EP3647667B1 - Continuous flow drinking water heater, drinking water heating system and method for operating a continuous flow drinking water heater - Google Patents

Description

The invention relates to a flow-through drinking water heater with a first heat exchanger, with a second heat exchanger, with a primary line arrangement for connecting the primary sides of the heat exchangers with a heat generator, with a secondary line arrangement for connecting the secondary sides of the heat exchangers with a hot water circulation line and with a cold water line, the primary line arrangement connects the primary sides of the heat exchanger in series, the secondary line arrangement connecting the secondary sides of the heat exchanger in series and connecting the cold water line through the second heat exchanger to the inlet of the first heat exchanger, with a controllable first pump for supplying hot water to the primary side of the first heat exchanger a controllable second pump for supplying hot water to the primary side of the second heat exchanger, with a first temperature arranged in the secondary line arrangement Temperature sensor for detecting the return temperature in the return of the first heat exchanger and with a control device for detecting the measured values of the temperature sensor and for controlling the first pump and the second pump. The invention also relates to a system for heating drinking water and a method for operating a flow-through drinking water heater.

The flow drinking water heater described works with two heat exchangers or heat exchangers, which are connected in series both on the primary side and on the secondary side. For this purpose, the return line of the first heat exchanger is fluidically connected to the inflow line of the second heat exchanger in the primary line arrangement. In the same way, the return line of the second is in the secondary line arrangement Heat exchanger fluidically connected to the inflow line of the first heat exchanger.

Thus, a heated thermal fluid, usually heated heating water, can initially flow through the first heat exchanger and thereby heat the drinking water in the hot water circulation line connected to the secondary side of the first heat exchanger. The thermal fluid then, already cooled in the first heat exchanger, flows through the second heat exchanger and there heats the stagnant or inflowing water from the cold water line. The fresh cold water preheated in this way then flows into the circulation line in order to ensure replenishment when hot water is withdrawn from the hot water circulation line and to maintain the water pressure in the hot water circulation line.

In the case of the flow-through drinking water heaters, the two heat exchangers each contribute part of the heat transfer power to be generated through the series connection, which is also referred to as the bulk power. For this purpose, both pumps arranged in the primary line arrangement are kept in continuous operation and both the first heat exchanger heats the water in the circulation line and the second heat exchanger permanently heats the stagnating or inflowing cold water.

The two heat exchangers can have different maximum heat transfer capacities, which add up to a total heat transfer capacity. The two heat exchangers are usually constructed in the same way, so that 50% of the total maximum heat transfer capacity can be applied by both heat exchangers.

The thermal fluid in the lines of the primary line arrangement has a temperature gradient starting from a hot thermal fluid with a Temperature of, for example, 70-90 ° C, which is drawn from the heater and fed into the first heat exchanger. A first heat transfer occurs in the heat exchanger and the heat fluid leaves the first heat exchanger cooled at a temperature of 45-55 ° C, for example, i.e. still with residual heat, which is then cooled to 20-40 ° C, for example, in the second heat exchanger.

Due to this heat distribution, the described flow-through drinking water heater is usually connected to a stratified storage tank, from which the hot thermal fluid is taken at the top and into which the cooled thermal fluid is fed again in a central layer and a lower layer.

A return temperature of approx. 60 ° C should be maintained in the secondary-side return of the first heat exchanger, while the secondary-side inlet temperature from the hot water circulation line in the first heat exchanger should not fall below 55 ° C. The temperature of the water in the cold water pipe is usually 10-20 ° C.

Due to the permanent operation of the second heat exchanger, the temperature of the drinking water there is in a temperature range of 25 to 45 ° C, even over long periods of time, in which conditions are favorable for the multiplication of legionella and other germs. Since both heat exchangers work permanently in series, the temperature problem occurs regularly, especially when the heat exchangers are loaded irregularly. Only in the case of a usually sporadic water withdrawal from the hot water circulation line does the cold water run into the second heat exchanger to cool the drinking water inside and behind the second heat exchanger.

The characteristic disadvantage of this arrangement is the heating of the second heat exchanger to an average temperature and subsequent stagnation of the drinking water, which can lead to hygienically questionable conditions within the flow-through drinking water heater.

Previously, a thermal fluid in the primary line arrangement was generally spoken of. Usually it is heating water. However, it is also possible to use a different thermal fluid such as, for example, a thermal oil. For the sake of simplicity, the invention is explained below with water as the thermal fluid, but this is not intended to mean a restriction to water as the thermal fluid.

One from the DE 10 2015 118 826 A1 known flow-through drinking water heater therefore provides a special flushing line between the circulation line and the cold water line in order to ensure temperature compensation by flushing. However, this means an increased technical effort without being able to permanently lower the temperature in the area of the second heat exchanger.

The described flow-through drinking water heater is also usually used with an ultrafiltration unit for the mechanical removal of legionella and other germs and their nutrients from the drinking water. The water flowing through is cleaned by means of one or more ultrafilters in the hot water circulation line or in a bypass to the hot water circulation line, such as from the EP 2 883 844 A1 is known. The installation effort for connecting the various components of such a system for heating drinking water is therefore high.

The present invention is therefore based on the technical problem, a flow-through drinking water heater mentioned at the beginning, a method for operation a flow-through drinking water heater and a system for heating drinking water to simplify and improve.

The aforementioned technical problem is solved according to the invention by a flow-through drinking water heater mentioned at the beginning in that the control device is set up to regulate the pumping power of the first pump to a predetermined secondary-side return temperature of the first heat exchanger, that the control device is set up to activate the pumping power of the second pump , when the required total heat transfer capacity exceeds a predetermined maximum heat transfer capacity of the first heat exchanger, and that the control device is set up to deactivate the pump capacity of the second pump when the required total heat transfer capacity falls below the predetermined maximum heat transfer capacity of the first heat exchanger.

The wording that the control device is "set up" for certain control functions means that the control device has a programmable electronic circuit to which the temperature sensor (and possibly the further sensors described below) is connected via a cable connection and / or a radio connection and records measured values and is connected to the pumps to be controlled via a cable and / or radio link and transmits control signals. The control device evaluates the recorded measured values by means of an algorithm running in the electronic circuit, generates control signals in accordance with the control instructions and control conditions, and transmits the control signals to the pumps.

In the case of the flow-through drinking water heater described, the first heat exchanger constantly heats the drinking water flow in the hot water circulation line and is thus integrated into the hot water circulation device.

Furthermore, the second heat exchanger is kept cold as long as possible for hygienic reasons as protection against legionella and other germs and as protection against calcification, in that the first heat exchanger takes over the supply of the warm drinking water as long as possible until a marginal heat transfer rate is reached, if necessary up to its maximum heat transfer capacity. The distinction between marginal and maximum heat transfer capacity means that, in the situations described below, the flow-through drinking water heater reaches a limit before the maximum heat transfer capacity is reached, above which the connection of the second heat exchanger is necessary or useful. Therefore, the marginal heat transfer capacity also includes the maximum heat transfer capacity.

Until the time of activation, the second heat exchanger is acted upon or flowed through by cold drinking water. The temperature of the drinking water on the secondary side of the second heat exchanger thus remains in the cold temperature range for as long as possible, in particular below 30 ° C or 25 ° C, in which legionella and other germs can only multiply slowly. A stagnation of drinking water that is too warm in the second heat exchanger is thus avoided or at least restricted, in particular in normal operation without a situation in which hot water is withdrawn from the hot water circulation line. In the same way, the risk of calcification of the second heat exchanger is avoided or at least reduced.

If the total heat transfer capacity required to maintain the secondary-side return temperature of the first heat exchanger increases due to a large amount of hot water being withdrawn from the hot water circulation line, the situation arises that the first heat exchanger cannot generate this required heat transfer capacity on its own. In this case, it is provided according to the invention that the control device activates the second heat exchanger. When the withdrawal of hot water decreases, occurs then the situation occurs that the control device deactivates the second heat exchanger again. Because after deactivating the second heat exchanger, water usually continues to flow into the hot water circulation line, at least for a short time.

Preferred embodiments of the flow-through drinking water heater are described below which, individually or in combination with one another, further improve the flow-through drinking water heater.

In a preferred embodiment of the flow-through drinking water heater, provision is made that a second temperature sensor is provided in the primary line arrangement for detecting the inlet temperature in the primary-side inlet of the first heat exchanger, that the control device is set up to detect the measured values of the second temperature sensor, and that the control device is set up to control the pump output the first pump and the second pump, taking into account the inlet temperature, to regulate a predetermined return temperature in the primary-side return of the first heat exchanger.

An important variable when calculating the heat transfer capacity is the temperature of the hot water in the primary-side inlet of the first heat exchanger. The higher the temperature, the more heat can be transferred to the water in the circulation line with the same pumping power of the first pump. Therefore, with the preferred embodiment, the regulating device can use the temperature value of the water flowing in on the primary side when calculating the pump outputs of the first pump and the second pump to be regulated.

In a further preferred embodiment of the flow-through drinking water heater, it is provided that a volume flow sensor in the secondary line arrangement in the inlet of the first heat exchanger and / or In the secondary-side return of the first heat exchanger it is provided that the control device is set up to record the measured values of the volume flow sensor and that the control device is set up to control the pump output of the first pump and the second pump as a function of the measured values of the volume flow sensor to maintain the specified return temperature in the secondary To regulate the return of the first heat exchanger.

Since cold water flows in when hot water is withdrawn from the hot water circulation line and the volume flow changes almost simultaneously in the entire line system on the secondary side, the occurrence of water withdrawal can be detected with the volume flow sensor. Such verification is faster than with temperature sensors, since the temperature change runs through the system from the cold water connection. The control device can thus work faster and in an optimized manner in order to decide according to the algorithm whether the second pump should be activated or not.

Another preferred embodiment of the flow-through drinking water heater is characterized in that a third temperature sensor is provided in the secondary line arrangement for detecting the inlet temperature of the water flowing in the inlet of the secondary-side first heat exchanger, that the control device is set up to detect the measured values of the third temperature sensor and that the control device is set up is to regulate the pump output of the first pump and the second pump to an inlet temperature that is greater than a predetermined inlet temperature.

The inlet temperature on the secondary side measured with the third temperature sensor is therefore measured in the common line of hot water circulation and the outlet from the second heat exchanger and, for hygienic reasons, must maintain a minimum value of 55 ° C in stationary operation without water extraction. This value can be used by the control device to control a circulation pump so that the inlet temperature is above the Limit value of 55 ° C is maintained. In the case of a withdrawal from the hot water circulation line, this value drops and the control can increase the heat transfer capacity of the first heat exchanger by increasing the pumping capacity of the first pump in order to keep the secondary-side return temperature constant. If the pump output cannot be increased any further, the total heat transfer output can be increased by activating the second pump and thus the second heat exchanger. A constant domestic hot water temperature can thus be ensured with little effort.

In a further preferred embodiment of the flow-through drinking water heater, provision is made that a fourth temperature sensor is provided in the primary line arrangement for detecting the return temperature of the water flowing from the primary-side return of the first heat exchanger, that the control device is set up to detect the measured values of the fourth temperature sensor, and that the control device is set up to regulate the pump output of the first pump and the second pump to a primary-side return temperature that is greater than a predetermined return temperature.

The control device thus additionally processes the primary-side return temperature of the first heat exchanger. If the return temperature on the primary side is too low and falls below a specified return temperature, then this is an indication that the heat transfer capacity of the first heat exchanger is not sufficient to reliably guarantee the required return temperature on the secondary side of the first heat exchanger and thus of the hot water in the hot water circulation line. If the primary line arrangement is also connected to a storage tank in layers, it can be ensured by checking the return temperature on the primary side that the temperature of the water returning to the storage tank in layers is not too low or too high. Maintaining a temperature range leads to a Energy savings when preparing the hot water in the storage tank in layers.

Another preferred embodiment of the flow-through drinking water heater is characterized in that a fifth temperature sensor is provided in the secondary line arrangement for detecting the return temperature of the water flowing in the return of the second heat exchanger, that the control device is set up to detect the measured values of the fifth temperature sensor and that the control device is set up to regulate the pump output of the first pump and the second pump to a minimum return temperature.

Since cold water flows in on the secondary side of the second heat exchanger, which, if necessary, flows heated from the return in the direction of the circulation line if water is taken from the hot water circulation line or if it stagnates there, the control device can use the return temperature by means of the algorithm in order to increase the pumping capacities of the two pumps set that the return temperature is as low as possible. In this way, the goal can be achieved even better that the return temperature and thus the temperature of all the water present in the secondary side is kept cold as long as possible for hygienic reasons and as protection against calcification.

In a further preferred embodiment of the flow-through drinking water heater, it is provided that a sixth temperature sensor is provided in the primary line arrangement for detecting the return temperature of the water flowing from the primary-side return of the second heat exchanger, that the control device is set up to detect the measured values of the sixth temperature sensor and that the control device is set up to regulate the pump output of the first pump and the second pump to a minimum return temperature.

The control device thus additionally processes the primary-side return temperature of the second heat exchanger. If the return temperature on the primary side is too high and exceeds a specified return temperature, this is an indication that the pumping capacity of the second pump is too high. In such a case, the algorithm of the control device can be designed in such a way that the pump output of the second pump is reduced. If the primary line arrangement is also connected to a storage tank in layers, it can be ensured by checking the return temperature on the primary side that the temperature of the water returning to the storage tank in layers is not too low or too high. Maintaining a temperature range leads to energy savings in the preparation of the hot water in the stratified storage tank.

Another preferred embodiment of the flow-through drinking water heater is characterized in that a seventh temperature sensor is provided in the secondary line arrangement for detecting the return temperature from the circulation circuit upstream of the mixing point of the water flowing out of the second heat exchanger, that the control device is set up to record the measured values of the seventh temperature sensor, that the control device is set up to detect pure circulation or a water withdrawal from the hot water circulation line and that the control device is set up to regulate the pump output of the first pump and the second pump to a return temperature that is greater than a predetermined return temperature.

By comparing with the measured values of other temperature sensors, in particular the third temperature sensor, the control device can detect water withdrawal at an early stage and set the pumping power of the two pumps so that the return temperature on the secondary side of the first heat exchanger is regulated to the specified value. Since only the circulation temperature is recorded before the mixing point, this can be regulated to at least 55 ° C if there is no water withdrawal and a controllable external circulation pump is available. For example, if the measured temperature values of the third temperature sensor and the third temperature sensor are the same, then there is no withdrawal of hot water. If there is a temperature difference due to the fact that cold water flows in, then there is a difference between the temperature measured values of the third temperature sensor and the third temperature sensor.

If the two heat exchangers are arranged one above the other, with the first heat exchanger being arranged above the second heat exchanger, the pipe routing in the primary line arrangement and the secondary line arrangement and positions of the heat exchangers are arranged in such a way that the temperature inside the flow-through drinking water heater rises from bottom to top. Cold drinking water with a temperature of preferably less than 15 ° C is fed to the second heat exchanger on the secondary side, and cool or cold heating water with a temperature of 10-25 ° C is discharged into the stratified storage tank on the primary side. In the middle of the arrangement, on the secondary side, warm returning circulation water with a prescribed temperature of greater than or equal to 55 ° C is supplied and warm heating water with a temperature of, for example, 50-60 ° C is removed if no water is drawn off. In the upper area of the arrangement, on the secondary side, warm drinking water with a temperature of greater than or equal to 60 ° C. is discharged and hot heating water, for example in the temperature range of 70-90 ° C., is supplied.

The resulting temperature gradient enables the lowest possible temperature in the lower region of the second heat exchanger, in which a cold or cool state is to be maintained for as long as possible.

In the case of the flow-through drinking water heater, it is preferably provided that the first heat exchanger and / or the second heat exchanger are provided with thermal insulation. This can prevent the mutual influence of the two heat exchangers and a heat loss of the first and heating of the second heat exchanger from outside can be reduced.

In a further preferred manner, alternatively or additionally, heat insulation is provided between the first heat exchanger and the second heat exchanger. This will further reduce the mutual temperature influence of the two heat exchangers.

Thus, within the flow-through drinking water heater, there is a separation into a warm zone and a cool zone, the first heat exchanger being in the warm zone and the second heat exchanger being in the cool zone. As a result, a reduced heat emission and thus energy losses to the outside can be restricted and energy savings can be achieved.

A method according to the invention for operating a flow-through drinking water heater is described below, which can be carried out with a flow-through drinking water heater and its preferred configurations. However, deviations from the structure described can nevertheless make it possible to carry out the method.

The technical problem outlined above is also solved by a method for operating a flow-through drinking water heater, in which the hot water of a hot water circulation line is heated on the secondary side to a specified return temperature with a first heat exchanger a second heat exchanger connected in series to the first heat exchanger is activated and the inflowing cold water is heated on the secondary side and in which the second heat exchanger is deactivated when the limit heat transfer output is not reached by the first heat exchanger.

The method is based on recognizing whether the heat transfer capacity of the first heat exchanger is sufficient to achieve the capacity of the first heat exchanger required by the removal of water from the hot water circulation line, or whether it is necessary to activate the second heat exchanger. In particular, if the two heat exchangers can generate the same heat transfer capacity, the limit from which the second heat exchanger must be activated is 50% of the total heat transfer capacity of the flow-through drinking water heater used. Thus, the limit can be set at 50% of the total heat transfer capacity or lower, from which the second heat exchanger is activated or deactivated. With the same configuration, the limit can also be 30% or 40%.

There are various possibilities, which can be used individually or in combination, as to how the exceeding of the marginal heat transfer performance predetermined by the first heat exchanger can be recognized.

In a preferred embodiment of the method, the reaching of the marginal heat transfer capacity of the first heat exchanger can be recognized by non-compliance with the return temperature in the circulation line. Failure to comply is an indication that the heat transfer capacity of the first heat exchanger is insufficient. In particular, the first temperature sensor described above can be used for this purpose.

Furthermore, the marginal heat transfer performance can be determined on the basis of the primary-side inlet temperature to the first heat exchanger. This is because the heat transfer capacity of the first heat exchanger depends on the temperature of the heating water supplied. The calculation of the current heat transfer capacity can thus be made using the primary-side Inlet temperature can be determined. In particular, the second temperature sensor described above can be used for this purpose.

In a further preferred embodiment of the method, reaching the marginal heat transfer capacity of the first heat exchanger can be recognized by exceeding the volume flow in the hot water circulation line above a predetermined limit volume flow. This is because when designing the operating parameters for the process, the maximum possible withdrawal volume from the hot water circulation line is recorded and the heat transfer capacities of the heat exchangers are determined. Thus, when a certain value of a volume flow is measured in the hot water circulation line, it can be determined that the specified maximum heat transfer capacity, thus thus the marginal heat transfer capacity of the first heat exchanger, is exceeded. Since a volume measurement can take place faster than a temperature measurement, the method can be carried out more quickly if a volume flow is also measured. In particular, the first volume flow sensor described above can be used for this purpose.

Furthermore, the method can be carried out in an advantageous manner by regulating the first heat exchanger and the second heat exchanger in such a way that the secondary-side inlet temperature to the first heat exchanger does not fall below a lower limit value. The inlet temperature from the hot water circulation line and the returning water from the second heat exchanger are thus used as a criterion for regulating the activation and deactivation of the second heat exchanger. If the inlet temperature falls below a prescribed value of, for example, 40 ° C., the heat transfer capacity of the first and / or the second heat exchanger is increased. In particular, the third temperature sensor described above can be used for this purpose.

In a further preferred embodiment of the method, the achievement of the marginal heat transfer capacity of the first heat exchanger can be recognized by failure to comply with a predetermined primary-side return temperature at the first heat exchanger. Because the primary-side return temperature must not be too low when feeding into a stratified storage tank for energetic reasons. If the return temperature on the primary side is too low, the water for the hot water circulation line can no longer be heated sufficiently within the specified operating temperature limits and the second heat exchanger is activated. In particular, the fourth temperature sensor described above can be used for this purpose.

Furthermore, the method can be carried out in an advantageous manner by regulating the first heat exchanger and the second heat exchanger in such a way that a minimum return temperature is reached at the secondary-side return of the second heat exchanger. This ensures that the second heat exchanger works with the lowest possible heat transfer capacity and the drinking water contained in the secondary side of the second heat exchanger is heated as little as possible and, in particular in the event of stagnation, a situation is avoided in which legionella and other germs multiply strongly. In particular, the fifth temperature sensor described above can be used for this purpose.

Finally, in the method, the first heat exchanger and the second heat exchanger can advantageously be regulated in such a way that the primary-side return temperature of the second heat exchanger does not exceed an upper limit value. This prevents the heating water fed back into a stratified storage tank, which may be connected, from having too high a temperature and unfavorable energetic conditions arise in the stratified storage tank, which make the use of certain heating systems, e.g. with condensing technology, inefficient. In particular, the sixth temperature sensor described above can be used for this purpose.

Furthermore, the method can advantageously be implemented by regulating the first and the second heat exchanger in such a way that the secondary return temperature of the first heat exchanger is determined by the detection of water withdrawal by the detection of the temperature in the circulation line shortly before the mixing point of the water flowing out of the second heat exchanger is regulated to a predetermined value. In order to detect water withdrawal, the control device can compare the measured temperature with other measured values from the arrangement of the flow-through drinking water heater, in particular the third temperature sensor. The seventh temperature sensor described above can be used for this purpose.

The above technical problem is also solved according to the invention by a system for heating drinking water with a first heater module having a previously described flow-through drinking water heater and with an ultrafiltration module having an ultrafiltration unit, which is characterized in that the one leading out of the heater module and with the hot water circulation line and the cold water line to connecting lines have predetermined vertical distances and horizontal distances from one another, that the lines leading into the ultrafiltration module and to be connected to the hot water circulation line and the cold water line have vertical distances and horizontal distances from one another and that the vertical distances and the horizontal distances of the lines leading into the ultrafiltration module with the vertical distances and the horizontal distances between the lines leading out of the heater module timely.

The connections of the secondary line arrangement with connections for the hot water circulation line and the cold water line on the side of the heater module and on the side of the ultrafiltration module and, if necessary, the housing dimensions of the modules are matched accordingly. The system with the heater module and the ultrafiltration module is accordingly constructed in such a way that an ultrafiltration unit can be simply and modularly coupled to a flow-through drinking water heater. This allows a time-saving addition or retrofitting of the flow-through drinking water heater and thus a quick and easy improvement in hygiene, so that the temperature reduction results in energy savings with good hygiene at the same time.

For example, the warm drinking water line, which is connected to the secondary-side return of the first heat exchanger, and the cold drinking water line, which are connected to the secondary-side inlet of the second heat exchanger, can be designed as an extension within the ultrafiltration module. The section of the circulation line running inside the ultrafiltration module back to the heater module can furthermore be connected to an ultrafiltration bypass, so that the ultrafiltration filter is integrated in the circulation line.

In particular, the lines leading out of the ultrafiltration module and to be connected to the hot water circulation line and the cold water line can advantageously have vertical and horizontal distances from one another and the vertical and horizontal distances between the lines leading out of the ultrafiltration module and the vertical and horizontal distances between the lines leading out of the heater module Lines match.

Another advantage of coupling the modules described is that the entire drinking water heating system, including the two modules, can be operated permanently at lower temperatures than described above, thus saving energy. Because ultrafiltration reduces the germ load even at low temperatures. Thus, the hot water of the hot water circulation line can also have an inlet temperature of, for example 45-50 ° C and return from the hot water circulation line at a temperature between 40 and 48 ° C. This reduces the temperatures in the entire drinking water heating system by around 10-15 ° C.

Fig. 1

eine schematische Darstellung eines Durchflusstrinkwassererwärmers in verschiedenen Variationen,

Fig. 2

eine weitere schematische Darstellung eines Durchflusstrinkwassererwärmers in verschiedenen Variationen und

Fig. 3

eine schematische Darstellung eines Systems zur Trinkwassererwärmung.

In the following, the invention is explained on the basis of exemplary embodiments with reference to the drawing. Show in the drawing

Fig. 1

a schematic representation of a flow drinking water heater in different variations,

Fig. 2

Another schematic representation of a flow drinking water heater in different variations and

Fig. 3

a schematic representation of a system for heating drinking water.

In the following description of the various exemplary embodiments according to the invention, components and elements with the same function and the same mode of operation are provided with the same reference numerals, even if the components and elements in the various exemplary embodiments may differ in their dimensions or shape.

Fig. 1 and 2 show schematic representations of a flow-through drinking water heater, the representations also having, in addition to an inventive embodiment, a plurality of further sensors that are optional, and wherein combinations of the individual sensors are possible. This type of representation of the several configurations was chosen for the sake of clarity and does not represent a restriction of the subject matter.

Fig. 1 shows an embodiment of a flow-through drinking water heater 2 (dashed line) with a first heat exchanger 4 and with a second Heat exchanger 6. On the primary side of the two heat exchangers 4 and 6 there is a primary line arrangement 8 for connecting the primary sides of the heat exchangers 4 and 6 to a heat generator, which in the present case is designed as a heater with a stratified storage tank 12.

The primary line arrangement 8 connects the primary sides of the heat exchangers 4 and 6 in series and the secondary line arrangement 10 connects the secondary sides of the heat exchangers 4 and 6 in series and connects the cold water line 18 through the second heat exchanger 6 with the primary-side inlet of the first heat exchanger 4 and thus with the Hot water circulation line 16. The temperature of the cold water is typically in the range of 15 ° C.

Furthermore, a controllable first pump 20 for supplying hot water from the stratified storage tank 12 to the primary side of the first heat exchanger 4 and a controllable second pump 22 for supplying hot water to the primary side of the second heat exchanger 6 are provided. For this purpose, the pumps 20 and 22 have interfaces (not shown) via which a control signal can be transmitted in order to control or activate or deactivate the pumping power of the pumps 20 and 22.

A first temperature sensor 24 for detecting the return temperature in the secondary-side return of the first heat exchanger 4 is arranged in the secondary line arrangement 10. The temperature sensor 24 thus measures the temperature of the drinking water that emerges from the return of the first heat exchanger 4 and is fed to the connected hot water circulation line 16. The temperature sensor 24 has an electronic interface (not shown) for data transfer.

The flow-through drinking water heater 2 has a control device 26 for acquiring the measured values of the temperature sensor 24 and for controlling the first pump 20 and the second pump 22. The control device 26, on the one hand, has an electronic one Circuit arrangement 28 and, on the other hand, an interface 30 for receiving data signals from temperature sensor 24 and an interface 32 for transmitting control signals to pumps 20 and 22. The electronic circuit arrangement 28 is programmable and enables the use of an algorithm with which the input signals can be evaluated, control instructions and control conditions can be processed and control signals can be generated, which are then transmitted to the pumps 20 and 22 via the interface 32. The interfaces mentioned can transmit data by means of cables and / or by means of a radio link. This also applies to all other sensors described below.

The regulating device 26 is set up in the manner described above to regulate the pumping power of the first pump 20 to a predetermined secondary-side return temperature of the first heat exchanger 4 of 60 ° C., for example. The pump output is increased when more heat transfer capacity of the first heat exchanger 4 is required in order to maintain the secondary-side return temperature. On the other hand, the pump power is reduced if less heat transfer power of the first heat exchanger 4 is required in order to maintain the secondary-side return temperature.

Furthermore, the control device 26 is set up to activate the pumping power of the second pump 22 when the required total heat transfer capacity exceeds a predetermined limit value, possibly maximum heat transfer capacity of the first heat exchanger 4. The exceeding of the marginal heat transfer capacity of the first heat exchanger 4 can be detected by various parameters, as will be explained in detail below. In the embodiment with the temperature sensor 24, the exceeding is determined by the fact that the target temperature of the hot water in the secondary-side return of the first heat exchanger 4 cannot be maintained and falls below a predetermined value of 60 ° C., for example.

Furthermore, the control device 26 is set up to deactivate the pumping capacity of the second pump 22 if the required total heat transfer capacity falls below the predetermined marginal heat transfer capacity of the first heat exchanger 4. This can be determined, for example, by the fact that the temperature of the hot water in the secondary-side return of the first heat exchanger 4 rises above the mentioned limit value of 60 ° C. at the maximum pump output of the first pump 20. The fact that the total heat transfer capacity is not reached can also be recognized, for example, by the fact that the pump capacity of the first pump 20 falls below a limit value, since the second heat exchanger 6 preheats the cold water sufficiently. After deactivating the second pump 22, the regulating device 26 controls the pump output of the first pump 20 again to such an extent that the first heat exchanger 4 alone takes over the heating of the hot water.

Various other sensors are described below, which are used in addition to the first temperature sensor 24 for regulating the flow-through drinking water heater 2. These sensors and the control options resulting therefrom can each be used individually or in combination with the first temperature sensor 24. Nevertheless, the sensors are all in the Fig. 1 shown. Numerous possible embodiments of the flow-through drinking water heater 2 thus result from FIG Fig. 1 .

A second temperature sensor 40 is provided in the primary line arrangement 8 for detecting the inlet temperature in the primary-side inlet of the first heat exchanger 4. The control device 26 records the measured values of the second temperature sensor 40 and regulates the pump output of the first pump 20 and the second pump 22, taking into account the inlet temperature in the range of, for example, 70-90 ° C to a specified return temperature in the return of the first heat exchanger 4 generating heat transfer capacity of the First heat exchanger 4 depends on the energy content of the supplied warm heating water, that is to say on its temperature, the control device can calculate the current heat transfer capacity and take it into account in the control algorithm.

Furthermore, a volume flow sensor 36 is provided in the secondary line arrangement 10 in the secondary-side inlet of the first heat exchanger 4. The control device 26 records the measured values of the volume flow sensor 36 and regulates the pump output of the first pump 20 and the second pump 22 as a function of the measured values of the volume flow sensor 36 in order to maintain the specified return temperature in the secondary-side return of the first heat exchanger 4. If the measured volume flow changes, If, for example, increases, this event is an indication of a withdrawal of hot water from the connected hot water circulation line 16. Depending on the strength of the change in the volume flow, the control device 26 can derive whether the first heat exchanger 4 can generate the required heat transfer capacity by controlling the first pump 20 alone or whether the second pump 22 and thus the second heat exchanger 6 must be activated.

A further embodiment consists in that a third temperature sensor 38 is provided in the secondary line arrangement 10 for detecting the inlet temperature of the water flowing in the secondary-side inlet of the first heat exchanger 4. The control device 26 detects the measured values of the third temperature sensor 38 and controls the pump output of the first pump 20 and the second pump 22 in the event of water withdrawal to an inlet temperature that is greater than or equal to a predetermined inlet temperature of 40 ° C., for example. The total heat transfer capacity can thus be increased and the return temperature is increased above the predetermined value, so that the inlet temperature at the third temperature sensor 38 is maintained. In order to achieve the increase in the heat transfer performance, the control device 26 can activate the second pump 22 and thus the second heat exchanger 6.

Furthermore, a fourth temperature sensor 34 is provided in the primary line arrangement 8 for detecting the return temperature of the water flowing out of the primary-side return of the first heat exchanger 4. The control device 26 is then set up to record the measured values of the fourth temperature sensor 34 and regulates the pump output of the first pump 20 and the second pump 22 to a return temperature that is greater than a specified return temperature of, for example, 40 ° C and preferably in the range of 40 ° C. 60 ° C.

A further embodiment consists in that a fifth temperature sensor 42 is provided in the secondary line arrangement 10 for detecting the return temperature of the water flowing in the return of the second heat exchanger 6. The control device 26 detects the measured values of the fifth temperature sensor 42 and controls the pump output of the first pump 20 and the second pump 22 to a minimum return temperature. This can be achieved in that the control device 26 keeps the pump output of the first pump 20 at a maximum value and the second pump 22 produces the lowest possible pump output. The aim of keeping the temperature increase of the drinking water in the second heat exchanger 6 low can thus be achieved.

Furthermore, a sixth temperature sensor 44 is provided in the primary line arrangement 8 for detecting the return temperature of the water flowing out of the primary-side return of the second heat exchanger 6. The control device 26 detects the measured values of the sixth temperature sensor 44 and regulates the pump output of the first pump 20 and the second pump 22 to a primary-side return temperature that is lower than a specified return temperature in the range of 10-25 ° C., for example. The primary-side return temperature can be maintained by reducing the pump output of the second pump 22 while increasing the pump output of the first pump 20 at the same time.

A seventh temperature sensor 45 is provided in the secondary line arrangement 10 and in the circulation line 16 in front of the mixing point of the water flowing out of the second heat exchanger 6. The control device 26 records the measured values of the seventh temperature sensor 45 and can control an external circulation pump, change the circulation flow and thus set it to a temperature of at least 55 ° C. The control device 26 can also detect a water withdrawal and switch on the pump output to the second pump 22, so that the secondary-side return temperature of the first heat exchanger 4 is maintained.

In Fig. 1 are also provided in series with the two pumps 20 and 22 valves 21 and 23, which are designed in a simple form as spring-loaded check valves. In another embodiment, the valves can be controlled and are controlled by the control device 26 by means of the interfaces described above.

Fig. 2 shows a further embodiment of the flow-through drinking water heater, which has the same elements or combinations of elements as they are based on Fig. 1 have been shown and described.

In contrast to the Fig. 1 is the embodiment according to Fig. 2 designed in such a way that the first heat exchanger 4 is provided with heat insulation 46 and the second heat exchanger 6 with heat insulation 48. As a result, the two heat exchangers are thermally shielded from one another, so that compliance with the temperature ranges described is facilitated. The control device 26 can thereby carry out the control of the pumps 20 and 22 more precisely.

As an alternative or in addition to the thermal insulation 46 and 48, thermal insulation 50 is provided between the first heat exchanger 4 and the second heat exchanger 6. The thermal insulation 50 also serves one thermal insulation of the two heat exchangers 4 and 6 with the same advantages described above.

Fig. 3 shows a further aspect of the present invention in the form of a system 60 for heating drinking water. A flow-through drinking water heater 2 is shown according to one of the Fig. 1 or 2 . Together with a housing 62 and adjustable standing elements 64 attached to it, the flow-through drinking water heater 2 forms a heater module 66. The flow-through drinking water heater 2 is connected in the manner described above to a stratified storage tank 12 with three lines 68 via shut-off valves 70. The stratified storage tank 12 can also have adjustable standing elements 13.

Furthermore, an ultrafiltration module 74 having an ultrafiltration unit 72 is provided, which is connected to the heater module 66. For this purpose, lines 76a, 76b and 76c on the side of the heater module 66 and lines 78a, 78b and 78c on the side of the ultrafiltration module 74 as well as valves 80a, 80b and 80c or other coupling devices connecting these lines are provided.

Lines 75a, 75b and 75c are arranged in the ultrafiltration module 74 and are connected to the lines 76a, 76b and 76c and 78a, 78b and 78c. The ultrafiltration unit 72 is connected to the middle line 75b via a bypass 73 and has, in a known manner, an ultrafilter that filters the water flowing through during operation and thereby filters out legionella and other germs as well as the smallest parts such as food particles for the legionella and germs. The ultrafiltration unit 72 can alternatively or additionally be connected to the line 75a and / or the line 75c.

Coordinate distances dx and dy are given below, each of which is measured within a Cartesian coordinate system that is connected to the housing of the corresponding module. Because only about relative distances are relevant, the coordinates are not discussed individually, only the distances dx and dy.

According to the invention, the lines 76a, 76b and 76c leading out of the heater module 66 and to be connected to the hot water circulation line 16 and the cold water line 18 have predetermined vertical distances dy1 and dy2 and horizontal distances dx1 and dx2 (in the direction perpendicular to the plane of the drawing, therefore not shown) to one another . Preferably, after the heater module 66 has been aligned, the lines 76a, 76b and 76c are arranged essentially vertically one above the other, so that the horizontal distances dx1 and dx2 are equal to zero.

Furthermore, the lines 78a, 78b and 78c leading into the ultrafiltration module 74 and to be connected to the hot water circulation line 16 and the cold water line 18 have vertical distances dy3 and dy4 and horizontal distances dx3 and dx4 (not shown) from one another, the vertical distances dy3 and dy4 and horizontal distances dx3 and dx4 of the lines 78a, 78b and 78c leading into the ultrafiltration module 74 correspond to the vertical distances dy1 and dy2 and the horizontal distances dx1 and dx2 of the lines 76a, 76b and 76c leading out of the heater module 66.

The ultrafiltration module 74 can thus be connected in a modular fashion to the heater module 66 without further adaptations and can be easily integrated into the entire drinking water system. Only the relative alignment of the modules 2 and 74 has to be set with the stand elements 64 and 71. A stratified storage tank 12 with adjustable standing elements 13 can further simplify the installation.

In addition, the lines 82a, 82b and 84c leading out of the ultrafiltration module 74 and to be connected to the hot water circulation line 16 and the cold water line 18 via valves 84a, 84b and 84c have vertical distances dy5 and dy6 and horizontal distances dx5 and dx6 (not shown) to one another, which correspond to the vertical distances dy1 and dy2 and the horizontal distances dx1 and dx2 of the lines 76a, 76b and 76c leading out of the heater module 66. The configuration of lines 82a, 82b and 82c thus corresponds to the configuration of lines 76a, 76b and 76c, which further increases compatibility.

Claims (20)

1. Flow-through drinking water heater

   - with a first heat exchanger (4),

   - with a second heat exchanger (6),

   - with a primary line arrangement (8) for connecting the primary sides of the heat exchangers (4, 6) to a heat generator (12),

   - with a secondary line arrangement (10) for connecting the secondary sides of the heat exchangers (4, 6) to a hot water circulation line (16) and to a cold water line (18),

   - wherein the primary line arrangement (8) connects the primary sides of the heat exchangers (4, 6) in series,

   - wherein the secondary line arrangement (10) connects the secondary sides of the heat exchangers (4, 6) in series and connects the cold water line (18) through the second heat exchanger (6) to the secondary-side inlet of the first heat exchanger (4),

   - with a controllable first pump (20) for supplying hot water to the primary side of the first heat exchanger (4),

   - with a controllable second pump (22) for supplying hot water to the primary side of the second heat exchanger (6),

   - with a first temperature sensor (24) arranged in the secondary line arrangement (10) for detecting the return temperature in the secondary-side return of the first heat exchanger (4) and

   - with a control device (26) for recording the measured values of the temperature sensor (24) and for controlling the first pump (20) and the second pump (22), characterised in,

   - that the control device (26) is set up to control the pumping capacity of the first pump (20) to a predetermined secondary-side return temperature of the first heat exchanger (4),

   - that the control device (26) is set up to activate the pumping capacity of the second pump (22) if the required total heat transfer capacity exceeds a predetermined threshold value heat transfer capacity of the first heat exchanger (4), and

   - that the control device (26) is set up to deactivate the pumping capacity of the second pump (22) if the required total heat transfer capacity falls below the predetermined threshold heat transfer capacity of the first heat exchanger (4).
2. A flow-through drinking water heater according to claim 1,
   characterized in

   - that a second temperature sensor (40) is provided in the primary line arrangement (8) for detecting the supply temperature in the primary-side supply of the first heat exchanger (4),

   - that the control device (26) is set up to record the measured values of the second temperature sensor (40) and

   - that the control device (26) is arranged to control the pumping capacity of the first pump (20) and the second pump (22) to a predetermined return temperature in the primary-side return flow of the first heat exchanger (4), taking into account the supply temperature.
3. A flow-through drinking water heater according to claim 1 or 2,
   characterized in

   - that a volume flow sensor (36) is provided in the secondary line arrangement (10) in the secondary-side feed of the first heat exchanger (4) and/or in the secondary-side return of the first heat exchanger (4),

   - that the control device (26) is set up to record the measured values of the volume flow sensor (36) and

   - that the control device (26) is arranged to control the pumping capacity of the first pump (20) and the second pump (22) in dependence on the measured values of the volume flow sensor (36) for maintaining the predetermined return temperature in the secondary-side return flow of the first heat exchanger (4).
4. A flow-through drinking water heater according to any one of claims 1 to 3, characterized in

   - that a third temperature sensor (38) is provided in the secondary pipe arrangement (10) for detecting the inlet temperature of the water flowing in the secondary-side inlet of the first heat exchanger (4),

   - that the control device (26) is set up to record the measured values of the third temperature sensor (38) and

   - that the control device (26) is arranged to control the pumping capacity of the first pump (20) and the second pump (22) to an inlet temperature which is higher than a predetermined inlet temperature.
5. Flow-through drinking water heater according to one of the claims 1 to 4, characterized in

   - that a fourth temperature sensor (34) is provided in the primary pipe arrangement (8) for detecting the return temperature of the water flowing from the primary-side return of the first heat exchanger (4),

   - that the control device (26) is set up to record the measured values of the fourth temperature sensor (34) and

   - that the control device (26) is arranged to control the pumping capacity of the first pump (20) and the second pump (22) to a secondary-side return temperature which is higher than a predetermined return temperature.
6. Flow-through drinking water heater according to one of the claims 1 to 5, characterized in

   - that a fifth temperature sensor (42) is provided in the secondary line arrangement (10) for detecting the return temperature of the water flowing in the secondary-side return of the second heat exchanger (6),

   - that the control device (26) is set up to record the measured values of the fifth temperature sensor (42) and

   - that the control device (26) is arranged to control the pumping capacity of the first pump (20) and the second pump (22) to a minimum return temperature.
7. Flow-through drinking water heater according to one of the claims 1 to 6, characterized in

   - that a sixth temperature sensor (44) is provided in the primary pipe arrangement (8) for detecting the return temperature of the water flowing from the primary-side return of the second heat exchanger (6),

   - that the control device (26) is set up to record the measured values of the sixth temperature sensor (44) and

   - that the control device (26) is arranged to control the pumping capacity of the first pump (20) and the second pump (22) to a return temperature which is lower than a predetermined primary-side return temperature.
8. Flow-through drinking water heater according to one of the claims 1 to 7, characterized in

   - that a seventh temperature sensor (45) is provided in the secondary line arrangement (10) for detecting the return temperature from the circulation circuit before the mixing point of the water flowing from the second heat exchanger (6),

   - that the control device (26) is set up to record the measured values of the seventh temperature sensor (45),

   - that the control device (26) is set up to detect a mere circulation or a water withdrawal from the hot water circulation pipe (16) and

   - that the control device (26) is arranged to control the pumping capacity of the first pump (20) and the second pump (22) to a return temperature which is greater than a predetermined return temperature.
9. Flow-through drinking water heater according to one of the claims 1 to 8, characterized in
   in that the first heat exchanger (4) and/or the second heat exchanger (6) are provided with thermal insulation (46, 48).
10. Flow-through drinking water heater according to one of the claims 1 to 9, characterized in that
    in that heat insulation (50) is provided between the first heat exchanger (4) and the second heat exchanger (6).
11. Method of operating a flow-through drinking water heater

    - in which a first heat exchanger heats the hot water of a hot water circulation pipe on the secondary side to a specified return temperature,

    - in which, when hot water is drawn from the hot water circulation pipe and a threshold value for heat transfer capacity specified by the first heat exchanger is exceeded, a second heat exchanger connected in series with the first heat exchanger is activated and the cold water flowing in is heated on the secondary side, and

    - in which the second heat exchanger is deactivated if the heat transfer rate falls below the threshold value specified by the first heat exchanger.
12. Method according to claim 11,
    in which the reaching of the threshold heat transfer capacity of the first heat exchanger is detected by a failure to maintain the return temperature in the circulation line.
13. Method according to claim 11 or 12,
    in which the threshold heat transfer capacity is determined on the basis of the primary side feed temperature to the first heat exchanger.
14. Method according to one of the claims 11 to 13,
    in which the attainment of threshold heat transfer capacity is detected by exceeding the volume flow in the hot water circulation pipe above a specified threshold volume flow.
15. Method according to one of the claims 11 to 14,
    in which the first heat exchanger and the second heat exchanger are controlled in such a way that the secondary-side feed temperature to the first heat exchanger does not fall below a lower threshold value.
16. Method according to one of the claims 11 to 15,
    in which the reaching of the threshold heat transfer capacity of the first heat exchanger is detected by a failure to maintain a specified primary-side lower return temperature at the first heat exchanger.
17. Method according to one of the claims 11 to 16,
    in which the first heat exchanger and the second heat exchanger are controlled in such a way that a minimum return temperature is achieved at the secondary-side return of the second heat exchanger.
18. Method according to one of the claims 11 to 17,
    in which the first heat exchanger and the second heat exchanger are controlled in such a way that the primary-side return temperature of the second heat exchanger does not exceed an upper threshold value.
19. System for domestic hot water heating

    - with a first heater module (66) comprising a flow-through drinking water heater (2) according to one of claims 1 to 10, and

    - with an ultrafiltration module (74) comprising an ultrafiltration unit (72), characterised in,

    - that the lines (76a, 76b, 76c) leading out of the heater module (66) and to be connected to the hot water circulation line (16) and the cold water line (18) have predetermined vertical distances (dy1, dy2) and horizontal distances (dx1. dx2) from each other,

    - that the lines (78a, 78b, 78c) leading into the ultrafiltration module (74) and to be connected to the hot water circulation line (16) and the cold water line (18) have vertical distances (dy3, dy4) and horizontal distances (dx3, dx4) from each other and

    - that the vertical distances (dy3, dy4) and the horizontal distances (dx3, dx4) of the lines (78a, 78b, 78c) leading into the ultrafiltration module (74) correspond to the vertical distances (dy1, dy2) and the horizontal distances (dx1, dx2) of the lines (76a, 76b, 76c) leading out of the heater module (66).
20. System according to claim 19,
    characterised in,

    - that the lines (82a, 82b, 82c) leading out of the ultrafiltration module (74) and to be connected to the hot water circulation line (16) and the cold water line (18) have vertical distances (dy5, dy6) and horizontal distances (dx5, dx6) to each other and

    - that the vertical distances (dy5, dy6) and the horizontal distances (dx5, dx6) of the lines (82a, 82b, 82c) leading out of the ultrafiltration module (74) correspond to the vertical distances (dy1, dy2) and the horizontal distances (dx1, dx2) of the lines (76a, 76b, 76c) leading out of the heater module (66).

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