Hot water supply heater

Abstract

To secure a flow rate of a primary heat exchanger and prevent a situation where boiling easily occurs in the primary heat exchanger.SOLUTION: A hot water supply heater 1 includes: a heating circuit 4A including primary and secondary heat exchangers, a cistern 33, a circulation pump 36, and connection piping 30; and a controller 21. The connection piping 30 includes a heating return pipe 32, a first connection pipe 47, a low-temperature outgoing pipe 49, a high-temperature outgoing pipe 58, and a bypass circuit 59. The bypass circuit 59 includes a flow regulation section 62. The controller 21 controls the flow regulation section 62 to limit a flow rate from the primary heat exchanger to the cistern 33 to a small flow rate when a detection temperature obtained by a second thermistor becomes a first reference temperature or lower, and opens a reheating flow control valve to control the amount of hot water to the primary heat exchanger to an intermediate flow rate between a flow rate when a bypass thermomotive valve is opened and a flow rate when the bypass thermomotive valve is closed when a detection temperature obtained by the second thermistor becomes equal to or higher than a second reference temperature that is higher than the first reference temperature.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a water heater and a heater.

Background Art

[0002] As a water heater equipped with a heating circulation circuit for circulating and supplying hot water to a high-temperature terminal heating device and a low-temperature terminal heating device, a water heater described in Japanese Patent Application Laid-Open No. 2005-61677 (hereinafter referred to as Patent Document 1) is known. In this water heater, the hot water heated by the sub-heat exchanger and introduced into the cistern is branched and supplied to the low-temperature terminal heating device and the main heat exchanger. The hot water supplied to the low-temperature terminal heating device warms the room and then returns to the sub-heat exchanger via the heating return pipeline, and is heated by this sub-heat exchanger and supplied again to the low-temperature heating terminal device or the like via the cistern. On the other hand, the hot water flowing through the main heat exchanger is supplied to a bypass pipeline or the like connected to the cistern after being heated by the main heat exchanger.

[0003] A low-temperature capacity switching thermostatic valve is provided in the bypass pipeline. When it is determined based on the detected temperature of the thermistor provided in the cistern that it is necessary to warm the path to the low-temperature terminal heating device, it is controlled to be in an open state, and when it is determined that warming is not necessary, it is controlled to be in a closed state. However, the low-temperature capacity switching thermostatic valve is not completely closed, and a gap is formed so that a very small amount of hot water can flow through the heating heat exchanger even when the supplementary heating thermostatic valve, the high-temperature terminal heating device, and all of the low-temperature terminal heating devices are closed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Compared with the above-described water heater, the present one is of low cost, but has a problem that the flow rate from the main heat exchanger to the cistern can only be adjusted in two steps, large and small. Therefore, when the required temperature is low and the flow rate is relatively large, if the low-temperature capacity switching thermostatic valve is opened, the main heat exchanger will be cooled too much and it will be in a state where drain is likely to occur in the main heat exchanger. On the other hand, if the low-temperature capacity switching thermostatic valve is closed, the flow of warm water from the main heat exchanger to the cistern will be restricted and boiling is likely to occur in the main heat exchanger.

Means for Solving the Problems

[0006] The water heater and space heater of the present disclosure includes a primary heat exchanger and a secondary heat exchanger heated by a gas burner, a cistern for storing hot water and provided with a first thermistor, a circulation pump, and connection pipes, and includes a heating circuit that forms a circulation path with an external heating terminal, a supplementary heating circuit for a bath, and a controller. The connection pipes include a heating return pipe that connects a heating return port to which a downstream end of the external heating terminal is connected and an upstream end of the secondary heat exchanger, a first connection pipe that connects a downstream end of the secondary heat exchanger and an inlet of the cistern, a low-temperature supply pipe that connects an outlet of the cistern and a low-temperature supply port that serves as an outlet to the external heating terminal and in which the circulation pump is interposed, a second connection pipe that branches from the middle of the low-temperature supply pipe and is connected to an upstream end of the primary heat exchanger, a high-temperature supply pipe that connects a downstream end of the primary heat exchanger and a high-temperature supply port that serves as an outlet to a high-temperature heating terminal different from the external heating terminal and is provided with a second thermistor for detecting an outlet temperature of the primary heat exchanger, and a bypass circuit that branches from the high-temperature supply pipe and is connected to the first connection pipe or the cistern. From the high-temperature supply pipe, a supplementary heating flow control valve and a liquid-liquid heat exchanger for heating the supplementary heating circuit for a bath are interposed in the middle. A supplementary heating circuit that merges into the heating return pipe branches. In the bypass circuit, a flow rate adjustment unit is provided that adjusts the amount of hot water flowing from the primary heat exchanger to the cistern in two steps of large and small by opening and closing a bypass thermostatic valve. The water heater and space heater is such that the controller controls the flow rate adjustment unit to limit the flow rate flowing from the primary heat exchanger to the cistern to a small flow rate when a first condition including that the detected temperature by the second thermistor is equal to or lower than a first reference temperature is satisfied, and then, when the detected temperature by the second thermistor becomes equal to or higher than a second reference temperature that is higher than the first reference temperature, opens the supplementary heating flow control valve to control the amount of hot water flowing through the primary heat exchanger to an intermediate flow rate between the flow rate when the bypass thermostatic valve is open and the flow rate when it is closed.

Effect of the Invention

[0007] According to the present disclosure, it is possible to ensure a certain flow rate of the primary heat exchanger and prevent the temperature in the primary heat exchanger from rising excessively and being in a state where boiling is likely to occur in the primary heat exchanger.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0009] [Description of Embodiments of the Present Disclosure] First, the embodiments of the present disclosure will be listed and described.

[0010] [1] The water heater and space heater of the present disclosure includes a primary heat exchanger and a secondary heat exchanger heated by a gas burner, a cistern for storing hot water and provided with a first thermistor, a circulation pump, and connection pipes, and includes a heating circuit that forms a circulation path with an external heating terminal, a supplementary heating circuit for a bath, and a controller. The connection pipes include a heating return pipe that connects a heating return port to which a downstream end of the external heating terminal is connected and an upstream end of the secondary heat exchanger, a first connection pipe that connects a downstream end of the secondary heat exchanger and an inlet of the cistern, a low-temperature supply pipe that connects an outlet of the cistern and a low-temperature supply port that serves as an outlet to the external heating terminal and in which the circulation pump is interposed, a second connection pipe that branches from the middle of the low-temperature supply pipe and is connected to an upstream end of the primary heat exchanger, a high-temperature supply pipe that connects a downstream end of the primary heat exchanger and a high-temperature supply port that serves as an outlet to a high-temperature heating terminal different from the external heating terminal and is provided with a second thermistor for detecting an outlet temperature of the primary heat exchanger, and a bypass circuit that branches from the high-temperature supply pipe and is connected to the first connection pipe or the cistern. From the high-temperature supply pipe, a supplementary heating flow control valve and a liquid-liquid heat exchanger for heating the supplementary heating circuit for a bath are interposed in the middle. A supplementary heating circuit that merges into the heating return pipe branches. In the bypass circuit, a flow rate adjustment unit is provided that adjusts the amount of hot water flowing from the primary heat exchanger to the cistern in two steps of large and small by opening and closing a bypass thermostatic valve. The water heater and space heater is such that when the controller satisfies a first condition including that the detected temperature by the second thermistor becomes equal to or lower than a first reference temperature, the controller controls the flow rate adjustment unit to limit the flow rate flowing from the primary heat exchanger to the cistern to a small flow rate. Thereafter, when the detected temperature by the second thermistor becomes equal to or higher than a second reference temperature that is higher than the first reference temperature, the supplementary heating flow control valve is opened to control the amount of hot water flowing through the primary heat exchanger to an intermediate flow rate that is between the flow rate when the bypass thermostatic valve is open and the flow rate when it is closed.

[0011] According to the above water heater and heater, when the flow rate adjustment unit is restricted (the bypass thermostatic valve is closed) and the temperature of the primary heat exchanger becomes high, the supplementary combustion flow control valve is opened so that the hot water in the primary heat exchanger flows into the supplementary combustion circuit. Therefore, a certain amount of the flow rate of the primary heat exchanger can be ensured, and it is possible to prevent the temperature in the primary heat exchanger from rising excessively and being in a state where boiling is likely to occur in the primary heat exchanger.

[0012] [Details of Embodiments of the Present Disclosure] A specific example of the water heater and heater of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, and is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0013] (Overall Configuration of Water Heater and Heater 1) The water heater and heater 1 of the present embodiment has a water heating function of heating supplied tap water and supplying hot water to the outside, and a heating function of supplying hot water to radiators installed outside in a room or under the floor to heat the room or the floor. As shown in FIG. 1, the water heater and heater 1 includes a box-shaped housing 50 in which a combustion device 17 is housed. The housing 50 includes a bottom plate portion 51 located on the lower side in a front view, a left side plate portion 52 located on the left side in a front view, a right side plate portion 53 located on the right side in a front view, a top plate portion 54 located on the upper side in a front view, a rear wall 55 located on the rear side, and a front cover (not shown) located on the front side. FIG. 1 is a front view of the water heater and heater 1 with the front cover removed.

[0014] FIG. 2 is a schematic diagram of the water heater and heater 1. The water heater and heater 1 includes a water heating circuit 2 that includes water heating burners 3, 3,... and a water heating heat exchanger 7 to heat tap water and discharge hot water, a heating circuit 4A that includes heating burners 5, 5,... and a heating heat exchanger 26 and is used for floor heating or the like, and a bathtub supplementary combustion circuit 4B that includes a liquid-liquid heat exchanger 40 and is used for supplementary combustion of a bathtub or the like.

[0015] In the hot water supply circuit 2, 6 is a water supply pipe that supplies water from the water pipe to the hot water supply heat exchanger 7, 8 is a hot water outlet pipe that discharges the hot water heated by the hot water supply heat exchanger 7, and 9 is a gas pipe that supplies gas to the hot water supply burner 3. A hot water supply water volume sensor 10 is provided in the water supply pipe 6, a hot water supply heat exchanger thermistor 11 is provided in the hot water outlet pipe 8, and an original solenoid valve 12 and a proportional valve 13 are provided in the gas pipe 9 from the upstream side. Hot water supply gas solenoid valves 14, 14... are provided in each branch pipe branched from the gas pipe 9 to each hot water supply burner 3.

[0016] The hot water supply heat exchanger 7 is composed of a hot water supply primary heat exchanger 7A which is a sensible heat recovery type heat exchanger and a hot water supply secondary heat exchanger 7B which is a latent heat recovery type heat exchanger. The water from the water supply pipe 6 passes through the hot water supply secondary heat exchanger 7B and the hot water supply primary heat exchanger 7A in this order, exchanges heat with the combustion exhaust gas of the hot water supply burner 3 and is heated, and then is discharged from the hot water outlet pipe 8.

[0017] On the other hand, in the heating circuit 4A, heating gas solenoid valves 29, 29 are provided in each branch pipe branched from the gas pipe 9 to each heating burner 5 of the heating heat exchanger 26. The heating heat exchanger 26 is composed of a heating primary heat exchanger 26A which is a sensible heat recovery type heat exchanger and a heating secondary heat exchanger 26B which is a latent heat recovery type heat exchanger.

[0018] The heating heat exchanger 26 forms a hot water circulation path together with a cistern 33 for storing hot water, a low-temperature radiator 34 for floor heating, and a high-temperature radiator 35 used for a bathroom heating and drying machine or a fan convector. A circulation pump 36 is provided in the circulation path. A part of the piping of this circulation path passes through a liquid-liquid heat exchanger 40 connected to the bathtub 39 by a forward pipe 37 and a return pipe 38 in the bath supplementary heating circuit 4B. The hot water heated by the heating heat exchanger 26 and circulating in the circulation path can heat the bath water passing through the liquid-liquid heat exchanger 40.

[0019] 41 is a supplementary heating flow control valve that sends hot water to the liquid-liquid heat exchanger 40, 42 is a bathtub pump that circulates bath water between the bathtub 39 and the liquid-liquid heat exchanger 40, 43 is a heating high-temperature thermistor that detects the outlet water temperature of the heating heat exchanger 26, and 44 is a heating low-temperature thermistor that detects the temperature of the hot water in the cistern 33. The bath water returns from the bathtub 39 through the return pipe 38 by the operation of the bathtub pump 42, passes through the liquid-liquid heat exchanger 40, is heated by exchanging heat with the hot water in the liquid-liquid heat exchanger 40, and then returns to the bathtub 39 from the supply pipe 37. The heating low-temperature thermistor 44 corresponds to the "first thermistor" of the present disclosure.

[0020] Each hot water burner 3 and each heating burner 5 are housed in a common combustion chamber 15. A common combustion fan 16 is provided below the combustion chamber 15 so that combustion air can be supplied to each burner 3, 5. Above the combustion chamber 15, a common exhaust port 18 for exhausting the combustion gas generated by the combustion of each burner 3, 5 is provided.

[0021] A drop pipe 19 connected to the return pipe 38 to the bathtub 39 is branched and connected to the hot water outlet pipe 8. By opening the drop water solenoid valve 20 provided in the drop pipe 19, the hot water heated in the hot water heat exchanger 7 can be supplied to the bathtub 39.

[0022] 21 is a controller, 22 is a kitchen remote control, and 23 is a bathroom remote control. When the water supply amount sensor 10 detects the water flow inside the appliance by opening the faucet connected to the hot water outlet pipe 8, the controller 21 first rotates the combustion fan 16 for a predetermined time to discharge the combustion gas stored in the combustion chamber 15 (purging). Then, the main solenoid valve 12 of the gas pipe 9 and each hot water gas solenoid valve 14 are opened, the proportional valve 13 is opened at a predetermined opening degree, gas is supplied to each hot water burner 3, and the hot water ignition plug 25 is continuously discharged to ignite the hot water burners 3, 3...

[0023] Next, the controller 21 monitors the hot water temperature using the hot water heat exchanger thermistor 11 provided in the hot water pipe 8, and controls the opening and closing of the hot water gas solenoid valve 14 and adjusts the opening degree of the proportional valve 13 so that the hot water temperature becomes the set temperature indicated by the kitchen remote control 22 or the bathroom remote control 23. At the same time, the controller continuously changes the air volume by controlling the rotational speed of the combustion fan 16.

[0024] The heating operation is performed as follows. First, when the controller 21 obtains the ON signal of the floor heating switch, it rotates the circulation pump 36. Here, if the temperature of the hot water obtained from the heating high-temperature thermistor 43 or the heating low-temperature thermistor 44 is below the specified value, the controller 21 pre-purgely rotates the combustion fan 16, then opens the heating gas solenoid valve 29, opens the proportional valve 13 at a predetermined opening degree, supplies gas to the heating burner 5, and continuously discharges the heating ignition plug 27 to ignite the heating burner 5. The hot water pressurized by the circulation pump 36 branches to the low-temperature radiator 34 side and the heating heat exchanger 26 side, and the heating operation is performed by circulating through the circulation path. The controller 21 monitors the temperature from the heating high-temperature thermistor 43 or the heating low-temperature thermistor 44, and maintains the set temperature by adjusting the combustion state of the heating burner 5. The adjustment of the combustion state of the heating burner 5 is determined by, for example, the ON / OFF of the combustion burner 5, the number of combustion burners 5 to be used, etc.

[0025] Also, the bath operation is performed as follows. When the automatic switch of the kitchen remote control 22 or the bathroom remote control 23 is pressed, the drop water solenoid valve 20 of the drop pipe 19 opens to allow water to flow through the appliance, so the hot water supply burner 3 burns, and the hot water heated by the hot water heat exchanger 7 is supplied to the bathtub 39 through the drop pipe 19 and the return pipe 38. When the cumulative hot water volume detected by the bath water volume sensor 45 provided in the drop pipe 19 reaches the set hot water volume, the drop water solenoid valve 20 closes and the hot water supply stops.

[0026] On one hand, a bath return thermistor 46 for detecting the bath water temperature is provided in the return pipe 38. When the detected bath return temperature is equal to or lower than the set temperature, the supplementary heating flow control valve 41 opens, the circulation pump 36 rotates, the heating burner 5 is ignited, and the bath pump 42 also rotates. Therefore, the bath water circulating between the liquid-liquid heat exchanger 40 and the bathtub 39 exchanges heat with the hot water heated by the heating heat exchanger 26 in the liquid-liquid heat exchanger 40 and is heated to the set temperature. When the set temperature is reached, the combustion of the heating burner 5 is stopped, the circulation pump 36 and the bath pump 42 are stopped, and the supplementary heating flow control valve 41 is closed.

[0027] And in this water heating and heating apparatus 1, when either the water heating burner 3 or the heating burner 5 performs a combustion operation, the controller 21 rotates the combustion fan 16 as described above, and after the combustion stops, a post-purge for discharging the combustion gas in the combustion chamber 15 is performed.

[0028] The heating circuit 4A includes the connection pipe 30. The connection pipe 30 forms a circulation path with the low-temperature radiator 34. The connection pipe 30 includes a heating return pipe 32 connecting the heating return port 31 to which the downstream end of the low-temperature radiator 34 is connected and the upstream end of the heating secondary heat exchanger 26B, a first connection pipe 47 connecting the downstream end of the heating secondary heat exchanger 26B and the inlet of the cistern 33, a low-temperature forward pipe 49 connecting the outlet of the cistern 33 and the low-temperature forward port 48 which is the outlet to the low-temperature radiator 34 and having the circulation pump 36 interposed therebetween, a second connection pipe 56 branching from the middle of the low-temperature forward pipe 49 and connected to the upstream end of the heating primary heat exchanger 26A, a high-temperature forward pipe 58 connecting the downstream end of the heating primary heat exchanger 26A and the high-temperature forward port 57 which is the outlet to the high-temperature radiator 35 and having a heating high-temperature thermistor 43 for detecting the outlet temperature of the heating primary heat exchanger 26A provided thereon, and a bypass circuit 59 branching from the high-temperature forward pipe 58 and connected to the first connection pipe 47 or the cistern 33. From the high-temperature forward pipe 58, a supplementary heating flow control valve 41 and a liquid-liquid heat exchanger 40 for heating the bath supplementary heating circuit 4B are interposed in the middle, and a supplementary heating circuit 60 that joins the heating return pipe 32 branches off.

[0029] The low-temperature radiator 34 corresponds to the external heating terminal of the present disclosure, and the high-temperature radiator 35 corresponds to the high-temperature heating terminal of the present disclosure. Further, the heating high-temperature thermistor 43 corresponds to the second thermistor of the present disclosure.

[0030] The bypass circuit 59 is provided with a flow rate adjustment unit 62 that adjusts the amount of hot water flowing from the heating primary heat exchanger 26A to the cistern 33 in two steps of large and small by opening and closing the bypass thermostatic valve 61. As shown in FIG. 3, the flow rate adjustment unit 62 includes a bypass thermostatic valve 61 and a bypass bypass circuit 63 that bypasses the bypass thermostatic valve 61. The bypass thermostatic valve 61 is controlled to be in an open state by the controller 21 when it is determined that it is necessary to warm the path to the low-temperature radiator 34 based on the detected temperature of the heating low-temperature thermistor 44 in the cistern 33, and is controlled to be in a closed state when it is determined that warming is not necessary. However, even when the bypass thermostatic valve 61 is closed, a small amount of hot water flows through the bypass circuit 59 through the bypass bypass circuit 63, ensuring the circulation of the hot water in the heating primary heat exchanger 26A.

[0031] When the high-temperature radiator 35 is not in use, the flow path from the heating primary heat exchanger 26A to the high-temperature radiator 35 is closed, so the hot water from the heating primary heat exchanger 26A flows toward the cistern 33. The hot water heating and heating machine 1 of the present embodiment has a lower cost compared to one provided with an opening / closing control valve whose opening can be adjusted steplessly in the bypass circuit 63, but the flow rate from the heating primary heat exchanger 26A to the cistern 33 can only be adjusted in two steps of large and small. Therefore, when the required temperature is low and the flow rate is relatively large, when the bypass thermostatic valve 61 is opened, the heating primary heat exchanger 26A is cooled too much and it is easy for drain to occur in the heating primary heat exchanger 26A. On the other hand, if the bypass thermostatic valve 61 is closed, the flow of hot water from the heating primary heat exchanger 26A to the cistern 33 is restricted and boiling is likely to occur in the heating primary heat exchanger 26A.

[0032] To avoid such a situation, first, when the controller 21 satisfies the first condition that the detected temperature by the heating high-temperature thermistor 43 is equal to or lower than the first reference temperature, the controller 21 controls the flow rate adjustment unit 62 to limit the flow rate flowing from the heating primary heat exchanger 26A to the cistern 33 to a small flow rate. After that, when the detected temperature by the heating high-temperature thermistor 43 becomes equal to or higher than the second reference temperature, which is higher than the first reference temperature, the controller 21 opens the supplementary heating flow rate control valve 41 to control the amount of hot water flowing through the heating primary heat exchanger 26A to an intermediate flow rate between the flow rate when the bypass thermostatic valve 61 is open and the flow rate when it is closed.

[0033] According to such control, when the flow rate adjustment unit 62 is restricted to a small flow rate (the bypass thermostatic valve 61 is closed), if the temperature of the heating primary heat exchanger 26A rises, by opening the supplementary heating flow rate control valve 41, the hot water in the heating primary heat exchanger 26A is configured to flow into the supplementary heating circuit 60. Therefore, a certain amount of the flow rate of the heating primary heat exchanger 26A can be ensured, and it is possible to prevent the temperature in the heating primary heat exchanger 26A from rising excessively and becoming a state where boiling is likely to occur in the heating primary heat exchanger 26A.

[0034] (Other Embodiments) The above embodiment can be implemented with the following modifications. The above embodiment and the following modification examples can be implemented in combination with each other within a technically non - conflicting range.

[0035] · In the above embodiment, the flow rate adjustment unit 62 is exemplified as including the bypass thermostatic valve 61 and the bypass bypass circuit 63, but it may be a flow rate adjustment unit including only the bypass thermostatic valve 61.

[0036] · In the above embodiment, the case where the detected temperature by the heating high-temperature thermistor 44 is equal to or lower than the first reference temperature is set as the first condition, but the case where the detected temperature is equal to or lower than the first reference temperature and the state of being equal to or lower than the first reference temperature continues for a predetermined time may be set as the first condition.

Description of Reference Numerals

[0037] 1: Water heater 2: Hot water supply circuit 3: Hot water supply burner 4A: Heating circuit 4B: Bath reheating circuit 5: Heating burner 6: Water supply pipe 7: Hot water heat exchanger 7A: Primary hot water heat exchanger 7B: Secondary hot water heat exchanger 8: Hot water outlet pipe 9: Gas pipe 10: Hot water supply volume sensor 11: Hot water heat exchanger thermistor 12: Main solenoid valve 13: Proportional valve 14: Hot water supply gas solenoid valve 15: Combustion chamber 16: Combustion fan 17: Combustion device 18: Exhaust port 19: Drop-in pipe 20: Drop-in water solenoid valve 21: Controller 22: Kitchen remote control 23: Bathroom remote control 25: Hot water supply ignition plug 26: Heating heat exchanger 26A: Primary heating heat exchanger 26B: Secondary heating heat exchanger 27: Heating ignition plug 29: Heating gas solenoid valve 30: Connecting pipe 31: Heating return port 32: Heating return pipe 33: Cistern 34: Low-temperature radiator (external heating terminal) 35: High-temperature radiator 36: Circulation pump 37: Forward pipe 38: Return pipe 39: Bathtub 40: Liquid-liquid heat exchanger 41: Reheating flow control valve 42: Bath pump 43: Heating high-temperature thermistor (second thermistor) 44: Heating low-temperature thermistor (first thermistor) 45: Bath water volume sensor 46: Bath return thermistor 47: First connecting pipe 48: Low-temperature forward port 49: Low-temperature forward pipe 50: Housing 51: Bottom plate part 52: Left side plate part 53: Right side plate part 54: Top plate part 55: Rear wall 56: Second connecting pipe 57: High-temperature forward port 58: High-temperature forward pipe 59: Bypass circuit 60: Reheating circuit 61: Bypass thermostatic valve 62: Flow adjustment part 63: Bypass bypass circuit

Claims

【Claim 1】 A primary heat exchanger and a secondary heat exchanger heated by a gas burner, A cistern that stores hot and cold water and is provided with a first thermistor, A circulation pump, A heating circuit including connecting pipes that forms a circulation path with an external heating terminal, A bath reheating circuit, A controller, and is provided with, The connecting pipes include a heating return pipe that connects a heating return port to which the downstream end of the external heating terminal is connected and the upstream end of the secondary heat exchanger, a first connecting pipe that connects the downstream end of the secondary heat exchanger and the inlet of the cistern, a low-temperature supply pipe that connects the outlet of the cistern and a low-temperature supply port that is the outlet to the external heating terminal and in which the circulation pump is interposed, a second connecting pipe that branches from the middle of the low-temperature supply pipe and is connected to the upstream end of the primary heat exchanger, a high-temperature supply pipe that connects the downstream end of the primary heat exchanger and a high-temperature supply port that is the outlet to a high-temperature heating terminal different from the external heating terminal and is provided with a second thermistor that detects the outlet temperature of the primary heat exchanger, and a bypass circuit that branches from the high-temperature supply pipe and is connected to the first connecting pipe or the cistern. From the high-temperature supply pipe, an afterburner flow control valve and a liquid-liquid heat exchanger for heating the bath reheating circuit are interposed in the middle, and an afterburner circuit that merges into the heating return pipe branches, The bypass circuit is a hot water supply and heating machine provided with a flow rate adjustment unit that adjusts the amount of hot water flowing from the primary heat exchanger to the cistern in two steps of large and small by opening and closing a bypass thermostatic valve, When the controller satisfies a first condition including that the detected temperature by the second thermistor is equal to or lower than a first reference temperature, the controller controls the flow rate adjustment unit to limit the flow rate flowing from the primary heat exchanger to the cistern to a small flow rate, Thereafter, when the detected temperature by the second thermistor becomes equal to or higher than a second reference temperature that is higher than the first reference temperature, the supplementary heating flow control valve is opened to control the amount of hot water flowing through the primary heat exchanger to an intermediate flow rate that is between the flow rate when the bypass thermostatic valve is open and the flow rate when it is closed, in a hot water supply and heating unit.

Images