JP6208633B2 - Heat pump water heater - Google Patents

Description

  The present invention relates to a heat pump type water heater.

The heat pump type hot water heater uses a heat pump cycle using a CO ₂ refrigerant in a heat source machine for boiling hot water. In order to boil hot water by a heat pump cycle, the pressure of the refrigerant needs to be at least 7.3 MPa which is a critical pressure. For this reason, pressure sensors, pressure switches, and the like are installed for the purpose of preventing breakage, bursting, and the like due to a sudden rise in pressure.

  Patent Document 1 discloses a heat pump type hot water heater having a protection means for detecting the pressure of a refrigerant by a pressure sensor and changing the opening of an expansion valve and the rotational speed of the compressor so as not to exceed the upper limit of use pressure. Yes.

JP 2013-79770 A

Since pressure sensors, pressure switches, and the like are expensive, it is desired to be able to control a heat pump type water heater without adding them from the viewpoint of cost reduction. When using a fluorocarbon refrigerant, for refrigerant state after the compressor discharge is a gas-liquid two-phase state, but can be easily estimated pressure from the temperature data, since the supercritical state in the CO ₂ refrigerant, the temperature It is difficult to estimate the pressure from the data.

  An object of the present invention is to protect a refrigerant circuit of a heat pump including a compressor, a refrigerant pipe and a heat exchanger from being damaged without attaching a pressure sensor or a pressure switch in a heat pump type hot water heater.

  The heat pump water heater of the present invention includes a compressor that compresses and discharges refrigerant, a water-refrigerant heat exchanger that heats water using the refrigerant discharged from the compressor, and a refrigerant that has passed through the water-refrigerant heat exchanger. A pressure reducing valve that depressurizes, an evaporator that exchanges heat between the refrigerant that has passed through the pressure reducing valve and air, a control unit that has a function of adjusting the rotation speed of the compressor, and an ambient temperature detecting unit that measures the ambient temperature The control unit calculates the value of the limit current of the compressor from the ambient temperature and the rotation speed of the compressor, and the value of the refrigerant pressure discharged from the compressor does not exceed the value of the limit pressure corresponding to the value of the limit current It has the function to make it. Here, the number of revolutions of the compressor is a value actually measured or a value corresponding to a control signal from the control unit issued as a command to the compressor.

  ADVANTAGE OF THE INVENTION According to this invention, in a heat pump type water heater, it can protect so that the refrigerant circuit of the heat pump containing a compressor, refrigerant | coolant piping, and a heat exchanger may not be damaged, without attaching a pressure sensor or a pressure switch.

It is a schematic block diagram which shows the heat pump type water heater of this invention. It is a graph which shows the example of the compressor rotation speed dependence of a limiting pressure. It is a graph which shows the example of the compressor rotation speed dependence of the limiting current corresponding to the limiting pressure of FIG. It is a flowchart which shows the example of the control which estimates a limitation current and performs the protection operation of a compressor. It is a flowchart which shows the other example of the control which estimates a limitation current and performs the protection operation of a compressor.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the present embodiment, a heat pump type water heater using water as the liquid to be heated will be described as an example.

  In the heat pump type hot water heater according to the present embodiment, the control unit calculates the value of the limit current of the compressor from the ambient temperature and the rotational speed (rotational speed) of the compressor, and sets the pressure of the refrigerant discharged from the compressor. It has a function of controlling so that the value does not exceed the limit pressure value (discharge pressure limit value). Here, the value of the limiting pressure has a corresponding value of the limiting current. The value of the limiting current also depends on the ambient temperature. Further, the rotational speed of the compressor may be a value obtained by actually measuring (detecting) a compressor rotational speed detection unit, or from a control unit issued as a command to the compressor. It may be a value corresponding to the control signal.

  Below, after demonstrated the whole structure of the heat pump water heater which concerns on this embodiment, and the basic operation | movement of a control part, the operation | movement of the control part concerning this invention is demonstrated more concretely.

  FIG. 1 is a schematic configuration diagram of a heat pump type water heater according to an embodiment of the present invention.

  In this figure, the heat pump type hot water supply apparatus 101 includes a heat pump unit 1 and a tank unit 2. The heat pump unit 1 and the tank unit 2 may be separated from each other or may be integrally disposed in one housing.

  The heat pump unit 1 includes a compressor 3, a water-refrigerant heat exchanger 4, a pressure reducing valve 5 (electric valve), an evaporator 6, and a control unit 50. The compressor 3, the water-refrigerant heat exchanger 4, the pressure reducing valve 5, and the evaporator 6 are annularly connected by piping so that the refrigerant circulates in this order. In the present embodiment, carbon dioxide, which is a refrigerant that does not affect the ozone layer, is used as the refrigerant. And in the heat pump part 1, since the discharge pressure of the refrigerant | coolant (carbon dioxide) by the compressor 3 uses the supercritical vapor compression type heat pump cycle used more than the critical pressure of the said refrigerant | coolant, and a refrigerant | coolant can be made into high temperature high pressure, For example, hot water such as 90 ° C. can be obtained.

  The compressor 3 compresses the refrigerant returned from the annular circuit, and sends out the compressed high-temperature gas refrigerant (hereinafter also referred to as “hot gas”) to the annular circuit again. More specifically, the compressor 3 sucks and compresses the refrigerant returned from the evaporator 6 and discharges it toward the water-refrigerant heat exchanger 4.

  The capacity of the compressor 3 can be controlled, and when high-temperature hot water storage (for example, 90 ° C.) is performed, the compressor 3 is operated at a higher rotational speed (for example, 3000 to 4000 rotations / minute) than usual. Further, when operating at a normal hot water storage temperature (for example, 65 ° C.), it is operated at a relatively slow rotational speed (for example, 2000 to 3000 rotations / minute). Further, the compressor 3 can control the rotation speed from a low speed (for example, 1000 rotations / minute) to a high speed (for example, 6000 rotations / minute) by PWM control, voltage control (for example, PAM control) or a combination control thereof. It has become.

  In the pipe connecting the compressor 3 and the water-refrigerant heat exchanger 4, the high-pressure side refrigerant temperature, that is, the temperature of the refrigerant discharged from the compressor 3 (the discharge temperature of the compressor 3) is close to the compressor 3. A temperature sensor 9 (temperature detection means) for detection is provided.

  The water-refrigerant heat exchanger 4 functions as a condenser, and is a liquid heat transfer tube 2a through which hot gas (refrigerant) discharged from the compressor 3 flows, and a liquid transfer through which water as the liquid to be heated flows. And a heat pipe 2b (water heat transfer pipe). These refrigerant heat transfer tubes 2a and liquid heat transfer tubes 2b are provided in close contact so that the refrigerant and the liquid to be heated exchange heat with each other. Moreover, the flow of each heat exchanger tube 2a, 2b is comprised so that it may oppose. In the water-refrigerant heat exchanger 4, heat exchange between the refrigerant discharged from the compressor 3 and the liquid to be heated (water) is performed.

  The pressure reducing valve 5 is provided in the middle of a pipe disposed between the water-refrigerant heat exchanger 4 and the evaporator 6, and here, an electric expansion valve is used. The pressure reducing valve 5 depressurizes the medium temperature and high pressure refrigerant flowing out of the water-refrigerant heat exchanger 4 and sends it to the evaporator 6 as a low pressure refrigerant that easily evaporates. The pressure reducing valve 5 can adjust the throttle opening (opening / closing degree), and the control unit 50 changes the throttle opening to adjust the refrigerant circulation amount in the heat pump unit 1. And the control part 50 will adjust the discharge temperature of the compressor 3 by changing the aperture opening degree of the pressure-reduction valve 5, so that it may mention later. In addition, when the control part 50 forms frost on the evaporator 6, in order to melt the frost attached to the evaporator 6, the decompression valve 5 is opened (throttle opening is fully opened) and the defrost operation is performed.

  The evaporator 6 takes in outside air by the rotation of the blower 7 and pumps heat from outside air by causing heat exchange between the refrigerant circulating in the evaporator 6 and the outside air (air blowing). That is, the evaporator 6 performs heat exchange between the refrigerant flowing out of the pressure reducing valve 5 and the air. The refrigerant that has passed through the evaporator 6 is returned to the compressor 3 again. The blower 7 rotates at a predetermined rotation speed (rotational speed) according to a control signal from the control unit 50.

  The temperature sensor 10 detects the temperature of the refrigerant flowing out of the evaporator 6. The controller 50 determines whether or not to perform defrosting in the evaporator 6 based on the temperature detected by the temperature sensor 10, and when performing defrosting, fully opens the pressure reducing valve 5. Reference numeral 14 denotes a temperature sensor (ambient temperature detector) that detects an outside air temperature (ambient temperature). In the present embodiment, the temperature sensor 14 is provided in the vicinity of the blower 7.

  Reference numeral 36 is a delivery pipe, and one end of the delivery pipe 36 is connected to the outlet of the liquid heat transfer tube 2 b of the water-refrigerant heat exchanger 4. The delivery pipe 36 feeds the liquid to be heated heated by the refrigerant from the water-refrigerant heat exchanger 4 to the tank unit 2. More specifically, the delivery pipe 36 extends toward the tank 16 side of the tank 2 and is connected to the top of the tank 16. Near the water-refrigerant heat exchanger 4 of the delivery pipe 36, a temperature sensor 12 is provided that detects the temperature of the liquid to be heated that exits from the water-refrigerant heat exchanger 4 (in this embodiment, the tapping temperature).

  Reference numeral 35 denotes a supply pipe, and the supply pipe 35 supplies the liquid to be heated heated by the refrigerant to the water-refrigerant heat exchanger 4. One end of the supply pipe 35 is connected to the inlet of the liquid heat transfer pipe 2 b of the water-refrigerant heat exchanger 4. The supply pipe 35 extends toward the tank 16 and is connected to the bottom of the tank 16. Near the water-refrigerant heat exchanger 4 of the supply pipe 35, a temperature sensor 11 is provided that detects the temperature of the heated liquid entering the water-refrigerant heat exchanger 4 (water temperature in the present embodiment). .

  In addition, a pump 13 (water circulation pump) is disposed on the upstream side of the water-refrigerant heat exchanger 4 in the supply pipe 35. The pump 13 is driven so as to send the liquid to be heated from the tank 16 to the inlet side of the liquid heat transfer tube 2b. The pump 13 is configured such that the flow rate (mass flow rate), flow rate, and pressure of circulating water can be freely selected.

  The tank unit 2 includes a tank 16 that stores a liquid to be heated (water in this embodiment). The tank 16 is connected to one end of each of a delivery pipe 36 and a supply pipe 35 extending from the heat pump unit 1 side. The tank 16 is also connected to one end of each of the hot water supply pipe 38b and the water supply pipe 38a. A hot water supply port (not shown) is provided at the other end of the hot water supply pipe 38b. A water supply port (not shown) is provided at the other end of the water supply pipe 38a.

  The water supply pipe 38a is connected to a branch pipe 38c that branches from the water supply pipe 38a on the upstream side of the tank 16 and that joins the hot water supply pipe 38b at the tip thereof. The branch pipe 38 c is connected to the hot water supply pipe 38 b through the hot water / mixing valve 17. The hot water mixing valve 17 adjusts the amount of water flowing into the hot water supply pipe 38b via the water supply pipe 38a and the branch pipe 38c according to the degree of opening thereof, thereby providing a hot water supply port provided at the other end of the hot water supply pipe 38b (illustrated). (Omitted) Adjust the temperature of the hot water coming out.

  In the present embodiment, the liquid to be heated is once taken into the tank 16 and then supplied to the heat pump unit 1 via the supply pipe 35. However, the present invention is not limited to this. For example, the heat pump is directly supplied from a water supply port (water supply pipe). The heated liquid may be supplied to the unit 1. In the present embodiment, the liquid to be heated heated by the heat pump unit 1 is once taken into the tank 16 and then supplied from the hot water supply port via the hot water supply pipe 38b. You may make it supply the to-be-heated liquid heated with the heat pump part 1 directly from the hot water supply port. Furthermore, instead of supplying hot water in the tank 16, a direct water supply hot water supply system including a heat exchanger that heats tap water using the heat of the hot water in the tank 16 may be used.

  The control unit 50 includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like, and comprehensively controls the heat pump water heater 101 according to the present embodiment according to a program stored therein. . For example, as described above, the controller 50 defrosts the evaporator 6 based on the temperature detected by the temperature sensor 10 (the outlet refrigerant temperature of the evaporator 6). Further, the control unit 50 calculates the target discharge temperature of the compressor 3 based on the temperatures detected by the temperature sensors 9, 11, 12, and 14.

  Next, the operation of the heat pump type water heater 101 will be described. In the heat pump hot water supply apparatus 101, when performing a boiling operation with midnight power, the hot water in the tank 16 is almost used up, and in this case, the tank 16 is filled with cold water (normal temperature water). Alternatively, hot water may remain at the top of the tank 16.

  Normally, the tank 16 is always full of water, and in this state, the heat pump hot water supply apparatus 101 performs a hot water storage operation process. The heat pump hot water heater 101 sends hot gas discharged from the started compressor 3 into the refrigerant heat transfer tube 2 a of the water-refrigerant heat exchanger 4. The hot gas sent into the refrigerant heat transfer tube 2a is condensed by releasing heat into the water in the liquid heat transfer tube 2b. And the water in the liquid heat exchanger tube 2b is heated with hot gas. Next, the refrigerant sent out from the refrigerant heat transfer tube 2 a of the water-refrigerant heat exchanger 4 is depressurized by the pressure reducing valve 5 (expansion valve) and then flows into the evaporator 6. When the refrigerant flowing into the evaporator 6 evaporates by the wind sent from the blower 7, it draws heat from the outside air. Thereafter, the refrigerant returns to the compressor 3 and is compressed again.

  On the other hand, the water filled in the tank 16 is sent into the liquid heat transfer tube 2 b of the water-refrigerant heat exchanger 4 from the bottom of the tank 16 through the supply pipe 35 when the pump 13 is activated. As described above, the water sent into the liquid heat transfer tube 2 b is heated by heat exchange with the refrigerant to become hot water and flows into the delivery pipe 36. The hot water that has flowed into the delivery pipe 36 returns to the top of the tank 16 and is stored. Since the hot water returned to the top of the tank 16 has a low density, it does not mix with the cold water at the bottom of the tank 16 and accumulates in order from the top. Thus, while water circulates between the tank 16 and the water-refrigerant heat exchanger 4, the heat pump water heater 101 ensures a predetermined amount of hot water in the tank 16 at a predetermined temperature.

  The control part 50 of the heat pump type hot water heater 101 controls the compressor 3, the pump 13, and the pressure reducing valve 5 as follows. The controller 50 controls the rotational speed of the compressor 3 based on the temperature of the hot water at the outlet of the water-refrigerant heat exchanger 4 detected by the temperature sensor 12. Specifically, the control unit 50 controls the rotation speed of the compressor 3 so that the temperature detected by the temperature sensor 12 becomes a preset target value of the tapping temperature. That is, when the detected value of the temperature sensor 12 is lower than the target value, the rotational speed of the compressor 3 is increased. Conversely, when the detected value is high, the rotational speed of the compressor 3 is decreased.

  Further, the control unit 50 controls the amount of water that the pump 13 sends to the liquid heat transfer pipe 2b of the water-refrigerant heat exchanger 4 in order to control the heating capacity. Number). Specifically, when the actual rotational speed (actual rotational speed) is slower than the target rotational speed of the compressor 3 (when the actual rotational speed is low), the amount of water fed into the liquid heat transfer tube 2b is reduced. The pump 13 is controlled to increase. On the contrary, when the actual rotational speed of the compressor 3 is high, the pump 13 is controlled so that the amount of water fed into the liquid heat transfer tube 2b is reduced. Thereby, it is possible to adjust the heating capacity to a target value (for example, 4.5 kW).

  The target rotational speed of the compressor 3 is not only the target value of the tapping temperature of the water-refrigerant heat exchanger 4, but also the target heating capacity (output) of the heat pump unit 1, the detection value (outside temperature) of the temperature sensor 14, and It can also be set based on the detection value (inflow water temperature) of the temperature sensor 11. Specifically, for example, as described above, the target rotational speed of the compressor 3 is set in a range of 3000 to 4000 revolutions / minute when performing high-temperature hot water storage (for example, 90 ° C.). In the case of operating at a temperature (for example, 65 ° C.), the speed is set in a range of 1000 to 2000 revolutions / minute, but is not limited thereto.

  The control unit 50 calculates the target discharge temperature of the compressor 3 and controls the opening of the pressure reducing valve 5 based on the difference between the discharge temperature of the compressor 3 detected by the temperature sensor 9 and the target discharge temperature. . That is, the control unit 50 controls the opening of the pressure reducing valve 5 so that the discharge temperature of the compressor 3 becomes a target value (target discharge temperature) calculated in advance by the control unit 50. Specifically, when the temperature detected by the temperature sensor 9 is higher than the target discharge temperature, the pressure reducing valve 5 is opened, and when the temperature is low, the pressure reducing valve 5 is adjusted to be closed. The target discharge temperature is determined by the control unit 50 in addition to the target value of the tapping temperature of the water-refrigerant heat exchanger 4, the target heating capacity (output) of the heat pump unit 1, the detected value (outside temperature) of the temperature sensor 14, and It can also be calculated and set based on the detection value (inflow water temperature) of the temperature sensor 11. The target discharge temperature is set so that the heat pump unit 1 has the maximum coefficient of performance (COP), but is not limited thereto.

  FIG. 2 is a graph showing an example of the dependency of the limit pressure set to prevent the compressor and other refrigerant circuits from being damaged, on the rotation speed of the compressor. The horizontal axis is the compressor speed, and the vertical axis is the limiting pressure. Here, the limiting pressure refers to the highest pressure set in advance to protect the compressor and other refrigerant circuits from damage. When the pressure of the refrigerant discharged from the compressor (usually the highest pressure in the heat pump cycle) exceeds an allowable value, the compressor's high-pressure chamber, shaft (rotating shaft), orbiting scroll, and other heat pump components May be damaged. In order for the compressor to continue operating safely, it is necessary to limit the pressure of the refrigerant.

  As shown in this figure, the limiting pressure is constant at the normal compressor speed (intermediate region of the compressor speed) in steady operation. On the other hand, when the compressor rotational speed is low as in the beginning of the operation of the compressor and when the compressor rotational speed is high as in full operation, the limiting pressure needs to be slightly reduced. This is because if the pressure of the refrigerant discharged from the compressor is higher than the allowable pressure when the compressor rotational speed is low or high, the shaft of the compressor and the orbiting scroll may be greatly shaken. This is because there is a risk of damage to bearings, orbiting scrolls, and the like.

  FIG. 3 is a graph showing an example of the dependency of the limiting current corresponding to the limiting pressure of FIG. 2 on the compressor rotation speed. The horizontal axis is the compressor speed, and the vertical axis is the current limit. Here, the limit current refers to a limit value of the current input to the heat pump type hot water heater (or compressor). Therefore, the current input as the power source of the heat pump water heater is AC, and the current input to the compressor is converted to DC. The pressure (discharge pressure) of the refrigerant discharged from the compressor depends not only on the current input to the compressor but also on the change with time of the power supply voltage and other conditions. Therefore, strictly speaking, the limiting current that corresponds to the limiting pressure does not uniquely correspond to the limiting pressure. However, by setting the limit current, the discharge pressure can be limited to a controllable error range.

  Of the two curves shown in the figure, the solid line indicates the case where the ambient temperature is low, and the broken line indicates the case where the ambient temperature is high. This indicates that the input current to the heat pump water heater (or compressor) that reaches the same limit pressure at the same compressor speed depends on the ambient temperature. That is, when the ambient temperature is low, the limit pressure is not reached unless the input current is relatively large. On the other hand, when the ambient temperature is high, the limit pressure is reached even if the input current is relatively small.

  FIG. 4 is a flowchart illustrating an example of control for estimating the limit current and performing the protection operation of the compressor.

  In this figure, the heating operation of the heat pump type hot water heater is started (S101), and then it is determined whether 20 seconds have passed (S102). When it is detected that 20 seconds have elapsed, the value of the limiting current is calculated from the ambient temperature Ta and the compressor rotational speed N (S103). Here, the compressor rotation speed N may be a value of a signal given as a command from the control unit to the compressor, or may be an actually detected compressor rotation speed.

  And it is discriminate | determined whether the electric current value of the power supply of a heat pump type hot water heater is higher than a limiting current (S104). As a result, when the current value of the power source of the heat pump type hot water heater is higher than the limit current, one or more of the following three operations are performed (S105).

  1) Reduction of compressor rotation speed: The compressor rotation speed is decreased by 100 rotations.

  Thereby, compression of a refrigerant can be controlled.

  2) Enlargement of the opening of the pressure reducing valve: open 5 pulses of the pressure reducing valve (motor valve).

  Thereby, the flow volume of a refrigerant | coolant can be increased and compression of a refrigerant | coolant can be suppressed.

  3) Increasing the rotation speed of the water circulation pump: Increase the rotation speed of the water circulation pump by 500 rotations.

  Thereby, the amount of water flowing into the liquid heat transfer pipe 2b of the water-refrigerant heat exchanger 4 in FIG. 1, that is, the amount of water circulating through the tank 16 and the water-refrigerant heat exchanger 4 can be increased. Thereby, the heat accumulated in the heat pump cycle (refrigerant circuit) generated by the operation of the compressor can be moved to the water side, and the temperature and pressure of the refrigerant can be suppressed.

  Thereafter, the process returns to S102. The range of change in numerical values such as the compressor rotation speed in the above operation is not limited to this example, and may be set according to the type and conditions of the device.

  On the other hand, if it is determined in S104 that the current value of the power source of the heat pump type hot water heater is not higher than the limit current, the process returns to S102 without performing the operation of S105.

  Thereby, the pressure of the refrigerant | coolant which flows through a compressor, refrigerant | coolant piping, and a heat exchanger can be controlled below to a limit pressure, and it can protect so that the refrigerant circuit of a heat pump may not be damaged.

  FIG. 5 is a flowchart illustrating another example of the control for estimating the limit current and performing the protection operation of the compressor.

  4 differs from the procedure of FIG. 4 in that the power supply voltage Vs is used in addition to the ambient temperature Ta and the compressor rotational speed N when calculating the value of the limiting current. As a result, a more accurate value of the limit current can be obtained by taking into account fluctuations in the power supply voltage Vs over time. Then, the value of the limit pressure can be estimated more accurately, and the refrigerant pressure can be controlled more accurately. This further ensures the protection of the compressor.

  The detailed procedure in FIG. 5 will be described below.

  The boiling operation of the heat pump hot water heater is started (S201), and then it is determined whether 20 seconds have passed (S202). When it is detected that 20 seconds have elapsed, the value of the limiting current is calculated from the ambient temperature Ta, the compressor rotation speed N, and the power supply voltage Vs (S203). Here, the compressor rotation speed N may be a value of a signal given as a command from the control unit to the compressor, or may be an actually detected compressor rotation speed. The power supply voltage Vs is measured by a voltage detection unit. The power source voltage Vs may be a voltage of an AC power source supplied as a power source of the heat pump type hot water heater, or a voltage of a DC power source supplied to the compressor (a signal generated from a control unit to determine this). Good.

  And it is discriminate | determined whether the electric current value of the power supply of a heat pump type hot water heater is higher than a limiting current (S204). As a result, if the current value of the power source of the heat pump type hot water heater is higher than the limit current, one or more of the following three operations are performed (S205).

  1) Decrease the compressor speed by 100 revolutions.

  2) Open the pressure reducing valve (motor valve) for 5 pulses.

  3) Increase the rotation speed of the water circulation pump by 500 rotations.

  Thereafter, the process returns to S202. The range of change in numerical values such as the compressor rotation speed in the above operation is not limited to this example, and may be set according to the type and conditions of the device.

  On the other hand, if it is determined in S204 that the current value of the power source of the heat pump type hot water heater is not higher than the limit current, the process returns to S202 without performing the operation of S205.

  In addition, there are the following two examples of modifications of the process of calculating the value of the limiting current shown in FIGS.

  1) In addition to the ambient temperature Ta and the compressor speed N, the temperature of the refrigerant flowing into the evaporator (evaporator inlet temperature) is used to calculate the value of the limiting current from these three values.

  2) Using the temperature of the refrigerant flowing into the evaporator (evaporator inlet refrigerant temperature) in addition to the ambient temperature Ta, the compressor speed N and the power supply voltage Vs, the value of the limiting current is calculated from these three values. .

  By using the evaporator inlet temperature, the value of the limit pressure can be estimated more accurately, the refrigerant pressure can be controlled more accurately, and the compressor can be further protected.

  1: heat pump unit, 2: tank unit, 2a: refrigerant heat transfer tube, 2b: liquid heat transfer tube, 3: compressor, 4: water-refrigerant heat exchanger, 5: pressure reducing valve, 6: evaporator, 7: blower, 9, 10, 11, 12, 14: Temperature sensor, 13: Pump, 16: Tank, 17: Hot water mixing valve, 35: Supply pipe, 36: Delivery pipe, 38a: Water supply pipe, 38b: Hot water supply pipe, 38c: Branch Piping, 50: control unit, 101: heat pump type water heater.

Claims (5)

A compressor that compresses and discharges the refrigerant;
A water-refrigerant heat exchanger for heating water with the refrigerant discharged from the compressor;
A pressure reducing valve that depressurizes the refrigerant that has passed through the water-refrigerant heat exchanger;
An evaporator that exchanges heat between the refrigerant that has passed through the pressure reducing valve and air;
A control unit having a function of adjusting the rotational speed of the compressor;
An ambient temperature detector for measuring the ambient temperature,
The number of revolutions of the compressor is a value actually measured or a value corresponding to a control signal from the control unit issued as a command to the compressor,
The control unit calculates a value of the limit current of the compressor from the ambient temperature and the rotation speed of the compressor, and a value of the pressure of the refrigerant discharged from the compressor is a limit corresponding to the value of the limit current. A heat pump type water heater having a function not to exceed a pressure value. Furthermore, an evaporator inlet refrigerant temperature detection unit for measuring an evaporator inlet refrigerant temperature which is a temperature of the refrigerant flowing into the evaporator,
The heat pump type hot water heater according to claim 1, wherein the evaporator inlet refrigerant temperature is used to calculate the value of the limiting current. Furthermore, a voltage detection unit for measuring the power supply voltage is provided,
The heat pump type water heater according to claim 1 or 2, wherein the power supply voltage is used to calculate a value of the limit current.   The said control part is a heat pump type hot water supply apparatus as described in any one of Claims 1-3 which emits the signal for performing operation of reduction of the rotation speed of the said compressor, or expansion of the opening degree of the said pressure-reduction valve. And a water circulation pump for supplying water to the water-refrigerant heat exchanger,
The said control part emits the signal for performing operation of reduction of the rotation speed of the said compressor, expansion of the opening degree of the said pressure reduction valve, or increase of the rotation speed of the said water circulation pump. The heat pump type water heater described in the item.

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