AND A REGULATOR THEREFOR

This invention relates to heaters, including boilers, solid fuel burners, stoves, cookers, and the like. More particularly, it relates to domestic heaters that burn solid fuel, such as wood, coal, coke, charcoal, etc. and to multi-fuel heaters which use solid fuels in combination with other (solid and non-solid) fuels.

Solid fuels such as wood and coal were the first fuels used in the home for heating and cooking purposes. Other methods, such as oil, electric and gas have become popular over the last several decades, as the technology has developed. However, solid fuels have remained popular, and there has been a resurgence in the use of solid fuels such as wood and charcoal, particularly in the home environment. There are various reasons for this, such as the appearance and feel they give to a home environment, and, in some areas, the availability of the fuel. Also, the use of wood and wood derived fuels for heating and cooking is beneficial in terms of reducing the impact of climate change.

Solid fuels have a reputation for producing greater than desirable levels of smoke, soot and other particulates, created during the burn process. There are various techniques used to reduce these levels at the burn stage. For example, air can be forced into a combustion chamber to increase the burn rate, and to increase the temperature within the chamber, to promote a cleaner burn. Also, some heaters provide a secondary air intake in an upper part of a burn chamber to encourage the burning and hence destruction of particulates that have been produced further down the chamber.

Furthermore, suitable positioning of an additional air intake can encourage an "air wash" effect that can help to keep a glass window in the chamber clear of soot.

However, the level of particulates produced by a heater that uses solid fuels does vary, and can go above acceptable limits at times. National and international regulations are increasingly imposing ever tighter limits on permitted emissions.

It is an objective of the present invention to provide a means for reducing the unwanted emissions from a solid fuel heater or burner.

According to a first aspect of the present invention there is provided a regulator for a domestic solid fuel burning heater, the regulator comprising: a housing containing a fan and at least one variable air valve, wherein the fan is arranged, when activated, to push air along the housing, and the variable air valve is configured to provide a variable restriction to air passing towards an output of the housing; an electronic controller connected to the fan and variable air valve, and being arranged to control the fan operation and to control the degree of restriction imposed by the valve, characterised in that: the housing has a primary air output, and at least one of a secondary and a tertiary air output, each connectable to corresponding primary, secondary and/or tertiary air inputs on the heater, and wherein the valve is located to restrict airflow through the primary air output; the electronic controller further comprises at least a first sensor input arranged to come from a temperature sensor in or about a combustion chamber of the heater, and a second sensor input arranged to come from a gas or particulate sensor in an upper part of the combustion chamber, or flue, of the heater, and wherein the controller is arranged to control airflow to the primary air output based upon the first or second sensor inputs, and to control airflow to the secondary and/or tertiary outputs based upon the second sensor input.

Embodiments of the invention thus provide a regulator that is able, by using the sensor inputs, to at least partially reduce undesirable particulates and/or gases from passing up the flue, and hence into the atmosphere, by increasing airflow to the secondary and/or tertiary outputs, which induces an improved burn, and hence reduction, of such particulates or gases. Advantageously, some embodiments may employ a second valve, controllable by the electronic controller, and arranged to allow restriction of airflow to the secondary and/or tertiary output(s).

Conveniently, some embodiments may be adapted to increase air flow to the primary air output whilst the temperature sensor reads below a threshold temperature, and to increase secondary and/or tertiary air flow to the secondary and/or tertiary air outputs if the second sensor indicates levels of gas or particulates above a given threshold.

When a solid fuel fire or heater is first lit (i.e. from a cold state), then the burn of the fuel within a combustion chamber of the heater tends to be rather inefficient until the temperature of the combustion chamber rises to within a working temperature range. The efficiency increases to an optimum or at least satisfactory level whilst it stays within the temperature range. As the fuel burns away, and the heater starts to cool down, its efficiency can start to dip. Also, if, for example, a log is added to an

otherwise hot fire, the relative coolness of the log can reduce the efficiency of the burn for a time, until the burn of the log becomes established.

Note that the efficiency of a heater is a measure of how much heat is produced in proportion to how much fuel is used. The efficiency is dependent upon a number of factors, one of which is the moisture level present in the fuel used. Wet logs, or logs that have not been sufficiently seasoned, can comprise well over 20% water by weight, sometimes significantly more, such as 40% or 50%. Such logs can reduce the efficiency of a heater due to the heat consumed to evaporate or boil off the water, before the log can be burnt.

Embodiments of the invention have the advantage that they can detect the heater working in an inefficient manner, and can act to reduce the time the heater is in its inefficient state by controlling an air supply to the heater.

Some embodiments of the invention provide a means for a degree of manual control of the airflow, e.g. using a controller, such as a remote controller to select a desired room temperature or to change the airflow to the heater. Primary air is air that is directed towards, in general, a lower part of the combustion chamber of the heater, with the aim of increasing or facilitating burning of the fuel sitting within the combustion chamber. Secondary and tertiary air is air that is directed, generally towards an upper part of the combustion chamber, or to peripheral regions, with the aim of promoting the burn of particulates or gases given off during the burn in the lower part of the chamber. Embodiments provide means for independently controlling aspects of the air supply to each of the primary and secondary air inputs of a heater.

Embodiments of the invention may generally use the fan as a gross or coarse control of air, as may be required on initial lighting of the fire, or if cold new fuel is added, and may generally use the air valve as a fine control of air, for thermostatic temperature control or for aiding removal of unwanted gases etc. as detected by one or more gas or particulate sensors. To this end, the fan may be used to provide a boost of air to one or more parts of the heater, whilst the valve(s) may be used to reduce airflow to one or more parts of the heater. Should the use of the air valve(s) alone to regulate aspects of combustion (including combustion temperature or levels of sensed particulates or gases) not be effective in keeping said aspects within desired parameters, then, where appropriate, the fan may be used to provide forced air to the heater.

When a fire in a heater is newly lit, the flue of the heater does not tend to promote a draft of air up through the combustion chamber. This is why the fan is more effective at these early stages. Once the fire has heated up, and hot gases are passing up through the flue, then a natural draft is achieved. This is due to the flue effectively providing a low density and low pressure region (due to the expanded hot gases) which tends to then suck air up from and through the combustion chamber. This natural flow of air is beneficial in providing oxygen to the fire and so promoting a clean burn. At that point the valve is effective at controlling combustion within the

combustion chamber, by having the ability to throttle airflow to the primary air output, according to demands determined by the sensor readings. Thus, in some embodiments of the invention, the fan may be used to control primary airflow primarily when the burn within the combustion chamber is out of condition, and the air valve is used to control airflow primarily when the combustion chamber is in-condition. Here, the terms "out of condition" and "in condition" refer to the state of combustion taking place within the combustion chamber; the former being when inputs from sensors indicate that the sensed quantity is outside of preferred limits, and the latter when most or all sensors indicate that the sensed quantity is within preferred limits. Note that some embodiments may initially use the valve to attempt to bring a burn back to an in- condition state, and if this does not work within a given time period then the fan may be used, where appropriate.

When a quantity of fuel is added to a wood burner, e.g. when a log is added to the combustion chamber, the heat within the chamber starts to heat up the log. In the early stages of this process the outside of the log will be heated first. Up to around 100 °C, the heat energy supplied to the log goes to evaporating, or boiling off, the water that is contained within the log. Unseasoned, or incompletely seasoned logs contain more water, and so tend to remain cooler for longer due to the extra energy required to remove the water. Once most of the water is removed from a given part of the wood, then the temperature will naturally tend to increase. Between temperatures from around 100 °C up to around 250 °C volatile compounds contained within the wood are released. These compounds will burn off inefficiently, in a process that tends to result in undesirable emissions. Above around 250 °C the volatiles tend to burn away with reduced undesirable emissions occurring. Embodiments of the invention may attempt to increase, or maximize the burn rate of the fuel during the early stages, as described herein, to reduce the time during which the wood is below around 250 °C, to improve the efficiency of the burning process while also reducing emissions.

The second sensor input may be arranged to connect to at least one of: an oxygen (O2) sensor, a nitrogen oxide or dioxide (NOx) sensor, a carbon monoxide (CO) sensor, a sulphur (S) sensor and a particulate sensor. Other inputs may be received from non-combustion related sensors, such as a door-open sensor. The combustion chamber temperature sensor may be arranged, in some embodiments, to measure the temperature of the combustion chamber, and to provide a temperature reading to the regulator. The regulator may be arranged to control the flow of air to the heater based upon the temperature measured. The regulator may be arranged to shut down or reduce the supply of air to the heater if a combustion chamber temperature is measured that is above a predetermined limit. It may do this by ensuring the fan is switched off, and/or by closing the variable air valve.

Should the combustion chamber temperature sensor indicate to the controller that the temperature of the combustion chamber is below a predetermined threshold, then the controller may, in some embodiments, act to increase the flow of air to the heater, by at least one of switching on or increasing the fan speed, or opening the air valve. This should act to increase the rate of burning of any solid fuel present in the combustion chamber, and hence increase its temperature. Should the temperature sensor not detect that the temperature has increased within some given time limit, or has only increased by unexpectedly small amount, then this may be indicative of a lack of solid fuel present in the chamber, or of poor quality fuel. In such circumstances the controller may provide an alert that the heater is short of fuel. The alert may be made in any convenient form, e.g. by generating a sound, activating a light, or providing a signal to a remote control unit which may in turn generate a sound or activate a light, or provide an indication on a display etc.

Some embodiments of the invention may be arranged to accept an input from a flue mounted temperature sensor. Some heaters may have such a sensor to help determine whether the flue temperature is over some predetermined value. If such a state is detected, then this may be indicative of a flue or chimney fire, and an alert may be generated and the flow of air to the primary and/or secondary chamber closed.

Some embodiments of the invention may be arranged to accept an input from an oxygen (e.g. O2) sensor. Some heaters may have such a sensor, generally located at an upper portion of the combustion chamber, or in the flue, to help determine whether the heater is working in a reasonably efficient manner. Should an amount of oxygen be measured that is greater than expected, then this may be indicative of the level of combustion being too low, or an incomplete, or inefficient combustion. The controller may then be arranged to increase the flow of air to the combustion chamber.

For this, and for other sensors, the flow of air to the primary output may be increased by either opening further the air valve, or switching on or increasing the speed of the fan. Some embodiments may change the flow of air in a graduated manner, by increasing the flow of air to a degree proportionate to the sensor measurement obtained. Other embodiments may change the flow of air in a more binary fashion, by switching airflow to a maximum (or minimum, according to the particular sensor) value when the sensor indicates a change in airflow is required. Likewise, the flow of air may be reduced by slowing down or switching off the fan (if the fan is running), or by closing the air valve.

Some embodiments of the invention may be arranged to accept an input from a carbon monoxide (CO) sensor. Some heaters may have such a sensor, generally located at an upper portion of the combustion chamber, or in the flue, to help determine whether the heater is working in a reasonably efficient manner. Should an amount of CO be measured that is greater than expected, then this may be indicative of the level of combustion being too low. The controller may then be arranged to increase the flow of air to the primary air input of combustion chamber.

Some embodiments of the invention may be arranged to accept an input from a nitrogen oxide or nitrogen dioxide (collectively referred to herein as NOx) sensor. NOx tends to be produced if excess air is provided to a particularly hot burning

environment, due to the large naturally occurring concentration of nitrogen in the air. Some heaters may have such a sensor, generally located at an upper portion of the combustion chamber, or in the flue, to help determine whether the heater is working in a reasonably efficient manner. Should an amount of NOx be measured that is greater than expected, then this may be indicative of too much air being pushed into the combustion chamber. The controller may then be arranged to decrease the flow of air to the primary air input of combustion chamber.

Some embodiments of the invention may be arranged to accept an input from a particulate sensor. Some heaters may have such a sensor, generally located at an upper portion of the combustion chamber, or in the flue. Generally, an increase in the size of particulates from a combustion chamber is indicative of poor or incomplete combustion. Should the sensor detect the particulate size becoming larger than a threshold value, or the quantity of detected particles exceeds a predetermined threshold value, then the controller may be arranged to take appropriate action. This may involve increasing the degree of secondary air to be supplied to an upper part of the combustion chamber, or, if the temperature of the combustion chamber is low, increasing air to a primary (lower) part of the combustion chamber. If the combustion chamber temperature is already high, then it may be desired to increase the degree of secondary air without increasing the degree of primary air. Some embodiments may accomplish this by closing, partially or fully, the air valve, whilst switching on or increasing the speed of the fan. This will then push air from the fan through to the secondary air input of the heater without substantially affecting primary airflow.

Some embodiments, particularly those designed for connection to dual fuel (coal and wood) burners, or those designed to exclusively burn some form of coal (including anthracite etc.), may also be arranged to have an input from a sulphur dioxide sensor. Should the degree of sulphur dioxide be found to be above a threshold, then the controller may be arranged to increase the degree of air to a primary air input of the combustion chamber.

Some embodiments of the invention may have a door open/closed sensor. The status of the door (i.e. either open or closed) may be provided to a user. This acts as a safety check, against inadvertent door opening etc., and may also act to provide an indication to the controller that a refueling may be occurring. Should the controller detect that the door has been opened, then it may advantageously also be arranged to switch off the fan, if the fan is on that that point. This improves the safety and comfort of a user of the heater. The fan may be restored to its former state when the door is closed, subject to the status of the sensor readings taken.

The regulator may apportion a priority to the sensors connected thereto. The highest priority may be accorded to the combustion chamber temperature sensor, such that, if the combustion chamber temperature exceeds some predetermined limit, the regulator acts to shut down or reduce the supply of air to the heater as its prime objective. In this manner the regulator acts as a high limit stat. Priority may also be given to maintaining an approximate room temperature, by, for example, controlling airflow to increase or decrease a room temperature. This priority may be over that of regulation of emitted gases or particulates, although, once an approximate temperature has been reached priority may switch to maintaining a low level of emissions.

Some embodiments of the invention may be arranged to provide an alert if there is a conflict between sensors. For example, if the combustion chamber temperature is high, and one or more chemical sensors indicate that more airflow is required (which would tend to push the combustion chamber temperature up further), then an alert would be provided. The user can then choose whether to prioritise the temperature or the emissions targets.

Some embodiments may use one of a CO, NOx or O2 sensor for determining the efficiency of combustion taking place, as a good idea of such efficiency can be gleaned from a single second sensor. Other embodiments may use more than one second sensor, and the controller may be arranged to fuse the results from the multiple sensors in determining whether the degree of air being supplied to the heater needs to be changed.

The controller may employ a fuzzy logic approach to fusing inputs from multiple sensors, or may employ simple Boolean logic. For example, some embodiments may decide to change the degree of air being supplied to the heater if a majority of sensor inputs indicate that this would be beneficial. Other embodiments may accord a priority to different sensors, or may analyse received sensor readings accord a priority according to the levels of different gases or temperatures measured. A higher priority may be accorded to those sensors that are indicating higher readings, or readings indicative of combustion being more out of condition than indicated by other sensors.

The controller may be arranged to receive readings from the sensors at suitable intervals, such as every second, 2 seconds, 5 seconds or 10 seconds. The controller may be arranged to record a plurality of readings from some or all of the sensors and to average the readings over a period of time, such as 15 seconds, 30 seconds, 1 , 2, or 5 minutes, and to use the averaged figures in making its decisions or indications regarding the values of the sensors. This is to remove or reduce the effects of short term spikes in emissions that sometimes take place as wood burns. Bigger heaters, which take larger quantities of wood, may tend to use longer averaging times compared to smaller ones. These emissions can occur due to the non-homogeneity of natural logs, and the exposure of pockets of resin, sap, moisture etc. in logs, to intense heat as the logs burn down.

Some embodiments of the invention incorporate a remote control unit that is adapted to communicate with the controller. The remote control unit may have a means for measuring ambient temperature, e.g. the temperature of a room in which it sits. The remote control unit may have an input means for allowing a user to input a desired room temperature. The remote control unit may be arranged to communicate with the controller to activate increase airflow into the heater if the measured temperature is below the desired room temperature, or to reduce airflow if the measured temperature is above the desired room temperature. In this manner the remote control unit may act as a room thermostat.

The remote control unit may be arranged to send temperature information (e.g.

desired and actual room temperature) to the controller on the regulator, and allow the controller to then control the fan and air valve as appropriate to regulate the room temperature. Alternatively, the remote control unit may send commands to the regulator controller to directly control the airflow, according to whether the room temperature is above or below the desired temperature. Thus, an automatic mode of operation may be provided

The remote control unit may be arranged to have a manual control mode, allowing a user to control airflow to the heater directly. For example, it may have controls allowing the fan to be switched on or off, or allowing the air valve to be opened or closed.

The remote control unit may be arranged to receive information from the heater controller. For example, it may be arranged to receive information relating to one or more of: an estimated fuel level within the heater (such as a low fuel alert), the heater combustion chamber temperature, airflow settings such as fan operation and air valve position, or any other information stored within the controller. The remote control unit may have a display for displaying such information.

The remote control unit may communicate with the heater controller using any convenient means. Advantageously a wireless communication technology may be used, such as by radio frequency communication or infra-red communication. A WIFI, Zigbee, or Bluetooth protocol may be conveniently be used. Alternatively, a wired connection may be used.

In some embodiments a mobile "smartphone" or tablet may be used, and in such embodiments a computer program, or "app" may act to send signals to, and receive signals from the controller. The signals may travel via a router or similar networking device.

Some embodiments of the invention may incorporate a manifold, located in use between the fan and the heater, that has an input that receives air from the fan, and provides it to two or more of a plurality of outputs of the manifold. One or more of the outputs, or passageways connecting thereto, of the manifold may have an air valve means arranged to either allow air through to the respective output, or to substantially block or reduce the flow of air thereto. This allows the embodiments to provide air to different regions of the heater. A primary output of the manifold may be arranged to feed air to a lower part of the combustion chamber, wherein airflow is used to promote burning of the solid fuel. The housing may incorporate the manifold.

The one or more air valves within the manifold may be controlled by the controller on the regulator, and/or by the remote control unit.

A further, secondary output of the manifold may be arranged to feed air to an upper part of the combustion chamber, such as a secondary air input, to attempt to achieve a relatively complete combustion, and hence reduce unwanted emissions. A yet further, tertiary output of the manifold may be arranged to feed air into other parts of the combustion chamber, for example to promote a airwash effect to keep parts, such as any windows into the combustion chamber, clear of soot. Airflow to these further outputs may be controlled automatically by the controller, and by, in some

embodiments, a manual input demand. Some embodiments may provide air to the secondary and tertiary air inputs of a heater together.

Embodiments having a single valve may be arranged to supply air to the secondary output independently to that of the primary output. By having the secondary output not within the airflow of the valve, but within the airflow of the fan, the secondary air can be boosted using the fan, with the air to the primary output being separately controlled by the valve, e.g. to cut air to the primary output (by reducing flow through the air valve). This is desirable e.g. if an excess of unwanted emissions is occurring, whilst at the same time the room temperature is already above the desired threshold. This acts to reduce the unwanted emissions without increasing room temperature.

Some embodiments of the invention may incorporate an air valve that comprises first and second aperture plates mounted in close proximity to each other, wherein the first plate is arranged to be moveable between a first and at least a second position in relation to the second plate, and wherein apertures in respective plates are arranged to align to a degree according to the respective positions of the plates, allowing air to pass through said at least partially aligned portions.

A motor, solenoid, or other such actuation means may be used to move one of the first and second plates. The first plate may be rotatably attached to the second plate, and may have apertures, orifices or the like that, in the first position do not align with corresponding apertures in the second plate, and which, in the second position, largely correspond with the apertures in the second plate. Thus, with the plate in the second position, the correspondence of the apertures provides a route for air to pass through the valve, whilst largely blocking airflow when in the first position.

The moveable plate of the valve may be arranged to have a plurality of discrete positions, each providing a different degree of airflow therethrough, or it may be arranged to be continuously moveable from a first stop position (e.g. in which no, or very little air can flow through the valve), to a second stop position (which corresponds to a fully open position allowing maximum airflow therethrough). The valve may be arranged to have an air bleed-through that provides a predetermined minimum flow of air even when in a fully closed position.

An advantage with such an arrangement of plates to form the air valve is that it can be made to occupy a small space axially within a duct, and its spatial requirements do not vary as the valve opens and closes. This is in contrast to, say, a butterfly valve, which occupies a greater space axially within a duct as it opens.

However, the normally skilled person will understand that other valves will be suitable in some embodiments of the invention, including butterfly valves, iris valves etc.

Conveniently, the fan and air valve may be located in a pipe, trunk, duct, or similar tubular structure. Conveniently, the tubular structure may be arranged to be

connectable to trunking used to provide air to the associated heater. Conveniently, the tubular structure may be of a similar diameter to that of the trunking. Embodiments of the invention may be mounted directly within the heater itself, or proximate to the heater.

The controller may have means for checking the status of one or more of its sensors. This may comprise any suitable means, such as a continuity test, use of any built-in- test facility in the sensor, or checking readings from the sensor(s) to check that the results are within acceptable bounds. The controller may have means for checking the operation of the air valve. This may be done by cycling the air valve between the fully open and fully closed positions (or vice versa), and obtaining feedback to indicate the movement has taken place. Such feedback may be in the form of limit switches activated by the moveable plate, or current sensing from the drive means, or any other suitable form.

Upon a reset, or when initiated, the controller may report the results of its status check to the user. This may be by suitable indication on an associated display, such as a wired display, or via the remote controller.

Some embodiments of the invention comprise the regulator, with inputs allowing sensors to be connected thereto. Some embodiments of the invention comprise the regulator and one or more sensors. Some embodiments of the invention comprise the regulator and the remote control unit. Some embodiments of the invention comprise the regulator, one or more sensors, and the remote control unit. Some embodiments may also comprise a manifold unit having a plurality of air outputs. Some

embodiments may also comprise a heater along with the various elements described above.

It will be appreciated that a heater may be provided by a manufacturer with one or more sensors built in. It will also be appreciated that, in general, it will be possible to retrofit one or more sensors to a heater installation, should it not already have the sensor(s) present. An embodiment to be fitted to a given heater will therefore be chosen according to what sensors are desired within a particular installation, and which are already present.

According to a second aspect of the invention there is provided a method of controlling a domestic solid fuel burning heater using a regulator having a fan and at least one air valve to supply air to the heater, and an electronic controller, the method comprising the steps of i) measuring the temperature T _c associated with a combustion chamber of the heater, and if the T _c is below a cold threshold, activating the fan and opening the air valve to boost airflow to a lower part of the combustion chamber; ii) measuring levels of undesirable gas and/or particulates present at an upper part of the combustion chamber, and controlling the fan and/or an air valve to boost airflow to an upper part of the combustion chamber should the levels exceed a predetermined level to encourage burning at the upper part of the combustion chamber.

According to a third aspect of the invention there is provided a method of controlling a domestic solid fuel burning heater using a regulator having a fan and at least one air valve to supply air to the heater, and an electronic controller, the method comprising the steps of i) measuring the temperature T _c associated with a combustion chamber of the heater, and if the T _c is below a cold threshold, providing power to the fan and opening the air valve to supply air to the combustion chamber; ii) cutting power to the fan if T _c reaches a steady-burn lower threshold; iii) closing the air valve if T _c exceeds a steady-burn upper threshold; iv) opening the air valve if T _c drops below the steady-burn lower threshold.

The method may further comprise the step of measuring the time taken for T _c to rise from the cold threshold to a steady-burn threshold, and to provide an alert if this time is greater than a predetermined time. In this manner, the method may provide an indication to a user that there is an issue with the fuel being used. This may be that not enough fuel has been added, or that the fuel being used is of a relatively poor quality, e.g. is insufficiently seasoned, or has too high a moisture content, e.g. >20%.

The method may further comprise the step of monitoring an input from a sensor, wherein the sensor readings are indicative of an aspect of a condition of the burn inside the chamber, and increasing or otherwise controlling the flow of air to either or both of the primary and secondary heater air inputs if the input from the sensor is indicative of the burn being out of condition. The condition of the burn may be the combustion chamber temperature, the degree or amount of a particular sensed gas, or the size or quantity of particulates, as present in an upper part of the combustion chamber or flue.

The method may further comprise taking an input from a room temperature sensor, and increasing the flow of primary air to the combustion chamber if the room

temperature is below a predetermined threshold temperature. The threshold may conveniently be settable by a user. Likewise, the method may further comprise decreasing the flow of air to the combustion chamber if the room temperature is above a predetermined threshold temperature.

When Tc lies between the steady-burn lower and steady-burn upper temperatures, then the airflow may, in some embodiments be controlled primarily by the air valve, with the fan switched off. If the temperature drops below the steady-state lower temperature, then, in some embodiments, the fan may be activated.

Embodiments of the invention are further described hereinafter, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 diagrammatically illustrates an embodiment of the present invention attached to a stove type heater;

Figure 2 diagrammatically illustrates an embodiment of the present invention in further detail; Figures 3a-c diagrammatically illustrate three variants of an air valve as used in some embodiments of the invention; along with a partial view of a second with an alternative motor connection;

Figure 4 diagrammatically illustrates an embodiment incorporating a manifold with three air outputs to a heater; Figure 5 shows a block diagram of how an embodiment of the invention may use temperature inputs to control air supply to a heater;

Figure 6 shows a block diagram of how an embodiment of the invention may use sensor inputs to control air supply to a heater;

Figure 7 shows a block diagram of how an embodiment of the invention may use sensor inputs to control secondary air supply to a heater whilst also independently controlling primary air; and

Figure 8 shows a simplified graph of typical combustion chamber temperatures during start-up and steady state running conditions.

Detailed Description

Figure 1 shows a first embodiment of the invention installed on a stove type wood burner. A wood burner 1 comprises a body 2, a flue 3 a grate 4 and supporting legs 12. The body 2 has a primary air input aperture 5 below the grate 4 to which is attached a primary air output 102 of an air duct 6. The body 2 has a secondary air input aperture 100, that is connected to a secondary air output 101 of duct 6 The duct 6 has an air supply valve 7 positioned close to the primary air output 102, and a fan 8 arranged to supply air to both the primary and secondary air outputs. A controller unit 9 is attached to the duct and has control lines 10 and 1 1 that control the valve 7 and fan 8 respectively.

A combustion chamber 15 within the body 2 of the burner 1 comprise a volume in which fuel such as wood logs 16 may burn. A temperature gauge 17 is mounted to the body 2 and is arranged to measure the temperature of the of the combustion chamber. The temperature gauge is connected to the controller unit 9, allowing the controller to measure the temperature of the combustion chamber. The burner 1 has further sensors mounted on the body 2 which allow the sensing of other characteristics of the burner operation. These sensors comprise a NOx sensor 18, a CO sensor 19, a particulate sensor 20 and a flue temperature sensor 21 . It should be noted that these sensors are shown on this embodiment, but alternative embodiments may have a different number of these sensors present, chosen according to the particular requirements of the embodiment.

The temperature sensors comprise of thermistors, which change their electrical resistance according to temperature. Other embodiments may use other temperature sensors, such as thermocouples. The combustion chamber temperature sensor may be located within the combustion chamber, or may be located at a point proximate to the combustion chamber, but from which the temperature of the combustion chamber may be extrapolated or inferred.

The various sensors described herein are commonly available, and may be any suitable, bearing in mind temperature and sensitivity constraints, and the skilled person will realise that these factors must be borne in mind when choosing an appropriate sensor. Potential suppliers include NGK and Parallax Inc. but the normally skilled person will appreciate the suitability of sensors from other manufacturers.

Some embodiments may have a secondary air input that is supplied to the heater at a point towards the base of the combustion chamber, and may guide secondary air up through e.g. a passage within a sidewall of the heater before releasing the air in an upper part of the combustion chamber. This therefore provides means for heating the air prior to it entering the combustion chamber.

The sensors 17, 18, 19, 20 and 21 all provide their respective measurements to the controller 9.

The controller controls the air valve 7 and fan 8 according to the measurements provided by the sensors, as detailed herein. Figure 2 shows in more detail the valve 7 and fan 8 positioned within duct pipe 6, along with primary 102 and secondary 101 air outputs. The tube providing the secondary air output 101 connects to the duct 6 between the fan 8 and the valve 7, and so its airflow is not restricted by the valve, and thus bypasses the valve. The duct 6 has an internal diameter of approximately 4 inches, or 100mm. Other diameters may be used according to particular

requirements. For example, larger heaters may require a larger air supply and so a larger duct may be appropriate.

When connected to a heater, the primary output is arranged to supply air to the combustion chamber of the heater, to promote burning of the fuel therein. The secondary output is arranged to be connected to an upper part of the combustion chamber. The controller is able to supply air through the secondary output whilst limiting or cutting off the flow of air to the primary output. To do this, the controller closes the air valve, blocking air to the primary output, whilst activating the fan. Thus, air is then blown down through to the secondary output.

The controller is arranged to do this based upon measurements taken from its sensors. For example, if the particulate sensor detects a degree of particulates above a predetermined threshold, then it increases the flow of air through the secondary output by increasing the speed of the fan. If the combustion chamber is above a predetermined threshold temperature, then additional air is not needed through the primary output, and so the air valve closes to prevent air from the fan being blown into the chamber. The air from the fan is therefore guided to the secondary output, to encourage burning at the top of the combustion chamber and hence help to reduce particulates being emitted up through the flue.

The embodiment therefore allows a nuanced approach to be used to increase the burn efficiency of certain parts of the heater. For example, air can be forced into just an upper part of the combustion chamber to reduce non-combusted gas and burn off particulates, or into a lower part of the flue to increase the burn at this point and help to reduce particulates and other unwanted by-products. The fan 8 is electrically driven, with an integral motor 20 mounted in its hub. When activated by the controller, the fan acts to increase flow of air along the duct 6 to the secondary air output, and to the primary air output as permitted by valve 7. Note that when the fan is not activated, air may still be drawn along the duct by other means (such as the natural draw from the burner) if not blocked by the air valve. The fan blades do not impose a significant impediment to this flow of air when stationary.

Indeed, the fan will tend to free-run when power is cut to it and a draw of air is running through the blades of the fan.

The air valve 7 comprises of two metal plates. As more clearly shown in Figure 3a, which shows components of the valve in exploded form, a first plate 21 is attached to the inside of the duct in a fixed arrangement using mounting lugs 22. The plate 21 has central spindle 23 running axially therethrough, that is able to rotate in relation to the plate. A second plate 24 is attached to the spindle, thus allowing the second plate to rotate in relation to the first. The plates are mounted to be substantially flush against each other, although manufacturing tolerances mean that there may be a small separation. In either case, a small amount of air may be able to leak past the plates even in the closed position. The spindle has a pulley wheel 27 affixed thereto, which provides a convenient means for rotating the second plate. The pulley wheel is attached, via a belt 28, to a motor 29 mounted on the fixed plate.

The first plate 21 has an array of apertures 25 cut or otherwise formed into it in a spaced arrangement. The second plate 24 similarly has an array of apertures 26 formed therein. The apertures are arranged such that, in a first position of the second plate relative to the first the apertures do not overlap, whereas in a second position the apertures on each plate are coincident. Thus it will be appreciated that when the second plate is in its first position the plates act to substantially block the flow of air through the duct, whereas with the second plate in the second position air may flow freely through each of the apertures.

The motor is arranged, in this embodiment, to move the second plate between the first and the second positions to allow minimum and maximum airflows through the duct. It is also arranged to move the second plate to various intermediate positions, where the apertures only partially overlap, to provide further control of the airflow through the duct. The motor in this embodiment is a stepper motor, although other embodiments may use other forms of motor, or electromechanical control means such as a solenoid.

Other embodiments may use an alternative arrangement to move the air valve plate. An alternative embodiment has a motor with a spindle having a toothed gear that engages directly with toothed elements mounted on the movable plate 24. The motor is a stepper motor, controlled by the controller.

A further alternative is shown in exploded form in Figure 3b. This comprises of two plates, one fixed 21 and one moveable 24, as in the embodiment shown in Figure 3a. Note that like numerals refer to the same, or similar components. Again, plate 21 is fixed to a duct or similar housing. A stepper motor 38 is fixed to plate 21 , and has a drive shaft that goes through a central hole in the plate 21 and which is fixably attached to moveable plate 24. The stepper motor 24 is electrically connected to a drive output from a controller, as described in relation to Figure 1 . Thus, when given suitable drive signal from the controller, the stepper motor rotates its drive shaft, which rotates plate 24 in relation to plate 21 . The variable alignment of apertures 25 and 26 in respective fixed and moveable plates allows varying degrees of air to flow through the pair of plates. Of course, it will be appreciated that the plates 21 and 24 are mounted in close proximity to each other, and so when the apertures are not overlapping, only a bleed of air will pass through the valve.

A further alternative is shown in Figure 3c. This shows a view of part of a moveable plate 30, broadly similar to that described in relation to Figure 3a. It differs in having a slot 31 formed therein which engages with an angled arm 32 that is attached to a spindle 33 of a stepper motor 34. The stepper motor is attached to the inside of a duct (not shown) by attachment tabs 35. The arm 32 is free to move within slot 31 as the spindle 33 rotates. Thus, upon a suitable activation command from the controller, the stepper motor 34 will rotate its spindle 33 and hence also rotate the eccentric arm 32. This will push against the plate 30, and cause it to rotate about its mounting point 35 to the fixed plate. This rotation causes differing degrees of alignment of slots 36 in plate 30 with corresponding slots in the fixed plate (not shown) as in Figure 3a

The fan is located within the duct in close proximity to the air valve, so that they both occupy a relatively small space within the duct, and the axial space occupied does not change as the valve opens and closes. This gives added flexibility when planning an installation as it may be fitted in areas where space is limited.

The controller 9 (of Figure 1 ) comprises signal conditioning and processing means for processing the input signals, and for converting analogue inputs from the sensors (for those sensors that do not provide their readings in digital form) to digital signals. The controller further comprises a microcontroller adapted to process the signals from the sensors, to determine appropriate settings for the fan and the air valve. The controller has outputs that are fed, via suitable drive means that will be clear to a normally skilled person, to the motors of the fan and the air valve.

The controller is adapted to have an input from the air valve, that is indicative of the position of the second plate. This input is provided in this embodiment by a switch that is activated when the second plate is at an end stop, but any other convenient means may be used. For example, in other embodiments the controller may be arranged to monitor the current supplied to the motor, and to detect an increase as being indicative of the plate reaching an end stop position. The controller may be arranged

periodically, or upon a reset, to move the air valve between the fully closed and fully open position and to detect each of these states using a means such as described above, to check that the air valve is operational. An alert may be flagged to a user console if an error is detected.

The controller further comprises a transceiver that is adapted to communicate wirelessly to a remote control unit. When a controller reset condition occurs, which may, in this embodiment, be initiated on power-on and/or at the command of a user, the controller checks the status of each of the sensors. It further initiates a handshake with any detected remote controller units and checks its pairing status. If it has not been previously paired with any detected remote controller units then it will initiate a pairing process. Once this is done then it will not allow pairing with any other remote controller unit until previous pairings are removed. If a confirmed (i.e. currently paired) remote controller unit is detected, then the controller will take instruction and provide data to the remote controller unit.

The controller is arranged to send, to the remote control unit, information relating to the measurements recorded by one or more of the sensors. The controller periodically sends to the remote unit the temperature of the combustion chamber. The controller also sends to the remote control unit information derived from the sensor

measurements.

The remote control unit has a display and a data input pad. The display is arranged to display various pieces of information, such as that relating to information received from the controller, and ambient temperature within the room etc. It may display, as desired, the temperature in the combustion chamber. The remote unit is also adapted to send instructions to the controller to, as desired, increase or decrease the degree of airflow to the heater, e.g. to increase or decrease the room temperature. The remote unit also has an integral temperature sensor for measuring ambient room temperature. The remote unit, in combination with the controller, has a thermostat mode wherein it acts as a thermostat to help maintain a desired room temperature selectable on the remote controller. The remote unit also has a manual control allowing a user to directly control the airflow by increasing airflow (switching on the fan and/or opening up the air valve), or decreasing airflow (switching off the fan or closing the valve) to increase or decrease the burn rate of the fuel and hence temperature of the room.

The controller has a mode providing for an efficient burn of the fuel, that attempts to minimize the particulates emitted into the flue, and to minimize the amounts of CO emitted. When operating in this mode, the controller takes measurements from its particulate sensor and from its CO sensor. Should the particulate sensor indicate that an excess of particulates over a predetermined size are being emitted by the burn process, then the controller may activate one or both of the fan or the air valve to increase the quantity of air that is fed to the heater. Similarly, if the CO sensor indicates a degree of CO being emitted that is greater than a predetermined threshold, then the controller may activate the fan and/or the air valve to increase airflow.

The controller has a mode that attempts to run the heater in an efficient manner when the heater is first lit from cold. When operating in this mode, the controller measures the temperature of the combustion chamber and, if it is below a predetermined burn temperature (as it will be when first lit from cold), it will open the air valve up fully, and run the fan at maximum speed, to attempt to get the fuel burning more strongly, and so get the combustion chamber up to a working temperature where the fuel burns in a suitably efficient manner. Once this temperature is reached, then the fan and the air valve will be adjusted to reduce the air flow to the heater, dependent upon whether further instruction is provided to increase the room temperature, by, for example, the operation of the thermostat system described earlier. The regulator may also control the fan and air valve based upon the readings taken from other sensors, as described earlier.

As the wood burns, its chemical composition changes, and the wood turns to charcoal, and a charcoal burn phase is entered. When in this phase, the fuel burns very efficiently, with little smoke, CO O2 or particulates being given off. This state is detectable by the controller based upon the temperature of the combustion chamber and measurements from the sensors such as the CO, O2 and particulate sensors. Once in this state, the controller may, dependent upon requirements of room

temperature as before, reduce the primary airflow.

As the charcoal is consumed by the burn process, then the temperature of the combustion chamber will start to decrease. This is detectable by the controller as an indication that the fuel supply in the combustion chamber is running low. This is detected by a drop in the combustion chamber temperature, and/or an increase in O2 levels, particularly if the drop still continues despite an increase in airflow being provided. On such a detection, the controller sends a signal to the remote control unit to provide an indication to a user that fuel levels may be low.

If a new log is added to an already warm combustion chamber, this will cool the chamber down. This will be detected by the combustion chamber temperature sensor, which will then act to increase the airflow as described above, to get the log into a state where it burns more efficiently. When a new log is added, and when the heater is started from cold with new wood, it is known that emissions of undesirable burning by-products tends to be at a high level, as previously described. Thus at this stage, forced air from the fan helps to push the wood past this initial burning stage and onto the more efficient burning stage, as detailed above.

Figure 4 shows another embodiment 50 of a multiple output regulator. As before, a fan 41 is positioned at an input end 42 of a short piece of duct. An output region 43 of the duct has a primary air output 45. Controlling egress of air through the primary output 45 is a valve 44. A secondary output pipe 46 is arranged to take air from between the fan and the primary air valve 44, and to provide air through its output 47. A tertiary output pipe 48 is similarly arranged to take air from the duct between the fan 41 and the primary air valve 44, and to supply air out through end 49. Secondary output 46 has, located towards an output end thereof, an electrically operated air valve 51 which is under the control of the controller (not shown).

Note that the embodiments are shown in a manner that indicates their functionality, and in practice the design may differ in appearance, to take into account airflow or thermal considerations, which would be clear to a normally skilled person.

This embodiment provides additional versatility in being able to supply air to primary, secondary, and tertiary outputs. In use, the primary and secondary air may be controlled with similar effect to that as described in relation to Figure 2, but with the additional ability to shut air to the secondary output. This is useful if the controller wishes to prevent air going to the secondary input of the heater (for example if the combustion chamber is too hot and there is a risk of a flue fire), while maintaining tertiary air that may be use, for example, as an airwash to help prevent a front glass door from becoming sooted

Figure 5 shows a block diagram of the basic operation of an embodiment of the type shown in Figure 2, of the regulator when a fire is first lit in a heater. It is assumed that the regulator is switched on, and is reset when the fire is lit (step 60), and the regulator is in communication with a remote controller unit. The regulator measures

temperature Tc (step 61 ) of the combustion chamber, and finds it (step 62) to be below a steady burn lower temperature threshold, which in this embodiment is set to 250 °C. It therefore switches the boost fan on, and opens the air valve fully (step 63).

It continues to monitor the combustion chamber temperature (step 64). When it reaches 250 °C, the boost fan is switched off (step 65) but the air valve remains open. As the temperature increases further due to progress of the burning of the fuel, the motor on the air valve is activated (step 66) to reduce the permitted airflow through to the primary air output. This is done according to a mode of operation selected for the regulator.

In a first, automatic mode, the regulator is in communication with a room temperature sensor located in a remote controller unit, and the valve is opened if the room temperature is below a threshold temperature, and is closed if the room temperature is above the predetermined temperature. The degree of opening and closing of the air valve is dependent upon the temperature difference between the room temperature, and the threshold temperature.

In a second, manual mode, the airflow is preset according to a demand from the remote controller unit.

In each mode, the temperature Tc is monitored. If it drops below 250 °C (step 67) the air valve is fully opened (step 68). If, after a short time 69 (set to 2 minutes in this embodiment) the temperature has not risen (measured at 70) then the fan is activated (step 71 ) to boost the airflow. The temperature is again measured (step 72) after a minute delay. If it is still falling then a low fuel alert is provided (step 73) to a user via the remote controller unit.

Note that the fan may be used, particularly in step 66, to boost air should the sensors indicate that the degree of pollutants or particulates indicate that increase airflow is desired, and the air valve is already fully open.

Some embodiments may adapt steps 63 and 64 to provide an alert if the temperature remains below 250 °C for too great a period, such as for greater than 5 minutes. Such a state is generally indicative of an insufficient quantity of fuel, or a low low quality fuel, such as badly seasoned timber.

Figure 6 shows a block diagram of the operation of the regulator of an embodiment of the invention in response to inputs from gas and particulate sensors. It is assumed that the heater to which the regulator is attached is up to its steady burn temperature, i.e. is operating within step 66 of Figure 5. It's further assumed that the heater has at least one of a CO, an O2, a NOx, an SU, or a particulate sensor arranged to measure the gas(es) and/or particulates at the base of the flue or upper part of the combustion chamber. At step 75 a measurement is taken from one or more sensors attached to the regulator. The sensor readings are averaged in a sliding 30 second window as described herein to remove effects of sudden temporary anomalies in the readings, and compared to predetermined limits (step 76). If the measurements are in condition, meaning that the gases are within predetermined limits and/or the particulates are within acceptable limits (according to the particular sensors present) then the air valve is moderated (step 77) according to the room temperature demands described in relation to Figure 5. If the sensor(s) indicate gases or particulates at unacceptable levels, then the air valve is opened (for CO or O2 sensors) (step 78) to increase the flow of primary air to the combustion chamber or closed (for an out-of-condition reading from a NOx sensor). The measurement cycle is iterated and the valve held open (or closed for NOx sensors) until the sensor measurements are once more in condition. If, after a predetermined time period (2 minutes in this embodiment) (step 79) the sensors indicate that combustion is still out of condition, and that more air may be beneficial, then the fan is activated. An alert may be provided if this condition remains for longer than a predetermined time period. The process of monitoring the sensors may be overridden by demand from a user, e.g. because room temperature is unacceptably hot, or if the temperature of the

combustion chamber gets unacceptably hot. It may also be overridden should the combustion temperature start to fall, i.e. as it enters step 68 of Figure 5.

Figure 7 shows a block diagram of a decision making process that may occur in an embodiment of the invention, for example within step 66 of Figure 5, when a sensor, such as a particulate sensor, indicates that secondary air is required. It assumes that the embodiment has a fan and a single valve controlling a primary air output, and that a secondary air output of the embodiment is not controlled by a valve and is arranged take air from the fan. Firstly, a sensor, such as a particulate sensor provides an input to the controller that secondary air is required (step 80). The fan will be switched on to provide air through to the secondary output of the regulator, and consequently into a secondary air input of the heater, (step 81 ). The controller continues to examine the status of other sensors (step 82) associated mainly with primary air, namely

combustion chamber temperature, O2, CO, NOx and/or S sensors. Should those indicate that no further primary air is required, then the air valve is at least partially closed to a level to regulate primary air to the heater (step 83) (i.e. air to the lower part of the combustion chamber) to offset the increased air flow from the fan. The air valve can continue to be adjusted to allow differing amounts of air to the primary input based upon the demands of these sensors, whilst the fan continues to provide air to the secondary input of the heater.

Note that the processes described in relation to the above Figures are not limiting, and many modifications and variations on these processes are possible. For example, the fan may be set to give a boost of air for a predetermined time, such as 2, 5 or 10 minutes to give increased heat output, or other manual commands may be used to override the various sensor inputs. Likewise, the fan may be programmed to switch on if a closure of a door of the heater is detected, and a temperature drop in the combustion chamber occurs. This may happen, for example, if the heater is refueled with a cold log.

Figure 8 shows a simplified temperature profile of a combustion chamber from when a heater is first lit. It assumes the chamber has kindling or similar initiating fuel, along with one or more larger wooden logs as a main fuel supply. At a start time of 0, the temperature of the chamber is at 20 °C. This rises steadily as kindling within the chamber burns and heats up the logs. As stated earlier, the heat from the kindling initially goes mainly into boiling off the moisture within the log, As exterior regions of the log rise above 100°C, the moisture will be removed, and volatile compounds will be heated, and emitted from the log. The combustion temperature is not sufficient at this point to fully burn them off, and so they will pass up the flue as undesirable emissions. When the temperature reaches around 250 °C, it is hot enough to destroy these compounds, and so the level of harmful emissions substantially reduces. This

"startup" time period is denoted as t _s . Following this, the regulation using the air valve (and, when required, the fan) is used to maintain the temperature between the upper and lower steady-state burn temperatures, here denoted as 350 °C and 250 °C respectively. Embodiments of the invention attempt to reduce the startup time t _s using the means and processes described herein. Should the combustion chamber temperature sensor show that time t _s is greater than some predetermined period, this may be indicative of a problem, such as a poor quality fuel. For example, badly seasoned logs may take too long to heat up, leading to a greater level of unwanted emissions occurring. Embodiments of the invention may therefore be adapted to measure t _s and provide an alert if it exceeds the predetermined time period, as stated above in relation to steps 63 and 64 in Figure 5.

The invention has utility in various types of solid fuel burner, and is particularly suited to domestic heaters such as log burners. The invention also has particular utility when used with catalytic wood burners, as it promotes a reduction of particulates.

Particulates produced by the burning of solid fuel such as logs can block the fine honeycomb structure used in catalytic burners. Embodiments of the invention therefore may provide reduced particulate production, leading to fewer instances of catalytic converter blocking.

The invention also has utility with non-catalytic wood burners, as various embodiments thereof are able to provide improved efficiency of burn, and so provide a reduced level of harmful emissions.

The invention also has utility with solid fuel burners designed for mixed solid fuels, or for single solid fuels including, but not limited to, coal, coke, anthracite and charcoal.

The functions described herein as provided by individual components could, where appropriate, be provided by a combination of components instead. Similarly, functions described as provided by a combination of components could, where appropriate, be provided by a single component.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.