JP2006090576A - Heat pump water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat pump water heater 101 capable of restraining a hot water storage tank 9 from running out of hot water. <P>SOLUTION: The heat pump water heater comprises a heat pump circuit; a water-refrigerant heat exchanger 5 for heating water with a refrigerant in the heat pump circuit; a water supply pipe for allowing a water supply source and a water supply port of the water-refrigerant heat exchanger 5 to communicate with each other; a hot water supply pipe for allowing a hot water outlet and a hot water supply port of the water-refrigerant heat exchanger 5 to communicate with each other; the hot water storage tank 9 with its top part communicating with the hot water supply pipe and with its bottom part communicating with the water supply pipe; a circulating pump 19 for circulating a heated water between the hot water storage tank 9 and the water-refrigerant heat exchanger 5; and a control means for controlling the circulating quantity of the circulating pump 19 so that the hot water temperature on the hot water outlet side of the water-refrigerant heat exchanger 5 is the set temperature. The set temperature has a high-temperature set temperature and a low-temperature set temperature. The hot water storage tank 9 can thereby be restrained from running out of hot water. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat pump water heater provided with a hot water storage tank for storing hot water heated by a heat pump.

  A conventional heat pump water heater has a large-capacity hot water storage tank like an electric water heater, operates a heat pump circuit using cheap electricity at night, and stores hot water in the hot water storage tank. The bath water is used during the day.

  However, in such a hot water supply system, the amount of hot water is insufficient on days when the amount of hot water used is large, while the remaining hot water cools down on days when the amount of hot water used is small, causing energy loss. In addition, if the hot water in the hot water tank is used up, it cannot be immediately heated up and the hot water may run out.

Therefore, the capacity of the hot water tank is reduced, for example, until the heat pump circuit starts up, hot water stored in the hot water tank is used to compensate for the lack of capacity of the heat pump circuit. There has been proposed a so-called instantaneous heat pump water heater that stops hot water supply and switches to single water supply of a heat pump circuit (see, for example, Patent Document 1).
In this case, the hot water tank is filled with hot and cold water in layers up and down, so when chasing the hot water tank, the water extracted from the bottom of the hot water tank The water is introduced into a water-refrigerant heat exchanger that condenses the refrigerant and heated, and the heated hot water is supplied to the top of the hot water storage tank.

JP 2002-106963 A

  However, in the conventional instantaneous heat pump water heater described in Patent Document 1, no consideration is given to the case where the amount of hot water used is larger than expected. For example, if the use and stop of hot water supply are repeated frequently, the reheating of the hot water tank that is normally performed when hot water supply is stopped may not be in time, and the hot water tank may run out.

  This invention makes it a subject to provide the heat pump water heater which can suppress the hot water out of a hot water tank.

  In order to solve the above problems, the present invention provides a heat pump circuit, a water refrigerant heat exchanger that heats water using the refrigerant of the heat pump circuit, a water supply pipe that communicates a water supply source and a water supply port of the water refrigerant heat exchanger, A hot water supply pipe that communicates the outlet and hot water outlet of the water refrigerant heat exchanger, a hot water tank that communicates with the hot water pipe at the top, and communicates with the water pipe at the bottom, and between the hot water tank and the water refrigerant heat exchanger A circulating pump that circulates the water to be heated, and a control means that controls the circulation amount of the circulating pump so that the hot water temperature on the outlet side of the water-refrigerant heat exchanger becomes the set temperature. And a low set temperature.

  According to this, for example, normally, the set temperature is set to a high temperature to reduce the circulation rate, and hot water is stored in the hot water tank, while the hot water is frequently used and stopped frequently. By switching to a low temperature to increase the amount of circulation and reheating to store low-temperature hot water, the reheating time can be shortened and hot water in the hot water tank can be suppressed.

  Here, the control means is used when the amount of remaining hot water equal to or higher than the specified temperature corresponding to the high temperature setting temperature of the hot water storage tank is reduced below the set amount, or when the outside air temperature is reduced below the predetermined temperature. When at least one of the conditions is satisfied, the set temperature may be switched to a low set temperature.

  Further, the control means switches to a low set temperature, and when the amount of remaining hot water equal to or higher than the specified temperature corresponding to the low temperature set temperature of the hot water tank reaches the set amount, the set temperature is changed from the low set temperature to the high set temperature. It is better to switch to. According to this, for example, reheating of a hot water tank is performed by increasing the circulation rate with low temperature hot water, ensuring the amount of hot water in the hot water tank, and then reheating with high temperature hot water, thereby causing the hot water tank to run out. Can be avoided and the amount of heat stored in the hot water tank can be increased.

  In this case, the control means may detect a hot water supply stop from the hot water supply port, and switch the set temperature to a high set temperature when the hot water supply stop continues for a set time or longer.

  The present invention also provides a heat pump circuit, a water refrigerant heat exchanger that heats water using the refrigerant of the heat pump circuit, a water supply pipe that communicates a water supply source and a water supply port of the water refrigerant heat exchanger, and water refrigerant heat exchange. Water to be heated between the hot water supply pipe communicating with the hot water outlet and the hot water supply opening of the water heater, the hot water storage tank having the top connected to the hot water supply pipe, and the bottom connected to the water supply pipe, and the hot water storage tank and the water refrigerant heat exchanger. And a control means for controlling the circulation rate of the circulation pump so that the hot water temperature on the outlet side of the water-refrigerant heat exchanger becomes the set temperature. The temperature is characterized by having a high set temperature and a low set temperature.

  That is, when the hot water is filled in a bathtub or the like, the hot water supply flow rate is large, so that the hot water supply capacity of the heat pump circuit may be supplemented by using part of the hot water in the hot water storage tank. In this case, it is necessary to reheat the hot water storage tank, but as above, the reheating time can be shortened by changing the set temperature to a low temperature and increasing the circulation rate. The hot water out of the hot water tank can be suppressed.

  In this case, the control means may switch the set temperature to a lower set temperature when detecting the filling of the bathtub or the completion of filling.

  ADVANTAGE OF THE INVENTION According to this invention, the heat pump water heater which can suppress the hot water out of a hot water storage tank is realizable.

(First embodiment)
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a heat pump water heater to which the present invention is applied.

  The heat pump water heater 101 of the present embodiment includes a heat pump circuit, a hot water supply path, and control means. The heat pump circuit employs a two-cycle system composed of two refrigerant circuits, and includes a first closed circuit in which a compressor 1a, a gas cooler 2a, an expansion valve 3a, and an evaporator 4a are sequentially connected in series via a refrigerant pipe, and a compressor 1b, a gas cooler 2b, an expansion valve 3b, and an evaporator 4b are sequentially connected in series via a refrigerant pipe, and a refrigerant is sealed in each circuit.

  The compressors 1a and 1b can be capacity-controlled. For example, when a large amount of hot water is supplied, the compressors 1a and 1b can be operated with a large capacity. Here, the rotation speeds of the compressors 1a and 1b can be controlled by, for example, PWM control, voltage control (for example, PAM control), and combinations thereof. The water-refrigerant heat exchanger 5 includes a refrigerant-side heat transfer tube and a water supply-side heat transfer tube, and the gas coolers 2a and 2b function as the refrigerant-side heat transfer tubes 2a and 2b, respectively. Heat exchange is performed between the water supply side heat transfer tubes 6a and 6b. The evaporators 4a and 4b are constituted by heat exchangers that exchange heat between air and refrigerant, and are provided with fans 7a and 7b that blow air and improve heat exchange efficiency, respectively. Pressure detectors 8a and 8b for detecting the discharge pressure of the compressors 1a and 1b are installed in the downstream piping of the compressors 1a and 1b, respectively.

  The hot water supply path includes a direct hot water supply circuit, a hot water tank hot water supply circuit, a hot water tank reheating circuit, a bath hot water circuit, and the like. In the direct hot water supply circuit, the water supply port 10 is connected to a water supply source (not shown), followed by the pressure reducing valve 11, the check valve 13, the water supply side heat transfer pipes 6a and 6b, the flow rate adjusting valve 14, the mixing valve 15, the mixing valve 16, The flow rate adjustment valve 17 and the faucet 18 are sequentially connected via a water pipe. In this direct hot water supply circuit, the water supplied from the water supply port is led to the water / refrigerant heat exchanger 5 through the water supply pipe and heat-exchanged and heated, and the heated hot water is supplied from the tap 18 through the water supply pipe. It has become.

  In the hot water tank hot water supply circuit, the water supply port 10 is connected to a water supply source (not shown). Subsequently, the pressure reducing valve 11, the hot water tank 9, the mixing valve 15, the mixing valve 16, the flow rate adjusting valve 17, and the faucet 18 are connected via a water pipe. Are connected in sequence. That is, since the hot water tank 9 is filled with water and hot water in layers, by introducing a water supply having a predetermined water pressure into the tank from the bottom of the hot water tank 9, Hot water is discharged from the top, and hot water is supplied from the tap 18.

  The hot water tank reheating circuit is configured by a closed circuit in which the hot water tank 9, the circulation pump 19, the water supply side heat transfer pipes 6a and 6b, the flow rate adjusting valve 14, and the mixing valve 15 are sequentially connected through a water pipe. That is, the water forcibly extracted from the bottom of the hot water tank 9 by the circulation pump 19 is guided to the water / refrigerant heat exchanger 5 and heated by heat exchange, and then supplied again from the top of the hot water tank 9. It is like that.

  In the hot water bathing circuit, the water supply port 10 is connected to a water supply source (not shown), and then the pressure reducing valve 11, the check valve 13, the water supply side heat transfer pipes 6a and 6b, the flow rate adjusting valve 14, the mixing valve 15, and the mixing valve 16 The flow rate adjusting valve 17 and the bathtub 20 are sequentially connected via a water pipe. In this direct hot water supply circuit, the water supplied from the water supply port is guided to the water-refrigerant heat exchanger 5 and heated by heat exchange, and the heated hot water is supplied to the bathtub 20 for hot water filling.

  The detectors installed in the hot water supply path described above include a feed water amount detector 21 that detects the amount of feed water, a water temperature detector 22 that detects the temperature of hot water discharged from the water-refrigerant heat exchanger 5, and a hot water temperature. Hot water supply temperature detector 23, water temperature detectors 24a, 24b, 24c for detecting the water temperature in the tank at a plurality of locations (for example, three locations) in the height direction of the hot water storage tank 9, an outside air temperature detector 25 for detecting the outside air temperature, etc. There is.

  The valves installed in the hot water supply path include a flow rate adjusting valve 14 for adjusting the circulating flow rate of the heated water circulating in the hot water tank reheating circuit, hot water generated in the water refrigerant heat exchanger 5 and the hot water tank 9. A mixing valve 15 for mixing the hot water stored in the tank at a predetermined ratio, a mixing valve 16 for adjusting the hot water temperature by mixing hot water supplied through the mixing valve 15 and hot water supplied through the pipe 26 And a flow rate adjusting valve 17 for adjusting the hot water supply flow rate.

  The control means includes a control device 30, compressor control devices 31a and 31b, and a remote control 32. The control device 30 is connected to the detectors and valves, the circulation pump 19, the compressor control devices 31a and 31b, the remote controller 32, etc., and receives, for example, a detection signal detected by a specific detector. Based on this, specific devices are controlled. The compressor control devices 31a and 31b are connected to the compressors 1a and 1b, respectively, and perform operation control of the compressors 1a and 1b based on commands from the control unit 30.

  Here, operation | movement of the heat pump water heater 101 of this embodiment is demonstrated. In the present embodiment, for example, hot water of about 60 to 90 ° C. is stored in the hot water tank 9, and normally 90 ° C. of hot water is stored. This hot water is used when hot water is supplied until the heat pump circuit is stabilized until it is stabilized, that is, until the water-refrigerant heat exchanger 5 is heated to a predetermined temperature, or when the hot water flow rate exceeds the heating capacity of the heat pump circuit. It is used to make up for shortages when there is a request. For example, at the start of hot water supply, the hot water storage tank hot water supply circuit functions in addition to the direct hot water supply circuit, and a part of the hot water stored in the hot water storage tank 9 may be used. For this reason, after the hot water supply, the hot water storage tank 9 is reheated by the hot water tank reheating circuit, and a predetermined amount of hot water of, for example, about 90 ° C. is secured.

  Next, the operation | movement which produces | generates warm water with a heat pump circuit is demonstrated using a 1st closed circuit. First, in the heat pump circuit, the refrigerant is compressed by the rotation operation of the compressor 1a, and circulates between the evaporator 4a and the water refrigerant heat exchanger 5 by opening and closing the expansion valve 3a. The refrigerant evaporates by exchanging heat with air in the evaporator 4a, and is then led to the compressor 1a to be compressed. Then, the refrigerant is liquefied by exchanging heat with water in the water / refrigerant heat exchanger 5. On the other hand, the feed water heated by heat exchange in the water / refrigerant heat exchanger 5 becomes hot water of a predetermined temperature and is discharged from the hot water outlet of the water / refrigerant heat exchanger 5.

  On the other hand, when hot water of a predetermined temperature is generated by the heat pump circuit and the hot water tank 9 is reheated, it is necessary to limit the circulation flow rate of the hot water tank reheating circuit corresponding to the maximum heating capacity of the heat pump circuit. That is, when the heating capacity of the heat pump circuit is constant, the temperature of the hot water discharged from the water-refrigerant heat exchanger 5 correlates with the feed water flow rate flowing through the water supply side heat transfer tubes 6a, 6b of the water-refrigerant heat exchanger 5.

  FIG. 2 shows the ratio of the feed water flow rate flowing into the water inlet of the water / refrigerant heat exchanger 5 and the water / refrigerant heat exchange when the power consumption of the heat pump water heater 101 of the present embodiment is the same during the reheating of the hot water tank 9. The relationship with the hot water temperature discharged from the hot water outlet of the vessel 5 is shown. In addition, the vertical axis | shaft water supply flow rate ratio is set to 1 when the tapping temperature is 90 degreeC. As is clear from the figure, when the hot water is discharged at 60 ° C., the water supply flow rate is about 2.5 times that at 90 ° C., so the reheating time can be reduced by about 40% and the power consumption can be reduced. it can.

  On the other hand, since the heat storage amount of the hot water tank 9 is 90 ° C. is larger than that of 60 ° C., in this embodiment, the reheating temperature of the hot water tank 9, that is, hot water discharged from the water refrigerant heat exchanger 5 is used. For example, when two types of temperature setting temperatures of 60 ° C. and 90 ° C. are prepared, for example, when the remaining amount of hot water in the hot water tank 9 that is equal to or higher than the specified temperature corresponding to the setting temperature of 90 ° C. falls below the setting amount First, the set temperature is changed to 60 ° C., the circulation flow rate is increased, and the reheating is performed in a short time. Then, after securing the amount of hot water exceeding the set amount, the set temperature is changed to 90 ° C., the circulation flow rate is reduced, and high temperature replenishment is performed.

  Specifically, for example, the control device 30 adjusts the valve opening degree of the flow rate adjustment valve 14 and controls the circulation flow rate of the circulation pump 19 so that the water temperature detected by the water temperature detector 22 becomes the above set temperature.

  Next, the chasing operation of the hot water storage tank 9 after hot water supply will be described with reference to the flowchart of FIG. First, in step S01, the hot water tank reheating circuit is operated to start the reheating operation of the hot water tank 9. Subsequently, in step S02, it is determined whether or not the detected temperature of the middle water temperature detector 24b of the hot water tank 9 is 60 ° C. or less. If the detected temperature is 60 ° C. or lower, the process proceeds to step S03, and it is determined whether or not the detected temperature of the outside air temperature detector 25 is 10 ° C. or lower. Here, when the detected temperature is 10 ° C. or lower, the process proceeds to step S04, and a hot water supply stop from a hot water supply port such as the faucet 18 is detected, and it is determined whether or not the hot water supply stop has continued for 30 minutes. The determination of whether or not hot water is supplied can be made based on whether or not the water supply amount detector 21 supplies water. Here, when the next hot water supply is performed within 30 minutes from the stop of the hot water supply, the process proceeds to step S05, and the hot water tank refilling circuit is performed so that the temperature of the hot water detected by the water temperature detector 22 becomes the set temperature 60 ° C. The recirculation flow rate of the hot water storage tank 9 is adjusted by adjusting the circulation flow rate.

  Next, in step S06, it is determined whether or not the detected temperature of the water temperature detector 24c in the lower stage of the hot water tank 9 is 60 ° C. or lower. If the detected temperature is higher than 60 ° C., the process returns to step S02. Detection of the amount of remaining hot water in the tank 9, hot water temperature, outside air temperature, hot water supply stop time, etc. is repeated. When the detected temperature is 60 ° C. or lower, the process returns to step S04, and when the duration of the hot water supply stop is less than the set time, the chasing of the set temperature of 60 ° C. is repeated.

  On the other hand, if the detected temperature exceeds 60 ° C. in step S02, if the detected temperature exceeds 10 ° C. in step S03, or if the hot water supply stop time exceeds 30 minutes in step S04, the process proceeds to step S07. Carry out ℃. In this case, the circulating flow rate of the hot water tank reheating circuit is approximately half the amount (L) compared to the circulating flow rate (2 L) when reheating at the set temperature of 60 ° C. When a predetermined amount of high-temperature hot water is stored in the hot water storage tank 9 in step S07, the process proceeds to step S08, and the chasing operation is completed.

  Thus, although the hot water tank 9 normally stores hot water of 90 ° C., the hot water temperature decreases to 60 ° C. or lower and the outside air temperature to 10 ° C. or lower due to the hot water supply operation, Furthermore, when the hot water supply stop time is less than 30 minutes, for example, the hot water supply flow rate is increased so that the temperature detected by the temperature detector 22 is 60 ° C. On the other hand, when the hot water temperature in the middle stage of the hot water tank 9 exceeds 60 ° C., the outside air temperature exceeds 10 ° C., and the hot water supply stop time exceeds 30 minutes, the set temperature is kept at 90 ° C. In this case, instead of or in addition to the detected value of the water temperature detector 22, the set temperature is read from the detected values of the water temperature detectors 24a, 24b, and 24c so that the detected value becomes the set temperature. The circulation flow rate may be limited.

  Next, the bathing hot water and the chasing operation of the hot water storage tank 9 after hot water filling will be described. In ordinary households, for example, a large amount of hot water of 200L or more is used in one bath bath, and when bathing, hot water such as a shower is provided after bathing, and in the kitchen, dishes are washed with currants. There is. That is, when the hot water in the hot water storage tank 9 is replenished after the bath water is filled, if the renewal is delayed, the remaining hot water amount in the hot water storage tank 9 is insufficient, and there is a possibility that the amount of hot water supply such as a shower or currant is insufficient.

  Therefore, similarly to the above, the set temperature at the time of reheating after bathing is set to 60 ° C., and the recirculation flow rate of the hot water tank reheating circuit is controlled in accordance with this to shorten the reheating time. It is possible to suppress the hot water out of the hot water tank 9. In this case, the hot water stored in the hot water tank 9 is about 60 ° C., and the amount of stored heat is less than that in the case where the set temperature is 90 ° C. However, if it is about 60 ° C., there is no problem in showering in the bathtub or dish washing in the kitchen. Can be used.

  Next, the chasing operation of the hot water storage tank 9 after the bath hot water filling will be described with reference to the flowchart of FIG. First, in step S11, the hot water tank reheating circuit is operated to start the reheating operation of the hot water tank 9. Subsequently, in step S12, it is determined whether or not the bathtub 20 is in a hot water operation. If the hot water filling operation is in progress, the process proceeds to step S14 following the hot water filling operation of step S13, and it is determined whether or not the hot water filling operation of the bathtub 20 has been completed once. Here, when the completion of the hot water filling operation is detected, the process proceeds to step S15, and the circulating flow rate of the hot water tank reheating circuit is adjusted so that the water temperature detected by the water temperature detector 22 becomes the set temperature 60 ° C. Do 9 memorials.

  Subsequently, in step S16, it is determined whether or not the detected temperature of the lower water temperature detector 24c of the hot water tank 9 is 60 ° C. or lower. If the detected temperature is higher than 60 ° C., the process returns to step S12 to return to the bathtub The detection of 20 hot water filling operations is repeated. When the detected temperature is 60 ° C. or lower, the process returns to step S15, and the reheating of the hot water tank 9 at the set temperature 60 ° C. is continued.

  On the other hand, in step S12, for example, when the user releases the bathtub filling button on the remote controller 32 and the filling operation is not performed, and in step S14, following the completion of the first filling of the bathtub 20. If the hot water filling has been completed several times within a certain period of time, the process proceeds to step S17, and the reheating is performed with the set temperature kept at 90 ° C. And if a predetermined amount of warm water is stored in the hot water storage tank 9, it will progress to step S18 and will complete a chasing operation.

  As described above, normally, hot water of about 90 ° C. is stored in the hot water tank 9, but the water temperature detector 22 detects the reheating of the hot water tank 9 during the hot water filling of the bathtub 20 or after the hot water filling. The hot water supply flow rate is increased so that the water temperature reaches the set temperature of 60 ° C. On the other hand, when the hot water filling of the bathtub 20 is interrupted or when the hot water filling of the bathtub 20 is continuously completed within a certain time, the set temperature is kept at 90 ° C. The set temperature is circulated so that the detected values of the water temperature detectors 24a, 24b, and 24c are read in place of or in addition to the detected value of the water temperature detector 22, and the detected values become the set temperature. The flow rate may be limited.

  As described above, according to the present embodiment, under a certain condition, first, the set temperature of the hot water heated by the water / refrigerant heat exchanger 5 is set to a low temperature, and the circulation amount of the circulation pump 19 is adjusted accordingly. Since the reheating is performed by increasing the time, the renewal time can be shortened and the hot water tank 9 can be prevented from running out. In addition, after completion of the chasing by the low temperature setting, since the chasing is performed by switching the set temperature to the high temperature, a high heat storage amount can be obtained.

  In the present embodiment, the set temperature of the hot water is 60 ° C. as the low temperature and 90 ° C. as the high temperature, but is not limited to these temperatures. However, the set temperature on the low temperature side is preferably 60 ° C. or higher for hygienic reasons.

  In this embodiment, the heat pump circuit is a two-cycle system. However, if necessary, one cycle may be used, or a multi-cycle system with a heat pump circuit of three or more cycles may be employed.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is an overall configuration diagram of a heat pump water heater to which the present invention is applied. In addition, the same code | symbol is attached | subjected about the component same or equivalent to 1st Embodiment, and description is abbreviate | omitted.

  In the first embodiment, the heat pump water heater 102 of the present embodiment adjusts the circulation flow rate of the hot water tank reheating circuit by the flow rate adjustment valve 14, but in this embodiment, the pump rotation speed can be variably controlled. The present embodiment is different from the first embodiment in that a DC pump 51 is provided and a pump inverter circuit 52 is connected to the DC pump 51 to control the rotational speed of the DC pump 51.

  According to this, since the flow control valve 14 can be deleted, it is possible to reduce the component cost and the internal pressure loss of the water heater.

  In the present embodiment, the DC pump 51 and the pump inverter circuit 52 are provided separately. However, the DC pump 51 may include the pump inverter circuit 52.

1 is an overall configuration diagram of a heat pump water heater according to a first embodiment to which the present invention is applied. It is a diagram which shows the relationship between the feed water flow rate ratio which flows in into a water-refrigerant heat exchanger, and the hot-water temperature discharged from a water-refrigerant heat exchanger at the time of reheating of a hot water storage tank. It is a flowchart explaining the chasing operation | movement of the hot water storage tank after hot water supply. It is a flowchart explaining the chasing operation | movement of the hot water storage tank after bathtub hot water filling. It is a whole block diagram of the heat pump water heater of 2nd Embodiment formed by applying this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Compressor 5 Water refrigerant | coolant heat exchanger 9 Hot water storage tank 14, 17 Flow control valve 18 Faucet 19 Circulation pump 20 Bathtub 21 Feed water quantity detector 22, 24a, 24b, 24c Water temperature detector 25 Outside temperature detector 30 Control apparatus 31a, 31b Compressor control device 32 Remote control 51 DC pump 52 Inverter circuit for pump 101, 102 Heat pump water heater

Claims (7)

A heat pump circuit; a water refrigerant heat exchanger that heats water using a refrigerant of the heat pump circuit; a water supply pipe that communicates a water supply source with a water supply port of the water refrigerant heat exchanger; and a hot water outlet of the water refrigerant heat exchanger A hot water pipe that communicates with the hot water outlet, a hot water storage tank whose top is connected to the hot water supply pipe, and whose bottom is connected to the water supply pipe, and between the hot water storage tank and the water-refrigerant heat exchanger, And a control means for controlling the circulation amount of the circulation pump so that the hot water temperature on the outlet side of the water-refrigerant heat exchanger becomes a set temperature, and the set temperature is set to a high temperature. A heat pump water heater having a temperature and a low set temperature. The control means switches the set temperature to the low set temperature when a remaining hot water amount equal to or higher than a specified temperature corresponding to the high set temperature of the hot water storage tank falls below a set amount. The heat pump water heater according to claim 1. 2. The heat pump water heater according to claim 1, wherein the control unit switches the set temperature to the low set temperature when the outside air temperature falls below a specified temperature. The control means switches the set temperature from the low set temperature to the high set temperature when a remaining hot water amount equal to or higher than a specified temperature corresponding to the low set temperature of the hot water storage tank reaches a set amount. The heat pump water heater according to claim 2, wherein the heat pump water heater is a heat pump water heater. The said control means detects the hot-water supply stop from the said hot-water supply port, and when this hot-water supply stop continues more than setting time, it switches the said setting temperature to the said high temperature setting temperature, The Claim 2 or 3 characterized by the above-mentioned. Heat pump water heater. A heat pump circuit; a water refrigerant heat exchanger that heats water using a refrigerant of the heat pump circuit; a water supply pipe that communicates a water supply source with a water supply port of the water refrigerant heat exchanger; and a hot water outlet of the water refrigerant heat exchanger A hot water pipe that communicates with the hot water outlet, a hot water storage tank whose top is connected to the hot water supply pipe, and whose bottom is connected to the water supply pipe, and between the hot water storage tank and the water-refrigerant heat exchanger, A circulation pump that circulates water, a bathtub connected to the hot water supply port, and control means for controlling the circulation amount of the circulation pump so that the hot water temperature on the outlet side of the water-refrigerant heat exchanger becomes a set temperature. And the set temperature has a high set temperature and a low set temperature. The heat pump water heater according to claim 6, wherein the control means switches the set temperature to the low set temperature when detecting the filling of the bathtub or the completion of filling.

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