US2969652A - Heating, ventilating and cooling unit - Google Patents

Description

Jan. 31, 1961 w. B. BLANCHARD HEATING, VENTILATING AND COOLING UNIT 2 Sheets-Sheet 2 Filed June 5, 1959 ROOM THE/P14403727 CONTROL United States Patent HEATING, VENTILATING AND COOLING UNIT Winborne Boyce Blanchard, Architects Bldg., 3415 Virginia Ave., Newport News, Va.

Filed June 5, 1959, Ser. No. 818,404

6 Claims. (Cl. 62-157) The present invention relates in general to combination room heating, cooling and ventilating units, and more particularly to reverse cycle refrigeration heating units or heat pumps and air-flow ducting and control means in association therewith adapted to selectively effect heating, cooling or ventilating of the air of a room or other enclosure.

An object of the present invention is the provision of improved apparatus for heating, cooling or ventilating the air of a room or other enclosure, wherein requirements for circulation of large quantities of fresh air in the room may be met in a novel and economical manner.

Another object of the present invention is the provision of improved heating and ventilating apparatus of the type employing a reversible cycle heat pump unit and air-flow control means associated therewith for use in quarters such as school rooms and the like, wherein vent 'air which is normally exhausted from the room at room temperature is exhausted through the evaporator section of the heat pump to yield heat to the refrigerant and increase the efliciency of operation of the heat pump unit.

Another object of the present invention is the provision of a heating, cooling and ventilating unit especially adaptable for school class rooms and the like where requirements of law as to a continuous supply of fresh air and continuous exhaust of stale air are applicable, which unit includes means for regaining in a novel manner some of the heat which is normally lost through exhaust of stale air to obtain operating economy.

Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings illustrating one preferred embodiment of the invention.

In the drawings:

Figure 1 is a schematic diagram of a heating, cooling and ventilating unit embodying the present invention.

Figure 2 is a horizontal section view of an exemplary physical installation of a heating, cooling and ventilating unit embodying the present invention, taken along line 2--2 of Fig. 3.

Figure 3 is a vertical transverse section view of the unit, taken along the line 3-3 of Figure 2.

Figure 4 is a horizontal section view taken along the line 44 of Figure 3.

The provision of proper heating, cooling and ventilating facilities for school classrooms and like quarters presents special problems. Since the schools are rarely in operation on 'a year-around basis, a unit designed to provide suitable heating, cooling and ventilation should be primarily intended for winter and spring-fall ventilation. In the case of school classrooms, the classrooms are usually required by law to have a continuous supply of fresh air and continuous exhaust of return or vent air. For example, the law of one State requires circulation of approximately 13 cubic feet of fresh air per minute per person. With conventional heating facilities, this would mean exhausting that quantity of warm Patented Jan. 31,

air at approximately 72 F. to the outdoors every minute of the school day. It is obvious that this would represent a tremendous waste of heat units or B.t.u.s.

It is also eminently desirable that each individual classroom have its separate, self-contained complete heating plant, which is entirely independent of the rest of the school building, and that the individual heating unit for each classroom be subject to temperature control for its associated classroom.

It is possible that due to variation in exposure to sunlight over the area of the school building, some of the classrooms on the sunny side of the building may require air cooling rather than heating while the units on the shaded side of the building should supply heat. It would thus be highly desirable to employ a unit for each classroom which is capable of selectively providing heating orcooling of the air, or ventilation without any heating or cooling.

Referring to the drawings, wherein like reference characters designate corresponding parts throughout the several figures, and particularly to Figure 1 illustrating diagrammatically -a system which provides these desirable characteristics, the heating, cooling and ventilating apparatus of the present invention comprises an enclosure or housing 10 adapted to be disposed in and project inwardly and outwardly from the outside building wall 11 of a school classroom or the like. The housing 10 is adapted to contain a reverse cycle refrigeration heatingcooling unit of the type generally known as a heat pump, indicated by the reference character 12. The heat pump 12 is preferably of the conventional, commercially available single package type arranged for reverse cycle refrigeration so as to have a heating cycle and a cooling cycle. Such a heat pump unit has the usual compressor,

a condenser coil and an evaporator coil, together withblowers or suction fans associated with both the condenser and evaporator coils to draw air over these coils, the labels applied to the condenser and the evaporator being in accordance with the functioning of these coils during the heating cycle. An internal bafiie is provided Within the heat pump unit so as to isolate the condenser section and the evaporator section from each other to prevent air flow therebetween. A four-way valve or other suitable refrigeration flow reversing means is provided to connect the compressor discharge or high side to the condenser coil, in the heating cycle of the heat pump, and to connect the compressor dis-charge with the evaporator coil in the cooling cycle of the heat pump.

During the heating cycle, the hot gaseous refrigerant is delivered from the compressor discharge to the condenser where it condenses and rejects its latent heat and super heat to the air drawn over the condenser coil, the heated air being delivered to the room or other enclosure served by the heat pump by the associated blower. The condensed refrigerant is delivered in metered quantities through an expansion device at the inlet to the evaporator coil, where the liquid refrigerant vaporizes at reduced pressure and withdraws heat from the air surrounding the evaporator, the vaporized refrigerant then being drawn to the suction line or low side of the compressor. The withdrawal of heat from the air surrounding the evaporator by the refrigerant as it vaporizes elfects cooling of the air blown over the evaporator coil. v

During the cooling cycle of the heat pump, the hot gaseous refrigerant discharged from the compressor is delivered to the evaporator, rather than the condenser, where it condenses and heats the air surrounding the evaporator through'the latent heat and'super heat yielded by the refrigerant during condensation, and the liquid refrigerant is rnetered through an expansion device to air. blown over the condenser coils anddischargedinto.v the classroom or associated area served by the heat pump. Efiicient operation of the heat pump 12 for classroom heating and cooling. purposes is. achieved: hy'providing; an;

the open outer end of the. chamber 13,. with return and.

exhaust ainindicatedby the arrows 19, drawn in through: the return. vent 16 and admitting this cormingled fresh and return air to the conventional. suction inlet of the condenser section of the heat pump 12, asindicated by the arrows 20. The chamber 14 is also open to. outside. air through the outer end 15 of the housing and.re-. ceives return air at its inner end through return and exhaust vent 21 communicating with the classroom. The chamber 14 is also provided with distributing valve or damper means 22 at its inner end for distributing a portion of the return air, indicated by the arrows 23, drawn in through the vent 21 to the suction inlet of the condenser section of the heat. pump 12, as indicated by the arrows 24, and for distributing the rest of the return air toward the rear of the chamber 14, as indicated by the arrows 25. The chamber 14 is also provided with a backdraft valve or damper means 26 near the outer end oflthe chamber 14, which permits passage of the return air distributed outwardly of the heat pump by the damper 22 to the suction inlet of the evaporator section of the heat pump 12, and prevents passage of fresh air in the opposite direction through the chamber 14.

By this arrangement, it will be seen that some of the return air will be recirculated by the dampers 17 and 22 by directing a portion of the return air to the suction inlet of the condenser section of the heat pump 12, and that fresh air admitted through the chamber 13 will be continuously co-mingled with this recirculated air by means of adjustment of the damper 17. The remainder of the return air will be diverted by the damper 22 to co-mingle with some fresh air through the action of the damper 26 and will be drawn into suction inlet of the evaporator section of the heat pump 12;, where it will be blown through the evaporator coils and exhausted to outside air through a suitable air exhaust duct 27.

This permits a highly efficient operation of the heat pump rendering it suitable for economical operation for classroom use by directing the return air which is required I to be exhausted to meet the requirements of law regarding fresh air supply in heat exchange relation with the evaporator coil, whereby the heated air will yield greater quantities of heat to the vaporizing refrigerant in the evaporator coil and cause the heat pump to operate in a condition whereby greater heat will be obtained per unit of energy expended. The system also provides an extremely versatile unit which may be subject to time clock control and thermostatic control to effect school classroom heating, cooling and ventilating in a highly novel and economical manner.

Referring now to Figures 2 and 3 showing a typical installation of a heating, cooling and ventilating unit of the type diagrammatically shown in Figure 1, the heating, cooling and ventilating unit is generally designated by the reference character 34 and is arranged in the exterior. buildingwall 31 of the classroom 32 so as to have a portion communicating with the classroom32 and a portion communicating with the outdoors. The unit. may be provided in an enclosure, indicated generally by the reference character 33 forming a tunnel or elongated opening. of rectangular cross-section extending through .the build ing wall 31 and framed by side walls 34, 35, a top wall estee 3.6.and..a.fioor 37 formed of masonry, concrete or other suitable building materials. The enclosure 33 in the form illustrated in Figures 2, 3 and 4 includes an outwardly projecting rectangular frame formed in part of masonry and in part of concrete, indicated at 38, which projects outwardly from the plane of the outer surface of the building wall 31. The enclosure side walls 34, 35 projectinwardly of the classroom from the inner surface of the building wall 31 a selected distance, either in alignment the inner surface of the. rectangular masonry frame 38 or offset therefrom,- sheet metal baflies 39a, 39b, being provided for this purpose.

A heat pump 12, which is herein illustrated as a rectangular or box-shaped unit, is centrally located within the enclosure 33 and may rest upon the concrete floor 37 of the enclosure 33. The dimension of the heat pump 12 and the spacing between the enclosure side walls 34, 35 is such that chambers 13, 14 forming supply and exhaust air chambers, respectively, are provided along the Qpposite sides of the heat pump 12 extending from the inner to the outer ends of the enclosure 33, these chambers 13, 14. being, in one preferred embodiment, approximately one foot-in width and of approximately the height of the heat pump unit. The outer end of the enclosure 33' is provided with arectangular opening 49 opening to outside air, which is protected by a suitable steel grating or the like 41. extending entirely across the opening 4e and spaced rearwardly from the outer end 42 of the heat pump 1-2: a selected distance, which isapproximately one-foot in one prefered embodiment.

'Fhesignificant components of the heat pump 12 necessaryto the understanding of the systemare illustrated in broken lines in Figure 3 in diagrammatic form and comprise a compressor 43, a condenser or heat coil 44, a condenser air inlet 45 opening through the lower portion of the inner end 46 of the heat pump 12 to receive air from the room, a condenser blower 47 and a condenser outlet 48 through which air drawn through the condenser inlet 45 and across the condenser coils 44 is discharged from the heat pump casing. An evaporator coil 49' is disposed adjacent the outer end 42 of the heat pump and communicates with the evaporator air inlet 50 in the outer end wall 42 of the heat pump 12, and an evaporator blower 51 draws air'through the evaporator inlet 50 and across the evaporator coils 49 and dis charges it through the evaporator outlet 52. A suitable outlet discharge duct 53 fitted over the usual flange framing the evaporator outlet 52 extends outwardly to the grating 41 to assist discharge of the air from the blower 51 externally of the enclosure 33. Suitable bafile means 54 isolate the air in the compressor section of the heat pump 12 from that in the evaporator section of the heatpump.

Suitable cabinet Work or the like is provided along .the inner surface of the building wall31 andforwardly of the enclosure 33 to form duct walls, generally indicated by the reference character 55, and a horizontal partition 56 extends from the inner end 46 of the heatpurnp 12 to the duct Walls55 to form a lower air return duct 57 disposed infront of and extending laterally beyond the sides of the heat pump 12 and an upper air discharge. duct 58 lying primarily inwardly of the heat pump 12. The air return duct 57 has a centralsection 57a in direct communication with the condenser inlet 45 and laterally flanking section 57b and 570. A plurality of return vent openings 59' are in the portions of the Walls 45 bounding the return duct section 5712 and 570 to admit return and exhaust air from the classroom 32 into the return duct section 57b and 57c. The upper air discharge duct 58 communicates with. the condenser outlet 48 and has a plurality of discharge vent openings 60 which may, for example, be in the top wall 61 of the discharge duct 58 forreturn of the-"air discharged from the heat pump con? denser section to the classroom.

Suitable return air dampers 62- and 63 extend across the lower air return duct 57, to regulate the flow of return air from the return vent openings 59 and return duct sections 57b and 570 to the portion 57a of the air return duct 57. The dampers 62 are disposed between the inner end of the chamber 13 and the return duct section 57b and the dampers 63 are disposed between the return duct sections 570 and 57a and located toward the heat pump from the inner end of chamber 14. Additional dampers 64 and 65 extend across the inner ends of the chambers 13 and 14 located to each side of the heat pump 12 to regulate the flow of air between the air return duct 57 and the chambers 13, 14. It will be noted from Figure 2 that the dampers 62 and 64 are linked together as a set, and the dampers 63 and 65 are linked together as a set, so that as the dampers 62 and 63 progressively close, the dampers 64 and 65 correspondingly and synchronously progressively open. The linked set of dampers 62, 64 and the linked set of dampers 63, 65 are also linked together through a linkage 66 and are controlled by a suitable control motor, such as electric modulating motor 67 of the type presently available on the market.

Additionally, a back draft damper 68 extends across the chamber 14 at a point intermediate the inner and outer ends thereof and is of a well-known type which responds to pressure differentials between its inner and outer sides to open when the pressure on its inner side is higher and permit flow toward the outer end of the chamber 14, but which closes in response to higher pressure at its outer side to prevent flow of air toward the inner end of the chamber 14. A suitable vertical bafiile 69 extends between the outer end of the heat pump 12 and the grating 41 at the side of the outlet discharge duct 53 adjacent the chamber 13 to minimize co-mingling of return air discharged outwardly through the chamber 14 with fresh air drawn inwardly through the chamber 13.

In a typical school classroom installation of the unit 30, it is desirable to have the unit automatically controlled by suitable time clock circuitry 70 of conventional construction and also by a room thermostat 71 controlling the motor 67 through suitable means such as control relays 72, all diagrammatically indicated in Figure 4. The time clock circuitry may be arranged to energize the motor for the compressor 43 to initiate the heating cycle of the heat pump 12 at a selected time of the day, for example at 7:30 a.m. The electric modulating motor 67 controlling the adjustment of the dampers 62, 63, 64 and 65 is controlled by suitable, conventional thermostat circuitry so that the motor 67 is actuated in response to temperature in the classroom. In the preferred example, the electric circuit to the modulating motor 67 may include a set of clock controlled relays establishing a condition of the motor 67 to position the dampers to return all of the return air admitted through the vents 59 to the return duct section 57a and the condenser air inlet 45 to provide 100% room air recirculation for a Warm-up period from the time the compressor motor is first energized until school opening time. The clock controlled relays will be conditioned, in this example, to energize the motor 67 at the time school starts, for example 8:45 a.m., to shift the dampers to a selected position to admit fresh air from the supply chamber 13 through dampers 64 to the return duct section 57a and to exhaust some return air through the damper 65 to the exhaust chamber 14, and thereby provide for circulation of the quantities of fresh air required by law. A small potentiometer may be provided in the control circuit for the modulating motor 67 which is adjusted to establish this position of the dampers. The dampers will stay in this position until the room temperature exceeds a predetermined setting of the thermostat. The thermostat is designed to override the above-mentioned potentiometer on a rising temperature and position the dampers 62, 63, 64 and 65 to further open or close the same to maintain the maximum temperature of the room at the setting of 6 the thermostat. The thermostat may, for example, be positioned in the return air duct 57.

At school closing time, the clock control circuitry will de-energize the whole heating unit.

An additional thermostat may be provided in the room which merely stops and starts the compressor in the heat pump to keep the room warm. Additionally, a low limit thermostat may be provided in the clock circuit to prevent the building from becoming too cold when the unit is turned off after school hours. This low limit thermostat may be set to maintain a minimum temperature of 55 throughout the night and over the weekends, and is arranged to override the clock and start the unit 30 to maintain the minimum of 55. The blowers 47 and 51 should be placed under the control of the clock circuit so that they will run continuously during the school hours.

Suitable control circuitry will also be provided to maintain the compressor motor de-energized while the blowers 47 and 51 are running, and to maintain the dampers in position to admit maximum fresh air to the classroom to provide suitable ventilation without heating or cooling, and additional controls of conventional nature may be provided to reverse the cycle of the heat pump so as to operate as an air-cooling system. Assuming a typical setting of the unit 30 with the dampers 62, 63, 64 and 65 in partially open position as illustrated in Figure 2, return air from the classroom 32 will be drawn into the right-hand return air duct section 57b through the associated return vent opening 59 and through the damper 62 into the return air duct 57a, where it is co-mingled with fresh air drawn in through the supply chamber 13 and dampers 64. Additional return air from the classroom 32 drawn into the left-hand return air duct section 570 through the associated vent openings 59 will be distributed by the dampers 63 and 65 so that part of this return air is admitted to the return air duct section 57a and part is discharged through the exhaust chamber 14 and back draft damper 68. The comingled return and fresh air in the return air duct 57a is drawn by the blower 47 through the compressor air inlet 45 and compressor coil 44, where it is heated by the rejection of latent heat and super heat upon condensation of refrigerant, and this heated air is discharged through the compressor outlet 48, air discharge duct 58 and discharge vet openings 60 to the classroom 32. The portion of return air distributed from the air return duct section 57c through dampers 65 to the exhaust chamber 14 co-mingles in the outer region of the enclosure 33 with fresh air admitted through the grating 41 and this comingled air is drawn by the blower 51 through the evaporator inlet 50 and evaporator coils 49, where heat is withdrawn from this air by evaporation of the refrigerant, and this air is then discharged through the evaporator outlet 52 and outlet discharge duct 53. In practice, it is found that the temperature of the return air exhausted through the evaporator coils 49 is cooled about 20, the heat yielded by this air to the refrigerant in the heat pump serving to supply part of the heat energy required to heat the air discharged through the condenser outlet 48 and thereby achieve greater economy of operation. It is, of course, contemplated that the heat pump unit 12 may include supplemental electrical resistance heating coils, where required, to give the total heating capacity necessary for the particular installation. The particular adjustment of the dampers to provide appropriate regulation of the temperature within the room and maintain the necessary fresh air flow requirements established by law will be made by the manufacturer or installation engineer. As a general guide, the settings of the dampers in normal installations are such that approximately of the room air is recirculated by comingling it with fresh air and drawing it into the heat pump condenser inlet, and about 20% of the room air is exhausted through the back draft temperature and the evaporator coils.

. aseaese While but one specific embodiment of. the present in. ventionis. specifically shown and described-it is apparent that various modifications. may bemade. therein vwithin the spirit and scope of the. invention, and, it is desired, therefore, that only such limitations be placed on the invention as are imposed by the prior art and set forth in the. appended claims.

I claim:

1. Heating and ventilating apparatus for a room or like enclosure comprising a heat pump including a condenser section and an evaporator section each having a coil and a blower, means for recirculating selected adjustable proportionsv of return air from theroom through said condenser. section to heat the air by condensation of refrigerant in the condenser coil including means for entraining therewith selected, adjustable proportions of fresh. outside air, and means for exhausting selected adjustable proportions of return room air through said evaporator section while recirculating. selected proportions of return room air through said condenser section to cause part of the heat of the return room air to. be yielded to the refrigerant in the evaporator.

2. Heating and Ventilating apparatus fora room or like enclosure comprising a reverse cycle refrigeration heat pump having a casing and including a condenser section and an evaporator section each having a coil, a blower, and inlet and outlet openings in. said casing, means. com.- municating the condenser inlet opening through first and second adjustable dampers to return room air and through a third adjustable damper. to outside air, means. communicating the evaporator inlet opening to outside air. and through a fourth adjustable damper to return room air, means communicating the condenser and evaporator outlet opening to the room to be served and to. outside air, respectively, first coupling means linking. said first and third dampers together in. a manner whereby the first damper progressively closes as the third damper progressively opens to vary comingling of selected proportions of fresh outside air and return room air communicated to the condenser inlet opening, second coupling means linking said second and fourth dampers together in a manner whereby the second damper progressively closes as the fourth damper progressively opens, to distribute selected proportions of return room air to said condenser inlet opening and to said evaporator inlet opening, and means responsive to room air temperature at a selected point in the area to be served by the heat pump to automatically adjust the dampers to establish a selected room temperature.

3. Heating and ventilating apparatus adapted to be located in the exterior building wall of a room or like enclosure comprising a heat pump unit located in the exterior building wall having a condenser section including condenser coils and blower means communicating. with the interior of the room for drawing air from the room over the condenser coil to be heated thereby upon condensation of refrigerant in the condenser coils and discharging the heated air into the room and an evaporator section including evaporator coils and blower means for drawing outside air from externally of the building wall over the evaporator coils and discharging the air externally of the. building, means for: cQ-mingling with. re.- turn air drawn from the room to be directed over the condenser coils selected quantities of fresh air drawn directly from outside of the building, means for distributing selected portions of the-return air from the room to the condenser section and to the evaporator section-of the heat pump to" cause a selected portion of the return air to be exhausted to outside air through the evaporator section of the heat pump to cause a portion of the heat in the return air to be given up to refrigerant in the evaporator coils, and means responsive to room air temperature to automatically adjust said means for comingling fresh air with return air and said means for distributing selected portionsof the return air to establish a selected room tem perature 4. Heating and ventilating apparatus-adapted to be located in the exterior building wall-of. a room or like enclosure comprising a heat pump unit located in the exterior building. wall having a condenser section including condenser coils and blower means communicating with theinterior of the room for drawing air from the room over the condenser coil. to be heated thereby upon condensation of refrigerant in the condenser coils and discharging the heated air into the room and an evaporator section including evaporator coils and blower means for drawing outside air from externally of the building wall overthe evaporator coils and discharging the air externally of.the building, means for cominglingw with return air drawn from the room to he directedfover the condenser coils selected quantities of fresh air drawn directly from outside. of the building, means for distributing selected portions of the return. air from the room to the condenser section and tothe evaporator section ofthe heat pump to cause a selected portion of the return air to be exhausted to outside air through the evaporator section of the heat pump. to cause a portion of the heat in the return air to be given up to refrigerant in the evaporator coils, thermostat means. for sensing the temperature of room air at a selected point, and control means for adjusting the relative proportions of fresh air entrained inthe return air delivered to the condenser section of the heat pump and the return air exhausted through the'evaporator section of the heat pump in response to the temperature sensed bysaid thermostat means.

5. Heating and ventilating apparatus adapted to be located in the exterior building wall of a room or like enclosure comprising an elongated tunnel enclosure extend ing through the building wall having an exterior end opening to outside air and an interior end located inwardly of the buildingwall, and side walls, a reverse cycle refrigeration heat pump unit disposed in said tunnel enclosure including a casing having sides spaced inwardly from side walls of the tunnel enclosure to define a supply chamber to one side of the heat pump casing and an exhaust chamber to the other side of the heat pump casing opening. adjacent the exterior of the tunnel enclosure to outside air, said heat pump unit including a condenser section and an evaporator section each having a coil, a blower, and inlet and outlet openings .in said casing, the outlet opening of said evaporator section communicating with outside air and the inlet opening of said evaporator section communicating. with outside air and with said exhaust chamber, an air returnduct disposed inwardly of saidheat pump casinghaving return vents for admitting return air from the room to the air return duct, the inlet opening of said: condenser section communicating with said air return duct, discharge duct means communicating with the outlet opening of said condenser section for discharging air from the condenser section outlet opening to the room, first damper means for admitting varying proportions of fresh air from said air supply chamber to said air return duct to be. entrained with return air from the room and admitted to the inlet opening of said condenser section to be heated by' passage over the condenser coil, second damper means for admitting varying portions of return air from said' air. return duct to said exhaust chamher for divertingvarying proportions of return air'to the evaporator section of the heat pump to yield partof its heat to the evaporator refrigerant andbe discharged externally of the enclosure, thermostat'means forsensing air temperature ata selected point in the space to be served by the heating apparatus, and control means responsive to said thermostat means for regulating the positionsof said first and second dam-per means to maintain a selected temperature in the room:

6; Heating and ventilating apparatus adapted to be located in the exterior building. wall of a room or like mlpsurecomprising an elongated tunnel enclosure extending through the building wall having an exterior end opening to outside air and an interior end located inwardly of the building wall, and side walls, a reverse cycle refrigeration heat pump unit disposed in said tunnel enclosure including a casing having sides spaced inwardly from side walls of the tunnel enclosure to define a supply chamber to one side of the heat pump casing and an exhaust chamber to the other side of the heat pump casing opening adjacent the exterior of the tunnel enclosure to outside air, said heat pump unit including a condenser section and an evaporator section each having a coil, a blower, and inlet and outlet openings in said casing, the outlet opening of said evaporator section communicating with outside air and the inlet opening of said evaporator section communicating with outside air and with said exhaust chamber, an air return duct disposed inwardly of said heat pump casing having return vents for admitting return air from the room to the air return duct, the inlet opening of said condenser section communicating with said air return duct, discharge duct means communicating with the outlet opening of said condenser section for discharging air from the condenser section outlet opening to the room, first damper means for admitting varying proportions of fresh air from said air supply chamber to said air return duct to be entrained with return air from the room and admitted to the inlet opening of said condenser section to be heated by passage over the condenser coil, second damper means for admitting varying portions of return air from said air return duct to said exhaust chamber for diverting varying proportions of return air to the evaporator section of the heat pump to yield part of its heat to the evaporator refrigerant and be discharged externally of the enclosure, means for preventing admission of fresh air from said exhaust chamber to said air return duct, said first damper means being operable from a position admitting only return air and no fresh air therethrough to the compressor inlet opening to a position admitting only fresh air and no return air therethrough to the compressor inlet, and said second damper means being operable from a position directing all the return air directed therethrough to the inlet opening of said condenser section to a position directing all of the return air directed therethrough into said exhaust chamber, thermostat means for sensing air temperature at a selected point in the space to be served by the heating apparatus, and control means responsive to said thermostat means for regulating the positions of said first and second damper means to maintain a selected temperature in the room.

References Cited in the file of this patent UNITED STATES PATENTS 2,257,478 Newton Sept. 30, 1941 2,293,482 Ambrose Aug. 18, 1942 2,342,566 Wolfert Feb. 22, 1944 2,718,119 Prince Sept. 20, 1955 2,739,794 Graham Mar. 27, 1956 2,755,072 Kreutner July 17, 1956 2,769,320 Kuhlenschmidt Nov. 6, 1956 2,835,476 Kohut May 20, 1958

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