Method for starting up a continuous flow heater, computer program, control device and continuous flow 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

[0001] The invention relates to a method for commissioning a continuous flow heater, a control and regulating device, a computer program and a continuous flow heater.

[0002] Electric instantaneous water heaters can be used very flexibly to heat domestic water because they only require an electrical power supply and also require very little installation space. The devices typically have a heating block designed to heat a volume flow of water. The desired water temperature can be achieved by regulating the outlet temperature or by controlling it based on the inlet temperature (with a known temperature spread of the heating block). When regulating the outlet temperature, a control of the mass flow of water flowing through the heating block is usually used. This control regulates the mass flow according to the desired outlet temperature when the instantaneous water heater is operating at its rated power.

[0003] Such instantaneous water heaters typically have a significant rated output to heat a sufficient flow rate of water, for example, for a shower. This high output can lead to damage to the instantaneous water heater, and especially to the heating block, if it is not subjected to a sufficient mass flow of water. This risk is particularly acute when the instantaneous water heater is first put into operation, as air may still be present in the instantaneous water heater or in the pipes, which can lead to overheating. Such problems can occur more frequently when an instantaneous water heater is put into operation in a building with newly installed or overhauled water pipes, for example, in a new construction.

[0004] To prevent overheating of an instantaneous water heater, DE 10 2019 004 320 A1 proposes detecting the presence of air bubbles in the fluid channel of the instantaneous water heater based on a change in the signal from a flow sensor and adjusting the heating output accordingly. However, detecting air bubbles using a flow sensor has proven to be imprecise or requires a very costly flow sensor.

[0005] DE 38 18 048 A1 also addresses the problem of overheating of an instantaneous water heater due to air bubbles. It proposes that the control system of the electric instantaneous water heater include a memory element that registers the duration of any interruption in the power supply to the heating coil that may occur within a predetermined period of time. If this duration falls below a predetermined limit, the system delays the start of the power-dependent control by a waiting time. This proposal cannot contribute to preventing possible overheating of the heating coil due to air bubbles during extended operation.

[0006] Based on this, the object of the invention is to propose a method for commissioning an instantaneous water heater, a computer program, and an instantaneous water heater that at least partially overcome the described problems of the prior art. In particular, the invention is intended to enable the safe commissioning of an instantaneous water heater without the occurrence of overheating, even in the presence of air bubbles in a cold water inlet or a fluid channel thereof.

[0007] In addition, the invention should at least not significantly increase the complexity of a continuous flow heater, require only minor structural changes and / or enable easy integration into an existing production process.

[0008] These objects are achieved by the features of the independent patent 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 technologically expedient manner and define further embodiments of the invention. Furthermore, the features specified in the patent claims are further specified and explained in the description, with further preferred embodiments of the invention being presented.

[0009] A method for commissioning a flow heater contributes to this. The flow heater comprises at least one electric heating block configured to heat fluid flowing through a fluid channel, a flow sensor, and means for detecting the thermal output of the flow heater. The method comprises at least the following steps: a) Commissioning of the instantaneous water heater with a first electrical power at which no damage to the instantaneous water heater is to be expected even if air occurs in the fluid channel, b) Recording an electrical power and a thermal power of the instantaneous water heater, c) Increasing the electrical power if a thermal power corresponding to the electrical power is recorded, and d) Reducing the electrical power of the instantaneous water heater to a second electrical power if the thermal power falls below the electrical power less a tolerance.

[0010] Steps a), b), c), and d) can be performed at least once in the specified order. In particular, step b) can be performed continuously, especially while performing steps c) and d). Steps c) and d) can be performed in parallel, or simultaneously. After performing step d), for example, step a) can be performed again.

[0011] The process is particularly designed to prevent overheating of the instantaneous water heater or its heating block and associated damage during commissioning after installation of the instantaneous water heater and / or installation of or work on the cold water supply lines, which could lead to air ingress. The process enables safe commissioning of the instantaneous water heater even if (residual) air bubbles occur in the cold water supply lines or in the fluid channel of the instantaneous water heater.

[0012] The instantaneous water heater may be a known instantaneous water heater. It may have a fluid channel leading from a cold water inlet to a hot water outlet and may include a heating block, a flow sensor, and means for determining its thermal output. Cold water flowing into the cold water inlet can be heated by the heating block and flow out through the hot water outlet and fed to a tapping point, for example, a faucet in a sink or shower. The heating block may include at least one heating element that can convert electrical current into heat in order to transfer this heat to the fluid flowing through the fluid channel. In particular, several heating elements may be provided, which are switched and thus activated via power switches, for example TRIACs (Triode for Alternating Current). For this purpose, the instantaneous water heater may include a control and regulation device.The heating elements can in particular be arranged in such a way that they come into close proximity or direct contact with the fluid flowing through the fluid channel.

[0013] The control and regulation device can regulate an outlet temperature, determined by a temperature sensor in the hot water outlet of the instantaneous water heater, based on the electrical output of the heating elements. The instantaneous water heater can also include a temperature sensor in the cold water inlet and a flow sensor for detecting the flow rate of the fluid flowing through the fluid channel. The flow sensor can be a mass flow or volume flow sensor. The outlet temperature can be predefined or entered by a user via an input device.

[0014] The instantaneous water heater can be particularly suitable for providing hot water for use in a building, for example, using a tap as a draw-off point. For this purpose, the instantaneous water heater can have an output in the range of 5 kilowatts to 35 kilowatts.

[0015] The thermal performance of an instantaneous water heater can be determined, for example, based on the temperature difference between the cold water inlet and the hot water outlet and the flow rate in the fluid channel, taking into account the specific heat capacity of the fluid flowing through the fluid channel. The flow rate could be measured directly or determined based on a pressure difference with a known pressure drop of the instantaneous water heater (e.g., by measuring two pressure values ​​from two pressure sensors).

[0016] According to step a), the instantaneous water heater can be commissioned with a first electrical power. The first electrical power is dimensioned such that, even if air is present in the fluid channel, no damage to the instantaneous water heater or the heating block is to be expected. In other words, the first electrical power can be selected such that, even during dry operation (with only air in the fluid channel in the heating block), no damage to the heating block occurs. The first electrical power can be determined mathematically or approximately, or even by means of (laboratory) tests.

[0017] According to one embodiment, in step a), the instantaneous water heater can be operated at the first power level for a safety period and / or a minimum flow rate. The safety period can be set such that, with sufficient probability, all air bubbles and gas residues in the cold water inlet and / or the fluid channel of the instantaneous water heater have drained away, i.e., have left the fluid channel of the instantaneous water heater through the hot water outlet. The minimum flow rate can be accumulated or determined by a control device of the instantaneous water heater based on the signal from the flow sensor.

[0018] According to one embodiment, the first power can also be zero, i.e. the heating block remains out of operation until a minimum flow rate has flowed through the instantaneous water heater.

[0019] According to step b), the electrical power and thermal power of the instantaneous water heater can be recorded. Step b) can be performed permanently or continuously during commissioning. For example, step a) can only be completed (and thus the safety period ended) when no temperature fluctuations in the hot water outlet occur, or only when temperature fluctuations in the hot water outlet are below a certain threshold (regarding amplitude and / or frequency).

[0020] According to step c), the electrical output of the instantaneous water heater can be increased if a thermal output corresponding to the electrical output is detected. The output of the instantaneous water heater can be increased according to a predetermined function, for example with a predetermined gradient. A reaction time of the instantaneous water heater can be included here. The reaction time here refers to the period from the switching of a power change until the power change is detected by a temperature measurement at the hot water outlet. The function or the gradient can be selected such that even if air bubbles occur (and a related drop in thermal output), if the electrical output is immediately reduced, the thermal energy accumulating in the heating block within the reaction time has no or only extremely low damage potential.

[0021] According to one embodiment, the electrical power can be increased gradually, and before a subsequent increase step, it is waited whether the increase in 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). A tolerance of the electrical power compared to the detected thermal power can also be taken into account.

[0022] According to one embodiment, a relative increase in electrical power can also be achieved. For this purpose, the electrical power could be increased gradually by a relative value (e.g., relative to the current or rated power), and a further increase could only be made once a corresponding relative increase in thermal power has been detected. It is advantageous to keep the tolerances to be included in a relative increase very small.

[0023] A suitable rate of increasing the electrical power in step c) can be determined based on the reaction time between a change in the electrical power and the detection of the corresponding change in the thermal power. The reaction time can be determined, for example, at the beginning of the process at a non-critical electrical power level.

[0024] According to one embodiment, when carrying out step c), the electrical power can also be increased continuously, for example over time from a minimum power to the maximum power within a period of increase. A temporal progression of the thermal power to be expected corresponding to this temporal progression can be calculated. The recorded temporal progression of the thermal power can be compared with the calculated temporal progression, and if the recorded temporal progression of the thermal power falls below the calculated temporal progression of the thermal power, it can be recognized that the recorded thermal power does not correspond to the electrical power. The rate of increase, i.e. the gradient of the ramp function of the electrical power, orA step size for a gradual increase in power should be chosen such that the electrical power is not increased by a critical amount within the reaction time.

[0025] Thermal power corresponding to electrical power exists when the thermal power is greater than the electrical power minus a tolerance. Typically, the thermal power is less than the electrical power, partly due to heat losses. Furthermore, measurement tolerances of sensors can occur. Therefore, a tolerance is necessary to implement the method proposed here.

[0026] A suitable tolerance can be determined or estimated in advance in laboratory tests. Proper process execution must be balanced against a low damage potential. Alternatively or cumulatively, a tolerance could also be determined / estimated during process execution in a non-critical, low power range. For this purpose, a switched electrical power could be compared with a determined thermal power, and the tolerance determined. Due to possible fluctuations in the tolerance, a determined tolerance should be slightly increased (for example, by 10 percent) to ensure trouble-free process operation.

[0027] If the thermal output drops below the electrical output minus the tolerance, this is a sign of gas or air bubbles in the fluid channel or heating block. According to step d), the electrical output of the instantaneous water heater can be (immediately, directly) reduced to a second electrical output. Thus, the drop in thermal output compared to the electrical output can mean that thermal energy is accumulating in the system, particularly in the heating block, and could potentially lead to damage.

[0028] Thus, by comparing the thermal output and electrical output of the instantaneous water heater, conclusions can be drawn about the medium flowing through the fluid channel. If the thermal output exceeds the electrical output minus a tolerance, it can be assumed that the medium flowing through the fluid channel has a significantly lower heat capacity than the assumed medium. The assumed medium is usually water, and if a portion of air is present, the thermal output can fall below the electrical output minus the tolerance.

[0029] The second electrical power can be selected so that damage to the heating block can be ruled out if air bubbles occur. For example, the second electrical power can be equal to the first electrical power.

[0030] According to one embodiment, the second electrical power can also be selected depending on the thermal power that has occurred.

[0031] According to one embodiment, if a thermal power corresponding to the electrical power is again determined, 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 a starting point for increasing the electrical power according to step c).

[0032] According to an alternative embodiment, if a thermal power corresponding to the electrical power is again determined, the method can be continued by carrying out step a).

[0033] According to one embodiment, even if fluctuations in the outlet temperature occur above a threshold value in terms of amplitude and / or frequency, the electrical power of the instantaneous water heater can be reduced to the second power level. Thus, if the thermal power measured in step b) fluctuates, it can be assumed that air bubbles are present in the heating block, and the electrical power can be reduced in response.

[0034] According to one embodiment, the rated power of the instantaneous water heater can be determined using a ratio of the electrical and thermal power determined in step b). This can be done, for example, based on the relative switching times of the semiconductor components controlling the heating wires (e.g., TRIACs (Triode for Alternating Current)) and the recorded thermal power. For example, with a switching time of 50 percent (100 percent would correspond to the rated power and mean uninterrupted operation) and a recorded thermal power of 13.5 kilowatts, a heating block with a rated power of 27 kilowatts can be assumed.

[0035] 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 using electrical energy, a flow sensor, and means for determining a thermal output of the continuous-flow heater. The thermal output can be determined, in particular, based on a detected temperature spread due to the heating of the continuous-flow heater, a detected flow rate, and a known, predetermined specific heat capacity of the fluid, in particular water. Thus, the continuous-flow heater can, in particular, comprise a temperature sensor for detecting a temperature in the cold water inlet, in the hot water outlet (thus, upstream and downstream of the heating block as seen in the flow direction), and a flow sensor.

[0036] According to a further aspect, a computer program is also proposed, which is configured to carry out a method presented here. In other words, this relates in particular to a computer program (product) comprising commands which, when the program is executed by the instantaneous water heater or a control and regulation device of the instantaneous water heater, cause the instantaneous water heater to carry out a method proposed here. For this purpose, the instantaneous water heater can have at least one flow sensor and means for determining its thermal output, to which a computer executing the method can be electrically connected.

[0037] According to a further aspect, a control and regulating device for an instantaneous water heater is also proposed, configured to carry out a method proposed here. For this purpose, the control and regulating device can, for example, have and / or be equipped with a processor. In this context, the processor can, for example, execute the method stored in a memory (of the control and regulating device). Advantageously, data for carrying out a method presented here can also be stored in the memory of the control and regulating device, for example a first and / or second electrical power, a function or gradient of an increase in the power of the instantaneous water heater, a tolerance (of the electrical power) and / or limit values ​​for fluctuations in the thermal power (with regard to amplitudes and / or a frequency) of occurrence.

[0038] According to a further aspect, a control device for an instantaneous water heater is also proposed, configured to carry out a method presented here. The control device can, for example, comprise or have a processor for this purpose. In this context, the processor can, for example, execute the method described above stored in a memory (of the control device).

[0039] The details, features, and configurations discussed in connection with the method may also occur in a flow heater proposed here, the computer program, and / or the control device, and vice versa. In this respect, reference is made in full to the explanations therein for a more detailed characterization of the features.

[0040] Thus, a method for commissioning an instantaneous water heater, an instantaneous water heater, a computer program, and a control device are provided, which at least partially solve the problems described with reference to the prior art. In particular, the method for commissioning an instantaneous water heater, the instantaneous water heater, the computer program, and the control device at least contribute to enabling safer commissioning of an instantaneous water heater following its installation or work on the cold water supply lines. This advantageously prevents damage to the instantaneous water heater and / or its heating block.

[0041] In addition, the proposed method advantageously does not require any structural changes to a flow heater and can be used simply by implementing a computer program product proposed here.

[0042] As a precaution, it should be noted that the numerals used here ("first", "second", ...) primarily serve (only) to distinguish between several similar objects, quantities, or processes, and therefore do not necessarily specify any interdependence and / or sequence of these objects, quantities, or processes. Should a dependence and / or sequence be required, this is explicitly stated here or will be obvious to the person skilled in the art upon studying the specifically described embodiment. To the extent that a component can occur multiple times ("at least one"), the description of one of these components may apply equally to all or part of the majority of these components, but this is not mandatory.

[0043] The invention and the technical environment are explained in more detail below with reference to the accompanying figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments cited. 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 components and findings from the present description. In particular, it should be noted that the figures and, in particular, the proportions shown are only schematic. They show: Fig. 1: a sequence of a method presented here, Fig. 2: a continuous flow heater presented here, Fig. 3: another continuous flow heater presented here.

[0044] Fig. 1 shows, by way of example and schematically, a sequence of a method proposed here. The method is used for the safe commissioning of an instantaneous water heater 1, in particular for the safe initial commissioning after installation or commissioning following work on or installation of pipes or other cold water supply equipment. The sequence of steps a), b), c) and d) shown in blocks 110, 120, 130 and 140 can occur during a regular process sequence. In particular, step b) can be carried out permanently or continuously, in particular while carrying out steps c) and d). Furthermore, steps c) and d) can be carried out in parallel or simultaneously.

[0045] Fig. 2 shows, by way of example and schematically, an electric instantaneous water heater 1 for heating a fluid flow, in particular a water flow, with a fluid channel 11 that can lead from a cold water inlet 8 via a heating block 3 to a hot water outlet 9. The fluid flow flows through the instantaneous water heater 1 in a flow direction 2. The heating block 3 can have resistance-based heating elements that can be in direct contact with the fluid flow.

[0046] The instantaneous water heater 1 can also have a control and regulation device 6, which can be configured to regulate and control the instantaneous water heater 1, in particular the heating elements of the heating block 3. For this purpose, the control and regulation device 6 can be electrically connected to a first temperature sensor 7 in the cold water inlet 8, a flow sensor 5, a motorized valve 4, and a second temperature sensor 10 in the hot water outlet 9. The motorized valve 4 can be used to throttle the flow rate of the fluid to ensure a constant, desired temperature at the hot water outlet 9 when the heating block 3 is operating at its rated power.

[0047] Fig. 3 shows an example of a fluid channel 11 of the instantaneous water heater 1. Cold water flows into the fluid channel 11 via the cold water inlet 8, and its temperature is detected by the first temperature sensor 7. A circuit board 12, which can be part of the control unit 6, controls the heating elements of the heating block 3 according to the heat demand. A second temperature sensor 10 is arranged at the hot water outlet 9 and can be used to regulate the temperature of the outgoing hot water. The flow sensor 5 can detect the flow rate of water flowing through the fluid channel.

[0048] The Fig. 4 shows, by way of example and schematically, a diagram which represents the power P (electrical or thermal) over time t during the implementation of a method proposed here during (initial) commissioning of the instantaneous water heater 1. In the example, the first power is 0, and the heating block 3 does not convert any electrical power. A first curve 13 shows the electrical power and a second curve 14 shows the determined thermal power. The thermal power can be determined based on the temperature of the cold water inlet 8, recorded at the first temperature sensor 7, the water flow rate recorded at the flow sensor 5 and the temperature of the water at the hot water outlet 9, recorded at the second temperature sensor 10.

[0049] In block 110, according to step a), the instantaneous water heater 1 is put into operation with a first electrical power at which no damage to the instantaneous water heater is to be expected even if air occurs in the fluid channel. Fig. 4 the first power is zero.

[0050] In block 120, according to step b), an electrical power and a thermal power of the instantaneous water heater are recorded. The electrical power can be recorded by the control and regulation unit 6. The thermal power can be determined as described above. Step b) can, in particular, be performed continuously during the implementation of a method proposed here.

[0051] In block 130, the electrical power is increased according to step c) 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 the Fig. 4 The curve 14 of the thermal power corresponds to the curve 13 of the electrical power. The thermal power is lower than the electrical power due to heat losses or tolerances. In the example according to Fig. 4 The electrical power can be increased according to the first curve 13, since the measured thermal power according to curve 14 is lower than the electrical power according to curve 13 minus the tolerance. Without taking the tolerance into account, this power difference between electrical power (curve 13) and thermal power (curve 14) would accumulate over time as heat energy in heating block 3. Only when the determined thermal power (curve 14), taking the tolerance into account, is safely below the electrical power (curve 13), must the electrical power be reduced immediately to avoid damage to heating block 3.

[0052] Fig. 4 shows a steady increase in electrical power in step c). It is advantageous to consider the increase in power relative to check whether the electrical power (curve 13) corresponds to the determined thermal power (curve 14). For example, a 5 percent increase in electrical power within a specified period must lead to a 5 percent increase in thermal power after the response time has elapsed. A tolerance can also be included here. The response time could have been determined in advance in a non-critical power range.

[0053] In block 140, according to step d), the electrical power of the instantaneous water heater 1 is reduced to a second electrical power if the thermal power falls below the electrical power minus a tolerance. The implementation of step d) is described in the Fig. 4not shown. The second electrical power could correspond to the first electrical power. Following the execution of step d), step c) could be performed again. List of reference symbols

[0054] 1Instant water heater 2Flow direction 3Heating block 4Motor valve 5Flow sensor 6Regulating and control unit 7First temperature sensor 8Cold water inlet 9Hot water outlet 10Second temperature sensor 11Fluid channel 12PCB 13First course 14Second course

Claims

1. A method for commissioning a continuous flow heater (1) with an electric heating block (3), a fluid channel (11) from a cold water inlet (8) and a hot water outlet (9) for the flow of a fluid to be heated, a flow sensor (5) and means for detecting a thermal output of the continuous flow heater, comprising at least the following steps: a) commissioning the continuous flow heater (1) with a first electrical output at which no damage to the continuous flow heater (1) is to be expected even if air occurs in the fluid channel (11), b) detecting an electrical output and a thermal output of the continuous flow heater (1), c) increasing the electrical output when a thermal output corresponding to the electrical output is detected, and d) reducing the electrical output of the continuous flow heater (1) to a second electrical output,when the thermal power falls below the electrical power less a tolerance.

2. Method according to claim 1, wherein the commissioning is an initial commissioning after installation of the instantaneous water heater (1) and / or after work on lines of the cold water inlet (8) which may lead to the occurrence of air in the lines of the cold water inlet (8), the cold water inlet (8) and / or the fluid channel (11).

3. Method according to claim 1 or 2, wherein the instantaneous water heater (1) comprises means for measuring a temperature at the hot water outlet (9) and in a step d) when fluctuations in the temperature at the hot water outlet (9) occur, the electrical power is reduced to a second power.

4. Method according to one of the preceding claims, wherein when carrying out step a) the instantaneous water heater (1) is operated at the first power for a safety period and / or a minimum flow rate.

5. Method according to one of the preceding claims, wherein a nominal power of the instantaneous water heater (1) is determined by means of a ratio of electrical power and thermal power.

6. A 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 flow heater, and means for carrying out a method according to one of the preceding claims.

7. Instantaneous water 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).

8. A computer program product comprising instructions that cause a continuous flow heater (1) according to one of claims 6 or 7 to carry out a method according to one of claims 1 to 5.

9. Regulating and control device (6) of a continuous-flow heater (1) arranged to carry out a method according to one of claims 1 to 5.

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