Device for a metallic water container, use of the device and water container of a heat pump system

Abstract

The invention relates to a device (1) for a metallic domestic hot water tank, comprising at least a sacrificial anode (3) which has electrical insulation (4) at least in the area of ​​a connecting section (5) to the domestic hot water tank (2) and is provided with a current conductor arrangement (6) for electrical contacting the metallic domestic hot water tank (2), which includes a current limiting circuit (7). Furthermore, the use of the device and a domestic hot water tank in a heat pump system is proposed.

Description

[0001] The invention relates to a device for a metallic domestic water tank, a use of the device and a domestic water tank of a heat pump system with such a device, wherein the device comprises a sacrificial anode.

[0002] The sacrificial anode is a metallic element intended to protect, for example, a hot water tank from corrosion damage. The sacrificial anode can be rod-shaped and held by the tank, bringing it into direct contact with the water inside. Sacrificial anode designs similar to impressed current anodes are known, comprising a magnesium material or a magnesium alloy. The material of the sacrificial anode is below the metal of the tank walls (usually steel) in the electrochemical series, making it less noble and therefore more susceptible to corrosion.

[0003] When a metal comes into contact with water and oxygen, a so-called galvanic cell forms. The oxygen reacts with the metal, causing the iron to oxidize and release electrons. Consequently, rust forms, and the metal decomposes over time. This effect can be reduced in a domestic water tank by using a less noble sacrificial anode. In this case, the material of the sacrificial electrode dissolves (first) instead of the metal of the domestic water tank. The free metal particles migrate through the water (the electrolyte) to the tank wall, which no longer decomposes in this arrangement.

[0004] Sacrificial anodes in domestic hot water storage tanks must be regularly checked for wear and replaced if necessary. This is particularly time-consuming and often neglected in highly integrated domestic hot water storage tanks, such as the indoor units of air-to-water heat pumps.

[0005] It is known to use insulated sacrificial anodes to indicate the need for anode replacement when the galvanic protection current falls below the specified level due to anode aging (e.g., through a visual indicator). This eliminates the need to remove the anode to check for wear.

[0006] The service life of sacrificial anodes depends on several factors, including the quality of the tank materials, damage to the tank's internal protective coating, and / or the mineral composition and resulting conductivity of the water in the tank.

[0007] The object of the invention is therefore to at least partially alleviate or even solve the aforementioned problems. In particular, the service life and usability of the sacrificial anode are to be extended, especially in the case of high electrical conductivities of the domestic water. Furthermore, the effort required for wear monitoring is to be reduced. Furthermore, a system is to be provided that can be easily retrofitted to existing hot water systems, operates independently, and / or is space-saving to install.

[0008] These objects are achieved by the subject matter of the independent claims. Advantageous embodiments are specified in the dependent claims. The features recited in the claims can be combined with one another in any technologically expedient manner, thereby providing further embodiments. The following description, particularly in conjunction with the accompanying figures, illustrates the invention and provides further embodiments.

[0009] For this purpose, a device for a metallic domestic water tank comprises at least one sacrificial anode. The sacrificial anode is electrically insulated at least in the area of ​​a connecting section to the domestic water tank. Furthermore, the device includes a current-conducting arrangement for electrically contacting the metallic domestic water tank, which arrangement includes a current-limiting circuit.

[0010] The sacrificial anode can be rod-shaped. It is possible for the sacrificial anode to have a (circumferential) connecting section, for example designed with a thread, a flange or the like, which allows a (detachable) attachment of the sacrificial anode to the domestic water tank, so that the sacrificial anode can also extend into the interior of the domestic water tank and come into contact with the water contained therein. The connecting section is electrically insulated, so that no electrical current can flow from the material of the sacrificial anode via the connecting section to the domestic water tank. The insulation can be a separate component and / or a coating of the sacrificial electrode. It is possible for the insulation to extend further (almost) to the inner end of the sacrificial electrode.

[0011] The (preferably sole) power line arrangement for electrically contacting the metal domestic water tank can, for example, be implemented with a cable that is or can be arranged in an electrically conductive manner on the one hand to the material of the sacrificial anode, and on the other hand is or can be arranged in an electrically conductive manner (externally) to the metal of the domestic water tank. The connections of the power line arrangement can be designed to be detachable, e.g., via clamps, clips, screw connections, or the like.

[0012] The power line arrangement also comprises (at least) one current-limiting circuit. This is an electrical path between two or more points along which electrical current can flow, wherein this current comprises at least one (preferably several) electronic or electrical components. The current-limiting circuit is configured such that the maximum flowing protective current is or is limited to a predetermined value. The current-limiting circuit can be a separate assembly connected to the power line arrangement. The current-limiting circuit can be partially or fully integrated into the power line arrangement. The current-limiting circuit can partially perform an (electrical) function of the power line arrangement, e.g., the electrical contacting of the domestic water tank.

[0013] The sacrificial anode can be made of magnesium. Suitable magnesium alloys are described, for example, in EN 12438.

[0014] The current-limiting circuit can be configured to limit the maximum current to 3 milliamperes [mA]. ​​Preferably, the current-limiting circuit is configured to limit the maximum current to 1.5 mA or even to 1.0 mA or 0.6 mA. By limiting the maximum current flowing between the sacrificial anode and the service water tank (e.g., made of steel), the service life of the sacrificial anode can be significantly extended. The sacrificial anode dissolves more slowly at a lower current flow.

[0015] The current-limiting circuit can be positioned adjacent to the connecting section. It is possible for the current-limiting circuit to be positioned in close proximity (outside) to the connecting section. Thus, holding means can be provided in the area of ​​the sacrificial anode to fix the current-limiting circuit in position. A type of (external) closure housing for the sacrificial anode can also be provided, which adjoins the connecting section and houses the current-limiting circuit. This creates a compact unit.

[0016] It is possible for the current-limiting circuit to be attached to the domestic water tank. For example, fastening means can be provided to ensure electrical contact between the current-limiting circuit and the domestic water tank. It is possible for the current-limiting circuit to be attached to the outer surface of the domestic water tank using a magnet and / or a flange.

[0017] The current-limiting circuit is specifically designed to operate without an additional supply voltage. In other words, this means that the sacrificial anode is not a so-called impressed current anode. The sacrificial anode therefore only has a current conduction arrangement leading to the wall of the domestic water tank.

[0018] According to a further aspect, the use of a device disclosed here for corrosion protection of a metallic domestic water tank, in particular made of steel, is proposed. A preferred use is one in which the metallic domestic water tank has an enamel coating on the inside. The sacrificial anode is most preferably an insulated magnesium anode. The domestic water tank is preferably one that is integrated into a heat pump system, in particular into an indoor unit of an air-water heat pump.

[0019] Furthermore, a domestic water tank of a heat pump system is proposed, comprising a device disclosed here, wherein the sacrificial anode is electrically insulated and held in a tank wall of the domestic water tank, and the power line arrangement electrically contacts the tank wall on the outside. This provides a preferred installation. In particular, when combining heat pumps with enamelled

[0020] Service water tanks allow for significantly extended maintenance cycles and thus lower maintenance costs for the end customer.

[0021] The statements regarding the device can also be used without restriction to characterise the use and / or the domestic water tank, and vice versa.

[0022] According to a preferred embodiment, the current is limited by using an insulated magnesium sacrificial anode, which prevents direct (electrical) contact between the magnesium sacrificial anode in the connecting section (the screw connection) and the domestic water tank. The current flows to the domestic water tank, in particular, via an electrical cable that runs from the magnesium sacrificial anode to the domestic water tank and is electrically connected to it. This cable is routed through a current-limiting circuit that limits the maximum protective current to, for example, 3 mA or even lower.

[0023] The invention and the technical environment will now be explained in detail with reference to the figures. It should be noted that the representations in the figures are not intended to limit the invention, but merely show individual exemplary embodiments. The features in the figures may be combined with related aspects of the description and / or other features from other figures, unless explicitly excluded below.

[0024] They represent schematically: Fig. 1: a heat pump system with a device disclosed here Fig. 2: a detail of an exemplary attachment of the device to a domestic hot water tank, and Fig. 3: an example of a current limiting circuit.

[0025] Fig. 1 schematically illustrates a domestic water tank of a heat pump system 14, which comprises a device 1, which is explained in detail below in connection with the other figures.

[0026] The heat pump system 14 comprises a heating device 15, which comprises, for example, a burner (not shown) and a heat exchanger, with which the domestic water 17 can be heated and fed via water pipes into the domestic water tank 2, where it can be stored and, if necessary, maintained (in a controlled manner) at a certain temperature via an (electric) heating element 16.

[0027] The domestic water tank 2 comprises a tank wall 9 that defines a storage volume for the domestic water 17. An enamel layer 8 can be applied to the inside of the tank wall as corrosion protection. Sensors (not shown) can be assigned to the domestic water tank 2, which can be used to adjust the fill level and / or temperature.

[0028] A single device 1 is attached to the upper area. One type of attachment is shown in Fig. 2 which will now be explained.

[0029] The device 1 comprises - as in Fig. 2 shown schematically - a (single) sacrificial anode 3, which has electrical insulation 4 at least in the region of a connecting section 5 to the domestic water tank 2 (here comprising an outer tank wall 9 made of steel and an inner enamel layer 8). This prevents a (direct) current flow from the material of the sacrificial anode 3 (e.g., magnesium) via the connecting section 5 (e.g., a screw connection) to the tank wall 9. Thus, the sacrificial anode 3 is held in an electrically insulated manner in the tank wall 9 of the domestic water tank 2.

[0030] Furthermore, a current-conducting arrangement 6 (e.g., in the form of a cable) is provided, which electrically contacts the material of the sacrificial anode 3 on the one hand and the (outer) container wall 9 on the other. The current-conducting arrangement 6 comprises a current-limiting circuit 7, which limits the maximum flowing current to 3 milliamperes. In the illustrated case, the current-limiting circuit 7 is positioned adjacent to the connecting section 5 and / or is attachable / attached to the container wall 9.

[0031] Fig. 3 shows an embodiment of a current-limiting circuit 7, which can be provided in the electrical path between the sacrificial anode 3 and the container wall 9. By appropriately designing or matching the first resistor 10 and second resistor 11, as well as the first transistor 12 and second transistor 13, the maximum flowing current can be limited to a predetermined value, e.g., even to 0.6 mA. List of reference symbols

[0032] 1Device 2Domestic water tank 3Sacrificial anode 4Electrical insulation 5Connection section 6Power line arrangement 7Current limiting circuit 8Enamel layer 9Tank wall 10First resistor 11Second resistor 12First transistor 13Second transistor 14Heat pump system 15Heating device 16Heating element 17Domestic water

Claims

1. Device (1) for a metallic service water tank (2), at least comprising a sacrificial anode (3) which has electrical insulation (4) at least in the region of a connecting section (5) towards the service water tank (2) and is provided with a current line arrangement (6) for electrically contacting the metallic service water tank (2), which comprises a current limiting circuit (7).

2. Device (1) according to claim 1, characterized in that the sacrificial anode (3) is formed with magnesium.

3. Device (1) according to claim 1 or 2, characterized in that the current limiting circuit (7) is set up so that the maximum current is limited to 3 milliamperes.

4. Device (1) according to one of claims 1 to 3, characterized in that the current limiting circuit (7) is positioned adjacent to the connecting section (5).

5. Device (1) according to one of claims 1 to 4, characterized in thatthe current limiting circuit (7) can be attached to the domestic water tank (2).

6. Device (1) according to one of claims 1 to 5, characterized in that the current limiting circuit (7) is designed to function without additional supply voltage.

7. Use of a device (1) according to one of the preceding claims for corrosion protection of a metallic domestic water tank (2).

8. Use according to claim 7, wherein the metallic domestic water tank (2) has an enamel layer (8) on the inside.

9. Domestic water tank (2) of a heat pump system (14), comprising a device (1) according to one of claims 1 to 6, wherein the sacrificial anode (3) is held in an electrically insulated manner in a tank wall (9) of the domestic water tank (2) and the power line arrangement (6) electrically contacts the tank wall (9) on the outside.

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