Hot water supply system

Abstract

To detect the opening failure of an instantaneous hot water opening / closing valve (84) in a hot water supply device (1) mounted with an instantaneous hot water function and a heating function.SOLUTION: A hot water supply device can execute instantaneous hot water operation by opening an instantaneous hot water opening / closing valve (84) to supply a part of a heat medium to an instantaneous hot water heat exchanger (54) while performing heating operation and circulating circulation hot water with an instantaneous hot water pump (51). In the hot water supply device, when executing maintenance action or freezing preventive operation of the instantaneous hot water pump, if the heating operation is executed, the instantaneous hot water opening / closing valve is controlled to be a valve-closing state and then the temperature of the circulation hot water is detected on the upstream side and the downstream side of the instantaneous hot water heat exchanger during the maintenance operation or the freezing preventive action. The temperature rising amount of the circulation hot water in the instantaneous hot water heat exchanger is calculated, and if a state that the temperature rising amount exceeds a predetermined threshold temperature continues a duration, it is determined that the instantaneous hot water opening / closing valve is in open failure. Therefore, when executing the maintenance action or the freezing preventive action during the heating operation in the hot water supply device, it is possible to determine the presence / absence of the open failure of the instantaneous hot water opening / closing valve.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a water supply device capable of generating hot water by heating water supplied from a water supply passage, supplying the generated hot water to a hot water faucet, and further heating a room by circulating the heated heat medium to a heating terminal through a heating supply passage and a heating return passage.

Background Art

[0002] There is known a water supply device that generates hot water by heating water supplied from a water supply passage and supplies the generated hot water to a hot water faucet through a hot water outlet passage. In this water supply device, when the user opens the hot water faucet, the raw water supplied from the water supply passage to the water supply device is heated in the water supply device to generate hot water, and the hot water flows out from the hot water faucet through the hot water outlet passage. When a long time has passed without the user opening the hot water faucet, the hot water in the hot water outlet passage may have cooled down to water. In this case, after the user opens the hot water faucet, it takes a certain amount of time for the water flowing out from the hot water faucet to become hot water.

[0003] Therefore, there is also known a water supply device equipped with a function (so-called instant hot water function) that hot water flows out immediately after the user opens the hot water faucet. In the water supply device equipped with the instant hot water function, the hot water outlet passage branches at a position upstream of the hot water faucet, and a circulation circuit (hereinafter, instant hot water circulation circuit) is formed by connecting the branched passage (hereinafter, return passage) to the more upstream hot water outlet passage. Further, a circulation pump (hereinafter, instant hot water pump) and heating means (hereinafter, instant hot water heating means) are installed in the return passage. When the instant hot water pump is operated, the hot water supplied up to the vicinity upstream of the hot water faucet circulates through the instant hot water circulation circuit. At this time, if the circulating hot water is heated by the instant hot water heating means, the hot water (hereinafter, circulating hot water) circulating through the instant hot water circulation circuit can be warmed, so that hot water can flow out immediately when the user opens the hot water faucet.

[0004] Furthermore, while electric heaters and other devices can be used as instant heating means to heat circulating hot water, if the hot water supply system has a heating function, it is common to use a portion of the heated heat transfer medium (for example, hot water for heating) to heat the circulating hot water in order to heat the room. Such hot water supply systems are equipped with a liquid-liquid heat exchanger (hereinafter referred to as an instant hot water heat exchanger) in the instant hot water circulation circuit. In addition, hot water supply systems with a heating function have a heating supply passage that supplies the heat transfer medium to the heating terminals of each room, and a heating return passage that returns the heat transfer medium, which has cooled after radiating heat at the heating terminals, back to the hot water supply system. Therefore, by branching off a passage from the heating supply passage and connecting it to the instant hot water heat exchanger, a portion of the heat transfer medium supplied to the heating terminals is guided to the instant hot water heat exchanger to heat the circulating hot water. Furthermore, an on-off valve (hereinafter referred to as an instant hot water on-off valve) is installed in the passage that branches off from the heating supply passage toward the instant hot water heat exchanger (hereinafter referred to as an instant hot water branch passage). Therefore, if the user does not use the instant hot water function, the instant hot water shut-off valve can be closed to prevent the heat transfer medium from being supplied to the instant hot water heat exchanger. Conversely, if the user does use the instant hot water function, the instant hot water shut-off valve can be opened to supply the heat transfer medium to the instant hot water heat exchanger.

[0005] Thus, when a heat transfer medium is guided to an instant hot water heat exchanger by branching off an instant hot water supply passage from the heating supply passage, it is crucial that the instant hot water shut-off valve installed in the instant hot water supply passage opens and closes reliably. For example, if the instant hot water shut-off valve remains closed despite an attempt to open it to provide the user with instant hot water (a so-called closed failure), the user will not be able to receive instant hot water. Also, if the instant hot water shut-off valve does not completely close despite the user attempting to stop the instant hot water function (a so-called open failure), the heat transfer medium will be supplied to the instant hot water heat exchanger and the circulating hot water will be heated. This could cause a sudden gush of hot water when the user opens the hot water tap, potentially surprising the user.

[0006] Therefore, a technique has been proposed in which the temperature of the circulating hot water is detected on the upstream and downstream sides of the instant hot water heat exchanger, and the presence or absence of a malfunction in the instant hot water shut-off valve is determined based on the detected temperature difference (Patent Document 1). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2001-193955 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, the conventional technology proposed above had the problem of not being able to detect an open malfunction of the instant hot water valve. The reason for this is as follows: First, an open malfunction of the valve means that even when the valve is closed it, it does not close completely, so in order to detect an open malfunction, the valve must be closed. However, in a hot water heater equipped with an instant hot water function, closing the instant hot water valve stops the instant hot water function, so the instant hot water pump stops operating and the circulating hot water stops circulating in the instant hot water circulation circuit. In this state, even if the temperature of the circulating hot water is detected at the position that was upstream and downstream of the instant hot water heat exchanger when the instant hot water pump was operating, and the temperature difference between these temperatures is calculated, only a meaningless value is obtained, and it is not possible to detect an open malfunction of the instant hot water valve. Furthermore, if an open malfunction of the instant hot water valve cannot be detected, there is a risk that hot water will suddenly flow out when the user opens the hot water tap, even though the user has stopped the instant hot water function, thus surprising the user.

[0009] This invention was made to solve the aforementioned problems of the conventional technology, and aims to provide a technology that can detect an open malfunction of the instant hot water on / off valve in a hot water supply device equipped with an instant hot water function and a heating function. [Means for solving the problem]

[0010] To solve the above-mentioned problems, the hot water supply device of the present invention employs the following configuration. That is, In a hot water supply system that generates hot water by heating water supplied from a water supply passage, performs hot water supply operation by supplying the hot water to a hot water tap via a hot water outlet passage, and performs heating operation by circulating the heated heat transfer medium to the heating terminal via a heating supply passage and a heating return passage, A return passage branches off from the hot water outlet passage at a branching point upstream of the hot water tap, and is connected to the hot water outlet passage at a merging point upstream of the branching point. A hot water pump mounted in the return passage draws hot water from the hot water outlet passage into the return passage from the branching point and returns it to the hot water outlet passage from the confluence point, thereby circulating the hot water in the hot water outlet passage and the return passage as circulating hot water. A hot water heat exchanger is mounted in the aforementioned return passage, through which the circulating hot water is passed by the hot water pump, A hot water branching passage that branches off from the aforementioned heating supply passage and supplies a portion of the heat transfer medium supplied to the heating terminal to the hot water heat exchanger, A hot water supply opening / closing valve for opening and closing the aforementioned hot water supply branch passage, An upstream temperature sensor for detecting the temperature of the circulating hot water is located upstream of the instant hot water heat exchanger. A downstream temperature sensor located downstream of the instant hot water heat exchanger detects the temperature of the circulating hot water, A control unit that controls the hot water supply operation, the heating operation, and the operation of the instant hot water pump and the instant hot water on / off valve. Equipped with, The control unit, An instant hot water operation execution unit performs an instant hot water operation in which, while performing the heating operation, it opens the instant hot water on / off valve to supply a portion of the heat medium to the instant hot water heat exchanger, and operates the instant hot water pump to circulate the circulating hot water, thereby heating the circulating hot water with the heat medium. A maintenance operation execution unit, which, when predetermined maintenance conditions are met, controls the instant hot water on / off valve to a closed state and operates the instant hot water pump to perform maintenance operations, When performing the aforementioned maintenance operation, a detectable condition determination unit detects whether the heating operation is in progress, and if the heating operation is in progress, determines that the conditions for detecting an open malfunction of the instant hot water on / off valve have been met. When the conditions for detecting an open fault are met, a temperature rise calculation unit calculates the amount of temperature rise of the circulating hot water in the instant hot water heat exchanger based on the temperature of the circulating hot water detected by the upstream temperature sensor and the temperature of the circulating hot water detected by the downstream temperature sensor. If the temperature rise does not reach a predetermined threshold temperature, or if a predetermined duration has not elapsed while the temperature has reached the threshold temperature, the instant hot water on / off valve is determined not to be open. If the temperature rise reaches the threshold temperature and the predetermined duration has elapsed, the instant hot water on / off valve is determined to be open. This is determined by the open failure detection unit. It is characterized by having the following features.

[0011] In the hot water supply system of the present invention, instant hot water operation can be performed by opening the instant hot water valve while performing heating operation, supplying a portion of the heat transfer medium to the instant hot water heat exchanger, and operating the instant hot water pump to circulate the circulating hot water. If instant hot water operation is not performed, the instant hot water valve is closed and the instant hot water pump is stopped. Furthermore, if predetermined maintenance conditions are met, maintenance operation is performed by operating the instant hot water pump. For example, maintenance conditions may be met if the instant hot water pump has been stopped for a predetermined time limit or longer. When performing maintenance operation, it is detected whether heating operation is in progress. If heating operation is in progress, the amount of temperature rise of the circulating hot water in the instant hot water heat exchanger is calculated based on the temperature of the circulating hot water detected upstream of the instant hot water heat exchanger and the temperature of the circulating hot water detected downstream of the instant hot water heat exchanger. If the amount of temperature rise reaches a predetermined threshold temperature and a predetermined duration has elapsed, it is determined that the instant hot water valve is open but not malfunctioning. Otherwise, it is determined that the instant hot water valve is not open but not malfunctioning.

[0012] This allows the system to determine whether the instant hot water valve is malfunctioning when performing maintenance while the hot water heater is operating in heating mode. As a result, it prevents situations where, even though the user has disabled the instant hot water function, a malfunctioning instant hot water valve causes a sudden gush of hot water when the user opens the tap, potentially startling them.

[0013] Furthermore, in order to solve the above-mentioned problems, the hot water supply device of the present invention may also adopt the following configuration. That is, In a hot water supply system that generates hot water by heating water supplied from a water supply passage, performs hot water supply operation by supplying the hot water to a hot water tap via a hot water outlet passage, and performs heating operation by circulating the heated heat transfer medium to the heating terminal via a heating supply passage and a heating return passage, A return passage branches off from the hot water outlet passage at a branching point upstream of the hot water tap, and is connected to the hot water outlet passage at a merging point upstream of the branching point. A hot water pump mounted in the return passage draws hot water from the hot water outlet passage into the return passage from the branching point and returns it to the hot water outlet passage from the confluence point, thereby circulating the hot water in the hot water outlet passage and the return passage as circulating hot water. A hot water heat exchanger is mounted in the aforementioned return passage, through which the circulating hot water is passed by the hot water pump, A hot water branching passage that branches off from the aforementioned heating supply passage and supplies a portion of the heat transfer medium supplied to the heating terminal to the hot water heat exchanger, A hot water supply opening / closing valve for opening and closing the aforementioned hot water supply branch passage, An upstream temperature sensor for detecting the temperature of the circulating hot water is located upstream of the instant hot water heat exchanger. A downstream temperature sensor located downstream of the instant hot water heat exchanger detects the temperature of the circulating hot water, A control unit that controls the hot water supply operation, the heating operation, and the operation of the instant hot water pump and the instant hot water on / off valve. Equipped with, The control unit, While executing the heating operation, the instant hot water on-off valve is opened to supply a part of the heat medium to the instant hot water heat exchanger, and the instant hot water pump is operated to circulate the circulating warm water, thereby executing an instant hot water operation for heating the circulating warm water with the heat medium. An instant hot water operation execution unit; When a predetermined freezing prevention condition is satisfied, a freezing prevention operation execution unit that executes a freezing prevention operation by controlling the instant hot water on-off valve to a closed state and operating the instant hot water pump; When executing the freezing prevention operation, a detectable condition determination unit that detects whether the heating operation is being executed, and if the heating operation is being executed, determines that the detectable condition for detecting an open failure of the instant hot water on-off valve is satisfied; When the detectable condition for the open failure is satisfied, a temperature rise amount calculation unit that calculates the temperature rise amount of the circulating warm water in the instant hot water heat exchanger based on the temperature of the circulating warm water detected by the upstream temperature sensor and the temperature of the circulating warm water detected by the downstream temperature sensor; If the temperature rise amount has not reached a predetermined threshold temperature or a predetermined continuous time has not elapsed in a state where the threshold temperature has been reached, it is determined that the instant hot water on-off valve has no open failure. If the continuous time has elapsed in a state where the temperature rise amount has reached the threshold temperature, an open failure detection unit that determines that the instant hot water on-off valve has an open failure It is characterized by comprising the above.

[0014] Even in such a hot water supply device of the present invention, while performing the heating operation, the instant hot water on-off valve is opened and the instant hot water pump is operated to circulate the circulating hot water, whereby the instant hot water operation can be executed. Further, when the instant hot water operation is not executed, the instant hot water on-off valve is closed and the instant hot water pump is stopped. Furthermore, when a predetermined freezing prevention condition is satisfied, a freezing prevention operation is executed by controlling the instant hot water on-off valve to a closed state and operating the instant hot water pump. Note that, as a case where the freezing prevention condition is satisfied, for example, it can be a case where the outside air temperature becomes equal to or lower than a predetermined freezing prevention temperature. And, when executing the freezing prevention operation, it is detected whether or not the heating operation is being executed. When the heating operation is being executed, based on the temperature of the circulating hot water detected upstream of the instant hot water heat exchanger and the temperature of the circulating hot water detected downstream of the instant hot water heat exchanger, the temperature rise amount of the circulating hot water in the instant hot water heat exchanger is calculated. And, when a predetermined duration has elapsed in a state where the temperature rise amount has reached a predetermined threshold temperature, it is determined that the instant hot water on-off valve has an open failure. Otherwise, it is determined that the instant hot water on-off valve does not have an open failure.

[0015] By doing so, when starting the freezing prevention operation during the heating operation, it is possible to determine whether or not the instant hot water on-off valve has an open failure. For this reason, even if the user has stopped the instant hot water function, it is possible to more reliably prevent a situation where, due to an open failure of the instant hot water on-off valve, hot water suddenly flows out when the hot water supply faucet is opened and startles the user.

Brief Description of Drawings

[0016] [Figure 1] It is an explanatory diagram showing the overall configuration of the hot water supply device 1 of this embodiment. [Figure 2] It is a block diagram showing the internal structure of the control unit 100 of this embodiment. [Figure 3] It is a flowchart showing the first half of the open failure determination process executed by the control unit 100 of this embodiment. [Figure 4] It is a flowchart showing the second half of the open failure determination process. [Figure 5]This is a flowchart of the open fault detection process performed within the open fault determination process. [Figure 6] This is a flowchart of the open fault detection process for a modified example. [Modes for carrying out the invention]

[0017] Figure 1 is an explanatory diagram showing the overall configuration of the hot water supply system 1 of this embodiment. This hot water supply system 1 is capable of performing a hot water supply operation by heating tap water and supplying hot water to a hot water tap, and is also capable of performing a heating operation by circulating a heat transfer medium (hot water) to heating terminals installed in each room. As shown in the figure, the hot water supply system 1 comprises a hot water heating unit 10 that heats tap water to generate hot water, and a heating unit 20 that heats the heat transfer medium circulated to the heating terminals.

[0018] The hot water heating unit 10 is equipped with a hot water burner 11 that burns fuel gas. Above the hot water burner 11 is a first hot water heat exchanger 12, and above the first hot water heat exchanger 12 is a second hot water heat exchanger 13. The first hot water heat exchanger 12 recovers sensible heat from the combustion exhaust generated by the combustion of fuel gas in the hot water burner 11, while the second hot water heat exchanger 13 recovers latent heat from the combustion exhaust. A combustion fan 14 is also equipped below the hot water burner 11 to supply combustion air to the hot water burner 11.

[0019] The heating section 20 is also equipped with a heating burner 21 that burns fuel gas. Above the heating burner 21 is a first heating heat exchanger 22 for sensible heat recovery, and above the first heating heat exchanger 22 is a second heating heat exchanger 23 for latent heat recovery. The combustion air supplied to the heating burner 21 is supplied from a combustion fan 14.

[0020] Fuel gas is supplied to the hot water burner 11 and the heating burner 21 from the gas passage 30. The gas passage 30 is equipped with a main valve 31 that opens and closes the gas passage 30, and a proportional valve 32 that adjusts the flow rate of fuel gas flowing through the gas passage 30. The gas passage 30 also branches into two downstream of the proportional valve 32, with one branch connected to the hot water burner 11 and the other branch connected to the heating burner 21. A hot water solenoid valve 33 that opens and closes the passage is installed in the middle of the passage connected to the hot water burner 11, and a heating solenoid valve 34 that opens and closes the passage is installed in the middle of the passage connected to the heating burner 21.

[0021] The water supply passage 40 that supplies tap water to the hot water supply system 1 is connected to the second hot water heat exchanger 13, and tap water is supplied from the water supply passage 40 to the second hot water heat exchanger 13. A flow control valve 42 that controls the flow rate of tap water supplied to the second hot water heat exchanger 13 (water supply flow rate) and a flow sensor 41 that detects the water supply flow rate are installed along the water supply passage 40. Furthermore, the downstream side of the second hot water heat exchanger 13 is connected to the upstream side of the first hot water heat exchanger 12 via a hot water supply connecting passage 43, and a hot water outlet passage 44 is connected to the downstream side of the first hot water heat exchanger 12.

[0022] A hot water tap 2 is connected to the hot water outlet passage 44. When the hot water tap 2 is opened, tap water in the water supply passage 40 flows out from the hot water tap 2, and the amount of tap water that flows out is replenished from the water supply passage 40 to the second hot water heat exchanger 13. When the water flow rate through the water supply passage 40 exceeds a predetermined ignition flow rate, combustion of fuel gas is started in the hot water burner 11, and the combustion in the hot water burner 11 is controlled according to the water flow rate. The tap water supplied to the hot water heating unit 10 through the water supply passage 40 is preheated in the second hot water heat exchanger 13, then heated in the first hot water heat exchanger 12, and flows out as hot water into the hot water outlet passage 44. A boiler temperature sensor 45 is installed in the hot water outlet passage 44 to detect the temperature of the hot water immediately after it flows out from the first hot water heat exchanger 12.

[0023] Furthermore, in this embodiment, the water supply passage 40 of the hot water supply device 1 has a bypass passage 46 branching off downstream of the flow control valve 42, and the bypass passage 46 is connected to the hot water outlet passage 44 at a connection point 44a downstream of the boiler temperature sensor 45. Therefore, it is possible to supply a portion of the tap water supplied from the water supply passage 40 to the hot water heating unit 10 to the hot water outlet passage 44 via the bypass passage 46 and mix it with the hot water flowing through the hot water outlet passage 44. In addition, a bypass control valve 47 is installed at the point where the bypass passage 46 branches off from the water supply passage 40, and the mixing ratio of tap water and hot water can be changed by controlling the opening degree of the bypass control valve 47. Furthermore, a hot water outlet temperature sensor 48 is installed in the hot water outlet passage 44 downstream of the connection point 44a of the bypass passage 46, and the temperature of the hot water (hot water outlet temperature) after the tap water from the bypass passage 46 and the hot water from the hot water outlet passage 44 have been mixed can be detected.

[0024] In addition, in this embodiment, the hot water outlet passage 44 of the hot water supply device 1 has a return passage 50 that branches off at branching position 44b just upstream of the hot water tap 2, and the branched return passage 50 is connected to the hot water outlet passage 44 at a confluence position 44c upstream of branching position 44b (but downstream of the connection position 44a of the bypass passage 46). In Figure 1, the return passage 50 is shown with a thicker line than the water supply passage 40 and the hot water outlet passage 44 in order to make it stand out. A hot water pump 51 and a check valve 52 are installed in the middle of the return passage 50, and when the hot water pump 51 is operated, hot water in the hot water outlet passage 44 is drawn out from branching position 44b, passes through the return passage 50, and then returns to the hot water outlet passage 44 from confluence position 44c. Therefore, while the instant hot water pump 51 is operating, hot water circulates in one direction within the circulation circuit formed by the hot water outlet passage 44 and the return passage 50 from the confluence point 44c to the branching point 44b. Hereafter, the hot water circulating within the circulation circuit will be referred to as "circulating hot water." In Figure 1, the direction in which the circulating hot water flows is indicated by an arrow.

[0025] Furthermore, a hot water flow sensor 53 is installed in the middle of the return passage 50 (upstream of the hot water pump 51 in the example shown in Figure 1), which can detect the flow rate of the circulating hot water. In addition, a hot water heat exchanger 54 is installed in the middle of the return passage 50 (downstream of the hot water pump 51 in the example shown in Figure 1). Therefore, even if the temperature of the circulating hot water decreases while circulating in the circulation circuit, the hot water can be heated by the hot water heat exchanger 54. Corresponding to this, a hot water return temperature sensor 56 is installed in the return passage 50 upstream of the hot water heat exchanger 54 to detect the temperature of the circulating hot water before it is heated by the hot water heat exchanger 54, and a hot water supply temperature sensor 57 is installed in the outlet passage 44 between the confluence position 44c and the branching position 44b downstream of the hot water heat exchanger 54 to detect the temperature of the circulating hot water after it has been heated by the hot water heat exchanger 54. Furthermore, the instant hot water return temperature sensor 56 in this embodiment corresponds to the "upstream temperature sensor" in the present invention, and the instant hot water supply temperature sensor 57 in this embodiment corresponds to the "downstream temperature sensor" in the present invention.

[0026] Furthermore, a hot water supply passage 60 branches off from the hot water outlet passage 44 downstream of the hot water temperature sensor 48 and upstream of the confluence point 44c of the return passage 50, making it possible to supply hot water to a bathtub (not shown) via the hot water supply passage 60. The hot water supply passage 60 is equipped with a solenoid valve 61 for opening and closing the hot water supply passage 60, a check valve 62 for preventing backflow of hot water from the bathtub side, and a hot water flow rate sensor 63 for detecting the flow rate of hot water flowing through the hot water supply passage 60.

[0027] The above describes the path by which hot water generated in the hot water heating section 10 of the hot water supply system 1 is supplied to the hot water tap 2 and a bathtub (not shown). On the other hand, the heat transfer medium (hot water) heated in the heating section 20 of the hot water supply system 1 is used for heating each room and for reheating the hot water in the bathtub. Accordingly, a heating supply passage 70 is connected to the downstream side of the first heating heat exchanger 22 of the heating section 20, and the heat transfer medium heated in the first heating heat exchanger 22 is supplied to a heating terminal (such as a floor heating panel) (not shown) via the heating supply passage 70. After the heat transfer medium supplied to the heating terminal loses heat, it returns to the second heating heat exchanger 23 through the heating return passage 71. In addition, the downstream side of the second heating heat exchanger 23 and the upstream side of the first heating heat exchanger 22 are connected by a heating connecting passage 72, and a cistern 73 for storing the heat transfer medium and a heating pump 74 are provided in the middle of the heating connecting passage 72.

[0028] The heat transfer medium returned to the second heat exchanger 23 via the heating return passage 71 is heated in the second heat exchanger 23 by recovering latent heat, and then flows into the cistern 73. It is then supplied to the first heat exchanger 22 by the heating pump 74, where it is further heated, and then supplied again to the heating terminal via the heating supply passage 70. The heating supply passage 70 is also equipped with a heating high-temperature sensor 76 that detects the temperature of the heat transfer medium supplied to the heating terminal. Furthermore, the heating communication passage 72 between the heating pump 74 and the second heat exchanger 23 is equipped with a heating low-temperature sensor 75 that detects the temperature of the heat transfer medium supplied from the heating pump 74 to the second heat exchanger 23.

[0029] Furthermore, a reheating branch passage 80 branches off from the heating supply passage 70 and connects to the heating return passage 71. A bath flow control valve 81 and a bath heat exchanger 82 are installed in the middle of the reheating branch passage 80. Therefore, by opening the bath flow control valve 81 while the heat transfer medium is flowing through the heating supply passage 70, a portion of the heat transfer medium can be directed to the reheating branch passage 80, pass through the bath heat exchanger 82, and then return to the heating return passage 71. In addition, the flow rate of the heat transfer medium passing through the bath heat exchanger 82 can be adjusted by changing the valve opening of the bath flow control valve 81.

[0030] The bath heat exchanger 82 is used to heat the hot water in the bathtub (not shown). Specifically, the bath heat exchanger 82 is connected to a bath return passage 90 and a bath supply passage 91, and a bath pump 92 is mounted in the bath return passage 90. When the bath pump 92 is operated, the hot water in the bathtub is supplied to the bath heat exchanger 82 via the bath return passage 90, passes through the bath heat exchanger 82, and is returned to the bathtub via the bath supply passage 91. Therefore, by opening the bath flow control valve 81 of the heating supply passage 70 and circulating the heat transfer medium to the bath heat exchanger 82, while operating the bath pump 92 to circulate the hot water in the bathtub to the bath heat exchanger 82, the hot water in the bathtub can be heated within the bath heat exchanger 82.

[0031] Furthermore, a hot water supply passage 83 branches off from the heating supply passage 70, and this hot water supply passage 83 is also connected to the heating return passage 71. A hot water flow control valve 84 and the aforementioned hot water heat exchanger 54 are installed in the middle of the hot water supply passage 83. Therefore, when a heat transfer medium is supplied to the heating supply passage 70 (for example, when heating is being performed at a heating terminal not shown, or when reheating of a bath not shown), opening the hot water flow control valve 84 allows a portion of the heat transfer medium flowing through the heating supply passage 70 to be supplied to the hot water heat exchanger 54. Thus, as described above, by operating the hot water pump 51 to circulate the heat transfer medium to the hot water heat exchanger 54, and opening the hot water flow control valve 84 to circulate a portion of the heat transfer medium from the heating supply passage 70 to the hot water heat exchanger 54, the circulating hot water can be heated in the hot water heat exchanger 54. In the following, the operation in which the instant hot water pump 51 is operated while the circulating hot water is heated in the instant hot water heat exchanger 54 will be referred to as "instant hot water operation".

[0032] Furthermore, the instant hot water flow control valve 84 in this embodiment employs a stepping motor type flow control valve, and by changing the valve opening, the flow rate of the heat medium supplied to the instant hot water heat exchanger 54 can be changed, thereby adjusting the amount of heating of the circulating hot water circulated by the instant hot water pump 51. In addition, if it is determined that the temperature of the circulating hot water is too high during instant hot water operation, the instant hot water flow control valve 84 can be closed to stop the heating of the circulating hot water. By performing instant hot water operation in this manner, when a user of the hot water supply device 1 opens the hot water tap 2, hot water can be dispensed immediately. Of course, if the user stops the instant hot water function, the instant hot water pump 51 can be stopped, and furthermore, the instant hot water flow control valve 84 can be closed to stop the heating of the circulating hot water. Such control is realized by the control unit 100 mounted on the hot water supply device 1. Note that the instant hot water flow control valve 84 in this embodiment corresponds to the "instant hot water on / off valve" in the present invention.

[0033] The control unit 100 has a built-in microcomputer and memory, and various programs are stored in the memory. Furthermore, the control unit 100 is connected to the aforementioned combustion fan 14, various solenoid valves and control valves, various sensors, and various pumps such as the instant hot water pump 51. The control unit 100 is also connected to an outside temperature sensor 100a that detects the temperature outside the hot water supply device 1. The control unit 100 then executes the programs stored in the memory and controls the operation of the combustion fan 14, various solenoid valves and control valves, and various pumps in accordance with the output of the various sensors, thereby performing hot water supply operation, which dispenses hot water from the hot water tap 2 when the tap is opened, heating operation, which supplies heat transfer fluid to the heating terminal to heat the room, bath filling operation, which supplies hot water to the bathtub, reheating operation, which reheats the hot water in the bathtub, and instant hot water operation, which realizes the instant hot water function according to the user's settings.

[0034] However, even though the control unit 100 has closed the instant hot water flow control valve 84, an open failure may occur in which the instant hot water flow control valve 84 does not close completely. When an open failure occurs in the instant hot water flow control valve 84, the heat transfer medium flowing through the heating supply passage 70 is supplied to the instant hot water heat exchanger 54, so when the hot water tap 2 is opened, heated hot water may flow out from the hot water tap 2 against the user's intention. Therefore, in order to detect an open failure of the instant hot water flow control valve 84, the control unit 100 in this embodiment has the following internal structure.

[0035] Figure 2 is a block diagram conceptually showing the internal structure of the control unit 100 mounted in the hot water supply device 1 of this embodiment. As shown in the figure, the control unit 100 is equipped with a hot water supply operation execution unit 101, a heating operation execution unit 102, an instant hot water operation execution unit 103, a maintenance operation execution unit 104, a freeze prevention operation execution unit 105, a detectable condition determination unit 106, a temperature rise amount calculation unit 107, and an open fault detection unit 108. Note that these "units" are abstract concepts representing the functions that the control unit 100 has for the purpose of detecting open faults of the instant hot water flow control valve 84, and do not indicate that the inside of the control unit 100 is divided into these "units" or that components corresponding to these "units" are mounted inside the control unit 100. These "units" can be implemented as software programs executed by a microcomputer built into the control unit 100, or as hardware such as LSIs and ICs mounted on the control unit 100. Furthermore, they may be implemented by combining software programs and hardware.

[0036] The hot water operation execution unit 101 performs various controls for the hot water supply device 1 to perform hot water operation, and the heating operation execution unit 102 performs various controls for the hot water supply device 1 to perform heating operation. The instant hot water operation execution unit 103 performs various controls to perform instant hot water operation according to the user's settings. Note that instant hot water operation is not performed while hot water is being dispensed from the hot water tap 2 (i.e., during hot water operation), so the instant hot water operation execution unit 103 obtains information from the hot water operation execution unit 101 about whether or not hot water operation is in progress, and stops instant hot water operation during hot water operation. In Figure 2, the arrows shown from the hot water operation execution unit 101 to the instant hot water operation execution unit 103 indicate that the instant hot water operation execution unit 103 is obtaining information from the hot water operation execution unit 101 about whether or not hot water operation is in progress.

[0037] Furthermore, the maintenance operation execution unit 104 performs various controls to perform maintenance operations on the instant hot water pump 51. Here, the maintenance operation of the instant hot water pump 51 refers to the operation of periodically rotating the instant hot water pump 51 to prevent problems such as the internal sliding parts of the instant hot water pump 51 becoming stuck if it does not rotate for a long period of time. Furthermore, the freeze prevention operation execution unit 105 performs various controls to perform freeze prevention operations on the hot water outlet passage 44 and the return passage 50. Here, the freeze prevention operation of the hot water outlet passage 44 and the return passage 50 refers to the operation of periodically rotating the instant hot water pump 51 to circulate the water in the hot water outlet passage 44 and the return passage 50 when the outside temperature of the hot water supply device 1 drops below a predetermined set temperature (hereinafter referred to as the freeze prevention temperature) in order to prevent the water inside the hot water outlet passage 44 and the return passage 50 from freezing due to a drop in the outside temperature of the hot water supply device 1.

[0038] Furthermore, the detectable condition determination unit 106 executes control to determine whether the conditions (detectable conditions) for detecting an open failure of the instant hot water flow control valve 84 have been met. To determine whether the detectable conditions have been met, the unit uses information on whether heating operation is in progress, whether the instant hot water pump 51 is operating, whether maintenance operation is in progress, and whether freeze prevention operation is in progress. The detectable condition determination unit 106 obtains this information from the heating operation execution unit 102, the instant hot water operation execution unit 103, the maintenance operation execution unit 104, and the freeze prevention operation execution unit 105. In Figure 2, the arrows pointing from the heating operation execution unit 102, the instant hot water operation execution unit 103, the maintenance operation execution unit 104, and the freeze prevention operation execution unit 105 to the detectable condition determination unit 106 indicate that the instant hot water operation execution unit 103 obtains this information.

[0039] Then, when the detectable condition determination unit 106 determines that the detectable condition has been met, it outputs information to that effect to the temperature rise amount calculation unit 107. The temperature rise amount calculation unit 107 then obtains the temperature of the circulating hot water detected by the instant hot water return temperature sensor 56 and the instant hot water supply temperature sensor 57, calculates the temperature rise amount due to the circulating hot water passing through the instant hot water heat exchanger 54, and outputs the obtained temperature rise amount to the open fault detection unit 108. The open fault detection unit 108 then determines whether or not the instant hot water branch passage 83 is open based on the temperature rise amount output from the temperature rise amount calculation unit 107. In Figure 2, the arrows displayed from the detectable condition determination unit 106 to the temperature rise amount calculation unit 107 indicate that information indicating that the detectable condition has been met is output, and the arrows displayed from the temperature rise amount calculation unit 107 to the open fault detection unit 108 indicate that the temperature rise amount is output.

[0040] Figure 3 is a flowchart showing the first half of the open fault determination process performed by the control unit 100 in this embodiment to detect an open fault in the instant hot water branch passage 83. Figure 4 is a flowchart showing the second half of the open fault determination process. As shown in Figure 3, the open fault determination process first determines whether the hot water supply device 1 is in instant hot water operation or not (STEP 1). An open fault in the instant hot water branch passage 83 is a fault in which the instant hot water branch passage 83 is not completely closed despite being closed. Therefore, in order to detect an open fault in the instant hot water branch passage 83, it is necessary to close the instant hot water branch passage 83 as a prerequisite, and for that to happen, it is necessary that the hot water supply device 1 is not in instant hot water operation. Thus, when the open fault determination process is started, the first thing to do is to determine whether or not instant hot water operation is in progress.

[0041] As a result, if the hot water heater 1 is in instant hot water operation (STEP1: yes), it is not possible to detect an open fault in the instant hot water branch passage 83, so the system enters a standby state by repeating the determination in STEP1. Then, when the instant hot water operation is stopped, it is determined that the system is no longer in instant hot water operation (STEP1: no), and then it is determined whether the instant hot water pump 51 has been stopped continuously for a predetermined time limit or longer (STEP2). If the instant hot water pump 51 is left stopped for a long period of time, internal seizing may occur and cause a malfunction, so in this embodiment, the hot water heater 1 performs a maintenance operation to rotate the instant hot water pump 51 if it has been stopped continuously for a predetermined time limit or longer. Therefore, in STEP2, it is determined whether the instant hot water pump 51 has been stopped continuously for a predetermined time limit or longer. The time limit in this embodiment is set to 720 hours.

[0042] As a result, if the instant hot water pump 51 is not stopped for longer than the time limit (STEP 2: no), then it is determined whether the outside air temperature of the hot water supply device 1 is lower than a predetermined freeze prevention temperature (STEP 3). In this embodiment, when the outside air temperature of the hot water supply device 1 falls below a predetermined freeze prevention temperature, the instant hot water pump 51 is rotated to circulate the water in the hot water outlet passage 44 and the return passage 50 in order to prevent the water from freezing inside the hot water outlet passage 44 and the return passage 50. Therefore, if "no" is determined in STEP 2, it is determined whether the outside air temperature of the hot water supply device 1 is lower than the freeze prevention temperature (STEP 3). The outside air temperature of the hot water supply device 1 can be detected by the outside air temperature sensor 100a (see Figure 1). The freeze prevention temperature in this embodiment is set to 3°C.

[0043] As a result, if it is determined that the outside temperature is not below the freeze prevention temperature (STEP3: no), the process returns to the beginning and determines whether or not instant hot water operation is in progress (STEP1). In this way, in the fault detection process, if instant hot water operation is in progress (STEP1: yes), or even if instant hot water operation is stopped, the process repeats the determinations in STEP1 to STEP3 described above until the time the instant hot water pump 51 has been continuously stopped reaches the time limit (STEP2: yes), or until the outside temperature falls below the freeze prevention temperature (STEP3: yes).

[0044] Then, after repeating these decisions, if the time the instant hot water pump 51 has been continuously stopped reaches the time limit (STEP 2: yes), the maintenance operation is started by rotating the instant hot water pump 51 (STEP 4). Also, if the outside air temperature falls below the freeze prevention temperature (STEP 3: yes), the freeze prevention operation is started by rotating the instant hot water pump 51 (STEP 5). In addition, electric heaters may be installed in the hot water outlet passage 44 and the return passage 50, and when performing the freeze prevention operation, the instant hot water pump 51 is rotated and the electric heaters are energized to heat the water in the hot water outlet passage 44 and the return passage 50.

[0045] Once the instant hot water pump 51 is rotated to start maintenance or freeze prevention operation (STEP 4 or STEP 5), it is determined whether the hot water supply system 1 is in heating operation (STEP 6). If the result is that the hot water supply system 1 is not in heating operation (STEP 6: no), it can be determined that the conditions for detecting an open fault of the instant hot water flow control valve 84 are not met, so the process returns to the beginning and it is determined again whether the instant hot water is in operation (STEP 1).

[0046] In contrast, if the hot water supply unit 1 is in heating operation (STEP 6: yes), it can be determined that the conditions for detecting an open fault in the instant hot water flow control valve 84 have been met, and the process for detecting an open fault in the instant hot water flow control valve 84 (open fault detection process) is started (STEP 20). Thus, the open fault detection process (STEP 20) is started when the detection conditions are met, which are not in instant hot water operation (STEP 1: no), maintenance operation (STEP 4), freeze prevention operation (STEP 5), and heating operation (STEP 6: yes). The details of the open fault detection process will be described later.

[0047] After completing the open fault detection process (STEP20), the system returns to the open fault determination process and then determines whether or not maintenance is in progress (STEP7 in Figure 4). If maintenance is in progress (STEP7: yes), the system determines whether a predetermined maintenance time has elapsed since the start of rotation of the instant hot water pump 51 (STEP8). In this embodiment, the maintenance time is set to 5 minutes. If the maintenance time has not elapsed (STEP8: no), the system checks whether or not heating operation is continuing (STEP10). If it is confirmed that heating operation is still in progress (STEP10: yes), the system starts the open fault detection process described later (STEP20).

[0048] In contrast, if the maintenance operation time has not yet elapsed (STEP8: no), but the heating operation has ended (STEP10: no), it is not possible to determine whether the instant hot water flow control valve 84 is open or not, so the open fault determination process shown in Figures 3 and 4 is terminated. Also, if the determination in STEP8 is that the maintenance operation time has elapsed (STEP8: yes), the maintenance operation is terminated by stopping the instant hot water pump 51 (STEP9), and then the open fault determination process is terminated.

[0049] Furthermore, as described above using Figure 3, the open fault detection process (STEP 20) is started either during maintenance operation or freeze prevention operation. Therefore, if it is determined in STEP 7, after returning from the open fault detection process (STEP 20), that maintenance operation is not in progress (STEP 7: no), then it is considered that freeze prevention operation is in progress. If "no" is determined in STEP 7, then it is determined whether a predetermined freeze prevention operation time has elapsed since the start of rotation of the instant hot water pump 51 (STEP 11). In this embodiment, the freeze prevention operation time is set to 15 minutes.

[0050] Then, if the freeze prevention operation time has not elapsed since the start of rotation of the instant hot water pump 51 (STEP11: no), it is checked whether heating operation is still continuing (STEP13). If it is confirmed that heating operation is still in progress (STEP13: yes), the open fault detection process described later is started (STEP20). On the other hand, if the freeze prevention operation time has not yet elapsed (STEP11: no), but heating operation has ended (STEP13: no), it is not possible to determine whether there is an open fault in the instant hot water flow control valve 84, so the open fault determination process shown in Figures 3 and 4 is terminated.

[0051] Figure 5 is a flowchart of the open fault detection process, which is performed to detect whether or not there is an open fault in the instant hot water flow control valve 84 during the open fault determination process. As described above using Figure 3, this process is started when it is determined during the open fault determination process that the conditions for detecting an open fault in the instant hot water flow control valve 84 have been met.

[0052] As shown in Figure 5, when the open fault detection process (STEP 20) is started, the first step is to check whether the instant hot water flow control valve 84 is set to the closed state (STEP 21). That is, in order to detect an open fault in the instant hot water flow control valve 84, it is necessary to set the instant hot water flow control valve 84 to the closed state. Therefore, the first step is to determine whether the instant hot water flow control valve 84 is set to the closed state (STEP 21). If it is not set to the closed state (STEP 21: no), the open fault in the instant hot water flow control valve 84 cannot be detected, so the open fault detection process in Figure 5 is terminated, and the process returns to STEP 7 of the open fault determination process in Figure 3.

[0053] Furthermore, the open fault detection process in Figure 5 is initiated when the conditions for detecting an open fault in the instant hot water flow control valve 84 are determined to be met during the open fault determination process shown in Figures 3 and 4. For the conditions for detecting an open fault to be met, the instant hot water operation must be stopped. Therefore, at the time the open fault detection process in Figure 5 is initiated, the instant hot water flow control valve 84 should normally be set to the closed state. However, it is possible that the instant hot water operation may have started for some reason, so in STEP 21, as a precaution, it is confirmed that the instant hot water flow control valve 84 is set to the closed state.

[0054] Next, it is determined whether a predetermined time has elapsed since the instant hot water pump 51 started rotating (STEP 22). That is, since the rotation of the instant hot water pump 51 has started in either STEP 4 or STEP 5 in Figure 3 before the open fault detection process in Figure 5 is started, it is determined whether a predetermined time has elapsed since the rotation started. The predetermined time is set to the time required (for example, 1 minute) for the water in the hot water outlet passage 44 and the return passage 50 to circulate stably through the hot water outlet passage 44 and the return passage 50. If the predetermined time has not yet elapsed (STEP 22: no), the system enters a standby state by repeating the determination in STEP 22.

[0055] As a result, if it is determined that a predetermined time has elapsed (STEP22: yes), the temperature of the hot water upstream of the instant hot water heat exchanger 54 and the temperature of the hot water downstream are detected (STEP23). The temperatures of the hot water upstream and downstream of the instant hot water heat exchanger 54 can be detected using the instant hot water return temperature sensor 56 and the instant hot water supply temperature sensor 57, respectively (see Figure 1).

[0056] Then, the temperature rise in the instant hot water heat exchanger 54 is calculated by subtracting the temperature of the hot water detected upstream from the temperature of the hot water detected downstream of the instant hot water heat exchanger 54 (STEP 24), and it is determined whether a predetermined duration has elapsed while the temperature rise is greater than a predetermined threshold temperature (STEP 25). The length of the duration can be set as appropriate. If a quick decision is prioritized, a short time (e.g., 3 to 5 seconds) may be set, and if avoiding misjudgment is prioritized, a long time (e.g., 60 seconds) may be set. As a result, if the duration has been reached while the temperature rise in the instant hot water heat exchanger 54 is greater than the threshold temperature (STEP 25: yes), it is determined that an open failure has occurred in the instant hot water flow control valve 84 (STEP 26). The reason for determining that the instant hot water flow control valve 84 has an open failure when the temperature rise is greater than the threshold temperature is as follows.

[0057] First, since the instant hot water flow control valve 84 is set to the closed position, the heat transfer medium from the heating supply passage 70 should not be supplied to the instant hot water heat exchanger 54. If the heat transfer medium from the heating supply passage 70 is not supplied to the instant hot water heat exchanger 54, even if the instant hot water pump 51 circulates the water in the outlet passage 44 and the return passage 50, the water will not be heated in the instant hot water heat exchanger 54. However, if the temperature of the water passing through the instant hot water heat exchanger 54 rises above the threshold temperature, this indicates that the heat transfer medium from the heating supply passage 70 is being supplied to the instant hot water heat exchanger 54. The fact that the heat transfer medium from the heating supply passage 70 is being supplied to the instant hot water heat exchanger 54 despite the instant hot water flow control valve 84 being set to the closed position can only mean that the instant hot water flow control valve 84 is malfunctioning and open. For these reasons, if the temperature rise calculated in STEP 24 of Figure 5 remains greater than the threshold temperature for a predetermined duration, it can be determined that the instant hot water flow control valve 84 is malfunctioning and open.

[0058] In contrast, if it is determined that the temperature rise in the instant hot water heat exchanger 54 has not reached the threshold temperature, or even if it has reached the threshold temperature, the duration of that state has not elapsed (STEP25: no), then it can be assumed that the instant hot water flow control valve 84 is not open. Once the presence or absence of an open fault in the instant hot water flow control valve 84 has been detected in this manner, the open fault detection process in Figure 5 is terminated, and the process returns to STEP7 of the open fault determination process in Figure 3.

[0059] As described above, the hot water supply system 1 of this embodiment can detect an open failure of the instant hot water flow control valve 84 based on the amount of temperature rise of the hot water on the upstream and downstream sides of the instant hot water heat exchanger 54. In order to detect an open failure of the instant hot water flow control valve 84, it is necessary to close the instant hot water flow control valve 84, but the open / closed state of the instant hot water flow control valve 84 is linked to the operating state of the instant hot water pump 51, and if the instant hot water flow control valve 84 is closed, the instant hot water pump 51 will stop. For this reason, it has been thought that it is impossible in principle to detect an open failure of the instant hot water flow control valve 84. However, when the hot water supply system 1 performs maintenance operations during heating operation, or when it performs freeze prevention operations during heating operation, the instant hot water flow control valve 84 may be closed and the instant hot water pump 51 may rotate. Therefore, the hot water supply system 1 of this embodiment detects when these conditions are met, and when heating operation is also in progress, and determines whether or not there is an open failure of the instant hot water flow control valve 84. This makes it possible to determine whether or not the instant hot water flow control valve 84 is malfunctioning by opening it, within the normal control of the hot water supply device 1.

[0060] As shown in Figure 1, in the hot water supply system 1 of this embodiment, the instant hot water return temperature sensor 56, which detects the temperature of the hot water upstream of the instant hot water heat exchanger 54, is located between the instant hot water pump 51 and the instant hot water heat exchanger 54, that is, relatively close to the instant hot water heat exchanger 54. In contrast, the instant hot water supply temperature sensor 57, which detects the temperature of the hot water downstream of the instant hot water heat exchanger 54, is located downstream of the confluence point 44c where the return passage 50 merges with the outlet passage 44, that is, far from the instant hot water heat exchanger 54. The reason for mounting the instant hot water supply temperature sensor 57 in this position is to shorten the distance from the instant hot water supply temperature sensor 57 to the hot water tap 2, thereby accurately detecting the actual temperature of the hot water flowing out of the hot water tap 2 when the user opens the tap 2. However, on the other hand, the distance from the instant hot water heat exchanger 54 to the instant hot water supply temperature sensor 57 becomes longer, so there is a possibility that the temperature of the hot water heated by the instant hot water heat exchanger 54 will decrease before it reaches the instant hot water supply temperature sensor 57.

[0061] Furthermore, when determining whether the instant hot water flow control valve 84 is open or not, since the instant hot water flow control valve 84 is set to the closed state (see STEP 21 in Figure 5), even if the instant hot water flow control valve 84 is open or malfunctioning, the flow rate of the heat medium supplied from the heating supply passage 70 to the instant hot water heat exchanger 54 is considered to be small. For this reason, even if the hot water circulating by the instant hot water pump 51 is heated in the instant hot water heat exchanger 54, the temperature may drop before reaching the instant hot water supply temperature sensor 57, making it impossible to detect the open or malfunctioning of the instant hot water flow control valve 84. Therefore, instead of the open or malfunction detection process in Figure 5, the following open or malfunction detection process may be performed.

[0062] Figure 6 is a flowchart of the modified open fault detection process performed by the hot water heater 1. This process is performed in place of the open fault detection process (STEP 20) in the open fault determination process shown in Figures 3 and 4.

[0063] As shown in the figure, when the modified fault detection process (STEP 30) is started, the first thing that happens is the instant hot water flow control valve 84 is set to the open state (STEP 31). That is, in the modified fault detection process described above using Figure 5, when the process is started, it is first confirmed that the instant hot water flow control valve 84 is in the closed state, but in the modified fault detection process, the instant hot water flow control valve 84 is opened. As a result, the heat transfer medium in the heating supply passage 70 is supplied to the instant hot water heat exchanger 54, heating the circulating hot water in the instant hot water heat exchanger 54, and the instant hot water pump 51 circulates this circulating hot water, so the outlet passage 44 and the return passage 50 are heated.

[0064] Once the instant hot water flow control valve 84 is opened (STEP 31), it is determined whether a predetermined heating time has elapsed (STEP 32). In this embodiment, the heating time is set to a short period of time, from 30 seconds to about 1 minute. If it is determined that the heating time has not elapsed (STEP 32: no), the system enters a standby state by repeating the determination in STEP 32. If it is determined that the heating time has elapsed (STEP 32: yes), the instant hot water flow control valve 84 is set to a closed state (STEP 33).

[0065] Next, it is determined whether a predetermined stabilization time has elapsed (STEP 34). If it is determined that the stabilization time has not elapsed (STEP 34: no), the system enters a standby state by repeating the determination in STEP 34. However, if it is determined that the stabilization time has elapsed (STEP 34: yes), the temperature of the hot water upstream of the instant hot water heat exchanger 54 and the temperature of the hot water downstream are detected (STEP 35). In other words, in the modified fault detection process, the instant hot water flow control valve 84 is closed, and the system waits for the stabilization time to elapse before detecting the temperature of the hot water. This is done for the following reasons.

[0066] As described above, in the modified fault detection process, when the process starts, the instant hot water flow control valve 84 is opened to supply a portion of the heat transfer medium from the heating supply passage 70 to the instant hot water heat exchanger 54 (STEP 31). Therefore, even if the instant hot water flow control valve 84 is closed in STEP 33, the instant hot water heat exchanger 54 remains heated for a while, causing the temperature of the circulating hot water to rise as it passes through the instant hot water heat exchanger 54. The circulating hot water that flows out of the instant hot water heat exchanger 54 then warms the downstream return passage 50 and outlet passage 44 before returning to the instant hot water heat exchanger 54. As a result, when the instant hot water pump 51 is running, the temperatures of the instant hot water heat exchanger 54, return passage 50, outlet passage 44, and instant hot water pump 51 become uniform and eventually stabilize. The stabilization time is the time required for the temperatures of the instant hot water heat exchanger 54, return passage 50, outlet passage 44, and instant hot water pump 51 to stabilize. In this embodiment, the stabilization time is set to 5 minutes.

[0067] After the stabilization time has elapsed (STEP34: yes), the temperature of the hot water is detected on both the upstream and downstream sides of the instant hot water heat exchanger 54 (STEP35). Then, in the same manner as the open fault detection process in this embodiment described above, the presence or absence of an open fault in the instant hot water flow control valve 84 is detected. Briefly, the temperature rise in the instant hot water heat exchanger 54 is calculated by subtracting the temperature of the hot water detected on the upstream side from the temperature of the hot water detected on the downstream side of the instant hot water heat exchanger 54 (STEP36), and it is determined whether a predetermined duration has elapsed while the temperature rise is greater than a predetermined threshold temperature (STEP37). The length of the duration can be set as appropriate.

[0068] As a result, if the temperature rise in the instant hot water heat exchanger 54 remains above the threshold temperature for an extended period (STEP37: yes), it is determined that an open fault has occurred in the instant hot water flow control valve 84 (STEP38), and the open fault detection process of the modified example is terminated. On the other hand, if it is determined that the temperature rise in the instant hot water heat exchanger 54 has not reached the threshold temperature, or even if it has reached the threshold temperature, the duration of that state has not elapsed (STEP37: no), it is considered that the instant hot water flow control valve 84 has not experienced an open fault, so the open fault detection process is terminated, and the process returns to the open fault determination process in Figure 3.

[0069] In the modified example described above, the open fault detection process can suppress the cooling of the hot water heated by the instant hot water heat exchanger 54 before it reaches the instant hot water supply temperature sensor 57, thereby enabling accurate detection of an open fault in the instant hot water flow control valve 84.

[0070] In the modified example described above, the open fault detection process was explained assuming that the same heating time and stabilization time are used regardless of whether it is initiated during maintenance or freeze prevention. However, if the open fault detection process is initiated during freeze prevention, it is also possible to use a longer heating time and stabilization time than when it is initiated during maintenance.

[0071] Alternatively, instead of performing the open fault detection process described above, an additional temperature sensor may be installed immediately downstream of the instant hot water heat exchanger 54, separate from the instant hot water supply temperature sensor 57. This allows for the detection of the temperature rise of the circulating hot water in the instant hot water heat exchanger 54 without being affected by the coldness of the return passage 50 or the outlet passage 44, thereby enabling accurate detection of whether or not the instant hot water flow control valve 84 is open.

[0072] Although the hot water supply device 1 of this embodiment and its modified form has been described above, the present invention is not limited to the above embodiment and its modified form, and can be implemented in various forms without departing from the spirit of the invention. [Explanation of symbols]

[0073] 1...Hot water supply unit, 2...Hot water tap, 10...Hot water heating unit, 11...Hot water burner, 12...Hot water supply heat exchanger 1, 13...Hot water supply heat exchanger 2, 14...Combustion fan, 20... Heating section, 21... Heating burner, 22... First heating heat exchanger, 23... Heating second heat exchanger, 30... Gas passage, 31... Main valve, 32…Proportional valve, 33…Hot water solenoid valve, 34…Heating solenoid valve, 40...Water supply passage, 41...Flow sensor, 42...Flow control valve, 43...Hot water supply connection passage, 44...Hot water outlet passage, 44a...Connection location, 44b...Branching point, 44c...Merging point, 45...Can body temperature sensor, 46... Bypass passage, 47... Bypass control valve, 48... Hot water temperature sensor, 50...Recirculation passage, 51...Instant hot water pump, 52...Check valve, 53...Instant hot water flow sensor, 54...Instant hot water heat exchanger, 56...Instant hot water return temperature sensor, 57... Instant hot water supply temperature sensor, 60... Hot water filling passage, 61... Hot water filling solenoid valve, 62... Check valve, 63... Hot water volume sensor, 70... Heating supply passage, 71... Heating return passage, 72... Heating connecting passage, 73... Cistern, 74... Heating pump, 75... Low-temperature heating sensor, 76... High-temperature heating sensor, 80... Reheating branch passage, 81... Bath flow control valve, 82... Bath heat exchanger, 83... Instant hot water branching passage, 84... Instant hot water flow control valve, 90... Bath return passage, 91... Bath supply passage, 92... Bath pump, 100... Control unit, 100a...Outside temperature sensor, 101...Hot water supply operation unit, 102...Heating operation execution unit, 103...Instant hot water operation execution unit, 104...Maintenance operation execution unit, 105...Freeze prevention operation execution unit, 106...Detectable condition determination unit, 107...Temperature rise amount calculation unit, 108...Open fault detection unit.

Claims

1. In a hot water supply system that generates hot water by heating water supplied from a water supply passage, performs hot water supply operation by supplying the hot water to a hot water tap via a hot water outlet passage, and performs heating operation by circulating the heated heat transfer medium to the heating terminal via a heating supply passage and a heating return passage, A return passage branches off from the hot water outlet passage at a branching point upstream of the hot water tap, and is connected to the hot water outlet passage at a merging point upstream of the branching point. A hot water pump mounted in the return passage draws hot water from the hot water outlet passage into the return passage from the branching point and returns it to the hot water outlet passage from the confluence point, thereby circulating the hot water in the hot water outlet passage and the return passage as circulating hot water. A hot water heat exchanger is mounted in the aforementioned return passage, through which the circulating hot water is passed by the hot water pump, A hot water branching passage that branches off from the aforementioned heating supply passage and supplies a portion of the heat transfer medium supplied to the heating terminal to the hot water heat exchanger, A hot water supply opening / closing valve for opening and closing the aforementioned hot water supply branch passage, An upstream temperature sensor for detecting the temperature of the circulating hot water is located upstream of the instant hot water heat exchanger. A downstream temperature sensor located downstream of the instant hot water heat exchanger detects the temperature of the circulating hot water, A control unit that controls the hot water supply operation, the heating operation, and the operation of the instant hot water pump and the instant hot water on / off valve. Equipped with, The control unit, An instant hot water operation execution unit performs an instant hot water operation in which, while performing the heating operation, it opens the instant hot water on / off valve to supply a portion of the heat medium to the instant hot water heat exchanger, and operates the instant hot water pump to circulate the circulating hot water, thereby heating the circulating hot water with the heat medium. A maintenance operation execution unit, which, when predetermined maintenance conditions are met, controls the instant hot water on / off valve to a closed state and operates the instant hot water pump to perform maintenance operations, When performing the aforementioned maintenance operation, a detectable condition determination unit detects whether the heating operation is in progress, and if the heating operation is in progress, determines that the conditions for detecting an open malfunction of the instant hot water on / off valve have been met. When the conditions for detecting an open fault are met, a temperature rise calculation unit calculates the amount of temperature rise of the circulating hot water in the instant hot water heat exchanger based on the temperature of the circulating hot water detected by the upstream temperature sensor and the temperature of the circulating hot water detected by the downstream temperature sensor. If the temperature rise does not reach a predetermined threshold temperature, or if a predetermined duration has not elapsed while the temperature has reached the threshold temperature, the instant hot water on / off valve is determined not to be open. If the temperature rise reaches the threshold temperature and the predetermined duration has elapsed, the instant hot water on / off valve is determined to be open. This is determined by the open failure detection unit. A hot water supply system characterized by being equipped with the following features.

2. In a hot water supply system that generates hot water by heating water supplied from a water supply passage, performs hot water supply operation by supplying the hot water to a hot water tap via a hot water outlet passage, and performs heating operation by circulating the heated heat transfer medium to the heating terminal via a heating supply passage and a heating return passage, A return passage branches off from the hot water outlet passage at a branching point upstream of the hot water tap, and is connected to the hot water outlet passage at a merging point upstream of the branching point. A hot water pump mounted in the return passage draws hot water from the hot water outlet passage into the return passage from the branching point and returns it to the hot water outlet passage from the confluence point, thereby circulating the hot water in the hot water outlet passage and the return passage as circulating hot water. A hot water heat exchanger is mounted in the aforementioned return passage, through which the circulating hot water is passed by the hot water pump, A hot water branching passage that branches off from the aforementioned heating supply passage and supplies a portion of the heat transfer medium supplied to the heating terminal to the hot water heat exchanger, A hot water supply opening / closing valve for opening and closing the aforementioned hot water supply branch passage, An upstream temperature sensor for detecting the temperature of the circulating hot water is located upstream of the instant hot water heat exchanger. A downstream temperature sensor located downstream of the instant hot water heat exchanger detects the temperature of the circulating hot water, A control unit that controls the hot water supply operation, the heating operation, and the operation of the instant hot water pump and the instant hot water on / off valve. Equipped with, The control unit, An instant hot water operation execution unit performs an instant hot water operation in which, while performing the heating operation, it opens the instant hot water on / off valve to supply a portion of the heat medium to the instant hot water heat exchanger, and operates the instant hot water pump to circulate the circulating hot water, thereby heating the circulating hot water with the heat medium. When predetermined freeze prevention conditions are met, the freeze prevention operation execution unit controls the instant hot water on / off valve to a closed state and operates the instant hot water pump to perform a freeze prevention operation, When performing the freeze prevention operation, the detectable condition determination unit detects whether the heating operation is in progress, and if the heating operation is in progress, it determines that the conditions for detecting an open malfunction of the instant hot water on / off valve have been met. When the conditions for detecting an open fault are met, a temperature rise calculation unit calculates the amount of temperature rise of the circulating hot water in the instant hot water heat exchanger based on the temperature of the circulating hot water detected by the upstream temperature sensor and the temperature of the circulating hot water detected by the downstream temperature sensor. If the temperature rise does not reach a predetermined threshold temperature, or if a predetermined duration has not elapsed while the temperature has reached the threshold temperature, the instant hot water on / off valve is determined not to be open. If the temperature rise reaches the threshold temperature and the predetermined duration has elapsed, the instant hot water on / off valve is determined to be open. This is determined by the open failure detection unit. A hot water supply system characterized by being equipped with the following features.

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