Method for operating at least one, in particular gas adaptive, combustion appliance

Abstract

The invention relates to a method for operating at least one, in particular gas adaptive, combustion appliance, wherein the method comprises the following steps: receiving a throttle element position of a throttle unit of the combustion appliance for controlling a fuel flow rate to a burner and / or a fuel valve setting of a fuel valve of the combustion appliance for controlling a fuel flow rate to a or the burner, determining a value that characterizes the calorific value of the fuel combusted by the combustion appliance from the combustion appliance, wherein the determination is dependent on the received throttle element position and / or the fuel valve setting, controlling an air flow rate to be supplied to the burner of the combustion appliance and / or the fuel flow rate to be combusted in the burner of the combustion appliance dependent on the determined value.

Description

[0001] 20.06.2025

[0002] 1

[0003] Method for operating at least one, in particular gas adaptive, combustion appliance

[0004] The invention relates to a method for operating at least one, in particular gas adaptive, combustion appliance. Additionally, the invention relates to a data processing device comprising means for carrying out the method, a computer program product, computer readable data carrier and a data carrier signal. In addition, the invention relates to a combustion appliance with such a data processing device.

[0005] Gas adaptive combustion appliances, such as gas adaptive boilers are known from the prior art. Such kind of combustion appliances, such as gas adaptive can be adapted to different fuel gas types.

[0006] Gas adaptive combustion appliances were developed to address the broad Wobbe value changes of the fuel supply in Europe and were introduced in 2001. The known gas adaptive combustion appliances are fully premixed appliances equipped with an Adaptive Combustion Control Function (ACCF) that are intended to be connected to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance including gas grids for natural gases of the second family where up to 20 mol% H2 is added to the natural gas. Gas adaptive combustion uses at least one sensor signal to adjust the air fuel mixture to maintain a preset value, such as an ionization signal or an 02 signal. The gas adaptive combustion appliance control uses the respective signal and, by controlling the blower and gas valve via for example using a pulse-width modulation (PWM) signal, adjusts the amount of air and gas entering the burner until it the desired value is reached. The gas adaptive combustion allows constant combustion monitoring for optimal efficiency. In addition, there is a scheduled calibration period which occurs based on run time cycles that confirms the system is operating within predetermined specifications.20.06.2025

[0007] 2

[0008] Usually, the boiler consists of a fan for modulating the boiler power and a fuel gas valve which controls the air to fuel ratio. The fuel gas valve can be adjusted manually to set air to fuel ratio at low load. On the fuel gas valve, a motor driven throttle is located which can electronically adjust the flow through a throttle opening right behind the fuel gas valve opening and adjusts the air to fuel ratio. In a gas adaptive combustion appliance, such as a boiler, the gas adaptive combustion appliance controls the throttle position and thus the throttle opening by controlling the throttle motor to get a desired air to fuel ratio. This ratio is measured with an oxygen sensor in the flue gas. Gas adaptive combustion appliances utilize the relationship between the 02 signal and the air-fuel ratio (also known as lambda A). Gas adaptive combustion appliances have a relationship between 02 and power that can be expressed by an 02 - power curve. At every firing rate, there is a flame ionization value that corresponds to the target lambda (A = 1.3 in figure below, indicating -30% excess air). Once defined, the flame ionization curve is used as a target setpoint to control the gas valve. When the 02 signal is lower than expected (high signal indicates low 02, or rich condition), the control decreases gas valve position to return to A = 1.3. Similarly, when 02 signal is higher than expected (indicating excess air too high, or lean condition), the control increases gas valve position to return to A = 1.3.

[0009] Gas adaptive combustion appliances commonly periodically calibrate to compensate for effects like combustion air temperature / humidity variation, component wear, and fuel composition. Calibration is commonly automatically initiated upon a boiler start several times per month based on an internal counter. When a calibration is required and demand is present, the gas adaptive combustion appliance starts and runs at a constant mid-range firing rate. As an example, the gas valve is opened until lambda equals 1 and a maximum ionization value is reached. This value is then used to shift the ionization setpoint curve. Following this phase, the gas adaptive combustion appliance ramps to low fire and calibrates the minimum opening point of the gas valve. The entire calibration sequence lasts about20.06.2025

[0010] 3

[0011] one minute. In case of using the 02 signal, calibration is done by purging and setting the measured value of 02 related to the 21 % 02 of ambient air.

[0012] Ignitions are more reliable with gas-adaptive combustion appliances compared to systems with pneumatic gas / air ratio control where the gas supply rate is pneumatically driven by the air supply rate or vice versa (definition 3.1.201.22 EN 12067-2:2022, 3.117). Gas adaptive ignitions can for example begin with the gas valve opening to a fixed point followed by an automatic ramp up until a flame is detected. This feature assures the system will always light at the proper air-fuel ratio. In contrast, pneumatic gas valves open to the same fixed point at every ignition, which is only changed by a manual adjustment of the gas valve or by changing the fan speed to increase ignition load. This can lead to light-off issues such as noise or ignition failure over time.

[0013] A gas adaptive boiler can be crucial due to the uncertainty in the quality of the future fuel gas supply. Both due to the ban of importing fuel gas from specific countries as well as alternative sources like biogas, with a gas adaptive boiler, the boiler is able to adapt its setting for different gas qualities in order to assure safe and stable operation.

[0014] Due to change in gas quality or change between gas families, an obtained burner load will differ, wherein the burner load depends on fuel gas flow, which is supplied to the burner. Said burner load change can result in overload of the combustion appliance or a reduced burner load. The burner load is specified on the data plate of the boiler.

[0015] Currently, the gas quality and / or gas family is considered by the installer. Specifically, for pneumatic combustion appliances, in particular boilers, the installer predefines a fan speed setting for different gas types and / or gas families. Additionally or alternatively it is possible that the installer manually adjusts the gas valve and / or a throttle unit setting dependent on the gas type and / or gas family. Further, it is20.06.2025

[0016] 4

[0017] possible that the installer selects a gas family during commissioning and with that selection the control unit of the combustion appliance selects the fan speed or fan speeds corresponding to the gas type and / or gas family.

[0018] The known approaches have the disadvantage that a manual action is required to select the gas type and / or change of fan speed, which could result in mistakes. Additionally, the corrections are only determined for a pre-selected gas type and since the correction is done at commissioning the gas quality change over time will not be automatically corrected.

[0019] For commercial use it is common to place multiple boilers in a cascade. These boilers are controlled using a cascade controller. This controller determines, based on the heat demand which boiler or boilers within the cascade should become operational. Over a time period it can happen that one of the boilers is standing still for a longer period. If during this period the gas quality is changed drastically, for example the Wobbe value changes by 3 MJ / m3, the boiler could face start issues or the safe and stable operation could be compromised.

[0020] The object of the invention is to provide a method for operating at least one combustion appliance which can be ignited and operated in a safe and stable manner even though the fuel gas quality changes.

[0021] The object is solved by a method for operating at least one, in particular gas adaptive, combustion appliance, wherein the method comprises the following steps:

[0022] receiving a throttle element position of a throttle unit of the combustion appliance for controlling a fuel flow rate to a burner and / or a fuel valve setting of a fuel valve of the combustion appliance for controlling a fuel flow rate to a or the burner,

[0023] determining a value that characterizes the calorific value of the fuel combusted by the combustion appliance from the combustion appliance, wherein20.06.2025

[0024] 5

[0025] the determination is dependent on the received throttle element position and / or the fuel valve setting,

[0026] controlling an air flow rate to be supplied to the burner of the combustion appliance and / orthe fuel flow rate to be combusted in the burnerof the combustion appliance dependent on the determined value.

[0027] According to the invention it is realized that the effect of fuel gas quality change can be taken into account by controlling an air flow rate and / or the fuel flow rate dependent on the determined value. In the end, it can be achieved that independent on the fuel gas quality the burner load does not change or changes less than in the known combustion appliances. Controlling the air flow rate and / or the fuel flow rate has the advantage that ignition issues can be avoided and a safe and stable operation of the combustion appliance is possible. A further advantage is that the fuel gas quality can be automatically considered during the operation without the need for an installer.

[0028] According to an aspect of the invention a combustion appliance is provided. The combustion appliance comprises

[0029] a fan for controlling an air flow,

[0030] a fuel valve, in particular fuel gas valve, for controlling a fuel flow, in particular fuel gas flow,

[0031] a burner for combusting an air and fuel mixture,

[0032] a throttle unit, for controlling the fuel flow, and

[0033] a data processing device comprising means for carrying out an inventive method.

[0034] A combustion appliance is a device designed to burn a fuel source in a controlled manner for the purpose of producing heat. This device typically comprises a combustion chamber where the combustion reaction occurs and means for conveying air and fuel, in particular fuel gas, into this chamber. The air and fuel, in particular fuel gas, can mix before the combustion chamber or inside the20.06.2025

[0035] 6

[0036] combustion chamber. The appliance may also include at least one heat exchanger for transferring the heat generated during combustion to a liquid or air, thereby converting the energy from the combustion process into usable heat. The combustion appliance may be designed to burn various types of fuels, including but not limited to natural gas, propane, oil, hydrogen, biogas, or solid fuels such as wood or pellets. A combustion appliance can be a boiler, space heater, oven, ora gas water heater.

[0037] An operation mode is a mode of the combustion appliance which is present after a commissioning mode is finalized. The operation mode can include an ignition phase, in which the combustion appliance is ignited, and a heating phase, in which the combustion appliance provides heat to be used by at least one consumer. Additionally, the operation mode can comprise a switch-off phase, in which the combustion appliance is switched off so that the combustion appliance for example can be maintained.

[0038] In the operation mode the parameters determined and set in the commissioning mode are used to operate the combustion appliance. Additionally, in particular merely, in the operation mode, in particular in the heating phase of the operation mode, the outputted heat of the combustion appliance is used in different kind of applications like for central heating and / or domestic water heating. Further application fields of the combustion appliance can be to provide process heating. Process heating is used in commercial use for industrial processes that needs heat. In said case a constant heat output has to be provided. In the ignition phase of the operation mode the air and fuel gas mixtures is ignited in the combustion chamber on the burner surface by the ignition electrode.

[0039] The combustion appliance can be in a standby mode in which the combustion appliance is switched on but the burner is networking. Alternatively, the combustion appliance can be in commissioning or in an operation mode in which it has a specific power output. At normal operation the boiler sets its power output by modulation.20.06.2025

[0040] 7

[0041] Controlling the combustion appliance covers all different modes, including the phases that can occur during the respective mode.

[0042] In the application a commissioning mode of a combustion appliance is a mode in which the components and / or components of the combustion appliance are set so that the combustion appliance can be operated in the operation mode. The commissioning mode can comprise an ignition phase. During the commissioning mode automatic or manual adjustments can be made to components. Specifically, the combustion appliance enables two adjustment possibilities. One possibility is to adjust the throttle unit by means of which the fuel flow is controlled. This can happen automatically by a throttle element that is adjusted by a throttle motor. Another possibility is to adjust the fuel valve setting. This can happen manually by manually adjusting an offset element of the fuel valve, namely an offset screw. Specifically, parameters can be determined in the commissioning mode that are used in the operation mode of the combustion appliance. In the present application, flue gas oxygen values are determined during the commissioning mode and stored in a memory of the combustion appliance. Said flue gas oxygen values are used for the operation of the combustion appliance in the operation mode. A control unit of the combustion appliance switches from the commissioning mode to the operation mode after all relevant parameters and / or components are determined and / or set.

[0043] The value characterizes the calorific value of the fuel to be combusted by at least one of the combustion appliance. Said value can be the calorific value or a Wobbe value of the fuel that is combusted by the combustion appliance. A calorific value represents the amount of energy released when a specific quantity of a substance is completely burned.

[0044] The Wobbe value is an indicator of the interchangeability of fuel gases. It is used to compare the combustion energy output of different composition fuel gases in an appliance. If two fuels have identical Wobbe values, then for given pressure and20.06.2025

[0045] 8

[0046] valve settings, the energy output will also be identical or will be considered as identical.

[0047] The gross Wobbe index or value is defined as the volume-basis gross calorific value, at specified reference conditions, divided by the square root of the relative density at the same specified metering reference conditions. In common usage, and in the absence of any other qualifier, the term Wobbe index is taken to mean the quantity that is identified here as gross Wobbe index or value (Definition 3.5 ISO 6976:2016).

[0048] The net Wobbe index or value is the volume-basis net calorific value, at specified reference conditions, divided by the square root of the relative density at the same specified metering reference conditions (Definition 3.6 ISO 6976:2016). Both Wobbe indices can be used for the purpose of comparison, as long as the same type of index is used for the respective comparison.

[0049] The Wobbe index or value can be expressed in MJ / Nm3accordingto ISO 13443:1996.

[0050] A failure state of the combustion appliance is a combustion appliance state in which a combustion appliance component malfunctions so that the combustion appliance does not operate as expected. Additionally or alternatively a combustion appliance failure state is a state in which inadequate conditions, e.g. insufficient fuel or air, are present so that the burner does not start and thus the combustion appliance does not operate as expected. Further, the ignition can be loud and rough due to suboptimal incomplete combustion conditions in a failure state of the combustion appliance. Thus, a failure state covers a failed ignition or no ignition. For the case that a failure state is determined, a combustion appliance ignition phase, or the operation mode of the combustion appliance is aborted and / or the combustion appliance can be blocked. Further, a failure state can be present when the measured air to fuel gas mixture does not correspond to the expected air to fuel gas mixture so that the combustion appliance does not operate as expected. Another advantage20.06.2025

[0051] 9

[0052] of the invention is that by considering the oxygen value a commissioning time in case of ignition failure is reduced.

[0053] A failure free state of the combustion appliance is a combustion appliance state in which the combustion appliance operates as expected.

[0054] As mentioned above the determined value can be a Wobbe value or a calorific value. The value can be determined when the combustion appliance is in an operation mode. Thus, fuel quality changes during the operation of the combustion appliance can be considered. The air flow rate can be an air mass flow rate or air volume flow rate. The fuel flow rate can be a fuel mass flow rate or fuel volume flow rate.

[0055] According to an embodiment the air flow rate can be controlled by controlling a fan of the combustion appliance. Specifically, the fan of the combustion appliance can be controlled dependent on the determined value. The fan can be controlled by controlling a fan speed to set the air flow rate. The fan can be modulated in a modulation range delimited by fan speed parameters.

[0056] The fan speed parameters can be a minimum fan speed and a maximum fan speed. The minimum fan speed is the fan speed at which the fan must be operated at minimum. The maximum fan speed can be the fan speed at which the fan can be operated at maximum, which is limited by the fan motor power . Alternatively or additionally, the "maximum fan speed" can be the maximum fan speed when a central heating demand is existent or the maximum fan speed when a hot water domestic demand is existent.

[0057] The fan speed can be assigned to a burner load percentage, wherein the burner load percentage is 0% at the minimum fan speed and 100% at the maximum fan speed. The maximum fan speed can be the maximum fan speed that is limited by the fan motor power or the maximum fan speed at which the fan can be operated when a central heating demand is existent or a maximum fan speed with which the fan can20.06.2025

[0058] 10

[0059] be operated when a domestic hot water demand is existent. By knowing the needed burner load, in particular burner load percentage, the fan speed to be set can be determined.

[0060] The fan speed can be calculated according to the following formulas:

[0061] Fan speed = Modulation range * Requested power setpoint + Minimum fan speed

[0062] Modulation range = maximum fan speed - minimum fan speed

[0063] The "requested power setpoint" is determined by a data processing device so that the combustion appliance can provide a target heat output or the burner can provide a target heat output. The "minimum fan speed" is the minimum fan speed according at which the fan can be operated. The "maximum fan speed" is the maximum fan speed at which the fan can be operated. Alternatively the "maximum fan speed" can be the maximum fan speed when a central heating demand or a domestic hot water demand is existent.

[0064] The at least one fan speed parameter can be dependent on the determined value, in particular Wobbe value or calorific value. The fan speed parameters can be stored in a data memory. Specifically, fan speed parameters that are dependent on the determined value can be stored in the data memory.

[0065] Thus, one or more fan speed parameters, in particular the minimum and / or maximum value, can change when the determined value changes. With "maximum value" it is meant the maximum value of the fan speed at which the fan can be operated or the maximum value of the fan speed at which the fan speed can be operated when a central heating demand or a domestic hot water demand is existent.20.06.2025

[0066] 11

[0067] This results in that the modulation range of the fan is dependent on the determined value. Thus, for the same burner load, the fan speed can differ for different determined values because different determined values can result in different modulation ranges of the fan. The minimum and / or maximum fan speed and the determined value can be assigned to each other by means of a table or a function. Thus, by knowing the determined value the assigned minimum and / or maximum fan speed and therefore the modulation range of the fan is known.

[0068] The data processing device can determine the value that characterizes the calorific value of the fuel combusted by the combustion appliance on the basis of the throttle element position. This is possible because the value is assigned to a throttle element position. In other words, different throttle element positions are assigned to a respective value, respectively. Thus, the value that corresponds to a throttle element position can be easily determined. The value and the throttle element position can be assigned to each other by means of a table or a function.

[0069] As is explained below more in detail, the throttle element position depends on a measured oxygen value, in particular flue gas oxygen value. That means, that the throttle element position can be set such that the oxygen value, in particular flue gas oxygen value fulfills a condition, in particular that the oxygen value is in a predetermined range. Thus, by measuring the oxygen value, in particular the flue gas oxygen value, and determining the throttle element position it is possible to determine the fuel gas quality.

[0070] The value that characterizes the calorific value of the fuel combusted by the combustion appliance can be determined when the throttle element position fulfills a condition. The condition can be time dependent. Specifically, the condition can be that the throttle element position does not change or changes within a predetermined range during a predetermined time. Thus, processing power can be saved.20.06.2025

[0071] 12

[0072] The fuel flow rate can be changed by controlling the throttle unit and / or the fuel valve setting dependent on the received value. Specifically, an opening of the fuel valve and / or a throttle element position of the throttle unit can be controlled to set a fuel flow rate. The air flow rate and / or fuel flow rate can be controlled such that a target burner load is achieved. Thus, it can be ensured by controlling the air flow rate and / or the fuel flow rate dependent on the determined value or the received throttle element position that the burner load does not significantly change independent on whether the fuel gas quality changes.

[0073] The fuel valve and / or the throttle unit can be controlled dependent on the determined value because the fuel valve setting, in particular an opening of the fuel valve, and / or the throttle element position is assigned to the determined value characterizing the calorific value of the fuel to be combusted. Additionally or alternatively, it is possible to control the fuel flow rate by a time duration during which the fuel valve and / or throttle element position is kept in a specific position. In the end the fuel flow and air flow can be easily adjusted to a target fuel flow rate and / or a target air flow rate that is needed to achieve the target burner load.

[0074] According to an embodiment several combustion appliances, which are connected to each other in cascade, can be operated, wherein one or more combustion appliances determine the value that characterizes the calorific value of the fuel to be combusted. The value is determined in a manner as described above. A control value can be determined on the basis of the received value. The combustion appliances can be controlled dependent on the received value. Thus, it is ensured that independent of the fuel gas quality the burner load of each of the combustion applications does not change or changes less than in known combustion appliances.

[0075] The determination of the control value can be done when the combustion appliance is operated in the commissioning mode and / or when the combustion appliance is operated in the operation mode. In both modes the combustion appliance can be controlled on the determined at least one control value, in particular Wobbe value.20.06.2025

[0076] 13

[0077] A data processing device that is assigned to the combustion appliance can determine the at least one control value, in particular Wobbe value, that is used for the control of the combustion appliance. In said case the data processing device is the master data processing device. The master data processing device can determine the control value on the basis of the determined or received at least one value that characterizes the calorific value of the fuel combusted by the combustion appliance. Additionally or alternatively, the data processing device that is assigned to the combustion appliance can receive the control value from a master data processing device and control the combustion appliance on the received control value, in particular Wobbe value.

[0078] According to an embodiment a non-operating combustion appliance can determine whether a control value is present before the combustion appliance is ignited. Specifically, a data processing device of the non-operating combustion appliance can establish a communication with a master data processing device to request whether a control value is present. If a control value is present, the operating mode of said combustion appliance can be controlled by using said control value. In particular, the ignition phase and / or heating phase of said combustion appliance can be controlled by using said control value. Thus, the newly operated combustion appliance receives all relevant information that it needs for a smooth ignition and / or operation.

[0079] The master data processing device can determine that the received or determined value is the control value. This case can happen, when only one combustion appliance is operating and a cascade control unit instructs another non-operating combustion appliance to start.

[0080] The master data processing device can receive several values, in particular Wobbe values, that characterize the calorific value of the fuel combusted by the combustion appliances. Further, the master data processing device can determine a variation of20.06.2025

[0081] 14

[0082] the received values and can determine that the control value corresponds to said variation. The combustion appliances are controlled dependent on said variation. The data processing device that is assigned to the combustion appliance can determine the value variation and / or can receive a value variation from a master data processing device.

[0083] Thus, controlling the combustion appliance dependent on the determined at least one control value, in particular Wobbe value, also means that the combustion appliance can be directly controlled on the determined or received control value, in particular Wobbe value. In said case the control value is not processed and the combustion appliance is controlled dependent on the determined or received control value. Alternatively, the control of the combustion appliance dependent on the determined control value also covers an indirect control of the combustion appliance dependent on the determined control value. In said case the determined control value is further processed to determine the value variation. The combustion appliance is directly controlled dependent on the value variation and thus indirectly controlled on the value, in particular Wobbe value.

[0084] The fuel valve, in particular the fuel gas valve, can be a pneumatic valve, in particular a pneumatic gas valve. The fuel valve, in particular the fuel gas valve, can also be a controllable pneumatic valve, or a stepper valve, or a modulator valve. In said fuel valve the fuel flow automatically changes when an air flow changes due to e.g. a different fan speed. The fuel gas valve can be arranged downstream a fuel gas source and upstream the throttle unit, in particular the throttle element. The data processing device can be data connected with the throttle unit. Additionally or alternatively the throttle unit can be attached on the fuel gas valve. Thus, a compact unit comprising the fuel gas valve and the throttle unit is provided.

[0085] The modulator valve, or modulating valve is a control valve that can be fully open, fully closed, or in-between open and closed allowing a partial flow. The modulator valve is automated with an electrical actuator in combination with the fuel valve. The20.06.2025

[0086] 15

[0087] electrical actuator is configured to carryout modulating control, often referred to as a digital positioning system. The electrical actuator is thus able to accurately position the fuel valve anywhere between the fully open and the fully closed position. Typically, modulation is achieved using a control loop system and a positioning circuit board placed in the actuator. The actuator using a feedback system to give feedback on the fuel valve's position to an operator. The modulation is achieved by comparingthe input position (desired position)to the physical position ofthe output shaft (actual position). The output shaft's location is fed back to the positioning circuit board by a potentiometer that is driven by the output shaft. The positioning circuit board then compares the two positions, and if there is a difference it considers this an 'error'. To correct the error, the control unit will operate the modulator valve until it reaches the desired position. The control signals are typically either 0-10 V DC or 4-20 mA. A 0 V DC or 4 mA signal completely closes the fuel valve while a 10 V DC or 20 mA completely open the fuel valve. Any signal between these would cause a corresponding partially opened or closed position. An example would be a 6mA signal that would result in a 12° turn.

[0088] The stepper valve comprises a stepper motor, also known as step motor or stepping motor, which is an electrical motor that rotates in a series of small angular steps. The stepper motor thus divides a full revolution into a number of equidistant steps. The stepper motor consists of several "toothed" electromagnets arranged as a stator around a central rotor. These electromagnets are activated by an external driver circuit or a microcontroller. Each step rotates the shaft through a fixed angle. The circular arrangement of electromagnets is divided into groups referred to as phases. A stepper motor can be precisely rotated through a specific angle by activating the electromagnets one after the other.

[0089] The controllable pneumatic valve is a valve wherein a fluid flow rate is controlled by varying the size of the flow passage via a restrictor. In an automatic control valve, the restrictor is directed by a signal from an actuator.20.06.2025

[0090] 16

[0091] Typical examples of controllable pneumatic valves are solenoid valves, in particular proportional solenoid valves. The proportional control solenoid valve utilizes a solenoid as an actuator for variable valve positioning. In a normally closed solenoid control valve, with zero current fed to the coil, the spring pushes the plunger downwards to a fully closed position. Applying current to the coil generates a magnetic field to move the plunger upward against the return spring. At 100% duty cycle, power is fully fed to the solenoid and the solenoid valve is completely open. The term duty cycle describes the proportion of on time to the cycle duration interval in a pulse-width modulation for controlling a load. Pulse-width modulation in other words is a method of controlling the average power or amplitude delivered by an electrical signal. A low duty cycle corresponds to low power, because the power is off for most ofthetime. Duty cycle is expressed in percent, with 100% being fully on. Duty cycles between 0 to 100 percent range proportionally change the flow of the valve. For example, a duty cycle of 50% fed to the solenoid moves the spring and the plunger to 50% of the operating range.

[0092] The combustion appliance can comprise a mixture device in which the fuel and the air are mixed before the mixture enters the combustion chamber of the combustion appliance. In an alternative embodiment the fuel and air are not mixed before the combustion chamber but in the combustion chamber.

[0093] The oxygen value, in particular a flue gas oxygen value, can be measured by an oxygen sensor. The oxygen sensor can measure the partial oxygen pressure and uses this to determine the oxygen concentration in the gas to be measured, wherein the measured concentration can be outputted. Specifically, the oxygen sensor can measure the oxygen volume percentage of oxygen in the gas being analyzed. The oxygen sensor can be an unheated or a heated oxygen sensor, or a paramagnetic sensor. Alternatively, the oxygen sensor can be a fast light off oxygen sensor or planar sensor, which uses layers of zirconia and alumina bonded together to allow a much faster warm up. The oxygen sensor can also be air fuel ratio and wideband sensors. A heated oxygen sensor can comprise or be thermally connected to an20.06.2025

[0094] 17

[0095] electrical heating element. The electrical heating element may be operable to heat the heated oxygen sensor in dependent on a heating signal, allowing to operate the electrical heating element to heat or not heat the oxygen sensor. The heating element can be a wire and / or resistor that provides heat when it is energized. The oxygen sensor can cooperate with an electrical heating element which is thermally connected to the sensing element of the oxygen sensor. The electrical heating element may be operable to heat the sensing element of the oxygen sensor in dependent on a heating signal, allowing to operate the electrical heating element to heat or not heat the sensing element of the oxygen sensor.

[0096] The oxygen sensor can be arranged downstream or upstream the burner. Specifically, the oxygen sensor can be arranged in the combustion chamber or an exhaust flue path or an air flow path. Thus, the oxygen sensor can easily measure the flue gas oxygen value and / or can quickly respond to oxygen value changes in the combustion chamber. The oxygen sensor can be heated and calibrated before the oxygen sensor can be used. The data processing device initiates the oxygen sensor heating and calibration. The oxygen sensor can measure the oxygen value of a non-combusted gas, for example of the air and fuel gas mixture or air alone if no fuel is inserted can be measured. In this case the oxygen value can be measured in the combustion chamber before the burner combusts the air and fuel gas mixture and / or in a part of the gas flow path being upstream of the combustion chamber in which the gas mixture comprising air and fuel gas flows.

[0097] The throttle unit can be located downstream of the fuel valve, wherein the data processing device is connected with the throttle unit, in particular a throttle motor. In this case the throttle unit can be attached on the fuel valve. Alternatively, the throttle unit can be arranged inside the fuel valve.

[0098] The throttle unit can be arranged fluidically downstream the fuel valve. Fluidically downstream means that the throttle unit as a hole component is arranged outside the fuel valve, in particular the fuel gas valve, and adjacent to the fuel valve.20.06.2025

[0099] 18

[0100] Alternatively, fluidically downstream means that at least a part of the throttle unit, in particular the throttle element, can be arranged inside the fuel valve, in particular the fuel gas valve. However, said throttle element is arranged inside the fuel valve such that it receives the fuel, in particular the fuel gas, that passed a valve element of the fuel valve, in particular the fuel gas valve.

[0101] The throttle unit comprises a throttle element for controlling a throttle opening cross section through which the fuel gas flows. The throttle unit has the advantage that the fuel gas flow coming from the fuel gas valve can be controlled independent of the fan speed so that it is possible to remain the measured oxygen value on a constant level. The data processing device can control the throttle unit and / or the fan and / or the fuel valve dependent on the measured at least one oxygen value. Specifically, the data processing device can control the throttle unit and / or the fan and / or the fuel valve that the measured oxygen value is within a predetermined range.

[0102] The provision of the throttle unit has the advantage that the data processing device can solve some failure types automatically by adjusting the position of the throttle element. An adjustment of the throttle element results in a change in fuel gas flow resulting in a different air to fuel gas mixture. The position of the throttle element can be adjusted several times. Specifically, the position of the throttle element can be adjusted such that the measured oxygen value, in particular fuel gas oxygen value, is between the lower and the upper threshold. The adjustment of the position of the throttle element is necessary to adapt the combustion appliance to changes in a fuel gas type quality. Likewise, to the adjustment of the throttle unit, the fuel valve can be adjusted such that the measured oxygen value, in particular fuel gas oxygen value, is between the lower and the upper threshold.

[0103] As mentioned above a system can be provided that comprises several combustion appliances. Said several combustion appliances can be connected to each other in cascade. Cascade systems linkup multiple combustion appliances, allowingthem to20.06.2025

[0104] 19

[0105] work in sync to provide heat. A cascade system is generally made up of between two and six combustion appliances, with the number of appliances determined by the heat output that's needed. The combustion appliances can be connected in series or parallel to each other. Such an arrangement of combustion appliances has the advantage that the system can satisfy a wide range of heat demands. In particular, it is not necessary to operate all combustion appliances the whole time but the number of combustion appliances can be operated that are needed to satisfy the heat demand. The system can also be configured as a hybrid system, which comprises at least one other heat source, in particular a heat pump, in addition to the several combustion appliances.

[0106] The system can comprise a master data processing device. The master data processing device determines the number of combustion appliances and / or the combustion appliances that are needed to satisfy the heat demand request. Thereto, the master data processing device can determine the heat output to be provided by each of the combustion appliances. It is possible that the master data processing device determines that the heat output of the combustion appliances is different for each combustion appliance. Each of the, in particular operating, combustion appliances can determine a value that characterizes the calorific value of the fuel combusted by the combustion appliance.

[0107] Additionally, each of the combustion appliances transmits the determined value, in particular Wobbe value, to the master data processing device. The master data processing device receives said values, in particular Wobbe values, and determines the control value, in particular Wobbe value, that shall be used to control the combustion appliances.

[0108] The data processing device can receive the determined value from one or more combustion appliances. Said combustion appliance can be at least one other combustion appliance in which a data processing device is determining the value of the combustion appliance that is assigned to said data processing device.20.06.2025

[0109] 20

[0110] Alternatively, the combustion appliance can be the combustion appliance to which the master data processing device is assigned. In said case the master data processing device receives said value by conducting internal calculations.

[0111] The master data processing device can transmit said determined control value, in particular Wobbe value, to at least one of the combustion appliances. In particular, the master data processing device can transmit the control, in particular Wobbe, value to all of the combustion appliances. The combustion appliances are controlled dependent on the control value, in particular Wobbe value, determined by the master data processing device. Specifically, the master data processing device can transmit the control value, in particular Wobbe value, to the data processing device of the respective combustion appliance. Said data processing device can control the combustion appliance dependent on the received control value, in particular Wobbe value.

[0112] The master data processing device can be a device that is separate from the data processing devices that are assigned to the combustion appliances. For example, the data processing device may be a cascade controller or be comprised in a cascade controller. Alternatively it is possible that the master data processing device corresponds to a data processing device that is assigned to a combustion appliance. In said case the master data processing device controls the combustion appliance dependent on the determined control value, in particular Wobbe value. Additionally, said master data processing device transmits the determined control value, in particular Wobbe value, to the remaining data processing devices that are assigned to the combustion appliances. As mentioned before the "determined control value, in particular Wobbe value" corresponds to the control value, in particular Wobbe value, that the master processing devices determines after it receives all values, in particular Wobbe values, from the combustion appliances. In other words, the "determined control value, in particular Wobbe value" is the control value, in particular Wobbe value, that is used to control the combustion appliances. The master data processing device can alternatively be a building management20.06.2025

[0113] 21

[0114] controller or a cloud base controller or can communicate with one of said controllers. The master data processing device can communicate with a cascade controller of the system comprising several combustion appliances.

[0115] Distributing the control value, in particular Wobbe value, to all combustion appliances has the advantage that a smooth start of a combustion appliance being in the standby mode is possible. The combustion appliance parameters of said combustion appliance being in the standby mode are not the best if said parameters are determined for a fuel gas having a different quality than the fuel gas that is currently combusted. Thus, sending the control value, in particular Wobbe value, to the combustion appliances ensures that the combustion appliances can be started without any issues and ensures that the combustion appliances can be operated stable and safe. This is possible as the value, in particular Wobbe value, of said combustion appliance that has not been operated for a certain amount of time is updated by the transmitted control value, in particular Wobbe value, that is consistent with the detected fuel gas quality.

[0116] A data processing device is assigned to a combustion appliance when the data processing device controls the parameters, e.g. burner parameters, for igniting the combustion appliances and controls the parameters, e.g. air to fuel gas ratio, when the combustion appliance is operated in the operation mode.

[0117] The master data processing device can transmit the value, in particular Wobbe value, that is determined or received for the latest operated combustion appliance as the control value to at least one combustion appliance. This is advantageous because then all combustion appliances that receive said control value, in particular Wobbe value, are controlled dependent on the calorific value characterizing value, in particular Wobbe value, that is consistent with the latest fuel gas quality.

[0118] According to an embodiment at least one ignition parameter of a non-operating combustion appliance or at least one parameter of an operating combustion20.06.2025

[0119] 22

[0120] appliance can be adjusted dependent on the control value, in particular Wobbe value determined for the, in particular latest operated, combustion appliance.

[0121] "Non-operating" combustion appliance also comprises a combustion appliance being in a standby mode. The parameter to be adjusted can be a throttle opening cross section of a throttle unit of the combustion appliance. By adjusting the throttle opening cross section the fuel gas flow is adjusted that flows into a combustion chamber of the combustion appliance. Furthermore, a fan speed and / or a gas valve opening can be adjusted. The fuel valve is a valve that is arranged upstream of the throttle unit when it is referred to the fuel gas flow.

[0122] According to an embodiment the value, in particular Wobbe value, can be determined by using a value, in particular Wobbe, table in which values, in particular Wobbe values, are assigned to throttle element positions. Said table can be used when the combustion appliance is operating or is non-operating.

[0123] For the case that the combustion appliance is non-operating, the value, in particular Wobbe value, determination comprises the step to check whether a flame is present and to determine a throttle element position when no flame is detected. For the case that no flame is detected, the throttle position is changed. The throttle element can be changed until a flame is detected. Then the value, in particular Wobbe value, of the fuel gas supplied to the combustion appliance corresponds to the value, in particular Wobbe value, that is assigned to the throttle element position. As mentioned above, the value, in particular Wobbe, table comprises said information. The determination of the value, in particular Wobbe value, of the fuel gas is started with a minimum throttle element position. If no flame is detected, the throttle opening cross section is increased until a flame is detected. Alternatively, the value, in particular Wobbe value, can be determined when the throttle element is not in a minimum position during operation or commissioning mode of the combustion appliance. Dependent on whether a flame is detected or not, controlling can take place to the correct calorific value characterizing value, in particular Wobbe value.20.06.2025

[0124] 23

[0125] For the case that the combustion appliance is operating, the value, in particular Wobbe value, can be determined as follows. The data processing device can determine the throttle element position. Additionally, the data processing device can determine the value, in particular Wobbe value, that is assigned to the determined throttle element position from the aforementioned value, in particular Wobbe, table.

[0126] Additionally, the determination of the value, in particular Wobbe value, can depend on a measured oxygen value, in particular a flue gas oxygen value. Considering the flue gas oxygen value increases the accuracy of the value, in particular Wobbe value, determination. The value, in particular Wobbe, determination can be aborted when the measured flue gas oxygen value does not fulfil a condition, in particular does not comprise a value that is arranged within a predetermined range. The range can be between 8% and 20% oxygen concentration in the gas that is measured. If the measured flue gas oxygen value fulfills the condition, the throttle element position is changed, and it is determined again whether a flame is present. The test whether the condition is fulfilled can be performed when no flame is detected. Thereto, the combustion appliance can comprise a flame detector.

[0127] According to an aspect of the invention a data processing device comprising means for carrying out an inventive method is provided. The data processing device determines or receives the Wobbe value. The data processing device can be the master data processing device. The data processing device can comprise at least one processor or be a processor. The data processing device can be part of a printed circuit board, in particular a printed circuit board assembly. The processor can have an internal memory.

[0128] Additionally, a computer program product is provided, which, when the program is executed by a computer, in particular a data processing unit, cause the computer, in particular the data processing unit, to carry out the inventive method.20.06.2025

[0129] 24

[0130] Furthermore, a computer readable data carrier having stored thereon the computer program product or data carrier signal carrying the computer program product is provided.

[0131] In the figures, the subject-matter of the invention is schematically shown, wherein identical or similarly acting elements are usually provided with the same reference signs.

[0132] Figure 1 an overview of a combustion appliance according to the invention. Figure 2 a structure of a data processing device.

[0133] Figure 3 a flow chart of an operation method executed by the data processing device according to a first embodiment.

[0134] Figure 3a a flow chart of an operation method executed by the data processing device according to a second embodiment.

[0135] Figure 4 a method for determining a throttle element position according to the first embodiment.

[0136] Figure 4a a method for determining a throttle element position according to the second embodiment.

[0137] Figure 5 a method for determining a flue gas oxygen values table in the commissioning mode according to the first embodiment wherein the table is used in an operation mode of the combustion appliance. Figure 5a a method for determining a flue gas oxygen values table in the commissioning mode according to the second embodiment wherein the table is used in an operation mode of the combustion appliance. Figure 6 a diagram showing a flue gas oxygen curve dependent on a power state of the combustion appliance accordingto the first embodiment. Figure 6a a diagram showing a flue gas oxygen curve dependent on a power state of the combustion appliance according to the second embodiment.

[0138] Figure 7 a flow chart relating to an operation of the combustion appliance in the operation mode according to the first embodiment.20.06.2025

[0139] 25

[0140] Figure 7a a flow chart relating to an operation of the combustion appliance in the operation mode according to the second embodiment.

[0141] Figure 7b shows the effect of different Wobbe values on fan speed parameters. Figure 8 a flowchart relatingto a transition method to prepare the combustion appliance to switch to a standby mode or to stop the combustion appliance according to the first embodiment.

[0142] Figure 8a a flow chart relatingto a transition method to prepare the combustion appliance to switch to a standby mode or to stop the combustion appliance according to the second embodiment.

[0143] Figure 9 a flow chart showing the method for setting the starting behavior of the combustion appliance according to the first embodiment.

[0144] Figure 9a a flow chart showing the method for setting the starting behavior of the combustion appliance according to the second embodiment. Figure 10 an overview of a system comprising several combustion appliances in a state in which all combustion appliances are in an operation mode. Figure 11 an overview on a system comprising several combustion appliances in a state in which some combustion appliances are in a standby mode.

[0145] Figure 12 a flow chart for detecting blockage in flue gas path of a combustion appliance.

[0146] Figure 13 a diagram illustrating how blockage in the flue gas path can be determined according to a first variant.

[0147] Figure 14 a diagram illustrating how blockage in the flue gas path can be determined according to a second variant.

[0148] Figure 15 a diagram illustrating how blockage in the flue gas path can be determined according to a third variant.

[0149] Figure 16 a flow chart illustrating how a combustion appliance failure state is determined.

[0150] Figure 17 a diagram showing different states of the combustion appliance during a ignition phase of the combustion appliance.20.06.2025

[0151] 26

[0152] Figure 18 a calibration of the oxygen sensor for a situation in which the oxygen sensor is always heated.

[0153] Figure 19 a calibration of the oxygen sensor for a situation in which the oxygen sensor is not constantly heated.

[0154] Figure 20 a calibration of the oxygen sensor for a situation in which the oxygen sensor is heated for a predetermined time.

[0155] Figure 1 shows an overview of a combustion appliance 1 according to the invention. The combustion appliance 1 comprises a fan 4, a fuel gas source 11 for providing fuel gas and a fuel valve 5, in particular a fuel gas valve, for controlling the fuel gas flow. The fuel valve 5 is a pneumatic valve so that the fuel flow depends on the fan speed. The combustion appliance 1 also comprises a throttle unit 6 that is located downstream the fuel valve 5.

[0156] The throttle unit 6 controls the fuel flow, in particular the fuel gas flow, coming from the fuel valve 5. The throttle unit 6 comprises a throttle motor 22 and a throttle element 21 shown in figure 2. The throttle motor 22 changes the position of the throttle element 21. The throttle element 21 delimits a throttle opening cross section through which the fuel, in particular fuel gas, can flow. Thus, the fuel flow that passes through the throttle unit 6 depends on the position of the throttle element 21. The throttle unit 6 is electrically connected with a data processing unit 9 of the combustion appliance 1 as is indicated with dotted line in figure 1.

[0157] The throttle element position depends on the instruction that is received from the data processing unit 9. For setting a throttle element position the data processing unit 9 transmits a throttle position signal P to the throttle unit 6, in particular the throttle motor 22. The throttle motor 22 changes the position of the throttle element 21 according to the received throttle position signal P. In a non-shown embodiment, there is no bidirectional communication between the throttle unit 6 and the data processing unit 9 but the data processing unit 9 transmits a throttle position signal20.06.2025

[0158] 27

[0159] P to the throttle unit 6. That means in said case the data processing unit 9 does not receive any response from the throttle unit 6.

[0160] The data processing device 9 comprises a processor and / or can be used to set the power state of the combustion appliance 1. Thereto, the data processing device 9 sends at least one operation signal S1-S4 to the fan 4 to set the fan speed. In particular, the data processing device 9 can set the combustion appliance 1 to operate in a minimum power state, a maximum power state or a power state that is between the maximum and minimum power state.

[0161] The combustion appliance 1 also comprises a manifold 13. The manifold 13 is arranged upstream of a burner 7 of the combustion appliance 1 and is used to mix the fuel, in particularthe fuel gas, passing the throttle unit 6 with air provided by the fan 4. The combustible mixed gas is burned in a combustion chamber 18 of the combustion appliance 1 by the burner 7. The combustion appliance 1 comprises a heat exchanger 12 that surrounds the combustion chamber 18 and that is used to transfer the heat to a liquid, in particular water, that is used for a central heating and / or for domestic hot water. The flue gas leaves the combustion chamber 18 via an exhaust flue path 17.

[0162] The combustion appliance 1 comprises an oxygen sensor 8 that is arranged in the combustion chamber 18. The oxygen sensor 8 is used to measure a flue gas oxygen value. In other words, the oxygen sensor measures the oxygen concentration in the flue gas when a combustion occurred in the combustion chamber 18. In a nonshown embodiment, the oxygen sensor 8 measures the oxygen concentration in air. The data processing device 9 is electrically connected to the oxygen sensor 8 and receives the measured flue gas oxygen values. An air to fuel gas ratio can be determined on the basis of the received flue gas oxygen value. The data processing device 9 can control the combustion appliance 1 on the basis of the determined air to fuel gas ratio in an operation mode of the combustion appliance.20.06.2025

[0163] 28

[0164] Figure 2 shows a structure of the data processing device 9. The data processing device 9 comprises a comfort unit portion 27, a safety unit control portion 28 and a throttle unit control portion 26. The comfort unit portion 27 is electronically connected to a temperature sensor 29 measuring a room temperature, which is used to determine a heat request. Thus, the comfort unit portion 27 can exchange data with the temperature sensor 29. In particular, the comfort unit portion 27 receives temperature values measured by the temperature sensor 29. The comfort unit portion 27 can control the heat output of the combustion appliance 1 dependent on the temperature value received from the temperature sensor 29.

[0165] The throttle unit control portion 26 is electronically connected to the throttle unit 6. Thus, the throttle unit control portion 26 exchanges data with the throttle unit 6 or is configured to only transmit data to the throttle unit 6. In particular, the throttle unit control portion 26 can transmit a control signal to the throttle unit 6 to control the fuel flow, in particular fuel gas flow, that flows through the throttle unit 6. The throttle unit 6 comprises the throttle motor 22 and the throttle element 21. The throttle motor 22 controls the position of the throttle element 21 and thus the throttle opening cross section through which the fuel, in particular the fuel gas, can flow. The throttle motor 22 controls the position of the throttle element 21 on the basis of the control signal that is received from the throttle unit control portion 26.

[0166] The safety unit control portion 28 is electronically connected to the oxygen sensor 8. Thus, the safety unit control portion 28 exchanges data with the oxygen sensor 8. In particular, the safety unit control portion 28 receives flue gas oxygen values QI-04 that are received by the oxygen sensor 8. The oxygen sensor comprises a sensing element 19 and a sensor data processing unit 20 that receives the values measured by the sensing element 19. The sensor data processing unit 20 is electronically connected to the safety unit control portion 28.

[0167] The combustion appliance 1 comprises a heating element 34 for electrically heating the sensing element 19. In the shown embodiment the heating element 34 is an20.06.2025

[0168] 29

[0169] integral part of the oxygen sensor 8. The heating element 34 can comprise or be a wire and / or resistor that outputs heat when it is energized. The sensor data processing unit 20 controls when the heating element 34 is energized, wherein the control is indicated by the dotted line in Fig. 2. In a non-shown embodiment, the heating element 34 can be a component that is not an integral part of the oxygen sensor 8 but is, in particular partly, arranged outside the oxygen sensor 8.

[0170] Figure 3 shows a flow chart of a method executed by the data processing device 9 according to a first embodiment. The method is explained below by referring to the figures 1 and 2.

[0171] In a first step G1 the data processing device 9 is powered-up. This is usually done when the combustion appliance 1 is started. In a second step G2 the data processing device 9 checks whether the combustion appliance 1 comprises an oxygen sensor 8. Thereto, it is checked whether the safety control portion 28 can communicate with the oxygen sensor 8. If this is not the case, it is determined in the third step G3, that the combustion appliance 1 is merely pneumatically controlled. That means, the throttle element position is not changed during the operation of the combustion appliance 1. In other words, the throttle element position is set manually by the installer. So, the third step G3 determines whether the combustion appliance 1 can be controlled as a gas adaptive combustion appliance 1. The determination in G3 thus means that the combustion appliance 1 comprises a traditional pneumatic gas valve - and therefore traditional pneumatic control (definition 3.1.201.22 of EN12067-2:2022, 3.117) and uses CO2, CO, and 02 readings that are taken using a combustion analyser during commissioning. These readings guide the installer while manually adjusting the screws on the gas valve. In case the combustion appliance 1 comprises an oxygen sensor 8, it is determined in step G2 that the system has an adaptive combustion control function (definition 3.1.201.23 of EN12067-2:2022, 3.117). By adaptive combustion control function is meant a control function, intended to maintain lambda constant in a range AA or within predetermined 02 boundaries (as shown in fig. 6) by adapting the flow of gaseous fuel20.06.2025

[0172] 30

[0173] and / or the flow of air and / or other physical quantities to compensate changes in input parameters relevant for the combustion process. The determination in G2 is thus that the combustion appliance 1 is a gas adaptive combustion appliance 1.

[0174] If the data processing device 9 determines in the second step G2 that the combustion appliance 1 comprises an oxygen sensor 8, a start position for the throttle element is initialized in a fourth step G4. Thereto, the data processing device transmits a throttle position signal P to the throttle motor 22, which sets the position of the throttle element dependent on the throttle position signal P to an initial position. This initial position can be predetermined or can correspond to a throttle element position that is determined in a previous operation of the combustion appliance 1. Alternatively, this initial position can be a fixed initial throttle element position which is the same at every start of second step G2. Alternatively, this initial position can be a position that is not known but that corresponds to the actual current throttle element position.

[0175] For the non-shown embodiment in which there is no bidirectional communication between the data processing device 9 and the throttle unit 6, the data processing device 9 changes the position by activating coils on the throttle motor 22 which results in fixed steps. There is no position information present. To set the throttle motor 22 into the initial position the throttle unit control portion 26 sends a number of steps to the throttle motor 22 that is greater than the real range that the throttle motor 22 can travel. Because the range is greater than a possible range the throttle motor 22 and / or the throttle element 21 reaches the end of the range and is now in a known position. From this position a step counter or bookkeeping is kept. That results in a known position of the throttle element 21 by the data processing device 9.

[0176] Alternatively, the actual position of the throttle element 21 is assumed to be appropriate for further operation. E.g., after commissioning, the actual position of the throttle element 21 may usually be appropriate as the gas quality will usually not20.06.2025

[0177] 31

[0178] have changed severely between commissioning and ignition. Also, after a previous operation in which heat is delivered, the position of the throttle element 21 may be assumed to be appropriate for further operation, irrespective of whether the actual position can be retrieved or not.

[0179] In the next fifth step G5 the oxygen sensor 8 is calibrated. The calibration is necessary as day-to-day variations of the ambient conditions influence the flue gas oxygen value measured by the oxygen sensor 8. The calibration can occur at different times. The calibration is explained below with respect to fig. 18 to 20.

[0180] In a sixth step G6 the data processing device 9 checks whether the combustion appliance 1 is commissioned. If not, a seventh step G7 is initialized by the data processing device 9. In the seventh step G7 the starting behavior of the combustion appliance 1 is set. The method for setting the start of the combustion appliance depends on the fuel gas quality. Said method is explained below more in detail with referring to figure 9.

[0181] In an eighth step G8 the data processing device 9 sets a position of the throttle unit 6. This setting is useful as the gas quality can change so that the throttle unit 6 is not set correctly. The setting of the throttle unit 6 is explained below more in detail when figure 4 is described.

[0182] Afterwards, in a nineth step G9 the data processing device generates a boundary table comprising flue gas oxygen values. The generated table is used when the combustion appliance 1 is operated in an operation mode, in particular in the ignition phase of the combustion appliance and / or in the heating phase of the combustion appliance for providing heat. The table generation is explained below when figure 5 is explained.

[0183] After the boundary table is generated, a sensor heating manager can be executed in a tenth step G10. Additionally in an eleventh step G11 a sensor calibration20.06.2025

[0184] 32

[0185] manager and in a twelfth step G12 a throttle starting positioning manager can be executed. The sensor heating manager ensures that the sensor heating, i.e. the heating of the sensing element 19 is turned on or off. The sensing element 19 can be electrically heated.

[0186] The calibration starts when the oxygen sensor is sufficiently heated and the oxygen sensor remains heated during the calibration. The calibration takes a few seconds; however, heating may take a few minutes. During operation of the combustion appliance 1 there are moments where no heat demand is expected, this means, the heating can be turned off resulting in energy savings.

[0187] The sensor calibration manager can calibrate the oxygen sensor 8 in the eleventh step G11 to prevent discomfort for the user. The data processing device 9 ensures that each 72 hours the oxygen sensor 8 is calibrated. By tracking a calibration timer, the most optimal moment can be found. A calibration is done in air, wherein the percentage of oxygen in air is known. The calibration can be done in a pre-purge and / or post-purge process.

[0188] The throttle starting positioning manager checks the throttle element position in the twelfth step G12 during burning. If the fuel gas quality changes and a correction of the throttle element position is needed, the throttle starting positioning manager detects the change and stores the corrected throttle element position or change. The next burner start will be done by using the corrected throttle element position. The stored throttle element position is used to initialize the combustion appliance 1 in the fourth step G4 discussed above. The stored throttle element position is also used for the next start without having a power cycle in the first step G1. In an alternative embodiment, the stored throttle element position is not used for the next start, but the next start starts with first step G1.

[0189] The throttle starting positioning manager, the sensor heating manager and the sensor calibration manager can be executed after the ninth method step G9.20.06.2025

[0190] 33

[0191] Additionally, said managers can be executed in cases after it is determined in the sixth step G6 that the combustion appliance has been commissioned. In particular, the managers can be executed before it is determined in a fourteenth step G14 whether a heat demand is present.

[0192] If no heat demand is present, the combustion appliance 1 is switched to a stand-by mode or is stopped in a fifteenth step G15. After the fifteenth step G15, it is possible to recheck in the fourteenth step G14, in particular after a predetermined timeperiod, whether a heat demand is present. This can be repeated until the combustion appliance 1 is stopped and deactivated and thus switched off. A timeperiod is a length of time and delimited by two time points.

[0193] If the data processing device determines in the fourteenth step G14 that a heat demand is present, a sixteenth method step G16 is initiated in which the starting behavior of the combustion appliance 1 is set. Likewise, to the seventh step G7 one part of the setting of the starting behavior can be to determine the fuel gas quality.

[0194] The sixteenth method step G16 corresponds to the seventh method step G7 explained above so that it is referred to said passages. The difference between the two method steps G7 and G16 is that in the seventh method step G7 the combustion appliance 1 is operated in the commissioning mode whereas in the sixteenth method step G16 the combustion appliance 1 is operated in the operation mode, in particular in the heating phase of the operation mode. In the heating phase of the operation mode, which is only possible afterthe commissioning mode is completed, the combustion appliance 1 provides a heat output that is used in an application like domestic hot water and / or central heating.

[0195] In a seventeenth method step G17 the data processing device 9 can control the throttle element position during a heat demand on the basis of the measured flue gas oxygen values. This is explained below more in detail together with figure 7.20.06.2025

[0196] 34

[0197] In an eighteenth method step G18 the combustion appliance 1 is prepared for the standby mode or the stop of the combustion appliance 1. In particular, the combustion appliance 1 is prepared such that a restart of the combustion appliancel is done by using the correct parameters. The method step G18 is explained more in detail in figure 8.

[0198] Figure 3a shows a flow chart of an operation method executed by the data processing device according to a second embodiment. The method described in figure 3a is similarto the method described in figure 3. Thus, in the following, merely the differences of the method according to the second embodiment to the method according the first embodiment are described.

[0199] A difference of the method according to the second embodiment is that after the start position for the throttle element is initialized in the fourth step G4, the throttle element is moved to a position that corresponds to the first row in the Wobbe entry table in a further fourth step G4a. Afterwards, the oxygen sensor 8 is calibrated in the fifth step G5.

[0200] A further difference of the method according to the second embodiment is that the system does not comprise a throttle starting positioning manager so that the twelfth step G12 described for the method shown in figure 3 is not executed in the method according to the second embodiment.

[0201] The method according to the second embodiment executes a sensor heating by using a sensor heating manager in a tenth step G10. Additionally, the method according to the second embodiment executes sensor calibration by using the sensor calibration manager in the eleventh step G11. However, in contrary to the method according to the first embodiment, the sensor heating manager and the sensor calibration manager are processed parallel to the steps G1 -G9 and the steps G14-G18 in the method according to the second embodiment.20.06.2025

[0202] 35

[0203] As discussed above in figure 3, in the method according to the first embodiment the sensor heating manager and the sensor calibration manager are processed after the ninth step G9 or after the sixth step G6.

[0204] Figure 4 shows a method for determining a throttle element position of the throttle unit 6 according to the first embodiment. Said figure shows the specifics of the eighth method step G8 shown in figure 3. In a first sub-step T1 the throttle element position setting is started. In a second sub-step T2, the data processing device 9 outputs a first operating signal S1 that causes that the combustion appliance 1 is operated in a maximum power state. Specifically, the first operating signal S1 is sent to the fan 4 to operate the combustion appliance 1 in the maximum power state. Additionally, the data processing device 9 receives a first flue gas oxygen value 01 measured by the oxygen sensor 8 when the combustion appliance is operated in the maximum power state. The throttle element position of the throttle unit 6 corresponds to the throttle element position that is set in the fourth method step G4.

[0205] Then, in a third sub-step T3 the data processing device checks whether the measured first flue gas oxygen value 01 fulfils a test condition. Specifically, the test condition comprises a check whether the first flue gas oxygen value 01 is arranged in a predetermined flue gas oxygen range assigned to maximum power state of the combustion appliance for a predetermined time-period. The predetermined flue gas oxygen band and the predetermined time-period can be saved in a memory of the combustion appliance 1, in particular data processing device 9.

[0206] If the test condition is not fulfilled the throttle element position is adjusted in a fourth sub-step T4. The throttle element position can be automatically adjusted. Thereto, the data processing device 9, in particular the throttle unit control portion 26, sends out a throttle position signal P to change the throttle element position of the throttle element 21 and thus to change the fuel gas flowing through the throttle unit 6. The sub-steps T3 and T4 are repeated until the test condition is fulfilled. As20.06.2025

[0207] 36

[0208] soon as the test condition is fulfilled the throttle position of the throttle unit 6 is stored in the memory in a fifth sub-step T5.

[0209] In a sixth sub-step T6, the data processing device 9 outputs a second operating signal S2 that causes the combustion appliance 1 to operate in a minimum power state. Specifically, the data processing device 9 outputs the second operating signal S2 to the fan 4 to operate the combustion appliance 1 in the minimum power state. Additionally, the data processing device 9 receives a second flue gas oxygen value 02 from the oxygen sensor 8 when the combustion appliance is operated in the minimum power state. The throttle element position of the throttle unit 6 that is set when the combustion appliance 1 is operated in the minimum power state corresponds to the throttle element position that fulfils the test condition of the third method sub-step T3.

[0210] In a seventh sub-step T7 the data processing device 9 determines whether the received second flue gas oxygen value 02 fulfils a further test condition. Specifically, the further test condition comprises a check whether the second flue gas oxygen value 02 is arranged in a predetermined further flue gas oxygen range assigned to a minimum power state of the combustion appliance 1 for a predetermined further time-period. The predetermined further flue gas oxygen band and the predetermined further time-period can be saved in a memory of the combustion appliance 1.

[0211] If the test condition is not fulfilled the fuel valve 5 is adjusted in an eighth sub-step T8. The fuel valve 5 can be manually adjusted by an installer by adjusting an offset screw of the fuel valve 5. Alternatively, the fuel valve 5 can be automatically adjusted by the data processing device 9. The sub-steps T7 and T8 are repeated until the further test condition is fulfilled.20.06.2025

[0212] 37

[0213] After the further test condition is fulfilled, the throttle element position determination is finished. As is evident from figure 4, in the next step the boundary table is created in the nineth method step G9.

[0214] Figure 4a shows a method for determining a throttle element position according to the second embodiment. The method described in figure 4a is similar to the method described in figure 4. Thus, in the following, merely the differences of the method according to the second embodiment to the method according the first embodiment are described.

[0215] The method according to the second embodiment differs from the method shown in fig. 4 in that the throttle element position of the throttle element of the throttle unit 6 is not stored in the memory in a fifth sub-step T5. Thus, in the method according to the second embodiment no fifth sub-step T5 exists and the data processing device 9 outputs a second operating signal S2 in the sixth sub-step T6 directly after the test condition is fulfilled in the third sub-step T3.

[0216] The creation of the boundary table is shown in figure 5 more in detail. Figure 5 shows a method for determining a flue gas oxygen values table in the commissioning mode according to the first embodiment wherein the table is used in an operation mode of the combustion appliance. As is discussed above, the boundary table is created when the combustion appliance 1 is operated in the commissioning mode. Said table is used in an operation mode as is explained below more in detail.

[0217] In a first sub-step C1 the data processing device 9 starts with creating the boundary table. Said creation can only be done when the combustion appliance 1 is operated in the commissioning mode. In other words, the determined values of the table cannot be changed, when the combustion appliance 1 is operated in the operation mode. In the first sub-step C1 an upper and lower threshold 2, 3 is determined for the first flue gas oxygen value 01 and for the second flue gas oxygen value 02, respectively.20.06.2025

[0218] 38

[0219] In a third sub-step C3 the data processing device 9 receives information about a third power state stored in a memory of the combustion appliance 1. The information can be stored in the memory in a second sub-step C2. Said second substep C2, namely the storing of data in the memory, can be conducted prior to the initialization of the first sub-step C1. The third power state is between the maximum power state and the minimum power state. In the third sub-step C3, the data processing device also sends a third operation signal S3, in particular to the fan, to cause the combustion appliance 1 to be operated in the third power state.

[0220] The data processing device 9 receives in a fourth sub-step C4 a third flue gas oxygen value 03. Additionally, the data processing device 9 determines in the fourth substep C4 an upper threshold value and a lower threshold value with respect to the third flue gas oxygen value 03. The measured third flue gas oxygen value 03 and the determined upper and lower threshold value are stored in a fifth sub-step C5.

[0221] In a sixth sub-step C6, the data processing device 9 determines whether the table is complete. If not, the data processing device sends a fourth operation signal S4 in a seventh sub-step C7, which results in that the combustion appliance 1 operates in power state that is between a maximum power state and a minimum power state, so that the combustion appliance 1 is operated in a fourth power state. The fourth power state differs from the first to third power state.

[0222] The data processing device 9 receives in a fourth sub-step C4, the fourth power state value from the memory likewise to the third power state from the memory, which comprises the data stored in the second sub-step C2, of the combustion appliance. In other words, the data processing device receives the fourth power state value and other power state values from the memory, which comprises the data stored in the second sub-step C2, in the third sub-step C3 or the seventh sub-step C7. Additionally, the data processing device 9 determines in the fourth sub-step C4 an upper threshold value and a lower threshold value with respect to the fourth flue20.06.2025

[0223] 39

[0224] gas oxygen value 04. The measured fourth flue gas oxygen value 04 and the determined upper and lower threshold value are stored in a fifth sub-step C5.

[0225] The sub-steps C4-C7 are repeated for all power states of the combustion appliance 1 that are stored in the memory as discussed above for sub-step C2. After the boundary table is created the boundary table creation method is finished in the eight sub-step C8.

[0226] A distance between the upper threshold 2 and the measured flue gas oxygen value can correspond to a distance between the lower threshold 3 and the measured flue gas oxygen value. Alternatively, it is possible that the determination of the upper and lower threshold is based on a value that depends on the measured flue gas oxygen value and a correction value. A distance between the upper threshold 2 and said value can correspond to a distance between the lower threshold 3 and said value. The correction value can be stored in an electrical memory or can be entered by an installer.

[0227] Figure 5a shows a method for determining a flue gas oxygen values table in the commissioning mode according to the second embodiment wherein the table is used in an operation mode of the combustion appliance. The method described in figure 5a is similar to the method described in figure 5. As is described below more in detail, the first and fourth sub-step C1a, C4a of the method according to the second embodiment differ from the method according to the first embodiment, which is the reason why the reference signs of said sub-steps differs from the reference signs of the sub-steps C1 and C4 used in fig. 5.

[0228] The data processing device 9 determines likewise to the method according to the first embodiment an upper and lower threshold value with respect to the first and second flue gas oxygen value 01, 02 in the first sub-step C1a. Additionally, the data processing device 9 determines a further upper threshold value 2a and further lower threshold value 3a for the first flue gas oxygen value 01 and a further upper20.06.2025

[0229] 40

[0230] and lower threshold value 2a, 3a for the second flue gas oxygen value for the second flue gas oxygen value in the first sub-step C1a.

[0231] The data processing device 9 determines likewise to the method according to the first embodiment an upper and lower threshold value 2, 3 with respect to the third flue gas oxygen value 03 and all other flue gas oxygen values resulted from operating the combustion appliance in different power states in the fourth sub-step C4a. Additionally, the data processing device 9 determines a further upper threshold value and lower threshold value 2a, 3a for the third flue gas oxygen value and all other flue gas oxygen values resulted from operating the combustion appliance in different power states in the fourth sub-step C4a.

[0232] A distance between the upper threshold 2 and the measured flue gas oxygen value can correspond to a distance between the lower threshold 3 and the measured flue gas oxygen value. Alternatively, it is possible that the determination of the upper and lower threshold is based on a value that depends on the measured flue gas oxygen value and a correction value. A distance between the upper threshold 2 and said value can correspond to a distance between the lower threshold 3 and said value. The correction value can be stored in an electrical memory or can be entered by an installer.

[0233] A distance between the further upper threshold 2a and the measured flue gas oxygen value can correspond to a distance between the further lower threshold 3a and the measured flue gas oxygen value. Alternatively, it is possible that the determination of the further upper and lower threshold is based on a value that depends on the measured flue gas oxygen value and a correction value. A distance between the further upper threshold 2a and said value can correspond to a distance between the further lower threshold 3a and said value. The correction value can be stored in an electrical memory or can be entered by an installer.20.06.2025

[0234] 41

[0235] Additionally, the method according to the second embodiment comprises a tenth sub-step C10, which is conducted when it is determined in the sixth sub-step C6 that the table is completed. In the tenth sub-step C10 the data processing device 9 sets a commissioning flag indicating that the commissioning is done.

[0236] Figure 6 shows a diagram showing a flue gas oxygen curve dependent on a power state of the combustion appliance according to a first embodiment. Specifically, figure 6 shows curves that are determined on the basis of the values that are determined in the method shown in figure 5.

[0237] Figure 6 shows the dependency of flue gas oxygen values O1-O4 from the power state of the combustion appliance. Specifically, figure 6 shows the first flue gas oxygen value 01 when the combustion appliance 1 is in the maximum power state and the second flue gas oxygen value 02 when the combustion appliance 1 is in the minimum power state. Further, figure 6 shows the third flue gas oxygen value 03 and the fourth as oxygen value 04 when the combustion appliance 1 is in at two intermediary power states in between the minimum power state and the maximum power state. Additionally, figure 6 shows upper thresholds 2 and lower thresholds 3. Each of the upper thresholds 2 and the lower thresholds 3 are assigned to one measured flue gas oxygen value. The upper and lower threshold curve defines a flue gas oxygen band that is used to control the combustion appliance as is explained more in detail in figure 7.

[0238] Figure 6a shows a diagram showing a flue gas oxygen curve dependent on a power state of the combustion appliance according to the second embodiment. In addition, to the upper thresholds 2 and the lower thresholds 3, figure 6a shows further upper thresholds 2a and further lower thresholds 3a. The further upper and lower thresholds are determined in the first and fourth sub-steps C1a, C4a shown in fig.

[0239] 5a. Each of the further upper thresholds 2 and the further lower thresholds 3a are assigned to one measured flue gas oxygen value20.06.2025

[0240] 42

[0241] The further upper and lower threshold curve defines a further flue gas oxygen band that is used to control the combustion appliance as is explained more in detail in figure 7a. As is evident from fig. 5a the further flue gas oxygen band is smaller than the flue gas oxygen band comprising the upper thresholds 2 and the lower thresholds 3. Additionally, the further flue gas oxygen band is a portion of the flue gas oxygen band.

[0242] Figure 7 shows a flow chart relating to a combustion control of the combustion appliance 1 in the operation mode according to a first embodiment. That means, the method steps are performed after the combustion appliance 1 is commissioned. Specifically, figure 7 shows the method sub-steps that are executed in the seventeenth method step G17 shown in figure 3.

[0243] In a first method step N1 the combustion control method is initiated by the data processing device 9. In a second sub-step N2 it is checked whether a burner off condition is present. Said burner off condition can result if there is no heat demand request and / or if a burner could not be started for a predetermined number of times. If the burner off condition is fulfilled, the combustion appliance 1 is prepared for a standby mode or a stop in the third sub-step N3. This transition process is shown in figure 8 more in detail.

[0244] If the data processing device 9 determines in the second sub-step N2 that the burner off condition is not reached, the oxygen sensor 8 measures the flue gas oxygen value in the combustion chamber 18 in a fourth sub-step N4. Specifically, the data processing device 9 receives the measured flue gas oxygen value in the fourth substep N4.

[0245] In a fifth sub-step N5 the data processing device 9 determines whether the measured flue gas oxygen value is within the flue gas oxygen range determined in the method shown in figure 5. Specially, the data processing device 9 determines whether the measured flue gas oxygen value is outside the flue gas oxygen range20.06.2025

[0246] 43

[0247] determined by an upper threshold curve and a lower threshold curve shown in figure 6. If this is not the case, the data processing device determines a normal operation and repeats the sub-steps N2-N5.

[0248] If the data processing device 9 determines in the fifth sub-step N5 that the measured flue gas oxygen value is outside the flue gas oxygen range, an adjusting process is started in a sixth sub-step N6. In said adjustment process it is checked in a seventh sub-step N7 whether the fan speed is above a fan threshold value. If this is not the case, the method is continued at the second sub-step N2.

[0249] If the fan speed is above a fan threshold, it is checked whether the throttle element position is kept constant for a predetermined time in an eighth step N8. If this is not the case the method is continued at the second sub-step N2. However, if the throttle element position is kept constant for a predetermined time, the present throttle element position is stored in the memory in a nineth step N9.

[0250] Figure 7a shows a flow chart relating to an operation of the combustion appliance in the operation mode according to a second embodiment. The method described in figure 7a is similar to the method described in figure 7.

[0251] The first sub-step N1 to fourth sub-step N4 are identical in both methods so that it is referred to the description of figure 7.

[0252] In a fifth sub-step N5a the data processing device 9 checks whether the flue gas oxygen value measured in the operation mode is lower than a predetermined value. The predetermined value can be the flue gas oxygen value that is obtained in the commissioning mode. Alternatively, the predetermined value can be dependent on the flue gas oxygen value that is obtained in the commissioning mode and a predetermined correction value that can be entered by the installer or that is stored in an electrical memory. In particular, the correction value can be added to the flue gas oxygen value obtained in the commissioning mode or subtracted from said flue20.06.2025

[0253] 44

[0254] gas oxygen value. Said value corresponds to the value described above in fig. 5, 5a that is the basis for the upper and lower threshold 2, 3 and / or the further upper threshold 2a, and further lower threshold 3a.

[0255] If the flue gas oxygen value measured in the operation mode is smaller than the predetermined value, the data processing device determines in a sixth sub-step N6a that the throttle unit, in particular the throttle element, is not arranged at its maximum position. Afterwards, the method is continued in a seventh sub-step N7a.

[0256] The method is also continued in the seventh sub-step N7a when the data processing device 9 determines in the fifth sub-step N5a that the measured flue gas oxygen value is not smaller than the predetermined value.

[0257] In the seventh sub-step N7a the data processing device 9 checks whether flue gas oxygen value measured in the operation mode is arranged outside the band delimited by the upper threshold 2 and the lower threshold 3. Additionally, the data processing device 9 determines the seventh sub-step N7a whether the throttle element is arranged in its maximum position so that the opening cannot open any further. If at least one of the two conditions is not fulfilled, position the method is continued at the second sub-step N2. In said case the measured flue gas oxygen value is not arranged outside the band delimited by the upper threshold 2 and the lower threshold 3 and / or it is determined that the throttle element is not arranged at its maximum.

[0258] If the measured flue gas oxygen value is arranged outside the band delimited by the upper threshold 2 and the lower threshold 3 and if it is determined that the throttle element is not arranged at its maximum position, the data processing signal sends a control signal to a combustion appliance component in an eight sub-step N8a. The control signal can result in a change of the fan speed and / or a change of the throttle element position.20.06.2025

[0259] 45

[0260] In a ninth step N9a, the data processing device 9 determines whether the flue gas oxygen value is arranged inside the band delimited by the further upper threshold 3a and the further lower threshold 3b. If the flue gas oxygen value is not arranged inside said band, the method is continued at the eight sub-step N8a. In said case the data processing device 9 amends the control signal resulting in a different fan speed and / or a different throttle element position.

[0261] If the data processing device 9 determines in the ninth sub-step N9a that the measured flue gas oxygen value is arranged inside the band delimited by the further upper threshold 2a and the further lower threshold 3a for a predetermined time, the method continues in the tenth sub-step N10a. Specifically, the method is continued in the tenth sub-step N10a only when the measured flue gas oxygen value is arranged inside the band delimited by the further upper threshold 2a and the further lower threshold 3a for the predetermined time.

[0262] Alternatively, the data processing device 9 determines in the ninth sub-step N9a whether the oxygen value is not arranged inside the band delimited by the further upper threshold 2a and the further lower threshold 3a for a predetermined further time. If the condition is fulfilled, the method is continued in the tenth sub-step N10a. In this case the situation is covered that the oxygen value does not get inside the defined band within the predetermined further time. Thus, the throttle element is arranged in the maximum position and after the further predetermined time lapsed, the ninth sub-step N9a results in a 'yes' The further time can be longer than the predetermined time that is also considered in the ninth sub-step N9a.

[0263] In the tenth sub-step N10a, the data processing device 9 determines whether the measured flue gas oxygen value is arranged outside the band delimited by the further upper threshold 2a and the further lower threshold 3a and whether the throttle element is arranged in its maximum position. If at least one of said two conditions is not fulfilled, the method continues in an eleventh sub-step N11 a.20.06.2025

[0264] 46

[0265] If both conditions are fulfilled, the data processing device 9 stores in a twelfth substep N12a that the throttle element is arranged in its maximum position. Afterwards, the method continues in the eleventh sub-step N11 a.

[0266] In the eleventh sub-step N11 a it is determined whether the fan speed is above a fan threshold value. If this is not the case, the method is continued at the second substep N2.

[0267] If the fan speed is above a fan threshold, it is checked whether the throttle element position is kept constant for a predetermined time in thirteenth sub-step N13a. If this is not the case the method is continued at the second sub-step N2. If it is determined in the thirteenth sub-step N13a that the throttle element is kept constant for a predetermined time, the method is continued in a fourteenth substep N14a.

[0268] In the fourteenth sub-step N14a the actual throttle element position is converted to a Wobbe value or calorific value. This can be done by using a table stored in the memory of the combustion appliance, wherein the table comprises information about Wobbe values or calorific values which are assigned to one throttle element position, respectively. Said table is discussed more in detail below in figure 9 and 9a.

[0269] In a fifteenth sub-step N15a, a fan speed or fan speed correction is determined dependent on the Wobbe value or calorific value that is determined in the fourteenth sub-step N14a. The data processing device can comprise information about the correlation between the fan speed and a burner load percentage, wherein the burner load percentage is 0% at minimum fan speed and 100% at maximum fan speed. The minimum and maximum fan speed delimit the modulation range of the fan.

[0270] A further table can be stored in the memory of the combustion appliance, wherein the table comprises information about minimum and / or maximum fan speed values20.06.2025

[0271] 47

[0272] which are dependent on the determined Wobbe value or calorific value. The minimum fan speed is the fan speed at which the fan must be operated at minimum. With "maximum fan speed value" it is meant the maximum value of the fan speed at which the fan can be operated or the maximum value of the fan speed at which the fan speed can be operated when a central heating demand or a domestic hot water demand is existent. The data processing device 9 checks whether the minimum and / or maximum fan speed is assigned to the determined Wobbe value or calorific value. If not, the minimum and / or maximum fan speed are changed accordingly. That means, the minimum and / or maximum value of the fan speed can be changed during the operation of the combustion appliance dependent on the determined Wobbe Value. This is shown more in detail in Figure 7b.

[0273] The fan speed can be calculated according to the following formula:

[0274] Fan speed = Modulation range * Requested power setpoint + Minimum fan speed

[0275] Modulation range = maximum fan speed - minimum fan speed

[0276] The "requested power setpoint" is determined by a control unit so that the combustion appliance can provide a target heat output or the burner can provide a target heat output. The "minimum fan speed" is the minimum fan speed at which the fan can be operated. The "maximum fan speed" is the maximum fan speed at which the fan can be operated. Alternatively the "maximum fan speed" can be the maximum fan speed when a central heating demand or a domestic hot water demand is existent.

[0277] As is evident from figure 7b the modulation range in the left region assigned to Wobbe value A is greater than the modulation range in the right region assigned to Wobbe value B. This results in different fan speeds for the same power setpoint.20.06.2025

[0278] 48

[0279] Thus, the minimum and / or maximum fan speed changes with changing gas quality resulting in that the modulation range of the fan changes with changing gas quality. By adapting the modulation range of the fan it is possible to provide a constant burner load and / or heat output from the combustion appliance even if the gas quality changes.

[0280] As is discussed above the data processing device 9 is configured such that it starts to control the combustion appliance components after the data processing device 9 determines that the measured flue gas oxygen value is arranged outside the band delimited by the upper threshold 2 and the lower threshold 3. After the control is initiated, the data processing device 9 controls the combustion appliance components, in particular fan and / or throttle element of throttle unit, such that the measured flue gas oxygen value is arranged inside the band delimited by the further upper threshold 2a and the further lower threshold 3a.

[0281] Figure 7b shows the effect on fan speed parameters dependent on the determined Wobbe value. Specifically, figure 7b shows the fan speed parameters, namely a minimum fan speed vmin and a maximum fan speed vmax, dependent on time in two regions, namely a left region in which a Wobbe value A is determined and in another right region in which a Wobbe value B is determined. The Wobbe value B differs in value from the Wobbe value A. In figure 7b the two regions are separated by a dotted vertical line.

[0282] The minimum fan speed vmin that is assigned to the Wobbe value A is lower than the minimum fans speed that is assigned to the Wobbe value B. The minimum speed is the fan speed at which the fan must be operated. The maximum fan speed vmax that is assigned to the Wobbe value A is greater than the maximum fan speed vmax that is assigned to the Wobbe value B. The Wobbe value B is larger than Wobbe value A.20.06.2025

[0283] 49

[0284] In this case the change of vmax is used to maintain the correct full load of the appliance, but could additionally also be used for e.g. better emissions when using the Wobbe Value B. The change of vmin is in this case used to improve the combustion performance, like acoustics, burner emissions, light back sensitivity on the minimum fan speed.

[0285] Figure 8 shows a flow chart relating to a transition process to switch the combustion appliance 1 from an operation mode to a standby mode or to stop the combustion appliance according to a first embodiment. Thereto, the switch off phase of the operation mode is initiated, which is described below.

[0286] In a first sub-step A1, the transition process is initiated and therefore the combustion appliance is operated in the switch off phase of the operation mode. The transition process can be initiated when the burner off condition is reached as it is explained in figure 7.

[0287] In a second sub-step A2 the data processing device 9 causes that the burner 7 is stopped. Thus, no combustion occurs after the second sub-step A2. In a third substep A3, the throttle element is moved to a stored throttle element position. In a fourth sub-step A4 a post-purge process is performed. In the post-purge process the oxygen sensor can be calibrated by using the calibration manager described above. In a fifth sub-step A5 the transition process is finalized so that the combustion appliance can be switched to a standby mode or stopped in the fifteenth step G15 shown in figure 3.

[0288] Figure 8a shows a flow chart relating to a transition method to prepare the combustion appliance to switch from an operation mode to a standby mode or to stop the combustion appliance according to the second embodiment. The method according to the second embodiment differs from the method according to the first embodiment in that the method does not comprise the third sub-step A3, in which the throttle element is moved to a stored throttle element position.20.06.2025

[0289] 50

[0290] That means, the post-purge process of the fourth sub-step A4 is directly initialized after the burner is stopped in the third sub-step A3.

[0291] Figure 9 shows a flow chart for setting the starting behavior of the combustion appliance 1 according to a first embodiment. In a first sub-step W1 it is checked whether the fuel gas type or fuel gas quality is known that is supplied to the nonoperating combustion appliance 1. The fuel gas type or fuel gas quality can be specified by a value, in particular a Wobbe value and / or a calorific value. In the following, the flow chart is explained by referring to the Wobbe value. However, the starting behavior can be set by using the calorific value instead of the Wobbe value.

[0292] Alternatively, the first sub-step W1 may assume a certain fuel gas type or fuel gas quality and a corresponding, assumed Wobbe value and / or assumed calorific value. The assumed certain fuel gas type or fuel gas quality and corresponding, assumed Wobbe value and / or a calorific value may be those determined in an earlier commissioning operation and may be the same for every start after the earlier commissioning operation.

[0293] If the fuel gas quality or fuel gas type is not known and / or not assumed, in a second sub-step W2 a Wobbe value is taken from a Wobbe table that is stored in a memory. Specifically, the Wobbe value being arranged at the first position of the Wobbe table is taken. The Wobbe table can be structured such that the Wobbe value decreases with increasing position in the Wobbe table. The table is a two-dimensional table with rows and columns. With increasing position, it is meant that the Wobbe value arranged in a subsequent lower row is considered. The lowest Wobble value is found at the last position, i.e. last row, of the Wobbe table.

[0294] In a third sub-step W3 the throttle element position of the throttle unit 6 is determined. In particular, the throttle element position is determined that is assigned to the Wobbe value determined in the second sub-step W2. Alternatively,20.06.2025

[0295] 51

[0296] the throttle element position is determined that is assigned to the assumed Wobbe value.

[0297] In a fourth sub-step W4 the fuel gas and air mixture that is present in the combustion chamber of the combustion appliance 1 is ignited. In a fifth sub-step W5 the data processing device 9 that is assigned to the combustion appliance 1 determines whether a flame is present. In other words, in the fifth sub-step W5 it is determined whether the ignition was successful. The combustion appliance 1 can comprise a flame detector for detecting a flame and thus for determining whether the ignition is successful.

[0298] In a sixth sub-step W6 the oxygen sensor 8 measures the oxygen value after the fuel gas and air mixture is ignited in the fifth sub-step W5. If the mixture is ignited, the oxygen sensor 8 will measure a flue gas oxygen value. Otherwise, the oxygen sensor 8 measures the oxygen proportion in the mixture.

[0299] If the data processing device 9 determines in the fifth sub-step W5 that a flame is present, the Wobbe value of the fuel gas and the throttle element position are known. Specifically, the Wobbe value corresponds to the Wobbe value that is assigned to the throttle element position in the Wobbe table. That means after the fifth step the fuel gas quality is known.

[0300] Additionally, it is checked in a seventh step W7 if the combustion appliance 1 is already commissioned. If this is the case, the method is continued in an eighth step W8 that corresponds to the seventeenth sub-step G17 shown in Fig. 3. If the data processing device 9 determines that the combustion appliance is not commissioned in the seventh step W7, the method is continued in a ninth sub-step W9 that corresponds to the eight step G8 shown in figure 3.

[0301] If the data processing device 9 cannot determine the presence of a flame in the fifth sub-step W5, the data processing device 9 checks whether a maximum number of20.06.2025

[0302] 52

[0303] ignition attempts are made in a tenth sub-step W10. If this is the case the data processing device aborts the ignition phase and can lock the combustion appliance 1 in an eleventh sub-step W11.

[0304] If the maximum number of ignition attempts is not reached, the data processing device checks in a twelfth sub-step W12 whether the oxygen value measured in the sixth sub-step W6 is arranged within a predetermined oxygen range. If this is not the case, a new ignition is initiated in the fourth sub-step W4.

[0305] However, if the measured oxygen value is arranged in the predetermined range, the data processing device 9 reads out the Wobbe value that is assigned to the next position, i.e. next row, of the Wobbe table discussed in the second sub-step W2 in the thirteenth sub-step W13. In other words, the next lower Wobbe value is read out. In a fourteenth sub-step W14 it is checked whether the new table position from which the Wobbe value is read out is the last position, i.e. the last row, of the Wobbe table. That means, it is determined whether Wobbe table is at the final position. If this is the case, the data processing device 9 initiates the ignition in the fourth substep W4.

[0306] If the new table position is not the last position, i.e. not the last row, the data processing device 9 determines the throttle element position that is assigned to the Wobbe value being in the newly determined position in a fifteenth sub-step W15. Additionally, the data processing device 9 receives the throttle element position that is saved in a memory in a sixteenth sub-step W16.

[0307] The data processing device 9 checks in a seventeenth sub-step W17 whether the saved throttle element position is greater than the throttle element position that is determined in the fifteenth sub-step W15. If the determined throttle element position isgreaterthan the saved throttle element position, the method is continued in the fourth sub-step W4. If the throttle element position is not greater than the20.06.2025

[0308] 53

[0309] saved throttle element position, the sub-step method is continued in the thirteenth sub-step W13.

[0310] Figure 9a shows a flow chart showing the method for setting the starting behavior of the combustion appliance according to a second embodiment. The starting behaviour of the combustion appliance as discussed in fig. 9a is explained by referring to the Wobbe value. However, the starting behavior can be alternatively set by using the calorific value instead of the Wobbe value.

[0311] In a first sub-step W1a the data processing device 9 determines whether the combustion appliance has already been commissioned. This is the case if a commissioning flag is set.

[0312] If the combustion appliance is not commissioned, in a second sub-step W2 a Wobbe value assigned to a first row of a Wobbe is taken. The Wobbe table is stored in an electronic memory of the combustion appliance. The Wobbe table can be structured such that it comprises several rows containing Wobbe values. The Wobbe value decreases with increasing position of the row in the Wobbe table, i.e. with increasing row number. The table is a two-dimensional table with rows and columns. With increasing position, it is meant that the Wobbe value arranged in a subsequent lower row is considered. The lowest Wobble value is found at the last position, i.e. last row, of the Wobbe table.

[0313] The Wobbe value identified in the second sub-step W2a and its corresponding row position is stored in a database in a third sub-step W3a.

[0314] In a fourth sub-step W4a the throttle element position of the throttle unit 6 is determined. In particular, the throttle element position is determined that is assigned to the Wobbe value determined in the second sub-step W2a. In a fifth substep W5a the throttle element of the throttle unit 6 is moved to the determined throttle element position and the method is continued with a sixth sub-step W6a.20.06.2025

[0315] 54

[0316] If the data processing device 9 determines in the first sub-step W1a that the combustion appliance is commissioned, the data processing device 9 determines in a further first sub-step W1 b whether an unexpected flame loss has occurred during a heat demand, in particular during the previous heating operation, or not. Hereto, in the further first sub-step W1 b the data processing device 9 can, in particular, check the presence or value of a blocking code that has been written in a memory at such unexpected occurrence. If it is determined that such flame loss occured, the method is continued with the second sub-step W2a. If not, the method continues with the sixth sub-step W6a.

[0317] In the sixth sub-step W6a the fuel gas and air mixture that is present in the combustion chamber of the combustion appliance 1 is ignited. In a seventh sub-step W7a the data processing device 9 that is assigned to the combustion appliance 1 determines whether a flame is present. In other words, in the seventh sub-step W7a it is determined whether the ignition was successful. The combustion appliance 1 can comprise a flame detector for detecting a flame and thus for determining whether the ignition is successful.

[0318] In an eight sub-step W8a the oxygen sensor 8 measures the oxygen value after the fuel gas and air mixture is ignited or after an attempt to ignite in the sixth sub-step W6a. If the mixture is ignited, the oxygen sensor 8 will measure a flue gas oxygen value. Otherwise, the oxygen sensor 8 measures the oxygen proportion in the mixture. The eight sub-step W8a is done in parallel to at least the fourteenth substep W14a.

[0319] If the data processing device 9 determines in seventh sub-step W7a that a flame is present, the Wobbe value of the fuel gas and the throttle element position are known. Specifically, the Wobbe value corresponds to the Wobbe value that is assigned to the throttle element position in the Wobbe table. That means after the seventh sub-step W7a the fuel gas quality is known.20.06.2025

[0320] 55

[0321] In a nineth sub-step W9a the data processing determines 9 whether a commissioning flag is set and thus the combustion appliance 1 is already commissioned. If this is the case, the method is continued in a tenth sub-step W10a. In the tenth sub-step W1 Oa it is waited for a predetermined time, for example 10 s, so that the measured oxygen values stabilize. Afterwards, the method is continued in an eleventh sub-step W11a that corresponds to the seventeenth sub-step G17 shown in fig. 3a. Alternatively, the method is also continued in the eleventh sub-step W11a when it is determined in the tenth sub-step W10a that the oxygen value is below the lower threshold 3. In this case the combustion mixture is too rich and the data processing device 9 does not wait for the predetermined time and acts immediately.

[0322] If the data processing device 9 determines that the combustion appliance is not commissioned in the nineth step W9a, the method is continued in a twelfth sub-step W12a that corresponds to the eight step G8 shown in fig. 3a.

[0323] After the combustion appliance is ignited in the seventh sub-step W7a, the data processing device 9 can determine whether the flue gas path is blocked in a thirteenth sub-step W13a. This method is explained more in detail in connection with figures 12 to 15 below.

[0324] If the data processing device 9 cannot determine the presence of a flame in the seventh sub-step W7a, the data processing device 9 checks whether a maximum number of ignition attempts are made in a fourteenth sub-step W14a. If this is the case the data processing device aborts the ignition phase and can lock the combustion appliance 1 in a fifteenth sub-step W15a.

[0325] If the maximum number of ignition attempts are not reached, the method the data processing device checks whether the oxygen value fulfills a condition that is dependent on at least one flue gas oxygen value. This is done a sixteenth sub-step20.06.2025

[0326] 56

[0327] W16a and seventieth sub-step W17a. The sixteenth sub-step W16a and the seventieth sub-step W17a are only conducted when they receive data from both the eight sub-step W8a and the fourteenth sub-step W14a.

[0328] In the sixteenth sub-step W16a the data processing device 9 determines whether the measured flue gas oxygen value is within a predetermined range of flue gas oxygen values. The predetermined range of flue gas oxygen values can be between 8% and 20%. In the seventieth sub-step W17a the data processing device determines whether the measured flue gas oxygen value is lower than predetermined value, in particular lower than 2%.

[0329] If the data processing device determines that the measured flue gas oxygen value is not within the predetermined range of flue gas oxygen values, the method is continued in the sixth sub-step W6a. If it is determined in the sixteenth sub-step W16a that the measured flue gas oxygen values is arranged within the predetermined range of flue gas oxygen values, the data processing device 9 determines in an eighteenth sub-step W18a whether the saved row of the Wobbe table is the last row of the Wobbe table. The data processing device 9 receives the saved row of the Wobbe table in a nineteenth sub-step W19a. The stored value can correspond to the value that is stored in the third sub-step W3a, in a twenty-first sub-step W21a, or in a twenty-fifth sub-step W25a that are described below. If the data processing device determines that the saved row is the last row of the Wobbe table, the method is continued in the sixth sub-step W6a.

[0330] If the data processing device 9 determines in the eighteenth sub-step W18a that the saved row is not the last row in the Wobbe table, the data processing device determines the Wobbe value that is assigned to a row that is at an increased position than the previous row. The row position is increased by 1 so that the next row is adjacent to the previous row of the Wobble table. As discussed above, the Wobbe value decreases with increasing position of the rows in the table. Said Wobbe value and row position is saved in twenty-first sub-step W21a and thus can be later used20.06.2025

[0331] 57

[0332] in the nineteenth step W19a. Additionally, in the twenty-second sub-step W22a the data processing device 9 acts on the throttle unit so that the throttle element is moved to the throttle element position that is assigned to said Wobbe value identified in the twentieth sub-step W20a. Afterwards, the method is continued with the sixth sub-step W6a.

[0333] If the data processing device determines that the measured flue gas oxygen value is not smaller than the predetermined value, in particular 2% in the seventeenth substep W17a, the method is continued in the sixth sub-step W6a. If it is determined in the seventeenth sub-step W17a that the measured flue gas oxygen values is smaller than the predetermined value, in particular 2%, the data processing device 9 determines in an twenty-third sub-step W23a whether the saved row of the Wobbe table is the first row of the Wobbe table. The data processing device 9 receives the saved row of the Wobbe table in the nineteenth sub-step W19a. If the data processing device determines that the saved row is the first row of the Wobbe table the method is continued in the sixth sub-step W6a.

[0334] If the data processing device 9 determines in the eighteenth sub-step W18a that the saved row is not the first row in the Wobbe table, the data processing device determines the Wobbe value that is assigned to a row that is at a decreased position than the previous row. The row position is decreased by 1 so that the next row is adjacent to the previous row of the Wobble table. As discussed above, the Wobbe value increases with decreasing position of the rows in the table. Said Wobbe value and row position is saved in twenty-fifth sub-step W25a and thus can be later used in the nineteenth sub-step W19a. Additionally, in the twenty-sixth sub-step W26a the data processing device 9 acts on the throttle unit so that the throttle element is moved to the throttle element position that is assigned to said Wobbe value identified in the twenty-fourth sub-step W24a. Afterwards, the method is continued with the sixth sub-step W6a.20.06.2025

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[0336] The combustion appliances mentioned in the following can executed the methods according to the first embodiment or the second embodiment, which are described in the figures 3-9a.

[0337] Figure 10 shows an overview of a system 10 comprising several combustion appliances, namely a first combustion appliance 1 a, a second combustion appliance 1 b, a third combustion appliance 1c and a fourth combustion appliance 1d. In the system 10 shown in figure 10 all combustion appliances 1a, 1 b, 1c, 1d are in an operating mode. The combustion appliances are arranged in a cascade and are connected in parallel to each other.

[0338] The system 10 comprises a fuel gas line 15 by means of which fuel gas can be supplied to the respective combustion appliances 1a, 1 b, 1c, 1d. Additionally, the system 10 comprises a data line 16 by means of which a data exchange can occur between the combustion appliances 1 a, 1 b, 1 c, 1 d and / or between the combustion appliances and a master data processing device 14. In the embodiment shown in figure 10 the data processing device of the first combustion appliance 1a corresponds to the master data processing device 14.

[0339] In an alternative embodiment, it is not fixed which of the data processing device of the combustion appliances 1 a, 1 b, 1 c, 1 d acts as the master data processing device, but the master role is taken by one of the data processing devices that are assigned to the combustion appliances 1 a, 1 b, 1 c, 1 d that are in operation mode.

[0340] In the following, the process is explained by referring to the Wobbe value. However, the process also works if the calorific value is used instead of the Wobbe value.

[0341] Each of the combustion appliances 1a, 1 b, 1c, 1d can be configured like the combustion appliance 1 shown in figure 1. The data processing device 9 of the second, third and fourth combustion appliance 1 b, 1c, 1d transmit the determined20.06.2025

[0342] 59

[0343] Wobbe value to the data processing device of the first combustion appliance 1 a that corresponds in this embodiment to a master data processing device 14

[0344] The Wobbe value for an operating combustion appliance 1a, 1b, 1c, 1d isdetermined as follows. The data processing devices 9 assigned to the respective combustion appliances 1 b, 1c, 1d determines the throttle element position of the respective throttle unit 6. Afterwards, the data processing device 9 determines the Wobbe value that is assigned to the throttle element position of the throttle unit 6. Each data processing device 9 can determine the Wobbe value in said manner.

[0345] Additionally, the master data processing device 14 also determines the Wobbe value of the first combustion appliance 1 a in said manner and receives the Wobbe values from the remaining data processing devices 9. The master data processing device 14 determines a control Wobbe value that shall be used to control the combustion appliances 1a, 1b, 1c, 1d from the received and determined Wobbe values. Specifically, the master data processing device 14 determines which of the present and received Wobbe values is the latest Wobbe value and / or determines an average Wobbe value on the basis of the received Wobbe values. Said control Wobbe value matches best the current fuel gas quality provided by the fuel gas line 15 to the combustion appliances 1 a, 1 b, 1 c, 1 d. Afterwards, the master data processing device 14 transmits said determined, latest Wobbe value to all data processing devices 9 of the combustion appliances 1 a, 1 b, 1 c, 1 d. Each of the combustion appliances 1 a-1 d is controlled dependent on said latest control Wobbe value.

[0346] Specifically, the throttle element position of the throttle unit 6 of each of the combustion appliances 1 a-1 d is controlled to match to the determined latest control Wobbe value. As discussed above, the throttle element position can be gathered from the Wobbe table that assigns Wobbe values to respective throttle element positions. Specifically, the throttle element position can be determined as each of the combustion appliances 1 a, 1 b, 1 c, 1 d comprises a table in which Wobbe values are assigned to throttle element positions. The Wobbe value or calorific value can20.06.2025

[0347] 60

[0348] be determined according to the method described in fig. 9. Alternatively, the Wobbe value or calorific value can be determined in the fourteenth sub-step N14a shown in figure 8a. The determined Wobbe value or calorific value can be used for information for e.g. an installer. In a cascade situation, the determined Wobbe value or calorific value is not stored in the appliance itself, but can be stored in the cascade controller 35.

[0349] Alternatively, the Wobbe value can be determined only for one of the plurality of combustion appliances and the Wobbe value from said one combustion appliance is used to control all remaining combustion appliances. Alternatively, the Wobbe value can be determined only for one of the plurality of operating combustion appliances and the Wobbe value from said one combustion appliance is used to control all remaining combustion appliances.

[0350] In fig. 10 a cascade controller 35 is provided that is connected with each of the data processing devices 9, 14 of the combustion appliances 1 a-1 d in a data manner. Thus, the cascade control device 35 and the data processing devices 9, 14 can exchange data. The cascade controller 35 determines which of the combustion appliances is operated and / or determines which of the data processing devices 9, 14 is the master data processing device 14.

[0351] Figure 11 shows an overview of a system 10 comprising several combustion appliances 1 a, 1 b, 1 c, 1 d in a state in which some combustion appliances are nonoperating. Specifically, the third combustion appliance 1c and the fourth combustion appliance 1d are non-operating and can be e.g. in a standby mode. For switching the third and fourth combustion appliance 1c, 1d to an operating mode the following steps are necessary. Likewise, to figure 10, the combustion appliances are arranged in a cascade and connected to each other in parallel.

[0352] The master data processing device 14 determines the Wobbe value for the first combustion appliance 1a and the data processing device 9 determines the Wobbe20.06.2025

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[0354] value for the second combustion appliance 1 b. Said determined Wobbe value of the second combustion appliance 1b is transmitted to the master data processing device 14. The master data processing device 14 and the data processing device 9 can determine the Wobbe value in the same way as it is described for the system shown in figure 10.

[0355] The master data processing device 14 determines which of the received Wobbe values is the latest one. Said Wobbe value is determined as control Wobbe value and transmitted to the second, third and fourth combustion appliance, in particular to the data processing device assigned to the respective combustion appliance 1 b, 1 c, 1d. The respective data processing device 9 controls the assigned combustion appliance 1 b, 1c, 1d dependent on the control Wobbe value that is received from the master data processing device 14. Specifically, the throttle element position of the throttle unit 6 is set dependent on the received control Wobbe value. Likewise, the master data processing device 14 can control the first combustion appliance 1 a on the basis of the determined control Wobbe value.

[0356] The non-operating combustion appliance 1c, 1d is transitioned from the standby mode to the operation mode as follows. After the data processing device 9 receives a transition signal from the master data processing device 14, the data processing device 9 initializes the ignition phase of the operation mode. Further, the master data processing device 14 sends the determined Wobbe value to the combustion appliance 1c, 1d to be transitioned to the operation mode. In other words, the combustion appliance 1 c, 1 d to be transitioned positions the throttle element of the throttle unit to the position that corresponds to the Wobbe value sent by the master data processing device 14. This can be done in the third sub-step W3 shown in figure 9 or the fourth sub-step shown in figure 9a.

[0357] Alternatively the non-operating combustion appliance 1c, 1d is transitioned from the standby mode to the operation mode as follows. Said combustion appliance 1 c, 1d is selected by the cascade controller 35, which determines the priority of the20.06.2025

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[0359] operation. After the data processing device 9 receives a transition signal from the cascade controller 35, the data processing device 9 initializes the ignition phase of the operation mode. Further, the cascade controller 35 sends the determined Wobbe value to the combustion appliance 1 c, 1 d to be transitioned to the operation mode. In other words, the combustion appliance 1 c, 1 d to be transitioned positions the throttle element of the throttle unit to the position that corresponds to the Wobbe value sent by the cascade controller 35. This can be done in the third substep W3 shown in figure 9 or the fourth sub-step shown in figure 9a.

[0360] Figure 12 shows a flow chart for detecting blockage in flue gas path of a combustion appliance. This method can be part of the setting of the starting behavior, in particular of the ignition phase, of the combustion appliance 1 that is done in the seventh step G7 or in the sixteenth step G16. Specifically, the blockage detecting can be executed before the starting behavior, in particular of the ignition phase, of the combustion appliance 1 is set. Additionally or alternatively, the blockage detection can be conducted in the thirteenth sub-step W13a shown in fig. 9a. The blockage detection is not limited to the determination whether the flue gas path is fully blocked or not but also determines the blockage level within the flue gas path.

[0361] In a first sub-step B1 the method for detecting blockage is initiated. As mentioned above this can happen when the ignition phase of the combustion appliance is initiated. In the first sub-step B1 the method for determining the flue resistance level can be selected. The selection can be done manually or according to preset order. The different methods for flue resistance detection are described below in figure 13-15.

[0362] In a second sub-step B2the parameterthat is used forflue resistance determination is measured. In a third sub-step B3 the measured parameter value is converted to a flue resistance value. Specifically, the measured value is converted to a flue resistance level, in particular to a percentage [%] of the flue resistance level. The conversion is made with an empirical relation determined in a lab environment.20.06.2025

[0363] 63

[0364] In a fourth sub-step B4 the determined flue resistance level is checked against a predetermined parameter in order to determine the flue resistance status, in particular to determine whether the blockage level of the flue gas path is too high or not. The factor is set by the manufacturer of the combustion appliance or by the installer.

[0365] Figure 13 shows a diagram illustrating how blockage in the flue gas path can be determined according to a first variant. The diagram shows the correlation between the flue resistance level in the flue gas path and a time.

[0366] For determining the blockage in the flue gas path, the time is determined that is needed to reach a predetermined oxygen value. Said oxygen value can be equal or greater than 7,5%. In the example shown in fig. 13, the oxygen value is reached at a time t.

[0367] The diagram shows a predetermined curve 31 that assigns the time to the flue resistance level and thus shows the correlation between the time and the flue resistance level. Said predetermined curve 31 is stored in a memory of the combustion appliance 1. As is it evident from figure 13 an increasing time correlates to an increased flue resistance level.

[0368] In the next step the determined time t is converted to the flue resistance value by using the curve 31. Thereto, a curve value V1 is determined that is assigned to the time t. The curve value V1 is also assigned to the flue resistance level. Said flue resistance level is checked against a parameter predetermined by the manufacturer or installer to determine whether the flue resistance level in flue gas path is considered to be too high or not.20.06.2025

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[0370] Figure 14 shows a diagram illustrating how blockage in the flue gas path can be determined according to a second variant. The diagram shows the correlation between the flue resistance level in the flue gas path and measured oxygen values.

[0371] In the second variant, the data processing device 9 ensures that the oxygen sensor measures the flue gas oxygen value at a predetermined time-point after the fuel valve 5 is opened. In this case the oxygen value OV was measured at the predetermined time point. For example, the data processing device can ensure that the oxygen value is measured after 2,4 seconds after the fuel valve 5 is opened. As is it evident from figure 14 increasing oxygen values correlate to increasing flue resistance levels.

[0372] The diagram shows a predetermined curve 31 that assigns the oxygen values to the flue resistance level and thus shows the correlation between the oxygen value and the flue resistance level. Said predetermined curve 31 is stored in a memory of the combustion appliance 1. As is it evident from figure 13 an increasing oxygen value correlates to an increased flue resistance level.

[0373] In the next step the measured oxygen value OV is converted to a flue resistance level by using the curve 31. Specifically, a curve value V1 is determined that is assigned to the oxygen value OV. The curve value V1 is also assigned to the flue resistance level. Said flue resistance level is checked against a parameter predetermined by the manufacturer or installer to determine whether the flue resistance level in flue gas path is considered to be too high or not.

[0374] Figure 15 shows a diagram illustrating how blockage in the flue gas path 17 can be determined according to a third variant. The diagram shows the correlation between the flue resistance level in the flue gas path and a gradient of the oxygen value. After the fuel gas valve is opened, the oxygen values are measured.20.06.2025

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[0376] The data processing device 9 receives several oxygen values and determines at least one gradient dependent on the received oxygen values. Additionally, the data processing device 9 determines the minimum gradient value MGV during the ignition phase of the combustion appliance 1.

[0377] The diagram shows a predetermined curve 31 that assigns the gradient values to the flue resistance level and thus shows the correlation between the gradient of the oxygen value and the flue resistance level. Said predetermined curve 31 is stored in a memory of the combustion appliance 1. As is it evident from figure 13 increasing gradient values correlate to an increased load loss.

[0378] In the next step the minimum gradient value MGV is converted to a flue resistance level by using a curve 31. In fig. 15 the curve value V1 is assigned to the determined minimum gradient MGV. The curve value V1 is also assigned to the flue resistance level. Said flue resistance level is checked against a parameter predetermined by the manufacturer or installer to determine whether the flue resistance level in flue gas path is considered to be too high or not.

[0379] Figure 16 shows a flow chart illustrating how a combustion appliance failure state is determined. In a first sub-step D1 the method is activated. The method can be part of the method by means of which the starting behavior of the combustion appliance 1 is determined and set. That means, the method can be performed in the seventh step G7 shown in fig. 3 when the combustion appliance is in the commissioning mode or in the sixteenth step G16 shown in fig. 3 when the combustion appliance is in the operation mode. In the first sub-step D1 the data processing device 9 receives an oxygen value measured by the oxygen sensor 8.

[0380] In the second sub-step D2 the data processing device 9 determines the combustion appliance state. Specifically, the data processing device 9 determines in the second sub-step D2 whether the combustion appliance 1 is in a failure state.20.06.2025

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[0382] In case that the data processing device 9 determines in the second sub-step D2 that the combustion appliance 1 is in a failure state, the data processing device 9 transmits a failure signal to a display device of the combustion appliance in a third sub-step D3. The failure state of the combustion appliance comprising the failure type is displayed on the display device in the third sub-step D3. Additionally, the data processing device 9 ensures in the third sub-step D3 that the commissioning mode or operating mode of the combustion appliance is stopped. The data processing device 9 then initiates a couple of re-attempts which can ultimately lead to stop the combustion appliance. However, it depends on the failure state whether the data processing device 9 initiates the re-attempts.

[0383] If the data processing device 9 does not determine in the second sub-step D2 that the combustion appliance 1 is in failure state, the starting behavior executed in the seventh step G7 or sixteenth step G16 shown in fig. 3, 3a is continued. Thereto, it is referred to the aforementioned statements referring to the setting of the combustion appliance 1 in the starting behavior.

[0384] Figure 17 shows a diagram showing different states of the combustion appliance 1 during a commissioning mode. The diagram shows a curve 32 of oxygen values that are measured by the oxygen sensor 8 and transmitted to the data processing device 9. Additionally, the diagram shows the time of a start attempt of the combustion appliance 1. As is evident from fig. 17, the time of a start attempt signal O has a rectangular shape, indicating that the fuel valve 5 is opened.

[0385] Additionally, a lower threshold 24, an upper threshold 23 and a further upper threshold 25 are shown in the diagram. The threshold values relate to oxygen values. Thus, the lower threshold 24 corresponds to an oxygen value that is smaller than the oxygen value corresponding to the upper threshold 23. The oxygen value of the upper threshold 23 is smaller than the oxygen value corresponding to the further upper threshold 25.20.06.2025

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[0387] The data processing device 9 determines a combustion appliance state dependent on the oxygen value measured by the oxygen sensor 8. As is explained below more in detail, the data processing device 9 can also consider other combustion parameters for the determination of the combustion appliance state. Dependent on the oxygen value it can be differentiated between the following states.

[0388] If the measured oxygen value is above the further upper threshold 25, the data processing device 9 determines that no fuel, in particular fuel gas, is present and thus determines a combustion failure state, which in the application is also indicated as fourth failure state. The further upper threshold can be 20% of oxygen. Said state is indicated as "State A" in the diagram. Said state is present for example during a time period until the time point t1 in figure 17.

[0389] The data processing device 9 transmits a failure signal to the display device of the combustion appliance stating that no fuel gas is present and / or that the fuel gas supply to the appliance is interrupted. Additionally, the data processing device 9 ensures that the ignition phase of the combustion appliance 1 is aborted and the combustion appliance 1 is switched to blocking or locking mode. A locking mode is the result of a failure state and requires a manual reset of the combustion appliance 1. A blocking mode is the result of a failure state and is a temporary block of the combustion appliance 1, wherein the combustion appliance 1 will resume an operation mode at a later time, automatically.

[0390] If the measured oxygen value is between the further upper threshold 25 and the upper threshold 23, the data processing device 9 determines that the fuel gas is not sufficiently present and thus determines a combustion appliance failure state, which in the application is also indicated as third failure state. Specifically, the data processing device 9 determines that the air to fuel gas ratio is not correct. Said state is indicated as "State B" in the diagram. To solve the problem, the fuel valve can be adjusted either automatically or manually by the installer. The upper threshold 2320.06.2025

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[0392] can be 10% of oxygen in the measured gas. State B is present for example in the time period between time point t2 and time point t3 in figure 17.

[0393] The data processing device 9 transmits a failure signal to the display device of the combustion appliance stating that the wrong air to fuel gas ration is detected and thus the air and fuel gas mixture being in the combustion chamber is too lean. Additionally, the failure signal comprises the information to the installer to adjust the fuel valve 5 shown in figure 1. The data processing device 9 ensures that the ignition phase of the combustion appliance 1 is aborted and the combustion appliance 1 is switched to blocking or locking mode or the throttle unit is adjusted such that richer start conditions are achieved during next ignition attempt.

[0394] If the measured oxygen value is between the upper threshold 23 and the lower threshold 24, the data processing device 9 determines that sufficient fuel gas is present or in other words that the measured oxygen value is in the correct range. Said state is indicated as "State C" in the diagram and for example is present in the time period between time point t4 and time point t5 in figure 17. Additionally, the data processing device checks whether the combustion appliancel is ignited. If the combustion appliance is not ignited and thus no flame is detected, the data processing device 9 determines that a combustion appliance component is malfunctioning and thus determines a combustion appliance failure state, which is indicated in the application as second failure state. At this point the data processing device 9 knows that the fan and fuel valve are operating. Most likely the ignition probe, ignition transformer and / or wire harness is malfunctioning. Said information is displayed on the display device of the combustion appliance.

[0395] The data processing device 9 transmits a failure signal to the display device of the combustion appliance stating that a correct air to fuel gas ratio is detected and that the installer should check for a component malfunctioning or wrong parameter setting. Additionally, the data processing device 9 ensures that the ignition phase of20.06.2025

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[0397] the combustion appliance 1 is aborted and the combustion appliance 1 is switched to blocking or locking mode.

[0398] However, if the data processing device 9 determines that the measured oxygen value is in the correct range and that the combustion appliance is ignited, the data processing device 9 determines that the combustion appliance 1 is in a failure free state so that the ignition phase or operation mode can be continued.

[0399] If the measured oxygen value is below the lower threshold value, for example lower than 2% oxygen, the data processing device 9 determines that the air and fuel gas mixture is too rich to start and thus determines a combustion appliance failure, which in the application is also indicated as first failure state. Said state is indicated as "State D" in the diagram and for example is present in the time period between time point t6 and time point t7 in figure 17. The data processing device 9 displays in the display that components malfunctioning is not expected to be the cause for the failure state. This helps the installer to find the reason for the failure state of the combustion appliance 1.

[0400] The data processing device 9 transmits a failure signal to the display device of the combustion appliance stating that a wrong air to fuel gas ratio is detected and that the detected air and fuel gas mixture is too rich. Additionally, the installer is informed to adjust the fuel valve 5 shown in figure 1 to resolve the combustion appliance failure state. Further, the data processing device 9 ensures that the ignition phase of the combustion appliance 1 is aborted and the combustion appliance 1 is switched to blocking or locking mode. Alternatively, the throttle element position is adjusted such that leaner start conditions can be achieved during the next ignition attempt.

[0401] In the present application "a lean combustion mixture" is a combustion mixture having an air to fuel ratio that is above 1.3. Further, in the application a "rich"20.06.2025

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[0403] combustion mixture is assumed when the air to fuel ratio of the combustion mixture is below 1.2.

[0404] The used time points t1 to t7 are different than the time points discussed below in connection with fig. 18-20.

[0405] Fig. 18 shows a calibration of the oxygen sensor for a situation in which the oxygen sensor 8 is always heated. The calibration process described below occurs in the fifth step G5 shown in fig. 3, 3a In fig. 18 the time-period in which exists a heat demand, which is known from, e.g., the thermostat settings for central heating, the calibration time interval in which the calibration time is expired, the time-period in which the oxygen sensor is heated and the time-period in which the burner is operated are indicated with blackfilled rectangles.

[0406] The data processing device 9 initiates a calibration of an oxygen sensor 8 for calibrating the oxygen sensor 8. Thereto, the safety unit control portion 28 of the data processing device 9 transmits a control signal to the sensor data processing unit 20 of the oxygen sensor 8. Additionally, the data processing device 9 initiates a purging of the combustion chamber 18. Thereto, the data processing device 9 transmits a control signal to the fan 5 to run the fan 5 at a predetermined speed for a predetermined time. The data processing device 9 ensures that the calibration initiation and the purging initiation is set such that the oxygen sensor 8 is calibrated duringthe purgingof the combustion chamber 18. The purging initiation can include a pre-purging or post-purging process. Additionally, the data processing device 9 ensures that the burner 7 is stopped during the calibration and / or purging of the combustion chamber 18. As the data processing device 9 knows when a heat request will occur in the intended appliance, such as central heating and / or domestic hot water, the data processing device can determine the time when to initiate pre-purging or post-purging to calibrate the oxygen sensor 8.20.06.2025

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[0408] In the situation shown in fig. 18, in which the combustion appliance is powered on, the oxygen sensor 8 is always heated. There exists a heat demand between the first time point t1 and a second time point t2. At said two time points the calibration time interval is not expired. Thus, the burner is operated between the two time points t1 and t2. At the second time point t2 the data processing device 9 initiates purging of the combustion chamber 18. At a third time point t3 the data processing device 9 initiates a calibration of the oxygen sensor 8 that is ended at a fourth time point t4. At the third time point t3 the purging can be finished. Alternatively, the purging can be continued until the fifth time point t5.

[0409] A second heat demand is existent between a fifth time point t5 and an eighth time point t8. The data processing device 9 determines that the time point between the firth time point t5 and a sixth time point t6 corresponds to a burner time point after which the burner is stopped. Specifically, the burner is stopped at the sixth time point t6. The data processing device 9 initiates a post-purging at the sixth time point t6 and a predetermined a calibration of the oxygen sensor 8 likewise as it is explained for the first heat demand. The calibration of the oxygen sensor 8 is ended at a seventh time point t7 and the burner is started again at the seventh time point t7. The burner is operated until an eighth time point t8. Afterwards, the data processing device 9 initiates a further purging and oxygen sensor calibration that is identical to the purging and calibration described before.

[0410] At a ninth time point t9 the calibration time of the oxygen sensor 8 expired. Thus, the data processing device 9 will ensure that the calibration will be done by the next burner start as result of a further heat demand. At a tenth time point t10 the data processing device receives a third heat demand. The data processing device 9 initiates a pre-purging of the combustion chamber 18 at the tenth time point t10 which is ended at the eleventh time point t12. At the eleventh time point t11 the data processing device initiates the burner starting so that the combustion appliance 1 outputs heat.20.06.2025

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[0412] Fig. 19 shows a calibration of the oxygen sensor for a situation in which the oxygen sensor is not constantly heated. The initiation of the calibration and purging is done in the same way as it is described in fig. 18.

[0413] Likewise, to the situation shown in fig. 18 the heat demands can be prescheduled so that the data processing device 9 knows when there will be a heat demand for the combustion appliance 1. In the present case there is a first heat demand between a second time point t2 and a third time t3 point and a second heat demand starting at a seventh time point t7. The data processing device can initiate an oxygen sensor heating and a pre-purging at a first time point t1 that is before the second time point t2 when the heat demand starts. Specifically, the data processing device can select the first time point t1 that the oxygen sensor 8 is heated up and calibrated such that the calibration ends at the second time point t2. Thus, there is no time loss and the combustion appliance 1 can output heat at the time point t2 without waiting that the oxygen sensor is heated up or calibrated.

[0414] The data processing device 9 initiates a post-purge at a third time point t3 and initiates the oxygen sensor calibration at a fourth time point t4. The oxygen sensor calibration ends at the fifth time point t5. The oxygen sensor can only be calibrated when the oxygen sensor is heated.

[0415] The data processing device 9 determines that the calibration time is expired at a sixth time point. Thus, the data processing device 9 ensures that the oxygen sensor 8 is calibrated when the next heat demand is received. This is the case for the second heat demand that is received at the seventh time point t7. The data processing device 9 initiates a pre-purge and a calibration of the oxygen sensor 8 at the seventh time point t7. The calibration and the pre-purging are ended at an eighth time point t8 so that the burner starts at the eighth time point t8.

[0416] Fig. 20 shows a calibration of the oxygen sensor for a situation in which the oxygen sensor is heated for a predetermined time. The predetermined time can be 1 h. The20.06.2025

[0417] 73

[0418] initiation of the calibration and purging is done in the same way as it is described in fig. 18.

[0419] Likewise, to the situations shown in fig. 18 and 19, the data processing device 9 knows the start time and end time of each heat demand. In this case there is a first heat demand between a second and third time point t2, t3, a second heat demand between a seventh and an eighth time point t7, t8 and a third heat demand between a tenth and eleventh time point t10, t11.

[0420] As the first heat demand starts on the second time point t2, the data processing device initiates to start heating the sensor at a first time point t1. Additionally, the data processing device 9 initiates a pre-purging and calibration of the oxygen sensor 8 at the first time point t1. The pre-purging and the calibration are ended at the second time point t2 so that the burner starts to combust the air and fuel mixture in the combustion chamber 18. The burner is stopped at the end of the heat demand at the third time point t3. The data processing device initiates at the third time point t3 a post-purging and at a fourth time point t4 a calibration of the oxygen sensor 8. The calibration is ended at a fifth time point t5.

[0421] Likewise, as it is done for the first heat demand, the data processing device 9 initiates to heat up the oxygen sensor 8 and a pre-purging of the combustion appliance at a sixth time point t6, which ends at a seventh time point t7. The burner starts at the seventh time point t7 and ends at an eight time point t8. Further, the data processing device 9 initiates the post-purging and calibration that ends at a nineth time point t9.

[0422] The third heat demand is present at a tenth time point t10. However, at the tenth time point t10 the oxygen sensor is still heated, and the calibration time is not expired. Thus, there is no need for a pre-purging and the burner starts at the tenth time point t10. The burner is stopped at the end of the heat demand, namely at an20.06.2025

[0423] 74

[0424] eleventh time pointtl 1.The data processing device then initiatesa post-purging and a new calibration of the oxygen sensor 8.20.06.2025

[0425] 75

[0426] Reference Signs

[0427] 1 Combustion appliance

[0428] 1a First combustion appliance

[0429] 1b Second combustion appliance

[0430] 1c Third combustion appliance

[0431] 1d Fourth combustion appliance

[0432] 2 Upper threshold referring to operate combustion appliance

[0433] 2a Further upper threshold referring to operate combustion appliance 3 Lower threshold referring to operate combustion appliance

[0434] 3a Further lower threshold referring to operate combustion appliance 4 Fan

[0435] 5 Fuel valve

[0436] 6 Throttle unit

[0437] 7 Burner

[0438] 8 Oxygen sensor

[0439] 9 Data processing device / control unit

[0440] 10 System

[0441] 11 Fuel gas source

[0442] 12 Heat exchanger

[0443] 13 Manifold

[0444] 14 Master control unit

[0445] 15 Fuel gas line

[0446] 16 Data line

[0447] 17 Exhaust flue path

[0448] 18 combustion chamber

[0449] 19 Sensing element

[0450] 20 Sensor data processing unit

[0451] 21 Throttle element

[0452] 22 Throttle motor

[0453] 23 Upper threshold referring to determining presence of failure state 24 Lower threshold referring to determining presence of failure state 25 Further upper threshold

[0454] 26 Throttle unit control portion

[0455] 27 Comfort unit portion

[0456] 28 Safety unit control portion

[0457] 29 Temperature sensor

[0458] 31 predetermined curve

[0459] 32 curve related to oxygen values

[0460] 34 heating element

[0461] 35 cascade controller

[0462] A1 -A5 Method steps for preparing the combustion appliance to standby mode or to stop20.06.2025

[0463] 76

[0464] B1 -B4 Method steps for detecting blockage according to the first and second embodiment

[0465] C1 -C10, C1 a, C4a Method steps in the commissioning mode according to the first and / or second embodiment

[0466] D1 -D4 Method steps for determining the combustion appliance state

[0467] G1 -G18, G4a Method steps of general operation procedure of the system according to the first and / or second embodiment

[0468] N1 -N9, N5a-N13a Method steps in normal operation of combustion appliance according to the first and / or second embodiment

[0469] 01 First flue gas oxygen value

[0470] 02 Second flue gas oxygen value

[0471] 03 Third flue gas oxygen value

[0472] 04 Fourth flue gas oxygen value

[0473] O Start attempt signal

[0474] P Throttle Position signal

[0475] 51 First operating signal

[0476] 52 Second operating signal

[0477] 53 Third operating signal

[0478] 54 Fourth operating signal

[0479] t time

[0480] T1 -T9 Method steps of testing operation in the commissioning mode t1-t11 time-point

[0481] V1 Determined Value

[0482] W1 -W17 Method steps for determining the gas quality according to the first embodiment

[0483] W1 a-W26a Method steps for determining the gas quality according to the second embodiment

[0484] OV Oxygen value

[0485] MGV Maximum gradient value

[0486] vmin minimum fan speed

[0487] vmax maximum fan speed

Claims

20. 06.202577PATENT CLAIMS1. Method for operating at least one, in particular gas adaptive, combustion appliance (1 , 1 a-1 d), wherein the method comprises the following steps:receiving a throttle element position of a throttle unit (6) of the combustion appliance (1, 1a - 1d) for controlling a fuel flow rate to a burner (7) and / or a fuel valve setting of a fuel valve (5) of the combustion appliance (1, 1 a, 1 d) for controlling a fuel flow rate to a or the burner (7),determining a value that characterizes the calorific value of the fuel combusted by the combustion appliance (1 , 1 a-1 d) from the combustion appliance (1 , 1 a-1 d), wherein the determination is dependent on the received throttle element position and / or the fuel valve setting,controlling an airflow rate to be supplied to the burner (7) of the combustion appliance (1, 1a-1d) and / or the fuel flow rate to be combusted in the burner (7) of the combustion appliance (1, 1a, 1d) dependent on the determined value.

2. Method according to claim 1, characterized in thata. the determined value is a Wobbe value or a calorific value and / or in thatb. the value is determined when the combustion appliance is in an operation mode.

3. Method according to claim 1 or 2, characterized in that the combustion appliance (1, 1 a-1 d) comprises a fan (4) for controlling the air flow rate and in that a. the fan (4) of the combustion appliance (1, 1a-1d) is controlled dependent on the determined value and / or in thatb. a fan speed of the fan (4) is controlled dependent on the determined value and / or in thatc. a fan speed, in particular a minimum and / or a maximum fan speed, of the fan (4) is assigned to the determined value.20.06.2025784. Method according to at least one of the claims 1 to 3, characterized in that a. the value that characterizes the calorific value of the fuel combusted by the combustion appliance (1, 1a-1d) is assigned to a throttle element position and / orb. the throttle element position depends on a determined oxygen value, in particular flue gas oxygen value.

5. Method according to at least one of the claims 1 to 4, characterized in that the value is determined when the throttle element position fulfills a time dependent condition.

6. Method according to at least one of the claims 1 to 5, characterized in that the fuel gas flow rate is controlled by controlling the fuel valve setting and / or by changing the throttle element position.

7. Method according to at least one of the claims 1 to 6, characterized in that the air flow rate and / or a fuel flow rate are controlled such that a target burner load is achieved.

8. Method according to at least one of the claims 1 to 7, characterized in that a throttle unit (6) for controlling the fuel flow rate and / or a fuel valve (5) for controlling the fuel flow rate is controlled dependent on the determined value.

9. Method according to at least one of the claims 1 to 8, characterized in that several combustion appliances (1, 1a-1d), which are connected to each other in cascade, are operated, wherein one or more of the combustion appliances (1, laid) determine the value that characterizes the calorific value of the fuel to be combusted.20.06.20257910. Method according to claim 9, characterized in that a control value is determined on the basis of the determined value and that the combustion appliances (1 , 1 a-1 d) are controlled dependent on the determined value.

11. Method according to claim 10, characterized in thata. a non-operating combustion appliance determines whether the control value is present before the combustion appliance (1 , 1 a-1 d) is ignited, in particular and controls the operating mode of said combustion appliance dependent on the control value when a control value is present, and / orb. it is determined that the control value corresponds to the received or determined value when only one value is determined.

12. Method according to at least one of the claims 9 to 11 , characterized in that several values are determined and that a variation of the determined values is determined, wherein it is determined that the control value corresponds to said determined variation.

13. Method according to at least one of the claims 9 to 12, characterized in that the value is determined for each of the combustion appliances (1, 1a-1d) and transmitted to a master data processing device (14).

14. Method according to at least one of the claims 9 to 13, characterized in that the or a master data processing device (14) determines the control value from the received values and transmits the determined control value to the several combustion appliances (1, 1 a-1 d), wherein the several combustion appliances (1, 1a-1 d) are controlled dependent on the received control value.

15. Method according to at least one of the claims 9 to 14, characterized in that20.06.202580a. the or a master data processing device determines that the control value is the value of the latest operated combustion appliance (1, 1a- 1 d) and / orb. at least one start parameter of a non-operating combustion appliance (1, 1a-1d) or at least one parameter of an operating combustion appliance (1, 1a-1d) is adjusted dependent on the control value determined for the, in particular latest operated, combustion appliance (1, 1 a-1 d).

16. Method according to at least one of the claims 9 to 15, characterized in that the determination of the control value is dependent on the presence of a flame and / or a throttle element position and / or at least one determined oxygen value, in particular flue gas oxygen value.

17. Method according to claim 16, characterized in thata. a throttle element position of the throttle unit (6) is changed until a flame is detected and / or in thatb. the throttle element position is changed when the determined oxygen value, in particular flue gas oxygen value, is not arranged within a predetermined range.

18. Data processing device (9, 14) comprising means for carryingout the method of at least one of the claims 1 to 17.

19. Computer program product which, when the program is executed by a computer, in particular a data processing device, cause the computer, in particular the data processing device, to carry out the method of at least one of the claims 1 to 18.20.06.20258120. Computer readable data carrier having stored thereon the computer program product of claim 19 or data carrier signal carrying the computer program product of claim 19.

21. Combustion appliance (1, 1a-1d) comprisinga fan (4) for controlling an air flow,a fuel valve (5), in particular a fuel gas valve, optionally a pneumatic valve, in particulara controllable pneumatic valve, or optionally a stepper valve or optionally a modulator valve, for controlling a fuel flow, in particular a fuel gas flow,a burner (7) for combusting an air and fuel mixture,a throttle unit (6) for controlling the fuel flow anda data processing device (9) according to claim 18 for controlling the combustion appliance (1, 1a-1d).

22. System (10) comprising several combustion appliances (1, 1a-1d) according to claim 21, wherein a master data processing device (14) transmits a determined value that characterizes the calorific value of a fuel, in particular a determined Wobbe value or calorific value, to at least one combustion appliance (1, 1a-1d), wherein the at least one combustion appliance is controlled dependent on said determined value.

23. System (10) according to claim 22, characterized in that the master data processing device (14) determines the heat output to be provided by each of the combustion appliances (1, 1a-1d).

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