EP2500650B1 - Method for regulating a heating device - Google Patents

Description

The invention relates to a method for controlling a heating device with a combustion chamber, as indicated in claim 1.

Simple, rigid control concepts are known from the prior art, which assume after each opening and closing of the combustion chamber door of a heater that new fuel has been introduced into the combustion chamber. However, if this has not been the case, for example because a user of the heater has only briefly looked around without introducing new fuel into the combustion chamber, the control assumes a wrong situation in the combustion chamber and the combustion is deficient.

DE 10 2009 005178 A1 discloses an apparatus for burning solid fuels, comprising a combustion chamber connected to a combustion air connection and a combustion chamber, a control module and a motor-operated adjustment device which is connected to the control module for changing the combustion air supply. Furthermore, in DE 10 2009 005178 A1 discloses that the combustion air supply in each case depending on the detected operating parameters of the combustion process via the control module of the adjusting device is controllable.

DE 10 2009 019118 A1 discloses a domestic combustion plant for continuous combustion of solid, shredded or pelletized fuels with a multi-phase operation with an ignition phase and a start phase arranged between ignition phase and stationary phase of operation. DE 10 2009 019118 A1 indicates to keep the primary air flow in the ignition phase constant and to regulate depending on the fuel flow during the start-up phase, and to regulate the secondary air flow during ignition and starting phase for various functions.

AT 506615 A1 discloses a device for burning biomass with a connectable to the primary air supply movable grate of movable grate elements, a feedable via a conveyor combustion chamber with a heat exchanger, a Ashtray and a control device, wherein the movable grate elements are pivotable from a use position in a cleaning position.

DE 10 2009 041 408 A1 discloses a device and a method for controlling the supply and / or exhaust air in or from a combustion chamber of a heater, which consists of at least two heaters of different types and wherein a heater in a vacuum combustion is provided in the combustion chamber

EP 1347241 A1 discloses a heater for burning off at least two dissimilar fuels with a regulator for regulating a flow of oxidizing air to selectively supply an adjustable amount of air to the first or the second fuel.

US 7870854 B2 discloses a heating device comprising a combustion chamber and a control system, where the control system uses a fuel key in which the parameter sets for the combustion of a first fuel and second fuel are stored.

Furthermore, for example, from the EP 0 985 883 A2 Heating devices are known which are suitable for at least two types of fuels and wherein a first type of fuel via the combustion chamber door and a second type of fuel can be automatically introduced via a feed device into the combustion chamber of the heater.

The present invention has for its object to provide a method for controlling a heater with a combustion chamber, which increases the efficiency of the combustion process, especially in the introduction of new fuel into the combustion chamber and thereby causes the least possible additional effort and / or an additional, practical Benefit to the operator of the heater offers.

This object of the invention is achieved by a method according to claim 1.

According to the invention, the control of the heating device during the operating phase with a first sensor continuously opens and closes the combustion chamber door of the heating device supervised. This continuous monitoring of the combustion chamber door is possible in a simple and reliable manner, in particular with a mechanical-electrical sensor, such a sensor having a long service life. By the detection of the opening and closing operations of the combustion chamber door, the control of the heating device can already severely limit the possible times at which new fuel, in particular firewood, has been introduced into the combustion chamber via the combustion chamber door to be opened as required. It is essential that it is determined after closing the combustion chamber door with at least one other sensor, if really new fuel was introduced into the combustion chamber. The assumption that new fuel is introduced into the combustion chamber each time the combustion chamber door is opened and closed is not always correct. Thus, assuming that new fuel is always present in the combustion chamber after opening and closing the combustion chamber door, and if the control settings of the heater are adjusted or changed, then in those cases where no new fuel is actually entering the combustion chamber was introduced, the control of the heater set incorrectly and there is a lack of combustion. If, however, it is determined with the at least one further sensor whether new fuel has been introduced into the combustion chamber, the control setting of the heating device can be reliably and correctly adapted to the respectively prevailing situation. In particular, the control of the heater can be set differently, depending on whether a new fuel has been introduced into the combustion chamber or not. This results in a more optimal combustion process in the different situations resulting in a higher energy yield and heat yield at the same amount of fuel and on the other hand a lower pollutant or ash development is achieved during the firing process.

The procedure according to the invention thus makes it possible in a simple way to optimize or adapt the combustion process in a heating device, in particular only in the phases in which really new fuel is introduced into the combustion chamber and thus the combustion conditions in the combustion chamber are changed. Of advantage here are the measures according to claim 2, since in particular by an at least short-term increase in the air supply into the combustion chamber of the combustion process is accelerated when new fuel was introduced into the combustion chamber. By increasing the air supply, the firing or ignition process is optimized for the newly introduced fuel and it is ensured at the same time that in this ignition process the lowest possible Amount of additional exhaust gases and soot particles is formed. In addition to a reduction in the environmental impact of the operation of the heater is thereby also about a sooting of the combustion chamber, any existing, closed with glass sight opening and / or the flue gas guide means inferred. If the combustion chamber door of the heating device is indeed opened and closed but no new fuel is introduced into the combustion chamber, this is detected by the at least one further sensor and the control settings relating to the air supply into the combustion chamber are kept essentially the same. This prevents, for example, that accelerated burning of the fuel already present in the combustion chamber is triggered by the increased air supply, whereby the burning time of the fuel would be relatively greatly reduced, the heating device would be relatively highly heated and the combustion process would not proceed optimally.

Of particular advantage are the measures according to claim 3, since the use of a temperature sensor is a very simple and cost-effective way to determine a successful introduction of new fuel into the combustion chamber. Such introduction of new fuel into the combustion chamber can be determined by means of a temperature sensor in particular by the fact that after closing the combustion chamber door, the temperature rises in the combustion chamber. The basically maintenance-free temperature sensor, which can also be based on many different, long-matured operating principles, also offers additional, practical benefits for the operation of the heater. For example, the temperature data of the sensor can also be used simultaneously for the exact determination of the actual heating power of the heating device. Likewise, these temperature data can be used as an input parameter for a control to optimize the combustion process, such as to optimize the air supply into the combustion chamber.

The measures according to claim 4 are also advantageous, since a carbon monoxide sensor (CO sensor) quickly and reliably provides information as to whether new fuel has been introduced into the combustion chamber or not. This can be determined in particular due to the fact that after the introduction of new fuel into the combustion chamber and after closing the combustion chamber door, the CO content in the combustion chamber increases at least in the short term, since a partially incomplete combustion occurs when igniting the newly added fuel. Based on the ideal CO content in the combustion Flue gases, which is in optimal and stable combustion conditions in about 30 ppm, so increases the CO content in the flue gas after the successful introduction of new fuel in the combustion chamber, which is detected by the CO sensor. In addition, the use of a CO sensor for the operator of the heater provides an additional, practical benefit, since the reliability of the heater can be improved in a simple and reliable manner. In particular, with the CO sensor, the CO content in the flue gas can be monitored continuously and, when a certain limit value is exceeded, countermeasures can be taken to avert risks to the health and life of the user of the heating device. In addition, the measured value for the CO content in the flue gas can also be used as input parameter for a control for optimizing the combustion conditions in the heating device, whereby a very high degree of optimization of the combustion process can be achieved.

Particularly advantageous is an embodiment according to claim 5, since thereby the efficiency of the combustion process is increased in heaters in which at least a first fuel via a need to open the combustion chamber door into the combustion chamber of the heater can be introduced and at least one further fuel with an automatic feeding means in the Combustion chamber is introduced. In particular, by the measures described, the efficiency of a heating device can be increased, in which wood pellets are used as the first fuel that can be supplied through the combustion chamber door and, as a further, automatically supplied fuel. On the one hand, it is ensured that in pellet operation, in which new pellets are automatically introduced as required and caused by the control of the heating means by means of the supply means in the combustion chamber, the control of the heater changes in the firewood operation when introducing firewood through the combustion chamber door in the combustion chamber , the automatic supply of wood pellets in the combustion chamber ends at the latest after the successful firing of newly introduced firewood and adjusts the control settings, so that the ignition or subsequently the burning of the newly introduced firewood runs under optimal conditions. This increases the efficiency of the combustion process in the heater. Furthermore, such an increase in efficiency in log operation of the heating device is achieved, since it is determined by the at least one further sensor in a reliable manner, whether actually new firewood is introduced into the combustion chamber and thus remain in the log operation and the control setting of the heater to ensure optimum ignition process of the newly added firewood are adjusted, whether the control setting of the heater are kept substantially the same because no new firewood was introduced into the combustion chamber or changed from firewood operation in the pellet plant is after the heating power of the heater has fallen below a certain value, in particular specified by the user.

The regulation of the heating device can therefore reliably and simply monitor any fuel supply into the combustion chamber. This includes not only the automatic supply of the additional fuel via the supply means, which is indeed caused by the regulation of the heater itself, but also the introduction of a first fuel in the combustion chamber, as this is determined with the at least one other sensor. Thus, the combustion conditions in the combustion chamber of the control of the heater can be optimally adapted to the prevailing situation, depending on whether a new first fuel was introduced into the combustion chamber or not.

Another advantage is the measures according to claim 6, since this ensures that no disturbing logs or ash residues remain in the pellet burner and could hinder the ignition or burning of wood pellets in pellet operation, which would affect the efficiency of the combustion process in pellet operation.

In the measures according to claim 7 is advantageous that when changing from firewood operation in the pellet operation of the tipping is only dumped when a large part of the possibly still present in the combustion chamber firewood is burned and thus no fuel is wasted.

In the measures according to claim 8 is advantageous that on the one hand an efficient commissioning of the heater is ensured in pellet operation and the operator of the heater is also offered a high level of comfort, and on the other in the following on the start phase of the heater operating phase efficient combustion process is ensured, as is changed reliably depending on the actual addition of firewood between pellet operation and firewood operation.

Finally, the measures according to claim 9 are advantageous since this ensures efficient combustion both during firing or ignition and during the burning off of the respectively introduced fuel and the control settings really only be changed when actually new fuel was introduced into the combustion chamber of the heater.

For a better understanding of the invention, this will be explained in more detail with reference to the following figures.

Fig. 1

eine Schrägansicht einer Heizeinrichtung mit einem Brennraum;

Fig. 2

eine Schnittdarstellung der in Fig.1 gezeigten Heizeinrichtung;

Fig. 3

ein Zustandsdiagramm zur Visualisierung des Verfahrens zur Regelung der Heizeinrichtung nach Fig. 1.

In each case, in a highly simplified, schematic representation:

Fig. 1

an oblique view of a heater with a combustion chamber;

Fig. 2

a sectional view of in Fig.1 shown heater;

Fig. 3

a state diagram for visualization of the method for controlling the heater according to Fig. 1 ,

By way of introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numerals or the same component names, wherein the disclosures contained in the entire description can be mutatis mutandis to the same parts with the same reference numerals or component names. Also, the location information chosen in the description, such as top, bottom, side, etc. related to the immediately described and illustrated figure and these position information in a change in position mutatis mutandis to transfer to the new location.

All statements on ranges of values in the description of the present invention should be understood to include any and all sub-ranges thereof, e.g. the indication 1 to 10 should be understood to include all sub-ranges, starting from the lower limit 1 and the upper limit 10, i. all subregions begin with a lower limit of 1 or greater and end at an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1 or 5.5 to 10.

In Fig. 1 is an exemplary embodiment of a heating device 1, which can be regulated according to the inventive method exemplified. The housing the heater 1 is not fully shown for reasons of clarity.

According to the illustrated embodiment, the heating device 1 comprises a bottom element 2 on which a furnace element 3 is mounted, so that the heating device 1 has a high stability. The furnace element 3 comprises a combustion space 4 open to the front, wherein the forwardly directed opening of the combustion chamber 4 is closed with a combustion chamber door 5 which can be opened as required. In particular, the combustion chamber door 5 can be provided with a glass pane 6, which releases the view into the combustion chamber 4 when the combustion chamber door 5 is closed, and enables improved space heating due to thermal radiation. About the combustion chamber door 5, a new, in its dimensions relatively large first fuel, in particular firewood, are introduced into the combustion chamber 4 of the heater 1. It is explicitly pointed out at this point that "new fuel always means the fuel newly introduced into the combustion chamber 4." Each opening and closing of the combustion chamber door 5 is registered by means of a first sensor 7 and reported to the control of the heating device 1. The first sensor 7 is designed in the present case as a mechanical-electrical limit switch, which is triggered by the lower portion 8 of the combustion chamber door 5.

The introduced via the combustion chamber door 5 into the combustion chamber 4 logs is deposited on the grate support 9 and burned there. The grate support 9 forms the largest part of the lower end of the combustion chamber 4. As best in the sectional view of the heater 1 in Fig. 2 can be seen, a pellet burner 10 is formed in the central region of the grate support 9, which extends in its depth extent starting from the grate support 9 down. The tipping grate 11 is provided on the one hand with small openings 12, so that the ashes obtained during combustion can continuously fall from the combustion chamber 4 into an ash tray arranged thereunder. In order to remove the ash tray from the furnace element 3 for emptying, the combustion chamber door 5 is provided with a lower portion 8, through which the ash tray after opening the combustion chamber door 5 is accessible. Furthermore, the tipping grate 11 is rotatably mounted via a shaft 13, so that ash and other materials located in the pellet burner trough 10 can be tipped over a signal of the control of the heater 1 in the ash tray.

In order to be able to automatically introduce a further fuel, which is relatively small in terms of its dimensions, into the combustion chamber 4 of the heating device 1, the heating device 1 is equipped with a supply means 14. The supply means 14 has, in particular, a screw conveyor 15 and a funnel 16, which are designed to convey wood pellets into the pellet burner 10 of the combustion chamber 4. The supply and the ignition of the wood pellets in the pellet burner 10 are controlled by the control of the heater 1. The wood pellets are stored in a reservoir, not shown, preferably formed above the hopper 16.

In order to set the optimal combustion conditions, the heater 1 is equipped with a continuously variable ventilation device 17. The regulation of the heating device 1 sets via the ventilation device 17 according to the situation in the combustion chamber 4 and according to user specifications, the air supply into the combustion chamber 4 and in particular in the pellet burner 10 a. Preferably, the ventilation device 17 allows a supply of primary air and secondary air into the combustion chamber 4. The primary air flows in particular from below into the pellet burner 10 and is preferably used in the ignition and burning of wood pellets and igniting logs. The secondary air flows downwards, in particular from above, on the inside of the combustion chamber door 5, thereby keeping the inside of a glass pane 6 which may be present free of soot deposits and the like. The secondary air is preferably used when firing logs.

The resulting during combustion in the combustion chamber 4 flue gas is passed through an opening 18 in the upper region of the combustion chamber 4 in flue gas guide means 19 and further discharged, for example, in the fireplace of a house. The discharge of the flue gas is supported in the embodiment shown by means of a suction device 20, so that the flue gas guide means 19 can extend, for example, in the entire back region 21 of the furnace element 3.

Since the described heating device 1 is usually used as a freestanding stove for heating a room via air convection or heat radiation, the furnace element 3 is equipped on its outside with heat exchanger elements 22, 23, whereby the efficiency of the heater 1 is increased.

According to the exemplary visualization of the inventive method for controlling the heating device 1, which in Fig. 3 is shown, the heater 1 is automatically taken by the scheme in a start phase 24 by the ignition of wood pellets in the pellet burner 10 in operation. This provides increased comfort for a user of the heater 1 and after successful completion of the starting phase 24, that is, after the wood pellets have been ignited in the pellet burner 10, the control of the heater 1 changes to an operating phase, in which after addition of firewood between pellet operation 25th and log operation 27 is changed. In an alternative process sequence, not shown, the user of the heating device 1 can already decide at startup whether the heating device 1 is put into operation automatically and exclusively by the ignition of wood pellets or with the help of the user by the ignition of firewood. In the latter case, however, it is also expedient to support the ignition of the billets by introducing at least a small amount of wood pellets into the pellet burner 10.

After the successful completion of the start phase 24 and the change to the normal operating phase of the heater 1 pellets 25 is transported in the pellet operation 25 of the control of the heater 1 by means of the feed 14 wood pellets in the pellet burner 10 and burned. In accordance with the control settings and the user's specifications, the control of the heating device 1 controls the supply of wood pellets and air by means of the ventilation device 17 into the combustion chamber 4 in particular so that a certain room temperature is reached or maintained. If the heater is stopped by the user, no more wood pellets are fed into the combustion chamber 4 and after the burning of the wood pellets still in the combustion chamber 4, the heater 1 is taken out of service.

Will now be in pellet mode from the first sensor 7 - see Fig. 1 - an opening and subsequent closing of the combustion chamber door 5, in particular also immediately after the conclusion of the start phase 24, detected, the measured values of the at least one further sensor 26 are evaluated. The further sensor 26 is in Fig. 2 shown and may be designed in particular as a temperature sensor or a CO sensor. Expediently, the further sensor 26 is located in the middle or upper region of the combustion chamber 4, in particular on or in the rear wall of the furnace element 3. However, an embodiment is also conceivable in which the further sensor 26 is located in the flue gas guiding means 19. An advantage would be that the further sensor 26 would not be under the direct action of fire and would thus be exposed to less stress or less wear. If now the regulation of the heating device 1 via the further sensor 26 determines that no new firewood has been introduced into the combustion chamber 4 after closing the combustion chamber door 5, then the control settings of the heating device 1 are kept essentially the same. This relates in particular to the air supply into the combustion chamber 4 via the ventilation device 17, which air supply is not significantly changed in this case. A temperature sensor detects an opening and closing of the combustion chamber door 5 without introduction of firewood characterized in that after closing the combustion chamber door 5, the temperature does not rise higher than it was before opening the combustion chamber door 5. With a CO sensor, this circumstance can be determined by the fact that, after closing the combustion chamber door 5, the CO content in the combustion chamber 4 returns to the value which prevailed in the combustion chamber 4 before opening the combustion chamber door 5.

If the other case 26 then detects the other case, namely that logs have been introduced into the combustion chamber 4, then the regulation of the heating device 1 changes into the log operation 27. The introduction of firewood over the combustion chamber door 5 into the combustion chamber 4 can be effected by the control depending on the embodiment of the other sensor 26 are detected in different ways. In a temperature sensor, the finding is based on the effect that after the introduction of firewood and after the closing of the combustion chamber door 5, the temperature rises in particular above the value that prevailed before the opening of the combustion chamber door 5 in the combustion chamber 4. In the case of a CO sensor, the detection takes place on the basis of the process that, after the introduction of firewood and after the closing of the combustion chamber door 5, the CO content increases, at least in the short term, above the value which prevailed before opening the combustion chamber door 5 in the combustion chamber.

After the change from pellet operation 25 in the firewood operation 27, the automatic pellet feed is stopped via the supply means 14 in the pellet burner 10 of the combustion chamber 4 at the latest after the successful ignition of newly introduced firewood, as long as the heater 1 reaches the particular desired by the user heating power. Furthermore, immediately after the change of the operating mode, the air supply in the Increase combustion chamber 4 via the ventilation device 17 to allow an optimal and quick ignition of the newly introduced firewood.

It is particularly useful if, after the introduction of logs from the pellet plant 25 in the log operation 27 is changed and still pellets are fed into the combustion chamber 4 for a short time to allow rapid and comprehensive firing of the newly added firewood. This is particularly necessary if the new firewood has not been optimally placed in the combustion chamber 4, so that the fire from the pellet burner 10 is difficult to spread to the new firewood. This is particularly the case when the new log has not been positioned directly over the opening in the grate pad 9, which opening leads into the underlying pellet burner 10. After the newly introduced billet has been fully ignited and when sufficient logs have been introduced into the combustion chamber 4 to achieve the user desired heating line, the automatic supply of pellets into the pellet burner 10 in log mode 27 is completely set.

According to a particularly advantageous embodiment, it is also determined in logwood operation 27 by means of the at least one further sensor 26 when opening and closing the combustion chamber door 5, whether new firewood has been introduced into the combustion chamber 4 or not. If it is determined that new billets have been introduced into the combustion chamber 4, then it is expedient to adapt at least the supply of air into the combustion chamber 4 such that a reliable and rapid ignition of the newly introduced billet is made possible. It is also expedient, if necessary, to supply a small amount of pellets into the pellet burner trough 10 in order to accelerate or optimize the firing process of the newly introduced firewood.

If it is determined in log operation 27 after opening and closing of the combustion chamber door 5 that no new firewood has been introduced into the combustion chamber 4, then the control settings of the heating device 1 and in particular the settings relating to the air supply into the combustion chamber 4 are substantially retained. Is now at least a majority of the introduced into the combustion chamber 4 firewood burned in log firing 27 or the heating power of the heater 1 has fallen below a certain, in particular predetermined by the user heating and no new firewood was introduced so wechseit the control of the heater 1 from the log operation 27 back into the pellet operation 25 and wood pellets are automatically introduced with the supply means 14 in the pellet burner 10 and burned. According to an alternative, not shown embodiment of the control method can also be specified by the user that after the switch from firewood operation 27 back into the pellet 25 no automatic supply of wood pellets is performed more, but the heater is taken out of service or stopped.

According to a particularly advantageous embodiment, the pellet burner 10 is equipped with a tipping grate 11, which is tilted when switching from the firewood operation 27 back into the pellet operation 25 so that disturbing logs or ash residues are removed from the pellet burner 10 before new wood pellets from the automatic feeding means 14th be introduced into the pellet burner 10. Preferably, the tilting of the Kipprosts 11 of the pellet 10 is only when falling below a temperature threshold and / or falling below a certain CO content in the combustion chamber 4 is performed when switching from logwood operation 27 in the pellet 25 to complete burning of the existing in the pellet burner 10 fuel materials to ensure. The determination of the Abkippzeitpunktes takes place in particular via the measured values of the at least one further sensor 26, which is preferably designed as a temperature sensor or a CO sensor. According to a particularly useful, not shown embodiment, several such sensors 26 are integrated in the heater 1, so that about the introduction of firewood into the combustion chamber 4, the current heating power of the heater 1 and / or the Abkippzeitpunkt the Kipprostes 11 can be determined more accurately ,

For the sake of order, it should finally be pointed out that, for a better understanding of the structure of the heating device, these or their components have been shown partly unevenly and / or enlarged and / or reduced in size.

The task underlying the independent inventive solutions can be taken from the description. <B> Reference Numbers </ b> 1 heater 16 funnel 2 floor element 17 aeration device 3 oven element 18 opening 4 combustion chamber 19 Flue gas guiding means 5 Combustion chamber door 20 suction 6 pane 21 back 7 first sensor 22 Heat exchanger element 8th lower section 23 Heat exchanger element 9 grid support 24 start-up phase 10 Pellet combustion bowl 25 pellet 11 Tilting grate 26 another sensor 12 breakthroughs 27 operating logs 13 wave 14 supply means 15 Auger

Claims (9)

1. A method for regulating a heating device (1) having a combustion chamber (4) for the combustion of at least one first fuel, in particular logs, wherein the first fuel can be introduced into the combustion chamber (4) via a combustion chamber door (5) which can be opened as required and wherein opening and subsequent closing of the combustion chamber door (5) is detected with a first sensor (7) at least during the operating phase of the heating device (1),
   wherein after closing the combustion chamber door (5) it is determined with at least one further sensor (26) whether a new first fuel has been introduced into the combustion chamber (4) and wherein the control settings of the heating device (1) are adjusted differently depending on whether or not a new fuel has been introduced into the combustion chamber (4), characterized in
   that the heating device (1) is provided with automatic feeding means (14) for at least one further fuel into the combustion chamber (4),
   and that the control settings of the heating device (1) are adjusted when a feeding of new first fuel is detected so that at the latest after ignition of the new first fuel, no new further fuel is automatically fed to the combustion chamber (4),
   wherein the detection of no feeding of new first fuel is carried out in that the heating power of the heating device (1) has fallen below a certain value, in particular a value specified by the user,
   and that upon detection of no feeding of new first fuel, the control settings of the heating device (1) are adjusted such that new further fuel is automatically fed to the combustion chamber (4) and caused to combust as soon as the heating power of the heating device (1) falls below a certain value, in particular a value specified by the user.
2. The method according to claim 1, characterized in that the air supply into the combustion chamber (4) is adjusted or changed, in particular increased, at least for a short time, if a new fuel has been introduced into the combustion chamber (4), and that the control settings with respect to the air supply are kept substantially constant if no new fuel has been introduced into the combustion chamber (4).
3. The method according to any one of claims 1 and 2, characterized in that the at least one further sensor is designed as a temperature sensor (26) and in that an introduction of new first fuel that has taken place is detected by the fact that the temperature in the combustion chamber (4) changes after closing the combustion chamber door (5), in particular that the temperature rises.
4. The method according to one of the preceding claims, characterized in that the at least one further sensor is designed as a CO sensor (26) and in that an introduction of new first fuel that has taken place is detected by the fact that the CO content in the combustion chamber (4) changes after closing the combustion chamber door (5), in particular that the CO content increases at least for a short time.
5. The method according to any one of the preceding claims, characterized in that the first fuel is formed from logs and the further fuel is formed from wood pellets whereby a logs operation (27) and a pellet operation (25) are made possible, and that in the pellet operation (25) the control settings of the heating device (1) are adjusted when new logs are introduced into the combustion chamber (4) such that switching to the log operation (27) takes place and that at the latest after the newly introduced logs have been ignited, no new wood pellets are introduced into the combustion chamber (4) by the automatic feeding means (14), in that, in the pellet operation (25), in the event that no new logs have been introduced into the combustion chamber (4), the regulating of the heating device (1) remains in pellet operation (25) and new wood pellets are introduced into the combustion chamber (4) by the automatic feeding means (14) as required, in that in the logs operation (27), when further new logs are introduced into the combustion chamber (4), the regulating of the heating device (1) remains in logs operation (27) and no new wood pellets are introduced into the combustion chamber (4) by the automatic feeding means (14), and in that in the logs operation (27), in the event that no new logs have been introduced into the combustion chamber (4) and the heating capacity of the heating device (1) falls below a certain value, in particular a value predetermined by the user, the control settings of the heating device (1) are adjusted such that switching to the pellet operation (25) takes place and new wood pellets are introduced into the combustion chamber (4) by the automatic feeding means (14).
6. The method according to claim 5, characterized in that new wood pellets are introduced from the automatic feeding means (14) into a pellet combustion trough (10) arranged in particular in the lower region of the combustion chamber (4), comprising a tilting grate (11) forming the lower end of the pellet combustion trough (10), and that when switching from the log operation (27) to the pellet operation (25), the tilting grate (11) is tilted, so that disturbing log or pellet residues are removed from the pellet combustion trough (10).
7. The method according to claim 6, characterized in that when switching from the log operation (27) to the pellet operation (25), the tilting grate (11) is tilted only when the temperature falls below a temperature threshold and/or when CO falls below a certain content in the combustion chamber (4).
8. The method according to any one of the preceding claims 5 to 7, characterized in that the regulation of the heating device (1) performs the first ignition of the heating device (1) in a starting phase (24) by means of the wood pellets introduced into the combustion chamber (4) by the automatic feeding means (14) and in that after the ignition has taken place, the regulation switches to an operating phase in which, depending on the addition of logs, switching between pellet operation (25) and logs operation (27) takes place.
9. The method according to one of the preceding claims 5 to 8, characterized in that a continuously adjustable ventilation device (17), via which primary air can be introduced into the combustion chamber (4) from below via the pellet combustion trough (10) and secondary air can be introduced from above along the inside of the combustion chamber door (5), is controlled by the regulation of the heating device (1) such that in the pellet operation (25) the ignition or, respectively, the combustion of the wood pellets is controlled by the introduction of primary air and only a minimal amount of secondary air is used to keep a glass pane (6) clean in the combustion chamber door (5), and that, when switching to the logs operation (27), primary air and secondary air are used to ignite the logs introduced and secondary air is used to burn the logs introduced.

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