Technical Field

The present disclosure relates to a method, a device and computer software adapted to provide a temperature value to a heating source.

Background

The indoor temperature in a building is affected by the energy that is supplied to the building and the energy losses from the building. Energy is often supplied to the building via a heating system. Energy is also provided to the building via indirect energy sources such as heat from people, electric appliances, solar radiation, etc.

The energy that leaves the building as transmission losses and ventilation losses is dependent on the difference between the indoor temperature and the outdoor temperature. The transmission losses are also dependent on the building's insulating shell (exterior walls, windows, doors, etc.). The ventilation losses depend on the airflow and the air infiltration through the building. The ventilation losses further depend on the temperature of the air leaving the building. The actual temperature of the air leaving a building is almost the same as the indoor temperature if no ventilation heat exchanger is used.

In order to keep the indoor temperature constant, the supplied amount of energy must match the amount of energy that disappears from the building.

Therefore, there is a need for precise control of the heating system in order for the heating system to supply the correct amount of energy to keep the indoor temperature constant.

The heating system often provides energy to the building via heated water supplied to a radiator system. The temperature of the heated water is determined based on the outdoor temperature. The temperature of the heated water is often determined based on a heating curve.

SUBSTITUTE SHEET (RULE 26) However, it is often hard to adapt the correct heating curve to different buildings and the amount of indirect energy sources such as people, electric appliances, solar radiation, etc.

Thus, there is a need for a solution that solves or at least mitigates the problem of adapting a heating system to the amount of indirect energy sources such as from people, electric appliances, solar radiation, etc.

Summary

Accordingly, it would be desirable to provide a device, a method, and computer software, which provide a temperature value to a heating source that takes into account various parameters relating to the outdoor temperature.

This is achieved by determining a temperature value based on an actual water temperature, an outdoor temperature and a balance temperature of the building, and providing the determined temperature value to a sensor input of the heating source. The heating source can then use this input value to provide hot water to the radiator system. To address one or more of these concerns a device and a method as defined in the independent claims are provided. Preferred embodiments are defined in the dependent claims.

According to a first aspect, the present disclosure relates to a device adapted to provide a determined flow water temperature value TFDET to a flow water temperature sensor input to a heating source. The device is adapted to be connectable to a flow water temperature sensor adapted to determine the actual flow water temperature T _F cfrom the heating source. The device comprising: a processor; and a memory storing software instructions that, when executed by the processor, cause the device to retrieve the actual flow water temperature value T _F Acfrom the flow water temperature sensor. The software instructions further cause the device to determine a AT _F value based on an outdoor temperature value TOUT, until the outdoor temperature reaches a balance temperature TBAL of the building, at which no energy from the heating source is required to maintain an indoor temperature of the building. The AT _F value is based on the outdoor temperature value Toursuch that the AT _F value increases when the outdoor temperature increases. Further, the software instructions cause the device to determine the determined flow water temperature value T _FD ETby adding the actual flow water temperature value T _FA c and the AT _F value. Yet further, the instructions cause the device to provide the determined flow water temperature value T _FD ETto the flow water temperature sensor input. Thus according to the first aspect, the device provides an inventive solution to the concerns described above by providing a determined flow water temperature value. The determined flow water temperature value is determined based on an outdoor temperature value until the outdoor temperature reaches a balance temperature T _B AL of the building, at which no energy from the heating source is required to maintain an indoor temperature of the building. The AT _F value is based on the outdoor temperature value Touysuch that the AT _F value increases when the outdoor temperature increases. Therefore, it is possible for the heating source to consider energy from other energy sources such as solar radiation, electrical appliances, people, etc. when determining the temperature of the flow water from the heating source. This since the heating source is provided with the determined flow water temperature value, which has been determined considering at least the balance temperature and the outdoor temperature.

The device according to the disclosure therefore provides an improved determination of the flow water temperature based on the outdoor temperature. This is because, when using the device, the building's balance temperature is also taken into account during the determination of the flow water temperature from the heating source. When the outdoor temperature changes, the ratio between the energy from the heating source and energy from other sources changes. Therefore, energy from solar radiation, electrical appliances, people, etc. will constitute a larger part of the building's total energy need when the outdoor temperature is higher.

Therefore, according to an exemplary embodiment of the present disclosure the AT _F value increases when the outdoor temperature increases until the outdoor temperature reaches a balance temperature TBAL of the building, at which no energy from the heating source is required to maintain an indoor temperature of the building.

According to one embodiment, the software instructions further cause the device to determine the AT _F based on a difference value TTDIPP between a set indoor temperature value T _SF Tand an actual indoor temperature T _A CT, T _T DI _FF = T _SF T- TACT- Such that the AT _F value increases when the difference value T _T DI _FF increases and such that the AT _F value decreases when the difference value TTDIPP decreases.

According to one embodiment, the software instructions further cause the device to determine the AT _F value based on a difference value TWDIPP between the actual flow water temperature T _FA c and a return water temperature value TR, T _W DIFF= TFAC- T _R , _S uch that the AT _F alue increases when the difference value TWDIFF increases and such that the AT _F value decreases when the difference value TWDIFF decreases.

According to one embodiment, the software instructions further cause the device to determine the AT _F based on determining the AT _F value according to the formula (a):

(a) ATF = (TFAC ^— TR) X (TSET ^— TACT)/ (TBAL ^— TOUT); wherein

TFAC = actual flow water temperature

T _R = return water temperature

T _S ET = set indoor temperature

T CT = actual indoor temperature

T _B AL = balance temperature of the building

T _O UT = outdoor temperature

According to one embodiment, the heating source uses the actual flow water temperature TFAC from the heating source to control the determined flow water temperature value TFDET from the heating source. In a case were the determined flow water temperature value TFDET is higher than the actual flow water temperature the heating source will lower the flow water temperature. Therefore, providing less energy to the building, which is a desired effect since when the outdoor temperature increases, energy from people, electrical appliances etc. constitute a larger part of the building total energy need.

According to one embodiment, the flow water temperature from the heating source is determined based on the outdoor temperature value TOUT such that the flow water temperature T _F increases when the outdoor temperature value TOUT decreases and such that the flow water temperature T _F decreases when the outdoor temperature value TOUT increases.

According to one embodiment, the heating source is a heat pump, a boiler, or a heat exchanger.

According to a second aspect, the present disclosure relates to method for providing a determined flow water temperature value TFDET to a flow water temperature sensor input to a heating source. The method is performed by a device adapted to be connectable to a flow water temperature sensor. The flow water temperature sensor is adapted to determine the actual flow water temperature T _F Ac,from the heating source. The method comprising a first step of retrieving the actual flow water temperature value TpAcfrom the flow water temperature sensor. Next a step of, determining a AT _F value based on an outdoor temperature value TOUT, until the outdoor temperature reaches a balance temperature TBAL of the building, at which no energy from the heating source is required to maintain an indoor temperature of the building. The AT _F value is based on the outdoor temperature value T _O uT$uch that the AT _F value increases when the outdoor temperature increases. Further, the method comprises a step of determining the determined flow water temperature value T _FDF T by adding the actual flow water temperature value T _FA c and the AT _F value. Next, the method comprises a step of providing the determined flow water temperature value T _FDF Tto the flow water temperature sensor input.

Objectives, advantages and features conceivable within the scope of the second aspect are readily understood by the foregoing discussion referring to the first aspect.

Further objectives, features and advantages of the present disclosure will become apparent when studying the following detailed description, the drawings and the appended claims. Those skilled in the art realize that different features of the present disclosure can be combined to create embodiments other than those described in the following.

Brief description of drawings

The invention will be described in the following illustrative and non-limiting detailed description of exemplary embodiments, with reference to the appended drawings, in which:

Figure 1 is a schematic illustration of a heating system, in which a device 200 according to an exemplary embodiment is connected.

Figure 2 is a schematic illustration of the device 200 according to an exemplary embodiment.

Figure 3 is a flow chart of a method according to an exemplary embodiment.

Figure 4 is a diagram illustrating the flow water temperature in relation to the outdoor temperature.

All figures are schematic, not necessarily to scale and generally only show parts, which are necessary in order to elucidate the invention, wherein other parts may be omitted or merely suggested. Detailed description

Embodiments of the invention will now be described with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the particular embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements.

Figure 1 illustrates a block diagram of a heating system 100, to which a device 200 according to an exemplary embodiment of the present disclosure can be connected. The heating system 100 comprises a heating source 110. The heating source 110 may be of many different types, for example a heat pump, a boiler or a heat exchanger 110. The heating source 110 adds energy to a building 120 by supplying heated water via flow water pipe 130 to the building's radiator system 140. The heated water returns to the heating source 110 via a return water pipe 150.

The heating system 100 comprises a flow water temperature sensor 160 adapted to determine the actual flow water temperature TFAC of water supplied from the heating source 110. In a heating system according to the prior art, the flow water temperature sensor 160 is directly connected to a flow water temperature sensor input 170 of the heating source 110. Thus, in prior art systems, the heating source is provided with the actual flow water temperature. The balance temperature is thus not considered in prior art control of heating sources based on flow water temperature.

In the heating source 110, the flow water temperature T _F from the heating source 110 is determined based on the outdoor temperature TOUT- The flow water temperature T _F is often determined based on a heating curve that determines the flow water temperature T _F for different outdoor temperatures TOUT-

The heating curve often plots the outdoor temperature T _ou t on the X-axis against the flow water temperature T _F on the Y-axis. A heating curve is provided where the outdoor temperature decreases, the flow water temperature increases.

Using the heating curve, in the heating system 100, the heating source 110 determines the flow water temperature T _F based on the outdoor temperature. In order for the heating source to control that the correct flow water temperature T _F is provided, the heating source is provided with the flow water temperature. In prior art, the flow water temperature is directly provided from a flow water temperature sensor. According to an exemplary embodiment, the determined flow water temperature TFDET is provided to the heating source. Thereby, enabling the heating source to consider the balance temperature of the building, when controlling the flow water temperature.

However, the inventor has realized that an improved determination of the flow water temperature T _F is obtained if the flow water temperature T _F is also determined based on the building's balance temperature.

A building's balance temperature is a generally known temperature concept. The balance temperature is the outdoor temperature at which no energy from the heating source is required to maintain an indoor temperature of the building. At the balance temperature, the building is able to maintain the desired indoor temperature with the energy provided from solar radiation, electrical appliances, people, etc. in the building.

A building's energy need constitutes the difference between the outdoor temperature and a desired indoor temperature. This energy need is supplied by solar radiation, electrical appliances, people, etc. and, if necessary, a heating system. If the outdoor temperature is sufficiently high (i.e., equal to or above the balance temperature), no energy from the heating system is needed.

When the outdoor temperature is lower than the balance temperature, the energy from solar radiation, electrical appliances, people, etc. is not sufficient for the building to reach the desired indoor temperature. Therefore, energy from the heating system is needed to make up the deficit. As the outdoor temperature approaches the balance temperature, the energy from solar radiation, electrical appliances, people, etc. constitutes a larger proportion of the building's energy need.

In so-called zero-energy houses or near zero-energy houses, the energy provided by people, electrical appliances, solar radiation, etc. provides the entire energy contribution to the building. This means that heating systems become redundant for these types of buildings.

The inventor has realized that one way of taking the energy from solar radiation, electrical appliances, people, etc. into account is to adjust an actual flow water temperature value that is provided to the heating source 110. Further, the inventor has realized that one way of adjusting the actual flow water temperature value is to connect a device 200 between the flow water temperature sensor 160 and the flow water temperature sensor input 170 to the heating source 110. The device 200 is adapted to provide a determined flow water temperature value T _F DET to the flow water temperature sensor input 170 of the heating source 110, instead of the actual flow water temperature value.

The device 200 therefore provides a low-cost solution that can be easily installed in an existing heating system 100. Further, only minor modification of the existing heating system 200 is required.

Figure 2 illustrates a block diagram of an exemplary embodiment of the device 200 adapted to provide a determined flow water temperature value TFDET to a flow water temperature sensor input of the heating source 110. The device 200 comprises a processor 210. The device 200 further comprises a memory 220 containing instructions executable by the processor 210, that when executed by the processor 210 cause the device 200 to retrieve the actual flow water temperature value T _F cfrom the flow water temperature sensor 160. The instructions further cause the device 200 to determine a AT _F value based on an outdoor temperature value TOUT, until the outdoor temperature reaches a balance temperature TBAL of the building, at which no energy from the heating source 110 is required to maintain an indoor temperature of the building. The AT _F value is based on the outdoor temperature value Toursuch that the AT _F value increases when the outdoor temperature increases. Further, the instructions cause the device 200 to determine the determined flow water temperature value T _FDF Tby adding the actual flow water temperature value T _FA c and the AT _F value. Yet further, the instructions cause the device 200 to provide the determined flow water temperature value TEDET IO the flow water temperature sensor input 170.

Therefore, by determining the determined flow water temperature value T _FD ET based on the outdoor temperature TOUT, it is possible to take the energy from solar radiation, electrical appliances, people, etc. into account when controlling the flow water temperature T _F . This is because, when using the device 200, the building's balance temperature will also influence the control of the flow water temperature T _F .

As mentioned above, in prior art systems, the heating source is provided with the flow water temperature. Therefore, in prior art the flow water temperature is directly provided from a flow water temperature sensor. Instead, according to an exemplary embodiment, the determined flow water temperature T _FD ET is provided to the heating source. Thereby, enabling the heating source to consider the balance temperature of the building, when controlling the flow water temperature. When the outdoor temperature changes, the ratio between the energy from the heating source and energy from other sources changes. Therefore, energy from solar radiation, electrical appliances, people, etc. will constitute a larger part of the building's total energy need when the outdoor temperature is higher.

Therefore, according to an exemplary embodiment of the present disclosure, the AT _F value is based on the outdoor temperature value Toirrsuch that the AT _F alue increases when the outdoor temperature increases. In an exemplary embodiment, the AT _F value increases until the outdoor temperature reaches a balance temperature TBAL of the building, at which no energy from the heating source 110 is required to maintain an indoor temperature of the building.

In another exemplary embodiment, the instructions further cause the device 200 to determine a AT _F value based on a difference value TTDIPP between a set indoor temperature value T _SF Tand an actual indoor temperature TACT, such thatT _T Di _FF = TSET- TACT- In one exemplary embodiment, the AT _F value increases when the difference value TTDIEE increases and the AT _F value decreases when the difference value TTDIEE decreases.

By also determining the determined flow water temperature value T _FDET based on a difference value T _T DI _FF between a set indoor temperature value T _SE Tand an actual indoor temperature TACT- It is possible to influence the heating source 110 control of the flow water temperature by a difference value TTDIPP. Where TTDIPP is a difference value between a set indoor temperature value TSET and an actual indoor temperature TACT-

The higher the set indoor temperature TSET is compared to the actual indoor temperature TACT, the higher the AT _F value will be. In the case that the set indoor temperature TSET is higher than the actual indoor temperature, TACT, the AT _F value will be positive. This will cause the heating source 110 to provide a higher flow water temperature T _F compared to the case where the set indoor temperature TSET is lower than the actual indoor temperature TACT.

In another exemplary embodiment, the instructions further cause the device 200 to determine a AT _F value based on a difference value TWDIEE between the actual flow water temperature T _FA C and a return water temperature value T _R , such thatT _W DiEE= T _FA C- T _R . In this embodiment, the AT _F value increases when the difference value TWDIEE increases. The AT _F value decreases when the difference value TWDIEE decreases. Therefore, by determining the determined flow water temperature value TFDET based on a difference value TWDIFF between the actual flow water temperature TFAC and a return water temperature value TR, it is possible to influence the heating source 110 control of the flow water temperature by a difference value TWDIFF between the actual flow water temperature TFAC and a return water temperature value TR.

The higher the return water temperature value T _R is compared to the flow water temperature T _F AC the lower the AT _F value will be. Therefore, the heating source 110 will be influenced to a lower extent when the return water temperature value TR is closer to the flow water temperature T _F . In the case that the return water temperature value TR is relatively close to the actual flow water temperature TFAC, the AT _F value will be low compared to the case where the return water temperature value TR is relatively far from the actual flow water temperature TFAC-

Therefore, the heating source 110 is influenced largely and provides a higher flow water temperature T _F when the difference value TWDIFF between the actual flow water temperature TFAC and the return water temperature value TR is high, compared to the case where the difference value TWDIFF is lower.

In yet another embodiment of the device 200, the software instructions further cause the device 200 to determine the AT _F value according to formula (a):

(a) ATF = (TFAC ^— TR) X (TSET ^— TACT)/(TBAL ^— TOUT); wherein

TFAC = actual flow water temperature

T _R = return water temperature

T _S ET = set indoor temperature

TACT = actual indoor temperature

T _B AL = balance temperature of the building

T _O UT = outdoor temperature

In yet another embodiment of the device 200, the software instructions further cause the device 200 to determine the AT _F value according to formula (b):

(b) (TFDET ^— TRDET) - (TFAC - TR) X (TBAL- TOUT + TTDIFF)/ (TBAL - TOUT) TTDIFF - (TSET ^— TACT)

AT F = (TFDET ^— TRDET) - (TFAC ^— TR)

The expression (TFDET - TRDET) is the calculated value for the difference between T _F and TR and does not denote the individual values on T _F or T _R .

In a further exemplary embodiment, the heating source uses the actual flow water temperature TFAC from the heating source to determine the determined flow water temperature value TFDET-

In one exemplary embodiment, the device 200 is arranged on a single printed circuit board (PCB).

In one exemplary embodiment, the PCB is smaller than 30*15 mm, thus allowing the PCB to be arranged in the heating source 210. According to one exemplary embodiment, the device is supplied with power from the heating source 210. Therefore, the device 200 does not need any further power supply in addition to the power supply from the heating source 210. In another exemplary embodiment, the device 200 has a contact for allowing connection of a computing device in order to update and/or modify the software instructions in the device 200. In another exemplary embodiment, the balance temperature of the device can be set via the contact. In another exemplary embodiment, the balance temperature of the device can be set via a wireless interface to the device 200. Therefore, it possible to set the balance temperature of the device 200 after the device has been installed. In some embodiments, the balance temperature may be adapted based on the number of people in the building. In another exemplary embodiment, the balance temperature is adapted based the amount of solar radiation. In other exemplary embodiments, the balance temperature may be adapted based on other factors that affect the balance temperature.

In yet another embodiment of the device 200, the actual flow water temperature TFAC from the heating source is determined based on the outdoor temperature value TOUT such that the flow water temperature increases when the outdoor temperature value TOUT decreases, and such that the flow water temperature decreases when the outdoor temperature value TOUT increases.

In one exemplary embodiment, the flow water temperature T _F from the heating source is determined based on a heating curve. In one exemplary embodiment, the outdoor temperature Tou s determined based on a linear equation for the heating curve. According another exemplary embodiment, TOUT can be replaced with an expression related to a linear equation for a heating curve. In one exemplary embodiment, T _OUT is received from an outdoor temperature sensor. Referring to figure 4, in another exemplary embodiment the outdoor temperature T _OUT is determined according to the expression: T _{OUT X} = (T _FX - M)/K, where K= (T _{F MAX} – T _{F MIN} )/ (T _DOT – T _BAL ) and M= T _FMIN – K x T _BAL or M= T _FMAX – K x T _DOT T _DOT is the statistic coldest outdoor temperature that the heating source 100 is dimensioned for. Referring to figure 4, the outdoor temperature can also be determined in terms of the following expression.   T _{OUT X} = T _BAL – (T _BAL – T _DOT ) ^T _{FR X} / ^T _FRMAX where ^T _FRmax = (T _FMAX - T _RMAX ) Referring back to figure 2, when the device 200 comprise a processor 210, the processor 210 is a central processing unit, CPU, microcontroller, digital signal processor, DSP, or any other suitable type of processor capable of executing computer program code. The memory 220 is a random-access memory, RAM, a read-only memory, ROM, or a persistent storage, e.g. a single or combination of magnetic memory, optical memory, or solid-state memory or even remotely mounted memory. According to one embodiment, the disclosure further relates to the above mentioned computer program, comprising computer readable code which, when run on the device 200 causes the device 200 to perform any of the embodiments of the disclosure described herein. The present disclosure also relates to a computer-readable storage medium, having stored there on a computer program which, when run in the device 200, causes the device 200 to operate as described above. According to one embodiment, the disclosure further relates to the above mentioned computer program, comprising computer readable code which, when run on the device 200, causes the device 200 to perform any of the embodiments of the disclosure described herein.

According to one embodiment of the disclosure, the processor 210 comprises: a retrieving module 211 adapted retrieve the actual flow water temperature value T _F Acfrom the flow water temperature sensor; a first determining module 212 adapted to determine a AT _F value based on an outdoor temperature value TOUT, until the outdoor temperature reaches a balance temperature TBAL of the building, at which no energy from the heating source (110) is required to maintain an indoor temperature of the building, the AT _F value is based on the outdoor temperature value Toursuch that the AT _F value increases when the outdoor temperature increases; a second determining module 213 adapted to determine the determined flow water temperature value T _F DETby adding the actual flow water temperature value T _FA c and the AT _F value; a providing module 214 adapted to provide the determined flow water temperature value T _FD ET to the flow water temperature sensor input.

The modules 211, 212, 213 and 214 are implemented in hardware or in software or in a combination thereof. According to one embodiment, the modules 211, 212, 213 and 214 are implemented as a computer program stored in the memory 220, which run on the processor 210. The device 200 is further configured to implement all the embodiments of the disclosure as described herein.

FIG. 3 illustrates a flow chart of a method 300 for providing a determined flow water temperature value T _FD ET to a flow water temperature sensor input to a heating source. The method is performed by the device 200 adapted to be connectable to a flow water temperature sensor. The flow water temperature sensor is adapted to determine the actual flow water temperature T _FA cfrom the heating source. In a first step 310, the method begins with retrieving the actual flow water temperature value T _FA c from the flow water temperature sensor. In step 320, the method determines a AT _F value based on an outdoor temperature value TOUT, until the outdoor temperature reaches a balance temperature TBAL of the building, at which no energy from the heating source 110 is required to maintain an indoor temperature of the building. The AT _F value is based on the outdoor temperature value Toursuch that the AT _F value increases when the outdoor temperature increases. In step 330, the determined flow water temperature value TFDET IS determined by adding the actual flow water temperature value T _F Ac and the AT _F value. In step 340, the method provides the determined flow water temperature value T _FD ETto the flow water temperature sensor input.

As such, the method provides an inventive solution to the concerns described above, by providing a determined flow water temperature value T _FD ET to a flow water temperature sensor input of a heating source. Since the method influence the flow water temperature value, it is possible to obtain an improved control of the flow water temperature T _F from the heating source.

According to one exemplary embodiment, the step of determining the AT _F value further comprises determining the AT _F value based set indoor temperature value T _SF Tand an actual indoor temperature TACT, such thatTTDi _FF = T _S ET- TACT- In this embodiment, the AT _F value increases when the difference value TTDIEE increases and such that the AT _F value decreases when the difference value TTDIEE decreases.

Therefore, it is possible to influence the heating source 110 control of the flow water temperature based on a difference value TTDIEE between a set indoor temperature value T _SF Tand an actual indoor temperature TACT, TTDIEE= TSET- TACT

The higher the set indoor temperature TSET is compared to the actual indoor temperature TACT, the higher the AT _F value will be. This causes the heating source to provide a lower flow water temperature T _F compared to the case where the set indoor temperature TSET is lower than the actual indoor temperature TACT.

In another exemplary embodiment of the method, a AT _F value is determined based on a difference value TWDIEE between the actual flow water temperature T _F cand a return water temperature value T _R , such that TWDIEE= T _F AC - T _R , such that the AT _F value increases when the difference value TWDIEE increases and the AT _F value decreases when the difference value TWDIEE decreases.

Therefore, it is possible to influence the heating source 110 control of the flow water temperature T _F based on a difference value. Where the difference value TWDIEE is a difference between the actual flow water temperature T _FA c and the return water temperature value TR.

The higher the return water temperature value T _R is compared to the flow water temperature T _F c, the lower the difference valueT _W Di _FF will be. A lower difference value TWDIEE gives a lower AT _F . Therefore, the heating source 110 is influenced to a lower extent when the return water temperature value T _R is higher. In case the return water temperature value T _R is relatively close to the actual flow water temperature T _FAC , the ^T _F value will be low compared to the case where the return water temperature value T _R is relatively far from the actual flow water temperature T _FAC . Furthermore, the heating source 110 is influenced to larger extent when the difference value T _WDIFF between the actual flow water temperature T _FAC and the return water temperature value T _R is high compared to the case where the difference value T _TDIFF is lower. According to yet another exemplary embodiment, the step of determining the ^T _F value further comprises determining the ^T _F value according to the formula (a): (a) ^T _F = (T _FAC – T _R ) x (T _SET – T _ACT )/ (T _BAL – T _OUT ), wherein T _FAC = actual flow water temperature T _R = return water temperature T _SET = set indoor temperature T _ACT = actual indoor temperature T _BAL = balance temperature of the building T _OUT = outdoor temperature According to yet another exemplary embodiment, the step of determining the ^T _F value further comprises determining the ^T _F value according to the formula (b): (b) (T _FDET – T _RDET ) = (T _FAC – T _R ) x (T _BAL – T _OUT + T _TDIFF )/ (T _BAL – T _OUT ) T _TDIFF = (T _SET – T _ACT ) ^ ^T _F = (T _FDET – T _RDET ) - (T _FAC – T _R ) According to a further exemplary embodiment of the method, the heating source uses the actual flow water temperature T _FAC from the heating source to control the determined flow water temperature value T _FDET . According to a further exemplary embodiment of the method, the low water temperature T _F Acfrom the heating source is determined based on the outdoor temperature value TOUT such that the flow water temperature T _F AC increases when the outdoor temperature value TOUT decreases, and such that the actual flow water temperature T _FA c decreases when the outdoor temperature value TOUT increases.

According to one exemplary embodiment, the heating source is a heat pump.

In the claims, the word "comprising" does not exclude other elements or steps and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the claims.