US2001704A

US2001704A - Apparatus for cooling and ventilating buildings

Info

Publication number: US2001704A
Application number: US666152A
Authority: US
Inventors: Claude A Bulkeley
Original assignee: Niagara Blower Co
Current assignee: Niagara Blower Co
Priority date: 1933-04-14
Filing date: 1933-04-14
Publication date: 1935-05-21
Anticipated expiration: 1952-05-21

Description

May 21, 1935. c. A. BULKELEY 2,001,704

APPARATUS FOR COOLING AND VENTILATING BUILDINGS IFiled April 14, 1953 2 sheets-sheer 1 AIR SUPPLY H EATER EXPANSO N TANK as i COOLER Z l fcoNDENS ER COMPRESSOR ATTORN EYS May 21, 1935. c, A. BULKELEY APPARATUS FOR COOLING AND VENTILATING BUILDINGS Filed April 14, 1933 2 Sheets-Sheet 2 INVENTOR Cfm 4 @MJ Q Af-w( 6) ATTORNEYg-um Patented May 21, 1935 PATENT OFFICE APPARATUS FOB COOLING AND VENTILAT- ING BUILDINGS Claude A. Bulkeley, New York, N. Y., asslgnor to Niagara Blower Company, New York, N. Y., a corporation of New York Application April 14, 1933, Serial No. 666,152

18 Claims.

fluctuating loads of heat and humidity occur and where it is desirable to provide a large air movement and to maintain, during the summertime, a definite ratio to the outside air temperature and at the same time provide an adequate amount of fresh air and to accomplish the dehumidification of the fresh and recirculated air with the minimum of refrigeration.

This application is a continuation in part of my copcnding applications, identified as follows:

Applicatox- Ser. No. 482,822, filed Sept. 18, 1930;

Patent No. 1,909,164, dated May 16, 1933; application Ser.No. 526,647, flled March 31, 1931.

'I'he principal object of the invention is to effect cooling and dehumidification by means of coils in place of the usual spray chamber which is not only space consuming but also requires the complete saturation of the air passing through it, this not being true where coils are employed, since only the air passing in contact with the coils is lowered below its dewpoint. Further, where the cooling medium is passed through coils a break in the ammonia line does not pass it directly into the air as is the case where sprays are employed. Further, the cooling coils permit of accurate control of the cooling and dehumidifying eil'ect by varying the rate of flow of the cooling medium through the coils.

Another object is to pass .the cooling medium through the coils counter-current to the air flow and to sectionalize the cooling coil so that different portions of the cooling c'oil are successively rendered operative as an increased load is placed upon the apparatus. The control is also preferably such that the flrstsection to be rendered operative is arranged in the path of the fresh air which, in summer operation, is more likely to be warmer and more humid than the recirculated air.

Another object is to provide such a system in which the circulation of the cooling water and the operation of the compressor occurs only when required and automatically shuts down when not required.

Another object is to avoid the inefllcient and space consuming oy-passes which have heretofore been employed to save refrigeration and to provide a system in which the desired relative humidily and temperature is obtained under extremely, adverse conditions without requiring adding exccssive heat to the cooled and dehumidiiled air to adjust the humidity of the air delivered to the auditorium.

4Another object is to provide a cooling system in which the cooling Water passes counter-current to the air iiow in several passes with the entering 5 water always at a constant temperature so that as the iiow of water through the coils is reduced, the leaving air is higher in temperature but at or near the same dewpoint as when an increased ow of cooling water obtains in response `to an increased load.

Other objects will appear from the following description of the construction and operation of the system.

In the accompanying drawings:

Fig. 1 is a diagrammatic sectional elevation of a building equipped with an air conditioning sys-l tem embodying the present invention and showing, diagrammatically, the arrangement and action of all the instrumentalities used to carry out the invention.

Fig. 2 is a fragmentary view, similar to Fig. 1, and showing a modied lform of control for the dehumidifying and cooling effect of the cooling coils.

Fig. 3 is a fragmentary View, similar to Fig. 1, showing a modified form of control for the dehumidifying and cooling effect of the cooling coils.

4 is a top plan view of one of the cooling coil units and showing six cooling water passes and the fiow of cooling water countercurrent to the air ow.

In its general organization this invention comprises means for drawing fresh air from the outside and room air from the enclosure and passing both through a cooling and dehumidifying coil, the fresh air being directed against that part of the cooling coil through which cooling water always passes when dehumidiflcation is being effected, so that the greater part of the cooling and dehumidiflcation is performed on the fresh air, means for varying the rate of flow of the cooling medium or the air through the coil so as not only to vary the cooling effect but also to vary the dehumidifying effect of the coil, means for conducting the air from said coils into the room and a plurality of thermostats and relays on an instrument board controlling the rate of flow of the cooling media passed through the coils or the air flow past the coils, said thermostats being responsive to the inside and outside temperatures to maintain, in the summertime, the desired relative humidity and to maintain the ternperature in the enclosure a. definite number of degrees lower than the outside air and, in the The air circulating and tempering system The numeral 5 represents an enclosure, such as an auditorium or other room, the air of which is to be conditioned under automatic control. The air from this room is drawn out through a return air duct 6. the flow of air through which is controlled by louvers 1 operated by an air motor 3, this air motor closing the louvers 1 when air pressure is admitted to lt. Excess air, in proportion to the admitted fresh air, is relieved from the return air duet 6 through an exhaust conduit 3, the exhaust of air through this conduit being effected by a motor and fan I and being controlled by louvers Il. 'Ihese louvers are opened on admitting pressure to their operating air motor I2 and the motors 3 and i 2 are operated, as will hereinafter be more fully explained, in opposition to one another so that as the exhaust air louvers Il open, the return air louvers 1 close and vice versa. From the return air duct 6 the return air enters a chamber I3. Fresh air from a fresh air duct I4 is admitted to the chambers I3 and i3', the amount of fresh air admitted to the chamber I3 being controlled by louvers I5, these louvers being operated by an air motor I6. 'I'his air motor i6 opens the louvers l5 when air pressure is impressed on its motor i6. In the lower part of the chamber i3 is arranged a partition which forms a lower fresh air intake I3'.

'I'he fresh and retin-n air from'the chambe i3 passes through cooling coils, indicated generally at 20 and thence passes humidiiying sprays 2i and 22 which are operative only when humidication is required. After passing the humiditying sprays 2l and 22 the air passes the coils of a steam heater 25 and is then drawn into the inlet of a fan 26, the outlet 21 of which discharges the air back into the room 5.

'Ihe cooling coils 26 are sectionalized and are composed of a number of tiered umts 36, one oi' which is illustrated in plan in Fig. 4. As shown in Fig. 4 each of the units consists of a vertically connecting these headers. Each ofthe finned tubes 33 is formed to provide four or more passes, six being shown, andthe flow of the cooling water through these passes ls countercurrent to the air flow through the unit 36 so that the warmest air strikes the last or warmest pass of cooling water'and the partially cooled air strikes the coldest or entering pass ofcooling water. The regulation of the cooling and dehumidifying eii'ect of the units 30 is obtained, as hereinafter more fully explained, either by controlling the number of units 30 used and the quantity of cooling water passed through the units used or by controlling the amount of air which is passed through the units.

' The numeral 35 represents a compressor which is driven by an electric motor 36 and delivers ammonia or other suitable refrigerant under compression through a condenser 34 to a cooler 31.

When required, cooling water for the coils 26 is circulated through this cooler by a pump 36, the outlet line 33 of which connects with a coolor. The cold water from the cooler passes through an outlet line 4i which conducts the cooled water to the cooling and dehumidifying coils 26. The return water from the coo coils 20 is conducted back to the inlet of the pump through a return line 42 which connects with the outlet header 32 of each ofthe units 36.4 The line 4I has three branches, the upper branch connecting with the inlet header '3i of the uppermost coil unit 33, the intermediate branch connecting with the inlet header 3l of the intermediate cooling unit 36 and the lowest branch connecting with the inlet header 3| of the lowermost cooling unit 30. In the lowest branch of the line 4I is arranged a reverse acting diaphragm valve V43 and in the intermediate and upper branches of the line 4i .are arranged reverse acting diaphragm vvalves 44 and 4I. 'I'hese valves 43, 44 and 45 are adapted to be successively opened, in the order set forth, upon admitting air pressure to their control line 46 so that with rising control air pressure in the line 46 the diaphragm valve 43 first opens to admit cooling water to the lowest cooling unit 36 and as the air-pressure in line 46 continues to rise the valves 44 and 45 are successively opened to admit cooling water to their respective units 36.

In order to secure a constant iiow of cooling water through the circulating system at all times a by-pass pipe 41 is provided around each of the vcoil units 30 and its corresponding control valve, these by-pass pipes connecting the supply and return lines 4i and 42 of the cooling water circulating system. The by-pass pipe 41 around the lowermost cooling unit 30 and its diaphragm valve 43 is provided with a direct acting diaphragm valve 43 which is adjusted to work in opposition to the reverse acting diaphragm valve 43 so that as the diaphragm valve 43 opens to pass the cooling water through the lowermost cooling unit 33 the direct acting diaphragm valve 43 closes to cut oif the by-passing of water around this unit. In a similar manner a direct acting diaphragm valve 4! is provided in the by-pass pipe around the intermediate cooling unit 30 and its A lin opposition to the control valve 45. The air' pressure control line 46, of course, connects with all of the direct acting valves 43, 49 and 50. The coil units receiving the recirculated air from chamber I3 can be grouped and provided with one pair of diaphragm valves to pass cooling water through them or a by-pass in response to room conditions. y

It will be observed that fresh air from the duct i3' is directed against the lowermost cooling unit 36 and inasmuch as this lowermost unit 30 is the rst to be placed in operation and the last to be retired during cooling operation, the greater part of dehumidication is performed on the fresh air when only a moderate4 amount of cooling and dehumidifying is required. I

'I'he water delivered by the cooler 31 is maintained at a constant temperature of, say, 40 F, and for this purpose a thermostat 53 is arranged in the cooler 31, the control line 54 from this thermostat 53 connecting with a controller 55 for the motor 36 which runs the compressor 35. As soon as the temperature of the water delivered by the cooler 31 rises above the assumed 40 F. the thermostat 53 operates the controller 55 to start or increase the speed of the motor 36 so that more refrigerant is supplied to the cooler and the temperature ot its outlet water reduced to the desired 40 F. The reverse action takes place on falling temperature in thermostat 53. The controller 55 for the compressor motor 36 is also controlled by a pressure switch 56 through an air pressure control line 51. 'I'he pressure switch 56 is responsive to the pressure in the outlet line 39 o! the circulating pump so that should the circulation of the cooling water fail, for any reason, the pressure switch 56 will operate the controller 55 to shut down the compressor motor 36 and thereby prevent freezing of the cooler 31. The expansion of the water in the system is permitted by an expansion tank 61 which can be overhead, keeping the entire system filled by gravity pressure or, as shown, it can be low and under constant air pressure in excess of the static head of water in the system when lled.

The control system The numeral 10 represents a bar which is shown as being in neutral and is swung to its extreme right position for lsummer operation and to its extreme left position for winter operation. The numeral '1| represents the air pressure supply line for the control system which supplies pressure at, say, 15 pounds. This air pressure supply line 1I, indicated as being heavier than the secondary control lines, connects with a direct acting master thermostat 12 which is in the fresh air intake and hence responsive to the outside temperature. A master thermostat has a comparatively wide range of temperature change and corresponding outlet pressure change, often having a range of temperature change of 20 F. to cause an outlet pressure change of 3 to l2 pounds. Such a master thermostat can be made by adjustment to cover different limited ranges, for example from '15 F. to 95 F. or from 60 F. to 80 F. The outlet line 13 of the master thermostat 12 connects with and controls the setting of a direct acting sub-thermostat 14 in the room 5 which is responsive to the room temperature. The purpose of the master and sub-thermostat combination is to secure a constant different between the temperature of the room and the outside temperature this, during the summertime, being a 10 lower temperature in the room than the outside temperature. Since the master thermostat 12 controls the setting of the sub-thermostat 14, as the outside temperature to which the master thermostat 12 is exposed varies, say, from 95 to 85 F. its outlet air pressure will vary from 12 to '1.5 pounds, which change in air pressure changes the setting of thesub-thermostat, say, from 85 F. to 15 F. Thus, the master and subthermostat in combination accomplish the purpose of maintaining constant differential temperatures between the two media in which the two instruments are located by having the subthermostat control the temperature of one medium.

The direct acting sub-thermostat 14 is connected to the main pressure supply line 1I so that it is supplied with pressureV at 15 pounds and its outlet 15 connects with a direct acting stop thermostat 16. This direct acting stop thermostat is responsive to room air temperatures and is set at, say 15 F. Assuming the direct acting master and sub-thermostats 12, 14 to be set to maintain 10 F. lower temperature inside than outside, if outside temperature is above 85 F. the stop thermostat 16, being set for 15 F. minimum, will have its ports open allowing the sub-thermostat to thermostat 14 and maintain a temperature above the setting'of the sub-thermostat 14 and the ports of the latter will therefore be open.

'I'he position of the sub-thermostat 14 and the stop thermostat 16 can 4be reversed and will work equally well, that is, air can be supplied to the stop thermostat 16 from line 1l and the subthermostat 14 supplied through the stop thermostat 16 by line 15. l

- The master thermostat 12, the sub-thermostat 14 and stop thermostat 16 are all ofthe direct acting intermediate type and consequently with a constant air pressure at 15 pounds supplied at the inlets of the master and sub-thermostats, the air pressure on the outlet of these thermostats rises with rising temperature of the air in which the sensitive parts of the thermostats are located. Conversely, with falling air temperature, the air pressure on the outlet of each thermostat falls. With the tire bar 10 moved to its extreme right position for cooling or summer operation, the outlet line 11 supplying control air pressure from the direct acting thermostats 12, 14 and 16 is directly connected with the line 45 controlling the direct and reverse acting diaphragm valves which determine the -amount of cooling water passed through the cooling coil units 38. Thus, with rising inside or outside temperature, the rising pressure in the thermostat outlet lines 11 and 46 first gradually opens the reverse acting diaphragm lvalve 43 and closes the direct acting diaphragm valve 48 thereby admitting cooling water to the lowermost coil unit 30. As the control pressure continues to rise the reverse acting diaphragm valves 44 and 45 are progressively opened and their corresponding by-pass valves 49 and 50 closed so that cooling water is admitted to the intermediate coil unit and then to the uppermost coil unit 30 as increased cooling and dehumidifying is required.

The thermostat outlet line 11 also connects through line 18 with the switch 19 which, when set for summer operation, carries this pressure to line 80. Line 83 connects with the snap relay 8| which on rising air pressure at two pounds in line 80 delivers air pressure from the main air pressure supply line 1I to its outlet line 82, and closes the controller 83. The wires 84 and 85 from this controller connect with the blades of a double pole, double throw knife switch 86, the operating handle of which is connected to the tie bar 10 so that during summer operation the blades of the switch are connected to the

lines

81 and 88 leading to the controller 89 for the motor of the circulating pump 38. By this means, during summer operation, when cooling is required the circulating pump 38 is maintained in operation. As soon, however, as the thermostat outlet pressure in

lines

11, 18 and 83 drops below two pounds the snap relay 8| cuts oi air pressure to its outlet line 82, thereby opening the controller 83, and through the controller 89 deenergizing the motor to the circulating pump 38. As soon as the pump 38 is so shut down, the pressure control 56 immediately acts through its control line 51 and the controller 55 to shut the compressor 35, the reverse vaction taking place when the pump 38 again comes into action. Therefore when cooling is-not required the circulating pumpis not in operation and an operating economy thereby eiiected. H

The numeral 99 represents a reverse `acting -hygrostat which is supplied with pressure from the main air supply line 1| and the outlet line 9| of which is connected by a branch 92 with a switch 99. This switch 99, when set for summer operation, delivers the control air pressure from the hygrostatoutlet lines 9| and 92 to a line 94 which connects with a direct acting diaphragm valve 95. This direct acting diaphragm valve controls the admission of steam from a steam supply line 95 to the heater 25. Should the outside air during summer be relatively cool, say, '15 to 80 and contain a relatively large amount of moisture, and theheat generated in the room be ,below nonnal, the stop thermostat 19 would set the diaphragm valves 49, 44 and 45 to pass greater quantities of cooling waterthrough their respective cooling coil units 39 and thereby cool the' air the correct amount to maintain the room temperature according to the setting of the stop thermostat 14. However, with excessively moist fresh air the thermosttic adjustment of the valves admitting the cooling water tothe cooling coils would probably not remove the required amount of moisture from the air in order to prevent the relative humidity in the room from rising toohigh. Excessively high relative humidityV in 5 theroom results in. the room feeling cool and chilly to the occupants. In order to prevent this conditin from occuring the reverse acting hygrostat199 set to prevent the relative humidity in the roomf-rom rising above Aa certain maximum say, 55%. `Since the hygrostat 99 is reverse acting, it deliversfalling air pressure with a rising relative humidity, so when the relative humidity in the room is rising and approaches the setting vof the hyg'rostat, the-air pressure in lines 9|, 92

and 94 will fall, thus openingthe direct acting diaphragm valve 95 and allowing steam to enter` the heaterl 25. 'I'his causes the room temperature to risejand the sub-thermostat 14 will function to admit more cooling water through the cooling coil units 39. The admission of more cooling water through the cooling coil units 39 not only further cools but also further dehumidiies the passing air causing the relativehumidity in the room to fall. Since 1 rise in temperature results in about a 2% drop in relative humidity vit 1s unnecessary that the hygrostat 99 turn more than enough steam into the heater 25 to heat the air more than 2 to 5. If the cooling system has been properly designed, this heating of the air to lower the relative humidity will seldom occur and then only when the outside air is relatively cool and damp and at the same time the occupancy heat load in the room much less than normal.

During the summer operation the heater |94 for the spray water of the humidifier is ren- -dered inoperative by the switch 299 as hereinafter more fully described.

With the tie bar 19 moved to its extreme left position for heating or winter operation the blades of the double pole, double throw switch 96 are disconnected from the wires 91 and 99 and con sequently no electrical energy is supplied to the motor driving the circulating pump '39 of the cooling water circulating system. Therefore the entire cooling water circulating system is rendered inoperative.` y

During winter operation the thermostat outlet control line 11 is connected through switch 93 to the air pressure line 94 which controls the direct acting valve 95. The direct acting stop thermostat 19 is set to maintain a minimum temperature of, say, 75 in the room and therefore when the room temperature rises above this setting, the rising pressure in the thermostat outlet line 'I1 through the switch 99 and line 94 closes the direct acting diaphragm valve 95 and reduces the iiow of steam to the heater 25 thereby bringing the room temperature back to the setting of the stop thermostat 19.

During winter operation the movement oi' the tie bar 19 to the left sets up the humidifying system for 'service and places thishumidifying system under the control of the hygrostat 99. For this purpose the hygrostat outlet line 9|, during winter operation, is connected through the Y switch 19 with the pressure line 99 leading to the snap relay 9|. With falling relative humidity in the room, since the hygrostat 99 is reverse acting, the pressure in its outlet line 9| and 99 rises and at two pounds actuates the snap relay 9| to deliver 15 pounds air pressure from the main air pressure vsupply line 1| to its outlet line 92. This actuates the controller 99 to deliver electric current through

lines

94 and 95 to the blades of the double pole, double throw switch 96 which, during winter operation, are connected with the

wires

96 and 91 leading to the controller l99 for a motor 99 which runs a circulating pump |99, The inlet line |9| to the pump |99 withdraws water from a pan |92, this pan receiving the excess water from the humidifying sprays 2| and 22. The outlet line A|93 from the pump |99 connects with the steam heater |94 which is supplied with steam from the steam line 99 under control of the reverse acting dia-v .nozzles |99 which are constructed to deliver the relatively coarse spray'22 of water into the air stream. The pipe |91 is continued beyond the relatively coarse spray nozzles |99 and terminates in spray nozzles |99 which are constructed tov deliver the relatively ne or misty'spray 2| into the air stream. Between the spray nozzles |99 and |99 a reverse acting diaphragm valve ||9 is arranged in the spray water pipe 91 and this diaphragm valve which is directly connected with the air pressure control line |96, this line connecting, during winter operation, with the outlet line 9| of the hygrostat 99 through the switch 299. 'I'he purpose of the switch 299 is to render the heater |94 inoperative during summer operation.

During winter operation, as the relative humidity in the room lowers-to a point where two A.

-spray nozzles 99, thereby` spraying water into the air stream, the ,excess water being received in the pan |92 and recirculated by the pump. As the relative humidity in the room continues to drop the rising air pressure in the hygrostat outlet lines 9| and |08 gradually opens the reverse acting diaphragm valve |05 and admits steam to the heater |04. The spray water delivered by the relatively coarse nozzles |08 is therefore heated and a greater amount of moisture is added to the air stream. Should the relative humidity of the room continue to drop in spite of the heating of the spray water delivered to the nozzles |08, the further rise in the air pressure of the hygrostat outlet lines 8| and |08 opens the reverse acting diaphragm valve ||0 which permits the hot spray water to be discharged through the relatively fine spray nozzles |09 in the form of a fine mist which adds further moisture to the passing air stream and maintains the relative humidity in the room at the setting of the hygrostat 90. A reverse action takes place on rising relative humidity until pressure in line 9| falls below two pounds and pump 99 is shut down.

The numeral represents a switch having a handle ||2. rI'his switch is designed to determine the proportions of fresh and recirculated air admitted to the room 5 and when the handle ||2 is thrown to the right or F position, admits the greatest amount of fresh air to the room 5 and when thrown to the left or R position returns the maximum amount of recirculated air and the minimum amount of fresh air. However, the apparatus is so designed that at no time is all the air handled by the apparatus recirculated air. When the switch has its handle ||2 set to position R, the main pressure supply line 1| is disconnected and the control line ||3 from this switch is open to the atmosphere. Under these conditions, pressure control line ||3 is under 0 pounds air pressure, and a pressure switch I4 to which this line ||3 is connected is open. This pressure switch ||4 controls the controller ||5 of the exhaust fan I0. At the same time, with 0 pounds 'pressure in line H3, the recirculation or return air dampers 1 are open, the exhaust dampers are closed and the fresh air dampers |5 are closed. Thus, any desired portion of the total air handled by the apparatus may be recirculated, the balance being fresh air drawn from the outside, according to the relative size of the recirculation, ex-f haustand fresh airdampers 1, and |5 and the size of the exhaust fan I0. Never is all the air recirculated. Enough fresh air must be supplied during recirculation operation to give proper ventilation, make up for any air exhausted mechanically from the room and cause a slight pressure in the room, sufficient to create outward leakage through cracks and crevices, around the doors and Windows or through other openings between the room and the surrounding space.

When the handle ||2 of switch is set to the F position to admit a greater proportion of fresh air, the outlet line H3 of this switch is directly connected with the main pressure supply line 1| so that a pressure of 15 pounds is impressed upon the damper motors 0, I2 and I8 and upon the switch ||4 which controls the exhaust fan I0. Under this condition of the switch the return or recirculation dampers 1 are closed to the maximum extent, the exhaust dampers are open, the exhaust fan I0 is operating and the fresh air dampers I5 are likewise open. Under this condition the maximum amount of fresh air is admitted to the enclosure 5, the relative amount of fresh and recirculated air being determined by the adjustment of the dampers.

During winter operation or when the outside temperature is less than, say, 10 F. above the setting of stop thermostat 16, the control of the room temperature is obtained exclusively by the stop thermostat 16, the master thermostat 12 and sub-thermostat 14 being inoperative.

It is obvious that instead of controlling the amount of cooling fluid passed through the coil units 30 by the direct and reverse acting

diaphragm valves

43, 44, 45, 48, 49 and 50, the same result can be accomplished by three-waydiaphragm valves. Such a construction is shown in Fig. 2. As there shown each of the

diaphragm valves

43a, 44a and 45a has a connection to the cooling iiuid supply pipe 4|, another connection to the inlet header of each of the coil units 30 and a third connection to the corresponding bypass pipe 41 which leads directly to the cooling water return pipe 42.

During the summertime, as the temperature rises above the setting of the thermostat control the air pressure in the thermostat outlet lines 11 and 48 rises. The first effect of this rising pressure is to operate the valve 43a to cut off the flow of cooling fluid from the lowest by-pass pipe 41 and divert this cooling fluid through the lowest coil unit 30. As the air pressure in line 4B continues to rise the

valves

44a and 45a are similarly operated in succession until all ofthe cooling water is diverted through the coil units 30 instead of the by-pass pipes 41, at which time the cooling coil is operating under full load.

Instead of controlling the cooling and dehumidifying effect of the coil miits 30 by regulating the rate of flow of the cooling water, the same result can be accomplished by regulating the rate of flow of the air through the coils. This regulation of the rate of flow of the air passing through the coils can be eifected by by-passing variable quantities of the air past the coils, the relative amounts of air passed through the coils and around the coils being under thermostatic control. Such a construction is shown in Fig. 3.

As there shown each of the coilunits 30 is the same as shown in Figs. 1, 2 and 4 and has its inlet and outlet headers 3| and 32 connected, respectively, with the cooling water supply and return lines 4| and 42 so that the cooling water is constantly circulated through the coil units 30 at a constant rate. The lowermost coil unit 30 is arranged within the fresh air duct |3 and a by-pass |20 is provided around this lowermostI coil unit 30. 'Ihe relative amounts of fresh air passed through the lowermost coil unit 30 and through the by-pass |20 is controlled by a bypass louver |2| and by louvers |22 in advance of the lowermost coil unit 30, these louvers being connected by a bar |23 to work in opposition to one another so that as the by-pass louver |2| opens, the louvers |22 close and vice versa. The movement of these louvers is effected by an air motor |24 which is connected, through a line |25, to the control line 11 from the thermostats. The motor |24 is designed to close the by-pms louver |2| and open the louvers |22 on rising pressure in its control line |25.

The two upper coil units 30 are arranged in the chamber I3 and are arranged to provide an air by-pass |30. The relative amounts of air by-passed through the by-pass |30 and passed through the uppermost coil units 30 are controlled by louvers |3| in the by-pass |30 and louvers |32 in advance of these uppermost coil units 30. The by-pass louvers |3| and the louvers |32 are connected by a bar |33 to work in opposition to one another so thatas the by-pass louvers |3| open the louvers |32 close and vice versa. 'I'hese louvers are moved by an air motor |21 which is connected to the air pressure line |25 from the thermostat outlet line 11. This motor |21 is designed so that as the pressure in control line |25 rises the by-pass louvers |3| are closed and the'louvers |32 opened. As the room temperature rises above the setting of the thermostat control, since the thermostats are direct acting, the pressure in the thermostat outlet lines 11 rises and causes a corresponding rise in pressure in the 'control line |25. The first effect of this rising pressure in control line |25 is to operate the motor |21 to gradually open the louvers |22 in advance of the lowermost coil unit 30 and close the corresponding by-pass louver |2|. The fresh air entering from the fresh air duct I3' therefore passed in increasing proportions through the lowermost coil unit l0, instead of its by-pass, thereby effecting an initial cooling and dehumidiflcation of this fresh air. If this is not suicient to bring the temperature in the room down to the setting of the thermostat controlthe air pressure in line |25 coninues to rise and operates the motor |21 to gradually open the louvers |32 in advance of the uppermost coil units 30 and close the corresponding byv-pass louvers I3I. When this occurs an increasing proportion of the mixed return air and fresh air passing through the chamber I3 is passed through the uppermost pair of cooling coil units 30 and is cooled and dehumidifled. Under maximum load all of the air from both the fresh air duct I3' and the chamber I3 is passed through the cooling coils 30 and the by-passes IZB and |30 are closed.

While the method of control shown in Fig. 3 is satisfactory the method of control illustrated in Figs. 1 and 2 is preferred because a more satisfactory control can be obtained of the rate of fiow of the cooling water than of the air since theformer avoids the use of dampers and air motors.

A system, such as herein described, when functioning as 'a cooling system, mustcirculate or discharge a suillcient quantity of air through vor linto the enclosure, so that the amount of heatand moisture added to this air-in passing through the enclosure-will result in the room being maintained at the desired conditions, as to temperature and moisture content of the air, and this must be done when the amount of this heat and moisture is at the maximum. Obviously, as this amount of heat and moisture to be absorbed becomes less, due to a decrease in any one or more of its factors, such as number of people, lights, etc., less cooling and dehumidifying of the air introduced into the room isr required. This can be accomplished by doing less cooling and dehumidifying of the entire volume of air handled or by continuing to cool and dehumidify only a portion of the air and mixing it with the remainder and the entire amount then delivered into the enclosure. a portion of the air handled may be cooled and dehumidifled a lesser amount than the maximum to absorb intermediate quantities of heat and moisture from the room. Furthermore, since, as previously statedthe recirculated air is essentially in the desired condition, it is unnecessary to either cool or dehumidify this recirculated air if the amount of fresh air introduced, cooled and dehumidied, is sufcient to absorb the heat and moisture to be gotten rid of within the enclosure,

thus, if one-third the air handled is fresh air, this one-third, properly cooled and dehumidiiled, will absorb one-third the maximum amount of heat and moisture from the room. For amounts of heat and moisture between one-third and the' maximum, the two-thirds of the air recirculated can be partially treated the required amount and the whole mixed and delivered to the room. Thus, on any installation, proper conditions can readily be maintained in the room to be conditioned. for any percentage of the maximum load equal to the percentage of fresh air handled by cooling and dehumidifying only the fresh air. Intermediate percentages, between this andthe maximum amount ofl heat and moisture to be absorbed can be met by a proportional treatment of the recirculated air. For percentages of the maximum load which are less than that equal to the fresh air handled, this fresh air can be cooled a less amount and then mixed with thel untreated recirculated air and delivered into the enclosure.

Operation For both summer and winter operation the fan 26 is running and drawing room air from the room i through return air duct I into chamber I3 andisalsodrawingfreshairinfromthe fresh air ducts Il and Il. 'Ihis air is drawn through the cooling coil units Il, past the humidifying spray nozzles III and |09, through the heater 25 and discharged into the room 5.

When it is desired to recirculate the maximum amount of room air the handle ||2 of switch is thrown to the left or R position. In this position the switch opens the lines Ill to the atmosphere thereby relieving the pressureon motors 8, I2 and I6 and also relieving the pressure on the pressure switch Il. This deenergizes the motor driving the exhaust fan I0; closes the fresh air louvers i; closes the exhaust air louvers Iand opens the recirculation louvers 1 so that the maximum amount of the air handled is recirculated room air. However, a minimum amount of fresh air is always provided to the fresh air duct [3'.

When it is desired to circulate all fresh air, or a maximum amount of fresh air. the handle ||2 of switch III is thrown to the right or F position, in which the control pressure line H3 is directly connected with the main air pressure supply line 1I and hence under l5 pounds air pressure. This pressure is" impressed on the motors 8, i2 and I6 and the pressure switch Ill. Under these conditions the motor for the fan l0 is energized. 'I'he dampers in advance of this fan are opened, the recirculation air dampers 1 are closed and the fresh air dampers l5 are opened. It is therefore apparent that the maximum amount of fresh air will be handled by the apparatus under these conditions.

Operation during summer During summer operation the bar is moved" renergized and when energized circulates cooling water through the cooler 31', pipe 4| and through either the cooling coil units Il orthefr by-pass pipes 41 to a return line l2 to the pump. -The water leaving the cooler 31 is kept at a constant temperature of, say, 40 by a thermostat 53 which, through the controller 55, controls the motor 36 for the compressor 35. T'he compressor motor 36 is only operated when the circulating pump 38 is nmning and Awhen this circulating pump stops, the pressure switch 56 in its outlet line 39 actuates the controller 55 to deenergize the motor 36.

vDuring summer operation the switch 288 is moved to the position in which it disconnects the line |88 from the hygrostat outlet line 9| and opens this line |86 to the atmosphere. With the line |88 open to the atmosphere, the reverse acting valve |85 is closed thereby preventing steam from entering the heater |84 and rendering this heater completely inoperative. The reverse acting valve I I8 is also closed, during summer operation by opening the control line |86 to the atmosphere through switch 288. Since, during summer operation, the electrical switch 86 cuts ofi the supply of electrical energy to the controller 98 and the spray water pump motor 99, it is apparent that the electrical switch 86 and the air switch 288, in combination, render the humidifying system completely inoperative when the tie bar 10 is set for summer or cooling and dehumidifying operation.

The direct acting master thermostat 12 in the fresh air intake sets the direct acting sub-thermostat 14 in the room to maintain, say, 10F. lower temperature in the room than outside. If the outside temperature is above 85 F., direct acting stop thermostat 16 being set for 75 F. minimum will have its ports open allowing subthermostat 14 to control. the air in stop thermostat outlet line 11 and carry higher room temperature. If outside temperature is below 85 F. the sub-thermostat 14 will be set by master thermostat 12 lower than 75 F. but since stop thermostat 16 is set at '15 F. it will throttle the control pressure, maintaining the temperature above the setting of sub-thermostat 14 and the ports of the latter will therefore be open.

The control from these direct acting therm stats, through line 11, switch 19 and line 88, actu-I ates the snap relay 8| when the control pressure rises to, say, two pounds. When this occurs the snap relay delivers 15 pounds air pressure from the main pressure supply line 1| to the line 82,

which pressure operates the controller 83 to deliver electrical energy through the switch 86. and through

lines

81 and 88 to the controller 89 for the motor of the circulating pump 38. This motor is thereby energized and starts the circulation of cooling water through the system. When the air pressure from the thermostat outlet control lines drops below the setting of the snap relay 8|, the snap relay cuts off the supply of air pressure to the line 82 and operates the controller 83 to cut off energy to the circulating pump motor, thereby putting the circulating pump out of operation when its operation is not required and effecting an operating economy.

The control line 11 from the direct acting thermostats 12, 14 and 16 is connected directly, through line 46, with the reverse acting diaphragm valves 43, 44 and 45, controlling the flow of water through the cooling coil units 38 and also connected directly to the direct acting diaphragm valves 48, 49 and 58 controlling the by-passing of the water around the cooling coil units 38. As the pressure in the thermostat

outlet control lines

11 and 46 rises the lowermost diaphragm valve 43 is opened and its companion direct acting a certain maximum, say, 55%.

diaphragm valve 48 closed so that cooling water passing through the lowermost by-Dass 41 is diverted through the lowermost cooling coil unit 38 and the fresh air passing through the lowermost cooling coil unit 38 is thereby cooled and dehumidied. If this cooling and dehmudiilcation is insuillcient to bring the room temperature down to that which the thermostats are set to maintain, the control air pressure in thermostat outlet lines 11 and 46 continues to rise and first opens and closes, respectively, the pair of diaphragm valves 44 and 49, thereby diverting the cooling water through the intermediate cooling coil unit 38 and cooling the mixed vfresh and recirculated air. Further rise in pressure in thermostat

outlet control lines

11 and 46 opens and closes, respectively, the last pair of companion diaphragm valves 45 and 58, thereby admitting cooling water to the last or uppermost coil unit 38, under which condition of operation the maximum amount of cooling and dehumidfying is effected.

The operation of the form of the invention shown in Fig. 2 is the same except that three-way diaphragm valves are substituted for the pairs of reverse and direct acting valves shown in Fig. l. Instead of controlling the rate of flow of the cooling water under thermostat control, the same can be effected by controlling the rate of ilow of the air through controlled by-passing of the air around the cooling coils. This form of the invention is illustrated in Fig. 3 in which rising pressure in the thermostat outlet lines 11 effectsrising pressure in its outlet control line |25 and rst operates the motor |24 to close the by-pass damper |,2| and open the dampers |22 in advance o f the lowermost coil unit 38 through which cooling water is continuously owing at a constant rate. By this means the fresh air from the fresh air duct I3 is passed through the lowest cooling coil 38 and cooled and dehumidified accordingly. As the pressure in the control line |25 continues to rise, with rising room temperature, this pressure operates the motor |21 to open the louvers |22 and close the b'y-pass louvers |3| until all of the air, both recirculated and fresh, is beingV air be relatively cool, say, '15 to 85, and contain a relatively large amount of moisture and the heat generated in the room be at a minimum, the stop thermostat 16, set for '15 minimum, would adjust the diaphragm valves 43, 44 and 45 (and their companion reverse acting diaphragm valves 48, 49 and 58) to pre-cool the air the correct amount to maintain the room temperature according to the setting of the stop thermostat. But this probably would not remove the required amount of moisture from the air to preventthe relative humidity in the room from rising too high. In order to prevent this condition from occurring the hygrostat 98 is set to prevent the relative humidity in the room from rising above Since the hygrostat 98 is reverse acting, it delivers falling air pressure with rising relative humidity, so when the relative humidity in the room is rising and approaches the setting of the hygrostat, the air pressure in lines 8|, 92 'and 9 4 will fall, thus opening the direct acting diaphragm valve 88 and admitting steam to the heater 28. This tends to cause the room temperature to rise and the sub or stop thermostats 18 and 18 will function to admit more cold water through the cooling coil units 88. Since the cooling coils have 40 F. water circulating through them at all times, the admission of more water not only cools but increases the dehumidication by the cous, causing the relative humidity in the room to fall. Since 1 rise in temperature results in about a 2% drop in relative humidity it is unnecessary that hygrostat 98 turn more than enough steam into the heater 25 to heat the air more than 2 to 5; 'Ihis heating oi the air to lower the relative humidity will seldom occur and then only when the outside air is relatively cool and damp and at the same time the occupancy heat load in the room much less than normal.

Heating and humidifying operation in the wintertime When heating or humidifying is required,the

' tie bar 18 is swung to its extreme left position for winter operation. This throws the blades of the double pole, double throw knife switch 8S out of contact with the

wires

81 and 88 which supply current to the motor for the circulating pump 38 and thereby renders inoperative the entire cooling system, the pressure switch 56 in the outlet 39 of the circulating pump 38 cutting the compressor motor 36 out of service whenever the circulating pump 38 is shut down.

During winter operation the thermostat control line 11 is connected through switch 93 with the line 94 controlling the direct acting diaphragm valve 95. Since under these conditions the coni trol of heating is effected exclusively by the stop thermostat 16, when the room temperature vdrops below the setting, say, 75 of the stop thermostat the falling air pressure in the

thermostat control lines

11 and 94 will open the direct acting diaphragm valve 95 and admit steam to the heater 25 suillcient to maintain the temperature of the room at the setting of the stop thermostat. The thermostat control line 11 is, of course, connected, during Winter operation, with the diaphragm valves 43, 48 and 45 but since no cooling water is being circulated through the lines which these valves control the operation of these valves during winter has no eiect.

The water in the entire cooling system is, of course, drained out during the heating season to prevent freezing and refilled at the beginning of the cooling season.

When the bar 18 is set to the left for heating, the controller 83 is connected through the electric switch 85 with the

lines

96 and 91 leading to the controller for the `motor 99 oi' the spray water circulating pump |83. This motor is only operated when humidiflcation is required and for this purpose the outlet line 9| from the hygrostat 98 is connected through switch 19 with the line 88 leading to the snap relay 8|. Since the hygrostat 9|) is reverse acting, a falling relative humidity results in rising pressure to the snap relay 8| and when this pressure reaches 2 pounds the snaprelay is actuated to admit full pressure from the main air pressure supply line 1| to its outlet line 82, this pressure actuating the controller 83 to provide energy, through the electric switch 86, for the operation of the motor 99 for the spray water pump. The reverse takes place when the relative humidity in the room approaches the setting oi the hygrostat and the air pressure in its outlet control line drops below the setting of the snap relay 8|. The spray water pump |88 withdraws water from the collecting pan |82, passes it through the heater IM and through line |81 to the relatively coarse spray nozzles |88 which discharges it into the air stream. In the event that i le relatively coarse sprays from the nozzles |88 is irwulllcient to raise the relative humidityinl the room to the point demanded by the hygrostat, the rising pressure in the hygrostat outlet line 8|, through switch 288 and line |88 opens the reverse acting diaphragm valve |88 and admits steam to the spray water heater |88 which heats the water discharged through the relatively coarse spray nozzles |88. If this heating is'still insumcient to obtain the desired relative humidity the continued rise in the outlet pressure from the hygrostat in line |88 operates the reverse acting diaphragm valve H8, thereby permitting the heated spray water to be discharged from the nozzles` |89 in the form of a fine spray or mistthis latter being calculated to obtain the desired relative humidity under all conditions oi' winter operation.

n will be understoody that the dehumidmcation Y o! the air in passing the coils is accomplished through chilling the air passing in immediate contact with the last or iirst water pass coils at least a part of which is chilled below its dewpoint but that inasmuch as only a portion of the air touches the coils the average temperature of the air leaving the coils is considerably above its dew point. y i

I claim as my invention:

l. In an apparatus for conditioning an enclosure, a multiple pass cooling coil, means iorvpassing air through said cooling coil over the exterior of the pipes thereof and into said enclosure, means for passing a cooling iluid through the inside of the pipes oi said cooling coil countercurrent to the flow of air and at an entering temperature substantially below the dewpoint of the air passing said coil whereby said air is dehumidiiled and cooled to an average temperature substantially above its dewpoint and said cooling fluid is warmed to a leaving temperature substantially above said dewpoint, and means responsive to the yair conditions in the enclosure for varying the velocity of said cooling fluid through said coil to vary the cooling and dehumidifying eilect of the coil.

2. In an apparatus for conditioning an enclosure, a multiple pass cooling coil, means for passing fresh air through said cooling coil over the exterior of the pipes thereof and into said enclosure, means for passing a cooling iluid through the inside of the pipes of said cooling coil countercurrent to thev flow of air and at an entering temperature substantially below the dewpoint of the said fresh'l air whereby said air is dehumidied and cooled to an average temperature substantially above its dewpoint and said cooling fluid is warmed to a leaving temperature substantially above said dewpoint, and means responsive to the air conditions in the enclosure for varying the velocity of the cooling fluid through said coil -to vary the cooling and dehumidifying eil'ect of the coil.

3. In an apparatus for conditioning the air wit-hin an enclosure, a multiple pass cooling coil,-

means for passing fresh air and air withdrawn is cooledan'd dehumidiiled on'passing said and said cooling fluid-is warmed to a leavin temperature substantially fabove said dewpoint,

and means responsive to the airconditions in the enclosure for varying the velocity of said cooling fluids through said coilto vary the cooling and dehumidifying eifect 'of the coil. l -l 4. In Van 'apparatus' for conditioning an enclosure, a multiple pass coolingl c oil, means for passing air through 'sa'idcoil over the outside of the pipes thereof and into said enclosure, means for passing a'cooling fluid'through the inside of said4 coil countercurrent to the air flow and at a sub'- a stantially constant entering Itemperature substan- 4 within an enclosure, a multiple pass cooling coil,

means for passing fresh air directly through said coil around the outside of the pipes thereof, means for passing a cooling iluid through the inside of said coil countercurrent to the air flow and at an entering temperature substantially below the dewpoint of the air passing said coil whereby said air is dehumidiiled on passing said coil and cooled to an average temperature substantially above its dewpoint, means for varying the rate of flow of one of the two fluids to varythe cooling and dehumidifying effect of said coil comprising a sub-thermostat responsive to the temperature of the air in the enclosure andcontrolling the flow of one of saidA two fluids, and a master thermostat responsive to the temperature ofthe fresh air and controlling the setting of said sub-thermostat to obtain a constant differential between the temperature of the fresh and enclosure air, and means for admitting the air from said coil to said enclosure.

6. In an apparatus for conditioning -the air within an enclosure, a multiple pass cooling coil,

means for passing fresh air directly through said coil around the outside of the pipes thereof, means for passing a cooling fluid through the inside of said coil countercurrent to the air flow and at an entering temperature substantially below the dewpoint of the air passing said coil whereby said air is dehumdifled on passing said coil and cooled to an average temperature substantially above its dewpoint, means for varying the rate of ilow of one of the said two fluids to vary the cooling and dehumidifying eect of said coil comprising a sub-thermostat responsive to thel temperature of the air in the enclosure and controlling the flow of one of said two fluids, a master thermostat responsive to the temperature of the fresh air and `controlling the setting of said sub-thermostat to obtain a constant differential between. the temperature of the fresh and enclosure air and a stop thermostat responsive to the temperature of the air in the enclosure and controlling the flow of one of said two fluids when the setting of said subthermostat is adjusted too low for human comfort, and means for admitting the air from said coil to said enclosure.

7. In an apparatus for conditioning an enclosure, a cooling coil, means for passing air through said coil around the outside of the pipes thereof, means for passing a cooling iluid through the in'- ing pump, means associated with' said cooler 'for maintaining the temperature of said cooling'iluld lat a substantially constant entering temperature l substantially below the dewpoint of the air passing said lcoil whereby said air is dehumidiiled and cooled to an average temperature substantially 'above' its dewpoint on passing said'coil, control means responsive to the air conditions in the enclosure for varying the ilowof one of the twoiluids through said coil to vary the cooling and dehumidifying effect of the coil, means responlsive to the air conditions in the enclosure for stopping said pump when cooling o`r dehumidifying is not required and 4for startng said pump when the air conditions in the room again require cooling or dehumidifying, and means for admitting the air vfrom the coil to the enclosure.

8. In an apparatus for 4conditioning an enclosure, a cooling coil, means'forr passing air through said coil around the outside of the pipes thereof, means for passing a cooling fluid through the inside of said coil including a cooler and a circulating pump, means associated with said cooler for maintaining the temperature of said cooling fluid at a substantially constant entering temperature substantially below the dewpoint `of the air passing said coil whereby said air is de- .humidiiied and cooled to an average temperature' substantially above its dewpoint on passing said coil, control means responsive to the air conditions in the enclosure for varying the flow of one 4 of the said two iluids through said coil to vary the cooling and dehumidifying eilect oi' the-coil, means including a snap relay in the control line from said control means for stopping said pump when cooling or dehumidifying is not required and for starting said 'pump when the air condi' .tions in the room again require cooling or dehumidifying, and means for admitting the air from the coil to the enclosure;

9. In an apparatus for conditioning an enclosure, a cooling coil, means for passing air through said coil around the outside of the pipes thereof, means for passing a cooling iluid through the inside of said coil including a cooler, a. circulating pump for circulating said cooling uid through said cooler and coil and a motor driven compressor for supplying refrigerant to said cooler, means for maintaining the entering temperature of said cooling fluid below the dewpoint of the air passing said coil whereby said air is dehumidied and cooled to an average temperature substantially above its dewpoint on passing said coil, control means responsive to the air conditions in the enclosure for varying the flow of one of the two fluids through said coil to vary the cooling and dehumidifying effect of the coil, means actuated through motion derived from the starting of the pump to start said motor driven compressor and to stop said motor driven compressor on stopping said pump and means forv admitting the air from said coil to said enclosure.

10. In an apparatus for conditioning an enclosure, a cooling coil,- means for passing air through said coil around the outside of the pipes thereof, means for passing a cooling fluid through the inside of said coil including a cooler, a circulating pump for circulating said cooling fluid through said cooler and coil and a motor driven compressor for supplying refrigerant to said cooler, means for maintaining the entering temperature of said cooling fluid below the dewpoint of the air passing said coil whereby said air is dehumidied and cooled to an average tempera- 11. In an apparatus for conditioning an enclosure, a cooling coil, means for passing air through said coil around the outside of the pipes thereof, means for passing a cooling fluid through the inside of said coil including a circulating pump, a cooler and a motor driven compressor for supplying refrigerant to said cooler, means for maintaining the temperature of said cooling fluid at an entering temperature below the dewpoint of the air passing said coil whereby said air is dehumidied and cooled to an average temperature substantially above its dewpoint on passing said coil, control means responsive to the air conditions in the enclosure for varying the iiow of one of said two fluids through said coil to vary the cooling and dehumidifying effect of the coil, means responsive to the air conditions in the enclosure for stopping said pump when cooling or dehumidifying is not required and for starting said pump when the air conditions in the room again require cooling or dehumidifying, means actuated through motion derived from the starting of said pump to start said motor driven compressor and to stop said motor driven compressor on stopping said pump and means for admitting the air from said coil to said enclosure.

12. In an apparatus for conditioning an enclosure, a cooling coil, means for passing air through said coil around the outside of the pipes thereof, means for passing a cooling fluid through the-inside of the pipes of said coil at an entering temperature below the dewpoint of the air passing said coil whereby said air is dehumidied on passing said coil and cooled to an average temperature substantially above its dewpoint, thermostat means responsive to the temperature in the enclosure for varying the flow of one oi' the said two iluids to cool and dehumidify the air passing the coils and maintain the air in the enclosure at a desired temperature, means for preventing the relative humidity in the enclosure from rising above a desired percentage when the preponderance of the air handled is cool and moist fresh air andthe heat load within the enclosure is light, comprising a heater through which the air leaving said cooling coil is passed and a hygrostat responsive to the humidity in said enclosure and admitting a heating medium to said heater when the relative humidity rises to its setting and means for passing the air from said heater to said enclosure, said heating of the air under hygrostat control affecting said thermostat means to admit more cooling duid to said coil to effect a greater dehumidiflcation of the passing air.

13. In an apparatus for conditioning an enclosure, a cooling coil, means for passing air temperature substantially above its dewpoint, thermostatic means responsive to the temperature of the air in the enclosure lfor varying the cooling and dehumidifying effect of said coils to maintain the air in the enclosure at a desired temperature, means for preventing the relative humidity in the enclosure from rising above a desired percentage during cooling when the preponderance of the air handled is cool and moist fresh air and the heat loadin the enclosure is light, comprising a heatenthrough which the air leaving the cooling coil isv passed,r means for vadmitting a heating medium to said heater, ahygrostat responsive to the humidity in said enclosure, switch means in the control line of said hygrostat and in one` position connecting said control line with said heating medium admitting means to admit the heating medium to said heater as the relative humidity rises to the setting of said hygrostat, means for passing the air from said heater to said enclosure, said heating of the air under hygrostat control affecting said thermostat means to admit more cooling fluid to said coil to effect a greater dehumidiiication of the passing air, means for humidifying the said air admitted to said enclosure, and means for varying the effect of said humidifying means, said switch means in its other position connecting the control line of said hygrostat with said means for varying the effect of said humidifying means whereby in winter operation said hygrostat maintains a predetermined relative humidity in said enclosure through humidiiication.

14. In an apparatus for conditioning an enclosure, a cooling coil, meansl for passing air through said coil around the outside of the pipes thereof, means for passing a uid through the inside of said coil, means for cooling'said uid to an entering temperature below the dewpoint of the air passing said coil whereby said air is dehumidied and cooled to an average temperature substantially above its dewpoint, a heater for heating the air leaving said cooling coil, means adapted to humidify the air leaving said coil, means for admitting the air from said humidifying means to said enclosure and switch means adapted to be thrown to one position for summer operation and adapted to be thrown to another position for winter operation, a thermostat in said enclosure, a hygrostat in said enclosure, said thermostat being connected to control the rate of now of one of .the two fluids through said coilV and said hygrostat being vconnected during winter through saidl switch means to control the effect of said humidifying means and obtain a desired humidiiicationof the air in the enclosure, and said hygrostat being connected during summer through said switch means to control the admission ot heat to said heater thereby to obtain under all conditions of summer operation a' desired low relative humidity by heating the cooled air admitted to the room and thereby adjusting the thermostat to increase the cooling and dehumidii'ying etl'ect of the coil. I

15. In an apparatus for conditioning an enclosure, a cooling coil, means for passing air through said coil around the outside of the pipes thereof,

means for passing a uid through the inside of said coil, means for cooling said iiuid to an entering temperature below the dewpoint of the air passing said coil whereby said air is dehumidiiied and cooled to an average temperature substantally above its dewpoint, a heater for heating the air leaving said cooling coil, means adapted to evaporate moisture into the air leaving said coil, means for admitting the air from said humidifying means to said enclosure, switch means adapted to be thrown to one position for summer operation and adapted to be thrown to another position for winter operation, a thermostat in said enclosure, a hygrostat in said enclosure, said thermostat being connected to control the rate of flow of one of the two fluids through said coil and said hygrostat being connected during winter through said switch means to control the e'ect of said humidifying means and obtain a desired humidiflcation of the air in the enclosure, and said hygrostat being connected during summer through said switch means to control the admission of heat to said heater thereby to obtain under all conditions of summer operation a desired low relative humidity by heating the cooled air admitted to the room and thereby adjusting the thermostat to increase the cooling and dehumidfying effect of the coil, and means connecting said switch means with said fluid cooling means and rendering said cooling means inoperative when said switch means are thrown to winter position.

16. In an apparatus for conditioning the air in an encloseure, a cooling coil composed of a series of coil units. means for passing fresh air and air withdrawn from said enclosure through said coil around the outside of the pipes thereof, means for passing a cooling fluid through the inside of the pipes of said coil at an entering temperature below the dewpoint of the air passing said coil whereby the air is dehumidifled and cooled to an average leaving temperature substantially above its dewpoint, a by-pass for said coil units, a valve associated with each coil unit and each controlling the relative amounts of cooling fluid passed through the corresponding unit and the by-pass. means responsive to the air conditions in the enclosure for progressively actuating said valves to divert by-passed cooling fluid into the coil units and thereby increase the cooling and dehumidifying leffect of the coil and means for admitting the air so cooled and dehumidifled te said enclosure.

17. In an apparatus for conditioning the air in an enclosure, a cooling coil composed of a series of coil units, means for passing fresh air and air withdrawn from said enclosure through said coil associated with each coil unit and each controlling the relative amounts of cooling fluid passed through the corresponding unit and by-pass, means responsive to the air conditions in the enclosure for progressively actuating said valves to divert by-passed cooling uid into the coil units and thereby increase the cooling and dehumidifying effect of the coil and means for admitting the air so cooled and dehumidied to said enclosure, the coil units rst rendered operative being -arranged in the path of the fresh air and the coil unit last becoming operative being arranged in the path of the air from said enclosure.

18. In an apparatus for conditioning the air within an enclosure, a cooling coil composed of a series of multiple pass units, means for passing fresh air and air withdrawn from said enclosure through said coil units over the outside of the pipes thereof and into said enclosure, said series being arranged transversely of the air flow, means for passing a cooling fluid through the inside of the pipes of said coil units counter-current to said air flow at an entering temperature below the dewpoint ofthe air passing said coil whereby said air is dehumidified and cooled to an average leaving temperature substantially above its dewpoint. means responsive to the air conditions in the enclosure for Varying the rate of flow of said cooling fluid through said coil units and for progressively stopping and starting the flow of cooling fluid through said units to vary the cooling and dehumidifying e'ect of the coil, that unit of said coil through which the cooling fluid is first admitted and last cut olf being arranged in the path of the fresh air and that unit of the coil through which the cooling fluid is lastadmitted and first cut being arranged in the path of the enclosure air whereby under operating conditions of less than i'ull load the greater amount of dehumio'iiication is performed on the fresh air.

CLAUDE A. BULKELEY.