US2154523A

US2154523A - Unit ventilator

Info

Publication number: US2154523A
Application number: US44899A
Authority: US
Inventors: Jr John T Midyette
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1935-10-14
Filing date: 1935-10-14
Publication date: 1939-04-18
Anticipated expiration: 1956-04-18

Description

April `18, 1939. J. T. MIDYETTE, JR

UNIT VENTILATOR Filed Oct. 14, 1935 2 Sheets-Sheet l @Jer l f 4 o i, w, 2,/ .md 2RM f f F Naar #l I .dT

y D5 ,M n J Y amounts of fresh air vary according to the re- UNIT VENTILATOR Minneapolis Minn., a corporation of Delaware Application October 14, 1935, Serial No. 44,899

10 Claims.

of the class described with control mechanisms responsive-to space temperature .and discharge temperature for positioning lthe damper and the radiator valves.

Another object of this invention is to provide a control system for a unit ventilator that is placed in operation when the room temperature reaches a predetermined value. V

In various parts of the country the heating and Ventilating codes call for a predetermined minimum amount of fresh air to be delivered to af space, and these predetermined minimum guirements of the various localities. It is, therefore, an object of this invention to provide a means for admitting a minimum amount of fresh air to the space with means for easily adjusting this minimum amount of fresh air whereby the various heating and Ventilating codes may be readily complied with.

Other objects and advantages will become apparent to those skilled in the art upon reference to the accompanying specication, claims an drawings, in which drawings: Y

.Figure l is a perspective view system applied to a unit ventilator with portions thereof broken away for purposes of illustration.

Figure 2 isa schematic wiring diagram of one form Aof the control system that may be applied to the unit ventilator shown inA Figure l.

Figure 3'is a schematic wiring diagram of 'another -form of the control system that may likewise be applied to the unit ventilator disclosed inliigure'l'. f l A Although my invention may be applied equally well to a plenary system, itis shown'as applied to .a unit ventilator generally designated at 10. The

,unit ventilator I comprisesfatfront wall ||V and rearwalls |2- and '.I3. The Arear walls |2'and '|3` are connected together by afhorizontally extending Wall I4. The top `of the ventilator I0 is closed bya top wall I5, Yand"likewise-the bottom of the unit .Ventilator is closedby a bottom wall or base,

[|6. Loc'ated'- within the. unit ventilator I0, is

of my control (ci. 23H8) vertically extending transverse partition I1 which divides the unit ventilator into two chambers, one chamber enclosing the air conditioning elements, and the other chamber enclosing the control elements.

Located in the front wall is a return air opening I8, and likewise located in the rear wall |3'is a fresh air opening I9. These openings I3 and' I9 may be provided with suitable' grills, not shown. Located between the openings I3 and I3 is a vertically extending heme-20,. dividing the lower portion of the air conditioning chamber into a fresh air chamber and 'a return air chamber. A damper 2| is suspended above the baille 20-by means of brackets 22 secured toshafts 23 so that when the damper 2| is moved into the position shown in Figure 1 the fresh air chamber is cut off, and when the damper 2| is moved to the right of the position shown in Figure 1 the return air chamber is cut off. The damper 2| is adapted to be positioned between either of these extreme positions in a manner to be described fully hereafter.

Located above the damper 2| is a fan 24, having an outlet opening 25. Fan 24 is driven through a shaft 26 by means of an electric vmotor 2l. Located above the fan 24 are superimposed radiators 23 and 29. The-top wall\|5 is provided with a discharge opening 39 so that the fan 24 -may draw either fresh air or return air, or a -mixture thereof, as determined .by the damper 2| over the radiators 28 and 29, to be discharged into the space to be conditioned through the discharge opening 3Il. Heating fluid such as steam may be-supplied to the radiators 28 and 29 by means of pipes 32 -and 33, respectively. The flow of heating uid through the pipe 32 is controlled by means of a valve 34, and likewise the flow of heating fluid through' the pipe 33-is controlled by a valve 35. The

valves

34 and 35 are provided with valve stems 36 and 31; respectively, which are forced outwardly by means Aof compression, springs 38 and 39, respectively. The springs 38 and 39 bias J-'thevalves 34 and 35 to `an open position. The

valve stemsA 36. and 311 carry rollers 4I! and 4I,

which are adapted toY co-act with cams\42 and 43 locatedson a shaft 44. Cams 42 and 43 are adapted upon turning movement ofthe same to actagainst -the rollers`40 and 4| to move the 'valves 34 and- 35. towards a closed position.

" Also mounted.. on the shaft .f-:44 :is a cam 45 co-acting with a roller 46 mounted yon a lever 41, pivoted as at 43. Lever 4I.acts through `a link 49 A and a-crank 50 secured tothe damperfshaft 23 by a proportioning motor 55 in a manner to be described hereafter. The motor 55 may take theY form of the motor disclosed in Patent No. 2,032,658`issued to W. H. Gille on March 3, 1936 or disclosed in application Serial No. 673,236 filed 'by Lewis L. Cunningham on May 27, 1933.

Located in the space to 'be conditioned is a thermostat 56 preferably of the potentiometer type shown and described in patent No. 2,041,050

issued to Lewis L. Cunningham.

Located in thecontrol chamber of unit ventilator |0 `is a controller 51, preferably of the potentiometertype. The controller 51 is connected by means of a capillary tube 58 to a bulb 59 located in the discharge opening 30 of the unit Ventilator I0, so that the controller 51 is operated in response to changes in temperature of the discharge air from the unit ventilator. The controller 51 may take the form also shown in Lewis L. Cunningham Patent No. 2,041,050.

Also located within the control chamber is a variable resistance 60 operated by a knob 6|.

Located in the return air opening I8 is a thermostat 62 which may be of the typev shown in Patent No. 1,676,921, issued to L. A. M. Phelan et al., on July 10, 1928.

The space temperature controller 56; the discharge temperature controller 51, the variable resistance 60, the return air temperature con troller 62 and the proportioning motor 55 are suitably connected together by means of conduits 63.

The manner in which these various control elements are associated and the manner in which they form the control function for the unit venti'- lator may be obtained by reference to Figure 2 of the drawings. In Figure 2 of the drawings I have shown the motor 55 to be of the type disclosed in the Willis H. Gille Patent No. 2,032,658. A lost motion connection of limited amount is shown to exist between the motor crank 53 and the associated link 52, this lost motion being accomplished by means of a slot 65 in the link 52 cooperating with a pin 66 carried by the crank 53. A spring 61 normally urges the link 52 upwardly and, consequently, urges the crank 53 in a clock-wise direction. However, when the link 52 is moved to its extreme upward position, which position corresponds to the position shown in Figure l, the crank 53 is allowed to move in a clockwise direction a limited amount by reason of the lost motion connection for reasons to appear more fully hereafter.

' The shaft 54 is operated through bevel gears 68' and 69 by means of a rotary shaft 10. The rotary shaft 10 carries a gear 1| which is rotated through a reduction gear train 12 by a motor rotor 13. The motorrotor 13 is operated by field windings 14, 15 and 16. The eld winding 14 performs a holding function and isv of sufficient strength to act against the spring 61- to maintain the shaft 10 in any given position but not sufiicient to move the shaft. The field winding -18 is an operating winding butis not sumciently strong in itself to-cause operation of the shaft'l! against the tension of the spring 81.

x knob 6| is shown to comprise three resistances 92,

However, when both windings 14 and 16 are energized simultaneously the vshaft 10 is rotated against the tension of the spring 61 to move the damper 2| from a fresh air restricting or closed position. opposition to the eld winding 14 so that when the eld windings 14 and 15 are energized, the maintaining or holding action of the field winding 14 is neutralized and the shaft 10 is allowed to be rotated by means of the `spring 61 to move the damper 2| towards a fresh air restricting position as shown in Figure 1.

The shaft 18` also carries a bevel gear 11 engaging the bevel gear 18 to operate an abutment member 19. The abutment member 19 carries a slider adapted to slide across a potentiometer coil 8|. The abutment member 19 also carries fingers 82 and 83. The finger 82 co-acts with a limit switch comprising contacts 84 and 85 and in a like manner the contact finger 83 co-acts with a limit

switch comprising contacts

86 and 81. When the damper 2| is moved to an extreme closed or fresh air restricting position the contact finger 82 breaks contact between the contacts 84 and 85 and when the draft damper 2| is moved to an extreme open or return air restricting'position the finger 83 breaks contact between the

contacts

86 and 81. v

For purposes of illustration, the space temperature controller 56 is shown to comprise a slider 88 adapted to slide across a potentiometer coiI 89 and the discharge temperature controller 51 is shown to comprise a slider 90 adapted to slide across a potentiometer coil 9|. Upon increases in temperature the sliders 88 and 90 are moved to the right, and upon decreases in temperature the sliders 88 and 90 are moved to the left as shown by the characters H and C, respectively.

The variable resistance 60 operated by the 93 and 94, adapted to be engaged by

sliders

95, 96 and 91, respectively.

When the coils |04 and |05 are equally ener- 5 gized, the contact arm |00 assumes a mid position as shown in Figure 2.

The return air thermostat 62 is shown to comprise a mercury switch |08 operated by a bimetallic member |09, so that upon an increase in reo turn'air temperature to a predetermined value the mercury switch |08 is moved to a circuit making position.

Line wires ||0 and lead from some source of power, not shown. A manually operated switch 0 ||2 co-acting with a contact ||3 is connected to ythe line wire ||0. The contact ||3 is connected by wires ||4 and H5 to the fan motor 21 which is in turn connected by'a wire ||6 to theother line wire IH. Therefore, when the switch army 7 H2 is moved into engagement with the contact H3 the fan motor 24 is-pl'aced in operation. One of theelectrodes of the mercury switch "l is connected by a wire ||T tothe. junction of the wires v||4 and H5. The other electrode o! the 1 The eld winding 15 acts in 5 aisance mercury switch |08 is connected by a wire |50 to one end of a primary I 9 of a. step-down transformer having a secondary i 2|. The other end of the primary i I8 is connected by a wire i22 to the junction of wires ||i and H8. By reason of these wiring connections when the manual switch H2 is closed and the mercury switch |00 is moved to a circuit making position the transformer |20 is energized.

From the above wiring connections it is seen that the left hand end of the secondary I2I, the lower end of the coil |00, the left hand end of the potentiometer coil 89, and the right hand end of the balancing potentiometer coil 8| are connected together. Likewise, the right hand end of the secondary I2I and the lower end of the coil |05, the right hand end of the potentiometer coil 89 and the left hand end of the balancing potentiometer coil 0| The upper ends of the relay coils |00 andV |05, and the sliders 88 and `80 are connected together. Therefore, it is seen that the coils |04 and |05, and the potentiometer coils 89 and 8|,y are connected in parallel with respect to each other and acrossthe secondary I2| vof the step-down trans# former |20. It isalso seen that when the slider 88 is moved to its extreme right hand position the right hand end of the potentiometer coil 9| is directly connected tothe, left hand end of the balancing potentiometer 8| and the left hand end of the potentiometercoii 0| is connected to the right hand end of the balancing potentiometer coil 8|. tremeright position as shown in Figure 2, the system is under thecontrol of,y slider 80 and its potentiometencoil 08, and that whenthe slider 88 is in its extreme right hand-position the sys- The resistance 82 associated with the v are connected together..

Therefore, with the slider 00 in its ex-' tem is under the control of the slider 00 and its potentiometer coil 0|.

With the parts in the position shown in the drawings the space or reqm is cold and the unit ventilator is shut down by, reason of the switch ||2 being -open. The damper 2| is located in a closed'or fresh air restricting position by means of the spring 51 and, consequently, the limit switch 00, 85 is open. The

valves

35 and 30 are open to admit heating uid to the radiators 20 and 29, and in response to the heated condition of the radiators 28 and 29, slider 80 is in the right hand position with respect 'to its potentiometer coil 9| Due to the fact that at this time the space or room is cold the slider 88 is at its extreme left hand position with respect to its potentiometer coil 89. Upon closing of the manual switch I2 the fan motor 20 is .placed in operation and return air from the space is forced over the radiators 28 and V20. and heated thereby. When the space temperature and, consequently, the return air temperature, has risen to agiven value, the mercury switch |08 is tilted to a cir-- cuit making position to supply energy to the step-down transformer |20. As the temperature in the space begins to rise the slider 08 is moved to the right to cause short circuiting or shunting of the coil |05 to increase the energization of the coil |04' and decrease the energization of the coil |05. This causes movement of the switch arm |00 into engagement with the contact |03 to complete a circuit from the secondary |2| through 'wires r|50 and |51, contact arm |00, contact |03,wire |52, coil |06, wire |53, iield winding 16, wire |50, contacts' 81 .and 86, and wires |55, |5|and |21, back tothe secondary |2|.- Completion of this circuit causesl energization of the-field winding 18 to start movement of the through wires |56 and |50,` field. winding 16,

I2I. Completion of this circuit causes energization of the fleldwindingm and the field -winding 14 lwill remain energized as long as the contacts 84 and 85 are in engagement. Since both the field windings 14 and 16 are energized in the manner pointed out above, the spring 61 is overcome and the damper 2| is moved further from the fresh air restricting position.

Movement of the damper 2| from the fresh air restricting position causes right hand movement of the slider 80 with respect to the balancing potentiometer coil 8|. This causes short circuiting or shunting of the coil |04 to decrease the energization thereof and increase the energization of the coil |05, it being remembered that the coil |04 was energized more than the coil |05 byreason of the right hand movement of the slider 88. When the slider 80 has moved sui.

ciently far to the right, the coils |04 and |05 will become equally energized to move the contact arm |00 out of engagement with the contact |03 and into the mid position as shown in Figure 2. This causes de-energization of the eld winding 16, it being remembered that the field winding 14 still remains energized. When the eld winding 16 is thus de-energlzed the damper 2| is maintained in the newly adjusted position by the energization of the field winding 14. Since the circuit through the field winding 16 hincludes the coil |06 the contact arm |00 is moved forcibly in engagement with the contact |03 to prevent relay chatter. i

Upon a decrease in space temperature, the

slider 88 moves toward the left with respect to the potentiometer coil 89 to short circuit or shunt the coil |04 to increase the energization of the coil |05 and decrease the -energization of the coil |04. 'I'his causes movement of the contact arm |00 into engagement with the contact |02. Movement of the contact arm I 00 into engagement with the contact .|02 completes a circuit from the secondary |2| through wires |56 and |51, contact arm |00,contact |02, wire |45,coil |01, wire |46, field winding 15, wires |41 and |48, contacts 85 and 84, wire |49, resistance |50 and wires |5| and |21 back to the secondary |2|. Completion of this circuit causes energization of the coil 15 `which neutralizes the holding action of the coil 14 to permit the spring 61 to move the damper 2| towards a fresh air restricting position. Movement of the damper 2| towards a fresh air restricting position causes left hand movement of the slider 80 with respect to its balancing coil 8| and when the slider 80 has moved sufliciently far to the left the coils |04 and |05 are again equally energized to move the contact arm |00 out of engagement with the contact |02 and tothe mid position as shown in Figure 2. This causes deenergizat-ion of the field winding 15, it being remembered that the eld winding 14 remains energized. Therefore, further movement of the damper 2| towards a fresh air restricting position is stopped. Since the circuit through the field winding 1 5 includes the coil |01, the contact arm |00 is forcibly held in engagement with the contact |02 to prevent relay chatter. The resistance |50 is included in lthe circuits through the field windings 14 and 15 to add resistance in the circuits to compensate for the decrease in resistance caused by the energization of the oppositely-acting field windings 14 vand 15.

Movement of the slider 80 to the extreme left hand position shown in Figure 2 is caused by complete closing movement of the damper 2|. Due-to the use of the resistance |32 a complete zie-balancing is not established by the complete left hand movement of the slider 80, whereby further movement of the damper 2| towards a closed position is permitted'to insure that the finger 82 will break contact between the contacts 84 and 85 lof the limit switch to completely shut off the supply of energyto the eld windings 14 and 15 to prevent undue heating of the same.

From the above it is seen that I have provided a system for accurately positioning a damper in accordance with space temperatures which system is placed in operation when the space ternperature or return air temperature rises to a predetermined value.

In some localities it is required to have a minimum amount of fresh air delivered to the space to be heated, and this amount may vary according to the various localities. To cause immediate partial opening of the damper 2| to provide this minimum amount of fresh air, I have provided in the circuit leading to the

controllers

56 and 51 the variable resistance 60. Movement of the slider's 95, 96 and 91 downwardly from the position shown in the drawings increases the resistance on the left hand end of the potentiometer coil 89 and decreases the resistance on the right hand end of the coil 91. This produces the same effect as moving the slider 88 to the right with respect to the potentiometer coil 89, so that with the slider 88 in the extreme left hand position shown in the drawings, movement of the

sliders

95, 96 and 91 downwardly causes opening movement of the damper 2|, the amount of opening movement being determined by the distance through which the

sliders

95, 96 and 91 are moved. Therefore, with the

sliders

95, 96 and 91 located in a downward position, the damper 2| will be immediately moved to some intermediate position upon closing of the mercury switch |08.

Referring now to Figure 1, I have diagrammatically shown four positions which the cams 42, 43 and 45 may assume. In the position shown wherein line a coincides with the roller 46, the damper 2| is closed and the

valves

34 and 35 are open. Movement of the cams 42, 43 and 45 to the position Where line b coincides with the roller 46, the damper 2| is partially open and the valve 35 is about to be closed. Movement of the cams 42,

43 and 45 tothe position Where line c coincides with the roller 46 the damper 2| is moved to a. further open position and the valve 35 is completely closed and the valve 34 is about to be v moved towards a closed position. Movement of the cams 42, 43 and 45 to a position where the line d coincides with the roller 46 causes complete -opening of the damper 2| and complete closing of the

valves

34 and 35. Movement of the cams 42, 43 and 45 in the opposite direction causes exactly the same operation but in the reverse order. The cams 42, 43 and 45 are so designed, and theV variable resistance is so positioned, that when the thermostat 62 places the control system in operation the damper 2| is moved to a partially open position corresponding to the line b. Upon an increase in room temperature so as to move the slider 88 to the right with respect to the potentiometer coil 89, the damper 2| is positioned towards an open position and the

valves

34 and 35 are positioned toward a closed position. Preferably, the thermostat 62 is set-so that the mercury switch |08 is moved to a circuit making position at 65 and the slider 88 is started in its movement from the left hand position of the potentiometer 89 at 68I and arrives at the right'hand position with respect to the potentiometer coil 89 when the space temperature has risen to 72". lBy reason of the above settings,

2,1 sacas re-circulated air is heated until the temperature of the air becomes 65, at which time the damper 2| is moved to a partially open position to admit a predetermined amount of fresh air to the space. When the temperature of the spacebegins to rise above 68 more fresh air is admitted and the amount of heat imparted to the air is decreased. When the temperature of the space has risen to 72, 100 per cent fresh air is admitted to the space and no heat is imparted to the air since at -this temperature the radiators 28 and 29 are cut off.

With the above operation, and with the room or space temperature at 72, and if the outdoor temperature is cold, raw. air may be delivered into the space or room, To prevent thisdelivery of raw air into the space or room, the discharge.

temperature controller 5l is provided and preferably this controller is adjusted so that when the temperature of the discharge air decreases below 65 the slider @d is moved from its right hand position towards its left hand position with respect to the potentiometer coil 9i. Since at this time the slider 66 is at the extreme right end of the potentiometer coil B9, and since the right hand end of the coil 9| is connected to the coil |65, and since the left hand end of potentiometer coil 6| is connected to the coil ills, movement of the slider Sil towards the left short circuits or shunts the coil |05 to increase the energization ofthe coil itl and decrease the energization of the coil ,IM to cause movement of the contact arm te@ into engagement with the contact m2. |This causes energization of the field winding l5 to neutralize the action of the ileldy winding l@ to allow the spring 6l to move the damper El towardsA a closed position, and to move the valve Sli towards an open position, the amount of movement of the damper, and, consequently, the valve 3Q being determinedby the position of the slider Sii. In extremely cold weather the slider Sil may be moved suciently far to the left to completely open the valve 3d and partially open the valve 35.

From the above it is seen that I have provided a heating and Ventilating `system which positions a damper and valves according tospace or room temperatures, and which also positions the damper and valves in accordance with discharge temvarious localities of the country. Provision is also made for closing the damper when the unit ventilater is rendered inoperative or in case of power failure. l,

Referring now to Figure-3, a system is provided which gives exactly thesame results as the system disclosed in Figure 2, but the manner for accomplishing these results is slightly different. This modication uses the same space temperature controller, the same discharge temperature controller, and the same relay mechanism, these various elements being connected together in the manner pointed out above. However, the wire |39 which connects the wire |38 to the resistance 63 in Figure 2 connects the wire 38 to a switch arm |62 in Figure 3. Switch arm |62 is-adapted to engage a contact |63, which is connected by a wire |39' to the resistance 93. Therefore, when the switch arm H62 is in engagement with the contact |63 the operation of this portion of the control system of Figure 3 is identical with that oiFigure 2. The switch arm |62 is also adapted to engage a contact itil, which is connected to the junction o1" wires |24 and |25 so that when the switch arm |62 is in engagement with the contact dell the temperature controllers 56 and el are rendered inoperative to control the proportioning motor and the coil l0@ is completely short circui'ted to move the contact arm |00 into engagement with the contact |02. The switch arm |62 is operated by means of a relay coil |66 so ihatwhen the relay coil |65 is energized the switch arm it is moved into engagement with the contact 563 to vplace the proportioning motor under automatic control, and when the relay coil |66 is (le-energized the switch arm |62 is moved into engagement with the contact |66 in any suitable manner to prevent automatic operation of the proportioning motor and to cause the proportioning motor to assume one extreme position.

Inthis modification line wires leading from some source of power, not shown, are designated at itil and 366. One end of the primary it@ of the step-down transformer i2@ having the secondary ii is connected to the line wire |66 and the other end thereof is connected to the line wire its. Therefore, in this modiilcation power is at all times supplied to the relay. The line wire iilil is also connected by a. wire Il@ to a switch arm' lll, co-acting with a contact H2. Contact l isconnected by wires H3 and i'lfi to the ian motor 2li, and the fan motor 2l is in turn connected by wires H5 and il@ to the other line wire 66S. The junction of Wires H3 and lid is connected by a wire i'l'l to one of the electrodes of the mercury switch M36. Theother electrode of the switch tilt is connected by a wire H6 to one end of the relay coil i66. The other end of relay coil M36 is connected by a wire ile to the junction of wires H5 and H6. Therefore, when the switch arm ill is moved into engagement with the contact H2 the fan motor 2l is placed in operation, and when the room temperature, or return air temperature, reaches a predetermined value, say 65 as in the previous modiiication, the mercury switch Eil@ is moved to a circuit making position to cause energization of the relay coil |66. This moves the switch arm ieg into engagement with the contact i163 to place the unit ventilator under automatic control and to permit movement of the proportioning motor out of its extreme position. f

The proportioning motor in the modicatlon shown in Figure 3 is different from that disclosed in Figure 2, and may be of the type disclosed in application Serial No. 673,236, flied by Lewis L. Cunningham, on May 27, 1933. For purposes of illustration, this motor is shown to comprise rotors |63 and 462 operating through the reduction gear train i2, andthe gear lli for operating the shaft liti. The rotors iti and |62 are operated by iield windings |83 and |36, respectively, so that upon energization of the field windingid the damper is moved towards a closed or fresh air restricting position, and upon energizationof the field winding l8r?, the damper 2i is moved towards an open or return air restricting position. The manner in which the slider t@ is moved with respect to the potentiometer balancing-coil 3i, and in which the limit switches 6ft, 65 86' and The contact |03 cooperating with the contact arm is connected by a wire |85 to one end of the coil |06, the other end of which is connected by a wire |81 to the contact 86 of the right hand limit switch. In a like manner the contact |02 cooperating with the contact arm |00 connected by a wire |86 to one end of the coil |01, the other end of which is in turn connected by a wireA |88 to the contact 84 of the left hand limit switch. Contact 81 is connected by a wire |90 to one end of the field winding 84, and the contact 85 is connected by a wire |9| to one end of the field winding 83. The other ends of the eld windings |83 and |84 are connected together and by a wire |92 to the junction of the wires |21 and |28. The contact arm |00 is connected by wires |93 and |23 to the secondary |2|.

contacts

Movement of the

sliders

95, 96 and 91 downwardly with respect to their

resistances

92, 93 and 94 has the same effect as in the previous modification, so that when the switch arm |62 is moved into engagement with the contact |63 under the command of the return air thermostat 62, the damper 2| is moved to a minimum fresh air position, -furthermovement of the damper being controlled by the movement of the slider 88 with respectto the potentiometer coil 89.

From the'above it is seen that I have pro-v vided a control system for an air conditioning unit which may be of the plenary type but which vfinds particular utility in connection with a unit ditioned, and that upon increases in space temperature the amount of fresh air delivered to the space is increased and the amount of heat delivered to the space is decreased. Provision is made whereby the amount of fresh air initially delivered to the space may be varied and provision is also made for controlling the damper and the valves, whereby raw air is prevented from being admitted to the space.

Although I have shown two exemplifcations of my invention, it is apparent that modifications thereof may become apparent to those skilled in the art, and, therefore, I intend that my invention shall be limited only by the scope of theappended' claims and the prior art.

I claim as my invention:

1. In a conditioning unit of the class described for discharging conditioned air to a space, damper means in said unit for controlling the supply of air to said unit, means in said unit for altering the temperature of .the air discharged into the space, a motor in control of said damper means and said temperature altering means, a relay comprising series connected coils in control of said motor, said series connected coils being connected across a source of electrical energy, a space temperature responsive adjustable potentiometer, a discharge yair temperature responsive adjustable potentiometer, connections between opposite ends of the series connected coils and opposite ends of the resistance of the first potentiometer, connections between one end of the resistances of each potentiometer, connections between the slider of the first potentiometer and the other end of the second potentiometer, and connections between the slider of the second potentiometer and the junction of the series connected coils, whereby when the discharge air temperature responsive potentiometer is in one extreme position the space temperature responsive potentiometer is in control of said motor and when the space temperature responsive potentiometer is in one extreme position the discharge air temperature responsive potentiometer is in control of said motor.

2. In an air conditioning device for conditioning a space, damper means for controlling the supply of fresh air and return air into said device, heat exchanger means for changing the temperature of the air discharged into the space, valve means for controlling4 the temperature changing eiect of the heat exchanger means, an electric motor, operating means operated by 'the electric motor for operating the damper means and the valve means in a predetermined sequence, means for biasing said operating means to a position to open the valve means wide and to prevent the supply of fresh air, control means for controlling the operation of the electric motor including means responsive to space temperature to position said damper means and said valve means in accordance with variations in space temperature, means included in said control means for preventing movement of the damper means to thev position which prevents the supply of fresh air, and means for interrupting the supply of energy to the electric motor whereby the biasing means moves the damper means to the extreme biasedposi tion.

3. In an airconditioning device for conditioning a space, damper means for controlling the lsupply of fresh air and return air 'into said devia'heat exchanger means forchanging the temperature of the air discharged into the space,

vvalve means for controlling the temperature changing'eiect of the heat exchanger means, an electric motor, operating means operated by the electric' motor for operating the damper means` and the valve means in a predetermined sequence, control means for controlling the op*- eration of the electric motor, including means responsive to space temperature to increase the supply of fresh air and close the valve means as the space temperature increases, means responsive to discharge temperature to decrease the supply of fresh air and open the valve means as the discharge temperature decreases, and means included in said control means for preventing movement of the damper means to a fresh air preventing position regardless of the controlling action of the temperature responsive means.

4. In an air conditioning device for conditioning a space, damper means for controlling the supply of fresh air and return air into said device, heat exchanger means for changing the temperature of the air discharged into the space, valve means for controlling the temperature changing effect of the heat vexchanger means, an electric motor, operating meansvoperated by the electric motor for operating the damper means and the valve means in a predetermined sequence, means for biasing said operating means to a position to open the valve means wide and to prevent the supply Vof fresh air, control means for controlling the operation of the electric motor including means responsive to space temperature to position said damper means and said valve means inaccordance with variations in space temperature, means included in said control means for preventing movement of the damper means to the position which prevents the v supply of fresh air, means for interrupting the supply of energy to the elect'ric motor whereby the biasing means moves the damper means to the extreme biased position, and means responsive to space temperature for controlling said last mentioned means.

5. In a conditioning unit of the class described for discharging conditioned air to a space, damper means in said unit for controlling the :dow of air through said unit, a motor in control of said' damper means, a' relay comprising series connected coils in control of said motor, said series connected coils being connected across a source of electrical energy, a space temperature responsive adjustable potentiometer, a discharge air temperature responsive adjustable potentiometer, connections between opposite ends of the series connected coils and opposite ends of the resistance of the first potentiometer, connections between one end of the resistances of each potentiometer, connections between the slider of the first lpotentiometer and the other end of the second potentiometer, and connections between the slider of the second potentiometer and the junction of the series connected coils, whereby when the discharge air temperatnre responsive potentiometer is in one extreme position the space temperature responsive potentiometer is in control of said motor and when the space temperature responsive potentiometer is in one extreme position the discharge air temperature responsive potentiometer is in control of said' motor.

6. In an air conditioning system, in combination, means for supplying fresh air to a space to be conditioned, damper means movable between closed and open positions for controlling the fresh air supply, electric motor means for moving said damper means to various positions, a control circuit for said electric motor means for controlling the operation thereof, a first temperature responsive electric current controlling means responsive to a temperature condition which is affected by the position of the fresh air damper means and being connected in said control cir'- cuit in a manner to position said electric motor means and hence said damper means to maintain said temperature condition substantially constant, a second temperature responsive electric current V controlling means responsive to another temperature condition and being connected in said motor control circuit with said iirst temperature responsive electric current controlling means in a manner to render said first temperature responsive current controlling means substantially ineffective to position said electric motor means andto position substantially independently said electric motor means and hence said damper means whenever the temperature condition to which said second temperature responsive electric current controlling means responds varies to a predetermined value, means included in said control circuit for normally preventing either of said temperature responsive electric current controlling means from completely closing said fresh Y air damper means, and meansfor completely closing said fresh air damper means regardless of the controlling action of the temperature responsive electric current controlling means.

'7. In combination, an air conditioning unit having temperature changing'means and means for supplying fresh air to a space to be conditioned, damper means movable between open and closed positions for controlling the fresh air supl ply, motor means for moving Said damper means to various positions, means including first temfective to position said motor means and to position substantially independently said motor means and hence, said damper means whenever the second temperature condition varies to a predetermined value, means for normally preventing either of said temperature responsive means from completely closing said fresh air damper means,A

and means operative as an incident to shutting downof a portion of the air conditioning unit for completely closing the fresh air damper means.

8. In combination, an air conditioning `unit having temperature changing means, fresh air supplying means and fan means for circulating air through the unit to a space to be conditioned, damper means movable between open and closed positions for controlling the fresh air supply, motor means for moving said damper means to various positions, means including rst temperature responsive means responsive to va temperature condition which is affected by the position of the fresh air damper for positioning said motor means and hence said dampermeans to maintain said temperature responsive means substantially inefmeans for normally preventing either of said` temperature responsive means from completely closing said fresh air damper means, and means operative upon stopping of the fan means for completely closing said fresh air damper means.

9. In an air conditioning system, in combination, damper means for controlling the supply of fresh air to a space to be conditioned, electric motor means for operating said means, a three A wire control circuit for 4said motor means, said three wire control circuit including a common wire, a first control wire which is adapted in cooperation with said common wire to cause said electric motor means to operate in one direction and a second control wire which is adapted in cooperation with said common wire to cause said motor meansto operate in the opposite direction, thermostatic electric current controlling means responsive to a temperature iniluenced by the damper position, said last mentioned means including a movable member connected to said common Wire and means contacted by said movable member and adapted to place said common and control wires in cooperation respectively, said thermostatic electric current .controlling means acting normally to cause positioning of said 'damper means in a manner to maintain said temperature condition substantially constant, a second thermostatic electric current' controlling means responsive to another temperature condition, said second thermostatic current controlling means including means connected to said common wire and one of said control Wires for rendering said flrst current controlling means inef-` direction when the temperature at said second thermostatic electric current controlling means is at one value, while placing said first current controlling means in control of said motor means when the temperature at said second thermostatic electric current controlling means is at another value.

10. In an air conditioning system, in combination, electrically operated fan means for supply- 'ing fresh air to a space to be conditioned, an

electric circuit for the fan means, damper means movable between open and closed positions for controlling the fresh air supply, electric motor means for moving said damper means to various positions, means for supplying power to the elec- .tric motor means from the electric circuit for the fan means, means for biasing the damper means toward a closed position, control means including first temperature responsive means responsive to a temperature condition which is affected by the position of the fresh air damper for positioning said electric motor means and hence said damper means to maintain said temperature condition substantially constant, said control means also including a second temperature responsive means responsive to another temperature condition to render said first temperature responsive control means substantially ineiective to position said electric motor means and to position substantially independently said electric motor means and 1 hence said damper means whenever the second temperature condition varies to a predetermined value, means for normally preventing either of said temperature responsive means from completely closing said fresh air damper means, and

means for interrupting the electric circuit for the fan means to stop the fan means and to stop the supply of power to the electric motor means whereby the biasing means moves the damper means to the complete closed position.

JNO. T. MIDYETTE, Jn.