Air conditioning system having heat pump and gas furnace

Abstract

An air conditioning system (90) comprises: a heat pump unit (40) that performs a cooling operation using a flammable or toxic refrigerant (R); a gas furnace unit (50) that performs a heating operation by burning a fuel gas (FG); and an air conditioning system controller (99). The heat pump unit (40) has a refrigerant shutoff valve that shuts off the refrigerant (R). The refrigerant shutoff valve includes at least some of an outdoor expansion valve (15), a liquid shutoff valve (17), and a gas shutoff valve (18). If a prescribed event occurs, the air conditioning system controller (99) closes the refrigerant shutoff valve to execute an inflow prevention operation for preventing the refrigerant (R) from flowing into a heat pump indoor unit (20).

Description

Air conditioning system having a heat pump and a gas furnace

[0001] The present disclosure relates to an air conditioning system having a heat pump and a gas furnace.

[0002] The air conditioning system disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2015-218940) has a heat pump and a gas furnace, both of which can be used for heating operation. This air conditioning system is intended to ensure sufficient heating capacity by performing heating operation with a gas furnace when the outside air temperature is low, and to improve energy efficiency by performing heating operation with a heat pump when the outside air temperature is high.

[0003] When the season with low outside air temperature in which the gas furnace is frequently used for heating operation arrives, the heat pump will not be used for a long time. At this time, although the heat pump is not used, the refrigerant may stay in the refrigerant circuit on the indoor unit side. When the refrigerant is flammable or toxic, it is not preferable from the viewpoint of ensuring the safety of the user that such a refrigerant stays in the indoor unit for a long time.

[0004] The air conditioning system of the first aspect includes a heat pump, a gas furnace, and a control unit. The heat pump performs a cooling operation using a refrigerant. The refrigerant is flammable or toxic. The gas furnace performs a heating operation by burning fuel gas. The heat pump has an outdoor unit and an indoor unit. The outdoor unit has a compressor, an outdoor heat exchanger, and an outdoor fan. The indoor unit has an indoor heat exchanger. The heat pump further has a refrigerant shut-off valve for shutting off the refrigerant. The control unit closes the refrigerant shut-off valve so as to execute an inflow prevention operation when a predetermined event occurs. The inflow prevention operation is an operation for preventing the inflow of the refrigerant into the indoor unit.

[0005] According to this configuration, the inflow of the refrigerant having flammability or toxicity into the indoor unit is suppressed when a predetermined event occurs. Therefore, the safety of the user using the heat pump and the gas furnace can be improved.

[0006] The second air conditioning system is the first air conditioning system, wherein the event is at least one of the following: [1] The control unit receives a command to end the cooling operation. [2] The control unit stops the compressor during the cooling operation. [3] The control unit receives a command to start the heating operation after the cooling operation has ended.

[0007] With this configuration, the inflow prevention operation is performed in situations where refrigerant may move into the indoor unit, such as at the end of cooling operation, during thermo-off control during cooling operation, or at the start of heating operation after cooling operation. Therefore, user safety can be improved.

[0008] The third air conditioning system is an air conditioning system according to the first or second perspective, wherein the control unit performs a second inflow blocking operation after a predetermined time has elapsed since the first inflow blocking operation when an event occurs.

[0009] In this configuration, if, after the first inflow blocking operation is completed, refrigerant passes through the supposedly closed refrigerant shut-off valve and moves from the outdoor unit side to the indoor unit side, a second inflow blocking operation is performed. This further suppresses the movement of refrigerant to the indoor unit.

[0010] The fourth air conditioning system is an air conditioning system from either the first or third perspective, wherein the heat pump further includes a refrigerant state sensor that detects the state of the refrigerant. The control unit performs a first inflow blocking operation when an event occurs, and then performs a second inflow blocking operation based on the output of the refrigerant state sensor.

[0011] In this configuration, a second inflow blocking operation is performed based on the output of the refrigerant state sensor. When the refrigerant passes through the refrigerant shut-off valve, which should be closed, and moves from the outdoor unit side to the indoor unit side, the control unit can detect this phenomenon based on the output of the refrigerant state sensor. Therefore, the execution of the second inflow blocking operation can more strictly suppress the movement of refrigerant to the indoor unit side.

[0012] The fifth air conditioning system is an air conditioning system from either the first or fourth perspective, wherein the control unit performs an inflow blocking operation whenever an event occurs.

[0013] With this configuration, an inflow blocking operation will always be performed if an event occurs. Therefore, the movement of refrigerant to the indoor unit is further suppressed.

[0014] The sixth air conditioning system is an air conditioning system from any one of the first to fifth perspectives, wherein the inflow blocking operation is at least one of the following: [1] Pump-down operation involving compressor operation and closure of refrigerant shut-off valve; [2] Refrigerant movement operation involving outdoor fan operation and closure of refrigerant shut-off valve; [3] Refrigerant shut-off operation involving closure of refrigerant shut-off valve.

[0015] In this configuration, when a predetermined event occurs, the compressor either draws in refrigerant from the indoor unit during the pump-down operation, or new refrigerant is drawn into the cooled outdoor heat exchanger during the refrigerant transfer operation, or the transfer of refrigerant is blocked. Therefore, the transfer of refrigerant to the indoor unit is suppressed.

[0016] The seventh aspect of the air conditioning system is an air conditioning system according to any one of the first to sixth aspects, wherein the refrigerant shut-off valve comprises a first refrigerant shut-off valve and a second refrigerant shut-off valve. The first refrigerant shut-off valve shuts off the refrigerant in a liquid state or a gas-liquid two-phase state. The second refrigerant shut-off valve shuts off the refrigerant in a gaseous state.

[0017] In this configuration, the first refrigerant shut-off valve shuts off the liquid refrigerant, while the second refrigerant shut-off valve shuts off the gas refrigerant. Therefore, when a predetermined event occurs, the movement of refrigerant to the indoor unit is more reliably suppressed.

[0018] The air conditioning system of the eighth perspective is the air conditioning system of the seventh perspective, wherein the first refrigerant shutoff valve is an electrically operated expansion valve. The electrically operated expansion valve reduces the refrigerant pressure by adjusting the cross-sectional area of ​​the refrigerant flow path.

[0019] In this configuration, the electrically operated expansion valve, which reduces the refrigerant pressure, also has the function of shutting off the refrigerant during inflow blocking operation. Therefore, the cost of the air conditioning system can be reduced compared to when the electrically operated expansion valve and the first refrigerant shut-off valve are separate valves.

[0020] The air conditioning system of the ninth perspective is the air conditioning system of the seventh perspective, wherein the first refrigerant shut-off valve is an electrically operated shut-off valve. The electrically operated shut-off valve is provided separately from the electrically operated expansion valve that reduces the pressure of the refrigerant. The electrically operated shut-off valve opens or closes the flow path of the refrigerant.

[0021] In this configuration, in addition to an electrically operated expansion valve whose opening degree can be adjusted to reduce the refrigerant pressure, a first refrigerant shut-off valve is provided to shut off the refrigerant during inflow blocking operation. Therefore, by using the highly responsive first refrigerant shut-off valve, the refrigerant can be shut off quickly.

[0022] The tenth air conditioning system is one of the air conditioning systems from the first to the ninth perspectives, and the control unit determines whether the current time is the first season or the second season, in which the probability of the air conditioning system being used for heating operation is lower compared to the first season. The control unit performs an inflow blocking operation when an event occurs in the first season, and does not perform an inflow blocking operation when an event occurs in the second season.

[0023] With this configuration, for example, in the first season, which is autumn or winter, the inflow blocking operation is performed when an event occurs, while in the second season, which is spring or summer, the inflow blocking operation is not performed even when an event occurs. Since the inflow blocking operation is not performed during seasons when there is a high probability that refrigerant is present on the indoor unit side, damage to the refrigerant shutoff valve can be suppressed.

[0024] The air conditioning system of the 11th perspective is the air conditioning system of the 10th perspective, further comprising an outside temperature sensor for detecting the outside temperature. The control unit determines, based on the outside temperature, whether the current time of year is the first season or the second season.

[0025] With this configuration, the determination of whether it is the first or second season is made based on the outside temperature. Therefore, the control unit does not need to have a clock for the determination.

[0026] The twelfth aspect air conditioning system is one of the first to eleventh aspects air conditioning systems, wherein the indoor unit of the heat pump and the gas furnace are arranged along a common airflow path.

[0027] In this configuration, the gas furnace, which could be an ignition source, shares an airflow path with the indoor heat exchanger, which may leak refrigerant. However, since there is little risk of refrigerant flowing into the indoor unit, the occurrence of ignition of flammable refrigerant can be suppressed.

[0028] The air conditioning system of the 13th perspective is an air conditioning system of any one of the 12th perspectives, wherein the heat pump has a four-way switching valve. The four-way switching valve is for performing heating operation in addition to cooling operation.

[0029] In this configuration, the heat pump has a four-way switching valve. Therefore, depending on the situation, either the heat pump or the gas furnace can be assigned to perform the heating operation.

[0030] The air conditioning system of the 14th perspective is an air conditioning system of any one of the 12th perspectives, wherein the heat pump does not have a four-way switching valve.

[0031] With this configuration, the heat pump does not have a four-way switching valve. Therefore, the air conditioning system can be constructed at a low cost.

[0032] This is a schematic diagram showing an installation example of an air conditioning system 90 according to one embodiment. This is a schematic diagram showing the configuration of the air conditioning system 90 according to one embodiment. This is a flowchart showing the control of the first inflow blocking operation (pump-down operation). This is a flowchart showing the control of the second inflow blocking operation (refrigerant transfer operation). This is a flowchart showing the control of the third inflow blocking operation (refrigerant shut-off operation). This is a flowchart showing the safety assurance control for the air conditioning system 90 according to one embodiment. This is a flowchart showing the safety assurance control according to the first modified example. This is a flowchart showing the safety assurance control according to the second modified example. This is a flowchart showing the safety assurance control according to the third modified example.

[0033] (1) Example of installation of the air conditioning system 90 Figure 1 shows an example of installation of the air conditioning system 90 according to one embodiment of the present disclosure. The air conditioning system 90 is installed in building B. Building B has a basement L0, a first floor L1, and a second floor L2. Basement L0 contains a basement R0. First floor L1 contains rooms R1 and R2. Second floor L2 contains rooms R3 and R4. Rooms R1 to R4 are the living spaces of the users.

[0034] The air conditioning system 90 includes a heat pump outdoor unit 10, a combined indoor unit 80, refrigerant communication piping 30, a return air duct 91, a supply air duct 92, and a control interface 93. The heat pump outdoor unit 10 is installed outside building B. The combined indoor unit 80 is installed in the basement R0. The heat pump outdoor unit 10 and the combined indoor unit 80 are connected by refrigerant communication piping 30. The combined indoor unit 80 is connected to the return air duct 91 and the supply air duct 92. The control interface 93 is not particularly limited, but for example, it is provided in room R1 on the first floor L1.

[0035] The combined indoor unit 80 performs air conditioning. The indoor air to be conditioned by the combined indoor unit 80 is collected from rooms R1, R2, R3, and R4 via the return air duct 91. The conditioned air released by the combined indoor unit 80 is supplied to rooms R1, R2, R3, and R4 via the supply air duct 92.

[0036] (2) Diagram 2 of the schematic configuration of the air conditioning system 90 shows the configuration of the air conditioning system 90. The heat pump outdoor unit 10 is a device that is in charge of the heat pump and has various refrigerant circuit components and an outdoor unit controller 19. The combined indoor unit 80 is a device that is in charge of both the heat pump and the gas furnace and has a heat pump indoor unit 20, a gas furnace unit 50, a fan unit 60 and an indoor unit controller 89.

[0037] The indoor heat pump unit 20 is connected to the outdoor heat pump unit 10 via the refrigerant communication pipe 30, thereby constituting the heat pump unit 40.

[0038] The outdoor unit controller 19 and the indoor unit controller 89 are both microcomputers composed of a processor, working memory, program memory, and other electrical circuit components. The outdoor unit controller 19 and the indoor unit controller 89 are connected to each other via a communication line 95, thereby forming an air conditioning system controller 99 as a whole.

[0039] The control interface 93 is for exchanging information with the user. The control interface 93 has multiple keys for receiving input from the user. The input may include, for example, the set temperature, operation instructions, and stop instructions. Furthermore, the control interface 93 has a display unit for displaying information about the operating status. The control interface 93 is communicated with the air conditioning system controller 99.

[0040] The combined indoor unit 80 has a housing 80a. Inside the housing 80a, the fan unit 60, the gas furnace unit 50, and the heat pump indoor unit 20 are arranged to align along the path of the airflow AF.

[0041] (3) Detailed configuration of the air conditioning system 90 The heat pump unit 40, gas furnace unit 50, and fan unit 60 will be described below.

[0042] (3-1) Heat pump unit 40 The heat pump unit 40 shown in Figure 2 can perform both cooling and heating operations. The refrigerant R circulating in the refrigerant circuit of the heat pump unit 40 is flammable or toxic, for example, propane. As described above, the heat pump unit 40 consists of a heat pump outdoor unit 10, a heat pump indoor unit 20, and refrigerant connecting piping 30.

[0043] (3-1-1) Heat pump outdoor unit 10 The heat pump outdoor unit 10 is for obtaining hot heat or cold heat from the outdoor air, which is the heat source. The heat pump outdoor unit 10 includes a compressor 11, a four-way switching valve 12, an outdoor heat exchanger 13, an outdoor fan 14, an outdoor expansion valve 15, an outdoor temperature sensor 16, a liquid shut-off valve 17, a gas shut-off valve 18, and an outdoor unit controller 19.

[0044] The compressor 11 has a suction pipe 11a and a discharge pipe 11b. The compressor 11 compresses the refrigerant R in a low-pressure gas state sucked in the suction pipe 11a and discharges the refrigerant R in a high-pressure gas state from the discharge pipe 11b. The four-way switching valve 12 is for switching between cooling operation and heating operation. The four-way switching valve 12 circulates the refrigerant R in the direction of arrow CO by forming the connection shown by the solid line in the figure during the cooling operation. The four-way switching valve 12 circulates the refrigerant R in the direction of arrow HO by forming the connection shown by the broken line in the figure during the heating operation. The outdoor heat exchanger 13 performs heat exchange between the outdoor air and the refrigerant R. The outdoor heat exchanger 13 functions as a condenser or radiator for the refrigerant R during the cooling operation and functions as an evaporator or heat absorber for the refrigerant R during the heating operation. The outdoor fan 14 has an outdoor fan blade 14b and an outdoor fan motor 14m. The outdoor fan 14 promotes the heat exchange of the outdoor heat exchanger 13 by the air flow generated by the outdoor fan blade 14b due to the rotation of the outdoor fan motor 14m. The outdoor expansion valve 15 is an electric expansion valve capable of adjusting the cross-sectional area of the flow path of the refrigerant R according to the control of the outdoor unit controller 19, thereby reducing the pressure of the refrigerant R. The outdoor expansion valve 15 can also close the flow path of the refrigerant R by setting the cross-sectional area of the flow path of the refrigerant R to zero. The outside air temperature sensor 16 acquires the outside air temperature and causes it to be acquired by the outdoor unit controller 19. The liquid shut-off valve 17 and the gas shut-off valve 18 are electric shut-off valves capable of opening or closing the flow path of the refrigerant R according to the control of the outdoor unit controller 19. Further, the liquid shut-off valve 17 and the gas shut-off valve 18 may be manually opened and closed by the installer. The outdoor unit controller 19 controls the compressor 11, the four-way switching valve 12, the outdoor fan motor 14m, the outdoor expansion valve 15, and other actuators not shown in the figure, and acquires the outputs of the outside air temperature sensor 16 and other sensors not shown in the figure.

[0045] (3-1-2) Heat pump indoor unit 20 The heat pump indoor unit 20 is for providing heat or cold to the user by performing air conditioning through heating operation or cooling operation. The heat pump indoor unit 20 has an indoor heat exchanger 23, a refrigerant state sensor 26, and an indoor temperature sensor 27.

[0046] The indoor heat exchanger 23 exchanges heat between the indoor air and the refrigerant R. The indoor heat exchanger 23 functions as an evaporator or a heat absorber of the refrigerant R during the cooling operation, and functions as a condenser or a radiator of the refrigerant R during the heating operation. The indoor heat exchanger 23 is arranged so as to fill an air flow path extending inside the housing 80a of the composite indoor unit 80.

[0047] The refrigerant state sensor 26 detects the state of the refrigerant R near the indoor heat exchanger 23. The state of the refrigerant R is, for example, temperature or pressure. The output of the refrigerant state sensor 26 is acquired by the indoor unit controller 89.

[0048] The indoor temperature sensor 27 acquires the temperature of the indoor area to be air-conditioned. The indoor temperature sensor 27 may be provided at a location separated from the heat pump indoor unit 20. For example, the indoor temperature sensor 27 may be installed in a room R2 (FIG. 1) separated from the basement R0. The output of the indoor temperature sensor 27 is acquired by the indoor unit controller 89 connected to the indoor temperature sensor 27 by wire or wirelessly.

[0049] (3-1-3) Refrigerant connection pipe 30 The refrigerant connection pipe 30 is for guiding the refrigerant R that moves between the heat pump outdoor unit 10 and the heat pump indoor unit 20. The refrigerant connection pipe 30 has a liquid refrigerant connection pipe 31 and a gas refrigerant connection pipe 32. The liquid refrigerant connection pipe 31 guides the refrigerant R in a liquid state or a gas-liquid two-phase state. The gas refrigerant connection pipe 32 guides the refrigerant R in a high-pressure or low-pressure gas state.

[0050] (3-1-4) Operation of the heat pump unit 40 When the heat pump unit 40 performs a cooling operation, the refrigerant R circulates in the direction of arrow CO. In the compressor 11, the refrigerant R is compressed into a high-pressure gas state. In the outdoor heat exchanger 13, the refrigerant R condenses into a liquid state and obtains heat from the outdoor air, which is the heat source, in the process. In the outdoor expansion valve 15, the refrigerant R is depressurized into a gas-liquid two-phase state. In the indoor heat exchanger 23, the refrigerant R evaporates into a low-pressure gas state and provides heat to the user in the process.

[0051] When the heat pump unit 40 is operating in heating mode, the refrigerant R circulates in the direction of arrow HO. In the compressor 11, the refrigerant R is compressed into a high-pressure gas state. In the indoor heat exchanger 23, the refrigerant R condenses into a liquid state, providing heat to the user in the process. In the outdoor expansion valve 15, the refrigerant R is depressurized into a gas-liquid two-phase state. In the outdoor heat exchanger 13, the refrigerant R evaporates into a low-pressure gas state, acquiring heat from the outdoor air, which is the heat source, in the process.

[0052] (3-2) Gas Furnace Unit 50 The gas furnace unit 50 shown in Figure 2 performs heating operation by burning a combustible fuel gas FG such as natural gas. The gas furnace unit 50 has an air supply pipe 51, a furnace fan 52, a combustion chamber 53, a gas burner 54, a fuel gas supply pipe 55, a fuel control valve 56, a furnace heat exchanger 57, an exhaust header 58, and an exhaust pipe 59.

[0053] The air supply pipe 51 supplies air AS to the combustion chamber 53. The furnace fan 52 adjusts the amount of air AS supplied to the combustion chamber 53 according to the control of the indoor unit controller 89. The combustion chamber 53 mixes air AS and fuel gas FG. The gas burner 54 burns the mixture of air AS and fuel gas FG contained in the combustion chamber 53. The fuel gas supply pipe 55 supplies fuel gas FG to the combustion chamber 53. The fuel control valve 56 adjusts the amount of fuel gas FG supplied to the combustion chamber 53 according to the control of the indoor unit controller 89. The furnace heat exchanger 57 transfers the heat from the mixture of air AS and fuel gas FG heated by combustion in the combustion chamber 53 to the indoor air. The exhaust header 58 connects the furnace heat exchanger 57 to the exhaust pipe 59. The exhaust pipe 59 discharges the exhaust gas WG that has passed through the furnace heat exchanger 57.

[0054] (3-3) Fan Unit 60 The fan unit 60 is located in the lower part of the internal space of the housing 80a of the composite indoor unit 80. The fan unit 60 has a common fan 61. The common fan 61 generates an airflow AF that moves from bottom to top in the internal space of the housing 80a in accordance with the control of the indoor unit controller 89.

[0055] As described above, within the enclosure 80a, the fan unit 60, the gas furnace unit 50, and the heat pump indoor unit 20 are arranged to align along the path of the airflow AF. Therefore, the airflow AF generated by the common fan 61 passes through both the furnace heat exchanger 57 and the indoor heat exchanger 23. The airflow AF can perform heat exchange in either the furnace heat exchanger 57 or the indoor heat exchanger 23. After that, the airflow AF passes through the supply air duct 92 (Figure 1) and is delivered to the user.

[0056] (4) Safety control of the air conditioning system 90 (4-1) Heating means The air conditioning system 90 in Figure 2 has two means for performing heating operation. The first heating means is a heat pump unit 40, and the second heating means is a gas furnace unit 50.

[0057] The heat pump unit 40 is capable of performing relatively energy-efficient heating operations. However, because the heat pump unit 40 needs to obtain heat from the outside air, which is the heat source, it may not be able to provide sufficient heating performance when the outside air temperature is low.

[0058] On the other hand, the gas furnace unit 50 obtains heat by burning fuel gas FG, so it can provide heating performance regardless of the outside temperature. However, the energy efficiency in the heating operation is not very high. In addition, the heating operation of the gas furnace unit 50 is accompanied by the generation of exhaust gas WG.

[0059] In the air conditioning system 90, the air conditioning system controller 99 selects the optimal one from two types of heating means. In other words, it is not usually necessary to select one of the two types of heating means according to input from the user via the control interface 93. The air conditioning system 90 ensures heating capacity by operating the gas furnace unit 50 for heating when the outside air temperature is below a predetermined threshold. On the other hand, the air conditioning system 90 improves energy efficiency by operating the heat pump unit 40 for heating when the outside air temperature is the same as or higher than a predetermined threshold.

[0060] Therefore, when a season arrives in which the outside temperature is low enough to require frequent use of the gas furnace unit 50, the heat pump unit 40 may remain unused for an extended period. In this case, the refrigerant circuit of the heat pump unit 40 will have extremely limited opportunities for refrigerant R circulation. The combined indoor unit 80 is located near the user's space. Therefore, from the perspective of ensuring user safety, it is preferable to minimize the occurrence of flammable or toxic refrigerant R accumulating in the heat pump indoor unit 20 of the combined indoor unit 80 for extended periods.

[0061] (4-2) Preliminary Events The air conditioning system controller 99 of the air conditioning system 90 detects the presence or absence of preliminary events that suggest the possibility of refrigerant R accumulating in the combined indoor unit 80 for a long period of time, in order to avoid such accumulation. The following are examples of preliminary events that can be used.

[0062] [First Precautionary Event] The air conditioning system controller 99 receives a command to end the cooling operation. [Second Precautionary Event] The air conditioning system controller 99 stops the compressor 11 during the cooling operation. [Third Precautionary Event] The air conditioning system controller 99 receives a command to start the heating operation after the cooling operation has ended. The first precautionary event means the end of the cooling operation. For example, the first precautionary event occurs when the heat pump unit 40 is performing a cooling operation and the user inputs an instruction to end the cooling operation to the control interface 93. The second precautionary event means thermo-off control during the cooling operation. For example, the second precautionary event occurs when the heat pump unit 40 is performing a cooling operation and the air conditioning system controller 99 decides to stop the cooling operation based on the output of the indoor temperature sensor 27 and the set temperature input from the control interface 93. The third precautionary event means the start of the heating operation after the cooling operation. For example, the third preliminary event occurs, for instance, when the season changes from summer to winter, and the user uses the control interface 93 to input a command to start heating operation to the air conditioning system 90, which had been operating in cooling mode.

[0063] (4-3) Inflow blocking operation The air conditioning system controller 99 of the air conditioning system 90 performs an inflow blocking operation when it detects a preliminary event. The inflow blocking operation is an operation that blocks the inflow of refrigerant R into the heat pump indoor unit 20, or a more effective operation that eliminates the accumulation of refrigerant R in the heat pump indoor unit 20.

[0064] During the inflow blocking operation, control is performed to close the refrigerant shut-off valve. Here, the term "refrigerant shut-off valve" refers to a valve that shuts off the circulation path of the refrigerant R, and is a general term for the "first refrigerant shut-off valve" and the "second refrigerant shut-off valve". The term "first refrigerant shut-off valve" refers to a valve that shuts off the refrigerant R in a liquid state or a gas-liquid two-phase state, and includes at least one of the outdoor expansion valve 15 and the liquid shut-off valve 17. The term "second refrigerant shut-off valve" refers to a valve that shuts off the refrigerant R in a gaseous state, and includes at least the gas shut-off valve 18.

[0065] The following are some examples of actions that can be used to block inflow:

[0066] [First Inflow Blocking Operation] Pump-down Operation [Second Inflow Blocking Operation] Refrigerant Transfer Operation [Third Inflow Blocking Operation] Refrigerant Shut-off Operation The pump-down operation of the first inflow blocking operation is an operation to extract the refrigerant R from inside the heat pump indoor unit 20 and store it in the heat pump outdoor unit 10. Figure 3 is a flowchart of the control of the first inflow blocking operation. In step S10, the first inflow blocking operation is started. In step S11, the air conditioning system controller 99 closes the first refrigerant shut-off valve (outdoor expansion valve 15 or liquid shut-off valve 17). Next, in steps S12 to S14, the air conditioning system controller 99 operates the compressor 11 for a predetermined time. Specifically, in step S12, the air conditioning system controller 99 starts operating the compressor 11. In step S13, it is determined whether a predetermined time Δt1 has elapsed since the start of operation of the compressor 11. If time Δt1 has not yet elapsed (S13: NO), the process returns to step S13 again. If time Δt1 has already elapsed (S13: YES), the process proceeds to step S14. In step S14, the air conditioning system controller 99 stops the operation of the compressor 11. During the operation of the compressor 11 for time Δt1, the refrigerant R contained in the indoor heat exchanger 23 is drawn into the compressor 11. In step S15, the air conditioning system controller 99 closes the second refrigerant shut-off valve (gas shut-off valve 18). Finally, in step S16, the first inflow blocking operation is completed. Note that during the first inflow blocking operation, the air conditioning system controller 99 may not only operate the compressor 11 but also rotate the common fan 61.

[0067] The refrigerant transfer operation of the second inflow blocking operation is an operation to move the refrigerant R located in the heat pump indoor unit 20 to the heat pump outdoor unit 10 without operating the compressor 11. Figure 4 is a flowchart of the control of the second inflow blocking operation. In step S20, the second inflow blocking operation is started. In step S21, the air conditioning system controller 99 closes the liquid-side first refrigerant shutoff valve. Next, in steps S22 to S24, the air conditioning system controller 99 operates the common fan 61 for a predetermined time without operating the compressor 11. Specifically, in step S22, the air conditioning system controller 99 starts rotating the common fan 61. In step S23, it is determined whether a predetermined time Δt2 has elapsed since the start of rotation of the common fan 61. If time Δt2 has not yet elapsed (S23: NO), the process returns to step S23. If time Δt2 has already elapsed (S23: YES), the process proceeds to step S24. In step S24, the air conditioning system controller 99 stops the rotation of the common fan 61. The rotation of the common fan 61 over time Δt2 promotes the evaporation of the gas-liquid two-phase refrigerant R, which is largely contained in the indoor heat exchanger 23, and the refrigerant R, now in a low-pressure gaseous state, moves to the heat pump outdoor unit 10. In step S25, the air conditioning system controller 99 closes the second refrigerant shutoff valve on the gas side. Finally, in step S26, the second inflow blocking operation is completed.

[0068] The third inflow blocking operation, which involves shutting off the refrigerant, prevents further inflow of refrigerant R into the heat pump indoor unit 20 by blocking the path of refrigerant R. Figure 5 is a flowchart of the control of the third inflow blocking operation. In step S30, the third inflow blocking operation is initiated. In step S31, the air conditioning system controller 99 closes the first refrigerant shut-off valve on the liquid side. In step S32, the air conditioning system controller 99 closes the second refrigerant shut-off valve on the gas side. Finally, in step S33, the third inflow blocking operation is terminated.

[0069] (4-4) Control flow diagram 6 shows the processing flow of safety assurance control performed by the air conditioning system controller 99. In step S100, safety assurance control is started, for example, when the air conditioning system 90 is started. In step S101, it is determined whether the air conditioning system controller 99 has already detected a preliminary event. The preliminary event to be detected here is, for example, at least one of the first preliminary event, second preliminary event, and third preliminary event described above. If no preliminary event has been detected (S101: NO), the process returns to step S101. If a preliminary event has already been detected (S101: YES), the process proceeds to step S102. In step S102, the air conditioning system controller 99 performs an inflow blocking operation. The inflow blocking operation performed here is, for example, one of the first inflow blocking operation, second inflow blocking operation, or third inflow blocking operation described above. Once the inflow blocking operation is completed, the process returns to step S101 again.

[0070] (5) Features (5-1) In the air conditioning system 90, an inflow blocking operation is performed when a preliminary event occurs. Examples of preliminary events include the first preliminary event (end of cooling operation), the second preliminary event (thermo-off control during cooling operation), and the third preliminary event (start of heating operation after cooling operation). The inflow blocking operation can be the first inflow blocking operation (pump-down operation), the second inflow blocking operation (refrigerant transfer operation), or the third inflow blocking operation (refrigerant shut-off operation). Therefore, when a preliminary event occurs, the flammable or toxic refrigerant R will not flow into the combined indoor unit 80. This improves the safety of users who receive conditioned air from the combined indoor unit 80.

[0071] (5-2) In the air conditioning system 90, the air conditioning system controller 99 always performs an inflow blocking operation whenever a preliminary event occurs. Therefore, the movement of refrigerant R to the combined indoor unit 80 is further suppressed.

[0072] (5-3) In the inflow blocking operation, the first refrigerant shutoff valve (outdoor expansion valve 15 or liquid shutoff valve 17) shuts off the refrigerant R in a liquid state or a gas-liquid two-phase state, and the second refrigerant shutoff valve (gas shutoff valve 18) shuts off the refrigerant R in a gaseous state. Therefore, when a preliminary event occurs, the movement of refrigerant R to the combined indoor unit 80 is suppressed.

[0073] The first refrigerant shut-off valve may be both the outdoor expansion valve 15 and the liquid shut-off valve 17. In this case, the refrigerant path on the liquid side is shut off in two ways, so the movement of refrigerant R to the combined indoor unit 80 is more reliably suppressed.

[0074] Alternatively, the first refrigerant shutoff valve may consist only of the outdoor expansion valve 15. In this case, the liquid shutoff valve 17 does not need to have a controlled opening and closing function, thus reducing the cost of the air conditioning system 90.

[0075] Alternatively, the first refrigerant shut-off valve may consist only of a liquid shut-off valve 17. In this case, by using a liquid shut-off valve 17 that has good responsiveness to control, the refrigerant R can be shut off quickly.

[0076] (5-4) In the air conditioning system 90, both the heat pump indoor unit 20 and the gas furnace unit 50 are located in the path of the airflow AF. Therefore, the gas furnace unit 50, which could be an ignition source, shares the path of the airflow AF with the indoor heat exchanger 23, which may leak refrigerant R. However, since there is little risk of refrigerant R flowing into the combined indoor unit 80, the occurrence of a situation in which the flammable refrigerant ignites can be suppressed.

[0077] (5-5) In the air conditioning system 90, the heat pump unit 40 has a four-way switching valve 12. Therefore, depending on the situation, the heating operation can be assigned to either the heat pump unit 40 or the gas furnace unit 50.

[0078] (6) Modifications (6-1) First Modification In the above-described embodiment, the inflow blocking operation is performed once in response to the detection of a preliminary event. Alternatively, the inflow blocking operation may be performed multiple times in response to the detection of a preliminary event.

[0079] Figure 7 shows the processing flow of the safety assurance control according to this modified example. In step S200, safety assurance control is started. In step S201, it is determined whether the air conditioning system controller 99 has already detected a preliminary event. If no preliminary event has been detected (S201: NO), the process returns to step S201. If a preliminary event has already been detected (S201: YES), the process proceeds to step S202. In step S202, the air conditioning system controller 99 performs the first inflow blocking operation. In step S203, it is determined whether a predetermined time ΔT has elapsed since the end of the inflow blocking operation. If time ΔT has not yet elapsed (S203: NO), the process returns to step S203. If time ΔT has already elapsed (S203: YES), the process proceeds to step S204. In step S204, the air conditioning system controller 99 performs the second inflow blocking operation. Once the inflow blocking operation is completed, the process returns to step S201.

[0080] With this configuration, if a small amount of refrigerant R passes through the refrigerant shutoff valve and moves toward the combined indoor unit 80 after the completion of the first inflow blocking operation in step S202, the second inflow blocking operation is performed in step S204. Therefore, the movement of refrigerant R toward the combined indoor unit 80 is further suppressed.

[0081] (6-2) Second Modification In the first modification described above, the start condition for the second inflow operation is the elapsed time ΔT. Alternatively, the start condition for the second inflow operation may be the state of the refrigerant R. In this case, the refrigerant state sensor 26 shown in Figure 2 may acquire the state of the refrigerant R, which is the start condition for the second inflow operation.

[0082] Figure 8 shows the processing flow of the safety assurance control according to this modified example. In step S300, safety assurance control is started. In step S301, it is determined whether the air conditioning system controller 99 has already detected a preliminary event. If no preliminary event has been detected (S301: NO), the process returns to step S301. If a preliminary event has already been detected (S301: YES), the process proceeds to step S302. In step S302, the air conditioning system controller 99 performs the first inflow blocking operation. In step S303, it is determined whether the output of the refrigerant state sensor 26 satisfies predetermined conditions. If the output of the refrigerant state sensor 26 does not satisfy predetermined conditions (S303: NO), the process returns to step S303. If the output of the refrigerant state sensor 26 satisfies predetermined conditions (S303: YES), the process proceeds to step S304. In step S304, the air conditioning system controller 99 performs the second inflow blocking operation. Once the inflow blocking operation is complete, the process returns to step S301.

[0083] The above-mentioned predetermined conditions only need to be such that it can be estimated that a relatively large amount of refrigerant R remains in the heat pump indoor unit 20. For example, the above-mentioned predetermined conditions may be considered satisfied when the output of the refrigerant state sensor 26 indicates that the pressure of the refrigerant R is greater than a predetermined threshold.

[0084] In this configuration, a second inflow blocking operation is performed in step S304 based on the output of the refrigerant state sensor 26. When the refrigerant R passes through the refrigerant shut-off valve, which should be closed, and moves from the heat pump outdoor unit 10 to the heat pump indoor unit 20, the air conditioning system controller 99 can detect this phenomenon based on the output of the refrigerant state sensor 26. Therefore, the execution of the second inflow blocking operation can more strictly suppress the movement of the refrigerant R to the heat pump indoor unit 20.

[0085] (6-3) Third Modification In the above embodiment, the inflow blocking operation is always performed when a preliminary event is detected. Alternatively, when performing the inflow blocking operation, other conditions may be added in addition to the detection of a preliminary event.

[0086] Figure 9 shows the processing flow of the safety assurance control according to this modified example. In step S400, safety assurance control is started. In step S401, it is determined whether the air conditioning system controller 99 has already detected a preliminary event. If no preliminary event has been detected (S401: NO), the process returns to step S401. If a preliminary event has already been detected (S401: YES), the process proceeds to step S402. In step S402, the air conditioning system controller 99 obtains the outside temperature from the outside temperature sensor 16. In step S403, the air conditioning system controller 99 determines the current season based on the outside temperature. The seasons are classified into first season and second season. The first season is the season in which the probability of the air conditioning system 90 being used for heating operation is high, and is typically autumn or winter. The second season is the season in which the probability of the air conditioning system 90 being used for heating operation is low compared to the first season, and is typically spring or summer. The process proceeds to step S404. If the current season is the second season (S404: second season), the process returns to step S401. On the other hand, if the current season is the first season (S404: first season), the process proceeds to step S405. In step S405, the air conditioning system controller 99 performs an inflow blocking operation. Once the inflow blocking operation is complete, the process returns to step S401.

[0087] In this configuration, the inflow blocking operation is performed when a preliminary event occurs during the first season (autumn or winter), but the inflow blocking operation is not performed even when a preliminary event occurs during the second season (spring or summer). Since the inflow blocking operation is not performed during the second season, when the presence of refrigerant R in the combined indoor unit 80 is highly likely, damage to the refrigerant shutoff valve can be suppressed. Furthermore, since the season is determined based on the outside temperature, the air conditioning system controller 99 does not need to have a clock for determination.

[0088] (6-4) Fourth Modification In the above embodiment, since the heat pump unit 40 has a four-way switching valve 12, the heat pump unit 40 can perform both cooling and heating operations. Alternatively, the heat pump unit 40 does not need to have a four-way switching valve 12. In this case, in the air conditioning system 90, the heat pump unit 40 performs only cooling operations, and the gas furnace unit 50 performs heating operations. Since the air conditioning system 90 does not have a four-way switching valve 12, it can be constructed at a low cost.

[0089] <Conclusion> The embodiments of this disclosure have been described above, but it should be understood that various modifications to the form and details are possible without departing from the purpose and scope of this disclosure as described in the claims.

[0090] 10: Heat pump outdoor unit (outdoor unit) 11: Compressor 12: Four-way switching valve 13: Outdoor heat exchanger 14: Outdoor fan 15: Outdoor expansion valve (refrigerant shut-off valve, first refrigerant shut-off valve, electric expansion valve) 16: Outdoor temperature sensor 17: Liquid shut-off valve (refrigerant shut-off valve, first refrigerant shut-off valve, electric shut-off valve) 18: Gas shut-off valve (refrigerant shut-off valve, second refrigerant shut-off valve) 19: Outdoor unit controller 20: Heat pump indoor unit (indoor unit) 23: Indoor heat exchanger 26: Refrigerant state sensor 27: Indoor temperature sensor 30: Refrigerant connecting piping 31: Liquid refrigerant connecting piping 32: Gas refrigerant connecting piping 40: Heat pump unit (heat pump) 50: Gas furnace unit (gas furnace) 80: Combined indoor unit 89: Indoor unit controller 90 : Air conditioning system 93 : Control interface 99 : Air conditioning system controller (control unit) AF : Airflow AS : Air FG : Fuel gas R : Refrigerant WG : Exhaust gas

[0091] Japanese Patent Publication No. 2015-218940

Claims

1. An air conditioning system (90) comprising: a heat pump (40) that performs cooling operation using a flammable or toxic refrigerant (R); a gas furnace (50) that performs heating operation by combustion of a fuel gas (FG); and a control unit (99), wherein the heat pump has an outdoor unit (10) and an indoor unit (20), the outdoor unit has a compressor (11), an outdoor heat exchanger (13), and an outdoor fan (14), the indoor unit has an indoor heat exchanger (23), the heat pump further has refrigerant shut-off valves (15, 17, 18) that shut off the refrigerant, and the control unit closes the refrigerant shut-off valves to perform an inflow blocking operation to prevent the refrigerant from flowing into the indoor unit when a predetermined event occurs.

2. The air conditioning system according to claim 1, wherein the event is at least one of the following: the control unit receiving a command to end the cooling operation; the control unit stopping the compressor during the cooling operation; or the control unit receiving a command to start the heating operation after the cooling operation has ended.

3. The air conditioning system according to claim 1 or 2, wherein the control unit performs the inflow blocking operation a second time after a predetermined period of time has elapsed since the first inflow blocking operation when the event occurs.

4. The air conditioning system according to any one of claims 1 to 3, wherein the heat pump further comprises a refrigerant state sensor (26) for detecting the state of the refrigerant, and the control unit performs the inflow blocking operation for the first time when the event occurs, and then performs the inflow blocking operation for the second time based on the output of the refrigerant state sensor.

5. The air conditioning system according to any one of claims 1 to 4, wherein the control unit performs the inflow blocking operation each time the event occurs.

6. The air conditioning system according to any one of claims 1 to 5, wherein the inflow blocking operation is at least one of the following: a pump-down operation involving the operation of the compressor and the closing of the refrigerant shut-off valve; a refrigerant transfer operation involving the operation of the outdoor fan and the closing of the refrigerant shut-off valve; or a refrigerant shut-off operation involving the closing of the refrigerant shut-off valve.

7. The air conditioning system according to any one of claims 1 to 6, wherein the refrigerant shutoff valve comprises a first refrigerant shutoff valve (15, 17) for shutting off the refrigerant in a liquid state or a gas-liquid two-phase state, and a second refrigerant shutoff valve (18) for shutting off the refrigerant in a gaseous state.

8. The air conditioning system according to claim 7, wherein the first refrigerant shutoff valve is an electrically operated expansion valve (15) that reduces the pressure of the refrigerant by adjusting the cross-sectional area of ​​the flow path of the refrigerant.

9. The air conditioning system according to claim 7, wherein the first refrigerant shutoff valve is an electric shutoff valve (17) that opens or closes the flow path of the refrigerant, and is provided separately from the electric expansion valve (15) that reduces the pressure of the refrigerant.

10. The control unit determines whether the current time is the first season or the second season in which the probability of the air conditioning system being used for heating operation is lower compared to the first season, and the control unit performs the inflow blocking operation when the event occurs in the first season and does not perform the inflow blocking operation when the event occurs in the second season, according to any one of claims 1 to 9.

11. An air conditioning system according to claim 10, further comprising an outside temperature sensor (16) for detecting the outside temperature, wherein the control unit determines, based on the outside temperature, whether the current time is the first season or the second season.

12. The air conditioning system according to any one of claims 1 to 11, wherein the indoor unit of the heat pump and the gas furnace are arranged along a common airflow (AF) path.

13. The air conditioning system according to any one of claims 1 to 12, wherein the heat pump has a four-way switching valve (12) for performing the heating operation in addition to the cooling operation.

14. The air conditioning system according to any one of claims 1 to 12, wherein the heat pump does not have a four-way switching valve (12).

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