JP3869749B2 - Hot water storage water heater - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hot water storage type hot water heater such as a heat pump type hot water heater utilizing the heat of condensation of a refrigerant. More specifically, the present invention relates to prevention of freezing of water in a pipe of a hot water storage type water heater provided with a hot water tank.
[0002]
[Prior art]
Conventionally, in a hot water storage water heater such as a heat pump hot water heater, a circulating pump is used to circulate the water in the hot water tank with a heat source such as a heat pump or a fuel cell to generate hot water for hot water storage. Store hot water inside.
[0003]
In the hot water storage type hot water heater, for example, when the outside air temperature decreases in winter, the water in the circulation pipe connected between the hot water storage tank and the heat source may freeze, and hot water supply may not be possible. In addition, if the water in the pipe freezes, the pipe may be broken due to expansion during freezing, or the pipe may crack and water leakage may occur, and this water leakage causes insufficient water circulation, Equipment such as a heat source was causing failure.
[0004]
[Problems to be solved by the invention]
When a heat source such as a heat pump unit is operated when the outside air temperature is lowered to prevent freezing in the piping of the hot water storage type hot water heater and hot water is circulated through the piping, the heat source for preventing freezing In order to consume electric power for the operation, there arises a problem that COP, which is the energy consumption efficiency of the year, decreases. In addition, there is a problem that the amount of power used increases and the burden of power charges on the user increases.
[0005]
In particular, in a hot water storage type water heater, a heat source is operated during the night when the electricity rate is low (for example, from 11 pm to 7 am), and the water in the hot water tank is heated to raise the temperature and store hot water. By using the hot water in the hot water tank during the daytime other than the nighttime when the electricity charge is high, the electricity charge burdened by the user is suppressed.
[0006]
However, if the heat source is operated as described above to prevent the piping from freezing in the daytime, it will consume the daytime power, which has a high power charge, and there will be a problem that the burden on the user's power charge will increase significantly. To do.
[0007]
In addition, in order to avoid the operation of the heat source to prevent freezing as much as possible, hot water in the hot water tank is supplied to the pipe when the outside air temperature drops, and the water whose temperature has dropped in the pipe is returned to the upper part of the hot water tank. The balance between the temperature layers of the hot water and the low-temperature water stored in the hot water tank is lost, the hot water in the hot water tank is uniformized as a whole, and there is a problem that the hot water cannot be supplied. .
[0008]
Accordingly, an object of the present invention is to prevent freezing of piping and to maintain a temperature layer in a hot water storage tank while suppressing an increase in power consumption of the hot water storage type hot water heater as much as possible.
[0010]
[Means for Solving the Problems]
  This is why the firstThe invention relates to a hot water storage type hot water heater provided with a hot water supply circuit that circulates water between a hot water storage tank and a heat source for heating by a circulation pump and enables hot water to be discharged from the hot water storage tank. A temperature detector for detecting the temperature of water in the pipe connected between the storage unit, a storage means for storing a first set temperature and a second set temperature lower than the first set temperature, and detection by the temperature detector When the temperature drops to the first set temperature stored in the storage means, the operation of the circulation pump is started, low temperature water in the lower part of the hot water tank is circulated in the pipe, and the temperature detector Control means for starting the operation of the circulation pump and circulating the hot water in the upper part of the hot water storage tank into the pipe when the detected temperature of the water drops to the second set temperature stored in the storage means. PreparedThatFeatures.
[0011]
  AlsoSecondAccording to the present invention, when the temperature detected by the temperature detector is lowered to the second set temperature stored in the storage means and the circulating pump is operating, the upper part in the hot water storage tank isFromA return pipe was provided for returning the returned water that was supplied and circulated through the pipe to the intermediate layer of the hot water tank.ThatFeatures.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of a circuit of a heat pump water heater as a hot water storage type hot water heater to which the present invention is applied. This heat pump water heater exchanges heat between refrigerant and water compressed by a compressor by a heat exchanger for heating. A heat pump unit 100 as a heat source including a refrigerant circuit, a hot water tank unit 200 including a hot water tank for storing high-temperature water whose temperature has risen in the heat pump unit 100, a hot water tank and the heating heat by using a circulation pump The main configuration is a hot water supply circuit 300 that circulates between the heat exchanger and allows hot water to be discharged from the hot water storage tank.
[0013]
The refrigerant circuit provided in the heat pump unit 100 includes a compressor 1 that sucks and compresses refrigerant to generate high temperature and pressure, a refrigerant-to-water heat exchanger 2 that heat-exchanges refrigerant and water, and an electric expansion valve 3. And an evaporator 4 as an outdoor heat exchanger that performs heat exchange between the outside air and the refrigerant, an accumulator 5, and the like.
[0014]
The hot water tank unit 200 includes a control board 9 to which a kitchen remote controller (remote controller) 7 operated in the kitchen and a bath remote controller (remote controller) 8 operated in the bathroom are connected, and a hot water tank 10 for storing hot water. The control board 9 is equipped with a microcomputer (hereinafter referred to as “microcomputer”) 40 as control means for controlling the heat pump water heater. The kitchen remote controller 7 and the bathroom remote controller 8 are provided with a time display device and the like.
[0015]
The hot water supply circuit 300 is connected to a hot water pressure reducing valve 11 with a check valve for supplying tap water to the hot water storage tank 10, a hot water discharge pipe 12 for taking out hot water from the upper part of the hot water storage tank 10, and a hot water supply pipe 12 from the outlet side of the water pressure reducing valve 11. The bypass pipe 14 reaching the mixing valve 13, the hot water filling pipe 15 branched from the hot water feeding pipe 12 to the bathtub 31, the flow rate adjusting valve 16 connected to the hot water filling pipe 15, and the hot water upstream of the mixing valve 13 A pressure relief valve 17 connected to the pipe 12, a forward pipe 18 connected between the lower end of the hot water storage tank 10 and the inlet side of the refrigerant-to-water heat exchanger 2, and connected in the middle of the forward pipe 18. A circulation pump 19 for supplying water from the hot water storage tank 10 to the refrigerant-to-water heat exchanger 2, an on-off valve (hereinafter referred to as “water inlet valve”) 20 connected to the upstream side of the circulation pump 19, the circulation pump 19 and the incoming valve 20 A high-temperature water circulation pipe 21 that branches from the hot water supply pipe 12, an on-off valve (hereinafter referred to as a “high-temperature valve”) 22 connected in the middle of the high-temperature water circulation pipe 21, and an outlet of the refrigerant-to-water heat exchanger 2 The first return pipe 23 connected between the side and the upper end of the hot water tank 10, the flow rate adjusting valve 24 as the flow rate adjusting means connected in the middle of the first return pipe 23, the first return pipe A second return pipe 25 branched from the middle of the hot water tank 10 and connected to the lower part of the hot water tank 10, and an on-off valve (hereinafter referred to as “return valve”) 26 connected in the middle of the second return pipe 25 are piped. Connected and configured.
[0016]
Further, a temperature sensor (hereinafter referred to as “inlet temperature sensor”) 28 and a temperature sensor (hereinafter referred to as “outlet temperature sensor”) as an outside air temperature sensor are respectively provided on the inlet side and the outlet side of the refrigerant-to-water heat exchanger 2. 29, and a temperature sensor 30 (hereinafter referred to as “hot water tank inlet temperature sensor”) 30 as an outside air temperature sensor is provided in the middle of the first return pipe 23 in the hot water tank unit 200.
[0017]
Next, description will be made based on the control block diagram of FIG. The microcomputer 40 provided on the control board 9 on the hot water tank unit 200 side includes a CPU (Central Processing Unit) 41 that performs overall control of operations related to the hot water tank unit 200 of the heat pump water heater, and a storage device that stores various data. RAM (Random Access Memory) 42 and a ROM (Read Only Memory) 43 for storing a program relating to hot water supply operation and freeze prevention operation. In the ROM 43, as shown in the table of FIG. 3, for example, the maximum amount of hot water, which is the maximum amount of hot water when boiling in the middle of the night using electric power in the hot water tank 10, and the minimum amount of hot water to start boiling, The amount of hot water at the end of reheating, which is the amount of hot water that stops boiling, is stored from mode 1 to mode 7 as the mode of boiling (increase) control, and these modes are changed based on changes in the amount of hot water stored. The program is set. Based on the data stored in the RAM 42, the CPU 41 controls the operation related to the hot water supply of the present heat pump water heater in accordance with the program stored in the ROM 43 and the above mode. In general, the microcomputer 40 controls the water heater so that the entire capacity of the hot water tank 10 is heated to a predetermined temperature.
[0018]
A kitchen remote controller CPU 7a is connected to the microcomputer 40 via a signal line. The kitchen remote controller CPU 7a has a boiling amount switch 7b for setting the amount of hot water when hot water is supplied to the bathtub 31, and a mode switch for switching the mode. A switch 7c is connected.
[0019]
Further, a microcomputer (hereinafter referred to as “microcomputer”) 50 as a control means on the heat pump unit 100 side includes a CPU 51 that performs overall control of operations related to the heat pump unit 100, a RAM 52 as a storage device that stores various data, and the heat pump unit 100. It is comprised from ROM53 which stores the program which concerns on this operation | movement. The compressor 1, the expansion valve 3, the inlet temperature sensor 28, the outlet temperature sensor 29, and the hot water tank inlet temperature sensor 30 are connected to the microcomputer 50 through signal lines.
[0020]
The microcomputer 40 and the microcomputer 50 are connected by a signal line 55, and detected temperatures of the inlet temperature sensor 28, the outlet temperature sensor 29 and the hot water tank inlet temperature sensor 30 are transmitted to the microcomputer 40 via the microcomputer 50 and the signal line 55, It is stored in the RAM 42 at any time. Further, the RAM 42 has a first set temperature (for example, 5 ° C.) when starting the freeze prevention operation by circulation of low-temperature water, which will be described later, and a second set temperature (for example, 10 ° C.) when ending the freeze prevention operation. ), A third set temperature (for example, 2 ° C.) at the start of the freeze prevention operation by circulation of high-temperature water and a fourth set temperature (for example, 10 ° C.) at the end of the freeze prevention operation are stored. .
[0021]
And the capacity | capacitance of the said hot water tank 10 is 370 liters, for example, and hot water temperature detection sensors TS1, TS2, TS3, TS4, TS5, TS6 and TS7 are vertically spaced from the lower part to the upper part of the hot water tank 10 in the hot water tank 10. Since the water heater can be heated up to 55 ° C., when the detected hot water temperature of each sensor is 55 ° C. or higher, the hot water storage from the upper end of the hot water storage tank 10 to the position is provided. It is judged that there is remaining hot water. At this time, the detection sensor TS1 is disposed at a position where the remaining hot water amount is 350 liters, TS2 is also 300 liters, TS3 is 250 liters, TS4 is 200 liters, TS5 is 150 liters, TS6 is 100 liters, and TS7 is 50 liters. .
[0022]
Here, the outside air temperature (for example, 25 ° C.) by the hot water tank inlet temperature sensor 30, the capacity of the heat pump (for example, 5.0 kW), the boiling temperature (for example, 75 ° C.), and the tap water with a check valve detected by the feed water temperature sensor 56. Supply temperature (for example, 20 ° C.) of tap water supplied to the hot water tank 10 via the pressure reducing valve 11, detection temperature (for example, 63 ° C.) of the hot water temperature detection sensor TS3, detection temperatures (for example, 50) of the hot water temperature detection sensors TS1 and TS2. Data) is stored in the RAM 42 of the microcomputer 40, and the microcomputer 40 determines the amount of hot water stored in the hot water tank 10 based on these data.
[0023]
That is, first, the microcomputer 40 searches for a combination of detection sensors including the boiling water temperature 55 ° C. between the two detection sensors from the seven hot water temperature detection sensors, and detects a temperature higher than 55 ° C. The detection temperature of the detection sensor is Thi, the amount of remaining hot water is Lhi, the detection temperature of the detection sensor detecting a low temperature is Tlo, and the amount of remaining hot water is Llo. The microcomputer 40 calculates the amount of stored hot water (the amount of remaining hot water) Lz from Lz = (Thi−55) / (Thi−Tlo) × (Llo−Lhi) + Lhi.
[0024]
Therefore, the microcomputer 40 determines that the remaining hot water amount Lz reaching 55 ° C. is about 286 liters from (63−55) / (63−50) × (300−250) +250.
[0025]
Next, the circulation flow rate (boiling amount per minute) is calculated by dividing the heating amount per minute by the heat pump by the temperature obtained by subtracting the water temperature from the boiling temperature. Specifically, the circulation flow rate = (heat pump The microcomputer 40 calculates from the capacity P × 860 (Kcal) / 60 (minutes) / (boiling temperature Tp− (outside air temperature Tt × 0.8 + 3)), that is, the feed water temperature at which the predetermined capacity is constant (refrigerant vs. water). The water temperature entering the heat exchanger 2) is calculated from conversion formulas obtained in various performance tests using the outside air temperature value.
[0026]
Therefore, the microcomputer 40 determines that the circulation flow rate is about 1.38 liters / minute from (5 × 860/60 / (75− (25 × 0.8 + 3)).₂In this case, when the boiling temperature is fixed and the feed water temperature (water temperature entering the refrigerant-to-water heat exchanger 2) rises, the heating capacity gradually decreases even if the frequency of the compressor 1 is kept constant, and the water temperature Since the curve of the rise and the decline in capacity is not completely linear, the operation of lowering the frequency of the compressor 1 step by step according to the inlet water temperature, including the protection of the compressor 1 with this water heater, is the result. Therefore, even if the inlet water temperature fluctuates, control is performed so as to perform an operation for maintaining a substantially constant circulation flow rate under the same outside air temperature condition.
[0027]
As described above, the microcomputer 40 determines the amount of hot water stored in the hot water storage tank 10 and calculates the circulation amount at the time of boiling (when boiling).
[0028]
Hereinafter, control at the time of hot water supply from the heat pump water heater will be described.
[0029]
When hot water is supplied from the hot water storage state (the hatched portion indicates the amount of hot water stored in the entire capacity) as shown in (a) of FIG. Water is supplied from the water pressure reducing valve 11 with a check valve so that the water is full. Hot water is used and the amount of hot water storage gradually decreases, and the hot water storage state shown in FIG. Furthermore, as shown in (c), the amount of hot water supplied is reduced and the amount of stored hot water is less than the minimum amount of stored hot water (for example, 150 liters in the case of mode 4), and the detection temperature of the detection sensor TS6 is the temperature at which the hot water storage state is determined. When the temperature falls below 55 ° C., the microcomputer 40 determines that the amount of stored hot water has become smaller than the position of the detection sensor, outputs an operation signal to the microcomputer 50 on the heat pump unit 100 side, and causes the heat pump water heater to start boiling and start operation.
[0030]
That is, the compressor 1 starts operation, and the refrigerant that has been compressed by the compressor 1 and has reached a high temperature is supplied to the refrigerant-to-water heat exchanger 2. Then, the circulation pump 19 is activated, and the water at the bottom of the hot water tank 10 is supplied to the refrigerant-to-water heat exchanger 2 through the water inlet valve 20 to start heat exchange between the refrigerant and water. As a result, the refrigerant loses heat and condenses, and the water rises in temperature due to the heat of condensation of the refrigerant, and becomes hot water, that is, hot water, and returns to the hot water storage tank 10 via the flow rate control valve 24.
[0031]
At this time, the microcomputer 40 operates based on the temperature detected by the outlet temperature sensor 29 and controls the opening degree of the flow rate control valve 24, so that the hot water whose temperature has increased to almost the set temperature (for example, 85 ° C.) It is supplied from the pipe 23 to the upper part of the hot water tank 10. Accordingly, the upper layer in the hot water tank 10 is hot water and the lower layer is water, and the hot water layer and the water layer are not mixed with the passage of time, and the hot water layer increases and the water layer decreases. In the normal operation state (corresponding to mode 7), the hot water storage tank 10 is finally filled with hot water. For example, when the heating control mode is mode 4, the state shown in FIG. As shown in the figure, when the hot water storage amount rises to 200 liters, which is the amount of completion of boiling, and when the detection temperature of the detection sensor TS5 reaches 55 ° C. or more, the CPU 41 operates and the microcomputer 40 sends a stop signal to the circulation pump 19. While outputting, a stop signal is output to the compressor 1 via the microcomputer 50, and the boiling increase operation is completed.
[0032]
As described above, during the heating operation, the heating operation is controlled according to the heating control mode shown in FIG. 3. Hereinafter, the control when changing the heating control mode will be described based on the flowchart of FIG. I will explain.
[0033]
First, it is determined whether the boiling control mode (operation mode) is manual or automatic. If the mode is manual, the boiling control mode is set to modes 1 to 3 based on the operation of the boiling amount setting switch 17b. Is set between. That is, the amount of boiling is divided into three stages, for example, large, medium, and small. Mode 3 is set when the amount is large, mode 2 is set when the amount is medium, and mode 1 is set when the amount is small. The operation of the heat pump water heater is controlled according to the set mode.
[0034]
When the heating control mode (operation mode) is automatic, for example, when the power to the heat pump water heater is turned on, the heating control mode 3 which is the standard mode is automatically set. For this reason, the amount of hot water is reduced by the hot water supply from the hot water storage tank 10, the detection temperature of the detection sensor TS6 is lower than 55 ° C., and the microcomputer 40 determines that the amount of hot water storage is less than 100 liters (determination A). With this determination, a timer (not shown) provided in the microcomputer 40 starts operating. After that, when the hot water storage amount does not become 50 liters or less, that is, when the detection sensor TS7 continues to detect a temperature of 55 ° C. or higher, the heating control mode 3 is set to a predetermined time (preliminary time set in the timer) For example 3 days).
[0035]
Note that when the amount of stored hot water decreases before the predetermined time elapses and the detection temperature of the detection sensor TS7 becomes lower than 55 ° C., the microcomputer 40 determines that the amount of stored hot water is less than 50 liters (determination B). Then, the heating control mode is shifted to a mode that is one level higher, that is, mode 4 that is a mode with a large mode number. For this reason, the minimum hot water storage amount at the start of boiling increase increases from 100 liters to 150 liters, and the final hot water storage amount at the boiling increase operation increases from 150 liters to 200 liters.
[0036]
When the microcomputer 40 determines that there is a hot water storage amount of 100 liters or more in the hot water storage tank 10 based on the detected temperature of the detection sensor TS6 (determination C), a timer (not shown) operates. When a hot water storage amount of 100 liters or more is maintained for a predetermined period (for example, 3 days) set in advance, the timer counts up, the microcomputer 40 operates, and a mode lower by one rank, that is, a mode number Shifts to mode 2, which is a mode with a small value. As a result, the maximum boiling amount is reduced from 370 liters to 300 liters.
[0037]
In each boiling control mode, the same determination as in the above mode 3 is performed. For example, in mode 5, when a hot water storage amount of 100 liters or more is maintained for a predetermined period, the timer counts up and the microcomputer 40 Operates and shifts to the next lower mode, that is, mode 4 which is a mode with a smaller mode number. As a result, the minimum hot water storage amount at the start of boiling increases from 200 liters to 150 liters, and the final hot water storage amount after the boiling increase operation decreases from 250 liters to 200 liters. Similarly, in modes 4 to 7, when a hot water storage amount of 100 liters or more is maintained for a predetermined period, the timer counts up, the microcomputer 20 operates, and the mode lower in rank, that is, the mode number is set. Transition to a mode that is a smaller mode. As a result, both the minimum hot water storage amount at the start of boiling increase and the hot water storage amount at the end of boiling operation are reduced by 50 liters.
[0038]
As a result, when the amount of hot water supply is large, that is, when the usage load is large, the mode number can be shifted to the larger one and, of course, it is possible to appropriately cope with the load. The number is shifted to the smaller one, the maximum boiling amount at midnight is reduced, and both the minimum hot water amount at the start of boiling and the hot water amount at the end of heating operation are reduced, thereby reducing the number of hot water tanks 10. It is possible to control a wide range of operations corresponding to the use load with capacity, that is, control of the amount of hot water stored or the amount of boiling, minimizing heat loss due to heat dissipation, and improving the operating efficiency of the heat pump water heater, that is, the hot water supply efficiency.
[0039]
Hereinafter, the antifreezing operation in winter or the like of the heat pump water heater in which the hot water supply operation is controlled as described above will be described.
[0040]
When the operation of the heat pump unit 100 is stopped, the outside air temperature decreases, and the detected temperature of any of the inlet temperature sensor 28, the outlet temperature sensor 29, or the hot water tank inlet temperature sensor 30 is the first set temperature (5 ° C.). Then, the microcomputer 40 operates to maintain the water inlet valve 20 in the open state, open the return valve 26, close the flow rate adjusting valve 24, and operate the circulation pump 19.
[0041]
Accordingly, the low-temperature water stored in the lower layer 10a at the lower part of the hot water tank 10 is operated by the operation of the circulation pump 19 so that the low-temperature water of the low-temperature layer is the refrigerant-to-water heat exchanger of the inlet valve 20, the circulation pump 19, the forward pipe 18, and the heat pump unit 100. 2. It circulates with the lower layer 10a without the hot water storage tank 10 through the first return pipe 23, the second return pipe 25 and the return valve 26, and particularly the heat pump unit 100 and the hot water storage tank of the forward pipe 18 and the first return pipe 23. Freezing of a portion located between the unit 200 is prevented.
[0042]
Then, the temperature of the circulation path such as the forward pipe 18 and the first return pipe 23 rises due to the freeze prevention operation, and the detected temperatures of the inlet temperature sensor 28, the outlet temperature sensor 29, and the hot water tank inlet temperature sensor 30 are all second. When the set temperature (10 ° C.) is reached, the microcomputer 40 operates to close the return valve 26, open the flow rate adjustment valve 24, and further stop the operation of the circulation pump 19. As a result, the circulation of the low temperature water from the hot water tank 10 is stopped, the freeze prevention operation by the supply of low temperature water with reduced power is completed, and the increase in power consumption by the freeze prevention operation can be minimized.
[0043]
However, when the low-temperature water in the hot water storage tank 10 as described above is circulated to the outgoing pipe 18 and the first and second return pipes 23 and 25 to prevent freezing, the incoming temperature is further reduced as the outside air temperature further decreases. When the temperature of the pipe 18 and the first return pipe 23 decreases and the detected temperature of any of the inlet temperature sensor 28, the outlet temperature sensor 29, or the hot water tank inlet temperature sensor 30 becomes the third set temperature (2 ° C.), The microcomputer 40 operates, closes the water inlet valve 20, opens the high temperature valve 22, maintains the return valve 26 open, maintains the flow rate adjustment valve 24 closed, and operates the circulation pump 19.
[0044]
Accordingly, the high-temperature water stored in the upper part (upper layer) of the hot water tank 10 is operated by the operation of the circulation pump 19, and the high-temperature valve 22, the high-temperature water circulation pipe 21, the forward pipe 18, the circulation pump 19, and the refrigerant to water heat exchanger 2. It circulates with the lower layer of the hot water tank 10 through the first return pipe 23, the second return pipe 25 and the return valve 26. As a result, high-temperature water flows in the forward pipe 18 and the first return pipe 23, particularly in the portion located between the heat pump unit 100 and the hot water tank unit 200, and this portion can be more reliably prevented from freezing.
[0045]
The temperature of the circulation path such as the forward pipe 18 and the first return pipe 23 rises due to the freeze prevention operation by the high-temperature water supply, and is detected by the inlet temperature sensor 28, the outlet temperature sensor 29, and the hot water tank inlet temperature sensor 30. When all the temperatures reach the fourth set temperature (10 ° C.), the microcomputer 40 operates to close the high temperature valve 22 and the return valve 26, open the water inlet valve 20 and the flow rate adjustment valve 24, and operate the circulation pump 19. To stop. As a result, the circulation of the low temperature water from the hot water tank 10 is stopped, the freeze prevention operation by the supply of the high temperature water is finished, and the increase in power consumption by the freeze prevention operation can be minimized.
[0046]
Next, a second embodiment will be described based on FIG. The first embodiment branches from the middle of the first return pipe 23, connects the second return pipe 25 to the lower part of the hot water tank 10, and pipes the return valve 26 in the middle of the second return pipe 25. Whereas the second embodiment is configured to be connected, the second return pipe 25 is branched from the middle of the first return pipe 23 to reach the intermediate layer 10b which is an intermediate part of the hot water tank 10. This is different in that the return valve 26 and the check valve 27 are connected by piping in the middle of the second return pipe 25. That is, the tip of the second return pipe 25 of the second embodiment faces the intermediate layer 10b (the intermediate layer between the hot and low temperature layers of hot water in the hot water tank 10) that is an intermediate part of the hot water tank 10. ing.
[0047]
Further, when the freeze prevention operation is performed by circulating the high-temperature water as described above, the return water is returned to the intermediate layer 10b, which is the intermediate portion of the hot water tank 10, through the second return pipe 25. In addition, it is possible to avoid that the intermediate temperature water affects the upper layer of the upper layer 10c and the lower layer 10a of the lower layer. That is, when the intermediate temperature water that has passed through the forward pipe 18 and the first return pipe 23 is returned to the low temperature water layer of the lower layer 10a or the high temperature water layer of the upper layer 10c of the hot water tank 10, the hot water in the hot water tank 10 is restored. There is a risk that the temperature difference between the upper and lower sides of the hot water tank 10 will be lost by breaking the layer, and high temperature water may not be supplied. However, by returning to the intermediate layer 10b, the collapse of the hot water tank 10 is prevented and the high temperature water is stabilized. Can be supplied.
[0048]
The temperature of the circulation path such as the forward pipe 18 and the first return pipe 23 rises due to the anti-freezing operation, and the detected temperatures of the inlet temperature sensor 28, the outlet temperature sensor 29, and the hot water tank inlet temperature sensor 30 are all fourth. When the set temperature (10 ° C.) is reached, the microcomputer 40 operates to close the high temperature valve 22 and the return valve 26, open the water inlet valve 20, open the flow rate adjustment valve 24, and further stop the operation of the circulation pump 19. As a result, the circulation of the high temperature water is stopped, the freeze prevention operation is finished, and the use of the high temperature water in the hot water tank 10 by the freeze prevention operation can be minimized.
[0049]
In the above embodiment, the flow rate adjusting valve 24 is closed during the temperature control and freezing prevention operation of the hot water supplied to the hot water tank 10 during operation, and the circulating water returns to the upper part (upper layer) of the hot water tank 10. However, an electromagnetic valve may be provided in series with the flow rate adjusting valve 24, and this electromagnetic valve may be closed during the freeze prevention operation.
[0050]
Further, by opening the high temperature valve 22 during the freeze prevention operation without providing the water inlet valve 20, the hot water in which the high temperature water in the upper part of the hot water tank 10 and the low temperature water in the lower part are mixed is circulated and the forward pipe 18 and the One return pipe 23 may be prevented from freezing.
[0051]
In addition, although the water temperature of the lower layer 10a of the hot water tank 10 is lowered by the freeze prevention operation, the temperature of the water flowing into the heat pump unit 100 is lower when the heat pump unit 100 is operated. Good heat exchange efficiency.
[0052]
Although the embodiments of the present invention have been described above, various alternatives, modifications, and variations can be made by those skilled in the art based on the above description, and the various alternatives and modifications described above are within the scope of the present invention. Or a modification is included.
[0053]
【The invention's effect】
As described above, the present invention uses the low-temperature water or high-temperature water in the hot water storage tank when the outside air temperature decreases in the hot water storage type water heater, and freezes the piping while suppressing the increase in power consumption of the hot water storage type water heater as much as possible. Can be prevented.
[0054]
Moreover, the temperature layer in the hot water tank can be maintained during the freeze prevention operation, and high-temperature water can be stably supplied.
[Brief description of the drawings]
FIG. 1 is a circuit explanatory diagram of a heat pump water heater.
FIG. 2 is a control block diagram.
FIG. 3 is a table showing a maximum boiling amount, a minimum hot water storage amount at the start of boiling increase, and a hot water storage amount at the end of boiling increase for each mode;
FIG. 4 is a diagram for explaining a change in the amount of stored hot water during a boiling increase operation.
FIG. 5 is a flowchart.
FIG. 6 is a circuit explanatory diagram of a heat pump water heater according to a second embodiment.
[Explanation of symbols]
1 Compressor
2 Refrigerant-to-water heat exchanger (heat exchanger for heating)
10 Hot water tank
18 Outward pipe
23 First return pipe
25 Second return pipe
40 Microcomputer
41 CPU
42 RAM
43 ROM
50 microcomputer
100 heat pump unit
200 Hot water tank unit

Claims (2)

In a hot water storage type hot water heater provided with a hot water supply circuit that circulates water between a hot water storage tank and a heat source for heating by a circulation pump and enables hot water to be discharged from the hot water storage tank, connected between the hot water storage tank and the heat source for heating A temperature detector for detecting a water temperature in the pipe, a storage means for storing a first set temperature and a second set temperature lower than the first set temperature, and a detected temperature of the temperature detector When the temperature is lowered to the first set temperature stored in the storage means, the operation of the circulation pump is started to circulate the low temperature water in the lower part of the hot water tank in the pipe, and the temperature detected by the temperature detector Control means for starting operation of the circulation pump when the temperature drops to the second set temperature stored in the storage means and circulating the high-temperature water in the upper part of the hot water storage tank into the pipe . It is characterized by Hot water heater. When the detected temperature of the temperature detector is lowered to the second set temperature stored in the storage means and the circulating pump is operating, it is supplied from the upper part in the hot water tank and circulates in the pipe. The hot water storage type hot water heater according to claim 1, further comprising a return pipe for returning the returned water to the intermediate layer of the hot water storage tank.

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