Heat pump water heater

Abstract

To continue a stable boil-up operation even at a smaller power limit value.SOLUTION: A decompressor control part 410C of a heat pump water heater 100 comprises a target opening limit part 410Cb for setting a minimum opening Xmin during a prescribed time after a start of a boil-up operation with respect to a target opening of an electronic expansion valve 16, and setting a minimum opening Xmin2 after the lapse of the prescribed time. When an atmospheric air temperature Tair is lower than a prescribed temperature, and in a first case that a power suppression signal is inputted, the target opening limit part 410Cb sets the prescribed time longer than that in a second case other than the first case, and largely sets the minimum openings Xmin, Xmin2. By this constitution, the fixed brake is put on the reduction of the openings of the electronic expansion valve 16, a rotation number N of a compressor 14 is prevented from being deviated from an operable pressure range, and a stable boil-up operation can be started even at a smaller power suppression limit value.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a heat pump hot water device that generates hot water by heat exchange with a refrigerant in a water-refrigerant heat exchanger. [Background technology]

[0002] Conventionally, in this type of heat pump hot water device, as described in Patent Document 1, when an instruction to reduce power consumption in the heat pump device is input, the heat pump device is controlled so that the power consumption is kept below an upper limit value corresponding to the instruction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-96510 A Summary of the Invention [Problem to be solved by the invention]

[0004] When power consumption is suppressed as in the conventional system described above, power suppression control is usually performed so that the power consumption of the heat pump device is within an upper limit, and the compressor rotation speed is restricted. When the compressor rotation speed is restricted and reduced, the refrigerant temperature on the high-pressure side in the refrigerant piping tends to decrease, so that the opening of the pressure reducer (expansion valve) is narrowed to maintain this.

[0005] Here, if boiling operation is enabled with a smaller power limit value, the compressor operates at a lower rotation speed, and the pressure reducer opening is further reduced. This increases the load on the compressor and increases power consumption, so the compressor rotation speed is controlled even lower by the power limit, and as a result, the pressure reducer opening is further reduced. As a result of this behavior being repeated, there is a problem that the compressor rotation speed may drop to below the lower limit rotation speed of the predetermined compressor operable pressure range, and the compressor may stop operating due to instability. [Means for solving the problem]

[0006] In order to solve the above problem, claim 1 of the present invention provides a heat pump hot water device comprising: a heat pump device having a compressor, a pressure reducer, and an air heat exchanger connected by refrigerant piping; a water-refrigerant heat exchanger that receives refrigerant from the heat pump device via the refrigerant piping and generates hot water for a hot water circulation circuit side by heat exchange with water; a compressor control means that controls the rotation speed of the compressor to increase or decrease to a target compressor rotation speed; a pressure reducer control means that controls an opening degree of the pressure reducer; a power reduction determination means that determines whether a power reduction signal that instructs reduction of power consumption in the heat pump device has been input; and an outside air temperature detection means that detects an outside air temperature, and that performs a boiling operation to generate hot water for the hot water circulation circuit side. When it is determined by the power reduction determination means that the power reduction signal has been input, the compressor control means controls the rotation speed of the compressor to be the target compressor rotation speed corresponding to the power consumption upper limit value allowed by the power reduction signal. The pressure reducer control means comprises a target opening determination means for determining a target opening of the pressure reducer such that the state value of the refrigerant on the high pressure side satisfies a predetermined target value condition, and a target opening limiting means for setting a first minimum opening as a lower limit value for the target opening determined by the target opening determination means for a predetermined time from the start of the boiling operation, and setting a second minimum opening smaller than the first minimum opening as a lower limit value after the predetermined time has elapsed from the start of the boiling operation, wherein the target opening determination means determines the target opening of the pressure reducer within a range equal to or greater than the lower limit value set by the target opening limiting means, and the target opening limiting means sets the predetermined time longer and sets the first minimum opening and the second minimum opening larger in a first case in which the outside air temperature detected by the outside air temperature detection means is lower than a predetermined temperature and the power reduction determination means has determined that the power reduction signal has been input, than in a second case other than the first case.

[0007] In addition, in claim 2, the second minimum opening degree when the power restriction determination means determines that the power restriction signal has been input is greater than the second minimum opening degree when, in the second case, the power restriction determination means does not determine that the power restriction signal has been input.

[0008] In addition, in claim 3, the heat pump device further includes a voltage detection means for detecting an input voltage value from an external power source to the heat pump device, a current detection means for detecting an input current value from the external power source to the heat pump device, and a release value setting means for setting a current release value based on the input voltage value detected by the voltage detection means, wherein when the input current value detected by the current detection means exceeds the current release value set by the release value setting means, the compressor control means controls the compressor rotation speed so that the target compressor rotation speed becomes lower than the target compressor rotation speed before the input current value detected by the current detection means exceeds the current release value set by the release value setting means, and when the input voltage value detected by the voltage detection means becomes less than a predetermined value, the target opening limiting means corrects the first minimum opening and the second minimum opening in the first case to values ​​larger than those in the case where the input voltage value is equal to or greater than the predetermined value.

[0009] In addition, in claim 4, the target opening determination means determines the target opening of the pressure reducer so that the temperature difference between the discharge temperature of the refrigerant from the compressor and the outflow temperature of the refrigerant flowing out of the water-refrigerant heat exchanger becomes a predetermined target temperature difference calculated based on the target hot water temperature of the hot water generated and the inlet water temperature of the hot water flowing into the water-refrigerant heat exchanger, or so that the temperature difference between the outflow temperature and the inlet water temperature of the hot water flowing into the water-refrigerant heat exchanger becomes constant, or so that the discharge temperature becomes the target discharge temperature.

[0010] In order to solve the above problem, claim 5 of the present invention provides a hot water circulation circuit including a hot water storage tank for storing hot water, a heat pump device having a compressor, a pressure reducer, and an air heat exchanger connected by refrigerant piping, a water-refrigerant heat exchanger that receives refrigerant from the heat pump device via the refrigerant piping and exchanges heat with water, a forward pipe from a lower part of the hot water storage tank to the water-refrigerant heat exchanger, and a return pipe from the water-refrigerant heat exchanger to an upper part of the hot water storage tank, a compressor control means for controlling the rotation speed of the compressor to increase or decrease to a target compressor rotation speed, and In a heat pump hot water device having a pressure reducing device control means for controlling an opening degree, a power reduction determination means for determining whether a power reduction signal instructing reduction of power consumption in the heat pump device has been input, and an outside air temperature detection means for detecting an outside air temperature, the refrigerant heated by the heat pump device is circulated in the refrigerant piping, and the hot water heated by being introduced into the water-refrigerant heat exchanger via the forward pipe is supplied to the hot water storage tank via the return pipe. When it is determined that the refrigerant state value on the high pressure side is set, the rotation speed of the compressor is controlled so as to become the target compressor rotation speed corresponding to the power consumption upper limit value allowed by the power suppression signal, and the pressure reducer control means includes a target opening determination means for determining a target opening of the pressure reducer such that a state value of the refrigerant on the high pressure side satisfies a predetermined target value condition, and a first minimum opening is set as a lower limit value for the target opening determined by the target opening determination means for a predetermined time from the start of the boiling operation, and a first minimum opening is set as a lower limit value after the predetermined time has elapsed from the start of the boiling operation. and a target opening limiting means for setting a second minimum opening smaller than the target opening of the pressure reducer, wherein the target opening determination means determines a target opening of the pressure reducer within a range equal to or greater than the lower limit value set by the target opening limiting means, and the target opening limiting means sets the specified time longer in a first case in which the outside air temperature detected by the outside air temperature detection means is lower than a predetermined temperature and the power reduction determination means has determined that the power reduction signal has been input than in a second case in which the power reduction signal has been input, and sets the first minimum opening and the second minimum opening larger. Effect of the Invention

[0011] According to claim 1 of the present invention, the target opening determination means provided in the pressure reducer control means determines the target opening of the pressure reducer such that the state value of the refrigerant on the high pressure side satisfies a predetermined target value condition. At that time, the target opening determination means determines the target opening of the pressure reducer within a range equal to or greater than a predetermined lower limit value set by the target opening limit means. In setting the lower limit value by the target opening limit means, a first minimum opening is set as the lower limit value for a predetermined time from the start of the boiling operation. After the predetermined time has elapsed from the start of the boiling operation, a second minimum opening smaller than the first minimum opening is set as the lower limit value. This prevents the opening of the pressure reducer from being excessively narrowed down during start-up immediately after the start of the boiling operation, ensuring stable operation.

[0012] Here, when a power suppression signal is input to suppress power consumption in the heat pump device and power suppression control is performed, in order to enable boiling operation at a smaller power limit value, it is necessary to avoid deviation from the compressor's operable pressure range due to a spiral of: decrease in compressor rotation speed → decrease in pressure reducer opening → increase in compressor power consumption → further decrease in compressor rotation speed →...

[0013] Therefore, in claim 1 of the present invention, when the power suppression determination means determines that a power suppression signal has been input and the outside air temperature detected by the outside air temperature detection means is lower than a predetermined temperature (first case), the target opening limiting means performs control to ease the reduction in the pressure reducer opening more than in other cases (second case). Note that the reason for limiting the case to low outside air temperatures is that when the outside air temperature is relatively high, the discharge temperature from the compressor is originally relatively high, and there is no need to excessively reduce the pressure reducer opening.

[0014] Specifically, in the first case, the target opening limiting means sets the predetermined time longer than in the second case, and sets both the first minimum opening and the second minimum opening larger. This makes it possible to put a certain stop to the decrease in the pressure reducer opening in the flow of decrease in compressor speed → decrease in pressure reducer opening → increase in compressor power consumption → decrease in compressor speed →..., so that it is possible to prevent the compressor speed from deviating from the operable pressure range. As a result, it is possible to stably start boiling operation even with a smaller power limit value. Then, after the predetermined time has passed, the heating capacity and COP are improved, and stable operation can be continued.

[0015] In addition, according to claim 2, when power suppression control is performed, the second minimum opening degree after a predetermined time has elapsed since the start of boiling operation is made larger than when power suppression control is not performed, so that even with a smaller power limit value, the heating capacity and COP can be improved and stable operation can be continued.

[0016] According to claim 3, a so-called release control is performed. That is, an input voltage value and an input current value from an external power source to the heat pump device are detected by a voltage detection means and a current detection means, respectively, and a current release value is set by a release value setting means based on the detected input voltage value. Then, when the detected input current value exceeds the set current release value, the compressor control means sets the target rotation speed of the compressor lower than the target rotation speed before the exceeding. When such a release control is performed, if the input voltage value from the external power source to the heat pump device drops for some reason, the target rotation speed of the compressor is set lower, so that deviation from the operable pressure range of the compressor is more likely to occur. Therefore, in claim 3 of the present invention, when the input voltage value detected by the voltage detection means falls below a predetermined value, the first minimum opening and the second minimum opening in the first case are corrected to larger values ​​by the target opening limiting means. This makes it possible to start and continue the boiling operation while preventing the compressor speed from deviating from the operable pressure range, even when the power source voltage is dropping.

[0017] According to claim 4, the target opening determination means determines the target opening of the pressure reducer so that the temperature difference between the refrigerant discharge temperature and the refrigerant outflow temperature becomes a predetermined target temperature difference based on the target hot water temperature and the inlet hot water temperature (so-called ΔH control), or so that the temperature difference between the refrigerant outflow temperature and the inlet water temperature becomes constant (so-called ΔT control), or so that the refrigerant discharge temperature becomes the target discharge temperature (so-called discharge temperature control), thereby maximizing the efficiency of the heat pump device. Also, when these various controls are being performed, the boiling operation can be stably started and continued even when power suppression control is performed with a smaller power limit value.

[0018] According to claim 5, in the same manner as above, in the flow of compressor speed reduction → pressure reducer opening reduction → compressor power consumption increase → compressor speed reduction → etc., it is possible to put a certain limit on the pressure reducer opening reduction, so that it is possible to prevent the compressor speed from deviating from the above-mentioned operable pressure range. As a result, it is possible to stably start boiling operation even with a smaller power limit value. Then, after a predetermined time has passed, the heating capacity and COP are improved, and stable operation can be continued. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic diagram of a heat pump hot water device according to an embodiment of the present invention; [Diagram 2] A functional block diagram showing the functional configuration of a heating control device [Diagram 3]FIG. 13 is an explanatory diagram showing an example of the behavior of the compressor rotation speed, discharge temperature, electronic expansion valve opening, boiling temperature, target temperature difference, and actual temperature difference when boiling operation is performed with a smaller power limit value during power suppression control. [Figure 4] A flowchart showing a control procedure executed by the heating control device. [Diagram 5] FIG. 13 is an explanatory diagram showing an example of the behavior of the compressor rotation speed, discharge temperature, electronic expansion valve opening, boiling temperature, target temperature difference, and actual temperature difference when the method of the present embodiment is executed and boiling operation is performed with a smaller power limit value during power suppression control. [Figure 6] FIG. 13 is an explanatory diagram showing an example of the behavior of the compressor rotation speed, discharge temperature, electronic expansion valve opening, boiling temperature, target temperature difference, and actual temperature difference when the method of the present embodiment is executed and boiling operation is performed with a smaller power limit value during power suppression control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Next, an embodiment of the present invention will be described with reference to the drawings.

[0021] <Schematic circuit configuration> As shown in FIG. 1, a heat pump hot water device 100 according to this embodiment includes a tank unit 1 having a hot water storage tank 2 for storing hot water, and a heat pump unit 3.

[0022] The heat pump unit 3 includes a water-refrigerant heat exchanger 15 (corresponding to a water-refrigerant heat exchanger) for heating the hot water in the hot water storage tank 2, and a heating circulation pump 19 (corresponding to a circulation pump). The water-refrigerant heat exchanger 15 has a refrigerant-side flow path 15b through which the refrigerant flows and a water-side flow path 15a, and exchanges heat between the high-temperature, high-pressure refrigerant and the hot water in the hot water storage tank 2. That is, the water-side flow path 15a of the water-refrigerant heat exchanger 15 and the hot water storage tank 2 are connected in a ring shape by a heating forward pipe 5 (corresponding to a forward pipe) and a heating return pipe 6 (corresponding to a return pipe), and a heating circulation circuit 4 is formed as a hot water circulation circuit spanning the tank unit 1 and the heat pump unit 3.

[0023] The heating forward pipe 5 is connected to the lower part of the hot water storage tank 2, and the heating return pipe 6 is connected to the upper part of the hot water storage tank 2. The heating circulation pump 19 is provided in the middle of the heating forward pipe 5, and circulates the hot water in the hot water storage tank 2 while circulating the hot water from the heating forward pipe 5 to the heating return pipe 6 via the water side flow path 15a. The heating forward pipe 5 is provided with an inlet water temperature sensor 23 that detects the inlet water temperature T1 (the inlet temperature of the hot water) flowing into the water side flow path 15a of the water-refrigerant heat exchanger 15, and the heating return pipe 6 is provided with a boiling temperature sensor 24 that detects the boiling temperature Tb of the water flowing out from the water side flow path 15a toward the hot water storage tank 2.

[0024] In the tank unit 1, a plurality of hot water temperature sensors 12 for detecting the temperature Tw of hot water in the hot water tank 2 are provided on the side surface of the hot water tank 2 from top to bottom. A water supply pipe 7 that supplies water to the hot water storage tank 2 is connected to the bottom of the hot water storage tank 2, and a hot water outlet pipe 8 that outlets the stored high temperature water is connected to the top of the hot water storage tank 2, and the hot water outlet pipe 8 has a negative pressure suction function that opens to introduce air into the hot water storage tank 2 when negative pressure occurs inside the hot water storage tank 2, and is provided with a pressure relief valve 119 that opens to relieve pressure when the pressure inside the hot water storage tank 2 exceeds the valve opening pressure, and a water supply bypass pipe 9 is branched off from the water supply pipe 7. The pressure relief valve 119 is provided with a manual lever (not shown) that can be opened manually. In addition, there is provided a mixing valve 10 that mixes hot water from the hot water outlet pipe 8 with water from the water supply bypass pipe 9 to produce hot water at the hot water supply set temperature, a hot water supply pipe 108a for supplying the hot water mixed in the mixing valve 10 to the hot water supply terminal 125, and a hot water supply temperature sensor 11 that detects the hot water supply temperature in the hot water supply pipe 108a.

[0025] In addition, a hot water supply pipe 108b is provided on the hot water terminal 125 side of the hot water supply pipe 108a outside the tank unit 1, and a gas heat source unit 130 capable of heating the hot water mixed in the mixing valve 10 is provided between these hot water supply pipes 108a, 108b.

[0026] The heat pump unit 3 also includes a compressor 14 that compresses the refrigerant, an electronic expansion valve 16 as a pressure reducer that reduces the pressure of the refrigerant after passing through the water-refrigerant heat exchanger 15, an air heat exchanger 17 as a heat source side heat exchanger that exchanges heat between the air as a heat source and the refrigerant, and an outdoor fan 67 that sends outside air to the air heat exchanger 17. The compressor 14, the refrigerant side flow path 15b of the water-refrigerant heat exchanger 15 through which the refrigerant discharged from the compressor 14 flows, the electronic expansion valve 16, and the air heat exchanger 17 are connected in a circular manner by refrigerant piping 18 to form a refrigerant circulation circuit 30.

[0027] The refrigerant pipe 18 connects the discharge side of the compressor 14 to the inlet side of the water-refrigerant heat exchanger 15, and also connects the suction side of the compressor 14 to the outlet side of the air heat exchanger. The refrigerant pipe 18 and the compressor 14, air heat exchanger 17, and electronic expansion valve 16 connected thereto correspond to a heat pump device. In this embodiment, the heat pump unit 3 including the compressor 14 and the like constituting the heat pump device and the tank unit 1 are not provided with a dedicated power source, and both the heat pump unit 3 and the tank unit are configured to operate by receiving power supply from a household power source or a storage battery, which is an external power source that supplies, for example, AC 100V.

[0028] In the refrigerant circulation circuit 30, for example, R32 refrigerant is used as a refrigerant, forming a heat pump cycle. A discharge temperature sensor 20 for detecting a refrigerant discharge temperature Tout of the refrigerant discharged from the compressor 14 is provided at a portion of the refrigerant piping 18 on the discharge side of the compressor 14, an outflow temperature sensor 21 for detecting an outflow temperature T2 (outlet temperature of the refrigerant) of the refrigerant flowing out from the refrigerant side flow path 15b toward the electronic expansion valve 16 is provided at the refrigerant piping 18 between the refrigerant side flow path 15b and the electronic expansion valve 16, and an outside air temperature sensor 22 (corresponding to an outside air temperature detection means) for detecting an outside air temperature Tair is provided at the air inlet side of the air heat exchanger 17.

[0029] The tank unit 1 is provided with a hot water storage control device 40 to which the detection results of the sensors 12 and 11 are input. Similarly, the heat pump unit 3 is provided with a heating control device 50 to which the detection results of the sensors 20, 22, 24, 21, and 23 are input. The heating control device 50 and the hot water storage control device 40 are connected to each other so as to be able to communicate with each other, and control the operation of each device in the tank unit 1 and the heat pump unit 3 while cooperating with each other based on the detection results of the sensors 12, 11, 20, 22, 24, 21, and 23, etc.

[0030] Note that there may be a master-slave relationship in terms of control between the heating control device 50 and the hot water control device 40, where, for example, the hot water control device 40 outputs an operation command or a power suppression signal (described later) based on the detection results of the sensors 12, 11 to the heating control device 50, and the heating control device 50 controls the operation of each device in the heat pump unit 3 based on the operation command or power suppression signal and the detection results of the sensors 20, 22, 24, 21, 23. In the following, this specification will be described taking such a case as an example.

[0031] <Heat pump input voltage / current detection device> The heat pump unit 3 is provided with a heat pump input voltage detection device 210 (corresponding to a voltage detection means) and a heat pump input current detection device 220 (corresponding to a current detection means) that use known sensors to detect the voltage value and current value input from the external power source to the heat pump unit 3. The input voltage value detected by the heat pump input voltage detection device 210 and the input voltage value detected by the heat pump input current detection device 220 are each output to the heating control device 50.

[0032] Furthermore, the heat pump unit 3 is provided with a heat pump power consumption detection device 200 that detects the power consumed within the heat pump unit 3 (hereinafter simply referred to as "HP power consumption" as appropriate, and the same applies in the drawings). The heat pump power consumption detection device 200 calculates the HP power consumption by integrating the voltage value detected by a heat pump input voltage detection device 210 and the current value detected by a heat pump input current detection device 220. The calculated HP power consumption is output to the heating control device 50.

[0033] <Heating control device> Next, a description will be given of the heating control device 50 provided in the heat pump unit 3. Although detailed illustration is omitted, the heating control device 50 includes a storage unit that stores various data and programs, and a control unit that performs calculation and control processing. The functional configuration of this heating control device 50 will be described with reference to FIG.

[0034] As shown in FIG. 2, the heating control device 50 functionally comprises an operation switching unit 410A, a compressor control unit 410B (corresponding to a compressor control means), an expansion valve control unit 410C (corresponding to a pressure reducer control means), an outdoor fan control unit 410D, a pump control unit 410F, and a power control unit 410G.

[0035] The operation switching unit 410A receives an operation command output by the hot water storage control device 40 and a power suppression signal (described in detail later). In response to the operation command, the operation switching unit 410A determines whether or not to perform a boiling operation (described later) in which the air heat exchanger 17 functions as an evaporator in the heat pump unit 3. The operation switching unit 410A also outputs operation information corresponding to the determination result to the compressor control unit 410B, the expansion valve control unit 410C, the outdoor fan control unit 410D, and the pump control unit 410F. The operation information includes the temperature Tw of the hot water in the hot water storage tank 2 detected by the hot water temperature sensor 12, a target boiling temperature Tbo determined appropriately, and the like.

[0036] In this example, the compressor control unit 410B receives the outdoor air temperature Tair detected by the outdoor air temperature sensor 22, the operation information corresponding to the operation command of the hot water storage control device 40, and the HP input current value from the heat pump input current detection device 220 (this may be input directly or indirectly; the same applies below). The compressor control unit 410B also receives a determination result from a power suppression determination unit 410Ga, which will be described later, and a current release value from a release value setting unit 410Gb. The compressor control unit 410B has a maximum rotation speed setting unit 410Bb and a target rotation speed determination unit 410Bc.

[0037] The maximum rotation speed setting unit 410Bb determines the maximum value of the target rotation speed (maximum target rotation speed) of the corresponding compressor 14 based on a predetermined condition. The target rotation speed determination unit 410Bc sets a target rotation speed (corresponding to the compressor target rotation speed) for the compressor 14 within the range of the set maximum target rotation speed based on the input outside air temperature Tair, the target boiling temperature Tbo, the power suppression signal, the judgment result of the power suppression judgment unit 410Ga, and the current release value, and controls the rotation speed of the compressor 14 to increase or decrease so as to reach this target rotation speed (in detail, it controls the motor that rotates the compressor 14).

[0038] In this example, the power control unit 410G receives as input the HP input voltage value from the heat pump input voltage detection device 210, the power reduction signal from the hot water storage control device 40, and the HP power consumption from the heat pump power consumption detection device 200. The power control unit 410G also has a power reduction determination unit 410Ga (corresponding to the power reduction determination means) and a release value setting unit 410Gb (corresponding to the release value setting means).

[0039] The release value setting unit 410Gb sets a current release value based on the HP input voltage value detected by the heat pump input voltage detection device 210. The set current release value is output to the target rotation speed determination unit 410Bc of the compressor control unit 410B. The power restriction determining section 410Ga will be described later.

[0040] In this example, the expansion valve control unit 410C receives the boiling temperature Tb detected by the boiling temperature sensor 24, the refrigerant discharge temperature Tout detected by the discharge temperature sensor 20, the refrigerant outflow temperature T2 detected by the outflow temperature sensor 21, the outside air temperature Tair detected by the outside air temperature sensor 22, the inflow water temperature T1 detected by the inflow water temperature sensor 23, the operation information corresponding to the operation command of the hot water storage control device 40, a power suppression signal from the hot water storage control device 40, and the HP input voltage value from the heat pump input voltage detection device 210. The expansion valve control unit 410C also has a target opening limiting unit 410Cb (corresponding to a target opening limiting means) and a target opening determining unit 410Cc (corresponding to a target opening determining means).

[0041] The target opening determination unit 410Cc determines the target opening of the pressure reducer such that the state value of the refrigerant on the high pressure side satisfies a predetermined target value condition. Specifically, in this example, the target opening determination unit 410Cc determines the target opening of the electronic expansion valve 16 such that the temperature difference Tout-T2 (corresponding to the state value of the refrigerant on the high pressure side) between the refrigerant discharge temperature Tout and the refrigerant outflow temperature T2 becomes a predetermined target temperature difference ΔH (corresponding to the predetermined target value condition) calculated based on the target boiling temperature Tbo and the inlet water temperature T1 (=ΔH control). The target opening limiting section 410Cb will be described later.

[0042] The outdoor fan control unit 410D receives the outdoor air temperature Tair detected by the outdoor air temperature sensor 22 and the operation information corresponding to the operation command of the hot water storage control device 40. The outdoor fan control unit 410D sets a target rotation speed of the outdoor fan 67 based on the input operation information and the outdoor air temperature Tair, and controls the rotation speed of the outdoor fan 67 to increase or decrease so as to reach the target rotation speed.

[0043] The pump control unit 410F receives the boiling temperature Tb detected by the boiling temperature sensor 24 and the operating information corresponding to the operation command of the hot water storage control device 40, and controls the rotation speed of the heating circulation pump 19 based on these.

[0044] <Boiling operation> As described above, in the heat pump unit 3 of this embodiment, the discharge side of the compressor 14 communicates with the inlet side of the water-refrigerant heat exchanger 15, and the suction side of the compressor 14 communicates with the outlet side of the air heat exchanger 17, thereby allowing the air heat exchanger 17 to function as an evaporator that evaporates the low-temperature, low-pressure refrigerant from the electronic expansion valve 16. That is, in the water-refrigerant heat exchanger 15, heat is released by the release of heat from the refrigerant in the refrigerant pipe 18, and hot water is generated in the heating circulation circuit 4. The generated hot water is supplied to the hot water storage tank 2 via the heating return pipe 6 by the flow of hot water in the heating circulation circuit 4 induced by the heating circulation pump 19, and the temperature of the hot water in the hot water storage tank 2 can be increased (= boiling operation as hot water generation operation).

[0045] <Target opening limit section> In order to ensure stable operation during the boiling operation, in this embodiment, the expansion valve control unit 410C is provided with a target opening limiting unit 410Cb. The target opening limiting unit 410Cb sets a minimum opening Xmin as a lower limit value for the target opening of the electronic expansion valve 16 determined by the target opening determination unit 410Cc. The target opening determination unit 410Cc determines the target opening of the electronic expansion valve 16 according to the minimum opening Xmin set by the target opening limiting unit 410Cb. This prevents the opening of the electronic expansion valve 16 from being excessively narrowed down, for example, during start-up immediately after the start of the boiling operation, thereby ensuring stable operation.

[0046] <Power suppression control and release control> Here, when the compressor 14 of the heat pump unit 3 and the like operate by receiving power supply from a household power source or a storage battery as described above, the limited power supply capacity is shared with the tank unit 1 and each electrical appliance in the home. For this reason, in this embodiment, a power suppression signal instructing suppression of power consumption in the compressor 14 and the like is input from the hot water storage control device 40 to the expansion valve control unit 410C and the power control unit 410G of the heating control device 50. The power suppression signal indicates an upper limit value of power consumption permitted to be consumed by the compressor 14 and the like.

[0047] At this time, as described above, the power control unit 410G is provided with a power restriction determination unit 410Ga. This power restriction determination unit 410Ga determines whether or not the power restriction signal has been input. If it is determined that the power restriction signal has been input, the power restriction determination unit 410Ga outputs the value of the power consumption upper limit value specified by the power restriction signal to the target rotation speed determination unit 410Bc of the compressor control unit 410B. Although not shown in the figure, the determination result by this power restriction determination unit 410Ga is also output to the target opening degree limiting unit 410Cb of the expansion valve control unit 410C. As described above, a current release value based on the HP input voltage value detected by the heat pump input voltage detection device 210 is output from the release value setting unit 410Gb to the target rotation speed determination unit 410Bc of the compressor control unit 410B.

[0048] In response to the above, a target rotation speed determination unit 410Bc of a compressor control unit 410B sets a target rotation speed of the compressor 14 within the range of the maximum target rotation speed set by a maximum rotation speed setting unit 410Bb and within a range in which the HP power consumption input from the heat pump power consumption detection device 200 is equal to or less than the power consumption upper limit value from the power suppression determination unit 410Ga (=power suppression control). Furthermore, when the HP input current value from the heat pump input current detection device 220 exceeds the current release value input from the release value setting unit 410Gb, the target rotation speed determination unit 410Bc sets the target rotation speed of the compressor 14 lower than before the exceedance (=release control). The target rotation speed determination unit 410Bc controls the rotation speed of the compressor 14 to increase or decrease so as to reach the target rotation speed set as described above.

[0049] <Possible impacts of power suppression control> As described above, when power restriction control is performed, the compressor control unit 410B limits the rotation speed of the compressor 14 so that the HP power consumption is within the power consumption upper limit. When the rotation speed of the compressor 14 is limited and reduced, the refrigerant temperature on the high pressure side in the refrigerant pipe 18 tends to decrease, so that the expansion valve control unit 410C reduces the opening degree of the electronic expansion valve 16 in order to maintain this.

[0050] Here, consider a case where boiling operation is performed with a smaller power limit value during the power suppression control. The behavior in such a case is shown in FIG. 3. FIG. 3 is a diagram showing an example of the time behavior of the rotation speed N [rps] of the compressor 14, the opening degree X [pulse] of the electronic expansion valve 16, the boiling temperature Tb [°C] detected by the boiling temperature sensor 24, the discharge temperature Tout [°C] detected by the discharge temperature sensor 20, the target temperature difference ΔH, and the actual temperature difference ΔH at the start of the boiling operation and thereafter. Note that the opening degree X is expressed by the opening degree of the electronic expansion valve 16 (for example, expressed as an opening degree ○○ [%]) by a driving means for driving the electronic expansion valve 16 to the opening degree, for example, the pulse of a pulse motor (similarly below).

[0051] In Fig. 3, the rotation speed N of the compressor 14 rises sharply immediately after the start of operation represented by time t = 0 [min], but is reduced by the power suppression control at time t = 2 [min], and as a result, the opening degree X of the electronic expansion valve 16 is also reduced from the opening degree Xc immediately after the start of operation at time t = 3 [min]. This reduction in the opening degree X increases the load on the compressor 14 and increases power consumption, so the power suppression control controls the rotation speed N of the compressor 14 to be even lower, and as a result, the opening degree X of the electronic expansion valve 16 is further reduced. In this way, a spiral behavior of reduction in the rotation speed N of the compressor 14 → reduction in the opening degree X of the electronic expansion valve 16 → increase in power consumption of the compressor 14 → reduction in the rotation speed N of the compressor 14 → ... is repeated.

[0052] At this time, in the illustrated example, the minimum opening Xmin set by the target opening limiting section 410Cb of the expansion valve control section 410C remains set relatively low, and as a result, the above-described behavior continues, and as a result, the rotation speed N of the compressor 14 drops to or below the lower limit Nmin of the predetermined operable pressure range, making it impossible to operate stably, and the compressor 14 stops operating (t = 20 [min]).

[0053] Therefore, in this embodiment, when the power suppression determination unit 410Ga determines that the power suppression signal has been input as described above and the outside air temperature detected by the outside air temperature sensor 22 is below a predetermined temperature (corresponding to the first case), the target opening limiting unit 410Cb of the expansion valve control unit 410C performs control to ease the decrease in the opening of the electronic expansion valve 16 more than in other cases (corresponding to the second case). Note that the reason for limiting the case to a low outside air temperature is that when the outside air temperature is relatively high, heat is easily taken from the atmosphere, so the discharge temperature Tout from the compressor 14 is originally relatively high, and there is no need to excessively narrow the opening of the electronic expansion valve 16.

[0054] <Control procedure> The control procedure executed by the heating control device 50 of this embodiment to realize the above method will be described with reference to the flowchart of FIG.

[0055] 5, first, in S5, the operation switching unit 410A determines whether or not a boiling start request has been made by an operation command from the hot water storage control device 40. If a boiling start request has been made, the determination is Yes, and the process proceeds to S10.

[0056] Then, in S10, the target opening limiting unit 410Cb of the expansion valve control unit 410C determines whether the outside air temperature Tair from the outside air temperature sensor 22 is less than a predetermined temperature, in this example, 5°C. If Tair ≥ 5°C, the result is No, and the process moves to S20, which will be described later. If Tair < ​​5°C, the result is Yes, and the process moves to S15.

[0057] In S15, the target opening limiting unit 410Cb determines whether or not the power restriction control is performed based on the determination result by the power restriction determination unit 410Ga by inputting the power restriction signal from the hot water storage control device 40. If the power restriction control is not performed, the determination is No, and the process proceeds to S20.

[0058] In S20, the target opening limiting unit 410Cb sets the minimum opening Xmin1 (corresponding to the first minimum opening; see FIG. 3 described later) of the electronic expansion valve 16 from the start of the boiling operation until a predetermined time has elapsed to 50 [pulses], and sets the minimum opening Xmin2 (corresponding to the second minimum opening; see FIG. 5 described later) after a predetermined time has elapsed from the start of the boiling operation to 40 [pulses]. Also, the predetermined time is set to 10 minutes. Then, the process proceeds to S40 described later.

[0059] On the other hand, if power suppression control is performed in S15, a Yes judgment is made, and the process proceeds to S25. In S25, the target opening limiting unit 410Cb sets the minimum opening Xmin1 (corresponding to the first minimum opening) of the electronic expansion valve 16 from the start of boiling operation until a predetermined time has elapsed to a value larger than the above S20, in this example 100 [pulses], and sets the minimum opening Xmin2 (corresponding to the second minimum opening) after a predetermined time has elapsed from the start of boiling operation to a value larger than the above S20, in this example 80 [pulses]. Also, the predetermined time is set to a value longer than the above S20, in this example 30 minutes. Then, the process proceeds to S30.

[0060] In S30, the target opening limiting unit 410Cb judges whether the HP input voltage value from the heat pump input voltage detection device 210 is less than a predetermined value, in this example, 100 [V]. If it is 100 [V] or more, the result is No, and the process proceeds to S40 described later. If it is less than 100 [V], the result is Yes, and the minimum opening Xmin1 of the electronic expansion valve 16 from the start of the boiling operation until a predetermined time has elapsed, and the minimum opening Xmin2 after the predetermined time has elapsed from the start of the boiling operation, which were set in S25, are corrected to larger values. In this example, 20 [pulses] are added to each of the minimum openings Xmin1 and Xmin2. Then, the process proceeds to S40.

[0061] In S40, the target opening degree determining unit 410Cc sets the initial opening degree of the electronic expansion valve 16 at the start of the boiling operation to a predetermined value, and the expansion valve control unit 410C starts controlling the opening degree of the electronic expansion valve 16.

[0062] Thereafter, in S45, the compressor control unit 410B starts the compressor 14, and controls the rotation speed N to increase or decrease so as to reach the target rotation speed determined as described above. In addition, the pump control unit 410F starts control of the rotation speed of the heating circulation pump, and the outdoor fan control unit 410D starts control of the rotation speed of the outdoor fan 67.

[0063] Then, in S50, the target opening limiting unit 410Cb judges whether the time for stabilizing control, in this example 30 seconds, has elapsed after completion of S45. If 30 seconds have elapsed, the judgment is Yes, and the process proceeds to S55.

[0064] In S55, the target opening limiting unit 410Cb sets the opening of the electronic expansion valve 16 to the above-mentioned minimum opening Xmin1. After that, the expansion valve control unit 410C starts a predetermined opening control for the electronic expansion valve 16 in S60, which in the above-mentioned example is the ΔH control.

[0065] Then, in S65, the target opening limiting unit 410Cb determines whether a predetermined time, 30 minutes (or 10 minutes in the above example), has elapsed after S60 starts to control the opening of the electronic expansion valve 16. If the predetermined time has elapsed, the determination is Yes, and the process proceeds to S70.

[0066] In S70, the target opening limiting unit 410Cb sets the opening of the electronic expansion valve 16 to the above-mentioned minimum opening Xmin2.

[0067] Thereafter, in S75, the operation switching unit 410A judges whether or not a boiling stop request has been made by an operation command from the hot water storage control device 40. If a boiling stop request has been made, the judgment is Yes, and the process proceeds to S80.

[0068] In S80, the boiling operation of the heat pump unit 3 is stopped by the drive control of the compressor 14 by the compressor control unit 410B, the rotation speed control of the heating circulation pump by the pump control unit 410F, and the rotation speed control of the outdoor fan 67 by the outdoor fan control unit 410D, and this flow is terminated.

[0069] The above steps are merely examples, and at least some of the steps may be deleted or changed, or steps other than those described above may be added. Furthermore, the order of at least some of the steps may be changed, or multiple steps may be combined into a single step.

[0070] <Effects of the embodiment> As described above, in the heat pump hot water device 100 of this embodiment, in the first case where the power suppression determination unit 410Ga determines that the power suppression signal has been input and the outdoor air temperature Tair is lower than the predetermined temperature, the target opening limiting unit 410Cb sets the predetermined time longer than in the second case, and sets both the minimum openings Xmin1 and Xmin2 larger (see S20 and S25 in FIG. 4). This makes it possible to put a certain brake on the decrease in the opening X of the electronic expansion valve 16 in the flow of decrease in the rotation speed N of the compressor 14 → decrease in the opening X of the electronic expansion valve 16 → increase in the power consumption of the compressor 14 → decrease in the rotation speed N of the compressor 14 →...

[0071] That is, for example, in FIG. 5 corresponding to FIG. 3, the rotation speed N of the compressor 14 rises immediately after the start of operation at time t=0 [min], and then drops to time t=2.5 [min] by power suppression control, and the opening degree X of the electronic expansion valve 16 also drops from the opening degree Xc immediately after the start of operation at time t=3.5 [min]. Thereafter, as in FIG. 3, a spiral behavior is repeated: decrease in the rotation speed N of the compressor 14 → decrease in the opening degree X of the electronic expansion valve 16 → increase in the power consumption of the compressor 14 → decrease in the rotation speed N of the compressor 14 → ··. However, in FIG. 5, the target opening degree limiting unit 410Cb of the expansion valve control unit 410C sets a minimum opening degree Xmin1 higher than that in FIG. 3, so that after the opening degree of the electronic expansion valve 16 reaches the minimum opening degree Xmin1 (see t=11.5 [min]), it will not drop below the Xmin1. As a result, the decrease in the rotation speed N of the compressor 14 also stops (see t=13 [min]). As a result, the rotation speed N of the compressor 14 does not decrease to the lower limit value Nc of the operable pressure range and does not deviate from the operable pressure range. As a result, the boiling operation can be started stably even with a smaller power limit value. Even after the above-mentioned predetermined time has elapsed, stable operation can be continued as shown in FIG. 6, which shows the behavior up to t=70 [min] including the range of t=0 to 25 [min] shown in FIG. 5. In particular, even if the lower limit value of the opening degree of the electronic expansion valve 16 is switched to the minimum opening degree Xmin2 lower than the minimum opening degree Xmin1 at t=33 [min] as the above-mentioned predetermined time, and the opening degree X of the electronic expansion valve 16 decreases to the minimum opening degree Xmin2, the behavior of the actual temperature difference ΔH can be made to approach the target temperature difference ΔH over time, and a high heating capacity and COP can be realized.

[0072] In particular, in this embodiment, when the power suppression control is performed, the minimum opening degree Xmin2 after a predetermined time has elapsed since the start of the boiling operation is set to be larger than when the power suppression control is not performed (see S20 and S25 in FIG. 4). This makes it possible to improve the heating capacity and COP and continue stable operation even with a smaller power limit value.

[0073] In particular, in this embodiment, the release control is performed in the power control unit 410G. That is, when the HP input current value detected by the heat pump input current detection device 220 exceeds the current release value set by the release value setting unit 410Gb based on the HP input voltage value detected by the heat pump input voltage detection device 210, the target rotation speed determination unit 410Bc of the compressor control unit 410B sets the target rotation speed of the compressor 14 to a lower value than before the exceeding. When such a release control is performed, if the input voltage value from the external power source to the heat pump unit 3 drops for some reason, the target rotation speed of the compressor 14 is set lower, so that the compressor 14 tends to deviate from the operable pressure range more easily. Therefore, in this embodiment, when the HP input voltage value detected by the heat pump input voltage detection device 210 falls below a predetermined value (100 [V] in the above example), the target opening limiting unit 410Cb of the expansion valve control unit 410C corrects the minimum openings Xmin1 and Xmin2 in the first case to larger values. This makes it possible to start and continue the boiling operation while preventing the rotation speed of the compressor 14 from deviating from the operable pressure range, even when the power source voltage is decreasing.

[0074] Furthermore, particularly in this embodiment, the target opening degree determination unit 410Cc of the expansion valve control unit 410C determines the target opening degree of the electronic expansion valve 16 by so-called ΔH control, in which the temperature difference Tout-T2 between the refrigerant discharge temperature Tout and the refrigerant outflow temperature T2 becomes a predetermined target temperature difference ΔH based on the target boiling temperature Tbo and the inlet water temperature T1. This maximizes the efficiency of the heat pump unit 3. Furthermore, when these various controls are being performed, the boiling operation can be stably started and continued even when power suppression control is performed using a smaller power limit value.

[0075] The present invention is not limited to the above aspects, and can be applied within the scope of the present invention without changing the gist of the invention. For example, the configurations described in the above embodiments can be appropriately combined or selected, and some of the configurations of the above embodiments can be added, deleted, or replaced.

[0076] For example, in the above embodiment, the target opening degree determining unit 410Cc of the expansion valve control unit 410C performs ΔH control on the electronic expansion valve 16, but the present invention is not limited to this. That is, the target opening determination unit 410Cc may perform so-called ΔT control, which is a feedback control of the opening of the electronic expansion valve 16, so that the temperature difference T2-T1 between the outlet temperature T2 of the refrigerant flowing out from the water-refrigerant heat exchanger 15 and the inlet temperature T1 of hot and cold water flowing into the water-refrigerant heat exchanger 15 is constant. Alternatively, the target opening determination unit 410Cc may perform so-called discharge temperature control, which is a feedback control of the opening of the electronic expansion valve 16, so that the refrigerant discharge temperature Tout becomes a target discharge temperature (for example, the target boiling temperature Tbo plus a constant value [°C]). In these cases, by setting the minimum openings Xmin1 and Xmin2 for the opening X of the electronic expansion valve 16 in the same manner as above, the boiling operation can be stably started and continued even when power suppression control is performed using a smaller power limit value.

[0077] In the above embodiment, the hot water storage tank 2 is connected to the load side of the water-refrigerant heat exchanger 15 via the heating circulation circuit 4 consisting of the heating forward pipe 5 and the heating return pipe 6, and the hot water generated by the water-refrigerant heat exchanger 15 is supplied to the hot water storage tank 2 to perform the boiling operation, but this is not limited to the above. That is, a suitable heat exchange terminal such as a fan coil, a floor heating panel, a panel convector, etc. may be connected via a circulation circuit for circulating hot water similar to the heating circulation circuit 4, and hot water may be supplied to the heat exchange terminal to perform heating, thereby performing a heating operation as a hot water generating operation. In this case, for example, the target return temperature according to the set temperature level of a remote control for operating the heat exchange terminal corresponds to the target hot water temperature. In this case, the same effect can be obtained by the same method as described above.

[0078] The heat pump cycle in the above embodiment may be an ejector cycle using an ejector as a pressure reducer.

[0079] In the above embodiment, the heat source unit is an air-source heat pump having an outdoor fan 67 that blows outside air while passing a refrigerant through the air heat exchanger 17 as a heat source side heat exchanger, and heat is exchanged between the outside air as a heat source and the refrigerant, but the present invention is not limited to this. That is, the heat source unit may be configured such that water or antifreeze liquid is supplied to the heat source side heat exchanger, and the liquid and the refrigerant exchange heat in the heat source side heat exchanger. In addition, a heat source side heat exchanger may be provided underground or in a relatively large-capacity water source, and the heat source side heat exchanger may exchange heat between the refrigerant and the underground or water source. Furthermore, a composite heat source type may be configured with a heat pump circuit using heat from the underground or water source and another heat pump circuit using air heat. Furthermore, in place of the liquid, the outside air, or the water source, other materials (for example, gases including smoke, exhaust fumes, and various high-temperature gases, or fluid solids including hot sand, dust, and various particles) may be passed through the heat source side heat exchanger as long as they are capable of exchanging heat with the refrigerant in the heat source side heat exchanger, or heat from sunlight, reflected light, and other radiation may be supplied to the heat source side heat exchanger.

[0080] In the above, the arrows shown in each of the drawings such as FIG. 1 and FIG. 2 show an example of the flow of signals, and do not limit the direction of the signal flow.

[0081] In addition to the above, the methods according to the above embodiments and their modifications may be used in appropriate combination.

[0082] Although not specifically illustrated, the present invention can be implemented with various modifications without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0083] 1 Tank unit 2 Hot water tank 3. Heat pump unit 4 Heating circulation circuit (hot water circulation circuit) 5. Heated feed pipe 6 Heat return pipe 14 Compressor 15 Water-refrigerant heat exchanger (water-refrigerant heat exchanger) 16 Electronic expansion valve (pressure reducer) 17 Air heat exchanger 18 Refrigerant piping 19 Heating Circulation Pump 20 Discharge temperature sensor 21 Outlet temperature sensor 22 Outside air temperature sensor (outside air temperature detection means) 23 Inlet water temperature sensor 30 Refrigerant circulation circuit 40 Hot water storage control device 50 Heating control device 100 Heat pump hot water system 210 Heat pump input voltage detection device (voltage detection means) 220 Heat pump input current detection device (current detection means) 410B Compressor control section (compressor control means) 410C Expansion valve control section (pressure reducer control means) 410Cb Target opening limiting unit (target opening limiting means) 410Cc Target opening determination unit (target opening determination means) 410G Power Control Unit 410Ga Power Suppression Judgment Unit (Power Suppression Judgment Means) 410Gb Release value setting unit (release value setting means) Tair Outside temperature Tout Refrigerant discharge temperature T1 Inlet water temperature T2 Outflow temperature Xmin1 Minimum opening (1st minimum opening) Xmin2 Minimum opening degree (2nd minimum opening degree)

Claims

1. A heat pump device in which a compressor, a pressure reducer, and an air heat exchanger are connected by refrigerant piping; A water-refrigerant heat exchanger that receives a refrigerant from the heat pump device through the refrigerant piping and generates hot water for the hot water circulation circuit side by heat exchange with water; A compressor control means for controlling the rotation speed of the compressor to be increased or decreased so as to become a target compressor rotation speed; a pressure reducer control means for controlling an opening degree of the pressure reducer; a power reduction determination means for determining whether a power reduction signal instructing reduction of power consumption in the heat pump device has been input; An outside air temperature detection means for detecting an outside air temperature; A heat pump hot water device having a boiling operation for generating hot water on the hot water circulation circuit side, The compressor control means When the power restriction determination means determines that the power restriction signal has been input, the rotation speed of the compressor is controlled so as to become the target compressor rotation speed according to the power consumption upper limit value permitted by the power restriction signal. The pressure reducer control means a target opening degree determining means for determining a target opening degree of the pressure reducing device such that a state value of the refrigerant on the high pressure side satisfies a predetermined target value condition; a target opening limiting means for setting a first minimum opening as a lower limit value for the target opening determined by the target opening determining means for a predetermined time from the start of the boiling operation, and setting a second minimum opening smaller than the first minimum opening as a lower limit value after the predetermined time has elapsed from the start of the boiling operation; Equipped with The target opening degree determining means determining a target opening degree of the pressure reducer within a range equal to or greater than the lower limit value set by the target opening degree limiting means; The target opening limiting means In a first case in which the outside air temperature detected by the outside air temperature detection means is lower than a predetermined temperature and the power restriction determination means determines that the power restriction signal has been input, the predetermined time is set longer than in a second case in which the power restriction signal has not been input, and the first minimum opening degree and the second minimum opening degree are set larger. A heat pump hot water device characterized by the above.

2. 2. The heat pump hot water device according to claim 1, wherein the second minimum opening degree when the power reduction determination means determines that the power reduction signal has been input is greater than the second minimum opening degree when the power reduction determination means does not determine that the power reduction signal has been input in the second case.

3. A voltage detection unit that detects an input voltage value from an external power source to the heat pump device; a current detection unit that detects an input current value from the external power supply to the heat pump device; a release value setting means for setting a current release value based on the input voltage value detected by the voltage detection means; and The compressor control means when the input current value detected by the current detection means exceeds the current release value set by the release value setting means, the rotation speed of the compressor is controlled so as to become the target compressor rotation speed which is lower than the target compressor rotation speed before the input current value detected by the current detection means exceeds the current release value set by the release value setting means; The target opening limiting means When the input voltage value detected by the voltage detection means becomes less than a predetermined value, the first minimum opening degree and the second minimum opening degree in the first case are corrected to values ​​larger than those in the case where the input voltage value is equal to or greater than the predetermined value.

2. The heat pump hot water system according to claim 1.

4. The target opening degree determining means The temperature difference between the discharge temperature of the refrigerant from the compressor and the outflow temperature of the refrigerant flowing out of the water-refrigerant heat exchanger is a predetermined target temperature difference calculated based on the target hot water temperature of the hot water to be generated and the inlet water temperature of the hot water flowing into the water-refrigerant heat exchanger, or The temperature difference between the outflow temperature and the inflow temperature of the hot and cold water flowing into the water-refrigerant heat exchanger is constant, or The discharge temperature is set to a target discharge temperature.

4. The heat pump hot water system according to claim 1, further comprising a step of determining a target opening degree of the pressure reducer.

5. A hot water storage tank for storing hot water; A heat pump device in which a compressor, a pressure reducer, and an air heat exchanger are connected by refrigerant piping; a water-refrigerant heat exchanger that receives a refrigerant from the heat pump device through the refrigerant piping and exchanges heat with water; A hot water circulation circuit including a forward pipe from the lower part of the hot water storage tank to the water-refrigerant heat exchanger and a return pipe from the water-refrigerant heat exchanger to the upper part of the hot water storage tank; A compressor control means for controlling the rotation speed of the compressor to be increased or decreased so as to become a target compressor rotation speed; a pressure reducer control means for controlling an opening degree of the pressure reducer; a power reduction determination means for determining whether a power reduction signal instructing reduction of power consumption in the heat pump device has been input; An outside air temperature detection means for detecting an outside air temperature; having In a heat pump hot water device, a boiling operation is performed in which the refrigerant heated by the heat pump device is circulated through the refrigerant piping, and the hot water heated by being introduced into the water-refrigerant heat exchanger through the forward pipe is supplied to the hot water storage tank through the return pipe. The compressor control means When the power restriction determination means determines that the power restriction signal has been input, the rotation speed of the compressor is controlled so as to become the target compressor rotation speed according to the power consumption upper limit value permitted by the power restriction signal. The pressure reducer control means a target opening degree determining means for determining a target opening degree of the pressure reducing device such that a state value of the refrigerant on the high pressure side satisfies a predetermined target value condition; a target opening limiting means for setting a first minimum opening as a lower limit value for the target opening determined by the target opening determining means for a predetermined time from the start of the boiling operation, and setting a second minimum opening smaller than the first minimum opening as a lower limit value after the predetermined time has elapsed from the start of the boiling operation; Equipped with The target opening degree determining means determining a target opening degree of the pressure reducer within a range equal to or greater than the lower limit value set by the target opening degree limiting means; The target opening limiting means In a first case in which the outside air temperature detected by the outside air temperature detection means is lower than a predetermined temperature and the power restriction determination means determines that the power restriction signal has been input, the predetermined time is set longer than in a second case in which the power restriction signal has not been input, and the first minimum opening degree and the second minimum opening degree are set larger. A heat pump hot water device characterized by the above.

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