US2154051A

US2154051A - Filter protection

Info

Publication number: US2154051A
Application number: US186565A
Authority: US
Inventors: William W Martenis
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1938-01-24
Filing date: 1938-01-24
Publication date: 1939-04-11
Anticipated expiration: 1956-04-11

Description

April 11, 1939. w, w RTENI 2,154,051

FILTER PROTECTION Filed Jan. 24, 1938 INVENTOR "VilliounW Marienis ATTORNEY Patented Apr. 11, 1939 PATENT OFFICE FILTER PROTECTION William W. Martenis,

Minneapolis, Minn, as-

signor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn.,

( Delaware a corporation of Application January 24, 1938, Serial No. 186,565

15 Claims.

The present invention relates generally to warm air heating systems and pertains more particularly to the elimination of the fire hazard attendant to the use of combustible air filters in such'systems.

In present warm air heating systems, it is customary to employ a fan for enforcing air circulation thus making possible the use of air filters for the purpose of removing foreign matter which may otherwise contaminate the air stream. It is quite general also to employ an economizerwhich is a tortuous passage-way through which the gases of combustion pass on the way to the stack or flue. The "economizer is arranged in heat. exchangerelation with the return air so as to preheat it. As the trend in modern furnace design is toward placing all the elements associated with the furnace in as small a casing as possible in the interests of compactness and economy of space it is usual that the filters and economizer are located in close proximity in the return air section of the furnace. The economizer temperature is rather high and particularly at times when the forced air circulation occasioned by the furnace fan fails there is grave danger of igniting the filters which ordinarily are made of combustion material. The fire hazard is especially serious when the return air ducts are formed between wooden joists and flooring of frame buildings. Furnace fan failure may occur as a result of the fan belts breaking or failure of power to the driving motor. From experience it has. been found that upon fan failure the economizer temperature quickly rises to a temperature 35 at which ignition of the filter material may take place. Failure of power for the fan motor is decidedly serious injthe case of coal fired hot air furnaces inasmuch as the fire continues after the fan stops and the economizer temperature quickly rises to the danger point.

It is the above described serious fire hazard attendant to the use of filters in furnace fan warm air heating systems which it is the primary objective of my invention to overcome.

Among other objects of my invention is to provide positive means for isolating the filters from the furnace in a warm air heating system whenever the forced air circulation occasioned by the furnace fan fails.

Another object is to provide a damper closin device in the return air chamber between the filters and the furnace in the above described system, the damper device to be held open only when forced circulation is" being provided by the 55 fan. Concurrently with this object it is a further object to provide a power failure motor for operating the damper device arranged to cause closing of the damper device whenever the motor is deenergized.

It is another object of-the invention to control the power failure motor referred to in the previous object from a sailswitch located in the path of the enforced air circulation.

Other objects and purposes of the invention will become apparent from an examination of the drawing and the more detailed description following.

The single figure of the drawings represents somewhat diagrammatically a warm air heating system having my invention incorporated therein.

- Referring to the drawing, numeral i0 represents generally a furnace casing forming part of a warm air heating system having conduits ii and I2 for conveying air to and from the casing of the furnace respectively. The conduits i2 and Il may have branch conduits l3 and id as shown for conveying air to and from various rooms of a building as shown. The furnace casing in is divided into three separate compartments or chambers designated l6, l1, and I8. The chamber l6 houses an electrically driven oil burner i9 of conventional type and located within the chamber i1 is a furnace or combustion chamber proper 20 which serves to heat the air within the chamber H. The nozzle of the oil burner 19 extends from the chamber I6 through the chamber ii and into the combustion chamber 20. The oil burner l9 has

electrical terminals

22 and 23 which connect to electrical conductors for supplying power to the oil burner. Within the combustion chamber 20 and adjacent the end of the nozzle of the oil burner is located a pipe 2| communicating with a supply of gas whereby a pilot flame 25 may be kept constantly burning for igniting the fuel from the oil burner whenever the burner is to be put into operation. Located adjacent to the pilot flame 25 so as to be heatedthereby is a bimetallic thermostatic element 25 forming with contact 21 an electrical switch serving as a safety device to shut oil the oil burner whenever the pilot flame should become accidently extinguished. The control instruments and wiring of the apparatus will be presently described.

The chamber l8 of the furnace casing forms a return air chamber through which the cooler air from the spaces being heated is passed before being forced over the furnace or heating chamber in the path of the return air chamber l8. Heat from the burnt gases of combustion is therefore given 011 to the return air and serves to preheat the return air on its passage through the furnace casing. The end of the tortuous passage-way in the economizer 2| communicates with a pipe 30 which serves to convey the burnt gases of combustion to av conventional stack or flue. The return air chamber I8 of the furnace casing includes a portion 3| within which are located filters 32 for removing impurities such as dirt and dust with which the air may have become contaminated in the spaces being heated. The filters comprise slabs of any suitable material which will filter out or remove impurities from the air without substantially obstructing the passage of air therethrough. The slabs 32 of filter material are supported between supporting members 33 and the walls of portion 3| of the furnace casing. It will be noted that portion 3| has an internal dividing wall 34 which divides it into two portions, the upper end of one of the slabs 32 resting against this internal dividing wall. By reason of the arrangement of the filters they may be removed at will from the furnace casing and replaced by new ones whenever they have become unduly fouled with foreign matter from the stream of air passed thereover. The return air from the spaces being heated is conveyed through conduit through the portion 3| of the return air chamber and past the economizer 2| to be preheated on its way through the return air chamber. At the lower part of the return air chamber is a fan or blower 36 which draws in air from the return air chamber and forces it through a conduit 31 through the air heating chamber I! to conduit 2 and thereby providing a forced circulation of air in the entire system. The fan 36 is of conventional type and is driven by an electric motor 31 through a belt 38 or other similar drive means.

Positioned so as to be affected by the circulation of the air in the discharge conduit 31 of the fan is a member pivoted at 39 having a mercury switch 4| located at the upper end thereof. The elements 40 and 4| form a sailswitch which is closed whenever the enforced circulation of air in the discharge conduit 31 causes the lower part of the member 40 to be moved to the left so that the mercury in the switch 4| engages the electrodes therein.

Positioned between the filter members 32 and the economizer 2| in the return air chamber l8 are a plurality of louvre members forming a damper for closing off the circulation of air which normally passes over the filter members and thence over the economizer. The louvre members 45 are pivotally connected to an operating link 46 so as to be moved in the conventional manner in which dampers are operated. The link 46 is connected by another link 41 to a rack 48 driven by a pinion 49. The pinion 49 is driven by a shaft 50 connected to an electrical damper motor 5| which may be of a conventional type. The damper motor 5| has

electrical terminals

53 and 54 for connecting to electrical conductors for supplying power to the damper motor. The damper operating link 46 has pivoted thereto a lever 56 the opposite end of which is pivoted to a link 51 which is connected to' a coil spring 58 which causes the lever 56 to be biased in a clockwise direction. When the link member 46 has been moved to the right sufficiently to position the louvre members 45 vertically the lever 56 engages a suitablestop member 60. In normal operation the damper motor 5| is energized and through pinion gear 49 and rack 48 retains the link 46 in its extreme right-hand position with the lever 56 engaging stop 60 and the louvres in vertical position. In this position the spring 58 is under tension and should motor 5| become deenergized the spring will move lever' 56 in a clockwise direction and close the dampers by moving the louvres 45 into a horizontal position.

The heating system is primarily controlled by a thermostat generally indicated at 63 which may be located in one of the rooms being heated. The thermostat is of conventional type comprising a circularly arranged bimetallic element 64 connected to a movable arm 65 having a switch contact 66. The switch contact 66 is arranged to make or break an electrical circuit through a fixed contact 61. The system is additionally controlled by

mercury switches

68 and 69 which are operated by a thermostatic element 10 of the helical type arranged to be responsive to the temperature of air being heated within the chamber IT. The thermostatic element 10 is adjusted so as to cause switch 69 to close the circuit therethrough at a predetermined temperature within the chamber Switch 68 is normally closed and is opened by element 10 at a predetermined relatively high temperature. 1

Referring to the electrical wiring connecting the various devices included in the system and the instruments for controlling them, numerals I2 and 13 indicate line conductors connected to an external source of power (not shown). The line conductor 13 is connected by a wire 14 to the motor 31 for driving the fan 36. The circuit to the motor 31 is completed by wire 15 which connects the motor to the switch 69 and the wire 16 which connects switch 69 to the line conductor 12. It will be seen therefore that whenever the thermostatic element 10 causes switch 69 to close, motor 31 operating the fan will be put into operation enforcing the circulation of air through the system.

The electrical circuit for providing power for the oil burner I9 is supplied through a wire 80 connected to the wire 14, a wire 8| which connects the oil burner to the thermostatic switch 26, a wire 82'connecting the thermostatic switch to the mercury switch 68, a wire 83 connecting the mercury switch 68 to the thermostatic switch 63 and a wire 84 connecting the latter switch to the line conductor 12. It will be seen that power is supplied to the oil burner through the above de scribed, circuit whenever the

switches

26, 68, and 63 are in closed position.

Switches

26 and 68 are normally closed and the burner circuit is complete whenever the switch formed by the thermostatic device 63 is closed. Switch 26 acts as a safety device breaking the burner circuit whenever the pilot flame 25 should for some reason become accidently extinguished and switch 68 acts as a high limit operating to break the burner circuit whenever the temperature in chamber |'I exceeds a predetermined relatively high value. Thus the

switches

26 and 68 shut down the system in the event of the temperature becoming too high or in the event of pilot flame failure thereby preventing fuel being forced into the combustion chamber when there is no means of igniting the same and causing consequent danger of explosion.

The circuit for providing electrical energy for operating the damper motor 5| is formed by a connection from line conductor 12 to terminal 54 of the motor, a. wire 8'! which connects to the tion of airin discharge conduit 31 of the fanhas closed the sailswitch M. In normal operation considerable heat is radiated from the economizer 2| which tends to heat the air in chamber l8 and also to raise the temperature in the pertion 3| of chamber ll. When the fan is in operation air is continually circulated through the chamber l8 carrying the heat from the economizer into chamber l1 and preventing the temperature in chamber II from rising unduly high. In conventional arrangements of this type whenever'the fan stops the radiation of heat from the economizer 2| tends to raise the temperature adjacent the filters 32 to a relatively high value at which there is danger of their becoming ignited and causing danger of fire. In my arrangement whenever the fan 36 stops for any-reason the switch I is open and the motor 5| becomes deenergized causing the dampers 45 to close. Likewise dampers 45 close whenever there is a failure of the supply of power to motor II. Closure of the dampers isolates the filters 32 from the economizer and obstructs the transfer of heat by radiation from the economizer to the filters. Positive assurance is therefore provided that'the temperature adjacent the filters will not rise to a high enough value to cause danger of their becoming ignited.

From the foregoing the operation of the apparatus described should be apparent to those skilled in the art. With the partsin the position shown the room temperature has fallen to a low enough value so that the thermostatic device 63 has closed the circuit thus calling for heat to be supplied to the room. The oil burner I! has been started throughthe circuit above described. When the temperature in chamber H has risen to a predetermined value switch 58 closes. Closure of switch 69 causes operation of the fan 36 and the pressure of the air in the discharge conduit i'lcauses closure of switch ll. Closure of this switch energizes the damper motor 5i causing the dampers 45 to be opened. Positive circulation of the air will now continue until the room thermostat'becomes satisfied at which time the burner circuit will be broken. The temperature within chamber I! will then fall to a predetermined value at which switch 89 will open thus deenergizing the fan motor. Upon the fan stopping switch ll will open and damper motor it will be deenergized permitting thedampers 45 tobe closed by the spring 58. It will be seen that at any time during which heat is being supplied to the rooms should the fan It be stopped due to power failure or the breaking of the belt or the like, the dampers 45 willbe closed preventing the temperature adjacent filters I2 rising to an unsafe value. Should switch 69 fail to close upon a rise in temperature in the chamber II when the room thermostat is calling for heat, the fan'motor 31 will not be energized and consequently the dampers .45 M11 not open. It-is apparent therefore that my device insures that at all times the filters provided L within the furnace casing will be protected from thereby set fire to the building. The safety features involved eliminate a'very serious fire hazard and the results are accomplished by a positive acting and easily installed device.

Having disclosed one embodiment of my invention it is to be understood that this disclosure is to be interpreted as illustrative only and the invention is to be limited only as determined by the appended claims. I "claim'as my invention:

/ 1. In a warm air heating system, in combination, means for heating air, means for enforcing circulation of air to and from said heating means, filter means for cleaning the circulating air exposed to heat from said heating means and means responsive to failure of the air circulation enforced by said circulation enforcing means for isolating said filter means from said heating means.

2. In a warm air heating system, in combine-.- tion, means for heating air, means forcing air to circulate to and from said means, filter means for cleaning said air exposed to heat from said heating means, means for isolating said filter means from said heating means, said isolating means being controlled by the forced air circulation provided byvsaid air forcing means so that said filter means becomes isolated from the heating means whenever the forced air circulation ails.

3. In a warm air heating system, in combination, air heating means, means for positively circulating air past said heating means, filter means for cleaning. said air exposed to heat from said heating means, means responsive to temperature of air being heated to control said air circulating means and means controlled in response to the circulation of air for isolating said filter means from the heating means whenever positive air circulation falls.

4. In a warm air heating system, in combination, an air heating means, duct means providing for circulation of air past said air heating means,

, filter means for cleaning air exposed to heat from said heating means, means operable between open and closed posltions'for closing off air circulation past said heating means and isolating said filter means from the heating means, means for enforcing air circulation in said duct means and means energized in response to forced air circulation for maintaining said closing means in open position, said energized means becoming deenergized whenever forced air circulation fails whereby said closing means closes.

5. In a warm air heating system, in combination, a furnace, duct means for conveying air to said furnace and a fan for positively circulatin air past said furnace, filter means adjacent saidfurnace and damper means between said filter means and said furnace, motor means operable when energized to maintain said damper means in open position, means comprising a sailswitch responsive to the air circulation controlling said motor means so that said motor means is deenergized when the air circulation does not close said sailswitch. I

6. In a warm air heating system, in combination, a furnace having a casing including a return air chamber, an economizer in said return air chamber and air filter means located adjacent said economizer, damper means between said filter means and economizer for isolating the filter means from the economizer, means for enforcing responsive to said enforced air circulation for controllingsaid damper means.

present in a large number 'of heating systems 7. In a warm air heating system, combination, a furnace having a casing, means for circulating air to be heated through said casing, means providing heat exchange relation between burnt gases of combustion and air to be heated in said casing, filter means for cleaning the air located in said casing and means comprising a sailswitch responsive to the air circulation for isolating said filter means from said heat exchange means at a predetermined rate of air circulation whereby the temperature adjacent said filter means cannot become excessive.

8. In a warm air heating system, in combination, a furnace, means for circulating air to be heated to and from said furnace, means forming part of said furnace for preheating the air circulated to said furnace, filter means for cleaning the air circulated to said furnace, means for shielding said filter means from radiant heat from said preheating means, means comprising a sailswitch responsive to the air circulation controlling said shielding means and arranged to cause said shielding means to be moved into shielding position at a predetermined rate of air circulation whereby the filter means are protected from overheating.

9. In a warm air heating system, in combination, a furnace, means comprising a fan for forcing air to be heated past said furnace, said furnace having a return air chamber, an economizer comprising a tortuous passageway for burn gases of combustion located so as to be in heat exchange relation with the return air passing through said chamber, air filter means located adjacent said economizer, means for obstructing radiant heat fiow between said economizer and said filter means, and means comprising a sailswitch and a motor controlled thereby responsive to the air forced by said fan for moving said obstructing means out of obstructing position when said sailswitch is closed.

10. In a warm air heating system, in combination, means for heating air, means for circulating air to and from said heating means, filter means for cleaning the circulating air exposed to heat from said heating means, and power controlled means operable upon failure of the power supply for isolating said filter means from said heating means.

11. In a Warm air heating system, in combination, means for heating air, means for circulating air past said heating means, filter means for cleaning said air exposed to heat from said heating means, means interposed between said filter means and heating means for isolating said filter means from heat, said interposed means being power controlled and assuming isolating position whenever power is not supplied thereto.

12. In a warm air heating system, in combination, means for heating air, means for circulating air past said heating means, air filter means for cleaning said air exposed to heat from said heating means, and power controlled means operable upon failure of power supply thereto to abruptly interpose a heat protective medium between said filter means and heating means.

13. In a warm air heatingsystem, means for heating air, means for enforcing air circulation past said heating means, filter means for cleaning said air exposed to heat from said heating means, means interposed between said filter means and heating means to protect the filter means from overheating, and control means for said interposed means comprising power operated means responsive to failure of the enforced air circulation to cause isolation of said filter means by said interposed means, said power operated means also being responsive to power failure for causing isolation of the filter means.

14. In an air heating system, in combination, means for heating air, means for circulating air over said heating means, filter means for cleaning the circulating air exposed to heat from said heating means, said filter means being susceptible to becoming overheated, and means responsive to a condition indicating that the said filter means may become overheated for isolating said filter means from said heating means.

15. In an air heating system, in combination, air heating means, duct means providing for circulation of air past said air heating means, filter means for cleaning air exposed to heat from said heating means, said filter means being susceptible to becoming overheated, means operable between open and closed positions for closing off said duct means and isolating said filter means from said heating means, means for enforcing air circulation through said duct means, and means responsive to a condition indicating danger of said filter WILLIAM W. MAR'IENIS.