US 3765398 A
The casing of a rooftop heating apparatus is formed with plenum and heat exchanger compartments separated by a partition formed with a passage for air flow from the plenum compartment to the burner in the heat exchanger compartment. Damper means is mounted in the air flow passage of the partition and is normally positioned for maximum air flow with the plenum pressurized by a constant speed blower. The intake of the blower is subject to varying wind pressures. The damper means is responsive to air pressure in the plenum to vary the areas of the air flow passage proportionate to the pressure in the plenum and accordingly, to maintain the air flow to the burner at a predetermined level, whereby the burner operation is not adversely affected by gusts of wind.
Description (OCR text may contain errors)
United States Patent [1 1 Morris Oct. 16, 1973  Inventor: Richard L. Morris, Indianapolis,
 Assignee: Carrier Corporation, Syracuse, NY.
 Filed: Oct. 19, 1972  Appl. No.: 298,971
Primary Examiner-William E. Wayner Assistant Examiner-William E. Tapolcai, Jr. AttorneyJ. Raymond Curtin [5 7] ABSTRACT The casing of a rooftop heating apparatus is formed with plenum and heat exchanger compartments separated by a partition formed with a passage for air flow from the plenum compartment to the burner in the heat exchanger compartment. Damper means is mounted in the air flow passage of the partition and is normally positioned for maximum air flow with the plenum pressurized by a constant speed blower. The intake of the blower is subject to varying wind pressures. The damper means is responsive to air pressure in the plenum to vary the areas of the air flow passage proportionate to the pressure in the plenum and accordingly, to maintain the air flow to the burner at a predetermined level, whereby the burner operation is not adversely affected by gusts of wind.
5 Claims, 3 Drawing Figures HEATING APPARATUS FOR OUTDOORS OPERATION BACKGROUND OF THE INVENTION Presently, in many instances air conditioning and heating apparatus is mounted on the rooftops of buildings, especially dwellings. In most cases, the heat exchanger of the apparatus is fired with a gas burner. It is well known that gas burners are adjusted as to require a flow of air of predetermined value for proper combustion.
In the arrangement of my invention, the air flow for supporting burner combustionis created by a blower operated at constant speed. However, because the apparatus is located out of doors, the output of the blower varies to a great extent due to gusts of wind entering the intake of the blower. Such sudden increases in the flow of air to the burner can adversely affect the operation of the burner, even to the extent of extinguishing the burner flame.
Many arrangements have been suggested for overcoming the problem above referred to. However, they involve complicated and expensive mechanisms which require periodic maintenance.
This invention has as an object a heating apparatus suitable for rooftop operation wherein the air supplied to the gas burner is maintained at a desired, predetermined level, regardless of ambient conditions.
SUMMARY OF THE INVENTION The casing of the apparatus is formed with a plenum compartment and a heat exchanger compartment in which there is mounted a gas fired heat exchanger. A partition separates the compartments and is formed with a passage for the flow of air from the plenum to the heat exchanger compartment. Normal air pressure is maintained in the plenum by a constant speed blower and a bypass is provided for bypassing a portion of the air in the plenum compartment to the exterior of the casing.
To maintain the air flow to the burner consistently at a desired level, a damper is mounted in the partition passage and is operative to vary the area of the passage in response to and proportionate to the air pressure in the plenum.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view schematically illustrating a heating apparatus embodying my invention, one side of the casing being removed;
FIG. 2 is an enlarged perspective view of the damper structure; and
FIG. 3 is a view looking to the left in FIG. 2 showing the damper in closed position.
DESCRIPTION OF THE PREFERRED EMBODIMENT The heating apparatus comprises a casing having side walls 10, 11; end walls 12, 13; a bottom wall 14 and a top wall 15. A vertically disposed partition, consisting of an upper section 17 and a lower section 18, divides the casing into a plenum compartment 20 and a heat exchanger compartment 21. The heat exchanger 22 is mounted in the heat exchanger compartment 21 and is fired by a gas burner 23 supplied with gas through a conduit 24.
An air intake 25 communicates with the area about the heat exchanger 22, the heated air being discharged through a conduit 28 in the top wall 15. The flow of air is indicated by the arrows 30.
A blower 31 is mounted in the plenum compartment 20 and is powered by a constant speed motor 33. The intake 35 of the blower communicates with the atmosphere. The blower functions to discharge air into the plenum compartment. Preferably, the casing is formed with a bypass extending from the plenum compartment 20 to the atmosphere. In the arrangement shown, a stack is provided for conveying products of combustion from the heat exchanger 22 to the atmosphere. As shown in FIG. 1, the bypass is incorporated in the stack structure. A tube 37, having communication with the heat exchanger 22, extends through the partition section 17 toward the end wall 12. A larger tube 40 has a horizontally disposed portion extending from the partition 17 outwardly through the end wall 12 for communication with the vertically disposed portion 41, communicating with the atmosphere. The tube 40 is arranged in spaced concentric relation to the tube 37. A portion of the underside of the tube 40 is cut away. In FIG. 1, the bottom side of the tube 40 terminates at 43. This presents an opening to the space between the tubes 37 and 40 through which air flows from the plenum 20 as indicated by the arrows 47, the flow continuing about the exterior of the tube 37 as indicated by arrows 48 to the vertical portion 41 of the stack.
The lower edge 50 of the upper partition section 17 is positioned in upwardly spaced relation to the lower section 18. The partition sections 17, 18 extend transversely of the casing between the side walls l0, 11. The space between the partition sections 17, 18 provides a passage for the flow of air from the plenum chamber to the heat exchanger compartment.
A damper means is mounted in the air flow passage and functions to automatically maintain the flow of air through the passage at a predetermined level, regardless of gusts of wind passing through the blower inlet 35.
The damper 60 is formed of sheet material and is of inverted V configuration. The damper 60 is pivotally supported on a member 61 extending transversely between the walls 10, 11 of the casing. The sides 62, 63 of the damper diverge downwardly from the support pivot 61 and terminate a distance below the lower edge 51 of the air flow passage. The upper and lower portions 17, 18 of the partition, above and below the air flow passage, are arranged in vertical alignment. The sides 62, 63 of the damper are of equal size whereby the sides of the damper are normally positioned in spaced straddling relation to the lower portion 18 of the partition as shown in FIGS. 1 and 2. The air flow from the plenum, indicated by the arrows 67, FIG. 1, strikes against the upstream side 62 of the damper and passes upwardly under the lower edge of the side 62 and over the edge 51 at the bottom of the air flow passage, as indicated by the arrows 70. The air flow over the edge 51 strikes against the inner surface of the side 63 of the damper. With the damper positioned as shown in FIGS. 1 and 2, the air flow to the burner is at a level providing correct combustion for heating the heat exchanger 22.
A gust of wind passing through the inlet 35 of the blower will increase the output of the blower, and the pressure in the plenum compartment 20. This increase in pressure acting against the outer side of the damper leg 62, and on the inner surface of the damper leg 63, will cause the damper to swing in a counter-clockwise direction, referring to the drawings, moving the side 62 of the damper toward the passage edge 51, and accordingly reducing the flow of air between the side 62 of the damper and the lower portion of the partition. This movement of the damper will be proportionate to the rise of pressure in the plenum compartment because of the bypass through the space between the stack tube 40 and the inner tube 37.
The air flow through the bypass and the weight of the damper 60 are coordinated relative to the output of the blower 31 such that in the absence of any wind pressure at the inlet of the blower 31, the damper hangs in the straddling position shown in FIGS. 1 and 2, and air flow to the burner is at the proper level. However, with wind pressure at the inlet 35 of the blower, causing an increase in the pressure in the plenum chamber 20, the
damper 60 will be moved in counterclockwise direction to reduce the spacing between the lower portion of the side 62 of the damper and the lower partition section 18. In other words, the air passage will be reduced in area proportionate to the pressure in the plenum 20. Accordingly, the air flow to the burner 23 will be maintained at the proper level.
Stop means is provided to prevent the side 62 of the damper from moving into direct contact with the lower portion 18 of the partition to completely. close the air flow passage. This stop means may be conveniently provided by one or more stops 80 fixed to the upstream side of the partition section 18.
While I have described the preferred embodiments of my invention, it is to be understood that the invention is not limited thereto, but may be otherwise embodied within the scope of the following claims.
1. Heating apparatus for outdoors operation comprising a casing formed with a heat exchanger compartment and a plenum compartment, said compartments being separated by a partition, a heat exchanger mounted in said heat exchanger compartment, a burner associated with said heat exchanger for heating the same, a constant speed air blower having an intake communicating with the outdoor atmosphere and subject to varying wind pressure, said blower being operable to discharge air into said plenum compartment, a stack connected to said heat exchanger for the conveyance of products of combustion from said heat ex changer to the exterior of said casing, a bypass means extending from said plenum compartment to the exterior of said casing for the flow of air therefrom, an air flow passage extending through said partition from said plenum compartment to the burner in said heat exchanger compartment, an air flow control damper means mounted in said air flow passage, said damper means being movable from normal maximum air flow position to minimum air flow position, such movement being proportionate to the variation in wind pressure at the intake of said blower, said damper being operable during such movement to maintain the volume of air flow through said air flow passage at a predetermined level.
2. Heating apparatus as set forth in claim 1 wherein said burner is a gas fired burner.
3. Heating apparatus as set forth in claim 1 wherein said bypass means communicates with said stack.
4. Heating apparatus as set forth in claim 1 wherein said partition is disposed vertically in said casing and said air flow passage is disposed upwardly from the bottom of said plenum compartment and extends transversely thereof, said damper means consisting of an inverted V shaped member, support means pivotally supporting said member in said air flow passage at the bight of said member for free pivotal movement, with the sides of said member diverging downwardly from said pivot and being normally positioned in spaced straddling relation to the bottom'side of said air flow passage whereby the upstream side of said damper member is moved toward said partition for reducing the area of said air flow passage proportionate to an increase in the air pressure from normal in said plenum.
5. Heating apparatus as set forth in claim 4 and including stop means for limiting movement of said upstream side of said damper toward said partition.