WO1996037737A1

WO1996037737A1 - Air conditioning system

Info

Publication number: WO1996037737A1
Application number: PCT/US1996/007651
Authority: WO
Inventors: Moshe Salman
Original assignee: Airtec Advanced Air Conditioning Industries Ltd.; Cohen, Julian, H.
Priority date: 1995-05-26
Filing date: 1996-05-24
Publication date: 1996-11-28
Also published as: AU5930296A

Abstract

A multi-room air conditioning system (10) comprising a controller (90), a compressor (87), a first heat exchanger (30) in refrigerant fluid communication with said compressor (87), a second heat exchanger (40) in refrigerant fluid communication respectively with said first heat exchanger (30) and said compressor (87), said second heat exchanger also being in heat exchange communication with a stream of air (73), a plenum (50) arranged to receive said stream of air downstream of said second heat exchanger, a plurality of air flow ducts (66, 68) for distributing said stream of air from said plenum to a plurality of rooms (62, 60) a plurality of fans (74, 76), each fan associated with one of the plurality of air flow ducts, a plurality of motors (80, 82) each motor drivingly associated with one of said plurality of fans, at least one temperature controller (91) located in at least one of said plurality of rooms, and wherein said controller (90) is operative to selectively control a speed of rotation of at least one of said plurality of motors at least partially in response to a signal from said at least one temperature controller.

Description

AIR CONDITIONING SYSTEM

The present invention relates to air conditioning systems in general and to central air conditioning systems in particular.

BACKGROUND OF THE INVENTION

Reference is made to Thermodynamics' by J. E. Lay published by Charles E. Merril, Columbus, Ohio, Second Printing. 1994, the contents of which are hereby incoφorated by reference. Particular reference is made to the following sections: Section 19.19, pages 579 - 580, Section 19.20, pages 580 - 582, and Section 19.26, pages 594 - 596.

Air conditioning systems known in the art comprise a compressor which compresses a refrigerant at low pressure in the vapor state to a higher pressure and temperature. Heat is removed from the high temperature refrigerant in a first heat exchanger which condenses the refrigerant at substantially constant pressure to the liquid state. The condensed and coolt-i liquid at high pressure is then expanded through an expansion valve thereby changing the state of the refrigerant to a mixture of saturated liquid and saturated vapor at low temperature and pressure. Heat is added to the low temperature refrigerant in a second heat exchanger in which the refrigerant evaporates at substantially constant pressure.

When the air conditioning system operates as an air conditioner to cool the air in a space such as a room, the first heat exchanger operates as a condenser and transfers heat to the atmosphere from the high temperature refrigerant. The second heat exchanger operates as an evaporator which transfers heat from the space to be cooled to the refrigerant, thereby lowering the temperature and humidity of the air in the space.

When the air conditioning system operates as a heat pump to heat the air in a space such as a room, the first heat exchanger operates as an evaporator which transfers heat from the atmosphere to the low temperature refrigerant. The second heat exchanger operates as a condenser and transfers heat from the high temperature refrigerant to the air in the space, thereby raising the temperature of the air.

Central air conditioning systems known in the art are used to heat or cool a plurality of rooms and several types of conditioned air distribution systems are«known in the art. Central air conditioners for home use generally distribute conditioned air via a series of ducts to the different rooms. One of the drawbacks in the prior art central air conditioning systems is the difficulty of regulating the temperature and air flow separately for each room.

U.S. Patent 4,635,445 to Otsuka shows a central air conditioning system comprising a fan for distributing conditioned air to a number of rooms with dampers controlling the amount of conditioned air to be provided to each room.

U.S. Patent 3,568,760 to Hogel shows a pneumatic control system for regulating room dampers.

United Kingdom Patent Application GB 2,194,651 shows a central air conditioning system with a variable capacity compressor. The temperature of each room to be conditioned is controlled by regulating the amount of refrigerant distributed to a heat exchanger provided for each room.

U.S. Patent 5,358,078 to Dushane shows a central heating and air conditioning system with a central air distribution fan with room registers or dampers controlling the amount of air entering each room.

U.S. Patent 3,653,589 to McGrath shows a central air conditioning system with a separate fan and heat exchanger provided in ducts leading to each room. A controllable outlet maintains substantially constant air velocity as the speed of the fan is adjusted.

U.S. Patent 2,952,991 to Pierre shows a control system for regulating the pressure at the outlet of the compressor in a refrigeration system. A mechanical pressure sensor is fluidically connected to the outlet of the compressor and this pressure sensor is used to control the speed of the condenser fan by varying the inductance of the fan motor.

U.S. Patent 4,560,103 to Schulz shows an air conditioning central for ventilating a vehicle compartment. The duct leading to the vehicle compartment contains separate blowers for mixing fresh air and conditioned air, thereby obtaining precise temperature control.

It is a purpose of the present invention to overcome the deficiencies in such prior art devices and provide an air conditioning system that is operable to control the temperature and air flow in a number of rooms and minimize the consumption of electrical energy when operating under partial thermal load. SUMMARY OF THE INVENTION

The present invention seeks to provide an air conditioning system which overcomes the drawbacks of the prior art devices and provides effective control of the temperature in each of the air conditioned spaces.

There is thus provided in accordance with a preferred embodiment of the present invention, a multi-room air conditioning system including a controller, a compressor, a first heat exchanger in refrigerant fluid communication with the compressor, a second heat exchanger in refrigerant fluid communication respectively with the first heat exchanger and the compressor, the second heat exchanger also being in heat exchange communication with a stream of air, a plenum arranged to receive the stream of air downstream of the second heat exchanger, a plurality of air flow ducts for distπbuting the stream of air from the plenum to a plurality of rooms, a plurality of fans, each fan associated with one of the plurality of air flow ducts, a plurality of motors, each motor drivingly associated with one of the plurality of fans, at least one temperature controller located in at least one of the plurality of rooms, and wherein the controller is operative to selectively control a speed of rotation of at least one of the plurality of motors at least partially in response to a signal from the at least one temperature controller.

Additionally in accordance with a preferred embodiment of the present invention the speed of rotation includes a low speed of rotation, the low speed of rotation substantially preventing a flow of air into at least one of the plurality of rooms.

Still further in accordance with a preferred embodiment of the present invention, at least one of the plurality of fans is a centrifugal fan wherein the speed of rotation includes a reverse speed of rotation, the reverse speed of rotation substantially preventing a flow of air into at least one of the plurality of rooms.

Further in accordance with a preferred embodiment of the present invention the reverse speed of rotation includes a speed in the range between about 10% and about 40% of a maximum speed of rotation of the motor.

Additionally in accordance with a preferred embodiment of the present invention, the speed of rotation also includes an intermediate speed of rotation, the intermediate speed of rotation operative to maintain a substantially constant supply of conditioned air to at least one of the plurality of rooms. Still further in accordance with a preferred embodiment of the present invention, the speed of rotation also includes a high speed of rotation, the high speed of rotation operative to supply a large amount of air to at least one of the plurality of rooms for rapid heating during a winter operation and rapid cool down during a summer operation.

Further in accordance with a preferred embodiment of the present invention the first heat exchanger is in heat exchange communication with a flow of outside air, the air conditioning system also including a variable speed outside motor drivingly associated with an outside main fan and wherein the outside main fan is arranged to direct the flow of outside air through the first heat exchanger, a pressure sensor in refrigerant fluid communication with a low pressure side of the compressor and wherein the outside motor is regulated at least partially in response to a pressure signal from the pressure sensor.

Further in accordance with a preferred embodiment of the present invention, the pressure sensor includes at least one pressure switch.

There is also provided in accordance with another preferred embodiment of the present invention a multi-room air conditioning system including a compressor, a first heat exchanger in refrigerant fluid communication with the compressor, a plurality of second heat exchangers each in refrigerant fluid communication respectively with the first heat exchanger and the compressor, the plurality of second heat exchangers also being in heat exchange communication with a plurality of streams of air to be conditioned, a plurality of plenums each arranged to receive each of the plurality of streams of air downstream of the second heat exchangers, a plurality of air flow ducts associated with at least one of the plenums for distributing the streams of air from the at least one plenums to a plurality of rooms, a plurality of fans, each fan associated with one of the plurality of air flow ducts, a plurality of motors, each motor drivingly associated with one of the plurality of fans, at least one temperature controller located in at least one of the plurality of rooms, and a control system operative to selectively control a speed of rotation of at least one of the plurality of motors at least partially in response to a signal from the at least one temperature controller.

Additionally in accordance with a preferred embodiment of the present invention, the multi-room air conditioning system also includes a heating unit in at least one of the plurality of air flow ducts, the heating unit operative to supplement the thermal output of the air conditioning system at least partially in response to a temperature signal from the at least one temperature controller. Still further in accordance with a preferred embodiment of the present invention the multi-room air conditioning system also includes an air purifier, the air purifier operative to substantially purify the stream of air.

Further in accordance with a preferred embodiment of the present invention, the air purifier is disposed in the plenum.

Additionally in accordance with a preferred embodiment of the present invention the purifier is disposed upstream of the second heat exchanger.

Still further in accordance with a preferred embodiment of the present invention the air purifier comprises an ozone generator.

There is also provided in accordance with a preferred embodiment of the present invention a room heat exchanger for providing conditioned air to a room, the room heat exchanger including at least one heat exchange coil, at least one fan and wherein the room heat exchanger is formed with a cavity in a top surface of the room heat exchanger, the cavity arranged for receiving a decorative item.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated from the following detailed description, taken in conjunction with the drawings in which:

Fig. 1 is an illustration of a central air conditioning system constructed and operative in accordance with a preferred embodiment of the present invention;

Fig. 2 is a simplified illustration of a controller useful in controlling operation of the air conditioning system shown in Fig. 1;

Fig. 3A is a simplified illustration of a temperature controller useful in providing temperature information to the controller of Fig. 2;

Fig. 3B is a simplified illustration of another temperature controller useful in providing temperature information to the controller of Fig. 2.

Fig. 4 is a simplified flow chart illustrating a method used to calibrate the controller shown in Fig. 1 ;

Fig. 5 is a simplified illustration of a central air conditioning system constructed and operative in accordance with another embodiment of the present invention;

Fig. 6 is a simplified illustration of a controller useful in controlling operation of the central air condition system shown in Fig. 5; Fig. 7A is a simplified illustration of part of the air conditioning system of Fig. 5 in which the system is operative to provide cooled air;

Fig. 7B is a simplified illustration of part of the air conditioning system of Fig. 5 in which the system is operative to provide heated air;

Fig. 8 is a simplified illustration of a central air conditioning system constructed and operative in accordance with yet another embodiment of the present invention;

Fig. 9 is a simplified illustration of a controller useful in controlling operation of the air conditioning system shown in Fig. 8;

Fig. 10 is a simplified illustration of a central air conditioning system constructed and operative in accordance with still another preferred embodiment of the present invention;

Fig. 1 1 is a simplified illustration of a central air conditioning system constructed and operative in accordance with a further preferred embodiment of the present invention;

Fig. 12 is a simplified illustration of a central air conditioning system constructed and operative in accordance with yet another preferred embodiment of the present invention;

Fig. 13 is a simplified illustration of a resistance heater useful in the air conditioning system shown in Fig. 12;

Fig. 14 is a simplified illustration of a central air conditioning system constructed and operative in accordance with still another preferred embodiment of the present invention;

Fig. 15 shows a portion of the air conditioning system of Fig. 14 in more detail;

Fig. 16A shows part of the logic used to control operation of the air conditioning system of Fig. 14 for 'summer operation';

Fig. 16B shows part of the logic used to control operation of the air conditioning system of Fig. 14 for 'winter operation';

Fig. 17 is a simplified illustration of a central air conditioning system constructed and operative in accordance with still another preferred embodiment of the present invention; Fig. 18 shows a portion of the air conditioning system of Fig. 17 in more detail;.

Fig. 19 shows an alternate embodiment of the central air conditioning system of Fig. 17;

Fig. 20 is a simplified illustration of a decorative room heat exchanger constructed and operative in accordance with a preferred embodiment of the present invention; and

Fig. 21 is a partially exploded view of the room heat exchanger of Fig. 20.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to Fig. 1 which illustrates an air conditioning system 10 constructed and operated in accordance with a preferred embodiment of the present invention, for providing air conditioned and temperature controlled air to a plurality of rooms and/or chambers.

It is appreciated that although only three rooms/chambers are illustr?.⁺^d in Fig. 1 and described in this specification, the number of rooms/chambers is non-limiting and is by way of example only. The air conditioning system of the present invention can be practiced for any number of rooms and/or chambers.

The air conditioning system 10 of the present invention comprises a compressor 20 drivingly connected to a compressor motor 87. The compressor motor 87 is connected to a controller 90 by means of a wiring connection 45. The compressor 20 includes a low pressure inlet side 22 and a high pressure outlet side 24. An air conditioner refrigerant, such as freon, enters the compressor at the low pressure inlet 22 and exits the compressor at the high pressure outlet 24.

A first heat exchanger 30 is fluidically connected to the high pressure outlet 24 of the compressor 20. The refrigerant flows from the compressor outlet 24 to the first heat exchanger 30. The refrigerant then flows to a conventional expansion valve 32, wherein the refrigerant experiences a large decrease in pressure and temperature. Alternatively, the refrigerant may flow from the first heat exchanger 30 to a capillary tube wherein the refrigerant experiences a large drop in pressure and temperature. The refrigerant then flows to a second heat exchanger 40 whence it flows back to the low pressure inlet 22 of the compressor 20, thereby returning to the starting point of the refrigeration cycle. The circulation of the refrigerant through the air conditioning system 10 is as indicated by the flow arrows 31 in Fig. 1.

The second heat exchanger 40 may be located in a plenum 50, and is a source of conditioned air to be delivered to the rooms 60, 62 and 64, via a plurality of ducts 66, 68 and 70. The plenum 50 may also be downstream of the second heat exchanger 40. The plenum 50 is arranged to receive air after the air has passed through the second heat exchanger 40 and has been conditioned thereby.

Conditioned air is induced to flow into the duct 66, by a fan 74, preferably driven by a motor 80. Similarly, air is induced to flow into duct 68 by a fan 76, preferably driven by a motor 82, and air is induced to flow into duct 70 by a fan 78, preferably driven by a motor 84. The fans 74, 76 and 78 are preferably located in proximity to the inlet to their respective ducts, as illustrated in Fig. 1. Alternatively a fan may be located at any convenient position along a duct.

The fans 74, 76 and 74 are preferably of the centrifugal type but may be of any suitable type.

The motors 80, 82 and 84 are preferably multi-speed motors which rotate at a discrete number of speeds, and may be two speed or three speed motors or any other number of discrete speeds and are capable of rotating in a reverse direction. Alternatively the motors 80, 82 and 84 may be variable speed motors which are capable of rotating in a reverse direction.

The motors 80, 82 and 84 are independently connected to a controller 90 by means of a plurality of connecting wires 51 so that the controller 90 may regulate the speed of each motor 80, 82 and 84 independently.

Preferably, return air ducts are provided for circulation of the conditioned air. Thus, for example, return air duct 55 may return the air from room 60 to the inlet of the filter 72 so as to maintain air circulation in room 60 as indicated by flow arrows 67 and 65. Similarly, return duct 56 may be provided for circulating the air in room 64. Alternatively, return air ducts may not be provided for one or all of the rooms, as is shown by way of example for room 62.

Rotation of the fans 74, 76 and 78 creates a region of low pressure in the plenum 50. Air flow into the plenum 50 is provided by air 73 entering the plenum 50 through an air filter 72 and through the second heat exchanger 40, as described hereinbelow. The filter 72 removes dust and grit from the air in order to provide a clean air flow to the rooms 60, 62 and 64. Outside air may also flow into the plenum 50 in order to maintain a steady air flow through the system.

A temperature controller 91, such as a thermostat, is located in an appropriate position in room 60, as is known in the art. Similarly, a temperature controller 93 is located in room 62, and a temperature controller 95 is located in room 64, as is known in the art. Alternately, temperature controllers may be placed in a selected number of rooms. The temperature controllers 91, 93 and 95, are located in their respective rooms for maintaining the rooms at a desired temperature. Each temperature controller 91, 93 and 95, is connected independently to the controller 90 by means of a plurality of connecting cables 41.

An outside fan motor 92 is drivingly connected to an outside main fan 99. Outside fan motor 92 preferably comprises a conventional variable speed motor. Alternatively, fan motor 92 may comprise a conventional multi-speed motor capable of rotating at a discrete number of speeds. Outside motor 92 is electrically connected to controller 90 by means of a connecting cable 47.

A conventional pressure sensor 98, which may be a pressure gauge or any other suitable pressure sensor, may be connected to the inlet side 22 of the compressor 20 via a conventional quick connect hydraulic coupling (not shown) or by any other suitable coupling. Pressure sensor 98 generally is connected to inlet 22 for purposes of calibration, as described hereinbelow, during installation and is removed thereafter.

The embodiment illustrated in Fig. 1 is operative to provide cooling air to the rooms 60, 62 and 64. The first heat exchanger 30 operates as a condenser and rejects heat to the outside air. The second heat exchanger 40 operates as an evaporator and provides cooled and conditioned air to the rooms.

It will be appreciated by one skilled in the art that air conditioning systems similar to that shown in Fig. 1 may operate as a heat pump to provide heated air to the rooms 60, 62 and 64. As known in the art, the outlet 24 of the compressor 20 is fluidically connected to the second heat exchanger 40 which operates as a condenser to reject heat to the conditioned rooms. The refrigerant then flows through the expansion valve 32 wherein it experiences a large decrease in temperature and pressure. The refrigerant then flows through the first heat exchanger 30 which operates as an evaporator to absorb heat from the outside air. ererence is now also maαe to J-ig. i wnicn is a simpnπeα wiring diagram or the controller 90. The controller is shown to have the capacity for controlling a six-room air conditioning system. This number of connections is non-limiting and given by way of example only. The signal connections will be described hereinbelow for the three-room arrangement of Fig. 1.

The controller 90 includes a control board 110 and preferably includes a plurality of potentiometers 114, 1 15 and 116. Each of the potentiometers 114, 115 and 1 16 corresponds to one of the rooms 60, 62 and 64. Thus for example, potentiometer 114 may correspond to room 60, potentiometer 115 may correspond to room 62 and potentiometer 116 may correspond to room 64. Each potentiometer 114, 1 15 and 116 is connected to a relay 126, 127 and 128 respectively. The control board 1 10 is operative to selectively activate the relays 126, 127 and 128 via relay control lines 121, 123 and 125 selectively to connect different combinations of the potentiometers to the control board. Thus, for example, if relay 126 is activated and relays 127 and 128 are not activated, the resistance of potentiometer 114 is sensed by the control board 110 via potentiometer signal line 120. If relays 127 and 128 are activated, and relay 126 not activated, the resistance of potentiometers 1 15 and 116, which are in a parallel electrical connection, is sensed by control board 110 via potentiometer signal line 120. If relays 126, 127 and 128 are all activated, the control board will sense the resistance of potentiometers 114, 115 and 116 in parallel. The potentiometers 114, 115 and 116 and relays 126, 127 and 128 are used for calibration and control of the air conditioning system 10 as described hereinbelow.

It will be appreciated that the potentiometers 114, 115 and 116, relays 126, 127 and 128, relay control lines 121, 123 and 125 and potentiometer signal line 120 may be located on the control board 110.

The input signals to controller 90 from the temperature controllers 91, 93 and 95 are sent through the connecting cables 41 to an input side 113 of controller 90. The motors 80, 82 and 84 are connected to the controller 90 via motor control lines 51 and a series of motor speed controllers 118. Motor speed controllers 118 may be of the conventional relay-type, or any other suitable type, for motors 80, 82 and 84 which are of the multi-speed type. Alternatively, motor speed controllers 118 may be conventional SCR-type controllers, such as conventional 'light dimmers', triacs, or any other suitable type, for motors 80, 82 and 84 which are of the variable speed type. It will be appreciated that multi-speed motors and variable speed motors and controllers may be used in any desired combination

The control board 110 is operative to send the necessary signals to the motors 80, 82 and 84 for regulating the rotational speed of the fans 74, 76 and 78, respectively, as required by the respective temperature measurements of the temperature controllers 91, 93 and 95.

The control board 1 10 is also connected electrically to an outside fan speed controller 124 via signal line 134. Speed controller 124 preferably is an SCR controller and may be of the conventional 'light dimmer' type, triac, or any other suitable type of controller for a variable speed outside fan motor 92. Alternatively, speed controller 124 may be of the relay type, or any other suitable device for a multi-speed outside fan motor 92.

Control board 110 is operative to regulate the speed of the outside fan motor 92 in response to signals from the temperature controllers 91 , 93 and 95 and the settings of the potentiometers 114, 115 and 116 such that the lower the resistance sensed by potentiometer signal line 120, the higher is the speed of outside fan motor 92.

Control board 110 is also connected to a power control device 122 via a signal line 132 which is in turn connected to connecting cable 45. Power control device 122 is preferably a conventional relay or any other suitable device, which is operable to turn the compressor motor 87 on and off.

Reference is now also made to Fig. 3A which illustrates a temperature controller 91 useful for controlling the room temperature. The temperature controller 91 includes a slideable selector 180 which may be a rotary potentiometer. Alternatively, slideable selector 180 may a linear potentiometer or any other suitable device. A temperature scale 182 indicates the preferred temperature of the room. Temperature controller 91 is operative to send a signal to controller 90, via cable 41, when the actual room temperature has reached the preferred value. Alternatively, temperature controller 91 is operative to send a signal to controller 90, via cable 41, which is proportional to the temperature in the room.

The temperature controller 91 may also include an "on/ofF' control switch 189. Thus, the 'switching-on' and 'switching-off of the air conditioning system 10 can be controlled in each individual room instead of having only a single central control switch. Alternatively, a temperature controller may be provided without the on-off control switch 189. Thus, for example, temperature controller 91 may contain an on-off control switch 189 π while temperature controllers 93 and 95 are not provided with on-off switches. In this example, the air conditioner system 10 can be turned on or off only from room 60.

Reference is now also made to Fig. 3B which illustrates an alternative embodiment of temperature controller 91 useful for controlling the temperature of a room. The temperature controller 91 includes a digital display 190 which is operative to display the room temperature. A display control switch 198 controls the information displayed by display 190 to selectively display either the measured room temperature or the preferred room temperature. Alternatively, the digital display 190 may display the measured temperature and the preferred temperature in sequence.

Temperature controller 91 may also include temperature control switches 194 and 192 for changing the preferred room temperature. Pressing switch 194 increases the preferred room temperature while pressing switch 192 decreases the preferred room temperature. Temperature controller 91 may also include an on-off switch as described hereinabove for the on-off switch of Fig. 3 A.

It will be appreciated that temperature controller 91 may also be equipped with a clock apparatus which turns the air conditioning system 10 on or off at predetermined times.

Reference is now also made to Fig. 4 which describes a preferred method for calibrating the air conditioning system 10. The following description pertains to calibrating the air conditioning system 10 for operation as a cooling system. It will be appreciated that calibration for operation of the air conditioning system 10 as a heating system is substantially identical.

At step 150, the air flow for all rooms except one is substantially closed. Thus, for example, to calibrate the air conditioner system 10 for room 60, the preferred temperature in rooms 62 and 64 is set by temperature controllers 93 and 95 to an arbitrarily high value to insure that no conditioned air is provided to rooms 62 and 64. The preferred temperature is set in room 60 by temperature controller 91 at an arbitrarily low value, to assure that conditioned air is provided to room 60.

Control board 110 is operative to disengage all of the relays 126, 127 and 128 except the relay that corresponds to room 60. Thus, in the present example, the control board 110 will disengage relay 127 and 128 and engage relay 126 so that the resistance of potentiometer 114 is sensed by potentiometer signal line 120. At step 152, the refrigerant pressure. Pin, is measured at the inlet side 22 of the compressor 20 by pressure sensor 98. The pressure sensor 98 is only inserted into the compressor inlet line during the calibration procedure of Fig. 4. In step 154, the pressure Pin is compared to the desired compressor input pressure, Plow. The value of Plow may be between 50 and 75 psi and preferably has the value of about 55 psi.

If the measured pressure Pin is substantially equal to the desired pressure Plow, the above procedure is repeated for subsequent rooms, step 164.

If the answer to step 154 is negative, the calibration procedure proceeds to step 156 and a comparison is made between Pin and Plow. If Pin is larger than Plow, the required compressor input pressure, the speed of the outside fan 99 is increased as indicated at step 158, by adjusting potentiometer 114 accordingly, thereby increasing the air flow over the second heat exchanger 30. This increased air flow increases the heat removed from the first heat exchanger 30 thereby decreasing the pressure of the refrigerant at the inlet side 22. Once the steady state conditions have been reached, step 162, the above procedure is repeated for the next room or group of rooms. If Pin is lower than Plow, the potentiometer 114 is adjusted to decrease the speed of the outside fan 99 as indicated at step 160, thereby decreasing the heat removed from first heat exchanger 30 and increasing the pressure at the inlet side 22.

A short period of time is allowed to pass at step 162 to allow the pressure at the inlet 22 to reach steady state. Once steady state conditions are attained, the method returns to step 152.

Steps 152, 154, 156, 158, 160 and 162 are repeated until the pressure Pin is substantially equal to Plow at step 154. On reaching the desired pressure, the next room is then calibrated by returning to step 150.

Operation of the air conditioning system 10 will now be described for the case when the air conditioning system is operative as a cooling system.

If the temperature of a room is above the preferred temperature as set by the temperature controller for that room, the temperature controller sends a signal to controller 90 which regulates the speed of the fan for that room to rotate at a high speed. Thus conditioned air flows from the plenum 50 to the room, and the temperature of the room is reduced. If the temperature of a room is about equal to or below the desired temperature for the room, the controller 90 is operative to rotate the fan for the room to substantially prevent the flow of conditioned air to that room. Additionally, controller 90 regulates the -φeed of rotation of the outside fan motor 92 via outside fan speed controller 124 and connecting cable 45.

Thus, by way of example, if the motors 80, 82 and 84 are of the multi-speed type, and the preferred temperature of room 60 is 20 degrees centigrade while the actual temperature of room 60 as measured by temperature controller 91 is 25 degrees, controller 90 is operative to rotate motor 80 at a high speed thereby causing fan 74 to provide a high flow of conditioned air from plenum 50 into room 60 via duct 66. This flow of conditioned air causes the temperature of room 60 to decrease.

Control board 110 is also operative to activate relay 126 so that the setting of potentiometer 1 14, which in this example corresponds to room 60, is sensed by potentiometer signal line 120. Thus, the speed of outside fan is regulated by the presence of a cooling air flow into room 60 and will increase so that the heat removed from room 60 by evaporator 40 may be rejected to the atmosphere via condenser 30.

When the temperature of room 60 reaches 20 degrees Centigrade, temperature controller 91 sends a signal to controller 90 via connecting cable 41. Upon receipt of this signal, controller 90 is operative to rotate motor 80 at a low speed. For a centrifugal fan 74, controller 90 preferably rotates motor 80 in a reverse direction at a speed which may be in the range of about 10% to about 40% of the maximum motor speed and is preferably about 20% of the maximum speed. The resulting airflow substantially prevents the flow of conditioned air into room 60.

Additionally, control board 1 10 is operative to disengage relay 126, thereby disconnecting the resistance of potentiometer 114 from the potentiometer signal line 120. The resistance sensed by the potentiometer signal line 120 increases and control board 110 sends a signal to outside fan speed controller 124 to decrease the speed of outside fan motor 92.

The speed of motor 80 is maintained at the low speed setting until the temperature of room 60 increases by a predetermined small amount delta above the desired room temperature. Delta may be in the range from about one half to three degrees Centigrade and is preferably about one degree Centigrade. Thus, in the current example, when the temperature in room 60 reaches about 21 degrees Centigrade, the temperature controller 91 sends a signal to controller 90 via cable 41. Upon receipt of this signal, controller 90 is operative to rotate motor 80 at the high speed to induce conditioned air once again from the plenum 50 into the room 60. It is appreciated that controller 90 regulates the temperature in each of the rooms 62 and 64 in a similar manner.

It will also be appreciated that for the case for which two of the rooms are above the preferred temperature, the fans for these two rooms will be activated at high speed to induce conditioned air from plenum 50 into the these rooms. Thus, for example, if rooms 60 and 62 are above the desired temperature setting as indicated by the temperature controllers 91 and 93, motors 80 and 82 are operated at the high speed setting to induce conditioned air into rooms 60 and 62.

As described hereinabove, rotation of the motors 80 and 82 at the high speed setting causes the pressure in the plenum 50 to decrease. To prevent the flow of air from the room 64 towards the plenum 50, motor 84 is operated at the low speed setting and in the reverse direction in the case where fan 78 is a centrifugal fan, to substantially prevent the flow of air into or out of room 64.

Additionally, controller 90 is operative to engage relays 126 and 127 so that the resistance of potentiometers 114 and 115 in parallel are sensed by potentiometer signal line 120. Control board 110 is operative to rotate outside fan motor 92 at a speed which is a function of the resistance of potentiometers 114 and 115 in parallel. Since the resistance of two potentiometers in parallel is lower than the resistance of a single potentiometer, the outside fan motor will rotate more rapidly to reject the increased heat gained by the evaporator 40 in order to cool rooms 60 and 62.

It will be appreciated by one skilled in the art that by matching the outside fan rotation speed to the thermal load on the air conditioning system, the electrical energy consumption by the air conditioner system may be reduced.

It will also be appreciated that if the motors 80, 82 and 84 are three speed motors, the highest rotation speed may be used for initially cooling a given room and an intermediate rotation speed used as the room temperature approaches the preferred temperature and the lowest speed setting used to substantially prevent the flow of conditioned air into the room as described hereinabove.

The highest speed of rotation is substantially equal to the maximum rated speed of the fan motors 80, 82 and 84. The intermediate rotation speed is preferably in the range 50% to about 95% and preferably about 75% of the maximum rated speed of the fan motors 80,82 and 84. The low speed of rotation is preferably in the range 10% to about 50% of the maximum rated speed of the motors 80, 82 and 84. It will also be appreciated that the speed of motors 80, 82 and 84 may be controlled in a continuous manner. In this case, the motors 80, 82 and 84 are capable of rotating at any speed, and the motor speed controllers 118 may be SCR type controllers or triacs as described hereinabove. The temperature controllers 91, 93 and 95 provide a signal to controller 90 via lines 41 which is proportional to the temperature in each room. Control board 110 is operative, using conventional closed loop feedback circuitry as is known in the art, to regulate the speed of the motors 80, 82 and 84 in a continuous manner so that the temperature in each room remains substantially constant.

It will further be appreciated that the low speed of rotation, the intermediate speed of rotation, and the high speed of rotation of the fan motors 80, 82 and 84 may be calibrated and set when the air conditioning system 10 has been installed.

It will also be appreciated that each of the temperature controllers 91, 93 and 95 may be set to different desired temperatures.

It will further be appreciated that the method of operation of air conditioning system 10 operating as a heat pump to provide heating to the rooms 60, 62 and 64, is substantially the same as followed during cooling.

It will further be appreciated that the calibration of the potentiometers 114, 115 and 116 is substantially the same for both cooling or heating operation of air conditioning system 10.

Reference is now made to Fig. 5 which is a simplified illustration of a central air conditioning system constructed and operative in accordance with a second preferred embodiment of the present invention. The air conditioning system 200 may be similar to that shown in Fig. 1, identical or equivalent elements being represented in Fig. 5 by the same reference numerals with the addition of the prefix 2.

The embodiment of Fig. 5 differs from the embodiment of Fig. 1 by the addition of a conventional changeover valve 236 in the refrigerant circuit. The changeover valve 236 allows the air conditioning system 200 to be used for either cooling rooms 260, 262 and 264 in 'Summer Operation' or heating rooms, 260, 262 and 264, in 'Winter Operation', as described in 'Thermodynamics' by J. E. Lay and referenced hereinabove.

Changeover valve 236 is electrically connected to controller 290 via changeover valve control line 253. Controller 290 is operative to set the changeover valve 236 in a 'summer setting' or a 'winter setting'. Reference is now made to Fig. 6 which is a simplified illustration of a circuit diagram of a controller useful in controlling the air conditioning system of Fig. 5. The controller 290 may be similar to that shown in Fig. 2, similar or equivalent elements being represented in Fig. 6 by similar reference numerals with the addition of the prefix 4.

The controller of Fig. 6 differs from the controller of Fig. 2 in that controller 290 includes a changeover relay 428. Control board 410 is electrically connected to changeover relay 428 via changeover signal line 435. Changeover relay 428 is in turn connected to changeover valve 236 by changeover valve control line 253.

For 'Summer Operation', control board 410 is operative to set changeover valve 236 to the 'summer setting' via signal line 435, relay 428 and control line 253. For 'Winter Operation', control board 410 is operative to set the changeover valve 236 to the 'winter setting'.

Reference is now made to Fig. 7A which illustrates part of the air conditioning system of Fig. 5 in which the air conditioning system is operative to provide cooled air for 'Summer Operation'.

For 'Summer Operation', the coolant flows from the high pressure outlet side 224 of compressor 220, through the changeover valve 236 which is disposed for operating in the 'summer setting'. The changeover valve directs the flow of refrigerant to the first heat exchanger 230, from whence the refrigerant flows to expansion valve 232. The refrigerant then returns to the low pressure side 222 of compressor 220 via the second heat exchanger 240, as shown by the flow arrows 231.

Reference is now made to Fig. 7B which illustrates part of the air conditioning system of Fig. 5 in which the air conditioning system is operative to provide heated air for 'Winter Operation'.

For 'Winter Operation', the coolant flows from the high pressure outlet side 224 of compressor 220, through the changeover valve 236 which is disposed for operating in the 'winter setting'. The changeover valve directs the flow of refrigerant from the high pressure outlet side 224 of compressor 220 to the second heat exchanger 240, from whence the refrigerant flows to expansion valve 232. The refrigerant then returns to the low pressure side 222 of compressor 220 via the first heat exchanger 230, as is shown by the flow arrows 231.

Reference is now made to Fig. 8 which is a simplified illustration of a central air conditioning system constructed and operative in accordance with a third preferred embodiment of the present invention. The air conditioning system 300 may be similar to that shown in Fig. 5, similar or equivalent elements being represented in Fig. 8 by similar reference numerals with the addition of the prefix 3.

The embodiment of Fig. 8 differs from the embodiment of Fig. 5 in that it includes a pressure sensor 325 in fluid contact with the low pressure side 322 of compressor 320. Pressure sensor 325 is operative to send a pressure signal to controller 390 via pressure signal line 359, the pressure signal being proportional to the refrigerant pressure at the inlet side 322 of the compressor 320. Pressure sensor 325 may be of the strain gauge type or any other suitable type.

Reference is now made to Fig. 9 which is a simplified illustration of a controller useful in controlling the air conditioning system of Fig. 8. The controller 390 of Fig. 9 includes a microprocessor control board 510 and allows automatically sensing the refrigerant pressure at the compressor inlet side 322, as described hereinbelow. The remaining elements of controller 390 may be similar to that shown in Fig. 6, similar or equivalent elements being represented in Fig. 9 by similar reference numerals with the addition of the prefix 5.

Control board 510 is also connected to pressure signal line 359.

Additionally, the controller 390 may also includes keypad 529. Keypad 529 may be used for inputting the required preferred coolant pressure at the low pressure side 322 of compressor 320. The controller 390 may also includes a digital display 526 which may be used for displaying the measured coolant pressure entering the compressor 320.

The preferred pressure Plow at the input side 322 of compressor 320 may be in the range of 50 psi to 75 psi and is preferably about 55 psi. The air conditioning system is generally supplied with a preferred value of Plow stored in the microprocessor control board 510. It will be appreciated that the preferred pressure Plow may be set to any desired value by the keypad 529 which may overwrite any prestored pressure value.

Operation of the air conditioning system 300 will now be described for 'summer operation'.

If the pressure of the refrigerant as measured by pressure sensor 325 is below Plow, control board 510 is operative to send a signal to the outside fan motor 392, via wire connections 347 and speed controller 524, to decrease the speed of the outside fan motor. Decreasing the speed of the fan reduces the amount of heat rejected by the first heat exchanger 330, thereby resulting in an increase in the refrigerant pressure at the inlet side 322 of compressor 320.

If the pressure of the refrigerant as measured by pressure sensor 325 is above Plow, control board 510 is operative to send a signal to the outside fan motor 392, via wire connections 347 and speed controller 524, to increase the speed of the outside fan motor. Increasing the speed of the fan increases the amount of heat rejected by the first heat exchanger 330, thereby resulting in a decrease in the refrigerant pressure at the inlet side 322 of compressor 320.

It will be appreciated that the controller 390 maintains the speed of outside fan motor 392 such that the refrigerant pressure at the inlet side 322 is maintained at a value which is substantially equal to Plow. Consequently, it is believed that the electrical energy consumption of the air conditioning system 300 is thereby minimized.

It is also believed that in the preferred embodiment the electrical energy consumption of air conditioning system 300 is minimized as the ambient conditions change and as the number of rooms being provided with conditioned air changes.

It is also believed that the electrical energy consumption of air conditioning system 300 is minimized for both 'summer operation' and 'winter operation'.

Reference is now made to Fig. 10 which is a simplified illustration of a central air conditioning system constructed and operative in accordance with yet another preferred embodiment of the present invention. The air conditioning system of Fig. 10 may be used as an air conditioning system for a multi-room complex such as a hotel. The air conditioning system 700 may be similar to that shown in Figs. 1, 5 and 8, similar or equiva¬ lent elements being represented in Fig. 10 by similar reference numerals with the prefix 7.

The embodiment of Fig. 10 differs from the embodiment of Figs. 1, 5 and 8 in that a group of rooms, including rooms 760 and 764, and a group of rooms including rooms 766 and 768 are connected to different air conditioning plenums 750 and 752 respectively, including the second heat exchangers 740 and 742, located respectively in plenums 750 and 752. The group of rooms, including rooms 760 and 764, are provided with conditioned air from plenum 750 and the group of rooms 766 and 768 are provided with conditioned air from plenum 752.

Alternatively, the plenums 750 and 752 may be placed downstream of the respective heat exchangers 740 and 742 and arranged to receive air from the heat exchangers after the air has passed therethrough. It is appreciated that the number of air conditioning plenums and connecting rooms, illustrated in Fig. 10, is not limiting but should be considered as example only. Any number of air conditioning plenums and connecting rooms may be connected to the air conditioning system 700 in the manner as shown in Fig. 10.

Reference is now made to Fig. 1 1 which is a simplified illustration of a central air conditioning system constructed and operative in accordance with still another preferred embodiment of the present invention. The air conditioning system 600 may be useful for installation in a confined space such as an attic. The air conditioning system 600 may be similar to that shown in Figs. 1, 5 and 8, similar or equivalent elements being represented in Fig. 10 by similar reference numerals with the prefix 6.

The embodiment of Fig. 11 differs from the embodiment of Figs. 1, 5 and 8 in that motors 680, 682 and 684, and fans 674, 676 and 678 are located at any convenient location along their respective air ducts 666, 668 and 670. This allows the plenum 650 to be of reduced size, thereby easing installation in a confined space.

Reference is now made to Fig. 12 which is a simplified illustration of a central air conditioning system constructed and operative in accordance with yet another preferred embodiment of the present invention. The air conditioning system of Fig. 12 may be similar to that shown in Fig. 11, identical or equivalent elements being represented in Fig. 12 by the same reference numerals with the prefix 8.

The embodiment of Fig. 12 differs from the embodiment of Fig. 11 by the addition of conventional resistance heating units indicated generally by 843, 845 and 847. The resistance heating units 843, 845 and 847 may be placed in proximity to and downstream of, the fans 874, 876 and 878 respectively. Alternately, the resistance heating units 843, 845 and 847 may be placed upstream of the fans 874, 876 and 878. The resistance heating units 843, 845 and 847, together with the motors 880, 882 and 884, respectively, are electrically connected to the controller 890 via fan control lines 851.

The embodiment of Fig. 12 also comprises an outside temperature sensor 897. The outside temperature sensor 897 may be located in any convenient location inside the case 889 which houses the first heat exchanger 830, compressor 887 and outside main fan 892. Alternatively, outside temperature sensor 897 may be located in any convenient location outside of the case 889. Outside temperature sensor 897 may be a thermistor or any other suitable temperature sensor known in the art. Outside temperature sensor 897 is operative lυ -.cπu an υui ue temperature signal suDSiamiaπy proportional 10 tne amDient temperature to controller 890 via temperature sensing wire 899.

Reference is now also made to Fig. 13 which is a simplified illustration of the resistance heating unit useful in the air conditioning system of Fig. 12. Resistance heating unit 843 comprises an electrical heating element 846 and an air flow sensor 844. Air flow sensor 844 may be placed in proximity to and downstream of the electrical heating element 846. Air flow sensor 844 may be a conventional anemometer or any other suitable flow sensing device. Air flow sensor 844 is operative to send a signal to the controller 890 via fan control lines 851 whenever the air flow drops below a predetermined level.

The electric heating element 846 may be any conventional resistive heating element or any other suitable heating unit and may comprise a number of separate heating coils for producing different amounts of heat in response to commands from the controller 890, as is well know in the art.

It will be appreciated that the resistance heating units 845 and 847 may be substantially the same as the heating unit 843. It will also be appreciated that resistance heating units need not be installed in all the ducts but only in those ducts which lead to rooms which have a tendency to be colder than the other rooms.

Operation of the resistance heating unit 843 in supplementing the heat supplied to room 860 will now be described by way of example, it being understood that operation of the heating units 845 and 847 is substantially similar to that of heating unit 843.

As is known in the art, the capacity of an air conditioning system operating as a heat pump decreases with decreasing temperature of the ambient air. Depending on the exact design details and the type of refrigerant used, the capacity of the heat pump begins to decrease when the ambient temperature falls below a typical value of about 7°C. When the ambient temperature falls below about 4°C, the capacity of the heat pump decreases substantially. This unavoidable effect causes complaints and service calls from users who believe that their heat pump is defective.

Upon receipt of the outside temperature signal from outside temperature sensor 897 that the ambient temperature has reached a value between 5°C and 9°C and preferably about 7°C controller 890 is operative to activate the resistance heating unit 843 via fan control line 851, thereby causing the heating element 846 to add a first amount of heat, typically between 1 and 3 kw but preferably about 2 kw to the air 887 flowing past the heating element 846, thereby supplementing the output of the heat pump.

Upon receipt of the outside temperature signal from the outside temperate sensor 897 that the ambient temperature has reached a value between about 2°C and about 5°C and preferably about 4°C, controller 890 is operative to activate the resistance heating unit 843 via connection cable 851, thereby causing the heating element 846 to add a second amount of heat, typically between 2 and 6 kw but preferably about 3 kw, to the air 887 flowing past the heating element 846.

It will be appreciated that the controller 890 may also be operative to cease operation of the compressor 887 and outside main fan 892 when the ambient temperature falls below about 2°C, thereby preventing the accumulation of ice on the first heat exchanger 830 and reducing the energy consumption of the air conditioning system 800. It will be appreciated that in this case, all of the heat added to the rooms will be generated by the resistance heating units.

It will also be appreciated that controller 890 may also be operative to activate resistance heating units 843, 845 and 847 when the air conditioning system 800 is first turned on, thereby increasing the thermal output of the air conditioning system until steady state temperature conditions are reached in one or more of the rooms 860, 862 or 864.

If the operation of the motor 880 or fan 874 is in any way defective, air flow sensor 844 is operative to send an air flow signal to controller 890 via fan control line 851 to cease operation of the heating element 846, thereby preventing possible damage caused by excessive temperature of the heating element 846. It will be appreciated that air flow sensor 844 may be replaced by a conventional temperature switch which is operative to cease operation of the heating element 846 if the temperature of the heating element 846 is excessive.

It will also be appreciated that the resistance heating units 843, 845 and 847 may be used in the embodiments of Figs. 1, 5, 8 and 10 as well as the embodiments described hereinbelow..

It will also be appreciated that the resistance heating units 843, 845 and 847 may be placed in any location in the ducts 866, 868 and 870, respectively.

Reference is now made to Fig. 14 which is a simplified illustration of a central air conditioning system constructed and operative in accordance with still another preferred embodiment of the present invention. The air conditioning system 900 of Fig. 14 may be similar to that shown in Fig. 12, identical or equivalent elements being represented in Fig. 14 by the prefix 9.

The embodiment of Fig. 14 differs from the embodiment of Fig. 12 in that the pressure sensor 825 is replaced by a first pressure switch 933 and a second pressure switch 934. The first pressure switch 933 and the second pressure switch 934 may be conventional pressure switches such as the Danfoss PK 15, manufactured by the Danfoss Corp. of Denmark, or any other suitable pressure switch.

The embodiment if Fig. 14 also comprises an outside fan controller 948, which may be located in any convenient location within the case 989. Alternatively, outside fan controller 948 may be placed in any convenient location outside the case 989, and may be incoφorated in to the controller 990. Outside fan controller 948 may comprise a conventional suitably program microcomputer. Alternatively, outside fan controller 948 may comprise any suitable electronic or electrical controller.

Outside fan controller 948 is operative to regulate the speed of outside fan motor 992 in response to signals from the first and second pressure switches, as will be described hereinbelow.

Reference is now also made to Fig. 15 which shows a portion of the air conditioning system of Fig. 14 in more detail. As may be seen in Fig. 15, first pressure switch 933 is in refrigerant fluid communication, via a first pressure switch connecting line 937, with a refrigerant line 938. Refrigerant line 938 provides refrigerant fluid connection between the changeover valve 936 and the second heat exchanger 940. The first pressure switch 933 is electrically connected to outside fan controller 948 via a first pressure switch connecting wire 945. The outside fan controller 948 is connected in turn to the outside fan motor 992 via outside fan control wire 949.

The first pressure switch 933 is adjusted so that the electrical contact associated with the pressure switch closes when the refrigerant pressure in first pressure switch connecting line 937 reaches a value of PSumHi . The first pressure switch 933 is also adjusted so that the electrical contact associated with the pressure switch opens when the refrigerant pressure in the first refrigerant pressure line 937 falls below PSumLo. The value of PSumHi may be in the range of about 55 psi to about 75 psi and is preferably about 62 psi. The value of PSumLo may be in the range of about 45 psi to about 54 psi and is preferably about 52 psi. The second pressure switch 934 is in fluid communication, via a second pressure switch connecting line 935, with refrigerant line 938. The second pressure switch 934 is electrically connected to outside fan controller 948 via a second pressure switch connecting wire 947.

The second pressure switch 934 is adjusted so that the electrical contact associated with the pressure switch closes when the refrigerant pressure in the second pressure switch connecting line 935 reaches a value of PWinHi . The second pressure switch 934 is also adjusted so that the electrical contact associated with the pressure switch opens when the refrigerant pressure in the second refrigerant pressure connecting line 935 falls below PWinLo. The value of PWinHi may be in the range of about 320 psi to about 400 psi and is preferably about 350 psi. The value of PWinLo may be in the range of about 250 to about 319 psi and is preferably about 300 psi.

Operation of the outside fan controller 948 in controlling operation of the outside fan motor 992 is now described for 'summer operation'. As described hereinabove with reference to Fig. 7A, for 'summer operation', the changeover valve 936 is operative to direct the flow of refrigerant from the compressor 920 to the first heat exchanger 930. It will be apparent that for 'summer operation', the first pressure switch 933 is in refrigerant fluid communication with the low pressure side of the compressor 920.

Referring now to Fig. 16A, at step 1010, the condition of the electrical contact of the first pressure switch 933 is determined. It will be appreciated that the outside fan controller 948 is operative to carry out the step 1010 after an initial starting period when the air conditioning system 900 has first been turned on. The duration of the starting period is in the range of about 5 minutes and about 30 minutes and is preferably about 10 minutes.

At step 1012, the outside fan controller 948 is operative to perform a boolean logic function, depending on the status of the first pressure switch 933.

If the pressure switch 933 is not activated, then the pressure at the low pressure side of the compressor 920 is below PSumLo. It will be apparent to one skilled in the art that the outside main fan 999 is removing more heat from the first heat exchanger 930 than the total thermal load of the rooms 960, 962 and 964.

At step 1016, the outside fan controller 948 is operative to reduce the speed of the outside fan motor 992 to a speed in the range of 30% and 70% of the maximum rated speed of the outside fan motor 992 and preferably about 50% of the maximum rated speed of the outside fan motor 992. After setting the speed of the outside fan motor 992, the outside fan controller 948 returns to step 1010 to again read the status of the first pressure switch 933.

If the pressure switch 933 is activated, then the pressure at the low pressure side of the compressor 920 is higher than PSumHi. It will be apparent to one skilled in the art that the outside main fan 999 is removing less heat from the first heat exchanger 930 than the total thermal load of the rooms 960, 962 and 964.

At step 1014, the outside fan controller 948 is operative to increase the speed of the outside fan motor 992 to about 100% of the maximum rated speed of the outside fan motor 992.. After setting the speed of the outside main fan 992, the outside fan controller 948 returns to step 1010 to again read the status of the first pressure switch 933.

It will be apparent therefore that for 'summer operation', the speed of the outside fan motor 992 will vary between about 50% of its maximum rated speed and 100% of its maximum rated speed while refrigerant pressure at the inlet of the compressor 920 will oscillate between PSumLo and PSumHi. It will also be apparent that as the thermal load of the rooms 960, 962 and 964 increases, the length of time that the speed of the outside fan motor 992 is at about 100% of its rated speed increases. It will also be apparent that as the thermal load of the rooms 960, 962 and 964 decreases, the length of time that the speed of the outside fan motor 992 is at about 50% of its rated speed increases.

It is believed that the outside fan controller 948 adjusts the thermal output of the compressor 920, in accordance with the thermal load of the rooms 960, 962 and 964 and the temperature of the ambient air, thereby optimizing the energy consumption of the air conditioning system 900 for 'summer operation'.

Operation of the outside fan controller 948 in controlling operation of the outside fan motor 992 is now described for 'winter operation'. As described hereinabove with reference to Fig. 7B, for 'winter operation', the changeover valve 936 is operative to direct the flow of refrigerant from the compressor 920 to the second heat exchanger 940 and thence via the expansion valve 932 to the first heat exchanger 930. It will be apparent that for 'winter operation', the second pressure switch 934 is in refrigerant fluid communication with the high pressure side of the compressor 920.

Referring now to Fig. 16B, at step 1020, the condition of the electrical contact of the second pressure switch 934 is determined. It will be appreciated that the outside fan controller 948 is operative to carry out the step 1020 after an initial starting period when the air conditioning system 900 has first been turned on. The duration of the starting period is in the range of about 5 minutes and about 30 minutes and is preferably about 10 minutes.

At step 1022, the outside fan controller 948 is operative to perform a boolean logic function, depending on the status of the second pressure switch 934.

If the second pressure switch 934 is not activated, then the pressure at the high pressure side of the compressor 920 is below PWinLo. It will be apparent to one skilled in the art that the outside main fan 999 is removing less heat from the first heat exchanger 930 than the total thermal load of the rooms 960, 962 and 964.

At step 1026, the outside fan controller 948 is operative to increase the speed of the outside fan motor 992 to about 100% of the maximum rated speed of the outside fan motor 992. After setting the speed of the outside fan motor 992, the outside fan controller 948 returns to step 1010 to again read the status of the first pressure switch 933.

If the pressure switch 933 is activated, then the pressure at the high pressure side of the compressor 920 is higher than PSumHi. It will be apparent to one skilled in the art that the outside main fan 999 is removing more heat from the first heat exchanger 930 than the total thermal load of the rooms 960, 962 and 964.

At step 1024, the outside fan controller 948 is operative to reduce the speed of the outside fan motor 992 the outside fan motor 992 to a speed in the range of 30% and 70% of the maximum rated speed of the outside fan motor 992 and preferably about 50% of the maximum rated speed of the outside fan motor 992. After setting the speed of the outside main fan 992, the outside fan controller 948 returns to step 1020 to again read the status of the second pressure switch 934.

It will be apparent therefore that for 'winter operation', the speed of the outside fan motor 992 will vary between about 50% of its maximum rated speed and 100% of its maximum rated speed while refrigerant pressure at the outlet of the compressor 920 will oscillate between PWinLo and PWinHi. It will also be apparent that as the thermal load of the rooms 960, 962 and 964 increases, the length of time that the speed of the outside fan motor 992 is at about 100% of its rated speed increases. It will also be apparent that as the thermal load of the rooms 960, 962 and 964 decreases, the length of time that the speed of the outside fan motor 992 is at about 50% of its rated speed increases.

It is believed that the outside fan controller 948 adjusts the thermal output of the compressor 920, in accordance with the thermal load of the rooms 960, 962 and 964 and the temperature of the ambient air, thereby optimizing the energy consumption of the air conditioning system 900 for 'winter operation'.

Reference is now made to Fig. 17 which is a simplified illustration of a central air conditioning system constructed and operative in accordance with still another preferred embodiment of the present invention. The air conditioning system 1100 of Fig. 17 may be similar to that shown in Fig. 14, identical or equivalent elements being represented in Fig. 17 by the prefix 11.

The air conditioning system of Fig. 17 differs from the system of Fig. 14 in that the air conditioning system of Fig. 17 also comprises an air purifier 1171 and a filter 1175. Air purifier 1171 may be a conventional ozonator such as that manufactured by Ecozone Technologies Ltd., P.O.B. 5552 of Herzliya, Israel. Alternately, air purifier 1171 may be any suitable air purifier. The filter 1175 may be a conventional charcoal filter or any other suitable filter. Ozonator 1171 also comprises an ozonator power supply (not shown) for generating the necessary high voltage required for producing ozone. Ozonator 1171 and its associated power supply are operative to produce ozone when air flows past the ozonator 1171.

Reference is now also made to Fig. 18 which shows a portion of the air conditioning system of Fig. 17 in more detail. As seen in Fig. 18, the plenum 1150 comprises an inlet region 1210, an outlet 1216 and an intermediate region 1214. The ozonator 1171 is preferably disposed in the inlet region 1210 and is arranged to receive at least part the air stream 1 173 flowing through second heat exchanger 1140 and into the intermediate region 1214. The filter 1175 surrounds the intermediate region 1214 and substantially separates the intermediate region 1214 from the outlet region 1216.

The temperature controller 1191 preferably comprises a switch (not shown) which is operative to send an ozone activating signal to controller 1990 via connecting cable 1141. The controller 1990 in turn is connected to the ozonator 1171 via ozonator connecting cable 1149. Upon receipt of the ozonator activating signal from temperature controller 1191, the controller 1990 is operative to activate the ozonator power supply, thereby converting some of the oxygen in the air flowing past the ozonator 1171 into ozone.

Operation of the ozonator 1171 is now described- Outside air 1173, which may be mixed with return air flow 1165 from room 1160 and with return air flow 1169 from room 1164 in an inlet mixing region 1212, flows through the second heat exchanger 1140 and is conditioned thereby. The air stream 1173 then passes through the ozonator 1171 and a portion of the oxygen in the air stream 1173 is converted into ozone. It will be apparent to one skilled in the art that the ozone substantially purifies and removes odor from the air stream 1173.

The now purified air stream 1173 thereupon flows into the intermediate region 1214 of the plenum 1150 and thence through the filter 1175. Filter 1175, which as described hereinabove substantially separates the intermediate region 1214 from the outlet region 1216, is operative to remove substantially all of the ozone from the air stream 1173.

The air stream 1 173 is now distributed to the various rooms from the outlet region 1216 to the various rooms via ducts 1166, 1168 and 1170.

Reference is now made to Fig. 19 which is a simplified illustration of another embodiment of the ozonator of Fig. 18. The embodiment of Fig. 19 may be similar to that shown in Fig. 18, identical or equivalent elements being represented in Fig. 19 by the prefix 13.

The embodiment of Fig. 19 differs from the embodiment of Fig. 18 in that the ozonator 1371 is disposed upstream of the second heat exchanger 1340. Outside air 1373, which may be mixed with return air flow 1365 from room 1160 and with return air flow 1356 from room 1164 in an inlet mixing region 1314, flows through ozonator 1371. The now substantially purified and deodorized air stream 1373 then passes through the filter 1375 which substantially removes residual ozone.

The air stream 1373 thereupon passes through the second heat exchanger 1340 and is distributed to the rooms via the ducts 1366, 1368 and 1370.

It is believed that the air purifier may reduce they need for outside air, thereby reducing the total energy requirement of the air conditioning system 1100.

It will further be appreciated by one skilled in the art that various combinations of features as described hereinabove with reference to the central air conditioning systems as described hereinabove with reference to Figs. 1, 5, 8,10, 11, 12, 14, 16 and 17 may be realized.

Reference is now made to Fig. 20 which is a simplified illustration of a decorative room heat exchanger 1400 constructed and operative in accordance with a preferred embodiment of the present invention.

As shown in Fig. 20, a cavity 1402 is formed along an upper surface 1404 of the room heat exchanger 1400. Cavity 1402 is arranged to receive a decorative element 1406 such as a plant. Alternatively, the decorative element 1406 may be placed on the upper surface 1404 of room heat exchanger 1400.

Room heat exchanger 1400 also comprises a cover unit 1410 removably attached to at least one of the sides 1412 of the room heat exchanger 1400.

Room heat exchanger 1400 also may also comprise refrigerant supply lines 1415 operative to provide refrigerant fluid from a conventional external unit of an air conditioning system (not shown). Room heat exchanger 1400 may also be provided with an electrical power supply (not shown).

Room heat exchanger 1400 may also comprise a plurality of wheels (not shown) arranged along a bottom surface 1420 of the room heat exchanger 1400 for easy portability to any desired location of a room 1401.

Reference is now made to Fig. 21 which is a partially exploded view of the room heat exchanger 1400 of Fig. 20.

As shown in Fig. 21, the cover unit 1410 may also comprise a decorative cover 1430 operative to allow substantially unhindered passage of an entering air flow 1432.

The room heat exchanger 1400 also comprises a plurality of heat exchange coils 1434 in refrigerant fluid communication with the refrigerant supply lines 1415. The heat exchange coils 1434 may be attached to the side 1412 of room heat exchanger 1400. The heat exchange coils 1434 may also comprise a plurality of fins (not shown) as is known in the art..

A conventional filter (not shown) may be disposed between the decorative cover 1430 and the heat exchange coils 1434.

A plurality of fans 1436 may be disposed in proximity to and substantially parallel to a top edge 1439 of the room heat exchanger 1400. A plurality of fans 1438 may also be disposed in proximity to and substantially parallel to a bottom edge 1440 of the room heat exchanger 1400. The fans 1436 and 1438 may be conventional fans such as those used for cooling computer or electronic circuitry. Al; amatively, fans 1436 and 1438 may be any other suitable fans.

The cover unit 1410 may also comprise a plurality of air flow directing vanes 1414 downstream of the fans 1436. The air flow directing vanes 1414 may be adjacent and substantially parallel to the top edge 1439. The air flow directing vanes 1414 are operative to direct an exiting flow of conditioned air 1416 into the room 1401. The cover unit 1410 may also comprise a plurality of air flow directing vanes 1415 downstream of the fans 1438. The air flow directing vanes 1415 may be adjacent and substantially parallel to the bottom 1440. The air flow directing vanes 1415 are operative to direct an exiting flow of conditioned air 1417 into the room 1401.

It will be appreciated that a plurality of fans and air flow directing vanes may also be disposed in proximity to and substantially parallel with vertical edges 1440 and 1442 of room heat exchanger 1400.

Operation of the room heat exchanger 1400 is now described.

The fans 1436 and 1438 are operative, in response to commands from a controller (not shown), to draw the incoming air flow 1432 through the decorative cover 1430. The incoming air flow 1432 then passes over the heat exchange coils 1434 and is conditioned thereby. The now conditioned air flow emerges through the air flow directing vanes 1414 and 1415 to provide the exit flow of conditioned air 1416 and 1417 to the room 1401.

It will be appreciated that additional cover units 1410 and heat exchange coils 1434 may be disposed along the other sides of the room heat exchanger 1400 to increase the thermal capacity of the room heat exchanger 1400.

It will also be appreciated that the plurality of fans 1436 and 1438 may be operative to direct the flow of exiting air outward though the decorative cover 1430. In this case, the direction of the arrows 1416, 1417 and 1432 are reversed.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the invention is defined only by the claims which follow:

Claims

1 A multi-room air conditioning system comprising: a controller; a compressor; a first heat exchanger in refrigerant fluid communication with said compressor; a second heat exchanger in refrigerant fluid communication respectively with said first heat exchanger and said compressor, said second heat exchanger also being in heat exchange communication with a stream of air; a plenum arranged to receive said stream of air downstream of said second heat exchanger; a plurality of air flow ducts for distributing said stream of air from said plenum to a plurality of rooms; a plurality of fans, each fan associated with one of said plurality of air flow ducts; a plurality of motors, each motor drivingly associated with one of said plurality of fans; at least one temperature controller located in at least one of said plurality of rooms; and wherein said controller is operative to selectively control a speed of rotation of at least one of said plurality of motors at least partially in response to a signal from said at least one temperature controller

2. A multi-room central air conditioning system according to claim 1 and wherein said speed of rotation comprises a low speed of rotation, said low speed of rotation substantially preventing a flow of air into at least one of said plurality of rooms.

3. A multi-room central air conditioning system according to claim 1 wherein at least one of said plurality of fans is a centrifugal fan and wherein said speed of rotation comprises a reverse speed of rotation, said reverse speed of rotation substantially preventing a flow of air into at least one of saiα plurality of rooms.

4. A multi-room air conditioning system according to claim 3 and wherein said reverse speed of rotation comprises a speed in the range between about 10% and about 40% of a maximum speed of rotation of said motor.

5. A multi-room air conditioning system according to claim 2 and wherein said speed of rotation also comprises an intermediate speed of rotation, said intermediate speed of rotation operative to maintain a substantially constant supply of conditioned air to at least one of said plurality of rooms.

6. A multi-room air conditioning system according to claim 5 and wherein said speed of rotation also comprises a high speed of rotation, said high speed of rotation operative to supply a large amount of air to at least one of said plurality of rooms for rapid heating during a winter operation and rapid cool down during a summer operation.

7. A multi-room air conditioning system according to claim 1 wherein said first heat exchanger is in heat exchange communication with a flow of outside air and also comprising: a variable speed outside motor drivingly associated with an outside main fan and wherein said outside main fan is arranged to direct said flow of outside air through said first heat exchanger; a pressure sensor in refrigerant fluid communication with a low pressure side of said compressor and wherein; said outside motor is regulated at least partially in response to a pressure signal from said pressure sensor.

8. A multi-room air conditioning system according to claim 7 and wherein said pressure sensor is operative to send said pressure signal when a pressure in said low pressure side of said compressor is in the range of about 50 psi and about 70 psi.

9. A multi-room air conditioning system according to claim 8 and wherein said pressure sensor is operative to send said pressure signal when the pressure in said high pressure side of said compressor is in the range of about 300 psi and about 400 psi.

10. A multi-room air conditioning system according to claim 7 and wherein said pressure sensor comprises at least one pressure switch.

11.. A multi-room air conditioning system comprising: a compressor; a first heat exchanger in refrigerant fluid communication with said compressor; a plurality of second heat exchangers each in refrigerant fluid communication respectively with said first heat exchanger and said compressor, said plurality of second heat exchangers also being in heat exchange communication with a plurality of streams of air to be conditioned; a plurality of plenums each arranged to receive each of said plurality of streams of air downstream of said second heat exchangers; a plurality of air flow ducts associated with at least one of said plenums for distributing said streams of air from said at least one plenums to a plurality of rooms; a plurality of fans, each fan associated with one of said plurality of air flow ducts; a plurality of motors, each motor drivingly associated with one of said plurality of fans; at least one temperature controller located in at least one of said plurality of rooms; and a control system operative to selectively control a speed of rotation of at least one of said plurality of motors at least partially in response to a signal from said at least one temperature controller.

12. A multi-room air conditioning system according to claim 1 and also comprising a heating unit in at least one of said plurality of air flow ducts, said heating unit operative to supplement the thermal output of said air conditioning system at least partially in response to a temperature signal from said at least one temperature controller.

13. A multi-room air conditioning system according to claim 1 and also comprising an air purifier, said air purifier operative to substantially purify said stream of air.

14. A multi-room air conditioning system according to claim 13 and wherein said air purifier is disposed in said plenum.

15. A multi-room air conditioning system according to claim 13 and wherein said air purifier is disposed upstream of said second heat exchanger.

16. A multi-room air conditioning system according to claim 13 and wherein said air purifier comprises an ozone generator.

17. A room heat exchanger for providing conditioned air to a room, said room heat exchanger comprising: at least one heat exchange coil; at least one fan; and wherein said room heat exchanger is formed with a cavity in a top surface of said room heat exchanger, said cavity arranged for receiving a decorative item.