|Publication number||US2271487 A|
|Publication date||Jan 27, 1942|
|Filing date||Mar 16, 1939|
|Priority date||Mar 16, 1939|
|Publication number||US 2271487 A, US 2271487A, US-A-2271487, US2271487 A, US2271487A|
|Inventors||Nessell Clarence W|
|Original Assignee||Honeywell Regulator Co|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (13), Classifications (7)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Jan. 27, 1942. C. w, NESSELL 2,271,487
ZONE AIR CONDITIONING SYSTEM Filed March 16, 1959 Patented Jan. 27, 1942 2,211,487 zoNE Am CONDITIONING SYSTEM Clarence W. Nessell, Dayton, Ohio, assigner to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a. corporation of Delaware Application March 16, 1939-, Serial No. 262,192
My invention as herein disclosed relates to control, particularly of temperature, in heating, ventilating, andair conditioning installations and the like, the invention being directed more especially to zone type systems. In such systems individual control instruments are used to control particular sections or zones of a building enclosure and the instruments usually also control equipment for treating or circulating air or other uld medium such as steam or water. When all the control instruments are satisfied, all the zones are ordinarily closed olf and dueto the sudden interruption in iiow of fluid medium away from the source a dangerous condition may quickly develop particularly if the source is a warm air furnace or a boiler, requiring that warm air or steam be released. My system comprehends opening one or at least one zone as soon as all the control instruments are satisfied thus preventing the development of such a condition and thereby eliminating the need of means for relieving it.
My invention is particularly adaptable to warm air systems employing an perature of which may quickly rise to a danger ously high value if stopped at the same time that the control instruments become satised. f
An object of my invention is to provide improved means for disposing of surplus uid conditioning medium available in zone type conditioning systems when all the zones are satised to prevent the development of a dangerous condition at the source of the conditioning medium.
Another object is to cause at least one zone of a zone type conditioning system to open when all zones are satised to prevent the 'sudden and immediate interruption of iiow of conditioning medium away from the source.
- VAmother object is the provision of a zone type warm air conditioning system having means for automatically opening one zone as soon as all zones are satisfied and continuing to circulate air away from the furnace to prevent the temperature rising too high.
Another object is the provision of zone type warm air conditioning system including a furnace having an economizer, a fan responsive to temperature of the economizer, and means to open at least one zone as soon as all zones are satisfied so that the fan can continue to -circulate air away from the furnace until the economizer has cooled. It is also an object of my invention to again close all the zones when the economizer has cooled.
economizer, the temair circulation is suddenly Another object of -my invention is to provide a warm air-heating system of the zone type wherein one zone opens immediately after all zones are satisfied, the said one zone being controlled from a furnace temperature responsive switch so that in the summer time when the furnace is not heated the zones all operate norma'lly, the furnace fan operating whenever any zone is demanding fan operation.
The single gure of the drawing represents diagrammatically a zone-type gas red warm air heating system having my invention embodied therein.
Referring to the drawing, I have shown at I0 a warm air furnace of a known type comprising an outer .casing Il forming a casing surrounding a combustion chamber I2, the upper part of the casing II forming a furnace bonnet. A second casing I3 may be formed as a part of the casing II and form an inlet chamber for air to bel circulated through the casing II and heated therein. The combustion chamber necting with an economizer I5 locatedl within the return air chamber or casing I3. The economizer I5 has internal baliies I6 and I1 by means of which three passes are formed which must be traversed by the gases of combustion in passing. through the economizer before being educted therefrom through a stack I8. A distributing duct I9 for conveying warm air II leads to spaces being hea-ted and air may be returned from the spaces being heated to the casing I3 through aA return air duct 20. A fan 2| driven by an electric motor having a terminal box 22' is located within the return air chamber I3 and discharges into the 'casing II. Air returned through the return air duct 20 passes over the economizer I5 to be pre-heated thereby and is then forced through the casing Il fan 2|. l
The particular furnace which I have disclosed 'is a gas fired furnace and within the combustion chamber- I2 is a gas burner 25 which is supplied with fuel through a conduit-26. Interposed in the conduit 26 is an electric gas control valve 21. Adjacent the burner 25 is aconstantly burning pilot burner 28 which is continuously supplied with fuel through a tube 29 communicating with the conduit 26 ahead of tlie valve 21. Numeral 30 designates a safety pilot comprising a bimetal element 3| whichv is normally flexed into engage- -ment with a fixed electrical contactj32 .by heat from the flame of the pilot burner.
The air distributing duct I9 has anumber of branch ducts 35, 36 and 31 which lead to differ- I2 has a flue I4 confrom the casing by the ent sections or zones of the building which I have designated as zones A, B and C. The supply of heated air to each zone is controlled by a separate thermostat and zone damper. The supply of air to zone A is controlled by a damper 39 located in the branch conduit 35. The damper 39 is driven by means of an electric damper mo-I tor 40 which may be constructed similarly to the damper motor disclosed in the patent of R. W. Johnson No. 1,835,307. The motor 40 drives a crank-arm 4| which is connected by means of a linkl 42 to an operating lever 43 which directly actuates the damper. The connections between the damper motor and the damper are such that when the motor 40 turns the crank-arm 4| through 180, the damper 39 is moved .through 90, the damper requiring a movement through 90 to adjust it from open to closed position or vice versa. Power for the motor 40 is supplied by wires 44 and 45 and it is controlled by wires' connecting to terminals 46, 41 and 48. Motor 40 is of the type which always rotates in the same direction and each time it isenergized, it moves the crank-arm 4| through 180 before stopping. Motor 40 also drives a cam 49 actuates a switch blade 50 cooperating with a xed electrical contact The cam 49 has a notch 52 so arranged that whenever the motor 40 moves the damper 39 into open position, the switch blade 5| drops into the notch so as to come .into engagement with the electrical contact 5|. The'switch 50 forms an auxiliary switch from which the operation of the furnace is conf trolled as will presently be described.
The motor 40 associated with zone A is controlled by a thermostat 55 located in zone A. The thermostat 55 comprises a bimetal element 56 arranged to operate a switch arm 51 cooperating with fixed electrical contacts 58 and 59. The thermostat 55 is of a known type which operates to cause the blade 51' to engage the conwhich/.25
position when blade 51 engages the hot contact, that is, contact 58. I
The damper, auxiliary switch, and thermostat of zones B and C are identical with those of zone A and therefore they need not be described again, corresponding elements in zones B and C being numbered the same as in zone A but having a distinguishing letter identifying the zone with which they are associated.
Numeral 10 designates an electrical relay comprising a coil winding 1| cooperating with an armature arranged to actuate a pair of switch blades 12 and 13, the blades being moved to the left when the coil 1| is energized so as to engage the fixed electrical contacts 14 and 15, respec' tively. When the coil 1| is deenergized, the blade- 13 engages a xed electrical contact 16. Numeral 11 designates a second relay comprising a coil winding 18 cooperating with an armature arranged to actuate a-pair of switch blades 19 and 80 which are moved to the left when the coil is energized, the blade 80 engaging a fixed contact 8| when coil 18 is energized. -When coil 18 is deenergized blade 19 engages a fixed contact 82 and blade 80 engages a fixed contact 83. Power for operation of the relay 10 is supplied by a tact 58 at a predetermined temperature which may be 72, for example, and to engage the contact 59 at a predetermined temperature which may be one or two degrees lower as 70, for ex ample. The contact 58. may be called the hot contact and contact 59 may be called the cold contact. When the blade 51 engages either the hot or cold contact, the motor 40 may bevoperated to either its open or closed position, depending upon the position of the pole changer 60. The pole changer 60 performs the function of a reversing switch, comprising poles 6| and 62 which are connected to switch blades 63 and 64 and poles 65, 66 and 61. The blades 63 and 64 are connected'so as to move together and they have one position wherein they are in contact with poles 65 and 66, respectively, and they have another position as shown in dotted lines wherein they are in contact with poles 66 and 61, respectively. During the winter time, the pole changer 60 is in the position shown and in this position contact 58 is connected to motor terminal 41 and contact 59 is connected to motor terminal 48, as will become apparent later when the electrical circuits are traced. Whenthe pole changer is in its summer or dotted line position, contacts 58 and 59 are connected'to motor terminals 48 and 41, respectively. In the winter time when blade 51 engages contact 59, motor 40 is operated so as to move damper 39 to open position and when blade 51 engages contact 58 motor 40 operates damper 39 to closed position. In the summer time, the action is the opposite, the motor 40 -operatingthe damper 39 to open step-down transformer 84 comprising a primary winding 85 and a secondary winding 88. Numerals.81 and 88 designate a pair of line conductors which may be connected to any suitable source of power and primary winding of transformer 84 is connected to line conductors 81 and 88 by wires 89 and 90, respectively.
Cooperating in the control of my system are thermostatic switches 9| and 92. These switches are of a known type, the switch 9| comprising a mercury switch tube 93 which is actuated by a helical thermostatic element 94 located in the bonnet of the furnace I0 so as to be responsive to the temperature therein. Mercury switch 93 is normally closedand is only opened when a relativelyA high temperature occurs within the bonnet at which it is no longer desired that fuel be suppliedto the burner 25. 'I'he switch 9| forms a high limit switch as 'will presently "ecome apparent, The switch 92 is of the same type comprising a mercury tube 95 which is operated by a helical thermostatic element 96 located in the stack |8 in a position so as to be responsive to the temperature ofthe products of combustion passing through the economizer I5. The mercury switch 95 is moved to closed position whenever the temperature to which element '96 responds is at a high enough value to insure that the air passing through the furnace has been heated sumciently so as to heat the space when admitted thereto.
Power for operation of the valve 21 is supplied by a transformer 91 which is similar to the trans-- For winter operation switch blade |02 is in its winter position engaging contact |0| and the pole changers 60 are in the position show n. Whenever the blade of any one of the zone thermostats engages with its cold contact, its associated damper is opened and the furnace is started in operation. Assuming that the temperature in zone A, for
example, falls to 70 causing blade 51 to engage with contact 59, a circuit for energizing motorv motor operates through 180 degrees so as to move the damper 39 through 90 degrees into its open position. Cam 49 lis also moved through 180 degrees so as to close switch 50 which completes a circuit energizing relay 10, this .circuit being as follows: from secondary windingli of transformer 84 through a wire I I I, wire II2, wire I I3, contact blade 50, wire II4, contact 82, blade 19, wire II5, wire H6, coil 1|,.and wire ll1'back to secondary winding 86. Energization of coil 1I causes blade 12 to move into engagement with contact 14 and blarde 13 moves into engagement with contact 15. Closure of switch 12 energizes and opens the electric valve 21 through the following circuit: from secondary winding 99 of transformer 91, through a,wire |20, valve 21, wire I2I, safety pilot 30, wire'l22, mercury switch 93, wire |23, switch blade 12, contact 14, wire |24 back to secondary winding 99. As soon as valve 21 opens, fuel is supplied to the burner 25 where it is ignited by the pilot burner and heating of the furnace begins. As soon as the temperature of the stack I8 has Arisen to a. sumciently high value to cause closure of mercury switch 95, the motor of fan 2l is placed directly across the line so as to start operation of the fan and circulation of warm air through the zone A. The circuit for starting the fan is as follows: from line conductor 81 through a wire |25, mercury switch 95, wire |26, wire |21, motorterminal box 22, and wire |28 back to line conductor 88. 'l Warm air is forc'ed through the duct I9 and branch duct 35 into the zone A until the temperature in zone A rises to 72 at which thermostat blade 51 will engage the contact 58. However, before the thermostat of zone A becomes satisfied, the thermostats of the other zones may call for heat opening their respective dampers in the same manner that the damper of zone A was opened.
The wiring of zone. A is slightly different than' that of zones B and C inasmuch as the relay 11 is associated with the control of zone A. It will be noted that in zone A motor terminal 46 is connected to the thermostat 55 by a circuit extending through relay switch 80 while inr zones IB and C, the motor terminal 46 is connected directly to the thermostat 56. The circuits whereby the thermostats of zones B and C control their respective damper motors are obvious in view of the description ofzone A. The auxiliary switch of either zone B or C may energize relay through circuits which are obvious. The furnace will be kept in operation as long as any one thermostat is calling for heat. Let iti-be assumed that the Y tact 83, and wire I I0 back to thermostat 56. Comthermostats of all the zones are satisfied and that the thermostat of zone A was the last to l become satised having just causo-l blade 51 to engage with .contact 58. This willcomplete a circuit for motor 40 as follows: from blade 51 of thermostat 56 to contact .58, wire-|30, pole 6I,v
blade 63, pole 65, wire I3I, wire |32, motor terminal 41, motor terminal 46, wire |09, blade 80, conpletion of this circuit will cause motor 40 to move the damper 39 into the position shown and open the switch 50. lOpening' of switch 50 will deener- `gize the relay 10. Deenergization of relay 10 will cause closure of valve 21 and termination of operation of the burner 25. The temperature within the stack I8 and in the economizer I5 will, however, not immediately drop due to the residual heat remaining in the furnace and therefore the fan 2| will remain in operation for an appreciable time. To provide for disposal of this residual heat remaining in the furnace and to preventthe economizer from becoming'too hot, I provide an arrangement whereby one damper which happens to be the damper of zone A moves to open position as soon as the thermostats become satisfied. Thus when relay 10 is deenergized, blade 13 moves into engagement with contact 16 completing a circuit energizing relay 11 as follows: from line conductor 81 to wire |25, mercury switch 95, wire |26, wire |33, blade 12, contact'16, Wire |34, coil 18, and wire |35 back toL lin'e conductor 88. Energization of relay 11 causes blade 19 to move out of engagement' with contact 82 and causes blade 80 to moveinto engagement with contact 8| completing a circuit connecting terminals 46 and 48 of motor causes motor 40 to again operate damper 39 into an open position so that the warm air being forced out of the furnace by the fan 2| can pass through the branch duct 35 into zone A. Relieving the A furnace of its residual heat in this manner prevents the temperature therein and particularly the temperature of the economizer from rising to an undesirably high value as it would do if the fan were suddenly stopped at the. same time that burner operation is discontinued when all the thermostats become satisfied. The additional heat supplied to zone A will cause the thermostat blade 51 to remain in engagement with the hot contact for alonger time. Closure of switch 50 when the damper 39 was opened in response to'energization of relay 11 will not now cause energization of relay 10 because the original circuit whereby relay 10 was energized through switch 50 is now interrupted due to the fact that blade 19 is now out of engagement with contact 82. The fan will now continue in operation until the temperature of the stack has fallen to a low enough value to cause opening of mercury switch 95. When mercury switch opens, relay 11 will be deenergized placing motor 40 back under control of the thermostat 56. Blade 51 may be in engagement with contact 58 at this time inasmuch previously described when damper 39 was origin nally opened.
' It is to be noted that should zone -B or C demand heat while zone A is open, having been opened in response to switch 95, relay 10 will be energized, relay 11 will be deenergized and normal zone control operation will be resumed.
During the foregoing operation,.the summerwinter switch |02 was in engagement with contact |0I, and each of the pole changers 60 were in the position shown in the drawings. For summer operation each of the pole changers 60 are moved into their summer positions and switch |02 is moved into engagement with contact |04. Obviously, transformer 91 is not now energized and therefore inasmuch as valve 21 cannot be energized and opened, the heating equipment will not operate in the summer time. When the pole changers 60 are in their positions as shown in broken lines, operation of the damper motors in response to the thermostats is reversed, as previously described. For example, when the tem-- perature in zone A rises to 72,Iblade 51 will engage contact 58 and motor terminals 48 and 46 will now be connected as follows: from blade 51 through contact 58, wire |30, pole 6|, blade 63, pole 66, wire |01, wire |08, motor terminal 48, motor terminal 46, wire |09, blade 80, contact 83, wire ||0, back to thermostat 56. Completion of this circuit will cause motor 40 to open the damper 39 and close switch 50.. Closure of switch 50 Will cause energization of relay 10 in the same manner as previously described. Upon energization of relay 10, blade 13 will be moved into engagement with contact 15 which will place the motor of fan 2| directly across the line as follows: from line conductor 81 through wire |05, switch blade |02, contact |04, wire |31, contact 15, blade predetermined value.
temperatures in their respective zones rise to a Each damper controls its individual zone and the fan operates whenever any one zone is demanding cooling. In the summer time when all the thermostats are satisfied, the fan immediately stops. Howevenif the fan switch should become short circuited in the summer time so as to cause fan operation when all the dampers are closed, the shorting of the fan 'switch will as well cause opening of the damper of zone A so as to take care of the air y being circulated by the fan in this event.
13, wire |33, wire |21, motor terminal box 22,
and Wire |28 back to line conductor 88. The fan will now continue in operation as long as relay 10 is energized and relay 10 will be 'energized Whenever the thermostat of any one zone has caused its associated damper to move to open position. Relay 11 will never be energized in the summer time because as there is no heating in the furnace the mercury ,switch 95 will not become closed, energization of relay 11 depending upon mercury switch 95. It is to be noted, however, that should the mercury switch 95 become short circuited in the summer time so as to' cause fan operation when all the zone dampers are closed, the damper of zone A will automatically open to release the air being circulated by the fan. energization of relay 11 as Well as operation of the fan, the circuit being as previously pointed out. Energization of the relay 11 will cause motor 40 to move damper 39 to open position as has also been described. Thus the contingency of the fan operating at an undesirable time is taken care of by causinga damper to automatically open at such time.
summarizing the operation of my complete system, it is to be seen that during the Winter time any zone thermostat may open its associated damper in response to a demand for heating which will in turn cause operation of the furnace. Operation of the furnace willlcontinue as long as any one thermostat is demanding heating and when all of the thermostats are satisfied, operation of the fan'will continue under control of the mercury switch 95. As soon-as all the thermostats are satisfied, the damper of zone A will open so that the residual lheat being forced away from the furnace by the fan will be conveyed to zone A. AS soon as the tempera-ture of the stack has dropped to a predetermined value, mercury switch 95 will open stopping the fan and causing reclosure of- 'ne damper of zone A so that all zones Will now remain closed until there is another demand for heating by one or more of the zones. In the summer time, the heating equipment is rendered inoperative and control of the dampers in response to the thermostats .is reversed so that the dampers are opened when the Short circuiting of switch 95 will cause It should be apparent to those skilled in the 4art from the foregoing that I have provided a novel and useful system whereby the adaptability oi a zone type system is increased. With my arrangement a la'rge overrun of temperature at the heat source is avoided when all of the zones become satisfied inasmuch as one zone opens as soon as all of them are satisfied. Instead of waiting for an undesirably high temperature to occur at the source of heat before relieving it, my system operates in a manner to preclude such a dangerous condition ever occurring and there is therefore no need of special means for relieving it.
I'he single representative embodiment of my invention which I have disclosed is illustrative and my invention is to be limited only in accordance with the scope of the appended claims.
I claim as my invention:
1. In a uid distributing system, in combination, a source of uid medium supply, means for circulating fluid medium to a plurality of different regions, a condition` responsive control device associated with each region and controlling the supply of iiuid medium thereto so as to shut olf the supply whenever said condition exceeds a limiting value, an electrical relay controlling said source of fluid medium supply and energizable in response to opening of each of said devices, means responsive to a condition at said source for placing said last named condition responsive means in control of at least one of said devices when said relay is deenergized.
2. In a heating system for a building having a plurality of zones, in combination, a source of l heating medium supply, means for circulating said medium to said zones including a device for forcing such circulation, means responsive to a condition at said source for controlling said device, thermostatically controlled means in each zone for controlling the supply of said medium thereto so as to shut olf the supply whenever the zone temperature is above a predetermined value, and means operative `upon closure of all said zone supply controlling means to transfer at least one of said zone supply controlling means from its associated thermostatic control to control of said condition responsive means.
3. In a heating system for a building having a plurality of zones, in'combination, a source of vheating medium supply, means for circulating ing to closed position wherever the zone temperature is above Aa predetermined value, relay means responsive to each of said zone supply controlling means for controlling said source, and means operated by said relay means upon closure means, a second relay of all said zoneF supply -controlling means to transfer at least one of said zone supply controlling means from its associated thermostatic control to control of said condition responsive means.
4. In a'iluid distributing system, in combination, a source of iiuid medium supply, means for circulating said medium toa plurality-of different regions, a condition responsive control device associated with each region and controlling the supply of fluid medium thereto, an electrical relay controlling said source and energizable in response to opening of each said device, means 'responsive to alcondition at said source operable to control said circulating means, a second electric-al relay controlling one of said devices, and a circuit for energizing said second relay including a switch controlled by said first-mentioned relay and a second switch controlled by said condition responsive means.
5. In a fluid distributing system, in combination, a source of fluid medium supply, means for circulating said medium to a plurality of different regions, damper means associated with each region for controlling the supply of fluid medium thereto, means in each region responsive to a condition indicative of the need for supply of said medium for controlling said damper means, an
electrical relay controlling said source and energizable in response to opening of each said damper means, means responsive to a condition at said source operable to control said circulating operable to control certain of said damper means to open position and siL multaneously interrupt control of said certain damper means by said regional condition responsive means, and an energizing circuit for said second relay controlled by said source condition responsive means and said first relay.
6.`Inl a fluid distributing system, tion, a source of uid medium supply, means `for circulating said medium to a plurality of different regions, damper means associated with each region for controlling the. supply of fluid medium thereto, means in each region responsive to a in combinacondition indicative of the need for 'supply of said medium for controlling said damper means, an electrical relay controlling said source and energizable in response to opening of ,each said damper means, means responsive to a condition at said source operable to control said circulating means, a second relay operable to control certain of said damper means to open position and simultaneously interrupt control of said certain damper means by said regional condition responsive means, and an energizing circuit for said second relay including a switch'controlled switch operated by said first-mentioned relay so as to close upon deenergization thereof.
'7. In a warm air heating system for a building havinga plurality of zones, in combination, a warm air furnace having a stack and including an economizer arranged to give up heat to air being heated at the furnace, said economi'zer conveying gasesof combustion of the furnace to the stack, means comprising a fan for circulating air to the' zones, damper means controlling the air supply to each zone, a thermostat controlling each damper means, means responsive to a condition indicative of the temperature in said economizen said last means controlling said means to by said condition responsive means and a second fan whereby said fan is' operated to force air over said economizer whenever said economizer is hot, an electrical relay for controlling said furnace and energizable upon opening of each said damper means, deenergization of said relay to remove certain of said damper means from control of the respective thermostats and place said ycertain damper means under control of said last named condition responsive means.
8. In a warm airheating system for a building having a plurality of zones, in combination, a furnace, a fan for circulating warm air from said furnace to said zones, damper means for regulating the supply of air to each zone, a thermostat'in each zone for controlling its associated damper means, a relay for controlling said furnace, switches operatively connected to said damper means so as to be closed when said damper means are for said relay including said switches in parallel, a thermostat 'at -said furnace for controlling operation of said fan, a switch operated to closed position by said relay upon deenergization thereof a circuit including'said last-mentioned switch, and effective when energized to transfer control of certain of said damper means from said zone thermostats to said furnace thermostat.
9. In a warm air heating system for a building having aplurality of zones, in combination,i a furnace, a fan for circulating warm air from said furnace to said zones, a thermostat at said furnace for controlling operation of said fan,
damper means for regulating the supply of air to each zone, thermostatic means in each zone for controlling its respective damper means, and means operable upon closure of all said damper means in response to said thermostatic means to transfer control of certain of said .damper means from said, zone thermostatic means to said furnace thermostat.
10. In a system for distributing a temperature changing fluid among a plurality of zones, damper means for controlling the supply of fluid to each zone, means for forcing circulation of said uid, temperature responsive means in each zone for controlling said damper means', means for energizing said circulation forcing means, and means effective upon closure of all said damper means t0 transfer' control of certain of said damper means from said temperature responsive said energizing means.
11. In a warm air heating system for a building havingi a plurality of zones, in combination, a,
furnace, a fan for circulating warm air from said furnace to said zones, a thermostat at said furnace for controlling operation of said fan, damper means for regulating the supply of air to each zone, thermostatic means in each zone for controlling its respective damper means, relay means responsive to eachof said damper means for. controlling said furnace, means operable upon closure of all said damper means in response to said thermostatic means to transfer control of certain 'of said damper means from said zone thermostatic means to said furnace thermostat, and means effective upon opening of said damper means under control of said furnace thermostat to interrupt control of said relay means by said certain damper means.
CLARENCE w. NEssELL.
and means operable upon opened, an energizing circuitl
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US2963225 *||Oct 1, 1956||Dec 6, 1960||Ewing Shelton Thayer||Heating apparatus|
|US3223325 *||Feb 20, 1964||Dec 14, 1965||Jacques Letourneau||Domestic heating system|
|US3297250 *||Mar 16, 1964||Jan 10, 1967||Multi Zoner Inc||Heating and cooling temperature control for a plurality of zones|
|US4381850 *||Oct 16, 1981||May 3, 1983||Grant Willie T||Automatic air register damper|
|US4401260 *||Dec 9, 1981||Aug 30, 1983||Grant Willie T||Self-operated air register damper|
|US4417687 *||Jun 7, 1982||Nov 29, 1983||Grant Willie T||Multi-blade automatic air register damper|
|US4506829 *||Jun 24, 1983||Mar 26, 1985||Grant Willie T||Variable speed damper means|
|US4518116 *||May 14, 1984||May 21, 1985||Grant Willie T||Automatic damper operator|
|US4557418 *||Dec 19, 1983||Dec 10, 1985||Leemhuis Louis J||Energy conservation conditioned air system|
|US4646962 *||Oct 1, 1985||Mar 3, 1987||Grant Willie T||Rotational means for automatic damper means|
|US8621884||Nov 12, 2009||Jan 7, 2014||Hoffman Enclosures, Inc.||AC unit with economizer and sliding damper assembly|
|US20100126208 *||Nov 12, 2009||May 27, 2010||Scott Dean Stammer||AC Unit with Economizer and Sliding Damper Assembly|
|WO2010039964A1 *||Oct 1, 2009||Apr 8, 2010||Mclean Midwest Corporation||Air conditioning unit with economizer and filter assembly|
|U.S. Classification||236/9.00A, 236/11, 237/2.00R|
|International Classification||F24D5/04, F24D5/00|