Hot water supply heater

Abstract

To promptly raise a temperature of hot water in a cistern or a low-temperature outgoing pipe, prevent stagnation of a flow of hot water in a primary heat exchanger, and prevent boiling 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. A reheating flow control valve 41 is provided in a reheating circuit 60 branched from the high-temperature outgoing pipe 58, and a flow regulation section 62 is provided in the bypass circuit 59. In the hot water supply heater 1, the controller 21 controls a bypass thermomotive valve 61 so that the amount of hot water flowing from the primary heat exchanger to the cistern 33 is changed from a second flow rate to a first flow rate when a predetermined condition where a heat amount in the cistern 33 or the low-temperature outgoing pipe 49 becomes insufficient is satisfied, and maintains a reheating flow control valve 41 in an open state until a predetermined time elapses from start of the control.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a water heater with a heating function.

Background Art

[0002] As a water heater with a heating function that circulates and supplies 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 (Patent Document 1 below) is known. This water heater with a heating function includes a cistern connection pipe that supplies hot water heated by a sub-heat exchanger to a cistern, a low-temperature terminal heating pipe that supplies hot water from the cistern to a low-temperature terminal heating device, an introduction pipe that branches from the middle of the low-temperature terminal heating pipe and leads to a main heat exchanger, and a high-temperature terminal heating pipe that connects the main heat exchanger and a high-temperature terminal heating device. Further, from the high-temperature terminal heating pipe, a bypass pipe that leads to the cistern and a supplementary heating pipe that includes a liquid-liquid heat exchanger for heating the bath-side circuit branch. A flow rate adjustment unit using a low-temperature capacity switching thermostatic valve is provided in the bypass pipe, and a supplementary heating thermostatic valve is provided in the supplementary heating pipe.

[0003] In this main water heater with a heating function, a target temperature is determined based on the settings (for example, flow rate, temperature) of the operation unit of the low-temperature terminal heating device, and the temperature in the cistern is controlled to approach the target temperature by feedback control. Further, when the amount of heat in the cistern becomes insufficient, the flow rate adjustment unit is controlled to the open state, and the hot water in the main heat exchanger is actively introduced into the cistern.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since it takes time for the low-temperature capacity switching thermostatic valve to shift to the open state, it takes time to supply sufficient heat to the hot water in the cistern. In addition, since the flow of the hot water heated by the primary heat exchanger is likely to stagnate before shifting to the open state, there is also a problem that boiling in the primary heat exchanger is likely to occur.

Means for Solving the Problems

[0006] The water 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 and cold water, 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 forward pipe that connects an outlet of the cistern and a low-temperature forward port that is 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 forward pipe and is connected to an upstream end of the primary heat exchanger, a high-temperature forward pipe that connects a downstream end of the primary heat exchanger and a high-temperature forward port that is an outlet to a high-temperature heating terminal different from the external heating terminal, and a bypass circuit that branches from the high-temperature forward pipe and is connected to the first connection pipe or the cistern. In the high-temperature forward pipe, a supplementary heating flow control valve and a liquid-liquid heat exchanger for heating the supplementary heating circuit for a bath are interposed. A supplementary heating circuit that merges into the heating return pipe further branches. The bypass circuit is provided with a flow rate adjustment unit that adjusts the amount of hot and cold water flowing from the primary heat exchanger to the cistern in two levels of magnitude, a first flow rate and a second flow rate smaller than the first flow rate, by opening and closing a bypass thermostatic valve. The water heater is configured such that when the controller satisfies a predetermined condition in which the amount of heat in the cistern or the low-temperature forward pipe becomes insufficient, the controller controls the bypass thermostatic valve so that the amount of hot and cold water flowing from the primary heat exchanger to the cistern changes from the second flow rate to the first flow rate, and holds the supplementary heating flow control valve in an open state until a predetermined time has elapsed since the start of this control.

Advantages of the Invention

[0007] According to the present disclosure, the hot water temperature in the cistern or the low-temperature pipe can be rapidly increased, the flow of hot water in the primary heat exchanger can be prevented from stagnating, and boiling in the primary heat exchanger can be prevented.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes 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, a circulation pump, connection pipes, a heating circuit forming 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 connecting 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 connecting a downstream end of the secondary heat exchanger and an inlet of the cistern, a low-temperature supply pipe connecting an outlet of the cistern and a low-temperature supply port serving as an outlet to the external heating terminal with the circulation pump interposed therebetween, a second connection pipe branching from a middle of the low-temperature supply pipe and connected to an upstream end of the primary heat exchanger, a high-temperature supply pipe connecting a downstream end of the primary heat exchanger and a high-temperature supply port serving as an outlet to a high-temperature heating terminal different from the external heating terminal, and a bypass circuit branching from the high-temperature supply pipe and connected to the first connection pipe or the cistern. 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 of the high-temperature supply pipe. A supplementary heating circuit merging into the heating return pipe further branches. The bypass circuit is provided with a flow rate adjustment unit that adjusts the amount of hot water flowing from the primary heat exchanger to the cistern to two levels of a first flow rate and a second flow rate smaller than the first flow rate by opening and closing a bypass thermostatic valve. The water heater and space heater is such that when the controller satisfies a predetermined condition where the amount of heat in the cistern or the low-temperature supply pipe is insufficient, the controller controls the bypass thermostatic valve so that the amount of hot water flowing from the primary heat exchanger to the cistern changes from the second flow rate to the first flow rate, and holds the supplementary heating flow control valve in an open state until a predetermined time has elapsed since the start of this control.

[0011] According to the above-described water heater and heater, until the bypass thermostatic valve is fully opened, the hot water heated by the primary heat exchanger can be introduced into the cistern via the booster circuit, the low-temperature forward pipe, and the secondary heat exchanger. Therefore, the water temperature in the cistern or the low-temperature forward pipe can be rapidly increased. Also, even when the bypass thermostatic valve is not fully opened, the flow of hot water in the primary heat exchanger is prevented from stagnating, and boiling in the primary heat exchanger can be prevented.

[0012] [2][1] In the water heater and heater according to [2][1], it is preferable that the predetermined condition includes the case where the operation unit of the external heating terminal is turned on when the temperature in the cistern or the low-temperature forward pipe is equal to or lower than a predetermined temperature.

[0013] [3][1] In the water heater and heater according to [3][1], it is preferable that the predetermined condition includes the case where the number of operating external heating terminals increases.

[0014] [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 intended to be represented by the claims and to include all modifications within the meaning and scope equivalent to the claims.

[0015] (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 indoors or under the floor outside 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.

[0016] FIG. 2 is a schematic diagram of the water heater 1. The water 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 to produce hot water, a heating circuit 4A that includes heating burners 5, 5... and a heating heat exchanger 26 and is used for floor heating etc., and a bath reheating circuit 4B that includes a liquid-liquid heat exchanger 40 and is used for reheating the bath etc.

[0017] In the water heating circuit 2, 6 is a water supply pipe that supplies water from the water pipe to the water heating heat exchanger 7, 8 is a hot water outlet pipe that discharges the hot water heated by the water heating heat exchanger 7, 9 is a gas pipe that supplies gas to the water heating burner 3. A hot water volume sensor 10 is provided in the water supply pipe 6, a water heating heat exchanger thermistor 11 is provided in the hot water outlet pipe 8, respectively. In the gas pipe 9, a main solenoid valve 12 and a proportional valve 13 are provided from the upstream side respectively. Hot water gas solenoid valves 14, 14... are provided in each branch pipe branched from the gas pipe 9 to each water heating burner 3.

[0018] The water heating heat exchanger 7 is composed of a water heating primary heat exchanger 7A that is a sensible heat recovery type heat exchanger and a water heating secondary heat exchanger 7B that is a latent heat recovery type heat exchanger. The water from the water supply pipe 6 passes through the water heating secondary heat exchanger 7B and the water heating primary heat exchanger 7A in this order, exchanges heat with the combustion exhaust gas of the water heating burner 3 and is heated, and then hot water is discharged from the hot water outlet pipe 8.

[0019] 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 that is a sensible heat recovery type heat exchanger and a heating secondary heat exchanger 26B that is a latent heat recovery type heat exchanger.

[0020] 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, a fan convector, etc. 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 a bathtub 39 by a forward piping 37 and a return piping 38 in a bath chasing heating circuit 4B, and the hot water heated by the heating heat exchanger 26 and circulating through the circulation path can heat the bath water passing through the liquid-liquid heat exchanger 40.

[0021] 41 is a chasing heating flow control valve for sending hot water to the liquid-liquid heat exchanger 40, 42 is a bath pump for circulating bath water between the bathtub 39 and the liquid-liquid heat exchanger 40, 43 is a heating high-temperature thermistor for detecting the hot water outlet temperature of the heating heat exchanger 26, and 44 is a heating low-temperature thermistor for detecting the temperature of the hot water in the cistern 33. The bath water passes through the liquid-liquid heat exchanger 40 from the bathtub 39 via the return piping 38 by the operation of the bath pump 42, exchanges heat with the hot water in the liquid-liquid heat exchanger 40 and is heated, and then returns to the bathtub 39 from the forward piping 37.

[0022] Each hot water supply 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 to supply combustion air to each burner 3, 5. A common exhaust port 18 for exhausting the combustion gas generated by the combustion of each burner 3, 5 is provided above this combustion chamber 15.

[0023] 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 by the hot water supply heat exchanger 7 can be supplied to the bathtub 39.

[0024] 21 is the controller, 22 is the kitchen remote control, and 23 is the bathroom remote control. When the water flow sensor 10 detects the water flow inside the appliance due to the opening of the faucet connected to the hot water 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, it opens the main solenoid valve 12 of the gas pipe 9 and each hot water gas solenoid valve 14, and opens the proportional valve 13 to a predetermined opening degree to supply gas to each hot water burner 3, and continuously discharges the hot water ignition plug 25 to ignite the hot water burners 3, 3...

[0025] Next, the controller 21 monitors the hot water temperature by the hot water heat exchanger thermistor 11 provided in the hot water pipe 8, and performs the opening and closing control of the hot water gas solenoid valve 14 and the opening degree adjustment 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, and continuously changes the air volume by controlling the rotation speed of the combustion fan 16.

[0026] 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, when 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 rotates the combustion fan 16 for purging, then opens the heating gas solenoid valve 29, opens the proportional valve 13 to a predetermined opening degree to supply 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.

[0027] Also, the bathtub operation is performed as follows. When the automatic switch of the kitchen remote control 22 or the bathroom remote control 23 is pressed, the dropping water solenoid valve 20 of the dropping pipe 19 opens to allow water to flow through the appliance. As a result, the water heater burner 3 burns, and the hot water heated by the water heating heat exchanger 7 is supplied to the bathtub 39 via the dropping pipe 19 and the return pipe 38. When the cumulative amount of hot water detected by the bathtub water volume sensor 45 provided in the dropping pipe 19 reaches the set water volume, the dropping water solenoid valve 20 closes and the hot water supply stops.

[0028] On the other hand, a bathtub return thermistor 46 for detecting the temperature of the hot water in the bathtub is provided in the return pipe 38. When the detected bathtub return temperature becomes 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 bathtub pump 42 also rotates. Therefore, the bathtub water circulating between the liquid-liquid heat exchanger 40 and the bathtub 39 is heat-exchanged with the hot water heated by the heating heat exchanger 26 in the liquid-liquid heat exchanger 40 and 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 bathtub pump 42 are stopped, and the supplementary heating flow control valve 41 is closed.

[0029] And in this hot water supply and heating machine 1, when either the water heater 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 is performed to discharge the combustion gas in the combustion chamber 15.

[0030] The heating circuit 4A includes a connecting pipe 30. The connecting pipe 30 forms a circulation path with the low-temperature radiator 34. The connecting pipe 30 includes a heating return pipe 32 that connects 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 connecting pipe 47 that connects the downstream end of the heating secondary heat exchanger 26B and the inlet of the cistern 33, a low-temperature forward pipe 49 that connects the outlet of the cistern 33 and the low-temperature forward port 48 that is the outlet to the low-temperature radiator 34 and in which a circulation pump 36 is interposed, a second connecting pipe 56 that branches from the middle of the low-temperature forward pipe 49 and is connected to the upstream end of the heating primary heat exchanger 26A, a high-temperature forward pipe 58 that connects the downstream end of the heating primary heat exchanger 26A and the high-temperature forward port 57 that is the outlet to the high-temperature radiator 35 and in which a heating high-temperature thermistor 43 for detecting the outlet temperature of the heating primary heat exchanger 26A is provided, and a bypass circuit 59 that branches from the high-temperature forward pipe 58 and is connected to the first connecting 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.

[0031] 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.

[0032] In the bypass circuit 59, a flow rate adjustment unit 62 is provided that adjusts the amount of hot water flowing from the heating primary heat exchanger 26A to the cistern 33 to two levels: a first flow rate and a second flow rate that is smaller than the first flow rate, by opening and closing a 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 the path to the low-temperature radiator 34 needs to be heated based on the detected temperature of the heating low-temperature thermistor 44 of the cistern 33, and is controlled to be in a closed state when it is determined that heating 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.

[0033] When the high-temperature radiator 35 is not in use, since the flow path from the heating primary heat exchanger 26A to the high-temperature radiator 35 is closed, the hot water from the heating primary heat exchanger 26A will flow toward the cistern 33. In the water heater 1 of the present embodiment, the target temperature is determined based on the settings (for example, flow rate, temperature) of the operation unit of the low-temperature radiator 34, and the temperature in the cistern 33 is controlled to approach the target temperature by feedback control. Further, when the amount of heat in the cistern 33 becomes insufficient, the bypass thermostatic valve 61 of the flow rate adjustment unit 62 is controlled to be in an open state, and the hot water in the heating primary heat exchanger 26A is introduced into the cistern 33. However, since it takes time for the bypass thermostatic valve 61 to shift to the open state, it takes time to supply sufficient heat to the hot water in the cistern 33. Further, since the flow of the hot water heated by the heating primary heat exchanger 26A is likely to stagnate until the bypass thermostatic valve 61 shifts to the open state, boiling in the heating primary heat exchanger 26A is likely to occur.

[0034] To avoid such a state, when the controller 21 satisfies a predetermined condition that the amount of heat in the cistern 33 or the low-temperature pipe 49 is insufficient, the bypass thermostatic valve 61 is controlled so that the amount of hot water flowing from the heating primary heat exchanger 26A to the cistern 33 changes from the second flow rate to the first flow rate, and the supplementary heating flow control valve 41 is held in an open state until a predetermined time has elapsed since the start of this control. The predetermined condition may include the case where the temperature in the cistern 33 or the low-temperature pipe 49 is equal to or lower than a predetermined temperature and the operation unit of the low-temperature radiator 34 is turned on, and may also include the case where the number of operating low-temperature radiators 34 increases.

[0035] According to such control, until the bypass thermostatic valve 61 is fully opened, the hot water heated by the primary heating heat exchanger 26A can be introduced into the cistern 33 via the supplementary heating circuit 60, the low-temperature forward pipe 49, and the secondary heating heat exchanger 26B. Therefore, the water temperature in the cistern 33 or the low-temperature forward pipe 49 can be rapidly increased. Also, even when the bypass thermostatic valve 61 is not fully opened, the stagnation of the hot water flow in the primary heating heat exchanger 26A can be prevented, and boiling in the primary heating heat exchanger 26A can be prevented.

[0036] (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.

[0037] · 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 a flow rate adjustment unit including only the bypass thermostatic valve 61 may also be used.

[0038] · In the above embodiment, the predetermined condition includes the case where the temperature in the cistern 33 or the low-temperature forward pipe 49 is below a predetermined temperature, but it may also include the case where the above temperature becomes below the predetermined temperature and the state of being below the predetermined temperature continues for a predetermined time.

[0039] · In the above embodiment, the predetermined condition includes the case where the number of low-temperature radiators 34 in the operating state increases, but it may also include the case where the model is changed from a low-temperature radiator 34 with low heating capacity to a low-temperature radiator 34 with high heating capacity.

Explanation of Reference Numerals

[0040] 1: Water heater and 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 flow 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 44: Heating low-temperature thermistor 45: Bath water flow 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 regulation part 63: Bypass detour circuit

Claims

1. A primary heat exchanger and a secondary heat exchanger heated by a gas burner, A cistern for storing hot and cold water, A circulation pump, A heating circuit including connecting pipes and forming a circulation path with an external heating terminal, A bath reheating circuit, And a controller, The connecting pipes include a heating return pipe connecting 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 connecting pipe connecting a downstream end of the secondary heat exchanger and an inlet of the cistern, a low-temperature supply pipe connecting an outlet of the cistern and a low-temperature supply port serving as an outlet to the external heating terminal and through which the circulation pump is interposed, a second connecting pipe branched from the middle of the low-temperature supply pipe and connected to an upstream end of the primary heat exchanger, a high-temperature supply pipe connecting a downstream end of the primary heat exchanger and a high-temperature supply port serving as an outlet to a high-temperature heating terminal different from the external heating terminal, and a bypass circuit branched from the high-temperature supply pipe and connected to the first connecting pipe or the cistern. A reheating flow control valve and a liquid-liquid heat exchanger for heating the bath reheating circuit are interposed in the middle of the high-temperature supply pipe. A reheating circuit that merges into the heating return pipe further branches, The bypass circuit is provided with a flow rate adjusting unit that adjusts the amount of hot water flowing from the primary heat exchanger to the cistern in two levels of magnitude, i.e., a first flow rate and a second flow rate smaller than the first flow rate, by opening and closing a bypass thermostatic valve. The hot water supply and heating apparatus, When the controller satisfies a predetermined condition in which the amount of heat in the cistern or the low-temperature supply pipe is insufficient, the controller controls the bypass thermostatic valve so that the amount of hot water flowing from the primary heat exchanger to the cistern changes from the second flow rate to the first flow rate, and holds the reheating flow control valve in an open state until a predetermined time has elapsed since the start of this control. The hot water supply and heating apparatus.

2. The hot water heater according to claim 1, wherein the predetermined condition includes a case where the operation unit of the external heating terminal is turned on when the temperature in the system or the low-temperature pipe is equal to or lower than a predetermined temperature.

3. The hot water heater according to claim 1, wherein the predetermined condition includes a case where the number of the external heating terminals in the operating state increases.

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