JPWO2012043297A1 - Hot water system - Google Patents

Abstract

A two-way refrigeration cycle is composed of a low temperature side refrigeration cycle (Rb) that requires a four-way switching valve (11) and a high temperature side refrigeration cycle (Ra) that does not require a four-way switching valve (11). Heat is exchanged in the intermediate heat exchanger (5) provided. A hot water pipe (H) is connected to the water heat exchanger (2) of the high temperature side refrigeration cycle (Ra), and water or hot water is supplied to the user side as hot water. The bypass circuit (B) has one end connected to the refrigerant pipe (P) between the high temperature side compressor (1) and the hydrothermal exchanger of the high temperature side refrigeration cycle (Ra), and the other end connected to the high temperature side expansion device ( Connected to the refrigerant pipe between 4) and the intermediate heat exchanger, a fluid control valve (8) is provided in the middle. The controller (S) controls to open the fluid control valve (8) and close the high temperature side expansion device during the defrosting operation for the air heat exchanger (12) of the low temperature side refrigeration cycle (Rb). Thus, control specific to the defrosting operation for the evaporator of the low-temperature side refrigeration cycle (Rb) is performed, and reduction of parts costs and efficient defrosting operation are enabled.

Description

  Embodiments of the present invention relate to a hot water supply system that supplies hot water using a two-way refrigeration cycle.

  The high temperature side refrigeration cycle and the low temperature side refrigeration cycle are connected via an intermediate heat exchanger, and the intermediate heat exchanger exchanges heat between the refrigerant circulating in the high temperature side refrigeration cycle and the refrigerant circulating in the low temperature side refrigeration cycle. There is a tendency that a binary refrigeration cycle for obtaining a high compression ratio is frequently used (for example, Japanese Unexamined Patent Publication No. 2000-320914).

  And a water heat exchanger is provided as a condenser which comprises a high temperature side refrigerating cycle, and water or warm water is guide | induced here through warm water piping. The water or hot water is supplied to the use side of the hot water piping destination instead of hot water. Therefore, efficient hot water supply operation is possible even in cold regions.

  By the way, in this hot water supply system, the air heat exchanger that constitutes the low temperature side refrigeration cycle acts as an evaporator during hot water supply operation, so that the air heat exchanger can be frosted especially during operation under low outside air temperature conditions. Is inevitable. If it passes in this state, since the heat exchange efficiency of an air heat exchanger will fall, it is necessary to perform a defrost operation.

  During the defrosting operation, the four-way switching valve of the high temperature side refrigeration cycle and the four way switching valve of the low temperature side refrigeration cycle are switched in reverse to reverse the refrigerant circulation direction. Since the heat source at the time of defrosting is the hot water led to the water heat exchanger of the high temperature side refrigeration cycle, it is possible to maintain the high pressure and the discharge temperature during the defrosting operation. Since the high-temperature gas refrigerant is directly guided to the air heat exchanger of the low-temperature refrigeration cycle, the air heat exchanger is efficiently defrosted.

  On the other hand, heat is absorbed from the hot water led to the water heat exchanger, which causes a demerit that the temperature of the hot water decreases.

  Further, the four-way switching valve is expensive. If possible, the four-way switching valve and the piping connected to the four-way switching valve are deleted to reduce the cost by reducing the parts cost. At the same time, there is a demand to improve the workability of piping work by eliminating the four-way switching valve and the space for connecting piping.

  However, if the four-way selector valve for both the low temperature side refrigeration cycle and the high temperature side refrigeration cycle is deleted, it will not be possible to maintain the high pressure and discharge temperature during the defrosting operation due to the lack of a heat source for defrosting. There is a possibility that good defrosting operation cannot be performed or defrosting cannot be completed. Therefore, it is necessary to consider deleting the four-way switching valve in conjunction with securing the heat source during the defrosting operation.

  This embodiment is based on the above circumstances, and is provided with a dual refrigeration cycle, and performs specific control during the defrosting operation for the evaporator of the low temperature side refrigeration cycle, thereby reducing the component cost and improving the efficiency. A hot water supply system capable of good defrosting operation is provided.

  In order to satisfy the above object, the hot water supply system in the present invention includes a low-temperature side compressor, a four-way switching valve, an intermediate heat exchanger, a low-temperature side expansion device, a low-temperature side refrigeration cycle that communicates an evaporator via a refrigerant pipe, and a high-temperature side. A high-temperature side refrigeration cycle configured to communicate a compressor, a water heat exchanger, a high-temperature side expansion device, and an intermediate heat exchanger via a refrigerant pipe, the refrigerant guided to the low-temperature side refrigeration cycle, and the high-temperature side refrigeration cycle The refrigerant led to the refrigerant is led to the binary refrigeration cycle for exchanging heat with the intermediate heat exchanger and the water heat exchanger of the high temperature side refrigeration cycle, and is introduced into the circulating water or hot water and the high temperature side refrigeration cycle. A hot water pipe for supplying heat to the user side, one end of which is connected to the refrigerant pipe between the high temperature side compressor and the water heat exchanger of the high temperature side refrigeration cycle, and the other end of the high temperature side refrigeration cycle. high temperature A bypass circuit connected to a refrigerant pipe between the expansion device and the intermediate heat exchanger and having a fluid control valve in the middle, and a fluid control valve of the bypass circuit during a defrosting operation for the evaporator of the low temperature side refrigeration cycle And controlling means for controlling to close the high-temperature side expansion device of the high-temperature refrigeration cycle.

FIG. 1 is a configuration diagram of a refrigeration cycle of a hot water supply system according to the present embodiment.

  FIG. 1 is a configuration diagram of a refrigeration cycle of a hot water supply system, and particularly shows a refrigeration cycle switching state during a defrosting operation.

  This hot water supply system includes a high temperature side refrigeration cycle Ra, a hot water pipe H, a low temperature side refrigeration cycle Rb, and a control unit (control means) S.

  If it demonstrates from the said high temperature side refrigerating cycle Ra, the discharge part a of the high temperature side compressor 1, the water heat exchanger 2, the liquid receiver 3, the high temperature side expansion apparatus 4, and the heat absorption part 5a of the intermediate heat exchanger 5 will be described. The gas-liquid separator 6 is sequentially connected via the refrigerant pipe P, and the gas-liquid separator 6 communicates with the suction part b of the high-temperature side compressor 1.

  Regardless of the hot water supply operation and the defrosting operation described later, the refrigerant compressed and discharged by the high temperature side compressor 1 is as follows:-water heat exchanger 2-liquid receiver 3-high temperature side expansion device 4-intermediate heat exchanger 5 Endothermic part 5a-gas-liquid separator 6-high temperature side compressor 1-. Therefore, the water heat exchanger 2 acts as a condenser, and the heat absorption part 5a of the intermediate heat exchanger 5 acts as an evaporator.

  A bypass circuit B is provided in such a high temperature side refrigeration cycle Ra. One end of the bypass circuit B is connected to the refrigerant pipe P between the discharge part a of the high temperature side compressor 1 and the water heat exchanger 2, and the other end is the heat absorption of the high temperature side expansion device 4 and the intermediate heat exchanger 5. It consists of a bypass pipe 9 connected to the refrigerant pipe P between the part 5a and having a fluid control valve 8 in the middle.

One end of the hot water pipe H is connected to a hot water return pipe or a condensate side buffer tank, and the other end is connected to a hot water outlet pipe or an outgoing side buffer tank (both not shown).
The middle part of the hot water pipe H is piped to the water heat exchanger 2 constituting the high temperature side refrigeration cycle Ra, and water or hot water led to the hot water pipe H and refrigerant led to the water heat exchanger 2 are connected. Heat exchange is possible.

  In the low temperature side refrigeration cycle Rb, the discharge part c of the low temperature side compressor 10 and the first port d1 of the four-way switching valve 11 are connected via the refrigerant pipe P, and the second port d2 of the four-way switching valve 11 is in the middle. The heat radiating part 5b of the heat exchanger 5 is connected via the refrigerant pipe P. In addition, the third port d3 of the four-way switching valve 11 is connected to the two air heat exchangers 12 and 12 here through a refrigerant pipe P branched from the middle part into two.

  The fourth port d4 of the four-way switching valve 11 is connected to the suction portion e of the low temperature side compressor 10 via the gas / liquid separator 13 via the refrigerant pipe P. On the other hand, the heat radiating part 5b of the intermediate heat exchanger 5 is connected to the liquid receiver 14 via the refrigerant pipe P, and the liquid receiver 14 and the two air heat exchangers 12 are branched from the middle part into two. Each is connected via a refrigerant pipe P provided with a low temperature side expansion device 15.

  In the low temperature side refrigeration cycle, during the hot water supply operation, the refrigerant compressed and discharged by the low temperature side compressor 10 is as follows:-Four-way switching valve 11-Heat radiation part 5b of the intermediate heat exchanger 5-Low temperature of the receiver 14-2 The side expansion device 15-2 air heat exchanger 12, the four-way switching valve 11, the gas-liquid separator 13, and the low temperature side compressor 10 − are led in this order.

  Therefore, the heat radiation part 5b of the intermediate heat exchanger 5 acts as a condenser, and the air heat exchanger 12 acts as an evaporator.

During the defrosting operation for the air heat exchanger 12 to be described later, the four-way switching valve 11 is switched in the direction shown in the figure, and the refrigerant compressed and discharged by the low-temperature side compressor 10 is: Air heat exchanger 12-2 low temperature side expansion device 15-liquid receiver 14-heat radiation part 5b of intermediate heat exchanger 5-four-way switching valve 11-gas-liquid separator 13-low temperature side compressor 10- It is burned.
At this time, the air heat exchanger 12 acts as a condenser, and the heat radiation part of the intermediate heat exchanger 5 acts as an evaporator.

  The controller S includes temperature sensors provided at the discharge portions a and c and the suction portions b and e of the high-temperature side compressor 1 and the low-temperature side compressor 10, and pressures provided at the discharge portions a and c and the suction portions b and e. Detected from a sensor, a temperature sensor provided in the water heat exchanger 2, a temperature sensor provided in the heat absorbing part 5a and the heat radiating part 5b of the intermediate heat exchanger 5, a temperature sensor provided in the air heat exchanger 12 (all not shown), etc. Receive a signal.

Further, the control unit S receives the instruction signal from the remote controller (remote controller), performs calculation, and compares it with the reference value (heating capacity or temperature at the intermediate heat exchanger 5) to be stored with the high-temperature side compressor 1. The operating frequency of the low temperature side compressor 10 is controlled.
Further, the superheat amount (hereinafter referred to as “SH amount”) of the heat exchanger is calculated from the difference between the refrigerant temperature of the heat exchanger and the suction side refrigerant temperature of the compressor, and the high temperature side expansion device 4 and the low temperature The throttle amount of the side expansion device 15 is controlled. Then, the fluid control valve 8 of the bypass circuit B is controlled to open and close.

In the hot water supply system configured as described above, during the hot water supply operation, the control unit S controls the high temperature side refrigeration cycle Ra and the low temperature side refrigeration cycle Rb to guide and circulate the refrigerant as described above.
In the intermediate heat exchanger 5, the refrigerant condenses and releases condensation heat in the heat radiating part 5 b on the low temperature side refrigeration cycle Rb side, and the refrigerant evaporates while absorbing heat of condensation in the heat absorbing part 5 a on the high temperature side refrigeration cycle Ra side. To do.

Therefore, as a whole hot water supply system, the temperature difference between the evaporation temperature in the air heat exchanger 12 and the condensation temperature in the water heat exchanger 2 becomes large, and a high compression ratio can be obtained. In the water heat exchanger 2 that performs the condensing action in the high temperature side refrigeration cycle Ra, the water or hot water led to the hot water pipe H absorbs the hot heat of condensation and the temperature rises efficiently.
In the water heat exchanger 2, the water or hot water changes into hot water having a high temperature, and circulates between the water heat exchanger 2 -the buffer tank on the warm water supply side, the load side condensate side buffer tank, and the water heat exchanger 2.

  In particular, if the hot water supply operation is continued under conditions where the outside air temperature is low, the air heat exchanger 12 in the low temperature side refrigeration cycle Rb performs the evaporation of the refrigerant, so that the condensed water generated here freezes and becomes frost. Adhere as it is. As time elapses, the thickness of the frost increases, and the heat exchange efficiency in the air heat exchanger 12 decreases.

  The control unit S receives a detection signal from a temperature sensor attached to the air heat exchanger 12 and receives a detection signal from other sensors to determine the necessity of a defrosting operation for the air heat exchanger 12. As a result, the defrosting operation is performed, but the control unit S actually performs the control described below immediately before the start of the defrosting operation.

  That is, the control unit S performs control to narrow down the high temperature side expansion device 4 provided in the high temperature side refrigeration cycle Ra at a timing immediately before the start of the defrosting operation. Therefore, in the high temperature side refrigeration cycle Ra, the flow rate of the refrigerant guided from the high temperature side expansion device 4 to the heat absorption part 5a of the intermediate heat exchanger 5 decreases.

  Therefore, the amount of heat absorbed by the heat absorption part 5a of the intermediate heat exchanger 5 decreases, the temperature of the heat absorption part 5a and the heat radiation part 5b rises, and the temperature of the intermediate heat exchanger 5 as a whole also rises. At this time, it is not necessary to change the operating frequencies of the high temperature side compressor 1 in the high temperature side refrigeration cycle Ra and the low temperature side compressor 10 in the low temperature side refrigeration cycle Rb.

  The suction temperature and suction pressure of the high-temperature compressor 1 communicating with the heat-absorbing part 5a of the intermediate heat exchanger 5 via the refrigerant pipe P also rise, but the refrigerant circulation rate decreases in the high-temperature refrigeration cycle Ra, so that the discharge There is almost no increase in pressure, and the compression ratio of the high temperature side compressor 1 decreases.

  However, there is an increase in the suction temperature of the high-temperature side compressor 1, and the difference from the evaporation temperature of the intermediate heat exchanger heat-absorbing part 5a that performs the evaporating action becomes large, so-called SH amount becomes excessive, and the high-temperature side compressor 1 The discharge temperature rises. In the low temperature side refrigeration cycle Rb, the compression ratio increases and the discharge temperature of the low temperature side compressor 10 increases as the temperature of the intermediate heat exchanger heat dissipating part 5b increases.

  As described above, the control unit S controls the high temperature side expansion device 4 of the high temperature side refrigeration cycle Ra to be throttled at a timing immediately before the start of the defrosting operation for the air heat exchanger 12. Therefore, without changing the operating frequency of the high temperature side compressor 1 and the low temperature side compressor 10, the evaporation temperature rise of the heat absorption part 5a and the condensation temperature rise of the heat radiating part 5b of the intermediate heat exchanger 5 and the high temperature side can be increased in a short time. The discharge temperature rise of the compressor 1 and the low temperature side compressor 10 can be obtained.

  In the high temperature side refrigeration cycle Ra, the temperature of the low pressure side piping components from the high temperature side expansion device 4 via the intermediate heat exchanger 5 to the high temperature side compressor 1 rises, and the compressor body of the high temperature side compressor 1 and the high temperature side The high-pressure side piping parts from the side compressor 1 to the water heat exchanger 2 also rise in temperature, and heat storage can be achieved.

  At the same time, in the low temperature side refrigeration cycle Rb, the temperature of the high pressure side piping components from the low temperature side compressor 1 and the low temperature side compressor 10 to the low temperature side expansion device 15 via the four-way switching valve 11 and the intermediate heat exchanger 5 rises. , Heat storage can be achieved.

  After the above heat storage action is continued for a predetermined time, the controller S controls the actual start of the defrosting operation for the air heat exchanger 12. At this time, the fluid control valve 8 of the bypass circuit B is opened, and the four-way switching valve 11 of the low-temperature side refrigeration cycle Rb is switched to supply the refrigerant in the direction opposite to the refrigerant circulation direction in the low-temperature side refrigeration cycle Rb. Circulate.

  However, if the four-way switching valve 11 is instantaneously switched in the low-temperature refrigeration cycle Rb while the driving of the low-temperature compressor 10 is continued, the refrigerant collides in the four-way switching valve 11 and generates noise. If the switching noise of the four-way switching valve 11 increases and leaks to the outside, the silent operation is impaired.

  Therefore, the control unit S temporarily stops the operation of the low-temperature side compressor 10 (several tens of seconds to several minutes) and performs necessary control such as opening the pressure equalizing pipe, so that the high-pressure side in the low-temperature side refrigeration cycle Rb. Balance the pressure on the low pressure side in a short time. In addition, by switching the four-way switching valve 11, the refrigerant flow inside the switching valve is lowered, the collision is calmed down, and switching noise can be suppressed.

Further, as a necessary control, the control unit S fully closes the high temperature side expansion device 4 while continuing the operation of the high temperature side compressor 1 in the high temperature side refrigeration cycle Ra. Therefore, the high pressure of the high temperature side refrigeration cycle Ra is maintained, the refrigerant recovered from the heat absorption part 5a of the intermediate heat exchanger 5 and discharged from the high temperature side compressor 1 is the water heat exchanger 2 and the receiver that are condensers. 3 is stored as a high-temperature liquid refrigerant.
Further, since the refrigerant is not supplied to the intermediate heat exchanger 5, the amount of heat absorbed from the heat absorbing portion 5a can be suppressed, and the heat storage effect is maintained.

  In addition, since the pump-down (refrigerant recovery) operation is performed in the high-temperature side refrigeration cycle Ra, the operation is performed by reducing the operation frequency of the high-temperature side compressor 1 as necessary so that the operation is not stopped due to a decrease in low-pressure pressure. It is desirable to extend the duration.

After continuing the above control for a predetermined time, the control unit S controls the opening of the fluid control valve 8 of the bypass circuit B while continuing the operation of the high temperature side compressor 1 of the high temperature side refrigeration cycle Ra. Further, the four-way switching valve 11 of the low temperature side refrigeration cycle Rb is switched, and the operation of the low temperature side compressor 10 is restarted.
At this time, in the low temperature side refrigeration cycle Rb, since the pressures on the high pressure side and the low pressure side are balanced, the switching sound of the four-way switching valve 11 hardly occurs.

  Hot gas, which is a high-temperature and high-pressure refrigerant gas discharged from the high-temperature side compressor 1, is led to the bypass circuit B, and is led to the heat absorption part 5 a of the intermediate heat exchanger 5 through the fluid control valve 8 to release high heat. Further, in the process in which the high pressure of the high temperature side refrigeration cycle Ra is decreasing, the liquid heat refrigerant 2 in the hydrothermal exchanger 2 as a condenser and the liquid receiver 3 is boiled under reduced pressure, gasified, and flows backward in the refrigeration cycle.

  The gasified refrigerant is led to the bypass circuit B and led to the intermediate heat exchanger 5 via the fluid control valve 8. Thus, heat is absorbed from the hot water on the use side, and a part of the heat source necessary for the defrosting operation can be covered.

  In the low temperature side refrigeration cycle Rb, with the intermediate heat exchanger 5 as a heat source, the refrigerant circulates in the direction opposite to that during hot water supply operation, and the refrigerant is condensed in each air heat exchanger 12 to release the condensation heat. Therefore, the frost adhering to the air heat exchanger 12 is gradually melted and dripped as drain water. The thickness of the frost decreases immediately, and the background of the air heat exchanger 12 is exposed.

As a result of the control performed at the timing immediately before the start of the defrosting operation described above, the low-pressure side piping component extending from the high-temperature side expansion device 4 of the high-temperature side refrigeration cycle Ra to the high-temperature side compressor 1 via the intermediate heat exchanger 5. A high-temperature side compressor 1 of the high-temperature side refrigeration cycle Ra and a high-pressure side piping part extending from the high-temperature side compressor 1 to the water heat exchanger 2, and a low-temperature side compressor 10 and a low-temperature side compressor 10 of the low-temperature side refrigeration cycle Rb. Then, the heat stored in the high-pressure side piping components extending from to the low-temperature side expansion device 15 via the intermediate heat exchanger 5 is released at this time.
Since all of these heat storages are spent for defrosting the air heat exchanger 12, the defrosting action is further promoted.

  In addition, when the defrosting operation for the air heat exchanger 12 takes a long time and the heat storage source is exhausted, the high pressures of the high temperature side refrigeration cycle Ra and the low temperature side refrigeration cycle Rb are reduced, and the high temperature side compressor 1 and There may be a situation where the input of the low temperature side compressor 10 becomes extremely small and the compressor input cannot be used as a heat source.

Accordingly, the control unit S controls the fluid control valve 8 of the bypass circuit B to be fully closed while detecting that the high pressure of the high temperature side refrigeration cycle Ra has dropped below a predetermined pressure, and the high temperature side expansion device 4 Control to fully open or optimal opening.
Thereby, the low temperature discharge gas of the high temperature side refrigerating cycle Ra can be heated by the heat of the hot water led to the water heat exchanger 2, and a heat source for the defrosting operation for the air heat exchanger 12 is secured. The temperature drop of the hot water led to the water heat exchanger 2 at this time is less than 1 ° C.

When the high temperature side expansion device 4 is adjusted to an optimal opening rather than fully opened, the high pressure of the high temperature side refrigeration cycle Ra can be slightly increased, so that the heat quantity is secured by the input of the high temperature side compressor 1 and intermediate heat exchange is performed. It is possible to adjust the amount of hot gas supplied to the vessel 5.
In this way, since the defrosting operation is performed on the air heat exchanger 12, the four-way switching valve in the high-temperature side refrigeration cycle Ra is not required, and the piping parts to be connected to the four-way switching valve are not required, thereby reducing component costs. In addition to improving workability and reducing costs by eliminating the need for piping work, it contributes to the downsizing of the apparatus by reducing the installation space.

  Instead of making the four-way switching valve unnecessary in the high temperature side refrigeration cycle Ra, the bypass pipe 9 and the fluid control valve 8 constituting the bypass circuit B are required, but both ends of the bypass pipe 9 constitute the high temperature side refrigeration cycle Ra. Since the fluid control valve 8 can be a simple on-off valve, it is possible to suppress the influence on the cost to a minimum.

Immediately before the start of the defrosting operation, the discharge temperature rises as the low-pressure rise of the high-temperature side refrigeration cycle Ra and the SH amount increase by the relatively simple control that only throttles the high-temperature side expansion device 4, and further the low-temperature side refrigeration cycle Rb high pressure rise and discharge temperature rise can be obtained.
As a result, the low pressure side piping component, the high temperature side compressor 1 and the high pressure side piping component in the high temperature side refrigeration cycle Ra, and the low pressure side compressor 10 and the high pressure side piping component in the low temperature side refrigeration cycle Rb are required during the defrosting operation. The amount of heat to be stored can be stored internally, and the defrosting efficiency can be improved.

  When the internal heat storage is completed and the defrosting operation is actually started, the operation of the low-temperature side compressor 10 in the low-temperature side refrigeration cycle Rb is stopped for a predetermined time, and the pressure balance between the high-pressure side and the low-pressure side is taken. Since the switching is made, the switching noise can be reduced and the silent operation can be performed.

  Then, the fluid control valve 8 of the bypass circuit B is opened while the operation of the high temperature side compressor 1 is continued, and the high temperature side expansion device 4 is closed. Therefore, almost no hot water is used as a heat source at the time of defrosting, and the temperature drop of the hot water led to the hot water pipe H can be suppressed. The high pressure of the high temperature side refrigeration cycle Ra can be maintained to maintain the heat storage state, which helps shorten the defrosting time.

  When the defrosting operation is continued and the high pressure of the high temperature side refrigeration cycle Ra falls below the threshold value, the fluid control valve 8 of the bypass circuit B is closed, and the high temperature side expansion device 4 is fully opened or controlled to an optimum opening degree. Therefore, even if the internal heat storage is exhausted and the inputs of the high temperature side compressor 1 and the low temperature side compressor 10 become extremely small, the discharge gas of the high temperature side compressor 1 can be warmed by the hot water of the hot water pipe H, and the heat source Therefore, the risk that defrosting is not completed can be reduced.

  As mentioned above, although this embodiment was described, the above-mentioned embodiment is shown as an example and does not intend limiting the range of embodiment. The novel embodiment can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

Claims (4)

Low-temperature side compressor, four-way switching valve, intermediate heat exchanger, low-temperature side expansion device, low-temperature side refrigeration cycle communicating the evaporator via refrigerant piping, high-temperature side compressor, water heat exchanger, high-temperature side expansion device, The intermediate heat exchanger includes a high-temperature side refrigeration cycle that communicates with the intermediate heat exchanger via a refrigerant pipe. A dual refrigeration cycle for heat exchange;
A hot water pipe which is piped to the water heat exchanger of the high temperature side refrigeration cycle and supplies the user side with heat exchange between circulating water or hot water and a refrigerant guided to the high temperature side refrigeration cycle;
One end is connected to a refrigerant pipe between the high temperature side compressor and the water heat exchanger of the high temperature side refrigeration cycle, and the other end is a refrigerant pipe between the high temperature side expansion device and the intermediate heat exchanger of the high temperature side refrigeration cycle. And a bypass circuit having a fluid control valve in the middle,
Control means for controlling to open the fluid control valve of the bypass circuit and close the high temperature side expansion device of the high temperature refrigeration cycle at the time of defrosting operation for the evaporator of the low temperature side refrigeration cycle;
A hot water supply system comprising: The control means includes
During the hot water supply operation, in the low temperature side refrigeration cycle, circulation control of the refrigerant is performed in the order of the low temperature side compressor-four-way switching valve-intermediate heat exchanger-low temperature side expansion device-evaporator-low temperature side compressor- In the refrigeration cycle, the refrigerant is circulated and controlled in the order of the high temperature side compressor-water heat exchanger-high temperature side expansion device-intermediate heat exchanger,
Prior to the start of the defrosting operation for the evaporator, the high temperature side expansion device of the high temperature side refrigeration cycle is throttled to reduce the refrigerant circulation amount, and control to perform the operation,
During the defrosting operation for the evaporator, the four-way switching valve of the low-temperature side refrigeration cycle is switched, and the low-temperature side compressor-four-way switching valve-evaporator-low-temperature side expansion device-intermediate heat exchanger-low-temperature side compressor- The hot water supply system according to claim 1, wherein circulation control of the refrigerant is performed in the order of. The control means includes
When switching the four-way switching valve of the low temperature side refrigeration cycle at the start of the defrosting operation for the evaporator, the high temperature side expansion device is fully closed while the operation of the high temperature side compressor of the high temperature side refrigeration cycle is continued, and The hot water supply system according to claim 2, wherein control is performed to temporarily stop the operation of the low temperature side compressor of the low temperature side refrigeration cycle. The control means includes
During the defrosting operation for the evaporator, when the high pressure of the high temperature side refrigeration cycle becomes a predetermined pressure or lower, the fluid control valve of the bypass circuit is closed and the high temperature side expansion device of the high temperature side refrigeration cycle is opened. The hot water supply system according to claim 2, wherein the hot water supply system is controlled as follows.

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