Heat pump water heater

Abstract

To provide a heat pump water heater capable of appropriately storing hot water, considering a defrosting operation.SOLUTION: A heat pump water heater (1) includes: a heat pump unit (4) in which a compressor (21), a condensation heat exchanger (22), expansion means (23) and an evaporation heat exchanger (24) are connected by a refrigerant circuit (25); a hot water storage unit (3) having a hot water storage tank (2) for storing hot water heated by the heat pump unit; and control means (18) for controlling a hot water storage operation for storing hot water in the hot water storage tank and a defrosting operation for removing frost adhered to the evaporation heat exchanger. The heat pump unit includes outside air temperature detection means (30) for detecting an outside air temperature. The control means learns and stores hot water delivery history from the hot water storage unit and defrosting history of the defrosting operation, makes an execution schedule of the hot water storage operation on the basis of a hot water storage heat quantity of the hot water storage tank and a hot water delivery time predicted from the hot water delivery history, and changes the execution schedule of the hot water storage operation on the basis of an execution cycle and execution time of the defrosting operation calculated on the basis of the defrosting history when execution of the defrosting operation is predicted on the basis of the outside air temperature.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a heat pump hot water heater that uses hot water heated by a heat pump unit and stored in a hot water storage tank for hot water supply. [Background technology]

[0002] Conventionally, heat pump water heaters that perform a hot water storage operation to store hot water heated by a heat pump unit in a hot water storage tank and use the stored hot water for hot water supply have been widely used. The heat pump unit is composed of a compressor, a condensing heat exchanger, an expansion valve, and an evaporating heat exchanger connected by a refrigerant circuit.

[0003] Although heat pump units are highly energy efficient, their heating capacity is small, making it difficult to heat hot water instantaneously. Therefore, heat pump water heaters use hot water storage operation to store the amount of heat required for hot water supply in a hot water storage tank in preparation for hot water supply. At this time, the heat pump water heater predicts the time of hot water supply (hot water supply) and the amount of heat required, etc., based on, for example, past hot water supply history, and performs hot water storage operation to store the amount of heat required by the predicted hot water supply time.

[0004] In hot water storage operation, heat is absorbed from the outside air by a refrigerant in the evaporative heat exchanger, the refrigerant is compressed, and the heat of the compressed refrigerant is used to heat hot water in the condensing heat exchanger. When the outside air temperature is low, the moisture contained in the outside air that has absorbed heat and its temperature has decreased condenses, making it easier for frost to form on the evaporative heat exchanger. Since frost on the evaporative heat exchanger prevents it from absorbing heat from the outside air, when frost is detected, a defrosting operation is performed to remove the frost.

[0005] Since hot water cannot be stored during this defrosting operation, there is a risk that the required amount of heat may not be stored in time for the start of hot water tapping. For this reason, for example, as in Patent Documents 1 and 2, there is known a technique for calculating the hot water storage time until the required amount of heat is stored, taking into account the defrosting operation according to the outside air temperature. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-078200 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-317025 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] In Patent Document 1, the defrosting operation time preset according to the outside air temperature is incorporated into the hot water storage time. In Patent Document 2, a heating correction coefficient considering the defrosting operation is preset according to the outside air temperature, and the hot water storage time is calculated based on this heating correction coefficient. Since the hot water storage time is calculated by the defrosting operation time or the heating correction coefficient preset according to the outside air temperature, depending on the operating environment of the heat pump water heater, the hot water storage time may be calculated in a state where the defrosting operation is excessive or insufficient, and there is a possibility that appropriate hot water storage cannot be achieved.

[0008] Therefore, an object of the present invention is to provide a heat pump water heater that can appropriately store hot water in consideration of the defrosting operation. [Means for Solving the Problems]

[0009] The heat pump water heater according to the invention of claim 1 includes a heat pump unit configured by connecting a compressor, a condensation heat exchanger, an expansion means, and an evaporation heat exchanger through a refrigerant circuit, a hot water storage unit having a hot water storage tank for storing the hot water heated by the heat pump unit, and a control means for controlling a hot water storage operation for storing hot water in the hot water storage tank and a defrosting operation for removing frost attached to the evaporation heat exchanger. In the heat pump water heater, the heat pump unit has an outside air temperature detection means for detecting the outside air temperature, and the control means learns and stores a hot water discharge history from the hot water storage unit and a defrosting history of the defrosting operation, and sets a planned execution of the hot water storage operation based on the amount of heat stored in the hot water storage tank and a predicted hot water discharge time predicted from the hot water discharge history. When the execution of the defrosting operation is predicted based on the outside air temperature, the planned execution of the hot water storage operation is changed based on the execution cycle and execution time of the defrosting operation calculated based on the defrosting history.

[0010] According to the above configuration, a planned execution of the hot water storage operation for storing the necessary amount of heat based on the hot water discharge history is set, and when the defrosting operation is predicted from the outside air temperature, the execution cycle and execution time of the defrosting operation are calculated based on the defrosting history, and the planned execution of the hot water storage operation is changed. Therefore, it is possible to set a planned execution of the hot water storage operation according to the operating environment, and it is possible to appropriately store hot water in consideration of the defrosting operation.

[0011] The heat pump water heater according to the invention of claim 2 is the heat pump water heater according to the invention of claim 1, wherein when the final hot water storage time from the end of the last defrosting operation to the end of the hot water storage operation in the planned execution of the hot water storage operation is less than a predetermined time set as a reference, the control means reduces the planned number of executions of the defrosting operation by extending the execution cycle. According to the above configuration, since the number of defrosting operations is reduced, the planned execution time of the hot water storage operation can be shortened.

[0012] The heat pump water heater according to the invention of claim 3 is the heat pump water heater according to the invention of claim 2, wherein the control means extends the execution cycle so that the amount of heat stored during the final hot water storage time is evenly stored during the hot water storage operation before the last defrosting operation. According to the above configuration, since the amount of heat for storing hot water is evenly divided, it is possible to suppress a decrease in the operating efficiency of the heat pump water heater by dispersing the stored hot water in a state where frosting has occurred and the operating efficiency has decreased.

Effect of the Invention

[0013] According to the heat pump water heater of the present invention, it is possible to appropriately store hot water in consideration of the defrosting operation.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0015] Hereinafter, modes for carrying out the present invention will be described based on examples.

Example

[0016] First, the configuration of the heat pump water heater 1 of the present invention will be described. As shown in Fig. 1, the heat pump water heater 1 includes a hot water storage unit 3 having a hot water storage tank 2, a heat pump unit 4 which is the main heat source machine, and an auxiliary heat source machine 5 such as a combustion type. This heat pump water heater 1 performs a hot water storage operation of heating the hot water from the hot water storage tank 2 to a predetermined target hot water storage temperature by the heat pump unit 4 and returning the heated hot water to the hot water storage tank 2 for hot water storage.

[0017] The auxiliary heat source machine 5 heats or does not heat the hot water discharged from the hot water storage unit 3 according to its temperature in order to supply hot water at the hot water supply set temperature from the hot water supply faucet 6, as shown by the arrow HW for example, and supplies it to the hot water supply faucet 6. Specifically, when there is hot water at a temperature at which hot water can be supplied at the hot water supply set temperature in the hot water storage tank 2, hot water is supplied without heating by the auxiliary heat source machine 5. When there is no hot water at a temperature at which hot water can be supplied at the hot water supply set temperature in the hot water storage tank 2, hot water is heated by the auxiliary heat source machine 5 and supplied.

[0018] Next, the hot water storage unit 3 will be described. At the lower part of the hot water storage tank 2 of the hot water storage unit 3, an outgoing passage 8 equipped with a hot water storage pump 7 is connected to supply the hot water of the hot water storage tank 2 to the heat pump unit 4. At the upper part of the hot water storage tank 2, a return passage 9 for returning the hot water heated by the heat pump unit 4 to the hot water storage tank 2 is connected. A switching valve 10 for switching the flow path of the hot water is arranged in the middle of the return passage 9. A return branch passage 9a branched from the return passage 9 in this switching valve 10 is connected to the upstream part of the hot water storage pump 7 in the outgoing passage 8.

[0019] On the upstream side of the switching valve 10 in the return passage 9, a return temperature sensor 9b for detecting the temperature of the hot water heated by the heat pump unit 4 is arranged. For example, immediately after the heat pump unit 4 is started, when the detected temperature of the return temperature sensor 9b is lower than a predetermined hot water storage set temperature, the switching valve 10 is switched from the hot water storage tank 2 side to the return branch passage 9a side, and the hot water can be circulated without returning it to the hot water storage tank 2 until it can be sufficiently heated.

[0020] At the bottom of the hot water storage tank 2, a water supply passage 11 for supplying make-up water indicated by the arrow CW is connected. At the top of the hot water storage tank 2, a hot water discharge passage 12 for discharging the hot water in the hot water storage tank 2 from the hot water storage unit 3 is connected. A mixing valve 14 is disposed in the middle of the hot water discharge passage 12, and a water supply branch passage 11a branched from the middle of the water supply passage 11 is connected to the mixing valve 14. Then, the hot water from the hot water storage tank 2 and the make-up water from the water supply branch passage 11a are mixed by the mixing valve 14 and discharged from the hot water storage unit 3.

[0021] A plurality of hot water storage temperature sensors 2a to 2d are arranged in the hot water storage tank 2 at predetermined intervals in the height direction, and can detect the temperature of the hot water stored in the hot water storage tank 2, the storage amount of the hot water at that temperature, that is, the stored heat amount of the hot water. And in order to prevent the stored hot water from cooling down, these hot water storage temperature sensors 2a to 2d and a heat insulating material (not shown) covering the hot water storage tank 2 are arranged.

[0022] A water supply temperature sensor 11b for detecting the temperature of the make-up water (water supply temperature) flowing through the water supply passage 11 is arranged in the water supply passage 11. A hot water discharge flow sensor 12a, a tank hot water discharge temperature sensor 12b, and a hot water discharge temperature sensor 12c are arranged in the hot water discharge passage 12. The hot water discharge flow sensor 12a detects the hot water discharge flow rate from the hot water storage unit 3. The tank hot water discharge temperature sensor 12b detects the temperature of the hot water discharged from the hot water storage tank 2 and supplied to the mixing valve 14. The hot water discharge temperature sensor 12c detects the temperature of the hot water discharged from the hot water storage unit 3 (hot water discharge temperature).

[0023] The downstream end of the hot water discharge passage 12 is connected to the water supply port 5a of the auxiliary heat source unit 5, and a hot water passage 16 is connected to the hot water supply port 5b of the auxiliary heat source unit 5. For example, a hot water tap 6 in the kitchen, a faucet or a shower in the bathroom (not shown), etc. are connected to the hot water passage 16 as the hot water supply destination.

[0024] The hot water storage unit 3 has a hot water storage unit control unit 18 (control means) that controls the temperature adjustment of the hot water discharged from the hot water storage unit 3. The hot water storage unit control unit 18 drives the heat pump unit 4 and the hot water storage pump 7 to control a hot water storage operation in which the hot water heated to the target hot water storage temperature by the heat pump unit 4 is stored in the upper part of the hot water storage tank 2. The amount of stored heat in the hot water storage tank 2 is calculated by the hot water storage unit control unit 18 based on the detected temperatures of the hot water storage temperature sensors 2a to 2d, for example.

[0025] When the hot water discharge flow sensor 12a detects a flow rate equal to or higher than a predetermined flow rate, the hot water storage unit control unit 18 adjusts the mixing ratio of the mixing valve 14 to discharge hot water. The mixing ratio is adjusted based on the detected temperatures of the water supply temperature sensor 11b and the tank hot water discharge temperature sensor 12b so that the detected temperature of the hot water discharge temperature sensor 12c becomes a predetermined hot water discharge temperature. This hot water storage unit control unit 18 learns and stores the history of various operations, and controls the hot water storage operation according to the user's usage pattern using, for example, the hot water discharge history.

[0026] An operation remote controller 19 for the user to set, for example, the hot water supply set temperature is connected to the hot water storage unit control unit 18 and the auxiliary heat source machine 5. A plurality of operation remote controllers 19 may be connected, and the operation remote controller 19 corresponding to the hot water storage unit 3 may be connected to the hot water storage unit control unit 18, and the operation remote controller corresponding to the auxiliary heat source machine 5 may be connected to the auxiliary heat source machine 5.

[0027] Next, the heat pump unit 4 will be described. As shown in FIG. 2, the heat pump unit 4 is configured by connecting a compressor 21, a condensation heat exchanger 22, an expansion valve 23 (expansion means), and an evaporation heat exchanger 24 with a refrigerant circuit 25. The refrigerant enclosed in the refrigerant circuit 25 circulates through the compressor 21, the condensation heat exchanger 22, the expansion valve 23, and the evaporation heat exchanger 24 in this order and returns to the compressor 21. A discharge temperature sensor 26 for detecting the temperature of the refrigerant discharged from the compressor 21 and an evaporation heat exchange outlet temperature sensor 27 for detecting the refrigerant temperature at the outlet of the evaporation heat exchanger 24 are disposed in the refrigerant circuit 25.

[0028] The heat pump unit 4 includes a blower fan 28 that circulates outside air through the evaporator heat exchanger 24, a heat pump unit controller 29 that controls the heat pump unit 4 based on commands from the hot water storage unit controller 18, and an outside air temperature sensor 30 that detects the outside air temperature. The heat pump unit controller 29 acquires the detected temperatures of the discharge temperature sensor 26, the evaporator heat exchange outlet temperature sensor 27, and the outside air temperature sensor 30, communicates with the hot water storage unit controller 18 via the communication line 29a, and controls the operating rotation speed of the compressor 21, the opening degree of the expansion valve 23, and the air volume of the blower fan 28.

[0029] In the hot water storage operation, the compressor 21 supplies the refrigerant compressed to a high temperature and high pressure to the condenser heat exchanger 22. In the condenser heat exchanger 22, the hot water supplied from the hot water storage tank 2 by the hot water storage pump 7 is heated to the target hot water storage temperature by heat exchange with the high-temperature refrigerant and then returned to the hot water storage tank 2. The high-pressure refrigerant whose temperature has dropped and which has partially liquefied due to the heat exchange in the condenser heat exchanger 22 is sent to the expansion valve 23.

[0030] The expansion valve 23 is, for example, an electric control valve capable of changing the throttling amount. When passing through the expansion valve 23, the refrigerant expands rapidly and becomes lower in temperature than the outside air, and is sent to the evaporator heat exchanger 24. Then, the refrigerant that absorbs heat from the outside air flowing through the evaporator heat exchanger 24, vaporizes, and has its temperature raised returns to the compressor 21, is compressed again to a high temperature and high pressure, and is supplied to the condenser heat exchanger 22. By the hot water storage operation using this heat pump cycle, the necessary amount of heat required for hot water discharge is stored in the hot water storage tank 2.

[0031] The hot water storage unit controller 18 learns and stores, as the hot water discharge history, the time of hot water discharge from the hot water storage unit 3, the amount of hot water discharge heat, etc., and based on this hot water discharge history, predicts the time of hot water discharge and the required amount of heat at the next hot water discharge to schedule the hot water storage operation. This hot water storage prediction will be described based on the flowchart of FIG. 3 and FIG. 4. Si (i = 1, 2, ···) in the figure represents steps.

[0032] When the hot water storage prediction starts, first at S1, the hot water storage heat quantity (current hot water storage heat quantity) of the current hot water storage tank 2, the outside air temperature, and the feed water temperature are acquired, and the process proceeds to S2. Next, at S2, based on the learned and memorized past hot water discharge history, the next hot water discharge time and the required heat quantity HA are calculated, and the process proceeds to S3. Then, at S3, based on the current hot water storage heat quantity, the hot water storage output (heating capacity) of the heat pump unit 4, the outside air temperature, and the feed water temperature, the hot water storage time T required for storing the required heat quantity HA is calculated, and the process proceeds to S4.

[0033] Next, at S4, the hot water storage start time t1 for starting the hot water storage is set so that the hot water storage of the required heat quantity HA is completed at the time te immediately before the next hot water discharge time, and the process proceeds to S5. In this way, as shown in Fig. 4(a), a plan for the hot water storage operation for completing the hot water storage of the required heat quantity HA at the time te is established. Note that since the required heat quantity HA is predicted and the hot water storage is performed so that there is no excess or deficiency, the current hot water storage heat quantity is usually zero before the hot water storage starts.

[0034] Next, at S5 in Fig. 3, it is determined whether the outside air temperature is lower than the frosting ambient temperature. The frosting ambient temperature is set in advance based on experiments or the like and is, for example, 4°C. Note that even if the outside air temperature is lower than the frosting ambient temperature, frosting does not necessarily occur and is affected by the humidity and temperature change of the outside air and the operating environment of the heat pump water heater 1. If the determination at S5 is Yes, the process proceeds to S6. At S6, based on the past defrosting history, the execution cycle B and the execution time C of the defrosting operation at the current outside air temperature are calculated, and the process proceeds to S7. The defrosting history includes, for example, the outside air temperature and the start time and end time of the defrosting operation.

[0035] Next, at S7, based on the hot water storage time T of the required heat quantity HA and the execution cycle B of the defrosting operation, the planned number of defrosting operations N during the hot water storage and the final hot water storage time (final hot water storage time D) for completing the hot water storage after performing the defrosting operation the planned number of times N are calculated, and the process proceeds to S8. The hot water storage of the required heat quantity HA is interrupted halfway due to the defrosting operation and is executed in multiple divided hot water storages, and the last of these hot water storages corresponds to the final hot water storage.

[0036] Next, in S8, it is determined whether the final hot water storage time D is equal to or longer than a predetermined time set as a reference. This predetermined time can be set based on, for example, the extendable time of hot water storage according to the outside air temperature and the planned number of defrost operations N so that the decrease in operating efficiency due to frosting does not become too large in the divided hot water storage. Alternatively, it may be a predetermined time determined in advance according to the outside air temperature based on experiments or the like.

[0037] If the determination in S8 is Yes, the process proceeds to S9. In S9, the hot water storage time T1 of the required heat amount HA is calculated including the defrost operation of the planned number of defrost operations N, and the process proceeds to S12. For example, when the hot water storage of the required heat amount HA in Fig. 4(a) is divided into four hot water storages for storing the hot water storage amounts HA1, HA2, HA3, and HA4 as shown in Fig. 4(b), the hot water storage amounts HA1, HA2, and HA3 stored until the defrost operation are equal, and the hot water storage amount HA4 is planned to be stored in the final hot water storage. Also, from the execution cycle B and the execution time C of the defrost operation, the hot water storage time A of the hot water storage amounts HA1, HA2, and HA3, the final hot water storage time D of the hot water storage amount HA4, and the hot water storage time T1 of the required heat amount HA are calculated.

[0038] On the other hand, if the determination in S8 of Fig. 3 is No, the process proceeds to S10. In S10, the extension time Δ of the execution cycle B of the defrost operation is calculated, and the process proceeds to S11. The extension time Δ of the execution cycle B is the time corresponding to the extension of the hot water storage time A in each hot water storage when the hot water storage amount HA4 at the final hot water storage time D in Fig. 4(b) is evenly distributed to a plurality of previous hot water storages as shown in Fig. 4(c).

[0039] Next, in S11 of Fig. 3, the hot water storage time T2 of the required heat amount HA is calculated including the defrost operation of the execution cycle B + Δ of the defrost operation extended by the extension time Δ, and the process proceeds to S12. For example, if the planned hot water storage of the required heat amount HA in Fig. 4(b) divided into four hot water storages of the hot water storage amounts HA1, HA2, HA3, and HA4 becomes a planned three - time hot water storage by extending the execution cycle of the defrost operation to B + Δ as shown in Fig. 4(c). Then, from the execution cycle B + Δ and the execution time C of the defrost operation and the hot water storage time A + Δ of the hot water storage amount HA4 distributed hot water storage, the hot water storage time T2 of the required heat amount HA is calculated.

[0040] Next, in S12 of FIG. 3, based on the hot water storage time T1 calculated in S9 or the hot water storage time T2 calculated in S11, the start time t1 of hot water storage is changed and set so that the storage of the required heat amount HA is completed at the time te immediately before the predicted next hot water discharge time, and the process proceeds to S13. As a result, the start time t1 of hot water storage for starting the hot water storage in FIG. 4(a) is changed and set to the time t1' in FIG. 4(b) or the time t1'' in FIG. 4(c) so that the storage of the required heat amount HA is completed at the time te immediately before the next hot water discharge time. On the other hand, when there is no risk of frosting and the determination in S5 of FIG. 3 is No, the process proceeds to S13 without changing the start time t1 of hot water storage.

[0041] Next, in S13, it is determined whether the hot water storage start time has been reached. If the determination in S13 is No, the process returns to S1. Even if there is time until the hot water storage start time and the outside air temperature, the current hot water storage heat amount, etc. change, it is possible to predict the next hot water discharge according to these changes and make a plan for the hot water storage operation. Note that it may be predicted at a predetermined cycle. If the determination in S13 is Yes, the process proceeds to S14, and in S14, the hot water storage operation is started and the hot water storage prediction is terminated.

[0042] Next, the hot water storage operation and the defrosting operation that may be performed during this hot water storage operation will be described. As described above, the hot water storage unit control unit 18 learns and stores the hot water discharge time, hot water discharge amount, etc. as a hot water discharge history, and predicts hot water discharge based on this hot water discharge history. Then, the required heat amount predicted until the predicted hot water discharge time is stored by the hot water storage operation at the target hot water storage temperature. Note that the target hot water storage temperature is appropriately changed so that the operation efficiency increases according to the required heat amount.

[0043] As shown in FIG. 5, when the hot water storage operation is started, in S21, the storage of the required heat amount based on the hot water storage prediction is started and the process proceeds to S22. Specifically, the heat pump unit 4 is operated, and the hot water storage pump 7 is driven. The heat pump unit 4 drives the blower fan 28, drives the compressor 21 at a predetermined operating rotation speed, sets the expansion valve 23 to a predetermined opening degree to flow the refrigerant in the refrigerant circuit 25, and heats the hot water supplied from the hot water storage tank 2 by the condensation heat exchanger 22.

[0044] Next, in S22, it is determined whether or not the stored hot water heat quantity has reached the required heat quantity or more, that is, whether or not the storage of the required heat quantity of hot water has been completed. If the determination in S22 is Yes, the process proceeds to S23, and in S23, a termination operation such as stopping the compressor 21 is performed to terminate the hot water storage operation.

[0045] On the other hand, if the determination in S22 is No, the process proceeds to S24, and in S24, it is determined whether or not the scheduled start time of the defrosting operation scheduled by the hot water storage prediction has been reached. If the determination in S24 is No, the process returns to S22. If the determination in S24 is Yes, the process proceeds to S25, and in S25, it is determined whether or not frosting of the evaporator heat exchanger 24 has been detected based on the variation of the refrigerant temperature at the outlet of the evaporator heat exchanger 24.

[0046] This frosting determination in S25 utilizes the fact that due to frosting, it becomes difficult for the refrigerant to absorb heat from the outside air, and the refrigerant temperature at the outlet of the evaporator heat exchanger 24 decreases. If the determination in S25 is No, since the predicted frosting has not actually occurred, there is no need for a defrosting operation, and the process returns to S2 to continue the hot water storage operation.

[0047] On the other hand, if the determination in S25 is Yes, the process proceeds to S26, where the hot water storage is interrupted by stopping the hot water storage pump 7, and the process proceeds to S27. Then, in S27, a defrosting operation for removing the frost on the evaporator heat exchanger 24 is started, and the process proceeds to S28. In the defrosting operation, for example, the blower fan 28 is stopped, the expansion valve 23 is set to the defrosting opening degree, the operating rotation speed of the compressor 21 is changed to the defrosting rotation speed, and the refrigerant with a high temperature after passing through the condenser heat exchanger 22 and the expansion valve 23 is supplied to the evaporator heat exchanger 24 to melt the frost.

[0048] Next, in S28, the refrigerant temperature at the outlet of the evaporator heat exchanger 24 is acquired, and the process proceeds to S29. Then, in S29, it is determined whether or not the refrigerant temperature at the outlet of the evaporator heat exchanger 24 has reached a predetermined defrosting end temperature (for example, 5°C) or more. This is a step for determining whether or not the defrosting has ended. When the frost attached to the evaporator heat exchanger 24 is removed, the heat radiation from the refrigerant in the evaporator heat exchanger 24 decreases, and the refrigerant temperature at the outlet of the evaporator heat exchanger 24 rises from, for example, 0°C. If the determination in S29 is No, the defrosting operation is continued, and the process returns to S28.

[0049] On the other hand, when the determination in S29 is Yes, defrosting is completed, so the process proceeds to S30. Then, in S30, the hot water storage is restarted and the process returns to S22. At this time, the blower fan 28 is driven, the compressor 21 is driven at a predetermined operating rotation speed, and the expansion valve 23 is set to a predetermined opening degree. However, similar to the startup, it takes about several minutes of warm-up time until the hot water from the hot water storage tank 2 can be heated to the hot water storage set temperature.

[0050] During long-term hot water storage operation when the outside air temperature is low, frosting of the evaporative heat exchanger 24 and defrosting operation to remove this frost may be repeated. However, since the hot water storage unit control unit 18 schedules the hot water storage operation including the defrosting operation time when frosting is predicted, it is possible to complete the hot water storage of the required heat amount by the hot water discharge time.

[0051] The operation and effects of the above heat pump water heater 1 will be described. The hot water storage unit control unit 18 (control means) learns and stores the hot water discharge history from the hot water storage unit 3 and the defrosting history of the defrosting operation. Then, based on the predicted hot water discharge time from the current hot water storage heat amount and hot water discharge history of the hot water storage tank 2, the schedule for executing the hot water storage operation is set. And when the execution of the defrosting operation is predicted based on the outside air temperature, the schedule for executing the hot water storage operation is changed based on the execution cycle and execution time of the defrosting operation calculated based on the defrosting history.

[0052] Therefore, when the defrosting operation is predicted based on the outside air temperature, the schedule for the defrosting operation is set based on the defrosting history, so the schedule for executing the hot water storage operation according to the operating environment can be set. Therefore, it is possible to appropriately store hot water in consideration of the defrosting operation.

[0053] When the final hot water storage time from the end of the last defrosting operation to the end of the hot water storage operation in the schedule for executing the hot water storage operation is less than a predetermined time set as a reference, the hot water storage unit control unit 18 reduces the scheduled number of defrosting operations by extending the execution cycle of the defrosting operation. Therefore, the scheduled time of the hot water storage operation can be shortened.

[0054] The hot water storage unit control unit 18 extends the execution cycle of the defrosting operation so that the amount of heat stored during the final hot water storage time is evenly stored in the hot water storage operations up to before the last defrosting operation among the planned number of executions. Therefore, since the amount of heat to be stored is evenly divided, it is possible to disperse the hot water storage in a state where frosting has occurred and the operation efficiency has decreased, and it is possible to suppress the decrease in the operation efficiency of the heat pump water heater 1.

[0055] In addition, those skilled in the art can implement the above-described embodiments in various modified forms without departing from the spirit of the present invention, and the present invention includes such modified forms.

Explanation of Reference Numerals

[0056] 1: Heat pump water heater 2: Hot water storage tank 2a to 2d: Hot water storage temperature sensors 3: Hot water storage unit 4: Heat pump unit 5: Auxiliary heat source machine 6: Hot water faucet 7: Hot water storage pump 8: Forward passage 9: Return passage 9a: Return branch passage 10: Changeover valve 11: Water supply passage 11a: Water supply branch passage 11b: Water supply temperature sensor 12: Hot water outlet passage 12a: Hot water outlet flow sensor 12b: Hot water storage tank hot water outlet temperature sensor 12c: Hot water outlet temperature sensor 14: Mixing valve 15, 16: Hot and cold water passages 18: Hot water storage unit control unit (control means) 19: Operation remote control 21: Compressor 22: Condenser heat exchanger 23: Expansion valve 24: Evaporator heat exchanger 25: Refrigerant circuit 26: Discharge temperature sensor 27: Evaporative heat exchange outlet temperature sensor 28: Blower fan 29: Heat pump unit control section 30: Outdoor air temperature sensor

Claims

1. A heat pump water heater comprising: a heat pump unit configured by connecting a compressor, a condensation heat exchanger, an expansion means, and an evaporation heat exchanger with a refrigerant circuit; a hot water storage unit having a hot water storage tank for storing hot water heated by the heat pump unit; and control means for controlling a hot water storage operation for storing hot water in the hot water storage tank and a defrosting operation for removing frost attached to the evaporation heat exchanger. The heat pump unit has outside air temperature detection means for detecting the outside air temperature. The control means learns and stores a hot water discharge history from the hot water storage unit and a defrosting history of the defrosting operation, determines a planned execution of the hot water storage operation based on a predicted hot water discharge time predicted from a hot water storage heat amount of the hot water storage tank and the hot water discharge history, and when execution of the defrosting operation is predicted based on the outside air temperature, changes the planned execution of the hot water storage operation based on an execution cycle and an execution time of the defrosting operation calculated based on the defrosting history.

2. When the final hot water storage time from the end of the last defrosting operation to the end of the hot water storage operation in the planned execution of the hot water storage operation is less than a predetermined time set as a reference, the control means reduces the planned number of executions of the defrosting operation by extending the execution cycle.

3. The control means extends the execution cycle so that the amount of heat stored during the final hot water storage time is evenly stored during the hot water storage operation before the last defrosting operation.

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