Patent Publication Number: US-11397012-B2

Title: Panel restrictor for HVAC system

Description:
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, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     HVAC systems are utilized in residential, commercial, and industrial environments to control environmental properties, such as temperature and humidity, for occupants of the respective environments. The HVAC system may include one or more heat exchangers, blowers, compressors, and/or a variety of other HVAC components that facilitate regulating such environmental properties through control of an air flow delivered to the environment. The HVAC components are typically positioned within an enclosure of the HVAC system that is configured to shield the HVAC components from direct exposure to precipitation, ultraviolet radiation, and/or other environmental elements. 
     Generally, HVAC enclosures may be assembled from a plurality of panel assemblies that are coupled to a frame or to another support structure of the HVAC enclosure. Certain of the panel assemblies may be pivotably coupled to the frame via one or more hinges that enable the panel assemblies to transition between respective open and closed positions. As such, the panel assemblies may selectively enable access to the HVAC components positioned within an interior of the HVAC enclosure for maintenance or other purposes. Unfortunately, the panel assemblies may be susceptible to movement during performance of such maintenance operations and may not remain stationary in the open or closed positions. 
     SUMMARY 
     The present disclosure relates to a panel restrictor for a heating, ventilation, and/or air conditioning (HVAC) unit. The panel restrictor includes a first bracket configured to couple to a structural support of the HVAC unit, where the first bracket includes a slot. The panel restrictor includes a second bracket configured to couple to a panel of the HVAC unit. An arcuate segment extends from the second bracket and is configured to extend through the slot. The panel restrictor also includes an engager configured to secure the arcuate segment within the slot at a plurality of discrete positions along the arcuate segment. 
     The present disclosure also relates to a heating, ventilation, and/or air conditioning (HVAC) unit. The HVAC unit includes a panel pivotably coupled to a structural support of the HVAC unit and a panel restrictor configured to retain the panel in a plurality of orientations relative to the structural support. The panel restrictor includes a first bracket coupled to the structural support, where the first bracket includes a slot. The panel restrictor also includes a second bracket coupled to the panel and including an arcuate segment extending through the slot. The panel restrictor further includes an engager configured to secure the arcuate segment within the slot at a plurality of discrete positions along the arcuate segment, where each of the plurality of discrete positions corresponds to one of the plurality of orientations of the panel. 
     The present disclosure also relates to a door assembly of a heating, ventilation, and/or air conditioning (HVAC) unit. The door assembly includes a panel configured to occlude an opening of the HVAC unit and a hinge pivotably coupling the panel to a structural support of the HVAC unit. The hinge enables pivotal motion of the panel about an axis relative to the structural support. The door assembly includes a panel restrictor configured to retain the panel in a plurality of orientations relative to the structural support. The panel restrictor includes a first bracket coupled to the structural support, where the first bracket includes a slot. The panel restrictor also includes a second bracket coupled to the panel and including an arcuate segment configured to extend through the slot, where the arcuate segment includes a plurality of apertures formed therein. The panel restrictor also includes an engager coupled to the first bracket and configured to engage with an aperture of the plurality of apertures to secure the first bracket to the second bracket at a discrete position along the arcuate segment, where the discrete position corresponds to one of the plurality of orientations of the panel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of a building that may utilize a heating, ventilation, and/or air conditioning (HVAC) system 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 perspective view of an embodiment of a split, residential HVAC system, in accordance with an aspect of the present disclosure; 
         FIG. 4  is a schematic diagram 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 an embodiment of an HVAC unit having pivotable panel assemblies, in accordance with an aspect of the present disclosure; 
         FIG. 6  is a perspective view of an embodiment of a panel restrictor for an HVAC unit, in accordance with an aspect of the present disclosure; 
         FIG. 7  is a perspective view of an embodiment of a portion of an HVAC unit having a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 8  is a top view of an embodiment of a portion of an HVAC unit having a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 9  is a top view of an embodiment of a portion of an HVAC unit having a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 10  is a perspective view of an embodiment of a portion of an HVAC unit having a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 11  is a perspective view of an embodiment of an HVAC unit having a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 12  is an exploded perspective view of an embodiment of a panel restrictor for an HVAC unit, in accordance with an aspect of the present disclosure; 
         FIG. 13  is a perspective view of an embodiment of a link for a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 14  is a perspective view of an embodiment of a portion of an HVAC unit having a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 15  is a perspective view of an embodiment of a portion of an HVAC unit having a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 16  is a perspective view of an embodiment of a portion of an HVAC unit having a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 17  is a close-up perspective view of an embodiment of a panel restrictor for an HVAC unit, in accordance with an aspect of the present disclosure; 
         FIG. 18  is a perspective view of an embodiment of an electrical box having a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 19  is an exploded perspective view of an embodiment of a panel restrictor for an electrical box, in accordance with an aspect of the present disclosure; 
         FIG. 20  is a perspective view of an embodiment of a portion of an electrical box having a bracket assembly of a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 21  is a bottom view of an embodiment of a portion of an electrical box having a bracket assembly of a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 22  is a perspective view of an embodiment of a portion of an electrical box having a bracket assembly of a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 23  is a perspective view of an embodiment of a cam for a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 24  is a perspective view of an embodiment of a cam for a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 25  is a side view of an embodiment of a portion of an electrical box having a panel restrictor, in accordance with an aspect of the present disclosure; 
         FIG. 26  is a side view of an embodiment of a portion of an electrical box having a panel restrictor, in accordance with an aspect of the present disclosure; and 
         FIG. 27  is a side view of an embodiment of a portion of an electrical box having a panel restrictor, in accordance with an aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present disclosure will be described below. These described embodiments are only examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     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. The HVAC system generally includes a vapor compression system that transfers thermal energy between a heat transfer fluid, such as a refrigerant, and a fluid to be conditioned, such as air. The vapor compression system typically includes a condenser and an evaporator that are fluidly coupled to one another via conduits to form a refrigerant circuit. A compressor of the refrigerant circuit may be used to circulate the refrigerant through the conduits and enable the transfer of thermal energy between the condenser and the evaporator. 
     The HVAC system generally includes an enclosure that may house certain HVAC components of the HVAC system, such as the evaporator and the compressor. As such, the enclosure may shield the HVAC components from direct exposure to precipitation, ultraviolet radiation, and/or other environmental elements surrounding the HVAC system. Moreover, the enclosure may define a flow path that enables a blower or fan to force an air flow along the flow path and across the evaporator during operation of the HVAC system. As such, the enclosure enables the blower to facilitate heat exchange between the air flow and the refrigerant circulating through the refrigerant circuit. Accordingly, the evaporator may output a flow of conditioned air that may be discharged from the enclosure and directed to a suitable room or space within the building. 
     The HVAC enclosure is typically formed from a plurality of panel assemblies that are coupled to a frame or to another support structure of the HVAC enclosure. As briefly discussed above, certain of the panel assemblies may be pivotably coupled to the frame via one or more hinges that enable the panel assemblies to rotate about respective axis between corresponding closed and open positions. As such, a service technician or other operator of the HVAC system may selectively transition the panel assemblies between the closed and open positions to obtain access to an interior of the HVAC enclosure. In this manner, the movable panel assemblies may facilitate performance of maintenance or inspection operations on the HVAC components positioned within the HVAC enclosure. 
     Unfortunately, conventional hinge assemblies may be unable the effectively retain the panel assemblies in particular positions, such as the open positions, when forces generated due to wind or other sources are imparted on the panel assemblies. As a result, the panel assemblies may not remain oriented in desired positions, and thus, may complicate maintenance operations on the HVAC system and increase a time period that may be involved to complete the maintenance operations. 
     It is now recognized that retaining a panel or a panel assembly of an HVAC enclosure in a particular position may enable personnel to more easily obtain access to an interior of the HVAC enclosure. More specifically, it is now recognized that retaining a panel assembly in an open position may enable personnel to access an interior of an HVAC enclosure without having to stabilize the panel assembly or otherwise manually retain the panel assembly in the open position. 
     Accordingly, embodiments of the present disclosure are directed to a panel restrictor that is configured to retain a panel assembly of an HVAC enclosure in various discrete positions or orientations relative to a frame of the HVAC enclosure. For example, in some embodiments, the panel restrictor may include a first end that is coupled to the frame or to another structural support of the HVAC enclosure and a second end that is coupled to the panel assembly. The panel restrictor may be selectively lockable in a plurality of positions to retain the panel assembly in an open position or in various partially open positions. As such, when in a locked configuration, the panel restrictor may ensure that the panel assembly remains substantially stationary relative to the HVAC enclosure and may inhibit movement of the panel assembly due forces generated by, for example, wind and/or gravity. These and other features will be described below with reference to the drawings. 
     It is important to note that, while the present disclosure describes the panel restrictor as configured for use with an enclosure of an HVAC system, it should be appreciated that the disclosed embodiments may be implemented with a variety of other enclosures, housings, and electrical boxes having various movable panels, doors, and/or access hatches. As a non-limiting example, the techniques described herein may be used with enclosures, doors, and/or panel assemblies used in automotive, marine, and/or aeronautical industries. 
     Turning now to the drawings,  FIG. 1  illustrates an embodiment of a heating, ventilation, and/or air conditioning (HVAC) system for environmental management that may employ one or more HVAC units. 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 . 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, integrated air handler, and/or auxiliary heating unit. In other embodiments, the HVAC unit  12  may be part of a split HVAC system, such as the system shown in  FIG. 3 , which includes an outdoor HVAC unit  58  and an indoor HVAC unit  56 . 
     The HVAC unit  12  is an air cooled device that implements a refrigeration cycle to provide conditioned air to the building  10 . Specifically, the HVAC unit  12  may include one or more heat exchangers across which an air flow is passed to condition the air flow before the air flow is supplied to the building. In the illustrated embodiment, the HVAC unit  12  is a rooftop unit (RTU) that conditions a supply air stream, such as environmental air and/or a return air flow from the building  10 . After the HVAC unit  12  conditions the air, the air is supplied to the building  10  via ductwork  14  extending throughout the building  10  from the HVAC unit  12 . For example, the ductwork  14  may extend to various individual floors or other sections of the building  10 . In certain embodiments, the HVAC unit  12  may be a heat pump that provides both heating and cooling to the building with one refrigeration circuit configured to operate in different modes. In other embodiments, the HVAC unit  12  may include one or more refrigeration circuits for cooling an air stream and a furnace for heating the air stream. 
     A control device  16 , one type of which may be a thermostat, may be used to designate the temperature of the conditioned air. The control device  16  also may be used to control the flow of air through the ductwork  14 . For example, the control device  16  may be used to regulate operation of one or more components of the HVAC unit  12  or other components, such as dampers and fans, within the building  10  that may control flow of air through and/or from the ductwork  14 . In some embodiments, other devices may be included in the system, such as pressure and/or temperature transducers or switches that sense the temperatures and pressures of the supply air, return air, and so forth. Moreover, the control device  16  may include computer systems that are integrated with or separate from other building control or monitoring systems, and even systems that are remote from the building  10 . 
       FIG. 2  is a perspective view of an embodiment of the HVAC unit  12 . In the illustrated embodiment, the HVAC unit  12  is a single package unit that may include one or more independent refrigeration circuits and components that are tested, charged, wired, piped, and ready for installation. The HVAC unit  12  may provide a variety of heating and/or cooling functions, such as cooling only, heating only, cooling with electric heat, cooling with dehumidification, cooling with gas heat, or cooling with a heat pump. As described above, the HVAC unit  12  may directly cool and/or heat an air stream provided to the building  10  to condition a space in the building  10 . 
     As shown in the illustrated embodiment of  FIG. 2 , a cabinet  24  encloses the HVAC unit  12  and provides structural support and protection to the internal components from environmental and other contaminants. In some embodiments, the cabinet  24  may be constructed of galvanized steel and insulated with aluminum foil faced insulation. Rails  26  may be joined to the bottom perimeter of the cabinet  24  and provide a foundation for the HVAC unit  12 . In certain embodiments, the rails  26  may provide access for a forklift and/or overhead rigging to facilitate installation and/or removal of the HVAC unit  12 . In some embodiments, the rails  26  may fit into “curbs” on the roof to enable the HVAC unit  12  to provide air to the ductwork  14  from the bottom of the HVAC unit  12  while blocking elements such as rain from leaking into the building  10 . 
     The HVAC unit  12  includes heat exchangers  28  and  30  in fluid communication with one or more refrigeration circuits. Tubes within the heat exchangers  28  and  30  may circulate refrigerant, such as R- 410 A, through the heat exchangers  28  and  30 . The tubes may be of various types, such as multichannel tubes, conventional copper or aluminum tubing, and so forth. Together, the heat exchangers  28  and  30  may implement a thermal cycle in which the refrigerant undergoes phase changes and/or temperature changes as it flows through the heat exchangers  28  and  30  to produce heated and/or cooled air. For example, the heat exchanger  28  may function as a condenser where heat is released from the refrigerant to ambient air, and the heat exchanger  30  may function as an evaporator where the refrigerant absorbs heat to cool an air stream. In other embodiments, the HVAC unit  12  may operate in a heat pump mode where the roles of the heat exchangers  28  and  30  may be reversed. That is, the heat exchanger  28  may function as an evaporator and the heat exchanger  30  may function as a condenser. In further embodiments, the HVAC unit  12  may include a furnace for heating the air stream that is supplied to the building  10 . While the illustrated embodiment of  FIG. 2  shows the HVAC unit  12  having two of the heat exchangers  28  and  30 , in other embodiments, the HVAC unit  12  may include one heat exchanger or more than two heat exchangers. 
     The heat exchanger  30  is located within a compartment  31  that separates the heat exchanger  30  from the heat exchanger  28 . Fans  32  draw air from the environment through the heat exchanger  28 . Air may be heated and/or cooled as the air flows through the heat exchanger  28  before being released back to the environment surrounding the 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 refrigerant before the refrigerant enters the heat exchanger  28 . The compressors  42  may be any suitable type of compressors, such as scroll compressors, rotary compressors, screw compressors, or reciprocating compressors. In some embodiments, the compressors  42  may include a pair of hermetic direct drive compressors arranged in a dual stage configuration  44 . However, in other embodiments, any number of the compressors  42  may be provided to achieve various stages of heating and/or cooling. As may be appreciated, additional equipment and devices may be included in the HVAC unit  12 , such as a solid-core filter drier, a drain pan, a disconnect switch, an economizer, pressure switches, phase monitors, and humidity sensors, among other things. 
     The HVAC unit  12  may receive power through a terminal block  46 . For example, a high voltage power source may be connected to the terminal block  46  to power the equipment. The operation of the HVAC unit  12  may be governed or regulated by a control board  48 . The control board  48  may include control circuitry connected to a thermostat, sensors, and alarms. One or more of these components may be referred to herein separately or collectively as the control device  16 . The control circuitry may be configured to control operation of the equipment, provide alarms, and monitor safety switches. Wiring  49  may connect the control board  48  and the terminal block  46  to the equipment of the HVAC unit  12 . 
       FIG. 3  illustrates a residential heating and cooling system  50 , also in accordance with present techniques. The residential heating and cooling system  50  may provide heated and cooled air to a residential structure, as well as provide outside air for ventilation and provide improved indoor air quality (IAQ) through devices such as ultraviolet lights and air filters. In the illustrated embodiment, the residential heating and cooling system  50  is a split HVAC system. In general, a residence  52  conditioned by a split HVAC system may include refrigerant conduits  54  that operatively couple the indoor unit  56  to the outdoor unit  58 . The indoor unit  56  may be positioned in a utility room, an attic, a basement, and so forth. The outdoor unit  58  is typically situated adjacent to a side of residence  52  and is covered by a shroud to protect the system components and to prevent leaves and other debris or contaminants from entering the unit. The refrigerant conduits  54  transfer refrigerant between the indoor unit  56  and the outdoor unit  58 , typically transferring primarily liquid refrigerant in one direction and primarily vaporized refrigerant in an opposite direction. 
     When the system shown in  FIG. 3  is operating as an air conditioner, a heat exchanger  60  in the outdoor unit  58  serves as a condenser for re-condensing vaporized refrigerant flowing from the indoor unit  56  to the outdoor unit  58  via one of the refrigerant conduits  54 . In these applications, a heat exchanger  62  of the indoor unit functions as an evaporator. Specifically, the heat exchanger  62  receives liquid refrigerant, which may be expanded by an expansion device, and evaporates the refrigerant before returning it to the outdoor unit  58 . 
     The outdoor unit  58  draws environmental air through the heat exchanger  60  using a fan  64  and expels the air above the outdoor unit  58 . When operating as an air conditioner, the air is heated by the heat exchanger  60  within the outdoor unit  58  and exits the unit at a temperature higher than it entered. The indoor unit  56  includes a blower or fan  66  that directs air through or across the indoor heat exchanger  62 , where the air is cooled when the system is operating in air conditioning mode. Thereafter, the air is passed through ductwork  68  that directs the air to the residence  52 . The overall system operates to maintain a desired temperature as set by a system controller. When the temperature sensed inside the residence  52  is higher than the set point on the thermostat, or the set point plus a small amount, the residential heating and cooling system  50  may become operative to refrigerate additional air for circulation through the residence  52 . When the temperature reaches the set point, or the set point minus a small amount, the residential heating and cooling system  50  may stop the refrigeration cycle temporarily. 
     The residential heating and cooling system  50  may also operate as a heat pump. When operating as a heat pump, the roles of heat exchangers  60  and  62  are reversed. That is, the heat exchanger  60  of the outdoor unit  58  will serve as an evaporator to evaporate refrigerant and thereby cool air entering the outdoor unit  58  as the air passes over the outdoor heat exchanger  60 . The indoor heat exchanger  62  will receive a stream of air blown over it and will heat the air by condensing the refrigerant. 
     In some embodiments, the indoor unit  56  may include a furnace system  70 . For example, the indoor unit  56  may include the furnace system  70  when the residential heating and cooling system  50  is not configured to operate as a heat pump. The furnace system  70  may include a burner assembly and heat exchanger, among other components, inside the indoor unit  56 . Fuel is provided to the burner assembly of the furnace  70  where it is mixed with air and combusted to form combustion products. The combustion products may pass through tubes or piping in a heat exchanger, separate from heat exchanger  62 , such that air directed by the blower  66  passes over the tubes or pipes and extracts heat from the combustion products. The heated air may then be routed from the furnace system  70  to the ductwork  68  for heating the residence  52 . 
       FIG. 4  is an embodiment of a vapor compression system  72  that can be used in any of the systems described above. The vapor compression system  72  may circulate a refrigerant through a circuit starting with a compressor  74 . The circuit may also include a condenser  76 , an expansion valve(s) or device(s)  78 , and an evaporator  80 . The vapor compression system  72  may further include a control panel  82  that has an analog to digital (A/D) converter  84 , a microprocessor  86 , a non-volatile memory  88 , and/or an interface board  90 . The control panel  82  and its components may function to regulate operation of the vapor compression system  72  based on feedback from an operator, from sensors of the vapor compression system  72  that detect operating conditions, and so forth. 
     In some embodiments, the vapor compression system  72  may use one or more of a variable speed drive (VSDs)  92 , a motor  94 , the compressor  74 , the condenser  76 , the expansion valve or device  78 , and/or the evaporator  80 . The motor  94  may drive the compressor  74  and may be powered by the variable speed drive (VSD)  92 . The VSD  92  receives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor  94 . In other embodiments, the motor  94  may be powered directly from an AC or direct current (DC) power source. The motor  94  may include any type of electric motor that can be powered by a VSD or directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor. 
     The compressor  74  compresses a refrigerant vapor and delivers the vapor to the condenser  76  through a discharge passage. In some embodiments, the compressor  74  may be a centrifugal compressor. The refrigerant vapor delivered by the compressor  74  to the condenser  76  may transfer heat to a fluid passing across the condenser  76 , such as ambient or environmental air  96 . The refrigerant vapor may condense to a refrigerant liquid in the condenser  76  as a result of thermal heat transfer with the environmental air  96 . The liquid refrigerant from the condenser  76  may flow through the expansion device  78  to the evaporator  80 . 
     The liquid refrigerant delivered to the evaporator  80  may absorb heat from another air stream, such as a supply air stream  98  provided to the building  10  or the residence  52 . For example, the supply air stream  98  may include ambient or environmental air, return air from a building, or a combination of the two. The liquid refrigerant in the evaporator  80  may undergo a phase change from the liquid refrigerant to a refrigerant vapor. In this manner, the evaporator  80  may reduce the temperature of the supply air stream  98  via thermal heat transfer with the refrigerant. Thereafter, the vapor refrigerant exits the evaporator  80  and returns to the compressor  74  by a suction line to complete the cycle. 
     In some embodiments, the vapor compression system  72  may further include a reheat coil in addition to the evaporator  80 . For example, the reheat coil may be positioned downstream of the evaporator relative to the supply air stream  98  and may reheat the supply air stream  98  when the supply air stream  98  is overcooled to remove humidity from the supply air stream  98  before the supply air stream  98  is directed to the building  10  or the residence  52 . 
     It should be appreciated that any of the features described herein may be incorporated with the HVAC unit  12 , the residential heating and cooling system  50 , or other HVAC systems. Additionally, while the features disclosed herein are described in the context of embodiments that directly heat and cool a supply air stream provided to a building or other load, embodiments of the present disclosure may be applicable to other HVAC systems as well. For example, the features described herein may be applied to mechanical cooling systems, free cooling systems, chiller systems, or other heat pump or refrigeration applications. 
     As noted above, HVAC enclosures may be configured to house a variety of HVAC components to shield the HVAC components from exposure to precipitation, ultraviolet radiation, and/or other environmental elements. For example, to provide context for the following discussion,  FIG. 5  is a perspective view of an embodiment of the HVAC unit  12 . As shown in the illustrated embodiment, the cabinet  24  may include a plurality of walls  100  and a plurality of panel assemblies  102  or doors that cooperate to enclose or partially enclose an interior volume  104  that is suitable for housing a compressor, an evaporator, and/or any other suitable HVAC component of the HVAC unit  12 . In some embodiments, the plurality of walls  100  may be fixedly coupled to a frame  106  of the HVAC unit  12  or to another suitable support structure of the HVAC unit  12 . The plurality of panel assemblies  102  may be pivotably coupled to the frame  106  and movable relative to the frame  106  to selectively enable access to the interior volume  104  of the cabinet  24 . As such, a service technician or other operator may access HVAC components that are housed within the cabinet  24  for inspection, maintenance, or other purposes. 
     For example, one or more hinge assemblies  112  or hinges may be configured to pivotably couple the panel assemblies  102  to the frame  106 . The hinge assemblies  112  enable the panel assemblies  102  to pivot about respective axes  114  relative to the frame  106 . As such, the panel assemblies  102  may be transitionable between respective closed positions  116 , in which the panel assemblies  102  block access to the interior volume  104 , and respective open positions  118 , in which the panel assemblies  102  enable access to the interior volume  104 . That is, in the closed positions  116 , the panel assemblies  102  may occlude respective openings of the cabinet  24  that provide access to the interior volume  104 . As noted above, it may be desirable to retain certain of the panel assemblies  102  in particular positions, such as in various open positions, while a service technician is performing an inspection and/or maintenance operation on the HVAC unit  12 . Accordingly, the panel assemblies  102  of the illustrated embodiment are equipped with respective panel restrictors  120  that, as discussed in detail below, may be configured to selectively retain the panel assemblies  102  in the closed positions  116 , in the open positions  118 , or in a variety of partially open positions. It should be appreciated that embodiments of the panel restrictors  120  discussed herein may be implemented in embodiments or components of the split residential heating and cooling system  50  shown in  FIG. 3 , a rooftop unit (RTU), or any other suitable air handling unit or HVAC system. Indeed, it should be understood that the panel restrictors  120  may be configured to retain any suitable doors, panels, hatches, or access covers in particular positions, in accordance with the techniques discussed herein. 
     With the foregoing in mind,  FIG. 6  is a perspective view of an embodiment of one of the panel restrictors  120 , referred to herein as a first panel restrictor  124 .  FIG. 7  is a perspective view of an embodiment of a portion of the cabinet  24  having the first panel restrictor  124 .  FIGS. 6 and 7  will be discussed concurrently below. The first panel restrictor  124  includes a first bracket  126  having a first flange  128  and a second flange  130  that extends generally cross-wise to the first flange  128 . The second flange  130  is configured to couple to a structural support  132  of the HVAC unit  12  using one or more fasteners  134 , adhesives, or a metallurgical process, such as welding or brazing. The structural support  132  may include a portion of the frame  106  or any other suitable railing or bracing of the HVAC unit  12 . Particularly, the second flange  130  may be coupled to an interior surface  136  of the structural support  132  that faces the interior volume  104  of the cabinet  24 . That is, the interior surface  136  may be positioned opposite to an exterior surface  138 , as shown in  FIG. 8 , of the structural support  132 , which faces the ambient environment surrounding the HVAC unit  12 . 
     In the illustrated embodiment, a slot  140  is formed within the second flange  130  and is configured to receive a second bracket  142  of the first panel restrictor  124 . The second bracket  142  includes an arcuate segment  144  that extends generally cross-wise to a mounting flange  146  or mounting portion of the second bracket  142 . As discussed below, in some embodiments, the arcuate segment  144  may include a generally constant radius of curvature that extends from the mounting flange  146  to a distal end  148  of the arcuate segment  144 . The mounting flange  146  is configured to couple to one of the panel assemblies  102 , referred to herein as a panel assembly  150  or a panel, using, for example, suitable fasteners  152 . In particular, the mounting flange  146  may be configured to couple to an inner wall  154  of the panel assembly  150  that faces the interior volume  104  and is positioned opposite to an outer wall  156 , as shown in  FIG. 8 , of the panel assembly  150 , which faces the ambient environment surrounding the HVAC unit  12 . In some embodiments, the first bracket  126 , the second bracket  142 , or both, may each be single-piece components formed from sheet metal or from another suitable material. 
     The panel assembly  150  may be pivotably coupled to the structural support  132  and/or to another portion of the frame  106  via the hinge assemblies  112 . For example, in some embodiments, the panel assembly  150  may be pivotably coupled to the structural support  132  and to a lower structural support, such as the frame rails  26 , via the hinge assemblies  112 . For clarity, it should be understood that, the structural support  132  and the frame rails  26  may collectively form a portion of the frame  106 . In any case, the hinge assemblies  112  enable the panel assembly  150  to pivot about an axis  160  of the hinge assemblies  112  relative to the frame  106 . In some embodiments, the hinge assemblies  112  may be configured to support a portion of or substantially all of a weight of the panel assembly  150 . As such, in some embodiments, the first panel restrictor  124  may support substantially none of the weight of the panel assembly  150 . For clarity, as used herein, the panel assembly  150 , the hinge assemblies  112 , and the first panel restrictor  124  may collectively be referred to as a door assembly of the HVAC unit  12 . 
     In the illustrated embodiment, the arcuate segment  144  is configured to translate through the slot  140  when the panel assembly  150  pivots about the axis  160 . In this manner, the arcuate segment  144  may permit the panel assembly  150  to transition between a closed position  162 , as shown in  FIG. 8 , and an open position  164 , as shown in  FIG. 9 , substantially without interference between the arcuate segment  144  and the first bracket  126 . 
     For example, to better illustrate and to facilitate the following discussion,  FIG. 8  is a top view of an embodiment of a portion of the cabinet  24 , illustrating the panel assembly  150  in the closed position  162 . For clarity, in the closed position  162 , a length  166  of the panel assembly  150  may extend substantially parallel to a length  168  of the structural support  132 . In some embodiments, a radial dimension  170  between the axis  160  and an edge  172  of the arcuate segment  144  may be substantially constant along a length of the edge  172 . As a result, the arcuate segment  144  may translate along a circumferential path  173  about the axis  160  when the panel assembly  150  is pivoted about the axis  160  from the closed position  162  to the open position  164 , or vice versa. Therefore, the arcuate segment  144  may translate through the slot  140  of the second bracket  142  without interference with the second bracket  142  when the panel assembly  150  pivots about the axis  160 . For clarity, the edge  172  may be indicative of a radially inward edge of the arcuate segment  144  that extends substantially between the mounting flange  146  and the distal end  148  of the arcuate segment  144 . 
     The following discussion continues with reference to  FIGS. 6 and 7 . In some embodiments, the first bracket  126  includes an engager assembly  174  that is coupled to the first flange  128  of the first bracket  126 . The engager assembly  174  is configured to selectively engage with one of a plurality of apertures  176  formed within the arcuate segment  144 . In this manner, the engager assembly  174  may selectively couple the first bracket  126  to the arcuate segment  144  to secure the arcuate segment  144  within the slot  140  at a plurality of discrete positions or discrete orientations. 
     For example, in some embodiments, the engager assembly  174  includes a nut  178  that is coupled to the first flange  128 . The nut  178  includes an aperture formed therein that is configured to align with an axis  180  of a corresponding aperture formed within the first flange  128 . The apertures within the nut  178  and the first flange  128  are configured to receive a bolt  182  and to support the bolt  182 . For example, in some embodiments, the bolt  182  may include external threads that are configured to engage with corresponding internal threads of the nut  178 . As such, the nut  178  may support the bolt  182 , while rotation of the bolt  182  relative to the nut  178  enables the bolt  182  to translate axially along the axis  180 . As discussed below, in this manner, an operator or other service technician may rotate the bolt  182  to selectively engage or disengage the bolt  182  with one of the apertures  176  formed within the arcuate segment  144 . As such, the operator may selectively couple or decouple the first bracket  126  and the second bracket  142  to disable or enable, respectively, movement between the first and second brackets  126 ,  142 . 
     It should be appreciated that, in other embodiments, the engager assembly  174  may include any other suitable mechanism or device that enables an operator to removably couple the first bracket  126  to the second bracket  142 . For example, in certain embodiments, the bolt  182  may be replaced with a pin, and a spring may be used to bias the pin in a biasing direction  188  toward the arcuate segment  144 . As such, the spring may force the pin through one of the apertures  176  when the pin is aligned with the aperture, thereby removably coupling the first bracket  126  to the second bracket  142 . In such embodiments, to decouple the first bracket  126  from the second bracket  142 , an operator may pull the pin in a releasing direction  190 , opposite to the biasing direction  188 , to remove the pin from the aperture  176  and enable movement of the arcuate segment  144  relative to the first bracket  126 . 
       FIG. 9  is a top view of an embodiment of a portion of the cabinet  24 , illustrating the panel assembly  150  in the open position  164 . To transition the panel assembly  150  from the closed position  162  to the open position  164 , an operator may rotate the panel assembly  150  about the axis  160  in a counter-clockwise direction  194 . Specifically, the operator may rotate the panel assembly  150  until one of the apertures  176 , such as a first aperture  196 , of the arcuate segment  144  is aligned with the bolt  182 . Upon alignment of the first aperture  196  with the bolt  182 , the operator may rotate the bolt  182  in accordance with the techniques discussed above to engage the bolt  182  with the first aperture  196  of the arcuate segment  144 . As such, the operator may removable couple the first bracket  126  to the second bracket  142 , such that the first panel restrictor  124  may retain the panel assembly  150  in the open position  164 . That is, the first panel restrictor  124  may block pivotal motion of the panel assembly  150  about the axis  160  while the first bracket  126  is coupled to the second bracket  142  via the engager assembly  174 , and the panel assembly  150  may be retained in a desired position. 
     It should be understood that the operator may engage the bolt  182  with any of the apertures  176  to retain the panel assembly  150  in various other open positions  164 . That is, by selecting the particular aperture  176  with which the bolt  182  is engaged, the operator may adjust an angular increment  198  by which the panel assembly  150  is offset from the structural support  132  when in the open position  164 . As an example,  FIG. 10  is a perspective view of an embodiment of a portion of the cabinet  24 , illustrating the bolt  182  engaged with a second aperture  200  of the arcuate segment  144  that is located near the distal end  148  of the arcuate segment  144 . It should be appreciated that, engaging the bolt  182  with one of the apertures  176  positioned near the distal end  148  increases the angular increment  198 , while engaging the bolt  182  with one of the apertures  176  positioned near the mounting flange  146  decreases the angular increment  198 . Indeed, it should be appreciated that engaging the bolt  182  with any of the apertures  176  may enable the first panel restrictor  124  to position and retain the panel assembly  150  in a plurality of discrete orientations with respect to the frame  106 . 
       FIG. 11  is a perspective view of an embodiment of the HVAC unit  12 , illustrating another embodiment of one of the panel restrictors  120 , referred to herein as a second panel restrictor  210 . Similar to the first panel restrictor  124  discussed above, the second panel restrictor  210  may be configured to selectively secure and retain the panel assembly  150  in a plurality of discrete positions. As shown in the illustrated embodiment, the hinge assemblies  112  may include a first hinge  212  and a second hinge  213  that are configured to pivotably couple the panel assembly  150  to the frame  106 . As such, the first and second hinges  212 ,  213  enable the panel assembly  150  to pivot about the axis  160 . 
     To better illustrate the second panel restrictor  210 ,  FIG. 12  is an exploded perspective view of an embodiment of the second panel restrictor  210 . The second panel restrictor  210  includes a first link  214  and a second link  216  having respective pivoting apertures  218  formed therein. A first pin  220  is configured extend through the pivoting apertures  218  to pivotably couple the first link  214  to the second link  216  and enable movement of the first link  214  relative to the second link  216  about a pivoting axis  222 . As discussed in detail below, the first link  214  includes a hook  224 , as also shown in  FIG. 13 , which is configured to engage with the second link  216  to limit pivotal motion of the second link  216 , relative to the first link  214 , about the pivoting axis  222 . In particular, the hook  224  is configured to limit pivotal motion of the second link  216 , relative to the first link  214 , in a clockwise direction  226  about the pivoting axis  222 . In some embodiments, the first link  214 , the second link  216 , or both, may each be a single-piece component that is formed from sheet metal or another suitable material. 
     The second panel restrictor  210  includes a second pin  228  that is configured to extend through a corresponding aperture  230  in the first link  214  to pivotably couple the first link  214  to the structural support  132  or to another suitable portion of the cabinet  24 . A third pin  232  is configured to extend through a corresponding aperture  234  in the second link  216  to pivotably couple the second link  216  to the panel assembly  150 . In particular, the third pin  232  may pivotably couple the second link  216  to an end face  236 , as shown in  FIG. 14 , of the panel assembly  150 . The first link  214  includes an ear  240  or ledge having a slot  242  or aperture formed therein. The slot  242  is configured to receive and support an engagement pin  243  that, as discussed below, is configured to engage with one of a plurality of apertures  244 , such as a first aperture  246  and a second aperture  248 , formed within the second link  216 . In this manner, the engagement pin  243  may be configured to removably couple the first link  214  to the second link  216  at a plurality of discrete positions. It should be understood that, in other embodiments, the plurality of apertures  244  may include any suitable quantity of individual apertures  244 , such as 1, 2, 3, 4, or more than four apertures  244 . Moreover, it should be appreciated that the engagement pin  243  may include a threaded rod or bolt, a spring and pin assembly, or another suitable mechanism or device configured to removably couple the first link  214  to the second link  216  at one or more discrete positions relative to one another. 
       FIG. 14  is a perspective view of an embodiment of a portion of the cabinet  24 , illustrating the second panel restrictor  210  in a first configuration  250 , in which the second panel restrictor  210  is configured to retain the panel assembly  150  in a first partially open position  252 . For example, to transition the panel assembly  150  from the closed position  162  to the first partially open position  252 , an operator may pivot the panel assembly  150  about the axis  160  in the counter-clockwise direction  194  until the slot  242  of the first link  214  is aligned with the first aperture  246  of the second link  216 . Upon alignment of the slot  242  with the first aperture  246 , the operator may insert the engagement pin  243  through the slot  242  and the first aperture  246  in a downward direction  256 , with respect to gravity, such that a head of the engagement pin  243  may rest on the ear  240  and a shaft of the engagement pin  243  extends through the slot  242  and the first aperture  246 . In this manner, the engagement pin  243  may removably couple the first link  214  to the second link  216  to block pivotal motion of the first link  214  relative to the second link  216  and to retain a particular position of the first link  214  relative to the second link  216 . As such, while the engagement pin  243  is engaged with the slot  242  and the first aperture  246 , the second panel restrictor  210  may retain the panel assembly  150  in the first partially open position  252  and block pivotal motion of the panel assembly  150  about the axis  160 . To re-enable pivotal motion of the panel assembly  150  about the axis  160 , the operator may disengage the engagement pin  243  from the first aperture  246  by, for example, removing the engagement pin  243  from the slot  242  and the first aperture  246 . 
       FIG. 15  is a perspective view of an embodiment of a portion of the cabinet  24 , illustrating the second panel restrictor  210  in a second configuration  260 , in which the second panel restrictor  210  is configured to retain the panel assembly  150  in a second partially open position  262 . To transition the panel assembly  150  from, for example, the first partially open position  252  to the second partially open position  262 , an operator may pivot the panel assembly  150  about the axis  160  in the counter-clockwise direction  194  until the slot  242  of the first link  214  is aligned with the second aperture  248  of the second link  216 . Upon alignment of the slot  242  with the second aperture  248 , the operator may insert the engagement pin  243  through the slot  242  and the second aperture  248  in the downward direction  256 , such that the head of the engagement pin  243  may rest on the ear  240  and the shaft of the engagement pin  243  extends through the slot  242  and the second aperture  248 . In this manner, the engagement pin  243  may removably couple the first link  214  to the second link  216  to block pivotal motion of the first link  214  relative to the second link  216  and to retain a particular position of the first link  214  relative to the second link  216 . As such, while the engagement pin  243  is engaged with the slot  242  and the second aperture  248 , the second panel restrictor  210  may retain the panel assembly  150  in the second partially open position  262  and block pivotal motion of the panel assembly  150  about the axis  160 . To re-enable pivotal motion of the panel assembly  150  about the axis  160 , the operator may disengage the engagement pin  243  from the second aperture  248  by, for example, removing the engagement pin  243  from the slot  242  and the second aperture  248 . 
       FIG. 16  is a perspective view of an embodiment of a portion of the cabinet  24 , illustrating the second panel restrictor  210  in a third configuration  270 , in which the second panel restrictor  210  is configured to retain the panel assembly  150  in a fully open position  272 .  FIG. 17  is a close-up perspective view of an embodiment of the second panel restrictor  210  in the third configuration  270 .  FIGS. 16 and 17  will be discussed concurrently below. To transition the panel assembly  150  from, for example, the second partially open position  262  toward the fully open position  272 , an operator may pivot the panel assembly  150  about the axis  160  in the counter-clockwise direction  194  until a body  274  of the second link  216  extends into and engages with the hook  224  of the first link  214 . Indeed, as noted above, the hook  224  may block pivotal motion of the second link  216  relative to the first link  214  in the counter-clockwise direction  194  beyond a particular angular increment. 
     As shown in the illustrated embodiment of  FIG. 17 , an aperture  276  may be formed within the first link  214  and configured to align with one of the first or second apertures  246 ,  248  of the second link  216  when the second link  216  engages with the hook  224 . Upon alignment of the aperture  276  with the first aperture  246  or the second aperture  248 , the operator may insert the engagement pin  243  through the aperture  276  and the first or second apertures  246 ,  248  in the downward direction  256 , such that the head of the engagement pin  243  may rest on a surface  280  of the first link  214  and the shaft of the engagement pin  243  extends through the aperture  276  and the first or second apertures  246 ,  248 . In this manner, the engagement pin  243  may block pivotal motion of the first link  214  relative to the second link  216  to retain a position of the first link  214  relative to the second link  216 . As such, the second panel restrictor  210  may retain the panel assembly  150  in the fully open position  272 . To re-enable pivotal movement of the panel assembly  150  about the axis  160 , the operator may disengage the engagement pin  243  from the aperture  276  and the first or second apertures  246 ,  248 . 
       FIG. 18  is a side view of an embodiment of an electrical box  300 , which may be included in embodiments of the HVAC unit  12  or embodiments of any of the aforementioned HVAC systems. The electrical box  300  is equipped with another embodiment of one of the panel restrictors  120 , referred to herein as a third panel restrictor  302 . Although the third panel restrictor  302  is described herein for use on the electrical box  300 , it should be appreciated that the third panel restrictor  302  may also be implemented on the panel assemblies  102  of the HVAC unit  12 . 
     As discussed in detail herein, the third panel restrictor  302  may be configured to hingedly couple a door  304 , also referred to herein as a panel or panel assembly, to a frame  306  of the electrical box  300 . For example, in the illustrated embodiment, the third panel restrictor  302  includes a frame bracket  308  that is coupled to the frame  306  and a support bracket  310  that is coupled to the door  304 . In particular, the support bracket  310  is coupled to a base, bottom portion, or underside of the door  304  and is above, relative to the direction of gravity, the frame bracket  308  coupled to the frame  306 . Further, the frame bracket  308  is pivotably coupled to the support bracket  310  via a pivoting assembly  312 . Accordingly, the pivoting assembly  312  supports the door  304  and enables pivotal motion of the door  304 , relative to the frame  306 , about an axis  314  of the pivoting assembly  312 . 
     In some embodiments, the electrical box  300  may include a hinge assembly  318  that is configured to cooperate with the third panel restrictor  302  to pivotably couple the door  304  to the frame  306 . As such, the third panel restrictor  302  and the hinge assembly  318  may enable the door  304  to be selectively transitioned between a closed position  320  and an open position via rotation of the door  304  about the axis  314 . 
     In some embodiments, the third panel restrictor  302  may be configured to support substantially all of a weight of the door  304  while enabling pivotal motion of the door  304  about the axis  314 . In other embodiments, the third panel restrictor  302  and the hinge assembly  318  may cooperatively support a weight of the door  304 . Moreover, in certain embodiments, a plurality of third panel restrictors  302  may be spaced along the axis  314  and used to pivotably couple to door  304  to the frame  306  and to collectively support a weight of the door  304 . In such embodiments, the hinge assembly  318  may be omitted from the electrical box  300 . 
     To better illustrate the third panel restrictor  302  and its respective components,  FIG. 19  is an exploded perspective view of an embodiment of the third panel restrictor  302 . The frame bracket  308  includes one or more apertures  324  that enable suitable fasteners  326  to couple a first flange  328  of the frame bracket  308  to the frame  306 . As shown in the illustrated embodiment, the frame bracket  308  includes a second flange  330  that extends generally cross-wise from the first flange  328 . The second flange  330  includes a first aperture  332  configured to receive a guide pin  334  and a second aperture  336  configured to receive a retention pin  338 . In some embodiments, one or more fastening nuts  340  may be used to secure the guide pin  334  and/or the retention pin  338  to the frame bracket  308 . In other embodiments, the guide pin  334  and the retention pin  338  may be coupled to the frame bracket  308  via an interference fit with the corresponding apertures  332 ,  336  or via another suitable technique. 
     The pivoting assembly  312  includes a lower cam  344  having respective apertures  346  that are configured to engage with the guide pin  334  and the retention pin  338 . As such, the guide pin  334  and the retention pin  338  may couple the lower cam  344  to the frame bracket  308 . In particular, the guide pin  334  and the retention pin  338  may cooperate to block rotational motion of the lower cam  344  relative to the frame bracket  308 . The pivoting assembly  312  also includes an upper cam  348  having a protrusion  350  with a cylindrical cavity  352 , as shown in  FIG. 24 , formed therein. The cylindrical cavity  352  is configured to receive a shaft  354  of the guide pin  334 . Accordingly, engagement between the shaft  354  and the cylindrical cavity  352  may pivotably couple the lower cam  344  to the upper cam  348 . The protrusion  350  of the upper cam  348  is configured extend through a corresponding aperture  356  formed within the support bracket  310 . As such, suitable fasteners may be used to couple the upper cam  348  to the support bracket  310 . The frame bracket  308 , the guide pin  334 , the retention pin  338 , and the lower cam  344  will collectively be referred to herein as a lower restrictor assembly  360 . Moreover, the support bracket  310  and the upper cam  348  will collectively be referred to herein as an upper restrictor assembly  362 . 
     The lower cam  344  includes a first lobed profile  364  that is configured to engage with a second lobed profile  366 , as shown in  FIG. 24 , of the upper cam  348 . As discussed in detail below, the engagement between the first and second lobed profiles  364 ,  366  enables the pivoting assembly  312  to retain the upper restrictor assembly  362  at a plurality of discrete rotational positions relative to the lower restrictor assembly  360 . 
       FIG. 20  is a perspective view of an embodiment of a portion of the electrical box  300 , illustrating the upper restrictor assembly  362  in an installed configuration  370  on the door  304 .  FIG. 21  is a bottom view of an embodiment of the door  304 , illustrating the upper restrictor assembly  362  in the installed configuration  370 .  FIGS. 20 and 21  will be discussed concurrently below. As shown in the illustrated embodiments of  FIGS. 20 and 21 , suitable fasteners  372  may be used to couple the support bracket  310  to a flange  374  or to another suitable portion of the door  304 . It should be appreciated that the protrusion  350  of the upper cam  348  may extend into an interior of the door  304  via a suitable aperture or slot formed within the flange  374 . As such, a mounting surface of the support bracket  310  may rest flush against the flange  374  in the installed configuration  370  of the upper restrictor assembly  362 . 
       FIG. 22  is a perspective view of an embodiment of a portion of the electrical box  300 , illustrating the lower restrictor assembly  360  in an installed configuration  380  on the frame  306 . As shown in the illustrated embodiment, suitable fasteners  382  may be used couple the frame bracket  308  to the frame  306 . It should be appreciated that, in the installed configuration  380  of the lower restrictor assembly  360 , the shaft  354  of the guide pin  334  may extend from the frame bracket  308  in a generally upward direction  284 , with respect to gravity. 
       FIG. 23  is a perspective view of an embodiment of the lower cam  344 . The lower cam  344  includes the first lobed profile  364  that extends about one of the apertures  346 . The first lobed profile  364  may be defined by a first plurality of protrusions  390  that extend from a body  392  of the lower cam  344  and by a first plurality of grooves  394  that are positioned between each of the first plurality of protrusions  390 . Although the lower cam  344  includes two protrusions  390  in the illustrated embodiment, in other embodiments, the lower cam  344  may include 2, 3, 4, 5, 6, or more than 6 protrusions  390  that define the first lobed profile  364 . The number of protrusions  390  may correlate with a number of discrete positions or orientations at which the third panel restrictor  302  may retain the door  304 . 
     As noted above, the first lobed profile  364  is configured to engage with the second lobed profile  366  of the upper cam  348 . For example, to better illustrate and to facilitate the following discussion,  FIG. 24  is a perspective view of an embodiment of the upper cam  348 . Similar to the lower cam  344 , the upper cam  348  includes the second lobed profile  366  that extends about an opening of the cylindrical cavity  352 . The second lobed profile  366  may be defined by a second plurality of protrusions  400  that extend from a body  402  of the upper cam  348  and by a second plurality of grooves  404  that are positioned between each of the second plurality of protrusions  400 . A quantity of the second plurality of protrusions  400  may correspond to a quantity of the first plurality of protrusions  390 . Accordingly, although the upper cam  348  includes two protrusions  400  in the illustrated embodiment, in other embodiments, the upper cam  348  may include 2, 3, 4, 5, 6, or more than six protrusions  400  that define the second lobed profile  366 . 
       FIG. 25  is a side view of an embodiment of a portion of the electrical box  300 , illustrating the third panel restrictor  302  positioned in a first configuration  420 . In the first configuration  420 , the third panel restrictor  302  may retain the door  304  in the closed position  320 . For example, when the third panel restrictor  302  is in the first configuration  420 , the first plurality of protrusions  390  of the lower cam  344  may be positioned in the second plurality of grooves  404  of the upper cam  348 , and the second plurality of protrusions  400  of the upper cam  348  may be positioned in the first plurality of grooves  394  of the lower cam  344 . The engagement between the first plurality of protrusions  390  and the second plurality of grooves  404 , and between the second plurality of protrusions  400  and the first plurality of grooves  394 , may inhibit free rotation of the upper cam  348 , relative to the lower cam  344 , about the axis  314 . Accordingly, the third panel restrictor  302  may block movement of the door  304  and ensure that the door  304  does not pivot from the closed position  320  to an open position when, for example, wind is impinging against the electrical box  300  and imparting a force on the door  304 . 
     To transition the door  304  from the closed position  320  to an open position, an operator may grab the door  304 , such as via a handle of the door  304 , and may rotate the door  304  about the axis  314  in the counter-clockwise direction  194  with sufficient force to cause the second plurality of protrusions  400  to translate along an inclined surface  430  of the first plurality of protrusions  390  and onto an upper surface  432  of the first plurality of protrusions  390 . Indeed, rotational movement of the upper cam  348  in the counter-clockwise direction  194  about the axis  314 , relative to the lower cam  344 , may force the upper cam  348  in the upward direction  284  due to the engagement between the first and second lobed profiles  364 ,  366 . As such, the upper cam  348  may force the upper restrictor assembly  362 , and thus the door  304 , in the upward direction  284  during rotation of the upper cam  348  relative to the lower cam  344 . It should be appreciated that the engagement between the shaft  354  of the guide pin  334  and the cylindrical cavity  352  of the upper cam  348  may guide the axial movement of the upper cam  348  along the axis  314 . Moreover, it should be understood that sufficient clearance along the axis  314  is provided between the frame  306  or housing of the electrical box  300  and the door  304  to ensure that axial movement of the door  304  along the axis  314  does not result in interference between the door  304  and other components of the electrical box  300 . As such, the operator may cause the third panel restrictor  302  to transition from the first configuration  420  to an intermediate configuration  440 , as shown in  FIG. 26 , by rotating the door  304  about the axis  314  with sufficient force to cause the upper cam  348  to move a weight of the door  304  in the upward direction  284  by a height of the first plurality of protrusions  390 . 
     Upon transitioning the third panel restrictor  302  to the intermediate configuration  440 , the operator may continue to rotate the door  304  in the counter-clockwise direction  194  about the axis  314  until the first plurality of protrusions  390  of the lower cam  344  re-engage with the second plurality of grooves  404  of the upper cam  348 , and the second plurality of protrusions  400  of the upper cam  348  re-engage with the first plurality of protrusions  390  of the lower cam  344 . That is, the operator may continue to rotate the door  304  in the counter-clockwise direction  194  about the axis  314  until the third panel restrictor transitions to a second configuration  442 , as shown in  FIG. 27 . The operator may transition the door  304  from the open position back to the closed position  320  by performing the aforementioned steps in reverse order. 
     It should be understood that a force utilized to lift a weight of the door  304 , when transitioning the third panel restrictor  302  from the first or second configurations  420 ,  442  to the intermediate configuration  440 , may be greater than, for example, a force acting on the door  304  due to wind impinging on the door  304  or due to other inadvertent contact with the door  304 . Accordingly, the third panel restrictor  302  may be configured to retain the door  304  in the closed position  320  or in an open position until an operator adjusts a position of the door  304 . Moreover, as noted above, it should be understood that increasing a quantity of the first plurality of protrusions  390  and a quantity of the second plurality of protrusions  400  may increase a quantity of discrete positions at which the third panel restrictor  302  may retain the door  304 . Accordingly, the third panel restrictor  302  may be used to retain the door  304  in the closed position  320 , in an open position, or in a plurality of intermediate positions between such open and closed positions. 
     In some embodiments, the guide pin  334 , the lower cam  344 , and/or the upper cam  348  may be formed from a polymeric material. For example, the guide pin  334 , the lower cam  344 , and/or the upper cam  348  may be formed from an injection molding process or via another suitable manufacturing process. As such, the guide pin  334 , the lower cam  344 , and the upper cam  348  may substantially block electric current flow across the pivoting assembly  312 . Accordingly, the third panel restrictor  302  may mitigate electrical discharge from the frame  306  to the door  304  or vice versa. 
     As set forth above, embodiments of the present disclosure may provide one or more technical effects useful for retaining a panel assembly or a door of an HVAC enclosure in a particular position. Particularly, the embodiments of the panel restrictors  120  disclosed herein facilitate retaining panel assemblies or other doors in various open positions without input from personnel using to doors. As such, the panel restrictors  120  may facilitate performance of maintenance, inspection, or other operations on an HVAC system. It should be understood that the technical effects and technical problems in the specification are examples and are not limiting. Indeed, it should be noted that the embodiments described in the specification may have other technical effects and can solve other technical problems. 
     While only certain features and embodiments 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.