Method for commissioning an instantaneous water heater, computer program, control and regulating device and instantaneous water heater

Abstract

A method for commissioning an instantaneous water heater (1) is proposed. The instantaneous water heater (1) comprises an electric heating block (3), a fluid channel (11) from a cold water inlet (8) to a hot water outlet (9) for the flow of a fluid to be heated, a flow sensor (5) and means for detecting the thermal power of the instantaneous water heater (1).The procedure comprises at least the following steps: a) commissioning the instantaneous water heater (1) at an initial electrical power level at which no damage to the instantaneous water heater (1) is to be expected, even if air is present in the fluid channel (11); b) detecting the electrical conductivity and thermal output of the instantaneous water heater (1); c) increasing the electrical power when a thermal output corresponding to the electrical power is detected; and d) reducing the electrical power of the instantaneous water heater (1) to a second electrical power level when the thermal output falls below the electrical power minus a tolerance. The procedure enables safe and damage-free initial commissioning of an instantaneous water heater (1) when air is to be expected in the fluid channel (11) or cold water inlet (8).

Description

The invention relates to a method for starting up a continuous-flow heater, a regulating and control device, a computer program and a continuous-flow heater.Electric continuous flow heaters can be used very variably for heating service water, because these require only an electric energy supply and, in addition, require only little installation space. The appliances generally have a heating block which is configured to heat a volume flow of water. The desired water temperature can be established by regulating the outlet temperature or by controlling it using the inlet temperature (with a known temperature spread of the heating block). In the regulation of the outflow temperature, a control of the mass flow of water flowing through the heating block is generally used, which controls the mass flow corresponding to the desired outflow temperature when the continuous heater is operated at rated power.Such continuous flow heaters generally have a considerable rated power in order to heat a sufficient flow rate of water, for example for a shower. This high power can lead to damage to the continuous-flow heater and, in particular, to the heating block if a sufficient mass flow of water does not flow through the latter. This risk exists in particular when the continuous-flow heater is put into operation, with any air still present in the continuous-flow heater or in lines, which can lead to overheating. When a continuous-flow heater is put into operation in a building with newly installed or revised water lines, for example, in the case of a new construction, problems of this kind can occur to a greater extent.To avoid overheating of a continuous-flow heater, DE 10 2019 004 320 A1 proposes detecting the presence of air bubbles in the fluid channel of the continuous-flow heater on the basis of a change in the signal of a flow sensor and to correspondingly adapt the heating power. A disadvantage of detecting air bubbles with the aid of the flow sensor has proven to be inaccurate, or requires a very cost-intensive flow sensor.Proceeding from this, it is an object of the invention to propose a method for commissioning a continuous-flow heater, a computer program and a continuous-flow heater, which at least partially overcome the outlined problems of the prior art. In particular, the invention is intended to enable a continuous-flow heater to be put into operation reliably without overheating occurring even in the case of air bubbles which may be present in a cold water inlet or a fluid channel thereof.In addition, the invention is intended at least not to substantially increase the complexity of a continuous-flow heater, to require only minor structural changes and / or to enable simple integration into an existing production process.These objects are achieved by the features of the independent claims. Further advantageous embodiments of the solution proposed here are specified in the independent patent claims. It is pointed out that the features listed in the dependent patent claims can be combined with one another in any desired, technologically meaningful manner and define further embodiments of the invention. In addition, the features specified in the patent claims are more precisely described and explained in the description, further preferred embodiments of the invention being presented.This is contributed by a method for starting up a continuous-flow heater. The continuous flow heater comprises at least one electrical heating block, configured to heat fluid flowing through a fluid channel, a flow sensor and means for detecting a thermal output of the continuous flow heater. The method comprises at least the following steps: a) starting up the continuous-flow heater with a first electrical power, in which damage to the continuous-flow heater is not to be expected even when air occurs in the fluid channel, b) detecting an electrical power and a thermal power of the continuous-flow heater, c) increasing the electrical power if a thermal power corresponding to the electrical power is detected, and d) lowering the electrical power of the continuous-flow heater to a second electrical power if the thermal power falls below the electrical power minus a tolerance.Steps a), b), c) and d) can be carried out at least once in the stated sequence. In particular, step b) can be carried out permanently or permanently, in particular during the execution of steps c) and d). Steps c) and d) can be carried out in particular in parallel or simultaneously. After step d) has been carried out, step a) can be carried out again, for example.The method serves in particular to avoid overheating of the continuous-flow heater or of its heating block and associated damage during startup after installation of the continuous-flow heater and / or installation of or working on pipes of the cold water feed thereof, which promote the occurrence of air in the pipes. The method enables reliable startup of the continuous-flow heater even when (residual) pressure drops occur in lines of the cold water inlet or in the fluid channel of the continuous-flow heater.The continuous flow heater can be a known continuous flow heater. This can have a fluid channel which leads from a cold water inlet to a hot water outlet and can comprise a heating block, a flow sensor and means for determining a thermal output thereof. Cold water flowing in in the cold water inlet can be heated by the heating block and can flow out through the hot water outlet and be supplied to a removal point, for example a fitting of a washbasin or a shower. The heating block may include at least one heating element capable of converting electrical current to heat to deliver the fluid passing through the fluid channel. In this case, in particular a plurality of heating elements can be provided, which are switched via power switches, for example TRIACs (Triode for Alternating Current) and are thus put into operation. For this purpose, the continuous-flow heater can comprise a regulating and control unit. The heating elements can be arranged in particular in such a way that they come in the immediate vicinity of or in direct contact with the fluid flowing through the fluid channel.The control and control device can control a flow-out temperature, determined by a temperature sensor in the hot water flow-out of the continuous-flow heater on the basis of the electrical power of the heating elements. In addition, the continuous flow heater can comprise a temperature sensor in the cold water inlet and a flow sensor for detecting a flow rate of the fluid flowing through the fluid channel. The flow sensor can be a mass flow sensor or a volume flow sensor. The outlet temperature can be predetermined or also entered by a user via an input device.The continuous-flow heater can be suitable in particular for supplying hot water for use in a building, for example by means of a fitting as a removal point. For this purpose, the continuous-flow heater can have a power in a range from 5 kilowatts to 35 kilowatts.A thermal output of the continuous-flow heater can be determined, for example, on the basis of the temperature spread between cold water inlet and hot water outlet and the flow rate in the fluid channel, with knowledge of the specific heat capacity of the fluid flowing through the fluid channel. The flow rate could be directly detected or determined on the basis of a pressure difference with a known pressure loss of the continuous flow heater (for example by detecting two pressure values of two pressure sensors).According to step a), the continuous flow heater can be put into operation with a first electrical power The first electrical power is dimensioned in such a way that no damage to the continuous flow heater or the heating block can be expected even if air occurs in the fluid channel. In other words, the first electrical power can be selected such that no damage to the heating block occurs even during a dry operation (with only air in the fluid channel in the heating block). The first electrical power can be determined in this case by calculation or approximately or else by means of (laboratory) experiments.According to one configuration, in step a) the continuous flow heater can be operated at the first power for a safety period and / or a minimum continuous flow quantity. The safety period can be dimensioned such that with sufficient probability all air bubbles and gas residues in the cold water inlet and / or in the fluid channel of the continuous flow heater have flowed away, i.e. have left the fluid channel of the continuous flow heater through the hot water outlet. The minimum flow rate can be cumulative or determined by a control and control unit of the continuous flow heater on the basis of the signal of the flow sensor.According to one embodiment, the first power can also be zero, i.e. the heating block can remain out of operation until a minimum flow rate has passed through the continuous-flow heater.According to step b), an electrical power and a thermal power of the continuous-flow heater can be detected. Step b) can be carried out in particular permanently or permanently during startup. For example, the execution of step a) can also be ended (and thus the safety period can be ended) only if no temperature fluctuations of the hot water outlet or only temperature fluctuations of the hot water outlet occur below a limit value (with respect to amplitude and / or frequency).According to step c), an increase in the electrical power of the continuous-flow heater can take place if a thermal power corresponding to the electrical power is detected. In this case, the output of the continuous-flow heater can be increased in accordance with a predefined function, for example with a predefined gradient. A reaction time of the continuous flow heater can be included here. The reaction time here denotes the time period from the switching of a power change to a determination of the power change by a temperature measurement at the hot water outlet. The function or the gradient can be selected such that even in the event of air bubbles occurring (and a drop in the thermal power associated therewith), and in the event of an immediate drop in the electrical power, the thermal energy collecting in the heating block within the reaction time has no potential for damage or only an extremely low potential for damage.According to one configuration, the increase in the electrical power can take place stepwise and it can be waited before a subsequent increase step whether the increase in the electrical power also results in a corresponding increase in the thermal power detected in step b) (and thus whether the detected thermal power corresponds to the electrical power). In this case, a tolerance of the electrical power with respect to the detected thermal power can also be included.According to one configuration, a relative increase in the electrical power can also take place. For this purpose, the electrical power could be increased stepwise by a relative value (for example, with respect to the current or rated power) and a further increase step could only take place when a corresponding relative increase in the thermal power was detected. Tolerances to be included are advantageously very small with a relative increase.A suitable rate of increase of the electrical power in step c) can be determined here on the basis of a reaction time between a change in the electrical power and a detection of the corresponding change in the thermal power. The reaction time can be determined, for example, at the beginning of the process execution at an non-critical electrical power.According to one configuration, when carrying out step c), the electrical power can also be increased steadily, for example in a time profile from a minimum power to the maximum power within an increase period. A temporal profile of the thermal power to be expected corresponding to this temporal profile can be calculated. The detected temporal profile of the thermal power can be compared with the calculated temporal profile and, if the detected temporal profile of the thermal power falls below the calculated temporal profile of the thermal power, it can be detected that the detected thermal power does not correspond to the electrical power. The rate of increase, i.e. the gradient of the ramp function of the electric power, or a step width in the case of a stepwise increase of the power, should be selected in such a way that the electric power is not increased by a critical amount within the reaction time.A thermal power corresponding to the electrical power is present if the thermal power is above the electrical power minus a tolerance. As a rule, the thermal power is lower than the electrical power, also due to heat losses. In addition, measurement tolerances of sensors can occur. Therefore, a tolerance is necessary for carrying out a method proposed here.A suitable tolerance can be determined or estimated in advance in laboratory tests. In this case, proper execution of the method with a low damage potential is to be weighed out. Alternatively or cumulatively, a tolerance could also be determined / estimated within the scope of the method execution in an non-critical, low power range. For this purpose, a switched electrical power could be compared with a determined thermal power and the tolerance could be determined. Due to possible variations in the tolerance, a determined tolerance should be slightly increased (for example, by 10 percent) in order to ensure a process sequence without problems.If the thermal power falls below the electrical power minus the tolerance, this is an indication of gas components or air bubbles occurring in the fluid channel or heating block and, according to a step d), the electrical power of the continuous-flow heater can be lowered (immediately, directly) to a second electrical power. Thus, the drop in the thermal power compared to the electrical power can mean that thermal energy collects in the system, in particular in the heating block, and possibly leads to damage to the latter.Thus, by comparing the thermal power and the electrical power of the continuous heater, the medium flowing through the fluid channel can be deduced and, if the electrical power is exceeded minus (minus) a tolerance due to the thermal power, a medium flowing through the fluid channel can be assumed which has a significantly lower heat capacity than the assumed medium. The assumed medium is usually water, and in the case of a proportion of air, the thermal power can drop below the electrical power minus the tolerance.The second electrical power can be selected in such a way that damage to the heating block in the event of air bubbles occurring can be prevented. For example, the second electrical power may correspond to the first electrical power.According to one configuration, the second electrical power can also be selected as a function of the thermal power that has occurred.According to one configuration, if a thermal power corresponding to the electrical power is ascertained again, the execution of step c) can be continued with the electrical power at which step d) was carried out or with the second electrical power as starting point for the increase in the electrical power according to step c)According to an alternative embodiment, if a thermal power corresponding to the electrical power is detected again, the method can be continued with the execution of step a).According to one embodiment, the electrical power of the continuous flow heater can be reduced to the second power even in the event of fluctuations in the outlet temperature above a limit value with respect to amplitude and / or frequency. Thus, if the thermal power detected in step b) fluctuates, air bubbles in the heating block can be assumed, and the electrical power can be reduced in response.According to one embodiment, a rated power of the continuous-flow heater can be determined by means of a ratio of electrical and thermal power determined in step b). This can be effected, for example, on the basis of the relative switching times of the semiconductor components controlling the heating wires (for example TRIACs (Triode for Alternating Current)) and the detected thermal power. For example, with a switching time of 50 percent (100 percent would correspond to the rated power and mean uninterrupted startup) and a detected thermal power of 13.5 kilowatts, a heating block with a rated power of 27 kilowatts can be assumed.According to a further aspect, a continuous flow heater is proposed, comprising at least one fluid channel and a heating block which are configured to heat fluid flowing through the fluid channel by means of electrical energy, a flow sensor and means for determining a thermal output of the continuous flow heater. The thermal output can be effected in particular on the basis of a detected temperature spread by the heating of the continuous-flow heater, a detected flow rate and a known, predefined specific heat capacity of the fluid, in particular water. Thus, the continuous-flow heater can in particular each comprise a temperature sensor for detecting a temperature in the cold water inlet, in the hot water outlet (thus, viewed in the direction of flow, in front of and behind the heating block) and a flow sensor.According to a further aspect, a computer program is also proposed, which is set up to carry out a method presented here. In other words, this relates in particular to a computer program (product) comprising instructions which, when the program is executed by the continuous-flow heater or a regulating and control device of the continuous-flow heater, cause the continuous-flow heater to execute a method proposed here. For this purpose, the continuous flow heater can have at least one flow sensor and means for determining a thermal output thereof, to which a computer carrying out the method can be electrically connected.According to a further aspect, a regulating and control device of a continuous-flow heater is also proposed, which is set up to carry out a method proposed here. For this purpose, the control and control device can have a processor, for example, and / or can have it. In this context, the processor can execute, for example, the method stored on a memory (of the regulating and control unit). Advantageously, data for carrying out a method presented here can also be stored on the memory of the regulating and control unit, for example a first and / or second electrical power, a function or gradient of an increase in the power of the continuous heater, a tolerance (of the electrical power) and / or limit values for occurring fluctuations in the thermal power (with respect to amplitudes and / or a frequency / frequency) of the occurrence.According to a further aspect, a regulating and control device for a continuous-flow heater is also proposed, which is set up to carry out a method presented here. For this purpose, the regulating and control device can have a processor or have it, for example. In this context, the processor can, for example, execute the method described above stored on a memory (of the regulating and control unit).The details, features and configurations discussed in connection with the method can correspondingly also occur in the case of a continuous-flow heater, the computer program and / or the regulating and control device proposed here, and vice versa. In this respect, reference is made to the full extent of the details given there for more detailed characterization of the features.Thus, a method for starting up a continuous flow heater, a continuous flow heater, a computer program and a regulating and control device are specified here, which at least partially solve the problems described with reference to the prior art. In particular, the method for starting up a continuous-flow heater, the continuous-flow heater, the computer program and the regulating and control device contribute at least to enabling a continuous-flow heater to be started up more safely following installation of the same or working on lines of the cold water feed. Damage to the continuous-flow heater and / or to the heating block thereof can advantageously be avoided in this case.In addition, the proposed method advantageously does not require any structural changes to a continuous-flow heater and can only be used by an implementation of a computer program product proposed here.As a precautionary measure, it should be noted that the numerical words used here ("first", "second",... ) are primarily (only) used for distinguishing a plurality of articles, sizes or processes of the same type, that is to say in particular do not necessarily specify a dependence and / or sequence of these articles, sizes or processes with respect to one another. If a dependence and / or sequence is required, this is explicitly stated here or it is obvious to the person skilled in the art when studying the specifically described configuration. If a component can occur multiple times ("at least one"), the description of one of these components can apply equally to all or a part of the plurality of these components, but this is not obligatory.The invention and the technical field are explained in more detail below with reference to the attached figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments listed. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and combine them with other constituent parts and findings from the present description. In particular, it should be pointed out that the figures and in particular the size relationships illustrated are only schematic. The following are shown: FIG. 1 : shows a sequence of a method presented here, FIG. 2 : a continuous-flow heater presented here, FIG. 3 : shows a further continuous-flow heater presented here.FIG. 1 shows, by way of example and schematically, a sequence of a method proposed here. The method serves for safe startup of a continuous flow heater 1, in particular safe initial startup after installation or startup following work or installation of pipes or other devices of the cold water supply. The sequence of steps a), b), c) and d) represented by blocks 110, 120, 130 and 140 can be set up during a regular method sequence. In particular, step b) can be carried out permanently or permanently, in particular during the execution of steps c) and d). In addition, steps c) and d) can be carried out in parallel or simultaneously.FIG. 2 shows, by way of example and schematically, an electric continuous-flow heater 1 for heating a fluid stream, in particular a water stream, having a fluid channel 11 which can lead from a cold water inlet 8 via a heating block 3 to a hot water outlet 9. The fluid stream flows through the continuous heater 1 in a flow direction 2. the heating block 3 can have resistance-based heating elements which can be in direct contact with the fluid stream.The continuous-flow heater 1 can also have a regulating and control unit 6, which can be configured to regulate and control the continuous-flow heater 1, in particular the heating elements of the heating block 3. For this purpose, the regulating and control unit 6 can be electrically connected to a first temperature sensor 7 in the cold water inlet 8, a flow sensor 5, an engine valve 4 and a second temperature sensor 10 in the hot water outlet 9. The flow rate of the fluid can be throttled by means of the engine valve 4 in order to ensure a constant, desired temperature at the hot water outlet 9 when the heating block 3 is operated at rated power.FIG. 3 shows an example of a representation of a fluid channel 11 of the continuous heater 1. cold water flows into the fluid channel 11 via the cold water inlet 8, wherein its temperature is detected by the first temperature sensor 7. A printed circuit board 12, which can be a component of the regulating and control device 6, controls the heating elements of the heating block 3 in accordance with the heat requirement. A second temperature sensor 10 is arranged on the hot water outlet 9, which can be used to control the temperature of the outgoing hot water. The flow sensor 5 can detect the flow rate of water flowing through the fluid channel.FIG. 4 shows, by way of example and schematically, a diagram which represents the power P (electrically or thermally) over time t during the execution of a method proposed here in the case of a (first) heating of the continuous-flow heater 1. A first curve 13 shows the electrical power and a second curve 14 shows the thermal power determined. The thermal output can be determined on the basis of the temperature of the cold water inlet 8, detected at the first temperature sensor 7, the flow rate of water detected at the flow sensor 5 and the temperature of the water at the hot water outlet 9, detected at the second temperature sensor 10.In block 110, according to step a), the continuous-flow heater 1 is put into operation with a first electrical power, at which no damage to the continuous-flow heater is to be expected even if air occurs in the fluid channel. In FIG. 4, the first power is zero.In block 120, according to step b), an electrical power and a thermal power of the continuous-flow heater are detected. The electrical power can be detected by the control and control unit 6. The thermal power may be determined as described above. Step b) can be carried out in particular permanently during the execution of a method proposed here.In block 130, according to step c), an increase in the electrical power takes place if a thermal power corresponding to the electrical power is detected / determined. FIG. 4 shows a first curve 13 of the electrical power and a second curve 14 of the determined thermal power. In FIG. 4, the curve 14 of the thermal power corresponds to the curve 13 of the electrical power. In this case, the thermal power due to heat losses or tolerances is lower than the electrical power. In the example according to FIG. 4, the electrical power according to first curve 13 can be increased, since the measured thermal power according to curve 14 is lower than the electrical power according to curve 13 minus the tolerance. Without including the tolerance, this power difference between electrical power (curve 13) and thermal power (curve 14) would accumulate over time as thermal energy in the heating block 3. Only when the thermal power determined (curve 14) is reliably below the electrical power (curve 13), including the tolerance, does the electrical power have to be immediately reduced in order to avoid damage to the heating block 3.FIG. 4 shows a steady increase in the electrical power in step c). In this case, a relative consideration of the power increase can advantageously be made in order to check whether the electrical power (curve 13) corresponds to the thermal power determined (curve 14). By way of example, an increase in the electrical power by 5 percent in a predefined period of time must therefore lead to an increase in the thermal power by 5 percent after the reaction time has elapsed. A tolerance can also be included in this case. The reaction time could have been determined in advance in an non-critical power range for this purpose.In block 140, according to step d), the electrical power of the continuous-flow heater 1 is lowered to a second electrical power if the thermal power falls below the electrical power minus a tolerance. The execution of step d) is not shown in FIG. 4. The second electrical power could correspond to the first electrical power. Following the execution of step d), step c) could be carried out again.List of reference characters1 Continuous flow heater 2 Flow direction 3 Heating block 4 Motor valve 5 Flow sensor 6 Regulating and control device 7 First temperature sensor 8 Cold water inlet 9 Hot water outlet 10 Second temperature sensor 11 Fluid channel 12 Circuit board 13 First course 14 Second courseReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 20196 320 A1

[0004]

Claims

Method for starting up a continuous-flow heater (1) having an electrical heating block (3), a fluid channel (11) from a cold water inlet (8) and a hot water outlet (9) for a fluid to be heated to flow through, a flow sensor (5) and means for detecting a thermal power of the continuous-flow heater, comprising at least the following steps: a) starting up the continuous-flow heater (1) with a first electrical power at which no damage to the continuous-flow heater (1) is to be expected even when air occurs in the fluid channel (11), b) detecting an electrical power and a thermal power of the continuous-flow heater (1), c) increasing the electrical power when a thermal power corresponding to the electrical power is detected, and d) lowering the electrical power of the continuous-flow heater (1) to a second electrical power, if the thermal power drops below the electrical power minus a tolerance.Method according to claim 1, wherein the startup procedure involves a first startup procedure after installation of the continuous heater (1) and / or after working on lines of the cold water inlet (8) which lead to the expectation of an occurrence of air in the lines of the cold water inlet (8), the cold water inlet (8) and or the fluid channel (11).Method according to Claim 1 or 2, wherein the continuous-flow heater (1) comprises means for measuring a temperature at the hot water outlet (9) and, in a step d), the electrical power is reduced to a second power if the temperature at the hot water outlet (9) fluctuates.Method according to one of the preceding claims, wherein, when carrying out step a), the continuous-flow heater (1) is operated at the first power for a safety period and / or a minimum continuous flow rate.Method according to one of the preceding claims, wherein a rated power of the continuous-flow heater (1) is determined by means of a ratio of electrical power and thermal power.Continuous flow heater (1) comprising a fluid channel (11) and a heating block (3) configured to heat fluid flowing through the fluid channel (11) by means of electrical energy, a flow sensor (5), means for determining a thermal output of the continuous flow heater and means for carrying out a method according to one of the preceding claims.Continuous flow heater (1) according to claim 6, wherein it comprises a first temperature sensor (7) in the cold water inlet (8) and a second temperature sensor (10) in the hot water outlet (9).A computer program product comprising instructions for causing a continuous flow heater (1) according to any one of claims 6 or 7 to perform a method according to any one of claims 1 to 5.Control and control device (6) of a continuous-flow heater (1) configured to carry out a method according to one of Claims 1 to 5.

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