Hot water supply system

Abstract

To provide a technology capable of securing power for defrosting operation during a power suppression state.SOLUTION: A control unit can perform defrosting operation to remove frost adhering to an evaporator using heat of a refrigerant pressurized by a compressor and heated when a predetermined defrosting start condition is established; when a water heater is operating in a power suppression state in which power consumption is suppressed compared to a normal state and an anti-freeze heater is heating water in a path, stops the anti-freezing heater when it is predicted that the defrosting start condition is established; and then may start the defrosting operation when the defrosting start condition is established.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] A heat pump device is disclosed in Patent Document 1. The heat pump device of Patent Document 1 includes a compressor that pressurizes a refrigerant, a condenser that heats water by heat exchange between water and the refrigerant to condense the refrigerant, an expansion valve that depressurizes the refrigerant, and an evaporator that absorbs heat from the outside air by heat exchange between the outside air and the refrigerant to evaporate the refrigerant. The heat pump device of Patent Document 1 can perform a normal defrosting operation to remove frost adhering to the evaporator by the heat of the refrigerant pressurized by the compressor and having its temperature increased. Further, when power consumption suppression is required by a power suppression signal, the heat pump device of Patent Document 1 performs a heat source side fan defrosting operation to defrost with the compressor stopped.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When performing a defrosting operation with a heat pump, it is difficult to secure power for the defrosting operation in a power suppression state where power consumption is suppressed. Therefore, this specification provides a technology that can secure power for the defrosting operation in a power suppression state.

Means for Solving the Problems

[0005] In a first aspect of this technology, the hot water supply system may include a hot water storage tank, a heat pump for heating the water in the hot water storage tank, a path communicating with the hot water storage tank for the flow of water entering or leaving the hot water storage tank, an antifreeze heater for preventing the water in the path from freezing, the antifreeze heater being attached to at least a part of the path and generating heat when energized to heat the water in the path, and a control unit. The heat pump may include a compressor for pressurizing a refrigerant, a condenser for heating water and condensing the refrigerant by heat exchange between water and the refrigerant, an expansion valve for reducing the pressure of the refrigerant, and an evaporator for evaporating the refrigerant by absorbing heat from the outside air through heat exchange between the outside air and the refrigerant. The control unit can perform a defrosting operation to defrost frost adhering to the evaporator using the heat of the refrigerant, which has been pressurized and its temperature has risen by the compressor, when predetermined defrosting start conditions are met. The control unit may, if it is predicted that the defrost start condition will be met when the hot water supply system is operating in a power-reduced state in which power consumption is reduced compared to the normal state, and the anti-freeze heater is heating the water in the path, stop the anti-freeze heater and then start the defrost operation if the defrost start condition is met thereafter. Alternatively, the control unit may, if the hot water supply system is operating in a power-reduced state in which power consumption is reduced compared to the normal state, and the anti-freeze heater is heating the water in the path, stop the anti-freeze heater and start the defrost operation if the defrost start condition is met.

[0006] With this configuration, if it is predicted that the defrosting start conditions will be met while the power is being reduced, power for the defrosting operation can be secured by stopping the anti-freeze heater before the defrosting start conditions are actually met. Also, if the defrosting start conditions are met while the power is being reduced, power for the defrosting operation can be secured by stopping the anti-freeze heater.

[0007] In a second embodiment, the hot water supply system may include a hot water storage tank, a heat pump for heating the water in the hot water storage tank, a path communicating with the hot water storage tank for the flow of water entering or leaving the hot water storage tank, an anti-freeze heater for preventing the water in the path from freezing, the anti-freeze heater being attached to at least a part of the path and generating heat when energized to heat the water in the path, and a control unit. The heat pump may include a compressor for pressurizing a refrigerant, a condenser for heating water and condensing the refrigerant by heat exchange between water and the refrigerant, an expansion valve for reducing the pressure of the refrigerant, and an evaporator for evaporating the refrigerant by absorbing heat from the outside air through heat exchange between the outside air and the refrigerant. The control unit can perform a defrosting operation in which, when predetermined defrosting start conditions are met, defrosts the frost adhering to the evaporator using the heat of the refrigerant that has been pressurized and whose temperature has risen by the compressor. The control unit may, if it is predicted that the defrost start condition will be met when the hot water supply system is operating in a power-reduced state in which power consumption is reduced compared to the normal state, and the anti-freeze heater is heating the water in the path, reduce the amount of power supplied to the anti-freeze heater, and then start the defrost operation if the defrost start condition is met thereafter. Alternatively, the control unit may, if the hot water supply system is operating in a power-reduced state in which power consumption is reduced compared to the normal state, and the anti-freeze heater is heating the water in the path, reduce the amount of power supplied to the anti-freeze heater and start the defrost operation.

[0008] With this configuration, if it is predicted that the defrosting start conditions will be met while the power is being suppressed, power for defrosting operation can be secured by reducing the amount of power supplied to the anti-freeze heater before the defrosting start conditions are actually met. Also, if the defrosting start conditions are met while the power is being suppressed, power for defrosting operation can be secured by reducing the amount of power supplied to the anti-freeze heater.

[0009] In a third embodiment, the hot water supply system may further include an auxiliary heat source unit for heating the water supplied from the hot water storage tank to the hot water supply location, in the first or second embodiment described above.

[0010] With this configuration, even if the water in the hot water storage tank cannot be heated by performing a defrosting operation, the auxiliary heat source unit can heat the water, and heated water can be supplied to the hot water supply location. [Brief explanation of the drawing]

[0011] [Figure 1] A schematic diagram showing the hot water supply system of the embodiment. [Figure 2] Flowchart of the boiling operation process in the example. [Figure 3] Flowchart of the freeze prevention treatment in the example. [Figure 4] Flowchart of the defrosting operation process in the example (1). [Figure 5] Flowchart of the defrosting operation process in the example (2). [Modes for carrying out the invention]

[0012] The hot water supply system 2 of the embodiment will be described with reference to the drawings. As shown in Figure 1, the hot water supply system 2 comprises an HP (heat pump) unit 4, a tank unit 6, and a burner unit 8. Power for the hot water supply system 2 is supplied, for example, from a commercial power source or a storage battery.

[0013] HP unit 4 is a heat source that heats water by absorbing heat from the outside air. HP unit 4 is equipped with a heat pump 17 consisting of a compressor 10, a condenser 12, an expansion valve 14, and an evaporator 16. The heat pump 17 heats water by absorbing heat from the outside air by circulating a refrigerant (for example, HFC refrigerants such as R32 or R410A, or CO2 refrigerant such as R744) 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 heats the water and cools the refrigerant by heat exchange between the water flowing through the circulation path 19 and the refrigerant, causing it to condense. The circulation path 19 is a path that 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 reduces the pressure of the refrigerant to make it low temperature and low pressure. The evaporator 16 heats and evaporates the refrigerant through heat exchange with outside air blown by the fan 13. The evaporator 16 is fitted with an evaporator thermistor 15 that detects the temperature of the evaporator 16. 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 into the condenser 12, a supply thermistor 22 that detects the temperature of the water flowing out of the condenser 12, an outside air temperature thermistor 23 that detects the outside air temperature, and an HP controller 24 that controls the operation of each component of the HP unit 4.

[0014] 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 stores water inside, with its exterior covered with insulating material. The capacity of the hot water storage tank 30 in this embodiment is, for example, 100 liters. When the circulation pump 18 of the HP unit 4 is driven, water is drawn from the bottom of the hot water storage tank 30 into the circulation path 19 and sent to the condenser 12. The water, heated to a high temperature in the condenser 12, flows through the circulation path 19 and is returned to the hot water storage tank 30 from the top. 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, in which a layer of high-temperature water is stacked on top of a layer of low-temperature water. The hot water storage tank 30 is equipped with an upper thermistor 36 for detecting the temperature of the water at the top, an intermediate thermistor 37 for detecting the temperature of the water in the middle, a lower thermistor 38 for detecting the temperature of the water at the bottom, and a bottom thermistor 39 for detecting the temperature of the water at the bottom. 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.

[0015] The tank unit 6 is supplied with tap water from a water source via a water supply path 40. The water supply path 40 is equipped with a pressure reducing valve 42 for reducing the water supply pressure and an inlet thermistor 44 for detecting the water supply temperature. 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 installed in the tank water supply path 46 and the tank bypass path 48, respectively. The tank bypass path 48 is also equipped with a water-side water flow sensor 54 for detecting the flow rate of tap water flowing into the mixing valve 32. The top of the hot water storage tank 30 and the mixing valve 32 are connected via a tank hot water outlet path 56. The tank hot water outlet path 56 is equipped with a check valve 58 and a hot water-side water flow sensor 60 for detecting the flow rate of water from the hot water storage tank 30 flowing into the mixing valve 32.

[0016] 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 mixture to the first hot water supply path 62. The mixing valve 32 is driven by a stepping motor to adjust the opening degree on the tank bypass path 48 side (opening degree on the cold 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 is installed in the first hot water supply path 62 to detect the temperature of the water sent out from the mixing valve 32.

[0017] Hot water is supplied from the tank unit 6 to hot water outlets such as kitchens, showers, and faucets via the second hot water supply route 66. The second hot water supply route 66 is equipped with a hot water thermistor 68 for detecting the temperature of the water supplied to the hot water outlets, and a check valve 70. The first hot water supply route 62 and the second hot water supply route 66 are connected by a hot water bypass route 72. A bypass control valve 34 is installed in the hot water bypass route 72.

[0018] The tank unit 6 is further equipped with multiple anti-freeze heaters 35. Anti-freeze heaters 35 are installed in each of the following paths within the tank unit 6: circulation path 19, water supply path 40, tank water supply path 46, tank bypass path 48, tank hot water outlet path 56, first hot water supply path 62, second hot water supply path 66, and hot water supply bypass path 72. Each anti-freeze heater 35 generates heat when energized to heat the water in each path (19, 40, 46, 48, 56, 62, 66, 72). The anti-freeze heaters 35 consume electricity to heat the water in the path. Each path (19, 40, 46, 48, 56, 62, 66, 72) is directly or indirectly connected to the hot water storage tank 30, and water flowing into or out of the hot water storage tank 30 flows through each path. Multiple anti-freeze heaters 35 heat the water flowing through multiple paths within the tank unit 6.

[0019] The tank unit 6 includes a tank controller 74 and a remote controller 76 that can communicate with the tank controller 74. The tank controller 74 controls the operation of each component of the tank unit 6. The tank controller 74 has a non-volatile memory 75. The remote controller 76 accepts various operation inputs from the user via switches, buttons, etc. Also, the remote controller 76 notifies the user of various information regarding the settings and operations of the water heater 2 through displays and sounds.

[0020] The burner unit 8 includes a burner 80, a heat exchanger 82, a bypass servo 84, a water volume servo 86, and a water pouring valve 88. The burner 80 is an auxiliary heat source device that heats the water flowing through the heat exchanger 82 by burning gas. Water from the first hot water supply path 62 of the tank unit 6 flows into the heat exchanger 82 via the 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 via the burner return path 92. A water volume servo 86 for adjusting the flow rate of the water flowing through the burner forward path 90 and a water volume sensor 91 for detecting the flow rate of the water flowing through the burner forward path 90 are attached to the burner forward path 90. The space between the burner forward path 90 and the burner return path 92 communicates via a burner bypass path 94. A bypass servo 84 is attached to the connection part between the burner forward path 90 and the burner bypass path 94. The bypass servo 84 adjusts the flow rate of the water flowing from the burner forward path 90 to the heat exchanger 82 and the flow rate of the water flowing into the burner bypass path 94. A burner outlet thermistor 96 for detecting the temperature of the water flowing out from the heat exchanger 82 as the burner outlet temperature is attached to the burner return path 92. 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 becomes small. A water pouring path 98 branches from the burner return path 92. A water pouring valve 88 is attached to the water pouring path 98. Water pouring to the bathtub, which is the hot water supply location, is performed from the burner unit 8 via the water pouring path 98. The burner unit 8 further includes a burner controller 100 that controls the operation of each component of the burner unit 8.

[0021] The HP controller 24 and the tank controller 74 can communicate with each other. The tank controller 74 and the burner controller 100 can communicate with each other. Therefore, by the HP controller 24, the tank controller 74, and the burner controller 100 cooperating to perform control, the water heater 2 can perform various operations such as a boiling operation and a hot water supply operation. Hereinafter, the HP controller 24, the tank controller 74, and the burner controller 100 may be collectively referred to simply as the controller.

[0022] (Boiling operation) In the boiling operation, the water heater 2 drives the HP unit 4 to boil the water in the hot water storage tank 30. The timing to start the boiling operation can be set from various viewpoints. For example, just before the end of the time zone when inexpensive late-night power can be used, the tank controller 74 may determine the start timing of the boiling operation so that the boiling of the water in the hot water storage tank 30 ends, and instruct the HP controller 24 to start the boiling operation. Alternatively, based on the hot water supply results until the previous day, the tank controller 74 may determine the start timing of the boiling operation so that the boiling of the water in the hot water storage tank 30 ends just before the time when a large hot water supply demand is expected, and instruct the HP controller 24 to start the boiling operation. Alternatively, when the user instructs to boil the water in the hot water storage tank 30 via the remote controller 76, the tank controller 74 may instruct the HP controller 24 to start the boiling operation.

[0023] When instructed to start the heating operation, the HP controller 24 drives the compressor 10 of the heat pump 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 hot water storage tank 30 and the condenser 12. As a result, the water drawn from the bottom of the hot water storage tank 30 is heated to the target heating temperature in the condenser 12 and returned to the top of the hot water storage tank 30. When the tank controller 74 detects that all the water in the hot water storage tank 30 has been replaced with high-temperature water, based on the temperatures detected by the upper thermistor 36, intermediate thermistor 37, lower thermistor 38, and bottom thermistor 39, as well as the temperature detected by the return thermistor 20, it instructs the HP controller 24 to end the heating operation. When the tank controller 74 instructs the HP controller 24 to end the heating operation, the HP controller 24 terminates the heating operation.

[0024] (Hot water supply operation) During hot water supply operation, the hot water supply unit 2 supplies water heated to the hot water supply set temperature to the hot water supply location. The hot water supply unit 2 performs non-combustion hot water supply operation if the temperature at the top of the hot water storage tank 30, detected by the upper thermistor 36 of the tank unit 6, is equal to or greater than the hot water supply set temperature. During non-combustion hot water supply operation, the tank controller 74 prohibits the burner controller 100 from operating the burner 80 in combustion mode. 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 is equal to the hot water supply set temperature. In this case, the high-temperature water supplied from the top of the hot water storage tank 30 and the low-temperature water supplied from the water supply path 40 are mixed in the mixing valve 32 to heat the water to the hot water supply set temperature and supplied to the hot water supply location.

[0025] If the temperature at the top of the hot water storage tank 30, as detected by the upper thermistor 36, is below the hot water supply set temperature, the hot water supply device 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 burner unit 8 to use the hot water supply set temperature as the target heating temperature. The tank controller 74 also closes the bypass control valve 34 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 top of the hot water storage tank 30 and the 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 hot water supply set temperature, and supplied to the hot water supply location. This allows heated water to be supplied to the hot water supply location by heating the water with the burner 80.

[0026] (Anti-freezing operation) In freeze prevention operation, the hot water heater 2 drives multiple freeze prevention heaters 35 to heat the water in multiple paths (19, 40, 46, 48, 56, 62, 66, 72). This prevents the water in multiple paths from freezing.

[0027] (Defrosting operation) In the hot water supply system 2, frost may accumulate on the evaporator 16 of the heat pump 17 when the outside air temperature is low. During defrosting operation, the hot water supply system 2 stops the circulation pump 18 and fan 13 of the HP unit 4, drives the compressor 10 of the heat pump 17, and defrosts the frost accumulated on the evaporator 16. When the start of defrosting operation is instructed, the HP controller 24 drives the compressor 10 to circulate the refrigerant in the order of compressor 10, condenser 12, expansion valve 14, and evaporator 16. In the heat pump 17, the refrigerant, which has been pressurized and heated by the compressor 10, passes through the evaporator 16. This defrosts the frost accumulated on the evaporator 16. In addition, during defrosting operation, the opening of the expansion valve 14 is increased compared to the boiling operation, making the temperature of the refrigerant supplied to the evaporator 16 higher than during the boiling operation.

[0028] (Power reduction state of water heater 2) The water heater 2 can operate in a normal state and a power-reduced state in which power consumption is reduced compared to the normal state. In the power-reduced state, the power consumption of the entire water heater 2 is reduced. For example, the power consumption of the water heater 2 may be reduced depending on the power supply and demand situation at the power company. Also, for example, if the water heater 2 is connected to a battery, the power consumption of the water heater 2 may be reduced depending on the charge status of the battery. Also, for example, if other devices other than the water heater 2 are connected to a battery, the power consumption of the water heater 2 may be reduced in order to supply power to the other devices. Furthermore, regardless of the power supply and demand situation at the power company, the power consumption of the water heater 2 may be limited depending on user instructions or the operating status of the water heater 2. The water heater 2 operates in either a normal state or a power-reduced state. When the water heater 2 is operating in the normal state, the controller generates a flag (first flag) indicating that it is operating in the normal state and stores it in the memory 75 of the tank controller 74. Furthermore, if the hot water heater 2 is operating in a power-reduced state, the controller operates it at the maximum power within a range where the total power consumption of the hot water heater 2 does not exceed the power reduction value, and generates a flag (second flag) indicating that it is operating in a power-reduced state, which is stored in the memory 75 of the tank controller 74.

[0029] (Boiling operation process; Figure 2) Next, the boiling operation process of the embodiment will be described. Figure 2 is a flowchart of the boiling operation process. The boiling operation process shown in Figure 2 is started, for example, when a predetermined boiling start time arrives. Alternatively, the boiling operation process may be started based on a boiling start instruction from the user. In S2 of the boiling operation process, the controller starts the boiling operation. Once the boiling operation starts, the water in the hot water storage tank 30 is heated by the heat pump 17 of the HP unit 4.

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

[0031] (Antifreezing treatment; Figure 3) Next, the freeze prevention treatment of the embodiment will be described. Figure 3 is a flowchart of the freeze prevention treatment. The freeze prevention treatment shown in Figure 3 starts, for example, when the power to the hot water heater 2 is turned on. In S10 of the freeze prevention treatment, the controller determines whether the ambient temperature detected by the ambient temperature thermistor 23 is below a predetermined reference ambient temperature (for example, 4°C). If the ambient temperature detected by the ambient temperature thermistor 23 is below the reference ambient temperature (YES in S10), the process proceeds to S12. If the ambient temperature is higher than the reference ambient temperature (NO in S10), the process proceeds to S14.

[0032] In S12, following a YES response in S10, the controller activates multiple anti-freeze heaters 35 in the tank unit 6. When multiple anti-freeze heaters 35 are activated, the water in the multiple pathways (19, 40, 46, 48, 56, 62, 66, 72) to which the anti-freeze heaters 35 are installed is heated. This prevents the water in the multiple pathways from freezing. On the other hand, in S14, following a NO response in S10, the controller deactivates the multiple anti-freeze heaters 35 in the tank unit 6. If multiple anti-freeze heaters 35 are already activated, they are deactivated. If multiple anti-freeze heaters 35 are not activated, that state is maintained. The process then returns to S10. Note that the anti-freeze process shown in Figure 3 terminates, for example, when the power to the hot water supply unit 2 is turned off.

[0033] (Defrosting operation; Figures 4 and 5) Next, the defrosting operation process of the embodiment will be described. Figures 4 and 5 are flowcharts of the defrosting operation process. The defrosting operation process shown in Figures 4 and 5 is started, for example, when the boiling operation is in progress and the outside air temperature is below a predetermined reference outside air temperature (e.g., 7°C). In S20 of the defrosting operation process, the controller determines whether the temperature of the evaporator 16 detected by the evaporator thermistor 15 is below a predetermined reference evaporator temperature. The reference evaporator temperature is, for example, the defrosting start temperature + 2°C. The defrosting start temperature is, for example, the outside air temperature detected by the outside air temperature thermistor 23 - 7°C. If the temperature of the evaporator 16 detected by the evaporator thermistor 15 is below the reference evaporator temperature (= defrosting start temperature + 2°C) (YES in S20), the process proceeds to S22. In this case, it is expected that the defrosting start conditions for defrosting operation (see S30), which will be described later, will be met in the near future. In S22, the controller determines that defrosting is necessary. On the other hand, if the temperature of the evaporator 16 detected by the evaporator thermistor 15 is higher than the reference evaporator temperature (NO in S20), the process will be put on hold.

[0034] In the following S24, the controller determines whether the hot water heater 2 is in a power-restricted state. The power-restricted state is a state in which the power consumption of the hot water heater 2 is reduced. The controller determines whether a second flag indicating that the hot water heater 2 is in a power-restricted state is stored in the memory 75 of the tank controller 74. If the hot water heater 2 is in a power-restricted state (i.e., the second flag is stored in memory 75, so S24 is YES), the process proceeds to S26. On the other hand, if the hot water heater 2 is not in a power-restricted state (i.e., the second flag is not stored in memory 75, so S24 is NO), the process proceeds to S30. If the hot water heater 2 is not in a power-restricted state, the hot water heater 2 is operating in a normal state, and the first flag is stored in memory 75.

[0035] In S26, following a YES response in S24, the controller determines whether the multiple anti-freeze heaters 35 of the tank unit 6 are operating. If the multiple anti-freeze heaters 35 are operating (YES in S26), the process proceeds to S28. If the multiple anti-freeze heaters 35 are stopped (NO in S26), the process proceeds to S30.

[0036] In S28, following a YES response in S26, the controller stops the multiple anti-freeze heaters 35 of the tank unit 6. When the anti-freeze heaters 35 are stopped, power is no longer consumed by them. If the controller stops multiple anti-freeze heaters 35, it generates a stop flag to indicate this and stores it in the memory 75 of the tank controller 74.

[0037] In the following S30, the controller determines whether a predetermined defrosting start condition is met. The defrosting start condition is met, for example, when the temperature of the evaporator 16 detected by the evaporator thermistor 15 falls below a predetermined defrosting start temperature (for example, the ambient temperature detected by the ambient temperature thermistor 23 - 7°C). If the defrosting start condition is met (YES in S30), the process proceeds to S34. If the defrosting start condition is not met (NO in S30), the process returns to S20.

[0038] In S34, the controller interrupts the ongoing heating operation. The controller stops the circulation pump 18 of the HP unit 4 to interrupt the heating operation. When the controller interrupts the heating operation, it generates an interruption flag to indicate this and stores it in the memory 75 of the tank controller 74. In the following S36, the controller starts the defrosting operation. The controller stops the circulation pump 18 of the HP unit 4 and, with the expansion valve 14 opened to a large degree, drives the compressor 10 of the heat pump 17 to circulate the refrigerant in the order of compressor 10, condenser 12, expansion valve 14, and evaporator 16. If power is suppressed at this point, the controller drives the HP unit 4 with the maximum power that does not exceed the power suppression value for the entire hot water supply system 2. When the defrosting operation starts, the frost attached to the evaporator 16 is defrosted by the heat of the refrigerant heated to a high temperature by the compressor 10.

[0039] In the following S38, the controller determines whether a predetermined defrosting completion condition is met. The defrosting completion condition is met, for example, when the temperature of the evaporator 16 detected by the evaporator thermistor 15 becomes equal to or above a predetermined defrosting completion temperature (e.g., 2°C). In a modified example, the defrosting completion condition is met when a predetermined defrosting operation time (e.g., 10 minutes) has elapsed since the defrosting operation started in S26. If the defrosting completion condition is met (YES in S38), the process proceeds to S40. In S40, the controller stops the compressor 10 of the heat pump 17 and terminates the defrosting operation. If the defrosting completion condition is not met (NO in S38), the process waits.

[0040] In the following step S42, the controller determines whether a stop flag (see S28) indicating that multiple anti-freeze heaters 35 have been stopped is stored in the memory 75 of the tank controller 74. If the stop flag is stored in memory 75 (YES in S42), the process proceeds to S44. In S44, the controller restarts the multiple anti-freeze heaters 35. If the stop flag is not stored in memory 75 (NO in S42), the process proceeds to S46.

[0041] In S46, the controller determines whether an interruption flag (see S34) indicating that the boiling operation has been interrupted is stored in the memory 75 of the tank controller 74. If the interruption flag is stored in memory 75 (YES in S46), the process proceeds to S48. If the interruption flag is not stored in memory 75 (NO in S46), the process returns to S20.

[0042] In S48, the controller restarts the heating operation. The controller drives the circulation pump 18 of the HP unit 4 and the compressor 10 of the heat pump 17. After that, the process returns to S20. Note that the defrosting operation shown in Figures 4 and 5 ends, for example, when the heating operation is completed or when the outside air temperature is above a predetermined standard outside air temperature (e.g., 7°C).

[0043] (effect) The hot water supply system 2 of the embodiment has been described above. As is clear from the above description, the hot water supply system 2 is equipped with an anti-freeze heater 35 that generates heat when electricity is applied and heats the water in the path (for example, the circulation path 19). The controller can perform a defrosting operation in which the frost adhering to the evaporator 16 is defrosted by the heat of the refrigerant heated to a high temperature by the compressor 10 of the heat pump 17 when predetermined defrosting start conditions are met. When the hot water supply system 2 is operating in a power-reduced state in which power consumption is reduced compared to the normal state, and the anti-freeze heater 35 is heating the water in the path (for example, the circulation path 19), the controller predicts that the defrosting start conditions will be met, so it stops the anti-freeze heater 35, and then starts the defrosting operation if the defrosting start conditions are met thereafter (see S20-S36 in Figures 4 and 5).

[0044] With this configuration, if it is predicted that the defrosting start conditions will be met while the hot water heater 2 is in a power-reduced state, the anti-freeze heater 35 can be stopped before the defrosting start conditions are actually met, thereby securing power for the defrosting operation. The power consumed by the anti-freeze heater 35 can be redirected to the HP unit 4. Therefore, the defrosting capacity of the defrosting operation can be improved compared to when the anti-freeze heater 35 is not stopped.

[0045] Furthermore, the hot water supply system 2 is equipped with a burner 80 that heats the water supplied from the hot water storage tank 30 to the hot water supply location using gas as fuel. With this configuration, even if the water in the hot water storage tank 30 cannot be heated due to the defrosting operation, heated water can be supplied to the hot water supply location by heating the water with the burner 80.

[0046] (modified version) (1) In the above embodiment, the controller stopped the antifreeze heater 35 in S28 of the defrosting operation process, but the configuration is not limited to this. In a modified example, the controller may reduce the amount of power supplied to the antifreeze heater 35 in S28. For example, the voltage applied to the antifreeze heater 35 may be reduced. Alternatively, the current supplied to the antifreeze heater 35 may be reduced. With this configuration, power for the defrosting operation can be secured by reducing the amount of power supplied to the antifreeze heater 35. The reduced amount of power supplied to the antifreeze heater 35 can be redirected to the HP unit 4. Therefore, the defrosting capacity of the defrosting operation can be improved compared to the case where the amount of power supplied to the antifreeze heater 35 is not reduced. In this case, in S44 of the defrosting operation process, the controller increases the amount of power supplied to the antifreeze heater 35 to return it to the state before the reduction. In this case, a reduction flag may be used instead of a stop flag.

[0047] (2) In the above embodiment, a burner 80 that heats water by burning gas was described as an example of an auxiliary heat source, but the configuration is not limited to this. In a modified example, a burner that heats water by burning kerosene may be used as an auxiliary heat source. Alternatively, a heater that generates heat when electricity is applied may be used as an auxiliary heat source.

[0048] (3) In the above embodiment, the controller stopped the anti-freeze heater 35 when it was predicted that the defrost start conditions would be met, and then started the defrost operation when the defrost start conditions were met thereafter. However, the configuration is not limited to this. In a modified example, the controller may stop the anti-freeze heater 35 and start the defrost operation when the defrost start conditions are met. Alternatively, the controller may reduce the amount of power supplied to the anti-freeze heater 35 and start the defrost operation when the defrost start conditions are met. Power for the defrost operation can also be secured with such a configuration.

[0049] (4) In a modified example, the controller does not need to stop the defrost heater 35 when the outside temperature is extremely low (for example, below -10°C). When the outside temperature is extremely low, protection of the equipment may be prioritized over defrosting.

[0050] Although each embodiment has been described in detail above, these are merely illustrative examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of Symbols]

[0051] 2: Hot water supply unit, 4: HP unit, 6: Tank unit, 8: Burner unit, 10: Compressor, 12: Condenser, 13: Fan, 14: Expansion valve, 15: Evaporator thermistor, 16: Evaporator, 17: Heat pump, 18: Circulation pump, 19: Circulation path, 20: Return thermistor, 22: Supply thermistor, 23: Ambient temperature thermistor, 24: HP controller, 30: Hot water storage tank, 32: Mixing valve, 34: Bypass control valve, 35: Antifreeze heater, 36: Upper thermistor, 37: Middle thermistor, 38: Lower thermistor, 39: Bottom thermistor, 40: Water supply path, 42: Pressure reducing Valve, 44: Inlet thermistor, 46: Tank water supply path, 48: Tank bypass path, 54: Cold water flow sensor, 56: Tank hot water outlet path, 60: Hot water flow sensor, 62: First hot water supply path, 64: Mixing thermistor, 66: Second hot water supply path, 68: Hot water supply thermistor, 72: Hot water supply bypass path, 74: Tank controller, 75: Memory, 76: Remote control, 80: Burner, 82: Heat exchanger, 84: Bypass servo, 86: Water flow servo, 90: Burner forward path, 91: Water flow sensor, 92: Burner return path, 94: Burner bypass path, 96: Burner outlet thermistor, 100: Burner controller

Claims

1. Hot water storage tank and A heat pump that heats the water in the aforementioned hot water storage tank, A path which is connected to the hot water storage tank and through which water flows in or out of the hot water storage tank, A freeze-prevention heater for preventing the water in the aforementioned path from freezing, the freeze-prevention heater being attached to at least a portion of the aforementioned path and generating heat when an electric current is applied to heat the water in the aforementioned path, A hot water supply system comprising a control unit, The heat pump comprises a compressor for pressurizing the refrigerant, a condenser for heating water and condensing the refrigerant through heat exchange between water and the refrigerant, an expansion valve for reducing the pressure of the refrigerant, and an evaporator for evaporating the refrigerant by absorbing heat from the outside air through heat exchange between the outside air and the refrigerant. The evaporator is equipped with an evaporator thermistor for detecting the temperature of the evaporator. The control unit, When the temperature of the evaporator detected by the evaporator thermistor falls below a predetermined defrosting start temperature, thus fulfilling a predetermined defrosting start condition, a defrosting operation can be performed in which the frost adhering to the evaporator is defrosted by the heat of the refrigerant, which has been pressurized and its temperature has risen by the compressor. A hot water supply system that, when the hot water supply system is operating in a power-reduced state in which power consumption is reduced compared to the normal state, and when the anti-freeze heater is heating the water in the path, and it is predicted that the defrost start condition will be met because the temperature of the evaporator detected by the evaporator thermistor is below a predetermined reference evaporator temperature that is higher than the defrost start temperature, stops the anti-freeze heater, and then starts the defrost operation if the defrost start condition is met thereafter.

2. Hot water storage tank and A heat pump that heats the water in the aforementioned hot water storage tank, A path which is connected to the hot water storage tank and through which water flows in or out of the hot water storage tank, A freeze-prevention heater for preventing the water in the aforementioned path from freezing, the freeze-prevention heater being attached to at least a portion of the aforementioned path and generating heat when an electric current is applied to heat the water in the aforementioned path, A hot water supply system comprising a control unit, The heat pump comprises a compressor for pressurizing the refrigerant, a condenser for heating water and condensing the refrigerant through heat exchange between water and the refrigerant, an expansion valve for reducing the pressure of the refrigerant, and an evaporator for evaporating the refrigerant by absorbing heat from the outside air through heat exchange between the outside air and the refrigerant. The evaporator is equipped with an evaporator thermistor for detecting the temperature of the evaporator. The control unit, When the temperature of the evaporator detected by the evaporator thermistor falls below a predetermined defrosting start temperature, thus fulfilling a predetermined defrosting start condition, a defrosting operation can be performed in which the frost adhering to the evaporator is defrosted by the heat of the refrigerant, which has been pressurized and its temperature has risen by the compressor. A hot water supply system that, when the hot water supply system is operating in a power-reduced state in which power consumption is reduced compared to the normal state, and when the anti-freeze heater is heating the water in the path, and it is predicted that the defrost start condition will be met because the temperature of the evaporator detected by the evaporator thermistor is below a predetermined reference evaporator temperature that is higher than the defrost start temperature, reduces the amount of power supplied to the anti-freeze heater, and then starts the defrost operation if the defrost start condition is met thereafter.

3. The hot water supply device according to claim 1 or 2, further comprising an auxiliary heat source unit for heating water supplied from the hot water storage tank to the hot water supply location.

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