US2711683A - Venting systems - Google Patents

Description

Filed Aug. 12, 1952 uunezs, 1955 F. A. RYDER 2,711,683

VENTING SYSTEMS so Zfieets-Sheet l ill a 2,711,683 Patented June 1955 VENTHNG SYSTEMS Frank A. Ryder, Indianapolis, Ind, assignor to Stewart- Warner COI'PGE'afiGIl, Indianapelis, Ind., a corporation of Virginia Application August 12, 1952, eriai No. 303,910

2 Claims. (Cl. 98-48) The present invention relates to venting systems and more particularly to a system of this character which permits the installation of an ordinary heater or furnace or similar equipment in a small enclosed space.

One of the objects of the present invention is to provide a novel heater or furnace venting system which permits the heater or furnace to be sealed into a small space within the dwelling or other building housing the equipment.

Another object is to adapt an ordinary combustion heating system to operation in a small sealed room or other space.

Still another object of the invention is to provide an improved venting system which does not require that cold air enter the building in order to provide air for combustion.

Yet another object is to provide a novel heater venting system that eliminates to a large extent the source of cold drafts within a dwelling or other building.

Yet another object is to provide a venting system for an ordinary heater or furnace which eliminates hack drafts.

Other objects and advantages will become apparent from the following description of a preferred embodiment of my invention which is illustrated in the accompanying drawings.

In the drawings, in which similar characters of reference refer'to similar parts throughout the several views:

Fig. 1 may be considered as a somewhat diagrammatic vertical, sectional view through a building of generally conventional construction showing a furnace room and the venting system of the present invention in vertical section;

Fig. 2 shows the vent termination at the top of Fig. l, drawn to larger scale and in vertical section; and

Fig. 3 is a top view of the vent fitting of Fig. 2, with,

portions thereof broken away so as to reveal the underlying structure.

Ordinary gas heaters or furnaces are connected to a chimney flue by a draft diverter fitting which essentially simply provides a baffled opening at the underside of the flue pipe between the furnace and chimneys. The reasons for this arrangement are several. One is that occasionally there are back drafts because of a downfiow of air at the chimney opening which momentarily causes the fiue gases within'the chimney to flow downwardly rather than upwardly. If it were not for the draft diverter opening at the lower end of the flue, there would be a reverse flow of combustion products within the heater which would under most conditions extinguish the fire Another reason for the draft diverter fitting is that it permits a considerable quantity of air to be drawn from the building along with the flue gases, thereby eliminating to a large extent condensation of water from the flue gases within the chimney. A further reason for the employment of a draft diverter fitting is that it largely eliminates the effect of the chimney upon the furnace. Furnaces or heaters are ordinarily constructed to have a pressure drop therethrough such that the proper amount of air for combustion is supplied to the combustion chamber by the vertical spacing between the air inlet and exhaust outlet openings. In a typical furnace for instance, the spacing between the combustion air inlet and the exhaust outlet may be a matter of four feet or so, although this differs widely with different equipment designs. The draft diverter simply connects the furnace outlet to the chimney in such fashion that although atmospheric conditions, the temperature within the chimney, and the length and restrictive effect thereof, determine the flow rate through the chimney, this will produce no substantial negative pressure at the furnace exhaust outlet. Were this not so it would be difiicult to balance each furnace to its own chimney conditions at the time of installation so as to obtain the proper flow rate through the combustion side of the furnace, and even were this accomplished, as pointed out previously, the conditions would not stay balanced excepting under some predetermined atmospheric condition. There are other influencing factors, but those given are sufiicient to illustrate the problem and the need under ordinary conditions for a draft diverter fitting.

A furnace installation of the type described above, which is that customarily employed, has serious disadvantages. For instance, both the air for combustion and the diluent air which enters the fine at the draft diverter fitting must be taken from the furnace room. Ordinarily therefore this air which passes up the chimney must be drawn into the dwelling by way of cracks under the doors, around windows and other openings to the outside. The result is that cold, uncomfortable drafts are encountered wherever this cold air is being drawn into the building. If the room in which the heater is installed is small and is comparatively well sealed, a combustion air inlet opening directly to the outside of the building is sometimes provided, and thus air drawn into the furnace or utility room may be extremely cold. This has the effect of making the walls of the utility room cold to the touch. Also if the room, as is ordinarily the case, contains other equipment of a utility nature it is possible that water pipes may freeze or that other cold damage may be suffered. As a rule, therefore, the ordinary furnace installation is costly and is a compromise of the features mentioned above.

The venting system of the present invention permits the furnace and other utility equipment to be placed inan extremely small room or closet-like enclosure and no air for combustion or for exhaust dilution needs fiow to this room from other portions of the dwelling. This can be accomplished with an ordinary furnace which will.

- ditions and, further, the temperature of the utility room will not fall to an unreasonably low level.

By referring to the drawings it will be seen that I have illustrated a portion of an ordinary frame building diagrammatically. The building is shown as having one story and an ordinary pitched roof, but may of course be of other construction. For purpose of reference. the house is comprised of a floor it), a roof 3.2 and interior ceiling 14, ordinary walls 16 and wall having a chimney forming arrangement 18, to be described in greater detail presently. These structural elements provide a small room 20 which hereafter will be referred to as a utility room. It may be considered that this utility r-com is no larger than is necessary to provide space for the furnace 22 and for any other utility equipment which may berequired in the dwelling, such as a hot water heater for instance. It may be assumed further that the room 2% is intended to be substantially sealed from the remainder of the building by a door which is designed to close tightly.

For the purpose of explaining the invention, the furnace 22 will be considered as being gas-fired and of course may be of the hot air, hot water, or steam type as desired. Such contemporary units are ordinarily quite small and have a grill or some other opening indicated at 24 for the entrance of air for combustion, and have an outlet flue fitting 26 near the top thereof through which the products of combustion are exhausted, the flow of combustion air through the furnace ordinarily being occasioned by the convection efiect produced by the high temperature Within the furnace and by the vertical spacing of the openings 24 and 26. 7

Within the room, or within a wall at one side thereof, according to choice, there is a chimney structure 18 which in the present instance will be considered as being comprised of an ordinary wall with a sheet metal tubular member 28 therein which may substantially till the open ing between the wall forming members and which extends from the floor to a position above the roof 12. Where this duct passes through the roof 12 it is flashed as at 30 to prevent the entrance of water or snow. At a position near the floor it the duct 28 is provided with an opening to the room and in the drawing this opening is represented by the grill 32.

Coaxially within the duct 28 there is a second duct 34 which has an open lower end at 36, this lower end being positioned approximately half way between the grill opening 32 and the furnace exhaust fitting 26 although the vertical position of the duct opening 36 is not particularly critical. It should, however, be somewhat above the grill 32. The interior duct 34 is somewhat smaller than the tubular member 28, thereby providing an annular space 38 between the two. At approximately the level of the furnace exhaust fitting 26 the interior duct 34 is connected to a branch duct 40 which extends to the side andis connected by whatever piping is necessary to the furnace fitting 26 so as to conduct the furnace products directly to the interior duct 34. The interior duct 34 extends within the exterior pipe 28 upwardly into a position slightly above the upper end of the pipe 28 and at this position the two ducts 28 and 34 are connected to an outlet and inlet vent fitting indicated generally by the numeral 42.

This fitting, which is generally similar to the one forming the subject matter of my copending application Serial No. 278,811, filed March 27, 1952, is attached to the upper end of the pipe 34 and is illustrated in greater detail in Figs. 2 and 3. In Fig. 2 it will be seen that the concentric pipes or ducts 28 and 34 extend into a position well above the roof of the building, and that the end of the inner duct 34 is somewhat above the top of the other. In the present example the vertical spacing between these two duct ends is about two and one-half inches or so. These ducts are supported rigidly with respect to each other in any suitable fashion, and the vent fitting is carried by the upper end of the interior duct 34. This fitting comprises a convex frusto conical sheet metal deflector 44 which has a circular periphery and which is extruded downwardly as at 46 at its center so that this extrusion fits the outside surface of the interior duct 34. -t may be secured thereto in any suitable manner, such as by sheet metal screws or by soldering for instance. This deflector may be considered as a disc which slopes downwardly from the central portion to the periphery at an angle of approximately 12 /2". In the specific example shown it has an external diameter of approximately ten inches, whereas the interior duct 34 to which it is fitted is approximately three inches in diameter.

The opening into the interior pipe 34 is protected by a sheet metal top member 48 which is circular in outline and generally conical in form. The angle of this cone is such that the top and deflector surfaces are approximately parallel, that is, the conical surfaces slope downwardly from the apex at an angle of approximately 12 /2 It is axially aligned with the deflector, is approximately seven and one-half inches in diameter, and is supported approximately one and one-quarter inches above the deflector by several sheet metal brackets 50 which are spotwelded or otherwise suitably attached to the top surface of the deflector 44 and the lower surface of the top member 48.

An air intake bafile member 52 is disc shaped and is supported in a horizontal position below the deflector 44 by several sheet metal brackets 54 spot-welded or otherwise suitably attached between these members. The brackets are of such length that the air intake baffle is approximately one and one-quarter inches below the outer edge of the intermediate deflector 44. The central portion of the air intake baffle 52 is cut out to form a circular opening 56 which surrounds the interior tube 44 and is vertically spaced about one-quarter inch above the top of the larger duct 28. In the present example this opening 56 is approximately five and three-eighths inches in diameter and is therefore somewhat larger than the external diameter of the exterior tube 28 which in the present instance is about five inches. The annular zone of the baflie plate immediately surrounding the opening 56 is perforated to provide a multiplicity of holes 60 approximately three-sixteenths of an inch in diameter extending therethrough. These holes are symmetrically arranged along circular concentric center lines approximately one-half inch apart with the first or innermost row of holes being spaced outwardly from the edge of the opening 56 about one-quarter of an inch. All together there are in the specific device shown one hundred twenty-six of these holes arranged in four rows. A suitable arrangement is to put thirty holes in the innermost row, thirty-one in the second row, thirty-two in the third and thirty-three in the fourth.

In the above description of a specific embodiment of the vent fitting, specific dimensions have been given for the purpose of illustration only and their use should not therefore be considered as limitative of the invention. The particular dimensions given are appropriate for a heater of comparatively small size, of the order of 75,000 B. t. u. for instance. They should be scaled upwardly or downwardly for larger or smaller heaters.

The system described functions in the following manner: When the furnace is operating, air for combustion is drawn into the grill opening 24 thereof and products of combustion are exhausted at the top through the fitting 26 and pipe section 40. These hot products of combustion pass to the interior duct 34 and rise to the roof and pass out between the cap 48 and deflector 44. This produces a low pressure within the room 20 with respect to the outside, and therefore air for combustion is drawn inwardly between the deflector 44 and baffle 52 and passes downwardly through the annular space 38 between the ducts 28 and 34. When this downwardly moving air reaches the level of the lower opening of the inner duct 34 a portion of this air will reverse its direction and pass into the opening 36 and thence upwardly to serve as diluent air for the products of combustion Another portion of the air flows downwardly beyond the duct opening 36 and passes outwardly through the grill opening 32 directly into the utility room 20. It thereby equalizes the pressure within the room 20 and continuously supplies air which is drawn into the furnace by way of its inlet opening 24. Because of the opening 36 at the lower end of the flue pipe 34, the rate of flow of hot products of combustion within the vertical stack 34 does not influence the rate of flow of air through the combustion side of the furnace. Temperature diiferences within the flue 34, and differentials between inside and outside temperatures have the effect merely of determining the amount of diluent air drawn into the opening 36.

Because of the fact that the incoming air for the room 20 passes through the annular space 38 for a considerable distance in direct contact with the interior duct 34, it will arrive at the grill opening 32 at a temperature considerably above the outside since heat is exchanged to the incoming air by the products of combustion passing upwardly through the stack 34. Furthermore, the downwardly moving sheath of air around the interior duct avoids any necessity for insulation of the assembly. The air within the space 20, therefore, cannot drop to an extremely low temperature as can happen with conventional installations which have outside air inlet connections.

The vent fitting 42 functions in the following manner: Under still air conditions products of combustion rise up the innermosttube and pass outwardly evenly in all directions around the cap member 48. Conversely, air for combustion is drawn inwardly in all directions through the space between the baffle 52 and deflector 44 and passes downwardly within the annular space provided between the ducts 34 and 28. There is ample space between the inlet and outlet passages in the vent fitting to prevent mixing of the products of combustion with the incoming air. This is partially because the incoming air moves principally in a radially inwardly direction, whereas products of combustion pass around the edge of the roof member 42 with an upward component inasmuch as these hot gases have less density than the surrounding air.

Under conditions of wind, when the wind is blowing from any angle excepting from directly above, that is, in a downwardly direction, the exhaust products will leave the device at one side whereas the incoming air will pass inwardly at the opposite side. Nevertheless the inlet and outlet are in such close proximity to each other that the static pressure created by the wind is substantially the same at both openings and thus there is little tendency for updrafts and no tendency for down drafts due to wind velocity. Tests have shown that this is true regardless of the direction of the wind and up to winds of whole gale force. At extremely high velocities, that is of the order of sixty miles an hour or so, there is some tendency for an up-draft to take place through the central tube 34. This effect, however, is not pronounced and does not appreciably affect the rate of air flow through the central tube, and because of the opening 36 at the lower end of this tube it has for all practical purposes no effect whatever upon the furnace 22, in fact far less than is produced by the ordinary chimney when connected to a furnace or heater by means of the usual draft diverter fitting.

Rarely does the wind ever blow straight downwardly but even under these conditions the -top member 48 protects the outlet opening and therefore shields the exhaust duct against down drafts. The top member also helps to prevent rain water or snow getting into either the inlet or outlet duct members. Of course when the wind is directly downwardly or has a strong downward component exhaust products are forced downwardly over the edge of the deflector 44 and it might be thought that they would under some conditions mix appreciably with the inlet air. It has been found, however, that the annular space between the air intake bafiie 52 and the air intake tube 28 permits air to flow upwardly to the center of the space between the battle and the deflector. Under these conditions the perforations 60 prevent there being too great a pressure differential between the upper and lower surfaces of the baffle 52 at the region about its center. Because the adjacent surfaces of the members 48 and 44 are parallel, no Venturi effect is produced at the outlet opening of the vent when the wind blows therethrough. The members 44 and 52 together, however, produce a very slight reverse Venturi effect at the inlet opening and thus an extremely slight but appreciable constant pressure is produced in the inlet duct relative to the outlet under high wind conditions. Be-

cause of the fact that the products of combustion reach the vent at a comparatively high temperature, the vent stays warm enough to prevent an accumulation of snow or ice thereon which might otherwise interfere with air flow through the device. Also rain water cannot reach the outlet because of the cap 48 and any which might otherwise accumulate upon the horizontal surface of the bafile 52 and run inwardly so as to fall through the opening 56 into the inlet pipe 28 is prevented from so doing because the diameter of the hole 56 is sufficiently larger than the diameter of the duct 28 to permit water to drip through the baffle opening outside the edges of duct 38. Water also of course drains through the holes 60 and falls away harmlessly.

From the above it will be seen that it is an important consideration of the present invention to provide a system such that air can be brought into the utility room so as to replace air passed through the heater or furnace and thence upwardly through the exhaust flue. In addition, this incoming air is heated by the exhaust so that it arrives at the utility room in a temperate condition. The system also provides adequate diluent air to prevent condensation within the exhaust flue and, further, because the fitting at the exhaust and inlet end of the system is substantially balanced under all conditions, there is no appreciable tendency for the rate of air flow through the system to be affected by anything other than the temperature of the exhaust gases. It is also greatly advantageous that no insulation is required, since the outer duct Wall is kept cool by the incoming air. The furnace, therefore, is unaffected by wind conditions or outside temperature conditions. The ultimate result is that the furnace has adequate air for combustion, the furnace room does not become cooled to an uncomfortable or dangerous degree, there are no cold drafts around door and window cracks caused by inflowing air which is ordinarily necessary for the combustion process and there is no possibility of down drafts which might cause products of combustion to be mixed with the air Within the space to be heated. Also, the system can be prefabricated at low cost, since the elements are simple and no insulation is required.

To aid others in practicing my invention I have described a specific embodiment thereof, but it will be appreciated that variations may be made therefrom without departing from the scope or spirit of my invention.

Having described my invention, what I claim as new and useful and desire to secure by Letters Patent of the United States is:

1. In a venting system for venting a heater and heater room to the outside of a building in which the room is located, means forming a first duct extending from a low position in the heater room to the outside of the building, means forming a second duct coaxial with the first and located within the first to form an annular space between the two, said second duct also having its upper end outside the building, a fitting secured to the outside ends of said ducts and having the effect of substantially cancelling atmospheric effects upon said ducts so as to make the flow rate through said ducts substantially insensitive to atmospheric conditions, said first duct having an opening to said room at a low position therein, said second duct having an opening within said first duct at a position above the last said opening, and a branch duct connected to said second duct at a point above said last opening, said branch duct extending through the side wall of said first duct so as to provide a means of attachment of a furnace exhaust fitting to said second duct.

2. In a venting system for venting an appliance having exhaust products and a requirement for incoming air and for venting the room in which said appliance is located, means forming a first duct extending from a low position in the room to the outside of the building within which the room is disposed, means forming a second duct coaxial with the first and located within the first to form an annular space between the two, said second duct also having its upper end outside the building, a fitting secured to the outside ends of said ducts and having the efiect of substantially cancelling atmospheric effects upon said ducts so as to make the flow rate through said ducts substantially insensitive to atmospheric conditions, said first duct having an opening to said room at a low position therein, said second duct having an opening Within said first duct at a position above the last said opening, and a branch duct connected to said second duct at a point above the last said opening, said branch duct extending through the side wall of said first duct so as to provide a means of connection of the exhaust of said appliance to said second duct.

References Cited in the file of this patent UNITED STATES PATENTS 2,274,341 Mueller Feb. 24, 1942 2,356,391 Fluor, Jr. Aug. 22, 1944 2,619,022 Hergenrother Nov. 25, 1952

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