EP3290802B1 - Method for controlling an inspection time in a heating system and a control unit and a heating system - Google Patents

Description

The invention relates to a method for determining an inspection time in a heating system. The invention also relates to a control unit designed to carry out the method according to the present invention and a heating system with the control unit according to the present invention.

State of the art

In order to ensure optimal combustion, it is necessary to ensure the correct fuel-air ratio when operating gas burners. For this purpose, the correct functioning of the sensors used to determine the fuel-air ratio must be guaranteed. For this purpose, inspections to check the functioning of the gas burner are provided. If necessary, wearing parts can be replaced as part of an inspection. The inspection must be carried out in good time before the functionality of the gas burner is severely restricted. In the prior art, the inspection is carried out after a predetermined time or operating time has elapsed. This has the disadvantage that inspections are also carried out on gas burners that do not require an inspection.

A method according to the preamble of claim 1 is out DE102013014379 known.

Disclosure of Invention benefits

The invention provides a method according to claim 1 for determining an inspection time in a heating system.

The term "heating system" means at least one device for generating thermal energy, in particular a heater or heating burner, in particular for use in heating a building and/or for generating hot water, preferably by burning a gaseous or liquid fuel. A heating system can also consist of several such devices for generating thermal energy as well as other devices that support the heating operation, such as hot water and fuel storage tanks.

Operation of the heating system can be checked using a sensor system that can record a combustion parameter. The heating system can be regulated, if necessary, depending on the combustion parameter recorded. A "combustion parameter" is to be understood in particular as a scalar parameter which is correlated in particular with a combustion, in particular of the mixture, in particular of the combustion air and the fuel. An example of a combustion parameter is an ionization current, which is measured on a flame of the heating system. The presence and/or quality of combustion and/or the presence and/or the Quality of combustion can be determined. The combustion parameter advantageously corresponds to at least one or exactly one measured value that depicts and/or characterizes the combustion, or the combustion parameter can be unambiguously assigned to such a measured value. Examples of a measured value that depicts and/or characterizes the combustion are a combustion signal, in particular a light intensity, pollutant emissions, a temperature and/or advantageously an ionization signal.

“Measurement” of the combustion parameter is to be understood as meaning direct acquisition of a measured value by a sensor system provided for this purpose or reception of a measured value acquired by an external device. A measured combustion parameter is advantageously stored in a memory. The combustion parameter can be measured at specific points in time and/or at time intervals and/or largely continuously.

A "calibration value" is intended to be a characteristic value derived from a detected combustion parameter, which is suitable for regulating and/or calibrating the heating system. For example, the calibration value can be the value of the combustion parameter for specific operating parameters and/or operating conditions. The calibration value can also be a value derived from a stored, time profile of the combustion parameter, for example a local maximum of the combustion parameter. "Regulation or calibration of the heating system" means the one-time or repeated, in particular periodic, adjustment of operating parameters of the heating system so that the heating system can largely meet the specified and/or required performance to the full extent, especially under changing internal and external conditions, especially in wear processes and changing boundary and environmental conditions. “Operating parameters” are to be understood as meaning parameters which are used by a controller of the heating system to control and monitor processes running in the heating system. Examples of "operating parameters" are the fan speed or the fan speed characteristic, a flame ionization characteristic or an opening width of a fuel control valve.

“Controlling the heating system” is to be understood as meaning a setting of operating parameters which is largely possible during normal, intended operation and largely does not interfere with normal, intended operation. For example, regulation of the heating system can be understood to mean a regulation process running in the controller, which adjusts the opening width of the fuel valve as a function of the detected combustion parameter. “Calibrating the heating system” is to be understood in particular as meaning an at least partially new setting, preferably a largely completely new setting, of a sensor system in the heating system, in particular a sensor system for measuring a fuel/air ratio. For this purpose, the heater can be operated in a special calibration mode, which at least partially restricts or interrupts the normal, intended operation. For example, a performance spectrum of the heater can be run through to test the sensors.

The method allows the state of a sensor system determining the combustion parameter to be estimated with the aid of the calibration value. Depending on the calibration value, an inspection time can be determined, which at least partially depends on the state of the sensor system determining the combustion parameter. This has the advantage that the inspection time is determined as needed. The procedure avoids unnecessary inspections, especially inspections that are too early.

Advantageous developments of the method according to the main claim are possible due to the features listed in the subclaims.

If the inspection time is determined depending on whether the calibration value falls below a quality threshold, this is a particularly robust and reliable criterion for a necessary inspection. A calibration value that falls over time can indicate a deterioration in the sensor system that determines the combustion parameter.

The method is further improved if the determination of the inspection time depends on at least one calibration value that is provided. A "calibration value provided" is to be understood as meaning a calibration value which is made available to the method according to the main claim. The calibration value provided can, for example, be stored in a memory of the heating device and/or be sent from an external device, in particular from a server or a cloud and/or from a measuring device. The calibration value provided can be a measured value determined directly or indirectly and/or a calculated value and/or a value taken from a table or a characteristic curve. The use of at least one provided calibration value has the advantage that, in addition to the calibration value, a further value is taken into account for determining the inspection time. The calibration value provided allows other influencing parameters on the state of the heating system to be included. In this way, the required inspection time can be determined more precisely.

The method according to the present invention is intended to be carried out repeatedly in succession. Will at least one If the calibration value provided is determined in a previous iteration of the method, in particular by measuring the combustion parameter, this allows calibration values determined in the past to be taken into account. In particular, it is possible to take into account a trend over time or a development of the calibration value over time when determining the inspection time. The development of the calibration value over time can be statistically evaluated in particular. This makes it possible, for example, to avoid an early inspection time caused by an outlier in the determination of the calibration value, for example a measurement error or unusual external conditions.

If the calibration value and/or, if available, the calibration value provided is determined during a test output, characterized by a constant burner output parameter, in particular a constant fan speed, this has the advantage that the calibration value is determined largely under sufficiently similar conditions in each iteration of the method . This makes it easier to determine the inspection time. An additional advantage is that calibration values determined in different iterations of the method can be compared particularly easily.

“Burner power parameter” is to be understood in particular as a parameter which is correlated with the power, in particular a heating power, of the heating system. The output, in particular heating output, of the heating system can advantageously be determined, in particular by the control and/or regulating unit of the heating system, at least on the basis of the burner output parameter. Advantageously, the burner output parameter corresponds to at least one or exactly one measured value representing the output or can be unambiguously assigned to such a measured value. Such a measured value can, for example, temperature, an air flow rate, a fan control signal or a fan speed.

The method is further improved if the determination of the inspection time depends on a burner performance parameter, in particular a blower speed, and/or if present, the quality threshold depends on the burner performance parameter, in particular the blower speed. This makes it possible to determine the inspection time depending on the calibration values determined for different burner output parameters. This makes it possible to check particularly frequently whether an inspection is necessary. This makes the determination of the inspection time particularly reliable. If the heating system is calibrated and/or regulated as a function of the calibration value, this has the advantage that the heating system is operated with largely optimal operating parameters. In this way, the process becomes even more reliable.

Since the calibration value is a maximum combustion parameter, this has the advantage that the calibration value can be determined particularly easily and reliably.

If the combustion characteristic is an ionization current, which is determined by an ionization current measurement on a flame of the heating system, this has the advantage that the ionization current has a particularly favorable relationship to the fuel-air ratio that can be evaluated. This allows precise and reliable control and/or calibration of the heating system. A sensor system provided for measuring the ionization current, for example an ionization probe, ages due to the formation of an ionization layer. The growing ionization layer results in an increasing resistance over time. Due to the ionization layer, the measured ionization current decreases over time under otherwise identical conditions. the The ionization layer at least partially restricts regulation or calibration of the heating system over time. A calibration value that falls sufficiently sharply over time, which was determined by measuring the ionization current, is a particularly good and reliable indicator of a required inspection.

The use of a control unit for a heating system, which control unit is set up to carry out the method according to the present invention, has the advantage that the availability and reliability of the heating system is increased by avoiding unnecessary inspections.

A heating system with a control unit according to the present invention, with at least one metering device for a fuel and/or for combustion air and/or for a mixture of a fuel and combustion air, and with an ionization probe on a flame and with a fan with a variable fan speed has the Advantage that a safe and cost-effective operation of the heating system is made possible. The heating system can be designed for a lower number of calibration processes, which enables cost-effective production.

drawings

• Figur 1 eine schematische Darstellung eines Heizsystems mit einer Steuereinheit gemäß der vorliegenden Erfindung,
• Figur 2 ein Verfahren zum Festlegen eines Inspektionszeitpunktes in einem Heizsystem gemäß der vorliegenden Erfindung,
• Figur 3 eine schematische Darstellung einer Abhängigkeit des Ionisationsstroms vom Brennstoff-Luft-Verhältnis,
• Figur 4 eine schematische Darstellung einer Zeitentwicklung eines Kalibrationswerts,
• Figur 5 eine schematische Darstellung einer Abhängigkeit des Kalibrationswerts von einem ohmschen Widerstand einer Oxidationsschicht einer Ionisationssonde des Heizsystems und
• Figur 6 eine Variante des Verfahrens gemäß der vorliegenden Erfindung.

The drawings show exemplary embodiments of the method for determining an inspection time in a heating system according to the present invention and a control unit according to the present invention and the heating system according to the present invention and explained in more detail in the following description. Show it

• figure 1 a schematic representation of a heating system with a control unit according to the present invention,
• figure 2 a method for determining an inspection time in a heating system according to the present invention,
• figure 3 a schematic representation of a dependence of the ionization current on the fuel-air ratio,
• figure 4 a schematic representation of a time development of a calibration value,
• figure 5 a schematic representation of a dependence of the calibration value on an ohmic resistance of an oxidation layer of an ionization probe of the heating system and
• figure 6 a variant of the method according to the present invention.

description

The same parts are given the same reference numbers in the different design variants.

In figure 1 a heater 10 is shown schematically, which is arranged on a memory 12 in the embodiment. The heater 10 has a housing 14 which accommodates different components depending on the degree of equipment.

The essential components are a heat cell 16, a control unit 18, one or more pumps 20 and piping 22, cables or bus lines 24 and holding means 26 in the heater 10. The number and complexity of the individual components also depends on the equipment level of the heater 10.

The heat cell 16 has a burner 28, a heat exchanger 30, a blower 32, a metering device 34 and an air supply system 36, an exhaust system 38 and, when the heat cell 16 is in operation, a flame 40. An ionization probe 42 projects into the flame 40 . The dosing device 34 is designed as a fuel valve 44 . A fan speed 54 of the fan 32 is variably adjustable. The heater 10 and the memory 12 together form a heating system 46. The control unit 18 has a data memory 48, a computing unit 50 and a communication interface 52. The components of the heating system 46 can be controlled via the communication interface 52 . The communication interface 52 allows data to be exchanged with external devices. External devices are, for example, control devices, thermostats and/or devices with computer functionality, for example smartphones.

figure 1 shows a heating system 46 with a control unit 18. In alternative embodiments, the control unit 18 is located outside the housing 14 of the heater 10. The external control unit 18 is designed as a room controller for the heating system 46 in special variants. In preferred embodiments, the control unit 18 is mobile. The external control unit 18 has a communication link to the heater 10 and/or other components of the heating system 46 . The communication connection can be wired and/or wireless, preferably a radio connection, particularly preferably via WLAN, Z-Wave, Bluetooth and/or ZigBee. In further variants, the control unit 18 can consist of several components, in particular components that are not physically connected. In special variants, at least one or more components of the control unit 18 can be present partially or entirely in the form of software that runs on internal or external devices, in particular on mobile computing units, such as smartphones and tablets, or servers, in particular a cloud. The communication connections are then corresponding software interfaces.

figure 2 shows a method 56 for determining an inspection time 58 in a heating system 46. In the exemplary embodiment, a calibration value 62 is determined in a step 60. In step 60 the calibration value 62 is determined from a measured maximum 64 combustion parameter. In the exemplary embodiment, the combustion parameter 64 is an ionization current 66. The ionization current 66 is recorded largely continuously by the ionization probe 42 and stored in the control unit 18.

figure 3 illustrates the determination of the calibration value 62. figure 3 shows the relationship between the ionization current 66 and a fuel-air ratio at a constant fan speed 54. The fuel-air ratio is also called the lambda value and describes the ratio of an air quantity to a fuel quantity in a burner 28 supplied fuel-air mixture. The fan speed 54 is a parameter determined by the control unit 18, which determines a fan control signal. The fan control signal is sent from the control unit 18 to the fan 32 and determines a speed of the area 32. The fan speed 54 is a burner performance parameter 70. A burner performance parameter 70 is a measure of a performance of the heating system 46. On a first ordinate axis 72 is the ionization current 66 applied. The fuel/air ratio is shown on a first abscissa axis 74 .

The profile of the ionization current 66 has a combustion parameter maximum 76 at a fuel/air ratio of 1. A "combustion parameter maximum" 76 should be understood to mean a maximum possible value of the combustion parameter 64 in at least certain operating states of the heating system with a constant burner output parameter 70 . Advantageous the maximum combustion parameter 76 can be clearly assigned to a well-defined value of the fuel/air ratio. A combustion parameter maximum 76 is a maximum possible value of the combustion parameter 64 with a constant burner output parameter 70.

When the fuel/air ratio increases or decreases, starting from the combustion parameter maximum 76, the ionization current 66 decreases, with the magnitude of the gradient increasing steadily. The heating system 46 is preferably operated with excess air, ie with a fuel/air ratio greater than 1, preferably with a fuel/air ratio between 1.2 and 1.4, particularly preferably with a fuel/air ratio of 1.3.

The combustion characteristic maximum 76 is determined by performing a fluid supply change. The fluid supply change is a short-term, pulsed change in an opening width of fuel valve 44. In regular operation, heating system 46 is operated with a largely constant or slowly changing opening width of fuel valve 44. When the fluid supply is changed, the opening width is increased from a control opening width as quickly as possible to a pulse opening width and, after a pulse duration, is reduced to the control opening width as quickly as possible. The pulse duration is short compared to other variations of the opening width that are common in regular operation. Due to the change in fluid supply, the fuel-air mixture is enriched for a short time, ie the proportion of fuel is increased. The fuel/air ratio is briefly lowered. A magnitude of the fluid supply change or the pulse opening width is selected in such a way that the fuel/air ratio is reduced to a value of less than 1 for a short time will. In the exemplary embodiment, the pulse opening times required for this are stored in a characteristic diagram in the control unit 18, which depends on the burner performance parameter 70 and the desired fuel/air ratio in control operation.

As a result of the change in the fluid supply, the ionization current 66 rises briefly to the maximum 76 combustion parameter. The combustion parameter maximum 76 is determined in the exemplary embodiment by the maximum ionization current 66 being determined in a first time beginning with the fluid supply change and a test time interval ending at a second time. The control unit 18 evaluates a stored course of the ionization current 66 over time. A longer test time interval is determined by the control unit 18 . The length of the test time interval depends on the burner output parameter 70. In this way, a running time of the fuel-air mixture from the fuel valve 44 to the burner 28 or to the ionization probe 42 is taken into account.

In the exemplary embodiment, the maximum 76 of combustion parameters is the calibration value 62. In the exemplary embodiment, the heating system 46 is regulated as a function of the calibration value 62, if necessary. A target combustion parameter is determined as a function of calibration value 62 . In the exemplary embodiment, the target combustion parameter is equal to the calibration value 62 multiplied by 0.7. The target combustion parameter is an operating parameter which is used as a target value for a combustion parameter 64 when controlling the heating system in order to achieve the intended or desired fuel/air ratio. In the exemplary embodiment, the heating system 46 is operated in such a way that the ionization current 66 largely assumes the value of the setpoint combustion parameter in normal operation. The opening width or the control opening width of the fuel valve 44 is set by a control process carried out by the control unit 18 in such a way that the ionization current 66 largely assumes the value of the setpoint combustion parameter. In the exemplary embodiment, the target combustion characteristic is stored in a target combustion characteristic curve in the control unit 18 . The setpoint combustion parameter characteristic curve allocates the setpoint combustion parameter required for this to the burner output parameter 70 and the desired fuel/air ratio. If necessary, the target combustion characteristic is at least partially updated using the calibration value 62 or the target combustion characteristic determined from the calibration value 62 .

In a further step 78 the inspection time 58 is determined. For this purpose, the control unit 18 checks whether the calibration value 62 falls below a quality threshold 80 . The quality threshold 80 is a lower limit for the calibration value 62 stored in the control unit 18. If the calibration value 62 falls below the quality threshold 80, the inspection time 58 is determined by adding an inspection time interval to a currently available date. In the exemplary embodiment, the inspection interval is two weeks. An inspection notice is displayed in a display of the heating system 46 in which an operator of the heating system 46 is advised to initiate an inspection by the inspection time 58 .

In alternative embodiments, the inspection time interval has any other value. It is conceivable that the inspection time interval depends on operating parameters, in particular on a distance between the calibration value 62 and the quality threshold 80. It is also conceivable that the inspection time 58 largely corresponds to a time at which the calibration value 62 exceeds the quality threshold 80. For example, an inspection notice can be displayed and/or transmitted, in which the operator of the heating system 46 is advised to initiate an inspection as soon as possible.

figure 4 shows a time development of the calibration value 62. The calibration value 62 is plotted on a second ordinate axis 81. FIG. An operating time of the heating system is shown on a second abscissa axis 82 . In figure 4 results for the calibration value 62 from many iterations of the method 56 are shown. A time scale of one in figure 4 The course of the calibration value 62 shown is about 3000 operating hours. The course of the calibration value 62 shows noise. The trend is that the calibration value 62 slowly decreases on average. A first calibration value 84 is 79 μA. A second calibration value 86 is 72 μA.

In the exemplary embodiment, one reason for the decrease in the calibration value is 62 (see figure 4 ) an oxidation layer slowly forming on the ionization probe 42. The oxidation layer has an insulating effect. figure 5 shows a dependency of the calibration value 62 on an ohmic resistance of the oxidation layer. The calibration value 62 is shown on a third ordinate axis 88 . A third abscissa axis 90 shows the ohmic resistance. In figure 5 different determinations of the calibration value 62 are shown for different ohmic resistances. A first determination 92 has a calibration value 62 of 75 μA with an ohmic resistance of 0 kΩ. The ionization probe 42 has no oxidation layer in the first determination 92 . A second determination 94 has a calibration value 62 of 62 μA with an oxidation layer with an ohmic resistance of 450 kΩ.

A strength or a signal strength of the detected combustion parameter 64 is reduced as a result of aging processes. In the exemplary embodiment, the ionization current 66 decreases as a result of a growing oxidation layer. A measure of the signal strength of the combustion parameter 64, which is restricted over time, is the calibration value 62, which decreases over time. A restricted combustion parameter 64 restricts the functionality of the heating system 46 at least in part. For example, the ionization current 66 stands out weaker from signal noise. A calibration value 62 that is too low makes determination of the target combustion parameter less precise. In this way, the desired fuel-air ratio cannot be set with a desired precision. If the signal of the combustion parameter 64 is reduced too much, it may be impossible for the heating system 46 to operate as intended and/or in accordance with the regulations, in particular with regard to emissions from the heating system 46 the quality threshold 80 can be operated as intended by the calibration value 62 at least within the inspection time interval or at least up to the inspection time 58 or can fully meet the intended requirements, in particular with regard to operational safety and emissions. In the exemplary embodiment, the quality threshold 80 is a value determined in laboratory tests.

In alternative embodiments, the inspection time interval depends on a deviation of the calibration value 62 from the quality threshold 80. The deviation can be a relative or absolute difference of the calibration value 62 from the quality threshold 80. For example the deviation can be the value of the quality threshold 80 minus the calibration value 62.

In further embodiments, in step 78 the calibration value 62 is assigned the inspection time 58 with an inspection function. The inspection function assigns an inspection time 58 or an inspection time interval to the calibration value 62 . The inspection function can also depend on other operating parameters, for example an operating time or a burner output parameter 70. The inspection function can be a table or a characteristic map which assigns an inspection time 58 or an inspection time interval to the calibration value 62 at least at intervals. The inspection function can also be an analytical, in particular a rational function. The inspection function or the function parameters that define it can be determined in particular in laboratory tests. It is conceivable that the inspection function is based on a self-learning or intelligent algorithm, for example on an artificial neural network.

In alternative embodiments, a provided calibration value 96 is taken into account in step 78 (see FIG figure 6 ). The calibration value 96 provided can be a value provided in particular in the memory 12 of the control unit 18 . The calibration value 96 that is provided can also be a value that can be determined by measuring the combustion parameter 64 . For example, the calibration value 96 provided can be determined using a different method than the calibration value 62 . In this way, the calibration value 96 provided can verify the calibration value 62 . It is conceivable that the calibration value 96 provided is determined from an alternative combustion parameter. It is also conceivable that the calibration value 62 is determined from an operating parameter of the heating system, for example a burner output parameter 70.

In further variants, several provided calibration values 96 are taken into account in step 78, in particular more than one provided calibration value 96. In special variants, a resulting calibration value is determined from the calibration value 62 and the at least one provided calibration value 96. For example, the resulting calibration value can be an average of the calibration value 62 and the at least one calibration value 96 provided, in special variants with a weighting.

The resulting calibration value is used instead of the calibration value 62 as in the variants of the method 56 described above for determining the inspection time 58 . For example, it can be checked whether the resulting calibration value falls below the quality threshold 80. It is also conceivable that the inspection time 58 or the inspection time interval is determined using an inspection function. The inspection function assigns an inspection time 58 or an inspection time interval to the resulting calibration value.

In further variants, the inspection time 58 or the inspection time interval is determined using an extended inspection function. The extended inspection function assigns an inspection time 58 or an inspection time interval to the calibration value 62 and the at least one provided calibration value 96 . The inspection function can also depend on other operating parameters, for example an operating time or a Burner output parameters 70. The inspection function can be a table or a characteristic map which assigns an inspection time 58 or an inspection time interval to the calibration value 62 and the at least one calibration value 96 provided, at least at intervals. The inspection function can also be an analytical, in particular a rational function. The inspection function or the function parameters that define it can be determined in particular in laboratory tests. It is conceivable that the inspection function is based on a self-learning or intelligent algorithm, for example on an artificial neural network.

figure 6 12 shows a current iteration 98 of method 56 and a previous iteration 100 of an alternative embodiment. The calibration value 62 from the previous iteration 100 is stored in memory 12 . In the current iteration 98 the calibration value 62 stored in memory from the previous iteration 100 is used as the calibration value 96 provided. In further variants, further provided calibration values 96 are used, which are determined in previous iterations 100 further back. In this way, the development of the calibration value 62 over time can be taken into account. For example, a resulting calibration value can be determined from the calibration value 62 and the other calibration values 96 provided, in particular in which the calibration values 96 provided are weighted the weaker the further back the point in time at which they were determined. In further variants, the calibration values 96 provided can be evaluated statistically. For example, statistical departures can be taken into account in this way.

In the exemplary embodiment, the calibration value 62 is determined at a constant fan speed 54 using the value of a test power 102 (see figure 2 ). The test power 102 is a constant value stored in the control unit 18 . The heating system 46 regularly performs calibrations, during which a calibration value 62 is determined. The method 56 is carried out if the fan speed 54 currently present largely corresponds to the test performance 102 . The test power 102 is selected in such a way that the fan speed 54 often assumes the value of the test power 102 in the control mode of the heating system 46 . In variants of the exemplary embodiment, the test power 102 is determined in a test phase after the heating system 46 has been installed. In the test phase, a typical operation of the heating system 46 is examined, in particular how long the heating system 46 is operated at which fan speed 54 . A value of the fan speed 54 is selected as the test power 102, with which the heating system 46 was operated long enough in the test phase. In variants of the exemplary embodiment, the calibration value 62 is determined for a burner output parameter 70 which has the value of the test output 102 . In further variants, the heating system 46 is repeatedly, preferably regularly, operated in a calibration mode in which the heating system 46 is operated at the test output 102 and the calibration value 62 is determined.

In alternative specific embodiments, calibration value 62 is determined for at least two different combustion parameters 64 . In particular, the calibration value 62 can be determined for almost all combustion parameters 64 . In these specific embodiments, the currently present combustion parameter 64 or a combustion parameter 64 present when the calibration value 62 is determined is recorded and taken into account in step 78 when determining the inspection time 58 . For example, the Quality threshold 80 depend on the fan speed 54. It is conceivable that the inspection function and/or the extended inspection function depend on the burner performance parameter 70 .

In the exemplary embodiment, the heating system 46 is regulated as a function of the calibration value 62 . In variants of the exemplary embodiment, the heating system 46 is calibrated as a function of the calibration value 62, if necessary. If the calibration value 62 deviates too much from the quality threshold 80, the heating system 46 is calibrated. The controlled operation of the heating system 46 is interrupted and the heating system 46 runs through a largely complete power range. For this purpose, the heating system 46 is operated with different values of the burner output parameter 70, which are arranged largely uniformly between a minimum burner output parameter and a maximum burner output parameter. Calibration value 62 is determined for each of these values of burner output parameter 70 and stored in control unit 18 . With the help of the calibration value 62 determined in this way for different burner output parameters 70, the setpoint combustion characteristic curve stored in the control unit 18 is largely completely updated.

According to the invention, the calibration value 62 is a combustion parameter maximum 76. The combustion parameter 64 is an ionization current 66. It is known for the ionization current 66 that it has a combustion parameter maximum 76 at a fuel/air ratio with the value 1. The maximum combustion parameter 76 is therefore a suitable calibration value 62. In alternative embodiments, the calibration value 62 is a combustion parameter 64 averaged over time.

In the exemplary embodiment, the combustion parameter 64 is an ionization current 66. The ionization current 66 is determined by an ionization current measurement on a flame 40 of the heating system 46. The ionization current 66 is determined by the ionization probe 42 and transmitted to the control unit 18 . In further specific embodiments, the combustion parameter 64 is a light intensity, a lambda value, pollutant emissions and/or a temperature. The light intensity at the flame 40 is determined by a photodiode. The lambda value is measured with a lambda probe in an exhaust gas. The exhaust system 38 has the lambda probe. The pollutant emission is determined by a sensor device which is located on the flame 40 and/or in the exhaust system 38 . The temperature is determined by a contact thermometer and/or a non-contact thermometer, in particular a pyrometer. The thermometer can be located in the exhaust system 38 and/or the flame 40 can be measured.

It is pointed out that the features of the different embodiments described above can of course be combined with one another.

Claims (10)

1. Method (56) for defining an inspection time (58) in a heating system (46), comprising the following steps:

   • determining a calibration value (62) by way of a measurement of a combustion characteristic variable (64), in particular an ionization current (66);

   • defining an inspection time (58) in a manner dependent on the calibration value (62);

   characterized in that the calibration value (62) is a combustion characteristic variable maximum (76).
2. Method (56) according to Claim 1, characterized in that the inspection time (58) is defined in a manner dependent on whether the calibration value (62) falls below a quality threshold (80).
3. Method (56) according to either of the preceding claims, characterized in that the definition of the inspection time (58) depends on at least one provided calibration value (96).
4. Method (56) according to Claim 3, characterized in that the at least one provided calibration value (96) is determined in a previous iteration (100) of the method (56), in particular by way of a measurement of the combustion characteristic variable (64).
5. Method (56) according to one of the preceding claims, characterized in that the calibration value (62) and/or, if available, the provided calibration value (96) are/is determined with a test power (102), characterized by a constant burner power parameter (70), in particular a constant blower rotational speed (54).
6. Method (56) according to one of the preceding claims, characterized in that the definition of the inspection time (58) depends on a or the burner power parameter (70), in particular a or the blower rotational speed (54), and/or in that, if present, the quality threshold (80) depends on the burner power parameter (70), in particular the blower rotational speed (54).
7. Method (56) according to one of the preceding claims, characterized in that the heating system (46) is calibrated and/or regulated in a manner dependent on the calibration value (62).
8. Method (56) according to one of the preceding claims, characterized in that the combustion characteristic variable (64) is an ionization current (66) which is determined by way of an ionization current measurement at a flame (40) of the heating system (46).
9. Control unit (18) for a heating system (46), wherein the control unit (18) is configured such that a method (56) according to one of the preceding claims can be carried out.
10. Heating system (46) having a control unit (18) according to Claim 10, having at least one dosing means (34) for a fuel and/or for combustion air and/or for a mixture of a fuel and combustion air, and also having an ionization probe (42) at a flame (40) and having a blower (32) with variable blower rotational speed (54).

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