Method for evaluating quasi-steady pressure differences in a gas boiler obtainable by a sensor and gas boiler

Abstract

The invention relates to a method for evaluating a quasi-steady pressure difference in a gas boiler, which can be obtained by a sensor, wherein the sensor is a differential pressure sensor or a mass flow sensor, wherein the gas boiler has a mixing device (4) for mixing fuel flowing in from a fuel inlet (G) and air flowing in from an air inlet (L) to form a fuel-air mixture, a blower (5) for drawing in the fuel and air through the mixing device, a main flow restrictor (3) for restricting the mass flow of the fuel in the mixing device (4), a regulating valve (2) arranged upstream of the main flow restrictor (3) and for regulating the mass flow of the fuel into the mixing device (4), and a safety valve (1) arranged upstream of the regulating valve (2) and for interrupting the mass flow of the fuel, wherein the sensor acquires the pressure difference between the pressure (p2) at a measurement point upstream of the main flow restrictor (3) and downstream of the regulating valve (2) and a reference pressure (p0, p1) at a reference measurement point and transmits it to an evaluation electronics, wherein the evaluation electronics compares the pressure difference in a pre-flush phase, in which the safety valve (1) is closed, with the pressure difference after the pre-flush phase and detects a fault by comparison.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for evaluating a quasi-steady pressure difference obtainable by a sensor in a gas boiler designed to carry out said method. BACKGROUND

[0002] Gas boilers are known in the prior art in which a pressure difference with respect to a reference pressure is measured upstream of a main flow restrictor by means of a sensor designed as a differential pressure sensor, and the fuel mass flow is regulated on the basis of the pressure difference.

[0003] A gas boiler generally comprises, among other components, a mixing device for mixing fuel flowing in from a fuel inlet and air flowing in from an air inlet to form a fuel-air mixture, a blower for drawing in fuel and air through the mixing device, a main flow restrictor for limiting the mass flow of fuel in the mixing device, a regulating valve arranged upstream of the main flow restrictor for regulating the mass flow of fuel in the mixing device, and a safety valve arranged upstream of the regulating valve for interrupting the mass flow of fuel. The gas-air mixture can then be fed to a burner in which the mixture is combusted.

[0004] In order to regulate the pressure flowing into the fuel, the regulating valve in the prior art often works as a mechanical-pneumatic gas valve, the pressure difference is obtained by means of a regulating membrane, and it is arranged between two areas of different pressure.

[0005] However, alternatively, a pressure sensor is also used in the so-called "electronic control" range, in which the pressure is obtained by a separate sensor and the pressure value is evaluated electronically in order to determine the pressure difference. Depending on the evaluation, an electronically controlled regulating valve or a gas valve can be controlled or regulated.

[0006] For example, in a device for regulating a gas-air mixture of a gas boiler, the pressure upstream of the main flow restrictor is measured with respect to a reference pressure by means of a differential pressure sensor, which measures the pressure difference or the pressure difference between the two pressure drops.

[0007] In this case, the electronic gas valve is usually controlled by a digital regulator, which is implemented, for example, in a microcontroller or other control device, and by means of which the determined compensation pressure or pressure difference is regulated to a desired or specified target value.

[0008] Since the target value of the pressure or pressure difference is usually 0 Pa, the term "electronic zero pressure regulation" is often used.

[0009] Whether it is electronic regulation or mechanical-pneumatic regulation, its function is limited to regulating the gas boiler depending on the pressure difference, and no additional functions can be provided.

[0010] However, it is desirable to be able to monitor further characteristic values related to the gas boiler in order to be able to detect faults in the gas boiler on the basis of the characteristic values and to be able to control or regulate the boiler and take other measures accordingly, in particular to prolong the service life of the boiler.

[0011] In order to be able to acquire additional characteristic values or detect faults in known gas boilers, additional sensors and evaluation devices are required, which is both complex and expensive. SUMMARY

[0012] It is therefore an object of the present application to overcome the above-mentioned disadvantages and to provide a method by which faults in a gas boiler can be acquired and evaluated in a simple and cost-effective manner.

[0013] This object is achieved by a combination of features according to the following.

[0014] According to the application, a method is therefore proposed for evaluating a quasi-stationary pressure difference in a gas boiler, which can be acquired by a sensor. The sensor is a differential pressure sensor or a mass flow sensor. It is further provided that the gas boiler has a mixing device for mixing fuel flowing in from a fuel inlet and air flowing in from an air inlet to form a fuel-air mixture, a blower for drawing in the fuel and air through the mixing device, a main flow restrictor for restricting the mass flow of the fuel in the mixing device, a regulating valve arranged upstream of the main flow restrictor and for regulating the mass flow of the fuel into the mixing device, and a safety valve arranged upstream of the regulating valve and for interrupting the mass flow of the fuel. The sensor acquires the pressure difference between a measurement point arranged upstream of the main flow restrictor and downstream of the regulating valve and a reference pressure at a reference measurement point and transmits it to the evaluation electronics. The evaluation electronics compares the pressure difference in a pre-flush phase in which the safety valve is closed with the pressure difference after the pre-flush phase and detects a fault by comparison.

[0015] In the pre-flush phase, the gas boiler is flushed with air without gas mixture, as is known to the person skilled in the art, which is achieved by the closed safety valve. In most cases, the pre-flush phase is carried out at the beginning of the operation or at the initialization of the gas boiler.

[0016] The fault detection after the pre-flush phase relates to all other operating phases or types after the pre-flush of the gas boiler, in particular to the adjustment operation, in which the gas boiler can be calibrated, and the continuous operation of the gas boiler.

[0017] Quasi-stationary pressure difference is to be understood as a pressure difference that is not fluctuating or fluctuates only within a predetermined tolerance range. For example, a pressure difference fluctuation of about 1% of the average value of the pressure difference can be understood as quasi-stationary.

[0018] If predetermined or previously known values ​​and / or ranges are involved, these values ​​and / or ranges may be stored or at least stored in the evaluation electronics.

[0019] For example, various states or errors in the system can be detected and / or rationale-checked based on known data stored in the evaluation electronics, which may be determined as part of calibrating the gas boiler or may be input by the user. In this case, the determination of states or faults is made particularly by physically and logically considering the main states and values ​​in the system. State detection can also be performed using machine learning (e.g., using neural networks). Furthermore, machine learning can often be used to generate or extend tolerance ranges or general tolerance values.

[0020] The proposed method is based on a signal from a differential pressure sensor, which measures, for example, the compensation pressure p2 during normal operation of "electronic zero-pressure regulation". If the gas type is known and the main flow limiter is defined, the compensation pressure can be used to calibrate, for example, the characteristic curve of a gas valve.

[0021] According to a first advantageous variant of the method, the fault is a faulty main flow limiter or a misused main flow limiter, and the method includes the following steps:

[0022] a. Determine the time point t during the pre-rinse phase using sensors. pp The first pressure difference p(t) pp During the pre-rinse phase, the safety valve is closed, and the regulating valve is positioned in a defined position, and the blower speed is controlled.

[0023] b. Determine the time point t using sensors. pp The time point t after s The second pressure difference p(t) s ), at the time point t s The second pressure difference p(t) at that time s It is quasi-steady at time point t. s The safety valve opens, and the regulating valve is positioned at a specific location, and the blower speed is controlled.

[0024] c. Specifically, through the second pressure difference p(t) s Subtract the first pressure difference p(t) pp Determine the second pressure difference p(t) s ) and the first pressure difference p(t) pp The pressure difference between the two is used to determine the fuel mass flow rate of the known fuel through the main flow limiter by evaluating the pressure difference and the defined position of the regulating valve using electronic devices.

[0025] d. Determine the actual pressure loss coefficient of the main flow limiter by evaluating the electronic device based on the mass flow rate of the fuel and the pressure difference;

[0026] e. Compare the actual pressure loss coefficient of the evaluation electronics with the target pressure loss coefficient of the expected main flow limiter stored in the evaluation electronics.

[0027] Therefore, if the deviation between the actual pressure loss coefficient and the target pressure loss coefficient exceeds the predetermined tolerance, the evaluation electronics detect that the main flow limiter used in the gas boiler does not correspond to the expected main flow limiter, and thus the main flow limiter used is incorrect or misused, which corresponds to the fault to be detected.

[0028] If a faulty or malfunctioning main flow limiter is detected, it is preferable to know the characteristics of the fuel used, the mixing device, and the valve characteristic curves of the regulating valve. These values ​​are predetermined and / or stored in the evaluation electronics.

[0029] As an alternative, a second advantageous variant specifies that the fault is an uncalibrated or incorrectly calibrated control valve, and the method includes the following steps:

[0030] a. Determine the time point t during the pre-rinse phase using sensors. pp The first pressure difference p(t) pp During the pre-rinse phase, the safety valve is closed, and the regulating valve is positioned in a defined position, and the blower speed is controlled.

[0031] b. Determine the second pressure difference p(t) at time point ts using a sensor. s ), at the time point t s The second pressure difference p(t) at that time s It is quasi-steady at the stated time point t. s The safety valve opens, and the regulating valve is positioned at a specific location, and the blower speed is controlled.

[0032] c. Specifically, the pressure difference between the second pressure difference p(ts) and the first pressure difference p(tpp) is determined by subtracting the first pressure difference p(tpp) from the second pressure difference p(ts), and the fuel mass flow rate of the known fuel through the control valve is determined by evaluating the pressure difference and the pressure loss characteristics defined by the main flow limiter from the electronic device, wherein the mass flow rate through the control valve and the defined position of the control valve form a pair of values ​​constituting the actual characteristic curve of the control valve;

[0033] d. The deviation between the actual characteristic curve of the control valve and the target curve of the control valve is determined by comparing the pair of values ​​with the target characteristic curve of the control valve using an evaluation electronic device.

[0034] wherein the regulating valve is detected as being misaligned or misaligned if the pair of values deviates from a target characteristic curve of the regulating valve beyond a predetermined tolerance.

[0035] In this case, it is preferably further provided that the target characteristic curve of the regulating valve is offset by the deviation, thereby approximating the actual characteristic curve.

[0036] It can also be provided that not only is the regulating valve identified as being misaligned or misaligned, but also that the regulating valve is aligned in situ. By determining the actual characteristic curve, it can be used as a target characteristic curve or measures can be taken to further approximate the actual characteristic curve to the target characteristic curve.

[0037] Here advantageously, the properties of the fuel, the main flow restrictor used and the mixing device are known. These values are predetermined and / or stored in the evaluation electronics.

[0038] In addition to the first two variants of the method, an alternative third variant provides that the fault is a faulty fuel and the method comprises the following steps:

[0039] a. determining a first pressure difference p(t pp ) at a point in time t pp in a preflushing phase in which the safety valve is closed and has a defined position of the regulating valve and a blower speed of the blower, by means of a sensor;

[0040] b. determining a second pressure difference p(t s ) at a point in time t s , the second pressure difference p(t s ) at the point in time t s being quasi-stationary, in which the safety valve is open and has a defined position of the regulating valve and a blower speed of the blower, by means of a sensor;

[0041] c. determining a pressure difference between the second pressure difference p(t s ) and the first pressure difference p(t pp ), in particular by subtracting the first pressure difference p(t s ) from the second pressure difference p(t pp );

[0042] d. determining an actual fuel flow from the fuel inlet on the basis of the pressure difference, the defined position of the regulating valve and a predetermined mass flow conveyed through the mixing device from the blower and a defined pressure loss characteristic of the main flow restrictor;

[0043] e. comparing the actual fuel with a predetermined target fuel.

[0044] It is provided here that the evaluation electronics detects an error fuel, i.e. a malfunction, when the actual fuel does not match the target fuel.

[0045] In this way, a plausibility check can be carried out to determine whether the fuel that should be used is actually used.

[0046] For determining or plausibility checking the fuel, it is also advantageous if the characteristics of the main flow restrictor, the mixing device and the gas valve characteristic curve of the regulating valve are known. These values are predetermined and / or stored in the evaluation electronics.

[0047] In addition or as an alternative to the method variants already described, it can be provided that a malfunction is a missing or too low fuel pressure pg of the fuel flowing in through the fuel inlet and / or is a main flow restrictor error or is not installed. If such a malfunction or these malfunctions are to be detected, the method comprises the following steps:

[0048] a. opening the safety valve;

[0049] b. igniting the burner of the gas boiler;

[0050] c. determining whether the burner has been ignited;

[0051] d. if the burner has not been ignited, determining a differential pressure curve by means of the sensor and the evaluation electronics while the safety valve is open for a predetermined time;

[0052] It is provided here that the evaluation electronics compares the differential pressure curve with a predetermined tolerance range and detects a malfunction if the differential pressure curve lies outside the tolerance range, since the differential pressure does not increase within the predetermined time, a missing or too low fuel pressure pg and / or a main flow restrictor error or not installed is detected.

[0053] For this purpose, the fuel used, the main flow restrictor used, the characteristics of the mixing device and the gas valve characteristic curve of the regulating valve are preferably known. These values are predetermined and / or stored in the evaluation electronics.

[0054] In a further advantageous refinement of this, the maximum permissible heating power of the gas boiler and / or the maximum permissible blower speed of the blower is reduced to a corresponding predetermined value to avoid damage if the fuel pressure pg is missing or too low.

[0055] Furthermore, an advantageous variant of the method can provide that the fault is the absence or non-connection of the sensor and / or a poor or non-existent connection of the sensor to the measurement point and / or to the reference measurement point. Here, the pressure difference between the pressure at the measurement point upstream of the main flow restrictor and downstream of the regulating valve and the reference pressure at the reference measurement point is determined. If the pressure difference is outside a predetermined tolerance range, the evaluation electronics detects the absence or non-connection of the sensor and / or a poor or non-existent connection to the measurement point and / or to the reference measurement point.

[0056] In order to prevent or at least minimize damage, an advantageous further development provides that, if the sensor is absent or not connected and / or a poor or non-existent connection to the measurement point and / or to the reference measurement point, the safety valve is closed.

[0057] Here, too, the fuel used, the main flow restrictor used, the properties of the mixing device and the gas valve characteristic curve of the regulating valve are preferably known. These values are predetermined and / or stored in the evaluation electronics.

[0058] As an alternative or in addition to the aforementioned method further development, it can be provided that the fault is a defective safety valve or a defective regulating valve, wherein the method comprises the following steps:

[0059] a. determining an actual pressure difference by means of the sensor with the safety valve open, the defined position of the regulating valve and a predetermined mass flow delivered from the blower through the mixing device;

[0060] b. determining a target pressure difference by means of the evaluation electronics and the defined position of the regulating valve;

[0061] c. determining a deviation of the actual pressure difference from the target pressure difference.

[0062] In this case, the evaluation electronics recognizes a fault or the fault when the deviation is greater than a predetermined tolerance value, which can be stored, in particular in the evaluation electronics.

[0063] A further aspect of the application relates to a gas boiler designed to implement the method according to the application.

[0064] The features disclosed above can be combined as desired, as long as this is technically feasible and they do not contradict each other. BRIEF DESCRIPTION OF DRAWINGS

[0065] Further advantageous further developments of the application are characterized above or are presented in more detail below together with the description of a preferred embodiment of the application with reference to the attached drawings. In the drawings:

[0066] Figure 1for a gas boiler. DETAILED DESCRIPTION

[0067] Figure 1 A part or section of a gas boiler is schematically shown, wherein a venturi mixer is shown as mixing device 4, wherein a blower 5 sucks in air from the environment with an air pressure p0 through an air inlet L. The inflowing air and fuel (gas) flowing in through a fuel source G are mixed in the mixing device 4 to form a fuel-air mixture.

[0068] The fuel, in particular gas, flowing in from the fuel source G flows through the safety valve 1, the regulating valve 2 and the main flow restrictor 3. The safety valve 1 preferably has an open and a blocked position, in which position the flow of fuel through the safety valve 1 is blocked. The regulating valve 2 is designed for controlling the volume flow of the fuel, so that the volume flow of the fuel through the regulating valve 2 to the mixing device 4 can be adjusted. The mixing ratio of the fuel-air mixture can thus be adjusted by adjusting or regulating the volume flow of the fuel through the regulating valve 2.

[0069] Furthermore, at least one differential pressure sensor is provided, which is designed for determining the pressure difference between the pressure p2 of the fuel upstream of the main flow restrictor 3 and downstream of the regulating valve 2 and a reference pressure, wherein the reference pressure is preferably the ambient pressure p0 or the pressure pi of the air in the air delivery supply line to the mixing device 4. To this end, the differential pressure sensor may, for example, have corresponding pressure sensors or pressure receivers for acquiring the corresponding pressures p0, pi, p2. Furthermore, further pressure sensors for acquiring further pressures pg, p3 and p4 can be provided, which can serve as reference pressure sensors for acquiring the reference pressure or for plausibility checking the pressures p0, pi, p2.

[0070] The fuel-air mixture is delivered by the blower 5 to a burner (not shown) of the gas boiler, in which the fuel-air mixture is combusted.

[0071] According to Figure 1 The system shown, the following errors or states will be detected by way of example, and if necessary, the values will be detected or plausibility checked.

[0072] In a first case, for example, the installed main flow restrictor 3 will be detected by the pressure difference determined by the differential pressure sensor.

[0073] It is advantageous here that the control pressure-venturi characteristic of the system, i.e. of the gas boiler, is known. The venturi mixer as mixing device 4 is not absolutely necessary, a pressure drop element with known pressure drop characteristic upstream of the mixing location of air and fuel (gas) is sufficient. Furthermore, the type of gas (fuel type) should be known. The type of gas can be stored by the installer or in the factory on the evaluation electronics or a sensor provided for this purpose detects the composition of the gas, for example at the gas inlet G.

[0074] By the preferably calibrated regulating valve 2, the gas mass flow through the regulating valve 2 in the installed state can be inferred at a given position of the actuator of the regulating valve 2. In this case, it is assumed that the pre-pressure regulator of the regulating valve 2 works ideally and that the mass flow through the regulating valve 2 is independent of the inlet pressure pg. The compensation pressure p2 upstream of the main flow restrictor 3 is measured, for example by a pressure sensor that is part of the differential pressure sensor.

[0075] For a given air mass flow, the air density influencing the control pressure of the mixing device 4 can be pre-manually input by the installer. Alternatively, the air density can also be determined by a sensor. By a suitable geometric arrangement, this can also be achieved by a sensor with which the type of gas can be determined when the safety valve 1 is open.

[0076] In the pre-blowing phase (time point t = t pp ) of the gas boiler with closed safety valve 1, the negative pressure pv generated by the rotational speed N of the blower 5 through the mixing device 4 is measured by the pressure sensor at the location p2.

[0077] Since the safety valve 1 is closed in the pre-blowing phase, the following applies: p2(t pp ) = p3(t pp ) = p4(t pp ) = pv(t pp ).

[0078] The air mass flow is calculated from the measured pressure p2 or pv and a function or table stored in the evaluation electronics for the system consisting of the mixing device 4 and the main flow restrictor 3. Depending on the accuracy requirements, the calculation can be corrected with the air density.

[0079] After the pre-blowing phase, the ignition of the gas boiler is first started with the same rotational speed N approaching the desired pre-control position of the actuator of the regulating valve 2, then the safety valve 1 is opened. As soon as a combustible mixture is present at the ignition electrode of the gas boiler, the fuel-air mixture burns on the burner of the gas boiler and the pressure p2 stabilizes from the time point t s and a quasi-steady state exists.

[0080] The measured (or specifically adjusted) pressure p2(t) s Now, using the previously measured pressure p2(t) pp The driving pressure difference dp = p2(t) is obtained across the flow resistance of the series connection including the main flow limiter 3 and the mixing device 4, and other resistances. s )-pv(t s Other flow resistances could be, for example, deflection downstream of the main flow limiter 3 and openings (“cavitation”) at the location of the air-gas mixture.

[0081] If necessary, the speed N of the blower 5 can also be changed to detect the installed main flow limiter 3 so that multiple measurement points can be used.

[0082] The pressure loss coefficient of the main flow limiter 3 can be calculated using the gas mass flow rate and pressure difference dp determined by the gas valve characteristic curve.

[0083] Pressure losses from other flow resistances should also be considered in this calculation. In particular, if the pressure loss on the main flow limiter 3 is dominant relative to the total pressure loss dp, the installed main flow limiter 3 (or the associated pressure loss factor) can be determined with sufficient accuracy.

[0084] If there is no ignitable mixture in the burner of the gas boiler at the ignition point, further ignition attempts can be made, and the pilot position of regulating valve 2 may need to be adjusted.

[0085] In principle, the main flow limiter 3 can also be installed for detection even when the gas-air mixture in the burner is not burning. It must always be ensured that the potentially flammable gas-air mixture is delivered out of the gas boiler by a safety purging (flushing) using a blower 5 after a certain safety time.

[0086] Another prerequisite is the measured pressure p2(t) s The pressure difference reaches a quasi-steady state. If the measured pressure difference is completely outside the predetermined tolerance range, the insufficient or missing inlet pressure may be the cause of the ignition failure.

[0087] In the second case, for example, it should be possible to detect incorrectly calibrated control valve 2, and if necessary, control valve 2 can be calibrated during operation (in situ).

[0088] Likewise advantageously, the control pressure characteristics of the system are known. Here, the Venturi mixer is not absolutely necessary as mixing device 4 either; a pressure drop element with known pressure drop characteristics upstream of the mixing location of air and fuel is sufficient as mixing device 4. In addition, the type of gas (fuel type) is known. The gas type can be stored on the evaluation electronics by the installer or in the factory, or can be detected by appropriate sensors.

[0089] In addition to the mentioned data, the system downstream of the main flow restrictor 3 (deflection and cavitation) and the main flow restrictor 3 with known pressure loss characteristics are advantageous for the in-situ calibration of the regulating valve 2. The installed main flow restrictor 3 can be stored on the evaluation electronics by the installer or in the factory, or the main flow restrictor 3 is mechanically / electronically / color-coded by the manufacturer in such a way that the evaluation electronics evaluating the measurement data detects the main flow restrictor 3.

[0090] As in the first case described, the pressure difference pv during the pre-purge phase and the pressure difference when the flame is ignited and in the quasi-stationary state are determined.

[0091] If necessary, the rotational speed N of the blower 5 can also be changed here in order to be able to determine a plurality of measurement points. In practice, however, usually only one measurement point is required to determine the compensation pressure of the regulating valve 2 characteristic curve.

[0092] The flow rate (mass flow) through the regulating valve 2 can be calculated from the pressure difference dp determined in this way and the known total pressure loss characteristics of the main flow restrictor 3 and, if necessary, the flow resistance arranged downstream.

[0093] If there is no ignitable mixture in the burner of the gas boiler at the time of ignition, further ignition attempts can be made, possibly also with an adjustment of the pilot position of the regulating valve 2. If these ignition attempts are also unsuccessful, the detection of the regulating valve 2 and / or the in-situ calibration of the regulating valve 2 can also be carried out without combustion of the gas-air mixture.

[0094] In addition, the calibration of the regulating valve 2 can in principle also be carried out without combustion of the gas-air mixture when the gas boiler is started up. It must always be ensured that the potentially flammable gas-air mixture is conveyed out of the gas boiler by means of the blower 5 by a safe purge (flush) after a certain safety time.

[0095] As already mentioned, the pressure difference p2(t s ) should be in a quasi-stationary state.

[0096] The described method for calibrating the regulating valve 2 can also be used during production, not in situ at the beginning of operation of the gas boiler. The calibration process can also be performed with air flowing through the regulating valve 2. If the in situ calibration is performed during production, the calibration parameters can be stored directly on the electronics of the regulating valve 2 without direct communication between the electronics of the production facility and the gas boiler.

[0097] In the third case, the gas used as fuel should be checked for plausibility or a wrong gas should be detected.

[0098] Also preferably, the control pressure Venturi characteristic of the known system is known. Here, the Venturi mixer as mixing device 5 is not absolutely necessary either. A pressure drop element upstream of the mixing location of air and fuel is sufficient as mixing device 5 with known pressure drop characteristic.

[0099] For the plausibility check of the gas used as fuel or the associated fault detection, advantageously the flow resistance system downstream of the main flow restrictor 3 (deflection and cavitation) is known and the main flow restrictor 3 with known pressure loss is used. The installed main flow restrictor 3 can be stored on the evaluation electronics by the installer or in the factory. Alternatively, the main flow restrictor 3 can also be mechanically / electronically / color-coded so that the evaluation electronics evaluating the measurement data detects the main flow restrictor 3.

[0100] As in the two cases described above, with the example of a factory calibration of the electronic regulating valve 2, the gas mass flow flowing through the regulating valve 2 in the installed state at a given position of the actuator of the regulating valve 2 can be inferred. In this case, it is assumed that the pre-pressure regulator of the regulating valve 2 works ideally and that the mass flow through the regulating valve 2 is independent of the inlet pressure pg of the gas by control. The compensation pressure p2 upstream of the main flow restrictor 3 is measured by a pressure sensor, which can be part of a differential pressure sensor. The pressure sensor can be installed upstream of the main flow restrictor 3 or on the electronics circuit board of other components and connected to the representative pressure measurement point upstream of the main flow restrictor 3 by a hose / pipe.

[0101] For a given air mass flow, the air density, which can influence the control pressure of the mixing device 4, can be pre-manually input by the user. Alternatively, the air density can also be determined by a sensor.

[0102] As described before, in the pre-blowing phase (time point t = t pp ) or flushing of the gas boiler, the negative pressure pv generated by the mixing device 5 at the rotational speed N of the blower 5 can be measured at point p2 by a pressure sensor. Since the safety valve 1 is closed in the pre-blowing phase, the following applies again: p2(t pp ) = p3(t pp)=p4(t pp ) = pv(t pp Using the measured pressure p2 and functions or tables stored in the evaluation unit, the air mass flow rate can be calculated for the system consisting of the mixing device 4 and the main flow limiter 3. This calculation can be corrected for accuracy requirements using the air density of the air flowing through the inlet L.

[0103] After the pre-purge phase, the gas boiler is ignited by first approaching the desired pre-control position of the actuator of regulating valve 2 at the same rotational speed N, and then safety valve 1 is opened. Once a combustible mixture is present at the ignition electrode of the gas boiler, the fuel-air mixture burns on the burner of the gas boiler, and pressure p2 increases from time point t. s It begins to stabilize, thus reaching a quasi-steady state with pressure p2 or pressure difference. The measured (or selectively adjusted) pressure p2(t) s Now, using the previously measured pressure p2(t) pp The driving pressure difference dp = p2(t) is obtained over the flow resistance of any other resistance in the series connection including the main flow limiter 3 and the mixing device 4. s )-pv(t s Other flow resistances could be, for example, deflection downstream of the main flow limiter 3 and openings (“cavitation”) at the location of the air-gas mixture in the mixing unit 4.

[0104] Here, the rotational speed N can also be changed as needed to allow for the use of multiple measurement points.

[0105] By using the measured pressure difference dp, the known mass flow rate at a fixed or constant position of the regulating valve 2, the known total pressure loss characteristics of the main flow limiter 3, and the flow resistance arranged downstream, it is reasonable to check the gas type or gas composition of the gas flowing in through the gas inlet G.

[0106] The implementation of this invention is not limited to the preferred exemplary embodiments specified above. Rather, even in cases of fundamentally different designs, various variations of the illustrated scheme can be contemplated.

Claims

1. A method for evaluating a quasi-steady pressure difference in a gas boiler, which can be obtained by a sensor, wherein the sensor is a differential pressure sensor or a mass flow sensor, wherein the gas boiler has a mixing device (4) for mixing fuel flowing in from a fuel inlet (G) and air flowing in from an air inlet (L) to form a fuel-air mixture, a blower (5) for drawing in the fuel and air through the mixing device (4), a main flow restrictor (3) for restricting the mass flow of the fuel in the mixing device (4), a regulating valve (2) arranged upstream of the main flow restrictor (3) and for regulating the mass flow of the fuel into the mixing device (4), and a safety valve (1) arranged upstream of the regulating valve (2) and for interrupting the mass flow of the fuel, wherein the sensor acquires the pressure difference between the pressure (p2) at a measurement point upstream of the main flow restrictor (3) and downstream of the regulating valve (2) and a reference pressure (p0, pi) at a reference measurement point and transmits it to an evaluation electronics, wherein, the evaluation electronics compares the pressure difference of a pre-purge phase in which the safety valve (1) is closed with the pressure difference after the pre-purge phase and detects a fault by the comparison, wherein the fault is a wrong main flow restrictor or a wrong use of the main flow restrictor (3), and the method comprises the following steps: a. Determining the time point t during the pre-rinsing phase using the sensor. pp The first pressure difference p(t) pp During the pre-rinse phase, the safety valve (1) is closed and has the defined position of the regulating valve (2) and the blower speed of the blower (5); b. determining a second pressure difference p(t s ) at a time point t s after the time point t s by means of the sensor, the second pressure difference p(t s ) at the time point t s being quasi-stationary, a safety valve (1) being open at the time point t pp and having a defined position of the regulating valve (2) and a blower speed of the blower (5); c. By means of the second pressure difference p(t) s Subtract the first pressure difference p(t) pp Determine the second pressure difference p(t) s ) and the first pressure difference p(t) pp The pressure difference between the two is used to determine the fuel mass flow rate of the known fuel through the main flow limiter (3) by means of the evaluation electronics from the pressure difference and the defined position of the regulating valve (2); d. determining, by the evaluation electronics, an actual pressure loss coefficient of the main flow restrictor (3) from the mass flow of the fuel and the pressure difference; e. comparing the actual pressure loss coefficient determined by the evaluation electronics with a target pressure loss coefficient of an expected main flow restrictor stored in the evaluation electronics; whereby, if the deviation of the actual pressure loss coefficient from the target pressure loss coefficient exceeds a predetermined tolerance, the evaluation electronics detects that the main flow restrictor (3) used in the gas boiler does not correspond to the expected main flow restrictor and, therefore, the used main flow restrictor (3) is a wrong main flow restrictor or a wrong used main flow restrictor (3).

2. A method for evaluating a quasi-steady pressure difference in a gas boiler, which can be obtained by a sensor, wherein the sensor is a differential pressure sensor or a mass flow sensor, wherein the gas boiler has a mixing device (4) for mixing fuel flowing in from a fuel inlet (G) and air flowing in from an air inlet (L) to form a fuel-air mixture, a blower (5) for drawing in fuel and air through the mixing device (4), a main flow restrictor (3) for restricting the mass flow of the fuel in the mixing device (4), a regulating valve (2) arranged upstream of the main flow restrictor (3) and for regulating the mass flow of the fuel into the mixing device (4), a safety valve (1) arranged upstream of the regulating valve (2) and for interrupting the mass flow of the fuel, wherein the sensor acquires a pressure difference between a pressure (p2) at a measurement point upstream of the main flow restrictor (3) and downstream of the regulating valve (2) and a reference pressure (p0, pi) at a reference measurement point and transmits it to an evaluation electronics, wherein the evaluation electronics compares the pressure difference of a pre-purge phase in which the safety valve (1) is closed with the pressure difference after the pre-purge phase and detects a fault by the comparison, wherein the fault is an uncalibrated or incorrectly calibrated regulating valve (2), and the method comprises the following steps: a. Determining the time point t during the pre-rinsing phase using the sensor. pp The first pressure difference p(t) pp During the pre-rinse phase, the safety valve (1) is closed and has the defined position of the regulating valve (2) and the blower speed of the blower (5); b. Determining time point t using the sensor. s The second pressure difference p(t) s ), at the time point t s The second pressure difference p(t) at that time s It is quasi-steady at the stated time point t. s When the safety valve (1) is open, it has the defined position of the regulating valve (2) and the blower speed of the blower (5); c. determining a pressure difference between the second pressure difference p(t s ) and the first pressure difference p(t pp ) by subtracting the first pressure difference p(t s ) from the second pressure difference p(t pp ) and determining, by means of the evaluation electronics, a fuel mass flow of the known fuel through the regulating valve (2) from the pressure difference and the defined pressure loss characteristic of the main flow restrictor (3), wherein the mass flow through the regulating valve (2) and the defined position of the regulating valve (2) form a pair of values which constitute an actual characteristic curve of the regulating valve (2); d. determining, by means of the evaluation electronics, a deviation of an actual characteristic curve of the regulating valve (2) from a target curve of the regulating valve (2) by comparing the pair of values with the target characteristic curve of the regulating valve (2); wherein an uncalibrated or incorrectly calibrated regulating valve (2) is detected if the pair of values deviates from the target characteristic curve of the regulating valve (2) beyond a predetermined tolerance.

3. The method according to claim 2, wherein the target characteristic curve of the regulating valve (2) is shifted by the deviation, thereby approximating the actual characteristic curve.

4. A method for evaluating a quasi-steady pressure difference in a gas boiler, which can be obtained by a sensor, wherein the sensor is a differential pressure sensor or a mass flow sensor, wherein the gas boiler has a mixing device (4) for mixing fuel flowing in from a fuel inlet (G) and air flowing in from an air inlet (L) to form a fuel-air mixture, a blower (5) for drawing in fuel and air through the mixing device (4), a main flow restrictor (3) for restricting the mass flow of the fuel in the mixing device (4), a regulating valve (2) arranged upstream of the main flow restrictor (3) and for regulating the mass flow of the fuel into the mixing device (4), a safety valve (1) arranged upstream of the regulating valve (2) and for interrupting the mass flow of the fuel, wherein the sensor acquires a pressure difference between a pressure (p2) at a measurement point upstream of the main flow restrictor (3) and downstream of the regulating valve (2) and a reference pressure (p0, pi) at a reference measurement point and transmits it to an evaluation electronics, the evaluation electronics compares the pressure difference of a pre-purge phase in which the safety valve (1) is closed with the pressure difference after the pre-purge phase and detects a fault by the comparison, wherein the fault is an uncalibrated or incorrectly calibrated regulating valve (2), and the method comprises the following steps: d. determining, by means of the evaluation electronics, a deviation of an actual characteristic curve of the regulating valve (2) from a target curve of the regulating valve (2) by comparing the pair of values with the target characteristic curve of the regulating valve (2); wherein an uncalibrated or incorrectly calibrated regulating valve (2) is detected if the pair of values deviates from the target characteristic curve of the regulating valve (2) beyond a predetermined tolerance.

3. The method according to claim 2, wherein the target characteristic curve of the regulating valve (2) is shifted by the deviation, thereby approximating the actual characteristic curve. wherein The evaluation electronics compares the pressure difference in the pre-purge phase with the pressure difference after the pre-purge phase, in which the safety valve (1) is closed, and detects a fault by comparison, wherein the fault is a wrong fuel, and the method comprises the following steps: a. Determining the time point t during the pre-rinsing phase using the sensor. pp The first pressure difference p(t) pp During the pre-rinse phase, the safety valve (1) is closed and has the defined position of the regulating valve (2) and the blower speed of the blower (5); b. a second pressure difference p(t s ) is determined by the sensor at a time point t s ) at the time point t s ) the second pressure difference p(t s ) is quasi-stationary, wherein the safety valve (1) is open and has a defined position (2) of the regulating valve and a blower speed (5) of the blower c. determining a pressure difference between the second pressure difference p(t s ) and the first pressure difference p(t pp ) by subtracting the first pressure difference p(t s ) from the second pressure difference p(t pp ). d. determining the actual fuel flowing in from the fuel inlet (G) from the pressure difference, the defined position of the regulating valve (2) and the predefined mass flow delivered from the blower (5) through the mixing device (4) and the defined pressure loss characteristic of the main flow restrictor (3); e. comparing the actual fuel with a predefined target fuel; wherein a wrong fuel is detected when the actual fuel does not match the target fuel.

5. The method according to any one of claims 1 to 4, wherein the fault is a missing or too low fuel pressure pg of the fuel flowing in through the fuel inlet (G) and / or is a wrong or missing main flow restrictor (3), and the method comprises the following steps: opening the safety valve (1); igniting the burner of the gas boiler; determining whether the burner has been ignited; if the burner has not been ignited, determining a pressure difference curve by the sensor and the evaluation electronics while the safety valve (1) is open for a predefined time; wherein the evaluation electronics compares the pressure difference curve with a predefined tolerance range and detects a fault if the pressure difference curve lies outside the predefined tolerance range, due to the fact that the pressure difference does not increase within the predefined time, a missing or too low fuel pressure pg and / or a wrong or missing main flow restrictor (3) is detected.

6. The method according to claim 5, wherein if the fuel pressure pg is missing or too low, reducing the maximum allowed heating power of the gas boiler and / or the maximum allowed blower speed of the blower (5) to a respective predefined value.

7. The method according to any one of claims 1 to 4, wherein the fault is a missing or not connected sensor and / or a bad or non-existing connection of the sensor to the measurement point and / or to a reference measurement point, wherein determining a pressure difference between the pressure (p2) at a measurement point upstream of the main flow restrictor (3) and downstream of the regulating valve (2) and a reference pressure (p0, pi) at a reference measurement point, and wherein the evaluation electronics detects a missing or not connected sensor and / or a bad or non-existing connection of the sensor to the measurement point and / or to the reference measurement point if the pressure difference lies outside a predefined tolerance range.

8. The method according to claim 7, wherein, in case of a missing or not connected sensor and / or a bad or non-existing connection to the measurement point and / or to the reference measurement point, the safety valve (1) is closed.

9. The method according to any one of claims 1 to 4, wherein the fault is a defective safety valve (1) or a defective regulating valve (2), the method comprises the following steps: determining an actual pressure difference by means of the sensor in the open safety valve (1), the defined position of the regulating valve (2) and the predetermined mass flow delivered from the blower (5) through the mixing device (4); determining a target pressure difference by means of the evaluation electronics and the defined position of the regulating valve; determining a deviation of the actual pressure difference from the target pressure difference; wherein the evaluation electronics detects a fault if the deviation is greater than a predetermined tolerance value.

10. Gas boiler designed to perform the method according to any one of claims 1 to 9.

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