WO2012076834A1

WO2012076834A1 - Stove for a heating system

Info

Publication number: WO2012076834A1
Application number: PCT/GB2011/001651
Authority: WO
Inventors: Geoffrey Asprey
Original assignee: Geoffrey Asprey
Priority date: 2010-12-09
Filing date: 2011-11-28
Publication date: 2012-06-14

Abstract

The invention relates to a stove (10, 150) for a heating system, comprising a housing (12) having a combustion chamber (14) and a grate (18) for the combustion of fuel thereon. The grate (18) at least partially comprises a first fluid heater (26) suitable for a liquid or gas. The stove (10) being operable to heat a liquid or gas in the first fluid heater (26) from the combustion of the fuel on the grate (18).

Description

STOVE FOR A HEATING SYSTEM

Technical Field

The invention relates to improvements in or relating to multi-fuel stoves and storage heater apparatus.

Background

Stoves may be used with many different types of solid and liquid fuel such as wood, coke, coal, charcoal, and oil. Typically, such stoves burn either a solid fuel or a liquid fuel, but not both types of fuel. Such stoves may be used in a home or a factory to provide heat to a room in which the stove is located, or to heat water for a central heating system, or to provide a hot water supply. The water heater may also be known as a boiler. It is a general aim of most stoves to provide a complete burn of the fuel which is used so that the efficiency of operation of the stove is improved. Providing a more complete burn may also reduce the amount of unburned combustion gases emitted from the stove which may also help to reduce air pollution.

In the case of a stove used for heating a room in which it is located the principal form of heat transfer from the stove to the room is provided by radiating heat from an external surface of the stove. In the case of a stove used for heating water it is typically the case that a large body of water is provided in a back-boiler which is a part of the stove. The back-boiler typically contains around 40 litres of water which represents a very large volume of liquid to be heated. Furthermore, the large volume of water means that the boiler requires a large amount of heat energy for operation. The back-boiler is typically a large unit which is at an upper part of the stove which may not be the hottest part of the stove. Furthermore such a large unit may be cumbersome and awkward to handle during installation of the stove.

In an oil burning stove, the oil is typically injected from a spray nozzle into a combustion chamber under high pressure using a high pressure pump. Such an arrangement is complex, and has multiple working components that may fail. For example, the spray nozzle often becomes blocked due to lumps in the oil. Furthermore, the spray nozzle erodes over time and is typically required to be replaced every year. In addition, the pump may wear or fail. All of these failures increase the cost of operation for the known oil burning stove.

In general, heating systems typically comprise a central heating arrangement whereby heat from a boiler is distributed around a building using a closed water circuit having wall mounted radiators or under floor pipe work. Whereas this is typically a suitable arrangement for distributing heat when the boiler is operational, the radiators and under floor pipe work typically have a low thermal capacity. Such a low thermal capacity means that the radiators and under floor pipe work may cool down quickly after the boiler has shut down. This may be a problem at night when a central heating system may be switched off, and results in the building cooling down rapidly, which may be undesirable. Furthermore, central heating systems comprising such a closed water circuit have many associated problems. One problem is that water from the closed circuit may leak, which is undesirable. Another problem is that the pipe work or radiators of the system may corrode due to the use water. Whereas a chemical inhibitor may be mixed with the water in the closed water circuit, this does not eliminate the problem, and is also an added expense and complexity.

It is broadly an object of the present invention to address one or more of the above mentioned disadvantages of previously known stoves and storage heater apparatus.

Summary

What is required is a stove and a storage heater apparatus, which may reduce or minimise at least some of the above-mentioned problems. According to a first aspect of the invention, there is provided a stove for a heating system, comprising a housing having a combustion chamber and a grate for the combustion of fuel thereon, wherein the grate at least partially comprises a first fluid heater suitable for a liquid or gas, the stove being operable to heat a liquid or gas in the first fluid heater from the combustion of the fuel on the grate.

Such a stove provides the advantage that the liquid or gas within the first fluid heater is close to the fuel on the grate which may provide an improved heating of the liquid or gas. It has been realised by the inventor that locating the first fluid heater closer to the burning fuel may also increase the thermal efficiency for the overall operation of the stove. Furthermore, the first fluid heater is combined with the grate which provides for a less complex stove, that may also be easier to install.

Preferably the first fluid heater comprises at least one duct. Preferably the first fluid heater comprises a plurality of ducts. Preferably the plurality of ducts comprise the grate. Such arrangements provide an effective way for combining the gate and the first fluid heaters.

Preferably the at least one duct is at an angle of greater than 2° from a horizontal for promoting a thermal siphon effect. In a preferred embodiment said angle is between 2° - 10°, and more preferably substantially 6°. This has the advantage of providing an improved movement for the liquid or gas through the first fluid heater.

Preferably the first fluid heater is in fluid communication with a first manifold which has a first chamber therein. Preferably the first fluid heater is in fluid communication with a second manifold which has a second chamber therein. Preferably the first and second manifolds are substantially horizontal and spaced apart from one another, and the first fluid heater is between the first and second manifolds so that the first and second chambers are in fluid communication with one another. Such an arrangement has the advantage that the volume of liquid or gas that is required for operation of the first fluid heater may be reduced. It has been realised by the inventor that the provision of a smaller volume of liquid or gas may increase the thermal efficiency for the overall operation of the stove. Preferably a portion of at least one manifold is provided on an exterior of the housing. Preferably substantially the entirety of at least one manifold is provided on an exterior of the housing. Such an arrangement may provide an advantageous configuration of the stove.

Preferably at least one manifold comprises a duct having a square or rectangular cross section. Such an arrangement may provide an advantageous way of connecting the first fluid heater to the manifold to construct the stove. Preferably the first manifold, the second manifold and the first fluid heater have a total volume of between 6 - 14 litres. In a preferred embodiment the first manifold, the second manifold and the first fluid heater have a total volume of substantially 10 litres. Such volumes may be considerably smaller than known arrangements for fluid heaters, which may lead to an overall improved efficiency of operation for the stove.

Preferably the first fluid heater has an inlet and an outlet such that the inlet is lower than the outlet for promoting a thermal siphon effect. This has the advantage of providing an improved movement for the liquid or gas through the first fluid heater. In one embodiment the stove further includes at least one air duct on an exterior of the housing, the air duct having a lower opening and an upper opening, the air duct operable to promote heat convection therethrough. This has the advantage of creating an additional heat transfer mechanism from the stove to a room in which the stove is located. Preferably the lower opening comprises a curved part of a free end of the at least one air duct. Such an arrangement may provide a convenient way for providing the lower opening.

Preferably the lower part of the at least one air duct is adjacent to the at least one manifold the portion thereof which is exterior of the housing. This may further promote heat convection through the air duct because the manifold is typically hot when the stove is burning fuel and liquid or gas is within the first fluid heater.

Preferably the stove includes a plurality of air ducts on an exterior of the housing. Such an arrangement may further improve the transfer of heat from the stove to the room in which it is located by heat convection. In one embodiment the stove further including a second fluid heater within the combustion chamber and which is above the grate, the second fluid heater being suitable for a liquid or gas, wherein the stove is operable to heat the liquid or gas in the second fluid heater from the combustion of the fuel therein. Such a second fluid heater may further be used to extract heat from the combustion chamber to heat the liquid or gas.

Preferably at least a portion of an underneath part of the second fluid heater is curved. Preferably the underneath part comprises a curved plate. Preferably the underneath part is convex. Preferably the second fluid heater comprises a convex housing with a chamber therein for the liquid or gas. Such arrangements provide an improved heating by the second fluid heater from the combustion gases due to a swirling effect thereof created by the curved underneath part.

Preferably the second fluid heater is adjacent to an exhaust of the combustion chamber. Such a configuration may provide a baffle for the exhaust using the second fluid heater.

Preferably the second fluid heater has an inlet and an outlet such that the inlet is lower than the outlet for promoting a thermal siphon effect. This has the advantage of providing an improved movement for the liquid or gas through the second fluid heater.

Preferably the second fluid heater has a volume of between 3 - 7 litres. In a preferred embodiment the first manifold, the second fluid heater has a volume of substantially 5 litres. In one embodiment the first fluid heater and the second fluid heater are in fluid communication with one another. Such an arrangement may provide an improved way of extracting heat from the stove. Such an arrangement may also provide an improved thermal siphon effect, particularly when the second fluid heater is above the first fluid heater.

In one embodiment the stove further includes a liquid fuel burner comprising a receptacle for holding the liquid fuel, the receptacle having an open top and being operable to allow the liquid fuel within the receptacle to at least partially vaporise for promoting combustion thereof. Such a liquid fuel burner provides a straight forward way to burn liquid fuel in a simple device which does not require frequent replacement of parts. Such an arrangement allows the combustion of many types of liquid fuel such as oil, fat, and candle wax. In one embodiment the liquid fuel burner is located above the grate and within the combustion chamber. This may further assist with allowing the liquid fuel to vaporise for promoting combustion thereof due to heat from the combustion of fuel on the grate. The vapours from the liquid fuel burner may also slow the combustion process and promote down-burning of fuel on the grate.

In one embodiment the liquid fuel burner is located beneath the grate. Such an arrangement may provide an improved heating for the liquid or has within the first fluid heater. Preferably the liquid fuel burner is below the second fluid heater. Such an arrangement may provide a convenient location for the liquid fuel burner so that it can heat the second fluid heater.

Preferably the receptacle includes a wick for the liquid fuel. Preferably the wick comprises a glass fibre, a stone fibre, or a ceramic fibre. Such a wick may improve combustion, and is less likely to degrade due to heat within the stove. Preferably the receptacle has an upright wall for concentrating the vaporised liquid fuel. Preferably the upright wall has a plurality of holes for promoting combustion of the liquid fuel. Such arrangements may further aid combustion of the liquid fuel. Preferably the stove further includes a gas chamber adjacent to the housing, the gas chamber having a gas inlet and a gas outlet, the gas chamber for providing a source of heated gas. Preferably the stove further includes a pump for driving the heated gas from the gas chamber and through the gas outlet. Such arrangements may be useful to provide a heated gas, such as air, which may be passed to a central heating system for heating one or more rooms in a building in which the stove is located.

Preferably the combustion chamber has an exhaust duct that is arranged to pass through the gas chamber. Such arrangements may provide different options to heat the gas within the gas chamber.

The stove further includes at least one additional air duct operable to promote heat convection therethrough, the at least one additional air duct being adjacent to the exhaust duct and an upper opening inside the gas chamber. Such an arrangement may provide an advantageous way of extracting the hot gas from the gas chamber.

Preferably the gas chamber is above the housing. Such an arrangement may be an advantageous configuration for the stove. Preferably the gas chamber is defined by a container around the housing. Preferably the gas chamber comprises a first volume above the housing, and a second volume around the sides of the housing. Preferably the container is spaced apart from the housing. Preferably the container is provided with heat insulation. Such arrangements for the container may be an advantageous way to construct the gas chamber.

Preferably the container is arranged to extend between a floor and a ceiling of a room in which the stove is located so that it acts as a chimney breast for the room. Preferably the gas chamber is accessible via a door. Such an arrangement may be used to operate the gas chamber as an oven, and/or to access the one or more air ducts.

According to a second aspect of the invention there is provided a storage heater apparatus, comprising at least one duct for a liquid or gas, and a void space for air, the apparatus for location within a wall or a floor, wherein the apparatus is adapted for operation such that when a heated liquid or gas is flowing in the at least one duct the heat is retained in the void space, and when the liquid or gas is not flowing in the at least one duct said retained heat is conducted to a wall or floor in which the apparatus is located.

Such a storage heater apparatus may provide the advantage of an improved thermal capacity because the void space provides a reservoir of heat. Such an arrangement may mean that a wall or a floor in which the storage heater apparatus is located retains heat for a longer period of time after the liquid or gas has stopped flowing in the at least one duct. It will be appreciated that the void space typically contains air. The liquid or gas within the at least one duct may alternatively be termed a fluid.

Preferably the storage heater apparatus further includes a conduit for providing the void space. Preferably the at least one duct is adjacent to the void space. Such arrangements may provide a convenient way of creating the void space when the conduit is embedded in a wall or floor.

Preferably the storage heater apparatus comprising a plurality of ducts. Preferably the plurality of ducts are adjacent to the void space. Such an arrangement may further improve the transfer of heat from the ducts to the wall or floor and/or the void space.

Preferably the at least one duct and the void space is embedded in an aggregate material vvithin the wall or floor. This may be a convenient way of embedding the storage heater apparatus in a wall or floor and providing the required thermal capacity.

Preferably the storage heater apparatus includes insulation provided on an exterior of the aggregate material. Such insulation may help to retain heat within the storage heater apparatus.

Preferably the at least one duct has an elongate insert therein. Preferably the insert comprises a metal bar. Preferably the insert is spaced apart from an inside wall of the at least one duct. Such an arrangement may provide the advantage of an improved thermal capacity because the insert provides a reservoir of heat. Furthermore, the insert reduces the volume of liquid or gas that is required for the at least one duct to operate which may permit a larger external surface of the at least one duct.

Preferably the insert has a plurality of transverse portions which extend in a direction away from the axis of the insert. The transverse portions operate to disrupt the flow of liquid or gas flowing in the duct so that the duct operates more efficiently

According to a third aspect of the invention there is provided a storage heater apparatus for location within a wall or a floor, comprising a vessel for storing water, the vessel having a heat exchanger device, the apparatus being adapted for operation such that when a heated liquid or gas is flowing in the heat exchanger device the heat is conducted to the water within the vessel, and when the liquid or gas is not flowing in the heat exchanger device said retained heat is conducted to a wall or floor in which the apparatus is located.

Such a storage heater apparatus may provide the advantage of an improved thermal capacity because the water within the vessel provides a reservoir of heat. Such an arrangement may mean that a wall or a floor in which the storage heater apparatus is located retains heat for a longer period of time after the liquid or gas has stopped flowing in the heat exchanger device.

Preferably the vessel is embedded in an aggregate material within the wall or floor. This may be a convenient way of embedding the storage heater apparatus in a wall or floor and providing the required thermal capacity. Preferably the storage heater apparatus includes insulation provided on an exterior of the aggregate material. Such insulation may help to retain heat within the storage heater apparatus.

According to a fourth aspect of the invention there is provided a stove according to the first aspect of the invention for providing hot liquid or gas to a storage heater apparatus according to the second or third aspect of the invention. According to a fifth aspect of the invention there is provided a wall or a floor including a storage heater apparatus according to the second or third aspects of the invention.

Preferably the plurality of ducts are between the void space and a surface of the wall or the floor. Such a configuration may provide an improved operation of the storage heater apparatus.

According to a sixth aspect of the invention there is provided a liquid fuel burner for burning a liquid fuel, comprising a receptacle for holding the liquid fuel, the receptacle having an open top and being operable to allow the liquid fuel within the receptacle to at least partially vaporise for promoting combustion thereof.

Such a liquid fuel burner provides a straight forward way to burn liquid fuel in a simple device which does not require frequent replacement of parts. Such an arrangement allows the combustion of many types of liquid fuel such as oil, fat, and candle wax. Preferably the receptacle includes a wick for the liquid fuel. Preferably the wick comprises a glass fibre, a stone fibre, or a ceramic fibre. Such a wick may improve combustion, and is less likely to degrade due to heat from the burning fuel. Preferably the receptacle has an upright wall for concentrating the vaporised liquid fuel. Preferably the upright wall has a plurality of holes for promoting combustion of the liquid fuel. Such arrangements may further aid combustion of the liquid fuel.

According to a seventh aspect of the invention there is provided a method of operating a stove for a heating system, the stove comprising a housing having a combustion chamber and a grate for the combustion of fuel thereon, wherein the grate at least partially comprises a first fluid heater suitable for a liquid or gas, the method including: combusting fuel on the grate; and

heating the liquid in the first fluid heater from the combustion of the fuel on the grate.

Such a method provides the advantage that the liquid or gas within the first fluid heater is close to the fuel on the grate which may provide an improved heating of the liquid. It has been realised by the inventor that locating the first fluid heater closer to the burning fuel may also increase the thermal efficiency for the overall operation of the stove. Furthermore, such a method provides for a less complex stove because the first fluid heater is combined with the grate. Preferably the first fluid heater is inclined at an angle of greater than 2° from a horizontal, the method including creating a thermal siphon effect within the first fluid heater. This has the advantage of providing an improved movement for the liquid or gas through the first fluid heater.

In one embodiment the stove further includes at least one air duct on an exterior of the housing, the air duct having a lower opening and ah upper opening, the method including providing heat transfer by heat convection through the at least one air duct. This has the advantage of creating an additional heat transfer mechanism from the stove to a room in which the stove is located.

In one embodiment the stove further includes a second fluid heater within the combustion chamber and which is above the grate, the second fluid heater being suitable for a liquid or gas, the second fluid heater having a curved portion of an underneath part thereof, the method including swirling the combustion gases using the curved portion to heat the liquid or gas in the second fluid heater. Such a second fluid heater may further be used to extract heat from the combustion chamber to heat the liquid. An improved heating of the second fluid heater by the combustion gases may be provide due to a swirling effect thereof created by the curved underneath part.

Preferably the second fluid heater has an inlet and an outlet such that the inlet is lower than the outlet, the method including creating a thermal siphon effect within the second fluid heater. This has the advantage of providing an improved movement for the liquid or gas through the second fluid heater. Preferably the method further includes using a second fluid heater having a volume of between 3 - 7 litres. Using such a volume may provide for an improved overall efficiency of the stove.

In one embodiment the method further includes providing the first fluid heater and the second fluid heater in fluid communication with one another. Such an arrangement may provide an improved way of extracting heat from the stove. Such an arrangement may also provide an improved thermal siphon effect, particularly when the second fluid heater is above the first fluid heater.

In one embodiment the stove further includes a liquid fuel burner comprising a receptacle for holding the liquid fuel, the method including at least partially vaporising the liquid fuel for promoting combustion thereof. Such a method provides a straight forward way to burn liquid fuel in a simple liquid fuel burner which does not require frequent replacement of parts. Such an arrangement allows the combustion of many types of liquid fuel such as oil, fat, and candle wax.

Preferably the method further includes using a first fluid heater having a volume of between 6 - 14 litres. Such volumes may be considerably smaller than known arrangements for fluid heaters, which may lead to an overall improved efficiency of operation for the stove. Preferably the stove has a gas chamber adjacent to the housing, the method comprising using the stove to heat gas within the gas chamber, and using the heated gas as a source of heat. Preferably the method further includes insulating the gas chamber. Such a method may be useful to provide a heated gas, such as air, which may be passed to a central heating system for heating one or more rooms in a building in which the stove is located.

In one embodiment the method further includes heating the air in the gas chamber using the at least one air duct. This has the advantage of creating an additional heat transfer mechanism from the stove to a room in which the stove is located.

Preferably the combustion chamber has an exhaust duct, the method including heating the air in the gas chamber using the exhaust duct. Such arrangements may provide an advantageous way to heat the gas within the gas chamber.

According to another aspect of the invention there is provided a stove for a heating system, comprising a housing having a combustion chamber for the combustion of fuel therein, the stove having at least one air duct on an exterior of the stove, the air duct having a lower opening and an upper opening, wherein the air duct is operable to promote heat convection therethrough.

According to another aspect of the invention there is provided a stove for a heating system, comprising a housing having a combustion chamber for the combustion of fuel therein, the stove having a fluid heater at an upper region of the combustion chamber which is suitable for a liquid or gas, at least a portion of an underneath part of the fluid heater being curved, wherein the stove is operable to heat the liquid in the fluid heater from the combustion of the fuel in the combustion chamber. According to another aspect of the invention there is provided a stove for a heating system, comprising a housing having a combustion chamber, the stove including a liquid fuel burner comprising a receptacle for holding the liquid fuel, the receptacle having an open top and being operable to allow the liquid fuel within the receptacle to at least partially vaporise for promoting combustion thereof.

Any preferred or optional features of one aspect of the invention may be preferred or optional feature of other aspects of the invention.

Brief Description of the Drawings

Other features of the invention will be apparent from the following description of preferred embodiments shown by way of example only with reference to the accompanying drawings, in which;

Figure 1 shows a perspective view of a stove according to an embodiment of the invention;

Figure 2 shows a perspective view of the stove of Figure 1 with a liquid fuel burner and a convection device;

Figure 3 shows a cross section through a storage heater device for use with the stove of Figures 1 and 2; Figure 3a shows a detail part of the arrangement of Figure 3 according to an embodiment of the invention;

Figure 3b shows a detail part of the arrangement of Figure 3 according to another embodiment of the invention;

Figure 4 shows a cross section through a storage heater device according to an alternative embodiment for use with the stove of Figures 1 and 2;

Figure 5 shows a diagram of a method according to an embodiment of the invention;

Figure 6 shows a perspective view of a stove according to another embodiment of the invention; and

Figure 7 shows a perspective view of the stove shown in Figure 6.

Detailed Description

Figure 1 shows a perspective view of a stove according to an embodiment of the invention, generally designated 10. Hidden detail of the stove 10 is shown with dashed lines. The stove 10 has a body 12 of steel with a combustion chamber 14 and an ash pit 16 therein. The body 12 may alternatively be termed a housing. The body 12 has a front panel which has been omitted for the purposes of clarity. The front panel may be detachable from the body 12, for example, with bolts. The front panel has an opening for accessing to the combustion chamber 14 and an opening for accessing the ash pit 16. The openings have respective doors. A grate 18 is provided between the combustion chamber 14 and the ash pit 16 for combustion of fuel thereon. The body 12 has feet 20 so that the stove 10 can stand on a floor. The combustion chamber 14 has an exhaust 22, also known as a flue, to allow the exhaust gases from combustion of fuel to escape from the stove 10 as shown at 24. The stove 10 has a vent or air inlet, for example, in the door for accessing the ash pit 16 which is suitable for controlling the amount of air in the combustion chamber 14 which in turn controls the combustion of the fuel. It will be appreciated that the combustion chamber 14 is substantially a sealed chamber, having the air inlet and the exhaust 22 for exhaust gases, so that the burning process can be controlled.

In Figure 1 the stove 10 is shown to comprise a first boiler 26, also known as a first fluid heater. The first boiler 26 comprises the grate 18 which has five substantially parallel pipes or ducts for a liquid or gas. In the context of the embodiments described herein a fluid is a liquid or gas. It will be appreciated that there may be more than five pipes as required. The first boiler 26 also comprises a first and second manifold 27, 28 on either side of the body 12. The pipes are located between the manifolds 27, 28 so that the pipes are within the body 12 and between the ash pit 16 and the combustion chamber 14. The first manifold 27 has an inlet 30, and the second manifold 28 has an outlet 32. In operation a liquid or gas, such as water or air, which is to be heated in the stove 10 enters the first manifold 27 via the inlet 30 as shown at 34. The liquid or gas then passes through the grate 18 towards the second manifold 28 as shown at 36. The liquid or gas then leaves the second manifold 28 via the outlet 32 as shown at 38. It will be appreciated that the liquid or gas is heated by fuel burning on the grate 18 as it passes through the first manifold 27, through the grate 18, and through the second manifold 28. In particular the liquid or gas is heated as it passes through the grate 18 most effectively because it is very close to fuel which is burning on the grate 18. It will be appreciated that the pipe work for connecting the liquid or gas supply and return to the first boiler

26 has been omitted for clarity.

In Figure 1 the inlet 30 is shown to be lower than the outlet 32 to promote a thermal siphon effect for the liquid or gas within the first boiler 26. In addition the first manifold

27 may be lower than the second manifold 28 to promote a thermal siphon effect. Furthermore, the pipes of the grate 18 may be included at an angle of greater than 2° from the horizontal to promote a thermal siphon effect. In one embodiment the angle is between 2° - 10°, and more preferably substantially 6°.

The manifolds 27, 28 are on the outside of the body 12 and have first and second chambers therein. Each manifold 27, 28 comprises a pipe or duct having a square or rectangular cross section. Each manifold 27, 28 is elongate and may be as long as the stove 10 is deep. In one arrangement each manifold is between 20 - 80 cm in length, and more preferably about 50cm in length. The manifolds 27, 28 are substantially straight and horizontal, and spaced apart from one another. It will be appreciated that each of the pipes comprising the grate 18 connect the first and second chambers of each of the manifolds 27, 28. One of the sides of each manifold 27, 28 is uppermost and substantially horizontal. Another side of each manifold 27, 28 is attached to a respective side of the body 12. It will be appreciated that substantially the entirety of the manifolds 27, 28 are provided on an exterior of the body 12 so that they are outside of the combustion chamber 14. The first boiler 26 comprising the grate 18 and the manifolds 27, 28 has a relatively low volume, for example between 6 - 14 litres, and preferably about 10 litres. Such an arrangement may increase the thermal efficiency for the overall operation of the stove 10.

The stove 10 also includes a second boiler 40, also known as a second fluid heater, at an upper region of the combustion chamber 1 . The second boiler 40 is above the grate 18, and is suitable for heating a liquid or gas, such as water or air, from heat produced by combustion of the fuel on the grate 18. The second boiler 40 comprises a housing 41 which is curved, and which has a chamber within it for the liquid or gas. The housing 41 comprises two curved plates which are adjacent to one another so that the chamber is between the plates. Two fillet side walls are provided between the two curved plates, each of which is the shape of part of a circular annulus or oval annulus. It will be appreciated that an underneath side of the housing 41 is convex from the perspective of viewing it from the grate 18. The shape of the second boiler 40 changes the dynamics of the burning within the combustion chamber 14 to provide a more efficient burn. The second boiler 40 is adjacent to the exhaust 22 of the combustion chamber 14 such that it is a baffle for the exhaust 22.

The second boiler 40 has an inlet 42 and an outlet 44 for the liquid or gas. The pipe work for connecting the liquid or gas supply and return to the second boiler 40 has been omitted for clarity. The inlet 42 is shown to be lower than the outlet 44 to promote a thermal siphon effect for the liquid or gas within the second boiler 40. In operation the liquid or gas to be heated in the second boiler 40 enters via the inlet 42 as shown at 46. The liquid or gas then passes through the second boiler 40 where it is heated. The liquid or gas then leaves the second boiler 40 via the outlet 44 as shown at 48. It will be appreciated that the liquid or gas in the second boiler 40 is heated by fuel burning on the grate 18 due to the heat within the combustion chamber 14 and by the combustion gases as they travel upwards as shown at 50. In particular the liquid or gas is heated by swirling combustion gases as shown at 52 which is due to the curved under side of the second boiler 40. In one embodiment the second boiler 40 has a horse shoe cross section or cross section comprising a segment of an annulus, which may improve the heating effect by the swirling combustion gases.

It will be appreciated that the first and second boilers 26, 40 have a relatively low volume when compared to the prior art. For example, the first boiler 26 comprising the first and second manifolds 27, 28 and the grate 18 may hold between 6 - 14 litres, and preferably about 10 litres of liquid or gas, and the second boiler 40 comprising the housing 41 may hold between 3 - 7 litres of liquid or gas, and preferably about 5 litres of liquid or gas. The inventor has realised that the provision of such a small volume of liquid or gas may increase the thermal efficiency for the overall operation of the stove 10.

The first and second boilers 26, 41 may be coupled to one another so that they work together to heat liquid or gas within them. Such an arrangement promotes a thermal siphon effect because the second boiler 41 is located above the first boiler 26. With such an arrangement the outlet 32 of the first boiler 41 may be connected with pipe work to the inlet 42 of the second boiler 41. With such an arrangement the stove 10 may operate to extract more heat from the fuel burning within the stove 10 so that it is more efficient. In addition the thermal siphon effect may be improved. Figure 2 shows a perspective view of the stove 10 of Figure 1 with an oil burner 60 and a convection device 62. In Figure 2 like features to the arrangements of Figure 1 are shown with like reference numerals. In Figure 2 the oil burner 60 comprises a tray 64 for burning oil 66 which is located in the combustion chamber 14. In one arrangement the oil burner 60 is removably mounted within the combustion chamber 14, for example by locating it on brackets attached to an inside of the body 12. The oil 66 is held in a reservoir 68 outside of the stove 10, and is fed into the tray 64 via a pipe 70 which passes through the body 12. A control device 72 in the pipe 70 may be used to control the amount of oil 66 delivered to the tray 64. The tray 64 is above the grate 18. The tray 64 is below the second boiler 40. In operable the tray 64 is heated by fuel burning on the grate 18 so that the oil 66 within the tray 64 at least partially vaporises. It will be appreciated that the tray 64 is relatively flat to present a large area to be heated. The tray has a low perimeter wall to hold a shallow pool of oil 66. Such an arrangement promotes combustion of the oil because the oil vapour is readily produced by heat from the fuel on the grate 18.

The tray 64 may have a wick 74 for the oil 66 within the tray 64. The wick 74 may be lit by a user to burn the oil 66, and/or to sustain burning of the oil 66. The wick 74 may comprise any suitable material and may comprise a glass fibre, a stone fibre, or a ceramic fibre. Such fibres have the advantage that they are less likely to melt due to the high temperatures in the combustion chamber 14. The tray 64 may also be provided with a combustion vessel 76 which is a duct open at both ends. The combustion vessel 76 is placed on the tray 64 so that one end of the combustion vessel 76 is substantially closed by the tray 64 at the bottom and the other end is open at the top. Placement of the combustion vessel 76 on the tray 64 also permits oil 66 to pass between the combustion vessel 76 and the tray 64 so that it can enter the combustion vessel 76. The wick 74 may be also located within the combustion vessel 76. The combustion vessel 76 has an upright wall for concentrating the vaporised oil, and promoting burning thereof. The upright wall may have a plurality of holes therein to allow air to enter for promoting combustion of the oil 66. It will be appreciated that together the tray 64 and the combustion vessel 76 may be known as a receptacle, and the upright wall of the combustion vessel 76 may be an upright wall of the receptacle.

In operation the oil burner 60 may be used to burn waste oils, fats and candle wax, which might otherwise be thrown away. The oil burner 60 may also be used with fuel oil. In either case, the oil 66 may be burned instead of solid fuel on the grate 18, or in addition to such solid fuel. Accordingly, the stove 10 may burn either a solid fuel or a liquid fuel, or both types of fuel at the same time. The vapours from the oil burner 60 may also slow the combustion process and promote down-burning of fuel on the grate 18. In addition the oil burner 60 may promote combustion of liquid fuel within it due to heat within the combustion chamber 14. In one embodiment the oil burner 60 may be configured as a separate device to the stove 10, so that it is operable to burn liquid fuel when it is not inside the stove 10. Such a separate oil burner may be used in, for example, an open fireplace. With such an arrangement the receptacle 64 and the combustion vessel 76 may be placed in a fireplace for use to burn fuel. The arrangement of the receptacle 64 and the combustion vessel 76 provides the advantage that it resists being blown out due to draught or wind when it is not inside the stove 10. In another embodiment the oil burner 60 is arranged to be below the grate 18 to assist with heating of liquid or gas within the grate 18. Alternatively the oil burner 60 is arranged to rest on grate 18 to assist with heating of liquid or gas within the grate 18. The location of the oil burner 60 within the stove 10 provides different uses of the stove 10. When the oil burner 60 is located underneath the grate 18 the stove 10 may be used to provide domestic hot water and low heat requirements to heat a room. When the oil burner 60 is located top of the grate 18 the stove 10 may be used to provide hot water and medium heat requirements to heat a room. When the oil burner 60 is located directly underneath the second boiler 40 as shown in Figure 2 the stove 10 may be used to provide hot water and high heat requirements to heat a room.

The oil burner 60, may alternatively be termed a liquid fuel burner. The liquid fuel burner may be used to combust many types of liquid fuel such as oil, fat, candle wax, or other waste liquid that are burnable such as sugar based products. Similarly the grate 18 may be used to burn any suitable type of solid fuel such as wood, coke, coal, charcoal, biomass, bio degraded grass, bones, straw bales, cooking waste, sugar based products, and mulch. Accordingly, the stove 10 may be termed a multi-fuel stove.

The convection device 62 is shown to comprise four air ducts 78 on an exterior of the stove 10. Each air duct 78 has a lower opening and an upper opening to promote convection of air therethrough as shown at 80 and 82. Each air duct 78 has a cross section which is large enough to promote convection therethrough. The air ducts 78 may be of any suitable material, for example, steel tube. The lower opening of each air duct 78 may comprise a curved part of a free end thereof. It will be appreciated that whereas only four air ducts 78 are shown on one side of the stove, there may be additional air ducts 78 on the opposite side of the stove 10 and on the back of the stove 10. These additional air ducts 78 have been omitted for the purposes of clarity. The air ducts 78 may be attached to the body 12 by straps. In operation the air ducts 78 heat up, due to heat conduction from the stove 10, which causes air within them to rise. A heat convection current is therefore generated through each air duct 78. A room in which the stove 10 is placed may therefor heat up in an improved manner due to the convection currents. In addition, the air ducts 78 may extend into a room above the stove 10 thereby providing heat to that room.

Figure 2 shows that a lower free end of each of the four air ducts 78 rests on the second manifold 28. A similar arrangement is provided for air ducts 78 on the opposing side of the stove 10 so that they rest on the first manifold 27. This may be advantageous because the first and second manifolds 27, 28 are relatively hot when the stove 10 is in operation which may further promote a heat convention current to flow through each of the air ducts 78. Figure 1 shows the stove 10 with the first boiler 26 and the second boiler 40, and Figure 2 shows the stove 10 with the first boiler 26, the second boiler 40, the oil burner 60 and the convection device 62. However, it will be appreciated that the stove 10 may have one or more of any of the features of the first boiler 26, the second boiler 40, the oil burner 60 and the convection device 62. Accordingly any of the features of the first boiler 26, the second boiler 40, the oil burner 60 and the convection device 62 may be used independently of each other, and in combination with a known stove or boiler.

Figure 3 shows a cross section through a storage heater device for use with the stove 10 of Figures 1 and 2, generally designated 90. The storage heater device 90 is for embedding within a floor to provide heating to a room and accordingly is shown to be substantially horizontal. Alternatively the storage heater device 90 may be embedded within a wall in which case it may oriented so that it is substantially vertical. The storage heater device 90 is shown to comprise three groups 92, 94, 96 of ducts 98 and void spaces 100. Each duct 98 may be a steel tube. Each group 92, 94, 96 may be considered to be a storage heater apparatus, and it will be appreciated that there may be more or less groups depending on the application of the storage heater device 90 to heat a particular room. Each storage heater apparatus 92, 94, 96 has five ducts associated with a single void space 100, although there may be more or less ducts as required. The void spaces 100 contain air. The storage heater apparatus 92, 94, 96 is embedded within a settable aggregate material 102 such as concrete. The aggregate material 102 may be any suitable material such as heavyweight or lightweight aggregate such that it is a particulate material such as sand, gravel, crushed stone, slag, recycled concrete and/or geosynthetic aggregates. The aggregate material 102 is encased in an insulation material 104 on all sides thereof, apart from a surface 106 that faces the room in which storage heater apparatus 92, 94, 96 is located. Typically the aggregate material 102 is about 80 - 100mm deep for a domestic application as shown at 103, although the dimension 103 may be larger than this for an industrial application, such as 100 - 150mm deep. It will be appreciated that the ducts 98 provide reinforcement to the aggregate material 102. Figure 3 shows that the ducts 98 are adjacent to the void space 100, and the ducts 98 are between the void space 100 and the surface 106 of the wall or the floor. Typically the ducts 98 are about 30mm from the surface 106 as shown at 108. It will be appreciated that whereas Figure 3 shows a cross section, the ducts 98 and the void spaces 100 may extend in a direction which is perpendicular to the cross section for an appropriate length to suit a particular room. A typical length might be 1 - 5m or more. The ducts 98 are coupled to a central heating system to provide hot water or hot air to the ducts 98 according to known methods and will not be described further. The ducts 98 may be connected to the first boiler 26 and/or the second boiler 40 shown in Figures 1 and 2 to provide hot water or hot air to the ducts 98. In Figure 3 the void spaces 100 extend to substantially the same length as the ducts 98 within the wall or floor, and are closed to the atmosphere such that they trap air within them. It is envisaged that there may be up to 30 or more ducts 98 in the storage heater device 90, which may be provided with a heated liquid or gas from the stove 10.

In an alternative arrangement the ducts are heated by a heated gas flowing in them, which is for example, provided by the air ducts 78. With such an arrangement the upper opening of the air ducts 78 are coupled to the ducts 98 with pipe work. The skilled person will know the arrangements for such pipe work.

In use the storage heater device 90 is adapted for operation such that when a heated liquid or gas is flowing in the ducts 98 the void space 100 is heated to retain heat therein. The aggregate material 102 also heats up and provides heat to the room in which the storage heater device 90 is located. When the liquid or gas is not flowing in the ducts 98 the retained heat in the void space 100 is conducted to a wall or floor in which the storage heater apparatus 90 is located. Such an arrangement may provide the advantage of an improved thermal capacity because the void space 100 provides a reservoir of heat. Such an arrangement may mean that a wall or a floor in which the storage heater apparatus 90 is located retains heat for a longer period of time after the liquid or gas has stopped flowing in the at least one duct 98.

In one embodiment the storage heater apparatus 92, 94, 96 includes a conduit for providing the void space 100. The conduit may be a convenient way of forming the void space 100 in the aggregate material 102. The ducts 98 and the conduit comprising the void space 100 are provided as a single unit, for example, the ducts 98 may be strapped to the conduit. Such an arrangement may be a convenient way of embedding the storage heater apparatus 92, 94, 96 in the aggregate material 102.

When the storage heater device 90 of Figure 3 is embedded in a wall the void space 100 may be omitted. With such an arrangement the aggregate material 102 surrounds the ducts 98. Omission of the void space 100 may provide an improved strength for the wall in which the storage heater device 90 is located.

Figure 3a shows a detail part 140 of the arrangement of Figure 3 according to an embodiment of the invention. In Figure 3 a like features to the arrangements of Figure 3 are shown with like reference numerals. In Figure 3 a at least one of the ducts 98 has an insert 142 which is within the duct 98 as shown by a dashed line. The insert 142 is elongate and is substantially the same length as the duct 98, or at least as long as the portion of the duct 98 that is adjacent to the void space 100. The insert 142 may be a metal bar or other item having a relatively high thermal capacity. Spacers (not shown) are provided to align the insert 142 with a centre of the duct 98 so that the insert 142 and the duct 98 are concentric. The insert 142 may have a transverse dimension, such as a diameter thereof, which is between 9 - 22mm. The duct 98 has an internal bore which may have an internal transverse dimension, such as a diameter thereof, which is between 15 - 28mm. It will be appreciated that the insert 142 should be of a relative size to the duct 98 such that it fits inside it. In one embodiment a gap between the insert 142 and the internal bore is at least 2mm, and may be between 2 - 19mm. The insert 142 operates to absorb heat from the liquid or gas within the duct 98, and retains heat therein. When the liquid or gas is not flowing in the duct 98 the retained heat in the insert 142 is conducted to the duct 98 and then to the aggregate material 102. Such an arrangement may provide the advantage of an improved thermal capacity because the insert 142 provides a reservoir of heat. Such an arrangement may mean that a wall or a floor in which the storage heater apparatus 90 is located retains heat for a longer period of time after the liquid or gas has stopped flowing in the duct 98. Furthermore, the insert 142 operates to restrict the flow of the liquid or gas within the duct 98, which may improve the conduction of the heat from the liquid or gas to the insert 142.

Figure 3 b shows a detail part 140 of the arrangement of Figure 3 according to another embodiment of the invention. In Figure 3 b like features to the arrangements of Figure 3 and 3a are shown with like reference numerals. In Figure 3b the insert 142 comprises a relatively lighter elongate metal bar. The insert 142 has transverse portions 144, which operate to disrupt the flow of liquid or gas flowing in the duct 98 so that there is a more efficient transfer of heat with the duct 98. It will be appreciated that the transverse portions 144 extend, at least in part, in a direction which is away from the axis of the insert 142.

The inserts 142, shown in Figures 3a and 3b, may operate to make the overall heating system very efficient and may help to reduce fuel consumption. It will be understood that the inserts 142 operate to provide a larger external surface of the duct 98 for a given volume of water. With the inserts 142 a reduced volume of liquid or gas is required to fill the duct. In addition the inserts 142 also operate to store heat which is conducted back to the duct 98 and the surrounding aggregate material 102 when the liquid or air has stopped flowing in the duct 98.

Figure 4 shows a cross section through a storage heater device according to an alternative embodiment for use with the stove 10 of Figures 1 and 2, generally designated 110. In Figure 4 like features to the arrangements of Figure 3 are shown with like reference numerals. The storage heater device 110 is for embedding within a floor to provide heating to a room and accordingly is shown to be substantially horizontal. Alternatively the storage heater device 110 may be embedded within a wall in which case it may be oriented so that it is substantially vertical. In Figure 4 the storage heater device 110 comprises a vessel 112 which is shown to be embedded in the aggregate material 102. The vessel 112 is for containing water, and has an inlet 114 and an outlet 116. The vessel 112 also has a heat exchanger device 117 which is, for example, a series of pipes within the vessel 112. The heat exchanger device 117 has an inlet 118 and an outlet 119. It will be appreciated that whereas Figure 4 shows a cross section, the vessel 112 may extend in a direction which is perpendicular to the cross section for an appropriate length to suit a particular room. A typical length might be 1 - 5m. The inlet 118 and the outlet 119 of the heat exchanger 117 may be coupled to the first and/or second boiler 26, 40 of the stove 10 shown in Figures 1 and 2 to receive heated water therefrom. Accordingly, the water within the vessel 112 is heated by the heat exchanger 117 so that it can be used, for example in a domestic hot water supply. It will be appreciated that the vessel 112 has its own supply of water, for example, from a small remote tank, or from a mains water supply. The small remote tank may also operate as an expansion and overflow tank for the storage heater device 110.

In an alternative arrangement the heat exchanger 117 is heated by a heated gas flowing therein. The gas may be air, and may be provided by the stove 10. In one arrangement the heated air is provided by the air ducts 78, for example, by coupling the upper opening of the air ducts 78 to the heat exchanger 117 with pipe work. The skilled person will know the arrangements for such pipe work.

In use the storage heater device 110 is adapted for operation such that when a heated liquid or gas is flowing in the heat exchanger 117 the water within the vessel 112 is heated to retain heat therein. The aggregate material 102 also heats up and provides heat to the room in which the storage heater device 110 is located. hen the liquid or gas is not flowing in the heat exchanger 117 the retained heat in the water in the vessel 112 is conducted to a wall or floor in which the storage heater apparatus 110 is located. Such an arrangement may provide the advantage of an improved thermal capacity because the water within the vessel 112 provides a reservoir of heat. Such an arrangement may mean that a wall or a floor in which the storage heater apparatus 110 is located retains heat for a longer period of time after the liquid or gas has stopped flowing in the heat exchanger 1 17. It is envisaged that the storage heater apparatus 110 may retain heat for several days after the liquid or gas has stopped flowing in the heat exchanger 117.

Figure 5 shows a diagram of a method according to an embodiment of the invention, generally designated 120. The method 120 is a method of operating a stove 10 for a heating system. The stove 10 comprises a housing 12 having a combustion chamber 14 and a grate 18 for the combustion of fuel thereon. The grate 18 at least partially comprises a first boiler 26 suitable for a liquid or gas. The method includes combusting fuel on the grate 18 and heating the liquid or gas in the first boiler 26 from the combustion of the fuel on the grate 18, as shown at 122. The first boiler 26 is inclined at an angle of greater than 2° from a horizontal, and in one arrangement the angle is between 2° - 10° from a horizontal, the method including creating a thermal siphon effect within the first boiler 26, as shown at 124. The stove 10 further includes at least one air duct 78 on an exterior of the stove 10, the air duct 78 having a lower opening and an upper opening, the method including providing heat transfer by heat convection through the at least one air duct 78, as shown at 126. The stove 10 further includes a second boiler 40 within the combustion chamber 14 and which is above the grate 18, the second boiler 40 being suitable for a liquid or gas, the second boiler 40 having a curved portion of an underneath part thereof, the method including swirling the combustion gases 52 using the curved portion to heat the liquid or gas in the second boiler 40, as shown at 128. The second boiler 40 has an inlet 42 and an outlet 44 such that the inlet 42 is lower than the outlet 44, the method including creating a thermal siphon effect within the second boiler 40, as shown at 130. The stove 10 further includes an oil burner 60 within the combustion chamber 1 , the oil burner 60 comprising a receptacle 64 for holding the oil 66, the method including at least partially vaporising the oil 66 for promoting combustion thereof, as shown at 132.

Figure 6 shows a perspective view of a stove according to another embodiment of the invention, generally designated 150. In Figure 6 like features to the arrangements of Figure 1 and 2 are shown with like reference numerals. In Figure 6 the reservoir 68 outside the stove 10 has been omitted for the purposes of clarity, but it will be appreciated that this may be used for the oil burner 60. The stove 150 is shown to be inside a container 152 shown in dashed outline, so that the remaining parts of the stove 150 are visible. The container 152 surrounds the body 12 and has solid side walls and a solid top. The body 12 is spaced apart from the container 152, for example, by between 5 - 15cm, and typically about 10cm. Spacing the container 152 from the body 12 allows air to convect therebetween. The container 152 has feet 153 so that it can stand on the floor. In the arrangement of Figure 6 the body 12 comprises an oven 153 which is above the combustion chamber 14. The oven 153 has an oven chamber 155 within it. The container 152 surrounds the body 12 so that a gas chamber 154 is provided above the body 12 for a gas, such as air. It will be appreciated that there are no manifolds 27, 28 on the stove 150 shown in Figure 6, and that the grate 18 comprising the parallel pipes or ducts is for heating air passing through it, as shown at 36. The lower ends of the air ducts 78 rest on the floor. The upper ends of the air ducts 78 pass through the chamber 154 and extend out of an upper surface of the container 152. The air ducts 78 are between the body 12 and the container 152. The lower openings of the air ducts 78 are between the body 12 and the container 152 so that they can receive air as shown at 80. In operation the air ducts 78 heat up, due to heat conduction from the stove 150, which causes air within them to rise. A heat convection current is therefore generated through each air duct 78. The lower openings and the upper openings of the air ducts 78 promote convection of air therethrough as shown at 80 and 82. In this manner hot air exits the container 152 when the stove 150 is burning fuel. It will be appreciated that whereas only four air ducts 78 are shown on one side of the body 12, there may be additional air ducts 78 on the opposite side of the body 12 and on the back of body 12. These additional air ducts 78 have been omitted for the purposes of clarity. The air ducts 78 may be attached to the body 12 by straps. Additional air ducts 156 are also shown around the exhaust 22. The additional air ducts 156 operate in the same way as the air ducts 78 and have upper and lower openings. Whereas only six additional air ducts 156 are shown on one side of the exhaust 22, there may be more additional air ducts 156 on the opposite side of the exhaust 22, which have been omitted for the purposes of clarity. The additional air ducts 156 may be attached to the exhaust 22 by straps. The additional air ducts 156 have lower openings within the oven 153, preferable low down in the oven 153. The additional air ducts 156 pass through a space between the exhaust 22 and the upper surface of the oven 153 so that the upper openings are inside the chamber 154. In this manner the chamber 154 acts as a reservoir of hot air. The chamber 154 is typically between 40 - 60 litres, which may be sufficient to act as a suitably sized reservoir. Also shown is a row of oven ducts 157 which surround the additional air ducts 156 only in the region of the oven 153. The oven ducts 156 have lower openings which are low down in the oven 153, and upper openings which are high up within the oven 153. The oven ducts 157 operate in the same way as the air ducts 78 to promote convection currents within them. Whereas only seven oven ducts 157 are shown on one side of the exhaust 22, there may be more oven ducts 157 on the opposite side of the exhaust 22, which have been omitted for the purposes of clarity. The oven ducts 157 may be attached to the exhaust 22 by straps and may be removed or added to as required. The oven ducts 157 operate to raise the temperature within the oven 157, or lower the temperature within the oven 157 if removed.

The oven 153 is accessible via a door (shown in Figure 7). The chamber 154 is provided with an air inlet 158 and an air outlet 60, for inflow and outflow of air as shown by respective arrows 162, 164. An electric fan 166 may be used to draw air into the chamber 154 and to push air out of the chamber 154. The electric fan 166 may be operated in the reverse direction to reverse the flow of air. The air inlet 158 and air outlet inlet 160 may be coupled to a central heating system of a building, such as the outlet 11 and inlet 118 shown in Figure 4, or one or more of the ducts 98 shown in Figures 3, 3a and 3b. The second boiler 40 may be configured for heating water, or for heating air so that it passes into the chamber 154. It will be appreciated that the chamber 154 is separated from the oven chamber 155 by the oven 153 so that the air within the oven stay clean. In operation the stove 150 heats air in the grate 18, in the ducts 78, in the additional ducts 156, and optionally in the second boiler 40. The heated air rises into the chamber 154. The electric fan 166 then moves the heater air around a central heating system of a house. Alternatively the electric fan 166 moves the heated air from the air outlet 160 into a room via pipe work or ducting (not shown) so that blown hot air enters the room. It will be appreciated that with a flow and return arrangement of the hot air as it circulates in a central heating system, the air entering the air inlet 158 is typically cooler than the air exiting the air outlet 160. The heated air from the air ducts 78 may also be input to a central heating system or it may be passed into a room via pipe work or ducting (not shown) so that hot air enters the room.

Figure 7 shows a perspective view of the stove shown in Figure 6. In Figure 7 like features to the arrangements of Figure 6 are shown with like reference numerals. In Figure 6 the container 152 is shown with solid outline and the remaining parts inside the container 152 are shown with a dashed outline. The container 152 is insulated so that when the stove 150 is burning fuel the container 152 can be touched by a person from the outside without it burning them. The container 152 may also be arranged to radiate an amount of heat so that a room in which it is located is provide with heat. In addition the container 152 has a door 168 in a front side thereof to gain access to the oven 153, and to remove or add the oven ducts 157 as required. The door 168 has a sufficient airtight seal for the purposes of cooking. The oven 153 may be provided with a temperature gauge. The container 152 shown in Figures 6 and 7 may be considered to be similar to a known chimney breast, and may extend between a floor and a ceiling in a room in which the stove 150 is located. Since the container 152 is insulated it is envisaged that in use the bottom quarter of the stove 150 does not get hot due to the efficient transfer of the heat from the burning fuel into the chamber 154. Accordingly, the container 152 may avoid or reduce burning of a person who may touch the container 152. Whereas it would be expensive to build a traditional brick chimney and chimney breast, the use of the stove 150 having a container 152 may be less expensive. In addition, such a stove 150 would be more fuel efficient and would avoid heat being absorbed into brickwork.

In the above embodiments the first and second boilers 26, 40 are described for use to heat a liquid, such as water, or a gas such as air. Accordingly, the first and second boilers 26, 40 may alternatively be termed heat exchangers, fluid heaters, air heaters or water heaters. In addition, in the above embodiments the ducts 78, 156 are described for use to heat a gas such as air. Accordingly, ducts 78, 156 may alternatively be termed heat exchangers, gas heaters or air heaters. It will be appreciated that any suitable liquid or gas may be used to provide the required working effect of removing heat from the stove 10, 150. It will also be appreciated that the stove 10, 150 may be coupled to a conventional central heating system or to a water storage tank to heat the water therein. A pump may be used for circulation of the liquid or gas within the first boiler 26, and/or the second boiler 40, and/or the storage heater apparatus 90, and/or the storage heater device 110. A fan or blower may be used for circulation of air through the air ducts 78, 156 of the convection device 62. Alternatively the stove 10, 150 may be coupled to the storage heater device 90, 110 shown in Figures 3 and 4. Such arrangements may be used to provide heating and/or a supply of hot water.

In the above embodiments the substantially parallel pipes or ducts of the grate 18 may be provided with a particular spacing to provide an improved operation thereof. If the pipes or ducts of the grate 18 are too close together ash or debris, such as nails from burnt wood, may rest on the grate 18, which is undesirable. If the pipes or ducts of the grate 18 are too far apart the fuel or burning embers may fall through the grate 18, which is also undesirable. The inventor has realised that an optimum spacing for the pipes or ducts comprising the grate 18 is between 7 - 12mm, which allows fuel and burning embers to remain on the grate 18, whilst also permitting ash and other debris to fall through the grate 18 so that the grate 18 is self cleaning to some extent.

Claims

1. A stove for a heating system, comprising a housing having a combustion chamber and a grate for the combustion of fuel thereon, wherein the grate at least partially comprises a first fluid heater suitable for a liquid or gas, the stove being operable to heat a liquid or gas in the first fluid heater from the combustion of the fuel on the grate.

2. A stove according to claim 1, wherein the first fluid heater comprises at least one duct.

3. A stove according to claim 2, wherein the first fluid heater comprises a plurality of ducts.

4. A stove according to claim 3, wherein the plurality of ducts comprise the grate.

5. A stove according to claim 2, 3 or 4, wherein the at least one duct is at an angle of greater than 2° from a horizontal for promoting a thermal siphon effect.

6. A stove according to claim 5, wherein said angle is between 2° - 10°.

7. A stove according to any preceding claim, wherein the first fluid heater is in fluid communication with a first manifold which has a first chamber therein.

8. A stove according to claim 7, wherein the first fluid heater is in fluid communication with a second manifold which has a second chamber therein.

9. A stove according to claim 8, wherein the first and second manifolds are substantially horizontal and spaced apart from one another, and the first fluid heater is between the first and second manifolds so that the first and second chambers are in fluid communication with one another.

10. A stove according to claim 7, 8 or 9, wherein a portion of at least one manifold is provided on an exterior of the housing.

11. A stove according to claim 10, wherein substantially the entirety of at least one manifold is provided on an exterior of the housing.

12. A stove according to any of claims 7 - 11, wherein at least one manifold comprises a duct having a square or rectangular cross section.

13. A stove according to any of claims 8 - 12, wherein the first manifold, the second manifold and the first fluid heater have a total volume of between 6 - 14 litres.

14. A stove according to claim 13, wherein the first manifold, the second manifold and the first fluid heater have a total volume of substantially 10 litres.

15. A stove according to any preceding claim, wherein the first fluid heater has an inlet and an outlet such that the inlet is lower than the outlet for promoting a thermal siphon effect.

16. A stove according to any preceding claim, and further including at least one air duct on an exterior of the housing, the air duct having a lower opening and an upper opening, the air duct operable to promote heat convection therethrough.

17. A stove according to claim 16, wherein the lower opening comprises a curved part of a free end of the at least one air duct.

18. A stove according to claim 16 or 17, when dependent on claim 10 or 11, wherein the lower part of the at least one air duct is adjacent to the at least one manifold or the portion thereof which is exterior of the housing.

19. A stove according to claim 16, 17 or 18, and further including a plurality of air ducts on an exterior of the housing.

20. A stove according to any preceding claim, and further including a second fluid heater within the combustion chamber and which is above the grate, the second fluid heater being suitable for a liquid or gas, wherein the stove is operable to heat the liquid or gas in the second fluid heater from the combustion of the fuel therein.

21. A stove according to claim 20, wherein at least a portion of an underneath part of the second fluid heater is curved.

22. A stove according to claim 21, wherein the underneath part comprises a curved plate.

23. A stove according to claim 21 or 22, wherein the underneath part is convex.

24. A stove according to claim 23, wherein the second fluid heater comprises a convex housing with a chamber therein for the liquid or gas.

25. A stove according to any of claims 20 - 24, wherein the second fluid heater is adjacent to an exhaust duct of the combustion chamber.

26. A stove according to any of claims 20- 25, wherein the second fluid heater has an inlet and an outlet such that the inlet is lower than the outlet for promoting a thermal siphon effect.

27. A stove according to any of claims 20 - 26, wherein the second fluid heater has a volume of between 3 - 7 litres.

28. A stove according to claim 27, wherein the first manifold, the second fluid heater has a volume of substantially 5 litres.

29. A stove according to any of claims 20 - 26, wherein the first fluid heater and the second fluid heater are in fluid communication with one another.

30. A stove according to any preceding claim, and further including a liquid fuel burner comprising a receptacle for holding the liquid fuel, the receptacle having an open top and being operable to allow the liquid fuel within the receptacle to at least partially vaporise for promoting combustion thereof.

31. A stove according to claim 30, wherein the liquid fuel burner is located above the grate and within the combustion chamber.

32. A stove according to claim 30, wherein the liquid fuel burner is located beneath the grate.

33. A stove according to claim 31 or 32, when dependent on any of claims 20 - 26, wherein the liquid fuel burner is below the second fluid heater.

34. A stove according to claim 31, 32 or 33, wherein the receptacle includes a wick for the liquid fuel.

35. A stove according to claim 34, wherein the wick comprises a glass fibre, a stone fibre, or a ceramic fibre.

36. A stove according to any of claims 31 - 35, wherein the receptacle has an upright wall for concentrating the vaporised liquid fuel.

37. A stove according to claim 36, wherein the upright wall has a plurality of holes for promoting combustion of the liquid fuel.

38. A stove according to any preceding claim, and further including a gas chamber adjacent to the housing, the gas chamber having a gas inlet and a gas outlet, the gas chamber for providing a source of heated gas.

39. A stove according to claim 38, and further including a pump for driving the heated gas from the gas chamber and through the gas outlet.

40. A stove according to claim 38 or 39, wherein the combustion chamber has an exhaust duct that is arranged to pass through the gas chamber.

41. A stove according to claim 40, and further including at least one additional air duct operable to promote heat convection therethrough, the at least one additional air duct being adjacent to the exhaust duct and having an upper opening inside the gas chamber.

42. A stove according to any of claims 38 - 41, wherein the gas chamber is above the housing.

43. A stove according to any of claims 38 - 42, wherein the gas chamber is defined by a container around the housing.

44. A stove according to claim 43, wherein the gas chamber comprises a first volume above the housing, and a second volume around the sides of the housing.

45. A stove according to claim 43 or 44, wherein the container is spaced apart from the housing.

46. A stove according to claim 43, 44 or 45, wherein the container is provided with heat insulation.

47. A stove according to any of claims 43 - 46, wherein the container is arranged to extend between a floor and a ceiling of a room in which the stove is located so that it acts as a chimney breast for the room.

48. A stove according to any of claims 38 - 47, wherein the gas chamber is accessible via a door.

49. A stove as substantially described herein with reference to Figures 1, 2, 6 and 7 of the accompanying drawings.

50. A storage heater apparatus, comprising at least one duct for a liquid or gas, and a void space for air, the apparatus for location within a wall or a floor, wherein the apparatus is adapted for operation such that when a heated liquid or gas is flowing in the at least one duct the heat is retained in the void space, and when the liquid or gas is not flowing in the at least one duct said retained heat is conducted to a wall or floor in which the apparatus is located.

51. A storage heater apparatus according to claim 50, and further including a conduit for providing the void space.

52. A storage heater apparatus according to claim 50 or 51, wherein the at least one duct is adjacent to the void space.

53. A storage heater apparatus according to claim 50, 51 or 52, comprising a plurality of ducts.

54. A storage heater apparatus according to claim 53, wherein the plurality of ducts are adjacent to the void space.

55. A storage heater apparatus according to any of claim 50 - 54, wherein the at least one duct and the void space is embedded in an aggregate material within the wall or floor.

56. A storage heater apparatus according to claim 55, and further including insulation provided on an exterior of the aggregate material.

57. A storage heater apparatus according to any of claim 50 - 56, wherein the at least one duct has an elongate insert therein.

58. A storage heater apparatus according to claim 57, wherein the insert comprises a metal bar.

59. A storage heater apparatus according to claim 57 or 58, wherein the insert is spaced apart from an inside wall of the at least one duct.

60. A storage heater apparatus according to claim 57, 58 or 59, wherein the insert has a plurality of transverse portions which extend in a direction away from the axis of the insert.

61. A storage heater apparatus for location within a wall or a floor, comprising a vessel for storing water, the vessel having a heat exchanger device, the apparatus being adapted for operation such that when a heated liquid or gas is flowing in the heat exchanger device the heat is conducted to the water within the vessel, and when the liquid or gas is not flowing in the heat exchanger device said retained heat is conducted to a wall or floor in which the apparatus is located.

62. A storage heater apparatus according to claim 61, wherein the vessel is embedded in an aggregate material within the wall or floor.

63. A storage heater apparatus according to claim 62, and further including insulation provided on an exterior of the aggregate material.

64. A stove according to any of claims 1 - 49 for providing hot liquid or gas to a storage heater apparatus according to any of claims 50 - 63.

65. A storage heater apparatus according to any of claim 50 - 63, as substantially described herein with reference to Figure 3, 3a, 3b or 4 of the accompanying drawings.

66. A wall or a floor including a storage heater apparatus according to any of claims 50 - 63.

67. A wall or a floor according to claim 66, when appended to claim 53 or 54, wherein the plurality of ducts are between the void space and a surface of the wall or the floor.

68. A wall or a floor according to claim 66 or 67, as substantially described herein with reference to Figure 3, 3a, 3b or 4 of the accompanying drawings.

69. A liquid fuel burner for burning a liquid fuel, comprising a receptacle for holding the liquid fuel, the receptacle having an open top and being operable to allow the liquid fuel within the receptacle to at least partially vaporise for promoting combustion thereof.

70. A liquid fuel burner according to claim 69, wherein the receptacle includes a wick for the liquid fuel.

71. A liquid fuel burner according to claim 70 wherein the wick comprises a glass fibre, a stone fibre, or a ceramic fibre.

72. A liquid fuel burner according to claim 69, 70 or 71, wherein the receptacle has an upright wall for concentrating the vaporised liquid fuel.

73. A liquid fuel burner according to claim 72, wherein the upright wall has a plurality of holes for promoting combustion of the liquid fuel.

74. A method of operating a stove for a heating system, the stove comprising a housing having a combustion chamber and a grate for the combustion of fuel thereon, wherein the grate at least partially comprises a first fluid heater suitable for a liquid or gas, the method including^*.

combusting fuel on the grate; and

75. A method according to claim 74, wherein the first fluid heater is inclined at an angle of greater than 2° from a horizontal, the method including creating a thermal siphon effect within the first fluid heater.

76. A method according to claim 74 or 75, wherein the stove further includes at least one air duct on an exterior of the housing, the air duct having a lower opening and an upper opening, the method including providing heat transfer by heat convection through the at least one air duct.

77. A method according to claim 74, 75 or 76, wherein the stove further includes a second fluid heater within the combustion chamber and which is above the grate, the second fluid heater being suitable for a liquid or gas, the second fluid heater having a curved portion of an underneath part thereof, the method including swirling the combustion gases using the curved portion to heat the liquid or gas in the second fluid heater.

78. A method according to claim 77, wherein the second fluid heater has an inlet and an outlet such that the inlet is lower than the outlet, the method including creating a thermal siphon effect within the second fluid heater.

79. A method according to claim 77 or 78, and further including using a second fluid heater having a volume of between 3 - 7 litres.

80. A method according to any of claims 77 - 79, and further including providing the first fluid heater and the second fluid heater in fluid communication with one another.

81. A method according to any of claims 77 - 80, wherein the stove further includes a liquid fuel burner comprising a receptacle for holding the liquid fuel, the method including at least partially vaporising the liquid fuel for promoting combustion thereof.

82. A method according to any of claims 74 - 81, and further including using a first fluid heater having a volume of between 6 - 14 litres.

83. A method according to any of claims 74 - 82, wherein the stove has a gas chamber adjacent to the housing, the method comprising using the stove to heat gas within the gas chamber, and using the heated gas as a source of heat.

84. A method according to claim 83, and further including insulating the gas chamber.

85. A method according to claim 83 or 84, when appended to claim 76, and further including heating the air in the gas chamber using the at least one air duct.

86. A method according to any of claims 74 - 87, wherein the combustion chamber has an exhaust duct, the method including heating the air in the gas chamber using the exhaust duct.

87. A method as substantially described herein with reference to Figure 5 of the accompanying drawings.