CN215175955U - Gas water heater and hot water supply system - Google Patents

Abstract

The utility model provides a gas heater and hot water supply system. The gas water heater comprises a heat exchanger, a burner, a water inlet pipeline and a control device. A water inlet pipeline is communicated between the first water inlet of the gas water heater and the second water inlet of the heat exchanger, a water pump and an inlet water temperature sensor are arranged on the water inlet pipeline, and the latter obtains the current inlet water temperature T in the water inlet pipeline. Control device forAt the first time and T is more than or equal to T₁+T₀The water pump is turned off at the second time interval and T is more than or equal to T₂Time-off of the water pump, T₁Inlet water temperature after starting the water pump for a first preset time period, T₀Is a preset value, T₂＞T₁+T₀. And different closing temperatures are set for the water pump at different air temperatures. Whether the current inlet water temperature T reaches T or not in the first cooler time₁+T₀As the closing temperature of the water pump, the condition of overheating outlet water temperature can not occur, so that scalding can be effectively avoided, and energy waste can not be caused.

Description

Gas water heater and hot water supply system

Technical Field

The utility model relates to a technical field of water heater specifically, relates to a gas heater and have this gas heater's hot water supply system.

Background

The gas water heater transfers heat to cold water flowing through the heat exchanger by a heating mode of generating high-temperature flue gas by burning gas, thereby achieving the purpose of quickly discharging hot water. The prior gas water heater with the pressurization function is popular among users because the water outlet flow of the gas water heater is much larger than that of a common water heater.

The water pump for pressurizing is divided into an internal water pump and an external water pump, wherein the pressurizing stop logic of the internal water pump does not combine with a signal generating device or an electromagnetic water valve on a circulating water path, and generally depends on the detection of inlet water temperature to stop when reaching a set value or a limit value. The stopping logic is judged by the sudden change of the water flow signal, and the judgment reliability is not very guaranteed because the water flow and the pipeline resistance of a user are different, and the judgment is usually carried out by combining the water inlet temperature.

In winter, the temperature is very low, and the heat loss of the pipeline is large. Even if the hot water in the gas water heater is already slightly above the set temperature, the return flow of hot water from the water outlet to the water inlet of the gas water heater may be below the set temperature. Thus, the pump-off condition of the water pump is not satisfied. The hot water in a gas water heater needs to be reheated and recirculated for one turn. At this time, even when the minimum load is used, the temperature rises by about 10 ℃. At this time, the inlet water temperature will far exceed the set temperature of the stop condition. Such secondary circulation can cause the gas extravagant, and goes out the water overheat, easily takes place to scald.

SUMMERY OF THE UTILITY MODEL

In order to at least partially solve the problems existing in the prior art, according to a first aspect of the present invention, a gas water heater is provided, which has a first water inlet and a first water outlet. The gas water heater includes: the heat exchanger is provided with a second water inlet and a second water outlet, and the second water outlet is communicated with the first water outlet; burning ofA heater for heating the heat exchanger; the water inlet pipeline is communicated between the first water inlet and the second water inlet, a water pump and a water inlet temperature sensor are arranged on the water inlet pipeline, and the water inlet temperature sensor is used for acquiring the current water inlet temperature T in the water inlet pipeline; and a control device for controlling T ≧ T at a first timing₁+T₀The water pump is shut off at the second time interval and T is more than or equal to T₂While turning off the water pump, wherein T₁For the water temperature of the inlet water after the water pump is started for a first preset time period, T₀Is a first predetermined value, T₂At a second predetermined value, T₂＞T₁+T₀The air temperature in the first time period is lower than the air temperature in the second time period.

This application has set up different shut-off temperatures at the time of the difference of temperature for the water pump respectively. Specifically, whether the current intake water temperature T reaches a lower temperature (T) or not is determined in the first cooler time period₁+T₀) As the closing temperature of the water pump, whether the current inlet water temperature T reaches a higher T or not is judged in a warmer second time period₂As the shut-off temperature of the water pump. The reason for this is that: the temperature of the water flowing out of the gas water heater is reduced more after the water returns through the return pipeline in the first cooler time period, and the temperature of the water inlet in the water inlet pipeline is not reduced more after the water returns through the return pipeline in the second warmer time period. For the closing temperature of the first cooler time, when the working state of the water pump reaches stability and the hot water pressurized by the water pump flows back to the gas water heater, the inlet water temperature T acquired by the inlet water temperature sensor₁On the basis of the preset value T, the preset value T is added₀I.e. T₁+T₀And T is₁+T₀Greater than T₂. Thus, the current inlet water temperature T reaches T₁+T₀In the process, the water temperature in the gas water heater can basically reach the set water temperature of a user, and the gas water heater is comfortable to use. At the same time, the temperature T of the collected inlet water is measured₁The closing temperature is determined by small-amplitude upward adjustment on the basis, then the pump is closed in time, the condition that the outlet water temperature is overheated because the water flow needs to be subjected to secondary circulation is avoided, and therefore scalding can be effectively avoidedThe injury can not cause the waste of energy.

The control device is further used for turning off the water pump when the inflow water is greater than or equal to a first preset flow threshold and maintains a second preset time period. When the inflow meets the above conditions, the situation that the pressurization is not obvious can be considered, and the control device can control the water pump to be closed, so that the service life of the water pump can be prolonged while the bathing comfort is ensured.

The control device is further used for restarting the water pump when the inflow water is smaller than or equal to a second preset flow threshold value. Because the discharge in the pipeline is unstable usually, through setting up into the flow of intaking and opening the water pump again when being less than or equal to the second and predetermine the flow threshold value and can avoid opening repeatedly of water pump and stop to can prolong the life-span of water pump effectively.

Illustratively, the gas water heater further comprises a water flow information detection device for detecting water flow information in the gas water heater, and the control device is further used for starting the burner according to the water flow information.

Exemplarily, the water flow information detection device is disposed on the water inlet pipeline and configured to obtain a water inflow rate in the water inlet pipeline, and the control device is further configured to start the burner when the water inflow rate is greater than or equal to a third preset flow threshold value. The burner is started by judging the inflow rate, so that the burner has the advantages of high precision, safety, reliability, stable working state and the like.

Exemplarily, the water pump further comprises a timer, wherein the timer is used for starting timing when the burner is started so as to obtain a starting time length, and the control device is further used for starting the water pump when the starting time length reaches a preset time length threshold value and the current inlet water temperature T is smaller than a preset temperature threshold value. The heat exchanger can basically finish preheating when the time condition is met, and the condition that the outlet water temperature of the gas water heater cannot reach the set value of a user is avoided.

According to a second aspect of the present invention, there is provided a hot water supply system comprising: any of the gas water heaters described above; the tap water pipeline is communicated to the first water inlet; the water inlet end of the return pipeline is communicated to the first water outlet, and the water outlet end of the return pipeline is communicated to the first water inlet; and the water using end is communicated with the return pipeline and the tap water pipeline.

Illustratively, a check valve is arranged on the return pipeline and is positioned between the water using end and the first water inlet.

A series of concepts in a simplified form are introduced in the disclosure, which will be described in further detail in the detailed description section. The summary of the invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

The advantages and features of the present invention are described in detail below with reference to the accompanying drawings.

Drawings

The following drawings of the present invention are used herein as part of the present invention for understanding the present invention. There are shown in the drawings, embodiments and descriptions thereof, which are used to explain the principles of the invention. In the drawings, there is shown in the drawings,

fig. 1 shows a schematic block diagram of a gas water heater according to an embodiment of the present invention; and

fig. 2 shows a schematic block diagram of a hot water supply system according to an embodiment of the present invention.

Wherein the figures include the following reference numerals:

100. a gas water heater; 101. a first water inlet; 102. a first water outlet; 110. a heat exchanger; 111. a second water inlet; 112. a second water outlet; 120. a water flow information detection device; 130. a burner; 131. an air inlet; 132. a gas proportional valve; 140. a water inlet pipeline; 141. a water pump; 142. an inlet water temperature sensor; 150. a control device; 160. a water outlet pipeline; 161. an effluent temperature sensor; 200. a return line; 220. a check valve; 300. a tap water line; 400. carrying out water termination.

Detailed Description

In the following description, numerous details are provided to provide a thorough understanding of the present invention. One skilled in the art, however, will understand that the following description illustrates only a preferred embodiment of the invention and that the invention may be practiced without one or more of these details. In addition, some technical features that are well known in the art are not described in detail in order to avoid obscuring the present invention.

In order to solve the technical problem at least partially, the embodiment of the utility model provides a gas heater. In these embodiments, the gas heater has into water temperature sensor, and the temperature of intaking in the inlet line based on the temperature sensor that intakes acquires provides the water pump for colder first time period and closes the temperature to guarantee that the water pump can stop when the hot water that flows out gas heater reaches suitable temperature, avoid causing the gas extravagant, avoid scalding the risk.

As shown in fig. 1, the gas water heater 100 has a first water inlet 101 and a first water outlet 102. The first water inlet 101 and the first water outlet 102 are water inlets and water outlets of the gas water heater 100, and the first water inlet 101 is used for receiving cold water and can be connected with a cold water pipeline, for example; the first water outlet 102 is used for outputting hot water heated by the gas water heater 100, and may be connected to one or more water using ends through a pipeline, for example.

The gas water heater 100 may include a heat exchanger 110, a burner 130, and a control device 150.

The heat exchanger 110 has a second water inlet 111 and a second water outlet 112. A water inlet pipeline 140 is communicated between the first water inlet 101 and the second water inlet 111. An outlet pipe 160 is communicated between the second water outlet 112 and the first water outlet 102. The burner 130 is used to heat the heat exchanger 110. The burner 130 has an air inlet 131. The gas delivered through the inlet 131 is combusted in the combustor 130, and the resulting heat heats the cold water flowing through the heat exchanger 110. The gas inlet 131 may be provided with a gas proportional valve 132, and the power of the burner 130 may be adjusted by adjusting the gas proportional valve 132, so as to ensure that the temperature of the hot water flowing out of the gas water heater 100 is at a set value. The outlet pipe 160 may be provided with an outlet temperature sensor 161, and the outlet temperature sensor 161 may detect the temperature of the water in the outlet pipe 160 in real time and feed the detected temperature back to the control device 150. The control device 150 can precisely adjust the gas proportional valve 132 based on the water temperature signal fed back by the outlet water temperature sensor 161, so as to further ensure that the temperature of the hot water flowing out of the gas water heater 100 is at the set value.

The water inlet pipe 140 may be provided with a water pump 141 and an inlet water temperature sensor 142. The water pump 141 is used to pump the water at the first water inlet 101 into the heat exchanger 110. The inlet water temperature sensor 142 is used to obtain the current inlet water temperature T in the inlet water pipe 140.

The water pump 141 may increase the flow of water output through the first water outlet 101 of the gas water heater 100. The water pump 141 may be turned on upon activation of the burner 130 to increase the outflow rate. Preferably, however, the gas water heater 100 may further include a timer for starting timing when the burner 130 is started to obtain the start-up time period. The timer may be integrated with the control device 150. The control device 150 is further configured to start the water pump 141 when the start time reaches the preset time threshold and the current inlet water temperature T is less than the preset temperature threshold. In the preferred embodiment, the water pump 141 is started up under two conditions, namely, a time condition (i.e., the starting time reaches a preset time threshold) and a temperature condition (i.e., the current inlet water temperature T is less than a preset temperature threshold).

For the time condition, the preset duration threshold may be, for example, between 1-5 seconds. Further, the preset duration threshold may be between 1-3 seconds. When the starting time reaches the preset time threshold, the heat exchanger 110 may have already been substantially preheated, so that after the water pump 141 is started, the water flow with a large flow rate can be heated, thereby avoiding the occurrence of the situation that the outlet water temperature of the gas water heater 100 does not reach the user set value. For temperature conditions, the preset temperature threshold may be, for example, between 40-46 degrees celsius. Further, the preset temperature threshold may be between 42-44 degrees Celsius. If the temperature of the inlet water exceeds the preset temperature threshold, the water pump 141 is not started to prevent the condition that the outlet water is overheated and scalds.

The control device 150 is used for controlling the first time interval T ≧ T₁+T₀The water pump 141 is turned off at the second hour and T is more than or equal to T₂The water pump 141 is turned off. Wherein, T₁The inlet water temperature after the first preset time period is started for the water pump 141; t is₀Is a first preset value; t is₂Is a second predetermined value and T₂＞T₁+T₀. The air temperature in the first time period is lower than the air temperature in the second time period.

For example, the first time section and the second time section may be divided by seasons, for example, the first time section may be winter, and the second time section may be spring, summer, and autumn. Illustratively, the first time period and the second time period may be divided by month according to the region where the gas water heater 100 is used. For example, in the Beijing area, a first time period may include months 11 to 3 months of the next year, and a second time period may include months 4-10. For example, in the black dragon river region, a first time period may include months 10 to months 4 of the next year, and a second time period may include months 5-9. After the water pump 141 is started for a first preset time period, the working state of the water pump 141 is stable, and the water flow pressurized by the water pump 141 can return to the gas water heater 100 through a return pipe 200 (described in detail later) connected between the first water inlet 101 and the first water outlet 102 outside the gas water heater 100, so as to obtain the water inlet temperature T at this time₁. The inlet line 140 is adapted to receive tap water and return water from the first outlet 102 through the return line 200. Illustratively, the first preset time period may be greater than or equal to 15 seconds. Further, the first preset time period may be less than or equal to 25 seconds. At T₁On the basis of the first preset value T, a first preset value T is added₀And then may be a condition for the water pump 141 to be turned off. That is, in the first time period, if the user stops using water, the water pump 141 circulates such that all the water heated by the heat exchanger 110 flows back to the water inlet pipe 140Causing the current inlet water temperature T in the inlet line 140 to increase. When the current inlet water temperature T reaches T₁+T₀When the water temperature in the gas water heater 100 reaches the set value of the user, the water pump 141 can be turned off; on the contrary, when the current water inlet temperature T is lower than T₁+T₀When it is, the water pump 141 is kept turned on. At the second time interval, the current inlet water temperature T reaches a second preset value T₂If so, the water pump 141 is turned off; otherwise, when the current inlet water temperature T is lower than the second preset value T₂When it is, the water pump 141 is kept turned on. Those skilled in the art can select the first preset value T according to the geographical location of the region where the gas water heater 100 is used, the air temperature in the first time period, and other factors₀. Illustratively, the first preset value T₀And may be between 6-22 degrees celsius. However, no matter the first preset value T₀Why is selected, T is guaranteed₂＞T₁+T₀. Exemplarily, the second preset value T₂May be between 41-45 degrees celsius and may be selected empirically by those skilled in the art. In the present application, different shutdown temperatures are set for the water pump 141 at different times of the air temperature. Specifically, whether the current intake water temperature T reaches a lower temperature (T) or not is determined in the first cooler time period₁+T₀) As the off temperature of the water pump 141, whether the current intake water temperature T reaches a higher T or not is determined in the warmer second time period₂As the off temperature of the water pump 141. The reason for this is that: the temperature of the water flowing out of the gas water heater 100 is more reduced after the water returns through the return line 200 at the first, cooler time period, and the temperature of the inlet water in the inlet line 140 is not reduced much after the water returns through the return line 200 at the second, warmer time period. For the turn-off temperature of the first time period, when the working state of the water pump 141 is stable and the hot water pressurized by the water pump 141 flows back to the gas water heater 100, the inlet water temperature T acquired by the inlet water temperature sensor 142₁On the basis of the preset value T, the preset value T is added₀I.e. T₁+T₀And T is₁+T₀Greater than T₂. Thus, the current inlet water temperature T reaches T₁+T₀At this time, the temperature of the water in the gas water heater 100 can substantially reach the user's settingWater temperature and comfortable use. At the same time, the temperature T of the collected inlet water is measured₁The closing temperature is determined by small-amplitude upward adjustment on the basis, and then the pump is turned off timely, so that the condition that the outlet water temperature is overheated due to the fact that water flow needs to be subjected to secondary circulation is avoided, scalding can be effectively avoided, and energy waste is avoided.

In another set of embodiments, another shut down condition is also provided for water pump 141. In some cases, the flow rate of the tap water pipe of the user's home is large, and when the influence of the water flow rate (referred to as the boost flow rate for short) caused by the water pump 141 on the total flow rate is not significant, the water pump 141 may be turned off. The original flow rate in the pipe is the flow rate when the water pump 141 is not turned on. The total flow rate is an actual flow rate in the pipe after the water pump 141 is turned on, and is substantially equal to the sum of the original flow rate and the supercharging flow rate. It is considered that when the ratio of the supercharging flow rate to the total flow rate is not higher than a preset ratio, which may be in the range of 5% to 15%, the supercharging is not significant. Of course, unstable conditions may also occur in the water flow in the line, so that a certain duration may also be provided for conditions in which the pressurisation is not significant.

Specifically, the gas water heater 100 may also include a first water flow detector. A first water flow detector may be disposed on the water inlet line 140 for obtaining the inlet water flow in the water inlet line 140. The control device 150 is further configured to turn off the water pump 141 when the inlet water flow rate is greater than or equal to the first preset flow rate threshold and is maintained for a second preset time period. Illustratively, the first preset flow threshold may be between 8-12L/min. Further, the first preset flow threshold may be between 9-11L/min. Illustratively, the second preset time period may be between 10-30 seconds. Further, the second preset time period may be between 15-25 seconds. When the inflow rate meets the above conditions, it is considered that the pressurization is not obvious, and the control device 150 may control the water pump 141 to be turned off, so that the life of the water pump 141 may be prolonged while the bathing comfort is ensured.

After the water pump 141 is turned off based on the situation where the pressurization is not obvious, if the water flow rate in the pipeline is reduced, it may be considered to turn on the water pump 141 again in order to improve the bathing comfort. Preferably, the gas water heater 100 may further include a second water flow detector. A second water flow detector may be disposed on the water inlet line 140 for obtaining the inlet water flow in the water inlet line 140. The control device 150 is further configured to restart the water pump 141 when the inlet water flow rate is less than or equal to a second preset flow rate threshold. The second preset flow threshold may be, for example, between 5-7L/min. Further, the second preset flow threshold may be between 5.5-6.5L/min. Because the water flow in the pipeline is usually unstable, the water pump 141 can be prevented from being repeatedly started and stopped by re-starting the water pump 141 when the inlet water flow is set to be less than or equal to the second preset flow threshold, so that the service life of the water pump 141 can be effectively prolonged.

Optionally, the gas water heater may further include a water flow information detecting device 120 for detecting water flow information in the gas water heater 100. The control device 150 may be used to activate the burner 130 based on the water flow information. The water flow information may include one or more of flow information, pressure information, etc. within the gas water heater 100.

Preferably, the water flow information detecting device 120 may be disposed on the water inlet pipe 140 for obtaining the water inlet flow rate in the water inlet pipe 140. In the case where the gas water heater 100 includes the first water flow rate detector, the water flow information detecting means 120 may be the same device as the first water flow rate detector. In the case where the gas water heater 100 includes the first water flow rate detector and the second water flow rate detector, the water flow information detecting means 120 may be the same device as the first water flow rate detector or the second water flow rate detector, or even the same device as the first water flow rate detector or the second water flow rate detector. The water flow information detection device 120 may include any suitable water flow detector, such as a water flow sensor or the like. The water flow sensor comprises a valve body, a water flow rotor component, a steady flow original and a Hall element. As water flows through the rotor assembly, the magnetic rotor rotates and the rotational speed varies linearly with the flow rate. The device has the advantages of sensitive response, long service life, rapid action, safety, reliability, convenient connection, low starting flow and the like. The control means 150 is also arranged to activate the burner 130 when the incoming water flow is greater than or equal to a third preset flow threshold. The third preset flow threshold may be in the range of 2.5L/min-3.0L/min. Further, the third preset flow threshold may be in the range of 2.6L/min-2.8L/min. Of course, the water flow information detecting device 120 may be disposed on the water outlet pipe 160, or any other suitable position. The water pressure in the water inlet pipeline 140 is stable, for example, the water flow information detecting device of the water flow sensor has a certain starting pressure, so that the water flow information detecting device 120 is disposed on the water inlet pipeline 140, and it can be ensured that the water flow information detecting device 120 has a stable working state.

The embodiment of the present invention further provides a hot water supply system, as shown in fig. 2, the hot water supply system includes any one of the gas water heater 100, the return line 200 and the tap water line 300 described above. The water inlet end of the return line 200 is connected to the first water outlet 102 of the gas water heater 100, and the water outlet end is connected to the first water inlet 101 of the gas water heater 100. Both the return line 200 and the tap water line 300 are provided outside the gas water heater 100. The water end 400 communicates the return line 200 with the water line 300. The water consuming end 400 may include a bathing fixture and/or a faucet, etc. The water line 300 is connected to the first water inlet 101 of the gas water heater 100. The tap water line 300 is used to deliver cold water to the gas water heater 100. The return line 200 can supply the hot water output from the gas water heater 100 to the water using end, and can also convey a part of the hot water or the whole hot water back to the first water inlet 101 of the gas water heater 100. In the present application, return line 200 is primarily used to provide a shut-down condition for water pump 141. Furthermore, zero cold water can also be achieved through the return line 200.

Preferably, a check valve 220 may be further disposed on the return line 200. The check valve 220 is located between the water use end 400 and the first water inlet 101 of the gas water heater 100. The check valve 220 is used to prevent cold water in the water line 300 from flowing back.

A person skilled in the art can understand the structure, operation mode and technical effect of the gas water heater by reading the above detailed description about the gas water heater, and can understand the specific steps in the control method for the gas water heater and the technical effect thereof, and therefore, for brevity, detailed description is omitted here.

Although the example embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the above-described example embodiments are merely illustrative and are not intended to limit the scope of the present invention thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present invention. All such changes and modifications are intended to be included within the scope of the present invention as claimed in the appended claims.

In the description provided herein, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Similarly, it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. However, the method of the present invention should not be interpreted as reflecting an intention that: rather, the invention as claimed requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

It will be understood by those skilled in the art that all of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the processes or elements of any method or apparatus so disclosed, may be combined in any combination, except combinations where such features are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.

Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The usage of the words first, second and third, etcetera do not indicate any ordering. These words may be interpreted as names.

The above description is only for the specific embodiments of the present invention or the description of the specific embodiments, the protection scope of the present invention is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present invention, and all should be covered within the protection scope of the present invention. The protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (8)

1. A gas water heater having a first water inlet and a first water outlet, comprising:

the heat exchanger is provided with a second water inlet and a second water outlet, and the second water outlet is communicated with the first water outlet;

a burner for heating the heat exchanger;

the water inlet pipeline is communicated between the first water inlet and the second water inlet, a water pump and a water inlet temperature sensor are arranged on the water inlet pipeline, and the water inlet temperature sensor is used for acquiring the current water inlet temperature T in the water inlet pipeline; and

control means for at a first time interval T ≧ T₁+T₀The water pump is shut off at the second time interval and T is more than or equal to T₂When the water pump is turned off,

wherein, T₁For the water temperature of the inlet water after the water pump is started for a first preset time period, T₀Is a first predetermined value, T₂At a second predetermined value, T₂＞T₁+T₀The air temperature in the first time period is lower than the air temperature in the second time period.

2. The gas water heater of claim 1, further comprising a first water flow detector disposed on the water inlet line for obtaining a flow of inlet water in the water inlet line, the control device further for turning off the water pump when the flow of inlet water is greater than or equal to a first preset flow threshold for a second preset period of time.

3. The gas water heater of claim 2, further comprising a second water flow detector disposed on said water inlet line for detecting a flow of inlet water in said water inlet line, said control means being further configured to restart said water pump when said flow of inlet water is less than or equal to a second predetermined flow threshold.

4. The gas water heater of claim 1, further comprising a water flow information detection device for detecting water flow information within the gas water heater, the control device further being configured to turn the burner on or off based on the water flow information.

5. The gas water heater as claimed in claim 4, wherein said water flow information detecting means is disposed on said water inlet pipeline for obtaining the water inflow rate in said water inlet pipeline, and said control means is further configured to activate said burner when said water inflow rate is greater than or equal to a third preset flow threshold.

6. The gas water heater of claim 1, further comprising a timer for starting a timer when the burner is activated to obtain a start-up duration, and the control means is further for starting the water pump when the start-up duration reaches a preset duration threshold and the current water intake temperature T is less than a preset temperature threshold.

7. A hot water supply system, comprising:

the gas water heater of any one of claims 1 to 6;

the tap water pipeline is communicated to the first water inlet;

the water inlet end of the return pipeline is communicated to the first water outlet, and the water outlet end of the return pipeline is communicated to the first water inlet; and

a water usage port communicating the return line and the tap water line.

8. The hot water supply system as claimed in claim 7, wherein a check valve is provided on the return line between the water using end and the first water inlet.

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