Method for operating a heating device, heating device, computer program and use of a hot water provision

Abstract

A method for operating a heating appliance (1) is proposed. The appliance comprises a heat generator (24) connected to a heating circuit (6) via a flow (19) and a return (20), and a domestic hot water supply (15) arranged between the flow (19) and return (20) with an electrically controlled three-way valve (17). The method includes at least the following steps: a) acquiring at least one parameter that allows conclusions to be drawn about the flow through the heat generator (24), b) comparing the at least one parameter acquired in step a) with at least one predetermined limit value, c) at least partially opening the three-way valve (17) depending on the comparison in step b). Furthermore, a heating appliance (1), a computer program (12), and the use of a domestic hot water supply (15) are proposed.

Description

[0001] The invention relates to a method for operating a heating appliance, a heating appliance, a computer program and a use of a hot water supply.

[0002] Heating appliances typically feature a differential pressure valve, also known as a bypass or overflow valve. This valve is often located between the flow and return lines of a heating circuit. Opening the differential pressure valve creates an internal circuit within the appliance, where the heat transfer fluid circulates through the heat generator and the differential pressure valve. An internal circuit can be advantageous for ensuring reliable operation of the heat generator, as it effectively prevents boiling effects (i.e., boiling of the heat transfer fluid within the heat generator, for example, caused by insufficient flow rate). A differential pressure valve can also be used to create a partial load range for the heating system, where it performs a mixing function.A differential pressure valve can also help to quickly reach a desired flow temperature by initially heating only the internal heating circuit of the boiler. Furthermore, a differential pressure valve can help to reduce hydraulic pressure spikes, for example those caused by a circulation pump, and thus prevent the associated noise in the heating circuit.

[0003] Such a heating device with a bypass valve is described by way of example in DE 40 39 644 A1.

[0004] A disadvantage of known differential pressure valves is that they often do not operate with sufficient precision. For example, it has been observed that differential pressure valves do not close completely, which can significantly reduce the energy efficiency of a heating appliance. Furthermore, a differential pressure valve typically requires a complex and inconveniently time-consuming adjustment of the opening pressure, which depends on the heating system, as well as additional installation work. In addition, the high flow rate that occurs when the bypass valve opens can negatively affect the control of the heat generator.

[0005] German patent DE 10 2012 003 502 A1 describes a method for operating a heating system in which, if a predetermined differential pressure is exceeded, a partial flow of the heat transfer fluid is diverted parallel to the system. For this purpose, the system differential pressure is determined using a flow meter in conjunction with a modulating pump and a characteristic curve. If the differential pressure exceeds a value that could correspond to the opening pressure of a differential pressure valve, the pump speed is reduced to such an extent that the opening of the differential pressure valve is prevented. This increases the efficiency of the heating system; however, the method is complex and requires a sophisticated heating system design.

[0006] A similar method is described in DE 10 2021 121 888 A1. It proposes to detect flow through the bypass valve and, after maintaining pump operation for a period of time, to reduce the pump output. This also requires a complex heating system design.

[0007] Based on this, the object of the invention is to propose a method for operating a heating device, a heating device, and a computer program that at least partially overcome the problems of the prior art described above. In particular, the heating device should operate energy-efficiently and have a simple design. Furthermore, the negative effects of an insufficient flow rate of heat transfer fluid in the heat generator should be avoided.

[0008] These problems are solved by the features of the independent claims. Further advantageous embodiments of the solution proposed here are specified in the dependent claims. It should be noted that the features listed in the dependent claims can be combined with one another in any technologically meaningful way and define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, which also presents further preferred embodiments of the invention.

[0009] A method for operating a heating device contributes to solving the problem, wherein the heating device has at least the following features: a heat generator connected to a heating circuit via a flow and return pipe, and a hot water supply which is equipped with an electrically controlled three-way valve between the flow and return pipes.

[0010] The procedure includes at least the following steps: a) Recording at least one parameter that allows conclusions to be drawn about the flow of a heat transfer medium through the heat generator, b) Comparing the at least one parameter recorded in step a) with at least one predetermined limit value, c) At least partially opening the three-way valve depending on the comparison in step b).

[0011] Steps a), b), and c) are performed at least once in the specified order during a regular operating procedure. In particular, steps a) and b) can be performed continuously during operation of the heating appliance. This procedure ensures the safe operation of the heating appliance and guarantees a minimum flow rate of heat transfer fluid through the appliance's heat generator.

[0012] The heating appliance can include any type of heat generator, for example a heat generator designed to burn a fuel or a heat pump.

[0013] The heating appliance can be, in particular, a gas-fired heating appliance designed to combust a fuel gas, such as natural gas or, in particular, hydrogen, with the addition of ambient air (combustion air) and to generate thermal energy, for example, to heat a heat transfer fluid in a heating circuit and to provide domestic hot water. The heating appliance can, in particular, be a condensing boiler. The heating appliance typically has a conveying device or a fan that can convey a mixture of fuel gas and combustion air in a flow direction through the heating appliance via a mixture channel into a combustion chamber in which a burner is located. At least one first heat exchanger can be arranged in or on the combustion chamber, which can transfer the heat generated during combustion to a heat transfer fluid, such as heating water, circulating in the at least one first heat exchanger.The heat transfer fluid can flow from a return connection to a supply connection through at least one initial heat exchanger. The return and supply connections can be connected to a building's heating circuit. This heating circuit, acting as a heat sink, can include consumers such as radiators, heating elements, or surface heating systems (underfloor or wall heating). A circulation pump can be installed to circulate the heat transfer fluid within the heating circuit. This circulation pump can be controllable and connected to the heating system's control unit via data transmission.

[0014] A volume of combustion air supplied by the conveying device can be mixed with a volume of fuel gas via a gas valve, corresponding to a predetermined combustion air ratio (also known as lambda or air ratio). The combustion products (exhaust gases) can then be discharged in the direction of flow through an exhaust system. The exhaust system can comprise an exhaust duct located within the housing of the heating appliance or an exhaust system located outside the heating appliance.

[0015] The heating appliance may include a control unit that manages and regulates the heating appliance and its combustion process. The control unit may be configured to carry out a procedure proposed here (fully automated).

[0016] The heating unit can adjust its heat output to an existing heat demand; this is also known as modulation. This is usually achieved by controlling the output of the delivery system, whereby a combustion control system adjusts the mass flow of fuel gas supplied to the set output of the delivery system and thus the mass flow of combustion air supplied.

[0017] The heating appliance includes a domestic hot water supply system located between the flow and return lines of the appliance. This system typically includes a second heat exchanger designed to allow the heat transfer fluid from the heating circuit to flow through, thereby transferring heat from the fluid to a mass flow of potable or domestic hot water. This second heat exchanger can be positioned between the flow and return lines of the heating appliance, ensuring that the heat transfer fluid flows from the flow to the return.

[0018] A three-way valve can initiate flow through the domestic hot water supply system. The three-way valve can assume a first opening position in which the entire mass flow of heat transfer fluid from the heat generator is supplied to the heating circuit, and no flow passes through the domestic hot water supply system. The three-way valve can assume a second opening position in which the entire mass flow of heat transfer fluid from the heat generator is supplied to the domestic hot water supply system, and no flow passes through the heating circuit. The three-way valve can assume several or any number of opening positions within the range defined by the first and second opening positions.In other words, in the first opening position, all the generated heat is supplied to the heating circuit, and in the second opening position, all the generated heat is supplied to the domestic hot water supply. The three-way valve is designed to distribute the heat flow generated by the heat generator between the domestic hot water supply and the heating circuit by dividing the mass flow of the heat transfer fluid. The three-way valve is electrically controllable, so that, for example, the control unit can set the opening position of the three-way valve using a control signal. The three-way valve can, for example, incorporate a stepper motor for this purpose.

[0019] The hot water supply can thus be understood as a bypass between the flow and return of the heating appliance. An aspect of the invention lies in the fact that the hot water supply ensures a minimum flow rate of heat transfer fluid through the heat generator or the at least one first heat exchanger. This minimum flow rate can guarantee the removal of the generated heat and / or prevent boiling effects of the heat transfer fluid in the at least one first heat exchanger. It is understood that this can also be a minimum mass flow rate of heat transfer fluid, enabling the transport of a predetermined heat flow. In this respect, the invention enables, or rather provides for, the hot water supply to be the only bypass between the flow and return of a heating system.

[0020] According to step a), at least one parameter is recorded that allows conclusions to be drawn about the flow through the heat generator. This recording can be fully automated, for example by the control unit of the heating appliance.

[0021] According to one embodiment, the parameter that allows conclusions to be drawn about the flow through the heat generator can be a measured differential pressure and / or a measured flow rate. For this purpose, signals from at least one corresponding pressure sensor or at least one flow sensor can be acquired. Advantageously, heating appliances often already have a suitable pressure or flow sensor, so that no additional sensors are necessary for the method proposed here. For example, well-known direct flow measurement methods such as ultrasound or vortex measurement can be used.Alternatively or cumulatively, an indirect method could be used to calculate the mass flow rate through the heat generator based on a known thermal output of the heat generator and measurements of the flow and return temperatures (mass flow rate = thermal output of heat generator / (specific heat coefficient of the heat transfer fluid x (flow temperature - return temperature))). Furthermore, electronically controlled circulation pumps can determine / estimate the volume flow rate (from differential pressure and electrical power).

[0022] According to step b), the at least one parameter recorded in step a) is compared with at least one predefined limit value. This at least one predefined limit value can be characteristic of a minimum flow rate through the heat generator. For this purpose, the at least one limit value can be determined in advance using a reference heating device and stored in a memory, for example, the control unit.

[0023] According to step c), the three-way valve is at least partially opened depending on the comparison in step b). Opening the valve ensures flow through the heat generator and / or prevents boiling in the heat exchanger, even in the case of a high differential pressure between the flow and return lines, which can be caused, for example, by closed consumer valves.

[0024] According to one embodiment, the three-way valve can be opened to a position that allows the minimum flow rate through the heat generator. In other words, the flow rate through the heat generator can be controlled by the opening position of the three-way valve.

[0025] This allows for particularly precise adjustment of the minimum flow rate, thereby improving the energy efficiency of the heating appliance. Furthermore, negative effects on the heat generator's control caused by a high flow rate resulting from the opening of a bypass valve can be avoided using state-of-the-art technology.

[0026] Another aspect proposes a heating appliance that includes a heat generator, a flow and return pipes designed to be connected to a heating circuit, and a domestic hot water supply. The latter is located between the flow and return pipes, and its flow rate is adjustable via a three-way valve. The domestic hot water supply can thus be understood as a bypass between the flow and return pipes and, in particular, as the only bypass of the heating appliance. In other words, the heating appliance can have exactly one bypass, designed as a domestic hot water supply.

[0027] The heating device may have a flow sensor to detect the mass or volume flow of heat transfer fluid through the heat generator, or a means to detect a differential pressure between the flow and return.

[0028] The heating appliance includes a control and regulating device which may be or is configured to regulate and control the heating appliance and the heat generator, in particular for carrying out a procedure proposed here.

[0029] In addition, a computer program (product) is proposed that causes a heating device proposed herein to execute steps a), b), and c) of a procedure proposed herein. The procedure can, for example, be carried out fully automatically on a control unit of the heating device. For this purpose, the control unit can include a processor capable of executing the instructions of the computer program. The control unit can also have a memory in which parameters for carrying out a procedure proposed herein are stored, particularly in digital form.

[0030] Another aspect proposes using a domestic hot water supply from a heating appliance to ensure a minimum flow rate through the appliance's heat generator. For this purpose, the domestic hot water supply is located between the supply and return lines of the heating appliance, and the three-way valve can control the flow through the domestic hot water supply.

[0031] The aforementioned problems are thus overcome, in particular, by a controllable hydraulic valve and the use of the domestic hot water heat exchanger as a bypass branch. An internal three-way valve within the heating unit, used to switch between heating operation and hot water storage charging, is actuated by an electric stepper motor and can assume any position between its two end stops (open / closed). The operating strategy is to monitor the current heating flow rate and, based on this, control the three-way valve so that a minimum flow rate is maintained by increasing the bypass flow rate through the domestic hot water charging circuit.

[0032] Unlike a mechanical bypass with a potentially high opening flow rate, this solution limits the required flow rate through the bypass branch to the specified value, while simultaneously minimizing the impact on the system's efficiency and / or the refrigerant circuit's control accuracy. No additional piping work is required because only existing hardware is used and no manual commissioning is necessary.

[0033] The details, features, and advantageous configurations discussed in connection with the process may also occur in the computer program, storage medium, control unit, and / or heating device presented here, and vice versa. In this respect, full reference is made to the explanations provided therein for a more detailed characterization of the features.

[0034] It should be noted as a precaution that the numerical terms used here ("first", "second", etc.) primarily serve (only) to distinguish between several similar objects, quantities, or processes, and thus do not necessarily dictate any dependency and / or sequence between these objects, quantities, or processes. Should a dependency and / or sequence be required, this is explicitly stated here, or it will be obvious to a person skilled in the art upon studying the specific configuration described. Where a component can occur multiple times ("at least one"), the description of one of these components may apply equally to all or some of the multiple components, but this is not mandatory.

[0035] This paper proposes a method for operating a heating device, a heating device itself, a computer program (product), and an application that at least partially solve the problems described with reference to the prior art. In particular, the method enables the safe and convenient operation of a heating device, especially with high energy efficiency and while preventing boiling effects in the heat exchanger of the heat generator. Furthermore, the method allows for a particularly simple design of the heating device.

[0036] The invention and its technical context are explained in more detail below with reference to the accompanying figures. It should be noted that the invention is not limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the situations described in the figures and combine them with other components and findings from the present description. It should be emphasized that the figure, and especially the depicted dimensions, are only schematic. It shows: Fig. 1: a sequence of a method proposed here, Fig. 2: a heating device proposed here, and Fig. 3: a further representation of a heating device proposed here.

[0037] Fig. 1 Figure 1 shows an exemplary and schematic representation of the sequence of steps proposed here. The sequence of steps a), b), and c), indicated by blocks 110, 120, and 130, can occur during a regular process flow. In particular, steps a), b), and c) can be carried out permanently or continuously during the operation of the heating device 1. The method helps to ensure the flow of a heat generator 24 of the heating device 1, especially a first heat exchanger 13 of the heat generator 24, with a minimum predetermined volume flow rate of heat transfer fluid.

[0038] Fig. 2 shows an exemplary and schematic representation of a heating appliance 1 proposed here. This appliance comprises a conveying device 2 that can draw in a mass flow of combustion air from a combustion air supply 4. Fuel gas from a fuel gas supply 25 can be added to the drawn-in mass flow of combustion air via a gas valve 5. The resulting combustion mixture can be fed via a mixture channel 11 to a burner 3 arranged in a combustion chamber 8 and combusted. The combustion products can be fed via an exhaust gas channel 9 to an exhaust system 10 of a building.

[0039] A flame monitoring device 14 can be provided in the combustion chamber 8 area. This device monitors the presence of a flame, and its signal can be used for combustion control of the heating appliance 1. Furthermore, a first heat exchanger 13 can be provided on or in the combustion chamber 8. This heat exchanger can transfer the heat generated during combustion to a heat transfer medium circulating in a heating circuit 6. The heat transfer medium can flow into the first heat exchanger 13 via a return line 20 and out of it via a supply line 19. The supply line 19 and return line 20 can be connected to a heating circuit 6. Consumers such as radiators or underfloor heating systems can be located in the heating circuit 6. A domestic hot water supply system 15 can be arranged between the supply line 19 and the return line 20. The domestic hot water supply system 15 can include a second heat exchanger 16.The second heat exchanger 16 is configured to heat a mass flow of potable or service water from a cold water inlet 21 and supply it to a hot water outlet 22. The hot water supply 15 includes a three-way valve 17, which is configured to distribute the heat transfer fluid flow to the hot water supply 15 and / or the heating circuit 6. A circulation pump 23 can also be arranged in the flow 19 and / or the return 20. Additionally, a flow sensor 18 can be arranged in the flow 19 and / or the return 20, which measures the flow rate of the heat transfer fluid through the heat generator 24.

[0040] The heating appliance 1 includes a control unit 7 that regulates the combustion in the heating appliance 1 and can also be configured to carry out a procedure proposed herein. For this purpose, the control unit 7 can be connected electronically to the gas valve 5, the conveying device 2, the flame monitoring device 14 of the circulation pump 23, the three-way valve 17, and the flow sensor 18. A computer program 12 that causes the control unit 7 to execute a procedure proposed herein can be stored in a memory of the control unit 7.

[0041] Fig. 3Figure 1 shows an exemplary and thematic representation of another heating appliance 1 proposed here. Here, too, a hot water supply 15 is connected to the flow 19 and return 20 of the heat generator 24 via a three-way valve 17. A consumer 27, for example, underfloor heating, is shown in the heating circuit 6 and can be controlled by a thermostatic valve 26. The hot water supply 15 comprises a storage tank 28 with a charging pump 29, which is connected to the second heat exchanger 16 via a cold water inlet 21 and a hot water outlet 22.

[0042] In block 110 according to step a), at least one parameter that allows conclusions to be drawn about the flow rate through the heat generator 24 can be recorded. For this purpose, the control unit 7 can record a signal from the flow sensor 18. The recorded parameter can, for example, be stored in the memory of the control unit 7.

[0043] In block 120 according to step b), the parameter recorded in step a) can be compared with at least one predefined limit value. The result of this comparison determines whether the heat generator 24 has sufficient flow. Step b) can also be performed by the control unit 7 of the heating appliance 1.

[0044] In block 130, according to step c), depending on the comparison in step b), the three-way valve 17 can be at least partially opened. Opening it can ensure a minimum flow rate of heat transfer fluid for the shower from the heat generator 24. Reference symbol list

[0045] 1 Heating unit 2 Conveyor 3 Burner 4 Combustion air supply 5 Gas valve 6 Heating circuit 7 Control unit 8 Combustion chamber 9 Exhaust duct 10 Exhaust system 11 Mixing channel 12 Computer program 13 First heat exchanger 14 Flame monitoring 15 Hot water supply 16 Second heat exchanger 17 Three-way valve 18 Flow sensor 19 Flow 20 Return 21 Cold water inlet 22 Hot water outlet 23 Circulating pump 24 Heat generator 25 Fuel gas supply 26 Thermostatic valve 27 Consumer 28 Storage tank 29 Charging pump

Claims

1. Method for operating a heating appliance (1) comprising a heat generator (24) connected to a heating circuit (6) via a flow (19) and a return (20), and a hot water supply (15) arranged between the flow (19) and return (20) with an electrically controlled three-way valve (17), comprising at least the following steps: a) detecting at least one parameter that allows conclusions to be drawn about the flow through the heat generator (24), b) comparing the at least one parameter detected in step a) with at least one predetermined limit value, c) at least partially opening the three-way valve (17) depending on the comparison in step b).

2. The method of claim 1, wherein the heating appliance (1) is a gas heating appliance.

3. Method according to one of the preceding claims, wherein the parameter detected in step a) is a detected differential pressure or a detected flow rate.

4. Method according to one of the preceding claims, wherein in step c) the three-way valve (17) is opened at least partially such that the heat generator (24) is supplied with a predetermined minimum volume flow.

5. Heating appliance (1) comprising a heat generator (24) connected to a heating circuit (6) via a flow (19) and a return (20), a hot water supply (15) arranged between the flow (19) and return (20) with an electrically controlled three-way valve (17), a control and regulating device (7) and means adapted to perform steps a), b) and c) of a method according to one of the preceding claims.

6. Computer program (12) comprising commands that cause a heating device (1) according to claim 3 to execute a method according to any one of claims 1 to 4.

7. Use of a hot water supply (15) of a heating appliance (1) to ensure a flow through a heat generator (24) of the heating appliance (1) with a minimum volume flow rate.

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