hot water supply equipment

Abstract

To provide a technology which can suppress a load on a compressor when there arises a possibility that the allowable pressure of the compressor of a heat pump is reduced.SOLUTION: In a boil-up operation for boiling up water in a hot water storage tank up to a target boil-up temperature by a heat pump, a control part can perform a first boil-up operation for setting the target boil-up temperature to a first target boil-up temperature, and a second boil-up operation for setting the target boil-up temperature to a second boil-up temperature which is lower than the first target boil-up temperature. The control part may perform the first boil-up operation when there is no limit on power consumption when performing the boil-up operation, may perform a limit operation of decreasing the rotation number of a compressor when there is limit on the power consumption than when there is no limit on the power consumption, and may perform the second boil-up operation when a temperature of water which is sent to a condenser from the hot water storage tank is equal to or higher than a prescribed standard temperature when performing the limit operation.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] The hot water heater disclosed in Patent Document 1 includes a hot water storage tank and a heat pump that absorbs heat from outside air to boil water in the hot water storage tank. The heat pump includes a compressor that pressurizes a refrigerant and a condenser that heats the water in the hot water storage tank by heat exchange between the refrigerant pressurized by the compressor and water sent from the hot water storage tank. The hot water heater in Patent Document 1 lowers the boiling temperature setting when the outside air temperature or water supply temperature rises. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-147846 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-33429 Summary of the Invention [Problem to be solved by the invention]

[0004] In hot water supply systems, the rotation speed of the heat pump compressor may be reduced when power consumption is limited. When the rotation speed of the compressor is low, the allowable pressure of the compressor tends to be low (see Patent Document 2), so it is desirable to reduce the load on the compressor. Therefore, this specification provides a technology that can reduce the load on the compressor when the allowable pressure of the heat pump compressor is likely to be low. [Means for solving the problem]

[0005] In a first aspect of the present technology, a hot water heater may include a hot water storage tank, a heat pump that absorbs heat from outside air to boil water in the hot water storage tank, and a control unit. The heat pump may include a compressor that pressurizes a refrigerant and a condenser that heats the water in the hot water storage tank by heat exchange between the refrigerant pressurized by the compressor and water delivered from the hot water storage tank. The control unit may be capable of executing a first boiling operation in which the target boiling temperature is set to a first target boiling temperature and a second boiling operation in which the target boiling temperature is set to a second target boiling temperature that is lower than the first target boiling temperature, in a boiling operation in which there is no limit on power consumption, and when there is a limit on power consumption, the control unit may execute the first boiling operation in which the rotation speed of the compressor is lower than when there is no limit on power consumption. When the limited operation is performed, the control unit may perform the second boiling operation if the temperature of the water sent from the hot water storage tank to the condenser is equal to or higher than a predetermined reference temperature.

[0006] According to this configuration, when there is a limit on the power consumption of the hot water heater, the power consumption of the compressor can be reduced by reducing the rotation speed of the heat pump compressor. However, reducing the rotation speed of the compressor may reduce the allowable pressure of the compressor. Furthermore, in a heat pump, the higher the temperature of the water sent to the condenser, the more difficult it is to lower the refrigerant temperature during heat exchange in the condenser. As a result, the temperature of the refrigerant pressurized by the compressor may be relatively high, and the pressure of the refrigerant during pressurization may be high. However, according to the above configuration, by performing the second boiling operation with a relatively low target boiling temperature, the temperature of the water during heat exchange in the heat pump condenser can be lowered compared to the first boiling operation. This reduces the temperature of the refrigerant pressurized by the heat pump compressor and the pressure of the refrigerant during pressurization. This reduces the load on the compressor. Therefore, the load on the compressor can be reduced when the allowable pressure of the heat pump compressor may be reduced.

[0007] In a second aspect, in the first aspect described above, when the control unit performs the restricted operation, if the outside air temperature is lower than a predetermined standard outside air temperature, it may perform the first boiling operation, and if the outside air temperature is higher than the standard outside air temperature and the temperature of the water sent from the hot water storage tank to the condenser is higher than a predetermined standard temperature, it may perform the second boiling operation.

[0008] In a heat pump, the higher the outdoor air temperature, the greater the amount of heat absorbed from the outdoor air, so the compressor speed may be reduced accordingly. This may further reduce the allowable pressure of the compressor. However, with the above configuration, by performing the second boiling operation, which has a relatively low target boiling temperature, the temperature of the water in the heat exchange in the heat pump's condenser can be made lower than in the first boiling operation. This allows the temperature of the refrigerant pressurized by the heat pump's compressor to be lowered, and the pressure of the refrigerant during pressurization can be reduced. This reduces the load on the compressor.

[0009] In a third aspect, in the second aspect described above, when the control unit performs the restricted operation, and when the outside air temperature is higher than the standard outside air temperature and the temperature of the water sent from the hot water storage tank to the condenser is higher than a predetermined standard temperature, the control unit may stop the heat pump without performing the second boiling operation if the target boiling temperature is restricted from being set to the second target boiling temperature.

[0010] With this configuration, no load is placed on the compressor of the heat pump.

[0011] In a fourth aspect, in any one of the first to third aspects, the hot water supply device may further include an auxiliary heat source unit that heats water supplied from the hot water storage tank to a hot water supply point.

[0012] With this configuration, for example, when a large amount of water is to be supplied to a hot water supply point, even if the hot water storage tank runs out of hot water, water at the hot water supply setting temperature can be supplied to the hot water supply point by heating the water with the auxiliary heat source unit. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram schematically illustrating a water heater according to an embodiment; [Figure 2] 4 is a flowchart of a boiling operation process according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] A water heater 2 of the embodiment will be described with reference to the drawings. As shown in Fig. 1, the water heater 2 includes an HP (heat pump) unit 4, a tank unit 6, and a burner unit 8. Power for the water heater 2 is supplied from, for example, a commercial power source or a storage battery.

[0015] The HP unit 4 is a heat source that absorbs heat from outside air to heat water. The HP unit 4 includes a heat pump 17 consisting of a compressor 10, a condenser 12, an expansion valve 14, and an evaporator 16. The heat pump 17 absorbs heat from outside air to heat water by circulating a refrigerant (e.g., an HFC refrigerant such as R32 or R410A, or a CO2 refrigerant such as R744) through the compressor 10, condenser 12, expansion valve 14, and evaporator 16 in that order. The compressor 10 pressurizes the refrigerant to a high temperature and high pressure. The condenser 12 heats water and cools the refrigerant through heat exchange between the refrigerant and water flowing through a circulation path 19. The circulation path 19 circulates water between the hot water storage tank 30 in the tank unit 6 and the condenser 12 in the HP unit 4. The expansion valve 14 decompresses the refrigerant to a low temperature and low pressure. The evaporator 16 heats the refrigerant through heat exchange between the refrigerant and outside air blown by a fan 13. The HP unit 4 further includes a circulation pump 18 that circulates the water in the circulation path 19 between the hot water storage tank 30 and the condenser 12, a return thermistor 20 that detects the temperature of the water flowing from the hot water storage tank 30 to the condenser 12, a feed thermistor 22 that detects the temperature of the water flowing from the condenser 12 to the hot water storage tank 30, 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. In the heat pump 17, the higher the outdoor air temperature, the greater the amount of heat absorbed from the outdoor air. Therefore, the HP controller 24 may reduce the rotation speed of the compressor 10 (more specifically, reduce the frequency of the three-phase AC of the motor of the compressor 10) as the outdoor air temperature detected by the outdoor air temperature thermistor 23 increases. When the rotation speed of the compressor 10 decreases, the allowable pressure may decrease.

[0016] The tank unit 6 includes a hot water storage tank 30, a mixing valve 32, and a bypass control valve 34. The hot water storage tank 30 is a sealed container that is covered on the outside with a heat insulating material and stores water inside. In this embodiment, the capacity of the hot water storage tank 30 is, for example, 100 liters. When the circulation pump 18 of the HP unit 4 is driven, water is sucked from the bottom of the hot water storage tank 30 into the circulation path 19 and sent to the condenser 12. The water heated in the condenser 12 and heated to a high temperature flows through the circulation path 19 and is returned to the hot water storage tank 30 from the top of the hot water storage tank 30. When the water heated by the HP unit 4 flows into the hot water storage tank 30, a temperature stratification is formed inside the hot water storage tank 30, with a layer of high temperature water stacked on top of a layer of low temperature water. An upper thermistor 36 that detects the temperature of the water in the upper portion, an intermediate thermistor 37 that detects the temperature of the water in the middle portion, a lower thermistor 38 that detects the temperature of the water in the lower portion, and a bottom thermistor 39 that detects the temperature of the water in the bottom portion are attached to the hot water storage tank 30. In this embodiment, the upper thermistor 36 is located 6 liters from the top of the hot water storage tank 30, the intermediate thermistor 37 is located 12 liters from the top of the hot water storage tank 30, the lower thermistor 38 is located 30 liters from the top of the hot water storage tank 30, and the bottom thermistor 39 is located 70 liters from the top of the hot water storage tank 30.

[0017] Tap water is supplied to the tank unit 6 from a water supply source via a water supply path 40. A pressure reducing valve 42 that reduces the water supply pressure and a water inlet thermistor 44 that detects 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 hot water storage 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 that detects the flow rate of tap water flowing into the mixing valve 32 is attached to the tank bypass path 48. The top of the hot water storage 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 that detects the flow rate of water from the hot water storage tank 30 that flows into the mixing valve 32 are attached to the tank hot water outlet path 56.

[0018] The mixing valve 32 mixes tap water flowing in from the tank bypass path 48 with water from the hot water storage 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 is driven by a stepping motor, 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 hot water 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.

[0019] Hot water is supplied from the tank unit 6 to hot water supply locations such as the kitchen, shower, and faucet via a second hot water supply path 66. A hot water supply thermistor 68 that detects the temperature of water supplied to the hot water supply locations 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.

[0020] Tank unit 6 includes tank controller 74 and remote control 76 capable of communicating with tank controller 74. Tank controller 74 controls the operation of each component of tank unit 6. Tank controller 74 includes non-volatile memory 75. Remote control 76 accepts various operational inputs from the user via switches, buttons, etc. Remote control 76 also notifies the user of various information related to the settings and operation of water heating apparatus 2 by display and audio.

[0021] 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 that heats water flowing through the heat exchanger 82 by burning gas. Water flows into the heat exchanger 82 from the first hot water supply path 62 of the tank unit 6 via a burner outflow path 90. The water that passes through the heat exchanger 82 flows out to the second hot water supply path 66 of the tank unit 6 via a burner return path 92. The burner outflow path 90 is equipped with a water volume servo 86 that adjusts the flow rate of water flowing through the burner outflow path 90 and a water volume sensor 91 that detects the flow rate of water flowing through the burner outflow path 90. The burner outflow path 90 and the burner return path 92 are connected via a burner bypass path 94. The bypass servo 84 is attached to the connection between the burner outflow path 90 and the burner bypass path 94. The bypass servo 84 adjusts the flow rate of water flowing from the burner forward path 90 to the burner bypass path 94. A burner outlet thermistor 96 is attached to the burner return path 92, which detects the temperature of the water flowing out of the heat exchanger 82 as the burner outlet temperature. In the burner unit 8, the heating capacity of the burner 80 is adjusted so that the difference between the burner outlet temperature and the target heating temperature is reduced. 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 from the burner unit 8 via the water filling path 98 into the bathtub, which is the hot water supply point. The burner unit 8 further includes a burner controller 100, which controls the operation of each component of the burner unit 8.

[0022] HP controller 24 and tank controller 74 can communicate with each other. Tank controller 74 and burner controller 100 can also communicate with each other. Therefore, HP controller 24, tank controller 74, and burner controller 100 cooperate to perform control, allowing water heating apparatus 2 to perform various operations such as boiling operation and hot water supply operation. Hereinafter, HP controller 24, tank controller 74, and burner controller 100 may be collectively referred to simply as controllers.

[0023] (Boiling operation) In the water heating operation, the water heating apparatus 2 drives the HP unit 4 to heat the water in the hot water storage tank 30. The timing to start the water heating operation can be set from various perspectives. For example, the tank controller 74 may determine the start timing of the water heating operation and instruct the HP controller 24 to start the water heating operation so that the water heating in the hot water storage tank 30 finishes just before the end of a time period when cheaper late-night electricity is available. Alternatively, the tank controller 74 may determine the start timing of the water heating operation and instruct the HP controller 24 to start the water heating operation so that the water heating in the hot water storage tank 30 finishes just before a time when a large demand for hot water is expected based on the hot water supply performance up to the previous day. Alternatively, the user may instruct the remote control 76 to heat the water in the hot water storage tank 30, which causes the tank controller 74 to instruct the HP controller 24 to start the water heating operation.

[0024] The water heater 2 can heat the water in the hot water storage tank 30 to a predetermined target boiling temperature through boiling operation. The water heater 2 can perform a first boiling operation and a second boiling operation during boiling operation. The first boiling operation is a boiling operation in which the target boiling temperature is set to a first target boiling temperature (e.g., 50°C). The second boiling operation is a boiling operation in which the target boiling temperature is set to a second target boiling temperature (e.g., 45°C) that is lower than the first target boiling temperature. By setting the target boiling temperature to the second target boiling temperature, the temperature of the refrigerant pressurized by the compressor 10 of the heat pump 17 can be lowered, and the pressure of the refrigerant during pressurization can be lowered. This reduces the load on the compressor 10.

[0025] When instructed to start the boiling operation, the HP controller 24 drives the compressor 10 of the heat pump 17 to circulate the refrigerant through the compressor 10, condenser 12, expansion valve 14, and evaporator 16 in that order, and also drives the circulation pump 18 to circulate water between the hot water storage tank 30 and the condenser 12. As a result, water sucked out from the bottom of the hot water storage tank 30 is heated to the target boiling temperature in the condenser 12 and returned to the top of the hot water storage tank 30. When the tank controller 74 detects from the temperatures detected by the upper thermistor 36, middle thermistor 37, lower thermistor 38, and bottom thermistor 39, as well as the temperature detected by the return thermistor 20, that all of the water in the hot water storage tank 30 has been replaced with high-temperature water, it instructs the HP controller 24 to end the boiling operation. When instructed to end the boiling operation by the tank controller 74, the HP controller 24 ends the boiling operation.

[0026] (Hot water operation) In hot water supply operation, the water heater 2 supplies water whose temperature has been adjusted to the hot water supply setting temperature to the hot water supply location. The water heater 2 performs non-combustion hot water supply operation when the temperature of the upper part of the hot water storage tank 30 detected by the upper thermistor 36 of the tank unit 6 is equal to or higher than the hot water supply setting temperature. In non-combustion hot water supply operation, the tank controller 74 instructs the burner controller 100 to prohibit the combustion operation of the burner 80. The tank controller 74 also opens the bypass control valve 34 and adjusts the opening of the mixing valve 32 so that the temperature detected by the mixing thermistor 64 becomes the hot water supply setting temperature. In this case, high-temperature water supplied from the upper part of the hot water storage tank 30 and low-temperature water supplied from the water supply path 40 are mixed in the mixing valve 32, and the water is adjusted to the hot water supply setting temperature and supplied to the hot water supply location.

[0027] If the temperature of the upper part of the hot water storage tank 30 detected by upper thermistor 36 is lower than the set hot water supply temperature, the water heater 2 performs combustion hot water supply operation. In combustion hot water supply operation, the tank controller 74 permits the burner controller 100 to perform combustion operation of the burner 80 and instructs the set hot water supply temperature as the target heating temperature for the burner unit 8. The tank controller 74 also closes the bypass control valve 34 and adjusts the aperture of the mixing valve 32 so that the temperature detected by the mixing thermistor 64 is lower than the set hot water supply temperature by the minimum heating capacity of the burner 80. In this case, high-temperature water supplied from the upper part of the hot water storage tank 30 and low-temperature water supplied from the water supply path 40 are mixed in the mixing valve 32, and then heated by the burner 80 to the target heating temperature, i.e., the set hot water supply temperature, and supplied to the hot water supply location.

[0028] (Power consumption limit) The power consumption of the water heating apparatus 2 may be limited. For example, the power consumption of the water heating apparatus 2 may be limited depending on the power supply and demand situation of the electric power company. Furthermore, for example, when the water heating apparatus 2 is connected to a storage battery, the power consumption of the water heating apparatus 2 may be limited depending on the power storage situation of the storage battery. Furthermore, for example, when a device other than the water heating apparatus 2 is connected to the storage battery, the power consumption of the water heating apparatus 2 may be limited in order to supply power to the other device. Furthermore, regardless of the power supply and demand situation of the electric power company, the power consumption of the water heating apparatus 2 may be limited depending on a user instruction or the operating status of the water heating apparatus 2. When the power consumption of the water heating apparatus 2 is limited, the controller generates a predetermined restriction flag and stores it in memory 75 of the tank controller 74. More specifically, when the power consumption is limited, predetermined restriction information indicating this is transmitted to the controller of the water heating apparatus 2, for example, from the electric power company or the storage battery. When the controller receives restriction information indicating that the power consumption is limited, the controller generates a restriction flag and stores it in memory 75. The controller may also generate and store a restriction flag in memory 75 when the power consumption of water heating apparatus 2 is restricted in accordance with an instruction from the user or the operating status of water heating apparatus 2.

[0029] (Boiling operation process; Figure 2) Next, the boiling operation process of the embodiment will be described. FIG. 2 is a flowchart of the boiling operation process. The boiling operation process shown in FIG. 2 is started, for example, when a predetermined boiling start time arrives. The boiling operation process may also be started based on a boiling start instruction from a user. In S2 of the boiling operation process, the controller starts the boiling operation. When the boiling operation is started, the water in the hot water storage tank 30 is boiled by the heat pump 17 of the HP unit 4. When the boiling operation is started, the target boiling temperature is set to a first target boiling temperature (for example, 50°C). Therefore, when the boiling operation is started, the controller executes the first boiling operation.

[0030] In the following S4, the controller determines whether a predetermined boiling stop condition is met. The boiling stop condition is met, for example, when the water temperature detected by bottom thermistor 39 attached to the bottom of hot water storage tank 30 is equal to or higher than a predetermined stop reference temperature (for example, the target boiling temperature -5°C (but up to 45°C)). In a modified example, the boiling stop condition may be met when the water temperature detected by return thermistor 20 attached to circulation path 19 is equal to or higher than the predetermined stop reference temperature. If the boiling stop condition is met (YES in S4), the process proceeds to S20. In S20, the controller stops compressor 10 of heat pump 17 to end the boiling operation. If the boiling stop condition is not met (NO in S4), the process proceeds to S6.

[0031] In S6, the controller determines whether or not there is a limit on power consumption. Specifically, the controller determines whether or not a limit flag indicating a limit on power consumption is stored in the memory 75 of the tank controller 74. If there is a limit on power consumption (i.e., if the limit flag is stored in the memory 75, YES in S6), the process proceeds to S8. If there is no limit on power consumption (i.e., if the limit flag is not stored in the memory 75, NO in S6), the process returns to S4.

[0032] In S8, the controller executes a limited operation to reduce the rotation speed of the compressor 10 of the heat pump 17. When there is a limit on power consumption (YES in S6), the controller reduces the rotation speed of the compressor 10 compared to when there is no limit on power consumption. When the rotation speed of the compressor 10 is reduced by the limited operation, the allowable pressure of the compressor 10 tends to decrease.

[0033] In the next step S10, the controller determines whether the outside air temperature detected by the outside air temperature thermistor 23 is equal to or higher than a predetermined reference outside air temperature (e.g., 16°C). If the outside air temperature is equal to or higher than the reference outside air temperature (YES in S10), the process proceeds to S12. If the outside air temperature is lower than the reference outside air temperature (NO in S10), the process returns to S4.

[0034] In S12, the controller determines whether the water temperature detected by the bottom thermistor 39 attached to the bottom of the hot water storage tank 30 is equal to or higher than a predetermined reference temperature (e.g., 19°C). If the temperature detected by the bottom thermistor 39 is equal to or higher than the reference temperature (YES in S12), the process proceeds to S14. If the temperature detected by the bottom thermistor 39 is lower than the reference temperature (NO in S12), the process returns to S4.

[0035] In S14, the controller determines whether the target boiling temperature can be changed to a temperature below the first target boiling temperature. In water heating device 2, for example, if the hot water supply setting temperature of water supplied to the hot water supply point is set to a low temperature (e.g., below 40°C), the target boiling temperature can be changed. If the target boiling temperature can be changed (YES in S14), the process proceeds to S16. On the other hand, for example, if the hot water supply setting temperature is set to a high temperature (e.g., 45°C or higher), the water in hot water storage tank 30 cannot be used to dispense hot water at the set hot water supply temperature, so the target boiling temperature cannot be changed. If the target boiling temperature cannot be changed (NO in S14), the process proceeds to S20.

[0036] In S16, the controller determines whether the current target boiling temperature is higher than a second target boiling temperature (e.g., 45°C). The second target boiling temperature (e.g., 45°C) is a temperature lower than the first target boiling temperature (e.g., 50°C). If the current target boiling temperature is higher than the second target boiling temperature (YES in S16), the process proceeds to S18. If the current target boiling temperature is equal to or lower than the second target boiling temperature (NO in S16), the process returns to S4. In S18, the controller changes the target boiling temperature to the second target boiling temperature. This causes the controller to perform the second boiling operation. After S18, the process returns to S4, and the boiling operation continues.

[0037] (effect) The hot water heater 2 of the embodiment has been described above. As is clear from the above description, the hot water heater 2 can perform a first boiling operation in which the target boiling temperature is set to a first target boiling temperature by the heat pump 17, and a second boiling operation in which the target boiling temperature is set to a second target boiling temperature that is lower than the first target boiling temperature. When performing the boiling operation, the controller performs the first boiling operation if there is no limit on power consumption. When there is a limit on power consumption, the controller performs a limited operation in which the rotation speed of the compressor 10 is lower than when there is no limit on power consumption. When performing the limited operation, the controller performs the second boiling operation if the outside air temperature is equal to or higher than a predetermined reference outside air temperature and the temperature of the water sent from the hot water tank 30 to the condenser 12 is equal to or higher than a predetermined reference temperature (S6, S8, S10, S12, S14, S16, S18). The controller executes the first boiling operation when the outside air temperature is lower than a predetermined reference outside air temperature, or when the temperature of the water sent from the hot water storage tank 30 to the condenser 12 is lower than a predetermined reference temperature.

[0038] According to this configuration, when power consumption is limited, the power consumption of the compressor 10 can be reduced by reducing the rotation speed of the compressor 10. However, reducing the rotation speed of the compressor 10 may reduce the allowable pressure of the compressor 10. Furthermore, in the heat pump 17, the higher the outdoor air temperature, the greater the amount of heat absorbed from the outdoor air. Therefore, the rotation speed of the compressor 10 may be reduced accordingly. This may further reduce the allowable pressure of the compressor 10. On the other hand, in a heat pump, the higher the temperature of the water sent to the condenser 12, the more difficult it is to lower the refrigerant temperature during heat exchange in the condenser 12. As a result, the temperature of the refrigerant pressurized by the compressor 10 may be relatively high, and the pressure of the refrigerant during pressurization may be high. However, according to the above configuration, by performing the second boiling operation with a relatively low target boiling temperature, the temperature of the water during heat exchange in the condenser 12 of the heat pump 17 can be lowered compared to the first boiling operation. This allows the temperature of the refrigerant pressurized by the compressor 10 of the heat pump 17 to be lower, thereby reducing the pressure of the refrigerant during pressurization. This reduces the load on the compressor 10. Therefore, when there is a possibility that the allowable pressure of the compressor 10 of the heat pump 17 will be reduced, the load on the compressor 10 can be reduced. In addition, the heating operation of the heat pump 17 can be continued, and the amount of heat stored in the hot water storage tank 30 can be increased.

[0039] Furthermore, when there is a limit on power consumption and the target boiling temperature is restricted from being set to the second target boiling temperature, the controller stops heat pump 17 without performing the second boiling operation (S6, S8, S10, S12, S14, S20). With this configuration, no load is placed on compressor 10 of heat pump 17.

[0040] The hot water supply device 2 described above includes a burner 80 that uses gas fuel to heat water supplied from the hot water storage tank 30 to the hot water supply location. With this configuration, for example, when a large amount of water is to be supplied to the hot water supply location, even if the hot water storage tank 30 runs out of hot water, water at the hot water supply setting temperature can be supplied to the hot water supply location by heating the water with the burner 80.

[0041] (Correspondence) The temperature of the water detected by the bottom thermistor 39 is an example of the "temperature of the water sent from the hot water storage tank to the condenser."

[0042] (Variation) (1) In the above embodiment, the water temperature detected by the bottom thermistor 39 attached to the bottom of the hot water storage tank 30 is an example of the "temperature of water sent from the hot water storage tank to the condenser," but this is not limiting. In a modified example, the water temperature detected by the return thermistor 20 attached to the circulation path 19 may be an example of the "temperature of water sent from the hot water storage tank to the condenser."

[0043] (2) In the second boiling operation, the controller may increase the flow rate of water sent from the hot water storage tank 30 to the condenser 12 compared to the first boiling operation. The controller increases the flow rate of water flowing through the circulation path 19 by controlling the operation of the circulation pump 18. By sending more water to the condenser 12, the temperature during heat exchange in the condenser 12 can be lowered. Accordingly, the temperature of the refrigerant pressurized by the compressor 10 can be lowered, and the pressure of the refrigerant during pressurization can be lowered. This reduces the load on the compressor 10.

[0044] 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. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0045] 2: Hot water heater, 4: HP unit, 6: Tank unit, 8: Burner unit, 10: Compressor, 12: Condenser, 13: Fan, 14: Expansion valve, 16: Evaporator, 17: Heat pump, 18: Circulation pump, 19: Circulation path, 20: Return thermistor, 22: Supply thermistor, 23: Outdoor air temperature thermistor, 24: HP controller, 30: Hot water storage tank, 32: Mixing valve, 34: Bypass control valve, 36: Upper thermistor, 37: Middle thermistor, 38: Lower thermistor, 39: Bottom thermistor, 40: Water supply path, 42: Pressure reducing valve, 44: Inlet water thermistor , 46: Tank water supply path, 48: Tank bypass path, 54: Water-side water volume sensor, 56: Tank hot water outlet path, 60: Hot water-side water volume sensor, 62: First hot water supply path, 64: Mixing thermistor, 66: Second hot water supply path, 68: Hot water supply thermistor, 72: Hot water bypass path, 74: Tank controller, 75: Memory, 76: Remote control, 80: Burner, 82: Heat exchanger, 84: Bypass servo, 86: Water volume servo, 90: Burner forward path, 91: Water volume sensor, 92: Burner return path, 94: Burner bypass path, 96: Burner outlet thermistor, 100: Burner controller

Claims

1. A hot water tank and a heat pump that absorbs heat from outside air and boils the water in the hot water storage tank; A water heater comprising: The heat pump includes a compressor that pressurizes a refrigerant, and a condenser that heats water in the hot water storage tank by heat exchange between the refrigerant pressurized by the compressor and water sent from the hot water storage tank, The control unit In a boiling operation in which the water in the hot water storage tank is boiled up to a target boiling temperature by the heat pump, a first boiling operation in which the target boiling temperature is set to a first target boiling temperature, and a second boiling operation in which the target boiling temperature is set to a second target boiling temperature that is lower than the first target boiling temperature can be executed, When the boiling operation is performed, if there is no limit on power consumption, the first boiling operation is performed, and if there is a limit on power consumption, a limited operation is performed in which the rotation speed of the compressor is reduced compared to when there is no limit on power consumption, When the limited operation is performed, if the temperature of the water sent from the hot water storage tank to the condenser is equal to or higher than a predetermined reference temperature, the hot water supply device performs the second boiling operation.

2. The water heater device of claim 1, wherein when the control unit performs the restricted operation, if the outside air temperature is lower than a predetermined standard outside air temperature, it performs the first boiling operation, and if the outside air temperature is higher than the standard outside air temperature and the temperature of the water sent from the hot water storage tank to the condenser is higher than a predetermined standard temperature, it performs the second boiling operation.

3. The water heater device of claim 2, wherein when the control unit performs the restricted operation, and when the outside air temperature is higher than the standard outside air temperature and the temperature of the water sent from the hot water storage tank to the condenser is higher than a predetermined standard temperature, the control unit stops the heat pump without performing the second boiling operation if the target boiling temperature is restricted from being set to the second target boiling temperature.

4. The hot water supply device according to claim 1 , further comprising an auxiliary heat source unit that heats water supplied from the hot water storage tank to a hot water supply point.

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