Storage-type hot water supply system

Abstract

When frost begins to accumulate on the air heat exchanger 15, there is a problem in that the discrepancy between the actual outside air temperature and the estimated outside air temperature widens. [Solution] The storage means 30 stores the outside air temperature at the start of the heating operation, and the storage means 30 holds the outside air temperature at the start of the heating operation until a first predetermined time has elapsed. After the first predetermined time has elapsed, the update means 31 updates the outside air temperature, and the determination means 29 determines that the period after the first predetermined time and the second predetermined time has elapsed is not included in the stable period. If the determination means 29 determines that it is not the stable period, the update means 31 does not update the outside air temperature even after the startup period. This prevents the discrepancy between the actual outside air temperature and the estimated outside air temperature from widening during the frost formation period when frost begins to accumulate on the air heat exchanger 15.

Description

Technical Field

[0001] This invention relates to a hot water storage type water supply device having a heat pump type heating means.

Background Art

[0002] Conventionally, in this type of hot water storage type water supply device, a hot water storage tank and a heating means are provided, and the hot water storage tank and the heating means are connected by a heating forward pipe that sends water from the lower part of the hot water storage tank to the heat pump type heating means and a heating return pipe that sends water from the heating means to the hot water storage tank to form a heating circulation circuit. A circulation pump provided in the heating circulation circuit circulates the hot water in the hot water storage tank and the heating means to perform a boiling operation to heat the water in the hot water storage tank to a target boiling temperature based on the outside air temperature, and the boiled hot water is stored in a laminated state from the upper part of the hot water storage tank.

[0003] Also, when the outside air temperature is low, if the boiling operation is continued by the heat pump type heating means, frost adheres to the air heat exchanger of the heating means, so it is necessary to perform a defrosting operation to melt the adhered frost. It is known that the start condition of this defrosting operation is that the outdoor heat exchange temperature of the air heat exchanger falls below a predetermined temperature (frost formation determination temperature).

[0004] Also, as in Patent Document 1, an air conditioner as in Patent Document 1 is disclosed as a means for predicting the outside air temperature without providing a dedicated outside air temperature sensor for detecting the outside air temperature. A method of estimating the outside air temperature by correcting the outdoor heat exchange temperature of the air heat exchanger detected by the outdoor heat exchange temperature sensor with a correction value corresponding to the rotation speed of the compressor is known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in order to reduce the number of parts in the heat pump heating means of this hot water storage system, if the outside air temperature sensor is eliminated, a method of correcting the outside air temperature based on the temperature of the air heat exchanger, as shown in Patent Document 1, can be considered. However, as shown in Figure 4, at the frost formation stage when frost begins to accumulate on the air heat exchanger before defrosting operation, the discrepancy between the actual outside air temperature and the estimated outside air temperature widens, and if the estimated outside air temperature becomes too low, the target heating temperature decreases, and the layering of hot water in the hot water storage tank collapses, which presents a problem. [Means for solving the problem]

[0007] According to the present invention, a hot water storage type hot water supply system comprises a hot water storage tank for storing hot water, a heat pump type heating means equipped with a compressor, a water refrigerant heat exchanger, an expansion valve, and an air heat exchanger, an outdoor heat exchanger temperature sensor for detecting the temperature of the air heat exchanger, a heating circulation circuit that connects the water side of the water refrigerant heat exchanger of the heat pump type heating means and the hot water storage tank in a ring shape, an outdoor air temperature estimation means for estimating the outdoor air temperature from the outdoor heat exchanger temperature detected by the outdoor heat exchanger temperature sensor, and a control device that determines a target boiling temperature based on the outdoor air temperature estimated by the outdoor air temperature estimation means, heats the hot water in the lower part of the hot water storage tank to the target boiling temperature, and controls the boiling operation to return it to the upper part of the hot water storage tank and boil it in a stacked manner, wherein the control device has a first predetermined time after the state of the heat pump type heating means starts boiling operation The system includes a determination means for determining whether it is the startup period until the interval has elapsed or the stable period after the outdoor heat exchanger temperature has stabilized following the startup period, a storage means for storing the outdoor temperature estimated by the outdoor temperature estimation means, and an update means for updating the outdoor temperature stored in the storage means. The storage means stores the outdoor temperature at the start of the boiling operation, and the storage means maintains the outdoor temperature at the start of the boiling operation until the first predetermined time has elapsed. After the first predetermined time has elapsed, the update means updates the outdoor temperature. The determination means determines that the period after the first predetermined time and the second predetermined time has elapsed is not included in the stable period. If the determination means determines that it is not the stable period, the update means does not update the outdoor temperature, even if it is after the startup period.

[0008] Furthermore, the determination means determines that the period is not included in the stable period if it is during a defrosting operation to remove frost adhering to the air heat exchanger, during a defrosting preparation operation in which the pressure reducing valve is opened before the defrosting operation to raise the temperature of the refrigerant flowing into the air heat exchanger, or if the outdoor heat exchanger temperature sensor falls below a predetermined determination temperature.

[0009] Furthermore, the determination means is configured such that the second predetermined time is shorter when the outside air temperature is below the predetermined outside air temperature compared to when the outside air temperature is above the predetermined outside air temperature. [Effects of the Invention]

[0010] According to this invention, it is possible to prevent a discrepancy between the actual outside air temperature and the estimated outside air temperature due to frost accumulating on the air heat exchanger, and to prevent the estimated outside air temperature from decreasing and the target heating temperature from decreasing during the heating operation, thereby preventing disruption of the layering of hot water in the hot water storage tank. [Brief explanation of the drawing]

[0011] [Figure 1] A schematic diagram showing one embodiment of this invention. [Figure 2] A time chart illustrating a first embodiment of this invention. [Figure 3] A flowchart illustrating the first embodiment of this invention. [Figure 4] A time chart showing the relationship between the difference between the conventional actual outside temperature and the estimated outside temperature, and the target boiling temperature. [Figure 5] A diagram showing the relationship between ambient temperature and the target boiling temperature. [Modes for carrying out the invention]

[0012] Next, a heat pump type water heater in one practical embodiment of this invention will be described based on the drawings. 1 is a hot water storage tank unit which contains a hot water storage tank 2 for storing hot water, a hot water outlet pipe 3 connected to the top of the hot water storage tank 2, a water supply pipe 4 connected to the bottom of the hot water storage tank 2, a hot water mixing valve 6 that mixes high-temperature water from the hot water outlet pipe 3 with low-temperature water from a water supply bypass pipe 5 branched from the water supply pipe 4, and a hot water temperature sensor 8 and a hot water flow sensor 9 provided on the hot water supply pipe 7 connected downstream of the hot water mixing valve 6.

[0013] 10 is a heat pump unit, comprising a heat pump type heating means 16 consisting of a compressor 11, a water refrigerant heat exchanger 12 as a condenser, an electronic expansion valve 13, and an outdoor fan 14, and an air heat exchanger 15 as an evaporator that exchanges heat with air; a circulation pump 20 that circulates the hot water in the hot water storage tank 2 to the heating means 16 via a heating circulation circuit 19 consisting of a heating supply pipe 17 and a heating return pipe 18; and a heat pump control unit 21 that controls the driving of these. Carbon dioxide is used as the refrigerant in the heating means 16, forming a supercritical heat pump cycle. Furthermore, because carbon dioxide is used as the refrigerant, it is possible to heat low-temperature water to a high temperature of approximately 90°C without an electric heater.

[0014] Here, the water-refrigerant heat exchanger 12 employs a counterflow system in which the refrigerant and the hot water in the storage tank 2, which is the water to be heated, flow in opposite directions. In the supercritical heat pump cycle, the refrigerant remains in a supercritical state and condenses during heat exchange, so the water to be heated can be efficiently heated to a high temperature. The expansion valve 13 is controlled so that the temperature difference between the inlet temperature of the water-refrigerant heat exchanger 12 and the outlet temperature of the refrigerant is constant, and the compressor 11 is controlled at a rotational speed predetermined by the ambient temperature. As a result, when the inlet temperature of the water-refrigerant heat exchanger 12 is a low temperature of about 5 to 20°C, it is possible to heat the water to be heated in a state with a very good COP (energy efficiency).

[0015] Furthermore, a switching valve 22 is provided in the middle of the heating return pipe 18. When preventing freezing, the switching valve 22 is switched to connect to the heating bypass pipe 23, which is connected to the water supply pipe 4 at the bottom of the hot water storage tank 2. This prevents freezing by creating a short-circuit circulation using the lower part of the hot water storage tank 2. This switching valve 22 is located at the branching point from the heating return pipe 18 to the heating bypass pipe 23.

[0016] Furthermore, when circulating hot water that has not been sufficiently heated during the initial heating phase of the heating means 16, the hot water is not returned to the upper part of the hot water storage tank 2, but is returned to the lower part of the hot water storage tank 2 via the heating bypass pipe 23. When circulating sufficiently heated hot water, the switching valve 22 is switched to the upper side of the hot water storage tank 2.

[0017] 24 is a control device composed of a microcomputer or the like, which controls the heat pump control unit 21 to perform temperature control of hot water supply such as boiling-up operation and boiling-up additional operation of the hot water storage tank 2 by the heating circulation circuit 19, and control of hot water filling, reheating, heat preservation, etc. of the bathtub.

[0018] 26 is a frosting determination means that determines that frost is attached to the heating means 16 when the outdoor heat exchanger temperature detected by the outdoor heat exchanger temperature sensor 25 near the outlet of the air heat exchanger 15 becomes lower than the frosting determination temperature (here, -8°C or lower). Specifically, the frosting determination temperature is set according to the driving time of the compressor 11 and the outside air temperature. For example, when the time elapsed since the start of driving of the compressor 11 is shorter than a predetermined time, the frosting determination temperature is lowered (for example, -8°C or lower → -15°C or lower). This is to prevent the defrosting operation from switching immediately after the boiling-up operation starts (or after the defrosting recovery) when the compressor 11 starts driving, and the frosting determination temperature is lowered at the initial stage of driving of the compressor 11 to make it difficult to enter the defrosting operation. Also, when the outside air temperature is higher than a predetermined outside air temperature, the frosting determination temperature is raised (for example, -8°C or lower → -5°C or lower). This is to prevent the defrosting operation from switching immediately after the boiling-up operation starts (or after the defrosting recovery) when the temperature difference from the outside air temperature is small, and the frosting determination temperature is lowered according to the outside air temperature to make it difficult to enter the defrosting operation.

[0019] 27 is a defrosting operation control means that controls the defrosting preparation operation and the defrosting operation for melting the frost on the heated means 16 that has frosted.

[0020] 28 is an outside air temperature estimation means that estimates the outside air temperature from the outdoor heat exchanger temperature detected by the outdoor heat exchanger temperature sensor 25. Specifically, the outside air temperature estimation means 28 estimates the outside air temperature by adding a correction value corresponding to the rotational speed of the compressor 11 and a predetermined value to the outdoor heat exchanger temperature detected by the outdoor heat exchanger temperature sensor 25. This estimation method is used to reduce the deviation between the actual outside air temperature and the estimated outside air temperature.

[0021] 29 is a determination means for determining whether it is a startup period from when the operation of the heat pump heating means starts until the first predetermined time elapses, a stable period after the outdoor heat exchange temperature stabilizes after the startup period, a frosting period when frost begins to adhere to the air heat exchanger 15, or a defrosting period for melting the frost adhering to the air heat exchanger 15 during the defrosting operation.

[0022] The startup period is the period until the first predetermined time (here, 10 minutes) elapses after the start of the boiling operation. In the initial stage of the start of the boiling operation, since the detected temperature of the outdoor heat exchange temperature sensor 25 of the air heat exchanger 15, which is the evaporator, rapidly decreases in order to quickly reach the boiling target temperature, if the outside air temperature is estimated during the startup period, there is a possibility that the estimated outside air temperature will deviate from the actual outside air temperature. Therefore, the outside air temperature is not estimated during this period.

[0023] The stable period is the period until the second predetermined time (here, 15 minutes) elapses after the startup period ends and the outdoor heat exchange temperature stabilizes. When the startup period ends, the heat pump cycle stabilizes, so the outdoor heat exchange temperature of the outdoor heat exchange temperature sensor 25 also stabilizes. Therefore, the deviation between the actual outside air temperature and the estimated outside air temperature is small, and it is a period suitable for estimating the outside air temperature. Thus, the outside air temperature is estimated.

[0024] Also, after the second predetermined time elapses, depending on the outside air temperature, there is a frosting period during which the outdoor heat exchange temperature gradually decreases and frost adheres to the air heat exchanger 15. Therefore, it is desirable that the second predetermined time be the time until the outdoor heat exchange temperature gradually decreases. During the frosting period, it is not suitable for estimating the outside air temperature.

[0025] Also, when the outdoor heat exchange temperature decreases during the frosting period and the outdoor heat exchange temperature detected by the outdoor heat exchange temperature sensor 25 becomes lower than the frosting determination temperature, the defrosting operation control means 27 enters the defrosting period for performing the defrosting preparation operation and the defrosting operation. Therefore, the outdoor heat exchange temperature also changes rapidly, so it is not suitable for estimating the outside air temperature.

[0026] Furthermore, once the defrost preparation and defrosting operations are complete and the defrosting period ends, the outdoor heat exchange temperature becomes unstable, similar to the startup period. This marks the beginning of the startup period (the period of unstable outdoor heat exchange temperature) following the defrosting period.

[0027] After the initial startup period following the defrosting period (the period of instability in the outdoor heat exchange temperature), once the first predetermined time (10 minutes in this case) has elapsed, the outdoor heat exchange temperature enters a stable period, and the estimation of the outdoor temperature can be started again during this stable period.

[0028] 30 is a storage means that stores the latest outside air temperature estimated by the outside air temperature estimation means 28. Based on the outside air temperature stored in the storage means 30, the control device 24 controls the boiling operation and determines frost formation.

[0029] 31 is an update means for updating the ambient temperature stored in the storage means 30, and the update means 31 decides whether or not to update the ambient temperature stored in the storage means 30 based on the determination result of the determination means 29.

[0030] Furthermore, the remote control 32 has a temperature setting switch 33 for setting the hot water supply temperature, a hot water filling switch 34 for instructing the bath to be filled with hot water, and a 35 for setting the amount of hot water to be filled. It also includes a display unit 36 ​​made of a dot matrix type fluorescent display tube and a remote control control unit 37 which consists of a microcomputer that controls the display unit 36 ​​and communicates with the control device 24.

[0031] Furthermore, the water-refrigerant heat exchanger 12 of the heating circulation circuit 19 is equipped with an inlet water temperature sensor 38 on the inlet side to detect the inlet water temperature, and an outlet temperature sensor 39 on the outlet side to detect the hot water temperature after heating. Of the multiple hot water temperature sensors 40 provided in the hot water storage tank 2 that detect the temperature of the hot water stored in the tank 2, the heating operation is terminated when either the outlet temperature sensor 39 or the uppermost hot water temperature sensor 40 continuously detects the target heating temperature.

[0032] 41 is a relief valve that communicates with the top of the hot water storage tank 2 and allows air to escape from the hot water storage tank 2 and the heating circulation circuit 19, and 42 is a pressure reducing valve installed in the water supply pipe 4.

[0033] Furthermore, 43 is a hot water supply valve that connects the hot water supply pipe 44 to the bathtub and supplies hot water to the bathtub, 45 is a bath temperature sensor that detects the temperature of the bath water supplied to the bath, and 46 is a bath flow sensor that detects the flow rate that has passed through the hot water supply pipe 44.

[0034] Next, I will explain the hot water supply operation. When the hot water tap is opened, water is supplied from the water supply pipe 4, flows into the lower part of the hot water storage tank 2, and passes through the water supply bypass pipe 5. The hot water pushed out from the upper part of the hot water storage tank 2 and the water supplied from the water supply bypass pipe 5 are mixed by the hot water mixing valve 6, and the hot water is supplied from the hot water tap after being adjusted so that the set temperature of the hot water supply and the temperature detected by the hot water supply temperature sensor 8 are the same.

[0035] Next, we will explain the process of filling the bathtub with hot water. When the hot water filling switch 34 on the remote control 32 is pressed, the control device 24 opens the hot water filling valve 43, supplying water from the water supply pipe 4. The water flows into the lower part of the hot water storage tank 2 and through the water supply bypass pipe 5. The hot water pushed out from the upper part of the hot water storage tank 2 and the water supplied through the water supply bypass pipe 5 are mixed by the hot water mixing valve 6, and the water is adjusted so that the bath set temperature and the temperature detected by the bath temperature sensor 41 are the same. This water then flows into the bathtub, and the filling process begins. The bath flow sensor 42 detects the flow rate, and when the total accumulated flow rate reaches the set amount, the control device 24 closes the hot water filling valve 43 to complete the filling process.

[0036] Next, I will explain the water heating operation. When the amount of heat stored in the hot water decreases or when there is a request to heat water during the nighttime hours, the control device 24 switches the switching valve 22 to a second state, which connects to the upper side of the hot water storage tank 2. The control device 24 then drives the circulation pump 20 located in the middle of the piping connecting the hot water storage tank 2 and the heating means 16 to pump water up from the bottom of the hot water storage tank 2, heat it with the heating means 16, and return it to the top of the hot water storage tank 2. This operation continues, gradually heating the water in the hot water storage tank 2 to a high temperature.

[0037] In the boiling operation, the rotation speed of the circulation pump 20 is controlled so that the temperature detected by the outlet temperature sensor 39 of the heating circulation circuit 19 reaches a predetermined target boiling temperature. The predetermined target boiling temperature is determined based on the estimated ambient temperature.

[0038] As shown in Figure 5, the refrigeration cycle can be circulated with the highest efficiency when the ambient temperature is between 1°C and 40°C, and the target water heating temperature can be set higher, allowing the hot water in the storage tank to be heated to a high temperature. Note that if the ambient temperature deviates slightly from this 1°C to 40°C range, the target water heating temperature will also decrease slightly.

[0039] Furthermore, when the ambient temperature is low (in this case, below -10°C), the difference between the refrigerant sent to the air heat exchanger 15 and the ambient temperature becomes smaller, making it difficult to absorb heat. As a result, the water cannot be heated to the target boiling temperature, and the boiling temperature decreases (in this case, it decreases from the target boiling temperature of 70°C to 45°C).

[0040] Furthermore, if frost accumulates on the air heat exchanger 15 during the heating operation and the estimated outside air temperature fluctuates significantly before and after the defrosting operation, the target heating temperature will change (for example, the target heating temperature will change from 70°C to 45°C to 70°C), causing the stacking in the hot water storage tank 2 to collapse. Therefore, it is preferable not to estimate the outside air temperature while the outside heat exchanger temperature is unstable, and to estimate the outside air temperature while the outside heat exchanger temperature is stable.

[0041] We will also explain the defrosting operation. During the heating operation, the frost determination means 26 determines that frost has formed on the heating means 16 if the outside air temperature is low and the outdoor heat exchanger temperature falls below the frost determination temperature. The control device 24 (defrosting operation control means 27) switches to a first state where the control device 24 is on the heating bypass pipe 23 side and communicates with the water supply pipe 4 at the bottom of the hot water storage tank 2. The control device 24 increases the output of the compressor 11 and fully opens the expansion valve 13, thereby sending the refrigerant heated by the compressor 11 directly to the air heat exchanger 15, and performs a defrosting preparation operation to rapidly raise the indoor heat exchanger temperature.

[0042] Furthermore, once the defrosting preparation operation is complete, the control device 24 (defrosting operation control means 27) stops the outdoor fan 14 and circulation pump 20, melts the frost by introducing high-temperature refrigerant into the air heat exchanger 15, and starts the defrosting operation of the heating means 16. The defrosting operation is then terminated when the outdoor heat exchanger temperature sensor 25, located near the outlet of the air heat exchanger 15, detects a temperature above a predetermined level. The heating operation is then resumed.

[0043] Next, we will explain in detail the changes from the start-up phase, stabilization phase, frost formation phase, and defrosting phase after the start-up operation begins, based on the time chart in Figure 2 and the flowchart in Figure 3. In the time chart in Figure 2, the left-hand numbers represent the outside air temperature and the outdoor heat exchanger temperature, the right-hand numbers represent the target boiling temperature, and the bottom-hand numbers represent the time.

[0044] The control device 24 instructs the start of the heating operation, and the heating operation begins (S1 is Yes). At this time, the control device 24 starts counting time and detects the outdoor heat exchanger temperature with the outdoor heat exchanger temperature sensor 25 installed near the outlet of the air heat exchanger 15 at the start of the heating operation (S2).

[0045] The outside air temperature estimation means 28 estimates the outside air temperature based on the detected outdoor heat exchanger temperature (S3). Here, the outdoor heat exchanger temperature detected by the outdoor heat exchanger temperature sensor 25 is used directly as the outside air temperature.

[0046] The memory means 30 stores the estimated outside temperature as the initial estimated outside temperature (S4).

[0047] When the count since the start of the heating operation reaches the first predetermined time (S5 is Yes), the count is restarted (S6), and it is monitored whether or not the second predetermined time has been reached (S10).

[0048] Thus, the period from the start of the heating operation until the first predetermined time has elapsed is the startup phase, and the outdoor heat exchanger temperature gradually decreases, so the outdoor heat exchanger temperature is unstable. If the outside air temperature is estimated based on the outdoor heat exchanger temperature at this time, it will be estimated that the outside air temperature is continuously decreasing. Therefore, during the startup phase, by storing the outside air temperature estimated based only on the outdoor heat exchanger temperature immediately before the start of the heating operation, the outside air temperature can be maintained regardless of the unstable changes in the outdoor heat exchanger temperature.

[0049] When the first predetermined time has elapsed and the outdoor heat exchanger temperature has entered a stable phase, the outdoor heat exchanger temperature sensor 25 detects the outdoor heat exchanger temperature (S7), and the outside air temperature estimation means 28 estimates the outside air temperature according to the detected outdoor heat exchanger temperature and the rotation speed of the compressor 11 (S8).

[0050] If the determination means 29 determines that the current state is the stable period after the outdoor heat exchanger temperature has stabilized since the startup phase, the update means 31 updates the estimated outdoor temperature stored in the storage means 30 to the new outdoor temperature (S9). Thereafter, until the second predetermined time has elapsed, the estimation of the outdoor temperature is continuously performed and the outdoor temperature is continuously updated.

[0051] The ambient temperature can be estimated continuously, or it can be estimated at predetermined intervals (for example, every minute).

[0052] In this way, during the stable period, by monitoring the outdoor heat exchanger temperature and precisely estimating the outside air temperature, the heating means 16 of the heat pump can be controlled with a thermal efficiency that is more in line with the outside air temperature.

[0053] Furthermore, although the second predetermined time is explained here as approximately 15 minutes, in cases where the ambient temperature is relatively warmer than winter, such as in early spring or late autumn (ambient temperature between 5°C and 8°C), rather than under low ambient temperatures in winter (in this case, ambient temperature below 5°C), the time it takes for frost to form on the air heat exchanger 15 and for the temperature to fall below the frost formation detection temperature will be longer, so the second predetermined time may be made longer than approximately 15 minutes (for example, the second predetermined time may be made 20 minutes).

[0054] Furthermore, when the outside air temperature is high (8°C or higher), the possibility of frost forming on the air heat exchanger 15 decreases, so it may be possible to estimate the outside air temperature continuously, except during the startup and defrosting periods, without setting a second predetermined time.

[0055] When the second predetermined time has elapsed after the first predetermined time (S10 is Yes), the control device 24 terminates the time count (S11) and stops updating the estimated outside air temperature.

[0056] Subsequently, during the boiling operation, if the frost determination means 26 determines that frost has formed on the heating means 16 and that the outdoor heat exchanger temperature has fallen below the frost determination temperature (in this case, below -8°C) (S12 is Yes), the control device 24 switches the boiling operation to a defrosting preparation operation (S13).

[0057] During the defrosting preparation operation, the expansion valve 13 is fully opened to raise the temperature of the refrigerant flowing into the air heat exchanger 15, making it easier to melt the frost that has accumulated on the air heat exchanger 15.

[0058] Then, when a predetermined full-open time (in this case, 1 minute) has elapsed since the start of the defrost preparation operation, the defrost operation control means 27 switches from the defrost preparation operation to the defrost operation, stops the drive of the circulation pump 20, and starts the defrost operation to melt the frost by retaining high-temperature refrigerant in the air heat exchanger 15 (S14).

[0059] Then, once the defrosting operation is complete (S15 is Yes), the water heating operation resumes and the counting restarts (S16).

[0060] Thus, if the heating operation continues after the second predetermined time has elapsed, frost will accumulate on the air heat exchanger 15, causing the outdoor heat exchanger temperature to gradually decrease. As a result, the estimated outdoor temperature will decrease even though the outdoor temperature has not changed. Therefore, the outdoor temperature is estimated until the second predetermined time has elapsed, and after the second predetermined time has elapsed, the latest estimated outdoor temperature is stored in the memory means 30. This allows the heating operation of the heat pump's heating means 16 to continue using a reliable outdoor temperature.

[0061] Furthermore, if frost accumulates on the air heat exchanger 15, the outdoor heat exchanger temperature will gradually decrease, and the estimated outside air temperature will also decrease, causing the target temperature for heating to drop and the temperature stratification inside the hot water storage tank 2 to collapse. However, by not estimating the outside air temperature after a second predetermined time has elapsed, when there is a possibility of frost accumulating on the air heat exchanger 15, it is possible to prevent the temperature stratification inside the hot water storage tank 2 from collapsing.

[0062] Furthermore, immediately after the defrosting operation is completed, the outdoor heat exchanger temperature is unstable, similar to the startup phase. Therefore, by estimating the outdoor temperature after a first predetermined time has elapsed since the end of the defrosting operation and entering a stable phase, and by repeatedly performing the control of this embodiment during the boiling operation, it is possible to prevent a large discrepancy between the actual outdoor temperature and the estimated outdoor temperature, and to continue the boiling operation at a stable boiling temperature.

[0063] It should be noted that the present invention is not limited to the embodiments, and modifications are permitted without altering the essence of the invention. For example, although the method for estimating the outside air temperature is corrected according to the rotational speed of the compressor 11, a method of adding a predetermined value to the outdoor heat exchanger temperature is also acceptable, and the method of correction is not limited.

[0064] Furthermore, in the embodiments of the present invention, it was explained that the second predetermined time may be set to 15 minutes if the ambient temperature is less than 5°C, and to 20 minutes if the ambient temperature is 5°C or higher but less than 8°C. However, the invention is not limited to this, and the second predetermined time may be determined more precisely according to the ambient temperature. For example, if the estimated ambient temperature is above the predetermined ambient temperature (here, 5°C or higher), the second predetermined time (15 minutes) may be increased by 1 minute for every 1°C increase above the predetermined ambient temperature (with an upper limit of 20 minutes). If the estimated ambient temperature is below the predetermined ambient temperature (here, less than 5°C), the second predetermined time (15 minutes) may be decreased by 1 minute for every 1°C decrease below the predetermined ambient temperature (with a lower limit of 10 minutes). [Explanation of symbols]

[0065] 2. Hot water storage tank 10 Heat pump units 11 Compressor 12 Water refrigerant heat exchanger 13 Expansion valve 14 Outdoor fan 15. Air heat exchanger 16 Heating means 24 Control device 25 Outdoor heat exchanger temperature sensor 26 Frost determination means 27 Defrosting operation control means 28. Means for estimating ambient temperature 29 Judgment means 30 Memory means 31 Update method

Claims

1. A hot water storage tank for storing hot water, A heat pump type heating means equipped with a compressor, a water refrigerant heat exchanger, an expansion valve, and an air heat exchanger, An outdoor heat exchanger temperature sensor for detecting the temperature of the air heat exchanger, A heating circulation circuit that connects the water side of the water-refrigerant heat exchanger of the heat pump type heating means and the hot water storage tank in a ring shape, An outdoor air temperature estimation means for estimating the outdoor air temperature from the outdoor heat exchange temperature detected by the outdoor heat exchange temperature sensor, A hot water supply system with a storage-type water heater includes a control device that determines a target boiling temperature based on the outside temperature estimated by the outside temperature estimation means, heats the hot water in the lower part of the hot water storage tank to the target boiling temperature, and controls the boiling operation to return it to the upper part of the hot water storage tank and boil it in a stacked manner, The control device includes: A determination means for determining whether the state of the heat pump heating means is in the startup phase, from the start of the boiling operation until a first predetermined time has elapsed, or in the stable phase, after the outdoor heat exchanger temperature has stabilized following the startup phase. A storage means for storing the outside temperature estimated by the outside temperature estimation means, The system includes an update means for updating the ambient temperature stored in the storage means, The storage means stores the ambient temperature at the start of the heating operation, The storage means maintains the ambient temperature at the start of the heating operation until the first predetermined time has elapsed, and once the first predetermined time has elapsed, the updating means updates the ambient temperature. The determination means determines that the period after the first predetermined time has elapsed and the second predetermined time has elapsed is not included in the stable period. A hot water storage type water heater characterized in that, if the determination means determines that it is not the stable period, the update means does not update the outside air temperature even after the startup period.

2. The hot water storage type hot water supply device according to claim 1, characterized in that the determination means determines that the period is not included in the stable period when the defrosting operation removes frost adhering to the air heat exchanger, when the expansion valve is opened before the defrosting operation to raise the temperature of the refrigerant flowing into the air heat exchanger, and when the outdoor heat exchanger temperature sensor falls below a predetermined determination temperature.

3. The hot water storage type hot water supply device according to claim 1 or 2, characterized in that the determination means is configured such that the second predetermined time is shorter when the outside air temperature is below the predetermined outside air temperature compared to when the outside air temperature is above the predetermined outside air temperature.

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