Domestic hot water preparation system

Abstract

The invention relates to a condensing gas boiler, comprising an outer casing (2) delimiting an internal volume (V), the boiler comprising a gas combustion chamber (9) and a heat exchanger (11) for circulating steam and fumes from the combustion of the gas in the combustion chamber (9) within the outer casing (2), at least one tank (15, 16) for holding water and disposed within the outer casing (2) such that, when the boiler (1) is operating, the water contained in said at least one tank (15, 16) can be heated by the steam and fumes circulating in the heat exchanger (11), the boiler comprising at least one water inlet (21) into said at least one tank and at least one water outlet (22) out of said tank (15, 16), at least one of said inlet (21) and outlet (22) being provided with an element (30), said compensating element, connected to the outer casing (2). and audit at least one reservoir (15, 16),the element (30) being shaped to compensate for deformations undergone by the boiler (1) during operation in at least one direction. Figure of the abstract: Figure 3,

Description

Title of the invention: Domestic hot water preparation system. Technical field.

[0001] The present invention relates to the field of domestic hot water preparation installations, in particular condensing gas boilers. Previous technique

[0002] Nowadays, heating has become a major societal issue and efforts are being made to reduce as much as possible the impact of domestic hot water heaters, and particularly gas boilers, on the environment, as well as to minimize heating costs for users.

[0003] A condensing gas boiler optimizes the operation of a gas boiler by recovering vapors and fumes from gas combustion.

[0004] More specifically, it is known that a condensing gas boiler comprises an outer casing enclosing an internal volume containing water, referred to as primary water. Gas combustion occurs in a combustion chamber of the boiler, which also includes a heat exchanger through which vapors and fumes from gas combustion circulate. The boiler is equipped with at least one domestic hot water tank, encapsulated within the outer casing, and arranged so that, when the boiler is operating, the domestic hot water in the tank is heated by the primary water, which is itself heated by the vapors and fumes circulating in the heat exchanger. During these heat exchanges, the vapors transfer their energy to the primary water and undergo condensation.

[0005] This type of boiler, while a technical advancement, has the drawback that, due to variations in pressure and / or temperature inside the tank and / or the outer casing, it generates deformation of the tank and / or the outer casing. By design, the water tank and the outer casing are subject to different pressure variations and / or are made of different materials and / or have a different design, and therefore deform to different degrees. There is thus a differential deformation between the two elements. A differential deformation between two encapsulated elements, such as the tank and the outer casing, inevitably generates stresses at the points of connection between the two elements, which, in the long term, can lead to fatigue failure of the connection. And, consequently, to water leaks and boiler malfunction.

[0006] The object of the invention is to remedy these drawbacks.

[0007] To this end, the invention relates to a domestic hot water preparation installation, comprising an outer casing delimiting an internal volume shaped to receive water, referred to as primary water, at least one tank intended to contain domestic water and disposed in the outer casing so that, when the installation is in operation, the water contained in said at least one tank can be heated by heat exchange with the primary water, the installation comprising at least one water inlet into said at least one tank and at least one water outlet out of said tank, at least one of said inlet and outlet being provided with an element, referred to as a compensation element, connected to the outer casing and to said at least one tank, the element being shaped to compensate for deformations suffered by the installation in operation in at least one direction, referred to as the principal deformation direction.

[0008] The compensation element allows a degree of freedom to be released at the connection points between the tank and the outer casing, which protects them from any fatigue and thus reduces the risks of malfunction of the installation.

[0009] According to another aspect, the compensation element includes a connecting conduit from the compensation element to said at least one tank and a connecting conduit from the compensation element to the outer casing.

[0010] According to another aspect, the connecting conduit of the compensation element to said at least one tank and the connecting conduit of the compensation element to the outer casing are shaped so that one of said conduits slides into the other of said conduits.

[0011] According to another aspect, the installation includes an intermediate portion integral with the connecting conduit of the compensation element to said at least one tank and with the connecting conduit of the compensation element to the outer casing.

[0012] According to another aspect, the intermediate portion is a flexible element.

[0013] According to another aspect, the intermediate portion is annular.

[0014] According to another aspect, the intermediate portion is at least partially mounted at the inside of one of the connecting conduits of the compensation element to at least one tank and to the outer casing.

[0015] According to another aspect, the intermediate portion is curved.

[0016] According to another aspect, at least one of the connecting conduits of the element of compensation audit at least one tank and the outer casing has an elbow.

[0017] According to another aspect, said water inlet and said water outlet are arranged in line with each other on either side of the outer casing.

[0018] The invention also relates to a domestic hot water preparation system, comprising a domestic hot water preparation installation as described above, and a heating device.

[0019] According to another aspect, the heating device includes a gas combustion chamber, and the installation is configured so that the system is a condensing gas boiler.

[0020] According to another aspect, the heating device comprises an electric resistance, and the installation is configured so that the system is an electric boiler. Brief description of the drawings

[0021] Other features, details and advantages will become apparent from reading the detailed description below and from analyzing the accompanying drawings, in which: Fig. 1

[0022] [Fig. 1] shows a schematic longitudinal cross-sectional view of a condensing gas boiler equipped with two compensation elements according to the present invention. Fig. 2

[0023] [Fig.2] shows a schematic longitudinal sectional view of the compensation element of [Fig.1], according to a first embodiment. Fig. 3

[0024] [Fig.3] shows a schematic longitudinal sectional view of the compensation element of [Fig.1], according to a second embodiment. Fig. 4

[0025] [Fig.4] shows a schematic perspective view of the compensation element of [Fig.1], according to a third embodiment. Fig. 5

[0026] [Fig.5] shows a schematic longitudinal sectional view of the compensation element of [Fig.1], according to a fourth embodiment. Description of the implementation methods

[0027] The present invention relates to a domestic hot water preparation installation comprising a compensation element, which will be detailed in this description.

[0028] The present invention relates to a domestic hot water preparation system, referenced 100, comprising the domestic hot water preparation unit, 1, and a water heating device. The water heating device is either integrated into the unit, as described with reference to [Fig. 1]. Alternatively, the heating device is separate from the unit, as detailed at the end of this description.

[0029] In [Fig. 1], system 100 is a condensing gas boiler. Such a boiler is known in particular from patent EP 1489366. However, the invention is not limited to this configuration and applies to any domestic hot water preparation installation in which at least one water tank is encapsulated in an outer casing.

[0030] In the figures, a coordinate system (X, Y, Z) is indicated to aid in the description. The Z direction is preferably vertical.

[0031] The boiler 100 indirectly provides domestic hot water heating using the thermal energy from the vapors and fumes produced by the combustion of the gas, which allows the vapors and fumes to be recovered before being released.

[0032] As seen in [Fig.1], the boiler 100 includes a domestic hot water preparation installation 1 comprising an outer casing 2, preferably cylindrical, extending between an upper sheet 3 and a lower sheet 4 and delimiting an internal volume V of the boiler 1. The volume V is shaped to contain water, called primary water.

[0033] The installation 1 is equipped with a separating partition 5 which divides the internal volume V into an upper part 6 and a lower part 7.

[0034] The upper part 6 extends between the separating partition 5 and the upper sheet 3, while the lower part 7 extends between the separating partition 5 and the lower sheet 4.

[0035] The separating partition 5 includes an orifice 8 for fluidic communication between the upper 6 and lower 7 parts.

[0036] The boiler 100 includes a gas combustion chamber 9 supplied by a burner 10 forming the heating device and arranged in the upper part 6 of the installation 1.

[0037] The installation 1 includes a heat exchanger 11 comprising tubes 12 for circulating vapors and fumes from the combustion of the gas in the combustion chamber 9. The tubes 12 extend parallel to the longitudinal axis L and are arranged between an outlet of the combustion chamber 9 and an inlet of a chamber 13.

[0038] The chamber 13 allows the recovery of fumes and condensate which have formed during the circulation of vapors in the tubes 12. As can be seen from [Fig.1], the chamber 13 is placed under the lower plate 4.

[0039] Each of the upper 6 and lower 7 parts includes an internal sanitary water tank 15, 16, the water contained in the tank 15, 16 being heated by the primary water (hence its name) from the internal volume V, itself heated by the vapors and fumes passing through the exchanger 11 in the tubes 12, when the boiler 1 is operating.

[0040] Preferably, each of the tanks 15, 16 is coaxial with the shell 1 and annular, in order to optimize heat exchange with the vapors and fumes.

[0041] A fluidic communication pipe 17 connects the tanks 15 and 16.

[0042] As can be seen from [Fig. 1], the boiler 1 includes a water inlet 18 into the lower part 7, a water outlet 19 out of the lower part 7 and a water outlet 20 out of the upper part 6.

[0043] Installation 1 also includes a water inlet 21 into the tank 16 and a water outlet 22 out of the tank 15.

[0044] The boiler 100 provides the heating of two water flows, a first flow, intended for heating radiators, being that of the primary water (from the internal volume V) and a second flow, intended for heating domestic water (from tanks 15, 16).

[0045] As can be seen from [Fig. 1], the inlet 21 and the outlet 22 are arranged in line with each other on either side of the outer casing 2 along a vertical direction. The inlet 21 is located in the lower part of the outer casing 2, and the outlet 22 in the upper part of the outer casing 2. For example, the inlet 21 and the outlet 22 are coaxial along the vertical direction.

[0046] The first flow of water enters the boiler 1 through the inlet 18 and exits the boiler 1 either through the outlet 19, having passed through the lower part 7, or through the outlet 20 after passing through the lower part 7, the orifice 8 and the upper part 6.

[0047] The second flow of water enters the boiler 1 through the inlet 21, then circulates through the tank 16, the pipe 17, the tank 15, and leaves the boiler 1 through the outlet 22.

[0048] At least one of the inlet 21 and the outlet 22 includes a compensating element 30. In [Fig.1], the inlet 21 and the outlet 22 both include a compensating element 30.

[0049] The compensating element 30 is now described in detail.

[0050] According to a first embodiment, illustrated in [Fig.2], the compensating element 30 comprises a hollow conduit 31.

[0051] The hollow conduit 31 comprises a body 32 having an intermediate portion 33, also called the central portion, extending between a first end portion 34 and a second end portion 35 along a longitudinal axis LL (on [Fig.2], the axis LL is directed along the Z direction).

[0052] The end 34 is shaped to be connected to one of the internal reservoirs 15, 16 while the other end 35 is shaped to be connected to the outer casing 2.

[0053] The body 32 is shaped to limit the stresses on the inlet 21 or the outlet 22 by being able to compress and stretch in the direction of the differential deformations, mainly along the Z direction, to compensate for them.

[0054] To achieve this, the central portion 33 is an annular flexible element comprising a set of coils 36. The central portion 33 advantageously has a straight cross-section. Thus, its cross-section varies according to an annular profile. The annular profile ensures an axial deformation of approximately + / -12% along the Z-axis, which allows for the absorption of differential deformation between the outer casing 2 and the internal reservoirs 15, 16. The modularity of the solution lies in adapting the length of the flexible element to the calculation of the differential deformation.

[0055] It is noted that the ringed profile also allows lateral deformations, in the X and Y axes, of the order of + / -1.5%, which allows more degrees of freedom in the parasitic differential deformations along these axes.

[0056] The profile of the central portion 33 ensures a good compromise between tensile / compressive strength and the service life of the boiler 1. It is noted that the profile can be chosen by increasing or decreasing the radius of curvature of the turns 36 and / or the pitch between the turns 36.

[0057] It is noted that the end portions 34, 35 are rigid, in the sense that they do not allow deformations in any direction.

[0058] As can be seen from [Fig.2], the end portion 34 extends along the axis LL between an end 34-1, called external, and an end 34-2, called internal, which is integral with the intermediate portion 33. The element 30 is integral with the reservoir 15, 16 by welding the end portion 34.

[0059] The intermediate portion 33 extends along the axis LL between an end 33-1 fixed to the end 34-2 of the end portion 34, and an end 33-2 fixed to the end portion 35.

[0060] The end portion 35 extends along the axis LL between an end 35-1, called internal, fixed to the end 33-2 of the intermediate portion 33 and an end 35-2, called external, free.

[0061] The end 35-2 advantageously includes a thread 37 for screwing the element 30 onto a connecting accessory, such as an elbow. The element 30 is secured to the outer casing 2 by welding the portion 35 between the end 35-1 and the thread 37.

[0062] In [Fig.2], the end portions 34 and 35 are tubes, the internal diameter of portion 34 being preferably equal to the internal diameter of portion 35 and the external diameter of portion 34 being equal to the external diameter of portion 35, which simplifies the manufacturing process of element 30.

[0063] According to a second embodiment, illustrated in [Fig.3], the compensating element 30 comprises a hollow conduit 31.

[0064] The hollow conduit 31 comprises a body 32 having a flexible intermediate portion 33, a first end portion 34 and a second end portion 35 along a longitudinal axis LL (on [Fig.3], the axis LL is directed along the Z direction). The two end portions 34 and 35 are rigid.

[0065] The end 34 is shaped to be connected to one of the internal reservoirs 15, 16 while the other end 35 is shaped to be connected to the outer casing 2.

[0066] The compensating element 30 according to the second embodiment is similar to the compensating element 30 according to the first embodiment. It differs from it in that the intermediate portion 33 extends at least partially into the end portion 34 or into the end portion 35, which makes the compensator 30 according to this embodiment more compact (compactness being the reduction of the distance between the end 34.1 and the end 35.2).

[0067] It is noted that, preferably, the intermediate portion 33 is integrated into the end portion 34, which allows the end portion 35, intended to be screwed to an accessory, to remain unchanged.

[0068] The body 32 is shaped to limit the stresses on the inlet 21 or the outlet 22 by being able to compress and stretch in the direction of the differential deformations, mainly along the Z direction, and also along the X and Y axes, to compensate for them, as already explained in detail in relation to [Fig.1].

[0069] In particular, the intermediate portion 33 is an annular flexible element comprising a set of coils 36. The central portion 33 advantageously has a straight cross-section. Thus, its cross-section varies according to an annular profile. The annular profile ensures an axial deformation of approximately + / -12% along the Z-axis, which allows for the absorption of differential deformation between the outer casing 2 and the internal reservoirs 15, 16. The modularity of the solution lies in adapting the length of the flexible element to the calculation of the differential deformation.

[0070] It is noted that the ringed profile also allows lateral deformations, in the X and Y axes, of the order of + / -1.5%, which allows more degrees of freedom in the parasitic differential deformations along these axes.

[0071] The profile of the central portion 33 ensures a good compromise between tensile / compressive strength and the service life of the boiler 1. It is noted that the profile can be chosen by increasing or decreasing the radius of curvature of the turns 36 and / or the pitch between the turns 36.

[0072] In the embodiment illustrated in [Fig.3], the intermediate portion 33 extends partially only in the end portion 34.

[0073] As can be seen from [Fig. 3], the end portion 34 extends along the axis LL between an end 34-1, referred to as the external end, and an end 34-2, referred to as the internal end. The end 34-1 is integral with the intermediate portion 33. The element 30 is integral with the reservoir 15, 16 by welding the end portion 34.

[0074] The intermediate portion 33 extends along the axis LL, mainly inside the end portion 34, between an end 33-1 fixed to the end 34-1 of the end portion 34, and an end 33-2 fixed to the end portion 35. The end 33-1 is disposed inside the intermediate portion 33 while the end 33-2 is preferably outside it.

[0075] The end portion 35 extends along the axis LL between an end 35-1, called internal, fixed to the end 33-2 of the intermediate portion 33 and an end 35-2, called external, free.

[0076] The end 35-2 advantageously includes a thread 37 for screwing the element 30 onto a connecting accessory, such as an elbow. The element 30 is secured to the outer casing 2 by welding the portion 35 between the end 35-1 and the thread 37.

[0077] As can be seen in [Fig.3], the inner diameter of the end portion 34 is greater than the outer diameter of the flexible element 33 and the end portion 35.

[0078] The compensating element 30 according to the second embodiment has a reduced total length, which maximizes the height of the internal tanks 15, 16 and therefore the performance of the boiler 1, without changing the height of the outer casing 2.

[0079] According to a third embodiment, illustrated in [Fig.4], the compensating element 30 comprises a hollow conduit 31.

[0080] The hollow conduit 31 comprises a body 32 having an intermediate portion 33, also called the central portion, extending between a first end portion 34 and a second end portion 35.

[0081] The end portion 34 is shaped to be connected to one of the internal reservoirs 15, 16 while the other end portion 35 is shaped to be connected to the outer casing 2.

[0082] The central portion 33 is a flexible element. The cross-section of the portion 33 is straight and can vary along its length. The central portion 33 is an annular flexible element comprising a set of turns 36.

[0083] As can be seen from [Fig.4], the end portion 34 extends into an end 34-1, called external, and an end 34-2, called internal, which is integral with the intermediate portion 33. The element 30 is integral with the reservoir 15, 16 by welding the end portion 34.

[0084] The end portion 34 has an angled shape, a first part, 34-1 forming a non-zero angle with a second part 34-11. The angle is preferably 90°. The first part 34-1 carries the external end 34-1 and the second part 34-11 carries the internal end 34-2.

[0085] As can also be seen from [Fig. 4], the end portion 35 extends between an end 35-1, referred to as the internal end, which is integral with the intermediate portion 33, and an end 35-2, referred to as the external end. The element 30 is integral with the outer casing 2 by welding the portion 35.

[0086] The end portion 35 has an angled shape, a first part 35-1 forming a non-zero angle with a second part 35-11. The angle is preferably 90°. The first part 35-1 carries the internal end 35-1 and the second part 35-11 carries the external end 35-2.

[0087] On [Fig.4], parts 34-1 and 35-11 extend parallel to the Z axis, while parts 34-11 and 35-1 extend parallel to the XY plane if the two angled shapes (34-11 and 35-11) have angles of 90°.

[0088] The intermediate portion 33 extends between an end 33-1 fixed to the end 34-2 of the end portion 34, and an end 33-2 fixed to the end 35-1 of the end portion 35.

[0089] The end 33-1 is arranged in the extension of the part 34-11 of the end part 34, and the end 33-2 is arranged in the extension of the part 35-I of the end part 35. The intermediate portion 33 is curved, in a principal plane (X, Y) if the two angled shapes (34-11 and 35-11) have angles of 90°.

[0090] Thus, the element 30 according to this third embodiment is capable of deforming in all directions, compensating in particular for differential deformations. The element 30 according to this embodiment has the advantage of being more compact than according to the two previous embodiments in the Z-axis, but is bulkier in the X and Y axes.

[0091] It should be noted that the preferred angle of 90° minimizes the size of element 30 along the Z-axis while allowing complete drainage of tanks 15 and 16 by gravity. The radius of the angle is preferably kept as small as possible within design limits to further minimize the overall size.

[0092] The flexible element 33 is a straight section whose cross-section varies like a corrugated profile, but unlike the elements 30 of the previous embodiments, where the impact of differential deformations generates axial deformations of the flexible element 33, the configuration of the third embodiment generates lateral deformations. An advantage of the element 30 according to this embodiment is an increase in the length of the flexible element, which, for the same differential deformation between the reservoir 15, 16 and the outer casing 2, reduces the required rate of lateral deformation.

[0093] According to a fourth embodiment, illustrated in [Fig. 5], the compensation element 30 comprises a connecting conduit 51 of the element 30 to the outer casing 2 and a connecting conduit 52 from element 30 to one of the tanks 15, 16.

[0094] The connecting conduit 51 extends along an axis LLL between a first free end 51-1 and a second end 51-2 attached to the outer casing 2, preferably by welding. The connecting conduit 52 extends along the axis LLL between a first end 52-1 and a second end 52-2. The element 30 is connected to one of the tanks 15, 16 by attaching the tank to the surface of the conduit 52, preferably by welding. A thread 53 allows for the attachment of an accessory, such as an elbow.

[0095] It is noted that, on [Fig.5], the longitudinal axis LLL is parallel to the Z axis.

[0096] As can be seen from [Fig. 5], the conduits 51, 52 are hollow cylinders, of right section.

[0097] The element 30 also includes an assembly nut 54 fixedly attached, for example screwed, inside the conduit 52, against the end 52-2 of the connecting conduit 52.

[0098] The primary water seal between the conduits 51 and 52 is ensured by a seal 55 compressed between an inner stop of the hollow conduit 52 and the assembly nut 54. The seal is chosen from various materials such as rubber, EPDM... with the criterion being its resistance to variations in pressure and temperature of the water contained in the outer casing and to the friction of the connecting conduit 51. This friction is generated by differential deformations.

[0099] Alternatively, the seal 55 may be one or more o-rings placed on bearing surfaces created for this purpose on either side of the nut 54.

[0100] It is noted that the assembly nut 54 allows both the compression of the seal 55 and the translational guidance of the connecting conduit 51 and / or allows dismantling and replacement of the sealing solution 55 in case of wear.

[0101] The connecting conduit 51 is mounted sliding within the connecting conduit assembly 52 and assembly nut 54. For this purpose, the outer diameter of the connecting conduit is smaller than the inner diameter of the hollow conduit 54.

[0102] The fact that the connecting conduit 51 translates along its longitudinal axis LLL ensures that it translates in the direction of the differential deformations in the Z axis to compensate for them.

[0103] With reference to [Fig.3], it is noted that it is possibly possible to encapsulate the annular portion 33 not only in the end portion 34 but also in the end portion 35.

[0104] It is noted that, for the first three embodiments, the end portion 34 forms a conduit for connecting the element 30 to the water tank and the portion end 35 form connecting conduit of element 30 to outer casing 2.

[0105] For each of the four embodiments described, the compensation element 30 releases one degree of freedom, which protects the inlet or outlet that the element 30 equips, despite the differential deformations to which the tank 15, 16 and the outer casing 2 are subjected.

[0106] In the first and second embodiments, the flexible element can compress and stretch in the direction of differential deformations in order to compensate for them. It is also capable of resisting unwanted displacements in other directions.

[0107] In the third embodiment, the flexible element can deform in all directions and thus compensate for all types of differential deformations.

[0108] In the fourth embodiment, the flexible element is free to slide in the direction of differential deformations to compensate for them while ensuring sealing.

[0109] In each of the illustrated embodiments, the differential deformations are due to the fact that the inlet 21 and the outlet 22 are arranged in the lower and upper parts, respectively, of the outer casing 2, which strongly constrains the domestic hot water heater.

[0110] An alternative solution consists of placing the inlet 21 also in the upper part of the outer casing 2 and extending a pipe to the bottom of the tank 15, 16 to allow the domestic hot water to enter the bottom of the tank 15, 16. However, this solution is less satisfactory in terms of performance, as the incoming water cools the hot water prepared in the upper part of the tank, thus reducing the temperature of this hot water available to the user. Furthermore, this solution cannot be drained by gravity.

[0111] As already indicated, the invention is not limited to the 100 condensing gas boiler.

[0112] According to another embodiment, not illustrated, the domestic hot water preparation system comprises the outer casing delimiting an internal volume V shaped to contain the primary water, a tank for containing the domestic hot water, a domestic hot water inlet into said tank, and a domestic hot water outlet from said tank. The inlet and outlet are located on either side of the outer casing, the inlet being in the lower part and the outlet in the upper part. The inlet and outlet are aligned with each other along the principal direction of deformation, as already explained with reference to the preceding embodiments. At least one of the inlet and outlet is provided with a compensating element 30, as detailed with reference to the preceding embodiments.

[0113] According to another embodiment, the heating device is an electric resistance element. Unlike the example of the domestic hot water heater with an integrated condensing gas heating element in the upper position, the resistance element is preferably located in the lower part (between the tank and the casing, preferably) of the electric domestic hot water heater.

Claims

Demands

1. A domestic hot water preparation installation comprising an outer casing (2) delimiting an internal volume (V) shaped to receive water, referred to as primary water, and at least one tank (15, 16) intended to contain domestic water and disposed within the outer casing (2) such that, when the installation (1) is in operation, the water contained in said at least one tank (15, 16) can be heated by heat exchange with the primary water. The installation (1) comprises at least one domestic water inlet (21) into said at least one tank and at least one domestic water outlet (22) out of said tank (15, 16), at least one of said inlet (21) and outlet (22) being provided with an element (30), referred to as a compensation element, connected to the outer casing (2) and to said at least one tank (15, 16), the element (30) being shaped to compensate for deformations undergone by the installation (1) operating in at least one direction,said principal deformation direction, characterized in that the compensation element (30) comprising a connecting conduit (34, 52) of the compensation element (30) to at least one tank (15, 16) and a connecting conduit (35, 51) of the compensation element (30) to the outer casing (2), it comprises an intermediate portion (33) integral with the connecting conduit (34) of the compensation element (30) to at least one tank (15, 16) and with the connecting conduit (35) of the compensation element (30) to the outer casing (2), the intermediate portion being at least partially mounted inside one of the connecting conduits (34, 35) of the compensation element (30) to at least one tank (15, 16) and to the outer casing (2).

2. Domestic hot water preparation installation according to claim 1, wherein the connecting conduit (34, 51) of the compensating element (30) to at least one tank (15, 16) and the connecting conduit (35, 52) of the compensating element (30) to the outer casing (2) are shaped so that one of said conduits slides into the other of said conduits.

3. Domestic hot water preparation installation according to claim 1, wherein the intermediate portion (33) is a flexible element.

4. Domestic hot water preparation installation according to the preceding claim, wherein the intermediate portion (33) is ringed.

5. Domestic hot water preparation installation according to claim 3 or 4, wherein the intermediate portion (33) is curved.

6. Domestic hot water preparation installation according to any one of the preceding claims, wherein at least one of the connecting conduits (34, 35) of the compensation element (30) to at least one tank (15, 16) and to the outer casing (2) has a bend.

7. Domestic hot water preparation installation according to any one of the preceding claims, wherein said water inlet (21) and said water outlet (22) are arranged in line with each other on either side of the outer casing (2).

8. Domestic hot water preparation system, comprising a domestic hot water preparation installation according to one of the preceding claims, and a heating device.

9. Domestic hot water preparation system according to claim 8, wherein the heating device comprises a gas combustion chamber, and the installation (1) is configured so that the system (1) is a condensing gas boiler.

10. Domestic hot water preparation system according to claim 8, wherein the heating device comprises an electric resistance, and the installation (1) is configured so that the system (1) is an electric boiler.

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