US2112520A

US2112520A - Air conditioning system

Info

Publication number: US2112520A
Application number: US607916A
Authority: US
Inventors: Robert B P Crawford
Original assignee: Frick Co Inc
Current assignee: Frick Co Inc
Priority date: 1932-04-28
Filing date: 1932-04-28
Publication date: 1938-03-29
Anticipated expiration: 1955-03-29

Description

29, 1938. R. B p C A O D 2,112,520

AIR CONDITIONING SYSTEM Filed April 28, 1932 3 Sheets-Sheet l /o 9 r 73 ea L -L n vENToR ATToR/YE Y Patented Man ZQ, a d I r I UNITED STATES? PATENT, orrlcs Robert B. Crawford, Brooklyn, N. Y., assignor to Frick Company, Waynesboro, Pa., a corporation of Pennsylvania Application April 28, 1932, Serial No. 6.0mm

29 Claims. (01. 257-1) This invention relates, in general, to air contioned air. If ,the predetermined pressure conditioning systems and, more particularly, to a ditions in any part'of the system are not mainsystem which, although of general application, tained, as for instance, if a window, or. windows, is especially suited for installation in hotels, in any of the floors or rooms, are-opened, the reapartments, hospitals, and similar buildings sult is that either the amount of conditioned air 5 wherein it is desirable, or necessary, to mainfed to each floor or room is changed 01' an ini tain diil'erent, or varying air-conditions in dif-' creased amount of air is passed th ou t e a ierent parts of the building conditioning unit and none of the floors or rooms In the prior types of ventilating and air condig ts the desired am n of P p y C nditi n d tioning systems used in buildings of the kinds air. In any v t, t Wh e Ventilating System mentioned, air is circulated from a central air is disorganized until the predetermined pressure conditioning unit through ducts to the floors or conditions throughout the whole system are rooms and back to the unit, or exhausted .to the again estab ThiS d sadvantage has not atmosphere. By reason of the large amount of been overcome in any of the known systems of duct work necessary, such systems are very ex- 'theart. 5

pensive and take up an inordinate amount of Th nown air Conditioning units are all despace. Furthermore, since all of the conditioning signed to take in atmospheric air or a mixture of of the air, both as to the humidity and temperaatmospheric and recirculated air, and in one step, ture, is effected at the central unit and is concool and dehumidify it. The air thus conditrolled by the operator of the unit, the air enter- 'tioned is then passed direct y to the point ing each floor or room is at the same tempera- Points-0f e, 0 39-8 in s e eases, heated to a deture and relative humidity. sired temperature, and then passed to the point,

To obtain some degree of individual control of 0 points, of usey this procedure, a greater the air temperature at the various floors or load than necessary is carr ed by dehumidirooms, various arrangements, such as the profi d no attempt is made to efficiently use the vision of dampers in the air outlet ducts and/or energy pp 0 the y air inlet ducts, the provision of heat exchangers s ve t n is directed to a Solution Of all in the floors or rooms, etc., suggest themselves. the P s above e o e d as o a These arrangements, when considered in the light object an air conditioning system adapted to supof the teachings of the prior art, are not satis- P y conditioned from a Central r conditio factory. The use of dampers can give only a ing unit to a plurality of floors or rooms of a limited control and seriously interferes with the building which provides for further controlled air circulation; the use of heat exchangers inconditioning of the air at the individual floors or volves, besides the exchangers themselves and the rooms and which permits the altering of prespiping necessary for the circulation of the heat sure conditions in any of said floors or rooms exchange fluid, additional piping for conducting without in any way affecting the conditioning of away water which may condense on the exthe air at the central unit or at the rest of said h n due to their temperature b in brought floors or rooms or altering the quantity of air below the dew point of the conditioned air. Furfed to the t of said floors or rooms, Said thermore, whether heat exchangers or individual tem involving a minimum f duct Work a app, conditioning units are used it is always necessary ratus and entirely eliminating the need of insulato thoroughly insulate i i g through which, tion on the piping used for circulating heat exthe heat exchange medium 1s clrculated to prechange medium. vent condensatlon of mmsture on piping The invention has also for an object a mecha- For these t f F P Is to use nism which may be used in any type of ventiseparate air conditioning umts in each floor, or te h r i is room, whenever it is necessary to provide for latmg or an con loltmg sys m w e em individual control at the floors or rooms. suppllee to p1ura'hty of enclosures whlch In the known Systems using a central unit f r mechanlsm w1l1 automatically cut out any ensupplying conditioned air to a plurality f Sena, closure or encl o sures from the system when the rate floors, or rooms, it is necessary that the pres- Pressure condltlons 111 531d enclosures chalege sure conditions throughout e whole System be from those necessary for the proper operatlon maintained substantially constant at predeter- Ofthe System and W111 automatleally -Ore S d mined values, in order that every floor or room enclosure or enclosures to the system when the be supplied withits required amount of condipressure conditions necessary for the proper operation of the system again attain in said enclosure or enclosures.

Ira-accordance with my copending application, Ser. No. 375,952, filed July 5, 1929 a system is disclosed wherein outside air is conditioned be-- fore being admitted to the enclosure, the pressure within the enclosure being maintained above atmospheric pressure to prevent infiltration of air except from the conditioner, and a separate conditioning of the air in the enclosure, and the commingling in the enclosure of the two streams out this heating the refrigerant of air produced by the two conditioners. With respect to such subject matter this application is a continuation in part..

The invention has for a further object an air conditioning and ventilating system wherein conditioned air is supplied to the floors or rooms of the building under a pressure sufiicient to prevent infiltration of airrfromthe atmosphere and to. allow a definite quantity of air to flow from the floors or rooms to the atmosphere, and wherein ventilating and heat exchange means. are provided in each of the floors or rooms for continuously mixing the air supplied to each floor or room with the air in the floor or room and for continuously modifying the temperature of mixed air to maintain itat a desired temperature; the 1 heat exchange medium supplied to the heat exchangers in said floors or rooms being passed through the dehumidifying zone of the central air conditioning unit in heat exchange relation with the air being dehumidified before it is supplied to the heat exchangers so that the temperature of the heat exchangers and the piping leading thereto and therefrom will automatically be maintained above the dew point of the conditioned air fed to the floors or rooms, whereby the need for drains and insulation is entirely eliminated.

This invention has for a further object an air conditioning and ventilating system in which air is supplied to a plurality of separate points of use in a building under a pressure sufiicient to insure a desired amount of air passing from said points of use to the atmosphere and to prevent infiltration of air from the atmosphere; the volume of air supplied to said points of use being varied as the resistance to flow from said points of use varies because of external weather conditions, so that a minimum pressure is employed to obtain the desired passage of air to the atmosphere and to prevent the undesired infiltration from the atmosphere.

This invention also has for an object a ventilating and air conditioning unit in which the air to be-conditioned is reduced to a temperature approaching the dehumidification temperature before it is passed through the dehumidifying element of the unit and is heated to a temperature approaching that desired at the point of use after being dehumidified, the cooling and heating being carried out in such a manner that a. portion of the heat abstracted is given back to the air after it is dehumidified. The other portion of the heat abstracted from the air is removed by a medium'which is subsequently used to cool the compressed refrigerant, and the other portion of the heat given to the air after dehumidification is supplied by the condensed partly cooled refrigerant so that in carrying is cooled to a temperature approaching the dehumidification temperature.

The particular nature of the invention, as well as other objects and advantages thereof, will appear most clearly from a description of preferred embodiments thereof, as shown in the drawings,

wherein v v Figure 1 is a section view, taken on line l-l of Figure 2, of a building in which an embodiment of the air conditioning and ventilating system of the invention, shown ina diagrammatic manner, is installed, 7

Figure 2 is a sectional plan view of a floor of the building taken on line 2-2 of Figure 3,

. Figure 3 is a section elevation of a corridor of the building taken on line 3-3 of Figure 2,

Figure 4 is a view similar to Figure. 3 showing certain arrangements used to control the air flow, Figure 5 is a diagrammatic view of another preferred embodiment of the air conditioning unit of my invention,

Figure 6 is a front view of the automatic pressure operated air flow control device of my invention,

The building I is typical of the buildings to which the air conditioning and ventilating system of this invention is best adapted. Building l3 includes floors ll whose floor. space is unobstructed by partitions and the like, and floors l2, one only being shown, which are divided by partitions l3 into a plurality of rooms I, and a main corridor l5. Doors l6 serve to communicate corridor I with rooms I. Building I0 is also provided with windows I1 and outside doors,

not shown. Windows I! may be of any construction but must allow suflicient air leakage through them in the closed position for the purpose explained hereinafter.

The air is conditioned. in an air conditioning unit l8, located in the basement of building I0, and is forced under pressure byblower l9 through an air duct 20 located in'one of the walls 2| of building Ill to outlets 22, located adjacent the ceiling of each floor. The use of a separate duct '20 to lead the conditioned air to the floors II and I2 is optional, as the air can be led if desired to floors II' and I2 through any convenient vertical shaft, such as an elevator shaft, a piping shaft, a stair case, etc.

In floors II, the air passes through openings 22 directly to the space to be ventilated, but in floors l2, it flows through the corridor l5 and from thence through openings 23 in partitions 13 to the rooms H. Openings 23 may occupy the positions of the usual transoms. If desired;

openings 23 may be omitted and the conditioned air passed from corridors iii to rooms I through the crannies and cracks in and around the doors I6 and their jams. In any event, the air conditioned in unit l3 flows under pressure from duct 20, through corridors l5 and'from thence to rooms l4. Thepressure under which the conditioned air is maintained by blower l9 should 2,112,52Q the occupants, or for the purpose to which the windows, as the relative size of the crack'around the partition door referred to the crack around a weather stripped window is of the order of magnitude of 5 to 1.

With thesystem so far described, if one of I windows I1 is opened, the floor I] or the room I4 whichcommunicates to the atmosphere through the particular window I! will have its pressure reduced to zero. ferential between the floor II or room l4 mentioned and the unit I8 will be greater than the differential between any other part of the building and unit l8 with the result that the greater volume of the air conditioned in unit I will tend to flow to the floor II or room l4 mentioned and the rest of the floor and rooms of the building will get less than their predetermined amount of conditioned air. To prevent such an undesirable occurrence, each of the

openings

22 and 23 is provided with a pressure operated device 24, best shown in Figures 6, '7, and 8, which automatically prevents the undesired flow of air above mentioned when any part of the building is put in direct communication with the atmosphere.

Pressure operated device 24 includes a rectangular metallic frame 25 of a size to snugly flt into the intended one of

openings

22 or 23. To the vertical sides of frame 25 are fastened bushings 26 in which are journalled the ends of rods 21. Each of rods 21 has fixed thereto a bent sheet metal member 28 of sufiicient length to overlap the next lower member 28 when device 24 is in the closed position. The corners of the high pressure side of all but the bottom one of members 28 are cut away so as not to interfere with bushings 26 when device 24 is closed. The lower end of the low pressure side of each of members 28 is cut away at regular intervals to provide tabs upon which may be placed the proper amount of slotted weight bars 29, one only being shown, which are held in place by cotter pins 30, or similar means. The amount of bars 29 used must be suflicient to maintain the members 28 in the position shown in Figure 7, when the predetermined pressure diflerential exists between the high and low pressure sides of device 24, in other words, during normal air flow therethrough. Device 24 is so constructed that when in the closed position, it does not completely prevent the passage of air therethrough.

If for any reason the pressure at the low pressure side of device 24 should be reduced below the predetermined value, the torque exerted by the static pressure on the high pressure side of members 28 will no longer be balanced by torque exerted by the static pressure on the low pressure side and weight bars 29 with the result that members 28 will rotate in a counterclockwise direction to the closed position to thereby reduce the flow of air therethrough. This closing movement is accelerated by the pressure of flow developed by the initial high velocity flow of the air through device 24. When communication to the atmosphere is again out on, the leakage of air through device 24 will rapidly bring the floor corridor l5, or room I 4 back to its predetermined pressure. Thus the pressure difierential will diminish and the torque exerted by the static pressure on the low pressure side and by weight bars 29 increase to the point where it will be suiiicient to rotate members 28 in a clockwise Thus the pressure difdirection to carry them back to their normal position. By the provision of devices 24 in

openings

22 and 23, it is impossible for the-system to be disorganized by reason of the opening of windows, doors, etc. f

Rooms l4 and floors II are each provided with combined heat exchange and ventilating units 3|. For purposes of illustration, one unit 3! .is shown in each of rooms l4 and two units 3| in each of floors ll. Each of units 3| is supplied with heat exchange fluid by pipe 32, which is" connected through pipe 33 to the heat exchange .fluid supply line 34. The heat exchange fluid,

after passing through unit 3| is returned to the heat exchange fluid return line 35 by pipes 36'- -unit, is a heat exchanger 43 which comprises a coil of finned tubes through which the heat exchange medium is adapted to pass. The inlet end of heat exchanger 43 is connected to pipe 32 and the outlet end is connected to pipe 36. In the inlet of exchanger 43 is provided a valve 44 for regulating the amount of heat exchange medium passed through exchanger 43. This valve 44 is controlled by a diaphragm 45 which is connected through'capillary tube 46 to a settable thermostat 41. A thermostat 41 is conveniently located in each of floors II and rooms [4.

The fans 42 takein air from the bottom or floors II or rooms l4 through aperture 39 and pass it through heat exchanger 43 to modify its temperature and then pass it back into the upper part of floor H or room I4, through aperture 48. By setting each of thermostats 41 to the temperature desired, the heat exchange fluid passed through each of exchangers 43' will be controlled to bring and maintain the whole body of air in each of the floors H and rooms l4 to the desired temperatures. Units 3| cause a continuous circulation and mixing of the air in each of floors II and" rooms l4 so that the air in each of floors II and rooms I4 is substantially homogeneous both as to moisture content and temperature.

A settable thermostat 48 is soldered or otherwise substantially made a part of the surface of the coil of heat exchanger and is connected to capillary tube 49 for purposes set forth hereinphere, and a separate circulation in each of rooms l4 and floors ll due to the units 3|.

In order to provide means for controlling the amount of conditioned air supplied to each of the floors II and I2, the frame 250i each of devices 24 located in conduit 20 is extended to house a damper 50 of the usual construction, as shown in Figs. 4 and 11. On the top of each of the extensions of frame 25 is mounted a motor 5| which, through mechanism of known character, not shown, is adapted to change the setting of damper 5|]. Motor 5|, at first floor H, is connected by a cable 52 to a control device 53; motor 5|, at the second floor I I, is connected by a cable 54 to a control device 55; and motor 5| at the third fioor I2 is connected by a cable 55 to a control device 51. Control devices 53, 55, and 51 are located in the basement of building "I, so as to be within easy reach of the operator of unit l8.

Cables

52, 54, and 55 are not intended to represent a single wire but the usual number of wires used to control motors at a remote point. By operating control devices 53, 55,, and 51, the settings of each of the dampers 51 maybe altered at will to allow a greater or lesser volume of air to pass to each of floors II and I2.

By reason of dampers 5|, it is possible to change the resistance ofiered to the flow of conditioned air into the floors II and I2 so that a predetermined amount of air may be passed through the floors into the atmosphere and infiltration prevented in spite of change of resistance to the flow of air to the atmosphere. Thus, if the resistance to'the flow of the air from the rooms l4 or floors I to the atmosphere is increased or diminished, as for instance, due to wind conditions outside of the building, all, or the necessary ones, of dampers 5| may be moved to decrease or increase the resistance to the flow of conditioned air into any one or all of the floors II and I2.

In order to determine when a change of resistance to the fiow of air from floors 'II and rooms H to the atmosphere has taken place and the amount of the change, a U-manometer tube 58. having one end opening into the atmosphere, is provided in the basement of the building. The other end of U-tube 58 is connected to a header 59 to which are connected tubes 50, 5|, and 52. A valve is provided in each of tubes 50, 5|, and 52. Tube 50 opens on the first floor tube 5|,

- on the second fioor II; and tube 52 opens on the third floor l2. Thus, byopening the appropriate valve, the pressure difierence between the atmosphere and any of the floors II and I2 may be observed by the operator of unit l8 and he may then adjust dampers 5| as required to maintain the required flow through the floors II and I2.

If, after the system is installed and adjusted, it is desired to put a floor II or |2 to a new use which requires a greater or lesser amount of conditioned air than the previous use, the damper 5| controlling that floor II or I2 is set to offer the proper resistance to the flow of conditioned air and the weights 29 of the device 24 which controls the conditioned air supplied the particular floor II or 2, changed as made necessary by the new pressure difierential. Thus the system is flexible and the amount of air supplied to any floor H or I2 may be altered at will.

Dampers 5| may, if desired, be provided on the low pressure side of the devices 24 which control the passage of the conditioned air into the rooms H to secure a further regulation and control of the amount of conditioned air supplied to each of rooms |4.

Unit |8 comprises a shell 53 in which is housed

heat exchangers

54, 55, 55, and 51, dehumidifier 58, separator 59, and humidifier 15. Each of the

heat exchangers

54,55, 55, and 51 and dehumidifier 58 is made up of a plurality of banks of tubes, three being shown. One end of the tubes of each bank is fastened in an inlet header and the other end of the tubes of each bank is fastened in an outlet header. Theoutlet header of the first bank is connected to the inlet header of the second bank and the outlet header of the second bank is connected to the inlet header of third bank. By this arrangement, the fluid passed to the inlet header of the first bank flows through the tubes of the first bank to the outlet header of the first bank, then to the inlet header of the second bank, through the tubes of the second bank to the outlet header or the second bank,

' and then to the inlet header of the third bank,

through the tubes of the third bank to the outlet header of the third bank. The separator 59 may be made up of a plurality of bent or corrugated spaced plates, as is well known in the art. The humidifier 15 comprises a water spraying means such as a. spray nozzle or a bank of spray nozzles.

being compressed in compressor 14, flows through pipe 15 to the bottom or condenser 15; from the topof condenser 15, it flows through pipe 11 to the inlet of heat exchanger 51. 1 From the outlet of heat exchanger 51, it flows through pipe 18 and expansion valve 19 to a heat exchanger 85, in which it abstracts heat from the heat exchange fluid returning from units 3| through line 35. From heat exchanger 85, the expanded refrigerant passes through pipe 8| to the compressor 14. The heat exchange fluid, after being cooled in heat exchanger 85, passes through piping 82 and pump 83 to dehumidifier 58. From dehumidifier 58, the heat exchange fluid passes to line34.

Heat exchanger 54 has its inlet header connected by pipe 84 to the city water mains or other source of cooling water supply, and its outlet header, which is adjacent air inlet 1|, connected through pipe 85, to the sprayer 85, which passes cooling water over the coils of condenser 15. A pan 81 collects the water falling from condenser 15 and pipe 89 leads it to the sewer or other point of disposal.

Heat exchanger 55 has its outlet header disposed adiacent the inlet header of heat exchanger 54. A pipe 89 connects the outlet header of heat exchanger 55 to the inlet of a pump 90. The outlet of pump 90 is connected through pipe 9| to the inlet header of heat exchanger 55, the outlet header 01' which is adjacent the separator 59,- and is connected through pipe 92 to the inlet header of heat exchanger 55. By this arrangement, a closed path for the circulation of a heat exchange fluid such as water or the like is provided for purposes to be explained hereinafter.

I The humidifier 10 is connected by a. valved line 93 to a water supply. This water may come directly from the city mains or, for winter use, may be heated. Steam condensate from the heating system is preferably used for supplying the energy of humidification. A pipe 94 leads the water separated at separator 59 to the sewer or other point of disposal.

The air entering inlet 1| first comes into contact with the tubes of heat exchanger 54 and gives up heat thereto; by reason of this counter-current exchange of heat, the air is cooled to substantially the temperature of the water supplied to heat exchanger 54, and the water heated to substantially the temperature of the incoming air. The air then comes into contact with the tubes of heat exchanger'55, and gives up heat thereto; 7

leaving the dehumidifier 68 is above the latter tem- I by reason of this counter-current exchange of heat, the air is further cooled to a temperature mentioned hereinafter and the water flowing through heat exchanger 65 heated to a temperature in the neighborhood of the temperature of the water supplied to heat exchanger 64. The air then passes through dehumidifier 68 and separator 69, wherein it is brought tothe desired dew point and the excess moisture removed. The finally cooled and dehumidified air then passes through heat exchanger 66 wherein it is heated to a temperature in the neighborhood of the temperatureof thewater supplied to heat exchanger 64 and the water cooled to a temperature in the neighborhood of the dew point of the dehumidifled air. Since this heat exchange medium passes through pipe 92 to heat exchanger 65, the temperature of the air leaving heat exchanger 65 is also in the neighborhood of the dew point of the conditioned air.

Since the compressed refrigerant is cooled in condenser 15 by the water leaving heat exchanger 64, it reaches heat exchanger 61 at about the temperature of the atmospheric air in extreme weather and considerably above it in mild weather. The partly heated dehumidifled air, in passing through heat exchanger 61, is heatedto a temperature in the neighborhood of atmospheric air and the condensed refrigerant is cooled to a temperature in the neighborhood of the temperature of the water supplied to heat exchanger 64.

From this, it should be obvious that the heat 'andcooling of the air, and the heat exchange mediums may be varied within considerable limits.

Thus, for example, by reducing the amount of water circulated through

heat exchangers

65 and 66, the air, when it reaches heat exchanger 61, may be of a sufficiently low temperature to cool the compressed refrigerant flowing therethrough to within a few degrees of the dew point of the conditioned air.

The capillary tube 49 previously mentioned is connected to a diaphragm 94 that controls a settable thermostat 95. A branched capillary tube 96 connects thermostat 95 to a diaphragm 91 that controls expansion valve 19 and to a diaphragm,

, not shown, in motor control device 9 8 that conrangement, thermostat 48 is called the master trols the motor of compressor 14. In this arthermostat and thermostat 95 is called the submaster thermostat. The function of thermostat 48 is to control the setting of thermostat 95 and the function of thermostat 95 is to control, through diaphragm 91 and motor control device 98, the expansion and the compression of the re-j frigerant. .The thermostat 48, chosen as the master thermostat, is the one located in the floor 'II or room- M which is to be kept at the lowest temperature. desired temperature, for instance, 60 F. and will operate through capillary tube 49 and diaphragm 94 to set thermostat 95 to a temperature somewhat below this, for instance, 55 F. If the air This thermostat 48 is set at the perature, diaphragm 91, through capillary tube 96, will increase the opening-of expansion valve 19 to lower the temperature of the refrigerant and consequently the temperature of the water leaving heat exchanger and motor control device will increase the speed of the motor of compressor 14. If the air leaving dehumidifier 68 is below 55 F.,'

. then thermostat 95 is effective to cause a decrease the arrangement just mentioned is used or not,

the temperature of the water circulated through line 34 and units 3| is always at a temperature somewhat above the dew point of the air and for that reason there is no necessity of insulating line 34.

In the system just described, the air is cooled to a temperature in the vicinity of the dehumidification temperature before it is passed through the dehumidifier so that the amount of work donein the dehumidifier is reduced to a minimum and the size of the refrigeration plant necessary to do the work is also kept to a minimum, This system makes it possible to bring the refrigerant to a temperature in the vicinity of the desired dew point before expanding it; thereby further reducing the amount of refrigerant necessary to do the required cooling. The system further makes it possible, in the summer time, to heat the air to a usable temperature without addition of outside heat to the system, considering the refrigeration plant as part of the system. Also, with this system, heat exchange fluid is supplied to units 3| at a temperature which renders it impossible for the units to be brought belowthe dew point of the conditioned air, thus eliminating the necessity of drains for units and insulation for

lines

34 and 35.

The system, as described, is intended primarily for summer operation; 1. e., operating under conditions which render it desirable to both dehumidify and cool the air. However, the system is also adapted for winter operation; i. e., operation under conditions which render it desirable to humidify and heat the air.

For operating under winter conditions, refrigeration plant I3 is not operated, water is not supplied to heat exchanger 64, and pump does not circulate water through

heat exchangers

65 and 66. On the other hand, the valve in pipe 93 is opened to supply water to the spray nozzles of humidifier 10; the valve in steam line 99 which connects to injector I00 is opened and the valve in line IOI is connected, in a manner not shown, to a float operated valve control mechanism, located in heat exchanger 80, not shown, to maintain the amount of heated water circulated through the system constant.

With the system so arranged, the air entering inlet H is heated by passing through dehumidifier 68, now used as a heater, and picks up the desired moisture by passing through the humidifier 10.

Thus heated and humidified, the air is forced by blower, is through duct 20, in the manner preseparator.

viously set forth, to rooms I4 and floors I I. The heated water, after passing through dehumidifier 68, enters the supply line 34 and passes to units 3I where it is used to heat the air in rooms I4 and floors II to a temperature desired by the occupants. The water is then returned to return line 35 and again heated at heat exchanger 80 that it may repeat the cycle just set forth.

If desired, the system may be modified to circulate the refrigerant instead of water through dehumidifier 68, line 34, unit 3|, and line 35 to thus further increase the efiiciency of the system and: reduce its initial cost. With the system thus modified, referring to Figure 5, pipe 18 is made to connect the outlet header of heat exchanger 61 with the inlet header of dehumidifier 68; expansion valve 19 is located in pipe 18 adjacent the inlet header of dehumidifier 68, and line 35 is connected to the intake of compressor 14. The condensed refrigerant will then pass from heat exchanger 61 through pipe 18 and be expanded in passing through valve 18. From valve 18, the expanded refrigerant will pass through dehumidifier 68, line 34, unit 3|, and back to compressor 14, through line 36. Except for the particulars just noted, the modified system will operate in the same manner as the system previously described.

For winter operation, still referring to Figure 5, water is not passed through pipe 84, the refrigerant plant 13-and pump 80 are not operated and valves I02 and I03, in pipe 18 and line 35 respectively are closed. However, the valve in line 83 is opened to supply water to dehumidifier 90 and valves I04 and I05 are opened to place the water heating unit I06 in communication with pipe 18 and line 35. Water heating unit I06 includes a hot water tank I01, a steam injector I08 to which steam is supplied by valved pipe I08, a valved overflow pipe IIII, a pipe III for connecting line 35 with tank I01, a pump II2 which passes the heated water from tank I01 through pipe II3 to pipe 16, and float actuated device, not shown,

for controlling in line IIO.

With the system so arranged, pump II2 passes heated water from tank I01 through pipes II 3 and 18 to dehumidifier 68, which is now used as an air heater. From dehumidifier 68, the heated water passes through line 34 to units 3I and from units 3| back to hot water tank I01, through line 35 and pipe I I I. The air entering inlet H is heated the desired amount in passing through dehumidifier 68 and picks up the required moisture in passing through humidifier 10, the excess water being removed as the air passes through The thus heated and humidified air is then passed by blower I8 through conduit 20 to fioors II and I2, corridors I5 and rooms I4, where it is further heated as desired by units 3I.

When an ample supply of sufilciently cold water is available the system of the invention may bemodified to use such water as the heat exchange medium passed through units 3 I. When the system is so modified, the outlet header of dehumidifier 68 of Figure 1 is connected to the water inlet of heat exchanger 80 and the outlet header of dehumidifier 68 of figure 5 is connected to the intake of compressor 14-. Line 34 of both Figures 1 and 2 is connected to the water supply line 98 and the return line 35 also of both Figures 1 and 2 is connected to pipe 84 or led to the sewer or other place of disposal. The construction and operation of the system is otherwise unchanged, with the exception that units 3| are modified as shown in Figure 10.

The modified units 3i are provided with a second valve H4 in the inlet of exchanger 43. This valve is operated by a diaphragm H5 which is connected to settable thermostat 48 by a branch 7 of capillary tube 49.

With the system thus modified, the air is conditioned in unit I8 and is supplied to floors II and I2 and rooms I4 as before described. Thermostats 41 in each of floors II and rooms I4 are also, as previously, set to maintain the temperature desired in each of said floors II and rooms I4 and diaphragms 46 and valves 44 also function as previously described to maintain such desired temperatures. However, with the modified system, each of thermostats 48 must be set at a temperature corresponding to or above the dew point of the air. Thus set, thermostats 48, through capillary tubes 49, and diaphragms II5, will so control the amount of water passing valves I I4 that the temperature of the tubes and fins of heat exchanger 43 will always be maintained at a temperature above the dew point of the air conditions in unit I8. The master and sub-master thermostatic control of the dew point of the air conditioned from a selected one of the fioors II departure from its principle as defined in the appended claims.

I claim 2 1. In a building having a plurality of rooms, a

ventilating system comprising a main air conditioning unit, means for conducting conditioned air from said unit to each of said rooms, said air conducting means including a fan for maintaining a predetermined air pressure in the said rooms sufiicient to prevent infiltration of atmospheric air and to permit a desired amount of air to filter out of each room to the atmosphere, and pressure operated means operable upon a substantial reduction of pressure in any one of said rooms to cut off the normal supply of air to the one or ones of said rooms in which the substantial reduction of pressure has taken place.

2. In a ventilating system, an air conditioning unit, a place of use for the conditioned air, means for passing conditioned air from said unit to said place of use and from said place of use to the atmosphere, and means for maintaining a substantially constant pressure dierential between said place and the atmosphere while maintaining the pressure at said unit substantially constant, said last-mentioned means comprising a pivoted member having spaced depending surfaces of such extent as to close the passage for conditioned air to the place of use upon rotation in either direction from the normal open position of said pivoted member.

3. In a ventilating system, the combinationof an air conditioning unit, a plurality of places of use for the conditioned air, each of said places of use having conditioned air inlets and means of fixed resistance allowing passage of air to the atmosphere, means for passing conditioned air from said unit to each of said conditioned air inlets, adjustable dampers in each of said air inlets for regulating the resistance offered by each of said air inlets to the flow of air therethrough, said dampers embodying movable pressure-responsive flow-controlling members whereby predetermined pressure difierentials are'maintained conditioning unit between said places of use and the atmosphere in spite of changing atmospheric conditions.

4. In a ventilating system, an air conditioning unit, means for conducting conditioned air from said unit to a place of use, means allowing a predetermined volume of air to pass from said place of use to the atmosphere at a predetermined pressure diiferential between said place of use and the atmosphere, and pressure-operated means operative to prevent abnormal flow of air from said place of use to the atmosphere upon the opening of a window or other relatively large vent between said place of use and the atmosphere and'for varying the resistance to air flow of said air conducting means whereby the predetermined pressure differential between said place of use and the atmosphere may be maintained in spite of varying atmospheric conditions.

5. In a ventilating system the combination of an air conditioning unit, a plurality of places of use for the conditioned air, each of said places of use having a conditioned air inlet and means allowing passage of air to the atmosphere, means for conducting conditioned air under pressure from said unit to each of sa d inlets to establish a, normal flow of air to each of said places of use and from said places of use to the atmosphere, and adjustable pressure-operated damper means in each of said inlets operable to maintain normal flow through said inlets under varying atmospheric conditions and to prevent abnormally large flow of conditioned air to one of said places of use.

6. In a building having a plurality of rooms, a ventilating system comprising a main air conditioning unit, means for conductingconditioned air from said unit to each of said rooms, means for supplying positive volumes of air to each room under varying external atmospheric pressures adjacent the respective rooms, temperature modifying means in each of said rooms, means for supplying heat exchange medium to said temperature modifying means, means in each of said rooms affected by the temperature of the air therein efl'ective to control the supply of heat exchange medium to the temperature modifying means, and means afiected by the temperature of the temperature modifying means effective to further control the supply of heat exchange medium to the temperature modifying means to prevent the temperature of the temperature modifying means being brought below the dew point of the air in the room. t

7. In a building having a plurality of rooms, a, ventilating system comprising a main air conditioning unit, means for conducting conditioned air from said unit-to each of said rooms, a heat exchanger in each of said rooms comprising a plurality of connected tubes, means for supplying heat exchange med um to each of said heat exchangers and means for controlling the heat exchange fluid supplied to each of said heat exchangers whereby the temperature of the air in each room may be maintained as desired by the occupant of the room and the temperature of the heat exchanger in each room maintained above the dew point of the air, said supply control means including a thermostat affected by the temperature of the air and a thermostat affected by the temperature of the heat exchanger.

8. A ventilating system compris ng a main air including dehumidification means, means for conducting air from said unit to a point of use, temperature modifying means at said point of use, means for passing heat exchange medium through said dehumidiflcation means, means for passing heat exchange medium through said temperature modifying -means. means for supplying the heat exchange fluid issuing from said dehumidification means to said temperature modifying means and heat exchange means for preheating the air before it is conducted to the point of use by contact with the heat exchange fluid being supplied to the dehumidification means.

9. A ventilating system comprising a main air conditioning unit, means for conducting air from said un t to a point of use, means at said point of use for modifying the temperature of the air thereat, raid unit including a heat exchanger for the dehumidification of the air having a heat exchange medium inlet and heatv exchange medium outlet, said temperature modifying means including a heat exchanger having a heat exchange medium inlet and a heat exchange medium outlet, means for connecting the outlet of the heat exchanger at the unit with the inlet of heat exchanger to the temperature modifying device and heat exchange means for preheating the dehum dified air from said first mentioned heat exchanger by contact with the heat exchange medium supplied to said first mentioned heat exchangen.

10. In a building having a plurality of rooms, a ventilating system comprising an air condition ng unit, means for conducting conditioned air from said unit to each of said rooms, means for supplying positive volumes of air to each room under varying external atmospheric pressures adjacent the respective rooms, temperature modifying means in each of said rooms, means for maintain ng the temperature of said temperature modifying means above the dew point of the air in the room and means affected by the temperature of said temperature modifying means for controlling the conditioning of the air at said unit.

11. In an air conditioning and ventilating system, an air conditioning unit including a dehumidifying section and having associated therewith the expansion valve and compressor of a refrigeration plant, means for conducting conditioned air from said unit to a place of use, temperature modifying means at said place of use, means including settable means in said section affected by the temperature of the air leaving said section effective to control said valve and said compressor, and settable means affected by the temperature of said temperature modifying means effective to set said sett-able means in said section.

12. In an air conditioning and ventilating system, an air conditioning unit including a dehumidifying section and having associated therewith a refrigeration plant for supplying cooling medium to said section, means for conducting conditioned air from said unit to a place of use, temperature modifying means at said place of use, means including settable means in said section affected by the temperature of the air leaving said section effective to control the operation of said plant to vary the characteristics of the cooling medium supplied to said section; and settable means affected by the temperature of said temperature modifying means effective to set said settable means in said section;

13. In an air conditioning and ventilating system, an air conditioning unit including a dehumidifying section having associated therewith the expansion valve and compressor of a refrigeration plant, a settable thermostat in said section aifected by the temperature of the air le'aving said section, means operated from said thermostat for controlling said expansion valve, means operated from said thermostat for controlling the operation of said compressor, means for conducting air from said unit to a place of use, a temperature modifying means at said place of use, a settable thermostat at said temperature modifying means adapted to be affected by the temperature of said temperature modifying means, and means at said section operated from said second thermostat for setting said first thermostat.

14. In an air conditioning and ventilating system, an air conditioning unit including a dehumidifying section and having associated therewith a refrigerating plant for supplying cooling medium to said section, a settable thermostat in said section afiected by the temperature of the air leaving said section, means operated from said thermostat for controlling the operation of said refrigerating plant to vary the characteristics of the fluid supplied to said section, means for conducting air from said unit to a place of use, a temperature modifying means at said place of use including a coil having a valved inlet and an outlet for heat exchange medium, a settable thermostat fixed to said cooling coil to be affected by the temperature of said coil, means operated from said second thermostat for controlling said valved inletand means also operated from said second thermostat for setting said first thermostat.

15. In a building having a plurality of rooms, a ventilating system comprising a main airconditioning unit, means for conducting conditioned air from said unit to each of a plurality of said rooms, means for causing circulation of conditioned air through said air conducting means to the rooms at a pressure sufficient to prevent infiltration of outside air to any of the rooms under ordinary conditions, and means for independently controlling the supply of conditioned air to each of said plurality of rooms and responsive to the reduction of pressure caused by opening a window in one of the rooms to cut oil? the supply of conditioned air thereto.

16. In a building having separate rooms, a ventilating system comprising a main air-conditioning unit, means for forcing conditioned air from said unit to each of a plurality of said rooms under pressure suflicient to prevent infiltration of outside air to anyof the rooms under ordinary conditions and pressure-responsive flow-controlling means for regulating the flow of conditioned air to each of said plurality of rooms, said fiowcontrolling means being responsive to the pressures in each of said plurality of rooms and the pressure of the conditioned air to insure the desired supply of air to each of said plurality of rooms irrespective oi variations in the external atmospheric air pressures on said rooms.

17. In a building having separate rooms provided with vent openings to the atmosphere of a size to permit limited exfiltration of air from each room to the atmosphere under normal pressure conditions in the rooms, a ventilating system comprising a main air-conditioning unit, means for forcing conditioned air from said unit to each of a plurality of said rooms at a pressure sufiicient to produce exfiltration of room air to the atmosphere under ordinary conditions, and pressureresponsive means for controlling the flow of air from said air conditioning unit to'each of said plurality of rooms, said pressure-responsive means being affected by the pressures of the air in said plurality of rooms and the pressure of the conditioned air supplied by said unit.

18. In an air conditioning system provided with an air supply duct connected to a space to be ventilated, air conditioning means to condition the air supplied through said duct to said space, regulating means for said air conditioning means responsive to the condition of the air in the system and means controlled by the pressure of the air in said supply duct and in the space to be ventilated for varying the amount of air supplied through said duct to the ventilated space.

19. In a building having a plurality of rooms, a ventilating system comprising an air conditioning unit, means for conducting conditioned air from said unit to each of said rooms, air cooling means in each of said rooms for bringing and maintaining the air to the temperature desired by the occupant, and means afiected by the temperature of the air cooling means in the room to be maintained at the lowest temperature for controlling said air conditioning unit to maintain the dew point of the air conditioned in said unit below the temperature of the air cooling means of said room, and means for controlling said air cooling means in each room in accordance with the temperature required therein.

20. An air conditioning system for an enclosure with two streams of air intermingling within the enclosure including, means for introducing one of said streams of air into the enclosure, means for effecting the second stream of air within the enclosure, one of said streams having temperature regulating means and the other having humidity varying means, a thermo-responsive device controlling both the tempering and humidity varying means, and a thermostat for controlling the temperature regulating means for maintaining the required temperature in the enclosure.

21. An air conditioning system for an enclosure including means for introducing a stream offresh air into the enclosure to maintain a substantially constant diflerential pressure within the enclosure above the pressure outside thereof to produce an exfiltration of air therefrom, means within the enclosure to produce a second stream of air to circulate therein and commingle with said first stream of fresh air, means for conditioning one of said streams of air to impart the desired humidity thereto, means for supplying tempering means to both streams of air, temperature responsive devices in the enclosure for controlling said humidity conditioning means and tempering means, and a thermostat operable to regulate the temperature in the enclosure, whereby the required ventilation, humidity and temperature are maintained in the enclosure.

22. In an air conditioning system for an enclosure, an air conditioning unit with means for passing air therethrough to the enclosure, a heat exchange member in the conditioning unit, a heat exchange member in the enclosure, and means for circulating a heat exchange medium first through the heat exchange member in the conditioning unit thereby modulating the temperature thereof and then through the heat exchange member in the enclosure.

23. In an air conditioning system for an enclosure, an air conditioning unit with means for passing air therethrough to the enclosure, a heat exchange member in the conditioning unit, a heat exchange member in the enclosure, means for circulating a heat exchange medium first through the heat exchange member in the conditioning unit thereby modulating the temperature thereof and then through the heat exchange member in the enclosure, and a thermostat associated with the heat exchange member in the enclosure controlling the temperature of the heat exchange medium circulated through said heat exchange members.

24. In a building having a plurality of rooms, an air conditioning system including a main air conditioning unit with means for conditioning the air to a required humidity value and passing air therethrough to each room, air cooling means in each of said rooms, and means interconnected with the air conditioning unit and a room air cooling means for maintaining the temperature of said air cooling means in each room above the dew point of the air introduced into the rooms.

25. An air conditioning system including a conditioning unit in which air is conditioned with respect to its humidity, a second-unit in which air is conditioned with respect to its temperature, and interconnected regulating means operable on the humidity conditioning means to condition the air to a predetermined absolute humidity-value and to maintain the temperature of the temperature conditioning unit above the dew point temperature of the air passing through the humidity conditioning unit.-

26. An air conditioning system for an enclosure 1 comprising a conditioning unit throughwhich air is passed for modifying one of its conditions on its way to the enclosure, a second conditioning unit associated with the enclosure modifying its other condition, means in one of the conditioning units for conditioning the air to an absolute humidity value, means in the other conditioning unit for conditioning the air to the required temperatuie, and interconnected regulating means between the two units to regulate the tempering means in accordance with the dew point temperature of the air conditioned to said absolute humidity value to maintain the temperatureof the temperature conditioning unit above said dew point temperature.

27. An air conditioning system for an enclosure comprising a conditioning unit through which air is passed for modiiying'one of its conditions on its way to the enclosure, a second conditioning unit associated with the enclosure modifying its other condition, means 'in one of the conditioning units for conditioning the air to an absolute humidity value, means in the other conditioning unit for conditioning the air to the required temperature, and interconnected regulating means between the two units to regulate the humidity varying means to reduce the dew point temperature of the air to a temperature below the temperature of the temperature conditioning unit.

28. In a building having a plurality of rooms each provided with an air inlet, a ventilating system ,including means for circulating air under pressure to said inlets, and an automatic flowcontrolling device in the inlet to each room for admitting predetermined quantities of air from said unit to each of said rooms to maintain air pressure therein above the atmospheric pressure outside of the building but operable to restrict the flow of air upon a reduction of pressure on either side of the inlet.

29. In a building having a plurality of rooms each provided with an air inlet, a ventilating system including means for circulating air under pressure to said inlets, and an automatic flowcontrolling device in the inlet to each room for admitting predetermined quantities 01' air from said unit to each of said rooms to maintain air pressure therein above the atmospheric pressure outside of the building but operable to restrict the flow of air through the inlet to a room upon a reduction oif'pressure in the room.

ROBERT B. P. CRAWFORD.