Patent Publication Number: US-11384594-B2

Title: HVAC systems having air-tight access doors

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 16/002,844, entitled “HVAC SYSTEMS HAVING AIR-TIGHT ACCESS DOORS,” filed Jun. 7, 2018, which claims the benefit of U.S. Provisional Application No. 62/663,872, entitled “HVAC SYSTEMS HAVING AIR-TIGHT ACCESS DOORS,” filed Apr. 27, 2018, all of which are hereby incorporated by reference in their entireties for all purposes. 
    
    
     BACKGROUND 
     The present disclosure relates generally to heating, ventilation, and air conditioning (HVAC) systems and, more particularly, to HVAC systems with air-tight access doors. 
     Many commercial buildings have one or more air handling units, which are often placed on the roofs of buildings. A typical air handling unit includes an enclosure with one or more access doors to allow personnel to gain access to internal components within the enclosure for visual inspection, service, and replacement of parts, for example. Because the HVAC equipment is used to maintain the building&#39;s temperature, it is important that the enclosure, as well as access doors through the enclosure, of the air handling unit are substantially air tight. More specifically, it is beneficial to seal the internal components and compartments within the enclosure against exposure to environmental effects, such as rain, snow, debris, and so forth. 
     SUMMARY 
     The present disclosure relates to an HVAC system door assembly that includes a door that includes a panel having a first side and a second side opposite the first side, and a first seal circuit. The first seal circuit is disposed on the first side. The HVAC system door assembly also includes a door frame that includes a second seal circuit. HVAC system door assembly further includes a ridge projecting from one of the first seal circuit or the second seal circuit configured to align with and engage a central portion of the other of the first seal circuit or the second seal circuit when the door is in a closed position with respect to the door frame. The ridge includes a cross-sectional profile having a flattened peak section with sloping side sections that extend from boundaries of the flattened peak section to a base of the ridge. 
     The present disclosure also relates to an HVAC unit that includes an enclosure that includes a plurality of walls. The HVAC unit also includes a door assembly disposed in one of the plurality of walls. The door assembly includes a door that includes a gasket disposed on a face of the door and forming a first circuit. The door assembly also includes a door frame that includes a ridge that projects from a side of the door frame and forms a second circuit. The ridge is positioned on the side of the door frame such that the ridge and the gasket are configured to align and engage when the door is in a closed position with respect to the door frame. In addition, the ridge includes a cross-sectional profile having a flattened peak section with sloping side sections that extend from boundaries of the flattened peak section to the side of the door frame. 
     The present disclosure further relates to an HVAC unit that includes an enclosure that includes a plurality of walls. The HVAC unit also includes a door assembly disposed in one of the plurality of walls. The door assembly includes a door frame, a gasket disposed on a face of the door frame and forming a first circuit, and a door hingedly coupled to the door frame. The door assembly also includes a ridge projecting from a side of the door and forming a second circuit. The ridge includes a cross-sectional profile having a flattened peak section with sloping side sections that extend from boundaries of the flattened peak section to the side of the door. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of an embodiment of a commercial or industrial HVAC system, in accordance with the present techniques; 
         FIG. 2  is an illustration of an embodiment of a portion of a packaged unit of the HVAC system shown in  FIG. 1 , in accordance with the present techniques; 
         FIG. 3  is an illustration of an embodiment of a split system of the HVAC system shown in  FIG. 1 , in accordance with the present techniques; 
         FIG. 4  is an illustration of an embodiment of a refrigeration system of the HVAC system shown in  FIG. 1 , in accordance with the present techniques; 
         FIG. 5  is an illustration of an embodiment of the packaged unit of the HVAC system shown in  FIG. 1 , in accordance with the present techniques; 
         FIG. 6A  is a perspective view of an embodiment of an access door assembly, in accordance with the present techniques; 
         FIG. 6B  is an exploded view of the access door assembly shown in  FIG. 6A , in accordance with the present techniques; 
         FIG. 7A  is a perspective view of an embodiment of the access door assembly shown in  FIG. 6A , with the access door in an opened position, in accordance with the present techniques; 
         FIG. 7B  is a zoomed in perspective view of a portion of a door frame of the access door assembly shown in  FIG. 7A , in accordance with the present techniques; 
         FIG. 8A  is a cross-sectional cutaway view of an embodiment of the access door assembly shown in  FIG. 6A , in accordance with the present techniques; 
         FIGS. 8B and 8C  are cross-sectional cutaway views of the access door assembly shown in  FIG. 8A , in accordance with the present techniques; 
         FIG. 9A  is a perspective view of another embodiment of an access door assembly, in accordance with the present techniques; 
         FIG. 9B  is an exploded view of the access door assembly shown in  FIG. 9A , in accordance with the present techniques; 
         FIG. 10A  is a perspective view of an embodiment of the access door assembly shown in  FIG. 9A , with the access door in an opened position, in accordance with the present techniques; 
         FIG. 10B  is a zoomed in perspective view of a portion of a door frame of the access door assembly shown in  FIG. 10A , in accordance with the present techniques; 
         FIG. 11A  is a cross-sectional cutaway view of an embodiment of the access door assembly shown in  FIG. 9A , in accordance with the present techniques; 
         FIGS. 11B and 11C  are cross-sectional cutaway views of the access door assembly shown in  FIG. 11A , in accordance with the present techniques; and 
         FIGS. 12A through 12I  are cross-sectional views of profiles of a projected ridge, in accordance with the present techniques. 
     
    
    
     DETAILED DESCRIPTION 
     In HVAC systems, air-tight sealing of an enclosure of an HVAC system is often provided by attaching a gasket near a perimeter of an access door and securing the access door against a door frame of the enclosure using latches. In this way, the gasket is compressed between the door frame and the access door to create a seal. However, often, the latches may distribute force across an entire area of the gasket, such that the force may not sufficiently transfer to far ends of the door to stop air leakage through the access door. 
     The present disclosure is directed to HVAC systems and units that include access doors that provide relatively air-tight sealing compared to conventional access doors. In particular, certain embodiments described herein include access door assemblies having door frames with ridges that project from sides of the door frames, and which are configured to align with gaskets of doors of the access door assemblies, such that the ridges of the door frames generally align with the gaskets of the doors when the doors are in closed positions with respect to their respective door frames. The interaction between the ridges of the door frames and the gaskets of the doors provides improved sealing between the doors and the door frames. In addition, the ridges of the door frames improve the rigidity of the door frames, thereby obviating the need for extra stiffening supports, such as flanges and ribs. 
     Turning now to the drawings,  FIG. 1  illustrates an HVAC system for building environmental management that may employ one or more HVAC units. In the illustrated embodiment, a building  10  is air conditioned by a system that includes an HVAC unit  12 . The building  10  may be a commercial structure or a residential structure. As shown, the HVAC unit  12  is disposed on the roof of the building  10 ; however, the HVAC unit  12  may be located in other equipment rooms or areas adjacent the building  10 . The HVAC unit  12  may be a single 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 a portion of the HVAC unit  12 . For example, the portion of the HVAC unit  12  illustrated in  FIG. 2  has certain features removed for clarity, including the side walls and roof that surround a cabinet of the HVAC unit  12 , and which provide protection for the internal compartments and components 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  32  that separates the heat exchanger  30  from the heat exchanger  28 . Fans  34  draw air from the environment through the heat exchanger  28 , where the heat exchanger  28  may be framed within the cabinet  24  of the HVAC unit  12  and/or containers  36  below the fans  34 . Air may be heated and/or cooled as the air flows through the heat exchanger  28  before being released back to the environment surrounding the rooftop unit  12 . A blower assembly  34 , powered by an associated motor, 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 . In the illustrated embodiment, the compressors  42  include two dual stage configurations  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 associated with the illustrated control board  46 . For example, a high voltage power source may be connected to the terminal block to power the equipment. The operation of the HVAC unit  12  may be governed or regulated by the control board  46 . The control board  46  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 may connect the control board  46  and the terminal block to the equipment of the HVAC unit  12 . 
     As described in greater detail herein, in certain embodiments, the HVAC unit  12  may also include access doors located in side walls and/or a roof of the HVAC unit  12 , which enable access to internal compartments and components of the HVAC unit  12 . For example,  FIG. 5  is a perspective view of an embodiment of the HVAC unit  12  illustrated in  FIG. 2 , with the side walls, roof, and various air-tight access doors as described herein. However, it will be appreciated that the air-tight access doors described herein may be used in any HVAC systems, with the HVAC systems described herein merely being exemplary of the types of HVAC systems that may benefit from the air-tight access doors described herein. 
       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 outdoor the 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. 
     Further, in accordance with present techniques, the HVAC systems described herein may utilize access doors as described herein to provide improved sealing, thereby minimizing exposure of the internal compartments and components of the HVAC system to environmental effects, such as rain, snow, debris, and so forth. For example,  FIG. 5  is a perspective view of an embodiment of the packaged HVAC unit  12  illustrated in  FIG. 2 , with side walls  40  and a roof  46  shown around the cabinet  24  of the HVAC unit  12  for illustration. In particular, the side walls  40  and the roof  46  collectively form an enclosure for the HVAC unit  12 , with the roof being a fifth wall. As illustrated, the HVAC unit  12  may include various access door assemblies  100  that enable access to the internal compartments and components of the HVAC unit  12 , while also providing improved sealing. 
     As illustrated in  FIG. 5 , in certain embodiments, the access door assemblies  100  may include door frames  102 , which may be installed within, for example, mounted into appropriately sized door frame openings through, the side walls  40  and/or the roof  46 , and the access doors  104  that are configured to open with respect to their respective door frames  102 , thereby enabling access to the internal compartments and components of the HVAC unit  12 . In particular, the access door assemblies  100  may include various handles  106  that facilitate opening of the access doors  104  with respect to their respective door frames  102 . As also illustrated in  FIG. 5 , while primarily described herein as including hinged access door assemblies  100 , such as the access door assemblies  100   a ,  100   b  having access doors  104  that are hinged to their respective door frames  102  via one or more hinges  108 , in other embodiments, the access doors  104  of the access door assemblies  100   c  may simply be removable from their respective door frames  102  where, for example, the access door  104  may be placed aside once removed from its respective door frame  102 . Regardless, as also illustrated in  FIG. 5 , in certain embodiments, once the access door  104  has been closed with respect to its door frame  102 , the access door  102  may be latched or locked into place in the closed position via one or more latches  110 , which are often located on a side of the respective access door  104  opposite the one or more hinges  108 . As illustrated, in certain embodiments, the one or more latches  110  may include accessible actuation mechanisms disposed on a side of the access door  104  opposite the door frame  102 . 
     As also illustrated in  FIG. 5 , the access door assemblies  100  may be used for myriad types of access into the HVAC unit  12 . For example, in certain embodiments, the access door assemblies  100  may only enable access to internal components of the HVAC unit  12 . For example, the access door assembly  100   a  in  FIG. 5  may enable access to the control board  46  illustrated in  FIG. 2 . However, in other embodiments, the access door assemblies  100  may enable access to entire internal compartments of the HVAC unit  12 . For example, the access door assembly  100   b  illustrated in  FIG. 5  may enable personnel to physically enter one or more internal compartments of the HVAC unit  12 . 
       FIG. 6A  is a perspective view of an embodiment of an access door assembly  100 , in accordance with the present techniques. In addition,  FIG. 6B  is an exploded view of the embodiment of the access door assembly  100  shown in  FIG. 6A , in accordance with the present techniques. As illustrated, in certain embodiments, the access door assembly  100  includes a door frame  102 , a door inner wall  112  and a door outer wall  114 , which collectively form a door wall  116 , and a gasket  118  positioned between the door frame  102  and the door inner wall  112 . In particular, the gasket  118  may be affixed to the door inner wall  112 , and the door inner wall  112  may be affixed to the door outer wall  114  to form the integrated door wall  116  to form the access door  104 . More specifically, the gasket  118  may be affixed to a side, or face, of the door inner wall  112  opposite the door outer wall  114  near a perimeter, circumference, periphery, or edge of the door wall  116 . The gasket  118  may be affixed to the door inner wall  112  in myriad ways including, but not limited to, being integral with the door inner wall  112 , having the door inner wall  112  overmolded around the gasket  118 , having the gasket  118  disposed in slot or groove cut into the door inner wall  112 , and so forth. As illustrated, in certain embodiments, the gasket  118  forms a seal circuit that extends around the side of the door inner wall  112  proximate the perimeter of the door wall  116 . In certain embodiments, the gasket  118  may not form a complete circuit around the side of the door inner wall  112 , but may instead be interrupted by one or more gaps or other discontinuities. In certain embodiments, the gasket  118  may be a band of flexible material, such as high density urethane, configured to deform when the gasket  118  interacts with a side  120  (or face) of the door frame  102 . 
     As illustrated, the door inner wall  112  and the door outer wall  114  both include solid, generally rectangular bodies that do not have openings therethrough. In contrast, as also illustrated, the door frame  102  and the gasket  118  are also generally rectangular in shape, but include generally rectangular openings that generally align with each other. In particular, the gasket  118  is generally shaped such that, when it is affixed to the door inner wall  112  and attached to the door frame  102 , for example, via one or more of the hinges  108  described herein, the gasket  118  is configured to be compressed against the door frame  102  when the access door  104  is in a closed position with respect to the door frame  102  and, for example, latched into the closed position via the one or more latches  110  described herein, to achieve air-tight sealing. In such an embodiment, the one or more hinges  108  and the one or more latches  110  generally provide the force to compress the gasket  118  against the door frame  102 . 
       FIG. 7A  is a perspective view of an embodiment of the access door assembly  100  shown in  FIG. 6A , with the access door  104  in an opened position, in accordance with the present techniques. In addition,  FIG. 7B  is a zoomed in perspective view of a portion of a door frame  102  of the access door assembly  100  shown in  FIG. 7A , in accordance with the present techniques. As illustrated, in certain embodiments, the side  120  of the door frame  102  that interfaces with the gasket  118  is substantially flat. As used herein, the term “substantially flat” or “substantially linear” is intended to be interpreted as a flat surface or line within reasonable manufacturing tolerances, for example, having greater than 95%, greater than 98%, greater than 99%, or even more, of the individual points on the substantially flat surface or line, such as on the side  120  of the door frame  102 , that exist in a single plane. As such, when the gasket  118  compresses against the side  120  of the door frame  102 , the force exerted from the gasket  118  against the side  120  of the door frame  102  is distributed substantially evenly across the entire area of the gasket  118 . 
       FIG. 8A  a cross-sectional cutaway view of an embodiment of the access door assembly  100  shown in  FIG. 6A , in accordance with the present techniques. In addition,  FIGS. 8B and 8C  are cross-sectional cutaway views of the access door assembly  100  shown in  FIG. 8A , in accordance with the present techniques.  FIGS. 8B and 8C  illustrate how the forces of compression F comp  between the gasket  118  and the substantially flat side  120  of the door frame  102  are substantially evenly distributed across the entire area of the gasket  118 . For example, in certain embodiments, the forces of compression F comp  between the gasket  118  and the substantially flat side  120  of the door frame  102  may vary by less than 5%, less than 2%, less than 1%, or even less, for any two points of contact between the gasket  118  and the flat side  120  of the door frame  102 . 
     The access door assemblies  100  illustrated in  FIGS. 6-8  provide certain advantages relating to creating air-tight sealing between the gasket  118  and the door frame  102 . However, it has been recognized that points of contact between the gasket  118  and the door frame  102  that are further away from the latch and hinge mounting points may experience reduced forces of compression F comp  between the gasket  118  and the door frame  102 , thereby leading to diminished sealing at this points. Furthermore, it has been recognized that it would be advantageous to minimize the reliance on hinges  108  and latches  110  to generate the forces of compression F comp  between the gasket  118  and the door frame  102 . 
       FIG. 9A  is a perspective view of another embodiment of an access door assembly  100 , in accordance with the present techniques. In addition,  FIG. 9B  is an exploded view of the embodiment of the access door assembly  100  shown in  FIG. 9A , in accordance with the present techniques. The embodiment illustrated in  FIGS. 9A and 9B  is substantially similar to the embodiment illustrated in  FIGS. 6A and 6B , except for the fact that, instead of being substantially flat, the side  120  of the door frame  102  includes a ridge  122  that projects outwardly from the side  120  of the door frame  102 . In general, the projected ridge  122  of the door frame  102  is configured such that it generally aligns with the gasket  118  of the access door  104  when the access door  104  is in a closed position with respect to the door frame  102  and, for example, latched into the closed position via the one or more latches  110  described herein, to achieve air-tight sealing. As illustrated, in certain embodiments, the projected ridge  122  forms a second seal circuit that extends around the side  120  of the door frame  102 . In certain embodiments, the projected ridge  122  may not form a complete circuit around the side  120  of the door frame  102 , but may instead be interrupted by one or more gaps or other discontinuities. In certain embodiments, the door frame  102 , and the projected ridge  122  formed in the door frame  102 , may be comprised of a rigid material, such as metal, whereby interaction of the projected ridge  122  with the gasket  118  at, for example, a center portion of the gasket  118  causes the gasket  118  to deform. In certain embodiments, the gasket  118  may have a width that is greater than projected ridge  122 , while in other embodiments, the projected ridge  122  may have a width that is greater than the gasket  118 . 
       FIG. 10A  is a perspective view of an embodiment of the access door assembly  100  shown in  FIG. 9A , with the access door  104  in an opened position, in accordance with the present techniques. In addition,  FIG. 10B  is a zoomed in perspective view of a portion of a door frame  102  of the access door assembly  100  shown in  FIG. 10A , in accordance with the present techniques. As illustrated, in certain embodiments, the side  120  of the door frame  102  that interfaces with the gasket  118  is not substantially flat, but includes the ridge  122 , which projects from the side  120  of the door frame  102 , and which is configured to generally align with and engage a central portion of the gasket  118  of the access door  104  when the access door  104  is in a closed position with respect to the door frame  102  and, for example, latched into the closed position via the one or more latches  110  described herein, to achieve air-tight sealing. As such, in this embodiment, the one or more hinges  108  and the one or more latches  110  are not the only components that generate the forces of compression F comp  between the gasket  118  and the door frame  102 . Rather, the projected ridge  122  helps generate additional forces of compression F comp  between the gasket  118  and the door frame  102 . Furthermore, due at least in part to the non-flat shape of the projected ridge  122 , the forces of compression F comp  exerted from the gasket  118  against the projected ridge  122  of the door frame  102  are not distributed evenly across the entire area of the gasket  118 . 
       FIG. 11A  a cross-sectional cutaway view of an embodiment of the access door assembly  100  shown in  FIG. 9A , in accordance with the present techniques. In addition,  FIGS. 11B and 11C  are cross-sectional cutaway views of the access door assembly  100  shown in  FIG. 11A , in accordance with the present techniques.  FIGS. 11B and 11C  illustrate how the forces of compression F comp  between the gasket  118  and the projected ridge  122  of the door frame  102  are not distributed evenly across the entire area of the gasket  118 . For example, as illustrated, in certain embodiments, the forces of compression F comp  between the gasket  118  and the projected ridge  122  of the door frame  102  may be greater at a centerline  124  of an area of the gasket  118 . For example, in certain embodiments, the forces of compression F comp  between the gasket  118  and the projected ridge  122  of the door frame  102  at the centerline  124  of the cross-sectional area of the gasket  118  may be greater than the forces of compression F comp  between the gasket  118  and the projected ridge  122  of the door frame  102  at the edges  126 ,  128  of the cross-sectional area of the gasket  118  by greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 60%, greater than 70%, greater than 80%, greater than 90%, greater than 100%, or even more, depending on the specific physical dimensions of the gasket  118  and the projected ridge  122 . The concentration of the forces of compression F comp  between toward the centerline  124  of the gasket  118  results in deeper penetration of the projected ridge  122  into the gasket  118 , thereby providing improved sealing as compared to conventional techniques. 
     In addition, the projected ridge  122  makes initial contact with the gasket  118  and begins sealing before the access door  104  is latched against the door frame  102 , for example, via the one or more latches  110  described herein. Once the one or more latches  110  are activated, the force exerted by the one or more latches  110  is distributed along the perimeter of the access door  104  from the gasket  118  to the projected ridge  122  for an improved sealing effect, with very little increase in cost. In particular, the projected ridge  122  may be formed in an existing door frame  102  using relatively easy manufacturing processes, such as turret presses. In addition, the projected ridge  122  provides increased rigidity for the door frame  102 , obviating the need for additional stiffening support structures, such as flanges and ribs, thereby eliminating additional costs relating to such support structures. 
     It should be noted that while the embodiments described herein have been primarily directed to access doors  104  having the gaskets  118  attached thereto, and the projected ridges  122  being formed in the door frames  102 , in other embodiments, the gaskets  118  and projected ridges  122  may be associated with the opposite components of the access door assemblies  100 . For example, in certain embodiments, the gasket  118  may be attached to the door frame  102  in the manner described herein, and the projected ridge  122  may be formed in the access door  104 , specifically in the door inner wall  112  of the door wall  116  of the access door  104 , in the manner described herein. It will be appreciated that, in such embodiments, the interaction between the gasket  118  and projected ridge  122  are substantially similar to the interaction between the gasket  118  and projected ridge  122  for the other embodiments described herein. 
     The projected ridges  122  illustrated in  FIGS. 6-11  are merely exemplary of the types of projected ridges  122  that may be used. More specifically, the projected ridge  122  may include various cross-sectional profiles.  FIGS. 12A through 12I  are cross-sectional views of profiles of various embodiments of the projected ridge  122 , in accordance with the present techniques. In general, each of the illustrated embodiments includes a cross-sectional profile having a height H ridge  of the projected ridge  122  that increases from zero at a first base end  130  at a base of the projected ridge  122 , to at least one maximum peak along the cross-sectional profile, then back to zero at a second base end  132  at the base of the projected ridge  122 . It will be appreciated that the base of the projected ridge  122  may be interpreted as the side  120  of the door frame  102 , as described herein, in certain embodiments. 
     As but a few non-limiting examples, each of the embodiments illustrated in  FIGS. 12A through 12F  includes a cross-sectional profile where a height H ridge  of the projected ridge  122  increases from zero at the first base end  130  at the base of the projected ridge  122 , to a maximum height H ridge  at a centerline  134  of the cross-sectional profile, then back to zero at the second base end  132  at the base of the projected ridge  122 . For example, in the embodiment illustrated in  FIG. 12A , the cross-sectional profile of the projected ridge  122  includes a substantially flat peak section  136  having sloping side sections  138 ,  140  that extend substantially linearly from boundaries  142 ,  144  of the substantially flat peak section  136  to the base of the projected ridge  122 . However, in other embodiments similar to the embodiment illustrated in  FIG. 12A , the sloping side sections  138 ,  140  may not be substantially linear, but may rather be arcuate or otherwise curvilinear, for example, not having a constant radius. For example, the sloping side sections  138 ,  140  may be convex curvilinear or concave curvilinear, as illustrated in  FIGS. 12B and 12C , respectively. It will be appreciated that, in certain embodiments, the sloping side sections  138 ,  140  may include any combination of linear, arcuate, or curvilinear sloping side sections  138 ,  140 . 
     In the embodiment illustrated in  FIG. 12D , the cross-sectional profile of the projected ridge  122  includes a single convex arcuate ridge section  146  that extends from the first base end  130  at the base of the projected ridge  122  to the second base end  132  at the base of the projected ridge  122 . In the embodiment illustrated in  FIG. 12E , the cross-sectional profile of the projected ridge  122  includes a single curvilinear ridge section  148  that extends from the first base end  130  at the base of the projected ridge  122  to the second base end  132  at the base of the projected ridge  122 . It is noted that the embodiment illustrated in  FIG. 12E  is substantially similar to the embodiments illustrated in  FIGS. 12A through 12C , however, the transitions from the base ends  130 ,  132  toward the maximum height H ridge  at the centerline  134  of the cross-sectional profile are relatively smoother. In contrast, in the embodiment illustrated in  FIG. 12F , the cross-sectional profile of the projected ridge  122  includes two ridge sections  150 ,  152  that extend substantially linearly from the respective base ends  130 ,  132  to the maximum height H ridge  at the centerline  134  of the cross-sectional profile, thereby forming a single triangular projected ridge  122 . 
     Although  FIGS. 12A through 12F  illustrate embodiments where the maximum height H ridge  of the projected ridge  122  occurs at its centerline  134 , in other embodiments, the maximum height H ridge  of the projected ridge  122  may occur closer to one of the base ends  130 ,  132  of the projected ridge  122 , thereby forming a projected ridge  122  having an asymmetrical cross-sectional profile. Specifically, it will be appreciated that a peak point (or points)  154  along the cross-sectional profiles for each of the embodiments illustrated in  FIGS. 12A through 12F  may be moved closer to one of the base ends  130 ,  132  of the projected ridge  122  in certain embodiments. 
     Also, although  FIGS. 12A through 12F  illustrate embodiments having a cross-sectional profile where the height H ridge  of the projected ridge  122  increases from zero at the first base end  130  at the base of the projected ridge  122 , to a maximum height H ridge  along the cross-sectional profile, then back to zero at the second base end  132  at the base of the projected ridge  122 , other embodiments of the projected ridge  122  may be used. For example, in the embodiment illustrated in  FIG. 12G , the cross-sectional profile of the projected ridge  122  includes a base projection  156  that projects outwardly from the base of the projected ridge  122 , and a peak projection  158  that projects further outwardly from the base projection  156 . In the embodiment illustrated in  FIG. 12H , the cross-sectional profile of the projected ridge  122  includes the base projection  156  that projects outwardly from the base of the projected ridge  122 , and two peak projections  158  that each project further outwardly from the base projection  156 . In the embodiment illustrated in  FIG. 12I , the cross-sectional profile of the projected ridge  122  includes two peak projections  158  that each project outwardly directly from the base of the projected ridge  122 , instead of projecting outwardly from the base projection  156 . 
     Although illustrated in  FIGS. 12H and 12I  as having a substantially similar peak height H ridge , in other embodiments, the two peak projections  158  may instead have different peak heights H ridge . In addition, although illustrated in  FIGS. 12H and 12I  as including two peak projections  158 , in other embodiments, the projected ridge  122  may instead include three, four, five, six, seven, eight, or even more, peak projections  158 . In addition, although primarily illustrated in  FIGS. 12G through 12I  as including triangular projections, such as illustrated in  FIG. 12F , the peak projections  158  described herein may take the form of any of the embodiments of the projected ridge  122  illustrated in  FIGS. 12A through 12F , in certain embodiments. 
     One or more of the disclosed embodiments, alone or in combination, may provide one or more technical effects useful in improving the design of HVAC access doors. For example, in general, embodiments of the present disclosure include relatively simple manufacturing designs that provide improved load distribution and deeper penetration between sealing components of an access door and its associated door frame to provide improved sealing along the perimeter of the access door with no additional latches for sealing, support structures for providing rigidity, and so forth. 
     While only certain features and embodiments of the present disclosure have been illustrated and described, many modifications and changes may occur to those skilled in the art, such as variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, and 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 present disclosure. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described, such as those unrelated to the presently contemplated best mode of carrying out the present disclosure, or those unrelated to enabling the claimed disclosure. 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.