Heater with emergency control system

Abstract

The invention relates to a method for operating a heating appliance (100) for heating a building, comprising the following steps: a) operating the heating appliance (100) with a primary combustion control, b) detecting an implausibility and / or fault of the primary combustion control, c) operating the heating appliance (100) with a secondary combustion control that differs from the primary combustion control when an implausibility and / or fault of the primary combustion control has been detected.

Description

[0001] The invention relates to a method for operating a heating device for heating a building and to a heating device for heating a building.

[0002] Heating appliances for building heating are known to use fossil fuels for hot water (heating and / or domestic hot water). Various environmental conditions or malfunctions can cause the combustion control strategy of the heating appliance to reach its system limits. In such cases, the hot water supply from the heating appliance may fail.

[0003] The state of the art in currently available systems involves attempting to provide the customer with a minimum level of comfort for as long as possible by limiting the operating range of the heating unit. However, limiting the operating range can only partially prevent the unit from shutting down when the combustion control system reaches its inherent limits, thus limiting customer satisfaction. In many cases, shutting down the unit is unavoidable.

[0004] A generic method is known from DE 196 01 517 A1. A method for controlling a circulating water heater is known from EP 0 327 785 A1.

[0005] The object of the invention is therefore to increase the working range of a heating device. Furthermore, it aims to provide the user with a higher level of comfort.

[0006] This task is solved using the features of independent claims. Advantageous embodiments result from the features of dependent claims.

[0007] This includes a method for operating a heating appliance for heating a building, comprising the following steps: a) Operating the heating appliance with a primary combustion control, b) Detecting an implausibility and / or fault in the primary combustion control, c) Operating the heating appliance with a secondary combustion control that differs from the primary combustion control when an implausibility and / or fault in the primary combustion control has been detected, whereby the secondary combustion control uses fewer sensors than the primary combustion control.

[0008] This method can be used, in particular, for adjusting the fuel-air mixture for a fuel-gas-operated burner in a heating appliance. Advantageously, the method allows for the provision of an emergency operating control in the event of a failure of the primary combustion control. In other words, this means that an advantageous redundant combustion control is provided by the secondary combustion control. The secondary combustion control contributes, in particular, to maintaining a minimum level of heating appliance functionality and thus to ensuring user comfort. In this context, the secondary combustion control can also be described as a comfort backup mode.

[0009] Operation with redundant (secondary) combustion control is primarily intended to maintain the device's operating range as much as possible until uninterrupted operation can be restored by eliminating external disturbances (emergency operation control). Combining more than one combustion control system in a single heating appliance for heating a building has not been considered to date, as this was deemed undesirable due to cost.

[0010] In the event of implausibility or malfunction of the primary combustion control (e.g., based on a CO sensor, mass flow sensor, and / or ionization electrode), hot water comfort can be ensured by using a secondary (redundant) combustion control system, preferably with the aid of a combined ignition and monitoring electrode. This can be achieved, in particular, by approaching the flame lift-off point, which is physically linked to a defined gas-air mixture ratio (defined lambda). Specifically, by detecting the signal change during flame lift-off and knowing the lambda value at that point, the blower and / or gas valve can be controlled to a target lambda, thereby ensuring advantageously clean combustion. By activating this process cyclically, particularly at sufficiently short intervals, a reliable control state can be assumed.

[0011] The heating appliance in question is typically a gas and / or oil-fired boiler. In other words, this refers specifically to a heating appliance designed to burn one or more fossil fuels, such as liquefied petroleum gas (LPG), natural gas, and / or heating oil, possibly with the addition of ambient air from a building, to generate energy for heating, for example, water for use in a dwelling within the building. The heating appliance might, for instance, be a so-called condensing gas boiler. The heating appliance generally has at least one burner and a conveying device, such as a fan, that delivers a mixture of fuel (gas) and combustion air (through a mixing channel within the boiler) to the burner. The exhaust gas produced by combustion can then be routed through an (internal) flue pipe of the heating appliance to a building's exhaust system. Several heating appliances are typically connected to this exhaust system.

[0012] The building can be either a residential building and / or a commercial building. The heating appliance can be used, in particular, to heat only a part of the building, such as a single apartment or a single room. Alternatively or in combination, the heating appliance can also be used to heat the building's water system (heating and / or domestic hot water) or the water system of an apartment.

[0013] The secondary combustion control system is simpler in design than the primary combustion control system. According to the invention, this is achieved by using fewer sensors in the secondary combustion control system than in the primary combustion control system. Therefore, the secondary combustion control system can operate with fewer input variables. This allows the secondary combustion control system to be more robust than the primary combustion control system. Furthermore, redundancy for the combustion control system can be created relatively cost-effectively. The robustness of the secondary combustion control system may come at the expense of accuracy, but this can be accepted in order to maximize the operating range of the device. Preferably, the secondary combustion control system uses (only) one sensor. This sensor is particularly preferably a flame monitoring electrode, especially an ionization electrode.Preferably, the secondary combustion control can, in addition to input data (measurement data) from a single sensor, also utilize performance data from a conveying device (e.g., a blower) and / or a gas valve of the heating appliance. In contrast, the primary combustion control can utilize a multitude of sensors (at least two sensors that detect different input variables).

[0014] In an advantageous embodiment, it is proposed that the primary combustion control is performed based on a (sensor or measurement) signal from at least one sensor of the heating appliance. For example, a gas flow sensor (volume or mass flow sensor), an air flow sensor (volume or mass flow sensor), a mixture flow sensor (volume or mass flow sensor), an exhaust gas sensor (e.g., CO sensor, O₂ sensor), a temperature sensor (e.g., for measuring the temperature of the flame and / or burner), and / or a radiation sensor (e.g., infrared sensor, in particular for measuring the temperature of the flame and / or burner) can be used, each of which typically transmits a measurement signal to the control unit. Furthermore, the primary combustion control can also utilize measurement signals from the flame monitoring electrode.Depending on one or more of these measurement signals, a controlled variable can be determined and regulated depending on a reference variable.

[0015] In a further advantageous embodiment, it is proposed that an implausibility and / or malfunction of the primary combustion control is detected via at least one sensor of the heating appliance and / or a flame monitoring electrode of the heating appliance. For example, an implausibility can be inferred if two or more of the sensors deliver contradictory measurement results. Alternatively or cumulatively, a malfunction can be inferred if one or more of the sensors deliver measurement results indicating flame failure (flame has gone out). Alternatively or cumulatively, it is also conceivable that an implausibility and / or malfunction of the primary combustion control is detected from information about external disturbances, such as environmental influences, weather conditions, etc. For this purpose, sensor data can be evaluated or external data (e.g., from a weather database) can be accessed.

[0016] In a further advantageous embodiment, it is proposed that the secondary combustion control is carried out depending on a signal from a flame monitoring electrode of the heating device. The flame monitoring electrode can, in particular, be an ignition and monitoring electrode, such as an ionization electrode. In this context, the secondary combustion control can be carried out, in particular, depending on a voltage or current signal from a flame monitoring electrode system.

[0017] In a further advantageous embodiment, it is proposed that the flame monitoring electrode be provided in addition to at least one (further) sensor of the heating appliance. Preferably, the flame monitoring electrode is provided in addition to one or more of the following sensors: gas flow sensor (volume or mass flow sensor), air flow sensor (volume or mass flow sensor), mixture flow sensor (volume or mass flow sensor), exhaust gas sensor (e.g., CO sensor, O₂ sensor), temperature sensor (e.g., for measuring the temperature of the flame and / or burner), and / or radiation sensor (e.g., infrared sensor, in particular for measuring the temperature of the flame and / or burner).

[0018] According to a further advantageous embodiment, it is proposed that the following intermediate steps be carried out in step c): i) Varying at least one operating parameter of the heating device, such as an air ratio (λ), to approach a flame lift-off point, ii) Monitoring the approach to the flame lift-off point using the flame monitoring electrode, iii) Setting the at least one operating parameter of the heating device to a value determined as a function of the value that the operating parameter had immediately before or at the time the flame lift-off point was reached.

[0019] In other words, this can also be described in particular as follows: during step c) (for providing secondary combustion control), the burner of the heating appliance is monitored by means of a flame monitoring electrode (e.g., ionization electrode), whereby the signal of the flame monitoring electrode is measured directly or indirectly, and whereby during operation of the burner (in step c)), the fuel gas-air mixture is leaned out and the signal of the flame monitoring electrode is continuously measured, thereby forming the gradient of the signal of the flame monitoring electrode, and if a certain gradient is exceeded or if the gradient increases disproportionately, the leaning of the fuel gas-air mixture is stopped and the fuel gas-air mixture is enriched in a defined manner.

[0020] The air can be supplied via a blower with a blower motor, and the gradient of the flame monitoring electrode signal can be determined by dividing the differential signal of the flame monitoring electrode by the differential speed of the blower motor. Alternatively or cumulatively, the fuel gas can be routed through a gas valve with an actuator, and the gradient of the flame monitoring electrode signal can be determined by dividing the differential signal of the flame monitoring electrode by the differential position of the actuator. Alternatively or cumulatively, the gradient of the flame monitoring electrode signal can be determined by dividing the differential signal of the ionization electrode by the differential time.Furthermore, a constant voltage source or constant current source can be connected in series with the flame of the burner and a resistor, and the voltage drop across the resistor can be measured as a signal from the flame monitoring electrode.

[0021] In a further advantageous embodiment, it is proposed that the intermediate steps i) to iii) be repeated cyclically at defined time intervals. This advantageously allows the secondary combustion control to provide continuous combustion control or redundancy to the primary combustion control that can be used over a longer period.

[0022] If the cause of the implausibility or malfunction of the primary combustion control is resolved (e.g., by a technician's intervention or the absence of external disturbances such as a storm), a switch from the secondary combustion control back to the primary combustion control is possible in most cases (reversibility). In cases where a switch back to the primary combustion control is no longer possible (defect in the primary control and / or a sensor of the primary control), the heating appliance can continue to operate permanently with the secondary combustion control. The occurrence of a malfunction in the secondary control then typically leads to a shutdown of the heating appliance.

[0023] Furthermore, a computer program for carrying out a procedure presented here can be described according to another aspect. In other words, this refers specifically to a computer program (product), comprising instructions that, when executed by a computer, cause it to perform a procedure described here. Another aspect that can be described is a machine-readable storage medium on which the proposed computer program is stored. This machine-readable storage medium is typically a computer-readable data carrier.

[0024] According to another aspect, a heating appliance for heating a building is proposed, comprising a burner, at least one sensor and a control device which is provided and set up to carry out primary combustion control depending on a signal from the at least one sensor, wherein the heating appliance further comprises a flame monitoring electrode projecting into the flame area of ​​the burner, which provides the control device with a signal to carry out secondary combustion control which differs from the primary combustion control, wherein the secondary combustion control uses fewer sensors than the primary combustion control.

[0025] The heating appliance is configured to carry out the procedure described here. In this context, the heating appliance's control unit can be specifically designed to execute the procedure. For this purpose, the control unit can, for example, have or access memory containing a program for carrying out the procedure. This program can be executed, for instance, by a processor within the control unit. The program could be, for example, the computer program described above. The memory can be, for example, the machine-readable storage medium described above. It is also conceivable that the procedure described above is executed directly by the heating appliance presented here.

[0026] Another aspect described is the use of an ionization electrode to maintain an emergency operating control of a heating device for heating a building.

[0027] The details, features, and advantageous configurations discussed in connection with the process may also occur in the computer program, storage medium, heating device, and / or use discussed here, and vice versa. In this respect, full reference is made to the explanations provided therein for a more detailed characterization of the features.

[0028] The invention will now be explained in detail using the figures.

[0029] They represent: Figure 1 : schematically illustrates an exemplary sequence of the procedure in the form of a flowchart, Figure 2 : schematically an exemplary setup of the heating device, and Figure 3: a course of an ionization signal, as it can result from the method presented here.

[0030] Figure 1 Figure 1 schematically illustrates an exemplary sequence of the procedure in the form of a flowchart. The procedure is used to operate a heating device 100 for heating a building (not shown here). The sequence of steps a), b), and c), represented by blocks 110, 120, and 130, is exemplary and can be followed in this way, for example, during regular operation. However, it is also conceivable that steps a), b), and c) could be carried out at least partially in parallel.

[0031] In block 110, according to step a), the heating appliance 100 is operated with primary combustion control. In block 120, according to step b), an implausibility and / or fault in the primary combustion control is detected. In block 130, according to step c), the heating appliance 100 is operated with a secondary combustion control that differs from the primary combustion control if an implausibility and / or fault in the primary combustion control has been detected.

[0032] Figure 2Figure 1 schematically shows an exemplary setup of the heating appliance 100 for heating a building. The heating appliance 100 comprises a burner 1, at least one sensor 20, 21, 22, 23, 24, 25, and a control unit 7, which is designed and configured to perform primary combustion control based on a signal from the at least one sensor 20, 21, 22, 23, 24, 25. Furthermore, the heating appliance 100 includes a flame monitoring electrode 3 projecting into the flame area 2 of the burner 1, which provides the control unit 7 with a signal to perform secondary combustion control that differs from the primary combustion control. The heating appliance 100, and in particular the control unit 7, is designed to carry out a procedure described herein (see Figure 1). Figure 1 ) furnished.

[0033] In particular, the primary combustion control is carried out depending on a signal from at least one sensor 20, 21, 22, 23, 24, 25 of the heating device 100. Examples are given in Figure 2 A gas flow sensor 20 for measuring a gas flow 30, an air flow sensor 21 for measuring an air flow 31, a mixture flow sensor 22, an exhaust gas sensor 23 for measuring an exhaust gas flow 32, a temperature sensor 24, and a radiation sensor 25 are provided, each transmitting a measurement signal to the control unit 7. In addition, the primary combustion control can also access measurement signals from the flame monitoring electrode 3. Depending on one or more of these measurement signals, a controlled variable can be determined and regulated relative to a reference variable.

[0034] For example, an implausibility and / or malfunction of the primary combustion control can be detected via at least one of the sensors 20, 21, 22, 23, 24, 25 of the heating unit 100 and / or the flame monitoring electrode 3 of the heating unit 100. For instance, an implausibility can be inferred if two or more of the sensors 20, 21, 22, 23, 24, 25 deliver contradictory measurement results. Alternatively or cumulatively, a malfunction can be inferred if one or more of the sensors 20, 21, 22, 23, 24, 25 deliver measurement results indicating flame failure (flame has gone out).

[0035] Furthermore, secondary combustion control can be carried out depending on a signal from the flame monitoring electrode 3 of the heating device 100. An ionization electrode is used here as an example of flame monitoring electrode 3; its function is explained in more detail below. Figure 1It is also shown that the flame monitoring electrode 3 is provided in addition to at least one further sensor 20, 21, 22, 23, 24, 25 of the heating device 100.

[0036] In step c), several intermediate steps can be performed, which are exemplified in block 130 by blocks 210, 220, and 230. In block 210, according to intermediate step i), at least one operating parameter of the heater 100 is varied to approach a flame lift-off point. In block 220, according to intermediate step ii), the approach to the flame lift-off point is monitored using the flame monitoring electrode 3. In block 230, according to intermediate step iii), at least one operating parameter of the heater 100 is set to a value determined based on the value the operating parameter had immediately before or at the time the flame lift-off point was reached.

[0037] An example of how secondary combustion control can be preferably carried out using sensor data from (only) the flame monitoring electrode 3 (and performance data from a conveying device (e.g., blower 8) and / or a gas valve 10) is given below using the Figure 2 and 3 described:

[0038] In Figure 2For example, burner 1 has a blower 8 with a blower motor 9 in an air inlet 12. A gas line 13 opens into the air inlet 12, containing a gas valve 10 with an actuator 11. The blower motor 9 and the actuator 11 are connected to the control unit 7. A flame 2 is located at burner 1, into which an ionization electrode 3 (as a flame monitoring electrode 3) protrudes. The ionization electrode 3 is connected to a voltage source 4. The second electrode of this voltage source is connected to a resistor 5, which in turn is connected to burner 1. A voltmeter 6 is connected in parallel to the resistor 5 and is connected to the control unit 7.

[0039] When burner 1 is operating, the blower 8 draws in combustion air through the air inlet 12. The speed n of the blower 8 can be continuously adjusted. The amount of fuel gas supplied via the gas line 13 can be continuously varied by means of the gas valve 10; the step count ns of the actuator 11 is measured. In the blower 8, fuel gas and air are mixed and ignited at the outlet of burner 1, forming a flame 2. Since the ions of the flame 2 are electrically conductive, a current can flow between the ionization electrode 3 and the burner 1. This results in an electrical voltage U across the flame. The ion flow through the flame 2 ensures that the electrical circuit (burner 1, ionization electrode 3, voltage source 4, resistor 5) is closed.

[0040] Figure 3In this context, the graph shows the curve of the voltage U measured across resistor 5 as a function of the air-fuel ratio λ and the blower speed n. U0 is the voltage of the voltage source 4. The following applies: U = U0 - Uflame. It is in Figure 3 It can be seen that the voltage U measured across resistor 5 is minimal during stoichiometric combustion (λ = 1.0). As the excess air is increased, the voltage U rises continuously. At an air-fuel ratio of approximately 1.6, the voltage U increases significantly more than before. At an excess air ratio of approximately λ = 1.7, the flame lifts off. No ionization signal can be measured anymore; a safety valve (not shown) shuts off the fuel gas supply.

[0041] In the secondary combustion control, burner 1 initially operates with an as-yet-unknown excess of air. With the gas valve 10 constantly open, the speed n of the blower 8 is increased. This increases the air-fuel ratio λ. This illustrates how, in intermediate step i), at least one operating parameter (here, for example, the air-fuel ratio λ) of the heating appliance 100 can be varied to achieve a flame lift-off point.

[0042] The voltage drop U across resistor 5 is continuously measured over time t and transmitted to the control unit 7. The control unit 7 calculates the gradient ΔU / Δn, where n is the rotational speed of the blower 8. If the gradient ΔU / Δn increases excessively from a certain point, this indicates that the flame is about to lift off and thus extinguish. The air-fuel ratio λ is then approximately 1.6. This illustrates how, in intermediate step ii), preferential monitoring of the approach to the flame lift-off point can be achieved using the flame monitoring electrode 3.

[0043] Starting from this point (with λ ≈ 1.6), the fan speed n is now deliberately reduced to achieve an air ratio λ ≈ 1.25. This illustrates how, in intermediate step iii), at least one operating parameter of the heater 100 can be set to a value determined based on the value the operating parameter had immediately before or at the point where the flame lift-off point was reached.

[0044] As an alternative to determining the gradient using the quotient of the difference signal and the difference speed ΔU / Δn, a gradient can also be calculated from the difference voltage ΔU to the differential position of the actuator Δn s if the fuel gas quantity is reduced instead of increasing the blower speed. As a further option, a gradient can also be calculated from time (ΔU / Δt) if the lean mixture is constant.

[0045] The operating state at which lift-off is imminent can be determined by comparing the current gradient with at least one previous gradient. If the current gradient exceeds the comparison value(s) by a certain percentage, the expected state is present. The lowest measured gradient can be used as the comparison value, for example. Alternatively, an absolute value can be specified. This illustrates how, as described in intermediate step ii), preferential monitoring of the approach to the flame lift-off point can be achieved using the flame monitoring electrode 3.

[0046] To eliminate the influence of signal noise (fluctuations of the measurement signal around a trend line), the time difference or speed difference should not be chosen too small. Instead of the voltage drop U across resistor 5, the voltage of the flame Uflame can also be measured directly. In this case, however, the ionization voltage is at its maximum during stoichiometric combustion, and the ionization voltage signal decreases as the air-fuel ratio increases. Instead of a constant voltage Uo, a constant current source with a constant current Io can also be connected in series with resistor 5 and the flame 2. A specific voltage will be established depending on the flame resistance.

[0047] The intermediate steps i) to iii) can be repeated cyclically at defined time intervals to enable continuous combustion control.

[0048] The described heating device 100 also represents an example of the use of an ionization electrode 3 to maintain an emergency operating control of a heating device 100 for heating a building.

[0049] The described method and heating device allow for an increase in the operating range of the heating device. Furthermore, it provides the user with a significantly higher level of comfort, as the heating device will fail less frequently. Reference symbol list

[0050] 100 Heater 1 Burner 2 Flame area 3 Flame monitoring electrode 4 Voltage source 5 Resistor 6 Voltmeter 7 Control device 8 Blower 9 Blower motor 10 Gas valve 11 Actuator 12 Air inlet 13 Gas line 20 Gas flow sensor 21 Air flow sensor 22 Mixture flow sensor 23 Exhaust gas sensor 24 Temperature sensor 25 Radiation sensor 30 Gas flow 31 Air flow 32 Exhaust gas flow

Claims

1. Method for operating a heating appliance (100) for heating a building, comprising the following steps: a) operating the heating appliance (100) with a primary combustion closed-loop control, b) detecting an implausibility and / or malfunction in the primary combustion closed-loop control, c) operating the heating appliance (100) with a secondary combustion closed-loop control which differs from the primary combustion closed-loop control, when an implausibility and / or malfunction of the primary combustion closed-loop control is detected; characterized in that the secondary combustion closed-loop control makes recourse to fewer sensors than the primary combustion closed-loop control.

2. Method according to claim 1, wherein the primary combustion closed-loop control is performed as a function of a signal of at least one sensor (20, 21, 22, 23, 24, 25) of the heating appliance (100).

3. Method according to any of the preceding claims, wherein an implausibility and / or malfunction of the primary combustion closed-loop control is detected by at least one sensor (20, 21, 22, 23, 24, 25) of the heating appliance (100) and / or a flame monitoring electrode (3) of the heating appliance (100).

4. Method according to any of the preceding claims, wherein the secondary combustion closed-loop control is performed as a function of a signal of a flame monitoring electrode (3) of the heating appliance (100).

5. Method according to claim 4, wherein the flame monitoring electrode (3) is an ignition and monitoring electrode.

6. Method according to claim 4 or 5, wherein the flame monitoring electrode (3) is an ionization electrode.

7. Method according to any one of claims 4 to 6, wherein the flame monitoring electrode (3) is provided in addition to at least one sensor (20, 21, 22, 23, 24, 25) of the heating appliance (100).

8. Method according to any one of claims 4 to 7, wherein in step c) the following intermediate steps are performed: i) varying at least an operating parameter of the heating appliance (100) in order to approach a flame lift-off point, ii) monitoring the approach of the flame lift-off point by means of the flame monitoring electrode (3), iii) setting the at least one operating parameter of the heating appliance (100) to a value which is determined as a function of the value which the operating parameter had immediately prior to or when reaching the flame lift-off point.

9. Method according to claim 9, wherein the intermediate steps i) to iii) are repeated cyclically at defined time intervals.

10. Heating appliance (100) for performing a method according to any of the preceding claims, comprising a burner (1), at least one sensor (20, 21, 22, 23, 24, 25) and a closed-loop control apparatus (7) which is provided and configured to perform a primary closed-loop control as a function of a signal of the at least one sensor (20, 21, 22, 23, 24, 25), wherein the heating appliance (100) furthermore comprises a flame monitoring electrode (3) projecting into the flame region (2) of the burner (1), which flame monitoring electrode provides to the closed-loop control apparatus (7) a signal for performing a secondary combustion closed-loop control which differs from the primary combustion closed-loop control; characterized in that the secondary combustion closed-loop control makes recourse to fewer sensors than the primary combustion closed-loop control.

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