US2998764A

US2998764A - Sealed heater venting system

Info

Publication number: US2998764A
Application number: US55748A
Authority: US
Inventors: Karl L Bedell; Charles R Fields
Original assignee: WILLIAMS FURNACE Co
Current assignee: WILLIAMS FURNACE Co
Priority date: 1960-09-13
Filing date: 1960-09-13
Publication date: 1961-09-05
Anticipated expiration: 1978-09-05

Description

Sept. 5, 1961 K. L. BEDELI. ET AL 2,998,764

SEALED HEATER VENTING SYSTEM Filed Sept. l5, 1960 2 Sheets-Sheet 1 55 l 5 lj:

IN V EN TORS. /f/PL 5505@ @mais A. F/fmf Sept 5, 1961 K. L. Esi-:DELL ET AL 2,998,764

SEALED HEATER VENTING SYSTEM Filed Sept. 13, 1960 2 sheets-sheet 2 b '111mm' 2r INVENToRs f7@ BY EMM@ 2,993,764 `SEALED HEATER VENTING SYSTEM Karl L. Bedell, Pasadena, and Charles R. Fields, Arcadia, Calif., assignors to Williams Furnace Co., Buena Park, Calif., a corporation of Delaware Filed Sept. '13,` 1960, Ser. No. 55,748 7 Claims. (Cl. 98-62) This invention relates to gas fired heating systems of the sealed type in which combustion air for the burner `vis admitted into the sealed combustion chamber from outside the heated space and products of combustion are exhausted outside the heated space, and has particular ref- Sence to a combined inlet and outlet vent for such a heating system.

A sealed heating system incorporates two separate air circulationl systems, one of which may be called the room air system and the other called the combustion air system. The typical sealed heating system of the type referred to comprises a heater located on the inner side of the Wall of a building, the heater having a sealed combustion chamber which derives combustion air and exhausts combustion gases, through inlet and outlet ducts which extend through the wall of the building and communicate with the atmosphere exterior of the building. As is well known, the flow rate of combustion air through the heater dependson convection, that is upon the rising of hot gases within the heater and outlet iiue. 'Ihe pressure differential between the inlet and outlet of such a heater system, which produces the ilow of combustion air therethrough, is` very small. Hence, it is very difficult to vent the inlet and exhaust openings to the atmosphere in amanner such that changes in the direction and velocityiof the wind outdoors will not appreciably affect the flow rate through the heater by upsetting this pressure differential.

Normally, there is a slight updraft in the heater which continually supplies fresh combustion air and carries to exhaust the combustion products.

Sealed heaters are particularly sensitive to downdrafts therein which will snuff out the pilot and in some cases the main burner too. Such a downdraft may be produced by wind stiiking the exterior inlet and outlet openings in a manner which produces a reversal of the pressure diiferential of the system. The possibility of this happening may be alleviated by designing the heater to have a relatively high convection rate such that an updraft within the heater is assured under all exterior wind conditions. Such overcompensation however reduces the eiliciency of the heater by producing excessive updrafts under normal wind conditions.

To avoid the requirement for overcompensation to prevent downdrafts, and for otherwise maintaining an eilicient and substantially constant flow rate for combustion gas, a great deal of attention has been devoted in recent times to the design of combined inlet and outlet vents which are less sensitive to changes in outsidewind velocity and direction. Such vents have met with som-e success under moderate wind conditions, in reducing the probability of downdrafts which will snulf out the pilot and in reducing the requirement for overcompensation. However, it is still found that wind conditions which prevail or at times exist in all areas where gasefn'ed heaters are installed produce excessive updrafts in the heater which markedly reduce the efficiency of the heater.

The present invention provides a combined inlet and outlet vent of. an improved nature which not only better prevents downdrafts' without requiring overcompensation in the heater design, but also prevents excessive updrafts from being created under a wide range of exterior wind conditions. The result is greater heater eiliciency.

In accordance with the present invention, a combined inlet and outlet vent is adaptedn to be mounted on the ttes Patent O ice vertical exterior wallofa buildingto' connect withfconcentric inlet and outlet openings of a sealed heaterv located inside the building. The vent comprises an ,inlet box adapted to Vcover the heater inletV opening and any outlet box adapted to covertheheater outlet opening. The inlet box is substantially closed on its.top, front and sides, and has a relatively large duct extending horizontally from the rear thereof for connecting with'the heater inlet opening. The inlet box is vented at the bottom thereof. The outlet box is mounted atthe front of the inlet box and is substantially closed on itsfrontandl sides.l It has a relatively small duct extending from .the rearl thereof through the inlet box approximately concentric with the relatively .large duct forconnecting` with the heater outletopening. The outlet box. is vented at the top and at a plurality of bailles mounted therein, including an upper baille extending laterally withinthe outer box at a position above the duct extending therefrom and oriented to divert downdrafts entering through the top of the box awayfrom the duct, and also lincluding a lower baille extending laterally within the outlet box at a position below the duct and oriented to divert updrafts entering through the bottom of said' box away from the duct.

In another embodiment of theinvention, the top of the inlet box as well as the bottom thereof, is vented. However,l this does not seem to work so well as when only the bottom of the inlet box is vented lunless the inlet through the top of the box is provided with a baille.

'Ihe foregoing and other aspects of the vent structure of the invention are explained in greater vdetail in the following description taken with reference to the accompanying drawings, in which:

FIG. l is a schematic representation of a gas tired sealed heating system with one embodiment of the combined inlet and outlet vent of the invention attached thereto;

FIG. 2 is a sectional velevation ofthe preferred embodiment of the combined vent structure of the invention;

FIG. 3 is a top View, partially broken away, of the apparatus of FIG. 2;

FIG. 4 is a rear View, partially broken away, of the apparatus of FIG. 2; and,

FIG. 5 is a graph and accompanying legend showing typical heater efficiency when the vent structure of the invention is employed Vas compared tothe case when conventional contemporary vent structure is employed. under varying wind conditions.

Referring now to FIG. l, a gas tired sealed heater 10 is mounted on the interior of a building wall 12 in a conventional manner. The heater has a sealed combustion chamber 14 which communicates with an inlet duct 16v and a concentric outlet duct y18, which in turn extend through the building wall 12 to communicate with the atmosphere exterior of the building. Within the combustion chamber 14 is a gas fired burner Z0, the combustion air for which is derived from the atmosphere exterior of the building through the inlet duct 16, Iand the combustion products from which are exhausted to the exterior atmesphere through the outlet duct 18. The combustion chamber 14 serves as heat exchanger imparting heat to the interior of the building by convection and radiation. As is indicated by the arrows, the combustion gases normally iloiw upward in the combustion chamber 14 by convection.

A combined inlet and outlet' vent 22, representing one embodiment ofthe invention is mounted on the exterior of the building wall 12, for the `purpose of venting` the heater inlet and outlet openingsI a' fashion which reduces or eliminates the effects of outside wind yconditions on the combustion system. The combined vent 22 has

concentric ducts

24, 26 which mate with the inlet and out-` n atented Sept. `5, 196:1

3v let ducts 16, 18 respectively of the heater in a telescoping fashion. The vent is supported on the wall by means of mounting screws (not shown).

Referring now to FIGS. 2, 3 and 4, there is depicted the preferred embodiment of the combined vent structure of the invention. The vent is made of sheet metal, and includes a substantially rectangular inlet box 24 adapted to cover the heater inlet opening, and a substantially rectangular outlet box 26 mounted on `the front of the inlet box and adapted to cover the heater outlet opening.

The inlet -box 24 has a closed top wall 28, a closed front wall 30 and closed

side walls

32, 34. The inlet box has a rear wall 36 having a flanged central opening therein. A relatively large duct 38 extends rearwardly from the flanged central opening of the rear wall of the inlet box for connecting with the heater inlet duct. The front edge of the duct 38 is spot welded to the anged opening in the rear wall of the inlet box, as indicated.

The front wall 30 of the inlet box 24 forms the rear wall of the outlet box 26. The wall 30 has a relatively small flanged central opening therein. Extending rearwardly from this wall through the inlet box andv coaxial with the large duct 38 is a relatively small duct 40 for communicating the outlet box 26 with the heater outlet. The small duct 40 is spot welded in the flanged opening in the wall 3D, as indicated.

The outlet box 26 has a closed front wall 42 and closed

side walls

44, 46. As can be seen, both the bottom and top of outlet box are open, and a substantial portion of the top and bottom edges of the front and side walls of the outlet box 26 extend inwardly at acute angles, so that the top and bottom of the outlet box has an exterior bevelled configuration adjacent the openings.

A plurality of internal baffles `are mounted within the outlet box, including first and second upper baflles 48, 50 and a lower baille 52. The baflles extend laterally between the

side walls

44, 46 of the outlet box, and are spot welded thereto. The upper bales are disposed in spaced parallel relationship at a position above the relatively small duct 40, and the lower baille is located at a position below the duct 40. Typical of the internal batlles, the lower baille 52 comprises a relatively small outer flange 54 which slopes forward and outward toward the exterior of the outlet box, and a relatively `large inner flange S6 which slopes forward and inward toward the interior of the box, such that it has a substantially V- shaped vertical cross section. Similarly the first upper baille 48 has an outer flange 56 and an inner flange 58; and, the second upper battle 50 has an outer llange 60 and an inner ilange 62.

The outlet box has an external lateral batlle 64 disposed adjacent the rear top edge thereof. This exterior baille 64 is spot welded along the top edge of the common wall 3) and slopes forward and upward over a rear portion of the outlet box.

The inlet box 24 has first and second

external baflles

66, 68 extending laterally adjacent the bottom edge of its front wall 30. The first exterior baille 66 is spot welded to the wall 30 and extends vertically downward therefrom well below the bottom edge of the outlet box 26. The second baille 68 is formed as an upturned lower lip of the wall 30 and extends horizontally forward from the first baille 66.

An examination of the drawings will show that the front wall of the outlet box, as well as the side walls of both the outlet box and the inlet box are formed in a single piece of sheet metal, suitably bent and patterned to serve this purpose. Similarly both the top and front Walls of the inlet box are of a single piece of sheet metal. The design of the combined vent structure permits this' simple economical construction.

For purposes of suitably insulating the vent from the building wall-on which it is mounted and sealing the necessary opening through the wall, a wall plate 68, substantially similar to the rear'wall 36 of the inlet box,

is disposed around the relatively large duct 38. The wall plate is spaced lfrom the rear wall 36 of the inlet box by means of a plurality of small metal angles 70, spot welded to the wall 36. The wall plate is held in place by a plurality of screws 72 which extend through the wall plate and engage the Wall 36. A layer of liberglass insulating material 74 fits around the periphery of the large duct 38 and is secured by an adhesive to the rear side of the wall plate 68.

The vent structure is installed by telescoping the

ducts

38, 40 into the corresponding inlet and outlet ducts of'. a heater, such as indicated in FIG. 1. The telescoping feature permits different wall thicknesses to be accom-` modated. The vent is pushed inwardly to compress the; fiberglass layer 74 against the exterior of the building*` wall, and is flxed in position by means of mounting screws (not shown), which extend into the wall, or by some other conventional means. As seen in FIG. 4, mounting screw holes 76 extend through peripheral corner por-` tions of the wall plate 68 and wall 36.

The vent structure of the invention embodies recognition of the fact that high winds have their main velocity component in the horizontal direction, hence impinge on the vent structure mainly in that direction as opposed to the vertical. Within the horizontal direction, the angle at .which the wind strikes the vent structure may vary from ninety degrees (meaning head-on) to zero degrees (meaning directly sideways). Since the vent structure is open only at the top and bottom thereof and since the openings in the vent structure are flush with the horizontal, the major changes in wind velocity and direction will not substantially alter the Way in which the wind strikes the openings, and the effect of striking the outlet openings will be compensated by the opposite effect produced at the inlet, such that the pressure difference between the inlet and outlet will be substantially unaffected. In this regard, the bevelled edges at the upper and lower end of the outlet box assist by cooperating to divert wind away from the outlet openings; and, the upper exterior baille 64, which serves the purpose of diverting flue gases away from the building wall under normal operating conditions, assists in balancing the pressure around the outlet area under high wind conditions. Respecting the inlet opening, the exterior battles 66, 68 extending below the outlet box cooperate to divert and spoil the wind in this area so as to over-pressurization of the air intake passage.

The normal flow of air through the vent structure is indicated in FIG. 2. Cool air passes upward into the inlet box and flows rearwardly in the annular space be tween the large duct 38 and small duct 40, and hence to the heater. Combustion products from the heater are returned from the central small duct 40 and emerge into the outlet box where, under normal conditions, this heated gas passes upwardly out the top opening of the outlet box. Cool air enters the bottom opening of the outlet box and mixes with the hot gases passing upwardly through the top opening, thereby lowering the temperature of the flue gases and hence of the exterior walls of the outlet box.

Considering the outlet box, what air strikes the openings at an angle from the horizontal, including direct updrafts and downdrafts, will be deflected away from the open end of the duct 40 by the baffles, so as to avoid such aspiration of the duct as would unduly increase the flow rate in the combustion system and reduce the eticiency of the heater.

Also, it will be noted that the battles in the outlet box are arranged to prevent rain from entering the duct 40; and, rain is prevented from entering the duct 38 since the inlet box is closed at its top.

While the theory under which the various elements of` the first structure above described cooperate to lessen 'the effect of wind on heater eiliciency is not completely understood, the foregoing is presented as one plausible explanation. Whatever the reasons however, comparative eiciency tests between the preferred embodimentv of the invention illustrated in FIGS. 2 to 4, and a typical contemporary and conventional vent structure, or rain hood in the prior article have demonstrated the advantages of the vent of the invention.

Typical results are shown in FIG. 5 ofV such a cornparative test, made with respect to winds varying from zero to thirty miles per hour at different angles. As can be seen from the three curves 7'8, 80, 82, representing horizontal winds striking the combined vent structure of the invention at angles of 45, 90 and' zero degrees repectively, the heater eiciency stayed above ninety percent of available heater output with winds ranging up to thirty miles per hour. As shown by the curve 84, which represents the conventional contemporary device, with the wind striking the device at an angle of forty-tive degrees, the efficiency decreased to about sixty percent of normal as the wind ranged up to thirty miles per hour.

Referring again to FIG. l, the Vent structure 22 represents schematically a second embodiment of the invention wherein the top of the inlet box is open rather than closed, as is indicated by the arrows depicting the flow of air. It will be appreciated that this embodiment of the invention may be constructed, so far as its details are concerned, in a fashion similar to that illustrated in FlGS. 2 to 4 respecting the preferred embodiment, and no additional illustration therefore is necessary.

ln the FIGS. 2 to 4 of the drawings dimensional proportions as shown are approximately correct as respecting the relative size of the ducts, boxes and openings. Such proportions are selected to provide an equal pressure drop through the inlet and outlet of the heater when the heater is in operation.

We claim:

l. A combined inlet and outlet vent adapted to be mounted on the vertical exterior wall of a building to connect with concentric inlet and outlet openings of a sealed heater located inside the building and comprising a vented inlet box adapted to cover the heater inlet opening, the inlet box being substantially closed on its front and sides and having a relatively large duct extending horizontally from the rear thereof for connecting with said heater inlet opening, and a vented outlet box mounted at the front of the inlet box and adapted to cover the heater outlet opening, the outlet box being substantially closed on its front and sides and having a relatively small duct extending from the rear thereof through the inlet box approximately concentric with the relatively large duct for connecting with said heater outlet opening.

2. A combined inlet and outlet Vent adapted to be mounted on the vertical exterior wall of a building to connect with concentric inlet and outlet openings of a sealed heater located on the opposite side of the wall and comprising an inlet box adapted to cover the heater inlet opening, the inlet box being substantially closed on its top, front and sides and having a relatively large duct extending horizontally from the rear thereof for connecting with said heater inlet opening, the inlet box being vented at the bottom thereof, and an outlet box mounted at the front of the inlet box and adapted to cover the heater outlet opening, the outlet box being substantially closed on its front and sides and having a relatively small duct extending from the rear thereof through the inlet box approximately concentric with the relatively large duct for connecting with said heater outlet opening, the outlet box being vented at the top and at the bottom thereof.

3. A combined inlet and outlet vent adapted to be mounted on the vertical exterior wall of a building to connect with concentric inlet and outlet openings of a sealed heater located on the opposite side of the wall and comprising an inlet box adapted to cover the heater inlet opening, the inlet box being substantially closed on its top, front and sides and having a relatively large duct extending'horizontally from they rear thereoffor'connecting with said heater inlet opening, the inlet boxv being vented at the bottom thereof, and an outlet box mounted at'tl'i'e front of the inlet box and adapted to cover the heater outlet opening, the outlet box being substantially closed on its front and sides and having a relatively small duct extending from the rear thereof through the inletv box approximately concentric with the relatively large duct for connecting with said heater outlet opening, the outlet' box being substantially open at the top and bottom there'- of and having a plurality of banales mounted therein, including an upper baile extending laterally within the outlet box at a position above said relatively small duct and oriented to divert downdrafts entering through the top of saidY box away from said duct and a lower baille extending laterally within the outlet box at a position below said duct and oriented to divert updrafts entering through the bottom of said box away from said duct.

4. Apparatus of claim 3 wherein said plurality of baffles includes a second upper bailie disposed approximately parallel in spaced relationship with the tirst, and wherein said upper and lowery baffles each comprise a relatively small outer ange which slopes forward and outward toward the exterior ofthe outlet box and a relatively large inner ilange which slopes forward and inward toward the interior of said box so that said baiiies each have a substantially V-shaped vertical cross-section.

5. A combined inlet and outlet vent adapted to be mounted on thevertical exterior wall of a building to connect with concentric inlet and outlet openings of a sealed heater located on the opposite side of the wall and comprising a substantially rectangular inlet box adapted to cover the heater inlet opening, the inlet box having closed top, front and side walls and having a relatively large duct extending from the rear wall thereof for connecting with said heater inlet opening, the inlet box being open at the bottom thereof, and a substantially rectangular outlet box mounted on the front wall of the inlet box and adapted to cover the heater outlet opening, the outlet box having closed front and side walls and having a relatively small duct extending from the rear wallthereof through the inlet box approximately concentric with the relatively large duct for connecting with said heater outlet opening, the outlet box being open at both the top and bottom thereof, and a substantial portion of the top and bottom edges of the front and side walls of the outlet box extending inwardly at acute angles so that the top and bottom of the box has an external bevelled conguration adjacent said openings.

6. Apparatus of claim 5 wherein the outlet box has an external lateral baille disposed adjacent the rear top edge thereof and sloping forward and upwardly over a rear portion of the box, and wherein the inlet box has iirst and second external batlies extending laterally adjacent the bottom edge of the the front wall thereof, with the iirst oriented approximately vertically downward therefrom and extending below the bottom edge of the outlet box, and the second oriented approximately horizontally forward from the first.

7. A combined inlet and outlet Vent adapted to be mounted on the Vertical exterior wall of a building to connect with concentric inlet and outlet openings of a sealed heater located on the opposite side of the wall and comprising a substantially rectangular inlet box adapted to cover the heater inlet opening and a substantially rectangular outlet box mounted on the front of the inlet box and adapted to cover the heater outlet opening, the inlet box having closed, top, front and side walls and having a relatively large duct extending from the rear wall thereof for connecting with said heater inlet opening, the inlet box being open at the bottom thereof and having first andk second exterior bafes extending laterally adjacent the bottom edge of the front wall thereof, with the rst oriented approximately vertically downward therefrom and extending below the bottom edge of the outlet box and the second oriented approximately horizontally forward from the first, the outlet box having closed front and side walls and having a relatively small duct extending from the rear wall thereof through the inlet box approximately concentric with the relatively large duct for connecting with said heater outlet opening, the outlet box being open at both the top and bottom thereof, a substantial portion of the top and bottom edges of the front and side walls of the outlet box extending inwardly at acute angles so that the top and bottom of the outlet box has an exterior bevelled conguration adjacent said openings, and the outlet box having a plurality of internal battles mounted therein, including rst and second upper battles extending laterally within the outlet box in spaced parallel relationship at a position above said relatively small duct and References Cited n the file of this patent UNITED STATES PATENTS 2,755,794 Wendell July 24, 1956 FOREIGN PATENTS 240,743 Switzerland Mar. 1, 1946