Control method of gas-fired heating water heater and gas-fired heating water heater

Abstract

The application relates to a control method of a gas heating water heater and the gas heating water heater. The method comprises the following steps: obtaining the water temperature of a return water pipe and the water temperature of an outlet water pipe; determining the return water temperature difference according to the water temperature of the return water pipe and the water temperature of the outlet water pipe; in the case that the return water temperature difference deviates from a preset temperature interval, adjusting the pump speed of a variable frequency pump and a constant speed pump and the on-off state of a bypass electric valve, so that the return water temperature difference is within the preset temperature interval; and the preset temperature interval is used for representing the temperature interval with the highest heat exchange efficiency of the water heater. The method can effectively avoid the situation that the return water temperature difference is too large and the service life of a heat exchanger is shortened, and the heat exchange efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of gas-fired heating and hot water boiler technology, and in particular to a control method for a gas-fired heating and hot water boiler and a gas-fired heating and hot water boiler. Background Technology

[0002] As people's living standards improve, gas-fired heating and hot water boilers are being used more and more widely in homes and commercial spaces. To meet the high demand for heating and hot water, a circulation pump is usually connected in series in the internal or external piping of the boiler to increase the system's circulation flow.

[0003] However, in actual operation, when the hot water boiler is running under low load, the simultaneous operation of two circulation pumps not only increases the user's operating costs but also wastes energy. To solve this problem, some technologies attempt to use only one circulation pump, but this may result in insufficient circulation flow, leading to an excessively large return water temperature difference.

[0004] Excessive return water temperature difference will cause greater thermal stress to the heat exchanger, thereby shortening its service life. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a control method for a gas-fired heating hot water boiler and a gas-fired heating hot water boiler, which can effectively avoid excessive return water temperature difference that would shorten the service life of the heat exchanger, while improving heat exchange efficiency.

[0006] The above-mentioned technical problems are solved by the following technical solutions:

[0007] A control method for a gas-fired heating hot water boiler, the gas-fired heating hot water boiler including an outlet pipe, a constant-speed pump installed on the outlet pipe, a return pipe, a variable-frequency pump installed on the return pipe, and a bypass electric valve installed in parallel with the constant-speed pump, the method comprising:

[0008] Obtain the water temperature in the return water pipe and the water temperature in the outlet water pipe;

[0009] Determine the return water temperature difference based on the return water temperature and the outlet water temperature.

[0010] When the return water temperature difference deviates from the preset temperature range, adjust the pump speed of the variable frequency pump, the on / off state of the constant speed pump and the bypass electric valve to keep the return water temperature difference within the preset temperature range; the preset temperature range is used to characterize the temperature range where the heat exchange efficiency of the hot water boiler is the highest.

[0011] The control method and gas-fired heating water boiler of the present invention, compared with the prior art, have the following beneficial effects: Based on the return water temperature difference determined by the return water temperature and the outlet water temperature, the variable frequency pump speed, the start and stop of the fixed speed pump, and the opening and closing of the bypass water circuit electric valve are controlled. When the circulation flow of the water boiler is insufficient, the fixed speed pump is started and the bypass electric valve is closed to increase the circulation flow; when the system circulation flow is too large, the bypass electric valve is opened and the fixed speed pump is closed. At the same time, the variable speed pump is PID regulated to control the return water temperature difference of the water boiler within a preset range, thereby avoiding excessive thermal stress on the heat exchanger caused by excessive temperature difference, which would affect the life of the heat exchanger, while improving heat exchange efficiency and saving energy.

[0012] In one embodiment, when the return water temperature difference deviates from the preset temperature range, the pump speed of the variable frequency pump, the on / off state of the constant speed pump, and the bypass electric valve are adjusted to bring the return water temperature difference within the preset temperature range, including:

[0013] When the return water temperature difference is less than the lower limit of the preset temperature range, the pump speed adjustment step of the variable frequency pump is obtained;

[0014] If the pump speed adjustment step is not at its minimum value, reduce the pump speed adjustment step by one step in the current cycle and return to the step of obtaining the return water temperature and the outlet water temperature.

[0015] In the above embodiments, the return water temperature difference is monitored in real time to determine whether the return water temperature difference is lower than the lower limit of the preset temperature range. If the return water temperature difference is lower than the lower limit of the preset temperature range, the pump speed adjustment step is reduced, thereby reducing the pump speed of the variable frequency pump, reducing the circulation flow of the hot water boiler, so that the energy can be more concentrated to heat the water flow, improving the heat exchange efficiency and avoiding unnecessary energy consumption.

[0016] In one embodiment, when the return water temperature difference deviates from the preset temperature range, the variable frequency pump speed, the constant speed pump, and the on / off state of the bypass electric valve are adjusted to bring the return water temperature difference within the preset temperature range. The method further includes:

[0017] When the pump speed adjustment step is at its minimum value and the constant speed pump is not turned on, the bypass electric valve is opened and the constant speed pump is turned off, and the process returns to the step of obtaining the return water temperature and the outlet water temperature.

[0018] In the above embodiments, when the return water temperature difference is less than the lower limit of the preset temperature range and the pump speed adjustment step is at the minimum value, the circulation flow of the hot water boiler is reduced by opening the bypass electric valve, so that the energy can be more concentrated to heat the water flow, improve the heat exchange efficiency, and avoid unnecessary energy consumption.

[0019] In one embodiment, the method further includes:

[0020] When the return water temperature difference is within the preset temperature range, the variable frequency pump is controlled to maintain the current pump speed and then return to the step of obtaining the return water temperature and the outlet water temperature.

[0021] In the above embodiments, when the return water temperature difference is within the preset temperature range, it indicates that the gas-fired heating and hot water boiler operates at the highest overall energy efficiency under this temperature range. At this time, controlling the variable frequency pump to maintain its current pump speed can avoid unnecessary energy consumption and further improve energy efficiency.

[0022] In one embodiment, when the return water temperature difference deviates from the preset temperature range, the variable frequency pump speed, the constant speed pump, and the on / off state of the bypass electric valve are adjusted to bring the return water temperature difference within the preset temperature range. The method further includes:

[0023] When the return water temperature difference is greater than the upper limit of the preset temperature range but less than or equal to the maximum allowable temperature difference threshold, the pump speed adjustment step of the variable frequency pump is obtained.

[0024] If the pump speed adjustment step is not at its maximum value, increase the pump speed adjustment step by one step in the current cycle and return to the step of obtaining the return water temperature and the outlet water temperature.

[0025] When the pump speed adjustment step is at its maximum value and the constant speed pump is not turned on, the bypass electric valve is closed and the constant speed pump is turned on, and the process returns to the step of obtaining the return water temperature and the outlet water temperature.

[0026] In the above embodiments, by real-time monitoring of the return water temperature difference, when the return water temperature difference is too large, the circulation flow of the hot water boiler is increased by adjusting the pump speed of the variable frequency pump, the constant speed pump, and the state of the bypass electric valve, so as to reduce the return water temperature difference and keep it within the preset temperature range, thereby improving the heat exchange efficiency and extending the service life of the hot water boiler.

[0027] In one embodiment, when the return water temperature difference deviates from the preset temperature range, the variable frequency pump speed, the constant speed pump, and the on / off state of the bypass electric valve are adjusted to bring the return water temperature difference within the preset temperature range. The method further includes:

[0028] If the return water temperature difference is greater than the maximum allowable temperature difference threshold and the constant speed pump is not turned on, the bypass electric valve is closed and the constant speed pump is turned on, and the process returns to the step of obtaining the return water temperature and the outlet water temperature.

[0029] In the above embodiments, when the return water temperature difference is greater than the maximum allowable temperature difference threshold, the circulation flow of the hot water boiler can be quickly increased by controlling the bypass electric valve to close and the constant speed pump to open, thereby quickly adjusting the return water temperature difference so that the return water temperature difference is within the preset temperature range, thereby improving the heat exchange efficiency and extending the service life of the hot water boiler.

[0030] In one embodiment, when the return water temperature difference deviates from the preset temperature range, the variable frequency pump speed, the constant speed pump, and the on / off state of the bypass electric valve are adjusted to bring the return water temperature difference within the preset temperature range. The method further includes:

[0031] When the return water temperature difference is greater than the maximum allowable temperature difference threshold, and the bypass electric valve is closed and the constant speed pump is open, the pump speed adjustment step of the variable frequency pump is obtained.

[0032] If the pump speed adjustment step is not at its maximum value, increase the pump speed adjustment step by one step in the current cycle and return to the step of obtaining the return water temperature and the outlet water temperature.

[0033] In the above embodiments, when the return water temperature difference is greater than the maximum allowable temperature difference threshold, and the bypass electric valve is in the closed state and the constant speed pump is in the open state, by gradually increasing the pump speed adjustment step, it is possible to minimize unnecessary energy consumption and improve energy efficiency while ensuring that the return water temperature difference is within the preset temperature range.

[0034] In one embodiment, the method further includes:

[0035] When the pump speed adjustment step is at its maximum value, the fan is controlled to perform a preset PID adjustment action according to the water temperature of the outlet pipe, so that the water temperature of the outlet pipe reaches the preset outlet water temperature, and then the process returns to the step of obtaining the water temperature of the return pipe and the water temperature of the outlet pipe.

[0036] In the above embodiments, when the pump speed adjustment reaches its limit but still cannot meet the requirement of keeping the return water temperature difference within the preset temperature range, the system load can be flexibly adjusted by controlling the fan to perform PID regulation, further reducing the return water temperature difference. At the same time, by controlling the water temperature in the outlet pipe to reach the preset outlet water temperature, the user's water needs can be met, providing a more comfortable user experience.

[0037] In one embodiment, when the return water temperature difference exceeds the maximum allowable temperature difference threshold, the method further includes:

[0038] If the return water temperature difference is still greater than the maximum allowable temperature difference threshold within the preset test cycle, and the fan speed is at its minimum, control the fan to maintain the current speed and execute the insufficient circulation flow alarm action.

[0039] And / or,

[0040] If the return water temperature difference changes to less than or equal to the maximum allowable temperature difference threshold within the preset test cycle, the fan will be controlled to maintain the current speed and an alarm action will be executed for insufficient circulation flow.

[0041] In the above embodiments, by continuously monitoring the return water temperature difference over multiple cycles, it can be confirmed that the system does indeed have a problem with insufficient circulation flow. After confirming the problem, an alarm action for insufficient circulation flow is immediately executed, which can promptly notify the user or operator of the problem in the system so that timely measures can be taken.

[0042] A gas-fired heating and hot water boiler includes an outlet pipe, a constant-speed pump installed on the outlet pipe, a return pipe, a variable-frequency pump installed on the return pipe, and a bypass electric valve and controller connected in parallel with the constant-speed pump.

[0043] The controller is connected to the constant speed pump, the variable frequency pump and the bypass electric valve respectively, and is used to execute the steps of the method as described in the above embodiments.

[0044] The gas-fired heating and hot water boiler provided in the above embodiments corresponds to the gas-fired heating and hot water boiler in the above method embodiments. Its implementation process and beneficial effects can be referred to the description of the above method embodiments, and will not be repeated here. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is an application environment diagram of a control method for a gas-fired heating hot water boiler in one embodiment.

[0047] Figure 2 This is an application environment diagram of the control method for a gas-fired heating hot water boiler in another embodiment;

[0048] Figure 3 This is a flowchart illustrating the control method for a gas-fired heating hot water boiler in one embodiment;

[0049] Figure 4 This is a flowchart illustrating the steps of adjusting the speed of the variable frequency pump, the on / off state of the constant speed pump and the bypass electric valve to bring the return water temperature difference within the preset temperature range when the return water temperature difference deviates from the preset temperature range in one embodiment.

[0050] Figure 5 This is a flowchart illustrating the steps of adjusting the speed of the variable frequency pump, the on / off state of the constant speed pump and the bypass electric valve to bring the return water temperature difference within the preset temperature range when the return water temperature difference deviates from the preset temperature range, as in another embodiment.

[0051] Figure 6This is a flowchart illustrating the steps of adjusting the speed of the variable frequency pump, the on / off state of the constant speed pump and the bypass electric valve to bring the return water temperature difference within the preset temperature range when the return water temperature difference deviates from the preset temperature range in another embodiment.

[0052] Figure 7 This is a flowchart illustrating the control method for a gas-fired heating hot water boiler in yet another embodiment;

[0053] Figure 8 This is a structural block diagram of the control device for a gas-fired heating hot water boiler in one embodiment;

[0054] Figure 9 This is an internal structural diagram of a computer device in one embodiment.

[0055] Explanation of reference numerals in the attached diagram: 2-Outlet water pipe, 4-Constant speed pump, 6-Return water pipe, 8-Variable frequency pump, 10-Bypass electric valve, 12-Controller, 14-Return water temperature sensor, 16-Outlet water temperature sensor, 18-Heat exchanger, 20-Fan, 22-Pulse igniter, 24-Ignition needle, 26-Feedback needle, 28-Gas valve, 30-Gas pipe, 32-Display, 34-Bypass pipe. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0057] The control method for gas-fired heating and hot water boilers provided in this application embodiment can be applied to, for example... Figure 1 The application environment shown is as follows. The gas-fired heating hot water boiler includes an outlet pipe 2, a constant-speed pump 4 mounted on the outlet pipe 2, a return pipe 6, a variable-frequency pump 8 mounted on the return pipe 6, and a bypass electric valve 10 connected in parallel with the constant-speed pump 4. It also includes a controller 12, which is connected to the constant-speed pump 4, the variable-frequency pump 8, and the bypass electric valve 10. The controller 12 is also connected to a return water temperature sensor 14 mounted on the return pipe 6 and an outlet water temperature sensor 16 mounted on the outlet pipe 2. The controller 12 obtains the water temperature of the return pipe 6 through the return water temperature sensor 14 and the water temperature of the outlet pipe 2 through the outlet water temperature sensor 16, and determines the return water temperature difference based on the return water temperature and the outlet water temperature. When the return water temperature difference deviates from a preset temperature range, the controller 12 adjusts the pump speed of the variable-frequency pump 8 and the on / off state of the constant-speed pump 4 and the bypass electric valve 10 to keep the return water temperature difference within the preset temperature range. The preset temperature range characterizes the temperature range where the heat exchange efficiency of the hot water boiler is highest. In this embodiment, the gas-fired heating and hot water boiler includes, in addition to the aforementioned components, elements such as... Figure 1The gas-fired heating and hot water boiler shown herein, as can be directly recognized by those skilled in the art, also includes a heat exchanger 18, a fan 20, a pulse igniter 22, an ignition needle 24, a feedback needle 26, a gas valve 28, a gas pipe 30, a display 32, and a bypass pipe 34. The specific locations and connections of each component can be directly obtained from [the diagram / information]. Figure 1 I learned this from the information provided, so I will not elaborate further here.

[0058] Secondly, the control method for gas-fired heating and hot water boilers provided in this application embodiment can be applied to, for example... Figure 2 In the application environment shown, terminal 202 communicates with server 204 via a network. A data storage system can store the data that server 204 needs to process. The data storage system can be integrated onto server 204 or placed in the cloud or on another network server. Server 204 acquires the return water temperature and outlet water temperature, and determines the return water temperature difference based on these temperatures. If the return water temperature difference deviates from the preset temperature range, it adjusts the speed of the variable frequency pump, the constant speed pump, and the on / off state of the bypass electric valve to keep the return water temperature difference within the preset temperature range. The preset temperature range characterizes the temperature range where the heat exchange efficiency of the hot water boiler is highest. Terminal 202 is a gas-fired heating hot water boiler. Server 204 can be implemented using a standalone server or a server cluster composed of multiple servers.

[0059] As described in the background section, existing high-load gas-fired heating and hot water boilers use a circulation pump connected in series inside or outside the boiler to increase system circulation flow. During boiler operation, both circulation pumps operate simultaneously at all load levels. However, during low-load operation, both pumps are unnecessary; only one is required to meet the boiler's circulation flow needs. Operating both pumps simultaneously increases user operating costs and wastes energy. Furthermore, using only one pump can lead to excessively large return water temperature differences when circulation flow is insufficient. These large temperature differences cause greater thermal stress on the heat exchanger, negatively impacting its lifespan and reducing heat exchange efficiency.

[0060] For the reasons stated above, in an exemplary embodiment, such as Figure 3 As shown, a control method for a gas-fired heating hot water boiler is provided, which is applied to... Figure 1 Taking controller 12 as an example, the explanation includes the following steps S302 to S306. Wherein:

[0061] S302, obtain the return water temperature and the outlet water temperature.

[0062] For example, such as Figure 1As shown, upon receiving a heat demand signal, the controller drives the hot water boiler to operate, causing the variable frequency pump to run at a given pump speed. Simultaneously, the bypass electric valve opens, and the constant speed pump closes. The fan is activated and controlled to operate at a given speed. A pre-ignition safety self-check is performed; after passing the self-check, ignition / valve opening occurs. Successful ignition is determined upon detecting a flame signal. At this point, the controller adjusts the fan speed via PID control to regulate the heat load based on the user-set outlet water temperature T, ensuring the outlet water temperature approaches T. Furthermore, the controller periodically monitors the return water temperature and outlet water temperature. The return water temperature is obtained through a return water temperature sensor installed in the return water pipe, and the outlet water temperature is obtained through an outlet water temperature sensor installed in the outlet water pipe.

[0063] S304, determine the return water temperature difference based on the return water temperature and the outlet water temperature.

[0064] The return water temperature difference is the difference between the return water temperature and the outlet water temperature, used to indicate whether the circulating flow rate in the hot water boiler is too high or too low.

[0065] S306, when the return water temperature difference deviates from the preset temperature range, adjust the pump speed of the variable frequency pump and the on / off state of the constant speed pump and the bypass electric valve to make the return water temperature difference within the preset temperature range; the preset temperature range is used to characterize the temperature range where the heat exchange efficiency of the hot water boiler is the highest.

[0066] Excessively low return water temperature difference not only wastes energy but also fails to improve heat exchange efficiency; while excessively high return water temperature difference not only reduces heat exchange efficiency but also causes significant thermal stress on the heat exchanger, shortening its lifespan. Therefore, maintaining the return water temperature difference within the range of highest heat exchange efficiency not only improves heat exchange efficiency but also extends the lifespan of the heat exchanger. It should be noted that the preset temperature range can be adjusted adaptively according to the specific structure of the gas-fired heating and hot water boiler. For example, the preset temperature range can be [T0, T1], where T0 ranges from [5℃, 10℃] and T1 ranges from [15℃, 25℃].

[0067] For example, if the return water temperature difference deviates from the preset temperature range, such as when the return water temperature difference is too large, the circulation flow in the hot water boiler can be increased by increasing the pump speed of the variable frequency pump, turning on the constant speed pump and closing the electric valve, so that the return water temperature difference is within the preset temperature range. Conversely, if the return water temperature difference is too small, the circulation flow in the hot water boiler can be reduced by decreasing the pump speed of the variable frequency pump, turning off the constant speed pump and opening the electric valve, so that the return water temperature difference is within the preset temperature range.

[0068] In the aforementioned control method for gas-fired heating and hot water boilers, the return water temperature difference is determined based on the return water temperature and the outlet water temperature. The variable frequency pump speed, the fixed-speed pump start / stop, and the bypass electric valve are controlled. When the boiler's circulation flow is insufficient, the fixed-speed pump is started, and the bypass electric valve is closed to increase the circulation flow. Conversely, when the system's circulation flow is excessive, the bypass electric valve is opened, the fixed-speed pump is closed, and the variable-speed pump is PID-regulated to control the return water temperature difference within a preset range. This prevents excessive temperature differences from causing significant thermal stress on the heat exchanger, affecting its lifespan, while simultaneously improving heat exchange efficiency and saving energy.

[0069] In one exemplary embodiment, such as Figure 4 As shown, step S306 includes steps S402 to S404. Wherein:

[0070] S402: When the return water temperature difference is less than the lower limit of the preset temperature range, the pump speed adjustment step of the variable frequency pump is obtained.

[0071] S404, if the pump speed adjustment step is not at its minimum value, reduce the pump speed adjustment step by one step in the current cycle and return to the step of obtaining the return water temperature and the outlet water temperature.

[0072] As mentioned above, the lower limit of the preset temperature range can refer to T0. When the return water temperature difference is less than the lower limit of the preset temperature range, it indicates that the return water temperature difference is too low, meaning that the circulation flow of the hot water boiler is too large, causing energy to be used for unnecessary circulation heating. The pump speed adjustment step can refer to a unit of pump speed adjustment, with each step potentially corresponding to a fixed change in pump speed. For example, assuming a pump speed adjustment step is 1%, then each reduction of one pump speed adjustment step will decrease the pump speed by 1%.

[0073] For example, when the return water temperature difference is less than the lower limit of the preset temperature range, the pump speed adjustment step of the variable frequency pump is acquired to determine whether the current pump speed adjustment step is at its minimum value. If the current pump speed adjustment step is not at its minimum value, the pump speed of the variable frequency pump is reduced by one pump speed adjustment step within the current cycle, thereby reducing the circulation flow rate. This ensures that energy can adequately heat the water flow, thus guaranteeing that the return water temperature difference remains within the preset temperature range. After adjusting the pump speed adjustment step within each cycle, the return water pipe temperature and the outlet water pipe temperature are acquired again to prepare for the next cycle of return water temperature difference monitoring and variable frequency pump speed adjustment. For example, assuming the preset temperature range is [10℃, 25℃], and the current return water temperature difference is 5℃, which is less than the lower limit of the preset temperature range of 10℃, if the minimum pump speed adjustment step is 1%, and the current pump speed adjustment step is 5%, then in the current cycle, the pump speed adjustment step is reduced by one step (e.g., 1%), so that the current pump speed adjustment step is reduced from 5% to 4%. After reducing the pump speed adjustment step, the process returns to the step of obtaining the return water pipe temperature and the outlet water pipe temperature, in preparation for the next round of return water temperature difference detection and pump speed adjustment.

[0074] In this embodiment, the return water temperature difference is monitored in real time to determine whether the return water temperature difference is lower than the lower limit of the preset temperature range. If the return water temperature difference is lower than the lower limit of the preset temperature range, the pump speed adjustment step is reduced, thereby reducing the pump speed of the variable frequency pump, reducing the circulation flow of the hot water boiler, so that the energy can be more concentrated to heat the water flow, improving the heat exchange efficiency and avoiding unnecessary energy consumption.

[0075] In one exemplary embodiment, such as Figure 4 As shown, when the return water temperature difference deviates from the preset temperature range, adjusting the pump speed of the variable frequency pump, the on / off state of the constant speed pump, and the bypass electric valve to keep the return water temperature difference within the preset temperature range also includes:

[0076] S406, when the pump speed adjustment step is at its minimum value and the constant speed pump is not turned on, control the bypass electric valve to open and control the constant speed pump to close, and return to the step of obtaining the return water temperature and the outlet water temperature.

[0077] For example, if the current pump speed adjustment step is detected to be at its minimum value, it means that the circulation flow of the hot water boiler cannot be further reduced by reducing the pump speed of the variable frequency pump. If the constant speed pump is not turned on at this time, the bypass electric valve connected in parallel with the constant speed pump is opened and the constant speed pump is kept closed to reduce the circulation flow of the hot water boiler so that the energy can fully heat the water flow and thus ensure that the return water temperature difference is kept within the preset temperature range.

[0078] In this embodiment, when the return water temperature difference is less than the lower limit of the preset temperature range and the pump speed adjustment step is at the minimum value, the circulation flow of the hot water boiler is reduced by opening the bypass electric valve, so that the energy can be more concentrated to heat the water flow, improve the heat exchange efficiency, and avoid unnecessary energy consumption.

[0079] In one exemplary embodiment, the method further includes:

[0080] When the return water temperature difference is within the preset temperature range, the variable frequency pump is controlled to maintain the current pump speed and then return to the step of obtaining the return water temperature and the outlet water temperature.

[0081] For example, when the return water temperature difference is within a preset temperature range, it indicates that the gas-fired heating and hot water boiler operates at the highest overall energy efficiency under this return water temperature difference. At this time, if the constant speed pump is on, it remains on, and the bypass electric valve remains closed; if the constant speed pump is off, it remains off, and the bypass electric valve remains open, so that the return water temperature difference is within the preset temperature range, and the return water pipe temperature and the outlet water pipe temperature are monitored in real time to obtain the return water temperature difference.

[0082] In this embodiment, when the return water temperature difference is within the preset temperature range, it indicates that the gas-fired heating and hot water boiler operates at the highest overall energy efficiency under this temperature range. Maintaining the variable frequency pump at its current speed at this time avoids unnecessary energy consumption and further improves energy efficiency.

[0083] In one exemplary embodiment, such as Figure 5 As shown, when the return water temperature difference deviates from the preset temperature range, adjusting the pump speed of the variable frequency pump, the on / off state of the constant speed pump, and the bypass electric valve to keep the return water temperature difference within the preset temperature range also includes:

[0084] S502: When the return water temperature difference is greater than the upper limit of the preset temperature range but less than or equal to the maximum allowable temperature difference threshold, the pump speed adjustment step of the variable frequency pump is obtained.

[0085] S504, if the pump speed adjustment step is not at its maximum value, increase the pump speed adjustment step by one step in the current cycle and return to the step of obtaining the return water temperature and the outlet water temperature.

[0086] S506, when the pump speed adjustment step is at its maximum value and the constant speed pump is not turned on, control the bypass electric valve to close and control the constant speed pump to turn on, and return to the step of obtaining the return water temperature and the outlet water temperature.

[0087] The maximum allowable temperature difference threshold characterizes the maximum return water temperature difference that the hot water boiler can withstand. The maximum allowable temperature difference threshold can range from 30℃ to 35℃. When the return water temperature difference exceeds this threshold, it may lead to problems such as overheating of the hot water boiler and damage to components.

[0088] For example, when the return water temperature difference is greater than the upper limit of the preset temperature range but less than or equal to the maximum allowable temperature difference threshold, it indicates that the return water temperature difference is too large. An excessively large return water temperature difference not only reduces heat exchange efficiency but also causes significant thermal stress on the heat exchanger in the hot water boiler, thus affecting its service life. In this case, the pump speed adjustment step of the variable frequency pump is obtained to determine if it is at its maximum value. If the pump speed adjustment step is not at its maximum value, the pump speed adjustment step is increased by one step in the current cycle to increase the circulating flow rate of the hot water boiler. After adjusting the pump speed adjustment step, the return water pipe temperature and the outlet water pipe temperature are continuously monitored to prepare for the next round of pump speed adjustment step adjustments, ensuring that the return water temperature difference is within the preset temperature range. When the pump speed adjustment step is at its maximum value, it means that the circulation flow of the hot water boiler cannot be increased by further increasing the pump speed of the variable frequency pump. Therefore, the circulation flow of the hot water boiler is increased by controlling the bypass electric valve to close and the constant speed pump to open. After adjustment, the return water temperature and the outlet water temperature are monitored to provide data support for further adjustments.

[0089] In this embodiment, by monitoring the return water temperature difference in real time, when the return water temperature difference is too large, the circulation flow of the hot water boiler is increased by adjusting the pump speed of the variable frequency pump, the constant speed pump, and the status of the bypass electric valve, so as to reduce the return water temperature difference and keep it within the preset temperature range, thereby improving the heat exchange efficiency and extending the service life of the hot water boiler.

[0090] In one exemplary embodiment, such as Figure 6 As shown, when the return water temperature difference deviates from the preset temperature range, adjusting the pump speed of the variable frequency pump, the on / off state of the constant speed pump, and the bypass electric valve to keep the return water temperature difference within the preset temperature range also includes:

[0091] S602, when the return water temperature difference is greater than the maximum allowable temperature difference threshold and the constant speed pump is not turned on, control the bypass electric valve to close and control the constant speed pump to turn on, and return to the step of obtaining the return water pipe temperature and the outlet water pipe temperature.

[0092] For example, when the return water temperature difference is greater than the maximum allowable temperature difference threshold, it means that the return water temperature difference has far exceeded the maximum return water temperature difference that the hot water boiler can withstand. In order to increase the circulation flow of the hot water boiler as quickly as possible, the bypass electric valve is closed and the constant speed pump is turned on to reduce the current return water temperature difference to the preset temperature range. Then, the return water pipe temperature and the outlet water pipe temperature are monitored to provide data support for further adjustment of the return water temperature difference.

[0093] In this embodiment, when the return water temperature difference is greater than the maximum allowable temperature difference threshold, the circulation flow of the hot water boiler can be quickly increased by controlling the bypass electric valve to close and the constant speed pump to open, thereby quickly adjusting the return water temperature difference so that the return water temperature difference is within the preset temperature range, thereby improving heat exchange efficiency and extending the service life of the hot water boiler.

[0094] In one exemplary embodiment, such as Figure 6 As shown, when the return water temperature difference deviates from the preset temperature range, adjusting the pump speed of the variable frequency pump, the on / off state of the constant speed pump, and the bypass electric valve to keep the return water temperature difference within the preset temperature range also includes:

[0095] S604: When the return water temperature difference is greater than the maximum allowable temperature difference threshold, and the bypass electric valve is closed and the constant speed pump is open, the pump speed adjustment step of the variable frequency pump is obtained.

[0096] S606, if the pump speed adjustment step is not at its maximum value, increase the pump speed adjustment step by one step in the current cycle and return to the step of obtaining the return water temperature and the outlet water temperature.

[0097] For example, when the return water temperature difference exceeds the maximum allowable temperature difference threshold, and the bypass electric valve is closed and the constant-speed pump is on, it indicates that even with the constant-speed pump on, the return water temperature difference still exceeds the maximum allowable temperature difference threshold. In this case, the circulation flow of the hot water boiler needs to be increased by increasing the pump speed of the variable frequency pump. Therefore, the pump speed adjustment step of the variable frequency pump is obtained. If the pump speed adjustment step is not at its maximum value, the pump speed adjustment step is increased by one step in the current cycle to increase the pump speed of the variable frequency pump. After increasing the pump speed of the variable frequency pump in each cycle, the return water temperature and the outlet water temperature are monitored in real time to prepare for the next round of pump speed adjustment.

[0098] In this embodiment, when the return water temperature difference is greater than the maximum allowable temperature difference threshold, and the bypass electric valve is in the closed state and the constant speed pump is in the open state, by gradually increasing the pump speed adjustment step, it is possible to minimize unnecessary energy consumption and improve energy efficiency while ensuring that the return water temperature difference is within the preset temperature range.

[0099] In one exemplary embodiment, the method further includes:

[0100] When the pump speed adjustment step is at its maximum value, the fan is controlled to perform a preset PID adjustment action according to the water temperature of the outlet pipe, so that the water temperature of the outlet pipe reaches the preset outlet water temperature, and then the process returns to the step of obtaining the water temperature of the return pipe and the water temperature of the outlet pipe.

[0101] For example, when the pump speed adjustment step is at its maximum value (including both the case where the constant-speed pump is on and the case where the constant-speed pump is off), if the return water temperature difference is still too large (including cases where the return water temperature difference is greater than the upper limit of the preset temperature range but less than the maximum allowable temperature difference threshold, and cases where the return water temperature difference is greater than the maximum allowable temperature difference threshold), the fan can be controlled to perform a preset PID adjustment action based on the outlet water temperature to reduce the load and decrease the return water temperature difference, while simultaneously ensuring that the outlet water temperature reaches the preset outlet water temperature to meet the user's water demand. After PID adjustment, the return water temperature and outlet water temperature will be monitored in real time, and it will be determined whether the return water temperature difference is within the preset temperature range to provide data support for subsequent adjustments.

[0102] In this embodiment, when the pump speed adjustment reaches its limit but still cannot meet the requirement of keeping the return water temperature difference within the preset temperature range, the system load can be flexibly adjusted by controlling the fan to perform PID regulation, further reducing the return water temperature difference. At the same time, by controlling the water temperature in the outlet pipe to reach the preset outlet water temperature, the user's water needs can be met, providing a more comfortable user experience.

[0103] In an exemplary embodiment, when the return water temperature difference exceeds the maximum allowable temperature difference threshold, the method further includes:

[0104] If the return water temperature difference is still greater than the maximum allowable temperature difference threshold within the preset test cycle, and the fan speed is at its minimum, control the fan to maintain the current speed and execute the insufficient circulation flow alarm action.

[0105] And / or,

[0106] If the return water temperature difference changes to less than or equal to the maximum allowable temperature difference threshold within the preset test cycle, the fan will be controlled to maintain the current speed and an alarm action will be executed for insufficient circulation flow.

[0107] For example, if the return water temperature difference is greater than the maximum allowable temperature difference threshold, after the constant speed pump is turned on and the pump speed adjustment step of the variable frequency pump is increased over multiple cycles, and the fan speed is at its minimum (i.e., at the lowest load), if the return water temperature difference is still greater than the maximum allowable temperature difference threshold within the preset test cycle, and / or the return water temperature difference changes to less than or equal to the maximum allowable temperature difference threshold within the preset test cycle, it indicates that no matter how it is adjusted, the circulation flow of the hot water heater can never meet the condition of keeping the return water temperature difference within the preset temperature range. Therefore, in addition to controlling the fan to maintain the current speed, an alarm action for insufficient circulation flow should also be performed, such as displaying alarm information on the display on the hot water heater.

[0108] In this embodiment, by continuously monitoring the return water temperature difference over multiple cycles, it can be confirmed that the system does indeed have a problem with insufficient circulation flow. After confirming the problem, an alarm action for insufficient circulation flow is immediately executed, which can promptly notify the user or operator of the problem in the system so that timely measures can be taken.

[0109] In an exemplary embodiment, this application also provides a gas-fired heating and hot water boiler, including an outlet pipe 2, a constant-speed pump 4 disposed on the outlet pipe 2, a return pipe 6, a variable-frequency pump 8 disposed on the return pipe 6, and a bypass electric valve 10 and a controller 12 disposed in parallel with the constant-speed pump 4; wherein, the controller 12 is connected to the constant-speed pump 4, the variable-frequency pump 8 and the bypass electric valve 10 respectively, and the controller 12 is used to perform the steps of the method as described in the above embodiment.

[0110] The gas-fired heating and hot water boiler provided in this embodiment corresponds to the gas-fired heating and hot water boiler in the above method embodiment. Its implementation process and beneficial effects can be referred to the description of the above method embodiment, and will not be repeated here.

[0111] To describe the method of this application in more detail, the following is combined with, for example: Figure 7 The flowchart shown is described in detail.

[0112] Step 1: When the gas-fired heating and hot water boiler detects heat demand, it starts up and activates the variable frequency pump. The variable frequency pump operates at a given speed, simultaneously opening the electric valve, while the constant speed pump closes. The fan is activated and controlled to operate at a given speed. A pre-ignition safety self-check is performed. If the safety self-check passes, the gas valve is ignited / opened. Once a flame signal is detected, ignition is considered successful.

[0113] Step 2: The controller executes PID regulation of the internal fan according to the user-set outlet water temperature T, controlling the water temperature in the outlet pipe to tend towards T.

[0114] Step 3: Within a preset cycle, detect the return water temperature difference ΔT and calculate which of the following ranges ΔT falls within: Δt < T0; T0 ≤ Δt ≤ T1; T1 < Δt ≤ T2; T2 < Δt. Based on the result, execute the corresponding steps. Here, T0 is the minimum temperature difference limit, ranging from 5℃ to 10℃. When Δt < T0, it indicates the return water temperature difference is too low, which is unnecessary and, besides wasting energy, does not improve heat exchange efficiency. T1 is the normal operating return water temperature difference limit, ranging from 15℃ to 25℃. The boiler water circulation operates at this temperature difference, resulting in the highest overall operating energy efficiency. T2 is the maximum return water temperature difference limit, ranging from 30℃ to 35℃. An excessively large return water temperature difference is detrimental to heat exchange and causes significant thermal stress on the heat exchanger, affecting its lifespan.

[0115] Step 4: When Δt < T0 is detected, check whether the pump speed adjustment step of the variable frequency pump is at the minimum value. If the pump speed adjustment step is not at the minimum value, decrease the pump speed adjustment step by one step within one cycle and return to execute step 3.

[0116] Step 5: Based on Step 4, if the pump speed adjustment step is at its minimum value, further check whether the constant speed pump is on. If the constant speed pump is on, open the electric valve, close the constant speed pump, and return to Step 3. If the constant speed pump is off, return to Step 2.

[0117] Step 6: When T0≤Δt≤T1 is detected, maintain the current variable frequency pump speed, maintain the current state of the fixed frequency pump, and return to step 2.

[0118] Step 7: When it is detected that T1 < Δt ≤ T2, check whether the pump speed adjustment step is at its maximum value. If the pump speed adjustment step has not reached its maximum value, increase the pump speed adjustment step by one step within one cycle and return to execute step 3.

[0119] Step 8: Based on Step 7, if the pump speed adjustment step reaches its maximum value, check if the constant speed pump is turned on. If the constant speed pump is not turned on, turn on the constant speed pump, close the electric valve, and return to Step 3. If the constant speed pump is detected to be turned on, return to Step 2.

[0120] Step 9: When T2 < Δt is detected, check if the constant speed pump is turned on. If the constant speed pump is not turned on, turn on the constant speed pump, close the electric valve, and return to step 3.

[0121] Step 10: Based on Step 9, if the constant speed pump is already turned on, check if the pump speed adjustment step is at its maximum value. If the pump speed adjustment step has not reached its maximum value, increase the pump speed adjustment step by one step within one adjustment cycle and return to Step 3.

[0122] Step 11: Based on Step 10, if the pump speed adjustment step is detected to be at its maximum value, the PID controller will adjust the fan speed within a preset adjustment period to reduce the load. Within a preset test period, it will check if Δt is greater than T2. ​​If it is not greater than T2, the controller will maintain the fan speed at this time, and simultaneously trigger a warning message on the display indicating insufficient circulating flow.

[0123] Step 12: Within the preset test cycle, check whether Δt is greater than T2. ​​If Δt is greater than T2, check whether the fan speed adjustment is at the minimum speed. If the fan speed adjustment is not at the minimum speed, return to step 11.

[0124] Step 13: Based on step 12, if the fan speed is detected to be at the minimum speed, the controller will maintain the fan speed at this time and trigger an insufficient circulation flow warning message on the display.

[0125] Step fourteen: When the controller detects that the heat demand signal is disconnected, the controller will open the electric valve (if the electric valve is closed), close the constant speed pump (if the constant speed pump is open), and simultaneously close the gas valve. The variable frequency pump will then continue to operate at the given pump speed for a period of time.

[0126] Step 15: When the controller detects a fault, it will open the electric valve (if the electric valve is closed), close the constant speed pump (if the constant speed pump is open), and simultaneously close the gas valve. It will also maintain the variable frequency pump running at the preset pump speed for a period of time and simultaneously trigger the display of the corresponding fault signal.

[0127] In this embodiment, by adjusting the pump speed of the variable frequency pump and controlling the on / off state of the constant speed pump, the circulating flow rate of the system is kept within a specified range, taking into account the return water temperature difference. By controlling the bypass electric valve, the increased system resistance when the constant speed pump is shut down is prevented, thus avoiding increased energy consumption of the variable frequency pump. Simultaneously, during shutdown, the constant speed pump is shut down first, maintaining the variable frequency pump at a given pump speed, further reducing the energy consumption of the circulating pump.

[0128] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0129] Based on the same inventive concept, this application also provides a control device for a gas-fired heating water boiler to implement the control method for the gas-fired heating water boiler described above. The solution provided by this device is similar to the solution described in the above method. Therefore, the specific limitations of one or more control device embodiments for gas-fired heating water boilers provided below can be found in the limitations of the control method for gas-fired heating water boilers described above, and will not be repeated here.

[0130] In one exemplary embodiment, such as Figure 8 As shown, a control device for a gas-fired heating and hot water boiler is provided, including: a water temperature acquisition module 802, a return water temperature difference determination module 804, and an adjustment module 806, wherein:

[0131] The water temperature acquisition module 802 is used to acquire the water temperature of the return water pipe and the water temperature of the outlet water pipe.

[0132] The return water temperature difference determination module 804 is used to determine the return water temperature difference based on the return water temperature and the outlet water temperature.

[0133] The adjustment module 806 is used to adjust the pump speed of the variable frequency pump, the on / off state of the constant speed pump and the bypass electric valve when the return water temperature difference deviates from the preset temperature range, so as to keep the return water temperature difference within the preset temperature range; the preset temperature range is used to characterize the temperature range in which the heat exchange efficiency of the hot water boiler is the highest.

[0134] In an exemplary embodiment, the adjustment module 806 includes:

[0135] The first pump speed adjustment step acquisition unit is used to acquire the pump speed adjustment step of the variable frequency pump when the return water temperature difference is less than the lower limit of the preset temperature range.

[0136] The first pump speed adjustment step adjustment unit is used to reduce the pump speed adjustment step by one step in the current cycle and return to the step of obtaining the return water temperature and the outlet water temperature when the pump speed adjustment step is not at the minimum value.

[0137] In an exemplary embodiment, the adjustment module 806 further includes:

[0138] The second pump speed adjustment step adjustment unit is used to control the bypass electric valve to open and control the constant speed pump to close when the pump speed adjustment step is at its minimum value and the constant speed pump is not turned on, and then return to the step of obtaining the return water temperature and the outlet water temperature.

[0139] In an exemplary embodiment, the control device for the gas-fired heating hot water boiler further includes:

[0140] The pump speed control module is used to control the variable frequency pump to maintain the current pump speed when the return water temperature difference is within the preset temperature range, and then return to the step of obtaining the return water pipe temperature and the outlet water pipe temperature.

[0141] In an exemplary embodiment, the adjustment module 806 further includes:

[0142] The second pump speed adjustment step acquisition unit is used to acquire the pump speed adjustment step of the variable frequency pump when the return water temperature difference is greater than the upper limit of the preset temperature range and less than or equal to the maximum allowable temperature difference threshold.

[0143] The third pump speed adjustment step adjustment unit is used to increase the pump speed adjustment step by one step in the current cycle when the pump speed adjustment step is not at its maximum value, and then return to the step of obtaining the return water temperature and the outlet water temperature.

[0144] The fourth pump speed adjustment step adjustment unit is used to control the bypass electric valve to close and control the constant speed pump to open when the pump speed adjustment step is at its maximum value and the constant speed pump is not turned on, and then return to the step of obtaining the return water temperature and the outlet water temperature.

[0145] In an exemplary embodiment, the adjustment module 806 further includes:

[0146] The fifth pump speed adjustment step adjustment unit is used to control the bypass electric valve to close and control the constant speed pump to open when the return water temperature difference is greater than the maximum allowable temperature difference threshold and the constant speed pump is not turned on, and then return to the step of obtaining the return water pipe temperature and the outlet water pipe temperature.

[0147] In an exemplary embodiment, the adjustment module 806 further includes:

[0148] The third pump speed adjustment step acquisition unit is used to acquire the pump speed adjustment step of the variable frequency pump when the return water temperature difference is greater than the maximum allowable temperature difference threshold, and the bypass electric valve is in the closed state and the constant speed pump is in the open state.

[0149] The sixth pump speed adjustment step unit is used to increase the pump speed adjustment step by one step in the current cycle when the pump speed adjustment step is not at its maximum value, and then return to the step of obtaining the return water temperature and the outlet water temperature.

[0150] In an exemplary embodiment, the adjustment module 806 further includes:

[0151] The blower regulating unit is used to control the blower to perform preset PID regulation actions according to the water temperature of the outlet pipe when the pump speed regulation step is at its maximum value, so that the water temperature of the outlet pipe reaches the preset outlet water temperature, and then return to the step of obtaining the return water temperature and the outlet water temperature.

[0152] In an exemplary embodiment, when the return water temperature difference exceeds the maximum allowable temperature difference threshold, the aforementioned adjustment module 806 further includes:

[0153] The first alarm unit is used to control the fan to maintain its current speed and execute an alarm action for insufficient circulation flow when the return water temperature difference is still greater than the maximum allowable temperature difference threshold and the fan speed is at its minimum within a preset test cycle.

[0154] And / or,

[0155] The second alarm unit is used to control the fan to maintain its current speed and execute an alarm action for insufficient circulation flow when the return water temperature difference changes to less than or equal to the maximum allowable temperature difference threshold within a preset test cycle.

[0156] The various modules in the control device of the aforementioned gas-fired heating and hot water boiler can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the corresponding operations of each module.

[0157] In one exemplary embodiment, a computer device is provided, which may be a server or a controller, and its internal structure diagram may be as follows: Figure 9 As shown, this computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The database stores water temperature data. The I / O interfaces are used for exchanging information between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements a control method for a gas-fired heating hot water boiler.

[0158] Those skilled in the art will understand that Figure 9 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0159] In one exemplary embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.

[0160] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps in the above method embodiments.

[0161] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0162] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0163] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0164] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A control method of a gas-fired combination boiler, characterized in that, The gas-fired heating water boiler includes an outlet pipe (2), a constant-speed pump (4) installed on the outlet pipe (2), a return pipe (6), a variable-frequency pump (8) installed on the return pipe (6), and a bypass electric valve (10) connected in parallel with the constant-speed pump (4). The method includes: Obtain the water temperature in the return water pipe and the water temperature in the outlet water pipe; The return water temperature difference is determined based on the return water temperature and the outlet water temperature. When the return water temperature difference deviates from the preset temperature range, the pump speed of the variable frequency pump, the on / off state of the constant speed pump and the bypass electric valve are adjusted to bring the return water temperature difference within the preset temperature range; the preset temperature range is used to characterize the temperature range in which the heat exchange efficiency of the hot water boiler is highest.

2. The method of claim 1, wherein, When the return water temperature difference deviates from the preset temperature range, adjusting the pump speed of the variable frequency pump, the on / off state of the constant speed pump and the bypass electric valve to bring the return water temperature difference within the preset temperature range includes: When the return water temperature difference is less than the lower limit of the preset temperature range, the pump speed adjustment step of the variable frequency pump is obtained; If the pump speed adjustment step is not at its minimum value, reduce the pump speed adjustment step by one step in the current cycle and return to the step of obtaining the return water temperature and the outlet water temperature.

3. The method of claim 2, wherein, The method of adjusting the pump speed of the variable frequency pump, the on / off state of the constant speed pump and the bypass electric valve when the return water temperature difference deviates from the preset temperature range, so as to keep the return water temperature difference within the preset temperature range, further includes: When the pump speed adjustment step is at its minimum value and the constant speed pump is not turned on, the bypass electric valve is opened and the constant speed pump is turned off, and the process returns to the step of obtaining the return water temperature and the outlet water temperature.

4. The method of claim 1, wherein, The method further includes: When the return water temperature difference is within the preset temperature range, the variable frequency pump is controlled to maintain the current pump speed and return to the step of obtaining the return water pipe temperature and the outlet water pipe temperature.

5. The method according to claim 1, characterized in that, The method of adjusting the pump speed of the variable frequency pump, the on / off state of the constant speed pump and the bypass electric valve when the return water temperature difference deviates from the preset temperature range, so as to keep the return water temperature difference within the preset temperature range, further includes: When the return water temperature difference is greater than the upper limit of the preset temperature range but less than or equal to the maximum allowable temperature difference threshold, the pump speed adjustment step of the variable frequency pump is obtained. If the pump speed adjustment step is not at its maximum value, increase the pump speed adjustment step by one step in the current cycle and return to the step of obtaining the return water temperature and the outlet water temperature. When the pump speed adjustment step is at its maximum value and the constant speed pump is not turned on, the bypass electric valve is controlled to close and the constant speed pump is controlled to turn on, and the process returns to the step of obtaining the return water temperature and the outlet water temperature.

6. The method of claim 1, wherein, The method of adjusting the pump speed of the variable frequency pump, the on / off state of the constant speed pump and the bypass electric valve when the return water temperature difference deviates from the preset temperature range, so as to keep the return water temperature difference within the preset temperature range, further includes: If the return water temperature difference is greater than the maximum allowable temperature difference threshold and the constant speed pump is not turned on, control the bypass electric valve to close and control the constant speed pump to turn on, and return to the step of obtaining the return water pipe temperature and the outlet water pipe temperature.

7. The method of claim 1, wherein, The method of adjusting the pump speed of the variable frequency pump, the on / off state of the constant speed pump and the bypass electric valve when the return water temperature difference deviates from the preset temperature range, so as to keep the return water temperature difference within the preset temperature range, further includes: When the return water temperature difference is greater than the maximum allowable temperature difference threshold, and the bypass electric valve is in the closed state and the constant speed pump is in the open state, the pump speed adjustment step of the variable frequency pump is obtained. If the pump speed adjustment step is not at its maximum value, increase the pump speed adjustment step by one step in the current cycle and return to the step of obtaining the return water temperature and the outlet water temperature.

8. The method according to claim 5 or 7, characterized in that, The method further includes: When the pump speed adjustment step is at its maximum value, the fan is controlled to perform a preset PID adjustment action according to the water temperature of the outlet pipe, so that the water temperature of the outlet pipe reaches the preset outlet water temperature, and then the process returns to the step of obtaining the water temperature of the return pipe and the water temperature of the outlet pipe.

9. The method of claim 8, wherein, If the return water temperature difference exceeds the maximum allowable temperature difference threshold, the method further includes: If the return water temperature difference is still greater than the maximum allowable temperature difference threshold within the preset test cycle, and the fan speed is at its minimum, control the fan to maintain the current speed and execute the insufficient circulation flow alarm action. And / or, If the return water temperature difference changes to less than or equal to the maximum allowable temperature difference threshold within the preset test cycle, the fan is controlled to maintain the current speed and an alarm action is executed for insufficient circulation flow.

10. A combination gas fired central heating and water heating appliance, characterised in that, It includes an outlet pipe (2), a constant speed pump (4) installed on the outlet pipe (2), a return pipe (6), a variable frequency pump (8) installed on the return pipe (6), and a bypass electric valve (10) and a controller (12) connected in parallel with the constant speed pump (4). The controller (12) is connected to the constant speed pump (4), the variable frequency pump (8) and the bypass electric valve (10) respectively, and the controller is used to perform the steps of the method as described in any one of claims 1-9.

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