CH714276A2 - Automatic three-way valve for connection of an expansion vessel in a district heating network and a district heating network with such a valve. - Google Patents

Abstract

The invention relates to an automatic three-way valve (9) for connecting an expansion vessel in a district heating network. It comprises a housing (10) with an interior space (11), a main connection (12) for a connection to an expansion vessel and a first and a second connection (14, 16) for each connection to a connection point on a district heating network. The interior space (11) is subdivided into a main chamber (13) which is pressure-connected to the main connection (12), a first pre-chamber (15) pressure-connected to the first connection (14) and a second pre-chamber (17) pressure-connected to the second connection (16) , Depending on a sealing disc (20, 21) is arranged in each prechamber (15, 17). They are rigidly connected to one another by a connection (22) and arranged so movably in the interior space (11) that, in use in the pre-chamber (15, 17) with the respective higher pressure, the sealing disc (20, 21) arranged therein is automatically controlled by pressure to a provided for this paragraph (23) of the antechamber (15, 17) can be pressed sealingly and thus the pressure connection of this pre-chamber (15, 17) to the main chamber (13) interrupts. At the same time by the rigid connection (22), the other sealing disc (20, 21) from a corresponding shoulder (23) of the other antechamber (17, 15) kept away and so the pressure connection from the pre-chamber (17, 15) with lower pressure to the main chamber (13) ensured. The invention also relates to a combination of such three-way valves (9) and a district heating network with such a three-way valve (9).

Description

description

Technical field The invention relates to a district heating network with a water circuit comprising a heat conductor and a PTC thermistor, between which a thermal source and several consumers are connected, each with a circulating pump, and an expansion vessel, wherein the circulating pumps optionally water from the heat conductor or from the PTC thermistor and can heat or cool the source as needed. In addition, it relates to an automatic three-way valve. The invention also relates to a combination of such valves.

Background Art A conventional district heating power plant has a decentralized heating plant in which water is typically heated to 70 ° C-90 ° C, and a circulation system of pipelines to which a plurality of consumers are connected. These draw hot water from a heat conductor and lead it cooled again to a PTC thermistor, in which it is led back to the heating plant. A circulation pump ensures the necessary circulation.

The input of this circulation pump is usually arranged an expansion vessel. This serves primarily to compensate for volume variations of the water in the network due to temperature variations. In addition, the pressure in the network is increased via the expansion vessel in order to avoid cavitation at the circulation pump. Cavitation is the formation of vapor bubbles in liquids and occurs when the pressure on the suction side of a circulation pump drops below the evaporation pressure. Cavitation can cause a lot of damage, as the imploding of the cavities temporarily causes extremely high accelerations, temperatures and pressures that can damage the material. To prevent this in circulating pumps, make sure that the suction pressure of the circulation pump never gets too low. The connection point of the expansion vessel is therefore usually the suction side of the circulation pump, there to a certain minimum pressure; to guarantee. No valve is necessary for this.

Recently, in the course of the energy transition in the field of district heating more and more low-temperature networks are built with a water temperature below 20 ° C. This allows the water to be used both for cooling purposes such as data centers or laboratories, as well as for heating such as hot water. For heating buildings, a heat pump is additionally required, whereby cooling is often possible directly. Low-temperature networks are operated most efficiently with several decentralized circulating pumps directly at the dispensers. In this case, water is purchased for heating from the heat conductor and for cooling from the PTC thermistor. This results in complex pressure conditions in the network, which make a variable connection point of the expansion vessel required to guarantee the suction side of each pump a minimum pressure. For systems with constantly changing pressure conditions, this is not easy.

On the other hand, a plurality of circulation pumps can be used in a conventional district heating network, partly present on the suction side of greatly different pressures. Even in such networks, it is important that each circulation pump is supplied with a minimum pressure on the suction side.

DESCRIPTION OF THE INVENTION It is the object of the present invention to describe how an expansion vessel is to be installed in a district heating network with several circulating pumps in order to prevent cavitation on the circulating pumps. It was found that ideally the connection point of the expansion vessel should always be located on the suction side of a circulation pump in order to supply it with sufficient pressure. In addition, an initially mentioned valve is to be described, with which in such a district heating network cavitation can be prevented. The object is achieved by the features of the independent claims of the respective categories. Further advantageous embodiments are specified in the subclaims.

According to the invention, an initially mentioned automatic three-way valve for connecting an expansion vessel in a district heating network is suitable. It comprises a housing with an interior space, a fastening device for a main connection for connection to an expansion vessel and in each case a fastening device for a first and a second connection for connection to connection points on a district heating network. The interior is subdivided into a main chamber, which is pressure-connected to the main connection, a first prechamber pressure-connected to the first connection, and a second prechamber pressure-connected to the second connection, the main chamber being arranged between the prechambers.

In such a valve, a respective sealing disc is arranged in each prechamber. The sealing disks are rigidly connected to one another by a connection and are movably arranged in the interior such that, in use, in the pre-chamber with the respective higher pressure, the sealing disk arranged therein is pressure-controlled in a self-sealing manner against a designated shoulder of the prechamber. This interrupts the pressure connection from this antechamber to the main chamber. At the same time the other sealing disc is kept away from a corresponding shoulder of the other antechamber by the rigid connection and so ensures the pressure connection from the lower chamber to the lower chamber to the main chamber. During a pressure change in the pre-chambers, the main chamber is always pressure-connected in at least one of the prechambers in each position of the sealing disks, for a short time even with both simultaneously.

The sealing discs change their position solely due to the pressure differences in the antechambers. In use, therefore, the expansion vessel is always pressure-connected to the connection point on the district heating network, which has the lower pressure. At the same time it is separated from the other connection point.

Since the valve has no other movable components and is very simple, its reliability and longevity is high. It is also important that no other forces acting on the sealing plates, which could cause a falsification of the setting, so that always the antechamber is pressure-connected to the low pressure with the expansion vessel. Also important is the constant pressure connection between the expansion vessel and one of the connection points, since even during a short decoupling of the expansion vessel from the district heating network could create a pressure difference to the connection points in the district heating network and the pressure in the district heating network could increase sharply. In addition, in a later restoration of the pressure connection violent bumps occur, which can lead to material damage.

In a preferred embodiment, such a valve is combined with one or more sub-valves of the same kind to form a combination. In this case, each sub-valve with its main connection to a first or second port of the valve or other sub-valve is connected pressure-connected. In use, this means that the expansion vessel at the main connection of the valve is always pressure-connected exactly to the connection point on the district heating network, which has the lowest pressure. At the same time it is separated from all other connection points.

The inventive district heating network includes a circuit with a heat conductor and a PTC thermistor, between which a thermal source and several consumers are connected, each with a circulating pump, and an expansion vessel. The circulation pumps may optionally draw water from the heat conductor or from the PTC thermistor, and the source may heat or cool as needed. Preferably, an inventive, automatic three-way valve with its main connection to the expansion vessel and with its first and second connection directly or indirectly connected to the hot and / or on or PTC thermistor, always on the input side of a circulating pump.

In this way, it is ensured that always that connection point is pressure-connected to the expansion vessel, which has the low pressure.

Preferably, a pressure valve is used with a one-piece housing. This has the advantage that no seals must be used. As seals become brittle over time, the life of a valve with a multi-part housing is significantly shorter than that of a valve with a one-piece housing. The connections themselves do not have to be part of the valve.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention will be explained in more detail with reference to the drawings. For the same terms, the same reference numerals are used in all figures. It shows:

1 shows a three-way valve according to the invention in a schematic longitudinal sectional view, in two different states a) and b) and in two different embodiments;

Fig. 2 detail solutions in the interior of the inventive valve for guiding the sealing disks, Figure 2a with guide elements between the connection and paragraph. FIG. 2b with several connections; FIG. Fig. 2c) with guide elements between sealing disks and housing; each in longitudinal section and in cross section through A-A, B-B respectively. C-C;

3 shows a combination of a valve according to the invention with similar sub-valves;

Fig. 4 shows a conventional district heating network according to the prior art;

5 shows a district heating network according to the invention;

Fig. 6 shows another district heating network according to the invention.

1 shows schematically an automatic three-way valve 9 according to the invention for connection to an expansion vessel 7 in a district heating network 1, as described later in FIG. 5, in two different states and embodiments. and b). It comprises a housing 10 with an interior 11 and fastening devices 18 for three connections, namely a main connection 12 for a line 19 to an expansion vessel 7 (shown in FIGS. 3, 5 and 6) and a first and a second connection 14, 16 for a respective line 19 to a connection point 8 at a district heating network 1, shown in Fig. 5. The fastening devices 18 shown as threaded can also be configured as flanges or other known connections to a line 19. The inner space 11 is subdivided into a main chamber 13, which is pressure-connected to the opening to the main connection 12, a first pre-chamber 15, which is pressure-connected to the opening to the first connection 14, and a second prechamber 17 which is pressure-connected to the second connection 16. In this case, the main chamber 13 is arranged between the prechambers 15, 17 and connected to at least one of these pressure-connected at all times. In each prechamber 15,17 is ever a sealing disc 20, 21 are arranged. These sealing discs 20, 21 are connected by a connection 22 rigidly connected to each other and movably arranged in the interior 11, such as an axially displaceable piston.

In use, one of the two atria 15, 17 will always have a higher, the other corresponding to a lower pressure. Since the pressures change with time, there may be a pressure change: The pressure conditions in the antechambers 15,17 are the same and change: The prechamber 15,17 with the formerly higher pressure now has a lower pressure, and vice versa. Sealing surfaces 27 between the shoulders 23 and the sealing disks 20, 21 provide a barrier between the pre-chamber 15, 17 with the respective higher pressure and the main chamber thirteenth

In those pre-chamber 15, 17 with the respective higher pressure, in Fig. 1a, this is the second pre-chamber 17 and in Fig. 1b), the first pre-chamber 15, the sealing disc 21 arranged therein is pressure-controlled automatically to a designated paragraph 23rd the pre-chamber 17 in Fig. 1a sealingly pressed. As a result, the pressure connection is interrupted by this pre-chamber 17 to the main chamber 13. At the same time, the other sealing disc 20 is kept away from a corresponding shoulder 23 of the other pre-chamber 15 by the rigid connection 22 and thus ensures the pressure connection from the pre-chamber 15 with lower pressure to the main chamber 13. It is important that the main chamber 13 is at the same time pressure-connected with at least one of the prechambers 15, 17, and during a change of pressure in the antechambers 15, 17 in each position of the sealing disks 20, 21, so that the expansion vessel 7 simultaneously , shown in Fig. 3, never with a pressure difference to the district heating network 1 is connected to this.

The sealing discs 20, 21 change their position solely due to the pressure differences in the antechambers 15, 17, so that in use the expansion vessel 7 is always pressure-connected to that connection point 8 on the district heating network 1, which has the lower pressure and at the same time from the other connection point 8 is disconnected. Only with equal pressure, so in particular briefly during pressure change, all three chambers 12, 15, 17 are pressure-connected to each other. In particular, no other force such as a spring force must be overcome in order to move the pressure plates in a pressure change in the other position, because the goal could not be met that the main terminal 13 is always connected to the pre-chamber 15, 17 with the lower pressure ,

Thus, the sealing discs 20, 21 friction can change their positions between the states of FIG. 1a and 1b and in particular not jammed, they or the connection 22 must be stored respectively. be guided. In a first embodiment, as shown in Fig. 1, the connection 22 may be mounted in the interior 11 in a guide 24. It should allow the required axial movement of the sealing disks 20, 21. For this purpose, the guide 24 is preferably formed in the main chamber 13.

In Fig. 1b, an embodiment is shown, in which the housing 10 of the three-way valve 9 is designed in one piece. Thus, the assembly of the inner sealing washers 20, 21 with the connection 22 is possible, provided for the first and second terminals 14, 16 openings on the housing 10 must be correspondingly large. These openings have fastening devices 18, which can preferably be designed as a thread, here as an internal thread and to corresponding fastening devices 18 of the terminals 14, 16 fit, which are configured for example as an external thread. The terminals 14, 16 can be connected in this way close to the housing 10. The inner diameters of the openings 14, 16 for the connections on the housing 10 are preferably larger than the respective sealing disks 20, 21 arranged behind them.

FIGS. 2 and 3 each show valves 9 according to FIG. 1a. In all embodiments but valves can be used with a one-piece housing 10 as shown in FIG. 1b. The connections 12, 14, 16 are not components of a valve 9, but the valves 9 can certainly be designed with these.

The advantages of a one-piece housing 10 are freedom from maintenance, since no seals need to be maintained or replaced, and in the low-cost manufacturing, since no screws must be used to hold the housing together. During assembly, only one of the sealing washers 21 with the connection 22 is brought into the guide 24, then the other sealing washer 20 is fastened to the connection 22, for example with a nut. Such valves are very durable and reliable, since they have no springs or other moving parts, apart from the secure with the connection 22 sealing washers 20, 21. At such a valve 9, finally, the terminals 14, 16 and the main terminal 12 can be easily mounted ,

In an alternative embodiment according to FIG. 2a, the shoulders 23 form the guide. The views of Fig. 2a represent two sections corresponding to each other by A-A. The same applies to Fig. 2b through B-B and Fig. 2c) through C-C. As an alternative to the axially symmetrical configuration of the sealing disks 20, 21 and the connection 22 shown in FIG. 2, it is also possible to select a rectangular or any other sectional shape, wherein the housing 10 and the interior 11 are adapted accordingly.

The connection 22 in Fig. 2a therefore comprises guide elements 25 which abut the heels 23 and are guided. Between the guide elements 25 intermediate spaces 26 are arranged to ensure the required pressure equalization. A circumferential groove 29 in the main chamber 13 provides for the connection of all the gaps 26 to the main terminal 12. Alternatively, the guide elements 25 and the interstices 26 may be designed lamellar to always ensure a pressure connection between one of the antechambers 15, 17 to the main chamber 13 ,

The pressure equalization in FIGS. 2a initially extends from the second connection 16 to the second prechamber 17, on all sides around the second sealing disk 21, further through the intermediate spaces 26 between the guide elements 25, possibly in the groove 29 around the connection 22 and in the main chamber 13, which is pressure-connected to the main port 12.

The guide elements 25 are attached to the connection 22 here. Alternatively, guide elements 25 may be mounted on the housing 23 at the shoulders, which is not shown here. In this case, they are designed to be shorter in the axial direction and extend at most up to the outer edges of the recesses 23, so that the sealing disks 20, 21 can rest against the sealing surfaces 27.

Alternatively, as shown in Fig. 2b, the connection 22 itself may consist of the guide elements 25, which is broken down into a plurality of sub-connections 22, between which the pressure can spread freely. The connection 22 shown here as a plurality of bars can also be designed as two opposite plates on both sides of the main terminal 12, which is advantageous in particular in the case of a rectangular cross section. In the case of the left-hand illustration of FIG. 2b, the plates are parallel to the plane of the drawing, so that they do not obstruct the access to the main connection 12 and leave the side of the main connection 12 and the pressure equalization gap 26 free from the latter.

In a further alternative embodiment according to FIG. 2 c, the sealing disks 20, 21 are mounted in their prechambers 15, 17 with guide elements 25. In longitudinal section two alternatives were presented. In both variants, the guide elements 25 on spaces 26, in which a pressure exchange can take place. In the first variant, as shown in the pre-chamber 15, the guide elements 25 are mounted with their interstices 26 inside the housing 10 and support the first sealing disc 20 from. In the second variant, as shown in the second pre-chamber 17, such guide elements 25 are mounted on the second sealing disc 21 and support them inside the housing 10 from. Alternatively, holes on the outer edge of the sealing disks 20, 21 may be configured.

As is apparent from FIGS. 1 and 2, the sealing discs 20, 21 on the main chamber 13 facing side and each shoulder 23 on the side facing away from the main chamber 13 sealing surfaces 27 which, respectively, for closing the respective prechambers 15. 17, correspond with each other. Alternatively, a cone seal, not shown, can be used by the surfaces of the sealing discs 20, 21 and / or the corresponding paragraph 23 in the region of the sealing surfaces 27 described here are conical.

In use, the pressure connection of a first or second port 14, 16 passes through the respective pre-chamber 15, 17 to the main chamber 13 each side of one of the sealing discs 20, 21 over and between the sealing surfaces 27 of the respective sealing disc 20, 21 and the corresponding paragraph 23, then next to the connection 22 to the main chamber 13 and the opening of the main terminal 12th

To connect an expansion vessel 7 in a district heating network 1 with more than two connection points 8, according to the invention a combination of two or more valves 9 described here is used, as shown in Fig. 3. In this case, the expansion vessel 7 is always pressure-connected to that connection point 8, which has the lowest pressure.

The inventive combination consists of such a valve 9 with one or more sub-valves 28 of the same kind as the valve 9. Each of these sub-valves 28 is in this case with its main terminal 12 at a first or second port 14,16 of the valve 9 or another Unterventils 28 connected directly or with a line 19 pressure connected. As a result, in use, the expansion vessel 7, which is still connected to the main terminal 12 of the valve 9, always exactly with the connection point 8 at the district heating network 1 pressure-connected, which has the lowest pressure, and at the same time separated from all other connection points 8. In FIG. 3, the expansion vessel 7 is pressure-connected to the connection point 8.3 and separated from the connection points 8.1, 8.2, 8.4 and 8.5. The connection point 8.3 has the lowest pressure. Due to the valve positions of the sub-valves 28, the pressure at connection point 8.2 is higher than at connection point 8.1 and at connection point 8.5 higher than at connection point 8.4. Thus, the connection points 8 are not pressure-connected to each other by a valve 9 or sub-valve 28, externally when pressure changes. The only pressure connection in the combination according to FIG. 3 is that between the connection point with the lowest pressure, the connection point 8.3, and the expansion vessel 7. If the pressure at connection point 8.4 becomes lower than at connection point 8.3, then the two pressure disks move in the right one Sub-valve 28 and ensure new the only pressure connection from the connection point 8.4 to the expansion tank. 7

Fig. 4 illustrates a water cycle of a district heating network 1, as known from the prior art and described in the introduction. Starting from a source 2, which supplies heat, runs a heat conductor 3, which is divided into several consumers 5. These use the heat from the water and conduct it cooled finally a common PTC thermistor 4, which leads back to the source 2. A circulating pump 6 provides the necessary circulation and an expansion vessel 7 arranged on the input side ensures a pressure equalization and a required minimum pressure for the inlet side of the circulating pump 6. No valve is required for this purpose.

An inventive district heating network 1 according to FIG. 5 in turn has a water cycle. This comprises a heat conductor 3 and a PTC thermistor 4, between which a thermal source 2 and a plurality of consumers 5, each with a circulating pump 6 are connected. In contrast to the circuit according to the prior art, this circuit comprises a plurality of circulation pumps 6. These can optionally refer water from the heat conductor 3 or from the PTC thermistor 4. In addition, the source 2 can be heated or cooled as needed. This circuit also comprises an expansion vessel 7. According to the invention, an automatic three-way valve 9 presented above is used for this purpose. It is connected with its main terminal 12 to the expansion tank 7, with its first terminal 14 through a line 19 at a connection point 8 on the heat conductor 3 and with its second terminal 16 at a further connection point 8 on the PTC thermistor 4. The first and second terminals 14, 16 are identical and can be reversed.

As long as the pressure differences within the cold resp. of the heat conductor 4, 3 are negligible, such a connected expansion vessel 7 is sufficient. At a low pressure suction side of a circulating pump 6, the expansion vessel 7 can ensure the necessary minimum pressure.

But as soon as this is no longer the case, if therefore the distances of the consumer 5 are very large and / or the cross sections of heat conductor 3 and PTC thermistor 4 are relatively low, the minimum pressure in the network at different positions in the PTC thermistor 4, respectively. occur in the heat conductor 3 and move accordingly. If the expansion vessel is connected, for example, to one end of the heat conductor and the pressure minimum is on the other side of the heat conductor, cavitation may occur at a circulating pump 6 connected to this end of the heat conductor.

In order to prevent this, a district heating network 1 according to FIG. 6 is proposed. In this district heating network 1, a combination of a valve 9 is used with one or more sub-valves 28 of the same kind, as shown in Fig. 3. All first and second ports 14,16, to which no sub-valve 28 is connected, are connected to lines 19 at various connection points 8 in the district heating network. The expansion vessel 7 is now always connected to that of the connection point 8, which has the lowest pressure. Preferably, one or more connection points 8 are arranged on the suction sides of the circulating pumps 6. In this way, cavitation can be prevented by suppressing the circulation pump 6.

In all these district heating networks, any type of valves described 9 can be used, in particular according to FIG. 1a or 1b, or according to a combination of Fig. 2a, 2b or 2c with Fig. 1b, with a one-piece housing 10th

List of Reference Numerals 1 District heating network 2 Source 3 Heat conductor 4 PTC thermistor 5 Load 6 Circulation pump 7 Expansion vessel 8, 8.1, 2.8, 8.3, 8.4, 8.5 Connection point in district heating network 9 Three-way valve, valve 10 Housing 11 Interior 12 Main connection resp. Opening to a main connection 13 Main chamber 14 First connection resp. Opening to a first port 15 First antechamber 16 Second port resp. Opening to a second connection 17 Second pre-chamber 18 Fastening device, thread 19 Line 20 First sealing washer 21 Second sealing washer 22 Connection, connections, partial connections 23 Paragraph 24 Guide 25 Guide element 26 Interspaces 27 Sealing surfaces 28 Sub-valve 29 Groove

Claims (15)

claims 1. district heating network (1) comprising a water circuit comprising a heat conductor (3) and a PTC thermistor (4) between which a thermal source (2) and a plurality of consumers (5) are connected, each with a circulating pump (6), and an expansion vessel ( 7), wherein the circulating pumps (6) can optionally draw water from the heat conductor (3) or from the PTC thermistor (4) and heat or cool the source (2) as required, characterized in that an automatic three-way valve (9) with a main terminal (12) and with a first and a second terminal (14, 16) is used, with its main terminal (12) on the expansion vessel (7), with its first terminal (14) on the heat conductor (3) and its second port (16) is connected to the PTC thermistor (4), and wherein the three-way valve (9) comprises a housing (10) having an interior space (11), the interior space (11) being in a main chamber pressure-connected to the main port (12) (13), one with the ers ten connection (14) pressure-connected first prechamber (15) and a second connection (16) pressure-connected second pre-chamber (17) is divided and the main chamber (13) between the prechambers (15, 17) is arranged, and wherein each a sealing disc (20, 21) in each pre-chamber (15, 17) is arranged, wherein the sealing discs (20, 21) by a connection (22) rigidly connected to each other and are movably arranged in the interior space (11) that in use in that antechamber (15, 17) with the respective higher pressure, the sealing disc (20, 21) arranged therein is pressure-controlled automatically pressed against a designated shoulder (23) of the antechamber (15, 17) and thus seals the pressure connection from this antechamber (15, 17) ) is interrupted to the main chamber (13), and at the same time by the rigid connection (15, 17) the other sealing disc (20, 21) from a corresponding shoulder (23) of the other antechamber (17, 15) is kept away and so the pressure connection of the Antechamber ( 17, 15) with lower pressure to the main chamber (13) ensures, wherein the main chamber (13) also during a pressure change in the antechambers (15, 17) in each position of the sealing discs (20, 21) always with at least one of the pre-chambers (15 , 17), is temporarily pressure-connected to both at the same time and the sealing disks (20, 21) change their position solely on account of the pressure differences in the pre-chambers (15, 17), so that in use the expansion vessel (7) always connects to that connection point (8). at the district heating network (1) is pressure-connected, which has the lower pressure and at the same time from the other connection point (8) is disconnected. 2. district heating network according to claim 1, characterized in that the housing (10) of the three-way valve (9) is designed in one piece. 3. district heating network according to claim 2, characterized in that the first and second connection (14, 15) fastening devices (18), preferably threaded, with which they respectively to corresponding fastening devices (18). Threads on the housing (10) are tightly secured. 4. district heating network according to one of the preceding claims using a combination of a valve (9) with one or more sub-valves (28) of the same kind, characterized in that each sub-valve (28) with its main terminal (12) at a first or second terminal ( 14, 16) of the valve (9) or another sub-valve (28) is connected pressure-connected, whereby the expansion vessel (7) at the main connection (12) of the valve (9) always pressure-connected exactly with the connection point (8) on the district heating network (1) is, which has the lowest pressure, and at the same time from all other connection points (8) is separated and that all first and second ports (14, 16) to which no sub-valve (28) is connected, at different connection points (8) in the district heating network (1) are connected. 5. district heating network according to claim 4, characterized in that one or more of the connection points (8) on the suction side of the circulation pumps (6) are arranged to prevent cavitation by suppressing the circulation pump (6). An automatic three-way valve (9) for connecting an expansion vessel (7) in a district heating network (1) comprising a housing (10) with an interior (11), an opening with a fastening device (18) for a main terminal (12) for a Connection to an expansion vessel (7) and in each case an opening with a fastening device (18) for a first and a second connection (14, 16) for each connection to a connection point (8) on a district heating network (1), the interior ( 11) into a main chamber (13) which is pressure-connected to the opening to the main connection (12), a first prechamber (15) pressure-connected to the opening to the first connection (14) and a second prechamber (17) pressure-connected to the opening to the second connection (16) ) is arranged and the main chamber (13) between the antechambers (15, 17) is arranged, wherein each a sealing disc (20, 21) in each prechamber (15,17) is arranged and wherein the sealing discs (20, 21) by a Ve Binding (22) are rigidly connected to each other and movably arranged in the interior (11), that in use in that prechamber (15, 17) with the respective higher pressure, the sealing disc (20, 21) arranged therein pressure controlled automatically to a designated paragraph (23) the prechamber (15, 17) is pressed sealingly and thus the pressure connection of this prechamber (15, 17) to the main chamber (13) interrupts, and at the same time by the rigid connection (15, 17) the other sealing disc (20, 21 ) is kept away from a corresponding shoulder (23) of the other pre-chamber (17, 15) and thus ensures the pressure connection from the pre-chamber (17, 15) with lower pressure to the main chamber (13), the main chamber (13) also during a pressure change in the antechambers (15, 17) in each position of the sealing discs (20, 21) always with at least one of the antechambers (15, 17), briefly simultaneously pressure-connected with both and the sealing discs (20, 21) solely on the basis of Pressure differences in the antechambers (15,17) change their position, so that in use the expansion vessel (7) is always connected to the connection point (8) on the district heating network (1), which has the lower pressure and at the same time separated from the other connection point (8) is, characterized in that the housing (10) of the three-way valve (9) is designed in one piece. 7. Valve according to claim 6, characterized in that a main terminal (12) and a respective first and second terminal (14, 15) on fastening devices (18), the housing (10) are mounted tightly fastened. 8. Valve according to claim 6 or 7, characterized in that the inner diameter of the opening to the first resp. second connection (14, 16) on the housing (10) is greater than the respectively behind arranged sealing washer (20, 21). 9. Valve according to one of claims 6 to 8, characterized in that the compound (22) is mounted in the interior (11) in a guide (24). 10. Valve according to claim 9, characterized in that the guide (24) in the main chamber (13) is formed. 11. Valve according to claim 9, characterized in that the shoulders (23) form the guide (24). 12. Valve according to one of claims 6 to 11, characterized in that the sealing discs (20, 21) are guided guided in their pre-chambers (15, 17). 13. Valve according to one of claims 6 to 12, characterized in that the sealing discs (20, 21) on the main chamber (13) facing side and each shoulder (23) on the main chamber (13) facing away from a lochscheibenförmige sealing surface ( 27) which, for closing an antechamber (17, 19), correspond to one another. 14. Valve according to claim 13, characterized in that the connection (22) extends within the perforated disk-shaped passages of these sealing surfaces (27). 15. A combination of a valve (9) according to any one of claims 6 to 14 with one or more sub-valves (28) of the same kind, characterized in that each sub-valve (28) with its main terminal (12) at a first or second port (14, 16) of the valve (9) or another sub-valve (28) is connected pressure-connected, whereby in use the expansion vessel (7) at the main connection (12) of the valve (9) always pressure-connected exactly with the connection point (8) on the district heating network (1) which has the lowest pressure and at the same time is separated from all other connection points (8).