US3693705A

US3693705A - Multizone air conditioning and ventilating unit

Info

Publication number: US3693705A
Application number: US108495A
Authority: US
Inventors: Robert B Stotz
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-01-21
Filing date: 1971-01-21
Publication date: 1972-09-26
Anticipated expiration: 1989-09-26

Abstract

A system for air conditioning, heating and ventilating a multistory building having a plurality of living spaces on several of the stories. Each story has a separate unit for air conditioning, heating and ventilating all the living spaces on each story.

Description

United States Patent Stotz 51 Sept. 26, 1972 154] MULTIZONE AIR CONDITIONING AND VENTILATING UNIT [72] Inventor: Robert B. Stotz, 1005 Greenridge Drive, Dayton, Ohio 45429 [22] Filed: Jan. 21,1971

[21] Appl. No.: 108,495

[52] US. Cl. ..165/22, 62/259, 165/50,

165/53, 165/59, 165/48 [51] Int. Cl. ..F241' 3/00 [58] Field of Search ..165/22, 50, 49,53, 59,48

[56] References Cited UNITED STATES PATENTS Goeman 165/22 Kreuttner 165/22 2,844,322 7/1958 Kautz 165/22 2,872,858 2/1959 Caldwell ..165/22 2,971,747 2/1961 Young ..165/48 3,089,649 5/1963 Curran 165/50 3,148,727 9/1964 Meckler ..165/49 3,567,115 12/1970 Nelson ..165/22 Prim zry Examiner-William J. Wye Am: ney-Talburtt & Baldwin 5 7 ABSTRACT A system for air conditioning, heating and ventilating a multistory building having a plurality of living spaces on several of the stories. Each story has a separate unit for air conditioning, heating and ventilating all the living spaces on each story.

13 Claims, 4 Drawing Figures MULTIZONE AIR CONDITIONING AND VENTILATING UNIT BACKGROUND OF THE INVENTION This invention relates to air conditioning and ventilating units and more particularly to a unit adapted to air condition and ventilate a plurality of individual units.

Presently, air conditioning, heating and ventilating or large buildings, including office buildings, apartment buildings, and dormitories or student apartment buildings, for example, are handled in many different ways. For example, a plurality of unit ventilators, there being one for each living space, may be provided. Unit ventilators can heat, dehumidify, ventilate, cool and filter the air. Each unit is usually arranged to introduce a fixed quantity of outdoor air for ventilating during warm periods in mild weather. They can also cool the air mechanically by being connected-to a refrigerant line. A unit ventilator normally does not include any means within itself for exhausting the air being supplied and hence, it is difficult to provide maximum cooling by bringing in outside air in many buildings. If a separate exhaust fan is used, a control problem is presented because the amount of exhaustair must be varied as the amount of intake air is varied. Thisv amount of exhaust air is different for different periods, such as during a heating function, a mechanical cooling function or an outside air cooling function. As noted above, the unit ventilator is suitable for only one living space. This does not make such a unit suitable for a building, such as a multistory building having a plurality of separate living quarters on each floor. A unit for each living space would be extremely costly.

Another type of air handling unit is the so-called central station unit. It may be of the multizone type which can control temperature relatively accurately in all parts of a large living space having varying thermal conditions. However, these units do not includeexhaust means within themselves and accordingly performance and control problems exist. Certain roof top multizone units include exhaust means, but such exhaust means are located outdoors. This presents control problems since the quantity of exhaust air is not varied as it should be.

The unit of this invention eliminates many of the problems encountered with the aforenoted equipment.

BRIEF SUMMARY OF THE INVENTION Briefly, this invention comprises a plurality of separate units for air conditioning, heating and ventilating each floor of a multifloor building having a plurality of living spaces on each floor.

One of the primary objects of this invention is to provide a unit adapted to provide proper air control to a plurality of living spaces within a building.

Another object of this invention is to provide a unit of the type described which is adapted to exhaust air in the desired volume.

A further object of this invention is to provide a unit of the type described in which mixing dampers are found in a single integrated assembly.

Another object of this invention is to provide a unit such as described which may be conveniently mounted in the building structure in such a manner as to handle the air requirements for a complete floor.

A further object of this invention is to provide a unit of the kind described which may be combined with a plurality of like units in an efficient and attractive manner for providing air conditioning, heating and ventilating for the entire building.

Other objects and advantages of this invention will be made apparent as the description progresses.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings in which one of various possible embodiments is illustrated,

FIG. 1 is a perspective of a building employing a plurality of air handling units of this invention arranged in a building air handling system;

FIG. 2 is an elevationof an individual unit of this invention, certain parts removed for clarity;

FIG. 3 is a plan view of the unit shown in FIG. 2; and

FIG. 4 is a side elevation of the unit shown in FIG. 2.

Like parts are shown by corresponding reference characters throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, a building, such as a student housing building having a plurality of floors with a plurality of student rooms on most of the floors, is shown at l.

A system of this invention includes a plurality of separate units 3, there being one unit on each floor of the building 1. A water chiller and boiler unit 5 is provided outside the building and is connected by a line 7 to each of the units 3. As described hereinafter, a return line 9 returns chilled water from the units 3 to the unit 5. Similarly, a heating line 11 is provided for supplying hot water to the units 3 and a return line 13 is adapted to return the hot water to the boiler.

A typical structure is shown in FIG. 1 and may'include structural members 15 which extend horizontally across the building and are spaced from one another. The structural members 15 may, as shown, separate the floor 17 of one story of the building from the ceiling 19 of the next adjacent story below.

The floors 17, ceilings l9 and structural members 15 form ducts or passages 21 which extend in the same direction as most of the structural members. Obviously, other types of separating structural members between the floors could be used without departing from the spirit of this inventionPThese passages 21 are interconnected by openings 23 in the structural members. As will be made apparent, the passages 21 provide the means by which air is returned from the individual living spaces. Return air inlets 29 are provided in the ceiling of each living space for admitting air into the passages 21.

Delivery or supply ducts 25 extend from the unit 3 associated with each floor through the openings 23 in the member 15 to outlets 27. As shown, there is one outlet in the ceiling of each living space. Obviously, additional outlets could be provided if desired.

Each unit 3 is mounted on a platform 31. It includes a housing 33 having a filter and damper section 35, a blower section 37, a coil section 37, a multizone damping section 39 and a return air section 41.

Section 35 includes a damper assembly 43 which can be opened to permit the ingress of outside air. The air is drawn through filters 45 by one or more blowers 47 driven by a motor 49. The air is directed from the blowers up through cooling and heating coils 51 and 53, respectively. Coil 51 is connected to lines 7 and 9 and coil 53 is connected to lines 11 and 13.

Multizone damper section 39 includes a heating or hot deck and a cooling or cold deck damper 55 and 57 for each of a plurality of connecting ducts 59, there being one for each delivery duct 25. The dampers 55, in turn, are controlled by motors 61 which in turn are controlled by thermostatic means (not shown) in each living space. The dampers 55 and 57 of each set are located on the same shaft 56 and in planes which are perpendicular to each other. Thus, rotation of shaft 56 causes one damper to close while the other is opening. The connecting ducts 59 are connected to the delivery ducts 25 as shown in FIG. 1.

Return air section 41 includes a blower or blowers 63 adapted to pull air from a plenum section 65 formed between each ceiling and floor combination adjacent each unit 3. The blowers are driven by a motor 66 and have an axis of rotation'located in a plane which is generally perpendicular to the axis of rotation of blowers 47. The axis of the blowers 63 is generally vertically extending and parallel to the wall of the structure 1. The air is pulled into the section 41 by the blowers 63 and is discharged into a transfer section 67 which extends along one side of the housing 33. Transfer section 67 is formed by one side of the hous ing and one internal partition 69. A damper 71 is provided adjacent the lower end of section 67 and may be moved from one position in which substantially all of 3 the return air is discharged through an outlet 73 through an infinite number of proportioning positions wherein the air discharge is split to another position in which substantially all ofthe air is recirculated through .the air filters 45. If the return air is recirculated, it may be mixed with fresh air by opening damper assembly 43. Operation of the apparatus is as follows:

During warm seasons it is desirable to air condition the living space by cooling. This is accomplished by delivering chilled water to the cooling coils 51 'of the unit 3. Blowers 47 force the air, which may, depending upon the location'of dampers 43 and 71, be formed of fresh air or return air or a combination of both, over the coiLSl. The motor 61 for each set of dampers 55, 57 is controlled by thermostatic means (not shown) in theliving quarters associated with that set of dampers to set the dampers in the position necessary to provide the correct blend of air passing over coil 53 and cooled air passing over coil 51. Obviously, during the warm season hot water is not supplied to the heating coil 53 so the air passing thereover may be referred to as bypass air. The air leaving each damper assembly 39 enters into one of the ducts 25 and is delivered therethrough to a particular living space.

Air is exhausted from the living spaces through return air inlets 29 into the passages 21. This air'passes through openings 23 in the members back to the return air plenum 65 and then through blowers 63 into the transfer section 67. Depending upon the setting of damper 71, the air is either discharged to the atmosphere or part or all of it is recirculated through filters 45 and the remainder of the system.

If it is desired to provide cooling by using outside air, commonly referred to as ventilating, the supply of cooling water to coil 51 may be terminated. The dampers 43 are opened and damper 71 is set to discharge air from the transfer section or plenum 67 to the atmosphere. This outside air will be distributed to the living spaces and returned to the units 3 in the same manner as described above.

Heating is attained by supplying hot water to the coils 53 and forcing air over them with blower 47. Rather than discharge the return air it is desirable to recirculate the same and this is accomplished by closing dampers 71 and 43. v

It will be noted that a unit of this invention includes a recirculated air or exhaust fan on the side of the mixed air damper to control the ventilation. Moreover, it will be seen that the location of the intake and exhaust dampers in the same plane minimize the wind effect when a ventilating operation is taking place.

In view of the foregoing, it will be seen that the several objects of this invention are achieved.

Although'only one embodiment of the invention has been disclosed and described, it is apparent that other embodiments and modifications of the invention are possible.

I claim:

1. An air conditioning, heating and ventilating unit for a plurality of separate spaces on one floor of a building comprising means for admitting outside air to said unit, filter means through which air may flow, a transfer section having a discharge outlet to the at mosphere and an outlet to said filter means, heater coil means through which heating fluid passes, cooling coil means through which cooling fluid passes, two blower means, duct means connecting one of the blower means to said separate spaces, said one blower means being adapted adapted to force air over said coils through said duct means toward said separate spaces, the other of said blower means being adapted to force air returned to said unit from said separate spaces toward said transfer section, a plurality. of sets of dampers on the downstream side of said coils and on the upstream side of said duct means, there being one setof dampers for each separate space, each set including a hot deck damper for controlling the passage thereby of air passing over the heating coil and a cold deck damper controlling the passage thereby of air passing over the cooling coil and damper means adjacent said transfer section for selectively directing the air passing through said transfer section into said discharge outlet and said outlet to said filter means.

2. An air conditioning, heating andventilating unit for a plurality of separate living spaces on one floor of a building comprising means for admitting outside air to said unit, filter means through which air may flow, a transfer section having a discharge outlet to the atmosphere and an outlet to said filter means, heater means adapted to heat air passing thereover, cooling coil means through which cooling fluid passes, two blower means, duct means connecting one of said blower means to said separate spaces, said one blower means being adapted to force air over said coils through said duct means toward said separate spaces,

the other said blower means being adaptedtoforce air returned to, saidiunit from said separate spaces toward said transfer section, a plurality of sets of dampers on the downstream sidelof said coils and on the upstream side of said duct means, there beingoneset of dampers for each separate space, each setincluding a hot'deck damper for controlling the pa'ssagethereby of air passing over the heating coil and a" cold deck damper controlling the passage thereby ofair passing over the-cooling coil. Y

' 3. An air conditioning, heating and ventilating unit for a plurality of separate living'spaces on'one floor of a building comprising means for admitting outside air, to

said' unit, filter means through which air may flow, a

transfer section having a discharge outlet to the. atmosphere and an outlet to said filter means, heater means adapted to heat air passing .thereover, cooling coil means through which cooling fluid passes, two

' blower means, one of said blower means being adapted to force air over said coils toward said separate spaces, the other of said blower means being adapted to force air returned to said unit from said separate spacestoward said transfer section, a plurality of sets-of dampers on the downstream side of said coils, there being one for each separate space, each set including a hot deck damper for controlling the passage thereby of air passing over the heating coil and a cold deck damper controlling the passage thereby of air passing over the cooling coil, said'other of said blower means comprising a pair of blowers.

transfer section having a discharge outlet to the atmosphere and an outlet to said filter means, heater means adapted to heat air passing thereover, cooling coil means through which cooling fluid passes, two blower'means, one of said blower means being adapted to force air over said coils toward said separate spaces, the .other of said blower means being adapted to force air returned to said unit from said separate spaces toward said transfer section, a plurality of sets of dampers on the downstream side of saidcoils, there being one of each separate space, each set including a hot deck damper for controlling the passage thereby of air passing over the heating coil and a cold deck damper controlling the passage thereby of air passing over the cooling coil, said one pair of blower means comprising at least one rotatable blower, and said other blower separate units, there being one for each story to be air conditioned, heated and ventilated, each separate unit including means for supplying cooled, heated or ventilating' air, a plurality of duct means in the space between two stories for delivering said air from one of said separate units to a plurality of said separate spaces on one-of said two stories, and return air means adjacent said duct means for permitting air to be exhausted'from said separate spaces on said one of said two stories back to said separate unit, means for'admitting outside air to said unit, filter means through which air 7 may flow, a transfer section having a discharge outlet to the atmosphere and an outlet to said filter means, heater coil means through which heating fluid passes, cooling coil means through which cooling fluid passes, two blower means, one of said blower means being adapted to force air over said coils toward said separate spaces, the other of said blower means being adapted to force an returned to said unit from said separate spaces toward said transfer section, a plurality of sets of dampers on the downstream side of said coils and on the upstream side of said duct means, there being one for each separate space, each set including a hot deck damper for controlling the passage thereby of air passing over the heating coil and a cold deck damper controlling the passage thereby of air passing over the cooling coil.

8. In a multistory building as set forth in claim 7 wherein said return air means comprises a plurality of structural members between said two stories,- the floor of the upper of said two stores and the ceiling of the lower ofsaid two stories, said structural members being formed and arranged to permit air to pass thereby.

9. Ina multistory building as set forth in claim 8 further including damper means adjacent said transfer section for selectively directing the air passing through said transfer section into said discharge outlet and said outlet to said filter means.

10. In a multistory building having a plurality of separate spaces on each story, an air conditioning, heating and ventilating system comprising a plurality of separate units, there being one for each story to be air conditioned, heated and ventilated, each separate. unit including means for supplying cooled, heated or ventilating air, a plurality of duct means in the space between two stories for delivering said air from one of said separate units toa plurality of said separate spaces means comprising at least two rotatable blowers rotata ble on a common axis, the axis of rotation of said one rotatable blower being generally perpendicular to a plane in which the axis .of rotation of said two rotatable blowers is located.

6. An air conditioning, heating and ventilating unit as set forth inclaim 5 including a motor for each set of dampers located on the downstream side of the coils.

1. in a multistory building having a plurality of separate spaces on each story, an air conditioning, heating and ventilating system comprising a plurality of on one ofsaid two stories, and return air means adjacent said duct means for permitting air to be exhausted from said separate spaces on said one of said two stories back to said separate unit, means for admitting outside to said unit, filter means through which air may flow, a transfer section having a discharge outlet to the atmosphere and an outlet to said filter means, heater coil means through which heating fluid passes, cooling coil means through which cooling fluid passes,

two blower means, one of said blower means being adapted to force air over said coils toward said separate spaces, the other of said blower means being adapted to force air returned to said unit from said separate spaces toward said transfersection, a plurality of sets of dam-' controlling the passage thereby of air passing over the cooling coil, said return air means comprising a pluralityof structural members between said two stories, the floor of the upper of said two stories and the ceiling of the lower of said two stories, said structural members being formed and arranged to permit air to pass thereby, and said other of said blower means comprising a pair of blowers.

11. In a multistory building as set forth in claim 10 wherein the axis of rotation of each of the blowers of said pair of blowers is generally parallel to the outside wall of said building. l

12. In a multistory building having a plurality of separate spaces on each story, an air conditioning, heating and ventilating system comprising a plurality of separate units, there being one for each story to be air conditioned, heated and ventilated, each separate unit filter means, heater coil means through which heating fluid passes, cooling coil means through which cooling fluid passes, two blower means, one of said blower means being adapted to force air over said coils toward said separate spaces, the otherof said blower means being adapted to force air returnedvto said unit from said separate spaces toward said transfer section, a plurality of sets of dampers on the downstream side of said coils, there being one for each separate space, each set including a hot deck damper for controlling the passage thereby of air passing over the heating coil and a cold deck damper controlling the passage thereby of air including means for supplying cooled, heated or ventilating air, a plurality of duct means in the space between two stories for delivering said air from one of said separate units to a plurality of said separate spaces on one of said two stories, and return air means adjacent said duct means for permitting air to be exhausted from said separate-spaces on said one of said two stories back to said separate unit, means for admitting outside air to said unit, filter means through which air may flow, atransfer section having a discharge outlet to the atmosphere and an outlet to said passing over the cooling coil, said return air means comprising aplurality of structural members between said two stories, the floor .of the upper of said two stories and the ceiling of the lower of saidtwo stories, said structural members being formedvand arranged to permit air to pass thereby, saidone pair of blower'means comprising at least one rotatable blower, and said other blower means comprising at least two rotatable blowers rotatable on a common axis, the axis of rotation of said one rotatable blower being generally perpendicular to a plane in which the axis of rotation of said two rotatable blowers is located.

13. In a multistory building as set forth in claim 12 including a motor for each set of dampers located on the downstream side of the coils.

F ORM PO-105O (1 0-69) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3.693.705

Dated s rg bgr 25' |9IZ2 Inven ROBERT Bi SIOTZ It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Onsthe cover sheet insert [73] Assignee Signed and sealed this 1st day of Ma 1973.

(SEAL) Attest:

ROBERT GOTTSCHALK Commissioner of Patents EDWARD M.FLETCHER,JR. Attesting Officer USCOMMDC 60376-P69 fl' U.S. GOVERNMENT PRINTING OFFICE: IBQ 0-366-334.

Claims

1. An air conditioning, heating and ventilating unit for a plurality of separate spaces on one floor of a building comprising means for admitting outside air to said unit, filter means through which air may flow, a transfer section having a discharge outlet to the atmosphere and an outlet to said filter means, heater coil means through which heating fluid passes, cooling coil means through which cooling fluid passes, two blower means, duct means connecting one of the blower means to said separate spaces, said one blower means being adapted adapted to force air over said coils through said duct means toward said separate spaces, the other of said blower means being adapted to force air returned to said unit from said separate spaces toward said transfer section, a plurality of sets of dampers on the downstream side of said coils and on the upstream side of said duct means, there being one set of dampers for each separate space, each set including a hot deck damper for controlling the passage thereby of air passing over the heating coil and a cold deck damper controlling the passage thereby of air passing over the cooling coil and damper means adjacent said transfer section for selectively directing the air passing through said transfer section into said discharge outlet and said outlet to said filter means.

2. An air conditioning, heating and ventilating unit for a plurality of separate living spaces on one floor of a building comprising means for admitting outside air to said unit, filter means through which air may flow, a transfer section having a discharge outlet to the atmosphere and an outlet to said filter means, heater means adapted to heat air passing thereover, cooling coil means through which cooling fluid passes, two blower means, duct means connecting one of said blower means to said separate spaces, said one blower means being adapted to force air over said coils through said duct means toward said separate spaces, the other of said blower means being adapted to force air returned to said unit from said separate spaces toward said transfer section, a plurality of sets of dampers on the downstream side of said coils and on the upstream side of said duct means, there being one set of dampers for each separate space, each set including a hot deck damper for controlling the passage thereby of air passing over the heating coil and a cold deck damper controlling the passage thereby of air passing over the cooling coil.

3. An air conditioning, heating and ventilating unit for a plurality of separate living spaces on one floor of a building comprising means for admitting outside air to said unit, filter means through which air may flow, a transfer section having a discharge outlet to the atmosphere and an outlet to said filter means, heater means adapted to heat air passing thereover, cooling coil means through which cooling fluid passes, two blower means, one of said blower means being adapted to force air over said coils toward said separate spaces, the other of said blower means being adapted to force air returned to said unit from said separate spaces toward said transfer section, a plurality of sets of dampers on the downstream side of said coils, there being one for each separate space, each set including a hot deck damper for controlling the passage thereby of air passing over the heating coil and a cold deck damper controlling the passage thereby of air passing over the cooling coil, said other of said blower means comprising a pair of blowers.

4. An air conditioning, heating and ventilating unit as set forth in claim 3 wherein the axis of rotation of each of the blowers of said pair of blowers is generally parallel to the outside wall of said building.

5. An air conditioning, heating and ventilating unit for a plurality of separate living spaces on one floor of a building comprising means for admitting outside air to said unit, filter means through which air may flow, a transfer section having a discharge outlet to the atmosphere and an outlet to said filter means, heater means adapted to heat air passing thereOver, cooling coil means through which cooling fluid passes, two blower means, one of said blower means being adapted to force air over said coils toward said separate spaces, the other of said blower means being adapted to force air returned to said unit from said separate spaces toward said transfer section, a plurality of sets of dampers on the downstream side of said coils, there being one of each separate space, each set including a hot deck damper for controlling the passage thereby of air passing over the heating coil and a cold deck damper controlling the passage thereby of air passing over the cooling coil, said one pair of blower means comprising at least one rotatable blower, and said other blower means comprising at least two rotatable blowers rotatable on a common axis, the axis of rotation of said one rotatable blower being generally perpendicular to a plane in which the axis of rotation of said two rotatable blowers is located.

6. An air conditioning, heating and ventilating unit as set forth in claim 5 including a motor for each set of dampers located on the downstream side of the coils.

8. In a multistory building as set forth in claim 7 wherein said return air means comprises a plurality of structural members between said two stories, the floor of the upper of said two stores and the ceiling of the lower of said two stories, said structural members being formed and arranged to permit air to pass thereby.

9. In a multistory building as set forth in claim 8 further including damper means adjacent said transfer section for selectively directing the air passing through said transfer section into said discharge outlet and said outlet to said filter means.

10. In a multistory building having a plurality of separate spaces on each story, an air conditioning, heating and ventilating system comprising a plurality of separate units, there being one for each story to be air conditioned, heated and ventilated, each separate unit including means for supplying cooled, heated or ventilating air, a plurality of duct means in the space between two stories for delivering said air from one of said separate units to a plurality of said separate spaces on one of said two stories, and return air means adjacent said duct means for permitting air to be exhausted from said separate spaces on said one of said two stories back to said separate unit, means for admitting outside to said unit, filter means through which aIr may flow, a transfer section having a discharge outlet to the atmosphere and an outlet to said filter means, heater coil means through which heating fluid passes, cooling coil means through which cooling fluid passes, two blower means, one of said blower means being adapted to force air over said coils toward said separate spaces, the other of said blower means being adapted to force air returned to said unit from said separate spaces toward said transfer section, a plurality of sets of dampers on the downstream side of said coils, there being one for each separate space, each set including a hot deck damper for controlling the passage thereby of air passing over the heating coil and a cold deck damper controlling the passage thereby of air passing over the cooling coil, said return air means comprising a plurality of structural members between said two stories, the floor of the upper of said two stories and the ceiling of the lower of said two stories, said structural members being formed and arranged to permit air to pass thereby, and said other of said blower means comprising a pair of blowers.

11. In a multistory building as set forth in claim 10 wherein the axis of rotation of each of the blowers of said pair of blowers is generally parallel to the outside wall of said building.

12. In a multistory building having a plurality of separate spaces on each story, an air conditioning, heating and ventilating system comprising a plurality of separate units, there being one for each story to be air conditioned, heated and ventilated, each separate unit including means for supplying cooled, heated or ventilating air, a plurality of duct means in the space between two stories for delivering said air from one of said separate units to a plurality of said separate spaces on one of said two stories, and return air means adjacent said duct means for permitting air to be exhausted from said separate spaces on said one of said two stories back to said separate unit, means for admitting outside air to said unit, filter means through which air may flow, a transfer section having a discharge outlet to the atmosphere and an outlet to said filter means, heater coil means through which heating fluid passes, cooling coil means through which cooling fluid passes, two blower means, one of said blower means being adapted to force air over said coils toward said separate spaces, the other of said blower means being adapted to force air returned to said unit from said separate spaces toward said transfer section, a plurality of sets of dampers on the downstream side of said coils, there being one for each separate space, each set including a hot deck damper for controlling the passage thereby of air passing over the heating coil and a cold deck damper controlling the passage thereby of air passing over the cooling coil, said return air means comprising a plurality of structural members between said two stories, the floor of the upper of said two stories and the ceiling of the lower of said two stories, said structural members being formed and arranged to permit air to pass thereby, said one pair of blower means comprising at least one rotatable blower, and said other blower means comprising at least two rotatable blowers rotatable on a common axis, the axis of rotation of said one rotatable blower being generally perpendicular to a plane in which the axis of rotation of said two rotatable blowers is located.