Abstract:
A heating, ventilation, and air conditioning (HVAC) system is disclosed which is capable of receiving interchangeable ventilation modules having varying degrees of air mixing abilities. A ventilation module fits inside the HVAC system and connects to a return air opening, an exhaust duct, an inlet air opening, and a supply air duct for proper routing of air to be conditioned. As ventilation needs change, a different module with appropriate ventilation characteristics can replace the existing module while keeping intact all other components of the HVAC system such as blowers, compressors, heaters, condensing coils and the like. Ventilation module functionality ranges from an economizer module which allows 100% outside air into a structure, to a motorized air damper module which can be controlled based on various factors such as room occupancy to provide a limited range of fresh and return air mixing, to a blank-off plate which completely prevents use of outdoor air thus leaving the system to condition return air only for supply to the structure. A ventilation module for efficient and economical system operation capable of energy transfer between incoming air and exhausted stale air from the structure is also provided, adaptable to various new or existing types of heating and cooling systems.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 016,153, filed on Feb. 5, 1993, now U.S. Pat. No. 5,301,744, the disclosure of which is incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to heating, ventilation, and air conditioning (HVAC) systems. More particularly, this invention relates to HVAC systems and the like which combine outdoor air with indoor air, perhaps condition it, and circulate it within a structure. 
     BACKGROUND OF THE INVENTION 
     With the increased emphasis on energy conservation over the last 20 years, buildings are being constructed with more insulation and tighter construction techniques, thus reducing natural ventilation to the building. This decrease in natural ventilation has resulted in less fresh air for occupants of a building leading to what is called &#34;sick building syndrome&#34;. In response to this problem, building standards have been changed to require controlled ventilation in adequate amounts to insure good &#34;indoor air quality&#34; a phrase which has recently become quite a buzzword in the heating, ventilation, and air conditioning industry. An example of this change is in ASHRAE Standard 62-1989 which has increased the ventilation requirements for schools to 15 CFM per student. Most standards previously called for 5 CFM per student. This has caused a large increase in a structure&#39;s HVAC load thus requiring larger, noisier and more expensive systems at significantly higher operating costs. In certain climatic regions, this also increases the latent (moisture removal) load of the building beyond the capability of conventional HVAC systems resulting in very high and uncontrolled humidity inside the building. 
     Prior HVAC systems employed different methods of varying sophistication to control the air which is conditioned and circulated within a structure. The control means used often depends on the type of structure for which ventilation is required as well as structure location. Temperature, humidity, and minimum outside air are three typical quantities which need be controlled. As previously mentioned, state statutes, building codes, ASHRAE standards, and the like often require that schools and other buildings provide minimum amounts of outside air. These facilities must use an HVAC system which can meet the necessary requirements. Frequently, a structure will require increased or decreased amounts of outdoor air when its use changes. A new or completely retrofitted HVAC system is then required to meet those new requirements. 
     As an example, portable classrooms have become popular in some parts of the United States where enrollment size shifts to various locations within a district. To meet the space requirements needed for such an enrollment flux, portable classrooms are moved from location to location. The HVAC unit attached to the portable classroom may be inadequate for the environmental conditions in the new location, thus requiring either a new HVAC system or a complete retrofit of the old system. A new HVAC system or retrofit can be expensive. For example, as codes and standards for indoor air quality change, an HVAC system must either be retrofitted or replaced to meet the new requirements. 
     Prior to the invention disclosed in U.S. application Ser. No. 016,153, existing HVAC systems could not be easily retrofitted with a new components and did not have modular ventilation units which were easily interchangeable. Methods or systems which could readily adapt to a structure&#39;s changed needs did not exist. Further, no systems were available which provided a heat recovery device as a built-in item in an air conditioner, heat pump or gas/electric type wall mounted heating and cooling system. The invention described in the above-mentioned application addressed the above concerns. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improvement to the modular HVAC system capable of changing to meet the needs of its environment or desired use. Specifically, the improvement relates to the adaptability of the aforementioned modular HVAC system to various methods of heating and cooling other than the standard electric heating and vapor compression air conditioning. The original invention contains a space capable of receiving ventilation unit modules which are interchangeable depending on a structure&#39;s needs. These units connect directly to the heat pump, air conditioner or other air handling system. The ventilation units range in function from a blank off plate (to prevent use of outdoor air) to an economizer (which can proportion outdoor air use from 0% to 100% of maximum). Other modules include a barometric fresh air damper module which opens during blower operations to provide fresh air to be mixed with the conditioned air, a motorized fresh air damper module which provides a higher degree of control in mixing fresh air with the return air, a commercial room ventilator which provides outdoor air intake (within a range of 0% to 100% of maximum) while also providing exhaust capabilities, and an energy transfer module capable of transferring energy between incoming ventilation air and outgoing exhaust air from the structure. The energy transfer module reduces applied operating cost or power consumption of the HVAC system while improving comfort by controlling adequate humidity levels. The energy transfer module can also provide improved indoor air quality with minimum increase in operating cost and without increasing the HVAC system size. Additionally, exhaust air from the structure is routed through an outdoor heat exchanger coil transferring energy between the two. This transfer, which enhances system performance, cannot be obtained from &#34;stand alone&#34; energy recovery devices, nor would it be realized if the exhaust air is routed in a different manner and not able to pass over the outdoor heat exchanger coil. 
     The ventilation modules of the present invention allow an HVAC system to be used for a wide range of applications, such as modular offices, school modernization, telecommunication structures, portable classrooms, correctional facilities and apartments. The ventilation module for a particular application can be installed in the factory, in the field at the time of system installation, or as a retrofit after system installation. The modules are installed within the HVAC system and thus may eliminate the need for hoods or damper assemblies on the exterior of the HVAC system. As in most HVAC systems, functions are controlled by one or more temperature-responsive components, either locally or remotely. 
     It is an object of this invention to provide an HVAC system capable of changing to meet a structure&#39;s specific ventilation requirements. 
     More particularly, it is an object of the invention to provide an HVAC system designed to accept modules of varying ventilation capabilities. 
     It is a further objective of the present invention to provide an HVAC system with a range of easily interchangeable ventilation modules which provide various ventilation options from 100% outdoor air to little or no outdoor air, i.e., using only conditioned return air. 
     Still another objective is to provide an HVAC system which is compatible with and adaptable to a variety of new or existing systems, including, but not limited to, gas or electric heating and conventional vapor compression or chilled water system cooling. 
     A further objective is to provide an HVAC system with a removable energy transfer module which improves indoor comfort and conserves energy. 
     Yet another objective is to provide an HVAC system capable of transferring energy between the exhaust air stream and an outdoor heat exchanger coil. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of a preferred embodiment of the air conditioning system of the present invention from a view outdoor of the structure to which the system would be attached. 
     FIG. 2 is an elevational view similar to FIG. 1 and additionally showing the economizer ventilation module as it is installed in the ventilation system. 
     FIG. 3 shows a more detailed view of the economizer ventilation module components. 
     FIG. 4 is a schematic diagram of air flow through the ventilation system with an economizer ventilator module installed operating in economizer mode. 
     FIG. 5 is a schematic diagram of air flow through the ventilation system with an economizer ventilator module installed operating in mechanical cooling mode. 
     FIG. 6 is an elevational view similar to FIG. 1 and additionally showing the commercial room ventilator module as it is installed into the ventilation system. 
     FIG. 7 shows a detailed illustration of the classroom ventilator module components. 
     FIG. 8 is an elevational view similar to FIG. 1 and additionally showing the motorized fresh air damper module as it is installed into the ventilation system. 
     FIG. 9 shows a detailed illustration of the motorized fresh air damper module components. 
     FIG. 10 is a schematic diagram of air flow through the ventilation system with a motorized fresh air damper module installed. 
     FIG. 11 is a schematic diagram of air flow through the ventilation system with a classroom ventilator module installed. 
     FIG. 12 shows the position of the barometric fresh air damper module as it is fastened onto a louvered front access door which attaches over the ventilation module receptacle space. 
     FIG. 13 shows the position of the blank-off plate as it is fastened onto a louvered front access door which attaches over the ventilation module receptacle space. 
     FIG. 14 is a schematic diagram of air flow through the ventilation system with a blank-plate installed. 
     FIG. 15 is a schematic diagram of air flow through the ventilation system with a barometric ventilator module installed. 
     FIG. 16 is an elevational view of the ventilation system from a perspective indoor of the structure to which the system would be attached. 
     FIG. 17 is an elevational view of the air conditioning system from a perspective outdoor of the structure to which the air conditioning system would be attached shown with access doors removed. 
     FIG. 18 shows a detailed illustration of the energy transfer module components as it would appear outdoor of the structure as installed in the system. 
     FIG. 19 shows a detailed illustration of the energy transfer module components similar to FIG. 18 but showing it as it would appear looking from the indoor of the structure. 
     FIG. 20 is an elevational view of the ventilation system similar to FIG. 17 also showing the energy transfer module as installed from a perspective outdoor of the structure to which the system would be attached. 
     FIG. 21 is an elevational view of the ventilation system similar to FIG. 16 also showing the energy transfer module as installed from a perspective indoor of the structure to which the system would be attached. 
     FIG. 22 shows a more detailed cut-away illustration of the energy transfer module components similar to FIG. 18 as it would appear outdoor of the structure as installed in the system. 
     FIG. 23 is a schematic diagram of air flow through the ventilation system with a energy transfer module installed showing system air flow when not in energy transfer mode. 
     FIG. 24 is a schematic diagram of air flow through the ventilation system with a energy transfer module installed showing system air flow when in energy transfer mode. 
     FIG. 25 is a perspective view of the air conditioning system with the outer casing removed showing air flow through the outdoor air exchanger coil. 
     FIG. 26 is a perspective view of the air conditioning system with the outer casing removed showing the configuration for use with a new or existing gas heating system and new or existing chilled water cooling system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows the HVAC system 10 as seen if mounted on the exterior of a structure (not shown). It can also be attached to the inside of a structure. The air conditioning system 10 is encased in a cabinet 20 made of any durable material, preferably of galvanized twenty-gauge zinc coated steel. A louvered or slotted door 32 allows internal access to the air conditioning system 10 for maintenance, such as changing filters. Door 32 has horizontal slots 34 for fresh air intake and may be completely removed by unscrewing fasteners 36 when changing ventilation modules. A lockable circuit breaker access panel 44 is provided on a side of the air conditioning system 10. Panel 46 affords access to internal electrical components and connections. System power is provided through electrical entrances 48 and low voltage electrical entrance 52. Alternate electrical entrance locations 50 are also provided (which may accommodate existing or new electrical lines carrying signals from the temperature-responsive components). See FIG. 16. Vertical mounting brackets 54 along the length of air conditioning system 10 attach it to the subject structure (not shown). Brackets 54 can be located elsewhere on cabinet 20 so that air conditioning system 10 can be mounted at various locations on a structure, including but not limited to, an inside location. Panel 56 covers the area in air conditioning system 10 which contains the indoor heat exchanger coil, the air circulating blowers, and the air supply duct. Perforated metal outlet grill 42a allows an exit for exhaust air from the structure while perforated metal inlet grill 42b allows intake of outside air to blow across the outdoor heat exchanger coil 544. Heater access panel 58 provides access to electrical heating strips elements 460. See FIG. 19. 
     Upon removal of door 32, a chamber 60 exists which is capable of receiving a ventilation module, such as economizer ventilation module 62 as shown in FIG. 2. The module has casing 64 and is made of any durable material, preferably steel. Ventilation module 62 slides into chamber 60 above plane 66 and is attached by screws (not shown). Exhaust opening 68 in plane 66 connects with exhaust duct 520. FIGS. 4 and 5. Ventilation module 62 fits over exhaust opening 68. Air filters 440 are accessed through door 32. 
     Economizer module 62 is shown in more detail in FIG. 3. Wires 114 provide electrical power to damper actuator 102a. Damper actuator 102a turns arm 118 which is connected to blade 106 by rod 104. Pivot joint 108 connects rod 104 with blade 106, which turns on hinge 116. Outdoor air temperature and humidity are sensed by temperature sensing device 110. Damper actuator 102a (which consists of a motor and associated computing electronics) processes temperature signals from remote temperature-responsive components (not shown) as well as other air conditioning system 10 parameters such as humidity, enthalpy, minimum blade 106 position, and mixed air sensing for control of blade 106. Electrical relay unit 102b contains electrical relays for the economizer unit. 
     FIG. 4 shows a schematic diagram of airflow through air conditioning system 10 with economizer module 62 installed and operating in economizer mode. In economizer mode, outside air is circulated into the structure thus saving wear on the air cooling compressor and extending its life. Return air is exhausted exteriorly. As outside air is drawn into the air conditioning system 10, it passes through slots 34 in door 32, through module screen 70, through space 72 and into chamber 60 if blade 106 is open. Blade 106 is in the completely open position resting on partition 78. The outside air passes through filter 440 and into air supply duct 510. 
     Air circulating is accomplished by device 410 in supply air duct 510. Air blowers, preferably twin blowers with multispeed motors, provide airflow adjustments for high and low static operation. Electric heater elements 460 with automatic limit and thermal cut-off safety control are provided for heat conditioning of the supply air. 
     The conditioned air circulates past indoor heat exchanger coils 420, which preferably are aluminum finned copper coils, and through supply air outlet 250 into the structure&#39;s interior. Conditioned supply air enters the structure forcing return air through air return opening 260 where it is routed by blade 106 through exhaust opening 68, into exhaust duct 520, through exhaust outlet grill 42a and to the structure&#39;s exterior. 
     In mechanical cooling mode, an option with economizer module 62 installed, no outdoor air is circulated and only indoor return air is routed through air conditioning system 10 as shown in FIG. 5. Blade 106 is in the fully closed position resting on partition 74 thus blocking space 72 and preventing outdoor air from entering the air supply duct 510 and also preventing return air from exiting through exhaust opening 68. Return air enters ventilation system 10 through return air inlet 260, passes through space 76 and is routed through filter 440 and into air supply duct 510. Air circulating is accomplished by device 410. The air then circulates past indoor heat exchanger coil 420 and through supply air outlet 250 into the structure&#39;s interior. Indoor heat exchanger coil 420 is drained through drain 430. 
     Other blade 106 positions allow various percentages of fresh air to be mixed with return air ranging from 0% to 100%. Those positions are based on control signals from a system control unit which can take into account parameters including but not limited to air temperature and humidity. 
     FIG. 6 shows commercial room ventilator module 82 as it would be installed into air conditioning system 10. FIG. 7 is a more detailed drawing of the commercial room ventilator module. The module consists of damper actuator 102a which controls blade 106 position. Operation is similar to that of the economizer module except no air temperature sensing capability exists for controlling damper 106. The module provides outside air intake along with exhaust capability. Control of the commercial room ventilator unit can be accomplished with a system control unit such as the Bard CS2000, which features total system control including adjustment of the commercial room ventilator unit based on occupancy, control for maximum heating and cooling settings, and automatic adjustments for vacation or no occupancy conditions. Control can also be accomplished with an electronic programmable temperature-responsive component or timer. 
     FIG. 11 is a schematic diagram of airflow through ventilation system 10 with classroom ventilator module 82 installed. Flow is similar to that when an economizer module is installed with preferably a maximum of 75% blade 106 opening with return air as opposed to 100% capability in the economizer module. 
     FIG. 8 shows a motorized fresh air damper module 92 as it would be installed into air conditioning system 10. This module replaces interior air lost due to exfiltration out windows, doors and other seepage in the structure. Space 68 is covered with exhaust cover plate 168 to prevent air from exhausting through the air conditioning system 10. 
     FIG. 9 is a more detailed drawing of the motorized fresh air damper 92. The module consists of damper actuator 102a, preferably a 24 volt electric motor and associated computing electronics, which controls damper 106 position. The module provides outside air to be mixed with return air, preferably a maximum of 25% fresh air. Damper 106 can be controlled by the air blower circuit or can be controlled based on other factors such as room occupancy or time-of-day. 
     FIG. 10 is a schematic diagram of airflow through air conditioning system 10 with motorized fresh air damper 92 installed. Blade 106 can be either fully open or fully closed. In the fully open position, as shown in FIG. 10, outside fresh air enters ventilation system 10 through slots 34, passes through motorized fresh air damper module 92, into chamber 60 where it mixes with return air from the structure drawn through return air inlet 260. The mixed air then passes through filter 440 and into air supply duct 510. Air circulating is accomplished by device 410. The air then circulates past indoor heat exchanger coil 420 and through supply air outlet 250 into the structure&#39;s interior. Indoor heat exchanger coil 420 is drained through drain 430. 
     A fourth ventilation alternative is shown in FIG. 12. The barometric fresh air damper 94 attaches to the inside of louvered or slotted door 32 by screws 98 thus extending the module into space 60 within air conditioning system 10. Blade 106 opens on hinge 118 during air blower operation due to pressure differential between the top and bottom surfaces of blade 106. Blade 106 closes when the blower is off. Adjustable stops 120 limit the amount of outside air mixed with return air for supply air to the structure, preferably with a maximum of 25% fresh air mixed with the return air. 
     FIG. 15 depicts airflow through conditioning system 10 with the barometric fresh air damper 94 installed. When the air circulating blower 410 is on, air is drawn through return air inlet 260 thus decreasing the air pressure in space 60. The outside barometric pressure forces blade 106 open allowing fresh air through slots 34, through space 126 and into space 60 where it mixes with return air. The mixed air then passes through filter 440 and into air supply duct 510. Air circulating is accomplished by device 410. The air then circulates past indoor heat exchanger coil 420 and through supply air outlet 250 into the structure&#39;s interior. 
     When no fresh air is required, air conditioning system 10 can be operated without a ventilation module in chamber 60. Blank-off plate 96 is attached to louvered or slotted door 32 by screws 98 to covering slots 34 to make it airtight as shown in FIG. 13. Airflow through ventilation system 10 with blank-off plate 96 installed is shown schematically in FIG. 14. As blower and air conditioner 410 turns on, return air is drawn from the structure&#39;s interior through return air opening 260 and into chamber 60. No outside fresh air is drawn into ventilation system 10 as blank-off plate 96 blocks passage through slots 34. The return air then passes through filter 440 and into air supply duct 510. Air circulating is accomplished by device 410. The air then circulates past indoor heat exchanger coil 420 and through supply air outlet 250 into the structure&#39;s interior. 
     A perspective view of air supply duct 510 in the interior of air conditioning system 10 is shown in FIG. 17. Air filter 440 is slidably mounted on brackets 442 below air circulating devices 410. Rotatable fan wheels 412 circulate air through air supply duct 510. 
     Energy transfer between incoming and outgoing air streams can be economically accomplished during ventilation when energy transfer module 310 is installed in space 60 of air conditioning system 10 as shown in FIG. 18. FIG. 19 shows an inside view of air conditioning system 10 with energy transfer module 310 installed. FIGS. 20 and 21 show energy transfer module 310 from outside and inside views, respectively. A detailed cut-away view of energy transfer module 310 is shown in FIG. 22. Encased in box 332 are blower housings 330 which have blower wheels (not shown) to draw outside air through intake space 334, through energy transfer disks 320, through blower inlets 340 and force it out through openings 333. The outside air is routed by backdraft dampers 336 into air supply duct 510. A drive motor (not shown) provides the power to rotate the energy transfer disks 320 around center pins 322. Plate 335 prevents outside air from passing into space 339. 
     FIG. 23 is a schematic diagram of airflow through air conditioning system 10 with energy transfer module 310 installed operating in recirculation mode, that is, without drawing outside air into the system. No energy transfer is accomplished in this mode of operation as blowers 330 are not activated. Air circulating devices 410 draw return air from the structure through return air opening 260, through filter 440 and into air supply duct 510. The air then circulates past indoor heat exchanger coil 420 and through supply air outlet 250 back into the structure&#39;s interior. Plate 341 prevents return air from entering case 322. 
     FIG. 24 shows schematically airflow through air conditioning system 10 with energy transfer module 310 installed operating in energy transfer mode. Blowers 330 in case 332 draw outdoor air into space 334, past energy transfer disks 320, into blowers 330, and exhaust it into air supply duct 510. Blowers 330 in space 339 draw return air from the interior of the structure through return air opening 260, through energy transfer disks 320, into blowers 330, and out exhaust duct 520. Energy transfer disks 320 rotate through a stream of outdoor air coming into air conditioning system 10 and a stream of return air from the structure. As the energy transfer disks 320 rotate, heat energy from one air stream is absorbed by the energy transfer disks 320 and is transferred to the other air stream, thus providing more efficient and economical energy usage. 
     The above described energy transfer can be effectively accomplished during both winter and summer ventilation operations. During the winter, part of the warmer interior return air stream passing through return air opening 260 will be drawn through energy transfer disks 320 by blowers 330 in space 339. See FIG. 24. This air stream will thus transfer some heat energy to the energy transfer disks 320. As energy transfer disks 320 rotate, they pass through the cooler outdoor air drawn into air conditioning system 10 from space 334 by blowers 330 in case 332. Heat energy which would have been exhausted absent use of the energy transfer module 310 is thus transferred to the incoming air stream as it passes through energy transfer disks 320. 
     During summer ventilation operations, part of the cooler interior air stream passing through return air opening 260 will be routed drawn through energy transfer disks 320 by blowers 330 in space 339. This air stream will thus absorb some heat energy from the energy transfer disks 320. As energy transfer disks 320 rotate, they pass through the warmer outdoor air drawn into air conditioning system 10 through space 334 by blowers 330 in case 332. Heat energy in the incoming air stream is transferred to the cooler energy transfer disks 320. By use of the energy transfer module 310, a cooler air stream is provided to air supply duct 510 for cooling by air conditioning system 10. A more economical and energy efficient air conditioning system results from use of the energy transfer module 310. 
     The system can be adapted for use with various new or existing heating and cooling systems, e.g., gas heating and chilled water cooling. As shown in FIG. 26, the electric beating coils can be replaced with gas heater 461 and the direct expansion heat exchanger coils can be replaced with chilled water coils 421 and connected to a new or existing chilled water system (not shown). 
     With the commercial room ventilator module 82, economizer module 62, or the energy transfer module 310 installed in air conditioning system 10, an additional system performance benefit is realized as a result of the exhaust air rout design. See FIG. 25. This benefit is realized as air is exhausted from the applied structure when the air conditioning system 10 is operating in the mechanical cooling or heating mode. &#34;Stand alone&#34; energy recovery devices cannot deliver this benefit, nor would it be realized if the exhaust air is routed in a different manner and not able to pass over the outdoor heat exchanger coil 544. 
     When air conditioning system 10 is operating in the air cooling mode, cooler exhaust air from the interior of the structure is routed through return air inlet 260, through exhaust opening 68, into exhaust duct 520 and to the inlet of outdoor fan 540. The cooler exhaust air is mixed with warmer outdoor air drawn through perforated metal inlet grill 42b and is blown through the outdoor heat exchanger coil 544. This reduces the temperature of the air stream passing through the outdoor heat exchanger coil 544 to a level below the outdoor ambient conditions and increases the air conditioning system 10 cooling capacity while reducing its power consumption. 
     When air conditioning system 10 operates with a heat pump operating in the heating mode, warmer exhaust air from the interior of the structure is routed through return air inlet 260, through exhaust opening 68, into exhaust duct 520 and to the inlet of outdoor fan 540. The warbler exhaust air is mixed with cooler outdoor air drawn through perforated metal inlet grill 42b and is blown through the outdoor heat exchanger coil 544. This increases the temperature of the air stream passing through the outdoor heat exchanger coil 544 to a level above the outdoor ambient conditions thus increasing the system capacity and energy efficiency. 
     The foregoing is a description of a preferred embodiment of the invention which is given here by way of example only. The invention is not to be taken as limited to any of the specific features as described, but comprehends all variations as come within the scope of the appended claims.