DE202022102207U1 - Hot water supply system with heat recovery - Google Patents

Abstract

Hot water supply system comprising
a connection to a fresh water supply (2) for letting cold drinking water into the hot water supply system,
a first heat exchanger (6) for heat transfer of heat from a primary heat transfer medium (P) to the cold drinking water,
a supply line (4) carrying the heated drinking water, to which at least one consumer (22) is connected,
a second heat exchanger (54) for heat recovery by heat transfer of heat from a secondary heat transfer medium (S) to the primary heat transfer medium (P) which has been cooled by heat release to the drinking water, and
a heat transfer medium pump (36) transferring flow energy to the primary heat transfer medium (P).

Description

The present invention relates to a hot water supply system with heat recovery.

With heat recovery (in short: WRG), waste heat from an upstream process is absorbed in order to feed it back into the system at another point, thereby saving energy costs. For efficient heat recovery, the medium to which the waste heat from the upstream process is released should be as cold as possible. In this way, maximum cooling of the medium that emits the waste heat is achieved, and this in turn can absorb larger amounts of energy through the upstream process. Examples of upstream processes are: cold stores; industrial processes; general processes that produce waste water; Cooling of server rooms; Industrial use freezer cooler.

Since heat can only be transferred from a warmer to a colder medium, it is efficient if the colder medium is kept as cool as possible. This is the reason why operators and planners of hot water supply systems with heat recovery now want to give the heat from the heat recovery preferentially to the cold water just before the main drinking water heater in the form of a preheating stage. There, the cold water is preheated to a certain extent. This has the positive effect that the main drinking water heater can be dimensioned smaller because the water no longer has to be heated from approx. 10°C to approx. 60°C, but only from approx. 35°C to approx. 60°, for example C

Despite this great potential, hot water supply systems with heat recovery are also associated with risks and normative conditions, which would be exemplary: According to DVGW W 511, preheating stages must be heated to >60°C at least daily from a volume >400 l; Preheating stages must be structurally designed in such a way that it is possible to heat them up to >60°C on a daily basis; Preheating stages generate an additional pressure loss in the drinking water pipe; After the preheating stage, the hot water is in a critical temperature range of around 40 °C and is therefore hygienically questionable; In periods of non-use, there are certain dead lines with stagnant water.

One object of the present invention is to specify a hot water supply system that meets the normative conditions and at least partially reduces or eliminates the risks mentioned.

To solve this problem, the present invention provides a hot water supply system with the features of claim 1.

The hot water supply system according to the present invention has a connection to a fresh water supply for letting cold drinking water into the hot water supply system. This connection is usually a connection to the public water supply network, with a connection to the public water supply network in the sense of the present invention being, in particular, such an area of a drinking and process water system of a building that communicates directly with the building water meter, however does not yet have a branch leading to one or more supply lines. The connection regularly corresponds to a point of transition from drinking water according to §3 paragraph 3 of the Drinking Water Ordinance. The hot water supply network is usually a drinking water installation according to this standard. The hot water supply system according to the present invention is therefore designed in particular as a drinking and service water system for providing hot drinking and service water or at least includes such a drinking and service water system.

To heat the cold drinking water, the hot water supply system has a first heat exchanger for transferring heat from a primary heat transfer medium to the cold drinking water. The drinking water and the primary heat transfer medium are fluidically separated from each other. For this purpose, the first heat exchanger has, for example, a heat-permeable and fluid-impermeable partition. This separation prevents the drinking water from being contaminated by the primary heat transfer medium. The first heat exchanger can be designed in particular as a plate heat exchanger.

The heated drinking water is fed through a supply line of the hot water supply system to at least one consumer that is connected to the supply line. The consumers can be connected to the supply line in a variety of ways. For example, several consumers can be connected to the supply line via a flow divider. The connection can be implemented just as well via a T-piece installation or a ring installation. The supply line can at least be designed in sections on the consumer side as a riser and/or as a floor line. A consumer within the meaning of the present invention can in particular any hot water extraction point of a building be, e.g. a shower or a sink. The supply line can be assigned a circulation line for returning drinking water cooling in the supply line to the first heat exchanger, the circulation line communicating with a circulation pump for generating a preferably constant circulation volume flow. The circulation line generally has a nominal diameter that is at least one nominal diameter jump smaller than the supply line.

A heat transfer medium pump is provided for transferring flow energy to the primary heat transfer medium. The primary heat transfer medium is conducted through the first heat exchanger by the heat transfer medium pump and corresponding lines.

The hot water supply system has a second heat exchanger for heat recovery. This is provided for the heat transfer of heat from a secondary heat transfer medium to the primary heat transfer medium, which has been cooled down by heat transfer to the drinking water. The second heat exchanger can be a plate heat exchanger or a heat pump.

The heat from the WRG is therefore first transferred to the primary heat transfer medium and not directly to the drinking water. As a result, the heat from the HRV is fed back into the system at a point that makes it easier to reduce or eliminate the risk of the drinking water stagnating at a hygienically unsafe temperature of around 40°C, for example. In particular, the primary heat transfer medium preheated by the WRG can be further heated to at least 60° C. before it is fed to the first heat exchanger to heat the cold drinking water. As a result, the cold drinking water can be heated to a specific target temperature without a preheating stage. This target temperature is preferably adjustable. It is particularly preferably in a range from 50°C to 60°C.

According to a preferred development of the present invention, the primary heat transfer medium consists largely or entirely of water. The primary heat transfer medium can be the heating water of a heating circuit of a building, for example. More preferably, the hot water supply system has a central heating system with which the primary heat transfer medium can be heated to a temperature that is preferably at least 60°C or greater than 60°C. The central heating system is preferably a heating system using primary energy.

According to a further preferred development of the present invention, the secondary heat transfer medium is a fluid containing waste heat and/or waste water or gray water, the temperature of the secondary heat transfer medium preferably being at least 35°C. More preferably, the temperature of the secondary heat transfer medium is less than 60°C. The waste heat can be waste heat from a cooling process and/or from an industrial process and/or from exhaust air. Alternatively or additionally, the secondary heat transfer medium can contain energy from the environment, ie the heat present in the ground or in the outside air. Especially when using a heat pump, it does not necessarily have to be heat recovery in the conventional sense. For the purposes of the present application, a transfer of heat from the environment should preferably also be subsumed under “heat recovery”.

According to a further preferred development of the present invention, the hot water supply system includes at least one buffer storage for the primary heat transfer medium. The buffer store is usually dimensioned and designed in such a way that thermal stratification of the primary heat transfer medium occurs automatically within the buffer store. As a rule, the primary heat transfer medium from the upper area of the buffer tank is used to heat the drinking water. The primary heat transfer medium from the middle and/or lower area of the buffer tank is usually heated to a temperature of at least 60°C by a central heating system or an electric heating rod of the hot water supply system, causing it to rise in the buffer tank to the upper, warmer area.

According to a further preferred development of the present invention, the hot water supply system comprises at least one main buffer tank which is connected to the first heat exchanger and communicates with a central heating system of the hot water supply system in order to keep part of the primary heat transfer medium at a temperature of at least 60° C. or higher, at least a secondary buffer storage connected to the second heat exchanger, which keeps another part of the primary heat transfer medium ready for heat recovery, a connecting line between the main buffer storage and the secondary buffer storage for transferring primary heat transfer medium heated by the heat recovery from the secondary buffer storage to the Main buffer storage, and a first return line connecting the first heat exchanger to the secondary buffer storage for the return of itself primary heat transfer medium cooled by heat transfer to the drinking water from the main buffer tank to the secondary buffer tank. The primary heat transfer medium runs through different stations, with it usually being heated up from a lowest temperature level in the second heat exchanger and being cooled down from a highest temperature level in the first heat exchanger. Between these two stations, the primary heat transfer medium is temporarily stored in the buffer tanks on the way from the second heat exchanger to the first heat exchanger, with the primary heat transfer medium temporarily stored in the main buffer tank being at least partially heated by the heating system to a target temperature for heating the drinking water.

According to a further preferred development of the present invention, the hot water supply system includes a switching valve provided between the first heat exchanger and the buffer storage tanks for switching between an inlet to the first heat exchanger from the secondary buffer tank and an inlet to the first heat exchanger from the main buffer tank. In this preferred development, the cold drinking water is heated to a preheated temperature level by the heat recovered from the WRG when the inflow to the first heat exchanger from the auxiliary buffer storage is activated. As a rule, the temperature level of the WRG and thus also the temperature level of the auxiliary buffer tank is lower than the target temperature mentioned at the beginning between 50°C and 60°C, so that the drinking water temperature at the preheated temperature level is below this range. Usually the temperature of the preheated level is 35°C, 40°C or 45°C, each ± 2.5°C. Due to the lower temperature level of the preheated temperature level, the return temperature of the primary heat transfer medium is also lower, so that on the one hand the efficiency of the HR increases. On the other hand, the lower temperature level of the WRG is also accompanied by the normative condition mentioned at the beginning that preheating stages from a volume >400 l must be heated to >60°C at least daily. In order to meet this condition, the switching valve can be switched over at least once a day in order to activate the inflow to the first heat exchanger from the main buffer tank.

According to a further preferred development of the present invention, the hot water supply system includes a third heat exchanger for heating the drinking water, which is connected to the supply line in parallel or in series with the first heat exchanger. The third heat exchanger can be a plate heat exchanger. As with the first heat exchanger, the thermal energy for heating the drinking water by the third heat exchanger is also provided by the primary heat transfer medium and preferably from the main buffer storage tank. This opens up the possibility of heating the drinking water in a cascade-like manner, with the cascade being triggered by the consumption of hot water by the consumer. Due to the hot water extraction, cold drinking water flows into the system via the connection to the fresh water supply and is heated in a first stage of the cascade by the first heat exchanger to a temperature that is, for example, in the range of 50-60°C. In a series connection, the drinking water heated by the first heat exchanger is then reheated by the third heat exchanger in a second stage of the cascade to a temperature of, for example, at least 60°C and then fed to the consumer. In a parallel connection, the drinking water heated by the first heat exchanger is combined with the drinking water heated by the third heat exchanger in the second stage of the cascade and then fed to the consumer. The supply lines between the buffer storage tanks and the first and the third heat exchanger are preferably no longer than 10 m, 15 m, 20 m or 25 m.

According to a further preferred development of the present invention, the hot water supply system comprises a circulation line and a circulation pump assigned to the circulation line for returning drinking water cooling down in the supply line to the third heat exchanger. Heat losses from the warm drinking water in the pipes can thus be compensated for by the third heat exchanger. As a result, warm drinking water at the desired temperature, usually 60°C, can always be kept ready even if no water is drawn off. The circulation flow is usually continuous, so that stagnation of drinking water is reliably avoided. A circulation line generally has a smaller diameter than the upstream supply line leading to the consumer. Usually, the third heat exchanger operates at a higher temperature level than the first heat exchanger, since either - in the case of series connection - the drinking water heated by the first heat exchanger or - in the case of parallel connection - the warm drinking water returned through the circulation line is fed to the inlet of the third heat exchanger , whereas the inlet of the first heat exchanger has the fri cal cold drinking water is supplied to the fresh water supply system.

According to a further preferred development of the present invention, the hot water supply system comprises a second return line for the primary heat transfer medium, which connects the third heat exchanger to the main buffer tank. Since the third heat exchanger usually operates at a higher temperature level, the return temperature of the primary heat transfer medium coming from the third heat exchanger is only slightly lower, so that it is not suitable for heat recovery and can be returned directly to the main buffer tank.

According to a further preferred development of the present invention, the hot water supply system includes a flushing device associated with the circulation line or the supply line and having a flushing valve for draining drinking water from the hot water supply system. As a result, the drinking water quality can be guaranteed at all times by flushing pipe sections with standing water due to long periods of non-use by opening the flushing valve. The flushed out stagnant water is replaced by fresh cold drinking water and heated by the first and/or the third heat exchanger. As a rule, the flushing valve is located downstream of the first and/or the third heat exchanger in the direction of flow. The flushing device can include several flushing valves.

According to a further preferred development of the present invention, the hot water supply system comprises at least one water temperature sensor, which is assigned to a drinking water outlet of the first heat exchanger, and a control unit for regulating the water temperature of the drinking water heated by the first heat exchanger by controlling the heat transfer medium pump.

According to a further preferred development of the present invention, the control unit is set up in such a way that it controls the heat transfer medium pump in such a way that the temperature measured by the water temperature sensor corresponds to a target value, with the target value being adjustable.

According to a further preferred development of the present invention, the control unit is set up in such a way that the setpoint value corresponds to a reduced hot water temperature value and is raised to a temperature value of at least 60° C. or greater than 60° C. at least once a day for a predetermined time or for a predetermined flow rate becomes. In this context, a reduced water temperature value is understood to mean in particular a value which is at least 1°C, preferably at least 3°C, 5°C, 10°C or 15°C lower than 60°C. How often or at what time intervals the increase takes place and for how long is preferably variable or adjustable. The duration of the increase can be dependent on consumption or the amount of water flushed out, e.g. it can only end when a certain minimum amount of hot water has been consumed by the consumer or flushed through the flushing device after the increase. For this purpose, the hot water supply system usually includes a flow meter for determining a flow rate.

By lowering the temperature level of the first stage of the cascade, a lower return temperature of the primary heat transfer medium fed to the secondary buffer tank can be achieved, thus increasing the efficiency of the HR. The lowering of the temperature level of the first stage of the cascade is preferably implemented with the previously described series connection of the first and third heat exchangers, so that the drinking water in the second stage of the cascade rises from the lowered temperature level to the desired temperature for warm drinking water, which is usually 60°C is heated before it is sent to the consumer.

According to a further preferred development of the present invention, the control unit controls the switchover valve in such a way that the feed to the first heat exchanger from the main buffer storage tank is released for the predetermined time or until a predetermined flow rate is reached at an elevated temperature, and before and after that the feed is closed the first heat exchanger from the secondary buffer storage is released. In other words, in this preferred development, the heat for the reduced water temperature is provided from the secondary buffer store and the heat for the temperature value of at least 60° C. or greater than 60° C. is provided from the main buffer store. Alternatively, the heat can be provided from the main buffer tank both for the lowered water temperature and for the temperature value of at least 60°C or greater than 60°C by using the heat for the temperature value of at least 60°C or greater than 60°C is provided, for example, from an upper thermal layer and for the lowered water temperature from an underlying thermal layer and / or the primary heat transfer medium cools down shorter on the cold drinking water.

According to a further preferred development of the present invention, the hot water supply system includes a flushing device control module for initiating a change of drinking water by controlling the flushing valve of the flushing device. In such a drinking water exchange, at least the entire amount of water between the flushing valve and the first heat exchanger is usually exchanged for fresh drinking water. The criteria and/or the interval time and/or the times at which a change of drinking water is initiated can preferably be programmed into the flushing device control module. The flushing device control module can be part of the control unit or a higher-level controller, in particular a functional software module of the control unit or the higher-level controller, or it can be designed as an independent component that is preferably adapted to communicate with the control unit or the higher-level controller . As an independent component, it can be provided in a common housing with the control unit or the higher-level controller, or separately at another point in the system.

A time-controlled flushing mode can be programmed into the flushing device control module, in which the flushing valve is opened at specific times and/or time intervals for a change of drinking water. For this purpose, the flushing device control module can have a timer that is set to 72 hours, for example.

A warm flush mode may be programmed into the flusher control module. For example, a drinking water change can be initiated as soon as the setpoint is increased from the lowered temperature value. This allows the water still in the pipes to be drained from the system at a reduced temperature. A stop criterion for the change of drinking water in the warm flushing mode can be generated from the water temperature measured by the temperature sensor. This means that the change of drinking water can be ended, for example, when the water temperature measured by the temperature sensor reaches a certain higher target temperature from a lower value.

A WRG flushing mode can be programmed into the flushing device control module, in which a drinking water change is triggered while the switching valve is set in such a way that the inflow to the first heat exchanger from the secondary buffer storage tank is activated.

In principle, several flushing modes can be programmed into the flushing device control module. The purge modes can be implemented to interact with each other. For example, a water change from another mode may reset the timer for the timed mode.

According to a further preferred development of the present invention, the control unit is set up in such a way that the heat transfer medium pump is deactivated during a cold flushing mode of the flushing device control module. To implement the cold flushing mode, the flushing device preferably comprises at least one flushing valve upstream of the third heat exchanger in the direction of flow. The cold rinsing mode can be triggered when the consumer stops drawing off hot water. In the cold flushing mode, the flushing valve is opened to exchange the drinking water between the first and the third heat exchanger and in the first heat exchanger with fresh cold drinking water. This can prevent the drinking water in the area of the first heat exchanger developing into a hygienically unsafe temperature range after water has been removed by the consumer. Nevertheless, the position of the flushing valve and the specified direction of flow ensure that the temperature level of the third heat exchanger, i.e. the second stage of the cascade, remains essentially unaffected. In addition, a non-return valve can be provided, which prevents hot drinking water from flowing back from the second stage of the cascade to the flushing valve. The cold flush mode can also be triggered without consumption. For example, the control unit can activate the heat medium pump in order to reach the target value of 60°C, for example, and then trigger the cold rinsing mode. As a result, the first heat exchanger can be heated up to the setpoint temperature at regular intervals even without the consumer drawing off drinking water.

According to a further preferred development of the present invention, the target value is set variably and is dependent in particular on a flow temperature of the first heat transfer medium from the secondary buffer storage tank and/or domestic hot water consumption. For example, the desired value can be set lower by a specific temperature difference ΔT than the flow temperature of the first heat transfer medium supplied from the secondary buffer store. The temperature difference ΔT can be 5°C or 10°C, for example. The temperature difference can be adjustable depending on an average domestic hot water consumption. For example, the temperature difference can be greater with higher domestic hot water consumption (e.g. 100 l/min). than with a smaller domestic hot water consumption (e.g. 20 l/min). In the event that the flow temperature should be greater than 60°C, the setpoint is preferably limited to a maximum of 60°C.

According to a further preferred development of the present invention, the first setpoint is set variably and is dependent in particular on a return temperature of the first heat transfer medium to the secondary buffer storage tank and/or domestic hot water consumption. The temperature difference ΔT is then usually set in such a way that a maximum cold return temperature is achieved for the primary heat transfer medium.

According to a further preferred development of the present invention, the hot water supply system includes a disinfection operating mode implemented in the control unit, in which the drinking water is heated to a target value of over 60° C. and drained from the hot water supply system by actuating the flushing valve. In the disinfection operating mode, the setpoint is raised to 60°C or higher and the switching valve, if present, is set for a predetermined time or until a predetermined flow rate is reached at an elevated temperature so that the inflow to the first heat exchanger from the main buffer tank is released. You can then switch back to the previous normal operating mode from the disinfection operating mode. For example, the switching valve can again be set in such a way that the inflow to the first heat exchanger from the secondary buffer store is released, and the first setpoint temperature can be reduced again. More preferably, the disinfection operating mode can be automatically interrupted by the consumer using domestic hot water and then continued or interrupted and postponed. The disinfection mode of operation is particularly preferably followed by one of the rinsing modes.

According to a further preferred development of the present invention, the hot water supply system includes a data logger for logging the duration, start, stop, date and/or time of a drinking water change by the flushing device and/or the duration, start, stop, date and/or time of activation of the disinfection operating mode and/or a flushing volume drained from the hot water supply system during a water change and/or the water temperature measured by a temperature sensor. The data logger is usually connected in terms of data to the control unit and the flushing device control module and/or a higher-level controller.

• 1 eine schematische Darstellung eines ersten Ausführungsbeispiels,
• 2 eine schematische Darstellung eines zweiten Ausführungsbeispiels und
• 3 eine schematische Darstellung eines dritten Ausführungsbeispiels.

Further particulars and details of the present invention result from the following description of exemplary embodiments in conjunction with the drawing. In this show:

• 1 a schematic representation of a first embodiment,
• 2 a schematic representation of a second embodiment and
• 3 a schematic representation of a third embodiment.

1 shows a hot water supply system schematically. The individual components of this hot water supply system can be provided in a building. The hot water supply system includes a connection 2 to a fresh water supply for letting in cold drinking water. Connection 2 is the point of transfer of drinking water from a water supply system in accordance with the Drinking Water Ordinance. The connection 2 to the fresh water supply is connected via a first line 4 to four first heat exchangers 6 and feeds them with fresh cold drinking water. The first heat exchanger 6 transfer heat from a primary heat transfer medium P to the cold drinking water. The first heat exchangers 6 can be designed as plate heat exchangers, for example. By passing through the first heat exchanger 6, the cold drinking water is heated from 10°C, for example, to a first temperature level, which can be in the range from 40°C to 60°C, for example.

The heated drinking water leaves the first heat exchanger 6 via a second line 10 which is connected to the outlets 8 of the first heat exchanger 6 and which opens into a circulation line 12 . The circulation line 12 is connected to four third heat exchangers 14 and communicates with a circulation pump 16 which conveys the heated drinking water in the direction of the third heat exchanger 14 . There, heat is supplied to the heated drinking water so that it is heated to a second temperature level of preferably at least 60°C. The first heat exchanger 6 and the third heat exchanger 14 are therefore connected in series to the supply line 20 . Heat from the primary heat transfer medium is also transferred to the drinking water in the third heat exchanger 14 . However, the drinking water is already at the warmer first temperature level before it is heated by the third heat exchanger 14 .

A supply line 20 is connected to the outlets 18 of the third heat exchanger 14 . The supply line 20 leads to a consumer 22, which is connected to the supply line 20 to this with warm drinking water to supply. The supply line 20 together with the circulation line 12 forms a circuit in which the hot drinking water circulates when the consumer is not using it. The circulation and the associated constant heat transfer through the third heat exchanger 18 can compensate for heat losses from the warm drinking water in the lines. Heat losses in the pipes can cool down the warm drinking water from 60°C to 55°C, for example.

A flushing device 24 with a flushing valve 26 is connected to the supply line 20 for draining drinking water from the hot water supply system. As a result, a drinking water change can be carried out during a longer phase of non-use, the stagnant water being drained from the lines via the flushing valve 26 and replaced with fresh cold drinking water from connection 2 . The flushing valve 26 is associated with a free outlet 28 which drains into a sewer line.

The first heat exchangers 6 are connected to two main buffer stores 32A, 32B, which are filled with the primary heat transfer medium P, by a first flow line 30. A second flow line 34 branches off from the first flow line 30 and connects the third heat exchanger 14 to the two main buffer storage tanks 32A, 32B. The first flow line 30 is connected to the uppermost area of the main buffer tanks 32A, 32B, i.e. where the primary heat transfer medium P located therein usually has the highest temperature. The first and second flow lines 30, 34 are preferably as short as possible; for example a maximum of 20 m long.

In the area of each first heat exchanger 6 and each third heat exchanger 14, the first flow line 30 and the second flow line 34 is assigned a heat transfer medium pump 36 that transfers flow energy to the primary heat transfer medium P. Each of these heat transfer medium pumps 36 is in turn assigned a control unit 38, which is connected in terms of control to the respective heat transfer medium pump 36, with the primary heat transfer medium for heating the drinking water being pumped through the heat exchangers 6 and 14 by controlling the heat transfer medium pumps 36. Each outlet 8 of the first heat exchanger 6 and each outlet 18 of the third heat exchanger 14 is assigned a temperature sensor 40 which is connected in terms of data to the control unit 38 of the respective heat exchanger 6 or 14 .

The control units 38 are adapted to control the heat transfer medium pump 36 assigned to them in such a way that the temperature measured by the temperature sensor 40 at the outlet 8 or 18 of the respective heat exchanger 6 or 14 corresponds to an adjustable setpoint or reaches this adjustable setpoint. As already indicated above, the control units 38 are usually set in such a way that the control units 38 of the first heat exchanger 6 specify a setpoint in a lower temperature range (e.g. in the range from 40° C. to 60° C.) than the control units 38 of the third heat exchanger 6, which usually specify a setpoint of at least 60°C. In particular, the setpoint values specified by the control units 38 of the first heat exchanger 6 can be set variably and depend, for example, on a flow temperature of the primary heat transfer medium P, a return temperature of the primary heat transfer medium P and/or a hot water consumption rate. The control units 38 can be designed as modules of a higher-level controller, which preferably also includes a flushing device control module 42 for controlling the flushing device 24 .

A third flow line 44 is connected to a lower area of the two main buffer stores 32A, 32B. It communicates with a central heating system 46 of the hot water supply system that uses primary energy in order to heat at least part of the primary heat transfer medium P to a temperature of 60° C. or higher.

In addition to the two main buffer tanks 32A, 32B, the hot water supply system includes a secondary buffer tank 48, which is filled with part of the primary heat transfer medium P, which is overall at a lower temperature level than the part contained in the main buffer tank 32A, 32B , because the primary heat transfer medium P, cooled by the cold drinking water in the first heat exchangers 6, is returned via a first return line 50 to the lower region of the secondary buffer store 48. A heat recovery flow line 52 is connected to the lower area of the secondary buffer store 48 and communicates with a second heat exchanger 54 for heat recovery. In this case, heat is recovered by heat transfer from heat from a secondary heat transfer medium S to the primary heat transfer medium P, which has been cooled by heat transfer to the drinking water. A fluid containing waste heat and/or waste water or gray water is generally used as the secondary heat transfer medium S. The waste heat can be waste heat from a cooling process and/or from an industrial process.

The primary heat transfer medium P heated by heat recovery via the second heat exchanger 54 is returned to an upper region of the auxiliary buffer store 48 through a heat recovery flow line 56 . From there it is conducted through a connecting line 58 into the lower areas of the main buffer storage tanks 32A, 32B, where it mixes with the warmer primary heat transfer medium P and/or rises and is further heated by the central heating system 46, in order to ultimately be fed back through the first or the second flow line 30, 34 to be fed to the first or third heat exchangers 6, 14 for heating the drinking water.

Since the third heat exchanger 14 is already supplied with a higher drinking water temperature due to the first heating stage by the first heat exchanger 6, less heat has to be transferred from the primary heat transfer medium to the drinking water in the third heat exchanger 14 in order to achieve the desired temperature for hot drinking water from in the generally reach 60°C. As a result, the return temperature of the primary heat transfer medium P coming from the third heat exchangers 14 is only slightly lower than the flow temperature of the primary heat transfer medium P routed to the third heat exchangers 14. The return from the third heat exchangers 14 is therefore not suitable for heat recovery and is routed via a second return line 60 directly back into the main buffers 32A, 32B.

The second return line 60 returns the primary heat transfer medium P from the third heat exchangers 14 to the lower areas of the main buffer storage tanks 32A, 32B. There it mixes with a warmer or colder primary heat transfer medium P and/or rises and is further heated by the central heating system 46 in order to finally be fed back through the first or the second flow line 30, 34 to the first or third heat exchangers 6, 14 to heat the to be supplied with drinking water.

A third return line 62 connects the central heating system 46 to the tops of the main storage tanks 32A, 32B.

This in 2 The hot water supply system shown is like the hot water supply system except for one difference 1 built up. The difference is that the second line 10 after the hot water supply system 2 not as with the hot water supply system after 1 into the circulation line 12 with the circulation pump 16, but into the supply line 20. At the mouth, the drinking water heated by the first heat exchanger 6 mixes with the drinking water heated by the third heat exchanger 14 and is routed through the supply line 20 to the consumer 22. The drinking water heated by the first heat exchanger 6 is not as in 1 passed through the third heat exchanger 14 before it is passed to the consumer 22. To this extent, the first heat exchanger 6 and the third heat exchanger 14 are connected in parallel to the supply line 20 . Just like with the hot water supply system after 1 the drinking water of the supply line 20 is returned to the third heat exchanger 14 through the circulation line 12 when the consumer 22 is not in use.

This in 3 The hot water supply system shown is like the hot water supply system except for one difference 1 built up. The difference lies in the fact that with the hot water supply system after 3 A third line 64 is connected between the connecting line 58 and the first flow line 30, with the connection of the third line 64 to the first flow line 30 being implemented via a switching valve 66 designed as a 3-way valve, which is located downstream of the branch of the second Flow line 34 is provided. The higher-level controller is connected to the switchover valve 66 and can set it up so that the first heat exchanger 6 is supplied with primary heat transfer medium P from the secondary buffer store 48 or so that the first heat exchanger 6 is supplied with primary heat transfer medium P from the main buffer store 32A, 32B. The third heat exchangers 14, however, are independent of the position of the switching valve 66 and as in the hot water supply system 1 or 2 fed by primary heat transfer medium P from the main buffer tanks 32A, 32B.

Some special features and control logics for the operation of the hot water supply systems described in connection with the drawing are discussed below by way of example. A heating medium should be used as the primary heat transfer medium P.

The hot water supply systems off 1 and 2 are very similar. As already explained, the difference between the two systems lies in the connection of the first and third heat exchangers 6, 14 to the supply line 20 (series connection in 1 and parallel connection in 2 ). The series connection has the advantage that very small withdrawals from the consumer 22, which are not detected by the first heat exchangers 6, are heated in the third heat exchangers 14 at the latest. However, this advantage generates an additional pressure loss compared to the parallel connection 2 .

At the hot water supply system after 2 the drinking water heated by the first heat exchanger 6 flows directly into the supply line 20 and mixes there with the drinking water from the third heat exchanger 14 to a mixed temperature. This mixing can result in a brief drop in the desired hot water temperature if, for example, the flow line 30 is not yet up to temperature. However, this drop in temperature is negligible if the circulation volume flow is sufficiently large.

How a tap works (example explained using Fig. 1):

1. 1. A larger amount of hot water is consumed by the consumer 22, so cold water of approx. 10°C flows from the first line 4 through the first heat exchanger 6 and is brought to a higher temperature, for example 50-60°C.
2. 2. Since it cannot be guaranteed that the flow line 30 was already "warm" before the consumer 22 was used, the heated hot water is integrated into the circulation line 12 through the second line 10 for reheating.
3. 3. The heating medium (e.g. 35°C or colder), which has been greatly cooled down by the heating of the drinking water, is routed via the first return line 50 into the secondary buffer tank 48 .
4. 4. The second heat exchanger 54 can then draw the cold return heating medium from the “cold” secondary buffer store 48 in order to cool the heat from the upstream processes (e.g. 40° C. or higher) on it.
5. 5. The heating medium heated by the WRG rises in the secondary buffer storage tank 48 and, when the first heat exchanger 6 is under load, is drawn from the secondary buffer storage tank 48 into the main buffer storage tank 32A, 32B by the heat transfer medium pumps 36 of the first heat exchanger 6. There it is either sucked in by the central heating system 46 or mixed in the main buffer tank 32A, 32B to a higher temperature, which can be used again for domestic hot water preparation.

How it works in the case of circulation (example explained using Fig. 1):

1. 1. When the consumer 22 is not in use, the domestic hot water flows through the circulation line 12 into the third heat exchanger 14 for reheating the circulation volume flow. This happens at a higher temperature level than in the case described above. The returning circulation water of, for example, 55°C flows into the third heat exchanger 14 and is again heated to approx. 60°C. The heated water then flows back to the consumer 22 via the supply line 20.
2. 2. Since the circulation volume flow is constantly flowing, the second flow line 34 is permanently at temperature. Since the circulation water, which cools the heating medium, has a temperature level of 55°C, the heating medium can only cool down minimally to this level.
3. 3. The slightly cooled heating medium (around 55°C) flows through the second return line 60 into the main buffer tanks 32A, 32B and is stratified there in the appropriate temperature zone. This can then be used again for domestic hot water production by reheating the central heating system 46 .
4. 4. In order to keep the long dead pipes hygienically safe when they are not in use, a rinsing device 24 is provided downstream of the first and third heat exchangers 6, 14 in the direction of flow. When this flushes water, fresh cold water flows into the system through port 2.

Special variant reduced hot water temperature in the system according to Fig. 1

In order to be able to achieve an even more effective mode of operation of the second heat exchanger 54 and to further cool the return temperature of the first heat exchanger 6 to the auxiliary buffer tank 48, the set hot water temperature (set value) of the first heat exchanger 6 to 50°C, for example, is reduced in combination with flushing measures adjustable by the higher-level control. Lowering the set hot water temperature to a minimum of 50°C results in colder return temperatures, since the heating medium does not have to heat up the hot water as much and can cool down longer on it. A further advantage of this variant is a high flow temperature, as this results in an even more cooled return compared to a "colder" flow.

With this more heavily cooled heating medium, the second heat exchanger 54 can again deliver more energy to the heating medium and the secondary buffer store 48 .

This special variant is subject to conditions that were described at the beginning in connection with a preheating stage. For this reason, the first heat exchangers 6 are heated to >60° C. every day in this special solution. In addition, in the special variant, a forced flushing of the second line 10 is implemented via the flushing device 24, so that a water change is guaranteed at least every 72 hours via the first heat exchanger 6.

How it works with switchover valve 66 (example explained in Fig. 3)

The installation variant 3 works on the drinking water side just like the installation variant 1 . Since this has already been described in advance, only the differences will be discussed below.

In principle, only the temperature level of the heating medium that is fed to the first heat exchangers 6 changes as a result of switching over the switching valve 66 .

The third heat exchangers 14 remain excluded from the function of the switchover valve 66 and function independently of the first heat exchangers 6. The switchover valve 66 means that the interconnection meets the requirements of the DVGW worksheet through daily switching between the auxiliary buffer tank 48 and the main buffer tank 32A, 32B. In this way, the first heat exchangers 6 can also be supplied daily with a heating medium >60° C. from the main buffer tank 32A, 32B. When switching over the switching valve 66 in the direction of the secondary buffer store 48 , the drinking water is preheated to a significantly lower temperature level based on the lower flow temperature of the secondary buffer store 48 . Since only a “colder” flow medium below 60° C. is then available to the first heat exchangers 6, a special controller logic is implemented, which will be described below. With this logic, the control regulates the first heat exchanger 6 in such a way that the desired value assumes a specific relationship to the flow temperature of the secondary buffer store 48 . The difference between the actually desired temperature for warm drinking water of approx.

How it works When tapping occurs with switchover valve 66 in the direction of the secondary buffer store 48

1. 1. The changeover valve 66 is positioned in such a way that the first heat exchanger 6 is supplied with heating medium from the secondary buffer tank 48 . The direction of flow corresponding to this position is referred to as "direction of flow A" or "direction of flow A" in the following text.
2. 2. The heating medium, which has been cooled down by the heating of the drinking water, is routed from the first heat exchangers 6 via the first return line 30 into the secondary buffer tank 48 .
3. 3. The second heat exchanger 54 can draw the cold return water from the “cold” secondary buffer store 48 in order to cool the heat from the upstream processes, for example to 40° C. or higher.
4. 4. Via flow direction A, the waste heat from the upstream processes is then completely sucked in again by the first heat exchangers 6 and used for preheating the drinking water.

Mode of operation Dispensing case with switching valve 66 in the direction of the main buffer store 32A, 32B

1. 1. Durch eine Regelung der übergeordneten Steuerung erhält das Umschaltventil 66 einen Kontakt oder Impuls die Stellung seiner innenliegenden Kugel zu verändern. Fließrichtung A wird dadurch verschlossen und Fließrichtung B wird geöffnet.
2. 2. Die ersten Wärmeübertrager 6 ziehen nun das hoch temperierte Heizungswasser aus den Haupt-Pufferspeichern 32A, 32B (Strömungsrichtung B) und verwenden dies für die Vorwärmung des kalten Trinkwassers.
3. 3. Aus dem „kalten“ Neben-Pufferspeicher 48 zieht sich der zweite Wärmeübertrager 54 das kalte Rücklaufwasser, um die Wärme der vorgelagerten Prozesse bspw. 40°C oder höher daran abzukühlen.
4. 4. Da die Fließrichtung A versperrt ist, strömt das durch die WRG erwärmte Heizungsmedium im Neben-Pufferspeicher 48 auf und wird im Lastfall der ersten Wärmeübertrager 6 durch die Wärmeträgermedium-Pumpen 36 vom Neben-Pufferspeicher 48 in die Haupt-Pufferspeicher 32A, 32B gezogen. Dort wird es entweder von der zentralen Heizanlage 46 angesaugt oder mischt sich im Haupt-Pufferspeicher 32A, 32B auf eine höhere Temperatur, die erneut zur Trinkwarmwasserbereitung verwendet werden kann.
5. 5. Nach einer definierten Zeit oder nach einem definierten Volumen erfolgt erneut ein Impuls und das Umschaltventil 66 verschließt die Strömungsrichtung B und öffnet die Strömungsrichtung A.

Due to the requirement to heat a preheat stage daily, the switching valve 66 is switched daily in the direction of the main storage tank 32A, 32B. The direction of flow corresponding to this position is referred to in the following text as "direction of flow B" or "direction of flow B".

1. 1. By regulating the higher-level controller, the changeover valve 66 receives a contact or pulse to change the position of its internal ball. This closes flow direction A and opens flow direction B.
2. 2. The first heat exchanger 6 now draws the high-temperature heating water from the main buffer tanks 32A, 32B (direction of flow B) and uses it to preheat the cold drinking water.
3. 3. The second heat exchanger 54 draws the cold return water from the “cold” secondary buffer store 48 in order to cool the heat from the upstream processes, for example to 40° C. or higher.
4. 4. Since flow direction A is blocked, the heating medium heated by the WRG flows up in the secondary buffer storage tank 48 and, when the first heat exchanger 6 is loaded, is drawn from the secondary buffer storage tank 48 into the main buffer storage tanks 32A, 32B by the heat transfer medium pumps 36 . There it is either sucked in by the central heating system 46 or mixed in the main buffer tank 32A, 32B to a higher temperature, which can be used again for domestic hot water preparation.
5. 5. After a defined time or after a defined volume, another pulse occurs and the switchover valve 66 closes flow direction B and opens flow direction A.

Control logic installation variant according to Fig. 1:

In the special variant, the first heat exchangers 6 are operated during the day with reduced hot water temperatures, for example 50°C. In order to operate this correctly according to the standards, the first heat exchangers 6 must be raised to a hot water temperature of 60° C. at least once a day. The interval at which the increase takes place and the duration of the increase can be variably adjusted by the higher-level control.

1. 1. Regulärer Betrieb der ersten Wärmeübertrager 6 mit abgesenkter Warmwassertemperatur, bspw. 50°C.
2. 2. Ein übergeordneter Befehl geht an die Steuerungseinheiten 38 der ersten Wärmeübertrager 6 zur Anhebung der Warmwassertemperatur (Sollwert) über einen definierten Zeitraum.
3. 3. Da den ersten Wärmeübertragern 6 der „heiße“ Vorlauf aus den Haupt-Pufferspeichern 32A, 32B zur Verfügung steht, ist ein Anheben der Warmwassertemperatur ohne weitere Schaltbefehle an zentrale Heizanlage 46 oder andere Bauteile möglich.
4. 4. Nach Ablauf des definierten Zeitraums schaltet ein übergeordneter Befehl die ersten Wärmeübertrager 6 wieder auf die reduzierte Warmwassertemperatur zurück.

In order to implement this in a hygienically flawless manner, the following control logic is proposed:

1. 1. Regular operation of the first heat exchanger 6 with a reduced hot water temperature, for example 50°C.
2. 2. A higher-level command is sent to the control units 38 of the first heat exchanger 6 to increase the hot water temperature (set value) over a defined period of time.
3. 3. Since the first heat exchangers 6 have the “hot” flow from the main buffer storage tanks 32A, 32B, the hot water temperature can be increased without further switching commands to the central heating system 46 or other components.
4. 4. After the defined period of time has elapsed, a higher-level command switches the first heat exchanger 6 back to the reduced hot water temperature.

Control logic installation variant according to Fig. 3:

The temperature to be reached after the first heat exchangers 6 in the second line 10 is largely dependent on the available temperature level from the heat recovery. The temperature can be raised by the first heat exchanger 6 at flow path A to this temperature level at most. However, such a strong increase does not make sense at all, since the heating medium volume flows become very high and the cooling of the heating medium becomes less and less. Thus, it makes sense to maintain a certain temperature difference between the flow temperature of the auxiliary buffer tank 48 and the set hot water temperature of the first heat exchanger 6 (set value).

• Großer Warmwasserbedarf (100 l/min): Vorlauftemperatur 50°C; Sollwert 40°C; Rücklauftemperatur 20°C.
• Geringer Warmwasserbedarf (20 l/min): Vorlauftemperatur 50°C; Sollwert 45°C; Rücklauftemperatur 20°C.
• Um eine maximal kalte Rücklauftemperatur zu erzielen ist auch ein von der Rücklauftemperatur abhängiger Sollwert denkbar.

The flow temperature of the secondary buffer tank 48 can vary greatly due to a fluctuating temperature level in the HR, which makes it difficult to define a constant temperature as a setpoint. It is therefore suggested to make the setpoint dependent on the flow temperature in flow direction A. E.g.: setpoint = (supply temperature of flow direction A) -X, where X= 5°C or X=10°C. A volume flow dependency is also conceivable: For example, the value for X can be higher if a large hot water requirement is expected and lower if a lower hot water consumption is expected. The following pairs of values are given as an example:

• Large hot water requirement (100 l/min): flow temperature 50°C; setpoint 40°C; Return temperature 20°C.
• Low hot water requirement (20 l/min): flow temperature 50°C; setpoint 45°C; Return temperature 20°C.
• In order to achieve a return flow temperature that is as cold as possible, a setpoint dependent on the return flow temperature is also conceivable.

Temperature control without consumption

The higher-level controller can be set in such a way that the first heat exchangers 6 are heated to at least 60° C. for disinfection, without the consumer drawing off the tap or rinsing with the rinsing device. For this purpose, the heat transfer medium pumps 36 are controlled accordingly. The first heat exchangers 6 are heated by the "hot" flow medium and, after a certain waiting time, are flushed with fresh cold water by a command from a higher-level control system. The cold rinsing takes place without heating the cold water. While the heat transfer medium pumps 36 of the first heat exchanger 6 are usually only in operation when used or for disinfection, the heat transfer medium pumps 36 of the third heat exchanger 14 are usually permanently in operation to ensure a constant circulation flow.

Control logic flush warm

During the routine heating of the first heat exchanger 6 to e.g because it was also operated at a low temperature level.

Control logic flushing cold

1. 1. Trinkwasserzapfung durch den Verbraucher endet, die ersten Wärmeübertrager 6 befinden sich auf Temperatur.
2. 2. Ein Befehl des Spüleinrichtungs-Steuerungsmoduls 42 öffnet das Spülventil 26 der Spüleinrichtung 24.
3. 3. Ein Befehl der übergeordneten Steuerung untersagt den Wärmeträgermedium-Pumpen 36 der ersten Wärmeübertrager 6 das Anlaufen trotz eines Volumenstroms, der durch die Spülung über die Geräte strömt.
4. 4. Durch das Öffnen des Spülventils 26 strömt zwangsläufig kaltes Frischwasser durch die erste Leitung 4 über die ersten Wärmeübertrager 6 und die zweite Leitung 10 in die Spüleinrichtung 24 und spült das hygienisch bedenkliche Wasser aus.
5. 5. Nach einem gewissen Volumen, der durch einen Sensor der übergeordneten Steuerung erfasst wird, kommt der Befehl zum Schließen der Spüleinrichtung 24 und Fortsetzen des regulären Betriebes.
6. 6. Die dritten Wärmeübertrager 14 bleiben von dieser Funktion ausgenommen, um die Rückerwärmung des Zirkulationsvolumenstroms sicher zu stellen. Das Spülventil 26 für diese Spülung, kalt, ist daher vorzugsweise in Strömungsrichtung den dritten Wärmeübertrager 14 vorgelagert angeordnet.

In addition to routine heating, it also makes sense to replace the water content at shorter intervals without heating it beforehand. When rinsing, cold, the water content is exchanged without heating.

1. 1. Tapping of drinking water by the consumer ends, the first heat exchanger 6 are at temperature.
2. 2. A command from the purge control module 42 opens the purge valve 26 of the purge 24.
3. 3. A command from the higher-level controller prohibits the heat transfer medium pumps 36 of the first heat exchanger 6 from starting despite a volume flow that flows through the flushing device over the devices.
4. 4. By opening the flushing valve 26, cold fresh water inevitably flows through the first line 4 via the first heat exchanger 6 and the second line 10 into the flushing device 24 and flushes out the hygienically unsafe water.
5. 5. After a certain volume, which is detected by a sensor of the higher-level control, the command is given to close the flushing device 24 and continue regular operation.
6. 6. The third heat exchangers 14 remain excluded from this function in order to ensure reheating of the circulation volume flow. The flushing valve 26 for this flushing, cold, is therefore preferably arranged upstream of the third heat exchanger 14 in the direction of flow.

Control logic flushing HR

In the case of the heat exchanger flushing control logic, the higher-level controller can be set in such a way that flushing takes place while the first heat exchanger 6 is being supplied with "cold" flow medium (flow direction A).

Flushing the circulation line

When the consumer is not using it, it can make sense to replace the water in the circulation line 12 as well. For this purpose, a flushing valve 26 of the flushing device 24 is connected to the supply line, so that the flushing device can initiate a time-controlled water change every 72 hours, for example.

So that the hot water temperatures in the downstream pipe network on the consumer side do not collapse, the flushing device 24 should flush a constant volume flow out of the system, with the cold water flowing in being constantly reheated directly by the first heat exchangers 6 .

Logging of flushing and thermal disinfection

After each thermal disinfection or flushing run, the relevant data should be written to a data logger for later verification of correct operation. These data are preferably: duration of the disinfection/rinse, start/stop of the disinfection/rinse, date/time of the disinfection/rinse, temperature reached during the disinfection/rinse or when switching the switching valve, rinse volume.

Reference List

2

Connection to a fresh water supply

4

first line

6

first heat exchanger

8th

Outlet of the first heat exchanger

10

second line

12

circulation line

14

third heat exchanger

16

circulation pump

18

Third heat exchanger outlet

20

supply line

22

consumer

24

flushing device

26

purge valve

28

free outlet

30

first flow line

32A; 32B

main buffer memory

34

second flow line

36

Heat transfer medium pump

38

control unit

40

temperature sensor

42

Flusher Control Module

44

third flow line

46

central heating system

48

sub-buffer

50

first return line

52

Heat recovery flow line

54

second heat exchanger

56

HR return line

58

connection line

60

second return line

62

third return line

64

third line

66

switching valve

P

primary heat transfer medium

S

secondary heat transfer medium

Claims (20)

Hot water supply system comprising a connection to a fresh water supply (2) for letting cold drinking water into the hot water supply system, a first heat exchanger (6) for heat transfer of heat from a primary heat transfer medium (P) to the cold drinking water, a supply line (4) carrying the heated drinking water, to which at least one consumer (22) is connected, a second heat exchanger (54) for heat recovery by heat transfer of heat from a secondary heat transfer medium (S) to the primary heat transfer medium (P) which has been cooled by heat release to the drinking water, and a heat transfer medium pump (36) transferring flow energy to the primary heat transfer medium (P). hot water supply system claim 1 , characterized in that the primary heat transfer medium (P) consists for the most part or entirely of water and can preferably be heated by a central heating system (46) of the hot water supply system to a temperature which is preferably at least 60°C or greater than 60°C. hot water supply system claim 1 or 2 , characterized in that the secondary heat transfer medium (S) is a fluid containing waste heat and/or waste water or gray water, the temperature of the secondary heat transfer medium (S) preferably being at least 35°C and less than 60°C. Hot water supply system according to any of Claims 1 until 3 , characterized by at least one buffer storage (32A, 32B, 48) for the primary heat transfer medium (P). Hot water supply system according to one of the preceding claims, characterized by at least one main buffer tank (32A, 32B) connected to the first heat exchanger (6) and communicating with a central heating system (46) of the hot water supply system in order to store part of the primary heat transfer medium (P). a temperature of at least 60°C or higher, at least one secondary buffer storage tank (48) connected to the second heat exchanger (54), which stores another part of the primary heat transfer medium (P) for heat recovery, a connecting line (58) between the Main buffer storage (32A, 32B) and the secondary buffer storage (48) for transferring primary heat transfer medium heated by heat recovery from the secondary buffer storage (48) to the main buffer storage (32A, 32B), and one the first heat exchanger (6) with the Auxiliary buffer storage (48) connecting first return line (50) for returning by heat emission the drinking water cooled primary heat transfer medium from the main buffer storage (32A, 32B) in the secondary buffer storage (48). hot water supply system claim 5 , characterized by a switching valve (66) provided between the first heat exchanger (6) and the buffer stores (32A, 32B, 48) for switching between an inlet to the first heat exchanger (6) from the secondary buffer store (48) and an inlet to the first heat exchanger (6) from the main buffer tank (32A, 32B). Hot water supply system according to one of the preceding claims, characterized by a third heat exchanger (14) for heating the drinking water, which is connected to the supply line (20) in parallel or in series with the first heat exchanger (6). hot water supply system claim 7 characterized by a circulation line (12) and a circulation pump (16) assigned to the circulation line (12) for returning drinking water cooling in the supply line (20) to the third heat exchanger (14). hot water supply system claim 7 or 8th , characterized by a third heat exchanger (14) with the main buffer storage (32A, 32B) connecting second Return line (60) for the primary heat transfer medium (P). Hot water supply system according to one of the preceding claims, characterized by a flushing device (24) assigned to the circulation line (12) or the supply line (20) and having a flushing valve (26) for draining drinking water from the hot water supply system. Hot water supply system according to one of the preceding claims, characterized by a water temperature sensor (40), which is assigned to a drinking water outlet (8) of the first heat exchanger (6), and a control unit (38) for controlling the water temperature of the drinking water heated by the first heat exchanger (6). by controlling the heat transfer medium pump (36). hot water supply system claim 11 , characterized in that the control unit (38) controls the heat transfer medium pump (36) in such a way that the temperature measured by the water temperature sensor (40) corresponds to an adjustable desired value. hot water supply system claim 12 , characterized in that the control unit (38) is set in such a way that the target value corresponds to a reduced hot water temperature value and is raised to a temperature value of at least 60°C or greater than 60°C at least once a day for a predetermined time or for a predetermined flow rate becomes. hot water supply system Claim 13 , characterized in that the control unit (38) controls the switching valve (66) in such a way that the feed to the first heat exchanger (6) from the main buffer store (32A, 32B) is released for the predetermined time or the predetermined flow rate and before that and then the feed to the first heat exchanger (6) from the secondary buffer store (48) is released. Hot water supply system according to one of the preceding claims, characterized by a flushing device control module (42) for initiating a change of drinking water by actuating the flushing valve (26) of the flushing device (24). hot water supply system claim 15 , characterized in that the control unit (38) is set up in such a way that the heat transfer medium pump (36) is deactivated for the duration of the open position of the flushing valve (26). Hot water supply system according to one of the preceding claims, characterized in that the setpoint value is set variably and is dependent in particular on a flow temperature of the first heat transfer medium from the secondary buffer storage tank (48) and/or domestic hot water consumption. Hot water supply system according to one of the preceding claims, characterized in that the set value is set variably and is dependent in particular on a return temperature of the first heat transfer medium to the auxiliary buffer tank (48) and/or domestic hot water consumption. Hot water supply system according to one of the preceding claims, characterized by a disinfection operating mode implemented in the control unit (38), in which the drinking water is heated to a temperature of over 60°C and is drained from the hot water supply system by actuating the flushing valve (26). Hot water supply system according to one of the preceding claims, characterized by a data logger for logging the duration, start, stop, date and/or time of a drinking water change by the flushing device and/or activation of the disinfection operating mode and/or one drained from the hot water supply system during a water change Flushing volume and/or the water temperature measured by a temperature sensor.

Images