Method for operating a heating device, computer program, control and control device and heating device

Abstract

A method for operating a heating appliance (1) is proposed, comprising a conveying device (2) for conveying a combustion mixture of fuel gas and combustion air to a burner (3) and a gas valve (5) for controlling a flow rate of fuel gas, wherein the method comprises at least the following steps: a) detecting a volume flow rate V̇Air(t0) of combustion air (17) supplied to the burner (3) at a time t0 (18), b) opening or closing the gas valve (5), c) detecting the volume flow rate V̇Air(t) of combustion air at a time t (19) after opening or closing the gas valve (5) in step b), d) determining a ratio R(t) with - Rt=V˙AirtV˙Airt0 when the gas valve (5) was opened in step b) and with - Rt=V˙Airt0V˙Airt when the gas valve (5) was closed in step b). The procedure allows for checking / verifying a combustion air ratio assumed and set by the combustion control system.Optionally, the combustion air ratio can be adjusted. Furthermore, a heating unit (1), a control and regulating unit (7), and a computer program are proposed.

Description

[0001] The invention relates to a method for operating a heating device, a computer program, a control and regulating device and a heating device.

[0002] When operating a heating appliance, a mass flow of combustion air is typically mixed with a mass flow of fuel gas corresponding to a predetermined combustion air ratio and fed to a burner. The current combustion air ratio can be deduced from a measured combustion parameter. This parameter is often the combustion ionization current, which can be measured using an ionization electrode. However, measuring the ionization current as a control variable for combustion regulation cannot be reliably performed with hydrogen as the fuel.

[0003] In heating appliances that use hydrogen as fuel, different combustion parameters are therefore measured for combustion control, in particular the flame temperature and / or optical parameters, such as the UV (ultraviolet) radiation emitted by the flame. However, these sensors can be subject to sensor drift, i.e., a gradual change in the sensor signal. Sensor drift can be caused, for example, by aging effects such as oxidation. If the signal is used as a control variable for combustion control, this can lead to a gradual change in the (control-set) combustion air ratio, which can result in critical conditions of the heating appliance, such as flame flashback. Furthermore, the energy efficiency of the combustion can decrease if the combustion air ratio shifts, or unburned fuel may even enter the exhaust gas.Last but not least, geometric tolerances of the heating appliance's components or environmental effects such as wind or exhaust gas recirculation can also lead to a shift in the combustion air ratio.

[0004] The solution proposed in EP 3 985 306 A1 involves transmitting the measured value from a temperature sensor located in the combustion chamber to a measuring and evaluation unit, which then monitors the measured value and its behavior over time. Two redundant sensors can also be used to increase operational reliability. A disadvantage of the proposed solution is its limited ability to detect sensor drift or to distinguish it from other effects that cause a shift in the measured value.

[0005] A generic process is known from EP 3 396 248 A1.

[0006] Based on this, the object of the invention is to propose a method for operating a heating device, a computer program, a control and regulation device, and a heating device that at least partially overcome the problems of the prior art described above. In particular, the invention is intended to enable the safe operation of a heating device, especially a hydrogen-powered heating device.

[0007] Furthermore, the process should be suitable for at least partial automation and require as few structural changes as possible compared to a state-of-the-art heating device.

[0008] These problems are solved by the features of the independent claims. Further advantageous embodiments of the solution proposed here are specified in the independent claims. It should be noted that the features listed in the dependent claims can be combined with one another in any technologically meaningful way and define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, which also presents further preferred embodiments of the invention.

[0009] This involves a method for operating a heating appliance. The heating appliance includes a conveying device for supplying a combustion mixture of fuel gas and combustion air to a burner and a gas valve for controlling the fuel gas flow rate. The method comprises at least the following steps: a) Capturing a volume flow supplied to the burner V̇ Air ( t 0) combustion air at a time t 0 , b) opening or closing the gas valve, c) measuring the volume flow V̇ Air ( t ) Combustion air at a time t after opening or closing the gas valve in step b), d) Determining a ratio R(t) with R t = V ˙ Air t V ˙ Air t 0 , when the gas valve was opened in step b) and with R t = V ˙ Air t 0 V ˙ Air t , when the gas valve was closed in step b).

[0010] Steps a), b), c), and d) can be performed at least once in the specified order. In particular, steps a) to d) can be performed at regular intervals during operation of the heating appliance. Alternatively or cumulatively, the procedure can also be carried out as needed or triggered by events, for example, if operating data from the heating appliance indicates a shift in the combustion air ratio. The procedure serves, in particular, to ensure the continuous and reliable operation of a heating appliance, especially one powered by hydrogen or a hydrogen-containing mixture as fuel.

[0011] The heating appliance can include at least one heat generator, in particular a gas condensing boiler, which releases thermal energy by burning a fuel and can transfer it to a heating circuit via at least one heat exchanger. Consumers in the heating circuit can be connected to the heating appliance via a flow and a return line. The exhaust gases produced during combustion can be routed to an exhaust system via an exhaust duct in the heating appliance. A circulation pump can be installed in the heating circuit within the heating appliance to circulate a heat transfer medium (heating water). Heated heat transfer medium is supplied to consumers, such as convectors or underfloor heating systems, via a heating flow line and returned to the heat generator or the at least one heat exchanger via a heating return line.

[0012] For this purpose, the heating appliance may include a conveying device, in particular a blower, which can supply a mixture of combustion air and fuel (hydrogen) to a burner of the heating appliance located in a combustion chamber. Combustion air can refer to the airflow conveyed by the conveying device, regardless of whether this air is actually used for combustion or is conveyed, for example, during commissioning, when starting up the conveying device, or during purging processes. The conveying device may include a power control, in particular a speed controller.The heating appliance can utilize a pneumatic gas-air system in which a mass flow of combustion air is mixed with a mass flow of fuel gas supplied via a gas inlet, corresponding to a negative pressure (control pressure) at a throttling point such as a Venturi nozzle. This allows for the establishment of a predefined (specified) air-fuel ratio (air ratio, lambda). Alternatively, the heating appliance can utilize an electronic gas-air system in which a signal from a flame monitor allows for inferences about the flames and the air-fuel ratio (also known as lambda or air ratio), thus enabling its regulation. The heating appliance can be specifically designed for the combustion of hydrogen as fuel or a (fuel) mixture containing hydrogen. The mixture can have a hydrogen content of at least 80% or at least 90%.

[0013] Furthermore, the heating appliance may feature flame monitoring. This often involves the use of an ionization electrode, which utilizes the flame's ionization current to detect its presence. However, this principle is not reliably applicable to hydrogen flames, as the combustion of hydrogen produces significantly fewer free charge carriers. Therefore, hydrogen-powered heating appliances frequently employ other methods, such as detecting the electromagnetic radiation emitted by the flame, particularly infrared (IR) and / or ultraviolet (UV) radiation, or measuring the flame temperature. A signal from flame monitoring can indicate the presence of a flame and also provide information about the flame's air-fuel ratio.

[0014] The commissioning of a heating appliance can proceed as follows. First, a control unit of the heating appliance, for example, can start a delivery system, usually a blower, to a predetermined starting power or starting speed. After reaching the predetermined starting power or starting speed, a purging phase of a predetermined duration can follow, during which the mass flow of combustion air in the flow path can stabilize. At the predetermined starting power or starting speed, a starting volume flow of combustion air is established. Now, a fuel flow rate (starting mass flow or starting volume flow of fuel) predetermined for the starting power or starting speed can be supplied by moving a gas valve to the corresponding opening position. With increasing volume flow of fuel gas... V̇ Gas Can the volume flow of combustion air be increased? V̇ Air ( t) decrease continuously over time t and the supplied volume flow of fuel gas decreases inversely proportionally V̇ Gas ( t The pressure increases until a predetermined combustion air ratio λ is reached, and an ignition process can be initiated. The described process of starting up a heating appliance can be carried out, in particular, by a control unit of the heating appliance.

[0015] According to step a), a) capturing a volume flow supplied to the burner is possible. V̇ Air ( t0) Combustion air is supplied at a time t 0. Time t 0 can represent a point in time during the operation of the heating appliance, at which it is operated with a combustion air ratio assumed by the control system. The assumed combustion air ratio can be set by the combustion control system based on a combustion parameter, in particular a signal from a temperature sensor to detect a flame temperature or an optical sensor to detect optical radiation (especially UV radiation) emitted by the flame, and a predefined relationship between the combustion parameter and the combustion air ratio.

[0016] Alternatively, at time t 0, the heating appliance can also be supplying a volume flow of combustion air and the gas valve can be closed. This can occur, for example, when restarting the burner operation following an interruption to carry out a procedure proposed here.

[0017] In particular, the recorded volume flow V̇ Air ( t 0) Combustion air / combustion mixture is stored on an electronic data storage device, for example, a memory of the control unit.

[0018] According to step b), the gas valve can now be opened or closed. When opening, the gas valve can be opened to a predetermined opening width, which can establish a combustion air ratio (assumed by the combustion control system). When closing the gas valve, it can be completely closed, so that only the volume of combustion air supplied by the delivery system is fed to the burner.

[0019] According to step c), the volume flow of combustion air can be measured. V̇ Air ( t) after the gas valve is opened or closed at a time t. Time t can be within a predetermined period after time t0. In particular, the measurement of the combustion air volume flow can be performed. V̇ Air ( t ) are carried out continuously or over a predetermined recording period, whereby the recording period is at least partially parallel to the opening process of the gas valve and / or the fully open gas valve.

[0020] According to one embodiment, the volume flow of combustion air can be measured. V̇ Air ( t 0 ) and / or the volume flow of combustion air V̇ Air ( t ) by means of a flow sensor (a mass flow or volume flow sensor) which may be located in a combustion air supply of the heating device, for example in a silencer of a combustion air supply.

[0021] According to one embodiment, according to one of the preceding claims, the volume flow can be adjusted in steps a) and c). V̇ Air ( t 0 ) or V̇ Air ( t ) can be deduced from the rotational speed n of the conveying device. In particular, the rotational speed can be kept constant or regulated for this purpose. For example, during operation at time t 0, the target rotational speed can be kept constant and regulated, a V̇ Air ( t The value 0) is established and can be detected. The gas valve can then be closed or opened. The speed of the conveying device remains constant, and a modified volume flow of combustion air can be achieved. V̇ Air ( t ) are recorded. Based on V̇ Air ( t 0 ) and V̇ Air ( t ) R(t) can now be determined.

[0022] In this context, it should be noted that a (gaseous) volumetric flow rate can be easily converted into a mass flow rate and vice versa. This can be approximated by multiplication using a conversion factor or by a precise conversion based on knowledge of the state parameters of the gas flow being measured, in particular its density, temperature, and pressure. Therefore, any reference to a mass flow rate within this document can always be understood as a reference to a volumetric flow rate, and vice versa.

[0023] According to step d), a ratio R(t) is determined with R t = V ˙ Air t V ˙ Air t 0 , when the gas valve was opened in step b), and with R t = V ˙ Air t 0 V ˙ Air t , this will happen when the gas valve was closed in step b).

[0024] The ratio is derived from the fact that the volume flow rate delivered by the conveying device at a constant rotational speed is constant (independent of density) and the volume flow rate of fuel gas V̇ Gas ( t ) thus by means of V̇ Gas ( t ) = V̇ Air ( t 0 ) - V̇ Air ( t ) when the gas valve is opened or V̇ Gas ( t ) = V̇ Air ( t ) - V̇ Air ( t 0) can be derived when the gas valve is closed.

[0025] Based on the ratio R(t) determined in step d), a conclusion can be drawn about the combustion air ratio at time t or t0. In particular, when the gas valve is closed, the combustion air ratio before closing can be inferred, and when the gas valve is opened, the combustion air ratio after opening can be inferred. For this purpose, the determined R(t) can, for example, be compared with a predefined reference range of R(t), and the combustion at time t can be evaluated.

[0026] According to one design, in one step e) a calculation of a virtual combustion air ratio λ V (t) using λ V t = R t A × 1 − R t take place.

[0027] Factor A represents the minimum air requirement for the combustion of the fuel gas, also known as the stoichiometric air requirement, i.e., the volume of combustion air needed to burn one cubic meter of fuel gas, assuming that the combustion air has an oxygen content of 21 percent. Knowing the chemical composition of the fuel, the minimum air requirement A can be calculated. For example, factor A (the minimum air requirement for combustion) is 2.381 for 100% hydrogen, 9.52 for 100% methane, 23.8 for 100% propane, and 31 for 100% butane. Factor A (the minimum air requirement) can be stored, for example, in the control unit of the heating appliance, perhaps as an average value for the gases within a gas family.

[0028] Alternatively, the minimum air requirement A could also be determined, for example, from a commissioning procedure and / or with the help of other control loops of the heating appliance. For this purpose, a lambda control loop of a heating appliance can be used, which can regulate the combustion air ratio of the heating appliance during operation independently of the gas type. Thus, after the gas valve is closed with R t = V ˙ Air t 0 V ˙ Air t and λ V t = R t A × 1 − R t The minimum air requirement A can be determined with knowledge of the combustion air ratio during operation.

[0029] An alternative method for determining the minimum air requirement A could involve reducing the air-fuel ratio from a non-ignitable range (thus increasing the fuel-air ratio in the combustion mixture) until successful ignition occurs, thereby determining an R(t) for the leanest ignitable mixture. Knowing the lambda limit of the device for ignition (i.e., the maximum lambda (air-fuel ratio) at which ignition is possible), the minimum air requirement A could be calculated using the determined R(t).

[0030] According to one embodiment, step e) could involve evaluating the virtual air-fuel ratio λV(t). This evaluation is carried out, in particular, to determine any deviation of the virtual air-fuel ratio λV(t) from the (set) air-fuel ratio assumed by the combustion control system based on the combustion parameter.

[0031] According to one embodiment, the assessment according to step e) could take into account the fact that a virtual combustion air ratio λ V (t) that is too low may indicate potentially occurring critical conditions of the heating device.

[0032] According to a further embodiment, the burner operation can be interrupted to carry out the procedure proposed here, and R(t) can be determined both during the associated closing and opening of the gas valve. Subsequently, the two determined R(t) values ​​(during closing and opening of the gas valve) and / or the derived virtual combustion air ratios λV(t) (during closing and opening of the gas valve) can be compared, and the comparison results can be evaluated.

[0033] According to one embodiment, during step e), the virtual air-fuel ratio λV(t) or the gradient G(t) determined in step d) can be compared with a (respective) reference range. A deviation from the reference range can indicate a critical operating condition, in particular a critical air-fuel ratio λ. The reference range can be defined by an upper and a lower limit, whereby a virtual air-fuel ratio λV(t) greater than the upper limit and / or less than the lower limit can indicate a potentially critical operating condition. The reference range can also be a limit, the exceeding or falling below of which can indicate a critical condition. In particular, falling below the limit can be critical, as this can indicate a low λ and thus a high proportion of fuel in the combustion mixture (rich mixture).

[0034] According to one embodiment, the reference range and / or limit value may have been determined in advance on a reference heating device in (laboratory) tests and stored on a memory of the heating device, in particular a control and regulating device of the heating device.

[0035] According to one embodiment, if the reference range is exceeded or not exceeded by the virtual combustion air ratio λ V (t) and / or the ratio R(t) in step e), the volume flow of fuel gas can be adjusted. V̇ Gas be adapted.

[0036] As described, a constant speed of the conveying device is crucial for determining R(t) or the virtual combustion air ratio λV(t). However, a brief speed deviation can occur when the gas valve opens or closes. According to one embodiment, this speed deviation can be compensated by additionally recording the speed n of the conveying device at time t0 and at time t0 and calculating a compensated volume flow rate. V ˙ Air Komp t = V ˙ Air × n t 0 n t The compensated volume flow rate can then be used to calculate the virtual combustion air ratio.

[0037] According to one embodiment, the supplied volume flow of fuel gas can be V̇ GasThe values ​​are adjusted according to the deviation of the determined R(t) from a target R(t) or the deviation of the determined virtual air-fuel ratio from a target air-fuel ratio. Depending on the deviation, various scenarios are conceivable: In the case of an implausibly large deviation (virtual air-fuel ratio significantly larger / smaller than the target air-fuel ratio), a reset of the gas valve's stepper motor may be advisable. If the virtual air-fuel ratio is significantly below the target air-fuel ratio, i.e., a significantly too rich combustion mixture, a correspondingly large correction can be made to shift the air-fuel ratio back into a leaner range. Furthermore, if the virtual air-fuel ratio deviates significantly towards a leaner mixture, the supplied fuel gas flow rate can be adjusted. V̇ GasThe amount should be increased in small increments. Increasing the amount in small increments can reduce the risk of jumping into a fat zone.

[0038] According to one embodiment, if the reference range is deviated from and / or the limit value is exceeded or fallen below by the virtual combustion air ratio λ V (t) and / or the ratio R(t), the heating device can be (automatically) put into a fault state in which commissioning is blocked and which, for safety reasons, can only be ended by a person familiar with the device, such as a service technician.

[0039] According to a further embodiment, information about the detection of a deviation from the reference range and / or an exceedance or fall below the limit value can be displayed via a display device (external or integrated into the heating appliance) and / or made available for retrieval via a network, in particular the internet, and / or sent as a message. For example, the information can be made available for retrieval on an appliance interface of the heating appliance or on network storage (cloud). Advantageously, this allows, for example, a user / operator of the heating appliance and / or a specialist company to be informed of the detected deviation via a message, and the specialist company can then schedule and carry out an appointment for maintenance and / or repair accordingly.In particular, this allows for a quick resolution of a fault condition in the heating device.

[0040] One proposed method thus calculates a virtual combustion air ratio λ V (t), which allows for an assessment and evaluation of the combustion mixture supplied to the burner.

[0041] In addition, a computer program is proposed that is designed to (at least partially) execute one of the procedures presented here. In other words, this specifically concerns a computer program (product) comprising commands that, when executed by a computer, cause it to carry out the procedure proposed here. The computer program can, in particular, be executed on a control unit of the heating device.

[0042] Another aspect that is proposed is a machine-readable storage medium on which the computer program is stored.

[0043] The machine-readable storage medium is usually a computer-readable data carrier.

[0044] In addition, a control unit for a heating appliance is proposed, designed to carry out a procedure proposed herein. This control unit may, for example, include a processor. In this context, the processor can execute the procedure stored in the control unit's memory. The control unit may be electrically connected to a conveying system and a flame monitor. Furthermore, data acquired or required during the execution of the proposed procedure, such as the combustion air flow rate recorded in step a), can be stored in the control unit's memory. V̇ Air ( t 0 ), a volume flow of combustion air recorded in step c). V Air ( t), a ratio R(t) and virtual combustion air ratio λV(t) determined in step d), a reference range and / or limit value.

[0045] Another aspect proposed is a heating appliance comprising a control and regulation device. The heating appliance can be a gas-fired appliance, in particular a hydrogen-powered gas-fired appliance. The gas-fired appliance can include a burner and a delivery system for supplying a mixture of fuel (hydrogen) and combustion air to the burner. According to one embodiment, the heating appliance can include a flow sensor for detecting the mass or volume flow of combustion air supplied.

[0046] The details, features, and advantageous configurations discussed in connection with the process can also occur in the computer program, control unit, and heating device presented here, and vice versa. In this respect, full reference is made to the explanations provided therein for a more detailed characterization of the features.

[0047] This document presents a method for operating a heating device, a computer program, a control unit, and a heating device itself, which at least partially solve the problems described with reference to the prior art. In particular, the method for operating the heating device, the computer program, the control unit, the heating device, and its application contribute, at least in part, to enabling the safe operation of a heating device, especially a hydrogen-powered one. Furthermore, the method proposed here is advantageously fully computer-implemented and requires no structural modifications to the heating device, but can usually be implemented using the existing sensors of the heating device.

[0048] This procedure is particularly advantageous when performed during operation of the heating appliance, for example, during a burner interruption, and helps to detect potentially critical conditions early on, before they can lead to damage to the heating appliance. If necessary, the heating appliance can be automatically shut down upon detection of a potentially critical condition.

[0049] The invention and its technical context are explained in more detail below with reference to the accompanying figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the situations described in the figures and combine them with other components and findings from the present description. It should be emphasized that the figures, and especially the depicted dimensions, are only schematic. They show: Fig. 1 : a sequence of a procedure proposed here, Fig. 2 : a heating device suggested here, and Fig. 3 : Parameter profiles that may occur when carrying out a procedure proposed here.

[0050] Fig. 1Figure 1 shows an exemplary and schematic representation of the sequence of a procedure proposed here. The execution of steps a), b), c), and d), depicted in blocks 110, 120, 130, and 140, can be carried out at least once in the specified order during a regular procedure. The procedure serves to increase the operational reliability of a heating appliance 1, particularly one operated with hydrogen or a hydrogen-containing mixture as fuel. Specifically, the described procedure can be carried out during operation of the heating appliance 1 to verify / check the combustion air ratio assumed by the combustion control system of the heating appliance 1 and, if necessary, to correct it.

[0051] Fig. 2Figure 1 shows an exemplary and schematic representation of a heating device 1 proposed here. This device can include a burner 3 arranged in a combustion chamber 8. A combustion air supply 4, in which a flow sensor 12 can be arranged, can be used to determine the volume flow of combustion air. V̇ Air are drawn in by a conveying device 2, in particular designed as a blower.

[0052] The conveying device 2 can be connected to a speed controller 6, which can regulate the speed n of the conveying device 2 by means of a pulse-width modulated (PWM) signal. A gas valve 5 can supply combustion air to the intake volume flow. V̇ Air a volume flow of fuel gas V̇ Gas from a gas supply 14 and a safety valve as well as a gas control valve for controlling the volume flow of fuel gas to be added V̇ GasThe combustion mixture of fuel gas and combustion air produced can flow to the burner 3 via a mixture channel 11. The burner 3 can have a cylindrical shape, the base of which can be attached to a burner door 15 in such a way that the combustion mixture can flow from the mixture channel 11 into the burner 3. After combustion, the combustion products can be discharged to the outside via an exhaust pipe 9 of the heating appliance and an exhaust system 10.

[0053] The heating device 1 proposed here can be configured specifically for the combustion of hydrogen. Furthermore, the heating device 1 can have a flame monitoring device 13 on / in the burner door 15, which can be designed as a sensor for UV (ultraviolet) radiation emitted by the flame.

[0054] A control unit 7 can be configured to control the heating appliance 1. For this purpose, it can be electrically connected, for example, to the speed controller 6, the conveying device 2, the gas valve 5, the flame monitoring device 13, the flow sensor 12, and a network 16 (Internet). The control unit 7 can be configured to carry out a procedure proposed here.

[0055] The Fig. 3 and 4 The parameter profiles shown are those that can occur when carrying out a procedure proposed here. Fig. 3Figure 20 shows, as an example, the rotational speed n of the conveying device 2 and an analogous curve 21 of the opening position P GV of the gas valve 5 over time t. It can be seen that during step b) of carrying out a procedure proposed here, the gas valve 5 is closed at time t = 6 seconds, thus setting the opening position P GV of the gas valve 5 to 0. The first time point 18 t 0 can be recorded immediately before the gas valve 5 closes. Furthermore,

[0056] Fig. 4 shows analogous to the one in Fig. 3 The given diagram shows the resulting course of the volume flow. V̇ Combustion air 17. Before the gas valve 5 closes at time t= 6 seconds, the volume flow decreases V̇ Combustion air shows a first value of 22, which V̇ Air ( t 0 ). With the closing of the gas valve 5, this rises to a second value 23 at the second time 19. V̇ Air ( t) based on the change in volume flow. V̇ According to a method proposed here, the volume flow rate of fuel gas can be determined V̇ Air ( t 0 ) determined at time t 0 and applied to a virtual combustion air ratio λ V (t) can be inferred.

[0057] In block 110 according to step a), the volume flow of combustion air supplied to the burner can be V̇ Air ( t 0 ) 17 at a first point in time 18 t 0 are recorded and, for example, stored on a memory of the control and regulating unit 7.

[0058] In block 120, according to step b), the gas valve 5 can be opened or closed. This can be done by controlling the gas valve 5 via the control unit 7.

[0059] In block 130 according to step c), the volume flow of combustion air 17 can be adjusted at the second time. V̇ Air ( t ) are recorded. The recorded volume flow V̇ Air (t ) can be stored on a memory, for example in the control unit 7.

[0060] In block 140, according to step d), a ratio R(t) can be determined with R t = V ˙ Air t V ˙ Air t 0 , when the gas valve 5 in step b) (block 120) was opened and with R t = V ˙ Air t 0 V ˙ Air t , when the gas valve 5 in step b) (block 120) was closed. The determined ratio R(t) can also be stored in a memory, for example in the control unit 7.

[0061] In block 150, according to an optional step d), a virtual combustion air ratio λ V (t) can be calculated using λ V t = R t A × 1 − R t take place.

[0062] The virtual air-fuel ratio λV(t) determined in step d) and / or the ratio R(t) determined in step c) in block 150 can now be evaluated according to step e). For this purpose, the virtual air-fuel ratio λV(t) and / or the ratio R(t) can be compared with a limit value or a limit range. If a deviation of the virtual air-fuel ratio λV(t) from the air-fuel ratio assumed by the combustion control system is detected, the air-fuel ratio can be corrected, for example by adjusting the fuel gas volume flow rate.

[0063] It should be noted as a precaution that the numerical terms used here ("first", "second", etc.) primarily serve (only) to distinguish between several similar objects, quantities, or processes, and thus do not necessarily dictate any dependency and / or sequence between these objects, quantities, or processes. Should a dependency and / or sequence be required, this is explicitly stated here, or it will be obvious to a person skilled in the art upon studying the specific configuration described. Where a component can occur multiple times ("at least one"), the description of one of these components may apply equally to all or some of the multiple components, but this is not mandatory. Reference symbol list

[0064] 1 Heater 2 Conveyor 3 Burner 4 Combustion air supply 5 Gas valve 6 Speed ​​controller 7 Control unit 8 Combustion chamber 9 Exhaust pipe 10 Exhaust system 11 Mixture channel 12 Flow sensor 13 Flame monitoring 14 Gas supply 15 Burner door 16 Network 17 Combustion air flow rate 18 First time t 0 19 Second time t 20 Speed ​​curve 21 Gas valve opening position curve P GV 22 First value 23 Second value

Claims

1. Method for operating a heating appliance (1), comprising a conveyor device (2) for conveying a combustion mixture of fuel gas and combustion air to a burner (3) and a gas valve (5) for controlling a flow rate of fuel gas, wherein the method comprises at least the following steps: a) V̇Air(t0)detecting a volume flow of combustion air (17) supplied to the burner (3) at a point in time t0(18), b) opening or closing the gas valve (5), c) V̇Air(t) Detecting the volume flow of combustion air (17) at a time t (19) after opening or closing the gas valve in step b), characterised by d) determining a ratio R(t) with - R t = V ˙ Air t V ˙ Air t 0 when the gas valve (5) was opened in step b) and - R t = V ˙ Air t 0 V ˙ Air t if the gas valve (5) was closed in step b).

2. Method according to claim 1, wherein in step e) a virtual combustion air ratio λV(t) is calculated by means of λ V t = R t A × 1 − R t , wherein factor A represents a minimum air quantity for combustion of the fuel gas, and an evaluation of the virtual combustion air ratio λ(V) (t) is performed.

3. Method according to claim 1 or 2, wherein in steps a) and c) the volume flowV̇Air(t0) andV̇Air(t) , respectively, is detected by means of a flow sensor (12).

4. Method according to one of the preceding claims, wherein in steps a) and c) the volume flowV̇Air(t0) andV̇Air(t) , respectively, is inferred from the rotational speed n of the conveyor (2).

5. Method according to one of the preceding claims, wherein the operation of the burner (3) is interrupted and the method is carried out both when the gas valve (5) is closed and when it is opened.

6. Method according to one of the preceding claims, wherein, when evaluating the ratio R(t) and / or the virtual combustion air ratio λV(t) in step e), it is compared with a predetermined reference range and / or a limit value.

7. Method according to claim 6, wherein, when the ratio R(t) and / or the virtual combustion air ratio λV(t) leaves the reference range or falls below or exceeds the limit value, at least one of the following actions is performed: - adjusting the volume flow of combustion gas V̇Gas , - deactivating the heating appliance (1) - putting the heating appliance (1) into an error state in which restarting is blocked, - displaying, providing and / or sending information about this.

8. Control and regulation device (7) for a heating appliance (1), the heating appliance comprising a conveyor device (2) and a flow sensor (12) for detecting a supplied volume flow of combustion air, wherein the control and regulation device ( ) is designed to cause the heating appliance (1) execute a method according to one of claims 1 to 7.

9. Heating appliance (1) comprising a conveyor device (2) and a flow sensor (12) for detecting a supplied volume flow of combustion airV̇Air(t)(17), , as well as a control and regulation device (7) according to claim 8.

10. Computer programme comprising instructions that cause a heating appliance (1) according to claim 9 to execute the method steps of a method according to one of claims 1 to 7.

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