US2323873A

US2323873A - Air conditioning system

Info

Publication number: US2323873A
Application number: US419302A
Authority: US
Inventors: William L Mcgrath
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1941-11-15
Filing date: 1941-11-15
Publication date: 1943-07-06
Anticipated expiration: 1960-07-06

Description

July 6, 1943. w, L, McGRATH 2,323,873

AIR CONDITIONING SYSTEM Filed NOV. 15, 1941 .INVENTOR.

William. L. 'M"? Grail L.

I Afioumey Patented July 6, 1943 AIR. CONDITIONING SYSTEM William L. McGrath,-.Philadelphia, Pa.) assignmto Minneapolis-Honeywell Regulator (hmpany, Minneapolis, Minn., a corporation of Delaware Application November 15, 1941, Serial No. 419,302

16 Claims. (Cl. 257-3) This invention relates to air conditioning systems and controls therefor.

The object of the invention is to provide a simple, inexpensive, but efiective arrangement for providing for both temperature and humidity control using a minimum of controls and control mechanism.

More specifically, the object of the invention is to provide means for shifting from modulating to substantially on andofi control in a system wherein cooling is normally modulated in response to temperature, when there is a need for dehumidification of the air being treated. Thus when the control is shifted to on and oil control, the temperature continues to be controlled, but when there is cooling it is efiected at a lower temperature, the cooling means operating at its maximum rate so that there will be more dehumidification and the humidity will be brought back to the desired value.

Another object is to control the cooling in response to load demands as measured by outdoor temperature when the control has been shifted to on and oil.

Many additional objects and advantages of my invention will become apparent from the following detailed description and annexed drawing.

Referring to thedrawin there is shown a heating and cooling system of the type wherein hot water'or cold water is circulated to spaces whereinthe air is to be kept at predetermined conditions of temperature and humidity. The water is circulated to the spaces by means of an electric motor driven circulatcr indicated on the draw- 'ing by the numeral it. The Water may be circulated through radiators in the space or spaces being served or it may be circulated to unit airconditioners or other similar devices in the spaces. The water is returned from the heat exchange devices in the various spaces through a pipe ll. The water returning through the pipe ll may be passed through a water heater designated by the numeral l2, by means of a pipe It or it may be passed through a water cooler it by means of pipe l5. The water heater l2 and the water cooler Hi may each be of any suitable type of heat exchanger such as the shell and tube type, for example. Steam is circulated through the Water heater l2 for heating the water going therethrough, the steam being admitted through a pipe I 6 and the condensate being withdrawn through pipe ll. Disposed in the pipe i6 is asteam control valve I8 of the thermostatic type, the valve being controlled by a thermostatic mechanism l9 including a thermal bulb 20 disposed in heat exchange relationship thermostatic mechanism l9 are preferably of the.

electric proportioning type or they may be of any other suitable type, for example, they might be of a self contained type. The function of the thermostatic mechanism and steam valve is to maintain a predetermined temperature in the heat exchanger, that is, in the water heater. Thus when heating is required in the spaces water at a suitably high temperature will be available for maintaining the temperature.

s pointed out, the water cooler l4 may be a heat exchanger of substantially the same type as the water heater l2 and any suitable type of cooling apparatus may be used for cooling the water in the cooler M.

The water which passes through the water heater and the water cooler is discharged into a riser pipe designated by the numeral 23.- The riser connects to the inlet side of'the circulator ill and the circulator then circulates the water to the heat exchange devices in the spaces as already pointed out.

Connected between the pipe H and the riser 23 is a by-pass pipe 26 which serves to by-pass water between the pipes I I and 23 without its passing through either the water heater or the water cooler. At the juncture of pipe 24 with riser 23 is disposed a three-way valve 25 which valve is of a type well known in the art and which is arranged to control the proportions of water going through the water cooler l4 and the by-pass pipe 243. This type of three-way valve control is well known in the art and need not be described in further detail. The valve member of the threeway valve is positioned by means of a rack and pinion designated by the numerals 26 and 21. The pinion 21 is driven by a reversible electric motor designated by the numeral 28, the

motor comprising windings

29 and 30, the two windings being associated with armatures 3| and 32 respectively. When one winding is energized the motor operates in one direction and when the other winding is energized the motor operates in the other direction. The motor drives the pinion 2! through a gear train designated diagrammatically by the numeral 33. On the shaft of one of the gears of the gear train, preferably the same shaft on which is mounted the pinion 21, is a. rotatable switch actuating finger 34. This finger cooperand 36. Each of the limit switches has a blade,

the end of which is extended slightly so as to be engageable by the finger 34 so that when the electric motor drives the three-way valve 25 to either of its limit positions that is, its wide open or fully closed positions, one of the limit switches will be opened by cooperation of the finger 34 with the extended blade of the respective switch. As will presently be pointed out the electric motor is deenergized when its windings are deenergized by opefiing of the limit switches.

At the juncture of the pipe which carries water away from the water heater l2 with the riser 23 is a second three-way valve 4|] which is of exactly the same construction as' the threeway valve 25, this valve serving to proportion the relative quantities of water which pass through the water heater l2 and through the by-pass 24. It may be mentioned at this time that when heating is required in the spaces the three-way valve 25 will be in aposition to prevent any water from going through the water cooler l4. In this position of three-way valve 25 water may freely pass through by-pass 24 to the riser 23. On the other hand when cooling is required in the spaces the three-way valve 40 will be in a position to prevent any water from going through the water heater I2 and in this position of three-way valve 40 water may freely pass upwardly in the riser 23 through the threeway valve 4|]. The three way valve 40 is driven by a reversible electric motor 28a which is of exactly the same type as the motor 28 so that it need not be described in detail. The motor 280. is controlled by a control arrangement corresponding to that which controls the motor 28 and these controls will be described hereinafter.

The controls for motor 28 of three-way valve 25 are of the electrical proportioning type. The controls for motor 28 include a potentiometer type controller 4| having a slide wire resistance 42 cooperating with which is a pivoted slider 43. The slider 43 is operated by an expansible and contractible bellows 44, the movable end of the bellows carrying a stem which abuts against the slider 43 at a point spaced from the pivot of the slider. The slider is normally urged in .to engagement with the operating stem of the bellows by a coil spring 45. The interior of the bellows is connected to a thermal bulb containing a volatile liquid the thermal bulb being designated by the numeral 45, and this bulb being disposed in intimate thermal contact with therriser 23 just beyond the three-way valve 25. The volatile liquid in the thermal bulb and bellows expands, that is it vaporizes and develops a pressure depending upon the temperature in the riser 23 and upon a rise in pressure in the bellows it expands, moving the slider 43 to the right along resistance 42, and upon a drop in temperature in the riser 23 the bellows 44 contracts moving the slider 43 to the left along the resistance 42. Numeral 49 designates a balanced relay comprising windings 50 and associated with an armature 52 which is normally in an intermediate balanced position when the windings 50 and 5| are equally energized. The armature 52 is connected to a switch blade 53 which cooperates with fixed

electrical contacts

54 and 55. When the energization of winding 50 preponderates over that of winding 5| the armature 52 is moved to the left bringing blade 53 into engagement with contact 54 and when the energization of winding 5| preponderates over that of winding 50 the armature 52 is moved to the right moving switch blade 53 into engagement with contact 55. When the relay is in a normally balanced position the blade 53 is in a position

intermediate contacts

54 and 55. The left end of resistance 42 is connected to the left end of winding 50 by wires 56, 51 and protective resistance 58. The right end of resistance 42 is connected to the right end of winding 5| by wires 59, 60 and protective resistance 5|. The slider 43 is-connected to the juncture of the windings 50 and 5| as will be pointed out.

Power for operation of balanced relay 49 is supplied by a transformer 62, having a primary winding 63. Connected to line conductors |2|] and |2| by wires I22 and |23. The transformer has a secondary winding 39, the left end of which is connected to winding 50 by wire 31 and the right end of which is connected to winding 5| by wire 38.

Numeral 65 designates a second potentiometer type controller similar to the controller 4|. The controller 55 comprises a slide wire resistance 66 cooperating with which is a pivoted slider 61 which is actuated by an expansible and contractible bellows 68, the movable end of which carries a stem which normally abuts the slider 61 at a point spaced from the pivot point of the slider. The slider is normally urged into engagement with the operating stem of the bellows by a coil spring 69. The interior of the bellows is connected to a thermal bulb 1|! by a capillary tube The thermal bulb 10 of controller 65 is disposed outdoors so as to be'responsive to outdoor temperature. Thus the volatile liquid in bulb 10 vaporizes and develops a pressure in accordance with outdoor temperature. When the outdoor temperature rises the pressure in the bulb and bellows increases thus moving slider 61 in a clockwise direction, that is upwardly on resistance 66. When the outdoor temperature falls, conversely there is a drop in pressure in bellows 68 and slider 61 is moved downwardly along resistance 56. The upper end 'of resistance 66 is connected to the right end of winding 5| by wires 12, 6|] and protective resistance 6|. The lower end of resistance 66 is connected to the left end of winding 50 by wire 13, wire 51 and protective resistance 58. The slider 61 like the slider 43 is connected to the juncture of windings 50 and 5| as will be pointed out.

The purpose of protective resistances 5B and 6| is to prevent the secondary of transformer 52 from ever being shorted as will appear.

Numeral 15 designates a humidity responsive controller which controls a relay which cooperates with the potentiometer controllers 4| and 65. The humidity controller comprises a humidity responsive element 16 which is of the type mally being biased in a clockwise direction by a coil spring 19. The controller 15 controls a relay 8|] having a winding 8| and an armature associated therewith which is connected to a movable switch blade 82 which is moved to the right out of engagement with a fixed electrical contact 83 when the winding 3| is energized. The armature of relay is connected to a second movable switch blade 84 which normally engages a fixed electrical contact 85 when the relay is deenergized and which moves to the right into engagement with a fixed electrical contact 86 when the relay is energized.

The slider 43 of controller 4| is connected to the juncture of windings50 and 5| by a,wire 81, contact '85, blade 84, and wire 89 this connection of course being complete when the relay 80 is deenergized. The slider 61-of controller 65 is connected to the juncture of windings 50 and 5| by wire 90, wire 81, contact 85, blade 84, and wire 89. From the foregoing circuits it can be seen that when the relay 80 is energized the sliders 51 v known in the art and which is normally employed in a heating system, for example, so as to control the operation of a heating plant so as to deliver heat to spaces being heated dependently upon heating requirements as measured by out--.

door weather conditions including the outdoor temperature, the amount of solar radiation, and wind velocity and so on as pointed out above. In carrying out this function the heater |0| of the controller bears a definite relationship to the heating capacity of the plant which is controlled by the controller. Thus, there is a definite relationship between the heating of the controller 95 and the heat supplied to the building or the structure being served. It follows that the controller 95 will maintain itself at a certain temperature and the heating plant will be operated to maintain a given predetermined temperature in the spaces being heated. However, in my parengagement with contact 54. As will be explained in the description of operation hereinafter this will cause the motor 28 to operate to move the three-way valve to a position wherein no water passes through the by-pass 24 and all of the water being circulated by the circulator I0 passes through the water cooler I4.

The controls for the motor 28a of three-way valve correspond to the controls for the motor 28 of three-way valve 25. The controller for motor 28a. which is responsive to the riser temperature is designated Ma and the controller associated with motor 28a which is responsive to outdoor temperature is designated a. In as much as these controls are exactly like the controls which they correspond to and which have already been described in detail they need not be further described. However, it is to be pointed out that the controls for motor 280. are not interlocked with the relay as are the controls associated with motor 28. That is, the the sliders of the potentiometer controllers included in the controllers 4|a and 550, are not connected to the balanced relay of. this control arrangement through contact of the relay 80. These particular controls in themselves are of course well known in the art.

The controls for the system include another controller responsive to outdoor conditions, this controller being designated by the numeral 95. The controller is of a type arranged to respond to outdoor temperature and other weather conditions such as solar radiation, wind conditions, etc. The controller 95 comprises an enclosure 96 which is formed of a material having a relatively great thermal mass. Within the upper part of this enclosure 96 is a bimetal element 91 which cooperates with a fixed electrical contact 98 and the bimetal element carries a switch blade 99 which cooperates with a, fixed electrical contact I00. In the lower part (if the controller 95 there is an open space within which is an electrical heater IOI which serves to heat the controller and as will be described its function is to main- ,ticular arrangement the controller 95 is used to control the cooling rather than the heating and this will be described presently. The controller 95 controls a relay I09'comprising a winding I04, having an armature associated therewith connected to movable switch blades I05 and I06. The blade I05 normally engages a fixed electrical contact I01 when the relay I03 is deenergized and when the relay is energized the blades I05 and I08 are moved to the left into engagement with fixed electrical contacts I08 and I09 respectively. Power for operation of the relay I03 is supplied by a step-down transformer I I0 having a primary winding III and a secondary winding I I2, the primary winding having the 'greater number of turns. Power is supplied to the primary winding through wires 3, and II 4 which may be connected to any suitable source of external power not shown. The operation of the controller 95 in connection with the relay I08 will be described in more detail hereinafter.

Referring now to the operation of the system as a whole, the operation will first be described when cooling of the spaces is required as in the summertime. During the summertime when cooling is required it is to be understood that the source of steam supply is inactive so that no steam is being supplied to the water heater l2. With the parts in the position shown on the drawing the humidity has not risen to too high a value, the relay is deenergized and the circulator I0 is in operation. Its circuit is-as follows:

from line I45 to wire I49, contact 83, blade 82,

tain the body of the controller at a temperature somewhat higher than the ambient temperature, that is, somewhat higher-than outdoor temperature. Thus heat will be dissipated from the controller at a rate dependent not only upon the outdoor temperature but also upon the amount of solar radiation, the wind velocity and so forth. I The controllc: 9 5 is in itself a device already wire I44, wire I50, the motor of clrculator I0, and wire I5I back to line conductor I48. The threeway valve 40 is in a position to prevent any water from circulating through the water heater I2 and to permit water to rise freely through the riser 23. Water, is being cooled in the water cooler I4 and the flow of water through the system is under control of the three-way valve 25 which is in turn being controlled by the controllers 4| and 85. Assuming that the outdoor temperature is at a given value the three-way valve 25 will be positioned in response to the controller 4| to maintain the water going through the riser 23 to the spaces at a predetermined temperature. This predetermined temperature will beone bearing a fixed relationship to the outdoor temperature as will presently appear. In other words, the function 01' the controller 55 is to adjust the control point of controller 4| so that the controller 4| will maintain a temperature in the riser at a value determined by outdoor temperature. Assuming now that the outdoor temperature is such that the control point of controller 4| has been adjusted so that it will maintain a riser temperature of 35. If now the temperature in the riser 23 rises above this value the bellows 44 will expand moving slider 43 to the right along resistance 42. This will partly shunt out the winding 5| and conse-- quently the energization of winding 50 will preponderate and will unbalance the relay moving the blade 53 to the left into engagement with contact 54. Winding 29 of the motor 28 will now be energized through the following circuit: from line conductor I through wire I26, blade 53, contact 54, wire I2'I, limit switch 35, wire I28, winding 29, wire I29, back to line conductor I2I. Motor 28 will now operate in a direction to position the three-way valve to cause more water to pass through the cooler I4 and less through the by-pass 24 so that the temperature in the riser 23 will tend to fall back to the desired value. When the temperature in the riser has fallen back to the desired value of for example, the controller 4| will reassume its original position rebalancing the relay 49 and thus moving blade 53 away from contact 54 and again deenergizing the motor 28 leaving the valve 25in its new position. .On the other hand, if the temperature in the riser falls below the desired value bellows 44 will contract moving slider 43 to the left along resistance 42. This will partly shunt out the winding 50 and so.the winding 5| will preponderate moving the blade 53 to the right into engagement with contact 55. This will complete a circuit energizing the winding 30 of the motor 28 as follows: from line conductor I20 through wire I26, blade 53, contact 55, wire I3I, limit switch 36, wire I32, winding 30, and wire I29 back to line conductor I2I. Motor 28 will now operate in a direction to move the three-way valve to a position to cause less water to go through the cooler I4 and more to go through the by-pass 24. Thus the temperature in the riser 23 will rise again to its desired value and the controller 4| will reassume its original position rebalancing the relay 49 and moving switch blade 53 to its intermediate position and interrupting the circuit of the motor 28. Thus the motor will stop leaving the three-way valve 25 in its adjusted position.

When there is a rise in outdoor temperature it will of course be necessary to circulate colder water to the spaces. Thus when the outdoor temperature rises, the slider 61 will be moved upwardly along resistance 66 and the result of this will be to partly shunt out the winding 5| in the same manner as it is partly shunted out when the slider 43 moves to the right. The relay 49 will again be unbalanced in a direction to bring the switch blade 53 into engagement with contact 54 and the three-way valve 25 will be operated in opening direction, that is, in a direction to cause more water to go through the water cooler I4 and less through the by-pass 24. As the threeway valve is now operated in this manner the riser temperature will of course tend to fall. Thus the bellows 44 will contract moving slider 43 to the left which will have an effect on the relay 49 just the opposite of course to the efiect of the movement of the slider 61 upwardly along resistance 66. Thus the controller 4| acts as a rebalancing controller and whenever the controller 65 assumes a new position to cause water to flow through the riser 23 at a different temperature the controller 4| will assume a new rebalancing position at which the motor 28 will stop leaving the valve 25 in its adjusted position. The controller 65 has the effect of a compensating controller. Whenever the outdoor temperature is stable the controller 4| will of course control in the manner described to maintain the temperature in the riser at a predetermined value which as pointed out is of course determined by the controller 65. The controller 4| preferably of course hasa relatively narrow operating differential, that is, it need move the slider 43 over only a small part of resistance 42 to. cause a relatively large movement of the valve 25. The function of the controller 65 is therefore. to adjust the control point of the controller 4| to any part of the resistance 42. Thus the controller 65 may act to cause the controller 4| to maintain the riser temperature at any value of from 0 to 70 for example. In practice the controller 65 will be adjusted to be effective within a range of from 60 to 100 F. for example. As the outdoor temperature rises the controller 4| will be so aifected as to maintain lower and lower riser temperatures and as the outdoor temperature falls the controller 4| will be so affected as to maintain higher and higher riser temperatures.

During summer operation when the humidity in the spaces rises to a predetermined relatively high value the humidity responsive controller I5 will respond to close its mercury switch 18 and energize the relay 80. When the mercury switch I8 closes, the relay is energized through the following circuit: from wire I32, to wire mercury switch I8, wire I33, winding 8|, back to wire I34, the wires I32 and I34 being connected to any suitable source of power not shown. When the relay is energized

switch blades

82 and 84 are moved to the right blade 84 moving into engagement with fixed contact 86 and blade 82 disengaging from contact 83. Disengagement of blade 82' from contact 83 places the circulator I0 under control of the controller 95 as will presently be described. Disengagement of blade 84 from contact 85 disconnects the controllers 4| and 65 from the balancing relay so that they have no further control. Engagement of blade 84 with contact 86 substantially shunts the winding 5| of the balanced relay so that the winding 50 preponderates causing blade 53 to engage contact 54. The motor 28 now operates in a direction to move valve 25 to a position wherein all of the water passes through the cooler I4 and none of it through the by-pass 24. The motor 28 will under these circumstances operate to its limiting position wherein limit switch 35 is opened and the valve 25 is in an extreme position wherein all of the water goes through the water cooler as pointed out.

The circulator I0 is now controlled by the relay |93 which is responsive to the controller 95. When the relay I03 is deenergized the heater IIlI is not energized and the temperature of the controller "95 falls due to dissipation of heat therefrom by reason of the outdoor temperature being lower than the temperature of the controller and due to heat being carried away as a result of wind and so on. When the temperature of the controller falls to a predetermined value the bimetal element 91 will be brought into engagement with contact 98 and blade 99 will engage contact I00. The arrangement is such that the blade 99 engages contact I00 before the bit by means of the circulator I0.

ature at which blade 99 engages contact I00. When both the switch contacts are engaged a circuit is completed for the winding I04 as follows: from secondary N2 of transformer IIO through wire I35, winding I04, wire I36, contact 98, bimetal element 91, blade 99,. contact I00,

.I04, wire I38, blade I05, contact I08, wire I39,

bimetal element 91, blade 99, contact I00, and wire I31 back to secondary II2. son of this maintaining circuit the relay will not be deenergized until the temperature of the controller 95 has risen to a high enough value to cause blade 99 to disengage from contact I00. Engagement of blade I06 with contact I09 completes a circuit for the heater IOI as follows; from wire I45, to blade I06, contact I09, wire I46, heater IOI and wire I41 back to wire I48, the wires I45 and IE8 being connected to any suitable source of power not shown. Whenever blade I06 is out of engagement with contact I01 the circuit for the motor of the circulator I is interrupted and the circulator does not act to forcibly circulate water to the spaces being served.

, When heater I M is energized the temperture of controller 95 will of course tend to rise, the heat being supplied at agreater rate than it is dissipated and bimetal elementv 91 will move to the righth disengaging from contact 98 and eventually causing blade 99 to disengage from contact I00 and deenergizing the relay. When relay I03 is deenergized a circuit is completed for the motor of circulator I0. This circuit is as follows: from wire I45 to blade I06, contact I01, wire I43, wire I50, the motor of circulator l0, wire II, back to wire I48. The circulator I0 will thus operate to forcibly circulate cold water through the spaces being served as long as the relay I0 is deenergized. The water being circulated will be at the lowest possible temperature because the valve 25 is in a position to circulate all of the water through the water, cooler. Thus, inasmuch as this water is at its lowest possible temperature, maximum dehumidiflcation will be efiected in the spaces being served and the humidity will tend to fall back to its desired value. Operating When the humidity drops back to the desired value the relay 80 is deenerized and the controllers M and 65 resume control of the three-way valve 25 and it is again positioned in response to Thus, by rea- Y in this manner the controller 95 will of coursk cycle on and 011 in the manner described, the circulator being turned on when the controller 5 'has the relay I03 deenergized and .the circulator-being stopped when the controller 95 has the relay I03 energized. In other words, cooling is efiected at a maximum rate in the spaces being served when the heater I M is oif, allowing the controller 95 to cool. On the other hand, when the heater IOI is in operation the circulator I0 is stopped and the temperature of the zone being served rises by reason of the outdoor temperature being relatively high. As is to be understood when the humidity is high and the relay 80 is energized and the circulator'l0 is turned off and on the control is primarily in response to the outdoor temperature and other weather conditions afiecting the controller 95. That is,

- closure of the mercury switch 18 the control is shifted from modulating control of the threeway valve 25 to substantially on and off control riser temperature and outdoor temperature.

When the outdoor temperature falls down to a range wherein heating of the spaces rather than cooling is desired the three-way valve 25 will be in a position wherein all of the water passes through the by-pass 24 and none of it through the cooler I 4. The outdoor controller 65 may be adjusted so that the three-way valve 25 assumes this position when the outdoor temperature reaches 70$,for example. As the outdoor temperature continues to fall the controller 65a in response to the bulb 10a will operate motor 280 so as to cause three-way valve 40 to move to a position wherein part of the water goes through the water heater I2. The three-way valve 40 will now be positioned in response to the controllers Ma and 65a in the same manner as the threeway valve 25 is controlled by the controllers M and 65 when cooling is required. In other words, the controller 4Ia will maintain a predetermined riser temperature depending upon the outdoor temperature. The thermostatic mechanism controlling the steam valve I8 will maintain the temperature of the watergoing through the water heater I2 at a'value suitable for heating in the spaces being served.

From the foregoing it should be apparent to those skilled in the art that I have provided a very eflici'ent and inexpensive system whereby both temperature and humidity conditions may be maintained at desired values with a minimum of controls and without resorting to a complex ing sense. The invention is to be limited only in accordance with the claims appended hereto.

I claim as my invention:

1. In a system of the class described, in combination, valve means for controlling a flow of medium for regulating the temperature of a space, temperatureresponsive means of the type arranged tomodulatinglyadjust the valve means, humidity responsive means arranged to cause the valve means to assume an extreme position when the humidity reaches a predetermined value, and control means whereby the flow of medium is at a maximum or-minimum after the humidity has reached said predetermined value.

2. In apparatus of the character described, in combination, a. conditioning system including a valve for controlling a flow of fluid medium for conditioning. air, means responsive to a temperature representative ofconditioning requirements arranged to modulatingly adjust the valve, means responsive to humidity of conditioned air for causing the valve to assume a,fiow position wherein the temperature of the fluid medium is at a minimum value, and meanslresponsive to temperature regulating requirements for adjusting the flow of medium between a maximum and a minimum rate after the humidity has caused the valve to assume said position.

3. In apparatus of the character described, in combination, a conditioning system including a valve for controlling a flow of fluid medium for conditioning air, means responsive to a temperature representative of conditioning requirements arranged to modulatingly adjust the valve, means responsive to humidity of conditionedair for causing the valve to assume a flow position wherein the temperature of the fluid medium is at a minimum value, and means responsive to temperature regulating requirements for adjusting the flow of medium between a maximum and a minimum rate after the humidity has caused the valve to assume a maximum flow position, said means responsive to temperature regulating requirements including means responsive to outdoor temperature.

4. In apparatus of the. character described, in combination, cooling means and means for circulating fluid medium from said cooling means to a space to be cooled, a by-pass for said fluid medium around said cooling means, three way valve means controlling the proportions of said fluid medium flowing through said cooling means and by-pass, and means responsive to temperature regulating requirements controlling the valve means so as to adjust the temperature of medium flowing to the space so as to maintain a desired temperature therein, humidity responsive means for adjusting the valve means to cause medium at a minimum temperature to flow to the space and means whereby medium at said minimum temperature flows to the space alternately at relatively high or relatively low rates.

5. In apparatus of the character described, in combination, cooling means and means for circulating fluid medium from said cooling means to a space to be cooled, a by-pass for said fluid medium around said cooling means, three way valve mean controlling the proportions of said fluid medium flowing through said cooling means and by-pass, and means responsive to temperature regulating requirements controlling the valve means so as to adjust the temperature of medium flowing to the space so as to maintain a desired temperature therein, humidity responsive means for adjusting the valve means to cause medium at a minimum temperature to flow to the space, means whereby medium at said minimum temperature flows to the space alternately at relatively high or relatively low rates, and means dependent upon the magnitude of the cooling load for selecting the rate of flow of said medium.

6. In apparatus of the character described, in combination, cooling means and means for circulating fluid medium from said cooling means to a space to be cooled, a bv-pass for said fluid medium around said cooling means, three way valve means controlling the proportions of said fluid medium flowing through said cooling means and by-pass, and means responsive to temperature regulating requirements controlling the valve means so as to adjust the temperature of medium flowing to the space so as to maintain a desired temperature therein, humidity responsive means for adjusting the valve means to cause medium at a minimum temperature to flow to the spaces, a circulator for circulating fluid medium to the spaces, and means responsive to a condition representative of cooling load requirements for turning the circulator on and off when the valve means have been adjusted by the humidity responsive means.

"I. In apparatus of the character described, in combination, cooling means and means for circulating fluid medium from said cooling means to a space to be cooled, a by-pass for said fluid medium around said cooling means, three way valve means controlling the proportions of said fluid medium flowing through said cooling means and by-pass, and means responsive to temperature of medium and outdoor temperature controlling the valve means so as to adjust the temperature of medium going to the space to maintain a desired temperature therein, humidity responsive means for adjusting the valve means to cause medium at minimum temperature to flow to the spaces. and means for stopping and starting the flow of medium.

8. In apparatus of the character described, in combination, cooling means and means for circulating fluid medium from said cooling means to a space to be cooled, a by-pass for said fluid medium around said cooling means, three way valve means controlling the proportions of said fluid medium flowing through said cooling means and by-pass, and means responsive to temperature of medium and outdoor temperature controlling the valve means so as to adjust the temperature of medium going to the space to maintain a desired temperature therein, humidity responsive means for adjusting the valve means to cause medium at minimum temperature to flow to the spaces, said last means including means responsive to temperature maintaining requirements of the space.

9. In apparatus of the character described, in combination, means for heating a fluid. medium, means for cooling said medium, means for circulating said medium to a space, means comprising two three-way valves whereby the medium can be made to flow through either the cooling means or the heating means and in bypass relation with the cooling and heating means, the valves controlling the proportion of medium by-passed, means responsive to temperature changing load requirements controlling said valves dependently on whether or not heating or cooling is necessary, means comprising a. humidity responsive device for causing all the medium to go through the cooling means, and means for causing the flow of medium to be substantially stopped and started in response to temperature regulating requirements when all the medium goe through the cooling means.

10. A system of the character described comprising in combination, temperature changing apparatus for cooling the air in a space to be conditioned, temperature responsive means for modulatingly varying the eifectiveness of said apparatus for maintaining said air at the desired temperature, and means including humidity responsive means for alternately rendering said apparatus ineffective and effective at substantially maximum capacity for removing moisture from the air when the humidity increases above a predetermined value.

11. A system of the character described comprising in combination, temperature changing apparatus for cooling the air in a space to be conditioned, temperature responsive means for modulatingly varying the efiectiveness of said apparatus for maintaining said air at the desired temperature, means including humidity responsive means for alternately rendering said ap paratus inefiective and efiective atosubstantially asaae'rs 7 maximum capacity for removing moisture from the air when the humidity increases above a predetermined value, and meansv for varying the relative lengths of said alternate ineffective and efiective periods in accordance with the cooling load on said system. 1

12. The method of controlling cooling apparatus for conditioning the air in a space, which comprises the steps of, modulating vthe effectiveness of said apparatus in accordance with the demand for cooling as long as the relative humidity of the air in said space is proper, and rendering said apparatus alternately inefiective and eifective at substantially maximum capacity when the relative humidity of the air in said space becomes too high.

13. The method of controlling cooling apparatus for conditioning the air in a space, which comprises the steps of, modulating the effective ness of said apparatus in accordance with the demand for cooling as long as the relative humidity of the air in said space is proper, and rendering said apparatus alternately ineflective and eflective at substantially maximum capacity when the relative humidity of the air in said space becomes too high, and varying the relative lengths of said alternate ineffective and effective periods in accordance with the cooling load.

14. A system of the character described comprising in combination, cooling apparatus, means for circulating a fluid medium through said cooling apparatus and to a heat exchanger for conditioning the air in a space, means for varying the efiectiveness of said cooling apparatus for regulating the temperature or said air, and means including a humidity responsive device for rendering said cooling apparatus eifective at sub stantially its maximum'capacity and for causing said fluid medium to flow intermittentl to said heat exchanger.

15. A system of the character described comprising in combination, cooling apparatus, means for circulating a fluid medium through said cooling apparatus and to a heat exchanger for con ditloning the air in a space, means for varying the effectiveness of said cooling apparatus for regulating the temperature of said air, means including a humidity responsive device for rendering said cooling apparatus effective at substantially its maximum capacity and means for causing said fluid medium to have alternate flow periods and non-flow periods wherein the relative lengths of said periods are varied in accordance with the cooling load.

16. A system of the character described comprising in combination, cooling means, means for circulating fluid medium from said cooling means to a heat exchanger for conditioning air for a space, valve means controlling the flow of fluid medium through said cooling means, means responsive to temperature requirements controlling the valve means so as to regulate the temperature of the fluid medium flowing to said heat exchanger so as to maintain the air in said space at the desired temperature, humidity responsive means for adjusting said valve means to cause medium at a minimum temperature to flow to said heat exchanger, and means causing said flow to take place alternately at relatively low and high rates.

7 WILLIAM L. McGRATH.