EP2659199B1 - Flow heater - Google Patents

Description

The invention relates to a water heater with a heat exchanger for heating a continuous liquid, which has a service water inlet for connection of a cold water pipe and a hot water outlet for connection of a hot water pipe, wherein a controller for controlling or regulating a temperature of the liquid is provided.

Furthermore, the invention relates to a method for operating such a flow heater with a heat exchanger for heating a flowing liquid.

Instantaneous water heaters are used, for example, for heating domestic water in households. Water is supplied to the water heater via a cold water line, heated within the flow heater by means of a heat exchanger and discharged via a hot water pipe. The heat exchanger can either be heated directly or via a secondary circuit. The term service water is to be understood generally and includes, for example, drinking water.

For proper operation of a water heater, it is necessary that the hot water pipe and the cold water pipe are correctly connected, so that the cold water pipe at the service water inlet and the hot water pipe are connected to the hot water outlet. Typically, then, a control of the heat input to the heat exchanger in response to a dispensed amount, which is detected by means of a flow sensor. However, a flow sensor works satisfactorily only if the desired direction of flow through the heat exchanger is maintained, so the cold water pipe at the service water inlet and the hot water pipe are connected to the hot water outlet. If the connections are interchanged, incorrect measurements of the dispensed liquid can occur. It is also possible that the Pass sensor does not give any signal, so it can not be determined whether liquid is discharged.

In conventional instantaneous water heaters a correct connection of the cold water pipe at the hot water outlet and the hot water pipe at the domestic water inlet is required for proper operation. A release of a heated liquid, in particular hot water, is usually not possible with exchanged connections.

That's how it shows DE 33 06 807 A1 shows a water heater with an electrically operable tubular heater for electric water heating. There are temperature sensors in front of and behind the tubular heater. A controller controls or regulates the temperature of the water to be heated. If the temperature at the first sensor is greater than at the second sensor, an inversion of the flow direction from the output to the input is concluded.

The US 2008/285964 A1 describes an electrically operated instantaneous water heater with a heat exchanger, a service water inlet and outlet and a controller for heating water. In the entrance and exit are temperature sensors.

The invention is based on the object to enable operation of the water heater even with a permutation of the connections.

According to the invention this object is achieved by a water heater having the features of claim 1. Advantageous developments can be found in the dependent claims.

By arranging a temperature sensor at the service water inlet, irrespective of the direction of flow of the liquid through the heat exchanger, ie regardless of whether the cold water pipe at the service water outlet or service water inlet and the hot water pipe is arranged correspondingly at the service water inlet or hot water outlet, heated liquid can be dispensed. A temperature change at the service water inlet suggests that liquid is dispensed or tapped. Such water delivery is also referred to as tapping. Shows the temperature sensor an increasing temperature at the domestic water input, this indicates that the hot water pipe is connected to the service water inlet, so the heat exchanger is thus passed through in a flow direction of the hot water outlet to the service water inlet. Thus, a control or regulation of the temperature of the dispensed liquid or the heat exchanger in dependence on the measured at the service water inlet actual temperature. A normal operation, which is set in a passage direction of the hot water inlet to the hot water outlet, can be issued, so that the water heater is operated in a fault mode.

Usually, a temperature sensor is arranged at the service water outlet. Such a temperature sensor at the hot water outlet is used with correct connection of hot water pipe and cold water pipe, so a direction of passage from the hot water inlet to the hot water outlet, for detecting the actual temperature in the hot water pipe and thus to control or regulate the heat transferred through the heat exchanger to the liquid heat. By the temperature sensor at the hot water outlet can thereby further improve error detection. A comparison of the temperature at the service water input and service water output provides relatively reliable information about whether the cold water pipe is connected to the service water inlet or the hot water outlet. If the temperature at the service water input exceeds the temperature at the dhw output, the connections are reversed so that the instantaneous water heater should be operated in fault mode.

Preferably, a flow sensor is arranged at the service water inlet and / or at the service water outlet. Such a flow sensor is present in many conventional instantaneous water heaters, wherein by means of the flow sensor, a discharge amount is determined, which serves to control the amount of heat transferred through the heat exchanger to the liquid. Such a flow sensor is usually reliable only in one direction of passage, according to the invention, the directional dependence of the flow sensor can also be used to detect whether the cold water pipe is correctly connected to the service water inlet and the hot water pipe correctly at the hot water outlet. If despite a temperature increase at the service water inlet of the flow sensor no signal, ie signal no discharge, are clearly interchanged connections, so that the water heater must be operated in error mode, in which the regulation of the discharged liquid as a function of the temperature at the service water inlet takes place.

In a preferred embodiment, the heat exchanger on a secondary circuit with a pump and a heat source, which are controllable by the controller. By means of the secondary circuit and the pump, heat generated by the heat source is brought into the heat exchanger and transferred from there to the liquid, so that it can be discharged heated. The heat source may have different configurations, for example, be designed as a gas or oil burner or as an electric heating element. It is also conceivable to form the secondary circuit, for example, as part of a central heating system.

• 0: Überprüfung notwendig,
• 1: Normalbetrieb,
• 2: Fehlerbetrieb,

wobei ein Betrieb des Durchlauferhitzers in Abhängigkeit vom hinterlegten Zustand erfolgt. Zur Speicherung des jeweiligen Zustandes ist dabei ein Byte erforderlich, was gegenüber einer Speicherung in einem einfachen Bit den Vorteil hat, dass es weniger fehleranfällig ist. Vor der ersten Initialisierung bzw. dem ersten Hochfahren des Durchlauferhitzers ist dabei im Speicher hinterlegt, dass eine Überprüfung notwendig ist. Dadurch wird sichergestellt, dass nach jedem Neuanschluss eine Überprüfung erfolgt, ob die Warmwasserleitung korrekt am Brauchwasserausgang und die Kaltwasserleitung korrekt am Brauchwassereingang angeschlossen ist. Wird dies bejaht, wird der Durchlauferhitzer im Normalbetrieb betrieben und dieser Zustand im Speicher hinterlegt. Im Normalbetrieb können durch einen Benutzer verschiedene Einstellungen vorgenommen werden, beispielsweise der Durchlauferhitzer in einem Eco-Modus oder einem Komfort-Modus betrieben werden. Im Eco-Modus wird zur Energieeinsparung eine weitgehende Abkühlung des Wärmetauschers zugelassen, wenn keine Flüssigkeit gezapft wird. Im Fehlerbetrieb, also wenn die Warmwasserleitung am Brauchwassereingang und die Kaltwasserleitung am Brauchwasserausgang angeschlossen sind, ist hingegen ein Betrieb im Eco-Modus nicht möglich, da im Fehlerbetrieb eine wiederholte Überprüfung der Anschlüsse erfolgen soll, was nur möglich ist, wenn der Wärmetauscher in einem Betriebstemperaturbereich betrieben wird. Auch weitere Einstellmöglichkeiten durch einen Benutzer können im Fehlerbetrieb eingeschränkt sein.Preferably, the controller has a memory in which the following states can be stored:

• 0: check necessary,
• 1: normal operation,
• 2: error operation,

wherein an operation of the water heater takes place in dependence on the stored state. One byte is required for storing the respective state, which has the advantage over storage in a simple bit that it is less error-prone. Before the first initialization or the first startup of the water heater is stored in the memory that a review is necessary. This ensures that a check is made after every new connection, whether the hot water pipe is correctly connected to the hot water outlet and the cold water pipe is correctly connected to the domestic water inlet. If this is affirmative, the water heater is operated in normal operation and this state is stored in the memory. In normal operation, various settings can be made by a user, for example, the water heater can be operated in an Eco mode or a comfort mode. In the Eco mode, a substantial cooling of the heat exchanger is allowed for energy saving, if no liquid is tapped. In fault mode, ie when the hot water pipe at the service water inlet and the cold water pipe are connected to the hot water outlet, however, is an operation in the Eco mode not possible, since in error operation a repeated check of the connections should be made, which is only possible if the heat exchanger is operated in an operating temperature range. Other settings by a user may be limited in error mode.

Preferably, the controller is designed such that when connecting the hot water pipe at the service water inlet warm liquid is available at the service water inlet and optionally displays the fault mode, in particular a temperature of the heat exchanger is increased or kept constant or regulated depending on the temperature at the service water inlet. Thus, a sufficient operation of the water heater is also possible with a permutation of the connections. By providing a corresponding display, an installer can then relatively quickly find out and fix the cause of the error. However, it is not necessary to shut down the water heater until the fault is rectified. Rather, limited but limited operation is possible.

The object is achieved by a method having the features of claim 6.

In this case, a passage direction of the liquid is determined by the heat exchanger, wherein a control of an actual temperature of the liquid to a predetermined desired temperature in dependence on the passage direction. The water heater is so both in a direction of passage from the hot water inlet to the hot water outlet, ie with correct connection of hot water pipe and cold water pipe, as well as in the reverse flow direction from the hot water outlet for domestic water input operable. In this case, different control parameters can be used depending on the direction of passage. For example, the target temperature in a direction of passage from the hot water output to the service water input can be fixed, while the target temperature at the right direction of passage from the hot water input to hot water output by a user is changeable, for example by selecting the Eco mode.

Advantageously, the passage direction by measuring the temperature at the service water inlet, optionally in conjunction with measuring the temperature on Hot water output and / or determined with a flow sensor at the dhw input or dhw output. An increase in temperature at the service water inlet is a sign that the hot water pipe is connected to the service water inlet, ie the direction of flow from the hot water outlet to the service water inlet leads. However, this fault detection can be made more reliable by the fact that the temperature at the hot water outlet is detected. If the temperature at the service water inlet when dispensing liquid with respect to the temperature rises at the hot water outlet, there is clearly a run from the hot water outlet to the hot water inlet. A directional flow sensor can also be used to determine the flow direction. However, to control the actual temperature of the liquid dispensed then a detection of the temperature at the service water inlet is required.

Preferably, a temperature T1 is measured at the service water inlet and a temperature T2 at the service water outlet, wherein the temperature T2 is controlled to target temperature when the temperature T2 is greater than the temperature T1, wherein the temperature T1 is controlled to target temperature, if Temperature T1 is greater than the temperature T2. Thus, both the temperature at the service water inlet and at the service water outlet are recorded. The basis for the regulation is always the warmer recorded temperature, which provides reliable information about the direction of flow within the heat exchanger. If the temperature T2 at the hot water outlet is greater than the temperature T1 at the domestic water input, there is a normal operation, while when the temperature T1 at the hot water inlet is higher than the temperature T2 at the hot water outlet, there is an error operation. Depending on whether normal operation or fault operation is present, the control can be operated with different programs or in different modes.

• 0: Überprüfung notwendig,
• 1: Normalbetrieb,
• 2: Fehlerbetrieb,

wobei beim Initialisieren des Durchlauferhitzers und/oder nach längeren Stillstandszeiten der Speicher auf "0" gesetzt wird, wobei insbesondere im Fehlerbetrieb eine Überprüfung der Durchlaufrichtung wiederholt wird. Im Auslieferungszustand, also vor einer ersten Initialisierung bzw. einem ersten Hochfahren des Durchlauferhitzers, ist im Speicher hinterlegt, dass eine Überprüfung notwendig ist. Demzufolge erfolgt beim ersten Hochfahren eine Überprüfung, ob die Warmwasserleitung und die Kaltwasserleitung korrekt angeschlossen sind. Dafür wird der Wärmetauscher erwärmt und die Temperatur am Brauchwassereingang erfasst. Gegebenenfalls wird zusätzlich die Temperatur am Brauchwasserausgang erfasst und mit der Temperatur am Brauchwassereingang verglichen. Es ist auch denkbar, mithilfe eines Durchlaufsensors zu erfassen, ob eine Abgabe an Flüssigkeit erfolgt. Wenn nun die Temperatur am Brauchwassereingang höher wird als am Brauchwasserausgang, wird im Speicher hinterlegt, dass der Durchlauferhitzer im Fehlerbetrieb betrieben wird. Steigt die Temperatur am Brauchwasserausgang jedoch über die Temperatur am Brauchwassereingang an, wird hinterlegt, dass der Durchlauferhitzer im Normalbetrieb betrieben wird. Im Fehlerbetrieb sind dabei Benutzervorgaben nur eingeschränkt zulässig, wobei beispielsweise der Betrieb im Eco-Modus nicht möglich ist, so dass kein übermäßiges Abkühlen des Wärmetauschers erfolgt. Dabei ist im Fehlerbetrieb vorgesehen, dass eine periodische erneute Überprüfung der Durchlaufrichtung erfolgt.It is particularly preferred that one of the following three states is stored in a memory:

• 0: check necessary,
• 1: normal operation,
• 2: error operation,

wherein the memory is set to "0" during initialization of the water heater and / or after longer periods of standstill, wherein in particular a check of the flow direction is repeated in error mode. In the delivery state, ie before a first initialization or a first startup of the water heater, is stored in the memory that a review is necessary. As a result, the first start-up will check whether the hot water pipe and the cold water pipe are correctly connected. For this purpose, the heat exchanger is heated and the temperature at the service water inlet is detected. If necessary, the temperature at the dhw output is additionally recorded and compared with the temperature at the dhw input. It is also conceivable to detect with the aid of a flow sensor whether a discharge of liquid takes place. If now the temperature at the dhw input is higher than at the dhw output, it is stored in the memory that the flow heater is operated in error mode. However, if the temperature at the service water outlet rises above the temperature at the service water inlet, it is deposited that the water heater is operated in normal operation. In error mode, user defaults are only permitted to a limited extent, for example, operation in the Eco mode is not possible, so that there is no excessive cooling of the heat exchanger. It is provided in error mode that a periodic re-examination of the direction of passage takes place.

Preferably, a temperature of the heat exchanger is maintained between an upper and a lower limit temperature in the error mode. This can be done for example by means of fuzzy control.

Preferably, a higher setpoint is used in error mode than in normal mode. This ensures that even with incorrect connection of the cold water pipe and the hot water pipe sufficiently warm liquid is discharged from the heat exchanger to the hot water pipe. At the same time, the error detection is improved by the increased setpoint, since the increase in the setpoint leads to an increased temperature increase in the dispensed liquid.

Fig. 1

einen Durchlauferhitzer in schematischer Ansicht und

Fig. 2

einen möglichen Verfahrensablauf.

The invention will be described below with reference to a preferred embodiment in conjunction with the drawings. Herein show:

Fig. 1

a flow heater in a schematic view and

Fig. 2

a possible procedure.

In Fig. 1 schematically a flow heater 1 is shown with a heat exchanger 2, wherein the heat exchanger 2 has a service water inlet 21 and a hot water outlet 22. Heat energy is supplied to the heat exchanger 2 via a secondary circuit 5 and is generated in a heat source 52. In this case, a transfer of heat energy from the heat source 52 to the heat exchanger 2 by means of a liquid, in particular water, which is moved by a pump 51.

In a correct installation, a cold water pipe 31 at the service water inlet 21 and a hot water pipe 32 at the hot water outlet 22 is arranged. A passage direction through the heat exchanger 2 is then from the service water inlet 31 to the hot water outlet 32. In the heat exchanger 2, a transfer of heat energy to the liquid, ie a heating of the liquid is heated to the hot water pipe 32 is discharged. In the following it is assumed that water is used as liquid, but also the use of other liquids is conceivable.

The transferable from the heat exchanger 2 to the water heat energy is regulated by a controller 4. Usually, a discharge amount is detected by means of a flow sensor 8, wherein the controller determines how much heat has to be transferred in the heat exchanger 2 as a function of the discharge quantity. The introduced by the secondary circuit 5 heat energy is then supplied accordingly. Such a control works with correct connection of cold water pipe and hot water pipe, so if the flow direction from the hot water inlet to the hot water outlet is satisfactory. A control by means of a temperature sensor 7, which is arranged at the service water outlet 22, thereby enables a control of the setpoint temperature.

In the reverse direction of passage, so if the cold water pipe 31 are connected to the hot water outlet 22 and the hot water pipe 32 at the service water inlet 21 in a faulty manner, the flow sensor 8, however, no longer outputs a signal and the temperature sensor 7 at the hot water outlet 22 shows always only a constant temperature, namely that of the supplied cold water. As a result, a controlled release of hot water is not possible. According to the invention, it is now provided to arrange a temperature sensor 6 at the service water inlet 21. Such a temperature sensor 6 has a correct connection, so a direction of passage from the hot water inlet 21 to the hot water outlet 22, another monitoring function, namely the detection of preheated water at the service water inlet 21. For example, to detect solar water preheating. As soon as the water temperature at the service water inlet 21 is above that at the service water outlet 22, the instantaneous water heater 1 or its heat source 52 is not activated. Furthermore, the temperature sensor 6 can be used to optimize the water temperature at the hot water outlet 22 with a predictive control, namely taking into account the water inlet temperature. However, it allows a reliable determination of the direction of flow and a control of the setpoint temperature of the liquid dispensed even when the hot water pipe is connected to the service water inlet 21, the water heater 1 is therefore passed through so to speak the wrong way round.

With correct connections, ie when connecting the cold water line 31 at the service water inlet 21 and the hot water line 32 at the hot water outlet 22, a normal operation is present. An error operation is when the heat exchanger 2 is operated in the reverse direction, ie the cold water pipe 31 is connected to the hot water outlet 22 and the hot water pipe 32 at the service water inlet 21. Whether a fault operation is present, can be displayed in a display 9, so that, for example, immediately recognizable by an installer, whether the hot water pipe 32 and the cold water pipe 31 are correctly connected to the heat exchanger 2.

In Fig. 2 schematically a possible sequence of the method according to the invention is shown. After a first installation, ie at a first startup of the water heater 1 or after a long interruption of the operation, the heat exchanger 2 is first heated. When a hot water delivery then the temperature at the service water inlet 21 is detected. Optionally, the heat source 52 can now provide more heat, in which case the temperature at the service water inlet 21 is detected continuously. A temperature at the service water inlet 21 before starting the heat source 52 will come with a later detected temperature compared. If a temperature increase has occurred, the passage direction from the hot water outlet 22 to the hot water inlet 21, so there is a fault operation. Accordingly, 21 hot water is discharged at the service water inlet and there is a control of the actual temperature at the service water inlet 21. When the temperature at the service water inlet 21 decreases, although the heat source 52 provides heat energy to the heat exchanger 2, the cold water pipe 31 and the hot water pipe 32 are correctly connected and There is a normal operation in which hot water is discharged at the hot water outlet 22, so that the temperature at the hot water outlet 22 is controlled to the target temperature.

The heating of the water heater 1 at the first start-up is carried out regardless of which mode of the water heater 1 is set, so if, for example, an Eco mode was selected, in which a heating of the heat exchanger 2 takes place only as needed.

If, in addition to the temperature detection at the service water inlet 21, a temperature detection is also carried out at the service water outlet 22, the passage direction can be determined relatively easily by comparing these two temperatures. If, during the discharge of liquid, the temperature at the service water outlet 22 rises above the temperature at the service water inlet 21, the water heater is in normal operation. In contrast, when the temperature at the service water inlet 21 rises from the temperature at the service water outlet 22, the instantaneous water heater 1 is in error operation. The error detection can be additionally improved by the provision of a flow sensor.

An error operation can also be assumed if during the delivery of liquid no cooling at the service water inlet 21, so no temperature decrease takes place.

The method according to the invention can easily be additionally implemented and also retrofitted into existing instantaneous water heaters. This method only comes into effect when the cold water pipe 31 and the hot water pipe 32 are not properly connected. This makes it possible to issue even reliably heated liquid, if no correct connections were made, the water heater 1 is thus operated in error mode. At the same time is one Detecting the error is very easy, so that rework can be done very quickly and thus cause few costs.

The check of the passage direction by warming the water heater 1 is carried out regardless of a set mode, that is, for example, regardless of whether the water heater 1 is operated in an Eco mode or a comfort mode. In fault mode, a temperature of the heat exchanger 2 is maintained between a lower and an upper limit temperature, that is, the heat exchanger 2 is always kept at an elevated temperature. In normal operation, it is possible, for example in the setting Eco mode, to allow a substantial cooling of the heat exchanger 2 in order to save energy.

While conventionally the heat energy transferred from the heat exchanger 2 to the liquid to be dispensed is controlled as a function of the dispensed quantity, it is provided according to the invention to detect a temperature at the service water inlet 21, so that a control of the temperature of the dispensed liquid is possible even if the cold water line 31 and hot water pipe 32 are connected reversed.

Claims (10)

1. Flow heater (1) having a heat exchanger (2) for heating a through-flowing liquid, which heat exchanger has a service water inlet (21) for the connection of a cold water line (31) and a service water outlet (22) for the connection of a hot water line (32), wherein a controller (4) is provided for controlling or regulating a temperature of the liquid, wherein a temperature sensor (6) is arranged on the service water inlet (21), characterized in that

   - the controller is designed to detect a temperature during hot water discharge by means of the temperature sensor (6) on the service water inlet (21) and to detect the temperature at the service water inlet (21) at a later point in time,

   - in that the controller is further designed to detect a throughflow direction of the liquid from the service water outlet (22) to the service water inlet (21) in the event of a temperature increase at the service water inlet (21),

   - and then to regulate the temperature at the service water inlet (21).
2. Flow heater according to Claim 1,
   characterized in that a flow sensor (8) is arranged on the service water inlet (21) and/or on the service water outlet (22).
3. Flow heater according to either of Claims 1 and 2, characterized in that the heat exchanger (2) is connected to a secondary circuit (5) which has a pump (51) and a heat source (52) which are controllable by the controller (4).
4. Flow heater according to one of Claims 1 to 3,
   characterized in that the controller (4) has a memory in which the following states can be stored:

   0: monitoring necessary,

   1: normal operation,

   2: fault operation,

   wherein an operation takes place in dependence on the stored state.
5. Flow heater according to one of Claims 1 to 4,
   characterized in that the controller (4) is configured in such a way that, with a connection of the hot water line (32) to the service water inlet (21), hot liquid can be obtained at the service water inlet (21), and, if appropriate, an indicator (9) indicates the fault operation, wherein in particular a temperature of the heat exchanger (2) is increased or kept constant, or is regulated in dependence on the temperature in the service water inlet (21).
6. Method for operating a flow heater according to one of Claims 1 to 5 having a heat exchanger for heating a through-flowing liquid, characterized in that a throughflow direction of the liquid through the heat exchanger is determined, wherein a regulation of an actual temperature of the liquid to a predetermined setpoint temperature takes place in dependence on the throughflow direction.
7. Method according to Claim 6,
   characterized in that a throughflow direction is determined by measuring the temperature at the service water inlet, if appropriate in conjunction with measuring the temperature at the service water outlet and/or with a flow sensor at the service water inlet or at the service water outlet.
8. Method according to either of Claims 6 and 7,
   characterized in that a temperature (T1) is measured at the service water inlet and a temperature (T2) is measured at the service water outlet, wherein the temperature (T2) is regulated to a setpoint temperature if the temperature (T2) is higher than the temperature (T1), whereas the temperature (T1) is regulated to a setpoint temperature if the temperature (T1) is higher than the temperature (T2).
9. Method according to one of Claims 6 to 8,
   characterized in that, in particular in fault operation, a temperature of the heat exchanger is kept between a lower and an upper limiting temperature.
10. Method according to one of Claims 6 to 9,
    characterized in that, in fault operation, a higher setpoint value is used than in normal operation.

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