Storage water heater

Abstract

To provide a storage water heater capable of efficiently executing a sterilization boiling-up operation.SOLUTION: A storage water heater includes: control means for controlling a boiling-up operation for causing water flowing out from a hot water storage tank to flow into a heat source machine and causing hot water flowing out from the heat source machine to flow into the hot water storage tank; and learning means for learning a load concentration time zone in which a hot water supply load concentrates. When there is hot water that might cause growth of Legionella bacteria in the hot water storage tank, the storage water heater can execute a sterilization boiling-up operation for taking out the hot water and returning the hot water to the hot water storage tank after heating the hot water by using the heat source machine. In the case where a time from a time of issuance of a request for performing the sterilization boiling-up operation to a start time of the load concentration time zone is a predetermined time or shorter, the sterilization boiling-up operation is started. In the case where the time from the time of issuance of the request for performing the sterilization boiling-up operation to the start time of the load concentration time zone exceeds the predetermined time, start of the sterilization boiling-up operation is postponed until a time before the start time of the load concentration time zone only by a predetermined time.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a storage type water heater. [Background technology]

[0002] In the conventional hot water storage type water heater disclosed in Patent Document 1 below, when there is a breeding layer, which is a layer of water in which Legionella bacteria may breed, and a non-breeding layer, which is a layer of water in which Legionella bacteria may not breed, in the hot water storage tank, low-temperature boiling operation is performed when water from the non-breeding layer flows out from the outlet, and sterilizing boiling operation is performed when water from the breeding layer flows out from the outlet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2022-128098 Summary of the Invention [Problem to be solved by the invention]

[0004] The standard boiling temperature for storage-type hot water heaters is generally considered to be 60°C or higher to prevent Legionella infection, and 65°C or higher is desirable when considering heat dissipation from pipes. However, a new study on the conditions for Legionella growth using an actual water heater with a sealed storage tank concluded that Legionella growth can be suppressed even if the lower limit of the standard boiling temperature is set at 55°C. Based on this, a low-temperature boiling operation, which boils hot water at a temperature lower than the previously established standard boiling temperature, could be considered. Low-temperature boiling operation increases the amount of medium-temperature water in the storage tank, where Legionella bacteria may grow. This necessitates sterilization boiling operation, which poses the issue of reduced energy efficiency.

[0005] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide a storage type hot water heater that can efficiently perform a sterilization-boiling operation. [Means for solving the problem]

[0006] The hot water storage type water heater of the present disclosure comprises a hot water storage tank, a heat source unit that heats water, a circulation pump that circulates hot water between the hot water storage tank and the heat source unit, a control means that controls boiling operation that causes water flowing out of the hot water storage tank to flow into the heat source unit and hot water flowing out from the heat source unit to flow into the hot water storage tank, and a learning means that learns load concentration time periods when hot water supply load is concentrated, and is capable of performing a sterilizing boiling operation in which, when there is hot water in the hot water storage tank in which Legionella bacteria may grow, the hot water is removed, heated in the heat source unit, and then returned to the hot water storage tank, and if the time from the time a request to perform the sterilizing boiling operation is made to the start of the load concentration time period is less than a predetermined time, the sterilizing boiling operation is started, and if the time from the time a request to perform the sterilizing boiling operation is made to the start of the load concentration time period exceeds the predetermined time, the start of the sterilizing boiling operation is postponed to a time a predetermined time before the start of the load concentration time period. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a storage type water heater that can efficiently perform sterilization boiling operation. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a storage type hot water heater according to a first embodiment. [Figure 2] 10 is a diagram showing an example of the relationship between the hot water temperature and the hot water position in the hot water storage tank immediately after low-temperature boiling operation is performed. FIG. [Figure 3] 3 is a diagram showing an example of the relationship between the hot water temperature and the hot water position in the hot water storage tank after a time has elapsed from the state of FIG. 2. FIG. [Figure 4] FIG. 10 is a diagram showing the relationship between a load concentration time period and the start timing of the sterilization boiling operation. [Figure 5] 4 is a flowchart showing a control operation executed by a control unit in the first embodiment. [Figure 6] FIG. 2 is a diagram illustrating an example of a configuration for realizing the functions of a control unit according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described with reference to the drawings. Common or corresponding elements in each drawing are designated by the same reference numerals, and descriptions thereof will be simplified or omitted. In the following description, terms such as "water," "hot water," "warm water," and "hot water" generally refer to liquid water, and may include cold water to boiling water. Furthermore, the configurations shown in the following embodiments are examples of the technical ideas of the present disclosure, and may be combined with other known technologies, or multiple technical ideas described in the present disclosure may be combined. Furthermore, parts of the configurations may be omitted or modified without departing from the spirit of the present disclosure.

[0010] Embodiment 1 FIG. 1 is a diagram showing a hot water storage type water heater 1 according to a first embodiment. As shown in FIG. 1, the hot water storage type water heater 1 includes a heat source machine 2 that utilizes a heat pump cycle and a hot water storage unit 3 that has a hot water storage tank 4. The heat source machine 2 consumes electricity to heat water. The heat source machine 2 is installed outdoors. The hot water storage unit 3 may be installed outdoors or indoors.

[0011] The heat source unit 2 has a refrigerant circuit including a compressor 5, a water-refrigerant heat exchanger 6, a pressure reducing device 7, an air-refrigerant heat exchanger 8, and an outdoor fan 9. The outdoor fan 9 blows outside air to the air-refrigerant heat exchanger 8. The pressure reducing device 7 may be a linear expansion valve.

[0012] The hot water storage type water heater 1 can perform a boiling operation. The boiling operation is an operation in which hot water heated by the heat source unit 2 flows into the hot water storage tank 4, thereby storing heat in the hot water storage tank 4. The hot water storage type water heater 1 in this embodiment performs a one-pass boiling operation in which water is heated to a target temperature by passing it through the heat source unit 2 only once.

[0013] The hot water storage unit 3 further includes a circulation pump 10, a hot water mixing valve 11, a city water pressure reducing valve 12, and a three-way valve 21. The circulation pump 10 circulates hot water between the hot water storage tank 4 and the heat source unit 2.

[0014] The three-way valve 21 has ports A, B, and C. The piping 13 connects an opening formed in the bottom of the hot water storage tank 4 to the port A of the three-way valve 21. The medium-temperature piping 22 connects an opening formed in the middle of the hot water storage tank 4 to the port B of the three-way valve 21. The port C of the three-way valve 21 is connected to the suction port of the circulation pump 10. The three-way valve 21 is switchable between a first state in which the port A is connected to the port C and the port B is blocked, and a second state in which the port B is connected to the port C and the port A is blocked.

[0015] The city water pressure reducing valve 12 is provided on a water supply pipe 14. The water supply pipe 14 is connected to an opening formed in the bottom of the hot water storage tank 4. A water supply pipe 15 branching off from the water supply pipe 14 is connected to the hot water supply mixing valve 11.

[0016] The HP supply pipe 16 connects the discharge port of the circulation pump 10 to the water inlet of the water-refrigerant heat exchanger 6. The HP return pipe 17 connects the water outlet of the water-refrigerant heat exchanger 6 to an opening formed in the top of the hot water storage tank 4.

[0017] When the three-way valve 21 is in the first state, low-temperature water flowing out from the bottom of the hot water storage tank 4 flows into the water-refrigerant heat exchanger 6 through the pipe 13 and the HP supply pipe 16. When the three-way valve 21 is in the second state, medium-temperature water flowing out from the middle part of the hot water storage tank 4 flows into the water-refrigerant heat exchanger 6 through the medium-temperature pipe 22 and the HP supply pipe 16.

[0018] The hot water outlet pipe 18 connects an opening formed in the top of the hot water storage tank 4 to the hot water mixing valve 11. The hot water mixing valve 11 mixes low-temperature water supplied from the water supply pipe 15 with hot water supplied from the hot water outlet pipe 18, and lets the resulting mixture flow into the hot water supply pipe 19. The hot water in the hot water supply pipe 19 is sent to a hot water terminal such as a bathtub, shower, or faucet. The hot water supply pipe 19 is provided with a hot water temperature sensor 23 that detects the temperature of the hot water flowing through the hot water supply pipe 19, and a hot water flow rate sensor 24 that detects the flow rate of the hot water flowing through the hot water supply pipe 19.

[0019] A plurality of hot water temperature sensors 20 are provided in the middle of the hot water tank 4 to detect the water temperature inside the hot water tank 4. The hot water temperature sensors 20 may be configured with thermistors. Hot water temperature sensors are also provided at the top and bottom of the hot water tank 4, but are not shown in the figure.

[0020] The hot water storage type water heater 1 is equipped with a control unit 50 that controls the operation of the hot water storage type water heater 1. The control unit 50 has a timer 51 that manages the date and time, and a learning means 52 that learns load concentration time periods when the hot water supply load is concentrated. The learning means 52 can learn the load concentration time periods when the hot water supply load is concentrated by learning the time periods when the hot water supply load detected by the hot water supply temperature sensor 23 and the hot water supply flow rate sensor 24 occurs.

[0021] The control unit 50 controls the heating operation by controlling the operation of the compressor 5, the pressure reducing device 7, the outdoor fan 9, the circulation pump 10, and the three-way valve 21. The temperature of the hot water flowing out of the heat source unit 2 during the heating operation is hereinafter referred to as the "heating temperature."

[0022] The control unit 50 can control the boiling temperature by controlling the rotation speed of the circulation pump 10. During normal boiling operation, the control unit 50 may control the boiling temperature to be between 50°C and 60°C. If the boiling temperature is 50°C or higher, the growth of Legionella bacteria can be suppressed. The lower the boiling temperature, the higher the energy efficiency, so by keeping the boiling temperature as low as possible within the range that can suppress the growth of Legionella bacteria, it is possible to increase energy efficiency. Boiling operation in which the boiling temperature is between 50°C and 60°C is referred to as "low-temperature boiling operation" below.

[0023] FIG. 2 is a diagram showing an example of the relationship between the hot water temperature and the hot water position in the hot water storage tank 4 immediately after low-temperature heating operation is performed. The hot water position is expressed as the volume from the top of the hot water storage tank 4. In the example shown in FIG. 2, the hot water temperature at the 170 L hot water storage position in the middle of the hot water storage tank 4 is 42°C. 42°C is a temperature at which Legionella bacteria may grow.

[0024] Fig. 3 is a diagram showing an example of the relationship between the hot water temperature and the hot water storage position in the hot water storage tank 4 after a time has elapsed from the state shown in Fig. 2. In the example shown in Fig. 2, the hot water temperature at the 170 L hot water storage position is 36°C. 36°C is a temperature at which Legionella bacteria may grow.

[0025] As shown in the examples of FIGS. 2 and 3 , when there is little change in the water temperature in the intermediate portion of the hot water storage tank 4 and the water is maintained at a temperature at which Legionella bacteria may grow, the control unit 50 determines that sterilizing boiling operation is necessary. The sterilizing boiling operation is an operation in which, when hot water in which Legionella bacteria may grow is stored in the hot water storage tank 4, the hot water is extracted, heated by the heat source unit 2, and then returned to the hot water storage tank 4. In the sterilizing boiling operation, the control unit 50 sets the three-way valve 21 to the second state to perform the boiling operation, whereby the intermediate-temperature water extracted from the intermediate portion of the hot water storage tank 4 to the intermediate-temperature pipe 22 is sent to the water-refrigerant heat exchanger 6 through the HP supply pipe 16 and heated and sterilized. This enables the intermediate-temperature water in the intermediate portion of the hot water storage tank 4 to be efficiently extracted. The control unit 50 may set the boiling temperature during the sterilizing boiling operation to be higher than the boiling temperature during the low-temperature boiling operation.

[0026] The control unit 50 determines whether or not a sterilizing boiling operation is required based on the stored hot water temperature detected by the stored hot water temperature sensor 20. For example, if a time has passed since the end of the boiling operation and there is zL or more hot water in the hot water storage tank 4 at x°C to y°C, which is the temperature range in which bacteria of the genus Legionella grow, the control unit 50 may determine that there is a request to perform a sterilizing boiling operation. x°C to y°C may be, for example, 35°C to 45°C.

[0027] The control unit 50 starts the sterilizing boiling operation when the time from when the request to perform the sterilizing boiling operation is made to the start time of the load concentration time period is less than or equal to a predetermined time n, and postpones the start of the sterilizing boiling operation until the time that is the predetermined time n before the start time of the load concentration time period when the time from when the request to perform the sterilizing boiling operation is made to the start time of the load concentration time period exceeds the predetermined time n.

[0028] Figure 4 is a diagram showing the relationship between the concentrated load time period and the start timing of the sterilizing boiling operation. When a request to perform the sterilizing boiling operation is made at time T1 in Figure 4, the time from time T1 to the start time of the concentrated load time period exceeds the predetermined time n. In this case, the start of the sterilizing boiling operation is postponed until the time that is the predetermined time n before the start time of the concentrated load time period.

[0029] In this way, with this embodiment, the sterilizing and boiling operation can be performed as close as possible to the load concentration time period, which shortens the time until the hot water produced in the sterilizing and boiling operation is consumed, thereby reducing the heat loss caused by heat dissipation from the hot water and improving energy efficiency.

[0030] Figure 5 is a flowchart showing the control operation executed by the control unit 50 in the first embodiment. In step S1 of Figure 5, the normal boiling operation or the sterilizing boiling operation ends. Next, in step S2, it is determined whether a predetermined time a has elapsed since the end of the boiling operation. If the time a has elapsed, the process proceeds to step S3, where it is determined whether or not there is zL or more of hot water in the hot water storage tank 4 at x°C to y°C, which is the temperature range in which Legionella bacteria grow.

[0031] If the determination in step S3 is Yes, the control unit 50 determines that there is a request to perform sterilizing boiling operation. In this case, the process proceeds to step S4, where it is determined whether the difference in time between the current time and the start time of the concentrated load period is less than or equal to a predetermined time n. If the determination in step S4 is Yes, the process proceeds to step S5, where the control unit 50 starts sterilizing boiling operation.

[0032] On the other hand, if the determination in step S4 is No, the process of step S4 is repeated. In this way, the start of the sterilization boiling operation is postponed until the difference in time between the current time and the start time of the concentrated load time period becomes equal to or less than the predetermined time n.

[0033] The predetermined time n may be determined according to the value obtained by dividing the amount of hot water to be sterilized in the sterilizing boiling operation by the flow rate of the circulation pump 10 during the sterilizing boiling operation. As a result, the predetermined time n becomes equal to the time required for the sterilizing boiling operation. This makes it possible to match the end time of the sterilizing boiling operation with the start time of the concentrated load time period. In other words, it becomes possible to complete the sterilizing boiling operation by the start time of the concentrated load time period. The flow rate of the circulation pump 10 during the sterilizing boiling operation may be detected by a flow rate sensor (not shown) or may be estimated from the rotation speed of the circulation pump 10.

[0034] In this embodiment, sterilization boiling operation is performed only when there is concern about the proliferation of Legionella bacteria and medium-temperature water that requires sterilization treatment is present in the hot water storage tank 4, thereby making it possible to suppress an increase in power consumption due to excessive sterilization boiling operation.

[0035] FIG. 6 is a diagram showing an example of a configuration for realizing the functions of the control unit 50 in the first embodiment. Each function of the control unit 50 is realized by, for example, a processing circuit. The processing circuit may be dedicated hardware 600. The processing circuit may include a processor 601 and a memory 602. A part of the processing circuit may be formed as the dedicated hardware 600, and the processing circuit may further include the processor 601 and the memory 602. In the example shown in FIG. 6, a part of the processing circuit is formed as the dedicated hardware 600. Furthermore, in the example shown in FIG. 6, the processing circuit further includes the processor 601 and the memory 602 in addition to the dedicated hardware 600.

[0036] The processing circuitry of which at least one portion is dedicated hardware 600 may be, for example, a single circuit, a multiple circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0037] When the processing circuit includes at least one processor 601 and at least one memory 602, the functions of each part of the control unit 50 are realized by software, firmware, or a combination of software and firmware.

[0038] The software and firmware are written as programs and stored in memory 602. The programs may be recorded on a computer-readable recording medium. The processor 601 realizes the functions of each unit by reading and executing the programs stored in memory 602. The processor 601 is also called a CPU (Central Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. The memory 602 may be, for example, a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, or EEPROM, or a magnetic disk, flexible disk, optical disk, compact disk, minidisk, DVD, etc.

[0039] In this way, the processing circuit can realize the functions of the control unit 50 by hardware, software, firmware, or a combination of these. Note that each function of the control unit 50 may be realized by multiple devices working together, or by a single device. Furthermore, at least some of the functions of the control unit 50 may be implemented in a server or the like on an external network. [Explanation of symbols]

[0040] 1 storage type water heater, 2 heat source machine, 3 water storage unit, 4 water storage tank, 5 compressor, 6 water-refrigerant heat exchanger, 7 pressure reducing device, 8 air-refrigerant heat exchanger, 9 outdoor fan, 10 circulation pump, 11 water supply mixing valve, 12 city water pressure reducing valve, 13 piping, 14 water supply piping, 15 water supply piping, 16 hot water supply forward piping, 17 hot water supply return piping, 18 hot water outlet piping, 19 hot water supply piping, 20 hot water storage temperature sensor, 21 three-way valve, 22 medium temperature piping, 23 hot water supply temperature sensor, 24 hot water supply flow rate sensor, 50 control unit, 51 timer, 52 learning means, 600 dedicated hardware, 601 processor, 602 memory

Claims

1. A hot water tank and A heat source machine that heats water; a circulation pump that circulates hot water between the hot water storage tank and the heat source unit; a control means for controlling a boiling operation that causes water flowing out of the hot water storage tank to flow into the heat source machine and causes hot water flowing out of the heat source machine to flow into the hot water storage tank; a learning means for learning a load concentration time period during which hot water supply load is concentrated; Equipped with When hot water in the hot water storage tank is likely to grow Legionella bacteria, the hot water is taken out, heated by the heat source device, and then returned to the hot water storage tank. A sterilization boiling operation can be performed. If the time from the time when the request to perform the sterilization boiling operation is issued to the start time of the load concentration time period is less than a predetermined time, the sterilization boiling operation is started, In a storage type hot water heater, when the time from the time when a request to perform the sterilizing boiling operation is made to the start time of the concentrated load period exceeds the predetermined time, the start of the sterilizing boiling operation is postponed until the time that is the predetermined time before the start time of the concentrated load period.

2. 2. The hot water storage type water heater according to claim 1, wherein the predetermined time is determined according to a value obtained by dividing the amount of hot water to be sterilized in the sterilizing boiling operation by the flow rate of the circulation pump during the sterilizing boiling operation.

3. 3. The hot water storage type water heater according to claim 1, wherein, during the sterilization boiling operation, hot water taken out from an opening formed in an intermediate portion of the hot water storage tank is heated by the heat source unit.

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