CN111912114B - Control method of gas water heater - Google Patents

Abstract

The invention discloses a control method of a gas water heater, which is characterized in that after the gas water heater enters a preheating mode, the gas water heater acquires the inlet water temperature T in the preheating process_{Feeding in} Temperature T of backwater_{Returning to} And the outlet water temperature T_{Out of} And the water inlet temperature T_{Feeding in} And backwater temperature T_{Returning to} Comparing to obtain the circulating water quantity V of single preheating according to the comparison result_{Total (S)} The current preheated circulating water quantity V_{Real world} With the circulating water quantity V preheated once_{Total (S)} Comparing the current water point temperature T according to the comparison result and a corresponding calculation formula according to the current comparison result_{By using} Calculating to obtain the current water point temperature T in the preheating process_{By using} . The method is simple and feasible, is convenient to use, and can rapidly calculate the real-time water temperature of the preheating process and the current water consumption point after the preheating.

Description

Control method of gas water heater

Technical Field

The invention relates to the technical field of water heaters, in particular to a control method of a gas water heater.

Background

In the related art, most of gas water heater displays or remote controllers can only display preset temperature or water outlet temperature of the water heater, but cannot display water consumption temperature, users cannot know the water consumption temperature in the zero-cold water preheating process, cannot know whether the preheating is sufficient, and whether the water consumption temperature has overheat or supercooling conditions, so that user experience is greatly influenced.

Disclosure of Invention

The invention aims to solve one of the problems in the prior related art to at least a certain extent, and therefore, the invention provides a control method of the gas water heater, which is simple and feasible, is convenient to use, and can rapidly calculate the real-time water temperature of the preheating process and the current water consumption point after the preheating.

The above object is achieved by the following technical scheme:

the control method of the gas water heater comprises a heat exchanger, a water inlet pipe, a water return pipe, a water outlet pipe and a plurality of water consumption points, wherein the water inlet end of the heat exchanger is communicated with one end of the water return pipe through the water inlet pipe, one end of the water outlet pipe is communicated with the water outlet end of the heat exchanger, the other end of the water outlet pipe is sequentially connected with a plurality of water consumption points and is communicated with one end of the water return pipe far away from the water inlet pipe, a circulating pipeline is formed by the heat exchanger, the water inlet pipe, the water outlet pipe and the water return pipe together, a circulating pump, a water inlet temperature probe, a water outlet temperature probe and a water flow sensing device are arranged on the heat exchanger, the gas water heater further comprises a controller which is respectively and electrically connected with the circulating pump, the water inlet temperature probe, the water outlet temperature probe and the water flow sensing device, and the control method of the gas water heater specifically comprises the following steps:

the gas water heater enters a preheating mode, and the circulating pump is started to start the gas water heater;

respectively collecting the water inlet temperature T_{Feeding in} Temperature T of backwater_{Returning to} And the outlet water temperature T_{Out of} ；

Judging the backwater temperature T_{Returning to} Whether or not it is greater than the water inlet temperature T_{Feeding in} The sum of the temperature rise temperature difference delta T and the temperature rise temperature difference delta T, and the circulating water quantity V of single preheating is obtained according to the judgment result_{Total (S)} ；

Collecting the current preheated circulating water quantity V_{Real world} ；

The current preheated circulating water quantity V_{Real world} With the circulating water quantity V of the single preheating_{Total (S)} Comparing according to the comparison result to obtain a comparison resultThe corresponding calculation formula is used for calculating the current water point temperature T_{By using} And (5) performing calculation.

In some embodiments, the determining the return water temperature T_{Returning to} Whether or not it is greater than the water inlet temperature T_{Feeding in} The sum of the temperature rise temperature difference delta T and the temperature rise temperature difference delta T, and the circulating water quantity V of single preheating is obtained according to the judgment result_{Total (S)} The specific steps of (a) include:

judging the backwater temperature T_{Returning to} Whether or not it is greater than the water inlet temperature T_{Feeding in} A sum of the temperature difference DeltaT and the temperature rise;

if yes, setting the average value of the circulating water quantity values of the last plurality of single preheats as the circulating water quantity V of the single preheats_{Total (S)} ；

If not, setting the circulating water quantity value of the last single preheating as the circulating water quantity V of the single preheating_{Total (S)} 。

In some embodiments, the current preheated amount of circulating water V_{Real world} With the circulating water quantity V of the single preheating_{Total (S)} Comparing the current water point temperature T according to the comparison result and a corresponding calculation formula according to the current comparison result_{By using} The specific steps of the calculation include:

judgment of V_{Real world} Whether a first preset condition is met, wherein the first preset condition is V_{Real world} ≤K×V_{Total (S)} (V)_{Real world} V is the current preheated circulating water quantity_{Total (S)} The circulating water quantity is preheated once, K is the ratio of the length of a water outlet pipe between the gas water heater and the water consumption point to the total length of a circulating pipeline;

if yes, calculating according to a first preset calculation formula to obtain the current water point temperature T_{With 1} Wherein the first preset calculation formula is T_{With 1} ＝T_{Feeding in} ；

If not, judge V_{Real world} Whether a second preset condition is satisfied.

In some embodiments, the calculation is performed according to a first preset calculation formula to obtain the current water point temperature T_{With 1} The following steps also include:

judging whether the gas water heater finishes the preheating work or not;

if yes, the circulating pump is turned off to exit the preheating mode, and calculation is carried out according to a fourth preset calculation formula to obtain the current water point temperature T_{By 4} Wherein the fourth preset calculation formula is T_{By 4} ＝T_{Returning to} ；

If not, returning to continuously judge the backwater temperature T_{Returning to} Whether or not it is greater than the water inlet temperature T_{Feeding in} And the temperature difference DeltaT.

In some embodiments, the determination V_{Real world} The step of whether the second preset condition is met specifically includes:

judgment of V_{Real world} Whether or not a second preset condition is satisfied, the second preset condition is KXV_{Total (S)} ＜V_{Real world} ＜V_{Total (S)} Wherein V is_{Real world} V is the current preheated circulating water quantity_{Total (S)} The circulating water quantity is preheated once, K is the ratio of the length of a water outlet pipe between the gas water heater and the water consumption point to the total length of a circulating pipeline;

if yes, calculating according to a second preset calculation formula to obtain the current water point temperature T_{With 2} The second preset calculation formula is T_{With 2} ＝[(1-k)×(T_{Pre-preparation} -T_{Feeding in} )]×(V_{Real world} -k×V_{Total (S)} )/(V_{Total (S)} -k×V_{Total (S)} )+T_{Feeding in} Wherein said T is_{Pre-preparation} Is a preset temperature value;

if not, calculating according to a third preset calculation formula to obtain the current water point temperature T_{With 3} Wherein the third preset calculation formula is T_{With 3} ＝T_{Returning to} +(1-k)×(T_{Out of} -T_{Returning to} )。

In some embodiments, the calculation is performed according to a second preset calculation formula to obtain the current water point temperature T_{With 2} The following steps also include:

judging whether the gas water heater finishes the preheating work or not;

if yes, closing the circulating pump to exit the preheating mode, and performing according to a fifth preset calculation formulaCalculating to obtain the current water point temperature T_{By 5} The fifth preset calculation formula is T_{By 5} ＝T_{Feeding in} +(T_{With 2} -T_{Feeding in} )×(T_{Go out to descend} -T_{Feeding in} )/(T_{Stop at the time of coming out} -T_{Feeding in} ) Wherein T is_{Stop at the time of coming out} T for stopping the water outlet temperature during preheating_{Go out to descend} The temperature of the water outlet after a certain time interval is used for stopping preheating;

if not, returning to continue to judge V_{Real world} Whether the second preset condition is satisfied.

In some embodiments, the calculation is performed according to a third preset calculation formula to obtain the current water point temperature T_{With 3} The following steps also include:

judging whether the gas water heater finishes the preheating work or not;

if yes, the circulating pump is turned off to exit the preheating mode, and calculation is performed according to a sixth preset calculation formula to obtain the current water point temperature T_{With 6} The sixth preset calculation formula is T_{With 6} ＝T_{Return drop} +(1-k)×(T_{Go out to descend} -T_{Return drop} ) Wherein T is_{Return drop} To stop preheating and to keep the return water temperature after a certain time interval, T_{Go out to descend} The temperature of the water outlet after a certain time interval is used for stopping preheating; if not, returning to calculate again according to a third preset calculation formula to obtain the current water point temperature T_{With 3} 。

In some embodiments, the gas water heater further comprises a display disposed on the heat exchanger, the display electrically connected to the controller for displaying the calculated current water temperature T_{By using} And displaying.

In some embodiments, the gas water heater further comprises a wireless communication module, and the controller is in communication connection with the external intelligent terminal device through the wireless communication module to inform a user of the current water consumption point temperature T_{By using} 。

Compared with the prior art, the invention at least comprises the following beneficial effects:

1. the control method of the gas water heater is simple and feasible, is convenient to use, and can rapidly calculate the preheating process and the real-time water temperature of the current water consumption point after the preheating.

2. The intelligent preheating device is reasonable in design, and can intelligently display the preheating process and the real-time water temperature of the current water consumption point after preheating, so that the use experience of a user is improved.

Drawings

FIG. 1 is a schematic diagram of a waterway system of a gas water heater according to an embodiment of the present invention;

FIG. 2 is a flow chart of a method for controlling a gas water heater according to an embodiment of the invention;

FIG. 3 is a graph showing the relationship between the water temperature during the preheating process and the amount of the circulating water for preheating in the embodiment of the present invention;

FIG. 4 is a graph showing the water temperature distribution of the circulation line in the second preheating stage according to the embodiment of the present invention;

FIG. 5 is a graph of the temperature profile of the circulating line at the third preheating stage and the temperature profile after temperature drop according to an embodiment of the present invention;

FIG. 6 is a graph showing the water temperature distribution of the circulation line in the second temperature drop stage according to the embodiment of the present invention.

Detailed Description

In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, based on the embodiments of the invention, which are obtained by a person of ordinary skill in the art without making any inventive effort, shall fall within the scope of the claimed invention.

As shown in fig. 1 to 6, the present embodiment provides a control method of a gas water heater, after the gas water heater enters a preheating mode, the gas water heater collects a water inlet temperature T during the preheating process_{Feeding in} Temperature T of backwater_{Returning to} And the outlet water temperature T_{Out of} And the water inlet temperature T_{Feeding in} And backwater temperature T_{Returning to} Comparing to obtain single preheated circulating water according to the comparison resultQuantity V_{Total (S)} The current preheated circulating water quantity V_{Real world} With the circulating water quantity V preheated once_{Total (S)} Comparing the current water point temperature T according to the comparison result and a corresponding calculation formula according to the current comparison result_{By using} Calculating to obtain the current water point temperature T in the preheating process_{By using} The method is simple and feasible, is convenient to use, and can rapidly calculate the real-time water temperature of the preheating process and the current water consumption point after the preheating.

In this embodiment, the gas water heater includes a heat exchanger 1, a water inlet pipe 2, a water return pipe 3, a water outlet pipe 4, a plurality of water consuming points 5 and a controller 6, wherein the water inlet end of the heat exchanger 1 is communicated with one end of the water return pipe 3 through the water inlet pipe 2, one end of the water outlet pipe 4 is communicated with the water outlet end of the heat exchanger 1, the other end is sequentially connected with a plurality of water consuming points 5, the other end of the water outlet pipe 4 is communicated with the water return pipe 3 at one end far away from the water inlet pipe 2, a one-way valve 8 is arranged between the water return pipe 3 and the water outlet pipe 4, a circulation pipeline is jointly formed through the heat exchanger 1, the water inlet pipe 2, the water outlet pipe 4 and the water return pipe 3, a circulation pump 11, a water inlet temperature probe 12, a water outlet temperature probe 13 and a water flow sensing device 14 which are respectively electrically connected with the controller 6 are arranged on a waterway of the heat exchanger 1, and the water inlet temperature probe 12 is arranged at the water inlet end position of the heat exchanger 1 to monitor the water inlet temperature T of tap water in real time_{Feeding in} Or the return water temperature T during preheating_{Returning to} The water outlet temperature probe 13 is arranged at the water outlet end position of the heat exchanger 1 to monitor the water outlet temperature T of the gas water heater in real time_{Out of} A display 7 electrically connected with the controller 6 is arranged on the heat exchanger 1, and the display 7 can display the calculated current temperature T of the water point 5_{By using} And the set temperature value of the gas water heater, in addition, the display 7 is also provided with "+", "-" temperature setting keys and preheating function keys, so that the operation and the use of the user are facilitated, and of course, the controller 6 can also be in communication connection with the external intelligent terminal equipment through the wireless communication module to inform the user of the current temperature T of the water consumption point 5_{By using} Or the user realizes remote control on the gas water heater through the external intelligent terminal equipment, and the wireless communication module in the embodiment is any one of a WIFI module, a Bluetooth module or an infrared module.

The control method of the gas water heater specifically comprises the following steps:

step S101, the gas water heater enters a preheating mode, and the circulating pump is started to start the gas water heater.

In this embodiment, the user turns on the preheating mode by the preheating function key on the display of the gas water heater, and after the gas water heater enters the preheating mode, the stored water in the water outlet pipe flows into the water path in the gas water heater again through the water return pipe so as to heat the water path by the heat exchanger.

Step S102, collecting the inlet water temperature T respectively_{Feeding in} Temperature T of backwater_{Returning to} And the outlet water temperature T_{Out of} 。

In the embodiment, the water inlet temperature probes are started to respectively control the water inlet temperature T_{Feeding in} Temperature T of backwater_{Returning to} Detecting, and simultaneously starting a water outlet temperature probe to perform water outlet temperature T_{Out of} And (5) detecting.

Step S103, judging the backwater temperature T_{Returning to} Whether or not it is greater than the water inlet temperature T_{Feeding in} A sum of the temperature difference DeltaT and the temperature rise;

step S113, if yes, setting the average value of the latest single-preheating circulating water quantity values as the single-preheating circulating water quantity V_{Total (S)} ；

Step S123, if not, setting the circulating water quantity value of the previous single preheating as the circulating water quantity V of the single preheating_{Total (S)} 。

In this embodiment, the circulating water amount V for single preheating in this embodiment_{Total (S)} After the gas water heater is started and preheated, the gas water heater reaches the current backwater temperature T_{Returning to} Is greater than the water inlet temperature T when preheating is started_{Feeding in} When the sum of the temperature rise temperature difference delta T and the current actual pre-heating circulating water quantity measured by the water flow sensing device is equal to the sum of the temperature rise temperature difference delta T, and in order to avoid errors of water flow detection, the average value of the last detected circulating water quantity values of a plurality of single pre-heats is preferably set as the circulating water quantity V of the single pre-heats_{Total (S)} . In the present embodiment, the temperature rising temperature difference Δt is a threshold value for determining whether the return water temperature has an increasing tendency in the preheating processThe Δt is preferably 1 ℃ to 3 ℃, but is not limited to the above-mentioned values, and suitable values may be selected according to actual needs.

Step S104, collecting the current preheated circulating water quantity V_{Real world} 。

In this embodiment, the water flow sensing device is started to detect the current preheated circulating water volume V_{Real world} 。

Step S105, judging V_{Real world} Whether the first preset condition is met, wherein the first preset condition is V_{Real world} ≤K×V_{Total (S)} Wherein V is_{Real world} V is the current preheated circulating water quantity_{Total (S)} The circulating water quantity for single preheating is the ratio of the length of a water outlet pipe between the gas water heater and the water consumption point to the total length of a circulating pipeline;

step S115, if yes, calculating according to a first preset calculation formula to obtain the current water point temperature T_{With 1} Wherein the first preset calculation formula is T_{With 1} ＝T_{Feeding in} ；

Step S125, if not, the process proceeds to step S106.

In this embodiment, K is the ratio of the length of the water outlet pipe between the gas water heater and the water consumption point to the total length of the circulation pipeline, and the K values of different water consumption points are different, and the K value can be set according to the actual pipeline condition, preferably in the range of 0-1, i.e. k=0.5 when the length of the water outlet pipe is equal to the length of the water return pipe 3.

In this embodiment, the current water consumption point temperature T is obtained by calculating according to a first preset calculation formula_{With 1} The following steps specifically include:

step S1151, judging whether the gas water heater finishes the preheating work;

if yes, the circulating pump is turned off to exit the preheating mode, and calculation is performed according to a fourth preset calculation formula to obtain the current water point temperature T_{By 4} Wherein the fourth preset calculation formula is T_{By 4} ＝T_{Returning to} ；

If not, returning to step S103 to continuously judge the backwater temperature T_{Returning to} Whether or not it is greater than the water inlet temperature T_{Feeding in} And the temperature difference DeltaT.

Step S106, judging V_{Real world} Whether or not a second preset condition is satisfied, the second preset condition is KXV_{Total (S)} ＜V_{Real world} ＜V_{Total (S)} Wherein V is_{Real world} V is the current preheated circulating water quantity_{Total (S)} The circulating water quantity for single preheating is the ratio of the length of a water outlet pipe between the gas water heater and the water consumption point to the total length of a circulating pipeline;

step S116, if yes, calculating according to a second preset calculation formula to obtain the current water point temperature T_{With 2} The second preset calculation formula is T_{With 2} ＝[(1-k)×(T_{Pre-preparation} -T_{Feeding in} )]×(V_{Real world} -k×V_{Total (S)} )/(V_{Total (S)} -k×V_{Total (S)} )+T_{Feeding in} Wherein said T is_{Pre-preparation} Is a preset temperature value;

step S126, if not, calculating according to a third preset calculation formula to obtain the current water point temperature T_{With 3} Wherein the third preset calculation formula is T_{With 3} ＝T_{Returning to} +(1-k)×(T_{Out of} -T_{Returning to} )。

In the present embodiment, when KXV_{Total (S)} ＜V_{Real world} ＜V_{Total (S)} At this time, as shown in FIG. 4, by V_{Real world} ＝V_{Total (S)} The geometric proportion relation of the water temperature distribution curve is obtained (V)_{Total (S)} -k×V_{Total (S)} )/V_{Total (S)} ＝[T_{By using} ’-(T_{Feeding in} +ΔT)]/[T_{Pre-preparation} -(T_{Feeding in} +ΔT)]By deduction: t (T)_{By using} ’＝(T_{Feeding in} +ΔT) + (1-k) × [ T pre- (T)_{Feeding in} +ΔT)]T, i.e_{By using} ' = (1-k) ×t pre+k (T)_{Feeding in} +Δt), and as shown in fig. 3, by geometric scaling with a water point temperature curve: (T)_{By using} -T_{Feeding in} )/(T_{By using} ’-T_{Feeding in} )＝(V_{Real world} -k×V_{Total (S)} )/(V_{Total (S)} -k×V_{Total (S)} ) By deduction: t (T)_{By using} ＝(T_{By using} ’-T_{Feeding in} )×(V_{Real world} -k×V_{Total (S)} )/(V_{Total (S)} -k×V_{Total (S)} )+T_{Feeding in} Substituted into the above T_{By using} ' a second preset calculation formula can be obtained: t (T)_{With 2} = [ (1-k) × (T pre-T)_{Feeding in} )]×(V_{Real world} -k×V_{Total (S)} )/(V_{Total (S)} -k×V_{Total (S)} )+T_{Feeding in} 。

In the present embodiment, when KXV_{Total (S)} ≧V_{Real world} ≧V_{Total (S)} When, i.e_{V real} ≧V_{Total (S)} As shown in fig. 5, the geometric proportion relationship of the temperature rise end curve in fig. 5 is as follows: (T)_{By using} -T_{Returning to} )/(T_{Out of} -T_{Returning to} )＝(V_{Total (S)} -k×V_{Total (S)} )/V_{Total (S)} Deriving to obtain a third preset calculation formula T_{With 3} ＝T_{Returning to} +(1-k)×(T_{Out of} -T_{Returning to} )。

In this embodiment, the current water consumption point temperature T is obtained by calculating according to a second preset calculation formula_{With 2} The following steps specifically include:

step S1161, judging whether the gas water heater finishes the preheating work;

if yes, the circulating pump is turned off to exit the preheating mode, and calculation is performed according to a fifth preset calculation formula to obtain the current water point temperature T_{By 5} The fifth preset calculation formula is T_{By 5} ＝T_{Feeding in} +(T_{With 2} -T_{Feeding in} )×(T_{Go out to descend} -T_{Feeding in} )/(T_{Stop at the time of coming out} -T_{Feeding in} ) Wherein T is_{Stop at the time of coming out} T for stopping the water outlet temperature during preheating_{Go out to descend} The temperature of the water outlet after a certain time interval is used for stopping preheating;

if not, returning to step S106 to continue judging V_{Real world} Whether a second preset condition is satisfied.

In this embodiment, as shown in fig. 6, the approximate geometric proportion relationship of the temperature distribution curve of the water after temperature drop is obtained: (V)_{Real world} -k×V_{Total (S)} )/V_{Total (S)} ＝(T_{Stop for use} -T_{Feeding in} )/(T_{Stop at the time of coming out} -T_{Feeding in} )＝(T_{By water} -T_{Feeding in} )/(T_{Go out to descend} -T_{Feeding in} ) Deriving to obtain a fifth preset calculation formula T_{By 5} ＝T_{Feeding in} +(T_{With 2} -T_{Feeding in} )×(T_{Go out to descend} -T_{Feeding in} )/(T_{Stop at the time of coming out} -T_{Feeding in} ). In addition, T_{Go out to descend} To stop preheating and after a certain time intervalThe water outlet temperature of (2) is preferably 10-30 min at intervals.

In this embodiment, the current water consumption point temperature T is obtained by calculating according to a third preset calculation formula_{With 3} The following steps specifically include:

step S1261, judging whether the gas water heater finishes the preheating work;

if yes, the circulating pump is turned off to exit the preheating mode, and calculation is performed according to a sixth preset calculation formula to obtain the current water point temperature T_{With 6} The sixth preset calculation formula is T_{With 6} ＝T_{Return drop} +(1-k)×(T_{Go out to descend} -T_{Return drop} ) Wherein T is_{Return drop} To stop preheating and to keep the return water temperature after a certain time interval, T_{Go out to descend} The temperature of the water outlet after a certain time interval is used for stopping preheating;

if not, returning to calculate again according to a third preset calculation formula to obtain the current water point temperature Tuse 3.

In this embodiment, as shown in fig. 5, the geometric proportion relationship of the curve after temperature drop can be obtained: (T)_{By lowering} -T_{Return drop} )/(T_{Go out to descend} -T_{Return drop} )＝(V_{Total (S)} -k×V_{Total (S)} )/V_{Total (S)} Deriving to obtain a sixth preset calculation formula T_{With 6} ＝T_{Return drop} +(1-k)×(T_{Go out to descend} -T_{Return drop} )。

What has been described above is merely some embodiments of the present invention. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit of the invention.

Claims (7)

1. The control method of the gas water heater comprises a heat exchanger, a water inlet pipe (2), a water return pipe (3), a water outlet pipe and a plurality of water consumption points, wherein the water inlet end of the heat exchanger is communicated with one end of the water return pipe (3) through the water inlet pipe (2), one end of the water outlet pipe is communicated with the water outlet end of the heat exchanger, the other end of the water outlet pipe is sequentially connected with a plurality of water consumption points and is communicated with the water return pipe (3) at one end far away from the water inlet pipe (2), a circulating pipeline is formed through the heat exchanger, the water inlet pipe (2), the water outlet pipe and the water return pipe (3), and a circulating pump, a water inlet temperature probe, a water outlet temperature probe and a water flow sensing device are arranged on the heat exchanger.

The gas water heater enters a preheating mode, and the circulating pump is started to start the gas water heater;

collecting a water inlet temperature Twater return temperature Twater and a water outlet temperature Twater outlet respectively;

judging whether the backwater temperature Tback is larger than the sum value of the water inlet temperature Tback and the temperature rising temperature difference delta T, and obtaining the circulating water quantity Vtotal of single preheating according to a judging result;

collecting the current preheated circulating water quantity V real;

comparing the current preheated circulating water quantity V with the single preheated circulating water quantity V, and counting the current water point temperature Tservice according to a calculation formula corresponding to the current comparison result according to the comparison result;

the specific step of judging whether the backwater temperature Tback is greater than the sum of the water inlet temperature Tback and the temperature rising temperature delta T, and obtaining the circulating water quantity Vtotal of single preheating according to the judging result comprises the following specific steps: judging whether the backwater temperature Tback is larger than the sum value of the water inlet temperature Tback and the temperature rising temperature difference delta T; if yes, setting the average value of the circulating water quantity values of the previous single preheating as the circulating water quantity Vtotal of the single preheating; if not, setting the circulating water quantity value of the previous single preheating as the circulating water quantity Vtotal of the single preheating;

the specific steps of comparing the current preheated circulating water quantity V with the single preheated circulating water quantity V, and calculating the current water point temperature T according to a calculation formula corresponding to the current comparison result according to the comparison result include: judging whether the vreal meets a first preset condition, wherein the first preset condition is vreal which is less than or equal to KxVtotal, wherein vreal is the current preheated circulating water quantity, vtotal is the circulating water quantity preheated for a single time, and K is the ratio of the length of a water outlet pipe between the gas water heater and a water consumption point to the total length of a circulating pipeline; if yes, calculating according to a first preset calculation formula to obtain the current water point temperature T1, wherein the first preset calculation formula is T1=Tin; if not, judging whether the V-real meets the second preset condition.

2. The method of claim 1, wherein the step of calculating according to the first preset calculation formula to obtain the current water point temperature tmax 1 further comprises:

judging whether the gas water heater finishes the preheating work or not;

if yes, the circulating pump is closed to exit the preheating mode, and calculation is carried out according to a fourth preset calculation formula to obtain the current water point temperature T4, wherein the fourth preset calculation formula is T4=Tback;

if not, returning to continuously judge whether the backwater temperature Tback is larger than the sum of the water inlet temperature Tback and the temperature rising temperature difference delta T.

3. The method for controlling a gas water heater according to claim 1, wherein the step of determining whether vjn meets a second preset condition specifically includes:

judging whether the V real meets a second preset condition, wherein the second preset condition is KXV total < V real < V total, wherein V real is the current preheated circulating water quantity, V total is the circulating water quantity preheated for a single time, and K is the ratio of the length of a water outlet pipe between the gas water heater and a water consumption point to the total length of a circulating pipeline;

if so, calculating according to a second preset calculation formula to obtain the current water consumption point temperature Tuse 2, wherein the second preset calculation formula is Tuse 2= [ (1-k) × (Tpre-Tin) ]× (Vreal-k×Vtotal)/(Vtotal-k×Vtotal) +Tin, and the Tpre-set is a preset temperature value;

if not, calculating according to a third preset calculation formula to obtain the current water consumption point temperature Tuse 3, wherein the third preset calculation formula is Tuse 3=Tback+ (1-k) X (Tout-Tback).

4. A control method of a gas water heater according to claim 3, wherein the step of calculating according to a second preset calculation formula to obtain the current water point temperature tmax 2 further comprises:

if yes, closing the circulating pump to exit the preheating mode, and calculating according to a fifth preset calculation formula to obtain the current water point temperature Tuse 5, wherein the fifth preset calculation formula is Tuse 5=Tuse+ (Tuse 2-Tuse) × (Tfall-Tuse)/(Tfall stop-Tuse), wherein Tout is the water outlet temperature when preheating is stopped, and Tout is the water outlet temperature after preheating is stopped and a certain time is left;

if not, returning to continuously judging whether the V-real meets the second preset condition.

5. A control method of a gas water heater according to claim 3, wherein the step of calculating according to a third preset calculation formula to obtain the current water point temperature tmaq 3 further comprises:

if yes, the circulating pump is closed to exit the preheating mode, and the current water point temperature Tuse 6 is obtained by calculation according to a sixth preset calculation formula, wherein the sixth preset calculation formula is Tuse 6=Tfall+ (1-k) x (Tfall-Tfall), the Tfall is the return water temperature after stopping preheating and a certain time interval, and the Tfall is the outlet water temperature after stopping preheating and a certain time interval;

if not, returning to calculate again according to a third preset calculation formula to obtain the current water point temperature Tuse 3.

6. The method according to any one of claims 1 to 5, further comprising a display disposed on the heat exchanger, the display being electrically connected to the controller for displaying the calculated current water temperature trending.

7. The method according to any one of claims 1 to 5, wherein the gas water heater further comprises a wireless communication module, and the controller is communicatively connected with an external intelligent terminal device through the wireless communication module to inform a user of the current water consumption point temperature tsui.