Hot water supply system

Abstract

To provide a hot water system which surely prevents seal water shortage at a trap part of an overflow pipe provided at a water supply tank.SOLUTION: A hot water system A includes: a heating heat source 500; a hot water storage tank 6; a water supply tank 2; a pump 37; a water supply pipe 10; a water supply valve 12; an overflow pipe 9 having an upstream end opening part 94 communicating with the inside of the water supply tank, and for draining redundant water in the water supply tank where the water level in the water supply surpasses a predetermined height; a trap part 92 provided in the middle of the overflow pipe, and for storing and sealing part of the water flowing in the overflow pipe; overflow water level detection means 22 for detecting that the water level in the water supply tank has reached a predetermined overflow water level at which the redundant water in the water supply tank almost flows into the overflow pipe from the upstream end opening part; and a control device C. After opening the valve of the water supply valve, the control device performs control for maintaining an opened state of the valve of the water supply valve until a predetermined time T1 has elapsed, after the overflow water level detection means detects that the water level has reached the overflow water level.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a hot water supply system including a hot water storage tank, a water supply tank, a pump, etc., and supplying hot water to a hot water outlet terminal such as a shower or a faucet.

Background Art

[0002] Conventionally, in a hot water supply system, in order to supply sufficient hot water even when multiple hot water supply taps (hot water outlet terminals) such as showers and faucets are used for hot water supply simultaneously, a heating heat source, a hot water storage tank for storing hot water heated by the heating heat source, a water supply tank for storing water from a water supply source, a water-side pump for supplying water from the water supply tank to the hot water supply tap, and a hot water-side pump for supplying hot water from the hot water storage tank to the hot water supply tap are provided (Patent Document 1).

[0003] Also, in a hot water supply device, a heating tank for storing hot water in a heating circuit connected to a heating device for performing heating, bathroom drying, etc., and an overflow pipe for discharging a predetermined amount or more of hot water in the heating tank to the outside of the device are provided (Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, also in the above-described hot water supply system, for example, an overflow pipe is provided in the water supply tank to drain surplus water exceeding a predetermined water storage amount outside the apparatus, and further, a trap portion is provided in the overflow pipe to store a part of the drained water from the water supply tank to prevent odors and various bacteria from entering from the downstream side of the overflow pipe.

[0006] However, if the situation where the water in the water supply tank does not flow into the overflow pipe continues, there is a possibility that the water in the overflow pipe evaporates and the trap portion is no longer sealed with water. When the water seal in the trap portion is broken, problems such as odors and various bacteria entering from the downstream side of the overflow pipe and mixing with the water in the water supply tank and the hot water in the hot water storage tank occur.

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to provide a hot water supply system capable of reliably preventing the water seal from breaking in the trap portion of the overflow pipe provided in the water supply tank.

Means for Solving the Problems

[0008] The first aspect of the hot water supply system according to the present invention is a heating heat source, a hot water storage tank for storing hot water heated by the heating heat source, a water supply tank for storing water from a water supply source, a pump for supplying the hot water in the hot water storage tank and the water in the water supply tank to a hot water outlet terminal, a water supply pipe for supplying water from the water supply source to the water supply tank, a water supply valve for opening and closing the water supply pipe, an overflow pipe having an upstream end opening communicating with the inside of the water supply tank, for draining surplus water in the water supply tank when the water level in the water supply tank exceeds a predetermined height, a trap portion provided in the middle of the overflow pipe for storing a part of the water flowing through the overflow pipe to seal the water, Overflow water level detection means for detecting that the water level in the water supply tank has reached a predetermined overflow water level at which surplus water in the water supply tank approximately flows into the overflow pipe from the upstream end opening; A control device, and is provided with; After the water supply valve is opened, the control device is configured to perform control to continue opening the water supply valve until a predetermined time (T1) elapses after the overflow water level detection means detects that the overflow water level has been reached.

[0009] According to the above configuration, when the water supply valve is opened and water is being supplied into the water supply tank, even if the water level in the water supply tank reaches the overflow water level and the overflow water level detection means detects that the overflow water level has been reached, the water supply valve remains open without being closed until the predetermined time (T1) elapses. Therefore, within this predetermined time (T1), the surplus water in the water supply tank flows into the overflow pipe from the upstream end opening. Here, the predetermined time (T1) can be set, for example, as the time it takes for the trap portion of the overflow pipe to become full of water due to the surplus water flowing into the overflow pipe after the overflow water level detection means detects that the overflow water level has been reached. Therefore, every time water is supplied into the water supply tank by opening the water supply valve, water surely flows into the overflow pipe and water is supplied to the trap portion. In this way, since water is supplied to the trap portion of the overflow pipe when water is supplied into the water supply tank, even if the water in the overflow pipe gradually evaporates, the evaporated water can be replenished every time water is supplied into the water supply tank to keep the trap portion in a full water state. Therefore, it is possible to surely prevent the water seal in the trap portion of the overflow pipe from breaking and prevent odors, various bacteria, etc. from entering the water supply tank from the downstream side of the overflow pipe. From the above, when the hot water outlet terminal is opened, hot water containing odors, various bacteria, etc. does not flow out from the hot water outlet terminal, and the user can hygienically use the hot water without feeling discomfort.

[0010] In the hot water supply system of the first embodiment, When the overflow water level detection means detects that the overflow water level has been reached even at the time when the predetermined time (T1) has elapsed, the control device can be configured to perform control to close the water supply valve. Accordingly, since it can be considered that the water level in the water supply tank has exceeded the overflow water level even during the predetermined time (T1), the surplus water in the water supply tank can flow from the upstream end opening to the overflow pipe within this predetermined time (T1).

[0011] In the hot water supply system of the first embodiment, When the overflow water level detection means detects that the overflow water level has been continuously reached for the predetermined time (T1), the control device can be configured to perform control to close the water supply valve. Accordingly, during the predetermined time (T1), since it can be surely considered that the water level in the water supply tank has exceeded the overflow water level, the surplus water in the water supply tank can flow from the upstream end opening to the overflow pipe within this predetermined time (T1).

[0012] Further, a second embodiment of the hot water supply system according to the present invention is a heating heat source, a hot water storage tank for storing hot water heated by the heating heat source, a water supply tank for storing water from a water supply source, a pump for supplying the hot water in the hot water storage tank and the water in the water supply tank to a hot water outlet terminal, a water supply pipe for supplying water from the water supply source to the water supply tank, a water supply valve for opening and closing the water supply pipe, an overflow pipe having an upstream end opening communicating with the inside of the water supply tank and an overflow hole, and draining surplus water in the water supply tank when the water level in the water supply tank exceeds a predetermined height, a trap portion provided in the middle of the overflow pipe for storing and sealing a part of the water flowing through the overflow pipe, Hi water level detection means for detecting that the water level in the water supply tank has reached a predetermined Hi water level at which surplus water in the water supply tank approximately flows into the overflow pipe from the overflow hole, comprising a control device The overflow hole is provided between the trap portion and the upstream end opening in the overflow pipe. The control device is configured to continue to open the water supply valve until a predetermined time (T2) elapses after the high water level detection means detects that the high water level has been reached after the water supply valve is opened.

[0013] According to the above configuration, when water is being supplied into the water supply tank with the water supply valve open, even if the water level in the water supply tank reaches the high water level and the high water level detection means detects that the high water level has been reached, the water supply valve remains open without being closed until the predetermined time (T2) elapses. Therefore, surplus water in the water supply tank flows from the overflow hole into the overflow pipe within this predetermined time (T2). Since the overflow hole is provided between the trap portion and the upstream end opening and is provided at a position lower than the upstream end opening, even when the water in the water supply tank is used at the hot water outlet terminal or the like and the water level in the water supply tank does not reach the upstream end opening of the overflow pipe, the surplus water in the water supply tank can flow from the overflow hole into the overflow pipe. Here, the predetermined time (T2) can be set, for example, as the time when the trap portion of the overflow pipe becomes full of water due to the surplus water flowing from the overflow hole into the overflow pipe after the high water level detection means detects that the high water level has been reached. Therefore, every time water is supplied into the water supply tank by opening the water supply valve, water surely flows into the overflow pipe and water is supplied to the trap portion. In this way, since water is supplied to the trap portion of the overflow pipe when water is supplied into the water supply tank, even if the water in the overflow pipe gradually evaporates, the evaporated water can be replenished every time water is supplied into the water supply tank to keep the trap portion in a full water state. Therefore, it is possible to surely prevent the water seal in the trap portion of the overflow pipe from breaking, and prevent odors, miscellaneous bacteria, etc. from entering the water supply tank from the downstream side of the overflow pipe. From the above, when the hot water outlet terminal is opened, hot water containing odors, miscellaneous bacteria, etc. does not flow out from the hot water outlet terminal, and the user can hygienically use the hot water without feeling discomfort.

[0014] In the hot water supply system of the second embodiment, When the water level detection means of the control device detects that the Hi water level has been reached even when the predetermined time (T2) has elapsed, the control device may be configured to perform control to close the water supply valve. Accordingly, since it can be considered that the water level in the water supply tank has exceeded the Hi water level even during the predetermined time (T2), the surplus water in the water supply tank can flow from the overflow hole to the overflow pipe within this predetermined time (T2).

[0015] In the hot water supply system of the second embodiment, When the water level detection means of the control device detects that the Hi water level has been continuously reached for the predetermined time (T2), the control device may be configured to perform control to close the water supply valve. Accordingly, during the predetermined time (T2), it can be surely considered that the water level in the water supply tank has exceeded the Hi water level, so that the surplus water in the water supply tank can flow from the overflow hole to the overflow pipe within this predetermined time (T2).

[0016] A third embodiment of the hot water supply system according to the present invention is In the hot water supply system of the first embodiment, An overflow hole communicating with the water supply tank is provided in the overflow pipe at a height position below the height at which the overflow water level is reached. When the overflow water level detection means detects that the overflow water level has been reached for a predetermined time (T3) even when a closing instruction for the water supply valve is given, the control device is configured to determine that there is an opening failure of the water supply valve.

[0017] In the configuration of the present invention, when the water supply valve is closed, the water supply into the water supply tank stops, and the surplus water in the water supply tank flows from the overflow hole into the overflow pipe in the water supply stop state. Therefore, when the water supply valve is normally closed according to the valve closing instruction of the water supply valve, the water level in the water supply tank drops below the overflow water level. Thus, the overflow water level detection means does not detect that the overflow water level has been reached until a predetermined time (T3) elapses after the valve closing instruction of the water supply valve. However, if the overflow water level detection means has detected that the overflow water level has been reached for a predetermined time (T3) even after the valve closing instruction of the water supply valve, it is considered that the water supply into the water supply tank continues and the water supply valve remains open without being normally closed according to the valve closing instruction. Therefore, it can be determined that the water supply valve has an open failure. Note that the detection of the open failure of the water supply valve can be continuously performed not only after the valve closing instruction of the water supply valve but also during the valve closing instruction of the water supply valve. Therefore, according to the configuration of the third aspect of the present invention, it is possible to determine the open failure of the water supply valve every time water is supplied into the water supply tank, and it becomes possible to quickly detect the open failure of the water supply valve.

[0018] In the hot water supply system according to the third aspect, Hi water level detection means is provided for detecting that the water level in the water supply tank has reached a predetermined Hi water level that is equal to or higher than the height at which the surplus water in the water supply tank flows from the overflow hole into the overflow pipe and lower than the overflow water level. The control device has a configuration in which, after the water supply valve is opened, control is performed to continue opening the water supply valve until a predetermined time (T2) elapses after the Hi water level detection means detects that the Hi water level has been reached, and also has a configuration in which, even when the valve closing instruction of the water supply valve is given, if the overflow water level detection means has detected that the overflow water level has been reached, or if the Hi water level detection means has detected that the Hi water level has been reached for a predetermined time (T4), it is determined that there is an open failure of the water supply valve.

[0019] Thus, in order to determine the open failure detection of the water supply valve from the detection state of either the overflow water level detection means or the Hi water level detection means, even when either the overflow water level detection means or the Hi water level detection means fails, or when the water in the water supply tank flows out due to the use of the hot water terminal and the water level in the water supply tank does not reach the overflow water level, etc., the open failure of the water supply valve can be detected more reliably. Therefore, according to the above configuration, every time water is supplied into the water supply tank, the open failure of the water supply valve can be determined more reliably, and the open failure of the water supply valve can be detected at an early stage.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0021] Hereinafter, a hot water supply system according to an embodiment of the present invention will be described. The hot water supply system A of the embodiment shown in FIG. 1 is a hot water supply system that can be used in commercial facilities such as beauty salons, etc. It includes a hot water supply pressurization tank unit 1, a heat source unit 500, and a control device C, and is configured to be able to supply a large amount of water or hot water to a plurality of hot water outlet terminals 400 such as showers and faucets that serve as hot water taps from the hot water supply pressurization tank unit 1. The heat source unit 500 has a first gas heat source machine 501 and a second gas heat source machine 502 that are heating heat sources. Note that as the heating heat source, one or three or more gas heat source machines may be provided, or a heat pump, an electric heater, etc. may be used instead of the gas heat source machine. The hot water supply pressurization tank unit 1 includes a water supply tank 2 that stores water supplied from a water supply source, and a hot water storage tank 6 that stores hot water heated by the heat source unit 500, and is configured to be able to supply a large amount of hot water to the hot water outlet terminal 400. Further, an outside air temperature sensor 80 that detects the outside air temperature is provided at the bottom of the housing of the hot water supply pressurization tank unit 1.

[0022] The first and second gas heat source machines 501, 502 are gas water heaters. Although not shown, they include a gas burner, a heat exchanger, a heat source machine control device that controls the operation of the heating heat source, etc. inside the housing. The first and second gas heat source machines 501, 502 and the hot water storage tank 6 are connected by a heating circulation circuit composed of a heating forward pipe 40 that sends hot water from the hot water storage tank 6 and water from the water supply tank 2 to the first and second gas heat source machines 501, 502, and a heating return pipe 44 that returns the hot water heated by the first and second gas heat source machines 501, 502 to the hot water storage tank 6.

[0023] One end of the heating forward pipe 40 is connected to the lower part of the hot water storage tank 6, and the other end is branched into a first heating forward pipe 41 and a second heating forward pipe 42 midway so as to be connected to the first gas heat source machine 501 and the second gas heat source machine 502. One end of the heating return pipe 44 is connected to the first heating return pipe 45 and the second heating return pipe 46 connected to each gas heat source machine 501, 502, and the other end is connected to the upper part of the hot water storage tank 6.

[0024] The heating return pipe 44 is provided with an automatic air vent valve 57 that opens when the pressure in the hot water storage tank 6 rises above a predetermined value, and a heating return temperature sensor 58 that detects the temperature of the hot water flowing into the hot water storage tank 6. Further, the heating supply pipe 40 merges with the water supply pipe 3, and a tank bottom temperature sensor 55 that detects the temperature of the hot water supplied from the hot water storage tank 6 to the heating supply pipe 40 and a manually operated on-off valve 56 (it may also be a valve whose opening and closing are controlled by the control device C) are provided upstream of the merging portion with the water supply pipe 3. A heating supply temperature sensor 50 is provided in the heating supply pipe 40 on the upstream side of the branch portion of the first and second heating supply pipes 41 and 42 and on the downstream side of the merging portion with the water supply pipe 3. The first and second heating supply pipes 41 and 42 are respectively provided with a first heating circulation pump 51 and a second heating circulation pump 52, and check valves 53 and 54 are provided on the downstream side of the first and second heating circulation pumps 51 and 52. By operating the first and second heating circulation pumps 51 and 52 and operating the first and second gas heat source machines 501 and 502, hot water at a predetermined hot water supply temperature heated by the first and second gas heat source machines 501 and 502 is supplied to the hot water storage tank 6.

[0025] The hot water storage tank 6 is a tank made of a metal with excellent corrosion resistance (for example, stainless steel), and although not shown, its outer periphery is covered with a heat insulating material. The capacity of the hot water storage tank 6 in this embodiment is, for example, 50 liters. A heating supply pipe 40 and a hot water supply return pipe 72 that returns the hot water from the hot water supply terminal 400 are connected to the lower part of the hot water storage tank 6, and a heating return pipe 44 and a hot water supply pipe 71 that leads to the hot water supply terminal 400 are connected to the upper part of the hot water storage tank 6. In the hot water storage tank 6, a first hot water storage temperature sensor 61, a second hot water storage temperature sensor 62, and a third hot water storage temperature sensor 63 for detecting the temperature of the hot water stored inside are attached at predetermined intervals in order from above.

[0026] The water supply tank 2 is arranged above the hot water storage tank 6 and supplies water to the gas heat source machines 501 and 502, the hot water storage tank 6, the hot water outlet terminal 400, etc. The capacity of the water supply tank 2 in this embodiment is, for example, 70 liters. A water supply pipe 10 for supplying city water as the water supply source to the water supply tank 2 is connected to the upper part of the water supply tank 2, and a water supply forward pipe 3 is connected to the lower part of the water supply tank 2. A governor 11 and a water supply valve 12 are provided in series in the water supply pipe 10 from the upstream side. The water supply valve 12 is composed of an electromagnetic valve that serves as an on-off valve. The water supply valve 12 is connected to the control device C and is controlled to open and close by a control signal from the control device C.

[0027] The water supply forward pipe 3 branches into a first water supply forward pipe 31 and a second water supply forward pipe 32 on the upstream side so that water flows in parallel. A water supply pressurizing pump 37 is provided on the upstream side of the branch portion of the first water supply forward pipe 31 and the second water supply forward pipe 32. This water supply pressurizing pump 37 constitutes a pump for supplying the hot water stored in the hot water storage tank 6 and the water stored in the water supply tank 2 to the hot water outlet terminal 400.

[0028] A check valve 33 and a pressure sensor 35 for detecting water pressure are provided in series in the first water supply forward pipe 31 from the upstream side, and a check valve 34 and a water volume sensor 36 for detecting the water flow rate are provided in series in the second water supply forward pipe 32 from the upstream side. Note that, without providing such a parallel water path, the pressure sensor and the water volume sensor can also be provided in a single water path. However, by forming a parallel water path with the first water supply forward pipe 31 and the second water supply forward pipe 32 so that water flows in parallel and providing the pressure sensor and the water volume sensor in each water path, the pressure loss in the water supply forward pipe 3 can be reduced. Although the water flow rate in each water path of the first and second water supply forward pipes 31 and 32 can be different, if the ratio of the pressure loss is known, the water flow rate of the entire water supply forward pipe 3 can be calculated from the water flow rate detected by the water volume sensor 36.

[0029] The first water supply pipe 31 and the second water supply pipe 32 merge at a confluence downstream of the pressure sensor 35 and the water volume sensor 36. The other end of the water supply pipe 3 is connected to a confluence with a heating pipe 40 connected to the lower part of the hot water storage tank 6. Further, the water supply pipe 3 branches into a water supply branch pipe 38 connected to the hot water outlet terminal 400 downstream of the confluence of the first and second water supply pipes 31, 32. The downstream side of the water supply branch pipe 38 branches into a plurality according to the number of showers, faucets, etc. of the hot water outlet terminal 400. A check valve 39 is provided in the water supply pipe 3 downstream of the branch portion of the water supply branch pipe 38. The water supply pipe 3 including the first and second water supply pipes 31, 32 and the water supply branch pipe 38 constitutes a water supply circuit, and by operating the water supply pressurizing pump 37, water is supplied from the water supply tank 2 to the gas heat source machines 501, 502 and the hot water outlet terminal 400.

[0030] One end of the hot water return pipe 72 connected to the lower part of the hot water storage tank 6 is connected to the hot water supply pipe 71 at the hot water outlet terminal 400 at the other end. An instantaneous hot water circulation pump 73 is provided in the hot water return pipe 72, and an instantaneous hot water return temperature sensor 74 and a check valve 75 are provided downstream of the instantaneous hot water circulation pump 73. The hot water supply pipe 71 and the hot water return pipe 72 arranged between the hot water storage tank 6 and the hot water outlet terminal 400 constitute an instantaneous hot water circulation circuit.

[0031] The hot water supply system A includes a remote controller R for the user to perform operations related to the operation of the hot water supply system A. The remote controller R is connected by wire or wirelessly so as to be communicable with the control device C and a heat source machine control device (not shown) provided in the first and second gas heat source machines 501, 502.

[0032] Remote controller R is a terminal device configured to instruct a control device C of a hot water supply system A with operation control information such as turning on and off the power of the hot water supply system A and setting the hot water storage set temperature (such as the hot water outlet temperature of the hot water discharged from the first and second gas heat source machines 501 and 502) in a hot water storage tank 6 according to an operation of an operation switch (not shown) by a user. The remote controller R is provided with a display for displaying various information of the hot water supply system A. Note that instead of the remote controller R or together with the remote controller R, a mobile terminal such as a smartphone or a tablet terminal communicably connected to the control device C can be used.

[0033] The control device C is composed of one or more electronic circuit units including a CPU, a ROM, a RAM, an interface circuit, etc. Various data such as various operation programs and set values for executing the operation programs are stored in the memory. Detection signals of various sensors and valves described above are input to the control device C, and operation control information is input from the remote controller R. Then, the control device C performs operation control of the entire hot water supply system A by performing operation control of the gas heat source machines 501 and 502, various pumps 37, 51, 52, and 73, the water supply valve 12, etc.

[0034] To outline the main operation control by the control device C, when the hot water outlet terminal 400 is opened, the water supply pressurizing pump 37 is activated to supply the water stored in the water supply tank 2 to the hot water outlet terminal 400 via the water supply forward pipe 3 and the water supply branch pipe 38, and at the same time, the water in the water supply tank 2 is supplied to the lower layer of the hot water storage tank 6 via the water supply forward pipe 3 and the heating forward pipe 40 under the tank, so that the upper layer of hot water in the hot water storage tank 6 is supplied to the hot water outlet terminal 400 via the hot water supply forward pipe 71 (hot water supply operation). Also, when the detected temperature of the third hot water storage temperature sensor 63 installed at the lower part of the hot water storage tank 6 becomes equal to or lower than a predetermined hot water storage start temperature, the first and second heating circulation pumps 51 and 52 are activated to supply the hot water in the hot water storage tank 6 from the lower part to the first and second gas heat source machines 501 and 502 via the heating forward pipe 40, the first and second heating forward pipes 41 and 42, and the hot water heated to a predetermined hot water supply temperature by the first and second gas heat source machines 501 and 502 is supplied to the upper part of the hot water storage tank 6 via the first and second heating return pipes 45 and 46 and the heating return pipe 44 (hot water storage operation). Also, when the temperature of the hot water staying in the hot water supply forward pipe 71 and the hot water supply return pipe 72 drops due to the elapse of a predetermined instant hot water start time or the like, the instant hot water circulation pump 73 is activated to send the hot water stored in the hot water storage tank 6 to the hot water supply forward pipe 71 (instant hot water operation). Also, when the water storage amount in the water supply tank 2 decreases, the water supply valve 12 is opened to supply the water from the water supply source to the water supply tank 2 via the water supply pipe 10 (make-up water operation).

[0035] Next, the characteristic configuration of the present invention will be described. (Configuration related to the water supply tank 2) As shown in Fig. 2, the water supply tank 2 has a drain port 21 on one side wall below the connection port of the water supply pipe 10 and above the connection port of the water supply forward pipe 3. An overflow pipe 9 is connected to the side of the drain port 21 inside the water supply tank 2. A drain pipe 200 is connected to the outside of the water supply tank 2 at the drain port 21 (see Fig. 1). On the other side wall of the water supply tank 2, an overflow float sensor (overflow water level detection means) 22, a Hi float sensor (Hi water level detection means) 23, a Lo float sensor 24, and a low water level float sensor 25 for detecting the water level in the water supply tank 2 are arranged at predetermined intervals from top to bottom. Since the installation heights of the overflow float sensor 22 and the Hi float sensor 23 are relatively close to each other, they are arranged with a lateral shift so that the sensors 22 and 23 can be set at predetermined height positions without interference during installation.

[0036] The overflow pipe 9 is a tubular member for draining surplus water in the water supply tank 2 when the water level in the water supply tank 2 exceeds a predetermined height, and is installed in the water supply tank 2 (see FIGS. 1 and 2). As shown in FIG. 3, this overflow pipe 9 has a rising portion 91 extending straight in the vertical direction, a substantially U-shaped trap portion 92 connected to the lower end of the rising portion 91 for storing and sealing a part of the drained water, and a nozzle portion 93 connected to the trap portion 92 and extending in the horizontal direction to connect to the drain port 21 of the water supply tank 2. The rising portion 91 of the overflow pipe 9 is arranged at a position higher than the trap portion 92, and the upper end is the upstream end opening 94. Further, an overflow hole 95 communicating with the inside of the water supply tank 2 is provided in the upper part of the side wall of the rising portion 91. Therefore, when the water level in the water supply tank 2 rises and reaches the height position of the overflow hole 95, the water (surplus water) in the water supply tank 2 flows into the overflow pipe 9 from the overflow hole 95. When the water level in the water supply tank 2 further rises and reaches the height position of the upstream end opening 94, the water (surplus water) in the water supply tank 2 also flows into the overflow pipe 9 from the upstream end opening 94. In this way, the surplus water in the water supply tank 2 flows into the overflow pipe 9 from the overflow hole 95 or the overflow hole 95 and the upstream end opening 94 and is discharged to the outside. Here, the upstream end opening 94 of the overflow pipe 9 is set to have a diameter such that the flow rate of the surplus water flowing in from the upstream end opening 94 is larger than the water supply flow rate of the water supply pipe 10, so that even if the water supply from the water supply pipe 10 to the water supply tank 2 continues, water will not overflow from the water supply tank 2. On the other hand, the overflow hole 95 of the overflow pipe 9 is not for preventing water from overflowing from the water supply tank 2. The hole diameter is set to such an extent that the water in the water supply tank 2 can flow into the overflow pipe 9. It has a relatively small diameter and is formed to be smaller than the opening area of the upstream end opening 94. Also, as the final water level of the water supply tank 2 after the water supply is completed, the water level in the water supply tank 2 becomes the lower end position of the overflow hole 95 of the overflow pipe 9, and the water level in the overflow pipe 9 becomes the lower end position of the drain port 21.Even if the water inside the overflow pipe 9 gradually evaporates, as long as the water level does not drop below the upper end of the horizontal portion of the trap portion 92, it is possible to maintain the water seal at the trap portion 92. In the embodiment, one overflow hole 95 is provided, but a plurality of them may be provided at the same height position.

[0037] In this embodiment, the overflow pipe 9 is installed inside the water supply tank 2, but it may also be installed outside the water supply tank 2. When installing the overflow pipe (9) outside the water supply tank 2, for example, by bending the rising portion (91) into an L shape, etc., connect the upstream end opening (94) of the overflow pipe (9) to the drain port 21 from outside the water supply tank 2, and connect the downstream end of the kiser portion (93) to the drain pipe 200. Also, for the overflow hole (95) provided in the rising portion (91), a straight connecting pipe may be horizontally connected so as to communicate with the inside of the water supply tank 2 at the height position of the overflow hole (95).

[0038] Regarding the height position relationship between each of the float sensors 22 to 25 in the water supply tank 2 and the overflow pipe 9, referring to FIG. 2 again, the low water level float sensor 25 is disposed corresponding to a height position below the trap portion 92, the Lo float sensor 24 is disposed corresponding to a height position slightly above the trap portion 92, the Hi float sensor 23 is disposed corresponding to a height position slightly above the overflow hole 95 in the vicinity of the overflow hole 95, and the overflow float sensor 22 is disposed corresponding to a height position slightly below the upstream end opening 94 in the vicinity of the upstream end opening 94.

[0039] When the water level in the water supply tank 2 rises to a height that submerges the float built into the sensor for each of the float sensors 22 to 25, the float moves and turns ON, and the water level in the water supply tank 2 is detected by this ON. Specifically, the low water level float sensor 25 turns ON when the water level in the water supply tank 2 reaches a low water level (for example, the 15-liter position in terms of the water storage volume of the water supply tank 2) which is a height position below the trap portion 92. The Lo float sensor 24 turns ON when the water level in the water supply tank 2 reaches a Lo water level (for example, the 45-liter position in terms of the water storage volume of the water supply tank 2) which is a height position slightly above the trap portion 92. The Hi float sensor 23 turns ON when the water level in the water supply tank 2 reaches a Hi water level (for example, the 60-liter position in terms of the water storage volume of the water supply tank 2) which is a height position slightly above the overflow hole 95 of the overflow pipe 9. The overflow float sensor 22 turns ON when the water level in the water supply tank 2 reaches an overflow water level (for example, the 64-liter position in terms of the water storage volume of the water supply tank 2) which is a height position slightly below the upstream end opening 94 of the overflow pipe 9 and can be said to almost reach the upstream end opening 94. The detection signals of the water levels detected by each of the float sensors 22 to 25 are output to the control device C. Note that the means for detecting the water level of the water supply tank 2 is not limited to the float sensors 22 to 25, and other contact type water level gauges such as capacitive type or non-contact type water level gauges such as ultrasonic type may be used.

[0040] (Make-up water operation) In the hot water supply system A of the present embodiment, in order to always have water with a predetermined water storage volume in the water supply tank 2, for example, when the water level in the water supply tank 2 drops to a level at which the Lo float sensor 24 is OFF or the low water level float sensor 25 is OFF due to the use of the hot water outlet terminal 400 or the like, the make-up water operation of the water supply tank 2 is performed. In this make-up water operation, make-up water valve control for opening and closing the make-up water valve 12 is performed. In the present embodiment, when making up water to the water supply tank 2, by controlling the closing operation of the make-up water valve 12, water is made to flow through the overflow pipe 9 to ensure a full water state of the trap portion 92. Hereinafter, in the make-up water operation of the water supply tank 2, in particular, the closing operation of the make-up water valve 12 will be described in detail.

[0041] Referring to the flowchart of FIG. 4, the control device C opens the water supply valve 12 in accordance with a water supply operation instruction to perform water replenishment of the water supply tank 2 (Steps S01, S02). As a result, water is supplied from the water supply pipe 10 into the water supply tank 2. Subsequently, the control device C monitors the water level in the water supply tank 2 using the overflow float sensor 22 and the Hi float sensor 23, and executes a closing process operation of the water supply valve 12.

[0042] When the water supply valve 12 is opened and water is supplied from the water supply pipe 10 into the water supply tank 2, the water level in the water supply tank 2 rises. That is, since the water supply flow rate from the water supply pipe 10 is set to exceed the maximum usage flow rate at the hot water outlet terminal 400, even when hot and cold water is used at the hot water outlet terminal 400 and water flows out from the water supply tank 2, the water level in the water supply tank 2 will rise when water is supplied from the water supply pipe 10. When the water level in the water supply tank 2 reaches the Hi water level, the Hi float sensor 23 turns ON. Next, when the water level in the water supply tank 2 reaches the overflow water level, the overflow float sensor 22 turns ON. Since the height position of the Hi float sensor 23 is slightly above the overflow hole 95 of the overflow pipe 9, when the Hi float sensor 23 turns ON, the water (excess water) in the water supply tank 2 surely flows into the overflow pipe 9 through the overflow hole 95. Since the height position of the overflow float sensor 22 is slightly below the upstream end opening 94 of the overflow pipe 9, when the overflow float sensor 22 turns ON, the water level in the water supply tank 2 almost reaches the upstream end opening 94 of the overflow pipe 9, and the water (excess water) in the water supply tank 2 begins to flow into the overflow pipe 9 from the upstream end opening 94.

[0043] As the closing operation of the water supply valve 12, the control device C determines whether the ON state of the overflow float sensor 22 has continued for a predetermined time T1 (for example, 3 seconds) (step S1). When the ON state of the overflow float sensor 22 has continued for the predetermined time T1 ( "YES" in step S1), the control device C controls to close the water supply valve 12 (step S2). When the ON state of the overflow float sensor 22 has not continued for the predetermined time T1 ( "NO" in step S1), the control device C determines whether the ON state of the Hi float sensor 23 has continued for a predetermined time T2 (for example, 20 seconds) (step S3). When the ON state of the Hi float sensor 23 has not continued for the predetermined time T2 ( "NO" in step S3), the process is shifted to step S1 to continue monitoring the predetermined time T1 during which the ON state of the overflow float sensor 22 continues. When the ON state of the Hi float sensor 23 has continued for the predetermined time T2 ( "YES" in step S3), the control device C controls to close the water supply valve 12 (step S2). By closing the water supply valve 12 in the above operation, the water supply pipe 10 is closed and the water supply to the water supply tank 2 is stopped, and the water replenishment of the water supply tank 2 is completed.

[0044] Here, supplementing the above steps S1 and S3, for example, when the water outlet terminal 400 is unused or has a low usage flow rate, the difference between the water supply flow rate of the water supply pipe 10 and the usage flow rate of the water outlet terminal 400 becomes large, and the water level in the water supply tank 2 rises above the overflow water level. At this time, it becomes "YES" in step S1. On the other hand, when all the water outlet terminals 400 are being used to the maximum, the difference between the water supply flow rate of the water supply pipe 10 and the usage flow rate of the water outlet terminal 400 becomes small. Also, with drainage from the overflow holes 95 of the overflow pipe 9, although the water level in the water supply tank 2 rises above the Hi water level but does not reach the overflow water level, at this time, it becomes "NO" in step S1 and "YES" in step S3. In this way, regardless of the usage situation at the water outlet terminal 400, since the rise in the water level in the water supply tank 2 can be recognized, the water supply valve 12 can be surely closed even when the water level in the water supply tank 2 does not reach the overflow water level. Note that when it is "NO" in step S3, it is the initial stage of water supply, and the water level in the water supply tank 2 has not yet reached the Hi water level.

[0045] Also, when the control device C issues an instruction to close the water supply valve 12 in step S2, it subsequently executes an operation to detect an opening failure of the water supply valve 12. This operation to detect an opening failure of the water supply valve 12 is performed by monitoring the ON state of the overflow float sensor 22 when the water supply valve 12 is closed. Specifically, the control device C also determines whether the overflow float sensor 22 remains in the ON state for a predetermined time T3 (for example, 600 seconds) after the instruction to close the water supply valve 12 in step S2 (step S4). If the ON state of the overflow float sensor 22 continues for the predetermined time T3 after the instruction to close the water supply valve 12 (step S4, "YES"), the control device C determines that the water supply valve 12 has an opening failure (step S5). If the overflow float sensor 22 turns OFF within the predetermined time T3, since the water supply valve 12 is operating normally without an opening failure, the control device C ends the process of detecting an opening failure of the water supply valve 12.

[0046] (Function and Effect of the Embodiment) As described above, in the present embodiment, when the water supply valve 12 is opened and water is supplied into the water supply tank 2, due to the closing operation of the water supply valve 12 (steps S1 to S3), even if the water level in the water supply tank 2 reaches the overflow water level and the overflow float sensor 22 is turned ON, in step S1, the water supply valve 12 remains open without being closed until the ON state of the overflow float sensor 22 continues for a predetermined time T1 (from "YES" in step S1 to the process of step S2). That is, even if the water level in the water supply tank 2 becomes equal to or higher than the overflow water level, the supply of water from the water supply pipe 10 into the water supply tank 2 continues during the predetermined time T1. Therefore, within this predetermined time T1, the surplus water in the water supply tank 2 flows into the overflow pipe 9 from the overflow hole 95 and the upstream end opening 94 of the overflow pipe 9. Here, the predetermined time T1 can be set, for example, as the time when the trap portion 92 of the overflow pipe 9 is filled with water by the surplus water flowing into the overflow pipe 9 from the overflow hole 95 and the upstream end opening 94 after the overflow float sensor 22 is turned ON.

[0047] In addition, in the processing operation of step S1, when the ON state of the overflow float sensor 22 continues for a predetermined time T1, the water supply valve 12 is closed. That is, since the closing condition of the water supply valve 12 requires the "continuation" of the predetermined time T1, during this predetermined time T1, it can be considered that the water level in the water supply tank 2 is surely above the overflow water level. For example, if the water supply valve 12 is closed after the elapse of the predetermined time T1 from the time when the overflow float sensor 22 is turned ON, even when the water surface in the water supply tank 2 fluctuates due to the falling water from the outlet of the water supply pipe 10 and the overflow float sensor 22 is temporarily turned ON, the predetermined time T1 is measured from this ON time point. Therefore, within this predetermined time T1, the water level in the water supply tank 2 may not have reached the overflow water level yet, that is, a state where surplus water does not flow into the overflow pipe 9 from the upstream end opening 94 of the overflow pipe 9 may be included. Therefore, by setting the predetermined time T1 that is the closing condition of the water supply valve 12 to the duration of the ON state of the overflow float sensor 22, during this predetermined time T1, it can be considered that the water level in the water supply tank 2 has risen above the overflow water level and surplus water is surely flowing into the overflow pipe 9 from the upstream end opening 94. In the present invention, the closing condition of the water supply valve 12 is not limited to the "continuation" of the predetermined time T1. After the overflow float sensor 22 detects ON, the opening of the water supply valve 12 may be continued for at least the predetermined time T1, and the water supply valve 12 may be closed after the elapse of the predetermined time T1. Also, the water supply valve 12 may be closed when the overflow float sensor 22 detects ON at the time when the overflow float sensor 22 first detects ON and at the time when the predetermined time T1 has elapsed. Even in such a case, during the predetermined time T1, it can be considered that the water level in the water supply tank 2 has exceeded the overflow water level.

[0048] From the above, during the predetermined time T1, the surplus water in the water supply tank 2 surely flows from the upstream end opening 94 and the overflow hole 95 into the overflow pipe 9, and water is supplied to the trap portion 92. Therefore, within this predetermined time T1, the trap portion 92 can be filled with water. That is, even if the water accumulated in the overflow pipe 9 evaporates little by little during the stop of the makeup water operation, by flowing water into the overflow pipe 9 every time water is supplied, the trap portion 92 can always be maintained in a full water state without breaking the water seal.

[0049] Also, even when the water level in the water supply tank 2 reaches the Hi water level and the Hi float sensor 23 is turned ON, if the ON state of the overflow float sensor 22 does not continue for the predetermined time T1, in step S3, since the water supply valve 12 remains open without being closed until the ON state of the Hi float sensor 23 continues for the predetermined time T2 (in step S3, "YES" → the process of step S2), the supply of water from the water supply pipe 10 into the water supply tank 2 continues. During the predetermined time T2, the surplus water in the water supply tank 2 at least flows from the overflow hole 95 into the overflow pipe 9. For example, the water supply flow rate from the water supply pipe 10 is set to exceed the maximum use flow rate at the hot water outlet terminal 400. However, when all the hot water outlet terminals 400 are being used at the maximum, the difference between the water supply flow rate of the water supply pipe 10 and the use flow rate of the hot water outlet terminal 400 becomes small. Therefore, because the water in the water supply tank 2 is being used at the hot water outlet terminal 400, etc., even if the water level in the water supply tank 2 does not reach the overflow float sensor 22, does not reach the upstream end opening 94 of the overflow pipe 9, etc., the surplus water in the water supply tank 2 flows from the overflow hole 95 into the overflow pipe 9 for at least the predetermined time T2. Here, the predetermined time T2 can be set, for example, as the time when the trap portion 92 of the overflow pipe 9 becomes full of water due to the surplus water flowing from the overflow hole 95 into the overflow pipe 9 after the Hi float sensor 23 is turned ON.

[0050] The predetermined time T2 is set to be longer than the predetermined time T1. That is, when there is a large difference between the water supply flow rate of the water supply pipe 10 and the usage flow rate of the hot water outlet terminal 400, the water level in the water supply tank 2 can flow a large amount of water into the overflow pipe 9 from the upstream end opening 94 in a short time exceeding the upstream end opening 94 of the overflow pipe 9. On the other hand, when the difference between the water supply flow rate of the water supply pipe 10 and the usage flow rate of the hot water outlet terminal 400 is small, the water level in the water supply tank 2 does not reach the upstream end opening 94 of the overflow pipe 9 and exceeds the overflow hole 95, and water flows into the overflow pipe 9 from the overflow hole 95, but the inflow amount from the overflow hole 95 is set to be less than the inflow amount from the upstream end opening 94. Therefore, by setting the predetermined time T2 to be longer than the predetermined time T1, a sufficient amount of water can flow into the overflow pipe 9 to fill the trap portion 92 even from the overflow hole 95 within the predetermined time T2.

[0051] Also in this case, since the closing condition of the water supply valve 12 requires the "continuation" of the predetermined time T2, when the Hi float sensor 23 is temporarily turned on, the measurement of the predetermined time T2 is not performed. Therefore, the predetermined time T2 that becomes the closing condition of the water supply valve 12 is set as the duration of the ON state of the Hi float sensor 23. During this predetermined time T2, it can be considered that the water level in the water supply tank 2 is higher than the Hi water level above the overflow hole 95 and surplus water is flowing into the overflow pipe 9 from the overflow hole 95. In the present invention, the closing condition of the water supply valve 12 is not limited to the "continuation" of the predetermined time T2. After the Hi float sensor 23 detects ON, the opening of the water supply valve 12 may be continued for at least the predetermined time T2, and the water supply valve 12 may be closed after the predetermined time T2 has elapsed. Also, the water supply valve 12 may be closed when the Hi float sensor 23 detects ON at the time when the Hi float sensor 23 first detects ON and at the time when the predetermined time T2 has elapsed. Even in such a case, during the predetermined time T2, it can be considered that the water level in the water supply tank 2 exceeds the Hi water level.

[0052] As described above, even when the ON state of the overflow float sensor 22 does not continue for the predetermined time T1, for the predetermined time T2, the surplus water in the water supply tank 2 surely flows from the overflow hole 95 into the overflow pipe 9 and water is supplied to the trap portion 92. Therefore, within this predetermined time T2, the trap portion 92 can be filled with water.

[0053] In addition, the closing operation control of the water supply valve 12 is performed when the ON state of the overflow float sensor 22 continues for the predetermined time T1 or when the ON state of the Hi float sensor 23 continues for the predetermined time T2. Therefore, after the water supply valve 12 is opened, if the water level in the water supply tank 2 never reaches the overflow float sensor 22, and also if either the overflow float sensor 22 or the Hi float sensor 23 fails in the OFF state, the water supply valve 12 can be closed to stop the water supply to the water supply tank 2.

[0054] In addition, since the overflow float sensor 22 is disposed corresponding to a height position slightly lower than the height position of the upstream end opening 94 of the overflow pipe 9, when the water level in the water supply tank 2 reaches the height position of the upstream end opening 94 of the overflow pipe 9, the overflow float sensor 22 surely turns ON. Also, since the overflow hole 95 of the overflow pipe 9 is set at a position lower than the height position of the overflow float sensor 22, when the water level in the water supply tank 2 drops from the height position of the upstream end opening 94 of the overflow pipe 9, the overflow float sensor 22 surely turns OFF. Therefore, by the ON of the overflow float sensor 22, it can be surely detected that the water level in the water supply tank 2 has reached above the upstream end opening 94 of the overflow pipe 9 and the surplus water in the water supply tank 2 has flowed into the upstream end opening 94. Also, by the OFF of the overflow float sensor 22, it can be surely detected that the water level in the water supply tank 2 has dropped from the height position of the upstream end opening 94.

[0055] The flow rate flowing into the overflow pipe 9 from the overflow hole 95 is smaller than the flow rate flowing into the overflow pipe 9 from the upstream end opening 94. Also, since the water supply flow rate of the water supply pipe 10 is set to be larger than the usage flow rate when used maximally at all the hot water outlet terminals 400, the water level in the water supply tank 2 rises to a height that at least exceeds the overflow hole 95 due to the water supply from the water supply pipe 10. Further, since the Hi float sensor 23 is disposed corresponding to a height position slightly above the height position of the overflow hole 95 of the overflow pipe 9, the Hi float sensor 23 surely turns ON when the water level in the water supply tank 2 is higher than the height position of the overflow hole 95 of the overflow pipe 9, and when the water level in the water supply tank 2 drops to the height position of the overflow hole 95 of the overflow pipe 9 due to the stop of the water supply of the water supply pipe 10, the Hi float sensor 23 surely turns OFF. Therefore, by the ON of the Hi float sensor 23, it can be surely detected that the water level in the water supply tank 2 has reached the overflow hole 95 of the overflow pipe 9 or higher and the surplus water in the water supply tank 2 is flowing into the overflow hole 95. Also, by the OFF of the Hi float sensor 23, it can be surely detected that the water level in the water supply tank 2 has substantially dropped to the height position of the overflow hole 95.

[0056] As described above, according to the closing process of the water supply valve 12 according to the present embodiment, every time water is supplied into the water supply tank 2 by the opening of the water supply valve 12, water surely flows into the overflow pipe 9 and is supplied to the trap portion 92. When water is supplied into the water supply tank 2, water is supplied to the trap portion 92 of the overflow pipe 9, and water accumulates in the overflow pipe 9 up to the lower end position of the drain port 21. Therefore, even if the water in the overflow pipe 9 gradually evaporates, the evaporated water can be supplemented every time water is supplied into the water supply tank 2 to keep the trap portion 92 in a full water state. Accordingly, the breakage of the water seal of the trap portion 92 of the overflow pipe 9 is surely prevented, and it is possible to prevent odors, various bacteria, etc. from entering the water supply tank 2 from the downstream side of the overflow pipe 9. Thus, when the hot water outlet terminal 400 is opened, hot water containing odors, various bacteria, etc. does not flow out from the hot water outlet terminal 400, and the user can hygienically use the hot water without feeling discomfort.

[0057] Also, in this embodiment, following the closing operation of the water supply valve 12, an open failure detection operation of the water supply valve 12 is performed (Steps S4 to S5), and the open failure of the water supply valve 12 is detected by monitoring the ON state of the overflow float sensor 22. That is, when the water supply valve 12 is closed, the water supply into the water supply tank 2 stops, and in this water supply stop state, the surplus water in the water supply tank 2 is drained from the overflow pipe 9. Therefore, when the water supply valve 12 is normally closed by the closing instruction of the water supply valve 12, the water level in the water supply tank 2 finally drops to the height position of the overflow hole 95. Thus, before the lapse of a predetermined time T3 from the closing instruction of the water supply valve 12, it drops to at least a position lower than the overflow water level, so the overflow float sensor 22 turns OFF. However, if it is detected that the overflow float sensor 22 remains in the ON state without turning OFF even after the closing instruction of the water supply valve 12 for a predetermined time T3, it is considered that the water supply into the water supply tank 2 continues and the water supply valve 12 remains open without being normally closed by the closing instruction. Therefore, it can be determined that the water supply valve 12 has an open failure. Note that the open failure detection of the water supply valve 12 can be always detected not only after the closing instruction of the water supply valve 12 but also during the opening instruction of the water supply valve 12. Therefore, according to the above-described open failure detection operation of the water supply valve 12, it is possible to determine the open failure of the water supply valve 12 every time water is supplied into the water supply tank 2, and the open failure of the water supply valve 12 can be detected at an early stage.

[0058] (Another form of open failure detection of the water supply valve) As a detection operation for the open failure of the water supply valve 12, in step S4 of FIG. 4, even when there is a closing instruction for the water supply valve 12, if either the overflow float sensor 22 or the Hi float sensor 23 is in the ON state for a predetermined time T4 (for example, 600 seconds), it may be determined that there is an open failure of the water supply valve 12 (step S4 in FIG. 4 is "Is overflow float sensor = ON or Hi float sensor = ON after a predetermined time (T4) has elapsed?"). In this case, since the open failure of the water supply valve 12 is determined based on the ON state of either the overflow float sensor 22 or the Hi float sensor 23, even if either the overflow float sensor 22 or the Hi float sensor 23 has an OFF failure, or when the water in the water supply tank 2 flows out due to the use of the hot water terminal 400 and the water level in the water supply tank 2 does not reach the overflow level, etc., the open failure of the water supply valve 12 can be determined more accurately. The predetermined time T4 may be set to the same time as the predetermined time T3 in step S4 of FIG. 4. Also, in order to more reliably confirm the ON state of the Hi float sensor 23 located at a position lower than the overflow float sensor 22, the predetermined time T4 needs to be equal to or longer than the time it takes for the water level in the water supply tank 2 to drop below the Hi level when the water supply valve 12 is normally closed, and a time longer than the predetermined time T3 may be set.

[0059] Note that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. For example, the water supply pipe 10 may be configured to branch into two or more branch pipes at the downstream portion connected to the water supply tank 2 and then connected to the water supply tank 2, and a water supply valve may be provided in each of the branched water supply pipes. Also, the overflow float sensor 22 may be disposed corresponding to the same height position as the upstream end opening 94 of the overflow pipe 9. Even in this case, when the overflow float sensor 22 is ON, it can be detected that the surplus water in the water supply tank 2 has started to flow into the upstream end opening 94 of the overflow pipe 9. Further, the Hi float sensor 23 may be disposed corresponding to the same height position as the overflow hole 95 of the overflow pipe 9 or a height position slightly lower than the overflow hole 95. Even in this case, when the Hi float sensor 23 is turned ON, it is possible to detect whether the surplus water in the water supply tank 2 has started to flow into the overflow hole 95 of the overflow pipe 9 or the state immediately before the start of the inflow. Further, the overflow pipe 9 may not be provided with the overflow hole 95.

Explanation of Signs

[0060] 1 Hot water supply pressurization tank unit 2 Water supply tank 3 Water supply pipe 6 Hot water storage tank 9 Overflow pipe 10 Water supply pipe 11 Governor 12 Water supply valve 21 Drain port 22 Overflow float sensor (overflow water level detection means) 23 Hi float sensor (Hi water level detection means) 24 Lo float sensor 25 Low water level float sensor 31 First water supply pipe 32 Second water supply pipe 33 Check valve 34 Check valve 35 Pressure sensor 36 Water volume sensor 37 Water supply pressurization pump (pump) 38 Water supply branch pipe 39 Check valve 91 Rising part 92 Trap part 93 Kiseru part 94 Upstream end opening 95 Overflow hole 200 Drain pipe 400 Hot water outlet terminal 500 Heat source unit A Hot water supply system C Control device R Remote Control

Claims

1. A heating heat source, a hot water storage tank for storing hot water heated by the heating heat source, a water supply tank for storing water from a water supply source, a pump for supplying the hot water in the hot water storage tank and the water in the water supply tank to a hot water outlet terminal, a water supply pipe for supplying the water from the water supply source to the water supply tank, a water supply valve for opening and closing the water supply pipe, an overflow pipe having an upstream end opening communicating with the inside of the water supply tank, for draining surplus water in the water supply tank when the water level in the water supply tank exceeds a predetermined height, a trap portion provided in the middle of the overflow pipe for storing and sealing a part of the water flowing through the overflow pipe, an overflow water level detecting means for detecting that the water level in the water supply tank has reached a predetermined overflow water level at which surplus water in the water supply tank approximately flows into the overflow pipe from the upstream end opening, a control device, and comprising, The control device performs control to continue opening the water supply valve until a predetermined time (T1) elapses after the overflow water level detecting means detects that the overflow water level has been reached after the water supply valve is opened. A hot water supply system.

2. In the hot water supply system according to Claim 1, When the overflow water level detecting means detects that the overflow water level has been reached even at the time when the predetermined time (T1) has elapsed, the control device performs control to close the water supply valve. A hot water supply system.

3. In the hot water supply system according to Claim 1, When the overflow water level detecting means continuously detects that the overflow water level has been reached for the predetermined time (T1), the control device performs control to close the water supply valve. A hot water supply system.

4. A heating heat source, a hot water storage tank for storing hot water heated by the heating heat source, a water supply tank for storing water from a water supply source, a pump for supplying the hot water in the hot water storage tank and the water in the water supply tank to a hot water outlet terminal, a water supply pipe for supplying the water from the water supply source to the water supply tank, a water supply valve for opening and closing the water supply pipe, an overflow pipe having an upstream end opening and an overflow hole communicating with the inside of the water supply tank, for draining surplus water in the water supply tank when the water level in the water supply tank exceeds a predetermined height, a trap portion provided in the middle of the overflow pipe for storing and sealing a part of the water flowing through the overflow pipe, a Hi water level detecting means for detecting that the water level in the water supply tank has reached a predetermined Hi water level at which surplus water in the water supply tank approximately flows into the overflow pipe from the overflow hole, a control device, and comprising, The overflow hole is provided between the trap portion and the upstream end opening in the overflow pipe. The control device is a hot water supply system that, after the water supply valve is opened, continues to control the opening of the water supply valve until a predetermined time (T2) elapses after detecting that the Hi water level detecting means has reached the Hi water level. **Claim 5** In the hot water supply system according to claim 4, when the control device detects that the Hi water level detecting means has reached the Hi water level even at the time when the predetermined time (T2) has elapsed, the control device performs control to close the water supply valve. The hot water supply system. **Claim 6** In the hot water supply system according to claim 4, when the control device detects that the Hi water level detecting means has continuously reached the Hi water level for the predetermined time (T2), the control device performs control to close the water supply valve. The hot water supply system. **Claim 7** In the hot water supply system according to any one of claims 1 to 3, an overflow hole communicating with the water supply tank is provided in the overflow pipe below the height position where the overflow water level is reached. When the control device detects that the overflow water level detecting means has reached the overflow water level for a predetermined time (T3) even by an instruction to close the water supply valve, the control device determines that there is a failure in opening the water supply valve. The hot water supply system. **Claim 8** In the hot water supply system according to claim 7, Hi water level detecting means for detecting that the water level in the water supply tank has reached a predetermined Hi water level that is higher than the height at which the surplus water in the water supply tank flows into the overflow pipe from the overflow hole and lower than the overflow water level is provided. The control device has a configuration in which, after the water supply valve is opened, control is performed to continue opening the water supply valve until a predetermined time (T2) elapses after detecting that the Hi water level detecting means has reached the Hi water level, and also by an instruction to close the water supply valve. When the overflow water level detecting means has reached the overflow water level or the Hi water level detecting means has reached the Hi water level for a predetermined time (T4), it has a configuration for determining that there is a failure in opening the water supply valve. The hot water supply system.

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