PORTABLE ELECTRIC IMMERSION WATER HEATER WITH DRY HEATING DETECTION

Abstract

PORTABLE ELECTRIC IMMERSION WATER HEATER WITH DRY HEATING DETECTION The invention relates to a portable electric immersion water heater (1) comprising an electric heating element (7) comprising two connection terminals (8a, 8b) configured to supply a heat dispersing part (10); an electrical power supply module (12) electrically connected to the two connection terminals (8a, 8b);and a thermostat (14) comprising a temperature sensor (15) disposed in a thermostat sleeve (16), the water heater (1) further comprising a thermal bridge (18) formed between the thermostat sleeve (16) and the heat-dispersing part (10), the temperature sensor (15) being a bimetallic thermal contact located in the sleeve (16) opposite the thermal bridge (18), the thermostat (14) being configured to cut off the power supply to the heating element (7) when the thermal contact detects that a predefined temperature threshold has been reached, particularly in the case of dry heating. Figure to be published with the abbreviation: Figure 3;

Description

Title of the invention: PORTABLE ELECTRIC IMMERSION WATER HEATER WITH DRY BOILING DETECTION

[0001] The present invention relates to the field of electric water heaters, and in particular relates to a portable electric immersion water heater with dry heating detection.

[0002] Portable electric immersion water heaters (also known as immersion heating rods or immersion heaters) are widely used to raise the temperature of water to be heated to extreme levels. They do not have a tank and are generally in the form of a heating rod or an elongated heating body to be immersed in water in order to heat it. These portable water heaters are generally used for domestic purposes to heat water in a container such as a basin, the heated water being then used, for example, for bathing, washing dishes and / or clothes, or for other domestic applications.

[0003] Existing portable immersion water heaters generally comprise a head portion under which a heating element is secured, the head portion comprising various electrical components for regulating a flow of electric current to the heating element, the heating element to be immersed in the water to be heated such that the head portion is above the surface of the water.

[0004] However, with these existing portable water heaters, in the event of dry heating (i.e., when the heating element heats up while not submerged and is in the air), there is a risk that the heating element will overheat and burn / melt the environment on which it rests (e.g., the floor of a dwelling or the material comprising the container in which the portable water heater is placed) and / or a protective plastic casing surrounding the heating element, which could lead to a fire. Furthermore, without dry heating detection, the heating element itself will be destroyed due to its extreme heat.

[0005] Existing portable water heaters sometimes have a thermostat for detecting the temperature of the water in which the heating element is immersed so as to regulate the flow of electric current in the heating element. However, the position of this thermostat is far from the heating zone of the heating element and thus does not allow for rapid detection of a significant rise in the temperature of the heating element in the event of dry heating. Indeed, due to this design, in the event of dry heating, the heat takes a fairly long time to reach the thermostat by convection transfer via the air. If the Dry heating detection takes several minutes, the life of the heating element is greatly reduced.

[0006] Existing portable water heaters do not have an effective dry heating detection system and heat continuously when in the air, which can cause the destruction of the product (resulting in an electrical risk), or even a fire in the home or premises in which the water heater is used. Thus, due to the lack of dry heating detection, the service life of the heating element is reduced.

[0007] For example, a test carried out on an existing portable water heater found that, when heating dry on the floor, the dry heating was not detected by the thermostat even after two minutes. Indeed, due to the significant distance between the thermostat and the heating element, after two minutes of dry heating, the temperature of the heating element was 248°C while the temperature detected by the thermostat was only 40°C. This test was even extended to the point where the copper surface of the heating element was incandescent (at more than 500°C), without a better result in detecting dry heating.

[0008] Thermostats generally used in existing portable water heaters may be bulb capillary thermostats or rod / stem thermostats. However, for both types of thermostats, the temperature measurement is made over a fairly large area in terms of length (e.g., about 90 mm for a bulb thermostat and about 270 mm by a rod thermostat). This long measuring surface is very effective for normal use in water when the temperature gradient in the water is small (for example, when heating in water, the water temperature near the heating element may be 65°C, and the water temperature at the thermostat measuring surface may be between 62°C and 60°C depending on the depth),but does not work correctly when heating in air since the heating surface is located only on a small part of the sensitive area of ​​the thermostat (for example, when heating dry in air, the temperature near the heating element can reach 300°C, and the temperature at the measuring surface of the thermostat can be between 180°C and 30°C depending on the depth, so that a wide temperature range is present on the sensitive area of ​​the thermostat which does not allow it to correctly detect dry heating).

[0009] The present invention aims to solve the drawbacks of the prior art, by proposing a portable electric immersion water heater allowing rapid and efficient detection in the event of dry heating, so that the water heater according to the present invention retains its safety in all heating conditions (namely, normal heating condition when the heating element is immersed, and abnormal heating condition when the heating element is not immersed in the event of misuse or accident).

[0010] The present invention therefore relates to a portable electric immersion water heater comprising: an electric heating resistor comprising two connection terminals which are fixed to a support and which are configured to supply a heat dispersive part which extends away from the support and which is configured to be immersed in water to be heated; a power supply module mounted on the support and electrically connected to the two connection terminals of the electric heating resistor in order to allow a flow of electric current through the electric heating resistor;and a thermostat connected to the power supply module and comprising a temperature sensor arranged inside a thermostat sleeve extending from the support towards the heat dispersive part of the electric heating resistor, said temperature sensor being configured to detect the temperature of the electric heating resistor, characterized in that the water heater further comprises a thermal bridge formed between the thermostat sleeve and the heat dispersive part of the electric heating resistor, and in that the temperature sensor is a bimetallic thermocontact located in the thermostat sleeve opposite the thermal bridge, the thermostat being configured to cut off the power supply to the electric heating resistor by the power supply module when the thermocontact detects the reaching of a predefined temperature threshold, in particular in the case of dry heating without immersion. ;

[0011] When the power supply module supplies an electric current to the electric heating resistor via its two connection terminals, the heat dispersive portion of the electric heating resistor has resistance to current flow, which leads to a temperature rise in the heat dispersive portion of the electric heating resistor.

[0012] The thermal bridge formed between the thermostat sleeve and the heat dispersive portion of the electric heating resistor allows more heat to come more quickly to the thermostat sleeve in which the temperature sensor is located, thereby greatly reducing the dry heating detection time. The thermal bridge thus improves the temperature detection of the heat dispersive portion of the electric heating resistor by the thermostat temperature sensor, thereby reliably and quickly detecting dry heating of the portable water heater.

[0013] The thermostat allows the power supply to the electric heating element to be cut off in the event of overheating in immersion conditions. The thermostat also allows the power supply to be cut off to the electric heating element in case of dry heating (i.e., when the electric heating element is energized in a non-immersed state) when the temperature detected by the temperature sensor is greater than or equal to the predefined temperature threshold.

[0014] The bimetallic thermocontact type temperature sensor is of small spatial extent and located at the thermal bridge, which makes it possible to accurately detect the temperature of the electric heating resistor and thus improve the speed of detection of possible dry heating, thus improving safety and preventing a risk of fire starting in the event of dry heating.

[0015] Dry heating can thus be detected in less than 50 seconds (a reactivity in the event of dry heating ranging from 35 to 40 seconds can be obtained in practice), which makes it possible to guarantee the safety of the product in all heating conditions, and which also makes it possible to guarantee the lifespan of the heating element even with multiple dry heatings undergone. Above this duration of 50 seconds, with a power of 1500W for example, the temperature of the electric heating resistor would directly impact any protective plastic casing formed around the electric heating resistor and thus the overall safety of the product. Indeed, the heat reached in the heating element itself would be such that it would be destroyed after a few minutes by melting of its conductive filament.

[0016] The thermostat of the present invention thus allows rapid detection of the rise in temperature in the air in the event of dry heating, but is also capable of correctly regulating the temperature of the water when the product is used in a normal immersion condition.

[0017] Thanks to the rapid detection of dry heating of the water heater according to the present invention, the service life of the electric heating resistor is extended, and there is no longer any risk of the product burning and causing a fire.

[0018] The present invention thus has good reactivity under all heating conditions, and is a low-cost solution compared to existing products.

[0019] It should be noted that the electric heating resistance needs a low power density to ensure the stability of the temperature sensor under all conditions and efficient detection of dry heating (for example, a power density limited to 1500W to ensure temperature stability in normal use).

[0020] According to a particular characteristic of the invention, the thermocontact is a normally closed bimetallic thermocontact, connected by wire to the electrical power supply module.

[0021] Thus, the bimetallic thermocontact is small in size and allows for good responsiveness. Such a sensor has a very small temperature measurement area (for example, 19 mm, i.e. 4 to 12 times smaller than usual sensors for water heaters). This small size allows the assembly to have good responsiveness both in a normal heating condition in water and an abnormal dry heating condition.

[0022] The bimetallic thermocontact comprises two blades composed of two separate metals, said two blades being in contact (thermocontact closed) when the temperature is lower than the predefined temperature threshold, and said two blades moving away from each other (thermocontact open) when the temperature becomes higher than or equal to the predefined temperature threshold, the thermostat then cutting off the electrical power supply to the electrical heating resistor as soon as the thermocontact opens.

[0023] According to a particular characteristic of the invention, the thermal bridge is at least one brazing.

[0024] Thus, the at least one solder makes it possible to create a permanent point of contact between the thermostat sleeve and the heat dispersive part of the electrical heating resistor, which allows faster heat transfer by conduction via the metal (for example, copper) forming the solder.

[0025] According to a particular characteristic of the invention, the heat dispersive part has a helical shape.

[0026] Thus, in immersion conditions, the helical shape of the electric heating resistor allows optimal heating of the water.

[0027] According to a particular characteristic of the invention, the thermal bridge is formed between the thermostat sleeve and the turn of the heat dispersive part of the electric heating resistor closest to the two connection terminals of the electric heating resistor.

[0028] Thus, the formation of the thermal bridge on the first turn of the helical heating resistor allows both rapid detection of dry heating and good detection of water temperature in normal immersion use.

[0029] According to a particular characteristic of the invention, the predefined temperature threshold at which the thermocontact is triggered is between 55°C and 75°C.

[0030] According to a particular characteristic of the invention, the thermocontact is mounted in a housing having a length of between 15 and 35 mm, a width of between 6 and 8 mm, and a thickness of between 3 and 5 mm.

[0031] Thus, the thermocontact has a small spatial extent and can therefore be placed directly at the height of the thermal bridge, so that the entire measuring zone of the thermocontact is located opposite the heat dispersive part of the electrical heating resistor, which makes it possible to detect overheating more quickly.

[0032] According to a particular characteristic of the invention, the electric heating resistor has a surface power density of between 3 and 7 W / cm2, preferably equal to 6 W / cm2.

[0033] According to a particular characteristic of the invention, the water heater further comprises a protective housing in which the electric heating resistor is arranged, said protective housing comprising at least one opening configured to allow water to pass therethrough when the heat dispersive part of the electric heating resistor is immersed in water.

[0034] Thus, the protective housing, for example of cylindrical shape, is close to the electric heating resistor so as to protect the environment and the user from the electric heating resistor, which makes it possible to avoid any risk of burning.

[0035] The protective casing also serves as a support to allow the portable water heater to stand upright on its own inside or outside the container of water to be heated.

[0036] Preferably, the protective housing has a plurality of openings to facilitate uniform heating of the water and to facilitate mixing of the water by reducing the temperature difference in the upper and lower portions of the volume of water to be heated.

[0037] According to a particular characteristic of the invention, the protective casing is made of polymer material, preferably plastic material.

[0038] Thus, the protective housing is made of a low conductivity material.

[0039] The dry heating protection of the water heater according to the present invention makes it possible to prevent the protective housing from heating too much and deforming in the event of dry heating, which would lead to an alteration of the protection of the user since he could have access to the hot zone of the water heater, and which would also lead to a high surface temperature of the protective housing and a risk of burns for the user in the event of contact with the protective housing.

[0040] According to a particular characteristic of the invention, the minimum distance between the protective housing and the electric heating resistor is greater than or equal to 30 mm.

[0041] According to a particular characteristic of the invention, the electric heating resistor is tubular and consists of a metal tube in which a metal wire is inserted over the entire length of the metal tube, the two ends of said metal wire forming the two connection terminals of the electric heating resistor, said metal wire having a portion with reduced cross-section arranged in the heat-dispersing portion of the metal tube of the electric heating resistor, the thermal bridge being formed on the metal tube of the electric heating resistor at a location in which the cross-section of the metal wire of the electric heating resistor is reduced.

[0042] Thus, the electric heating resistor has a so-called hot zone formed by the heat dispersive part in which the metal wire has a reduced section, and a so-called cold zone formed by the remaining part of the electrical heating resistance which connects the heat dispersive part to the two connection terminals and in which the section of the metal wire is larger.

[0043] Preferably, the reduced section portion of the metal wire is spiraled.

[0044] The change in the cross-section of the metal wire makes it possible to generate significant friction at the junction between the hot and cold zones, which will generate heat in the part with the reduced cross-section.

[0045] The contact zone of the thermal bridge with the electric heating resistor is located downstream of the junction between the cold and hot zones, so as to allow the temperature sensor to accurately and reactively detect the temperature of the hot zone of the electric heating resistor.

[0046] To better illustrate the object of the present invention, a preferred embodiment will be described below, by way of illustration and not limitation, with reference to the appended drawings.

[0047] In these drawings:

[0048] [Fig. 1] is a perspective view of a portable electric water heater according to the present invention immersed in a container filled with water to be heated;

[0049] [Fig.2] is a perspective view of the portable electric water heater according to the present invention;

[0050] [Fig.3] is a sectional view of the portable electric water heater according to the present invention;

[0051] [Fig.4] is an exploded view of the portable electric water heater according to the present invention;

[0052] [Fig.5] is a side view of the electric heating resistor-thermostat assembly of the portable electric water heater according to the present invention;

[0053] [Fig.6] is a perspective view of the electric heating resistor-thermostat assembly, at the thermal bridge; and

[0054] [Fig.7] is a side view of the electric heating resistor-thermostat assembly on which the thermostat temperature sensor has been shown in dotted lines.

[0055] Referring to [Fig. 1], it can be seen that there is shown a portable electric immersion water heater 1 according to a preferred embodiment of the invention.

[0056] The portable electric immersion water heater 1 is placed by the user inside a basin or bucket type container 2 filled with water, and allows the water to be heated to then allow the user to use the heated water for example for washing, for washing dishes and / or clothes, or for other domestic applications.

[0057] The portable water heater 1 has a protective casing 3 of substantially cylindrical shape in which is arranged a heating element which will be described in more detail later.

[0058] It should be noted that the protective housing 3 could also take any other form, without departing from the scope of the present invention.

[0059] The protective housing 3 serves to protect the environment and the user from the heating element, in order to avoid any risk of burns.

[0060] The protective casing 3 also serves as a support to allow the portable water heater 1 to stand on its own in a vertical position inside the container 2 of water to be heated, in particular with the aid of three feet 3f (visible in [Fig.2]) provided in the lower part of the protective casing 3.

[0061] The protective housing 3 is made of polymer material, preferably plastic material, i.e. a material of low conductivity.

[0062] Openings 3a are formed in the protective housing 3 so as to allow water to enter inside the protective housing 3 to be in contact with the heating element.

[0063] A handle 4 is formed in the upper part of the protective housing 3 so as to allow the user to easily carry the portable water heater 1 without risk of burning.

[0064] An electrical cable 5 extends from the upper part of the protective housing 3, a male electrical plug (not visible in [Fig.l]) being arranged at the free end of said electrical cable 5 to allow the user to electrically connect the portable water heater 1 to a female electrical outlet.

[0065] Two indicator lights 6 are provided on the top of the protective housing 3 so as to allow the user to know the operating status of the portable water heater 1. For example, one of the indicator lights 6 may be green to indicate when the portable water heater 1 is connected to the electrical network, and the other of the indicator lights 6 may be red to indicate when the heating element is heating.

[0066] Referring to Figures 2 to 4, it can be seen that the portable electric immersion water heater 1 according to the preferred embodiment of the invention is shown therein.

[0067] The protective housing 3 is formed in two parts 3b and 3c assembled using screws inserted into through holes 3e formed in the protective housing 3.

[0068] The portable electric immersion water heater 1 comprises, as a heating element, an electric heating resistor 7 comprising two connection terminals 8a and 8b which are fixed to a support 9 and which are configured to supply electric current to a helical-shaped heat dispersive portion 10 which extends away from the support 9 and which is configured to be immersed in the water to be heated.

[0069] It should be noted that the heat dispersive portion 10 of the electric heating resistor 7 could also take any other shape such as a U shape or a serpentine shape, without departing from the scope of the present invention.

[0070] As shown in [Fig.7], the electric heating resistor 7 is tubular and consists of a metal tube 7a in which a metal wire 7b is inserted over the entire length of the metal tube 7a, the two ends of said metal wire 7b forming the two connection terminals 8a and 8b of the electric heating resistor 7, said metal wire 7b having a spiral reduced section portion 19 arranged in the helical heat dispersive portion 10 of the electric heating resistor 7.

[0071] The portable water heater 1 further comprises an electrical power supply module 12 mounted on the support 9 and electrically connected to the electrical cable 5 and to the two connection terminals 8a and 8b of the electrical heating resistor 7 in order to allow a flow of electrical current through the metal wire 7b of the electrical heating resistor 7.

[0072] When the power supply module 12 supplies an electric current to the electric heating resistor 7 via its two connection terminals 8a and 8b, the heat dispersive part 10 of the electric heating resistor 7 has a resistance to the flow of current, which leads to an increase in its temperature.

[0073] The electrical heating resistor 7 thus has a hot zone formed by the helical-shaped heat-dispersing part 10, and a cold zone formed by the remaining rectilinear part 11 of the electrical heating resistor 7 which connects the heat-dispersing part 10 to the two connection terminals 8a and 8b.

[0074] The minimum distance between the protective housing 3 and the electric heating resistor 7 is greater than or equal to 30 mm so as to avoid any risk of damage to the protective housing 3 by the electric heating resistor 7.

[0075] The support 9 and the power supply module 12 are mounted in a receptacle 3d formed inside the protective housing 3 in the upper part of its part 3c.

[0076] Two light-emitting diodes 13 are mounted on the power supply module 12 in correspondence with the two indicator lights 6.

[0077] The portable water heater 1 further comprises a thermostat 14 connected to the power supply module 12 and comprising a temperature sensor 15 arranged inside a thermostat sleeve 16 extending from the support 9 towards the heat dispersive part 10 of the electric heating resistor 7.

[0078] The temperature sensor 15 is a bimetallic thermocontact located at the lower end of the thermostat sleeve 16 and connected to the power supply module. electrical 12 by two electrical wires 17 extending inside the thermostat sleeve 16.

[0079] The temperature sensor 15 of the bimetallic thermocontact type makes it possible to detect the exceeding of a predefined temperature threshold.

[0080] If we refer to Figures 5 to 7, we can see that the electric heating resistor 7 and the thermostat 14 of the portable water heater 1 are represented there.

[0081] A thermal bridge 18 in the form of a solder is formed between the lower end of the thermostat sleeve 16 and the heat dispersive portion 10 of the electric heating resistor 7, such that the thermal bridge 18 is formed at the temperature sensor 15 of the bimetallic thermocontact type, which enables the temperature sensor 15 to detect with high precision and responsiveness the temperature of the heat dispersive portion 10 of the electric heating resistor 7.

[0082] The thermostat 14 is configured to cut off the electrical power supply to the electric heating resistor 7 by the electrical power supply module 12 when the temperature sensor 15 detects that the predefined temperature threshold has been reached, in particular in the case of dry heating without immersion.

[0083] The brazing type thermal bridge 18 formed between the thermostat sleeve 16 and the heat dispersive part 10 of the electric heating resistor 7 allows for faster heat transfer by conduction via the metal (for example, copper) forming the brazing, and thus allows the dry heating detection time to be greatly reduced.

[0084] The thermal bridge 18 is advantageously formed between the thermostat sleeve 16 and the upper turn of the helical heat dispersive part 10 (i.e., the turn closest to the two connection terminals 8a and 8b of the electric heating resistor 7), which allows both rapid detection of dry heating and good temperature detection in normal immersion use.

[0085] It should be noted that the thermal bridge 18 could also be formed on any other turn of the heat dispersive part 10, the thermostat sleeve 16 then descending to this turn, without departing from the scope of the present invention.

[0086] The predefined temperature threshold at which the thermocontact type sensor 15 is triggered can be between 55°C and 75°C.

[0087] The electric heating resistor 7 may have a surface power density of between 3 and 7 W / cm2, preferably equal to 6 W / cm2.

[0088] Specifically, the thermoswitch type sensor 15 may be a normally closed bimetallic thermoswitch mounted in a housing having a length of between 15 and 35 mm, a width of between 6 and 8 mm, and a thickness of between 3 and 5 mm.

[0089] The temperature sensor 15 thus has a small spatial extent and can therefore be placed at the height of the thermal bridge 18, so that its entire measurement zone is located opposite the heat dispersive part 10 of the electrical heating resistor 7, which allows it to detect overheating more quickly.

[0090] The small size of the temperature sensor 15 thus allows it to have good responsiveness both in a normal condition of heating in water and in an abnormal condition of dry heating, and to be located as close as possible to the zone where the heating is greater.

[0091] Specifically, the bimetallic thermocontact type sensor 15 comprises two blades composed of two separate metals, said two blades being in contact (thermocontact closed) when the temperature is lower than the predefined temperature threshold, and said two blades moving away from each other (thermocontact open) when the temperature becomes higher than or equal to the predefined temperature threshold, the thermostat 14 then cutting off the electrical power supply to the electrical heating resistor 7 as soon as the thermocontact type sensor 15 opens.

[0092] Thus, when the temperature detected by the temperature sensor 15 is greater than or equal to the predefined temperature threshold, the thermostat 14 makes it possible to cut off the electrical power supply to the electric heating resistor 7 in the event of overheating in normal immersion conditions, and it also makes it possible to cut off with high reactivity the electrical power supply to the electric heating resistor 7 in the event of dry heating (i.e., when the electric heating resistor 7 is powered in a non-immersed state).

[0093] The thermostat 14 thus makes it possible to detect dry heating in less than 50 seconds (typically in 35 to 40 seconds) and to interrupt heating immediately after detection, which guarantees the safety of the product and prevents any risk of fire starting.

[0094] The dry heating protection of the portable water heater 1 according to the present invention makes it possible to prevent the protective housing 3 from heating too much and deforming in the event of dry heating, which would lead to an alteration of the protection of the user given that he could have access to the electric heating resistor 7, and which would also lead to a high surface temperature of the protective housing 3 and a risk of burns for the user in the event of contact with the protective housing 3.

[0095] It should be noted that, although this would not be ideal for the safety of the user, the portable water heater 1 according to the present invention could also not include a protective housing 3, the electric heating resistor 7 then being exposed, without departing from the scope of the present invention.

[0096] It is understood that the particular embodiment which has just been described has been given for informational purposes and is not limiting, and that modifications may be made without departing from the present invention.

Claims

Claims

1. A portable electric immersion water heater (1) comprising: - an electric heating resistor (7) comprising two connection terminals (8a, 8b) which are fixed to a support (9) and which are configured to supply power to a heat dispersive portion (10) which extends away from the support (9) and which is configured to be immersed in water to be heated; - a power supply module (12) mounted on the support (9) and electrically connected to the two connection terminals (8a, 8b) of the electric heating resistor (7) in order to allow a flow of electric current through the electric heating resistor (7); and - a thermostat (14) connected to the power supply module (12) and comprising a temperature sensor (15) arranged inside a thermostat sleeve (16) extending from the support (9) towards the heat dispersive part (10) of the electric heating resistor (7),said temperature sensor (15) being configured to detect the temperature of the electric heating resistor (7), characterized in that the water heater (1) further comprises a thermal bridge (18) formed between the thermostat sleeve (16) and the heat dispersive part (10) of the electric heating resistor (7), and in that the temperature sensor (15) is a bimetallic thermocontact located in the thermostat sleeve (16) opposite the thermal bridge (18), the thermostat (14) being configured to cut off the electrical power supply to the electric heating resistor (7) by the electrical power supply module (12) when the thermocontact detects the reaching of a predefined temperature threshold, in particular in the case of dry heating without immersion.,

2. Water heater (1) according to claim 1, characterized in that the thermocontact is a normally closed bimetallic thermocontact, wired to the electrical power supply module (12).

3. Water heater (1) according to claim 1 or 2, characterized in that the thermal bridge (18) is at least one brazing.

4. Water heater (1) according to one of claims 1 to 3, characterized in that the heat dispersive part (10) has a helical shape.

5. Water heater (1) according to claim 4, characterized in that the thermal bridge (18) is formed between the thermostat sleeve (16) and the coil of the heat dispersive part (10) of the heating resistor electric (7) closest to the two connection terminals (8a, 8b) of the electric heating resistor (7).

6. Water heater (1) according to one of claims 1 to 5, characterized in that the predefined temperature threshold at which the thermal contact is triggered is between 55°C and 75°C.

7. Water heater (1) according to one of claims 1 to 6, characterized in that the thermocontact is mounted in a housing having a length of between 15 and 35 mm, a width of between 6 and 8 mm, and a thickness of between 3 and 5 mm.

8. Water heater (1) according to one of claims 1 to 7, characterized in that the electric heating resistor (7) has a surface power density of between 3 and 7 W / cm2, preferably equal to 6 W / cm2.

9. Water heater (1) according to one of claims 1 to 8, characterized in that the water heater (1) further comprises a protective housing (3) in which the electric heating resistor (7) is arranged, said protective housing (3) comprising at least one opening (3a) configured to allow water to pass therethrough when the heat dispersive part (10) of the electric heating resistor (7) is immersed in water.

10. Water heater (1) according to claim 9, characterized in that the protective housing (3) is made of polymer material, preferably plastic material.

11. Water heater (1) according to claim 9 or 10, characterized in that the minimum distance between the protective housing (3) and the electric heating resistor (7) is greater than or equal to 30 mm.

12. Water heater (1) according to one of claims 1 to 11, characterized in that the electric heating resistor (7) is tubular and consists of a metal tube (7a) in which a metal wire (7b) is inserted over the entire length of the metal tube (7a), the two ends of said metal wire (7b) forming the two connection terminals (8a, 8b) of the electric heating resistor (7), said metal wire (7b) having a reduced section portion (19) arranged in the heat dispersive portion (10) of the metal tube (7a) of the electric heating resistor (7), the thermal bridge (18) being formed on the metal tube (7a) of the electric heating resistor (7) at a location in which the section of the metal wire (7b) of the electric heating resistor (7) is reduced.

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