Fire prevention control methods for electric water heaters and electric water heaters

Abstract

This invention relates to the field of electric water heater technology, and discloses a fire prevention control method and an electric water heater. The electric water heater has a temperature detection unit installed in its electrical compartment to detect the temperature inside. The fire prevention control method includes the following steps: during the heating process of the electric water heater, the temperature rise rate inside the electrical compartment is calculated based on the temperature detected by the temperature detection unit. If the temperature rise rate is greater than or equal to a preset temperature rise rate, a fire risk is determined, and the electric water heater stops heating; and / or if the current detected temperature is greater than or equal to a preset threshold, a fire risk is determined, and the electric water heater stops heating. The preset threshold is calculated based on influencing factors, including the temperature rise in the electrical compartment caused by the water temperature inside the tank, the temperature rise caused by the heating of the electrical circuit system inside the electrical compartment, and the ambient temperature. This fire prevention control method for electric water heaters has high detection sensitivity.

Description

Technical Field

[0001] This invention relates to the field of electric water heater technology, and in particular to a fire prevention control method for electric water heaters and an electric water heater. Background Technology

[0002] With the rapid development of modern science and technology and the increasing awareness of safety, higher requirements have been placed on the safety of water heaters. In the electrical compartment of an electric water heater, where electrical components (such as heating elements and thermostats) are concentrated, the small, enclosed space limits heat dissipation. Under prolonged power supply, heat cannot be dissipated in time, thus posing a fire hazard.

[0003] In existing technologies, a temperature sensor is typically installed inside the appliance compartment. The temperature detected by the sensor is compared with a preset temperature. If the detected temperature is higher than the preset temperature, a fire risk is identified. However, because the preset temperature needs to be universally applicable under different conditions, the preset temperature is often set too high. This makes the water heater insensitive to fire risk detection, and it may only be detected when the water heater catches fire, thus rendering the water heater ineffective in preventing fires. Summary of the Invention

[0004] The purpose of this invention is to provide a fire prevention control method and an electric water heater, which can detect the risk of fire in an electric water heater in a more sensitive way, thereby stopping the electric water heater from heating and preventing the occurrence of danger.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] This invention provides a fire prevention control method for an electric water heater. The electric water heater has a temperature detection unit installed in its electrical compartment. The temperature detection unit is used to detect the temperature inside the electrical compartment. The fire prevention control method for the electric water heater includes the following steps:

[0007] During the heating process of the electric water heater: the heating rate of the appliance compartment is calculated based on the temperature detected by the temperature detection unit, and the heating rate is compared with a preset heating rate. If the heating rate is greater than or equal to the preset heating rate, a fire risk is determined, and the electric water heater stops heating; and / or

[0008] The current detected temperature is compared with a preset threshold. If the current detected temperature is greater than or equal to the preset threshold, it is determined that there is a fire risk, and the electric water heater stops heating. The preset threshold is calculated based on influencing factors, including the temperature rise in the electrical compartment caused by the water temperature inside the tank, the temperature rise caused by the heating of the circuit system inside the electrical compartment, and the ambient temperature.

[0009] The fire prevention control method for electric water heaters involves installing a temperature detection unit inside the appliance compartment. During the heating process, the temperature detection unit calculates the temperature rise rate inside the appliance compartment and compares it with a preset temperature rise rate. If the temperature rise rate is greater than or equal to the preset rate, a fire risk is identified, and the water heater stops heating. Alternatively, the current detected temperature is compared with a preset threshold. If the current detected temperature is greater than or equal to the preset threshold, a fire risk is identified, and the water heater stops heating. This more sensitive method detects the fire risk of the water heater and stops heating to prevent danger.

[0010] As a preferred embodiment of the above-mentioned fire prevention control method for electric water heaters, the fire prevention control method for electric water heaters further includes the following steps:

[0011] The current detected temperature is compared with the preset temperature. If the current detected temperature is greater than or equal to the preset temperature, it is determined that there is a fire risk, and the electric water heater stops heating.

[0012] The system simultaneously detects the fire risk by comparing the heating rate with the preset heating rate and by comparing the current detected temperature with the preset temperature. If either method detects a fire risk, the electric water heater will stop heating.

[0013] The system simultaneously detects the fire by comparing the current temperature with a preset threshold and by comparing the current temperature with a preset temperature. If either method detects a fire risk, the water heater will stop heating.

[0014] By using at least two methods for simultaneous detection, problems caused by errors in one detection method can be avoided, thereby improving detection accuracy.

[0015] As a preferred embodiment of the fire prevention control method for the aforementioned electric water heater, before comparing the heating rate with a preset heating rate and / or before comparing the current detected temperature with a preset threshold, the following steps are further included:

[0016] The current detected temperature is compared with the preset temperature. If the current detected temperature is greater than or equal to the preset temperature, it is determined that there is a fire risk, and the electric water heater stops heating.

[0017] If the current detected temperature is lower than the preset temperature, then the heating rate is compared with the preset heating rate and / or the current detected temperature is compared with the preset threshold.

[0018] By comparing the current detected temperature with the preset temperature, if the current detected temperature is greater than or equal to the preset temperature, it is determined that there is a fire risk, and there is no need to perform the steps of comparing the heating rate with the preset heating rate or comparing the current detected temperature with the preset threshold.

[0019] If the current detected temperature is lower than the preset temperature, the heating rate is compared with the preset heating rate or the current detected temperature is compared with the preset threshold to make the ignition judgment of the electric water heater more accurate.

[0020] As a preferred embodiment of the fire prevention control method for the above-mentioned electric water heater, the preset threshold is defined as (tank temperature - ambient temperature) * proportional constant + maximum ambient temperature + temperature rise caused by heating of the circuit system in the electrical room, wherein the tank temperature is the temperature inside the inner tank of the electric water heater.

[0021] The preset threshold is obtained through the above calculation formula, which covers the temperature rise in the electrical compartment caused by the water temperature inside the tank, the temperature rise caused by the heating of the circuit system inside the electrical compartment, and the influence of the ambient temperature.

[0022] As a preferred embodiment of the fire prevention control method for the above-mentioned electric water heater, when the electric water heater is powered on, the current detected temperature is compared with a comparison value. If the current detected temperature is less than the comparison value, the electric water heater starts heating.

[0023] The comparison value is the higher of the preset threshold and the detection preset value, and the detection preset value = the current detection temperature + the preset value.

[0024] By following the steps above, you can avoid the risk that the electric water heater will stop heating due to the high temperature in the appliance compartment when the power is on.

[0025] As a preferred embodiment of the fire prevention control method for the aforementioned electric water heater, the current preset threshold is compared with the previously calculated preset threshold. If the current preset threshold is greater than or equal to the previously calculated preset threshold, the preset threshold is updated to the current preset threshold.

[0026] By following the steps above, it is possible to determine in a timely manner whether there is a risk of fire from the electric water heater.

[0027] As a preferred embodiment of the fire prevention control method for the above-mentioned electric water heater, the current preset threshold is compared with the previously calculated preset threshold. If the current preset threshold is less than the previously calculated preset threshold, the decrease in the preset threshold is calculated according to the calculation formula: Decrease in preset threshold = (Current preset threshold - Previously calculated preset threshold) * proportional coefficient, so as to obtain the decreased preset threshold, and the preset threshold is updated to the decreased preset threshold.

[0028] The above steps take into account the situation when the water heater's time-lapse rate decreases, making the detection more accurate.

[0029] As a preferred embodiment of the fire prevention control method for the aforementioned electric water heater, before comparing the current detected temperature with a preset threshold, the method further includes:

[0030] Determine if the current detected temperature is greater than or equal to the preset temperature value. If so, compare the current detected temperature with the preset threshold.

[0031] Based on the above judgment, there is a risk of fire only when the current detected temperature is greater than or equal to the preset temperature value. If the current detected temperature is less than the preset temperature value, there is no risk of fire, and it is not necessary to compare the current detected temperature with the preset threshold.

[0032] As a preferred method for fire prevention control of the aforementioned electric water heater, the number of times the electric water heater stops heating when a fire risk is detected is accumulated, and it is determined whether the accumulated number is greater than or equal to a preset number. If so, the electric water heater issues an alarm.

[0033] The risk of fire can be prevented by stopping the attempt to heat the electric water heater; however, if the cumulative number of attempts exceeds or equals the preset number, and stopping heating cannot eliminate the risk, the electric water heater will issue an alarm to remind the user to check.

[0034] As a preferred embodiment of the fire prevention control method for the aforementioned electric water heater, before comparing the heating rate with the preset heating rate, it is determined whether the number of temperature rises within a preset time is greater than or equal to the preset number of temperature rises. If so, the heating rate is compared with the preset heating rate.

[0035] By following the steps above, we can avoid the water heater stopping heating due to short-term fluctuations in its heating rate, making the detection more accurate.

[0036] As a preferred embodiment of the fire prevention control method for the aforementioned electric water heater, the preset heating rate = heating power of the electric water heater / (specific heat capacity of water * volume of inner tank * density of water).

[0037] The preset heating rate is calculated using the formula above, which is relatively easy to obtain.

[0038] The present invention also provides an electric water heater, which is controlled by the above-mentioned fire prevention control method for electric water heaters.

[0039] This electric water heater uses the aforementioned fire prevention control method, which can avoid the risk of fire, has more sensitive detection, and extends the service life of the electric water heater.

[0040] The beneficial effects of this invention are:

[0041] The fire prevention control method for electric water heaters proposed in this invention involves installing a temperature detection unit inside the appliance compartment. During the heating process of the electric water heater, the temperature rise rate inside the appliance compartment is calculated based on the temperature detected by the temperature detection unit, and compared with a preset temperature rise rate. If the temperature rise rate is greater than or equal to the preset temperature rise rate, a fire risk is determined, and the electric water heater stops heating; and / or the current detected temperature is compared with a preset threshold. If the current detected temperature is greater than or equal to the preset threshold, a fire risk is determined, and the electric water heater stops heating. This method detects the fire risk of the electric water heater in a more sensitive way, thereby stopping the heating of the electric water heater and preventing the occurrence of danger.

[0042] The electric water heater proposed in this invention uses the aforementioned fire prevention control method to avoid the risk of fire, has more sensitive detection, and extends the service life of the electric water heater. Attached Figure Description

[0043] Figure 1 This is a flowchart of the fire prevention control method for an electric water heater provided in Embodiment 1 of the present invention;

[0044] Figure 2 This is a flowchart of the fire prevention control method for an electric water heater provided in Embodiment 2 of the present invention;

[0045] Figure 3 This is a flowchart of how to obtain a preset threshold provided in Embodiment 2 of the present invention;

[0046] Figure 4 This is a flowchart of the fire prevention control method for an electric water heater provided in Embodiment 3 of the present invention. Detailed Implementation

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0048] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0049] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0050] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0051] Example 1:

[0052] This embodiment provides a fire prevention control method for an electric water heater. The electric water heater's electrical compartment is equipped with a temperature detection unit, which is used to detect the temperature inside the electrical compartment. Figure 1 As shown, the fire prevention control method for electric water heaters includes the following steps:

[0053] During the heating process of the electric water heater, the temperature detection unit detects the temperature and calculates the heating rate of the electrical compartment based on the detected temperature. This heating rate is then compared with a preset heating rate. If the heating rate is greater than or equal to the preset heating rate, a fire risk is identified, and the water heater stops heating. Alternatively, the current detected temperature is compared with a preset threshold. If the current detected temperature is greater than or equal to the preset threshold, a fire risk is identified, and the water heater stops heating. The preset threshold is calculated based on influencing factors, including the temperature rise in the electrical compartment caused by the water temperature inside the tank, the temperature rise caused by the heating of the electrical circuit system inside the electrical compartment, and the ambient temperature.

[0054] The fire prevention control method for electric water heaters involves installing a temperature detection unit inside the appliance compartment. During the heating process, the temperature detection unit calculates the temperature rise rate inside the appliance compartment and compares it with a preset temperature rise rate. If the temperature rise rate is greater than or equal to the preset rate, a fire risk is identified, and the water heater stops heating. Alternatively, the current detected temperature is compared with a preset threshold. If the current detected temperature is greater than or equal to the preset threshold, a fire risk is identified, and the water heater stops heating. This more sensitive method detects the fire risk of the water heater and stops heating to prevent danger.

[0055] Example 2:

[0056] This embodiment provides a fire prevention control method for electric water heaters. This embodiment is a further improvement on Embodiment 1. The fire prevention control method for electric water heaters includes the following steps:

[0057] When the electric water heater is powered on, the current detected temperature is compared with a comparison value. If the current detected temperature is lower than the comparison value, the water heater begins heating. The comparison value is the higher of a preset threshold and a preset detection value. The preset detection value = current detected temperature + preset value. The preset value is set according to requirements; in this embodiment, the preset value is 5℃. These steps avoid the risk of the water heater stopping heating due to a high temperature in the appliance compartment when powered on. It is important to note that the current detected temperature must not be greater than or equal to the comparison value. This prevents a situation where the appliance compartment is high immediately after water use, even if there is no actual fire risk, thus avoiding a misjudgment of a potential fire risk.

[0058] The fire prevention control method for electric water heaters also includes: comparing the current detected temperature with a preset temperature; if the current detected temperature is greater than or equal to the preset temperature, a fire risk is determined, and the electric water heater stops heating. The preset temperature is greater than or equal to the highest temperature measured in the appliance room under normal operating conditions. In this embodiment, the preset temperature is 80℃; however, in other embodiments, it is not limited to 80℃ and can be set to other temperatures.

[0059] The system simultaneously detects a fire risk by comparing the heating rate with a preset heating rate and by comparing the current detected temperature with a preset temperature. If either method detects a fire risk, the water heater stops heating. Alternatively, it simultaneously detects a fire risk by comparing the current detected temperature with a preset threshold and by comparing the current detected temperature with a preset temperature. If either method detects a fire risk, the water heater stops heating.

[0060] By simultaneously detecting using at least two methods, problems caused by errors in one detection method are avoided, thus improving detection accuracy. If either method determines "yes," a fire risk is identified, and the electric water heater stops heating.

[0061] Specifically, the preset threshold is calculated as follows: (Inner tank temperature - Ambient temperature) * Proportional constant + Maximum ambient temperature + Temperature rise caused by heating of the electrical system in the appliance compartment, where the inner tank temperature is the temperature inside the inner tank of the electric water heater. The preset threshold is derived from the above formula and covers the temperature rise in the appliance compartment caused by the water temperature inside the tank, the temperature rise caused by heating of the electrical system in the appliance compartment, and the influence of ambient temperature.

[0062] The temperature inside the tank is obtained by a temperature sensor installed inside the tank of the electric water heater. If multiple temperature sensors are installed, the highest temperature is used for calculation. The ambient temperature can be measured by a temperature sensor or set as a constant.

[0063] In this embodiment, the correlation formula for the rise in appliance room temperature caused by the water temperature inside the tank is: 50% * (tank temperature - ambient temperature) = appliance room temperature - ambient temperature. The ambient temperature for the fitting experiment is 20℃.

[0064] An appliance is considered problematic if its internal temperature rises by more than 15°C due to heat generation. (A 3kW current flowing through a 0.1Ω contact resistance will cause a temperature rise of approximately 15°C). The maximum ambient temperature is set at 30°C, so the offset is 30°C + 15°C = 45°C. Therefore, the preset threshold is calculated as (internal temperature - 20°C) * 0.5 + 45. When the internal temperature is below 20°C, 20°C is used as the threshold in this formula.

[0065] like Figure 3 The diagram illustrates how to obtain a preset threshold. Specifically, the current preset threshold is compared with the previously calculated preset threshold. If the current preset threshold is greater than or equal to the previously calculated preset threshold, the preset threshold is updated to the current preset threshold. These steps enable timely assessment of whether there is a fire risk associated with the electric water heater.

[0066] Because the water temperature drops rapidly when a water heater is in use, the actual temperature inside the appliance compartment doesn't drop immediately as the water temperature decreases. The calculated preset threshold is lower than the actual temperature inside the appliance compartment, easily leading to the assumption of a fire risk. Therefore, the calculated preset threshold cannot be directly used in this situation. When hot water is being used, the calculated preset threshold gradually decreases; therefore, comparing the difference between the calculated and calculated preset thresholds determines whether the water heater is in use.

[0067] Specifically, the current preset threshold is compared with the previously calculated preset threshold. If the current preset threshold is less than the previously calculated preset threshold, the decrease in the preset threshold is calculated according to the formula: Preset threshold decrease = (Current preset threshold - Previously calculated preset threshold) * Proportional coefficient, to obtain the decreased preset threshold. The preset threshold is then updated to the decreased preset threshold. The proportional coefficient is obtained based on time; in this embodiment, the proportional coefficient is 0.03. The minimum temperature difference is 1℃. These steps take into account the delayed decrease in the preset threshold of the electric water heater, resulting in more accurate detection.

[0068] It should be noted that the power-on detection also includes the following steps before comparing the current detected temperature with the preset threshold:

[0069] The system determines whether the current detected temperature is greater than or equal to a preset temperature value. If so, it compares the current detected temperature with a preset threshold. Based on this determination, there is a risk of fire only if the current detected temperature is greater than or equal to the preset temperature value. If the current detected temperature is less than the preset temperature value, there is no risk of fire, and therefore, there is no need to compare the current detected temperature with the preset threshold.

[0070] Optionally, the preset temperature value is between 40℃ and 60℃. In this embodiment, the preset temperature value is 50℃.

[0071] The temperature detection unit inside the electric water heater monitors the temperature in real time, and the temperature sensor inside the tank also monitors the tank temperature in real time. It accumulates the number of times the water heater stops heating when a fire risk is detected, and checks if the accumulated number is greater than or equal to a preset number. If so, the water heater issues an alarm; otherwise, the water heater is powered on again. By attempting to stop heating, it aims to prevent the risk of fire. However, when the accumulated number exceeds or equals the preset number, stopping heating alone cannot eliminate the risk, and the water heater issues an alarm to remind the user to check. It should be noted that the preset number of times can be set according to needs, such as two, three, four, etc.

[0072] Optionally, before comparing the heating rate with the preset heating rate, it is determined whether the number of temperature increases within a preset time is greater than or equal to the preset number of temperature increases. If so, the heating rate is then compared with the preset heating rate. These steps prevent the water heater from stopping heating due to short-term fluctuations in its heating rate, resulting in more accurate detection.

[0073] In this embodiment, the preset heating rate = heating power of the electric water heater / (specific heat capacity of water * volume of the inner tank * density of water). The preset heating rate is calculated using the above formula, which is relatively convenient.

[0074] Example 3:

[0075] like Figure 4 As shown, this embodiment provides a fire prevention control method for an electric water heater. This embodiment differs slightly from Embodiment 2 in that, before comparing the heating rate with a preset heating rate and / or before comparing the current detected temperature with a preset threshold, the following steps are also included:

[0076] The current detected temperature is compared with the preset temperature. If the current detected temperature is greater than or equal to the preset temperature, it is determined that there is a fire risk and the electric water heater stops heating.

[0077] If the current detection temperature is lower than the preset temperature, the heating rate will be compared with the preset heating rate and / or the current detection temperature will be compared with the preset threshold.

[0078] By comparing the current detected temperature with the preset temperature, if the current detected temperature is greater than or equal to the preset temperature, it is determined that there is a fire risk, and there is no need to perform the steps of comparing the heating rate with the preset heating rate and / or comparing the current detected temperature with the preset threshold.

[0079] If the current detected temperature is lower than the preset temperature, the heating rate will be compared with the preset heating rate and / or the current detected temperature will be compared with the preset threshold to make the ignition judgment of the electric water heater more accurate.

[0080] The subsequent detection steps are consistent with those in Example 2, and will not be repeated here.

[0081] Example 4:

[0082] The present invention also provides an electric water heater that is controlled using the fire prevention control method for electric water heaters in any of the above embodiments. This electric water heater, controlled using the aforementioned fire prevention control method, can avoid the risk of fire, has more sensitive detection, and extends the service life of the electric water heater.

[0083] Electric water heaters have a temperature detection unit installed in the appliance compartment to detect the temperature inside the appliance compartment.

[0084] In this embodiment, the temperature detection unit is a temperature sensor, which has a simple structure, low cost, and is convenient for temperature measurement.

[0085] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A fire prevention control method for an electric water heater, characterized by, The temperature detection unit is arranged in the electric appliance chamber of the electric water heater and is used to detect the temperature in the electric appliance chamber. During the heating process of the electric water heater, the temperature rising rate in the electric appliance chamber is calculated according to the detection temperature of the temperature detection unit, and the temperature rising rate is compared with a preset temperature rising rate; if the temperature rising rate is greater than or equal to the preset temperature rising rate, it is determined that there is a fire risk, and the electric water heater stops heating; the current detection temperature is compared with a preset threshold value; if the current detection temperature is greater than or equal to the preset threshold value, it is determined that there is a fire risk, and the electric water heater stops heating; wherein the preset threshold value is calculated according to influencing factors, and the influencing factors include the temperature rise of the electric appliance chamber caused by the water temperature in the inner tank, the temperature rise caused by the heating of the circuit system in the electric appliance chamber, and the environmental temperature; The current preset threshold value is compared with the preset threshold value calculated last time; if the current preset threshold value is greater than or equal to the preset threshold value calculated last time, the preset threshold value is updated to the current preset threshold value; The preset threshold value = (the temperature in the inner tank - the environmental temperature) * the proportional constant + the highest environmental temperature + the temperature rise caused by the heating of the circuit system in the electric appliance chamber, wherein the temperature in the inner tank is the temperature in the inner tank of the electric water heater. The proportional constant is 0.

5.

2. The control method of preventing fire of an electric water heater according to claim 1, wherein The fire prevention control method of the electric water heater further includes the following steps: The current detection temperature is compared with a preset temperature; if the current detection temperature is greater than or equal to the preset temperature, there is a fire risk, and the electric water heater stops heating; The temperature rising rate is compared with the preset temperature rising rate, and the current detection temperature is compared with the preset temperature; if any one of the two ways detects that there is a fire risk, the electric water heater stops heating; and / or The current detection temperature is compared with the preset threshold value, and the current detection temperature is compared with the preset temperature; if any one of the two ways detects that there is a fire risk, the electric water heater stops heating; the preset temperature is greater than or equal to the highest temperature in the electric appliance chamber under normal working conditions of the electric water heater.

3. The control method of preventing fire of an electric water heater according to claim 1, wherein Before comparing the temperature rising rate with the preset temperature rising rate and / or comparing the current detection temperature with the preset threshold value, the following steps are further included: The current detection temperature is compared with a preset temperature; if the current detection temperature is greater than or equal to the preset temperature, there is a fire risk, and the electric water heater stops heating; If the current detection temperature is less than the preset temperature, the temperature rising rate is compared with the preset temperature rising rate and / or the current detection temperature is compared with the preset threshold value.

4. The control method of preventing fire of an electric water heater according to claim 1, wherein When the electric water heater is powered on, the current detection temperature is compared with a comparison value; if the current detection temperature is less than the comparison value, the electric water heater starts heating; The comparison value is the higher one of the preset threshold value and a detection preset value, and the detection preset value = the current detection temperature + a preset value.

5. The control method of preventing fire of an electric water heater according to claim 1, wherein The current preset threshold is compared with the preset threshold calculated last time, if the current preset threshold is less than the preset threshold calculated last time, the descending amount of the preset threshold is calculated according to the calculation formula: the descending amount of the preset threshold = (the current preset threshold - the preset threshold calculated last time) * the proportion coefficient, to obtain the preset threshold after descending, and the preset threshold is updated to the preset threshold after descending; The proportion coefficient is 0.

03.

6. The control method for preventing fire of an electric water heater according to any one of claims 1 to 5, wherein Before comparing the current detection temperature with the preset threshold, further comprising: It is judged whether the current detection temperature is greater than or equal to a preset temperature value, if yes, the current detection temperature is compared with the preset threshold; the preset temperature value is between 40℃ and 60℃.

7. The control method of preventing fire of an electric water heater according to any one of claims 1 to 5, wherein The number of times that the electric water heater stops heating after detecting the existence of fire risk is accumulated, and it is judged whether the accumulated number of times is greater than or equal to a preset number of times, if yes, the electric water heater issues an alarm.

8. The control method for preventing fire of an electric water heater according to any one of claims 1 to 5, wherein Before comparing the temperature rising rate with the preset temperature rising rate, it is judged whether the number of temperature rising in a preset time is greater than or equal to a preset number of temperature rising, if yes, the temperature rising rate is compared with the preset temperature rising rate.

9. The control method of preventing fire of an electric water heater according to any one of claims 1 to 5, wherein The preset temperature rising rate = the heating power of the electric water heater / (the specific heat capacity of water * the volume of the inner container * the density of water).

10. An electric water heater, characterised in that, The electric water heater is controlled by the anti-fire control method of any one of claims 1-9. The electric water heater is controlled by the anti-fire control method of any one of claims 1-9.

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