JP2011141050A - Storage water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a storage water heater preventing generation and accumulation of scale on the inner side of a hot water supply circuit after stop of boiling operation in the storage water heater. <P>SOLUTION: The storage water heater includes a hot water storage tank 9 storing hot water and the hot water supply circuit 10 in which water supplied to the upper part of the hot water storage tank 9 flows. The storage water heater also includes a water refrigerant heat exchanger 4 arranged in the middle of the hot water supply circuit 10 and heating water supplied to the upper part of the hot water storage tank 9. The storage water heater further includes a means executing the boiling operation for heating water within the hot water supply circuit 10 by the water refrigerant heat exchanger 4 and then supplying the water to the upper part of the hot water storage tank 9. After stop of the boiling operation, scale generation preventing operation is executed for replacing hot water present in a portion (connection piping 12a of second heat pump piping 12) between the water refrigerant heat exchanger 4 in the hot water supply circuit 10 and the upper part of the hot water storage tank 9 with water having a temperature lower than that of the hot water. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hot water storage type water heater.

  Water such as tap water and groundwater used in conventional hot water storage water heaters usually contains hardness components such as calcium and magnesium, and in some areas water containing many hardness components is used. is there. When water containing a large amount of this hardness component is heated by, for example, a water refrigerant heat exchanger of a heat pump type hot water heater, scale (for example, calcium carbonate) is deposited in the vicinity of the water channel outlet of the water refrigerant heat exchanger that becomes high temperature. . The deposited scale flows into the hot water storage tank from the upper part of the hot water storage tank together with water boiled by heat exchange by the water / refrigerant heat exchanger by a pump provided in the hot water supply circuit. As a result, the scale that has flowed into the connection pipe connecting the upper part of the hot water storage tank and the water refrigerant heat exchanger accumulates inside the connection pipe and blocks the flow path, and the pressure loss in the connection pipe is reduced. It increases and increases the input (load) of the pump. Furthermore, if the scale adheres to the connection pipe, the hot water supply circuit is blocked, and there is a possibility that the operation by the heat pump type hot water heater becomes impossible.

  In order to solve the above problems, the following hot water storage type hot water heaters have been proposed. That is, for example, there is one in which a perforated plate is provided inside a hot water storage tank upstream from a suction pipe of a pump of a hot water supply circuit (see, for example, Patent Document 1). With such a structure, the scale can be collected by the porous plate inside the hot water storage tank so that the scale does not enter the suction hole of the hot water supply circuit or the hot water supply circuit.

JP 2006-275445 A

  The scale deposited near the outlet of the water flow path of the water refrigerant heat exchanger during the operation of the hot water storage water heater (boiling operation) is transferred from the water refrigerant heat exchanger to the hot water storage tank by a pump provided in the hot water supply circuit. Flow into. For this reason, according to the prior art, the scale that has flowed into the hot water storage tank during the boiling operation can be collected by the porous plate in the hot water storage tank. In this way, in a state where water is circulating during the boiling operation, the scale that has flowed into the hot water circuit is unlikely to accumulate in the hot water circuit, and the hot water circuit connected to the upper part of the hot water tank is connected. The amount of scale that accumulates inside the pipe is not large.

  On the other hand, the scale tends to accumulate when the flow of water stops. More specifically, when the flow of water in the hot water supply circuit stops after the boiling operation is stopped, the connection pipe connected to the upper part of the hot water storage tank is connected to a water refrigerant heat exchanger as a heating means. The hot water after being heated will stay. Then, the scale deposited in the connection pipe falls down to the lower part of the connection pipe with its own weight. As a result, the accumulation of scale on the horizontal pulling portion (horizontal portion) below the connection pipe is promoted. In addition, the scale also falls on the horizontal pulling portion at the top of the connection pipe, and the accumulation of the scale is promoted. Therefore, it is necessary to consider preventing the scale from being generated and deposited inside the hot water supply circuit (particularly, the connection pipe) after the boiling operation is stopped. However, in the above conventional technique, no countermeasure is taken for this point.

  The present invention has been made to solve the above-described problems, and can prevent scales from being generated and deposited in the hot water supply circuit after the boiling operation in the hot water storage hot water supply is stopped. The purpose is to provide a hot water storage hot water heater.

  The hot water storage type hot water heater according to the present invention is disposed in the middle of the hot water storage channel, the hot water storage channel for storing hot water, the hot water supply channel through which the water supplied to the upper part of the hot water storage tank flows, and is supplied to the upper part of the hot water storage tank A heating means for heating water, a boiling operation executing means for performing a heating operation for supplying water to the upper part of the hot water storage tank after the water in the hot water flow path is heated by the heating means, and hot water supply after the boiling operation is stopped. Water replacement execution means for replacing the hot water present in the portion between the heating means in the water flow path and the upper part of the hot water storage tank with water having a temperature lower than that of the hot water.

  According to the present invention, it is possible to provide a hot water storage type hot water heater capable of preventing the scale from being generated and deposited in the hot water supply circuit after the boiling operation in the hot water storage type hot water heater is stopped.

It is the schematic which shows the whole structure of the hot water storage type water heater in Embodiment 1 of this invention. It is a flowchart which shows the scale production | generation prevention driving | operation in Embodiment 1 of this invention. It is the schematic which shows the whole structure of the hot water storage type water heater in Embodiment 2 of this invention. It is a figure showing the cross-sectional shape of the integrated piping shown in FIG. It is a figure showing the cross-sectional shape of the integrated piping in Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram showing an overall configuration of a hot water storage type hot water heater 100 according to Embodiment 1 of the present invention. A hot water storage type water heater 100 shown in FIG. 1 includes a heat pump unit 1 and a tank unit 2. In the heat pump unit 1, a compressor 3, a water / refrigerant heat exchanger 4, an expansion valve 5 and an evaporator 6 are sequentially connected in an annular shape, and outside air is supplied to the evaporator 6 and a refrigeration cycle 7 in which the refrigerant circulates. A fan 8 for blowing air is mounted. As the refrigerant of the refrigeration cycle 7, a refrigerant capable of producing high-temperature hot water, for example, a refrigerant such as carbon dioxide, R410A, or propane is suitable, but is not particularly limited thereto.

  On the other hand, the tank unit 2 includes a hot water storage tank 9 for storing hot water. The tank unit 2 also includes a hot water supply water circuit 10 for boiling water in the hot water storage tank 9 by using the water refrigerant heat exchanger 4 of the heat pump unit 1 as a heating means. Specifically, the hot water supply circuit 10 includes a first heat pump pipe 11 that connects a lower part (first lower part) of the hot water storage tank 9 and the water refrigerant heat exchanger 4, a water refrigerant heat exchanger 4, and a hot water storage tank 9. 2nd heat pump piping 12 which connects an upper part is provided.

  In addition, a pump 13 that feeds water, which is a load-side medium, to the water-refrigerant heat exchanger 4 is mounted in the tank unit 2. The pump 13 is installed in the middle of the first heat pump pipe 11. This pump 13 is a pump for circulating the water coming out from the lower part of the hot water storage tank 9 to the upper part of the hot water storage tank 9 after passing through the water-refrigerant heat exchanger 4. Here, in the 1st heat pump piping 11, between the pump 13 and the lower part (1st lower part) of the hot water storage tank 9 is called the connection piping 11a, and between the pump 13 and the water refrigerant | coolant heat exchanger 4 is connected piping 11b. Called. The pump 13 is not necessarily installed in the tank unit 2 and may be mounted on the heat pump unit 1 side. Moreover, the drainage channel 14 is connected in the middle of the connection piping 11a.

  A three-way valve 16 is installed in the middle of the second heat pump pipe 12 (more specifically, a part close to the connection port 15 on the upper part of the hot water storage tank 9). Here, in the 2nd heat pump piping 12 (12a, 12b), between the water-refrigerant heat exchanger 4 and the three-way valve 16 is called the connection piping 12a, and the connection port 15 of the upper part of the three-way valve 16 and the hot water storage tank 9 is connected. The space is referred to as a connection pipe 12b. One end of a bypass pipe 17 is connected to the remaining connection port of the three-way valve 16. That is, the bypass pipe 17 is connected to the second heat pump pipe 12 at a portion close to the connection port 15 at the upper part of the hot water storage tank 9. The other end of the bypass pipe 17 is connected to the lower part (second lower part) of the hot water storage tank 9.

  The three-way valve 16 flows through the first heat pump pipe 11 from the first lower portion of the hot water tank 9 and passes through the water / refrigerant heat exchanger 4, and passes through the second heat pump pipe 12 as it is to form the hot water tank 9. A means for switching between a first flow path configuration for returning water to the upper portion of the water and a second flow path configuration for returning water to the second lower portion of the hot water storage tank 9 from the second heat pump pipe 12 (connection pipe 12a) via the bypass pipe 17 It is.

  The hot water storage type hot water heater 100 includes a device for supplying hot water to a predetermined hot water supply destination such as a bathtub. More specifically, a water supply pipe 18 for supplying water into the hot water storage tank 9, a pressure reducing valve 19 for reducing the water supply pressure in the path of the water supply pipe 18 to a predetermined pressure or less, A mixed hot water supply pipe 20 connected, a mixed hot water supply pipe 21 having one end connected to the hot water supply pipe 18, a hot water supply mixing valve 22 for mixing high temperature water from the mixed hot water supply pipe 20 and low temperature water from the mixed hot water supply pipe 21; And a hot water supply pipe 23 for transporting high temperature water mixed by the hot water supply mixing valve 22. With such a configuration, the hot water storage water heater 100 uses the hot water supply circuit 10 to heat the hot water stored in the hot water storage tank 9 and supply hot water.

  In addition, a control device 24 is provided in the heat pump unit 1 so that the pressure and temperature of the refrigerant discharged from the compressor 3 can be changed, and in the tank unit 2, the heat pump unit 1 and In order to control the entire tank unit 2 as a system, a system controller 25 is provided. Note that FIG. 1 illustrates only a basic circuit, and it is permissible to add another object structure to the configuration of FIG.

  Furthermore, the connection pipe 11b is provided with an incoming water temperature sensor 26a for detecting the temperature of water (incoming water temperature) flowing into the water / refrigerant heat exchanger 4, and the connection pipe 12a is provided with the water / refrigerant heat exchanger 4 A hot water temperature sensor 26 b that detects the temperature of the water (hot water temperature) that is heated and flows out of the water-refrigerant heat exchanger 4 is installed. The system control device 25 is based on the measurement information by the temperature sensors 26a and 26b and the contents of the operation command information instructed by the remote control device (not shown) from the user of the hot water storage hot water supply device 100. The operation method, the opening degree of the expansion valve 5, the operation method of the fan 8, the operation method of the pump 13, etc. are controlled.

  Next, the operation of the hot water storage type water heater 100 having the above-described configuration will be described. Here, the boiling operation will be described. In the boiling operation, the three-way valve 16 is controlled so that the first flow path configuration is selected, and the refrigeration cycle 7 and the hot water supply circuit 10 are operated to operate the bottom of the hot water storage tank 9 (first lower part). ) From the low-temperature water using a pump 13 and sent to the water-refrigerant heat exchanger 4, and the water sent to the water-refrigerant heat exchanger 4 is boiled up by exchanging heat with the refrigerant. It is the operation | movement which returns to the inside of the hot water storage tank 9 from the upper part.

  More specifically, in the refrigeration cycle 7 of the heat pump unit 1, the high-temperature and high-pressure gas refrigerant discharged from the compressor 3 radiates heat (heats water) to the hot water supply water circuit 10 side by the water-refrigerant heat exchanger 4. The temperature drops. At this time, if the high-pressure side refrigerant pressure is equal to or higher than the critical pressure, the refrigerant radiates heat by lowering the temperature without undergoing a gas-liquid phase transition in a supercritical state. If the high-pressure side refrigerant pressure is lower than the critical pressure, the refrigerant dissipates heat while liquefying. In this way, the heat radiated from the refrigerant is applied to the load-side medium (here, water flowing through the hot water supply circuit 10), thereby heating (boiling) the water inside the hot water storage tank 9. The high-pressure and low-temperature refrigerant flowing from the water-refrigerant heat exchanger 4 by heating the water flowing through the hot water supply circuit 10 passes through the expansion valve 5. The refrigerant that has passed through the expansion valve 5 is decompressed to a low-pressure gas-liquid two-phase state. The refrigerant that has passed through the expansion valve 5 flows into the evaporator 6, where it absorbs heat from the outside air and evaporates to become a gas. The low-pressure refrigerant exiting the evaporator 6 is sucked into the compressor 3 and circulates again through the refrigeration cycle 7.

  On the other hand, on the hot water supply circuit 10 side, the water in the hot water storage tank 9 is guided from the bottom (first lower part) of the hot water storage tank 9 by the pump 13 and passes through the first heat pump pipes 11 (11a, 11b). It is conveyed in the heat exchanger 4. Then, it is heated (boiling) by exchanging heat with the refrigerant, passes through the second heat pump pipes 12 (12a, 12b), and flows into the hot water storage tank 9 from the upper part of the hot water storage tank 9. Thereby, the inside of hot water storage tank 9 will be in the state where it filled with the high temperature layer of high temperature water in parts other than the lower part.

  Next, the structure and control for preventing the scale from being generated and deposited inside the second heat pump pipe 12 (particularly the connection pipe 12a) on the upper side of the hot water storage tank 9 in the hot water storage type hot water heater 100 will be described.

  The solubility in water of scale (for example, calcium carbonate) contained in tap water, groundwater, etc. has a property of decreasing as the water temperature increases. For this reason, when the water temperature rises from, for example, temperature T1 to T2 and the saturation solubility is lowered, a scale of the solubility difference is deposited. That is, the amount of scale deposition increases when the temperature difference between the water inlet temperature and the water outlet temperature of the water refrigerant heat exchanger 4 is large during the boiling operation. However, water flows through the water-refrigerant heat exchanger 4 during the boiling operation. For this reason, the scale deposited due to the difference in solubility flows from the water / refrigerant heat exchanger 4 into the hot water storage tank 9 through the second heat pump pipe 12 (12a, 12b) by the pump 13 provided in the hot water supply water circuit 10. . Therefore, during the boiling operation, the amount of scale deposited on the upper and lower horizontal pulling portions (horizontal portions) of the connecting pipe 12a is not large.

  On the other hand, when the flow of water is stopped after the boiling operation is stopped, the scale deposited in the connection pipe 12a in which high-temperature water stays because the water refrigerant heat exchanger 4 is located on the downstream side of the water refrigerant heat exchanger 4 The scale is poured from the upper part to the lower part by its own weight, and the accumulation of the scale is promoted to the horizontal pulling part at the lower part of the connection pipe 12a. .

  Therefore, in the present embodiment, in order to prevent the scale from being generated and accumulated in the second heat pump pipe 12 (connection pipe 12a) on the upper side of the hot water storage tank 9, one end of the water refrigerant heat exchanger 4 is provided. The three-way valve 16 is provided between the connection pipe 12a to be connected and the connection pipe 12b having one end connected to the upper part of the hot water tank 9, and the other side of the three-way valve 16 and the lower part of the hot water tank 9 (second lower part). And a bypass pipe 17 is used. And after the required heat storage amount of the hot water storage tank 9 was ensured by the said boiling operation, the scale production | generation prevention operation demonstrated with reference to the following FIG. 2 was performed.

  FIG. 2 is a flowchart showing the scale generation preventing operation in the first embodiment of the present invention. When the system controller 25 determines to stop the boiling operation, first, the operation of the compressor 3 is stopped. Then, the system control device 25 starts the scale generation preventing operation shown in FIG. 2 in a state where the operation of the compressor 3 is stopped. That is, the system control device 25 first switches the three-way valve 16 so that the connection pipe 12a and the bypass pipe 17 communicate with each other (so that the second flow path configuration is selected), and then the rotational speed of the pump 13 The pump 13 is operated in a state where β is β (a value larger than the number of rotations during the boiling operation) (step S1). Thus, in this embodiment, the circulation flow rate per unit time of water by the pump 13 when circulating water during the scale generation prevention operation is the circulation flow rate per unit time of water by the pump 13 during the boiling operation. Is set to be more.

  Next, the system control device 25 detects the hot water temperature and the incoming water temperature by the hot water temperature sensor 26b and the incoming water temperature sensor 26a, respectively, and determines whether or not the temperature difference between them is equal to or less than a predetermined value γ (step). S2). As a result, when the system controller 25 determines that the temperature difference exceeds the predetermined value γ in this temperature difference determination step S2, that is, the tapping temperature on the water outlet side of the water refrigerant heat exchanger 4 is sufficiently high. If not, the operation of the pump 13 is continued.

  On the other hand, when the system control device 25 determines that the temperature difference has decreased to a predetermined value γ or less, it starts a timer operation (step S3). Then, when a predetermined time has elapsed from the start of the timer operation (step S4), the system control device 25 stops the pump 13 (step S5). As a result, the scale generation prevention operation ends.

  The scale generation preventing operation described above is performed in a state where the operation of the compressor 3 is stopped. For this reason, the hot water in the connection pipe 12a and the bypass pipe 17 on the water outlet side of the water-refrigerant heat exchanger 4 is the low-temperature water transported by the pump 13 from the water intake at the bottom (second lower part) of the hot water storage tank 9. The temperature drops by mixing with. That is, after the boiling operation is stopped (immediately after the stop), the temperature of the water outlet of the water-refrigerant heat exchanger 4 is gradually decreased by continuing the pump operation and circulating low-temperature water in the hot water supply circuit 10. Can be made. As described above, after the boiling operation is stopped, the second flow path configuration is selected and the pump operation is continued to introduce the high-temperature water existing in the connection pipe 12a and the bypass pipe 17 from the lower part of the hot water storage tank 9. By replacing with the low-temperature water, the generation of scale can be suppressed by eliminating the high-temperature water present in these pipes 12a and 17.

  As described above, in this embodiment, after the boiling operation is stopped, the boiling operation is performed so that the scale does not precipitate due to the temperature difference (solubility difference) between the water inlet temperature and the water outlet temperature of the water refrigerant heat exchanger 4. By stopping the scale generation prevention operation, in other words, the cooling operation (delay control operation) of the water refrigerant heat exchanger 4, the water refrigerant heat exchanger 4, the connection pipes 11a, 11b, 12a, and the bypass pipe are stopped. It is possible to prevent the scale from being deposited in the interior of 17 (particularly the laterally drawn portion). Further, by introducing a component (calcium carbonate) that can be a scale nucleus deposited after the boiling operation is stopped to the lower part of the hot water storage tank 9 through the bypass pipe 17, the scale does not accumulate in the hot water supply circuit 10. can do. Thereby, it is possible to prevent the hot water supply circuit 10 from being blocked due to the accumulation of scale.

  Further, in the present embodiment, as described above, the bypass pipe 17 is connected to the second heat pump pipe 12 at a portion close to the connection port 15 at the upper part of the hot water storage tank 9. That is, in the configuration shown in FIG. 1, the three-way valve 16 is set at a position close to the connection port 15 on the upper side of the hot water storage tank 9, whereby the scale generation prevention operation (cooling operation of the water refrigerant heat exchanger 4 is performed). (Delayed control operation)) is considered to extend to the vicinity of the connection port 15 in the upper part of the hot water storage tank 9 of the hot water supply circuit 10. Thereby, the obstruction | occlusion by the accumulation of the scale to the inside (especially horizontal drawing part) of the connection piping 12a and the bypass piping 17 can be prevented.

  By the way, in Embodiment 1 mentioned above, after stopping a boiling operation, a 2nd flow path form is selected in the state which stopped the operation of the compressor 3, and the low temperature water of the lower part of the hot water storage tank 9 is the hot water supply water circuit 10. It is controlled to circulate inside. However, the present invention replaces hot water (hot water) existing in a portion between the heating means in the hot water flow path and the upper part of the hot water storage tank with water having a temperature lower than that of the hot water after the boiling operation is stopped. As long as it is configured as described above, the hot water supply flow path is not limited to the one configured as a circulation circuit (hot water supply water circuit 10) as in the first embodiment. That is, for example, after the boiling operation is stopped, while supplying water having a temperature lower than that of hot water existing in a portion between the heating means in the hot water flow path and the upper portion of the hot water storage tank, It is also possible to provide a structure for draining outside (rather than circulating through the hot water storage tank).

Embodiment 2. FIG.
FIG. 3 is a schematic diagram showing an overall configuration of a hot water storage type hot water heater 200 according to Embodiment 2 of the present invention. FIG. 4 is a view showing a cross-sectional shape of the integrated pipe 27 shown in FIG. The configuration of the hot water storage type hot water heater 200 shown in FIG. 3 is the same as that of the hot water storage type hot water heater 100 shown in FIG. 1 except that the configuration related to the integrated pipe 27 is different.

  As shown in FIGS. 3 and 4, in the present embodiment, a part of the connection pipe 12 a of the second heat pump pipe 12 and a part of the bypass pipe 17 are integrated, and a single unit in which both are partitioned by a partition 27 a. The pipe 27 is configured. When the bypass pipe 17 is provided separately from the second heat pump pipe 12 and the bypass pipe 17 extends from the lower part to the upper part of the hot water storage tank 9 as in the configuration of the first embodiment described above, the inside of the tank unit 2 As a result, the mounting layout of the bypass pipe 17 deteriorates, the material cost of the bypass pipe 17 increases, and the assembly process of the bypass pipe 17 increases. On the other hand, as in the present embodiment, the connection pipe 12a and the bypass pipe 17 that are originally laid out are made as an integrally molded product by a mold, thereby reducing the influence on the mounting space and the material cost is gold. It is possible to reduce the initial investment of the mold and increase by expanding the pipe diameter, and to reduce the influence on the assembly process.

  According to the hot water storage type water heater 200 of the present embodiment described above, the tank has the effect described in the first embodiment and has a structure in which the connection pipe 12a and the bypass pipe 17 are integrally molded. It is possible to simplify the piping inside the unit 2, suppress the increase in cost, and minimize the influence on the assembly process.

Embodiment 3 FIG.
FIG. 5 is a diagram showing a cross-sectional shape of the integrated pipe 28 according to Embodiment 3 of the present invention. In the integrated pipe 28 shown in FIG. 5, the partition between the connection pipe 12a and the bypass pipe 17 has a double structure by the partitions 28a and 28b. The integrated pipe 27 according to the second embodiment described above. Is different. An air layer 29 is provided between the partitions 28a and 28b, and the connection pipe 12a and the bypass pipe 17 are isolated in the integrated pipe 28 with the air layer 29 interposed. ing.

  According to the integrated pipe 28 of the present embodiment described above, the flow A of water in the connection pipe 12a from the water / refrigerant heat exchanger 4 side toward the three-way valve 16 side is provided by providing the air layer 29 therein. And it becomes possible to suppress effectively the energy loss by the heat transfer of the water by the water flow B in the bypass piping 17 which goes to the lower part (2nd lower part) side of the hot water storage tank 9 from the three-way valve 16 side.

DESCRIPTION OF SYMBOLS 1 Heat pump unit 2 Tank unit 3 Compressor 4 Water refrigerant heat exchanger 7 Refrigeration cycle 9 Hot water storage tank 10 Hot water supply circuit 11 1st heat pump piping 11a, 11b Connection piping 12 in 1st heat pump piping 2nd heat pump piping 12a, 12b 2nd 2 Connection pipe 13 in heat pump pipe 13 Pump 15 Connection port 16 at upper part of hot water storage tank Three-way valve 17 Bypass pipe 24 Controller 25 System controller 26a Inlet temperature sensor 26b Hot water temperature sensor 27, 28 Integrated pipe 29 Air layer 100, 200 Hot water storage water heater

Claims (6)

A hot water storage tank for storing hot water,
A hot water flow path through which water supplied to the upper part of the hot water storage tank flows;
A heating means that is disposed in the middle of the hot water flow path and heats water supplied to the upper part of the hot water storage tank;
A boiling operation executing means for performing a boiling operation for heating the water in the hot water flow path by the heating means and supplying the water to the upper portion of the hot water storage tank;
After the boiling operation is stopped, water replacement execution means for replacing the hot water present in the hot water supply passage between the heating means and the upper part of the hot water storage tank with water having a temperature lower than that of the hot water;
A hot water storage type water heater characterized by comprising: The hot water flow path is a hot water circuit connecting the upper part of the hot water storage tank and the first lower part of the hot water storage tank,
The boiling operation execution means is means for taking out water from the first lower part of the hot water storage tank into the hot water supply circuit and executing the boiling operation,
The water replacement execution means is
A bypass flow path having one end connected to a portion between the heating means in the hot water supply circuit and the upper part of the hot water storage tank, and the other end connected to a second lower part of the hot water storage tank;
As a flow path form of water after flowing out from the first lower part of the hot water storage tank to the hot water supply circuit and passing through the heating means, the first returns the water to the upper part of the hot water storage tank through the hot water supply circuit as it is. Channel switching means capable of selecting a channel configuration and a second channel configuration for returning water from the hot water supply circuit to the second lower portion of the hot water storage tank via the bypass channel;
After the boiling operation is stopped, the second flow path configuration is selected in a state where heating of the water by the heating means is stopped, and water is circulated between the hot water supply circuit, the bypass flow path, and the hot water storage tank. The hot water storage type water heater according to claim 1, further comprising low-temperature water circulation means.   The hot water storage hot water supply apparatus according to claim 2, wherein the one end of the bypass passage is connected to the hot water supply circuit at a portion close to the upper portion of the hot water storage tank.   A part of the flow path between the heating means and the connection part of the bypass passage in the hot water supply circuit and a part of the bypass flow path are configured as a single pipe that divides both by a partition. The hot water storage type water heater according to claim 2 or 3, wherein the hot water storage type water heater is provided. The partition in the one pipe has a double structure,
5. The air layer partitioned by the double-structured partition is provided between the flow path and the bypass flow path inside the one pipe. Hot water storage water heater.   The circulating flow rate per unit time when water is circulated by the low temperature water circulating means is larger than the circulating flow rate per unit time of water during the boiling operation. The hot water storage water heater described.

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