DE102012101850A1 - Method for controlling heating system of building, involves providing flow rate of heat carrier in generator circuit as input variable by which control variable of power of generator is affected, where generator controls heating power - Google Patents

Abstract

The method involves heating a heat transfer medium i.e. wood pellet, by a heat generator (2) to inlet temperature. The medium flow is automatically controlled by a room temperature controller. Flow of a heat carrier in a generator circuit is determined and utilized as an input variable. Control of a heating system (1) is demand-guided by a determined flow rate of the heat carrier that is provided in the generator circuit as the input variable by which a control variable of scheme preferably power of the generator is affected, where the generator controls delivered heating power.

Description

The invention relates to a method for demand-controlled control of a heat generator in a heating system.

From practice known methods for controlling a heating system are largely limited to the control of the flow temperature as a function of the outside temperature. Also the DE 42 11 914 C2 proposes, depending on the outside temperature to specify the amount of heat emitted by the heat generator per unit time. In this case, the flow temperature of the heat transfer medium (usually water) is measured and connected as a controlled variable a controller. The reference variable is guided depending on the outside temperature with the result that each outdoor temperature is assigned a corresponding flow temperature. In this case, an economic, needs-based regulation is sought by z. B. a lowering of the flow temperature is provided with increasing outside temperatures and, accordingly, the heat generator can be operated at a lower power.

The dependence of the flow temperature on the outside temperature is represented by a number of heating curves. The adjustment of the optimum heating curve to be made is tedious and difficult. It can only be preset by the skilled person and must be adapted by the operator during operation. For example, different slopes can be set for the heating curves and also the heating curves can be raised or lowered. In practice, it is often observed that these setting options overwhelm the operator of a heating system. As a result, in most cases, the heating curve is set "too high" to ensure sufficient heating comfort in all the heated conditions in the heated rooms, which means uneconomical operation of the heating system. In other cases, it can cause problems at certain outdoor temperatures, for example by insufficient heating power.

Although thermostatic valves in the rooms can influence the flow through the individual radiators depending on the room temperature, a feedback of the room temperatures to the heat generator of the heating system is usually missing completely or is realized only indirectly, for example by defining a room as a reference room and its room temperature is used to control the heating system , Depending on whether it is a thermally well-protected, inside building space that does not border on an outer wall of the building, or how large the windows of the reference space, and to which direction they are aligned, significant differences in the heating requirements of other rooms to the heating demand of the reference space can not be excluded, so that such arrangements are inaccurate in the result. This in turn means that the relevant heating system is set too hot or too high to ensure sufficient heating comfort in all rooms, which is associated with economic disadvantages. In the reverse case, the reference space can influence the heating control due to external heat input to the effect that the system is provided a lower flow temperature and thus adjacent rooms are undersupplied.

It is known to set and regulate the room temperatures in the individual rooms either by acting on the radiator valve electronic control unit with setpoint adjuster, temperature sensor and regulator or by the mentioned, in practice widespread thermostatic radiator valves and regulate. This type of control regulates the volume flow through the radiator, which is thus variable. This type of room control works very well, but has the distinct disadvantage that there is no feedback to the heat generator. Therefore, the heat generator usually holds a temperature which is higher than would be necessary for sufficient heating of the rooms. Even with optimum setting of the heating curve, this is almost always the case, since this is set for the "worst case" in which the rooms are still to be sufficiently heated.

For the operation of a boiler, this results in frequent clocking, so switching on and off of the burner. Even so-called modulating burners, which can provide different levels of precisely defined power, only come into the modulation range when the internal back modulation takes effect, which is usually the case only when the temperature spread between flow and return in the boiler a certain Value falls below. Then, however, the boiler could completely shut down because the system is already oversaturated with energy.

Based on purely exemplary values, the problem should be clarified: at an outside temperature of 0 ° C, strong wind, overcast skies and without internal heat loads, a target temperature of 20 ° C should be maintained in the building. For this purpose, a corresponding flow temperature according to the heating curve of 55 ° C is maintained. However, if it is windless at the same outside temperature of 0 ° C, the sun is shining, and there is some early heat in the form of internal loads such as lighting, people and electrical equipment, the Heating controller also a flow temperature of 55 ° C available. The heat generator thus holds more power than is needed. En economical operation of the heating system is not achievable under these circumstances.

If the same heating system is to heat up the cold rooms early in the morning after the building has cooled down overnight due to the heating night setback, the heating controller will again "only" provide the preset flow temperature 55 ° C, although a higher heating rate may be required the maximum heating power required or at least desirable for comfort reasons would be desirable.

• • Üblicherweise ist keine Kopplung des Verbraucher- und des Erzeugerkreises vorgesehen.
• • Die Regelung des Wärmeerzeugers erfolgt nicht lastabhängig, da keine Rückmeldung über den momentanen Verbrauch erfolgt.
• • Die Installation der Heizungsanlage, insbesondere dabei ihrer Regelung, ist vergleichsweise kompliziert. Es werden Sensoren verwendet, die häufig in größerer Entfernung von dem Heizkessel bzw. Brenner installiert werden müssen, wie z. B. ein Außenthermometer.
• • Die Bedienung der Heizung ist vielfach so kompliziert, dass der Betreiber oft überfordert ist. Daher wird häufig selbst für kleinere Anpassungen oder Umstellungen Fachpersonal hinzugezogen.
• • Die Heizung wird in vielen Fällen mit einem schlechten Jahresnutzungsgrad und dementsprechend unwirtschaftlich betrieben, beispielsweise aufgrund häufigen Taktens des Wärmeerzeugers und / oder aufgrund hoher Rücklauftemperaturen.

In summary, the following disadvantages of a heating control result with the current state of the art:

• • Usually there is no coupling of the consumer and generator circuits.
• • The control of the heat generator does not depend on the load, as there is no feedback about the current consumption.
• • The installation of the heating system, especially its regulation, is comparatively complicated. Sensors are used, which often have to be installed at a greater distance from the boiler or burner, such. B. an outdoor thermometer.
• • The operation of the heating is often so complicated that the operator is often overwhelmed. Therefore, specialized personnel are often called in even for minor adjustments or changes.
• • In many cases, the heating is operated with a poor annual efficiency and, accordingly, uneconomical, for example due to frequent heating of the heat generator and / or due to high return temperatures.

Proposals have been made to measure the volume flow of a heating system and to include the measured values in the control of a heating system:

From the DE 32 02 168 A1 It is known to measure the volume flow and to calculate with the help of additionally measured flow and return temperatures to a power. Here, a system-specific flow rate setpoint is fixed, which should be kept constant by adjusting the flow temperature. The volume flow measurement takes place in the consumer circuit, so that in practice there are only a few suitable applications for this method in which the heating load is always covered by a specific volume flow. For example, for a partial load operation of the heating system, this control method is not suitable.

Also from the DE 102 17 272 A1 It is known to measure the volume flow and to calculate with the help of additional temperature measurements to a power. In this case, a deliberate power adjustment is provided in the lowering of the heating system, as z. B. in the context of the so-called night reduction, and usually via a reduction in the flow temperature. There is the problem that this lowering of the flow temperature, the properties of thermostatic valves arranged on the radiators oppose: these thermostatic valves open further to compensate for an increased volume flow, the reduction of the supplied heating energy again. The DE 102 17 272 A1 proposes to influence the volume flow via an additional control valve, so that the installation, maintenance and operability of the heating system are made difficult by their relatively complex structure.

Object of the invention

The invention has for its object to provide a method which allows the simplest possible means economic operation and easy operation of the heating system.

This object is achieved by a method according to claim 1.

In other words, the invention proposes that the input variable of the controller is the flow of the heat carrier in the generator circuit, and that the control variable of the controller is the output of the heat generator. For this purpose, it is provided that a modulating heat generator which can be regulated with regard to its output is used. In addition, the proposal assumes that room temperature controllers are provided in the rooms, z. B. by the radiator are provided with thermostatic valves, so that in any case the flow rate is automatically changed depending on the temperature. As a heat source for the radiators of the heating system come - purely by way of example - oil or gas boiler in question, or the primary valve in front of a heat exchanger of a district heating supply, or a mixing valve that controls the proportion of the higher heated heat carrier from the generator circuit in the load circuit. The control signal of the flow regulator acts as proposed on the actuator for the power supply of the heat generator.

As heating systems are usually variable-volume systems, the volume flow can be used directly as a measure of the power requirement of a heating system. A change in the volume flow thus says something directly about a change in the current power requirement.

By the proposed method, it is possible to produce the previously non-existent connection from the consumer to the generator circuit of the heating system with simple means. Due to the fact that the power requirement of the system is now known by the measurement of the volume flow, the power of the heat generator can be regulated as required.

First, thus, the heating system can be operated as economically as possible.

Second, the control can be easily installed, since the volume flow can be measured, for example in the boiler room. Wall breakthroughs are therefore not required, either inside the building or to the outside.

Third, the heating system can also be operated by non-trained users / operators in a simple manner by a single position in the sense of "plus / minus" or "colder / warmer" or "more / less" needs to be pressed, and which Defines the target value of the heating power at a certain flow rate. This setting usually only has to be made once based on the design data and then not changed any more. If necessary, however, the heating owner / heating operator can easily do this themselves.

The principle of operation of the proposed procedure is as follows: If the room temperature falls in individual rooms, for example due to a decreasing outside temperature, the radiator valves are opened via the room temperature controller and the flow in the heating circuit increases.

The controller responds to this flow change by increasing the output of the heat generator. As a result, the plant is immediately provided more energy and the heat loss is compensated. If the room controllers close again due to the now rising room temperature, the volume flow decreases and the output of the heat generator is throttled. This control works very sensitive and fast, so that the thermostatic valves can be operated in a particularly favorable operating point of their characteristic. This considerably improves the room temperature control with thermostatic valves with regard to their control accuracy.

Q .

= Wärmeleistung (in W)

ṁ

= Massenstrom des Heizmediums (in kg/h)

c

= die spezifische Wärmekapazität des Heizmediums (in KJ/kg·K)

dt

= Temperaturdifferenz (in K)

About the formula Q. = ṁ · c · dt With

Q.

= Heat output (in W)

m '

= Mass flow of the heating medium (in kg / h)

c

= the specific heat capacity of the heating medium (in KJ / kg · K)

dt

= Temperature difference (in K)

is the power at full flow and the temperature difference known and almost constant over the temperature profile. Prerequisite for this is a hydraulic adjustment of the heating system, which is state of the art and legally prescribed today. Therefore, the mass flow is the only variable in the above formula. In heating technology, with water as the heat transfer medium, the mass flow corresponds with sufficient accuracy to the volumetric flow which can be easily measured, so that in the above formula instead of m correctly V. (for the volume flow in l / h).

The method can also be used with other heat transfer media; only the measured volume flow needs to be offset with a different heat capacity and density.

The functional principle is explained in more detail below using an application example. The numbers used are used by way of example and serve only to illustrate the proposed method:
In a central heating system of a building in the boiler water is heated as a heat transfer medium and transported by a circulation pump to the individual rooms of the building. In the rooms, the water releases its heat energy to the room via radiators. It then flows back to the boiler with reduced temperature and is reheated there.

The result for a house with a heat requirement of 20 kW and design temperatures of 70 ° C flow and 55 ° C return temperature a mass flow of 1146 l / h. When 20 kW are supplied through the boiler at this mass flow, the water leaves the boiler with a 15K higher temperature than before. Due to this direct relationship of the physical quantities mass flow, supplied power and temperature difference, the determination of the mass flow is sufficient to control the boiler output in such a way that the desired temperatures result.

As the thermostatic valves close in the rooms, the mass flow decreases and the heat generator capacity is adjusted accordingly. After a certain period of time, a steady-state condition occurs, in which the rooms have reached their setpoint temperature and the boiler provides exactly the power that is needed. The associated temperature level also adjusts accordingly. For the implementation of the proposed method therefore no temperature must be detected, either inside or outside the building. When using the proposed method hydraulic self-regulation effects are used and integrated into an easy-to-use control.

However, it may be provided to operate a heating system permanently not exclusively as proposed: for example, it may be useful in the Aufheizfall the system after a lowering phase, deviating from the described method to provide a higher power of the heat source available, as the scheme according to the proposed Would provide method. Thus, the heating phase could be significantly shortened so that they could start later and therefore the lowering phase could be extended accordingly. This in turn would lead to an improvement in economic efficiency, because a higher temperature gradient between the temperature inside the building and the outside temperature causes higher heat losses. A longer heating phase therefore results in higher heat losses, since over a correspondingly longer period of time there is a higher temperature in the interior of the building compared to the lowering phase.

Therefore, it may be provided to include beyond the detection of the flow rate and temperatures in the control concept, for example, the return temperature. In the example case described above, a very low return temperature would then be determined during the morning ramp up of the heating system after the night setback, so that despite the low determined flow rate of the heat generator would be adjusted to the delivery of high power. Thus, the inhabited rooms can be heated quickly to a comfortable temperature. If the return temperature then reaches a predetermined, higher value, it can be switched to the proposed method, which allows a demand-driven, economic operation of the heating system.

The installation of the heating system does not have to be complicated by the fact that the return temperature should also be recorded: the flow measurement can be done either in the flow or in the return of the heating system. If it is in the return, a temperature sensor may be provided on the flowmeter, and a cable extending from the flowmeter to the control circuit may serve to communicate both the flow and temperature values.

Even if only the flow rate needs to be detected for the implementation of the proposed method, it may be desirable to provide additional sensors to the heating system. This can be provided in particular for reasons other than for controlling the heat generator: If, for example, the detection of the return temperature is provided for the reason described above, can be made possible by a minor extension of the installation, the calculation of the annual efficiency, namely by means of another temperature sensor and the Flow temperature is detected so that information about the temperature difference and the mass or volume flow can be obtained.

In the case of a heating night reduction can be provided to switch off the pump, by means of which the heat transfer medium circulates through the heating system, so that the consumers and consequently the rooms can be lowered to a lower temperature level than during the day. When the pump is switched off, however, no flow through the generator circuit takes place, so that there is no input variable available for the proposed regulation of the heating system. Therefore, it can be advantageously provided, in the case of a pump shutdown to avoid excessive cooling of the heating system by the pump is automatically started in time intervals and a flow through the generator circuit is effected. This then automatically sets the proposed method in motion, because now again an input for the heating control is available. In the context of the night reduction, however, a lower setpoint value of the heating power than the daytime for the specific volume flow can be set.

It is also conceivable to realize a pure shutdown operation up to a certain outside temperature. This would then be the measurement of the outside temperature required. This procedure is particularly suitable for renovations, since a cable that is usually available can be used to make an outdoor sensor.

Particularly easy and comfortable, however, is the use of more and more enforcing electronic room temperature controller, with which the temperatures of each room are controlled very accurately and on the space a time-dependent lowering mode can be controlled.

At the moment these systems still have the disadvantage that they only intervene on the consumer side and that there is usually no feedback to the heat generator (except for very complex extremely expensive and complicated single-room control systems to be operated with valve position feedback to a data processing unit).

In connection with such systems, the proposed method plays out its strengths, since exactly this connection between the consumer and generator circuit is produced and without further technical effort a direct influence on the heat generation by the volume flow control at the consumers takes place.

Based on the purely schematic representation of the present proposal is explained in more detail below.

The drawing shows a heating system 1 which is a heat generator 2 with a burner 3 having, wherein the heat generator 2 for example, in the basement of a building is arranged. The burner 3 is operated with gas, oil, wood pellets or other fuel and is designed in terms of its performance adjustable as a modulating burner.

In three heated rooms of the building are space heaters 4 . 5 and 6 arranged. The space heaters 4 . 5 and 6 are shown the same due to the schematic representation. However, they can be different, for. B. in terms of design and size. Depending on the heating power requirement of the respective room, influenced by z. B. size, location and windows of the room and design of the respective space heater, the maximum flow rate for each of the space heaters 4 . 5 and 6 set by the entire heating system 1 hydraulically balanced.

Each of the space heaters 4 . 5 and 6 is an electronic or thermostat controlled room temperature controller 24 . 25 and 26 assigned, each having an actuator 34 . 35 respectively. 36 which is actuated in a manner known per se by a motor or by means of an expansion element in order to control the flow through the respectively assigned space heating element 4 . 5 respectively. 6 and thus to influence the temperature in the room in question.

From the heat generator 2 heated water flows as a heat transfer medium through a flow line 7 to the space heaters 4 . 5 and 6 flows through them and flows through a return line 8th with lower temperature than the flow temperature back to the heat generator 2 , so that the heat transfer medium is circulated. The circulation of the heat transfer medium is by means of a pump 9 supported.

One as a heating control 10 designated electronic circuit is with the burner 3 of the heat generator 2 connected, as well as with the pump 9 and a flow meter 11 , which allows the detection of the volume flow of the heat transfer medium. In the illustrated embodiment, the flowmeter is 11 in the return line 8th provided, but it may alternatively also in the flow line 7 Be provided because the flow rates and thus the flow rates in the flow and return are the same.

A signal line 12 runs from the flowmeter 11 for heating control 10 , so that the flow rate in the heating control 10 can be used as their input variable to influence the manipulated variable based on this input variable, namely the power of the heat generator 2 , For this purpose, another signal line 14 provided by the heating system 10 to the burner 3 runs.

If a high heating power is requested in the rooms, the room temperature controllers open 24 . 25 and 26 far, a high flow rate through the space heaters 4 . 5 and 6 to enable. In this case, there is a large volume flow in the heating circuit and it is by means of the flowmeter 11 a high flow rate was measured. The heating control 10 accordingly controls the burner 3 so on, that the heat generator 2 provides a high heating power.

Conversely, the heating control works 10 if the room temperature controller is due to a low heating demand in the rooms 24 . 25 and 26 Close and accordingly in the heating circuit by means of the flowmeter 11 a low flow rate is measured: in this case throttles the heating control 10 the power of the burner 3 so that the heat generator 2 a low heating power provides.

If, due to a night setback or other reasons, the requested heating capacity is so low that the pump 9 can be switched off, there is no flow through the flow line 7 and the return line 8th , so by means of the flowmeter 11 no flow can be measured anymore. In this case, the pump may from time to time 9 be controlled to a flow through the flow line 7 and the return line 8th to enforce, so that then the proposed control behavior of the heating control 10 can be started again. Therefore, another signal line 15 provided by the heating system 10 to the pump 9 runs, so that by means of the heating control 10 the speed of the pump 9 can be influenced, for example, the pump 9 can be turned on.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4211914 C2 [0002]
• DE 3202168 A1 [0011]
• DE 10217272 A1 [0012, 0012]

Claims (3)

Method for controlling a heating system, wherein a heat transfer medium is heated by means of a heat generator to a flow temperature, the heat transfer medium is conveyed by means of a pump to at least one consumer is further circulated back to the heat generator, where it has a return temperature which is lower than that Flow temperature, the flow rate of the heat transfer medium is automatically controlled by the consumer by means of a room temperature controller, the heat transfer medium flows through a so-called generator circuit which passes through the heat generator, and flows through a so-called consumer circuit, which runs through the consumer, and the flow of the heat carrier in the generator circuit determined and used as input of the control, characterized in that the control of the heating system ( 1 ) is carried out on demand, by using only the determined flow of the heat carrier in the generator circuit as an input variable of the control, on the basis of which the control variable of the control, namely the power of the heat generator ( 2 ), wherein a modulating, with regard to its output heating controllable heat generator ( 2 ) is used. A method according to claim 1, characterized in that the heating system ( 1 ) has a plurality of heat consumers and is first hydraulically balanced before the method is carried out according to claim 1. A method according to claim 1 or 2, characterized in that after a shutdown of the pump ( 9 ) the pump ( 9 ) is automatically turned on again at certain time intervals and so a flow of the heat carrier in the generator circuit is effected before the process is performed.

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