DE3702080A1 - Method for controlling the switching of a heat consumer between a heat source heated with fuel or electricity and a heat pump, and device for implementing the method - Google Patents

Abstract

Method for controlling the switching of a heating system between a flow-temperature-regulated boiler and a return-temperature-regulated compression heat pump. When switching over from heat-pump operation to boiler operation, a calculated flow-temperature setpoint (TVsum), the actual flow temperature (TVium), and the actual return temperature (TRium) are measured, calculated and stored. From the actual values of the flow and return temperatures (TVi, TRi), the difference um is computed and stored. During boiler operation, the flow-temperature setpoint TVs and the difference between the actual values TVi and TRi are determined, and the heating system is switched back to the heat pump if the flow-temperature setpoint TVs computed during boiler operation is smaller that the setpoint TVsum stored when switching over from heat-pump operation to boiler operation, and the difference calculated during heat-source operation is less than the difference um stored when switching over.

Description

The present invention relates to a method to control the switching of a heat absorbing consumer between a fuel or electrical Electrically heated heat source and one Heat pump according to the generic terms of the subordinate Claims or to a facility for implementation of the procedure.

A fuel-heated heat source can be used here Continuous or circulating water heater as well as a gas or oil-fired boiler or an electrically heated one Water heaters are understood, and the term Heat pump includes all types of absorption, absorption or compression heat pumps, regardless of  the type of drive unit (oil or gas burner or Gas engine or electric motor). Under the heat absorbing Consumer can use both a heating system in the form of a large number in parallel and / or in series horizontal radiators and convectors as well as underfloor heating or a domestic hot water tank to be charged or a combination of the alternatives just described or a water heater for preparation warm domestic water can be understood.

A large number of bivalent heating systems have become known, where such a heat absorbing consumer up to a certain one heat pump operation permissible temperature is coupled to the heat pump, to fall below such a limit temperature which is no longer profitable heat pump operation it is possible to switch to the heat source. If this is a central heating system, so the switching of the heating circuit of the central heating system usually depending on the Outside temperature, because you can assume that at outside temperatures of 0 ° or colder than Evaporators do not have sufficient power in the Heat pump circuit can be done more.

Since such switching devices are increasingly microprocessors  and operate their peripherals, it is possible, the switching criteria much more differentiated to specify.

The present invention is based on the object the heat-absorbing consumer then on the with a flow or return temperature control Heat pump with previous return or switch back flow-controlled heat source operation, if it is ensured that this heat pump operation is promising. It is essential that a return temperature control for heat pump operation, in addition, a flow temperature control for heat source operation or vice versa.

The solution to the problem lies in the characteristic Features of the two independent claims. The fourth claim gives parallel to this Features to perform the procedure.

Further embodiments and particularly advantageous further developments of the invention are explained object of remaining sub-claims respectively opposite from the following description the reference to FIG. One to five one embodiment of the invention.

Show it:

Fig. One is a diagrammatic schematic diagram of a central heating,

Figs. two the structure of the control device as a block diagram,

Fig. Three is a graph and the

Fig. Four and five another diagram.

In all five figures, the same reference numerals mean in each case the same details.

The central heating system 1 of FIG. One made of a heat-receiving consumer 2, which may be a plurality of parallel and / or in series opposing radiators or convectors, as well as a floor heating system without a domestic water storage tank, via a consumer supply line 3, in which a Circulation pump 6 driven by a motor 4 is connected to a combination of two heat generators 8 and 9 , one of which is designed as a boiler 8 , the other as a heat pump 9 . The heat source 8 can be a gas or oil-fired boiler, a likewise heated circulating water heater or an electrically heated instantaneous heater, the heat pump 9 can be designed as an absorption, absorption or compression heat pump, in the case of the absorption or absorption heat pump it can be a heated with gas or oil, in the case of the compression heat pump, a heat pump driven by a combustion or electric motor.

The return line 6 is connected upstream of a branch point 10 to a return temperature sensor 11 which is connected to a control and regulating unit 13 via a measuring line 12 .

Downstream of the branch point 10, a heat pump return line 14 or a heat source return line 15 branch off, which lead through the heat-emitting heat exchangers 16 and 17 of the two elements and which continue as heat source or heat pump supply lines 18 and 19 and to a 3-way - Guide switch valve 20 , which is controlled by a servomotor 21 , which receives control signals from the control and regulating unit 13 via a line 22 . The 2-way valve 20 is constructed such that either the heat source 8 or the heat pump is switched to the consumer supply line 3 9, wherein the consumer's supply line 3 is connected to the connection of the output of the 3-way valve.

The motor 4 of the circulating pump receives its energy via a control line 23 from the control and regulating unit 13 , the same applies to the heat source 8 , which has a burner 24 , which is fed via a gas line 26 provided with a solenoid valve 25 , the solenoid valve has an electromagnet 27 which can be controlled by the control unit via a control line 28 . The heat pump 9 is designed as a compression heat pump, the motor 29 of the compressor 30 is likewise connected by means of a control line 31 to the control and regulating device, which also controls the expansion valve 33 of the heat pump via a line 32 . The heat pump also has an evaporator 34 through which the outside air passes. The temperature of the outside air is sensed by a temperature sensor 35 , which is connected to the control and regulating unit 13 via a measuring line 36 .

The control and regulating unit 13 are assigned target value transmitters 37 for the return temperature and 38 for the supply temperature. It is particularly provided that the target value of the flow temperature is specified and varied as a heating curve depending on the outside temperature.

A flow temperature sensor 39 is connected to control unit 13 via a line 40 .

The structure and function of the control and regulating unit 13 can be seen from FIG .

The control and regulating unit 13 contains two regulators 41 and 42 , of which the regulator 41 is a return temperature regulator and the regulator 42 is a flow temperature regulator. The return temperature sensor 11 is connected to the return temperature controller 41 , its target value transmitter 37 is acted upon by the outside temperature sensor 35 , that is to say the target value of the controller is carried out in accordance with the prevailing outside temperature. The flow temperature controller 39 is connected to the flow temperature controller 42 , and the set value transmitter 38 is also connected to it, the set value of which is likewise guided by the outside temperature sensor 35 . Both controllers therefore either control the return temperature or the supply temperature in accordance with a setpoint that is based on the outside temperature. This target value does not necessarily have to be guided by the outside temperature, it is also possible to have a dependency in which the outside temperature is one of several variables; manual setting would also be conceivable, as well as keeping the target value dependent on the room temperature of a selected test room and mixtures of all these settings.

A further line 44 branches off from line 43 , which connects the return temperature sensor to controller 41 , which leads to a changeover switch 45 , which is used to switch from heat pump to heat source operation. This changeover switch contains a comparator, it is connected via a line 46 to the outside temperature sensor 35 . An output line 47 is connected to a switching amplifier 48 which has two outputs, of which the output 49 is connected to a first AND element 50 and the output 51 is connected to a second AND element 52 . The outputs 53 and 54 of the undersections are connected to the heat source 9 and the boiler 8 , respectively. The second input of the AND element 50 is connected via a line 55 to the output of the return temperature controller 41 . The second input of the AND element 52 is connected via a line 56 to the output of the flow temperature controller 42 .

The line 47 is connected via a line 57 to a coupling switch 58 , which in turn is connected to a memory 60 via a line share 59 . A line of lines 61 leads from the memory 60 to a coupling circuit 62 which is connected to a command line 63 as a further input which leads to line 51 .

A comparator 64 is provided, which is responsible for switching from boiler to heat pump operation. It has a number of inputs, one input of which represents a line set 65 which originates from the coupling circuit 62 . Another input 66 is connected to line 44 , a second input 67 is connected to the desired flow temperature value transmitter 38 and a third input 68 is connected to line 69 , which connects the flow temperature sensor 39 to the flow temperature controller 42 .

The flow temperature setpoint generator 38 is connected to the flow temperature controller via a line 70 , and the return temperature setpoint generator 37 is connected to the return temperature regulator 41 via a line 71 . A line 72 leads from the inputs 66, 67 and 68 to the coupling switch 58 . A line 73 leads from the comparator 64 to the switching amplifier 48 . This is so constructed that it individually amplifies the signals present on lines 47 and 73 and gives the signal on line 47 to output 49 and the signal on line 73 to output 51 .

For the function of this control and regulating unit 13 , the boiler 8 , that is to say the heat source, is provided with a flow temperature control, whereas the heat pumps are provided with a return temperature control. The situation can also be exactly the opposite, which will be discussed later.

For the functioning it is assumed that the Heat pump is able to operate during the summer and one Part of the transition times, the building heating alone perform. Only in the areas of the transition period, in which the outside temperatures are too low, and in high winter, the boiler must be switched on.

Thus, the state is first considered that the heat pump with its assigned return temperature control is in operation. For the explanation of this function, reference is now made to FIG. Three. The top diagram in FIG. 3 shows the dependence of temperatures in Kelvin on the time t in seconds. Four curves are shown in detail. First of all, the actual value of the flow temperature TVi and the actual value of the return temperature TRi are shown . At a specific point in time t _um , the temperature values _at this point in time are referred to as switchover temperature values TVi _um and TRi _um . The temperature difference between the two values is denoted by Δ _um . Furthermore, setpoint value curves are drawn in, firstly the setpoint value of the return temperature TRs and the resulting setpoint value of the supply temperature TVs . Since the heat pump is currently in operation and its return temperature is regulated, the return temperature setpoint is specified in accordance with the prevailing outside temperature.

The flow temperature setpoint is then only a fictitious quantity that can be calculated using a specified difference. In boiler mode, the set flow temperature TVs is the decisive set point, then the set return temperature is fictitious. Another special feature is that both the flow temperature and the return temperature controller work in two-point operation. However, continuous controllers with P, I or D behavior or a mixture of all three characteristics would also be conceivable. The curves would look different accordingly.

From the beginning of time until time t _to find accordingly, a two-point return temperature control of the heat pump instead. The actual value of the return temperature oscillates like a sawtooth around the return temperature setpoint TRs . If the outside temperature now falls below a predefinable limit value, the system switches from heat pump operation to heat source operation at this time. This point in time is defined as the changeover point in time t _um . The switch 45 receives this value of the outside temperature in accordance with the signals on the lines 44 and 46 . If the outside temperature falls below the predeterminable value, the changeover switch switches, that is, a corresponding signal appears on line 47 , which is amplified in amplifier 48 and is stored on line element 50 via line 49 . This signal may be in a de-energized state, so that the AND element blocks its output 53 , that is to say the heat pump is shut down. At the same time, the coupling switch 58 is activated via the lines 47 and 57 . This means that the signals on lines 66, 67 and 68 , that is to say actual value signals and desired value signals, are fed into memory 60 via the open coupling switch. Here, the stored signals of the flow temperature actual value of the return temperature actual value and the difference between the two at time t _{in order.} Likewise, the desired flow temperature value is saved at the time.

In parallel to this, the switching logic 48 generates a signal on the output 51 , which arrives at the gate 52 . Since the flow temperature controller 42 is already in operation, the AND element 52 switches through and controls the boiler 8 via its output 54 . Thus, the heat supply to the consumer _is no longer supplied by the heat pump but by the heat source from the time t . It is essential that the values TVi _um , TRi _um , TVs _um and Δ _um are stored for a downshift from the heat source to the heat pump. If they are immediately available on lines 66, 67 and 68 , they can be easily saved. If they result from links with other variables, they must be calculated. It is also possible to provide an invoice instead of a measurement.

After the switchover, the control and regulating unit 13 now checks automatically whether conditions are present that can be switched back from heat source operation to heat pump operation. For this purpose, it is determined in particular whether the flow temperature setpoint TVs becomes smaller than the flow temperature setpoint TVs _um at the time of the last switchover and additionally whether the difference Δ becomes smaller than the difference Δ _um at time t _by . As soon as both criteria are met, the system switches back to heat pump operation. The comparator 64 determines this. The stored values are made available to the comparator 64 via the coupling circuit 62 and the values for the desired flow temperature value TVs are available via line 67 or for the difference Δ as the difference of the signals on lines 66 and 68 .

According to the diagram in FIG. 3, this should be the case, for example, at the switch-back time t _R. From time t _R , heat pump operation with return temperature control then takes place again.

It is important that until the time t _to a result of the return temperature control of the heat pump only the target value is TRs outdoor temperature set by the timer 37th Since the return temperature of the heat pump is controlled, an associated supply temperature actual value curve TVi is more or less random. The target value TVs before the time t _um is obtained by averaging the minima and maxima of the flow temperature TVi .

Only after the time t ₁ can the curve for TVs be addressed as the desired flow temperature value because it is then generated by the transmitter 38 . It is therefore likely that there will _be a jump between the values of TVs on both sides of the time t . The leap is greater the wrong the heating system is designed or the more the characteristics of the two controllers differ.

If the two regulator designed as a continuous controller 41 and 42, then the actual value of the return temperature TRi only very slightly, by the value of TRs before the time t _to vary, which means that practically coincide with it. The same applies to the value of TVi with respect to the value of TVs .

Finally, it should be mentioned that the control and regulating unit 13 can of course be designed as a microprocessor.

If the controllers 41 and 42 are constructed as continuous controllers with P, PI or PID behavior, the method according to the invention can also be used in a modified form, as can be seen from FIG. Four. Before the time t _at , heat pump operation prevails, that is, the return temperature setpoint TRs is predetermined. This results in a practically identical return temperature actual value TRi if the controller's pivoting operations are neglected. An actual value of the flow temperature TVi and a target value for the flow temperature TVs also result more or less randomly, which in turn is almost identical to the actual value. The time t _um is chosen so that it is concluded from the values of the outside temperature that the heat pump is no longer able to heat the associated building. At the point in time t _um determined thereby, the difference Δ _{um is} calculated from the difference between the values TRi and TVi . This difference and TVs are stored in memory 60 . Then continue to heat with the heat source. The control and regulating device 13 is now constantly checks whether the target value of the flow temperature _{falls to} current value of the flow temperature TVS among the switching time t. If this is the case and if the resulting continuous difference Δ is smaller than the difference Δ _um at the time of the switchover, the system switches back to heat pump operation.

Fig. Five shows the switching behavior when the heat source is provided with a constant flow temperature controller, while the heat pump is equipped with a two-point return temperature controller. Then, the flow temperature setpoint value TVs by averaging the extreme values of the actual value of the flow temperature is formed is obtained prior to the time t _for a two-point control mode for the return temperature. For switching back from heat source to heat pump operation, on the other hand, the target value of the flow temperature TVs must be lower than the calculated average value TVS _{by at} the time of switching t _around and that the running difference must also be smaller than the difference Δ _by at the time of switching.

Claims (7)

1. A method for controlling the switching of a heat-absorbing consumer between a fuel or heat-heated heat source and a heat pump, the heat source having a flow temperature and the heat pump has a return temperature two-point control, characterized in that when switching from heat pump to heat source operation a calculated flow temperature setpoint ( TVSum ), the flow temperature actual value ( TVium ) and the return temperature actual value ( TRium ) are measured or calculated and saved and that the actual values of flow and return temperature TVi, TRi the difference Δ _{um is} calculated and stored and that the flow temperature setpoint TVs and the difference between the actual values TVi and TRi are determined during heat source operation and that the consumer is switched back to the heat pump when the one calculated during heat source operation Flow temperature setpoint TVs less than al s the target value TVs _um when switching from heat pump to heat source operation is _um and the difference Δ calculated during heat source operation is smaller than the difference Δ _um stored when changing _over . 2. A method for controlling the switchover of a heat-absorbing consumer between a fuel source or a heat source heated by electric current and a heat pump, the heat source having a return temperature and the heat pump having a flow temperature control, characterized in that the return temperature when switching from heat pumps to heat source operation -Setpoint TRs _um , the actual return temperature value TRi _um and the actual supply temperature value TVi _{um are} measured or calculated and stored and that the difference Δ _{um is} calculated from the actual values of the supply and return temperature TVi, TRi and is stored and that the return temperature setpoint TRs and the difference Δ is determined from the actual values TVi and TRi during heat source operation and that the consumer is switched back to the heat pump when the return temperature setpoint calculated during heat source operation is determined TRs is smaller than that when switching from Heat pump stored in heat source operating target value _by the calculated TRs in the heat source operating difference, and when the stored when switching difference Δ is smaller _by. 3. The method according to claim 1, characterized in that the return temperature in the two-point process is regulated. 4. Device for performing the method according to claim 1 or 2, characterized in that a control and regulating unit ( 13 ) which contains a two-point controller for regulating the return temperature of the medium leaving the heat-absorbing consumer, and that means for storing the desired flow temperature -value and the difference between the flow and return temperature actual value during the last heat pump operation and a computer are provided, the target value of the flow temperature TV _to target value TVs compares the value stored with the calculated, and that further a comparator is present , which compares the stored difference Δ _um with the value Δ determined by the computer. 5. A method for controlling the switchover of a heat-absorbing consumer between a fuel or heat-heated heat source and a heat pump, the heat source having a constant flow temperature and the heat pump having a constant return temperature control, characterized in that when switching from heat pumps to heat source operation the desired flow temperature value ( TVs _um ), the actual flow temperature value ( TVi _um ) and the actual return temperature value ( TRi _um ) are measured or calculated and stored and that from the actual values of the flow and return temperature TVi, TRi the difference Δ _{um is} calculated and stored and that the flow temperature setpoint TVs and the difference from the actual values TVi and TRi are determined during heat source operation. 6. A method for controlling the switchover of a heat-absorbing consumer between a fuel or heat-heated heat source and a heat pump, the heat source having a constant flow temperature and the heat pump having a return temperature two-point control, characterized in that when switching from heat pumps to Heat source operation, the target value of the supply temperature TVi and the difference Δ _um between the actual value of the supply temperature TVi and the actual value of the return temperature TRi are measured, calculated and stored, and then switch back to heat pump operation when the target value of the supply temperature TVs becomes smaller than the target value of the flow temperature TVs _um at the time of switching and the running difference becomes smaller than the difference Δ _{um at} the time of switching. 7. A method for controlling the switchover of a heat-absorbing consumer between a fuel or heat-heated heat source and a heat pump, the heat source having a flow temperature two-point control and the heat pump having a constant return temperature control, characterized in that when switching from heat pumps to heat source operation a calculated flow temperature setpoint ( TVs _um ), the flow temperature actual value ( TVi _um ) and the return temperature actual value ( Tri _um ) are measured or calculated and stored and that from the actual values of flow and Return temperature TVi, TRi the difference Δ _{um is} calculated and saved and that the heat pump mode is then switched back to when the set value of the flow temperature TVs becomes lower than the calculated target value at the time of switching and at the same time the running difference Δ becomes smaller than that Difference Δ _um at the time of switching t _um .