node 212 and the first set of limit switches 214. Additionally, in such configurations of the power supply control system 136, the second threshold value at which an air temperature detected by one or more of the second set of limit switches 220 is tripped (e.g., transitioned to an open configuration) may be less than the first threshold value at which an air temperature detected by one or more of the first set of limit switches 214 is tripped (e.g., transitioned to an open configuration). Therefore, the first set of limit switches 214 may be configured to trip (e.g., open) when the second set of limit switches 220 do not operate as intended (e.g., open in response to a detected air temperature equal to or greater than the second threshold value). As implemented and intended, one or more of the second set of limit switches 220 may be configured to trip (e.g. open) in response to a detected air temperature equal to or greater than the second threshold value, while the first set of limit switches 214 may remain closed (e.g., based on a detected air temperature exceeding the second threshold value but not exceeding the first threshold value).

In the illustrated embodiment, the first set of limit switches 214 (e.g., backup limit switches) are electrically coupled to a backup set of electrical contactors 226. In response to transition of one or more of the first set of limit switches 214 to an open configuration (e.g., tripping), transmission of the signal 160 to the backup set of electrical contactors 226 may be blocked, which may inhibit actuation of the backup set of electrical contactors 226 to supply the electrical power 162 to the heating coils 132. Further, in some embodiments, one or more of the limit switches 208 may be electrically coupled to the control system 150 (e.g., processing circuitry 152) to enable transmission of a signal (e.g., alert signal) to the control system 150 in response to transition of one or more limit switches 208 to an open (e.g., tripped) configuration to indicate detection of an abnormal (e.g., elevated) air temperature (e.g., within the HVAC system 100).

With each of the limit switches 208 in a respective closed configuration, the signal 160 may be transmitted along the power supply control circuit 206 to the switch 166 (e.g., air proving switch), which is arranged along the power supply control circuit 206 between (e.g., in series with) the limit switches 208 and the heating system relay 210. As described above, the switch 166 may be in a closed configuration or an open configuration based on a parameter indicative of the air flow 112 directed across the heating coils 132 detected by the switch 166. For example, based on a value of the detected parameter being greater than a threshold value, which may correspond to a lower limit value of the air flow 112 that is sufficient to enable heat transfer from the heating coils 132 to the air flow 112 to maintain a temperature (e.g., surface temperature) of the heating coils 132 at or below a desired value (e.g., associated with reaction of a low GWP refrigerant), the switch 166 (e.g., a switching contact 228 of the switch 166) may transition from an open configuration (e.g., normally open configuration) to a closed configuration. Accordingly, operation of the power supply control system 136 may demand establishment of a normal, expected, intended, and/or adequate amount of the air flow 112 directed across the heating coils 132 before the switch 166 is closed to enable supply of the electrical power 162 to the heating coils 132 and initiate operation of the heating coils 132. However, based on a value of the detected parameter being less than the threshold value, the switch 166 (e.g., switching contact 228) may remain in the open configuration, and transmission of the signal 160 along the power supply control circuit 206 to the heating system relay 210 may be interrupted and/or blocked.

Transmission of the signal 160 along the power supply control circuit 206 to the heating system relay 210 (e.g., via the switch 166 and/or switching contact 228 in the closed configuration) enables supply of the electrical power 162 to the heating coils 132 and thereby enables operation of the heating coils 132 to heat the air flow 112. The heating system relay 210 includes a coil 230 that may be energized via the signal 160 directed to the heating system relay 210. When the signal 160 (e.g., 24V) is not directed to the heating system relay 210 (e.g., due to the switch 166 being in an open configuration) the coil 230 may be de-energized.

The heating system relay 210 also includes a first relay contact 232 and a second relay contact 234. The first relay contact 232 is disposed along a first signal path 236 (e.g., stage one call signal path) extending between the control system 150 (e.g., processing circuitry 152) and a first set of electrical contactors 238 (e.g., first primary electrical contactors, electrical contactors 170), and the second relay contact 234 is disposed along a second signal path 240 (e.g., stage two call signal path) extending between the control system 150 (e.g., processing circuitry 152) and a second set of electrical contactors 242 (e.g., second primary electrical contactors, electrical contactors 170). In response to receipt of a call for heating from the thermostat 200 indicative of a call for first stage heating, the control system 150 may output a first stage signal 244 along the first signal path 236 toward the first set of electrical contactors 238. For example, the thermostat 200 may output a call for first stage heating in response to a determination that a detected temperature within a conditioned space serviced by the HVAC system 100 is less than a set point temperature by a first amount less than a threshold amount. In response to receipt of a call for heating from the thermostat 200 indicative of a call for second stage heating, the control system 150 may output the first stage signal 244 along the first signal path 236 toward the first set of electrical contactors 238 and may also (e.g., concurrently, simultaneously) output a second stage signal 246 along the second signal path 240 toward the second set of electrical contactors 242. The thermostat 200 may output a call for second stage heating in response to a determination that the detected temperature within the conditioned space serviced by the HVAC system 100 is less than the set point temperature by a second amount greater than the threshold amount.

The first relay contact 232 and the second relay contact 234 may each be configured as normally open contacts and/or normally open switches. Upon energization of the coil 230 via the signal 160 directed along the power supply control circuit 206 from the switch 166 to the heating system relay 210, the coil 230 (e.g., electromagnet) may draw the first relay contact 232 and the second relay contact 234 to respective closed configurations, thereby enabling transmission of the first stage signal 244 (e.g., 24V signal) along the first signal path 236 to the first set of electrical contactors 238 and enabling transmission of the second stage signal 246 (e.g., 24V signal) along the second signal path 240 to the second set of electrical contactors 242.

The first stage signal 244 may be received by the first set of electrical contactors 238 and, in response, the first set of electrical contactors 238 may transition to a closed circuit configuration to enable supply of the electrical power 162 to a first subset of the heating coils 132. Thus, in response to a call for first stage heating received from the thermostat 200, the first subset of the heating coils 132, instead of all heating coils 132, may be operated via the electrical power 162 to transfer heat to the air flow 112. Similarly, the second stage signal 246 may be received by the second set of electrical contactors 242 and, in response, the second set of electrical contactors 242 may transition to a closed circuit configuration to enable supply of the electrical power 162 to a second subset of the heating coils 132. Thus, in response to a call for second stage heating received from the thermostat 200, the first subset of the heating coils 132 and the second subset of the heating coils 132 (e.g., all heating coils 132 of the heating system 130) may be operated via the electrical power 162 to transfer heat to the air flow 112. In some embodiments, each of the first set of electrical contactors 238 and the second set of electrical contactors 242 may include a respective coil (e.g., electromagnet) configured to energize in response to receipt of the first stage signal 244 and/or the second stage signal 246, which may cause the first set of electrical contactors 238 and the second set of electrical contactors 242 to transition to closed circuit configurations to enable supply of the electrical power 162 to the respective subsets of heating coils 132 associated with the first set of electrical contactors 238 and the second set of electrical contactors 242. However, in response to detection of an operating parameter value (e.g., differential pressure value, pressure value) less than a corresponding threshold value, the switch 166 may transition to an open configuration, which may de-energize the coil 230 of the heating system relay 210, cause the first relay contact 232 and the second relay contact 234 to transition to respective open configurations (e.g., normally open configurations), and interrupt transmission of the first stage signal 244 to the first set of electrical contactors 238 and transmission of the second stage signal 246 to the second set of electrical contactors 242. In this way, operation of the switch 166 may interrupt and/or block transmission of the electrical power 162 to the heating coils 132 in response to detection of the air flow 112 being less than desired (e.g., less than a threshold amount, less than a threshold value).

In some embodiments, the power supply control system 136 may be configured to transmit feedback to the control system 150, such as feedback indicative of a state or configuration of the switch 166. For example, the power supply control system 136 may include a feedback path 248 (e.g., trace, circuit, connection) extending from the power supply control circuit 206 (e.g., switch 166) to the control system 150 (e.g., processing circuitry 152). In response to transition of the switch 166 from one configuration to another configuration (e.g., from closed to open, tripping) and/or in response to detection of the signal 160 along the power supply control circuit 106 (e.g., between the fourth limit switch 224 and the switch 166), the power supply control circuit 206 may transmit feedback to the control system 150 via the feedback path 248. In some instances, the feedback may be indicative of the switch 166 being in an open configuration (e.g., indicative of insufficient air flow within the supply air section 118) in conjunction with an existing call for conditioning (e.g., signal 160, signal 204) that may not be satisfied due to interrupted and/or blocked operation of the heating system 130 (e.g., via the switch 166 in the open configuration).

As described above, the switch 166 may be configured to detect a pressure differential indicative of an amount of the air flow 112 directed across the heating coils 132 and through the supply air section 118. To this end, the switch 166 may be fluidly coupled to the supply air section 118 (e.g., a first pressure within the supply air section 118) and be fluidly coupled to the power component section 138 (e.g., a second pressure within the power component section 138).

FIG. 9 is a perspective view schematic of a portion of an embodiment of the heating system 130, illustrating an arrangement of components of the heating system 130 described herein. For example, the illustrating embodiment includes the supply air section 118 having the heating coils 132 disposed therein and components of the power supply control system 136 disposed within the power component section 138. In particular, the switch 166 and the heating system relay 210 are disposed within the power component section 138. In some embodiments, the switch 166, the heating system relay 210, or both may be mounted to a surface 260 of the partition 140 facing (e.g., exposed to) the power component section 138.

To enable the functionalities and benefits described herein, some embodiments of the switch 166 may be configured to detect a pressure within the supply air section 118 and a pressure within the power component section 138 to detect a pressure therebetween that is indicative of an amount of the air flow 112 directed across the heating coils 132 within the supply air section 118. To this end, the switch 166 (e.g., air proving switch) may include a first pressure port 262 fluidly coupled to an internal volume 264 of the power component section 138 and a second pressure port 266 fluidly coupled to an internal volume 268 of the supply air section 118. As the switch 166 is mounted to the partition 140 within the power component section 138, the switch 166 may be implemented with one or more additional features to enable fluid coupling of the second pressure port 266 with the internal volume 268 of the supply air section 118. For example, in the illustrated embodiment, a conduit 270 (e.g., tube, hose) is fluidly coupled to the second pressure port 266 and is secured to the switch 166. The conduit 270 from the second pressure port 266 to a fitting 272 (e.g., fluid connector, barbed fitting, connector port, grommet, bushing, conduit connector) secured to and extending through the partition 140 (E.g., through an opening or aperture formed in the partition 140). The fitting 272 may be configured to establish a sealing engagement with the partition 140 to block inadvertent flow of air (e.g., air flow 112) between the partition 140 and the fitting 272. Thus, the fitting 272 and the conduit 270 may enable fluid coupling of the second pressure port 266 to the internal volume 268 of the supply air section 118 without undesired bypass or escape of the air flow 112 through the partition 140 and into the power component section 138. However, it should be appreciated that other embodiments of power supply control system 136 may include other arrangements of components (e.g., switch 166, heating system relay 210) within the power component section 138 and/or elsewhere within the HVAC system 100.

While certain features and embodiments 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, such as temperatures and pressures, mounting arrangements, use of materials, colors, orientations, and so forth, 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, or those unrelated to enablement. 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.

The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).