EP3779286A1 - Method for operating a heating system - Google Patents

Abstract

Method for operating a heating system with a central pump (4), at least one consumer (5) and at least one heat generator (1), with the volume flow and/or the signal of the heat generator power being recorded and/or the gradient of the flow temperature and/or the integration the control deviation between the target and actual flow temperature over time is formed, and the adaptation of the flow temperature is adjusted depending on the effects resulting from the heat gain or user intervention.

Description

The invention relates to a method for operating a heating system, in particular for adapting the flow temperature of a heating system with a pump, at least one consumer and at least one heat generator.

In such a heating system, a heating medium is used to transport heat from the generator to individual heat exchangers. In a heating system, the heating medium, e.g. water, is circulated by means of e.g. a central pump. The heating medium is heated by the heat generator. The heated heating medium flows to the individual heat exchangers, known as radiators or pipe coils in underfloor heating. The heating medium can be distributed to the heat exchangers as required using the adjustable valves. The heating medium is thereby cooled and flows back to the heat generator. Boilers, heat pumps or transfer stations for district heating can serve as heat generators.

In current heating systems, components such as heat generators, pumps and thermostatic valves work largely independently of one another. The thermostatic valves throttle the mass flows depending on the room temperatures. The pump is controlled according to the delivery head and the heat generator output according to the heating curve. The heating curve is dependent on the outside temperature and can be determined using the design parameters, which are usually not available.

Furthermore, the design of heating systems is based on the worst case (worst case). A heating system must be able to supply the building without heat gain. As the outside temperature rises, the building's heat losses decrease. This results in a lower target flow temperature. In other words, the heating curve is intended to compensate for heat losses. It is considered as if there were no heat gains throughout the year. The volume flow would therefore be constant over the heating period.

In reality, there is a heat gain during the period of use. On the other hand, users turn off the thermostatic valves to save energy. The use of electronic radiator drives is also increasing significantly due to the drop in prices and is already being used widely today. Entering schedules for the presence or absence of users generally leads to a lower heating requirement. This means that less heat is required to heat the building than can be deduced from the outside temperature. The thermostatic valves throttle the volume flows through the radiators. As a result, the total volume flow through the heat exchanger of the heat generator is reduced. With a low volume flow or low flow velocity, the transport time required for the heating water to travel from the generator to the consumer is correspondingly long. This means that the heating water cools down significantly on the way. The heat losses in the pipelines are therefore high. The phenomenon described occurs in particular in heating systems with uninsulated pipes, which are the norm in practice. This means that most of the energy that heats the heating water is not used to heat the rooms, but is lost along the way.

The target flow temperature results from the heating curve, which is either set high as a safety measure or left with the factory setting, which is usually higher than necessary. The heat generator output is regulated according to the control deviation between the actual and the target flow temperature. The volume flow does not matter. However, the current generation energy does not correspond to the current demand. If there is any heat gain in the rooms, the radiator valves move in the CLOSE direction. This reduces the volume flow. Thus, the output of the heat generator decreases accordingly. This means that the temperature level on the generation side is higher than that of the actual demand on the consumer side. Due to the decreasing volume flow, the transport time and the temperature drop from the generator to the consumers increase.

Since the radiator valves react with a time delay and when they close, much less heat is released into the rooms, the room temperatures drop again. This results in the reopening of the radiator valves. As a result, the volume flow and the heat generator output decrease again to. This process repeats itself, occurs cyclically (time-shifted) and is comparable to the propagation of a "heat wave" through the heating system, from the place of production to consumption. In other words, the radiator valves and heat generators do not work in a stable control range. The instability is intensified by an oversized heat generator, by a high-set heating curve and by the occurrence of heat gains. The plant operation is therefore energetically inefficient.

With district heating, the power output is regulated via the control valve. Exact power regulation is no longer possible in the small area of the valve opening. This causes a higher return temperature, which reduces the efficiency of the power plant.

In addition, due to the subsequent reduction (economy mode), the heat generator is greatly oversized in order to provide a power reserve for heating. Furthermore, the heat generator output can be varied in a fixed range, the so-called modulation range. If the heat generator output falls below the lower modulation limit, the heat generator works in cyclic operation, so-called ON / OFF.

Coupled with the overdimensioning of the heat generator with the occurrence of heat gains while the building is in use and with a high heating curve, the heat generator works predominantly in cyclic operation. Intermittent operation not only causes increased starting emissions. Immediately after the heat generator has been switched off, the mass of the heat generator is at a high temperature. The heat is lost to the outside through the chimney draft. The storage masses cool down and are heated again the next time the heat generator is started. Even the condensation heat in condensing heat generators does not benefit the heating of the rooms during cyclical operation, but is either lost through the chimney draft into the open air or on the way through long transport times.

In the case of wall-mounted heat generators, which are usually equipped with a small volume, and with a low volume flow, the local temperature increases during cyclic operation, since the starting power is usually many times higher than the lower modulation limit. The processes such as limescale deposits, corrosion, etc. in places with excessive temperatures are accelerated. These worsen the process of heat transfer, which in turn leads to higher temperatures. This creates a vicious circle that leads to failure or shortening of the service life of the heat generator.

Too high a flow temperature causes greater heat losses from the heat generator, the pipes, flue gas losses, loss of efficiency, frequent cycling and a low COP (coefficient of performance) in the heat pump.

The procedure EP 1 752 852 A2 enables continuous adjustment of the heating curve. Instead of thermostatic valves, the speed-controlled pumps are used on each individual radiator.

In the process DE 10 2012 018 778 the procedure for dynamic hydraulic balancing, for pump adaptation and for adapting the heating curve is described. However, it assumes that the electronic radiator drives are used instead of mechanical thermostatic valve heads. An exchange of information between radiator drives and heat generator is also required.

The proceedings DE 197 05 486 A1 , DE 195 12 025 A1 and DE 10 2011 009 750 A1 form the gradient of a temperature rise in the flow line. If the gradient exceeds a specified limit value, either the heat generator output is reduced or the heat generator is switched off completely. In the process EP 2 163 822 A1 the temperature gradient is also formed when the heat generator starts.

Depending on the gradient mentioned, the heat generator pause time can be varied in order to reduce the cycle frequency of the heat generator operation. The procedure EP 2 218 967 A2 forms the switch-on and switch-off integral to switch the heat generator on and off. In all of the processes mentioned, the target flow temperature of the heating curve remains unchanged.

In the process DE 10 2005 005 760 A1 the heating requirement is determined based on the measurement of the heat generator running time, the pause time and the modulation value. The procedure calculates analogously DE 10 2008 054 043 A1 the current heating requirement from the measured values such as return and flow temperatures and volume flow. From the The required flow temperature can be derived with the help of a stored logic.

The invention is based on the object of reducing the disadvantages arising from the above-mentioned prior art.

The object is achieved according to the invention by a method according to claim 1 and a heating system according to claim 11.

According to the invention, in addition to an adjustment according to the heating curve, the flow temperature is adjusted as a function of the change in the heat generator output or a value derived therefrom or as a function of the change in the volume flow.

The method can be used for heating systems that have a (e.g. central) heat generator, a (e.g. central) pump and at least one radiator. The above signals are recorded and analyzed during operation. The effects of the heat gains are thus recognized. This is followed by the adjustment of the target flow temperature.

As described above, according to the prior art, the heating curve is provided to compensate for the heat losses, the heat losses being dependent on the outside temperature. Heat gains are unknown and are not taken into account. As a result, the volume flow decreases towards zero with high heat gains.

In the present invention of a method for adapting the target flow temperature of a heating system, it is provided that the heating curve is left at the factory setting. Manual setting is no longer necessary. During operation, the target flow temperature is then adjusted depending on the effects resulting from the heat gains or user interventions or specifications.

There is a fundamental difference between heating systems with and without hydraulic system separation. In systems with hydraulic separation, a heat exchanger or a hydraulic switch is connected between the generator and the consumers, which means that a primary and a secondary volume flow are independent arise from each other. The systems with hydraulic separation and with the option of heat storage represent a special feature. For example, the heat pump loads the buffer storage that supplies the heat for the heating system. In this case, the buffer tank serves as a hydraulic separation with the heat storage facility.

In systems without hydraulic separation, there is no differentiation between the primary and secondary side. The central volume flow is therefore the sum of all volume flows through the individual consumers. In the following, the behavior of the systems without hydraulic system separation is described in more detail. The system behavior with the hydraulic separation without storage facility can be derived analogously.

In order to save energy, the rooms are not heated to the comfort level at night but to the economy mode with a room temperature of e.g. 17 ° C, so-called setback mode. Shortly before or from the beginning of the period of use, the heating system switches to normal heating mode, whereby the rooms are heated to the comfort level with the room temperature of e.g. 20 ° C.

The rooms are still cold in the early morning hours, especially immediately after the changeover from reduced to heating mode, and the valves (thermostatic valves for radiators, control valves for underfloor heating) are completely open. As a result, maximum volume flows through the individual consumers (radiators or underfloor heating circuits), which are much larger than those in the design. In addition, the temperature of the heating water that flows back to the heat generator is low, as the heating system was previously in economy mode. Paired with the largest volume flow with the low return temperature, the heat generator delivers the maximum available power to achieve the target flow temperature. During this heating-up time, the maximum heat generator output is usually too small, whereby the maximum heat generator output is 100% output of the heat generator. In other words, the target flow temperature remains unchanged in this phase and is calculated from the set heating curve depending on the outside temperature.

In general, the heating phase can be recognized by the fact that the volume flow is large and the heat generator is working with maximum output. Because of the big Flow, the actual flow temperature increases slowly and steadily. This means that the flow temperature gradient is small. In addition, in this phase the actual flow temperature is lower than the target flow temperature. The system deviation from the difference between the target and the actual value is therefore positive. Consequently, the integration of the control deviation over time is also positive.

A sensor for recording the flow temperature is usually installed on the heat generator. This measured value can be used both for the formation of the gradient of the flow temperature and for the calculation of the integration of the control deviation over time. The heat generator output signal is available from the control unit. These three signals are sufficient to recognize the heating phase. If a sensor is installed to record the central volume flow, another signal is available for recognizing the heating phase.

If the heating-up phase is recognized, the target flow temperature remains unchanged at the level of the heating curve so that the rooms are supplied quickly and adequately. If internal and external heat gains occur in this phase, these are used to heat up the rooms more quickly.

After the heating-up phase, which, depending on the pipe network structure and the installed system components, can take up to several hours, the heating system goes into normal operation, whereby the target flow temperature is maintained. This means that there is no system deviation. This means that the flow temperature gradient and the integration of the control deviation over time are almost zero. The rooms are heated to the required level of comfort. The heat gains increase during this "normal operation" phase. As a result, less heat is required for heating. The thermostatic valves therefore move in the CLOSED direction (closed) or work in the small stroke range, whereby constant room temperature control is no longer possible. Thus, the volume flow through the heat generator decreases or fluctuates. This leads to the heat generator output decreasing or fluctuating accordingly in order to maintain the target flow temperature. In other words, the decrease in the heat generator output is to be understood as a compensation for the heat gains that occur.

According to the invention, the target flow temperature is gradually reduced when the average heat generator output decreases and / or there is a strong fluctuation in the heat generator output.

If there is a reduction or a sharp drop in the heat generator output or a strong fluctuation in the heat generator output, the set flow temperature is gradually reduced from the set heating curve (e.g. 1, 2 or 3 K every 30 minutes). The size of the reduction in the target flow temperature (1 or 3 K) depends on the drop or fluctuation in the heat generator output. For example, the outside temperature remains almost unchanged, while the heat generator output fluctuates e.g. between 70% and 40% within the observation interval of e.g. 30 minutes, the target flow temperature is lowered e.g. by 3 K. This corresponds to a reduction in the target flow temperature of, for example, 1 K with a fluctuation in the heat generator output of 10%. By reducing the target flow temperature, the thermostatic valves move in the OPEN (open) direction, whereby the volume flow increases. On the other hand, the lowering of the target flow temperature means a reduction in the temperature difference between the flow and return temperatures of the heat generator. The result of the multiplication of the temperature difference by the volume flow remains almost unchanged and corresponds to the heat generator output. After reducing the target flow temperature, the heat generator output stabilizes or remains approximately constant. This ensures the heat supply and the associated comfort compliance.

If the heat generator output continues to decrease after the specified observation interval (e.g. 10, 20 or 30 minutes or even 1 hour), this means a further increase in heat gains. The target flow temperature can be further reduced from this. If the heat generator output increases noticeably during the observation period, the target flow temperature is increased again because either the heat gains may be lost or the user interventions by opening the thermostatic valves are present.

According to the invention, the lowering of the target flow temperature of the heating curve does not take place abruptly but step by step, on the one hand to maintain a stable control behavior of the entire heating system and on the other hand to avoid possible loss of comfort, since the heat gains differ in different rooms attack. If an increased demand is determined due to a higher heat generator output, the target flow temperature is increased again immediately. The adjustment of the target flow temperature leads to the more efficient system operation, whereby the maintenance of the user comfort has priority.

When adapting the target flow temperature, the outside temperature signal is taken into account to determine whether it has changed significantly during the observation period. The outside temperature is available for determining the target flow temperature from the heating curve anyway. If a sensor for recording the (central) volume flow is installed in the system, the set flow temperature can be adjusted depending on the current volume flow as well as the tendency to change (increase / decrease) in the volume flow.

In other words, according to the invention, the actual target flow temperature is different from the set heating curve. The adjustment of the heating curve takes place under the aspect of compensation of the heat losses with consideration of the heat gains.

The control mode phase is characterized by compliance with the set flow temperature (no control deviation). The current heat generator output is smaller than the maximum. If the phase control mode is recognized, the target flow temperature is adjusted from the heating curve as described above.

Alternatively or additionally, the object can also be achieved in a different way according to the invention. The heating curve is a function of the outside temperature and begins at the design point, which depends on the location and the design specification. For example, for the location in Berlin, Germany, where the standard outside temperature is -14 ° C, the desired target flow temperature should be 70 ° C, for example. This means that the design point for the Berlin location (outside temperature -14 ° C; target flow temperature 70 ° C). If the outside temperature rises to 20 ° C, the target flow temperature drops approximately linearly to 20 ° C. A target flow temperature is clearly assigned to each outside temperature. At an outside temperature of 20 ° C, the target flow temperature is also 20 ° C. This means that the heat generator output is zero at an outside temperature of 20 ° C. At the standard outside temperature of -14 ° C, the Theoretically, the heat generator output is 100%. The assignment of the theoretical heat generator output to the outside temperature is therefore also clear. In other words, a theoretical heat generator output can be determined for every outside temperature. From this, the relationship between the target flow temperature and the theoretical heat generator output can be derived. It is assumed that the heat generator is not oversized. If the heat generator is oversized, a corresponding scaling must be carried out.

When the outside temperature is recorded, both the target flow temperature and the theoretical heat generator output can be determined. Due to the heat gain, the heat generator produces an average heat generator output - which is referred to below as heating output - that is smaller than the theoretical one. If the heating output is set equal to the new theoretical output, the heating curve results in a target target flow temperature that is also lower than the previously determined target flow temperature from the heating curve. This means that the heating curve is gradually reduced to the target set flow temperature. The step-by-step adjustment can take place in steps of 1, 2 or 3 K per 30 minutes, for example, or the step size can take place depending on the difference between the actual and target flow temperature and the target target flow temperature, e.g. 50% of the difference.

If the heat gains break away or if the user intervenes by opening the thermostatic valves, the heating output increases noticeably during the observation period. This results in a new target target flow temperature, which is accordingly higher than the current target flow temperature. The current target flow temperature is then gradually increased to the new target target flow temperature.

According to the invention, the target target flow temperature is determined again after a predetermined time interval, for example the observation time interval. The target target flow temperature is a target corridor on which the target flow temperature is approached step by step so that there is no instability in the entire heating system. Large jumps in the target flow temperature cause an unstable one Combustion control, as the volume flow and the return temperature react with a delay.

If, on the other hand, the oversizing factor is not known, the theoretical heat generator output and thus the target target flow temperature cannot be determined. In this case, according to the invention, the target flow temperature is gradually reduced or increased with an almost unchanged outside temperature as a function of the reduction or increase size of the heating output. If the outside temperature remains almost unchanged, while the heating output decreases e.g. from 70% to 50% within the observation interval of one hour, the target flow temperature is lowered e.g. by 2 K. This corresponds to a reduction in the set flow temperature of, for example, 1 K with a reduction in the heat generator output of 10%. Immediately after the reduction, the behavior of the heating output is monitored within a given time interval of e.g. 1 hour. If the heating output continues to decrease after the specified observation interval, this means a further increase in heat gains. The target flow temperature can be further reduced from this. If, on the other hand, the heating output increases during the observation interval, it means that the heat demand is increasing. As a result, the target flow temperature is increased again in order to cover the demand or to maintain user comfort.

Alternatively, the oversizing factor can be detected during operation. For example, in normal operation in the early morning hours, when there is no heat gain, the heat generator has a heating output of z. B. 50%, while the theoretical heat generator output is e.g. 75%. The ratio of the theoretical heat generator output to the actual heating output results in the oversizing factor. For the example mentioned, the oversizing factor is 1.5. The theoretical heat generator output can be determined from the outside temperature.

According to the invention, the two methods described above are used in combination in order to carry out a reliable adjustment of the target flow temperature without sacrificing user comfort.

If the heat gains continue to increase during normal operation, the heat generator output decreases accordingly. Falls below the The heat generator output at the lower modulation limit results in cyclic operation. The heat generator switches on and off. The volume flow is so low that the actual flow temperature rises quickly, although the heat generator is working with the minimum output. If the actual flow temperature exceeds the upper limit value, which is, for example, 5 K above the current target flow temperature, the heat generator switches off. A high rise (gradient) in the actual flow temperature during the heat generator ON phase means that the need for heating is low. This is shown by a short heat generator run time. When the heat generator is started, the actual flow temperature is lower than the lower limit value, which is, for example, 5 K below the current target flow temperature. This results in a positive control deviation. However, the actual flow temperature rises rapidly and exceeds the upper limit value, the actual temperature in turn being greater than the set flow temperature. The control deviation is negative when the heat generator is switched off. The integration of the control deviation between the setpoint and actual flow temperature over the time while the heat generator is ON is almost zero in terms of amount. According to the invention, the integration of the control deviation is only started when the actual flow temperature exceeds the target flow temperature.

As mentioned above, the system operation is very inefficient in terms of energy if the target flow temperature from the heating curve is used in cyclic operation. The high target flow temperature causes high exhaust and radiation losses. Frequent cycling means that the components wear out accordingly. The service life of the heat generator is shortened. Due to the high heat gains and the low volume flow, the transport time from the generator to the consumer is long, which means that the heating water cools down considerably on the way.

The cyclic operation can be recognized by the minimum heat generator output, short heat generator running time (heat generator ON and OFF), negative control deviation or negative integration area of the control deviation over time. The volume flow is small. If cyclic operation is recognized, the target flow temperature is gradually reduced from the heating curve. This opens the thermostatic valves and the volume flow increases. The next time the heat generator starts, the heat generator runtime is longer. The gradient of the flow temperature is therefore smaller. If a sensor is installed to record the volume flow, the adjustment of the The target flow temperature is based on the current volume flow and the tendency to change (increase / decrease) in the volume flow.

If the gradient of the actual flow temperature drops sharply or if the control deviation is equal to zero or if the volume flow increases sharply, this means that the heat demand is increasing. As a result, the target flow temperature is increased again to meet the demand.

1. a) Bestimmung der Soll- Vorlauftemperatur der Heizungsanlage in Abhängigkeit der Außentemperatur (Heizkurve),
2. b) Feststellen, ob sich die Heizungsanlage im Aufheiz-, Regel-, oder Taktbetrieb befindet,
3. c) Für den Regelbetrieb: Erfassung der Heizleistung des Wärmeerzeugers und/oder eines Volumenstroms eines Heizmediums durch den/die Verbraucher und Bestimmung deren/dessen Verlauf über die Zeit,
   und Reduzierung der Soll-Vorlauftemperatur der Heizungsanlage bei Überschreiten eines Grenzwertes der Reduzierung der Heizleistung und/oder des Volumenstroms des Heizmediums innerhalb eines vorgegebenen Zeitraums und/oder bei Überschreiten eines Grenzwertes für die Schwankung der Heizleistung bzw. bei Überschreiten eines Grenzwertes für den entsprechenden Gradienten.
4. d) Für den Taktbetrieb: Erfassung der Wärmeerzeugerlaufzeit und/oder der Ist-Vorlauftemperatur über die Zeit, und Reduzierung der Soll-Vorlauftemperatur der Heizungsanlage bei Überschreiten eines Grenzwertes der Erhöhung der Ist-Vorlauftemperatur innerhalb eines vorgegebenen Zeitraums bzw. bei Überschreiten eines Grenzwertes für den entsprechenden Gradienten oder bei Unterschreiten eines Grenzwertes der Wärmeerzeugerlaufzeit oder bei Unterschreiten eines Grenzwertes für den

Volumenstrom oder Unterschreiten eines Grenzwertes für den absoluten Betrag der Integration der Regelabweichung über die Zeit. Zusätzlich oder anstelle der Schritte b) bis d) können gemäß einer Ausführung auch folgende Schritte durchgeführt werden:

• e) Berechnung der theoretischen Wärmeerzeugerleistung durch Multiplikation der Heizleistung mit dem Überdimensionierungsfaktor der Heizungsanlage,
• f) Bestimmung der Ziel-Soll-Vorlauftemperatur aus der Heizkurve.

According to one embodiment, the method according to the invention comprises the following steps:

1. a) Determination of the target flow temperature of the heating system depending on the outside temperature (heating curve),
2. b) Determine whether the heating system is in heat-up, control or cycle mode,
3. c) For normal operation: recording the heating output of the heat generator and / or a volume flow of a heating medium through the consumer (s) and determining their course over time,
   and reduction of the target flow temperature of the heating system when a limit value for the reduction of the heating power and / or the volume flow of the heating medium is exceeded within a specified period and / or when a limit value for the fluctuation of the heating power is exceeded or a limit value for the corresponding gradient is exceeded.
4. d) For cyclic operation: Acquisition of the heat generator run time and / or the actual flow temperature over time, and reduction of the target flow temperature of the heating system when a limit value of the increase in the actual flow temperature is exceeded within a specified period or when a limit value for the corresponding gradient or when the heat generator runtime falls below a limit value or when a limit value for the

Volume flow or falling below a limit value for the absolute amount of the integration of the control deviation over time. In addition to or instead of steps b) to d), the following steps can also be carried out according to one embodiment:

• e) Calculation of the theoretical heat generator output by multiplying the heating output by the oversizing factor of the heating system,
• f) Determination of the target target flow temperature from the heating curve.

The method was explained using a two-pipe heating system with an inserted heat generator (1) without hydraulic separation, but is not limited to this type of system. The functional principle naturally also applies to systems with hydraulic separation without heat storage facilities or with other types of heat generators (heat pumps, district heating, etc.).

According to the invention, in the case of transfer stations for district heating, instead of the heat generator output, the control valve signal or the position of the control valve is used to adjust the setpoint flow temperature.

The following is the derivation of the above-mentioned method according to the invention for a typical, mostly used system with hydraulic separation and with a heat storage facility, which consists of a heat pump, a buffer store and consumers. The remaining systems with hydraulic separation can be described in the same way.

The primary volume flow through the heat pump is large and constant, whereas the secondary volume flow depends on the demand and is equal to the sum of all volume flows through the consumers. The constant volume flow is important for maintaining the functionality of the heat pump.

In the heating-up phase, the heat consumption on the consumer side is greater than the heat generated by the heat pump. The actual flow temperature is lower than the target flow temperature, although the heat pump is working at maximum output.

The heating ends and changes to the control mode phase when the actual flow temperature reaches the target flow temperature. If heat gains occur while the building is in use, the heat consumption is reduced. The secondary volume flow is thereby reduced. The buffer storage has a large volume in relation to the heating side of the heat pump, so that the return temperature from the storage to the heat pump increases gradually and steadily. Coupled with the constant volume flow with the rising return temperature, the heating output is continuously reduced with a modulating heat pump.

In other words, the large storage volume has the damping function so that no major fluctuations in the heat pump output are to be expected. If a limit value for the reduction in heating output is exceeded and the outside temperature remains unchanged, the target flow temperature is gradually reduced by the heating curve. The step-by-step adjustment can take place in steps of 1, 2 or 3 K per 30 minutes, for example, or the step size can be made depending on the change in heating output, e.g. 2 K per 10% reduction in heating output.

The reduction of the target flow temperature means a reduction in the storage tank temperature and thus the storage loss. The coefficient of performance of the heat pump increases. The system works more efficiently overall. On the other hand, the valves of the consumers open, which increases the secondary volume flow again. The heat consumption remains unchanged and user comfort is maintained.

If the heating output increases noticeably during the observation period, the target flow temperature is increased again, as either the heat gains may be lost or the user interventions by opening the thermostatic valves are present. If a sensor for recording the secondary volume flow is installed in the system - hereinafter referred to as volume flow, the target flow temperature can be adjusted depending on the current volume flow and the tendency to change (increase / decrease) in the volume flow.

Similar to the systems without hydraulic separation, the normal operation phase is characterized by compliance with the target flow temperature (no control deviation) and a lower heating output than the maximum. If the control mode phase is recognized, the target flow temperature is adjusted as described above, based on the heating curve.

The term "based on the heating curve" describes the selection of the target flow temperature based on the heating curve as a function of the outside temperature. On the basis of this value, the target target flow temperature or the target flow temperature is adapted according to the invention.

If the heat gains continue to increase during normal operation, the heating output decreases. If the heat pump output falls below the lower modulation limit, the heat pump switches to cyclic operation. The Heat pump with the minimum power and switches on and off. Since the large storage volume has the damping function, this does not result in a rapid increase or a large gradient in the actual flow temperature as in the case of systems without hydraulic separation. Otherwise, the description given above for the adjustment of the target flow temperature in systems without hydraulic separation for cyclic operation applies in full.

According to the invention, the lower and / or upper limit value for switching the heat pump on / off in cyclic operation will vary depending on either the current target flow temperature or the reduction value of the target flow temperature from the heating curve - for example, the upper limit value is 4 K above the target Flow temperature of 50 ° C; 5 K above the target flow temperature of 35 ° C or increasing the upper limit value by 1 K when reducing the target flow temperature from the heating curve by 2 K, in order to reduce the frequent cycling of the heat pump.

The mode of operation of single-stage heat pumps, which either switch on or off, corresponds to cyclic operation, for which the adjustment of the target flow temperature is carried out as described above. In the case of hydraulic separation with the option of heat storage (single-stage heat pump, buffer storage, consumer), the target flow temperature is preferably adapted depending on the reduction in the heating output, with the heating output being determined from the heat pump run time and break time. Due to the large buffer storage volume, no major change in the temperature gradient is to be expected.

The method according to the invention for operating a heating system with a two-pipe system without hydraulic separation is explained in more detail below using a simplified exemplary embodiment. The process can be applied to the full extent, without any restrictions, on the system with hydraulic separation or with other heat generators such as heat pumps, district heating, etc.

Fig. 1

eine vereinfachte Darstellung einer konventionellen Zweirohrheizung,

Fig. 2

eine vereinfachte Darstellung der Heizkurve,

Fig. 3

Soll-Vorlauftemperatur mit / ohne Adaption,

Fig. 4

Verhalten des Volumenstromes und der Wärmeerzeugerleistung ohne Adaption der Soll-Vorlauftemperatur,

Fig. 5

Verhalten des Volumenstromes und der Wärmeerzeugerleistung bei adaptierter Soll-Vorlauftemperatur.

Show it

Fig. 1

a simplified representation of a conventional two-pipe heating system,

Fig. 2

a simplified representation of the heating curve,

Fig. 3

Target flow temperature with / without adaptation,

Fig. 4

Behavior of the volume flow and the heat generator output without adaptation of the target flow temperature,

Fig. 5

Behavior of the volume flow and the heat generator output with an adapted target flow temperature.

Fig. 1 shows a simplified example of a conventional central two-pipe heating system with a heat generator (1), a sensor for recording the flow temperature (2), a flow line (VL), a return line (RL), a central pump (4) and consumer (5). A sensor for recording the central volume flow (3) is optionally provided. However, this sensor is not absolutely necessary in order to carry out the method according to the invention.

To clarify the process, a system operation is selected for a period from 6:00 a.m. to 5:00 p.m., the outside temperature being around -6 ° C at 6:00 a.m. and rising to -3 ° C over time. From the heating curve ( Fig. 2 ) a target flow temperature of around 60 ° C can be found. Fig. 3 shows the heating curve with the target flow temperature of 61 ° C at 6:00 a.m. and drops to 59 ° C from 2:00 p.m.

At 6:00 a.m., the heat generator switches from economy mode to normal heating mode. The heat generator output is 100% immediately after the switchover. The heating operation ends at approx. 7:00 a.m. In other words, normal operation starts at 7:00 a.m.

Fig. 4 shows the system operation without adapting the target flow temperature. The volume flow tends to decrease over the course of the day, with the volume flow fluctuating from 12:00. This creates an unstable control of the heat generator output, which fluctuates between 40% and 80%.

At around 9:30 a.m. the drop (gradient) in the heat generator output is large due to the heat gains ( Fig. 5 ), the target flow temperature is reduced ( Fig. 3 ). The heat generator output then stabilizes at 60%. Shortly before 12:00 noon and after 12:00 noon, the heat gains continue to increase, so that the heat generator output drops sharply. The target flow temperature is accordingly gradually increased to 55 ° C reduced ( Fig. 3 ). The volume flow remains constant during the day ( Fig. 5 ). The heat generator output stabilizes at approx. 50%.

This example concerns a building with a heating load of 19 kW. The nominal output of the heat generator used is 26 kW. Thus the oversizing factor is 1.37. In Fig. 2 this results in a theoretical heat generator output of 80% and a target flow temperature of 60 ° C at an outside temperature of -6 ° C. In the course of operation, the heat gains increase. The average actual heating output drops to 51% from 12:00 p.m. ( Fig. 4 ). If the actual output is multiplied by 51% by the oversizing factor 1.37, the result is a new theoretical heat generator output of 70%. From the new theoretical heat generator output, the new target target flow temperature of 55 ° C ( Fig. 2 ) to calculate. The new target target flow temperature is the target corridor to which the heating curve is gradually reduced. The heat generator works with the minimum output in cycle operation. The heating output is determined via the time ratio between the heat generator ON and the heat generator OFF. List of reference symbols: 1 Heat generator 2 Flow temperature sensor 3 Volume flow sensor 4th pump 5 consumer VL leader RL Rewind ϑ _Au Outside temperature ϑ _Should Target flow temperature

Claims (11)

Method for adjusting the target flow temperature of a heating system, the heating system using a heat generator (1), a sensor for detecting the flow temperature (2), a line system with at least one flow line (VL) and at least one return line (RL) and at least one in between arranged consumer (5) and a control unit, characterized in that the target flow temperature is reduced in the course of operation based on the heating curve if at least one of the following conditions is present within a specified period: - If a limit value of the reduction of the heating power is exceeded; - If a limit value is exceeded, the reduction in the volume flow of the heating medium; - when a limit value for the fluctuation of the heating power is exceeded or when a limit value for the corresponding gradient is exceeded. Method according to Claim 1, characterized in that the target target flow temperature is determined from the heating power, the target flow temperature being able to approach the target target flow temperature in sections. Method according to Claim 1, characterized in that, when the system is operated in cycles, the target flow temperature of the heating system is reduced if at least one of the following conditions is present: - Exceeding a limit value of the increase in the actual flow temperature within a predetermined period or when a limit value for the corresponding gradient is exceeded; - The heat generator runtime falls below a limit value; - Falling below a limit value for the volume flow; - Falling below a limit value for the absolute amount of the integration of the control deviation over time. Method according to Claim 1, characterized in that the adaptation takes place step-by-step after a predetermined observation time interval has elapsed. Method according to one of the preceding claims, characterized in that the target flow temperature is determined again either after a predetermined time has elapsed and / or when a limit value for the change in the outside temperature is exceeded in a predetermined time interval or when a limit value for the corresponding gradient is exceeded . Method according to claim 4, characterized in that during an observation interval when an increasing heating power for the control mode or a longer heat generator run time or a drop in the gradient of the flow temperature or a control deviation almost zero for the cyclic operation is detected, the last adjustment of the target flow temperature is immediately reversed becomes. Method according to one of the preceding claims, characterized in that a control mode is recognized when a certain flow temperature has been reached or when the integration of the control deviation between the set flow temperature and the actual flow temperature is equal to zero. Method according to one of the preceding claims, characterized in that cyclic operation is recognized when the heat generator switches on and off. Method according to one of the preceding claims, characterized in that, in cyclic operation, the lower and / or upper limit value for switching the heat generator on / off is varied as a function of either the current target flow temperature or the reduction value of the target flow temperature from the heating curve. Method according to one of the preceding claims, characterized in that a step-by-step approximation of the target flow temperature in cycle and / or in regular operation to a target target flow temperature calculated with the help of an oversizing factor of the heating system is carried out, the target target flow temperature after a certain period of time is determined again, and wherein the target target flow temperature is determined by the steps: Calculation of the theoretical heat generator output by multiplying the heating output by the oversizing factor of the heating system, Determination of the target set flow temperature from the heating curve. Heating system with a heat generator (1), a sensor for detecting the flow temperature (2), a line system with at least one Flow line (VL) and at least one return line (RL) and at least one consumer (5) arranged in between, as well as a control unit, characterized in that the heating system is designed to carry out the adjustment of the target flow temperature according to one of Claims 1 to 10.

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