Water heater

Abstract

To provide a technique which can restrict energy consumption of an auxiliary heat source machine, when an upper limit of electric power consumption of a heat pump is set.SOLUTION: If a restriction mode is set, a controlling unit prohibits an execution of a sterilization operation, when an upper limit of electric power consumption of a heat pump is set below a predetermined reference value, and permits the execution of the sterilization operation, when the upper limit of electric power consumption of the heat pump is set to the reference value or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a water heater. [Background technology]

[0002] Patent Document 1 discloses a technology for executing a sterilization operation when a predetermined sterilization condition is met in order to sterilize the water in a hot water storage tank. In the technology of Patent Document 1, when the sterilization condition is met, hot water is prohibited from being discharged from the hot water storage tank to the hot water supply point so that the water in the hot water storage tank is not supplied to the hot water supply point. The sterilization operation of Patent Document 1 includes a high-temperature heating process in which the water in the hot water storage tank is heated to a high temperature by a heat pump. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-191493 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the sterilization operation for sterilizing the water in the hot water storage tank, the water in the hot water storage tank is heated to a high temperature by the heat pump, so the power consumption of the heat pump becomes large.

[0005] Here, in a water heater equipped with a heat pump, an upper limit of the power consumption of the heat pump may be set. In this case, if a sterilization operation is performed with the upper limit of the power consumption of the heat pump set, the power consumption of the heat pump is suppressed, and it takes time to heat the water in the hot water storage tank to a high temperature during the sterilization operation. As a result, it takes a long time to complete the sterilization operation.

[0006] In addition, since hot water is prohibited from being discharged from the hot water storage tank to the hot water supply point during sterilization operation, in order to supply high-temperature water to the hot water supply point, the water supplied to the hot water supply point from a water supply source other than the hot water storage tank must be heated by an auxiliary heat source device other than a heat pump. In a state in which it takes a long time to complete the sterilization operation, there are many opportunities to heat water by the auxiliary heat source device, which causes a problem of increased energy consumption by the auxiliary heat source device.

[0007] In addition, when setting an upper limit on the power consumption of the heat pump, it is possible to prohibit the execution of sterilization operation even if the sterilization implementation condition is met. Even in this case, since the supply of hot water from the hot water storage tank to the hot water supply point is prohibited when the sterilization implementation condition is met, in order to supply high-temperature water to the hot water supply point, the water supplied to the hot water supply point from a water supply source other than the hot water storage tank needs to be heated by an auxiliary heat source device other than the heat pump. This causes a problem of increased energy consumption in the auxiliary heat source device.

[0008] Typically, the energy efficiency of an auxiliary heat source unit is lower than the energy efficiency of a heat pump. Therefore, even if an upper limit is set on the power consumption of the heat pump, it is possible that the energy efficiency of the water heater will decrease due to energy consumption by the auxiliary heat source unit.

[0009] This specification provides a technique that can suppress energy consumption in an auxiliary heat source unit when an upper limit value for power consumption of a heat pump is set. [Means for solving the problem]

[0010] In a first aspect of the present technology, a water heater may include a hot water storage tank, a heat pump for heating water in the hot water storage tank, an auxiliary heat source unit capable of heating water drawn from the hot water storage tank and supplied to a hot water supply location, and water supplied to the hot water supply location from a water supply source other than the hot water storage tank, and a control unit. The control unit may be capable of executing a sterilization operation in which the water in the hot water storage tank is heated by the heat pump to a temperature equal to or higher than a predetermined sterilization reference temperature in order to sterilize the water in the hot water storage tank in a state in which water is not supplied from the hot water storage tank to the hot water supply location, and may be capable of setting a normal mode in which an upper limit value of the power consumption of the heat pump is not set, and a suppression mode in which an upper limit value of the power consumption of the heat pump is set. The control unit may be configured to set an upper limit value of the power consumption of the heat pump in the suppression mode according to the power consumption of elements in the water heater other than the heat pump, and to operate the heat pump so that the power consumption of the heat pump is less than the set upper limit value. When setting the suppression mode, the control unit may prohibit execution of the sterilization operation if the upper limit value of the power consumption of the heat pump is set to less than a predetermined reference value, and may permit execution of the sterilization operation if the upper limit value of the power consumption of the heat pump is set to equal to or greater than the reference value.

[0011] In the suppression mode in which the upper limit of the power consumption of the heat pump is set, if the sterilization operation is always prohibited when the sterilization execution condition is satisfied, water cannot be supplied from the hot water storage tank to the hot water supply location, and the auxiliary heat source unit has many opportunities to heat water. In contrast, according to the above configuration, when the upper limit of the power consumption of the heat pump is set to a value less than the reference value in the suppression mode, the sterilization operation is prohibited from being performed, so that the sterilization operation, which takes time, can be avoided. On the other hand, when the upper limit of the power consumption of the heat pump is set to a value equal to or greater than the reference value in the suppression mode, the sterilization operation is permitted to be performed, so that the upper limit of the power consumption is relatively relaxed even when the sterilization operation is performed in the suppression mode, and the time required for the sterilization operation can be shortened. This reduces the opportunities for heating water by the auxiliary heat source unit during the execution of the sterilization operation, and suppresses energy consumption in the auxiliary heat source unit.

[0012] In a second aspect, in the first aspect described above, when setting the suppression mode, the control unit may allow the sterilization operation to be performed when the upper limit value of the power consumption of the heat pump is set to be equal to or higher than the reference value and when the time to start the sterilization operation is a time when there are few opportunities for water to be supplied to the hot water supply location.

[0013] For example, since there are few opportunities for water to be supplied to the hot water supply point at night, the above configuration allows the sterilization operation to be performed when there are few opportunities for water to be supplied to the hot water supply point. This reduces the opportunities for heating water by the auxiliary heat source unit during the execution of the sterilization operation, and suppresses energy consumption by the auxiliary heat source unit. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a storage type water heater according to an embodiment of the present invention. [Diagram 2] 1 is a flowchart of a sterilization operation process in an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] (Storage type water heater 104) As shown in FIG. 1, a storage type water heater 104 of the embodiment includes an HP (heat pump) unit 4, a tank unit 6, and a burner unit 8.

[0016] (HP unit 4) The HP unit 4 is a heat source that uses electric power to absorb heat from outside air and heat water. The HP unit 4 includes an HP heat source 17 that includes a compressor 10, a condenser 12, an expansion valve 14, and an evaporator 16. The HP unit 4 absorbs heat from outside air and heats water by circulating a refrigerant (e.g., a fluorocarbon-based refrigerant) through the compressor 10, the condenser 12, the expansion valve 14, and the evaporator 16 in that order. 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. An HP forward path 19 and an HP return path 21 are connected to both ends of the water flow path of the condenser 12, respectively. The expansion valve 14 depressurizes the refrigerant to make it low temperature and low pressure. The evaporator 16 heats the refrigerant by heat exchange with outside air. The HP unit 4 further includes a circulation pump 18 that circulates water through the condenser 12, a feed thermistor 20 that detects the temperature of the water flowing into the condenser 12, a return thermistor 22 that detects the temperature of the water flowing out of the condenser 12, an outdoor air temperature thermistor 23 that detects the outdoor air temperature, and an HP controller 24 that controls the operation of each component of the HP unit 4.

[0017] (Tank Unit 6) The tank unit 6 includes a hot water storage tank (hereinafter referred to as "tank") 30, a mixing valve 32, and a bypass control valve 34. The tank 30 is a sealed container that is covered with a heat insulating material on the outside and stores water inside. The capacity of the tank 30 in this embodiment is, for example, 100 liters. When the circulation pump 18 of the HP unit 4 is driven, the water at the bottom of the tank 30 is sent to the condenser 12 via the tank forward path 31 and the HP forward path 19. The water heated in the condenser 12 and heated to a high temperature is returned from the top of the tank 30 to the inside 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 stratification is formed inside the tank 30, in which a layer of high temperature water is piled up on a layer of low temperature water. The tank 30 is equipped with an upper thermistor 36 that detects the temperature of the upper water, an intermediate thermistor 37 that detects the temperature of the intermediate water, and a lower thermistor 38 that detects the temperature of the lower water.

[0018] The tank unit 6 is supplied with tap water from, for example, a waterworks (an example of a water supply source other than a hot water tank) via a water supply path 40. A pressure reducing valve 42 for reducing the water supply pressure and a water inlet thermistor 44 for detecting the water supply temperature are attached to the water supply path 40. The water supply path 40 branches into a tank water supply path 46 that communicates with the bottom of the tank 30 and a tank bypass path 48 that communicates with the mixing valve 32. Check valves 50 and 52 are attached to the tank water supply path 46 and the tank bypass path 48, respectively. A water-side water volume sensor 54 for detecting the flow rate of tap water flowing into the mixing valve 32 is attached to the tank bypass path 48. The top of the tank 30 and the mixing valve 32 are connected via a tank hot water outlet path 56. A check valve 58 and a hot water volume sensor 60 for detecting the flow rate of water from the tank 30 that flows into the mixing valve 32 are attached to the tank hot water outlet path 56.

[0019] The mixing valve 32 mixes tap water flowing in from the tank bypass path 48 and water from the tank 30 flowing in from the tank hot water outlet path 56, and sends the mixed water to a first hot water supply path 62. The mixing valve 32 drives a valve body by a stepping motor (not shown) and adjusts the opening degree on the tank bypass path 48 side (opening degree on the water side) and the opening degree on the tank outlet path 56 side (opening degree on the hot water side). A mixing thermistor 64 that detects the temperature of the water sent out from the mixing valve 32 is attached to the first hot water supply path 62.

[0020] Hot water is supplied from the tank unit 6 to hot water supply locations such as a kitchen, shower, and faucet via a second hot water supply path 66. A hot water supply outlet thermistor 68 for detecting the temperature of water supplied to the hot water supply location, and a check valve 70 are attached to the second hot water supply path 66. The first hot water supply path 62 and the second hot water supply path 66 are connected by a hot water supply bypass path 72. A bypass control valve 34 is attached to the hot water supply bypass path 72. The tank unit 6 further includes a tank controller 74 for controlling the operation of each component of the tank unit 6.

[0021] (Burner unit 8) The burner unit 8 includes a burner 80, a heat exchanger 82, a bypass servo 84, a water volume servo 86, and a water filling valve 88. The burner 80 is an auxiliary heat source device that heats water flowing through the heat exchanger 82 by burning fuel gas (e.g., city gas). Fuel gas is supplied to the burner 80 through a gas supply pipe (not shown). Water flows into the heat exchanger 82 from the first hot water supply path 62 of the tank unit 6 through a burner forward path 90. The water that has passed through the heat exchanger 82 flows out to the second hot water supply path 66 of the tank unit 6 through a burner return path 92. The burner forward path 90 is equipped with a water volume servo 86 that adjusts the flow rate of water flowing through the burner forward path 90 and a water volume sensor 91 that detects the flow rate of water flowing through the burner forward path 90. The burner forward path 90 and the burner return path 92 are connected through a burner bypass path 94. A bypass servo 84 is attached to the connection between the burner outward path 90 and the burner bypass path 94. The bypass servo 84 adjusts the flow rate of water flowing from the burner outward path 90 to the burner bypass path 94. A burner hot water thermistor 96 that detects the temperature of the water flowing out from the heat exchanger 82 is attached to the burner return path 92. A water filling path 98 branches off from the burner return path 92. A water filling valve 88 is attached to the water filling path 98. Water is filled into the bathtub, which is the hot water supply point, from the burner unit 8 via the water filling path 98.

[0022] The burner unit 8 further includes a burner controller 97 and a remote control 99 capable of communicating with the burner controller 97. The burner controller 97 controls the operation of each component of the burner unit 8. The remote control 99 accepts various operational inputs from the user via switches, buttons, etc. The remote control 99 also notifies the user of various information related to the settings and operation of the storage type water heater 104 by display and voice.

[0023] The HP controller 24, the tank controller 74, the burner controller 97, and the remote control 99 each include a control unit such as a CPU, a ROM, and a RAM, and a storage unit such as an EEPROM, and the control unit executes various processes according to the programs stored in the storage unit. The HP controller 24 and the tank controller 74 can communicate with each other. The tank controller 74 and the burner controller 97 can communicate with each other. Therefore, the HP controller 24, the tank controller 74, and the burner controller 97 cooperate to perform control, and the hot water storage type water heater 104 can perform various operations such as boiling operation, hot water supply operation, and sterilization operation. Hereinafter, the HP controller 24, the tank controller 74, and the burner controller 97 are collectively referred to simply as controllers (an example of a control unit).

[0024] (Boiling operation) In the boiling operation, the storage type water heater 104 drives the HP unit 4 to heat the water in the tank 30. When the boiling operation is started, the controller drives the compressor 10 of the HP heat source 17 to circulate the refrigerant through the compressor 10, the condenser 12, the expansion valve 14, and the evaporator 16 in that order, and drives the circulation pump 18 to circulate the water between the tank 30 and the condenser 12. As a result, the water sucked out from the bottom of the tank 30 is heated to the boiling target temperature in the condenser 12 and returned to the top of the tank 30. When the temperature detected by the forward thermistor 20 reaches the boiling target temperature, the controller determines that all the water in the tank 30 has been replaced with water heated to the boiling target temperature, and ends the boiling operation.

[0025] The boiling operation is performed periodically, for example. Specifically, the controller starts the boiling operation when a predetermined boiling start time arrives. The controller may also start the boiling operation when a user inputs an instruction to start the boiling operation. The boiling operation is performed, for example, when a large amount of hot water flows out of the tank 30 as a result of the bathtub being filled with hot water. Specifically, the controller starts the boiling operation when the flow rate detected by the hot water side water volume sensor 60 is equal to or greater than a predetermined reference flow rate. The boiling operation is performed, for example, when the amount of hot water stored in the tank 30 is small. Specifically, the controller starts the boiling operation when the temperature detected by the upper thermistor 36 is lower than the hot water supply setting temperature.

[0026] (Hot water supply operation) In hot water supply operation, the storage type water heater 104 supplies water at the hot water supply setting temperature to the hot water supply location. The hot water supply setting temperature is a temperature set by the user. When the combined flow rate (also called the hot water supply flow rate) of the flow rate detected by the water side water flow sensor 54 and the flow rate detected by the hot water side water flow sensor 60 reaches or exceeds the minimum operating flow rate, the controller determines that hot water supply to the hot water supply location has started by opening the faucet or filling the bathtub with water. Depending on the temperature detected by the upper thermistor 36, the controller executes the following non-combustion hot water supply operation or combustion hot water supply operation.

[0027] The controller executes non-combustion hot water supply operation when the temperature detected by the upper thermistor 36 is equal to or higher than the hot water supply set temperature. In non-combustion hot water supply operation, the controller prohibits the combustion operation of the burner 80 and adjusts the opening of the mixing valve 32 so that the temperature detected by the mixing thermistor 64 becomes the hot water supply set temperature. As a result, water whose temperature has been adjusted to the hot water supply set temperature is supplied to the hot water supply location.

[0028] Moreover, when the temperature detected by the upper thermistor 36 is lower than the hot water supply set temperature, the controller executes the combustion hot water supply operation. In the combustion hot water supply operation, the controller permits the combustion operation of the burner 80 and adjusts the opening of the mixing valve 32 so that the temperature detected by the mixing thermistor 64 is lower than the hot water supply set temperature by the minimum heating capacity of the burner 80. In this case, the high-temperature water supplied from the upper part of the tank 30 and the low-temperature water supplied from the water supply path 40 are mixed in the mixing valve 32, heated to the hot water supply set temperature by the burner 80, and supplied to the hot water supply location. The controller adjusts the heating capacity of the burner 80 so that the water heated by the burner 80 becomes the hot water supply set temperature. The combustion hot water supply operation also includes a case where the opening of the mixing valve 32 on the tank hot water outlet path 56 side (opening on the hot water side) is fully closed. That is, a case where water is not supplied from the tank 30 and only the water supplied from the water supply path 40 is heated by the burner 80 is also included.

[0029] If the hot water flow rate falls below the minimum operating flow rate while the above-mentioned non-combustion hot water supply operation or combustion hot water supply operation is being performed, the controller determines that hot water supply to the hot water supply point has ended due to the faucet being closed or the bathtub being filled with water, for example, and ends the hot water supply operation.

[0030] (Sterilization operation) In the sterilization operation, the storage type water heater 104 heats the water in the tank 30 to a temperature equal to or higher than a predetermined sterilization reference temperature (for example, 65°C). The sterilization reference temperature is a temperature higher than the boiling target temperature in the boiling operation described above. When the sterilization operation is started, the controller drives the compressor 10 of the HP heat source 17 to circulate the refrigerant through the compressor 10, the condenser 12, the expansion valve 14, and the evaporator 16 in that order, and drives the circulation pump 18 to circulate the water between the tank 30 and the condenser 12. As a result, the water sucked out from the bottom of the tank 30 is heated in the condenser 12 to a temperature equal to or higher than the sterilization reference temperature and returned to the top of the tank 30. In the sterilization operation, the storage type water heater 104 may heat the water in the tank 30 to a temperature equal to or higher than the sterilization reference temperature in a plurality of stages. For example, the storage type water heater 104 may heat the water in the tank 30 to a temperature below the sterilization reference temperature (e.g., 40°C) in the first stage, and heat the water in the tank 30 to a temperature equal to or higher than the sterilization reference temperature (e.g., 65°C) in the second stage. When the temperature detected by the outgoing thermistor 20 reaches a temperature equal to or higher than the sterilization reference temperature, the controller determines that all of the water in the tank 30 has been heated to a temperature equal to or higher than the sterilization reference temperature, and ends heating by the HP heat source 17.

[0031] Furthermore, in the sterilization operation, the controller may resume heating by the HP heat source 17 when the temperature detected by the lower thermistor 38 at the bottom of the tank 30 drops to a temperature below the sterilization reference temperature. This maintains the temperature of the water in the tank 30 at or above the sterilization reference temperature. The hot water storage type water heater 104 can maintain the state in which the temperature of the water in the tank 30 is at or above the sterilization reference temperature for a predetermined period of time (e.g., two hours) or more. This allows the water in the tank 30 to be sterilized.

[0032] The above sterilization operation is performed in a state where water in the tank 30 is not supplied to the hot water supply point. Specifically, in the sterilization operation, the controller fully closes the opening of the tank hot water outlet path 56 side (opening on the hot water side) of the mixing valve 32. This prohibits water from being supplied from the tank 30 to the hot water supply point. If a hot water supply operation is performed while the sterilization operation is being performed, a combustion hot water supply operation is performed. In the combustion hot water supply operation while the sterilization operation is being performed, water is not supplied from the tank 30, and only the water supplied from the water supply path 40 is heated by the burner 80.

[0033] (Normal mode, Suppression mode) In the storage type water heater 104 of the embodiment, a normal mode or a suppression mode is set as the mode of power consumption during operation. The normal mode is a mode in which an upper limit value of the power consumption of the HP unit 4 is not set. In the normal mode, the storage type water heater 104 is capable of performing boiling operation and sterilization operation. In the boiling operation and sterilization operation in the normal mode, the storage type water heater 104 heats the water in the tank 30 in a state in which an upper limit value of the power consumption of the HP unit 4 is not set. The HP unit 4 consumes power, for example, in the compressor 10 and the circulation pump 18.

[0034] The suppression mode is a mode in which an upper limit value of the power consumption of the HP unit 4 is set. In boiling operation and sterilization operation in the suppression mode, the storage type water heater 104 heats the water in the tank 30 in a state in which an upper limit value of the power consumption of the HP unit 4 is set. The upper limit value of the power consumption of the HP unit 4 in the suppression mode is configurable. For example, the controller sets and changes the upper limit value of the power consumption of the HP unit 4 in the suppression mode according to the power consumption of the tank unit 6 and the power consumption of the burner unit 8. The controller changes the upper limit value of the power consumption of the HP unit 4 at a predetermined time interval (for example, 10 second intervals), for example. The controller may sequentially change the upper limit value of the power consumption of the HP unit 4 in the suppression mode, for example, every time the power consumption of the tank unit 6 and / or the power consumption of the burner unit 8 changes.

[0035] The storage type water heater 104 can perform boiling operation within a limited range in the suppression mode. When performing boiling operation in the suppression mode, the controller controls the operation of the HP unit 4 so that the power consumption of the HP unit 4 is less than a set upper limit value.

[0036] Furthermore, in the suppression mode, the storage type water heater 104 can perform a sterilization operation only when the set upper limit value of the power consumption of the HP unit 4 is equal to or greater than a predetermined reference value. When performing a sterilization operation in the suppression mode, the controller controls the operation of the HP unit 4 so that the power consumption of the HP unit 4 is less than the set upper limit value (an upper limit value equal to or greater than a predetermined reference value).

[0037] On the other hand, in the suppression mode, the storage type water heater 104 cannot perform the sterilization operation if the set upper limit value of the power consumption of the HP unit 4 is less than the predetermined reference value. The controller prohibits the execution of the sterilization operation if the set upper limit value of the power consumption of the HP unit 4 is less than the predetermined reference value.

[0038] The controller sets either a normal mode or a suppression mode in controlling the storage type water heater 104. For example, the controller sets the normal mode when the storage type water heater 104 is connected to a storage battery and the amount of electricity stored in the storage battery is equal to or greater than a predetermined reference amount. On the other hand, the controller sets the suppression mode when the amount of electricity stored in the storage battery is less than a predetermined reference amount. When the controller sets the normal mode, for example, the controller generates information indicating that the normal mode is set (for example, a normal mode flag) and stores this in the storage unit of the controller. When the controller sets the suppression mode, for example, the controller generates information indicating that the suppression mode is set (for example, a suppression mode flag) and stores this in the storage unit of the controller.

[0039] In a modified example, the suppression mode may be set regardless of the amount of electricity stored in the storage battery. For example, the controller may set the suppression mode according to the supply and demand situation of electricity at a power company. In addition, the controller may set the suppression mode in the storage type water heater 104 in order to supply electricity to other devices when other devices are connected to the storage battery, for example. In addition, the controller may set the suppression mode in the storage type water heater 104 according to an instruction from a user or the operating status of the storage type water heater 104.

[0040] (Sterilization process; Figure 2) Next, the sterilization operation process executed by the controller will be described. The sterilization operation process is started, for example, when the power supply of the storage type water heater 104 is turned on. As shown in FIG. 2, in S10 of the sterilization operation process, the controller monitors whether or not the execution condition of the sterilization operation is satisfied. The execution condition of the sterilization operation is satisfied, for example, when a predetermined time (for example, 100 hours) has passed since the previous sterilization operation ended. In a modified example, the execution condition of the sterilization operation may be satisfied when a predetermined time (for example, 1:00) of a day arrives. In another modified example, the execution condition of the sterilization operation may be satisfied when a start instruction of the sterilization operation is input by a user operation. If the execution condition of the sterilization operation is satisfied (YES in S10), the process proceeds to S12, and if the execution condition is not satisfied (NO in S10), the process of S10 continues.

[0041] In S12, the controller fully closes the opening degree of the tank hot water outlet path 56 side (hot water side opening degree) of the mixing valve 32. This prohibits water from being supplied from the tank 30 to the hot water supply point.

[0042] In the next step S14, the controller determines whether or not suppression mode is set in the storage type water heater 104. The suppression mode is a mode in which an upper limit value for power consumption of the HP unit 4 is set. The controller determines that the suppression mode is set, for example, if a suppression mode flag exists in the memory unit. If the suppression mode is set (YES in S14), the process proceeds to S16, and if it is not set (NO in S14), the process proceeds to S30. In this embodiment, if the suppression mode is not set, the normal mode is set.

[0043] In S30 after NO in S14, the controller permits the storage type water heater 104 to perform a sterilization operation, and performs the sterilization operation. When the sterilization operation is performed, the water in the tank 30 is heated by the HP unit 4 to a temperature equal to or higher than a predetermined sterilization reference temperature (for example, 65°C) without water being supplied from the tank 30 to the hot water supply point.

[0044] In the next step S32, the controller judges whether the sterilization operation has been completed. For example, if a predetermined time (e.g., 3 hours) has passed since the start of the sterilization operation without the sterilization operation being stopped, the sterilization operation is judged to be completed. If it is judged that the sterilization operation has been completed (YES in S32), the process proceeds to S34. If it is judged that the sterilization operation has not been completed (NO in S32), the process returns to S30 and the sterilization operation continues.

[0045] In S34, the controller releases the fully closed state of the tank hot water outlet path 56 side (hot water side opening) of the mixing valve 32. This makes it possible to supply water to the hot water supply point from the tank 30. After that, the process returns to S10.

[0046] In S16 after YES in S14 above, the controller determines whether or not the upper limit of power consumption of the HP unit 4 set in suppression mode is equal to or greater than a predetermined reference value (condition 1). If the upper limit of power consumption of the HP unit 4 set in suppression mode is equal to or greater than the predetermined reference value (YES in S16), the process proceeds to S18, and if it is less than the predetermined reference value (NO in S16), the process proceeds to S24.

[0047] In S16 of the modified example, the controller may determine whether the start time of the sterilization operation (i.e., the time when the execution condition of the sterilization operation is established in S10 above) is a time when there are few opportunities for water to be supplied to the hot water supply location (for example, between 22:00 and 6:00) (Condition 2). The time when there are few opportunities for water to be supplied to the hot water supply location is, for example, a time at night. The time when there are few opportunities for water to be supplied to the hot water supply location may also be set by the user. The time when there are few opportunities for water to be supplied to the hot water supply location may also be set by learning the hot water supply history. If the above Conditions 1 and 2 are determined to be positive, that is, if the upper limit value of the power consumption of the HP unit 4 set in the suppression mode is equal to or greater than a predetermined reference value and the start time of the sterilization operation is a time at night (YES in S16 of the modified example), the process proceeds to S18. On the other hand, if the determination of Condition 1 or Condition 2 is negative (NO in S16 of the modified example), the process proceeds to S24.

[0048] In S18 after YES in S16, the controller permits the storage type water heater 104 to perform a sterilization operation, and performs the sterilization operation. When performing the sterilization operation, the controller operates the HP unit 4 so that the power consumption of the HP unit 4 is less than the upper limit value set in the suppression mode. When the sterilization operation is performed, the water in the tank 30 is heated by the HP unit 4 to a temperature equal to or higher than a predetermined sterilization reference temperature (for example, 65°C) without water being supplied from the tank 30 to the hot water supply location.

[0049] In the next S20, the controller judges whether the sterilization operation is completed. If the answer is YES in S20, the process proceeds to S26, and if the answer is NO in S20, the process proceeds to S22. Note that the process of S20 is the same as the process of S32 described above, and therefore a detailed description thereof will be omitted.

[0050] In S26, the controller releases the fully closed state of the tank hot water outlet path 56 side (hot water side opening) of the mixing valve 32. This makes it possible to supply water to the hot water supply point from the tank 30. After that, the process returns to S10.

[0051] In S22 after NO in S20, the controller judges whether the upper limit value of the power consumption of the HP unit 4 set in the suppression mode is less than a predetermined reference value. The controller sets the upper limit value of the power consumption of the HP unit 4 in the suppression mode, for example, according to the power consumption of the tank unit 6 and the power consumption of the burner unit 8. Therefore, the upper limit value of the power consumption of the HP unit 4 set in the suppression mode may fluctuate. If the upper limit value of the power consumption of the HP unit 4 set in the suppression mode is less than the predetermined reference value (YES in S22), the process proceeds to S24. If not, that is, if the state in which the upper limit value of the power consumption of the HP unit 4 set in the suppression mode is equal to or greater than the predetermined reference value is maintained (NO in S22), the process returns to S18, and the sterilization operation is continued.

[0052] In S24 after YES in S22 or NO in S16, the controller prohibits the execution of sterilization operation in the suppression mode. Therefore, the hot water storage type water heater 104 does not execute sterilization operation (if sterilization operation is already being executed, the sterilization operation being executed is stopped). Then, the process returns to S10.

[0053] The above describes the storage type water heater 104 of the embodiment. As described above, when the sterilization execution condition is satisfied, the storage type water heater 104 prohibits water from being supplied from the tank 30 to the hot water supply point, and can execute a sterilization operation in which the water in the tank 30 is heated to a temperature equal to or higher than a predetermined sterilization reference temperature by the HP unit 4 in order to sterilize the water in the tank 30. When the suppression mode is set in the storage type water heater 104, if the upper limit value of the power consumption of the HP unit 4 is set to less than a predetermined reference value, the controller prohibits the execution of the sterilization operation (see S24 in FIG. 2). On the other hand, when the upper limit value of the power consumption of the HP unit 4 is set to a predetermined reference value or more in the suppression mode, the controller allows the execution of the sterilization operation (see S18 in FIG. 2).

[0054] In the suppression mode in which the upper limit of the power consumption of the HP unit 4 is set, if the sterilization operation is always prohibited when the sterilization execution condition is satisfied, water cannot be supplied from the tank 30 to the hot water supply location, and the opportunities for heating water by the burner 80 are increased. In contrast, according to the above configuration, when the upper limit of the power consumption of the HP unit 4 is set to a value less than the reference value in the suppression mode, the sterilization operation is prohibited from being performed, so that the sterilization operation that takes time can be avoided. On the other hand, when the upper limit of the power consumption of the HP unit 4 is set to a value equal to or greater than the reference value in the suppression mode, the sterilization operation is permitted to be performed, so that the upper limit of the power consumption is relatively relaxed even when the sterilization operation is performed in the suppression mode, and the time required for the sterilization operation can be shortened. This reduces the opportunities for heating water by the burner 80 during the execution of the sterilization operation, and the energy consumption by the burner 80 can be suppressed.

[0055] Furthermore, when setting the suppression mode, the controller permits the execution of sterilization operation if the upper limit value of power consumption of the HP unit 4 is set to a reference value or higher and the time to start the sterilization operation is during the night.

[0056] Since there are few opportunities for water to be supplied to the hot water supply point at night, the above configuration allows the sterilization operation to be performed when there are few opportunities for water to be supplied to the hot water supply point. This reduces the opportunities for heating water by the burner 80 during the sterilization operation, and reduces energy consumption by the burner 80.

[0057] (Modification) (1) The storage type water heater 104 may have one or more modes other than the normal mode and the suppression mode. The controller may be capable of performing the boiling operation and the sterilization operation in the normal mode, the suppression mode, and one or more modes other than those.

[0058] (2) Although the above-described auxiliary heat source unit is configured to heat water by burning fuel gas, the present invention is not limited to this configuration. A modified auxiliary heat source unit may be configured to heat water by electrical energy.

[0059] Although each embodiment has been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0060] 4:HP unit 6: Tank unit 8: Burner unit 17: HP heat source 30: Tank 80: Burner 104: Storage water heater

Claims

1. A hot water tank and A heat pump that heats the water in the hot water storage tank; an auxiliary heat source device capable of heating water drawn from the hot water storage tank and supplied to a hot water supply location and water supplied to the hot water supply location from a water supply source other than the hot water storage tank; A water heater comprising: The control unit is When a predetermined sterilization execution condition is satisfied, a sterilization operation is performed in which water is prohibited from being supplied from the hot water storage tank to the hot water supply location, and the water in the hot water storage tank is heated to a temperature equal to or higher than a predetermined sterilization reference temperature by the heat pump in order to sterilize the water in the hot water storage tank. a normal mode in which an upper limit value of the power consumption of the heat pump is not set; A suppression mode that sets an upper limit value of the power consumption of the heat pump; In the suppression mode, an upper limit value of the power consumption of the heat pump is set according to the power consumption of elements other than the heat pump in the water heater, and the heat pump is operated so that the power consumption of the heat pump is less than the set upper limit value, A water heater which, when setting the suppression mode, prohibits the execution of the sterilization operation if an upper limit value of the power consumption of the heat pump is set to less than a predetermined reference value, and allows the execution of the sterilization operation if an upper limit value of the power consumption of the heat pump is set to equal to or greater than the reference value.

2. The water heater of claim 1, wherein the control unit allows the sterilization operation to be performed when the suppression mode is set such that an upper limit value of the power consumption of the heat pump is set to be equal to or higher than the reference value, and when the time to start the sterilization operation is a time when there are few opportunities for water to be supplied to the hot water supply location.

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