Heat pump device

Abstract

To provide a heat pump device which can prohibit a decrease in heating efficiency.SOLUTION: A heat pump device includes condensation determination means 39b that determines whether or not there is condensation of refrigerant that passes through a second load-side heat exchanger 34 during multiple operations. When multiple operations are started based on a result of calculation by a required output calculation means 39a during single operation, a second control unit 29 sets the opening of a second expansion valve 24 larger than a predefined drive opening until it is determined by the condensation determination means 39b that the refrigerant passing through the second load-side heat exchanger 34 is condensing. As a result, the temperature of the refrigerant passing through the second heat source-side heat exchanger 25 does not extremely decline, so that a detection value at a second heat exchanging temperature sensor 27b does not decline below a defrost start temperature and defrosting operation of the second heat pump device 20 is not performed. A reduction in heat efficiency with a heater terminal 40 can be prevented in advance by starting defrosting in a short time period after the start of the multiple operations, thus improving product features.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a heat pump device that utilizes a plurality of heat sources. [Background technology]

[0002] Conventionally, this type of heat pump device has a first heat pump circuit and a second heat pump circuit in which a compressor, a load-side heat exchanger, an expansion valve, and a heat source-side heat exchanger are connected in a ring shape by refrigerant piping. The piping connecting the first load-side heat exchanger of the first heat pump circuit and the second load-side heat exchanger of the second heat pump circuit is connected to a heating terminal, and a load-side circulation circuit is installed in the middle of the piping and drives the circulating fluid heated in the two load-side heat exchangers to the heating terminal. In this type of heat pump device, when the required heating output is small, a standalone operation is performed in which only the first heat pump circuit is driven, and when the required heating output cannot be met by the first heat pump circuit alone, a multiple operation is performed in which the second heat pump circuit is also driven, thereby meeting the required heating output (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6381725 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with this conventional system, if a command to start multiple operation is issued during standalone operation, the refrigerant temperature in the second heat pump circuit remains low for a while after multiple operation begins, resulting in heat transfer from the high-temperature circulating fluid to the low-temperature refrigerant in the second load-side heat exchanger. As a result, the refrigerant does not condense in the second load-side heat exchanger but passes through the expansion valve in a gaseous state, causing a rapid drop in refrigerant temperature. This drastically reduces the temperature of the refrigerant passing through the second heat source-side heat exchanger, increasing the likelihood of defrosting operation in the second heat pump circuit. When defrosting operation is performed in the second heat pump circuit, heat transfer from the refrigerant to the circulating fluid in the second load-side heat exchanger is significantly reduced, reducing heating efficiency, leaving room for improvement. [Means for solving the problem]

[0005] In order to solve the above problem, in claim 1 of the present invention, there is provided a heat pump system including a first compressor, a first load-side heat exchanger, a first expansion valve, and a first heat source-side heat exchanger, and a first heat pump circuit in which a refrigerant circulates; a second heat pump circuit including a second compressor, a second load-side heat exchanger, a second expansion valve, and a second heat source-side heat exchanger, and through which a refrigerant circulates; a load-side circulation circuit including a heating terminal connected to the first load-side heat exchanger and the second load-side heat exchanger and heated by the flow of circulating liquid, and a load-side circulation pump for causing the circulating liquid to flow; An instruction means for issuing an instruction to start heating operation by the heating terminal; a required output calculation means for calculating a heating output required during the heating operation, The heating operation is an independent operation in which the first compressor is driven to set the first expansion valve to a predetermined drive opening degree and the load side circulation pump is driven; a plurality of operations in which the first compressor is driven to set the first expansion valve to the predetermined drive opening degree, the second compressor is driven to set the second expansion valve to the predetermined drive opening degree, and the load side circulation pump is driven, a control unit that, when it is determined that the instruction means has issued the instruction to start the heating operation, performs either the single operation or the multiple operation based on the heating output calculated by the required output calculation means, a condensation determination means for determining whether or not condensation has occurred in the refrigerant passing through the second load-side heat exchanger during the multiple operations; When the multiple operation is started based on the calculation result of the required output calculation means during the single operation, the control unit increases the second expansion valve beyond the predetermined drive opening until the condensation determination means determines that the refrigerant passing through the second load side heat exchanger is condensed.

[0006] In addition, in claim 2, a second discharge temperature sensor that detects the temperature of the refrigerant discharged from the second compressor; a forward temperature sensor that detects the temperature of the circulating fluid that passes through the second load-side heat exchanger and flows toward the heating terminal; The condensation determination means is characterized in that it determines that the refrigerant passing through the second load side heat exchanger has condensed when the detected value of the second discharge temperature sensor becomes equal to or greater than the detected value of the feed temperature sensor.

[0007] In addition, in claim 3, a second discharge temperature sensor that detects the temperature of the refrigerant discharged from the second compressor; a second refrigerant temperature sensor that detects the temperature of the refrigerant passing through the second load-side heat exchanger and heading toward the second expansion valve; The condensation determination means is characterized in that it determines that the refrigerant passing through the second load side heat exchanger has condensed when the detection value of the second discharge temperature sensor becomes equal to or greater than the detection value of the second refrigerant temperature sensor.

[0008] In addition, in claim 4, there is provided a counting means for counting the time elapsed from the start of the multiple operations, The condensation determining means determines that the refrigerant passing through the second load side heat exchanger has condensed when the time counted by the counting means reaches or exceeds a predetermined elapsed time.

[0009] In addition, claim 5 is characterized in that when the condensation determination means determines that the refrigerant passing through the second load side heat exchanger is condensed, the control unit sets the second expansion valve to the predetermined drive opening degree. [Effects of the Invention]

[0010] According to this invention, when multiple operations are started based on the calculation results of the required output calculation means during single operation, the control unit increases the second expansion valve to a greater than predetermined drive opening until the condensation determination means determines that the refrigerant passing through the second load side heat exchanger is condensed.This prevents the temperature of the refrigerant passing through the second heat source side heat exchanger from dropping extremely when multiple operations start, and prevents the second heat pump circuit from starting defrosting operation shortly after the start of multiple operations, thereby preventing a decrease in heating efficiency, thereby improving product quality. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a configuration diagram showing a main unit of a heat pump device according to a first embodiment of the present invention. [Figure 2] 1 is a configuration diagram showing the overall configuration of a first embodiment. [Figure 3] FIG. 2 is a control block diagram of the first embodiment. [Figure 4] 10 is a timing chart illustrating a case where a single operation is changed to a multiple operation in a comparative example. [Figure 5] 10 is a flowchart illustrating a case where the single operation is changed to a multiple operation in the first embodiment. [Figure 6] 10 is a timing chart illustrating a case where the single operation is changed to a multiple operation in the first embodiment. [Figure 7] 10 is a flowchart illustrating a case where the single operation is changed to the multiple operation in the second embodiment. [Figure 8] 10 is a flowchart illustrating a case where the single operation is changed to a multiple operation in the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will be described below with reference to the accompanying drawings.

[0013] Example 1 Referring to Fig. 1, the hot water heating system 1 has a first heat pump unit 10, a second heat pump unit 20, a circulation pump unit 30, a heating terminal 40, and a remote control 50. The first heat pump device 10 and the circulation pump unit 30 are connected by a first refrigerant piping 12 that constitutes a first heat pump circuit 11, and the second heat pump device 20 and the circulation pump unit 30 are connected by a second refrigerant piping 22 that constitutes a second heat pump circuit 21. The circulation pump unit 30 and the heating terminal 40 are connected by a forward pipe 32 a and a return pipe 32 b that constitute the load side circulation circuit 31 . The remote control 50, which serves as an instruction means, is equipped with multiple switches and a screen (not shown), and by pressing a switch that corresponds to the user's instruction, the screen display changes, and the drive units in the first heat pump device 10, the second heat pump device 20, and the circulation pump unit 30 are operated, bringing them into a state that corresponds to the user's instruction.

[0014] Referring to Fig. 2, the first heat pump unit 10 has a circular first refrigerant pipe 12 that constitutes a first heat pump circuit 11. Installed midway along the first refrigerant pipe 12 are: a first compressor 13 that functions as a variable speed drive unit that compresses the refrigerant; a first expansion valve 14 that functions as a drive unit and is first pressure reducing means that reduces the pressure of the refrigerant; a first heat source side heat exchanger 15 that functions as an evaporator in which the refrigerant flowing inside exchanges heat with air blown by a first blower fan 16 that also functions as a drive unit and evaporates; and a first four-way valve 18 that switches the flow direction of the refrigerant.

[0015] The first heat pump device 10 is also equipped with a first discharge temperature sensor 17a that detects the temperature of the refrigerant discharged from the first compressor 13, a first heat exchanger temperature sensor 17b that detects the temperature of the refrigerant passing through the first heat source side heat exchanger 15, a first outside air temperature sensor 17c that detects the outside air temperature, and a first control unit 19 that is composed of a microcomputer and has a memory unit and a calculation unit.

[0016] When the first control unit 19 determines that an abnormally high temperature has been detected by the first discharge temperature sensor 17a, it ensures safety by forcibly stopping the driving units in the first heat pump unit 10, the second heat pump unit 20, and the circulation pump unit 30. Furthermore, the first control unit 19 determines whether defrosting of the first heat source side heat exchanger 15 is necessary based on the detected value of the first heat exchanger temperature sensor 17b.

[0017] The second heat pump unit 20 has a circular second refrigerant pipe 22 that constitutes a second heat pump circuit 21. The second refrigerant pipe 22 is provided with a second compressor 23 as a drive unit with a variable rotation speed that compresses the refrigerant, a second expansion valve 24 as a drive unit and second pressure reducing means that reduces the pressure of the refrigerant, a second heat source side heat exchanger 25 as an evaporator in which the refrigerant flowing inside exchanges heat with air blown by a second blower fan 26 as a drive unit and evaporates, and a second four-way valve 28 that switches the flow direction of the refrigerant.

[0018] The second heat pump device 20 is also equipped with a second discharge temperature sensor 27a that detects the temperature of the refrigerant discharged from the second compressor 23, a second heat exchanger temperature sensor 27b that detects the temperature of the refrigerant passing through the second heat source side heat exchanger 25, a second outside air temperature sensor 27c that detects the outside air temperature, and a second control unit 29 that is composed of a microcomputer and has a memory unit and a calculation unit.

[0019] If the second control unit 29 determines that an abnormally high temperature has been detected by the second discharge temperature sensor 27a, it ensures safety by forcibly stopping the driving units in the first heat pump unit 10, the second heat pump unit 20, and the circulation pump unit 30. Furthermore, the second control unit 29 determines whether defrosting of the second heat source side heat exchanger 25 is necessary based on the detected value of the second heat exchanger temperature sensor 27b.

[0020] The circulation pump unit 30 includes a first load-side heat exchanger 33 connected to the first refrigerant pipe 12 constituting the first heat pump circuit 11 and a forward pipe 32a constituting the load-side circulation circuit 31, a second load-side heat exchanger 34 connected to the second refrigerant pipe 22 constituting the second heat pump circuit 21 and a return pipe 32b constituting the load-side circulation circuit 31, a load-side circulation pump 35 that is located in the pipes and circulates a circulating liquid such as water or antifreeze, and a pressure adjusting device that can store only a predetermined amount of the circulating liquid. The heat exchanger is provided with a cistern tank 36, a return temperature sensor 37a that detects the temperature of the circulating fluid flowing through the return pipe 32b, a supply temperature sensor 37b that detects the temperature of the circulating fluid flowing through the supply pipe 32a, a first refrigerant temperature sensor 37c that detects the temperature of the refrigerant flowing out from the first load side heat exchanger 33, a second refrigerant temperature sensor 37d that detects the temperature of the refrigerant flowing out from the second load side heat exchanger 34, and a main control unit 39 that is constituted by a microcomputer and has a memory unit and a calculation unit.

[0021] The first load-side heat exchanger 33 and the second load-side heat exchanger 34 are connected by a relay pipe 32c. Thus, in the load-side circulation circuit 31, the first load-side heat exchanger 33 and the second load-side heat exchanger 34 are installed in series, and the circulating fluid that has passed through the first load-side heat exchanger 33 on the upstream side passes through the second load-side heat exchanger 34 on the downstream side and flows into the heating terminal 40 via the outgoing pipe 32a. This allows the temperature of the circulating fluid to be efficiently increased, improving heating efficiency.

[0022] The first load-side heat exchanger 33 and the second load-side heat exchanger 34 are each configured as a plate-type heat exchanger. This plate-type heat exchanger is made up of a plurality of stacked heat transfer plates, with refrigerant flow paths for circulating a refrigerant and fluid flow paths for circulating a fluid such as a circulating liquid alternately formed on either side of each heat transfer plate.

[0023] The heating terminal 40 is composed of a floor heating panel installed under the floor of the house or a fan coil unit installed on the interior wall of the house, and is capable of providing heating by dissipating heat as high-temperature circulating fluid passes through it. The number of heating terminals 40 is not limited to one; multiple heating terminals 40 can be installed by adding additional supply pipes 32a and return pipes 32b. When multiple heating terminals 40 are installed, the user can select the heating terminal 40 that will perform heating operation using the remote control 50, and multiple heating terminals 40 can be operated in heating mode simultaneously.

[0024] Referring to Fig. 3, the main control unit 39 has a required output calculation means 39a that calculates the required heating output based on the type, number, and set temperature of the heating terminal 40 to which a command to start heating operation has been issued via the remote control 50, a condensation determination means 39b that determines whether or not the refrigerant passing through the second load-side heat exchanger 34 has condensed after the drive unit in the second heat pump unit 20 has started to drive, and a counting means 39c that counts the time that has elapsed since the drive unit in the second heat pump unit 20 has started to drive.

[0025] The remote control 50 and the main control unit 39 are connected by a communication line, and the main control unit 39 is also connected by communication lines to the first control unit 19 and the second control unit 29. When the remote control 50 receives an instruction from the user, the instruction is transmitted to the main control unit 39, and the main control unit 39 transmits the drive instructions for the load-side circulation pump 35 and the operation instructions for the drive units in accordance with the instruction to the first control unit 19 and the second control unit 29, thereby enabling the operation in accordance with the instruction received by the remote control 50 to be executed.

[0026] Next, the operation of the hot water heating system 1 will be described.

[0027] When it is determined that a switch (not shown) on the remote control 50 has been operated and a command to start heating operation has been issued by the user, the required heating output is calculated by the required output calculation means 39a. The main control unit 39 determines whether it is possible to satisfy the heating output calculated by the required output calculation means 39a by simply driving the drive unit of the first heat pump unit 10, or whether it is necessary to drive the drive units of the first heat pump unit 10 and the second heat pump unit 20.

[0028] If it is determined that the required heating output can be met by simply driving the drive unit of the first heat pump device 10, the first compressor 13 is driven and the first expansion valve 14 is adjusted to a predetermined drive opening that matches the refrigerant pressure estimated from the temperature detected by the first discharge temperature sensor 17a, and the load side circulation pump 35 is driven to perform standalone operation in which heating operation is performed at the heating terminal 40. When it is determined that the drive units of the first heat pump device 10 and the second heat pump device 20 need to be driven to meet the required heating output, the first compressor 13 is driven and the first expansion valve 14 is adjusted to a predetermined drive opening that matches the refrigerant pressure estimated from the temperature detected by the first discharge temperature sensor 17a, the second compressor 23 is driven and the second expansion valve 24 is adjusted to a predetermined drive opening that matches the refrigerant pressure estimated from the temperature detected by the second discharge temperature sensor 27a, and the load side circulation pump 35 is driven, thereby performing multiple operations to perform heating operation at the heating terminal 40.

[0029] In the case of standalone operation, the main control unit 39 drives the load side circulation pump 35 at a predetermined rotation speed and sends a signal to the first control unit 19. Upon receiving the signal, the first control unit 19 drives the first compressor 13 at a predetermined rotation speed and adjusts the first expansion valve 14 to a predetermined drive opening to heat the circulating liquid in the first load side heat exchanger 33, and sends the circulating liquid to the heating terminal 40 via the delivery pipe 32a, thereby performing heating operation in the room in which the heating terminal 40 is installed.

[0030] In the case of multiple operation, the main control unit 39 drives the load side circulation pump 35 at a predetermined rotation speed and sends a signal to the first control unit 19 and the second control unit 29. Upon receiving the signal, the first control unit 19 drives the first compressor 13 at a predetermined rotation speed and adjusts the first expansion valve 14 to a predetermined drive opening to heat the circulating liquid in the first load side heat exchanger 33. Upon receiving the signal, the second control unit 29 drives the second compressor 23 at a predetermined rotation speed and adjusts the second expansion valve 24 to a predetermined drive opening to heat the circulating liquid in the second load side heat exchanger 34, and sends the circulating liquid to the heating terminal 40 via the delivery pipe 32a, thereby performing heating operation in the room in which the heating terminal 40 is installed.

[0031] Next, the defrosting operation performed in the first heat pump unit 10 and the second heat pump unit 20 will be described.

[0032] When heating operation is performed when the outside air temperature is low, frost forms on the surfaces of the first heat source side heat exchanger 15 and the second heat source side heat exchanger 25, which serve as evaporators, and as the frost grows, it impedes heat exchange, leading to a decrease in heating efficiency. During heating operation, if the first control unit 19 determines that the detected value of the first heat exchanger temperature sensor 17b is equal to or lower than a predetermined defrost start temperature, it determines that the defrost start condition is satisfied, stops the first compressor 13, operates the first four-way valve 18, switches the refrigerant flow direction to the opposite direction from that during heating operation, and then drives the first compressor 13. This allows high-temperature refrigerant to flow into the first heat source-side heat exchanger 15, melting frost adhering to the surface of the first heat source-side heat exchanger 15. Thereafter, if the first control unit 19 determines that the detected value of the first heat exchanger temperature sensor 17b is equal to or higher than a predetermined defrost completion temperature, it stops the first compressor 13, operates the first four-way valve 18, switches the refrigerant flow direction to that during heating operation, and then drives the first compressor 13. This resumes heating operation.

[0033] In the second heat pump device 20, if the second control unit 29 determines that the detected value of the second heat exchanger temperature sensor 27b has fallen below a predetermined defrost start temperature during heating operation, it determines that the defrost start condition has been met and performs control similar to that of the first heat pump device 10. When both the first heat pump unit 10 and the second heat pump unit 20 satisfy the defrost start conditions, the main control unit 39 performs control so that the first heat pump unit 10 performs defrosting operation first, and then the second heat pump unit 20 performs defrosting operation once the defrosting operation in the first heat pump unit 10 is completed. While one heat pump unit is performing defrosting operation, the other heat pump unit continues heating operation. This prevents a sudden drop in the temperature of the circulating fluid flowing into the heating terminal 40, which could cause a loss of warmth.

[0034] Furthermore, when a defrosting operation is performed, the main control unit 39 continues to drive the load-side circulation pump 35. While one heat pump unit is performing a defrosting operation, the other heat pump unit is performing a heating operation, so that the circulating fluid can be heated by the load-side heat exchanger of the heat pump unit performing the heating operation. By continuing to send the heated circulating fluid to the heating terminal 40, heating can be performed at the heating terminal 40, and a decrease in the user's sense of warmth can be prevented.

[0035] Here, a case where multiple operation is started during stand-alone operation will be described.

[0036] When an instruction to start heating operation is given via the remote control 50 and the calculation result of the required output calculation means 39a determines that the required heating output can be met by driving only the drive unit of the first heat pump device 10 and the device is operating in standalone mode, a situation may arise in which the required heating output cannot be met in standalone heating operation due to reasons such as a user issuing an instruction to start heating operation via the remote control 50 on a stopped heating terminal 40 and increasing the required heating output, or a drop in the outside temperature causing a decrease in the heat exchange efficiency of the first heat pump device 10. In such a case, the main control unit 39 sends a signal to the second control unit 29 to operate the drive unit of the second heat pump device 20, and the second control unit 29, upon receiving the sent signal, starts multiple operations by driving the second compressor 23 and setting the second expansion valve 24 to a predetermined drive opening degree.

[0037] See Figure 4. During standalone operation by the first heat pump unit 10, if the main control unit 39 determines from the calculation results of the required output calculation means 39a that the required heating output cannot be met through standalone operation, it starts multiple operation at point (1) to drive the drive unit of the second heat pump unit 20, and causes the second control unit 29 to drive the second compressor 23 and set the second expansion valve 24 to a predetermined drive opening. For a while after the start of multiple operation, the refrigerant temperature in the second heat pump circuit 21 is low and the temperature of the circulating fluid flowing through the load-side circulation circuit 31 is higher than the temperature of the refrigerant, so that in the second load-side heat exchanger 34, heat transfers from the circulating fluid side to the refrigerant side. As a result, heat would normally transfer from the refrigerant side to the circulating liquid side within the second load-side heat exchanger 34, causing the refrigerant to liquefy. However, the direction of heat transfer is reversed, causing the refrigerant to flow out of the second load-side heat exchanger 34 in a gaseous state and flow into the second expansion valve 24. When the gaseous refrigerant flows into the second expansion valve 24, the speed at which the refrigerant moves within the second expansion valve 24 increases, causing a large pressure drop and a sudden drop in the temperature of the refrigerant. When the suddenly dropped refrigerant flows into the second heat source-side heat exchanger 25, the detection value of the second heat exchanger temperature sensor 27b becomes equal to or lower than the predetermined defrost start temperature at time (2), and the second heat pump unit 20 starts a defrosting operation. During defrosting operation, the circulating fluid cannot be heated by the second load-side heat exchanger 34, which reduces the heating efficiency at the heating terminal 40. If the defrosting operation of the second heat pump unit 20 starts shortly after the start of multiple operation, the feeling of heating at the heating terminal 40 will be impaired, which is not preferable.

[0038] In the present invention, when multiple operations are started during an individual operation, a decrease in heating efficiency can be prevented by preventing the second heat pump unit 20 from starting a defrosting operation early. Details of the control will be explained using the flowchart in Fig. 5.

[0039] When the first heat pump unit 10 performs an independent operation, the required output calculation means 39a calculates the required heating output based on the type and number of heating terminals 40 for which heating operation is to be performed as instructed by the remote control 50 and the detected value of the first outdoor air temperature sensor 17c (step S101). The main control unit 39 compares the heating output calculated in step S101 with the current heating output and determines whether the current heating output is lower than the required heating output and multiple operation is required (step S102). If the main control unit 39 determines in step S102 that multiple operation is required to meet the required heating output, it causes the second control unit 29 to start driving the second compressor 23 and fully open the second expansion valve 24 (step S103). If the main control unit 39 determines in step S102 that the required heating output can be met by independent operation and multiple operation is not required, it repeats the processing of step S101.

[0040] In step S103, when the second compressor 23 is driven and the second expansion valve 24 is fully opened, the condensation determination means 39b determines whether the value detected by the second discharge temperature sensor 27a is equal to or greater than the value detected by the forward temperature sensor 37b and whether the refrigerant passing through the second load-side heat exchanger 34 is condensed (step S104). If the value detected by the second discharge temperature sensor 27a is equal to or greater than the value detected by the forward temperature sensor 37b and it is determined that the refrigerant is condensed, the second control unit 29 sets the second expansion valve 24 to a predetermined drive opening and continues multiple operation (step S105). If the condensation determination means 39b determines in step S104 that the value detected by the second discharge temperature sensor 27a is not equal to or greater than the value detected by the forward temperature sensor 37b and the refrigerant is not condensed, the determination in step S104 is repeated.

[0041] See FIG. 6. As described above, when multiple operation is started during isolated operation, the condensation determination means 39b compares the detected value of the second discharge temperature sensor 27a with the detected value of the feed temperature sensor 37b, and maintains the second expansion valve 24 in a fully open state until it determines that the refrigerant passing through the second load-side heat exchanger 34 is condensed. If it determines that the heating output calculated by the required output calculation means 39a cannot be satisfied through isolated operation during isolated operation, the second compressor 23 is driven at point (3) to fully open the second expansion valve 24. By fully opening the second expansion valve 24, the movement speed of the refrigerant when it passes through in a gaseous state can be reduced, and the refrigerant pressure drop is not large, so the refrigerant temperature does not drop extremely, and the detected value of the second heat exchanger temperature sensor 27b does not drop below the defrost start temperature. At time (4), if the condensation determination means 39b determines that the value detected by the second discharge temperature sensor 27a is equal to or greater than the value detected by the feed temperature sensor 37b and that the refrigerant passing through the second load-side heat exchanger 34 is condensing, the second expansion valve 24 is opened to a predetermined degree and multiple operations are continued. Since the second heat pump unit 20 can be prevented from starting defrosting operation in a short time after the start of multiple operations, a decrease in the feeling of heating at the heating terminal 40 due to a decrease in heating output can be prevented.

[0042] The determination by the condensation determination means 39b of whether the refrigerant passing through the second load side heat exchanger 34 is condensed during multiple operations includes cases where the refrigerant is deemed to be condensed. When multiple operations are performed, if the detected value of the second discharge temperature sensor 27a becomes equal to or greater than the detected value of the feed temperature sensor 37b, the direction of heat transfer within the second load side heat exchanger 34 changes from the refrigerant side to the circulating liquid side, and therefore it can be assumed that the refrigerant in a gas state has condensed and become a liquid state (including a gas-liquid two-phase state).

[0043] Next, the effects of the present invention will be described.

[0044] The system includes condensation determination means 39b for determining whether the refrigerant passing through the second load-side heat exchanger 34 is condensed during multiple operation. When multiple operation is initiated based on the calculation results of the required output calculation means 39a during isolated operation, the second control unit 29 opens the second expansion valve 24 to a greater than predetermined drive angle until the condensation determination means 39b determines that the refrigerant passing through the second load-side heat exchanger 34 is condensed. This prevents an extreme drop in temperature even if the refrigerant passing through the second load-side heat exchanger 34 in a gaseous state passes through the second expansion valve 24 when multiple operation is initiated during isolated operation. Since the temperature of the refrigerant passing through the second heat source-side heat exchanger 25 does not drop too dramatically, the detection value of the second heat exchanger temperature sensor 27b does not drop below the predetermined defrost start temperature, and the second heat pump unit 20 does not perform a defrost operation. Starting defrosting shortly after the start of multiple operation prevents a decrease in heating efficiency at the heating terminal 40, improving product quality.

[0045] Furthermore, the condensation determination means 39b determines that the refrigerant passing through the second load side heat exchanger 34 has condensed when the detection value of the second discharge temperature sensor 27a is equal to or higher than the detection value of the feed temperature sensor 37b. When multiple operations are performed, if the temperature of the refrigerant flowing into the second load side heat exchanger 34 is higher than the temperature of the circulating fluid flowing out of the second load side heat exchanger 34, heat is transferred from the refrigerant side to the circulating fluid side within the second load side heat exchanger 34, and it can be assumed that the refrigerant has condensed. Whether the refrigerant has condensed can be determined by simple means.

[0046] Furthermore, if the condensation determination means 39b determines that the refrigerant passing through the second load-side heat exchanger 34 is condensed, the second control unit 29 sets the second expansion valve 24 to a predetermined drive opening. If the refrigerant is condensed and there is no longer any risk of starting defrosting operation, the normal heating operation state is carried out, so that heating operation can be carried out at the heating terminal 40 without reducing heating efficiency.

[0047] <Example 2> Next, control when multiple operation is performed during independent operation in the second embodiment to which the present invention is applied will be described with reference to the flowchart in Fig. 7. Note that the configuration of the second embodiment is common to the first embodiment, and therefore the description will be omitted.

[0048] When the first heat pump unit 10 performs an independent operation, the required output calculation means 39a calculates the required heating output based on the type and number of heating terminals 40 for which heating operation is to be performed as instructed by the remote control 50 and the detected value of the first outdoor air temperature sensor 17c (step S201). The main control unit 39 compares the heating output calculated in step S201 with the current heating output and determines whether the current heating output is lower than the required heating output and multiple operation is required (step S202). If the main control unit 39 determines in step S202 that multiple operation is required to meet the required heating output, it causes the second control unit 29 to start driving the second compressor 23 and fully open the second expansion valve 24 (step S203). If the main control unit 39 determines in step S202 that the required heating output can be met by independent operation and multiple operation is not required, it repeats the process of step S201.

[0049] In step S203, when the second compressor 23 is driven and the second expansion valve 24 is fully opened, the condensation determination means 39b determines whether the value detected by the second discharge temperature sensor 27a is equal to or greater than the value detected by the second refrigerant temperature sensor 37d and whether the refrigerant passing through the second load-side heat exchanger 34 is condensed (step S204). If the value detected by the second discharge temperature sensor 27a is equal to or greater than the value detected by the second refrigerant temperature sensor 37d and it is determined that the refrigerant is condensed, the second control unit 29 sets the second expansion valve 24 to a predetermined drive opening and continues the multiple operation (step S205). If the condensation determination means 39b determines in step S204 that the value detected by the second discharge temperature sensor 27a is not equal to or greater than the value detected by the second refrigerant temperature sensor 37d and the refrigerant is not condensed, the determination in step S204 is repeated.

[0050] As described above, when multiple operation is started during independent operation, the condensation determination means 39b compares the detected value of the second discharge temperature sensor 27a with the detected value of the second refrigerant temperature sensor 37d, and maintains the second expansion valve 24 in a fully open state until it determines that the refrigerant passing through the second load heat exchanger 34 is condensed. When multiple operation is being performed, if the temperature of the refrigerant discharged from the second compressor 23 and flowing into the second load heat exchanger 34 is higher than the temperature of the refrigerant after heat exchange with the circulating liquid in the second load heat exchanger 34, heat is transferred from the high-temperature refrigerant to the circulating liquid side in the second load heat exchanger 34, and it can be assumed that the refrigerant is condensed. Therefore, it is possible to determine by simple means whether the refrigerant passing through the second load heat exchanger 34 is condensed.

[0051] Next, the effects of the second embodiment will be described. Note that the description of the effects common to the first embodiment will be omitted.

[0052] The condensation determination means 39b determines that the refrigerant passing through the second load-side heat exchanger 34 has condensed when the detection value of the second discharge temperature sensor 27a is equal to or greater than the detection value of the second refrigerant temperature sensor 37d. When multiple operations are performed, if the temperature of the refrigerant flowing into the second load-side heat exchanger 34 is higher than the temperature of the refrigerant flowing out of the second load-side heat exchanger 34, it can be determined that heat is being transferred from the refrigerant side to the circulating liquid side within the second load-side heat exchanger 34 and that the refrigerant is condensed. Therefore, whether or not the refrigerant has condensed can be determined with a simple configuration, improving product quality.

[0053] Example 3 Next, control when multiple operation is performed during independent operation in the third embodiment to which the present invention is applied will be described with reference to the flowchart in Fig. 8. Note that the configuration of the third embodiment is common to the first embodiment, and therefore the description will be omitted.

[0054] When the first heat pump unit 10 performs standalone operation, the required output calculation means 39a calculates the required heating output based on the type and number of heating terminals 40 for which heating operation is to be performed as instructed by the remote control 50 and the detected value of the first outdoor air temperature sensor 17c (step S301). The main control unit 39 compares the heating output calculated in step S301 with the current heating output and determines whether multiple operation is required because the current heating output is lower than the required heating output (step S302). If the main control unit 39 determines in step S302 that multiple operation is required to satisfy the required heating output, it causes the second control unit 29 to start driving the second compressor 23 and fully open the second expansion valve 24, and causes the counting means 39c to start counting the time elapsed since multiple operation began and the drive unit of the second heat pump unit 20 was driven (step S303). If the main control unit 39 determines in step S302 that the required heating output can be satisfied by single operation and that multiple operation is not necessary, it repeats the process of step S301.

[0055] In step S303, the second compressor 23 is driven, the second expansion valve 24 is fully opened, and time counting begins. Then, the condensation determination means 39b determines whether the time counted by the counting means 39c is equal to or greater than a predetermined elapsed time t at which the refrigerant passing through the second load-side heat exchanger 34 is considered to be condensed (step S304). If the counted time is equal to or greater than the predetermined elapsed time t and it is determined that the refrigerant is condensed, the second control unit 29 sets the second expansion valve 24 to a predetermined drive opening and continues multiple operation (step S305). If the condensation determination means 39b determines in step S304 that the counted time is shorter than the predetermined elapsed time t and that the refrigerant is not condensed, the determination in step S304 is repeated.

[0056] The predetermined elapsed time t, which is compared with the elapsed time counted from the start of operation of the drive unit of the second heat pump unit 20 in step S304, is set to the time required for the temperature of the refrigerant discharged from the second compressor 23 to become higher than the temperature of the circulating liquid passing through the second load-side heat exchanger 34. The predetermined elapsed time t may be set by storing a value determined from test results in advance in the main control unit 39, or may be set based on the elapsed time until the value detected by the second discharge temperature sensor 27a becomes equal to or higher than the value detected by the feed temperature sensor 37b during trial operation after installation of the second heat pump unit 20. In other words, the predetermined elapsed time t is set to the time at which the refrigerant passing through the second load-side heat exchanger 34 can be considered to be condensed during multiple operation.

[0057] As described above, when multiple operation is started during standalone operation, the condensation determination means 39b compares the elapsed time counted from the start of operation of the drive unit of the second heat pump unit 20 with the predetermined elapsed time t at which the refrigerant is considered to have condensed in the second load-side heat exchanger 34, and maintains the second expansion valve 24 in a fully open state until it is determined that the refrigerant passing through the second load-side heat exchanger 34 has condensed. When multiple operation is performed, the temperature of the refrigerant discharged from the second compressor 23 increases as time passes from the start of operation of the drive unit of the second heat pump unit 20. When the temperature of the refrigerant discharged from the second compressor 23 reaches or exceeds the predetermined elapsed time t at which it is considered that the temperature has risen sufficiently, heat is transferred from the high-temperature refrigerant to the circulating liquid side, and it can be determined that the refrigerant is condensed. Therefore, it is possible to determine by simple means whether the refrigerant passing through the second load-side heat exchanger 34 has condensed.

[0058] Next, the effects of the third embodiment will be described. Note that the description of the effects common to the first embodiment will be omitted.

[0059] The condensation determination means 39b determines that the refrigerant passing through the second load-side heat exchanger 34 has condensed when the time counted by the counting means 39c reaches or exceeds a predetermined elapsed time t. If the time counted from the start of multiple operation and the start of drive of the drive unit of the second heat pump unit 20 is considered to be a time when the temperature of the refrigerant discharged from the second compressor 23 has increased and heat is being transferred from the refrigerant side to the circulating liquid side within the second load-side heat exchanger 34, it can be determined that the refrigerant passing through the second load-side heat exchanger 34 has condensed. Therefore, whether or not the refrigerant has condensed can be determined with a simple configuration, improving product quality.

[0060] Although several embodiments of the present invention have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the claims. These novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their modifications are within the scope and spirit of the invention, and are included in the inventions and their equivalents as defined in the claims.

[0061] In the above-described embodiments, after starting multiple operation during isolated operation, whether or not the refrigerant passing through the second load-side heat exchanger 34 is condensed is determined by comparing the detected values of the temperature sensors installed in the second heat pump circuit 21 and the load-side circulation circuit 31 and by the time elapsed since the drive unit of the second heat pump unit 20 started operating. However, this is not limited to this. For example, a pressure sensor capable of detecting the pressure of the refrigerant discharged from the second compressor 23 may be installed, and the detected value of the pressure sensor may be confirmed after starting multiple operation and the second compressor 23 of the second heat pump unit 20 starts operating. The second expansion valve 24 may be fully opened until the detected value of the pressure sensor reaches or exceeds a predetermined value at which the refrigerant passing through the second load-side heat exchanger 34 is considered to be condensed. In other words, the present invention falls within the scope of the present invention as long as there is a means for determining whether or not the refrigerant passing through the second load-side heat exchanger 34 is condensed when starting multiple operation during isolated operation.

[0062] In addition, in each of the described embodiments, when a multiple operation is started during an isolated operation, the second expansion valve 24 is fully opened until the condensation determination means 39b determines that the refrigerant passing through the second load-side heat exchanger 34 is condensed. However, this is not limited to this. After the start of a multiple operation, it is only necessary to prevent the temperature of the refrigerant sent from the second expansion valve 24 to the second heat-source-side heat exchanger 25 from dropping too low. Therefore, the second expansion valve 24 may be set to an opening greater than a predetermined drive opening based on the value detected by the second discharge temperature sensor 27a. In other words, if the second expansion valve 24 is set to an opening greater than the predetermined drive opening, the temperature does not drop too low even when gaseous refrigerant passes through the second expansion valve 24. This prevents the second heat exchanger temperature sensor 27b from detecting a temperature below the defrost start temperature and starting a defrosting operation. Therefore, the second expansion valve 24 may be set to an opening greater than the predetermined drive opening.

[0063] In addition, while the described embodiments illustrate the first heat pump circuit 11 and the second heat pump circuit 21 being connected in series to the load-side circulation circuit 31, this is not limiting. For example, a header for collecting the circulating fluid may be installed midway between the supply pipe 32a and the return pipe 32b, and the first heat pump circuit 11 and the second heat pump circuit 21 may be connected in parallel to the load-side circulation circuit 31. Even when the first heat pump circuit 11 and the second heat pump circuit 21 are connected in parallel to the load-side circulation circuit 31 and multiple operation is started during standalone operation, the temperature of the circulating fluid will be higher than the temperature of the refrigerant passing through the second load-side heat exchanger 34 for a while after the drive unit of the second heat pump unit 20 starts operating. Therefore, by applying the present invention, it is possible to prevent the defrosting operation in the second heat pump unit 20 from being performed shortly after the start of multiple operation, thereby preventing a decrease in heating efficiency.

[0064] Furthermore, although the embodiments described above are directed to the hot water heating system 1 that heats a room by passing heated circulating fluid through the heating terminal 40, the present invention is not limited to this. For example, the present invention can also be applied to a storage-type hot water supply system in which city water flows through the load-side circulation circuit 31, and the city water heated by the first load-side heat exchanger 33 and the second load-side heat exchanger 34 is stored in a hot water storage tank and used for hot water supply, baths, etc. [Explanation of symbols]

[0065] 10. First heat pump device 11 First heat pump circuit 13 First compressor 14 First expansion valve 15 1st heat source side heat exchanger 20 Second heat pump device 21 Second heat pump circuit 23 Second compressor 24 Second expansion valve 25 2nd heat source side heat exchanger 27a Second discharge temperature sensor 29 Second Control Section 31 Load side circulation circuit 33 1st load side heat exchanger 34 2nd load side heat exchanger 35 Load side circulation pump 37b Forward temperature sensor 37d Second refrigerant temperature sensor 39 Main control unit 39a Required output calculation means 39b Condensed judgment means 39c Counting Method 40 Heating terminal 50 Remote Control

Claims

1. a first heat pump circuit including a first compressor, a first load-side heat exchanger, a first expansion valve, and a first heat source-side heat exchanger, and through which a refrigerant circulates; a second heat pump circuit including a second compressor, a second load-side heat exchanger, a second expansion valve, and a second heat source-side heat exchanger, and through which a refrigerant circulates; a load-side circulation circuit including a heating terminal connected to the first load-side heat exchanger and the second load-side heat exchanger and heated by the flow of circulating fluid, and a load-side circulation pump for circulating the circulating fluid; An instruction means for issuing an instruction to start heating operation by the heating terminal; a required output calculation means for calculating a heating output required during the heating operation, The heating operation is an independent operation in which the first compressor is driven to set the first expansion valve to a predetermined drive opening degree and the load side circulation pump is driven; a plurality of operations in which the first compressor is driven to set the first expansion valve to the predetermined drive opening degree, the second compressor is driven to set the second expansion valve to the predetermined drive opening degree, and the load side circulation pump is driven, a control unit that, when it is determined that the instruction means has issued the instruction to start the heating operation, performs either the single operation or the multiple operation based on the heating output calculated by the required output calculation means, a condensation determination means for determining whether or not condensation has occurred in the refrigerant passing through the second load side heat exchanger during the multiple operations; When the multiple operation is started based on the calculation result of the required output calculation means during the single operation, the control unit increases the second expansion valve beyond the predetermined drive opening until the condensation determination means determines that the refrigerant passing through the second load side heat exchanger is condensed.

2. a second discharge temperature sensor that detects the temperature of the refrigerant discharged from the second compressor; a forward temperature sensor that detects the temperature of the circulating fluid that passes through the second load-side heat exchanger and flows toward the heating terminal; 2. The heat pump device according to claim 1, wherein the condensation determination means determines that the refrigerant passing through the second load side heat exchanger has condensed when the detection value of the second discharge temperature sensor becomes equal to or greater than the detection value of the feed temperature sensor.

3. a second discharge temperature sensor that detects the temperature of the refrigerant discharged from the second compressor; a second refrigerant temperature sensor that detects the temperature of the refrigerant passing through the second load-side heat exchanger and heading toward the second expansion valve; 2. The heat pump device according to claim 1, wherein the condensation determination means determines that the refrigerant passing through the second load side heat exchanger has condensed when the detection value of the second discharge temperature sensor becomes equal to or greater than the detection value of the second refrigerant temperature sensor.

4. a counting means for counting the time elapsed since the start of the multiple operations; 2. The heat pump device according to claim 1, wherein the condensation determination means determines that the refrigerant passing through the second load side heat exchanger has condensed when the time counted by the counting means reaches or exceeds a predetermined elapsed time.

5. 5. The heat pump device according to claim 1, wherein when the condensation determination means determines that the refrigerant passing through the second load side heat exchanger is condensed, the control unit sets the second expansion valve to the predetermined drive opening degree.

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