DE2720526C3 - Device for regulating a collective heating system - Google Patents

Description

F i g. 1 b the linear dependence of the flow temperature on the outside temperature,

F i g. 2 a hot water heating system that is controlled by a regulation that is based on the continuous Query of thermal balances based on the invention,

F i g. 3 shows a symbolic diagram of a control device according to the invention,

F i g. 4 the scheme of a step-by-step control of the servo motor driving the mixing valve,

F i g. FIG. 5 is a symbolic diagram of a modified embodiment of the electrical circuit of FIG Control device according to the invention,

F i g. 6a shows an embodiment of a step-by-step Control of the servomotor with limitation of the regulated flow temperature to the outside temperature,

6b shows the curve of the limit flow temperature in the case of FIG. 6a,

Fig.7a shows an embodiment of a step-by-step Control of the servo motor with limitation of the regulated return temperature to the outside period

F i g. 7b the curve of the limit return temperature in the case of FIG. 7a,

F i g. Figure 8 shows the scheme of a control circuit according to the invention, which is adapted to reduce the internal temperature of the rooms during the night ^; st

The following terms and designations are used in the description and the figures:

a) Temperatures

te: Current outside temperature

td: flow temperature of the heating water

in return temperature

te- target temperature

Tb: Minimum outside temperature for which the

System has been calculated
Tdb ' flow temperature of the water if the

Outside temperature is equal to T _ß
Tnc- flow temperature of the water for te = u Trb ' return temperature of the water for te = Ta Trc return temperature of the water for fe = / ₍

b) Elements of an installation

CH: Boiler or generator for producing hot water

V. M .: three-way mixing valve, which mixes the return water with the water coming from the boiler. So this is the regulating device of the heating flow.

SM: Servo motor to control the mixing valve. It has two directions of movement, which are marked with "+ warm" and "- warm".

P: circulation pump, which has a constant pressure

ensures flow rate Q of the water in the radiators.

Wheel: radiators or radiators

Reg: regulator

Td: sensor for measuring the flow temperature of the water

Tr: sensor for measuring the return temperature of the water

Tt sensor for measuring the outside temperature te

Ts: sensor, which corresponds to the influence of the sun

radiation is exposed to measure a temperature ts. The sunlight is brisk measure ts by the difference.

In Fig. La a known control device is shown which obeys the linear law and controls the pre-Jauf Temperatur td of the water according to the outside temperature te

The circuit has a boiler Ch , which is connected to a radiator Rad [which represents the various heating devices in an apartment) via a mixing valve VM and a circulating pump P. The return flow takes place directly from the radiator Rad to the boiler Ck Ein

Part of the return water is taken off and, after metering, sent back into the circuit through the mixing valve VM.

The outside temperature te is picked up by a sensor Te , and the flow temperature td of the water is picked up by a sensor Td , which is arranged at the entrance of the radiator wheel . These two quantities are introduced into a controller that is programmed according to the following law:

td = t (te)

This controller controls the servomotor SM of the mixing valve VM, which doses the amount of return water with the temperature fr that is to be mixed with the pre-water.

In Fig. Ib shows the change in the flow temperature tdln as a function of the outside temperature between the basic temperature Tb (given) and the setpoint temperature / r.

The needs of a building depend on a certain number of climate parameters where the outside temperature, solar radiation and wind are the most important. In the good sealed and insulated buildings, the influence of the wind can be neglected. Only that Outside temperature and solar radiation play a significant role.

The heat balance of a building includes:

The heat losses due to the difference between the indoor and outdoor temperature,

the solar heat supplies,

the heat input due to the heating,

the internal feeders.

The internal supplies are in the area of the room by supplementary regulation depending on the Internal temperature taken into account when the heating system is provided with suitable devices. the

so the setpoint temperature of the central controller is regulated to a value that is at least equal to the internal temperature Ti . Stf. they are taken into account across the board by central regulation if the system does not have any additional regulations depending on the environment. If ζ / Γ / denotes the temperature rise obtained by the internal supplies, the set temperature is regulated to the following value:

It is not always possible to get the heat balance to balance momentarily, since the solar heat supplies z. B. the losses at certain hours of the day can exceed to a large extent. It is therefore necessary to be able to postpone the compensation of the heat balance. Fortunately, this can take place without a negative impact on comfort, because the heat capacity of the building

Changes in outside temperature, solar radiation and that provided by the heating system Energy does not immediately affect the internal temperature.

The energy to be supplied by the heating system is such that for a more or less long Time interval depending on the thermal inertia of the building, the following equation is fulfilled:

Summed heat flux provided by the heating system
= total heat losses of the building based on the difference / between indoor and outdoor temperature

In order to simplify the representation / u, the following the case of a rectangular building viewed with a heating system determined by the facade.

The following designations are used for half of the building under consideration:

Cl; VcliirTjeiri.'icher heat loss coefficient in

W / mV C.

Sv; Glazing area of the facade in m ² .

V: Habitable volume of half the building under consideration in m ³ .

f: solar factor of the glass windows.

R: Solar radiation hitting the facade in W / m ² .

Q: Volumetric flow rate of the water supplying all the radiators in mVsec.

C: volumetric heat of water in

J / mVC.

The solar supplies per unit of habitable volume are the same:

The heat input due to heating has the following value per habitable volume unit:

The heat losses per habitable volume unit are:

C {ic-ie).

The regulatory law can therefore be written as follows:

i ^ Γ GU ₁ -IJdZ-

Here the variables are:

Measured by the outside temperature sensor.

Measured by the solar radiation sensor.

(td-try. Measured by the sensors for the supply and return water of the heating system.

z: The time.

The parameters C, Sv and V are the characteristics of the building.

The product Q ■ C is considered to be constant.

The flow of the tub water can be large Approximation can be considered constant, so that it is in in many cases need not be measured by a flowmeter.

If this is not the case, it is necessary to measure the flow with a suitable measuring device.

- totalized solar heat supply.

In Fig.2 is a heating device with a Control according to the invention shown based on the continuous integration of the heat balances is based.

The heating circuit has in succession a boiler Ch, a radiator Rad, a mixing valve VM with its servomotor SAf and a circulation pump ″.

The outside temperature and the solar radiation temperature are measured by two sensors Te and T.

The flow temperature Td and the return temperature Tr are taken before and after the radiator by sensors Tp and Tr . The parameters are integrated in the Reg controller, in which the following values are displayed:

The target temperature te,

the water flow per living volume ψ , the volumetric heat loss coefficient C and

the ratio / "^! -,
ι

In Fig.3 is the control system according to the invention

JO

csteüt.

40

45 rgcsteüt.

An analog computer 10 has the following elements:

One feeler Te. which responds to the outside temperature,

a sensor Ts to the solar radiation temperature addresses,

a rheostat Tc, with which a target temperature can be entered into the device, a sensor Ta which responds to the flow temperature of the heating water in the entirety of the radiators,
a sensor Tr, which responds to the return temperature of the water after passing through the radiators

so The sensors Te and Ts, which are arranged in a bridge circuit, are connected to a comparator Δ \ , which in turn is connected to an amplifier E \ which provides the temperature difference supplied by the comparator Δ \ with a coefficient that is derived from a negative feedback circuit arranged potentiometer is supplied.

The sensor Te is also connected to a comparator 4j, as is the rheostat Tc. The comparator Δι is connected to an amplifier £ 2 which is provided with a negative feedback circuit which has a potentiometer through which a coefficient is fed.

The sensors Tr and To are connected in the same way in a bridge and connected to a comparator Δ ^ , which is followed by an amplifier £ 3 with its negative feedback circuit

The three amplifiers Ei, E ₂ and E ₃ are connected to the input of a summer 2). The signal from the totalizer £ is shown in

a numerical integrator 2, which is connected to a memory 30. The memory 30 is connected on the one hand to a pulse generator 40 and on the other hand to two relays, one of which controls a changeover contact C \ and the other controls an interrupter contact.

These contacts, arranged in series, control the operation and direction of operation of the motor M which causes the rotation of the mixing valve which controls the temperature of the water entering the radiators.

The principle of the regulation is as follows:

The analog computer 10 creates as a function of the variable quantities (le. R. ld and ir) and the fixed quantities

an instantaneous power or heat balance, which is expressed in the following by the value Φ , and supplies a voltage proportional to this balance.

You integration memory (20.30) continuously sums up the current power balances:

Δ Φ dz.

3) The memory is polled periodically. B. a'lcfive Minutes) with the help of the encoder 40. The state of the memory at the time of the query represents the The heat balance of the building. Depending on the application, the desired level of information will be more or less complete. In In certain cases the information you want is simply to know if the heater is on ahead of needs (Φ is smaller O here) or behind (Φ is here > 0). Capturing the sign of Φ is therefore sufficient. In Fig. 3 such an embodiment is shown

For other applications (not shown here) it might be necessary to determine the exact value of Φ know. Incidents can also be taken into account, e.g. B. to know whether Φ outside or inside one of two values + ε and - e is a certain dead zone. It is noted that it is required to limit the capacity of the memory.

If z. If, for example, the heating of a building is switched off for ten days, it would be absurd to say that the energy which the heating must initially compensate when restarting should correspond to the integral of the heat losses G (te - te) that occurred during the previous ten days were measured by the scheme. In this case, the fixed setpoint temperature ic (e.g. 20 ⁰ C) no longer corresponds to the actual indoor temperature 77. After the heating has been switched off, the indoor temperature gradually becomes equal to the outdoor temperature at the end of a certain period depending on the cooling time constant of the building.

In practice, the integral φ - \ ΔΦ dz has two symmetrical or non-symmetrical limit values. One corresponds to z. B. the integral of the heat losses during a momentary shutdown of the heating (priority is given to the production of hot water for sanitary facilities by turning off the heating; turning off the heating during part of the night, etc.). The other limit corresponds to e.g. B. the integral of the solar supplies that the building can effectively recover without sacrificing comfort.

4) Depending on the information received about the state of the memory, the controller acts on the device for regulating the Heizungsflußcs Φ Δ Tein, in such a way that the integral Φ - IΔ Φ dz is deleted as quickly as possible.

In the exemplary embodiment cited, the controller acts turn on the mixing valve by moving the servomotor step by step in the direction of "+ warm" if Φ> Oist, and in the direction of "- warm" when Φ <Oist.

In Fig.4 is the control circuit of the servo motor shown.

The changeover contact d, which determines the direction of rotation of the servomotor SM , is in the "+ warm" position if the sign of the integral \ Δ Φ dz is positive, and in the "- warm" position if the sign of the integral is negative.

The contact Cj determines the running time Z \ of the servomotor within the period Zo, which represents the time interval that separates two successive surveys of the memory.

The ratio - = ¹ - is in the described embodiment

A>

example fixed. However, it can be regulated according to the absolute value of the integral \ ΔΦ dz , if it is desired that the operating speed of the servomotor increases with the amplitude of the imbalance in the balance * o The regulation law in its general form

- ^ - j (id-ir) dz-G j (/,.-/,) Ä-yy. J Rdz

links four parameters on the controller ('o C ^ and / -

which complicates the start-up regulations, all the more since the parameters G and Q are often only insufficiently known in existing buildings. After dividing by G one obtains from the before going equation

Kr J (id- tr) di = J Uc - te) dz-Ks \ Rdz

with

QC GV

and

Sv GV

The parameter Kr is nothing other than the ratio

Kr =

Δ Tnoninal

ic denotes the target temperature.

Day denotes the outside temperature for which

the system is calculated.

Δ Γ nominal is the temperature drop in the water that continuously circulates in the radiators when the outside temperature is the same as the basic calculation temperature. These values are known with considerably greater accuracy than the values of G and Q. Since the parameter Kr is the essential parameter of the control. it is important to define it with the greatest possible accuracy.

As far as the parameter Ks is concerned, which represents the compensation of the solar heat input, this is of less importance. Naturally, it is relatively imprecise due to the coefficient / (solar factor of the glass window). The errors made in estimating the coefficient G are therefore less important in calculating Ks than in calculating Kr. Therefore, there is an interest in being able to determine Kr using the indirect method described above.

In FIG. 5, the principle scheme of the control is shown, which is similar to the principle described in the above illustration (see FIG. 3). In Fig. 5, the amplifiers E \ and E ₃ correspond to the amplifiers £ i and Ey. The coefficients with which the signals emanating from the comparators Δ \ and A ₃ are provided have become Ks and Kr , respectively. These coefficients are obtained by dividing the coefficients assigned to the amplifiers £ i, £ 2 and £ 3 by the factor G, the amplifier £ 2, which now has the coefficient 1, is omitted.

It is sometimes necessary to limit the flow temperature td below a certain fixed or variable threshold value, e.g. B. To avoid noise problems due to rapid and frequent changes in the temperature of the water supplying the radiator. In the regulatory act described above, nothing limits this temperature outside the aquastat of the boiler, but appropriate precautions can be taken.

In Fig.6a the case is shown in which it is desired that the flow temperature as a function of the outside temperature in accordance with the straight line A in FIG. 6b is limited.

The control circuit of the servomotor has a changeover contact L. This contact is in position 1, 2 when the flow temperature td for an outside temperature te is below straight line A. This represents normal operation.

When the flow temperature exceeds straight line A , contact L opens circuit 1,2 and establishes connection 1,3. whereby the servo motor is returned to the less warm position.

With geothermal heating, it is important to work with the greatest possible temperature difference between the extraction and return of the geothermal water. Since the temperature of the water obtained is constant, the temperature must the water must be monitored before it is returned. In In this case, the control mode is based on the return temperature ir set

In Figure 7a, an embodiment is shown with a restriction of the return temperature tr as a function of the outside temperature.

Contact L closes circuit 1, 2 when the return temperature / r for a given outside temperature te is below curve B (normal operation) (Fig. 7b).

If the flow temperature is above curve B

is, the contact L interrupts the circuit 1,2 and establishes the connection 1, 3, whereby the servomotor is returned to its less warm position.

The maximum mean temperature of the living spaces is set at 20 "C. For existing buildings with a large proportion of glazed surface, a daytime temperature of 21 ° C is often required. in the In contrast, users prefer lower temperatures at night. The general problem of regulated heating is therefore a comfort to ensure sensation for the day and night sten. The control will reduce the night temperature in order to be able to increase the day temperature, whereby it is ensured that over an entire day (24 Hours) the mean internal temperature does not exceed 20 ° C strides.

A conventional control system without a storage tank does not make it possible to strictly maintain this mean temperature steer. More or less complicated and more or less precise solutions have been developed been to solve this problem. The most commonly used solution is the following: The control has three heating cycles.

1) A normal range from 8 a.m. to 11 p.m. 2) A reduced area from 11pm to 6am.

Its beginning coincides with the end of the television scorching. The lowering of the setpoint of the regulation is in the order of 3 to 5 ° C this lowering the heating is continued, whereby the energy sent to the radiator is proportional to the The difference between the reduced temperature and the outside temperature is that the actual Night temperature drop less than the desired one or as the one who is one by the natural The apartment cools down when the heating is switched off. The users have the propensity that Open the windows of the rooms to have fresh air. This results in overconsumption. Confirm this Incidentally, various studies carried out in situ, in the course of which has been found to be based on the difference between the indoor and outdoor temperatures attributable consumption increases by about 10% at night

3) An accelerated area from 6 a.m. to 8 a.m.

During this period of time, the heating deficit should be reported as quickly as possible during the night in accordance with the occupants' occupational activities be compensated, but this compensation is very imprecise. The regulation did not determine the energy losses during the night; she doesn't even calculate the excess power delivered during the entire duration of the accelerated range.

With the present control it is possible to switch the heating on e.g. from 11 p.m. to 6 a.m. switch off. This can result in more substantial waste

the internal temperature can be achieved. On the other hand, thanks to the storage of the balances, the control remembers when it is restarted at 6 o'clock in the morning "■ 'Loss or the lack of energy output during the night. It therefore first brings this backlog? .Uf, by using all of the available power. If then the balance of the balance sheets again is achieved, it regulates depending on the immediate needs.

For very cold days it is advisable to switch off the heating 11 p.m. to 6 a.m. may be too long for the heater to recover the losses altogether can catch up. It is therefore desirable to reduce the heating interruption time can. This is done with the aid of the arrangement according to FIG. 8 possible.

Contacts Ci (1 Cj, 2 Ci) C ₂ and L operate in the same way as those in FIG. 6a shown. In particular, the contact 2 Ci only closes if the accumulated biiance is "now or negative (the heating is ahead of the needs!"

Contact H (time contact) is closed between 11 p.m. and 6 a.m.

So that the relay C ₃ , which controls the contacts 1 Cj and 2 Q , is energized, so that the contact 2 Q interrupts the connection 4. ö to open the connection 4, 6 and turn the servomotor in the "- warm" direction until the rooms are heated two conditions are required:

I) That the time contact / - / is closed (in the exemplary embodiment 11 p.m. to 6 a.m.).

2) That contact 2 G is closed, i.e. H. the heating system is ahead of the needs.

ίο Only when these two conditions are met is it possible to switch off the heating during the night.

Contact 1 Ci is a self-holding contact which eliminates the influence of contact 2 Ci when relay Q has been switched on.

Instead of switching off the heating during part of the night, a reduction in the Target temperature can be made. In this case one would have two setpoints:

A first target temperature determines the mean TempCTHtüf uCS vjCcruüuCS 'while CiPiCS ßcSiimtcn TitgCS (24 hours). The building losses are always determined in relation to this target temperature. One second setpoint temperature determines the maximum ·: energy that is used by the heating during the reduction period is delivered.

In addition 5 sheets of drawings

Claims (1)

Claim: Device for regulating a hot water collective heating system of a building depending on the heat demand, with the circulation of the Radiators leaking water is controlled with an adjustable controller and the outside temperature, the solar radiation temperature, the flow temperature of the water in the radiators and the return temperature can be measured after the radiators, characterized in that that the heat demand is calculated from the time integral of the current heat balance, including the difference between the heat supply and the heat load in a computer (10) is formed. and the current heat balance continuously supplied by the computer (10) is stored in an integration memory (20, 30),
The heat supply is determined by measuring the flow and return temperatures, the radiator flow rate, if this changes over time, as well as the solar radiation temperature and the heat loss results from the difference between the soli temperature inside and the outside temperature, and that the integration memory (20, 30) periodically receives one of the signals for understanding <: n of the control element fVM ^ the generating device is queried. The invention relates to a device according to the preamble of the patent claim. The usual control systems of a collective heating system, which work with a linear dependency between the current outside temperature fe and the flow temperature door ld of the water supplying the radiators (cf. Radiator emissions from the water temperature and especially solar radiation are not taken into account. In addition, an exact linearity is difficult to achieve in practice because of the limited accuracy of the mixing valve and the boiler aquastat and because of the more or less long response time and limited stability of the control loop. It is already known from the journal "Sanitär- und Heizstechnik", 1975. H. 10. S. 595-599 a flow temperature control system based on the outside temperature, both external influences and Wind and solar radiation as well as disturbance variables in the room, such as B. heat radiating people should be taken into account. The solar radiation can do this measured by a bridge circuit with two different absorbing temperature sensors and the Control can be switched on as a reference variable. To take into account changes in disturbance variables in the room Thermostatic radiator valves are recommended in simple cases and the device connected downstream c electrical room temperature control circuits. If only temperature changes are taken into account, it can be but do not achieve optimal control accuracy. In particular, the heat input from the sun can only be limited must be taken into account. If it is smaller than the heat loss, it can be reduced by reducing it and, in the borderline case, by Switching off the heating can be compensated. On the other hand, solar radiation that exceeds the heat losses at certain times of the day remains not taken into account, which can lead to overheating of the rooms and a corresponding waste of energy, if removed the additional solar radiation from the outside temperature led heating is switched on again. Neither does the well-known regulation later take into account, if z. B. the flow temperature of the water was higher than intended. From DE-OS 19 23 848 a heating system with a circuit for regulating the room temperature is known, one is the temperature difference between the set indoor temperature and the outdoor temperature proportional first signal and one of the temperature difference between the heating water temperature and the A second signal proportional to the temperature is generated. The heating system is controlled depending on the relationship between these two signals. One does this makes use of the knowledge that the amount of heat given off by the radiator to the room in the stationary Operation is equal to the heat loss from the room to the outside. The problems discussed above can but not remedied by this. The invention is based on the object of a device for regulating a collective heating system the regulation of the heat to be supplied by the heating system depends more precisely than before on the heat demand to make in order to achieve an energy saving. This object is achieved according to the invention by what is stated in the characterizing part of the patent claim Features solved. The control device according to the invention carries out an accurate calculation of the amounts of heat supplied to the building and the amount of heat escaping from the building, in which the time integral over the momentary heat balance is formed. The regulation is then carried out as a function of this time integral. The individual items that make up the amount of heat supplied to the building. loading ■ »5 are made available by the heating system Amount of heat that is determined by measuring the flow and return temperatures and from solar radiation, which is calculated from the irradiation temperature. From the sum of these that warm the building The amount of heat lost to the outside is subtracted from the difference is calculated between the target temperature inside and the outside temperature. In dependence of The mixing valve, for example, is controlled according to the time integral in order to achieve a constant or desired setpoint temperature. Because the control device depends on the amount of heat and not just on temperature changes works, it is much more accurate and enables a much more economical heating of buildings as before. Compared to known control systems, energy savings of between 5 and 20% are possible. Further advantages and possible applications of the invention emerge from the following description of exemplary embodiments. In the drawing shows Fi g. la a well-known heating system, the mil linear Dependency between outside temperature and flow temperature controlled will.