JP2021004697A - Water heater and hot water supply system - Google Patents

Abstract

To stabilize an operation by simple control on temperature control in an instantaneous water heating operation mode by a circulation path to which a cross over valve is connected.SOLUTION: In an instantaneous water heating operation mode in which a circulation pump 80 is actuated when a hot water tap 330 is closed, a water heater 100 is configured so as to form instantaneous hot water circulation path by an internal path including a heating mechanism by a combustion mechanism 30 and a heat exchanger 40, and an external path that bypasses the hot water tap 330 outside the water heater 100. The external path includes a crossover valve 200. In the instantaneous water heating operation mode in which intermittent combustion in which a minimum combustion state in which output heat quantity of the combustion mechanism 30 is restricted to a minimum value and a combustion stop state are provided alternately is introduced, a controller 10 controls a detection temperature by a temperature sensor 71 to a preset temperature.SELECTED DRAWING: Figure 1

Description

The present invention relates to a hot water supply device and a hot water supply system, and more specifically, to a hot water supply device and a hot water supply system having an immediate hot water function.

As a type of hot water supply device, there is a type having a so-called immediate hot water function that outputs hot water at an appropriate temperature immediately after the start of hot water supply even after the hot water supply is turned off for a long time. Normally, in order to realize the immediate hot water function, it is necessary to provide a mode (hereinafter, "immediate hot water operation mode") for forming a circulation path via the heat source even while the hot water supply is off.

Further, in US Pat. No. 6,536,464 (Patent Document 1), a thermostat-controlled bypass valve (hereinafter, also referred to as “crossover valve”) using a wax thermostat is externally connected for the above-mentioned immediate hot water function. The configuration that forms the circulation pathway of is disclosed. As a result, the immediate hot water function can be realized by simple installation work without adding the control function of the crossover valve to the hot water supply device side.

Japanese Patent Application Laid-Open No. 2015-230151 (Patent Document 2) also describes a configuration in which an immediate hot water operation is executed by using a path in which a temperature-sensitive valve similar to the crossover valve is connected.

U.S. Pat. No. 6,536,464 Japanese Unexamined Patent Publication No. 2015-230151

However, in the circulation path to which the crossover valve (or temperature sensitive valve) is connected, the circulation flow rate is relatively small because the pressure loss of the path passing through the wax thermostat is large. Therefore, in the immediate hot water operation mode, it is required to control the fluid having a relatively low flow rate to the set temperature.

Therefore, in a hot water supply device using a combustion mechanism such as a combustion burner as a heat source, there is a concern that it may be difficult to control the temperature by adjusting the amount of heat generated (the amount of fuel to be burned) in the combustion mechanism.

The present invention has been made to solve such a problem, and an object of the present invention is to simply control the temperature in the immediate hot water operation mode by the circulation path to which the crossover valve is connected. It is to stabilize the operation.

In a certain aspect of the present invention, it is a hot water supply device that discharges hot water to a hot water tap, and controls a heating mechanism including a combustion mechanism, a first temperature detector, a second temperature detector, and a flow rate detector. Equipped with a vessel. In the hot water supply device, in the immediate hot water operation mode in which the circulation pump arranged inside or outside the hot water supply device is operated when the hot water supply plug is closed, the fluid is heated together with an external path that bypasses the hot water supply plug outside the hot water supply device. It is further provided with an internal route that forms an immediate hot water circulation route that passes through. The external path includes a heat-sensitive water-stop bypass valve having a path that closes when the temperature rises. The first temperature detector detects the fluid temperature on the upstream side of the heating mechanism of the immediate hot water circulation path. The second temperature detector detects the fluid temperature on the downstream side of the heating mechanism of the hot water circulation path. The flow rate detector detects the circulating flow rate in the immediate hot water circulation path. The controller controls the heating mechanism and the circulation pump. The controller includes a calorific value control unit and a combustion control unit. The calorific value control unit sets the output calorific value command value of the combustion mechanism for controlling the temperature detected value by the second temperature detector to the set temperature in the immediate hot water operation mode in the immediate hot water operation mode. The combustion control unit controls the combustion mechanism according to the output heat quantity command value. In the combustion state of the combustion mechanism, the output calorific value command value is limited to a range between the minimum calorific value and the maximum calorific value. In the combustion control unit, in the immediate hot water operation mode, the output calorific value command value is set to the minimum calorific value value, and the temperature detected value by the second temperature detector rises to the set upper control upper temperature higher than the set temperature. Occasionally, the combustion mechanism is controlled so as to alternately provide a minimum combustion state that operates according to the minimum calorific value and a combustion stop state.

In another aspect of the present invention, the hot water supply system connects between a hot water supply device having a water inlet and a hot water outlet, a low temperature water pipe for introducing low temperature water into the water inlet port, and a hot water outlet and a hot water tap. It is provided with a high-temperature water pipe and a circulation pump arranged inside or outside the hot water supply device. The hot water supply device includes a heating mechanism including a combustion mechanism, a first temperature detector, a second temperature detector, a flow rate detector, and a controller. The water heater forms an immediate hot water circulation path through which the fluid passes through the heating mechanism together with an external path that bypasses the hot water tap outside the hot water supply device in the immediate hot water operation mode in which the circulation pump operates when the hot water tap is closed. It also has an internal route. The external pathway is configured to include a thermal water stop bypass valve with a pathway that closes when the temperature rises. The first temperature detector detects the fluid temperature on the upstream side of the heating mechanism of the immediate hot water circulation path. The second temperature detector detects the fluid temperature on the downstream side of the heating mechanism of the immediate hot water circulation path. The flow rate detector detects the circulating flow rate in the immediate hot water circulation path. The controller controls the heating mechanism and the circulation pump. The controller includes a calorific value control unit and a combustion control unit. The calorific value control unit sets the output calorific value command value of the combustion mechanism for controlling the temperature detected value by the second temperature detector to the set temperature in the immediate hot water operation mode in the immediate hot water operation mode. The combustion control unit controls the combustion mechanism according to the output heat quantity command value. In the combustion state of the combustion mechanism, the output calorific value command value is limited to a range between the minimum calorific value and the maximum calorific value. In the combustion control unit, in the immediate hot water operation mode, the output calorific value command value is set to the minimum calorific value value, and the temperature detected value by the second temperature detector rises to the set upper control upper temperature higher than the set temperature. Occasionally, the combustion mechanism is controlled so as to alternately provide a minimum combustion state that operates according to the minimum calorific value and a combustion stop state.

According to the present invention, it is possible to stabilize the operation of the temperature control in the immediate hot water operation mode by the circulation path to which the crossover valve is connected by simple control.

It is a block diagram explaining the structure of the hot water supply system including the hot water supply apparatus which concerns on this embodiment. It is a block diagram explaining the hardware configuration example of a controller. It is a figure explaining the switching of the flow path by the crossover valve shown in FIG. A state transition diagram relating to immediate hot water operation by the hot water supply device according to the present embodiment is shown. It is a block diagram explaining temperature control in a hot water operation mode. This is an example of an operation waveform diagram of temperature control in the immediate hot water operation mode. It is a flowchart explaining the control process which determines the establishment of the stop condition of the immediate hot water operation mode. It is a flowchart explaining the control process which determines the establishment of the restart condition of the immediate hot water operation mode. It is a flowchart explaining the control process of the abnormality diagnosis of the immediate hot water circulation path executed in the immediate hot water operation mode. It is a block diagram explaining the structure of the hot water supply device and the hot water supply system which concerns on the modification of this Embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the figure are designated by the same reference numerals, and the explanations will not be repeated in principle.

FIG. 1 is a block diagram illustrating a configuration of a hot water supply system 1A including a hot water supply device according to the present embodiment.

With reference to FIG. 1, the hot water supply system 1A includes a hot water supply device 100, a low temperature water pipe 110, a high temperature water pipe 120, and a crossover valve 200. The hot water supply device 100 has a water inlet port 11, a hot water outlet port 12, and a circulation port 13.

Cold water is supplied to the low temperature water pipe 110 via the check valve 112. Cold water is typically supplied from a water pipe (not shown). The low temperature water pipe 110 is connected to the water inlet port 11 and the circulation port 13.

The hot water supply device 100 includes a controller 10, a water inlet path 20, a hot water outlet path 25, a circulation path 28, a bypass path 29, a combustion mechanism 30, a heat exchanger 40, a circulation pump 80, and a flow rate adjusting valve 90. To be equipped.

The water entry path 20 is formed between the water entry port 11 and the input side (upstream side) of the heat exchanger 40 via the check valve 21. The combustion mechanism 30 is typically composed of a burner that generates heat from combustion of gas, petroleum, or the like.

The heat exchanger 40 raises the temperature of the low-temperature water (fluid) introduced by the water entry path 20 by using the amount of heat generated by the combustion mechanism 30. The combustion mechanism 30 and the heat exchanger 40 constitute an embodiment of the "heating mechanism".

The hot water outlet path 25 is formed between the output side (downstream side) of the heat exchanger 40 and the hot water outlet port 12. The bypass route 29 connects between the water inlet route 20 and the hot water outlet route 25 without passing through the heat exchanger 40. By controlling the flow rate adjusting valve 90 by the controller 10, the ratio of the flow rate of the bypass path 29 (bypass flow rate ratio) to the total flow rate (sum of the flow rate of the heat exchanger 40 and the flow rate of the bypass path 29) can be adjusted.

In such a bypass configuration, a part of the low temperature water is bypassed by the heat exchanger 40 and mixed in the downstream of the heat exchanger 40 without being heated, so that the high temperature water is supplied from the hot water outlet port 12. As a result, the output temperature from the heat exchanger 40 (heating mechanism) can be increased, which is advantageous in suppressing drainage generated by cooling the exhaust gas of the combustion mechanism 30 on the surface of the heat exchanger 40. ..

A flow rate sensor 81 that outputs a flow rate value of low-temperature water is arranged in the water entry path 20, and a flow rate sensor 82 is arranged in the circulation path 28. The values detected by the flow rate sensors 81 and 82 are input to the controller 10. The flow rate sensor 81 is arranged so as to be included in the immediate hot water circulation path described later.

Further, a temperature sensor 71 is arranged in the hot water outlet path 25, and a temperature sensor 73 is arranged in the water entry path 20. Further, a temperature sensor 72 is arranged in the circulation path 28. The fluid temperature detected by the temperature sensors 71 to 73 is input to the controller 10. Further, a temperature sensor for detecting the water entry temperature during the hot water supply operation is also arranged in the water entry path 20. The temperature sensor 72 arranged on the upstream side of the heat exchanger 40 corresponds to one embodiment of the "first temperature detector", and the temperature sensor 71 arranged on the downstream side of the heat exchanger 40 corresponds to the "second temperature detector". Corresponds to one embodiment of the "temperature detector".

FIG. 2 is a block diagram illustrating a hardware configuration example of the controller 10.
With reference to FIG. 2, the controller 10 is typically configured by a microcomputer. The controller 10 includes a CPU (Central Processing Unit) 15, a memory 16, an input / output (I / O) circuit 17, and an electronic circuit 18. The CPU 15, the memory 16, and the I / O circuit 17 can exchange signals with each other via the bus 19. The electronic circuit 18 is configured to execute predetermined arithmetic processing by dedicated hardware. The electronic circuit 18 can exchange signals with the CPU 15 and the I / O circuit 17.

The CPU 15 receives output signals (detected values) from each sensor including the temperature sensors 71 and 72 and the flow rate sensors 81 and 82 through the I / O circuit 17. Further, the CPU 15 receives a signal indicating an operation instruction input to the remote controller 92 through the I / O circuit 17. The operation instruction includes, for example, an on / off operation of the operation switch of the hot water supply device 100, a hot water supply set temperature, and various time reservation settings (also referred to as “timer setting”). The CPU 15 controls the operation of each component device including the combustion mechanism 30 and the circulation pump 80 so that the hot water supply device 100 operates according to the operation instruction.

By controlling the notification device 95, the CPU 15 can output information that can be visually or audibly recognized. For example, the notification device 95 can output information by displaying visible information such as characters and figures on the screen. In this case, the notification device 95 can be configured by the display screen provided on the remote controller 92. Alternatively, the notification device 95 may be configured by a speaker and output information using voice, a melody, or the like.

The operation of the hot water supply device 100 will be described with reference to FIG. 1 again.
When the hot water supply tap 330 is opened, the low temperature water is introduced into the water entry path 20 due to the supply pressure of the low temperature water. When the flow rate sensor 81 detects a flow rate exceeding the minimum operating flow rate (MOQ) while the operation switch of the hot water supply device 100 is on, the controller 10 operates the combustion mechanism 30.

As a result, the high-temperature water heated by the combustion mechanism 30 and the heat exchanger 40 is mixed with the low-temperature water passing through the bypass path 29, and then output from the high-temperature water pipe 120 via the hot water outlet port 12.

During the normal hot water supply operation, the circulation pump 80 is stopped by the controller 10, and the fluid temperature (hot water temperature Th) detected by the temperature sensor 71 is controlled to the hot water supply set temperature input to the remote controller 92. Specifically, the hot water temperature can be controlled by combining the control of the heating amount (heat generated) by the combustion mechanism 30 (heating mechanism) and the control of the bypass flow rate ratio by the flow rate adjusting valve 90.

The circulation path 28 is formed between the circulation port 13 and the water entry path 20 (connection point 22). The circulation pump 80 is connected to the circulation path 28. Alternatively, the circulation pump 80 may be connected to the circulation port 13 outside the water heater 100. The operation and stop of the circulation pump 80 are controlled by the controller 10.

When the hot water supply operation is stopped, the temperature of the fluid staying in the hot water outlet path 25 and the high temperature water pipe 120 drops, so that it takes time to supply the high temperature water to the hot water tap 330 after the start of the next hot water supply operation. Is a concern. Therefore, the hot water supply device 100 is provided with an immediate hot water function for promptly supplying high temperature water after the start of the hot water supply operation. The immediate hot water function is realized by forming an immediate hot water circulation path including a combustion mechanism 30 and a heat exchanger 40 by operating the circulation pump 80 when the hot water supply plug 330 is closed.

For example, the user can specify the execution period of the immediate hot water operation by setting the timer. The timer setting can be input by, for example, operating the remote controller 92. Alternatively, the execution period of the immediate hot water operation may be automatically set by learning the past usage history of the user. It is also possible to start or end the execution period of the immediate hot water operation directly according to the switch operation of the user.

In the hot water supply system 1A, the crossover valve 200 can be used to execute the immediate hot water operation mode accompanied by the operation of the circulation pump 80. The crossover valve 200 is configured similar to the thermostat-controlled bypass valve described in Patent Document 1 and has ports 201-204 and a wax thermo 210. Ports 201 and 203 communicate internally, and ports 202 and 204 communicate internally. The wax thermo 210 is connected between ports 201 and 203 and ports 202 and 204.

The wax thermo 210 forms a thermal bypass path between ports 201 and 203 and ports 202 and 204 at low temperatures. On the other hand, the wax thermo 210 is configured to block the heat-sensitive bypass path by a coefficient of thermal expansion at high temperatures. The switching temperature for forming and closing the heat-sensitive bypass path is designed in advance depending on the material and configuration of the wax thermo 210. Hereinafter, when the fluid temperature in the crossover valve 200 is higher than the switching temperature is referred to as a high temperature, and when the fluid temperature is lower than the switching temperature is referred to as a low temperature.

As described above, the crossover valve 200 corresponds to one embodiment of the "heat-sensitive water-stop bypass valve". Further, the pressure loss of the heat-sensitive bypass path is designed to be higher than the pressure loss of each of the path through which the ports 201 and 203 communicate and the path through which the ports 202 and 204 communicate.

The port 201 is connected to the high temperature water pipe 120, and the port 202 is connected to the low temperature water pipe 110. Ports 203 and 204 are connected to the hot water tap 330. The hot water tap 330 is provided as a mixing curan that mixes the hot water from the port 203 and the low temperature water from the port 204. Valves 331 and 332 for adjusting the mixing ratio of hot water and cold water can be provided between the ports 203 and 204 and the hot water tap 330.

FIG. 3 shows a chart illustrating switching of the flow path by the crossover valve 200 shown in FIG.

With reference to FIGS. 3 and 1, when the route from the ports 203 and 204 to the hot water tap 330 is formed, the high temperature water pipe 120 is formed at both high and low temperatures due to the pressure loss described above. And the flow path Pa between the hot water supply plug 330, and the flow path Pb between the low temperature water pipe 110 and the hot water supply plug 330 are formed.

On the other hand, when the route from the ports 203 and 204 to the hot water tap 330 is blocked, the flow path is switched between the low temperature and the high temperature. At low temperatures, the heat-sensitive bypass path by the wax thermo 210 forms a heat-sensitive bypass path Pc between the ports 201 and 202, that is, between the high-temperature water pipe 120 and the low-temperature water pipe 110. On the other hand, when the temperature is high, the heat-sensitive bypass path is blocked, so that the flow path between the high-temperature water pipe 120 and the low-temperature water pipe 110 is cut off.

In the hot water supply system 1A, during the hot water supply operation, the low temperature water introduced from the low temperature water pipe 110 to the water inlet port 11 is heated by the combustion mechanism 30 and the heat exchanger 40 (heating mechanism) to obtain high temperature water. The hot water is output from the hot water tap 330 via the hot water outlet port 12, the hot water pipe 120, and the crossover valve 200 (flow path Pa).

In the immediate hot water operation mode, the circulation pump 80 operates to access the outside of the hot water supply device 100 from the hot water outlet port 12 via the high temperature water pipe 120, the crossover valve 200 (heat sensitive bypass path Pc), and the low temperature water pipe 110. Therefore, a fluid path (external path) leading to the circulation port 13 can be formed. Further, inside the hot water supply device 100, a circulation port 13, a circulation path 28, a water entry path 20 (downstream from the connection point 22), a heat exchanger 40 (heating mechanism), a hot water discharge path 25, and a hot water discharge port 12 are provided. The including fluid path (internal path) can be formed. By forming an immediate hot water circulation path by such an internal path and an external path, high-temperature water is passed through the immediate hot water circulation path even when the plug is closed, so that high-temperature water is supplied to the hot water tap 330 immediately after opening. It becomes possible.

In the immediate hot water circulation path, the temperature sensor 72 can detect the fluid temperature before heating (return temperature Tb), and the temperature sensor 71 can detect the fluid temperature after heating (outflow temperature Th).

Considering that the pressure loss of the heat-sensitive bypass path due to the wax thermo 210 is large and the flow rate of the immediate hot water circulation path including the crossover valve 200 is small, the hot water supply device 100 has a bypass flow rate ratio r (0) in the immediate hot water operation mode. It is preferable to control the flow rate adjusting valve 90 so that ≦ r <1.0) is maintained at the minimum value (including r = 0 due to fully closed).

FIG. 4 shows a state transition diagram relating to the immediate hot water operation by the hot water supply device 100. The state transition shown in FIG. 4 is controlled by the controller 10.

With reference to FIG. 4, when the execution period of the immediate hot water operation specified by the user by the timer setting or the like is started, the controller 10 changes the hot water supply device 100 from the “immediate hot water operation off mode” to the “immediate hot water operation on mode”. To transition to.

When the hot water supply operation is stopped (closed) and the detection temperature (outflow temperature) of the temperature sensor 71 is lower than the predetermined mode reference temperature in the immediate hot water operation on mode, the controller 10 starts the start condition J0. Is determined to be satisfied, and the circulation pump 80 is operated. As a result, the immediate hot water operation mode is started.

When the hot water supply interrupt condition J1 or the stop condition J2 described later is satisfied during the immediate hot water operation mode, the controller 10 stops the circulation pump 80 and starts the standby mode. For example, the hot water supply interrupt condition is satisfied in response to an increase in the flow rate detection value of the flow rate sensor 81.

In the standby mode, when the restart condition J3 described later is satisfied, the controller 10 ends the standby mode and restarts the circulation operation mode. In the standby mode, when the execution period of the immediate hot water operation ends due to timer setting, switch operation, or the like, the hot water supply device 100 is returned to the immediate hot water operation off mode. When the execution period of the immediate hot water operation ends during the immediate hot water operation mode, the hot water supply device 100 is returned to the immediate hot water operation off mode after the transition to the standby mode.

In the immediate hot water operation mode, the fluid temperature of the immediate hot water circulation path can be raised by operating the combustion mechanism 30 in a state where the immediate hot water circulation path is formed by the operation of the circulation pump 80 during closing. Therefore, in the immediate hot water operation mode, the temperature control of the immediate hot water circulation path is executed by controlling the operation of the combustion mechanism 30.

On the other hand, in the hot water supply system 1A, the crossover valve 200 included in the immediate hot water circulation path has a large pressure loss in the heat-sensitive bypass path of the wax thermo 210. Therefore, in the immediate hot water operation mode, the flow rate of the circulating fluid that performs the heat exchanger 40 becomes low, so that the amount of temperature rise of the fluid with respect to the amount of heat generated by the combustion mechanism 30 becomes large. On the other hand, there is a limit to reducing the amount of heat generated by the combustion mechanism 30 from the viewpoint of ensuring stable combustion. As a result, even if the amount of heat generated by the combustion mechanism 30 is controlled to the minimum value, there is a concern that the temperature control may become unstable due to excessive heating.

Therefore, in the present embodiment, stable temperature control is realized by a simple calculation by controlling the combustion mechanism as described below.

FIG. 5 is a block diagram illustrating temperature control in the immediate hot water operation mode.
With reference to FIG. 5, the controller 10 includes a calorific value calculation unit 10A and a combustion control unit 10B. The functions of the calorific value calculation unit 10A and the combustion control unit 10B can be realized by software processing by the controller 10 and / or hardware processing.

The heat amount calculation unit 10A calculates a command value (Pset) of the amount of heat generated by the combustion mechanism 30 for temperature control. In a hot water supply device, the amount of heat generated is generally calculated in units of "number". The number = 1 corresponds to the amount of heat required to raise the fluid temperature by 25 ° C. under a flow rate of 1 (L / min). Therefore, in the following, the command value of the amount of heat generated is also referred to as the number command value Pset.

The required temperature rise amount ΔT in the immediate hot water operation mode is indicated by ΔT = Tr−Tb using the temperature detected by the temperature sensor 72 (return temperature Tb) and the set temperature Tr in the immediate hot water operation mode. For example, the amount of heat generated by the combustion mechanism 30 can be calculated by the following formula (1) according to the product of the circulation flow rate Qt (L / min) in the immediate hot water circulation path and the temperature rise amount ΔT. The set temperature Tr in the immediate hot water operation mode may be the same value as the hot water supply set temperature, or may be a different value. Alternatively, the set temperature Tr may be set so as to have a predetermined temperature difference from the hot water supply set temperature.

Pset = Qt × (Tr-Tb) / 25 ... (1)
The circulating flow rate Qt can be detected by the flow rate sensor 82. Alternatively, the circulating flow rate Qt can also be obtained by multiplying the flow rate detected value by the flow rate sensor 81 (the flow rate of the heat exchanger 40) by 1 / (1-r) using the bypass flow rate ratio r. That is, each of the flow rate sensors 81 and 82 corresponds to an embodiment of a "flow rate detector" for detecting a circulating flow rate.

In the calculation of the number command value Pset, it is actually necessary to consider the ratio (thermal efficiency) of the amount of heat generated by the combustion mechanism 30 to the amount of heat used for raising the temperature in the heat exchanger 40. In (1), in order to simplify the explanation, the thermal efficiency is assumed to be 1.0.

The calorific value calculation unit 10A sets the number command value Pset by limiting it within the range of the minimum number Pmin to the maximum number Pmax. That is, when the Pset calculated by the equation (1) is larger than Pmax (Pset> Pmax), it is corrected to Pset = Pmax. Similarly, when the Pset calculated by the equation (1) is smaller than Pmax (Pset <Pmax), it is corrected to Pset = Pmin. The number command value Pset corresponds to the "output heat quantity command value", the minimum number Pmin corresponds to the "minimum calorific value", and the maximum number Pmax corresponds to the "maximum calorific value".

The circulating flow rate Qt in the formula (1) is replaced with a value obtained by multiplying the flow rate detection value Q by the flow rate sensor 81 by 1 / (1-r) above, and the term of the return temperature Tb is replaced by the temperature sensor 73. By substituting the hot water detection value (water entry temperature Tw) and replacing the set temperature Tr with the hot water supply set temperature, the calorific value calculation unit 10A can calculate the number command value Pset in common even during normal hot water supply operation. Can be done.

The combustion control unit 10B operates the combustion mechanism 30 based on the number command value Pset from the calorific value calculation unit 10A, the temperature detected by the flow rate sensor 81 (hot water temperature Th), and the set temperature Tr in the immediate hot water operation mode. Generate a command value.

The combustion mechanism 30 includes a plurality of burners 31a to 31f, a proportional valve 34, and a solenoid valve 36 to 38. The proportional valve 34 is arranged between the original fuel supply pipe 32 and the fuel supply pipe 33. The flow rate of fuel supplied to the fuel supply pipe 33 can be controlled by the opening degree of the proportional valve 34. An ignition device (not shown) is arranged in each of the plurality of burners 31a to 31f. The number of burners can be any number.

The solenoid valve 36 is connected between the fuel supply pipe 33 and one burner 31a. The solenoid valve 37 is connected between the fuel supply pipe 33 and the two burners 31b and 31c. The solenoid valve 38 is connected between the fuel supply pipe 33 and the three burners 31d to 31f. Combustion in the burners 31a to 31f can be turned on and off by turning on and off the solenoid valves 36 to 38. Therefore, the number of burners for burning fuel (hereinafter, also referred to as the number of combustion burners Nbrn) can be controlled by combining the on / off commands of the solenoid valves 36 to 38.

In the example of FIG. 5, when the solenoid valves 36 to 38 are turned off, Nbrn = 0, and the combustion mechanism 30 is put into the combustion off state. On the other hand, when all the solenoid valves 36 to 38 are turned on, Nbrn = 6, and by turning on a part of the solenoid valves 36 to 38, Nbrn = 1 to 5 can be set stepwise. In the combustion-on state in which at least one of the solenoid valves 36 to 38 is turned on, the amount of heat generated by the combustion mechanism 30 is determined by the combination of the number of combustion burners Nbrn and the fuel flow rate.

Therefore, the operation command value of the combustion mechanism 30 by the combustion control unit 10B includes the on / off command of the solenoid valves 36 to 38 and the opening command value of the proportional valve 34 in the example of FIG.

The combustion control unit 10B stores in advance a table for determining the number of combustion burners and the combination with the fuel flow rate in accordance with the number command value Pset. The combustion control unit 10B refers to the on / off command (the number of combustion burners) of the solenoid valves 36 to 38 and the opening command of the proportional valve 34 for generating the amount of heat according to the number command value Pset by referring to the table. A value (fuel flow rate) can be generated.

On the other hand, when the combustion control unit 10B controls the combustion mechanism 30 to the combustion stop state, the combustion control unit 10B generates an off command for all of the solenoid valves 36 to 38. When the flow rate detection value Q by the flow rate sensor 81 is lower than the minimum operating flow rate MOQ, an off command is generated for all of the solenoid valves 36 to 38 and the fuel supply is also cut off in order to stop the combustion mechanism 30. Will be done.

FIG. 6 shows an example of an operation waveform diagram of temperature control in the immediate hot water operation mode.
With reference to FIG. 6, the combustion control unit 10B uses the combustion mechanism 30 based on a comparison between the control upper limit temperature Th and the control lower limit temperature Trl set according to the set temperature Tr and the hot water discharge temperature Th (flow rate sensor 81). Control combustion on / off.

In FIG. 6, since the circulating flow rate Qt is small, the state in which the value calculated by the equation (1) is lower than the minimum number Pmin continues and is fixed to the number command value Pset = Pmin by the calorific value calculation unit 10A. Illustrated. In this case, before time t1, even in a state where the combustion mechanism 30 outputs a calorific value according to the minimum number Pmin (hereinafter, also referred to as "minimum combustion state"), the hot water temperature Th rises above the set temperature Tr. ..

In the minimum combustion state of Pset = Pmin, the combustion control unit 10B outputs an operation command for turning on the solenoid valve 36 and turning off the solenoid valves 37 and 38 in order to set the number of combustion burners Nbrn = 1. Further, the combustion control unit 10B outputs an opening command value of the proportional valve 34 corresponding to the minimum fuel flow rate for stabilizing the combustion state in the burner 31a.

When the hot water temperature Th rises to the control upper limit temperature Th at time t1, the combustion control unit 10B burns the combustion mechanism 30 at time t2 when a predetermined time T1 (for example, about 1 second) elapses from time t1. Control to a stopped state. In the combustion stopped state, an operation command for turning off the solenoid valves 36 to 38 is output from the combustion control unit 10B.

After time t2, the amount of heat output from the combustion mechanism 30 becomes 0, so that the hot water temperature Th gradually decreases. Then, at time t3, when the hot water temperature Th drops to the control lower limit temperature Trl, at time t4 when a predetermined time T2 (for example, about 1 second) elapses from time t3, the combustion control unit 10B uses the combustion mechanism 30. Is controlled to the combustion on state. In the combustion on state, an operation command of the combustion mechanism 30 is generated so that the amount of heat according to the number command value Pset is output from the combustion mechanism 30. Here, as in the case before time t2, the operation command of the combustion mechanism 30 corresponding to the minimum combustion state of Pset = Pmin is output from the combustion control unit 10B.

As a result, after the time t4 when the combustion mechanism 30 is controlled to the minimum combustion state, the hot water temperature Th rises as before the time t2, and at the time t5, the hot water temperature Th rises to the control upper limit temperature Th. At the time t6 when T1 elapses from t5, the combustion mechanism 30 is controlled to the combustion stop state again.

As described above, in the hot water supply device and the hot water supply system according to the present embodiment, when the flow rate of the immediate hot water circulation path is small by introducing the intermittent combustion in which the minimum combustion state and the combustion stop state are alternately provided (typically). Can be stably controlled even in the case of Pset = Pmin) without excessively increasing the hot water temperature Th. In particular, intermittent combustion can be stably controlled by simple control using the number command value Pset, which can be calculated in common with normal hot water supply operation, without directly judging the change in flow rate due to the behavior of the wax thermo 210. can do.

Although FIG. 6 illustrates a state in which the number command value Pset = Pmin is fixed, the same control can be applied even in a state where Pset> Pmin. That is, even if Pset> Pmin, the combustion mechanism 30 is controlled to the combustion stop state and the combustion mechanism 30 is controlled in response to the rise in the hot water temperature Th to the control upper limit temperature Th in the combustion on state of the combustion mechanism 30. In the combustion off state, the combustion mechanism 30 can be controlled to the combustion on state according to the number command value Pset according to the decrease of the hot water temperature Th to the control lower limit temperature Trl.

Next, the stop condition (J2) of the immediate hot water operation mode and the restart condition (J3) of the immediate hot water operation mode in the standby mode shown in FIG. 4 will be described. In the hot water supply system 1A, the immediate hot water circulation path is formed or cut off by the crossover valve 200 according to the fluid temperature. Therefore, the stop condition (J2) and the restart condition (J3) should be set in consideration of this point. is required. The setting of the stop condition (J2) and the restart condition (J3) described below may be combined with the intermittent combustion control described with reference to FIGS. 5 and 6, but may not be combined with the intermittent combustion control. Confirmably describe the points that can be realized.

FIG. 7 is a flowchart illustrating a control process for determining the establishment of the stop condition of the immediate hot water operation mode. The control process shown in FIG. 7 is repeatedly executed by the controller 10 during the immediate hot water operation mode.

With reference to FIG. 7, the controller 10 determines whether or not the circulating flow rate Qt has decreased to a predetermined flow rate value (first flow rate value) in step 110 (hereinafter, simply referred to as “S”) 110. judge. For example, S110 is determined to be YES when the MOQ off state in which the flow rate detection value Q of the flow rate sensor 81 is lower than the minimum operating flow rate (MOQ) continues for a certain period of time (for example, 2 to 3 seconds). In this case, the minimum operating flow rate (MOQ) in S110 corresponds to the "first flow rate value".

Further, in S120, the controller 10 determines whether or not the temperature detection value (return temperature Tb) by the temperature sensor 72 has increased. For example, if the state in which the return temperature Tb rises above the determination temperature Tth1 continues for a certain period of time (for example, about 1 to 2 seconds), the rise in the return temperature Tb is detected, and S120 is determined to be YES. The determination temperature Tth1 in S120 corresponds to the "first determination temperature".

When both the decrease in the circulation flow rate and the increase in the return temperature Tb are not detected (NO determination in S110 and S120), the controller 10 determines in S130 that the stop condition (J2) is not satisfied. As a result, the operation of the circulation pump 80 is maintained, and the immediate hot water operation mode is continued.

On the other hand, when the controller 10 detects at least one of a decrease in the circulation flow rate and an increase in the return temperature Tb (when YES is determined in S110 or S120), the stop condition (J2) of the immediate hot water operation mode is satisfied by S140. Is determined. When the stop condition (J2) is satisfied, the circulation pump 80 is stopped, and in FIG. 4, a transition from the immediate hot water operation mode to the standby mode occurs. In the standby mode, the combustion mechanism 30 is also stopped.

By setting the stop condition of the immediate hot water operation mode as shown in FIG. 7, the circulation pump 80 operates in a state where the thermal bypass path in the crossover valve 200 is blocked as the fluid temperature of the immediate hot water circulation path rises. Can be prevented from doing so. As a result, it is possible to prevent the life of the circulation pump 80 from being shortened by avoiding the operation of the circulation pump 80 in a state where the immediate hot water circulation path is cut off.

In the standby mode in which the combustion mechanism 30 and the circulation pump 80 are stopped, the fluid temperature gradually decreases while the fluid in the immediate hot water circulation path stays. On the other hand, in the immediate hot water circulation path including the crossover valve 200, when the standby mode is ended and the immediate hot water operation mode is restarted, not only the temperature condition but also the state of the thermal bypass path in the crossover valve 200 It is also necessary to confirm.

FIG. 8 is a flowchart illustrating a control process for determining the establishment of the restart condition (J3) of the immediate hot water operation mode. The control process shown in FIG. 8 is repeatedly executed by the controller 10 during the standby mode.

With reference to FIG. 8, the controller 10 determines in S210 whether or not the standby mode elapsed time has reached a value corresponding to a predetermined time Tx (for example, about 10 minutes). The elapsed time of the standby state is timed when the transition from the immediate hot water operation mode to the standby mode is started.

When the standby mode elapsed time reaches Tx (when YES is determined in S210), the controller 10 determines in S220 whether or not the fluid temperature in the immediate hot water circulation path has decreased.

In S220, a YES determination is made when the detection temperature (outflow temperature Th or return temperature Tb) of the temperature sensor 71 or 72 continues to be lower than the determination temperature Tth2 for a certain period of time (for example, about 10 seconds). be able to. For example, the determination temperature Tth2 can be set by subtracting a predetermined temperature γ (for example, around γ = 5 ° C.) from the set temperature Tr in the immediate hot water operation mode (Tth2 = Tr−γ). The determination temperature Tth2 corresponds to the "second determination temperature".

The controller 10 performs processing in S270 until the elapsed time of the standby mode reaches Tx (when NO is determined in S210) or when the fluid temperature in the immediate hot water circulation path is not lowered (NO is determined in S220). Proceeding, it is determined that the restart condition (J3) is not satisfied. As a result, the standby state mode is continued, and the stoppage of the circulation pump 80 and the combustion mechanism 30 is maintained.

On the other hand, when the standby mode elapsed time reaches Tx and the fluid temperature in the immediate hot water circulation path drops (when YES is determined in S210 and S220), the controller 10 operates the circulation pump 80 by S230 and S240. It is determined whether or not the circulating flow rate Qt rises to a predetermined flow rate value (second flow rate value). For example, in S240, the flow rate detection value by the flow rate sensor 81 (or flow rate sensor 82) increased from the minimum operating flow rate (MOQ) within a certain time (for example, about 1 minute) from the operation of the circulation pump 80 (S230). Whether or not MOQ on is detected is determined.

If the MOQ on is not detected within a certain period of time, the controller 10 determines S240 as NO. In this case, S260 clears the timer value for measuring the standby mode elapsed time. Further, S270 determines that the restart condition (J3) is not satisfied, and the standby state mode is continued. As a result, S210 is maintained at the NO determination and the circulation pump 80 does not operate until Tx (minutes) elapses again. That is, Tx in S320 corresponds to the "first time".

On the other hand, when the controller 10 detects MOQ ON in response to the operation of the circulation pump 80, it determines that S240 is set to YES and S250 determines that the restart condition (J3) of the immediate hot water operation mode is satisfied. When the restart condition (J3) is satisfied, the transition from the standby mode to the immediate hot water operation mode occurs in FIG. 4, so that the operation of the circulation pump 80 from S230 is maintained.

By setting the restart condition of the immediate hot water operation mode as shown in FIG. 8, the heat-sensitive bypass path in the crossover valve 200 is blocked when the circulation pump 80 is operated in response to the decrease in the temperature of the retained fluid. Therefore, it is possible to prevent the immediate hot water operation mode in which the circulation pump 80 is continuously operated from being restarted. This can prevent the life of the circulation pump 80 from being shortened.

Further, by combining the determination of the standby mode elapsed time by S210, the number of operations of the circulation pump 80 in the state where the heat-sensitive bypass path in the crossover valve 200 is blocked can be reduced.

In the hot water supply system 1A, it is preferable to consider the influence of the heat-sensitive bypass path in the crossover valve 200 also for the abnormality diagnosis of the immediate hot water circulation path formed by the operation of the circulation pump 80.

FIG. 9 is a flowchart illustrating a control process for abnormal diagnosis of the immediate hot water circulation path executed in the immediate hot water operation mode.

With reference to FIG. 9, when the controller 10 detects the transition from the immediate hot water operation off mode shown in FIG. 4 to the immediate hot water operation off mode by S310 (when YES is determined in S310), the combustion mechanism is determined by S320. It is determined whether or not a predetermined time Tc (for example, about 5 to 6 hours) has elapsed since the previous combustion at 30 was stopped. S310 is determined to be YES only at the start of the execution period of the immediate hot water operation by a timer or the like, and is determined to be NO during the continuation of the execution period of the immediate hot water operation. When S310 or S320 is NO determination, the controller 10 does not execute the abnormality determination of the immediate hot water circulation path by S315. Tc corresponds to the "second time".

On the other hand, the controller 10 advances the process to S330 only when both S310 and S320 are YES determination, and activates the abnormality determination of the immediate hot water circulation path.

When the abnormality determination is activated, the controller 10 operates the circulation pump 80 by S330. In the operating state of the circulation pump 80, in S334, it is determined whether or not the circulation flow rate Qt is higher than the diagnostic reference flow rate Qtst. In S334, the circulating flow rate Qt based on the flow rate detection value of the flow rate sensor 81 or 82 is compared with a predetermined diagnostic reference flow rate Qtst.

If it is not detected that the circulation flow rate Qt exceeds the diagnostic reference flow rate Qtst within a certain period of time (for example, about 1 minute) from the operation (S32) of the circulation pump 80, the controller 10 determines S334 as NO. The process proceeds to S335. In S335, the abnormal count value Ncnt is increased by 1, and the increased abnormal count value Ncnt is compared with the preset determination value Nth by S336.

When the abnormality count value Nct reaches the determination value Nth (when YES is determined in S336), the controller 10 detects an abnormality in the immediate hot water circulation path by S338. In this case, the notification device 95 of FIG. 3 is used to notify the user of the occurrence of the abnormality.

On the other hand, when it is detected that the circulation flow rate Qt exceeds the diagnostic reference flow rate Qtst by the operation of the circulation pump 80 (S32) (when YES is determined in S334), or until the abnormality count value Nct reaches the determination value Nth. During the period (when NO is determined in S336), the abnormality determination of the immediate hot water circulation route is completed by S339 without detecting the abnormality. In this case, at the start of the execution period of the next immediate hot water operation, the processing after S320 is executed again in response to the determination of YES in S310.

In the abnormality diagnosis of the immediate hot water circulation path shown in FIG. 9, the abnormality diagnosis is limited to the timing when the crossover valve 200 is surely in a low temperature state and the heat-sensitive bypass path is formed by the determination of S310 and S320. Can be started. As a result, it is possible to prevent erroneous detection of an abnormality in the immediate hot water circulation route. Further, it is possible to avoid operating the circulation pump 80 unnecessarily when the heat-sensitive bypass path in the crossover valve 200 is blocked.

If no abnormality is detected by S339 based on the YES determination in S334, the abnormality count value Nct at that time can be cleared to the initial value (0). In this case, the possibility that the previously detected NO determination of S334 is a temporary phenomenon caused by clogging of foreign matter or the like is taken into consideration.

Further, the abnormality diagnosis of the immediate hot water circulation path shown in FIG. 9 may be combined with the intermittent combustion control described in FIGS. 5 and 6 and / or the mode transition condition described in FIGS. 7 and 8. However, the points that can be realized even when not combined with these are described in a confirmatory manner.

Next, a modified example of the configuration of the hot water supply device and the hot water supply system according to the present embodiment will be further described.

FIG. 10 shows a block diagram illustrating a modified example of the configuration of the hot water supply device and the hot water supply system according to the modified example of the present embodiment.

With reference to FIG. 10, the hot water supply system 1B includes a hot water supply device 100X, a low temperature water pipe 110, a high temperature water pipe 120, and a crossover valve 200. The hot water supply device 100X has a water inlet port 11 and a hot water outlet port 12 without providing a circulation port 13. Therefore, unlike the hot water supply device 100 of FIG. 1, the circulation path 28 is not provided inside the hot water supply device 100X.

The low temperature water pipe 110 that receives the low temperature water supply via the check valve 112 has a first end connected to the water inlet port 11 of the hot water supply device 100X and a second end connected to the port 202 of the crossover valve 200. Has. The connection between the crossover valve 200, the low temperature water pipe 110, the high temperature water pipe 120, and the hot water supply tap 330 is the same as that of the hot water supply system 1A shown in FIG. The circulation pump 80 is connected to the water inlet port 11.

In the hot water supply system 1B, at least a part of the low temperature water introduced from the low temperature water pipe 110 to the water inlet port 11 is heated by the heating mechanism (combustion mechanism 30 and heat exchanger 40) during the hot water supply operation. Similar to the hot water supply system 1A, the high temperature water obtained by heating is output from the hot water supply tap 330 via the hot water outlet port 12, the high temperature water pipe 120, and the crossover valve 200 (flow path Pa). As a result, the hot water supply device 100X can also execute the hot water supply operation in the same manner as the hot water supply device 100.

In the immediate hot water operation mode, the circulation pump 80 operates at the time of closing, so that the high temperature water pipe 120, the crossover valve 200 (heat sensitive bypass path Pc), and the low temperature water pipe are connected to the outside of the hot water supply device 100 from the hot water outlet port 12. A fluid path (external path) leading to the water inlet port 11 can be formed via the 110. Further, inside the hot water supply device 100X, as in FIG. 1, an internal path passing through the water inlet port 11, the water inlet path 20, the heat exchanger 40 (heating mechanism), the hot water outlet path 25, and the hot water outlet port 12 is formed. Can be done. By the internal route and the external route, an immediate hot water circulation route can be formed also in the hot water supply system 1B.

Also in the hot water supply system 1B, the flow rate sensor 81 can detect the circulation flow rate Qt in the immediate hot water circulation path, and the temperature sensor 73 can detect the return temperature Tb in the immediate hot water circulation path. Therefore, in the hot water supply system 1B as well, the intermittent combustion control described with reference to FIGS. 5 and 6 can be applied in the immediate hot water operation mode as in the hot water supply system 1A. Further, also in the hot water supply system 1B, it is possible to control the mode transition including the immediate hot water operation mode according to FIGS. 4, 7 and 8, and to diagnose the abnormality of the immediate hot water circulation path according to FIG. It is possible to do it.

The crossover valve 200 described in Patent Document 1 shown in the present embodiment is only an example of a "heat-sensitive water-stop bypass valve", and provides a heat-sensitive bypass valve whose formation and occlusion can be switched according to the temperature. As long as it has a valve, it can be used in place of the crossover valve 200 in the present embodiment.

In the hot water supply systems 1A and 1B, if the circulation pump 80 can form the same immediate hot water circulation path as described above, the circulation pump 80 is not limited to the examples in FIGS. 1 and 10, and is outside or inside the hot water supply device 100. It can be placed at any location. That is, even in a configuration in which the circulation pump 80 is not built in the hot water supply device 100, the immediate hot water operation mode described in the present embodiment can be realized by providing the controller 10 for controlling the stop and operation of the circulation pump 80. Is.

Further, in the present embodiment, an example in which the hot water supply devices 100 and 100X have a bypass configuration (bypass path 29 and flow rate adjusting valve 90) has been described, but the present invention also includes a configuration in which the bypass configuration is removed from the hot water supply devices 100 and 100X. It is possible to realize the immediate hot water operation mode described in the embodiment.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1A, 1B hot water supply system, 10 controller, 10A heat calculation unit, 10B combustion control unit, 11 water inlet port, 12 hot water outlet port, 13 circulation port, 16 memory, 17 input / output circuit, 18 electronic circuit, 19 bus, 20 water inlet path, 21,112 check valve, 22 connection point, 25 hot water outlet path, 28 circulation path, 29 bypass path, 30 combustion mechanism, 31a to 31f burner, 32 source fuel supply pipe, 33 fuel supply pipe, 34 proportional valve, 36 to 38 Electromagnetic valve, 40 heat exchanger, 71-73 temperature sensor, 80 circulation pump, 81,82 flow sensor, 90 flow control valve, 92 remote controller, 95 alarm device, 100, 100X hot water supply device, 110 low temperature water piping, 120 high temperature Water piping, 200 crossover valves, 201, 202, 203, 204 ports, 210 wax thermostats, 330 hot water taps, 331 valves, Pa, Pb flow paths, Pc heat-sensitive bypass paths, Pmax maximum number, Pmin minimum number, Pset Number command value, Q flow rate detection value, Qt circulation flow rate, Qtst diagnostic reference flow rate, Tb return temperature (temperature sensor 72), Th hot water discharge temperature (temperature sensor 71), Tr set temperature (immediate hot water operation mode), Thr control upper limit Temperature, Trl control lower limit temperature.

Claims (8)

It is a hot water supply device that discharges hot water to the hot water tap.
A heating mechanism including a combustion mechanism and
In the immediate hot water operation mode in which the circulation pump arranged inside or outside the water heater operates when the water heater is closed, the fluid heats the water heater together with an external path that bypasses the water heater outside the water heater. An internal route that forms an immediate hot water circulation route that passes through the mechanism,
A first temperature detector for detecting the fluid temperature on the upstream side of the heating mechanism of the immediate hot water circulation path, and
A second temperature detector for detecting the fluid temperature on the downstream side of the heating mechanism of the immediate hot water circulation path, and
A flow rate detector for detecting the circulation flow rate of the immediate hot water circulation path, and
The heating mechanism and the controller for controlling the circulation pump are provided.
The external path is configured to include a thermal water stop bypass valve having a path that closes when the temperature rises.
The controller
In the immediate hot water operation mode, a calorific value control unit for setting an output calorific value command value of the combustion mechanism for controlling the temperature detected value by the second temperature detector to the set temperature in the immediate hot water operation mode.
It includes a combustion control unit that controls the combustion mechanism according to the output heat quantity command value.
The output calorific value command value is limited to a range between the minimum calorific value and the maximum calorific value in the combustion state of the combustion mechanism.
In the immediate hot water operation mode, the combustion control unit is set to the output calorific value command value to the minimum calorific value value, and the temperature detection value by the second temperature detector is set to be higher than the set temperature. A hot water supply device that controls the combustion mechanism so as to alternately provide a minimum combustion state that operates according to the minimum calorific value and a combustion stop state when the temperature rises to the control upper limit temperature. The combustion control unit controls the combustion mechanism to the combustion stop state when the temperature detection value by the second temperature detector exceeds the control upper limit temperature, at least in the immediate hot water operation mode, while the combustion mechanism. When the temperature detection value by the second temperature detector drops to the control lower limit temperature set lower than the set temperature in the combustion stop state, the combustion mechanism is moved to the combustion state according to the output calorific value command value. The hot water supply device according to claim 1, which is controlled by the above. In the immediate hot water operation mode, the controller is used when the circulation flow rate is lower than the predetermined first flow rate value, or when the temperature detected by the first temperature detector is predetermined. The hot water supply device according to claim 1 or 2, wherein when the temperature rises to the determination temperature of, the immediate hot water operation mode is stopped and the standby mode in which the circulation pump and the pre-combustion mechanism are stopped is started. In the standby mode, when the temperature detected by the first or second temperature detector drops to a predetermined second determination temperature, the controller operates the circulation pump and operates the circulation pump. The hot water supply device according to claim 3, wherein when the circulation flow rate rises to a predetermined second flow rate value in this state, the standby mode is terminated and the immediate hot water operation mode is restarted. The hot water supply device according to claim 4, wherein the controller does not operate the circulation pump until the elapsed time of the standby mode reaches a predetermined first time. In the controller, the hot water tap is closed and the temperature detected by the second temperature detector drops to a predetermined mode reference temperature during the mode-on period in which the execution of the immediate hot water operation mode is permitted. Then, it is configured to execute the immediate hot water operation mode.
At the start of the mode-on period, the controller makes an abnormality diagnosis of the immediate hot water circulation path when the elapsed time from the previous combustion stop in the combustion mechanism is longer than a predetermined second time. And
In the abnormality diagnosis, any of claims 1 to 5, wherein an abnormality in the immediate hot water circulation path is detected when the circulation flow rate does not rise to a predetermined diagnostic reference flow rate in a state where the circulation pump is operated. The hot water supply device according to item 1. The controller causes an abnormality in the immediate hot water circulation path when a phenomenon occurs in which the circulation flow rate does not rise to the diagnosis reference flow rate in a state where the circulation pump is operated in a plurality of predetermined abnormality diagnoses. The hot water supply device according to claim 6, which is detected. A water heater with a water inlet port and a hot water outlet port,
A low-temperature water pipe that introduces low-temperature water into the water inlet port,
A high-temperature water pipe that connects the hot water outlet and the hot water tap,
A circulation pump arranged inside or outside the hot water supply device is provided.
The hot water supply device
A heating mechanism including a combustion mechanism and
In the immediate hot water operation mode in which the circulation pump operates when the hot water tap is closed, an immediate hot water circulation path through which the fluid passes through the heating mechanism is formed together with an external path that bypasses the hot water tap outside the hot water supply device. Internal route to do
A first temperature detector for detecting the fluid temperature on the upstream side of the heating mechanism of the immediate hot water circulation path, and
A second temperature detector for detecting the fluid temperature on the downstream side of the heating mechanism of the immediate hot water circulation path, and
A flow rate detector for detecting the circulation flow rate of the immediate hot water circulation path, and
The heating mechanism and the controller for controlling the circulation pump are provided.
The external path is configured to include a thermal water stop bypass valve having a path that closes when the temperature rises.
The controller
In the immediate hot water operation mode, a calorific value control unit for setting an output calorific value command value of the combustion mechanism for controlling the temperature detected value by the second temperature detector to the set temperature in the immediate hot water operation mode.
It includes a combustion control unit that controls the combustion mechanism according to the output heat quantity command value.
The output calorific value command value is limited to a range between the minimum calorific value and the maximum calorific value in the combustion state of the combustion mechanism.
In the immediate hot water operation mode, the combustion control unit is set to the output calorific value command value to the minimum calorific value value, and the temperature detection value by the second temperature detector is set to be higher than the set temperature. A hot water supply system that controls the combustion mechanism so as to alternately provide a minimum combustion state that operates according to the minimum calorific value and a combustion stop state when the temperature rises to the control upper limit temperature.

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