EP3889511B1 - Heating system and method for controlling a heating circuit of a heating system, control unit for a heating system - Google Patents

Description

The invention relates to a method for controlling a heating system according to the preamble of the independent claim. The invention also relates to a control unit for a heating system for carrying out such a method and to a heating system with such a control unit.

State of the art

If the heating water in a heating circuit of a heating system starts to boil, this is associated with undesirable noise. The heating system can become increasingly calcified and a heat exchanger in the heating system can become more worn out. For this reason, in the prior art the maximum temperature difference between the flow and return temperatures is limited in order to prevent the heating water from boiling. This has the disadvantage that the ease of use can be limited. If the maximum temperature difference is exceeded, the heating output can be limited or the heating system can be switched off. Heating up the heating system takes more time.

Out of EP 0 282 886 A2 a method is known that uses a 3D characteristic field that takes a load level or a circulation flow into account. The load level describes the difference between room temperature and outside temperature. A connection with system pressure is not mentioned. A flow temperature is assigned to the load level. The actual heat loss flow is calculated from the difference between the flow and return temperatures (for each load level). The difference between the flow and return temperatures is determined, which is necessary to overcome the difference between the room and outside temperatures to achieve the desired temperature.

Disclosure of the invention Advantages

The present invention describes a method for controlling a heating circuit of a heating system. A return temperature of the heating circuit is measured and a system pressure of the heating circuit is measured. According to the invention, a maximum temperature difference is determined depending on the return temperature and the system pressure. The maximum temperature difference describes the Maximum permissible temperature difference between the return temperature and a flow temperature of the heating circuit. A flow temperature of the heating circuit is measured and the existing temperature difference between the flow temperature and return temperature is determined. The flow temperature is reduced if the temperature difference exceeds the maximum temperature difference.

This has the advantage that the heating system can be operated with a higher temperature difference between the flow and return than in the prior art if there is a sufficiently high system pressure and/or the return temperature is low enough. This can enable a higher heating output compared to the prior art, which in particular increases the comfort of use.

The term heating system should in particular be understood to mean at least one device for generating thermal energy, in particular a heater or heating burner, in particular for use in heating a building, preferably by burning a gaseous or liquid fuel. A heating system can also consist of several such devices for generating thermal energy as well as other devices that support the heating operation, such as hot water and fuel storage. The heating system is advantageously designed as a forced-air burner, in which combustion air is sucked in by a fan. A fuel is added to the sucked-in combustion air and the air-fuel mixture is passed into a combustion chamber or to a burner plate. The fuel can advantageously be injected into the intake combustion air, for example in a venturi. A forced air burner is a special premix burner.

The return temperature is the temperature at which the heating water flows back into the heating system after passing through one or more heating surfaces, in particular radiators or radiators, surface heaters or fan heaters. The return temperature can be determined via a return temperature determination unit of the heating system. The return temperature determination unit is advantageously a sensor or a sensor unit which is arranged in or on the heating system. For example, the return temperature on a return line of the heating system be arranged. For example, the return temperature determination unit can have a thermometer or a thermocouple. It is also conceivable that the return temperature determination unit receives temperature information from an external sensor, for example a sensor on a line of the heating circuit, which supplies the heating water to the heating system.

The flow temperature is the temperature that the heating system provides for heating, at which in particular the heating water flows out of the heating system and is intended to pass through one or more heating surfaces, in particular radiators, surface heaters or fan heaters. The flow temperature can be determined via a flow temperature determination unit of the heating system. The flow temperature determination unit is advantageously a sensor or a sensor unit which is arranged in or on the heating system. For example, the flow temperature can be arranged on a flow line of the heating system. For example, the flow temperature determination unit can have a thermometer or a thermocouple. It is also conceivable that the flow temperature determination unit receives temperature information from an external sensor, for example a sensor on a line of the heating circuit, which directs the heating water from the heating system and in particular supplies it to a radiator.

The system pressure is the pressure of the heating water or the pressure of the heating circuit on the heating system. The system pressure can be determined via a system pressure determination unit of the heating system. The system pressure determination unit is advantageously a sensor or a sensor unit which is arranged in or on the heating system. In particular, the system pressure determination unit can have a pressure gauge or pressure sensor

The temperature difference between the flow temperature and return temperature is sometimes referred to as the spread. The maximum temperature difference is the maximum permissible spread or maximum spread.

The maximum temperature difference is advantageously determined by a controller of the heating system. For example, the controller can use the currently available Receive return temperature and receive the current system pressure and determine the maximum difference depending on this. It is also conceivable that the maximum temperature difference is determined entirely or partially externally by the heating system, for example on a server, in particular cloud, on a mobile or stationary device such as a smartphone, tablet, home computer, or a wall controller. The heating system advantageously has a data interface, for example a network connection or a mobile phone modem, in particular for connecting to the Internet, which is intended to send the data required to determine the maximum temperature difference, in particular the return temperature and the system pressure, and which is intended to to receive the determined maximum temperature difference.

The fact that a maximum temperature difference is determined depending on the return temperature and the system pressure should be understood in particular to mean that the maximum temperature difference is determined on the basis of the return temperature and the system pressure or that the value of the return temperature and the value of the system pressure as parameters in the calculation of the maximum temperature difference is included.

The flow temperature is advantageously reduced until the temperature difference corresponds to or falls below the maximum temperature difference. An iterative procedure is conceivable in which the flow temperature is reduced step by step and the temperature difference is determined after each step. The flow temperature is reduced until the temperature difference corresponds to or falls below the maximum temperature difference. Lowering the flow temperature in the manner of a control loop is also conceivable, with the flow temperature being regulated down via a control parameter that influences the flow temperature, for example the heating output, so that the temperature difference as a controlled variable is regulated to the maximum temperature difference as a setpoint.

The features listed in the subclaims make advantageous developments of the method possible.

The flow temperature can advantageously be lowered by lowering a current heating output of the heating system. For this purpose, for example in the case of a forced-air burner, the speed of the fan of the heating system can be reduced and/or its maximum speed can be limited. For example, to lower the flow temperature, the maximum possible fan speed can be reduced to a value between 50% and 95% of the previously maximum permissible fan speed, preferably between 60% and 90%, particularly preferably between 70% and 80%.

It is also conceivable that the heating output of the heating system is reduced by adjusting a fan speed characteristic. A fan speed curve assigns a required fan speed to a requested power. To reduce the current heating output, for example, the fan speed characteristic can be adjusted so that the fan speed assigned to a desired heating output does not exceed a predetermined maximum value.

Furthermore, it is conceivable that the heating output of the heating system is reduced by switching off the heating system or combustion in a combustion chamber of the heating system, preferably switching off until the flow temperature has dropped to such an extent that the existing temperature difference is below that maximum temperature difference.

The process is further improved if the maximum temperature difference falls linearly with the return temperature. This makes it particularly easy to take the existing heating water temperature into account. The fact that the maximum temperature difference falls linearly with the return temperature should in particular be understood to mean that when determining the maximum temperature difference, the return temperature enters linearly with a negative proportionality factor at least for a sub-range or sub-interval of all possible return temperature values. In other words, the maximum temperature difference is calculated using a formula or an expression which has at least one return temperature term, which is determined by the return temperature multiplied by a negative, preferably dimensionless proportionality factor is formed, at least on a sub-range or sub-interval of all possible return temperature values. This means in particular that the maximum temperature difference becomes smaller, at least in the sub-range or sub-interval of the possible return temperature values, when the return temperature becomes larger. Preferably, the maximum temperature difference decreases monotonically with the return temperature, ie the maximum temperature difference decreases or remains constant when the return temperature is increased.

The process is also improved if the maximum temperature difference increases linearly with the system pressure. This makes it particularly easy to take the existing system pressure into account. The fact that the maximum temperature difference increases linearly with the system pressure should be understood in particular to mean that when determining the maximum temperature difference, the system pressure enters linearly with a positive proportionality factor at least for a sub-range or a sub-interval of all possible system pressure values. In other words, the maximum temperature difference is calculated using a formula or an expression which has at least one pressure term, which is formed by the system pressure multiplied by a positive proportionality factor, at least on a sub-range or sub-interval of all possible system pressure values. This means in particular that the maximum temperature difference becomes larger, at least in the sub-range or sub-interval of the possible system pressure values, as the system pressure increases. Preferably, the maximum temperature difference increases monotonically with the system pressure, i.e. the maximum temperature difference increases or remains constant when the system pressure is increased.

The pressure term advantageously has the physical unit of a temperature, so that the proportionality factor in the pressure term has the physical unit of a temperature divided by the physical unit of a pressure. For example, if the maximum temperature difference is given in the unit °C and the system pressure in the unit bar, the proportionality factor has the unit °C divided by bar. But it is also conceivable that the temperature and/or pressure in Dimensionless quantities are given, i.e. as pure numerical values without a physical unit.

It is advantageous if the maximum temperature difference is determined from the sum of a constant base temperature, a return temperature contribution and a system pressure contribution, with values between 40 ° C and 65 ° C, preferably between 45 ° C and 60, being a particularly advantageous value range for the base temperature °C, particularly preferably between 50°C and 55°C.

In particular, the return temperature contribution is determined as a function of the return temperature. The return temperature contribution advantageously has the return temperature term or is equal to the return temperature term.

In particular, the system pressure contribution is determined as a function of the system pressure. The system pressure contribution advantageously has the pressure term or is equal to the pressure term.

It has proven to be a particularly advantageous parameterization if the maximum temperature difference depends linearly on a scaled return temperature, the scaled return temperature being determined by measuring the positive return temperature in °C with a negative temperature factor between -0.9 and -0.4 , preferably between -0.8 and -0.5, particularly preferably between -0.7 and -0.6. The return temperature contribution and/or the return temperature term advantageously corresponds to the scaled return temperature.

A further advantageous parameterization is given if the maximum temperature difference depends linearly on a scaled system pressure, the scaled system pressure being determined by measuring the positive system pressure in bar with a positive pressure factor between 7 ° C / bar and 12 ° C / bar, preferably between 8°C/bar and 11°C/bar, particularly preferably between 9°C/bar and 10°C/bar. The system pressure contribution and/or the pressure term advantageously corresponds to the scaled system pressure.

The method becomes particularly stable and reliable if the maximum temperature difference is no more than an absolute maximum temperature difference, which is between 25°C and 50°C, preferably between 30°C and 45°C, particularly preferably between 35°C and 40°C . In this way it is ensured that a maximum temperature that is too high is not determined by mistake - for example due to an incorrect measurement. In this way, the process is doubly protected against boiling of the heating water. For example, it is conceivable that a preliminary maximum temperature difference is first calculated using a formula that depends linearly on the return temperature and linearly on the system pressure. It is then checked whether the provisional maximum temperature difference is smaller than the absolute maximum temperature difference. If the provisional maximum temperature difference is smaller than the absolute maximum temperature difference, the determined maximum temperature difference is equal to the provisionally determined maximum temperature difference. If the provisional maximum temperature difference is greater than the absolute maximum temperature difference, the determined maximum temperature difference is equal to the absolute maximum temperature difference.

It is also conceivable that the maximum temperature difference for predetermined parameter ranges of the return temperature and/or the system pressure is determined using a formula which depends linearly on the return temperature and linearly on the system pressure, the parameter ranges being selected such that the absolute maximum temperature difference is not exceeded .

A control unit for a heating system is also advantageous, the control unit being set up so that a method according to the present invention can be carried out.

A heating system with a control unit according to the present invention is also advantageous, having a return temperature determination unit, a flow temperature determination unit and a system pressure determination unit. Such a heating system has the advantage that it has a high Maximum temperature difference provides a high level of comfort, since rapid heating is always possible, and at the same time provides a very robust and reliable heating system, since despite the high maximum temperature difference, the heating water is prevented from boiling and thus wear and tear on the heating system is minimized.

drawings

• Figur 1 eine schematische Darstellung eines Heizkreises mit einem Heizsystem welches zur Ausführung des Verfahrens gemäß der vorliegenden Erfindung eingerichtet ist und
• Figur 2 eine Illustration des Verfahrens gemäß der vorliegenden Erfindung.

Exemplary embodiments of the method according to the present invention are shown in the drawings and explained in more detail in the following description. Show it

• Figure 1 a schematic representation of a heating circuit with a heating system which is set up to carry out the method according to the present invention and
• Figure 2 an illustration of the method according to the present invention.

Description

In the different design variants, the same parts receive the same reference numbers.

In Figure 1 A heater 10 is shown schematically, which forms a heating circuit with a radiator 12. By way of example, the heating circuit has a radiator 12; depending on requirements, the heating circuit can have additional radiators and/or heating surfaces. The heater 10 provides hot heating water, which is transported to the radiator via a flow line 14. In the radiator 12, the heat of the heating water is released to the environment. The cooled heating water is transported via a return line 16 back to the heater 10, where it can be heated again.

The essential components of the heater 10 can in particular be a heat cell, a control unit, one or more pumps and piping on. The number and complexity of the individual components also depend on the level of equipment of the heater 10, for example a hot water tank is conceivable.

The heat cell preferably has a burner, a heat exchanger, a fan and a fuel valve. When the burner is in operation, an ionization probe projects into the flame on the burner, which is intended in particular for flame monitoring. With the help of the ionization probe, further flame parameters can be determined, for example it is conceivable that the lambda value, i.e. the fuel-air ratio of the burned fuel-air mixture, is determined via an ionization current measured on the flame. A fan speed of the fan can be variably adjusted. The fan speed is advantageously adjusted depending on the power requirement. In particular, the amount of air conveyed by the fan per unit of time is proportional to the heating output. In the exemplary embodiment, the heater 10 is a forced-air burner.

The fuel is advantageously injected into the air stream sucked in by the fan in a fuel-air mixing device, for example a venturi. The desired fuel-air ratio is advantageously set via the fuel valve in order to ensure clean combustion and, in particular, to reduce emissions.

The control unit has, for example, a data memory, a computing unit and a communication interface or data interface. The components of the heating system can be controlled via the communication interface. The communication interface enables data exchange with external devices. External devices are, for example, control devices, thermostats and/or devices with computer functionality, such as smartphones.

For example, the fuel valve can be designed as an electronic control valve, which has a data connection to the control unit connected is. The ionization probe can also be connected to the control unit via a data connection. In this way, regulation by the control unit is conceivable, in which the existing fuel-air ratio is determined with the help of the ionization probe and, if necessary, adjusted to a setpoint by the electronic control valve.

The fan is advantageously connected to the control unit via a data connection. The desired fan speed can be adjusted using appropriate control signals. For example, a fan speed characteristic is stored in the control unit, which assigns a fan speed to a desired heating output. If the control unit receives a desired heating output, for example triggered by a room temperature input on an HMI, the necessary fan speed is determined based on the fan speed characteristic and the fan is controlled accordingly via the data connection.

The heater 10 has a return temperature determination unit, which is intended to determine the return temperature. For example, the return temperature determination unit has a thermocouple and a data connection to the control unit. The return temperature determination unit is arranged on an internal heating water pipe, which carries the heating water in the heater 10 flowing back to the heater 10 via the return line 16. The return temperature determination unit is set up to send the current return temperature to the control unit at regular intervals.

The heater 10 has a flow temperature determination unit, which is intended to determine the flow temperature. For example, the flow temperature determination unit has a thermocouple and a data connection to the control unit. The flow temperature determination unit is arranged on an internal heating water pipe, which leads the heating water heated in the heater 10 to the flow line 14. The flow temperature determination unit is set up to do this on a regular basis To send the current flow temperature to the control unit at intervals.

The heater 10 has a system pressure determination unit, which is intended to determine the system pressure of the heater 10 or the heating water in the heater 10. The system pressure determination unit is designed, for example, as a pressure sensor and is arranged on an internal heating water pipe. The system pressure determination unit has a data connection to the control unit and is set up to send the current system pressure to the control unit at regular intervals.

In this context, regular intervals should be understood to mean a time interval of less than 1 minute, preferably less than 10 seconds, particularly preferably less than 1 second. In this way, it is possible to quickly detect sudden changes in system parameters and, if necessary, take the necessary measures.

In the exemplary embodiment, a method for regulating the heating circuit runs on the control unit, in which the current temperature difference between the flow temperature and return temperature is monitored. For this purpose, the difference is formed from the currently received measured flow temperature and return temperature, which defines the current temperature difference. This is compared with a maximum temperature difference 22, which is determined from the current return temperature and the current system pressure.

If the current temperature difference exceeds the maximum temperature difference 22, the flow temperature is reduced. In the exemplary embodiment, for example, the heating power or fan speed is gradually reduced until the existing temperature difference falls below the maximum temperature difference 22.

wobei dT_Max die Maximaltemperaturdifferenz in °C ist, T_B die Basistemperatur, B(T_Rück) der Rücklauftemperaturbeitrag und B(p_Sys) der Systemdruckbeitrag. Beispielhaft beträgt die Basistemperatur T_B 50,3°C. Im Ausführungsbeispiel hängt der Rücklauftemperaturbeitrag linear mit der Rücklauftemperatur zusammen, beispielhaft wird der Rücklauftemperaturbeitrag ermittelt, indem die Rücklauftemperatur mit einem negativen Temperaturfaktor multipliziert wird: $$\mathrm{B}\left({\mathrm{T}}_{\mathrm{Rück}}\right)={\mathrm{T}}_{\mathrm{Rück}}\times {\mathrm{T}}_{\mathrm{Rück}},$$

wobei T_Rück die ermittelte Rücklauftemperatur in °C ist und F_Rück der Temperaturfaktor, welcher beispielhaft den Wert -0,6 hat.In the exemplary embodiment, the maximum temperature difference 22 is calculated from the sum of a base temperature, a return temperature contribution and a system pressure contribution: $${\mathrm{dT}}_{\mathrm{Max}}={\mathrm{T}}_{\mathrm{b}}+\mathrm{b}\left({\mathrm{T}}_{\mathrm{back}}\right)+\mathrm{b}\left({\mathrm{p}}_{\mathrm{Sys}}\right),$$

where dT _Max is the maximum temperature difference in °C, T _B is the base temperature, B(T _Rück ) is the return temperature contribution and B(p _Sys ) is the system pressure contribution. For example, the base temperature T _B is 50.3°C. In the exemplary embodiment, the return temperature contribution is linearly related to the return temperature; for example, the return temperature contribution is determined by multiplying the return temperature by a negative temperature factor: $$\mathrm{b}\left({\mathrm{T}}_{\mathrm{back}}\right)={\mathrm{T}}_{\mathrm{back}}\times {\mathrm{T}}_{\mathrm{back}},$$

where T _Rück is the determined return temperature in °C and F _Rück is the temperature factor, which for example has the value -0.6.

wobei p_Sys der Systemdruck, ermittelt in der Einheit bar, ist und F_p der Druckfaktor, welcher beispielhaft den Wert 9°C/bar hat.In the exemplary embodiment, the system pressure contribution is linearly related to the system pressure; for example, the system pressure contribution is determined by determining the system pressure with a positive pressure factor: $$\mathrm{b}\left({\mathrm{p}}_{\mathrm{Sys}}\right)={\mathrm{F}}_{\mathrm{p}}\times {\mathrm{p}}_{\mathrm{Sys},}$$

where p _Sys is the system pressure, determined in the unit bar, and F _p is the pressure factor, which, for example, has the value 9°C/bar.

After the current maximum temperature difference 22 is determined from the current system pressure and the current return temperature, it is compared with an absolute maximum temperature difference 26 stored in the control unit. Should the determined current maximum temperature difference 22 exceed the value of the absolute maximum temperature difference 26, the value of the maximum temperature difference 22 is set to the value of the absolute Maximum temperature difference 26 set. In the exemplary embodiment, the absolute maximum temperature difference is 26-40°C. The maximum temperature difference 22 determined in this way is used by the control unit to check the current temperature difference.

In Figure 2 the course of the maximum temperature difference 22 is shown schematically as a function of the system pressure and the return temperature. The return temperature is shown on the abscissa axis 18. The ordinate axis 20 shows the maximum temperature difference 22. The graphs 28, 30, 32, 34 and 36 illustrate the course of the maximum temperature difference as a function of the return temperature for different system pressures. For all system pressures, the maximum temperature difference 22 falls linearly with the return temperature, with the maximum temperature difference 22 for each system pressure being limited to the absolute maximum temperature difference 26, which is 40 ° C in the illustrated embodiment.

By way of example, the illustration is cut off at a first return temperature 24 of 70°C. Graph 28 shows the course of the maximum temperature difference 22 at a system pressure of 3.0 bar. Here the maximum temperature difference 22 at the first temperature 24 is 35.3°C. As the return temperature decreases, the maximum temperature difference 22 increases linearly and reaches the absolute maximum temperature difference 26 at approximately 62.2 ° C.

Graph 30 shows the course of the maximum temperature difference 22 at a system pressure of 2.0 bar. Here the maximum temperature difference 22 at the first temperature 24 is 26.3°C. As the return temperature decreases, the maximum temperature difference 22 increases linearly and reaches the absolute maximum temperature difference 26 at approximately 47.2 ° C.

Graph 32 shows the course of the maximum temperature difference 22 at a system pressure of 1.5 bar. Here the maximum temperature difference 22 at the first temperature 24 is 21.8°C. As the return temperature decreases, it increases Maximum temperature difference 22 increases linearly and reaches the absolute maximum temperature difference 26 at around 39.7 ° C.

Graph 34 shows the course of the maximum temperature difference 22 at a system pressure of 1.0 bar. Here the maximum temperature difference 22 at the first temperature 24 is 17.3°C. As the return temperature decreases, the maximum temperature difference 22 increases linearly and reaches the absolute maximum temperature difference 26 at approximately 32.2 ° C.

Graph 36 shows the course of the maximum temperature difference 22 at a system pressure of 0.5 bar. Here the maximum temperature difference 22 at the first temperature 24 has the lower maximum temperature difference value 27 of 12.8 ° C. As the return temperature decreases, the maximum temperature difference 22 increases linearly and reaches the absolute maximum temperature difference 26 of 40°C at the second temperature of approximately 24.7°C.

wobei dann bei der Ermittlung der Maximaltemperaturdifferenz 22 gegebenenfalls die Basistemperatur T_B angepasst werden muss. Es ist auch eine mathematisch äquivalente alternative Darstellung der Maximaltemperaturdifferenz 22 denkbar, bei welcher zur Ermittlung des Systemdruckbeitrags zunächst ein Druckoffset p_off vom Systemdruck subtrahiert wird und anschließend das Ergebnis der Subtraktion mit dem Druckfaktor multipliziert wird: $$\mathrm{B}\left({\mathrm{p}}_{\mathrm{Sys}}\right)={\mathrm{F}}_{\mathrm{p}}\times \left({\mathrm{p}}_{\mathrm{Sys}}-{\mathrm{p}}_{\mathrm{off}}\right),$$

wobei dann ebenfalls bei der Ermittlung der Maximaltemperaturdifferenz 22 gegebenenfalls die Basistemperatur T_B angepasst werden muss. Es ist auch denkbar, dass der Ermittlung der Maximaltemperaturdifferenz 22 ein Temperaturoffset und ein Druckoffset berücksichtigt werden. Beispielsweise könnte im Ausführungsbeispiel der Temperaturoffset 80°C betragen, der Druckoffset könnte beispielsweise 0,8 bar betragen. Der entsprechend korrigierte Basistemperatur beträgt dann 9,5°C, falls der Temperaturfaktor den Wert -0,6 und der Druckfaktor den Wert 9°C/bar hat.A mathematically equivalent alternative representation of the maximum temperature difference 22 is also possible, in which, to determine the return temperature contribution, a temperature offset T _off is first subtracted from the return temperature and then the result of the subtraction is multiplied by the temperature factor: $$\mathrm{b}\left({\mathrm{T}}_{\mathrm{back}}\right)={\mathrm{F}}_{\mathrm{back}}\times \left({\mathrm{T}}_{\mathrm{back}}-{\mathrm{T}}_{\mathrm{off}}\right),$$

whereby the base temperature T _B may then have to be adjusted when determining the maximum temperature difference 22. A mathematically equivalent alternative representation of the maximum temperature difference 22 is also conceivable, in which, to determine the system pressure contribution, a pressure offset p _off is first subtracted from the system pressure and then the result of the subtraction is multiplied by the pressure factor: $$\mathrm{b}\left({\mathrm{p}}_{\mathrm{Sys}}\right)={\mathrm{F}}_{\mathrm{p}}\times \left({\mathrm{p}}_{\mathrm{Sys}}-{\mathrm{p}}_{\mathrm{off}}\right),$$

whereby the base temperature T _B may then also have to be adjusted when determining the maximum temperature difference 22. It is also conceivable that a temperature offset and a pressure offset are taken into account when determining the maximum temperature difference 22. For example, in the exemplary embodiment, the temperature offset could be 80 ° C, the pressure offset could be, for example, 0.8 bar. The correspondingly corrected base temperature is then 9.5°C if the temperature factor has the value -0.6 and the pressure factor has the value 9°C/bar.

Claims (10)

1. Method for regulating a heating circuit of a heating system (10), wherein a return temperature of the heating circuit is measured, a system pressure of the heating circuit is measured, and a maximum temperature difference (22, dTMax) is determined as a function of the return temperature (TRet) and the system pressure (pSys), wherein the maximum temperature difference (22) describes the maximum permissible temperature difference between the return temperature and a feed temperature of the heating circuit, wherein a feed temperature of the heating circuit is measured and, from this, the temperature difference that prevails between the feed temperature and return temperature is determined, and wherein the feed temperature is lowered if the temperature difference exceeds the maximum temperature difference (22).
2. Method according to Claim 1, wherein the feed temperature is lowered in that a present heating power of the heating system (10) is lowered.
3. Method according to either of the preceding claims, characterized in that the maximum temperature difference (22) decreases linearly with the return temperature.
4. Method according to one of the preceding claims, characterized in that the maximum temperature difference (22) increases linearly with the system pressure.
5. Method according to one of the preceding claims, characterized in that the maximum temperature difference (22, dTMax) is determined from the sum of a constant base temperature (TB), a return-temperature contribution (B(TRet)) and a system-pressure contribution (B(pSys)), wherein the base temperature (TB) has a value of between 40°C and 65°C, preferably of between 45°C and 60°C, particularly preferably of between 50°C and 55°C.
6. Method according to one of the preceding claims, characterized in that the maximum temperature difference (22) is linearly dependent on a scaled return temperature, wherein the scaled return temperature is determined in that the positive return temperature (TRet) measured in °C is multiplied by a by a negative temperature factor (FRet) of between 0.9 and 0.4, preferably of between 0.8 and 0.5, particularly preferably of between -0.7 and -0.6.
7. Method according to one of the preceding claims, characterized in that the maximum temperature difference (22) is linearly dependent on a scaled system pressure, wherein the scaled system pressure is determined in that the positive system pressure (pSys) measured in bar is multiplied by a positive pressure factor (Fp) of between 7°C/bar and 12°C/bar, preferably of between 8°C/bar and 11°C/bar, particularly preferably of between 9°C/bar and 10°C/bar.
8. Method according to one of the preceding claims, characterized in that the maximum temperature difference (22) is not above an absolute maximum temperature difference (26), which is between 25°C and 50°C, preferably between 30°C and 45°C, particularly preferably between 35°C and 40°C.
9. Control unit for a heating system (10), wherein the control unit is configured such that a method according to one of the preceding claims is able to be carried out, having a return-temperature-determining unit, a feed-temperature-determining unit and a system-pressure-determining unit.
10. Heating system (10) having a control unit according to Claim 9.

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