DE102020204482A1 - Method for regulating a heating circuit of a heating system, control unit for a heating system and heating system - Google Patents

Abstract

The invention relates to a method for regulating a heating circuit of a heating system (10), a return temperature of the heating circuit being measured, a system pressure of the heating circuit being measured, a maximum temperature difference (22, dTMax) as a function of the return temperature (TRück) and the system pressure (pSys) ), whereby the maximum temperature difference (22) describes the maximum permissible temperature difference between the return temperature and a flow temperature of the heating circuit, whereby a flow temperature of the heating circuit is measured and the temperature difference between the flow temperature and return temperature is determined therefrom and the flow temperature is lowered, if the temperature difference exceeds the maximum temperature difference (22).

Description

The invention relates to a method for regulating 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 of a heating circuit in a heating system starts to boil, this is associated with undesirable noise. The heating system can become more calcified and a heat exchanger of the heating system can wear out more. 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 it can limit the convenience of use. If the maximum temperature difference is exceeded, the heating output can be limited or the heating system can be switched off. It takes more time to heat up the heating system.

Disclosure of the invention

advantages

The present invention describes a method for regulating 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 as a function of 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 temperature difference between the flow temperature and return temperature is determined from this. 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 compared to the prior art if the system pressure is sufficiently high 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 heating system should be understood to mean in particular at least one device for generating thermal energy, in particular a heating device 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 tanks. The heating system is advantageously designed as a fan burner in which combustion air is sucked in by a fan. A fuel is added to the intake combustion air and the air-fuel mixture is fed 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 draft burner is a special premix burner.

The return temperature is the temperature at which the heating water flows back into the heating system after it has passed through one or more heating surfaces, in particular radiators, surface heating systems 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 can be arranged on a return line of the heating system. 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 heating systems 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 guides the heating water from the heating system and in particular feeds 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 manometer or pressure sensor

The temperature difference between the flow temperature and the return temperature is sometimes also 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 receive the currently present return temperature and receive the currently present system pressure and determine the maximum difference as a function of 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 the 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 cellular 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 as a function of 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 enter into the calculation of the maximum temperature difference.

The flow temperature is advantageously reduced until the temperature difference corresponds to the maximum temperature difference or falls below it. An iterative procedure is conceivable in which the flow temperature is gradually reduced and the temperature difference is determined after each step. The flow temperature is reduced until the temperature difference equals or falls below the maximum temperature difference. It is also conceivable to lower the flow temperature in the manner of a control circuit, with the flow temperature being regulated down using a setting parameter that influences the flow temperature, for example the heating power, so that the temperature difference as a control variable is regulated to the maximum temperature difference as the setpoint.

The features listed in the subclaims allow advantageous developments of the method.

The flow temperature can advantageously be lowered by lowering a current heating output of the heating system. For this purpose, in the case of a forced draft burner, for example, 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 power of the heating system is reduced by adapting a fan speed characteristic. A fan speed rotation line assigns a required fan speed to a requested output. In order to lower the current heating output, the fan speed characteristic can be adapted, for example, in such a way that the fan speed assigned to a desired heating output does not exceed a predetermined maximum value.

Furthermore, it is conceivable that the heating power of the heating system is reduced by switching off the heating system or a combustion in a combustion chamber of the heating system, preferably switching it off until the flow temperature has dropped so far that the temperature difference present is below the Maximum temperature difference is.

The method is further improved if the maximum temperature difference falls linearly with the return temperature. This enables the existing heating water temperature to be taken into account in a particularly simple manner. The fact that the maximum temperature difference falls linearly with the return temperature should be understood in particular to mean that when determining the maximum temperature difference, the return temperature is included 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 that is multiplied by the return temperature 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 partial range or partial interval of the possible return temperature values, when the return temperature increases. The maximum temperature difference is preferably falling monotonically with the return temperature, ie the maximum temperature difference falls or remains constant when the return temperature is increased.

The method is also improved if the maximum temperature difference increases linearly with the system pressure. This enables the existing system pressure to be taken into account in a particularly simple manner. The fact that the maximum temperature difference rises linearly with the system pressure is to be understood in particular to mean that the system pressure is included linearly with a positive proportionality factor at least for a sub-range or a sub-interval of all possible system pressure values when determining the maximum temperature difference. In other words, the maximum temperature difference is calculated with a formula or with 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 increases at least in the partial range or partial interval of the possible system pressure values when the system pressure increases. The maximum temperature difference is preferably increasing 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. However, it is also conceivable that the temperature and / or pressure are specified in dimensionless quantities, that is, 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 the 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 the same as 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 the same as the pressure term.

It has been found to be 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.

Another advantageous parameterization is given when 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 when the maximum temperature difference is not 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 . This ensures that an excessively high maximum temperature is not erroneously determined - 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 is linearly dependent on the return temperature and linearly on the system pressure. It is then checked whether the preliminary maximum temperature difference is smaller than the absolute maximum temperature difference. If the preliminary maximum temperature difference is smaller than the absolute maximum temperature difference, the determined maximum temperature difference is equal to the preliminary determined maximum temperature difference. If the preliminary maximum temperature difference is greater than the absolute maximum temperature difference, the The determined maximum temperature difference is equal to the absolute maximum temperature difference.

It is also conceivable that the maximum temperature difference for previously defined parameter ranges of the return temperature and / or the system pressure is determined using a formula that is linearly dependent on the return temperature and linearly on the system pressure, the parameter ranges being selected so 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, having a return temperature determination unit, a flow temperature determination unit and a system pressure determination unit is also advantageous. Such a heating system has the advantage that it provides a high level of comfort due to a high maximum temperature difference, since rapid heating is always possible, and at the same time provides a very robust and reliable heating system, because despite the high maximum temperature difference, boiling of the heating water is prevented and thus the Wear of the heating system is minimized.

Figure list

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

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

• 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
• 2 an illustration of the method according to the present invention.

description

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

In 1 is a heater 10 shown schematically, which with a radiator 12th forms a heating circuit. As an example, the heating circuit has a radiator 12th on, the heating circuit can have additional heating elements and / or heating surfaces as required. The heater 10 provides hot heating water, which is supplied via a flow line 14th is transported to the radiator. In the radiator 12th the heat of the heating water is released into the environment. The cooled heating water is returned via a return line 16 back to the heater 10 transported where it can be reheated.

The heater can be used as an essential component 10 in particular a heat cell, a control unit, one or more pumps and piping. The number and complexity of the individual components also depend on the degree of equipment in the heater 10 from, 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 protrudes into the flame on the burner, which is provided in particular for flame monitoring. With the aid of the ionization probe, further flame parameters can be determined, for example it is conceivable that the lambda value is determined via an ionization current measured on the flame, that is to say the fuel-air ratio of the burned fuel-air mixture. A fan speed of the fan is variably adjustable. The fan speed is advantageously set 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 is the heater 10 a fan 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, for example smartphones.

For example, the fuel valve can be designed as an electronic control valve which is connected to the control unit via a data link. 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 present fuel-air ratio is determined with the aid of the ionization probe and, if necessary, is adapted to a setpoint value by the electronic control valve.

The fan is advantageously connected to the control unit via a data connection. The required fan speed can be set 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 required 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 provided 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 is connected via the return line 16 back to the heater 10 flowing heating water in the heater 10 leads. The return temperature determination unit is set up to send the currently existing return temperature to the control unit at regular intervals.

The heater 10 has a flow temperature determination unit which is provided 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 is in the heater 10 heated heating water to the flow line 14th leads. The flow temperature determination unit is set up to send the currently prevailing flow temperature to the control unit at regular intervals.

The heater 10 has a system pressure determination unit, which is provided to determine the system pressure of the heater 10 or the heating water in the heater 10 to investigate. 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 currently available 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, to initiate 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 the 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 with a maximum temperature difference 22nd compared which is determined from the currently available return temperature and the currently available system pressure.

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

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: $$\text{B}\left({\text{T}}_{\text{R}\ddot{\text{u}}\text{ck}}\right)={\text{F}}_{\text{R}\ddot{\text{u}}\text{ck}}\times {\text{T}}_{\text{R}\ddot{\text{u}}\text{ck}},$$

wobei T_Rürk 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 is 22nd calculated from the sum of a base temperature, a return temperature contribution and a system pressure contribution: $${\text{dT}}_{\text{Max}}={\text{T}}_{\text{B.}}+\text{B.}\left({\text{T}}_{\text{R.}\ddot{\text{u}}\text{ck}}\right)+\text{B.}\left({\text{p}}_{\text{Sys}}\right),$$

where dT _{Max is} the maximum temperature difference in ° C, T _B the base temperature, B (T _Rück ) the return temperature contribution and B (p _Sys ) the system pressure contribution. _{The base temperature T B} is, for example, 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: $$\text{B.}\left({\text{T}}_{\text{R.}\ddot{\text{u}}\text{ck}}\right)={\text{F.}}_{\text{R.}\ddot{\text{u}}\text{ck}}\times {\text{T}}_{\text{R.}\ddot{\text{u}}\text{ck}},$$

where T _{Rürk is} the determined return temperature in ° C and F _{Rück is} the temperature factor, which has the value -0.6 as an example.

wobei psys 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: $$\text{B.}\left({\text{p}}_{\text{Sys}}\right)={\text{F.}}_{\text{p}}\times {\text{p}}_{\text{Sys}},$$

where psys is the system pressure, determined in the unit bar, and F _{p is} the pressure factor, which is an example of 9 ° C / bar.

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

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

The illustration at a first return temperature is an example 24 cut off from 70 ° C. graph 28 shows the course of the maximum temperature difference 22nd at a system pressure of 3.0 bar. Here is the maximum temperature difference 22nd at the first temperature 24 35 , 3 ° C. As the return temperature falls, the maximum temperature difference increases 22nd linearly and reaches the absolute maximum temperature difference at around 62.2 ° C 26th .

graph 30th shows the course of the maximum temperature difference 22nd at a system pressure of 2.0 bar. Here is the maximum temperature difference 22nd at the first temperature 24 26th , 3 ° C. As the return temperature falls, the maximum temperature difference increases 22nd linearly and reaches the absolute maximum temperature difference at around 47.2 ° C 26th .

graph 32 shows the course of the maximum temperature difference 22nd at a system pressure of 1.5 bar. Here is the maximum temperature difference 22nd at the first temperature 24 21 , 8 ° C. As the return temperature falls, the maximum temperature difference increases 22nd linearly and reaches the absolute maximum temperature difference at around 39.7 ° C 26th .

graph 34 shows the course of the maximum temperature difference 22nd at a system pressure of 1.0 bar. Here is the maximum temperature difference 22nd at the first temperature 24 17th , 3 ° C. As the return temperature falls, the maximum temperature difference increases 22nd linearly and reaches the absolute maximum temperature difference at around 32.2 ° C 26th .

graph 36 shows the course of the maximum temperature difference 22nd at a system pressure of 0.5 bar. Here has the maximum temperature difference 22nd at the first temperature 24 the lower maximum temperature difference value 27 of 12.8 ° C. As the return temperature falls, the maximum temperature difference increases 22nd linearly and reaches the absolute maximum temperature difference at the second temperature of about 24.7 ° C 26th from 40 ° 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: $$\text{B}\left({\text{p}}_{\text{Sys}}\right)={\text{F}}_{\text{p}}\times \left({\text{p}}_{\text{Sys}}-{\text{p}}_{\text{off}}\right),$$

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.It is also a mathematically equivalent alternative representation of the maximum temperature difference 22nd 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: $$\text{B.}\left({\text{T}}_{\text{R.}\ddot{\text{u}}\text{ck}}\right)={\text{F.}}_{\text{R.}\ddot{\text{u}}\text{ck}}\times \left({\text{T}}_{\text{R.}\ddot{\text{u}}\text{ck}}-{\text{T}}_{\text{off}}\right),$$

where then when determining the maximum temperature difference 22nd the base temperature T _B may have to be adjusted. It is also a mathematically equivalent alternative representation of the maximum temperature difference 22nd 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: $$\text{B.}\left({\text{p}}_{\text{Sys}}\right)={\text{F.}}_{\text{p}}\times \left({\text{p}}_{\text{Sys}}-{\text{p}}_{\text{off}}\right),$$

where then also when determining the maximum temperature difference 22nd the base temperature T _B may have to be adjusted. It is also conceivable that the determination of the maximum temperature difference 22nd a temperature offset and a pressure offset are taken into account. For example, in the exemplary embodiment, the temperature offset could be 80 ° C., and the pressure offset could be 0.8 bar, for example. 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)

The method of the heating circuit is measured for controlling a heating circuit of a heating system (10), a return temperature of the heating circuit is measured, a system pressure, depending on the return temperature (T _return) and the system pressure (p sys), a maximum temperature difference (22, dT _Max ) is determined, the maximum temperature difference (22) describing the maximum permissible temperature difference between the return temperature and a flow temperature of the heating circuit, a flow temperature of the heating circuit being measured and the temperature difference between the flow temperature and return temperature being determined and the flow temperature being reduced if the temperature difference exceeds the maximum temperature difference (22). Procedure according to Claim 1 , wherein the flow temperature is lowered by a current heating output of the heating system (10) is lowered. Method according to one of the preceding claims, characterized in that the maximum temperature difference (22) falls linearly with the return temperature. Method according to one of the preceding claims, characterized in that the maximum temperature difference (22) increases linearly with the system pressure. Method according to one of the preceding claims, characterized in that the maximum temperature difference (22, dT _Max ) from the sum of a constant base temperature (T _R ), a return _{temperature contribution (B (T Rück} )) and a system pressure contribution (B (p _Sys )) is determined, the base temperature (T _B ) having a value between 40 ° C and 65 ° C, preferably between 45 ° C and 60 ° C, particularly preferably between 50 ° C and 55 ° C. Method according to one of the preceding claims, characterized in that the maximum temperature difference (22) is linearly dependent on a scaled return temperature, the scaled return temperature is determined by the positive return temperature (T _return) measured in ° C with a negative with a temperature factor (F _Rück ) is multiplied between -0.9 and -0.4, preferably between -0.8 and -0.5, particularly preferably between -0.7 and -0.6. Method according to one of the preceding claims, characterized in that the maximum temperature difference (22) depends linearly on a scaled system pressure, the scaled system pressure being determined by the positive system pressure (p _Sys ) measured in bar with a positive pressure factor (F _p ) 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. Method according to one of the preceding claims, characterized in that the maximum temperature difference (22) is no more than 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. Control unit for a heating system (10), the control unit being set up so that a method according to one of the preceding claims can be carried out. Heating system (10) with a control unit according to Claim 9 , having a return temperature determination unit, a flow temperature determination unit and a system pressure determination unit.

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