Instant hot water system and water heater

Abstract

To provide an instant hot water system and a water heater that enables builing of an instant hot water system without requiring an extensive piping work and can suppress a decrease in the amount of hot water at a point of water supply.SOLUTION: In an instant hot water system, a water supply pipe is formed of a double pipe including an outer pipe and an inner pipe. A bypass passage is provided between a water supply passage and a hot water supply passage, the outer pipe of the double pipe being connected to a hot water outlet of a heat source, and the inner pipe of the double pipe being connected to the bypass passage via a circulation pump. A valve device is provided on the bypass passage. During a hot water operation at a hot water outlet plug, the circulation pump and the valve device are controlled to supply hot water from the heat source to a gap between the outer pipe and the inner pipe of the double pipe, and to supply hot water to the inner pipe of the double pipe via the bypass passage to supply hot water to the outlet plug. During a heat retention operation on the hot water in the hot water pipe, the hot water in the hot water pipe is made to flow out to the hot water passage from the inner pipe of the double pipe via the bypass passage, and then the hot water is flown into the gap between the outer pipe and the inner pipe of the double pipe via the heat source to circulate and heat it in the heat source.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an instant hot water supply system and a water heater that can immediately supply hot water when hot water is supplied. [Background technology]

[0002] A conventional circulating, heat-retaining hot water supply system uses a double-pipe hot water supply piping system consisting of an outer pipe and an inner pipe to supply hot water from a hot water storage tank to a hot water supply point (see Patent Document 1). This circulating, heat-retaining hot water supply system includes a piping configuration in which the outer pipe of the double-pipe hot water supply piping is connected to a hot water supply branch pipe connected to the hot water supply point, and a return port on the outer pipe is connected to the inlet of the inner pipe via a circulation piping system equipped with a circulation pump, a heating coil, and a check valve. During hot water supply, hot water from the hot water storage tank is supplied to the gap between the outer and inner pipes of the double pipe, and the hot water is supplied from the outer pipe to the hot water supply point. During heat-retaining operation, the circulation pump is operated to allow the hot water remaining in the hot water supply piping to flow out of the return port, pass through the heating coil, and into the inlet of the inner pipe, circulating the hot water between the outer and inner pipes and the heating coil. This heat-retaining operation provides an instant hot water supply system that can immediately dispense hot water when hot water supply begins. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-14381 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional circulating, heat-retaining hot water supply system, the hot water supply piping is constructed as a double pipe, which makes it possible to provide an instant hot water system without the need for extensive piping work, such as connecting an external circulating pipe to the end of the hot water supply piping. However, since hot water is supplied to the hot water supply point only through the gap between the outer pipe and the inner pipe of the double pipe, the hot water passage area during hot water supply decreases depending on the outer diameter of the inner pipe, which reduces the hot water flow rate and makes it difficult to supply a sufficient amount of hot water to the hot water supply point, which can reduce usability for users.

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide an instant hot water supply system and a water heater that can be constructed without requiring large-scale piping work and that can suppress a decrease in the amount of hot water at the hot water supply point during hot water supply. [Means for solving the problem]

[0006] The instant hot water supply system according to the present invention comprises: A water supply pipe for supplying water from a water supply source is connected to a water supply inlet of the heat source device to form a water supply passage, and a hot water supply pipe for supplying hot water to a hot water tap is connected to a hot water outlet of the heat source device to form a hot water supply passage; The hot water supply piping is constructed of a double pipe consisting of an outer pipe and an inner pipe, and a bypass passage is provided between the water supply passage and the hot water supply passage to bypass the pipe. On the heat source machine connection side of the hot water supply piping, an outer pipe connection part provided on the outer pipe of the double pipe is connected to the hot water outlet part of the heat source machine, and an inner pipe connection part provided on the inner pipe of the double pipe is connected to a bypass pipe connection part provided in the middle of the bypass passage via a circulation pump; a valve device is provided in the bypass passage for communicating between the bypass pipe connection portion and the hot water supply passage or for communicating between the bypass pipe connection portion and the water supply passage; Controlling the circulation pump and valve device During hot water supply operation to the hot water tap, hot water from the heat source unit is supplied to the gap between the outer and inner pipes of the double pipe, and is also supplied to the inner pipe of the double pipe through the bypass passage, and hot water is supplied from the outer and inner pipes of the double pipe to the hot water tap. During the warming operation of the hot water in the hot water supply pipe, the hot water in the hot water supply pipe is discharged from the inner pipe of the double pipe through a bypass passage into the water supply passage, and then flows into the gap between the outer pipe and inner pipe of the double pipe via the heat source machine, where it is circulated and heated by the heat source machine.

[0007] With this configuration, by configuring the hot water supply piping as a double pipe, piping work can be easily performed without the need for large-scale piping work, such as when connecting an external circulation pipe to the end of the hot water supply piping, and an instant hot water supply system with a simple, space-saving piping configuration can be provided. Furthermore, during hot water supply operation, by controlling the valve device of the bypass passage, hot water from the heat source unit is supplied not only to the gap between the outer pipe and the inner pipe of the double pipe, but also to the inner pipe. In this way, hot water supplied to the outer pipe and the inner pipe of the double pipe is discharged from the hot water tap, so even if the hot water supply piping is configured as a double pipe, a decrease in the amount of hot water at the hot water tap can be suppressed. Therefore, user convenience during hot water supply operation can be prevented from being reduced.

[0008] The water heater according to the present invention comprises: A water heater used as a heat source machine for an instant hot water supply system, a water supply pipe and a hot water outlet pipe connected to the heat exchanger; a bypass passageway connected between the water supply pipe and the hot water outlet pipe to bypass the water supply pipe; A hot water outlet section to which the hot water outlet of the hot water outlet pipe is connected, and a hot water supply pipe that supplies hot water to the hot water tap is composed of a double pipe consisting of an outer pipe and an inner pipe. A first connection section to which an outer pipe connection section provided on the outer pipe of the double pipe is connected. a second connection portion as a connection port portion to which a bypass pipe connection portion provided in the middle of the bypass passage is connected via a circulation pump and to which an inner pipe connection portion provided in an inner pipe of a double pipe constituting the hot water supply piping is connected; The bypass passage is provided with a first solenoid valve provided between the bypass pipe connection part and the hot water outlet pipe, and a second solenoid valve provided between the bypass pipe connection part and the water supply pipe, During hot water supply operation to the hot water tap, the first solenoid valve is opened and the second solenoid valve is closed. During the operation for keeping the hot water in the hot water supply pipe warm, the circulation pump is operated, the first solenoid valve is closed, and the second solenoid valve is opened.

[0009] With this configuration, during hot water supply operation to the hot water tap, by opening the first solenoid valve and closing the second solenoid valve, hot water from the hot water outlet pipe can be supplied to the gap between the outer pipe and the inner pipe of the double pipe, and can also be supplied to the inner pipe of the double pipe through the bypass passage. Therefore, during hot water supply operation, hot water heated in the heat exchanger is not only supplied to the gap between the outer pipe and the inner pipe of the double pipe, but also to the inner pipe, and the hot water supplied to the outer pipe and the inner pipe of the double pipe is discharged from the hot water tap. Therefore, even if the hot water supply piping is configured with double pipes, a decrease in the amount of hot water at the hot water tap can be suppressed, and usability for users during hot water supply operation can be prevented.

[0010] During the warmth maintenance operation for the hot water in the hot water supply pipe, the circulation pump is operated, the first solenoid valve is closed, and the second solenoid valve is opened, causing the hot water in the hot water supply pipe to flow from the inner pipe of the double pipe through the bypass passage to the water supply pipe, where it is heated in the heat exchanger and flows into the gap between the outer and inner pipes of the double pipe. Therefore, during the warmth maintenance operation, the hot water in the outer and inner pipes of the double pipe that make up the hot water supply pipe can be circulated and heated between the heat exchanger, and hot water can be supplied immediately when hot water supply starts.

[0011] In addition, this water heater allows for the installation of a double-pipe hot water supply pipe using the first and second connection parts, making it easy to perform piping work for circulating and heating hot water in the hot water supply pipe, and it is possible to provide an instant hot water supply system with a simple piping configuration that saves space.

[0012] In the water heater, The double pipe can be constructed by inserting a catheter pipe as an inner pipe into a single hot water supply pipe.

[0013] According to the above configuration, when changing from an existing hot water supply system to an instant hot water supply system, an instant hot water supply system can be provided by simple piping work of inserting a catheter pipe into a single-pipe hot water supply pipe and connecting the catheter pipe to a bypass passage provided in the water heater. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing the overall configuration of an instant hot water supply system according to the present embodiment. [Figure 2] This is a schematic diagram of a connection part (outer pipe connection part) into which a catheter pipe is inserted to make the hot water supply pipe a double pipe. [Figure 3] 3(a) and 3(b) are schematic diagrams for explaining the operation of the instant hot water supply system according to the present embodiment during hot water supply operation (FIG. 3(a)) and during heat retention operation (FIG. 3(b)). DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in Figure 1, instant hot water supply system 1 according to the embodiment has an instant hot water function that allows hot water to be supplied promptly when hot water tap 4 is opened, and includes water heater 2 as a heat source machine, to which water supply piping 3 that supplies water from a water supply source and hot water supply piping 5 that supplies hot water to hot water tap 4 are connected. Instant hot water supply system 1 includes control device 6 that controls the operation of instant hot water supply system 1, and is also provided with remote control 7 for remotely operating instant hot water supply system 1. Water heater 2 has an outer shell formed by housing 8, and housing 8 includes combustion chamber 9 and heat exchanger 10 installed above combustion chamber 9.

[0016] The combustion chamber 9 is equipped with a burner unit 11, and combustion exhaust is generated by the combustion of the burner unit 11. A gas pipe 12 that supplies fuel gas to the burner unit 11 is connected to the burner unit 11. The gas pipe 12 is provided with, in order from the upstream side, a main gas solenoid valve 13 that opens and closes the gas pipe 12, a gas proportional valve 14 that adjusts the amount of fuel gas supplied, and a switching solenoid valve 15 that switches the number of combustion units in the burner unit 11. A fan 16 that supplies combustion air to the burner unit 11 is disposed on the underside of the combustion chamber 9. The burner unit 11 is ignited by a spark plug 17, and the combustion state is detected by a flame rod 18 and a flame detector 19. The spark plug 17 is driven by an igniter 20.

[0017] The heat exchanger 10 includes a first heat exchanger 21 disposed above the burner unit 11 and a second heat exchanger 22 disposed above the first heat exchanger 21. The first heat exchanger 21 has a heat transfer tube 23 and fins 24, and the second heat exchanger 22 has a heat transfer tube 25. The first and second heat exchangers 21, 22 heat the water or hot water flowing through the heat transfer tubes 23, 25 with the combustion exhaust gas generated by the burner unit 11 to generate hot water.

[0018] The water heater 2 is also provided with a water supply pipe 26 connected to the inlet of the heat transfer pipe 25 of the second heat exchanger 22, a hot water outlet pipe 27 connected to the outlet of the heat transfer pipe 23 of the first heat exchanger 21, a connecting pipe 28 connecting the outlet of the heat transfer pipe 25 of the second heat exchanger 22 to the inlet of the heat transfer pipe 23 of the first heat exchanger 21, and a bypass pipe 29 connecting the water supply pipe 26 and the hot water outlet pipe 27 to bypass them. This bypass pipe 29 is a pipe for mixing some of the water flowing through the water supply pipe 26 with the hot water flowing out of the hot water outlet pipe 27.

[0019] The water supply pipe 26 is provided with, from the upstream side, a flow rate sensor 30 that detects the flow rate of water flowing through the water supply pipe 26, a water supply temperature sensor 31 that detects the temperature of the water flowing through the water supply pipe 26, a water volume servo 32 that changes the opening degree of the water supply pipe 26 (including fully closing it), and a bypass servo 33 that changes the opening degree of the bypass pipe 29 (including fully closing it). The hot water outlet pipe 27 is provided with, from the upstream side, a boiler body temperature sensor 34 that detects the temperature of the hot water immediately after it flows out of the first heat exchanger 21, and an outlet hot water temperature sensor 35 that is provided downstream of the junction with the bypass pipe 29 and detects the temperature of the hot water flowing out of the water heater 2. A high limit sensor 36 is provided near the inlet of the first heat exchanger 21 in the connecting pipe 28 to detect overheating of the first heat exchanger 21.

[0020] The upstream end of water supply pipe 26 is connected to water supply inlet 37 provided at the bottom of casing 8. Water supply piping 3, which supplies water from a water supply source, is connected to water supply inlet 37, and a water supply passage is formed by water supply piping 3 and water supply pipe 26. Water supply piping 3 is provided with a check valve 38 that prevents water from flowing in from water supply pipe 26. The downstream end (hot water outlet) of hot water outlet pipe 27 is connected to hot water outlet 39 provided at the bottom of casing 8. Hot water supply piping 5, which supplies hot water to hot water tap 4, is connected to hot water outlet 39, and a hot water supply passage is formed by hot water supply piping 5 and hot water outlet pipe 27. Hot water supply piping 5 can be made of metal or resin.

[0021] The hot water supply pipe 5 extends to the location where the hot water tap 4 is installed. Connected to the hot water tap 4 are a hot water supply branch pipe 40 that branches off from the hot water supply pipe 5 and carries hot water from the hot water supply pipe 5, and a water supply branch pipe 41 that branches off from the water supply pipe 3 and carries water from the water supply source. Near the location of the hot water tap 4 on the hot water supply pipe 5, an overpressure relief valve 42, an air-water separator 43 with an air vent valve, and an expansion tank 44 are provided, and these devices 42, 43, and 44 prevent the generation of abnormal pressure caused by air bubbles in the hot water passage and volume expansion due to hot water.

[0022] Next, a configuration for establishing the instant hot water function in the instant hot water supply system 1 will be described. The hot water supply pipe 5 is configured as a double pipe consisting of an outer pipe 51 and an inner pipe 52. The water heater 2 is provided with a bypass passage 45 that connects the water supply pipe 26 and the hot water outlet pipe 27 to form a bypass. This bypass passage 45 is connected to the water supply pipe 26 at a position upstream of the flow rate sensor 30, and is connected to the hot water outlet pipe 27 at a position downstream of the hot water outlet temperature sensor 35. The outer pipe 51 of the double pipe that configures the hot water supply pipe 5 is connected to the hot water outlet port 39 of the water heater 2 to which the hot water outlet of the hot water outlet pipe 27 is connected, and the inner pipe 52 of the double pipe is connected via a circulation pump 49 to a bypass pipe connection port 46 provided midway along the bypass passage 45. The circulation pump 49 has a discharge port connected to the bypass pipe connection port 46 and a suction port connected to a connection port 50 provided in the housing 8 of the water heater 2. That is, inner pipe 52 of the double pipe is connected to connection port 50, and is thereby connected to bypass pipe connection portion 46 of bypass passage 45 via circulation pump 49. In bypass passage 45, a first solenoid valve 47 is provided between bypass pipe connection portion 46 and hot water outlet pipe 27, and a second solenoid valve 48 is provided between bypass pipe connection portion 46 and water supply pipe 26. In addition, an instant hot water return temperature sensor 53 is provided at the position of bypass pipe connection portion 46 to which circulation pump 49 is connected. First solenoid valve 47 and second solenoid valve 48 constitute a valve device. Note that, although bypass passage 45 is provided inside water heater 2 in this embodiment, it may also be provided outside water heater 2, i.e., to bypass water supply pipe 3 by connecting outer pipe 51 of hot water supply pipe 5.

[0023] As shown in FIG. 2 , the double pipe constituting the hot water supply pipe 5 can be constructed by inserting a catheter pipe, which serves as the inner pipe 52, into an existing single-pipe hot water supply pipe using a connecting part, which serves as the outer pipe connection part 60. In this case, the single-pipe hot water supply pipe serves as the outer pipe 51 of the double pipe. The catheter pipe, which serves as the inner pipe 52, is made of a flexible, heat-resistant resin pipe such as a polyethylene pipe. The outer pipe connection part 60 has a tube body 61 and a branch joint 62 branching from the tube body 61. The catheter pipe, which serves as the inner pipe 52, is inserted into the branch joint 62 and is arranged so that it extends from one end of the tube body 61. One end of the tube body 61 is formed with an attachment part 63 that is inserted and connected to the single-pipe hot water supply pipe, and the other end of the tube body 61 is formed with a water heater-side connection part 64. The water heater-side connection part 64 is connected to the first connection part, which is the hot water outlet 39 of the water heater 2. The catheter piping that becomes the inner pipe 52 has an inner pipe connection part 65 at the end that is pulled out from the branch joint 62. The inner pipe connection part 65 is connected to the second connection part, which is the connection port part 50 of the water heater 2 to which the circulation pump 49 is connected.

[0024] With this configuration, when changing from an existing hot water supply system to an instant hot water supply system, for example, instant hot water supply system 1 can be provided by simple piping work of inserting a catheter pipe as inner pipe 52 into a single-pipe hot water supply pipe and connecting the catheter pipe to bypass passage 45 provided in water heater 2. Furthermore, since water heater 2 allows double-pipe hot water supply pipe 5 to be installed using first connection part (hot water outlet part 39) and second connection part (connection port part 50), piping work for circulating and heating hot water in hot water supply pipe 5 is simple, and instant hot water supply system 1 can be provided with a simple piping configuration that saves space.

[0025] Next, a description will be given of the operation during hot water supply operation in the instant hot water supply system 1. The operation during hot water supply operation is controlled by the control device 6. Referring to FIG. 3(a), when a user opens a predetermined hot water tap 4, water from a water supply source is supplied to a water supply pipe 26 through a water supply pipe 3. When the flow rate of water flowing through the water supply pipe 26 detected by a flow rate sensor 30 provided in the water supply pipe 26 exceeds the ignition water rate, the burner unit 11 is ignited and combustion is initiated, and in the bypass passage 45, a first solenoid valve 47 is opened and a second solenoid valve 48 is maintained in a closed state. The water supplied to the water supply pipe 26 flows into a heat exchanger 10, where it is heated by the combustion exhaust gas from the burner unit 11 and becomes hot water, which then flows out to a hot water outlet pipe 27. The hot water that flows through the hot water outlet pipe 27 and reaches a hot water outlet 39 is supplied to a gap between an outer pipe 51 and an inner pipe 52 of a double pipe that constitutes the hot water supply pipe 5. In addition, since the first solenoid valve 47 in the bypass passage 45 is open, the hot water flowing out to the hot water outlet pipe 27 is also supplied from the bypass passage 45 through the circulation pump 49, which is stopped, to the inner pipe 52 of the double pipe that makes up the hot water supply piping 5.

[0026] In this way, the hot water heated in the heat exchanger 10 and flowing out to the hot water outlet pipe 27 is supplied to the outer pipe 51 and inner pipe 52 of the double pipe that constitutes the hot water supply pipe 5. The hot water supplied to the outer pipe 51 and inner pipe 52 of the double pipe is supplied from the hot water supply branch pipe 40 to the opened hot water tap 4, where it is mixed with water from the water supply branch pipe 41 by the user and adjusted to the desired temperature before being dispensed. The hot water supplied to the inner pipe 52 flows into the gap between the outer pipe 51 and inner pipe 52 at the end of the hot water supply pipe 5 and is supplied to the hot water tap 4 that is in use. In this way, during hot water supply operation, the hot water heated in the heat exchanger 10 is not only supplied to the gap between the outer pipe 51 and inner pipe 52 of the double pipe that constitutes the hot water supply pipe 5, but also to the inner pipe 52, and the hot water supplied to the outer pipe 51 and inner pipe 52 of the double pipe is dispensed from the hot water tap 4. Therefore, even if the hot water supply piping 5 is configured as a double pipe, it is possible to suppress a decrease in the amount of hot water at the hot water tap 4, and it is possible to prevent a decrease in usability for the user during hot water supply operation.

[0027] Next, a description will be given of the operation during heat retention of the hot water remaining in the hot water supply pipe 5 in the instant hot water supply system 1. The operation during heat retention is controlled by the control device 6. Referring to FIG. 3(b), when a predetermined time (e.g., 30 minutes) has elapsed since the hot water supply operation was stopped, the circulation pump 49 is operated, the first solenoid valve 47 in the bypass passage 45 is closed, and the second solenoid valve 48 is kept open. The burner unit 11 is also ignited and combusted. Note that the burner unit 11 may be configured to ignite when hot water remaining in the hot water supply pipe 5 is supplied from the bypass passage 45 to the water supply pipe 26 and the flow rate sensor 30 in the water supply pipe 26 detects a flow rate equal to or greater than the ignition water rate, as described below. The operation of the circulation pump 49 causes the hot water remaining in the hot water supply pipe 5 to flow out from the inner pipe 52 of the double pipe constituting the hot water supply pipe 5 to the bypass passage 45. In this case, the hot water remaining in the gap between the outer pipe 51 and the inner pipe 52 of the double pipe flows into the inner pipe 52 at the end of the hot water supply pipe 5 and then flows out from the inner pipe 52 to the bypass passage 45. In the bypass passage 45, the first solenoid valve 47 is closed and the second solenoid valve 48 is maintained in an open state, so all of the hot water flowing out from the inner pipe 52 into the bypass passage 45 is supplied to the water supply pipe 26. Note that, since the water supply piping 3 is provided with a check valve 38, the hot water supplied to the water supply pipe 26 flows into the heat exchanger 10, where it is heated, and then flows out to the hot water outlet pipe 27. Since the first solenoid valve 47 in the bypass passage 45 is closed, all of the hot water that flows out to the hot water outlet pipe 27 flows to the hot water outlet port 39 and flows into the gap between the outer pipe 51 and inner pipe 52 of the double pipes that make up the hot water supply piping 5.

[0028] In this way, hot water is circulated through the outer pipe 51 and the inner pipe 52 of the double pipe constituting the hot water supply pipe 5 and heated by the heat exchanger 10, so that the hot water in the hot water supply pipe 5 is kept at a predetermined temperature. Therefore, when the hot water tap 4 is opened and hot water supply operation is started, hot water can be supplied immediately from the start of hot water supply. If the hot water tap 4 is opened and hot water supply operation is started during keep-warm operation, the keep-warm operation is stopped, the circulation pump 49 is deactivated, the first solenoid valve 47 in the bypass passage 45 is opened, and the second solenoid valve 48 is kept closed. When the hot water supply operation is started during keep-warm operation, water from the water supply source is supplied from the water supply pipe 3 to the water supply pipe 26. Therefore, the temperature of the hot water detected by the water supply temperature sensor 31 provided in the water supply pipe 26 changes from being approximately the same temperature as the hot water temperature detected by the instant hot water return temperature sensor 53 provided in the bypass passage 45 to being detected as a temperature lower than that. This makes it possible to determine that the hot water supply operation has started during keep-warm operation.

[0029] When the temperature of the hot water detected by the instant hot water return temperature sensor 53 provided in the bypass passage 45 reaches or exceeds a predetermined temperature (e.g., 60°C) as a result of the execution of the heat retention operation, or when a predetermined heat retention time (e.g., one hour) has elapsed since the temperature detected by the instant hot water return temperature sensor 53 reached or exceeds the predetermined temperature, the circulation pump 49 may be stopped and the burner unit 11 may be stopped from firing, thereby temporarily suspending the heat retention operation. Then, when a predetermined temporary suspension time (e.g., 60 minutes) has elapsed since the heat retention operation was temporarily suspended without the hot water supply operation being performed, the circulation pump 49 may be operated, the burner unit 11 may be fired, and the heat retention operation may be resumed.

[0030] As described above, according to this embodiment, piping work can be easily performed without the need for large-scale piping work such as connecting an external circulation pipe to the end of the hot water supply pipe, and an instant hot water supply system 1 with a simple, space-saving piping configuration can be provided. Furthermore, during hot water supply operation, hot water from the heat exchanger 10 can be supplied to the outer pipe 51 and inner pipe 52 of the double pipe that constitutes the hot water supply pipe 5 by controlling the first solenoid valve 47 and the second solenoid valve 48 of the bypass passage 45. Therefore, even if the hot water supply pipe 5 is configured as a double pipe, a decrease in the amount of hot water at the hot water tap 4 can be suppressed, and usability for the user can be prevented from being reduced.

[0031] 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, in this embodiment, the heat source machine is a gas combustion water heater 2, but it may also be a heat pump water heater. Also, a liquid-liquid heat exchanger may be used as the heat exchanger 10. Also, the heat source machine may be a water heater equipped with a bath circuit and a heating circuit. [Explanation of symbols]

[0032] 1. Instant hot water supply system 2. Water heater 3 Water supply piping (water supply passage) 4 Hot water tap 5 Hot water supply piping (hot water passage) 6. Control device 7 Remote Control 8. Housing 9 Combustion chamber 10 Heat exchanger 11 Burner unit 21 1st heat exchanger 22 Second heat exchanger 23,25 Heat transfer tubes 24 Finn 26 Water supply pipe (water supply passage) 27 Hot water outlet pipe (hot water passage) 28 Connecting pipe 29 Bypass pipe 30 Flow sensor 31 Water supply temperature sensor 32 Water volume servo 33 Bypass servo 34 Can body temperature sensor 35 Outlet water temperature sensor 36 High limit sensor 37 Water supply inlet 38 Check valve 39 Hot water outlet (first connection) 40 Hot water branch pipe 41 Water supply branch pipe 45 Bypass Passage 46 Bypass pipe connection 47 First solenoid valve 48 Second solenoid valve 49 Circulation Pump 50 Connection port (second connection part) 51 Outer tube 52 Inner tube 53 Instant rehydration temperature sensor 60 Outer tube connection 61 Cylinder body 62 Branch joint 63 Mounting part 64 Water heater side connection 65 Inner pipe connection

Claims

1. A water supply pipe for supplying water from a water supply source is connected to a water supply inlet of the heat source device to form a water supply passage, and a hot water supply pipe for supplying hot water to a hot water tap is connected to a hot water outlet of the heat source device to form a hot water supply passage; The hot water supply piping is configured as a double pipe consisting of an outer pipe and an inner pipe, and a bypass passage is provided between the water supply passage and the hot water supply passage to bypass the water supply passage, On the heat source machine connection side of the hot water supply piping, an outer pipe connection part provided on the outer pipe of the double pipe is connected to the hot water outlet part of the heat source machine, and an inner pipe connection part provided on the inner pipe of the double pipe is connected to a bypass pipe connection part provided in the middle of the bypass passage via a circulation pump; a valve device is provided in the bypass passage for communicating between the bypass pipe connection portion and the hot water supply passage or for communicating between the bypass pipe connection portion and the water supply passage; Controlling the circulation pump and valve device During hot water supply operation to the hot water tap, hot water from the heat source unit is supplied to the gap between the outer and inner pipes of the double pipe, and is also supplied to the inner pipe of the double pipe through the bypass passage, supplying hot water from the outer and inner pipes of the double pipe to the hot water tap. The instant hot water supply system is configured such that, during the warming operation of the hot water in the hot water supply pipe, the hot water in the hot water supply pipe is made to flow from the inner pipe of the double pipe through a bypass passage into a water supply passage, and is made to flow into a gap between the outer pipe and the inner pipe of the double pipe via a heat source machine, where it is circulated and heated by the heat source machine.

2. A water heater used as a heat source machine for an instant hot water supply system, a water supply pipe and a hot water outlet pipe connected to the heat exchanger; a bypass passageway connected between the water supply pipe and the hot water outlet pipe to bypass the water supply pipe; a hot water outlet portion to which the hot water outlet of the hot water outlet pipe is connected, and a hot water supply pipe that supplies hot water to the hot water tap is composed of a double pipe of an outer pipe and an inner pipe, and a first connection portion to which an outer pipe connection portion provided on the outer pipe of the double pipe is connected; a second connection portion as a connection port portion to which a bypass pipe connection portion provided in the middle of the bypass passage is connected via a circulation pump and to which an inner pipe connection portion provided in an inner pipe of a double pipe constituting the hot water supply piping is connected, The bypass passage is provided with a first solenoid valve provided between the bypass pipe connection portion and the hot water outlet pipe, and a second solenoid valve provided between the bypass pipe connection portion and the water supply pipe, During hot water supply operation to the hot water tap, the first solenoid valve is opened and the second solenoid valve is closed. The water heater is configured such that, during an operation for keeping the hot water in the hot water supply pipe warm, the circulation pump is operated, the first solenoid valve is closed, and the second solenoid valve is opened.

3. The water heater according to claim 2, A double-pipe water heater is constructed by inserting an inner catheter pipe into a single-pipe hot water supply pipe.

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