Air conditioning system

Abstract

This air conditioning system comprises a heat pump device, a heating device, a blower, and a control device. A circulation refrigerant circuit of the heat pump device has a heat-source-side refrigerant circuit, a usage-side refrigerant circuit, a liquid-side shutoff valve that blocks the flow of refrigerant from the heat-source-side refrigerant circuit to the usage-side refrigerant circuit via liquid-side piping when in a closed state, and a gas-side shutoff valve that blocks the flow of the refrigerant from the heat-source-side refrigerant circuit to the usage-side refrigerant circuit via gas-side piping when in a closed state. The blower generates an airflow that passes through a heating part and then passes through the usage-side refrigerant circuit. The control device opens the liquid-side shutoff valve and the gas-side shutoff valve in a state in which the heat pump device is operating, closes the liquid-side shutoff valve and the gas-side shutoff valve when the operation of the heat pump device is stopped, and opens at least one of the liquid-side shutoff valve and the gas-side shutoff valve when it is assessed that a first condition related to the start of the operation of the heating device is satisfied while the operation of the heat pump device is stopped.

Description

air conditioning system

[0001] The present disclosure relates to air conditioning systems.

[0002] There is known an air conditioning system (air conditioning system) that includes a heat pump unit (heat pump device) that includes a refrigerant radiator (use-side heat exchanger), a gas furnace unit (heating device) that includes a heating section that heats the air passing through, and a blower that generates an air flow that passes through the radiator and the heating section (see, for example, Patent Document 1).

[0003] Patent No. 6384057

[0004] In air conditioning systems, a shutoff valve is considered to prevent refrigerant from leaking from a user unit having a radiator into the space to be air-conditioned when the heat pump unit is stopped. However, when the gas furnace unit is operated with the shutoff valve closed, the radiator of the user unit heats up, causing the refrigerant in the piping of the user unit to expand. This increases the pressure of the refrigerant in the piping of the user unit, damaging the piping and potentially causing refrigerant to leak from the damaged area. This creates a risk that the leaked refrigerant could flow into the space to be air-conditioned.

[0005] In view of the above circumstances, one of the objects of the present disclosure is to provide an air conditioning system that can reduce the risk of refrigerant leaking into a space to be air-conditioned.

[0006] One aspect of an air conditioning system according to the present disclosure includes a heat pump device having a heat source side unit and a user side unit, a heating device having a heating section capable of heating air passing through it, a blower that generates an air flow that passes through the heating section, and a control device that controls the heat pump device, wherein the heat pump device has a circulating refrigerant circuit through which a refrigerant circulates, the circulating refrigerant circuit including a heat source side refrigerant circuit having a compressor and a heat source side heat exchanger and provided in the heat source side unit, a user side refrigerant circuit having a user side heat exchanger and provided in the user side unit, liquid side piping and gas side piping that connect the heat source side refrigerant circuit and the user side refrigerant circuit, and a control device that controls the circulating refrigerant circuit from the heat source side refrigerant circuit to the user side refrigerant circuit through the liquid side piping in a closed state. and a gas-side shutoff valve that, in a closed state, shuts off the flow of the refrigerant through the gas-side piping from the heat-source-side refrigerant circuit to the use-side refrigerant circuit, wherein the blower generates an air flow that passes through the heating unit and then the use-side heat exchanger, and the control device opens the liquid-side shutoff valve and the gas-side shutoff valve when the heat pump device is operating, closes the liquid-side shutoff valve and the gas-side shutoff valve when the operation of the heat pump device stops, and opens at least one of the liquid-side shutoff valve and the gas-side shutoff valve when it is determined that a first condition related to the start of operation of the heating device when the operation of the heat pump device is stopped is satisfied.

[0007] According to the present disclosure, in an air conditioning system, the risk of refrigerant leaking into a space to be air-conditioned can be reduced.

[0008] Fig. 1 is a refrigerant circuit diagram showing a schematic configuration of an air conditioning system in embodiment 1. Fig. 2 is a perspective view showing a user-side unit and a heating device in embodiment 1. Fig. 3 is a cross-sectional view showing a user-side unit and a heating device in embodiment 1. Fig. 4 is a flowchart showing a part of the control procedure of a control device in embodiment 1. Fig. 5 is a flowchart showing a part of the control procedure of a control device in embodiment 2. Fig. 6 is a flowchart showing a part of the control procedure of a control device in embodiment 3. Fig. 7 is a flowchart showing a part of the control procedure of a control device in embodiment 4. Fig. 8 is a flowchart showing a part of the control procedure of a control device in embodiment 5.

[0009] Embodiment 1. Fig. 1 is a refrigerant circuit diagram showing a schematic configuration of an air conditioning system 100 in embodiment 1. The air conditioning system 100 is a system capable of adjusting the temperature of a space to be air-conditioned. The space to be air-conditioned is, for example, an indoor space. In the following description, the space to be air-conditioned is referred to as an air-conditioned space AS. As shown in Fig. 1, the air conditioning system 100 includes a heat pump unit 100a, a heating unit 40, and a control unit 100b.

[0010] The heat pump device 100a is a device capable of adjusting the temperature of an air-conditioned space AS using a heat pump. The heat pump device 100a includes a heat source unit 10, a usage unit 20, and a circulating refrigerant circuit 30. The heat source unit 10 is installed, for example, outdoors of a building having the air-conditioned space AS. The usage unit 20 is installed, for example, indoors of the building having the air-conditioned space AS. The usage unit 20 may be installed indoors or within the wall of a room. The heat pump device 100a is capable of adjusting the temperature of the air in the air-conditioned space AS by exchanging heat between a refrigerant 90 flowing through the circulating refrigerant circuit 30 and the air in the air-conditioned space AS. The heat pump device 100a is capable of performing a cooling operation to cool the air in the air-conditioned space AS and a heating operation to warm the air in the air-conditioned space AS.

[0011] The refrigerant circulation circuit 30 is a refrigerant circuit through which a refrigerant 90 circulates. Examples of the refrigerant 90 include a fluorine-based refrigerant or a hydrocarbon-based refrigerant with a low global warming potential (GWP). In the first embodiment, the refrigerant 90 is a flammable refrigerant such as an A2L refrigerant. Specifically, the refrigerant 90 is, for example, R454B.

[0012] The refrigerant 90 may be a refrigerant other than R454B. Examples of the refrigerant 90 include a single refrigerant selected from R1234yf, R1234ze, R32, and R290, a mixture of two or more of these, or a mixture of any of these with other refrigerants. Examples of the refrigerant 90 include a mixed refrigerant containing R1132(E) or a mixed refrigerant containing R1123. Examples of the refrigerant 90 include a mixed refrigerant containing R516A, R445A, R444A, R454C, R444B, R454A, R455A, R457A, R459B, R452B, R447B, R447A, R446A, and R459A.

[0013] The circulating refrigerant circuit 30 has a heat source side refrigerant circuit 31, a usage side refrigerant circuit 32, a liquid side piping 35, and a gas side piping 36. The heat source side refrigerant circuit 31 is a portion of the circulating refrigerant circuit 30 that is included in the heat source side unit 10. The usage side refrigerant circuit 32 is a portion of the circulating refrigerant circuit 30 that is included in the usage side unit 20.

[0014] The heat source-side refrigerant circuit 31 has a compressor 12, a heat source-side heat exchanger 13, a four-way valve 16, a pressure vessel 17, a heat source-side expansion valve 51, and an internal heat exchanger 70. The compressor 12, the heat source-side heat exchanger 13, the four-way valve 16, the pressure vessel 17, the heat source-side expansion valve 51, and the internal heat exchanger 70 are housed inside the housing of the heat source-side unit 10. A heat source-side blower 15 is provided inside the housing of the heat source-side unit 10, and generates an airflow that passes through the heat source-side heat exchanger 13.

[0015] The user-side refrigerant circuit 32 has a user-side heat exchanger 22 and a user-side expansion valve 24. The user-side heat exchanger 22 and the user-side expansion valve 24 are housed inside the housing of the user-side unit 20.

[0016] The liquid side piping 35 and the gas side piping 36 are piping that connect the heat source side refrigerant circuit 31 and the user side refrigerant circuit 32. The circulating refrigerant circuit 30 is configured by connecting the heat source side refrigerant circuit 31 and the user side refrigerant circuit 32 via the liquid side piping 35 and the gas side piping 36. The heat source side unit 10 and the user side unit 20 are connected to each other via the liquid side piping 35 and the gas side piping 36. The liquid side piping 35 connects the portion of the piping of the heat source side refrigerant circuit 31 that connects to the internal heat exchanger 70 to the piping of the user side refrigerant circuit 32. The gas side piping 36 connects the portion of the piping of the heat source side refrigerant circuit 31 that connects to the four-way valve 16 to the piping of the user side refrigerant circuit 32. Liquid refrigerant 90 or refrigerant 90 in a gas-liquid two-phase state flows through the liquid side piping 35. Gas state refrigerant 90 flows through the gas side piping 36.

[0017] The circulating refrigerant circuit 30 has a liquid-side shutoff valve 52 and a gas-side shutoff valve 53. In the first embodiment, the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 are included in the heat-source-side refrigerant circuit 31 of the heat-source-side unit 10. The liquid-side shutoff valve 52 is provided in a portion of the heat-source-side refrigerant circuit 31 to which the liquid-side piping 35 is connected. In the first embodiment, a user-side expansion valve 24 is provided between the liquid-side shutoff valve 52 and the user-side heat exchanger 22. The gas-side shutoff valve 53 is provided in a portion of the heat-source-side refrigerant circuit 31 to which the gas-side piping 36 is connected.

[0018] In the first embodiment, the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 are solenoid valves that can be switched between an open state that allows the refrigerant 90 to pass through and a closed state that shuts off the flow of the refrigerant 90. In the closed state, the liquid-side shutoff valve 52 shuts off the flow of refrigerant 90 via the liquid-side piping 35 from the heat-source-side refrigerant circuit 31 to the use-side refrigerant circuit 32. In the closed state, the liquid-side shutoff valve 52 shuts off the flow of refrigerant 90 via the liquid-side piping 35 from the use-side refrigerant circuit 32 to the heat-source-side refrigerant circuit 31. In the closed state, the gas-side shutoff valve 53 shuts off the flow of refrigerant 90 via the gas-side piping 36 from the heat-source-side refrigerant circuit 31 to the use-side refrigerant circuit 32. In the closed state, the gas-side shutoff valve 53 shuts off the flow of refrigerant 90 via the gas-side piping 36 from the use-side refrigerant circuit 32 to the heat-source-side refrigerant circuit 31.

[0019] The liquid-side shutoff valve 52 may be any valve as long as it is capable of shutting off the flow of refrigerant 90 from the heat-source-side refrigerant circuit 31 to the user-side refrigerant circuit 32 via the liquid-side piping 35 in a closed state. The gas-side shutoff valve 53 may be any valve as long as it is capable of shutting off the flow of refrigerant 90 from the heat-source-side refrigerant circuit 31 to the user-side refrigerant circuit 32 via the gas-side piping 36 in a closed state. The liquid-side shutoff valve 52 and the gas-side shutoff valve 53 may be valves whose opening degree can be continuously adjusted, such as motor-operated valves. The liquid-side shutoff valve 52 may be provided midway through the liquid-side piping 35, or may be provided in a portion of the user-side refrigerant circuit 32 to which the liquid-side piping 35 is connected. The gas-side shutoff valve 53 may be provided midway through the gas-side piping 36, or may be provided in a portion of the user-side refrigerant circuit 32 to which the gas-side piping 36 is connected.

[0020] The compressor 12 is a fluid machine that compresses the low-pressure refrigerant 90 that it draws in and discharges it as high-pressure refrigerant 90. The compressor 12 is, for example, a capacity-controllable inverter compressor. When the compressor 12 is driven, the refrigerant 90 circulates within the circulating refrigerant circuit 30.

[0021] The four-way valve 16 is disposed on the discharge side of the compressor 12. The four-way valve 16 switches a portion of the path of the circulating refrigerant circuit 30, thereby reversing the direction of the refrigerant 90 flowing through the circulating refrigerant circuit 30. When the path connected by the four-way valve 16 is the path shown by the solid line at the four-way valve 16 in Fig. 1, the refrigerant 90 flows through the circulating refrigerant circuit 30 in the direction shown by the solid arrow in Fig. 1. On the other hand, when the path connected by the four-way valve 16 is the path shown by the dashed line at the four-way valve 16 in Fig. 1, the refrigerant 90 flows through the circulating refrigerant circuit 30 in the direction shown by the dashed arrow in Fig. 1.

[0022] The flow of the refrigerant 90 shown by the solid line in Fig. 1 is the direction of flow of the refrigerant 90 during cooling operation. The flow of the refrigerant 90 shown by the dashed line in Fig. 1 is the direction of flow of the refrigerant 90 during heating operation. During cooling operation, low-temperature, low-pressure refrigerant 90 is supplied into the user-side heat exchanger 22. During heating operation, high-temperature, high-pressure refrigerant 90 is supplied into the user-side heat exchanger 22.

[0023] The heat source-side heat exchanger 13 is a heat exchanger that functions as an evaporator during heating operation and as a condenser during cooling operation. In the heat source-side heat exchanger 13, heat is exchanged between the refrigerant 90 flowing inside the heat source-side heat exchanger 13 and the air (outside air) blown by the heat source-side blower 15.

[0024] The user-side heat exchanger 22 is a heat exchanger that functions as a condenser during heating operation and as an evaporator during cooling operation. In the user-side heat exchanger 22, heat is exchanged between the refrigerant 90 flowing inside the user-side heat exchanger 22 and the air (room air) blown by a blower 42 (described later) provided in the heating device 40.

[0025] FIG. 2 is a perspective view showing the user-side unit 20 and the heating device 40. FIG. 3 is a cross-sectional view showing the user-side unit 20 and the heating device 40. The Z axis in FIGS. 2 and 3 indicates the vertical direction. The side toward which the arrow on the Z axis points (+Z side) is the upper side in the vertical direction. The opposite side to the side toward which the arrow on the Z axis points (-Z side) is the lower side in the vertical direction. In the following description, the upper side in the vertical direction may be simply referred to as the upper side, and the lower side in the vertical direction may be simply referred to as the upper side.

[0026] As shown in Figures 2 and 3, the user-side unit 20 has a housing 21. In the first embodiment, the housing 21 has a rectangular box shape. A user-side control unit 28, which will be described later, is attached to the outer surface of the housing 21. As shown in Figure 3, the housing 21 has an inlet 21a and an outlet 21b. The inlet 21a is provided in a lower wall portion of the wall portions constituting the housing 21. An outlet 41b in a housing 41, which will be described later, of the heating device 40 is connected to the inlet 21a. The outlet 21b is provided in an upper wall portion of the wall portions constituting the housing 21. A second duct 82 is connected to the outlet 21b. The second duct 82 has an outlet 82a. The outlet 82a opens into the air-conditioned space AS.

[0027] The utilization-side heat exchanger 22 is housed inside the housing 21. In the first embodiment, the utilization-side heat exchanger 22 has a first heat exchange section 22 a and a second heat exchange section 22 b. The first heat exchange section 22 a and the second heat exchange section 22 b approach each other as they move upward.

[0028] As shown in Fig. 1, pressure vessel 17 is disposed on the suction side of compressor 12. Pressure vessel 17 is capable of storing excess refrigerant 90 therein. Liquid refrigerant 90 is stored inside pressure vessel 17. In the first embodiment, pressure vessel 17 is an accumulator. Note that pressure vessel 17 may be any container as long as it is capable of storing excess refrigerant 90.

[0029] In the first embodiment, the heat source-side expansion valve 51 is an electronic linear expansion valve whose opening degree can be continuously adjusted. The opening degree of the heat source-side expansion valve 51 is adjusted by the control device 100b. For example, during cooling operation, the heat source-side expansion valve 51 is fully opened. As a result, during cooling operation, the heat source-side expansion valve 51 does not contribute to changes in the state of the refrigerant 90 passing through the heat source-side expansion valve 51. On the other hand, during heating operation, the heat source-side expansion valve 51 further decompresses and expands the refrigerant 90 that has been expanded and decompressed by the user-side expansion valves 24. During heating operation, the refrigerant 90 that flows into the heat source-side expansion valve 51 after passing through the user-side expansion valves 24 is a liquid refrigerant or a two-phase gas-liquid refrigerant.

[0030] In the first embodiment, the user-side expansion valve 24 is an electronic linear expansion valve whose opening is continuously adjustable. The opening of the user-side expansion valve 24 is adjusted by the control device 100b. At least during cooling operation, the user-side expansion valve 24 decompresses and expands the liquid refrigerant 90 that has condensed in the heat-source-side heat exchanger 13 and passed through the fully open heat-source-side expansion valve 51.

[0031] When the heat pump unit 100a is in cooling operation, the refrigerant 90 flowing in the circulating refrigerant circuit 30 flows in the direction indicated by the solid arrow in Fig. 1. In other words, when the heat pump unit 100a is in cooling operation, the refrigerant 90 flowing in the circulating refrigerant circuit 30 circulates through the compressor 12, four-way valve 16, heat source-side heat exchanger 13, heat source-side expansion valve 51, internal heat exchanger 70, liquid-side shut-off valve 52, liquid-side piping 35, user-side expansion valve 24, user-side heat exchanger 22, gas-side piping 36, gas-side shut-off valve 53, four-way valve 16, and pressure vessel 17, in that order, before returning to the compressor 12.

[0032] On the other hand, when the heat pump unit 100a is in heating operation, the refrigerant 90 flowing through the circulating refrigerant circuit 30 flows in the direction shown by the dashed line in Fig. 1. In other words, when the heat pump unit 100a is in heating operation, the refrigerant 90 flowing through the circulating refrigerant circuit 30 circulates through the compressor 12, four-way valve 16, gas-side shut-off valve 53, gas-side piping 36, user-side heat exchanger 22, user-side expansion valve 24, liquid-side piping 35, liquid-side shut-off valve 52, internal heat exchanger 70, heat-source-side expansion valve 51, heat-source-side heat exchanger 13, four-way valve 16, and pressure vessel 17, in that order, before returning to the compressor 12.

[0033] The state change of the refrigerant 90 flowing through the circulating refrigerant circuit 30 during heating operation will be described in more detail. During heating operation, low-temperature, low-pressure gaseous refrigerant 90 is drawn into the compressor 12 and becomes high-temperature, high-pressure gaseous refrigerant 90. The high-temperature, high-pressure gaseous refrigerant 90 is discharged from the compressor 12, passes through the four-way valve 16, and then flows into the user-side heat exchanger 22. The high-temperature, high-pressure gaseous refrigerant 90 that flows into the user-side heat exchanger 22 exchanges heat with air supplied from a blower 42 (described later) to release heat and condense, becoming high-temperature, high-pressure liquid refrigerant 90 and flowing out of the user-side heat exchanger 22. The liquid refrigerant 90 that flows out of the user-side heat exchanger 22 is expanded and decompressed in two stages by the user-side expansion valve 24 and the heat-source-side expansion valve 51, becoming low-temperature, low-pressure, gas-liquid two-phase refrigerant 90 and flowing into the heat-source-side heat exchanger 13. The refrigerant 90 in a gas-liquid two-phase state that has flowed into the heat source-side heat exchanger 13 absorbs heat and evaporates by exchanging heat with outdoor air supplied by the heat source-side blower 15 provided in the heat source-side unit 10, becoming low-temperature, low-pressure gaseous refrigerant 90 that flows out of the heat source-side heat exchanger 13. The low-temperature, low-pressure gaseous refrigerant 90 that has flowed out of the heat source-side heat exchanger 13 is again drawn into the compressor 12, compressed again, and discharged. During heating operation, the above-described circulation of the refrigerant 90 is repeated.

[0034] The change in the state of the refrigerant 90 during cooling operation is similar to the change in the state of the refrigerant 90 during heating operation, except that the heat source side heat exchanger 13 functions as a condenser and the user side heat exchanger 22 functions as an evaporator.

[0035] The heat pump apparatus 100a includes a bypass refrigerant circuit 33 connected to the circulation refrigerant circuit 30. The bypass refrigerant circuit 33 branches from one part of the circulation refrigerant circuit 30 and merges with another part of the circulation refrigerant circuit 30. In the first embodiment, the bypass refrigerant circuit 33 connects a branching portion 33a located between the liquid-side shutoff valve 52 and the internal heat exchanger 70 in the circulation refrigerant circuit 30 and a merging portion 33b located between the pressure vessel 17 and the four-way valve 16 in the circulation refrigerant circuit 30. In the first embodiment, the merging portion 33b is located before the pressure vessel 17. The bypass refrigerant circuit 33 passes through the internal heat exchanger 70. In other words, the bypass refrigerant circuit 33 branches from the branching portion 33a of the circulation refrigerant circuit 30, passes through the internal heat exchanger 70, and merges with the merging portion 33b of the circulation refrigerant circuit 30 on the suction side of the compressor 12.

[0036] As shown by the solid arrows in FIG. 1 , the refrigerant 90 flowing through the circulating refrigerant circuit 30 during cooling operation branches at the branching point 33 a into refrigerant 90 that flows through the liquid-side shutoff valve 52 and the user-side expansion valve 24 to the user-side heat exchanger 22, and refrigerant 90 that flows into the bypass refrigerant circuit 33.

[0037] The refrigerant 90 branched into the circulation refrigerant circuit 30 and the bypass refrigerant circuit 33 at the branching portion 33a joins at the confluence portion 33b and flows through the pressure vessel 17 to the compressor 12. During cooling operation, the refrigerant 90 branched into the bypass refrigerant circuit 33 at the branching portion 33a joins at the confluence portion 33b with the refrigerant 90 flowing in the circulation refrigerant circuit 30 that passes through the user-side heat exchanger 22, the gas-side shutoff valve 53, and the four-way valve 16 and flows toward the pressure vessel 17. In the first embodiment, the branching portion 33a is located between the liquid-side shutoff valve 52 and the internal heat exchanger 70, but this is not limiting. The branching portion 33a may be located, for example, between the internal heat exchanger 70 and the heat-source-side expansion valve 51.

[0038] The bypass refrigerant circuit 33 is provided with an expansion valve 54. In the first embodiment, the expansion valve 54 is an electronic linear expansion valve whose opening degree can be continuously adjusted. The opening degree of the expansion valve 54 is adjusted by the control device 100b.

[0039] In the internal heat exchanger 70, heat is exchanged between the refrigerant 90 flowing in the circulation refrigerant circuit 30 and the refrigerant 90 flowing in the bypass refrigerant circuit 33. In the first embodiment, during cooling operation, the internal heat exchanger 70 exchanges heat between the refrigerant 90 flowing between the heat source side expansion valve 51 and the branching portion 33a in the circulation refrigerant circuit 30 and the refrigerant 90 flowing between the expansion valve 54 and the junction portion 33b in the bypass refrigerant circuit 33. The refrigerant 90 flowing between the expansion valve 54 and the junction portion 33b in the bypass refrigerant circuit 33 is the refrigerant 90 that has been decompressed by the expansion valve 54. In the first embodiment, the internal heat exchanger 70 is a double-pipe heat exchanger having an outer pipe 71 and an inner pipe 72 passing through the inside of the outer pipe 71. The outer pipe 71 and the inner pipe 72 form an outer flow path portion 37 provided between the outer pipe 71 and the inner pipe 72. The inner surface of the outer flow path portion 37 is formed by the inner surface of the outer pipe 71 and the outer surface of the inner pipe 72. The outer flow path portion 37 forms part of the circulating refrigerant circuit 30. The inner pipe 72 forms the inner flow path portion 38. The inner surface of the inner flow path portion 38 is formed by the inner surface of the inner pipe 72. The inner flow path portion 38 forms part of the bypass refrigerant circuit 33. A low-pressure refrigerant 90 decompressed by the expansion valve 54 flows through the inner flow path portion 38.

[0040] For example, the outer flow path portion 37 may constitute a part of the bypass refrigerant circuit 33, and the inner flow path portion 38 may constitute a part of the circulation refrigerant circuit 30. In this case, low-pressure refrigerant 90 decompressed by the expansion valve 54 flows through the outer flow path portion 37. Furthermore, the internal heat exchanger 70 is not limited to a double-pipe heat exchanger, and may be, for example, a plate-type heat exchanger.

[0041] The heat pump device 100a has a first pressure sensor 61, a second pressure sensor 62, a first temperature sensor 23, a third temperature sensor 14, a fourth temperature sensor 19, and a fifth temperature sensor 63. The first pressure sensor 61, the second pressure sensor 62, the third temperature sensor 14, the fourth temperature sensor 19, and the fifth temperature sensor 63 are provided in the heat source side unit 10. The first temperature sensor 23 is provided in the user side unit 20.

[0042] The first pressure sensor 61 is provided in a pipe in the heat source side refrigerant circuit 31 that is connected to the discharge side of the compressor 12. The first pressure sensor 61 is capable of detecting the pressure of the refrigerant 90 discharged from the compressor 12. The second pressure sensor 62 is provided in a pipe in the heat source side refrigerant circuit 31 that connects the four-way valve 16 and the pressure vessel 17. The second pressure sensor 62 is capable of detecting the pressure of the refrigerant 90 that is sucked into the compressor 12.

[0043] The first temperature sensor 23 is capable of detecting the temperature of the refrigerant 90 in the use-side refrigerant circuit 32. In the first embodiment, the first temperature sensor 23 is attached to the outer surface of a heat transfer tube included in the use-side heat exchanger 22. The first temperature sensor 23 is capable of detecting the temperature of the outer surface of the heat transfer tube to which the first temperature sensor 23 is attached, thereby detecting the temperature of the refrigerant 90 inside the heat transfer tube.

[0044] The third temperature sensor 14 is capable of detecting the temperature of the refrigerant 90 in the heat source-side heat exchanger 13. In the first embodiment, the third temperature sensor 14 is attached to the outer surface of a heat transfer tube included in the heat source-side heat exchanger 13. The third temperature sensor 14 is capable of detecting the temperature of the outer surface of the heat transfer tube to which the third temperature sensor 14 is attached, thereby detecting the temperature of the refrigerant 90 inside the heat transfer tube.

[0045] The fourth temperature sensor 19 is capable of detecting the temperature of the air outdoors where the heat source side unit 10 is placed, that is, the temperature of the outside air. The fourth temperature sensor 19 is attached to the housing of the heat source side unit 10, for example.

[0046] The fifth temperature sensor 63 can detect the temperature of the refrigerant 90 flowing into the heat source side refrigerant circuit 31 via the liquid side piping 35 and the temperature of the refrigerant 90 flowing out from the heat source side refrigerant circuit 31 via the liquid side piping 35. In the first embodiment, the fifth temperature sensor 63 is attached to the outer surface of the piping connecting the liquid side shutoff valve 52 and the branch portion 33a. The fifth temperature sensor 63 can detect the temperature of the outer surface of the piping to which it is attached, thereby detecting the temperature of the refrigerant 90 inside the piping.

[0047] The heating device 40 is a device capable of heating the air in the air-conditioned space AS. In the first embodiment, the heating device 40 is a gas furnace unit. A gas furnace unit is a heating device that heats the air in the target space by using heat generated by burning gas such as natural gas. There is no particular limitation on the type of gas burned in the gas furnace unit. As shown in Figures 2 and 3, a usage-side unit 20 is attached to the heating device 40. In the first embodiment, the usage-side unit 20 is located above the heating device 40. As shown in Figure 3, the heating device 40 has a housing 41, a blower 42, and a heating section 43.

[0048] The housing 41 accommodates a blower 42 and a heating unit 43. In the first embodiment, the housing 41 is shaped like a rectangular parallelepiped box. In the first embodiment, the housing 41 has an inlet 41a and an outlet 41b. The inlet 41a is provided in one of the walls constituting the housing 41, the wall being located in a horizontal direction perpendicular to the vertical direction. A first duct 81 is connected to the inlet 41a. The first duct 81 has an inlet 81a. The inlet 81a opens into the air-conditioned space AS. The outlet 41b is provided in an upper wall of the walls constituting the housing 41. The outlet 41b is connected to the inlet 21a formed in the housing 21 of the user-side unit 20.

[0049] The heating unit 43 is capable of heating the air passing through the heating unit 43. In the first embodiment, the heating unit 43 is capable of heating the air passing through the heating unit 43 by burning a gas such as natural gas. Although not shown in the drawings, the heating unit 43 has, for example, a burner that burns the gas. Note that the type of gas burned in the heating unit 43 is not particularly limited.

[0050] The blower 42 generates an airflow AF that passes through the heating section 43 and the use-side heat exchanger 22. The air of the airflow AF generated by the blower 42 is drawn into the first duct 81 from the air-conditioned space AS through the inlet 81a. The air drawn into the first duct 81 flows into the heating device 40 through the inlet 41a. The air that has flowed into the heating device 40 is drawn into the blower 42. The air drawn into the blower 42 is blown upward, passes through the heating section 43, and then flows into the use-side unit 20 through the outlet 41b and the inlet 21a. The air that has flowed into the use-side unit 20 passes through the use-side heat exchanger 22 and flows into the second duct 82 through the outlet 21b. In this way, the blower 42 generates an airflow AF that passes through the heating section 43 and then the use-side heat exchanger 22. The air that has flowed into the second duct 82 is blown out from the air outlet 82a into the air-conditioned space AS.

[0051] When the heat pump unit 100a is operating, the air blown out from the air outlet 82a into the air-conditioned space AS exchanges heat with the refrigerant 90 in the use-side heat exchanger 22. When the heating unit 40 is operating, the air blown out from the air outlet 82a into the air-conditioned space AS is heated in the heating unit 43. As a result, the air blown out from the air outlet 82a into the air-conditioned space AS can be cooled or heated. Therefore, the air conditioning system 100 can adjust the temperature of the air in the air-conditioned space AS.

[0052] The air conditioning system 100 includes a second temperature sensor 83. The second temperature sensor 83 is capable of detecting the temperature of air drawn into the heating device 40 by the blower 42. In the first embodiment, the second temperature sensor 83 is provided at the end of the first duct 81 that connects to the inlet 41 a. The temperature of the air detected based on the second temperature sensor 83 is the same as or approximately the same as the temperature of the air in the air-conditioned space AS.

[0053] 2 and 3 are merely examples of the structure of the user-side unit 20 and the structure of the heating device 40. The structure of the user-side unit 20 and the structure of the heating device 40 are not particularly limited.

[0054] The control device 100b is a device that controls the air conditioning system 100. In Embodiment 1, the control device 100b controls the heat pump device 100a, the heating device 40, and the blower 42. As shown in FIG. 1 , the control device 100b has a heat source-side control unit 18 and a usage-side control unit 28. The heat source-side control unit 18 is provided in the heat source-side unit 10. The usage-side control unit 28 is provided in the usage-side unit 20.

[0055] The heat source-side control unit 18 is a control unit that oversees the overall control of the air conditioning system 100. The heat source-side control unit 18 receives the detection results of the first pressure sensor 61, the second pressure sensor 62, the first temperature sensor 23, the second temperature sensor 83, the third temperature sensor 14, the fourth temperature sensor 19, and the fifth temperature sensor 63. The detection results of the first temperature sensor 23 and the second temperature sensor 83 are sent from the use-side control unit 28 to the heat source-side control unit 18 via wired or wireless communication. The heat source-side control unit 18 controls the heat source-side expansion valve 51, the liquid-side shut-off valve 52, the gas-side shut-off valve 53, and the expansion valve 54. The use-side control unit 28 controls the use-side expansion valve 24 and the heating device 40. The use-side control unit 28 controls the use-side expansion valve 24 and the heating device 40, for example, based on commands from the heat source-side control unit 18.

[0056] The control device 100b can switch the operation of the air conditioning system 100 between cooling operation and heating operation. The cooling operation of the air conditioning system 100 is performed by the heat pump unit 100a performing cooling operation. The heating operation of the air conditioning system 100 is performed by the heat pump unit 100a performing heating operation or by operating the heating unit 40.

[0057] When performing heating operation, the control device 100b determines whether to use the heat pump unit 100a or the heating unit 40 to heat the air in the air-conditioned space AS based on the temperature of the air in the air-conditioned space AS. For example, when the difference between the air temperature in the air-conditioned space AS and the set temperature of the air conditioning system 100 is equal to or greater than a predetermined fifth threshold, the control device 100b operates the heating unit 40 to heat the air in the air-conditioned space AS. For example, when the difference between the air temperature in the air-conditioned space AS and the set temperature of the air conditioning system 100 is smaller than the fifth threshold, the control device 100b operates the heat pump unit 100a to heat the air in the air-conditioned space AS. In the first embodiment, the control device 100b acquires the temperature of the air in the air-conditioned space AS based on the detection result of the second temperature sensor 83.

[0058] When performing heating operation, the control device 100b determines whether to use the heat pump device 100a or the heating device 40 to heat the air in the air-conditioned space AS based on the outdoor air temperature, i.e., the outside air temperature. For example, when the outside air temperature is lower than a predetermined sixth threshold, the control device 100b operates the heating device 40 to heat the air in the air-conditioned space AS. For example, when the outside air temperature is equal to or higher than the sixth threshold, the control device 100b operates the heat pump device 100a to heat the air in the air-conditioned space AS. In the first embodiment, the control device 100b obtains the outside air temperature based on the detection result of the fourth temperature sensor 19.

[0059] When operating the heat pump unit 100a, the control device 100b drives the compressor 12, the heat-source-side blower 15, and the blower 42 of the heating device 40, and stops driving the heating unit 43. The control device 100b opens the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 while the heat pump unit 100a is operating. As a result, while the heat pump unit 100a is operating, refrigerant 90 flows between the heat-source-side refrigerant circuit 31 and the use-side refrigerant circuit 32. When operating the heating device 40, the control device 100b drives the blower 42 and heating unit 43 of the heating device 40, and stops driving the compressor 12 and the heat-source-side blower 15.

[0060] Fig. 4 is a flowchart showing part of the control procedure of the control device 100b in embodiment 1. Fig. 4 shows an example of the control procedure for controlling the liquid-side shutoff valve 52, the gas-side shutoff valve 53, and the use-side expansion valves 24 when the operation of the heat pump device 100a is stopped. Note that the determination and control by the control device 100b described below may be performed by the heat source-side control unit 18, may be performed by the use-side control unit 28, or may be performed by the heat source-side control unit 18 and the use-side control unit 28 working together.

[0061] 4, when the operation of the heat pump unit 100a is stopped (step S1), the control device 100b stops the compressor 12 (step S2). After stopping the compressor 12, the control device 100b closes the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 (step S3). In other words, when the operation of the heat pump unit 100a is stopped, the control device 100b closes the liquid-side shutoff valve 52 and the gas-side shutoff valve 53.

[0062] In step S3 of the first embodiment, the control device 100b reduces the opening of the user-side expansion valve 24. In step S3, the control device 100b closes the opening of the user-side expansion valve 24 to a state close to a fully closed state, leaving the user-side expansion valve 24 slightly open. This reduces the flow of the refrigerant 90 within the user-side unit 20 when the heat pump device 100a is stopped, thereby preventing people in the air-conditioned space AS from hearing the sound of the refrigerant 90 flowing. On the other hand, by not completely closing the user-side expansion valve 24, the pressure of the refrigerant 90 in the portions of the user-side refrigerant circuit 32 on both sides of the user-side expansion valve 24 can be more easily equalized when the heat pump device 100a is stopped. This makes it easier to equalize the pressure in the liquid-side pipe 35 and the pressure in the gas-side pipe 36, making it easier to drive the compressor 12 when the heat pump device 100a is restarted.

[0063] After step S3, the control device 100b determines whether a first condition related to the start of operation of the heating device 40 is satisfied (step S4a). The first condition related to the start of operation of the heating device 40 is a condition that may be satisfied due to the start of operation of the heating device 40. In the first embodiment, the first condition related to the heating device 40 is that the value of a first temperature Ta, which is the temperature of the refrigerant 90 in the use-side refrigerant circuit 32, is equal to or greater than a predetermined first threshold value α1. In the first embodiment, the first condition is a condition expressed as Ta≧α1.

[0064] When the heating device 40 starts operating while the heat pump device 100a is not operating, the airflow AF generated by the blower 42 is heated by the heating unit 43 and then passes through the use-side heat exchanger 22. Therefore, when the heating device 40 starts operating while the heat pump device 100a is not operating, the temperature of the refrigerant 90 in the use-side heat exchanger 22 increases. In other words, the value of the first temperature Ta increases as a result of the start of operation of the heating device 40, and the first condition that the value of the first temperature Ta becomes equal to or greater than the first threshold value α1 can be satisfied.

[0065] In the first embodiment, the value of the first temperature Ta is a value of a temperature acquired based on the first temperature sensor 23. That is, in the first embodiment, the value of the first temperature Ta is a value of the temperature of the refrigerant 90 in the heat transfer tube included in the use-side heat exchanger 22.

[0066] The first threshold value α1 is, for example, 60° C. The first threshold value α1 is the temperature at which the pressure of the refrigerant 90 in the use-side refrigerant circuit 32 becomes equal to or lower than the design pressure of the piping when the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 are closed. The first threshold value α1 is determined, for example, based on the saturation temperature of the refrigerant 90 when the pressure of the refrigerant 90 in the use-side refrigerant circuit 32 is equal to the design pressure. The first threshold value α1 may be determined taking into account an error in the value detected by the first temperature sensor 23 and a time delay in the temperature rise of the piping directly detected by the first temperature sensor 23. The first threshold value α1 may be determined based on the upper limit of the guaranteed temperature of the use-side unit 20.

[0067] In step S4a, if the control device 100b determines that the first temperature Ta is equal to or greater than the first threshold value α1 based on the first temperature sensor 23, the control device 100b determines that the first condition is satisfied (step S4a: YES). If the control device 100b determines that the first condition is satisfied in step S4a, the control device 100b opens the target shutoff valve (step S5a). In the first embodiment, the target shutoff valve is the gas-side shutoff valve 53. That is, in the first embodiment, if the control device 100b determines that the first condition is satisfied while the operation of the heat pump device 100a is stopped, the control device 100b opens the gas-side shutoff valve 53. In step S5a in the first embodiment, the control device 100b opens only the gas-side shutoff valve 53 out of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53, and keeps the liquid-side shutoff valve 52 closed. If it is determined in step S4a that the first temperature Ta is less than the first threshold value α1, the control device 100b determines that the first condition is not satisfied (step S4a: NO) and keeps the liquid side shut-off valve 52 and the gas side shut-off valve 53 in a closed state.

[0068] When step S5a is executed, the heating device 40 is in operation. Although not shown in Fig. 4, in the first embodiment, the control device 100b starts the operation of the heating device 40 during the period from step S3 to step S5a.

[0069] After opening the target shutoff valve in step S5a, the control device 100b determines whether a second condition is satisfied (step S6a). In the first embodiment, the second condition is a condition related to the operation of the heating device 40 being stopped. The second condition related to the operation of the heating device 40 being stopped is a condition that may be satisfied due to the operation of the heating device 40 being stopped. In the first embodiment, the second condition is that the value of the first temperature Ta, which is the temperature of the refrigerant 90 in the use-side refrigerant circuit 32, is equal to or less than a predetermined third threshold value α2. In the first embodiment, the second condition is a condition expressed as Ta≦α2.

[0070] When the heating device 40, which had been operating while the heat pump device 100a is stopped, is stopped, the blower 42 and the heating unit 43 stop, and heated air no longer flows through the use-side heat exchanger 22. As a result, the temperature of the refrigerant 90 in the use-side heat exchanger 22 decreases. In other words, the value of the first temperature Ta decreases due to the heating device 40 being stopped, and the second condition that the value of the first temperature Ta becomes equal to or less than the third threshold value α2 may be satisfied. The third threshold value α2 is smaller than the first threshold value α1. The third threshold value α2 is, for example, 5°C or more and 15°C or less than the first threshold value α1. The third threshold value α2 is, for example, 50°C.

[0071] In step S6a, the control device 100b determines that the second condition is satisfied if it determines that the value of the first temperature Ta is equal to or less than the third threshold value α2 based on the first temperature sensor 23 (step S6a: YES). If it determines that the second condition is satisfied in step S6a, the control device 100b closes the target shutoff valve (step S7a). In step S7a of the first embodiment, the control device 100b closes the gas-side shutoff valve 53. Thus, in the first embodiment, if the control device 100b determines that the first condition is satisfied and opens at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53, the control device 100b closes the shutoff valve that is open between the liquid-side shutoff valve 52 and the gas-side shutoff valve 53. If it is determined in step S6a that the value of the first temperature Ta is greater than the third threshold value α2, the control device 100b determines that the second condition is not satisfied (step S6a: NO) and keeps the target shut-off valve, i.e., the gas side shut-off valve 53, in the open state.

[0072] After performing step S7a, the control device 100b performs step S4a again. The control device 100b repeatedly executes steps S4a to S7a until the operation of the heat pump device 100a is started.

[0073] When step S7a is performed, it is highly likely that the operation of the heating device 40 has been stopped before step S7a. If the operation of the heating device 40 has been stopped, the control device 100b stops the operation of the heating device 40 between step S5a and step S7a, although this is not shown in FIG.

[0074] According to the first embodiment, the air conditioning system 100 includes a heat pump device 100a having a heat source unit 10 and a user unit 20, a heating device 40 having a heating section 43 capable of heating air passing through it, a blower 42 that generates an airflow AF that passes through the heating section 43, and a control device 100b that controls the heat pump device 100a. The heat pump device 100a has a circulating refrigerant circuit 30 through which a refrigerant 90 circulates. The circulating refrigerant circuit 30 includes a heat source side refrigerant circuit 31 having a compressor 12 and a heat source side heat exchanger 13 and provided in the heat source side unit 10, a use side refrigerant circuit 32 having a use side heat exchanger 22 and provided in the use side unit 20, a liquid side piping 35 and a gas side piping 36 connecting the heat source side refrigerant circuit 31 and the use side refrigerant circuit 32, a liquid side shutoff valve 52 that, in a closed state, shuts off the flow of refrigerant 90 from the heat source side refrigerant circuit 31 to the use side refrigerant circuit 32 via the liquid side piping 35, and a gas side shutoff valve 53 that, in a closed state, shuts off the flow of refrigerant 90 from the heat source side refrigerant circuit 31 to the use side refrigerant circuit 32 via the gas side piping 36. The blower 42 generates an airflow AF that passes through a heating section 43 and then through the use side heat exchanger 22. The control device 100b opens the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 when the heat pump device 100a is operating, and closes the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 when the heat pump device 100a is stopped. Therefore, when the heat pump device 100a is stopped, the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 can prevent the refrigerant 90 from flowing from the heat-source-side refrigerant circuit 31 to the user-side refrigerant circuit 32. This reduces the risk of the refrigerant 90 in the heat-source-side refrigerant circuit 31 leaking into the air-conditioned space AS. The control device 100b opens at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 when it determines that a first condition related to the start of operation of the heating device 40 while the heat pump device 100a is stopped is satisfied. When at least one of the liquid side shut-off valve 52 and the gas side shut-off valve 53 is opened, the refrigerant 90 in the user side refrigerant circuit 32 can move into the heat source side refrigerant circuit 31 through the shut-off valve that is opened.Therefore, even if the heating device 40 is operated and the temperature of the refrigerant 90 in the use-side refrigerant circuit 32 rises and the refrigerant 90 expands, a portion of the refrigerant 90 in the use-side refrigerant circuit 32 can be released into the heat-source-side refrigerant circuit 31. This prevents the pressure of the refrigerant 90 in the use-side refrigerant circuit 32 from increasing excessively, thereby preventing damage to the piping of the use-side refrigerant circuit 32. This prevents the refrigerant 90 from leaking from the piping of the use-side refrigerant circuit 32, reducing the risk of the refrigerant 90 in the use-side refrigerant circuit 32 leaking into the air-conditioned space AS. As described above, according to the first embodiment, the risk of the refrigerant 90 leaking into the space to be air-conditioned, i.e., the air-conditioned space AS, can be reduced. Note that the internal volume of the heat-source-side refrigerant circuit 31 is larger than the internal volume of the use-side refrigerant circuit 32. This allows a portion of the refrigerant 90 in the use-side refrigerant circuit 32 to be sufficiently released into the heat-source-side refrigerant circuit 31.

[0075] According to the first embodiment, the circulating refrigerant circuit 30 includes a user-side expansion valve 24 disposed between the liquid-side shutoff valve 52 and the user-side heat exchanger 22. When the control device 100b determines that the first condition is satisfied while the heat pump device 100a is not operating, the control device 100b opens the gas-side shutoff valve 53. This allows a portion of the refrigerant 90 in the user-side refrigerant circuit 32 that has been heated and expanded by the heating device 40 to escape into the heat-source-side refrigerant circuit 31 via the gas-side piping 36. This prevents damage to the piping of the user-side unit 20. Furthermore, because it is the refrigerant 90 in the user-side heat exchanger 22 that is heated by the heating device 40, the refrigerant 90 flowing to the heat-source-side refrigerant circuit 31 is the refrigerant 90 pushed into the heat-source-side refrigerant circuit 31 by the expanded refrigerant 90 in the user-side heat exchanger 22. Therefore, for example, when the gas-side shutoff valve 53 is closed and the liquid-side shutoff valve 52 is opened, the refrigerant 90 flows from the user-side heat exchanger 22 toward the liquid-side shutoff valve 52, making it easier for the refrigerant 90 to flow to the user-side expansion valve 24. Here, regardless of the opening degree of the user-side expansion valve 24, the resistance the refrigerant 90 encounters when flowing through the user-side expansion valve 24 is likely to be greater than the resistance the refrigerant 90 encounters when flowing through the piping. Therefore, when the gas-side shutoff valve 53 is closed and the liquid-side shutoff valve 52 is opened, the resistance in the user-side expansion valve 24 may make it difficult for the refrigerant 90 to flow from the user-side refrigerant circuit 32 to the heat-source-side refrigerant circuit 31. In contrast, in the first embodiment, by opening the gas-side shutoff valve 53 when the first condition is satisfied, the refrigerant 90 flowing from the user-side heat exchanger 22 toward the heat-source-side refrigerant circuit 31 can be made to bypass the user-side expansion valve 24. Therefore, a portion of the refrigerant 90 expanded by the heating device 40 can be easily released to the heat source side refrigerant circuit 31 .

[0076] According to the first embodiment, the first condition related to the start of operation of the heating device 40 is that the value of the first temperature Ta, which is the temperature of the refrigerant 90 in the use-side refrigerant circuit 32, is equal to or greater than a predetermined first threshold value α1. Therefore, when the first temperature Ta of the refrigerant 90 in the use-side refrigerant circuit 32 rises and the pressure of the refrigerant 90 becomes high to a certain extent, at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 can be opened. This allows a portion of the refrigerant 90 in the use-side refrigerant circuit 32 to escape into the heat-source-side refrigerant circuit 31 before the pressure of the refrigerant 90 in the use-side refrigerant circuit 32 becomes excessively high. This prevents damage to the piping of the user-side unit 20. In particular, setting the first threshold value α1 to an appropriate value prevents damage to the piping of the user-side unit 20 caused by the heating device 40 being operated while the heat pump device 100a is not operating. This reduces the risk of the refrigerant 90 in the user-side unit 20 leaking into the air-conditioned space AS. Furthermore, even if the heating device 40 is operating, when the first temperature Ta is less than the first threshold value α1, the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 can be closed. Therefore, compared to when at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 is open throughout the entire period during which the heating device 40 is operating, it is possible to suppress the movement of refrigerant 90 from the heat-source-side refrigerant circuit 31 to the user-side refrigerant circuit 32.

[0077] According to the first embodiment, if the control device 100b determines that the first condition is satisfied and opens at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53, and then determines that the second condition is satisfied, the control device 100b closes the shutoff valve that is currently open, either the liquid-side shutoff valve 52 or the gas-side shutoff valve 53. Therefore, by appropriately setting the second condition, both the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 can be closed when the state of the refrigerant 90 in the use-side refrigerant circuit 32 is not at a level that would damage the piping of the use-side unit 20. This prevents at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 from being unnecessarily opened. This prevents the refrigerant 90 from moving from the heat-source-side refrigerant circuit 31 into the use-side refrigerant circuit 32. Furthermore, when at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 is open, the refrigerant 90 that flows from the use-side refrigerant circuit 32 to the heat-source-side refrigerant circuit 31 can be contained within the heat-source-side refrigerant circuit 31 by closing the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 again. This reduces the amount of refrigerant 90 remaining in the use-side refrigerant circuit 32, and reduces the risk of the refrigerant 90 in the use-side refrigerant circuit 32 leaking into the air-conditioned space AS.

[0078] According to the first embodiment, the second condition is that the value of the first temperature Ta, which is the temperature of the refrigerant 90 in the use-side refrigerant circuit 32, is equal to or less than a predetermined third threshold value α2. Therefore, when the temperature of the refrigerant 90 in the use-side refrigerant circuit 32 drops and the pressure of the refrigerant 90 drops, the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 can be closed. Therefore, it is possible to prevent at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 from being unnecessarily opened.

[0079] According to the first embodiment, the third threshold value α2 is smaller than the first threshold value α1. Therefore, even when the first temperature Ta fluctuates around the first threshold value α1, it is possible to prevent at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 from repeatedly switching between the open state and the closed state. Furthermore, by setting the second condition that the first temperature Ta be equal to or less than the third threshold value α2, which is smaller than the first threshold value α1, it is possible to close the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 when the pressure of the refrigerant 90 in the use-side refrigerant circuit 32 has sufficiently decreased.

[0080] Embodiment 2. Fig. 5 is a flowchart showing part of the control procedure of the control device 100b in embodiment 2. Fig. 5 shows an example of the control procedure for controlling the liquid-side shutoff valve 52, the gas-side shutoff valve 53, and the user-side expansion valve 24 when the operation of the heat pump device 100a is stopped. Note that in the following description, the same configurations and methods as those in the above-described embodiment may be appropriately denoted by the same reference numerals and descriptions thereof may be omitted.

[0081] As shown in Fig. 5, in the second embodiment, step S4b is provided instead of step S4a, and step S6b is provided instead of step S6a, unlike in the first embodiment. The other control procedures shown in Fig. 5 are the same as the other control procedures in the first embodiment shown in Fig. 4.

[0082] In the second embodiment, after step S3, the control device 100b determines whether a first condition related to the start of operation of the heating device 40 is satisfied (step S4b). In the second embodiment, the first condition related to the heating device 40 is that the difference between a first temperature Ta, which is the temperature of the refrigerant 90 in the use-side refrigerant circuit 32, and a second temperature Tb, which is the temperature of the air drawn into the heating device 40 by the blower 42, is equal to or greater than a predetermined second threshold value β1. In the second embodiment, the second condition is a condition expressed as Ta - Tb ≧ β1.

[0083] As in the first embodiment, when the heating device 40 starts operating while the heat pump device 100a is stopped, the use-side heat exchanger 22 is heated by the air heated by the heating unit 43. Therefore, when the heating device 40 starts operating while the heat pump device 100a is stopped, the difference between the second temperature Tb, which is the temperature of the air before being heated, and the first temperature Ta of the refrigerant 90 warmed by the heated air, increases. That is, the difference between the first temperature Ta and the second temperature Tb increases due to the start of operation of the heating device 40, and the first condition that the difference between the first temperature Ta and the second temperature Tb is equal to or greater than the second threshold value β1 may be satisfied. In the second embodiment, the value of the second temperature Tb is a temperature value acquired based on the second temperature sensor 83. The value of the first temperature Ta is a temperature value acquired based on the first temperature sensor 23, as in the first embodiment.

[0084] The second threshold value β1 is, for example, 20 K (Kelvin). In this case, for example, when the second temperature Tb is 25°C, the first condition is satisfied if the first temperature Ta is 45°C or higher. The second threshold value β1 may be determined based on, for example, the first threshold value α1 of the first embodiment and the average value of the second temperature Tb. The second temperature Tb is the same as or approximately the same as the temperature of the air in the air-conditioned space AS.

[0085] In step S4b, the control device 100b determines that the first condition is satisfied if it determines, based on the first temperature sensor 23 and the second temperature sensor 83, that the difference between the first temperature Ta and the second temperature Tb is equal to or greater than the second threshold value β1 (step S4b: YES). In step S4b, the control device 100b compares the value obtained by subtracting the second temperature Tb from the first temperature Ta with the second threshold value β1 to determine whether the first condition is satisfied. If it determines that the first condition is satisfied in step S4b (step S4b: YES), the control device 100b opens the corresponding shutoff valve (step S5a), as in the first embodiment. If it determines that the difference between the first temperature Ta and the second temperature Tb is less than the second threshold value β1 in step S4b, the control device 100b determines that the first condition is not satisfied (step S4b: NO) and keeps the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 closed.

[0086] After opening the target shutoff valve in step S5a, the control device 100b determines whether a second condition is satisfied (step S6b). In the second embodiment, the second condition is that the difference between a first temperature Ta, which is the temperature of the refrigerant 90 in the use-side refrigerant circuit 32, and a second temperature Tb, which is the temperature of the air drawn into the heating device 40 by the blower 42, is equal to or less than a predetermined fourth threshold value β2. In the second embodiment, the second condition is expressed as Ta - Tb ≦ β2.

[0087] As in the first embodiment, when the heating device 40, which had been operating while the heat pump device 100a is stopped, is stopped, the blower 42 and the heating unit 43 are stopped, and the temperature of the refrigerant 90 in the use-side heat exchanger 22 decreases. In other words, the difference between the first temperature Ta and the second temperature Tb decreases as the heating device 40 is stopped, and the second condition that the difference between the first temperature Ta and the second temperature Tb is equal to or less than the fourth threshold value β2 may be satisfied. The fourth threshold value β2 is smaller than the second threshold value β1. For example, the fourth threshold value β2 is smaller than the second threshold value β1 by approximately 5 K (Kelvin) or more and 15 K (Kelvin) or less. The fourth threshold value β2 is, for example, 10 K (Kelvin).

[0088] In step S6b, the control device 100b determines that the second condition is satisfied if it determines, based on the first temperature sensor 23 and the second temperature sensor 83, that the difference between the first temperature Ta and the second temperature Tb is equal to or less than the fourth threshold value β2 (step S6b: YES). In step S6b, the control device 100b compares the value obtained by subtracting the second temperature Tb from the first temperature Ta with the fourth threshold value β2 to determine whether the second condition is satisfied. If it determines that the second condition is satisfied in step S6b (step S6b: YES), the control device 100b closes the target shutoff valve (step S7a), as in the first embodiment. If it determines that the difference between the first temperature Ta and the second temperature Tb is greater than the fourth threshold value β2 in step S6b, the control device 100b determines that the second condition is not satisfied (step S6b: NO) and maintains the target shutoff valve in an open state.

[0089] After performing step S7a, the control device 100b performs step S4b again. The control device 100b repeatedly executes steps S4b to S7a until the operation of the heat pump device 100a is started. The other control procedures of the control device 100b in the second embodiment are the same as the other control procedures of the control device 100b in the first embodiment.

[0090] According to the second embodiment, the first condition is that the difference between the first temperature Ta, which is the temperature of the refrigerant 90 in the use-side refrigerant circuit 32, and the second temperature Tb, which is the temperature of the air drawn into the heating device 40 by the blower 42, is equal to or greater than a predetermined second threshold value β1. Therefore, the control device 100b can detect, using the second temperature Tb as a reference, that the first temperature Ta of the refrigerant 90 in the use-side refrigerant circuit 32 has increased and the pressure of the refrigerant 90 has increased. This allows at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 to be opened before the pressure of the refrigerant 90 in the use-side refrigerant circuit 32 becomes excessively high, thereby facilitating the release of a portion of the refrigerant 90 in the use-side refrigerant circuit 32 into the heat-source-side refrigerant circuit 31. This prevents damage to the piping of the user-side unit 20. In particular, setting the second threshold value β1 to an appropriate value prevents damage to the piping of the user-side unit 20 caused by the heating device 40 operating while the heat pump device 100a is stopped. This reduces the risk of refrigerant 90 leaking into the air-conditioned space AS. Furthermore, even when the heating device 40 is operating, if the difference between the first temperature Ta and the second temperature Tb is less than the second threshold value β1, the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 can be closed. Therefore, compared to a case where at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 is open throughout the entire period that the heating device 40 is operating, it is possible to prevent refrigerant 90 from moving from the heat-source-side refrigerant circuit 31 to the user-side refrigerant circuit 32.

[0091] According to the second embodiment, the second condition is that the difference between the first temperature Ta, which is the temperature of the refrigerant 90 in the use-side refrigerant circuit 32, and the second temperature Tb, which is the temperature of the air drawn into the heating device 40 by the blower 42, is equal to or less than a predetermined fourth threshold value β2. Therefore, when the temperature of the refrigerant 90 in the use-side refrigerant circuit 32 drops and the pressure of the refrigerant 90 drops, the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 can be closed. This prevents at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 from being unnecessarily opened.

[0092] According to the second embodiment, the fourth threshold value β2 is smaller than the second threshold value β1. Therefore, even if the difference between the first temperature Ta and the second temperature Tb fluctuates around the second threshold value β1, it is possible to prevent at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 from repeatedly switching between the open state and the closed state. Furthermore, by setting the second condition that the difference between the first temperature Ta and the second temperature Tb is equal to or smaller than the fourth threshold value β2, which is smaller than the second threshold value β1, it is possible to close the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 when the pressure of the refrigerant 90 in the use-side refrigerant circuit 32 has sufficiently decreased.

[0093] In the second embodiment, the second temperature Tb may be the temperature of the air in the space to be air-conditioned, i.e., the air-conditioned space AS. Even in this case, when the first condition is satisfied, at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 is opened, thereby preventing damage to the piping of the user-side unit 20, as described above. By setting the second threshold value β1 to an appropriate value, it is possible to prevent damage to the piping of the user-side unit 20 caused by the heating device 40 operating while the heat pump device 100a is not operating. Even in this case, when the second condition is satisfied, the shutoff valve that is open is closed, thereby preventing at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 from being opened unnecessarily, as described above.

[0094] Embodiment 3. Fig. 6 is a flowchart showing part of the control procedure of the control device 100b in embodiment 3. Fig. 6 shows an example of the control procedure for controlling the liquid-side shutoff valve 52, the gas-side shutoff valve 53, and the user-side expansion valve 24 when the operation of the heat pump device 100a is stopped. Note that in the following description, the same configurations and methods as those in the above-described embodiments may be appropriately denoted by the same reference numerals and descriptions thereof may be omitted.

[0095] As shown in Fig. 6, in the third embodiment, step S4c is provided instead of step S4a, and step S6c is provided instead of step S6a, unlike in the first embodiment. The other control procedures shown in Fig. 6 are the same as the other control procedures in the first embodiment shown in Fig. 4.

[0096] In the third embodiment, after step S3, the control device 100b determines whether a first condition related to the start of operation of the heating device 40 is satisfied (step S4c). In the third embodiment, the first condition related to the heating device 40 is that the operation of the heating device 40 is started while the operation of the heat pump device 100a is stopped. In step S4c in the third embodiment, the control device 100b determines whether the operation of the heating device 40 is started, and determines whether the first condition is satisfied.

[0097] In the third embodiment, the control device 100b controls the heating device 40 and can switch the heating device 40 between an operating state and a stopped state. Therefore, the control device 100b determines that the first condition is satisfied when it has decided to operate the heating device 40. On the other hand, the control device 100b determines that the first condition is not satisfied when it has not decided to operate the heating device 40. If it determines that the first condition is satisfied in step S4c (YES in step S4c), the control device 100b opens the target shutoff valves (step S5a), as in the first embodiment. If it determines that the first condition is not satisfied in step S4b (NO in step S4c), the control device 100b maintains the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 in a closed state. Although not shown in FIG. 6 , the control device 100b, for example, executes step S5a and starts operation of the heating device 40.

[0098] After opening the target shutoff valve in step S5a, the control device 100b determines whether the second condition is satisfied (step S6c). In the second embodiment, the second condition is that the operation of the heating device 40 is stopped while the operation of the heat pump device 100a is stopped. In step S6c in the third embodiment, the control device 100b determines whether the operation of the heating device 40 is stopped and determines whether the first condition is satisfied. In the third embodiment, the control device 100b determines that the second condition is satisfied if it has decided to stop the heating device 40. On the other hand, the control device 100b determines that the second condition is not satisfied if it decides to continue the operation of the heating device 40.

[0099] If it is determined in step S6c that the second condition is satisfied (step S6c: YES), the control device 100b closes the target shutoff valve (step S7a), as in embodiment 1. If it is determined in step S6c that the second condition is not satisfied (step S6c: NO), the control device 100b keeps the target shutoff valve open.

[0100] After performing step S7a, the control device 100b performs step S4c again. The control device 100b repeatedly executes steps S4c to S7a until the operation of the heat pump device 100a is started. The other control procedures of the control device 100b in the third embodiment are the same as the other control procedures of the control device 100b in the first embodiment.

[0101] According to the third embodiment, the first condition is that the heating device 40 is started while the heat pump device 100a is stopped. Therefore, when the heating device 40 is started, at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 can be opened. This more effectively suppresses an increase in the pressure of the refrigerant 90, even if the temperature of the refrigerant 90 in the use-side refrigerant circuit 32 increases as the heating device 40 operates. This prevents damage to the piping of the use-side unit 20 caused by the heating device 40 operating while the heat pump device 100a is stopped. This reduces the risk of the refrigerant 90 leaking into the air-conditioned space AS. Furthermore, when the control device 100b controls the heating device 40, it only needs to open at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 upon determining to start the operation of the heating device 40. Therefore, determining whether to start the operation of the heating device 40 and determining whether the first condition is satisfied can be performed in a single determination process. This reduces the control load on the control device 100b.

[0102] According to the third embodiment, the second condition is that the operation of the heating device 40 is stopped while the operation of the heat pump device 100a is stopped. Therefore, the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 can be closed when the operation of the heating device 40 is stopped. As a result, the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 can be quickly closed after the heating device 40 no longer heats the refrigerant 90 in the use-side refrigerant circuit 32. Therefore, the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 can be prevented from being unnecessarily open.

[0103] Embodiment 4. Fig. 7 is a flowchart showing part of the control procedure of the control device 100b in embodiment 4. Fig. 7 shows an example of the control procedure for controlling the liquid-side shutoff valve 52, the gas-side shutoff valve 53, and the user-side expansion valve 24 when the operation of the heat pump device 100a is stopped. In the following description, the same configurations and methods as those in the above-mentioned embodiments may be appropriately denoted by the same reference numerals and descriptions thereof may be omitted.

[0104] As shown in Fig. 7, the fourth embodiment differs from the first embodiment in that step S6a is replaced with step S6d. The other control procedures shown in Fig. 7 are the same as the other control procedures in the first embodiment shown in Fig. 4.

[0105] After opening the target shutoff valve in step S5a in the fourth embodiment, the control device 100b determines whether the second condition is satisfied (step S6d). In the fourth embodiment, the second condition is that a predetermined time γ has elapsed since the control device 100b determined that the first condition was satisfied and opened at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53. In step S6d, the control device 100b determines whether the time t from the time step S5a was performed is equal to or greater than the predetermined time γ. In the fourth embodiment, the second condition is expressed as t≧γ. If the time t is equal to or greater than the predetermined time γ in step S6d, the control device 100b determines that the second condition is satisfied (step S6d: YES) and closes the target shutoff valve (step S7a), as in the first embodiment. If the time t is less than the predetermined time γ in step S6d, the control device 100b determines that the second condition is not satisfied (step S6d: NO) and maintains the shutoff valve opened in step S5a in the open state. The predetermined time γ is, for example, 5 minutes or more and 20 minutes or less. The predetermined time γ is, for example, 10 minutes. There are no particular limitations on the predetermined time γ.

[0106] Other control procedures of the control device 100b in the fourth embodiment are similar to other control procedures of the control device 100b in the first embodiment.

[0107] According to the fourth embodiment, the second condition is that a predetermined time γ has elapsed since the first condition was determined to be satisfied and at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 was opened. Therefore, the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 can be closed within a fixed time regardless of the state of other devices, such as temperature. This allows the control device 100b to easily close the shutoff valves that were opened when the first condition was satisfied. If the first condition is still satisfied after the predetermined time γ has elapsed, steps S4a and S5a open at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 again. This prevents damage to the piping of the user-side unit 20 and reduces the risk of the refrigerant 90 in the user-side unit 20 leaking into the air-conditioned space AS.

[0108] The first condition in the fourth embodiment is not limited to the first condition in the first embodiment, but may be the first condition in either the second embodiment or the third embodiment.

[0109] Embodiment 5. Fig. 8 is a flowchart showing part of the control procedure of the control device 100b in embodiment 5. Fig. 8 shows an example of the control procedure for controlling the liquid-side shutoff valve 52, the gas-side shutoff valve 53, and the user-side expansion valve 24 when the operation of the heat pump device 100a is stopped. In the following description, the same configurations and methods as those in the above-mentioned embodiments may be appropriately denoted by the same reference numerals and descriptions thereof may be omitted.

[0110] As shown in Fig. 8, in the fifth embodiment, step S5b is provided instead of step S5a, and step S7b is provided instead of step S7a, unlike in the first embodiment. The other control procedures shown in Fig. 8 are the same as the other control procedures in the first embodiment shown in Fig. 4.

[0111] If it is determined in step S4a of the fifth embodiment that the first condition is satisfied, the control device 100b opens the relevant shutoff valve and increases the opening degree of the use-side expansion valve 24 (step S5b). That is, in the fifth embodiment, if it is determined that the first condition is satisfied while the operation of the heat pump device 100a is stopped, the control device 100b increases the opening degree of the use-side expansion valve 24. In step S5b of the fifth embodiment, the control device 100b maximizes the opening degree of the use-side expansion valve 24, bringing the use-side expansion valve 24 into a fully open state.

[0112] If it is determined in step S6a of the fifth embodiment that the second condition is satisfied, the control device 100b closes the relevant shutoff valve and reduces the opening of the user-side expansion valve 24 (step S7b). That is, in the fifth embodiment, the control device 100b determines that the first condition is satisfied and increases the opening of the user-side expansion valve 24, and then reduces the opening of the user-side expansion valve 24 if it determines that the second condition is satisfied. In step S7b of the fifth embodiment, the control device 100b reduces the opening of the user-side expansion valve 24 to a state close to a fully closed state, so that the user-side expansion valve 24 is slightly open but almost closed.

[0113] Other control procedures of the control device 100b in the fifth embodiment are similar to other control procedures of the control device 100b in the first embodiment.

[0114] According to the fifth embodiment, the control device 100b increases the aperture of the user-side expansion valve 24 when it determines that the first condition is satisfied while the heat pump device 100a is not operating. Therefore, when the first condition is satisfied and at least one of the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 is opened, the user-side expansion valve 24 can be prevented from acting as a resistance to the refrigerant 90 as it flows from the user-side refrigerant circuit 32 to the heat-source-side refrigerant circuit 31. For example, when only the gas-side shutoff valve 53 is opened when the first condition is satisfied, the refrigerant 90 in the piping between the user-side expansion valve 24 and the liquid-side shutoff valve 52 can easily flow through the user-side expansion valve 24 to the user-side heat exchanger 22 and the gas-side piping 36. This allows the refrigerant 90 to escape from the user-side refrigerant circuit 32 to the heat-source-side refrigerant circuit 31 more quickly than when the aperture of the user-side expansion valve 24 is small. This effectively prevents a pressure increase of the refrigerant 90 in the use-side refrigerant circuit 32. This prevents damage to the piping of the use-side unit 20, and reduces the risk of the refrigerant 90 in the use-side unit 20 leaking into the air-conditioned space AS.

[0115] According to the fifth embodiment, the control device 100b determines that the first condition is satisfied and increases the opening of the use-side expansion valve 24, and then decreases the opening of the use-side expansion valve 24 when it determines that the second condition is satisfied. This makes it possible to prevent the opening of the use-side expansion valve 24 from being unnecessarily large, for example, when the heating device 40 is stopped. This allows the use-side expansion valve 24 to prevent the refrigerant 90 from flowing within the user-side unit 20 when there is no need to release a portion of the refrigerant 90 within the use-side refrigerant circuit 32 into the heat-source-side refrigerant circuit 31. This prevents the sound of the refrigerant 90 flowing within the user-side unit 20 from being heard by people in the air-conditioned space AS.

[0116] The first condition in the fifth embodiment is not limited to the first condition in the first embodiment, but may be the first condition in any one of the second and third embodiments. The second condition in the fifth embodiment is not limited to the second condition in the first embodiment, but may be the second condition in any one of the second, third, and fourth embodiments.

[0117] Embodiment 6. In Embodiment 6, the shutoff valves targeted in steps S5a and S7a are different from those in Embodiment 1. In the following description, the same configurations and methods as those in the above-described embodiments may be denoted by the same reference numerals as appropriate, and the description thereof may be omitted.

[0118] In the sixth embodiment, the control device 100b controls the liquid-side shutoff valve 52, the gas-side shutoff valve 53, and the user-side expansion valves 24 in accordance with the flowchart shown in FIG. 4 , as in the first embodiment. In the sixth embodiment, the shutoff valves that are the target of steps S5a and S7a are both the liquid-side shutoff valve 52 and the gas-side shutoff valve 53. That is, in the sixth embodiment, the control device 100b opens both the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 when it determines that the first condition is satisfied while the heat pump device 100a is not operating. Furthermore, in the sixth embodiment, the control device 100b closes both the liquid-side shutoff valve 52 and the gas-side shutoff valve 53 when it determines that the second condition is satisfied after determining that the first condition is satisfied and opening both the liquid-side shutoff valve 52 and the gas-side shutoff valve 53.

[0119] Other control procedures of the control device 100b in the sixth embodiment are similar to other control procedures of the control device 100b in the first embodiment.

[0120] According to the sixth embodiment, when the control device 100b determines that the first condition is satisfied while the heat pump device 100a is not operating, it opens both the liquid-side shutoff valve 52 and the gas-side shutoff valve 53. Therefore, when the refrigerant 90 in the use-side refrigerant circuit 32 is heated by the heating device 40, a portion of the refrigerant 90 in the use-side refrigerant circuit 32 can escape into the heat-source-side refrigerant circuit 31 via both the liquid-side piping 35 and the gas-side piping 36. This makes it easier to escape a portion of the refrigerant 90 in the use-side refrigerant circuit 32 into the heat-source-side refrigerant circuit 31 in a shorter time. Therefore, damage to the piping of the user-side unit 20 can be suppressed, and the risk of the refrigerant 90 leaking into the air-conditioned space AS can be reduced.

[0121] In addition, in the above-mentioned embodiments 2 to 5, the shut-off valves that are to be opened when the first condition is satisfied may be both the liquid side shut-off valve 52 and the gas side shut-off valve 53.

[0122] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the configurations of the above-described embodiments, and the following configurations and methods may also be adopted.

[0123] The heating device may be a heating device other than a gas furnace unit. The heating device is not particularly limited as long as it has a heating unit. The heating unit may heat the air by any method, and may heat the air by a method other than burning gas. The heating unit may heat the air using, for example, an electric heating wire. The heating device does not need to have a blower that generates an air flow that passes through the heating unit. In this case, as long as it is possible to generate an air flow that passes through the heating unit and then through the use-side heat exchanger, the use-side unit may have the blower, or the blower may be provided separately from the use-side unit and the heating device.

[0124] As long as the control device in the air conditioning system can control the heat pump device, it does not have to be able to control the heating device or the blower that generates the airflow that passes through the heating unit. In this case, the air conditioning system may be provided with other control devices that control the heating device and the blower, respectively. The control device that controls the heat pump device may be composed of only one control unit, or may be composed of two or more control units. When the control device that controls the heat pump device is composed of two or more control units, the two or more control units may include a control unit provided in the heating device.

[0125] As shown by the two-dot chain lines in FIGS. 2 and 3 , the air conditioning system may include a heating device control unit 44 that controls the heating device, separate from the control device that controls the heat pump device. In this case, the heating device control unit 44 can control the heating unit and the blower provided in the heating device. When starting operation of the heating device, the heating device control unit 44 may send an operation start signal indicating that operation of the heating device should be started to the control device that controls the heat pump device. In this case, if the first condition is the first condition of the third embodiment, the control device may determine, upon receiving the operation start signal from the heating device control unit 44, that the first condition, that operation of the heating device is started while operation of the heat pump device is stopped, is satisfied. When stopping operation of the heating device, the heating device control unit 44 may send an operation stop signal indicating that operation of the heating device should be stopped to the control device that controls the heat pump device. In this case, if the second condition is the second condition of the third embodiment, the control device may determine, upon receiving the operation stop signal from the heating device control unit 44, that the second condition, that operation of the heating device is stopped while operation of the heat pump device is stopped, is satisfied.

[0126] When the heating device control unit 44 described above is provided, there may be cases where the heating device control unit 44 does not send the heating device operation start signal or operation stop signal to the control device, or where the control device does not properly receive the heating device operation start signal or operation stop signal. In such cases, the control device cannot directly detect the operating state of the heating device. Even in such cases, the control device can indirectly detect the operating state of the heating device by acquiring the temperature of the refrigerant in the use-side refrigerant circuit, as in the first and second embodiments described above.

[0127] The control device may open only the liquid-side shutoff valve of the liquid-side shutoff valve and the gas-side shutoff valve when it determines that a first condition related to the start of operation of the heating device is satisfied while the heat pump device is stopped. The first condition is not particularly limited as long as it is a condition related to the start of operation of the heating device. When the first condition includes the refrigerant temperature and when the second condition includes the refrigerant temperature, the control device may indirectly detect the refrigerant temperature by using a temperature sensor to detect the temperature of the piping through which the refrigerant flows, or may directly detect the refrigerant temperature by, for example, placing a temperature sensor inside the piping. The first condition may be that the pressure of the refrigerant in the use-side refrigerant circuit is equal to or greater than a predetermined threshold. The second condition may be that the pressure of the refrigerant in the use-side refrigerant circuit is equal to or less than a predetermined threshold. The first and second conditions in each of the above-described embodiments may be combined in any manner. The second condition is not particularly limited and may be any condition.

[0128] When the control device increases the opening of the user-side expansion valves when it is determined that the first condition is satisfied, the amount by which the control device increases the opening of the user-side expansion valves is not particularly limited. When the control device determines that the first condition is satisfied, the control device may reduce the opening of the user-side expansion valves to an opening smaller than fully open. When the control device determines that the second condition is satisfied, the amount by which the control device reduces the opening of the user-side expansion valves is not particularly limited. When it determines that the second condition is satisfied, the control device may fully close the user-side expansion valves. When operation of the heat pump device stops, the control device may fully close the user-side expansion valves, or may not change the opening of the user-side expansion valves.

[0129] At least some of the functions of the control devices described in the above-described embodiments are realized by, for example, a processor such as a CPU executing a program stored in a storage unit (not shown), i.e., software. Note that at least some of the functions of each control device may be realized by hardware including circuit units such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), and a GPU (Graphics Processing Unit), or may be realized by a combination of software and hardware. The storage unit (not shown) is realized by a storage medium such as a RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), a flash memory, etc. The storage unit (not shown) may be provided in the air conditioning system, or may be provided outside the air conditioning system and be able to communicate with the air conditioning system via wired or wireless communication.

[0130] The configurations and methods described in this specification can be combined as appropriate within the scope of not contradicting each other.

[0131] 10...heat source side unit, 12...compressor, 13...heat source side heat exchanger, 20...user side unit, 22...user side heat exchanger, 24...user side expansion valve, 30...circulating refrigerant circuit, 31...heat source side refrigerant circuit, 32...user side refrigerant circuit, 35...liquid side piping, 36...gas side piping, 40...heating device, 42...blower, 43...heating section, 52...liquid side shut-off valve, 53...gas side shut-off valve, 90...refrigerant, 100...air conditioning system, 100a...heat pump device, 100b...control device, AF...air flow, γ...predetermined time, Ta...first temperature, Tb...second temperature, α1...first threshold, α2...third threshold, β1...second threshold, β2...fourth threshold

Claims

1. A heat pump system having a heat source unit and a utilization unit, A heating device having a heating section capable of heating the air passing through it, A blower that generates an airflow passing through the heating section, A control device for controlling the heat pump device, Equipped with, The heat pump device has a circulating refrigerant circuit through which the refrigerant circulates. The aforementioned circulating refrigerant circuit is A heat source side refrigerant circuit provided in the heat source side unit, having a compressor and a heat source side heat exchanger, A user-side refrigerant circuit provided in the user-side unit, having a user-side heat exchanger, Liquid-side piping and gas-side piping connecting the heat source-side refrigerant circuit and the utilization-side refrigerant circuit, A liquid-side shut-off valve that, in a closed state, blocks the flow of refrigerant from the heat source-side refrigerant circuit to the utilization-side refrigerant circuit via the liquid-side piping, A gas-side shut-off valve that, in a closed state, blocks the flow of the refrigerant from the heat source-side refrigerant circuit to the utilization-side refrigerant circuit via the gas-side piping, A utilization-side expansion valve is provided between the liquid-side shut-off valve and the utilization-side heat exchanger, It has, The blower generates an airflow that passes through the heating section and then through the heat exchanger on the utilization side. The aforementioned user-side expansion valve is a valve whose opening degree can be continuously adjusted. The control device is While the heat pump device is in operation, the liquid-side shutoff valve and the gas-side shutoff valve are opened. When the operation of the heat pump device stops, the liquid-side shut-off valve and the gas-side shut-off valve are closed, and the opening degree of the user-side expansion valve is reduced while the user-side expansion valve is open. When it is determined that the first condition related to the start of operation of the heating device is met while the operation of the heat pump device is stopped, the gas-side shutoff valve is opened and the liquid-side shutoff valve remains closed. The first condition is that the value of the first temperature, which is the temperature of the refrigerant in the refrigerant circuit on the user side, is equal to or greater than a predetermined first threshold, in an air conditioning system.

2. The air conditioning system according to claim 1, wherein the control device determines that the first condition is met and opens the gas-side shut-off valve, and then determines that the second condition is met, closes the gas-side shut-off valve.

3. The air conditioning system according to claim 2, wherein the second condition is that the value of the first temperature is less than or equal to a predetermined third threshold.

4. The air conditioning system according to claim 3, wherein the third threshold is smaller than the first threshold.

5. The air conditioning system according to claim 2, wherein the second condition is that the difference between the first temperature and a second temperature, which is the temperature of the air drawn into the heating device by the blower or the temperature of the air in the space to be air-conditioned, is less than or equal to a predetermined fourth threshold.

6. The air conditioning system according to claim 2, wherein the second condition is that the operation of the heating device is stopped when the operation of the heat pump device is stopped.

7. The air conditioning system according to claim 2, wherein the second condition is that a predetermined amount of time has elapsed since the time it was determined that the first condition was met and the gas-side shut-off valve was opened.