US2170232A

US2170232A - Air conditioning system

Info

Publication number: US2170232A
Application number: US179317A
Authority: US
Inventors: George D Bower
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1937-12-11
Filing date: 1937-12-11
Publication date: 1939-08-22
Anticipated expiration: 1956-08-22

Description

AUS- 22, 1939- G. D. BowER AIR CONDIT'IONING SYSTEM Filed Deo. 11

v INVENTOR George D. Bowen BY /mw fg/.4 ATTORNEY Patented Aug. 22, 1939 A UNITED STATES 2,170,232 am CONDITIONING SYSTEM George D. Bower, Columbia Heights, Minn., as-

signor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware l Application December 11, 1937, serial No. 179,317

' 8 Claims.

'Ihis invention relates to an air conditioning system` and more particularly to a warm air heating system in which a circulating fan circulates air through the heating chamber of a furnace and through a space to be heated,-and

in which a draft and a check damper are operated to control the rate of combustion in the furnace. The invention is more particularly concerned with the controls for the fan and dampers.

In such a'system, it is often desirable to circulate unheated air through the heating chamber andv the space during thesuxnmer-time so that the circulation of unheated air will have a cooling effect on the occupants of the space, and to provide means responsiveto the temperature of the space for controlling the operation of the air circulating means. It often happens that during the summer-time when the furnace is shut down, that an unseasonable cold spell occurs, in which case it; may be desirable to burn some trash in the furnace to take the chill olf the house, and in such case the dampers should be in draft producing position in order that the trash may burn readily, but should the temperature in the heatdampers should be moved to draft retarding position to check the combustion of the trash.

When the system is being used for a heating system, the dampers should be placed in draft furnacea in order to prevent smoke or gas from blowing out of the fixing door of the furnace, as would be liable to happen particularly should the check damper be open.

. In order to conveniently control the operation of the dampers and fan in winter and summer, and to control the dampers during the stoking period I have devised a system in which the control is changed merely by the manipulation of a three-position-switch. When the switch is in one position, the fan is under the control of la. room thermostat and a switch responsive to the temperatures of the heating chamber, so that the fan is operated only upon a call for heat in said room providing the temperature of the heating chamber is sufficiently high. In'this position of the switch; the dampers are moved to draft producing position only when there is a call for. heat in said room. When the switch is moved unalected, but the dampers are moved to draft producing position regardless of the temperature of the room. The' dampers are under the control of a switch which opens should the-temperature of the heating chamber attain an excessive'preing chamber be. raised to an excessive value, the

producing position when it is desired to stoke thel to a second position, the operation of the fan isdetermined value whereupon the dampers are moved to draft retarding position. When the three-position switch is moved to a third position, the dampers are controlled in the same way as when the switch is in the second position, be- 5 ing normally in draft producing position, and the control of the fan by the room thermostat is changed so that the fan is operated only when the temperature of the room is above a certain value. 'Ihis third position is the summer posilo tion, and since the dampers are normally in draft producing position, further manipulation thereof is unnecessary should it be desired to burn trash in the furnace during the summer operation of the system. f

It is therefore an object o my invention to provide an improved operating system-for a warm air coal fired furnace in which air circulating means are provided to circulate air over the heating chamber and through a. space to be heated. 20

More specifically, it is an object of my invention to provide, in such a system, a single threeposition switch by means of which the system operates as a heating system in one position of the switch to circulate air through the heating 25 chamber of the furnace and through a space to be heated'only when heat is required in said space, and to move draft controlling dampers to draft producing position at such time; by means of which the dampers are moved to draft .producing 30 position for purposes of stoking the furnace, regardless of the temperature of the space in a second position of the switch; and by means of which the fan is caused to operate when the temperature of the space is above a predetermined value in the third, or summer position of theswitch, and in which position of the switch the dampers are normally held in draft producing position.

It is a further object of my invention to pro- 40 vide control means for draft dampers in such a system, whereby the dampers are moved to draft producing position only when heat is required in the space being heated during the normal winter operation of the system, and whereby the dampers are normally held in draft producing position in the summer operation of the system, there being a switch responsive to the temperature of the heating chamber whereby the dampers are moved to draft retarding position whenever the temperature of the heating chamber rises above a predetermined value, in either the winter or summer operation of the system.

Qther objects will become apparent upon an. examination of the specincaticn, claims and drawing, in which the single view illustrates the preferred form of my system.

Referring more particularly to the drawing a warmair furnace is indicated by a reference character I8. This furnace includes the usual warm air ducts |I), an outlet stack I2, a draft damper I3, a checkldamper I4, and a firing door I5. A blower I6 is provided for circulating air through the heating chamber of said furnace and through a space or spaces being heated. For driving said blower I6 a motor I1 is provided, said motor having a pulley I8 connected by a belt I9 to a pulley 28 which is connected to the blower.

Mounted in the heating chamber of the furnace is a bimetallic element 2| of conventional design operatively connected by a rod 22 to mercury switches 23, 24, and 25 in a well known manner.

Switch 23 includes a mercury element 26 and

contacts

21 and 28 which are normally closed by the mercury element 26. Switch 24 includes a mercury element 38 and contacts 3| and 32, and switch 25 includes a mercury element 33 and contacts 34 and 35, these last two switches being normally in open position as illustrated. Switch 24 is designed to tilt to closed position upon the Vattainment of one predetermined temperature in the heating chamber, switch 23tilts to open poi sition upon the attainment of a higher predetermined temperature in the heating chamber and switch 25 tilts -to closed position upon the attainment of a still higher temperature in the heating chamber.

For operating the draft and check dampers I3 and I4 an arm 48 is provided, said arm being connected to the draft damper I3 by means of a cable or like member 4|, the other end of said arm being connected to the check damper I4 by means of a cable 42 passing over a pulley 43. The arm 48 is mounted at its center on a shaft 44 and movement of arm 40 by shaft 44 in a clockwise direction will cause the opening of draft damper I3 and the closing of check damper I4 as will be apparent.

For rotating shaft 44, a motor generally indicated -by the reference character 58 isprovided, this motor including anI armature 5I and

eld windings

52 and 53. Field winding 52 acts as a lifting coil for the armature 5| and winding 53 -acts as a holding coil. Thus, if winding 52 is initially energized, shaft 44 will be rotated to move arm 48 in a clockwise direction, after which this w,coil is deenergized as will be explained hereafter but the arm 48 will remain in its new position as long as field winding 53 remains energized. Rigidly mounted on the shaft 44 is an arm 54 to which is connected a spring 55 for biasing said arm in a counter-clockwise direction when the eld winding 53 is deenergized. A stop 56 limits the movement imparted to arm 54 by the spring 55.- Shaft 44 is connected to the armature 5| through a. reduction gearing 51.

In the circuit of field winding 52 is a switch 68 which includes a switch arm 6| and a fixed contact 62. Mounted on shaft 44 for rotation therewith is a cam 63 having a recessed portion 64. Switch arm 6I has a projection 65 for cooperating with said recess 64 when the cam 63 has rotatedthrough' approximately 98. As will. be apparent cam 63 bears against the portion 65 of the switch arm and normally holds said arm in engagement with the xed contact 62 but upon suiiicent rotation of shaft 44 the recess 64 will lie directly above the portion 65 of the switch arm and permit said arm to move upwardly and away from fixed contact 62.

Slidably mounted in walls 18 and 1| is a switch actuator 12 normally biased toward the right by vmeans of a spring 13 acting upon the shoulder 14 of said actuator. Member 12 has a reduced portion 15 for cooperation with an aperture 16 in the arm 54. At the o-pposite end of member 12 left against the action of spring 13. When the motor 58 is deenergized, damper operating arm 48 may be moved in a clockwisedirection by hand and if it is moved to a position wherein the aperture 16 is opposite the reduced portion 15 of member 12, this member may be forced to the left to a position wherein the reduced portion 15 of member 12 passes through the aperture 16 in the arm 54. With the parts in this position, the spring 55 will bias arm 54 in a counter-clockwise direction and the frictional engagement between the reduced portion 15 of member 12 and the wall of aperture 16 will hold member 12 in the switch closing position against the action of spring 13. A slight movement of arm 54 in a clockwise direction will relieve the frictional engagement between reduced portion 15 of member 12 and the wall of aperture 16 whereupon the switch actuating member 12 will be moved to the right by means of the spring 13 and switch arm 19 will move away from switch arm 88. The function of

switch arms

19 and 88 will be explained later. y l l A three-position switch generally indicated by thereference character 84 `is provided and includes an actuator 85, switch arms 86 and 81 and

contacts

88 and 89 cooperating with said switch arms. Switch arm 86 is normally biased toward the right and arm 81 is normally biased toward the left. If the actuator is rotated in a clockwise direction through 98, the switch arm 81 will be permitted to move into engagement with the contact 89. Movement of actuator 85 in the same direction through another 90 will cause the contact 88, arm 81 remaining in engagement with contact 89. This switch is for the purpose of providing forvsummer and winter operation of the system and for placing the draft dampers in a ring position during the winter time as will be hereinafter explained.

Mounted in the space to be heated is a thermostat 98, said thermostat including a bimetallic element 9| and arms 92 and 93 arranged to be moved thereby. Arm 92 is relatively flexible and is arranged to engage a fixed contact 94 upon a predetermined drop lin .the room temperature. Arm 93 does not engage its fixed contact 95 until a further slight drop in room temperature, movement of this arm into engagement with contact -95 being permitted by reason of the flexibility of cooperating with switch arm I8| are contacts |84 and |85, and cooperating with the switch arm |82 is a fixed contact |86. These switch arms are normally in the positions illustrated when the coil 98 is not energized, in which position switch miV anonce arm is in engagement with contact |05 and switch arms |00 and |02 are out oi' engagement with their respective contacts. Energizatlon of the coil 98 causes switch arms |00, |0I, and |02 to move into engagement with contacts |03, |04, and |06, respectively.`

For energizing the damper motor'and blower motor, lines ||0 and are provided, these lines being connected to a suitable source of power (not shown). A step-down transformer ||2 ris provided for furnishing power tothe relay 91, this transformer including a high tension primary ||3 connected by means of conductors ||4 and H5 to the lines I|0 andlil, and a low tension secondary ||6.

With ythe parts in the position illustrated, the room thermostat is satisied, that is, it isy not calling -for more heat in the space being heated.

Damper' motor 50 is deenerglzed and spring 55 biases the arm 54 against the stop 56 in which position the damper arm 40 is positioned as illustrated, the check damper |4 is open and the draft damper |3 is closed so that the draft through the furnace is at a minimum. Also the blower motor |1 is denergized so that no a-ir is being circulated through the system by the blower 6.

Assume the temperature in the space drops to a certain predetermined value. I'he bimetallic element 9| will cause arm 92 to move into engagement with contact 94, butno circuit through the relay 98 is created at this time; If the temperature drops to a further predetermined value arm 93 will be moved into engagement with contact 95 whereupon the coil 98 of relay 91 will be energized through the following circuit: from the low tension secondary ||6 of transformer ||2 through conductor |20, contact 94, arms 92 and 93 of the thermostat 80, contact 95, conductor |2|, coil 98 and conductor |22 to theother side of secondary IIB. Energization of coil 98 will cause switch arms |00, |0|, and |02 to move into engagement with contacts |03, |04, and |06 as explained heretofore. Movement offarm |00 into engagement with contact |03 energizes a holding circuit for the relay coil 98, which circuit is independent of the arm 93, this circuit being as follows: from the, low tension secondary ||6 through conductor |20, contact 94, thermostat arm 92, bimetallic element; 9|, conductor |23, contact |03, switch arm |00, vconductor-|24 through the relay coil 98 and conductor |22 to the other side of secondary H6. It will therefore be seen that relay coil 98 will be energized as long as blade 92 remains in contact 94 so that the circuit through coil 98 will not be broken at the same temperature as that at which it is made but rather at a slightly higher temperature.

Movement of switch arm |02 into engagement with contact |06 energizes the damper motor 50 through the following circuit: from the line 0 through conductors |30, |3I,

contacts

28 and 21 whichare closed by the mercury element 26, conductors |32, |33, contact |06, switcharm |02, conductors |34, |35, |36, contact 62, switch arm 6|'. conductor |31 through thelifting coil 52 of the damper motor and conductor |38 to the line Energization of coil 52causes rotation of the armature 5| to move the shaft 44 in a clockwise direction. At the same time a circuit is established through a holding 4coil 53 which circuit is as follows: from the line ||0 through conductors |30, |3l.

contacts

that the circuit through the holding coil 53 is independent of switch 60 whereas the circuit through the lifting coil 52 passes through this switch. After the shaft 44 has rotated through approximately the cam 63 moves to a position wherein t'he recess 64 lies directly over the projecting portion 65 of switch arm 6|, whereupon switch arm 6| is permitted to move upwardly 'and out of engagement' with contact 82 thus deenergizing the liftingcoil 52. 'Holding coil 63 is designed to maintain shaft 44 in its new position against the action of spring 55 which tends to move it back to its original position.

In this new position of shaft 44 the arm 4l has moved clockwise through 90 causing the draft damper I3 toopen and the check damper |4 to close. The temperature of the heating chamber now commences to rise by reason of the increased combustion of fuel inthe furnace causes a circulation of air through the heating chamber of the furnace and the space within which the thermostat 90 is located.

After the temperature of said space reaches a certain high value wherein the arms 92 and 93 are moved out of engagement with their respective contacts, the circuit through the relay coil 98 is broken and the switches move back to their original positions. vThis causes deenergization of the blower and damper motors since the circuits for these motors pass through theswitch arms |0|, |02 and contacts |04 and |06, respectively. Spring 55 causes arm 54 and shaft 44 to move back to its original position whereupon arm 40 is also 'moved back to its orlginalposition in which position the draft damper I3 is closed and the check damper I4 is open. 4

Assume now that before the room thermostat 90 is satised that the temperature of the heating chamber rises beyonda certain predetermined value. Switch 23 will be tilted to its open position whereupon the damper motor is deenergized but the blower motor |1 continues to operate until the room thermostat 90 is satisfled. If the temperature of the heating chamber rises to a still higher value after the room thermostat is satisfied and the damper motor is deenergized, the switch 25 will be tilted to a position wherein the mercury e1ement'33 closes the contacts 34 and 35.

The blower motor I1 will again be energized to cause a dissipation y of this excessive heat in the heating chamber,

the circuit through the motor now being as follows: from the line H0 through conductors |30,

, |60, contacts 35 and 34, conductors |6| and |40,

nace at a time when the dampers are in their draft checking positions as illustrated it will be desirable to'move them to draft producingpositions to prevent smoke and gases from being.

blown out of the firing door |5 and into the furnace room. Since the damper motor 50 is deenergized, it being assumed now that the room thermostat is satisfied when it is desired to throw on the fuel, switch "actuator 85 may be moved clockwise 90 in which position the switch arm 81 engages contact 89 and will cause operation of the damper motor regardless of the ternperature in the space being controlled, the circuit through the lifting coil 52 of the motor being as follows: from line ||0 through conductors |30, |3|,

contacts

28 and 21 of switch 23, conductors |32, |65, contact 89, switch arm 81, conductors |66, |35, |36, contact 62, switch arm 6|, conductor |31, lifting coil 52 and conductor |38 to the line The circuit is. established through the holding coil 53 as follows: from the line ||0 through conductors |30, |3|,

contacts

28, 21, conductors |32, |65, contact 89, switch arm 81,V conductors |66, |35, |39, the holding coil 53 and .conductor |40 to the line It will be apparent now that the dampers will be moved to their draft producing positions whereupon fuel may be thrown on the re bed. After the furace has been red the switch 85 should be moved back to its original position placing the damper motor under the control of the room thermostat. Should the operator of the furnace neglect to do this however, the temperature of the heating chamber will gradually rise until the switch 23 is tilted to open position, thus breaking the circuits through the damper motor. Since the blower motor is not placed in operation, very little heat will be delivered to the space being heated.

In case of power failure the dampers may be manually moved to open position should the temperature of the space being heatedfall to an undesirable low value. This is done by manually moving arm 40 in a clockwise direction until aperture 16 is opposite the portion 15 of member 12, and then moving memberl 12 to-` ward the left until member 15 passes throughI the aperture 16. Spring 55 holds the member 1,5 'g in its new position by reason of the frictional engagement of the wall of the .aperture 'and the, `member 15. This causes the dampers to rerl'iainl in their draft producing Position' aS '101.1% vmotor 50 is energized through the circuit previthe frictional engagement produced by the biasing effect of spring 55 exists. 19 and 80 are now closed by reason of the movement of member 12 to the left. Members 54 and 63 are so related that when reduced portion 15 of member 12 extends through aperture 16 the recess 64 has not quite reacheda position which permits the arm 6| to move upwardly out of engagement with ontact 62.

Upon a retstoration of power to the lines ||0 and the damper motor will revert back to automatic operation. A circuit through the lifting coil 52 will be established regardless of the temperature of the space being heated and of the heating chamber, this circuit being as )follows: from line ||0 through conductors |10?l |1|, switch; members and 19, conductors |12, |39, |36, contact 62, switch arm 6|, conductor |31 through the lifting coil 52 and through conductor |38 to the line Damper motor 5| now causes shaft 44 to commence rotating in a clockwise direction and as soon as this happens the frictional engagement between members 15 v and Switch elements aperture 16 is relieved and spring 13 causes member 12 to move to the right thus breaking the circuit through

switches

19 and 80. If the room thermostat 90 is not satisfied at this time and the temperature of the heating chamber is below the value required to open switch 23, it will be apparent that the damper motor will remain energized, holding the dampers in their draft producing position. If, however, the room thermostat is satisfied or the temperature of the heating chamber is high enough to cause switch 23 to move to open position the damper motor will be deenergized as soon as

switch elements

19 and 80 are-moved apart and biasing spring 55 will cause a return of the dampers to their draft retarding positions. i

In the summer-time when there is no fire in the furnace it may be desirable in hot Weather to operate the blower I6 to circulate unheated air through the heating chamber of the furnace and the space under control of the thermostat 90 whenever the temperature of the space is above a certain predetermined value. In order to do this switch member is rotated through 180 from the position shown, in which position switch blades 86 and 81 are in engagement with

contacts

88 and 89, respectively. i

contacts

94 and 95, respectively, causing relay coil 98 to be energized, as previously ex-. plained, whereupon the switch arm |0| is moved lout of engagement with contact |05 and the. circuit through the blower motor is interrupted.

It is thus seen that during the summer-time the blower motor operates only when-the room :tem-

perature reaches a .certain high value assuming this switch 85 to be in its summer position.v

"In the summer position of switch 85 the damper ously described' when the switch 85 was in rits firing position since switch blade 81 is engaged with contact 89 in both the firing and summer positions of the switch actuator 85. it is desired to burn some trash in the furnace to raise the temperature of the space during an unseasonable cold spell duringthe summer-time for example, there will be sufficient draft through damper motor will be deenergized and the damper arm 40 moved back to the position' illustrated by reason of the biasing effect of spring 55. The room thermostat 90, if the temperature of the space has fallen low enough, will cause a cir- Thus, if

' of the space when the switch is moved to a seccuit through the relay coil 98 to be established aslpreviously explained and cause the switch arm lili to move into engagement with contact |04. When the temperature of the furnace reaches a certain high value, which as explained.

, nace by burning ofthe trash will now be' circulated through the space under the control of the thermostat 90 thus raising the temperature to a desirable value.

It will thus be seen that with my system, when switch 84 is in the winter position, or the position illustrated, the energization'of the blower andv damper motors are under the control of the room thermostat and the blower motor is also under thecontrol of the switch 24 responsive to the temperatureof the heating chamber o1' the furnace so that it will -not operate until the tem- Derature reaches a certain high value. The damper motor is also under the control of the switch 23 which causes it to be deenergized upon the attainment of a still further high value in the heating chamber and a third switch 25 is provided for causing operation of the blower motor regardless of the'space temperature should the temperature of the heating chamber for any reason reach a 'dangerously high value,` whereby the heat may be dissipated, upon movement of switch `82' to its second or firing position the damper motor isoperated to place the dampersin draft producing position to facilitate the firing of the furnace, the damper motor still being under the control of th switch responsive to temperatures of the hea ing chamber whereby the damper motor is deenergized should the attendant fail to move the switch 84` back to its normal winter position after he has finished firing the furnace. With the switch 84 in its third or summer position, the dampers are normally held in draft producing position, the damper motor being normally energized andthe blower motor is under the control of the room thermostat but is operated only when the room temperature reaches a certain high value unless the temperature of the heating chamberof the furnace is for some reason raised to a certain value during .the summer-time in which case the damper. motor is automatically deenergized.

While I have illustrated and described the preferred embodiment of my invention it is capable of many modifications as will' be apparent to those skilled in the art and I wish it to be understood that my invention is limited only by the scope of the appended claims.

I claim as my invention: l

1. In a heating system, a warm air furnace, air circulating means for circulating air through the heating chamber of said furnace and through a. space to be heated, a damper forv controlling the draft through fthe furnace, a three-position switch, means for causing .operation of said air circulating means when the temperature of the spacez isbelow a predetermined value and the temperature of the heating chamber is above a l predetermined value and causingthe damper to be moved to draft producing positionwhen the temperature of the space is below -a predetermined value when said switch is in one position, means causing the damper to be moved to draft producing position regardless o f the temperature ond position and means causing operation of said air circulating means when the temperature in the space is above a predetermined value in response to ithe placing of the switch in. a third position.

2. In a heating system, a warm air furnace, air circulating meansy for circulating air through the heating chamber of said furnace and through a space to be heated, a damper for controlling `the draft through the furnace, a three-position switch, means for causing operation of said air circulating means when the temperature of the heating chamber is above a predetermined value and the temperature of the space is below a predetermined value and causing the damper to be moved to draftproducing position when the temperatures of the heating chamber and space are below predetermined values in response to the.

placing of the switch in one position, means causing the damper to be moved to draft producing position when the temperature of the heating chamber is below a predetermined value regardless of the temperature of the space, in response to the placing of said switch in a second position, and means causing operation of said air circulating means when the temperature of the space is above a predetermined value in response to 'the placing of the switch in a third position.

3. In a warm air heating system, a warm air ftunace having a heating chamber, air circulat-l ing means for circulating air through said chamber and through a space to be heated, a. thermostat responsive to temperatures in the space to be heated, a switching means having a winter position, a firing position and a summer position, means responsive to movement of said switching means to winter position for causing operation of the air circulating neanswhen the tempera-v movement of the switching means .to firing position to change thecontrol of the damper only to cause the same to be moved to draft producing position regardless of the temperature of the space, and means responsive to the movement of the switching means to summer position to ature of the space is above a predetermined value and to cause movement of thed'ampers to draft producing position.-

4. In a warm air heating system, a warm air furnace having a heating chamber, air circulatcause operation of the fan. whenever the tempering means for circulating air through said chamber and through a space to be heated, a thermostat responsive to temperatures in the space to be heated, a switching means having a winter position, a firing position and a summer position, means responsive to movement of said switching means to the winter position for causing operation of said air circulating means when the temperatureof the heating chamber is above a predetermined value and the ltemperature of the space is below a predetermined value and causing movement of the damper to draft producing position when the temperatures of the heating chamber and space are below predetermined values, means responsive to the movement of the 'switchingmeans to firing position to change the control of the damper only to cause the same to be moved to draft producing position providing the temperature of the heating chamber is below a certain predetermined value regardless of the temperature of the space, and means responsive to the movementl of the switching means to summer position to cause operation of the fan whenever the temperature of the space is above a'. predetermined value and to cause mov-ement of the dampers to draft producing position whenever the temperature of the heating chamber is below a predetermined value.

5. In a heating system, a warm air furnace, means for circulating air through the heating chamber of said furnace and through a space to be heated, a damper for ,controlling the temperature of said heating chamber, a motor for operating said damper, space temperature responsive means, a three-position switch, a first temperature responsive switch, a second temperature responsive-switch, said first switch closing upon the attainment of a predetermined temperature in the heating chamber and the second switch opening upon the attainment of a higher predetermined temperature in the heating cham-I ber, means placing the air circulating means under the control of the space temperature responsive means and the first temperatiue responsive switch and means placing the damper motor under the control of said space temperature responsive means and said second temperature responsive switch with the three-position switch in one position, means placing the damper motor under control of the second temperature responsive switch alone whereas the space temperature responsive means and the rst temperature switch retain control of the air circulating means in the second position of the threeposition switch, and means placing the air circulating means under control of the space temperature responsive means alone while the second temperature responsive switch retains control of the damper motor in the third position of said switch. Y I

6. In a heating system, a warm air furnace, means for circulating air through the heating chamber of said furnace and through a space to be heated, a. damper for controlling the temperature of said heating chamber, a motor for operating said damper, space temperature responsive means, a three-position switch, a first temperature responsive switch, a second temperature responsive switch, a third temperature responsive switch, said first temperature responsive switch closing upon the attainment of a predetermined temperature in the heating chamber, said second temperature responsive switchA being normally closed and opening in response to the attainment of a higher temperature in the heating chamber, said third temperature responsive switch being normally open and closing in response to the attainment of a still higher temperature in said heating chamber, means whereby the air circulating means is under the control of the space temperature responsive means and the first temperature responsive switch and whereby the damper motor is under the control of the space temperature responsive means and said second temperature responsive switch with the threeposition switch in one position,'means whereby the damper is under control of the second temperature responsive switch alone whereas the space temperature means and the first temperature responsive switch retain control of the air circulating means with the three-position switch in a second position, means whereby the space temperature responsive means alone may control the air circulating means while the second temperature responsive switch retains control of the damper motor in the third position of said switch,l and means independent of said threeposition switch for causing operation of said air circulating means in response to the closing of said third temperature responsive switch.

7. In an air conditioning system, a warm air furnace, means for circulating air through the heating chamber of said furnace, a damper for controlling the draft through said furnace, a motor for operating said damper, a summerwinter switch, means causing said motor to operate to open said damper in response to the attainment of a low predetermined temperature in said space and causing said air circulating means to operate in response to the attainment of a low predetermined temperature in said space and the attainment of a high predetermined temperature in said heating chamber when said switch is in the winter position, means causing said damper motor to open the damper in response td movement of said switch to summer position, means causingA said air circulating means to operate in response to the attainment of a high predetermined temperature in said space when said switch is in summer position, and means, independent of .said switch, for causing said damper motor to close said damper in response to the attainment of a high predetermined temperature in said heating chamber.

8. In a temperature controlling system, a warm air furnace including a -heating chamber and means for circulating air through said heating chamber and through a space to be heated, controlling means rendering said circulating means selectively responsive either to the attainment of a low predetermined temperature in said space Jor to the attainment of a high predetermined temperature in said space, draft controlling means for controlling the draft through said furnace, means for causing operation of said draft controlling means to cause maximum draft through said furnace in response to the attainment of a low predetermined temperature in said space when said controlling means is operated to render said air circulating means responsive to the attainment of a low predetermined temperature in said space, and means causing operation of said draft controlling means to normally maintain maximum draft through said furnace when said controlling means is operated to render said air circulating means responsive to the attainment of a high predetermined temperature in said space, but causing operation of said draft controlling -means tocause minimum draft through said furnace in response to the attainment of a high predetermined temperature in said heating chamber.

GEORGE D. BOWER.