DE2720526B2 - Device for regulating a hot water heating system in a building - Google Patents

Description

The invention relates to a device for regulating a Warmwasserheizuiigr, plant of a building, according to the generic term of claim 1.

The control systems normally used consist in ensuring a linear relationship between the current outside temperature te and the flow temperature td of the water supplying the radiators (cf. Fig. Ia, Ib).

This method poorly expresses the complexity of the phenomena involved. So is z. B. the Emission curve of the radiators not linear as a function of the temperature of the supply water.

In addition, the outside temperature is not the only disturbance in the expression for the heat balance of the rooms. The heat input resulting from the sun's rays contribute to this balance and often result in unpleasant changes in the internal temperature.

The majority of traditional regulations do not charge for solar radiation and those who those who charge them do so only imperfectly.

If it is possible, momentarily the solar heat input, which is smaller than the heat loss, to compensate by reducing the heating as much, it is no longer the same when these supplies become more significant. There would be a shutdown of the heating, but the additions of the sundials are not posted; or these are not negligible. This results in overheating of spaces and a waste of energy.

A traditional regulation based on the linear dependency has no storage function and therefore cannot remember previous actions. If z. B. the flow temperature of the water is higher is than the planned one, the regulation does not charge this later. You can only have the relationship ensure a temperature with a different temperature.

It is therefore indispensable in traditional systems that the flow temperature strictly follows the outside temperature. However, this is difficult in practice achievable because of the limited accuracy of the mixing valve and the more or less long response time and the more or less good stability of the

in control loop and the more or less fast and significant changes in the water temperature of the boiler. One often comes across systems in which the dynamic differential or error signal of the aquastat of the boiler is greater than 15 ° C.

The invention is based on the object of a device for regulating a collective heating system not to regulate by changing temperatures, but by the heating system precisely regulate the heat to be emitted in order to achieve a

2t) to achieve energy saving.

According to the invention, this object is achieved by the features specified in the characterizing part of claim 1
An advantageous embodiment of the device according to the invention is specified in claim 2.

In the device according to the invention, the control device performs an accurate calculation of the dem The amount of heat supplied to the building and the amount of heat escaping from the building through, and

jo these amounts of heat then become a heat balance summarized The control is then carried out as a function of this heat balance individual items that make up the amount of heat supplied to the building

i ^r , the amount of heat made available by the heating system, which is determined by measuring the flow and return temperatures, furthermore from the amount of heat generated by heat-emitting devices, machines or the number of rooms occupied

4Ii is given, and from the solar radiation that comes from the irradiation temperature is calculated. From the sum of these heat quantities that heat the building the amount of heat lost to the outside is subtracted from the difference between

4 ^r ) the target temperature inside and the outside temperature is calculated. The control device according to the invention therefore sets up a complete heat balance and, as a function thereof, regulates, for example, the mixing valve to a constant setpoint temperature or

V) to achieve a desired target temperature.

The control device according to the invention is because it depends on the amount of heat and not only the temperature changes works, much more precisely, and it can be with this device a

γ, achieve significantly more economical heating of buildings, whereby amounts of energy between 15 and 20% can be saved compared to the known control method.

Further advantages and possible uses of the

M) present invention emerge from the following Description of exemplary embodiments in conjunction with the drawings. In it shows

Fig. La a heating system by a linear Regulation is controlled,

h ^r > Fig. Ib the change in the flow temperature as a function of the outside temperature according to a linear relationship,

Fig. 2 shows a hot water heating system, which of

a scheme is controlled based on the continuous query of thermal balances according to the Invention based,

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

6a an embodiment of a step-by-step control of the servo motor with limitation of the regulated flow temperature to the outside temperature,

Fig. 6b the curve of the limit flow temperature in r> Case of the F i g. 6a,

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

F i g. 7b the curve of the limit return temperature in Trap of fig. 7a,

F i g. 8 shows the scheme of a control circuit according to the invention, which is used for reducing the internal temperature adapted to the rooms during the night

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

a) Temperatures

te: Current outside temperature «>

ld: flow temperature of the heating water

tr. return temperature

Tc target temperature

Tb: Minimum outside temperature for which the

Plant has been calculated r>

Tob: flow temperature of the water when the

Outside temperature equals Te is Toc flow temperature of the water for te = Tc return temperature of the water for te = Tb Rick flow temperature of the water for te = T _c w

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, starting with »+ warm« -> <i and "- warm" are designated.

P: Circulation pump, which ensures a constant flow rate Q of the water in the radiators.

Wheel: radiators or radiators v,

Reg: regulator

Tp: sensor for measuring the flow temperature of the water

Tr: sensor for measuring the return temperature

of the water wi

Ti :: 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 solar radiation is measured by the difference is- ie.

In Fig. La a known control device is shown, which obeys the linear law and controls the flow temperature ld of the water according to the outside temperature te.

The circuit has a boiler Ch , which is connected to a radiator wheel (which has the various heating devices in an apartment) via a mixing valve VM and a circulation pump P. The return flow takes place directly from the radiator wheel to the boiler Ch. Part of the return water is drawn off and sent back into the circuit after dosing through the mixing valve VM

The outside temperature te is picked up by a sensor 7>, and the flow temperature ld of the water is picked up by a sensor To , which is located at the input of the radiator Rad.These two variables are fed into a controller that is programmed according to the following law:

td = f (te)

This controller controls the SE-vomotor SM of the mixing valve VAi, which doses the amount of return water with the temperature fr that is to be mixed with the supply water.

In Fig. Ib shows the change in the flow temperature td'm as a function of the outside temperature between the basic temperature T _B (given) and the setpoint temperature Tc

The needs of a building depend on a certain number of climatic 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 supplies due to heating, the internal supplies.

The internal supplies are taken into account: Either in the area of the room through additional control depending on the internal temperature, if the heating system is equipped with such devices. The setpoint temperature of the central controller is regulated to a value that is at least equal to the internal temperature Tc = T /,

or across the board through centralized control if the system does not have any additional controls depending on the environment. If ΔΤΊ denotes the temperature rise that is obtained from the internal supplies, the setpoint temperature is regulated to the following value:

7 "C = Ti-ATi

It is not always possible to equalize the heat balance at the moment, since the solar heat supply f .. B. at certain hours of the day can exceed the losses to a large extent. It is therefore necessary to be able to shift the compensation of the heat balance over time. Fortunately, this can be done without any negative impact on comfort, as the changes in outside temperature, solar radiation and the heating system provided by the heat capacity of the building

Energy does not immediately affect the internal temperature.

is the amount of energy to be supplied by the heating system such that for a more or less long line interval depending on the thermal Inertia of the building the following equation is satisfied:

Λ By cliis Hei / imus \\ siem uelicfcrlcr WiiimdluH

1 Wiirnicverlusle des ( icbäiiilcs ; iufi; i tinil des I 'nlcischiedes / w ischen indoor and outdoor temperature

Λ Solar energy supplies.

To simplify the illustration, the following is the case of a rectangular building viewed with a heating system designed differently due to the facade.

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

G: Volumetric coefficient of heat loss in

W / m V C.

Sv. Glazing area of the facade in m ² .

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

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

| / mV "C.

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:

QC

till - tr)

The heat losses per unit of habitable volume

G (Tc- te)

The regulatory law can therefore be written as follows:

'■ / .SY

I UiI - / r » ih - = I G (7, - NI ih - j

Here the variables are:

te: Measured by the outside temperature sensor.

R: 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 G. Sv and V are the characteristics of the building.

The product Q ■ C is considered constant.

The flow of hot water can be regarded as constant with a great approximation, so that it does not need to be measured by a flow meter.

If this is not the case, it is sufficient to measure the flow with a suitable measuring device measure and no longer regard it as a fixed parameter).

In Fig. 2 a heating device with a control according to the invention is shown, which is based on CiCr f \ opfunUiCriiCnCn iriiCg "aiiGM dCT ντ3ΓϊΤϊ" ί5ϊϊ £ ΠϊΧΜ .

The heating circuit has a boiler Ch, a radiator wheel, a mixing valve VM with its servomotor SM and a circulation pump P in succession.

The outside temperature and solar radiation

■ temperature are measured by two sensors Tc and Ts.

The uptemperature Td and the return temperature Tr are taken upstream and downstream of the radiator by sensors To and Tr . The parameters are integrated in the regulator Reg , in which the following values are displayed:

The target temperature Tc.

the water flow per living volume ρ , the volumetric heat loss coefficient G and

the ratio / ' ψ.

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

An analog computer 1 has the following elements:

A sensor door that responds to the outside temperature,

a sensor Ts. which responds to the solar radiation temperature.

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.

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 £ Ί, which provides the temperature difference supplied by the comparator Δ \ with a coefficient that of one in a negative feedback circuit arranged potentiometer is supplied.

The sensor Te is also connected to a comparator Δ2 , as is the rheostat Ta. The comparator Δ2 is connected to an amplifier £ ₂ , d ( χ is provided with a negative feedback circuit which has a potentiometer through which a coefficient is fed.

The sensors Tr and T _D are connected in the same way in a bridge and with a comparator Δζ

connected to an amplifier ΛΊ with his Negative feedback cycle follows.

The three amplifiers Et. H ₂ and Ei are connected to the input of a summer £.

The signal emanating from the adder £ is integrated in a numerical integrator 2 which is connected to a memory 3. The memory 3 is connected on the one hand to a pulse generator 4 and on the other hand to two relays, one of which controls an interrupter (\ and the other an interrupter Cj.

These serially arranged switches control the operation and the 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:

I) The analog computer I rrsfpllt depending on the variable values (te. R, Id and Ir) and

the fixed quantities (G. Tc. f p-, - ^) a momentary power balance and supplies a voltage proportional to this balance.

dz

at,

Ic)

Ud ir) t /

2) The storage integrator (2, 3) continuously adds up the current power balances:

I 'Λ ih

3) The memory is queried periodically (e.g. every five minutes) with the help of the transmitter 4. The state of the memory at the time of the query represents the heat balance of the building. Depending on the application, the desired level of information will be more or less complete. In certain cases, the required information is simply to know whether the heating is ahead of the needs (Φ is less than 0) or behind (Φ is> 0). Capturing the sign of Φ is therefore sufficient. In Fig. Such an exemplary embodiment is shown in FIG.

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

If z. B. the heating of a building is switched off for ten days, it would be absurd to say that the energy which the heating must first compensate when restarting corresponds to the integral of the heat losses G (Tc - te) that during the previous ten days of the scheme has been measured. In this case, the fixed setpoint temperature T _c (Tc = 20 ° C for example) no longer corresponds to the actual internal temperature Ti. After the heating has been switched off, this internal temperature gradually becomes equal to the external temperature at the end of a certain period of time, depending on the cooling time constant of the building.

In practice, the integral Φ - \ ΑΦ dz has two symmetrical or non-symmetrical limit values.

One corresponds to / .. 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 the Heating is turned off; Shutdown of the heating during part of the night, etc.). The other Limit corresponds to z. B. the integral of the solar supplies that the building can effectively recover, without compromising comfort.

4) Depending on the information received about the status of the memory, the controller acts on the device for regulating the heating flow Φ A Tein in such a way that the integral Φ = J Δ Φ (^ is deleted as quickly as possible.

In the exemplary embodiment cited, the controller acts on the mixing valve. in which the servo motor is controlled step by step in the direction of »+ warm« if Φ> Oist, and in the direction of »- warm« if Φ < 0ist.

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

The changeover contact Ci, which determines the direction of rotation of the servo motor SM , is in the "-t warm" position if the sign of the integral \ Δ Φ dz is positive, and in the "- warm" position if the sign of the preceding integral is negative is.

The contact C2 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

example fixed.

However, it can be regulated according to the absolute value of the integral \ ΑΦ dz if it is desired that the operating speed of the servomotor increases with the amplitude of the imbalance in the balance.

The regulatory law in its general form

l fr / - tr) ti: = G

- U) i

h - J ^ 'f

links four parameters on the controller (Tc. G. -Zy- and fy ), which complicates the controls a little at start-up, all the more since the parameters G and Q are often insufficiently known in existing buildings.

After dividing by G one obtains from the previous equation

Kr J Ud - tr) dz = j [T, - te) dz - Ks f Rdz

Ks = /

QC Gl

Slav

The parameter Kr is nothing other than the ratio

Tc - T "
! T nominal

Kr =

Tc denotes the target temperature.

To denotes the outside temperature, for soft

the system is calculated.

Δ Tnominal is the Tcmpcralurabfall of 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 Krdzr is an essential parameter of the control, it is important to determine it with the highest possible accuracy.

As far as the parameter Ks is concerned, which represents the compensation of the solar heat input, this is of less importance. It is naturally relatively imprecise due to the coefficient f (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.

| i ~ * · # * " λ J ΤΛ * * LJ ΓΪ I

shown, which is completely the same as the principle described in the above illustration (see. Fig. 3). In this FIG. 5, the amplifiers Er and E ₁ correspond to the amplifiers E \ and Ej of FIG . 3. The coefficients with which the signals emanating from the comparators Δ \ and Δι are provided have each become Ks and Kr . These coefficients are obtained by dividing the coefficients assigned to the amplifiers E], Ei and E ₁ by the factor G, the amplifier E ₂ , which now has the coefficient I, is omitted.

It is sometimes necessary to limit the flow temperature td below a certain threshold value, e.g. B. to avoid the noise problems due to rapid and frequent changes in the temperature of the water supplying the radiator. In the regulation law described above, nothing limits this temperature outside the aquastat of the boiler. But nothing prevents you from doing it.

The accumulated balances are now deleted by keeping the flow temperature below of a certain fixed. "or changeable value.

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 of FIG. 6b is limited.

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

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

With geothermal heating it is important to work with as large a temperature difference as possible between the extraction and re-injection of the geothermal water. Since the temperature of the recovered water is constant, the temperature of the water must be monitored before it is re-injected. In this case, the control mode is set to the return temperature tr

Ir, Fig. 7a shows an embodiment with a restriction of the return temperature tr as a function of the outside temperature

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

If the flow temperature is above curve B , contact L breaks circuit I, 2 and establishes connection 1, 3, as a result of which the servomotor is returned to its less warm position.

The maximum mean temperature of the living spaces is set at 20 ^° C. Existing buildings with a large proportion of glazed surfaces often require a daytime temperature of 21 ° C. In contrast to this, users prefer lower temperatures at night.

The general problem with heating is therefore to ensure a feeling of comfort for the day and oil: night, whereby the regulation is observed. The control will reduce the night temperature

₆ gp

it is ensured that the mean internal temperature does not exceed ^{20 ° C. over an entire day (24 hours).}

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 slowed down area from 11pm to 6am.

The beginning of this section coincides with the end of the television broadcasts. Lowering the The set point of the regulation is in the order of 3 to 5 ° C.

Despite this lowering, heating continues, using the energy sent to the radiators is proportional to the difference between the slowing temperature and the outside temperature. This results in, that the actual nighttime temperature drop is less than that determined by the deceleration or as the one obtained by the natural cooling of the apartment when the heating is on is switched off. Users have a tendency to open the windows of the rooms to get fresh air. This results in over-consumption. This is confirmed by various studies carried out in situ, in the course of which has been determined to be due to 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.

This time period is set according to the occupational activities of the residents. The goal this accelerated range consists in trying to compensate for the partial loss of energy output be compensated during the night in order to avoid any temporal drift in the internal temperature that would arise in his absence.

Unfortunately, this compensation is very imprecise. The scheme has the energy losses during not determined by night; it also does not charge for the entire duration of the accelerated Area delivered excess power.

With the present scheme, it is possible to use the heating z. B. from 11 p.m. to 6 a.m.

switch off. In this way, a more significant drop in the internal temperature can be achieved. Thanks to the storage On the other hand, the regulation remembers the elilances when resuming at 6 a.m. Loss or lack of energy output during the night. It is therefore initially catching up on this deficit. 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.

Switching off the heating between 11 p.m. and 6 a.m. may be too long for very cold days. so that the heating system can recover all of the losses. Rs is therefore desirable to the To be able to reduce the interruption duration of the heating. This is done with the aid of the arrangement according to FIG. 8th possible.

Contacts G (I G. 2 G) C ₂ and L operate in the same way as those in FIG. b shown. In particular, contact 2 G (making connection 7, 8) closes only when the accumulated balance is zero or negative (heating is ahead of needs).

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

So that the relay Ci, which the contacts 1 Gi and 2 G) controls, is excited so that the contact 2 Cj breaks the connection 4, 5 to the connection 4, 6 and turn the servomotor in the "- warm" direction until the rooms are heated two conditions are required:

1) That the time or switch contact; is made (in Embodiment 23 to 6 o'clock).

2) That the contact 2 C, is made. d. H. the Heating is ahead of the needs.

It is only when these two conditions are met possible to switch off the heating during the night.

The contact I Gi is a self-holding contact that the Influence of contact 2 G eliminated when relay G] 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 setpoint temperature, designated Tt ₁ , which determines the average temperature of the building during an entire day (24 hours). The building losses are always determined in relation to this target temperature.

A setpoint temperature marked with 7r, \, which the determines the maximum energy delivered by the heater during the reduction period.

llicr / u 5 Mimt

Claims (2)

Patent claims: I. Device for regulating a collective heating system of a building with hot water that circulates in radiators whereby the circulation of the water exiting the radiators is controlled and the outside temperature, the solar radiation temperature, the flow temperature of the water in the radiators and the return temperature after the radiators are measured, thereby characterized in that the regulation depends on the sum of the current heat balance takes place the difference between the heat input, which differs by measuring the Flow and return temperatures as well as the solar radiation temperature results and the Heat loss resulting from the difference between the target temperature inside and outside temperature results as speaks 2. Apparatus according to claim 1, characterized by a computer (1) for continuous delivery the current heat balance, an integration memory (2, 3) to store the current Heat balance and a device for periodic polling of the memory and delivery of the signals for Adjustment of the control organ.