[01 ] The invention refers to a control method for a hydronic system, to a hydraulic supply unit for a hydronic system and to a hydronic system.

[02] Hydronic systems are for example used for heating and/or cooling of buildings. Usually, they consist of a thermal source like a heat or cooling source and one or more load circuits. The load circuits are connected to the thermal source via a pipe system inside which a liquid heat transfer medium is circulating. In such a system there may be several load circuits having different demands for thermal energy. Thus, it is required to control the transfer of thermal energy from the thermal source to the different load circuits to match the supply of thermal energy to the demand of load circuits.

[03] In those systems it is desired to achieve the highest thermal sufficiency on one side and on the other side to ensure a maximum comfort for the user.

[04] It is the object of the invention to improve the energy efficiency of a hydronic system without reducing the comfort for the user.

[05] This object is achieved by a control method having the features defined in claim 1 , by a hydraulic supply unit having the features defined in claim 14 and by a hydronic system having the features defined in claim 18. Preferred embodiments are defined in the dependent subclaims, the following description and the accompanying drawings. [06] The control method according to the invention is configured for use in a hydronic system being a cooling and/or heating system using a liquid heat transfer medium as for example water. Such a hydronic system comprises at least one thermal source being a heat and/or cooling source supplying thermal energy to the heat transfer medium. In the understanding of this invention thermal energy may be heat or cold. Cold may be regarded as a negative thermal energy transferred from the thermal source, for example a chiller to the heat transfer medium. For cooling the heat transfer medium transfers heat from a load circuit to the thermal source, i.e. transfers cold from the thermal source to the load circuits so that the load circuits may for example cool a part of a building. The hydronic system comprises a hydraulic supply unit which is connected to an outlet of the thermal source and is controlling a supply of heat transfer medium to the at least one load circuit. The control method is used to control the hydraulic supply unit. According to this control method the hydraulic supply unit causes the heat source to adapt the outlet temperature of the heat source if at least one predefined criterion in the hydraulic supply unit is fulfilled. This method allows to adapt the output of thermal energy, i.e. to adapt the outlet temperature of the thermal source such that the efficiency of the hydronic system can be optimized. In prior art systems the thermal source provides a certain outlet temperature of the heat transfer medium, and the hydronic system is controlling the supply to the load circuit on basis of this default temperature. This may result in a too high flow or short duty cycles in the hydronic system, i.e. a reduced thermal efficiency and/or a reduced comfort for the user. By allowing to directly influence the outlet temperature of the thermal source by the hydraulic supply unit a further increase in efficiency and comfort is possible. The hydraulic supply source may for example cause the heat source to set the outlet temperature to a desired value or to shift or offset the outlet temperature by a certain amount. [07] The thermal source may be controlled by a source control. Such a source control may be an electronic control device controlling the operation of the thermal source, in particular controlling the outlet temperature of the thermal source, for example to provide a desired or predefined outlet temperature and/or to keep the outlet temperature in a desired or predefined temperature range. The control device of the source control for example comprises at least one processing unit and storage means configured to execute a control program configured for controlling the thermal source. The electric control device may be connected to sensor means, for example to detect the outlet temperature and/or for example the environmental temperature outdoor. In a possible embodiment the source control may be configured to adjust the outlet temperature based on the outdoor temperature. For example, a predefined setpoint of the outlet temperature is determined on basis of the outdoor temperature by use of a heating curve. The source control for example may be connected to heating and/or cooling means, valves and/or pumps such that by control of these components a temperature, for example the outlet temperature obtains a desired setpoint temperature.

[08] According to a further possible embodiment, the hydraulic supply unit may be controlled by a supply unit control. Such a supply unit control preferably is a control device configured such that it controls the hydraulic devices in the supply unit, for example at least one pump and/or at least one valve. Furthermore, the supply unit control may be connected to one or more sensors configured for controlling the supply unit on basis of sensor signals output by these sensors. Preferably, the supply unit control outputs an offset signal to the source control, which offset signal causes the source control to adapt the outlet temperature or the output of thermal energy, respectively. The offset signal for example may define a desired outlet temperature or a desired shift or offset of the outlet temperature. In a first possible embodiment the source control and the supply unit control are separate control devices, each having own control electronics, for example consisting of a microprocessor, memory and being configured to run a respective control program. The source control and the supply unit control may be arranged distanced from one another and connected via a communication link which may be a wired or wireless connection for data transmission. In an alternative embodiment the source control and the supply unit control may be integrated into one control device and further preferably they may be integrated into one control electronics, for example using the same microprocessor and/or memory. Furthermore, it may be possible to integrate both controls into the same software application. With all these solutions it is possible to adapt the output of thermal energy provided by the thermal source on basis of a control signal resulting or produced from the hydraulic supply unit. Deferring from known systems the hydraulic supply unit is not influenced by the control of the thermal source only, but the hydraulic supply unit in opposite way can influence the thermal source to adapt the output of thermal energy.

[09] According to a further possible embodiment of the method the hydraulic supply unit causes the thermal source to reduce the output of thermal energy if at least one first criterion is fulfilled. Additionally, or alternatively the hydraulic unit causes the thermal source to increase the output of thermal energy if at least one second criterion is fulfilled. The decrease of output of thermal energy in case of a heating may be a reduction of the outlet temperature of the heat transfer medium. In case of cooling the reduction of the output of thermal energy may be an increase of the outlet temperature of the heat transfer medium. In the opposite, the increase of the output of thermal energy may be an increase of the outlet temperature in case of heating and a decrease of the outlet temperature in case of cooling. The first criterion for example may be a flow value. Thus, if the hydraulic supply unit detects a min- imum flow, indicating a reduced demand of thermal energy, the hydraulic supply unit may cause the thermal source to reduce the output of thermal energy which increases the overall efficiency. Furthermore, this for example ensures a continuous flow of heat transfer medium in a load circuit allowing a constant heating or cooling with an improved comfort in the heated or cooled object or building. Under certain operational conditions, however, it may be favorable to adapt the outlet temperature without changing the output of thermal energy. For example, the outlet temperature may be reduced with increasing the flow at the same time to maintain a constant output of thermal energy.

[10] The thermal source may be any suitable thermal source. The thermal source may be a local source or for example a district heating and/or cooling supply which is connected to several users, for example by a hydraulic grid. According to a preferred embodiment the thermal source comprises a compressor-based heating and/or cooling device and preferably a heat pump. For a heat pump it is beneficial to keep the outlet temperature level as low as possible. Therefore, the method according to the invention allows to improve the efficiency, since the hydraulic supply unit causes the control of the thermal source to reduce the outlet temperature if possible and/or to reduce the output of thermal energy, in case that there is a lower demand of thermal energy in the load circuit.

[1 1 ] According to a further possible embodiment the hydraulic supply unit comprises a changeover valve configured for switching a flow of heat transfer medium between at least two different load circuits. These may be different load circuits for heating and/or cooling different parts of a building or an object. Furthermore, one load circuit for example may be a load circuit used for heating domestic hot water via a heat exchanger. These different load circuits may have different demands of thermal energy. The method according to the invention al- lows to easily adapt the output of the thermal source to these different demands of the different load circuits.

[12] The at least one predefined criterion may be a predefined switching position of the aforementioned changeover valve. This allows to cause the thermal source to adapt the outlet temperature and/or the output of thermal energy to match the demands of the respective load circuit activated in the respective switching position of the changeover valve. For example, the output of thermal energy may be increased if the switchover valve is in a position activating a load circuit supplying the heat exchanger for heating domestic hot water.

[13] According to a further possible embodiment an offset signal, preferably an offset signal output by the supply unit control, initiating a decrease of the outlet temperature, is sent to the heat source, preferably to the source control, if the mentioned changeover valve in the hydraulic supply unit activates a low temperature heating circuit. This is a load circuit having a lower supply temperature than another load circuit in the system. By this offset signal the hydraulic supply unit, i.e. a control of the hydraulic supply unit can inform the thermal source to reduce the outlet temperature to match the demand of the heating circuit, which for example may be a floor heating circuit. This allows to automatically reduce the temperature level of the output of the thermal source which in particular is beneficial in case of a heat pump. This avoids not required high temperature levels at the outlet of the thermal source.

[14] According to a further possible embodiment of the method said at least one predefined criterion may be a value representing the current flow through a load circuit. If for example the flow reaches a predefined minimum this is a criterion showing a reduced demand of thermal energy in the respective load circuit allowing to reduce the output of thermal energy from the thermal source, preferably by reducing the outlet temperature. In case of cooling this in an opposite way would mean an increase of the temperature on the outlet side of the thermal source in case that less cooling is required in the load circuit.

[15] The value representing the flow may be a Kv-value calculated on basis of the current flow and pressure detected in the system. The Kv-value is a flow factor Kv which may be calculated according to the following equation

Kv [m ³ /h] = Q [m ³ /h] / ^/Apfhar] wherein Q is the flow rate and Ap is the differential pressure across the device regarded, in this case preferably the load circuit. During set up or system balancing the highest possible Kv-value of the system may be detected and stored. This may be done by the supply unit control. During operation the Kv-value is controlled and may be kept in a window defined by a lower and an upper threshold, for example 60% and 80% of the detected maximum Kv-value. The lower limit of this Kv-value may be a first predefined criterion as discussed above and the upper limit may be the second predefined criterion as explained above. If the Kv- value reaches the lower limit the output of thermal energy of the thermal source, in particular the outlet temperature may be reduced. When reaching the upper limit of the Kv value the thermal output may be increased, i.e. the outlet temperature may be increased. This is the case for a heating system. In a cooling system or during cooling this is the opposite. When reaching the lower Kv-limit value the outlet temperature is increased as a reduction of the output of thermal energy and when reaching the upper limit, the outlet temperature is reduced, which for cooling is an increase in the output of thermal energy. [16] According to a further possible solution a flow value may be derived from a look-up table. The look-up table preferably is set up in advance by measurements in the system, for example when balancing or set up of the system. Preferably the flow value is derived from the lookup table on basis of a detected pressure value and a current operational condition of the circulator pump, for example indicated by the rotational speed or detected electric valves. This may be done by use of the characteristic pump curves of the pump during set up with the maximum opening of the load circuit, a table of values can be detected for different pressures to detect respective curves in a HQ-diagram. During the operation by use of a detected pressure and the curves a flow value for the current operational state can be detected. By knowing the pump characteristics, it can be evaluated whether it is possible to further increase the power or output of the pump to achieve a higher flow. If this is impossible a respective offset signal can be send to the source control to increase the output of thermal energy, for example increase the outlet temperature in case of heating or decrease the outlet temperature in case of cooling. The use of the look-up table is advantageous since it is not necessary to detect the flow during the operation of the hydronic system. It is just sufficient to detect the pressure and to know the operational condition of a pump in the hydronic system, which can be derived from electric values of a drive motor. This allows to simplify the control.

[17] According to a further possible embodiment of the method there is determined a flow value representing the flow through a load circuit. The flow may be measured or detected on basis of electrical values of the pump in knowledge of the pump characteristics and preferably on basis of a detected pressure as described above. The determined flow value is compared with a predefined maximum and an offset signal is sent to the thermal source which initiates an increase of the output of thermal energy if the flow value reaches or exceeds the predefined maximum. The predefined maximum may be a maximum defined by the maximum power of the pump, as described before.

[18] Alternatively, or additionally, it is possible to compare the determined flow value with a predefined minimum and to send an offset signal to the thermal source which initiates a decrease of the output of thermal energy, for example a reduction of the outlet temperature in case of heating or an increase of the outlet temperature in case of cooling, if the flow value reaches or exceeds the predefined minimum. This in particular ensures an improved efficiency of the thermal source, since it can for example be operated with the lowest admissible outlet temperature reducing energy consumption.

[19] Preferably the hydraulic supply unit in which the control method is used comprises a circulator pump which preferably is controlled by the supply unit control. The circulator pump more preferably allows a speed control, for example by use of a frequency converter inside the circulator pump. By controlling, in particular adjusting the speed of the pump it is possible to adjust the pump curve along which the pump is operated (curve in HQ-diagram). This allows in particular to adjust the flow. By adjusting the flow, the amount of heat or thermal energy transferred into the load circuit can be changed or adjusted.

[20] According to a further preferred embodiment the offset signal causes an offset of an outdoor temperature compensation curve used in the source control. This offers a simple way to influence the source control, since the control may be a common source control without requiring substantial changes for implementing the control method according to the invention. Usually, a source control of a thermal source like a heating source uses a heating temperature compensation according to which in case of heating the outlet temperature of the thermal source is increased when the outdoor temperature is lowering. In case of cooling the outlet temperature of the thermal source may be reduced with an increasing outdoor temperature. Thus, the heat source may already have an input for connection to an outdoor temperature sensor. According to a preferred embodiment of the invention the hydraulic supply unit control may receive the temperature signal from an outdoor temperature sensor and the signal may be offset before transmitting it to the source control. In case that according to the invention the output of thermal energy of the thermal source should be increased, the outdoor temperature signal may be offset towards a lower outdoor temperature, i.e. to manipulate the temperature signal such that it presents a lower outlet temperature to the source control as actually measured. This allows to easily offset the output of thermal energy without need of changing the control electronics of the source control.

[21 ] Beside the control method described above a hydraulic supply unit is subject of the present invention. The hydraulic supply unit is in particular configured to carry out a control method according to the preceding description. Preferred embodiments described with reference to the control method should therefore be regarded as preferred embodiments of the hydraulic supply unit, too. Vice versa, preferred embodiments described with reference to the hydraulic supply unit in the following should also be regarded as preferred embodiments of the control method as described above. The hydraulic supply unit is configured for supply of a heat transfer medium from a thermal source to at least one load circuit. The thermal source may be a heating and/or cooling source and thermal energy is transferred from the thermal source to the load circuit by circulating the heat transfer medium which for example may be water, glycol or any other suitable heat transfer medium. The thermal energy in the meaning of this application shall be heat and/or cold, although in case of cooling actually heat is trans- ferred from the load circuit to the thermal source being a cooling device, for example a chiller. Nevertheless, in this application in case of cooling the transfer of thermal energy is described as a transfer of cold from the thermal source towards the loaf circuit for an easier understanding.

[22] The hydraulic supply unit is a device arranged between the thermal source and the least one load circuit and is configured to supply and in particular to control the supply of the heat transfer medium from the hydraulic supply unit to the at least one load circuit. In special embodiments the hydraulic supply unit may be configured to distribute the heat transfer medium between several load circuits and/or to adjust the flow of the heat transfer medium through the at least one load circuit. By control of the hydraulic supply unit, therefore, preferably the amount of heat or thermal energy, respectively, transferred between the thermal source and the at least one load circuit can be adjusted. The supply unit comprises a supply unit control device which is configured for controlling the hydraulic supply unit and being configured such that it outputs an offset signal recommending an adaption of an outlet temperature, i.e. an adaption of the output of thermal energy, of the heat source if at least one predefined criterion in the hydraulic supply unit is fulfilled. The offset signal may be a signal which represents an information concerning the energy demand of the hydraulic supply unit. The thermal source may comprise a source control device configured to further process the received signal and finally making the decision whether to adapt the output of thermal energy, to adapt the outlet temperature of the thermal source. Alternatively, the signal recommending the adaption of the outlet temperature may be a command initiating the adaption of the output of thermal energy, preferably also defining the amount of adaption of the outlet temperature. By this the supply unit control device can partly take over the control of the ther- mal source by influencing the outlet temperature and adapting the outlet temperature to the demands of the at least one load circuit.

[23] The hydraulic supply unit may comprise at least one circulator pump and/or at least one changeover valve. The at least one circulator pump is configured to provide a flow of the heat transfer medium through the at least one load circuit and preferably between the thermal source and the least one load circuit. Preferably the circulator pump is a speed controlled circulator pump allowing to change the flow depending on the demands of heat transfer. The circulator pump preferably is controlled by the supply unit control device. The supply unit control device may be a control device integrated with the control device of the circulator pump, i.e. the supply unit control device preferably is a software application running on the control electronics of the pump device, the control electronics in particular comprising at least one microprocessor and for example necessary storage means. The entire control electronics according to a further preferred embodiment may be integrated into an electronics housing directly attached to the circulator pump and/or integrated into a motor housing of the circulator pump.

[24] A changeover valve for example may be used to change the fluid flow between several load circuits and further preferably to adjust the fluid flow through the different load circuits. The changeover valve may be activated or controlled by the supply unit control device. The changeover valve may comprise a valve drive which is connected to the supply unit control device and can be activated by the supply unit control device. In a special embodiment the changeover valve may be a changeover valve which is hydraulically activated by the fluid flow produced by the circulator pump. This allows to change the position of the changeover valve by a special control of the circulator pump which is carried out by the supply unit control device and/or a control device of the circulator pump. Such a hydraulically activated changeover valve is for example known from EP 3 376 037 Bl . Preferably the changeover valve is configured such that it opens several load circuits in an alternating manner such that, preferably, only one load circuit is activated at the same time. According to a further possible embodiment at least one port of the changeover valve may be connected to a manifold which is connected with several load circuits, for example circuits of an underfloor heating system.

[25] According to a further possible embodiment the supply unit control device is configured such that the at least one criterion as described before is a switching position of the changeover valve and/or a value representing the current flow through a load circuit. The use of the switching position as a criterion allows to adjust the outlet temperature of the thermal source to the specific according the demand of the respective load circuit. For example, the load circuits may require different temperatures of the heat transfer medium. The temperature can be adapted by a mixing device, preferably, included in the hydraulic supply unit and mixing a part of a return flow to the feed flow. Thus, according to a preferred embodiment a mixing device is integrated into the hydraulic supply unit. Furthermore, the supply unit control device preferably is configured to control the mixing device, too. However, beside adjusting the temperature by use of a mixing device or in addition to adjust the temperature by use of a mixing device the supply unit control device can initiate to amend the outlet temperature of the heat source by sending a respective signal to the thermal source. By this the thermal efficiency can be improved since it is of course advantageous if the thermal source provides an outlet temperature which matches to the demand of the activated load circuit. For example, one load circuit may be a floor heating circuit whereas a second load circuit is a heating circuit having radiators. In a floor heating circuit usu- ally a reduced temperature of the heat transfer medium is used compared to the load circuit comprising radiators.

[26] If the at least one first criterion is a value representing the current flow this allows an adaption of the outlet temperature of the thermal source to the current demands of the activated load circuit. As described before the supply unit control device may control the heat transfer towards the activated load circuit by adjusting the flow. For example, if the demand for thermal energy of the activated load circuit decreases, the supply unit control device would decrease the flow of heat transfer mediums through the respective load circuit. If the flow reaches a minimum this may be a first criterion. When this criterion is reached the supply unit control device preferably sends a signal towards the thermal source or the source control device, respectively recommending an adaption of the outlet temperature, for example a reduction of the outlet temperature in case of heating. This may be achieved by an offset signal.

[27] According to a further possible embodiment the supply unit control device is configured such that an offset signal recommending or commanding a decrease of the outlet temperature is sent to thermal source if the changeover valve is in a switching position activating a port provided for a heating circuit requiring a lower temperature, for example a floor heating circuit, as described before. Alternatively, the offset signal may recommend or demand an increase of an output of thermal energy, i.e. an increase of the outlet temperature for example, if a flow in the supply unit reaches or exceeds a predefined maximum. If the flow reaches the predefined maximum, this may for example be the maximum flow which can be provided by the circulator pump. The maximum flow defines a maximum of energy transfer at a given temperature. Therefore, the offset signal initiating an increase of an output of thermal energy allows to further increase the transfer of thermal en- ergy by amending the temperature level of the heat transfer medium. In case of heating this is an increase of the temperature. In case of cooling this is a decrease of temperature.

[28] Furthermore, a hydronic system comprising a hydraulic supply unit as described before is subject of the present invention. In addition to the described hydraulic supply unit the hydronic system comprises at least one thermal source, preferably at least one heat pump. Further preferably the hydronic system comprises at least one load circuit. The thermal source comprises a source control device connected with a supply unit control device via a communication link. The source control device is configured to adapt the outlet temperature of the thermal source, i.e. to adapt the output of thermal energy, in response to the offset or control signal received from the supply unit control device, as for example described before. The source control device may be a separate control device having control electronics separate from the control electronics of the supply unit control device. Furthermore, both control devices may be arranged distanced from one another, and the communication link can be wired or a wireless connection between both. In an alternative embodiment the supply unit control device and the source control device may be at least partly integrated, i.e. at least partly using the same control electronics. In a special embodiment both the source control and the supply unit control may be set up as software programs running on the same control electronics, for example control electronics dedicated to the source control. Nevertheless, according to a preferred solution the supply unit control device is a separate control device allowing to adjust the outlet temperature of a thermal source having a conventional separate control device. This allows the use of a hydraulic supply unit offering the improved control method as described above in combination with a conventional thermal source, wherein preferably no changes of the control electronics and control software of the thermal source are required. [29] As described above one simple way to adapt the outlet temperature of the thermal source is to manipulate or change an outdoor temperature compensation curve, in particular to change an outdoor temperature signal supplied to the thermal source. Thus, preferably the source control device is configured to offset an outdoor temperature compensation curve in response to the offset signal received from the supply unit control device. This may be done by special control steps incorporated into the control program of the source control. However, this may be realized by just changing or manipulating the signal received from an outdoor temperature sensor. For this the signal may be processed in the supply unit control device. For further details it is referred to the above-mentioned description concerning the control method.

[30] In the following the invention is described by way of example with reference to the accompanying drawings. In these:

Fig. 1 shows a diagram of a hydronic system according to the invention,

Fig. 2 shows a flow chart of a first example of a control method according to the invention, and

Fig. 3 shows a flow chart of a second example of a control method according to the invention.

[31 ] Fig. 1 shows an example of a hydronic system in form of a heating system. The system comprises a thermal source, in this example a heat pump 2, a first load circuit 4, in this case a radiator heating circuit, and a second load circuit 6, in this example a floor heating circuit. For supplying the first load circuit 4 and the second load circuit 6 with thermal energy delivered by the heat pump 2, there is arranged a hydraulic device, i.e. an integrated hydraulic supply unit 8. The thermal energy is transferred via a heat transfer medium circulating in the hydronic system and transferred and distributed by the hydraulic supply unit 8, which comprises a circulator pump 10 with a control unit or control device 12, which serves as a supply unit control device. The circulator pump 10 circulates the heat transfer medium in the hydronic system. The control device 12 is arranged in a motor or electronics housing attached to the circulator pump 10, i.e. to the pump housing of the circulator pump 10. Furthermore, the hydraulic supply unit 8 comprises a changeover valve 16 and a mixing valve 18. The changeover valve 16 and the mixing valve 18 are controlled by the control device 12, which is provided for control of the circulator pump 10, too. The hydraulic supply unit 8 in this example comprises six hydraulic connections or ports A-F. A first hydraulic connection A and a second hydraulic connection B are connected with a changeover valve 16 which can selectively connect one of the connections A and B with the inlet or suction side of the circulator pump 10. In this example the first hydraulic connection A is a return for the second load circuit 6, whereas the hydraulic connection B acts as a return port for the first load circuit 4. The third hydraulic connection or port C is an inlet port connected to the heat pump 2, i. e. is a feed connection through which hot heat transfer medium, like water, enters the hydraulic supply unit 8. The fourth hydraulic connection D is a feed connection connected to the inlet side of the second load circuit 6. The fifth hydraulic connection or port E is a feed connection for the first load circuit 4 and the sixth hydraulic connection F is a return connection connected to a return line towards the heat pump 2.

[32] Inside the hydraulic supply unit 8 there is a flow path 20 directly connecting the two hydraulic connections C and E allowing a direct fluid flow from the outlet side of the heat pump 2 towards the feed or inlet side of the first load circuit 4. The mixing valve 18 is connected to the hydraulic connection C, too, and on its outlet side connected to the hydraulic connection D being a feed connection for the second load circuit 6. There is a further flow path 22 connecting the outlet or pressure side of the circulator pump 10 with the third port of the mixing valve 18. Via this flow path 22 heat transfer medium from the return of the load circuits 4, 6 flows towards the mixing valve 18. Inside the mixing valve a flow from the flow path 22 and a flow from the hydraulic connection C are mixed to reduce the temperature of the fluid entering via port C and to provide a reduced temperature of heat transfer medium at the hydraulic connection or port D, i. e. the feed towards the second load circuit 6, which in this example is a floor heating circuit. The mixing ratio achieved by the mixing valve 18 is adjusted by the control device 12 connected to an actor 24, for example a thermoelectric actor moving or adjusting the mixing valve 18. The changeover valve 16 is controlled by the control device 12, too, either by an electric actor integrated into or attached to the changeover valve 16 or hydraulically via pressure and/or flow produced by the circulator pump 10. The changeover valve 16 depending on its valve or switching position either activates a fluid flow through the first load circuit 4 or through the second load circuit 6 by opening the respective return connection.

[33] For the control in this example, there are provided three temperature sensors Ti, T2, and T3. Furthermore, there is a flow detection means or flow sensor S integrated into the circulator pump 10. All the sensors are connected to the control device 12 so that the control device 12 can control the actors and the circulator pump 10 based on values detected by these sensors.

[34] The temperature sensor T 1 detects the supply temperature for the first load circuit 4. The temperature sensor T2 detects the supply temperature for the second load circuit 6 and the third temperature sensor Ts detects the return temperature from the load circuit 4 or 6, depending on the switching position of the changeover valve 16. Furthermore, the control device 12 detects the flow provided by the circulator pump 10. This may be done by a separate flow sensor or the flow S can be derived from electrical parameters detected in the pump 10. On basis of the inlet temperature and the outlet temperature and the flow the control device 12 calculates the energy demand, i.e. the actual and current energy demand of the activated load circuit 4 or 6. In particular the control device 12 controls the speed of the circulator pump 10 to adjust the flow through the load circuits 4 and 6 to change the amount of thermal energy supplied to the load circuit.

[35] To further control and adjust the thermal energy amount supplied to the load circuits the supply unit control 12 according to the invention sends an offset signal to the thermal source 2. The thermal source 2 comprises a source control device 26 including control electronics like a microprocessor, storage means and further required electronics components. The source control device 26 is configured for control of the thermal source 2 by use of respective control software or algorithms processed in said control electronic. There is provided a communication link 28 between the supply unit control device 12 and the source control device 26 which may be a wired or wireless connection. In this example the source control device 26, furthermore is connected to an outdoor temperature To detecting the outdoor temperature To and performing an outdoor temperature compensation on basis of the current outdoor temperature. This outdoor temperature compensation may be carried out on basis of a heat curve in known manner.

[36] On basis of an offset signal sent from the supply unit control device 12 to the source control device 26, the source control device 26 adapts the outlet temperature of the heat transfer medium entering the hydraulic unit 8 at port 10. By this adjustment the thermal energy output from the thermal source 2 is adjusted. This can be done by offsetting the outdoor temperature compensation mentioned before.

[37] The supply unit control device 12 may initiate an adjustment of the outlet temperature of the thermal source 2 for example depending on the switching position of the changeover valve 16 or depending on the flow through the load circuits 4 and/or 6. Examples for this are explained in more detail with reference to figures 2 and 3.

[38] A first possible control strategy based on the switching positions of the changeover valve 16 is described with reference to figure 2. In step SI the control is paused for a certain interval. In step S2 the supply temperature is set according to an outdoor temperature, for example detected by the outdoor temperature sensor To. In step S3 it is evaluated whether the outdoor temperature To is below a certain threshold, for example below minus 5 degree. If yes, the temperature set in step S2 is unchanged and the set point is finalized in step E and the heat pump 2 and, in particular its compressor is controlled accordingly. If the result of the evaluation in step S3 is No, i.e. the outdoor temperature is above the threshold, in step S4 the switching position of the changeover valve 16 is evaluated. If it is a first switching position A opening the hydraulic connection A and activating the floor heating circuit in step S5 an offset signal is created, initiating a reduction of the outlet temperature of the heat pump 2 to reduce the temperature level to avoid an unnecessary high mixing ratio in the mixing valve 18. In the following the set temperature in step E is finalized and send to the compressor for respective control of the compressor. The steps S3 to S5 may be carried out by the supply unit control device 12 whereas the control according to step SI, S2 and E may be carried out by the source control device 26. In case the evaluation in step S4 detects the changeover valve 16 being in the second switching position opening the hydraulic port B and activating the load circuit 4 having radiators, no offset signal is sent out and the heat pump 2 is controlled on basis of the temperature defined in step S2.

[39] According to figure 3 a further control strategy is described according to which an offset signal is produced based on a Kv-value or a flow detected in the hydronic system. In step Al the control is paused for a certain interval to stabilize the control. In step A2 the switching position of the changeover valve 16 is evaluated. If the changeover valve 16 is in a first switching position A activating the second load circuit 6 being a floor heating circuit in this control strategy no change of the set point is initiated. In this case, in step E the current set point is finalized and the control of the heat pump 2 is unchanged. In case that the switching position of the changeover valve 16 is the second switching position B opening the hydraulic port B and activating the first load circuit 4 having radiators, it is further evaluated whether a change of the switching position occurred or whether the changeover valve 16 has been in the second switching position before. In case that there is no change in step A3 the set point is maintained without change. In case that there has been a changed from the fist switching position to the second switching position in step A4 the supply temperature of the heat transfer medium is changed to an initial supply temperature used for the radiator load circuit 4, i.e. in case of heating the supply temperature is increased to the initial higher temperature. In step A5 the supply temperature set point is checked. In case that the set point is below a predefined minimum threshold in step A6 the supply temperature is set to a predefined minimum supply temperature. In case that the supply temperature set point has reached or exceeds a maximum threshold in step S7 the set point is set to the maximum temperature allowed.

[40] In case the set point is between a minimum and maximum threshold in step A8 and in case the flow reaches a predefined maximum threshold for example the upper third of the allowable flow range, in step A9 the temperature set point is increased by a predefined temperature step, for example 0.5° C. In case that the actual flow detected for example by a flow sensor S has reached a minimum flow, i.e. a predefined minimum threshold (for example the lower third of the allowable range) in step A10 the temperature set point is reduced by a predefined step, i.e. fixed temperature value, for example 0.5° C. In case that the current flow, as for example detected by flow sensor S is between minimum and maximum in to step Al 1 the temperature set point is maintained.

[41 ] The change of the temperature set point may be achieved by sending an offset signal to the source control 26 which for example offsets the outdoor temperature compensation. In case that a maximum flow, i.e. a maximum threshold for the flow, is reached it is beneficial to increase the outlet temperature of the heat pump 2 to increase the output of thermal energy to ensure a sufficient supply of thermal energy to the respective load circuit. In case that a minimum flow has been reached, to increase the efficiency, it is beneficial to reduce to output of thermal energy from the heat pump 2 by reducing the outlet temperature. As describe, a current flow is regarded in step A8. This may be done on basis of a look-up table 30 or a direct measurement of the flow. Alternatively, it would be possible to carry out the evaluation on basis of a Kv-value derived in the system.

[42] In the foregoing the control strategies have been described for a heating system. However, the same control strategies may be applied for a cooling system with the difference that instead of increasing a temperature the temperature is decreased and vice versa. List of reference numerals

2 heat pump

4 first load circuit

6 second load circuit

8 hydraulic supply unit

10 circulator pump

12 supply unit control device

16 changeover valve

18 mixing valve

20 flow path

22 flow path

24 actor

26 source control device

28 communication link

30 look-up table

Al to Al l method steps

SI to S5 method steps

E step for finalizing setpoint

To outdoor temperature sensor

TI, T ₂ , T3 temperature sensors

A to F hydraulic ports