Method for starting up a heating device, computer program, regulating and control device and heating device

Abstract

A method for commissioning 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) measuring a volume flow rate of combustion air V̇Air(t0) (17) supplied to the burner (3) before opening the gas valve (5) of the heating appliance (1) at time t0, b) measuring the volume flow rate of combustion air VAir(t) (17) after opening the gas valve (5) at time t, c) determining a ratio R(t) with Rt=V˙AirtV˙Airt0, and d) determining a virtual combustion air ratio λV(t) using λVt=RtA×1−Rt, where the factor A represents a minimum air quantity for the combustion of the fuel gas.

Description

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

[0002] Critical conditions can arise when a heater is put into operation. Examples of such critical conditions can be hard ignition, deflagration or flashback, i.e. the spread of flame during a start-up or ignition process from the burner into a feed line for the mixture of fuel gas and combustion air. This can cause damage to the heater. When hydrogen is used as the fuel gas, the probability of such critical conditions occurring is considerably higher because the significantly higher flame speed, volatility and low density of hydrogen result in significantly poorer repeatability during a start-up process. Delayed ignition and excessive gas output are particularly critical in this case. The initial start-up of a cold heater (cold start) can generally be particularly difficult.

[0003] To avoid such critical conditions, EP 3 992 529 A1 proposes using a pilot flame with its own fuel supply to ignite a main burner, the function of which can be monitored by a sensor and which is also arranged in such a way that the pilot flame cannot be extinguished by air escaping from the main burner. However, such a design is associated with considerable complexity.

[0004] To enable more reliable ignition of a heater, DE 10 2019 121 973 A1 proposes arranging a catalyst material in the heater, particularly in the gas-air mixture stream. Due to its properties, the catalyst material can generate the necessary activation energy to start combustion without additional thermal energy, such as an ignition spark or a pilot flame. This solution is also associated with considerable effort and expense.

[0005] DE 10 2019 131 346 A1 proposes a method for determining a fuel type that can be performed during the commissioning of a heater. For this purpose, a parameter can be recorded that allows conclusions to be drawn about the air flow supplied to the heater. The recorded parameter can be compared with a reference value to determine the fuel type. The poor repeatability of commissioning described above when using hydrogen as the fuel cannot be mitigated by this method.

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

[0007] In addition, the method should be suitable for being carried out at least partially in an automated manner and require as few structural changes as possible compared to a heater according to the state of the art.

[0008] These objects are achieved by the features of the independent patent claims. Further advantageous embodiments of the solution proposed here are specified in the independent patent claims. It should be noted that the features listed in the dependent patent claims can be combined with one another in any technologically expedient manner and define further embodiments of the invention. Furthermore, the features specified in the patent claims are further specified and explained in the description, with further preferred embodiments of the invention being presented.

[0009] To this end, a method for commissioning a heating device (1) 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 contributes, wherein the method comprises at least the following steps: a) Detecting a volume flow of combustion air supplied to the burner (3) V̇ Air ( t 0 ) (17) before opening the gas valve (5) of the heater (1) at a time t 0 , b) detecting the volume flow of combustion air V Air ( t ) (17)after opening the gas valve (5) at a time t, c) determining a ratio R(t) with R t = V ˙ Air t V ˙ Air t 0 , and d) determining a virtual combustion air ratio λ V (t) by means of λ V t = R t A × 1 − R t , where the factor A represents a minimum air quantity for the combustion of the fuel gas.

[0010] . Steps a), b), c) and d) can be carried out at least once in the specified order. In particular, steps b) to c) or d) can be carried out permanently (permanently repeated) or at regular intervals during commissioning. The method is used in particular for the safe commissioning or ignition of a heater, in particular a heater operated with hydrogen or a hydrogen-containing mixture as fuel. In particular, the method can be carried out during commissioning prior to an ignition process in order to avoid critical conditions.

[0011] The heater can comprise at least one heat generator, in particular a gas condensing boiler, which releases thermal energy through the combustion of a fuel and can transfer it to a heating circuit via at least one heat exchanger, wherein consumers of the heating circuit can be connected to the heater via a flow and a return. The exhaust gases produced during combustion can be fed to an exhaust system via an exhaust duct of the heater. In the heater, a circulating pump in the heating circuit can be configured to circulate a heat transfer medium (heating water), wherein heat transfer medium heated via a heating flow can be fed to consumers, such as convectors or surface heating systems, and returned to the heat generator or the at least one heat exchanger via a heating return.

[0012] For this purpose, the heater can have a conveying device, in particular a fan, which can supply a mixture of combustion air and fuel (hydrogen) to a burner of the heater arranged in a combustion chamber. Combustion air can refer to the air flow conveyed by the conveying device, regardless of whether it is actually supplied to combustion or, for example, is conveyed during commissioning, when starting up the conveying device, or during purging processes. The conveying device can comprise a power control, in particular a speed controller.The heater can form a pneumatic gas-air system in which a mass flow of combustion air is added to a mass flow of combustion air according to a negative pressure (control pressure) of a throttle point, such as a Venturi nozzle, so that a predefined (specified) combustion air ratio (air ratio, lambda) can be established. The heater can alternatively have an electronic gas-air system in which a signal from a flame monitor can be used to draw conclusions about the flames and the combustion air ratio (also referred to as lambda or air ratio), thus enabling control of the same. The heater can be designed in particular to burn hydrogen as a fuel or a (fuel) mixture containing hydrogen. The mixture can have a hydrogen content of at least 80% or at least 90%.

[0013] The heater can also have flame monitoring. An ionization electrode is often used for this purpose, which can use the ionization current of the flame to detect it. However, this principle cannot be used robustly with a hydrogen flame, since significantly fewer free charge carriers are produced during the combustion of hydrogen. Therefore, other methods are often used in hydrogen-powered heaters, such as detecting the electromagnetic radiation emitted by the flame, in particular infrared (IR) and / or UV (ultraviolet) radiation, or detecting the flame temperature. A signal from a flame monitor can indicate the presence of a flame and allow conclusions to be drawn about the combustion air ratio of the flame.

[0014] Commissioning of a heater can proceed as follows. First, a control unit of the heater, for example, can start a conveying device, which is usually designed as a fan, to a specified starting power or starting speed. After reaching the specified starting power or starting speed, a purge phase with a specified duration can follow, during which the mass flow of combustion air in the flow path can stabilize. At the specified starting power or starting speed, a starting mass flow of combustion air Air ( t 0 ). Now, a fuel flow rate (starting mass flow or starting volume flow of fuel) specified for the starting power or starting speed can be supplied by moving a gas valve to a corresponding opening position. With increasing volume flow of fuel gas V̇ GasThe volume flow of combustion air can decrease continuously over time t and the supplied volume flow of fuel gas can decrease inversely proportionally V̇ Gas increase until a predetermined combustion air ratio λ is established and an ignition process can be initiated. The described process of commissioning a heater can be carried out in particular by a control unit of a heater.

[0015] According to step a), a volume flow of combustion air supplied to the burner can be detected V̇ Air ( t 0 ) at a time t 0 before a gas valve of the heater is opened. The supplied combustion air volume flow corresponds in particular to the combustion air volume flow delivered at the starting power or starting speed of the delivery system. In this context, the combustion air volume flow can also be understood as the delivery volume flow of the delivery system.

[0016] In particular, the measured volume flow of combustion air V̇ Air ( t 0 ) are stored on an electronic data storage device, for example a memory of the control and regulation device.

[0017] According to step b), the volume flow of combustion air can be recorded V Air ( t ) during the opening or after the opening of the gas valve at a time t. The time t can be a predetermined period after the time t 0. In particular, the detection of the volume flow of combustion air V̇ Air ( t ) continuously or over a predetermined detection period, wherein the detection period is at least partially parallel to the opening process of the gas valve and / or the fully opened gas valve.

[0018] According to one embodiment, the volume flow of combustion air can be detected V̇ Air ( t0 ) 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 can be or is arranged in a combustion air supply of the heater, for example in a silencer of a combustion air supply.

[0019] In this context, it should be noted that a (gaseous) volume flow can be easily converted into a mass flow and vice versa. This can be achieved by multiplying the flow by a conversion factor or by performing a precise conversion based on the state parameters of the gas flow to be measured, in particular density, temperature, and pressure. A reference to a mass flow in this document can therefore always be understood as a reference to a volume flow, and vice versa.

[0020] According to step c), a ratio R(t) can be determined: R t = V ˙ Air t V ˙ Air t 0 . The ratio is derived from the fact that the volume flow conveyed by the conveyor at constant speed is constant (independent of density) and the volume flow of fuel gas V̇ Gas ( t ) thus by means of V ˙ Gas t = V ˙ Air t 0 − V ˙ Air t can be derived.

[0021] Based on the ratio R(t) determined in step c), a conclusion can be drawn about the combustion air ratio at time t. For this purpose, the determined R(t) can be compared, for example, with a predefined reference range of R(t) and the combustion at time t can be evaluated.

[0022] According to a step d), a virtual combustion air ratio λ V (t) can be calculated by means of λ V t = R t A × 1 − R t take place.

[0023] According to one embodiment, in a step e) an evaluation of the virtual combustion air ratio λV(t) can be carried out.

[0024] The 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 required to burn one cubic meter of fuel gas, assuming that the combustion air has an oxygen content of 21 percent [%]. With knowledge of the chemical composition of the fuel, the minimum air requirement A can thus be calculated. For example, the factor A (the minimum air requirement for combustion) is 2.381 for hydrogen (100%), 9.52 for (100%) methane, 23.8 for (100%) propane, and 31 for (100%) butane. The factor A (the minimum air requirement) can be stored for this purpose, for example, in a memory of the control unit of the heater, e.g., an average value for the gases in a gas family.

[0025] Alternatively, the minimum air requirement A could also be determined, for example, from a commissioning procedure and / or with the help of other control circuits of the heater. For this purpose, a lambda control circuit of a heater can be used, which can regulate the combustion air ratio of the heater during operation independently of the gas type. Thus, after closing the gas valve with R t = V ˙ m Air t 0 V ˙ Air t and λ V t = R t A × 1 − R t the minimum air requirement A can be determined knowing the combustion air ratio during operation.

[0026] An alternative approach could be to reduce the combustion air ratio from a non-ignitable range (thus increasing the proportion of fuel in the combustion mixture) until successful ignition occurs, thus determining an R(t) for the leanest ignitable mixture. Knowing the ignition device's lambda limit (i.e., the maximum lambda (combustion air ratio) at which ignition is possible), the minimum air requirement A could be calculated using the determined R(t).

[0027] According to one embodiment, an evaluation of the virtual combustion air ratio λ V (t) could take place in a step e). The evaluation is carried out in particular with a view to determining a critical commissioning and uses the virtual combustion air ratio λ V (t) and / or a gradient of the virtual combustion air ratio λ V (t) for this purpose. The gradient G(t) of the virtual combustion air ratio λ V (t) can be the increase in the virtual combustion air ratio λ V (t) determined by a mathematical derivation.

[0028] According to one embodiment, the evaluation according to step e) could take into account the fact that a virtual combustion air ratio λ V (t) that is too low could indicate potentially occurring critical conditions of the heater. Thus, aborting an ignition process could be considered if the virtual combustion air ratio λ V (t) is too low. In contrast, an excessively high virtual combustion air ratio λ V (t) is unlikely to lead to critical conditions, and aborting for safety reasons is not necessary; the ignition attempt can be continued until it is terminated (by the end of the safety time or by flame formation).

[0029] According to one embodiment, a plausibility check of the ratio R(t) and / or the virtual combustion air ratio λ V (t) can be performed when the gas valve is closed. The following steps can be performed for this purpose: a1) Detecting a volume flow of combustion air supplied to the burner (3) V̇ Air ( t P 0 ) before closing the gas valve of the heater at a time t P0 . b1) Determining the combustion air flow rate V Air ( t ) (17) after closing the gas valve at a time t, c1) Determining a ratio RP(t) with RP t = V ˙ m Air t P 0 V ˙ Air t . Closing of the gas valve can be initiated in particular by a described interruption of the ignition process, by an end of the safety time for the ignition process or by an operational burner shutdown (for example due to a lack of heat demand).

[0030] According to a further embodiment, in a step d1) in analogy to step d) a virtual combustion air ratio λ VP (t) can be determined from RP(t).

[0031] According to a further embodiment, a comparison of the ratios R(t) and RP(t) and / or the virtual combustion air ratios λ V (t) and λ VP (t) and an evaluation of the comparison results can be carried out.

[0032] According to one embodiment, when carrying out step e), the virtual combustion air ratio λ V (t) or the gradient G(t) determined in step d) can be compared with a (respective) reference range. Departing from the reference range can indicate a critical condition during commissioning, in particular a critical combustion air ratio λ . The reference range can be defined by an upper and a lower limit value, whereby a virtual combustion air ratio λ V (t) greater than the upper limit value and / or less than the lower limit value can indicate a possibly critical condition during commissioning, in particular in connection with delayed ignition. In contrast, an excessively low combustion air ratio means a lower flame speed and lower power and can therefore lead to slower or even no flame formation during an ignition process.The reference range can also be a limit value, which, if exceeded or undershot, can indicate a critical condition. In particular, falling below the limit value can be critical, as this can indicate a low λ and thus a high fuel content in the combustion mixture (rich mixture).

[0033] According to one embodiment, the reference range and / or limit value may have been determined in advance on a reference heater in (laboratory) tests and stored in a memory of the heater, in particular a control and regulating device of the heater.

[0034] According to one embodiment, when it is determined that the reference range has been left and / or the limit value has been exceeded or not reached by the virtual combustion air ratio λ V (t) and / or the ratio R(t) in step e), the volume flow of fuel gas V̇ Gas be adjusted.

[0035] According to one embodiment, if it is determined that the reference range has been exceeded and / or the limit value has been exceeded or undershot by the virtual combustion air ratio λ V (t) and / or the ratio R(t) in step e), in particular if the virtual combustion air ratio λ V (t) is below a reference range or limit value, the ignition process can be aborted. If the gas valve is closed, steps a1), b1) and c1) could be carried out and the virtual combustion air ratio λ V (t) or the ratio R(t) could be checked for plausibility. Subsequently, a new attempt at commissioning could be made with an adjusted volume flow of fuel gas. V̇ Gas in which, in particular, a procedure proposed here can be carried out again.

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

[0037] According to one embodiment, in particular during a renewed attempt at commissioning, the supplied volume flow of fuel gas V̇ Gasadjusted according to the deviation of the determined R(t) from a target R(t) or the deviation of the determined virtual combustion air ratio from a target combustion air ratio. Depending on the deviation, various scenarios are conceivable: In the case of an implausibly large deviation (virtual combustion air ratio significantly larger / smaller than the target combustion air ratio), a reset of the stepper motor of the gas valve can be useful. In the case of a virtual combustion air ratio significantly below the target combustion air ratio, i.e. a combustion mixture that is significantly too rich, a correspondingly large correction can be made, which can shift the combustion air ratio back into a lean range, if possible. In the case of a larger deviation of the virtual combustion air ratio towards lean, the supplied volume flow of fuel gas can be adjusted in small steps. V̇ GasBy increasing the fuel consumption in small steps, the risk of a jump into a rich range can be reduced. An increase in the supplied volume flow of fuel gas could also V̇ Gas be made dependent on a plausibility check of the virtual combustion air ratio.

[0038] According to one embodiment, the ignition process sequence can be adapted to the deviation of the determined R(t) from a target R(t) or the deviation of the determined virtual combustion air ratio from a target combustion air ratio. The adaptation of the ignition process sequence can particularly affect the safety time and the ignition power (ignition intensity). For example, with a combustion air ratio of less than one, the safety time can be shortened. For example, with a combustion air ratio of 0.7, the safety time could also be shortened by a factor of 0.7.

[0039] Alternatively or cumulatively, a power factor can be determined, which can be used to adjust the ignition process. The power factor can be Q Soll Q λ _ Virt = 1 + A × λ Virt 1 + A × λ Soll can be determined. A shortening factor for the safety time can be determined from the power factor, whereby a constant amount of energy per ignition attempt can be decisive for the shortening. The power factor can also be used to determine a necessary power change for a subsequent ignition attempt.

[0040] According to a further refinement, if a specified maximum number of heater startup attempts is reached and the heater exits the reference range or exceeds or falls below the limit value, the heater startup can be aborted. Typically, the specified maximum number of startup attempts will be in the range of 2 to 10 attempts, in particular 4 to 6 attempts. Country-specific regulations or standards often limit the number of startup attempts.

[0041] According to one embodiment, after the maximum number of commissioning attempts has been unsuccessful, the heater can be (automatically) put into an error state which, for safety reasons, can only be ended by a person familiar with the device, such as a service technician.

[0042] According to a further embodiment, in a step f), information about the maximum number of startup attempts being reached can be displayed via a display device (external or integrated into the heater) 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 heater or on a network storage device (cloud). Advantageously, for example, a user / operator of the heater and / or a specialist company can be informed of an error during startup via a message, and the specialist company can plan and carry out an appointment for maintenance and / or repair accordingly. In particular, this can lead to a rapid resolution of an error condition in the heater.

[0043] A proposed method thus computationally determines a virtual combustion air ratio λ V (t), which allows for an estimation and evaluation of the combustion mixture supplied to the burner. In this respect, the method proposed here is also very well suited as a redundant method for checking / monitoring existing control mechanisms.

[0044] According to a further aspect, a computer program is also proposed, which is configured to (at least partially) carry out a method presented here. In other words, this relates in particular to a computer program (product) comprising instructions which, when executed by a computer, cause the computer to carry out a method proposed here. The computer program can in particular be executed on a control and regulation device of the heating device.

[0045] According to a further aspect, a machine-readable storage medium on which the computer program is stored is also proposed.

[0046] The machine-readable storage medium is usually a computer-readable data carrier.

[0047] According to a further aspect, a control and regulating device for a heating device is also proposed, configured to carry out a method proposed here. The control and regulating device can, for example, have a processor and / or be equipped with one. In this context, the processor can, for example, execute the method stored in a memory (of the control and regulating device). For this purpose, the control and regulating device can, in particular, be electrically connected to a conveying device and a flame monitor. In addition, data acquired or required within the scope of carrying out a method proposed here can be stored in a memory of the control and regulating device, for example, a supplied volume flow of combustion air acquired in step a). V̇ Air ( t 0 ) , a volume flow of combustion air recorded in step b) V Air ( t ) ,a ratio R(t) and virtual combustion air ratio λV(t) determined in step c), a reference range and / or limit value and / or the number of commissioning attempts already made or the specified maximum number of commissionings.

[0048] According to a further aspect, a heating device is also proposed, comprising a control and regulation device as proposed here. The heating device can be a gas heater, in particular a hydrogen-powered gas heater. The gas heater can have a burner and a conveying device with which a mixture of fuel (hydrogen) and combustion air can be supplied to the burner.

[0049] The details, features, and advantageous embodiments discussed in connection with the method can also be found in the computer program, the control unit, and the heater presented here, and vice versa. In this respect, reference is made in full to the explanations therein for a more detailed characterization of the features.

[0050] Thus, a method for operating a heater, a computer program, a control device, and a heater are provided, which at least partially solve the problems described with reference to the prior art. In particular, the method for operating a heater, the computer program, the control device, the heater, and the use at least contribute to enabling safe commissioning or a safe ignition process of a heater, in particular in the case of a hydrogen-powered heater. Furthermore, a method proposed here can be carried out entirely using computer implementation and thus requires no structural modifications to a heater.

[0051] The method can be particularly advantageously implemented prior to an ignition process, helping to detect potentially critical conditions during the ignition process. This allows the ignition process to be aborted and can thus significantly increase operational reliability.

[0052] The invention and the technical environment 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 cited. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and combine them with other components and findings from the present description. In particular, it should be noted that the figures and, in particular, the illustrated proportions are only schematic. They show: Fig. 1: a sequence of a method proposed here, Fig. 2: a heating device proposed here, and Fig. 3: parameter curves that can occur when carrying out a method proposed here.

[0053] Fig. 1 shows, by way of example and schematically, a sequence of a method proposed here. The execution of steps a), b), c) and d) represented by blocks 110, 120, 130 and 140 can be carried out at least once in the specified order in a regular method sequence, with steps b) to d) of the method being repeated in particular continuously or at short time intervals (1 / 10 to 1 / 1000 of a second). The method serves to increase the safety of a heating device 1, in particular one operated with hydrogen or with a hydrogen-containing mixture as fuel, during commissioning.

[0054] Fig. 2shows, by way of example and schematically, a heating device 1 proposed here. This can comprise a burner 3 arranged in a combustion chamber 8. Via a combustion air supply 4, in which a mass flow sensor 12 can be arranged, a volume flow of combustion air V̇ Air by a conveying device 2, in particular designed as a blower. A mass flow sensor (12) detects Mass flow Combustion air Air can be easily converted into a volume flow of combustion air V̇ Air The conveyor device 2 can be connected to a speed controller 6, which can regulate a speed n of the conveyor device 2 by means of a pulse width modulated (PWM) signal. A gas valve 5 can adjust the intake volume flow of combustion air V Air a volume flow of fuel gas V̇ Gas from a gas supply 14 and a safety valve and a gas control valve to control the volume flow of fuel gas to be added V̇ Gas The generated combustion mixture of fuel gas and combustion air can flow to the burner 3 via a mixture channel 11. The burner 3 can have a cylindrical shape, which can be attached by a base surface to a burner door 15 such 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 heater and an exhaust system 10.

[0055] The heater 1 proposed here can be configured, in particular, for the combustion of hydrogen. Furthermore, the heater 1 can have a flame monitoring device 13 on or in the burner door 15, which can be configured here as a sensor for UV (ultraviolet) radiation emitted by the flame.

[0056] A control and regulation device 7 can be configured to regulate the heater 1. For this purpose, it can be electrically connected, for example, to the speed controller 6, the conveyor device 2, the gas valve 5, the flame monitor 13, the mass flow sensor 12, and a network 16 (Internet). The control and regulation device 7 can be configured to implement a method proposed here.

[0057] The Fig. 3 and 4 show parameter curves that can occur when implementing a method proposed here. A volume flow of combustion air V̇ Air ( t ) 17 and a volume flow of fuel gas V̇ Gas ( t ) 18 as a function of time t during commissioning of the heater 1. Initially, a starting power or starting speed of the conveyor 2 was reached, resulting in a constant volume flow of combustion air V̇ Air ( t 0 ) 21 can be set.

[0058] In block 110 according to step a), the volume flow of combustion air supplied to the burner V̇ Air ( t 0 ) 21 before the opening of a gas valve 5 at a first time t 0 19 and stored, for example, in a memory of the control unit 7.

[0059] Following the first time t 0 19, the gas valve 5 is opened, whereby the gas control valve moves to an opening position which corresponds to the starting volume flow of combustion air V̇ Air ( t 0 ) 21 corresponding starting volume flow of fuel gas 22.

[0060] In block 120 according to step b), the volume flow of combustion air can now be continuously V̇ Air ( t ) 21. By opening the gas valve 5, the volume flow of fuel gas 18 increases to the starting volume flow of fuel gas 22, while at the same time the volume flow of combustion air V̇ Air ( t) 17 decreases by the amount of the volume flow of fuel gas 18, so that at a constant speed of the conveying device (2) a constant volume flow of combustion mixture results at every time the combustion mixture is formed.

[0061] In block 130, according to a step c), a ratio R(t) can be determined with, and R t = V ˙ Air t V ˙ Air t 0 . The ratio R(t) can be used to estimate the combustion air ratio of the combustion mixture.

[0062] In block 140, according to a step d), a virtual combustion air ratio λ V (t) can be calculated by means of λ V t = R t A × 1 − R t take place.

[0063] In block 150, according to an optional step e), the virtual combustion air ratio λ V (t) determined in block 140 (step d)) can be evaluated. In particular, the virtual combustion air ratio λ V (t) can be compared with a limit value. In this case, the limit value was undershot at a second time 20 by the virtual combustion air ratio λ V (t), which can indicate an excessively low virtual combustion air ratio λ V (t) and thus an excessively high proportion of fuel gas in the combustion mixture, which can be associated with a high risk of problems during ignition, for example, a flashback. Due to the undershooting of the limit value, the start-up attempt is aborted at the second time 20 and the gas valve 5 is closed, whereby the volume flow of fuel gas V̇ Gas ( t ) 18 returns to zero and the volume flow of combustion air V̇ Air ( t) 17 can rise again to the combustion air volume flow 21.

[0064] When closing the gas valve (5) when aborting the attempt to start up the heater (1), a plausibility check of the ratio R(t) and / or the virtual combustion air ratio λ V (t) can be carried out (optionally) by carrying out the following steps: a1) Detecting a volume flow of combustion air supplied to the burner (3) V̇ Air ( t 0 ) (17) before closing the gas valve (5) of the heater (1) at a time t P0 , b1) Detecting the volume flow of combustion air V Air ( t ) (17) after closing the gas valve (5) at a time t, c1) Determining a ratio RP(t) with RP t = Vm . Air t P 0 V ˙ Air t .

[0065] According to a method proposed here, a new attempt at commissioning can now be made, whereby the supplied volume flow of fuel gas 22 can be adjusted.

[0066] As a precaution, it should be noted that the numerals used here ("first", "second", ...) primarily serve (only) to distinguish between several similar objects, quantities, or processes, and therefore do not necessarily specify any interdependence and / or sequence of these objects, quantities, or processes. Should a dependence and / or sequence be required, this is explicitly stated here or will be obvious to the person skilled in the art upon studying the specifically described embodiment. To the extent that a component can occur multiple times ("at least one"), the description of one of these components may apply equally to all or part of the majority of these components, but this is not mandatory. List of reference symbols

[0067] 1Heater 2Feeding device 3Burner 4Combustion air supply 5Gas valve 6Speed controller 7Control unit 8Combustion chamber 9Exhaust pipe 10Exhaust system 11Mixture duct 12Mass flow sensor 13Flame monitoring 14Gas supply 15Burner door 16Network 17Combustion air flow 18Fuel gas flow 19First time 20Second time 21Combustion air flow before the gas valve opens 22Fuel gas flow before the gas valve opens

Claims

1. Method for starting up a heating appliance (1), having a conveying device (2) for conveying a combustion mixture of combustion gas and combustion air to a burner (3) and a gas valve (5) for controlling a flow rate of combustion gas, the method comprising at least the following steps: a) detecting a volume flow of combustion airV̇Air(t0) (17) supplied to the burner (3) before the gas valve (5) of the heating appliance (1) is opened at a time t0, b) Detecting the volume flow of combustion airV̇Air(t) (17) after the gas valve (5) is opened at a time t, c) determining a ratio R(t) with R t = V ˙ Air t V ˙ Air t 0 and d) determining a virtual combustion air ratio λ(V) (t) by means of λ V t = R t A × 1 − R t , where the factor A represents a minimum air volume of the combustion of the fuel gas.

2. Method according to claim 1, wherein in a step e) an evaluation of the virtual combustion air ratio λV(t) takes place.

3. Method according to claim 1 or 2, wherein in steps a) and b) a volumetric flow of combustion airV̇Air(t0) orV̇Air(t) is detected by means of a mass flow sensor (12).

4. Method according to one of the preceding claims, wherein the ratio R(t), the virtual combustion air ratio λ(V) (t) and / or a gradient G(t) of the virtual combustion air ratio λ(V) (t) in step e) is compared with a predetermined reference range.

5. Method according to claim 4, wherein the ratio R(t), the virtual combustion air ratio λ(V) (t) and / or a gradient G(t) of the virtual combustion air ratio λ(V) (t) in step d) is compared with a predetermined limit value.

6. Method according to one of the preceding claims, wherein when the gas valve (5) is closed, a plausibility check of the ratio R(t) and / or the virtual combustion air ratio λ(V) (t) is carried out by performing the following steps: a1) Recording a volume flow of combustion airV̇Air(t0) (17) supplied to the burner (3) before the gas valve (5) of the heating appliance (1) is closed at a time tP0, b1) Recording the volume flow of combustion airV̇Air(t) (17) after closing the gas valve (5) at a time t, c1) Determining a ratio RP(t) with - RP t = Vm . Air t P 0 V ˙ Air t 7. Method according to claims 4 to 6, wherein when the reference range is left or the limit value is undershot or exceeded by the ratio R(t) and / or the virtual combustion air ratio λ(V) (t), the volume flow of combustion gas V̇Gas (18) is adjusted and / or commissioning of the heating appliance (1) is cancelled.

8. Method according to one of the preceding claims, wherein after an unsuccessful or cancelled start-up of the heating appliance (1), the volume flow of fuel gasV̇Gas (18) is adjusted during a subsequent start-up.

9. Method according to claim 7 or 8, wherein, when a predetermined maximum number of start-ups is reached, λ(V) (t) is determined in step d) when the virtual combustion air ratio leaves the reference range or falls below or exceeds the limit value, information on this is displayed in step f), made available for retrieval via a network (16) or sent as a message and / or the heating appliance (1) is placed in an error state in which renewed start-up is blocked.

10. A regulating and control device (7) for a heating appliance (1), wherein the regulating and control device (7) is arranged to cause the heating appliance (1) to carry out a method according to any one of claims 1 to 9.

11. A heating appliance (1) comprising a conveying device (2) and a mass flow sensor (12) for detecting a supplied volume flow of combustion airV̇Air(t) (17) and a regulating and control device (7) arranged to cause the heating appliance (1) to perform a method according to any one of claims 1 to 9.

12. A computer program comprising instructions which, when executed by the regulation and control device (7) of a heating appliance (1) according to claim 11, cause the heating appliance (1) to perform the method steps of a method according to any one of claims 1 to 9.

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