Electric water heater with secondary heating function

Abstract

The utility model discloses a secondary heating electric water heater, which relates to the field of electric water heaters, and comprises a water storage part, a water delivery part and a heating part, the heating part comprises a first heating element and a second heating element, the water delivery part is connected with a water storage inner container, the water delivery part comprises a water inlet assembly and a water outlet assembly, and the water inlet assembly is connected with the second heating element. The water storage part comprises a water storage inner container, and the second heating piece is connected with the water outlet assembly. The ceramic heater is arranged at the water outlet of the water heater to conduct secondary heating, the hot water yield of the electric water heater is increased, the capacity increasing effect of the electric water heater is achieved, meanwhile, the NTC sensor is additionally arranged at the water outlet of the ceramic heater to verify the water temperature output by the water heater, the water outlet temperature of the water heater is accurately controlled to be adjusted within the suitable use range, and the service life of the water heater is prolonged. The use comfort of the water heater is improved; and an insulating liner tube is additionally arranged at a water outlet pipeline, so that the current in water is reduced, and the water use safety of a user is ensured.

Description

Technical Field

[0001] The utility model relates to the field of electric water heaters, in particular to an electric water heater with secondary heating. Background Art

[0002] Existing electric water heaters mainly include two types: storage electric water heaters and instant electric water heaters. The storage electric water heater heats the water in a fixed-capacity inner tank to the required temperature. To meet the increased hot water demand in winter and other situations, it is necessary to increase the volume of the storage inner tank; the required heating time is long, and when the hot water consumption is small, it will cause waste of energy. The instant water heater does not have a storage inner tank. To heat a sufficient amount of water to the temperature required for bathing, for example, it requires a very high power of the electric heating element and has high requirements for the installation circuit. Therefore, there is an urgent need to provide an electric water heater with effective hot water capacity increase and easy installation.

[0003] Chinese patent document CN212566273U discloses a "hot water secondary heating device for electric water heaters". It adopts a storage inner tank, a water inlet pipe, a water outlet pipe and an electric heating element installed in the storage inner tank. The water outlet of the water inlet pipe is adjacent to the bottom of the storage inner tank, and the water inlet of the water outlet pipe is adjacent to the top of the storage inner tank. The electric heating element includes a first electric heating pipe adjacent to the bottom of the storage inner tank and a second electric heating pipe adjacent to the top of the storage inner tank. However, the water heater in this patent has problems such as general hot water capacity increase effect and difficult installation. Summary of the Invention

[0004] The utility model mainly solves the technical problems of less effective hot water volume and difficult installation of the original electric water heater, and provides an electric water heater with secondary heating. A first heating component is arranged in the storage inner tank part of the water heater for initial heating of the water temperature, a ceramic tube heater is arranged at the connection of the storage inner tank and the water outlet component for secondary heating, an insulating lining tube is added at the upper end of the ceramic tube heater, and an NTC sensor is arranged at the lower end of the ceramic heater, which can not only accurately calibrate and confirm that the water temperature after secondary heating reaches the use standard, but also filter out the current in the water outlet of the water heater, improving the safety of use.

[0005] The above technical problems of the utility model are mainly solved by the following technical solutions: The utility model includes a water storage part, a water conveyance part and a heating part. The heating part includes a first heating member and a second heating member. The water conveyance part is connected to the storage inner tank. The water conveyance part includes a water inlet component and a water outlet component. The water storage part includes a storage inner tank. The second heating member is arranged in the water outlet component.

[0006] Preferably, the second heating element includes a ceramic tube heater. A ceramic tube flow hole is provided in the center of the ceramic tube heater and penetrates through the ceramic tube heater. An upper plastic screw head is installed outside the ceramic tube heater, and a lower plastic screw head is provided below the upper plastic screw head.

[0007] Preferably, the water outlet assembly includes a water outlet pipe, a water storage inner tank water outlet pipe, and a plastic screw head. An insulating lining tube is provided between the water outlet pipe and the water storage inner tank water outlet pipe.

[0008] Preferably, the lower end of the ceramic tube heater is connected to an insulating lining tube. The insulating lining tube is divided into upper and lower sections. The upper section insulating lining tube includes an inner insulating lining tube and an outer metal tube. The lower section insulating lining tube includes an insulating lining tube and an inner metal tube. The lower end of the inner insulating lining tube is connected to the outer insulating lining tube. An outer metal tube is provided outside the inner insulating lining tube, and an inner metal tube is provided inside the outer insulating lining tube. An insulating connecting tube is provided between the upper section insulating lining tube and the lower section insulating lining tube.

[0009] Preferably, the upper end of the plastic screw head is connected to the water storage inner tank water outlet pipe, and the water storage inner tank water outlet pipe is arranged in the water storage inner tank.

[0010] Preferably, the water inlet assembly includes a water inlet pipe, a water storage inner tank water inlet pipe, and a plastic screw head. The water storage inner tank water inlet pipe is arranged in the water storage inner tank. A flow dividing valve is provided on the water inlet pipe, and the water inlet pipe is connected to the water storage inner tank water inlet pipe through the flow dividing valve.

[0011] Preferably, the water outlet pipe is arranged below the insulating lining tube. A mixing valve is provided on the water outlet pipe. The mixing valve is connected to the flow dividing valve, and a one-way cold water pipe is provided between the mixing valve and the flow dividing valve.

[0012] Preferably, the outer side of the water storage inner tank is wrapped with an electric heater housing. An NTC sensor is additionally provided at the lower end of the ceramic tube heater, and the NTC sensor is arranged between the electric water heater housing and the water storage inner tank.

[0013] Preferably, a first heating element is installed on one side of the water storage inner tank, and the first heating element is close to the connection position between the water inlet assembly and the water storage inner tank.

[0014] The beneficial effects of the present utility model are as follows: A ceramic heater is arranged inside the water outlet pipe of the water heater of the present utility model for secondary heating, increasing the hot water output of the electric water heater and achieving a capacity expansion effect. At the same time, an NTC sensor is additionally arranged at the water outlet of the ceramic heater to calibrate the water temperature output by the water heater, accurately controlling the water temperature of the water heater to be adjusted within a suitable range for use, improving the comfort of using the water heater; an insulating lining tube is also installed at the water outlet pipe to reduce the current in the outlet water, ensuring the water use safety of users. Description of the Drawings

[0015] Figure 1 It is a structural diagram of an electric water heater with secondary heating of the present utility model.

[0016] Figure 2 It is a structural diagram of a ceramic tube heater of the present utility model.

[0017] Figure 3 It is a structural diagram of an insulating liner at the water outlet pipe of the present utility model.

[0018] In the figure, 10 is the water storage inner tank, 11 is the water inlet pipe of the water storage inner tank, 12 is the water outlet pipe of the water storage inner tank, 13 is the one-way cold water pipe, 14 is the electric water heater shell, 101 is the first heating element, 201 is the second heating element, 202 is the ceramic tube flow hole, 203 is the lower plastic screw head, 204 is the upper plastic screw head, 21 is the NTC sensor, 301 is the inner insulating liner, 302 is the insulating connecting pipe, 303 is the inner metal pipe, 304 is the outer metal pipe, 305 is the outer insulating liner, 31 is the flow dividing valve, and 32 is the mixing valve. Specific embodiments

[0019] Next, through embodiments and in combination with the accompanying drawings, the technical solutions of the present utility model will be further specifically described.

[0020] Embodiment: For a secondary heating electric water heater in this embodiment, one existing water heater solution during use is to set an auxiliary electric heating tube near the water outlet pipe inside the water storage tank. By heating with the auxiliary electric heating tube, the water temperature in the water storage inner tank is increased. However, when trying to heat the entire amount of water stored in the water storage inner tank with a single auxiliary electric heating tube, the result is that the auxiliary electric heating tube is relatively long. When the relatively long electric heating tube is installed into the water storage inner tank, it is more likely to get stuck at the installation opening of the water storage inner tank and the electric heating tube is damaged, thus greatly increasing the installation difficulty. At the same time, although a single auxiliary electric heating tube only heats the water near the water outlet pipe, it cannot avoid the problem of heat dissipation to the entire water storage inner tank. Therefore, more energy consumption is required to maintain the water temperature on the water outlet side within an appropriate range. Another water heater solution is to install a double inner tank and double heating tubes in the water heater, but this solution also has problems such as complex technology, high cost, and general expansion effect. Therefore, on this basis, a secondary heating electric water heater is proposed. In this embodiment, a plastic screw head is provided at the bottom of the pipe fitting of the water outlet pipe to connect the inner tank and the external water outlet pipeline. The internal thread joint at one end of the plastic screw head is hermetically connected to the threaded water outlet on the inner tank, and the other end of the plastic screw head is an external thread interface connecting to the external water outlet pipeline. Since the water stored in the water storage inner tank is directly connected to the heating tube, during the heating process, it is inevitable that the flowing water is charged. Therefore, there is an insulating liner made of insulating material inside the stainless steel pipe of the water outlet pipe structure. Since water itself has resistance, when the stored water passes through a section of insulating pipeline, the current is reduced through the resistance of the water itself, and the current carried by the water at the water outlet is reduced to a safe current, ensuring the safety of users.

[0021] According to the above design concept, as Figure 1 shown, the water heater in this example includes a water storage part, a water delivery part, and a heating part. The water storage part includes a water storage inner tank and an electric water heater outer shell 14, and the water storage inner tank is arranged inside the electric water heater outer shell. The water delivery part includes a water inlet assembly and a water outlet assembly. The water outlet assembly and the water inlet assembly are respectively arranged on both sides of the electric water heater outer shell 14 and are connected to the water storage inner tank. A water inlet assembly is arranged on the right side of the electric water heater outer shell 14. The water inlet assembly includes a water inlet pipe and a flow dividing valve 31. The water inlet pipe passes through the electric water heater outer shell and is connected to the internal water storage inner tank. Unheated cold water flows into the water storage inner tank through the water inlet pipe to ensure that the water storage volume in the water storage inner tank is maintained within the normal use limit, which can not only maintain the daily use of the water heater but also prevent the water heater from dry burning. A flow dividing valve 31 is arranged on the water inlet pipe, and controlling the opening and closing of the flow dividing valve 31 can control the water diversion here.

[0022] A water outlet assembly is installed on the left side of the electric water heater outer shell 14. The water outlet assembly includes a water storage inner tank outlet pipe 12, a water outlet pipe, and an insulating lining pipe. The water storage inner tank outlet pipe 12 is arranged inside the water storage inner tank. A first heating element 101 and a second heating element 201 are also arranged in the water storage inner tank. The first heating element 101 is arranged on one side close to the connection between the water inlet pipe of the water storage inner tank 11 and the water storage inner tank. The water stored in the water storage inner tank is heated by the first heating element 101 to ensure that the water stored in the entire water storage inner tank is maintained within a constant temperature range, avoiding excessive cooling of the stored water and reducing the heating pressure during subsequent water outlet. At the same time, the first heating element is close to the inlet where the water inlet pipe conveys water into the water storage inner tank, and can directly heat the cold water entering the water heater, quickly raising the temperature of the incoming water, keeping the water temperature in the entire water heater as consistent as possible, and also reducing the energy loss during heating. The second heating element 201 is arranged at the connection between the water storage inner tank and the water outlet pipe. The second heating element 201 is an instant heating electric element. In this embodiment, the second electric heating element is a ceramic tube heater, which heats the water flowing through it, and uses the ceramic heater to heat the outlet water a second time to increase the outlet water temperature. More cold water needs to be mixed at the mixing valve to maintain the use water temperature within a suitable range, thereby increasing the hot water output of the electric water heater and achieving the technical effect of capacity expansion. As Figure 2As shown, the second heating element 201 includes a ceramic heater, and is provided with an upper plastic screw head 204 and a lower plastic head. The ceramic heater has a non-heating section at the bottom end, and a ceramic tube through-flow hole 202 is provided at the center of the non-heating section of the ceramic tube heater and penetrates through the ceramic tube heater. The ceramic tube heater is connected to the water storage inner tank outlet pipe 12 through the upper plastic screw head. The plastic screw head is divided into two parts, the upper plastic screw head 204, and a lower plastic screw head 203 is provided below the upper plastic screw head 204. The ceramic tube heater has a flange made of ceramic or metal, and the mating surface of the ceramic tube heater and the plastic screw head is hermetically connected by means of an O-ring, interference fit, adhesive bonding, etc. At the same time, the wires of the ceramic tube heater are routed through the wire outlet holes reserved in the plastic screw head.

[0023] An insulating liner tube is provided at the outlet pipe connected to the ceramic heater. As Figure 3 shown, at this place, the outlet pipe is divided into upper and lower sections at the upper position of the port of the ceramic tube heater, and the upper and lower sections are connected by an insulating connecting pipe 302 in the middle. In the upper section of the outlet pipe, an outer metal tube 304 is arranged on the outside, and an inner insulating liner tube 301 is arranged on the inside; in the lower section of the outlet pipe, an outer insulating liner tube 305 is arranged on the outside, and an inner metal tube 303 is arranged inside the outer insulating liner tube 305. The insulating connecting pipe 302 connecting the two insulating liner tubes is made of insulating material, which can separate the metal tubes in the upper and lower sections. By arranging the two-section insulating liner tubes inside and outside in a staggered manner, it is possible to prevent electricity in the water from being transmitted to the inside of the outlet pipe through the metal tubes. An NTC sensor 21 is provided at the connection between the second heating element 201 and the outlet pipe. Through this sensor, the temperature of the hot water flowing out of the outlet pipe after being heated by the second heating element 201 can be obtained in real time, and the first heating element 101, the second heating element 201, and the NTC sensor 21 are all connected to the control circuit of the electric water heater. According to the data detected and transmitted by the NTC sensor 21, it can be known whether the outlet water temperature of the water heater meets the usage requirements, and the control circuit judges whether it is necessary to adjust the heating temperatures of the first heating element 101 and the second heating element 201 and the opening and closing size of the flow dividing valve 31 based on the feedback result, and then maintains the outlet water temperature within an appropriate range by the temperature of the heating source and the amount of mixed cold water.

[0024] The usage process of the water heater in this embodiment during actual operation is as follows: Cold water enters the water storage inner tank unidirectionally from the water inlet pipe through the flow dividing valve 31. The first heating element 101 can preheat the cold water in the water storage inner tank. After reaching the set temperature, the first heating element 101 keeps warm. The preheated water in the upper layer of the water storage inner tank can flow out of the inner tank through the water outlet pipe, pass through the second heating element 201 placed in the water outlet pipe. The NTC sensor 21 measures the temperature of the preheated water. If the temperature meets the requirements, the second heating element 201 does not heat. The preheated water and the cold water diverted to the one-way cold water pipe 13 in the flow dividing valve 31 enter the mixing valve 32, and the output water temperature is made to meet the final usage requirements by adjusting the cold water flow rate. As the hot water is continuously used, the temperature of the preheated water in the water outlet pipe drops. When the temperature of the preheated water is lower than the minimum requirement of the outlet water temperature, the second heating element 201 is powered on to perform secondary heating on the flowing preheated water. The NTC sensor 21 detects that the temperature of the reheated water does not exceed the safety standard. The reheated water and the cold water diverted to the one-way cold water pipe 13 in the flow dividing valve 31 enter the mixing valve 32, and the output water temperature is made to meet the final usage requirements by adjusting the cold water flow rate. In this embodiment, the second heating element 201 is arranged inside the water outlet pipe, and the entire water outlet pipe component can be screwed out from the electric water heater, which is convenient for the maintenance and replacement of the second heating element 201. After setting the second heating element 201, the preheated water can be secondarily heated, which can reduce the temperature control of the preheated water in the water storage inner tank, save energy when hot water is not in use, and at the same time, the lower water temperature can reduce the scale in the water storage inner tank. At the same time, on the basis of realizing the secondary heating of the outlet water, this installation method does not change the structures of other components and the outlet water mode of the existing electric water heater, reduces the requirements for structural design, and saves the setting cost. By means of the instant heating type second heating element 201, the hot water volume of the electric water heater can be increased without increasing the volume of the water storage inner tank, achieving the effect of hot water expansion and improving the usage convenience. In addition, by connecting the first heating element 101, the second heating element 201, and the NTC sensor 21 to the control circuit of the electric water heater, the outlet water temperature of the second heating element 201 can be accurately controlled, and the stability of the outlet water temperature can be improved.

[0025] Embodiment 2: A secondary heating electric water heater in this embodiment is basically the same as the embodiment, such as Figure 1As shown in the figure, the water heater in this example includes a water storage part, a water delivery part, and a heating part. The water storage part includes a water storage inner tank and an electric water heater housing 14, and the water storage inner tank is arranged inside the electric water heater housing. The water delivery part includes a water inlet assembly and a water outlet assembly. The water outlet assembly and the water inlet assembly are respectively arranged on both sides of the electric water heater housing 14 and are connected to the water storage inner tank. The water inlet assembly is arranged on the right side of the electric water heater housing 14. The water inlet assembly includes a water inlet pipe and a flow dividing valve 31. The water inlet pipe passes through the electric water heater housing and is connected to the internal water storage inner tank. Unheated cold water flows into the water storage inner tank through the water inlet pipe to ensure that the water storage volume in the water storage inner tank is maintained within the normal use limit, which can not only maintain the daily use of the water heater but also prevent the water heater from dry burning. A flow dividing valve 31 is arranged on the water inlet pipe, and controlling the opening and closing of the flow dividing valve 31 can control the diversion of cold water here.

[0026] The water outlet assembly is installed on the left side of the electric water heater housing 14. The water outlet assembly includes a water storage inner tank outlet pipe 12, a water outlet pipe, and an insulating liner. The water storage inner tank outlet pipe 12 is arranged in the water storage inner tank. A first heating element 101 and a second heating element 201 are also arranged in the water storage inner tank. The first heating element 101 is arranged on one side close to the connection between the water inlet pipe 11 of the water storage inner tank and the water storage inner tank. The water stored in the water storage inner tank is heated by the first heating element 101 to ensure that the water stored in the entire water storage inner tank is maintained within a constant temperature range, avoiding excessive cooling of the stored water and reducing the heating pressure during subsequent water outlet. At the same time, the first heating element is close to the inlet where the water inlet pipe conveys water into the water storage inner tank, and can directly heat the cold water entering the water heater, quickly raising the temperature of the incoming water, improving the heating efficiency, keeping the water temperature in the entire water heater as consistent as possible, and also reducing the energy loss during heating. The second heating element 201 is arranged at the connection between the water storage inner tank and the water outlet pipe. The second heating element 201 is an instant heating electric element. In this embodiment, the second electric heating element is a ceramic tube heater, which heats the water flowing through it to increase the water outlet temperature. It is necessary to mix more cold water in the mixing valve to maintain the use water temperature within a suitable range, thereby increasing the hot water output of the electric water heater and achieving the technical effect of capacity expansion. As Figure 2 shown, the second heating element 201 includes a ceramic heater. An upper plastic screw head 204 and a lower plastic head are arranged outside the ceramic heater. The ceramic heater has a non-heating section at the bottom end. A ceramic tube through-flow hole 202 is arranged at the center of the non-heating section of the ceramic tube heater and penetrates through the ceramic tube heater. Different from the embodiment, in this embodiment, the ceramic heater includes an MCH ceramic heater and a PTC ceramic heater. The ceramic tube heater is a hollow structure, forming two water outlet channels, namely the inner side of the ceramic tube and the outer side of the ceramic tube, in the water outlet pipeline, which can enable the water flow in the inner and outer channels, increasing the heating area of the ceramic heater and improving the heating efficiency.

[0027] The upper end of the ceramic tube heater is connected to the water outlet pipe 12 of the water storage inner tank. A plastic screw head is installed on the outer side of the bottom end of the ceramic tube heater. The plastic screw head is divided into two parts: the upper plastic screw head 204, and the lower plastic screw head 203 is connected below the upper plastic screw head 204. The ceramic tube heater has a flange made of ceramic or metal, and the mating surfaces of the ceramic tube heater and the plastic screw head are connected through an O-ring, interference fit, gluing, etc. At the same time, the wire of the ceramic tube heater is routed through the wire outlet hole reserved on the plastic screw head.

[0028] An insulating liner tube is provided at the water outlet pipe connected to the ceramic heater. As Figure 3 shown, at this location, the water outlet pipe is divided into upper and lower sections above the port of the ceramic tube heater, and the upper and lower sections are connected through an insulating connecting pipe 302 in the middle. The outer metal tube 304 of the upper section is arranged on the outside, and the inner insulating liner tube 301 is arranged on the inside. The outer insulating liner tube 305 of the lower section is arranged on the outside, and the inner metal tube 303 is arranged on the inside. The insulating connecting pipe 302 connecting the two insulating liner tubes is made of insulating material, which can separate the metal tubes of the upper and lower sections. By staggering the inner and outer insulating liner tubes in a two-stage manner, it is possible to prevent electricity in the water from being transmitted to the inside of the water outlet pipe through the metal tube. An NTC sensor 21 is provided at the connection between the second heating element 201 and the water outlet pipe. Through this sensor, the hot water temperature after flowing out of the water outlet pipe after being heated by the second heating element 201 can be obtained in real time, and the first heating element 101, the second heating element 201, and the NTC sensor 21 are all connected to the control circuit of the electric water heater. According to the data detected and transmitted by the NTC sensor 21, it can be known whether the water outlet temperature of the water heater meets the usage requirements, and the control circuit judges whether it is necessary to adjust the heating temperatures of the first heating element 101 and the second heating element 201 and the opening and closing size of the flow dividing valve 31 based on the feedback result, and then maintains the water outlet temperature within an appropriate range through the temperature of the heating source and the amount of mixed cold water.

[0029] The usage process of the water heater in this embodiment during actual operation is as follows: Cold water enters the water storage inner tank unidirectionally from the water inlet pipe through the flow dividing valve 31, and the first heating element 101 can preheat the cold water in the water storage inner tank. After reaching the set temperature, the first heating element 101 keeps warm. The preheated water in the upper layer of the water storage inner tank can flow out of the inner tank through the water outlet pipe, pass through the second heating element 201 placed in the water outlet pipe, and the NTC sensor 21 measures the temperature of the preheated water. If the temperature meets the requirements, the second heating element 201 does not heat, and the preheated water and the cold water diverted to the one-way cold water pipe 13 in the flow dividing valve 31 enter the mixing valve 32, and the output water temperature is made to meet the final usage requirements by adjusting the cold water flow rate; as the hot water is continuously used, the temperature of the preheated water in the water outlet pipe drops. When the temperature of the preheated water is lower than the minimum requirement of the outlet water temperature, the second heating element 201 is powered on to perform secondary heating on the flowing preheated water, and the NTC sensor 21 detects that the temperature of the reheated water does not exceed the safety standard. The reheated water and the cold water diverted to the one-way cold water pipe 13 in the flow dividing valve 31 enter the mixing valve 32, and the output water temperature is made to meet the final usage requirements by adjusting the cold water flow rate. In this embodiment, the second heating element 201 is arranged inside the water outlet pipe, and the entire water outlet pipe component can be screwed out from the electric water heater, which is convenient for the maintenance and replacement of the second heating element 201. After setting the second heating element 201, the preheated water can be secondarily heated, which can reduce the temperature of the preheated water controlled by the water storage inner tank, save energy when hot water is not in use, and at the same time, the lower water temperature can reduce the scale in the water storage inner tank. At the same time, on the basis of realizing the secondary heating of the outlet water, this installation method does not change the structures of other components and the outlet water mode of the existing electric water heater, reduces the requirements for structural design, and saves the setting cost. By means of the instant heating type second heating element 201, the amount of hot water in the electric water heater can be increased without increasing the volume of the water storage inner tank, achieving the effect of hot water expansion and improving the usage convenience. Connecting the first heating element 101, the second heating element 201, and the NTC sensor 21 to the control circuit of the electric water heater can accurately control the outlet water temperature of the second heating element 201 and improve the stability of the outlet water temperature. In addition to the above technical effects, in this embodiment, the ceramic tube heater arranged at the water outlet pipe heats the flowing preheated water simultaneously inside and outside, and the heat can be efficiently transferred into the water outlet pipe, further improving the heating efficiency of the outlet water temperature.

Claims

1. An electric water heater for secondary heating, characterized in that, It includes a water storage part, a water delivery part and a heating part. The heating part includes a first heating element and a second heating element. The water delivery part is connected to the water storage inner tank. The water delivery part includes a water inlet assembly and a water outlet assembly. The water storage part includes a water storage inner tank. The second heating element is connected to the water outlet assembly. The water outlet assembly includes a water storage inner tank outlet pipe. The second heating element includes a ceramic tube heater, and the ceramic tube heater is connected to the water storage inner tank outlet pipe at its upper end.

2. The electric water heater with secondary heating according to claim 1, characterized in that, The second heating element includes a ceramic tube heater. A ceramic tube through-flow hole is provided in the center of the ceramic tube heater, and the ceramic tube through-flow hole penetrates the ceramic tube heater. An upper plastic screw head is installed outside the ceramic tube heater, and a lower plastic screw head is provided below the upper plastic screw head.

3. The electric water heater with secondary heating according to claim 2, characterized in that, The water outlet assembly includes a water outlet pipe, a water storage inner tank outlet pipe and a plastic screw head. An insulating lining tube is provided between the water outlet pipe and the water storage inner tank outlet pipe.

4. The electric water heater with secondary heating according to claim 3, characterized in that The upper end of the ceramic tube heater is connected to an insulating lining tube. The insulating lining tube is divided into upper and lower sections. The upper section insulating lining tube includes an inner insulating lining tube and an outer metal tube. The lower section insulating lining tube includes an insulating lining tube and an inner metal tube. The lower end of the inner insulating lining tube is connected to the outer insulating lining tube. An outer metal tube is provided outside the inner insulating lining tube, and an inner metal tube is provided inside the outer insulating lining tube. An insulating connecting tube is provided between the upper section insulating lining tube and the lower section insulating lining tube.

5. A secondary heating electric water heater according to claim 2 or 3 or 4, characterized in that, The upper end of the ceramic tube heater is connected to a water storage inner tank outlet pipe, and the water storage inner tank outlet pipe is arranged in the water storage inner tank.

6. The electric water heater with secondary heating according to claim 3, wherein The water inlet assembly includes a water inlet pipe, a water storage inner tank inlet pipe and a plastic screw head. The water storage inner tank inlet pipe is arranged in the water storage inner tank. A flow dividing valve is provided on the water inlet pipe, and the water inlet pipe is connected to the water storage inner tank inlet pipe through the flow dividing valve.

7. The electric water heater with secondary heating according to claim 5, characterized in that, The water outlet pipe is arranged below the insulating lining tube. A mixing valve is provided on the water outlet pipe, and the mixing valve is connected to the flow dividing valve. A one-way cold water pipe is provided between the mixing valve and the flow dividing valve.

8. The electric water heater with secondary heating according to claim 3, wherein, The outer side of the water storage inner tank is wrapped with an electric water heater shell. An NTC sensor is additionally provided at the lower end of the ceramic tube heater, and the NTC sensor is arranged between the electric heater shell and the water storage inner tank.

9. The electric water heater with secondary heating according to claim 1, wherein A first heating element is installed on one side of the water storage inner tank, and the first heating element is close to the connection position between the water inlet assembly and the water storage inner tank.

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