Abstract:
Disclosed herein is an apparatus, in the form of a package air conditioning unit (PAC) for conditioning air in a space. The space may comprise the interior space(s) of buildings such as hospitals, enclosed shopping malls, warehouses, factories, etc. The PAC comprises a first arrangement, in the form of a suction chamber for receiving an air stream from the space (e.g. return air) and discharging an air stream to the space (e.g. supply air). The PAC has a second arrangement, in the form of second chamber for receiving an air stream from outside the space (e.g. fresh air) and discharging an air stream to outside the space (e.g. exhaust air). The second chamber is configured to receive a portion of the return air via the suction chamber.

Description:
TECHNICAL FIELD 
       [0001]    Disclosed is an air delivery unit for cooling or heating air supplied to a building, largely using the refrigeration cycle, with integrated spill air, spill air heat recovery, and smoke spill extraction from the building. 
       BACKGROUND 
       [0002]    Buildings can have air conditioning or ventilation systems in which the air is heated or cooled by externally located air delivery units. The primary cooling and heating equipment of such air delivery units can largely be contained within a single weather-proof unit or piece of apparatus, known as a packaged air conditioner (PAC), which is externally located. This primary cooling and heating equipment can include indoor refrigeration cycle components such as compressors, reversing valves (for heating), evaporators and condensers, and associated fans. 
         [0003]    PACs cool or heat return air from a building and outdoor air, or can cool or heat a blend of the two, for example, made up predominantly of return air (unless delivering economiser mode “free cooling” of predominantly cool outdoor air) before delivering this conditioned air to the building. The greater the amount of outdoor air so supplied, the greater the amount of air that needs to be relieved from the building as spill air to avoid over pressurisation of the building. Buildings are being constructed with increasing air tightness as the demand for sustainable buildings rises. Consequently, spill air, increasingly, needs to be provided with a spill air path—usually fan assisted—in order to be relieved from modern buildings, rather than simply escaping as leakage. Disadvantages with PACs of the prior art include their inability to remove spill air from a building while supplying air to a building. 
         [0004]    Ventilation systems in buildings can include smoke control systems operable to remove smoke from a building. Smoke control systems include a combination of fans, dampers, warning devices and control equipment. Buildings that can have smoke control systems include hospitals, enclosed shopping malls, warehouses, factories and high rise buildings. Smoke control systems are installed in buildings to protect the lives of occupants and reduce damage to property. National building codes (eg the Building Code of Australia) can require that a smoke control system be fitted to certain types of buildings. 
         [0005]    Smoke control systems may be classed as dedicated or non-dedicated systems. Non-dedicated smoke control systems are used during normal HVAC (heating, ventilation and air-conditioning) operation and during a smoke event. When smoke control mode is activated in a non-dedicated smoke control system, the operation of the building&#39;s HVAC equipment changes. These systems involve a specialised control strategy and may also require additional control and monitoring points. 
         [0006]    Dedicated smoke control systems can include mechanically powered smoke exhaust fans that are automatically switched on in a smoke event to maintain a negative pressure in a smoke filled space. The intention of a mechanically powered smoke exhaust fan is to maintain a negative pressure relative to the surrounding space so that the smoke does not migrate to undesirable areas. To maintain a negative pressure in a smoke filled area, the supply air and return air fans of an air handling unit (AHU) or PAC are usually disabled. This also prevents smoke from being re-circulated back into the building. In spaces with a high void above the occupancy space, warm smoke will rise by natural convection to fill the void, which will act as a smoke reservoir in which smoke is collected. In such instances, smoke exhaust fans may be used to draw smoke from the smoke reservoir to prevent the smoke level from dropping down to the height of occupants, and for a sufficient period of time to allow the occupants to escape. 
         [0007]    Disadvantages of dedicated smoke control systems are that they require additional space, structural support, ducts, dampers and electrical wiring to the building&#39;s normal operation HVAC system. Dedicated smoke exhaust systems must be capable of continuous operation at elevated temperatures for a long period of time. 
         [0008]    The above references to the background art do not constitute an admission that the art forms a part of the common general knowledge of a person of ordinary skill in the art. The above references are also not intended to limit the application of the apparatus as disclosed herein. 
       SUMMARY OF THE DISCLOSURE 
       [0009]    In some embodiments, there is disclosed an apparatus for conditioning air in a space. The apparatus may include a first arrangement for receiving an air stream from the space, and discharging an air stream to the space. The apparatus may also include a second arrangement for receiving an air stream from outside the space and discharging an air stream to outside the space, the second arrangement being configured to receive a first portion of the air stream received from the space via the first arrangement. 
         [0010]    In some forms, the first portion of air received from the space is combined in the second arrangement with the air stream received from outside the space. In some forms, the combined air stream is discharged outside the space. 
         [0011]    In at least one embodiment, the second arrangement is able to be isolated to the receipt of air from the first arrangement. 
         [0012]    In some forms, the first arrangement receives another air stream from outside the space. 
         [0013]    In at least one embodiment, the other air stream is combined with a second portion of the air stream received from the space, with this combined stream being discharged to the space. In some forms, the first arrangement comprises a first heat exchanger. In some forms, the second arrangement comprises a second heat exchanger. 
         [0014]    In at least one embodiment, the first and second heat exchangers are fluidly connected. 
         [0015]    In some forms, in a first mode of operation, when the temperature of the first portion of the air stream is greater than the temperature of the air stream received from outside the space; and when the streams are combined in the second arrangement, the first portion heats the stream received from outside. 
         [0016]    In some forms, in a second mode of operation, when the temperature of the first portion of the air stream is less than the temperature of the air stream received from outside the space; and when the streams are combined in the second arrangement, the first portion cools the stream received from outside. 
         [0017]    In some forms, in the first mode of operation, the second heat exchanger extracts heat from the first portion of the air stream and the first heat exchanger emits the extracted heat. 
         [0018]    In some forms, in the second mode of operation, the second heat exchanger extracts coolth from the first portion of the air stream and the first heat exchanger emits the extracted coolth. 
         [0019]    In some forms, in the first mode of operation, the heat emitted heats the combined stream discharged to the space. In some forms, in the second mode of operation, the coolth emitted cools the combined stream discharged to the space. 
         [0020]    In at least one embodiment, the air stream received from the space includes spill air and return air. In some forms, the second arrangement further comprises an assembly to hold a fluid. 
         [0021]    In some forms, the first arrangement further comprises at least one fan configured to discharge the second combined air stream to the space. 
         [0022]    In some forms, the second arrangement further comprises at least one fan that is able to discharge the first combined air stream to outside the space. 
         [0023]    In some forms, the first or second arrangement further comprises at least one other fan which is able to cause the second arrangement to receive the first portion of the air stream received from the space. 
         [0024]    In some forms, the second arrangement further comprises a discharging assembly arranged to discharge the fluid. 
         [0025]    In some forms, the discharging assembly and the fluid holding assembly are fluidly connected. In at least one embodiment, the fluid discharged by the discharging assembly mixes with the air stream received from outside the space in the second arrangement. 
         [0026]    In some forms, the said mixing of the fluid and the outside air stream evaporatively cools the air stream in the second arrangement. In at least one embodiment, the fluid is a liquid such as water. 
         [0027]    In some forms, the discharge assembly is arranged to discharge the liquid as a spray or mist. In some forms, at least a portion of the liquid comprises condensate from the first heat exchanger. 
         [0028]    In some forms, the apparatus is a package unit. 
         [0029]    In some forms, isolation of the second arrangement to the receipt of air from the first arrangement is caused by closing a spill air damper. 
         [0030]    In some forms, the spill air damper is fire rated. 
         [0031]    In at least one embodiment, the package unit is able to extract smoke from the space, and discharge the smoke outside the space, as part of a smoke extraction system. 
         [0032]    In some embodiments, an apparatus forming part of a package unit for conditioning a space. The apparatus may comprise an arrangement for receiving and discharging an air stream from outside the space. The apparatus may also comprise a holder for a fluid. The apparatus may also comprise a discharging assembly arranged to receive fluid from the holder and to discharge the fluid. 
         [0033]    In some forms, the discharging assembly is arranged such that the fluid discharged thereby mixes with the air stream received from outside the space in the arrangement. 
         [0034]    In some forms, the said mixing of the fluid and the outside air stream evaporatively cools the air stream in the arrangement. 
         [0035]    In some embodiments, the fluid is a liquid such as water. In at least one embodiment, at least a portion of the water comprises condensate from a heat exchanger. 
         [0036]    In some forms, the apparatus forming part of a package unit for conditioning a space is the second arrangement. 
         [0037]    The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]    Further embodiments of the present apparatus will become apparent from the following description, which is given by way of example only, and with reference to the accompanying drawings in which: 
           [0039]      FIG. 1  shows the front and side section views of typical Package Air Conditioning Unit (PAC) of the prior art; 
           [0040]      FIG. 2  shows the front, side and section views of a PAC comprising a holding tank; 
           [0041]      FIG. 3  shows the front, side and section views of a PAC comprising a holding tank and a spill air damper; 
           [0042]      FIG. 4  shows front, side and section views of a PAC comprising heat reclaim dampers; 
           [0043]      FIG. 5  shows another front, side and section views of a PAC comprising heat reclaim dampers; 
           [0044]      FIG. 6  shows another front, side and section views of a PAC; 
       
    
    
     DETAILED DESCRIPTION 
       [0045]    Buildings are being constructed with increasing air tightness as the demand for sustainable buildings rises. Consequently, spill air, increasingly, needs to be provided with a spill air path—usually fan assisted—in order to be relieved from modern buildings, rather than simply escaping as leakage. As the spill air has already been cooled or heated, it often contains significant cooling or heating potential—energy that could be reclaimed. 
         [0046]    Displacement ventilation systems are becoming increasingly popular as a sustainable means of cooling or heating buildings. In these systems, conditioned air is supplied, with largely minimal mixing, to a space within a building at or near floor level to create a low level occupancy microclimate of enhanced indoor air quality of, typically, 23° C. or similar. Heat and contaminants from occupants, computers, lights, etc. are removed from the space at a high level, where they accumulate in concentrated form after rising by natural convection to stratify in layers of air that often exceed 30° C. The air temperature that is removed from the space is, thus, usually substantially higher than a traditional “mixed flow” distribution system&#39;s return air temperature, especially in applications where there is sufficient height for well-developed stratification to occur, such as in cinemas. Such well-developed stratification increases the temperature differential between the air supplied to the space and that removed from the space, thereby allowing the airflow rate to and from the space to be reduced relative to that of a traditional “mixed flow” air distribution system of similar sensible cooling capacity. Consequently, in order to maintain adequate indoor air quality with a displacement system, if the amount of outdoor air to be supplied to the space is fixed then the outdoor air proportion relative to the total airflow rate to the space increases. This also increases the proportion of spill air relative to the total amount of return air. 
         [0047]    Due to displacement supply air generally being supplied at close to ankle level, supply air temperatures typically need to be higher than they are for traditional overhead “mixed flow” supply systems so as to avoid the threat of draughts; typically no lower than 17° C. for displacement systems, rather than the more traditional minimum of about 11° C. for “mixed flow” systems. This relatively high supply air temperature requirement combined with the high proportion of outdoor air typical of displacement systems often requires supply air to be heated (especially in mild winter conditions) before being supplied to spaces that are to be cooled (ie the supply air to the space is cooler than the air being removed from the space). The high temperature of the stratified air being removed from the space often contains significant heating potential that could be reclaimed for such heating of the supply air, but PACs of the prior art do not incorporate inexpensive heat reclaim capabilities to utilise this free heating. 
         [0048]    Moreover, PACs of the prior art generally supply air, even in cooling mode, at a temperature that is too low for use in displacement systems, especially if this is to be done without wastefully reheating the supply air, or with limited reheat. 
         [0049]    Furthermore, the supply air temperature in PACs of the prior art generally fluctuates strongly during refrigeration circuit defrost. Such temperature fluctuations are problematic for displacement systems, however. This is because displacement supply air temperature needs to be more tightly controlled than the supply air temperature of traditional overhead “mixed flow” systems, given that the supply of air directly into the low level occupancy microclimate carries with it a high risk of creating draughts, especially at ankle level. 
         [0050]    Referring now to  FIG. 1 , sections i-a, i-b, ii-a and ii-b show a PAC of the prior art ( 31 ) with at least one supply fan ( 1 ) that draws an air stream from the space ( 7 ), in the form of a supply air stream, from the first arrangement ( 2 ), in the form of a suction chamber ( 2 ), through filter ( 3 ) and the first heat exchanger ( 4 ) to be discharged through supply air outlet ( 5 ) into supply duct ( 6 ). An air stream discharged to the space ( 13 ), in the form of return air, is drawn into the suction chamber ( 2 ) through return air inlet ( 8 ) from return duct ( 9 ). Outdoor air ( 14 ) is drawn into the suction chamber ( 2 ) through outdoor air inlet ( 10 ) from the outdoors ( 11 ) via weather cowl ( 12 ). The flow rates of the return air ( 13 ) and the outdoor air ( 14 ) are regulated by return air damper ( 15 ) and outdoor air damper ( 16 ), respectively, which may be adjusted by electric actuators (not shown). Metal or canvas transition pieces ( 17 ) typically join the supply air ( 6 ) and return air ( 9 ) ducts to spigots surrounding the supply air outlet ( 5 ) and return air inlet ( 8 ), respectively. 
         [0051]    Condensate from the first heat exchanger ( 4 ) collects in a condensate tray ( 18 ) to be drained to the outdoors via condensate pipe ( 19 ). Components ( 1 ,  2 ,  3 ,  4 ,  15 ,  16 , and  18 ) are largely housed in a largely thermally insulated casing ( 20 ). At least one compressor ( 21 ), controlled by controller ( 22 ) in control panel ( 23 ), is connected via refrigeration piping and associated refrigeration components (not shown) to the first heat exchanger ( 4 ) and to the second heat exchanger ( 27 ). At least one fan ( 24 ) is located in a second arrangement ( 2   b ), in the form of another chamber, draws air stream ( 26 ) from the outdoors ( 11 ) through the second heat exchanger ( 27 ) to be discharged to the outdoors via at least one air outlet ( 25 ). Condensate from the second heat exchanger ( 27 ) drains onto roof sheeting ( 28 ), which is supported by purlins ( 29 ) attached to roof beams ( 32 ). Supply duct ( 6 ) and return duct ( 9 ) penetrate roof sheeting ( 28 ) via upstands (not shown) with suitable under-flashing and over-flashing to seal to roof sheeting ( 28 ). The PAC of the prior art ( 31 ) typically stands on a platform ( 30 ) supported by platform legs ( 33 ) connected to roof beams ( 32 ) via seals (not shown) in roof sheeting ( 28 ). 
         [0052]    Referring now to  FIG. 2 , sections i-a, i-b, ii-a and ii-b show a PAC in accordance with the present disclosure ( 31   a ) with at least one supply fan ( 1 ) that draws supply air stream ( 7 ) from the suction chamber ( 2 ) through filter ( 3 ) and the first heat exchanger ( 4 ) to be discharged through supply air outlet ( 5 ) into supply duct ( 6 ). Return air ( 13 ) is drawn from return duct ( 9 ) via return air inlet ( 8 ) and through return air chamber ( 2   a ) into the suction chamber ( 2 ). Outdoor air ( 14 ) is drawn from the outdoors ( 11 ) into the suction chamber ( 2 ) through outdoor air inlet ( 10 ), which may include a weather louvre (not shown). 
         [0053]    The flow rates of the return air ( 13 ) and the outdoor air ( 14 ) are regulated by return air damper ( 15 ) and outdoor air damper ( 16 ), respectively, which may be adjusted by electric actuators (not shown). Gaskets ( 17   a ) join the supply air ( 6 ) and return air ( 9 ) ducts, which may be contained in common housing ( 6   a ) to the flat underside ( 17   b ) of the PAC directly surrounding the supply air outlet ( 5 ) and return air inlet ( 8 ). Condensate from the first heat exchanger ( 4 ) collects in a condensate tray ( 18 ) and may be drained into holding tank ( 34 ) via condensate pipe ( 19 ). Components ( 1 ,  2 ,  3 ,  4 ,  15 ,  16 , and  18 ) are largely housed in a largely thermally insulated casing ( 20 ). At least one compressor ( 21 ), controlled by controller ( 22 ) in control panel ( 23 ), is connected via refrigeration piping and associated refrigeration components (not shown) to the first heat exchanger ( 4 ) and to the second heat exchanger ( 27 ). At least one fan ( 24 ) draws air stream ( 26 ) from the outdoors ( 11 ), via outdoor air damper ( 41 ) through the second heat exchanger ( 27 ) to be discharged to the outdoors via at least one air outlet ( 25 ). 
         [0054]    Condensate from the second heat exchanger ( 27 ) drains into holding tank ( 34 ), as does rain water that largely falls onto the PAC ( 31   a ). Whenever the second heat exchanger ( 27 ) is cooled by air stream ( 26 ), holding tank water ( 38 ) may be pumped by condensate pump ( 37 ), and filtered and sterilised by water treatment module ( 39 ), before being discharged by evaporative fogger ( 40 ), which sprays a water mist that evaporatively cools air stream ( 26 ) directly upstream of second heat exchanger ( 27 ). Mains water may be piped (not shown) to holding tank ( 34 ) to maintain a minimum holding tank water level ( 38 ) via a suitable flow valve and associated mechanism (not shown). Overflow water from holding tank ( 34 ) drains via a suitable overflow pipe (not shown) to a suitable drainage point or onto roof sheeting ( 28 ), which is supported by purlins ( 29 ) attached to roof beams ( 32 ). 
         [0055]    Supply duct ( 6 ) and return duct ( 9 ), which may be contained in common housing ( 6   a ), penetrate roof ( 28 ) via upstand ( 33   a ) with suitable under-flashing (not shown) to seal to roof sheeting ( 28 ). Upstand ( 33   a ) may be structurally supported by roof beams ( 32 ) to carry a substantial portion of the weight of PAC ( 31   a ), such as the weight of thermally insulated casing ( 20 ) and the components that it houses. Support flange ( 35 ) rests on upstand ( 33   a ), which may also serve as overflashing ( 36 ), and on a gasket (not shown) to create a watertight seal onto upstand ( 33   a ). The largely flat underside ( 17   b ) surrounding supply air outlet ( 5 ) and return air inlet ( 8 ) of PAC ( 31   a ) rests on support flange ( 35 ), which largely carries the weight of thermally insulated casing ( 20 ) and its components via gasket ( 17   a ), which in turn forms an airtight seal between PAC ( 31   a ), supply duct ( 6 ) and return duct ( 9 ). Supply duct ( 6 ) and return duct ( 9 ) are suspended from support flange ( 35 ) via common housing ( 6   a ). PAC ( 31   a ) is additionally supported by support legs ( 33   b ) connected to roof beams ( 32 ) via seals (not shown) in roof sheeting ( 28 ). 
         [0056]    Referring now to  FIG. 3 , sections i-a, i-b, ii-a and ii-b show a PAC in accordance with the present disclosure ( 31   a ) with at least one supply fan ( 1 ) that draws supply air stream ( 7 ) from the suction chamber ( 2 ) through filter ( 3 ) and the first heat exchanger ( 4 ) to be discharged through supply air outlet ( 5 ) into supply duct ( 6 ). Return air ( 13 ) is drawn from return air chamber ( 2   a ) into the suction chamber ( 2 ). Another air stream ( 14 ), in the form of outdoor air, is drawn from the outdoors ( 11 ) into the suction chamber ( 2 ) through outdoor air inlet ( 10 ), which may include a cowl or weather louvre (not shown). The flow rates of the return air ( 13 ) and the outdoor air ( 14 ) are regulated by return air damper ( 15 ) and outdoor air damper ( 16 ), respectively, which may be adjusted by electric actuators (not shown). 
         [0057]    Return air and spill air combined ( 26   b ) are drawn from return duct ( 9 ) via return air inlet ( 8 ) into return air chamber ( 2   a ). Gaskets ( 17   a ) join the supply air ( 6 ) and return air ( 9 ) ducts, which may be contained in common housing ( 6   a ) to the flat underside ( 17   b ) of the PAC directly surrounding the supply air outlet ( 5 ) and return air inlet ( 8 ). Condensate from the first heat exchanger ( 4 ) collects in a condensate tray ( 18 ) and may be drained into holding tank ( 34 ) via condensate pipe ( 19 ). Components ( 1 ,  2 ,  3 ,  4 ,  15 ,  16 , and  18 ) are largely housed in a largely thermally insulated casing ( 20 ). At least one compressor ( 21 ), controlled by controller ( 22 ) in control panel ( 23 ), is connected via refrigeration piping and associated refrigeration components (not shown) to the first heat exchanger ( 4 ) and to the second heat exchanger ( 27 ). At least one fan ( 24 ) draws a first portion of the return air stream ( 26   a ), in the form of spill air, from return air chamber ( 2   a ) through a spill air damper ( 42 ), which may be adjusted by at least one electric actuator (not shown), into suction chamber ( 2   b ). Fan ( 24 ) also draws air stream ( 26 ) from the outdoors ( 11 ), via outdoor air damper ( 41 ) through the second heat exchanger ( 27 ) to be discharged to the outdoors. 
         [0058]    Condensate from the second heat exchanger ( 27 ) drains into holding tank ( 34 ), as does rain water that largely falls onto the PAC ( 31   a ). Whenever the second heat exchanger ( 27 ) is cooled by air stream ( 26 ), an assembly to hold a fluid ( 38 ), in the form of a holding tank, water ( 38 ) may be pumped by condensate pump ( 37 ), and filtered, demineralised and sterilised by water treatment module ( 39 ), before being discharged by a discharging assembly ( 40 ), in the form of an evaporative fogger, which sprays a liquid mist that mixes and evaporatively cools air stream ( 26 ) directly upstream of second heat exchanger ( 27 ). Mains water may be piped (not shown) to holding tank ( 34 ) to maintain a minimum holding tank water level ( 38 ) via a suitable flow valve and associated mechanism (not shown). Overflow water from holding tank ( 34 ) drains via a suitable overflow pipe (not shown) onto roof sheeting ( 28 ), which is supported by purlins ( 29 ) attached to roof beams ( 32 ). 
         [0059]    Supply duct ( 6 ) and return duct ( 9 ), which may be contained in common housing ( 6   a ), penetrate roof sheeting ( 28 ) via upstand ( 33   a ) with suitable under-flashing (not shown) to seal to roof sheeting ( 28 ). Upstand ( 33   a ) may be structurally supported by roof beams ( 32 ) to carry a substantial portion of the weight of PAC ( 31   a ), such as the weight of thermally insulated casing ( 20 ) and the components that it houses. Support flange ( 35 ) rests on upstand ( 33   a ), which may also serve as overflashing ( 36 ), and on a gasket (not shown) to create a watertight seal onto upstand ( 33   a ). The largely flat underside ( 17   b ) surrounding supply air outlet ( 5 ) and return air inlet ( 8 ) of PAC ( 31   a ) rests on support flange ( 35 ), which largely carries the weight of thermally insulated casing ( 20 ) and its components via gasket ( 17   a ), which in turn forms an airtight seal between PAC ( 31   a ), supply duct ( 6 ) and return duct ( 9 ). Supply duct ( 6 ) and return duct ( 9 ) are suspended from support flange ( 35 ) via common housing ( 6   a ). PAC ( 31   a ) is additionally supported by support legs ( 33   b ) connected to roof beams ( 32 ) via seals (not shown) in roof sheeting ( 28 ). 
         [0060]    Referring now to  FIG. 4 , sections i-a, i-b, ii-a and ii-b show a PAC in accordance with the invention ( 31   a ) with at least one supply fan ( 1 ) that draws supply air stream ( 7 ) from the suction chamber ( 2 ) through filter ( 3 ) and the first heat exchanger ( 4 ) to be discharged through supply air outlet ( 5 ) into supply duct ( 6 ). Return air ( 13 ) is drawn from return air chamber ( 2   a ) into the suction chamber ( 2 ). Outdoor air ( 14 ) is drawn from the outdoors ( 11 ) into the suction chamber ( 2 ) through outdoor air inlet ( 10 ), which may include a cowl or weather louvre (not shown). The flow rates of the return air ( 13 ) and the outdoor air ( 14 ) are regulated by return air damper ( 15 ) and outdoor air damper ( 16 ), respectively, which may be adjusted by electric actuators (not shown). 
         [0061]    Return air and spill air combined ( 26   b ) are drawn from return duct ( 9 ) via return air inlet ( 8 ) into return air chamber ( 2   a ). Gaskets ( 17   a ) join the supply air ( 6 ) and return air ( 9 ) ducts, which may be contained in common housing ( 6   a ) to the flat underside ( 17   b ) of the PAC directly surrounding the supply air outlet ( 5 ) and return air inlet ( 8 ). Condensate from the first heat exchanger ( 4 ) collects in a condensate tray ( 18 ) and may be drained into holding tank ( 34 ) via condensate pipe ( 19 ). Components ( 1 ,  2 ,  3 ,  4 ,  15 ,  16 , and  18 ) are largely housed in a largely thermally insulated casing ( 20 ). At least one compressor ( 21 ), controlled by controller ( 22 ) in control panel ( 23 ), is connected via refrigeration piping and associated refrigeration components (not shown) to the first heat exchanger ( 4 ) and to the second heat exchanger ( 27 ). At least one fan ( 24 ) draws spill air with heat reclaim potential ( 26   c ) from return air chamber ( 2   a ) through heat reclaim spill air damper ( 43 ), which may be adjusted by at least one electric actuator (not shown), and then through the second heat exchanger ( 27 ). Fan ( 24 ) also draws air stream ( 26 ) from the outdoors ( 11 ), via outdoor air damper ( 41 ) through the second heat exchanger ( 27 ) to be discharged to the outdoors via at least one air outlet ( 25 ). 
         [0062]    The spill air stream ( 26   c ) and the air stream ( 26 ) are combined in the suction chamber ( 2   b ). The combined air stream ( 26   c  and  26 ) is discharged to the outdoors via at least one air outlet ( 25 ). Spill air damper ( 42 ) and heat reclaim dampers ( 43 ) can isolate suction chamber ( 2   b ) from suction chamber ( 2 ), thereby preventing the flow of spill air stream ( 26   c ) into suction chamber ( 2   b ). The second portion of the air stream received from the space, in the form of return air ( 13 ), is combined with outdoor air stream ( 14 ) in suction chamber ( 2 ) to form the supply air stream ( 7 ). 
         [0063]    In a first mode of operation, when the temperature of air stream ( 26   c ) is greater than the temperature of the air stream received from outside the space ( 26 ), and when the streams are combined in suction chamber ( 2   b ), air stream ( 26   c ) heats air stream ( 26 ). In the first mode of operation, the second heat exchanger ( 27 ) extracts heat from air stream ( 26   c ) and the first heat exchanger ( 4 ) emits, or rejects, the extracted heat to increase the temperature of supply air stream ( 7 ). 
         [0064]    In a second mode of operation, when the temperature of air stream ( 26   c ) is less than the temperature of the air stream received from outside the space ( 26 ), and when the streams are combined in suction chamber ( 2   b ), air stream ( 26   c ) cools air stream ( 26 ). In the second mode of operation, the second heat exchanger ( 27 ) extracts coolth, whereby coolth is the opposite of heat, from air stream ( 26   c ) and the first heat exchanger ( 4 ) emits, or rejects, the extracted coolth to decrease the temperature of supply air stream ( 7 ). 
         [0065]    Condensate from the second heat exchanger ( 27 ) drains into holding tank ( 34 ), as does rain water that largely falls onto the PAC ( 31   a ). Whenever the second heat exchanger ( 27 ) is cooled by air stream ( 26 ), holding tank water ( 38 ) may be pumped by condensate pump ( 37 ), and filtered, demineralised and sterilised by water treatment module ( 39 ), before being discharged by evaporative fogger ( 40 ), which sprays a water mist that evaporatively cools air stream ( 26 ) directly upstream of second heat exchanger ( 27 ). Mains water may be piped (not shown) to holding tank ( 34 ) to maintain a minimum holding tank water level ( 38 ) via a suitable flow valve and associated mechanism (not shown). Overflow water from holding tank ( 34 ) drains via a suitable overflow pipe (not shown) onto roof sheeting ( 28 ), which is supported by purlins ( 29 ) attached to roof beams ( 32 ). 
         [0066]    Referring now to  FIG. 5 , sections i-a, i-b, ii-a and ii-b show a PAC in accordance with the invention ( 31   a ) with at least one fire rated outdoor air damper ( 41 ) and at least one fire rated return air damper ( 15 ) and at least one fire rated spill air damper ( 42 ) or fire rated heat reclaim spill air damper ( 43 ), which also serves as a smoke spill air damper ( 42  and/or  43 ). Smoke spill air ( 26   d ) is drawn from return duct ( 9 ), which is fire rated, via return air inlet ( 8 ) into return air chamber ( 2   a ), which is also fire rated. Gaskets ( 17   a ) join the supply air ( 6 ) and return air ( 9 ) ducts, which may be contained in common housing ( 6   a ) to the flat underside ( 17   b ) of the PAC directly surrounding the supply air outlet ( 5 ) and return air inlet ( 8 ). At least one fan ( 24 ), which is fire rated, draws smoke spill air ( 26   d ) through at least one smoke spill air damper ( 42  and/or  43 ) from return air chamber ( 2   a ) to be discharged to the outdoors via at least one air outlet ( 25 ). Each fire rated damper may be adjusted by at least one electric actuator suitable for smoke spill damper operation (not shown). 
         [0067]    Referring now to  FIG. 6 , sections i-a, i-b, ii-a and ii-b show a PAC in accordance with the invention ( 31   a ) and as described by any one of the embodiments shown in  FIGS. 2 to 5 , except that one other fan ( 44 ), in the form of a spill air fan, has been added and outdoor air damper ( 41 ) has been deleted. 
         [0068]    In relation to the description relating to  FIG. 3 , spill air fan ( 44 ) draws spill air ( 26   a ) from return air chamber ( 2   a ) and discharges this air through at least one spill air damper ( 42 ). Thereafter, this air vents passively to the outdoors ( 11 ) via the second heat exchanger ( 27 ) and fan ( 24 ), or it is drawn by at least one fan ( 24 ) via type 2 outlet ( 25 ) to be discharged to the outdoors ( 11 ). 
         [0069]    In relation to the description relating to  FIG. 4 , spill air fan ( 44 ) draws spill air with heat reclaim potential ( 26   c ) from return air chamber ( 2   a ) and discharges this air through at least one heat reclaim spill air damper ( 43 ). Thereafter, this air vents passively to the outdoors ( 11 ), both directly as well as indirectly via the second heat exchanger ( 27 ) and fan ( 24 ), or it is drawn by at least one fan ( 24 ) across at least one the second heat exchanger ( 27 ) to be discharged via type 2 outlet ( 25 ) to be discharged to the outdoors ( 11 ). 
         [0070]    In relation to the description relating to  FIG. 5 , spill air fan ( 44 ) is fire rated and draws smoke spill air from return air chamber ( 2   a ) and discharges this air through at least one fire rated spill air damper ( 42 ) or one fire rated heat reclaim spill air damper ( 43 ). Thereafter, this air vents passively to the outdoors ( 11 ), both directly as well as indirectly via the second heat exchanger ( 27 ) and fan ( 24 ). 
         [0071]    It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. For example, the evaporative mister onto type 2 heat exchanger may be connected directly to the main water supply of the building rather than to a pump system that draws a combination of mains water, collected rain water and collected condensate water from heat exchangers type 1 and 2. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. 
         [0072]    An air delivery system incorporating the PAC described herein provides the potential for substantial energy savings, extended outdoor temperature operation range, and greater suitability for use in displacement ventilation systems, as well as simplified smoke extract, and reduced capital costs. 
         [0073]    HVAC systems that condition supply air via PACs in accordance with the embodiments of the invention incorporate a fan assisted spill air function and therefore do not require separate spill air fan systems. 
         [0074]    HVAC systems that condition supply air via PACs in accordance with the embodiments of the invention benefit from reduced power consumption in applications requiring outdoor air to be delivered to the space being conditioned, as such PACs include the facility to reclaim heat from the spill air venting from the conditioned space. 
         [0075]    HVAC systems that condition supply air via PACs in accordance with the embodiments of the invention benefit from being able to operate in an extended outdoor air temperature range (both colder and warmer than that of PACs of the prior art), especially when introducing large quantities of outdoor air to the space, as heat reclaim from the spill air raises the air temperature onto the outdoor heat exchanger in winter and reduces it in summer, and also reduces defrost requirements in winter. 
         [0076]    The summer operating outdoor temperature range of HVAC systems that condition supply air via PACs in accordance with the embodiments described in this invention may operate in an even further extended summer outdoor temperature range, as the integration of water spray, mist or flash fogging onto the outdoor heat exchanger reduces the temperature of the outdoor exchanger. 
         [0077]    HVAC systems that condition supply air via PACs in accordance with the embodiments of the invention may be designed to operate efficiently and effectively with displacement ventilation systems in winter, given that spill air heat recovery in winter minimises defrost frequency and duration, and hence associated supply air temperature fluctuations—indeed, outdoor coil defrosting is very often eliminated entirely. 
         [0078]    HVAC systems that incorporate PACs in accordance with the embodiments described in this invention may benefit from the elimination of additional smoke system rated fan and ducting requirements for the removal of smoke in the event of a fire, as such PACs include a fan assisted smoke spill function. 
         [0079]    In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e., to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the apparatus.