Hot water supply system

Abstract

A hot water supply system comprises a hot water storage tank, a heat source device, and a control unit. The control unit is configured to be capable of executing a sterilization operation for operating the heat source device and heating at least some of the water stored in the hot water storage tank to a temperature equal to or higher than a prescribed sterilization reference temperature. The control unit is provided with: a time-setting unit that sets a system time in the hot water supply system; a sterilizationschedule-setting unit that sets a sterilization start time, which is the time at which the next sterilization operation is to start, with respect to the system time; and a time measurement unit that measures an elapsed time from a prescribed time point after the time point at which the immediately preceding sterilization operation was started. The control unit starts the sterilization operation when at least one of a first condition that the system time exceeds the sterilization start time and a second condition that the time measured by the time measurement unit is equal to or longer than a prescribed time is satisfied.

Description

Hot water supply system

[0001] The technology disclosed herein relates to a hot water supply system.

[0002] Japanese Patent Publication No. 2021-116969 discloses a hot water supply system comprising a hot water storage tank for storing water to be supplied to a predetermined hot water supply location, a heat source device for heating the water stored in the hot water storage tank, and a control unit. The control unit is configured to operate the heat source device and perform a sterilization operation in which at least a portion of the water stored in the hot water storage tank is heated to a temperature above a predetermined sterilization standard temperature. The control unit includes a time setting unit for setting the system time in the hot water supply system, and a sterilization schedule setting unit for setting the sterilization start time, which is the time when the sterilization operation will be started next time, relative to the system time. The control unit starts the sterilization operation when the condition that the system time has elapsed past the sterilization start time is met.

[0003] If water stored in a hot water storage tank is left at low temperatures for a long period of time, bacteria (e.g., Legionella) in the water may proliferate. For this reason, the hot water supply system described in Japanese Patent Publication No. 2021-116969 is capable of performing a sterilization operation to heat and sterilize the water stored in the hot water storage tank. However, in the hot water supply system described in Japanese Patent Publication No. 2021-116969, the start timing of the sterilization operation depends on the system time, so depending on the system time setting, the sterilization operation may not start in a timely manner. For example, if there is a change in the system time, the start timing of the sterilization operation may be delayed compared to the initial assumption. If the start timing of the sterilization operation is delayed excessively compared to the initial assumption, bacteria may proliferate in the hot water storage tank. This specification provides a technology that can suppress the proliferation of bacteria in a hot water storage tank.

[0004] In a first aspect of the present technology, the hot water supply system may include a hot water storage tank for storing water to be supplied to a predetermined hot water supply location, a heat source device for heating the water stored in the hot water storage tank, and a control unit. The control unit may be configured to execute a sterilization operation that operates the heat source device to heat at least a part of the water stored in the hot water storage tank to a temperature equal to or higher than a predetermined sterilization reference temperature. The control unit may include a time setting unit for setting a system time in the hot water supply system, a sterilization schedule setting unit for setting a sterilization start time, which is the time to start the sterilization operation next, with respect to the system time, and a timing unit for measuring the elapsed time from a predetermined time point after the start of the immediately preceding sterilization operation. The control unit may start the sterilization operation when at least one of a first condition that the system time has passed the sterilization start time and a second condition that the time measured by the timing unit is equal to or longer than a predetermined time is satisfied.

[0005] According to the above configuration, for example, when the system time is advanced and the timing at which the first condition is satisfied (i.e., the timing at which the system time has passed the sterilization start time) is delayed from the original assumption, the sterilization operation can be started at the timing at which the second condition is satisfied (i.e., the timing at which the measured time is equal to or longer than a predetermined time). Thereby, it is possible to suppress the start timing of the sterilization operation from being delayed from the original assumption, and thus it is possible to suppress the growth of various bacteria in the hot water storage tank.

[0006] In a second aspect of the present technology, in the above first aspect, a time included in a predetermined time period within a day may be set as the sterilization start time.

[0007] According to the above configuration, the sterilization operation can be executed during a predetermined time period within a day and in the vicinity thereof. Thereby, for example, the sterilization operation can be executed during a time period when the user does not use water, or during a time period when the electricity charge is low.

[0008] In a third aspect of this technology, in the first or second aspect described above, the control unit may start the sterilization operation when the second condition is met, regardless of whether the first condition is met or not, if the system time is not set.

[0009] With the above configuration, even if the system time is not set and it is not possible to start the sterilization operation based on the sterilization start time, the sterilization operation can be started based on the measured time.

[0010] In a fourth aspect of this technology, in any one of the first to third aspects described above, the control unit may start the sterilization operation when the first condition is met, regardless of whether the second condition is met, if the system time has not been changed since the start of the previous sterilization operation. The control unit may start the sterilization operation when either the first condition or the second condition is met, if the system time has been changed since the start of the previous sterilization operation.

[0011] For example, if the system time is advanced after the previous sterilization operation has started, the timing at which the first condition is met (i.e., the timing at which the system time has passed the sterilization start time) will be later than originally intended. In this case, if the sterilization operation is started at the timing at which the first condition is met, the start timing of the sterilization operation will be later than originally expected. If the start timing of the sterilization operation is excessively delayed compared to the originally expected timing, there is a risk that bacteria will proliferate in the hot water storage tank. With the above configuration, if the system time is changed, even if the first condition is not met, the sterilization operation will start when the second condition is met (i.e., the time measured by the timing unit exceeds a predetermined time). Therefore, even if the system time is advanced and the timing at which the first condition is met is later than originally intended, the sterilization operation can be started before the first condition is met. This prevents the start timing of the sterilization operation from being delayed compared to the originally expected timing, thus preventing the proliferation of bacteria in the hot water storage tank.

[0012] In a fifth aspect of this technology, in any one of the first to fourth aspects described above, the hot water supply system may further include a temperature sensor for detecting the temperature of the water stored in the hot water storage tank. If at least one of the first and second conditions is met, but the temperature detected by the temperature sensor is above a predetermined temperature, the control unit does not need to start the sterilization operation. If at least one of the first and second conditions is met, and the temperature detected by the temperature sensor is below the predetermined temperature, the control unit may start the sterilization operation.

[0013] If the system time is advanced and the timing at which the first condition is met (i.e., the timing at which the system time passes the sterilization start time) is delayed compared to the original, the second condition may be met before the first condition is met, and the sterilization operation may start. In this case, the first condition will be met (i.e., the system time passes the sterilization start time) without any delay after the sterilization operation has started, but since the sterilization operation was performed immediately before that, it is acceptable to postpone the execution of the sterilization operation at the timing when the first condition is met. In addition, the hot water supply system may operate a heat source device to heat the water stored in the hot water storage tank, for example, based on instructions from the user, separate from the sterilization operation. If the water in the hot water storage tank has been heated in this way, it is expected that most of the bacteria in the water will have been killed, so it is acceptable to postpone the execution of the sterilization operation. According to the above configuration, if the water in the hot water storage tank is at a high temperature (i.e., the water in the hot water storage tank has been heated immediately before by a sterilization operation, or the water in the hot water storage tank has been heated immediately before separately from the sterilization operation), the execution of the sterilization operation will be postponed. This prevents unnecessary sterilization operations from being performed, thereby preventing the hot water system from consuming unnecessary electricity.

[0014] In a sixth aspect of this technology, in the fifth aspect described above, if at least one of the first and second conditions is met and the temperature detected by the temperature sensor is equal to or greater than the predetermined temperature, the control unit may reset the time measured by the timing unit and then restart the timing by the timing unit.

[0015] Even if the sterilization operation is postponed because the water in the hot water storage tank is too hot, if the time measured by the timing unit is not reset, the second condition may be met immediately afterward, and the sterilization operation may be performed. As a result, the sterilization operation may be performed unnecessarily even though the water in the hot water storage tank is still too hot. With the above configuration, when the sterilization operation is postponed, the time measured by the timing unit is reset, which prevents the second condition from being met immediately afterward. Therefore, the sterilization operation is prevented from being performed immediately after it has been postponed. This prevents the sterilization operation from being performed unnecessarily, and thereby prevents the hot water supply system from consuming electricity unnecessarily.

[0016] In a seventh aspect of this technology, in any one of the first to sixth embodiments described above, the hot water supply system may further include a notification unit that notifies the timing at which the sterilization operation will be started next time. For example, the notification unit may notify the timing at which the first condition is met (i.e., the timing at which the system time has passed the sterilization start time) as the timing at which the sterilization operation will be started next time. Alternatively, the notification unit may notify the timing at which the second condition is met (i.e., the timing at which the time measured by the timing unit becomes a predetermined time or longer) as the timing at which the sterilization operation will be started next time.

[0017] With the above configuration, the user can know when the next sterilization operation will start.

[0018] This is a schematic diagram showing the configuration of the hot water supply system 100 according to the embodiment. This is a schematic diagram showing the configuration of the HP controller 24 of the hot water supply system 100 according to the embodiment. This is a schematic diagram showing the configuration of the tank controller 74 of the hot water supply system 100 according to the embodiment. This is a schematic diagram showing the configuration of the remote control 99 of the hot water supply system 100 according to the embodiment. This is a flowchart of the first sterilization start process executed by the controller of the hot water supply system 100 according to the embodiment. This is a diagram visualizing the progress of the system time and timing time in the hot water supply system 100 according to the embodiment. This is a flowchart of the second sterilization start process executed by the controller of the hot water supply system 100 according to the embodiment. This is a flowchart of the sterilization start time adjustment process executed by the controller of the hot water supply system 100 according to the embodiment. This is a schematic diagram showing how the prohibited time period is changed and the sterilization start time is changed accordingly in the hot water supply system 100 according to the embodiment.

[0019] Representative and non-limiting examples of the present invention are described in detail below with reference to the drawings. This detailed description is intended simply to show those skilled in the art details for carrying out preferred examples of the present invention and is not intended to limit the scope of the invention. Furthermore, the disclosed additional features and inventions may be used separately from or in conjunction with other features and inventions to provide a further improved hot water supply system.

[0020] Furthermore, the combinations of features and processes disclosed in the following detailed description are not essential for carrying out the present invention in the broadest sense, and are described solely to illustrate representative examples of the present invention. Moreover, the various features of the following representative examples, as well as the various features described in the claims, do not necessarily have to be combined in the same way as the examples described herein, or in the order listed, to provide additional and useful embodiments of the present invention.

[0021] All features described herein and / or in the claims are intended to be disclosed individually and independently of each other, as limitations to the specific matters described in the original disclosure and in the claims, separate from the features described in the examples and / or in the claims. Furthermore, all descriptions of numerical ranges and groups or clusters are intended to disclose intermediate configurations as limitations to the specific matters described in the original disclosure and in the claims.

[0022] (Example; Hot water supply system 100) As shown in Figure 1, the hot water supply system 100 includes an HP (heat pump) unit 4 and a tank unit 6.

[0023] (HP Unit 4) HP Unit 4 uses electricity to heat water by absorbing heat from the outside air. HP Unit 4 comprises an HP device 17 including a compressor 10, a condenser 12, an expansion valve 14, a fan 15, and an evaporator 16. The HP device 17 heats water by absorbing heat from the outside air by circulating a refrigerant (e.g., a fluorocarbon refrigerant) in the order of compressor 10, condenser 12, expansion valve 14, and evaporator 16. The compressor 10 pressurizes the refrigerant to make it high temperature and high pressure. The condenser 12 cools the refrigerant by heat exchange with water. HP supply path 19 and HP return path 21 are connected to both ends of the water flow path of the condenser 12, respectively. The expansion valve 14 reduces the pressure of the refrigerant to make it low temperature and low pressure. The fan 15 sends outside air to the evaporator 16. The evaporator 16 heats the refrigerant by heat exchange with the outside air sent from the fan 15. The HP unit 4 further includes a circulation pump 18 for circulating water to the condenser 12, a forward thermistor 20 for detecting the temperature of the water flowing into the condenser 12, a return thermistor 22 for detecting the temperature of the water flowing out of the condenser 12, and an HP controller 24 for controlling the operation of each component of the HP unit 4. As shown in Figure 2, the HP controller 24 includes a memory 152 and a processor 154 that performs processing based on the information stored in the memory 152.

[0024] (Tank Unit 6) As shown in Figure 1, the tank unit 6 includes a tank 30. The tank 30 is a sealed container that stores water inside, with its exterior covered with an insulating material. The capacity of the tank 30 in this embodiment is, for example, 100 liters. Figure 1 shows regions A, B, C, D, E, and F defined to divide the inside of the tank 30 into six equal parts vertically. Regions A and B are also called the upper regions. Regions C and D are also called the intermediate regions. Regions E and F are also called the lower regions.

[0025] The tank unit 6 further includes a tank supply path 31 and a tank return path 33 for circulating water in the tank 30 to the condenser 12 of the HP unit 4. The upstream end of the tank supply path 31 is connected to region F (i.e., the lower region) of the tank 30. The downstream end of the tank supply path 31 is connected to the upstream end of the HP supply path 19. The upstream end of the tank return path 33 is connected to the downstream end of the HP return path 21. The downstream end of the tank return path 33 is connected to region A (i.e., the upper region) of the tank 30. When the circulation pump 18 of the HP unit 4 is driven, water from the lower region of the tank 30 is sent to the condenser 12 via the tank supply path 31 and the HP supply path 19. The water, heated to a high temperature in the condenser 12, is returned to the upper region of the tank 30 via the HP return path 21 and the tank return path 33. When the water heated by the HP unit 4 flows into the tank 30, a temperature-straightened layer is formed inside the tank 30, in which a layer of high-temperature water is stacked on top of a layer of low-temperature water.

[0026] The tank unit 6 is supplied with tap water from a water source (not shown), such as a public water supply, via a water supply path 40. The downstream end of the water supply path 40 is connected to area F (i.e., the lower area) of the tank 30. Hot water is also supplied from the tank unit 6 to hot water supply locations (not shown), such as kitchens, showers, and faucets, via a hot water supply path 60. The upstream end of the hot water supply path 60 is connected to area A (i.e., the upper area) of the tank 30. When the hot water supply system 100 supplies hot water, high-temperature water is sent from the upper area of ​​the tank 30 to the hot water supply path 60, and low-temperature water flows from the water supply path 40 into the lower area of ​​the tank 30.

[0027] The tank unit 6 further comprises an intermediate thermistor 37, a lower thermistor 38, and an electric heater 39. The intermediate thermistor 37 is located in region C and detects the temperature of the water in region C. The intermediate thermistor 37 is located, for example, at a distance from the top of the tank 30 that corresponds to 45% of the total height of the tank 30 (i.e., the distance from the top to the bottom of the tank 30). The lower thermistor 38 is located in region F and detects the temperature of the water in region F. The lower thermistor 38 is located, for example, at a distance from the top of the tank 30 that corresponds to 90% of the total height of the tank 30. In another example, the lower thermistor 38 may be located in the tank supply path 31 (see Figure 1) connected to region F. The electric heater 39 is located in region D. The electric heater 39 is located, for example, at a distance from the top of the tank 30 that corresponds to 50% of the total height of the tank 30. The electric heater 39 generates heat when power is supplied to it. The tank unit 6 can heat the water in the tank 30 by operating the electric heater 39.

[0028] The tank unit 6 further includes a tank controller 74 that controls the operation of each component of the tank unit 6. The tank controller 74 can communicate with the HP controller 24. As shown in Figure 3, the tank controller 74 includes a memory 156 and a processor 158 that performs processing based on the information stored in the memory 156. In a modified example, the tank controller 74 may be provided in the HP unit 4. The HP controller 24 may function as the tank controller 74.

[0029] As shown in Figure 1, the hot water supply system 100 further includes a remote control 99 that can communicate with the tank controller 74. The remote control 99 is installed, for example, indoors. As shown in Figure 4, the remote control 99 includes a memory 160, a processor 162 that performs processing based on the information stored in the memory 160, an operating unit 164 (for example, switches and buttons) operated by the user, a display unit 166 (for example, a display) that shows various information, and an acoustic unit 168 (for example, a speaker) that announces various information by voice.

[0030] The hot water supply system 100 shown in Figure 1 can perform various operations such as boiling operation and sterilization operation, as well as various processes such as first sterilization start process, second sterilization start process, and sterilization start time adjustment process, through coordinated control by the HP controller 24, tank controller 74, and remote control 99.

[0031] As shown in Figure 2, the memory 152 of the HP controller 24 stores information including, for example, the system time, prohibited time zones, sterilization start time, and timing time. This information is also stored in the memory 156 of the tank controller 74 shown in Figure 3 and the memory 160 of the remote control 99 shown in Figure 4, and is periodically synchronized between the HP controller 24, the tank controller 74, and the remote control 99.

[0032] The system time is the specific time of the hot water supply system 100. The system time is first set by the user via the remote control 99, and then managed by the HP controller 24, the tank controller 74, and / or the RTC (Real Time Clock) built into the remote control 99. The prohibited time period represents the time period during which the operation of the HP device 17 is prohibited and is set relative to the system time. The prohibited time period is set, for example, by the user via the remote control 99. The sterilization start time represents the time at which the sterilization operation begins and is set relative to the system time. The sterilization start time is set, for example, by the user via the remote control 99. The sterilization start time may be set automatically by the HP controller 24, the tank controller 74, and / or the remote control 99. The timing time is the time measured by the timer function of the HP controller 24, the tank controller 74, and / or the remote control 99.

[0033] Although not shown in the diagram, memories 152, 156, and 160 also store the boiling start time for initiating the boiling operation, the target boiling temperature which is the target temperature of the water that the HP device 17 will heat during the boiling operation, and so on. Both the boiling start time and the target boiling temperature are set by the user via the remote control 99.

[0034] In the following, the HP controller 24, the tank controller 74, and the remote control 99 will be collectively referred to simply as "controllers."

[0035] (Boiling Operation) In boiling operation, the hot water supply system 100 shown in Figure 1 drives the HP unit 4 to heat the water in the tank 30. Boiling operation is performed periodically, for example. Specifically, the controller starts boiling operation when the system time has elapsed to the boiling start time. The controller may also start boiling operation when a command to start boiling operation is input from the user to the remote control 99. Boiling operation is also performed when the amount of hot water stored in the tank 30 is low. Specifically, the controller starts boiling operation when the temperature detected by the intermediate thermistor 37 falls below a predetermined temperature (for example, 45°C).

[0036] When the boiling operation begins, the controller drives the compressor 10 and fan 15 of the HP device 17 to circulate the refrigerant in the order of compressor 10, condenser 12, expansion valve 14, and evaporator 16, and also drives the circulation pump 18 to circulate water between the tank 30 and the condenser 12. As a result, the water drawn from the lower region of the tank 30 is heated in the condenser 12 to the target boiling temperature and returned to the upper region of the tank 30. The target boiling temperature is set to, for example, 45°C, 50°C, 55°C, or 60°C. When the temperature detected by the lower thermistor 38 reaches the target boiling temperature, the controller stops the compressor 10, fan 15, and circulation pump 18 to terminate the boiling operation. After the boiling operation is completed, the controller may operate the electric heater 39 while the circulation pump 18 is running. As a result, after the boiling operation is completed, the water in the tank 30 may be heated by the electric heater 39.

[0037] (Sterilization Operation) In sterilization operation, the hot water supply system 100 heats the water in the tank 30 to a temperature above a predetermined sterilization standard temperature (for example, 65°C). The sterilization standard temperature is a temperature (for example, 60°C) that is sufficient to kill bacteria (for example, Legionella) in the water. When sterilization operation is started, the controller drives the compressor 10 and fan 15 of the HP device 17 to circulate the refrigerant in the order of compressor 10, condenser 12, expansion valve 14, and evaporator 16, and also drives the circulation pump 18 to circulate water between the tank 30 and the condenser 12. As a result, the water drawn from the bottom of the tank 30 is heated in the condenser 12 to a temperature above the sterilization standard temperature and returned to the top of the tank 30. In sterilization operation, the hot water supply system 100 may heat the water in the tank 30 to a temperature above the sterilization standard temperature in multiple stages. For example, the hot water supply system 100 may, in the first stage, heat the water in the tank 30 to a temperature below the sterilization standard temperature (e.g., 40°C), and in the second stage, heat the water in the tank 30 to a temperature above the sterilization standard temperature (e.g., 65°C).

[0038] The controller repeatedly performs either the first sterilization start process shown in Figure 5 or the second sterilization start process shown in Figure 7 while the hot water supply system 100 is powered on. For example, the controller performs the first sterilization start process if a system time is set, and performs the second sterilization start process if a system time is not set. The first and second sterilization start processes are processes to start the sterilization operation.

[0039] (First sterilization start process; Figure 5) In S2, the controller sets the sterilization start time. Specifically, the controller stores a time that is not included in the prohibited time period as the sterilization start time in memory 152, 156, 160 (see Figures 2, 3, and 4). The controller may also start the sterilization operation in S2 and then set the sterilization start time for the next sterilization operation. After S2, the process proceeds to S4.

[0040] In S4, the controller starts timing using the timer function. The controller stores the timed time in memories 152, 156, and 160 (see FIGS. 2, 3, and 4) as the timed time. After S4, the process proceeds to S6.

[0041] In S6, the controller refers to memories 152, 156, and 160 (see FIGS. 2, 3, and 4) to determine whether the system time has elapsed since the sterilization start time. If the system time has not elapsed since the sterilization start time (in the case of NO), the process proceeds to S8.

[0042] In S8, the controller determines whether the system time has been changed by, for example, an input operation made to the remote controller 99 from the user after the immediately preceding sterilization operation was started. If the system time has not been changed after the immediately preceding sterilization operation was started (in the case of NO), the process returns to S6. If the system time has been changed after the immediately preceding sterilization operation was started (in the case of YES), the process proceeds to S10.

[0043] In S10, the controller determines whether the timed time is equal to or greater than a first predetermined time. The first predetermined time is set to a time during which it is expected that even if the water in the tank 30 is left in a low temperature state (for example, less than 60°C) for that time, the miscellaneous bacteria in the water will not grow significantly. In this embodiment, the first predetermined time is set to 24 hours. If the timed time is less than the first predetermined time (in the case of NO), the process returns to S6.

[0044] If the system time has elapsed since the sterilization start time in S6 (in the case of YES), or if the timed time is equal to or greater than the first predetermined time in S10 (in the case of YES), the process proceeds to S12. In S12, the controller determines whether the temperature detected by the intermediate thermistor 37 (also referred to as the tank temperature) is equal to or greater than a first predetermined temperature. In this embodiment, the first predetermined temperature is the same value as the sterilization reference temperature (for example, 60°C).

[0045] If the tank temperature is less than the first predetermined temperature in S12 (in the case of NO), the process proceeds to S14. In S14, the controller starts the sterilization operation.

[0046] If the tank temperature is equal to or higher than the first predetermined temperature in S12 (YES), the process proceeds to S16. In S16, the controller defers the execution of the sterilization operation.

[0047] After S14 or after S16, the process proceeds to S18. In S18, the controller sets the sterilization start time for the next sterilization operation. The controller stores, in memories 152, 156, 160 (see FIGS. 2, 3, and 4), as the sterilization start time for the next sterilization operation, for example, the time after the first predetermined time of S10 has elapsed from the sterilization start time used in the determination of S6. In this embodiment, the controller stores, in memories 152, 156, 160, as the sterilization start time for the next sterilization operation, the time 24 hours after the sterilization start time used in the determination of S6. Thereby, the sterilization start time can be set at a fixed time of the day. After S18, the process proceeds to S20.

[0048] In S20, the controller resets the time measured and stored in memories 152, 156, 160 (see FIGS. 2, 3, and 4) to zero. After S20, the process returns to S4.

[0049] (Advantages of the First Sterilization Start Process) As shown in Figure 6, if the system time is advanced after the start of the previous sterilization operation, the actual time elapsed from the previous sterilization start time (i.e., the time when the previous sterilization operation started) to the next sterilization start time will be longer than initially expected. In the example in Figure 6, because the system time was advanced by two hours, the actual time elapsed from the previous sterilization start time to the next sterilization start time became 26 hours, which is two hours longer than initially expected (i.e., 24 hours). In this case, if the sterilization operation were to start when the system time had passed the sterilization start time, the sterilization operation would not be performed for a longer period than initially expected. As a result, there is a risk of bacteria growing in the tank 30. However, with the first sterilization start process (see Figure 5), the sterilization operation can be started when the timing reaches the first predetermined time (i.e., 24 hours). This avoids the situation where the sterilization operation is not performed for a longer period than initially expected. This suppresses the growth of bacteria in the tank 30.

[0050] Furthermore, in the example shown in Figure 6, the system time will have passed the sterilization start time two hours after the sterilization operation has started. However, at the time the system time has passed the sterilization start time, the sterilization operation has been performed two hours earlier, so the tank temperature is still high (i.e., above the first predetermined temperature), and it is expected that most of the bacteria in the water will have been killed. According to the first sterilization start process (see Figure 5), in this case, the execution of the sterilization operation is postponed. Moreover, according to the first sterilization start process, the timing is reset and the timing is restarted at the time the execution of the sterilization operation is postponed. This prevents the unnecessary execution of the sterilization operation, thereby preventing the hot water supply system 100 from consuming electricity unnecessarily.

[0051] (Second sterilization start process; Figure 7) In S32, the controller starts timing using the timer function. Alternatively, in S32, the controller may start the sterilization operation and then start timing using the timer function. The controller stores the timed time as the timing time in memories 152, 156, and 160 (see Figures 2, 3, and 4). After S32, the process proceeds to S34.

[0052] In S34, the controller determines whether the time taken is equal to or greater than the second predetermined time. The second predetermined time is set to a time during which, similar to the first predetermined time (see S10 in Figure 5), it is expected that bacteria in the water will not proliferate significantly even if the water in the tank 30 is left at a low temperature (for example, below 60°C) for that time. In this embodiment, the second predetermined time is set to the same value as the first predetermined time (i.e., 24 hours). If the time taken is less than the second predetermined time (NO), the process repeats S34. If the time taken is equal to or greater than the second predetermined time (YES), the process proceeds to S36.

[0053] In S36, the controller determines whether the tank temperature (i.e., the temperature detected by the intermediate thermistor 37) is above the second predetermined temperature. In this embodiment, the second predetermined temperature is the same as the sterilization standard temperature (for example, 60°C), i.e., it is the same as the first predetermined temperature.

[0054] If the tank temperature is below the second predetermined temperature in S36 (NO), the process proceeds to S38. In S38, the controller starts the sterilization operation.

[0055] If the tank temperature is above the second predetermined temperature in S36 (YES), the process proceeds to S40. In S40, the controller postpones the execution of the sterilization operation.

[0056] After S38 or S40, the process proceeds to S42. In S42, the controller resets the timing stored in memories 152, 156, and 160 (see Figures 2, 3, and 4) to zero. After S42, the process returns to S32.

[0057] (Advantages of the second sterilization initiation process) With the second sterilization initiation process, even if the system time is not set and it is not possible to start the sterilization operation based on the sterilization start time, the sterilization operation can be started based on the time measured.

[0058] (Sterilization start time adjustment process; Figure 8) The controller further repeatedly executes the sterilization start time adjustment process shown in Figure 8 while the hot water supply system 100 is powered on. The sterilization start time adjustment process is a process to adjust the sterilization start time in accordance with changes in the prohibited time period.

[0059] In S52, the controller determines whether or not an operation to change the prohibited time period has been performed on the remote control 99. If no operation to change the prohibited time period has been performed (NO), the process repeats S52. If an operation to change the prohibited time period has been performed (YES), the process proceeds to S54.

[0060] In S54, the controller changes the prohibited time period according to the operation performed on the remote control 99. After S54, the process proceeds to S56.

[0061] In S56, the controller determines whether the currently set sterilization start time falls within the prohibited time period after it was changed in S54. If the sterilization start time does not fall within the changed prohibited time period (NO), the process returns to S52. If the sterilization start time falls within the changed prohibited time period (YES), the process proceeds to S58.

[0062] In S58, the controller changes the sterilization start time to a time that is not included in the revised prohibited time period. For example, the controller changes the sterilization start time to the time closest to the current time that is not included in the revised prohibited time period. After S58, the process returns to S52.

[0063] (Advantages of the Sterilization Start Time Adjustment Process) In the example shown in the upper part of Figure 9, the prohibited time period is set to the time from 6:00 to 24:00, and the sterilization start time is set to 4:00. If, for example, the prohibited time period is changed to the time from 0:00 to 6:00 and the time from 12:00 to 24:00, the sterilization start time (i.e., 4:00) will be included in the changed prohibited time period (see the middle part of Figure 9). With the sterilization start time adjustment process, in this case, the sterilization start time can be changed to a time that is not included in the changed prohibited time period (for example, 6:00) (see the lower part of Figure 9). Note that in the example of Figure 9, for clarity, the time period not set as a prohibited time period is shown as a "permitted" time period.

[0064] (Exceptions to the Prohibited Time Period) The process shown in Figure 8 prevents the sterilization start time from being included in the prohibited time period. Therefore, as long as the system time is included in the prohibited time period, the first sterilization start process shown in Figure 5 will not proceed to the process of starting the sterilization operation (i.e., the process in S14) when the system time has passed the sterilization start time (i.e., the result is YES in S6). However, even if the system time is included in the prohibited time period, the process of starting the sterilization operation (i.e., the process in S14) may be reached when the timing time exceeds the first predetermined time (i.e., the result is YES in S10). In this case, the controller of this embodiment is configured to exceptionally operate the HP device 17 and start the sterilization operation, even though the system time is included in the prohibited time period. With this configuration, it is possible to suppress the time from the previous sterilization start time to the next sterilization start time from exceeding the first predetermined time (i.e., the time in which it is expected that bacteria in the water will not proliferate to a considerable extent even if the water in the tank 30 is left at a low temperature). This makes it possible to suppress the proliferation of bacteria in the tank 30.

[0065] (Notification function of remote control 99) The remote control 99 notifies the timing of when the next sterilization operation will start via the display unit 166 and / or the sound unit 168. For example, the remote control 99 notifies the next sterilization start time, the time difference from the current system time to the next sterilization start time, and / or the time obtained by subtracting the current timing from a first predetermined time, as the timing of when the next sterilization operation will start.

[0066] (Modification) The hot water supply system 100 may also be equipped with a heat source device other than the HP device 17 (for example, a burner that burns fuel) as a heat source device for heating the water in the tank 30 during sterilization operation.

[0067] In the sterilization operation, the hot water supply system 100 may heat the water in the tank 30 using an electric heater 39 instead of using the HP device 17. Alternatively, the hot water supply system 100 may heat the water in the tank 30 using both the HP device 17 and the electric heater 39 in the sterilization operation. In this case, the controller may operate the HP device 17 and the electric heater 39 alternately, or operate the HP device 17 and the electric heater 39 simultaneously during the sterilization operation.

[0068] The hot water supply system 100 may be configured to heat almost all of the water in the tank 30 to a temperature equal to or higher than the sterilization reference temperature during sterilization operation. Specifically, the controller may be configured to terminate heating by the HP device 17 when the temperature detected by the lower thermistor 38 (or supply thermistor 20) reaches a temperature equal to or higher than the sterilization reference temperature during sterilization operation. In this example, in S12 of the first sterilization initiation process shown in Figure 5, and S36 of the second sterilization initiation process shown in Figure 7, the controller may refer to the temperature detected by the lower thermistor 38 (or supply thermistor 20) as the tank temperature.

[0069] The cycle for initiating sterilization operation of the hot water supply system 100 is not limited to a 24-hour cycle. The cycle for initiating sterilization operation of the hot water supply system 100 may be, for example, a 100-hour cycle or a 1-week cycle. Specifically, in S18 of the first sterilization initiation process shown in Figure 5, the controller may set the time 100 hours (or 1 week) after the sterilization initiation time set for the previous sterilization operation as the next sterilization initiation time. Furthermore, the first predetermined time (see S10 in Figure 5) and the second predetermined time (see S34 in Figure 7) may be set to 100 hours (or 1 week).

[0070] In the first sterilization initiation process shown in Figure 5 and / or the second sterilization initiation process shown in Figure 7, the controller may start (or reset) the timer at another point after the sterilization operation has started (for example, when the sterilization operation has finished), instead of starting (or resetting) the timer when the sterilization operation has started.

[0071] In the first sterilization initiation process shown in Figure 5, if the controller is NO in S6, it may skip S8 and execute S10. In other words, the controller may start the sterilization operation if the timing time is equal to or greater than the first predetermined time (i.e., YES in S10) and the tank temperature is below the first predetermined temperature (i.e., NO in S12), regardless of whether the system time has been changed or not.

[0072] In the first sterilization initiation process shown in Figure 5, the controller may skip S12 and execute S14 if the answer is YES at S6 or S10. In other words, the controller may start the sterilization operation regardless of the tank temperature if the system time has elapsed past the sterilization start time (i.e., YES at S6) or if the timing time is equal to or greater than the first predetermined time (i.e., YES at S10). Similarly, in the second sterilization initiation process shown in Figure 7, the controller may skip S36 and execute S38 if the answer is YES at S34. In other words, the controller may start the sterilization operation regardless of the tank temperature if the timing time is equal to or greater than the second predetermined time (i.e., YES at S34).

[0073] If the system time falls within the prohibited time period while the first sterilization start process shown in Figure 5 is being executed, the controller may postpone the execution of the sterilization operation even if the process reaches S14. In other words, if the system time falls within the prohibited time period, the controller does not need to start the sterilization operation even if the timekeeping period is longer than the first predetermined time.

[0074] The sterilization start time may be set by the controller on behalf of the user. For example, the controller may set the sterilization start time based on the sterilization end time (i.e., the time when the sterilization operation ends) set by the user. In this case, the controller may set the sterilization start time so that the sterilization operation ends at the sterilization end time, taking into account the time required for the sterilization operation.

[0075] (Correspondence) In the embodiment, the hot water supply system 100 is an example of a "hot water supply system". The tank 30 is an example of a "hot water storage tank". The HP device 17 is an example of a "heat source device". The controller is an example of a "control unit". The memories 152, 156, 160 and the processors 154, 158, 162 are examples of a "time setting unit", a "sterilization schedule setting unit", and a "timing unit", respectively. The first predetermined time and the second predetermined time are examples of "predetermined time", respectively. The judgment condition in S6 of the first sterilization start process is an example of a "first condition". The judgment condition in S10 of the first sterilization start process and the judgment condition in S34 of the second sterilization start process are examples of "second conditions", respectively. The forward thermistor 20, the return thermistor 22, the intermediate thermistor 37, and the lower thermistor 38 are examples of "temperature sensors", respectively. The first predetermined temperature and the second predetermined temperature are examples of "predetermined temperature", respectively. Remote control 99 is an example of a "notification unit".

Claims

1. A hot water supply system comprising: a hot water storage tank for storing water to be supplied to a predetermined hot water supply location; a heat source device for heating the water stored in the hot water storage tank; and a control unit, wherein the control unit is configured to operate the heat source device and perform a sterilization operation to heat at least a portion of the water stored in the hot water storage tank to a temperature equal to or higher than a predetermined sterilization standard temperature, wherein the control unit comprises: a time setting unit for setting the system time in the hot water supply system; a sterilization start time setting unit for setting the system time, which is the time at which the next sterilization operation will be started; and a timing unit for measuring the elapsed time from a predetermined point in time since the time at which the previous sterilization operation was started, wherein the control unit starts the sterilization operation when at least one of the following conditions is met: a first condition that the system time has elapsed to the sterilization start time, and a second condition that the time measured by the timing unit is equal to or greater than a predetermined time.

2. The hot water supply system according to claim 1, wherein a time within a predetermined time period of the day is set as the sterilization start time.

3. The hot water supply system according to claim 1 or 2, wherein the control unit starts the sterilization operation when the second condition is met, regardless of whether the first condition is met or not, if the system time is not set.

4. The hot water supply system according to any one of claims 1 to 3, wherein the control unit starts the sterilization operation when the first condition is met, regardless of whether the second condition is met, if the system time has not been changed since the start of the previous sterilization operation, and the control unit starts the sterilization operation when either the first condition or the second condition is met, if the system time has been changed since the start of the previous sterilization operation.

5. The hot water supply system further comprises a temperature sensor for detecting the temperature of water stored in the hot water storage tank, wherein if at least one of the first and second conditions is met, but the temperature detected by the temperature sensor is above a predetermined temperature, the control unit does not start the sterilization operation, and if at least one of the first and second conditions is met and the temperature detected by the temperature sensor is below the predetermined temperature, the control unit starts the sterilization operation, according to any one of claims 1 to 4.

6. The hot water supply system according to claim 5, wherein when at least one of the first and second conditions is met, and the temperature detected by the temperature sensor is equal to or greater than the predetermined temperature, the control unit resets the time measured by the timing unit and then restarts the timing by the timing unit.

7. The hot water supply system according to any one of claims 1 to 6, further comprising a notification unit that notifies the timing of when the sterilization operation will be started next time.

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