JP7622768B2 - Storage water heater - Google Patents

Description

This disclosure relates to a storage type water heater.

In a storage type water heater, in order to concentrate heating operations during the nighttime hours when electricity rates are cheaper, it is common for the entire amount of hot water in the hot water storage tank to be heated to the highest temperature that can be set during the nighttime hours. In a storage type water heater, it is common for the hot water storage tank to be combined with a heating means that has the heating capacity to complete heating of the entire amount during the nighttime hours.

Patent Document 1 also describes a storage-type water heater that can change its heating capacity. In the late-night boiling operation of the storage-type water heater described in Patent Document 1, the boiling operation is performed with a heating capacity that can complete boiling of the entire amount of water by the end of the late-night period. If hot water is used unexpectedly during this boiling operation, and it is determined that the required amount of hot water will not be boiled, the heating capacity is changed to a higher heating capacity.

Japanese Patent Publication No. 2010-127569

If the heating capacity for the boiling operation during the nighttime hours is set to a heating capacity that can boil the entire amount of hot water in the hot water storage tank, there is a risk that energy efficiency will actually be reduced if there is no need to boil the entire amount of hot water in the hot water storage tank.

The present disclosure has been made to solve the above problems, and aims to provide an improved storage-type water heater that can perform boiling operation with efficient heating capacity even when it is not necessary to boil the entire amount.

The storage type water heater of the present disclosure comprises a heating means configured to be able to change the heating capacity for heating water, a hot water storage tank in which water heated by the heating means can be stored, and a control device configured to control switching of the heating capacity of the heating means and to control a boiling operation in which water heated by the heating means is stored in the hot water storage tank. The rated heating capacity of the heating means is the capacity when operating under JIS performance evaluation conditions, and is lower than the heating capacity that can complete full boiling of the entire amount of water in the hot water storage tank to the settable maximum hot water storage temperature during a low price period, which is a period of time during a 24-hour day when the electricity rate unit price is lower than other periods , and the heating means is capable of operating at a high heating capacity higher than the rated heating capacity, and the control device has a first mode in which the target hot water storage temperature during boiling operation is set to a target temperature lower than the maximum hot water storage temperature, and a second mode in which full boiling is performed with the target hot water storage temperature during boiling operation set to the maximum hot water storage temperature, and when boiling is performed in the first mode, boiling operation is performed with the heating capacity of the heating means at the rated heating capacity, and when full boiling is performed in the second mode during the low price period, if it is expected that full boiling will not be completed by the end of the low price period with boiling operation at the rated heating capacity, boiling operation at high heating capacity is performed for the time required for full boiling to be completed at the end of the low price period.

According to the present disclosure, when the amount of heat that needs to be boiled is small, boiling operation can be performed with efficient heating capacity.

1 is a diagram showing a schematic diagram of the overall configuration of a storage type water heater according to a first embodiment of the present disclosure; A figure showing the relationship between the heating capacity and the amount of boiled water of a heat pump unit of a storage type water heater according to embodiment 1 of the present disclosure. A figure showing the change in the amount of boiled water when the heating capacity of the heat pump unit 7 is switched midway through full-volume boiling in the storage type water heater of embodiment 1 of the present disclosure.

Below, an embodiment of the present disclosure will be described with reference to the drawings. Elements common to each drawing will be given the same reference numerals, and duplicate explanations will be omitted. In this disclosure, when "water" or "hot water" is simply stated, it can include liquid water at any temperature, from low temperature water to high temperature hot water. In addition, in this disclosure, the amount of heat contained in hot water may be treated as the amount of water converted into hot water at a specified temperature. In other words, in this disclosure, the term "amount of hot water" may essentially mean the amount of heat.

Embodiment 1.
1 is a diagram showing a schematic diagram of an overall configuration of a storage type hot water heater according to the first embodiment of the present disclosure. The storage type hot water heater 35 includes a tank unit 33, an HP (heat pump) unit 7, and a remote control device 44. The HP unit 7 and the tank unit 33 are connected via an HP forward pipe 14, an HP return pipe 15, and electrical wiring (not shown).

A control device 36 is built into the tank unit 33. The operation of the various valves, pumps, etc. equipped in the tank unit 33 and HP unit 7 is controlled by the control device 36 that is electrically connected to them.

The control device 36 and the remote control device 44 are connected by wire or wirelessly in a state in which they can communicate with each other. The remote control device 44 is an example of a user interface. Although not shown in the figure, the remote control device 44 is equipped with a display unit that displays information such as the operating status of the hot water storage type hot water heater 35, an operation unit such as switches operated by the user, a speaker, a microphone, etc. The operation unit accepts user operations regarding operating commands for the hot water storage type hot water heater and changes to setting values, etc.

The remote control device 44 may be installed on a wall in, for example, the kitchen, living room, or bathroom. Multiple remote control devices 44 may be capable of communicating with the control device 36. Also, a mobile terminal such as a smartphone may have a function as a user interface like the remote control device 44. In this case, the mobile terminal and the control device 36 may be capable of communicating with each other via a network.

The HP unit 7 functions as a heating means for heating water. The HP unit 7 has a compressor 1, a water-refrigerant heat exchanger 3, an expansion valve 4, and an air heat exchanger 6 connected in a ring shape by refrigerant piping 5 to form a heat pump cycle. The water-refrigerant heat exchanger 3 is for exchanging heat between the refrigerant flowing through the refrigerant piping 5 and the low-temperature water guided from the tank unit 33.

In this embodiment, the value of the heating capacity of the refrigerant circuit of the HP unit 7 can be changed. In the following description, the heating capacity of the HP unit 7 may be simply referred to as "heating capacity." The heating capacity corresponds to, for example, the amount of heat that the HP unit 7 provides to water per hour. The unit of heating capacity is, for example, kW (kilowatts).

The tank unit 33 incorporates the following various components and pipes. The hot water tank 8 is for storing hot water. A third water supply pipe 9c is connected to a water inlet 8a provided at the bottom of the hot water tank 8. Water supplied from a water source such as a mains water supply is adjusted to a predetermined pressure by a pressure reducing valve 31 and flows into the hot water tank 8 through the third water supply pipe 9c. A hot water supply pipe 21 and a hot water delivery pipe 13 are connected to a hot water inlet outlet 8d provided at the top of the hot water tank 8 for supplying the hot water stored in the hot water tank 8 to the outside of the hot water storage type water heater 35.

The high-temperature water heated by the HP unit 7 flows into the hot water storage tank 8 from the hot water inlet outlet 8d. Meanwhile, low-temperature water from the third water supply pipe 9c flows into the hot water storage tank 8 from the water inlet 8a. This causes hot water to be stored in the hot water storage tank 8 so that a temperature difference occurs between the top and bottom. Multiple hot water temperature sensors 42, 43 are attached at different heights on the surface of the hot water storage tank 8. By detecting the temperature distribution of the hot water in the hot water storage tank 8 with these hot water temperature sensors 42, 43, the amount of hot water remaining in the hot water storage tank 8 is grasped, and based on this, the start and stop of the hot water boiling operation in the hot water storage tank 8 by the HP unit 7 is controlled.

The heat source pump 12 and the bath heat exchanger 20 are built into the tank unit 33. The heat source pump 12 is a pump for circulating hot water through various pipes in the tank unit 33, which will be described later, and is provided on the HP supply pipe 14.

The bath heat exchanger 20 is a heat exchanger that uses high-temperature hot water supplied from the hot water storage tank 8 or HP unit 7 to heat the water to be heated on the secondary side (such as bath water or heating water). In this embodiment, the secondary side configuration of the bath heat exchanger 20 is illustrated and explained using a bath supply pipe 27 and a bath return pipe 28 that circulate the hot water in the bathtub 30. The bath heat exchanger 20 is installed midway between the bath supply pipe 27 and the bath return pipe 28. In addition, a bath circulation pump 29 for circulating the bath water is installed midway in the bath return pipe 28.

The three-way valve 11 is a flow path switching means having ports a and b through which hot and cold water flows in, and port c through which hot and cold water flows out, and can switch between two paths, a-c and bc. The four-way valve 18 is a flow path switching means having ports b and c through which hot and cold water flows in, and ports a and d through which hot and cold water flows out, and is configured to be able to switch between four paths, b-a, c-a, b-d, and c-d.

The water outlet pipe 10 connects the water outlet 8b provided at the bottom of the hot water storage tank 8 to the a port of the three-way valve 11. The HP forward pipe 14 connects the c port of the three-way valve 11 to the inlet side of the HP unit 7. The HP return pipe 15 connects the outlet side of the HP unit 7 to the c port of the four-way valve 18. The hot water supply pipe 13 connects the d port of the four-way valve 18 to the hot water inlet outlet 8d at the top of the hot water storage tank 8. The first bypass pipe 16 connects the a port of the four-way valve 18 to the hot water inlet 8c provided between the center and the bottom of the hot water storage tank 8. The hot water supply pipe 20a branches off from the hot water supply pipe 13 and is connected to the primary side inlet of the bath heat exchanger 20. The hot water outlet pipe 20b connects the primary side outlet of the bath heat exchanger 20 to the b port of the three-way valve 11. The second bypass pipe 17 branches off from the HP forward pipe 14 between the heat source pump 12 and the inlet side of the HP unit 7, and is connected to port b of the four-way valve 18.

One end of the first water supply pipe 9a is connected to a water source such as a water line, and the other end of the first water supply pipe 9a is connected to the second water supply pipe 9b and the third water supply pipe 9c via a pressure reducing valve 31. The second water supply pipe 9b branches off midway and is connected to the hot water supply mixing valve 22 and the bath mixing valve 23. The hot water supply pipe 21 branches off midway and is connected to the hot water supply mixing valve 22 and the bath mixing valve 23. The first hot water supply pipe 24 is connected to the outlet of the hot water supply mixing valve 22, and the second hot water supply pipe 25 is connected to the outlet of the bath mixing valve 23. A bath solenoid valve 26 that opens and closes the second hot water supply pipe 25 and a bath flow rate sensor 45 that detects the flow rate of hot water passing through the second hot water supply pipe 25 are provided midway in the second hot water supply pipe 25.

The hot water supply mixing valve 22 and the bath mixing valve 23 adjust the flow rate ratio between the high-temperature water supplied from the hot water supply pipe 21 and the low-temperature water supplied from the second water supply pipe 9b to produce hot water at the set temperature set by the user via the remote control device 44. The hot water adjusted to the set temperature by the hot water supply mixing valve 22 is supplied from the first hot water supply pipe 24 via the hot water tap 34 to a faucet (not shown) such as a shower or faucet used by the user. Meanwhile, the hot water adjusted to the set temperature by the bath mixing valve 23 is supplied from the second hot water supply pipe 25 via the bath solenoid valve 26, the bath flow sensor 45, the bath supply pipe 27, and the bath return pipe 28 to the bathtub 30.

In the past, in a hot water storage type water heater, an HP unit capable of completing the boiling of the entire amount of water at the rated heating capacity during the late night hours, which are low-cost hours in a day when the unit price of electricity is lower than other times, for example, during the 8 hours from 11:00 p.m. to 7:00 a.m. the next day, is combined according to the capacity of the hot water storage tank. As an example, the heating capacity of the HP unit is 4.5 kW for a tank capacity of 370 L, and the heating capacity of the HP unit is 6.0 kW for a tank capacity of 460 L. With this capacity, boiling of the entire amount of water, from a temperature of 5° C. entering the HP unit to a maximum hot water storage temperature of 90° C., can be completed within 8 hours during the late night hours. In the disclosure of this embodiment, the late night hours are exemplified as a time period in which the unit price of electricity is lower than other times during the 24 hours of a day, but this is not limited to this, and the present disclosure can also be applied to a time period in which the unit price of electricity is lower than other times during the 24 hours of a day when there is a low-cost time period.

However, in general, the lower the heating capacity of the HP unit, the better its efficiency (i.e., COP; Coefficient of Performance), and operating it at a high heating capacity that would allow full boiling even when full boiling is not necessary will result in reduced efficiency.

Therefore, the rated heating capacity of the HP unit 7 of the storage type hot water heater 35 according to this embodiment is lower than the heating capacity that can complete heating of the entire amount during late night hours. In other words, the rated heating capacity of the HP unit 7 in this embodiment is lower than the heating capacity of an HP unit installed in a conventional storage type hot water heater having a hot water storage tank of the same capacity as the hot water storage tank 8. The rated heating capacity corresponds to the heating capacity when operating under performance evaluation conditions according to JIS, for example. The HP unit 7 has a standard heating capacity at the rated heating capacity, and the heating capacity during normal times is set to the rated heating capacity.

Figure 2 is a diagram showing the relationship between the heating capacity of the HP unit 7 in embodiment 1 and the amount of hot water boiled. In the hot water storage type hot water heater 35 in this embodiment, as shown in Figure 2, for example, if the capacity of the hot water storage tank 8 is 370 L, an HP unit 7 with a rated heating capacity of 4.1 kW is combined, and if the capacity of the hot water storage tank 8 is 460 L, an HP unit 7 with a rated heating capacity of 5.1 kW is combined. As shown in Figure 2, these combinations of hot water storage tank capacity and heating capacity are combinations where there is a possibility that the entire amount of hot water cannot be boiled completely within, for example, an 8-hour period during the middle of the night.

In the storage type hot water heater 35 according to this embodiment, the rated heating capacity of the HP unit 7 is set lower than in the past, so that it can be operated at a lower heating capacity when the amount of water heated is small late at night and during daytime heating operation, thereby improving the COP.

The control device 36 controls the operation of the boiling operation. The boiling operation is an operation in which low-temperature hot water is taken out from the bottom of the hot water storage tank 8, heated in the HP unit 7, and the heated high-temperature water is allowed to flow into the hot water storage tank 8 from the top of the hot water storage tank 8. During the boiling operation, if the control device 36 predicts that the heating capacity of the HP unit 7 will be insufficient, it switches the heating capacity of the HP unit 7 from the rated heating capacity to a high heating capacity a2 that is higher than the rated heating capacity.

The control device 36 also controls the heating of the hot water in the hot water storage tank 8 to the target hot water storage temperature during late night hours every day. This is to concentrate heating operations during late night hours when electricity rates are cheaper.

In this embodiment, the boiling operation during the night hours is performed in one of two modes, the first mode and the second mode. Meanwhile, the first mode is a mode in which the boiling operation is performed with the target hot water storage temperature set to a temperature lower than the maximum hot water storage temperature. The maximum hot water storage temperature is the highest temperature within the range that can be set as the hot water storage temperature. Hereinafter, the target hot water storage temperature in the first mode will also be referred to as the "low target temperature". The second mode is a mode in which the target hot water storage temperature is set to the maximum hot water storage temperature, and the entire amount of hot water in the hot water storage tank 8 is boiled to the maximum hot water storage temperature. Hereinafter, the boiling in the second mode will also be referred to as "full boiling". In other words, the second mode is a mode in which more boiling is performed than in the first mode. The maximum hot water storage temperature is 90°C as an example, and in this case, the low target temperature is, for example, 85°C.

The control device 36 is normally configured to perform heating operation in the first mode during the late night hours. The heating capacity of the HP unit 7 when heating is performed in the first mode is the rated heating capacity. The control device 36 starts the heating operation at the start of the late night hours each day, and ends the heating operation when the temperature of the hot water taken out from the bottom of the hot water storage tank 8 and flowing into the HP unit 7 reaches the low target temperature.

Full-volume heating in the second mode is performed when it is judged necessary to heat a larger amount of water than usual during the night, for example when hot water usage is expected to be higher than usual the next day. When full-volume heating is performed in the second mode, if it is expected that the heating capacity will be insufficient for the amount of heat required to heat the entire amount (hereinafter "required amount of heat for boiling"), the heating capacity of the HP unit 7 is switched from the rated heating capacity to high heating capacity.

Figure 3 shows the change in the amount of water being boiled when the heating capacity of the HP unit 7 is switched during full boiling during the nighttime hours. In the example of Figure 3, the heating capacity is switched from the rated heating capacity to a high heating capacity that is higher than the rated heating capacity four hours after the start of the nighttime hours, making it possible to complete full boiling during the nighttime hours.

The timing for switching the heating capacity in the second mode is calculated as follows. First, the amount of remaining hot water (i.e., the amount of stored heat) in the hot water storage tank 8 at the start of the late-night period is subtracted from the amount of heat required when the entire amount of hot water in the hot water storage tank 8 is brought to the maximum hot water storage temperature, to calculate the amount of heat required to boil the water during the late-night period.

Next, the first time H1 for boiling at the rated heating capacity and the second time H2 for boiling at the high heating capacity are set so that boiling is completed during the nighttime hours in the boiling operation at the rated heating capacity in the first mode and the boiling operation at the high heating capacity in the second mode. More specifically, for example, if the value of the low heating capacity is a1, the value of the high heating capacity is a2, and the length of the nighttime hours is H0, the first time H1 and the second time H2 are set to satisfy the following relationship.
a1 x H1 + a2 x H2 = required boiling heat H1 + H2 = H0

When heating water in the second mode, the control device 36 performs heating operation at the rated heating capacity for the first hour H1 from the start of the late-night hours, and when the first hour H1 has elapsed, switches the heating capacity of the HP unit 7 from the rated heating capacity to high heating capacity and continues the heating operation. The control device 36 ends the heating operation when the temperature of the hot water flowing into the HP unit 7 reaches the maximum hot water storage temperature. This ensures that a sufficient amount of hot water can be secured in the hot water storage tank 8 when hot water usage is high during the daytime hours. Note that if the second hour H2 calculated as above is equal to or less than zero, heating capacity is not switched because it is expected that heating of the entire amount can be completed at the rated heating capacity during the late-night hours.

As described above, according to the storage type water heater 35 of this embodiment, during normal times, water is heated at a rated heating capacity that is lower than the heating capacity required to heat the entire amount of water during late night hours. This makes it possible to increase the energy efficiency of the storage type water heater 35, and when full heating is required, the heating capacity is switched to high for the minimum amount of time required to ensure sufficient heat. This makes it possible to prevent hot water shortages during the daytime.

In this embodiment, the rated heating capacity is at least lower than the maximum heating capacity of the HP unit 7 and lower than the high heating capacity. The rated heating capacity is set to a capacity that is at least equal to or greater than the capacity that can complete the heating of water at the low target temperature in the first mode during the night hours. By configuring the water heater to be able to complete the heating of water to the low target temperature during the night hours, the operating costs of the hot water storage type water heater 35 can be reduced and the water heater can be recognized as a night-time heat storage type device. If the rated heating capacity is set too low, the COP may decrease. Therefore, the rated heating capacity may be configured to be set to the capacity that provides the best COP.

In addition, in this embodiment, when boiling water in the first mode, the heating capacity of the HP unit 7 is set to the rated heating capacity. This can improve the COP. However, this is not limited to the above, and for example, if the rated heating capacity is low and a shortage of heating capacity is expected even when boiling water in the first mode, the configuration may be such that the heating capacity is switched to high midway, as in the case of the second mode. This can ensure that the required amount of heat is secured.

The storage type water heater 35 according to this embodiment may also have a configuration that allows the user to use the remote control device 44 to set the heating capacity to be fixed at the rated heating capacity. While the setting is set to fix the heating capacity at the rated heating capacity, the control device 36 does not change the heating capacity to high even when full heating is performed during late-night hours, but maintains the rated heating capacity and heats the water with the target storage water temperature set to the low target temperature. For example, when the user places importance on COP, the user's setting takes priority, and the user's experience of using the storage type water heater 35 can be improved.

The storage type water heater 35 according to this embodiment may also have a configuration that allows the user to use a remote control device to set the heating capacity to a fixed high heating capacity. While the setting is set to fix the heating capacity at high heating capacity, the control device 36 performs heating operation at high heating capacity with the target storage temperature set as the maximum storage temperature, even when heating is performed in the first mode during late-night hours. For example, when the user places importance on preventing a shortage of hot water, the user's setting can be prioritized, and the user's experience of using the storage type water heater 35 can be improved.

The storage type hot water heater 35 according to this embodiment may also be configured so that the user can use the remote control device 44 to set the amount of hot water to be heated during the night hours to the full amount. When this setting is made, the heating operation during the night hours is set to the second mode, and the full amount is heated. In this case as well, if the heating capacity is insufficient for the required amount of heat for boiling, the second time H2, which is the time for heating operation at high heating capacity, is calculated as described above, and at the point in time before the second time H2 when the night hours end, the HP unit 7 is switched to high heating capacity and heating is performed. This allows the user to secure the amount of hot water storage desired.

The storage type water heater 35 according to this embodiment may also be configured so that the user can use the remote control device 44 to instruct the start of full-volume boiling. In this case, the remote control device 44 may be provided with a "full tank" button for full-volume boiling, and the start of full-volume boiling can be instructed by pressing this button. When the remote control device 44 receives the "full tank" instruction, the control device 36 immediately switches the heating capacity of the HP unit 7 to high heating capacity and starts operation in the second mode. This makes it possible to prioritize quick boiling in response to the user's instruction.

In this embodiment, when the entire amount of water is boiled during the night hours and it is expected that the rated heating capacity will be insufficient, the water is first boiled at the rated heating capacity for the first hour H1, and then boiled at high heating capacity for the second hour H2. It is expected that other devices will also be using a lot of electricity at the start of the night hours. Therefore, peak power consumption can be suppressed by performing boiling operation at the rated heating capacity, which consumes less power, from the start of the night hours through the first hour H1.

However, the hot water storage type hot water heater 35 according to this embodiment is not limited to a configuration in which operation at the rated heating capacity is performed first. When the entire amount is boiled, the configuration may be such that boiling is performed at high heating capacity for the above-mentioned second time H2 from the start of the late-night period, and then the boiling operation is continued by switching to the rated heating capacity. By starting boiling at high heating capacity at the start of the late-night period, it is possible to deal with the case where hot water is used during the period and the amount of hot water remaining in the hot water storage tank 8 decreases. In other words, if hot water is used for hot water supply during boiling at high heating capacity, the operating time of boiling at high heating capacity can be extended so that the required amount of heat for boiling is secured even after the hot water supply is used. In addition, if hot water is used for hot water supply after switching to the rated heating capacity, the required amount of heat can be secured by switching back to high heating capacity.

Furthermore, the storage type hot water heater 35 according to this embodiment may be configured so that the user can set, via the remote control device 44, whether to perform boiling operation at the rated heating capacity first or boiling operation at the high heating capacity first. In this case, the control device 36 is configured to switch the heating capacity in the order selected by the user when performing full boiling.

1 Compressor, 3 Water-refrigerant heat exchanger, 4 Expansion valve, 5 Refrigerant piping, 6 Air heat exchanger, 7 HP unit, 8 Hot water tank, 8a Water inlet, 8b Water outlet, 8c Hot water inlet, 8d Hot water inlet outlet, 9a First water supply piping, 9b Second water supply piping, 9c Third water supply piping, 10 Water outlet piping, 11 Three-way valve, 12 Heat source pump, 13 Hot water supply piping, 14 HP forward piping, 15 HP return piping, 16 First bypass piping, 17 Second bypass piping, 18 Four-way valve, 20 Bath heat exchanger, 20a Hot water inlet piping, 20b Hot water outlet piping, 21 Hot water supply piping, 22 Hot water supply mixing valve, 23 Bath mixing valve, 24 First hot water supply pipe, 25 Second hot water supply pipe, 26 Bath solenoid valve, 27 Bath supply pipe, 28 Bath return pipe, 29 Bath circulation pump, 30 Bathtub, 31 Pressure reducing valve, 33 Tank unit, 34 Hot water tap, 35 Storage water heater, 36 Control device, 42, 43 Storage water temperature sensor, 44 Remote control device, 45 Bath flow rate sensor

Claims (7)

A heating means configured to be able to change a heating capacity for heating water;
a hot water storage tank capable of storing the water heated by the heating means;
A control device configured to control switching of the heating capacity of the heating means and to control a boiling operation for storing water heated by the heating means in the hot water storage tank;
Equipped with
The rated heating capacity of the heating means is a capacity when operating under JIS performance evaluation conditions, and is a capacity lower than a heating capacity capable of completing the heating of the entire amount of water in the hot water storage tank to a settable maximum hot water storage temperature during a low-price time period during which the electricity rate unit price is lower than other time periods during a 24-hour day,
The heating means is operable at a heating capacity higher than the rated heating capacity,
The control device includes:
a first mode in which a target stored hot water temperature during the heating operation is set to a target temperature lower than the maximum stored hot water temperature;
a second mode in which the target stored hot water temperature during the heating operation is set to the maximum stored hot water temperature and the entire amount of the water is heated;
When the water is boiled in the first mode, the heating capacity of the heating means is set to the rated heating capacity to perform the boiling operation.
When the full amount of water is boiled in the second mode during the low price time period,
When it is predicted that the boiling operation at the rated heating capacity will not be completed by the end time of the low-price time slot, the boiling operation at the high heating capacity is performed for the time required for the boiling operation to be completed at the end time of the low-price time slot.
A storage type water heater characterized by the above . The storage-type hot water heater according to claim 1, characterized in that the rated heating capacity is the heating capacity that provides the best energy efficiency. An operation unit that receives a command from a user to fix the heating capacity of the heating means to the rated heating capacity,
The control device is configured to set the heating capacity of the heating means in the boiling operation to the rated heating capacity when the operation unit receives a command to fix the heating capacity to the rated heating capacity.
3. The hot water storage type water heater according to claim 1 or 2 . An operation unit that receives a command from a user to fix the heating capacity of the heating means to the high heating capacity,
The control device is configured to set the heating capacity of the heating means in the boiling operation to the high heating capacity when the operation unit receives a command to fix the heating capacity to the high heating capacity.
4. The hot water storage type water heater according to claim 1 , wherein the hot water storage type water heater comprises: An operation unit that receives a command from a user to start the full boiling,
The control device is configured to execute the boiling operation at the high heating capacity when the operation unit receives a command to start the full amount boiling.
5. The hot water storage type water heater according to claim 1 , When the control device performs the full amount of heating during the low price time period,
After performing the boiling operation at the rated heating capacity, the boiler is configured to switch to the high heating capacity.
6. The storage type hot water heater according to claim 1 , When the control device boils the entire amount of water during the low price time period,
After performing the boiling operation at the high heating capacity, the boiling operation is switched to the rated heating capacity.
7. The storage type hot water heater according to claim 1 ,

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