US2286604A

US2286604A - Air conditioning system

Info

Publication number: US2286604A
Application number: US215805A
Authority: US
Inventors: Robert B P Crawford
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1938-06-25
Filing date: 1938-06-25
Publication date: 1942-06-16
Anticipated expiration: 1959-06-16

Description

June 9 R. B. P. CRAWFORD 2,236,604

AIR CONDITIONING SYSi'EM Filed June 25, 1958 2 Sheets-Sheet l Robert BQFZ Cruwlmrd attorney June 16, 1942. p CRAWFORD I 2,286,604

AIR CONDITIONING SYSTEM Filed June 25, 1938 2 Sheets-Sheet 2 ISnnentor Robert Bap. Crmlwfinrdl 2 w KM v Qttorn eg Patented June 16, 1942 AIR CONDITIONING SYSTEM Robert B. P. Crawford, Miami, Fla., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application June 25, 1938, Serial No. 215,805

30 Claims.

This invention relates to an air conditioning system and more particularly to an air conditioning system wherein a supply of water such as well water is utilized for heating or cooling a building.

In accordance with my invention I provide an air conditioning chamber provided with suitable heat exchanger coils through which water is circulated, this water coming from a suitable source of supply such as a well with means for further heating or cooling the water in accordance with the heating or cooling demand of the building. The invention is more particularly concerned with the provision of suitable control means for controlling the temperature and rate flow through the heat exchanger coils and for maintaining a suitable pressure within the coils so as to insure a suitable heat exchange condition within the coils.

It is therefore an object of my invention to provide a novel air conditioning system for a space to be conditioned.

More particularly it is an object of my invention to provide an air conditioning system of the type utilizing water from a suitable source of supply such as a well for heating or cooling the air to be conditioned with means for regulating the temperature and the rate of flow of water to the air conditioning unit in accordance with the heating or cooling demand on the system.

A further object of my invention is the provision of means for preventing the freezing of the water in the coils during the winter-time by providing automatic means for draining the water from the coils should the temperature of the water leaving the coils drop to a dangerously low value.

A further object of my invention is the provision of suitable control means for a system of the class described for controlling the temperature and rate of flow of the cooling fluid in such a manner as to insure economical operation thereof and to prevent exhausting of the source of supply without unduly heating or cooling the source of supply as the case may be when the source of supply is adequate.

Other objects and advantages of my invention will become apparent upon a study of the specifiaction, claims, and appended drawings wherein like reference characters represent like parts in the two views, and wherein Figure 1 is a schematic diagram of an air conditioning system embodying my invention, and

Figure 2 is a wiring diagram of the control system illustrated in Figure 1.

Referring more particularly to Figure 1 an air conditioning chamber is represented generally by the reference character It! and is illustrated as being located within a chamber or penthouse located upon a roof l2 of the building to be conditioned. While the air conditioning chamber is illustrated as being located on the roof of a building it will be understood that this chamber may be otherwise suitably located. The chamber It includes a fresh air inlet l3 and a return air inlet M which communicates with the interior of the building to be conditioned. The flow of air through the fresh air inlet l3 and the return air inlet |4 may be controlled by suitable dampers I5 and 16 which are suitably connected to a motor 20 operating in a manner to be hereinafter described. A fan 2| is provided for drawing air into the chamber I0 and exhausting it through the outlet 22 which communicates with the interior of the building being conditioned. A motor 23 is provided for driving the fan 2| and this motor is illustrated in Figure 2 as being a multispeed motor.

Located within the chamber I0 is a heat exchanger coil 25 having an inlet at 26 and an outlet at 21. Water or other cooling medium is caused to flow through the coil 25 in counterfiow relationship with respect to the flow of air by the fan 2|. Water may be supplied to the coil 25 from a well 30 or any other suitable source of supply, the water being drawn through the pipe 3| by means of the pump 32 driven by a motor 33 and forced through a heat exchanger unit 34. The water flows from the upper portion of the unit 34 through a pipe 35 to a second heat exchanger unit 36 from which it flows through a pipe 31 to the inlet 26 of the coil 25, the flow of water to the coil being controlled by a valve 40 operated in a manner to be described. A sec and heat exchanger 4| is located in the air conditioning chamber l0 downstream of the heat exchanger unit 25, this unit 4| serving as a reheater in the cooling season. The water leaving the unit 25 flows through a pipe 42 to a threeway valve 43 which valve controls the flow of water to the reheater 4| and the water may also flow through a pipe 45 which by-passes the reheater 4|, the amount of water flowing through the reheater and by-passing the reheater depending upon the setting of the valve 43 which is operated in a manner to be set forth.-

From the reheater 4| and the by-pass 45 the water flows through a pipe 46 through a heat exchanger 48 which forms a condenser of a refrigeration system to be described and from the condenser 48 the water flows through pipe 48 to a pipe 50 provided with outlets 5| and 52.

Valves

53 and 54 control the now of water to the outlets 5| and 52, respectively, these valves being controlled in a manner to be henceforth set out. The outlet 5| communicates with a subterranean channel 55 which in turn communicates with the well 30. The outlet 52 empties into a waste pipe 58 by means of which the water may be led to a sewer or may be otherwise disposed of. L0- cated above the roof I2 is a spray 50 which communicates by means of a valve 8| with the outlet of the heat exchanger 4| and the by-pass 45. The outlet from the condenser 48 also communicates by means of a pipe 54 with a tank 55 for providing water for domestic purposes to suitable faucets 68, etc. Communications between the pipe 84 and the tank 65 may be controlled by a float valve 68 of suitable well known construction and the upper portion of the tank may be provided with air under pressure to cause the to the heat exchanger 25 when outside condi-- tions require, the heat exchanger 35 is provided and steam is admitted to this heat exchanger by means of a pipe 85 controlled by a valve 80 which is controlled in a manner to be described, the steam leaving the heat exchanger 36 through a pipe 01.

The bottom loops of the coils 25 and 4I communicate by means of check valves I00 with a water from the tank 65 to rise to the faucets 88 when these faucets are opened.

For cooling the water leading to the coil 25, I have illustrated a refrigeration system of any suitable construction the system herein disclosed comprising a compressor I0 driven by a motor H which is controlled in a manner to be set forth. The outlet of the compressor I0 communicates by means of a pipe I2 with the con-.

denser 48 and from the condenser the refrigerant flows by means of a pipe I3 and a valve 14 to the inlet 15 of the heat exchanger. 34 which serves as the evaporator of the refrigeration system. The valve 14 is illustrated as being a solenoid type valve, this valve including a solenoid 16 which is controlled by means of a suitable float-switch I8 so that when the level of refrigerant in the evaporator 34 drops to a predetermined value the solenoid will be energized by means of conductors I9, switch I8, and conductor 80, it being understood that conductors I8 and 80 are connected to a suitable source of power (not shown). From the evaporator 34 the refrigerant flows through a pipe 80, a trap 8|, and a pipe 82 back to the inlet of the compressor I0. Liquid refrigerant is prevented from getting back to the compressor since this refrigerant is caught in the trap 8I and is returned to the evaporator 34. It will now be understood that when the compressor I0 is in operation the refrigerant surrounding the coil through which water flows in the evaporator 34 will reduce the temperature of the water therein so that the water will be supplied to the coil in the air conditioning chamber l0 at a temperature which is lower than the temperature of the water in the well or other source of supply.

In order to increase the heat transfer within the evaporator 34 the water is caused to circulate through the coil therein at an increased rate by means of a pump 85 driven by means oil a motor 86 controlled in a manner to be described. The inlet of the pump 85 communicates by means of a pipe 88 'with the outlet of the coil in the evaporator 34 and the water flows from the pump 85 through a pipe 80 which communicates with the inlet of the coil in the evaporator 34. A check valve 9| is provided in the pipe 80 to prevent water flowing from the pump 32 to the outlet of the pump 85 and a second check valve 92 is provided in the outlet of the pump 32 to prevent flow of water by the pump 85 back to the outlet of the pump 32.

For the purpose of heating the water leading pipe IOI which serves .todrain' the temperature of the water from thecoils when the water in the outlet of the coil 25 drops to a dangerously low value. The flow of water through the. pipe IN is controlled by a valve I02 and when the valve I02 is opened in a manner to be described the water flows from the coils through the pipe IN to the outlet I03 which may empty onto the roof or be connected to a suitable waste pipe.

Referring now to Figure 2 the means for controlling the operation of th fan motor 23 will be described. This motor is connected by means of a suitable starter box I05 which is in turn connected by means of conductors I08, I01, and I05 with asuitable source of power (not shown). It will be understood that this starter box includes suitable'windings which control the speed of the motor 23 but since the construction of this starter unit forms no part of the present invention' the details thereof are not being illustrated. When the terminals I08 and H0 are connected together the fan motor runs at low speed, when terminals I08 and II I are connected together the motor runs at a higher speed and when terminals I08 and H2 are connected together the fan runs at a still higher speed. A suitable step controller indicated generally by the reference character H5 is provided for controlling the speed of the motor 23. This controller includes a motor H8 which may be a proportioning motor of the type illustrated in Patent 2,028,110 issued to D. G. Taylor on January 14, 1936. This motor carries on its shaft H'I a plurality of cams designated by the reference characters H8, H9, I20, and I2I. These cams control the positions of mercury switches I22, I23, I24, and I25 as is apparent from the drawings. When the cams rotate in a counter-clockwise direction the switch I25 will first be moved to open position followed by the opening of the switch I24 which is in turn followed by the simultaneous opening of the switch I23 and moving of the switch I22 to open the contacts which are illustrated as being closed and to bridge the opposite set of contacts. With the switches in the positions illustrated it will be apparent that the terminal I 09 of the starter unit I05 is connected to the terminals I I0, I I I, and H2 so that the motor 23 is operating at its highest speed and the fan 2| driven thereby is causing a maximum flow of air through the airconditioning chamber I0. The terminals H0, III, and H2 are connected by conductors I30, I3I, and I32 to the switches I23, I24, and I25, respectively. The terminal I09 is connected by means of the conductors I33, I34, and I35 to the mercury switches I 23, I24, and I24, respectively. A manual switch I40 controls the connection between the terminal I09 and all the mercury switches so that the motor 23 may be stopped at any time by operation of the manual switch I 40.

The operation of the motor H5 is controlled by the controllers I40 and I. The controller I40 includes a bulb I42 connected by means of the capillary tube I43 to a bellows I44, this tube, bulb, and bellows being provided with a suitable volatile fluid so that the bellows I44 will bev caused to expand or contract inaccordance with variations in temperature affecting the bulb I42. The controller |4I similarly includes a bulb I45 connected by means of a capillary tube I46 to a bellows I41, this tube. bulb, and bellows also being provided with a suitable volatile fill. As will be noted upon reference to Figure 1 the bulbs I42 and I45 are mounted in a chamber I50 which comprises the connection between the outlet 21 of the heat exchanger 25 and the pipe 42 The bulbs I42 and I45 are therefore subject to the temperature of the water leaving the heat exchanger unit and accordingly the bellows operated thereby will expand or contract in accordance with changes in temperature of the water leaving the unit 25.

The controller I40 also includes a bell crank lever pivoted at I52, one arm I53 of this lever being biased by means of a spring I54 into engagement with the upper portion of the bellows I44 and the other arm I55 being arranged to sweep across a potentiometer resistance I56. A link I51 provided with an insulated portion I58 is connected to a control arm I60 pivoted at |6| and arranged to sweep across the potentiometer resistance I65. As the bellows I44 expands or contracts the arms I55 and I60 will be caused to move in unison as will be understood across their respective resistances. The resistances are so arranged that the arm I55 will move to the right end of its resistance before the arm I60 will start to move across its resistance I65. The arm I60 and resistance I65 form the main con trol elements for the proportloning motor 6 of the step controller H5. The upper terminal of the motor |I6 designated B is connected to the left end of the resistance I65 by means of a conductor I10. The terminal W of the motor 6 is connected by means of a conductor I12, the adjustable resistance I13 and conductors I14 and I15 to the right end of the resistance I65. The center terminal R of the motor 8 is connected to the control arm I60 by means of a conductor I18, a switch arm I18, contact I80, and conductor I8I. Power may be supplied to the motor 6 by means of conductors I85 and I86 to a suitable source of power (not shown). Upon reference to the above mentioned Taylor patent it will be understood that the shaft 1 driven by the motor II6 will assume positions corresponding with the position of arm I60 with respect to resistance I65. In the position illustrated with the arm I60 at the extreme right end of the resistance I65 the shaft 1 has been rotated by the motor |I6 to one extreme position. When the temperature of the water leaving the unit 25 drops to a low enough value which may be 75 F., the contraction of the bellows I44 will cause the arm I60 to start moving across the resistance I65 towards the right. When this happens the shaft II1 will start moving the cams carried thereby in a counter-clockwise direction so that as the temperature of the water leaving the unit 25 drops the speed of the motor 23 will be reduced in a step by step manner. The provision of the resistance I13 in the circuit to the terminal W of the motor II6 prevents the motor from moving far enough to open the mercury switch I23 under the influence of the controller I40.

The controller I45 controls the position of a mercury switch I80 carried by a lever |9| biased by means of a spring I82 into engagement with the upper portion of the bellows I41. This mercury switch I80 is arranged to short-circuit the resistance I13 when the switch is moved to closed position, this short-circuiting taking place by means of conductors I83 and I84 connected to opposite ends of the resistance I13. Thuswhen the temperature at the bulb I45 which is at the outlet of the heat exchange unit 25 drops to a sufllciently low value such for example as 34 F., the mercury switch I will be-moved to closed position through shunting out the resistance I13 whereupon the motor II6 will cause clockwise movement of the .cams H8 and H8 so that the switches controlled thereby will be tilted in the opposite direction from that illustrated. When this happens the motor 23 stops operating so that no air is drawn through the air conditioning chamber I0 by the fan 2|. A spring arm I88 is positioned to hold the lever I8I in the position it assumes when the switch I90 is tilted to closed position regardless of a subsequent rise in temperature at the,bulb I45 so that it will require manual attention to permit the switch I80 to move back to its open position and thus breaking the shunt around the resistance I13.

The'valve I02 which permits the water to drain from the coils 25 and 4| is controlled by the switch I22 operated by the cam 8 of the step controller II5. A solenoid 200 is provided for opening the valve I02 when the solenoid is energized. When the switch I22 is tilted to its opposite position by reason of a drop in temperature at the outlet of the coil 25 the solenoid 200 is energized through the conductor 20I, switch I22, conductor'202 to the solenoid 200 and conductor 203, the conductors MI and 203 beingconnected to a suitable source of power (not shown). From the foregoing it will be understood that the speed of the fan 2| is controlled by the controller I40 so that as the temperature of the water leaving the heat exchanger unit 25 drops from a value of say 75 F. to 70 F., the speed of the fan will be reduced in a step by step manner from a maximum speed to a minimum speed. Whenever the temperature of the water leaving the unit 25 is sufficiently high so that the arm I60 is at the extreme left of the resistance I65 the fan will operate at its maximum speed. Should the temperature of the water leaving the unit 25 drop to a sufliciently low value as for example to 34 F., indicating that upon a further drop there might be danger of freezing the coils 25 and 4| the controller I interrupts the operation of the fan and opens the drain valve I02 thus permitting the water to drain from the coils and stopping the flow of air thereof by the fan 2|.

The motor 33 for operating the pump 32 which pumps water from the well 30 to the heat exchangers in the air conditioning chamber is shown as being controlled by means of a relay designated by the reference character 2I0. This relay includes a relay coil 2| I, an armature 2|2 and switch arms 2I3, 2I4, 2|5, and 2|6 operatively connected to the armature 2I2. Power is supplied to the motor 33 by means of conductors 2|1, 2|8, and 2I8 and it will be understood that when the relay 2I0 is energized and the arms 2|3, 2|4, and 2|5 move into engagement with their cooperating contacts the motor 33 will be energized and water will be pumped from the well by means of the pump 32 to the coils 25 and 4| in the air conditioning chamber I0. The relay 2I0 is designed to be manually energized by means of a normally open switch 224. When this switch isdepressed current will flow through the relay coil 2" as follows: from the conductor 2" through conductors 226, 221, switch 224, conductor 223, relay coil 2| I, conductor 223, the mercury switch I22, it beingassumedthat this switch is in the'position illustrated and conductor 233 to the conductor 2I3 connected to the source of power. The relay is now energized and upon movement of arm 2" into engagement with its cooperating fixed contact a holding or maintaining circuit for the relay 2 which is independent of the manual switch 224 is established this maintaining circuit for the relay 2I3 is as follows: from the conductor 2I9 through conductors 226, 235, the switcharm 2I6, conductor 236, a switch member 233, conductor 233, a normally closed mercury switch 243, conductor 2. relay coil 2| I, conductor 229 through the mercury switch I22 in the step controller 5 and conductor 233 to the conductor 2I3 connected to the source of power. that the energization of relay 2 I 3 is not dependent upon the manual normally opened switch 224 remaining in its closed position. The provision of the switch 233 permits manual deenergization of the relay coil 2 when desired. Since the maintaining circuit for the relay 2I3 includes the mercury switch I22 in the step controller III it will be apparent that when the temperature of the water leaving the conditioning unit 25 drops to such a low, value that the switch I22 is moved to its other position and the fan motor 23 is deenergized and drain valve I32 is opened. the relay 2I3 will simultaneously be deenergized whereupon the motor 33 which drives the pump 32 will stop so that water will no longer be supplied to the coils in the air conditioning chamber I3. In this manner whenever the temperature of the water leaving the coil 25 becomes dangerously low indicating the inadvisability of pumping more water thereto the pump 32 stops operating.

The maintaining circuit for relay 2I3 also includes a mercury switch 243 and this switch is carried by an arm of a lever 253. One arm of this lever is biased by means of a spring 25I into engagement with the upper portion of a bellows 252 which has its interior in communication with the pipe 94 which is in communication with the outlet of the pump 32. As the pressure of the water in the outlet of the pump 32 varies the bellows 252 will be caused to expand or contract and thus control the position of the lever 253 as will be apparent. This lever also includes an arm 255 which is arranged to sweep across a potentiometer resistance 256. The arm 255 and resistance 256 form the control potentiometer for a motor 263 which includes an arm 26I connected by means of a link 262 to the stem 263 of the valve 53 which controls the flow of water from the outlet of the coils 25 and 4i to the channel 56 leading to the well 33. The motor 263 may be a proportioning motor similar to the motor II 6 of the step controller H5 and the position of the valve 53 will therefore depend upon the position of the arm 255 with respect to the resistance 256-. As the arm 255 moves towards the right in response to a drop in pressure at the outlet of the pump 32 the valve 53 will move towards open position a proportionate amount. A drop in pressure at the outlet of the pumpmay be an indication that the supply of water in the well 33 is becoming depleted and it is therefore advisable to send the water back to the well instead of allowing it to go to waste. When there is sufllcient water in the well however it may be advisable to It will now be understood permit the water to so to waste so that the water assaeos in the well will not become too warm during the cooling season, for example. or-will not become too cold during the heating season. Obviously if the water is raised in temperature in the air conditioning chamber and then recirculated back to the well the supply of water in the well will increase in temperature. By sending the water through the subterranean channel 53 before it reaches the well it will tend to assume the temperature of the water in the well. It is preferable however when there is an ample. supply of well water to not recirculate this water but when the supply is becoming depicted as evidenced by a drop in the pressure at the outlet of the pump 32 then the water should be returned thereto and this is readily done by controlling the valve 53 in the manner set forth above. Should the pressure drop to a sufllciently low value indicating that the supply of water in the well is so low that it is useless to run the pump 32, the switch 243 carried by the lever 253 will be moved to open position thus interrupting the maintaining circuit for the relay 2" so that the operation of the motor 32 is interrupted and the pump 32 will not continue to operate.

Situated above the penthouse II is a control device indicated generally by the reference character 215. This control device may include a bulb 236 having a portion thereof located within a small insulated casing 231 but having its interior subject to the outside temperature and humidity conditions by means of the aperture 233. That portion of the bulb 236 located within the casing 231 is subject to the wet bulb temperature of the air, this portion being provided with a suitable wick or the like 239 having a portion located in a pan of water 293 as is conventional in the art. The extreme outer portion of the bulb I 236 may be blackened so that it will respond to radiant heat and the portion to the left of this blackened portion will be subject to the dry bulb temperature of the air. The bulb 286 is connected by means of a capillary tube 292 to a bellows 294, this tube, bulb, and bellows being provided with a suitable volatile fill whereupon the bellows will expand or contract in response to variations in the dry bulb temperature of the outside air as well as variations in the wet bulb temperature and radiant heat. Accordingly the bellows will respond to variations in the actual external cooling load on the building.

The bellows 294 form a portion of a control device '295, this control device also including a lever 296 having an arm biased by means of a spring 291 into engagement with the top of the bellows. The arm 293 of the lever 296 moves over the resistance 299 as the bellows expands and contracts. The arm 293 and resistance 299 form a control potentiometer for a proportioning motor 333 which operates the step controller 332. The shaft 333 of the motor 333 moves between two extreme positions in response to movement of the arm 293 between the ends of-the resistance 299.

troller 215 varies from 77 to approximately although these so-called resultant temperatures will depend of course upon the radiant heat as well as the humidity.

The potentiometer 305 forms one of the control devices for a motor 3I0 which may also be a proportioning motor similar to the motor 6 and this motor is provided for controlling the position of the valve 40 which controls the flow of water to the heat exchanger unit 25. An arm 3I2 carried by the motor 310 is connected by means of a link 3I3 to the stem 3I4 of the valve 40. The extreme left end of the resistance 305 is connected to the B terminal of .the motor 3I0 by means of conductors 3I6 and 3I8 whereas the lower terminal marked W is connected to the opposite end of resistance 305 by means of conductors 320, 311, and 32I. The arm 304 is connected to the center terminal of the motor 3I0 by means of a conductor 325, an adjustable resistance 326,

conductors

321, 328, a mercury switch 330, and conductor 33I'. When the mercury switch is in the position illustrated the position of the motor 3I0 will be controlled by the position of the arm 304 with respect to the resistance 305 and as the arm 304 moves to the left the valve 40 will tend to move towards open position and vice versa, but at the same time the controller I42 will tend to move the valve towards open position as explained below.

The operation of the motor 3I0 is also controlled by the controller I40 which is responsive to the temperature of the water leaving the unit 25. The center terminal R of the motor 3I0 is connected to the control arm I55 of the controller I40 by means of conductors 33I, the mercury switch 330, conductors 328, .340 and the center tapped resistance 345. The upper terminal B of the motor 3I0 is connected by means of conductors 3H! and 345 to the left end of the resistance I56 while the opposite end of this resistance is connected by means of

conductors

346 and 320 to the bottom or W terminal of the motor 3I0. Since the circuit to the arm 304 of the controller 302 includes the resistance 326 this controller is less sensitive than the controller I40. In other words, if movement of arm 304 from one extremity to the other of the resistance 305 is required to cause movement of the valve 40 from open to closed position a similar movement will be imparted to the motor upon movement of the arm I55 through a small distance as indicated at X. The effect of the controller 304 is therefore to adjust the control range of the controller I40 on the motor 3I0. Thus as the load on the cooling system rises and arm 305 moves toward the right, the control range X of the controller I40 will be moved toward the left so that a higher temperature of the water leaving the coil 25 in the air conditioning chamber will be maintained and in the end more water will be circulated through valve 40. The provision of the center tapped resistance 345 in the controller I40 insures that the control range will always be of the same magnitude regardless of the position of this control range with respect to the resistance l'56. The arrangement is such that the temperature of the water leaving the heat exchanger unit 25 during the cooling season will be maintained at very nearly the temperature of the air entering the air conditioning chamber so that the maximum cooling capacity of the water will be utilized. I

To summarize the operation of the valve =40, the main control of this valve is by the controller I40 which positions the valve in accordance with the temperature of the water leaving.

the coil 25, and the temperature which is maintained at the outlet of the coil is varied as the outside cooling load varies so that as the cooling load increases, the temperature of the water leaving the coil will be increased to cause the water to have a temperature nearly ashigh as the temperature of the air entering the air conditioning chamber. The result is that'the valve 40 is operated to permit an increased supply of water to the coil 25 as the cooling load increases and vice versa. While the controller 215 responding to the cooling load tends to move the valve towards closed position as the cooling load increases, the temperature of the water leaving the coil will simultaneously increase as the cooling load increases and since the main control over'the valve is by the controller I40, the net result is that an increase in the cooling load means an increase in the amount of water entering the coil 25 and an increase in the temperature of the water leaving the coil, and vice versa.

Provision is also made for positioning the .valve 40 in a fixed partially open position during the wintertime so that regardless of the temperature of the outside air there will be a fixed flow of water to the heat exchanger units in the air conditioning chamber I0. For this purpose the mercury-switch 330 in the step controller 302 is utilized. When the outside temperature drops to a certain low value the cam 360 carried by the shaft 303 of the motor 300 is rotated in a counterclockwise direction until the switch 330 operated thereby is tilted in the opposite direction from that illustrated. The R and W terminals of the motor 3I0 are now connected together as 101- lows: from the R terminal through conductor.

33I, the mercury switch 330, conductor 362, a variable resistance 363*, and conductors 364, 3H, and 320 to the W terminal of the motor 3I0. This will cause the motor'3l0 to move the valve 40 to a minimum open position, the position of the valve being determined by the setting of the resistance element 326. Before the valve is moved by the switch 330 to this minimum open position during the heating season it will have been moved to entirely closed position by the controllers 305 and I40 at an outside temperature of, say 77 F., since the control range of the arm I55 will be shifted to the extreme right end of the resistance I56 and when the water temperature drops to F. for example, the R and W terminals of the motor will be directly connected together and the valve will be entirely closed but as the temperature continues to drop and the switch 330 is moved to its opposite position the placing of the resistance 363 in the circuit to the W terminal of the motor will cause this motor to open the valve to a predetermined position.

The step controller 302 also includes a cam 310 which controls the operation of the valve 6| for admitting water to the spray 60 located on the roof of the building being conditioned. The valve 6| may be operated by a motor 315 connected by conductors 316 and 311 to line wires so that the valve 8| is inits open position and water is supplied to the spray 88 for additionally cooling the building. If the cooling load on the building should decrease the motor 388 will be operated by the controller 215 to move the cam 318 in a counter-clockwise direction and after the load drops to a predetermined value the switch 388 will be tilted in the opposite direction and close a circuit through the conductors 38I and 383 which are connected to the R and W terminals of the motor 315 so that this motor now causes the valve to move to closed position and stop the flow of water to the spray 68.

It is intended to supply water to the spray 88 only when the cooling load is quite heavy since when the cooling load is not sufliciently great it is advisable to cause the water to flow either to the outlet 5| or the outlet 52 to take advantage of the syphonic action to reduce the load on the pump 32. If this syphonic action is great enough however the pressure within the coils 25 and 4| may be so reduced that the rate of heat exchange at the coils 25 and 4| may drop and reduce the efficiency of these units. In order to overcome this difllculty the pressure responsive device 398 is provided. This device includes a bellows 39! connected by cams of a pipe 392 to the pipe leading to the inlet 28 of the heat exchanger unit 25, between this unit and the valve 48. A lever 395 carries a mercury switch 398 on one arm thereof and this arm is biased by means of a spring 391 into engagement with the upper portion of the bellows. A second arm 398 of this lever is arranged to sweep over a potentiometer resistance 488, this arm and resistance forming a control potentiometer for a motor 8 which is connected to the valve 54 controlling the flow to the outlet 52. It will be understood that upon a drop in pressure between the valve 48 and the coil 25 the bellows 39| will contract and move the arm 398 towards the right and upon an increase in pressure the arm 398 will be moved toward the fan 2I would result in circulating unheated air through the space tobe conditioned in the wintertime or hot'air through the space in the summertime. For this purpose the relay 438 is provided. This relay includes relay coil 43I, an armature 432, the arm I19 positioned thereby cooperating with the flxed contact I88 and contact 434. When the relay coil-43| is deenergized the arm I19 is maintained in engagement with the fixed contact I88 under the influence of gravity or any suitable biasing means (not shown) and upon energization of the coil 43I the arm I19 is moved into engagement with the fixed contact 434. The energization of the relay 438 is controlled by the mercury switch 396 operated by the pressure responsive controller 398 and by a second mercury switch 448 carried by the arm I of a bell crank lever having its other arm 442 situated in the path of movement of the arm 3I2 operated by the motor 3 I 8 which controls the position of the valve 48. The arm I is normally in engagement with a stop 445 but whenever the valve is moved to its fully closed position the bell crank lever is tilted to a position wherein the left. Conductors H2 and 4|3 connect the right I and left hand ends of the resistance 488 with the B andW terminals of the motor 4I8, and the R. terminal of this motor is connected by the conductor- M5 to the control arm 398 of the controller 398.

The arm 4|8 of the motor 4|8 is connected by means of a link M9 to the valve stem 428 of the valve 54. Upon a decrease in pressure of the water the movement of arm 398 of the controller 398 towards the right will cause the valve 54 to be moved towards closed position by the motor 4| 8 so as to reduce the rate of flow from the outlet 52 and build up a back pressure in the system or reduce the syphonic action so that the pressure of the water in the units 25 and 4| will be high enough to insure efiicient operation thereof. When the pressure becomes too high in these units the valve 54 is opened to a greater extent so as to prevent the pressure from becoming excessive. Valve 54 may be placed in line 49 if the characteristics of the pump 32 and well 38 are such that they do not allow this pressure building to take place in the manner described.

Provision is also made for interrupting the operation of the fan 2| and the pump 32 should the pressure in the system become abnormally low. This is advisable since if the pressure is willciently low between the valve 48 and the coil 25 it indicates that sufficient fluid is not being pumped through the coil to affect any appreciable heating or cooling of the air in the chamber I8 as the case may be so that continued operat on Oi tilt switch 448 is tilted in its other position. When the valve 48 is positioned in its fixed minimum open position during the wintertime the switch 448 will be in the position illustrated and it should be understood that this switch is moved to its other position only during the summertime when :he valve 48 is in full or nearly fully closed posiion.

When the pressure between the valve 48 and the coil 25 becomes sufilciently low that the mercury switch 396 of the controller 398 is tilted to its closed position and with the switch 448 in the position illustrated the relay coil 43I of the relay 438 will be energized as follows: from the line wire 319 through conductors 458, 45I, mercury switch 396, conductor 454, mercury switch 448, conductor 458, the relay coil 438 and conductor 451 to the line wire 318. It will now be understood that the relay 438 is energized only when the valve 48 is at least partially .open and the pressure between this valve and the coil 25 drops sufficiently. The energization of the relay 438 causes arm I 19 thereof to be moved into engagement with the contact 434 whereupon the R and W terminals of the motor II6 of the step controller 5 are directly connected together as follows: from the R terminal of the motor through conductor I18, arm I 19, contact 434, conductors 468 and I12 to the W terminal of the motor. The motor H6 is now operated to move the various cams controlled thereby in a counter-clockwise direction to a position wherein the mercury switches I22 to I25 are tilted in their other positions. The circuit to the fan motor 23 is now interrupted at the mercury switch I23, the circuit to the motor 33 driving the pump 32 is interrupted at the mercury switch I22 and at the same time the motor 288 for the drain valve I82 is energized. It will now be seen that when the pressure of the water entering the coil 25 drops sufiiciently the circulation of air through the air conditioning chamber is stopped, the main pump motor 33 is stopped, andthe water is drained from the heat exchanger units. It is advisable to drain the water from the heat exchanger units particularly in the wintertime since otherwise all of the water in these coils might freeze up and to avoid this danger the water is drained therefrom at the same time that the pump 32 and fan 2| are stopped. It may often happen in the summertime that the valve 48 will be positioned in very nearly closed position but the system is operating properly to give the necessary cooling effect to the air passing through the chamber l0. With the valve 40 in this very nearly closed position the pressure of the water between the valve and the coils 25 may become very low but 'it is not advisable at thistime to shut the system down since this drop in pressure may result from this minimum opening of the valve 40. When this happens therefore the switch 440 will be moved to open position by the arm 3|2 of the motor 3|0 so that the relay 430 cannot be energized and the system will not therefore shut down.

During the summer cooling season the temperature of the well water may not be low enough to give the necessary cooling to the air being conditioned and the refrigeration system including the compressor 10, the condenser 48, and the evaporator 34 is provided. The operation of the compressor is controlled by a controller 415, this controller including a bulb 416 mounted in engagement with the pipe. 35 through which the water is flowing, this bulb being connected by a capillary tube 418 to a bellows 480, the tube, bulb, and bellows being provided with a suitable volatile fill so that expansion and contraction of the bellows will take place in accordance with variations in the temperature. An arm 48| of a bell crank lever is biased by means of spring 482 into engagement with the upper portion of the bellows 480 and the other arm 485 of this lever is arranged to sweep across a potentiometer resistance 486 in accordance with variations in pressure within the bellows 480. The potentiometer 486 controls the operation of a motor 490 of a step controller 492 which controls the operation and speed of the compressor motor 1|. The right end of resistance 486 is connected by means of conductor 494 to the B terminal of motor 490 and the opposite end of the resistance is connected by means of conductors 496 and 491 to the W terminal of the motor 490. The arm 485 is connected by means of a conductor 499, mercury switch 500 and conductor 50| to the R terminal of the motor 490. The mercury switch 500 is operated by a cam 582 of the step controller 302 and this switch will be in the position illustrated Whenever the cooling load on the system is sufli ciently high. When the outside temperature drops to a low enough value however, the switch 500 will be tilted in its other position for a purpose to be set forth.

The step controller 492 for controlling the operation of the compressor motor 1| includes

cams

505, 506, and 501 which control the position of mercury switches 508, 509, and 5I0, respectively. These cams are moved by the motor 490 in a clockwise direction in response to an increase in temperature at the bulb 416 and as the tempera. ture of the water decreases and the control arm 485 of the controller 415 moves to the left decreasing the resistance between the R. and W terminals of the motor 490 the cams of the step controller 492 will move in a counter-clockwise direction to sequentially open the mercury switches. In the position illustrated the mercury switches 508 and 509 are closed and the switch 5I0 is open. The switch 508 controls the low speed operation of the compressor motor 1|, this switch closing a circuit between the terminals 5|5 and 5I6 of the control box 520 of the compressor motor 1| as follows: from the terminal 5| 5 through conductor 52 the switch 508 and conductor 522 to the terminal 5|6. Conductors 523 are provided for connecting the control box 520 to a suitable source of power (not shown). It will accordingly be seen that when the temperature outdoors is high enough so that mercury switch 500 of the step controller 302 is in the position illustrated and the temperature of the water is sufficiently high so that mercury switch 508 is in closed position the compressor motor 1| will operate at low speed to cool the water flowing through the evaporator 34 to further increase the cooling effected by the coil 25 in the air conditioning chamber.

If the temperature of the water affecting the bulb 416 is still too high the mercury switch 509 of the step controller 492 will be in closed position and this will cause the energization of the motor 86 driving the pump 85. 525 and 526 of the control box 521 for the motor 85 will be connected together through the mercury switch 509 by means of the conductors 530 and 53|. The pump 85 will therefore operate to recirculate some of the water through the evaporator 34 thus increasing the amount of heat exchange in the evaporator so as to further reduce the temperature of the water flowing through the pipe 35 and to the heat exchanger 25.

Should the temperature of the water in the pipe 35 still be too high the motor 490 will be operated by the controller 415 to rotate cam 501 to a position wherein the switch 5I0 is in closed position thus closing a circuit between the high speed terminals 5| 6 and 5| 1 of the starter box 520 as follows: from the terminal 5| 6 through conductor 522, mercury switch 508 will still be in its closed position, the conductor 540, switch 5I0, and conductor 54| to the terminal 5|1 of the control box 520. The compressor will now operate at high speed to increase the flow of refrigerant through the evaporator and to further reduce the temperature of the water flowing to the coil 25.

It will now be seen that the system for cooling the water being supplied to the coil 25 first causes the operation of the compressor 1| at low speed, then causes the operation of pump 85 to increase the amount of heat exchange in the evaporator 34 and if this is not sufficient to reduce the temperature of the water the necessary amount the compressor is then operated at high speed so that the water will be delivered to the heat exchanger 25 at the proper temperature. When the outdoor temperature or cooling load becomes sufiiciently low the cam 502 of the step controller 302 rotates to a position wherein the switch 500 is tilted in the opposite direction. The R and W terminals of the motor 490 of the step controller 492 will now be directly connected together as follows: from the R terminal through conductor 50I, mercury switch 500, conductors 545 and 491 to the W terminal of the motor 490. The motor 490 will now operate to move the

cams

505, 506, and 501 in a counter-clockwis direction to an extreme position wherein all the mercury switches controlled thereby are in open positions. The operation of the compressor motor 1| will now be interrupted as will the operation of pump since the cooling load on the system is sufiiciently low that no auxiliary cooling of the cooling water is necessary. Since the cooling water will be of approximately the same temperature at all times the various controls can be so adjusted that the auxiliary cooling means for the cooling water can be shut oif as the cooling load de- The terminals creases and the valve 48 which controls the flow of water to the cooling coils will be suflicient to control the amount of cooling efiected thereby.

Located in the discharge outlet from the fan 2| is the bulb 550 of a controller 552. The bulb 558 is connected by means of a capillary tube 558 to a bellows 554-, this tube, bulb, and bellows being provided with a suitable volatile fill so that the bellows will expand or contract in accordance with variations in temperature at the fan discharge. A bell crank lever 555 has an arm 558 biased by means of a spring 551 into engagement with the upper portion of the bellows 554 and the arm 558 of this lever is arranged to sweep over a potentiometer resistanc 588. As the temperature of the air leaving the air conditioning chamber drops the arm 558 will move to the right and upon an increase in this discharge temperature the arm will be moved toward the left over the resistance 588. This controller 552 controls the position of the valv 48 by means of which the amount of water leaving the heat exchanger 25 and passing through the reheater 4| may be effectively controlled. The controller 552 is arranged to control the operation of the valve 43 in accordance with the discharge.temperature during the cooling season only but during the heating season this valve will be moved to a position wherein all the water will be caused to now through the by-pass 45. This valve might also be controlled by a humidostat in the space to be treated.

For this purpose a relay indicated generall by the reference character 515 is provided, this relay including a coil 518, an armature 511, and switch arms 589, 58l, 582, 593, and 594. When the relay is deenergized the arm 588 is in engagement with the contact 598 and the arms '582, 583, and 584 are in engagement with

contacts

592, 593, and 594, these arms being moved to these positions under the influence of gravity or any suitable biasing means (not shown). Upon energization of the relay the switch arms will all be moved toward the left, the arm- 588 being moved out of engagement with the contact 598 and the remaining switch arms being moved into engagement with the fixed

contacts

598, 591, 598, and 599, respectively. The energization of the relay 515 is controlled by the step controller 392 and more particularly by means of the cam 888 thereof. The mercury switch 6M is controlled by the cam 589 of this step controller and during the cooling season this switch will be in open position as illustrated. When the outside temperature is sufllciently low however and the cams are moved in a counter-clockwise direction to their extreme positions the switch 88| will be moved to closed position and will energize the relay coil 518 as follows: from the line wire 319 through conductor 805, switch 8M, conductor 808, relay coil 515, and conductor 881 to the line wire 318. It will therefore be seen that when the outside temperature is sufliciently low the relay coil 518 will be energized and the various switch arms operated thereby will be moved to the left into engagement with their respective contacts.

Assuming that the outside temperature is sufficiently high so that the relay 515 is deenergized and the system is being used for cooling the air supplied to the building the motor 8H] for controlling the position of the three-way valve 43 will be operated in accordance with the discharge temperature from the fan 2|. The B terminal of the motor 8|8 is connected to the V W mam arm 828 of the motor with the valve stem 821.

This motor 8" may be a proportioning motor similar to the motor 8 and it will be understood that the position of arm 828 of the motor and accordingly the position of the valve 48 will vary proportionately with the position of the control arm 558 of the controller 552 with respect to the resistance 588 or in other words, will vary in accordance with the temperature of the air leaving the air conditioning chamber l8. As the discharge temperature drops the valve will move to a position wherein more of the water is caused to flow through the reheater 4| and a lesser amount by-passes this reheater. Therefore the controller 552 acts to prevent the temperature of the air entering the space being conditioned from dropping below a predetermined value byutilizing the relatively warm water leaving the coil 25 for reheating the air as may often be necessary, particularly where the outside relative humidity is high and the coil 25 is being utilized for removing latent heat from the air by reducing the temperature of the air below its dew-point.

During the heating season it is desirable to use only the heat exchanger 25 for heating purposes since the temperature of the water leaving the coil 25 might be considerably lower than the temperature of the airleaving the coil 25 by reason of the counterflow relationship, and it is therefore desirable to cause all of the water leaving the coil 25 to flow through the by-pass 45. Accordingly the valve 48 is positioned so that all the water will have to flow through the by-pass 45. When the outside temperature drops sufficiently low so that the mercury switch 88| of the controller 882 is moved to closed position and the relay 515 is energized the R and W terminals of the motor 8l8 will be directly connected together so that the' valve will be moved to the position wherein all the water will by-pass the coil 4|, the connection between these terminals being as follows: from the R terminal through conductors 82|, 88|, contact 598, arm 58|, conductors 832 and H5 to the W terminal of the motor 8| 8. Accordingly when the relay 515 is energized due to a drop in outside temperature the controller 552 will have no eifect whatever upon the valve 48 which will be maintained in the position wherein all the water flows through the by-pass 45.

In order to heat the water during the wintertime the heat exchanger 88 through which the water flows on the way to the air conditioning chamber is provided and steam is admitted to this heat exchanger through the pipe 95, the flow of steam being controlled by the valve 98. A proportioning motor 848 may be provided for controlling the position of the valve 88, the arm 5 of this motor being connected to the valve by means of a link 842. The motor 848 is controlled primarily by the controller 552 in the wintertime but during the cooling season the valve 98 may be maintained in its fully closed position by the motor 848. When the relay 515 is deenergized the R and W terminals of the motor 848 are directly connected together and the valve 95 is maintained in its closed position. The connection between the R and W terminals at'this time is as follows: from the R terminal through conductors 544, 545, contact 590 of the relay 515, Mm 580, conductors 548, 555, 549, a mercury switch 550 whose function will be hereinafter set forth but which will be in closed position during the heating season and

conductors

552 and 553 to the W terminal of the motor 540. The controller 552 will therefore have no effect upon the motor 540 during thesummertime but during the heating season when the relay 515 is energized the controller 552 will control the operation of the motor 540 and determine the position of the valve 95. With the relay 515 energizedthe W terminal of motor 540 will be connected to the left end of resistance 550 by means of

conductors

553, 552, mercury switch 550, conductors 549, 555,

551, contact 591 of relay 515, arm 582, and conductor 5I5 whereas the opposite end of resistance 550 will be connected by means of conductor 550, arm 584, contact 599 of relay 515, and conductor 55I to the B terminal of motor 540. The R terminal of the motor will be connected by means of conductors 544, 552, contact 599, arm 583, and conductor 5I5 to the control arm 55-8 of the controller 552. Accordingly upon a decrease in temperature at the bulb 550 the arm 558 will be moved toward the right decreasing the resistance between the R and B terminals of the motor 540 and thus opening the steam valve to heat the water flowing to the air conditioning chamber.

In order to further safeguard the coils 25 and 4I against freezing during cold weather provicold air over the units and M.

' I5 and I5 will be caused to assume positions by sion is made for causing valve 95 to be opened to at least a minimum position when the outside temperature is sufficiently low and for this purpose the controller 515 is provided. The controller 515 includes a bulb 515 located in the fresh air inlet and connected by means of a capillary tube 511 to the bellows 518, this tube, bulb', and bellows being provided with a suitable volatile fill so that the bellows 518 will expand or contract in accordance with variations in the fresh air temperature. The mercury switch 550 is carried by a lever 580 biased by means of a spring 58I into engagement with the upper portion of the bellows and when the fresh air temperature drops sumciently low the contraction of the bellows 518 will cause the switch 550 to move to open position. The connection between the W terminal and motor 540 and the left end of resistance 550 of the controller 552 now includes the variable resistance 590 which was previously shunted out by the conductor 552 and the mer- Positioned just ahead of the heat exchanger unit 25 is the bulb 100 of a controller-10I which may be of a construction similar to the construc tion of the controller 552 and this controller is suitably connected to a proportioning motor 20 so that this motor operates in accordance with the temperature of the mixture of fresh and return air passing through the air conditioning chamber 'prior to being conditioned.

Arms

102 and 103 operated by this motor are connected by means of links 104 and-105 to the dampers I5 and I5, respectively. This controller forms a further means to safeguard the coils within the chamber-I0 against freezing and is adapted to start closing; the fresh air damper I5 and open the return air damper I5 when the temperature of the air passing over the coil 25 drops below a predetermined value of say 35 F. As the fresh air dampers I5 start to close and the return air dampers I5 start to open the fresh air entering at I3 will mix with the relatively warm return air and thus prevent the passage of extremely The dampers the controller 10I so that the temperature of the air passing over the air conditioning units will be at all times high enough to prevent freezing of the coils. If desired these dampers may be so arranged that the dampers I5 in the fresh air inlet are never moved to fully closed position so that there will always be a certain amount of fresh air taken into the system for ventilating purposes. These dampers function as a safety feature toavoid the danger of freezing of the air conditioning units and also serve to reduce the heating load during the wintertime when the outdoor temperature becomes abnormally low. If desired, however, these dampers might be omitted and a fixed amount of fresh air taken into the system at all times, the controller I operating as a safety device to prevent freezing of the coils 25 and 4|. However, if the dampers are also used and controlled in the manner decury switch 550 when this switch was closed.

The circuit between the W terminal of the motor and the controller 552 is now as follows: through the conductor 553, 59I, variable resistance 590, conductors. 592, 555, 551, contact 591 of relay 515, arm 582, and conductor 5l8. Accordingly regardless of the discharge temperature at the fan 2I if the outside temperature is sufliciently low there will always be a certain resistance between the R and W terminals and motor 540 will cause the valve 95 to be opened a predetermined amount, this resistance being variable so that the minimum opening of the valve may be variedat will. Accordingly when the outside temperature drops to a sufficiently low value a. certain amount of heat will at all times be supplied to the water entering the heat exchanger units 25 and M to further safeguard these units against freezing.

scribed then the danger of freezing is very unlikely by reason of the two devices which safeguard the coils 25 and M.

Operation The operation of the system should be apparent from the preceding description thereof but may be summarized as follows: during the cooling season the flow of water to the coil 25 will be controlled by the valve 40 and this valve is controlled by the controller I40 responsive to the temperature of the water leaving the coil and this controller will be compensated by the controller 215 which measures the total cooling load on the system since this controller responds to the wet bulb temperature of the air, the dry bulb temperature of the air, and the radiant heat of the air. It should be understood however that this controller 215 may be of any conventional form for measuring the total cooling load on the system. The temperature of the water leaving coil 25 will be maintained at a value only slightly below the temperature of the air so that the maximum cooling effect of the water being circulated therethrough may be utilized. When the cooling load is sufliciently high the auxiliary cooling system for the cooling water will be placed into operation to maintain the temperature of the water entering the coil 25 at a, predetermined value by means of the controller 415 controlling the operation of the compressor 10 and the circulating pump 85. As the water temperature increases the compressor will first be operated at low speed, the pump 35 will then be put into operation and upon a further increase in the water temperature the compressor 70 will operate at high speed.

The water is returned to the source of supply only when the source is becomingdepleted as evidenced by a drop in pressure at the controller 252 and when this pressure drops the valve 53 is opened a corresponding amount to return the water to the source by way of the subterranean temperature leveling channel 58. When the pressure at 252 is sufliciently high indicating an ample supply of cooling water at the source 30 the valve 53 will be closed and the water will go to waste through-the drain 58. The valve 54 controlling the flow to the drain 58 will be operated in accordance with the pressure of the water between the valve 40 and the coil 25 in a manner to insure that the pressure of the water in this coil will be sufflciently high to insure a high rate of heat exchange. Should the pressure between the valve 40 and the coil 25 drop the pressure responsive controller 390 will move valve 54 towards closed position to increase the back pressure on the coils 25 and 4|. When the cooling load is sufficiently high the valve 6| is opened so that the water leaving the air conditioning units may be sprayed on to the roof of the building byway of the spray 60 to further cool the building. This spray is not utilized however except when the cooling load is excessively high since the system may be more economically perated by allowing this water to pass through the drain 58 or to the well 30' so that the syphonic action of the water will assist the pump 32' in circulating the water through the cooling coils and thus relieve the load on this pump.

The temperature of the air entering the space being conditioned will not be allowed to fall below a predetermined value, the controller 552 which responds to the discharge air operating the valve 43 to cause the water leaving the coil 25 to pass through the reheater 4| by an amount which will reheat the air sufliciently to prevent this discharge air temperature from dropping below a predetermined value.

During the heating season, the control of the valve 43 will be taken away from the controller 552 through the operation of the relay 515 and this valve will be maintained in a position wherein all the water will flow through the by-pass 45. The steam valve 96 controlling the flow of steam to the heat exchanger 35 will be operated in the wintertime by the controller 552 so that the temperature of the air entering the space will be maintained at a predetermined value whereas in the summertime this steam valve will be maintained in a closed position. The valve 40 controlling the flow of water to the coil 25 will be maintained in a fixed predetermined position during the wintertime. During the summertime the speed of the fan 23 will be controlled in accordance with the temperature of the water leaving the coil 25 and as the temperature of this water drops from say 75 F. to,70 F. the fan speed will be reduced in a step by step manner from high speed to low speed. During the wintertime this fan will operate at a low speed at extremely cold weather to prevent the temperature of the air passing to the coil 25 from dropping below a predetermined value to avoid the danger of freezing the water in the coils. As a further safegiiard against freezing of the water in the coils the controller I which responds to the temperature of the water leaving the coil 25 operates when this temperature drops below a safe value suc as 34 F. to open the drain valve 200, thus draining the water from the coils 25 and 4| and also stops the fan 23 and the pump 32 so that cold air will not be admitted 'to the space being conditioned and so that water will not be supplied to the coil 25.

Whenever the pressure of the water entering the coil 25 becomes sufliciently low and this pressure drop is not due to the valve 40 being in closed position or substantially closed position during the cooling season it is an indication that the supply of water at the source is becoming so depleted that the system should be shut down or it may be an indication that the pump 32. is not operating properly. The controller 390 accordingly will stop the pump 32 and the fan 23 since it is not desirable to circulate air over the coils 25 when these coils are not being properly supplied with a conditioning fluid. The drain valve I02 will also be opened at this time since it would be inadvisable to leave the coils full of water particularly if the outside temperature was low and this forms an additional safety'feature for the system.

During the heating season the supply of steam to the coils is controlled as previously disclosed by the'discharge air temperature but the controller 615 additionally controls the supply 'of steam to insure a predetermined supply of steam thereto when the outside temperature drops sufficiently low to further insure the system against freezing during severly cold weather. It will thus be seen that there are many safeguards against the possibility of.the coils 25 and 4| freezing so that should anyone of these safeguards fail to operate for any particular reason the other safeguards will operate to prevent the system from freezing.

The water leaving the coils 25 and 4| is effectively utilized for the domestic water supply through the medium of the tank 65 containing a fixedsupply of water under pressure, this supply heing controlled by the float valve 68.

Having described the preferred form of my invention many modifications may become apparent to those skilled in the art and it should be understood that my invention is limited only by the scope of the appended. claims.

I claim as my invention:.

1. In an air conditioning system, an air conditioning chamber, a heat exchanger in said air conditioning chamber, means for circulating air over said heat exchanger, means for circulating a cooling fluid through said heat exchanger, valve means controlling the flow of cooling fluid to said heat exchanger. means for controlling said valve means so as to maintain the tem perature of the fluid leaving said heat exchanger at a given value, means responsive to the outside temperature for varying the temperature at which said fluid is maintained, and means responsive to a drop in outside temperature to a predetermined value for maintaining said valve means open a predetermined amount.

2. In an air conditioning system, a heat exchanger, means for circulating a cooling fluid through said heat exchanger, means for circulating air over said heat exchanger in counterflow relationship with respect to the flow of cooling fluid, a reheating coil over which the air being conditioned is circulated, valve controlled means for conducting fluid from the outlet of said heat exchanger through said reheating coil, means responsiveto the temperature of the air leaving said reheating coil in control of said valve means, valve means controlling the flow of cooling fluid to said heat exchanger, and means responsive to the temperature of the fluid leaving said heat exchanger and to a psychrometric condition of the outdoor air in control of said valve means.-

3. In a system of the class described, heat exchanger means, means for circulating a fluid through said heat exchanger means, said heat exchanger means being located above said fluid circulating means, .conduit means connected to said heat exchanger means and having an outlet positioned below said heat exchanger means whereby the siphonic action produced by the fluid flowing from the heat exchanger means, lessens the load on the circulating means. valve means controlling the flow of fluid to said heat/ exchanger means, condition responsive means in control of said valve means; second valve means controlling the flow of fluid from said conduit means, and means responsive to the pressure of the fluid between said first valve means and said heat exchanger means in control of said second valve means to maintain a predetermined pressure of the fluid. in said heat exchange means.

4. In an air conditioning system, an air conditioning chamber, means for circulating outside air through said air conditioning chamber and through a space to be conditioned, heat exchanger means in said chamber in the path of the flow of air, a source of cooling fluid, means for circulating said cooling fluid through sa d heat exchanger means, means conducting the fluid leaving the heat exchanger back to the source of supply or to waste, valve means controlling the flow of the fluid to waste, valve means controlling the flow of fluid back to the source of supply, means responsive to the pressure at the inlet of the heat exchanger means in control of said first named valve means, and means responsive to the pressure at the outlet of the cooling fluid circulating means in control of said last named valve means.

5. In an air conditioning system, an air conditioning chamber, means for circulating outside air through said air conditioning chamber and through a space to be conditioned, heat exchanger means in said chamber in thepath of the flow of air, a source of cooling fluid, means a for circulating said cooling fluid through said heat exchan er means, means for controllably conducting the cooling fluid leaving the heat exchanger means back to the source of supply, means responsive to a drop in pressure at the outlet of the fluid circulating means for increasing the flow of fluid back to the source of supply, and means responsive to a drop in pressure at the outlet of the fluid circulating means to a predetermined value for interrupting the operation of the fluid circulating means.

6. In an air conditioning system, an air conditioning chamber, means for circulating outside air through said air conditioningchamber and through a space to be conditioned, heat exchanger means in said air conditioning chamber in the path of air flow therethrough, a source of cooling fluid, means for circulating fluid from said source through said heat exchanger means valve means controlling the flow of fluid to said heat exchanger means, means for operating said I at a value which bears a definite relationship with a psychrometric condition of the outside air, means for reducing the tempera ure of the cooling fluid before it reaches the heat exchanger means, and means responsive to a predetermined psychometric condition of the outside air for initiating operation of the temperature reducing means.

' 7. In an air conditioning system, an air conditioning chamber, means for circulating outside air through said air conditioning chamber and through a space to be conditioned, "heat exchanger means in said air conditioning chamber in the path of air flow therethrough, a source of cooling fluid, means for circulating fluid from said source through said heat exchanger means, valve means controlling the flow of fluid to said heat exchanger means, means for operating said valve means so as to maintain the temperature of the fluid leaving the heat exchanger means at a value which bears a definite relationship with a psychrometric condition of the outside air, means for reducing the temperature of the cooling fluid before it reaches the heat. exchanger means, means responsive to a predetermined psychrometrio condition of the outside air for initiating operation of the temperature reducing means, and means responsive to the temperature of the cooling fluid leaving the temperature reducing means for controlling the cooling capacity of the temperature reducing means.

8. In an air conditioning system, an air conditioning chamber, means for circulating outside air through said air conditioning chamber and through a space to be conditioned, heat exchanger means in said air conditioning chamber in the path of air flow therethrough, a source of fluid, means for circulating fluid from said source through said heat exchanger means, a second heat exchanger means through which fluid leaving the first heat exchanger means may flow, valve means controlling the flow of fluid through said second heat exchanger means, means for heating the fluid entering the first heat exchanger means, means responsive to the temperature of the air leaving said air conditioning chamber in control of said valve means and said heating means, and changeover means for selectively placing said last named means in control of said valve means or said heating means.

9. In an air conditioning system, an air conditioning chamber, means for circulating outside air through said air conditioning chamber and through a space to be conditioned, heat exchanger means in said air conditioning chamber in the path of air flow therethrough, a source of fluid, means for circulating fluid from said source through said heat exchanger means, a second heat exchanger means through which fluid leaving the first heat exchanger means may flow, valve means controlling the flow of fluid through said second heat exchanger means, means for heating the fluid entering the first heat exchanger means, means responsive to the temperature of the air leaving said air conditioning chamber in control of said valve means and said heating means, changeover means for selectively placing said last named means in control of said valve means or said heating main inoperative when the valve means is under the control of said temperature responsive means, and means causing said valve means to remain in a position preventing flow of fluid through said second heat exchanger means when the heating means is under the control of said temperature responsive means.

10. In a system of the class described, an air conditioning chamber, heat exchanger means in said air conditioningchamber, means for circulating air over said heat exchanger means and through a space to be conditioned, means for circulating fluid through said heat exchanger means so as to change the temperature of the air passing over said heat exchanger means, valve means for draining fluid from said heat exchanger means, and means responsive to a low predetermined temperature at the outlet of the heat exchanger means for opening said valve means.

11. In a system of the class described, an air conditioning chamber, heat exchanger means in said air conditioning chamber, means for circulating air over said heat exchanger means and through a space to be conditioned, means for circulating fluid through said heat exchanger means so as to change the temperature of the air passing over said heat exchanger means, valve means for 'draining fluid from said heat exchanger means, means for changing the temiii perature of the-fluid being circulated through said heat exchanger means, means responsive to the temperature of the air leaving said air conditioning chamber in control of said temperature changing means, means responsive to the temperature of the fluid leaving the heat exchanger means in control of the amount of air circulated by the air circulating means, and means responsive to a drop in temperature of the fluid at the outlet of the heat exchanger means t9 a low predetermined value to open said valve means and to interrupt operation of said air circulating means.

12. In an air conditioning system, an air conditioning chamber, means for circulating outside air through said air conditioning chamber and through a space to be conditioned, first and second heat exchanger means in said air conditioning chamber in the path of air flow therethrough, means for circulating a conditioning fluid through said first heat exchanger means, means responsive to the temperature of the air entering said space for controlling the flow of fluid from said first heat exchanger means through said second heat exchanger means, and means responsive to a predetermined low outside temperature for causing all of the fluid to by-pass said second heat exchanger means.

13. In an air conditioning system, an air conditioning chamber, means for circulating outside air through said air conditioning chamber and through a space to be conditioned, first and second heat exchanger means in said air conditioning chamber in the path of air flow therethrough, means for circulating a conditioning fluid through said first heat exchanger means, means responsive to the temperature of the air entering said space for controlling the flow of fluid from said first heat exchanger means through said second heat exchanger means, means responsive to a predetermined low outside temperature for causing all of the fluid to by-pass said second heat exchanger means, and means responsive to an outdoor psychrometric condition for controlling the flow of fluid to said first heat exchanger means.

14. In an air conditioning system, an air conditioning chamber, means for circulating outside air through said air conditioning chamber and through a space to be conditioned, first and second heat exchanger means in said air conditioning chamber in the path of air flow therethrough, means for circulating a conditioning fluid through said first heat exchanger means, means responsive to the temperature of the air entering said space for controlling the flow of fluid from said first heat exchanger means through said second heatexchanger means, means responsive to a predetermined low outside temperature for tially causing circulation of refrigerant at a low rate, for causing recirculation of the cooling fluid through said heat exchanger, and for causing circulation of refrigerant at a high rate.

16. In an air conditioning system, a sourceof cooling fluid, means for reducing the temperature of thefluid, said means including a heat exchanger through which the cooling fluid and a cold fluid are circulated in heat exchange relationship, means for circulating the cold fluid through said heat exchanger at different rates of flow, means for causing a recirculation of said cooling fluid through said heat exchanger, and

means responsive to the temperature of the cooling fluid leaving said heat exchanger for controlling the rate at which said cold fluid is circulated through said heat exchanger and for controlling the operation of the recirculation causing means.

1'7. In an air conditioning system, a source of conditioning fluid, means for reducing the temperature of the conditioning fluid, said means including a heat exchanger through which said fluid is circulated, said heat exchanger including an evaporator of a refrigeration system, a, variable capacity compressor means for circulating a refrigerant through said vaporator, means responsive to an increase in the load on the air conditioning system to a predetermined value to initiate operation of the compressor means at low capacity, means responsive to a rise in temperature of the conditioning fluid leaving said evaporator above a predetermined value while the load on the air conditioning system is high to increase the rate of flow of the conditioning fluid through said evaporator, and means responsive to a further rise in temperature of the cooling fluid leaving the evaporator to cause operation of the compressor means at high capacity.

18. In an air conditioning system, a conditioning chamber, means for passing air through said conditioning chamber, a heat exchanger in said chamber, said heat exchanger comprising a plurality of serially connected passages for cooling fluid, said passages being disposed in series with respect to air flow, means for passing cooling fluid through said heat exchanger for cooling and dehumidifying the air, said last named means causing the cooling fluid to pass through aaeaeoe the heat exchanger in counter flow relationship with the air flow whereby the temperature or the cooling fluid leaving the heat exchanger is warmer than the temperature of theair leaving the heat exchanger,- 9. reheater downstream oi the heat exchanger for reheating the air, means for passing cooling fluid from the outlet of said heat exchanger through said reheater, a by-pass for the fluid around said reheater, valve means for varying the proportions of the fluid passed through and by-passed around said reheater, means for controlling said valve means in accordance with the demand for reheat, valve means controlling the flow of fluid through said heat exchanger, and means responsive to the temperature of the fluid leaving said heat exchanger and to a temperature condition which is a measure of the load on the system in control of said last-named valve means.

19. In an air conditioning system, a conditioning chamber, means for passing air through said conditioning chamber, a heat exchanger in said chamber, said heat exchanger comprising a plurality of serially connected pasages for cooling fluid, said passages being disposed in series with respect to air flow, cooling means for cooling the cooling fluid, said cooling means comprising a refrigeration system including a condenser, means for passing the cooled cooling fluid through said heat exchanger for cooling and dehumidifying the air, said last named means causing the cooling fluid to pass through the heat exchanger in counter flow relationship with the air flow whereby the temperature of the cooling fluid leaving the heat exchanger is warmer than the temperature of the air leaving the heat exchanger, a reheater downstream of the heat exchanger for reheating the air, means for passing cooling fluid from the outlet of said heat exchanger through said reheater, and means for conveying the fluid from the reheater to the condenser for cooling the same.

20. In an air conditioning system, a conditioning chamber, means for passing air through said conditioning chamber, a heat exchanger in said conditioning chamber for cooling and dehumidifying the air, a supply of fluid for the heat exchanger means for reducing the temperature of said fluid before it passes to the heat exchanger including a refrigeration system having a condenser, a reheater for reheating the air passing from the heat exchanger, means for supplying the fluid leaving said heat exchanger to said reheater, and means for then passing the fluid leaving the reheater through the con- -denser, thereby utilizing the cooling effect of the air being reheated for partially cooling said condenser.

21. In a system of the class described, heat exchanger means, means for circulating a fluid through said heat exchanger means, conduit means connected to the outlet of said heat exchanger means, valve means controlling the flow of fluid from said conduit means, and motor means influenced by the pressure of the fluid.

on the inlet side of said heat exchanger means for variably positioning said valve means in a manner to maintain a predetermined pressure withof said heat exchanger means controlling the within the heat exchanger means to insure an emcient heat exchange relationship therein.

23. In a system of the class described, a heat exchanger, a source of supply or heat exchange medium, means including conduit means for delivering medium from said source to said heat exchanger, conduit means for normally delivering heat exchange medium from said heat exchanger to a location other than said source, other conduit means for returning heat exchange medium from said heat exchanger to said source. control means for normally preventing substantial flow of heat exchange medium through said other conduit means, and means actuated upon shortage of heat exchange medium at said source for controlling said control means in a manner to cause return of the heat exchange medium to said source upon the occurrence of such shortage.

24. In a system of the class described, a heat exchanger, 9. source of supply of heat-exchange medium, means including conduit means for delivering medium from said source to said heat exchanger, conduit means for normally de'livering heat exchange medium from said heat exchanger toa location other than said source, other conduit means for returning heat exchange medium from said heat exchanger to said source, control means for normally preventing substantial flow of heat exchange medium through said other conduit means, flow control means for varying the flow of heat exchange medium through said heat exchanger in accordance with the demand for heat exchange, and means influenced by the relationship between the rate of supply of heat exchange medium from said source and the demand for heat exchange medium by said flow control means for actuating said first control means in a manner to return heat exchange medium to the source when the supply of heat exchange medium falls below the demand therefor.

25. In an air conditioning system utilizing water from a well or the like for conditioning the air in a space, a heat exchanger in heat exchange relationship with air for a space, means including a pump for causing water from the in said heat exchanger means to insure an effiwell to flow through said heat exchanger, conduit means for conveying water from the heat exchanger to a location other than the well, return conduit means for returning water from the heat exchanger to the well, valve means for normally preventing return of water from the heat exchanger through said return conduit means, and means responsive to pressure varied by said pump for controlling said valve means in a manner to operate said valve means for returning the water to the well upon fall in said pressure.

26. In a system of the class described, an air conditioning chamber, heat exchanger means in said air conditioning chamber, means for circulating air over said heat exchanger means and through a space to be conditioned, means for circulating fluid through said heat exchanger means so as to change the temperature of the air passing over said heat exchanger means, valve means for draining fluid from said heat exchanger means, and means respcnsive'to a lowpredetermined temperature at the outlet of the heat exchanger means for interrupting delivery or fluid to said heat exchanger means and for opening said valve means.

27. In an air conditioning system, an air conditioning chamber, cooling means in said chamber, means for causing a circulation 01' fresh outside air through said air conditioning chamher in contact with said cooling means and into a space to be conditioned, means for varying the capacity of said cooling means and said air circulating means, and a single means responsive to the wet bulb temperatureof the outside air, the dry bulb temperature of the outside air and the radiant heat of the outside air in control of said varying means for increasing the capacity 01. the cooling means and of the air circulating means as the total outside cooling load on the air conditioning system increases.

28. In an air conditioning system, an air conditioning chamber, a heat exchanger in said air conditioning chamber, means for circulating air over said heat exchanger, means for circulating heat exchange fluid through said heat exchanger, flow control means controlling the flow of fluid through said heat exchanger, means for controlling-said flow control means so as to vary when the load on the system lies'within a predetermined range of values.

29. In a heat exchange system, in combination, a source of heat exchange fluid, means for changing the temperature oi'said fluid including a heat exchanger through which said fluid flows, means for controlling said temperature changing means to operate the same at varying rata, means for causing a recirculation of said heat exchange fluid through said heat exchanger, and means responsive to the temperature of the heat exchange fluid leaving the heat exchanger for controlling the rate at which said temperature changing means is operated and for controlling the operation of the recirculation causing means.

30. In a heat exchange system, in combination, a source 01' heat exchange fluid, means for changing the temperature of said fluid including a heat exchanger through which the fluid and a temperature changing medium are circulated in heat exchange relationship, means for circulating the medium through the heat exchanger at different rates of flow, means for causing a recirculation of said heat exchange fluid through said heat exchanger, and means responsive to the temperature of the heat exchange fluid leaving said heat exchanger for controlling the rate at which said temperature changing medium is circulated through said heat exchanger and for controlling the operation oi. the recirculation causing means.

ROBERT B. P. CRAWFORD.