Air Conditioning Apparatus

Abstract

Apparatus for supplying treated air to an enclosure, including heat exchanger through which a heat exchange medium flows and a fan arranged to route air to be treated over the heat exchanger in heat transfer relation with the medium. The temperature of the air in the enclosure is sensed and the area of the outlet provided for discharging the treated air into the enclosure is modulated in response to the temperature of the enclosure. A variable control signal, the magnitude thereof being related to the area of the outlet, is generated and is supplied to a control operable to vary the speed of the fan motor to maintain a substantially constant static pressure in the air passage regardless of the area of the outlet, to maintain a substantially constant discharge velocity.

Description

BACKGROUND OF THE INVENTION

This invention relates to air conditioning apparatus and more particularly to an arrangement for controlling the discharge of treated air from said apparatus.

Air conditioning apparatus of the type employing a heat exchange coil to circulate a heat exchange medium therethrough, for example, chilled or warmed water, and having a fan for bringing air to be conditioned into heat exchange relation with the medium flowing through the coil are well known and widely employed by those skilled in the air conditioning art. Such apparatus are generally referred to as fan coil units.

Fan coil units are employed with central station cooling and heating machinery for conditioning multi-room buildings, such as motels, hotels, and apartments. Such apparatus afford a relatively effective means for simultaneously conditioning a plurality of areas in a common enclosure, while providing individual control by the occupants of each area. In addition, fan coil units are relatively simple to install and to maintain in operating condition and are relatively inexpensive, making such units particularly suitable for low-cost multiple dwelling housing. However, some problems have been encountered which reduce the overall efficiency and effectiveness of their operation.

For example, the on-off cycling of the typical fan coil unit creates annoying sound variances. In addition, an on-off type of control does not provide uniform air distribution. Particularly, temperature variations of a considerable magnitude above and below the room setpoint may be produced in portions of the room, the variations being caused by stratification of the air during the off cycle.

To overcome these problems, a variable speed control for the fan motor, to modulate the discharge of conditioned air from the apparatus, has been considered.

The variable fan speed control obviates the noise problem by continuously operating the fan at the lowest speed consistent with the cooling or heating load thereon.

However, at low fan speeds, problems have resulted due to the low velocity of the conditioned air being discharged into the conditioned space, particularly when the air is at a relatively cold temperature. Such low velocity causes the air stream to lose momentum, resulting in the relatively cold air spilling into the room, rather than following a trajectory above the occupied space until mixing is complete, thus causing discomfort to the occupants by producing wide variations in temperature across the room and from floor to head level.

Furthermore, it has been determined that a more efficient control of the humidity level, when the apparatus is operating on cooling mode, may be obtained by continuously operating the fan rather than employing an on-off cycle of fan operation, or modulating the cold water flow to the heat exchange coil, as heretofore has been the practice.

The object of this invention is an improved air conditioning apparatus employing a novel arrangement for controlling the flow of treated air to the enclosure which is compatible with a variable speed control for the fan motor.

SUMMARY OF THE INVENTION

This invention relates to an air conditioning apparatus and, more particularly, to an improved arrangement for controlling the flow of treated air from such apparatus.

The apparatus includes a heat exchanger adapted to receive a heat exchange medium, such as chilled or warm water, which may be treated at a central station or other remote location A fan is operable to route air to be treated over said heat exchange coil in heat transfer relationship with the medium flowing therethrough. The treated air from the heat exchange medium is passed to one or more outlets. The air passes from the heat exchange coil to the outlet via an air passage.

A temperature sensing element is installed in the area being treated and is operable to generate a control signal, the magnitude thereof being related to the sensed temperature of the treated area. The signal is supplied to means for regulating the discharge area of the outlet; the area of the outlet is varied as a function of the magnitude of the control signal.

Means responsive to the area of the outlet generate a second control signal which is a function thereof and supplies the signal to means operable to vary the speed of said motor. The speed of the fan motor is modulated in response to the discharge area of the outlet to maintain a substantially constant static pressure in the air passage to thus maintain a substantially constant discharge velocity for the treated air being supplied to the enclosure, irrespective of the area of the outlet, and thus irrespective of the quantity of air being discharged into the enclosure.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view of a fan coil unit of the type described equipped with a control circuit illustrating the invention; and

FIG. 2 is a schematic diagram illustrating the circuit used to convert conventional AC voltage to DC voltage to provide a source of power for the circuit illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawing, there is shown a preferred embodiment of air conditioning apparatus including the invention disclosed herein.

Reference numeral 10 indicates an area in an enclosure which is to be treated by having air at a predetermined temperature discharged therein. Although it is within the scope of the invention to have only one such area or room being conditioned, it should be understood several rooms, each employing apparatus embodying the subject of this invention, may be conditioned simultaneously.

The illustrated embodiment includes air conditioning apparatus 12. Apparatus 12 includes a heat exchange coil 13 to which a heat exchange medium, such as cold or warm water, is supplied via conduit 14. The heat exchange medium is supplied at a predetermined temperature which is regulated by central station refrigeration machinery (not shown). The heat exchange medium is returned to the central station machinery via conduit 15. Fan 16 operatively connected to a motor, routes ambient air over the heat exchange coil in heat transfer relation therewith. The ambient air is treated by passing in heat transfer relation with the heat exchange medium flowing through the coil.

The air conditioning apparatus 12 is mounted in a structure 17 which defines an air passage through which the treated air is supplied to at least one outlet 18 for delivery to the room or enclosure being treated. Damper 19 regulates the passage of air to the enclosure from outlet 18. The manner in which damper 19 is controlled in accordance with the invention disclosed herein shall be more fully explained hereinafter.

As noted hereinbefore, it is desirable to regulate the quantity of treated air being supplied to the enclosure in accordance with the load requirements thereof. By regulating the position of damper 19 to vary the discharge area from outlet 18, it is possible to modulate the supply of treated air as is desired by varying the speed of fan 16, thereby eliminating the prior art difficulties noted hereinbefore.

The novel arrangement herein disclosed operates to maintain the velocity of the treated air discharged into the enclosure substantially constant regardless of the quantity of air being supplied. Any desirable velocity level, within the capability of the fan, may be selected, either by adjustment or design, to be compatible with the requirements of the space.

The control circuit provided for obtaining the desirable features hereinbefore described is merely illustrative, and other control schemes that might perform a similar function may be employed in lieu thereof.

The control circuit includes a voltage transformer operable to reduce the line voltage represented by lines L.sub.1 and L.sub.2 to a smaller voltage for control purposes. The voltage transformer includes a primary winding 20 and a secondary winding 21. Preferably, the current flowing through lines L.sub.1 and L.sub.2 is 60 cycle alternating current. Since the control circuit, to be more fully explained herein, utilizes solid state components operable on direct current, a full wave diode rectifier circuit 22 is provided as a source of DC voltage, the DC voltage source being represented by +E.sub.s and -E.sub.s. Resistors 66 and 67 and capacitors 68 and 69 are provided to filter the DC voltage signal.

Thermostat elements 23 and 24 are connected in series with the source of DC voltage. Element 24 is preferably a variable resistance element, such as a potentiometer, that may be selectively regulated by the occupant to obtain a desired temperature in the enclosure. Element 23 is preferably a NTC thermistor positioned to sense the temperature of the air in the enclosure. Elements 23 and 24 operate in combination to provide a variable voltage signal. When the temperature of the enclosure is above the setpoint established by thermal element 24, the voltage signal is of a relatively large magnitude and of a positive polarity, whereas when the temperature is below the setpoint, the voltage signal is of a relatively large magnitude and of a negative polarity.

The voltage signal from elements 23 and 24 is supplied to a first input of operational amplifier 26 through resistor 25. The manner in which operational amplifier 26 functions shall be more fully explained hereinafter. Operational amplifier 26 also has supplied thereto a +E.sub.s voltage through line 70 and a -E.sub.s voltage through line 71.

Connected to the output of the operational amplifier is a first diode 27 and a second diode 28. Diode 28 permits only passage of a negative voltage signal whereas diode 27 only permits passage of a positive voltage signal.

Connected in series with diode 27 is relay coil 32, the energization thereof operating to close normally open switch 33. Connected in series with diode 28 is relay coil 30, the energization thereof operating to close normally open switch 31.

Connected to the output from either switch 31 or switch 33 is double-pole, double throw switch 34. Switch 34 includes a first arm 39 which selectively connects either terminal 37 or terminal 38 in the circuit. Terminal 37 is connected into the circuit when the apparatus is providing relatively cold air, whereas terminal 38 is connected in the circuit when the apparatus is providing relatively warm air. Switch 34 also includes arm 40 which selectively places either terminal 35 or terminal 36 into the circuit. Terminal 35 is placed in the circuit when the apparatus is providing relatively cold air, and terminal 36 is placed in the circuit when the apparatus is providing relatively warm air.

Switch 34 may be controlled manually or may be operated automatically by means such as a bimetal switch which would be placed in heat transfer relation with the heat exchange medium flowing to heat exchange coil 13.

Connected in series with switch 34 are windings 41 and 42 of a reversible motor 43, connected to the source of alternating current as represented by lines L.sub.1 and L.sub.2. The energization of winding 41, prior to the energization of winding 42, will actuate the motor so that the damper will rotate in a counterclockwise direction so that the discharge area of outlet 18 is increased.

Conversely, the energization of winding 42, prior to the energization of winding 41, will actuate motor 43 so that damper 19 will rotate in a clockwise direction to decrease the discharge area from outlet 18. Motor 43 is operatively connected to damper 19 via shaft 44. Capacitor 65 is included between windings 41 and 42 to establish the necessary phase displacement therebetween.

Operatively connected to shaft 44 is shaft 47. Shaft 47 has movably connected thereto wiper 46 of potentiometer 45. The rotation of shaft 44 so as to decrease the area of discharge outlet 18 will rotate wiper 46 in a clockwise direction, whereas rotation of shaft 44 so as to increase the area of discharge outlet 18 will rotate wiper 46 in a counterclockwise direction.

Connected in series with potentiometer 45 is a second double-pole, double throw switch 50. Switch 50 includes arm 51 and arm 52. As shown by the solid line, arms 51 and 52 are positioned for cooling mode operation. As shown by the dotted lines of the Figure, arms 51 and 52 are positioned for heating mode operation. The operation of switch 50 may be manually or automatically regulated.

Connected in series with switch 50 and potentiometer 45 are fixed resistors 48 and 49. Lines 76 and 77 are connected to the source of rectified DC voltage so as to bring the supply voltage to potentiometer 45.

Depending upon the mode of operation and the position of wiper 46 as controlled by the position of damper 19, either a positive polarity or a negative polarity voltage signal, the signal being proportional to the position of the damper, will be supplied via line 72, and resistor 54, to a second input of operational amplifier 26.

The operational amplifier compares he voltage signal regulated by potentiometer 45 to the voltage signal regulated by thermal elements 23 and 24, to operate motor 43 so that the position of damper 19 is modulated in response to the temperature of the enclosure.

Connected to rotate with shaft 44 is wiper 59 of a second potentiometer 58. One portion of the potentiometer is connected to receive line current as represented by line L.sub.1. The second portion of the potentiometer is connected to the junction between capacitor 57 and the gate of a trigger diode 55 sold under the trademark "Diac." Capacitor 57 is connected to the other side of the source of alternating current represented by L.sub.2. Connected to the output terminal from diode 55 is the gate 56 ' of a solid state bi-directional gated switch 56 of a type sold under the trademark "Triac."

Switch 56 is triggered to a conducting state by either a positive or a negative pulse being applied to gate 56'. Switch 56 should be sufficiently fast in operating so it may be switched on during any desired portion of each half cycle of alternating current supplied to the motor driving fan 16, to arrive at a desired average power. The motor speed and the fan speed are thus varied in accordance with the capacity demand of the room served by the system.

As shall be more fully explained hereinafter, the position of wiper 59 will determine the period of time during the half-cycle of alternating current flow during which current will pass through diode 55 and switch 56 to the motor operating fan 16. By proper regulation of the voltage passing to the motor, the speed thereof may be regulated to obtain the desired air flow of treated air in proportion to the temperature of the enclosure.

To better understand the manner in which the control circuit operates in accordance with the invention, assume that cooling mode operation is desired and that the temperature of the enclosure is above the setpoint.

The magnitude of the variable voltage control signal controlled by thermal elements 23 and 24 will be sufficient to cause operational amplifier 26 to pass a positive polarity voltage signal from line 70 to line 29.

The +E.sub.s voltage signal will pass through diode 27 and energize coil 32, thereby closing switch 33.

Upon closure of switch 33, line voltage represented by L.sub.1 and L.sub.2 will pass through arm 39 of double-pole, double throw switch 34 which is in contact with terminal 37, to first energize coil 41 of motor 43. The motor will thus be actuated to turn shaft 44 in a counterclockwise direction to open damper 19.

As damper 19 moves in a counterclockwise direction, wiper 46 of potentiometer 45 simultaneously moves in the same direction, the position thereof being related to the position of the damper. Double-pole, double throw switch 50 is set for cooling mode operation. Therefore, arm 52 is in a position in which the +E.sub.s control signal will pass through resistor 49 and wiper 46 to line 72, the magnitude of the signal being proportional to the position of the damper. When the position of the damper has reached an equilibrium point in relation to the temperature of the enclosure, the magnitude of the control signal in line 72, as determined by the position of wiper 46, will be equal to the magnitude of the variable voltage control signal regulated by thermal elements 23 and 24 and will thus place operational amplifier 26 in a nonconducting state, turning off motor 43.

Simultaneously, with the rotation of shaft 44 in a counterclockwise direction, wiper 59 of potentiometer 58 moves in a counterclockwise direction, thereby reducing the resistance presented by potentiometer 58.

By increasing the voltage flow, the rate at which capacitor 57 is charged is increased. When capacitor 57 is charged to a predetermined value, the trigger diode 55 will be placed in its conducting state, thereby passing a pulse to gate 56' of switch 56. When switch 56 is placed in its conducting state, current will flow to the motor driving fan 16 at an increased rate to increase the speed thereof.

Thus, it is apparent that as the position of the damper is moved in a counterclockwise direction to increase the area of the discharge opening 18, the speed of the fan has increased to increase the quantity of air being discharged into the enclosure.

If the temperature of the enclosure has fallen below the setpoint during cooling mode operation, the magnitude of the variable voltage control signal supplied to operational amplifier 26 will be such that a negative polarity control signal will pass from line 71 to line 29.

The -E.sub.s control signal will pass through diode 28, thereby energizing relay coil 30, thus closing switch 31.

When switch 31 closes, line voltage will pass to terminal 35 of double-pole, double throw switch 34 and will flow through arm 40 to first energize coil 42, thus energizing motor 43 to cause shaft 44 to rotate in a clockwise direction.

Wiper 46 of potentiometer 45 will simultaneously move in a clockwise direction. Arm 51 of double-pole, double throw switch 50 will provide a -E.sub.s voltage signal through line 76 and resistor 48 to the wiper. The magnitude of the voltage signal will be determined by the position of the wiper relative to the resistance elements of potentiometer 45. The variable voltage signal will then flow through line 72 to resistor 54 and operational amplifier 26. When the magnitude thereof is equal to the magnitude of the variable control signal regulated by thermal elements 23 and 24, operation amplifier 26 will become nonconductive.

Simultaneously, as the damper is moved in a clockwise direction, wiper 59 of potentiometer 58 moves in a clockwise direction, thereby increasing the resistance thereof.

As the resistance of the potentiometer is increased, the rate at which capacitor 57 is charged is decreased, thereby delaying the time during the half cycle in which trigger diode 55 is placed in a conducting state to supply a pulse to gate 56'.

As the pulse to gate 56' is delayed, the placing of switch 56 into a conducting state is similarly delayed, thereby delaying the time during the half cycle in which the current is passed to the motor driving fan 16, thereby reducing the speed thereof.

Thus, the speed of the fan is reduced as desired as the damper is moved to reduce the area of the discharge outlet 18.

Assume now that the enclosure requires heating. Double-pole, double throw switch 34 will be set so that arm 39 will be in contact with terminal 38, and arm 40 will be in contact with terminal 36. If the temperature of the enclosure is below the setpoint, the variable voltage control signal passing through resistor 25 to operational amplifier 26 will be of a magnitude to provide a negative polarity control signal through line 71 to line 29. The -E.sub.s voltage signal will pass through diode 28, thereby energizing coil 30 and closing switch 31.

Line voltage will then pass through terminal 35, terminal 38, and arm 39, to first energize coil 41, thereby causing motor 43 to rotate in a counterclockwise direction to open damper 19 as is desired to obtain a greater quantity of treated air. Wiper 46 will simultaneously move in a counterclockwise direction. Double-pole, double throw switch 50 is set for heating mode operation. The -E.sub.s voltage signal will pass through line 76, arm 51, and resistor 49 to wiper 46. The variable voltage signal thus generated will then pass through line 72 to resistor 54, terminating at operational amplifier 26.

Similarly, as in the cooling mode of operation, when the damper 19 has moved in a counterclockwise direction, the wiper of potentiometer 58 has also moved in a counterclockwise direction, thereby increasing the rate at which capacitor 57 is increased, the speed of the motor driving fan 16 is also increased as is desired when the damper is moved so as to increase the discharge area of outlet 18.

If, during heating mode operation, the temperature of the enclosure rises above the setpoint, the control circuit will operate to close the damper 19 to the proper position for the required quantity of treated warm air.

The invention disclosed herein will permit operation of the fan at a variable speed to supply a variable quantity of treated air in proportion to the demands of the enclosure. By regulating the speed of the fan as the position of the damper is varied, the static pressure in the air passage will remain substantially constant, thereby maintaining the discharge velocity of the treated air substantially constant as is desired to obviate the problems hereinbefore discussed.

As is apparent to one skilled in the art, the control circuit may be suitably modified to permit simultaneous control of more than one damper being served by the same air conditioning apparatus.

While I have described and illustrated a preferred embodiment of my invention, it should be understood that the invention is not limited thereto but may be otherwise embodied within the scope of the following claims.

Claims

I claim:

1. A method of regulating the temperature of air circulating within an enclosure having communication with a structure serving as an air passage and provided with at least one outlet through which treated air is delivered, comprising the steps of:

A. sensing the temperature of the air in the enclosure;

B. creating a first variable electronic control signal which is a function of the sensed temperature;

C. modulating the area of the outlet from the air passage, as a function of the first control signal;

D. generating a second variable electronic control signal which is a function of the position of the outlet; and

E. discharging the treated air into the enclosure at a substantially constant velocity irrespective of the area of the outlet by maintaining a substantially constant static pressure in the air passage by varying the quantity of air delivered to the air passage in response to the second variable control signal.

2. Air conditioning apparatus for regulating the temperature of air circulating within an enclosure having communication with a structure serving as an air passage and provided with at least one outlet through which treated air is delivered, comprising:

A. means for sensing the temperature of the air in the enclosure;

B. means for supplying a first variable electronic control signal which is a function of the sensed temperature;

C. means operable for receiving the first control signal, including means to modulate the area of the outlet from the air passage as a function of the magnitude of the control signal;

D. means operable to generate a second variable electronic control signal which is a function of the area of the outlet; and

E. means to discharge treated air into the enclosure at a substantially constant velocity irrespective of the area of the outlet, said means including means responsive to said second variable control signal to regulate the quantity of treated air passing through the air passage to maintain a substantially constant static pressure in the air passage regardless of the area of said outlet.

3. Air conditioning apparatus in accordance with claim 2 wherein said means operable to receive said first control signal includes an operational amplifier, and first and second diodes, said second diode being operable to permit passage of only a negative polarity voltage signal, and said first diode being operable to permit passage of only a positive polarity voltage signal.

4. Air conditioning apparatus in accordance with claim 3 wherein said means responsive to said second variable control signal includes a trigger diode and a bi-directional gated solid state switch.

5. Air conditioning apparatus in accordance with claim 4 including means for selectively operating the apparatus on either heating mode or cooling mode.

6. Air conditioning apparatus in accordance with claim 2 including means for selectively operating the apparatus on either heating mode or cooling mode.