JP2020070978A - Water heater - Google Patents

Abstract

To provide a water heater which has a bypass passage and can enhance temperature stability of hot water when a heating section undergoes operation with repeated switchover between an on-state and an off-state.SOLUTION: A control device 30 which performs operation control of a heating section 4 (burner) of a water heater 1: has a function to control operate of the heating section 4 in a manner that alternately repeats an on-state and an off-state while performing temperature control of hot water; and switches the heat section 4 from the on-state to the off-state or from the off-state to the on-state in accordance with a detection value of a temperature sensor 26 indicating a temperature of hot water discharged from a heat exchanger.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a hot water supply device.

  In the hot water supply device, it has been conventionally proposed to perform an intermittent operation of the heating unit when the required heat amount of the heating unit configured by a burner or the like (the required heat amount for controlling the hot water temperature to the target temperature) is low. There is. For example, in Patent Document 1, when the required heat load (required heat amount) is small, the burner is intermittently burned with a cycle corresponding to the required heat load and an ignition / extinguishing time ratio (a ratio of the ignition time and the extinguishing time). Those who drive are proposed.

  Further, for example, in Patent Document 2, the burner is determined by determining the ratio of the combustion time and the extinguishing time in each cycle of the intermittent combustion operation of the burner according to the average value of the required heat amount of the burner in the immediately preceding cycle. It has been proposed to perform intermittent combustion operation.

  Further, for example, Patent Document 3 proposes that the burner performs intermittent combustion operation by setting the combustion time and the extinguishing time in the intermittent combustion operation of the burner according to the required heat quantity.

  Further, for example, Patent Document 4 proposes that the combustion period and the non-combustion period of the combustion mechanism are switched according to the comparison between the required heat generation amount of the combustion mechanism and the estimated heat generation amount.

JP 62-22956 A Japanese Patent Publication No. 3-28663 JP-A-6-249501 JP, 2008-100810, A

  By the way, in the hot water supply apparatus, the temperature of the hot water discharged from the heat exchanger heated by the heating unit (hereinafter, also referred to as heat exchanger hot water temperature) changes from the ON state (operating state) to the OFF state (operating state). Even if it is switched to the (stop state), it does not immediately start to drop in response to the switching, and the drop of the heat exchanger outlet hot water temperature generally starts after the switching of the heating part to the off state.

  Further, even if the heating part is switched from the off state to the on state, the heat exchanger outlet hot water temperature does not immediately start to rise in response to the switching. It starts with a delay from the time when the parts are switched to the ON state.

  In addition, the response characteristics of the change in the hot water temperature of the heat exchanger depending on the switching from one of the ON state and the OFF state of the heating unit to the other depend on various factors such as the model of the water heater, the installation environment, the outside air temperature, and the incoming water temperature. Susceptible to.

  Therefore, as seen in Patent Documents 1 to 3, the burner combustion time (heating section on time), fire extinguishing time (heating section off time), or the ratio thereof is adjusted according to the required heat quantity. As described in the above-mentioned technology or Patent Document 4, depending on the comparison between the required amount of heat generation and the estimated amount of heat generation, the combustion period (heating period ON period) and non-combustion period (heating unit OFF) of the combustion mechanism are determined. In the technique of switching the period, the fluctuation range of the hot water supply temperature may become large.

  In particular, in a hot water supply device (for example, a hot water supply device as seen in Patent Document 4) having a bypass passage for bypassing hot water for hot water supply from a water supply passage on the inlet side of the heat exchanger to a hot water supply passage on the outlet side, the water is heated by the heat exchanger. The temperature of the hot water is higher than the actual hot water temperature on the downstream side of the hot water supply passage (downstream from the connection between the hot water supply passage and the bypass passage). The change of the heat exchanger hot water temperature due to the switching is likely to occur remarkably. As a result, the fluctuation range of the actual hot water supply temperature tends to be large.

  In addition, as a mode of switching on / off of the heating unit, for example, switching of the heating unit from the ON state to the OFF state is performed when the temperature detected by the temperature sensor that detects the hot water supply temperature becomes higher than a predetermined temperature. However, it is conceivable that the switching from the off state to the on state is executed when the temperature detected by the temperature sensor becomes lower than the predetermined temperature.

  However, in the hot water supply device including the bypass passage, the temperature sensor for detecting the hot water supply temperature is located on the downstream side of the joining portion between the hot water supply passage connected to the outlet of the heat exchanger and the bypass passage. It takes a time depending on the flow rate of the water until the hot water flowing out reaches the temperature sensor. In particular, the intermittent operation of the heating unit is performed in a situation where the water flow rate is low, so that the time required for the hot water flowing out of the heat exchanger to reach the temperature sensor becomes long. For this reason, the timing of switching the heating unit on and off tends to be delayed, and the fluctuation range of the actual hot water supply temperature tends to be large.

  The present invention has been made in view of such a background, and in a hot water supply device including a bypass passage, it is possible to increase the stability of the hot water supply temperature during operation in which the heating section is repeatedly switched between the ON state and the OFF state. The purpose is to provide a device.

In order to achieve the above object, the hot water supply device of the present invention has a heating unit, a heat exchanger heated by the heating unit, and a water supply passage connected to an inlet and an outlet of the heat exchanger, respectively. A hot water supply passage, a bypass passage that connects the water supply passage to the hot water supply passage so that water can be passed from the water supply passage to the hot water supply passage by bypassing the heat exchanger, and an outflow from the heat exchanger to the hot water supply passage. The temperature of the hot water flowing to the downstream side of the connection portion of the hot water supply passage with the bypass passage by performing the operation control of the first temperature sensor detecting the hot water temperature of the heat exchanger, which is the temperature of the hot water. And a controller having a function of controlling the hot water supply temperature that is
The control device has a function of controlling the operation of the heating unit so as to alternately repeat the ON state and the OFF state of the heating unit when controlling the hot water supply temperature, and from the ON state of the heating unit to the OFF state. And at least one of the switching of the heating unit from the OFF state to the ON state are configured to be performed in accordance with the detected value of the heat exchanger outlet hot water temperature by the first temperature sensor. (1st invention).

  In the present invention, the "ON state" of the heating unit means a state in which the heating unit is activated (a state in which the heating unit heats the heat exchanger), and the "OFF state" of the heating unit means the heating unit. Means the state where the operation of is stopped.

  According to the first aspect of the present invention, at least one of the switching of the heating unit from the ON state to the OFF state and the switching of the heating unit from the OFF state to the ON state is performed by detecting the heat exchanger outlet hot water temperature. Since it is executed according to the value, the heat exchanger hot water temperature rises excessively immediately after the heating part is switched from the on state to the off state, or immediately after the heating part is switched from the off state to the on state. The switching can be performed so as to prevent the outlet hot water temperature from dropping too much.

  Consequently, it becomes possible to enhance the stability of the hot water supply temperature during the operation in which the heating section is repeatedly switched between the ON state and the OFF state.

  More specifically, in the first aspect of the present invention, the control device may switch the heating unit from an ON state to an OFF state such that a detected value of the heat exchanger outlet hot water temperature is higher than a predetermined temperature. When it is detected, it is preferably configured to be executed in response to the detection (second invention).

  According to this, it is possible to effectively prevent the hot water outlet temperature of the heat exchanger from becoming too high immediately after the heating unit is switched from the ON state to the OFF state. Consequently, it becomes possible to effectively prevent the actual hot water supply temperature from rising too high immediately after the heating section is switched from the ON state to the OFF state.

  In the second aspect of the invention, a second temperature sensor that detects the hot water supply temperature is provided, and the control device switches the heating unit from an on state to an off state by the second temperature sensor. It is preferable that the detection value is set to be higher than a target value of the hot water supply temperature by a predetermined value or more as a necessary condition (third invention).

  According to this, when the actual hot water supply temperature is higher than the target value by a predetermined value or more, that is, when the amount of heat generated by the heating unit is excessive, the heating unit is turned off. It is possible to effectively prevent the temperature from becoming higher than the target value.

  In the said 1st-3rd invention, the said control apparatus detects the fall start of the detected value of the said heat exchanger tapped water temperature after switching from the ON state of the said heating part to an OFF state, in the said detection. Accordingly, it is preferable that the heating section is configured to be switched from the off state to the on state (the fourth invention).

  According to this, the heating unit can be switched from the OFF state to the ON state in a situation in which the hot water outlet temperature of the heat exchanger does not become too low after the switching of the heating unit from the ON state to the OFF state. As a result, it is possible to effectively prevent the actual hot water supply temperature from becoming too low.

The figure which shows the structure of the water heater of embodiment of this invention. 3 is a flowchart showing a control process of the control device shown in FIG. 1.

  An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Referring to FIG. 1, hot water supply device 1 of the present embodiment includes heat source device 2 installed outdoors. A combustion casing 3 having a combustion chamber 3a formed therein is mounted on the heat source device 2, and a burner 4 as a heating unit is arranged below the combustion chamber 3a in the combustion casing 3.

  The burner 4 is a gas burner in the present embodiment, and is composed of a plurality of burners capable of separately performing combustion operation, for example, three burners of a first burner 4a, a second burner 4b, and a third burner 4c. In the illustrated example, the combustion areas of the first burner 4a, the second burner 4b, and the third burner 4c are different from each other, but the combustion areas of the two or more burners forming the burner 4 are different from each other. May be the same as each other.

  In the heat source device 2, as a component for supplying the fuel gas to the burner 4, a main gas supply path 5 to which the fuel gas is supplied from a gas supply source (not shown) and a branch 3 from the main gas supply path 5 are provided. One sub gas supply path 6a, 6b, 6c is provided. Each of the sub gas supply passages 6a, 6b, 6c is supplied to the combustion chamber 3a from the outside of the combustion casing 3 so that the fuel gas can be separately supplied to each of the first burner 4a, the second burner 4b and the third burner 4c. Has been introduced.

  The main gas supply path 5 is provided with a main valve 7 constituted by an electromagnetic valve for opening and closing the main gas supply path 5, and a gas amount adjusting valve 8 for adjusting the supply amount of the fuel gas to the burner 4. The gas amount adjusting valve 8 is composed of, for example, a proportional valve, and can supply the burner 4 with a flow rate of combustion gas according to the energizing current. Further, switching valves 9a, 9b, 9c, which are electromagnetic valves that open and close each of the sub-gas supply paths 6a, 6b, 6c, are provided respectively.

  Therefore, during the combustion operation of the burner 4, by switching the combination of the open / close states of the switching valves 9a, 9b, 9c with the main valve 7 opened, the combustion heat quantity of the entire burner 4 can be adjusted in a wide range. It is possible to change.

  In this case, the minimum combustion heat amount of the burner 4 is the predetermined one switching valve among the switching valves 9a, 9b, 9c, for example, in the state where only the switching valve 9a corresponding to the first burner 4a is opened, This is realized by performing the combustion operation of only the first burner 4a with the lower limit fuel supply amount. Further, the maximum combustion heat amount of the burner 4 is the fuel supply amount with the upper limit of all the combustion operations of the first to third burners 4a, 4b, 4c with all the switching valves 9a, 9b, 9c open. It is realized by doing in. Then, by changing the switching valve of the switching valves 9a, 9b, 9c to be opened and the fuel supply amount to the burner 4, the total combustion heat amount of the burner 4 is set to the minimum combustion heat amount and the maximum combustion heat amount. It is possible to change between and.

  Further, the heat source device 2 is equipped with a combustion fan 10 which is rotationally driven by an electric motor (not shown) as an air blower for supplying combustion air to the burner 4. This combustion fan 10 sucks outside air as combustion air by its rotational drive and supplies the sucked combustion air to the burner 4 (first to third burners 4a, 4b, 4c as a whole). It is attached to the bottom of 3. The amount of combustion air supplied to the burner 4 can be changed by variably controlling the number of rotations (rotational speed) of the combustion fan 10.

  An exhaust port 3b for exhausting the combustion exhaust gas of the burner 4 from the combustion chamber 3a is provided in the upper part of the combustion casing 3. The exhaust port 3b communicates with the outside of the heat source device 2.

  Further, by operating an igniter (not shown) mounted on the heat source unit 2 in the combustion casing 3, an ignition electrode 12 for generating a spark discharge for igniting the burner 4 and the presence or absence of combustion flame of the burner 4 are detected. The flame detection sensor 13 for doing so is attached. The flame detection sensor 13 is composed of, for example, a frame rod, a thermocouple, or the like.

  The heat source unit 2 is provided with not only the above-described configuration related to the combustion operation of the burner 4 but also a configuration related to passing hot water for hot water supply. Specifically, a heat exchanger 21 that is heated by the combustion heat of the burner 4 is arranged above the burner 4 in the combustion chamber 3 a inside the combustion casing 3. A water passage 22 that allows water to pass through the heat exchanger 21 is provided.

  The water passage 22 is connected to an inlet of the water passage 21a of the heat exchanger 21, and is connected to a water supply passage 22a to which hot water is supplied from a water supply source (not shown) and an outlet of the water passage 21a of the heat exchanger 21. A hot water supply passage 22b, and a bypass passage 22c connecting the water supply passage 22a to the hot water supply passage 22b so that the heat exchanger 21 can be bypassed from the water supply passage 22a and the hot water supply water can be circulated to the hot water supply passage 22b. Further, the downstream side of the hot water supply passage 22b is arranged so as to be able to supply hot water for hot water supply to an unillustrated hot water supply target portion (calan or the like) such as a kitchen, a washroom, and a bathroom.

  Therefore, during the combustion operation of the burner 4, the hot water supply water heated from the water supply passage 22a via the heat exchanger 21 and the hot water supply water passing from the water supply passage 22a to the bypass passage 22c are joined together in the hot water supply passage 22b. The water passage 22 is configured so that the hot water supplied can be supplied from the hot water supply passage 22b to the hot water supply target portion.

  In the water supply passage 22a, an electrically operated water amount control valve 23 for adjusting the water supply flow amount which is the water flow amount of the water supply passage 22a, and a water amount sensor 24 for detecting the water supply flow amount are provided at the branch portion of the bypass passage 22c. Is installed upstream. Further, in the hot water supply passage 22b, a temperature sensor 25 that detects a hot water supply temperature that is the temperature of the hot water supply water supplied to the hot water supply target portion (the temperature of the hot water flowing downstream from the connection portion between the bypass passage 22c and the hot water supply passage 22b). And a temperature sensor 26 for detecting the hot water outlet temperature of the heat exchanger, which is the temperature of the hot water for hot water supply flowing from the heat exchanger 21 to the hot water supply passage 22b. The temperature sensors 25 and 26 correspond to the second temperature sensor and the first temperature sensor in the present invention, respectively.

  The control valve for adjusting the ratio (so-called bypass ratio) between the flow rate of the hot water supply water passing through the bypass passage 22c and the flow rate of the hot water supply water passing through the water passage 21a of the heat exchanger 21 is the bypass passage 22c and the water supply. It may be provided at a connection portion with the passage 22a or the hot water supply passage 22b, or in the middle of the bypass passage 22c.

  Next, a configuration related to the operation control of the hot water supply device 1 (including the combustion operation control of the burner 4) will be described. The hot water supply device 1 includes a control device 30 that controls the operation of the hot water supply device 1 and a remote controller 40 for operating the hot water supply device 1.

  The remote controller 40 is a terminal device installed in a kitchen, a bathroom, etc., and is provided with a plurality of operation switches (not shown), a display device, and the like. By operating the operation switch of the remote controller 40, it is possible to perform operations such as turning on / off the hot water supply operation of the hot water supply device 1 and setting a target value of the hot water supply temperature (hereinafter referred to as the target hot water supply temperature). The hot water supply device 1 may include a plurality of remote controllers including the remote controller 40.

  The control device 30 is composed of one or more electronic circuit units including a microcomputer, a memory, an interface circuit and the like (not shown), and is mounted on the heat source device 2. The control device 30 can communicate with the remote controller 40 by wire or wirelessly, and operation information of the remote controller 40 (ON / OFF signal for hot water supply operation, target hot water temperature setting value, etc.) is input by this communication. It Further, the control device 30 receives detection signals of the respective sensors (including the flame detection sensor 13, the water amount sensor 24, and the temperature sensors 25 and 26) provided in the hot water supply device 1.

  The control device 30 has a function of controlling the combustion operation of the burner 4 as a function realized by one or both of the installed hardware configuration and the program (software configuration).

  Next, the operation of the hot water supply device 1 of the present embodiment will be described. First, the operation of the hot water supply device 1 during a normal hot water supply operation will be described. In addition, the normal hot water supply operation specifically means a hot water supply operation in which heating of the water through the combustion operation of the burner 4 is continuously performed.

  When the water passage in the water passage 22 is started due to the opening of the Karan at the downstream end of the hot water supply passage 22b or the like, the control device 30 detects the start of the water passage based on the detection signal of the water amount sensor 24. At this time, the control device 30 operates the combustion fan 10 at a predetermined rotation speed for ignition of the burner 4 (thus, supplies combustion air with an air volume for ignition to the burner 4), and controls the main valve 7 and A predetermined switching valve (for example, the switching valve 9a) among the switching valves 9a to 9c is controlled to be opened, and a proportional valve current having a predetermined value for ignition is supplied to the gas amount adjusting valve 8 (therefore, the first burner). The first burner 4a is ignited by performing the operation of supplying an ignition gas amount of fuel gas to 4a) and the operation of an igniter (not shown) (thus generating a spark discharge at the ignition electrode 12). To do. As a result, the combustion operation of the first burner 4a is started.

  In the ignition process of the burner 4, a burner different from the first burner 4a (second burner 4b or third burner 4c) is ignited, or two of the first to third burners 4a, 4b, 4c are used. The above burners may be ignited.

  When the combustion operation of the burner 4 is started as described above, the controller 30 burns the burner 4 so that the hot water supply temperature detected by the temperature sensor 25 matches or substantially matches the target hot water supply temperature set by the remote controller 40. Control the amount of heat.

  Specifically, the operation control unit 31 sets a required heat amount (a required value of the combustion heat amount of the burner 4) for making the hot water supply temperature detected by the temperature sensor 25 match or substantially match the target hot water supply temperature with a predetermined control processing cycle. Will be decided sequentially.

  The required heat quantity is a predetermined calculation based on the target hot water supply temperature and the detection data of the temperature sensors 25 and 26 and the water quantity sensor 24 (each detected value of the hot water supply temperature, the heat exchanger outlet hot water temperature and the water supply flow rate). It is sequentially determined using a formula or map data. Further, control device 30 sets an upper limit value of the water supply flow rate according to the target hot water supply temperature and the like.

  Then, the control device 30 controls the combustion operation of the burner 4 according to the determined required heat amount for each control processing cycle. In this case, the control device 30 selects one or more burners of the first to third burners 4a, 4b, 4c for performing the combustion operation according to the required heat amount, and the actual combustion heat amount of the burner 4. The target combustion heat quantity that is the target value of is determined within a range between a predetermined lower limit value and a predetermined upper limit value. Then, the control device 30 controls the opening of one or more switching valves 9a to 9c so as to supply the fuel gas to the selected burner, and rotates the combustion fan 10 so as to realize the determined target combustion heat quantity. The number and the energizing current of the gas amount adjusting valve 8 are controlled. Further, when the water supply flow rate detected by the water amount sensor 24 exceeds the set upper limit value, the control device 30 controls the water amount control valve 23 so as to limit the water supply passage to the upper limit value. If the heat source device 2 includes a control valve for adjusting the bypass ratio, the target value of the bypass ratio is also determined, and the control valve is controlled according to the target value.

  The normal hot water supply operation of the hot water supply device 1 is performed as described above. Thus, basically, the combustion operation of the burner 4 is controlled so that the hot water supply temperature detected by the temperature sensor 25 can be made to match or substantially match the target hot water supply temperature.

  On the other hand, when the target hot water supply temperature is set to a low temperature, the difference between the target hot water supply temperature and the water entering temperature of the water supply passage 22a may be small. In this case, if the combustion operation of the burner 4 is continuously performed, the actual hot water supply temperature rises to a temperature higher than the target hot water supply temperature even if the combustion heat amount of the burner 4 is maintained at the lower limit value. There are cases. Further, when the control valve for adjusting the bypass ratio is provided, even if the ratio of the water flow rate of the bypass passage 22c is maximized and the combustion heat amount of the burner 4 is maintained at the lower limit value, the actual hot water temperature May rise to a temperature higher than the target hot water supply temperature. Therefore, in the present embodiment, the control device 30 causes the combustion operation of the burner 4 to be appropriately and intermittently performed by executing the processing shown in the flowchart of FIG. 2 during the hot water supply operation.

  Specifically, in STEP 1, control device 30 determines whether or not target hot water supply temperature To_cmd is set to a low temperature (for example, 32 ° C.), and if this determination result is negative, then from STEP 1 Continue processing. In STEP 1, it may be determined whether target hot water supply temperature To_cmd is equal to or lower than a predetermined value. Alternatively, instead of determining whether or not the target hot water supply temperature To_cmd is low, for example, whether or not the target combustion heat amount of the burner 4 is the lower limit value (or whether or not it is a low heat amount below a predetermined value) is determined. You may make a judgment.

  If the determination result in STEP1 is affirmative, the control device 30 further determines in STEP2 that the difference (= To-To_cmd) between the detected value of the hot water supply temperature To by the temperature sensor 25 and the target hot water supply temperature To_cmd is a predetermined value. It is determined whether or not dT0 (for example, 1 ° C.) or higher, in other words, whether or not the detected value of the hot water supply temperature To is higher than the target hot water supply temperature To_cmd by a predetermined value dT0 or higher. Then, if this determination result is negative, the control device 30 repeats the processing from STEP1.

  If the determination result in STEP2 is affirmative, the control device 30 further determines in STEP3 that the detected value of the heat exchanger outlet hot water temperature Th by the temperature sensor 26 is higher than the predetermined value Th0 (for example, 60 ° C.). It is determined whether or not the temperature is rising, and if the result of this determination is negative, the control device 30 repeats the processing from STEP1.

  Here, according to various experiments and studies by the inventor of the present application, when the target hot water supply temperature To_cmd is low (or when the target combustion heat amount of the burner 4 is low), when the heat exchanger outlet hot water temperature Th becomes too high, the burner 4 Even if the combustion operation of No. 1 is stopped, the hot water supply temperature is likely to rise further after that, and the fluctuation range of the actual hot water supply temperature To is likely to be large.

  Therefore, when the detected value of the heat exchanger outlet hot water temperature Th becomes higher than the predetermined value Th0 and the determination result of STEP3 becomes affirmative, the control device 30 causes the burner 4 to perform the combustion operation in STEP4. The on state as the running state is switched to the off state as the fire extinguishing state. In this case, the control device 30 extinguishes the burner 4 by controlling all the switching valves 9a, 9b, 9c (or the main valve 7) in the closed state.

  It should be noted that the predetermined value Th0 in STEP3 that defines the timing for switching the burner 4 to the off state is set in advance by an experiment so that the heat exchanger outlet hot water temperature Th does not rise excessively after the burner 4 is switched to the off state. It is set based on the above.

  Next, in STEP 5, control device 30 monitors whether or not the detected value of heat exchanger outlet hot water temperature Th has started to decrease until the decrease starts.

  In this case, the control device 30 calculates, for example, every time a predetermined time interval elapses (for example, every one second), an average value of the detected values of the heat exchanger outlet hot water temperature Th within the time interval, and the latest value is calculated. When the average value becomes smaller than the average value in the previous time interval, it is detected that the detection of the heat exchanger outlet hot water temperature Th has started to decrease.

  The method of detecting the start of the decrease in the detected value of the heat exchanger outlet hot water temperature Th is not limited to the above method. For example, instead of the average value of the detected values of the heat exchanger outlet hot water temperature Th within each time interval, the median value of the detected values of the heat exchanger outlet hot water temperature Th within the time interval may be used. Further, for example, based on the average value of the temporal change rate (differential value) of the detected value of the heat exchanger outlet hot water temperature Th in each time interval, the start of the fall of the detected value of the heat exchanger outlet hot water temperature Th is detected. It is also possible to do so.

  When the start of the decrease of the detected value of the heat exchanger hot water temperature Th is detected and the determination result of STEP 5 is affirmative, the control device 30 switches the burner 4 from the OFF state to the ON state in STEP 6. , The combustion operation of the burner 4 is restarted.

  In this case, the control device 30 controls the opening of the main valve 7 and the switching valve 9a as well as the combustion fan 10, the gas amount adjusting valve, as in the case of the ignition process of the burner 4 at the start of the water passage of the water passage 22. The first burner 4a is ignited by operating 8 and the igniter. Then, after the ignition of the first burner 4a, the first burner 4a is burned with the lower limit value of the combustion heat amount.

  Further, the control device 30 starts the combustion operation of the burner 4 in STEP6, and then executes the processing from STEP1 again. Note that the control device 30 ends the intermittent operation in which the burner 4 is repeatedly turned on and off when the water supply flow rate detected by the water amount sensor 24 reaches or exceeds a predetermined amount.

  By executing the processing of the flowchart of FIG. 2 as described above, when the target hot water supply temperature To_cmd is low (or when the combustion heat amount of the burner 4 is low), the detected value of the hot water supply temperature To is higher than the target hot water supply temperature To_cmd. When the value dT0 or more increases and the detected value of the heat exchanger outlet hot water temperature Th becomes higher than the predetermined value Th0, the burner 4 is switched from the on state to the off state. Then, when the detected value of the heat exchanger outlet hot water temperature Th starts decreasing, the combustion operation of the burner 4 is restarted. As a result, the burner 4 is repeatedly turned on and off (burning operation of the burner 4 is intermittently performed) so that the heat exchanger outlet hot water temperature Th remains at or below the predetermined value Th0. As a result, it is possible to effectively prevent the actual hot water supply temperature To from largely fluctuating up and down with respect to the target hot water supply temperature To_cmd, and improve the stability of the hot water supply temperature To.

  The present invention is not limited to the embodiment described above, and other embodiments can be adopted. For example, in the intermittent operation in which the burner 4 is repeatedly turned on and off, the time width for keeping the burner 4 in the on state or the time width for keeping it in the off state may be set according to the heat exchanger outlet hot water temperature Th. It is also possible to set one of the time widths for maintaining the burner 4 in the ON state and the time width for maintaining the burner 4 to the predetermined value.

  Further, in the above-described embodiment, the predetermined value Th0 in STEP3 that defines the timing for switching the burner 4 from the ON state to the OFF state is set to a constant value, but the predetermined value Th0 is variable according to the target hot water supply temperature To_cmd, for example. Or may be variably set according to the target hot water supply temperature To_cmd and the water inlet temperature (detected value or estimated value) of the water supply passage 22a. For example, the predetermined value Th0 may be set higher as the target hot water supply temperature To_cmd is higher, or the predetermined value Th0 may be set lower as the difference between the target hot water supply temperature To_cmd and the incoming water temperature is smaller.

  Further, in the above-described embodiment, the burner 4 is composed of a plurality of burners (first to third burners 4a, 4b, 4c) capable of separately performing combustion operation, but the burner 4 is composed of a single burner. It may have been done. The burner 4 is not limited to a gas burner, but may be a burner that burns liquid fuel such as kerosene.

  Further, the heating unit of the hot water supply device of the present invention is not limited to the combustion type, and may be one that converts electric energy into heat energy.

DESCRIPTION OF SYMBOLS 1 ... Hot water supply device, 4 ... Burner (heating part), 21 ... Heat exchanger, 22a ... Water supply path, 22b ... Hot water supply path, 22c ... Bypass path, 25 ... Temperature sensor (2nd temperature sensor), 26 ... Temperature sensor ( First temperature sensor), 30 ... Control device.

Claims (4)

A heating unit, a heat exchanger heated by the heating unit, a water supply passage and a hot water supply passage respectively connected to an inlet and an outlet of the heat exchanger, and the heat exchanger from the water supply passage to the hot water supply passage. A bypass passage for connecting the water supply passage to the hot water supply passage so as to allow water to flow by bypassing, and a heat exchanger outlet hot water temperature that is the temperature of hot water flowing from the heat exchanger to the hot water supply passage Hot water supply provided with a temperature sensor and a control device having a function of controlling the hot water supply temperature, which is the temperature of hot water flowing downstream of the connection part of the hot water supply path with the bypass path, by controlling the operation of the heating section. A device,
The control device has a function of controlling the operation of the heating unit so as to alternately repeat the ON state and the OFF state of the heating unit when controlling the hot water supply temperature, and from the ON state of the heating unit to the OFF state. And at least one of the switching of the heating unit from the OFF state to the ON state are configured to be performed in accordance with the detected value of the heat exchanger outlet hot water temperature by the first temperature sensor. Hot water supply device characterized in that. The water heater according to claim 1,
When it is detected that the detected value of the heat exchanger outlet hot water temperature is higher than a predetermined temperature, the control device switches the heating part from the on state to the off state in response to the detection. A hot water supply device configured to operate. The water heater according to claim 2,
A second temperature sensor for detecting the hot water supply temperature is provided, and the control device switches the heating unit from an on state to an off state when the detected value of the hot water supply temperature by the second temperature sensor is the hot water supply temperature. The hot water supply device is configured to be executed as a necessary condition that the target value is higher than the target value by a predetermined value or more. The water heater according to any one of claims 1 to 3,
The control device, after switching from the ON state of the heating unit to the OFF state, when the decrease start of the detected value of the heat exchanger outlet hot water temperature is detected, from the OFF state of the heating unit according to the detection. A hot water supply device characterized by being configured to perform switching to an ON state.