Storage-type hot water supply system

Abstract

This invention provides a hot water storage type water heater that reliably dissipates heat from the ultraviolet irradiation unit 42 after the sterilization operation, thereby enabling stable sterilization operation. [Solution] A water-cooled ultraviolet irradiation unit 42 is provided in the middle of the heating supply pipe 25 to kill bacteria by irradiation with ultraviolet light and to dissipate heat with the hot water flowing through the heating supply pipe 25. The main unit control means 41 has a sterilization operation control means 44 that controls the sterilization operation by the ultraviolet irradiation unit 42 during the boiling operation, and a UV permission determination means 45 that determines whether to permit the execution of the sterilization operation. The sterilization operation control means 44 executes the sterilization operation during the boiling operation if the UV permission determination means 45 determines that permission is granted. The UV permission determination means 45 permits the execution of the sterilization operation if the detected value of the boiling temperature sensor 29 is within a predetermined temperature range for a predetermined time.

Description

Technical Field

[0001] The present invention relates to a hot water storage type water supply device that performs a sterilization operation in a hot water storage tank.

Background Art

[0002] Conventionally, in this type of hot water storage type water supply device, as shown in Patent Document 1, there has been a hot water storage type water supply device provided with an ultraviolet irradiation device that irradiates ultraviolet rays to a heating forward pipe connecting a heating means and a hot water storage tank, and having a sterilization operation for sterilizing Legionella bacteria.

[0003] Also, as shown in Patent Document 2, it has been known that it is necessary to perform a heat dissipation operation to cool the ultraviolet irradiation device after the sterilization operation using the ultraviolet irradiation device in order to prevent failure due to high temperature.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a hot water storage type water supply device in which a heating means and a hot water storage type water supply device are connected by a heating circulation circuit and the heating circulation circuit is provided with an ultraviolet irradiation device, as in Patent Document 1, during construction when connecting the heating circulation circuit, if air is mixed into the heating circulation circuit, air accumulates in the circulation pump, causing the circulation pump to run idle and preventing the circulation of hot water. As a result, the heat of the ultraviolet irradiation device cannot be effectively dissipated, leading to failure due to heat.

Means for Solving the Problems

[0006] To solve the above problems, the present invention provides a hot water storage type hot water supply system comprising: a hot water storage tank for storing hot water; a heating means for heating the hot water in the hot water storage tank; a heating supply pipe connecting the lower part of the hot water storage tank and the heating means; a heating return pipe connecting the heating means and the upper part of the hot water storage tank; a circulation pump for circulating the heating means and the hot water in the hot water storage tank; a boiling temperature sensor for detecting the temperature of the hot water returning from the heating means to the upper part of the hot water storage tank; and a main control means for controlling the boiling operation to store the hot water heated by the heating means in the hot water storage tank, wherein the heating supply pipe is equipped with ultraviolet light A water-cooled ultraviolet irradiation unit is provided that kills bacteria by irradiation and dissipates heat with hot water flowing through the heating supply pipe. The main unit control means includes a sterilization operation control means that controls the sterilization operation by the ultraviolet irradiation unit during the boiling operation, and a UV permission determination means that determines whether to permit the execution of the sterilization operation. The sterilization operation control means executes the sterilization operation during the boiling operation if the UV permission determination means determines that permission is granted, and the UV permission determination means permits the execution of the sterilization operation if the detected value of the boiling temperature sensor is within a predetermined temperature range for a predetermined time.

[0007] Furthermore, the UV permission determination means is configured to reset the determination each time the power supply to the hot water storage type water heater is cut off.

[0008] Furthermore, the heating return pipe is provided with a heating bypass pipe that branches off from the heating return pipe and connects to a water supply pipe connected to the bottom of the hot water storage tank, and a heating bypass valve that switches between the heating bypass pipe and the heating return pipe. The main unit control means switches the heating bypass valve to the heating bypass pipe side and drives the circulation pump to dissipate heat from the ultraviolet irradiation unit when the boiling operation is completed. [Effects of the Invention]

[0009] According to the present invention, if the boiling temperature detected by the boiling temperature sensor remains within a predetermined temperature range for a period exceeding a predetermined time, it is determined that no air has entered the heating circulation circuit, and the heat dissipation operation of the ultraviolet irradiation unit by the circulation of hot water can be reliably performed, thereby preventing malfunctions due to high temperatures. [Brief explanation of the drawing]

[0010] [Figure 1] Schematic diagram showing the configuration of one embodiment of the present invention. [Figure 2] A flowchart illustrating the operation of the sterilization operation in this embodiment. [Figure 3] Time chart showing the boiling operation and sterilization operation of the same embodiment [Figure 4] Flowchart illustrating the reset of the permission decision in the same embodiment [Modes for carrying out the invention]

[0011] Next, a storage-type hot water supply system according to one embodiment of the present invention will be described based on the drawings.

[0012] Figure 1 is a schematic diagram showing the configuration of a storage-type hot water supply system, where 1 is a hot water storage tank for storing hot water, 2 is a water supply pipe supplying water to the bottom of the hot water storage tank 1, 3 is a hot water outlet pipe dispensing hot water from the top of the hot water storage tank 1, 4 is a water supply bypass pipe branched from the water supply pipe 2, 5 is a hot water mixing valve that mixes hot water from the hot water outlet pipe 3 with cold water from the water supply bypass pipe 4, 6 is a hot water pipe connecting the outlet of the hot water mixing valve 5 to the hot water tap 7, 8 is a hot water flow sensor that detects the flow rate of hot water through the hot water pipe 6, 9 is a hot water temperature sensor that detects the temperature of hot water flowing through the hot water pipe 6, and 10 is a water supply temperature sensor that detects the temperature of cold water flowing through the water supply bypass pipe 4.

[0013] 11 is a bath mixing valve that mixes hot water from the hot water outlet pipe 3 with cold water from the water supply bypass pipe 4, 12 is a hot water filling pipe that fills the bathtub 13 installed in the bathroom with hot water from the bath mixing valve 11, 14 is a hot water filling flow sensor that detects the flow rate of hot water through the hot water filling pipe 12, 15 is a hot water filling temperature sensor that detects the temperature of the hot water flowing through the hot water filling pipe 12, 16 is a hot water filling solenoid valve that opens and closes the flow path of the hot water filling pipe 12, 17a to 17e are hot water storage temperature sensors that are provided in multiple quantities on the upper and lower sides of the hot water storage tank 1 to detect the temperature of the stored hot water, and 17e is provided at the bottom of the hot water storage tank 1 and can detect the temperature of the water entering the heating means 24. In addition, the temperature distribution of the hot water in the hot water storage tank 1 can be detected according to the detected values ​​of the hot water storage temperature sensors 17a to 17e.

[0014] 18 is a stainless steel bellows located inside the hot water storage tank 1 and is a bath heat exchanger for heating the bath water in the bathtub 13; 19 is a bath circulation circuit that connects the bathtub 13 and the bath heat exchanger 18 so that the bath water can circulate; 20 is a bath circulation pump that draws in the bath water from the bathtub 13 and pumps it to the bath heat exchanger 18 to circulate the bath water; 21 is a bath temperature sensor for detecting the temperature of the bath water; 22 is a water level sensor that detects the water level in the bathtub 13 by detecting the water pressure, and a hot water filling pipe 12 is connected in the middle of the bath circulation circuit 19.

[0015] 23 is a three-way valve installed in the middle of the bath circulation circuit 19 and configured to bypass the bath heat exchanger 18.

[0016] Reference numeral 24 denotes a heat pump type heating means for heating the hot water in the hot water storage tank 1; 25 denotes a heating supply pipe connecting the lower part of the hot water storage tank 1 and the heating means 24; 26 denotes a heating return pipe connecting the heating means 24 and the upper part of the hot water storage tank 1; 27 denotes a heating circulation pump for circulating the hot water; 28 denotes a water inlet temperature sensor for detecting the water inlet temperature of the water entering the heating means 24; and 29 denotes a boiling temperature sensor for detecting the temperature of the hot water boiled up by the heating means 24. Here, the heat pump type heating means 24 includes a compressor 30, a water-cooled refrigerant heat exchanger 31, an expansion valve 32, an air heat exchanger 33, a blower 34, and an outside air temperature sensor 35 for detecting the outside air temperature, and is configured to boil up the hot water such that the temperature detected by the boiling temperature sensor 29 becomes an arbitrary temperature within the range of 40°C to 90°C. The hot water storage tank 1, the heating supply pipe 25, the heating means 24, and the heating return pipe 26 constitute a heating circulation circuit.

[0017] Here, the relationship between Legionella bacteria that may flow into the hot water storage tank 1 and the temperature will be described. Since the water supplied into the hot water storage tank 1 contains chlorine, only an extremely small amount of Legionella bacteria remains. However, if the temperature layer in the hot water storage tank 1 is at a relatively low temperature, the Legionella bacteria in the temperature layer may proliferate. Here, even if Legionella bacteria proliferate in a part of the temperature layer in the hot water storage tank 1, by performing a boiling operation to boil up the hot water in the hot water storage tank 1 to 65°C or higher every day, the Legionella bacteria could be sterilized.

[0018] However, as described above, since the heating means 24 can heat to an arbitrary boiling temperature within the range of 40°C to 90°C, the necessary amount of heat in the hot water storage tank 1 is calculated to determine the boiling temperature, and whether to heat up to 65°C at which Legionella bacteria can be sterilized was determined by the necessary amount of heat for hot water supply required by the user.

[0019] Reference numeral 36 denotes a heating bypass pipe that branches from the heating return pipe 26 and is connected to the water supply pipe 2 connected to the lower part of the hot water storage tank 1, and 37 denotes a heating bypass valve for switching either the heating bypass pipe 36 or the heating return pipe 26.

[0020] Reference numeral 38 denotes an outdoor remote controller provided outside the bathroom. It includes a display unit 38a as a notification unit for notifying the operating state and setting state of the water supply device, a speaker 38b for outputting voice data and notification sounds stored in advance, a bath switch 38c for starting the filling of the bathtub 13 with hot water, a change switch 38d for changing the set bath temperature, and other switches 38e.

[0021] Reference numeral 39 denotes an indoor remote controller provided inside the bathroom. It includes a display unit 39a as a notification unit for notifying the operating state and setting state of the storage-type water supply device, a speaker 39b for outputting voice data and notification sounds stored in advance, a bath switch 39c for starting the filling of the bathtub 13 with hot water, a change switch 39d for changing the set bath temperature, other switches 39e, and a bathroom temperature sensor 40 for detecting the room temperature inside the bathroom.

[0022] Reference numeral 41 is the main control means for controlling the operation of this storage-type water supply device. The detected values of the hot water supply flow sensor 8, hot water supply temperature sensor 9, water supply temperature sensor 10, filling flow sensor 14, filling temperature sensor 15, hot water storage temperature sensor 17, bath temperature sensor 21, water level sensor 22, outside air temperature sensor 35, and bathroom temperature sensor 40 are input. It controls the operation of the hot water supply mixing valve 5, bath mixing valve 11, filling solenoid valve 16, bath circulation pump 20, and heating means 24, and is connected to be able to transmit and receive necessary information with the outdoor remote controller 38 and the indoor remote controller 39. Here, the main control means 41 has a logic circuit such as an MPU and controls its operation according to a program stored in advance while referring to the memory.

[0023] Reference numeral 42 is an ultraviolet irradiation unit provided on the hot water supply pipe 25. The ultraviolet irradiation unit 42 irradiates ultraviolet rays to the hot water flowing inside the hot water supply pipe 25. Specifically, the ultraviolet irradiation unit 42 is composed of an LED module on which deep ultraviolet LEDs (UV-C) that emit deep ultraviolet rays with a high sterilization and disinfection effect are mounted.

[0024] Furthermore, if the ultraviolet irradiation unit 42 is subjected to ultraviolet irradiation for a long period of time, it will generate heat, and if this condition continues, it will cause a decrease in irradiation intensity and a reduction in the lifespan of the components. Therefore, in this embodiment, a water-cooled ultraviolet irradiation unit 42 that dissipates heat with circulating hot water is used.

[0025] Furthermore, since the ultraviolet irradiation unit 42 may experience a decrease in irradiation intensity and reduced component lifespan if it is heated by the flow of high-temperature water or prolonged irradiation, it is preferable to install it on the heating supply pipe 25 side before it is heated by the heating means 24.

[0026] Alternatively, the ultraviolet irradiation unit 42 may be installed by making an opening in the middle of the heating supply pipe 25 and attaching a deep ultraviolet LED, or the ultraviolet irradiation unit 42 may be placed at the end or beginning of the heating supply pipe 25, or between pipes if the heating supply pipe 25 is composed of two or more connected pipes.

[0027] 43 is a heating operation control means that heats the hot water in the hot water storage tank 1 to a high temperature. The heating operation control means 43 performs a heating operation that heats the hot water in the hot water storage tank 1 using the heating means 24 via a heating circulation circuit during off-peak hours when electricity rates are low.

[0028] 44 is a sterilization operation control means that controls a sterilization operation in which ultraviolet light is irradiated with ultraviolet light by an ultraviolet irradiation unit 42 during the heating operation to sterilize Legionella bacteria contained in the hot water flowing through the heating supply pipe 25 and suppress the growth of Legionella bacteria in the hot water in the hot water storage tank 1.

[0029] Furthermore, the sterilization operation control means 44 stops heating of the heating means 24 after the sterilization operation is completed and circulates the hot water in the heating circulation circuit equipped with the ultraviolet irradiation unit 42 using the heating circulation pump 27, thereby performing a heat dissipation operation to cool the high-temperature ultraviolet irradiation unit 42 with the circulating hot water and release heat.

[0030] Reference numeral 45 denotes a UV permission determination means that determines whether to permit the execution of the aforementioned sterilization operation. If the UV permission determination means 45 determines that the execution of the sterilization operation is permitted, the sterilization operation control means 44 executes the sterilization operation during the boiling operation. If the UV permission determination means 45 does not determine that the execution of the sterilization operation is permitted, the sterilization operation control means 44 does not execute the sterilization operation during the boiling operation.

[0031] Furthermore, if the UV permission determination means 45 permits the execution of the sterilization operation, the UV permission determination means 45 transmits the information of the permission determination for the sterilization operation to the main unit control means 41, and the main unit control means 41 stores and retains the permission determination for the sterilization operation in memory. The main unit control means 41 then transmits the permission determination for the sterilization operation stored in memory to the sterilization operation control means 44, and the sterilization operation control means 44 executes the sterilization operation. Note that the permission determination of the UV permission determination means 45 stored in the main unit control means 41 is reset when the power to the hot water storage type water heater is cut off, and the UV permission determination means 45 makes the determination again.

[0032] Furthermore, the UV permission determination means 45 checks whether the boiling temperature detected by the boiling temperature sensor 29 is stable within a predetermined temperature range (in this case, within ±2°C of the target boiling temperature) for a predetermined period of time (in this case, 10 minutes). If the boiling temperature detected by the boiling temperature sensor 29 is stable, it is determined that there is no air mixed into the heating circulation circuit, that it is completely filled with hot water, and that the boiling temperature is stable. If the boiling temperature is not stable and fluctuates, it is determined that air has mixed into the heating circulation circuit. If air is mixed in, the outdoor remote control 38 and the indoor remote control 39 may display an indication that air has not been properly vented and prompt the user to vent the air.

[0033] Next, the operation of the hot water storage type hot water supply system of the present invention will be described. <Water heating operation> When the amount of stored hot water decreases or when there is a request to heat water during a predetermined time period (nighttime) when electricity rates are low, the heating operation control means 43 starts driving the heating circulation pump 27 located in the middle of the piping connecting the hot water storage tank 1 and the heating means 24, and also drives the heating bypass valve 37 to the heating return pipe 26 side. It also sends a target heating temperature that matches the required amount of hot water supply and an instruction to start heating to the heating means 24, and continues the operation of pumping water from the bottom of the hot water storage tank 1, heating it with the heating means 24, and returning it to the top of the hot water storage tank 1, thereby heating the water in the hot water storage tank 1 to a high temperature in a sequential layering manner. If the heating temperature has not reached the target temperature, the heating bypass valve 37 may be driven to the heating bypass pipe 36 side, and after the heating temperature has risen sufficiently, the heating bypass valve 37 may be driven to the heating return pipe 26 side.

[0034] Then, the heating operation control means 43 heats the water until the bottom of the hot water storage tank 1 or the inlet water temperature reaches the final heating temperature, or when the predetermined time period ends, it instructs the heating means 24 to stop heating, and the heating means 24 stops driving the compressor 30, expansion valve 32, blower 34 and heating circulation pump 27 to end the heating operation.

[0035] <Hot water supply> When the hot water tap 7 is opened, city water flows into the bottom of the hot water storage tank 1 from the water supply pipe 2, and hot water is discharged from the top of the hot water storage tank 1 via the hot water outlet pipe 3. This hot water is mixed with water from the water supply bypass pipe 4 by the hot water mixing valve 5 and then passes through the hot water pipe 6. When the hot water flow sensor 8 detects a water flow rate above the minimum operating water flow rate, the main control means 41 provides feedback control of the valve opening of the hot water mixing valve 5 so that the temperature detected by the hot water temperature sensor 9 matches the hot water set temperature, thereby supplying hot water at the set temperature. When the hot water flow sensor 8 detects a water flow rate below the minimum operating water flow rate, such as when the hot water tap 7 is closed, the main control means 41 stops the feedback control of the valve opening of the hot water mixing valve 5 and stops the hot water supply.

[0036] <Water filling operation> When the main control unit 41 instructs the bath to be filled with hot water, it opens the hot water filling solenoid valve 16 and provides feedback control to the valve opening of the bath mixing valve 11 so that the temperature detected by the hot water filling temperature sensor 15 matches the hot water filling temperature instructed by the main control unit 41, thereby starting to fill the bathtub 13 with hot water at the instructed temperature.

[0037] Then, when the main control means 41 detects that the cumulative value of the hot water flow rate detected by the hot water flow rate sensor 14 is equal to the bath set amount, or when the water level sensor 22 detects the bath set water level, it closes the hot water solenoid valve 16 and ends the hot water filling operation.

[0038] <Reheating operation> The water level sensor 22 detects the water pressure and water level, and if there is remaining water in the bathtub 13, the main control means 41 drives the bath circulation pump 20 to circulate the bath water through the bath circulation circuit 19 and the bath heat exchanger 18, and heats the bath water in the bath heat exchanger 18. Then, when the bath temperature sensor 21 confirms that the temperature of the bath water has risen to the set bath temperature, the drive of the bath circulation pump 20 is stopped.

[0039] <Sterilization operation> Next, the sterilization operation performed during the boiling operation of the first embodiment will be explained based on the flowchart shown in Figure 2 and the time chart shown in Figure 3. When the start time of a designated period with low electricity rates (nighttime) or when the amount of stored hot water decreases, the main unit control means 41 sends an instruction to the heating means 24 to start the boiling operation. The heating means 24 then starts driving the compressor 30, expansion valve 32, blower 34, and heating circulation pump 27, and drives the heating bypass valve 37 toward the heating return pipe 26 to start the boiling operation (S1 is Yes).

[0040] The main unit control means 41 checks whether the permission determination made by the UV permission determination means 45 is stored (S2). If the permission determination is not stored (S2 is Yes), the process proceeds to S4, where it determines whether the sterilization operation can be performed.

[0041] In S2, the main unit control means 41 determines that no permission judgment has been stored and that this is the first water heating operation since power was restored after the power was cut off. The water heating temperature sensor 29 detects the temperature of the water flowing through the heating return pipe 26 (S3), and the UV permission judgment means 45 starts counting on the timer (S4).

[0042] The UV permission determination means 45 uses a timer to measure the duration during which the boiling temperature detected by the boiling temperature sensor 29 remains within a predetermined temperature range (in this case, within ±2°C of the target boiling temperature) (S5).

[0043] The UV permission determination means 45 resets the timer count (S6) if the boiling temperature detected by the boiling temperature sensor 29 exceeds a predetermined temperature range (S5 is No), confirms the boiling temperature detected by the boiling temperature sensor 29 (S3), restarts the timer count (S4), and measures the duration using the timer.

[0044] Then, if the boiling temperature detected by the boiling temperature sensor 29 remains within a predetermined temperature range (in this case, within ±2°C of the target boiling temperature) for a period exceeding a predetermined time (S7), the UV permission determination means 45 determines that no air has entered the heating circulation circuit and that the heat dissipation operation can be performed properly by circulating the hot water, and terminates the timer count to determine permission to perform the sterilization operation (S8).

[0045] At this time, the UV permission determination means 45 transmits the decision to permit the execution of the sterilization operation to the main unit control means 41 and the sterilization operation control means 44. The main unit control means 41 stores the permission decision, and the sterilization operation control means 44 executes the sterilization operation during the boiling operation (S9).

[0046] Thus, if the boiling temperature detected by the boiling temperature sensor 29 remains within a predetermined temperature range for a period exceeding a predetermined time, it means that no air has entered the heating circulation circuit, and the heat dissipation operation of the ultraviolet irradiation unit 42 by the circulation of hot water can be reliably performed, thereby preventing malfunctions due to high temperatures.

[0047] Furthermore, if the boiling temperature detected by the boiling temperature sensor 29 does not stabilize within a predetermined temperature range, there is a possibility that air has entered the heating circulation circuit. By preventing the sterilization operation from being performed, malfunctions due to high temperatures can be reliably prevented.

[0048] Then, the sterilization operation control means 44 and the boiling operation control means 43 continue the sterilization operation and boiling operation until the water is heated to the bottom of the hot water storage tank 1, or when the predetermined time period ends (S10 is Yes), the boiling operation control means 43 instructs the heating means 24 to stop boiling, and the heating means 24 stops driving the compressor 30, expansion valve 32, and blower 34 to complete the boiling operation.

[0049] Once the boiling operation is complete, the sterilization operation control means 44 terminates the ultraviolet irradiation of the ultraviolet irradiation unit 42 and ends the sterilization operation. At this time, the sterilization operation control means 44 performs a heat dissipation operation to cool the heat accumulated in the ultraviolet irradiation unit 42 with water (S11).

[0050] To explain the specific heat dissipation operation, after the boiling operation and sterilization operation are completed, the sterilization operation control means 44 drives the heating bypass valve 37 toward the heating bypass pipe 36, continues driving the heating circulation pump 27 for a certain period of time, and then stops driving the heating circulation pump 27.

[0051] Thus, when the UV permission determination means 45 determines that permission to perform the sterilization operation has been granted, the hot water can be circulated properly, and the UV irradiation unit 42, which has become hot, can be cooled down by the hot water in a normal heat dissipation operation.

[0052] Furthermore, the heat dissipation operation stops heating by the heating means 24 and continues circulation by the heating circulation pump 27, causing the temperature of the hot water to decrease and allowing heat from the ultraviolet irradiation unit 42 to be dissipated.

[0053] Next, we will explain in detail how to skip the permission check. When the start time of a designated period with low electricity rates (nighttime) or when the amount of stored hot water decreases, the main unit control means 41 sends an instruction to the heating means 24 to start the boiling operation. The heating means 24 then starts driving the compressor 30, expansion valve 32, blower 34, and heating circulation pump 27, and drives the heating bypass valve 37 toward the heating return pipe 26 to start the boiling operation (S1 is Yes).

[0054] The main unit control means 41 checks whether the permission determination made by the UV permission determination means 45 is stored (S2). If there is a memory of an already granted permission determination (S2 is No), the process proceeds to S9 and the sterilization operation is started (S9).

[0055] Thus, when the main unit control means 41 has stored a permission determination to allow the execution of the sterilization operation at the start of the heating operation, the operation of the permission determination means 45 is skipped, and the sterilization operation during the heating operation is permitted, thereby reliably preventing malfunctions due to high temperatures. Furthermore, by performing the sterilization operation from the start of the heating operation, Legionella bacteria in the hot water storage tank 1 can be sterilized regardless of the heating temperature.

[0056] Next, the resetting of the memory for the permission determination to execute the sterilization operation of the main unit control means 41 will be explained based on the flowchart shown in Figure 4. The main unit control means 41 checks whether the device is in a permit determination state (S12). If information has been transmitted from the UV permit determination means 45 in S9 and the device is in a permit determination state (S12 is Yes), the device maintains the permit determination state and performs the sterilization operation.

[0057] Then, if the power supply to the storage-type hot water heater (not shown) is interrupted due to replacement work such as replacing parts of the storage-type hot water heater or replacing the ultraviolet irradiation unit 42, or due to a power outage (S13 is Yes), the permission determination for executing the sterilization operation stored in the main unit control means 41 is reset (S14). Then, the process returns to S12.

[0058] In this way, if work is performed that may cause air to enter the heating circulation circuit again, the UV permission determination means 45 can perform the determination operation again to reliably determine the presence of air. This prevents malfunctions in which the UV irradiation unit 42 cannot dissipate heat due to poor circulation caused by the heating circulation pump 27 running dry, thereby preventing failure of the UV irradiation unit 42.

[0059] It should be noted that the present invention is not limited to this embodiment, and modifications are permitted without altering the gist of the invention. For example, while the present invention determines whether air is accumulating in the heating circulation circuit by checking whether the temperature detected by the boiling temperature sensor 29 is within a predetermined temperature range, it is sufficient to detect whether or not there is a flow of hot water in the heating circulation circuit. Other methods include estimating this using a water flow sensor or estimating it from the change in the hot water storage temperature detected by the hot water storage temperature sensor 17.

[0060] Furthermore, for example, the ultraviolet irradiation unit 42 can be any unit that emits light in the ultraviolet region, and is not limited to units that emit deep ultraviolet (UV-C) light.

[0061] Furthermore, although it was explained that the ultraviolet irradiation unit 42 is constantly irradiating during the sterilization operation, it is not necessary to keep the irradiation ON at all times. By switching ON and OFF at predetermined intervals during the sterilization operation, the burden on the ultraviolet irradiation unit 42 can be reduced compared to continuous irradiation. [Explanation of Symbols]

[0062] 1. Hot water storage tank 17. Hot water storage temperature sensor 24 Heating means 29. Water heating temperature sensor 36. Heating bypass tube 37. Heating bypass valve 41 Main unit control means 42 UV irradiation unit 43. Water heating operation control means 44 Sterilization operation control means 45 UV permission determination means

Claims

1. A hot water storage tank for storing hot water, A heating means for heating the hot water in the hot water storage tank, A heating supply pipe connecting the lower part of the hot water storage tank and the heating means The heating means and the heating return pipe connected to the upper part of the hot water storage tank, The heating means and a circulation pump that circulates the hot water in the hot water storage tank, A heating temperature sensor detects the temperature of the hot water returning from the heating means to the top of the hot water storage tank, In a hot water supply system with a storage-type hot water supply system, the system includes a main control means for controlling the boiling operation to store the hot water heated by the heating means in the hot water storage tank, A water-cooled ultraviolet irradiation unit is provided in the middle of the heating supply pipe, which kills bacteria by irradiation with ultraviolet light and dissipates heat with the hot water flowing through the heating supply pipe. The main unit control means includes a sterilization operation control means that controls the sterilization operation by the ultraviolet irradiation unit during the boiling operation, and a UV permission determination means that determines whether to permit the execution of the sterilization operation. The sterilization operation control means, if the UV permission determination means determines that permission is granted, executes the sterilization operation during the boiling operation. The storage-type hot water supply system is characterized in that the UV permission determination means grants permission to perform the sterilization operation if the detected value of the boiling temperature sensor is within a predetermined temperature range for a predetermined period of time.

2. The hot water storage type water heater according to claim 1, characterized in that the UV permission determination means resets the determination each time the power supply to the hot water storage type water heater is cut off.

3. The heating return pipe is provided with a heating bypass pipe that branches off from the heating return pipe and connects to a water supply pipe connected to the lower part of the hot water storage tank, and a heating bypass valve that switches between the heating bypass pipe and the heating return pipe. The storage-type hot water supply device according to claim 1 or 2, characterized in that the main unit control means, after the boiling operation is completed, switches the heating bypass valve to the heating bypass pipe side and drives the circulation pump to dissipate heat from the ultraviolet irradiation unit.

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