US2266202A - Air conditioning system - Google Patents

Description

' c. E. HEINKEL AIR CONDITIONING SYSTEM Dec. 16, 1941.

Filed June 5, 1940 AIR SUPPLY djharles E. H

MW M eirLke l Giiomg Patented Dec. 16, 1941 AIR CONDITIONING SYSTEM Charles E. Heinkel, Portland, reg., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application June 5, 1940, Serial N0. 338,937

14 Claims.

This invention relates to heating and air conditioning systems wherein fresh air from outdoors is passed over a steam heating coil or other heating medium. When the supply of steam or other heating substance to such a coil is modulated, condensate or other partially cooled media may collect in the coil, and when the temperature of the outdoor air is below 32 the condensate or other media may freeze and fill up the coil with ice causing it to crack. This is apt to happen when the supply of steam or media has been modulated down to a small amount insufficient to keep all parts ofthe coil above freezing. If the supply of steam or other media is controlled in an on and off manner there will be.

suflicient steam or media in the coil when there is condensate or other cooled media present to prevent it from freezing.

An object of the invention is to control a heating coil or other heating medium in a system of the type above described in a manner to prevent freezing of condensate or other cooled heating media therein.

Another object is to prevent freezing of condensate or partially cooled heating media in a steam heating coil or other heating medium the supply of media to which is ordinarily modulated, by controlling the supply of media in an on and off manner when the temperature of the air to be heated is below freezing.

Another object is to provide freeze-up protection in a heating system wherein outdoor air is heated by a steam coil or other heating medium to which the supply of media is normally modulated by controlling the media supply in an on and off manner when the temperature of the outdoor air is substantially freezing.

Another object is to provide a heating system having means for passing outdoor air over a steam coil or other heating medium wherein the supply of media is normally modulated by a thermostat and is controlled in an on and oil manner when the temperature of the air passing through the coil or heating medium is low enough so that there is danger of freezing'condensate or partially cooled media in the coil.

For a more complete understanding of my invention and knowledge of its advantages reference may be had to the following detailed description and. annexed drawing wherein,

Figure 1 represents diagrammatically a heat ing system employing a steam coil and having electrical controls therefor embodying my inven-;

tion.

Figure 2 represents diagrammatically a similar system employing pneumatic controls.

Referring to Figure 1 of the drawing a portion of an air conditioning system for a building is represented, the system being of the type wherein outdoor air is introduced into the building to.

be heated and a part of the heated air is recir culated after having been delivered to the spaces to be heated. Numeral III designates an air duct which communicates with the outdoor air and disposed in this air duct is a steam heating coil generally indicated at I I. The duct I0 communicates with the intake side of a motor driven fan I2, the discharge of the fan being connected to a duct I3 which conveys heated air to the various spaces to be heated. Numeral I 4 designates a duct for recirculating air which communicates with the duct I0 to the left of the steam coil II so that a mixture of fresh and recirculated air is passed over the steam coil.

The supply of steam to the coil I I is controlled by a steam valve I'5 which is of the type which may be modulatingly adjusted to various posi- .tions.

proportioning type of control system, this type of control system being well known in the art and being disclosed and described in detail in the patent to D. G, Taylor No. 2,028,110 to which reference is had. The proportioning system includesa proportioning motor I6 which operates the valve I5 and a proportioning type thermostat generally designated-at I'I. The thermostat I'I includes a bimetal element I8 arranged to actuate an arm which sweeps over a resistance as the temperature affecting the element I8 varies. As in the Taylor patent the proportioning motor I6 drives a rebalancing potentiometer generally designated at 2|, this potentiometer being illustrated diagrammatically as comprising an arm 22 on the shaft of the motor I6 which sweeps over a resistance 23 as the shaft of the motor is rotated. The endsof the resistance 20 of the potentiometer thermostat are connected to the proportioning motorby wires 25 and 28 and the element I8 of the thermostat is connected to the proportioning motor by wire 3|, the

connections between thethermostat and the mog tor corresponding to those of the Taylor patent.

Theends of the resistance 23"are connected to wires 25 and 28 by wires 33 and 35, respectively. Normally in proportioning control systems of the type disclosed, the slider of the rebalancing potentiometer is connected to the wire which leads from the thermostat to the proportioning motor. In my arrangement I have provided a The steam valve I5 is controlled by a switch whereby the slider of the rebalancing potentiometer may be disconnected so as to render it ineffective. Numeral 3'l designates generally a temperature responsive switch device which comprises a bellows element 33 connected to a tem- 5 perature responsive bulb 38 which is disposed in the path of fresh air being admitted to the conduit Ill. The bulb and bellows and connecting means are filled with a volatile liquid so that the bellows contracts and expands in response to temperature changes affecting the bulb, and the bellows actuates a pivoted switch arm 40 which carries a mercury switch 4!. Normally the mercury switch 4! is tilted so that the electrical circuit is completed but when the temperature.af-

fecting the bulb 33 drops to a predetermined minimum such as 32 F., the mercury switch 4i is tilted and the electrical circuit is broken. The slider 22 of the rebalancing potentiometer is connected to the mercury switch 4| by a wire 42 go and the mercury switch is connected to wire 3! by a wire 43 so that when. the mercury switch is tilted so that the electrical circuit is broken, the slider of the rebalancing potentiometer is disconnected and the rebalancing potentiometer has no effect on the proportioning system.

Numeral 43 designates generally an additional temperature responsive controller comprising a slider 48 arranged to sweep over a resistance 41,

the slider 46 having an integral arm 43 at right 9 angles thereto which cooperates with an expanslble and contractible bellows 48 which is adapted to move the slider 48 over the resistance 47. The J bellows 48 communicates with a bulb 50 by means of a tube. thebulb'liil being disposed in the path of air being discharged from the fan I2. The bellows and bulb are filled with a volatile liquid so as to cause the bellows to expand and contract in response to changes in temperature affecting the bulb 50. The ends of the resistance 41 are The slider 48 is connected to the 63 that when slider 48 is at the left end of resistance 80 41 the controller 43 causes no unbalancing of the circuit. Whenever the temperature affecting bulb drops below a predetermined minimum the bellows 49 is contracted sufficiently to cause the slider 48 to move to the right along resistance 41, the effect of this being to move the valve I! in opening direction as will presently be described. the controller 45 serving as a low limit controller to maintain the discharge air temperature above a predetermined minimum.

Normally the proportioning system so far de- I scribed operates in the manner of that disclosed in the Taylor patent. When the temperature is at the desired value in the space being heated the thermostat if has the arm or slider It at the mid point of resistance 20. If the temperature should fall the thermostat moves the slider It to the left along resistance 20. thus unbalancing the voltage drops existing between wires 23 and 3| and between wires 23 and ii. of slider It, to the left along resistance 20 causes the motor 13 to operate in a direction opening the valve I! to increase the supply of steam so as to cause the temperature to come back to nor- This movement mal, when the system has thus been unbalanced 76 by movement of the slider, consequent movement of the rebalancing potentiometer 2i rebalances the system as described in the Taylor patent for stopping the motor when the valve position corresponds to the position of slider i8 on resistance 20. If the slider IQ of the thermostat II moves to the right along resistance 20 the motor i3 is operated in the opposite direction to move valve It in closing direction.

As pointed out above whenever the temperature aflecting bulb 30 drops below a predetermined minimum the slider 48 is moved to the left along resistance 41, this movement having the same effect as movement of slider It to the left along resistance 20 inasmuch as it reduces the voltage drop between wires 23 and 3|. Thus whenever the temperature affecting bulb l0 falls below a predetermined minimum the motor it is operated in a direction to open valve It so as to increase the supply of steam irrespective of thermostat il whereby the air being delivered to the heated spaces never falls below a predetermined temperature.

In a system of the type which I have disclosed the temperature of the outdoor air being delivered through the conduit it may be low enough to freeze condensate before it reaches the outlet of the coil. Particularly at times when the steam valve It has been modulated to a nearly closed position such that only a very little steam is being admitted to the coil ii, the condensate is very apt to freeze because of the small amount of steam being admitted to the coil, the amount of steam being admitted being too small to keep all parts of the coil above freezing temperatures. In order to obviate this undesirable condition wherein the steam coil might become entirely filled with ice, in my arrangement whenever the temperature of the outdoor air passing bulb 39 falls below a predetermined minimum the electrical circuit at switch 4| is opened and the rebalancing potentiometer is rendered inoperative. Under these circumstances whenever the slider ll of thermostat i1 moves out of mid position the motor I8 is started in one direction or the other and inasmuch as the rebalancing potentiometer is now ineffective to rebalance the unbalanced condition produced by the thermostat I! the motor it will continue operating until the valve iii is fully opened or closed. It will be seen therefore that underlthese circumstances the thermo- I stat ll now controls the valve I! in an on and off manner. the valve either being fully opened or closed depending upon which side of the mid point of resistance 20 the slider l8 deviates to. Thus when the outdoor temperature is low enough to cause switch II to break the electrical circuit the steam coil ii is supplied with the maximum amount of steam or else the supply of steam is cut off entirely. Thus there is never a condition wherein there is only a very small amount of steambeing admitted to the coil such that condensate would freeze in the unfilled portion of the coil.

Those skilled in the art will appreciate from the foregoing description that I have provided a very simple means for providing what is called freeze-up protection for steam coils or other heating mediums and yet wherein the advantages of modulating control may be enjoyed under normal conditions when the temperature of the outdoor air is not too low.

Referring to Figure 2 I have disclosed the same heating system utilizing a similar manner of control but wherein the controls are of a pneu- I matic type rather than of an electrical type as in Figure 1, like numerals designating like parts in both figures. In Figure 2 the valve II5 controlling the supply of steam to the .coil I I is of a pneumatic type being adjustable to various positions depending upon the pressure in a bellows element I I6 which is connected to the stem of the valve.

valve I I5 is positioned temperature in duct I3. Thus the valve H5 is Numeral ll4'designates a pipe leading to a source of air supply which 'in this type of control system is normally at a pressure of lbs. per

sq. inch.

Numeral I 50 designates a pneumatic, thermostat of known type responsive to the temperature in discharge duct I3 of fan I2. this thermostat controllinga bleed port in the usual manner.

Numeral I designates a pressure operated three-way valve comprising a valve element I2I cooperable with oppositely disposed seats I22 and I23. Air may be communicated .to the valve chamber of the three-way valve I20 through pipes I 24 and I and air maybe discharged from the valve chamber through a pipe I26. The three-way valve has its stem connected to a pressure responsive element I 21 which is of a type which operates at a predetermined pressure to shift the three-way valve from one position to the other with a snap action. In the position of the three-way valve shown, the valve element I 2| is in engagement with the seat I22 whereby there is communication between the pipes I25 and I26. Whenever the pressure element I2! is subjected to a predetermined pressure the valve is operated to place the valve I2I in engagement with the seat I23 so as to provide communication with the pipes I24 and I26.

Numeral I39 designates a pneumatic type thermostat similar to the thermostat I 50 and responsive to the temperature of the outdoor air being admitted to the conduit I0. Numeral I28 designates a manually adjustable needle valve' and numeral I29 designates a pressure responsive valve controlling a bleed port I30, the valve being operable by a pressure element I3I. I3I is of a type which operates valve I20 to either close or open port I30 with a snap action.

Pressure at the supply value of 15 lbs. per sq. inch is communicated to the thermostat I39 through a pipe I32 and the thermostat I 39 controls its bleed port so as to bleed ofi a certain amount of air so as to reduce the pressure, and

air at the reduced pressure is communicated from the thermostat I39 to the pressure element I21 by the pipe I33. Similarly air at 15 lbs. pressure is communicated from pipe I I4 to the thermostat I50, pipes I34 and I35, and the thermostat I50 controls its bleed port whereby air is bled ofi at a given rate depending upon the temperature affecting the thermostat I50, and the air at reduced pressure is then communicated to the three-way valve by the pipes I36 and I25.

-Air at reduced pressure from the thermostat I50 is also communicated to the pressure element I3I through pipes I36 and I40.- Air from the supply pipe II4 is communicated through the pipe I34, pipe I4I, needle valve I28, pipe I42 and pipe I24 to the three-way valve I20.

When outside temperature is above 32 F'., the thermostat I39 causes the three-way valve I20 to be in the position shown. Under these circumstances the discharge duct thermostat I50 controls the pressure being communicated to the operator II 8 of valve II 5, the thermostat I50 governing this pressure in accordance with the temperature in the discharge duct whereby the Element bleed port same manner as in the previous embodiment.

admitted to the conduit I0 drops to a low value such might cause freezing of the condensate in the coil 'I I, the thermostat I30 will have adjusted its bleed port so that the to element I21 through pipe I33 will be such as to cause the three-way valve I20 to be operated to its opposite position placing pipe I24 in communication with pipe I26 andcuttingoiicommunication between pipes I25 and I26. Thermostat I50 will now obviously not be able to control directly the valve II5. Pressure will now be communicated from the source II4 through the needle valve I28 and pipes I42, I24 the threeway valve I20 and pipe I26 to the operator I I6 of the valve II5 so that the valve II5 will be adjusted its bleed port so as to lower the pressure in pipes I36 and I40 to such a value that the element I3I will be operated to move the valve I29 away from the bleedport I 3|. When the valve I20 is moved away from the bleed port I 3I the pressure in pipes I42 and I24 is of course immediately released and therefore inasmuch as there is then no appreciable pressure being communicated to the operator II6, the valve II5 will be moved back to open position. The thermostat I50 operates at a predetermined temperature to cause the valve I29 to either close the I 30 or fully open it. When the bleed port I30 is closed the full pressure of the air is moved away from the bleed port I30 the pressurein the pipes beyond the needle valve I28 is immediately released so that there is no pressure communicated to the operator II6 so that the valve II 5 is fully open. Thus in this manner when the three-way valve I 20 is in the opposite position to that in which it is shown in Figure 2 the thermostat I50 controls the valve H5 in an on-ofi manner or in other words, the valve H5 is either fully will be seen that the operation of the mechanism of Figure 2 is substantially the same as that of Figure 1 except that the discharge duct thermostat is in sole control of the valve I I5.

The two representative embodiments of my invention which I have disclosed are merely illustrative of forms which it may take and of types of control equipment which may be utilized for carrying out the invention. My invention is not to belimited by my disclosure but only by the appended claims.

I claim as my invention:

1. In a heating system fora building in combination, means comprising a heat exchanger, means for passing outdoor air in heat exchange relation with said heat exchanger, means for controlling the heating media supply and a thermostat for variably adjusting the heating media control means position, and means responsive to the temperature of air passing to the exchanger cooperating with said control means for modifying the action of said last means whereby said heating media control means is operated in an on-and-ofl manner when the temperature of the in accordance with the pressure communicated.

opened or fully closed. Thus it air passing to the heat exchanger is below freezinl- 2. In a system for heating outdoor air for use in a building, in combination, a heat exchanger, means for passing outdoor air over said heat exchanger to be heated thereby, valve means controlling the media supply. means responsive to the temperature of heated air for modulating the position of the valve means, and means responsive to the temperature of outdoor air cooperably associated with said modulating means whereby when the outdoor air temperature is below freezing said first mentioned temperature responsive means controls the valve in an on-and-ofi manner.

3. In a' system for heating outdoor air for use in a building, in combination, a heat exchange means, means for passing outdoor air over said heat exchanger to be heated thereby, valve means controlling the heating media supply, means responsive to the temperature of heated air for modulating the. position of the valve means, said modulating means being of a type readily adapted to being converted into a type which operates the valve means in an on-and-oi! manner, and means responsive to the temperature oi outdoor air cooperably associated with the modulating means for converting said modulating means whereby the valve means are operated in an on-and-oii manner when the temperature of the outdoor air is below freezing.

4. In a system for heating outdoor air for use in a building, in combination, a heat exchanger, means for passing outdoor air over the heat exchanger to be heated thereby, valve means controlling the heating media supply, means responsive to the temperature oi heated air for modulating the position oi. the valve means, means responsive to temperature of air discharged from said heat exchanger also controlling said valve means to maintain a minimum air temperature. and means responsive to the temperature of outdoor air cooperably associated with said modulating means whereby when the outdoor air temperature is below freezing said first mentioned temperature responsive means controls the valve means in an on-and-oii manner.

5. In a system for heating outdoor air for use in a building, in combination, a heat exchanger, means for passing outdoor air over the heat exchanger to be heated thereby, valve means controlling the heating medium supply means responsive to the temperature of heated air tor modulating the position of the valve means, said temperature responsive means being of the proportioning type including a potentiometer type thermostat and a rebalancing potentiometer, and means responsive to the temperature of outdoor air for disconnecting said rebalancing potentiometer when the outdoor air temperature is below freezing whereby said thermostat operates said valve means in an on-and-oi'i manner.

6. In a system for heating outdoor air for use in a building, in combination, a heat exchanger, means for passing outdoor air over the heat exchanger to be heated thereby, valve means controlling the heating medium supply, means responsive to the temperature of heated air for modulating the position of the valve means, said temperature responsive means being of the proportioning type including a potentiometer thermostat and a rebalancing potentiometer, means responsive to temperature of air discharged from said heat exchanger for maintaining a minimum air temperature, and means responsive to the 7. In a system for heating outdoor air for use v in a building, in combination, a heat exchanger,

means for passing outdoor air over the heat exchanger to be heated thereby, valve means controlling the heating medium supply. said valve means being of a pneumatically operable type adiustable to various positions means forming a source of air pressure supply for said valve means, a thermostat controlling a supply of air pressure to said valve means whereby the valve means is modulatingly adjusted in accordance with temperature, a pneumatic thermostat responsive to outdoor air temperature and control means whereby said first thermostat either admits pressure to said valve means or wholly interrupts it whereby said valve means is either fully open or closed, said control means being operable in response to said thermostat responsive to outdoor air temperature.

8. In a system for heating outdoor air for use in a building, in combination. a heat exchanger. means for passing outdoor air over the heat exchanger to be heated thereby, valve means controlling the heating medium supply, said valve means being or a pneumatically operable type adiustable to various positions, means forming a source of air pressure supply for said valve means. a thermostat controlling a supply of air pressure to said valve means whereby the valve means is modulatingly adjusted in accordance with temperature, means ior diverting the air supply for said valve means, means responsive to said thermostat for controlling the diverted air supply in an on-and-ofl manner so that the valve means are operated in an on and oil manner and means responsive to outdoor air temperature controlling the diverting means.

9. In a system tor heating outdoor air for use in a building, in combination, a heat exchanger, means for passing outdoor air over the heat exchanger to be heated thereby, valve means controlling the heating medium supply. said valve means being oi a pneumatically operable type adjustable to various positions, means forming a source oi air pressure supply for said valve means. means forming a first passage for communicating pressure to said valve means. a modulating type thermostat for controlling the prasure in said first passage, a second passage for communicating pressure to said valve mean-s, an on and oil device responsive to said thermostat controlling said second passage, and means responsive to outdoor temperature for selectively connecting said passages to said valve means.

10. In combination, a pneumatically driven device. a source or air pressure. a pipe for communicatingpressure for operating said device. a thermostat for modulatingly adjusting the pressure in said pipe. a second pipe for communicating pressure for operating said device. means responsive to said thermostat for controlling the pressure in said second pipe in an on and an all manner, and means whereby either pipe may be connected to said device.

11. In a heating system for a building. in combination. means comprising a heat exchanger, means for passing outdoor air in heat exchange relation with said heat exchanger. control means comprising a valve controlling the heating medium supply and a thermostat ior modulatingly adjusting the valve position, and means responsive to the temperature of air passing to the heat exchanger associated with said control means whereby the supply of heating medium is controlled in an on-and-off manner when the temperature of the air passing to the heat exchanger is below freezing.

12. In a heating system for a building, in combination, means comprising a heat exchanger, means for passing outdoor air in heat exchange relation with said heat exchanger, control means comprising a valve controlling the heating medium supply and a thermostat for modulatingly adjusting the valve position, and means responsive to the temperature of air passing to the heat exchanger associated with said control means whereby the supply of heating medium is controlled in an on-and-ofi manner when the temperature of the air passing to the heat exchanger is below freezing, said last named temperature responsive means comprising a control device and a temperature responsive device operatively connected to said control device in such a manner as to cause said control device to always assume one or two controlling positions.

13. In a heating system for a building, in combination, means comprising a heat exchanger. means for passing outdoor air in heat exchange relation with said heat exchanger,

the other of control means comprising a valve controlling the heating medium supply and a thermostat for modulatingly adjusting the valve position,

and means responsive to a temperature condition indicative of danger of freezing of con densate or partially cooled heating medium in the heat exchanger associated with said control means for causing said heating medium supply to be controlled in an on-and-ofi manner.

14. In a heating system for a building, in combination, means comprising a heat exchanger, means for passing outdoor air in heat exchange relation with said heat exchanger, control means comprising a valve controlling the heating medium supply and a thermostat for modulatingly adjusting the valve position, and means responsive to a temperature condition indicative of danger of freezing of condensateor partially cooled heating medium in the heat exchanger associated with said control means for causing said heating medium supply to be controlled in an on-and-ofi manner, said last named temperature responsive means comprising a control device and a temperature responsive device operatively connected to said control device in such a manner as to cause said control device to always assume one or the other of two controlling positions.

CHARLES E. HEINKEL.

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