US2847831A

US2847831A - Control mechanism for cooling and condensing equipment

Info

Publication number: US2847831A
Application number: US571771A
Authority: US
Inventors: Thomas W Carraway
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-03-15
Filing date: 1956-03-15
Publication date: 1958-08-19
Anticipated expiration: 1975-08-19

Description

Aug. 19, 1958 T. w. CARRAWAY 2,847,831

CONTROL MECHANISM FOR COOLING AND CONDENSING EQUIPMENT Filed March 15. 1956 2 Sheets-Sheet l RESERVO/R DUMP VAL VE 000 00 0000000 pooooo *voooooo 52 HEAT/N6 ELEMENT IN VENTOR 7720mm Wfzrrazwz y ATTORNEYS Aug. 19, 1958 T. w. CARRAWAY 2,847,831

CONTROL MECHANISM FOR COOLING AND CONDENSING EQUIPMENT Filed Maich 15. 1956 v 2 Sheets-Sheet 2:

u\\ ll 1 N VENTOR 27mm W. Chm-away BY 5% +M% A ATTORNEYS United States Patent CONTROL MECHANISM FOR COOLING AND CONDENSING EQUIPMENT Thomas W. Carraway, Dallas, Tex.

Application March 15 1956, Serial No. 571,771

16 Claims. (Cl. 62'-158) This application is a continuation-impart of the applications of Thomas W. Carraway, Serial No. 72,406, filed January 24, 1949 (now abandoned) and Serial No. 374,565, filed August 17, 1953.

This invention relates to mechanism for controlling cooling andcondensing equipment, and more particularly to mechanism for controlling the operation of. systems including evaporative condensers.

Condensers of this kind customarily include an air duct, a heat exchanger, such as a set of coils positioned within the air duct in the path of a stream of air flowing therethrough, and a means for dispersing evaporative liquid such as Water within the duct. Such condensers may be used, for example, for condensing refrigerant after it has been compressed by a compressor operating in conjunction with refrigerating equipment usually including an evaporative coil or chamber. The equipment frequently is used in localities in which atmospheric conditions, especially the dry bulb temperature and wet bulb temperature, are subject to considerable seasonal variations. When operating under normal summer conditions with the atmospheric temperature relatively high, the condensing load usually is such as to require operation of the air fan and the liquid disperser conjointly for producing the required cooling effect on the heat exchanger, whereas when operating under winter conditions with relatively low atmospheric temperature, it usually is not only suflicient but preferable to discontinue operation of the liquid disperser, leaving it to air alone to produce sufiicient cooling of the heat exchanger. More over, even during summer operation, atmospheric conditions and the functioning of the refrigerating equipment may be such that it is not necessary or even desirable to continue operation of both the fan and the evaporative liquid disperser to produce a cooling effect suflicient to carry the condensing load. Under such conditions it is economical to disable the fan from. operation, and to relay upon the cooling effect of liquid for carrying the condensing load.

A general object of the present invention is to provide improved mechanism or apparatus for automatically and flexibly controlling the operation of equipment of the kind referred to. More particularly considered, it is a broad object of the invention to provide control mechanism or apparatus of the character stated capable of automatically conditioning or adapting the condenser equipment for the kind of operation which is most econo-mical under existing atmospheric conditions.

Another object of the invention is to provide improved equipment of the kind referred to comprising air and liquid condensing media supplying means automatically selectively or combinably operable according to conditions determining the condensing load, and mechanism for controlling the operation of condensing equipment indirectly in response to operation of a thermostat, the immediate controlling of the condenser equipment, including the compressor, being effected by pressure in the refrigerating and condensing circuit.

2,847,831 Patented Aug. 19, 1958 Another object of the invention is to provide control. equipment of the kind referred to which is so'arranged as to maintain component parts of the condensing equipment conditioned for operation at all times under the immediate control of devices responsive to the condenser load, the arrangement being such that even at the time of and immediately following a change-over from winter operating conditions to summer operating conditions or viceversa there will be no lag or interim during which the parts are not so conditioned for operation.

Another object ofthe invention is to provide improved. control mechanism for disabling the condensing equipment from operation in the event of the existence of such abnormal conditions as high pressure. in the refrigerant circuit or non-availability of evaporative liquid.

A further object of the invention is to provide control equipment operable automatically in response to falling of the atmospheric temperature below a predetermined point for emptying the supply of evaporative. liquid from a reservoir or pan in the air duct,

Other objects of the invention will become apparent from a reading of the description to follow, the appended claims, and the accompanying drawings, in which: Figure 1 is a schematic view showing refrigerating and condensing equipment associated with, control mechanism and apparatus embodying the invention in a preferred form; and Figure 2 is a somewhat schematic view of a temperature responsive switching unit or assembly, drawn on. an enlarged scale as compared to Figure l.

Mechanism according to the invention may be embodied in, or used in connection with condensing equipment of various kinds, for example, evaporative condensing equipment of the kind shown in the co-pending application of Thomas W. Carraway, Serial No. 374,565, filed August 17, 1953. As illustrated schematically in the drawing, a representative cooling or refrigerating system includes an evaporative condenser, generally designated 1, a refrigerating or evaporator coil equipment 2, and a compressor 3 operable by an electric motor 4, for receiving expanded refrigerant through an intake pipe 5 and delivering compressed refrigerant through a pipe 6 to condenser coils 7 incorporated in the evaporative condenser equipment 1. Refrigerant condensed in the coil 7 is delivered to a liquid refrigerant receiver 8, from which it may be delivered through a pipe 9, controlled by a solenoid valve 10, to an expansion valve 11 of conventional construction controlling the passage of refrigerant to and expansion of the refrigerant in the evaporatorcoil 2. The expansion valve 11 may be controlled in a con-ventional manner, for example, by means including a gas container or bulb 12 in heat conducting contact with the lower part of the evaporator coil, and having communication with the expansion valve through a tube 13. The refrigerating system may be charged with any suitable refrigerant, F-IZ Freon being a preferred one.

In general, the basic refrigerating cycle is conventional, the compressor receiving gaseous refrigerant through the intake or suction pipe 5, compressing it and delivering it through the pipe 6 to the condenser coils 7 where it is condensed, the condensate being delivered to the liquid receiver 8 under pressure sufficient to force refrigerant through the pipe 9, past the solenoid valve 10 when the latter is open, and thence through the expansion valve 11 to the evaporator coil 2 in which the refrigerant, is expanded and then returned in gaseous condition to the compressor intake pipe 5.

The evaporative condenser equipment 1 is not conventional in the generally accepted sense of the term, but does not, per se, constitute the present invention, this equipment, instead, being substantially like the evaporative condenser equipment disclosed in co-pending application 374,565, previously referred to. As shown schematically in Figure 1 of the present application, the evaporative condenser equipment includes an air duct 14 which houses the condensing coils 7 over which a current of air may be forced by a fan or blower mounted within the duct 14 and being drivable by an electric motor 16. Under some conditions, for example, in cold winter weather with a temperature of 35 F. or below, the cur rent of air driven over the coils 7 by the fan 15 will be suflicient to provide the necessary cooling effect or capacity. At higher air temperatures, for example, during 1 the summer, it is desirable to augment the cooling effect of the 'air by supplying the interior of the duct 14 in the region of the coils 7 with a mist or fog of evaporative liquid. For this purpose, a liquid disperser including a plurality of rotatable discs, one of which is shown at 17, is mounted in the bottom of the duct 14, and an electric motor 18 is arranged to drive the discs 17 so that the latter will pick up water or other evaporative liquid from a pan or reservoir 19 in the bottom of the duct, and throw the liquid off in the form of a fog or mist in the part of the duct between the fan 15 and the condensing coil 7 in a manner to envelope the coil and maintain it wet. Preferably, a deflector 20 is provided for directing liquid thrown 011 by the discs 17 toward the coil 7 and away from the blower 15. at the outlet end of the duct 14 for intercepting relatively large drops of liquid which may have passed the coil 7 and returning the intercepted liquid to the pan or reservoir 19. A water make-up or supply valve 22, controlled by a float 23 responsive to the liquid level in the pan 19, is arranged to eifect delivery of evaporative liquid to the pan 19 when the liquid level in the pan reaches a predetermined low level as a result of liquid having been evaporated and carried out of the duct 14 in the air cur rent. The make-up valve 22 is shown outside of the tank 19 in Figure 1 because of the schematic nature of this illustration, but it will be understood that the valve 22 is so positioned or arranged as to control the delivery of make-up liquid from a convenient source to the pan or reservoir 19. So, too, the float 23 is positioned within the pan 19 so as to rest upon the surface of the liquid in the pan, but for clarity of illustration it is shown somewhat removed from the pan in Figure 1. The pan 19 is shown fragmentarily in such association with the valve 22 and float 23.

Control means according to the present invention includes devices responsive to and automatically adjustable in accordance with changing refrigerating load and atmospheric conditions for selecting and effecting different kinds of operation of the condensing equipment most suitable for the existing conditions and load requirements. The controlling of the condensing equipment when operating under normal summer conditions is somewhat different from the controlling effected when operating under winter conditions, as will be particularly explained hereinafter. It will be convenient, first, to consider the operation under summer conditions, and then the operation under winter conditions, although, as will become apparent, there is some overlapping of the functioning of various control devices for summer and winter conditions.

Operation under summer conditions The normal summer operating conditions may be considered to include a refrigerating load and wet and dry bulb atmospheric air temperatures such as to require both a delivery of a current of air over the condenser coil 7 and the dispersing of evaporative liquid in the current of air in order to produce sufficient condensing capacity to maintain the refrigerating system efficient in operation and capable of carrying the refrigerating load. Under such conditions, it is necessary for the compressor 3, the fan 15, and the disperser discs 17 all to be operable from time to time according to the cooling load demand. Power for operating the compressor motor 4, the blower motor 16, and the disperser motor 18, is derived from

power supply conductors

24 and 25. The lower conductor 25 Baflles or louvers 21 are arranged leads through a power supply switch 26 which is normally held closed by a coil 26 and the lower bar or pole 27 of a normally open switch 27 to a continuation conductor 25 The upper supply conductor 24 leads through the upper bar or pole 27 of the switch 27 to a continuation conductor 24 The switch bars or

poles

27 and 27 are mechanically connected by an insulating stem 27 from which extends a bar 27 of magnetic material projecting into a solenoid winding or coil 27 The arrangement is such that when the coil 27' is energized the switch assembly, including the

switch poles

27 and 27*, will be raised so as to connect the

supply conductors

24 and 25, respectively, with the

continuation conductors

24 and 25.

When the switch 27 is closed, a circuit is completed from the conductor 24 through a conductor 24 to the compressor motor 4 and thence through a conductor 25 to the conductor 25*, causing the compressor 3 to be operated by the motor 4. Thus, closing of the switch 27 will always cause the compressor to be driven.

Under summer operating conditions, the fan 15 may or may not be operating, according to atmospheric conditions both as to wet bulb and dry bulb temperatures and the resultant pressure existing in the compressor discharge line 6. When the pressure in the line 6 is above a predetermined low, requiring the operation of the fan 15 as well as the disperser 17 for carrying the condensing load, the fan motor 16 is connected in circuit with the power supply by the conductor 24, leading to the motor 16, and a conductor 25 leading from the motor 16 through a normally closed switch 28 to the conductor 25*.

In summer operation, closing of the normally open switch 27 will close a circuit through the disperser motor 18, this circuit including a branch conductor 24 leading from the continuing conductor 24 to the disperser motor 18, and a conductor 25 leading through a normally closed temperature responsive micro-switch 29 to the conductor 25 The microswitch 29 is maintained closed during all summer operation.

The switch 28 normally is held closed by compressor delivery pressure in the line 6 acting through a branch line 6* and in a Sylphon bellows 28 connected to the switch 23. Under normal summer conditions, the pressure in the bellows 28 will be sufiicient to maintain the switch 28 closed so that when the switch 27 is also closed, the fan motor 16, as well as the compressor motor and the disperser motor 18 will be operated.

The main control switch 27 is open when conditions in the cooling area or the temperature of the evaporator coil 2 do not call for delivery of refrigerant under pres sure through the liquid refrigerant line 9. Closing of the switch 27 to effect delivery of condensed liquid refrigerant through the line 9 is effected automatically, but indirectly, by the response of a thermostat 30 to a rise in temperature in the cooled area or space. For this purpose, a transformer 31 has its primary winding connected across the

supply conductors

24 and 25 by

branch conductors

31 and 31 the secondary winding providing low voltage potential for the circuit controlled by the thermostat 30. One end of the transformer secondary Winding is connected to a low voltage conductor 32 which leads to the solenoid valve 1i? controlling the delivery of liquid refrigerant to the expansion coil 11. The valve lit is connected through a conductor 33 to the thermostat 319 which, in turn, is connected through the conductor 33 to the other end of the transformer secondary winding. When the rise in temperature in the cooled area causes the thermostat 36 to close a low voltage circuit through the solenoid associated with the valve 10, the latter will be opened and refrigerant will be delivered through the e pansion valve 11 into the evaporator coil 2 and thence to the compressor intake line 5, but closing of the thermostat 30 is not effective immediately or directly to close the control switch 27 for starting operation of the compressor, the fan, and the disperser. When delivery of -refrigerant to the evaporator coil 2, caused by opening f the valve 10, has resulted in building up of pressure in the compressor suction line 5, this pressure will act through a branch pipe 161' "ling to a Sylphon bellows 34* so as to expand the latter and cause it to close a normally open switch 34: connected to the bellows. Closing of the switch 34 in this manner will cause the operating and holding coil 2) of the main control switch 27 to be energized through a circuit comprising the conductor 24 leading from the supply conductor 24 and through a branch conductor 24 the closed switch 34 and a normally closed additional switch 35 to the coil 27 and thence to the conductor 25. Energizing of the coil 27 will cause the magnetic stem or rod 27 and the connected switch bars or

poles

27 and 27 to be raised, thus closing the switch 27 and connecting the compressor motor 4, the fan motor 16, and the disperser motor 18 in circuit with the

power supply conductors

24 and 25 in the manner previously described.

The controlling of the compressor 3 directly in response to pressure in the intake line 5 and only indirectly by the thermostat 30 reduces the next succeeding starting load on the compressor and condenser 1 under freqently encountered conditions. This is because the compressor continues to run for a short time after the solenoid valve 10 has been closed by opening of the thermostat contacts, thereby removing from the evaporator coil 2 and the intake pipe 5 a substantial portion of the refrigerant which is in these elements at the time the valve 10 is closed and which has been augmented by flow of further refrigerant from the pipe between the valves 10 and 11 past the latter and into the evaporator coil. With less refrigerant in the evaporator 2 and the pipe 5 during non operation of the compressor 3, less heat can be absorbed by the residual refrigerant. Consequently, when the compressor is started again the immediate condensing load is less than it would be if the compressor and condenser were called upon at the beginning of the next operating cycle to compress and condense a. relatively large quantity of refrigerant then in the coil 2 and pipe 5 and containing a relatively large amount of heat.

If the flow of refrigerant from the liquid receiver 8 to the suction side of the compressor should be abnormally restricted, the pressure in the compressor intake pipe 5 would fall below a predetermined value, and it then would be desirable for the compressor, the fan, and the disperser to be stopped until the cause of the abnormal pressure conditions has been located and eliminated. Such stopping of the compressor, the fan and the disperser is effected by the lowering of the pressure in the branch pipe 5 and in the bellows 34 consonantly with the lowering of the pressure in the compressor intake pipe 5, resulting in opening of the switch 34 and consequent de-energizing of the coil 27 and opening of the main control switch 27.

Should the fan 15 or disperser 17 fail in performing its intended function during normal summer operation, excessive pressure may be built up in the compressor delivery pipe 6 which, if permitted to continue, would be unsafe. Stopping of the compressor 3, the fan 15, and the disperser 17 under any such abnormally high pressure condition is accomplished by means of a branch pipe 6' leading from the compressor delivery pipe 6 to the Sylphon bellows which is expanded by the abnormally high pressure to open the normally closed switch 35, thusdeenergizing the coil 27 and opening the switch 27.

As previously stated, under some operating conditions, even during the summer season, it may be desirable for the fan 15 to be disabled and for the necessary condenser cooling to be accomplished by throwing evaporative liquid against the condenser coil 7. For example, when the dry bulb air temperature is below 72 F. and the wet bulb temperature is low, operation of both the fan 15 and the disperser 17 may lower the condensing pressure to a value below 100 p. s. i. gauge, and the eflici ency of the condensing equipment will be reduced. Under such conditions, with low pressure in the

pipes

6 and 6 the bellows 2t; will contract so as to open the switch 28 thereby breaking the circuit to the fan motor 16. Opening of the switch 28, however, will not interrupt the circuits to the compressor motor 4 and the disperser motor 18 so that the compressor 3 and the disperser 17 will continue to operate with the fan 15. being out of operation. The condensing equipment will then operate as a water cooled condenser only, which is eflicient when the atmospheric air is-at a temperature somewhat 'below 70 F. dry bulb, but nowhere near freezing, and the Wet bulb temperature is also low. Should the water cooling effect on the condenser coil 7 be insuflicient, the pressure in the delivery pipe 6 and the branch pipe 6 will rise sufliciently to expand the bellows 28 and reclose the switch 28, restoring the motor 16 and fan 15 to operation. I

Most eflicient operation of the condenser equipment depends upon evaporation of a considerable portion of the moisture or liquid delivered by the disperser 17 into the duct 14,. and it consequently is. necessary, from time to time, to add make-up water or other evaporative liquid to the pan or reservoir 19. The addition of the make-up liquid is controlled by the solenoid valve 22, which, as previously stated, is controlled by the float 23. The circuit for energizing the solenoid associated with the valve 22 to cause the latter to open includes the conductor 24 leading from the supply conductor 2.4 and through a branch conductor 24 and a normally open micro-switch 36' and a conductor 24 to the solenoid .valve 22. A conductor 37 leads from the solenoid valve 22. through a normally closed micro-switch 38 and

conductors

39 and 40 to the supply conductor 25 on the input side of the normally closed power supply switch 26. Normally, the circuit including the solenoid valve 22 is open at the micro-switch 36. Closing of the liquid supply control switch 36 to eifect opening of the valve 22 is effected by a cam 36 on a rockable shaft 23 on which the float 23 is mounted. When the liquid in the pan or reservoir 19' falls below a predetermined level and the float 23 descends accordingly, the cam 36 is turned to close the micro-switch 36, thus completing a circuit through the solenoid valve 22, and causing the valve to open to effect addition of evaporative liquid to the tank 19. When the liquid in the tank has been restored to the proper operating level, the float 23 will be raised to return the cam 36 and thus to open the micro-switch 36 and effect closing of. the liquid make-up valve 22.

When operating under summer conditions, and if the supply of evaporative liquid to the valve 22 should fail with consequent exhaustion of the liquid from the pan 19, it is desirable for the compressing and cooling equipment to be stopped. For this purpose, means are provided for opening the switch 26 and consequently the switch 27 when the liquid in the pan 19 has been exhausted or has descended to a dangerously low level. Normally, the coil 26 for maintaining the switch 26 closed is energized by a circuit including a conductor 25 leading from the supply conductor 25 through the coil 26*, a conductor 41 leading to a normally closed micro-switch 42, and a conductor 24 leading from the micro-switch 42 to the conductor 24 which leads to the supply conductor 24. Thus, under normal conditions, that is, when the liquid in the tank 19 is not exhausted nor at a dangerously low level, the coil 26* remains energized and the switch 26 remains closed. When the liquid in the pan 19 descends to a dangerously low level, the float 23 falls accordingly, causing the cam 42*, which normally maintains the control switch 42 closed, to .turn to a position in which the switch 42 is opened, thus disabling or breaking the circuit including the coil 26* and opening the switch 26. This will immediately break the circuits to the compressor motor. 4,. the fan motor 16, and the disperser motor 18. The

7 switch 26, when opening under these conditions, serves as a low level cut out switch and as a signal for indicating that the liquid supply has failed. To render operation and signalling of the switch more readily detectable, it may be provided with a flag schematically shown at 26 It will be observed that the solenoid valve 22 which controls the delivery of make-up liquid to the tank 19, is connected to the supply line on the input side of the switch 26, this connection being eflected by the conductor 37, the normally closed switch 33, and the

conductors

39 and 44!). Consequently, opening or the switch 26 as a result of liquid in the pan 19 reaching a dangerously low level, will not disable the circuit to the solenoid valve 22. Therefore, if the supply of evaporative liquid to the make-up valve 22 is restored, the switch 36 then being closed because of the low position of the float, the valve 22 will be energized so as to effect resumed delivery of evaporative liquid to the pan 19. When the normal operating liquid level in the pan 19 has been restored and the float 23 raised accordingly, the switch 42 will be re-closed by the cam 42 thus reenergizing the coil 26 and re-closing the switch 26, whereby the thermostat and the pressure

responsive switches

34, 35, and 28 will be enabled to resume controlling the operation of the compressor, the fan, and the disperser.

The drawing is not intended to disclose the specific UiZ-liSilllClZiOI'lS of the various control devices, that is, switches, solenoids, valves and the like. However, reference may be had to the patent to Thomas W. Carraway, No. 2,631,829 granted March 17, 1953, for a disclosure of a pair of float operated switches which may be used for performing the functions of the

switches

36 and 42 shown schematically in the present application drawing.

As previously stated, the

micro-switches

29 and 38 normally, that is, during summer operating conditions, are closed so as to condition the disperser motor 13 and the make-up valve 22 for operation. The

microswitches

29 and 33 are arranged to be opened automatically, for purposes later to be pointed out, when the condensing apparatus is called upon to operate under winter conditions when the temperature is below, say 35 F. The mechanism for automatically opening and closing the

switches

29 and 38 to condition the apparatus for Winter or summer operation includes a. bar 43 formed with

fingers

29 and 33 operatively associated respectively with the

switches

29 and 38. The bar 43 also is provided with a shank 43 connected to a Sylphon bellows 44 which communicates through a tube 45 with a bulb or receptacle 46 containing an expensive gas. The bulb or receptacle 46 is mounted so as to be subjected to the heating or cooling effect of atmospheric air and preferably is mounted on a fixed part of the duct 14 so as to be in the air stream passing through the duct. When the gas in the container 46 is heated due to high or normal summer atmospheric temperature it expands, causing the bellows 44 to expand and move the bar 43 toward the left as viewed in Figure 1, thus closing the

microswitches

29 and 33. When the gas in the container 46 contracts in response to lowering of the atmospheric air temperature to or below 35 F., the bellows 44 also contracts and moves the bar 43 toward the right so as to open the

micro-switches

29 and 38. Normally, thatis during operation under summer conditions, the temperature

responsive switches

29 and 38 will be closed so that the disperser motor 18 will be conditioned for operation under the control of the thermostat 30, and the make-up valve 22 will be conditioned for operation under the control of the float operated micro-switch 36. During operation under winter conditions the open switch 29 will prevent the disperser motor 18 from runn ng and the open switch 38 will prevent the make-up valve 22 from being opened.

The bar 43 connected to the Sylphon bellows 44 also is provided with two fingers 47 and 48 adapted respectively to operate two additional temperature

responsive micro-switches

47 and 43 for providing controlling effects to be pointed out later. The switches 47 and 48 operate oppositely to the

switches

29 and 38, that is, the switches 47 and 48 are held open under summer conditions when the bar 43 has been moved to the left to close the

switches

29 and 38, and are closed when the bar 43 has been moved to the right under winter conditions for opening the switches and 38. The open condition of the switches 47 and 48 during summer operation prevents these switches from having any effect upon the con' trolling of the compressor 3, the fan 15, and the dis- 7 perser 17, the make-up valve 22 and the low level control by float operated switches 42 and 26.

Operation under winter conditions When operating under winter conditions when the temperature is at or below say 35 F., air alone will provide suflicient cooling effect upon the heat exchanger coil 7 to carry the condensing load, and it would be uneconomical and ineflicient to use evaporative liquid in conjunction with an air stream. Furthermore, when operating with the air temperature below freezing, use of evaporative liquid such as water would produce difliculties and damage because of freezing on the surfaces of the heat exchanger coil 7 and in the pan or reservoir 19. It consequently is desirable to disable the disperser 17 and the liquid make-up valve 22 for winter operation, and this is accomplished by the opening of the

switches

29 and 38 caused by contraction of the gas in the container 46 and the bellows 44 and movement of the bar 43 toward the right. Opening of the switch 29 breaks the circuit to the disperser motor 18, and opening of the switch 38 breaks the circuit to the make-up valve 22.

At the time the bellows 44 operates automatically to change the control equipment from summer operating condition to winter operating condition, a considerable quantity of evaporative liquid will be in the pan or reservoir 19. This liquid would remain in the reservoir despite the disabling of the make-up valve 22 caused by opening of the switch 38, because opening of the switch 38 will be accompanied by simultaneous opening of the switch 29 and disabling of the disperser motor 18. If the residual evaporative liquid were permitted to remain in the reservoir 19 it would freeze upon lowering of the atmospheric temperature below 32 F., and the reservoir and duct equipment might be damaged. To prevent this, a dump valve 49 is provided in the bottom of the reservoir 19 and is adapted to be opened automatically in consequence of the movement of the bar 43 to its right or winter position for discharging the residual evaporative liquid from the reservoir immediately and rapidly. In Figure 1, the dump valve 49 is shown associated with a detached or fragmentary representation of the tank 19, to avoid encwnbering the main showing of the tank 19. The three smaller representations of the tank 19 in association respectively with the makeup valve 22, the float 23 and the dump valve 49 are all one and the same element as the tank 19 shown immediately above at the bottom of the duct 1. The dump valve 49 may be a known solenoid or electrically operated construction, and is connected in a circuit including the supply conductor 24, the conductor 24 the valve 49 itself, a conductor 50, the microswitch 47, the conductor 40, and the supply conductor 25. When the bar 43 moves to its right to its winter position, the normally open micro-switch 47 is closed so as to complete the dump valve circuit and cause the valve to open and empty the reservoir 19.

It is possible that the change-over from summer to Winter conditioning of the control equipment could be effected by rightward movement of the bar 43 at a time when the liquid level in the reservoir 19 is so low that the float controlled switch 42 and consequently the magnetic switch 26 would be open. If the circuit for operating the dump valve 49 were subject to the control of the

switches

42 and 26, it would not be possible to open the valve 49 under low level liquid condition in the reservoir 19. In order to insure that the valve 49 will be opened when the temperature responsive bar 43 is moved to its winter position, the conductor 40, which is included in the circuit for operating the valve 49, is connected to the supply line 25 on the input side of the low level cut-out switch 26. Consequently, operation of the dump valve 49 will be assured in response to closing of the micro-switch 47 irrespective of the open or closed position of the low level cut-out switch 26.

After the equipment has been conditioned automatically for winter operation, the reservoir 19 will be empty, no evaporative liquid can be introduced into the duct or reservoir, and the disperser 17 cannot be operated. The compressor 3 and the fan will still be conditioned to operate under the indirect control of the thermostat 30 in the same manner as when the equipment is conditioned for summer operation, and the compressor and fan operation will still be subject to the control of the high and low pressure cut-

out switch equipment

35, 34, and 27, the fan also still being subject to the control of the predetermined low pressure cut-out switch 28. During winter operation when the disperser 17 is prevented from running, if the pressure in the line or pipe 6 becomes too low for eflicient condenser functioning, the fan 15 will be stopped by opening of the predetermined low pressure cut-out switch 28, but since the atmospheric temperature is low, the cooling of the heat exchanger 7 required to carry the condensing load can be effected by natural or convection :air'flow through the duct 14.

During winter operation, and after the dumping of the liquid from the pan 19, the float operated switch 42 will be open so as not to complete a circuit through the relay coil 26 ofthe switch 26. If the coil 26 were deenergized upon changing over from summer to winter operation, the switch 26 would be opened and it would not be possible for the switch 27 to be closed and the compressor and fan could not be operated. To prevent disabling of the switch 27 and the compressor and fan as a result of opening of the float operated switch 42, means are provided for superceding the control of the switch 42 to maintain the relay coil 26 energized and the switch 26 closed when the bar 43 moves to its winer condition position. In the form shown, the normally open control switch 48 previously referred to, is shunted across the switch 42 and is arranged to be closed substantially simultaneously with the opening of the float operated circuit disabling switch 42. When the switch 48 has been closed, a circuit independent of the disabling switch 42 will be established through the relay coil 26 by way of the supply conductor 24, the conductor 24, a conductor 24 the closed micro-switch 48, a conductor 41 the conductor 41, the coil 26 itself, and the conductor 25 leading to the supply conductor 25. Therefore, at the time of changing over from summer operation to winter operation, the dump valve 49 will be opened, the switch 26 will be held closed independently of the float operated switch 42 so that when the pan 19 has been emptied and the switch 42 opened, the switch 26 will remain closed and the compressor and fan will still be operable under the control of the main switch 27 which, in turn, will still be controlled by the thermostat 30 and the pressure

responsive switches

34 and 35, the fan also still being under thecontrol of the predetermined low pressure cut-out switch 28. Consequently, changing over from summer to winter operating condition will involve no interruption in the controlled operation of the compressor and fan.

The make-up valve 22 should be insulated against heat transfer to prevent its freezing during winter operation. The dump valve will not freeze because it will be kept 1t) heated by the constant energizing of the associated sole noid during winter operation.

Change-over from winter operating conditions to summer operating conditions Rising of the atmospheric temperature above 35 F. requires restoring of the disperser to the, control of the switch 27, closing of the dump valve 49, restoring of the make-up valve 22 to the control of the float operated switch 36 and restoring of the low level cut-out switch 26 to the control of the float operated switch 42. These restorations of controls are effected by expansion of the bellows 44 and movement of the bar 43 to the left which closes the

switches

29 and 38 and opens the switches 47 and 48. Closing of the switch 29 restores the disperser motor 18 to the control of the switch 27, opening of the switch 47 effects closing of the dump valve 49, and closing of the switch 38 again places the liquid make-up valve 22 under the control of the float operated switch 36. At the same time, that is when the bar 43 is moved to the left, the switch 48 is opened, thus removing the shunt from the float controlled switch 42 while the latter is still open because of there being no fluid in the pan 19.. Hence, with both switches 48 and 42 open, the coil 26 would be deenergized and the switch 26 would open unless provision were made for maintaining the coil 26 energized until the liquid in the pan 19 is restored to a level sufficient to effect closing of the switch 42. In accordance with the invention, means operable temporarily for a predetermined time is provided for maintaining the relay coil 26 energized at the time of and immediately following the change-over from winter operating conditions to summer operating conditions. In the form shown, a switch comprising

bi-metallic contacts

51 and 51 connected, respectively to the

conductors

24 and 41 is shunted across the low level float operated switch 42. Thecontacts 51 51 normally, that is during summer operation, are open so as not to interfere with the control eifected by the float operated micro-switch 42. During winter oper ation the contacts 51* and 51 are closed upon each other by the influence of heat generated by an electric heating element 52 connected by a conductor 50? to theconductor 50 and by a conductor 24 to the conductor 24 When operating under winter conditions, a circuit is established through the heating element 52 by way of, the

conductors

24, 24 24 the heating element 52, the conductors 50 and 50, the switch 47, and the conductors 40. and 25.

After winter operation conditioning of the various control elements has been effected, continued operation under winter conditions will take place with two switches, namely, the switch 48 and the thermally responsive switch 51 51 shunting the float controlled switch 42. Upon the next change-over to summer operating conditions, the leftward movement of the bar 43 will immediately open the switch 48 and remove its shunt across the switch 42. Such movement of the bar 43 will also immediately open the switch 47 so as to break the circuit to the heater element 52, the heating of, which was responsible for closing the shunt switch 51 51 However, the heating eifect on the switch 51 51 carries over for a predetermined period so as to maintain the contacts 51 51 closed to provide a continued shunting of the float operated switch 42. This will maintain the relay coil 26 energized, and the switch 26 consequently closed for enabling the compressor 3, the fan 15, and the. disperser 17 to be operated while evaporative liquid is being restored to the pan 19 and before the liquid has reached a level sutficiently high to cause closing of the float operated switch 42. Otherwise stated, the switch 51 51 establishes a circuit through the coil 25 prior to re-establishing the supply of liquid to the pan 19 and disperser 17. By the time. the heating of the

switch contacts

51 and 51 has been dissipated with resultant opening of the contacts, the liquid in the pan 19 will have been restored to a level sufliciently l high to cause closing of the float operated switch 42 and continued energizing of the relay coil 26 Consequently, changing over from winter operation conditions to summer operation conditions will not be accompanied by any period during which the compressor 3, the fan 15, and the disperser 17 would be disabled from operating under the control of the thermostat 3t] and the pressure operated switches 28, 34, and 35. The functioning of the time

delay shunt switch

51 and 51 in maintaining the switch 26 closed immediately following the movement of the temperature responsive bar to its summer position is particularly important, because at this time the load on the condensing equipment is being increased.

The time delay switch 51*, 51 could also function in the absence of the shunt switch 48 for shunting the float controlled switch 42 to maintain the coil 26 energized during winter operation. .Thus, assuming there were no switch corresponding to the switch 48, chang ing from summer operation to winter operation with resultant dumping of the liquid from the pan 19 and opening of the switch 42 would open the switch 26 immediately. This would disable the compressor 3 and fan only temporarily, because the heater element 52 would be energized through the circuit including the

conductors

24, 24 and 24 the element 52, the conductors 50 and 50, the closed micro-switch 47 and the conductors and 25. After some delay, the heating of the

switch contacts

51 and 51 by the heating element 52 would cause the contacts to be closed so as to energize the relay coil 26* and close the switch 26 and again place the compressor 3 and the fan 15 under the indirect control of the thermostat 30. In some cases, temporary disabling of the compressor 3 and the fan 15 immediately following a change-over from summer operation to winter operation would not be serious, because at that time the condenser load is lessening; but normally it is preferred to avoid even temporary disabling of the compressor and the fan, irrespective of atmospheric conditions or changes.

The temperature responsive device comprising the bulb 46, bar 43 and switches 29, 47, 48 and 38 may be selected or adjusted to operate at different predetermined temperatures, the change-over temperature of 35 F. being a typical but not the only suitable one. Similarly, the operating pressures of the bellows associated with the

switches

28, 34 and 35 may variously be selected or adjusted. Adjustable temperature and pressure responsive control components of these kinds are well known and are commercially available so that illustration of details in this application is unnecessary.

Although the compressor, fan, and disperser are shown as being electrically driven, control equipment in accordance with the invention may be used in connection Wlfl'l elements driven other than electrically, e. g. by internal combustion engines, in which case the control equipment may be connected with electrically operated motors provided for starting the combustion engines in the usual way.

'Control apparatus embodying the present invention is very flexible in adapting or effecting operation of the cooling and condensing equipment including the compressor, the fan and the disperser to different loads caused by different atmospheric conditions. During summer operation, with relatively high condenser loading, the compressor, the fan and the disperser are all operable under the indirect control of a thermostat responsive to the temperature in the cooled space. Evaporative liquid is automatically supplied to make up for liquid used or lost by evaporation. Useless operation of the disperser when no evaporative liquid is available is avoided. The fan is disabled in response to abnormally low pressure on the high or discharge side of the compressor so as to avoid wasteful and unnecessary use of power under conditions such that the condensing load may be carried by supplying of evaporative liquid to the heat exchanger. As a safety measure the compressor, the fan and the disperser are all adapted to be disabled in response to abnormally high pressure on the discharge side of the compressor. Following automatic change-over to winter operating conditions, evaprative liquid is dumped from the reservoir so as to avoid freezing danger, and the supply of more evaporative liquid is prevented. When operating under winter conditions, abnormally low pressure on the high side of the compressor disables the fan and enables the condensing load to be carried economically by natural or convection air flow. Changing over from winter to summer operating conditions or vice versa does not result in even temporary removal of the condensing equipment components from the control of the pressure andtemperature responsive controlling devices.

The apparatus disclosed embodies the invention in a preferred form, but it is intended that the disclosure be illustrative rather than definitive. The invention is defined in the claims.

I claim:

1. In evaporative condenser apparatus, an air duct; a blower for causing a stream of air to flow through said duct; a heat exchanger mounted in said duct; means for dispersing evaporative liquid in said duct; temperature responsive means for controlling said dispersing means to disperse liquid only when the atmospheric temperature is above a predetermined point; disabling means responsive to a failure in the evaporative liquid supply for rendering both said dispersing means and said blower inoperable when the atmospheric temperature is above said predetermined point; and means operable at atmospheric temperatures below said predetermined point for preventing said disabling means from rendering said blower inoperable in response to failure of the evaporative liquid supply.

2. In evaporative condenser apparatus, an air duct; a motor driven fan for causing a stream of air to flow through said duct; a heat exchanger in said duct; an electrically operated dispenser for dispersing evaporative liquid in said duct; means for supplying evaporative liquid to said disperser; a temperature responsive switch in circuit with said disperser for causing said disperser to operate only when the atmospheric temperature is above a predetermined point; a normally closed power supply switch in circuit with both the fan motor and said disperser; a relay coil adapted, when energized, to maintain said power supply switch closed; a circuit including a normally closed control switch for normally maintaining said relay coil energized; means responsive to failure of the evaporative liquid supply for opening said normally closed control switch; a normally open control switch shunted across said normally closed control switch; and means responsive to falling of the atmospheric temperature below said predetermined point for closing said normally open control switch.

3. Apparatus as set forth in claim 2 in which the means responsive to failure of the evaporative liquid supply for opening said normally closed control switch comprises a float.

4. Apparatus as set forth in claim 2 comprising means for simultaneously opening said temperature responsive switch and closing said normally open control switch in response to falling of the atmospheric temperature below said predetermined point.

5. Apparatus as set forth in claim 2 comprising an electrically operable valve for controlling the supplying of evaporative liquid to said disperser; and a float operated switch for controlling the operation of said valve.

6. Apparatus as set forth in claim 2 comprising an electrically operable valve for controlling the supplying of evaporative liquid to said disperser; a liquid supply control switch in circuit with said valve; and another and normally closed switch in circuit with said valve and being openable in response to falling of the atmospheric temperature below said predetermined point for preventing operation of said valve irrespective of operation of said liquid supply control switch.

7. Apparatus as set forth in claim 6 comprising a further switch shunted across said normally closed control switch for completing a circuit through said relay coil prior to the re-closing of said normally closed control switch when the atmospheric temperature rises above said predetermined point and prior to re-establishing of the supply of evaporative liquid to said disperser.

8. Apparatus as set forth in claim 7 comprising means for conditioning said further switch to remain closed for a predetermined time after the atmospheric temperature has risen above said predetermined point and then automatically to open, thereby to restore the energizing of said relay coil to the control of said normally closed control switch.

9. Apparatus as set forth in claim 8 in which said further switch is normally open and is closable in response to heat, said conditioning means comprising an electrical heater in heating association with said further switch and means for closing a circuit through said electrical heater when the atmospheric temperature is below said predetermined point and for breaking the circuit through said electrical heater when the atmospheric temperature rises above said predetermined point. r

10. In evaporative condenser apparatus, an air duct; a motor driven fan for causing an air stream to flow through said duct; a heat exchanger in said duct; a reservoir in the bottom of said duct for containing evaporative liquid; a motor driven disperser for dispersing evaporative liquid from said reservoir into said air stream; means for supplying make-up evaporative liquid to said reservoir; a temperature responsive switch in circuit with the disperser motor for causing said disperser motor to operate only when the atmospheric temperature is above a predetermined point; a normally closed power supply switch in circuit with both the fan motor and the disperser motor; a relay coil adapted, when energized, to maintain said power supply switch closed; a circuit including :a normally closed control switch for normally maintaining said relay coil energized; a float responsive to lowering of the liquid level in said reservoir for opening said normally closed control swicth; a normally open control switch shunted across said normally closed control switch; and means responsive to falling of the atmospheric temperature below said predetermined point for closing said normally open control switch, thereby to maintain said power supply switch closed independently of said normally closed control switch.

11. In evaporative condenser apparatus, an air duct; a motor driven fan for causing an air stream to flow through said duct; a heat exchanger in said duct; a reservoir in the bottom of said duct for containing evaporative liquid; a motor driven disperser for dispersing evaporative liquid from said reservoir into said air stream; means for supplying make-up evaporative liquid to said reservoir; a dump valve for discharging evaporative liquid from said reservoir; and means responsive to falling of the atmospheric temperature below a predetermined point for disabling said make-up liquid supplying mean and opening said dump valve.

12. In evaporative condenser apparatus, an air duct; a motor driven fan for causing an air stream to flow through said duct; a heat exchanger in said duct; 21 reservoir in the bottom of said duct for containing evaporative liquid; a motor driven disperser for dispersing evaporative liquid from said reservoir into said air stream; an electrically operable supply valve for controlling supplying of make-up evaporative liquid'to said reservoir; an electrically operable dump valve for discharging evaporative liquid from said reservoir; and means responsive to falling of the atmospheric temperature below a predetermined point for breaking an electrical circuit to said supply valve for preventing operation thereof and for closing an electrical circuit to said dump valve for opening the latter to efiect emptying of said reservoir.

13. In evaporative condenser apparatus, an air duct; a motor driven fan for causing an air stream to flow through said duct; 21 heat exchanger in said duct; a reservoir in the bottom of said duct for containing evaporative liquid a motor driven disperser for dispersing evaporative liquid from said reservoir into said air stream; an electrically operable supply valve for controlling supplying of make-up evaporative liquid to said reservoir; means including a fioat operated switch for energizing said supply valve and causing it to open when the evaporative liquid in said reservoir descends to a lower than normal level; an electrically operable dump valve for discharging evaporative liquid from said reservoir; means responsive to falling of the atmospheric temperative below a predetermined point for breaking the electrical circuit to said supply valve and thereby removing it from the control of said float operated switch and for closing an electrical circuit to said dump valve for opening the latter to effect emptying of said reservoir; and a temperature responsive switch in circuit with the disperser motor for causing said disperser motor to operate only when the atmospheric temperature is above said predetermined point.

14. In evaporative condenser apparatus, an air duct; a motor driven fan for causing an air stream to flow through said duct; a heat exchanger in said duct; a reservoir in the bottom of said duct for containing evaporative liquid; a' motor driven disperser for dispersing evaporative liquid from said reservoir into said air stream; an electrically operable supply valve for controlling supplying of make-up evaporative liquid to said reservoir; means including a float operated switch for energizing said supply valve and causing it to open when the vaporative liquid in said reservoir descends to a relatively high but lower than normal level; an electrically operable dump valve for discharging evaporative liquid from said reservoir; means responsive to falling of the atmospheric temperature below a predetermined point for breaking the electrical circuit to said supply valve and thereby removing it from the control of said float operated switch and for closing an electrical circuit to said dump valve for opening the latter to effect emptying of said reservoir; a temperature responsive switch in circuit with the disperser motor for causing said disperser motor to operate only when the atmospheric temperature is above said predetermined point; a normally closed power supply switch in circuit with both the fan motor and the disperser motor; a relay coil adapted, when energized, to maintain said power supply switch closed; a circuit including a normally closed control switch for normally maintaining said relay coil energized; float operated means for opening said normally closed control switch in response to descent of the evaporative liquid in said reservoir to a level lower than said relatively high level; a normally open control switch shunted across said normally closed control switch; and means responsive to falling of the atmospheric temperature below said predetermined point for closing said normally open control switch, thereby to maintain said relay coil energized and maintain said power supply switch closed independently of said normally closed control switch.

15. In evaporative condenser apparatus, an air duct; a motor driven fan for causing an air stream to flow through said duct; a heat exchanger in said duct; a motor operated compressor for compressing refrigerant; a pipe for delivering compressed refrigerant from said compressor to said heat exchanger; a reservoir in the bottom of said duct for containing evaporative liquid; a motor driven disperser for dispersing evaporative liquid from said reservoir into said air stream; means for supplying make-up evaporative liquid to said reservoir; a temperature responsive switch in circuit with the disperser motor for causing said disperser motor to operate only when the atmospheric temperature is above a predetermined point; a normally closed power supply switch in circuit with the compressor motor, the fan motor and the disperser motor; a relay coil adapted, when energized, to maintain said power supply switch closed; a circuit including a normally closed control switch for normally maintaining said relay coil energized; a normally closed pressure responsive switch in circuit with said fan motor and being openable in response to falling of the refrigerant pressure in said pipe below a predetermined value for stopping said fan motor; a float responsive to lowering of the liquid level in said reservoir for opening said normally closed control switch; a normally open control switch shunted across said normally closed control switch; and means responsive to falling of the atmospheric temperature below said predetermined point for closing said normally open control switch, thereby to maintain said power supply switch closed independently of said normally closed control switch.

16. In cooling apparatus, an evaporator; a compressor for compressing evaporated refrigerant received from said evaporator; a heat exchanger; means for delivering compressed refrigerant from said compressor to said heat exchanger; rneans for delivering condensed refrigerant from said heat exchanger to said evaporator; a first valve for controlling delivery of condensed refrigerant to said evaporator; a thermostat responsive to cooling demand for opening said first valve; means including a first electrical switch responsive to building up of pressure of refrigerant on the intake side of said compressor caused by opening of said first valve while said compressor is not operating for starting operation of said compressor; an air duct enclosing said heat exchanger; a motor driven fan for causing an air stream to flow through said duct and in contact with said heat exchanger; a reservoir in the bottom of said duct for containing evaporative liquid; a disperser for dispersing liquid from said reservoir into said air stream and onto said heat exchanger; an electrical power supply switch for controlling operation of said compressor, said fan and said disperser conjointly subject to the operation of said first switch; a second valve for controlling addition of make-up evaporative liquid to said reservoir; a third valve for controlling dumping of evapd rative liquid from said reservoir; first float operated means for controlling said second valve according to the liquid level in said reservoir; second float operated means responsive to descending of the liquid in said reservoir to a predetermined low level for operating said power supply switch to prevent operation of said compressor, said fan and said disperser when the air stream is above a predetermined temperature; means responsive to falling of the air stream temperature below said predetermined temperature for superseding the controlling effect of said first float operated means and preventing liquid adding operation of said second valve; means responsive to falling of the air stream temperature below said predetermined temperature for opening said third valve to empty said reservoir; means responsive to falling of the air stream temperature below said predetermind temperature for superseding the operating effect of said second float operated means and maintaining said power supply switch conditioned to cause operation of said compressor and said fan; means responsive to falling of the air stream temperature below said predetermined temperature for preventing operation of said disperser; and means operable when the air stream temperature is above said predetermined temperature and in response to predetermined low refrigerant pressure in said compressed refrigerant delivering means for preventing operation of said fan while permitting operation of said compressor and said disperser.

References Cited in the file of this patent UNITED STATES PATENTS 2,047,827 Lamb July 14, 1936 2,067,638 Hornaday Ian. 12, 1937 2,210,325 Newton Aug. 6, 1940 2,213,622 Carraway Sept. 3, 1940 2,233,633 Mollenberg Mar. 4, 1941 2,286,538 Guler June 16, 1942