EP4600556A1

EP4600556A1 - Method for detecting blockage in an exhaust flue path

Info

Publication number: EP4600556A1
Application number: EP24156001.0A
Authority: EP
Inventors: Evert Gerhard TEN HAAKEN; Sander Klein Nijenhuis; Teunis Keizer
Original assignee: BDR Thermea Group BV
Current assignee: BDR Thermea Group BV
Priority date: 2024-02-06
Filing date: 2024-02-06
Publication date: 2025-08-13

Abstract

The invention relates to a method for detecting blockage in an exhaust flue path (17) of a combustion appliance (1, 1a-1d), wherein the method comprises the following steps:receiving at least one oxygen value referring to a gas in a gas flow path, in particular relating to a gas being in a combustion chamber (18) of the gas flow path, of the combustion appliance (1, 1a-1d) anddetermining whether the exhaust flue path (17) is at least partially blocked dependent on the received at least one oxygen value.

Description

The invention relates to a method for detecting blockage in an exhaust flue path of a 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.
Gas adaptive combustion appliances, such as gas adaptive boilers are known from the prior art. Such kind of gas adaptive combustion appliances boilers can be adapted to different fuel gas types.
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 O2 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.
Usually, the boiler consists of a fan for modulating the boiler power and a fuel gas valve which controls the gas-air ratio. The fuel gas valve can be adjusted manually to set the gas-air 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 downstream of the fuel gas valve opening and adjusts the gas-air 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 gas-air ratio.
This ratio is measured with an oxygen sensor in the flue gas. Gas adaptive combustion appliances utilize the relationship between the O2 signal and the air-fuel ratio (also known as lambda λ). Gas adaptive combustion appliances have a relationship between O2 and power that can be expressed by an O2 - power curve. At every firing rate, there is a flame ionization value that corresponds to the target lambda (λ = 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 O2 signal is lower than expected (high signal indicates low 02, or rich condition), the control decreases gas valve position to return to λ = 1.3. Similarly, when O2 signal is higher than expected (indicating excess air too high, or lean condition), the control increases gas valve position to return to λ = 1.3.
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 about one minute. In case of using the O2 signal, calibration is done by purging and setting the measured value of O2 related to the 21% O2 of ambient air.
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. This can lead to light-off issues such as noise or ignition failure over time.
During operation of the boiler a flue gas side resistance increases due to pollution and/or a partly blockage of an exhaust for example by a bird nest. Said flue gas side resistance causes reduction in power output of the boiler. Furthermore, the flue gas side resistance can increase when a flue duct is not installed well. For example, a flue gas pipe with a bend downwards and downstream a bend upwards. An error like this will cause condensation build up. The condensate will block the flue causing shutdown of the burner. Alternatively, it is possible that the flue side resistance can decrease due to flue pipe suction as a result of windy conditions.
If the flue gas side resistance is not correctly detected, a heat exchanger can be fouled beyond repair. For example, condensing heat exchangers can suffer from corrosion. The corrosion products can block the small passageways inside the heat exchanger. When the build-up of corrosion products is not cleaned in time the corrosion products can form a solid bank. The solid bank is much more difficult to clean sometimes leading to replacement of the heat exchanger. Furthermore, a flue blockage can generate ignition problems.
Thus, there is the need to detect the flue gas side resistance to give relevant information to the customer so that a maintenance session can be planned preventing replacement of the heat exchanger and/or ignition problems.
Thus, the object of the invention is to provide a method by means of which it can be determined whether the exhaust flue path of a combustion appliance is blocked.
The object is solved by a method for detecting blockage in an exhaust flue path of a combustion appliance, wherein the method comprises the following steps:

receiving at least one oxygen value referring to a gas in a gas flow path, in particular relating to a gas being in a combustion chamber of the gas flow path, of the combustion appliance and
determining whether the exhaust flue path is at least partially blocked dependent on the received at least one oxygen value.

According to the invention it is realized that it is possible to easily determine whether the exhaust flue path of a combustion appliance is at least partially blocked, by considering a determined oxygen value. Thus, by considering the oxygen value it can be easily determined when a maintenance of the combustion appliance is needed. Thus, the risk is reduced to replace the heat exchanger due to the blocked exhaust flue path. This results in less servicing effort for the manufacturers. Additionally, ignition problems of the combustion appliance resulting from the flue gas blockage can be prevented.
With "blockage in exhaust flue path" it is meant that the exhaust flue path of the combustion appliance can be partly or fully blocked. The determination of blockage in the exhaust flue path dependent on the received at least one oxygen value means that the oxygen value is used in the determination of blockage. However, further factors can in addition be used for determining the blockage of the exhaust flue path. For example, a fan speed and/or a reference point in time can be used. Additionally or alternatively a time signal comprising information about the curse of oxygen values via time can be used for determining the blockage of the exhaust flue path.
The oxygen value can be measured in the flue gas. In this case a burner of the combustion appliance combusts the gas mixture comprising air and fuel gas being in the combustion chamber. The oxygen value of the combusted gas being in the combustion chamber of the combustion appliance can be measured. Additionally or alternatively, the oxygen value of a non-combusted gas, for example of the air and fuel gas mixture 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.
The gas flow path comprises the exhaust flue path by means of which the flue gas leaves the combustion appliance. The exhaust flue path can comprise the combustion chamber and an exhaust pipe through which the combusted gas leaves the combustion chamber. Additionally, the gas flow path covers the part upstream of the exhaust flue path, i.e. the air flow path, the fuel gas path and a path in which the air and fuel gas mixture flow for the case that the air to fuel gas is mixed before entering the combustion chamber.
According to an aspect of the invention a combustion appliance is provided. The combustion appliance comprises:

a fan for controlling an air flow,
a fuel valve, in particular fuel gas valve, for controlling a fuel flow, in particular fuel gas flow,
an oxygen sensor for measuring at least one oxygen value in a gas flow path, in particular in a combustion chamber of the gas flow path, of the combustion appliance and
a data processing device comprising means for carrying out an inventive method.

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 gas into this chamber. The air and fuel, in particular the fuel gas, can mix before the combustion chamber or inside the 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 or a gas water heater.
In the application a commissioning mode of a combustion appliance is a mode in which the components and/or parameters of the combustion appliance are set so that the combustion appliance can be operated in the operation mode. 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. This can happen automatically by throttle element that is adjusted by a throttle motor. Another possibility is to adjust the fuel valve. 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.
The determination of the at least one Wobbe 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 Wobbe value.
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 and valve settings, the energy output will also be identical.
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).
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.
The Wobbe index or value is expressed in MJ/Nm³.
An operation mode is a mode of the combustion appliance which is present after the commissioning is finalized and includes the starting of the combustion appliance and/or its operation for providing heat. 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 the outputted heat of the combustion appliance outputs 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. Processing heating is used in commercial use for industrial processes that needs heat. In said case a constant heat output has to be provided.
A starting mode of the combustion appliance is a mode in which the air and fuel gas mixtures is ignited in the combustion chamber on the burner surface by the ignition electrode. Alternatively, the combustion appliance can be in a standby mode in which the combustion appliance is switched on, but the burner is not working. Additionally, 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 determines its power output by modulation.
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. Thus, a failure state covers a failed ignition or no ignition. For the case that a failure state is determined, a combustion appliance starting process, or the operation process 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 advantage of the invention is that by considering the oxygen value a commissioning time in case of ignition failure is reduced.
A failure free state of the combustion appliance is a combustion appliance state in which the combustion appliance operates as expected.
The combustion appliance, in particular a data processing unit of the combustion appliance, can determine the flue gas oxygen value which is a measure for air to fuel gas ratio. The data processing unit can control the combustion appliance on the basis of the determined air to fuel gas ratio. Thus, the combustion appliance can be easily controlled by measuring the flue gas oxygen value.
The oxygen value, in particular a flue gas oxygen value, can be measured by the 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.
According to an embodiment the determination whether the exhaust flue path is blocked is performed during a start of the combustion appliance. This has the advantage that the ignition process can be aborted very fast, namely as soon as the flue gas blockage is determined. If a flue gas blockage is detected, the user can be informed about the flue gas blockage. It is possible to indicate on a human machine interface of the combustion appliance that the flue gas path is blocked. Thus, the user easily knows the failure type.
The blockage of the exhaust flue path can be easily determined by measuring the oxygen value after the fuel valve of the combustion appliance is opened. Specifically, the blockage of the flue path, in particular a blockage value like a load loss value indicating the blockage of the flue path, can be easily determined by comparing a determined parameter, in particular time and/or oxygen value and/or gradient which are all discussed below more in detail, with predetermined parameters. The predetermined parameter, in particular a predetermined time and/or oxygen value and/or gradient, can be determined in a laboratory and can be stored in an electric memory of the combustion appliance. Said predetermined parameters are assigned to blockage values, in particular a load loss of the combustion appliance. The data processing device determines whether the exhaust flue path is at least partially blocked dependent on the comparison result or comparison results.
It is advantageous for the determination of the flue gas path when the data process device determines a time between an opening of the fuel valve, in particular fuel gas valve, of the combustion appliance and the measurement of the oxygen value. The data processing device can determine whether the exhaust flue path is blocked dependent on the time. In this case the oxygen value is used indirectly to determine the blockage of the flue gas path. The indirect use results as the time is used for the blockage determination wherein the time is dependent on the measured oxygen value.
The time is the time after which the oxygen sensor measures an oxygen value that fulfills a condition. Specifically, the measured oxygen value has to have a value that is greater than a predetermined threshold. In other words, the data processing device can determine the time between the opening of the fuel valve and the measured oxygen value passing a threshold. According to the invention it is realized that the time has a correlation with the blockage of the flue gas path. Specifically, the blockage is higher the longer the time is. The blockage can be determined by determining a blockage value that is assigned to the determined time. This is possible as blockage values can be stored in a memory of the combustion appliance that are assigned to times. Thus, by determining a time the assigned blockage value can be easily determined.
Additionally or alternatively, the blockage of the flue gas path can be determined by measuring the oxygen value at predetermined time period after the fuel valve is opened wherein the blockage of the exhaust flue path depends on the received oxygen value. It was realized that the blockage, i.e. the blockage amount, of the flue gas path can be easily determined by considering the oxygen value. This is possible because the blockage of the flue gas path correlates with the oxygen value. The blockage can be determined by determining a blockage value that is assigned to the determined oxygen value. This is possible as blockage values can be stored in a memory of the combustion appliance that are assigned to oxygen values. Thus, by determining an oxygen value the assigned blockage value can be easily determined.
Additionally or alternatively, the blockage of the flue gas path can be determined by measuring several oxygen values. The data processing device can receive said plurality of measured oxygen values. Additionally, the data processing device can determine a gradient on the basis of the received oxygen values. In particular, the data processing device can determine a maximum gradient from the received oxygen values. The determined gradient correlates with the blockage of the flue gas path. That means, several blockage values are assigned to several gradient values. Thus, the data processing device can easily determine the blockage of the flue gas path, i.e. a blockage value indicating the blockage of the flue gas path, by determining a gradient from the received oxygen values. In this case the received oxygen value is indirectly used, namely by determining the gradient, to determine the blockage of the flue gas path. This method has the advantage that it can be used during the operation of the combustion appliance.
The data processing device can abort a starting process of the combustion appliance when a blockage of the flue gas path is determined. The starting process can be aborted when the determined blockage of the flue gas path is greater than a predetermined threshold. The threshold can correspond to the load loss within the combustion appliance. In said a descriptive information can be displayed on a human machine interface of the combustion appliance.
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 receives the flue gas oxygen value from the oxygen sensor of the combustion appliance. 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.
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. Furthermore, a computer readable data carrier having stored thereon the computer program product or data carrier signal carrying the computer program product is provided.
The fuel valve can be a pneumatic gas valve. In said fuel valve, in particular fuel gas valve, the fuel flow automatically changes when an air flow changes due to e.g. a different fan speed. The fuel valve can be arranged downstream a fuel gas source and upstream the throttle unit, in particular the throttle element.
The combustion appliance can comprise a mixture device in which the fuel gas and the air are mixed before the mixture enters the combustion chamber of the combustion appliance. In an alternative embodiment the fuel gas and air are not mixed before the combustion chamber but in the combustion chamber.
The oxygen sensor can be arranged in the combustion chamber. Thus, the oxygen sensor can easily measure the flue gas oxygen value and/or can quickly response to oxygen value changes in the combustion chamber. Additionally or alternatively, the oxygen sensor can be arranged upstream of the burner. This is possible as the method does not need the flue gas to detect a change in oxygen.
The combustion appliance can comprise a throttle unit. 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.
The throttle unit can be arranged fluidically downstream of the fuel valve, wherein the data processing device is connected with the throttle unit, in particular a throttle motor. Fluidically downstream means that the throttle unit as a hole component is arranged outside the fuel valve, in particular fuel gas valve, and adjacent to the fuel valve. 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 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 fuel gas valve.
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 flow coming from the fuel valve can be controlled independent of the fan speed. 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.
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 upper the threshold.
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 valve, in particular fuel gas valve. Thus, a compact unit comprising the fuel valve, in particular fuel gas valve, and the throttle unit is provided.
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. The electrical actuator is configured to carry out 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, in other words in any position between 0° and 90°. 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 comparing the input position (desired position) to the physical position of the 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 Vdc 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.
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.
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.
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 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 of the time. 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.
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.

Figure 1: an overview of a combustion appliance according to the invention.
Figure 2: a structure of a data processing device.
Figure 3: a flow chart of an operation method executed by the data processing device.
Figure 4: a method for determining a throttle element position.
Figure 5: a method for determining a flue gas oxygen values table in the commissioning mode 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.
Figure 7: a flow chart relating to an operation of the combustion appliance in the operation mode.
Figure 8: a flow chart relating to a transition method to prepare the combustion appliance to switch to a standby mode or to stop the combustion appliance.
Figure 9: a flow chart showing the method for setting the starting behavior of the combustion appliance.
Figure 10: an overview of a system comprising several combustion appliances in a state in which all combustion appliances are in an operating 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.
Figure 12: a flow chart for detecting blockage in flue gas path of a combustion appliance.
Figure 13: a diagram illustrating how blockage in the flue gas path can be determined according to a first variant.
Figure 14: a diagram illustrating how blockage in the flue gas path can be determined according to a second variant.
Figure 15: a diagram illustrating how blockage in the flue gas path can be determined according to a third variant.
Figure 16: a flow chart illustrating how a combustion appliance failure state is determined.
Figure 17: a diagram showing different states of the combustion appliance during a starting phase of the combustion appliance.
Figure 18: a calibration of the oxygen sensor for a situation in which the oxygen sensor is always heated.
Figure 19: a calibration of the oxygen sensor for a situation in which the oxygen sensor is not constantly heated.
Figure 20: a calibration of the oxygen sensor for a situation in which the oxygen sensor is heated for a predetermined time.

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.
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 flow, in particular the 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.
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 signal 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.
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.
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 particular 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.
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 non-shown 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.
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.
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.
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 01-04 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.
Figure 3 shows a flow chart of a method executed by the data processing device 9. The method is explained below by referring to the figures 1 and 2.
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 O2 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 Δλ or within pre-determined O2 boundaries (as shown in fig. 6) by adapting the flow of gaseous fuel 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.
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.
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 21 which results in fixed steps. There is no position information present. To set the throttle motor 21 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.
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.
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.
In an eighth step G8 the data processing device 8 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.
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. The table generation is explained below when figure 5 is explained.
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 calibration 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. If the oxygen sensor 8 is not heated, the sensor needs to be calibrated. 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.
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.
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. 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.
The throttle starting positioning manager, the sensor heating manager and the sensor calibration manager can be executed after the ninth method step G9. 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.
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 time-period, whether a heat demand is present. This can be repeated until the combustion appliance 1 is stopped and deactivated. A time-period is length of time and delimited by two time points.
If the data processing device determines in the fifteenth step G15 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.
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 the operation mode, which can only be possible after the 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.
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.
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 appliance1 is done by using the correct parameters. The method step G18 is explained more in detail in figure 8.
Figure 4 shows a method for determining a throttle element position of the throttle unit 6. Said figure shows the specifics of the eighth method step G8 shown in figure 3. In a first sub-step T1 the throttle 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 O1 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.
Then, in a third sub-step T3 the data processing device checks whether the measured first flue gas oxygen value O1 fulfils a test condition. Specifically, the test condition comprises a check whether the first flue gas oxygen value O1 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.
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. As 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.
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 O2 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.
In a seventh sub-step T7 the data processing device 9 determines whether the received second flue gas oxygen value O2 fulfils a further test condition. Specifically, the further test condition comprises a check whether the second flue gas oxygen value O2 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.
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.
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.
The creation of the boundary table is shown in figure 5 more in detail. 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 operating mode as is explained below more in detail.
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 a second sub-step C2 the data processing device 9 receives information about a third power state stored in a memory of the combustion appliance 1. The third power state is between the maximum power state and the minimum power state. In a third sub-step C3, the data processing device 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.
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 sub-step 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 O3 and the determined upper and lower threshold value are stored in a fifth sub-step C5.
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, 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. The data processing device 9 receives the fourth power state value from the memory likewise to the third power state described in sub-step C2. 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 eighth sub-step C8.
Figure 6 shows a diagram showing a flue gas oxygen curve dependent on a power state of the combustion appliance. Specifically, figure 6 shows curves that are determined on the basis of the values that are determined in the method shown in figure 5.
Figure 6 shows the dependency of flue gas oxygen values 01-04 from the power state of the combustion appliance. Specifically, figure 6 shows the first flue gas oxygen value O1 when the combustion appliance 1 is in the maximum power state and the second flue gas oxygen value O2 when the combustion appliance 1 is in the minimum 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.
Figure 7 shows a flow chart relating to a combustion control of the combustion appliance 1 in the operation mode. 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 seventh method step G17 shown in figure 3.
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 received. 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 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.
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 sub-step N4.
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 range 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.
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.
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 a eight 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.
Figure 8 shows a flow chart relating to a transition process to switch the combustion appliance 1 to a standby mode or to stop the combustion appliance. In a first sub-step A1, the transition process is initiated. This can happen when the burner off condition is reached as it is explained in figure 7.
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 sub-step A3, the throttle element position 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.
Figure 9 shows a flow chart for setting the starting behavior of the combustion appliance 1. 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 non-operating combustion appliance 1. The fuel gas type or fuel gas quality can be specified by a Wobbe value.
If the fuel gas quality or fuel gas type is not known, 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.
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.
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.
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.
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.
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.
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 of ignition attempts are made in a tenth sub-step W10. If this is the case the data processing device aborts the ignition process and can lock the combustion appliance 1 in an eleventh sub-step W11.
If the maximum number of ignition attempts are not reached, the method the data processing device checks whether the oxygen value measured in the sixth sub-step W6 is arranged within a predetermined oxygen range in a twelfth sub-step W12. If this is not the case, a new ignition is initiated in the fourth step W4.
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 it is checked whether the new table position from the 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 sub-step W4.
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.
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 is greater than the saved throttle element position, the method is continued in the fourth sub-step W4.
If the throttle element position is not greater than the saved throttle element position, the method is continued in the fourth sub-step W4.
Figure 10 shows an overview of a system 10 comprising several combustion appliances, namely a first combustion appliance 1a, a second combustion appliance 1b, a third combustion appliance 1c and a fourth combustion appliance 1d. In the system 10 shown in figure 10 all combustion appliances 1a, 1b, 1c, 1d are in an operating mode. The combustion appliances are arranged in a cascade and are connected in parallel to each other.
The system 10 comprises a fuel gas line 15 by means of which fuel gas, in particular a mixture of fuel gas and air, can be supplied to the respective combustion appliances 1a, 1b, 1c, 1d. Additionally, the system 10 comprises a data line 16 by means of which a data exchange can occur between the combustion appliances 1a, 1b, 1c, 1d 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.
Each of the combustion appliances 1a, 1b, 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 1b, 1c, 1d transmit the determined Wobbe value to the data processing device of the first combustion appliance 1a that corresponds in this embodiment to a master data processing device 14.
The Wobbe value for an operating combustion appliance 1a, 1b, 1c, 1d is determined as follows. The data processing devices 9 assigned to the respective combustion appliances 1b, 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.
Additionally, the master processing device 14 also determines the Wobbe value of the first combustion appliance 1a in said manner and receives the Wobbe values from the remaining data processing devices 9. The master data processing device 14 determines a Wobbe value that shall be used to control the combustion appliances 1a, 1b, 1c, 1d from the received and determined Wobbe value. Specifically, the master data processing device 14 determines which of the present Wobbe values is the latest Wobbe value and/or determines an average Wobbe value on the basis of the received Wobbe values. Said Wobbe value matches best the current fuel gas quality provided by the fuel gas line 15 to the combustion appliances 1a, 1b, 1c, 1d. Afterwards, the master processing device 9 transmits said determined, latest Wobbe value to all data processing devices 9 of the combustion appliances 1a, 1b, 1c, 1d. Each of the combustion appliances 1a-1d is controlled dependent on said latest Wobbe value.
Specifically, the throttle element position of the throttle unit 6 of each of the combustion appliances 1a-1d is controlled to match to the determined latest 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 1a, 1b, 1c, 1d comprises a table in which Wobbe values are assigned to throttle element positions.
Figure 11 shows an overview of a system 10 comprising several combustion appliances 1a, 1b, 1c, 1d in a state in which some combustion appliances are non-operating. 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.
The master data processing device 14 determines the Wobbe value for the first combustion appliance 1a and the data processing device 9 determines the Wobbe value for the second combustion appliance 1b. 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.
The master data processing device 14 determines which of the Wobbe values is the latest one. Said Wobbe value is transmitted to the second, third and fourth combustion appliance, in particular to the data processing device assigned to the respective combustion appliance 1b, 1c, 1d. The respective data processing device 9 controls the assigned combustion appliance 1b, 1c, 1d dependent on the 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 Wobbe value. Likewise, the master data processing device 14 can control the first combustion appliance 1a on the basis of the determined Wobbe value.
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 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 of the combustion appliance 1 is set.
In a first sub-step B1 the method for detecting blockage is initiated. As mentioned above this can happen when the combustion appliances are in a starting process, i.e. the ignition phase is initiated. In a second sub-step B2 the data processing device 9 detects whether the flue gas path 17 is blocked. Thereto, the data processing device 9 uses the oxygen values measured by the oxygen sensor 8. As mentioned above the blockage detection can be performed before the burner combusts the air to fuel gas mixture or after combustion. In the following, it is assumed that the detection is performed after the combustion so that the oxygen sensor 8 measures flue gas oxygen values.
If the data processing device 9 detects that the flue gas path is blocked, the starting process, i.e. the ignition phase, is aborted in a third step B3. Specifically, the starting phase can be aborted when the load loss, which can be a parameter for characterizing the blockage of the flue gas path of the combustion appliance, in the flue gas path is greater than a predetermined load loss. The load loss indicates how much the flue gas path is blocked. If the data processing device 9 detects that the flue gas path is not blocked, the method is continued in a fourth step. Specifically, the starting behavior of the combustion appliance can be set as it is explained in the seventh step G7 or in the sixteenth step G16.
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 a factor indicating the blockage, namely the load loss in the flue gas path, and a time between the time when the fuel valve 5 is opened and a time when the oxygen sensor 8 measures a flue gas oxygen value that is above a predetermined threshold. In the shown case the predetermined threshold is that the flue gas oxygen value has to be equal or greater than 7,5%.
The diagram shows a predetermined curve 31 that assigns the time to load loss and thus shows the correlation between the time and the load loss. 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 load loss. For a determined value V1, in particular determined time, the data processing device 9 detects the load loss and thus blockage of the flue gas path. This can be done in the second sub-step B2 discussed above in figure 12.
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 a factor indicating the blockage, namely the load loss in the flue gas path, and measured oxygen values. In the second variant, the data processing device 9 ensures that the oxygen sensor measures the flue gas oxygen value at a predetermined time period after the fuel valve 5 is opened. 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 load loss. For a determined value V1, in particular a measured oxygen value, that is measured after the predetermined time period, the data processing device 9 detects the load loss and thus blockage of the flue gas path. This can be done in the second sub-step B2 discussed above in figure 12.
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 a factor indicating the blockage, namely the load loss in the flue gas path, and a gradient of the oxygen value. Thereto, 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 determines the minimum gradient value during the starting phase of the combustion appliance 1. In fig. 15 the determined value V1 corresponds to the determined minimum gradient. The load loss and thus the blockage of the flue gas path can be determined after the minimum gradient is determined. This can be done in the second sub-step B2 discussed above in figure 12.
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.
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.
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 or starting 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.
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 is continued. Thereto, it is referred to the aforementioned statements referring to the setting of the combustion appliance 1 in the starting behavior.
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.
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.
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.
If the measured oxygen value is above the further upper threshold 25, the data processing device 9 determines that no fuel gas is present and thus determines a combustion 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.
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 starting mode 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.
A starting mode of the combustion appliance is a mode in which the air and fuel gas mixtures being in the combustion chamber is ignited in the combustion chamber.
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. 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 23 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.
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 5. The data processing device 1 ensures that the starting mode 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.
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. Additionally, the data processing device checks whether the combustion appliance1 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. 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.
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 starting mode of the combustion appliance 1 is aborted and the combustion appliance 1 is switched to blocking or locking mode.
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 starting process or operation mode can be continued.
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. 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. 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.
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 starting mode 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.
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 In fig. 18 the time-period in which exists a heat demand, the time-period 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 black filled rectangles.
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 during the purging of the combustion chamber 18. 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, the data processing device can determine the time when to initiate pre-purging or post-purging to calibrate the oxygen sensor 8.
In the situation shown in fig. 18 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-period is not expired. Thus, the burner is operated between the two time-periods 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.
A second heat demand is existent between a fifth time point t5 and a seventh time point t7. The data processing device 9 determines that the time-period between the firth time point t5 and a sixth time point t6 corresponds to a burner time-period after which the burner is stopped. Specifically, the burner is stopped at the sixth time-period t6. The data processing device 9 initiates a post-purging at the sixth time-period 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-period 7 and the burner is started again at the seventh time-period t7. The burner is operated until an eight time-period 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.
At a ninth time-period 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-period 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-period t10 which is ended at the eleventh time-period t12. At the eleventh time-period t11 the data processing device initiates the burner starting so that the combustion appliance 1 outputs heat.
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.
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 and a third time 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 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.
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 is ended at the fifth time point t5.
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-period t7. The data processing device 9 initiates a pre-purge and a calibration of the oxygen sensor 8 at the seventh time-period t7. The calibration and the pre-purging are ended at an eighth time-period t8 so that the burner starts at the eighth time-period t8.
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 1h. The initiation of the calibration and purging is done in the same way as it is described in fig. 18.
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-period t2, t3, a second heat demand between a seventh and an eighth time-period t7, t8 and a third heat demand between a tenth and eleventh time-period t10, t11.
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.
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-period 6, which ends at a seventh time-period t7. The burner starts at the seventh time-period t7 and ends at an eight time-period t8. Further, the data processing device 9 initiates the post-purging and calibration that ends at a nineth time-period t9.
The third heat demand is present at a tenth time-period t10. However, at the tenth time-period 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-period t10. The burner is stopped at the end of the heat demand, namely at an eleventh time-period t11. The data processing device then initiates a post-purging and a new calibration of the oxygen sensor 8.

Reference Signs

1: Combustion appliance
1a: First combustion appliance
1b: Second combustion appliance
1c: Third combustion appliance
1d: Fourth combustion appliance
2: Upper threshold referring to operate combustion appliance
3: Lower threshold referring to operate combustion appliance
4: Fan
5: Fuel valve
6: Throttle unit
7: Burner
8: Oxygen sensor
9: Data processing device/control unit
10: System
11: Fuel gas source
12: Heat exchanger
13: Manifold
14: Master control unit
15: Fuel gas line
16: Data line
17: Exhaust flue path
18: combustion chamber
19: Sensing element
20: Sensor data processing unit
21: Throttle element
22: Throttle motor
23: Upper threshold referring to determining presence of failure state
24: Lower threshold referring to determining presence of failure state
25: Further upper threshold
26: Throttle unit control portion
27: Comfort unit portion
28: Safety unit control portion
29: Temperature sensor
31: predetermined curve
32: curve related to oxygen values
33: activation signal

A1-A5: Method steps for preparing the combustion appliance to standby mode or to stop
B1-B4: Method steps for detecting blockage
C1-C9: Method steps in the commissioning mode
D1-D4: Method steps for determining the combustion appliance state
G1-G18: Method steps of general operation procedure of the system
N1-N9: Method steps in normal operation of combustion appliance
O1: First flue gas oxygen value
O2: Second flue gas oxygen value
O3: Third flue gas oxygen value
O4: Fourth flue gas oxygen value

O: Opening signal
P: Throttle Position signal
S1: First operating signal
S2: Second operating signal
S3: Third operating signal
S4: Fourth operating signal

T1-T9: Method steps of testing operation in the commissioning mode
t1-t11: time-period

V1: Determined Value

W1-W17: Method steps for determining the gas quality

Claims

Method for detecting blockage in an exhaust flue path (17) of a combustion appliance (1, 1a-1d), wherein the method comprises the following steps:
receiving at least one oxygen value referring to a gas in a gas flow path, in particular relating to a gas being in a combustion chamber (18) of the gas flow path, of the combustion appliance (1, 1a-1d) and

determining whether the exhaust flue path (17) is at least partially blocked dependent on the received at least one oxygen value.
Method according to claim 1, characterized in that the determination whether the exhaust flue path (17) is blocked is performed during a start of the combustion appliance (1, 1a-1d).
Method according to claim 1 or 2, characterized in that
a. the oxygen value is measured after a fuel valve (5) of the combustion appliance (1, 1a-1d) is opened and/or in that

b. a shape of a measured oxygen signal is determined and/or in that

c. the received at least one oxygen value is compared with a predetermined value and it is determined whether the exhaust flue path (17) is at least partially blocked dependent on the comparison result.
Method according to at least one of the claims 1 to 3, characterized in that a time between an opening of a fuel valve (5) of the combustion appliance (1, 1a-1d) and the received oxygen value is determined wherein the determination of the blockage of the exhaust flue path (17) is dependent on the time.
Method according to claim 4, characterized in that the time is determined when the received oxygen value fulfills a predetermined condition, in particular when the received oxygen value is greater than a predetermined threshold.
Method according to at least one of the claims 1 to 5, characterized in that the oxygen value is determined at a predetermined time period after the fuel valve (5) is opened, wherein the blockage of the exhaust flue path depends on the received oxygen value.
Method according to at least one of the claims 1 to 6, characterized in that several oxygen values are determined and at least one gradient is determined on the basis of the determined oxygen values, wherein the determination whether the exhaust flue path (17) is blocked is dependent on the determined at least one gradient.
Method according to at least one of the claims 1 to 7, characterized in that the combustion appliance (1, 1a-1d) start is aborted when a blockage of the flue gas path is determined.
Data processing device (9) comprising means for carrying out the method of at least one of the claims 1 to 8.
Computer program product which, when the program is executed by a computer, in particular a data processing device, cause the computer, in particular the control unit, to carry out the method of at least one of the claims 1 to 8.
Computer readable data carrier having stored thereon the computer program product of claim 10 or data carrier signal carrying the computer program product of claim 10.
Combustion appliance (1, 1a-1d) comprising
a fan (4) for controlling an air flow,

a fuel valve (5), in particular fuel gas valve, for controlling a fuel flow,

an oxygen sensor (8) for measuring at least one oxygen value in a gas flow path, in particular in a combustion chamber (18) of the gas flow path, of the combustion appliance (1, 1a-1d) and

a data processing device (9) comprising means for carrying out the method of at least one of the claims 1 to 8.
Combustion appliance (1, 1a-1d) according to claim 12, characterized in that the fuel valve (5), in particular the fuel gas valve (5), is a pneumatic valve, in particular a controllable pneumatic valve, or a stepper valve or a modulator valve.
Combustion appliance (1, 1a-1d) according to claim 12 or 13, characterized in that the combustion appliance (1, 1a-1d) comprises a throttle unit (6) that is arranged fluidically downstream the fuel valve (5), wherein the data processing device (9) is connected with the throttle unit (6), in particular a throttle motor (22).
Combustion appliance (1) according to claim 14, characterized in that the data processing device (9) controls the throttle unit (6) and/or the fan (4) and/or the fuel valve (5) dependent on the determined at least one oxygen value.