DE10057942A1 - Controlling central heating system, involves immediately switching burner again on after switching off if return line temperature falls below defined level or waiting for defined delay period - Google Patents

Abstract

The method involves measuring the temperature in the feed line (3) for a heat transfer medium and/or in the boiler (2) and switching off a burner (11) if a predefined temperature is reached. When the temperature falls to a second lower temperature level the temperature measured in the return line (4) is compared with a predefined temperature level and the burner is immediately switched on if it is below the level, otherwise an additional defined delay period is observed before the burner is switched on again. Independent claims are also included for the following: an arrangement for controlling a central heating system.

Description

The invention is directed to a method and a device for control a central heating system with one circulating in a heating circuit Heat transfer medium that is heated in a boiler by a burner which is switched on and off in the manner of a two-point control, whereby the temperature in the flow of the heat transfer medium and / or in the Boiler measured and when a first, upper temperature level is reached the burner is switched off. The device according to the invention is intended Can be retrofitted to existing heating systems, in particular, without major effort his.

All fossil fuels are of organic origin and therefore only in limited scope available. The discrepancy between one is not increasing amount of raw material on the one hand and a constant or even constant Rising energy requirements, on the other hand, lead to an ever increasing one Shortage that is already clearly noticeable in the oil and is for the End consumers, for example, by increasing the cost of heating oil noticeable. In the long run, therefore, basically a substitute for everyone fossil fuels can be found by one if possible economical energy consumption at least the remaining period if possible be stretched out to allow time for the development of equipment for the production of to gain renewable energies. The most economical use of heating oil is therefore not only in the interest of the individual, but also has a considerable one economic importance. Here are next to Thermal insulation measures on the rooms to be heated as well as in Area of a boiler itself further measures for a particular effective combustion has been proposed. However, it turns out that a considerable heat loss also in the entire heating system and here in particular in the area of the heating medium supply and return lines, by making up a not inconsiderable proportion of the amount of energy used to completely unimportant areas of a building such as cellars, external walls,  Deliver storage rooms etc. This is due to the decentralized arrangement of the Radiators in a building and therefore cannot be used avoid completely. However, this fact gives rise to the position of Task, the resulting energy losses at least as low as to keep possible.

The solution to this problem is achieved by comparing the temperature T _back measured in the return with a predetermined level T _G1 at the time the temperature T _before in the flow for the heating medium or in the boiler drops to a second, lower temperature level T _U is carried out, and if this level is undershot, the burner B is switched on immediately, while otherwise an additional, time-determined or determinable delay time interval τ _{2 is} waited until the burner B is switched on again.

In order not to impair the comfort of the heating system, a distinction is first made in the context of the method according to the invention in the case of the normal continuous heating phase, where only the heat losses emitted on the outer walls of a building are to be regenerated, from the heating phase, where the building or at least individual parts thereof first must be heated to a comfortable room temperature. This distinction is made on the basis of the return temperature of the heating medium, because a maximum amount of heat is extracted from the heating circuit during a heating phase, so that the temperature of the returning heating medium is comparatively low. So that the rooms in question can be heated up in the shortest possible time, additional energy-saving measures are dispensed with during such a phase. If, on the other hand, the heating system is in a largely stable, permanent state, only a small amount of energy is required overall, so that the returning heating medium is relatively warm. In this case, a high dynamic of the heating is not necessary and energy saving measures can be taken instead. In this case, the burner is switched on with a delay compared to the temperature requirement, so that on the one hand a small amount of residual heat is still released from the radiators, while the further cooling rate on the conduit pipes is reduced anyway due to the low temperature level. By forced further circulation of the heating medium, an attempt is made to dissipate stored energy from particularly warm places in the heating system and instead to release it at cooler points. Since the delay time is not temperature-controlled, but is specified in intervals, the heating intensity can be reduced without appreciably influencing the upper and possibly also an average temperature setpoint of the heating control, and thus ideally by the persons concerned, without being recognized. The primary trigger here is a lowering of the temperature value in the heating system, averaged over a time interval, without, however, changing the maximum heating temperature and thus a parameter which is decisive for the well-being of the people living in the rooms in question. The length of the delay time interval τ _{2 is} largely dependent on the individual characteristics of the building to be heated in general and the heating system in particular. This delay time interval can therefore be preselected individually or calculated according to an individually influenceable pattern.

It has proven to be advantageous that a timer Z is started to determine the delay time interval τ ₂ when the burner B is switched off and is stopped when the temperature T _before drops in the flow of the heat transfer medium or in the boiler to a second, lower temperature level T _U , and that a variable proportional to this time interval τ ₁ is multiplied by an adjustable parameter K in order to obtain a corresponding measure for the delay time interval τ ₂ to be waited for. Here, the invention is based on the knowledge that the cooling phase in a building or part of a building is approximately inversely related to the heating power currently required. Because a long cooling phase shows that, for example, due to increased outside temperatures, due to good insulation, etc., only little heat is lost and must therefore be replaced. A rapid cooling rate, on the other hand, is caused, for example, by an external drop in temperature or by other influences which draw excessive energy from the building. In this case, the delay time must be reduced so that no unpleasant, further cooling of the rooms concerned takes place during the delay time. This adjustment of the delay time can be carried out continuously in the simplest way by measuring the cooling time interval as a measure of the cooling rate and multiplying it by a constant but individually adjustable parameter to form an individual delay time. By adjusting this proportionality factor, an adjustment to the local conditions can be made.

Further advantages result from the fact that the delay time interval τ _{2 is} limited. Such a limitation ensures that the delay time interval τ ₂ does not increase to impermissibly high values after the heating has been idle for a long time, for example when it is switched off during the summer months.

The invention also offers the possibility that when the burner B starts after the delay time interval τ _{2 has} elapsed, a second timer is started and stopped as soon as the temperature T _before in the flow of the heat transfer medium or in the boiler reaches the second, lower temperature level T _U again has to determine a third time interval τ ₃ . The length of this third time interval τ ₃ can be evaluated in the context of the method according to the invention in order to obtain a conclusion as to how great is the increase in the burning time due to the insertion of the switch-on delay. In the context of a hardware-wired circuit, this can be a further component which, like the timing element, is triggered to determine the time interval τ ₁ on certain start and stop events. In the case of a software implementation, the calculation of the time interval τ ₁ is of course carried out by the same circuit components as the calculation of the time interval τ ₃ .

The invention can be further developed in such a way that a third timer is started as soon as the temperature T _before in the flow for the heating medium or in the heating boiler has reached the second, lower temperature level T _U again, and is stopped as soon as the burner B reaches it of the first, upper temperature level T _{O is} switched off in order to determine a fourth time interval τ ₄ . This fourth time interval τ ₄ contains a statement as to how long the burning time would have been in the event of an instantaneous switch-on, and is therefore included in any profitability calculations that may be carried out automatically.

Another feature according to the invention is that from the measured values τ ₁ . , , τ ₄ an energy saving due to the delayed burner activation is calculated. Naturally, this calculation could also be carried out with hardware-implemented components, for example in the manner of an analog computing circuit; however, it is advisable to use a programmable module for this, since it can work far more precisely and reliably.

According to the invention, it is further provided that the energy saving is based on the Energy consumption without delayed burner activation. By a such relationship between energy saving and "normal" Energy consumption, both in the form of a fraction and in the form of Percentages can be specified is in many cases more descriptive than that Output of an abstract energy value that is lacking knowledge of relevant conversion factors are difficult for some people can be assessed.

It has been proven that the energy saving µ obtained is calculated using the following formula:

This formula only applies to those known at the end of a burner cycle Sizes back and can be determined with simple, arithmetic functions become; it is a dimensionless quantity, the fraction the energy saving, based on the original, not reduced Energy requirement corresponds. If the percentage is given, it is for µ to multiply the determined value by a factor of 100.

The invention can be supplemented by the fact that the currently calculated energy saving is shown on a display element. This can preferably be an alphanumeric display on which a multi-digit decimal number can be read. In order to avoid strong fluctuations in the displayed value, averaging can be carried out in each case over several previous burner cycles, preferably with a weighting of the individual μ-values with the relevant cycle duration τ ₁ + τ ₂ + τ ₃ + τ ₄ , in order to achieve the to get exact value.

The idea of the invention allows further development such that during the time interval τ _{1 of} the cooling phase until the start of the delay time, the difference between the temperature T _vor in the flow of the heat transfer medium or the boiler and the temperature T _zurück in the return line is determined at least at regular intervals, and that a pump P circulating the heat transfer medium is switched off for a predetermined time interval if the temperature difference does not exceed a predetermined, possibly adjustable value T _G2 . If a low temperature difference between these measuring points indicates that the heating medium has scarcely cooled down on its way through the heating system, the circulation pump can be stopped for time intervals of, for example, a few minutes in order to give the heating medium in the radiators the opportunity to to exchange its energy more intensively with the ambient air. As a result, the temperature in the return line is reduced somewhat and the energy loss is reduced in this area. If, on the other hand, excessive cooling within the piping system was detected during the normal cooling phase of the heating medium, the circulation pump operation must not be interrupted accordingly, so that the warm heating medium flowing in can replace the energy given as far as possible and improve the circulation evenly Temperature distribution is achieved in the entire system.

It is within the scope of the invention that the circulation pump P runs continuously during the remaining time intervals τ ₂ , τ ₃ and τ ₄ . This continuous operating mode of the circulation pump results from the consideration that the heating medium should be circulated as intensely as possible during the burning period τ ₃ , τ ₄ , so that it is heated up as completely as possible and not only in the boiler. During the delay time τ _2, on the other hand, the circulation of the heating medium should transport the warm medium still in the boiler to the specially cooled points within the piping system in order to cover the increased heating requirements there and thus prevent the occurrence of "cold holes" within an apartment , As a result, the various rooms supplied by the heating in question are "short-circuited" in terms of heat technology and accordingly act like an enlarged heat reservoir, the comparatively large heat capacity of which results in a uniformly low cooling phase everywhere.

A device for controlling a central heating system after the The method according to the invention comprises, in addition to an output connection OUTB for the burner has an input connection TRÜCK for one with the return coupled temperature sensor. Unlike a variety of regulations, those with sensors in the area of the flow for the heating medium or the Working boiler itself is for the distinction according to the invention between a heating phase and the normal permanent state of the heating Sensor in the return line is particularly advantageous because of its output signal less by the heat output of the burner than by the  Heat demand in the heated rooms is influenced and therefore a far allows better conclusions about the current situation than a near the burner installed temperature sensor.

The invention is further characterized by an input connection IN for a higher-level control of the central heating system, for example Safety shutdown. This feature makes it possible to get a Retrofit device according to the invention on almost any heater by between the output of the existing control unit and the Burner input is switched on and in such a case in particular Shutdown commands from the then higher-level control system take over and preferably passes on without delay to the burner, so that, for example, emergency or Safety shutdowns when one in the area of the boiler responds arranged safety sensor can be reliably caused. Still exists often a considerable saving potential, especially with older heating systems that the device according to the invention is used here with particular advantage can be. In such a case, this can also be done in the previous control provided controller including the temperature setpoint specification there continue to be used, so that the handling of such a retrofitted Heating system hardly changed. If the adjustable parameters of the retrofit device according to the invention are entered by the installer, the user does not have to deal with the new device at all.

The device according to the invention comprises an input connection T _before for a temperature sensor coupled to the flow of the heat transfer medium or the boiler. Such a connection enables the device according to the invention to be able to track the temperature rise and fall in the lead itself, so that the heating phase during which the temperature is raised again to the temperature value present during the request for the burning activity is increased over the entire burning time is distinguished from the actual heating phase, in which the temperature in the heating medium circuit is raised to the upper burner shutdown threshold. This in turn makes it possible to calculate the absolute and also the related energy savings per burner interval relatively precisely.

Part of the device according to the invention is formed by a first comparator, which is coupled on the input side to the input connection TRÜCK for the temperature sensor on or in the return line of the heat transfer medium on the one hand and an optionally adjustable reference value T _G1 on the other hand, and whose output signal is inverted in one branch and in another Branch is not inverted coupled to burner B to activate it. It is up to this first comparator to determine whether the prerequisites for looping in a switch-on delay between the controller output signal and the ignition device for the burner are present. Depending on whether the comparator detects an over or differentiation of the reference value T _G1 when comparing the temperature in the return line, the respectively assigned branch of the comparator output signal is then switched on and thus the time delay of the switch-on signal is optionally activated or not.

The invention has an advantageous embodiment in that the output branches of the first comparator are locked by the output signal of a second comparator, which on the input side has the temperature sensor on or in the flow line of the heat transfer medium or the boiler on the one hand and at least one optionally adjustable reference value T _O , T _U on the other hand is coupled. This interconnection means that the burner can only be activated if the temperature in the flow for the heating medium is below an upper limit value T _O. Accordingly, this second comparator has the function of a temperature controller, and by using an upper and a lower temperature limit value T _O , T _U, a hysteresis can be realized which gives the controller a characteristic in accordance with a two-point temperature controller.

A further optimization can be achieved in that the output branches of the first comparator by the output signal of the parent Control or are locked by a signal derived therefrom, where appropriate  also the second comparator as part of a higher-level control can be realized. Control units are often included in existing regulations provided according to the most diverse principles built controllers Use of the device according to the invention can continue to be used. In this case, often only the controller output signal can be used tap in which the controller function as well as the emergency shutdown among the various requirements are combined. In this case is in the context of the inventive method to an independent Control dispenses and the controller output signal of the existing control and / or control unit used. In this case, either one in the additional comparator according to the invention existing control comparator shut down be, or such a need for such special applications at all not to be provided.

To perfect the construction according to the invention, it can be provided that the output signal of the second comparator and / or the output signal of the higher-level controller is coupled directly and once via a switch-on delay τ ₂ to the control output OUTB for the burner. This double coupling fulfills several functions: On the one hand, the direct coupling and thus the instantaneous control of the burner take effect at low return temperatures (TRÜCK <T _G1 ), while the direct coupling in the case of high return temperatures (TRÜCK <T _G1 ) takes place through an AND Linking with the delayed signal ensures that a switch-off edge of the higher-level regulation and / or control reaches the burner control without delay.

An advantageous arrangement can be found in that the delay time τ _{2 can be} changed. By changing the delay time τ ₂ it is avoided that the temperature in the rooms to be heated fluctuates with a fixed cycle, which would be easily recognizable by a person by his internal clock; rather, a constant fundamental cycle can be avoided by a certain irregularity in the delay time τ ₂ .

In addition, by varying the delay time τ _{2, it is} possible to react to changing heating conditions and, in particular, requirements.

A not unimportant element of a device according to the invention is at least one timer Z, which is coupled to the higher-level control and / or to output signals of the temperature sensors in order to measure time intervals τ ₁ , τ ₃ and / or τ ₄ . These time intervals, which are defined according to the criteria defined above, give the controller according to the invention information about the current state of the heating or the rooms to be heated, and thus allow the controller to vary, for example, the delay time τ ₂ or the current energy saving to calculate.

The timer τ ₂ determining the switch-on delay is preferably coupled to the output of a timer Z via an optionally adjustable proportional member K. Such a proportional factor, which is easy to implement, already provides an excellent adaptation of the delay time to the current heating requirements, since the delay time is reduced accordingly during a rapid cooling phase, so that the temperature in the heated rooms does not drop too much.

Through at least one memory for storing measured time intervals τ ₁ , τ ₃ , τ ₄ , information obtained sequentially is kept ready for a later energy calculation. If the same timer Z is used to determine the different and successive time intervals τ ₁ , τ ₃ , τ _4, the measurement results must be temporarily stored so that at the end of a burner cycle all time intervals τ ₁ , τ ₃ , τ ₄ and possibly the resulting delay time τ _{2 is available} for further calculations.

A valuable component of the device according to the invention is a Arithmetic unit for calculating the current energy savings. Such one Arithmetic unit can be easily done using a microprocessor  realize who is able, depending on the specified control program to perform a wide variety of tasks. Unless - as the invention continues provides - the timer Z, for example, as with a constant pulse frequency clocked counter is realized, the zero before the time interval to be measured is set and similar to a stopwatch at the beginning of the relevant time interval started and stopped at the end, the information lies on the time interval τ in the form of digital values and these can be with standard commands such as addition implemented in modern microprocessors, Multiplication, division without major programming effort to determine the Link current energy savings.

The functionality of the device according to the invention is further increased by an alphanumeric display device for displaying the current energy savings. The operator of a heating system supplemented by the device according to the invention is continuously informed of the achievable savings by means of a readable output of the current energy savings. The most diverse additional information can also be displayed, such as the energy savings averaged over a specified period of time, such as an hour or a day, and the energy saved can be displayed as an absolute value or as a percentage, based on the energy value to be used without delay technology. It is also possible to output internally set parameters, for example the proportionality factor K or the switching limit values T _G1 , T _G2, on request, so that an interactive setting and / or adjustment of such parameters is possible. If, for example, the currently set parameters are stored for longer-term mean values of energy savings, e.g. daily values, an operator and / or the arithmetic unit itself is able to recognize the effect of parameter changes on energy savings and, if necessary, to optimize the parameter settings , In the context of such an optimization program, it can be provided that a (small) parameter change is carried out at regular intervals even without manual adjustment of the parameters, in order to research the system reaction and, based on this, to propose or carry out parameter optimization.

An output connection OUTP for controlling one is of great advantage Circulation pump for the heat transfer medium P. The control of a Circulation pump for the heat transfer medium is the responsibility of delay technique according to the invention is of increased importance. Because here On the one hand, clocking can result in considerable energy savings can be achieved, on the other hand, the circulation pump both during the Delay time as well as during the subsequent heating phase be operated continuously for optimal temperature compensation between the rooms to be heated. Most of it all for such control of the circulation pump for the Heat transfer medium required information in the The device according to the invention is present anyway, it can be used Realize additional functionality with minimal additional effort.

Finally, it is in accordance with the teaching of the invention that the control output OUTP for the circulation pump for the heat transfer medium P as a switching output to control a between the supply voltage and the electrical Connections of the circulation pump for the heat transfer medium switched-on relay is formed. As with existing heating medium systems the most varied types of pumps are used, e.g. Two-phase or three-phase pumps, the invention provides for each existing pump to use a suitable relay, which then each can be actuated with an armature coil. In order also for the relay actuation To be able to design the required nominal voltage variably, the output of the Control device according to the invention be designed as a switch, the one hand with the relevant relay coil and on the other hand with the one suitable for this Power supply can be coupled.  

Other features, details, advantages and effects of the invention will be apparent from the following description of preferred embodiments of the Invention and with reference to the drawing. Here shows:

Figure 1 is a schematic circuit diagram of a heating system.

Fig. 2 is a block diagram of an inventive control device; such as

Fig. 3 is a time chart showing the temperature changes in the heating system of Fig. 1 when using the controller in FIG. 2.

The heating system 1 of Fig. 1 comprises a boiler 2 , which is coupled via a flow line 3 for the heating medium and a return line 4 for the heating medium with a variety of radiators, not shown, installed in the rooms to be heated. The water circulating in this pipe system 3 , 4 is circulated by a pump 5 . On the flow line 3 , in the example shown, a temperature sensor 6 for the flow temperature T _is arranged downstream of the circulation pump 5 , the electrical output signal 7 of which is coupled to a control and regulating device 8 of a conventional type. This was originally connected with its output 9 directly to a corresponding input 10 of the burner so that the boiler 2 to thereby 11 to control the burner of the boiler 2 and a firing circuit connected upstream.

A preferred circuitry structure of the control and regulating device 8 is shown in FIG. 2 above. It can be seen that the output signal 7 of the flow temperature sensor 6 is compared by a comparator 12 with a lower switching threshold T _{U in} order to switch on the burner 11 with a high level at the output 9 , and a comparison is also made with an upper temperature limit value T _O in order to switch off the burner 11 with a low level at the output 9 . The switching thresholds T _U , T _O can be implemented in different ways, and these limit values can preferably be set.

Usually, one or more switch-off switches 13 are also looped into the signal path 9 , which can be arranged within the boiler 2 and can be designed, for example, as an emergency switch-off switch or as an excess temperature switch or as other safety cut-off switches. If one of the switches 13 is opened, the potential on the output line 9 drops to ground potential as a result of an internal resistance 14 and thus causes the burner 11 to be extinguished immediately.

The operation of such a conventional heating control system is shown in part in dashed lines in FIG. 3: It can be seen that the flow temperature T _before the heating medium only fluctuates between the two limit values T _U and T _O , in the present example the heating phase with τ ₄ and the Cooling phase is designated τ ₁ . These individual periods fluctuate depending on the heating requirements on the radiators and the displayed cooling phase τ ₁ corresponds to a very high heating requirement, for example when heating up a cooled room for the first time. It can be seen that the flow temperature T _vor fluctuates with a comparatively short frequency, and in the example shown the heating phase τ _{4 is} even greater than the cooling phase τ ₁ .

According to the teaching of the invention, a further control device 15 is switched on in the signal path from the output 9 of the control and regulating device 8 to the burner connection 10 of the boiler 2 such that the output signal 9 of the original control and regulating device 8 with the input IN of the additive - Control unit 15 is connected, while its output OUTB is connected to the burner connection 10 . However, this interconnection is not sufficient for the function according to the invention. Rather, an additional temperature sensor 16 is provided in the return line 4 for the heating medium, and this is coupled to the signal input TRÜCK of the additional control unit 15 via a two-pole signal line 17 . With this minimum circuit, the additional control unit 15 is able to control the heating system 1 in a more energy-saving manner than the conventional control and regulating unit 8 can under certain conditions. For this purpose, the sensor output signal is compared 17 by a comparator 18 with an internal, adjustable constant voltage T _G1 to display by a high or low level at its output 19 if the voltage measured at the reflux 4 16 temperature T _back is greater than a reference value (TRÜCK <T _G1 ) or less than this reference value. If the return temperature T _back has dropped below the temperature T _G1 , this indicates an enormous heating requirement in the rooms in question, and in this case it is not possible to save energy in the context of heating system 1 , but rather by mediating the inverted 20 comparator output signal 19 , which arrives at an input 22 of an AND gate 23 via a downstream OR gate 21 , from which the input signal IN is directly switched through to the burner control output OUTB, so that the controller output signals 9 act directly on the burner 11 without any change.

However, if the return temperature T _back not fallen below the limit temperature T _G1, the auxiliary control device 15 causes a power-saving modification of the original control signal. 9 For this purpose, the output signal 19 of the comparator 18 is connected in an uninverted form to an input 24 of a further AND gate 25 , the second input 26 of which is fed by the input signal IN of the additional control device 15 via a delay module 27 . If the potential at the input 24 of the AND gate is high due to a lack of a sufficient temperature in the return line 4 , the delayed 27 input signal IN can pass through the AND gate 25 and from there via a further input 28 of the OR gate 21 and the downstream AND gate 23 reach the burner input 10 as long as the input signal IN also has a high level. It is thereby achieved that, at a high temperature in the return line 4, the burner switch-on signal IN delayed 27 by the delay time τ ₂ leads to the burner 11 being switched on, while the switch-off edge by the second input 29 of the AND gate 23 leads to an immediate switch-off of the burner 11 leads.

In the embodiment shown, the delay time τ _{2 is} not constant, but a function of the duration τ _{1 of} the cooling phase. For this purpose, the input signal IN, which has a low level during this phase, is fed inverted 30 to a counter 31 , which is started on the positive edge of its input signal and stopped on the negative edge. The counting result 31 , which is proportional to the cooling phase τ _1, is multiplied 33 by an adjustable 32 constant K and in this way reaches the delay module 27 , which uses the value 34 calculated in this way as the delay time.

When the burner 11 is operated in this way, the time profile of the temperature T _before in the flow line 3, shown as a solid line in FIG. 3, results. This is followed by the normal cooling phase τ ₁ , which ends when the temperature T _{U is} undershot, followed by the calculated 30-34 delay time τ ₂ until the output signal OUTB of the additional control unit 15 then switches over and thus activates the burner 11 . A heating-up phase begins immediately, but is now extended by an additional interval τ ₃ , which is necessary in order to initially heat the further-cooled heating liquid down to the lower temperature level T _U. Only then does the normal heating phase τ ₄ follow, which is required to raise the temperature level from T _U to T _O. As can be seen in FIG. 3, the duration of a burner cycle is now extended by τ ₂ and τ ₃ to τ ₁ + τ ₂ + τ ₃ + τ ₄ . A calculation example should explain these relationships:
With a set value of K = 0.5, the cooling phase τ _{1 is} equal to 13.25 minutes, which results in a delay time τ ₂ of 6.625 minutes. The resulting additional heating phase τ ₃ is 1.5 min, and the normal heating phase τ ₄ is 5.0 min. This results in the following relationship:

Using the formula:

thus arises for the additional control device according to the invention achieved energy saving µ a value of 10.05%.

The invention further provides for the determination of this value, the additional and standard heating times τ ₃ and τ ₄ also to be measured and supplied together with τ ₁ and τ _{2 to} an arithmetic unit, which determines the energy saving μ according to the above formula and then to the calculated value an alphanumeric display unit. To avoid major fluctuations in this value, averaging can be carried out over several previous burner cycles, in which case the actual burner cycle times should be weighted.

In the context of the heating control system according to the invention, the circulation pump 5 is of greater importance since it is its task to bring about a uniform distribution of the temporary energy deficit to all rooms coupled to the heating during the delay time τ ₂ by means of a maximum degree of circulation within the heating circuit 3 , 4 thereby avoiding excessive cooling of a single room. Therefore, the pump 5 must start at the beginning of the delay time τ ₂ and should then remain active until the end of the burning time τ ₄ , since it is also their responsibility to ensure that the entire heat transfer medium within the heating circuit 3 , 4 is heated as evenly as possible.

During the normal cooling phase τ ₁ , the pump 5 can, however, be temporarily switched off to save energy if this is only possible with a moderate heating requirement. This is determined in the context of the additional device 15 according to the invention by means of a subtractor 35 , the two inputs TVOR and TRÜCK of which are coupled to the temperature sensors 6 , 16 in the supply and return line 3 , 4 for the heating medium, so that one of them is connected to its output 36 Temperature difference TVOR - TRÜCK proportional signal can be tapped, which is compared in a further comparator 37 with a second temperature limit T _G2 .

The output 38 of this comparator 37 , like the input signal IN of the additional control unit 15, is applied in inverted form to each input of a further AND gate 39 , so that its AND condition is only fulfilled if τ ₁ during the cooling phase Temperature condition TVOR - TRÜCK <T _{G2 is} not fulfilled. In this case, the output signal 40 of the AND gate 39 reaches the output OUTB for the control of the pump 5 via a multivibrator 41 and a downstream OR gate 42 . This signal 43 controls a relay 44 in the supply line to the pump 5 , which then switches on and off in accordance with the switching frequency and the duty cycle of the multivibrator 41 . As a result, the flow rate in the heating circuit 3 , 4 is reduced, the heat transfer medium stays longer in the radiators and can cool down more there, so that the return lines 4 have a lower temperature level and consequently the heat loss on the return line 4 is further reduced.

If, on the other hand, the return temperature TRÜCK is more than T _G2 below the supply temperature TVOR, or if the input signal IN of the additional control unit 15 shows a logic high level, the output signal of the AND gate 39 becomes negative, and this signal passes through an inverted branch 45 and the downstream OR gate 42 to the output OUTB, so that in this case the pump 5 runs continuously.

Because the relay 44 is connected between the previous power connection 46 of the boiler 2 and the pump 5 , an AND operation is effected, so to speak, with the safety shutdowns of the boiler 2 taking effect at the output 46 .

Claims (26)

1. Method for controlling a central heating system ( 1 ) with a heat transfer medium circulating in a heating circuit ( 3 , 4 ), which is heated in a boiler ( 2 ) by a burner ( 11 ), which is switched on and off in the manner of a two-point control, wherein the temperature T _before in the flow line ( 3 ) for the heat transfer medium and / or in the boiler ( 2 ) is measured and the burner ( 11 ) is switched off when a first, upper temperature level 10 is reached, characterized in that at the time of the sinking the Temperature T _before in the flow ( 3 ) of the heat transfer medium or in the boiler ( 2 ) to a second, lower temperature level T _U a comparison (18) of the temperature T _back measured in the return flow ( 4 ) is made with a predetermined level T _G1 , and falling below this level, the burner ( 11 ) is switched on immediately, while otherwise an additional, timed or best immable delay time interval τ _{2 is} waited until the burner ( 11 ) is switched on again. 2. The method according to claim 1, characterized in that τ started when switching off of the burner (11), a timer (31) and in the lowering of the temperature T _present in the flow (3) the heat transfer medium or in the boiler ₂ for determining the delay time interval ( 2 ) is stopped at a second, lower temperature level T _U , and that a quantity ( 31 ) proportional to this time interval τ ₁ is multiplied ( 33 ) by an adjustable ( 32 ) parameter K in order to obtain a corresponding measure ( 34 ) for what is to be awaited Obtain delay time interval τ ₂ . 3. The method according to claim 2, characterized in that the delay time interval τ _{2 is} limited. 4. The method according to any one of claims 1 to 3, characterized in that when the burner ( 11 ) starts after the delay time interval τ _2, a second timer is started and stopped as soon as the temperature T _before in the flow ( 3 ) of the heat transfer medium or in the boiler ( 2 ) has reached the second, lower temperature level T _U again in order to determine a third time interval τ ₃ . 5. The method according to any one of the preceding claims, characterized in that a third timer is started as soon as the temperature T _before in the flow ( 3 ) of the heat transfer medium or in the boiler ( 2 ) has reached the second, lower temperature level T _U again, and is stopped as soon as the burner ( 11 ) is switched off when the first, upper temperature level T _O is reached in order to determine a fourth time interval τ ₄ . 6. The method according to any one of the preceding claims, characterized in that from the measured values τ ₁ . , , τ ₄ an energy saving caused by the delayed ( 27 ) activation of the burner ( 11 ) is calculated. 7. The method according to claim 6, characterized in that the energy saving µ is based on the energy consumption without delayed activation of the burner ( 11 ). 8. The method according to claim 7, characterized in that the related energy saving µ is calculated as follows:
9. The method according to any one of claims 6 to 8, characterized in that the currently calculated energy saving µ on a display element is pictured. 10. The method according to any one of the preceding claims, characterized in that during the time interval τ _{1 of} the cooling phase to the start of the delay time τ ₂ at least at regular intervals the difference ( 35 ) between the temperature T _before in the flow ( 3 ) of the heat transfer medium or the boiler ( 2 ) and the temperature T _back in the return line ( 4 ) is determined, and that a pump ( 5 ) circulating the heat transfer medium is switched off ( 41 ) for a predetermined time interval if the temperature difference ( 35 ) reaches a predetermined, possibly adjustable value T _G2 does not exceed. 11. The method according to claim 10, characterized in that the circulation pump ( 5 ) runs continuously during the remaining time intervals τ ₂ , τ ₃ and τ ₄ . 12. Device ( 15 ) for controlling a central heating system ( 1 ) with a in a heating circuit ( 3 , 4 ) circulating heat transfer medium, which is heated in a boiler ( 2 ) by a burner ( 11 ), according to a method according to any one of the preceding claims , with an output connection OUTB for the burner ( 11 ), characterized by an input connection TRÜCK for a temperature sensor ( 16 ) coupled to the return line ( 4 ) of the heat transfer medium. 13. Apparatus according to claim 12, characterized by an input connection IN for a higher-level control ( 8 ) of the central heating system ( 1 ), for example for the purpose of safety shutdown ( 13 ). 14. Device according to one of claims 12 or 13, characterized by an input connection TVOR for a with the flow line ( 3 ) of the heat transfer medium or the boiler ( 2 ) coupled temperature sensor ( 6 ). 15. Device according to one of claims 12 to 14, characterized by a first comparator ( 18 ) on the input side with the input connection TRÜCK for the temperature sensor ( 16 ) on or in the return line ( 4 ) of the heat transfer medium on the one hand and an optionally adjustable reference value T _G1 coupled on the other hand, and whose output signal ( 19 ) is inverted ( 20 ) in one branch and non-inverted ( 24 ) in another branch is coupled to the burner ( 11 ) to activate it. 16. The device according to claim 15, characterized in that the output branches ( 20 , 21 ) of the first comparator ( 18 ) are locked by the output signal ( 9 ) of a second comparator ( 12 ), the input side ( 7 ) with the temperature sensor ( 6 ) is coupled to or in the flow line ( 3 ) of the heat transfer medium or the boiler ( 2 ) on the one hand and at least one optionally adjustable reference value T _O , T _U on the other hand. 17. Apparatus according to claim 15 or 16, characterized in that the output branches ( 20 , 24 ) of the first comparator ( 18 ) are locked by the output signal ( 9 ) of the higher-order controller ( 8 ) or a signal (IN) derived therefrom, wherein if necessary, the second comparator ( 12 ) can also be implemented as part of a higher-level control ( 8 ). 18. Apparatus according to claim 16, characterized in that the output signal ( 9 ) of the second comparator ( 12 ) and / or the output signal ( 9 ) of the higher-level controller ( 8 ) once directly ( 29 ) and once via a switch-on delay ( 27 ) the control output OUTB for the burner ( 11 ) is coupled. 19. Apparatus according to claim 18, characterized in that the delay time τ _{2 can be} changed. 20. Device according to one of claims 12 to 18, characterized by at least one timer ( 31 ), which is coupled to the higher-order controller ( 8 ) and / or to output signals ( 7 , 17 ) of the temperature sensors ( 6 , 16 ) by time intervals To measure τ ₁ , τ ₃ and / or τ ₄ . 21. Apparatus according to claim 19 in conjunction with claim 20, characterized in that the timer ( 27 ) determining the switch-on delay τ _{2 is} coupled to the output of a timer ( 31 ) via an optionally adjustable ( 32 ) proportional member ( 33 , K) ( 34 ) is. 22. Apparatus according to claim 20, characterized by at least one memory for storing measured time intervals τ ₁ , τ ₃ , τ ₄ . 23. The apparatus of claim 22, characterized by an arithmetic unit for Calculation of current energy savings. 24. Device according to claim 23, characterized by an alphanumeric Display device for displaying the current energy savings. 25. Device according to one of claims 12 to 24, characterized by an output connection OUTP for controlling a circulation pump ( 5 ) for the heat transfer medium. 26. Apparatus according to claim 25, characterized in that the control output OUTP for the circulation pump ( 5 ) for the heat transfer medium is designed as a switching output for controlling a relay ( 44 ) switched on between the supply voltage ( 46 ) and the electrical connections of the circulation pump ( 5 ) ,