Liquid heating device

Abstract

To suppress erroneous detection of liquid leakage in a heating path in a liquid heating device.SOLUTION: At an inflow side of a heating path where a liquid flowing in from an upstream side is heated by heating sections 12 and 18 and then flows out to a downstream side, an inflow-side on-off valve 20 is provided and at an outflow side, an outflow-side on-off valve 25 is provided. A pressure sensor 23 capable of detecting a pressure of the liquid is provided between both the on-off valves in the heating path. Further, in a state where the heating path is closed by closing the outflow-side on-off valve and the inflow-side on-off valve, a control section 29 controls execution of liquid leakage detection processing for detecting liquid leakage in the heating path based on a reduction situation of the detected pressure of the pressure sensor. After a predetermined temperature stabilization condition on which it is estimated that a temperature of the liquid in the heating path is reduced and stabilized is established, the control section executes the liquid leakage detection processing. Therefore, an influence of a temperature change to be exerted upon the pressure of the liquid in the closed heating path can be reduced, such that erroneous detection of the liquid leakage in the heating path caused by the temperature reduction can be suppressed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a liquid heating device having a heating path through which liquid flowing in from upstream is heated in a heating section and then flows out downstream, and more particularly to a technique for detecting liquid leakage in the heating path. [Background technology]

[0002] A liquid heating device that heats a liquid is known that has a heating path through which the liquid to be heated flows, in which liquid flowing in from upstream is heated in a heating section such as a heat exchanger and then flows out downstream.

[0003] In such liquid heating devices, it has been proposed to install an on-off valve on both the inlet and outlet sides of the heating path, and to install a pressure sensor in the heating path between the two on-off valves to detect the pressure of the liquid; both on-off valves are then closed to seal the heating path, and liquid leakage in the heating path is detected based on a decrease in the pressure detected by the pressure sensor (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-174458 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in liquid heating devices that detect liquid leakage in the heating path as described above, the pressure of the liquid in the sealed heating path is easily affected by temperature changes, and there is a problem that a liquid leakage may be erroneously detected when no liquid leakage actually occurs due to a decrease in pressure caused by a drop in temperature.

[0006] The present invention has been made in response to the above-mentioned problems in the conventional technology, and aims to provide a technology that can suppress erroneous detection of liquid leakage in a heating path in a liquid heating device. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the liquid heating device of the present invention adopts the following configuration. In a liquid heating device having a heating path through which liquid flowing in from an upstream side is heated in a heating section and then flows out downstream, an inlet side opening / closing valve that opens and closes the inlet side of the heating path; an outlet side opening / closing valve that opens and closes the outlet side of the heating path; a pressure sensor provided between the inlet side on-off valve and the outlet side on-off valve in the heating path and capable of detecting a pressure of the liquid; a control unit that controls execution of a liquid leakage detection process to detect liquid leakage in the heating path based on a decrease in the pressure detected by the pressure sensor after sealing the heating path by closing the outlet-side on-off valve and the inlet-side on-off valve; Equipped with The control unit executes the liquid leakage detection process after a predetermined temperature stabilization condition is satisfied under which it is assumed that the temperature of the liquid in the heating path has been reduced and stabilized. It is characterized by:

[0008] In the liquid heating device of the present invention, by waiting until the temperature stabilization condition is met before executing the liquid leakage detection process, the effect of temperature changes on the pressure of the liquid in the sealed heating path can be reduced compared to when the temperature stabilization condition is not set, thereby making it possible to suppress erroneous detection of liquid leakage in the heating path due to a drop in temperature.

[0009] The liquid heating device of the present invention described above may be configured as follows: First, the heating section stops heating when the flow rate of hot and cold water in the heating path falls below a predetermined flow rate. The temperature stabilization condition is that a predetermined stabilization time has elapsed with the flow of liquid in the heating path stopped.

[0010] In a liquid heating device configured in this manner, when the flow of liquid in the heating path stops, heating in the heating section stops and heated liquid does not flow into the heating path from elsewhere.Therefore, the temperature of the liquid in the heating path decreases and stabilizes through heat dissipation until the stabilization time has elapsed in this state, thereby reducing erroneous detections in the liquid leakage detection process that is subsequently performed.

[0011] Furthermore, the temperature stabilization condition in the liquid heating device of the present invention described above may be a stabilization time that has elapsed in a state in which the flow of liquid in the heating path has stopped due to the closure of the outlet-side on-off valve.

[0012] In a liquid heating device configured as described above, when the outlet valve is closed, the outflow of liquid from the heating path is blocked, and the flow of liquid in the heating path stops. Then, when the stable time has elapsed, the outlet valve is already closed, and the heating path can be sealed simply by closing the inlet valve, so that the liquid leakage detection process can be performed quickly.

[0013] In the liquid heating device of the present invention, when the flow of liquid in the heating path has stopped and a predetermined advance stabilization time that is shorter than the stabilization time has elapsed, the liquid leakage detection process is executed ahead of schedule, and if no liquid leakage in the heating path is detected, the liquid leakage detection process after the stabilization time has elapsed is omitted, whereas if there is a possibility of liquid leakage in the heating path, the heating path may be temporarily unsealed and the liquid leakage detection process may be executed again after the stabilization time has elapsed.

[0014] In the liquid heating device configured in this way, if no leakage is detected in the liquid leakage detection process executed ahead of schedule, the subsequent liquid leakage detection processes can be omitted, so that normal use can be resumed early even if use is restricted until the completion of the liquid leakage detection process. On the other hand, even if there is a possibility of leakage, it is suspected to be due to a drop in temperature, so that erroneous detection can be suppressed by waiting for the stabilization time to elapse and executing the liquid leakage detection process again.

[0015] In such a liquid heating device of the present invention, a temperature sensor is provided that can detect the temperature of the liquid in the heating path, and if the detected temperature of the temperature sensor fluctuates beyond a predetermined allowable value during execution of the liquid leakage detection process even when the temperature stability condition is met, the liquid leakage detection process may be interrupted.

[0016] In a liquid heating device configured in this manner, it is presumed that the temperature of the liquid in the heating path has stabilized when the temperature stabilization condition is met, but if the temperature is not yet stable when actually checked with the temperature sensor, the pressure of the liquid in the heating path will be affected by temperature changes, so it is possible to suppress erroneous detection by interrupting the liquid leakage detection process that is currently being performed. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is an explanatory diagram showing the overall configuration of a linked hot water supply system 1 of the present embodiment as an example of a liquid heating device. [Diagram 2] 1 is an explanatory diagram showing the configuration of a water heater 10 of the present embodiment. [Diagram 3] 13 is a flowchart of a water leakage detection control process executed by a controller 29 of the “slave” water heater 10 of the present embodiment. [Figure 4] 5 is a flowchart of a stable temperature condition monitoring process executed in the water leakage detection control process according to the embodiment; [Diagram 5] 4 is a flowchart showing most of the water leakage detection process of the present embodiment that is executed in the water leakage detection control process. [Figure 6] 13 is a flowchart of the remaining part of the water leakage detection process of the present embodiment, which is executed in the water leakage detection control process. [Figure 7] 4 is a flowchart of a precedent water leakage detection process according to the present embodiment, which is executed in the water leakage detection control process. [Figure 8] FIG. 13 is an explanatory diagram showing the configuration of another example including a hot water storage tank 30. [Figure 9] 13 is an explanatory diagram showing the configuration of another example including a filtration unit 40. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 1 is an explanatory diagram showing the overall configuration of a linked hot water supply system 1 of this embodiment as an example of a liquid heating device. The linked hot water supply system 1 shown in the figure has two linked hot water heaters 10 that burn fuel gas to generate hot water, and includes a gas pipe 2 that supplies fuel gas to each hot water heater 10, a water supply pipe 3 that supplies clean water to each hot water heater 10, and a hot water outlet pipe 4 that guides hot water heated by each hot water heater 10.

[0019] Details of the water heater 10 will be described later using another drawing, but the two water heaters 10a, 10b are basically of the same specifications, can be operated in the same way, and are connected in parallel. That is, a gas pipe 2 that supplies fuel gas branches off and is connected to each of the two water heaters 10a, 10b, and similarly, a water supply pipe 3 that supplies clean water branches off and is connected to each of the two water heaters 10a, 10b. In addition, the hot water outlet pipes 4 extended from each of the two water heaters 10a, 10b merge into one and deliver hot water.

[0020] A plurality of hot water taps 5 (so-called faucets) (three in the illustrated example) are connected to the hot water outlet pipe 4 downstream of the junction. In addition, the downstream side of the connection point of the hot water taps 5 in the hot water outlet pipe 4 is connected to the upstream side of the branch point of the water supply pipe 3 by a circulation pipe 6, and the circulation pipe 6 is provided with a circulation pump 7 that sends hot water from the hot water outlet pipe 4 to the water supply pipe 3. The linked hot water supply system 1 of this embodiment has a so-called instant hot water function, and when the hot water tap 5 is closed and hot water is not being consumed, the circulation pump 7 operates to return hot water from the hot water outlet pipe 4 to the water supply pipe 3 through the circulation pipe 6 and circulates it while keeping it warm by heating the water heater 10, so that hot water can be supplied immediately when the hot water tap 5 is opened.

[0021] In addition, the two water heaters 10a, 10b are connected to each other so that they can communicate with each other, and a master-slave relationship is set up in which one water heater 10 is the "master" and the other water heater 10 is the "slave". When the amount of hot water consumed is small, only the "master" water heater 10 operates, and the "slave" water heater 10 is in standby mode. When the amount of hot water consumed increases, the "slave" water heater 10 operates in addition to the "master" water heater 10. The master-slave relationship between the two water heaters 10a, 10b is periodically alternated. The number of water heaters 10 to be connected is not limited to two, and may be three or more, in which case one of them is the "master" and the rest are the "slave".

[0022] Furthermore, a remote control 8 that can be operated by an administrator of the linked hot water supply system 1 is connected to each water heater 10 so as to be able to communicate with it via wired or wireless communication. The remote control 8 has an operation unit 8a on which are installed various switches that can be operated to make various settings such as the temperature of the hot water to be supplied, to switch various functions on / off, and to perform resetting, and also has a display unit 8b that can display the setting status and operating status of the linked hot water supply system 1, information about the water heater 10, etc.

[0023] 2 is an explanatory diagram showing the configuration of a water heater 10 of this embodiment. As shown in the figure, the water heater 10 is equipped with a burner 12 housed in a combustion chamber 11 for burning fuel gas, and a combustion fan 13 for sending air for combustion from below toward the burner 12, and the fuel gas is supplied to the burner 12 through the gas piping 2 described above. The gas piping 2 in the water heater 10 is provided with a main valve 14 for opening and closing the gas piping 2, and a proportional valve 15 for adjusting the flow rate of the fuel gas flowing through the gas piping 2. In addition, the combustion chamber 11 is provided with an ignition plug 16 for igniting by spark discharge toward the burner 12, a flame rod 17 for detecting the combustion state in the burner 12, and the like.

[0024] A heat exchanger 18 is provided above the burner 12, and high-temperature combustion exhaust gas generated by combustion in the burner 12 passes through the heat exchanger 18 and is discharged to the outside from an exhaust port 19 provided at the top of the water heater 10. The heat exchanger 18 is connected to the water supply pipe 3 at one end (upstream side) and to the hot water outlet pipe 4 at the other end (downstream side). The water supply pipe 3 in the water heater 10 is provided with a water volume servo 20 that opens and closes the water supply pipe 3 and controls the flow rate, a flow rate sensor 21 that detects the flow rate of hot water supplied to the heat exchanger 18, an inflow side temperature sensor 22 that detects the temperature of the hot water flowing into the heat exchanger 18 (inflow side temperature), and a pressure sensor 23 that detects the pressure of the hot water in the water supply pipe 3, in this order from the upstream side. The water volume servo 20 in this embodiment corresponds to the "inflow side opening and closing valve" of the present invention.

[0025] When the water volume servo 20 is open, the hot water that flows into the heat exchanger 18 is heated by heat exchange with the combustion exhaust gas from the burner 12 in the heat exchanger 18, and then flows out to the hot water outlet pipe 4. In the hot water outlet pipe 4 in the water heater 10, an outlet temperature sensor 24 that detects the temperature of the hot water flowing out from the heat exchanger 18 (outlet temperature) and a hot water volume servo 25 that opens and closes the hot water outlet pipe 4 and controls the flow rate are provided in this order toward the downstream side. The burner 12 and the heat exchanger 18 in this embodiment correspond to the "heating section" of the present invention. The hot water volume servo 25 in this embodiment corresponds to the "outlet opening and closing valve" of the present invention, and the outlet temperature sensor 24 in this embodiment corresponds to the "temperature sensor" of the present invention.

[0026] In the water heater 10 of this embodiment, the upstream side of the water volume servo 20 of the water supply pipe 3 and the downstream side of the hot water volume servo 25 of the hot water outlet pipe 4 are connected by a bypass pipe 26. This bypass pipe 26 is provided with a bypass servo 27 that opens and closes the bypass pipe 26 and controls the flow rate. A part of the hot water supplied to the water heater 10 by the water supply pipe 3 can pass through the bypass pipe 26 without being supplied to the heat exchanger 18, and the rest is supplied to the heat exchanger 18. The hot water heated by the heat exchanger 18 is mixed with the hot water that has passed through the bypass pipe 26 and is supplied to the hot water tap 5. The mixture ratio of the hot water heated by the heat exchanger 18 and the hot water that has passed through the bypass pipe 26 can be changed by the opening of the bypass servo 27, the hot water volume servo 25, and the water volume servo 20.

[0027] A hot water temperature sensor 28 that detects the temperature of the hot water (hot water temperature) supplied to the hot water tap 5 is provided downstream of the connection point of the bypass pipe 26 in the hot water outlet pipe 4. Because the bypass pipe 26 is connected as described above, the temperature detected by the hot water temperature sensor 28 is lower than the temperature detected by the outlet temperature sensor 24 located upstream, and by adjusting the mixing ratio, it is possible to suppress temperature fluctuations in the hot water supplied to the hot water tap 5. Thermistors, whose electrical resistance changes in response to changes in temperature, are used as the various temperature sensors in this embodiment.

[0028] Furthermore, water heater 10 is equipped with controller 29 that individually controls the entire device, and controller 29 is electrically connected to the above-mentioned combustion fan 13, main valve 14, proportional valve 15, ignition plug 16, flame rod 17, water volume servo 20, flow rate sensor 21, inlet temperature sensor 22, pressure sensor 23, outlet temperature sensor 24, hot water volume servo 25, hot water temperature sensor 28, etc. Controller 29 controls the opening and closing of water volume servo 20 and hot water volume servo 25, and controls the amount of combustion (amount of heat) in burner 12 according to the flow rate detected by flow rate sensor 21 and the temperature detected by inlet temperature sensor 22, etc., and stops combustion in burner 12 when the flow rate detected by flow rate sensor 21 falls below a predetermined flow rate.

[0029] In addition, the controllers 29 of the two water heaters 10a, 10b are electrically connected to each other and to the circulation pump 7 of the circulation pipe 6. As described above, a master-slave relationship is set between the two water heaters 10a, 10b, and the controller 29 of the "master" water heater 10 controls the operation of the circulation pump 7 and gives instructions to the controller 29 of the "slave" water heater 10. In the "slave" water heater 10 in this embodiment, when the "slave" water heater 10 is in standby mode, the hot water volume servo 25 is fully closed, and the flow of hot water stops upstream of the hot water volume servo 25 (the flow rate detected by the flow rate sensor 21 becomes less than the predetermined flow rate), so that no combustion is performed in the burner 12 and the hot water heated from the "master" water heater 10 during circulation does not flow through the water volume servo 20. In addition, in the "slave" water heater 10 in standby mode, bypass servo 27 is also kept fully closed in conjunction with the fully closed hot water volume servo 25, thereby cutting off the flow of hot water in standby mode. Note that, even in the "master" water heater 10 in standby mode (a state in which combustion in burner 12 is stopped), the hot water volume servo 25 and bypass servo 27 are kept open (opening according to the temperature set in remote control 8 and the temperatures detected by various temperature sensors, etc.) to ensure the flow of hot water.

[0030] In the linked hot water supply system 1 of this embodiment, in the "slave" hot water supply device 10 in the standby state, the water volume servo 20 as well as the hot water volume servo 25 are fully closed to seal the path from the water volume servo 20 to the hot water volume servo 25 (hereinafter referred to as the heating path), so that it is possible to detect a water leak in the heating path based on the drop in the detected pressure by the pressure sensor 23. However, since the pressure of the hot water in the sealed heating path is easily affected by temperature changes, for example, a drop in the hot water pressure due to a temperature drop such as the cooling of residual heat in the heat exchanger 18 may result in a false detection of a water leak in the heating path. Therefore, in the linked hot water supply system 1 of this embodiment, the controller 29 of the "slave" hot water supply device 10 executes the following water leak detection control process, thereby enabling the detection of a water leak in the heating path while suppressing false detection. The controller 29 of this embodiment corresponds to the "controller" of the present invention.

[0031] 3 is a flow chart of the water leakage detection control process executed by controller 29 of "slave" water heater 10 of this embodiment. This water leakage detection control process is repeatedly executed at a predetermined cycle in water heater 10 set as "slave" when connected hot water supply system 1 is powered on. As shown in the figure, when the water leakage detection control process of this embodiment is started, first, a process (temperature stable condition monitoring process) is executed to monitor whether or not a predetermined temperature stable condition, which is presumed to indicate that the temperature of the hot water in the heating path has dropped and stabilized, has been established (STEP 1). The temperature stable condition in this embodiment is set to "a predetermined stable time (e.g. 90 minutes) has elapsed with hot water volume servo 25 fully closed and the flow of hot water in the heating path stopped."

[0032] 4 is a flowchart of the stable temperature condition monitoring process of this embodiment, which is executed in the leakage detection control process. In the stable temperature condition monitoring process, first, it is determined whether or not either the stable temperature condition satisfaction flag or the preceding stable temperature condition satisfaction flag is set to ON (STEP 10). As will be described later, the stable temperature condition satisfaction flag is a flag indicating that the stable temperature condition is satisfied, and the preceding stable temperature condition satisfaction flag is a flag indicating that the preceding stable temperature condition is satisfied prior to the satisfaction of the stable temperature condition. A storage area for the flags is secured in the storage unit (not shown) of the controller 29.

[0033] If both the temperature stable condition establishment flag and the preceding temperature stable condition establishment flag are set to OFF (STEP 10: no), then it is determined whether the stable time standby timer and the preceding stable time standby timer are timing (STEP 11). Both the stable time standby timer and the preceding stable time standby timer are timers for measuring elapsed time when the hot water volume servo 25 is fully closed, and as described later, the time measured by the preceding stable time standby timer (preceding stable time) is shorter than the time measured by the stable time standby timer (stable time). Then, if the stable time standby timer and the preceding stable time standby timer are not timing (STEP 11: no), then it is determined whether 24 hours have passed since the previous determination of the presence or absence of water leakage in the heating path (STEP 12). In each water heater 10 of this embodiment, the frequency of performing the process of detecting water leakage in the heating path (water leakage detection process) is set to be at least 24 hours after the previous determination of the presence or absence of water leakage. Therefore, if 24 hours have not yet passed since the last time the presence or absence of a water leak was determined (STEP 12: no), the water leak detection process is not performed regardless of whether the temperature stability condition is met or not, and the temperature stability condition monitoring process of FIG. 4 is temporarily terminated, and the water leak detection control process of FIG. 3 is resumed.

[0034] On the other hand, if 24 hours have passed since the previous leak detection (STEP 12: yes), it is determined whether hot water volume servo 25 is fully closed (STEP 13). If hot water volume servo 25 is not fully closed and is in the open state (STEP 13: no), the "slave" water heater 10 is not in standby and combustion is occurring in burner 12, so the temperature stability condition is not met, so the temperature stability condition monitoring process in Fig. 4 is temporarily terminated and the process returns to the water leakage detection control process in Fig. 3.

[0035] On the other hand, if hot water volume servo 25 is fully closed (STEP 13: yes), it is determined that slave water heater 10 is in standby and that no combustion is occurring in burner 12, and so timing is started by the above-mentioned stable time standby timer and advanced stable time standby timer (STEP 14). Once timing is started by the stable time standby timer and advanced stable time standby timer, it is determined whether hot water volume servo 25 has been opened after timing has started (STEP 15). Also, if it is determined in STEP 11 that the stable time standby timer and advanced stable time standby timer are already timing (STEP 11: yes), the processes in STEP 12 to STEP 14 are omitted, and it is determined whether hot water volume servo 25 has been opened (STEP 15). Then, if hot water volume servo 25 is opened (STEP 15: yes), the standby state of "slave" water heater 10 is released and combustion begins in burner 12, so the stable time standby timer and the preceding stable time standby timer are reset (stopped) (STEP 16), after which the stable temperature condition monitoring process of Fig. 4 is temporarily terminated and the process returns to the water leak detection control process of Fig. 3. Note that the use of "slave" water heater 10 may be restricted and hot water volume servo 25 may be kept fully closed until the end of the water leak detection process.

[0036] On the other hand, if the hot water volume servo 25 remains fully closed (STEP 15: no), the stable time standby timer determines whether a predetermined stable time (90 minutes in this embodiment) has elapsed (STEP 17). If the stable time has not yet elapsed (STEP 17: no), the advanced stable time standby timer then determines whether a predetermined advanced stable time (15 minutes in this embodiment) that is shorter than the stable time has elapsed (STEP 18). If the advanced stable time has not yet elapsed either (STEP 18: no), the stable temperature condition monitoring process in FIG. 4 is temporarily terminated, and the process returns to the leak detection control process in FIG. 3.

[0037] Thereafter, if the preceding stable time has elapsed in the preceding stable time wait timer while repeatedly executing the leak detection control process of Fig. 3 (step 18: yes), a preceding temperature stable condition establishment flag is set to ON (step 19), indicating that the preceding stable time has elapsed with the hot water volume servo 25 fully closed, and the preceding temperature stable condition has been established. Note that the preceding stable time wait timer is automatically reset when the preceding stable time has elapsed. Thereafter, the temperature stable condition monitoring process of Fig. 4 is temporarily terminated, and the process returns to the leak detection control process of Fig. 3.

[0038] Furthermore, if the stable time has elapsed in the stable time standby timer while repeatedly executing the water leakage detection control process of Fig. 3 (STEP 17: yes), this means that the temperature stable condition of this embodiment is satisfied, and a temperature stable condition satisfaction flag indicating that the temperature stable condition is satisfied is set to ON (STEP 20). Note that the stable time standby timer is automatically reset when the stable time has elapsed. When the temperature stable condition satisfaction flag is set to ON in this manner, the temperature stable condition monitoring process of Fig. 4 is temporarily terminated, and the process returns to the water leakage detection control process of Fig. 3.

[0039] Then, in the judgment in STEP 10 immediately after starting the stable temperature condition monitoring process in Fig. 4, if either the stable temperature condition satisfaction flag or the preceding stable temperature condition satisfaction flag has already been set to ON (yes in STEP 10), it is judged whether the hot water volume servo 25 has been opened (STEP 21). If the hot water volume servo 25 remains fully closed (no in STEP 21), the stable temperature condition monitoring process in Fig. 4 is temporarily terminated while the stable temperature condition satisfaction flag or the preceding stable temperature condition satisfaction flag that has been set to ON is still set to ON, and the process returns to the leak detection control process in Fig. 3.

[0040] In contrast, if hot water volume servo 25 is opened (STEP 21: yes), the standby state of the "slave" water heater 10 is released and combustion begins in burner 12. Therefore, after setting either the temperature stability condition satisfaction flag or the leading temperature stability condition satisfaction flag, which are set to ON, to OFF (STEP 22), the temperature stability condition monitoring process of Figure 4 is temporarily terminated and the process returns to the water leak detection control process of Figure 3.

[0041] In the water leakage detection control process, when returning from the temperature stable condition monitoring process (STEP 1), it is determined whether or not the temperature stable condition establishment flag is set to ON (STEP 2). If the temperature stable condition establishment flag is set to ON (STEP 2: yes), the following water leakage detection process is executed (STEP 3). After the leakage detection process is completed, the water leakage detection control process in Fig. 3 is temporarily terminated, and the water leakage detection control process in Fig. 3 is executed again at a predetermined cycle. The water leakage detection process in this embodiment corresponds to the "liquid leakage detection process" of the present invention.

[0042] 5 and 6 are flow charts of the leakage detection process of this embodiment executed in the leakage detection control process. In the leakage detection process, first, it is determined whether the water volume servo 20 is fully closed (STEP 30). In this embodiment, the water volume servo 20 is basically in an open state, and in order to seal the heating path when detecting leakage in the heating path, the water volume servo 20 is also fully closed in addition to the hot water volume servo 25. Therefore, if the water volume servo 20 is not fully closed and is in an open state (STEP 30: no), the water volume servo 20 is fully closed to seal the heating path (STEP 31), and the temperature (outflow temperature) of the hot water in the hot water outlet pipe 4 is detected by the outflow temperature sensor 24 included in the heating path, and the pressure of the hot water in the water supply pipe 3 is detected by the pressure sensor 23 also included in the heating path (STEP 32).

[0043] When the hot water outlet temperature and pressure in the sealed heating path are detected in this way, the outlet temperature (hot water temperature in the heating path) detected by the outlet temperature sensor 24 is monitored, and it is determined whether or not the temperature has changed by a predetermined allowable value (1 degree in this embodiment) or more with respect to the outlet temperature detected in the processing of STEP 32 (STEP 33). If the change in the outlet temperature is less than 1 degree (STEP 33: no), it is then determined whether or not the judgment time has elapsed (STEP 34). In the water leakage detection processing of this embodiment, a judgment time is set between fully closing the water volume servo 20 and judging whether or not there is a water leakage in the heating path, and this judgment time is set according to the hot water pressure detected in the processing of STEP 32, and the higher the detected pressure, the longer the judgment time is set. For example, if the detected pressure is 200 kPa, the judgment time is set to 3 seconds, whereas if the detected pressure is 600 kPa, the judgment time is set to 20 seconds.

[0044] If the determination time has not yet elapsed (STEP 34: no), the water leakage detection process in Figures 5 and 6 is temporarily terminated while the heating path is kept sealed, and the process returns to the water leakage detection control process in Figure 3. After that, if the temperature stability condition establishment flag remains set to ON, the water leakage detection process in Figures 5 and 6 will be executed again at a predetermined cycle, and since the determination in STEP 30 indicates that the water volume servo 20 is already fully closed (STEP 30: yes), the processes in STEP 31 and STEP 32 are omitted, and it is determined again whether the outflow side temperature has changed by 1 degree or more (STEP 33).

[0045] If the outflow temperature fluctuates by 1 degree or more before the judgment time has elapsed (STEP 33: yes), the temperature of the hot water in the heating path is not yet stable, so the temperature stability condition establishment flag is set to OFF without detecting water leakage (STEP 35). The water volume servo 20 is opened to unseal the heating path (STEP 36). Then, in order to wait for the temperature stability condition or the preceding stability condition to be established again, the stable time standby timer and the preceding stability time standby timer start timing again (STEP 37), and the water leakage detection process of Fig. 5 and Fig. 6 is temporarily terminated, and the process returns to the water leakage detection control process of Fig. 3. In the water leakage detection process of this embodiment, the fluctuation of the outflow temperature is monitored before the judgment time has elapsed, but it may be determined whether the fluctuation of the outflow temperature during the judgment time is 1 degree or more when the judgment time has elapsed.

[0046] On the other hand, if the outflow side temperature does not fluctuate by more than 1 degree (STEP 33: no) and the judgment time has elapsed (STEP 34: yes), the temperature of the hot water in the heating path is stable, so it is judged whether the pressure of the hot water in the water supply pipe 3 (sealed heating path) detected by the pressure sensor 23 is equal to or higher than a predetermined reference pressure (30 kPa in this embodiment) (STEP 38).If the detected pressure is equal to or higher than 30 kPa (STEP 38: yes), it is judged that there is no water leakage because sufficient pressure of the hot water in the sealed heating path remains (STEP 39).

[0047] When it is thus determined that there is no water leakage, the temperature stabilization condition establishment flag is set to OFF (STEP 40), and then the water volume servo 20 is opened to unseal the heating path (STEP 41). Furthermore, in order to provide an indication of when to perform the next water leakage detection process (see STEP 12 in FIG. 4), a determined timer is operated to count the time since it was determined that there is no water leakage (STEP 42), and the water leakage detection process in FIG. 5 and FIG. 6 is terminated, and the water leakage detection control process in FIG. 3 is resumed.

[0048] On the other hand, if it is determined in STEP 38 that the pressure detected by the pressure sensor 23 is lower than 30 kPa (STEP 38: no), "1" is added to the water leakage detection counter (STEP 43 in FIG. 6). This water leakage detection counter is a counter that stores the number of times that the pressure detected by the pressure sensor 23 has dropped below 30 kPa and it has been confirmed that there is a possibility of water leakage. In the water leakage detection process of this embodiment, even if the pressure detected by the pressure sensor 23 has dropped below 30 kPa, it is not immediately determined that there is water leakage in one go, but the check is repeated until a predetermined upper limit number of times (three times in this embodiment) is reached. Therefore, after "1" is added to the water leakage detection counter, it is then determined whether the water leakage detection counter has reached "3" (STEP 44).

[0049] If the water leakage detection counter has not yet reached "3" (STEP 44: no), the water volume servo 20 is opened to temporarily release the sealing of the heating path (STEP 45). This causes hot water to be supplied to the heating path to apply pressure. After that, the water leakage detection process of FIG. 5 and FIG. 6 is temporarily terminated, and the process returns to the water leakage detection control process of FIG. 3. At this time, the temperature stability condition establishment flag is not set to OFF, so the water leakage detection process of FIG. 5 and FIG. 6 is executed again at a predetermined period, and the processes of STEP 30 to STEP 38 described above are repeated. That is, after the water volume servo 20 is fully closed to seal the heating path, the fluctuation of the hot water outlet side temperature is monitored, and when the judgment time has elapsed, the decrease in the detected pressure by the pressure sensor 23 is judged, and if it is lower than 30 kPa (STEP 38: no), "1" is added to the water leakage detection counter (STEP 43). The water leakage detection counter is reset when the temperature stability condition establishment flag is set to OFF.

[0050] If the water leakage detection counter reaches the upper limit of "3" while repeating the process (STEP 44: yes), it is confirmed repeatedly that the hot water pressure in the sealed heating path is escaping, so it is determined that there is a water leak (STEP 46) and a notice is issued that a water leak has been detected (STEP 47). In this embodiment, the water leakage is notified by displaying it on the display unit 8b of the remote control 8. Note that the manner of notification is not limited to this, and the notice may be issued by audio output from a speaker (not shown) built into the remote control 8. Thereafter, the water leakage detection process of Figs. 5 and 6 is terminated, and the process returns to the water leakage detection control process of Fig. 3.

[0051] In the above, the process executed when the temperature stable condition establishment flag is set to ON in STEP 2 of the water leakage detection control process (STEP 2: yes) has been described. On the other hand, when the temperature stable condition establishment flag is set to OFF (STEP 2: no), it is next determined whether the preceding temperature stable condition establishment flag is set to ON (STEP 4). As described above, the preceding temperature stable condition establishment flag is a flag indicating that the preceding temperature stable condition is established by the lapse of the preceding stable time (15 minutes in this embodiment) with the hot water volume servo 25 fully closed. Then, when the preceding temperature stable condition establishment flag is not set to ON (STEP 4: no), the water leakage detection control process of FIG. 3 is temporarily terminated, and the water leakage detection control process of FIG. 3 is executed again at a predetermined cycle.

[0052] On the other hand, if the precedent temperature stabilization condition establishment flag is set to ON (STEP 4: yes), the following precedent water leakage detection process is executed (STEP 5). After the precedent water leakage detection process is completed, the water leakage detection control process in Fig. 3 is temporarily terminated, and the water leakage detection control process in Fig. 3 is executed again at a predetermined cycle. Note that the precedent water leakage detection process has many parts in common with the above-mentioned water leakage detection process, so the common contents will be explained briefly.

[0053] 7 is a flowchart of the anticipatory water leakage detection process of this embodiment, which is executed in the water leakage detection control process. In the anticipatory water leakage detection process, first, it is determined whether the water volume servo 20 is fully closed (STEP 50). If the water volume servo 20 is not fully closed and is in the open state (STEP 50: no), the water volume servo 20 is fully closed to seal the heating path (STEP 51), and then the pressure of hot and cold water in the water supply pipe 3 is detected by the pressure sensor 23 included in the heating path (STEP 52).

[0054] When the pressure of hot and cold water in the sealed heating path is thus detected, it is determined whether or not the judgment time has elapsed (STEP 53). This judgment time is set according to the pressure of hot and cold water detected in the process of STEP 52, and the judgment time is set longer if the detected pressure is high. If the judgment time has not yet elapsed (STEP 53: no), the advance water leak detection process of FIG. 7 is temporarily terminated while the heating path is kept sealed, and the process returns to the water leak detection control process of FIG. 3. Thereafter, when the advance water leak detection process of FIG. 7 is executed again at a predetermined cycle, since the judgment in STEP 50 indicates that the water volume servo 20 is already fully closed (STEP 50: yes), the processes of STEP 51 and STEP 52 are omitted, and it is determined again whether or not the judgment time has elapsed (STEP 53).

[0055] If the determination time has elapsed (STEP 53: yes), it is determined whether the pressure of the hot water in the water supply pipe 3 (sealed heating path) detected by the pressure sensor 23 is equal to or higher than a predetermined reference pressure (30 kPa in this embodiment) (STEP 54). At this time, if the detected pressure is equal to or higher than 30 kPa (STEP 54: yes), it is determined that there is no water leakage because sufficient pressure of the hot water remains in the sealed heating path (STEP 55).

[0056] If it is determined that there is no water leakage, the precedent temperature stabilization condition establishment flag is set to OFF (STEP 56), and then the water volume servo 20 is opened to release the sealing of the heating path (STEP 57). In this embodiment, the precedent water leakage detection process (FIG. 7) is performed when the precedent stabilization time (15 minutes) that is shorter than the stabilization time (90 minutes) has elapsed, and if it is determined that there is no water leakage, the water leakage detection process (FIGS. 5 and 6) after the stabilization time has elapsed is omitted. Therefore, the stable time waiting timer that is timing is reset (stopped) (STEP 58). Furthermore, when the determined timer that counts the time since it was determined that there is no water leakage is operated (STEP 59), the precedent water leakage detection process of FIG. 7 is terminated, and the process returns to the water leakage detection control process of FIG. 3.

[0057] On the other hand, if the pressure detected by the pressure sensor 23 is lower than 30 kPa in the judgment of STEP 54 (STEP 54: no), the hot water pressure in the sealed heating path is released and there is a possibility of leakage, but the advance leakage detection process of this embodiment (Fig. 7) does not judge that there is leakage, and leaves the final judgment to the leakage detection process (Figs. 5 and 6) performed later. Also, until the stabilization time (90 minutes) has elapsed, the advance leakage detection process can be repeatedly performed every time the advance stabilization time (15 minutes) has elapsed.

[0058] Therefore, after setting the precedence temperature stabilization condition establishment flag to OFF (STEP 60), the water volume servo 20 is opened to release the sealing of the heating path (STEP 61). Then, in order to wait for the precedence stabilization condition to be established again, the precedence stabilization time standby timer starts timing again (STEP 62), and the precedence water leakage detection process of FIG. 7 is terminated and the process returns to the water leakage detection control process of FIG. 3. Thereafter, the precedence stabilization time elapses again in the precedence stabilization time standby timer, and the precedence temperature stabilization condition establishment flag is set to ON (see STEP 19 in FIG. 4), and the precedence water leakage detection process of FIG. 7 is executed again. Furthermore, if it is not determined that there is no water leakage in the precedence water leakage detection process, the stabilization time standby timer also continues timing, and as the stabilization time elapses and the temperature stabilization condition establishment flag is set to ON (see STEP 20 in FIG. 4), the water leakage detection process of FIG. 5 and FIG. 6 is executed, and the presence or absence of water leakage is determined as described above.

[0059] As described above, in the linked hot water supply system 1 of this embodiment, in the "slave" hot water heater 10 in the standby state, the hot water volume servo 25 and the water volume servo 20 are fully closed to seal the path (heating path) from the water volume servo 20 to the hot water volume servo 25, and then a process (leak detection process) can be executed to detect a leak in the heating path based on the drop in the detected pressure by the pressure sensor 23. This leak detection process is executed after a predetermined temperature stabilization condition is met, which presumably indicates that the temperature of the hot water in the heating path has dropped and stabilized.

[0060] According to the connected hot water supply system 1 of this embodiment, by waiting until the temperature stabilization condition is met before executing the leakage detection process, the effect of temperature changes on the pressure of hot water in the sealed heating path can be reduced compared to when the temperature stabilization condition is not set, thereby making it possible to suppress erroneous detection of leakage in the heating path due to a drop in temperature.

[0061] Furthermore, in the linked hot water supply system 1 of this embodiment, the temperature stabilization condition is set to "a predetermined stabilization time (90 minutes) has elapsed with the flow of hot water in the heating path stopped" on the premise that combustion in the burner 12 is stopped when the flow of hot water in the heating path detected by the flow sensor 21 falls below a predetermined flow rate. If the flow of hot water in the heating path stops, the combustion in the burner 12 stops and heated hot water does not flow in from elsewhere (for example, the "main" hot water heater 10). As a result, the temperature of the hot water in the heating path drops and stabilizes due to heat dissipation until the stabilization time has elapsed in that state, which makes it possible to suppress erroneous detection in the leak detection process executed thereafter.

[0062] In particular, in the linked hot water supply system 1 of this embodiment, the temperature stabilization condition is "a predetermined stabilization time has elapsed with the flow of hot water in the heating path stopped by fully closing the hot water volume servo 25." If the hot water volume servo 25 is fully closed, the outflow of hot water from the heating path is blocked, and the flow of hot water in the heating path stops. Then, the hot water volume servo 25 is already fully closed when the stabilization time has elapsed, and the heating path can be sealed simply by fully closing the water volume servo 20, so it is possible to quickly execute the water leakage detection process. Note that, although the flow of hot water in the heating path can be stopped by fully closing the water volume servo 20, in that case, in order to supply hot water to the heating path and add pressure after the stabilization time has elapsed (when starting the water leakage detection process), it is necessary to open the water volume servo 20 once, fully close the hot water volume servo 25, and then fully close the water volume servo 20 again.

[0063] In addition, in the linked hot water supply system 1 of this embodiment, when a predetermined advance stable time (15 minutes) shorter than the stable time (90 minutes) has elapsed with the flow of hot water in the heating path stopped, the advance water leakage detection process is executed (part of the water leakage detection process is executed ahead of time) prior to the water leakage detection process, and if no water leakage in the heating path is detected, the water leakage detection process after the stable time has elapsed is omitted, whereas if there is a possibility of water leakage in the heating path, the sealing of the heating path is once released and the water leakage detection process is executed after the stable time has elapsed. As a result, if no water leakage is detected in the advance water leakage detection process executed prior to the water leakage detection process, the subsequent water leakage detection process is omitted, so that the water heater 10 can be quickly restored to normal use even if the use of the water heater 10 is restricted until the end of the water leakage detection process. On the other hand, even if there is a possibility of water leakage, it is suspected that it is due to a drop in temperature, so by waiting for the stable time to elapse and executing the water leakage detection process again, erroneous detection can be suppressed.

[0064] Furthermore, in the linked hot water supply system 1 of this embodiment, if the outflow temperature detected by the outflow temperature sensor 24 fluctuates to a predetermined allowable value (1 degree) or more during the execution of the water leakage detection process even though the temperature stabilization condition is met, the water leakage detection process is interrupted. Although the establishment of the temperature stabilization condition presumes that the temperature of the hot water in the heating path has stabilized, if the temperature is not yet stable when actually checked by the outflow temperature sensor 24, the pressure of the hot water in the heating path will be affected by the temperature change, and therefore, by interrupting the ongoing water leakage detection process, it is possible to suppress erroneous detection.

[0065] The above describes the connected hot water supply system 1 of this embodiment as a liquid heating device, but the present invention is not limited to the above embodiment and can be embodied in various forms without departing from the gist of the present invention.

[0066] For example, the temperature stabilization condition in the above-mentioned embodiment was set to "a predetermined stabilization time (90 minutes) has elapsed with the hot water volume servo 25 fully closed and the hot water flow in the heating path stopped." However, the temperature stabilization condition is not limited to this, and may be any condition that is presumed to have lowered and stabilized in temperature in the heating path. For example, instead of confirming that the hot water volume servo 25 is fully closed, the halt of the hot water flow in the heating path may be confirmed based on the detected flow rate by the flow rate sensor 21. In addition, the stabilization time in this embodiment was set to 90 minutes on the assumption that heat is naturally dissipated, but if the blowing of air by the combustion fan 13 (so-called post-purging) is continued after the combustion in the burner 12 is stopped, the temperature drop of the hot water in the heating path (mainly the heat exchanger 18) is promoted by forced cooling, so the stabilization time may be shortened (for example, set to 10 minutes).

[0067] The temperature stabilization condition may also be that "the outflow temperature detected by the outflow temperature sensor 24 has dropped to a predetermined temperature," and this predetermined temperature may be set based on the outside air temperature. Alternatively, the temperature stabilization condition may be that "the amount of fluctuation in the outflow temperature detected by the outflow temperature sensor 24 at a fixed period (e.g., every 5 minutes) has fallen below a predetermined value (e.g., 1 degree)."

[0068] Also, in the above-mentioned embodiment, a linked hot water supply system 1 having a circulation type instant hot water function in which two hot water heaters 10 are linked has been described as an example of a liquid heating device. However, the liquid heating device is not limited to this, and the water heater 10 may be a single unit, or the circulation piping 6 and circulation pump 7 may be omitted to form a non-circulation type without an instant hot water function (a configuration in which the water heater 10 starts heating as hot water flows out when the hot water tap 5 is opened). Of course, the liquid heating device is not limited to such a hot water supply system, and may be a heating system in which heated liquid is circulated for heating, and in this case, the liquid to be heated is not limited to hot water, and silicone oil or the like may be used.

[0069] In addition, in the above-mentioned embodiment, the hot water tap 5 is directly connected to the hot water outlet pipe 4 of the linked hot water supply system 1 as shown in FIG. 1. However, as shown in FIG. 8, a hot water storage tank 30 for storing hot water may be installed between the hot water outlet pipe 4 and the hot water tap 5. That is, the downstream side of the hot water outlet pipe 4 is connected to the hot water storage tank 30 to supply hot water, and the upstream side of the circulation pipe 6 is connected to the hot water storage tank 30 to circulate the hot water in the hot water storage tank 30 back to the water supply pipe 3 by operating the circulation pump 7, while keeping it warm by heating the water heater 10. In addition to this circulation, the upstream and downstream sides of the hot water supply circulation pipe 31 are connected to the hot water storage tank 30, and the hot water in the hot water storage tank 30 is circulated to the hot water supply circulation pipe 31 by operating the hot water supply circulation pump 32 provided in the hot water supply circulation pipe 31. By connecting the hot water tap 5 to the hot water supply circulation pipe 31, it is possible to supply hot water from the hot water storage tank 30 immediately after the hot water tap 5 is opened.

[0070] Furthermore, as shown in Fig. 9, the downstream side of the hot water outlet pipe 4 and the upstream side of the circulation pipe 6 may be connected via a filtration unit 40. That is, a filtration unit 40 and a bath circulation pump 43 are installed in a bath circulation pipe 42 that circulates hot water in a bathtub 41, and the hot water sucked out of the bathtub 41 by the operation of the bath circulation pump 43 is filtered by the filtration unit 40 and returned to the bathtub 41. At the same time, the hot water supplied through the hot water outlet pipe 4 is circulated by the operation of the circulation pump 7 by returning it to the water supply pipe 3 through the filtration unit 40 via the circulation pipe 6, while being heated by the water heater 10. As a result, the hot water in the bathtub 41 circulating through the bath circulation pipe 42 is reheated (so-called reheating) by liquid-liquid heat exchange in the filtration unit 40.

[0071] Here, in the linked hot water supply system 1 of the embodiment described above, when the "slave" water heater 10 of the two linked water heaters 10 goes into a standby state (a state in which combustion in the burner 12 is stopped), the hot water volume servo 25 and the bypass servo 27 are fully closed. In contrast, in the type having the hot water storage tank 30 of FIG. 8 or the type having the filtration unit 40 of FIG. 9, the heating amount (number) of the water heaters 10 is determined in advance according to the amount of heat required by the hot water storage tank 30 or the filtration unit 40, and the "master" water heater 10 and the "slave" water heater 10 may operate in sync, in which case, even if the "slave" water heater 10 goes into a standby state, the hot water volume servo 25 and the bypass servo 27 are kept in an open state (opening according to the temperature set in the remote control 8, the temperatures detected by the various temperature sensors, etc.) just like the "master" water heater 10. Therefore, if the above-mentioned processes (Figs. 3-7) are to be applied to these types, it is necessary to fully close hot water volume servo 25 and bypass servo 27 before the stable time standby timer and the advanced stable time standby timer start timing (STEP 14 in Fig. 4). Then, if it is determined that there is no water leakage, the hot water volume servo 25 and bypass servo 27 can be opened in conjunction with opening the water volume servo 20 (STEP 41 in Fig. 5, STEP 57 in Fig. 7). The same is true when there is a single water heater 10 or when a leak is detected by the "main" water heater 10, since the hot water volume servo 25 and bypass servo 27 are left open in the standby state.

[0072] Also, in the type equipped with the hot water storage tank 30 in Fig. 8 and the type equipped with the filtration unit 40 in Fig. 9, it is desirable to execute the waiting for the temperature stabilization condition to be met and the leak detection process one by one so that the timing of execution does not overlap for the linked water heaters 10 (the "master" and "slave" if there are two, or the "master" and each of the multiple "slave" if there are three or more). In this way, it is possible to minimize the number of water heaters 10 that become unusable due to the full closure of the hot water volume servo 25, and to maintain operation as a system with the remaining water heaters 10.

[0073] In the above-mentioned embodiment, the outflow temperature sensor 24 checks for fluctuations in the outflow temperature during the execution of the leak detection process after the temperature stabilization condition is established (STEP 33, STEP 35 to STEP 37 in FIG. 5). However, checking for such fluctuations in the outflow temperature is not essential and may be omitted (see the advance leak detection process in FIG. 7). In that case, in the process of STEP 32, it is sufficient to detect only the hot water pressure with the pressure sensor 23 without detecting the outflow temperature with the outflow temperature sensor 24. However, by checking for fluctuations in the outflow temperature as in the above-mentioned embodiment, it is possible to eliminate the influence of temperature changes on the hot water pressure in the sealed heating path and to enhance the effect of suppressing false detection of leaks.

[0074] In the above embodiment, the hot water volume servo 25 is fully closed first, and then the water volume servo 20 is fully closed to seal the heating path. However, the order in which the hot water volume servo 25 and the water volume servo 20 are fully closed when sealing the heating path is not limited to this. For example, if the hot water heater 10 is a standalone non-circulating type, the flow of hot water in the heating path stops if the hot water tap 5 is closed, even if the hot water volume servo 25 is open. Therefore, while checking the stop of the hot water flow based on the detected flow rate of the flow rate sensor 21, if the temperature stabilization condition is established by the lapse of the stabilization time, either the hot water volume servo 25 or the water volume servo 20 may be fully closed first, or both may be fully closed almost simultaneously.

[0075] In the above embodiment, the bypass pipe 26 connects the upstream side of the water volume servo 20 of the water supply pipe 3 to the downstream side of the hot water volume servo 25 of the hot water outlet pipe 4, and the bypass pipe 26 is not included in the heating path that is the target of the water leakage detection (see FIG. 2). However, by connecting the downstream side of the water volume servo 20 of the water supply pipe 3 to the upstream side of the hot water volume servo 25 of the hot water outlet pipe 4 with the bypass pipe 26, the bypass pipe 26 may be included in the heating path that is the target of the water leakage detection. In this case, the mixture ratio of the hot water heated by the heat exchanger 18 and the hot water that has passed through the bypass pipe 26 can be changed by the opening degree of the bypass servo 27. Note that the flow of hot water in the bypass pipe 26 also stops when the hot water volume servo 25 is fully closed, so there is no need to fully close the bypass servo 27 in conjunction with the full closure of the hot water volume servo 25.

[0076] In the above-mentioned embodiment, the controller 29 of the "master" water heater 10 gives instructions to the controller 29 of the "slave" water heater 10. However, a system controller (not shown) that controls the entire linked hot water supply system 1 may be provided, and the remote control 8 and the controller 29 of each water heater 10 may be connected to this system controller so as to be communicable by wire or wirelessly, and the circulation pump 7 may be electrically connected. The system controller may control the operation of the circulation pump 7, assign a master-slave relationship to the multiple water heaters 10, and give operation instructions to the controller 29 of each water heater 10. In this case, when the controller 29 of the "slave" water heater 10 determines that there is a leak (STEP 46 in FIG. 6), a leak notification (STEP 47) may be displayed on the display unit 8b of the remote control 8 via the system controller. [Explanation of symbols]

[0077] 1...Connected hot water system, 2...Gas piping, 3...Water supply piping, 4...Hot water outlet pipe, 5...Hot water tap, 6...Circulation pipe, 7...circulation pump, 8...remote control, 8a...operation unit, 8b...display unit, 10...water heater, 11...combustion chamber, 12... burner, 13... combustion fan, 14... main valve, 15...proportional valve, 16...spark plug, 17...flame rod, 18...heat exchanger, 19...exhaust port, 20...water volume servo, 21...flow rate sensor, 22...inlet temperature sensor, 23...pressure sensor, 24...Outlet temperature sensor, 25...Water volume servo, 26...Bypass piping, 27...Bypass servo, 28...Hot water temperature sensor, 29...Controller, 30...hot water storage tank, 31...hot water circulation piping, 32...hot water circulation pump, 40...filtration unit, 41...bathtub, 42...bath circulation piping, 43...Bath circulation pump.

Claims

1. In a liquid heating device having a heating path through which liquid flowing in from an upstream side is heated in a heating section and then flows out downstream, an inlet side opening / closing valve that opens and closes the inlet side of the heating path; an outlet side opening / closing valve that opens and closes the outlet side of the heating path; a pressure sensor provided between the inlet side on-off valve and the outlet side on-off valve in the heating path and capable of detecting a pressure of the liquid; a control unit that controls execution of a liquid leakage detection process to detect liquid leakage in the heating path based on a decrease in the pressure detected by the pressure sensor after sealing the heating path by closing the outlet-side on-off valve and the inlet-side on-off valve; Equipped with The control unit executes the liquid leakage detection process after a predetermined temperature stabilization condition is satisfied under which it is assumed that the temperature of the liquid in the heating path has been reduced and stabilized. A liquid heating device comprising:

2. 2. The liquid heating device according to claim 1, The heating unit stops heating when the flow rate of the liquid in the heating path becomes less than a predetermined flow rate, The temperature stabilization condition is that a predetermined stabilization time has elapsed with the flow of the liquid in the heating path stopped. A liquid heating device comprising:

3. 3. The liquid heating device according to claim 2, The temperature stabilization condition is that the stabilization time has elapsed in a state in which the flow of the liquid in the heating path has stopped due to the outlet-side on-off valve being closed. A liquid heating device comprising:

4. In the liquid heating device according to claim 2 or 3, The control unit advances the execution of the liquid leakage detection process when a predetermined preceding stable time shorter than the stable time has elapsed in a state in which the flow of the liquid in the heating path has stopped, and if no liquid leakage in the heating path is detected, the control unit omits the liquid leakage detection process after the stable time has elapsed, whereas if there is a possibility of liquid leakage in the heating path, the control unit temporarily releases the sealing of the heating path and executes the liquid leakage detection process again after the stable time has elapsed. A liquid heating device comprising:

5. The liquid heating device according to any one of claims 1 to 3, A temperature sensor capable of detecting a temperature of the liquid in the heating path is provided, The control unit interrupts the liquid leakage detection process when the temperature detected by the temperature sensor fluctuates to a predetermined allowable value or more during the execution of the liquid leakage detection process even though the temperature stabilization condition is established. A liquid heating device comprising:

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