A method for controlling a mixing system for a hydronic system, a mixing system for a hydronic system and a hydronic system

Abstract

Disclosed and claimed is a method for controlling a mixing system (9) for a hydronic system. The mixing system (9) comprises a supply line (13), a return line (15) and a bypass line (17) connecting the return line (15) to the supply line (13). On the primary side of the mixing system (9) a two-way-valve is provided for controlling a supply flow from a supply unit (3) of the hydronic system (1) to a load (5) of the hydronic system. The secondary side of the mixing system (9) comprises as circulation pump (27) controlling flow through the load (5). When the supply valve (23) is fully opened and the consumer temperature of the outlet flow to the load (5) cannot be maintained at a target temperature, the circulation pump (27) decreases the outlet flow to increase the consumer temperature back to the target temperature. Further, a mixing system (9) for a hydronic system (1) as well as a hydronic system (1) are described and claimed.

Description

[0001] Applicant: GRUNDFOS HOLDING A / S

[0002] Title: A method for controlling a mixing system for a hydronic system, a mixing system for a hydronic system and a hydronic system

[0003] Our Ref.: GP 3815 WO

[0004] Description

[0005]

[0001] The present invention is directed to a method for controlling a mixing system for a hydronic system. The invention is further directed to a mixing system for a hydronic system as well as a hydronic system comprising a corresponding mixing system.

[0006] 5

[0002] Mixing systems or mixing loops are used in heating and cooling applications to control the temperature in different zones of a building. A mixing system is generally made up of a supply line, a return line, and a bypass line. The supply line enables a flow from a source or a supply unit to at least one consumer circuit or load. The supply unit may, for ex10 ample, be a boiler providing a heated heat transfer medium ora cooling unit providing a cold heat transfer medium. The at least one consumer circuit may, for example, be a set of radiators, an underfloor heating unit, heat exchangers of air handling units, or another set of devices for distributing the energy transferred using the heat transfer medium in one or more rooms of a building. A return flow from the at least one consumer circuit to the supply unit flows through the return line. The temperature of the heat transfer medium flowing through the supply line can be modified using the bypass line which allows to mix at least part of the return flow coming from the at least one consumer circuit with the supply flow 20 from the supply unit.

[0007]

[0003] The second type of the mixing system employs a two-way valve either on the supply line between the supply unit and the bypass line or

[0008] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 on the return line between the bypass line and the supply unit. The two- way valve is used to actively control the amount of heat transfer fluid supplied from the supply unit to the at least one consumer circuit. The contribution of heat transfer medium taken from the bypass line is not 5 actively or directly regulated. Subsequently, the flow of heat transfer medium between the supply unit and the bypass line will also be referred to as the supply flow, the flow through the bypass line will be referred to as the bypass flow and the combined flow to the at least one consumer circuit will be referred to as the forward or outlet flow.

[0009] 10

[0004] For maintaining the outlet flow, a supply pressure is required on a secondary side of the mixing system. The secondary side of the mixing system is formed by the supply line between the bypass line and the at least one consumer circuit as well as the return line between the at least one consumer circuit and the bypass line. Correspondingly, the primary side of the mixing system is formed by the supply line between the supply unit and the bypass line as well as the return line between the bypass line and the supply unit. The supply pressure in the secondary side of the mixing system can, for example, be maintained using a pump that is placed on the secondary side of the supply line or the secondary side of the 20 return line. In other words, the pump either pressurizes the outlet flow between the bypass line and the at least one consumer circuit or an inlet flow between the at least one consumer circuit and the bypass line.

[0010]

[0005] The mixing system is mainly controlled using a temperature sensor which senses the temperature of the outlet flow. Conventionally, when the temperature is lower than a target temperature, the supply valve provided on the primary side of the mixing system will be opened further to increase the supply flow and provide the required additional heating or cooling power. However, in some cases a supply pressure at which the supply flow is provided by supply unit may be too low. Opening up the 30 supply valve might not increase the supply flow to the level there the target temperature can be met in the outlet flow. This can lead to a so- Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 called temperature collapse as possible controllers at the load will call for more flow which will increase the flow through the bypass line. In consequence, the consumer temperature deviates even further from the target temperature and the mixing system enters a vicious cycle which will 5 eventually lead to a lack of heating or cooling power in the at least one consumer circuit.

[0011]

[0006] In view of the above it can be considered an object of the present invention to provide an improved method for controlling a mixing system, an improved mixing system as well as an improved hydronic system com10 prising a mixing system reducing at least some of the problems identified above.

[0012]

[0007] The problem is solved using a method for controlling a mixing system for a hydronic system, a mixing system for a hydronic system as well as a hydronic system according to the independent claims. Preferred 15 embodiments of the method for controlling a mixing system as well as of the mixing system are the subject matter of the dependent claims.

[0013]

[0008] In a first aspect, the invention is directed to a method for controlling a mixing system for a hydronic system. The mixing system comprises a supply line enabling a flow from a supply unit to at least one consumer 20 circuit, a return line enabling a flow from the at least one consumer circuit to the supply unit, and a bypass line enabling a flow from the return line to the supply line. A primary side of the mixing system is formed by the supply line between the supply unit and the bypass line as well as the return line between the bypass line and the supply unit. A secondary side of the mixing system is formed by the supply line between the bypass line and the at least one consumer circuit as well as the return line between the at least one consumer circuit and the bypass line. A contribution of a supply flow from the supply unit via the primary side of the supply line to an outlet flow of the secondary side of the supply line can be con30 trolled by a supply valve placed in the primary side of the mixing system. Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 The outlet flow can be controlled by a circulation pump placed in the secondary side of the mixing system. A temperature sensor for sensing a consumer temperature is placed on the secondary side of the supply line or in the at least one consumer circuit. Preferably, the consumer temper5 ature is sensed in the outlet flow. The circulation pump decreases the outlet flow for reducing a deviation of the consumer temperature deviates from a target temperature, if the supply valve is open up to or beyond a supply threshold, and if a deviation of the consumer temperature from the target temperature cannot be compensated by further open10 ing or by closing the supply valve or shall at least in its entirety not be compensated by further opening the supply valve.

[0014]

[0009] In other words, a method is disclosed for controlling a mixing system which comprises a two-way valve for controlling the contribution of a supply flow from a supply unit which is placed in a primary side of the mixing system. The supply unit may also be simply referred to as a source. The primary side of the mixing system comprises the supply line extending between the supply unit and the bypass line as well as the return line between the bypass line and the supply unit. The supply valve can be placed either in the supply line or in the return line, i.e., it can be used to 20 control either the supply flow from the supply unit or the return flow to the supply unit.

[0015]

[0010] The method is suitable both for heating systems as well as cooling systems. Thus, the supply unit can either be a heat source supplying a heat transfer medium that has been heated or a cooling unit supplying a heat transfer medium that has been cooled. For example, the heating unit may be a gas boiler, an oil boiler, ora heat pump. The cooling system may, for example, be a heat exchanger of an air conditioning system.

[0016]

[0011] The mixing system further comprises a secondary side formed by the part of the supply line extending between the bypass line and the at 30 least one consumer circuit as well as the return line between the at least Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 one consumer circuit and the bypass line. Examples of consumer circuits are space heating systems, conventional radiator systems, underfloor heating systems, or heat exchanger in air handling units. The consumer circuits may also be referred to as the load of the mixing system. In the 5 secondary side of the mixing system a circulation pump is provided. The circulation pump may, for example, be a centrifugal pump which can be placed either in the secondary side of the supply line, i.e., between the bypass line and the at least one consumer circuit or in the secondary side of the return line, i.e., between the at least consumer circuit and the 10 bypass line. The circulation pump pressurizes the flow through the secondary side of the mixing system. The terms primary side and primary part as well as secondary side and secondary part are used synonymously.

[0017]

[0012] Furthermore, the mixing system comprises a temperature sensor which is placed either on the secondary side of the supply line or in the at least one consumer circuit. The temperature sensor is used to determine a consumer temperature. The consumer temperature is preferably measured in a forward or outlet flow, i.e. between the bypass line and the at least one consumer circuit, but may alternatively also be measured directly in the at least one consumer circuit or be an air temperature 20 in an air handling unit. For example, the consumer temperature may be measured in an outlet air flow of a space heating system or may be a room temperature measured in a room supplied by an underfloor heating system or a conventional radiator.

[0018]

[0013] According to the method, both the opening of the supply valve as well as the operation of the circulation pump are controlled to minimize a deviation of the consumer temperature from a target temperature. The method particularly addresses the case where for reducing the difference between the consumer temperature and the target temperature, the supply valve would commonly be opened further but opening 30 the control valve further is not possible because the valve has already been fully opened or at least been opened to a supply threshold that Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 shall not be exceeded. Alternatively, a situation may arise where a further opening of the supply valve would be possible, however, the temperature difference shall not be solely compensated by further opening the supply valve. This situation arises when the consumer temperature is 5 below the target temperature in a heating system or when the consumer temperature is above the target temperature in a cooling system. The method does not address the case where the deviation between the consumer temperature and the target temperature can be resolved by closing the supply valve at least partially, i.e., when the target tempera10 ture is below the consumer temperature in a heating system or when the target temperature is above the consumer temperature in a cooling system.

[0019]

[0014] In the present embodiment, the circulation pump advantageously reduces the outlet flow to reduce the deviation of the consumer temperature from the target temperature. Reducing the outlet flow while keeping the supply valve at its current position or opening it up even further advantageously maintains the supply pressure of the heat transfer medium from the supply unit while reducing the flow through the bypass line. Thereby, the relative contribution of the supply flow from the supply 20 unit to the outlet flow compared to the relative contribution of the bypass flow to the outlet flow increases. In turn, the deviation of the consumer temperature from the target temperature is advantageously reduced. For example, in case the mixing system is part of a heating system, reducing the outlet flow results in an increase of the consumer temperature as the relative contribution of the hotter supply flow increases. Correspondingly, in case the mixing system is part of a cooling system, reducing the outlet flow results in a reduction of the consumer temperature as the contribution of the cooler supply flow from the supply source increases. The method according to the present invention thus advanta30 geously allows to avoid the so-called temperature collapse or low Delta-

[0020] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 T-Syndrome by actively controlling the circulation pump in the secondary side of the mixing system.

[0021]

[0015] In a preferred embodiment, the supply threshold corresponds to a supply valve being open to 80%. Preferably, the supply threshold cor5 responds to the supply valve being open to 90%. Further preferably, the supply threshold corresponds to the supply valve being completely open.

[0022]

[0016] The preferred embodiment includes several preferred valve positions for the supply valve referred to as supply thresholds. If the respective 10 supply threshold is exceeded, and the deviation between the consumer temperature and the target temperature would commonly be reduced by further increasing the valve opening, the present method reduces the outlet flow by turning down the operation of the circulation pump in the secondary side of the mixing system. The operation of the circulation pump may, for example, be turned down by shifting a pressure setpoint or a flow setpoint in a pump controller but will eventually result in a reduction of the pump speed. In many mixing systems, opening the supply valve fully will result in the best performance. However, in certain mixing system, it may be advantageous to already commence reducing the 20 outlet flow provided by the circulation pump when the supply valve has only been opened to 90% or even when the supply valve has only been opened to 80%. For the sake of completeness, it is noted that reducing the outlet flow provided by the circulation pump can in the latter embodiment be accompanied by further opening of the supply valve.

[0023]

[0017] In a further preferred embodiment, in case that the consumer temperature deviates from the target temperature, the supply valve is opened up to a supply threshold to compensate deviations of the consumer temperature from the target temperature. The circulation pump decreases the outlet flow in order to reduce the deviation of the con30 sumer temperature from the target temperature if the deviation of the Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 consumer temperature from the target temperature can or shall not be compensated by further opening the supply valve. Hence, in the preferred embodiment the deviation between the consumer temperature and the target temperature is solely compensated by reducing the out5 let flow provided by the circulation pump once the outlet valve has been opened up to the supply threshold.

[0024]

[0018] In a further preferred embodiment, the supply valve and the circulation pump are controlled using the same temperature control signal but different temperature control functions. Thus, in the preferred em10 bodiment, a temperature control signal is derived from the deviation of the consumer temperature from the target temperature. This single temperature control signal is used to control both the opening of the supply valve as well as the operation of the circulation pump by using different control functions that both use the temperature control signal as an input. Using the same temperature control signal to control both the operation of the supply valve as well as of the circulation pump advantageously simplifies the operation of the mixing system and also ensures that the supply valve and the circulation pump are controlled on the basis of the same variable. This avoids complications in case the supply 20 valve and the circulation pump would be controlled using different input signals which may not also be linked to each other and could result in competing behaviors of the controlled appliances.

[0025]

[0019] Preferably, the temperature control function for the supply valve controls the opening of the supply valves up to the supply threshold as a function of the temperature control signal and keeps the opening constant when the opening of the supply valve has reached the supply threshold. Preferably, the valve position xpdefining the opening of the supply valve is given by the temperature control function xp= g(u) with u < 1 when the opening of the supply valve is below the supply threshold 30 and xp= gmaxwith u > 1 when the opening of the supply valve is at the

[0026] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 supply threshold. Here, u is the temperature control signal, g(u) is the function defining the relationship between the temperature control signal and the opening of the supply valve, and gmaxis the supply threshold. g(u) may, for example, describe a linear relationship. However, other re5 lationships may be possible as g(u) depends on the application and the valve design.

[0027]

[0020] In other words, in the preferred embodiment a temperature control function is used for the supply valve that is split in two parts with the transition from one part to the other part occurring when the opening of 10 the supply valve has reached the supply threshold. In the preferred embodiment, the supply threshold is reached when the temperature control signal u > 1. As long as the temperature control signal is below 1, the opening of the supply valve xpfollows the preferably linear function g(u). Once u has reached 1, the opening of the supply valve is kept constant.

[0028]

[0021] Preferably, the temperature control function for the circulation pump keeps the outlet flow constant when the opening of the supply valve is below the supply threshold and reduces the outlet flow as a function of the temperature control signal when the opening of the supply valve has reached the supply threshold. Further preferably, in case the 20 circulation pump operates in a flow control mode with flows kept constant or in a constant speed mode, the pump control signal a controlling the operation of the circulation pump is given by the temperature control function a = 1 when the opening of the supply valve is below the supply threshold and a = 1 / u with u > 1 when the opening of the supply valve is at or above the supply threshold. Again, u is the temperature control signal. Alternatively, in case the circulation pump operates in a pressure control mode where the pressure of the circulation pump is kept constant or in a proportional pressure mode, the pump control signal a controlling the operation of the circulation pump is preferably given by 30 the temperature control function a = 1 when the opening of the supply

[0029] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 valve is below the supply threshold and a = 1 / u2with u > 1 when the opening of the supply valve is at or above the supply threshold.

[0030]

[0022] Hence, in the preferred embodiment the temperature control function for the circulation pump operates on the basis of the same tem5 perature control signal as the temperature control function for the supply valve. As is the case for the supply valve control function, the pump control function is split in two parts with the split between the two parts being defined by the point where the supply valve has been opened up to the supply threshold. Below the value of the temperature control signal at 10 which the supply valve reaches the supply threshold, the circulation pump keeps the outlet flow constant. When the temperature control signal reaches the value at which the supply valve reaches the supply threshold, the outlet flow is reduced as a function of the temperature control signal. Preferably, the temperature control signal is scaled or defined in a way, that the supply valves reaches the supply threshold when the temperature control signal reaches 1. In consequence, the outlet flow is kept constant if the temperature control signal u is below 1 and reduced if the temperature control signal exceeds 1.

[0031]

[0023] In the exemplary preferred embodiment, the temperature control 20 function a is constant, for example, equal to 1 while the temperature control signal is below 1 and corresponds to 1 / u or 1 / u2when the temperature control signal is greater than 1. The control function a = 1 / u is used in case the circulation pump operates in a flow control mode where the flow is kept constant or in a constant speed mode. In case the 25 circulation pump operates in a constant pressure mode ora proportional pressure mode, which are together referred to as pressure control modes, the temperature control function for the circulation pump corresponds to 1 / u2. The pump manipulation signal can either be a scaled version of the pressure reference ora set point influence signal.

[0032] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025

[0024] In a preferred embodiment, the hydronic system is operated as a heating system. In this case the circulation pump decreases the outlet flow to reduce the deviation of the consumer temperature from the target temperature if the consumer temperature is below the target tem5 perature. Alternatively, the hydronic system is operated as a cooling system. In this case, the circulation pump decreases the outlet flow to reduce the deviation of the consumer temperature from the target temperature of the consumer temperature is above the target temperature.

[0033]

[0025] In a second aspect, the present invention is directed to a mixing system for a hydronic system. The mixing system comprises a supply line for enabling a flow from a supply unit to the at last one consumer circuit, a return line for enabling a flow from the at least one consumer circuit to the supply unit, and a bypass line for enabling a flow from the return line to the supply line. A primary side of the mixing system is formed by the 15 supply line between the supply unit and the bypass line as well as the return line between the bypass line and the supply unit. A secondary side of the mixing system is formed by the supply line between the bypass line and the at least one consumer circuit as well as the return line between the at least one consumer circuit and the bypass line. A supply valve 20 located in the primary side of the mixing system is configured for controlling a contribution office by other primary side of the supply line to an outlet flow in the secondary side of the supply line. A circulation pump located in the secondary side of the mixing system is configured for at least partially controlling the outlet flow. A temperature sensor located on the secondary side of the supply line or in the at least one consumer circuit is configured for sensing a consumer temperature. The consumer temperature is preferably sensed in the outlet flow. The system further comprises further a control unit. The control unit is configured to instruct the circulation pump to decrease the outlet flow in order to reduce a 30 deviation of the consumer temperature from a target temperature, if the

[0034] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 consumer temperature deviates from the target temperature, if the supply valves is opened up to or beyond a supply threshold, and if the deviation of the consumer temperature from the target temperature cannot be compensated by further opening or closing the supply valve or shall 5 at least in its entirety not be compensated by further opening the supply valve.

[0035]

[0026] Preferably, the supply threshold corresponds to the supply valve being open to 80%. Preferably, the supply threshold corresponds to the supply valve being open to 90%. Further preferably, the supply threshold 10 corresponds to the supply valve being completely open.

[0036]

[0027] In case the consumer temperature deviates from the target temperature, the control unit is configured to instruct the supply valve to open up to a supply threshold to compensate deviations of the consumer temperature from the target temperature. The control unit is fur15 ther configured to instruct the circulation pump to decrease the outlet flow in order to reduce the deviation of the consumer temperature from the target temperature if the deviation of the consumer temperature from the target temperature can or shall not be compensated by further opening the supply valve.

[0037] 20

[0028] In a preferred embodiment, the supply valve and the circulation pump are controlled by the control unit using the same temperature control signal but different temperature control function.

[0038]

[0029] In a further preferred embodiment, the control unit is part of the circulation pump or the control unit is a part of the supply valve. In par25 ticular, the control unit may be formed by an electronics unit of the circulation pump or an electronics unit of the supply valve. This avoids the need to have an additional control unit that controls the operation of the mixing system. However, it is noted that external control units may be used. The term control unit should thus not be construed in a limiting way. Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 In particular, the control unit may be formed by a distributed system and may involve both the electronics unit of the circulation pump and the supply valve or may even be formed by a completely distributed unit hosted in the cloud or in a supervisory control and data acquisition 5 (SCADA) system. Evidently, also external dedicated control units may be used to operate and implement the control of the circulation pump and the supply valve.

[0039]

[0030] In a preferred embodiment, the temperature control function for the supply valve controls the opening of the supply valve up to the sup10 ply threshold as a function of the temperature control signal and keeps the opening constant when the opening of the supply valve has reached the supply threshold. The valve position xpdefining the opening of the supply valve is preferably given by the temperature control function xp= g(u) with u < 1 when the opening of the supply valve is below the supply threshold and xp= gmaxwhen the opening of the supply valve is at the supply threshold. Here, u is the temperature control signal, g(u) is the function defining the relation between the temperature control signal and the opening of the supply valve, and gmaxis the supply threshold.

[0040]

[0031] In a further preferred embodiment, the temperature control func20 tion for the circulation pump keeps the outlet flow provided by the circulation pump constant when the opening of the supply valve is below the supply threshold and reduces the outlet flow as a function of the temperature control signal when the opening of the supply valve has reached the supply threshold. In case the circulation pump operates in 25 a flow control mode where the flow is kept constant or in a constant speed mode, the pump control signal a controlling the operation of the circulation is preferably given by the temperature control function a = 1 when the opening of the supply valve is below the supply threshold and a = 1 / u with u > 1 when the opening of the supply valve is at or above

[0041] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 the supply threshold. Again, u is the temperature signal. In case the circulation pump operates in in a pressure control mode where the pressure of the circulation pump is kept constant or in a proportional pressure mode, the pump control signal a controlling the operation of the circu5 lation pump is preferably given by the temperature control function a = 1 when the opening of the supply valve is below the supply threshold and a = 1 / u2with u > 1 when the opening of the supply valve is at or above the supply threshold.

[0042]

[0032] In a further preferred embodiment, the hydronic system is a heat10 ing system. In this case, the control unit is configured to instruct the circulation pump to decrease the outlet flow to reduce the deviation of the consumer temperature from the target temperature if the consumer temperature is below the target temperature.

[0043]

[0033] Alternatively, the hydronic system may be a cooling system. In this 15 case, the control unit is configured to instruct the circulation pump to decrease the outlet flow to reduce the deviation of the consumer temperature from the target temperature if the consumer temperature is above the target temperature.

[0044]

[0034] With regard to the advantages of the preferred embodiment of 20 the mixing system as well as the details of the preferred embodiments, reference is made to the preceding description of the preferred embodiments of the method for controlling a mixing system which comprises method features that correspond to the system features of the mixing system.

[0045] 25

[0035] In a third aspect, the invention is directed to a hydronic system comprising a supply unit providing a supply flow, at least one consumer circuit, and a mixing system according to any of the preferred embodiments. The at least one consumer circuit is configured to receive the outlet flow provided by the mixing system. The at least one consumer circuit Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 is configured to provide the return flow received by the mixing system.

[0046] With regard to the details and advantages of the hydronic system, references made to the proceeding description of the preferred embodiment of the mixing system used as part of the hydronic system.

[0047] 5

[0036] Subsequently, the invention will be described in more detail with reference to the drawings, wherein

[0048] Fig 1 shows a schematic drawing of a first exemplary embodiment of a mixing system,

[0049] Fig 2 shows a schematic drawing of a second exemplary embodiment of a mixing system,

[0050] Fig 3 shows a schematic drawing of a third exemplary embodiment of a mixing system,

[0051] Fig 4 shows a schematic drawing of a fourth exemplary embodiment of a mixing system,

[0052] 15 Fig 5 shows a schematic drawing of a fifth exemplary embodiment of a mixing system,

[0053] Fig 6 shows a flow chart of an exemplary embodiment of a method for controlling a mixing system,

[0054] Fig 7 shows a pump curve for an exemplary embodiment of a circulation pump

[0055] Fig 8 shows results of a first simulation of an exemplary embodiment of a mixing system controlled using an exemplary embodiment of a method for controlling the mixing system,

[0056] 25 Fig 9 shows results of a second simulation of an exemplary embodiment of a mixing system controlled using an exemplary embodiment of a method for controlling a mixing system,

[0057] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 Fig 10 shows results of a third simulation of an exemplary embodiment of a mixing system controlled using an exemplary embodiment of a method for controlling a mixing system,

[0058] 5 Fig 11 shows a comparison between results of simulations obtained by simulating an exemplary embodiment of a mixing system controlled using different methods.

[0059]

[0037] Fig 1 shows an exemplary embodiment of a hydronic system 1 comprising a source or supply unit 3, a load 5 formed by at least one 10 consumer circuit 7 and a mixing system 9 placed between the supply unit 3 and the at least one consumer circuit 7. In the exemplary embodiment shown in figure 1, the at least one consumer circuit 7 comprises a plurality of conventional radiators 11.

[0060]

[0038] The mixing system 9 comprises a supply line 13, a return line 15 and 15 a bypass line 17 connecting the return line 15 to the supply line 13. The supply line 13 has a primary part 13a extending between the supply unit 3 and the bypass line 17 as well as a secondary part 13b extending between the bypass line 17 and the load 5. Similarly, the part of the return line 15 extending between the supply unit 3 and the bypass line 17 is referred to as the primary part 15a of the supply line 15 and the part of the supply line 15 extending between the bypass line 17 and the load 5 is referred to the secondary part 15b of the return line 15. The primary part 13a of the supply line 13 and the primary part 15a of the return line 15 are together also referred to as the primary part 19 of the mixing system 9. In 25 the same manner, the secondary part 13b of the supply line 13 and the secondary part 15b of the return line 15 are referred to as the secondary part 21 of the mixing system 9.

[0061]

[0039] The mixing system 9 further comprises a supply valve 23 which is located in the primary part 13a of the supply line 13. The supply valve 23

[0062] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 is used to control a supply flow qAfrom the supply unit 3. The opening xpof the supply valve 23 is controlled by a control unit 25 of the mixing system 9.

[0063]

[0040] On the secondary side 13b of the supply line 13, a circulation 5 pump 27 for the secondary side 21 of the mixing system 9 is provided. The circulation pump 27 delivers a pressure ΔpABresulting in a flow qABthrough the load 5. The flow qABthrough the load 5 is also referred to as the outlet flow qAB. The circulation pump 27 is controlled by the control unit 25 using a pump manipulation signal a.

[0064] 10

[0041] The mixing system 9 further comprises a temperature sensor 29 which has also been placed in a secondary side 13b of the supply line 13. The temperature sensor 29 measures the temperature TABof the outlet flow qAB. The temperature TABsensed by the temperature sensor 29 is fed back as an input into the control unit 25. The temperature sensor 29 can, for example, be a separate part or be integrated into the circulation pump 27.

[0065]

[0042] Furthermore, a non-return or check valve 31 is located in the bypass line 17. The check valve 31 enables a flow from the return line 15 to the supply line 13 and prevents a flow in the opposite direction. Further, 20 it is noted for the sake of completeness that the supply unit 3 provides the supply flow qAat a supply temperature TAand delivers a pressure ΔpA. The temperature TBdesignates the temperature of the return flow coming out of the load 5.

[0066]

[0043] The control unit 25 is shown with two different control blocks 33, 35.

[0067] 25 The control blocks 33, 35 are merely shown for illustrative purposes and do not imply any structural elements in the control unit 25. In particular, the control unit 25 could include a single control block. The first control block 33 establishes on the basis of the temperature TABof the outlet flow qABfrom a target temperature TABa common temperature control signal Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 u. The second control block 35 derives from the temperature control signal u the pump manipulation signal a and the valve opening xp. While shown as a separate unit 25 in figure 1, the control unit 25 is part of the electronics and control unit of the circulation pump 27.

[0068] 5

[0044] During operation of the mixing system 9, the control unit 25 is configured to increase the valve opening xpif the temperature TABof the outlet flow qABis below the target temperature TAB. In this context it is noted that the hydronic system 1 shown in figure 1 operates as a heating system. When the opening xpof the supply valve 23 reaches a supply 10 threshold gmaxand the temperature TABof the outlet flow qABis still below the target temperature TAB, the control unit 25 modifies the pump manipulation signal a to reduce the flow qABthrough the secondary side 21 of the mixing system 9. By reducing the outlet flow qAB, the relative contribution of the supply flow qAfrom the supply unit 3 to the outlet flow qABincreases compared to the contribution of the bypass flow through the bypass line 17. This in turn results in an increase of the temperature TABof the outlet flow. The temperature TABof the outlet flow qABis subsequently also referred to as the consumer temperature TAB. Thus, by reducing the outlet flow qABwhen the supply valve 23 has been open up to the supply 20 threshold gmax, a temperature collapse of the mixing system 9 can be prevented.

[0069]

[0045] The operation of the control unit 25 will subsequently be explained in more detail. However, before going into detail of the control unit 25, some basics of the operation of the circulation pump 27 will be established. The supply pressure ΔpABof the circulation pump 27 is a function of the rotational speed rABand the flow qABthrough the pump 27. The flow qABthrough the pump 27 corresponds to the outlet flow qAB. The relation between the pump flow qABand the pump pressure ApABis typically defined by the maximum rotational speed ωABof the circulation pump 27. An example of a corresponding pump curve is shown in figure 7 with

[0070] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 the abscissa showing the outlet flow qABand the ordinate showing the outlet pressure ApAB.

[0071]

[0046] The circulation pump 27 is equipped with different control modes. For example, in a constant pressure mode, the circulation pump 27 de5 livers a constant pressure Ap / Bregardless of the outlet flow qAB. In a proportional pressure mode, there is a linear relationship between the pump pressure ppABand the outlet flow qAB. The circulation pump 27 further includes a constant flow mode, in which the outlet flow qABis determined by a constant flow setpoint qAB. Finally, the circulation pump 27 may also 10 operate in a constant speed mode, in which the outlet flow qABand the pump pressure ApABare defined by the constant speed set point ωAB.

[0072]

[0047] Depending on the control mode in which the circulator pump 27 is operating, different temperature control functions are used to determine the valve opening xpand the pump manipulation signal a. Subsequently, it will always be assumed that the valve position xpand the pump manipulation signal a are all scaled to be between the 0 and 1.

[0073]

[0048] For example, in case that the circulation pump 27 works in a constant speed mode, the valve position xpand the pump manipulation signal a are given by

[0074] 20

[0075]

[0076] In the present exemplarily embodiment, the supply threshold gmaxcorresponds to the supply valve being fully opened, i.e., gmax= 1. The pump manipulation signal a can either be a scaled reference signal or can be used as a set point influence signal. In case the pump manipulation sig25 nal a is used with a scaled reference signal, the constant flow setpoint qAB= Kq· a. In case the pump signal a is a set point influence signal,

[0077] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 the pump flow qAB= a · qAB. If the pump operates in a constant speed mode and the pump manipulation signal a is a scaled reference signal, the constant speed set point ωAB=

[0078]

[0079] • a. Similarly, if the pump operates in a constant speed mode and the pump manipulation signal a is a set 5 point influence signal, the pump speed ωABwill be given by ωAB=ωAB· a.

[0080] In other words, when the circulation pump 27 operates in one of a constant flow mode or in a constant speed mode, the valve opening is increased with the temperature control signal u until the temperature control signal u = 1. At this point, the valve opening xphas reached the supply threshold gmax. If the temperature control signal increases further of one, the valve opening xpis kept constant. In contrast, the pump manipulation signal a is kept constant as long as the temperature control signal u is at or below 1. If the temperature control signal u exceeds 1, the pump manipulation signal a = 1 / u.

[0081] 15

[0049] In case the circulation pump 27 operates in a constant pressure mode or in proportional pressure mode, the relation between the temperature control signal u and the pump manipulation signal a is given by

[0082] (Equation 2)

[0083]

[0084]

[0050] The pump manipulation signal a can be a scaled version of the pressure reference KApor a setpoint influence signal. If the pump manipulation signal a is a scaled version of the pressure reference, the constant pressure setpoint ΔpAB= KΔp· a and in case of a proportional pressure mode the proportional pressure set point ppAB= Kpp· a. If the pump manipulation signal is a setpoint influence signal, the actual pump pressure 25 will be ΔpAB= a · ΔpABfor a constant pressure mode and ΔppAB= a · ppABfor a proportional pressure mode.

[0085] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025

[0051] Hence, in case the pump operates either in a constant pressure mode or proportional pressure mode, the control unit 25 largely controls the valve opening xpand the pump manipulation signal a in a similar way as for the constant flow mode or the constant speed mode. The only 5 difference is that the pump manipulation signal a is given by 1 / u2in case the supply valve 23 has been fully opened, i.e., opened to the supply threshold.

[0086]

[0052] Figure 2 shows a second exemplary of a hydronic system 1 with a mixing system, 9. For the sake of brevity only the differences to the exem10 plary shown in figure 1 will be described in more detail. It is noted that throughout the figures, the same reference numerals are used in all embodiments.

[0087]

[0053] In the exemplary embodiment as shown in figure 2, no details of the at least one consumer circuit 7 are shown. Thus, it is understood that 15 the embodiment can be realized for different consumer circuits 7 which is the same case in the exemplary embodiment shown in figure 1 where the radiators 11 can be replaced, for example, by an underfloor heating circuit or other heat distribution systems.

[0088]

[0054] Otherwise, the difference between the exemplary embodiments 20 shown in figures 1 and 2 is that the circulation pump 27 is not provided in the secondary side 13b of the supply line 13 but in the secondary side 15b of the return line 15. In all other aspects, the exemplary embodiment shown in figure 2 corresponds to the exemplary embodiment shown in figure 1. In particular, the control unit 25 operates in the same way.

[0089] 25

[0055] Figure 3 is a third exemplary embodiment of a hydronic system 1 comprising a mixing system 9. Again, the hydronic system 1 and the mixing system 9 shown in figure 3 largely correspond to the exemplary embodiment of a hydronic system 1 and a mixing system 9 shown in figure

[0090] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 1. Therefore, only the differences between the two embodiments will be described in further detail.

[0091]

[0056] Similar to the exemplary embodiment shown in figure 2, no details of the load 5 and the at least one consumer circuit 7 are shown in figure 5 3. Additionally, the supply valve 23 has been moved from the primary side 13a of the to the primary side 15a of the return line 15. In all other aspects, the embodiments shown in figure 3 correspond to the embodiments shown in figure 1. In particular, the control unit 25 operates in the same way.

[0092] 10

[0057] Figure 4 shows a fourth exemplary embodiment of a hydronic system 1 with an exemplary embodiment of a mixing system 9. The exemplary embodiment shown in figure 4 is a combination of the exemplary embodiments shown in figures 2 and 3. Thus, compared to the first exemplary embodiment shown in figure 1, the circulation pump 27 is placed in the secondary side 15b of the return line 15 and the supply valve 23 is placed in the primary side 15a of the return line 15. Since the exemplary embodiment corresponds in all other aspects to the exemplary embodiment shown in figure 1, for the sake of brevity reference is made to preceding description of the exemplary embodiment shown in figure 1.

[0093] 20

[0058] Finally, figure 5 shows a fifth exemplary embodiment of a hydronic system 1 comprising an exemplary embodiment of a mixing system 9. The exemplary embodiment shown in figure 5 is largely identical to the exemplary embodiment of figure 1. The main difference is that in the exemplary embodiment of figure 5, a heat exchanger system 37 is used as 25 a consumer circuit 7 or the load 5. Furthermore, the temperature sensor 29 has not been placed on the secondary side 13b of the supply line 13. Rather, the temperature sensor 29 is placed in the room, zone, or air duct heated or cooled using the heat exchanger 37. The air temperature TAreplacing the outlet flow temperature TABas one of the inputs for the

[0094] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 control unit 25. Likewise, the target temperature T*ABis replaced by a target air temperature T*Airas input for the control unit 25. However, in all other aspects and, in particular, in the way the control unit 25 operates the circulation pump 27 and the supply valve 23 the exemplary embod5 iment of figure 5 corresponds to the exemplary embodiment of figure 1.

[0095] Therefore, for the sake of brevity reference is made to the previous detailed discussion of the first exemplary embodiment of a hydronic system and the included exemplary embodiment of a mixing system 9.

[0096]

[0059] Figure 6 shows a flow chart depicting an exemplary embodiment 10 of a method for controlling a mixing system 9 according to one of the preceding first two exemplary embodiments. In a first step 39 a temperature TABof an outlet flow qABor a room temperature TAiris measured using the temperature sensor 29. The measured temperature is subsequently referred to as the consumer temperature TABregardless as to whether the temperature was measured in the air or in the outlet flow TAB-

[0097]

[0060] In a second step 41 the consumer temperature is compared to a target temperature which may either be formed by the target temperature T*ABfor the outlet flow qABin the first to fourth exemplary embodiment 20 or the target air temperature TAir. If the consumer temperature corresponds to the target temperature, the method cycles back to the first step 39, i.e., the temperature measurement using the temperature sensor 29 is repeated. Further, in case the consumer temperature deviates from the target temperature, the method moves to the third step 43.

[0098]

[0061] In the third step 43, the control unit 25 determines whetherthe supply valve 23 is fully open or not yet fully open. In other words, in the third step 43 the method checks whether the supply valve 23 has been opened less than a supply threshold or all the way up to the supply threshold. In case it is determined that the supply valve 23 has not yet 30 been fully opened, the method moves to the fourth step 45. In the fourth Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 step 45, the opening of the supply valve 23 is modified according to the supply valve opening function g(u) where u is the temperature control signal. Once the fourth step has been completed, the method moves back to the first step 39.

[0099] 5

[0062] In case it has been determined in the third step 43 that the supply valve 23 has already been fully opened or at least up to the supply threshold gmax, the method moves to the fifth step 47. In the fifth step the opening of the supply valve 23 is kept constant and the operation of the circulation pump 27 is modified. Once the fifth step 47 has been com10 pleted, the method moves back to the first step 39.

[0100]

[0063] With regard to the details of implementing the temperature control functions which are used to determine the valve opening xpor the pump manipulation signal a that is used to control the actuation of the circulation pump 27, reference is made to the detailed description of the 15 exemplary embodiments of a mixing system 9. The exemplary embodiment of a method for controlling a mixing system 9 advantageously prevents a temperature collapse in case the supply pressure ApABprovided by the supply unit 3 is too low when the supply valve 23 has already been fully opened.

[0101] 20

[0064] Figure 8 shows a simulation of the operation of the mixing system 9 shown in the first exemplary embodiment. In the simulation it assumed that the circulation pump 27 operates in a constant flow mode, i.e., the circulation pump 27 keeps the outlet flow qABconstant at a constant pressure setpoint Q B- For the sake of completeness, it is noted that the 25 time on the abscissa of the three diagrams shown in figure 8 is given in seconds. The top diagram shows the evolution of the pump manipulation signal a and the valve opening xpof the supply valve 23 over time. The center chart shows the simulation development of the supply flow qAand

[0102] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 the outlet flow qABover time. Finally, the bottom diagram shows the development of the consumer temperature TABand the target temperature which is indicated by Trefin figure 8.

[0103]

[0065] At the beginning of the simulation, the supply pressure ApAis suffi5 ciently high and the target temperature can be reached by opening the supply valve to roughly 90%, i.e., the valve opening xpis at approximately 0.9. At about 1.200s, a drop in the supply pressure ApAoccurs. In consequence, consumer temperature TABfalls and is now below the target temperature Tref. The control unit 25 consequently moves to increase the 10 valve opening xpwhich quickly reaches 1, i.e., the supply valve 23 is fully opened or saturated. At this point, the control unit 25 moves to reduce the outlet flow qABas can be seen in the center diagram. The reduction in the outlet flow also causes a reduction of the supply flow qA. However, the relative contribution of the supply flow qAto the outlet flow qABincreases which results in the outlet temperature TABmoving eventually back to the target temperature Tref.

[0104]

[0066] Thereby, the mixing system 9 and the method for controlling a mixing system 9 embodied therein advantageously prevent a temperature collapse of the mixing system 9 which would have occurred if the outlet 20 flow qABof the circulation pump 27 had not been reduced.

[0105]

[0067] At about 2.400s, the supply pressure ApAincreases back to the original value which causes a spike... in the supply flow qAand the consumer temperature TAB. In other words, the consumer temperature TABis now above the target temperature Tref. The control unit 25 now moves to in25 crease the flow provided by the circulation pump 27 by increasing the pump manipulation signal a back to 1. When the pump manipulation signal a reaches 1 without the consumer temperature TABbeing back at the target temperature, the control unit 25 begins to decrease the valve

[0106] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 opening xp. Eventually, the valve opening xpis back at 0.9 and the consumer temperature TABis back at the target temperature TAB.

[0107]

[0068] Figure 9 shows the results of a second simulation based on a mixing system 9 as shown in any of the figures 1 to 5. In the simulation it was 5 assumed that the circulation pump 27 operates in a constant pressure mode. '

[0108]

[0069] At the beginning of the simulation, the control unit 25 quickly settles at a valve opening xpof about 0.7 at which the consumer temperature rABof the mixing system 9 corresponds to the target temperature Tref.

[0109] 10 At about 1.200s, a step occurs in the load 5, i.e., the demand of heat transfer medium increases at that point in time which results in the outlet flow qABof the mixing system 9 nearly doubling. The control unit 25 responds by fully opening the supply valve 23. To this end, the valve opening xpis increased to 1, essentially opening the supply valve 23 fully. Further, as can be seen in the bottom diagram, opening the supply valve 23 fully is insufficient to keep the consumer temperature TABat the target temperature as the supply pressure ApAis insufficient.

[0110]

[0070] Since the supply valve 23 is fully opened, the control unit 25 moves to reduce the outlet flow qABprovided by the circulation pump 27 by 20 reducing the pump pressure. To this end, the pump manipulation signal a is reduced down from 1 to about 0.5. As can be seen in the center diagram, reducing the outlet flow qABresults in an increase of the supply flow qA. At the same time, the consumer temperature TABmoves back up to the target temperature. Thus, by reducing the outlet flow qABof the 25 circulation pump 27, the control unit 25 operating according to an exemplary embodiment of a method for operating a mixing system prevents a temperature collapse.

[0111]

[0071] At about 2.400s, the outlet flow qABdrops back to the initial value. The control unit 25 responds by first increasing the pump manipulation Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 signal a back to 1 which already causes a drop in the supply flow qA. to compensate the previously observed increase in the consumer temperature TAB. Since the increase in the pump manipulation signal a is insufficient to compensate the temperature increase, the control unit further 5 moves to reduce the valve opening when the pump manipulation signal is at a = 1.

[0112]

[0072] For the sake of completeness, it is noted that in figure 9 the top, center and bottom diagram show corresponding values on the ordinates and abscissas as the diagram shown in figure 8. The same is true 10 for subsequently discussed diagrams in figure 10.

[0113]

[0073] Figure 10 shows the result of a third simulation of an operation of an exemplary embodiment of a mixing system 9 as shown in of the figures 1 to 5. Here, the circulation pump 27 operates in a constant speed mode. Like the two previous simulations, at the beginning the supply pressure pA15 is sufficiently high to support the required outlet flow qAB. The consumer temperature TABtherefore quickly reaches the target temperature Tref.

[0114]

[0074] At about 1.200s, a drop in the supply pressure occurs. Adapting the supply pressure results in an immediate drop of the supply flow qAand, in response, a drop in the consumer temperature TAB. The control 20 unit 25 in response increases the opening of the supply valve 23 all the way. When the supply valve 23 is fully opened (xp= 1) and the consumer temperature TABis not yet back at the target temperature Tref, the control unit 25 instructs the circulation pump 27 to reduce the outlet flow qABby reducing the pump manipulation signal a. The reduced outlet flow qABat 25 a nearly constant supply flow qAresults in an increase of the consumer temperature TABback to the target temperature TABas the ratio of the supply flow qAto the outlet flow qABincreases.

[0115]

[0075] At about 2.400s, the supply pressure data qAincreases back to the original value as can be seen by the corresponding spike in the supply Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 flow qAand the spike in the consumer temperature TABcauses by the increased supply flow qA. The control unit 25 responds by first increasing the pump manipulation signal a back to 1. If this is insufficient to reduce the consumer temperature back to the target temperature Tref, the con5 trol unit 25 further begins to close the supply valve 23 as can be seen by the decrease in the valve opening xp. Thus, also in the third simulation of an exemplary embodiment the mixing system 9 and the exemplary embodiment of a method for controlling a mixing system a temperature collapse is effectively prevented.

[0116] 10

[0076] Finally, figure 11 shows the comparison of a mixing system 9 with and without the proposed control. The top diagram shows the outlet flow qABin m3 / h over time in seconds. The dashed line shows the outlet flow qABwhen the control is not used, i.e., the pump operation is not controlled, and the solid line shows the flow if the control mode reducing the outlet flow of the circulation pump 27 is used. In the center diagram, the corresponding consumer temperature TABis shown for the simulations. The target temperature is set at 45°C. In the center diagram the ordinate shows the temperature in degree Celsius and the abscissa also shows the time in seconds. The bottom diagram shows the energy transferred from 20 the source 3 to the load 5. The power is given kW on the ordinate.

[0117]

[0077] The simulation with the proposed control mode on is the same as shown in figure 8, i.e., the circulation pump 27 operates in a constant flow mode. At about 1.200s a drop occurs in the supply pressure. As already seen in figure 8, when the control unit 25 reduces the outlet flow qABin case the valve opening xpof the supply valve 23 is saturated, the target temperature can be maintained and there is actually a higher energy transfer from the source 3 to the load 5 as compared to when the outlet flow qABis not reduced.

[0118]

[0078] In the conventional approach, the drop in the supply flow qAdoes 30 not affect the outlet flow qABas shown in the top diagram. However, the Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 conventional mixing system is not able to maintain the consumer temperature TABat the target temperature as shown in the center diagram once the supply pressure ApAdrops as about 1.200s since the reduction in the supply pressure causes an increase of the cooler bypass flow in the 5 outlet flow. And although the flow qABis overall higher in the conventional operating mode of the mixing system, the overall power transfer from the source 3 to the load 5 is higher when the modified control mode is used. Thus, the comparison between the conventional mixing system and the modified mixing system 9 clearly shows the benefit of reducing the outlet 10 flow qABwhen the supply valve 23 has been fully opened.

[0119] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 List of Reference Characters

[0120] I hydronic system

[0121] 3 source, supply unit

[0122] 5 load

[0123] 5 7 consumer circuit

[0124] 9 mixing system

[0125] I I radiators

[0126] 13 supply line

[0127] 13a primary side of the supply line

[0128] 13b secondary side of the supply line

[0129] 15 return line

[0130] 15a primary side of the return line

[0131] 15b secondary side of the return line

[0132] 17 bypass line

[0133] 15 1 primary side of the mixing system

[0134] 21 secondary side of the mixing system

[0135] 23 supply valve

[0136] 25 control unit

[0137] 27 circulation pump

[0138] 20 29 temperature sensor

[0139] 31 checkvalve

[0140] 33 first control block

[0141] 35 second control block

[0142] 37 heat exchanger system

[0143] 39 first step

[0144] 41 second step

[0145] 43 third step

[0146] 45 fourth step

[0147] 47 fifth step

[0148] 30 qAsupply flow

[0149] xpopening of the supply valve

[0150] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025 ΔpABpump pressure, pressure delivered by circulation pump qABflow through load, outlet flow, pump flow

[0151] a pump manipulation signal

[0152] TABtemperature of the outlet flow, consumer temperature 5 TAsupply temperature

[0153] ΔpAsupply pressure

[0154] TBtemperature of the return flow

[0155] TAB*target temperature

[0156] u temperature control signal

[0157] 10 <wABrotational speed of the circulation pump

[0158] >ABmaximum rotational speed of the circulation pump

[0159] ΔpAB*constant pressure setpoint

[0160] qAB*constant flow setpoint

[0161] ppAB*proportional pressure setpoint

[0162] 15 <wABconstant speed setpoint

[0163] Kqflow reference

[0164] KΔppressure reference

[0165] g(u) valve opening function

[0166] Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025

Claims

Claims1. A method for controlling a mixing system (9) for a hydronic system, wherein the mixing system (9) comprises a supply line (13) enabling a flow from a supply unit (3) to at least one consumer circuit (7), a 5 return line (15) enabling a flow from the at least one consumer circuit (7) to the supply unit (3), and a bypass line ( 17) enabling a flow from the return line ( 15) to the supply line ( 13),wherein a primary side of the mixing system (9) is formed by the supply line ( 13) between the supply unit (3) and the bypass line (17) as well as the return line ( 15) between the bypass line ( 17) and the supply unit (3) and wherein a secondary side of the mixing system (9) is formed by the supply line (13) between the bypass line ( 17) and the at least one consumer circuit (7) as well as the return line (15) between the at least one consumer circuit (7) and the by15 pass line (17),wherein a contribution of a supply flow from the supply unit (3) via the primary side of the supply line (13) to an outlet flow in the secondary side of the supply line ( 13) can be controlled by a supply valve (23) placed in the primary side of the mixing system,20 wherein the outlet flow can be controlled by a circulation pump (27) placed in the secondary side of the mixing system, wherein a temperature sensor (29) for sensing a consumer temperature is placed on the secondary side of the supply line ( 13) or in the at least one consumer circuit (7), wherein the consumer temperature is preferably sensed in the outlet flow, and wherein the circulation pump (27) decreases the outlet flow in order to reduce a deviation of the consumer temperature from a target temperature, if the supply valve (23) is opened up to or beyond a supply threshold and if the deviation of the consumer tem30 perature from the target temperature cannot be compensated by further opening or by closing the supply valve (23) or shall at least inatentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025its entirety not be compensated by further opening the supply valve (23).

2. Method according to claim 1, wherein the supply threshold corresponds to the supply valve (23) being open to 80%, wherein prefer5 ably the supply threshold corresponds to the supply valve (23) being open to 90%, and wherein further preferably the supply threshold corresponds to the supply valve (23) being completely open.

3. Method according to claim 1 or 2, wherein in case that the consumer temperature deviates from the target temperature, the sup10 ply valve (23) is opened up to a supply threshold to compensate deviations of the consumer temperature from the target temperature, and wherein the circulation pump (27) decreases the outlet flow in order to reduce the deviation of the consumer temperature from the target temperature if the deviation of the consumer temperature from the target temperature can or shall not be compensated by further opening the supply valve (23).

4. Method according to any of the preceding claims, wherein the supply valve (23) and the circulation pump (27) are controlled using the same temperature control signal but different temperature con20 trol functions.

5. Method according to claim 4, wherein the temperature control function for the supply valve (23) controls the opening of the supply valve (23) up to the supply threshold as a function of the temperature control signal and keeps the opening constant when the open25 ing of the supply valve (23) has reached the supply threshold,wherein the valve position xpdefining the opening of the supply valve (23) is preferably given by the temperature control function xp= g(u) with u < 1 when the opening of the supply valve (23) is below the supply threshold and xp= gmaxwith u ≥ 1 when the opening of the supply valve (23) is at the supply threshold, where u is the temperature control signal, g(u) is the function defining the relation between the temperature control signal and the opening of the supply valve (23), and gmaxis the supply threshold.5 6. Method according to claim 4 or 5, wherein the temperature control function for the circulation pump (27) keeps the outlet flow constant when the opening of the supply valve (23) is below the supply threshold and reduces the outlet flow as a function of the temperature control signal when the opening of the supply valve (23) has reached the supply threshold,wherein in case the circulation pump (27) operates in a flow control mode where the flow is kept constant or in a constant speed mode, the pump control signal a controlling the operation of the circulation pump (27) is preferably given by the temperature con15 trol function a = 1 when the opening of the supply valve (23) is below the supply threshold and a = 1 / u with u ≥ 1 when the opening of the supply valve (23) is at or above the supply threshold, wherein u is the temperature control signal, or wherein in case the circulation pump (27) operates in in a pressure control mode where the pressure of the circulation pump (27) is kept constant or in a proportional pressure mode, the pump control signal a controlling the operation of the circulation pump (27) is preferably given by the temperature control function a = 1 when the opening of the supply valve (23) is below the supply threshold 25 and a = 1 / u2with u ≥ 1 when the opening of the supply valve (23) is at or above the supply threshold, wherein u is the temperature control signal.circulation pump (27) decreases the outlet flow to reduce the deviation of the consumer temperature from the target temperature if the consumer temperature is below the target temperature, or wherein the hydronic system (1) is operated as a cooling sys5 tem, and the circulation pump (27) decreases the outlet flow to reduce the deviation of the consumer temperature from the target temperature if the consumer temperature is above the target temperature.

8. A mixing system (9) fora mixing loop in a hydronic system, wherein the mixing system (9) comprises a supply line ( 13) for enabling a flow from a supply unit (3) to the at least one consumer circuit (7), a return line (15) for enabling a flow from the at least one consumer circuit (7) to the supply unit (3), and a bypass line ( 17) for enabling a flow from the return line ( 15) to the supply line (13),15 wherein a primary side of the mixing system (9) is formed by the supply line ( 13) between the supply unit (3) and the bypass line (17) as well as the return line ( 15) between the bypass line ( 17) and the supply unit (3) and wherein a secondary side of the mixing system (9) is formed by the supply line (13) between the bypass line 20 ( 17) and the at least one consumer circuit (7) as well as the return line (15) between the at least one consumer circuit (7) and the bypass line (17),wherein a supply valve (23) located in the primary side of the mixing system (9) is configured for controlling a contribution of a supply flow from the supply unit (3) via the primary side of the supply line (13) to an outlet flow in the secondary side of the supply line (13),wherein a circulation pump (27) located in the secondary side of the mixing system (9) is configured for at least partially controlling 30 the outlet flow,atentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025wherein a temperature sensor (29) located on the secondary side of the supply line (13) or in the at least one consumer circuit (7) is configured for sensing a consumer temperature, wherein the consumer temperature is preferably sensed in the outlet flow, and 5 wherein the system further comprises a control unit (25), wherein the control unit (25) is configured to instruct the circulation pump (27) to decrease the outlet flow in order to reduce a deviation of the consumer temperature from a target temperature, if the consumer temperature deviates from the target temperature, if the 10 supply valve (23) is opened up to or beyond a supply threshold, and if the deviation of the consumer temperature from the target temperature cannot be compensated by further opening or by closing the supply valve (23) or shall at least in its entirety not be compensated by further opening the supply valve (23).

9. Mixing system (9) according to claim 8, wherein the supply threshold corresponds to the supply valve (23) being open to 80%, wherein preferably the supply threshold corresponds to the supply valve (23) being open to 90%, and wherein further preferably the supply threshold corresponds to the supply valve (23) being completely 20 open.

10. Mixing system (9) according to claim 8 or 9, wherein in case that the consumer temperature deviates from the target temperature, the control unit (25) is configured to instruct the supply valve (23) to open up to a supply threshold to compensate deviations of the consumer temperature from the target temperature, and wherein the control unit (25) is further configured to instruct the circulation pump (27) to decrease the outlet flow in order to reduce the deviation of the consumer temperature from the target temperature if the deviation of the consumer temperature from the target temper30 ature can or shall not be compensated by further opening the supply valve (23).atentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 202511. Mixing system (9) according to claim 8, 9 or 10, wherein the supply valve (23) and the circulation pump (27) are controlled by the control unit (25) using the same temperature control signal but different temperature control functions and / or5 wherein the control unit is (25) part of the circulation pump (27) or wherein the control unit (25) is part of the supply valve (23).

12. Mixing system (9) according to claim 11, wherein the temperature control function for the supply valve (23) controls the opening of the supply valve (23) up to the supply threshold as a function of the 10 temperature control signal and keeps the opening constant when the opening of the supply valve (23) has reached the supply threshold,wherein the valve position xpdefining the opening of the supply valve (23) is preferably given by the temperature control function xp= g(u) with u < 1 when the opening of the supply valve (23) is below the supply threshold and xp= gmaxwhen the opening of the supply valve (23) is at the supply threshold, where u is the temperature control signal, g(u) is the function defining the relation between the temperature control signal and the opening of the supply valve 20 (23), and gmaxis the supply threshold.

13. Mixing system (9) according to claim 11 or 12, wherein the temperature control function for the circulation pump (27) keeps the outlet flow provided by the circulation pump (27) constant when the opening of the supply valve (23) is below the supply threshold and reduces the outlet flow as a function of the temperature control signal when the opening of the supply valve (23) has reached the supply threshold,wherein in case the circulation pump (27) operates in a flow control mode where the flow is kept constant or in a constant speed 30 mode, the pump control signal a controlling the operation of theatentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025circulation pump (27) is preferably given by the temperature control function a = 1 when the opening of the supply valve (23) is below the supply threshold and a = 1 / u with u ≥ 1 when the opening of the supply valve (23) is at or above the supply threshold, wherein 5 u is the temperature control signal, or wherein in case the circulation pump (27) operates in in a pressure control mode where the pressure of the circulation pump (27) is kept constant or in a proportional pressure mode, the pump control signal a controlling the operation of the circulation pump (27) is 10 preferably given by the temperature control function a = 1 when the opening of the supply valve (23) is below the supply threshold and a = 1 / u2with u ≥ 1 when the opening of the supply valve (23) is at or above the supply threshold, wherein u is the temperature control signal.

14. Mixing system (9) according to any of the claims 9 to 13, wherein the hydronic system ( 1 ) is a heating system, and wherein the control unit (25) is configured to instruct the circulation pump (27) to decrease the outlet flow to reduce the deviation of the consumer temperature from the target temperature if the consumer temperature 20 is below the target temperature, orwherein the hydronic system (1) is a cooling system, and wherein the control unit (25) is configured to instruct the circulation pump (27) to decrease the outlet flow to reduce the deviation of the consumer temperature from the target temperature if the consumer temperature is above the target temperature.

15. Hydronic system (1) comprising a supply unit (3) providing a supply flow, at least on consumer circuit (7) and a mixing system (9) according to any of claims 8 to 14, wherein the at least one consumer circuit (7) is configured to receive the outlet flow provided by the 30 mixing system (9) and wherein the at least one consumer circuit (7)atentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025is configured to provide the return flow received by the mixing system.Patentanwdlte Hemmer Lindfeld Frese GP 3815 WO, 23 / 10 / 2025

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