Air conditioning system, control device, control method and program

Abstract

To suppress the repeated on / off cycles of the ventilation system. [Solution] An air conditioning system (201) comprising: a ventilation device (1) that takes in air from outside a target space (SP), passes it through a first heat exchanger (22) and supplies it to the target space, and passes air taken in from the target space through a second heat exchanger (12) and exhausts it to the outside of the target space; an air conditioning device (2) that draws in air from the target space, exchanges heat with a refrigerant flowing through a third heat exchanger (83), and blows the air back into the target space; and a control unit (3) that changes a threshold for the ventilation device to perform cooling or heating operation when transitioning from a first operating mode in which the ventilation device is operated alone to a second operating mode in which both the ventilation device and the air conditioning device are operated.

Description

Technical Field

[0001] The present disclosure relates to an air conditioning system, a control device, a control method, and a program.

Background Art

[0002] Conventionally, there is known an air conditioner in which a heat source side unit having a compressor and a heat source side heat exchanger, a utilization side unit having a utilization side heat exchanger, an intake unit provided with an auxiliary heat exchanger in an intake passage for sucking outdoor air into the room, and an exhaust unit provided with an auxiliary heat exchanger in an exhaust passage for discharging indoor air to the outside are connected by piping.

[0003] During the cooling operation in which the utilization side heat exchanger acts as an evaporator, the auxiliary heat exchanger of the intake unit acts as an evaporator, while the auxiliary heat exchanger of the exhaust unit acts as a condenser. Thereby, the auxiliary heat exchanger of the intake unit acting as an evaporator cools fresh air to prevent the room temperature from rising, while the auxiliary heat exchanger of the exhaust unit acting as a condenser recovers waste heat from the dirty air discharged to the outside, so that the cooling operation efficiency is improved.

[0004] On the other hand, during the heating operation in which the utilization side heat exchanger acts as a condenser, the auxiliary heat exchanger of the intake unit acts as a condenser, while the auxiliary heat exchanger of the exhaust unit acts as an evaporator. Thereby, the auxiliary heat exchanger of the intake unit acting as a condenser heats fresh air to prevent the room temperature from dropping, while the auxiliary heat exchanger of the exhaust unit acting as an evaporator recovers waste heat from the dirty air discharged to the outside, so that the heating operation efficiency is improved.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] Patent Document 1 discloses a configuration that combines an air conditioning system that provides cooling or heating using a heat source unit and a user unit, with a ventilation system that provides ventilation using an intake unit and an exhaust unit. However, Patent Document 1 does not describe how to switch from a mode in which the ventilation system is operated alone to a mode in which both the ventilation system and the air conditioning system are operated.

[0007] When transitioning from a mode in which the ventilation system operates independently to a mode in which both the ventilation system and the air conditioning system operate, the air conditioning system and the ventilation system share the responsibility of handling the heat load of the target space in the transitioned mode. However, if the threshold for the ventilation system to perform cooling or heating operations remains fixed before and after the mode transition, the ventilation system may repeatedly start and stop cooling or heating operations in the transitioned mode. Repeated starting and stopping of the ventilation system leads to a decrease in the energy efficiency of the air conditioning system.

[0008] This disclosure provides an air conditioning system, a control device, a control method, and a program capable of suppressing repeated on / off cycles of a ventilation device. [Means for solving the problem]

[0009] The air conditioning system of the first embodiment is A ventilation device (1) comprising: a first compressor (51); a supply unit (20) which includes a first heat exchanger (22) functioning as a condenser or evaporator and supplies air taken in from outside the target space (SP) through the first heat exchanger; an exhaust unit (10) which includes a second heat exchanger (12) functioning as a condenser or evaporator and exhausts air taken in from the target space through the second heat exchanger and exhausts it to the outside of the target space; and a refrigerant circuit (60) through which the first compressor, the first heat exchanger and the second heat exchanger are connected by refrigerant piping (61) and through which refrigerant flows. An air conditioning system (2) having a third heat exchanger (83) that functions as a condenser or evaporator and a second compressor (71) that compresses a refrigerant, and drawing in air from the target space and blowing out air that has exchanged heat with the refrigerant flowing through the third heat exchanger back into the target space, The air conditioning system (201) includes a control unit (3) that changes a threshold for the ventilation system to perform cooling or heating operation when transitioning from a first operating mode in which the ventilation system is operated independently to a second operating mode in which both the ventilation system and the air conditioning system are operated.

[0010] According to the first embodiment, compared to control that does not change the threshold when transitioning from the first operating mode to the second operating mode, the repeated starting and stopping of the cooling operation or the heating operation of the ventilation device is suppressed in the second operating mode. Since the repeated starting and stopping of the ventilation device is suppressed, the energy-saving performance of the air conditioning system in the first embodiment is ensured.

[0011] The air conditioning system of the second embodiment is the air conditioning system of the first embodiment, The control unit compares the temperature difference between the outside air temperature outside the target space and the target supply air temperature of the ventilation device with the threshold value.

[0012] According to the second embodiment, the criteria for the ventilation device to perform cooling or heating operations can be changed according to the temperature difference.

[0013] The third embodiment of the air conditioning system is the air conditioning system of the second embodiment, The control unit, When transitioning from the first operating mode to the second operating mode, the threshold is changed from the first threshold to the second threshold. When the system transitions from the second operating mode to the first operating mode and the temperature difference reaches the first threshold, the threshold is changed from the second threshold to the first threshold.

[0014] According to the third embodiment, in the first operating mode after transitioning from the second operating mode, repeated starting and stopping of the cooling operation or the heating operation of the ventilation device is suppressed. This is because if the threshold is returned to the first threshold immediately after transitioning from the second operating mode to the first operating mode, there is a risk that the cooling operation or the heating operation of the ventilation device will start and stop.

[0015] The fourth embodiment of the air conditioning system is the second or third embodiment of the air conditioning system, The aforementioned temperature difference is the value obtained by subtracting the target supply air temperature from the ambient air temperature. When the control unit transitions from the first operating mode to the second operating mode, it lowers the threshold for the ventilation device to perform cooling operation.

[0016] According to the fourth embodiment, compared to control in which the threshold is not changed when transitioning from the first operating mode to the second operating mode, the repeated starting and stopping of the cooling operation of the ventilation device is suppressed in the second operating mode. Since the repeated starting and stopping of the cooling operation of the ventilation device is suppressed, the energy-saving performance of the air conditioning system in the fourth embodiment is ensured.

[0017] The fifth embodiment of the air conditioning system is the second or third embodiment of the air conditioning system, The aforementioned temperature difference is the value obtained by subtracting the target supply air temperature from the ambient air temperature. When the control unit transitions from the first operating mode to the second operating mode, it raises the threshold value for the ventilation device to perform heating operation.

[0018] According to the fifth embodiment, compared to control in which the threshold is not changed when transitioning from the first operating mode to the second operating mode, the repeated starting and stopping of the heating operation of the ventilation device is suppressed in the second operating mode. Since the repeated starting and stopping of the heating operation of the ventilation device is suppressed, the energy-saving performance of the air conditioning system in the fifth embodiment is ensured.

[0019] The air conditioning system according to the sixth aspect is the air conditioning system according to any one of the first to fifth aspects, and the transition from the first operation mode to the second operation mode is performed when a period during which a difference between a set temperature of the ventilation device and an internal air temperature in the target space is equal to or greater than a predetermined value exceeds a predetermined period.

[0020] According to the sixth aspect, when a period during which a difference between a set temperature of the ventilation device and an internal air temperature in the target space is equal to or greater than a predetermined value exceeds a predetermined period, there is a risk that the air conditioning capacity for reducing the difference may be insufficient in the first operation mode in which the ventilation device is operated alone. When a period during which a difference between a set temperature of the ventilation device and an internal air temperature in the target space is equal to or greater than a predetermined value exceeds a predetermined period, by shifting from the first operation mode to the second operation mode, the shortage of the air conditioning capacity of the ventilation device can be compensated by the air conditioning capacity of the air conditioner.

[0021] The air conditioning system according to the seventh aspect is the air conditioning system according to any one of the first to fifth aspects, and the transition from the first operation mode to the second operation mode is performed when the air conditioning load of the target space increases beyond a predetermined load.

[0022] According to the seventh aspect, when the air conditioning load of the target space increases beyond a predetermined load, there is a risk that the air conditioning capacity for processing the air conditioning load may be insufficient or may be insufficient in the first operation mode in which the ventilation device is operated alone. When the air conditioning load of the target space increases beyond a predetermined load, by shifting from the first operation mode to the second operation mode, the shortage of the air conditioning capacity of the ventilation device can be compensated by the air conditioning capacity of the air conditioner.

[0023] The air conditioning system according to the eighth aspect is the air conditioning system according to any one of the first to seventh aspects, and the transition from the second operation mode to the first operation mode is performed when the stop time of the second compressor exceeds a predetermined time.

[0024] According to the eighth embodiment, if the stopping time of the second compressor exceeds a predetermined time, it can be said that the air conditioning load of the target space has decreased to the extent that the stopping time of the second compressor exceeds the predetermined time. In this case, if the system remains in the second operating mode, in which both the ventilation device and the air conditioning device are operated, the air conditioning capacity to handle the air conditioning load may be excessive or excessive. By switching from the second operating mode to the first operating mode when the stopping time of the second compressor exceeds a predetermined time, the state of excessive air conditioning capacity to handle the air conditioning load is suppressed, and the energy saving of the air conditioning system of the eighth embodiment is ensured.

[0025] The ninth embodiment of the air conditioning system is an air conditioning system according to any one embodiment of the first to seventh embodiments, The transition from the second operating mode to the first operating mode occurs when the air conditioning load of the target space falls below a predetermined load.

[0026] According to the ninth embodiment, if the air conditioning load of the target space falls below a predetermined load, the air conditioning capacity to handle the air conditioning load may be excessive or excessive if the second operating mode, which operates both the ventilation device and the air conditioning device, is maintained. By switching from the second operating mode to the first operating mode when the air conditioning load of the target space falls below a predetermined load, the state of excessive air conditioning capacity to handle the air conditioning load is suppressed, and the energy-saving performance of the air conditioning system of the ninth embodiment is ensured.

[0027] The control device of the tenth embodiment is A ventilation device (1) comprising: a first compressor (51); a supply unit (20) which includes a first heat exchanger (22) functioning as a condenser or evaporator and supplies air taken in from outside the target space (SP) through the first heat exchanger; an exhaust unit (10) which includes a second heat exchanger (12) functioning as a condenser or evaporator and exhausts air taken in from the target space through the second heat exchanger and exhausts it to the outside of the target space; and a refrigerant circuit (60) through which the first compressor, the first heat exchanger and the second heat exchanger are connected by refrigerant piping (61) and through which refrigerant flows. A control device (3) for controlling an air conditioning system (2) which has a third heat exchanger (83) that functions as a condenser or evaporator and a second compressor (71) that compresses a refrigerant, and which draws in air from the target space and blows out air that has exchanged heat with the refrigerant flowing through the third heat exchanger back into the target space, The control device (3) includes a control circuit (5) that changes a threshold for the ventilation device to perform cooling or heating operation when transitioning from a first operating mode in which the ventilation device is operated independently to a second operating mode in which both the ventilation device and the air conditioning device are operated.

[0028] According to the tenth embodiment, compared to control in which the threshold is not changed when transitioning from the first operating mode to the second operating mode, the repeated starting and stopping of the cooling operation or the heating operation of the ventilation device is suppressed in the second operating mode. Since the repeated starting and stopping of the ventilation device is suppressed, energy saving is ensured for the air conditioning system comprising the ventilation device and the air conditioning device.

[0029] The control method of the 11th embodiment is: A ventilation device (1) comprising: a first compressor (51); a supply unit (20) which includes a first heat exchanger (22) functioning as a condenser or evaporator and supplies air taken in from outside the target space (SP) through the first heat exchanger; an exhaust unit (10) which includes a second heat exchanger (12) functioning as a condenser or evaporator and exhausts air taken in from the target space through the second heat exchanger and exhausts it to the outside of the target space; and a refrigerant circuit (60) through which the first compressor, the first heat exchanger and the second heat exchanger are connected by refrigerant piping (61) and through which refrigerant flows. A method for controlling an air conditioning system (2) having a third heat exchanger (83) that functions as a condenser or evaporator and a second compressor (71) that compresses a refrigerant, the air conditioning system (2) that draws in air from the target space and blows out air that has exchanged heat with the refrigerant flowing through the third heat exchanger back into the target space, This control method involves changing the threshold for the ventilation system to perform cooling or heating operation when transitioning from a first operating mode in which the ventilation system is operated independently to a second operating mode in which both the ventilation system and the air conditioning system are operated.

[0030] According to the eleventh embodiment, compared to control in which the threshold is not changed when transitioning from the first operating mode to the second operating mode, the repeated starting and stopping of the cooling operation or the heating operation of the ventilation device is suppressed in the second operating mode. Since the repeated starting and stopping of the ventilation device is suppressed, energy saving is ensured for the air conditioning system comprising the ventilation device and the air conditioning device.

[0031] The program of the 12th embodiment is A ventilation device (1) comprising: a first compressor (51); a supply unit (20) which includes a first heat exchanger (22) functioning as a condenser or evaporator and supplies air taken in from outside the target space (SP) through the first heat exchanger; an exhaust unit (10) which includes a second heat exchanger (12) functioning as a condenser or evaporator and exhausts air taken in from the target space through the second heat exchanger and exhausts it to the outside of the target space; and a refrigerant circuit (60) through which the first compressor, the first heat exchanger and the second heat exchanger are connected by refrigerant piping (61) and through which refrigerant flows. A program to be executed by a control unit (3) that controls an air conditioning system (2) having a third heat exchanger (83) that functions as a condenser or evaporator and a second compressor (71) that compresses a refrigerant, and which draws in air from the target space and blows out air that has exchanged heat with the refrigerant flowing through the third heat exchanger back into the target space, This program causes the control unit to perform a process to change the threshold for the ventilation system to perform cooling or heating operation when transitioning from a first operating mode in which the ventilation system is operated independently to a second operating mode in which both the ventilation system and the air conditioning system are operated.

[0032] According to the twelfth embodiment, compared to control in which the threshold is not changed when transitioning from the first operating mode to the second operating mode, the repeated starting and stopping of the cooling operation or the heating operation of the ventilation device is suppressed in the second operating mode. Since the repeated starting and stopping of the ventilation device is suppressed, energy saving is ensured for the air conditioning system comprising the ventilation device and the air conditioning device. [Brief explanation of the drawing]

[0033] [Figure 1] This figure shows an example configuration of an air conditioning system according to one embodiment. [Figure 2] This is a refrigerant circuit diagram showing an example of the configuration of an air conditioning system. [Figure 3] This is a state transition diagram illustrating an example of a control method that can suppress repeated starting and stopping of the cooling operation of a ventilation system. [Figure 4] This is a state transition diagram illustrating an example of a control method that can suppress repeated starting and stopping of heating operation in a ventilation system. [Figure 5] This flowchart shows an example of how to switch the operation of a ventilation system. [Figure 6] This flowchart shows an example of how to change the threshold for a ventilation system to operate in cooling mode. [Figure 7] This flowchart shows an example of how to change the threshold for a ventilation system to perform heating operation. [Figure 8] This is an example of a hardware configuration diagram for a control device. [Modes for carrying out the invention]

[0034] The embodiments will be described below.

[0035] Figure 1 shows an example configuration of an air conditioning system according to one embodiment. The air conditioning system 201 shown in Figure 1 is a system that provides air conditioning in a target space SP contained within a building such as a house, office building, factory, or facility. The target space SP is, for example, an indoor space such as a living room in a building BL. The air conditioning system 201 comprises a ventilation device 1, an air conditioning device 2, and a control device 3.

[0036] The air conditioning system 201 switches the operating state of the ventilation device 1 and the air conditioning device 2 when a command is input to a remote control 4, which is installed inside or outside the target space SP. The control device 3 controls the operating state of the ventilation device 1 and the air conditioning device 2 according to the command input to the remote control 4 (commands related to starting / stopping, operation type, set temperature, set airflow, etc.).

[0037] Next, we will explain the configuration of the air conditioning system 201 in more detail.

[0038] Ventilation device 1 ventilates the target space SP. Ventilation device 1 adjusts the temperature of the outside air OA taken in from outside and supplies it to the target space SP as supply air SA, and also discharges the air taken in from the target space SP (return air RA) to the outside as exhaust air EA. Ventilation device 1 is also called an outside air treatment device.

[0039] In the example shown in Figure 1, the ventilation system 1 is a device that recovers the heat (exhaust heat) from the exhaust EA from the target space SP to the outdoors and reuses it for supplying air to the target space SP. The ventilation system 1 recovers the waste heat during disposal instead of simply discarding it and reuses it to adjust the temperature of the air supplied to the target space SP, thus improving energy efficiency. The ventilation system 1 comprises an air supply unit 20, an exhaust unit 10, a compressor unit 50, and a refrigerant circuit 60.

[0040] The air supply unit 20 includes an outside air heat exchanger 22 and an air supply fan 21. The air supply unit 20 may also include a sensor 24. The air supply unit 20 drives the air supply fan 21 to take in outside air OA from outside the building BL and exchanges heat between the outside air OA and the refrigerant flowing through the outside air heat exchanger 22. The outside air OA that has passed through the outside air heat exchanger 22 is cooled or heated by heat exchange with the refrigerant and supplied to the target space SP as air supply SA.

[0041] The outside air heat exchanger 22 exchanges heat between the incoming outside air OA and the refrigerant flowing through the outside air heat exchanger 22. The outside air heat exchanger 22 is, for example, a cross-fin tube type or a microchannel type heat exchanger. The outside air heat exchanger 22 is an example of a first heat exchanger that functions as a condenser or evaporator.

[0042] The supply air fan 21 is a blower that takes in outside air OA into the supply air unit 20 and sends it to the supply air duct P1 via the outside air heat exchanger 22. The supply air fan 21 has a fan motor. The rotation speed of the supply air fan 21 is adjusted by inverter control of the fan motor, so the airflow rate of the supply air SA to the target space SP is variable.

[0043] Sensor 24 is an outside air temperature sensor that detects the temperature of the outside air OA taken into the air supply unit 20. Sensor 24 may also detect the humidity of the outside air OA taken into the air supply unit 20. The air supply unit 20 may also further include an air supply temperature sensor that detects the temperature of the air supply SA (air supply temperature), and a sensor that detects the surface temperature of the outside air heat exchanger 22 or the temperature of the refrigerant flowing through the outside air heat exchanger 22. In this embodiment, sensor 24 is installed in the air supply unit 20, but if the compressor unit 50 is located outside the room, it may be installed in the compressor unit 50.

[0044] The air supply unit 20 is connected to an air intake port 94 that takes in outside air OA from outside the building BL, and to an air supply port 92 that supplies supply air SA to the target space SP. In the air conditioning system 201, the air supply unit 20 is connected to the air supply port 92 via an air supply duct P1.

[0045] The air supply duct P1 is an air supply passage for supplying heated or cooled air SA from the air supply unit 20 to the target space SP through the air supply port 92. In the air conditioning system 201, the air supply port 92 is located in the ceiling of the target space SP. The air supply port 92 may be located in other places such as the wall or floor. The air supply duct P1 is an example of a first air passage.

[0046] One end of the air supply duct P1 is connected to the air supply unit 20 so that outside air OA flows into the air supply unit 20 when the air supply fan 21 is driven. The other end of the air supply duct P1 is connected to an air supply port 92 formed in the target space SP so as to communicate with the target space SP. A damper for adjusting the airflow is provided in the air supply port 92. There may be one or more air supply ports 92.

[0047] The air supply unit 20 may be connected to the air intake port 94 via a duct, or it may be connected directly to the air intake port 92 without going through the air supply duct P1. Alternatively, the air intake port 92 may not have a damper, and a fan unit may be connected to the air supply duct P1. The fan unit may comprise a fan, a casing housing the fan, an airflow detection unit for detecting airflow, and a control unit for controlling the fan speed. The fan unit may be configured such that the control unit controls the fan speed so that the airflow detected by the airflow detection unit matches the airflow instruction value instructed by the control device 3.

[0048] The exhaust unit 10 includes a return air heat exchanger 12 and an exhaust fan 11. The exhaust unit 10 may also be equipped with a sensor 14. The exhaust unit 10 takes in return air RA from the target space SP by driving the exhaust fan 11 and exchanges heat between the return air RA and the refrigerant flowing through the return air heat exchanger 12. The return air RA that has passed through the return air heat exchanger 12 is cooled or heated by heat exchange with the refrigerant and discharged to the outside of the building BL as exhaust EA.

[0049] The return air heat exchanger 12 exchanges heat between the return air RA and the refrigerant flowing through the return air heat exchanger 12. The return air heat exchanger 12 is, for example, a cross-fin tube type or a microchannel type heat exchanger. The return air heat exchanger 12 is an example of a second heat exchanger that functions as a condenser or evaporator.

[0050] The exhaust fan 11 is a blower that takes in return air RA into the exhaust unit 10 and sends it to the exhaust port 95 via the return air heat exchanger 12. The exhaust air EA is discharged from the exhaust port 95. The exhaust fan 11 has a fan motor. The exhaust fan 11 rotates when the fan motor is inverter controlled.

[0051] Sensor 14 is a return air temperature sensor that detects the temperature of the return air RA taken into the exhaust unit 10. Sensor 14 may also detect the humidity of the return air RA taken into the exhaust unit 10. The exhaust unit 10 may also be further equipped with an exhaust temperature sensor that detects the temperature of the exhaust EA taken into the exhaust unit 10 (exhaust temperature), and a sensor that detects the surface temperature of the return air heat exchanger 12 or the temperature of the refrigerant flowing through the return air heat exchanger 12. In this embodiment, sensor 14 is installed in the exhaust unit 10, but it is sufficient for it to be able to detect the room temperature, and it may also be installed in the remote control 4.

[0052] The exhaust unit 10 is connected to a return air port 91 that takes in return air RA from the target space SP, and to an exhaust port 95 that discharges exhaust air EA to the outside of the building BL. In the air conditioning system 201, the exhaust unit 10 is connected to the return air port 91 via a return air duct P2.

[0053] The return air duct P2 is a return air passage for sending air (return air RA) taken in from the return air port 91 of the target space SP to the exhaust unit 10. In the air conditioning system 201, the return air port 91 is located on the ceiling of the target space SP. The location of the return air port 91 may be on a wall or floor or other part. There may be one or more return air ports 91. The return air duct P2 is an example of a second air passage.

[0054] The exhaust unit 10 may be connected to the exhaust port 95 via a duct, or it may be connected directly to the return air port 91 without going through the return air duct P2. Alternatively, the return air port 91 may not have a damper, and a fan unit may be connected to the return air duct P2. The fan unit may comprise a fan, a casing housing the fan, an airflow detection unit for detecting airflow, and a control unit for controlling the fan speed. The fan unit may be configured such that the control unit controls the fan speed so that the airflow detected by the airflow detection unit matches the airflow instruction value instructed by the control device 3.

[0055] The compressor unit 50 comprises a compressor 51, a four-way switching valve 53, and an expansion valve 54. The compressor unit 50 is installed outside the target space SP, for example, outside the machine room or building BL.

[0056] The compressor 51 draws in low-pressure gaseous refrigerant and discharges high-pressure gaseous refrigerant. The compressor 51 is equipped with a motor 52 whose operating speed can be adjusted by inverter control. The compressor 51 is a variable-capacity type (variable-capacity type) whose capacity (performance) can be changed by inverter control of the motor 52. However, the compressor 51 may also be a constant-capacity type. The compressor 51 is an example of a first compressor that compresses refrigerant.

[0057] The four-way switching valve 53 reverses the flow of refrigerant in the refrigerant piping, switching the supply of refrigerant discharged from the compressor 51 to either the outside air heat exchanger 22 or the return air heat exchanger 12. This allows the ventilation system 1 to switch between a cooling operation that cools the outside air OA and a heating operation that heats the outside air OA.

[0058] The expansion valve 54 is comprised of an electrically operated valve capable of adjusting the flow rate and pressure of the refrigerant. In the ventilation system 1, the opening degree of the expansion valve 54 is controlled to adjust the pressure of the refrigerant supplied to the outside air heat exchanger 22 or the return air heat exchanger 12.

[0059] The refrigerant circuit 60 includes a compressor 51, an outside air heat exchanger 22, a return air heat exchanger 12, a four-way switching valve 53, an expansion valve 54, and refrigerant piping 61 connecting these. The refrigerant circuit 60 is a circuit through which refrigerant flows, circulating the refrigerant between the outside air heat exchanger 22 and the return air heat exchanger 12. The refrigerant piping 61 is a flow path for the refrigerant and includes liquid pipes F1, F4 and gas pipes F2, F3.

[0060] In the ventilation system 1 with the above configuration, when the supply unit 20 cools and supplies outside air OA, the four-way switching valve 53 is held in the state shown by the solid line in Figure 1. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 51 flows into the return air heat exchanger 12 of the exhaust unit 10 via the four-way switching valve 53 and gas pipe F3. At this time, the return air heat exchanger 12 functions as a condenser, and the refrigerant condenses and liquefies through heat exchange with the return air RA due to the operation of the exhaust fan 11. The liquefied refrigerant is supplied to the expansion valve 54 via the liquid pipe F4. The liquefied refrigerant is depressurized in the expansion valve 54 and flows into the outside air heat exchanger 22 via the liquid pipe F1. At this time, the outside air heat exchanger 22 functions as an evaporator, and in the outside air heat exchanger 22, the refrigerant evaporates through heat exchange with the outside air OA. The outside air OA cooled by the evaporation of the refrigerant is supplied to the target space SP as supply air SA by the supply fan 21. The refrigerant evaporated in the outside air heat exchanger 22 returns to the compressor unit 50 through the gas pipe F2 and is drawn into the compressor 51 via the four-way switching valve 53.

[0061] In the ventilation system 1 with the above configuration, when the supply unit 20 heats and supplies outside air OA, the four-way switching valve 53 is held in the state shown by the dashed line in Figure 1. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 51 passes through the four-way switching valve 53 and the gas pipe F2 and flows into the outside air heat exchanger 22 of the supply unit 20. At this time, the outside air heat exchanger 22 functions as a condenser, and in the outside air heat exchanger 22, the refrigerant exchanges heat with the outside air OA and condenses and liquefies. The outside air OA heated by the condensation of the refrigerant is supplied to the target space SP by the supply fan 21. The refrigerant liquefied in the outside air heat exchanger 22 goes through the liquid pipe F1 to the compressor unit 50, is reduced to a predetermined low pressure by the expansion valve 54, and flows into the return air heat exchanger 12 through the liquid pipe F4. At this time, the return air heat exchanger 12 functions as an evaporator, and in the return air heat exchanger 12, the refrigerant exchanges heat with the return air RA and evaporates. The refrigerant evaporated and vaporized in the return air heat exchanger 12 returns to the compressor unit 50 through the gas pipe F3 and is drawn into the compressor 51 via the four-way switching valve 53.

[0062] The ventilation device 1 has a ventilation control unit 23.

[0063] The ventilation control unit 23 controls the operation of the ventilation device 1. The ventilation control unit 23 is communicatively connected to the control device 3 or the remote control 4. The ventilation control unit 23 may also be communicatively connected to the air conditioning control unit 76, which will be described later. The ventilation control unit 23 consists of one or more control units. The ventilation control unit 23 may be located inside or outside the ventilation device 1, or it may be located in one place or distributed.

[0064] The ventilation control unit 23 sets the target supply air temperature based on the set temperature set by the user via the remote control 4 and the room temperature. The target supply air temperature is the target value of the supply air temperature. The ventilation control unit 23 controls the ventilation device 1, for example, the compressor unit 50 and the exhaust fan 11, based on the target supply air temperature. This adjusts the operating capacity (air conditioning capacity) of the ventilation device 1. The target supply air temperature may also be set by the control device 3.

[0065] The air conditioning unit 2 draws in air from the target space SP, exchanges heat with the refrigerant flowing through the indoor heat exchanger, and blows the resulting air back into the target space SP to adjust the temperature of the air (indoor air) in the target space SP. The air conditioning unit 2 is a device that performs a vapor compression type refrigeration cycle to cool or heat the target space SP. The air conditioning unit 2 may be a device that performs only cooling, only heating, or both cooling and heating. The air conditioning unit 2 mainly consists of one outdoor unit 70 which serves as a heat source unit and multiple indoor units 81, 82 (two in this example).

[0066] In the air conditioning system 2, the outdoor unit 70 and a plurality of indoor units 81, 82 are connected by a connecting pipe F5. The connecting pipe F5 includes liquid refrigerant connecting pipes and gaseous refrigerant connecting pipes. This realizes a refrigerant circuit 62 in which refrigerant circulates between the outdoor unit 70 and the plurality of indoor units 81, 82. When refrigerant circulates within the refrigerant circuit 62, a vapor compression type refrigeration cycle is performed in the air conditioning system 2. The control mode of the air conditioning system 2 is not particularly limited. For example, the air conditioning system 2 performs variable refrigerant flow rate control.

[0067] The outdoor unit 70 is located outside the target space SP (in this example, outside the building BL). The outdoor unit 70 is equipped with a heat exchanger and discharges the air that has exchanged heat with the refrigerant flowing through the heat exchanger to the outdoors.

[0068] The indoor units 81 and 82 are placed in the target space SP. The indoor units 81 and 82 are equipped with heat exchangers and blow air that has exchanged heat with the refrigerant flowing through the heat exchangers into the target space SP. In this embodiment, the indoor units 81 and 82 are ceiling-mounted units installed on the ceiling of the target space SP. In particular, the indoor units 81 and 82 of this embodiment are ceiling-embedded air conditioning indoor units, and the heat-exchanged air is blown out from the air outlets 93A and 93B. In this embodiment, an example in which the air outlets 93A and 93B are installed on the ceiling is described, but there are no particular restrictions on the location in which the air outlets 93A and 93B are installed. Note that the indoor units 81 and 82 are not limited to ceiling-embedded units, but may also be ceiling-suspended units. In addition, the indoor units 81 and 82 may be wall-mounted or floor-standing units, or other types of units other than ceiling-mounted units.

[0069] Figure 2 is a refrigerant circuit diagram showing an example of the configuration of an air conditioning system. Air conditioning system 2 includes a refrigerant circuit 62. In air conditioning system 2, the refrigerant circuit 62 is formed by connecting the outdoor unit 70 and a number of indoor units 81, 82 via connecting pipes F5.

[0070] The outdoor unit 70 includes, for example, a compressor 71, a four-way switching valve 72, an outdoor heat exchanger 73, an outdoor expansion valve 74, and an outdoor fan 75.

[0071] The compressor 71 is a device that compresses the low-pressure refrigerant in the refrigeration cycle until it reaches high pressure. The compressor 71 is an example of a second compressor that compresses the refrigerant.

[0072] The four-way switching valve 72 is a flow path switching means for switching the direction of refrigerant flow in the refrigerant circuit 60.

[0073] The outdoor heat exchanger 73 is a heat exchanger that exchanges heat between the refrigerant and the airflow passing through it (outdoor airflow generated by the outdoor fan 75). During heating operation, the outdoor heat exchanger 73 functions as a refrigerant evaporator, and during cooling operation or defrosting operation, it functions as a refrigerant condenser or radiator.

[0074] The outdoor expansion valve 74 is a valve that functions as a means of reducing the pressure or adjusting the flow rate of the refrigerant, and is, for example, an electrically operated expansion valve with controllable opening. The outdoor expansion valve 74 is located between the outdoor heat exchanger 73 and the liquid refrigerant connecting pipe 63.

[0075] The outdoor fan 75 is a blower that generates an outdoor airflow. The outdoor airflow is the flow of outside air that flows into the outdoor unit 70, passes through the outdoor heat exchanger 73, and flows out of the outdoor unit 70. The outdoor airflow is the heat source for the refrigerant in the outdoor heat exchanger 73 during heating operation, and the cooling source for the refrigerant in the outdoor heat exchanger 73 during cooling operation or defrosting operation. The outdoor fan 75 has a fan motor. The rotation speed of the outdoor fan 75 is adjusted by inverter control of the fan motor, so the amount of airflow to the outside of the outdoor unit 70 is variable.

[0076] Furthermore, various sensors are installed on the outdoor unit 70. For example, the outdoor unit 70 is equipped with an intake pressure sensor to detect the pressure of the refrigerant drawn into the compressor 71, and a discharge pressure sensor to detect the pressure of the refrigerant discharged from the compressor 71.

[0077] The indoor units 81 and 82 include, for example, an indoor heat exchanger 83, an indoor expansion valve 84, and an indoor fan 85.

[0078] The indoor heat exchanger 83 is a heat exchanger that exchanges heat between the refrigerant and the airflow passing through it (the indoor airflow generated by the indoor fan 85). During heating operation, the indoor heat exchanger 83 functions as a refrigerant condenser or radiator, and during cooling operation or defrosting operation, it functions as a refrigerant evaporator. The indoor heat exchanger 83 is an example of a third heat exchanger that functions as a condenser or evaporator.

[0079] The indoor expansion valve 84 is a valve that functions as a means of reducing the pressure or adjusting the flow rate of the refrigerant, and is, for example, an electrically operated expansion valve with controllable opening. The indoor expansion valve 84 is located between the indoor heat exchanger 83 and the liquid refrigerant communication pipe 63.

[0080] The indoor fan 85 is a blower that generates indoor airflow. The indoor airflow is the flow of indoor air that flows into the indoor units 81 and 82, passes through the indoor heat exchanger 83, and flows out of the indoor units 81 and 82. The indoor airflow is a cooling source for the refrigerant in the indoor heat exchanger 83 during heating operation, and a heating source for the refrigerant in the indoor heat exchanger 83 during cooling operation or defrost operation. The indoor fan 85 has a fan motor. The rotation speed of the indoor fan 85 is adjusted by inverter control of the fan motor, so the amount of air blown from the indoor units 81 and 82 to the target space SP is variable.

[0081] Furthermore, various sensors are installed in each of the indoor units 81 and 82. For example, each of the indoor units 81 and 82 is equipped with an indoor temperature sensor to detect the temperature of the indoor airflow (internal air) drawn into the indoor unit, an indoor humidity sensor to detect the humidity of the indoor airflow drawn into the indoor unit, and a carbon dioxide concentration sensor to detect the carbon dioxide concentration of the indoor airflow drawn into the indoor unit. For example, each of the indoor units 81 and 82 is equipped with a refrigerant temperature sensor to detect the temperature of the refrigerant in the indoor heat exchanger 83.

[0082] In Figure 1, the air conditioning unit 2 has an air conditioning control unit 76.

[0083] The air conditioning control unit 76 controls the operation of the air conditioning system 2. The air conditioning control unit 76 is communicatively connected to the control device 3 or the remote control 4. The air conditioning control unit 76 may also be communicatively connected to the ventilation control unit 23. The air conditioning control unit 76 consists of one or more control units. The air conditioning control unit 76 may be located inside or outside the air conditioning system 2, and may be located in one place or distributed.

[0084] The air conditioning control unit 76 sets the target evaporation temperature for each of the indoor units 81 and 82 according to the set temperature and the room temperature. The target evaporation temperature is the target value of the evaporation temperature. The air conditioning control unit 76 controls the state of each part of the air conditioning system 2 (for example, the capacity of the compressor 71 and the airflow rate of the outdoor fan 75) based on the target evaporation temperature. This adjusts the operating capacity (air conditioning capacity) of the air conditioning system 2. The target evaporation temperature may also be set by the control device 3.

[0085] The control device 3 is an example of a control unit and comprehensively controls the operation of the air conditioning system 201. The control device 3 is electrically connected to the ventilation control unit 23 and the air conditioning control unit 76 and transmits and receives signals from each other. The control device 3 is installed in the same location where the ventilation device 1 and the air conditioning device 2 are installed (for example, building BL). However, the control device 3 may be installed in a location away from the ventilation control unit 23 and the air conditioning control unit 76 so as to be able to communicate remotely with them.

[0086] The control device 3 controls the operation of the ventilation unit 1 and the air conditioning unit 2 by transmitting predetermined signals (for example, control signals to set the target supply air temperature and target evaporation temperature) to the ventilation control unit 23 and the air conditioning control unit 76. The control device 3 acquires detection values ​​from various sensors located in the ventilation unit 1 and the air conditioning unit 2, as well as information identifying the operating status of the ventilation unit 1 and the air conditioning unit 2. The control device 3 includes a control circuit 5 that executes various control operations of the control device 3.

[0087] Remote control 4 is an input device for the user to input various commands to individually switch the operating status of ventilation system 1 and air conditioning system 2 (start / stop, operation type, set temperature, set humidity, set airflow, etc.). Remote control 4 also functions as a display device to show predetermined information (for example, the operating status of ventilation system 1 and air conditioning system 2, the indoor and outdoor temperatures, and the indoor and outdoor humidity).

[0088] Next, the control in the air conditioning system 201 of this embodiment will be described in more detail.

[0089] In this embodiment, the ability of the ventilation device 1 to adjust the temperature of the target space SP is defined as the first capacity Av, and the ability of the air conditioning device 2 to adjust the temperature of the target space SP is defined as the second capacity Ac. The units of the first capacity Av and the second capacity Ac are expressed, for example, in kW (kilowatts).

[0090] The larger the first capacity Av, the greater the heat load that the ventilation unit 1 can handle in the target space SP. Similarly, the larger the second capacity Ac, the greater the heat load that the air conditioning unit 2 can handle in the target space SP. The heat load is also called the air conditioning load. The air conditioning load of the target space SP consists of a cooling load handled by cooling operation and a heating load handled by heating operation.

[0091] The first capacity Av of ventilation device 1 is the air conditioning capacity adjusted within a predetermined first capacity range by the ventilation control unit 23 controlling ventilation device 1. The second capacity Ac of air conditioning device 2 is the air conditioning capacity adjusted within a predetermined second capacity range by the air conditioning control unit 76 controlling air conditioning device 2. The lower and upper limits of the first capacity range are determined by the compressor capacity and the adjustable range of the airflow.

[0092] When the control device 3 reduces the first capacity Av of the ventilation device 1 during cooling operation, the supply air temperature from the ventilation device 1 to the target space SP increases, or the supply air volume from the ventilation device 1 to the target space SP decreases. When the control device 3 increases the first capacity Av of the ventilation device 1 during cooling operation, the supply air temperature from the ventilation device 1 to the target space SP decreases, or the supply air volume from the ventilation device 1 to the target space SP increases. On the other hand, when the control device 3 reduces the first capacity Av of the ventilation device 1 during heating operation, the temperature or air volume (supply air temperature or supply air volume) of the supply air SA from the ventilation device 1 to the target space SP decreases. When the control device 3 increases the first capacity Av of the ventilation device 1 during heating operation, the supply air temperature or supply air volume from the ventilation device 1 to the target space SP increases.

[0093] When the control device 3 reduces the second capacity Ac of the air conditioner 2 during cooling operation, the discharge temperature from the air conditioner 2 to the target space SP increases, or the discharge air volume from the air conditioner 2 to the target space SP decreases. When the control device 3 increases the second capacity Ac of the air conditioner 2 during cooling operation, the discharge temperature from the air conditioner 2 to the target space SP decreases, or the discharge air volume from the air conditioner 2 to the target space SP increases. On the other hand, when the control device 3 reduces the second capacity Ac of the air conditioner 2 during heating operation, the temperature or air volume (discharge temperature or discharge air volume) of the air supplied from the air conditioner 2 to the target space SP decreases. When the control device 3 increases the second capacity Ac of the air conditioner 2 during heating operation, the discharge temperature or air volume from the air conditioner 2 to the target space SP increases.

[0094] The ventilation system 1 has an efficiency characteristic in which its energy efficiency (COP) increases as the first capacity Av decreases within the first capacity range. On the other hand, the COP of the air conditioning system 2 may be lower than that of the ventilation system 1, and the air conditioning system 2 may have an efficiency characteristic in which its COP decreases as the second capacity Ac decreases within the second capacity range.

[0095] When the heat load of the target space SP is lower than a predetermined amount L (low heat load condition), the control device 3 executes a first operating mode in which the temperature of the target space SP is adjusted by the ventilation device 1, rather than by the air conditioning device 2. In the first operating mode, the control device 3 stops the air conditioning device 2 from adjusting the temperature of the target space SP and has the ventilation device 1 adjust the temperature of the target space SP. By executing the first operating mode in the low heat load condition, the control device 3 improves energy efficiency, such as COP, compared to when both the ventilation device 1 and the air conditioning device 2 adjust the temperature of the target space SP in the low heat load condition. The predetermined amount L is, for example, the amount of heat load of the target space SP that the air conditioning device 2 can handle with its minimum second capacity Ac.

[0096] The COP of ventilation unit 1 when operating at a low load is higher than that of air conditioning unit 2 when operating at the same low load. Therefore, by stopping the operation of air conditioning unit 2 under low heat load conditions, control device 3 improves energy efficiency, such as COP.

[0097] As the heat load of the target space SP gradually increases, the first capacity Av of the ventilation device 1 for adjusting the temperature of the target space SP becomes insufficient in the first operating mode. When the ventilation device 1 can no longer handle the heat load of the target space SP with its first capacity Av, the control device 3 switches from the first operating mode, in which the temperature of the target space SP is adjusted by the ventilation device 1 without adjustment by the air conditioning device 2, to the second operating mode, in which the temperature of the target space SP is adjusted by both the air conditioning device 2 and the ventilation device 1.

[0098] For example, if the difference between the amount of heat load in the target space SP that the ventilation device 1 can handle with its first capacity Av and the actual heat load in the target space SP falls below a predetermined threshold, the control device 3 determines that condition A, indicating insufficient first capacity Av, has been met. When condition A, indicating insufficient first capacity Av, is met, the control device 3 switches the operating mode from the first operating mode to the second operating mode.

[0099] Upon transitioning from the first operating mode to the second operating mode, the air conditioning system 201 processes the increased heat load of the target space SP through the first capacity Av of the ventilation device 1, which adjusts the temperature of the target space SP, and the second capacity Ac of the air conditioning device 2, which adjusts the temperature of the target space SP. In the second operating mode, the air conditioning system 201 distributes the processing of the heat load of the target space SP between the air conditioning device 2 and the ventilation device 1.

[0100] However, if the threshold for ventilation device 1 to perform cooling operation is fixed before and after the transition from the first operating mode to the second operating mode, there is a risk that ventilation device 1 will repeatedly start and stop cooling operation in the second operating mode after the transition. Similarly, if the threshold for ventilation device 1 to perform heating operation is fixed before and after the transition from the first operating mode to the second operating mode, there is a risk that ventilation device 1 will repeatedly start and stop heating operation in the second operating mode after the transition. This repeated starting and stopping will be explained with reference to Figures 3 and 4.

[0101] First, Figure 3 will be explained with reference to Figure 1. Figure 3 is a state transition diagram showing an example of a control method that can suppress repeated starting and stopping of the cooling operation of a ventilation system.

[0102] Figure 3 shows an example of a mode transition between a first operating mode in which the ventilation system 1 is operated independently and a second operating mode in which both the ventilation system 1 and the air conditioning system 2 are operated. Figure 3 illustrates a mode transition when both the ventilation system 1 and the air conditioning system 2 are running and the ventilation system 1 is performing control using the target supply air temperature. In both the first and second operating modes, the ventilation system 1 switches between cooling operation, fan operation, and heating operation according to the temperature difference ΔT, which is the value obtained by subtracting the target supply air temperature from the outside air temperature outside the target space SP.

[0103] The outside air temperature outside the target space SP is, for example, the temperature of the outside air OA, and is detected by the sensor 24. The target supply air temperature is set by the ventilation control unit 23 or the control device 3 according to the set temperature obtained, for example, from the remote control 4.

[0104] The ventilation control unit 23 compares the temperature difference ΔT with a threshold Tc or a threshold Th in either the first or second operating mode. Threshold Tc represents the threshold value that serves as the basis for the ventilation device 1 to perform cooling operation. Threshold Th represents the threshold value that serves as the basis for the ventilation device 1 to perform heating operation. By comparing the temperature difference ΔT with the threshold Tc, the ventilation control unit 23 can switch whether or not the ventilation device 1 performs cooling operation according to the temperature difference ΔT. By comparing the temperature difference ΔT with the threshold Th, the ventilation control unit 23 can switch whether or not the ventilation device 1 performs heating operation according to the temperature difference ΔT.

[0105] The ventilation control unit 23 operates the ventilation device 1 in cooling mode when the temperature difference ΔT is greater than or equal to the threshold Tc. When the ventilation device 1 operates in cooling mode, it cools the outside air OA and supplies it to the target space SP as supply air SA.

[0106] The ventilation control unit 23 operates the ventilation device 1 in heating mode when the temperature difference ΔT is less than the threshold Th. When the ventilation device 1 operates in heating mode, it heats the outside air OA and supplies it to the target space SP as supply air SA.

[0107] The ventilation control unit 23 operates the ventilation device 1 in fan mode when the temperature difference ΔT is greater than or equal to the threshold Th and less than the threshold Tc. When the ventilation device 1 operates in fan mode, it supplies outside air OA to the target space SP as supply air SA without cooling by cooling operation or heating by heating operation.

[0108] If condition A, which indicates that the ventilation device 1 lacks the first capacity Av required to lower the temperature of the target space SP, is met during the first operating mode, the control device 3 transitions the operating mode of the air conditioning system 201 from the first operating mode to the second operating mode, as shown in Figure 3. At this time, if the threshold Tc is fixed before and after the transition from the first operating mode to the second operating mode, the ventilation device 1 may repeatedly start and stop cooling operation in the second operating mode after the transition.

[0109] As a first example of starting and stopping cooling operation, when switching to the second operating mode, the cooling operation of the air conditioning unit 2 is performed in addition to the cooling operation of the ventilation unit 1, thereby reducing the cooling load of the target space SP. When the cooling load of the target space SP is large, that is, when there is a large difference between the indoor temperature and the set temperature, the target supply air temperature is set to a temperature lower than the outside air temperature. For example, when the outside air temperature is 30°C, the target supply air temperature is set to 20°C. When the cooling load of the target space SP decreases, the target supply air temperature is set higher to approach the outside air temperature, so the temperature difference ΔT decreases. As a result, when the temperature difference ΔT falls below the threshold Tc, the ventilation unit 1 switches from cooling operation to fan operation, causing the cooling operation of the ventilation unit 1 to start and stop. The starting and stopping of the cooling operation of the ventilation unit 1 leads to a decrease in the energy efficiency of the ventilation unit 1 and the air conditioning system 201.

[0110] As a second example of the starting and stopping of cooling operation, when the temperature difference ΔT is near the threshold Tc (when the difference between the temperature difference ΔT and the threshold Tc is less than a first predetermined amount), slight fluctuations in the outside air temperature or target supply air temperature may cause the ventilation device 1 to repeatedly switch between cooling operation and fan operation. Repeated starting and stopping of the cooling operation of the ventilation device 1 leads to a further decrease in the energy efficiency of the ventilation device 1 and the air conditioning system 201.

[0111] In this embodiment, when transitioning from the first operating mode to the second operating mode, the control device 3 lowers the threshold Tc by a first predetermined amount or more, as shown in Figure 3. This expands the range in which the ventilation device 1 operates in cooling mode according to the temperature difference ΔT, thereby suppressing repeated starting and stopping of the cooling operation of the ventilation device 1 in the second operating mode. Since repeated starting and stopping of the cooling operation of the ventilation device 1 is suppressed, energy saving of the ventilation device 1 and the air conditioning system 201 is ensured.

[0112] In the example shown in Figure 3, when the control device 3 transitions from the first operating mode to the second operating mode, it lowers the threshold Tc from the standard upper limit to the cooling priority upper limit. The standard upper limit is an example of the first threshold, and is the value set when the threshold Tc is normally determined. The cooling priority upper limit is an example of the second threshold, which is lower than the first threshold by at least one predetermined amount, and is the value set when the threshold Tc is normally determined.

[0113] For example, the control device 3 may determine that condition A, indicating a deficiency in the first capacity Av that the ventilation device 1 has to lower the temperature of the target space SP, has been met if the difference between the set temperature of the ventilation device 1 and the indoor air temperature in the target space SP exceeds a predetermined value for a period exceeding a predetermined period. When condition A is met, the control device 3 determines that the first capacity Av that reduces the difference between the set temperature of the ventilation device 1 and the indoor air temperature in the target space SP is insufficient or likely to be insufficient. When condition A is met, the control device 3 can compensate for the deficiency in the air conditioning capacity that the ventilation device 1 has to handle the cooling load by switching from the first operating mode to the second operating mode, with the air conditioning capacity that the air conditioning device 2 has to handle the cooling load.

[0114] The set temperature of the ventilation device 1 is obtained, for example, from a remote control 4. The indoor air temperature in the target space SP may be detected by sensor 14, or by sensors placed in each of the indoor units 81 and 82.

[0115] For example, if the cooling load of the target space SP rises above a predetermined first load, the control device 3 determines that condition A has been met, indicating that the ventilation device 1 has insufficient first capacity Av to lower the temperature of the target space SP. If condition A is met, the control device 3 determines that the ventilation device 1 has insufficient or is likely to have insufficient first capacity Av to handle the cooling load. If condition A is met, the control device 3 can compensate for the insufficient air conditioning capacity of the ventilation device 1 to handle the cooling load by switching from the first operating mode to the second operating mode, with the air conditioning capacity of the air conditioning device 2 handling the cooling load.

[0116] The control device 3 may measure or estimate the cooling load of the target space SP using either or both of the detection values ​​from various sensors located on the ventilation device 1 and the air conditioning device 2, and information that identifies the operating status of the ventilation device 1 and the air conditioning device 2, respectively. The same applies to the heating load, which will be described later.

[0117] For example, the control device 3 determines that the cooling load of the target space SP has risen above a predetermined first load if the number of people in the target space SP detected by the sensor is greater than a predetermined number. The control device 3 may also determine that the cooling load of the target space SP has risen above a predetermined first load if the detected power consumption of the ventilation device 1 is greater than a predetermined power. The control device 3 may also determine that the cooling load of the target space SP has risen above a predetermined first load if the calculated COP of the ventilation device 1 is less than or equal to a predetermined COP. The same applies to the heating load described later.

[0118] If condition B, which indicates an excess of the second capacity Ac by the air conditioning unit 2 in lowering the temperature of the target space SP, is met during the second operating mode, the control device 3 will switch the operating mode of the air conditioning system 201 from the second operating mode to the first operating mode, as shown in Figure 3.

[0119] For example, the control device 3 determines that condition B is met if the shutdown time of the compressor 71 of the air conditioning unit 2 exceeds a predetermined time. The control device 3 may also determine that condition B is met if the cooling load of the target space SP falls below a predetermined second load. The predetermined second load is smaller than the predetermined first load described above. When condition B is met, the control device 3 determines that the air conditioning capacity to handle the cooling load is excessive or likely to be excessive if the second operating mode, which operates both the ventilation unit 1 and the air conditioning unit 2, is maintained. When condition B is met, the control device 3 switches from the second operating mode to the first operating mode, thereby suppressing the state of excessive air conditioning capacity to handle the cooling load and ensuring energy saving of the air conditioning system 201.

[0120] The case in which the compressor 71 is stopped for a predetermined period exceeds a predetermined time may be when the proportion of the compressor 71's stopped time within a predetermined period exceeds a predetermined proportion, or when the compressor 71 is stopped for a predetermined period continuously.

[0121] If condition C, which indicates an increase in the cooling load of the target space SP, is met during the first operating mode, the control device 3 changes the threshold Tc from the cooling priority upper limit to the standard upper limit, as shown in Figure 3. For example, the control device 3 determines that condition C is met when it transitions from the second operating mode to the first operating mode and the temperature difference ΔT reaches and exceeds the standard upper limit. This suppresses repeated starting and stopping of the cooling operation of the ventilation device 1 in the first operating mode after transitioning from the second operating mode. This is because if the threshold Tc is returned to the standard upper limit immediately after transitioning from the second operating mode to the first operating mode, there is a risk that the cooling operation of the ventilation device 1 will start and stop.

[0122] During the transition from the second operating mode to the first operating mode, the cooling load of the target space SP decreases, and the cooling operation of the air conditioning unit 2 stops due to the shutdown of the compressor 71 of the outdoor unit 70. Immediately after transitioning from the second operating mode to the first operating mode, the ventilation unit 1 operates independently while maintaining the threshold Tc at the cooling priority upper limit. If the cooling operation of the ventilation unit 1 continues independently, the cooling load of the target space SP begins to increase. If the cooling load of the target space SP increases and it is detected that the temperature difference ΔT exceeds the standard upper limit, the control device 3 returns the threshold Tc from the cooling priority upper limit to the standard upper limit.

[0123] Next, Figure 4 will be explained with reference to Figure 1. Figure 4 is a state transition diagram showing an example of a control method that can suppress repeated starting and stopping of heating operation of a ventilation system.

[0124] Figure 4 shows an example of a mode transition between a first operating mode in which the ventilation system 1 is operated independently and a second operating mode in which both the ventilation system 1 and the air conditioning system 2 are operated. Figure 4 illustrates a mode transition when both the ventilation system 1 and the air conditioning system 2 are running and the ventilation system 1 is performing control using the target supply air temperature. In both the first and second operating modes, the ventilation system 1 switches between cooling, fan operation, and heating operation according to the temperature difference ΔT, which is the value obtained by subtracting the target supply air temperature from the outside air temperature outside the target space SP. The ventilation control unit 23 switches between cooling, fan operation, and heating operation based on the result of comparing the temperature difference ΔT with a threshold Tc or threshold Th, which is the same as described above in Figure 3, so the explanation is omitted.

[0125] If condition D, which indicates that the ventilation device 1 lacks the first capacity Av to raise the temperature of the target space SP, is met during the first operating mode, the control device 3 transitions the operating mode of the air conditioning system 201 from the first operating mode to the second operating mode, as shown in Figure 4. At this time, if the threshold Th is fixed before and after the transition from the first operating mode to the second operating mode, the ventilation device 1 may repeatedly start and stop heating operation in the second operating mode after the transition.

[0126] As a first example of starting and stopping heating operation, when switching to the second operating mode, the heating operation of the air conditioning system 2 is performed in addition to the heating operation of the ventilation system 1, thereby reducing the heating load of the target space SP. When the heating load of the target space SP is large, that is, when there is a large difference between the indoor temperature and the set temperature, the target supply air temperature is set to a temperature higher than the outside air temperature. For example, when the outside air temperature is 5°C, the target supply air temperature is set to 20°C. When the heating load of the target space SP decreases, the target supply air temperature is set lower to approach the outside air temperature, so the temperature difference ΔT becomes large (a negative temperature difference ΔT approaches zero). As a result, when the temperature difference ΔT exceeds the threshold Th, the ventilation system 1 switches from heating operation to fan operation, causing the heating operation of the ventilation system 1 to start and stop. The starting and stopping of the heating operation of the ventilation system 1 leads to a decrease in the energy efficiency of the ventilation system 1 and the air conditioning system 201.

[0127] As a second example of the start and stop of heating operation, when the temperature difference ΔT is near the threshold Th (when the difference between the temperature difference ΔT and the threshold Th is less than a second predetermined amount), slight fluctuations in the outside air temperature or target supply air temperature may cause the ventilation device 1 to repeatedly switch between heating operation and fan operation. Repeated starting and stopping of the heating operation of the ventilation device 1 leads to a further decrease in the energy efficiency of the ventilation device 1 and the air conditioning system 201.

[0128] In this embodiment, when transitioning from the first operating mode to the second operating mode, the control device 3 raises the threshold Th to a second predetermined amount or more, as shown in Figure 4. This expands the range in which the ventilation device 1 operates in heating mode according to the temperature difference ΔT, thereby suppressing repeated starting and stopping of the heating operation of the ventilation device 1 in the second operating mode. Since repeated starting and stopping of the heating operation of the ventilation device 1 is suppressed, energy saving of the ventilation device 1 and the air conditioning system 201 is ensured.

[0129] In the example shown in Figure 4, when the control device 3 transitions from the first operating mode to the second operating mode, it raises the threshold Th from the standard lower limit to the heating priority lower limit. The standard lower limit is an example of the first threshold, and is the value set when the threshold Th is normally determined. The heating priority lower limit is an example of the second threshold, which is at least a second predetermined amount higher than the first threshold, and is the value set when the threshold Th is determined to prioritize heating.

[0130] For example, the control device 3 may determine that condition D has been met, indicating a deficiency in the first capacity Av that the ventilation device 1 has to raise the temperature of the target space SP, if the period during which the difference between the set temperature of the ventilation device 1 and the internal air temperature in the target space SP is greater than or equal to a predetermined value exceeds a predetermined period. When condition D is met, the control device 3 determines that the first capacity Av that reduces the difference between the set temperature of the ventilation device 1 and the internal air temperature in the target space SP is insufficient or likely to be insufficient. When condition D is met, the control device 3 can compensate for the deficiency in the air conditioning capacity that the ventilation device 1 has to handle the heating load by switching from the first operating mode to the second operating mode, with the air conditioning capacity that the air conditioning device 2 has to handle the heating load.

[0131] For example, if the heating load of the target space SP rises above a predetermined first load, the control device 3 determines that condition D has been met, indicating that the ventilation device 1 has insufficient first capacity Av to raise the temperature of the target space SP. If condition D is met, the control device 3 determines that the ventilation device 1 has insufficient or is likely to have insufficient first capacity Av to handle the heating load. If condition D is met, the control device 3 can compensate for the insufficient air conditioning capacity of the ventilation device 1 to handle the heating load by switching from the first operating mode to the second operating mode, with the air conditioning capacity of the air conditioning device 2 handling the heating load.

[0132] If condition E, which indicates an excess of the second capacity Ac by the air conditioning unit 2 in raising the temperature of the target space SP, is met during the second operating mode, the control device 3 will switch the operating mode of the air conditioning system 201 from the second operating mode to the first operating mode, as shown in Figure 4.

[0133] For example, the control device 3 determines that condition E is met if the shutdown time of the compressor 71 of the air conditioning unit 2 exceeds a predetermined time. The control device 3 may also determine that condition E is met if the heating load of the target space SP falls below a predetermined second load. The predetermined second load is smaller than the predetermined first load described above. When condition E is met, the control device 3 determines that the air conditioning capacity to handle the heating load is excessive or likely to be excessive if the second operating mode, which operates both the ventilation unit 1 and the air conditioning unit 2, is maintained. When condition E is met, the control device 3 switches from the second operating mode to the first operating mode, thereby suppressing the state of excessive air conditioning capacity to handle the heating load and ensuring energy saving of the air conditioning system 201.

[0134] If condition F, which indicates an increase in the heating load of the target space SP, is met during the first operating mode, the control device 3 changes the threshold Th from the heating priority lower limit to the standard lower limit, as shown in Figure 4. For example, the control device 3 determines that condition F is met when it transitions from the second operating mode to the first operating mode and the temperature difference ΔT reaches and falls below the standard lower limit. This suppresses repeated starting and stopping of the heating operation of the ventilation device 1 in the first operating mode after transitioning from the second operating mode. This is because if the threshold Th is returned to the standard lower limit immediately after transitioning from the second operating mode to the first operating mode, there is a risk that the heating operation of the ventilation device 1 will start and stop.

[0135] During the transition from the second operating mode to the first operating mode, the heating load of the target space SP decreases, and the heating operation of the air conditioning system 2 stops due to the shutdown of the compressor 71 of the outdoor unit 70. Immediately after transitioning from the second operating mode to the first operating mode, the ventilation system 1 operates independently while maintaining the threshold Th at the heating priority lower limit. If the heating operation of the ventilation system 1 continues independently, the heating load of the target space SP begins to increase. If the heating load of the target space SP increases and it is detected that the temperature difference ΔT falls below the standard lower limit, the control device 3 returns the threshold Th from the heating priority lower limit to the standard lower limit.

[0136] Next, we will explain the operation flow of the ventilation system using a flowchart.

[0137] Figure 5 is a flowchart illustrating an example of how the ventilation system switches between modes. The control device 3 switches between cooling, fan operation, and heating operation in both the first and second operating modes according to the method shown in Figure 5, based on the temperature difference ΔT, which is the difference between the outside air temperature outside the target space SP and the target supply air temperature. The control device 3 repeatedly executes the operation switching method shown in Figure 5 in both the first and second operating modes.

[0138] Furthermore, the ventilation control unit 23 may switch between cooling operation, fan operation, and heating operation in either the first operating mode or the second operating mode, according to the method shown in Figure 5, depending on the temperature difference ΔT.

[0139] In step S1, the control device 3 compares the current temperature difference ΔT with a threshold Tc or a threshold Th. Threshold Tc represents the threshold value that serves as the basis for the ventilation device 1 to perform cooling operation. Threshold Th represents the threshold value that serves as the basis for the ventilation device 1 to perform heating operation. By comparing the temperature difference ΔT with the threshold Tc, the control device 3 can switch the ventilation device 1 between cooling operation and fan operation according to the temperature difference ΔT. By comparing the temperature difference ΔT with the threshold Th, the control device 3 can switch the ventilation device 1 between heating operation and fan operation according to the temperature difference ΔT.

[0140] If the control device 3 determines in step S1 that the temperature difference ΔT is greater than or equal to the threshold Tc, it operates the ventilation device 1 in cooling mode (step S3). When the ventilation device 1 operates in cooling mode, it cools the outside air OA and supplies it to the target space SP as supply air SA. If the control device 3 determines in step S1 that the temperature difference ΔT is less than the threshold Th, it operates the ventilation device 1 in heating mode (step S5). When the ventilation device 1 operates in heating mode, it heats the outside air OA and supplies it to the target space SP as supply air SA. If the control device 3 determines that the temperature difference ΔT is greater than or equal to the threshold Th but less than the threshold Tc, it operates the ventilation device 1 in fan mode (step S7). When the ventilation device 1 operates in fan mode, it supplies the outside air OA to the target space SP as supply air SA without cooling by cooling mode or heating by heating mode.

[0141] Figure 6 is a flowchart illustrating an example of how to change the threshold Tc required for the ventilation system to perform cooling operation. The control device 3 changes the threshold Tc used in the operation switching method shown in Figure 5 according to the method shown in Figure 6. The control device 3 repeatedly executes the threshold changing method shown in Figure 6. Alternatively, the ventilation control unit 23 may change the threshold Tc used in the operation switching method shown in Figure 5 according to the method shown in Figure 6.

[0142] In step S21, after the ventilation device 1 is started, the control device 3 sets the operating mode of the air conditioning system 201 to a first operating mode in which the ventilation device 1 is operated independently. In step S23, the control device 3 sets the threshold Tc in the first operating mode to the standard upper limit value (Figure 3).

[0143] In step S25, the control device 3 determines whether condition A (Figure 3), which indicates a deficiency of the first capacity Av at which the ventilation device 1 lowers the temperature of the target space SP, is met. If condition A is not met in step S25, the control device 3 returns to the process in step S21. As a result, the first operating mode continues and the threshold Tc is maintained at the standard upper limit.

[0144] On the other hand, if condition A is met in step S25, in step S27, the control device 3 changes the operating mode of the air conditioning system 201 from a first operating mode in which the ventilation device 1 is operated independently to a second operating mode in which both the ventilation device 1 and the air conditioning device 2 are operated. This allows the air conditioning device 2 to compensate for any insufficient air conditioning capacity of the ventilation device 1 in handling the cooling load by handling the cooling load.

[0145] In step S29, the control device 3 sets the threshold Tc in the second operating mode to a cooling priority upper limit (Figure 3) that is lower than the standard upper limit. This expands the range in which the ventilation device 1 operates in cooling mode according to the temperature difference ΔT, thereby suppressing repeated starting and stopping of the cooling operation of the ventilation device 1 in the second operating mode.

[0146] In step S31, the control device 3 determines whether condition B (Figure 3), which indicates an excess of the second capacity Ac that the air conditioning unit 2 uses to lower the temperature of the target space SP, is met. If condition B is not met in step S31, the control device 3 returns to the process in step S27. As a result, the second operating mode continues, and the threshold Tc is maintained at the upper limit of the cooling priority.

[0147] On the other hand, if condition B is met in step S31, in step S33, the control device 3 changes the operating mode of the air conditioning system 201 from a second operating mode in which both the ventilation device 1 and the air conditioning device 2 are operated to a first operating mode in which the ventilation device 1 is operated independently. This suppresses an excessive state of air conditioning capacity to handle the cooling load and ensures energy efficiency of the air conditioning system 201.

[0148] In step S35, the control device 3 determines whether condition C (Figure 3), which indicates an increase in the cooling load of the target space SP, is met. If condition C is not met in step S35, the control device 3 returns to the process in step S33. As a result, the first operating mode continues, and the threshold Tc is maintained at the cooling priority upper limit.

[0149] On the other hand, if condition C is met in step S35, the control device 3 sets the threshold Tc in the first operating mode to a standard upper limit (Figure 3) that is higher than the cooling priority upper limit in step S37. This suppresses the repeated starting and stopping of the cooling operation of the ventilation device 1 immediately after transitioning from the second operating mode to the first operating mode due to the meeting of condition B in step S31.

[0150] Figure 7 is a flowchart illustrating an example of how to change the threshold Th required for the ventilation system to perform heating operation. The control device 3 changes the threshold Th used in the operation switching method shown in Figure 5 according to the method shown in Figure 7. The control device 3 repeatedly executes the threshold changing method shown in Figure 7. Alternatively, the ventilation control unit 23 may change the threshold Th used in the operation switching method shown in Figure 5 according to the method shown in Figure 7.

[0151] In step S41, after the ventilation device 1 is started, the control device 3 sets the operating mode of the air conditioning system 201 to a first operating mode in which the ventilation device 1 is operated independently. In step S43, the control device 3 sets the threshold Th in the first operating mode to the standard lower limit (Figure 4).

[0152] In step S45, the control device 3 determines whether condition D (Figure 4), which indicates a deficiency of the first capacity Av that the ventilation device 1 has in raising the temperature of the target space SP, is met. If condition D is not met in step S45, the control device 3 returns to the process in step S41. As a result, the first operating mode continues and the threshold Th is maintained at the standard lower limit.

[0153] On the other hand, if condition D is met in step S45, in step S47, the control device 3 changes the operating mode of the air conditioning system 201 from a first operating mode in which the ventilation device 1 is operated independently to a second operating mode in which both the ventilation device 1 and the air conditioning device 2 are operated. This makes it possible to compensate for any insufficient air conditioning capacity of the ventilation device 1 to handle the heating load with the air conditioning capacity of the air conditioning device 2 to handle the heating load.

[0154] In step S49, the control device 3 sets the threshold Th in the second operating mode to a heating priority lower limit (Figure 4) that is higher than the standard lower limit. This expands the range in which the ventilation device 1 operates in heating mode according to the temperature difference ΔT, thereby suppressing repeated starting and stopping of the heating operation of the ventilation device 1 in the second operating mode.

[0155] In step S51, the control device 3 determines whether condition E (Figure 4), which indicates an excess of the second capacity Ac that the air conditioning unit 2 uses to raise the temperature of the target space SP, is met. If condition E is not met in step S51, the control device 3 returns to the process in step S47. As a result, the second operating mode continues, and the threshold Th is maintained at the heating priority lower limit.

[0156] On the other hand, if condition E is met in step S51, in step S53, the control device 3 changes the operating mode of the air conditioning system 201 from a second operating mode in which both the ventilation device 1 and the air conditioning device 2 are operated to a first operating mode in which the ventilation device 1 is operated independently. This suppresses an excessive state of air conditioning capacity to handle the heating load and ensures energy efficiency of the air conditioning system 201.

[0157] In step S55, the control device 3 determines whether condition F (Figure 4), which indicates an increase in the heating load of the target space SP, is met. If condition F is not met in step S55, the control device 3 returns to the process in step S53. As a result, the first operating mode continues, and the threshold Th is maintained at the heating priority lower limit.

[0158] On the other hand, if condition F is met in step S55, the control device 3 sets the threshold Th in the first operating mode to a standard lower limit (Figure 4) that is lower than the heating priority lower limit in step S57. This suppresses the repeated starting and stopping of the heating operation of the ventilation device 1 immediately after transitioning from the second operating mode to the first operating mode due to the meeting of condition E in step S51.

[0159] Thus, according to this embodiment, it is possible to suppress the repeated starting and stopping of the ventilation device 1.

[0160] In this embodiment, the control circuit 5, ventilation control unit 23, and air conditioning control unit 76 are electronic circuits such as a CPU (Central Processing Unit), FPGA (Field Programmable Gate Array), or ASIC (Application Specific Integrated Circuit). The control circuit 5, ventilation control unit 23, and air conditioning control unit 76 perform the various control operations described in this specification by executing a program such as instruction code stored in memory, or by being circuit-designed for special applications.

[0161] Figure 8 is an example of a hardware configuration diagram of a control device. Computer 500 is an example of a control device 3. Computer 500 has a drive device 508, an auxiliary storage device 502, a memory device 503, a CPU 504, and an interface device 505, etc., which are all interconnected by a bus 506.

[0162] The program that enables processing on the computer 500 is provided by the recording medium 507. When the recording medium 507 containing the program is set in the drive device 508, the program is installed from the recording medium 507 to the auxiliary storage device 502 via the drive device 508. However, the program does not necessarily have to be installed from the recording medium 507; it may also be downloaded from another computer via a network. The auxiliary storage device 502 stores the installed program as well as necessary files and data.

[0163] The memory device 503 reads a program from the auxiliary storage device 502 and stores it when a program startup command is received. The CPU 504 is a processor that executes functions related to the computer 500 according to the program stored in the memory device 503. The interface device 505 is used as an interface for connecting to the outside world.

[0164] Examples of recording media 507 include portable recording media such as CD-ROMs, DVD discs, or USB memory sticks. Examples of auxiliary storage devices 502 include HDDs (Hard Disk Drives) or flash memory. Both recording media 507 and auxiliary storage devices 502 are computer-readable recording media.

[0165] As described above, embodiments have been explained, but these embodiments are presented as examples only, and the present invention is not limited by these embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0166] 1. Ventilation system 2 Air conditioner 3. Control device 4 Remote control 5 Control circuits 10 Exhaust Units 11 Exhaust fan 12 Return air heat exchanger 14 sensors 20 Air supply units 21 Intake fan 22 Outdoor heat exchanger 23 Ventilation Control Unit 24 sensors 50 Compressor Units 51 Compressor 52 Motors 53 Four-way switching valve 54 Expansion valve 60, 62 Refrigerant Circuit 61 Refrigerant piping 63 Liquid refrigerant connecting piping 70 Outdoor unit 71 Compressor 72 Four-way switching valve 73 Outdoor heat exchanger 74 Outdoor expansion valve 75 Outdoor fan 76 Air Conditioning Control Unit 81,82 Indoor unit 83 Indoor heat exchanger 84 Indoor expansion valve 85 Indoor fan 91 Return air port 92 Air supply port 93A,93B Air outlet 94 Air intake 95 Exhaust vent 201 Air Conditioning System 500 Computers

Claims

1. A ventilation device (1) comprising: a first compressor (51); a supply unit (20) which includes a first heat exchanger (22) functioning as a condenser or evaporator and supplies air taken in from outside the target space (SP) through the first heat exchanger; an exhaust unit (10) which includes a second heat exchanger (12) functioning as a condenser or evaporator and exhausts air taken in from the target space through the second heat exchanger and exhausts it to the outside of the target space; and a refrigerant circuit (60) through which the first compressor, the first heat exchanger, and the second heat exchanger are connected by refrigerant piping (61) and through which refrigerant flows. An air conditioning device (2) having a third heat exchanger (83) that functions as a condenser or evaporator and a second compressor (71) that compresses a refrigerant, and which draws in air from the target space and blows out air that has exchanged heat with the refrigerant flowing through the third heat exchanger back into the target space, An air conditioning system (201) comprising: a control unit (3) that changes a threshold for the ventilation system to perform cooling or heating operation when transitioning from a first operating mode in which the ventilation system is operated independently to a second operating mode in which both the ventilation system and the air conditioning system are operated.

2. The air conditioning system according to claim 1, wherein the control unit compares the temperature difference between the outside air temperature outside the target space and the target supply air temperature of the ventilation device with the threshold value.

3. The control unit, When transitioning from the first operating mode to the second operating mode, the threshold is changed from the first threshold to the second threshold. The air conditioning system according to claim 2, wherein when the system transitions from the second operating mode to the first operating mode and the temperature difference reaches the first threshold, the threshold is changed from the second threshold to the first threshold.

4. The aforementioned temperature difference is the value obtained by subtracting the target supply air temperature from the ambient air temperature. The air conditioning system according to claim 2, wherein the control unit lowers the threshold for the ventilation device to perform cooling operation when transitioning from the first operating mode to the second operating mode.

5. The aforementioned temperature difference is the value obtained by subtracting the target supply air temperature from the ambient air temperature. The air conditioning system according to claim 2, wherein the control unit raises the threshold for the ventilation device to perform heating operation when transitioning from the first operating mode to the second operating mode.

6. The air conditioning system according to claim 1, wherein the transition from the first operating mode to the second operating mode is performed when the period during which the difference between the set temperature of the ventilation device and the indoor air temperature in the target space exceeds a predetermined value exceeds a predetermined period.

7. The air conditioning system according to claim 1, wherein the transition from the first operating mode to the second operating mode is performed when the air conditioning load of the target space rises above a predetermined load.

8. The air conditioning system according to claim 1, wherein the transition from the second operating mode to the first operating mode is performed when the stop time of the second compressor exceeds a predetermined time.

9. The air conditioning system according to claim 1, wherein the transition from the second operating mode to the first operating mode is performed when the air conditioning load of the target space falls below a predetermined load.

10. A ventilation device (1) comprising: a first compressor (51); a supply unit (20) which includes a first heat exchanger (22) functioning as a condenser or evaporator and supplies air taken in from outside the target space (SP) through the first heat exchanger; an exhaust unit (10) which includes a second heat exchanger (12) functioning as a condenser or evaporator and exhausts air taken in from the target space through the second heat exchanger and exhausts it to the outside of the target space; and a refrigerant circuit (60) through which the first compressor, the first heat exchanger, and the second heat exchanger are connected by refrigerant piping (61) and through which refrigerant flows. A control device (3) for controlling an air conditioning system (2) which has a third heat exchanger (83) that functions as a condenser or evaporator and a second compressor (71) that compresses a refrigerant, and which draws in air from the target space and blows out air that has exchanged heat with the refrigerant flowing through the third heat exchanger back into the target space, A control device (3) is provided with a control circuit (5) that changes a threshold for the ventilation device to perform cooling or heating operation when transitioning from a first operating mode in which the ventilation device is operated independently to a second operating mode in which both the ventilation device and the air conditioning device are operated.

11. A ventilation device (1) comprising: a first compressor (51); a supply unit (20) which includes a first heat exchanger (22) functioning as a condenser or evaporator and supplies air taken in from outside the target space (SP) through the first heat exchanger; an exhaust unit (10) which includes a second heat exchanger (12) functioning as a condenser or evaporator and exhausts air taken in from the target space through the second heat exchanger and exhausts it to the outside of the target space; and a refrigerant circuit (60) through which the first compressor, the first heat exchanger, and the second heat exchanger are connected by refrigerant piping (61) and through which refrigerant flows. A method for controlling an air conditioning device (2) having a third heat exchanger (83) that functions as a condenser or evaporator and a second compressor (71) that compresses a refrigerant, the device drawing in air from the target space and blowing out air that has exchanged heat with the refrigerant flowing through the third heat exchanger back into the target space, A control method for changing the threshold for the ventilation device to perform cooling or heating operation when transitioning from a first operating mode in which the ventilation device is operated independently to a second operating mode in which both the ventilation device and the air conditioning device are operated.

12. A ventilation device (1) comprising: a first compressor (51); a supply unit (20) which includes a first heat exchanger (22) functioning as a condenser or evaporator and supplies air taken in from outside the target space (SP) through the first heat exchanger; an exhaust unit (10) which includes a second heat exchanger (12) functioning as a condenser or evaporator and exhausts air taken in from the target space through the second heat exchanger and exhausts it to the outside of the target space; and a refrigerant circuit (60) through which the first compressor, the first heat exchanger, and the second heat exchanger are connected by refrigerant piping (61) and through which refrigerant flows. A program to be executed by a control unit (3) that controls an air conditioning system (2) having a third heat exchanger (83) that functions as a condenser or evaporator and a second compressor (71) that compresses a refrigerant, and which draws in air from the target space and blows out air that has exchanged heat with the refrigerant flowing through the third heat exchanger back into the target space, A program that causes the control unit to perform a process to change the threshold for the ventilation unit to perform cooling or heating operation when transitioning from a first operating mode in which the ventilation unit is operated independently to a second operating mode in which both the ventilation unit and the air conditioning unit are operated.

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