JPH09303861A - Hot water supplier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a rapid boiling phenomenon from being produced even when additional burning hot water supply is interrupted by common hot water supply. SOLUTION: When outlet hot water temperature exceeds primary danger temperature (quasi-danger temperature) higher than set temperature upon additional boiling during additional boiling hot water supply, primary regulation is executed, the regulation performing prohibition of an increase of the amount of combustion by combustion amount adjusting means 24 and prohibition of reduction of valve opening by hot water supply amount adjusting valve control means 25. When the outlet hot warter temperature exceeds secondary danger temperature higher than the quasi-danger temperature, secondary regulation is executed, the secondary regulation performing reduction of the amount of combustion by the combustion amount adjustimng means 24 and expansion of the valve opening by the hot water supply amount adjusting valve control means 25. Hereby, a rapid boiling phenomenon is avoided upon interruption of common hot water supply during additional boiling hot water supply where the amount of hot water supply is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water heater, and more specifically, in addition to bathroom hot water supply such as hot water supply to a bathtub or hot water supply for hot water supply and general hot water supply to a kitchen or washroom, The present invention relates to a hot water supply device that can also perform interrupted hot water supply of general hot water supply.

[Prior art]

In a water heater capable of interrupting general hot water during hot water supply in a bathroom for filling and reheating, a water flow rate sensor for measuring the amount of water supplied to the water heater per unit time. In addition to the (water volume sensor), a hot water supply flow rate sensor (interruption sensor) that measures the amount of hot water supply per unit time of general hot water supply is provided, and the interrupt sensor detects a hot water supply flow rate above a certain level during filling or reheating. First, the hot water filling valve and the hot water heating valve are temporarily closed to interrupt hot water filling and hot water heating, and general hot water is supplied at the hot water temperature set by the remote controller. Then, when the interrupt hot water supply ends and the interrupt sensor no longer detects a hot water supply flow rate above a certain level, the hot water filling and reheating are automatically restarted. As described above, the water heater capable of interrupting the general hot water supply during the hot water supply in the bathroom is very convenient because the general hot water supply can be performed without any trouble even during the hot water supply in the bathroom which is continuously performed for a long time.

[0003]

However, in the conventional water heater, there is no particular problem with interruption of general hot water during hot water supply, but when there is interrupt hot water during hot water heating, additional hot water is supplied. There is a problem in that the boiling water is boiled and the hot water spills out into the bathtub, which is dangerous. Conventionally, when the hot water supply flow rate detected by the interrupt sensor is, for example, 2 liters / minute or more, reheating is completely interrupted, and the hot water supply flow rate detected by the interrupt sensor is 1-2.
In the case of liter / min, [Additional hot water supply flow rate detected-interruption sensor detected hot water supply flow rate] is used as the additional hot water supply flow rate, and the opening degree of the additional heating valve is adjusted without interrupting additional heating. If the hot water supply flow rate detected by the interrupt sensor is less than 1 liter / minute, the hot water flow detected by the interrupt sensor is ignored and no additional changes are made to continue the hot water heating during the interrupt hot water supply. Is configured.

By the way, a general-purpose hot water supply tap (faucet) is opened only slightly, or the interrupted hot water supply is not completely closed, or foreign matter such as dust is caught in the flow path closing valve. Alternatively, when the sealing performance of the flow rate control valve is deteriorated, the detected hot water supply flow rate of 1 liter / min or less is detected by the interrupt sensor. However, in the flow rate region of 1 liter / min or less, the variation in the flow rate measurement result is large and the accuracy is low, and the measurement result cannot be used for control, so the cutting is unavoidable.

On the other hand, during interruption of general hot water supply, a fixed amount of water supplied to the hot water supply device is not sent to the heat exchange device for the purpose of adjusting the hot water temperature by mixing the hot water and the water before it is collected. Has been bypassed. Therefore, if there is an interruption of 1 liter / minute or less during hot water heating, and if the flow control valve opening during hot water is large and the total amount of water supplied to the heat exchanger is large, a fixed amount of water will be supplied. Even if it is collected in the middle of the process, the effect is small, and the amount of water supplied to the heat exchanger can be maintained at almost the required amount. When the amount of water is small, the amount of water taken out in the middle is large, and the amount of water supplied to the heat exchanger is much less than the required amount, resulting in the rapid boiling phenomenon.

The present invention solves the above-mentioned problems, and even if there is an interruption of general hot water supply during reheating hot water, it is possible to avoid the occurrence of the rapid boiling phenomenon and the water heater has high reliability. The purpose is to provide.

[0007]

In order to achieve the above object, the water heater according to the present invention heats water by performing heat exchange between a burner for burning fuel and inflowing water and combustion gas from the burner. A heat exchanger, a hot water temperature measuring means for detecting the temperature of the water discharged from the heat exchanger (outlet hot water temperature), and fuel combustion for the heat exchanger based on the hot water outlet temperature measured by the hot water temperature measuring means. Combustion amount adjusting means for adjusting the amount of water, water supply flow rate measuring means for measuring the amount of water supply to the water heater per unit time, hot water supply flow rate for measuring the amount of hot water supply per unit time by general hot water supply to the kitchen or washroom A heating means for heating the hot water supply is provided with a measuring means, a hot water supply quantity control valve for adjusting the hot water supply quantity for reheating the bath, and a hot water supply quantity control valve control means for controlling the opening degree of the hot water supply quantity control valve. Bathroom hot water supply including In addition to hot water, a hot water supply device configured to be able to perform interrupt hot water supply of general hot water supply in the hot water supply in the bathroom, wherein during the reheating hot water supply, the fuel combustion amount is adjusted by the combustion amount adjusting means, and The hot water supply amount control valve is configured to control the hot water temperature by adjusting the opening of the hot water supply amount control valve by the control means, and in order to prevent sudden boiling during hot water reheating, Based on the outlet hot water temperature measured by the temperature measuring means, the combustion amount adjusting means and the hot water supply amount adjusting valve control means are provided with operation restricting means for executing operation restriction for rapid boiling prevention, When the operation regulating means exceeds the quasi-dangerous temperature (primary dangerous temperature) at which the outlet hot water temperature is higher than the preset temperature at the time of additional heating, prohibition of increase in the combustion amount by the combustion amount adjusting means and the hot water supply When the outlet valve temperature exceeds the dangerous temperature (secondary dangerous temperature) higher than the primary dangerous temperature by executing the primary regulation for prohibiting the valve opening reduction by the regulating valve control means, the combustion amount It is characterized in that a secondary regulation is executed in which the combustion amount is reduced by the adjusting means and the valve opening degree is enlarged by the hot water supply amount adjusting valve control means.

[0008] The primary regulation is also performed when the operation regulation means has passed a certain period of time while the outlet hot water temperature is in the temperature range below the primary dangerous temperature from the caution temperature, which is slightly lower than the set temperature at the time of additional heating. It is characterized by performing.

Further, it is characterized in that the operation restricting means includes alarm means for issuing an alarm when the execution of the secondary restriction is started.

[0010]

When hot water is reheated by the water heater of the present invention, the hot water temperature is controlled based on the hot water temperature of the outlet measured by the hot water temperature measuring means on the outlet side of the heat exchanger. That is, the outlet hot water temperature is compared with a preset temperature for additional heating, and the combustion amount adjusting means adjusts the fuel combustion amount of the heat exchanger so that the difference between the two is eliminated, and the hot water supply amount adjusting valve control is performed. The amount of water flowing into the heat exchanger is adjusted by increasing / decreasing the valve opening of the hot water supply amount adjusting valve by the means so that the temperature of the additional heating water becomes accurate. Further, during the additional hot water supply, the operation restriction means restricts the operation of the combustion amount adjusting means and the hot water supply amount adjusting valve control means to prevent rapid boiling.

That is, when the outlet hot water temperature exceeds a quasi-critical temperature (primary dangerous temperature) higher than the set temperature at the time of additional heating, the combustion amount adjusting means prohibits the increase of the fuel combustion amount and the hot water supply amount adjusting valve control means. The operation regulation means executes the primary regulation for prohibiting the reduction of the valve opening degree due to. Both the increase in fuel combustion amount, which increases the heat supply, and the reduction in valve opening, which reduces the flow rate of water in the heat exchanger, both promote the rise in hot water temperature. By prohibiting and by the primary regulation, the occurrence of the rapid boiling phenomenon when the interruption of the general hot water supply with a small amount of hot water supply is performed during the additional hot water supply is avoided.

Further, when the outlet hot water temperature exceeds a dangerous temperature (secondary dangerous temperature) higher than the primary dangerous temperature, the combustion amount adjusting means reduces the fuel combustion amount and the hot water supply amount adjusting valve control means increases the valve opening degree. The secondary regulation for performing is performed by the operation regulation means. Both the reduction of the fuel combustion amount, which reduces the heat supply, and the increase of the valve opening, which increases the flow rate of water in the heat exchanger, are means for suppressing the heat exchange action by the heat exchanger and lowering the hot water temperature. By reducing the fuel combustion amount and increasing the valve opening degree by the secondary regulation, it is possible to more reliably prevent the rapid boiling phenomenon when the interruption of the general hot water supply with a small amount of hot water supply is performed during the additional hot water supply. You will be able to avoid it.

Also, when the outlet hot water temperature is not higher than the primary dangerous temperature but a certain period of time has passed from the caution temperature slightly lower than the set temperature for reheating to the temperature range lower than the primary dangerous temperature, Occurrence of rapid boiling phenomenon when there is an interruption of general hot water supply with a small amount of hot water during additional heating by performing primary control by the operation control means to prevent the heat exchange action of the heat exchanger from increasing. Can be avoided more reliably.

Further, when the operation regulating means is provided with an alarm means for issuing an alarm when the secondary regulation is executed, it is necessary to inform the user that the outlet hot water temperature is at the secondary dangerous temperature. It will be possible to take measures reliably and quickly,
The present invention can be effectively realized by surely avoiding the occurrence of the rapid boiling phenomenon.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be shown and features thereof will be described in more detail. FIG.
Is a block diagram showing a schematic configuration of a water heater according to an embodiment of the present invention, FIG. 2 is a view showing a general hot water supply remote controller (kitchen remote controller) of the water heater according to the embodiment, and FIG. 3 is a remote controller for bathroom hot water supply ( It is a figure which shows a bathroom remote control.

As shown in FIG. 1, the water heater 1 of this embodiment includes a main burner 3 for burning fuel gas, and a heat exchanger 2 for exchanging heat between inflowing water and combustion gas from the main burner 3. , A fan 4 for sending combustion air to the main burner 3. The fuel gas is supplied to the main burner 3 by means of a safety valve 5, a gas proportional valve 6 and three main valves 7.
Done through. Water supply to the water heater 1 is performed through a water supply flow rate sensor 8 that measures the amount of water supply to the water heater 1 per unit time, and water is normally sent to the heat exchanger 2 after passing through the water supply flow rate sensor 8. It is sent to the mixing valve 11 via the bypass valves 9 and 10.

The temperature of hot water flowing out from the heat exchanger 2 (exit hot water temperature) is a hot water temperature measuring sensor (hot water temperature measuring means) such as a thermistor.
12 is measured. The hot water flowing out of the heat exchanger 2 is
It is sent to the mixing valve 11 via the check valve 13 or to the hot water supply amount adjusting valve 14 for adjusting the hot water supply amount at the time of additional hot water supply. The hot water that has flowed into the mixing valve 11 is mixed with water as needed, and then is discharged to a currant or the like on the general hot water supply side through a hot water supply flow rate detection sensor (interruption sensor) 15 that measures the hot water supply amount per unit time by the general hot water supply. Alternatively, the hot water is discharged from the bath adapter 17 to the bathtub 18 or the like through the hot water filling valve 16. The mixing valve 11 controls the mixing ratio of hot water and water so that the temperature detected by the hot water temperature detection sensor 19 becomes a predetermined hot water temperature. Further, the hot water sent from the heat exchanger 2 to the hot water supply control valve 14 flows into the bathtub 18 from the bath adapter 17 as it is without being mixed with water, and is reheated.

Further, the water heater 1 is equipped with the controller box 21 shown in FIG. 1, the kitchen remote controller 22 shown in FIG. 2 installed in a kitchen, the bathroom remote controller 23 shown in FIG. 3 installed in a bathroom, and the like. As shown in FIG. 5, a combustion amount adjusting unit (combustion amount adjusting means) that adjusts the gas combustion amount for the heat exchanger 2 based on the outlet hot water temperature measured by the hot water temperature sensor 12
24, a hot water supply amount control valve controller (hot water supply amount control valve control means) 25 for adjusting the opening degree of the hot water supply amount control valve 14 for increasing or decreasing the amount of hot water supply at the time of additional heating hot water The controller box 2 includes an operation restriction unit 26 that executes operation restriction for preventing rapid boiling of the combustion amount adjustment unit 24 and the hot water supply amount adjustment valve control unit 25 based on the temperature.
1, the kitchen remote controller 22, the bathroom remote controller 23, etc. are provided in a centralized or distributed arrangement.

In the above water heater, during the hot water heating, the combustion amount adjusting unit 24 makes the fuel combustion amount (gas combustion amount) so that there is no difference between the outlet hot water temperature and the preset temperature at the time of additional heating. ) Is controlled, and the hot water supply amount control valve control unit 25 adjusts the opening degree of the hot water supply amount control valve 14 to control the flow rate. Further, as will be described later in detail, the operation restriction unit 26 prohibits the combustion amount adjustment unit 24 from increasing the fuel combustion amount and the hot water supply amount adjustment valve control unit 25 from reducing the valve opening degree according to the outlet temperature. The primary regulation is performed, or the secondary regulation is performed by the combustion amount adjusting unit 24 to reduce the fuel combustion amount and to increase the valve opening degree by the hot water supply amount adjusting valve control unit 25. In addition,
The bathroom remote controller 23 is provided with an alarm device 27 that emits a warning sound when the operation restriction unit 26 starts executing the secondary restriction control.

Next, the operation of the water heater 1 of this embodiment will be described with reference to the drawings.

First, the operation in the case of general hot water supply (when not an interrupt) will be described. When the operation switch 22a of the kitchen remote controller 22 is pressed, a hot water supply tap (not shown) is opened, and water is supplied to the heat exchanger 2 and the mixing valve 11 via the water supply flow rate sensor 8. At this time, the hot water filling valve 16 and the hot water supply amount control valve 1 for additional hot water supply
4 is closed. When the feed water flow rate sensor 8 detects the flow of water, the combustion amount adjusting unit 24 and the like cause the fan 4 to start rotating, while the spark plug 31 starts to spark, and the safety valve 5 and the main valve 7 open. On the other hand, the gas for fuel is set to the slowly ignited gas amount by the gas proportional valve 6,
It flows to the main burner 3. When the fire transfer is completed, the frame rod 32 detects the flame and the kitchen remote controller 2
The second combustion lamp 22b lights up and the spark stops. At the same time, the hot water warmed in the heat exchanger 2 and the water from the bypass valves 9 and 12 are mixed in the mixing valve 11 and then discharged from the interrupt sensor 15 at the preset hot water temperature.

Next, the case of performing hot water supply of hot water in the bathroom will be described. When the operation switch 23a of the bathroom remote control 23 is pressed, the hot water filling valve 16 is opened, the flame rod 32 detects the flame, and the combustion lamp 23b is turned on. At this time, since the currant on the general hot water supply side is closed, the hot water is discharged from the mixing valve 11 through the hot water filling valve 16 to the bathtub 18 at the set hot water temperature,
Hot water supply is provided.

Next, a case of performing additional hot water supply in the hot water supply in the bathroom will be described. When the reheating switch 23c of the bathroom remote controller 23 is pressed, the water filling valve 16 remains closed,
Except that the hot water supply amount adjusting valve 14 is opened and the additional heating lamp 23d is lit, the same operation as in the case of hot water supply is performed, but during the additional heating hot water, hot water is supplied from the heat exchanger 2 to the hot water supply amount adjusting valve. It is sent to the bathtub 18 via 14.
Note that the additional hot water supply is automatically completed after a predetermined time (for example, 10 minutes).

Next, the operation when there is an interrupt hot water supply during the additional hot water supply will be described. When the general-purpose hot water is opened and hot water is discharged during hot water heating, the interrupt sensor 15 detects the interrupt hot water supply amount. When the interrupt hot water supply amount is equal to or more than a certain amount (2 liters / minute now), the hot water supply amount control valve 14 is closed and the additional hot water supply is temporarily interrupted. When the interrupt hot water supply is completed, the hot water supply amount control valve 14 is opened, and the hot water supply is restarted. Interrupted hot water supply is above a certain level (currently 1 liter / min) ~ 2
In the case of liter / min, the opening degree of the hot water supply amount adjusting valve 14 is adjusted by the hot water supply amount adjusting valve control unit 25 using [detected water supply flow rate of water supply flow rate sensor-detected hot water supply flow rate of interrupt sensor] as the additional hot water supply flow rate. While performing, additional hot water supply is continued in parallel with interrupt hot water supply. When the interrupt hot water supply rate is 1 liter / min or less, the additional hot water supply and the interrupt hot water supply are performed in parallel, with the flow rate of the hot water discharged by the interrupt hot water supply being cut.

In the water heater 1 of the present invention, the operation restriction unit 26 performs the restriction operation on the combustion amount adjustment unit 24 and the hot water supply amount adjustment valve control unit 25 during the additional hot water supply. This restriction operation will be described with reference to the flowchart shown in FIG.

The operation regulating section 26 determines the outlet temperature t of the water heater 1.
When the temperature is below the caution temperature of 92 ° C, the combustion amount control unit 24
Also, no operation restriction is applied to the hot water supply amount adjustment valve control unit 25. At this time, all the four flags (combustion amount increase prohibition flag, valve opening reduction prohibition flag, combustion amount reduction execution flag, valve opening increase execution flag), which are the control command signals, are in the OFF state ( Step S
1). On the other hand, the outlet hot water temperature t is the set temperature for reheating 93 ° C.
It is checked whether or not the temperature range is 1 ° C lower than the caution temperature 92 ° C to a temperature range of less than 94 ° C which is the primary dangerous temperature (semi-critical temperature) (step S2), and the outlet hot water temperature t is within this temperature range Sometimes, the timer is started to measure the time during which the outlet hot water temperature t continues in the range of 92 ° C to 94 ° C (step S3), and it is checked whether or not the measurement time has passed 2 seconds ( Step S4).

If 2 seconds have passed, the combustion amount adjusting section 24
The primary regulation (preliminary regulation) is executed to prohibit the increase of the fuel combustion amount and to inhibit the opening degree of the hot water supply amount control valve 14 by the hot water supply amount control valve control unit 25. As a result, the combustion amount increase prohibition flag and the valve opening reduction prohibition flag of the restriction command signal are turned on (step S5). This primary regulation checks whether or not the outlet hot water temperature t exceeds a primary dangerous temperature 94 ° C which is 1 ° C higher than the set temperature 93 ° C for additional heating (step S6), and exceeds the primary dangerous temperature. Sometimes also run. In this way, the primary regulation of the operation regulation section 26 prevents the heat exchange action of the heat exchanger 2 from being promoted more than ever, so that there is an interruption of the general hot water supply with the hot water supply amount of 1 liter / min or less. In this case, the rapid boiling phenomenon can be prevented.

Subsequently, the outlet hot water temperature t is the primary dangerous temperature 94 °.
It is also checked whether or not the secondary dangerous temperature 1 ° C higher than 95 ° C is exceeded (step S7), and the secondary dangerous temperature 9
When the temperature exceeds 5 ° C., the operation regulation unit 26 executes secondary regulation in which the combustion amount regulation unit 24 reduces the fuel combustion amount and the hot water amount regulation valve control unit 25 expands the opening degree of the hot water amount regulation valve 14. It Thus, the combustion amount reduction execution flag and the valve opening increase execution flag of the regulation command signal are turned on (step S8). Since the heat exchange effect by the heat exchanger 2 is suppressed more than before, even if there is an interruption of general hot water supply with a hot water supply rate of 1 liter / min or less,
It becomes possible to reliably prevent the occurrence of the rapid boiling phenomenon. Further, at the same time when the operation restricting section 26 enters the execution of the secondary restriction, a warning sound is emitted from the alarm device 27 (step S).
9).

In the above embodiment, the water heater using gas as fuel has been described as an example, but the present invention can also be applied to a water heater using fuel other than gas such as petroleum. Further, although the water heater of the above-described embodiment includes the alarm device, the water heater without the alarm device is also included in the embodiments of the present invention. Further, the temperature values of the caution temperature, the primary dangerous temperature, and the secondary dangerous temperature in the above embodiment are merely examples, and it is possible to select appropriate numerical values according to the specific form of the water heater.

[0030]

The hot water supply device of the present invention, during the hot-water reheating, when the outlet hot water temperature exceeds the primary dangerous temperature (semi-critical temperature) higher than the set temperature at the time of the additional heating, the heat exchange is performed. The heat exchange action by the heat exchanger is prevented from being further accelerated, and further, when the outlet hot water temperature exceeds the secondary dangerous temperature higher than the primary dangerous temperature, the heat exchange action by the heat exchanger is suppressed. Since the restriction is applied to the hot water supply, it is possible to avoid the occurrence of the rapid boiling phenomenon even when the general hot water supply with a small hot water supply amount is interrupted during the hot water supply for additional heating.

Also, when the outlet hot water temperature is not higher than the primary dangerous temperature but a certain time elapses from the caution temperature slightly lower than the set temperature for reheating to the temperature range lower than the primary dangerous temperature. Occurrence of rapid boiling phenomenon when there is an interruption of general hot water supply with a small amount of hot water during additional heating by performing primary control by the operation control means to prevent the heat exchange action of the heat exchanger from increasing. It is possible to more reliably avoid the above, and it is possible to more effectively present the present invention.

Further, when the operation regulating means is provided with an alarm means for issuing an alarm when the secondary regulation is executed, the user is informed that the outlet hot water temperature is at the secondary dangerous temperature, and it is necessary. It will be possible to take measures reliably and quickly,
The present invention can be effectively realized by surely avoiding the occurrence of the rapid boiling phenomenon.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a water heater according to an embodiment of the present invention.

FIG. 2 is a front view showing the kitchen remote controller of the water heater according to the embodiment of the present invention.

FIG. 3 is a front view showing the bathroom remote controller of the water heater according to the embodiment of the present invention.

FIG. 4 is a partial block diagram showing the configuration around the operation restricting portion of the water heater according to the embodiment of the present invention.

FIG. 5 is a flowchart showing a flow of a restricting operation by the operation restricting unit of the water heater according to the embodiment of the present invention.

[Explanation of symbols]

1 Hot Water Heater 2 Heat Exchanger 3 Main Burner 4 Fan 5 Safety Valve 6 Gas Proportional Valve 7 Main Valve 8 Water Supply Flow Rate Sensor 9, 10 Bypass Valve 11 Mixing Valve 12 Hot Water Temperature Measuring Sensor 13 Check Valve 14 Hot Water Supply Control Valve 15 Hot Water Supply Flow rate detection sensor (interruption sensor) 16 Hot water filling valve 17 Bath adapter 18 Bathtub 19 Hot water temperature detection sensor 21 Controller box 22 Kitchen remote control 23 Bathroom remote control 24 Combustion amount adjusting unit (combustion amount adjusting means) 25 Hot water supply amount adjusting valve control unit (hot water supply) Amount control valve control means) 26 Operation restriction unit 27 Alarm device

Claims (3)

[Claims] 1. A burner for burning fuel, a heat exchanger for heating water by heat exchange between inflowing water and combustion gas from the burner, and a temperature of water discharged from the heat exchanger (exit hot water). Temperature), a combustion amount adjusting unit for adjusting the fuel combustion amount for the heat exchanger based on the outlet hot water temperature measured by the hot water temperature measuring unit, and Water flow rate measuring means for measuring the amount of water supply,
Hot water supply flow rate measuring means for measuring the hot water supply amount per unit time by general hot water supply to the kitchen or washroom, hot water supply amount adjusting valve for adjusting the hot water supply amount when reheating the bath, and the hot water supply amount adjustment A hot water supply amount adjusting valve control means for controlling the opening degree of the valve is provided, and in addition to the bathroom hot water including the reheating hot water and the general hot water, it is possible to perform the interrupt hot water supply of the general hot water during the hot water supply in the bathroom. In the hot water heater, the hot water temperature is adjusted by adjusting the combustion amount of fuel by the combustion amount adjusting means and adjusting the opening degree of the hot water amount adjusting valve by the hot water amount adjusting valve control means during hot water heating. The combustion amount adjusting means is configured to control and, based on the outlet hot water temperature measured by the hot water temperature measuring means, to prevent rapid boiling during additional hot water supply. The hot water supply amount control valve control means is provided with an operation control means for executing operation control for preventing rapid boiling, and the operation control means has the outlet hot water temperature higher than a set temperature at the time of additional heating. When the temperature exceeds a quasi-dangerous temperature (primary dangerous temperature), the primary regulation is executed to prohibit the combustion amount increase by the combustion amount adjusting means and the valve opening reduction by the hot water supply amount adjusting valve control means. When the outlet hot water temperature exceeds a dangerous temperature (secondary dangerous temperature) higher than the primary dangerous temperature, the combustion amount is decreased by the combustion amount adjusting means and the valve opening is increased by the hot water supply amount adjusting valve control means. A water heater characterized by executing secondary regulation. 2. Even when the operation regulating means has a certain period of time while the outlet hot water temperature is in the temperature range below the primary dangerous temperature from the caution temperature, which is slightly lower than the set temperature at the time of additional heating, the primary temperature Claim 1 which enforces regulation.
The water heater described. 3. The water heater according to claim 1 or 2, further comprising alarm means for issuing an alarm when the operation restriction means enters into execution of secondary restriction.