Domestic hot water preparation installation

Abstract

The invention relates to a condensing gas boiler, comprising an outer casing (2) delimiting an internal volume (V), the boiler comprising a combustion chamber (9) for the gas and an exchanger (11) for circulating in the outer casing (2) steam and fumes resulting from the combustion of the gas in the combustion chamber (9), at least one tank (15, 16) intended to contain water and arranged in the outer casing (2) so 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 exchanger (11), the boiler comprising at least one water inlet (21) in 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), called a compensation element, connected to the outer casing (2) and said at least one reservoir (15, 16),the element (30) being shaped to compensate for deformations undergone by the boiler (1) in operation in at least one direction. Abstract figure: Figure 3,

Description

Title of the invention: Installation for preparing domestic hot water Technical field

[0001] The present invention relates to the field of installations for preparing domestic hot water, in particular condensing gas boilers. Prior art

[0002] Nowadays, heating has become a major societal issue and we are seeking 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 makes it possible to optimize the operation of a gas boiler by recovering the vapors and fumes from the combustion of the gas.

[0004] More specifically, it is known that a condensing gas boiler comprises an outer casing delimiting an internal volume containing water, called primary. The combustion of the gas occurs in a combustion chamber of the boiler which also comprises a heat exchanger, in which vapors and fumes from the combustion of the gas circulate. The boiler is provided with at least one domestic water tank, encapsulated in the outer casing, and arranged so that, when the boiler is operating, the domestic water contained in the tank is heated by the primary water, itself heated by the vapors and fumes circulating in the exchanger. During the heat exchanges, the vapors transmit their energy to the primary water and undergo condensation.

[0005] This type of boiler, even though it constitutes a technical advance, has the disadvantage that, because the pressures and / or temperatures inside the tank and / or inside the outer casing vary, this generates a deformation of the tank and / or the outer casing. By design, the water tank and the outer casing undergo different pressure variations and / or are made of different materials and / or have a different design and therefore deform in different proportions. There is therefore 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 connection points between the two elements which, in the long term, can lead to failure due to fatigue of the connection. And, by the same token, to water leaks and malfunction of the boiler.

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

[0007] For this purpose, the invention relates to an installation for preparing domestic hot water, comprising an outer casing delimiting an internal volume shaped to receive water, called primary water, at least one tank intended to contain domestic water and arranged in the outer casing so that, when the installation is operating, 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 from said tank, at least one of said inlet and outlet being provided with an element, called a compensation element, connected to the outer casing and to said at least one tank, the element being shaped to compensate for deformations undergone by the installation in operation in at least one direction, called the main 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 comprises a conduit for connecting the compensation element to said at least one reservoir and a conduit for connecting the compensation element to the outer casing.

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

[0011] According to another aspect, the installation comprises an intermediate portion integral with the conduit for connecting the compensation element to said at least one tank and with the conduit for connecting 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 ringed.

[0014] According to another aspect, the intermediate portion is at least partially mounted on inside one of the connecting conduits of the compensation element to said 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 to 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 the extension of one another on either side of the outer casing.

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

[0019] According to another aspect, the heating device comprises 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 electrical resistance, and the installation is shaped so that the system is an electric boiler. Brief description of the drawings

[0021] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which: Fig.l

[0022] [Fig.l] shows a schematic view in longitudinal section of a condensing gas boiler equipped with two compensation elements according to the present invention. Fig. 2

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

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

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

[0026] [Fig.5] shows a schematic view in longitudinal section of the compensation element of [Fig.l], according to a fourth embodiment. Description of the embodiments

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

[0028] The present invention relates to a domestic hot water preparation system, referenced 100, comprising the domestic hot water preparation installation, 1, as well as a water heating device, 101. The water heating device is either integrated into the installation, as will be described with reference to [Fig.l]. Alternatively, the heating device 101 is remote from the installation, as will be detailed at the end of the description.

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

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

[0031] The boiler 100 indirectly provides heating of domestic water by the thermal energy of the vapors and fumes resulting from the combustion of the gas, which allows the vapors and fumes to be recovered before they are evacuated.

[0032] As visible in [Fig.l], the boiler 100 comprises 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.

[0033] The installation 1 is provided 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 comprises an orifice 8 for fluid communication between the upper 6 and lower 7 parts.

[0036] The boiler 100 comprises a gas combustion chamber 9 supplied by a burner 10 forming the heating device 101 and arranged in the upper part 6 of the installation 1.

[0037] The installation 1 comprises a heat exchanger 11 comprising tubes 12 for circulating vapors and fumes resulting 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 condensates which have formed during the circulation of vapors in the tubes 12. As can be seen from [Fig.l], the chamber 13 is placed under the lower sheet 4.

[0039] Each of the upper 6 and lower 7 parts comprises an internal sanitary water tank 15, 16, the water contained in the tank 15, 16 being heated by the primary water (hence its name) of 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 reservoirs 15, 16 is coaxial with the casing 1 and annular, in order to optimize the thermal exchanges with the vapors and fumes.

[0041] A fluid communication pipe 17 connects the reservoirs 15 and 16 together.

[0042] As can be seen from [Fig.l], the boiler 1 comprises a water inlet 18 in the lower part 7, a water outlet 19 from the lower part 7 and a water outlet 20 from the upper part 6.

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

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

[0045] As can be seen from [Fig.l], 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 arranged 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 leaves the boiler 1 either through the outlet 19, having passed through the lower part 7, or through the outlet 20 after having passed 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 in 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 comprises a compensating element 30. In [Fig.l], the inlet 21 and the outlet 22 both comprise 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 a central portion, extending between a first end portion 34 and a second end portion 35 along a longitudinal axis LL (in [Fig.2], the axis LL is directed in the direction Z).

[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 constraints on the inlet 21 or the outlet 22 by being capable of compressing and stretching in the direction of the differential deformations, mainly in the Z direction, to compensate for them.

[0054] To do this, the central portion 33 is an annular flexible element comprising a set of turns 36. The central portion 33 is advantageously of straight section. Thus, its section varies according to a ringed profile. The ringed profile ensures acceptance of an axial deformation of the order of + / -12% in the Z axis, which makes it possible to absorb a differential deformation between the outer casing 2 and the internal tanks. 15, 16. The modularity of the solution lies in the adaptation of 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 the tensile / compressive strength and the service life of the boiler 1. It is noted that the profile can be chosen by increasing or reducing 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, secured to the intermediate portion 33. The element 30 is secured to 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 secured to the end 34-2 of the end portion 34, and an end 33-2 secured to the end portion 35.

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

[0061] The end 35-2 advantageously comprises a thread 37 in order to screw the element 30 to a connection 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 the portion 34 being preferably equal to the internal diameter of the portion 35 and the external diameter of the portion 34 being equal to the external diameter of the portion 35, which simplifies the manufacturing process of the 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 (in [Fig. 3], the axis LL is directed in the direction Z). 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 therefrom 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 makes it possible to leave the end portion 35, intended to be screwed to an accessory, unchanged.

[0068] The body 32 is shaped to limit the constraints on the inlet 21 or the outlet 22 by being capable of compressing and stretching in the direction of the differential deformations, mainly along the Z direction, or even also along the X and Y axes, to compensate for them, as already explained in detail in relation to [Fig.l].

[0069] In particular, the intermediate portion 33 is an annular flexible element comprising a set of turns 36. The central portion 33 is advantageously of straight section. Thus, its section varies according to a ringed profile. The ringed profile ensures acceptance of an axial deformation of the order of + / -12% in the Z axis, which makes it possible to absorb a differential deformation between the outer casing 2 and the internal reservoirs 15, 16. The modularity of the solution lies in the adaptation of 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 the tensile / compressive strength and the service life of the boiler 1. It is noted that the profile can be chosen by increasing or reducing 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 into 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, called the external end, and an end 34-2, called 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 secured to the end 34-1 of the end portion 34, and an end 33-2 secured to the end portion 35. The end 33-1 is arranged 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, integral with the end 33-2 of the intermediate portion 33 and an end 35-2, called external, free.

[0076] The end 35-2 advantageously comprises a thread 37 in order to screw the element 30 to a connection 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 visible in [Fig.3], the inner diameter of the end portion 34 is greater than the outer diameter of the flexible element 33 and of 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 external 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 a 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 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 is apparent from [Fig.4], the end portion 34 extends one end 34-1, called external, and one end 34-2, called internal, 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 a bent 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 also emerges from [Fig.4], the end portion 35 extends between an end 35-1, called internal, integral with the intermediate portion 33, and an end 35-2, called external. The element 30 is integral with the outer casing 2 by welding the portion 35.

[0086] The end portion 35 has a bent 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 inner end 35-1 and the second part 35-11 carries the outer end 35-2.

[0087] In [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 90° angles.

[0088] The intermediate portion 33 extends between an end 33-1 secured to the end 34-2 of the end portion 34, and an end 33-2 secured 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 35-1 of the end part 35. The intermediate portion 33 is curved, in a main plane (X, Y) if the two bent 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, in particular compensating 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 more cumbersome in the X and Y axes.

[0091] It is noted that the preferably chosen angle of 90° makes it possible to minimize the size of the element 30 in the Z axis while allowing complete emptying of the tanks 15, 16, by gravity. The radius of the angle is preferably as small as possible within the design limits to also minimize the size.

[0092] The flexible element 33 is a straight section whose section varies like a ringed profile, but unlike the elements 30 of the previous embodiments, the impact of the differential deformations of which 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 tank 15, 16 and the outer casing 2, reduces the necessary lateral deformation rate.

[0093] According to a fourth embodiment, illustrated in [Fig.5], the compensation element 30 comprises a connecting conduit 51 from the element 30 to the outer casing 2 and a connecting conduit 52 from the element 30 to one of the reservoirs 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 secured 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 securing the tank to the surface of the conduit 52, preferably by welding. A thread 53 allows an accessory, such as an elbow, to be fitted.

[0095] Note that, in [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 straight section.

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

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

[0099] Alternatively, the seal 55 may be one or more o-rings (toric seals) placed on 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 connection conduit 51 and / or allows disassembly and replacement of the sealing solution 55 in the event of wear.

[0101] The connecting conduit 51 is slidably mounted in the connecting conduit 52 and assembly nut 54 assembly. To do this, the outside diameter of the connecting conduit is smaller than the inside 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 end portion 35 forms a conduit for connecting the element 30 to the outer casing 2.

[0105] For each of the four embodiments described, the compensation element 30 releases a 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 may compress and stretch in the direction of differential deformations in order to compensate for them. It is also capable of resisting parasitic displacements in other directions.

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

[0108] In the fourth embodiment, the flexible element is free to slide in the direction of the 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 places significant constraints on the domestic hot water heater.

[0110] An alternative solution consists of arranging the inlet 21 also in the upper part of the outer casing 2 and plunging a rod to the bottom of the tank 15, 16 to allow the sanitary water to penetrate to the bottom of the tank 15, 16. However, this solution is less satisfactory in terms of performance, the incoming water cooling the hot water prepared in the top of the tank, thus reducing the temperature of this hot water available to the user. In addition, this solution cannot be drained by gravity.

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

[0112] According to another embodiment, not illustrated, the sanitary water preparation installation comprises the outer casing delimiting an internal volume V shaped to contain the primary water, a tank intended to contain the sanitary water, a sanitary water inlet into said tank and a sanitary water outlet out of said tank. The inlet and outlet are arranged 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 in the extension of one another according to the main direction of deformation, as already explained with reference to the previous embodiments. At least one of the inlet and the outlet is provided with a compensating element 30, as detailed with reference to the previous embodiments.

[0113] According to another embodiment, the heating device 101 is an electrical resistor. Unlike the example of the domestic hot water heater with an integrated condensing gas heating device in the upper position 101, the position of the resistor is preferably in the lower part (between the tank and the casing, preferably) of the electric domestic hot water heater.

Claims

Claims

1. Installation for preparing domestic hot water, comprising an outer casing (2) delimiting an internal volume (V) shaped to receive water, called primary water, at least one tank (15, 16) intended to contain domestic water and arranged in the outer casing (2) so that, when the installation (1) is operating, the water contained in said at least one tank (15, 16) can be heated by heat exchange with the primary water, the installation (1) comprising at least one domestic water inlet (21) in said at least one tank and at least one domestic water outlet (22) from said tank (15, 16), at least one of said inlet (21) and outlet (22) being provided with an element (30), called 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) in operation in at least one direction,called the main deformation direction.,

2. Domestic hot water preparation installation according to claim 1, the compensation element (30) comprising a connection conduit (34, 52) of the compensation element (30) to said at least one tank (15, 16) and a connection conduit (35, 51) of the compensation element (30) to the outer casing (2).

3. Domestic hot water preparation installation according to the preceding claim, in which the connection conduit (34, 51) of the compensation element (30) to said at least one tank (15, 16) and the connection conduit (35, 52) of the compensation element (30) to the outer casing (2) are shaped so that one of said conduits slides in the other of said conduits.

4. Installation for preparing domestic hot water according to claim 2 or 3, comprising an intermediate portion (33) integral with the connection conduit (34) of the compensation element (30) to said at least one tank (15, 16) and with the connection conduit (35) of the compensation element (30) to the outer casing (2).

5. Installation for preparing domestic hot water according to the preceding claim, in which the intermediate portion (33) is a flexible element.

6. Installation for preparing domestic hot water according to the preceding claim, in which the intermediate portion (33) is corrugated.

7. Installation for preparing domestic hot water according to one of claims 4 to 6, in which the intermediate portion is at least partially mounted inside one of the connection conduits (34, 35) of the compensation element (30) to said at least one tank (15, 16) and to the outer casing (2).

8. Installation for preparing domestic hot water according to one of claims 4 to 7, in which the intermediate portion (33) is curved.

9. Installation for preparing domestic hot water according to the preceding claim, in which at least one of the connection conduits (34, 35) of the compensation element (30) to said at least one tank (15, 16) and to the outer casing (2) has an elbow.

10. Installation for preparing domestic hot water according to one of the preceding claims, in which said water inlet (21) and said water outlet (22) are arranged in line with each other on either side of the outer casing (2).

11. Domestic hot water preparation system, comprising a domestic hot water preparation installation according to one of the preceding claims, and a heating device (101).

12. A domestic hot water preparation system according to claim 11, wherein the heating device (101) comprises a gas combustion chamber, and the installation (1) is configured so that the system (1) is a condensing gas boiler.

13. Domestic hot water preparation system according to claim 11, wherein the heating device (101) comprises an electrical resistance, and the installation (1) is configured so that the system (1) is an electric boiler.

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