JP3487889B2 - Water heater combustion control method - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a combustion control method of the water heater and its for stabilizing the initial pouring temperature of the combustion water heater.

[0002]

2. Description of the Related Art In a combustion type water heater, when the combustion is stopped after its use, the hot water in the heat exchanger is gradually cooled. Therefore, when the hot water is discharged next time, the heat exchanger itself and the hot water in the heat exchanger are cooled, and when the hot water is discharged again, hot water at a temperature considerably lower than the set temperature of the water heater comes out.
It's inconvenient.

For this reason, in recent hot water heaters, the following method has been taken in order to stabilize the hot water discharge temperature. For example, after using a water heater, delay the fire extinguishing timing, do not stop the combustion immediately even after closing the faucet, and continue the combustion for a short time to keep the hot water temperature in the heat exchanger immediately. In this way, the hot water can be discharged at a temperature as close to the set temperature as possible when the hot water is again discharged.

According to another method, in addition to the main burner for heating the heat exchanger, a pilot burner for locally heating the heat exchanger is provided, and after the combustion is stopped, the combustion by the pilot burner is shortened. This is continued for a period of time to prevent the temperature of the hot water in the heat exchanger from decreasing. As a result, the next time the hot water is discharged, the hot water is discharged at a temperature as close to the set temperature as possible.

[0005]

Each of these methods has the following drawbacks. First, in the method of continuing combustion for a short time after using the water heater, the hot water in the heat exchanger is heated more than necessary during this continuous combustion, and the hot water temperature rises above the upper limit allowable temperature for the set temperature. Will end up.

Therefore, if the faucet is opened again and hot water is discharged immediately after the faucet is closed, hot water will come out, which is dangerous.

Further, in the method equipped with a pilot burner, since this pilot burner has much lower heating energy than the main burner, there is no concern that hot water will come out when re-leaving hot water as described above, but heat exchange will occur. Since the inside of the vessel is heated locally, there is a problem in that the temperature distribution in this heat exchanger becomes uneven, and the hot water cannot be re-sprayed at a stable temperature during the next use.

The present invention has been made to solve the above-mentioned problems, and when hot water is again discharged after combustion of the water heater is stopped, hot water can be stably discharged at a temperature as close as possible to a set temperature. And a combustion control method therefor.

[0009]

According to the invention of claim 1, the above object is obtained after the boiling of the water heater is stopped and after the after-boiling.
The water temperature in the heat exchanger which is cooled by the radiation detected by the temperature detecting means, the water temperature is, the lower limit temperature or is determined based on the set temperature is set as the hot water temperature, or corresponding to the lower limit temperature When the ignition temperature, which is the specified temperature, is reached, the hot water supply burner is burned for a predetermined time, and the hot water temperature in the heat exchanger is set to the upper limit temperature determined based on the set temperature or to correspond to this. Achieved by the combustion control method of the water heater, which raises the temperature.

According to the above method, the combustion of the water heater is stopped.
After that, the hot water temperature in the heat exchanger of this water heater is directly detected.
This detection result is determined based on the set temperature.
Either the temperature limit or the temperature corresponding to this lower limit temperature
When the ignition temperature is reached, the heat exchanger is burned and heated.
I have to. Therefore, it is extremely close to the set temperature of the water heater.
Hot water can be discharged at a high temperature. In particular, the ignition temperature
It is set according to the change in the set temperature of the water heater.
Therefore, let the hot water temperature accurately follow the changed set temperature.
You can

Further, according to the invention of claim 2, the temperature detecting means detects the hot water temperature in the heat exchanger cooled by heat radiation after the post-boiling after the combustion of the water heater is stopped, Calculate the backup heat quantity for heating from this hot water temperature to the upper limit temperature defined within the upper limit allowable range or the corresponding temperature with respect to the set temperature of the water heater, and obtain the combustion time required to compensate for this backup heat quantity. This is achieved by the combustion control method of the water heater, which burns the hot water supply burner according to the combustion time obtained by the means.

According to the configuration of claim 2, the invention of claim 1
In addition to the function of
Ignition / fire extinguishing if decided according to the amount of heat up
The combustion frequency can be suppressed and smooth combustion control can be performed.

Further, according to the invention of claim 3, there is provided a hot water supply device comprising a heat exchanger for discharging hot water by using heat generated by burning fuel and a combustion control unit, wherein the combustion control unit is provided. , Means for setting the set temperature as the hot water temperature, and a water heater
After the combustion of the
A temperature detecting means for detecting the water temperature in the heat exchanger,
An ignition temperature setting unit for setting an ignition temperature, which is a lower limit temperature determined based on the set temperature set as the tap water temperature or a temperature corresponding to the lower limit temperature, is provided. Is the lower limit temperature determined based on the set temperature set as the hot water discharge temperature, or when the ignition temperature is reached, the hot water supply burner is burned for a predetermined time, and the hot water in the heat exchanger is heated. It is also achieved by a water heater having a structure in which the temperature is raised to an upper limit temperature determined based on the set temperature or a temperature corresponding thereto.

According to a fourth aspect of the present invention, in the structure of the third aspect , the relationship between the hot water temperature detected by the temperature detecting means and the set temperature is changed.
The upper limit temperature within the upper limit allowable range or
Determine the amount of backup heat for heating to the desired temperature
It is characterized by comprising a calculation means for

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings. The examples described below are
Since it is a preferred specific example of the present invention, various technically preferable limitations are attached, but the scope of the present invention is, unless otherwise stated to limit the present invention, in the following description.
It is not limited to these modes.

FIGS. 1 and 2 show an example of a combustion type water heater system to which the method of this embodiment is applied. FIG. 1 shows a single-function water heater, and FIG. 2 shows an example of a combined water heater. Shows.
The water heater 30 of FIG. 1 has a water supply pipe 5 connected to the inlet side. A flow sensor 7 is connected to the water supply pipe 5 so that the amount of water entering can be detected. Further, a water supply temperature sensor 6 is connected to the water supply pipe 5, and is also connected to the heat exchanger 1. Further, preferably, the water supply pipe 5 is branched and connected to a bypass pipe 11 that does not pass through the heat exchanger 1, and the bypass pipe 11 is connected to a hot water outlet pipe 8 described later.

The outlet of the heat exchanger 1 is connected to a hot water outlet pipe 8, which is provided with a hot water outlet temperature thermistor 10 and a hot water tap 25 as temperature detecting means in this embodiment. The tapping temperature thermistor 10 plays an important role different from the conventional one in the method of this embodiment. That is, the outlet hot water temperature thermistor 10 has a control unit 23 described later.
, The temperature of the hot water in the heat exchanger 1 is detected and sent. For this reason, it is not preferable that the outlet hot water temperature thermistor 10 is arranged at a place far away from the heat exchanger 1.

Specifically, this tap water temperature thermistor 10
The location of is preferably attached to the upper portion of the heat exchanger 1 or a pipe that is passed through the heat exchanger 1 and is exposed from the side surface of the casing. In the latter case,
Since the thermistor 10 is installed in the middle of the heat exchanger, the final hot water outlet temperature cannot be directly measured. However, the final tapping temperature can be known by calculating based on the heat contribution rate of the remaining portion according to the mounting position of the pipe. Further, instead of the hot water temperature thermistor, other temperature detecting means such as a thermocouple may be used.

A burner 3 for heating the heat exchanger 1 is provided in the water heater 30. A gas valve 4 for sending fuel gas is connected to the burner 3, and a gas amount detection sensor 4a is connected to the gas pipe in order to detect the gas supply amount from the gas valve 4.

A fan 22 is built in the water heater 30 so as to supply combustion air to the combustion chamber. A rotation detecting sensor 9 for detecting the number of rotations of the fan 22 is provided, and an outside air temperature detecting means 19 for detecting an intake air temperature sucked by the fan 22 is provided.

Further, the water heater 30 includes the above-mentioned flow sensor 7, water supply thermistor 6, heater 13, hot water thermistor 10, gas valve 4, gas amount detection sensor 4a, and fan 2.
2, a fan rotation detection sensor 9, and an outside air temperature detection sensor (outside air temperature thermistor) 19 are connected to the controller 23. The control unit 23 operates the water heater 30 under the conditions set by the remote controller 24 by receiving a predetermined signal from each of these connection points or issuing a command. The remote controller 24 has a button 24a for the user to set a set temperature as the hot water temperature,
A set temperature display unit 24b and the like are provided.

The combined water heater 35 shown in FIG. 2 is obtained by adding a reheating function to the single-function water heater 30 shown in FIG. 1, and has the (hot water) heat exchanger 1 and the bath heat exchanger 2 side by side. That is,
A bath burner 12 is set in the bath heat exchanger 2, and the bath heat exchanger 2 is heated by the bath burner 12.

A return pipe 16 of the circulation pipe 15 is connected to the inlet of the bath heat exchanger 2. The return pipe 16 has a hot water outlet pipe 8
The branch pipe 20 from is connected. The reheating circulation pump 14 is connected to the return pipe 16, and the outlet side of the bath heat exchanger 2 and the bath 17 are connected by a forward pipe 18. Further, in the case of the water heater 35, the bath side fan 27 for supplying combustion air to the bath side combustion chamber, the fan rotation detection sensor 28a and the outside air temperature detection sensor 18 are provided.
b is set.

In the composite water heater 35, the fans 22 and 27 are individually set for hot water supply and bath use, but they may be combined into one fan. Further, the hot-water supply side exhaust A1 and the bath-side exhaust A2 join together in one exhaust passage 36.

The water heaters 30 and 35 are provided with the faucet 25.
The flow sensor 7 detects the flow of water entering the heat exchanger 1 (hot water supply) by opening. In response to the signal from the flow sensor 7, the controller 23 supplies gas and ignites an igniter electrode (not shown).

As a result, the burner 3 (for hot water supply) is burned to heat the heat exchanger 1, and the water passing through the heat exchanger 1 is turned into warm water and discharged from the hot water discharge pipe 8 through the hot water tap 25. . Then, when the faucet 25 is closed and the OFF signal from the flow sensor 7 is no longer detected, the control unit 23 stops the combustion of the burner 3.

When hot water in the bathtub 17 is reheated in the water heater 35, the valve 21 is closed, the reheat circulation pump 14 is operated, and the bath burner 12 is ignited. The heat exchanger 2 for bath is heated by burning. As a result, the hot water in the bathtub 17 is heat-exchanged by passing through the heat exchanger 2 while circulating in the circulation pipe line 15 for additional heating.

Here, when the combustion of the water heater 30 and the burner 3 is stopped, that is, when the combustion of the water heater 30 is stopped, the water in the water pipe surrounded by the heat exchanger 1 is heated by the heat exchanger 1. The heat possessed by is transferred and becomes hot water. This phenomenon is called "after boiling". Next, the fan 22 is rotated, and after combustion is stopped, the combustion exhaust gas remaining in the device is discharged from the exhaust passage 36 for safety (post fan).
Then, the heat exchanger 1 is cooled by the wind caused by the introduction of the outside air. Therefore, the heat quantity of the hot water in the heat exchanger 1 is deprived to the heat exchanger 1 side, and the temperature of the hot water gradually decreases.

The method of the present embodiment prevents low-temperature hot water from coming out of the hot water outlet pipe 8 when the hot water heaters 30 and 35 are re-combusted, especially in such a case.
It is intended to stably supply hot water having a temperature not much different from the temperature set by the remote controller 24.

Incidentally, the same problem occurs in the composite water heater 35 when additional heating is performed. That is, in this case, the rotation of the fan 27, the combustion exhaust A3 from the bath burner 2, resulting in recirculation is guided to the hot water supply side combustion chamber from a common exhaust passage 36. This is because in order to prevent this, the fan 22 must be rotated even when hot water supply combustion is not performed, which cools the hot water supply heat exchanger 1.

Therefore, the method of this embodiment is also applied to the case of heat radiation of the hot water supply heat exchanger 1 that occurs when the combined hot water heater 35 is reheated. Even when the combined water heater 35 has only one fan, the wind of the fan that is rotated during the reheating operation is sent not only to the bath side but also to the hot water supply heat exchanger 1, so that heat exchange is also required. A similar problem occurs when the container 1 is cooled. Also in this case, the method according to the present embodiment is effective.

FIG. 3 is a block diagram showing a main portion of the control unit 23, which is particularly closely related to the combustion method of this embodiment. The combustion control unit 40 includes the temperature detecting means 10 such as the hot water discharge thermistor 10, an ignition temperature setting unit 31, and a combustion control unit 32. Further, a calculation unit 33 can be provided as described later.

The temperature detecting section 10 always detects the hot water temperature in the heat exchanger 1 and supplies it to the ignition temperature setting section 31. In the ignition temperature setting unit 31, based on the set temperature of the water heater set via the remote controller 24, the lower limit temperature within the lower limit allowable temperature range (in the water heater including the bypass pipe 11, the lower limit temperature is supported) Temperature) is set as the temperature at which the burner 3 should be ignited. That is, in the method of the present embodiment, hot water is always discharged from the hot water discharge pipe 8 within the upper and lower limit temperature ranges allowed for the set temperature of the water heater. Therefore, when the hot water in the heat exchanger 1 is cooled to the lower limit temperature, it is directly heated.

Here, for example, if the temperature set by the remote controller 24 is 40 ° C. and the water temperature is 15 ° C., and if the bypass pipe 11 is not provided, these temperatures are 43 ° C. (upper limit). Temperature), 40 degrees C (set temperature), 3
It becomes 7 degrees C (lower limit temperature). Therefore, since each of these temperatures can be uniquely determined, it is stored in advance in the memory of the control unit 23, and the ignition temperature setting unit 31 reads the corresponding data from the conditions of the water temperature and the set temperature, and the ignition temperature is set. Make the decision.

On the other hand, when the water heater has the bypass pipe 11, the upper limit temperature and the lower limit temperature of the temperature set by the remote controller 23 are plus or minus 3 degrees C.
If the bypass ratio is 8 (heat exchanger 1 side) to 2 (bypass side), it is determined by an arithmetic expression given in advance based on conditions such as water temperature at that time. For example, the temperature corresponding to the upper limit temperature in the heat exchanger 1 is 50 degrees C, the set temperature is 46.2 degrees C, and the temperature corresponding to the lower limit temperature is 42.5 degrees C.

The combustion control unit 32 receives a command from the ignition temperature setting unit 31 based on a signal regarding the timing of burning the burner 3, and carries out the combustion which is set for a predetermined time, for example, 2 seconds according to a built-in timer. As described above, the gas valve 4 of the burner 3 is opened, and an ignition instruction is given to an igniter (not shown). On the other hand, when the combustion is performed for the time determined in this way, for example, in the winter, the water temperature decreases and the heat radiation condition of the heat exchanger 1 changes, so that the combustion reaches the upper limit temperature in the combustion for a certain time. The calculation unit 33 may be provided in consideration of a case where the frequency of ignition and combustion is too high without increasing the hot water temperature.

FIG. 4 shows a detailed block configuration diagram in consideration of such a point, and the arithmetic unit 33 in FIG.
4 corresponds to the backup calorie calculation unit 34 and the combustion time calculation unit 35 in FIG. In this case, the ignition temperature setting unit 3
1 sets a lower limit temperature or a temperature corresponding to the lower limit temperature as an ignition temperature, and supplies the value to the backup calorie calculation unit 34.

The backup calorie calculation unit 34 includes the control unit 2
3, the hot water temperature in the heat exchanger 1 is set from the lower limit temperature or a temperature corresponding to the lower limit temperature based on information such as gas capacity, water supply temperature, and water supply amount stored in a memory unit (not shown). The backup heat quantity required to rise to the preset upper limit temperature (the temperature corresponding to the upper limit temperature when the bypass pipe 11 is provided) within the upper limit allowable temperature range of the temperature is calculated.

This backup heat quantity is given to the combustion time calculation section 35. In the combustion time calculation unit 35, the combustion time required for compensating for this backup heat quantity based on the information on the outside air temperature from the outside air temperature thermistor 19 and the information such as the presence or absence of fan rotation from the fan rotation detection sensor 9 and the number of revolutions. Is calculated.

The calculation result regarding the ignition time and the combustion time is given to the combustion control unit 32. As a result, the combustion control unit 32 opens the gas valve 4 and gives an ignition instruction to the ingniter, and performs combustion in accordance with the combustion time. Here, when the water heater 30 is provided with two burners 3a and 3b arranged in parallel below the heat exchanger 1 as shown in FIG. 6, for example, the burner 3a on one side for a predetermined combustion time is set. You may make it burn. In this case, at the time of the next combustion, the combustion control unit 3 is configured to burn the other burner 3b.
If the combustion is switched and burned in 2, heat unevenness of the heat exchanger 1 can be prevented, and accordingly hot water can be discharged at a stable hot water temperature.

Next, the combustion method of this embodiment will be described in detail with reference to the flowchart of FIG. When the water heater 30 is performing an automatic operation of discharging hot water at the set temperature (S
At T1), when the flow sensor 7 receives a signal of water flow rate 0 from the control unit 23 (ST2), the control unit 23 determines that the combustion is stopped (ST3) and sets the ignition temperature (ST).
4).

The ignition temperature is set so that after the combustion is stopped, there is a post boiling of the hot water in the heat exchanger 1, and after the hot water temperature rises, the heat exchanger 1 is cooled and the hot water in it is deprived of heat. In the process
Set the temperature at which combustion occurs when the temperature reaches a certain level. In the case of the present embodiment, the lower limit temperature with respect to the set temperature (the temperature corresponding to the lower limit temperature in the water heater having the bypass 11)
When the temperature of the hot water in the heat exchanger 1 is lowered to 1), this temperature is set as the ignition temperature.

Next, the combustion time calculation unit 34 calculates the time for which the burner 3 should burn, and the combustion control unit 32 performs combustion control based on the calculation result. Here, the calculation of the combustion time by the combustion time calculation unit 34 is performed in response to the calculation result from the backup calorie calculation unit 34, as described above. By doing so, the hot water temperature in the heat exchanger 1 is always corresponded to the upper limit temperature or the upper limit temperature with respect to the set temperature in accordance with the temperature environment (natural cooling condition) in which the water heater is placed and the water temperature. Heat to the desired temperature.

On the other hand, in ST5, combustion can be performed for a predetermined time, for example, 2 seconds. In this case, there is an advantage in that the process is simple in terms of control, but in the cold season, for example, until the hot water temperature in the heat exchanger 1 reaches the upper limit temperature or a temperature corresponding thereto in this fixed combustion time. It may not rise enough. Therefore, after the combustion is stopped, the hot water temperature immediately falls to the ignition set temperature, and the interval of intermittent combustion becomes short.

That is, in ST6, the control section 23 detects the hot water temperature after combustion with the thermistor (temperature detecting means) 10.
It is judged whether this is lower than the lower limit temperature or the temperature corresponding to the lower limit temperature. If a positive result is obtained, ST described later
If the result is negative , the process proceeds to ST7.

In ST7, the control unit 23 detects the hot water temperature after combustion by the thermistor 10 and determines whether it is higher than the upper limit temperature or the temperature corresponding to the upper limit temperature. When a positive result is obtained, the process proceeds to ST8, and the fan rotation time for cooling the excessively raised hot water temperature by the rotation of the fan 22 is calculated. In this case, the hot water temperature in the heat exchanger 1 is cooled to an upper limit temperature or a temperature corresponding to the upper limit temperature with respect to the set temperature based on the intake temperature of the fan 22, the capacity of the fan (fan air volume), the natural cooling condition, and the like. To calculate the fan rotation time.

Based on the calculation result, the control section 23 sends an ON signal to the fan 22 to rotate the fan (ST9,
ST10). After that, the rotation of the fan 22 is stopped, or the fan is rotated by the post fan after combustion (S
Go to T11) and ST12.

On the other hand, when a positive result is obtained in ST6, the process proceeds to ST13, in which the calorific value backup calorie calculation unit for heating from the temperature detected by the thermistor 10 to the upper limit temperature or the temperature corresponding to the upper limit temperature with respect to the set temperature. Three
Calculate with 4. Based on this calculation result, the burner 3 is ignited by the igniter (ST13), burned for a fixed time, for example, 2 seconds, and the burner is extinguished (ST1).
6) Go to ST12.

Here, the control unit 23 detects the hot water temperature of the heat exchanger 1 by the thermistor 10 and determines whether the hot water temperature is equal to or lower than the ignition set temperature.
When a negative result is obtained, the process returns to ST4. When a positive result is obtained, the control unit 23 ignites the burner 3 to perform combustion for a predetermined time (ST18), extinguishes the burner (ST19), and returns to ST4.

As described above, according to the combustion control method of the present embodiment, the hot water temperature in the heat exchanger of the water heater is directly detected after the combustion of the water heater is stopped. Therefore, the hot water temperature can be grasped more accurately than in the case where a drop in the hot water temperature in the heat exchanger is obtained by calculation after the combustion is stopped and after boiling. Since it is possible to accurately know the timing of heating by detecting the hot water temperature, it is possible to constantly discharge hot water at a temperature extremely close to the set temperature of the water heater by performing the intermittent combustion accordingly.

Therefore, as in the conventional case, after the combustion is stopped,
Since the heat exchanger is not cooled and the temperature of the hot water in the heat exchanger is not taken away, it is possible to effectively prevent unpleasant feelings due to the low temperature hot water coming out when the hot water is again discharged.

[0052]

As described above, according to the present invention, when hot water is discharged again after the hot water heater has stopped burning, it is possible to stably discharge hot water at a temperature as close as possible to the set temperature. A combustion control method can be provided.

[Brief description of drawings]

FIG. 1 is a system diagram showing a configuration example of a single-function water heater to which a combustion control method according to a preferred embodiment of the present invention is applied.

FIG. 2 is a system diagram showing a configuration example of a combined water heater to which a combustion control method according to a preferred embodiment of the present invention is applied.

FIG. 3 is a block configuration diagram showing a main part of a control unit that performs combustion control according to the present embodiment.

FIG. 4 is a diagram of another example of a block configuration showing a main part of a control unit that performs combustion control according to the present embodiment.

FIG. 5 is a flowchart showing an example of a combustion control method according to this embodiment.

FIG. 6 is a diagram showing a schematic structure of a combustion part in a water heater to which the combustion control method of the present embodiment is applied.

[Explanation of symbols] 1 (for hot water supply) heat exchanger 3 (for hot water supply) burner 4 Gas amount detection sensor 5 water pipe 6 Water entry thermistor 7 Flow sensor 8 Hot water pipe 10 Hot water thermistor 11 Bypass pipe 12 Burner (for bath) 13 Return pipe 14 Reheating circulation pump 15 Circulation pipeline 17 bathtub 18 Outgoing 19 Outside temperature thermistor 22 fans 23 Control unit 24 remote control 27 fans 30 single-function water heater 31 Ignition temperature setting unit 32 Combustion control unit 34 Backup calorie calculator 35 Burning time calculator

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuyuki Iizumi, 3-4 Fukamidai, Yamato-shi, Kanagawa Stock Company, Gaster (72) Inventor, Eiji Usui 3-4, Fukamidai, Yamato-shi, Kanagawa Stock Company Inside Gaster (72) Inventor Kazuhiro Sumida 3-4 Fukamidai, Yamato City, Kanagawa Prefecture Gaster Inside Stock Company (56) Reference JP-A-4-217716 (JP, A) JP-A-61-107045 (JP, A) ) Actual Kaihei 2-6950 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F24H 1/10 F23N 5/14

Claims (4)

(57) [Claims] 1. After the combustion of the water heater is stopped and after boiling occurs
The water temperature in the heat exchanger which is cooled by the radiation detected by the temperature detecting means, the water temperature is, the lower limit temperature or is determined based on the set temperature is set as the hot water temperature, or corresponding to the lower limit temperature When the ignition temperature, which is the specified temperature, is reached, the hot water supply burner is burned for a predetermined time, and the hot water temperature in the heat exchanger is set to the upper limit temperature determined based on the set temperature or to correspond to this. A method for controlling combustion in a water heater, comprising raising the temperature to a temperature. 2. After boiling of the water heater has stopped and after boiling has occurred.
The water temperature in the heat exchanger which is cooled by the radiation detected by the temperature detecting means, heat from the hot water temperature to the temperature corresponding to the maximum temperature to or defined in the upper allowable range with respect to water heater set temperature For determining the backup heat amount for the hot water supply bar according to the combustion time obtained by the means for obtaining the combustion time required to compensate for this backup heat amount.
A method for controlling combustion in a water heater, characterized in that the combustion of the water is performed. 3. A water heater provided with a heat exchanger for discharging hot water by using the heat of burning fuel, and a combustion control unit, wherein the combustion control unit is a setting means for setting a set temperature as a discharge temperature. After stopping the combustion of the water heater, cool down by radiating heat after there is post-boiling
The temperature detection means for detecting the temperature of the hot water in the rejected heat exchanger, and the ignition temperature, which is the lower limit temperature determined based on the set temperature set as the outlet hot water temperature or the temperature corresponding to this lower limit temperature, An ignition temperature setting unit for setting, and the hot water temperature detected by the temperature detecting means is a lower limit temperature determined based on a set temperature set as a hot water outlet temperature, or when the ignition temperature is reached, supply only determined time
Combustion of the hot water burner, the temperature of the hot water in the heat exchanger is set to the upper limit temperature determined based on the set temperature or to a temperature corresponding thereto, characterized in that,
Water heater. 4. A calculation means for determining a backup heat quantity for heating from the hot water temperature detected by the temperature detection means to an upper limit temperature defined within an upper limit allowable range for the set temperature or a temperature corresponding to the upper limit temperature. Characterized by,
The water heater according to claim 3.