JP7062267B2 - Water heater - Google Patents

Description

The present invention relates to a so-called one-can, two-water channel type water heater in which a hot water supply heat exchanger on the hot water supply circuit side and a bath heat exchanger on the bath circuit side are provided in one combustion chamber provided with a burner.

The water heater connects the water supply pipe and the hot water outlet pipe to the hot water supply heat exchanger heated by the burner, and the water supplied from the water supply pipe via the water supply pipe by opening the external hot water supply tap to which the hot water outlet pipe is connected. It is equipped with a hot water supply circuit that exchanges heat with the combustion exhaust of the burner to discharge hot water. In addition to this, a bath circuit is formed in which an external bathtub is connected to the bath heat exchanger via a pipe, and hot water is circulated by a pump provided in the pipe to heat the bath heat exchanger for reheating. Things are also known.
In such a water heater, in addition to a configuration in which a hot water supply heat exchanger and a bath heat exchanger are installed in different combustion chambers and heated by different burners (two-can two-water channel type), as disclosed in Patent Document 1. In addition, a one-can, two-water channel type configuration is also often used in which a hot water supply heat exchanger and a bath heat exchanger are installed side by side in one combustion chamber, and the two heat exchangers are heated by a common burner. ..

Japanese Unexamined Patent Publication No. 2017-155956

However, in a one-can, two-water channel type water heater that has both a hot water supply circuit and a bath circuit, if the bathtub is reheated by using the bath circuit alone, the hot water supply heat exchanger will also be heated by the same burner. Become. For this reason, the hot water temperature may reach a high temperature of 100 ° C. or higher in the heat transfer tube of the hot water supply heat exchanger in which hot water is retained. There is a risk that hot water will be discharged from the hot water pipe. The hot water supply circuit is provided with a bypass pipe that connects the water supply pipe and the hot water outlet pipe to bypass the hot water supply heat exchanger, and when hot water is discharged, water is mixed from the bypass pipe to control the hot water outlet temperature. However, if a component such as a distribution valve that controls the amount of water to the bypass pipe fails, it becomes impossible to avoid high temperature hot water.

Therefore, according to the present invention, even when the hot water supply circuit is used after the bath circuit is used alone in the one-can-two-water channel type in which one water flow path is a hot water supply circuit and the other water flow path is a bath circuit. The purpose is to provide a water heater that can effectively suppress high-temperature hot water output.

In order to achieve the above object, the invention according to claim 1 comprises a combustion chamber in which a burner is arranged at a lower portion and a combustion chamber.
A hot water supply circuit including a hot water supply heat exchanger arranged at the upper part of the combustion chamber and heated by a burner, and a water supply pipe and a hot water discharge pipe connected to the hot water supply heat exchanger.
A bath heat exchanger that is installed in the upper part of the combustion chamber and is heated by a burner, a pipe that is connected to the bath heat exchanger and connected to an external bathtub, and a pump that is installed in the pipe. The bath circuit that includes it,
Hot water temperature detecting means for detecting the temperature of hot water in the hot water supply heat exchanger,
A drop pipe that connects the hot water outlet pipe and the pipe and can supply hot water from the hot water outlet pipe to the bathtub via the pipe,
Opening and closing means for opening and closing the flow path of the drop pipe,
With a fan that can supply combustion air to the combustion chamber,
A water heater equipped with a controller that controls the combustion of the burner and the operation of the pump.
After the burner is burned by using the bath circuit alone, the controller operates the pump to circulate the hot water in the bath circuit and rotate the fan.
After that, the detection temperature detected by the hot water temperature detecting means is monitored, and if the detected temperature exceeds a predetermined temperature, the flow path of the drop pipe is opened by the opening / closing means, and the hot water in the hot water supply heat exchanger is bathed. On the other hand, when the detected temperature is equal to or lower than the predetermined temperature, the operation of the pump and the rotation of the fan are stopped .

According to the invention of claim 1, the controller operates the pump after the burner is burned by the sole use of the bath circuit, and the temperature detected by the hot water temperature detecting means becomes a predetermined temperature or less. Since hot water is circulated in the bath circuit up to, heat can be transferred from the hot water heat exchanger to the hot water circulating in the bath heat exchanger to lower the temperature of the hot water in the hot water heat exchanger. Therefore, in the one-can-two-water channel type, even when the hot water supply circuit is used after the bath circuit is used alone, high-temperature hot water discharge can be effectively suppressed. In particular, when a bypass pipe is provided that connects the water supply pipe and the hot water outlet pipe to bypass the hot water supply heat exchanger, the operation of the pump is such that the distribution valve provided in the bypass pipe fails and sufficient water is supplied from the bypass pipe. Even if it cannot be mixed, it is performed regardless, so it is possible to prevent high temperature hot water with high reliability.
In addition , when the pump operates, the controller opens the flow path of the drop pipe by opening and closing means, and drops the hot water in the hot water supply heat exchanger into the bathtub, so that the hot water in the hot water supply heat exchanger is discharged. It can be replaced with water to quickly lower the temperature of the hot water in the hot water supply heat exchanger.
Further , the controller can effectively lower the temperature of the hot water in the hot water supply heat exchanger by the heat dissipation action using the combustion air by rotating the fan with the operation of the pump.

It is a schematic circuit diagram of a water heater. It is a flowchart of high temperature hot water prevention control. It is a flowchart of the change example of the high temperature hot water prevention control. It is a flowchart of the change example of the high temperature hot water prevention control. It is explanatory drawing which shows the arrangement example of each heat transfer tube of a hot water supply heat exchanger and a bath heat exchanger.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic circuit diagram showing an example of a water heater. The water heater 1 supplies combustion air to each of the three burner units 3, 3 ..., Which are provided with a plurality of burners 4, 4, ... A combustion fan 5 is provided, and a hot water supply heat exchanger 6 and a bath heat exchanger 7 through which the combustion exhaust of the burners 4, 4, ... Passes are installed in the upper part of the combustion chamber 2. 8 is a spark plug, 9 is a frame rod, an exhaust hood 10 for exhausting combustion exhaust that has passed through both heat exchangers 6 and 7 is provided at the upper part of the combustion chamber 2, and combustion is performed outside the combustion chamber 2. A sheet-shaped overheat prevention device 11 printed with a fuse circuit for detecting the leakage of combustion exhaust from the chamber 2 is wound around.

A gas pipe 12 to which a gas pipe from the outside is connected is connected to the gas inlet of the appliance accommodating the combustion chamber 2 and the like, and each burner unit 3 is connected to the branch pipes 13, 13 and branch pipes 13 and 13 branching from the gas pipe 12. Each branch pipe 13 is provided with a gas electromagnetic valve 14 that opens and closes a gas flow path. Further, the gas pipe 12 before branching is provided with a source gas solenoid valve 15 and a gas proportional valve 16 from the upstream side, respectively.

The hot water supply heat exchanger 6 includes a hot water supply heat transfer tube 18 that serpentinely penetrates a plurality of fins 17, 17 ... Arranged at predetermined intervals, and a water inlet of an instrument is provided at the inlet of the hot water supply heat transfer tube 18. The water supply pipe 19 connected to the hot water supply pipe 19 is connected, and the hot water outlet pipe 20 connected to the hot water outlet of the appliance is connected to the outlet of the hot water supply heat transfer pipe 18. A water pipe thermistor 21 for detecting the temperature of the hot water supply heat transfer tube 18 is provided at a bent portion of the hot water supply heat transfer tube 18 exposed to the outside of the hot water supply heat exchanger 6. Further, a bypass pipe 22 that bypasses the hot water supply heat exchanger 6 is connected between the water supply pipe 19 and the hot water outlet pipe 20, and the connection portion between the water supply pipe 19 and the bypass pipe 22 is driven by a stepping motor. A distribution valve 23 for variably controlling the flow rate of the bypass pipe 22 is provided.
There is.

Further, on the upstream side of the connection portion of the water supply pipe 19 with the bypass pipe 22, a water inlet thermistor 24 for detecting the water inlet temperature and a hot water supply water amount sensor 25 for detecting the amount of water flowing through the water supply pipe 19 are provided.
A hot water supply heat exchanger thermistor 26 for detecting the outlet temperature is provided at the outlet of the hot water supply heat exchanger 6 in the hot water outlet pipe 20, and the hot water outlet temperature is detected on the downstream side of the connection portion with the bypass pipe 22. A hot water supply and hot water thermistor 27 and a water amount control valve 28 that is driven by a stepping motor to variably control the flow rate of the hot water discharge pipe 20 are provided.
Therefore, a hot water supply circuit A including a hot water supply heat exchanger 6 heated by the burner unit 3, a water supply pipe 19 connected to the hot water supply heat exchanger 6, a hot water outlet pipe 20, and a bypass pipe 22 is formed here.

On the other hand, the bath heat exchanger 7 includes a bath heat transfer tube 30 that penetrates the fins 17, 17, ... In a serpentine manner, and at the entrance of the bath heat transfer tube 30, the bath adapter 32 of the external bathtub 31 is provided via an external pipe. A bath return pipe 33 connected to the bath return pipe 33 is connected, and a bath going pipe 34 connected to the bath adapter 32 via an external pipe is connected to the outlet of the bath heat transfer pipe 30. The bath return pipe 33 is provided with a pump 35, a bath return thermista 36 for detecting the bath return temperature is provided on the upstream side thereof, and hot water in the bath return pipe 33 is provided on the downstream side of the pump 35. A bath water flow switch 37 that operates ON / OFF according to the flow and a water level sensor 38 that detects the water level in the bathtub 31 by the water pressure are provided. Further, the bath going tube 34 is provided with a bath going thermistor 39 for detecting the bath going temperature.
Therefore, here, the bath circuit B including the bath heat exchanger 7 heated by the burner unit 3, the bath return pipe 33 and the bath going pipe 34 connected between the bath heat exchanger 7 and the bathtub 31. Is formed.
In this way, the water heater 1 is heated by a common burner unit 3, 3 ... In which a hot water heat exchanger 6 and a bath heat exchanger 7 having different water flow paths are installed side by side in one combustion chamber 2. It is a one-can, two-water channel type.

Then, between the hot water supply circuit A and the bath circuit B, a drop pipe 41 is connected between the downstream side of the water amount control valve 28 in the hot water discharge pipe 20 and the pump 35 and the bath return thermistor 36 in the bath return pipe 33. There is. The drop pipe 41 is provided with a bath water amount sensor 42 for detecting the amount of water flowing through the drop pipe 41 on the upstream side, and a drop water solenoid valve 43 for opening and closing the drop pipe 41 on the downstream side. Further, two check valves 44, 44 are provided on the downstream side of the drop water solenoid valve 43, respectively, and hot water flowing back from the bath return pipe 33 is discharged between the check valves 44, 44 from the overflow port. A check valve 45 for discharging is connected.
Reference numeral 50 denotes a controller, which is provided with a drive circuit for each motor, a detection circuit for each thermistor and a sensor, and the like in addition to a microcomputer and a memory. Controls the filling of the bathtub 31 with hot water. 51 is a hot water supply remote controller, and 52 is a bath remote controller.

In the water heater 1 configured as described above, first, normal hot water supply is performed as follows.
When the hot water tap of the external pipe connected to the hot water outlet is opened and water is passed through the appliance, and the water flow is detected by the hot water supply water amount sensor 25, the controller 50 rotates the combustion fan 5 for a predetermined time to burn. The combustion exhaust stored in the chamber 2 is discharged (prepurge). After that, the original gas solenoid valve 15 of the gas pipe 12 and each gas solenoid valve 14 are opened, the gas proportional valve 16 is opened at a predetermined opening degree, gas is supplied to each burner unit 3, and the igniter is operated. Then, the spark plug 8 ignites the burners 4, 4, ....
As a result, in the hot water supply heat exchanger 6, the water flowing through the hot water supply heat transfer tube 18 is heat-exchanged with the combustion exhaust of the burner 4, and the heated hot water is discharged from the hot water supply plug through the hot water outlet pipe 20 and the external pipe.

The controller 50 monitors the outlet temperature by the hot water supply heat exchanger thermistor 26 of the hot water supply pipe 20, drives the stepping motor of the distribution valve 23, and the outlet temperature prevents the generation of drainage and overheating in the hot water supply heat exchanger 6. The flow rate (bypass rate) to the bypass pipe 22 is controlled so as to be maintained within a possible temperature range.
Further, the controller 50 monitors the hot water outlet temperature by the hot water supply hot water thermistor 27, and controls the opening and closing of each gas electromagnetic valve 14 and the gas proportion so that the hot water discharge temperature becomes the set temperature set by the hot water supply remote controller 51 or the bath remote controller 52. The opening degree of the valve 16 is adjusted, and the amount of air is continuously changed by controlling the rotation speed of the combustion fan 5.
When the hot water tap is closed, the controller 50 confirms that the signal from the hot water amount sensor 25 is stopped, closes the original gas solenoid valve 15 and the gas solenoid valve 14, extinguishes the burner 4, and rotates the combustion fan 5 for a predetermined time (post). purge).

On the other hand, when the automatic switch of the hot water supply remote controller 51 or the bath remote controller 52 is pressed, the controller 50 opens the drop water solenoid valve 43 of the drop pipe 41 to allow water to pass through the hot water supply heat exchanger 6 to burn the burner 4. The hot water from the hot water outlet pipe 20 is supplied to the bathtub 31 through the drop pipe 41, the bath return pipe 33, and the bath outbound pipe 34. When the amount of water detected by the bath water amount sensor 42 provided in the drop pipe 41 reaches the set amount of water, the drop water solenoid valve 43 is closed to end the drop.
Next, the pump 35 is operated to circulate hot water between the bath heat exchanger 7 and the bathtub 31. Therefore, the bath circulating water circulating between the bath heat exchanger 7 and the bathtub 31 is heat-exchanged with the combustion exhaust of the burner 4 when flowing through the bath heat transfer tube 30, and is reheated to a set temperature. When the set temperature is reached, the combustion of the burner 4 is stopped and the pump 35 is stopped. Further, by operating the reheating switch of the bath remote controller 52, reheating can be performed at any timing.

Then, after the bath circuit B is used independently and the reheating is executed, the controller 50 operates the pump 35 to operate the hot water in the hot water transfer tube 18 of the hot water heat exchanger 6 heated by the burner 4. The temperature is lowered to prevent hot water from being discharged even if the hot water supply circuit A is used thereafter. Hereinafter, this high temperature hot water discharge prevention control will be described with reference to the flowchart of FIG.

First, when it is confirmed by the determination of S1 that the reheating in the bath circuit B is completed, the controller 50 operates the pump 35 in S2 to execute the circulation of hot water in the bath circuit B. By this circulation, the heat of the hot water supply heat transfer tube 18 heated by the burner 4 when the bath circuit B is used alone is transferred to the bath heat transfer tube 30 via the fins 17, 17, ..., And circulates in the bath heat transfer tube 30. Will move to the hot water. Therefore, the temperature of the hot water staying in the hot water supply heat transfer tube 18 decreases.

Next, in the determination of S3, it is determined whether or not the detection temperature of the hot water supply heat transfer tube 18 obtained from the water pipe thermistor 21 is 60 ° C. or lower. Here, if the temperature is 60 ° C. or lower, it is determined in the subsequent determination of S4 whether or not the outlet temperature obtained from the hot water supply heat exchanger thermistor 26 is 60 ° C. or lower. Here, if either the detected temperature in S3 or the outlet temperature in S4 still exceeds 60 ° C., the operation of the pump 35 is continued, but it is confirmed that both temperatures are 60 ° C. or lower. Then, the controller 50 stops the operation of the pump 35 in S5 and ends the control.
Since the hot water temperature in the hot water supply heat transfer tube 18 is lowered by this high temperature hot water discharge prevention control, even if the hot water supply plug is opened and the hot water supply circuit A is used after that, hot water having a high temperature of 100 ° C. or higher is discharged from the hot water supply pipe 20. There is no risk of being overwhelmed.

As described above, according to the water heater 1 of the above-described embodiment, the controller 50 operates the pump 35 after the burner 4 is burned by the single use of the bath circuit B, and the temperature detected by the water pipe thermista 21. By circulating hot water in the bath circuit B until the temperature drops below a predetermined temperature (60 ° C. in this case), heat is transferred from the hot water supply heat transfer tube 18 to the hot water circulating in the bath heat transfer tube 30, and the hot water in the hot water transfer tube 18 is transferred. The temperature of the water heater can be lowered. Therefore, in the one-can-two-water channel type, even when the hot water supply circuit A is used after the bath circuit B is used alone, the high-temperature hot water discharge can be effectively suppressed. In particular, the pump 35 is operated regardless of the case where the distribution valve 23 or the like fails and sufficient water cannot be mixed from the bypass pipe 22, so that high-temperature hot water discharge can be prevented with high reliability.

In the above embodiment, a water pipe thermistor and a hot water supply heat exchanger thermistor are used as hot water temperature detecting means to turn off the pump when both detection temperatures are 60 ° C. or lower. The pump may be turned off by monitoring only the detected temperature of the water pipe thermistor without using the detected temperature. The predetermined temperature at which the pump is turned off is not limited to 60 ° C. and can be appropriately increased or decreased.

Further, as shown in FIG. 3, in the routine of FIG. 2, after confirming the end of reheating in S11, in S12, the pump 35 is operated and the combustion fan 5 is also rotated to send air into the combustion chamber 2. You may do so.
In this case, the air sent into the combustion chamber 2 passes through the hot water supply heat exchanger 6 and comes into contact with the hot water supply heat transfer tube 18 and the fins 17 around it, so that heat dissipation in the hot water supply heat exchanger 5 can be promoted. can.
Then, when it is confirmed by the discrimination of S13 and S14 that the detected temperature of the hot water supply heat transfer tube 18 and the outlet temperature from the hot water supply heat exchanger 6 are 60 ° C. or less, the controller 50 operates the pump 35 in S15. This control is terminated by stopping and stopping the rotation of the combustion fan 5.

As described above, according to the modification of FIG. 3, since the combustion fan 5 is rotated with the operation of the pump 35, the hot water supply heat transfer tube 18 is provided with the heat dissipation action using the combustion air in addition to the hot water temperature lowering action by the pump 35. The temperature of the hot water inside can be effectively lowered.
In the modified example of FIG. 3, the ON / OFF of the combustion fan 5 does not have to be the same timing as the ON / OFF of the pump 35, and the ON / OFF of the combustion fan 5 is delayed from the ON / OFF of the pump 35. You may shift the timing.
Further, in this modification as well, the pump and the combustion fan may be turned off by monitoring only the detected temperature of the water pipe thermistor without using the detected temperature of the hot water supply heat exchanger thermistor. The temperature at which the pump is turned off is not limited to 60 ° C. and can be increased or decreased.

Further, in the modification shown in FIG. 4, in the routine of FIG. 3, after confirming the end of reheating in S21 and turning on the pump 35 and the combustion fan 5 in S22, the detection temperature of the water pipe thermistor 21 is determined by S23. If the temperature exceeds 60 ° C., the controller 50 drops water in S24. In this water drop, the drop water solenoid valve 43 is opened, and the hot water in the hot water supply circuit A is dropped from the drop pipe 41 into the bathtub 31 via the bath return pipe 33 and the bath outbound pipe 34. It is performed until the amount of water detected by the bath water amount sensor 42 reaches a predetermined amount without burning. By this water drop, the hot water in the hot water supply heat transfer pipe 18 is replaced with the water newly supplied from the water supply pipe 19.

After executing the water drop, the detected temperature of the water pipe thermistor 21 is confirmed again in S23, and if the detected temperature still exceeds 60 ° C., the process of dropping water in S24 is repeated. If the detected temperature is 60 ° C. or lower, S25 determines whether or not the outlet temperature from the hot water supply heat exchanger thermistor 26 is 60 ° C. or lower.
If the outlet temperature exceeds 60 ° C. in S25, the same water drop as in S24 is performed in S26, and the process is repeated until the outlet temperature becomes 60 ° C. or lower. When the outlet temperature becomes 60 ° C. or lower, the pump 35 and the combustion fan 5 are turned off in S27 to end this control.

As described above, according to the modification of FIG. 4, when the pump 35 is operated, the controller 50 opens the flow path of the drop pipe 41 by the drop water electromagnetic valve 43, and the inside of the hot water supply heat exchanger 6 is opened. Since the hot water is dropped into the tub 31, in addition to the action of lowering the hot water temperature by the pump 35 and the combustion fan 5, the hot water in the hot water supply heat transfer tube 18 is replaced with water to quickly lower the hot water temperature in the hot water supply heat transfer tube 18. Can be made to.

In this modified example as well, the water drop and the pump and the combustion fan may be turned off by monitoring only the detected temperature of the water pipe thermistor without using the detected temperature of the hot water supply heat exchanger thermistor. The temperature at which the pump is turned off is not limited to 60 ° C. and can be increased or decreased.
Further, in this modified example, water is dropped at the timing when it is confirmed that the detection temperature of the water pipe thermistor and the hot water supply heat exchanger thermistor exceeds the predetermined temperature, but the detection temperature drops after the lapse of a predetermined time. If you do not see, you may try to drop the water. Further, the water may be dropped at the same time as the pump is turned on without setting such a condition.
Then, it is also possible to add water drop to the ON / OFF control of the pump as shown in FIG. 2 without using the combustion fan.

In addition, if the configuration of the water heater itself is also a one-can, two-water channel type, each heat exchanger may be equipped with an auxiliary heat exchanger for latent heat recovery, which is common to the above-mentioned form and each modification example. There is no problem.
On the other hand, in the one-can, two-water channel type, the hot water supply heat exchanger and the bath heat exchanger are installed side by side, in which the heat transfer tubes of both heat exchangers are separately arranged on the left and right, front and back, or top and bottom in one combustion chamber. In addition to the form, there may be a mixed form in which the heat transfer tubes of both heat exchangers are alternately arranged on the left and right, front and back, or top and bottom.
FIG. 5 shows an example of arrangement of the heat transfer tube in the water heater 1 of the above-described embodiment. Here, the straight pipe portions 18a, 18a ... Of the hot water supply heat transfer tubes 18 arranged in a serpentine manner in the combustion chamber 2 are arranged separately in the upper and lower stages, and the hot water supply heat transfer tubes 18 and fins connected from the lower stage to the upper stage. The hot water supply heat exchanger 6 is formed by the hot water supply heat exchanger 6, and the straight pipe portions 30a, 30a ... The bath heat exchanger 7 is formed by the bath heat transfer tube 30 and the fins 17 connected in the middle stage, and the hot water supply heat transfer tube 18 and the bath heat transfer tube 30 are alternately arranged in the vertical direction. ing.

1 ... water heater, 2 ... combustion chamber, 3 ... burner unit, 4 ... burner, 5 ... combustion fan (fan), 6 ... hot water supply heat exchanger, 7 ... bath heat exchanger, 12 ...・ Gas pipe, 17 ・ ・ Fin, 18 ・ ・ Hot water supply heat transfer pipe, 19 ・ ・ Water supply pipe, 20 ・ ・ Hot water pipe, 21 ・ ・ Water pipe thermista (hot water temperature detection means), 22 ・ ・ Bypass pipe, 23 ・ ・ Distribution Valve, 24 ... Water inlet thermista, 25 ... Hot water supply water amount sensor, 26 ... Hot water supply heat exchanger thermista (hot water temperature detecting means), 27 ... Hot water supply hot water supply thermista, 28 ... Water volume control valve, 30 ... Bath heat transfer pipe , 31 ... water heater, 33 ... bath return pipe (piping), 34 ... bath going pipe (piping), 35 ... pump, 37 ... bath water flow switch, 41 ... drop pipe, 42 ... bath water volume sensor , 43 ... Drop water electromagnetic valve (opening and closing means), 50 ... Controller, 51 ... Hot water supply remote control, 52 ... Bath remote control, A ... Hot water supply circuit, B ... Bath circuit.

Claims (1)

A combustion chamber with a burner at the bottom and
A hot water supply circuit including a hot water supply heat exchanger arranged in the upper part of the combustion chamber and heated by the burner, and a water supply pipe and a hot water outlet pipe connected to the hot water supply heat exchanger.
A bath heat exchanger that is installed in the upper part of the combustion chamber and is heated by the burner along with the hot water supply heat exchanger, a pipe that is connected to the bath heat exchanger and is connected to an external bathtub, and a pipe that is provided in the pipe. The pump, which includes the bath circuit,
A hot water temperature detecting means for detecting the temperature of hot water in the hot water supply heat exchanger,
A drop pipe that connects the hot water pipe and the pipe and can supply hot water from the hot water pipe to the bathtub via the pipe.
An opening / closing means for opening / closing the flow path of the drop pipe,
A fan that can supply combustion air to the combustion chamber,
A water heater comprising a controller for controlling the combustion of the burner and the operation of the pump.
After the burner is burned by using the bath circuit alone, the controller operates the pump to circulate hot water in the bath circuit and rotate the fan.
After that, the detection temperature detected by the hot water temperature detecting means is monitored, and when the detected temperature exceeds a predetermined temperature, the flow path of the drop pipe is opened by the opening / closing means, and the hot water supply heat exchanger is used. A water heater characterized in that the operation of the pump and the rotation of the fan are stopped when the detected temperature is equal to or lower than the predetermined temperature while the hot water in the water is dropped into the bathtub .

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