GB2435321A

GB2435321A - Stove comprising a thermally insulated water boiler chamber

Info

Publication number: GB2435321A
Application number: GB0702964A
Authority: GB
Inventors: Jonathan Greenall
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-02-15
Filing date: 2007-02-15
Publication date: 2007-08-22
Also published as: GB0603047D0; EP1821038A2; GB0702964D0; GB0702946D0; EP1821038A3

Abstract

A stove 101 comprises a grate 108, a fire-box 110 above the gate, thermal insulation 123 defining a back surface of the fire-box space, and a boiler water chamber 107 or heat exchanger at a back wall of the stove at the level of the fire-box. The insulation is disposed between the fire-box space and at least a lower part of the water chamber or heat exchanger that is adjacent the gate so as to provide thermal insulation between the lower part of the fire-box space and the water chamber. Also disclosed is a method of manufacturing a stove with a boiler which maintains a higher combustion temperature in the fire-box of the stove, where the boiler chamber is positioned outside the fire-box and is insulated from at least part of the fire-box. The insulation may comprise refractory brick or insulating board. Preferably, the insulation comprises ceramic, mineral wool, glass fibre, cement, mica, diatomaceous earth, silica or vermiculite. In use, by having the boiler water chamber situated behind thermal insulation, a higher combustion temperature is maintained.

Description

STOVES

This invention relates to stoves, especially but not exclusively wood burning stoves, or stoves capable of burning wood properly. It is especially but not exclusively applicable to stoves which have windows for viewing the fire inside them.

There is a growing realisation that burning wood is good for the environment compared to burning fossil fuels. It is "carbon neutral" in modern terminology, and wood has less embodied energy per unit weight than coal, or oil, for example.

Burning wood can cause smoke and pollution. The hotter the burn the less pollution there is. Combustion can be more complete/efficient at hot temperatures, especially for particulates e.g. soot and smoke. Also, the hotter the burn the less tars and residues, and even water from logs, condense in the stove or chimney or flue. Burning fuel more completely *::::* is also good for energy efficiency. S.

Our earlier patent GB 2251302A discloses a way of pre-heating air to I. improve combustion/achieve high combustion temperatures in a stove, and * of passing a wash of heated air over a glass window in the door of the *. stove. The product made to that design is very successful.

People want to have less smoke produced by their stoves. When there is a window in the door of the stove they want to be able to see the flames/logs burning. If the window soots up too quickly this detracts from the experience/effect. Our "airwash" system discussed in GB 225 1302A helps to keep the window clear, as well as often making the stove suitable for low emissions areas/smoke control geographic areas. By passing air over the glass window in the door of the stove in GB 225 1302A we help keep the window clear of discolouration. By pre-heating the air that enters the fire-box through the grate we improve combustion, and by pre-heating the airwash air we also achieve more complete combustion and help to burn residues/particulates in the vicinity of the window (as well as stopping them settling on the window). A clear view of the fire through the window is achieved.

Some people want to heat water in a boiler in the fire-box of a stove.

Putting a boiler in a stove heats water, but reduces the combustion temperature in the fire-box, causing less complete combustion, and causing the problems associated with that. We have historically discouraged people from having boilers in their stove because of the reduction in combustion temperature/increase in pollution/greater tendency to cause the glass in the stove door to get dirty and obscure the view of the fire.

According to an aspect the invention comprises a stove having a grate, a *1* fire-box above the grate, thermal insulation defining a back surface of a fire-box space, and a boiler water chamber or heat exchanger at a back wall of the stove at the level of the fire-box, and in which the insulation is disposed between the fire-box space and at least a lower part of the water chamber or heat exchanger that is adjacent the grate so as to provide thermal insulation between the lower part of the fire-box space and the water chamber.

Preferably a pre-heating chamber for pre-heating air is provided beneath an ash pan chamber of the stove and/or at side regions of an ash pan chamber of the stove, an air delivery chamber or slot is provided to deliver pre-heated air from the pre-heating chamber to the inside of a window of the stove, and at least one pre-heated air communication channel(s) is/are provided communicating the pre-heating chamber with the air delivery chamber or slot. The air communication channel(s) is/are provided at the front wall of the stove.

We have realised that it is possible to have a boiler with a stove, and in particular with the stove of GB 2251302A, without significantly increasing particulate pollution and/or increasing the tendency for the glass in the stove door to get dirty. We have realised that in prior art stoves the boiler is actually in the fire-box in direct contact with the fuel being burned and the flames. This produces a fast heating performance in the boiler -heat is efficiently transferred to water in the boiler and the heat per unit of time that is transferred to the water in the boiler can be high. So heavy use of hot water can be accommodated. However, having the boiler water chamber directly in the fire-box, as one of the surfaces that constrains the fuel/fire, reduces the temperature of combustion because of the high rate of heat extraction from the fire-box to the water in the boiler (and then the external water pipework/tanks outside of the boiler). This can result in incomplete combustion, sluggish response from the fire in the stove to changes, and build up of residue in the flue way and chimneys, and possibly in dirty venting windows * 20

U *.*

* By having the boiler water chamber behind thermal insulation at least in part, e.g. at the lower parts of the fire-box, we maintain a high I...

combustion temperature. It seems odd at first to insulate a boiler from the fire in the fire-box; it is wanted that heat gets to the boiler.

However, we have realised that what is better, in order to maintain a high combustion temperature, is for heat that seeps through the insulation should heat the water in the boiler, rather than heating the air in the room after being transferred through the sides/back wall of the stove, and/or for heat to be selectively taken from parts of the fire-box where combustion does not occur to a great extent.

The "leaked" heat should be used, and/or heat that would otherwise go up the flue.

This may reduce the rate of heat transfer to the water, but we do not think that this is unacceptable.

Put another way, we do not put a heat exchanger in the part of the fire-box where the majority of insulation takes place: we put it outside of the actual fire-zone itself.

The insulation may extend from the level of the grate to about halfway up the height of the fire-box space, from the grate to the top wall of the stove, and the water chamber may extend from the base of the fire-box space to a height that is more than insignificantly above the top of the insulation.

The insulation may comprise any suitable material that has low thermal *::::* conductivity. The insulation may comprise any non-metal material, preferably with thermal conductivity less than the thermal conductivity of * 20 metal. The insulation may comprise an air space between two layers of material. The insulaton may be a solid material. * * ****

*:*. The thermal conductivity of the insulation may be about 0.05 W/mK to about 1 W/mK at the temperature range of between about 200 C to about 600 C. The thermal conductivity of the insulation may be about 0.10 W/mK to about 0.30 W/mK at the temperature range of between about 200 C to about 600 C. The thermal conductivity of the insulation may be about 0.14 W/mK at the temperature of about 400 C.

The insulation may comprise at least one refractory brick or at least one insulating board. The insulation may comprise any of the group comprising ceramic, mineral wool, glass fiber, cement, mica, diatomaceous earth, silica and vermiculite.

The insulation may be about 5 mm thick to about 110 mm thick, or about 10 mm thick to about 100mm thick. The insulation may be about 20 to about 40 mm thick. The insulation may be about 30 mm thick. The insulation may vary in thickness with regions of relatively thicker insulation and regions of relatively thinner insulation.

Each of the ranges and values of insulation material thickness given, combined with one of the ranges or values of thermal conductivity given, will produce a range or value of thermal resistance in units of m2K/W.

The insulation may be of any material and thickness which has those ranges or values of thermal insulation.

The water chamber may extend upwards insulated by insulation for at least about 1/4 of the fire-box height. * I *1*I

In some embodiments we can put the boiler, or a part of the boiler, at the : . 20 top of a stove housing, typically above a baffle. Again, not I..

* much/practically no combustion occurs there: combustion is largely complete by then, and so removing heat from a region where little I...

*:*. combustion is taking place anyway is not so bad. Indeed, it is good for the point of view of thermal efficiency of the stove as a whole.

A deflector plate or baffle may be provided part way up the height of the fire-box space, extending away from the back of the fire- box space, and there may be insulation at the back of the fire-box space from the level of the grate up to the level of the rear of the deflector plate or baffle, or to about that level, and significantly less insulation, or no insulation, above about the level of the back of the deflection plate or baffle.

The stove may comprise a housing carcass having front, back and side walls, and the back wall may define a boiler water chamber receiving aperture, and a boiler unit, comprising the boiler water chamber and an associated mounting formation, may be mounted to the back wall with the boiler water chamber extending through the boiler water chamber receiving aperture, the mounting formation mounting the boiler unit to the back wall. The mounting formation may be releasably fastened to, or clamped to, the back wall of the carcass by releasable mechanical fasteners. The aperture in the back wall may comprise substantially the whole of the back wall above the grate, the aperture being surrounded by a back wall mounting flange to which the mounting formation is affixed.

The mounting formation may comprise a mounting flange extending around the periphery of the boiler water chamber.

:.** The water chamber may have an upright portion and a laterally projecting *SS.

portion extending into the fire-box space, away from the back wall portion. The projecting portion may extend for about 1/4 to about " of the back-to-front depth of the fire-box space.

The boiler water chamber may extend upwards from at least about the level of the grate to the top of the stove, or nearly so.

There may be a water inlet conduit at or near to the bottom of the upright extent of the water chamber and a water outlet at or near to the top of the upright extent of the water chamber.

According to another aspect the invention comprises a method of manufacturing a stove with a boiler which maintains a higher combustion temperature in the fire-box of the stove, the method comprising positioning a boiler chamber outside of the fire-box itself and insulated from at least part of the fire-box by insulation.

There may be a back wall aperture in the back wall of the stove and the method may comprise introducing a boiler unit into the stove from the outside of the stove through the back wall aperture, and fixing the boiler unit to the back wall of the stove.

In some embodiments the boiler water chamber is welded, or otherwise attached, permanently to the stove housing. However, it is preferred to have the boiler chamber attached to a plate defining an exterior surface of the stove housing, and to have that plate removable from the stove housing. This can help in repair or maintenance. The back wall of the stove is our preferred place for such a removable unit.

In some embodiments the boiler water chamber has a substantial **I.

vertical/upright extent, typically for substantially the full height of the r* fire-box from the grate to the top wall of the stove. This enables the water inlet to the boiler water chamber to be well spaced vertically from the water outlet from the boiler water chamber, which can help with * thermal siphoning water flow in the boiler water chamber. e. * * S * * S.

The water chamber may have an upright region and a projecting region extending into the stove, away from the upright region. The projecting region and the upright region may be generally at right angles to each other.

According to another aspect of the present invention there is provided a domestic heating stove or cooking range the body or casing of which incorporates a removeable panel or an open section to facilitate the addition of a water boiler.

The body or fire-box of the stove is lined with refractory brick or insulating board. The body of the Stove or door of the stove or range incorporates a means of distributing air over the glass viewing windows to prevent soot deposits and provide clear vision of the fire.

According to the present invention the boiler or water jacket does not form a wall or panel in direct contact with the fire. The boiler or water jacket is separated from direct contact with the fire by means of refractory bricks or insulating boards, thus the heat transfer is slower than a conventional direct contact system. However the water container or boiler is less prone to cool the combustion, high efficiency is maintained offering cleaner chimneys and reduced air pollution. The hot fire will not be sluggish and a clear fire view can be maintained by pre-heated air distribution over the fire viewing door or window. IS.,

Condensation often forms on the cool surface of a conventional boiler.

Corrosion of the boiler is reduced by insulating the fire from the boiler * condensation.

S I...

A stove or range may be provided in which the boiler can be added or . .: removed by providing an absent or removable stove body section enabling the boiler to be in close contact with refractory bricks or lining panels maintaining hot combustion and reducing condensation by direct contact between the fire and cold boiler surfaces.

Embodiments of the invention will now be discussed by way of example only, with reference to the accompanying Figures, of which:- Figure 1 is a front view of a prior art stove (without its door); Figure 2 is a side view of the prior art stove of Figure 1 showing some internal structure and including a door; Figure 3 is a perspective view of the prior art stove of Figure 1 (without its door); Figure 4 is a view similar to that of Figure 2, but showing airflow in more detail; Figure 5 shows a schematic perspective view of a new stove with the door and ash pan removed for clarity; Figure 6 shows a schematic side cross-section of the stove of Figure 5, with the door and ash pan shown; S. * Figure 7 shows a schematic view of a boiler chamber of the stove of *.S. S *

Figure 5, with some associated insulation material; S. * * S * S Figures 8 and 9 show the boiler chamber in more detail; IS..

Figure 10 shows a view from the rear, and outside of the stove, of a boiler chamber unit disassembled from the stove; Figure 11 shows detail of insulation layers provided at the sides and back of the fire- box of the stove of Figure 5; and Figure 12 shows schematic details of the back wall of the stove of Figure 5.

Figures 1 to 4 show our existing, prior art, stove discussed in GB 2251302A, the contents of which are hereby incorporated by reference. The Patent Law of some countries do not allow incorporation by reference and so a description of the prior art stove follows in this patent application itself. The disclosure will be useful in understanding the structure of the example embodiment of Figures 5 to 12 since that stove has been developed from the prior art stove of Figure 1 to 4.

A solid fuel stove 1 (typically a wood burning stove) is shown in Figures 1 to 4 of the drawings and has a main body 2 standing on legs 3; a fire-box 4 inside the stove 1 in its upper portion; an ash chamber 5 inside the stove 1 below the fire-box 4; and pre-heating means 6 inside the stove 1 below the ash-chamber 5 and extending up the inside of a front panel 7 of the stove 1. A dividing wall 17' separates the fire box from the ash chamber, and a grate 19 is provided in the dividing wall.

There is a large door aperture 8 in the upper part of the front panel 7 of :.** the stove 1 which provides access into the fire-box 4 to replace fuel (not shown). S. * S *

* .:. In the lower part of the front panel 7 is a small aperture 10 beneath the large aperture 8. The small aperture 10 provides access into the *...

ash-chamber 5 to empty ash created by the combustion of fuel.

Both of the apertures are closed by a door 35 which is mounted on hinge lugs 9 fixed to the front panel 7 of the stove 1. The door 35 has a transparent window 36 and an air inlet 37 which can allow air to enter the ash chamber. The air inlet 37 is controlled by aperture control means, such as a "spinner" 38, which may be thermostat controlled. A sealing band 39 extends around the peripheral edge of the door and seals the closed door to the front panel 7 of the body.

The fire-box 4 is in the upper portion of the stove 1 and is formed by the front, back, and side walls of the box 2, and by the dividing wall 17'.

A back wall 11 of the fire-box 4 is protected from the heat of the fire and the hot solid fuel by an insulating/heat resisting layer 12. Insulation is also provided on the side walls of the fire box.

Above the insulating/heat resistant layer of the back wall 11 is an exhaust aperture 13 through which the exhaust gases of the fire pass on the way to a chimney (not shown). Removably mounted on the back wall 11 between the insulating/heat resisting layer 12 and the exhaust aperture is a deflection plate 14, which extends across the entire width of the fire-box 4 and rests on the insulation on the side walls of the fire-box.

The deflection plate 14 stops short of the door 35 and so provides a gap 16 between itself and the front panel of the stove. The deflection : ... plate is inclined, and the edge at the back wall 11 of the fire-box 4 is at a a...

level slightly below the top of the large aperture 8 while the front free edge 15 is at a level slightly above the top of the large aperture 8. S..

As described earlier, the bottom of the fire-box 17 has a dividing Sal.

wall 17'. The dividing wall 17' is provided with an ash aperture 18 . .: which is covered by a removable grate 19 on which solid fuel can stand.

The grate 19 also serves the purpose of allowing communication between the fire-box 4 and the ash-chamber 5 so that waste ash can fall into the ash-chamber 5 and air can rise up through the grate to feed the fire from beneath, The ash-chamber 5 has two apertures, the small aperture 10 and the waste aperture 18 both of which have been mentioned previously. The ash-chamber 5 collects the waste that falls through the waste aperture 18 in a collection pan 20 which sits beneath the grate 19. The collection pan 20 can be removed from the stove 1 through the small aperture 10 in order to empty the collection pan 20 of waste material.

Beneath the ash-chamber 5. occupying a space across the width and depth of the stove 1 is an air chamber 21 which constitutes part of the pre-heating means 6. The air chamber 21 is at the bottom of the stove 1 inside the body 2. In the bottom of the body 2 is an air aperture 23 which communicates the air chamber 21 with air outside of the stove 1. A regulator plate 24 is slidably movable to cover, partially cover, or uncover the air aperture 23. The regulator plate 24 is moved by a knob 25 which is attached to the plate by a rod 26. Pulling or pushing the knob 25 in or out slides the regulator plate 24 in relation to the air aperture 23.

Air delivery means 27 is provided above the large aperture 8, running :*, across the front panel 7 in the inside of the box 2. The air delivery *.S.

S

means 27 is a passage or chamber that has an exit point or slot 28 along its bottom. The slot 28 is provided next to the top of the door and the top : of the large aperture 8. * S..

The air chamber 21 and the air delivery means 27 are connected by .: communication channels or passageways 30. The passageways 30 comprise two conduits 30' that run up either side of the large aperture 8 and cut through the dividing wall 17'. There is no direct communication between the passageways 30 and the fire box, only through the slot 28. A Continuous air path is formed from the outside of the stove (beneath the stove) to the fire-box 4, through the air aperture 23, along the flat bed of the air chamber 21, up the passageways 30, into the air delivery means 27 and through the slot 28 and into the fire-box 4. This path is shown by the arrows A of Figures 1 and 2. It will be noted that the conduits 30' pass through the dividing wall 17'.

The stove 1 is supported by legs 3 for its base 31 to be standing above the level of the floor in order for air to be supplied readily to the air aperture 23 In operation the fire-box 4 is loaded through the large aperture 8 with solid fuel which rests on the grate 19. The fuel is ignited and once it is burning steadily the door is closed. Until this point the fire was fed by air entering through the large aperture 8, as well as possibly air through the air intake aperture 23 and air through the spinner 38. The knob 25 is pulled out so that the aperture 23 is open to its fullest extent. The fire draws air to be combusted and air is sucked through the air aperture 23 into the air chamber 21 to rise up the passageway 30 and into the air delivery means 27 and out of he slot 28 into the fire-box. In this way air is drawn through the system comprising the pre-heatirig means. *S..

During burning, fuel becomes spent and the ash that is created falls into the collection pan 20 in the ash-chamber 5. The ash is hot and the bottom 31 of the ash-chamber 5 becomes hot. The burning of the fuel heats the fire-box 4 considerably and' the walls and the connecting * means 5 become hot. The hot air from the combustion process rises *. upwards. The exhaust air hits the deflection plate 14 and as the air continues to rise, it flows along the deflection plate 14 towards the front panel 7. As the exhaust air passes the front edge 15 of the deflection plate, it overshoots and plays over the rear face 29 of the air supply means 27. This may cause a draft in the region of the slot 28.

Furthermore, pre-heated air is leaving the slot 28 in a downwards direction. The two airflows mix, Figure 4 illustrates schematically the airflow which is believed to occur in the fire box. There are three main inputs of air: air rising from the fire itself (referenced as B), rising air deflected by the plate 14 (referenced as C), and pre-heated air moving downwards from slot 28 (referenced as D). As the deflected air C meets the pre-heated air D at the top of the door 35 they mix and cause turbulence E at the region of the window 36.

This turbulence pushes air, and more importantly soot and smoke F rising from the fire away from the window and keeps the window cleaner than in conventional fires. The introduction of pre-heated air also enables a higher temperature to be achieved, which results in less soot and smoke, Uncombusted air passing through the pre-heating means 22 is warmed firstly by contacting the bottom 31 of the ash-chamber 5. The draw on air for combustion takes the air up the connecting conduits 30' which are by now hot an the air is heated further. The air receives further pre-heating in passing through the slot 28 and some mixing occurs with the rising and escaping air rising from the deflection plate 14. The draft : *.. and/or turbulence caused by the exhaust gases in the region of the front edge 15 of plate 14 may draw air from slot 28, or assist in doing so. S. ** * . S

* .:. Once the fire in the stove is fully burning, it can be controlled by adjusting the knob 25 which controls the amount of air entering into the *...

S...,. fire-box 4.

I * . S S **

It is an advantage of the stove that it is constructed to intake an air supply from the room. In this way it is very simple to install and it does not require a conduit to have been previously installed in the house. The only connection that needs to be made is to connect the flue of the stove to a suitable system to deal with exhaust gases, for example a chimney.

Otherwise all that is required is a flat area on which the legs of the stove can stand. A hearth area would be suitable.

In addition, the stove is very compact since all of its elements with the exception of the flue can be housed in a small box.

The fire is clean, can be seen through the window which does not readily dirty, is efficient, and has a relatively high air flow for its compact size.

The "air-wash" system of slot 28, passageways 30, and air-chamber 21 help to keep the window clean.

Figures 5 to 12 show our new stove 101. It has a similar construction to that of Figures 1 to 4, except that the airwash system now has a chamber down both sides of the grate and along the back of the grate (as well as below the ash-pan chamber, and except for a boiler arrangement (the subject of this invention).

Figure 5 shows stove 101 having a front wall 102, a back wall 103, and opposed side walls 104 and 105, and a top wall 106. The stove has a boiler water chamber 107 shown largely in dotted outline provided at the back wall, and a grate 108 in a dividing waIl 109 separating a *e*.

fire-box 110 from an ash-pan chamber 111. A pre-heating chamber 112 (best seen in Figure 6) extends beneath the ash-pan chamber 111. An air delivering slot or channel 114 extends above a door aperture 115 and is intended to deliver pre-heated airwash air down over the inside surface of a glass window 116 of a door 117 (shown in Figure 6). Upright corner-post air communication channels 118 and 119 extend from the passage or chamber 112 beneath the ash chamber 111 to the above-door air delivery channel 114. They help to provide rigidity at the front of the stove. The stove is made from sheet metal that has been bent and welded.

Insulation 120, such as firebricks, or refractory thermal insulation, has been omitted from Figure 5 for clarity, but is shown in Figure 6 and in Figure 110. The insulation 120 has side portion 123 which extends along, and defines a boundary at, the bank of the fire-box space 110.

A deflector plate or baffle 124 is also not shown in Figure 5, but is shown in Figure 6. This rests on the insulation 121, 122, and 123. It may be fixed in place (e.g. with adhesive). The baffle plate 124 may be solid, or may provide an air supply to the fire-box space 110 (in which case it may have an air supply channel extending to the outside of the stove, for example to the back wall 103).

Figure 6 also shows an ash-pan 126, beneath the grate 108.

An air inlet 127, with a manual control 128, is provided to control the supply of air to the chamber 112. Another air supply, with manual control, is provided (not shown) to provide a controllable air supply to : ..* the ash-pan chamber, under the grate. S...

S **S.

The stove 101 rests on legs 130 lifting it about 3 inches (8cm) off a base :. surface upon which it stands. This second air control is often provided in the door of the stove.

The boiler water chamber 107 is shown in Figures 6 to 10, Figures 8 and 9 showing it on its side. The boiler chamber is provided as part of a boiler unit 140 comprising a back wall mounting plate 141, an L-shaped, bent, internal boiler water chamber -defining wall 142, a projecting wall 143 projecting away from the mounting plate 141, and side plates 144 and 145.

The water chamber 107 has a first, generally upright, portion 146 which extends up the back wall 103 of the stove, and an internally projecting portion 147 which extends into the housing of the stove, into a space 148above the baffle 124. A flue aperture 149 is provided in the upright portion 146, and is provided by welding a pipe 150 to aperture-defining surfaces of the walls 141 and 142.

The walls 144 and 145 may be folded portions of wall 143, or they may be separate components. The walls 144 and 145 are welded to L-shaped bent wall 142, and to projecting wall 143 and to upright wall 141. Bent L-shaped wall 142 is also welded to upright wall 141 and to projecting wall 143. Wall 143 is welded to wall 141. Together, the pipe 150, and the walls 141, 142, 143, 144 and 145 define an L-shaped boiler water chamber space 151.

Two water inlets 152 and 153 are provided at the bottom of the upright portion 146. Two water outlets 154 and 155 are provided at the top of the upright portion 146. **.

S.'... Figure 12 illustrates schematically the back wall 103 of the stove viewed from the front of the stove. A large boiler unit-receiving aperture 160 is provided in the back wall 103, defined by a mounting flange 161 surrounding the aperture. Holes 162 are shown in the flange 161. These S..

holes 162 have welded in them (not shown) captive bolts projecting outwards/backwards of the stove.

Figure 12 also shows that the ash-pan chamber 111 has airwash air (to be delivered to the passageway 114 above the door) pre-heating channels 163 and 164 to either side of the ash-pan chamber, and airwash air pre-heating channel 165 at the back of the ash chamber, all in communication with the upright channels 118 and 119 shown in Figure 5.

To manufacture the stove 101 the unit 140 is inserted into the internal space within the carcass 102 from the back of the stove through the aperture 160. The mounting plate 141 has a peripheral mounting portion, or flange 170, surrounding the region of plate 141 which part-defines chamber space 151. Holes 171 are provided in the mounting portion 170 which marry up with the projecting captive bolts mounted in holes 162 of the back wall 103. The mounting portion 170 is fitted over the bolts and nuts are then put on its projecting screw threaded bolts, and the nuts tightened.

A gasket/seal (not shown) is provided surrounding the aperture 160, clamped between the flange 161 and the flange 170.

To install the stove in a domestic kitchen, or the like, pipe 150 is connected to a flue pipe. Water inlet pipes of a hot water system are connected to inlets 152, 153, and water outlet pipes of the hot water system are connected to the outlets 154, 155. **

Figure 11 shows schematic detail of the insulation 120, 121, 123, and shows the flue aperture 149 disposed above the top of the insulation. * S

S "S

The stove has not had the combustion temperature of the fire units firebox *Ss.

space reduced significantly in comparison with the stove of Figures 1 to 4 s *e: since the insulation 120 prevents too fast heat transfer to the water in the boiler water chamber. The lower part of the water chamber, adjacent the grate where the fire is burning, and where most combustion takes place, is insulated. Higher up, away from the wood that is burning, the water chamber is uninsulated (or we could provide less insulation). This permits heat to be taken out of the space at the top of the fire-box, above the baffle. This heat previously, in the main, leaked away to the room in which the stove was located and/or went up the flue.

Reducing flue gas temperatures by extracting heat using a boiler there is not detriment to the hot combustion effect we want. It may even help to achieve better thermal efficiency figures.

We have realised that it is not simply a question of choosing between on the one hand high combustion temperatures and low pollution, and a window that stays clean for longer, but no boiler, and on the other hand having a boiler but sacrificing high combustion temperatures and having a window that gets dirtier. We can have both, if we are careful where in the fire-box we extract heat and insulate the near-grate part of the fire-box to retain heat.

An unexpected additional synergistic benefit of the invention is that we : ... can position our now stove closer to combustible surfaces. Current UK *SeS legislation requires a stove to be about 450 mm or so away from combustible material (such as a plasterboard wall). This is a big gap to have behind a stove placed in front of a wall (e.g. in a new house/partition wall of plasterboard, or even a plasterboard-clad stone or brick wall). s S * S.

However, the regulations allow the Stove to be closer (about 150 mm away from the material) if the temperature of the outside of the stove is not more than 65 C above ambient temperature.

Tests have shown that our new stove has a back wall temperature which is not more than 65 C above ambient, and so we can position the stove closer to the wall behind it. The back wall of our stove may have, in use, a temperature of about 50 or 60 C, or perhaps 70 C, or even 80 C. It should not exceed about 85 C.

A further spin-off benefit is that users can now have a bigger stove, with a bigger window so that they can see more of the fire burning, than before. Previously, the heat emitted by the stove all went to the room (or up the flue) and thus meant that people had to accept smaller stoves (high temperature combustion clean-fire stoves) in order to avoid sweltering temperatures in their kitchen/other stove-containing room. Now, the boiler will take Out some heat, so a bigger stove (possibly with a better view of the fire) is possible.

The boiler is arranged to take out about A to % of the heat generated by the stove, preferably between about and " of the heat generated, or between and " of the heat generated. * S

We envisage a stove which is primarily for space-heating the room, looks S...

good and has a good view of the fire burning, and which burns clean ** using high temperature combustion, but also heats some hot water, (rather than central heating boiler which has modest temperature combustion and being primarily a central heating boiler which also heats a room directly). S...

. : Our stove may have a towel rail, which will get hot/warm, and the top of * 20 the stove (if it has a flat top) will typically still get hot enough to boil a kettle.

The simple design of our boiler unit, removably inserted from the back of the stove, complements the design of the earlier stove where the air-wash channels are at the front. We may make our earlier stove 20, 30, or 40 mm or so deeper so that the fire-box remains the same depth even with the boiler unit projecting to the back of the insulating material. This will enable the same refractory material inserts to be used, and the same baffle, to be used as we use for the boiler-less stove.

S

The viewing window for the fire may not be present at all (but usually will). In addition to, or instead of, a window in the door one or more other fire-viewing windows may be provided (e.g. in side walls).

The airwash pre-heating channels need not be in the front of the carcass by the door; they could for example be in the door itself.

The standard test for measuring the efficiency of stoves is EN 13240.

This measures the calorific value of the fuel burned, the temperature of the flue gases, and the levels of carbon monoxide, carbon dioxide and oxygen in the flue gases to produce an efficiency figure. Our new stove performs well.

The boiler water chamber may not project laterally into the fire-box. We prefer that it does, but it may not be essential. SS **

The boiler water chamber may not extend down to the level of the grate. I..

We prefer that it does. This increases the vertical height between the water inlet and outlet, improving circulation of water in the hot water system coupled to the stove/in the water chamber. The boiler water chamber, or water jacket, may conceivably be provided solely above the baffle, but we strongly prefer providing it with at least some vertical component.

We may provide air convection panels at the sides of the stove to provide air-insulation of the sides/cooler to touch side surfaces to the stove. The convection panels may effectively trap/partially trap a body of air between them and the side walls of the main carcass.

The boiler unit may include, or be associated with, a thermostat controller to control water flow through the water chamber.

Claims

CLAIMS

1. A stove having a grate, a fire-box above the grate, thermal insulation defining a back surface of a fire-box space, and a boiler water chamber or heat exchanger at a back wall of the stove at the level of the fire-box, and in which the insulation is disposed between the fire-box space and at least a lower part of the water chamber or heat exchanger that is adjacent the grate so as to provide thermal insulation between the lower part of the fire-box space and the water chamber.

2. A stove according to claim 1 in which a deflector plate or baffle is provided part way up the height of the fire-box space, extending away from the back of the fire-box space, and in which there is insulation at the :... back of the fire-box space from the level of the grate up to the level of S...

the rear of the deflector plate or baffle, or to about that level, and significantly less insulation, or no insulation, above about the level of the * back of the deflection plate or baffle. S..

3. A stove according to claim 1 or claim 2 in which a pre-heating *..: 20 chamber for pre-heating air is provided beneath an ash pan chamber of the stove and/or at side regions of an ash pan chamber of the stove, an air delivery chamber or slot is provided to deliver pre-heated air from the pre-heating chamber to the inside of a window of the stove, and at least one pre-heated air communication channel(s) is/are provided communicating the pre-heating chamber with the air delivery chamber or slot.

4. A stove according to claim 3 in which the air communication channel(s) is/are provided at the front wall of the stove.

5. A stove according to any preceding claim, in which the insulation extends from the level of the grate to about halfway up the height of the fire-box space, from the grate to the top wall of the stove, and in which the water chamber extends from the base of the fire-box space to a height that is more than insignificantly above the top of the insulation.

6. A stove according to claim 5 in which the water chamber extends upwards insulated by insulation for at least about 1/4 of the fire-box height.

7. A stove according to any preceding claim which comprises a housing carcass having front, back and side walls, and in which the back wall defines a boiler water chamber receiving aperture, and in which a boiler unit, comprising the boiler water chamber and an associated I...

mounting formation, is mounted to the back wall with the boiler water chamber extending through the boiler water chamber receiving aperture, :. the mounting formation mounting the boiler unit to the back wall.

8. A stove according to claim 7 in which the mounting formation is . .: 20 releasably fastened to, or clamped to, the back wall of the carcass by releasable mechanical fasteners.

9. A stove according to claim 7 or claim 8 in which the aperture in the back wall comprises substantially the whole of the back wall above the grate, the aperture being surrounded by a back wall mounting flange to which the mounting formation is affixed.

10. A stove according to claim 9 in which the mounting formation comprises a mounting flange extending around the periphery of the boiler water chamber.

S

11. A stove according to any preceding claim in which the water chamber has an upright portion and a laterally projecting portion extending into the fire-box space, away from the back wall portion.

12. A stove according to claim ii in which the water chamber is generally L-shaped in cross-section.

13. A stove according to claim ii or claim 12 in which the projecting portion extends for about A to about " of the back-to-front depth of the fire-box space.

14. A stove according to any of claims 11 to 13 as they depend directly or indirectly from claim 6, in which the projecting portion of the water : chamber extends into a space above the deflector plate or baffle. 0*** * S

15. A stove according to any preceding claim in which the boiler water :. chamber extends upwards from at least about the level of the grate to the top of the stove, or nearly so. S... * . S...

16. A stove according to any preceding claim in which there is a water inlet conduit at or near to the bottom of the upright extent of the water chamber and a water outlet at or near to the top of the upright extent of the water chamber.

17. A stove substantially as described and illustrated herein with reference to Figures 5 to 12 of the accompanying drawings.

18. A method of manufacturing a stove with a boiler which maintains a higher combustion temperature in the fire-box of the stove, the method comprising positioning a boiler chamber outside of the fire- box itself and insulated from at least part of the fire-box by insulation. b I,

19. A method according to claim 18 comprising having a back wall aperture in the back wall of the stove and introducing a boiler unit into the stove from the outside of the stove through the back wall aperture, and fixing the boiler unit to the back wall of the stove.

20. A method of manufacturing a stove substantially as described herein with reference to Figures 5 to 12 of the accompanying drawings. I. * * * I*I **.. * * **.* ** a. a * . * **. * a a... a. a a a a.