US2257478A - Air conditioning system - Google Patents

Description

Sept. 30, 1941. A. B. NEWTON AIR CONDITIONING SYSTEM Filed Oct. 22, 1938 HULO OF finng 'ntorr B. Newton win ' Gitorngg it has become usual to Patented Sept. 30, 1941 Alwln B. Newton, Minneapolis, Minn, Minneapolis-Honeywell Regulator Minneapolis, Minn, a corporation of Company, Delaware Application October 22, 1938, Serial No.2!!!

9Claims.

This invention relates to air conditioning systems and more particularly to systems of the type utilizing absorption or adsorption type dehumidifiers for dehumidifying the air.

In systems of this type which utilize silica-gel or other hygroscopic dehumidifying material for condensing the water from the air, it is necessary to provide for reactivating the dehumidifying material at intervals in order that the material may continue its dehumidiiylng action. This is done by heating the material for driving oi! the collected water vapor. Due to the fact that a single bed of dehumidifying material cannot remain in use continuously but mustbe reactivated, provide a pair of Separate beds and to reactivate and place these beds in operation in alternation. Thus while one bed is being reactivated, the other bed of material is dehumldifying the air being conditioned.

Heretofore it has been customary to reverse the operation of the dehumidifier by means of atlmer which operates to reverse the operation periodically. This type of control, while being satisfactory for certain load conditions on the system is wasteful during periods of light load, and may not provide for suificient reactivation during periods of heavy load. This wasteful operation of the system during light load periods is due to the fact that in order to reactivate a bed of material it is necessary to heat the bed sufficiently for driving oh the water contained therein. This requires, in the first place, the supupon the dehumidifier,

the system emciency for lighter loads will be lowered still further. 7 It is an object .of this lnventionto provide a control system for dehumidifiers of this type which provides for reactivating the dehumidifying material in accordance with the'actual load losses of the dehumidifier to a minimum, while at the same time obtaining the necessary amount of dehumidification for all load conditions.

More specifically it is an object of this invention to provide a control system for controlling a dehumidifier of this general type in accordance with the temperature of the dehumidified air leaving the dehumidifier.

Another object of this invention is the provislon of a reactivating control arrangement for a dehumidifier which controls the supply of reactivatlng heat in accordance with the condition of the material being reactivated, thereby supplying just enough reactivatlng'heat to efficiently obtain the necessary reactivation.

A further object of this invention is the provision of a reactivating arrangement for a dehumidifier which secures the reactivation by passing heated air through the dehumidifying material, and which recirculates a portion of this reactivating air thus reducing to a minimum the amount of heat necessary for reactivation of the plying of a considerable quantity of heat to the bed. Then due to the bed being hot at the'end of its reactivating period, it must be cooled which involves an additional loss. If this bed is cooled by passing cooled air therethrough the bed will act to dehumidify this cooling air and thus pick up water, thus losing a portion' of its dehumidifying effect. On the other hand if the bed is not cooled before passing the air being dehumidified therethrough, the bed will heat this air can-- cessively thereby throwing an additional load upoirthe cooling system. Therefore, each time that the dehumldifylng apparatus is changed from dehumidifying to reactivating, a definite loss occurs. If this reversal is controlled by a timer, the reversals will occur more frequently than necessary, thus causing the efiiciency to be lowered. Also, unless the timer is set to provide for reversing the dehumidifier at a suflicient rate to carry the maximum load, the system will not provide sufficient dehumidification during heavy load periods. On the other hand if the timer is set to provide for carrying maximum load, then material.

Still another object of this invention is the provision of an air conditioning system utilizing the type of dehumi er mentioned, and which utilizes the air cooling system for supplying additional reactlvating. heat when the dehumidifying load becomes excessive while the cooling load is light.

Other objects of this invention lie in Various combinations and sub-combinations of the control system and will become apparent from the following description and appended claims.

For a full disclosure of my invention reference is made to the following detailed description and to the accompanying drawing, the single figure of which illustrates diagrammatically an air conditioning system embodying the novel features oi my invention.

Referring to the drawing, reference character l indicates a conventional type silica-gel dethereby reducing reversal or screen bottom pans 5 and unit is an inlet 1 for air to be conditioned, and this inlet is connected by duct 8 to a duct a'which supplies the air to be dehumidifled to the dehumidifying unit. This duct 9 may either supply all outside air to the unit or may supply tp this unit a mixture of outside air and air withdrawn from the space being conditioned. At the top of the dehumidifying unit I is an outlet It for discharging dehumidified air This outlet I is connected by a duct II to a conditioning chamber |2 which contains a' precooling coil l3 and a direct expansion cooling coil l4. This conditioning chamber I2 is connected to a fan I5 which acts to draw air to be conditioned through the dehumidifying unit I and the conditioning chamber l2. this fan discharging the air to the space being conditioned through a discharge duct |6.

In order to control the relative humidity within the space, a by-pass duct I1 is provided between the supply duct 9 and the duct II for thereby permitting air to be by-passed around the dehumidifying unit I. The proportions of air passed through the dehumidifying unit and by-passed therearound are controlled by means of dampers l8 and I9 which may be actuated I by means of a proportioning motor 20. This motor may be of the type shown and described in the Taylor Patent 2,028,110 issued January 14, 1936, and is adapted to be controlled by means of a potentiometer controller, assuming intermediate positions in accordance with the position of the potentiometer slider upon its resistance. In the present case, this motor 20 is controlled by means of a potentiometer type space relative humidity controller 2|. This controller may be of any suitable construction and is diagrammatically illustrated as comprising a bell crank lever pivoted at 22 and having an actuating arm 23 and a control arm or slider 24 which cooperates with a resistance 25 to form a control potentiometer for themotor 20. The

actuating arm 23 ;rr'lay beconnected to a humidity responsive device 26 which may comprise a plurality of strands of hair or other moisture responsive material. Upon an increase in relative humidity within the space, the strands 26 will increase in length for permitting movement of slider 24 to the left across resistance 25 under the action of a spring 21, this action causing the proportioning motor 20 to move damper l9 towards closed position while moving damper l8 towards open position. This will increase the proportion of the air passed through the dehumidifying unit, this tending to counteract the rising space relative humidity. -Upon a decrease in relative humidity the strands 216 will decrease in length which will cause movement of motor 26 in the opposite direction for decreasing the amount of air passed through the dehumidifier.

The space relative humidity controller 2| is also provided with an auxiliary switch which is diagrammatically illustrated as comprising a mercury switch 28- which is arranged so as to remain in open position as long as the slider 22 is not engaging the left hand end of resistance 25. However when the relative humidity rises to an excessive value which causes the slider 22 to engage the left hand end of'resistance 26, the mercury switch 28 will be tilted sufliciently for bridging its electrodes. The purpose of this auxiliary switch will become apparent asthis description proceeds.

Referring again to the dehumidifying unit I arate beds of dehumidifying material and re-' activate one of these beds while the other is in use for dehumidifying the air. In order to pro-' vide for reactivating the dehumidifying material the dehumidifying unit I is provided with an inlet duct 30 which conveys heated air for reactivation into the unit This inlet duct 30 extends to the center of the casing and is provided withdampers 3| and 32 which are connected together by means of a link 33. At the lower part of the dehumidifying unit is an outlet duct 34 for the reactivating air. This outlet duct extends into the casing and is provided with dampers 35 and 36 which are connected together by a link 31. All of these dampers are actuated in unison through any suitable linkage which is diagrammatically illustrat ed as including bell crank levers 38 and 39' and links 40, 4|, 42, and 43 by means of a motor causing air tobe dehumidified to flow from inlet 1 through the passage 3 to the outlet It. When the lever 46 assumes a. position from the position shown the dampers will be shifted to their dotted line positions which will cause the air for reactivation to pass downwardly through the passage 3 to the outlet duct 34, while causing air to be dehumidified to flow from inlet I around duct 34 through passage 2 and around duct 30 to the outlet 10. The motor 44 therefore, acts to reverse the operation of the dehumidifying unit for alternately causing the material in one passage to be reactivated while the material in the other passage dehumidifles the air being conditioned, and vice versa.

Referring now to the arrangement for providing reactivating air for the dehumidifying unit I, reference character 48 indicates a duct which supplies outside air, this duct being connected to the inlet of a fan ,43 This fan in turn discharges air through a duct 60 into a heating chamber 5| which in turn is connected to the inlet duct 35 of the unit I. The outlet duct 34 within the unit I is connected to a duct 52 which leads back to the inlet of fan 43. A discharge duct 53 is connected to the duct 52 so as to discharge a portion of the air passing through this duct. Located within the heating the reactivating air passing through the duct 62, this valve 66 having a thermostatic bulb 560 located within the duct 52. The heating chamber 5| also includes an auxiliaryheating coil 61.

In operationthe fan 43 draws fresh air through the heating chamber 5| where it is heated to a temperature which is sufliciently high for driving ofi the water from the dehumidifying material within the unit. The air after passing through the dehumidifying unit passes through the duct 52 back to the inlet of the fan 43 and air, however, is discharged through the. discharge duct 53. The amount of air which is recirculated in this manner may be varied as desired by means of dampers 58 and 59 located in ducts 46 and 52, respectively. Due to this recirculation of a portion of the reactivating air, the fresh air being supplied for reactivation is preheated. This preheating is obtained without a proportionate reduction in reactivation effect of the air, as the recirculated air is still capable of absorbing considerable water. This recirculating of the reactivating air thus provides for decreasing the operating expense of the system.

A further economy in operation is obtained by the control of the heater 55 in accordance with the temperature of the reactivating air leaving the dehumidifier. When the dampers are positioned for reactivating a bed of dehumidifying material which has just been in operation, this bed will be relatively cool and consequently the temperature at the thermostat bulb 51 will decrease which will open valve 56 wide for operating the heater 54 at maximum capacity. At this time the bed of dehumidifying material being reactivated will be saturated with water and consequently this water will evaporate rapidly which will cause the reactivating air to be cooled considerably as it passes through the bed. As the reactivation continues, the amount of water in the gel bed being reactivated is progressively decreased and consequently less cooling of the reactivating air occurs as it passes through the gel bed.. This will cause the temperature of the reactivating air leaving the dehumidifier to tend to rise. However in response to this rise in temperature the valve 56 will decrease the supply of gas to the burner 55 and thereby decrease the amount of heat supplied to the reactivating air. Thus the valve 56 acts to prevent the reactivating air from being discharged from the unit at a temperature higher than necessary to secure eiiicient reactivation and thus materially conserves on operating'expenses of the system. It will be apparent that by controlling the heater 54 in accordance with the temperature of the air being discharged from the heater, and the recirculation of the reactivating air provides for materially reducing the operating expense of the system as compared to systems heretofore utilized in which no recirculation is provided and in which the heater operates continuously'at the same rate.

Referring now to the motor 44 which drives the dampers from one position to another, this motor may comprise a rotor 60 and a fleld coil 6| which together form rotor 60 drivesthe operating shaft 45 through a gear train 62. This shaft 45 in addition to actuating the operating lever 46 also actuatesthe switch arm 53 of a switching mechanism generally indicated as 64. This switching mechanism comprises a pair of contact buttons 66 and 61 which are located 180 apart, and contact segments 65 and 69. This motor 44 is controlled by the conjoint action of a timer 16 and a thermostat 1| Referring to the timer 16, this timer may include bimetallic element 12 which is fixedly secured at its upper end, and which carries contacts at its lower end cooperating with contacts 13 and 14. The bimetallic element 121s subjected to the influence of a heating element 15 which may be adjustable as indicated. When an induction motor. The

, for engaging contact 14.

the heating element 15 is energized, the bimetallic element 12 will warp to the left for contacting the contact 13. However, when the heating element 15 is deenergized, 12 will cool which causes Referring to the thermostat 1|, this thermostat may be of any suitable type and *is illustrated as comprising a bellows 16 which is connected by a capillary tube 11 to a control bulb 16 located within the duct The bellows 16 actuates a switch carrier 19 which carries a mercury switch 80. When the temperature of the dehumidified air leaving unit I is above a predetermined value such as 100 F. the bellows 16 will be expanded sufllciently for tilting the mercury switch 60 to open position. However, when the temperature of the dehumidifled air falls below this value the bellows will contract for tilting mercury switch to closed position.

When the. air being dehumidifled passes through the dehumidifying material, the hygroscopic effect of this material causes the water vapor in the air to condense, thus causing the latent heat of evaporation of the condensing water vapor to be transferred to the air. This latent heat of evaporation'causes the air to be considerably raised in temperature and consequently the air leaving the dehumidifying unit will be quite hot and above the setting of thermo-- stat 1| as long as the dehumidifying material is operating satisfactorily. However as air continues to flow through the dehumidifying mate- ,rial this material gradually becomes saturated with water and consequently does not absorb as much water vapor from the air. Consequently less latent heat of evaporation will be transfer-red to the air and this will cause the temperature of the air leaving the dehumidifying unit to grad ually fall. When the temperature of the dehumidified air falls to a dehumidifying material ficiently for causing this time the heating element 15 of timer 10 is energized as follows: line wire 82, wire 83, motor field coil 6|, wire 84, switch arm 63, contact button 61, wire 84a, heater 15, wire 85, and wire 66 to line wire 81. It gizing circuit is through the motor field coil 6|. However, due to the resistance of the heater 15, the current flow through this circuit will be insufficient for operating the motor. The heating element 16 will gradually heat up and after a period of time, such as two minutes, will cause the bimetallic element 12 to engage contact 13. At this time no action will occur and the heating element will remain energized and the bimetallic element 12 will remain engaged with contact 13. Eventually the dehumidifying material within the passage 3 of unit I will become saturated and the temperature of the dehumidiiied air will fall below the setting of thermostat 1|. Due to the resulting closure of mercury switch 80 an energizing circuit for the motor 44 will be established as follows: line wire 62, wire 83, field coil 6|, wire the bimetallic element it to warp to the right value indicating that the requires reactivation, the bellows 16 of the thermostat 1| will contract sufwill be noted that this ener- 84, switch arm 83, contact button 81, wire: 84a, rial is quite hot and imposes a substantial cooling contact 13, bimetallic element 12, wire 88, nierload upon the system due to the air being first cury switch 88, wire 89, and wire 88 to line wire passed through this hot bed and then into con- 81. This energization of field coil 8I will cause tact with the cooling apparatus. In systems rotation of the shaft 45 in a clockwise direction 5 heretofore in use this reversing of the dehumidiand the switch arm 83 will engage the contact fying unit has been controlled by means of a segment 88 while disengaging the contact button timer which reverses the dampers periodically 81. Due to the engaging of switch arm 83 with regardless of the load upon the syste Thus contact segment 88 the field coil 8I will remain during light dehumidifying load conditions the energized as follows: line wire 82, wire 83, field 10 dehumidifier is reversed considerably more than coil 8|, wire 84, switch arm 83, contact segment necessary thus imposing an unnecessary cooling 88, wire 98, wire 89, and wire 88 to line wire 81. load upon the system and also consuming an un- The operating shaft 45 of motor 44 will thus ronecessary amount of gas or other heating metate through 180 at which time the switch arm dium for heating the reactivating air. By con- 83 disengages the contact segment 88 and entrolling the dampers in accordance with the acgages the contact button 88. At this time the tual condition of the dehumidifying material in field coil 8| will become deenergized and the mooperation, the losses due to reversal of operation tor will stop with the dampers in their dotted of the dehumidifying unit are reduced to a minline positions. Due to the air being dehumidifier! imum.

now flowing through a freshly reactivated bed of Also by controlling the dampers in this mandehumidifying material the "temperature of the nor, it is assured that the dampers will be shifted dehumidified air will rise in a short period of frequently enough during periods of maximum time for causing thethermostat 1| to reopen its load for properly carrying the load. In this conmercury switch 88. Also due to the switch arm nection, it should be noted that before the damp- 83 now being disengaged from the contact buters can be shifted, the timer 18 must either heal ton 81 the energizing circ 't for the heater 15 or cool. This provides for a positive minimum will be broken and consequently this heater will time period for each cycle and thus prevents the now be deenergized. This will permit cooling of system from cycling too often.

the bimetallic element 12 for permitting it to en- It should be noted that during light dehumidigage contact 14. Eventually the dehumidifying fying load conditions the bed of material which material within the passage 2 will become satuis being reactivated will become fully reactivated rated and the mercury switch 88 of thermostat a considerable time before the bed of material 'II will close. This will establish an energizing in operation becomes saturated. At this time the circuit for motor field 8I as follows: line wire 82, reactivated bed of dehumidifying material will wire 83, motor field coil 8|, wire 84, switch arm absorb no more heat and consequently the ther- 83, contact button 88, wire 9|, contact 14, bimemostatic valve 58 will close substantially for v tallic element 12, wire 88, mercury switch 88, reducing the supply of gas to the burner 55.

wire 89, and wire 88 to line wire 81. This will Due to the feature ofrecirculating a portion of cause rotation of the shaft 45 again in a clockthe reactivating air only a relatively small porwise direction and the switch arm 83 will disen- 40 tion of heated air will be discharged through the gage contact button 88 and engage the contact discharge duct 59. Consequently during the segment 89. Engagement of switch arm 83 with period following completion of the reactivation the contact segment 89 will establish a holding of one bed and preceding the saturation of the circuit for maintaining the motor energized until other, the burner 55 will be operated at a very its shaft is rotated through an angle of 180 5 low rate thus further increasing the economy of at which time the switch arm 83 disengages conthe system. The automatic damper control thus tact segment 89 and reengages the contact butcooperates with the thermostatic control for the ton 81. This will cause the dampers within the heater, and the reactivating air recirculating dehumidifying unit to be repositioned to their arrangement for decreasing the operating exfull line positions as shown, and will also reestabpense of the system to a minimum.

lish the energizing circuit for heater 15 which In accordance with my inventionI also provide will cause the bimetallic element 12 to reengage for supplying additional heat for reactivation the contact 13. This cycle of operation will be when the dehumidifying load upon the system peat d continuous becomes very heavy and the cooling load upon From the foregoing it should be noted that the 5 the system is light. Preferably this supplying thermostat 1| and the timer 18 cooperate to conof additional reactivating heat is performed by trol the damper motor 44 in a manner to shift the cooling system which is operated upon the the dampers of the dehumidifying unit only reverse cycle for thus supplying heat when the when the dehumidifying material in operation cooling system is not necessary for cooling the becomes saturated or ineffective to dehumidify space. Referring nowto the refrigeration system the air. This arrangement further provides for and controls, reference character I88 indicates a decreasing the operating expense of the system. compressor which may be driven by a motor I8l It will be apparent that with a dehumidifying under the control of an automatic starter I82, system of this type a certain amount of heating This automatic starter may be of the usual type load must be thrown upon the cooling system, including a relay coil I83 which actuates the and a certain amount of additional heat for reswitch arms I84. When this coil is energized activation must be supplied each time that thethe switch arms I84 will be brought into engageoperation of the dehumidifying unit is reversed, ment with their respective contacts for completwhile one bed of dehum'difying material is in ing a power circuit to the motor I8I, while when operation for dehumidifying the space, the other coil I83 ls deenergized the motor I8I will be bed is being highly heated in order to drive the stopped. The discharge of the compressor is water vapor therefrom. When the dampers are connected by pipe I85 to the inlets of valves I88 reversed, the relatively cool bed must be heated and I81. The valve I81 is of the two-position to this relatively high temperature for reactivamotorized type. and the valve I88 is similar but tion while the other bed of dehumidifying mateis a three-way valve. These valves I88 and I81 heating coil 51' located in are Controlled by means of a relay I03 which consists of a relay coil I09 which actuates a switch arm IIO cooperating with contacts III and H2. When the relay coil I09 is deenergized the switch arm IIO will engage contact II2, which will complete a circuit from the transformer secondary II3 through wire H4 and IN and back to the transformer secondary II3 through wire II5. This will cause the valve I 01 to close and will cause valve I08 to assume a position for placing port IIO into communication with port I" while blocking off the port I I3. If the compressor is in operation at this time refrigerant will pass from the outlet III through pipe II9 into condenser I20, then into receiver I2I and through liquid line I22 to the expansion valve I23 located at the inlet of cooling coil I4.

to the valves I The evaporated refrigerant will then flow from the cooling coil I4 through suction line I24 to the suction header I25 which is connected to the inlet of the compressor. Thus with the relay coil I09 deenergized, the compressor will operate to cause chilling of the cooling coil I4 in the usual manner. Now if the relay coil I09 isenergized it will cause switch arm IIO to engage contact III which will shift valves I 06 and I 01 to their other positions in be closed, and the valve I00 will be positioned for blocking off port I I0, and placing ports I" and Ill into communication. Now refrigerant will flow from the compressor through pipe I and valve I01 and through pipe I to the prethe heating chamber 5I This coil will now act as a condenser and liquid refrigerant will pass from this coil into receiver I21, and from this receiver through liquid line I23 to the expansion valve I29 and will pass from the outlet of this expansion valve through the heat exchanger I20 which acts as an evaporator and absorbs heat from the water or other heat exchange medium supplied thereto. The evaporated refrigerant then passes from heat exchanger I20 through pipe H9 and valve I05 to the suction header I and back to the inlet of the compressor. From the foregoing description it should be apparent that when relay coil I09 is deenergized the refrigeration system will operate on the cooling cycle for cooling the air in the space. However, when the relay coil I09 is energized, the refrigeration system will operate on a reversed cycle for supplying additional heat to the reactivating air, and at this time the cooling coil. I4 in the air conditioning chamber is placed out of operation. 1

Reference character I30 indicates a space thermostat which may consist of 'a bimetallic element I3I which actuates a switch arm I32 cooperating I with contacts I33 and I34. This thermostat may be so designed and adjusted as to cause the switch arm I32 to engage the contact I34when the space temperature rises to 76 F. When the space temperature falls slightly below this value the switch arm I32 will remain disengaged from both contact I34 and contact I33. When the space temperature falls to 72 F. the switch arm I32 will engage contact I33. I I

Assuming now that the space temperature rises to 76 F. the switch arm I32 of thermostat I30- will engage contact I34 which will energize the coil I03 of the compressor starter as follows: secondary I35 of transformer I30, wire III'I, switch arm I32, contact -I34, wire I38, wire I39, coil I03, wire I40, and wire I to secondaryI35. This will placethe compressor into operation for cooling the space, as the relay coil I09 of the which the valve I 0'! will the system will be sufllciently engage the contact I33. coil I09 of relay I03 as follows:

relay I03 controlling the valves I 06 and I0! will be deenergized at this time. Air from the space will flow through the dehumidifying unit I and through the by-pass I1 in proportions determined ;hy the space relative humidity, and the heated and dehumidified air will pass into the conditioning chamber I2 and will be precooled by the coil I3 and further cooled by the direct expansion cooling coil I4. The compressor I00 will continue to operate until the space is cooled sufflciently for causing mostat I30 to disengage the contact I34. Thus the compressor will be started and stopped for maintaining a predetermined temperature and the dampers I8 and I9 will be positioned for maintaining a desired relative humidity within the space. Meanwhile the dampers within the dehumidifyi ng unit will be shifted from one position to another each time that a bed of dehumidifying material becomes suiiiciently saturated to require reactivation, and the heater 54 will be controlled for supplying just the proper amount of heat necessary for obtaining the necessary reactivation.

During relatively dampand cool weather the dehumidifying had upon the system )tvill be quite heavy while at this time the cooling load upon light as to make operation of the direct expansion cooling coil I4 unnecessary. Under such conditions-the relative humidity will rise to a point for causing the bypass If to be closed for thereby passing all of the air being conditioned through the dehumiditying unit. If this fails to carry the prevailing humidifying load, the crease which will the humidity controller 2| to be closed. This switch, it will be noted, is connected in parallel with the switch arm I32 and contact I34 of the thermostat I30, and consequently places the compressor into operation independently 'of the space thermostat. If this operation of the compressor is not necessary for carrying the cooling load upon the system. the space temperature will begin falling and finally the switch arm I32 will This will energize the transformer secarm I32, contact wire I43, andwire I to will cause the switch arm IIO to engage contact III which will position the valves I06 and M1 in a manner to place the cooling coil I4 out of operation and to operate the heating coil 51 as a condenser for therebyadditionally heating the reactivated air. At this time, dueto the heavy dehumidifying load on the beds of dehumidifying material, these beds will require reactivation at frequent intervals and consequently the bed being reactivated must be reactivated in a short period of time. utilization of the compression refrigeration system for providing additional heat during periods when the cooling load is light and the dehumidifying load is heavy provides for supplying the necessary additional heat for reactivation in an inexpensive manner. While the heating coil 51 is shown in chamber 56, this coil may be located in fresh air duct 40 if so desired. L

From the foregoing description it should be apparent that m invention provides a control system for" air conditioning systems utilizing absorption or adsorption type dehumidifiers and provides for reducing the losses involved in systems of this type to a minimum and also provides for utilizing the refrigeration system of the air conditioner for supplying additional heatto ondary I35, wire I31, switch I33, wire I42, coil I09, secondary I35. This the switch arm I32 of therrelative humidity will in cause the mercury switch 23 of 1 said compressor to operate the reactivating air under conditions wherein the dehumidifying load is heavy while the cooling load is light. While I have shown and described my system as applied to a dehumidifier of the type wherein the air is shifted from one bed of material to another it will be apparent that my invention is equally adaptable to a system utilizing a single bed of material, and to systems utilizing an arrangement for mechanically withdrawing the dehumidifying material from the air path when it requires reactivation. Also while I prefer to control the operation of the dehumidiher by means of a thermostat responsive to the dehumidified air it will be apparent that my invention is of broader scope and includes the control of the dehumidifier reversals in accordance with the actual dehumidifying load upon the system. As many modifications and adaptations of my improved control apparatus will occur to those skilled in the art I desire to be limited only by the scope of the appended claims.

I claim as my invention:

1. In an air conditioning system for controlling the temperature and humidity in a space to be conditioned, in combination, 'a pair of dehumidifying chambers containing a dehumidifying material requiring reactivation, means for passing dehumidifled air from said chambers to said space being conditioned, a cooling device for cooling said dehumidiiied air, fan means for discharging air for reactivation to said chambers,

I for alternately supplying air for reactivation and air to be dehumidified to said chambers in a manner to pass air for reactivation through one of said chambers while passing air to be dehumidified through the other of saidchamhers, heating means located between said fan means and said chambers for heating The reactivation air, means for returning said reactivation air from said chambers to said fan means, means for discharging a portion of said reactivation air and replacing said discharged portion with fresh air, a compressor selective control means for selectively causing said cooling device for cooling said space or to operate said heating change-over valve means means for heating the reactivation air, means responsive to space temperature and humidity for placing said compressor into operation when either the space temperature or humidity becomes excessive, means responsive to a low space temperature for actuating 'said change-over valve means in a manner to operate said heating means, and means responsive to the temperature of the dehumidified air for controlling said selective control means.

2. In an air. conditioning system, in combination, a dehumidifier of the type utilizing a hygroscopic material for dehumidifying the air being passed to a space being conditioned, said dehumidifier requiring heat. for reactiva'ting said material, means including a refrigeration systern for cooling the dehumidified air, means responsive to space temperature and humidity for placing said refrigeration system into operation when either. space temperature or relative humidity becomes excessive, and means for causing said refrigeration system to supply heat for reactivating said d umidifying material when 'space .temperature falls to a predetermined-low value: I

3. In an air conditioning system, a space to be conditioned, means for conveying air to said' space, dehumidiiying means of the type connected to" said cooling coil, and to said heating: means,

a hygroscopic material associated with said conveying means to dehumidify the air being passed to said space, said of a type utilizing heat for reactivation of said material, means for varying the effect of said dohumidifier on the total volume of air going to said space, a refrigeration system having an evaporator in heat transfer relation with the air being passed to said space and a condenser in heat transfer relation with said hygroscopic material to reactivate the same, means independent of said condenser to heat said hygroscopic material, and means responsive to the humidity in said space for controlling said. varying means and said refrigeration system and operable as the space humidity increases to cause said varying means gradually to increase to its maximum capacity the effect of said dehumidifier on the air going to the space without causing operation of said refrigeration system and thereafter to cause operation of said refrigeration system.

4. In an air conditioning system, a space to be conditioned, means for conveying air to said space, dehumidifying means of the type utilizing a hygroscopic material associatedmith said conveying means to dehumidify the air being passed to said space, said dehumidifying means being of a type utilizing heat for reactivation of said material, a refrigeration system having an evaporator in heat transfer relation with the air being passed to said space, a condenser, and a heat exchanger adapted to act as an evaporator, means for placing said condenser in heat transfer relation with said hygroscopic material ,to reactivate the same. means for placing said evaporatorinto operation upon demand'for cool- Qing. and means for placing said condenser into operation and for operating said heat exchanger as an evaporator upon demand for dehumidifl-' cation which is unaccompanied by a demand for cooling.

5. In an air conditioning system, a space to be conditioned, means for conveying air to said a space, dehumidifying means of the type utilizing a hygroscopic material associated with said conveying means to dehumidify the air being passed to said space, said dehumidifying means being of a type utilizing heat for reactivation of said material, a refrigeration system having an evaporator in heat transfer relation with the air beingpassed .to said space, a condenser, and a heat exchanger adapted to act as an evaporator, means for placing said condenser in heat transfer relation with said' hygroscopic material to reactivate the same, means for placing said evaporator into operation and operating said heat exchanger as a condenser upon demand for cooling, and

7 means for placing said condenser into operation and for operating said heat exchanger as an evaporator upon demand for dehumidification mien is unaccompanied by a'demand for cool- 6. In an air conditioning system, a space to be conditioned, means for conveying air to said space, dehumidifying means of the type utilizing a hygroscopic material associated with said conveying means .to dehumidify the air being passed to said space, said dehumidifying means being of a type utilizing heat for reactivation of said material, a reverse cycle refrigeration system operable in a first phase of operation to cool the air being passed to said space and in a second phase of operation to supply heat to said hygroscopic material without cooling s id space,

utilizing 'lfi change-over means associated with said refrig-- dehumidifying means being.

to said space, said dehumidifying means being of a type utilizing heat for reactivation of said operable in a first phase of operation to cool the air being passed to to place one of said bodies into material for absorbing vapor from means operative in a first position absorbing operation and to place the other body upon reactivation, a, motor for operating said control means between said first and second positions, means responsive to a condition afiected by the moisture content of the body then in operation in control of said motor and operative to shift said a gas, control control means between its two positions whenoperation, a timing device, and means for causing said timing device also to control said motor to prevent too frequent cycling'ofthe motor.

ALWIN'. B. NEWTON.

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