EP2372259B1 - Method for heating water according to the circulation principle and water heating system - Google Patents

Description

The invention relates to a method for heating water flow variable volume according to the flow principle according to the preambles of claims 1 and 3, in which a heat generator heated by a pump in a circulating heating fluid, the heating fluid heats a guided run water, and at least one arranged in a waterway sensor measures an outlet temperature T _W and / or a volume flow V _{W of} the water. Furthermore, the invention relates to a water heating system according to the flow principle according to the preamble of claim 10 with a heat generator, a heated by the heat generator heating fluid circuit, which is funded by a pump, heated by Heizfluidkreislauf water flow and at least one arranged in a waterway sensor for detecting an outlet temperature T. _W and / or a volume flow V _{W of} the water.

These methods are used, for example, in so-called combination heaters. Combination heaters can solve two heating tasks, such as hot water heating for room heating and domestic hot water for applications in the kitchen and sanitary area. In general, a heater arranged in the heater (heat source) via a primary heat exchanger heats a circulating heating fluid (heating water), which is conveyed in a space heating mode by a pump (circulation pump) from the heater via flow and return lines to the rooms to be heated and there emits the heat, for example via space heaters (consumers, heat sink) to the room. In a mode for domestic hot water preparation, a diverter valve directs the heating fluid to a secondary heat exchanger (eg, plate heat exchanger), often also located in the heater, where it transfers the heat to a flowing drinking water.
That's how it describes EP 0 886 110 A2 a process for supplying hot water, in which burner ignition and starting of the circulation pump are controlled during the starting process. After the starting process, the speed of the circulation pump is increased according to the temperature increase. During the drinking water tap, a constant speed is set.

The DE 197 25 952 A1 shows a method for heating water, which shortens the heating time of the water. After reaching a third temperature value, the circulating pump remains switched on during the tap of the drinking water, wherein the setpoint for the outlet temperature of the water is controlled even when changing the flow rate through the heat generator.
The EP 0 556 736 A1 describes a method for space heating and water heating. A short-term increase in the delivery rate of the circulation pump increases the volume flow of the heating water in a primary circuit when a measured temperature is above a setpoint. If this temperature is low, the performance of the circulation pump is reduced.
The heat generator may be a burner fueled with fuel oil or natural gas, but also a heat generator operating with electrical energy. The heat generator can switch its heat output on and off and, as a rule, also modulate it between a minimum power different from zero and a maximum power (nominal power). In DHW mode, drinking water of different volume flows can be heated. For DHW heating, a set DHW temperature as well as minimum and maximum outflow temperatures can be set via a thermostat, a control unit and / or other components. The amount of a request made to the heat generator heat demand to achieve the target hot water temperature results from the drinking water volume flow, the temperature of the incoming into the secondary heat exchanger cold drinking water (inlet temperature), the set temperature of expiring from the secondary heat exchanger warm drinking water (drinking water) and the efficiency chain for the Heat transfer between heat generator and domestic hot water.

Only those heat requirements that lie in the range between the minimum power and the maximum power of the heat generator can be fulfilled continuously and reliably. If the heat requirement is greater than the maximum heat output, then either the setpoint temperature or the volume flow of the domestic hot water is not reached (undershot). If the heat requirement is less than the minimum heat output, the heat generator and the circulation pump either remain permanently switched off or they must be clocked. The heat generator is then in a cyclic operation, if at minimum heat output, the measured water outlet temperature exceeds the predetermined target water temperature or the predetermined maximum allowable outlet temperature. Cycle means that the heat generator and / or the circulation pump repeatedly switch on and off at short intervals and so in time Provide average averaged heat outputs that are less than the minimum heat output.

During cyclic operation of the heat generator and circulation pump, the outlet temperature of the domestic hot water can not be kept constant at target temperature T _W0 , but fluctuates synchronously and possibly a little time offset with the input and Austaktaktungen (on and off) between a minimum allowable outlet temperature T _W0 , _MIN and a maximum permissible outlet temperature T _{W0, MAX} . These minimum and maximum permissible outlet temperatures form a permissible setpoint temperature interval (hysteresis). Since the heat generator generates too much heat even at minimum power measured on the heat demand, the outlet temperature of the water flowing through the secondary heat exchanger increases rapidly when the heat generator and the circulating pump is switched on and soon reaches the maximum permissible outlet temperature. At this time, the heat generator and the circulation pump are turned off by the thermostat or the controller to prevent exceeding the maximum allowable outlet temperature and a possible scalding of a user. Thus, when the heat generator is switched off and the circulating pump is switched off, unheated, cold water flows out of the secondary heat exchanger, the outlet temperature drops rapidly and soon reaches the minimum permissible outlet temperature, whereupon the heat generator and the circulating pump finally switch on again.

Especially from drinking water heaters, a high hot water comfort is required, which means the most accurate compliance with the hot water target temperature for different DHW tap behavior. The relevant standards check, for example, the deviation of the outlet temperature from the setpoint temperature with continuous tapping with low and high volume flows, with interrupted tapping with shorter and longer tapping pauses and much more. Especially the cyclic operation of heat generator and circulating pump is a critical operating point in terms of comfort requirements because of the above-described fluctuations in the outlet temperature.

In addition to the unfavorable effects of a cycle operation on the domestic hot water comfort, there are also aspects of life and efficiency that speak against a cycle operation. Frequent switching on and off reduces the service life and reduces the maintenance intervals of the components used due to the high number of mechanical and thermal load cycles. In addition, the Heat transfer efficiency reduced by frequent and repeated cooling losses of the heat generator.

In the case of heat requirements for heating water, which lie between a minimum and a maximum heat generator heat output, the setpoint temperature can be achieved in continuous operation and without cycles from the heat generator and the circulation pump. Changes in heat demand, such as those resulting from a change in water volume flow, water inlet temperature, or setpoint temperature, must equally change the heat generator heat output. However, sudden changes in the heat demand can generally not be fulfilled immediately, but only with a time delay. This is due to the thermal inertia of the heat transfer system consisting of heat generator, primary heat exchanger, heating fluid circuit and secondary heat exchanger. The time delay also adversely affects DHW comfort.

The heat generator usually has a predetermined rate of change (speed) that can not be exceeded, with which the power modulation can be changed. Due to their mass and the specific heat capacity and the thermal conductivity of the material, the heat exchangers have a thermal inertia, which acts like a heat accumulator. The Heizfluidkreislauf has its thermal inertia due to its water volume and the mass and the material of the pipe elements used. Only two flow states are known for the heating fluid circuit according to the current state of the art for domestic hot water preparation: circulation at a nominal circulation volume (heating fluid volume) or nominal pump speed and zero circulation when the pump is switched off.

Thus, if the heat demand changes abruptly, the heat output transferred to the water is adjusted only with a time delay and the setpoint temperature is reached only with a time delay. For example, in the event of a sudden increase in the water volume flow, the heat generator heat output will increase at the predetermined rate of change and the heat transfer system will adjust to the new heat demand until the outlet temperature returns to the setpoint temperature after an initial undershooting of the setpoint temperature and / or the minimum allowed outlet temperature. In the event of a sudden decrease in the water volume flow, on the other hand, the outlet temperature will initially exceed the setpoint temperature or the maximum permissible outlet temperature, namely, until correspondingly reduced the heat output with its rate of change and adapted the heat transfer system to the new heat requirement. By poorly adapted to the thermal inertia of the heat transfer system parameters of the temperature control underlying control algorithm 'it may also come to several overshoot and undershoot the outlet temperature to the setpoint temperature.

One possible solution for ensuring a high domestic hot water comfort, a protection of the components and an increase in efficiency is the expansion of the power modulation range of the heat generator. Today widespread heat generators are, for example, oil burners and gas burners. They often cover a power modulation range of about 1: 4, meaning that they can modulate between 25% and 100% of their rated heat output. For heat requirements below 25% they go into the clocking operation. With a widening of the power modulation range to, for example, 1:10, significantly smaller heat requirements can be met without clocking. However, this extension of the modulation range often requires the use of expensive components.

The invention has for its object to provide a method for heating water by the flow principle and a water heating system, which overcome the disadvantages mentioned in low and changing heat requirements while largely retaining conventional components and provide a high DHW convenience and improved operation in terms of component life ,

This is achieved by the objects with the features of claims 1, 3 and 10 according to the invention. Advantageous developments can be found in the dependent claims.

The method according to the invention for heating water of variable volume flow according to the continuous flow principle in which a heat generator heats a heating fluid circulated by a pump, heats the heating fluid in a continuous flow, and at least one sensor arranged in a waterway has an outlet temperature T _W and / or measures a volume flow V _{W of} the water, based on the fact that the outlet temperature T _{W of} the water based on a modulatable and / or switchable heat output Q of the heat generator and a modulatable and / or switchable volume flow V _{H of} the heating fluid is controlled to a predetermined target temperature T _W0 .

In this case, to regulate the outlet temperature T _W and if the temperature deviation .DELTA.T the outlet temperature T _W of the target temperature T _W0 , where .DELTA.T = T _W - T _W0 , either only the heat generator heat output Q, or only the Heizfluidvolumenstrom V _H , or both the heat generator heat output Q as well as the Heizfluidvolumenstrom V _H modulated and / or switched.

Thus, this method with the Heizfluidvolumenstrom V _H next to the conventional variable parameter of the heat output Q nor a second variable parameter with which the outlet temperature T _{W can be} influenced and regulated. The heat output Q and the volume flow V _H have different inertias or reaction times or rates of change and can thus adapt in different ways the heat transfer system to a requested heat demand. In this way, it is possible to react more quickly and more appropriately to a particular situation with respect to overshoot and undershoot of the outlet temperature T _W with respect to the setpoint temperature T _W0 .

According to the invention, in a pulsating heat generator operation with alternating on and off circuits of the heat generator, wherein a heat request for heating the water is less than a minimum, non-zero heat generator heat output Q _MIN , the outlet temperature T _{W is} controlled in a permissible set temperature interval.

So on for about the time of reaching a minimum allowable outlet temperature T _{W0, MIN} the heat generator at a non-zero heat output (for example, O _MIN), while the pump to a low, non-zero Heizfluidvolumenstrom (for example, V _{H, MIN)} switches. Because of the low Heizfluidvolumenstroms and the associated low flow rate, the heat transfer from the heat generator on the heating fluid to the water is not optimal, the temperature rise in the water is slowed down compared to the method of the prior art. The heat stored in the heat transfer system, including heat generator, primary heat exchanger, heating fluid and secondary heat exchanger, increases.

At about the time of reaching a maximum allowable outlet temperature T _{W0, MAX} , the heat generator turns off while the pump is switching to a high heating fluid volume flow (eg, V _{H, MAX} ). Because of the high Heizfluidvolumenstroms and the associated high flow rate, the heat transfer from the heat generator via the heating fluid to the water compared to the above-described case is now significantly improved, the temperature drop in the water is slowed down compared to the method of the prior art. The heat stored in the heat transfer system decreases. The slower temperature rise and fall is made possible by a more effective utilization of the heat storage capacity in the heat transfer system. This lengthens the clock frequencies of the heat generator, which makes the components involved less stressed, so spared.

In one embodiment of the method, the switching on or off of the heat generator takes place shortly before or simultaneously with the achievement of the minimum or maximum allowable outlet temperature, while switching the pump to a low or high Heizfluidvolumenstrom each time with or shortly after reaching the minimum or the maximum permissible outlet temperature. The size of the time intervals "shortly before" or "shortly after" arise as a function of the given (thermal or flow-mechanical) inertias or reaction times or rates of change of the heat generator heat output and the pump delivery rate, these inertias, reaction times or rates of change interacting with the respectively connected ones Systems (transfer from the heat generator via the primary heat exchanger to the heating fluid circuit (thermal) or from the pump to the Heizfluidkreislauf (mechanical)) must be seen.

In a heat generator operation, wherein a heat demand for heating the water is greater than or equal to a minimum heat generator heat output Q _MIN , the outlet temperature T _{W is} controlled in a permissible set temperature interval. The permissible setpoint temperature interval in the heat generator continuous operation may be identical to or deviate from the permissible setpoint temperature interval in the cyclic heat generator mode.

Thus, at any first heat request, the heat generator heats with a heat output corresponding to the heat demand while the pump is delivering a nominal heating fluid volume flow V _{H, NOM} .

According to the invention heats the heat generator at a relation to the first heat demand increased heat demand (for example, increased water volume flow) with a heat demand corresponding to the increased heat output, while the pump first switches to an increased Heizfluidvolumenstrom and then back to the nominal Heizfluidvolumenstrom V _{H, NOM} . The increase in the heat generator heat output is gradual with a predetermined, finite (non-erratic) rate of change. Until this increased heat output on the sluggish chain of the heat transfer system in the water volume flow noticeable, the outlet temperature T _{W would} have dropped according to the method of the prior art (undershoot), only gradually approach the target temperature again. According to the method of the invention, the rapidly increased heating fluid volume flow ensures a rapidly increased heat transfer to the water, whereby a drop in the outlet temperature T _{W is} prevented. With increasing heat generator heat output and heating of the heat transfer system, the Heizfluidförderleistung is gradually reduced back to the nominal Heizfluidvolumenstrom V _{H, NOM} . The assumed highest possible rate of change of the heating fluid volume flow (corresponds approximately to the speed change rate of the pump) is significantly higher than the assumed highest possible rate of change of the heat generator heat output. Also, the influence of the outlet temperature T _W by the relatively low-mass secondary heat exchanger is much more direct and therefore faster than by the complete, relatively slow heat transfer system. Therefore, the outlet temperature T _W can be corrected by means of the Heizfluidvolumenstroms much faster than by means of the heat output.

In the case of a heat requirement (for example reduced water volume flow) which is reduced in comparison with the first and / or increased heat requirement, the heat generator heats up with a reduced heat output corresponding to the reduced heat requirement, while the pump first switches to a reduced heating fluid volume flow and then back to the nominal heating fluid volume flow V _{H, Resets NOM} . Here, the ratios are exactly reversed from what has been described above: The reduction of the heat generator heat output is gradual with a predetermined, finite (non-erratic) rate of change. Until this decreased Heat power over the sluggish chain of the heat transfer system in the water volume flow noticeable, would have been the method of the prior art, the outlet temperature T _W already increased (overshoot), only gradually approach the target temperature again. According to the inventive method, the rapidly reduced Heizfluidvolumenstrom ensures a rapidly reduced heat transfer to the water, whereby an increase in the outlet temperature T _{W is} prevented. With decreasing heat generator heat output and cooling also of the heat transfer system, the Heizfluidförderleistung is gradually reduced back to the nominal Heizfluidvolumenstrom V _{H, NOM} .

An embodiment of the method is characterized in that a first period of predefinable duration for monitoring a time course of a current temperature deviation .DELTA.T the outlet temperature T _W of the target temperature T _W0 and a second period of predetermined duration for controlling the outlet temperature T _W to target temperature T _W0 alternately to repeat. The duration of the first and second time periods can be predetermined as a fixed value or change depending on the temperature deviation, the operating state or other situations.

In another embodiment of the method, when an average temperature deviation ΔT _D over time assumes the value zero, only the Heizfluidvolumenstrom modulated to control the outlet temperature T _W. The duration of a considered period of time may not be too great. This case occurs, for example, when the water volume flow slightly fluctuates around an average. The outlet temperature T _W would fluctuate at constant heat output and constant Heizfluidvolumenstrom proportional to the change in water flow. The heat generator then provides the energy required to heat the water to the setpoint temperature. By means of an adapted modulation of the Heizfluidvolumenstroms according to the invention the amount of heat allocated to the instantaneous water flow rate is always provided in the secondary heat exchanger and so the outlet temperature is kept constant at the setpoint temperature.

In a further refinement of the method, if an average temperature deviation ΔT _D assumes a value different from zero over time, at least the heat generator heat output is modulated to regulate the outlet temperature T _W. This corresponds essentially to the conventional power modulation of the heat generator, if in addition the time course of the current Temperature deviation .DELTA.T is constant. However, if the time course is not constant, the modulation of the heat generator heat output is supplemented by a modulation of the heating fluid volume flow.

In a further embodiment of the method, for regulating the outlet temperature T _{W is} at least the Heizfluidvolumenstrom when a current temperature difference .DELTA.T predeterminable time within a period comprising at least two zero crossings modulated. The outlet temperature here is sometimes greater, sometimes smaller than the setpoint temperature, which can be considered an indication that it is on average approximately equal to the setpoint temperature. The regulation of the outlet temperature corresponds approximately to the above-described case in which an average temperature deviation ΔT _D over time assumes the value zero.

In an advantageous embodiment of the method, a frequency F of an outlet temperature fluctuation is detected to control the outlet temperature T _W and compared with a predefinable limit frequency F _G. At a frequency F greater than the limit frequency F _G , at least the Heizfluidvolumenstrom is modulated. This case corresponds, for example, shorter-term fluctuations of the outlet temperature to the setpoint temperature. To regulate the outlet temperature, at least the heating fluid volume flow must be modulated, since the complete inert heat transfer system would not be "behind" these changes. At a frequency F less than the cutoff frequency F _G , at least the heat generator heat output is modulated. This case corresponds, for example, to longer-term fluctuations in the outlet temperature around the setpoint temperature. To adjust the outlet temperature then often enough a modulation of the heat generator heat output, since the heat transfer system is fast enough despite its inertia.

A further advantageous embodiment of the method is characterized in that a value pair W is detected from the amount and gradient of the temperature deviation .DELTA.T and compared with a predeterminable limit value pair W _G of magnitude and gradient. If there is a value pair W with a relatively small amount and a relatively large gradient, then at least the heating fluid volume flow is modulated. In this case, because of the small amount of deviation, the heat generator heat output need not be largely corrected, on the other hand, the deviation is so fast (large gradient) that modulation of the heat output could not react reasonably fast, here Thus, it is possible to react appropriately (initially) only by means of a modulation of the heating fluid volume flow. On the other hand, if a value pair W with a relatively large amount and a relatively small gradient is present, at least the heat generator heat output is modulated, which can react sufficiently quickly with such slow changes.

The water heating system according to the invention according to the flow principle with a heat generator, a heated by the heat generator Heizfluidkreislauf, which is circulated by a pump, heated by the Heizfluidkreislauf water flow and at least one arranged in a waterway sensor for detecting an outlet temperature T _W and / or a volume flow V _W of Water, is characterized in that for controlling the outlet temperature T _W to a predetermined target temperature T _W0 the heat output of the heat generator and the volume flow of Heizfluidkreislaufs are modulated and / or switchable according to an embodiment of the method according to the invention.

An advantageous embodiment of the water heating system is characterized by a control unit connected to the heat generator, the pump and the at least one sensor, which comprises an input device for setting desired values and / or constants and / or limit values, which influences the operation of the connected components and thus the Outlet temperature T _W controls.

With this invention, a method for heating water by the continuous flow principle and a water heating system is provided, which provide a high hot water comfort with low deviations of the outlet temperature of the target temperature and with the extended cycle times an improved operation in terms of component life even with low and changing heat requirements.

Fig. 1

ein der Erfindung zugrundeliegendes Wassererwärmungssystem,

Fig. 2

einen Signalflussplan eines Regelkreises zur Trinkwarmwasserbereitung nach dem Stand der Technik,

Fig. 3

einen Signalflussplan eines Regelkreises zur Trinkwarmwasserbereitung nach der vorliegenden Erfindung,

Fig. 4

beispielhafte Verläufe von typischen Betriebsdaten bei einer unter der minimalen Wärmeerzeugerwärmeleistung liegenden Wärmeanforderung,

Fig. 5

beispielhafte Verläufe von typischen Betriebsdaten bei einer über der minimalen Wärmeerzeugerwärmeleistung liegenden Wärmeanforderung.

The drawings illustrate various aspects of embodiments of the invention and show in the figures:

Fig. 1

a water heating system on which the invention is based,

Fig. 2

a signal flow plan of a control loop for domestic hot water preparation according to the prior art,

Fig. 3

a signal flow diagram of a loop for domestic hot water according to the present invention,

Fig. 4

exemplary courses of typical operating data at a heat requirement below the minimum heat generator heat output,

Fig. 5

exemplary histories of typical operating data at a heat demand above the minimum heat generator heat output.

Fig. 1 schematically shows a combination heater for space heating and domestic hot water. The heater comprises a heat generator 1 (heat source), a heated by the heat generator 1 via a primary heat exchanger 2 Heizfluidkreislauf 3, which is promoted (circulated) by a pump 4, and a connected to the heater heat consumer 5, for example, a space heater 5. The circulating heating fluid (Heat transfer medium) transports the heat from the heat source 1 to the heat consumer 5. For domestic hot water, the heater comprises a working according to the flow principle water heating system with a heated by Heizfluidkreislauf 3 via a secondary heat exchanger 6 water flow 7, at least one arranged in a waterway 7 sensor 8, 9 10 for detecting an outlet temperature T _W and / or an inlet temperature T _K and / or a volumetric flow V _{W of} the water and at least one arranged in a Heizfluidweg 3 sensor 11, 12 for detecting a flow temperature T _HV and / or a Rückla temperature T _{HR of} the heating fluid. For regulating the outlet temperature T _W to a predefinable setpoint temperature T _W0 , the heat output Q of the heat generator 1 and the volume flow V _{H of} the heating fluid circuit 3 can be modulated and / or switched. The two heating tasks of space heating and DHW heating are usually not fulfilled simultaneously, but individually. For this purpose, the heating fluid circuit 3 between the two heat consumers space heater 5 and secondary heat exchanger 6 is switched by means of a switching valve 13.

Fig. 2 shows the schematic signal flow plan of a control circuit for domestic hot water production according to the input variable (setpoint) T _W0 , the output (outlet temperature) T _W , the controller R, the actuator (heat generator 1) and the manipulated variable Q. With the heat generator 1 is the outlet temperature T _W influenced.

Fig. 3 shows the schematic signal flow plan of a control circuit for domestic hot water according to the present invention with the input variable (setpoint) T _W0 , the output (outlet temperature) T _W , the controller R, the actuators (Heat generator 1 and pump 4) and the control variables Q and V _H. With the heat generator 1 and the pump 4, the outlet temperature T _{W is} influenced.

Fig. 4 FIG. 11 shows exemplary profiles of typical operating data at a heat requirement below the minimum heat generator heat output. FIG. The water volume flow V _W and / or the required temperature increase from the inlet temperature T _K (cold water) to the setpoint temperature T _W0 are so low that the heat generator must clock (on and off). Upon reaching or shortly before reaching the minimum permissible outlet temperature T _{W0, MIN} , the heat generator (Q) is switched on with a small heat output Q _MIN . Upon reaching or shortly after reaching the minimum permissible outlet temperature T _W0 , _MIN , the delivery rate of the pump is reduced to a small heating fluid volume flow V _{H, MIN} . Upon reaching or shortly before reaching the maximum permissible outlet temperature T _{W0, MAX} , the heat generator is switched off (Q off). Upon reaching or shortly after reaching the maximum permissible outlet temperature T _{W0, MAX} , the delivery capacity of the pump is raised to a high heating fluid volume flow V _{H, MAX} .

Fig. 5 shows exemplary courses of typical operating data at a heat request lying above the minimum heat generator heat output. The water volume flow V _W and / or the required temperature increase from the inlet temperature T _K (cold water) to the setpoint temperature T _W0 are so high that the outlet temperature in the heat generator continuous operation reaches the setpoint temperature. In a sudden increase in the heat demand by a sudden increase in the water volume flow V _W , the heat generator increases its heat output Q. However, the increase in the heat output Q is relatively slow. In a prior art method without pump modulation (V _H = constant), the outlet temperature T _W would drop sharply (dashed line) until the heat generator and the complete, inert heat transfer system (...) have reached the new water volume flow V _W and Set temperature T _W0 corresponding heat output Q provides. In the inventive process, the pump delivery rate increases their short term (V _H ≠ constant), and thus the conveyed Heizfluidvolumenstrom V _H from a nominal volume flow V _{H, NOM} to an increased value. Soon after, and in the meantime increased heat output, the pump starts to Heizfluidvolumenstrom _VH gradual to the nominal volume flow V _{H, NOM} lower. By this method, the transferred to the water heat output is always adapted to the increasing water volume flow V _W and the setpoint temperature T _W0 , whereby the outlet temperature T _{W is} almost constant at the lowest temperature fluctuations at the target temperature T _W0 . At a In the event of a sudden reduction in the heat requirement, for example as a result of a sudden reduction in the water volume flow V _W , the pump briefly modulates its flow rate to a low volume flow in order to avoid an otherwise sharp rise in temperature (dashed line). At the same time, the heat generator also begins to reduce its heat output Q. Soon after, and in the meantime fallen thermal power the pump begins to Heizfluidvolumenstrom _VH gradual to the nominal volume flow V _{H, NOM} raise.

The control signals for the heat generator 1 and the pump 4 with regard to the modulation of the heat output Q and the Heizfluidvolumenstrom V _H are given by a control device R, the control algorithm on readings of the outlet temperature T _W and / or the water volume flow V _W.

Claims (11)

1. Method for heating water with a variable volume flow according to the circulation principle, in which a heat generator (1) heats a heating fluid which is conveyed in a circuit (3) by a pump (4), the heating fluid heats circulated water, and at least one measuring sensor (8, 9, 10) which is arranged in a waterway measures a discharge temperature Tw and/or a volume flow Vw of the water, wherein the discharge temperature Tw of the water is regulated to a predefinable water setpoint temperature Two on the basis of a heating capacity Q, which can be modulated and/or switched, of the heat generator (1) as well as of a volume flow V_H which can be modulated and/or switched, of the heating fluid,
   characterized in the case of a clocking in heat-generator operation with alternating switching on and off of the heat generator, wherein a heating request to heat the water is lower than a minimum heat-generator heating capacity Q_MIN which is different from zero, the discharge temperature T_W is regulated, in that

   • for example when a minimum permissible discharge temperature T_W0,MIN is reached, the heat generator switches on at a heating capacity which is different from zero, and the pump (4) switches over to a low heating fluid volume flow V_H,MIN which is different from zero, and

   • for example when a maximum permissible discharge temperature T_W0,MAX is reached, the heat generator (1) switches off and the pump (4) switches over to a high heating fluid volume flow V_H,MAX.
2. Method according to Claim 1,
   characterized in that the switching on or off of the heat generator (1) takes place in each case just before or at the same time as the minimum or the maximum permissible discharge temperature is reached, and the switching over of the pump (4) to a low or high heat fluid volume flow takes place in each case at the same time as or just after the minimum or the maximum permissible discharge temperature is reached.
3. Method for heating water with a variable volume flow according to the circulation principle, in which a heat generator (1) heats a heating fluid which is conveyed in a circuit (3) by a pump (4), the heating fluid heats circulated water, and at least one measuring sensor (8, 9, 10) which is arranged in a waterway measures a discharge temperature Tw and/or a volume flow V_W of the water, wherein the discharge temperature Tw of the water is regulated to a predefinable water setpoint temperature Two on the basis of a heating capacity Q, which can be modulated and/or switched, of the heat generator (1) as well as of a volume flow V_H which can be modulated and/or switched, of the heating fluid,
   characterized in the case of a heat generator continuous operation, wherein a heating request to heat water is greater than or equal to a minimum heat-generator heating capacity Q_MIN, the discharge temperature Tw is regulated, in that

   • in the case of a first heating request the heat generator (1) heats with a heating capacity which corresponds to the heating request, and the pump (4) feeds a rated heating fluid volume flow V_H,NOM, and

   • in the case of a heating request which is increased compared to the first heating request, the heating generator heats with an increased heating capacity which corresponds to the increased heating request, and the pump (4) initially switches over to an increased heating fluid volume flow, and subsequently resets again to the rated heating fluid volume flow V_H,NOM, and

   • in the case of a heating request which is reduced compared to the first and/or the increased heating request the heat generator (1) heats with a reduced heating capacity corresponding to the reduced heating request, and the pump (4) initially switches over to a reduced heating fluid volume flow, and subsequently resets again to the rated heating fluid volume flow V_H,NOM.
4. Method according to one of the preceding claims, characterized in that

   • a first time period with a predefineable duration for observing a time profile of a current temperature deviation ΔT which results from the discharge temperature Tw and the setpoint temperature Two, wherein ΔT = Tw - Two, and

   • a second time period with a predefinable duration for regulating the discharge temperature Tw repeat alternately, wherein the duration of the first and second time periods is predefined as a fixed value or changes as a function of a temperature deviation and/or an operating state.
5. Method according to Claim 4,
   characterized in that for the regulation of the discharge temperature Tw only the heating fluid volume flow is modulated if an average temperature deviation ΔT_D of the discharge temperature Tw from the setpoint temperature Two assumes that value zero.
6. Method according to one of the preceding Claims 4 and 5,
   characterized in that for the regulation of the discharge temperature Tw at least the heat-generator heating capacity is modulated if an average temperature deviation ΔT_D assumes a value which is different from zero.
7. Method according to one of the preceding Claims 4 to 6,
   characterized in that for the regulation of the discharge temperature T_W at least the heating fluid volume flow is modulated if a temperature deviation ΔT has at least two zero crossings within a time period of the predefineable duration.
8. Method according to one of the preceding claims,
   characterized in that a frequency F of a discharge temperature fluctuation is detected and compared to a predefinable limiting frequency F_G, and in that for the regulation of the discharge temperature Tw

   • at least the heating fluid volume flow V_H is modulated at a frequency F which is higher than the limiting frequency F_G, and

   • at least the heat-generator heating capacity Q is modulated at a frequency F which is lower than the limiting frequency F_G.
9. Method according to one of the preceding Claims 4 to 8,
   characterized in that a value pair W composed of the absolute value and the gradient of the temperature deviation ΔT is detected and compared with a predefinable limiting value pair W_G composed of the absolute value and the gradient, and in that in order to regulate the discharge temperature Tw

   • in the case of a value pair W with a relatively small absolute value and a relatively large gradient at least the heating fluid volume flow V_H is modulated and in that

   • in the case of a value pair W with a relatively large absolute value and a relatively small gradient at least the heat-generator heating capacity Q is modulated.
10. Water-heating system according to the circulation principle, having

    • a heat generator (1),

    • a heating fluid which is heated by a heat generator (1) and is conveyed in the circuit (3) by a pump (4),

    • circulated water which is heated by the heating fluid, and

    • at least one measuring sensor (8, 9, 10), arranged in a waterway, for detecting a discharge. temperature Tw and/or a volume flow Vw of the water,

    characterized in that for the regulation of the discharge temperature Tw the heating capacity Q of the heat generator (1) and the volume flow V_H of the heating fluid circuit (3) can be modulated and/or switched to a predefineable setpoint temperature Two in accordance with a method according to one of the preceding claims.
11. Water-heating system according to Claim 10, characterized by a regulator unit which is connected to the heat generator (1), the pump (4) and the at least one measuring sensor (8, 9, 10),

    • which comprises an input device for setting setpoint values and/or constant and/or limiting values,

    • which influences the operation of the connected components, and

    • therefore regulates the discharge temperature Tw.

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