Method for operating a heating system of a building, associated heating system and computer program product

Abstract

The invention relates to a method (28) for operating a heating system (6) of a building (2), which comprises a heat pump (8) with a compressor (16) and with a heat exchanger (14) through which a refrigerant is circulated. An operating parameter (36) is recorded, and a time value (44) is generated based on the operating parameter (36). The time value (44) is added to a counter (46), and the counter (46) is compared with a first limit value (48). Depending on the comparison, the heat exchanger (14) is defrosted. The invention further relates to a heating system (6) and a computer program product (26).

Description

[0001] The invention relates to a method for operating a building heating system comprising a heat pump. The invention further relates to a heating system and a computer program product.

[0002] Heat pump heating systems are increasingly being used to heat buildings. These systems have a refrigerant circuit with a compressor driven by an electric motor. The compressor compresses a gaseous refrigerant, usually supplied through pipes, which is then fed to a first heat exchanger. This heat exchanger is, for example, thermally connected to another component of the heating system. There, heat energy is extracted from the refrigerant, causing it to cool and liquefy. The liquefied refrigerant is then directed to an expansion valve, which reduces the pressure, causing some of the liquid refrigerant to evaporate. The cooled refrigerant is then fed to a second heat exchanger, which, in the case of an air-to-water heat pump, is typically exposed to ambient air. Here, heat is extracted from the surroundings, and the refrigerant is reheated.The refrigerant is then returned to the compressor.

[0003] To enable the transfer of a comparatively large amount of energy in the second heat exchanger, it is usually designed with a relatively large surface area. The second heat exchanger is also typically located outside a building, resulting in a relatively large volume of ambient air flow. To assist this airflow, a fan is usually present, featuring a fan wheel driven by a separate electric motor.

[0004] The refrigerant supplied to the second heat exchanger typically has a temperature below 0 °C, which is why the second heat exchanger is cooled down considerably. This leads to the condensation of the moisture contained in the ambient air. If the ambient air is also at a relatively low temperature, the moisture may condense directly into ice in the area of ​​the second heat exchanger before it can be dissipated. This obstructs the flow of ambient air, thus reducing heat transfer to the ambient air. If a significant amount of ice accumulates due to prolonged operation, the fan may become blocked, further restricting the airflow. Furthermore, a large volume of ice may prevent ambient air from reaching the second heat exchanger altogether.In other words, no heat is absorbed from the ambient air, or the amount absorbed is too low, which is why the building can essentially no longer be heated.

[0005] To remedy this, the operating state of the heat pump is determined, taking the current ambient temperature into account. The operating state determined in this way is compared with a multidimensional characteristic curve. Depending on the comparison, the second heat exchanger is then defrosted, for example, by running the compressor in reverse or by activating a heating element associated with the second heat exchanger. The characteristic curve is usually created on a test bench, with each point on the curve corresponding to a measured operating state. These points are chosen so that the efficiency of the heating system begins to be excessively reduced at these points due to the onset of icing. Creating the characteristic curve is relatively time-consuming, and it is necessary to generate a corresponding characteristic curve for each different type of heat pump.Furthermore, subsequent adjustment of the map is comparatively complicated and unintuitive.

[0006] The invention is based on the objective of providing a particularly suitable method for operating a heating system of a building, as well as a particularly suitable heating system and a particularly suitable computer program product, wherein, expediently, effort, manufacturing costs and / or complexity are reduced.

[0007] With regard to the method, this problem is solved according to the invention by the features of claim 1, with regard to the heating system by the features of claim 11, and with regard to the computer program product by the features of claim 12. Advantageous further developments and embodiments are the subject of the respective dependent claims.

[0008] The procedure serves to operate a heating system, also simply referred to as a heating system. The heating system is used to heat a building, such as a single-family home, an apartment building, or a factory building. Specifically, the heating system has a nominal heat output between 2.6 kW and 15 kW, or up to 60 kW. The heating system is particularly suitable, appropriately designed, and equipped for this purpose.

[0009] The heating system includes a heat pump. For example, the heating system may consist solely of a heat pump, or it may include other components such as multiple heat pumps or additional heat sources. Ideally, the heat pump should have a nominal heat output between 2.6 kW and 15 kW, or up to 60 kW.

[0010] The heat pump comprises a compressor, preferably driven by a first electric motor. The first electric motor is, in particular, a brushless direct current (BLDC) motor. The compressor, also referred to as a compressor unit, suitably serves to compress a refrigerant in the heat pump's refrigerant circuit. The compressor, for example, the compressor head, is expediently connected fluidically, particularly by means of a pipe, to a further heat exchanger. For example, the further heat exchanger is either an integral part of the heat pump or located separately from it. The further heat exchanger is expediently connected fluidically to an expansion valve, which in turn is preferably connected to a heat exchanger. This heat exchanger is connected to the compressor, thus creating a refrigerant circuit. In particular, the refrigerant circuit is filled with the refrigerant.In summary, the heat pump thus has a compressor and a heat exchanger, through which the refrigerant is, at least in part, conveyed.

[0011] The heat exchanger preferably has fins / cooling fins or a cooling core, which are preferably fluidically connected to an air inlet of the heat exchanger. Preferably, the heat exchanger is designed as a so-called finned heat exchanger or "fin tube heat exchanger." Advantageously, the heat exchanger is equipped with a fan that has an impeller driven by a second electric motor. This motor is advantageously designed as a brushless DC motor (BLDC). When the fan is operating, an airflow is generated that is guided over the fins / cooling fins / through the cooling core. For this purpose, the heat pump suitably includes appropriate air guide elements. Preferably, the fan is arranged in the air inlet of the heat exchanger.

[0012] In particular, the heat pump has a housing within which the compressor, the first electric motor, the heat exchanger, and the fan are arranged. Advantageously, the housing is suitable for outdoor use, and in particular, designed and equipped for it. Preferably, the housing includes one or more openings through which ambient air can be drawn to the heat exchanger. In a further development, for example, the additional heat exchanger and / or the expansion valve are also arranged within the housing, or they are arranged in a further housing, which is, for example, spaced apart.

[0013] The method involves recording an operating parameter. Specifically, this is an operating parameter of the heat pump. For example, the operating parameter is predefined and corresponds to a setpoint, which is then used to control the system. Alternatively, the operating parameter may result from the operation of the heat pump or at least the heating system. The operating parameter is measured directly, preferably using an associated sensor. In other words, the operating parameter is a measured value. Alternatively, the operating parameter is derived from one or more measured values, which are also measured using an associated sensor. Preferably, the heating system, and expediently the heat pump, includes appropriate sensors for this purpose.Preferably, the method uses an operating parameter that is also used for the general operation of the heat pump. Alternatively, or in combination with this, the operating parameter is determined based on a measured value that is otherwise required for the operation of the heat pump. This eliminates the need for additional sensors or similar components, thus reducing manufacturing costs.

[0014] A time value is generated based on the operating parameter. Therefore, if the operating parameter changes, the time value preferably also changes. Conversely, if the operating parameter does not change, the time value remains unchanged. In summary, the operating parameter is mapped to the time value, and a functional relationship exists between them. The time value is added to a counter. If the counter initially has a certain value, after the addition, it will have a value increased by the time value. In this process, the time value is always positive, so the counter is always incremented.

[0015] The meter reading is compared to an initial limit value. This initial limit value is preferably constant. Alternatively, it can be variable and adapted to current requirements and / or the specific heating system. For example, the initial limit value might be entered during commissioning of the heating system or set by the heating system manufacturer. Alternatively, the initial limit value could be dynamically adjusted based on current requirements, environmental conditions, or other parameters.

[0016] Depending on the comparison, the heat exchanger is defrosted. In other words, the comparison serves as a condition for initiating the defrosting process of the heat exchanger. Specifically, defrosting occurs when the counter reading exceeds the first threshold. The defrosting process itself is, for example, a component of the process or, preferably, of another, downstream process. For defrosting, the refrigerant circuit is operated in reverse, so that heated refrigerant is directed to the heat exchanger. Alternatively, heating elements associated with the heat exchanger, which are primarily electrically powered, are used.

[0017] This method ensures that the heat exchanger does not ice up, or at least that any icing is not excessive before the defrosting process begins. No characteristic map or comparatively complex determination of the heat pump's operating point is required; instead, only the operating parameter needs to be recorded and compared to the first limit value, which is specifically one-dimensional. This reduces complexity. Furthermore, it is not necessary to determine this value on a test bench or similar device, thus reducing effort. If necessary, the value can be adjusted, which is relatively intuitive. This reduces hardware requirements. In summary, both effort and manufacturing costs are reduced.Since only a comparison with the first limit value is made, complexity is reduced and thus the robustness of the method is increased.

[0018] For example, the process is performed only once, or expediently several times. For instance, the process is repeated continuously so that, after the comparison, if defrosting of the heat exchanger is not yet required, the operating parameter is recorded again. Particularly preferably, however, there is a time interval between these steps that is suitably between 10 minutes and 10 ms, and preferably between 5 seconds and 0.5 seconds. Expediently, the operating parameter is recorded every second, in particular the associated sensor is sampled. This ensures that no, or at least excessive, unwanted icing of the heat exchanger occurs, while requiring comparatively little computational effort.

[0019] For example, the process is terminated when the heat exchanger is defrosted. Alternatively, it is continued, and the counter is adjusted accordingly. Preferably, however, the process is suspended during defrosting, and the counter is reset. After defrosting is complete, the operating parameter is expediently recorded again, the time value is calculated, and added to the counter.

[0020] For example, the process is started when the heating system / heat pump is first commissioned. Preferably, however, the process is started when the heat pump begins operating, specifically when the compressor is running. The process is terminated when the heat pump is switched off. This reduces the effort required. Alternatively, the process is only started when a specific condition is met. This further reduces the effort required.

[0021] For example, only a single operating parameter is recorded. This reduces the effort. However, it is particularly preferable to record multiple operating parameters. For example, the time value is then directly determined based on all operating parameters, especially using a function. Even more preferable, however, is to first create an auxiliary value for each operating parameter. This allows the creation of the auxiliary values ​​to be independent of each other, reducing complexity and effort. It is also possible to perform the creation of the auxiliary values ​​independently of each other, particularly in terms of timing. Advantageously, there is a functional relationship between each operating parameter and its associated auxiliary value. The auxiliary values ​​are then processed together to create the time value. Thus, the time value is based on all auxiliary values.The use of auxiliary values ​​reduces the complexity of determining the time value, and some of the necessary calculations can be performed during the generation of these auxiliary values. This can be done sequentially, eliminating the need for high-performance hardware. The multiple operating parameters ensure that defrosting is not overly frequent while preventing excessive icing of the heat exchanger. In other words, this approach allows for the consideration of different operating scenarios, avoiding unnecessary defrosting. Ideally, all operating parameters and / or measured values ​​used to determine the respective operating parameters are also used for other aspects of the heating system / heat pump operation.Therefore, the process does not require additional sensors or similar components, and consequently, no additional hardware is needed. As a result, manufacturing costs are not increased.

[0022] For example, the auxiliary values ​​are processed using a function to generate the time value. This might involve adding or, more conveniently, multiplying them together. Therefore, generating the time value does not require a comparatively complex calculation. This method is also relatively robust. Because of the multiplication, the auxiliary values, and thus the operating parameters, are considered or assumed to be independent of each other. This allows for intuitive adjustment of the function / procedure used to generate each auxiliary value. In other words, fine-tuning is possible by adjusting the function used to generate each auxiliary value, preventing unwanted effects.Fine-tuning can also be performed if, during operation of the heating system, excessively frequent and unnecessary defrosting is observed, or if icing is present. In particular, the functions for the auxiliary value(s) are adjusted where the operating parameters have changed significantly. The other functions, however, are preferably left unchanged. This reduces the effort required for configuring and / or optimizing the heating system. Furthermore, no comparatively complex training is required. In summary, the multiplication process assumes that the auxiliary values ​​are independent of each other, or at least that they are treated as such, which is why the functions / procedures used to create each auxiliary value based on its assigned operating parameter can be determined relatively easily.If this is done on a test bench, the required time is reduced.

[0023] For example, to determine each or at least some of the auxiliary values ​​based on the assigned operating parameter, a one-dimensional characteristic map is used, which is stored in a lookup table. This map can be adapted relatively precisely to the current installation situation of the heating system. Preferably, however, a function is used. In other words, each auxiliary value is generated using an assigned function, which reduces the memory requirement. This also facilitates adaptation. For example, each function is adapted to the respective physical relationship. Preferably, however, one, some, or all auxiliary values ​​are generated using a linear function. In particular, the operating parameter represents the function argument, and the auxiliary value is the function value.The slope and offset are entered and / or adjusted, or can at least be adjusted, by the heating system manufacturer, the heating system installer, or the heating system user. Alternatively, they may remain unchanged.

[0024] Due to the linear functions, the effort required to determine the auxiliary values ​​is comparatively low. Since multiple auxiliary values ​​are used, it can be ensured that defrosting is not excessively frequent and unnecessary, while simultaneously preventing icing or at least ensuring that it does not lead to a significant change in the heating system's efficiency. Furthermore, adjusting the parameters of the linear functions, i.e., the slope and the shift, is relatively intuitive. For example, only one such linear function is used for each auxiliary value / parameter. In other words, the slope and the shift are constant. Alternatively, several such pairs of slope and shift are available, resulting in multiple linear sections.Thus, accuracy is improved, but it is not necessary to establish a comparatively complicated formulation of the functional relationship between the respective auxiliary value and the associated operating parameter.

[0025] For example, the refrigerant pressure ratio across the compressor is used as an operating parameter. In other words, the pressure at the compressor outlet and inlet is measured, and the ratio between these pressures is calculated. This pressure ratio is then used as an operating parameter. The two pressures, or at least the pressure ratio, depend on the current heating output of the heat pump, which in turn has a relatively significant influence on the cooling of the refrigerant and thus the heat exchanger. Consequently, a change in this operating parameter also changes the probability or severity of icing of the heat exchanger.Because it is related to the current heat output of the heat pump, this operating parameter is already determined in order to regulate or at least control the heating system to a desired heat output / heat demand. Therefore, no additional effort is required.

[0026] Alternatively, the compressor's operating speed is used as an operating parameter. In other words, the rotational speed of any primary electric motor associated with the compressor is used. This operating parameter at least partially determines the heat pump's current heating output, which in turn affects the refrigerant temperature and thus whether the heat exchanger ices up. This operating parameter is also commonly used, particularly for controlling the primary electric motor and / or as part of a predefined setpoint to achieve the desired heating output.

[0027] It is advantageous to calculate the respective auxiliary values ​​based on the operating speed and the pressure ratio. Both are related to the current heat output, with the pressure ratio primarily describing the actual heat output achieved and the compressor's operating speed primarily describing the desired heat output. If there is a comparatively large deviation between these values, efficiency is reduced, for example, due to icing of the heat exchanger. This relationship is taken into account, at least implicitly, by the two auxiliary values ​​and / or the way they are processed to determine the time value.

[0028] Alternatively, or preferably in combination, the temperature of the refrigerant is used as an operating parameter. This is determined, and expediently measured, at the inlet of the heat exchanger. The temperature of the refrigerant at the inlet of the heat exchanger corresponds, in particular, to the evaporation temperature of the refrigerant. In other words, the evaporation temperature of the refrigerant is preferably used as the operating parameter. This is measured directly, for example, using a thermometer. Alternatively, it is derived from other measured values, such as the pressure. The evaporation temperature can thus be derived from the phase diagram of the refrigerant used. Consequently, the pressure of the refrigerant is measured to determine the operating parameter.

[0029] The refrigerant temperature at the heat exchanger inlet, or the evaporation temperature, represents, for example, the coldest temperature in the refrigerant circuit. This temperature is used, in particular, to determine the current efficiency of the heat pump. The lower this temperature, the greater the likelihood of icing in the heat exchanger. The refrigerant temperature at the heat exchanger inlet can also be used to check, adjust, and / or control the expansion valve. Alternatively, or as a condition, the temperature at a compressor inlet is measured and used as an operating parameter. This is recorded specifically to adjust the compressor's operation accordingly and, in particular, to ensure that the compressor is not damaged.In particular, the temperature at the compressor inlet is essentially the same as the temperature of the refrigerant at the heat exchanger outlet.

[0030] Alternatively, the ambient temperature of the heat exchanger can be used as an operating parameter. Preferably, the temperature of the ambient air exposed to the heat exchanger is measured. In particular, the air at an air inlet of the heat exchanger is measured, expediently directly. If this temperature is relatively high, the required heat output is low, while heat transfer, i.e., energy absorption by the refrigerant, is simplified. This temperature is then used to set the flow temperature of the heating system.

[0031] Preferably, both the temperature of the refrigerant at the inlet of the heat exchanger and the temperature of the surrounding environment are used to determine an operating parameter. For example, these temperatures are added together. However, it is particularly preferred that the difference between the two temperatures be used as the operating parameter. This difference is functionally related to the heat absorbed from the environment by the heat exchanger. Preferably, the heat pump is operated at least partially based on this difference, and more preferably, the expansion valve is also operated based on this difference.

[0032] Another alternative uses, for example, the operating speed of any fan / second electric motor as an additional operating parameter. This influences the volume flow of ambient air through the heat exchanger, which also affects the resulting icing.

[0033] Preferably, the evaporation temperature of the refrigerant is measured and compared with a second limit value. This comparison is used, for example, in conjunction with determining one or more operating parameters based on this temperature. However, the comparison can also be performed independently, so that the operating parameter(s) used are, in particular, independent of the refrigerant's evaporation temperature. The second limit value is suitably chosen such that icing of the heat exchanger is (in principle) only possible at a temperature below this value. The second limit value is expediently between 0 °C and -5 °C. Preferably, -2 °C is used as the second limit value.

[0034] For example, the comparison takes into account whether icing is currently possible, and this is specifically considered during the execution of the procedure. For instance, the time value is set to 0 (zero) or another predetermined value if the refrigerant's evaporation temperature is greater than the second limit. Alternatively, or in combination with this, the procedure is only started if the refrigerant's evaporation temperature is less than the second limit. In other words, this is used as a condition for starting the procedure. For example, the procedure is stopped as soon as the refrigerant's evaporation temperature is greater than the second limit. Alternatively, the procedure is essentially carried out continuously.Based on the comparison, it is at least possible to carry out the procedure in a targeted manner, specifically when icing is fundamentally possible, whereas when icing is fundamentally impossible, it is more practical not to carry out the procedure, or at least not to calculate the current value. This reduces the effort involved.

[0035] Advantageously, the first time period is determined by how long the refrigerant's evaporation temperature has been below the second limit. Thus, the first time period increases as long as the refrigerant's evaporation temperature remains below the second limit. In particular, the first time period is determined at specific intervals, preferably every second. For example, after the refrigerant's evaporation temperature rises above the second limit and subsequently falls, the first time period is recalculated. Preferably, however, the first time period is extended so that it cumulatively represents all periods during which the refrigerant's evaporation temperature is / was below the second limit. The first time period is advantageously used as one or more of the operating parameters.Thus, the time value is (also) determined based on the first time period, i.e., the operating time during which icing is theoretically possible.

[0036] Alternatively or in combination with this, the counter is reset if the refrigerant's evaporation temperature remains above the second limit for a second period of time. In other words, the counter is reset in this case. Preferably, the first period is also reset, particularly if it is calculated cumulatively. The second period is, for example, predefined and can be expediently adjusted. Suitablely, the second period is between 10 and 30 minutes, and, for example, essentially equal to 20 minutes. After the second period has elapsed, icing of the heat pump is essentially prevented due to the comparatively high evaporation temperature of the refrigerant, thus preventing unnecessary defrosting by resetting the counter. Preferably, the second period is selected accordingly.

[0037] The heating system is suitable, appropriately designed, and configured for heating a building. Preferably, in its installed state, the heating system forms an integral part of the building and is, for example, permanently connected to it. The heating system includes a heat pump and is, for example, formed by means of this or includes further components. The heat pump includes a compressor, which is appropriately driven by a first electric motor. Furthermore, the heat pump includes a heat exchanger and, appropriately, a second heat exchanger. The heat pump also appropriately includes an expansion valve and / or a fan with a fan wheel and a second electric motor. A refrigerant is circulated at least by means of the compressor and the heat exchanger, and appropriately also by means of any second heat exchanger and / or expansion valve. The heat pump is preferably an air-to-water heat pump.

[0038] The heating system is operated according to a method in which an operating parameter is recorded. A time value is generated based on this operating parameter, and this time value is added to a counter. The counter is compared to a first limit value, and the heat exchanger is defrosted depending on the result of this comparison. Advantageously, the heating system includes a heating element associated with the heat exchanger. The heating system particularly includes a control unit designed and configured to carry out the method. The control unit comprises, for example, an application-specific integrated circuit (ASIC) or, more preferably, a computer, which is suitably programmable.In particular, the control unit comprises a storage medium on which a computer program, also referred to as a computer program, is stored, wherein, upon execution of this computer program, i.e., the program, the computer is instructed to carry out the process. Advantageously, the control unit is connected to the compressor, preferably to the first and / or any second electric motor and / or all or at least some of the sensors of the heat pump via signal transmission, for example, separately or by means of a bus system.

[0039] The invention further relates to such a control unit. The control unit is designed and configured to carry out a method for operating a building heating system comprising a heat pump with a compressor and a heat exchanger through which a refrigerant is circulated. In the method, an operating parameter is detected, and a time value is generated based on this parameter. The time value is added to a counter, and the counter value is compared to a first limit value. Depending on the comparison, the heat exchanger is defrosted.

[0040] The control unit comprises, for example, an application-specific integrated circuit (ASIC) and / or a microprocessor, by means of which the method is at least partially carried out. In particular, the control unit includes a computer program stored in memory, which, when executed by a computer, such as the microprocessor, causes the computer to carry out the method. Preferably, the control unit, when installed, is a component of the heat pump or a higher-level control system for the heating system. For example, the control unit also performs other functions. In particular, the control unit operates the heat pump in response to a heat demand.

[0041] The computer program product comprises a number of instructions which, when executed by a computer, cause it to perform a method for operating a building's heating system. The system includes a heat pump with a compressor and a heat exchanger through which a refrigerant is circulated. In this method, an operating parameter is recorded, and a time value is generated based on this parameter. The time value is added to a counter, and the counter is compared to a first limit value. Depending on this comparison, the heat exchanger is defrosted. The computer is expediently a component of a control unit and is, for example, formed by means of such a unit. The computer preferably includes a microprocessor or is formed by means of one.The computer program product is, for example, a file or a data carrier containing an executable program that, when installed on a computer, automatically performs the procedure.

[0042] The invention further relates to a storage medium on which the computer program product is stored. Such a storage medium is, for example, a CD-ROM, a DVD, or a Blu-ray Disc. Alternatively, the storage medium is a USB flash drive or other storage medium that is, for example, rewritable or write-only. Such storage medium is, for example, flash memory, RAM, or ROM.

[0043] When an object is referred to as the first, second, ... object, this simply refers to a specific object. In particular, this does not mean that a corresponding number of such objects exist.

[0044] The further training and advantages explained in connection with the procedure can also be applied analogously to the heating system / the control unit / the computer program product / the storage medium as well as to each other and vice versa.

[0045] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows: Fig. 1 schematically shows a building with a heating system that includes a heat pump, and Fig. 2 shows a method for operating the heating system.

[0046] Corresponding parts are marked with the same reference symbols in all figures.

[0047] In Figure 1The schematically simplified representation is of a building 2, namely a single-family or multi-family house. Building 2 has an exterior wall 4, by means of which all rooms and the like are enclosed. Building 2 also includes a heating system 6, which serves to heat the individual rooms of building 2.

[0048] The heating system 6 includes a heat pump 8, which is designed as an air-to-water heat pump. The heat pump 8 comprises an outdoor unit 10 and an indoor unit 12. The outdoor unit 10 is located outside the outer walls 4, whereas the indoor unit 12 is enclosed by the outer walls 4. The outdoor unit 10 and the indoor unit 12 are connected to each other fluidically via several pipes and signalally via several signal lines.

[0049] The outdoor unit 10 includes a heat exchanger 14 and a compressor 16, which comprises a compressor head driven by a first electric motor (not shown). The heat exchanger 14 has several cooling fins through which several cooling tubes pass. A fan (not shown) with a fan wheel, driven by a second electric motor, is also associated with the heat exchanger 10. When the fan is operating, ambient air is directed onto the heat exchanger 14 and drawn or blown through it.

[0050] The indoor unit 12 includes an expansion valve (not shown) and another heat exchanger 18. The indoor unit 12 also comprises a control unit 20, which includes a computer 22 in the form of a microprocessor and a memory 24. The control unit 20 controls and / or regulates the compressor 16 and the other components of the heat pump 8.

[0051] When there is a heat demand on the heating system 6, the compressor 16 is operated, compressing the refrigerant it carries. As a result, this refrigerant is heated. The heated refrigerant is then directed to the heat exchanger 18, where at least some of the heat is transferred to heating water or the like, which is then distributed to the individual rooms of building 2. The refrigerant, cooled in this process, is then directed to the expansion valve, where its pressure is reduced back to its original value. This causes the refrigerant to cool further. It is then directed to the heat exchanger 14, where it is heated again by exposure to the ambient air, at least to a temperature slightly below the outside temperature, i.e., the temperature of the surroundings of the heat exchanger 14. To close the refrigerant circuit, the refrigerant is then directed back to the compressor 16.

[0052] As the cooled refrigerant passes through the heat exchanger 14, it cools down, causing the moisture in the ambient air to condense. If the ambient temperature of the heat exchanger 14 is relatively low, the moisture may condense as ice on the heat exchanger 14. This reduces the flow rate of the ambient air, and consequently, the refrigerant is heated less by the heat exchanger 14. Therefore, the efficiency of the heat pump 8 is reduced. It is also possible that the fan may be blocked by the ice.

[0053] To remedy this, a computer program product 26 is stored in memory 26, which comprises several instructions that, when the program is executed by the computer 22, cause it to perform a function in Figure 2The described procedure 28 is carried out. Procedure 28 is carried out as soon as the compressor 16 is operated by means of the control unit 20. Consequently, the heating system 6 is operated according to procedure 28.

[0054] In a first step 30, the evaporation temperature of the refrigerant is measured and compared with a second limit value 32. The second limit value 32 is set at -2 °C. As long as the evaporation temperature of the refrigerant is higher than the second limit value 32, the first step 30 is carried out, at least as long as the compressor 16 is operating.

[0055] Only when the evaporation temperature of the refrigerant falls below the second limit value 32 is a second work step 34 carried out. In other words, the second work step 34 is carried out for the first time, and thus the process 28 is continued, when the evaporation temperature of the refrigerant is lower than the second limit value 32. In the second work step 34, several operating parameters 36 are recorded.

[0056] One such operating parameter 36 is the refrigerant pressure ratio across the compressor 16. In other words, the refrigerant pressure at the compressor 16 outlet is divided by the refrigerant pressure at the compressor 16 inlet. Consequently, this operating parameter 36 represents the compression capacity of the compressor 16. This pressure ratio can also be used, at least indirectly, to control the compressor 16 according to the heat demand. Another operating parameter 36 is the operating speed of the compressor 16. For this, the rotational speed of the first electric motor, which is already used for controlling the compressor 16, is determined.

[0057] Another operating parameter, 36, is the temperature of the refrigerant at the inlet of the heat exchanger 14. This operating parameter 36 is used for the operation of the expansion valve, since the temperature of the refrigerant at the inlet of the heat exchanger 14 is essentially the same as the temperature of the refrigerant at the outlet of the expansion valve. Furthermore, the ambient temperature of the heat exchanger 14 is determined, and the difference between these two temperatures is calculated and used as operating parameter 36. This difference is determined by subtracting the temperature of the refrigerant at the inlet of the heat exchanger 14 from the ambient temperature of the heat exchanger 14, or vice versa.

[0058] Furthermore, a first time period 38 is determined. This corresponds to the period during which the evaporation temperature of the refrigerant is lower than the second limit value 32, as long as the procedure 28 is carried out. Therefore, when the second work step 34 is performed for the first time, the first time period 38 is equal to 0 (zero). The first time period 38 is also used as one of the operating parameters 36.

[0059] In summary, several operating parameters 36 are determined in the second step 34. Based on each operating parameter 36, a corresponding auxiliary value 40 is created. A linear function is used for this purpose, so that each auxiliary value 40 is generated using the respective linear function. The respective operating parameter 36 is the function argument, and the auxiliary value 40 is the function value of the respective linear function. Thus, the auxiliary values ​​40 are generated independently of each other. The slope and the shift of the respective linear function are specified by the manufacturer of the heat pump 8 and are determined, for example, on a test bench. Alternatively or in combination, these are determined, for example, using an optimization procedure and / or an artificial intelligence algorithm.It is also possible that different slopes / shifts are used for different value ranges of the respective operating parameter 36, so that piecewise linear functions are used to determine the auxiliary values ​​40. These are, in particular, continuous and thus transition into each other without discontinuities.

[0060] After completion of the second work step 34, six different auxiliary values ​​40 are available. A third work step 42 is then performed. In this step, the auxiliary values ​​40 are multiplied together to create a time value 44. In summary, the time value 44 is created based on the operating parameters 36, and the auxiliary values ​​40 are processed together to create the time value 44. The time value 44 is added to a counter 46, which was reset, for example, when the first work step 30 was performed, specifically to a value of 0 (zero), or at least when the second work step 34 is performed for the first time.

[0061] The counter 46 is compared with a first limit value 48. This first limit value 48 is fixed by the manufacturer of the heat pump 8, but can be conveniently changed by a user or a technician of the heating system 6. Alternatively or in combination with this, an optimization procedure and / or an artificial intelligence algorithm is used, for example, to adjust the first limit value 48 appropriately.

[0062] If the counter 46 is less than the first limit value 48, a fifth step 50 is performed after one second. In this step, the evaporation temperature of the refrigerant is recorded again and compared with the second limit value 32. If the evaporation temperature of the refrigerant remains less than the second limit value 32, the first time duration 38 is adjusted accordingly, namely increased by one second, and then the second step 34 is performed again, i.e., the operating parameters 36 are recorded and the auxiliary values ​​40 are generated. Since one second has passed since the previous execution of the second step 34, the operating parameters 36 and the auxiliary values ​​40 may have changed. In the third step 42, which is then performed again, the time value 44 is recalculated and added to the then valid counter 46.

[0063] If the evaporation temperature of the refrigerant is greater than the second limit value 32, the first time duration 38 in the fourth work step 50 is not extended. However, another counter is incremented by one second. Then the second work step 34 is carried out again.

[0064] The second, third, and fourth steps 34, 42, 50 are essentially repeated continuously. If the evaporation temperature of the refrigerant falls below the second limit value 32 again, the next counter is reset. The first time period 38 is then also extended by one second.

[0065] If, however, the evaporation temperature of the refrigerant is continuously greater than the second limit value 32 for a second time period 52, a fifth operation 54 is carried out. The further counter is used in particular to determine whether the fifth operation 54 is carried out.

[0066] In the fifth step 54, the counter 46 is reset, as is the first time duration 38. The process 28 is then terminated, or, if the compressor 16 continues to operate, the first step 30 is performed again. The first step 30 is then carried out until either the compressor 16 is switched off, or the evaporation temperature of the refrigerant is again below the second limit value 32. In this case, the second step 34 is then performed again.

[0067] However, if the comparison in the third step 42 shows that the counter 46 is greater than the first limit value 48, a sixth step 56 is carried out. In this step, a defrosting procedure for the heat exchanger 14 is performed or at least initiated. This procedure is, for example, a component of procedure 28 or a separate procedure. At a minimum, the heat exchanger 14 is defrosted depending on the comparison of the counter 46 with the first limit value 48. For this purpose, for example, a heating element associated with the heat exchanger 14 is energized, or a reverse cycle is used.

[0068] Advantageously, the individual slopes / shifts of the linear functions used to generate the auxiliary values ​​40, as well as the two limit values ​​32 and 48, and the second time duration 52, are chosen such that the sixth step 56 is only or primarily performed when icing of the heat exchanger 14 has already begun, but has not yet resulted in a significant reduction in efficiency. Advantageously, the sixth step 56 is not performed if no icing is present. In particular, an optimization procedure or an artificial intelligence algorithm, such as a neural network, is used to determine the slopes / shifts of the linear functions, the two limit values ​​32 and 48, and the second time duration 52.

[0069] The invention is not limited to the embodiment described above. Rather, other variants of the invention can also be derived by those skilled in the art without departing from the subject matter of the invention. In particular, all individual features described in connection with the embodiment can also be combined with one another in other ways without departing from the subject matter of the invention. Reference symbol list

[0070] 2 Building 4 Exterior wall 6 Heating system 8 Heat pump 10 Outdoor unit 12 Indoor unit 14 Heat exchanger 16 Compressor 18 Additional heat exchanger 20 Control unit 22 Computer 24 Storage 26 Computer program product 28 Procedure 30 First step 32 Second limit value 34 Second step 36 Operating parameters 38 First duration 40 Auxiliary value 42 Third step 44 Time value 46 Counter 48 First limit value 50 Fourth step 52 Second duration 54 Fifth step 56 Sixth step

Claims

1. Method (28) for operating a heating system (6) of a building (2) comprising a heat pump (8) with a compressor (16) and with a heat exchanger (14) by means of which a refrigerant is circulated, in which - an operating parameter (36) is recorded, - a time value (44) is created on the basis of the operating parameter (36), - the time value (44) is added to a counter (46), and - the counter (46) is compared with a first limit value (48), whereby the heat exchanger (14) is defrosted depending on the comparison.

2. Method (28) according to claim 1, characterized by that Several operating parameters (40) are recorded, each of which is used to create an auxiliary value (40), the auxiliary values ​​(40) being processed together to create the time value (44).

3. Method (28) according to claim 2, characterized by that The auxiliary values ​​(40) are multiplied together.

4. Method (28) according to claim 2 or 3, characterized by that Each auxiliary value (40) is created using a linear function.

5. Method (28) according to any one of claims 1 to 4, characterized by that The operating parameter (36) is a pressure ratio of the refrigerant via the compressor (16).

6. Method (28) according to any one of claims 1 to 5, characterized by that The operating parameter (36) is an operating speed of the compressor (16).

7. Method (28) according to any one of claims 1 to 6, characterized by that The operating parameter (36) is a temperature of the refrigerant at an inlet of the heat exchanger (14) and / or the environment of the heat exchanger (14).

8. Method (28) according to any one of the preceding claims, characterized by that an evaporation temperature of a refrigerant is recorded and compared with a second limit value (32).

9. Method (28) according to claim 8, characterized by that as an operating parameter (36) a first time period (38) is used during which the evaporation temperature of the refrigerant is less than the second limit value (32).

10. Method (28) according to claim 8 or 9, characterized by that the counter (46) is reset if the evaporation temperature of the refrigerant is continuously greater than the second limit (32) for a second period of time (52).

11. Heating system (6) for a building (2) comprising a heat pump (8) with a compressor (16) and with a heat exchanger (14) by means of which a refrigerant is circulated, and which is operated according to a method (28) according to one of claims 1 to 10.

12. Computer program product (26), comprising instructions which, when the program is executed by a computer (22), cause the computer to execute a method (28) according to any one of claims 1 to 10.

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