JPH1151470A - Bath furnace with hot water feeder and method for controlling bath furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the temperature of water within a heat exchanger to be increased up to its appropriate temperature within a short period of time for preparation for a next feeding of hot water without giving any uncomfortable feeling to a person taking bath when an operation for feeding water into a bath tub through the heat exchanger under a state in which a burner is not ignited is finished. SOLUTION: After finishing an operation for feeding water into a bath tub through a communicating pipe 36 without igniting a burner 12, a bath furnace 10 having a hot water feeder causes the burner 12 to be ignited under a state in which fed water in a heat exchanger 13 is not flowed, and a temperature of water in the heat exchanger 13 is increased up to a target temperature. In addition, in this case, the ignition at the burner 12 is divided into a plurality of times and performed intermittently within a range in which a temperature of water at a location where the water is heated directly by the burner 12 and its temperature is partially increased up to its high temperature does not exceed a predetermined upper limit temperature and then the temperature of hot water is increased up to a target temperature within a short period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burner, a heat exchanger for transmitting heat from the burner to feed water, a tapping pipe for guiding feed water passing through the heat exchanger to a tap hole, and the heat exchanger. The present invention relates to a bathtub with a water heater having a function of injecting water into the bathtub through the communication tube without igniting a burner, and a control method thereof.

[0002]

2. Description of the Related Art Conventionally used bath kettles with a water heater have a function of guiding water supplied through a heat exchanger to a hot water outlet.
Hot water can be poured into the bathtub through a communication pipe provided with a solenoid valve or the like. In recent years, there is a type provided with a function of filling water into a bathtub through a communication pipe without burning a burner in order to fill hot water in the bathtub when the hot water is hot (filling function).

[0003] If water that is not heated by the filling function is poured into the bath tub, the temperature of the water in the heat exchanger becomes low when the filling operation is completed. It comes out and gives the user discomfort. Therefore, a bath kettle with a water heater improved so as to raise the water temperature in the heat exchanger to an appropriate temperature at the end of the water injection operation by the filling function has been devised and disclosed in Japanese Utility Model Laid-Open No. 2-52050. ing.

[0004] In this bath kettle with a water heater, the burner is burned for a certain period of time immediately before the water injection operation by the filling function ends, and hot water of a predetermined temperature remains in the heat exchanger at the time of the end of the water injection. .

[0005] On the other hand, in order to further improve the comfort as a water heater, the hot water is supplied within a temperature range of about the set temperature ± 3 degrees immediately after the start of the hot water supply without causing a large temperature fluctuation with respect to the set temperature. There is a demand for a device having a function that can perform the function (heat insulation function).

In such an appliance, the temperature of the hot water in the heat exchanger is usually monitored by a temperature sensor, and the burner is repeatedly burned for about two seconds every few minutes without being opened, so that the hot water is repeatedly heated. Is kept within the target temperature range.

[0007]

Problems to be Solved by the Invention
In the technique disclosed in Japanese Patent Laid-Open Publication No. H07-115, warm water is poured into the bathtub at the final stage of water injection, so that the amount of water required to lower the temperature of the hot water in the bathtub is increased more than necessary. In addition, since the hot water finally flows into the bathtub, there is a problem that the bather feels strange.

On the other hand, in a device having a heat retaining function, since the water temperature in the heat exchanger at the time when the water injection by the filling function is completed is low, if the heat retaining function is on, the burner is required to maintain the target temperature. Is performed. However, since the combustion based on the heat retention function is performed for only about 2 seconds every few minutes, it takes a long time to raise the water temperature in the heat exchanger to the target temperature range, and when tapping is started during that time. Has a problem that low-temperature hot water below the allowable range is discharged. In addition, even if the device has a heat retaining function, if the function is not turned on, cold water will flow for a relatively long time when the plug is opened after the end of water injection.

The present invention has been made in view of such problems of the prior art. When the operation of injecting water into a bath tub via a heat exchanger without burning a burner is completed, An object of the present invention is to provide a bath kettle with a water heater that can raise the water temperature in a heat exchanger to an appropriate temperature in a short time in preparation for the next hot water without giving a bather a sense of discomfort.

[0010]

The gist of the present invention to achieve the above object lies in the following inventions. [1] Burner (12), heat exchanger (13) for transferring heat from burner (12) to feed water, and heat exchanger (13)
And a connecting pipe (36) for guiding the water supplied through the heat exchanger (13) to the bathtub (40), and igniting the burner (12). Water can be supplied through the connecting pipe (36) without using the bathtub (4).
Bath kettle with water heater with function to inject water into 0) (10)
In the above, after the water is completely injected into the bathtub (40) without igniting the burner (12), the burner (1) is supplied in a state where the water in the heat exchanger (13) does not flow.
2) A bathtub (10) with a water heater characterized in that the water temperature in the heat exchanger (13) is raised to a target temperature by burning 2).

[2] The burner (12) and the burner (1)
2) A heat exchanger (13) for transmitting heat from the feed water to the feed water, a tapping pipe (21a) for guiding the feed water through the heat exchanger (13) to the tap hole side, and a feed water through the heat exchanger (13). And a connecting pipe (36) for guiding water to a bathtub (40), and supplying water without igniting a burner (12).
After the water supply to the bathtub (40) is completed without igniting the burner (12) in the bathtub (10) having a function of pouring water into the bathtub (40) through the heat exchanger, The burner (12) is burned in a state where the water supply in (13) does not flow, and the heat exchanger (13) is burned.
The temperature of the water in the internal combustion chamber is raised to a target temperature, and at this time, the combustion of the burner (12) is performed within a range in which the temperature of the water that is directly heated by the burner (12) and becomes partially high does not exceed a predetermined upper limit temperature. Is performed intermittently in a plurality of times.

[3] A single combustion of the burner (12) raises the water temperature at a portion where the temperature is directly heated by the burner (12) and becomes partially high to near the upper limit temperature. The bath kettle (10) with a water heater according to [2].

[4] The amount of combustion of the burner (12) at a time is reduced to a predetermined small amount, and the number of intermittent combustions is increased, so that the entire water temperature in the heat exchanger (13) reaches the target temperature. The bath kettle (10) with a water heater according to [2], which is raised.

[5] Burner (12) and burner (1)
2) A heat exchanger (13) for transmitting heat from the feed water to the feed water, a tapping pipe (21a) for guiding the feed water through the heat exchanger (13) to the tap hole side, and a feed water through the heat exchanger (13). And a connecting pipe (36) for guiding water to a bathtub (40), and supplying water without igniting a burner (12).
In a method for controlling a bathtub with a water heater provided with a function of injecting water into a bathtub through a bathtub, the water is supplied to the bathtub without igniting the burner. After the water injection is completed, the burner (1) is placed in a state where the water supply in the heat exchanger (13) does not flow.
A method for controlling a bathtub with a water heater, characterized in that the water temperature in the heat exchanger (13) is raised to a target temperature by burning 2).

The present invention operates as follows. The bath kettle with water heater (10) burns the burner (12) with the water supply in the heat exchanger (13) not flowing when the water supply to the bathtub (40) is completed based on the filling function. Then, the water temperature in the heat exchanger (13) is raised to the target temperature.

After the water injection is stopped, the burner (12)
Is burned to raise the water temperature, so that more water than necessary is not injected into the bathtub (40), and since the hot water does not flow into the bathtub (40) at the end of the water injection operation, the bather feels uncomfortable. Without giving, the water temperature in the heat exchanger (13) can be raised to an appropriate temperature.

Further, when the water temperature in the heat exchanger (13) is heated by burning the burner (12) after water injection, the water temperature of a portion which is directly heated by the burner (12) and partially becomes high in temperature is increased. The combustion of the burner (12) is performed intermittently in a plurality of times within a range not exceeding a predetermined upper limit temperature.

Thus, even if the burner (12) is burned in a state where the water supply does not flow, the remaining water in the heat exchanger (13) may partially boil or burn at the time of tapping. Can be prevented. Further, by performing the combustion intermittently, the temperature distribution in the heat exchanger (13) can be made uniform while the combustion is stopped.

Further, in the case where the water temperature of a portion which is directly heated by the burner (12) and is partially heated to one temperature by a single combustion of the burner (12) is raised to near the upper limit temperature at a stretch, heat exchange is not performed. The water in the heat exchanger (13) can be raised to the target temperature in a relatively short time while preventing the remaining water in the vessel (13) from partially boiling. As a result, even when tapping is started after a relatively short time after the operation based on the filling function, it is possible to reduce the possibility of tapping out of the low-temperature tapping water below the allowable range.

In addition, the amount of one burn of the burner (12) may be reduced to a predetermined small amount to increase the number of intermittent burns. By reducing the amount of heating in one combustion, it is not necessary to precisely control the amount of heating in each combustion, and the combustion control can be simplified.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Each drawing shows an embodiment of the present invention. The bath kettle 10 with a water heater according to the present invention has a function of supplying hot water into a faucet or bathtub 40, a function of reheating the hot water in the bathtub, and a function of pouring unheated water into the bathtub through the reheating path 31. It has. In addition, the burner is burned for 1 to 2 seconds every few minutes without opening to keep the remaining water in the heat exchanger within a predetermined target temperature range so that hot water of the set temperature is discharged immediately after opening. It has a heat retention function.

As shown in FIG. 1, a bath kettle 10 with a water heater is provided.
Has a combustion chamber 11, a burner 12 is disposed below the combustion chamber 11, and a heat exchanger 13 that transmits heat from the burner 12 to water supply and the like is disposed above the combustion chamber 11, respectively. I have. The heat exchanger 13 has both a hot water supply pipe 21 for flowing hot water and a reheating circulating pipe 31 for circulating water in the bathtub for reheating. It has a function of transferring heat from the burner 12 to the fluid in both of the pipes 21 and 31 to heat them.

A fixed bypass passage 22 is provided between a water supply-side flow path 21a as a portion of the hot-water supply pipe 21 toward the heat exchanger 13 and a hot-water supply-side flow path 21b from the heat exchanger 13.
And the bypass passage 24 in which the flow control valve 23 is inserted. The hot water heated by the heat exchanger 13 is mixed with feed water through the fixed bypass passage 22 and the bypass passage 24, and the bypass ratio can be controlled by the flow control valve 23. A flow control valve 25 for controlling the total flow rate of hot water and the bypass ratio is provided on the hot water supply pipe 21 on the hot water outlet side flow path 21b side.

In the vicinity of the inlet and outlet of the hot water supply pipe 21, flow sensors 26a and 26b for detecting the presence or absence of water flow and the amount of water flow are provided. In addition, a water input thermistor 27 for detecting the temperature of the water supply is provided near the inlet of the hot water supply pipe 21, and a heat exchange thermistor for measuring the temperature of the heated water is provided near the outlet of the heat exchanger 13. Further, near the outlet of the hot water supply pipe 21, a tapping thermistor 29 for detecting tapping temperature is attached.

The recirculation pipe 31 for reheating includes a bath return pipe section 31 a for guiding water in the bathtub 40 to the heat exchanger 13,
A bath-out pipe portion 31b for returning hot water heated by the heat exchanger 13 to the bathtub 40. Bath return pipe section 31
a, a circulation pump 32 and a bath return pipe section 31a
A bath water switch 33 is provided for detecting the presence or absence of water inside. In addition, near the bath water switch 33,
A bath temperature thermistor 34 for detecting the temperature of hot water flowing from the bathtub 40 is attached.

A tapping-side flow path 21b of the hot-water supply pipe 21;
The bath return pipe portion 31a is connected by a pouring pipe 36 provided with a pouring electromagnetic valve 35, and supplies the water heated by the heat exchanger 13 or the water that is not heated without igniting the burner 12 to the bath. Bathtub 40 through pouring pipe 36
It can be poured into. The amount of hot water or water poured into the bathtub is detected by the flow sensor 26a.

The supply and exhaust are forcibly performed by blowing supply air from below the combustion chamber 11 by the combustion fan 14, and the exhaust is discharged from the upper part of the combustion chamber 11. An ignition device 15 not shown in FIG. 1 is provided near the burner 12. The combustion gas supplied to the burner 12 is supplied to the gas solenoid valve 16 and the original gas solenoid valve 1.
7. On / off control is performed by the gas switching valve 18. Further, the amount of combustion gas supplied to the burner 12 is adjusted by a gas proportional valve 19.

FIG. 2 shows a circuit configuration of a control board included in the bath kettle 10 with a water heater. The control base of the bathtub 10 with the water heater is a C that performs the central function of various controls.
A PU (central processing unit) 51 is provided. Various circuit devices are connected to the CPU 51 via various buses 52 such as a data bus and an address bus.

The ROM (read only memory) 53 is a read-only memory for storing programs executed by the CPU 51 and various fixed data. R
An AM (random access memory) 54 is a working memory for storing data temporarily required for executing a program. An operation unit 55 is provided on the bus 52.
In addition, an input / output interface circuit section 56 for inputting and outputting electric signals between various circuit devices and the CPU 51.
Is connected.

The operation unit 55 has a temperature setting switch for setting the tap water temperature, an automatic switch for automatically operating the bath, and a low-temperature water through the reheating circulation pipe 31 when the hot water in the bathtub is hot. A switch or the like for instructing to pour water into the bathtub 40 is arranged. In addition, as the operation unit 55, there is a so-called bath remote controller installed in a bath, in addition to a main remote controller installed in a kitchen or the like.

The input / output interface circuit section 56 includes:
Flow sensors 26a, 26b, various thermistors 27-2
9 and 34, an ignition device 15, a combustion fan 14, various gas control valves 16 to 19, flow control valves 23 and 25, a pouring solenoid valve 35, and a pump drive circuit 32a for driving a circulation pump 32 are connected. In addition, various control devices are connected to the input / output interface circuit unit 56 as needed.

Next, the operation will be described. FIG. 3 shows a flow of the operation performed by the bath kettle 10 with the water heater when the swell switch is pressed. When the filling switch is pressed (step S101; Y), the CPU 51 opens the pouring solenoid valve 35 in a state where the burner 12 is not burned, and passes through the heat exchanger 13 and the pouring pipe 36 to the bathtub 40.
Water that is not heated is injected (step S102).
During water injection, even if the heat retention function is on, the burner is prevented from burning based on the function.

After opening the pouring solenoid valve 35, the CPU 51
The amount of water injected is monitored based on the signal from the flow sensor 26a,
When the water injection amount reaches a predetermined reference amount (step S1)
03; Y), the pouring solenoid valve 35 is closed, and the pouring operation is terminated (step S104). In this case, every time the filling switch is pressed once, water is injected at a predetermined reference amount, but after receiving the water injection instruction from the user until the water injection stop instruction is issued. Water can also be injected. For example, water may be injected from when the filling switch is pressed to when it is pressed again.

When the injection of water is stopped, the temperature of the water in the heat exchanger 13 has dropped to the temperature of the feed water. 12 is burned to raise the temperature of the hot water in the heat exchanger 13 to the target temperature.

First, the CPU 51 determines the amount of combustion required until the water temperature of the part of the remaining water in the heat exchanger 13 which is directly heated by the burner 12 and becomes partially high reaches a predetermined upper limit temperature ( (Step S105), the burner 12 is burned until the obtained combustion amount is reached (Step S106).

FIG. 4 shows how to determine the amount of combustion (combustion time) required until the water temperature at a location where it is directly heated by the burner 12 and partially becomes high in temperature reaches a predetermined upper limit temperature. The combustion amount of the burner 12 is obtained by referring to a combustion amount data table (not shown) stored in the ROM 53 in advance. The combustion amount data table is directly heated by the burner 12 in association with conditions such as the temperature difference between the water temperature in the heat exchanger 13 detected by the heat exchange thermistor 28 and the upper limit temperature and the outside air temperature. The combustion time required for the portion to rise by the temperature difference is registered in advance. Here, the burning time when the burner 12 is burned on the entire surface and with the minimum gas amount is registered.

Before starting the combustion of the burner 12, the CPU 51 measures conditions such as the water temperature and the outside air temperature detected by the heat exchange thermistor 28 (steps S201 and S20).
2). Then, a temperature difference between the upper limit temperature and the current water temperature is obtained (step S203), and the current combustion time is obtained by referring to the combustion amount data table based on the temperature difference and the outside air temperature (step S204).

The burner 1 is used for the time obtained in this manner.
2 is burned (FIG. 3, step S106), the burner 12 is heated until the temperature of the hot water inside the heat exchanger 13 becomes substantially uniform.
Is extinguished (step S107). The standby time may be a predetermined sufficiently long constant time, or the standby time may be set according to the current combustion time. Here, the standby time corresponding to the combustion time is registered in advance in the combustion amount data table, and when the combustion time is obtained, the standby time is also acquired at the same time.

When the standby time has elapsed after the combustion was stopped, the water temperature inside the heat exchanger 13 is measured by the heat exchange thermistor 28 (step S108). If the water temperature is lower than the target temperature range to be kept warm (step S108; N), the process returns to step S105, and the intermittent combustion is performed again.

By repeating such intermittent combustion a plurality of times, the water temperature in the entire heat exchanger 13 gradually increases to the target temperature. Then, when the water temperature in the heat exchanger 13 rises to the target temperature, it is checked whether or not the heat retaining function is turned on (step S110). When the heat retention function is on (Step S110; Y), the mode shifts to the heat retention operation mode (Step S111), and when the heat retention function is off, the process ends (End).

In the heat retaining operation mode, when the water temperature in the heat exchanger 13 detected by the heat exchange thermistor 28 falls below a predetermined lower limit temperature, the burner 12 is turned on at intervals of 2 to 3 minutes.
By burning for 2 seconds, the temperature of the hot water in the heat exchanger 13 is maintained in a target temperature range. The heat retention function can be sequentially turned on and off via the operation unit 55, and the operation time can be set in advance as a timer from 7:00 am to 7:00 pm. It is also possible to set the heat retention function to operate for only a minute.

FIG. 5 shows the temperature rise characteristics of the water in the heat exchanger 13 after the water injection operation is completed. A rectangular wave 81 at the bottom of the figure indicates a combustion period of the burner 12. During the ON (waveform high level) state, the burner 12
Is burned, and the burner 12 is extinguished during the off (waveform low level) state.

The solid line 82 in the upper part of the figure shows the temperature change in the portion directly heated by the burner 12, and the dashed line 83 shows the change in the hot water temperature at the place where the heat exchange thermistor 28 is attached. . Here, the target temperature to be kept warm is 46.2 ° C., and the upper limit temperature of the part where the temperature becomes high partially is set to 50 ° C.

When the water injection based on the filling function is completed, the burner 12 is burned from time T11 to time T12 in a state where the water does not flow through the heat exchanger 13.
One combustion time is 5 minutes at a part where the temperature becomes high partially.
It is set to the time predicted to rise to 0 ° C.

Shortly after the time T12 when the fire of the burner 12 is extinguished, the temperature of the water at a part where the temperature becomes partially high has risen to about 50 ° C. by this combustion. From time T12 to time T13, combustion of the burner 12 is stopped, and the process waits until the temperature distribution in the heat exchanger 13 becomes uniform. During this time, the water temperature of the part where the temperature was partially high gradually decreases, while the water temperature of the part detected by the heat exchange thermistor 28 gradually increases due to heat conduction and convection. Are almost the same.

At this time, since the temperature detected by the heat exchange thermistor 28 is lower than the target temperature of 46.2 ° C., the temperature of the portion where the temperature becomes partially high again is predicted to be 50 ° C. Combustion is performed, and the water temperature in the entire heat exchanger 13 is gradually increased to the target temperature.

Thus, heating toward the target temperature is
Since the temperature of the part where the temperature becomes high partially is controlled so as not to exceed the upper limit temperature, even if the user opens during heating to the target temperature, hot water higher than the target temperature will be discharged and used. No discomfort or burns to the person.

Further, since the burner 12 is burned at once until reaching the upper limit temperature, the time required to reach the target temperature can be shortened. Further, if continuous combustion or the like is performed, the temperature difference between the solid line 82 and the dashed line 83 in FIG. 5 increases, and this causes distortion of the heat exchanger 13. Temperature unevenness does not increase and the heat exchanger 13 is hardly distorted, and even if heated in a closed state, its durability is hardly reduced.

FIG. 6 shows a temperature rise characteristic when the amount of one burn of the burner 12 is reduced. The rectangular wave 91 at the bottom of the figure represents the combustion period of the burner 12. The burner 12 burns during the ON (waveform high level) state, and the burner 12 during the OFF (waveform low level) state.
Is extinguished.

A solid line 93 in the upper part of the figure shows a state of a temperature change in a portion directly heated by the burner 12, and a dashed line 92 shows a state of a temperature change in a place where the heat exchange thermistor 28 is attached. . Here, the target temperature to be kept warm and the upper limit temperature are both set to 50 ° C.

One combustion time is changed from time T21 to time T2.
By reducing the amount of combustion in each time to a short time of up to 2, even at a part where the temperature becomes high, the temperature does not rise to the upper limit temperature during heating.

As described above, if the amount of combustion at one time is reduced and the temperature rise width at a part where the temperature becomes partially high is reduced in each combustion, the amount of combustion of the burner 12 based on the combustion amount data table or the like is obtained. Need not be obtained each time. That is, after performing the combustion for a short time, the combustion may be intermittently repeated until the measured temperature reaches the target temperature after waiting until the temperature becomes uniform. This eliminates the need to change the combustion amount for each combustion,
Control of heating can be simplified.

Further, the burner 12 is repeatedly burned at intervals necessary for making the temperature of the hot water in the heat exchanger 13 uniform, so that the burner 12 burns once every two to three minutes for about two seconds. The water temperature in the heat exchanger 13 can be raised to the target temperature in a short time as compared with the case where the hot water temperature is raised by the performed heat retaining function.

In the above-described embodiment, the so-called one-can-two-bath type water bath with a water heater is used, in which one heat exchanger 13 performs both reheating and hot water supply. It may be performed in a separate heat exchanger 13. In the embodiment, the upper limit temperature is set to 50 ° C. However, as shown in FIG. 1, when the hot water from the heat exchanger 13 is mixed with the water supplied from the bypass to discharge the hot water, the heat exchanger 13 is used. And the upper limit temperature is set to a higher temperature according to the bypass ratio.

[0055]

According to the bath kettle with a water heater according to the present invention, the burner is burned in a state where the water supply in the heat exchanger does not flow when the water supply to the bathtub is finished, and the water temperature in the heat exchanger is set at the target. As the temperature is raised, the water is not injected more than necessary, and the hot water does not flow into the bathtub at the end of the water injection operation, so that the temperature of the water in the heat exchanger is raised to an appropriate temperature without giving the bather a sense of discomfort. be able to.

Further, when the water temperature in the heat exchanger is heated by burning the burner, the combustion of the burner is performed within a range in which the water temperature of a portion which is directly heated by the burner and partially becomes high does not exceed a predetermined upper limit temperature. Is performed several times intermittently, the water temperature in the heat exchanger rises to the target temperature in a relatively short time while preventing the remaining water in the heat exchanger from boiling partially. Can be done.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a bath kettle with a water heater according to one embodiment of the present invention.

FIG. 2 is a block diagram showing an outline of a circuit configuration of a bath kettle with a water heater according to one embodiment of the present invention.

FIG. 3 is a flowchart showing a flow of an operation performed by a bath kettle with a water heater according to one embodiment of the present invention when a filling switch is pressed.

FIG. 4 is a flow chart showing a flow of an operation at the time of obtaining a combustion amount for each time.

FIG. 5 is an explanatory diagram showing a rise characteristic of water temperature in a heat exchanger after a water injection operation is completed.

FIG. 6 is an explanatory diagram showing a rise characteristic of water temperature when the amount of one combustion is reduced.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Bath tank with a water heater 12 ... Burner 13 ... Heat exchanger 21 ... Hot water supply pipe 26a, 26b ... Flow sensor 28 ... Heat exchange thermistor 31 ... Circulation pipe for reheating 35 ... Pouring electromagnetic valve 36 ... Pouring pipe 40 … Bathtub

Claims (5)

[Claims] 1. A burner, a heat exchanger for transmitting heat from the burner to the feed water, a tapping pipe for guiding the feed water via the heat exchanger to a tap hole side, and a connection for guiding the feed water via the heat exchanger to a bathtub. A water bath with a function of injecting water into the bathtub through the connecting pipe without igniting a burner, after finishing pouring water into the bathtub without igniting the burner. A bath kettle with a water heater, characterized in that the burner is burned in a state where the water supply in the heat exchanger does not flow to raise the water temperature in the heat exchanger to a target temperature. 2. A burner, a heat exchanger for transmitting heat from the burner to the feed water, a tapping pipe for guiding the feed water via the heat exchanger to a tap hole side, and a communication for guiding the feed water via the heat exchanger to a bathtub. A water bath with a function of injecting water into the bathtub through the connecting pipe without igniting a burner, after finishing pouring water into the bathtub without igniting the burner. The burner is burned in a state where the water supply in the heat exchanger does not flow to raise the water temperature in the heat exchanger to a target temperature. Wherein the combustion of the burner is performed intermittently in a plurality of times within a range in which the water temperature does not exceed a predetermined upper limit temperature. 3. The method according to claim 2, wherein a single combustion of the burner raises the water temperature at a portion where the temperature is directly heated by the burner and becomes partially high, near the upper limit temperature. Bath kettle with water heater. 4. The water temperature of the entire heat exchanger is raised to a target temperature by reducing the amount of one combustion of the burner to a predetermined small amount and increasing the number of intermittent combustions. A bath kettle with a water heater according to claim 2. 5. A burner, a heat exchanger for transmitting heat from the burner to the feed water, a tapping pipe for guiding the feed water via the heat exchanger to a tap hole side, and a connection for guiding the feed water via the heat exchanger to a bathtub. A method for controlling a bathtub with a water heater that has a function of injecting water into the bathtub through the connecting pipe without igniting a burner, wherein the water is supplied without igniting the burner. After the water is completely poured into the bathtub, the burner is burned in a state where the water supply in the heat exchanger does not flow to raise the water temperature in the heat exchanger to a target temperature. Hook control method.