EP1310736B1 - Controller and control method for a burner - Google Patents

Abstract

Device for regulating an instantaneous water heater has a burner (2) for heating a heat carrying medium, an inlet for supply of heat carrying medium, with a given inlet temperature and an outlet with an outlet temperature. A regulator (1) measures the rate of increase of the outlet temperature for a given burner capacity, which enables the flowrate of output carrying medium to be calculated. The regulator adjusts the heating of the medium based on the calculated flowrate. <??>Independent claims are made for a regulator and a method for controlling an instantaneous heater.

Description

The present invention relates to a control method for controlling a burner of a heater, in particular for controlling the burner of a hot water instantaneous water heater according to the preamble of claim 1, a controller for controlling such a burner according to the preamble of claim 14 and a preferred use of the method or of the regulator according to claim 16.

Such control methods and regulators for controlling a burner, in particular for controlling the burner of a domestic hot water heater for heating a heat transfer medium, such as water, are already known (e.g., CH 667516 A), where basically two different principles are applied. Thus, in some manufacturers of such heaters, the service water or the heat transfer medium to be heated in the flow principle directly via a heat exchanger heated by a burner, while other manufacturers, a second heat exchanger, i. a so-called. Secondary heat exchanger for domestic water heating is used.

In the known baths or water heaters, the heat transfer medium is heated either directly via a primary heat exchanger or indirectly by means of the heated water of the heater via a secondary heat exchanger and removed at suitable tapping points, for example in the kitchen or bathroom. The control of the burner such spas takes place in the prior art by measuring the outlet temperature at the outlet of the heater. The supplied via an inlet of the heater heat transfer medium there has a certain inlet temperature and at the outlet of the heater a certain outlet temperature. The heating of the heat transfer medium is controlled, for example, by means of a PI controller or a PID controller as a function of a desired temperature and the outlet temperature. The controller is the control difference supplied while this then a suitable manipulated variable, for example, a signal for power adjustment of the burner, outputs.

The outlet temperature changes depending on the tap quantity, the condition of the burner and the burner output. After switching on the burner, for example, due to a request of the heat transfer medium or because a lower switch-on of the heat transfer medium was exceeded, the temperature of the heat transfer medium initially falls slightly from then to rise due to the heating by the turned on burner. In the course of the further tapping of the heat transfer medium, the burner is switched on or off in response to an upper switch-off temperature or a lower switch-on temperature. When first tapping of heat transfer medium it comes systemic to greater fluctuations in the temperature of the heat transfer medium. These temperature fluctuations arise, for example, by the heat transfer medium still in the pipes, which must be removed, or by the necessary heating of the pipeline to the tap.

In principle, two important requirements are placed on such a regulatory procedure. On the one hand, the outlet temperature should be kept as constant as possible, i. as close as possible to the set by the user of the heat transfer medium setpoint. On the other hand, a too frequent switching on and off of the burner should be avoided, since this not only pollutes the burner, but is also unfavorable as regards exhaust technology and fuel consumption.

The invention is therefore based on the object to improve conventional control method for controlling such burner or corresponding controller such that on the one hand avoid frequent switching on and off of the burner and at the same time as constant a discharge temperature is achieved.

The invention solves the underlying object by the characterizing features of the independent claims 1 and 14. An advantageous use of the control method according to the invention or the regulator according to the invention is claimed in claim 16. Further preferred embodiments of the invention are described in the subclaims and characterized there.

The invention is based on the finding that although fluctuations in the outlet temperature are acceptable when switching on a burner by the aforementioned irregularities during heating of the pipe to the tap and by the ejection of the heat transfer medium still in the pipes, but this after a decay short transient. The invention therefore provides a dynamic variable switch-off difference which lies in a corridor between a maximum switch-off temperature and a minimum switch-off temperature.

The control method measures at a predeterminable burner output the rise of the outlet temperature, in particular after the first switching on of the burner and detects a first maximum of the outlet temperature, i. every point at which the temperature of the heat transfer medium, after a first increase, for example, due to an increased bleed in comparison to the set burner power drops again. Subsequently, the control method according to the invention uses as the next switch-off temperature, i. as the next upper limit of the dynamic switch-off difference, a value between the previously set maximum switch-off temperature and the first maximum of the outlet temperature, which was previously measured accordingly.

Advantageously, after switching on the burner, the first maximum of the outlet temperature is measured in order then to calculate a first difference between the maximum switch-off temperature and the first maximum of the outlet temperature. Following this, the next switch-off temperature is determined by means of this first calculated difference. This can be repeated for each subsequent, resulting maximum temperature of the heat transfer medium. In the following calculations, the difference between the current switch-off temperature and the maximum is then formed.

Advantageously, the difference between the current switch-off temperature and half of the first difference is used as the next switch-off temperature. In general, the following rule applies:

The next switch-off temperature is the difference between the ith switch-off temperature and the half of the i-th difference and the ith maximum outlet temperature. This corresponds to the previous switch-off temperature minus half of the i-th difference.

The control method according to the invention advantageously uses, as ith difference, the difference between the maximum switch-off temperature or the previous switch-off temperature and a minimum switch-off temperature if the i-th maximum of the outlet temperature is below the minimum switch-off temperature. On the other hand, the maximum switch-off temperature is advantageously used as the next switch-off, if the i-th maximum outlet temperature above the maximum switch-off, i. is above the originally set upper limit of the dynamic switch-off difference.

Furthermore, according to a preferred embodiment of the present invention, the control method starts the measurement of the i-th maximum only after the measurement of a previous (i-1) th minimum, i. that after the measurement of the (i-1) -th maximum, only a further (i-1) -th minimum has to be detected before the control method begins with the measurement of the i-th maximum.

Furthermore, a time counting is started with advantage after switching on the burner at the same time to use the minimum switch-off temperature as the next switch-off after a predeterminable time. This serves to ensure the safety of the regulatory procedure. For example, if no maximum of the temperature of the heat transfer medium can be detected by a very high tapping power, i. if the temperature only gradually approaches the lower limit of the dynamic turn-off difference, i. the minimum switch-off temperature approaches, can be switched directly after the predeterminable period of time to the minimum switch-off, so as to obtain the minimum possible switching difference between the switch-on temperature and the switch-off.

Advantageously, all temperature and switch-off values are reset after switching off the burner and the calculation starts again at the next burner start from the front. Furthermore, according to a preferred embodiment of the invention, the maximum switch-off temperature is limited as a function of the setpoint temperature. With lower setpoint values for the outlet temperatures, a larger switching differential can be allowed for the first overshoot than with higher setpoints. If the switching difference is set too high at a desired value of, for example, 60 ° C., this leads to a short-term overshoot and thus possibly to a scalding of the person tapping, when the taps are geographically close to the spa. The switch-off difference can therefore be limited depending on the setpoint temperature to be set.

If due to large bleed the temperature does not reach the setpoint temperature at a predeterminable burner power after a predeterminable period of time, the burner power is changed modulating in accordance with a preferred embodiment of the present control method.

According to a further preferred embodiment of the invention is in the heating of the heat transfer medium in the clock mode, i. switched at very small amounts of heat transfer medium removed, after a start of the burner of an ignition as directly as possible to a predeterminable and storable clock power. As a clock power is advantageously used the last power before the shutdown of the burner or the minimum adjustable power of the burner. This has the advantage that a large overshoot is avoided after restarting the burner, without the switching differential must be increased.

For small discharged amounts of heat transfer medium, the problem is that after a renewed involvement of the burner, the modulation controller must downshift the burner performance of a starting power (starting power) when the extracted amount of heat transfer medium is very low. If this does not happen fast enough, the condition occurs that the temperature in the heat exchanger, ie in the heater quickly reaches the Brennerausschaltpunkt and the burner is switched off again. This leads to a large Brennerschalthäufigkeit, which is undesirable. With the help of this preferred embodiment of the control method according to the invention However, the burner is not "started" in the modulation mode, but initially switched to the "remembered" burner power immediately.

During the switched-off state of the burner in the cycle operation, the blower of the burner is advantageously not switched off, but preferably continues to operate at an ignition speed. This makes it possible to start the burner faster, which reduces a "sagging" of the outlet temperature.

An inventive controller for controlling a burner of a heater has corresponding means for measuring a first maximum of the outlet temperature, which is achieved at a predeterminable burner output, and further means for calculating a next switch-off, which is a value between the maximum switch-off and the first maximum Outlet temperature occupies. In addition, the controller advantageously has means for measuring gradients of temperature profiles, in order in particular to be able to determine the corresponding maxima and minima.

An advantageous use of the control method according to the invention or the controller according to the invention consists in the control of a domestic hot water heater or boiler control or heating circuit control.

Figur 1

die schematische Darstellung eines Durchlauferhitzers mit Primärwärmetauscher (Auslauftemperatur-Regelung);

Figur 2

die schematische Darstellung eines Durchlauferhitzers mit Sekundärwärmetauscher (optional mit Komforttemperatur-Regelung);

Figur 3

ein schematisches Diagramm eines ersten Einschwingvorgangs der Temperatur des Wärmeträgermediums;

Figur 4

ein schematisches Diagramm eines weiteren Einschwingvorgangs der Temperatur des Wärmeträgermediums; und

Figur 5

die graphische Darstellung des Setzens der Startleistung im Taktbetrieb des Brenners.

A preferred embodiment of the present invention will be explained in more detail with reference to the following drawings for the two principles of outlet temperature control (FIG. 1) and the so-called comfort temperature control (FIG. 2). Showing:

FIG. 1

the schematic representation of a water heater with primary heat exchanger (outlet temperature control);

FIG. 2

the schematic representation of a water heater with secondary heat exchanger (optional with comfort temperature control);

FIG. 3

a schematic diagram of a first transient of the temperature of the heat transfer medium;

FIG. 4

a schematic diagram of a further transient process of the temperature of the heat transfer medium; and

FIG. 5

the graphical representation of setting the starting power in the cyclic operation of the burner.

Figure 1 shows the schematic representation of a water heater with primary exchanger 7 (primary heat exchanger), which is heated by a burner 2 (shown only schematically). The cold water KW is fed via a cold water inlet 5 to the primary exchanger 7 and heated there. The heated water is taken from a tapping point 6 as hot water WW. To measure the outlet temperature θ _Aus is an outlet temperature sensor B3 (temperature sensor 9). Via a flow switch FS the tap of hot water WW is detected. The burner 2 also serves to heat a heating medium, such as water for example, to heat a house. Only schematically shown is a boiler heat exchanger 8 with flow temperature sensor B2, return temperature sensor B7, flow pump or heating circuit pump Q1, consumer 3 (radiator) and water pipe. 4

A regulator 1 controls or controls the burner 2 for heating the cold water KW in the primary exchanger 7.

Figure 2 shows the schematic representation of a water heater with secondary heat exchanger, where the cold water KW is not heated directly from the burner 2, but via a secondary exchanger 10 (secondary heat exchanger). The secondary exchanger 10 is supplied with heat by the heating medium via a three-way valve UV which heats the cold water. Again, an outlet temperature sensor B3 is used to measure the outlet temperature θ _out . An inlet temperature sensor B5 and a buffer medium temperature sensor B4 is also indicated schematically. A flow switch FS is arranged on the output side at the tapping point 6 for measuring a tap of hot water WW. The heating circuit pump Q1 is in this case on the return side of the boiler 8 in front of the return temperature sensor B7 and at the same time ensures the circulation of the heating medium in the secondary exchanger 10th

Too large a switching difference between the switch-on temperature Sdin and the switch-off temperature Sdout is now to be avoided at the taps 6 in FIGS. 1 and 2 Otherwise, the user will receive large fluctuations in the outlet temperature θ _out .

Figure 3 shows an example of the schematic representation of a transient process of the temperature of the heat transfer medium, ie the outlet temperature θ _Aus , which is measured for example at the outlet of the heater. FIG. 3 shows a maximum switch-off temperature SdOff from _max and a minimum switch-off temperature SdOff _min , which represent the upper and lower values of the dynamic switch-off difference. The dynamic switch-off is set when the burner 2 in the present control method first to the maximum switch SdAus _max. At the same time, a timer (Sd_counter) is started when starting the burner. This counter is used to reset the switch-off difference to the minimum switch-off temperature SdOff _min after a settable time. This ensures that the fluctuations of the outlet temperature θ _{Aus are} limited.

• 1. Aufgrund einer Anforderung des Wärmeträgermediums beispielsweise über das Ansprechen eines Strömungsschalters FS oder weil die Einschalttemperatur SdEin unterschritten wurde, wird der Brenner 2 eingeschaltet.
• 2. Mit Einschalten des Brenners 2 wird der Zeitzähler (Sd_Zähler) gestartet. Das Zeitende kann ggf. durch die Bedienperson oder durch den Heizungsinstallateur als Abbruchkriterium veränderlich einstellbar gestaltet werden.
• 3. Gleichzeitig wird auch die Berechnung des ersten Maximums 1a gestartet. Der Startwert für die Maximumberechnung wird beim Brennerstart auf "0" gesetzt.
• 4. Die im ersten Maximum 1 a der Ausschalttemperatur berechnete Differenz Δϑ₁ zwischen der maximalen Ausschalttemperatur SdAus_max und dem ersten Maximum 1a der Auslauftemperatur ϑ_Aus bestimmt die Reduzierung der Ausschaltdifferenz für die nächste Schwingung der Auslauftemperatur des Wärmeträgermediums.
• 5. Nach der Berechnung des Maximums 1a erfolgt das Zurücksetzen der Schaltdifferenz auf den berechneten Wert. Als oberer Wert der dynamischen Ausschaltdifferenz wird daher mit Vorteil genau die Mitte zwischen der maximalen Ausschalttemperatur SdAus_max und dem ersten Maximum 1a genommen.
• 6. Wird das erste Minimum 1b erkannt, so wird hier eine erneute Berechnung des nächsten Maximums gestartet und der Startwert für diese Maximumberechnung auf 0 gesetzt.
• 7. Wird ein zweites Maximum 2a erkannt, so wird die Differenz Δϑ₂ zwischen der aktuellen oberen Ausschalttemperatur SdAus (k+1) und dem zweiten Maximum 2a bestimmt. Die Reduzierung der Schaltdifferenz für die nächste Schwingung berechnet sich wie oben bereits beschrieben.

The algorithm shown in FIG. 3 is described below by way of example as a preferred embodiment of the invention:

• 1. Due to a request of the heat transfer medium, for example, via the response of a flow switch FS or because the turn-on temperature SdEin was exceeded, the burner 2 is turned on.
• 2. When the burner 2 is switched on, the time counter (Sd_counter) is started. If necessary, the end of the time can be made variably adjustable by the operator or by the heating contractor as a termination criterion.
• 3. At the same time, the calculation of the first maximum 1a is started. The start value for the maximum calculation is set to "0" at the burner start.
• 4. The first maximum 1 a switch-off of the calculated difference Δθ ₁ between the maximum switch SdAus _max and the first maximum of the outlet temperature θ 1a _off determines the reduction of the switch-off for the next oscillation of the outlet temperature of the heat carrier medium.
• 5. After calculating the maximum 1a, the switching difference is reset to the calculated value. As the upper value of the dynamic switch-off difference is therefore made with advantage of the exact middle between the maximum switch SdAus _max and the first maximum 1a.
• 6. If the first minimum 1b is detected, a new calculation of the next maximum is started here and the starting value for this maximum calculation is set to 0.
• 7. If a second maximum 2a is detected, the difference Δθ ₂ between the current upper switch-off temperature SdOff (k + 1) and the second maximum 2a is determined. The reduction of the switching difference for the next oscillation is calculated as already described above.

If the calculated maximum lies below the lower switch-off temperature SdOff _min , then the difference between the current upper value of the switch-off temperature SdOff (k + i) and the minimum switch-off temperature SdOff _{min is} formed. With the help of this control method, any transient process can be handled, as shown for example in FIG.

Figure 4 shows a further possible transient of the outlet temperature of the heat carrier medium, the minimum switch-off temperature SdAus _min never exceeds the dynamic switch-off. Here, too, with each detecting a maximum, the i-th difference between the previous switch-off temperature SdAus (k + i-1) (or the first time between the maximum switch SdAus _max) and the minimum switch-off temperature SdAus _min is calculated, if the i te maximum of the outlet temperature θ _Off below the minimum switch-off temperature SdAuS _min is. As shown in Figure 4, the upper limit of the dynamic turn-off difference, ie the upper turn-off temperature SdOff (k + i) iteratively approaches infinitely near the lower turn-off temperature, ie the minimum possible turn-off temperature SdOff _min .

Here also if the difference between the current switch-off upper SdAus (k + i) and the minimum switch-off temperature SdAuS (2-5 K Ex.) May also be provided as a switch-off, the minimum switch-off temperature SdAus _min to use _min a certain limit below.

Figure 5 shows the schematic representation of setting the starting power in the cyclic operation of the burner 2, ie at small bleed amounts. While it has been applied in the upper part of FIG 5 as shown in Fig. 4, the outlet temperature θ _from versus time, in the lower part of the figure 5 is shown the power of the burner 2 with respect to the time corresponding to the overlying outlet temperature θ _off. Once a clock mode has been detected, ie the tap particularly small amounts of hot water WW and the burner 2 turns off, the last related power of the burner 2 is stored in a memory of the controller 1.

While the burner 2 remains switched off, it is possible to keep the fan of the burner running in order to get into the appropriate speed range as quickly as possible when the burner is switched on again. As soon as the outlet temperature θ _out crosses the lower limit of the switching difference SdOn, the burner 2 switches back on, in which case the previously "remembered" power, ie the power stored in the controller 1, is used, which can then also be used, for example, to measure the slew rate v _A if this has not been done before. After the identification phase (power constant), the modulation controller is enabled.

While the control method according to the invention or the controller according to the invention are advantageously suitable for controlling a hot water instantaneous water heater, they can also be used, for example, for the heating operation of a heating system. In this case, only the parameters between service water operation and heating operation must be differentiated, ie switched over. The controller has suitable input means for separately setting the minimum and maximum switch-off temperatures SdAus _min and SdAus _max for heating operation.

Claims (16)

1. Control method for controlling a burner (2) of a heating device, in particular for controlling the burner of a service water continuous flow heater, the burner (2) heating a thermal transfer medium which has a particular inlet temperature (θ_Ein) at an inlet of the heating device and a particular outlet temperature (θ_Aus) at an outlet of the heating device, and the heating of the thermal transfer medium being controlled at least as a function of a setpoint temperature (θ_Soll) and the outlet temperature (θ_Aus), characterized in that a first maximum (1a) of the outlet temperature (θ_Aus) is measured, and in that a value between a maximum switch-off temperature (SdAus_max) and the first maximum (1a) of the outlet temperature (θ_Aus) is used as a next switch-off temperature (SdAus(k+1)).
2. Control method according to Claim 1, characterized in that the first maximum (1a) of the outlet temperature (θ_Aus) is measured after switching on the burner (2), in that a first difference (Δθ₁) between the maximum switch-off temperature (SdAus_max) and the first maximum (1a) of the outlet temperature (θ_Aus) is calculated, and in that the next switch-off temperature (SdAus(k+1)) is calculated by means of this first difference (Δθ₁).
3. Control method according to one of Claims 1 and 2, characterized in that the difference between the current switch-off temperature (SdAus(k)) and half the i-th difference (Δθ_i) is used as the next switch-off temperature (SdAus(k+i)).
4. Control method according to one of the preceding claims, characterized in that the difference between the maximum switch-off temperature (SdAus_max) or the previous switch-off temperature (SdAus(k+i-1)) and a minimum switch-off temperature (SdAus_min) is used as the i-th difference (Δθ_i) if the i-th maximum (ia) of the outlet temperature (θ_Aus) lies below the minimum switch-off temperature (SdAus_min).
5. Control method according to one of the preceding claims, characterized in that the maximum switch-off temperature (SdAus_max) is used as the next switch-off temperature (SdAus(k+i)) if the i-th maximum (ia) of the outlet temperature (θ_Aus) lies above the maximum switch-off temperature (SdAus_max).
6. Control method according to one of the preceding claims, characterized in that after measuring the i-th maximum (ia) the measurement of a further maximum ((i+1)a) is not started until after measuring an i-th minimum (ib).
7. Control method according to one of the preceding claims, characterized in that a timer is started after switching on the burner (2), and in that the minimum switch-off temperature (SdAus_min) is used as the next switch-off temperature (SdAus(k+i)) after a predeterminable time has elapsed.
8. Control method according to one of the preceding claims, characterized in that all the temperature and switch-off values are reset after switching off the burner (2), and the calculation is freshly restarted the next time the burner is started.
9. Control method according to one of the preceding claims, characterized in that the maximum switch-off temperature (SdAus_max) is limited as a function of the setpoint temperature (θ_Soll).
10. Control method according to one of the preceding claims, characterized in that with the predeterminable burner power and if the setpoint temperature (θ_Soll) is not reached after a predeterminable time has elapsed, the controller (1) changes the burner power in a modulating fashion.
11. Control method according to one of the preceding claims, characterized in that an ignition power is switched over to a predeterminable and storable cycle power after a start of the burner (2).
12. Control method according to Claim 11, characterized in that the cycle power is the last power before switching off the burner (2) or the minimum adjustable power of the burner (2).
13. Control method according to one of Claims 11 and 12, characterized in that the fan of the burner (2) is not switched off and is preferably operated with an ignition speed during the cycle operation, i.e. with small delivered quantities of the thermal transfer medium.
14. Controller for controlling a burner (2) of a heating device, in particular for controlling the burner of a service water continuous flow heater, the burner (2) heating a thermal transfer medium which has a particular inlet temperature (θ_Ein) at an inlet of the heating device and a particular outlet temperature (θ_Aus) at an outlet of the heating device, and the heating of the thermal transfer medium being controlled at least as a function of a setpoint temperature (θ_Soll) and the outlet temperature (θ_Aus), characterized in that the controller comprises means for measuring a first maximum (1a) of the outlet temperature (θ_Aus), and in that the controller comprises means for calculating a next switch-off temperature (SdAus(k+1)), which takes a value between a maximum switch-off temperature (SdAus_max) and the first maximum (1a) of the outlet temperature (θ_Aus).
15. Controller according to Claim 14, characterized in that the controller comprises means for measuring gradients of temperature profiles.
16. Use of the control method according to one of Claims 1 to 13 and/or a controller according to one of Claims 14 or 15 for controlling a service water continuous flow heater or for boiler control or for heating circuit control.

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