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Publication numberUS3006613 A
Publication typeGrant
Publication dateOct 31, 1961
Filing dateMar 21, 1960
Priority dateMar 21, 1960
Publication numberUS 3006613 A, US 3006613A, US-A-3006613, US3006613 A, US3006613A
InventorsCoyne Gerard G
Original AssigneeGen Electric
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Self-contained air conditioning apparatus adapted for heating, cooling and dehumidification
US 3006613 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

1961 G. G. COYNE 3,006,613

' SELF-CONTAINED AIR CONDITIONING APPARATUS ADAPTED FOR HEATING, COOLING AND DEHUMIDIFICATION Filed March 21, 1960 a l w 16 I 4 as j i 103 1 INVENTOR.

GERARD G. COYNE HlS ATTORNEY United States Patent 3,006,613 SELF-CONTAINED AIR CONDITIONING APPA- RATUS ADAPTED FOR HEATING, COOLING AND DEHUMIDIFICATION Gerard G. Coyne, Louisville, Ky., assignor to General Electric Company, a corporation of New York Filed Mar. 21, 1960, Ser. No. 16,474 3 Claims. (Cl. 257-290) The present invention relates to self-contained air conditioning apparatus and more particularly to heat pumps or reversible cycle air conditioning apparatus having a control arrangement adapted to permit selective operation for either heating, cooling or dehumidifying the air from within an enclosure.

Self-contained air conditioning units of the reversible type or of the heat pump type, which are adapted for mounting in an outer wall of an enclosure and utilized for heating air from enclosure during the winter and cooling air from the enclosure during the summer, are ordinarily provided with an auxiliary heater that may be energized to supply additional heat to the enclosure whenever the refrigeration system of the unit is incapable of maintaining the enclosure at the temperature desired by the occupants. The arrangement of the control systems of these units is such that the auxiliary heater is ordinarily energized by the room thermostat whenever the air temperature of the enclosure drops a certain number of degrees below the desired temperature set on the thermostat. However, when the unit is conditioned for cooling, there is no provision for energization of the auxiliary heater. Thus, although a heat pump is normally provided with all of the components necessary for dehumidifying air without cooling, the control for these components prevents them from being employed for this purpose.

It is, therefore, an object of the present invention to provide new and improved control arrangements for a self-contained heat pump unit which is designed to permit operation of the components of the unit in a manner to provide dehumidification of the air from the enclosure without substantial cooling of this air.

More specifically, it is an object of the present invention to provide an improved control arrangement in a heat pump type air conditioning unit which contains overridingmeans for energizing the auxiliary heater of the unit during operation of the unit on the cooling cycle so that de-humidification of the air can be obtained with little cooling effect on the air.

It is a further object of the present invention to provide a simple control arrangement for a self-contained air conditioning unit, having 'a reversible refrigeration system and an auxiliary heater, adapted to permit selective operation of the unit to provide either heating, cooling or de-humidifi-cation of the air from within the enclosure.

Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In carrying out the present invention there is provided a self-contained air conditioning unit adapted for mounting in *an outer wall of an enclosure for heating, cooling, and dehumidifying air from the enclosure. The air conditioning unit includes a reversible refrigeration system having a compressor and pair of heat exchangers, one inside and one outside of the enclosure. Means are provided for routing the high pressure refrigerant firom the compressor either directly into the indoor heat exchanger or directly into the outdoor heat exchanger in order to operate each of these heat exchangers interchangeably as a condenser or as an evaporator according to the desires of the operator. Air moving means are provided for circulating outdoor air over the outdoor heat exchanger and indoor air over the indoor heat exchanger. Mounted on the downstream side of the indoor heat exchanger is an auxiliary heater for providing additional heat whenever the refrigeration system is unable to supply sufficient heat to maintain the enclosure at a proper temperature. The auxiliary heater is controlled during the heating cycle by the thermostat of the unit which is responsive to indoor air temperature and which energizes the heater whenever the temperature within theenclosure falls a certain amount below the temperature set on the room thermostat. Also provided in the unit is an overriding or switching means for energizing at least a part of the auxiliary heater under temperature conditions that would normally prevent energization of the auxiliary heater by the thermostat, the overriding means thereby permitting the heater to be selectively operated during operation of the refrigeration system on the cooling cycle in order to adapt the conditioner for dehumidiiying the air from the enclosure.

For a better understanding of the invention reference may be had to the accompanying drawing, the single figure of which is a schematic diagram of a reversible type air conditioner including the electrical control circuitry adapted for controlling the unit in accordance with the present invention.

Referring now to the drawing, there is shown schematically an air conditioning unit of the self-contained type including a reversible cycle refrigeration system and having the improved control circuitry of the present invention. The refrigeration system includes a compressor 2 having a discharge line 3 and a suction line 4. The discharge and suction lines are both connected to a reversing valve 6. Also connecting to the reversing valve 6 are a pair of conduits 7 and 8 which lead respectively to indoor and outdoor heat exchangers or coils 9 and 11. This system is arranged in an outer case 10 (only a portion of which is shown) adapted for mounting in an outer wall of an enclosure. The air conditioner is provided with means for circulating an air stream from outdoors over the outdoor heat exchanger 11 and for circulating an air stream from within the enclosure or indoors over the heat exchanger 9. More specifically, the flow of indoor air over the heat exchanger 9 is accomplished by a fan 12 which is driven by a motor 13 that is schematically shown mounted on the barrier 14 dividing the case 10 into the inner and outer compartments respectively designated 10a and 10b. Air is moved through the outside coil by a fan 16 which is also preferably driven by a shaft from the motor 13. The fan motor is generally operated by a control circuit (not shown) which is energized when the main switch 15 for the air conditioner is closed. It has been the normal practice to have the fans run continuously during operation of the air conditioner for either heating or cooling purposes although this is not an absolute necessity and the operation of the fans could be made to coincide with that of the compressor. The indoor heat exchanger 9 is arranged for cooling or heating air circulated through the unit from the enclosure to be conditioned, and the outdoor heat exchanger 11 is arranged for either rejecting heat to or absorbing heat from the outside air as this air stream is blown thereover.

Included in the refrigeration system for the purpose of expanding the refrigerant from the condensing pressure to evaporator pressure is a two-way expansion means such as the capillary tube 18. This tube operates as an expansion rneans during both the cooling and heating cycles and is normally so arranged that an efficient flow rate is obtained in either direction through the system during both the cooling or heating cycles.

In the illustrated embodiment of the invention, the air from the enclosure and from the outside enters the respective compartments a and 1% through the sides of the case as is shown by the arrows in the drawing. The air is then circulated out the front and rear portions respectively of the case after having passed through the heat exchangers. It should be noted that the particular direction of air flow through the case or the manner in which air enters and is discharged from the unit is not essential to the invention, but the relative positions of certain components of the air conditioner with respect to the air stream is important. For example, it is essential that the room thermostat 21 having a sensing device arranged upstream from the heat exchanger 9 so that it senses the temperature of air from the enclosure prior to the time it passes over the heat exchanger.

The reversing valve 6 is controlled by a suitable electrical actuating means such as the solenoid 1'7. The valve 6 is normally biased to one position but is movable against the biasing means to a second position by the solenoid 17 when it is energized. When the solenoid is again de-energized, the valve 6 returns automatically to its first position. Reversing valves of this general type are well known in the art and any suitable reversing valve having these characteristics may be used for the above purpose. In its first position, which will be referred to as the cooling position, the reversing valve 6 connects the suction line 4 and discharge line 3 of the compressor 2 to the conduits '7 and 8 respectively and thus directs the hot gaseous refrigerant from the compressor 2 through the outdoor heat exchanger 11 wherein the heat is rejected to the outside atmosphere and the refrigerant is condensed. The condensed refrigerant then passes through the capillary tube 13 and is expanded thereby. The cool expanded refrigerant next absorbs heat from the room in the inside heat exchanger 9 and finally returns to the compressor 2 through the conduit 7 and the compressor suction line 4. Thus during the cooling cycle, the coil 9 acts as an evaporator to absorb heat from the indoor air and the coil 11 acts as a condenser to reject the absorbed heat to the outdoor air. However, if the reversing valve 6 is energized to its second position by means of the solenoid 17, the compressor discharge is then fed directly to the inside heat exchanger 9. The heat exchanger 9 thus rejects heat from the hot, gaseous refrigerant to warm the air from the room. During this heating cycle, the refrigerant, after being condensed in the coil 9, then passes through the capillary tube 18 where it is expanded to evaporator pressure and temperature. The cool, expanded refrigerant next absorbs heat from the outside atmosphere in the heat exchanger 11. After absorbing heat from the outside air being passed over this heat exchanger 11, the refrigerant returns to the compressor through the conduit 8 and the suction line 4.

Positioned within the unit at some point in the air stream upstream from the heat exchanger 9, is the thermostat 21 which controls the operation of the compressor during operation of the unit on either the heating or cooling cycles. The thermostat is of the type well known in the art including means responsive to the ternperature of indoor air for actuating a switch controlling the compressor circuit. In the illustrated embodiment of the invention, the temperature responsive means includes a bulb '22 arranged in the air stream from the enclosure and containing an expansible fluid for operating a bellows (not shown) or other device which, in turn, actuates the thermostat switch 29 between two separate positions according to the temperature of the indoor air stream. The thermostat may be adjusted by the occupants of the enclosure to vary over a fairly wide range, the temperature at which the thermostat switch 29 moves to one or the other of its two separate positions. The unit is also provided with a master control or selector control 23 through which electrical power is connected to the unit and through which the operator of the unit may select any of three air conditioning operations, namely heating, cooling or dehumidifying. More specifically, the operator can move the master control switch 24 of the selector control to a first or cooling position where it engages cooling contact 26 and thus adapts the thermostat 21 to operate the compressor 2 according to temperature increases in the air stream being circulated over the heat exchanger 9. The contact 26 is connected to the thermostat cooling cycle contact 27 through a line 23. Thus, whenever the thermostat switch 29 is in contact with the cooling cycle contact 27, which occurs whenever the temperature of the indoor air flowing over the bulb 22 is above the predetermined temperature set on the thermostat 21 by the occupants of the enclosure such as, for example, 72 F., then power is supplied to the compressor through the circuit including line 28, switch 29 and lines 31, 32 and 33. Whenever the operator wishes to operate the unit on the heating cycle, the master control switch 24 is adjusted across the heating contact 34 of the selector control which then supplies power through the line 36 to the thermostat heating cycle contact 37. When the temperature of the indoor air stream circulating over the bulb 22 drops below the predetermined temperature, or below 72 F for example, the bulb 22 and its expansion device cause the thermostat switch 29 to engage the heating cycle contact 37 thereby adjusting the thermostat for heating. Thus, when power is supplied to the heating contact 37 through the line 36, the compressor 2 is cycled on according to decreases in indoor air temperature as determined by the bulb 22. During heating, power is supplied to the compressor through the circuit which includes the line 36, thermostat switch 29 and lines 3 1, 32 and 33.

In order to reverse the system so that refrigerant is first routed through the heat exchanger 9, whenever the conditioner is operated on the heating cycle, it is necessary, as previous stated, to energize the solenoid 17 there by placing the reversing valve 6 in its second position. Power is supplied to the solenoid 17 by means of a circuit which is energized simultaneously with the energization of the thermostat heating cycle contact 37 and which includes the line 38, the defrost switch 44 (the operation of which will be more clearly described later on in the specification) and the solenoid energization line 41. As can be seen in the drawing, whenever the operator connects the master control switch 24 across the heater contact 34, power is continously supplied to the reversing valve as long as the defrost switch 44 engages contact 40. This supplies electrical current for energizing the solenoid of the reversing valve to place the reversing valve in its second position thereby routing refrigerant from the compressor directly through the heat exchanger 9 and thus, supplying heat to the indoor air stream flowing over heat exchanger 9 whenever the compressor circuit is energized by the thermostat switch 29. It should be mentioned that, when the master control switch 24 is moved into engagement with the cooling cont-act 26, the solenoid circuit is not energized and the reversing valve 6 remains in its first or normal position, thus routing refrigerant from the compressor through the outdoor heat exchanger 11.

There are times during the operation of the heat pump on the heating cycle when the refrigeration system may not provide sufficient heat to maintain the temperature of the indoor air at the desired temperature. It is contemplated therefore, that the thermostat bulb 22 of the thermostat 21, at such times when the temperature drops a certain amount below the predetermined temperatures set on the thermostat such as 6 below this temperature, actuate a thermostat heater switch 49, which will then energize a circuit leading to an auxiliary heater 50 in order to supply additional heat to the indoor air circulating over the heat exchanger 9. The auxiliary heater 50 is arranged on the downstream side of the heat exchanger 9 and comprises a pair of heating or resistance elements 50a and 50b. When the heater switch 49 closes, power is supplied to the auxiliary heater through the circuit comprising the line 36, line 52, thermostat heater switch 49 and the line 47. It will be noted, that, whenever power is supplied to the auxiliary heater 50 through the line 47, only that portion 59a of the auxiliary heater is energized and, thus, the resistance of the heater is much less than if the current were supplied in series through both the portions 50a and 50b of the heater.

During the cooling cycle, frosting of the heat exchanger 9 is not likely to occur since relatively warm air from the enclosure is passed thereover and this causes the heat exchanger 9 to operate at a temperature high enough to prevent frosting. However, during the heating cycle, the outside coil 11 is acting as the evaporator of the system. Rather than being exposed to 75 to 80 F. temperature, as is the coil 9 during the cooling cycle, the coil 11 is exposed during the heating cycle, to an ambient temperature of anywhere from 60 F. down to and below freezing. As a result, the outside coil 11 operates at a much lower temperature and pressure than does the heat exchanger 9 during the cooling cycle. In fact, as the outside temperature drops, the operating temperature and pressure of the coil also drops and, if the outside temperature drops far enough, as for example, to 40 1- the coil 11 then operates below freezing. As a result, frost formation may occur on the outside coil L1 during the heating cycle. Frost formation on this coil is, of course, disadvantageous in that it impairs the heat transferability between the coil and the outside air flowing over it. -A layer of frost formed on the coil tends to act as an insulator so as to lower the heat transfer rate between the surface of the coil and the outside atmosphere. Under frost conditions less heat can be absorbed from the outdoor air by the refrigerant flowing through the coil and this results in less heat being available at the heat exchanger 11 for purposes of warming the room. Thus, for proper operation of the system, the heat exchanger 11 should be defrosted whenever appreciable amounts of frost form thereon during the heating operation. In order to defrost the outdoor coil 11 when necessary during the heating cycle, there is provided a defrost control device 42 which includes a temperature sensing bulb 43, or other frost sensing means, arranged adjacent the heat exchanger 11 and designed to operate a bellows, or other expansion device (not shown), whenever a frost build-up occurs on the heat exchanger 11. The expansion device operates the switch 44 which breaks the circuit supplying current to the solenoid 17, thereby causing the reversing valve 6 to move to its first or normal position, and, accordingly, reverses the flow of refrigerant to the respective heat exchangers 9 and 11. This, of course, causes the heat exchanger 11 to be utilized as the condenser of the system thereby heating this heat exchanger and promoting the defrost thereof. It is contemplated that when the defrost switch 44 is moved away from the contact 40, which energizes the line leading to the coil of the solenoid, it will be moved across the contact 45 thereby energizing a circuit leading to the portion 50a of the auxiliary heater 50. Thus, whenever the switch '44 is in the defrost position with the solenoid 17 deenergized, the switch 44 also connects the auxiliary heater circuit, comprising the line 46, line 47 and the portion 50a of the auxiliary heater, into the circuit. Therefore, whenever the defrost cycle occurs and the heat exchanger 9 is operated as an evaporator, the auxiliary heater Stla is energized to add heat to the air being circulated over the heat exchanger 9 and thus compensates for the cooling which occurs in the heat exchanger at this time.

Inasmuch as heating means are already provided in the heat pump in the form of an auxiliary heater, the present invention provides an arrangement whereby this heating means can be utilized in the summer, or cooling season, to heat the air which is first cooled by the heat exchanger 9 to provide dehumidification only of this air without substantially lowering the temperature of the air flowing into the enclosure. This is accomplished through the use of an overriding or dehumidification control switch 53 which can be moved by the operator to engage the dehumidification contact 54 which, in turn, energizes a second circuit leading to the auxiliary heater. This, of course, only energizes the heater 50 whenever the thermostat switch 29 is closed. For example, when the selector control is on the cooling cycle with the master control switch 214 engaging the contact 26 and the thermostat switch contact 29 closed across the cooling cycle contact 27, power is supplied to the auxiliary heater through a circuit comprising line 28, thermostat switch 29, line 55, dehumidification control switch 53 and line 56, which connects with both portions 50a and 50b of the auxiliary heater arranged in series. The dehumidification switch 53 is arranged in series with the thermostat switch 29 so that, whenever power is supplied through the switch 29 and the dehumidification switch 53 is closed, then the auxiliary heater is energized. In the preferred embodiment of the invention, the auxiliary heater is arranged with separate portions 50a and 50b in series. -It should be noted that, during the energization of the heater by the switch 49, current only flows through that portion 50a of the heater while, during energization of the heater by the switch 53, current flows in series through both portions 50b and 50a of the auxiliary heater. Inasmuch as the voltage across the heater in both instances is approximately the same,

that is the voltage across the heater 50a when the thermo stat heater switch 49 is closed is approximately the same as the voltage across both portions of the heater 50b and 50a when the dehumidification switch 53 is closed, it will be obvious that less heat is generated by the auxiliary heater with the two portions connected in series than when the current is passed through the single portion 50a. This is because the resistance of the two portions 50a and 5% connected in series is so much greater than the resistance of the single heater 50a that the current flow through the portions 50a and 50b connected in series is much less than that for the single portion 50a. Thus, during the dehumidification cycle a lesser amount of heat is supplied than during the heating cycle when it is desirable to supply greater amounts of heat to implement the heat produced by the heat pump itself. This, of course, is the preferred arrangement of the invention, but only a single heater portion 50a is necessary and the line 56 could be connected to the same end of heater portion 50a as is the line 47.

By the present invention there is provided a control arrangement for a heat pump designed to provide not only heating and cooling for the enclosure but designed to utilize all of the components normally found in a heat pump to provide dehumidification of the indoor air during the summer or cooling operation of the air conditioner. This simple control arrangement is provided by means of an overriding or dehumidification switch which energizes the auxiliary heater under those conditions when the thermostat heater switch would ordinarily not call for energization of the heater.

While in accordance with the patent statutes there has been described what at present is considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art, that various changes and modifications may be made therein without departing from the invention, and it is, therefore, the aim of the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a self-contained air conditioning unit for heating and cooling an enclosure, a reversible cycle refrigeration system having indoor and outdoor interconnected heat exchangers, each of said heat exchangers operable interchangeably as a condenser or as an evaporator, means for circulating an air stream from indoors over said indoor heat exchanger and means for circulating an air stream from outdoors over said outdoor heat exchanger, means to condition said refrigeration system for operation on the heating cycle with the inside heat exchanger operating as a condenser, means to condition said system for operation on a cooling cycle with the inside heat exchanger operating as an evaporator, an auxiliary heater for heating air from said enclosure, said auxiliary heater being arranged on the downstream side of said indoor heat exchanger, a thermostat arranged on the upstream side of said indoor heat exchanger in said indoor air stream, said thermostat including a compressor control switch responsive to the temperature of said indoor air stream for energizing an electrical circuit to said compressor according to the temperature of said indoor air stream, said thermostat also having a heater switch adapted to energize a circuit including said auxiliary heater when said temperature within said enclosure falls a certain number of degrees below a predetermined temperature, and a normally open overriding heater switch for energizing a circuit including said auxiliary heater under indoor air temperature conditions which would normally cause said thermostat heater switch controlling said auxiliary heater to de-energize said heater thereby permitting selective operation of said auxiliary heater dur ing cooling operation of said air conditionng unit to permit de-humidification of said indoor air.

2. In a self-contained air conditioning unit for heating and cooling an enclosure, a reversible cycle refrigeration system having indoor and outdoor interconnected heat exchangers, 'means including a two-way expansion means connecting said heat exchangers, means for circulating an air stream from indoors 'over said indoor heat exchanger, means for circulating an air stream from the outdoors over said outdoor heat exchanger, an electrically energizable reversing valve movable between a first position wherein refrigerant is routed from said compressor to said outdoor heat exchanger for air cooling operation to a second position wherein refrigerant is routed from said compressor to said indoor heat exchanger for air heating operation, an auxiliary heater for heating air from said enclosure, said auxiliary heater being arranged on the downstream side of said indoor heat exchanger, a thermostat arranged on the upstream side of said indoor heat exchanger in said indoor air stream, said thermostat including a compressor control switch responsive to the temperature of said indoor air stream and adaptable to control the operation of said compressor according to the temperature of said indoor air stream, said thermostat also having a heater switch for energizing said auxiliary heater during said heating cycle when said temperature within said enclosure falls a certain number of degrees below a predetermined temperature, and a selector control means including a master control switch movable between first and second positions to control the operation of said air conditioner for cooling or heating respectively, said master control switch in said first position conditioning said reversing valve for routing refrigerant from said compressor to said outdoor heat exchanger and conditioning said thermostat to cycle said compressor on whenever the indoor air temperature increases above a predetermined temperature, said master control switch in said second position conditioning said reversing valve to route refrigerant from said compressor to said indoor heat exchanger and conditioning said thermostat to cycle said compressor on Whenever said indoor air temperature falls below a predetermined temperature, said selector control having a normally open overriding heater switch connected in series with said compressor control switch of said thermostat for permitting energization of at least a portion of said auxiliary heater under indoor air temperature conditions which would normally cause said thermostat heater switch to de-energize said auxiliary heater thereby permitting selective operation of said auxiliary heater during cooling operation of said air conditioning unit to promote dehumidification of said indoor air.

'3. In a self-contained air conditioning unit for heating and cooling an enclosure, a reversible cycle refrigeration system having indoor and outdoor interconnected heat exchangers, a capillary expansion means connecting said heat exchangers, means for circulating an air stream from indoors over said indoor heat exchanger and means for circulating an air stream from the outdoors over said outdoor heat exchanger, an electrically energizable reversing valve movable between a first position wherein refrigerant is routed from said compressor to said outdoor heat exchanger for air cooling operation to a second position wherein refrigerant is routed from said compressor to said indoor heat exchanger for air heating operation, an auxiliary heater for heating air from said enclosure, said auxiliary heater being arranged on the downstream side of said indoor heat exchanger and including first and second resistance heating units connected in series, a thermostat arranged on the upstream side of said indoor heat exchanger and said indoor air stream, said thermostat including a compressor control switch responsive to the temperature of said indoor air stream for controlling the operation of said compressor according to said indoor air temperature, said thermostat also having a thermostat heater switch energizing said first resistance heater during said heating cycle when said temperature within said enclosure falls a certain number of degrees below a predetermined temperature, and a selector control means including a master control switch movable between first and second positions, said master control switch in said first position conditioning said reversing valve for routing refrigerant from said compressor to said outdoor heat exchanger and conditioning said thermostat to cycle said compressor on whenever the indoor air temperature increases above a predetermined temperature, said master control switch in said second position conditioning said reversing valve to route refrigerant from said compressor to said indoor heat exchanger and conditioning said thermostat to cycle said compressor on whenever said indoor air temperature falls below a predetermined temperature, said selector control means also having a normally open overriding heater switch for energizing a circuit including said first and second resistance heater units in series under indoor air temperature conditions which would normally cause said thermostat heater switch to de-energize said auxiliary heater so that said first and second resistance heater units can be selectively operated during cooling operation of said air conditioning unit to promote dehumidification of said indoor air.

References Cited in the file of this patent UNITED STATES PATENTS 2,468,626 Graham Apr. 26, 1949 2,672,734 Ditzler et al, Mar. 23, 1954 2,902,220 Myck et al. L Sept. 1, 1959

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3166120 *May 23, 1962Jan 19, 1965Acme Ind IncHeating or cooling system for heat exchangers
US3183965 *Aug 1, 1961May 18, 1965Carrier CorpHeat pump control circuit
US4141408 *Jun 16, 1976Feb 27, 1979Rheem Manufacturing CompanySupplementary heat control for heat pump system
US4263962 *Jun 13, 1977Apr 28, 1981General Electric CompanyHeat pump control system
US4384608 *Aug 11, 1980May 24, 1983Ford Motor CompanyReverse cycle air conditioner system
US4550770 *Oct 4, 1983Nov 5, 1985White Consolidated Industries, Inc.Reverse cycle room air conditioner with auxilliary heat actuated at low and high outdoor temperatures
US5117652 *Jan 31, 1991Jun 2, 1992Kabushiki Kaisha ToshibaAir conditioner
US5332028 *Mar 12, 1993Jul 26, 1994Carrier CorporationMethod and apparatus for controlling supplemental electric heat during heat pump defrost
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Classifications
U.S. Classification165/240, 62/160, 62/203, 62/429, 392/349
International ClassificationF24F1/02, F25B13/00
Cooperative ClassificationF25B13/00, F24F1/02
European ClassificationF24F1/02, F25B13/00