A control method of a gas water heater

Abstract

The application discloses a control method of a gas water heater, which comprises the following steps: after a user turns off hot water, entering a water stop temperature control program; obtaining a circulating flow Q of the water heater and a total volume V of all heat exchange tubes; starting a circulating pump and recording a working time t1 of the circulating pump; before or after starting the circulating pump, calculating a first preset time ts1 according to the total volume V and the circulating flow Q; continuously judging whether the working time t1 is greater than a first reference value, the first reference value including the first preset time ts1, and if yes, shutting down the circulating pump. The application provides a control method of a gas water heater, which effectively solves the problem that the temperature in the heat exchange tubes of the gas water heater is too high after the water is stopped, thereby causing scaling.

Description

Technical Field

[0001] This invention relates to the field of water heater technology, and more particularly to a control method for a gas water heater. Background Technology

[0002] When the water supply to the water heater is turned off, the residual heat inside the combustion chamber continues to heat the hot water in the heat exchange tubes, causing the water temperature inside the tubes to become excessively high, exceeding 60℃ or 65℃. At this temperature, the stagnant high-temperature water inside the tubes is prone to scale buildup on the tube walls. Over time, this scale can clog the heat exchange tubes, severely affecting heat exchange efficiency and water flow. Furthermore, the scale buildup prevents the timely transfer of heat from the high-temperature flue gas side to the water, leading to localized high temperatures and overheating in the heat exchange tubes. This can potentially cause quality problems such as burn-through, deformation, and leaks in the heat exchange tubes. Summary of the Invention

[0003] This invention aims to at least partially solve one of the problems existing in the prior art. To this end, this invention proposes a control method for a gas water heater, which can calculate a preset time based on the total volume of all heat exchange tubes in the water heater and the circulation flow rate, and use the preset time to control the temperature of the heat flow in the tubes after the water supply is stopped, effectively solving the problem of scale formation caused by excessively high temperature in the heat exchange tubes after the water supply is stopped in the gas water heater.

[0004] The control method for a gas water heater provided above is achieved through the following technical solution:

[0005] A control method for a gas water heater, the control method comprising the following steps:

[0006] S1: After the user turns off the hot water, the water outage temperature control program is activated.

[0007] S2, obtain the circulating flow rate Q of the water heater and the total volume V of all heat exchange tubes;

[0008] S3, start the circulation pump and record the working time t1 of the circulation pump. Before or after starting the circulation pump, calculate the first preset time ts1 based on the total volume V and the circulation flow rate Q.

[0009] S4, continuously determine whether the working time t1 is greater than the first reference value, the first reference value includes the first preset time ts1, if so, shut down the circulation pump.

[0010] In some implementations, the formula for calculating the first preset time ts1 is: In the formula, k is 0.5 to 1.

[0011] In some implementations, the first reference value further includes a first time fluctuation value; the specific steps for continuously judging whether the working time t1 is greater than the first reference value are: continuously judging whether the working time t1 is greater than the sum of the first preset time ts1 and the first time fluctuation value; if so, the circulation pump is turned off; otherwise, step S4 is continued.

[0012] In some implementations, the circulation flow rate Q is 1.5–3.5 L / min; the total volume V = V0 × χ max , where χ max V0 represents the maximum number of heat exchange tubes and the internal volume of a single heat exchange tube.

[0013] In some implementations, before entering the water outage and temperature control procedure, the duration of the user's hot water shut-off is first obtained and determined to be greater than a time threshold; if so, the water outage and temperature control procedure is entered.

[0014] In some embodiments, the control method further includes the following steps:

[0015] S5, after shutting down the circulation pump, obtain the pump shutdown time of the circulation pump;

[0016] S6, continuously check whether the pump shut-off time of the circulating pump is greater than or equal to the set value. If so, proceed to the next step.

[0017] S7, restart the circulation pump and record the restart time t2 of the circulation pump;

[0018] S8 continuously checks whether the restart time t2 is greater than the second reference value. If so, it shuts down the circulation pump and exits the water stop temperature control program.

[0019] In some implementations, the second reference value includes a second preset time ts2, which is a preset value or calculated based on the total volume V and the circulation flow rate Q.

[0020] In some implementations, the formula for calculating the second preset time ts2 is: .

[0021] In some implementations, the second reference value also includes a second time fluctuation value; the specific steps for continuously judging whether the restart time t2 is greater than the second reference value are: continuously judging whether the restart time t2 is greater than the sum of the second preset time ts2 and the second time fluctuation value; if so, the circulation pump is turned off and the water stop temperature control program is exited; otherwise, step S8 is continued.

[0022] In some implementations, the specific steps of restarting the circulation pump and recording the restart time t2 of the circulation pump are as follows: obtain and determine whether the outlet water temperature of the heat exchanger of the water heater is less than the temperature threshold. If so, exit the water stop temperature control program; otherwise, restart the circulation pump and record the restart time t2 of the circulation pump.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] 1. This invention automatically calculates the preset time based on the circulating flow rate in the water heater and the total volume of all heat exchange tubes, and uses the preset time to control the temperature of the heat flow in the tubes after the water is turned off. This solves the risk of high-temperature scaling on the tube walls caused by the residual heat continuing to heat the water heater after the water is turned off. At the same time, it achieves very low cost and helps to extend the service life of the heat exchanger.

[0025] 2. By adding a temperature control chamber between the water outlet pipe and the water outlet connector, the hot water that has been replaced in the heat exchange tube flows into the temperature control chamber through the water outlet pipe for mixing. This not only allows for the prediction of temperature changes after mixing in the temperature control chamber, but also compensates for the heat loss generated by the temperature control chamber and improves the problem of excessive temperature drop after water outages and water restarts. Attached Figure Description

[0026] Figure 1 This is a flowchart of the control method for a gas water heater in Embodiment 1 of the present invention;

[0027] Figure 2 This is a schematic diagram of the gas water heater in Embodiment 1 of the present invention;

[0028] Figure 3 This is a schematic diagram of the distribution of the heat pipe system in Embodiment 1 of the present invention; Figure 4 This is a flowchart of the control method for a gas water heater in Embodiment 2 of the present invention. Detailed Implementation

[0029] The following embodiments illustrate the present invention, but the present invention is not limited to these embodiments. Modifications to the specific embodiments of the present invention or equivalent substitutions for some technical features, without departing from the spirit of the present invention, should all be covered within the scope of the technical solutions claimed in the present invention.

[0030] Example 1

[0031] refer to Figure 2This embodiment provides a control method for a gas water heater. The gas water heater includes a burner 1, a heat exchanger 2, a water flow sensor 3, a controller 4, a circulation pump 5, a circulation pipeline (not shown in the figure), and a control panel 7. The heat exchanger 2 is located above the burner 1 and has a heat exchange pipeline 21. The circulation pipeline includes an inlet pipe 61, an outlet pipe 62, and a return pipe 63. The inlet end of the inlet pipe 61 is connected to tap water through an inlet connector, and the outlet end of the inlet pipe 61 is connected to the inlet end of the outlet pipe 62 through the heat exchange pipeline 21 on the heat exchanger 2. One end of the return pipe 63 is connected to the outlet end of the outlet pipe 62 through an outlet connector 12, and the other end is connected to the inlet end of the inlet pipe 61 through a return connector 13.

[0032] A water flow sensor 3 is installed on the inlet pipe 61 and is used to obtain the inlet water flow rate L or the circulation flow rate Q of the circulation pipe 21. A circulation pump 5 is installed on the inlet pipe 61. A controller 4 is electrically connected to the water flow sensor 3, the circulation pump 5, and the control panel 7. The controller 4 is used to control the start or stop of the circulation pump 5 according to the pump operation command, and is also used to receive the water flow information collected by the water flow sensor 3 and control the working status of the corresponding components according to the water flow information.

[0033] refer to Figure 3 The heat exchanger 2 has multiple heat exchange tubes 211, an inlet 212, and an outlet 213. The number of heat exchange tubes 211 can be seven, nine, or eleven. This embodiment uses seven heat exchange tubes 211 as an example. The heat exchange pipeline 21 is composed of the inlet 212, seven heat exchange tubes 211, and the outlet 213 connected sequentially. When water flows through the heat exchange pipeline 21, the water temperature flowing into the inlet 212 is the inlet temperature T0, and the water temperature flowing out of the outlet 213 is the outlet temperature T8. The controller 4 is used to calculate the first preset time ts1 and the second preset time ts2 based on the circulation flow rate Q of the water heater's circulation pipeline and the total volume V of all heat exchange tubes 211. The controller 4 is also used to control the operating time of the circulation pump based on the first preset time ts1 or the first preset time ts1 and the second preset time ts2 after entering the water outage temperature control program. Thus, the preset time is automatically calculated based on the circulating flow rate in the water heater and the total volume of all heat exchange tubes. The preset time is used to control the temperature of the heat flow in the tubes after the water is turned off. This solves the risk of high-temperature scaling on the tube wall of heat exchange tube 211 caused by the residual heat continuing to heat the water heater after the water is turned off. At the same time, the cost is very low, which helps to extend the service life of heat exchanger 2.

[0034] The gas water heater also includes a temperature control chamber 8, through which the outlet end of the water outlet pipe 62 is connected to the outlet connector 12. Thus, by adding a temperature control chamber 8 between the water outlet pipe 62 and the outlet connector 12, the risk of scaling due to excessively high temperatures inside the heat exchange tube 211 is effectively addressed. Simultaneously, the hot water that has been replaced in the heat exchange tube 211 flows into the temperature control chamber 8 through the water outlet pipe 62 for mixing. This not only allows for anticipation of temperature changes after mixing within the temperature control chamber 8 but also compensates for heat loss generated by the temperature control chamber 8 and mitigates the problem of excessive temperature drop after water outages and refills.

[0035] refer to Figure 1 The control method for gas water heaters includes the following steps:

[0036] S1: After the user turns off the hot water, the water outage temperature control program is activated.

[0037] Specifically, after the user turns off the hot water, the water supply to the water heater stops and the burner 1 in the water heater is turned off. Because the water temperature inside the heat exchange tube 211 is still high after the water supply stops during showering, the temperature will continue to rise under the residual heat from the combustion chamber of the water heater. This temperature is very likely to exceed the temperature point where scale easily forms, resulting in scale deposits on the tube wall. Over time, this can lead to uneven heat exchange, overheating, and even burnout of the heat exchanger, posing safety hazards. Therefore, after the user turns off the hot water, a water shut-off temperature control program needs to be activated to reduce or eliminate the risk of high-temperature scale formation caused by residual heat continuing to heat the heat exchanger after the water supply stops.

[0038] Users sometimes turn off the water while using hot water, especially during showering. To prevent the water heater from entering the water shut-off temperature control program after the user turns off the water, this embodiment first obtains and determines whether the duration of the user turning off the hot water exceeds a time threshold after the user turns off the water and before entering the water shut-off temperature control program. If it does, the water shut-off temperature control program is entered; otherwise, it is not.

[0039] S2, obtain the circulating flow rate Q of the water heater and the total volume V of all heat exchange tubes;

[0040] Specifically, after entering the water outage and temperature control program, the circulating flow rate Q of the circulating pipeline and the total volume V of all heat pipes 211 are obtained through the water flow sensor 3.

[0041] The set flow range of the circulating flow rate Q is related to the PWM duty cycle set by the circulating pump 5. In order to take into account the user's inconvenience caused by the operating noise of the circulating pump 5, the set flow range of the circulating flow rate Q in this embodiment is designed to be 1.5~3.5L / min.

[0042] The total volume V of all heat exchange tubes 211 is equal to V0 × χmax, where χmax is the maximum number of heat exchange tubes 211, and V0 is the internal volume of a single heat exchange tube 211. In this embodiment, taking seven heat exchange tubes 211 as an example, the internal volume of each heat exchange tube 211 is V0, and the total volume V of the seven heat exchange tubes 211 is 7V0.

[0043] In other variations, the total volume V of all heat exchange tubes 211 can be replaced by the total volume V of the entire heat exchange tube 211. In this case, the total volume V' of the entire heat exchange tube 21 is 7V0 + Vin + Vout, where Vin is the volume of the water inlet 212 and Vout is the volume of the water outlet 213. In existing heat exchangers 2, the heat exchange tubes 211 are usually placed in a water box to change the direction of water flow. Therefore, the total volume V' of the entire heat exchange tube 21 can also be the sum of 7V0, Vin, Vout, and the volume of the water box.

[0044] S3, start the circulation pump and record the working time t1 of the circulation pump. Before or after starting the circulation pump, calculate the first preset time ts1 based on the total volume V and the circulation flow rate Q.

[0045] Specifically, the circulation pump 5 is started to make the water in the circulation pipe and heat exchange pipe 21 flow in the direction of water flow, and at the same time, the timer on the water heater starts recording the working time t1 of the circulation pump 6. Before, during or after the circulation pump 6 is started, the controller 4 calculates the first preset time ts1 based on the total volume V and the circulation flow rate Q.

[0046] S4, continuously determine whether the working time t1 is greater than the first reference value, the first reference value includes the first preset time ts1, if so, shut down the circulation pump.

[0047] Specifically, the first reference value may only include the first preset time ts1. When the first reference value only includes the first preset time ts1, it is continuously determined whether the working time t1 is greater than the first preset time ts1. If so, the circulation pump is turned off to complete the first circulation replacement cooling control of the heat exchanger 2. Otherwise, step S4 is continued.

[0048] Of course, the first reference value may include the first preset time ts1 and the first time fluctuation value. When the first reference value includes the first preset time ts1 and the first time fluctuation value, it is continuously determined whether the working time t1 is greater than (the first preset time ts1 + the first time fluctuation value). If so, the circulation pump is turned off to complete the first circulation replacement cooling control of the heat exchanger 2. Otherwise, step S4 is continued.

[0049] Therefore, in this embodiment, after the water heater enters the water outage temperature control program, the first preset time ts1 is calculated based on the total volume V of all heat exchange tubes and the circulation flow rate Q. The system then determines whether to shut down the circulation pump based on the relationship between the circulation pump's operating time t1 and the first preset time ts1. This achieves automatic determination of the first preset time ts1 by combining the heat exchange tubes 211 and the circulation flow rate, improving the product's adaptability and matching capabilities. Furthermore, by controlling the temperature of the heat flow inside the heat exchange tubes 211 after water outage, the highest water temperature inside the heat exchange tubes 211 can be reduced to below 50℃. This solves the risk of scale formation caused by residual hot water continuously heating up under residual heat in the heat exchange tubes 211, thus extending the service life of the heat exchanger 2.

[0050] In this embodiment, the formula for calculating the first preset time ts1 is: The first cycle of heat exchanger 2 is controlled by a first preset time ts1. The coefficient k is defined to proportionally divide the water volume within heat exchange tubes 1-7, so k is 0.5 to 1. The first preset time ts1 calculated using the above formula is an ideal calculated value.

[0051] refer to Figure 3 When the coefficient k is 0.5, it means that after water circulation, the water flow in heat exchanger tube 1 just reaches the vicinity of heat exchanger tube 4. The instantaneous temperature of heat exchanger tubes 1-7 becomes: T1'=T2'=T3'=T4'=inlet water temperature T0. At this time, T5' is close to T1, T6' is close to T2, T7' is close to T3, and T8' is close to T4. Compared with the temperature of heat exchanger tubes 5-7 (T5 to T7) and the temperature of outlet hole 213 (T8) when the user turns off the water, since the temperatures of heat exchanger tubes T1, T2, T3, and T4 are relatively low, this circulation can significantly reduce the temperature rise in heat exchanger tubes 1-7.

[0052] Optionally, the coefficient k can be set according to the load of different water heaters. When the number of heat exchange tubes 211 is the same, the larger the load, the larger the value of coefficient k should be. That is, coefficient k is positively correlated with the load of water heater, ensuring that products with different loads can adaptively adjust the first preset time ts1, further improving the adaptability and versatility of the product.

[0053] Example 2

[0054] refer to Figure 4 The difference between this embodiment and Embodiment 1 is that the control method for the gas water heater further includes the following steps:

[0055] S5, after shutting down the circulation pump, obtain the pump shutdown time of the circulation pump;

[0056] Specifically, at the same time the circulation pump 6 is turned off, the timer on the water heater starts recording the pump-off time of the circulation pump 6. The controller 6 obtains the pump-off time of the circulation pump 6 through the timer.

[0057] S6, continuously check whether the pump shut-off time of the circulating pump is greater than or equal to the set value. If so, proceed to the next step.

[0058] Specifically, the set value is preferably 6 minutes, but it can also be designed to be greater than 6 minutes or greater than 3 minutes but less than 6 minutes. When the pump shutdown time reaches the set value (e.g., 6 minutes), the second cycle begins, which is the first cycle of heat exchanger 2 for temperature control. This further reduces the water temperature after the previous waste heat heating, ultimately achieving uniform temperature within heat exchanger 2 and further improving the service life of heat exchanger 2 and the product's durability and reliability. If the pump shutdown time does not reach the set value (e.g., 6 minutes), the process continues until step S6.

[0059] S7, restart the circulation pump and record the restart time t2 of the circulation pump;

[0060] Specifically, during the period from shutting down the circulating pump to restarting it, i.e., during the pump shutdown time, the water temperature in heat exchanger 2 will decrease over time. Since the first preset time ts1 is related to the coefficient K, the circulation flow rate Q, and the total volume V of all heat exchange tubes, if the value of coefficient K is close to 1, after the first circulation displacement cooling control of heat exchanger 2 is completed, the outlet water temperature T8 of heat exchanger 2 will be close to the inlet water temperature T0. Therefore, during the circulating pump shutdown period, the outlet water temperature T8 of heat exchanger 2 may decrease below the temperature threshold, which can be lower than or equal to the inlet water temperature T0. It is therefore necessary to obtain and determine the relationship between the outlet water temperature of heat exchanger 2 and the temperature threshold before restarting the circulating pump 5 to improve the flexibility of the control method and reduce energy consumption and operating costs.

[0061] Optionally, the specific steps for restarting the circulation pump and recording the restart time t2 are as follows: obtain and determine whether the outlet water temperature of the water heater is lower than the temperature threshold. If so, exit the water outage temperature control program directly; otherwise, restart the circulation pump and record the restart time t2.

[0062] S8 continuously checks whether the restart time t2 is greater than the second reference value. If so, it shuts down the circulation pump and exits the water stop temperature control program.

[0063] Specifically, the second reference value may only include the second preset time ts2. When the second reference value only includes the second preset time ts2, it is continuously determined whether the restart time t2 is greater than the second preset time ts1. If so, the circulating pump 5 is turned off and the water stop temperature control program is exited to complete the second circulation replacement cooling control of the heat exchanger 2. Otherwise, step S8 is continued.

[0064] Of course, the second reference value may include the second preset time ts2 and the second time fluctuation value. When the second reference value includes the second preset time ts2 and the second time fluctuation value, it is continuously determined whether the restart time t2 is greater than (the second preset time ts2 + the second time fluctuation value). If so, the circulating pump 5 is turned off and the water stop temperature control program is exited to complete the second circulation replacement cooling control of the heat exchanger 2. Otherwise, step S8 is continued.

[0065] It can be seen that by using two cycles of heat exchanger cooling control, the heat flow inside the heat exchanger 2 after water outage is controlled in multiple stages, so that the highest water temperature inside the heat exchanger tube 211 can be reduced to below 50℃. The control method is flexible and effectively solves the problem of scale formation caused by excessive temperature inside the heat exchanger tube after water outage in gas water heaters, thus extending the service life of heat exchanger 2.

[0066] Optionally, the second preset time ts2 can be a system preset value or a manually preset value. Alternatively, the second preset time ts2 can also be calculated based on the total volume V and the circulation flow rate Q. In this embodiment, the formula for calculating the second preset time ts2 is: Therefore, during the second cycle of displacement cooling control, by... The second preset time ts2 is calculated, and the circulating pump is shut down and the water stop temperature control program is exited only when the restart time t2 is greater than ts2 or (ts2 + Δt). This effectively ensures that the outlet water temperature T8 of heat exchanger 2 is necessarily equal to the inlet water temperature T0 of heat exchanger 2, thus further reducing the water temperature after the previous waste heat heating, ultimately achieving uniform temperature in each heat exchange tube 211 and improving product reliability. The above descriptions are merely some embodiments of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A control method for a gas water heater, characterized in that, The control method includes the following steps: S1: After the user turns off the hot water, the water outage temperature control program is activated. S2, obtain the circulating flow rate Q of the water heater and the total volume V of all heat exchange tubes; S3, start the circulation pump and record the working time t1 of the circulation pump. Before or after starting the circulation pump, calculate the first preset time ts1 based on the total volume V and the circulation flow rate Q. S4, continuously determine whether the working time t1 is greater than the first reference value, the first reference value includes the first preset time ts1, if so, shut down the circulation pump; The formula for calculating the first preset time ts1 is: In the formula, k is 0.5 to 1; Total volume V = V0 × χ max , where χ max V0 represents the maximum number of heat exchange tubes and the internal volume of a single heat exchange tube.

2. The control method for a gas water heater according to claim 1, characterized in that, The first reference value also includes a first time fluctuation value; the specific steps for continuously determining whether the working time t1 is greater than the first reference value are as follows: Continuously determine whether the working time t1 is greater than the sum of the first preset time ts1 and the first time fluctuation value. If so, shut down the circulation pump; otherwise, continue to execute step S4.

3. The control method for a gas water heater according to claim 1, characterized in that, The circulating flow rate Q is 1.5 to 3.5 L / min.

4. The control method for a gas water heater according to claim 1, characterized in that, Before entering the water outage and temperature control program, it is determined whether the duration of the user's hot water shut-off exceeds the time threshold. If so, the water outage and temperature control program is entered.

5. A control method for a gas water heater according to claim 1 or 4, characterized in that, The control method further includes the following steps: S5, after shutting down the circulation pump, obtain the pump shutdown time of the circulation pump; S6, continuously check whether the pump shut-off time of the circulating pump is greater than or equal to the set value. If so, proceed to the next step. S7, restart the circulation pump and record the restart time t2 of the circulation pump; S8 continuously checks whether the restart time t2 is greater than the second reference value. If so, it shuts down the circulation pump and exits the water stop temperature control program.

6. The control method for a gas water heater according to claim 5, characterized in that, The second reference value includes a second preset time ts2, which is a preset value or calculated based on the total volume V and the circulation flow rate Q.

7. The control method for a gas water heater according to claim 6, characterized in that, The formula for calculating the second preset time ts2 is: .

8. A control method for a gas water heater according to claim 6 or 7, characterized in that, The second reference value also includes a second time fluctuation value; the specific steps for continuously determining whether the restart time t2 is greater than the second reference value are as follows: Continuously determine whether the restart time t2 is greater than the sum of the second preset time ts2 and the second time fluctuation value. If so, shut down the circulation pump and exit the water stop temperature control program. Otherwise, continue to execute step S8.

9. The control method for a gas water heater according to claim 5, characterized in that, The specific steps for restarting the circulation pump and recording the restart time t2 are as follows: Determine if the outlet water temperature of the water heater's heat exchanger is lower than the temperature threshold. If so, exit the water shut-off temperature control program; otherwise, restart the circulation pump and record the restart time t2.

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