JP7840239B2 - Hot water supply system - Google Patents

Description

This invention relates to a hot water supply system capable of generating hot water by heating water supplied from a water supply passage, supplying the generated hot water to a hot water tap, and further heating a room by circulating the heated heat transfer medium to a heating terminal via a heating supply passage and a heating return passage.

A water heater is known that generates hot water by heating water supplied from a water supply passage and supplies the generated hot water to a hot water tap via a hot water outlet passage. In this water heater, when the user opens the hot water tap, tap water supplied from the water supply passage to the water heater is heated within the water heater to generate hot water, which then flows through the hot water outlet passage and is dispensed from the hot water tap. If a long period of time passes without the user opening the hot water tap, the hot water in the hot water outlet passage may cool down to cold water. In this case, after the user opens the hot water tap, a certain amount of time will be required for the water flowing out of the tap to become hot again.

Therefore, there are also known water heaters equipped with a function that allows hot water to be dispensed immediately after the user opens the hot water tap (a so-called instant hot water function). In water heaters equipped with an instant hot water function, the hot water outlet passage branches upstream of the tap, and the branched passage (hereinafter referred to as the return passage) connects to the hot water outlet passage further upstream, forming a circulation circuit (hereinafter referred to as the instant hot water circulation circuit). Furthermore, a circulation pump (hereinafter referred to as the instant hot water pump) and a heating means (hereinafter referred to as the instant hot water heating means) are installed in the return passage. When the instant hot water pump is operated, the hot water that had been supplied up to near the upstream of the tap 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 circulating in the instant hot water circulation circuit (hereinafter referred to as the circulating hot water) can be kept warm, so that hot water can be dispensed immediately when the user opens the tap.

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 the 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 the 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 the instant hot water branch passage). Therefore, if the user does not use the instant hot water function, the instant hot water valve can be closed to prevent the supply of heat transfer fluid to the instant hot water heat exchanger. Conversely, if the user uses the instant hot water function, the valve can be opened to supply heat transfer fluid to the instant hot water heat exchanger.

Thus, when guiding the heat transfer medium to the instant hot water heat exchanger by branching off the heating supply passage into an instant hot water branch passage, it is crucial that the instant hot water shut-off valve installed in the instant hot water branch 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 be unable to receive instant hot water. Furthermore, 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, heating the circulating hot water. This could cause a sudden gush of hot water when the user opens the hot water tap, potentially startling them.

Therefore, a technique has been proposed (Patent Document 1) that detects the temperature of the circulating hot water on the upstream and downstream sides of the instant hot water heat exchanger and determines whether or not there is a malfunction in the instant hot water shut-off valve based on the detected temperature difference.

Japanese Patent Publication No. 2001-193955

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 does not completely close. Therefore, to detect an open malfunction, the valve must be closed. However, in a hot water supply system equipped with an instant hot water function, closing the instant hot water valve stops the instant hot water function, causing the instant hot water pump to stop operating and the circulating hot water to cease circulating in the instant hot water circulation circuit. In this state, even if the temperature of the circulating hot water is detected at the upstream and downstream positions 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 meaningless values are obtained, making it impossible 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, even if the user has stopped the instant hot water function, opening the hot water tap will suddenly release hot water, potentially startling the user.

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 system equipped with both an instant hot water function and a heating function.

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,
The system includes 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,
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.
The present invention is characterized by comprising: an open failure detection unit that determines that the instant hot water on/off valve is not open if the temperature rise amount has not reached a predetermined threshold temperature or if a predetermined duration has not elapsed while the temperature has reached the threshold temperature, and determines that the instant hot water on/off valve is open if the duration has elapsed while the temperature rise amount has reached the threshold temperature.

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 and malfunctioning; otherwise, it is determined that the instant hot water valve is not open and malfunctioning.

This allows for the determination of whether the instant hot water valve is malfunctioning during maintenance while the water heater is operating in heating mode. As a result, it prevents situations where, even if the user has disabled the instant hot water function, a malfunctioning valve causes a sudden gush of hot water when the tap is opened, potentially startling the user.

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,
The system includes 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,
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.
The present invention is characterized by comprising: an open failure detection unit that determines that the instant hot water on/off valve is not open if the temperature rise amount has not reached a predetermined threshold temperature or if a predetermined duration has not elapsed while the temperature has reached the threshold temperature, and determines that the instant hot water on/off valve is open if the duration has elapsed while the temperature rise amount has reached the threshold temperature.

In this 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, and operating the instant hot water pump to circulate the 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, when predetermined freeze prevention conditions are met, the instant hot water valve is controlled to a closed state and the instant hot water pump is operated to perform freeze prevention. The conditions for meeting freeze prevention conditions can be, for example, when the outside air temperature falls below a predetermined freeze prevention temperature. When performing freeze prevention, the system detects whether heating operation is in progress. If heating operation is in progress, the 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 temperature rise reaches a predetermined threshold temperature and a predetermined duration has elapsed, it is determined that the instant hot water valve is malfunctioning; otherwise, it is determined that the instant hot water valve is not malfunctioning.

This allows the system to determine whether the instant hot water valve is malfunctioning when the freeze prevention function is activated during heating operation. Therefore, it becomes possible to more reliably prevent situations where, even if the user had disabled the instant hot water function, a sudden gush of hot water occurs when the tap is opened due to a malfunctioning instant hot water valve, thus surprising the user.

This is an explanatory diagram showing the overall configuration of the hot water supply system 1 in this embodiment. This is a block diagram showing the internal structure of the control unit 100 in this embodiment. This flowchart shows the first half of the open fault determination process executed by the control unit 100 in this embodiment. This is a flowchart showing the latter part of the open fault detection process. This is a flowchart of the open fault detection process performed within the open fault determination process. This is a flowchart of the open fault detection process for a modified example.

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 hot water supply operation, which heats tap water and supplies hot water to the hot water taps, and is also capable of heating operation, which circulates 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.

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 mounted below the hot water burner 11 to supply combustion air to the burner 11.

The heating unit 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. Combustion air supplied to the heating burner 21 is supplied by a combustion fan 14.

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 for opening and closing the gas passage 30, and a proportional valve 32 for adjusting the flow rate of fuel gas through the gas passage 30. Furthermore, the gas passage 30 branches into two downstream of the proportional valve 32; one branch is connected to the hot water burner 11, and the other branch is connected to the heating burner 21. A hot water solenoid valve 33 for opening and closing the passage is installed in the middle of the passage connected to the hot water burner 11, and a heating solenoid valve 34 for opening and closing the passage is installed in the middle of the passage connected to the heating burner 21.

The water supply passage 40, which 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, which controls the flow rate of tap water supplied to the second hot water heat exchanger 13, and a flow sensor 41, which detects the water 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.

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 in 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 of the first hot water heat exchanger 12.

Furthermore, in this embodiment, the water supply passage 40 of the hot water supply device 1 branches off into a bypass passage 46 downstream of the flow control valve 42. 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, a portion of the tap water supplied from the water supply passage 40 to the hot water heating unit 10 can be supplied to the hot water outlet passage 44 via the bypass passage 46 and mixed with the hot water flowing through the hot water outlet passage 44. A bypass control valve 47 is installed at the point where the bypass passage 46 branches off from the water supply passage 40. By controlling the opening of the bypass control valve 47, the mixing ratio of tap water and hot water can be changed. Additionally, 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, allowing detection of the temperature of the 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 mixed.

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 immediately upstream of the hot water tap 2. 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. 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 of flow of the circulating hot water is indicated by arrows.

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.

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, allowing hot water to be supplied 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 passage, a check valve 62 to prevent backflow of hot water from the bathtub, and a water flow sensor 63 for detecting the flow rate of hot water flowing through the passage 60.

The above describes the supply path of hot water generated in the hot water heating unit 10 of the hot water supply system 1 to the hot water tap 2 and the bathtub (not shown). Meanwhile, the heat transfer medium (hot water) heated in the heating unit 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 unit 20. 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. Furthermore, 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 communication passage 72. A cistern 73 for storing the heat transfer medium and a heating pump 74 are provided along the heating communication passage 72.

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 before being supplied again to the heating terminal via the heating supply passage 70. The heating supply passage 70 is 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.

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 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. 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.

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, with a bath pump 92 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 then returned to the bathtub via the bath supply passage 91. Therefore, by opening the bath flow control valve 81 in the heating supply passage 70 to circulate the heat transfer medium to the bath heat exchanger 82, and 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.

Furthermore, a hot water supply branch passage 83 also branches off from the heating supply passage 70, and this branch 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 branch 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 is being performed in 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 simultaneously 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 of heating circulating hot water in the instant hot water heat exchanger 54 while operating the instant hot water pump 51 will be referred to as "instant hot water operation."

Furthermore, the instant hot water flow control valve 84 in this embodiment employs a stepping motor type flow control valve. 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. Moreover, 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 the instant hot water flow control valve 84 can be closed to stop the heating of the circulating hot water. This 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.

The control unit 100 incorporates a microcomputer and memory, which stores various programs. 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 ambient temperature outside the hot water supply system 1. By executing the programs stored in memory, the control unit 100 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. This allows for the execution of various functions, including hot water supply operation (dispensing hot water from the hot water tap 2 when it is opened), heating operation (supplying heat transfer fluid to heating terminals to heat the room), bath filling operation (supplying hot water to the bathtub), reheating operation (reheating the hot water in the bathtub), and instant hot water operation (providing an instant hot water function according to user settings).

However, even though the control unit 100 has closed the instant hot water flow control valve 84, an open failure may occur where the instant hot water flow control valve 84 does not completely close. 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. Therefore, when the hot water tap 2 is opened, heated hot water may flow out of the tap 2 against the user's intention. To enable detection of an open failure in the instant hot water flow control valve 84, the control unit 100 in this embodiment has the following internal structure.

Figure 2 is a conceptual block diagram showing the internal structure of the control unit 100 mounted in the hot water supply system 1 of this embodiment. As shown, the control unit 100 contains a hot water 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, among others. Note that these "units" are abstract concepts representing the functions that the control unit 100 possesses for the purpose of detecting open faults of the instant hot water flow control valve 84. They do not indicate that the inside of the control unit 100 is divided into these "units," nor do they indicate 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 or ICs mounted in the control unit 100. Furthermore, they can be implemented by combining software programs and hardware.

The hot water supply operation execution unit 101 performs various controls for the hot water supply device 1 to perform hot water supply 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 for 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 supply operation). Therefore, the instant hot water operation execution unit 103 obtains information from the hot water supply operation execution unit 101 regarding whether or not hot water supply operation is in progress, and stops instant hot water operation during hot water supply operation. In Figure 2, the arrows pointing from the hot water supply 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 supply operation execution unit 101 regarding whether or not hot water supply operation is in progress.

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. The freeze prevention operation execution unit 105 also 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 decrease in the outside temperature.

Furthermore, the detectable condition determination unit 106 executes control to determine whether the conditions (detectable conditions) for detecting an open malfunction of the instant hot water flow control valve 84 have been met. To determine whether the detectable conditions have been met, information regarding 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 is used. The detectable condition determination unit 106 acquires 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 acquires this information.

The detectable condition determination unit 106 then determines that the detectable condition has been met and outputs information to that effect to the temperature rise calculation unit 107. The temperature rise calculation unit 107 then acquires 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 due to the circulating hot water passing through the instant hot water heat exchanger 54, and outputs the obtained temperature rise to the open fault detection unit 108. The open fault detection unit 108 then determines whether the instant hot water branch passage 83 is experiencing an open fault based on the temperature rise output from the temperature rise calculation unit 107. In Figure 2, the arrows displayed from the detectable condition determination unit 106 to the temperature rise calculation unit 107 indicate that information indicating the detectable condition has been met is output, and the arrows displayed from the temperature rise calculation unit 107 to the open fault detection unit 108 indicate that the temperature rise is output.

Figure 3 is a flowchart showing the first half of the open fault detection 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 detection process. As shown in Figure 3, the open fault detection process first determines whether the hot water supply device 1 is in instant hot water operation (STEP 1). An open fault in the instant hot water branch passage 83 is a fault where 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 have the instant hot water branch passage 83 closed as a prerequisite, and for this to happen, the hot water supply device 1 must not be in instant hot water operation. Therefore, when the open fault detection process starts, the first thing to determine is whether or not instant hot water operation is in progress.

As a result, if the hot water heater 1 is in instant hot water operation (STEP 1: 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 STEP 1. Then, when the instant hot water operation is stopped, it is determined that it is no longer in instant hot water operation (STEP 1: no), and the system then determines whether the instant hot water pump 51 has been stopped continuously for a predetermined time limit or longer (STEP 2). Since the instant hot water pump 51 may malfunction due to internal seizing if it remains stopped for a long period of time, the hot water heater 1 in this embodiment 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 STEP 2, 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.

As a result, if the instant hot water pump 51 has not stopped for more than the limited time (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 the predetermined freeze prevention temperature, it performs a freeze prevention operation by rotating the instant hot water pump 51 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 then 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). Also, the freeze prevention temperature in this embodiment is set to 3°C.

As a result, if it is determined that the outside temperature is not below the freeze prevention temperature (STEP 3: no), the process returns to the beginning to determine whether or not instant hot water operation is in progress (STEP 1). Thus, in the fault detection process, if instant hot water operation is in progress (STEP 1: yes), or even if instant hot water operation is stopped, if the time the instant hot water pump 51 has been continuously stopped reaches the time limit (STEP 2: yes), or until the outside temperature falls below the freeze prevention temperature (STEP 3: yes), the above-described STEP 1 to STEP 3 determinations are repeated.

Then, after repeating these judgments, 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). Alternatively, 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 power is supplied to the electric heaters to heat the water in the hot water outlet passage 44 and the return passage 50.

Once the instant hot water pump 51 is rotated to initiate 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 indicates 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 in the instant hot water flow control valve 84 are not met. Therefore, the process returns to the beginning, and it is determined again whether the instant hot water is in operation (STEP 1).

In contrast, if the hot water supply system 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 only when the detection conditions are met: the system is not in instant hot water operation (STEP 1: no), is in maintenance operation (STEP 4), is in freeze prevention operation (STEP 5), and is in heating operation (STEP 6: yes). The details of the open fault detection process will be described later.

After completing the open fault detection process (STEP 20), the system returns to the open fault determination process and then determines whether maintenance is in progress (STEP 7 in Figure 4). If maintenance is in progress (STEP 7: yes), the system determines whether a predetermined maintenance time has elapsed since the start of rotation of the instant hot water pump 51 (STEP 8). In this embodiment, the maintenance time is set to 5 minutes. If the maintenance time has not elapsed (STEP 8: no), the system checks whether heating operation is still ongoing (STEP 10). If it is confirmed that heating operation is still in progress (STEP 10: yes), the system starts the open fault detection process described later (STEP 20).

In contrast, if the maintenance operation time has not yet elapsed (STEP 8: no), but the heating operation has ended (STEP 10: no), it is not possible to determine whether the instant hot water flow control valve 84 is open or not. Therefore, the open fault determination process shown in Figures 3 and 4 is terminated. Furthermore, if the determination in STEP 8 indicates that the maintenance operation time has elapsed (STEP 8: yes), the maintenance operation is terminated by stopping the instant hot water pump 51 (STEP 9), and then the open fault determination process is terminated.

Furthermore, as described above using Figure 3, the open fault detection process (STEP 20) is initiated 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. Therefore, 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.

Then, if the freeze prevention operation time has not elapsed since the start of rotation of the instant hot water pump 51 (STEP 11: no), it is checked whether heating operation is still continuing (STEP 13). If it is confirmed that heating operation is still in progress (STEP 13: yes), the open fault detection process described later is started (STEP 20). On the other hand, if the freeze prevention operation time has not yet elapsed (STEP 11: no), but heating operation has ended (STEP 13: 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.

Figure 5 is a flowchart of the open fault detection process, which is executed to detect whether or not the instant hot water flow control valve 84 has an open fault during the open fault determination process. As described above using Figure 3, this process is initiated when the conditions for detecting an open fault in the instant hot water flow control valve 84 are met during the open fault determination process.

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. Therefore, 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.

Furthermore, the open fault detection process shown 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 these conditions 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, since it is possible that the instant hot water operation may have started for some reason, STEP 21 confirms that the instant hot water flow control valve 84 is set to the closed state as a precaution.

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 started in either STEP 4 or STEP 5 of Figure 3 before the open fault detection process in Figure 5 began, 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.

As a result, when it is determined that a predetermined time has elapsed (STEP 22: 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 23). 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).

Then, 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, the temperature rise in the instant hot water heat exchanger 54 is calculated (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 longer 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.

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.

Conversely, if the temperature rise in the instant hot water heat exchanger 54 has not reached the threshold temperature, or if the threshold temperature has been reached but the duration of that state has not elapsed (STEP 25: no), then it can be considered that the instant hot water flow control valve 84 is not malfunctioning. Once the presence or absence of a malfunction in the instant hot water flow control valve 84 has been detected in this manner, the malfunction detection process shown in Figure 5 is terminated, and the process returns to STEP 7 of the malfunction determination process shown in Figure 3.

As described above, the hot water supply system 1 of this embodiment can detect an open malfunction 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 malfunction 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 malfunction 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 also when heating operation is in progress, and determines whether or not there is an open malfunction 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 during the normal control of the hot water supply system 1.

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 in the instant hot water heat exchanger 54 may decrease before it reaches the instant hot water supply temperature sensor 57.

Furthermore, when determining whether the instant hot water flow control valve 84 is open, 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, 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. Therefore, 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, potentially making it impossible to detect the open fault of the instant hot water flow control valve 84. Therefore, instead of the open fault detection process in Figure 5, the following open fault detection process may be performed.

Figure 6 is a flowchart of the modified open fault detection process performed by the hot water supply unit 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.

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, the first thing that was confirmed when the process started was that the instant hot water flow control valve 84 was in the closed state. However, in the modified fault detection process, the instant hot water flow control valve 84 is opened. Therefore, 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. The instant hot water pump 51 then circulates this circulating hot water, thus heating the outlet passage 44 and the return passage 50.

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, approximately 30 seconds to 1 minute. If it is determined that the heating time has not elapsed (STEP 32: no), the process is repeated until the system enters a standby state. 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).

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, after closing the instant hot water flow control valve 84, the system waits for the stabilization time to elapse before detecting the temperature of the hot water. This is done for the following reasons.

As described above, in the modified fault detection process, when the process starts, the instant hot water flow control valve 84 is opened, and a portion of the heat transfer medium in the heating supply passage 70 is supplied 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. Therefore, 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, the return passage 50, the outlet passage 44, and the instant hot water pump 51 to stabilize. In this embodiment, the stabilization time is set to 5 minutes.

After the stabilization period has elapsed (STEP 34: yes), the temperature of the hot water is detected on both the upstream and downstream sides of the instant hot water heat exchanger 54 (STEP 35). Then, similar to the open fault detection process described in this embodiment, 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 detected on the upstream side from the temperature detected on the downstream side (STEP 36), and it is determined whether a predetermined duration has elapsed while the temperature rise is greater than a predetermined threshold temperature (STEP 37). The length of this duration can be set as appropriate.

As a result, if the temperature rise in the instant hot water heat exchanger 54 remains above the threshold temperature for an extended period (STEP 37: yes), it is determined that an open fault has occurred in the instant hot water flow control valve 84 (STEP 38), and the open fault detection process of the modified example is terminated. Conversely, if the temperature rise in the instant hot water heat exchanger 54 has not reached the threshold temperature, or if it has reached the threshold temperature but the duration of that state has not elapsed (STEP 37: no), it is considered that the instant hot water flow control valve 84 has not experienced an open fault. Therefore, the open fault detection process is terminated, and the system returns to the open fault determination process shown in Figure 3.

In the modified version 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. Therefore, it becomes possible to accurately detect an open fault in the instant hot water flow control valve 84.

Furthermore, in the modified example described above, the open fault detection process was explained assuming the same heating time and stabilization time were used regardless of whether it was initiated during maintenance or freeze prevention. However, if the open fault detection process is initiated during freeze prevention, it may be necessary to use a longer heating time and stabilization time than when initiated during maintenance.

Alternatively, instead of performing the open fault detection process described in the above-mentioned modification, 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, thus enabling accurate detection of whether or not the instant hot water flow control valve 84 is open.

The above describes the hot water supply device 1 in this embodiment and its modified form. However, the present invention is not limited to the above embodiment and its modified form, and can be implemented in various ways without departing from its essence.

1...Hot water supply unit, 2...Hot water tap, 10...Hot water heating unit, 11...Hot water burner,
12...Hot water supply first heat exchanger, 13...Hot water supply second heat exchanger, 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 (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,
The system includes 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,
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.
A hot water supply device comprising: an open fault detection unit that determines that the instant hot water on/off valve is not open if the amount of temperature rise has not reached a predetermined threshold temperature or if a predetermined duration has not elapsed while the temperature has reached the threshold temperature, and determines that the instant hot water on/off valve is open if the duration has elapsed while the amount of temperature rise has reached the threshold temperature. 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,
The system includes 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,
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.
A hot water supply device comprising: an open fault detection unit that determines that the instant hot water on/off valve is not open if the amount of temperature rise has not reached a predetermined threshold temperature or if a predetermined duration has not elapsed while the temperature has reached the threshold temperature, and determines that the instant hot water on/off valve is open if the duration has elapsed while the amount of temperature rise has reached the threshold temperature.