US2805648A

US2805648A - Water heater

Info

Publication number: US2805648A
Application number: US182565A
Authority: US
Inventors: Edmond H Haugen
Original assignee: SCAIFE Co
Current assignee: SCAIFE Co
Priority date: 1950-08-31
Filing date: 1950-08-31
Publication date: 1957-09-10
Anticipated expiration: 1974-09-10

Description

Sept 10, 1957 E. H. HAUGEN 2,805,648

WATER HEATER 1N VENTOR EDMoN D H.- HAUGEN ATTORNEYS.

5 Sheets-Sheet 2 E. H. HAUGEN WATER HEATER Sept. l0, 1957 Filed Aug. 51. 195o INVENTOR, EDMrjxo' H. HAUGEN BY Y ATTQRNEYS Sept. l0, 1957 E. H.` HAUGEN 2,805,648

y WATER HEATER l Filed Aug. 31. 1950 5 Sheets-Sheet 3 INVENTOR EDMoND H. HAUGEN n @JJM ATTORNEYS Sept. 10, 1957 V E. H. HAUGEN 2,805,648

WATER HEATER y Filed Aug. 3l, 1950 5 Sheets-Sheet 4 /5 I l I I Fi ..5 I I i I l i /2 s l I .9 s .-.2/ a II 7 l g I i I I g I 4/ I l I@ l INVENTOR EDMNo H. HAUGEN ATTORNEYS Sept. 10, 1957 E. H. HAUGEN WATER HEATER 5 Sheets-Sheet 5 Filed Aug. 31, 1950 INVENTOR .EoMoNu H. HAUGEN.

"VBY

v ATTORNEYS nited States arent WATER HEATER Edmond H. Haugen, Birmingham, Mich., assignor, by mesne assignments, to Scaife Company, Uakrnont, Pa., a corporation of Pennsylvania Application August 31, 1950, Serial No. 182,565

7 Claims. (Cl. 122=33) This application relates to heater apparatus and particularly to such wherein domestic hot water and hot water for the radiators or other space heating devices are heated by acommon burner.

Since the recent war there has been considerable expansion in housing, particularly in the eld of small houses, more of which are being built because of the increased costs of building. Many of these small houses have no basements and must install the entire heating unit in either the kitchen or a utility room on the first floor. The -heater apparatus of the present invention is particularly adaptable for small houses, and essentially it comprises a special fabricated boiler within which is mounted a Wall llame oil burner, the boiler being surrounded by an insulating cabinet so that it is a fire proof insulated unit that does not radiate much heat into the surrounding room, and special arrangements are provided for heating the domestic hot water. Preferably the domestic hot water coil is suspended within the water space of the boiler. Details of these and other novel assemblies and sub-assemblies will appear as the description proceeds.

It is a major object of my invention to provide a novel heater apparatus wherein the coil assembly for instantaneously heating domestic hot Water is suspended within the water space of the boiler in such a manner as to be out of Contact with the walls of the boiler and at the same time not to interfere unduly with circulation of the boiler water.

A further object of the invention is to provide a novel boiler construction for a hot water heater wherein certain of the walls are eccentric or otherwise relatively more widely spaced than others to provide room for a coil for circulating domestic water to be heated through the hot water boiler space without unduly interfering with circulation of boiler Water.

It is a further object of the invention to provide a novel combination of a boiler and domestic hot water heater wherein the coil for the domestic hot water is mounted as a unit upon a plate or other closure member secured to the top wall of the boiler whereby the coil is suspended freely in the boiler water.

lt is a further object ofthe invention to provide a novel domestic water coil arrangement and mounting for a hot water heater.

A further object of the invention is to prvide a novel automatic draft stabilizer assembly wherein air from a point adjacent the bottom of the heater is drawn upwardly through a passage and combined with the outgoing combustion products. Y

Further objects of the invention will presently appear as the description proceeds in connection with the appended claims and the annexed drawings wherein:

Figure l is a top plan view of a hot water heater according to a preferred embodiment of the invention, par tially broken away to show certain details and particularly showing the arrangement of the boiler, the domestic water together with water tight joints to heater coill mounting, the pump and distribution piping, and the expansion tank;

Figure 2 is a front elevation of the water heater of Figure l, broken away to illustrate the suspension mounting of the coil assembly for heating domestic hot water;

Figure 3 is a side elevation of the water heater of Figures l and 2, illustrating the water distribution arrangements and partially broken away to show the pump mounting and the draft stabilizer;

Figure 4 is a top plan view of a unitary welded sheet metal boiler having eccentric inner and outer walls which is used in the preferred embodiment of myinvention;

Figure 5 is a side elevation mainly in section through the boiler of Figure 4;

Figure 6 is a rear elevation of the draft stabilizer unit apart from its assembly with the rest of the water heater illustrating particularly the deector where the draft air joins the combustion gases before passing into the llue; and

Figure 7 is a photographic view of a domestic water heating coil and mounting plate wherein only a single coil is used and which may be substituted for the dual coil unit illustrated in Figures 1 and 2.

The novel water heater apparatus of my invention cornprises a cabinet 11 surrounding a boiler 12 which has mounted in it a domestic hot water heating coil assembly indicated at 13. Boiler 12 is connected to an expansion tank 14, as by a suitable pipe 15. A burner unit, which is preferably a wall flame oil burner 16, is mounted on a hearth at the bottom of the boiler, and after traversing the combustion chamber within the boiler the products of combustion escape through a flue assembly.

Boiler 12 is best illustrated in Figures 4 and 5 wherein the boiler walls are all made of sheet steel sections having a gage of about one-fourth of an inch permanently welded provide a novel vunitary Water backed combustion chamber.

The boiler assembly comprises an outer cylindrical member 17 that defines the outer wall of the water space 18 within the boiler. The lower part of the combustion chamber within the boiler or what is known as the primary combustion chamber 19 is surrounded by a cylindrical member 21 displaced rearwardly from the front of the unit so as to appear in plan (Figure 4) as eccentric with respect to outer wall member 17. Member 21 defines the lower inner wall of the boiler Water space. l

The upper or secondary combustion chamber 22 is surrounded by a wall member 23 which is mairdy cylindrical and concentric with thelower combustion chamber wall 21 but is formed with rearwardly projecting

walls

24 and 25 to provide a ilue connecting throat as indicated in Figure 4. The bottom of lower combustion chamber 19 is open as indicated at 26 to receive the burner and flame rim as will appear. The bottom of the water space between

walls

17 and 21 is closed by a suitably shaped annular steel member 27 which'is known as a mud ring and Yis welded at its inner and outer peripheries to

walls

17 and 21, thereby sealing off the entire bottom of the vboiler assembly. The top of lower combustion chamber 19 is defined by a circular steel plate 28 welded about its periphery to member 21 and it has a circular opening 29 concentric with member 21. The bottom of secondary combustion chamber 22 is closed by a generally circular welded plate 31 concentric with member 23Ywhich, at the flue outlet side, is provided with an extension 32 that extends into Contact with the inner surface of the outer boiler wall 17. A central aperture 33 is formed in plate 31.

Walls

28 and 31 are parallel and horizontal and are spaced apart as illustrated. A series of small spacer blocks 34 are welded between them in the water space to aid in maintaining them apart. In addition `

walls

28 and 31 are connected by a cylindrical collar 35 which is welded within -

openings

29 and 33, and projects up into the upper combustion chamber as illustrated in Figure 5. The boiler top wall is a generally C-shaped steel. plate 36 that` extends from `wall 24 to wall 2S, being welded to the tops of these walls and member 23 so as to complete the top closure of the boiler water space.

I have thus provided an all steel welded plate boiler unit wherein the entire water space is sealed by welded joints. Lower wall `21 provides a continuous smooth water backed surface in the primary combustion chamber. The products of combusiton successively traverse t primary combustion chamber 19, throat 35, upper combustion chamber 22 andthe outlet above extension32 between walls 24 `and 25. The eccentric arrangement of the inner and outerboiler walls provides a largeforward water space 37 wherein the coil assembly for the domestic hot water supply may be disposed as will appear. It is obvious that space 37 need not be dened by eccentric circular walls, although that structure has been found extremely adaptable to speed of assembly and eiicient boiler operation, but may `be defined by other wall arrangements.

While I have here described my boiler as made up of circular walled sections, it will be understood that the overall scope of the invention is not so limited. One limit on the size of circular boilers is the maximum diameter than can pass through the usual building doorway. The boiler therefore may be oval or generally rectangular in shape, since sheet steel may be readily worked to obtain the optimum shape. It has been found that generally rectangular and oval boilers can be increased in length while maintaining the maximum permissible width, thereby providing a higher output.

Within the boiler unit, supportstrips 38 and 39 welded to

walls

23 and 17 respectively help to support upper wall 36 from below. Above bottom wall 27 a series of spaced projections 41 are welded to the boiler walls for locating wall 27 in the assembly. A plurality of lugs 42 are welded to depend from mud ring 27 below the level ofthe surrounding

walls

21 and 17 for mounting the boiler on the rest of the hearth assembly.

Figures 1-3 illustrate the water distribution system for pumping the hot water from the boiler to the radiators or other space heating devices of the house and return. It essentially comprises a pump 43 driven by an electric motor 44. The pump and motor assembly may be mounted on a bracket 45 connected to the frame of the surrounding cabinet. vention, however, the pump assembly and connected piping provide a self supporting rigid assembly needing'no added support from the cabinet. The outlet side of the pump is connected by means of a coupling or T tting 46 with a pipe 47 whichleads downand thence to the t.

space heaters. A `valve 48 is provided in this line. A pipe 49 is connected to another outlet in coupling 46 and to a fitting 51 threaded into a iiange 52 in wall 17 of the boiler. Fitting 51 is located at the top of the boiler water space so that any Water pumped up through pipe 49 will return directly into thte top of the boiler. A valve 53 is'provided in line 49.`

Valves

48 and 53 are adjustable to control the rate of flow of water therethrough but either may be shut off completely as will appear.

The inlet side of pump 43 s connectedby a pipe S4 with a coupling or T fitting 55 having one inlet connected to the return line S6 from the space heaters (not shown). The other inlet ofcoupling S is connected by a pipe 57V to a fitting 58 threaded into a flanged outlet 59 in the lower part of boiler wall 17. The inlet and outlet sides of pump 43 are connected to pipes 49 and 54 respectively through`

adapter flange assemblies

61 and 62 respectively which enable the pump to be readily removed for repair or replacement.

In most `embodiments of the int During operation of the pump, hot water from the lower part of the boiler is drawn off through pipe 57, coupling 55 and pipe 54 and pumped out through coupling 46. If valve 48 is closed, as it may be during the summer when space heating is not necessary and the action of convection currents within the boiler water space is not adequate to suitably heat the domestic hot water and with valve 53 open, all of the hot water will be pumped through pipe 49 into the top of the boiler, thus providing a forced recirculation of the boiler water that speedily results in heating of all the boiler water for quickly indirectly heating the suspended domestic water coil.

When, as in the winter, it is desired to circulate hot water through the radiators as when heat is demanded in the house, both

valves

48 and 53 are open and the ow through coupling 46 split as indicated in Figure 3. The

valves

48 and 53 are suitably adjusted to provide the desired rate of flow of water in each circuit. Under these conditions the hot water being pumped out of the boiler where it is lowest in temperature is admixed with some of the cooler return water before it is pumped up- Y wardly to pass partly out through and, into the system c water.

and partly back into the top of the boiler. In this manner I am enabled to raise the average boiler water tempera ture and maintain a more uniform heating temperature for the Water in the space heating system throughout the house and to maintain the temperature of the domestic hot water at a higher level. If for some reason it is desired to maintain circulation through the radiators while the coil for the domestic water tank is being repaired, or if the coil is omitted and a substitute or separate source of domestic hot water is used, valve 53 in the upper pipe may be closed.

The verticaltexpansion tank 14 is shown in Figures l, 2 and 3. This tank is rigidly supported on the framework within one corner of the cabinet preferably with its bottom spaced above the oor of the cabinet. Above tank 14 is a coupling 63 from which depends a pipe 64 that extends through a top flanged opening in the tank down nearly to the bottom within the tank, so that any Water which enters the tank will be deposited near its bottom. Expansion tank 14 is connected to the boiler through coupling 63 and pipe 1S, the latter being shown in Figure l as extending over the top of the boiler to a union 65 that is threaded into an aperture in the plate 66 that supports the domestic water heating coil. In this manner, any excess water in the space heating system that arises out of expansion of the heated boiler water will overflow through pipe 15 into the expansion tank. A safety valve 60 for the system is also connected to coupling 63 asillustrated in Figure l. By thus providing such a vertical expansion tank in the assembly, I supply the system with a greater capacity expansion tank having a larger air cushion therewithin.

An extremely important 'feature of my invention is the fact that ythe coil assembly 13 for heating the domestic hot water is readily removably mounted in the heater. Top wall 36 of the boiler is formed with an arcuate elongated, generally kidney-shaped opening 67 that is closed by similarly shaped plate 66 attached to the top wall of the boiler unit as by a plurality of studs 68. Plate 66 in eiect forms a part of the top boiler wall and the coil 13 itself is entirely suspended from it in the boiler Normally plate 66 is tightly fastened upon the top wall of the boiler with suitable gaskets between them.

Referring to Figure 2, the domestic hot water heating coil assembly comprises two separate coils of copper `

tubing

71 and 72. Plate 66 is formed with suitable openings through which project threaded nipples upstanding from

fittings

73, 74, 75 and 76. Nuts 77-80 on the respective nipples clamp these fittings tightly to the underside of the plate 66. 4Coil 71 comprises a continuous tube having an end portion 81 connected to fitting 73, three vertically spaced cylindrically coiled

horizontal sections

82, 83 and 84 in series, and a riser 85 connected to fitting 74. Coil 72 comprises a continuous tube having an end portion 86 connected to fitting 76, three Vertically spaced cylindrically coiled horizontal sections 87, 88 and 89 in series and a riser 91 connected to fitting 75.

Coils

71 and 72 are connected in series by a jumper tube 92 connecting the nipples of fittings 74 and 75 above plate 66. The fitting 73 is connected to the cool water inlet pipe 93, and fitting 76 is connected to pipe 94 that goes to the domestic hot water tap (not shown). As hot water is drawn from the coil, it will be automatically refilled with cool water entering from pipe 93 under normal line pressure to be instantly heated by the boiler water as will appear.

Each of

coils

71 and 72 is made of thin-walled copper tubing having an outer diameter of 3% inch to 1-/2 inch, and the coils are substantially rigid self sustaining units extending down into the boiler water. The arrangement provides a large area for heat exchange, preferably at least ten square feet or more for the entire coil assembly 13. As illustrated in Figure 1, coil assembly 13 forms a generally arcuate or kidney-shaped unit that follows the circumferential contour of space 37 without touching any of the boiler side walls.

The rotary wall flame oil burner unit 16 may be of the type illustrated in Powers et al. Patent 2,491,517 or the United States Letters Patent of Edmond H. Haugen No. 2,616,402, issued November 4, 1952, and it projects upwardly through a suitable opening in a hearth assembly rigidly secured across the bottom of primary combustion chamber 19. The hearth assembly comprises a steel plate 95 secured as by bolts 96 to a boiler base structure 97 that supports the entire heater assembly on the floor. The burner unit 16 is secured to plate 95 as by the bolts 98. A cylindrical steel shell 99 upstanding from plate 95 surrounds a layer 101 of fire resistant cement or other refractory material which serves as the hearth surface, and an annular flame rim 102 is welded above the inner periphery of shell 99 to a series of spaced upright brackets 99' which serve as attachment members for securing shell 99 and ame rim 102 to the plate 95. See Figure 2. A series of grilles 103 are mounted on the flame rim in accord with usual practice.

The plate 95, shell 99, cement hearth 101 and the flame rim 102 are preferably factory assembled, and in installation in the field the hearth is completed by filling refractory cement into the space between shell 99 and wall 21 as illustrated in Figure 2.

Above the hearth, oil droplets from the rotating inger tubes 104 are atomized at the flame rim 102 and admixed with air pumped outwardly by fan 105. An igniter 100 is provided adjacent the flame rim. This burner assembly provides an even annular iiame around the lower periphery of wall 21 which is free of openings and pro- I jections and is heated uniformly by the hot products of combustion that pass upwardly over it and through throat 35 into the secondary combustion chamber 22. Instead of the hearth assembly above described, a steel hearth and shield ring assembly such as disclosed in Haugen Patent No. 2,616,402, issued November 4, 1952 may be used.

The top of the secondary combustion chamber is closed by a suitable cover assembly 110 as illustrated in Figure 3. A tubular baffle 106 having a top plate 106a and an opening 107 facing forwardly away from the flue passage between

walls

24 and 25 extends between' the cover and boiler wall 31. Baffie 106 isfreely seated on wall 31 so as to be removable when the cover is taken off. 'A plate 108 secured to baffle top plate 106g projects over the top of the passage between

walls

24 and 25. The purpose of the cover and baiiie assembly is to extend over the top of the secondary combustion chamber and to direct flow of the hot combustion gases along the wall 23 as indicated by the arrows in Figure 1.

Cover assembly 110 is secured to the top of the boiler unit as by studs 110a.

Preferably the cover assembly and its association with the boiler is the same as disclosed in said above men tioned Haugen patent, to which attention is directed for any detail needed to understand the present invention.

A novel smoke hood and draft stabilizer assembly is mounted at the rear of the boiler. This assembly comprises in essence a head 111 which has at opposite sides arcuate fianges 112 and 113 (Figure 6) secured as by bolts 114 `to the adjacent wall 17 of the boiler. Head 111 is forwardly open at 115 so as to provide an outlet which is continuous with the passage between

walls

24 and 25 for conducting the products of combustion from the secondary combustion chamber. Head 111 has a rearwardly projecting bottom wall 116 that terminates at the juncture of the head with a vertical tubular passage defining member 117 that extends down to the bottom of the cabinet. Tube 117 is closed at its lower end except for an opening wherein is fitted a short collar 118 opening into cabinet space below the boiler. Air may enter collar 118 and pass up the'tube 117 into head 111 to join the outgoing combustion products.

An automatic draft stabilizer assembly 119 is provided in the inner end of collar 118 and comprises a support plate 120 inserted into the open end of collar 118 and held there as by screw 121. A damper plate 122 having pivots 123 at opposite sides journaled in support 120 serves to limit entry of air into collar 118. Plate 122 has a recessed portion through which extends a threaded rod 124 on the lopposite ends of which are mounted weights 125' and 126. Rod 124 is clamped to plate 122 as by nuts'127.

In operation, when the liue is cold, the weights are so located and balanced that weight 125 exerts the strongest leverage to urge the damper counterclockwise until a projection 128 encounters a fixed stop 129 on the support. In this situation, damper 122 is almost closed and little or no air passes up tube 117. As the fiue temperature increases, the draft increases and the air fiow tends to rock plate 122 toward amore open position where it admits more air. Eventually a condition is reached where damper plate 122 assumes a fairly constant open position, which may be determined by preadjustment of the weights on rod 124. I have thus provided an arrangement'for maintaining a substantially constant velocity draft in the heater.

At the upper end of tube 117 at the junction of the draft air and the combustion products is mounted a deiector plate 131 having a fiange secured to wall 116 and a deflector ledge 132 that extends upwardly and rearwardly at about 45 degrees whereby the air coming up through tube 117 will be deflected outwardly thereby providing a controlled draft which will aid in movement of the products of combustion outward through the flue. The def tiector plate 131 insures against any tendency of the products of combustion to descend through tube 117. VAt its rear, head 4111 is open to receive a short flue connecting tube 133 that projects rearwardly through the cabinet wall (Figure 1). The above described draft stabilizer assembly 119 may be the same as that disclosed in United States Letters Patent No. 2,514,446, issued to ELA. Field on July 11, 1950, to which reference is made for further de tail. The novel smoke hood and draft stabilizer assembly of the invention may be used in a furnace as well as a boiler. f v

One decided advantage of this arrangement that particularly adapts it forthe kitchensV of small houses is that the entire draft ,assembly isV within the cabinet and the entire unit may be backed up fiush against a wall in the kitchen with the projecting flue tube 133 thrust into a Vfireproof ue in the kitchen wall. This is a novel and useful space saving feature which is made possible by the rarrangement above described in conjunction with the other parts of the apparatus.

A diaphragm actuated switch assembly 134 is mounted on the cabinet frame near the top of the boiler. A thermostat bulb 13S is mounted in theboiler water adjacent the suspended coil 13 and near the portion of the coil connected to the cold water inlet 93, so as to be quickly responsive to any change in thel boiler water induced by entry of cold water into coil assembly 13. Thermostat 135, which may be of any suitable conventional type, is connected by a fluid conduit 136, `fitting 137 and fluid conduit 133` to switch assembly 134 whichis included in a control circuit shown in Figure 1.

A second thermostat bulb 139 is mounted in the boiler water about an inch below the toprof the boiler as illustrated in Figure 2, so as to lie near the outlet of the coil assembly 13. It is connected by fluid conduit 141, fitting 142 and fluid` conduit 143 to switch assembly 134.

The circuit controlled by the switch assembly 134 comprises two selectively operable circuits, one including the burner 16 and the other including both the burner 16 and the pump motor 44. These two circuits are in parallel and one or the other is selected by a suitablemanual switch S for incorporation in the control circuit. When it is desired to energize only the burner as will be described later,the rst of these two circuits is included in the control circuit.` When it is desired to energize both the burner and pump the other is included.`

The operation will now be further described. For summertime operation, or other periods when space heating in the house is not required, it has been found that the domestic hot water supply may be adequatelymaintained by action of convection currents within the boiler water space. Assume to start that the boiler water is hot and has suitably heated the water within the suspended `coil assembly 13. The above-described manual l switch S is in open position to include the burner in the control circuit but not the pump motor.

When domestic hot water is drawn out of the coil assembly 13, the incoming cold water from pipe 93 `chills the coil and cools the surrounding boiler water. When the temperature of the surrounding boiler water drops below a predetermined amount, say 190 F., the thermostat 135 acts to cause the burner 16 to be energized to start heating the boiler water. Convection currents within the boiler water space will cause hotter water at the bottom of the boiler to displace upwardly toward the coil i3 and this circulation by convection within the boiler soon results in even heating of all the boiler water and rapid raising of the temperature of the water in the coil assembly 13. When heat exchange stability is established between the water in coil 13 and the surrounding boiler water which has been raised aboveV the predetermined setting for the thermostat, the burner is deenergized. This feature of rapidly following the change in temperature of the boiler water is extremely important in small capacity boilers such as that at 12.

The above provides an operational control insuring almost instantaneous hot water for the domestic tap. The thermostat at 139 provides a limit control in that it prevents the hot water emerging from the coil assembly 13 from exceeding a safe limit. This control may be for example set to deenergize .the burner control circuit when the surrounding water at the top of the boiler is at 220 F. or above. I have thus provided a dual control for the domestic hot water which insures speedy response to use of the water and a safe limit control.

When the boiler water capacity is small it may be desirable as in the summertime to speed upheating of the domestic` hot water by providing forced recirculation of the boiler water.. .This is done byelosing the above described manualswiteh S to include both the burner and pump motor 44 in the control circuit. The operation is then substantially as above, except for 'forced recirculation of the boiler water from the bottom of the boiler through conduits 57 and 54, pump 43iand conduit 49.`

8 Valve 48 may be closed at this time to avoid space heating circulation.

When it is desired both to heat domestic hot water and supply hot water to space heating means such as radiators or panels, as in the winter time, the above mentioned manual switch S is closed to include both the burner and the pump motor in the control circuit. The thermostats and 139 act to control as above when domestic hot water is used. Valve 48 is open so as to obtain the split flow described above in describing the pump connections. A conventional control thermostat (not shown) responsive to space heating demands independently of the

thermostats

135 and 139 is also provided. Thus, whenever the burner and pump motor are now energized, water from the boiler water space is recirculatcd through the boiler and at the same time circulated through the radiator or panel system. The pump` must be large enough to handle both iiows. In a specific embodiment of the invention, wherein hot water is drawn out of the bottom of the boiler and admixed with return water from the space heater panels so that the water at the pump outlet was 20 F. higher than the return water and 40 F. cooler than the boiler water drawn out of the bottom of the boiler, and the outlet of the pump was split between recirculation of boiler water and circulation of the space heater water, a satisfactory pump flow rate was about 8.6 `gallons per minute, of which 3.4 gallons per minute were recirculated boiler water and 5.2 gallons per minute were space heater water. This ratio can be varied by adjustment of

valves

53 and 48, and, in any installation, the flow rate is calculated according to the maximum expected loads in the boiler and panel circuits. In the above, the maximum expected boiler output was 80,000 B. t. u. of which 12,000 B. t. u. represented domestic hot water requirements and the maximum expected space heater load was 52,000 B. t. u. My invention requires a larger' pump than would be used in the conventional house heater boiler where the pump merely forces water through the space heater circuit.

A thermostat bulb 144 is inserted into the head 111 above and forwardly of deector ledge 132 which prevents thc upcoming cool air from directly impinging on the thermostat bulb. So protected by ledge 132, thermostat 144 is directly and accurately .responsive to the tcmperature of the outgoing flue gases. As illustrated in Figure l, the thermostat bulb 144 is connected to a master relay device 145 which controls the entire electrical circuit of the yheater and shuts off the burner should the flue temperature rise above a predetermined value.

Figure 7 illustrates an alternative domestic hot water heating coil assembly 146 wherein, instead of being made up of two separate coils, the coil assembly comprises a single continuous coil made up of eight vertical banks of convoluted tubing in series with its opposite ends secured to fixtures 147 and 148 that are clamped to plate 149 as by

nuts

151 and 152 threaded on the projecting fixture nipples above the plate. The coil assembly is stiliened by

straps

153 and 154 which extend adjacent the respective from xtures down and around the bottom ofthe stack of coils and are secured to the fixtures. The coil assembly of Figure 7 is suspended in the boiler water in the same manner as that of Figures l-6. The coil assembly 146 is arcuate to follow the circumferential contour of the boiler walls and tit within the space 37 without contacting the boiler walls, as in the earlier embodiment.

The heater above described is compact and etiicient and may be safely placed in a room having a combustible iioor. The body of the boiler is insulated, as by a blanket of insulating fiber secured around wall 17, and very little heat is radiated into the kitchen. No separate hot water storage tank is required, as the boiler action is instantaneous and reliable.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. rIlhe present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all 4changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. In heating apparatus, a boiler shell comprising a cylindrical outer wall and vertically spaced cylindrical inner walls surrounded by said outer wall to deiine a boiler water -space therebetween, `at least the upper of `said inner walls being eccentric with respect to said outer wall to provide at one side a wide water space for receivi-ng a domestic hot water coil, said inner walls detining combustion chambers, means providing a restricted throat passage between the combustion chambers defined by said inner walls, a plurality of end walls completing closure of the water space between said inner and outer cylindrical walls, said inner cylindrical walls being relatively thin sheet metal walls of high heat conductivity having smooth uninterrupted inner surfaces along which products of combustion may flow without turbulence for enabling a maximum of rapid heat exchange between the products of combustion and the water column in the boiler shell, said water space between the boiler walls being continuous about the combustion chambers except for a lateral ilue outlet from the upper combustion chamber, and the upper of said end walls having a circumferentially elongated opening above said Wide water space, a removable closure secured upon said opening, and a circumferentially elongated domestic hot water |heating coil assembly supported on said closure so as to be suspended in said large area water space, the inlet and outlet connections to said coil assembly being secured to said closure member.

2, In heating apparatus, a boiler shell comprising an outer cylindrical wall member, an inner cylindrical wall member surrounded by the outer member, a wall member secured between the lower ends of said cylindrical wall members, `a second cylindrical inner wall member surrounded by the upper part of said outer member, an apertured top wall member secured between the upper ends of said outer member and said second inner member, at least said upper inner wall member being eccentric with respect to said outer wall member so as to provide at one side an enlarged boiler water space below the aperture in said top wall and said inner members being spaced vertically, a tubular throat defining member bridging the space between said inner members, and spaced wall members secured between said throat member and the adjacent ends of said inner members respectively, all of said wall members being sheet metal `elements secured together with water tight joints between them to provide a permanent unit, a removable closure member for said top wall aperture, and a hot water heating coil assembly mounted on said closure member suspended in said enlarged boiler water space.

3. Heating apparatus comprising a cabinet, a boiler in said cabinet supported at a level to provide a space therebelow within the cabinet, said boiler comprising an internal combustion chamber closed at its bottom above said space and having a tiue outlet through the upper part of a boiler side wall, a draft control assembly enclosed entirely within said cabinet beside the boiler comprising means defining a passage open at its lower end into the cabinet space below said boiler and connected at its upper end to said ilue outlet and draft regulating means within said pass-age, and a flue connecting tube projecting from the upper end of said passage defining means through the cabinet.

4. In a hot water heater apparatus, a boiler unit, a

cabinet surrounding said boiler unit, means deli-ning a combustion chamber surrounded by said boiler unit and closed at its lower end by a hearth and burner assembly, a flue `conduit extending from the upper end of said combustion lchamber through said boiler unit, means enclosed entirely by said cabinet defining a draft control passage entending from top to ybottom of the cabinet having its lower end opening into the cabinet space below said hearth and bur-ner `assembly and having its upper end connected at one side to said ilue conduit, a iiue outlet connection projecting from the other side of said draft control passage through the cabinet wall, draft regulation means in said passage below said outlet connection, and means projecting into the upper end of said draft control passage defining means for deecting air rising through said draft control passage outwardly toward said liue outlet connection.

5. In the heater apparatus defined in claim 4, said deecting means comprising an a-ngular ledge at the intersection of said passage and conduit.

6. In the heater apparatus defined in claim 4, -a burner control thermostat responsive to temperature of outgoing products of combustion rfrom the boiler mounted in the upper end of said draft control passage defining means so as to be shielded from 'draft air by said dellecting means.

7. In a hot water heating apparatus, a boiler having inner and outer continuously curved smooth inner surface side walls bounding la water column continuously surrounding ya combustion chamber, said side walls at one side being spaced apart a greater distance than at other parts for a predetermined arcuate distance to provide therebetween a wide coil receiving space in at least the upper section of said water column, top and bottom walls on said boiler, the top Wall having a circumferentially elongated aperture above said coil receiving space, a plate remov-ably mounted over said aperture, and an arcuate coil assembly comprising a plurality of turns and shaped to follow the adjacent side wall contours suspended wholly from said plate and disposed within said space out of contact with said side walls.

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