GB2447777A

GB2447777A - Heat storage stove comprising a timer controller

Info

Publication number: GB2447777A
Application number: GB0805188A
Authority: GB
Inventors: David Ian Carpenter; Patrick James Collins
Original assignee: AGA Consumer Products Ltd
Current assignee: AGA Consumer Products Ltd
Priority date: 2007-03-22
Filing date: 2008-03-20
Publication date: 2008-09-24
Anticipated expiration: 2028-03-20
Also published as: GB2447777B; GB0805188D0; GB0705482D0

Abstract

A heat-storage stove comprises a thermally insulated shell containing at least one heating compartment in thermal communication with a system of ducts communicating with a chamber which serves as a controllable heat source 1. A timer controller is provided for controlling the amount of heat applied by the heat source at any given time according to at least one control scheme. The stove includes a user operable control unit (100, fig.2) which comprises at least one input device for modifying the control scheme. The control scheme comprises a timing sequence of at least two operating modes which each correspond to a different demanded temperature in the heating compartment. Preferably, the control unit is a remote control unit (200, fig.2) comprising a programmable timer that may be located separate and distant from the rest of the stove. The control scheme may include three different operating modes to provide a first normal operating temperature, a second low temperature, and a third still lower slumber temperature. In use, the invention provides a stove in which the heating compartment is only held at its optimal cooking temperature at the times that it is needed for cooking and is allowed to drop to a lower temperature outside of these times.

Description

IMPROVEMENTS IN AND RELATING TO STOVES

This invention relates to heat-storage stoves such as are used for cooking and similar domestic purposes.

Such cooking stoves are well known per se and examples thereof have been available on the market for many years under the trade names AGA and RAYBURN , and they typically comprise a thermally insulated shell containing one or more cooking plates and one or more cooking compartments in thermal contact with a system of ducts communicating with a combustion chamber which serves as heat source.

The combustion chamber is fed with a solid fuel, or, and more commonly nowadays, with fuels such as kerosene, natural gas or propane. By making the shell from cast iron, heat from the heat source is stored residually allowing the device to provide constant high temperatures with heat source constantly topping it up if heat is lost (for instance by opening a door to the oven).

It is also known to provide a heat storage stove with the chamber containing one or more resistance heating elements. Two types of electric heat store stoves have been proposed. In the first the heat store is "charged" with heat to a high level using a high power heating element rated at 30 amps at 240 volts. This charging can be performed overnight when electricity is cheaper and then released from the store during the day as required to keep the stove at its operating temperature.

Alternatively, a lower power heat element (of, say, less than 13 amps) may be provided which is carried by a refractory armature and arranged so that air can freely circulate between the elements and the armature.

This has the advantage that it requires no specialist wiring in most homes and therefore can be installed with little or no disruption.

In the later arrangement the heat element must generally be almost always ON whenever heat is required for cooking (the element being incapable of generating enough heat in the heat store overnight to supply the required temperature at the ovens for any extended period when the heat element is OFF). Traditionally, therefore heat store stoves of this later kind have required the heating element to be operated substantially at all times of the day and night to keep the temperature of the stove at the correct level.

According to a first aspect the invention provides in combination: a heat-storage stove comprising a thermally insulated shell containing at least one heating compartment in thermal communication with a system of ducts communicating with a chamber which serves as a controllable heat source and a timer controller for controlling the amount of heat to be applied to the heat source at any given time according to at least one control scheme; and a user operable control unit comprising at least one input device such that a user can modify the at least one control scheme through operation of the input device, and in which the control scheme comprises a timing sequence of at least two operating modes which each correspond to a different demanded temperature in the heating compartment.

The invention therefore provides a heat-store stove which operates in accordance with a control scheme that can be modified by a user operable control unit such that, in at least one advantageous arrangement, the control scheme can ensure that the heating compartment is only held at its optimal cooking temperature at the times that it is needed for cooking and is allowed to drop to a lower temperature outside of these times.

Previously heat storage stoves have only been known to have been operated such that the temperature of the oven remains at a constant high temperature (or at least the heat source tries to maintain the constant high temperature) at all times.

The user operable control unit is preferably a remote control unit that can be located separate and distant from the rest of the stove and the stove may include a link which connects the control unit to the controller such that modifications to the control scheme made on the remote control unit are passed to the controller. The remote control unit may comprises a programmable timer, or may be operable to control the controller which comprises a programmable timer.

The user operable control unit may include a display. A backlight may be provided. The backlight may operate for a period of time after a user input is operated before switching itself off. This period may be 15 seconds for example. The display may remain on after this time for a longer period, for example 5 minutes after which it will be turned off.

The control scheme may include at least three different operating modes with the controller controlling the heat source in each operating mode to provide a different temperature in the heating compartment, a first (normal) mode corresponding to a first temperature, a second (low) mode to a lower temperature and a third (slumber) to a still lower temperature.

These modes may be in addition to an OFF mode in which the stove is turned off.

The modes may, for example, correspond to a temperature in the oven of around 240 degrees C, around 200 degrees C and around 150 degrees C respectively. These temperatures could be varied but should be chosen to correspond with a maximum cooking temperature for the hottest oven of the device, a lower (but still usable) temperature, and a much lower temperature at which the oven cannot really be used for cooking most foods but still provides residual heat. This residual heat can be used to provide heating to the surroundings of the oven which many users find to be a significant benefit of a heat storage stove. These temperatures may be user definable to enable a user to set their preferred temperatures for each mode. For example, if they want more residual heat in the third mode by trading off cost savings then they can do so.

The control scheme may indicate times at which each mode starts and stops.

The stove may be provided with a default control scheme which comprises the following timing sequence over a 24 hour period: a first period of time in which the heat source is controlled in the first mode, followed by a period of the second mode, followed again by a period of time in the first mode, and then for a period of the third mode until the 24 hours has elapsed.

The first mode (normal mode) may last for between 5 minutes and 3 hours and may be a period of time in the morning, and similarly for between 5 minutes and 3 hours in the evening to correspond with the times at which meals will be made and the oven is needed at its highest setting. The time in between in the second mode (low mode) will allow enough heat to cook some foods, and the time remaining will be at the lower setting as it is envisaged that the stove is unlikely to be used overnight. This fits round breakfast and evening meal times, and can offer a considerable saving over operating constantly in the first mode. To date all stoves of this type have only operated in the first mode, or in and OFF mode in which they are fully cooled.

The duration and start/stop times of each mode may be user defined and modified through the remote control unit.

More than one control scheme may be provided. For instance a 24 hour (1 day) scheme for use on weekdays may be provided with a different scheme for weekend days.

An alternative scheme may be provided called a holiday scheme in which the controller will set the stove to the second mode or third operating mode (or a combination of the two) for an entire 24 hour period or longer. This will enable the cost of running the stove to be reduced during periods in which the user is on holiday. The scheme may include a date range over which the holiday will extend.

Any scheme provided may be stored in memory accessible by the controller of the heat source.

The controller may receive a measurement of the temperature in at least one part of the stove from a temperature sensor such as a thermocouple.

It may use this in a closed loop control system to achieve the demanded temperature determined by the mode set by the control scheme.

The stove controller may also include a manual override which permits a user to dictate what constant temperature the stove is to be operating at instead of using the control schemes. A rotary knob for instance could be provided to indicate temperature, and a two or three position switch could be used to select manual or control scheme operation (and possibly off).

The switch and rotary knob could be mounted to a panel on the stove. A light may be provided which visually indicates that the manual override has been selected.

Because the stove will take some time to change temperature from one mode to another, the controller may be arranged to anticipate a change from a mode to a mode at which a higher temperature is demanded and start to increase the heat by operating the heat source in advance. Ideally this will increase the temperature so that it reaches the higher temperature at the time demanded by the control scheme. This may require the heat source to be operated at least 30 minutes, or perhaps 1 hour or more before the actual time of the mode change.

The stove may include one or more resistive electric heating elements which provide heat to the heat source and which are supported by a refractive block. The heat element may have a rating of 2,5 kwatts or thereabouts and draw 13 amps or less from a domestic mains supply at 230 volts. An example of such a device which is available in the art as the AGA 13 Amp electric oven.

The controller may operate the resistive heating element between an On condition in which heat is applied to the heat source by current from a power source passing through the element and an Off condition in which the element is isolated from the power source so that no heat is applied to the heat source.

Of course the stove may include an alternative heat source such as a gas burner, oil burner or solid fuel burner so long at the heat source can be controlled by the controller.

The remote control unit may include a battery as a power source for the display and may be wall mountable.

The link may comprise an RF link with a transmitter in the remote control unit sending the users input information to a corresponding RF receiver of the stove which communicates with the controller. The information sent across this link may be coded such that the remote controller and stove are "paired'.

The remote control unit may also include an RF receiver and the Stove controller and RF transmitter such that two way communication with the stove controller can be established. This allows the stove to send information to the remote control unit about the stove status/temperature etc. The remote control unit may include a display which shows one or more of the following items of information: The current date; the current operating mode; the current time of day; the stove temperature, the battery status of the remote unit, the stove status (manual over-ride or control scheme operating); holiday scheme status (on or off).

The user input devices may comprise one or more switches or buttons which operate respective micro switches. Alternatively a touch screen could be provided which may also be provided in combination with one or more switches or buttons.

The controller may also, optionally, be configured to receive information from a modem device which enables the controller to be programmed remotely from any telephone or modem.

A fan may be included in the stove which may be operated by the remote control. The status of the fan may be indicated on the display of the remote control unit (where provided) and optionally on the stove using a light source, eg a neon light.

According to a second aspect there is provided a remote control unit and a controller for use in combination with a heat storage stove to provide an apparatus of the first aspect of the present invention.

It is envisaged that the remote control unit and controller may be retrofitted to an existing stove. The controller may comprise a programmable timer.

According to a third aspect the invention provides a remote control unit for use in combination with a Stove having a controller for a heat source to provide apparatus in accordance with the first aspect of the invention.

According to a fourth aspect the invention provides a method of modifying a heat storage stove of the kind comprising a thermally insulated shell containing at least one heating compartment in thermal communication with a system of ducts communicating with a chamber which serves as a controllable heat source, the modification comprising: fitting a timer controller to the stove which controls the operation of the heat source according to at least one control scheme.

The control scheme may be arranged such that the stove is controlled between a first operating mode in which the temperature is held at a first temperature suitable for cooking for at least two periods in any 24 hour period and is held in between these two periods at a second, lower temperature operating mode.

It may be held substantially constantly at the second lower temperature operating mode between the first modes.

One of the first modes may correspond to a time in the morning for breakfast and the other in the evening for evening meal.

The retrofitted controller may include an interface through which the control scheme can be modified. For example it may permit the start and stop time of each first mode to be modified. This interface may connect the controller to a remote device, the controller and remote control unit being in accordance with the second aspect of the invention.

More than one control scheme may be provided, and the interface may enable a user to select which scheme to use at a given time or on a given day or group of days.

A preferred embodiment of the invention will now be described with reference to the accompanying diagrammatic drawings in which: Figure 1 is a cut away view of a stove incorporating a heating assembly and a controller in accordance with a first aspect of the present invention; Figure 2 is a schematic illustration of an embodiment of the controller and remote control unit of the heat store stove of Figure 1; Figure 3 shows the remote unit and its display and layout of its control buttons in more detail; Figures 4(a) and 4(b) is a schematic illustration of a default control scheme that can be implemented by the controller and which is stored in the controller memory; Figure 5 is a first state diagram illustrating the operating logic of the remote control unit; Figure 6 is a second state diagram illustrating the operating logic of the remote control unit; Figure 7 is a third state diagram illustrating the operating logic of the remote control unit; Figure 8 is a fourth state diagram illustrating the operating logic of the remote control unit; Figures 9 and 10 are respectively elevations of two parts of an armature of a heating assembly; Figures 11 and 12 are respectively a side elevation and a plan view of the heating assembly; Figure 13 is a plan view of a stand of a heating assembly; and Figures 14 (a) to 14 (d) are examples of representative displays provided by the remote control in different operating modes.

Figure 1 shows a cut-away section of the internal parts of a standard Aga stove having a body designed to allow the installation of gas or oil burners or to allow for combustion of solid fuel in a combustion chamber 6 and a barrel 7. The stove is provided with a top oven 8 and a bottom oven 9. Further ovens may be provided as desired. Air constantly recirculates through the stove by convection. Air heated in the combustion chamber 6 rises through a barrel 7 to heat the underside of a first hot plate (not shown) also located above that chamber and then across beneath a second hot plate (not shown) located above the ovens 8, 9 to pass through a flue 10 above the top oven 8 to an air circulation box 11 and down a return flue 12 to the combustion chamber 6.

As illustrated, instead of having a gas or oil burner or being arranged for solid fuel combustion, an electric heating assembly 1, is installed in the stove in this example. The heating assembly 1 substantially fills an opening 13 at the base of the barrel 9, and extends into the barrel 9 by between 60 and 160 mm. The plates from which the armature is formed may for example measure 250x 175 mm. It is desirable that the top of the heating element should be at least as high as the bottom of the top oven 8.

The return flue 12 terminates in a combustion chamber air inlet 14 located at the base of the combustion chamber 6. The heating element 2 and armature 3 of the heating assembly 4 are supported above the level of that return inlet 14 by the use of the stand 5. As shown, the top plate 51 of the stand 5 occupies substantially the full plan area of the combustion chamber with the result that recirculating air is substantially constrained to flow through the holes 52 in that top plate and thus up between the plates 30, 31 of the armature 3 and the heating element 2. This promotes an efficient transfer of heat energy to that air.

The heat-storage stove shown in Figure 1 would in practice be enclosed within a shell, with thermally insulating material between the parts shown and such shell. The heat source would be continuously controlled such that the temperature inside the oven is at an ideal, maximum, cooking temperature at all time. This is typically a temperature of 240 degrees at the hottest oven.

Control of the electric heating element 1 of the heat source is achieved by use of a suitable drive circuit which modulates the heating element between a fully ON state and a fully OFF state. The element 1 is changed from one state to another using a high rating relay switch which selectively connects it to the power supply. This switch is controlled by a controller as shown in Figure 2.

The purpose of the controller is to enable the output of the heat source to be varied with time over a 24 hour period to include periods at which the temperature is held lower than its 240 degrees optimum such that the amount of electricity consume is reduced compared with a traditional device operating at full heat all the time.

The controller controls the heat source according to a control scheme which is stored in memory. The scheme tells it what mode the stove is to be operated in (a mode loosely speaking defining an operating temperature) and at what time the stove it to be in a given mode in a 24 hour period. The modes available within the scheme are: Normal mode-When the controller is operating in this first mode, the heat store stove is effectively functioning in the manner of a standard heat store stove whereby the temperature in the heating compartment is kept as close as possible to an optimal cooking temperature. In this example this corresponds to around 240 degrees. The controller measures the temperature constantly and operates the heating element if the temperature drops below this level, cutting the heating element off as appropriate to prevent overheating. The controller operates in a closed ioop mode. The control scheme will set the stove in this mode when a period of cooking time is required.

Low mode-In this second mode the controller operates in the same closed loop manner as the normal mode but the temperature of the heating compartment is held at a lower level, say 200 degrees. This still allows some cooking but importantly requires less energy consumption of the stove. The controller scheme will enter this mode when cooking "may" be required but it is not anticipated that a lot of cooking will be needed.

Slumber mode-In this third mode the controller again controls the temperature of the heating compartment using closed ioop control but the temperature is held lower then for the second, Low, mode. This will typically comprise a temperature of around 150 degrees. This is to be used when no cooking is required but rather than letting the oven cool down completely it ensures some residual heating from the stove to its surroundings can be provided.

For ease of use and installation the stove is supplied with a default control scheme which is stored in memory that can be accessed by the controller. An example of a typical default control scheme is shown in Figure 4(a). As can be seen here, the control scheme determines the modes, and hence temperature, for the heating compartment at all times over a given 24 hour period. In this example it can be send that the stove is set so that it is in the Normal mode at a time of high demand between the hours of 7am and lOam. This corresponds to the time it will be needed to cook a good breakfast to start the day. After that it is set to the standby mode until 5pm when the stove again returns to the ON mode until 8pm during the time that evening meals are to be cooked. After this it switches to the slumber mode overnight when it is not expected that the stove will be needed. As some residual heat will remain it could still be used to cook porridge overnight for example. Thus, over the 24 hours it is running with far less power consumption than if it were in the ON mode at all times.

An important feature of the controller is that it does not simply switch the stove from one mode to the other at the set times, but it predicts in advance when the modes are required so that the oven is at the required temperature when the set time for that mode arrives. This is important when the thermal lag of the stove is taken into account which can lead to a significant time delay between turning the element on and the stove reaching a desired temperature. This is achieved using logic built into the controller to start increasing heat before a mode is entered. The change in temperature is shown in Figure 4(b) of the drawings.

The default control scheme can be modified by a user through a control interface which, as will become apparent, includes a remote control unit.

Additionally, more than one control scheme can be stored in the memory.

A calendar function allows different control schemes to be associated with different days of the week, month, or year.

For example, a holiday scheme can be stored in the memory in which the stove is to be set in the slumber mode for a complete 24 hour period (or longer) corresponding to a holiday. The scheme can be associated in the memory with one or more date ranges over which it is to be operative.

A manual override function is also provided by the controller which enables a user to override any control scheme that would otherwise by used at any given time with a manual setting of desired temperature.

Having established the key functionality of the controller the exact parts of the controller required to achieve the functionality will be explained with reference to Figures 2 and 3 of the accompanying drawings.

The timing controller comprises a controller unit 100 that is fitted to the cooker and includes a radio frequency transceiver 110, a memory 120 which stores control schemes and operating instructions, a microprocessor 130 which executes the operating instructions and a temperature sensor (not shown) which measures the temperature in the oven cavity. Also provided is a remote control unit 200 which also includes an RF transceiver 210 that is paired to the RF transceiver 110 of the stove. The remote control unit 200 provides the facility by which the user can modify the control schemes stored in the memory 120. It could, of course, if required by integrated into the stove such that it is not actually remote but still provides the required means for modifying the control scheme(s), for example as part of a control panel attached to the stove.

This may also enable the RF link to be replaced with a simple hard wired link. The remote control unit 200 is shown in detail in Figure 3.

The remote control unit 200 physically comprises a housing 205 with a display 220 and a plurality of operating buttons 230. Inside the housing is a circuit board (not shown) which carries switches which are activated as the buttons 230 are pressed, a battery 260 which provides power, a microprocessor 240 which monitors the operation of the switches, an RF transceiver 210 and a back light (not shown) for the display 220 which operates whenever a button is pressed and keeps the display backlit for 15 seconds. The unit also includes a memory 250 which stores program instructions that are executed by the microprocessor 240. The microprocessor 240 controls the operation of the transceiver and sends a coded signal to the stove whenever a button is pressed or a change in control scheme is requested.

Each button 230 when operated causes the microprocessor to perform a different function. When a user presses a button 230 it generates a signal which is transmitted to the controller 100 of the stove through the RF link 110, 210. In turn the display is configured to present information giving the user feedback on the effect of operating a button.

The displayed information includes an indication of the mode that the cooker is in, the time and the date. It may also display a battery charge indicator. This information can be stored in a temporary memory in the remote device so that it does not have to be transmitted continuously and only needs to be updated when new information is received.

Specifically, in this embodiment the remote control unit includes 10 major buttons. The name of each button is as follows: -Settings -Program -Holiday -Plus -Minus -Cancel -Copy -Mode -Fan -On/off -Settings Each button carries an appropriate label (not shown) to tell the user which of the above functions it corresponds to. For instance the plus button may carry a + symbol.

In use the user can modify the control schemes using the buttons described and the modified schemes will be stored in the memory of the controller. This allows the user a large amount of convenience when setting the control schemes. The use of the buttons allows the use to step the program executed by the processor of the remote device 200 through a range of different functional states as follows: OFF state The remote control unit will enter this state if it has been unused for an extend period (i.e. if no buttons are pressed) which helps to conserve battery power. In this mode, the display is turned off, along with the backlight and the RF transmitter. The microprocessor will be set to a low power sleep mode.

Home state: When the remote control unit is in the OFF state and a button is then pressed (any button) it will enter the Home state. A constant p011 of the buttons is therefore performed in the OFF state. In this mode the display will show a summary of the current status of the stove and other data including: time and date, stove mode, stove state (manual override on or off). The ON/OFF button can be pressed to switch back to the OFF mode if required. If the remote control unit cannot establish a link to the stove controller to retrieve this information, a suitable error message could be displayed or the screen left blank.

In this mode the display may show the information in figure 14 (a). The functions available to the user through the buttons are as follows: Settings If HOLIDAY is not active enter settings state -Program If HOLIDAY is nol active enter program state Holiday Enter HOLIDAY state Plus --Minus -- Cancel -- Copy --Mode If HOLIDAY is not active then cycle round the manual override modes Fan If HOLIDAY is not active then toggle the fan sUite.

Program state: lithe program button is pressed whilst the remote control unit is in the HOME state, it will enter the program state. This state provides the user with the option to review or change any parameter of any control scheme that has been set, or to create new schemes. The user can switch from this state back to the HOME state in a number of ways. For instance, if all of the schemes for the days Monday to Sunday have been reviewed or modified, or if the cancel button is pressed.

In this mode, the display will show to the user the information asshown in Figure 14 (b).

The functionality available to the user through the buttons is as set out in

the following table:

Settings --Program Progress to next program step (relurn to HOME state if current day is _________ Sunday and "period 2" cud time is highlighted) Holiday --Plus Encrement the currently "highlighted" variable Minus Decrement the currently "highlighted" variable Cancel Accept the modifications up to this point and return to HOME state Copy Copy the profile for the current day to the next (return to HOME state if _________-current day is Sunday) Mode -- Fan --Figure 5 shows the functionality of the program mode in more detail.

This shows how the user can step through each aspect of the control scheme. Note that period I and period 2 are the times that the stove is controller in the ON mode (temperature 240 degrees).

Settings state: In this state the user is given the option to review or change the date or time. The user can leave this state and return the unit to the home state in a number of ways. If all times or calendar values have been reviewed, it will return to the home state. Alternatively the cancel button could be pressed.

In this state the display will show the user the information as presented in Figure 14 (c).

The functionality available to the user in this state are as shown in the

following table:

Settings Progress to next settings step Prograni -- Holiday --Plus increment the currently "highlighted" variable Minus Decrement the currently "highlighted' variable Cancel Accept the modifications up to this point and return to HOME state Copy -- Mode -- Fan --Figure 6 shows the functionality of the settings mode in more detail.

Holiday state: In this state the user has the option to review or change dates on which a holiday control scheme is implemented by the controller or to change the parameters of the holiday control scheme. This mode can be exited in the same way as the program and settings states.

In this state the display will show the user the information provided in Figure 14 (d).

The functionality available through the buttons in this state is set out in

the following table:

Settings -- Program --Holiday Progress to next holiday step (return to HOME state if holiday cnd time is _________ highlighted, enable holiday mode).

Plus Increment the currently "highlighted" variable Minus Decrement the currently "highlighted" variable Cancel Accept the modifications up to this point (return to HOME state but ________ DISABLE holiday mode).

Copy --Mode Rotate round the modes the cooker should he in during holiday mode Fan --Figure 7 shows the functionality of the holiday state in more detail.

To enable the holiday state, the user can press the holiday button and set a start and end date/time. The start will default to today's date and the end to a date two days on from this. Repeated presses of the holiday button will cycle through the different dates/times (which can be altered if required). A message on return to the home screen will show that the holiday mode is enabled or is pending if the start date is later than the current date.

These states and their inter-dependence are shown in Figure 8 of the accompanying drawings.

The controller can control a wide range of heat sources but as already stated it is envisaged that it can be used to good effect with an electric heat source as shown in Figures 9 to 12.

The heat store assembly 1 comprises a resistance heating element 2 carried by a refractory armature 3 and arranged so that air can freely circulate between the element 2 and the armature 3. In order that the heating element may be powered from an ordinary domestic electric power supply, some preferred embodiments provide that the heating element be rated at less than 13 amp. We have found that a 2.5kW (10.9 amp at 230 volts) heater yields an ample heat output for most domestic cooking purposes.

The armature 3 is cruciform in cross section. The armature is assembled from a pair of generally similar plates 30, 31 having slots 34 extending half the length of each plate, the slot of one plate being fitted over and accommodating the other plate. The slots 34 have a width substantially equal to the thickness of the plates. The armature may be formed of an aluminium silicate material.

In order to promote secure retention of the heating element 2, the armature 3 is provided with holes 32 through which such element leads.

The armature 3 also includes holes 33 for locating lead-in wires 4 supplying current to the heating element 2.

The heating assembly 1 includes a stand 5 for the armature 3 which stand comprises a refractory top plate 51, having holes 52 (Figure 13) for the up draught of air between the heating element 2 and the armature 3, carried on supports 53 allowing the inflow of air to beneath that top plate 51. The top plate 51 is suitably of a ceramic material.

Claims

1. A heat-storage Stove comprising a thermally insulated shell containing at least one heating compartment in thermal communication with a system of ducts communicating with a chamber which serves as a controllable heat source and a timer controller for controlling the amount of heat to be applied to the heat source at any given time according to at least one control scheme; and a user operable control unit comprising at least one input device such that a user can modify the at least one control scheme through operation of the input device, and in which the control scheme comprises a timing sequence of at least two operating modes which each correspond to a different demanded temperature in the heating compartment.

2. A stove according to claim 1 in which the user operable control unit is a remote control unit that can be located separate and distant from the rest of the stove and the stove includes a link which connects the control unit to the controller such that modifications to the control scheme made on the remote control unit are passed to the controller.

3. A stove according to claim 2 in which the remote control unit comprises a programmable timer.

4. A stove according to any preceding claim in which the user operable control unit includes a display.

5. A stove according to any preceding claim in which the at least one control scheme includes at least three different operating modes with the controller controlling the heat source in each operating mode to provide a different temperature in the heating compartment, a first mode corresponding to a first temperature, a second mode to a lower temperature and a third mode to a still lower temperature.

6. A stove according to claim 5 in which the first mode corresponds to a temperature in the oven of around 240 degrees C, the second mode to around 200 degrees C and the third mode to around 150 degrees C.

7. A stove according to claim 5 or claim 6 in which the control scheme indicates times at which each mode starts and stops.

8. A stove according to any one of claims 5, 6 or 7 which is provided with a default control scheme which comprises the following timing sequence over a 24 hour period: a first period of time in which the heat source is controlled in the first mode, followed by a period of the second mode, followed again by a period of time in the first mode, and then for a period of the third mode until the 24 hours has elapsed.

9. A stove according to any one of claims 5 to 8 which also includes an alternative scheme in which the controller will set the stove to the second mode or third operating mode (or a combination of the two) for an entire 24 hour period or longer.

10. A stove according to any preceding claim which includes a manual override which permits a user to dictate what constant temperature the stove is to be operating at instead of using the control schemes.

11. A stove according to any preceding claim which includes one or more resistive electric heating elements which provide heat to the heat source and which are supported by a refractive block.

12. A remote control unit and a controller for use in combination with a heat storage stove to provide an apparatus of any one of claims 1 to 11.

13. A remote control unit for use in combination with a stove having a controller for a heat source to provide apparatus of any one of claims 1 to 11.

14. A method of modifying a heat storage stove of the kind comprising a thermally insulated shell containing at least one heating compartment in thermal communication with a system of ducts communicating with a chamber which serves as a controllable heat source, the modification comprising: fitting a timer controller to the stove which controls the operation of the heat source according to at least one control scheme.

15. The method of claim 14 in which the control scheme is arranged such that the stove is controlled between a first operating mode in which the temperature is held at a first temperature suitable for cooking for at least two periods in any 24 hour period and is held in between these two periods at a second, lower temperature operating mode.

16. The method of claim 15 in which the temperature is held substantially constantly at the second lower temperature operating mode between the first modes.

17. The method of claims 14, 15 or 16 in which one of the first modes corresponds to a time in the morning for breakfast and the other in the evening for evening meal.

18. A heat storage stove substantially as described herein with reference to the accompanying drawings.