DE20201190U1 - Pressure protection arrangement on an open hot water tank - Google Patents

Description

Pressure relief arrangement on an open hot water tank

The present innovation relates to a pressure relief arrangement on an open hot water tank, which has at least one water inlet pipe, one water outlet pipe, a heating element and a storage tank.

Such hot water storage tanks are preferably used when hot water is to be produced and provided in the immediate vicinity of the point of use. Hot water storage tanks are available in different sizes, in particular with varying storage volumes and heating outputs.

For example, the German patent DE 197 22 635 C2 discloses a hot water tank that has a storage tank made up of two tank shells. By selecting the right material, this tank can be designed to be pressure-resistant. However, if a pressure-free design is preferred, there is a risk of the hot water tank being destroyed if the hot water tank is incorrectly connected or if it is defective.

It is generally known that hot water tanks can be operated without pressure, whereby it must be ensured that the water drain pipe is always open (and/or an overflow pipe is present) in order to allow pressure to equalize with the environment at all times. Only when cold water is fed into the storage tank via the water inlet pipe does the water level in the storage tank rise to such an extent that the stored and possibly heated water flows out through the water drain pipe.

·

·

·

Rev: January 23, 2002 · £t& SuM SinbJI . JJ. Ol 0311 006

To operate pressure-free hot water tanks, special fittings must be used that ensure that the water drain pipe is permanently open via the connected water tap. However, if a fitting designed for pressure operation is used when installing pressure-free hot water tanks, this can lead to the hot water tank being destroyed when it is first put into operation. There is also a risk that further damage could be caused by an explosion in the storage tank.

However, pressure-free hot water tanks can be damaged even when the correct fitting is used if the inlet pressure of the water being fed into the hot water tank is too high, which can happen, for example, if the line pressure is above average and there is no throttling device. Finally, the pressure in a hot water tank that is to be operated without pressure can increase to an unacceptable level if the line cross-section at the outlet of the hot water tank is severely restricted by unsuitable jet formers or outlet elements or by dirt particles or limescale deposits.

One of the objectives of the present innovation is therefore to provide a pressure safety arrangement that detects an incorrectly applied overpressure in hot water storage devices that are to be operated without pressure and prevents further operation of the hot water storage until the error is rectified in order to prevent the hot water storage from being destroyed. These and other objectives are achieved by the present innovation in that a pressure sensor is coupled to the water inlet pipe, which monitors the water pressure in the water inlet pipe, wherein the pressure sensor is connected to an electrical switch

Rev: 23.01.2002

• JE£& Suftl fcmSfe · J ,·

01 0311 006

which interrupts the supply circuit of the heating element in the event of excess pressure detected by the pressure sensor.

This pressure safety arrangement offers the advantage that if an overpressure initially occurs, the power supply to the heating element is immediately interrupted, so that on the one hand a further increase in pressure due to heating of the stored water is avoided and on the other hand the user of the hot water tank is clearly informed that the hot water tank is not operational due to a fault. It is therefore not possible to use the hot water tank if the overpressure still exists. In the event that the overpressure only occurs during operation, for example due to a cross-section restriction in the water outlet pipe, the pressure sensor reacts in time to prevent a further increase in pressure due to additional heat supply.

Preferably, the switching threshold of the pressure sensor is set so that the switching process is triggered by an overpressure which is in any case below the required bursting pressure of the storage tank.

According to a preferred embodiment, the pressure sensor has a pressure cylinder coupled to the water inlet pipe, in which a piston runs, which is pre-tensioned by a spring against the pressure prevailing in the water inlet pipe and is coupled to the electrical switch via a switching plunger. It is particularly advantageous if the pressure cylinder is formed in the form of a side flange on the water inlet pipe. This results in a very simple, reliable and functional without auxiliary energy.

Rev: 23.01.2002

·* jEjis suSi €itib« . · ; .·

01 0311 006

Structure of the pressure relief arrangement. The few components ensure a high level of reliability.

If, in addition, the wall of the water inlet pipe in the connection area of the pressure cylinder has a breakthrough area that is only broken through or drilled out when the piston is arranged in the pressure cylinder in the desired manner, the pressure relief arrangement according to the new version can be offered as a selectable option that is only activated when required.

In special designs of the hot water tank, which allow both under-sink and over-sink operation (known as such from the above-mentioned prior art), the side flange can be present on both connection pipes and only be fitted with the remaining components of the pressure relief arrangement when the operating mode of the hot water tank is determined, so that the pressure relief arrangement can be arranged on the water inlet pipe in any case.

According to an expedient embodiment, the electrical switch is a microswitch which is tiltably mounted in a switch holder, whereby the switching plunger causes the microswitch to tilt when there is excess pressure, whereby an actuating pin of the microswitch is actuated by striking the switch holder. In this way, the permissible switching path can be dimensioned within relatively large limits. Depending on the spring acting on the piston (and the spring force of the microswitch), a switch-off process is thus possible even at a relatively low excess pressure, without the pressure sensor or the switch being destroyed by a potentially significantly higher excess pressure.

Rev: 23.01.2002

01 0311 006

In a further developed embodiment, the electrical switch comprises a holding element which maintains the interruption of the supply circuit of the heating element even when the excess pressure drops. This holding element can be designed as a mechanical locking element which fixes the microswitch in the switch holder when it is switched and thus maintains the separation of the circuit. The holding element ensures that the user of the hot water tank registers a fault with certainty, since at least after a certain period of time there is no longer any hot water available in the storage tank.

By arranging the pressure relief device on the water inlet pipe, it remains easily accessible as it is located outside the thermal insulation that is usually present in the storage tank. The pressure relief device can therefore be reset manually without any major assembly work.

Further advantages, details and developments of the present innovation emerge from the following description of a preferred embodiment, with reference to the drawing. They show:

Fig. 1 is a perspective view of a section of a hot water tank with the elements of a pressure relief arrangement in the form of an assembly drawing;

Fig. 2 is a sectional view of the pressure relief arrangement attached to the hot water tank in the assembled state.

Rev: 23.01.2002

01 0311 006

Fig. 1 shows a perspective view of a section of a hot water storage tank 1. The hot water storage tank 1 has a storage tank 2 and two connecting pipes, one of which is designed as a water inlet pipe 3 and the other as a water outlet pipe 4. A heating element (not shown) is arranged inside the storage tank 2. The storage tank is normally encapsulated by thermal insulation and a housing (not shown).

To monitor the internal pressure in the storage tank, a pressure relief arrangement is provided which controls the pressure in the water inlet pipe 3, which (at least from a static point of view) is identical to the pressure in the storage tank, since the water inlet pipe 3 opens directly into the storage tank 2. The pressure relief arrangement comprises a pressure sensor which, in the embodiment shown, consists of a pressure cylinder 6 and a piston 7 slidably mounted therein. The pressure cylinder β is formed on the water inlet pipe 3 in the form of a side flange. In the embodiment shown, a second side flange 8 is formed on the water outlet pipe 4. This opens up the possibility of swapping the functioning of the two connection pipes if this is necessary for a changed operating position of the hot water tank.

To seal the piston 7 in the pressure cylinder 6, two sealing rings 9 are fastened in corresponding annular grooves in the piston 7. On the outward-facing side, the piston 7 is connected to a switching tappet 10, on which a spring 11 is guided.

Rev: 23.01.2002

0311 006

-&igr; Furthermore, the pressure relief arrangement comprises an electrical microswitch 13, which in the embodiment shown is mounted in a switch holder 14 on an axis 15 so that it can rotate or tilt.

Fig. 2 shows a simplified sectional view of the hot water tank 1 with the assembled pressure relief arrangement. The pressure cylinder 6 communicates with the interior of the water inlet pipe 3 via an open breakthrough area 17. As already explained above, each of the two connecting pipes has a side flange that can be used as a pressure cylinder. The breakthrough area 17 is only opened in the side flange to which the pressure relief arrangement is to be connected in order to monitor the pressure in the water inlet pipe. The water pressure acts on the piston 7 via the breakthrough area 17. The spring 11 is pre-tensioned after the piston has been installed so that the spring force counteracts the water pressure force generated by the water flowing into the storage tank. The sensitivity of the pressure relief arrangement is adjusted by selecting the appropriate spring force.

The hot water tanks used in Germany for pressure-free operation are designed to withstand a short-term maximum pressure of 5 bar when not heated. If a hot water tank designed to be operated without pressure is mistakenly connected to a pressure fitting, the spring force of the pressure safety arrangement that must be overcome must be selected in such a way that a switch is triggered when the hot water tank is first put into operation in order to signal the incorrect installation.

Rev: 23.01.2002

• :eJgs Suäl €mfcfi . : I ♦*

01 0311 006

This error can also occur if, for example, the water pressure introduced is too high, so that even when a pressure-free fitting is used, the pressure in the storage tank is too high. Finally, excessive pressure can occur if the pipe cross-section on the outlet side is reduced too much during normal operation and the pressure in the storage tank increases, for example due to the heating process. The pressure relief arrangement should be dimensioned so that a switching process is triggered in the range between 1.5 and 2 bar in order to avoid undesirable overpressure in the storage tank even at a maximum permissible heating temperature of 85 ⁰ C.

As can also be seen from Fig. 2, the switching plunger 10 extends into the switch holder 14 and acts there on the microswitch 13. The switch holder can be attached directly to the side flange that provides the pressure cylinder. When excess pressure occurs, the pressure plunger 10 moves further into the switch holder 14, causing the microswitch 13 to tilt about the axis 15. This triggers a switching process because an actuating pin 18 of the microswitch is actuated by striking a wall of the switch holder. This switching process separates the supply circuit of the heating element in order to immediately interrupt the further supply of heat output when an excess pressure situation occurs. If necessary, the microswitch can also generate an error signal.

In the embodiment shown, the switch holder 14 also comprises a locking element 19, which serves to maintain the switched-off state. As soon as the microswitch 13 is tilted upwards by the switching plunger 10,

¹ iäsS.Su&l JSirijH . i · _# **

Rev: 01/23/2002 'i&SS. S.ufcl JSirijH . i · _# ** 01 0311 006

-S-

the locking element 19 snaps into place on the underside of the microswitch 13, so that even if the excess pressure drops and the switching plunger 10 drops as a result, the latter does not return to its original position and the supply circuit of the heating element remains interrupted. The pressure safety arrangement can then only be reset by manual intervention. By positioning the pressure safety arrangement outside the insulation of the storage tank 2, the pressure safety arrangement remains easily accessible, so that the reset can be carried out without completely dismantling the hot water tank. If this self-holding effect is not desired, the locking element 19 can be dispensed with.

It is obvious to the person skilled in the art that structural modifications to the pressure safety arrangement are possible. For example, the pressure sensor and the electrical switch can be integrated in a closed unit, which may simplify assembly. It is also conceivable to arrange a membrane in place of the breakthrough area 17 in order to prevent tap water from penetrating the pressure sensor. The pressure sensor can also be designed in a different way, for example by using a spring membrane, which itself applies the required restoring force and is connected to the switching plunger.

Rev: 23.01.2002 * '!&SS Suhl J3mkfii . *. '. *' 01 0311

- 10 -

List of reference symbols

1 hot water tank

2 Storage tank 3 Water inlet pipe

4 Water outlet pipe

6 printing cylinders

7 pistons

8 second side flange 9 sealing rings

10 Switch tappets

11 Spring

13 Microswitch

14 Switch holder 15 Axis

17 Breakthrough area

18 Actuating pin

19 Locking element

Claims (12)

1. Pressure protection arrangement on an open hot water tank ( 1 ) which has a water inlet pipe ( 3 ), a water outlet pipe ( 4 ), a heating element and a storage tank ( 2 ), characterized in that a pressure sensor ( 6 , 7 , 11 ) which monitors the water pressure in the water inlet pipe ( 3) is coupled to the water inlet pipe (3 ) , and that the pressure sensor is coupled to an electrical switch ( 13 ) which interrupts the supply circuit of the heating element in the event of an excess pressure detected by the pressure sensor. 2. Pressure safety arrangement according to claim 1, characterized in that the pressure sensor has a pressure cylinder ( 6 ) coupled to the water inlet pipe ( 3 ), in which a piston ( 7 ) runs, which is prestressed by a spring ( 11 ) against the pressure prevailing in the water inlet pipe and is coupled to the electrical switch ( 13 ) via a switching plunger ( 10 ). 3. Pressure safety arrangement according to claim 2, characterized in that the electrical switch is a microswitch ( 13 ) which is tiltably mounted in a switch holder ( 14 ), wherein the switching plunger ( 10 ) causes a tilting of the microswitch ( 13 ) in the event of excess pressure, whereby an actuating pin ( 18 ) of the microswitch is actuated by a stop on the switch holder ( 14 ). 4. Pressure relief arrangement according to claim 2 or 3, characterized in that the pressure cylinder ( 6 ) is formed in the form of a side flange on the water inlet pipe ( 3 ). 5. Pressure safety arrangement according to claim 4, characterized in that the wall of the water inlet pipe ( 3 ) in the connection area of the pressure cylinder ( 6 ) has a breakthrough area ( 17 ) which is only broken through when the piston ( 7 ) is arranged in the pressure cylinder ( 6 ) in the desired way in order to establish the pressure coupling between the water inlet pipe ( 3 ) and the pressure sensor. 6. Pressure safety arrangement according to one of claims 1 to 5, characterized in that the electrical switch ( 13 ) comprises a holding element ( 19 ) which maintains the interruption of the supply circuit of the heating element even when the excess pressure decreases. 7. Pressure safety arrangement according to claim 6, insofar as this is directly or indirectly related to claim 3, characterized in that the holding element is formed by a locking element ( 19) incorporated in the switch receptacle (14 ) , which causes the microswitch ( 13 ) tilted when excess pressure is applied to be fixed in this switching position. 8. Pressure safety arrangement according to claim 7, characterized in that the microswitch ( 13 ) can be manually reset to its initial position after a switching operation and in the absence of excess pressure. 9. Pressure relief arrangement according to one of claims 1 to 8, characterized in that the storage container ( 2 ) is composed of two container shells. 10. Pressure relief arrangement according to claim 5, or according to one of claims 6 to 9, insofar as these are directly or indirectly related to claim 5, characterized in that the storage tank ( 2 ) is equipped with two connecting pipes ( 3 , 4 ), each having a side flange ( 8 ) which can be configured as a pressure cylinder ( 6 ) by breaking through the breakthrough area ( 17 ), depending on the installation position of the hot water tank and the use of the respective connecting pipe as a water inlet pipe ( 3 ). 11. Pressure relief arrangement according to one of claims 1 to 10, characterized in that the electrical switch ( 13 ) continues to generate an error signal when the supply circuit is interrupted. 12. Pressure safety arrangement according to one of claims 1 to 11, characterized in that the switching threshold of the pressure sensor is selected such that the interruption of the supply circuit of the heating element occurs at a pressure below the bursting pressure of the storage container.