Ventilation equipment and ventilation method

Abstract

To enable efficient defrosting.SOLUTION: A ventilation device includes: a compressor; a first heat exchanger; a first air flow passage indicating a flow passage that enables air taken in from an outdoor side to pass through the first heat exchanger and then to be discharged to an indoor space; a second heat exchanger; a second air flow passage indicating a flow passage that enables air taken in from the indoor space to pass through the second heat exchanger and then to be discharged to the outdoor side; a refrigerant circuit in which the compressor, the first heat exchanger and the second heat exchanger are connected by refrigerant piping and a refrigerant flows; and a control section that while the second heat exchanger is functioning as an evaporator, when the second heat exchanger is determined to be in a frost formation state, outputs a predetermined command to an actuator for controlling a state of the refrigerant in the refrigerant circuit to raise the temperature of the refrigerant flowing into the second heat exchanger so as to cause the second heat exchanger to function as a condenser and cause the first heat exchanger to function as an evaporator, and switches a flow of the air in the first air flow passage so as to discharge the air from the indoor space to the outdoor side.SELECTED DRAWING: Figure 2

Description

Technical Field

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[0001] The present disclosure relates to a ventilation device and a ventilation method.

Background Art

[0002] Conventionally, while performing indoor ventilation by an exhaust fan and an intake fan, outdoor air heat-exchanged with a refrigerant by a first heat exchanger is blown into the room, and indoor air heat-exchanged with the refrigerant by a second heat exchanger is discharged outdoors. A ventilation and air-conditioning device is known (see Patent Document 1). The ventilation and air-conditioning device described in Patent Document 1 proposes a technique of defrosting by switching the refrigerant flow in the first heat exchanger and the second heat exchanger when defrosting is performed. When performing such defrosting, the heating operation is temporarily stopped.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the ventilation and air-conditioning device described in Patent Document 1, when temporarily stopped for defrosting, defrosting can be performed by releasing heat in the second heat exchanger by switching the operation, but it may take time.

[0005] An object of the present disclosure is to perform efficient defrosting.

Means for Solving the Problems

[0006] The present disclosure is a compressor, a first heat exchanger functioning as a condenser or an evaporator, a first air flow path that supplies air taken in from the outside to an indoor space after passing through the first heat exchanger, A second heat exchanger that functions as a condenser or evaporator, A second air passage that takes in air from the indoor space, passes it through the second heat exchanger, and then exhausts it to the outdoors, The compressor, the first heat exchanger, and the second heat exchanger are connected by refrigerant piping, and a refrigerant circuit through which refrigerant flows is formed. When it is determined that the second heat exchanger is frosted, a control unit outputs a predetermined command to an actuator that controls the state of the refrigerant in the refrigerant circuit in order to raise the temperature of the second heat exchanger by directing the airflow from the indoor space to the second heat exchanger, and to raise the temperature of the refrigerant flowing into the second heat exchanger. To provide a ventilation system equipped with the following features.

[0007] The ventilation system improves the defrosting efficiency of the second heat exchanger by guiding the airflow in the indoor space to the second heat exchanger and controlling the state of the refrigerant in the refrigerant circuit to raise the temperature of the refrigerant flowing into the second heat exchanger.

[0008] Regarding the ventilation system mentioned above, If it is determined that the second heat exchanger is frosted, the system outputs the predetermined command indicating that the compressor should be stopped.

[0009] According to this ventilation system, stopping the compressor makes it possible to raise the temperature of the refrigerant in the second heat exchanger, thereby improving the defrosting efficiency of the second heat exchanger.

[0010] Regarding the ventilation system mentioned above, The number of the aforementioned second heat exchangers is multiple. The refrigerant circuit further includes a first valve section for adjusting the opening degree of the flow path connected to each of the second heat exchangers, When the control unit determines that a predetermined second heat exchanger, among the plurality of second heat exchangers, is frosted, it outputs a predetermined command to close the first valve corresponding to that predetermined second heat exchanger.

[0011] According to this ventilation device, by closing the first valve, the temperature of the refrigerant in a predetermined second heat exchanger can be increased, thereby improving the defrosting efficiency of the second heat exchanger.

[0012] According to this ventilation device, by closing the first valve, the temperature of the refrigerant in a predetermined second heat exchanger corresponding to the first valve can be increased, thereby improving the defrosting efficiency of the second heat exchanger.

[0013] Regarding the ventilation system mentioned above, When the control unit determines that multiple second heat exchangers are frosted, it outputs a predetermined command to close multiple first valve units corresponding to the multiple second heat exchangers that are determined to be frosted, in a predetermined order.

[0014] According to this ventilation system, by closing the first valve in a predetermined order, simultaneous defrosting of the second heat exchanger can be suppressed, thereby preventing a reduction in comfort.

[0015] Regarding the ventilation system mentioned above, The refrigerant circuit is provided between the first heat exchanger and the second heat exchanger and has a second valve section for adjusting the opening of the flow path. If the control unit determines that the second heat exchanger is frosted while it is functioning as an evaporator, it outputs a predetermined command to increase the opening degree of the second valve compared to before the determination of frost formation.

[0016] According to this ventilation system, by increasing the opening degree of the second valve and closing the first valve in a predetermined order, simultaneous defrosting of the second heat exchanger can be suppressed, thereby preventing a reduction in comfort.

[0017] Regarding the ventilation system mentioned above, While the second heat exchanger is functioning as an evaporator, a third valve is further provided downstream of the second heat exchanger in the flow of the refrigerant in the refrigerant circuit. When the control unit further determines that the second heat exchanger is in a frosting state while the second heat exchanger is functioning as an evaporator, the control unit outputs the predetermined command to reduce the opening degree of the third valve unit compared to before the state of being determined to be frosting.

[0018] According to the ventilation device, by reducing the opening degree of the third valve unit, the temperature of the refrigerant flowing through the upstream second heat exchanger is increased, and the defrosting efficiency of the second heat exchanger is improved.

[0019] Regarding the above ventilation device, The refrigerant circuit has a bypass pipe that allows the refrigerant to flow from the compressor to the second heat exchanger without passing through the first heat exchanger while the second heat exchanger is functioning as an evaporator. When the control unit determines that the second heat exchanger is in a frosting state, the control unit outputs the predetermined command so that the refrigerant compressed by the compressor flows through the bypass pipe to the second heat exchanger.

[0020] According to the ventilation device, by allowing the refrigerant to flow through the bypass pipe to the second heat exchanger, the temperature of the refrigerant flowing through the second heat exchanger is increased, and the defrosting efficiency of the second heat exchanger is improved.

[0021] Regarding the above ventilation device, As control for guiding the air flow in the indoor space to the second heat exchanger, the control unit controls a first guiding mechanism that can switch whether to guide air from the ceiling space adjacent to the upper part of the indoor space to the second heat exchanger, or controls a second guiding mechanism that can switch whether to guide air from the indoor space to the second heat exchanger.

[0022] According to the ventilation device, by flowing warm air through the second heat exchanger, the temperature of the refrigerant flowing through the second heat exchanger is increased, and the defrosting efficiency of the second heat exchanger is improved.

[0023] Regarding the above ventilation device, The system further includes a bypass guide mechanism that guides the air from which heat has been exchanged by the first heat exchanger to the second heat exchanger. If the control unit determines that the second heat exchanger is frosted, and determines that the temperature of the air whose heat has been exchanged by the first heat exchanger is higher than a predetermined temperature, it controls the bypass guidance mechanism to guide the air whose heat has been exchanged to the second heat exchanger.

[0024] According to this ventilation system, warm air is circulated to the second heat exchanger via a bypass guidance mechanism, thereby increasing the temperature of the refrigerant flowing through the second heat exchanger and improving the defrosting efficiency of the second heat exchanger.

[0025] Regarding the ventilation system mentioned above, The number of the aforementioned second heat exchangers is multiple. Each of the second heat exchangers is provided with a second air passage for exhausting air taken in from the indoor space to the outdoors. The control unit adjusts the airflow rate of the air flowing through the second air passage corresponding to the second heat exchanger based on the status of each of the multiple second heat exchangers.

[0026] This ventilation system adjusts the airflow rate according to the condition of each of the multiple second heat exchangers, thereby suppressing simultaneous defrosting of the second heat exchangers and preventing a decrease in comfort.

[0027] Regarding the ventilation system mentioned above, If the control unit determines that one of the multiple second heat exchangers has a greater degree of frost formation than the other second heat exchanger, it controls the first airflow rate of the second air passage corresponding to one second heat exchanger to be increased compared to the second airflow rate of the second air passage corresponding to the other second heat exchanger.

[0028] According to this ventilation system, defrosting of the second heat exchanger is performed according to the degree of frost accumulation on the second heat exchanger, thereby suppressing a reduction in comfort.

[0029] Regarding the ventilation system mentioned above, According to the ventilation device, when the control unit controls the first airflow to increase, it controls the second airflow to decrease compared to before the control to increase the first airflow.

[0030] This ventilation system helps maintain comfort by preventing negative pressure in indoor spaces.

[0031] Regarding the ventilation system mentioned above, When the control unit determines that the second heat exchanger is covered in frost, it outputs a signal to the air conditioner installed in the indoor space to raise the temperature set on the air conditioner.

[0032] According to this ventilation system, raising the temperature set in the air conditioner increases the temperature of the refrigerant flowing through the second heat exchanger, thereby improving the defrosting efficiency of the second heat exchanger.

[0033] Regarding the ventilation system mentioned above, The air flowing through the second air passage is provided with a switching mechanism that switches whether the air is supplied from the indoor space or from the outdoors. The control unit controls the switching mechanism to supply air from whichever of the indoor and outdoor temperatures is higher.

[0034] According to this ventilation system, by supplying air from the higher temperature side and flowing warm air to the second heat exchanger, the temperature of the refrigerant flowing through the second heat exchanger is increased, thereby improving the defrosting efficiency of the second heat exchanger.

[0035] Regarding the ventilation system mentioned above, After the control unit receives a signal from the air conditioner to perform a defrosting operation, if it determines that the second heat exchanger is frosted, it suppresses outputting the predetermined command to the actuator that controls the state of the refrigerant in the refrigerant circuit.

[0036] According to this ventilation system, by suppressing defrosting of the second heat exchanger, simultaneous defrosting of the air conditioner and the ventilation system can be suppressed, thereby preventing a reduction in comfort.

[0037] Regarding the ventilation system mentioned above, Furthermore, when the control unit receives a signal from the air conditioner to perform a defrosting operation, it controls the airflow rate supplied from the first air passage to the indoor space to increase compared to before receiving the signal from the air conditioner to perform a defrosting operation, and also controls the airflow rate exhausted from the second air passage to the outdoors to increase compared to before receiving the signal from the air conditioner to perform a defrosting operation.

[0038] This ventilation system allows for increased airflow, thereby improving the heating capacity of the ventilation system instead of using an air conditioner, and maintaining comfort.

[0039] Regarding the ventilation system mentioned above, If the control unit determines that the second heat exchanger is frosted, it further transmits a signal to the air conditioner instructing it not to perform defrosting.

[0040] This ventilation system suppresses defrosting of the air conditioner, thereby preventing simultaneous defrosting of the air conditioner and the ventilation system, and thus minimizing the reduction in comfort.

[0041] This disclosure is, Compressor and, A first heat exchanger that functions as a condenser or evaporator, A first airflow path is provided which shows a flow path that allows air taken in from outdoors to be discharged into the indoor space after passing through the first heat exchanger, A second heat exchanger that functions as a condenser or evaporator, A second airflow path is provided which allows air taken in from the indoor space to be exhausted to the outdoors after passing through the second heat exchanger, The compressor, the first heat exchanger, and the second heat exchanger are connected by refrigerant piping, and a refrigerant circuit through which refrigerant flows is formed. The present invention provides a ventilation system comprising: a control unit that, when it is determined that the second heat exchanger is frosted while the second heat exchanger is functioning as an evaporator, outputs a predetermined command to an actuator that controls the state of the refrigerant in the refrigerant circuit to raise the temperature of the refrigerant flowing into the second heat exchanger, causing the second heat exchanger to function as a condenser and the first heat exchanger to function as an evaporator.

[0042] According to this ventilation system, the defrosting efficiency of the second heat exchanger is improved by making the second heat exchanger function as a condenser.

[0043] Regarding the ventilation system mentioned above, If the control unit determines that the second heat exchanger is frosted while it is functioning as an evaporator, it outputs the predetermined command and switches the airflow in the first air passage to exhaust air from the indoor space to the outdoors.

[0044] According to this ventilation device, by switching the airflow in the first air passage to exhaust to the outside, the temperature of the refrigerant flowing through the refrigerant circuit rises, thereby improving the defrosting efficiency of the second heat exchanger.

[0045] Regarding the ventilation system mentioned above, The control unit further determines that the second heat exchanger is frosted while it is functioning as an evaporator, and switches the flow of the second air passage to supply air from the outdoors to the indoor space.

[0046] This ventilation system prevents the indoor space from becoming negatively pressurized by supplying air from outdoors to the indoor space, thereby preventing a decrease in comfort.

[0047] Regarding the ventilation system mentioned above, A first casing housing at least a portion of the first heat exchanger and the first air passage, The invention further comprises a second heat exchanger and a second casing that houses at least a portion of the second air passage, The first casing and the second casing are separable.

[0048] With this ventilation system, the first casing and the second casing are separable, which simplifies the layout and reduces the burden of installation.

[0049] This disclosure is, A ventilation method using a plurality of ventilation devices provided in a predetermined space, each comprising: a compressor; a first heat exchanger functioning as a condenser or evaporator; a first airflow path for supplying air taken in from outdoors to an indoor space after passing it through the first heat exchanger; a second heat exchanger functioning as a condenser or evaporator; a second airflow path for exhausting air taken in from the indoor space to the outdoors after passing it through the second heat exchanger; and a refrigerant circuit through which the compressor, the first heat exchanger, and the second heat exchanger are connected by refrigerant piping and through which refrigerant flows. The control unit, The frost formation status of multiple second heat exchangers is obtained, If it is determined that multiple second heat exchangers are frosted while they are functioning as evaporators, multiple patterns are generated for performing defrosting operations on the multiple second heat exchangers. The conditions of the predetermined space are acquired, and based on the frost formation state and the conditions of the predetermined space, defrost control of the second heat exchanger is performed using one of the multiple generated patterns. Provide a ventilation method.

[0050] This ventilation method allows for defrost control in an appropriate pattern, thereby improving the defrost efficiency of the second heat exchanger.

[0051] This disclosure is, A control unit that controls a ventilation system comprising a compressor, a first heat exchanger functioning as a condenser or evaporator, a first airflow path that supplies air taken in from outdoors to an indoor space after passing it through the first heat exchanger, a second heat exchanger functioning as a condenser or evaporator, a second airflow path that exhausts air taken in from the indoor space to the outdoors after passing it through the second heat exchanger, and a refrigerant circuit through which the compressor, the first heat exchanger, and the second heat exchanger are connected by refrigerant piping and through which refrigerant flows, determines that the second heat exchanger is frost-covered, and outputs a predetermined command to an actuator that controls the state of the refrigerant in the refrigerant circuit to raise the temperature of the second heat exchanger by directing the airflow from the indoor space to the second heat exchanger, and to raise the temperature of the refrigerant flowing into the second heat exchanger. Provide a ventilation method.

[0052] According to this ventilation method, the defrosting efficiency of the second heat exchanger is improved by guiding the airflow in the indoor space to the second heat exchanger and controlling the state of the refrigerant in the refrigerant circuit to raise the temperature of the refrigerant flowing into the second heat exchanger. [Brief explanation of the drawing]

[0053] [Figure 1] Figure 1 is a diagram showing an example of the configuration of a ventilation system and air conditioner according to the first embodiment. [Figure 2] Figure 2 shows an example of the configuration of a ventilation system, air conditioner, and higher-level control device according to the second embodiment. [Figure 3] Figure 3 shows a refrigerant circuit according to the second embodiment. [Figure 4] Figure 4 is a sequence diagram showing the processing flow between the higher-level control device, the compressor unit, and the exhaust unit group when frost forms on each of the exhaust unit groups according to a modified example of the second embodiment. [Figure 5] Figure 5 shows a refrigerant circuit according to Modification 1 of the third embodiment. [Figure 6] Figure 6 shows a refrigerant circuit according to the fourth embodiment. [Figure 7] Figure 7 shows an example of the configuration of a ventilation system and air conditioner according to the sixth embodiment. [Figure 8] Figure 8 shows an example of the configuration of a ventilation system and air conditioner according to the seventh embodiment. [Figure 9] Figure 9 shows an example of the configuration of a ventilation system and air conditioner according to the eighth embodiment. [Figure 10] Figure 10 is a diagram illustrating the arrangement of a group of devices including a higher-level control device according to the tenth embodiment. [Figure 11] Figure 11 is a flowchart showing the processing procedure performed by the higher-level control device according to the 11th embodiment. [Modes for carrying out the invention]

[0054] The embodiments described below will be explained with reference to the drawings. The following embodiments are essentially preferred examples and are not intended to limit the scope of the disclosure, its applications, or uses.

[0055] (First Embodiment) Figure 1 is a diagram showing an example configuration of a ventilation system and air conditioner according to the first embodiment. In the example shown in Figure 1, a ventilation system 1 and an air conditioner 2 are provided to provide air conditioning for an indoor space.

[0056] In this embodiment, an example of an indoor space having a living room space R11 and an attic space R12 will be described. However, the indoor space is not limited to the living room space R11 and the attic space R12, and may be any space inside the building, for example, it may include an underfloor space.

[0057] Living space R11 is, for example, a living room inside an office or house. Ceiling space R12 is the space adjacent to living space R11, located above it. Because ceiling space R12 is located above living space R11, warm air tends to accumulate there.

[0058] The air conditioner 2 includes an outdoor unit 70 and two indoor air conditioning units 81 and 82. Note that this embodiment does not limit the number of indoor air conditioning units to two; it may be one or three or more.

[0059] Air conditioner 2 is a device that performs a vapor compression type refrigeration cycle to cool or heat the living space R11. The air conditioner 2 according to this embodiment is a device that can both cool and heat the living space R11. However, this embodiment is not limited to an air conditioner that can both cool and heat, and may, for example, be a device that can only cool.

[0060] The outdoor unit 70 and the two indoor air conditioning units 81 and 82 are connected by a connecting pipe F5. The connecting pipe F5 includes a liquid refrigerant connecting pipe and a gaseous refrigerant connecting pipe (not shown). This creates a refrigerant circuit in which refrigerant circulates between the outdoor unit 70 and the two indoor air conditioning units 81 and 82. When refrigerant circulates within this refrigerant circuit, a vapor compression refrigeration cycle is performed in the air conditioner 2.

[0061] The outdoor unit 70 is located outdoors. 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.

[0062] The indoor air conditioning units 81 and 82 are equipped with a heat exchanger and blow out air that has exchanged heat with the refrigerant flowing through the heat exchanger into the living space R11. In this embodiment, the indoor air conditioning units 81 and 82 are ceiling-mounted units installed on the ceiling of the living space R11. In particular, the indoor air conditioning units 81 and 82 in this embodiment are ceiling-embedded units, and the heat-exchanged air is blown out from the ventilation openings 93A and 93B. In this embodiment, an example in which the ventilation openings 93A and 93B are provided on the ceiling is described, but the position in which the ventilation openings 93A and 93B are provided is not particularly limited. Note that the indoor air conditioning units 81 and 82 are not limited to ceiling-embedded units, but may also be ceiling-suspended units. In addition, the indoor air conditioning units 81 and 82 may be wall-mounted or floor-standing units, or other types other than ceiling-mounted units.

[0063] The ventilation system 1 comprises an exhaust unit 10, a supply unit 20, a compressor unit 50, refrigerant circuits F1, F2, F3, F4, a supply air passage P1, and a return air passage P2.

[0064] Ventilation device 1 is a device that supplies outdoor air taken in to the living space R11, and exhausts air taken in from the indoor space (including the living space R11) to the outside. In this way, ventilation device 1 achieves air exchange in the living space R11.

[0065] Furthermore, the ventilation system 1 according to this embodiment suppresses the temperature difference between the temperature of the air taken in from outside and the temperature of the living space R11 by exchanging heat between the exhaust unit 10 and the supply unit 20.

[0066] The air supply passage P1 (an example of the first air passage) is a passage for supplying air taken in from outside (outside air) to the living space R11 through the ventilation opening 92 after passing it through the air supply unit 20 having the first heat exchanger 22. This embodiment describes an example in which the ventilation opening 92 is installed on the ceiling, but there are no particular restrictions on the location where the ventilation opening 92 is installed.

[0067] The return air passage P2 (an example of a second air passage) is a passage for exhausting air (return air) taken in from the ventilation opening 91 of the living space R11 to the outside after passing it through the exhaust unit 10 having a second heat exchanger 12. This embodiment describes an example in which the ventilation opening 91 is installed on the ceiling, but there are no particular restrictions on the location where the ventilation opening 91 is installed.

[0068] Refrigerant circuits F1, F2, F3, and F4 are circuits that connect the compressor unit 50, the first heat exchanger 22 of the supply air unit 20, and the second heat exchanger 12 of the exhaust unit 10 by refrigerant piping, and allow refrigerant to flow through them.

[0069] The control unit 52 of the compressor unit 50, the control unit 23 of the air supply unit 20, and the control unit 13 of the exhaust unit 10 are connected by a signal line S1, which is shown as a dotted line in Figure 1. This enables the transmission and reception of information between the control unit 52 of the compressor unit 50, the control unit 23 of the air supply unit 20, and the control unit 13 of the exhaust unit 10.

[0070] The compressor unit 50 includes a drive motor 51 and a control unit 52, and controls the circulation of refrigerant in refrigerant circuits F1, F2, F3, and F4 by compressing one of the refrigerant circuits F1, F2, F3, and F4. For example, when the second heat exchanger 12 in the exhaust unit 10 functions as an evaporator, the compressor unit 50 circulates the refrigerant in refrigerant circuits F1, F2, F3, and F4 by compressing the refrigerant in refrigerant circuit F2.

[0071] The drive motor 51 is a motor used to rotate (drive) the compressor for compressing the refrigerant.

[0072] The control unit 52 controls the configuration within the compressor unit 50. For example, the control unit 52 outputs a command to the drive motor 51 to rotate (drive) the compressor.

[0073] The air supply unit 20 comprises a fan 21, a first heat exchanger 22, a control unit 23, and a temperature detection unit 24, and takes in outside air (OA) and supplies it (SA) to the living space R11.

[0074] Fan 21 functions to supply (SA) the outside air (OA) taken in to the living space R11.

[0075] The first heat exchanger 22 functions as a condenser or evaporator.

[0076] The temperature detection unit 24 detects the ambient temperature outdoors, the surface temperature of the first heat exchanger 22, and the temperature of the refrigerant flowing through the first heat exchanger 22.

[0077] The control unit 23 controls the internal configuration of the air supply unit 20. The control unit 23 performs various controls according to the detection results from the temperature detection unit 14. For example, the control unit 23 adjusts the function of the first heat exchanger 22 as a condenser or evaporator according to the detection results from the temperature detection unit 24.

[0078] The exhaust unit 10 comprises a fan 11, a second heat exchanger 12, a control unit 13, and a temperature detection unit 14, and takes in return air (RA) from the living space R11 and exhausts it outdoors (EA).

[0079] Fan 11 functions to exhaust (EA) the return air (RA) taken in from the living space R11 to the outside.

[0080] The second heat exchanger 12 functions as a condenser or evaporator.

[0081] The temperature detection unit 14 detects the outdoor temperature, the surface temperature of the second heat exchanger 12, and the temperature of the refrigerant flowing through the second heat exchanger 12. Furthermore, the temperature detection unit 14 may also detect the temperature of the air in the living space R11 and the temperature of the air in the ceiling space R12 via a sensor unit (not shown).

[0082] The control unit 13 controls the internal configuration of the exhaust unit 10. The control unit 13 performs various controls according to the detection results from the temperature detection unit 14. For example, the control unit 13 adjusts the function of the second heat exchanger 12 as a condenser or evaporator according to the detection results from the temperature detection unit 14.

[0083] The following describes the process performed by the ventilation system 1 when the temperature is low. When the temperature is low, the ventilation system 1 warms the outside air (OA) taken in from outside in the supply air unit 20 and then supplies it to the living space R11 (SA), and cools the return air (RA) taken in from the living space R11 in the exhaust unit 10 and then exhausts it to the outside (EA). In other words, the first heat exchanger 22 in the supply air unit 20 functions as a condenser, and the second heat exchanger 12 in the exhaust unit 10 functions as an evaporator. Because the second heat exchanger 12 functions as an evaporator, the temperature of the refrigerant flowing through the second heat exchanger 12 becomes low, which may cause frost to form on the second heat exchanger 12. Therefore, in this embodiment, if it is determined that frost has formed on the second heat exchanger 12, a defrosting operation is performed.

[0084] Specifically, the control unit 13 of the exhaust unit 10 determines, based on the detection results from the temperature detection unit 14, whether the second heat exchanger 12 is frosted while it is functioning as an evaporator. The predetermined criteria for indicating frost formation on the second heat exchanger 12 could be that the temperature of the refrigerant passing through the second heat exchanger 12 remains below a predetermined value (e.g., 0 degrees Celsius) for a certain period of time (e.g., 10 minutes). This embodiment is not limited to using the refrigerant temperature to determine the frosted state; the refrigerant pressure may also be used for detection. Furthermore, a further method for determining the frosted state may be used. For example, the control unit 13 may detect that the surface temperature of the second heat exchanger 12 remains below a predetermined value (e.g., 0 degrees Celsius) for a certain period of time (e.g., 10 minutes). Another example is that the control unit 13 may use an imaging device to image the surface of the second heat exchanger 12 and make a determination based on the degree of agreement between the captured image data and the image data under normal conditions. Furthermore, if it is possible to determine whether or not frost has formed on the second heat exchanger 12, methods other than those described above may be used.

[0085] In this embodiment, the control unit 13 of the exhaust unit 10 performs control to defrost the second heat exchanger 12 when it determines that a predetermined criterion is met. As control for defrosting, the control unit 13 controls the flow of air from the living space R11 to the second heat exchanger 12 in order to raise the temperature of the second heat exchanger 12. Specifically, the control maintains the rotation of the fan 11 of the exhaust unit 10. This allows the warm air from the living space R11 to flow to the second heat exchanger 12.

[0086] Furthermore, the control unit 13 of the exhaust unit 10 outputs a command (an example of a predetermined command) to the drive motor 51 (an example of an actuator) of the compressor unit 50 via the control unit 52 of the compressor unit 50 to stop the compressor inside the compressor unit 50.

[0087] In this embodiment, the drive motor 51 stops the compressor based on the command, thereby stopping the circulation of refrigerant in the refrigerant circuits F1, F2, F3, and F4.

[0088] In this embodiment, the control unit 13, as an example of control for defrosting the second heat exchanger 12, stops the circulation of refrigerant in the refrigerant circuits F1, F2, F3, and F4, and then flows warm air from the living space R11 to the second heat exchanger 12, thereby raising the temperature of the refrigerant flowing through the second heat exchanger and performing defrosting.

[0089] Incidentally, in conventional defrosting of the second heat exchanger, when the outside air temperature was low, there was a tendency to reverse the circulation cycle of the refrigerant circuit before performing the defrosting operation. In defrosting operations switched to the reverse cycle, the supply air to the indoor space is supplied from the evaporator side, so the temperature of the supply air becomes low, and it was common to stop the supply air. In this case, ventilation becomes insufficient. Also, if it was necessary to ensure the supply airflow, heating by auxiliary heaters or the like was required in the supply air passage, but this heating had the problem of low thermal efficiency.

[0090] Therefore, in this embodiment, by stopping the circulation of refrigerant circuits F1, F2, F3, and F4 and using the warm air (heat) from the living space R11 to defrost the second heat exchanger 12, highly thermally efficient defrosting can be achieved.

[0091] (Second embodiment) In the above-described embodiment, an example in which one exhaust unit is provided was explained. However, the number of exhaust units to be defrosted is not limited to one, and multiple units may be provided. Therefore, in the second embodiment, a configuration in which multiple exhaust units are provided and each of the exhaust units can be defrosted will be described.

[0092] Figure 2 shows an example configuration of a ventilation system, air conditioner, and higher-level control device according to the second embodiment. In this embodiment, a higher-level control device, located above the air conditioner and ventilation system, performs the control. Components similar to those in the above-described embodiment are assigned the same reference numerals and their descriptions are omitted.

[0093] In the example shown in Figure 2, a higher-level control device 100 is provided to coordinate the ventilation device 1B and the air conditioner 2B.

[0094] The air conditioner 2B includes an outdoor unit 170 and two indoor air conditioning units 81 and 82. Note that this embodiment does not limit the number of indoor air conditioning units to two; it may be one or three or more.

[0095] The outdoor unit 170 includes a control unit 171 along with a heat exchanger (not shown).

[0096] The control unit 171 controls the entire air conditioner 2B. The control unit 171 also transmits and receives information with the higher-level control unit 100. The control unit 171 then performs various controls in response to control signals from the higher-level control unit 100.

[0097] The ventilation system 1B comprises a first exhaust unit 110A, a second exhaust unit 110B, a first supply unit 120A, a second supply unit 120B, a compressor unit 150, refrigerant circuits F101, F102, F103, F104, a first supply air passage P101, a second supply air passage P102, a first exhaust air passage P103, and a second exhaust air passage P104.

[0098] The first air supply channel P101 takes in air from outside, passes it through the first air supply unit 120A which has a first heat exchanger 22, and then supplies it to the living space R11 through the ventilation opening 92A.

[0099] The second air supply channel P102 takes in air from outside, passes it through the second air supply unit 120B which has the first heat exchanger 22, and then supplies it to the living space R11 through the ventilation opening 92B.

[0100] The first exhaust flow path P103 takes in air (return air) from the ventilation opening 91A in the indoor space, passes it through the first exhaust unit 110A which has a second heat exchanger 12, and then exhausts it to the outside.

[0101] The second exhaust passage P104 takes in air (return air) from the ventilation opening 91B in the indoor space, passes it through the second exhaust unit 110B which has a second heat exchanger 12, and then exhausts it to the outside.

[0102] Refrigerant circuits F101, F102, F103, and F104 are circuits that connect the compressor unit 150, the first heat exchanger 22 of the first supply unit 120A and the second supply unit 120B, and the second heat exchanger 12 of the first exhaust unit 110A and the second exhaust unit 110B via refrigerant piping, and through which refrigerant flows.

[0103] The control unit 152 of the compressor unit 150, the control unit 123 of the first supply unit 120A, the control unit 123 of the second supply unit 120B, the control unit 113A of the first exhaust unit 110A, and the control unit 113B of the second exhaust unit 110B are connected by a signal line S101, indicated by a dotted line. This enables the transmission and reception of information between the control unit 152, the two control units 123, the control unit 113A, and the control unit 113B.

[0104] The control unit 152 of the compressor unit 150 transmits the status of the ventilation device 1B, received from the two control units 123, control unit 113A, and control unit 113B, to the higher-level control unit 100. This enables the higher-level control unit 100 to perform control according to the status of the ventilation device 1B.

[0105] The first air supply unit 120A comprises a fan 21, a first heat exchanger 22, a control unit 123, and a temperature detection unit 24, and takes in outside air (OA) and supplies it (SA) to the living space R11 through the ventilation opening 92A.

[0106] The second air supply unit 120B includes a fan 21, a first heat exchanger 22, a control unit 123, and a temperature detection unit 24, and takes in outside air (OA) and supplies it (SA) to the living space R11 through the ventilation opening 92B.

[0107] The control unit 123 controls the configuration within each air supply unit. Furthermore, the control unit 123 transmits the detection results from the temperature detection unit 24, etc., within each air supply unit to the control unit 152 of the compressor unit 150. The control unit 152 of the compressor unit 150 recognizes the current status from the detection results and transmits the recognition result to the higher-level control device 100. This allows the higher-level control device 100 to recognize the status of the first air supply unit 120A and the second air supply unit 120B.

[0108] The first exhaust unit 110A comprises a fan 11, a second heat exchanger 12, a control unit 113A, and a temperature detection unit 14, and takes in return air (RA) from the ventilation opening 91A of the living space R11 and exhausts it outdoors (EA).

[0109] The second exhaust unit 110B comprises a fan 11, a second heat exchanger 12, a control unit 113B, and a temperature detection unit 14, and takes in return air (RA) from the ventilation opening 91B of the living space R11 and exhausts it outdoors (EA).

[0110] Control units 113A and 113B control the configuration within their respective exhaust units. Furthermore, control units 113A and 113B transmit the detection results from the temperature detection unit 14, etc., within their respective exhaust units to the control unit 152 of the compressor unit 150. The control unit 152 of the compressor unit 150 recognizes the current status from the detection results and transmits the recognition result to the higher-level control device 100. This allows the higher-level control device 100 to recognize the status of the first exhaust unit 110A and the second exhaust unit 110B.

[0111] The higher-level control device 100 performs various controls to coordinate the operation of the ventilation device 1B and the operation of the air conditioner 2B.

[0112] The higher-level control device 100 receives the status of the air conditioner 2B from the control unit 171 of the outdoor unit 170 and the status of the ventilation device 1B from the control unit 152 of the compressor unit 150. The higher-level control device 100 then performs various controls according to the status of the air conditioner 2B and the ventilation device 1B.

[0113] Furthermore, when the higher-level control device 100 recognizes that frost has formed on either the second heat exchanger 12 of the first exhaust unit 110A or the second exhaust unit 110B, it performs control to stop the circulation of refrigerant to the frosted second heat exchanger 12. In this embodiment, the circulation of refrigerant can be stopped for each second heat exchanger 12. Next, the refrigerant circuit will be described.

[0114] Figure 3 is a diagram showing a refrigerant circuit according to the second embodiment. In the example shown in Figure 3, the flow of refrigerant is shown when the second heat exchangers 12 of the exhaust units 110A and 110B are functioning as evaporators. Components similar to those in the embodiments described above are assigned the same reference numerals and their descriptions are omitted.

[0115] In the example shown in Figure 3, an air supply unit 120A, 120B, an exhaust unit 110A, 110B, and a compressor unit 150 are provided.

[0116] The air supply units 120A and 120B each include a fan 21, a first heat exchanger 22, a control unit 123, a temperature detection unit 24, a drive motor 25, and an electric valve 26.

[0117] The drive motor 25 controls the airflow of the fan 21 through control by the control unit 123.

[0118] The electric valve 26 functions as an expansion valve that adjusts the opening of the flow path through which the refrigerant flows in order to reduce the pressure of the refrigerant, and switches whether or not to reduce the pressure based on the control unit 123. The electric valve 26 functions to reduce the pressure when the first heat exchanger 22 is functioning as an evaporator, and not to reduce the pressure when the first heat exchanger 22 is functioning as a condenser. As shown in Figure 3, the electric valve (expansion valve) 26 is provided in the flow path connected to the first heat exchanger 22 for each first heat exchanger.

[0119] The exhaust unit 110A comprises a fan 11, a second heat exchanger 12, a control unit 113A, a temperature detection unit 14, a drive motor 15, and an electric valve 16.

[0120] The exhaust unit 110B includes a fan 11, a second heat exchanger 12, a control unit 113B, a temperature detection unit 14, a drive motor 15, and an electric valve 16.

[0121] The drive motor 15 controls the airflow of the fan 11 by control of the control unit 113A or control unit 113B.

[0122] The electric valve 16 functions as an expansion valve that adjusts the opening of the flow path through which the refrigerant flows in order to reduce the pressure of the refrigerant, and switches whether or not to reduce the pressure based on control by the control unit 113A or the control unit 113B. The electric valve 16 functions to reduce the pressure when the second heat exchanger 12 is functioning as an evaporator, and not to reduce the pressure when the second heat exchanger 12 is functioning as a condenser. As shown in Figure 3, the electric valve (expansion valve) 16 is provided in the flow path connected to the second heat exchanger 12 for each second heat exchanger.

[0123] The compressor unit 150 includes a drive motor 51, a control unit 152, a compressor 53, a four-way valve 54, an electric valve 55, and a bypass electric valve 56.

[0124] The compressor 53 compresses the refrigerant flowing through the refrigerant circuit.

[0125] The drive motor 51 is an actuator that drives the compressor 53. In this embodiment, the drive motor 51 drives the compressor 53 at a rotational speed controlled by the control unit 152.

[0126] The control unit 152 controls the internal configuration of the compressor unit 150. For example, the control unit 152 controls the drive motor 51 and the four-way valve 54 shown below.

[0127] The four-way valve 54 functions as a valve that switches the outlet destination of the refrigerant compressed by the compressor 53 from the refrigerant circuits F101 and F104. For example, when the second heat exchanger 12 is made to function as an evaporator based on the control of the control unit 152, the four-way valve 54 is switched to direct the refrigerant compressed by the compressor 53 to the refrigerant circuit F101.

[0128] The electric valve 55 functions as a valve that controls the opening and closing of the refrigerant circuit according to the control unit 152. When the second heat exchanger 12 functions as an evaporator, the electric valve 55 is in a closed state, preventing the flow of refrigerant.

[0129] The control units 113A and 113B output the detection results from the temperature detection unit 14 to the control unit 152 of the compressor unit 150.

[0130] Then, the control unit 152 of the compressor unit 150 determines from the input detection result whether or not the second heat exchanger 12 meets predetermined criteria indicating that frost has formed on it. The predetermined criteria are the same as in the first embodiment, so their explanation will be omitted.

[0131] In this embodiment, the control units 113A and 113B of the exhaust units 110A and 110B notify the higher-level control unit 100 that frost has formed on the second heat exchanger 12 of the exhaust units 110A and 110B when they determine that a predetermined criterion has been met. This allows the higher-level control unit 100 to recognize that frost has formed on the second heat exchanger 12.

[0132] Then, the higher-level control device 100 outputs a control signal (an example of a predetermined command) to the exhaust unit (first exhaust unit 110A or second exhaust unit 110B) that includes the frosted second heat exchanger 12, causing the motorized valve 16 located upstream of the second heat exchanger 12 to close.

[0133] Then, the control unit (control unit 113A or control unit 113B) of the exhaust unit (first exhaust unit 110A or second exhaust unit 110B) receives a control signal from the higher-level control device 100 via the compressor unit 150 to close the electric valve 16. In this case, the control unit (control unit 113A or control unit 113B) of the exhaust unit (first exhaust unit 110A or second exhaust unit 110B) controls the electric valve 16 to a closed state by outputting a signal to an actuator (not shown) that adjusts the opening degree of the electric valve 16 (an example of an actuator that controls the state of the refrigerant in the refrigerant circuit) to close the electric valve 16.

[0134] When the electric valve 16 is closed, the inflow of refrigerant into the second heat exchanger 12 located downstream of the electric valve 16 is suppressed. The rotation control of the fan 11 is maintained, as in the embodiment described above.

[0135] In other words, in this embodiment, when there are multiple second heat exchangers 12, as an example of control for defrosting a second heat exchanger 12 that has accumulated frost, the electric valve 16 upstream of the second heat exchanger 12 that has accumulated frost is closed to stop the inflow of cold air into the second heat exchanger 12, and then warm air from the living space R11 is flowed into the second heat exchanger 12 to raise the temperature of the refrigerant flowing through the second heat exchanger, thereby performing defrosting.

[0136] In this embodiment, by using the warm air (heat) from the living space R11 to defrost the second heat exchanger 12, highly thermally efficient defrosting can be achieved.

[0137] (Modification 1 of the second embodiment) In the embodiment described above, an example was explained in which the electric valve 16 corresponding to the second heat exchanger 12 is controlled to a closed state when frost forms on the second heat exchanger 12. However, if multiple second heat exchangers 12 are frosted and multiple electric valves 16 are controlled to a closed state, the air conditioning capacity of the ventilation device 1B will decrease. Therefore, in this modified example, an example is described in which, when multiple second heat exchangers 12 are frosted, defrosting is not performed on multiple second heat exchangers 12 simultaneously.

[0138] Figure 4 is a sequence diagram showing the processing flow between the upper control device 100, the compressor unit 150, and the exhaust unit groups 110A and 110B when frost forms on each of the exhaust unit groups according to Modification 1 of the second embodiment.

[0139] First, the control unit 113A of the first exhaust unit 110A obtains the temperature of the refrigerant in the second heat exchanger 12 from the temperature detection unit 14 (S1401).

[0140] The control unit 113A then notifies the control unit 152 of the compressor unit 150 of the detected refrigerant temperature (1402).

[0141] Furthermore, the control unit 113B of the second exhaust unit 110B obtains the temperature of the refrigerant in the second heat exchanger 12 from the temperature detection unit 14 (S1411).

[0142] The control unit 113B then notifies the control unit 152 of the compressor unit 150 of the detected refrigerant temperature (1412).

[0143] The control unit 152 of the compressor unit 150 determines, based on the detected refrigerant temperature received from the control unit 113A of the first exhaust unit 110A and the control unit 113B of the second exhaust unit 110B, whether or not predetermined criteria indicating frost formation on the second heat exchangers 12 of the first exhaust unit 110A and the second exhaust unit 110B are met (S1421). In the example shown in Figure 4, it is determined that the predetermined criteria are met for each of the second heat exchangers 12 of the first exhaust unit 110A and the second exhaust unit 110B. The predetermined criteria are the same as those described in the embodiment above, so their explanation is omitted.

[0144] The control unit 152 of the compressor unit 150 notifies the higher-level control device 100 of the determination result indicating that frost has formed (S1422).

[0145] The higher-level control device 100 determines the order in which to perform frost avoidance control for the first exhaust unit 110A and the second exhaust unit 110B based on the received determination result (S1431). Any method can be used to determine this order. For example, the control may be set to perform frost avoidance on the unit with a higher probability of frosting first, or it may be determined according to the priority order that has been pre-assigned to the first exhaust unit 110A and the second exhaust unit 110B. The example shown in Figure 4 is an example in which it is determined that defrosting is performed on the first exhaust unit 110A and then the second exhaust unit 110B.

[0146] The higher-level control device 100 transmits a signal to the control unit 152 of the compressor unit 150 indicating that the electric valve 16 of the first exhaust unit 110A is closed (S1432).

[0147] Then, the control unit 152 of the compressor unit 150 transmits a signal to the control unit 113A of the first exhaust unit 110A indicating an instruction to close the electric valve 16 (S1423).

[0148] As a result, the control unit 113A of the first exhaust unit 110A controls the electric valve 16 to a closed state (S1403). This suppresses the inflow of refrigerant from the first exhaust unit 110A into the second heat exchanger 12.

[0149] After a predetermined time has elapsed (for example, a suitable time for the second heat exchanger 12 of the first exhaust unit 110A to complete defrosting), the higher-level control device 100 transmits a signal to the control unit 152 of the compressor unit 150 indicating that the electric valve 16 of the first exhaust unit 110A should be opened (S1433).

[0150] Then, the control unit 152 of the compressor unit 150 transmits a signal to the control unit 113A of the first exhaust unit 110A indicating an instruction to open the electric valve 16 (S1424).

[0151] As a result, the control unit 113A of the first exhaust unit 110A controls the electric valve 16 to open (S1404). This restarts the flow of refrigerant from the first exhaust unit 110A to the second heat exchanger 12.

[0152] The higher-level control device 100 transmits a signal to the control unit 152 of the compressor unit 150 indicating an instruction to close the electric valve 16 of the second exhaust unit 110B (S1434).

[0153] Then, the control unit 152 of the compressor unit 150 transmits a signal to the control unit 113B of the second exhaust unit 110B indicating an instruction to close the electric valve 16 (S1425).

[0154] As a result, the control unit 113B of the second exhaust unit 110B controls the electric valve 16 to a closed state (S1413). This suppresses the inflow of refrigerant into the second heat exchanger 12 of the second exhaust unit 110B.

[0155] In this manner, when the higher-level control device 100 determines that multiple second heat exchangers 12 are frosted, it sends a signal to close multiple electric valves 16 corresponding to the multiple second heat exchangers that are determined to be frosted, in a predetermined order.

[0156] Therefore, the control unit 152 and the higher-level control device 100 of the compressor unit 150 according to this embodiment can defrost the second heat exchangers 12 by suppressing the inflow of refrigerant into any one of the multiple second heat exchangers 12 while maintaining the inflow of warm air from the living space R11 by the fan 11, when they determine that a predetermined criterion has been met while the multiple second heat exchangers 12 are functioning as evaporators.

[0157] Furthermore, this embodiment suppresses simultaneous defrosting of the second heat exchangers 12 of multiple exhaust units by performing defrosting on each of the multiple exhaust units in a predetermined order, thereby further suppressing the decrease in room temperature R11.

[0158] (Third embodiment) Furthermore, other methods may be used for defrosting the second heat exchanger 12. Therefore, in the third embodiment, an alternative method for adjusting the opening degree of the electric valve 16 inside the exhaust unit 310 will be described. Note that the configuration of the higher-level control device 100, air conditioner 2B, and ventilation device 1B according to the third embodiment is the same as in the second embodiment and will not be described further.

[0159] As shown in Figure 4, when the second heat exchanger 12 is functioning as an evaporator, the electric valve 16 (an example of the second valve section) is located between the first heat exchanger 22 and the second heat exchanger 12.

[0160] When the second heat exchanger 12 is functioning as an evaporator, the electric valve 16 functions as a valve that reduces the pressure of the high-pressure liquid refrigerant flowing out of the first heat exchanger 22 in order to make it easier to evaporate, according to the control unit 313. As the opening of the electric valve 16 decreases, the pressure is reduced, and the temperature of the refrigerant decreases. In other words, as the opening of the electric valve 16 increases, the temperature of the refrigerant increases.

[0161] Then, while the second heat exchanger 12 is functioning as an evaporator, the higher-level control device 100 recognizes that frost has formed on the second heat exchanger 12 based on the determination result from the control unit 152 of the compressor unit 150. The determination by the control unit 152 of the compressor unit 150 is the same as in the embodiments and modifications described above, so the explanation is omitted.

[0162] The higher-level control device 100 then outputs a control signal to the exhaust unit (for example, the first exhaust unit 110A or the second exhaust unit 110B) that includes the second heat exchanger 12 which has been determined to have frost formation, to increase the opening degree of the electric valve 16 compared to before the determination of frost formation.

[0163] Then, when the control unit 113A of the first exhaust unit 110A or 113B of the second exhaust unit 110B receives the control signal, it outputs a control signal (an example of a predetermined command) to an actuator (not shown) that adjusts the opening degree of the electric valve 16 (an example of an actuator that controls the state of the refrigerant in the refrigerant circuit) compared to before it was determined that frost had formed, thereby increasing the opening degree of the electric valve 16.

[0164] This causes the temperature of the refrigerant flowing through the second heat exchanger 12 to rise. In addition, warm air from the living space R11 flows into the second heat exchanger 12 by the fan 11. This enables defrosting of the second heat exchanger 12.

[0165] (Modification 1 of the third embodiment) Defrosting of the second heat exchanger 12 may be performed using methods other than those described in the embodiments above. Therefore, in Modification 1 of the third embodiment, an example of adjusting the refrigerant pressure with an electric valve installed downstream of the exhaust unit will be described.

[0166] The configuration of the third embodiment modification 1 is the same as that of the second embodiment described above, except for the refrigerant circuit.

[0167] Figure 5 shows a refrigerant circuit according to Modification 1 of the third embodiment. In the example shown in Figure 5, the refrigerant flow is shown when the second heat exchangers 12 of the exhaust units 110A and 110B are functioning as evaporators. Components similar to those in the embodiments described above are assigned the same reference numerals and their descriptions are omitted.

[0168] In the example shown in Figure 5, when the second heat exchanger 12 of exhaust units 110A and 110B is functioning as an evaporator, electric valves 161 and 162 (an example of a third valve section) are provided downstream of the second heat exchanger 12 of each of the exhaust units 110A and 110B.

[0169] The electric valves 161 and 162 are located downstream of the refrigerant flowing through the second heat exchanger 12 and have a mechanism for adjusting the flow rate of the refrigerant.

[0170] Then, the control unit 152 of the compressor unit 150 according to this modified example determines whether a predetermined criterion indicating frost formation on the second heat exchanger 12 is met, based on the temperature of the refrigerant flowing through the second heat exchanger 12 while the second heat exchanger 12 is functioning as an evaporator. The predetermined criterion is the same as in the embodiment described above, so its explanation is omitted. The control unit 152 of the compressor unit 150 notifies the higher-level control device 100 of the determination result.

[0171] In this modified example, when the higher-level control device 100 recognizes that a second heat exchanger 12 that meets a predetermined criterion exists, it outputs a control signal (a predetermined command) to the control unit (control unit 113A or control unit 113B) of the exhaust unit including the second heat exchanger 12 (for example, the first exhaust unit 110A or the second exhaust unit 110B) that causes the opening degree of the electric valve (electric valve 161 or electric valve 162) to be reduced compared to before the predetermined criterion was met. As a result, the control unit (control unit 113A or control unit 113B) outputs a control signal (an example of a predetermined command) to the actuator (an example of an actuator that controls the state of the refrigerant in the refrigerant circuit) that adjusts the opening degree of the electric valve (electric valve 161 or electric valve 162), thereby reducing the opening degree of the electric valve (electric valve 161 or electric valve 162).

[0172] Thus, in this modified example, in addition to the electric valve 16 provided on the upstream side of the second heat exchanger 12, an electric valve for adjusting the flow rate of the refrigerant is provided on the downstream side of the second heat exchanger 12.

[0173] By reducing the opening of the electric valve (electric valve 161 or electric valve 162), the pressure of the refrigerant flowing through the second heat exchanger 12, which is located upstream of the electric valve (electric valve 161 or electric valve 162), can be increased. This increases the evaporation temperature of the refrigerant flowing through the second heat exchanger 12. In addition, warm air from the living space R11 continues to flow into the second heat exchanger 12 by the fan 11. Therefore, defrosting of the second heat exchanger 12 can be achieved.

[0174] (Fourth embodiment) Defrosting of the second heat exchanger 12 may be performed using methods other than those described in the embodiments above. In the fourth embodiment, an example of providing a bypass flow path (an example of bypass piping) in the refrigerant circuit will be described. In the fourth embodiment, compared to the third embodiment, one exhaust unit 110B is removed, and an example is provided in which two supply air units 120A and 120B and one exhaust unit 110A are provided. Other configurations are the same as in the third embodiment and will not be described.

[0175] Figure 6 is a diagram showing a refrigerant circuit according to the fourth embodiment. In the example shown in Figure 6, the refrigerant flow is shown when the second heat exchanger 12 of the exhaust unit 110A is functioning as an evaporator. Components similar to those in the embodiments described above are assigned the same reference numerals and their descriptions are omitted.

[0176] In the example shown in Figure 6, an air supply unit 120A, 120B, an exhaust unit 110A, and a compressor unit 150 are provided.

[0177] The air supply units 120A and 120B each include a fan 21, a first heat exchanger 22, a control unit 23, a temperature detection unit 24, a drive motor 25, and an electric valve 26.

[0178] The exhaust unit 110A comprises a fan 11, a second heat exchanger 12, a control unit 113A, a temperature detection unit 14, a drive motor 15, and an electric valve 16.

[0179] In this modified example, while the second heat exchanger 12 is functioning as an evaporator, the control unit 113A of the exhaust unit 110A outputs the detection result of the temperature detection unit 14 (the temperature of the refrigerant flowing through the second heat exchanger 12) to the control unit 152 of the compressor unit 150.

[0180] The control unit 152 of the compressor unit 150 determines whether a predetermined criterion indicating frost formation on the second heat exchanger 12 is met, based on the input temperature of the refrigerant flowing through the second heat exchanger 12. The predetermined criterion is the same as in the embodiment described above, so its explanation is omitted. The control unit 152 of the compressor unit 150 notifies the higher-level control device 100 of the determination result.

[0181] In this modified example, when the higher-level control device 100 recognizes the existence of a second heat exchanger 12 that meets predetermined criteria, it outputs a control signal to the control unit 152 of the compressor unit 150 to flow refrigerant through the bypass flow path F106 as defrost control for the second heat exchanger 12.

[0182] The compressor unit 150 includes a drive motor 51, a control unit 152, a compressor 53, a four-way valve 54, an electric valve 55, and a bypass electric valve 156.

[0183] The control unit 152 controls the internal configuration of the compressor unit 150. For example, the control unit 152 controls the drive motor 51 and the four-way valve 54 shown below.

[0184] In this embodiment, when the second heat exchanger 12 functions as an evaporator, a bypass channel F106 is provided to allow the refrigerant compressed by the compressor 53 to flow directly to the second heat exchanger 12 in order to raise the temperature of the refrigerant flowing through the second heat exchanger 12.

[0185] The bypass passage F106 is provided as a refrigerant passage that bypasses the compressor 53 and the four-way valve 54, and the refrigerant circuit F103. In other words, the bypass passage F106 functions as a pipe that allows refrigerant to flow to the second heat exchanger 12 without going through the first heat exchanger 22 while the second heat exchanger 12 is functioning as an evaporator.

[0186] The bypass electric valve 156 functions as a valve for switching whether or not to allow refrigerant to flow through the bypass passage F106, according to control from the control unit 152.

[0187] Specifically, when the higher-level control device 100 determines that the second heat exchanger 12 is frosted, it outputs a control signal to the control unit 152 of the compressor unit 150 to flow refrigerant through the bypass flow path F106.

[0188] Then, when the control unit 152 of the compressor unit 150 receives a control signal from the higher-level control device 100 to flow refrigerant through the bypass flow path F106, it outputs a control signal (an example of a predetermined command) to an actuator (not shown) that controls the opening degree of the bypass electric valve 156 (an example of an actuator that controls the state of refrigerant in the refrigerant circuit), thereby controlling the bypass electric valve 156 to an open state.

[0189] When the bypass electric valve 156 is open, the refrigerant, which has been compressed by the compressor 53 and become a high-temperature, high-pressure gas, flows into the refrigerant circuit F103 via the bypass passage F106. By passing through the bypass passage F106, a portion of the refrigerant, which has become a high-temperature, high-pressure gas, flows through the refrigerant circuit F103 without passing through the first heat exchanger 22. As a result, the temperature of the refrigerant flowing through the refrigerant circuit F103 rises. Consequently, the refrigerant with the increased temperature flows through the second heat exchanger 12.

[0190] In other words, in this modified configuration, when certain criteria are met, a portion of the refrigerant, which has been converted into a high-temperature, high-pressure gas by the compressor 53, is controlled to flow to the second heat exchanger 12 via the bypass flow path F106. Along with this control, the fan 11 brings warm air from the living space R11 to the second heat exchanger 12. This enables defrosting of the second heat exchanger 12.

[0191] (Modification 1 of the fourth embodiment) Defrosting of the second heat exchanger 12 may be performed using methods other than those described above for the embodiments and modifications. Modification 1 of the fourth embodiment describes an example in which a heater is provided in the refrigerant circuit. Modification 1 of the fourth embodiment is an example in which the bypass flow path F106 and the bypass electric valve 56 are removed compared to the fourth embodiment, and a heater is provided on the refrigerant circuit (for example, refrigerant circuit F103). The other configurations are the same as in the fourth embodiment and will not be described.

[0192] In this modified example, while the second heat exchanger 12 is functioning as an evaporator, the control unit 113A of the exhaust unit 110A outputs the detection result of the temperature detection unit 14 (the temperature of the refrigerant flowing through the second heat exchanger 12) to the control unit 152 of the compressor unit 150.

[0193] The control unit 152 of the compressor unit 150 determines whether a predetermined criterion indicating frost formation on the second heat exchanger 12 is met, based on the input temperature of the refrigerant flowing through the second heat exchanger 12. The predetermined criterion is the same as in the embodiment described above, so its explanation is omitted. The control unit 152 of the compressor unit 150 notifies the higher-level control device 100 of the determination result.

[0194] In this modified example, when the higher-level control device 100 recognizes that a second heat exchanger 12 that meets predetermined criteria exists, it instructs the control unit 152 of the compressor unit 150 to start heating the refrigerant circuit with the heater as defrost control for the second heat exchanger 12.

[0195] When the control unit 152 of the compressor unit 150 receives an instruction to start heating from the higher-level control unit 100, it starts heating the heater.

[0196] This causes the temperature of the refrigerant flowing through the refrigerant circuit F103 to rise. Consequently, the refrigerant with the increased temperature flows into the second heat exchanger 12. Along with this control, the fan 11 brings warm air from the living space R11 into the second heat exchanger 12. This enables defrosting of the second heat exchanger 12.

[0197] (Modification 2 of the fourth embodiment) Defrosting of the second heat exchanger 12 may be performed using methods other than those described above for the embodiments and modifications. Modification 2 of the fourth embodiment describes an example in which the pressure of the refrigerant flowing through the refrigerant circuit is increased. Modification 2 of the fourth embodiment is, for example, an example having the same configuration as the second embodiment. Other configurations are the same as in the fourth embodiment and will not be described.

[0198] In this modified example, while the second heat exchanger 12 is functioning as an evaporator, the control unit 113A of the exhaust unit 110A outputs the detection result of the temperature detection unit 14 (the temperature of the refrigerant flowing through the second heat exchanger 12) to the control unit 152 of the compressor unit 150.

[0199] The control unit 152 of the compressor unit 150 determines whether a predetermined criterion indicating frost formation on the second heat exchanger 12 is met, based on the input temperature of the refrigerant flowing through the second heat exchanger 12. The predetermined criterion is the same as in the embodiment described above, so its explanation is omitted. The control unit 152 of the compressor unit 150 notifies the higher-level control device 100 of the determination result.

[0200] In this modified example, when the higher-level control device 100 recognizes that there is a second heat exchanger 12 that meets predetermined criteria, it instructs the control unit 152 of the compressor unit 150 to increase the compressor pressure as defrost control for the second heat exchanger 12.

[0201] When the control unit 152 of the compressor unit 150 receives a pressure increase instruction from the higher-level control device 100, it controls the drive motor 51 to increase the pressure compared to before frost formation was determined, thereby increasing the pressure of the refrigerant flowing through the refrigerant circuit.

[0202] As a result, the pressure of the refrigerant flowing through the refrigerant circuit F103 increases, and consequently, the temperature of the refrigerant also rises. The refrigerant with the increased temperature flows into the second heat exchanger 12, and at the same time, the fan 11 brings warm air from the living space R11 into the second heat exchanger 12. Therefore, defrosting of the second heat exchanger 12 can be achieved.

[0203] (Fifth embodiment) Defrosting of the second heat exchanger 12 may be performed using methods other than those described in the embodiments above. In the fifth embodiment, an example of reversing the flow of the refrigerant circuit will be described. In the fifth embodiment, the description will be omitted as it is the same as in the third embodiment.

[0204] In this embodiment, while the second heat exchanger 12 is functioning as an evaporator, the control unit 113A of the exhaust unit 110A outputs the detection result of the temperature detection unit 14 (the temperature of the refrigerant flowing through the second heat exchanger 12) to the control unit 152 of the compressor unit 150.

[0205] The control unit 152 of the compressor unit 150 determines whether a predetermined criterion indicating frost formation on the second heat exchanger 12 is met, based on the input temperature of the refrigerant flowing through the second heat exchanger 12. The predetermined criterion is the same as in the embodiment described above, so its explanation is omitted. The control unit 152 of the compressor unit 150 notifies the higher-level control device 100 of the determination result.

[0206] In this embodiment, when the higher-level control device 100 recognizes that there is a second heat exchanger 12 that meets predetermined criteria, it instructs the control unit 152 of the compressor unit 150 to reverse the flow of refrigerant as a defrost control for the second heat exchanger 12.

[0207] When the control unit 152 of the compressor unit 150 receives an instruction from the higher-level control device 100 to reverse the flow of the refrigerant, it outputs a control signal (an example of a predetermined command) to an actuator (an example of an actuator that controls the state of the refrigerant in the refrigerant circuit) that drives the four-way valve 54 provided in the refrigerant circuit as shown in Figure 3 (not shown), causing the flow of the four-way valve 54 to be switched. As a result, the refrigerant compressed from the compressor is switched to flow to the exhaust units 110A and 110B. At the same time, the opening degrees of the electric valves 16 and 26 are also adjusted.

[0208] Then, the second heat exchanger 12 of the exhaust units 110A and 110B functions as a condenser as compressed refrigerant flows through it. On the other hand, the first heat exchanger 22 of the supply units 120A and 120B functions as an evaporator.

[0209] As a result of the control described above, the refrigerant flowing through the refrigerant circuit is reversed, causing the second heat exchanger 12 to function as a condenser, and thus the temperature of the refrigerant flowing through the second heat exchanger 12 rises. In addition, the fan 11 brings warm air from the living space R11 into the second heat exchanger 12. This enables defrosting of the second heat exchanger 12.

[0210] (Modification 1 of the fifth embodiment) In the fifth embodiment, the refrigerant circuit flow was reversed, but the airflow was not switched. Therefore, in Modification 1 of the fifth embodiment, an example is described in which the cycle is reversed and the airflow is switched. Modification 1 of the fifth embodiment has the same configuration as the fifth embodiment.

[0211] In this modified example, when the higher-level control device 100 recognizes the existence of a second heat exchanger 12 that meets predetermined criteria, following a procedure similar to that of the fifth embodiment, it instructs the control unit 152 of the compressor unit 150 to reverse the flow of refrigerant, and outputs a control signal to the control units 123 of the supply air units 120A and 120B to switch the airflow by the fan 21 so that the refrigerant is exhausted to the outside from the living space R11 through the first supply air passage P101 and the second supply air passage P102.

[0212] In this modified configuration, the aforementioned airflow switching control allows warm air to flow into the first heat exchanger 22, which functions as an evaporator, thereby increasing the temperature of the refrigerant flowing through the refrigerant circuit. By increasing the temperature of the refrigerant flowing through the first heat exchanger 22, which functions as an evaporator, the temperature of the refrigerant flowing through the second heat exchanger 12 can also be increased. Therefore, the temperature of the refrigerant flowing through the second heat exchanger 12 can be further increased, thereby improving defrosting efficiency.

[0213] (Modification 2 of the fifth embodiment) Modification 1 of the fifth embodiment described an example of switching the airflow on the supply air units 120A and 120B. However, in Modification 1 of the fifth embodiment, the airflow on the exhaust units 110A and 110B was controlled in the same way as before frost formation. Therefore, Modification 2 of the fifth embodiment describes an example in which the airflow on the exhaust units 110A and 110B is also switched. Note that Modification 2 of the fifth embodiment has the same configuration as the fifth embodiment.

[0214] In this modified example, when the higher-level control device 100 recognizes the existence of a second heat exchanger 12 that meets predetermined criteria, following the same procedure as in the fifth embodiment, it instructs the control unit 152 of the compressor unit 150 to reverse the refrigerant flow cycle, and outputs a control signal to the control units 123 of the supply air units 120A and 120B to switch the airflow by the fan 21 so that air is exhausted from the living space R11 to the outside via the first supply air passage P101 and the second supply air passage P102. Then, the higher-level control device 100 outputs a control signal to the control unit 113A of the exhaust unit 110A and the control unit 113B of the exhaust unit 110B to switch the airflow by the fan 11 so that air is supplied from the outside to the living space R11 via the first exhaust passage P103 and the second exhaust passage P104.

[0215] In this modified configuration, the airflow switching control described above allows warm air to flow into the first heat exchanger 22, which functions as an evaporator, while the second heat exchanger 12, which functions as a condenser, receives air supplied from outside.

[0216] In other words, in this modified example, the refrigerant cycle and the supply and exhaust of air are all switched, so ventilation can be continued while heat exchange is performed, and the comfort of the living space R11 can be maintained while defrosting the second heat exchanger 12.

[0217] (Sixth embodiment) Defrosting of the second heat exchanger 12 may be performed using methods other than those described in the embodiments above. In the sixth embodiment, an example of adjusting the airflow to the exhaust unit will be described.

[0218] Figure 7 shows an example configuration of a ventilation system and air conditioner according to the sixth embodiment. In the example shown in Figure 7, a ventilation system 1C and an air conditioner 2 are provided to air condition an indoor space. The ventilation system 1C has an exhaust unit 210 that performs different control than the embodiment described above, and an air supply unit 20. Components similar to those in the embodiment described above are assigned the same reference numerals and their descriptions are omitted.

[0219] The return air passage P202 (an example of a second air passage) is a passage for exhausting air (return air) taken in from the ventilation opening 91 of the living space R11 to the outside after passing it through the exhaust unit 10 which has a second heat exchanger 12.

[0220] In this embodiment, the return air passage P202 is branched into two air intake points to allow air to be taken in from multiple chambers. These are referred to as the first return air branch passage P202A (an example of the second air passage) and the second return air branch passage P202B (an example of the third air passage).

[0221] The first return air branch passage (an example of a second air passage) P202A is an air passage provided to exhaust air taken in from the living space R11 to the outside after passing it through the exhaust unit 10 which has a second heat exchanger 12. The first return air branch passage P202A takes in air from a ventilation opening 91 provided in the ceiling of the living space R11.

[0222] The second return air branch passage (an example of a third air passage) P202B is an air passage provided to exhaust air taken in from the ceiling space R12 to the outside after passing it through the exhaust unit 10 having a second heat exchanger 12. In this embodiment, the second return air branch passage P202B will be described as an example where the room from which the air is taken in is the ceiling space R12, which is different from the room from which the air is taken in from the first return air branch passage P202A. However, the room from which the air is taken in is not limited to the ceiling space R12, but may also be the underfloor space. Thus, the room from which the air is taken in by the second return air branch passage P202B may be any room in the indoor space that is different from the living room space R11.

[0223] Furthermore, an opening / closing damper 240 is provided at the tip of the second return air branch passage P202B. The opening / closing damper 240 is normally in the closed state. The opening / closing damper 240 (an example of the first guidance mechanism) can adjust the amount of air taken in from the ceiling space R12 by control via a signal line S202 from a control unit 13 provided in the exhaust unit 10.

[0224] The exhaust unit 210 includes a control unit 213 that performs a different process from that of the embodiment described above.

[0225] The control unit 213 controls the internal configuration of the exhaust unit 210. The control unit 213 performs various controls according to the detection results from the temperature detection unit 14. For example, the control unit 213 adjusts the function of the second heat exchanger 12 as a condenser or evaporator according to the detection results from the temperature detection unit 14.

[0226] Furthermore, the control unit 213 according to this embodiment can adjust the amount of air taken in from the ceiling space R12 by controlling the opening / closing damper 240 based on the detection result of the temperature detection unit 14.

[0227] In this embodiment, while the second heat exchanger 12 is functioning as an evaporator, the control unit 213 of the exhaust unit 210 determines, based on the detection results from the temperature detection unit 14, whether or not the second heat exchanger 12 meets predetermined criteria for frost formation. The predetermined criteria are the same as those in the embodiment described above, so their explanation is omitted.

[0228] In this embodiment, the control unit 213 of the exhaust unit 210 detects the temperature of the air in the ceiling space R12 when it determines that a predetermined criterion is met. If it determines that the temperature of the air in the ceiling space R12 is higher than the temperature of the air in the living space R11, the control unit 213 controls the opening / closing damper 240 to guide the air present in the ceiling space R12 to the second heat exchanger 12 through the second return air branch passage P202B as defrost control for the second heat exchanger 12. In other words, since the ceiling space R12 is located above the living space R11, warm air accumulates there. Therefore, if it is determined that the second heat exchanger 12 is frosted, the control unit 213 controls the opening / closing damper 240. As a result of this control, the warm air present in the ceiling space R12 and the air present in the living space R11 are mixed together and guided to the second heat exchanger 12.

[0229] In this embodiment, the control unit 13 controls the flow of warm air from the ceiling space R12 to the second heat exchanger 12 as an example of controlling the temperature of the refrigerant flowing through the second heat exchanger 12. This enables defrosting of the second heat exchanger 12. The output of commands to the actuator that controls the state of the refrigerant in the refrigerant circuit to raise the temperature of the refrigerant flowing into the second heat exchanger 12 may be any of the methods described in the above embodiment, and therefore its description is omitted.

[0230] (Modification 1 of the 6th embodiment) In the embodiments described above, an example was explained in which an opening / closing damper 240 is used to control the flow of warm air from the ceiling space R12 to the second heat exchanger 12 by mixing it with the air from the living space R11. However, the sixth embodiment is not limited to the method of mixing warm air from the ceiling space R12 with the air from the living space R11. Modification 1 of the sixth embodiment describes an example in which only the warm air from the ceiling space R12 is controlled to flow to the second heat exchanger 12.

[0231] In this modified version, similar to the embodiment described above, the return air passage P202 is branched into a first return air branch passage P202A (an example of a second air passage) and a second return air branch passage P202B (an example of a third air passage).

[0232] In the embodiment described above, an example is given in which an opening / closing damper 240 is provided in the second return air branch P202B. However, in this modified example, an opening / closing damper (an example of a second guide mechanism) is also provided in the first return air branch P202A. In all other respects, it is the same as the sixth embodiment.

[0233] The opening / closing damper installed in the first return air branch passage P202A is normally in the open position. This allows return air (RA) from the living space R11 to be taken in. The opening / closing damper installed in the first return air branch passage P202A can adjust the amount of air taken in from the living space R11 by control via a signal line (not shown) from the control unit 313 installed in the exhaust unit 310.

[0234] Then, the control unit 213 of the exhaust unit 210 according to this modified example detects the temperature of the air in the ceiling space R12 when it determines that the second heat exchanger 12 has met a predetermined criterion for frost formation. If it determines that the temperature of the air in the ceiling space R12 is higher than the temperature of the air in the living space R11, the control unit 213 controls the opening / closing damper 240 to open and the opening / closing damper provided in the first return air branch passage P202A to close.

[0235] This suppresses the intake of return air (RA) from the living space R11, and warm air present in the ceiling space R12 flows into the second heat exchanger 12. Therefore, the defrosting efficiency of the second heat exchanger 12 can be improved.

[0236] (Seventh Embodiment) The airflow to the exhaust unit may be adjusted using methods other than those described in the sixth embodiment. Therefore, the seventh embodiment will describe another way of adjusting the airflow to the exhaust unit.

[0237] Figure 8 shows an example configuration of a ventilation system and air conditioner according to the seventh embodiment. In the example shown in Figure 8, a ventilation system 1D and an air conditioner 2 are provided to air condition an indoor space. The ventilation system 1D has an exhaust unit 310 that performs different control than the embodiment described above. Components similar to those in the embodiment described above are assigned the same reference numerals and their descriptions are omitted.

[0238] The first return air passage P301 (an example of the second air passage) is a passage for exhausting air (return air) taken in from the ventilation opening 91 of the living space R11 to the outside after passing it through the exhaust unit 10 which has the second heat exchanger 12.

[0239] Furthermore, a first on / off damper 341 (an example of a switching mechanism) is provided at the tip of the first return air passage P301. The first on / off damper 341 is normally in the open state. The first on / off damper 341 can adjust the amount of air taken in from the living space R11 by control via a signal line S302 from a control unit 313 provided in the exhaust unit 310.

[0240] The second return air passage P302 is a passage for exhausting air (return air) taken in from outdoors to the outdoors after passing it through the exhaust unit 10 which has the second heat exchanger 12.

[0241] Furthermore, a second on / off damper 342 (an example of a switching mechanism) is provided on the flow path of the second return air passage P302 (an example of a second air passage). The second on / off damper 342 is normally in the closed state. The second on / off damper 342 can adjust the amount of air taken in from outside by control via a signal line S202 from a control unit 313 provided in the exhaust unit 310.

[0242] The first on / off damper 341 and the second on / off damper 342 function as a mechanism for switching whether the air flowing to the second heat exchanger 12 is supplied from the living space R11 or from the outside.

[0243] The exhaust unit 310 includes a control unit 313 that performs a different process from that of the embodiments described above.

[0244] The control unit 313 controls the internal configuration of the exhaust unit 310. The control unit 313 performs various controls according to the detection results from the temperature detection unit 14. For example, the control unit 313 adjusts the function of the second heat exchanger 12 as a condenser or evaporator according to the detection results from the temperature detection unit 14.

[0245] Furthermore, the control unit 313 according to this embodiment controls the first on / off damper 341 and the second on / off damper 342 based on the detection result of the temperature detection unit 14, thereby changing the intake destination of the air flowing into the second heat exchanger 12.

[0246] In this embodiment, while the second heat exchanger 12 is functioning as an evaporator, the control unit 313 of the exhaust unit 310 determines, based on the detection results from the temperature detection unit 14, whether or not the second heat exchanger 12 meets predetermined criteria for frost formation. The predetermined criteria are the same as those in the embodiment described above, so their explanation is omitted.

[0247] The control unit 313 of the exhaust unit 310 according to this embodiment detects the temperature of the living space R11 and the outdoor air when it determines that a predetermined criterion is met. If the temperature of the air in the living space R11 is higher than that of the outdoor air, no control is performed on the first opening / closing damper 341 and the second opening / closing damper 342.

[0248] If the control unit 313 determines that the temperature of the outside air is higher than the temperature of the air in the living space R11, it controls the defrosting of the second heat exchanger 12 by opening the second on / off damper 342 so that the air present outside is guided to the second heat exchanger 12 through the second return air passage P302. Furthermore, the control unit 313 controls the first on / off damper 341 to prevent air from the living space R11 from flowing into the second heat exchanger 12 through the first return air passage P301.

[0249] In other words, if frost forms on the second heat exchanger 12 while it is functioning as an evaporator, the control unit 313 controls the first on / off damper 341 and the second on / off damper 342 to supply air from the higher of the temperatures detected from the living space R11 and the outside.

[0250] If it is possible to take in warm air from outside, the control unit 313 controls the first on / off damper 341 and the second on / off damper 342 to take in air from outside.

[0251] In this embodiment, for example, when the control unit 313 compares the temperature TA of the air around the intake port of the first heat exchanger 22, the temperature TB of the air in the living space R11, and the temperature TC of the air around the outlet port of the second heat exchanger 12, it determines that the temperature TC > temperature TB > temperature TA, and performs the above-described process.

[0252] Examples of situations where the air temperature TC is higher than the air temperatures TB and TA include: when the outlet of the second heat exchanger 12 is on the south side of the building and the surrounding air is warmed by sunlight, etc.; when the intake of the first heat exchanger 22 is on the north side of the building and the surrounding air is cold in the shade; when there is still snow remaining near the intake of the first heat exchanger 22 in early spring and the surrounding air is cold; and when the duct between the second heat exchanger 12 and the outlet is installed for a long distance in the ceiling space R12, the air passing through the duct may be warmed by the heat in the ceiling space R12.

[0253] In this situation, the control unit 313 controls the flow of warm outdoor air to the second heat exchanger 12. This enables defrosting of the second heat exchanger 12. The output of the command to the actuator that controls the state of the refrigerant in the refrigerant circuit to raise the temperature of the refrigerant flowing into the second heat exchanger 12 may be any of the methods described in the above embodiment, and therefore its explanation is omitted.

[0254] In this embodiment, by introducing the air with the higher temperature between the living space R11 and the air detected from the outside into the second heat exchanger 12, the temperature of the second heat exchanger 12 can be further increased, thereby improving defrosting efficiency.

[0255] (Eighth embodiment) The airflow to the exhaust unit may be adjusted using methods other than those described in the embodiments above. Therefore, in the eighth embodiment, a method of providing a bypass passage for direct airflow between the supply unit and the exhaust unit will be described.

[0256] Figure 9 shows an example of the configuration of a ventilation system and air conditioner according to the eighth embodiment. In the example shown in Figure 9, a ventilation system 1E and an air conditioner 2 are provided to provide air conditioning for an indoor space. In the third embodiment, the same reference numerals are assigned to components similar to those in the embodiments described above, and their descriptions are omitted.

[0257] As shown in Figure 9, a bypass passage P402 is provided between the air supply unit 20 and the exhaust unit 410. The bypass passage P402 consists of a first bypass partial passage P402A on the side of the air supply unit 20 from the air supply passage P401, a third bypass partial passage P402C on the side of the exhaust unit 10 from the return air passage P403, and a second bypass partial passage P402B that connects the first bypass partial passage P402A and the third bypass partial passage P402C.

[0258] Furthermore, an on / off damper 440 (an example of a bypass guidance mechanism) is provided on the second bypass section flow path P4102B. The on / off damper 440 is normally in the closed state. The on / off damper 440 can guide the air heated in the supply air unit 20 directly to the exhaust unit 410 by control from the control unit 413 provided in the exhaust unit 410 via the signal line S401.

[0259] The air supply unit 20 takes in outside air (OA) and then normally supplies it (SA) to the living space R11 via the first bypass partial flow path P402A and the air supply flow path P401.

[0260] The exhaust unit 410 comprises a fan 11, a second heat exchanger 12, a control unit 413, and a temperature detection unit 14. It takes in return air (RA) from the living space R11 via the return air flow path P403 and the third bypass partial flow path P402C, and exhausts it outdoors (EA).

[0261] The control unit 413 of the exhaust unit 410 in this modified example detects whether a predetermined criterion indicating frost formation on the second heat exchanger 12 is met while the second heat exchanger 12 is functioning as an evaporator. The predetermined criterion is the same as in the embodiment described above, so its explanation is omitted.

[0262] When the control unit 13 determines that a predetermined standard is satisfied, it further determines whether the temperature of the air after passing through the first heat exchanger 22 is higher than a predetermined temperature (which may be a preset reference value or the temperature of the air in the living space R11). The predetermined temperature is determined according to the embodiment. When the control unit 13 determines that the temperature of the air after passing through the first heat exchanger 22 is higher than the predetermined temperature, it performs control to open the opening / closing damper 440.

[0263] As described above, when it is determined that the second heat exchanger 12 is in a frosting state, the control unit 413 according to this modification performs control to open the opening / closing damper 440 when it is determined that the temperature of the air exchanged with heat by the first heat exchanger 22 is higher than a predetermined temperature. Thereby, the air warmed in the exhaust unit 410 can flow directly through the bypass flow path P402 to the second heat exchanger 12, so that the defrosting efficiency of the second heat exchanger 12 can be improved. Note that the output of a command to an actuator that controls the state of the refrigerant in the refrigerant circuit so as to raise the temperature of the refrigerant flowing into the second heat exchanger 12 may be omitted from the description as it may use any method among the methods described in the above-described embodiment.

[0264] (The Ninth Embodiment) The flow of air to the exhaust unit may be adjusted using a method other than the above-described embodiment. Therefore, in the ninth embodiment, the case of cooperation with the air conditioner 2 will be described.

[0265] In the present embodiment, similar to the second embodiment, an example including the ventilation device 1B, the air conditioner 2B, and the upper control device 100 is used. The present embodiment has the same configuration as the second embodiment as shown in FIG. 2.

[0266] The control units 113A and 113B control the configurations within their respective exhaust units. Further, the control units 113A and 113B transmit the detection results by the temperature detection unit 14 and the like within their respective exhaust units to the control unit 152 of the compressor unit 150.

[0267] Based on the detection results, the control unit 152 of the compressor unit 150 determines whether or not a predetermined criterion is met indicating that the second heat exchangers 12 of the exhaust units 110A and 110B are frosted.

[0268] The control unit 152 of the compressor unit 150 transmits the determination result to the higher-level control unit 100. This allows the higher-level control unit 100 to recognize the status of the first exhaust unit 110A and the second exhaust unit 110B.

[0269] The higher-level control device 100 performs various controls to coordinate the operation of the ventilation device 1B and the operation of the air conditioner 2B.

[0270] For example, if the higher-level control device 100 recognizes that at least one of the second heat exchangers 12 among the first exhaust unit 110A and the second exhaust unit 110B is frosted, it outputs a control signal to the air conditioner 2B installed in the living space R11 to raise the temperature currently set on the air conditioner 2B.

[0271] The air conditioner 2B increases its heating capacity in accordance with the control signal. This raises the temperature of the air in the living space R11. Consequently, the temperature of the air flowing into the second heat exchanger 12 can be increased. Therefore, the defrosting efficiency of the second heat exchanger 12 can be increased.

[0272] Furthermore, if there are multiple indoor air conditioning units, the higher-level control device 100 may select an indoor air conditioning unit to improve heating capacity according to the arrangement of the indoor air conditioning units. In the example shown in Figure 2, if frost forms on the second heat exchanger 12 of the exhaust unit 110A, the higher-level control device 100 may improve the heating capacity of the indoor air conditioning unit 81 located near the ventilation opening 91A of the exhaust unit 110A, and if frost forms on the second heat exchanger 12 of the exhaust unit 110B, it may improve the heating capacity of the indoor air conditioning unit 82 located near the ventilation opening 91B of the exhaust unit 110B. Note that the output of commands to the actuator that controls the state of the refrigerant in the refrigerant circuit to raise the temperature of the refrigerant flowing into the second heat exchanger 12 may be any of the methods described in the above-described embodiment, and therefore the explanation is omitted.

[0273] In other words, if the temperature of the refrigerant in the refrigerant circuit shown in the above embodiment is increased, even if the temperature adjustment capacity of the ventilation device 1B decreases, the comfort of the living space R11 can be maintained by improving the heating capacity of the air conditioner 2B.

[0274] (Tenth embodiment) The airflow to the exhaust unit may be adjusted using methods other than those described in the embodiments above.

[0275] In this embodiment, similar to the second embodiment, the system includes a ventilation device 1B, an air conditioner 2B, and a higher-level control device 100. This embodiment has the same configuration as the second embodiment, as shown in Figure 2.

[0276] Similar to the embodiment described above, the higher-level control device 100 can recognize the status of the first exhaust unit 110A and the second exhaust unit 110B from the determination result from the control unit 152 of the compressor unit 150.

[0277] Then, when the higher-level control device 100 recognizes that frost has formed on at least one of the second heat exchangers 12 of the first exhaust unit 110A and the second exhaust unit 110B, it outputs a control signal to the exhaust unit including the frosted second heat exchanger 12 (for example, the first exhaust unit 110A or the second exhaust unit 110B) to increase the airflow rate of the fan 11.

[0278] Thus, in this embodiment, the higher-level control device 100 controls the fan 11 corresponding to each of the multiple second heat exchangers 12 based on the status of each of the second heat exchangers 12, thereby adjusting the airflow rate of the air that flows to the second heat exchangers 12.

[0279] This increases the amount of air flowing to the frosted second heat exchanger 12, thereby enabling defrosting of the second heat exchanger 12. In other words, in this embodiment, defrosting is achieved by increasing the airflow on the exhaust heat recovery unit side to improve the efficiency of heat exchange and suppressing the decrease in the temperature of the refrigerant flowing through the second heat exchanger 12.

[0280] In this embodiment, even when there are multiple second heat exchangers 12, defrosting can be achieved according to the degree of frost accumulation on the second heat exchangers 12 while maintaining the comfort of the indoor space by adjusting the airflow volume of the air flowing to the second heat exchangers 12 according to the condition of each second heat exchanger 12.

[0281] (Modification 1 of the 10th embodiment) This modified example describes an example in which, when multiple second heat exchangers 12 are frosted, the control is varied according to the degree of frosting on the multiple second heat exchangers 12. Note that Modification 1 of the 10th embodiment has the same configuration as the 10th embodiment.

[0282] When the upper control device 100 according to this modification example recognizes that frosting has occurred in a plurality of second heat exchangers 12, it acquires the frosting level of each of the plurality of second heat exchangers 12. The frosting level is, for example, a value set according to the degree of frosting of the second heat exchanger 12 based on the determination result by the control unit 152 of the compressor unit 150, and is a value set according to the time since frosting started and the current refrigerant temperature.

[0283] Then, when it is determined that the frosting level (degree of frosting) of one of the plurality of second heat exchangers 12 is greater than that of the other second heat exchanger 12, the upper control device 100 controls to increase the air volume (an example of the first air volume) of the fan 11 corresponding to one of the second heat exchangers 12 compared to the air volume (an example of the second air volume) of the fan 11 corresponding to the other second heat exchanger 12.

[0284] Furthermore, when the upper control device 100 controls to increase the air volume of the fan 11 corresponding to one of the second heat exchangers 12, it may control to decrease the air volume of the fan 11 corresponding to the other second heat exchanger 12 compared to before the control to increase the air volume. Thereby, since the total value of the air discharge amount is maintained, it is possible to suppress the indoor space R11 from becoming a negative pressure.

[0285] After the defrosting of one of the second heat exchangers 12 is completed, the upper control device 100 controls to increase the air volume of the fan 11 corresponding to the other second heat exchanger 12 and controls to decrease the air volume of the fan 11 corresponding to one of the second heat exchangers 12.

[0286] In this embodiment, since the one with a larger degree of frosting among the plurality of second heat exchangers 12 can be preferentially defrosted, it is possible to improve the defrosting efficiency.

[0287] (Modification Example 2 of the 10th Embodiment) Therefore, in Modification 2, we will describe a case in which the amount of air drawn in from the outside by the supply air unit group is increased when the amount of air exhausted from the exhaust unit group is increased. Note that Modification 2 of the 10th embodiment has the same configuration as the 10th embodiment.

[0288] The control unit 152 of the compressor unit 150 in this modified example, similar to the tenth embodiment, determines whether a predetermined criterion is met indicating that frost has formed on the second heat exchangers 12 of the first exhaust unit 110A and the second exhaust unit 110B, based on the temperature of the outside air received.

[0289] Then, if the control unit 152 of the compressor unit 150 determines that one or more of the first exhaust unit 110A and the second exhaust unit 110B meet predetermined criteria, the higher-level control device 100 instructs the exhaust unit to increase its airflow. The method of giving this instruction is the same as in the tenth embodiment and will not be explained further.

[0290] The higher-level control device 100 in this modified example, instead of issuing an instruction to decrease the airflow rate as shown in Modification 1 of the 10th embodiment, instructs an increase in the amount of air (airflow rate) supplied to one or more of the first air supply unit 120A and the second air supply unit 120B. This instruction to increase the airflow rate is given from the higher-level control device 100 to the control units 423 of the first air supply unit 120A and the second air supply unit 120B via the control unit 152 of the compressor unit 150.

[0291] The target of the instruction to increase the amount of air supplied (airflow) may be either the first air supply unit 120A or the second air supply unit 120B, or it may be either the first air supply unit 120A or the second air supply unit 120B individually. However, the higher-level control device 100 adjusts the amount of air discharged by the first exhaust unit 110A and the second exhaust unit 110B to be the same as the amount of air taken in by the first air supply unit 120A and the second air supply unit 120B.

[0292] As described above, in this modified configuration, when the higher-level control device 100 controls a fan 11 associated with one of the multiple second heat exchangers 12 included in the exhaust unit group to increase the amount of air flowing to the second heat exchanger 12, it controls a fan 21 included in the supply unit group to increase the amount of air flowing to the first heat exchanger 22 compared to before the predetermined standard was met, based on the increased amount of air. As a result, in this modified configuration, the amount of air taken in and the amount of air exhausted are approximately equal, so that the living space R11 does not become negatively pressurized.

[0293] (11th embodiment) The coordination between the air conditioner and the ventilation system is not limited to the control described above. Therefore, the 11th embodiment will describe the case when the air conditioner starts defrosting operation. The configuration of the 11th embodiment is assumed to be the same as that of the second embodiment.

[0294] The higher-level control device 100 receives the status of the air conditioner 2B from the control unit 171 of the outdoor unit 170 and the status of the ventilation device 1B from the control unit 152 of the compressor unit 150. The higher-level control device 100 then performs various controls according to the status of the air conditioner 2B and the ventilation device 1B.

[0295] For example, if the higher-level control device 100 recognizes that the air conditioner 2B is performing defrosting operation based on information received from the control unit 171 of the outdoor unit 170, it performs control to improve the heating capacity of the ventilation device 1B.

[0296] In other words, when air conditioner 2B performs defrosting, air conditioner 2B does not function as a heater, which may cause the temperature inside the living space R11 to drop. On the other hand, if the supply air temperature of the first supply air unit 120A and the second supply air unit 120B is increased to compensate for the reduced function of air conditioner 2B when it performs defrosting, the temperature of the refrigerant flowing to the second heat exchanger 12 of the first exhaust unit 110A and the second exhaust unit 110B, which are connected by refrigerant circuits F101, F102, F103, and F104, will drop. In this case, the possibility of frost formation on the second heat exchanger 12 of the first exhaust unit 110A and the second exhaust unit 110B increases.

[0297] Therefore, when the higher-level control device 100 receives a signal from the air conditioner 2B indicating that defrosting operation is being performed, it controls the supply air units 120A and 120B to increase the amount of air supplied to the living space R11 from the first supply air passage P101 and the second supply air passage P102 compared to before receiving the signal from the air conditioner 2B indicating that defrosting operation is being performed. It also controls the exhaust units 110A and 110B to increase the amount of air exhausted to the outside from the first exhaust air passage P103 and the second exhaust air passage P104 compared to before receiving the signal from the air conditioner 2B indicating that defrosting operation is being performed.

[0298] In this embodiment, when the air conditioner 2B is in defrosting operation, the higher-level control device 100 increases the airflow rate of the ventilation device 1B's supply and exhaust without raising the supply air temperature, thereby improving the heating capacity and suppressing a decrease in temperature within the living space R11.

[0299] (11th embodiment) In the above-described embodiment, an example was given in which the higher-level control device 100 controls one compressor unit 150. However, the higher-level control device 100 does not limit the number of compressor units it controls to one. Therefore, in the seventh embodiment, an example will be described in which the higher-level control device 100 controls multiple ventilation devices and multiple air conditioners.

[0300] Figure 10 is a diagram illustrating the arrangement of a group of devices including a higher-level control device 500 according to the tenth embodiment. The example shown in Figure 10 includes at least living spaces R501, R502, R503, restrooms R511, R512, and a pipe shaft R521.

[0301] Restrooms R511 and R512 are equipped with ventilation openings 595A and 595B, respectively.

[0302] The air conditioning unit 2F also includes three outdoor units 571, 572, and 573. Outdoor unit 571 is connected to four indoor air conditioning units 581, 582, 583, and 584 by connecting pipes (not shown). Outdoor unit 572 is connected to two indoor air conditioning units 585 and 586 by connecting pipes (not shown). Outdoor unit 573 is connected to two indoor air conditioning units 587 and 588 by connecting pipes (not shown).

[0303] Furthermore, the three outdoor units 571 to 573 are connected to the higher-level control unit 500 via signal lines. This allows the three outdoor units 571 to 573 to perform air conditioning control according to the control of the higher-level control unit 500.

[0304] The first ventilation system 1F_1 is a ventilation system installed in the living space R501 and includes a first compressor unit 550A, a first supply air unit 520A, and a first exhaust unit 510A.

[0305] The first supply air unit 520A supplies air (SA) through ventilation port 592A. The first exhaust air unit 510A returns air (RA) through ventilation port 591A. The first compressor unit 550A, the first supply air unit 520A, and the first exhaust air unit 510A are connected by a connecting pipe F501. The connecting pipe F501 includes multiple refrigerant connecting pipes. This allows the refrigerant to be circulated between the first compressor unit 550A, the first supply air unit 520A, and the first exhaust air unit 510A.

[0306] Furthermore, the first compressor unit 550A, the first air supply unit 520A, and the first exhaust unit 510A are connected by signal lines (not shown). This allows information to be transmitted and received between the units. The internal configurations of the first compressor unit 550A, the first air supply unit 520A, and the first exhaust unit 510A are the same as those of the compressor unit 150, the first air supply unit 120A, and the first exhaust unit 110A shown in Figure 2, so their explanation is omitted.

[0307] The second ventilation system 1F_2 is a ventilation system installed in the living space R502 and includes a second compressor unit 550B, a second supply air unit 520B, and a second exhaust unit 510B.

[0308] The second supply air unit 520B supplies air (SA) through the ventilation port 592B. The second exhaust air unit 510B returns air (RA) through the ventilation port 591B. The second compressor unit 550B, the second supply air unit 520B, and the second exhaust air unit 510B are connected by a connecting pipe F502. The connecting pipe F502 includes multiple refrigerant connecting pipes. This allows the refrigerant to be circulated between the second compressor unit 550B, the second supply air unit 520B, and the second exhaust air unit 510B.

[0309] Furthermore, the second compressor unit 550B, the second supply unit 520B, and the second exhaust unit 510B are connected by signal lines (not shown). This allows information to be transmitted and received between the units. The internal configurations of the second compressor unit 550B, the second supply unit 520B, and the second exhaust unit 510B are the same as those of the compressor unit 150, the first supply unit 120A, and the first exhaust unit 110A shown in Figure 2, so their explanation will be omitted.

[0310] The third ventilation system 1F_3 is a ventilation system installed in the living space R503 and includes a third compressor unit 550C, a third supply air unit 520C, and a third exhaust unit 510C.

[0311] The third supply unit 520C supplies air (SA) through the ventilation port 592C. The third exhaust unit 510C returns air (RA) through the ventilation port 591C. The third compressor unit 550C, the third supply unit 520C, and the third exhaust unit 510C are connected by a connecting pipe F503. The connecting pipe F503 includes multiple refrigerant connecting pipes. This allows the refrigerant to be circulated between the third compressor unit 550C, the third supply unit 520C, and the third exhaust unit 510C.

[0312] Furthermore, the third compressor unit 550C, the third supply unit 520C, and the third exhaust unit 510C are connected by signal lines (not shown). This allows information to be transmitted and received between the units. The internal configurations of the third compressor unit 550C, the third supply unit 520C, and the third exhaust unit 510C are the same as those of the compressor unit 150, the first supply unit 120A, and the first exhaust unit 110A shown in Figure 2, so their explanation is omitted.

[0313] As described above, this embodiment includes multiple combinations of compressor units, supply units, exhaust units, and connecting piping. The first compressor unit 550A, the second compressor unit 550B, and the third compressor unit 550C are located in the pipe shaft R521.

[0314] The higher-level control unit 500 is connected to the first compressor unit 550A, the second compressor unit 550B, and the third compressor unit 550C by signal lines. This allows the higher-level control unit 500 to recognize the status of each of the first ventilation system 1F_1 to the third ventilation system 1F_3 and to control each of them.

[0315] With the above configuration, while the second heat exchanger 12 of each of the first exhaust units 510A to the third exhaust units 510C is functioning as an evaporator, the control units (not shown) of the first compressor units 550A to the third compressor units 550C receive the temperature of the refrigerant flowing through the second heat exchanger 12 from each of the first exhaust units 510A to the third exhaust units 510C.

[0316] The control units of the first compressor units 550A to the third compressor units 550C in this embodiment determine, based on the temperature of the refrigerant in the second heat exchanger 12, whether or not predetermined criteria indicating frost formation in the second heat exchanger 12 are met while the second heat exchanger 12 is functioning as an evaporator. The predetermined criteria are the same as those in the embodiments described above, so their explanation is omitted.

[0317] If the higher-level control device 500 determines that the predetermined criteria are met, it raises the room temperature of the air conditioner 2F corresponding to the area (same zone) where the exhaust unit including the frosted second heat exchanger 12 is installed.

[0318] For example, if it is determined that frost has formed on the second heat exchanger 12 of the exhaust unit 510C, the set temperature of the air conditioner 2F installed in the same living space R503 is increased. In particular, by increasing the set temperature of the indoor air conditioner unit 582 installed near the ventilation opening 591C of the exhaust unit 510C, the defrosting efficiency of the second heat exchanger 12 of the exhaust unit 510C can be increased.

[0319] Furthermore, by increasing the capacity of the 2F air conditioner, the capacity of the ventilation system can be reduced. In other words, the temperature of the refrigerant passing through the exhaust unit of the ventilation system can be increased, thereby enabling rapid defrosting of the heat exchanger. The method for increasing the temperature of the refrigerant passing through the exhaust unit of the ventilation system is the same as in the embodiment described above, so its explanation will be omitted.

[0320] Furthermore, the higher-level control device 500 may use any of the methods described in the above embodiments to output commands to the actuators that control the state of the refrigerant in the refrigerant circuit in order to raise the temperature of the refrigerant flowing into the second heat exchanger 12 of the exhaust unit 510C. For example, as shown in the fifth embodiment, the temperature of the refrigerant flowing into the second heat exchanger 12 may be increased by controlling the flow in the refrigerant circuit including the second heat exchanger 12 of the exhaust unit 510C to reverse the cycle. In addition, the flow in the refrigerant circuit including the second heat exchanger 12 of the exhaust unit 510C may be controlled to increase the temperature of the refrigerant flowing into the second heat exchanger 12 while maintaining a forward cycle.

[0321] For example, in the higher-level control device 100 according to this embodiment, the control may increase the amount of air exhausted from the exhaust unit 510C compared to before the defrosting operation of the air conditioner 2F was started, in order to defrost the second heat exchanger 12 of the exhaust unit 510C of the ventilation device 1F_3. In this case, the higher-level control device 500 may also reduce the amount of air exhausted from the exhaust unit 510A of the ventilation device 1F_1, which is on a different system from the ventilation device 1F_3, and the amount of air exhausted from the exhaust unit 510B of the ventilation device 1F_2. The control to increase the amount of air and the control to decrease the amount of air are the same as in the embodiment described above and will not be explained further. By this control, defrosting of the second heat exchanger 12 of the exhaust unit 510C can be achieved, and by maintaining the amount of air discharged, it is possible to suppress the room spaces R501, R502, and R503 from becoming negative pressure.

[0322] In this embodiment, the temperature of the living space is increased, thereby increasing the temperature of the air flowing to the second heat exchanger 12 and improving the defrosting efficiency.

[0323] In this embodiment, when defrosting is performed on ventilation devices 1F_1 to 1F_3, comfort can be maintained by compensating for the decrease in the heating capacity of the ventilation devices by improving the heating capacity of the air conditioner installed in the same area as ventilation devices 1F_1 to 1F_3.

[0324] (Modification 1 of the 11th embodiment) Modification 1 of the 11th embodiment describes the case when the air conditioner 2F starts defrosting operation. In the embodiment described above, when it is determined that the second heat exchanger 12 is frosted, an example was described in which a predetermined command is output to the actuator that controls the state of the refrigerant in the refrigerant circuit. In contrast, in the modification of this embodiment, even when it is determined that frost has formed, the output of the predetermined command is suppressed if certain conditions are met.

[0325] After receiving a signal from the air conditioner 2F indicating that defrosting operation should be performed, the higher-level control unit 500 receives a determination result from the control units of the first compressor unit 550A to the third compressor unit 550C, which determines that the second heat exchanger 12 is frosted.

[0326] In this case, while the air conditioner 2F is performing defrosting operation, the higher-level control device 500 suppresses the output of a predetermined command to the actuator that controls the state of the refrigerant in the refrigerant circuit in order to raise the temperature of the refrigerant flowing through the frosted second heat exchanger 12.

[0327] Furthermore, the higher-level control device 500 may increase the airflow of the fan 11 corresponding to the frosted second heat exchanger 12 while the air conditioner 2F is performing defrosting operation.

[0328] (Modification 2 of the 11th embodiment) As a further variation, the higher-level control device 500 may send a command to the compressor unit (e.g., compressor unit 550C) to reduce the flow rate of refrigerant to the second heat exchanger 12, which has been determined to be prone to frost formation, while the air conditioner 2F is performing defrosting operation. This can suppress the progression of frost formation. In other words, by suppressing the progression of frost formation on the second heat exchanger 12, simultaneous defrosting operation with the air conditioner 2F, which is currently performing defrosting operation, can be suppressed.

[0329] This prevents the heating capacity of the first heat exchanger 22 of the air supply unit (for example, air supply unit 520C) from stopping, thus maintaining a minimum level of comfort.

[0330] As a criterion for determining the possibility of frost formation, for example, the surface temperature of the second heat exchanger 12 and the temperature of the indoor air in the living space (e.g., living space R505) can be measured, and the surface temperature of the second heat exchanger 12 can be lower than the dew point temperature of the air, and the surface temperature of the second heat exchanger 12 can be 0°C or lower. The temperature of the indoor air can be measured, for example, by a sensor installed near the ventilation opening.

[0331] Furthermore, the higher-level control device 500 may monitor the frost formation status of the second heat exchangers 12 of multiple exhaust units and the frost formation status of multiple air conditioners 2F, and sequentially perform defrosting operations on equipment that is determined to be prone to frost formation, thereby shortening the time that multiple equipment is in defrosting operation simultaneously, or suppressing the simultaneous defrosting operation of multiple equipment.

[0332] (Modification 3 of the 10th embodiment) The higher-level control device 500 according to Modification 3 of the 10th embodiment, similar to Modification 1 of the 11th embodiment, receives a signal from the air conditioner 2F indicating that defrosting operation should be performed, and then receives a determination result from the control units of the first compressor unit 550A to the third compressor unit 550C indicating that the second heat exchanger 12 is in a frosted state.

[0333] In this case, while the air conditioner 2F is performing defrosting operation, the higher-level control device 500 suppresses the output of a predetermined command to the actuator that controls the state of the refrigerant in the refrigerant circuit in order to raise the temperature of the refrigerant flowing through the frosted second heat exchanger 12.

[0334] Furthermore, when the higher-level control device 500 receives a signal from the air conditioner 2F to perform defrosting operation, it controls the supply air unit (e.g., supply air unit 520C) to increase the amount of air supplied from the supply air path to the living space (e.g., living space R503) compared to before the air conditioner 2F performed defrosting operation, and also controls the exhaust unit (e.g., exhaust unit 510C) to increase the amount of air exhausted from the second air passage to the outside compared to before the air conditioner 2F performed defrosting operation.

[0335] In this modified version, the sum of the supply and exhaust air volumes is maintained, thus preventing the living space from becoming negatively pressurized. Furthermore, increasing the airflow of the ventilation system helps to suppress a decrease in heating capacity.

[0336] (Modification 4 of the 10th embodiment) Furthermore, control may be implemented to suppress simultaneous defrosting of the air conditioner on the second floor and the ventilation system.

[0337] In this modified example, the higher-level control device 500 starts defrosting control of the second heat exchanger 12 of the exhaust unit when it determines that the second heat exchanger 12 of the exhaust unit is frosted. Any defrosting method shown in the above-described embodiment may be used.

[0338] Furthermore, when the higher-level control device 500 starts defrost control of the second heat exchanger 12, it transmits a control signal to the air conditioner 2F instructing it not to perform defrost operation.

[0339] In this modified example, it is possible to prevent the air conditioner on the second floor and the ventilation system from performing defrosting operations simultaneously. By preventing simultaneous defrosting, it is possible to prevent a decrease in air conditioning capacity.

[0340] (11th embodiment) Furthermore, if multiple ventilation devices are provided, the defrosting control may be varied according to the degree of frosting on the second heat exchangers 12 of the multiple ventilation devices when frost forms on them.

[0341] In this embodiment, an example is described in which the higher-level control device 500 controls four ventilation devices. The number of air conditioners 2F controlled by the higher-level control device 500 is arbitrary.

[0342] Figure 11 is a flowchart showing the processing procedure performed by the higher-level control device 500 according to this embodiment. In this embodiment, an example of processing performed by the higher-level control device 500 is described, but the process is not limited to the higher-level control device 500, and processing may be performed on a centralized management server located in a remote location or on the cloud.

[0343] The higher-level control device 500 acquires the detection results from the temperature detection unit 14 from each of the multiple ventilation devices (S2201).

[0344] Based on the detection results, the higher-level control device 500 identifies the number of exhaust units (or their second heat exchangers 12) that have frost accumulation (S2202). For example, it may determine that four exhaust units have frost accumulation.

[0345] The higher-level control device 500 then determines whether the detection result of the exhaust unit with frost is less than or equal to the first determination logic (S2203). The first determination logic is, for example, whether the evaporation temperature t of the refrigerant flowing through the second heat exchanger 12 of the exhaust unit is less than a predetermined value x1, or whether the pressure p of the refrigerant flowing through the second heat exchanger 12 of the exhaust unit is less than a predetermined value y1. Further determination methods may also be used as the determination logic. For example, the determination may be made by determining whether the surface temperature t2 of the second heat exchanger 12 is less than a predetermined value z1. Another example is that the imaging means photographs the surface of the second heat exchanger 12, calculates the degree of agreement between the captured image data and the image data under normal conditions, and determines whether the difference is greater than w%.

[0346] If the higher-level control device 500 determines that the detection result is below the first judgment logic (S2203: Yes), it determines that the frost level for the exhaust unit is 1 (S2204).

[0347] On the other hand, if the higher-level control device 500 determines that the detection result is greater than the first determination logic (S2203: No), it determines whether the detection result of the exhaust unit with frost is less than or equal to the second determination logic (S2205). The second determination logic is, for example, whether the evaporation temperature t of the refrigerant flowing through the second heat exchanger 12 of the exhaust unit is less than a predetermined value x2, or whether the pressure p of the refrigerant flowing through the second heat exchanger 12 of the exhaust unit is less than a predetermined value y2. Note that predetermined value x1 < predetermined value x2 and predetermined value y1 < predetermined value y2.

[0348] If the higher-level control unit 500 determines that the detection result is below the second judgment logic (S2205: Yes), it determines that the frost level for the exhaust unit is 2 (S2206).

[0349] On the other hand, if the higher-level control device 500 determines that the detection result is greater than the first determination logic (S2205: No), it determines that the frost level for the exhaust unit is 3 (S2207).

[0350] Subsequently, the higher-level control device 500 determines whether or not a frost level has been set for all exhaust units that have frost (S2208). If it determines that none of them have been set (S2208: No), it proceeds from S2203.

[0351] On the other hand, if the higher-level control device 500 determines that it has set a frost level for all exhaust units that have frosted (S2208: Yes), it calculates the time required for frosting operation for each exhaust unit (S2209). The method for calculating the time required for frosting operation is not limited to well-known methods; any method may be used. The time required for frosting operation may be predetermined for each frost level.

[0352] Furthermore, the higher-level control device 500 calculates an index of required comfort in the living space based on the current conditions of the living space (S2210). The current conditions of the living space are, for example, the detection results of sensors installed near the ventilation openings in the living space. The index of required comfort is an index of the comfort required in the current living space. The comfort index is determined, for example, according to the required temperature value of the air blown out from the ventilation openings, the required airflow for ventilation, and the number of people currently in the living space. The higher the comfort index, the more necessary it is to maintain the comfort of the living space.

[0353] The higher-level control unit 500 determines whether the calculated required comfort index is greater than the reference value k (S2211).

[0354] If the higher-level control device 500 determines that the calculated required comfort index is greater than the standard value k (S2211: Yes), it sets the multiple exhaust units to perform defrosting operations sequentially (S2212). In other words, the higher-level control device 500 maintains comfort in the living space by suppressing simultaneous defrosting operations through the setting to perform sequential defrosting operations. The order in which defrosting is performed is set according to the frost level. For example, if there is one exhaust unit with frost level 1, two exhaust units with frost level 2, and one exhaust unit with frost level 3, the system sets the exhaust unit with frost level 1 to perform defrosting in the order of one of the exhaust units with frost level 2, the other of the exhaust units with frost level 2, and then the exhaust unit with frost level 3.

[0355] On the other hand, if the higher-level control device 500 determines that the calculated required comfort index is below the standard value k (S2211: No), it sets the device to perform simultaneous defrosting operation on multiple exhaust units (S2213). In other words, the higher-level control device 500 shortens the defrosting operation by setting it to perform simultaneous defrosting operation. Note that defrosting operation is not performed on all exhaust units at the same time. The order in which defrosting operations are performed may also be set according to the defrosting level. For example, if there is one exhaust unit with frost level 1, two exhaust units with frost level 2, and one exhaust unit with frost level 3, the device can be set to perform defrosting operation on the exhaust unit with frost level 1 and the exhaust unit with frost level 3 simultaneously, and then perform defrosting operation on the two exhaust units with frost level 2 simultaneously. This setting makes it possible to balance the load on the living space with the completion of defrosting operation.

[0356] Then, the higher-level control unit 500 outputs a defrosting operation instruction for each exhaust unit according to the settings (S2214).

[0357] As described above, the higher-level control device 500 according to this embodiment acquires the frost status of the second heat exchangers 12, and if it is determined that the multiple second heat exchangers 12 are frosted while the multiple second heat exchangers 12 are functioning as evaporators, it generates multiple patterns for defrosting the multiple second heat exchangers 12, and performs defrosting control using one of the multiple generated patterns based on the frost status of the multiple second heat exchangers and the current conditions of the living space.

[0358] In this embodiment, defrosting operations are performed sequentially, starting with the exhaust units with the highest frost levels. If comfort is required, the system can be controlled so that the defrosting operations of multiple exhaust units are not performed simultaneously, thereby maintaining comfort.

[0359] Furthermore, if comfort is not a critical factor, the temperature control of multiple ventilation systems can be stopped simultaneously, and defrosting can be performed simultaneously on the exhaust units of those ventilation systems. This reduces comfort because the temperature control is stopped, but it allows for defrosting to be completed in a short period of time.

[0360] In the embodiments and modifications described above, the supply air unit is a casing (an example of a first casing) that houses at least a portion of the first heat exchanger 22 and the air passage (an example of a first air passage), and the exhaust unit is a casing (an example of a second casing) that houses at least a portion of the second heat exchanger 12 and the air passage (an example of a second air passage), and the two units are separated by casings.

[0361] This makes it possible to place the exhaust unit and the supply unit in separate locations. As a result, the ventilation system capable of heat recovery offers greater flexibility in placement compared to conventional designs.

[0362] However, the embodiments and modifications described above are not limited to cases where the casings of the air supply unit and exhaust unit are separate; the air supply unit and exhaust unit may be integrated. In other words, if the first heat exchanger 22 and the second heat exchanger 12 are connected by a refrigerant circuit, and a fan 21 corresponding to the first heat exchanger 22 and a fan corresponding to the second heat exchanger 12 are provided, then the airflow adjustment and refrigerant temperature adjustment shown in the embodiments and modifications described above can be applied. Thus, the methods shown in the embodiments and modifications described above may be applied even when the air supply unit and exhaust unit are integrated.

[0363] The embodiments and modifications described above are illustrative examples of defrosting methods. The methods shown in the embodiments and modifications described above are not limited to being used alone, but may be used in combination with one or more defrosting methods shown in other embodiments and modifications.

[0364] Although embodiments have been described above, it will be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims. Various modifications and improvements are possible, such as combinations or substitutions with parts or all of other embodiments. [Explanation of symbols]

[0365] 1, 1B, 1C, 1D, 1E, 1F_1, 1F_2, 1F_3 Ventilation system 2, 2B, 2F air conditioner 10, 110A, 110B, 210, 310, 510A, 510B, 510C Exhaust Unit 11 Fans 12 Second heat exchanger 13, 113A, 113B, 213, 313, 413 Control Unit 14 Temperature detection unit 15 Drive motor 16 Electric Valve 20, 120A, 120B, 220A, 220B, 520A, 520B, 520C Air Intake Unit 21 Fans 22 1st heat exchanger 23, 123, 423 Control Unit 24 Temperature detection unit 25 Drive motor 26 Electric Valve 240, 440 Opening / Closing Damper 341 First Opening / Closing Damper 342 Second Opening / Closing Damper 50, 150, 550A, 550B, 550C Compressor Units 51 Drive motor 52, 152 Control Unit 53 Compressor 54 Four-way valve 55 Electric Valve 156 Bypass electric valve 70, 170, 571, 572, 573 outdoor unit 71, 171 Control Unit 81, 82, 581, 582, 583, 584, 585, 586, 587, 588 Indoor air conditioning units 100, 500 Higher-level control unit 161, 162 Electric valve F1, F2, F3, F4, F101, F102, F103, F104 Refrigerant circuit F106 Bypass Channel F5, F501, F502, F503 connecting piping P1 Air intake path P2 Return air flow path P101 First air intake passage P102 Second air intake passage P103 First exhaust passage P104 Second exhaust passage P202 Return air flow path P202A 1st return air branch P202B 2nd return air branch P402 Bypass Channel P403 Return air flow path

Claims

1. Compressor and, A first heat exchanger that functions as a condenser or evaporator, A first airflow path is provided which shows a flow path that allows air taken in from outdoors to be discharged into the indoor space after passing through the first heat exchanger, A second heat exchanger that functions as a condenser or evaporator, A second airflow path is provided which allows air taken in from the indoor space to pass through the second heat exchanger and then be exhausted to the outdoors. The compressor, the first heat exchanger, and the second heat exchanger are connected by refrigerant piping, and a refrigerant circuit through which refrigerant flows is formed. If it is determined that the second heat exchanger is frosted while it is functioning as an evaporator, a control unit outputs a predetermined command to an actuator that controls the state of the refrigerant in the refrigerant circuit to raise the temperature of the refrigerant flowing into the second heat exchanger, causing the second heat exchanger to function as a condenser and the first heat exchanger to function as an evaporator, and also switches the airflow in the first air passage to exhaust from the indoor space to the outdoors, A ventilation system equipped with the following features.

2. The control unit further determines that the second heat exchanger is frosted while it is functioning as an evaporator, and switches the flow of the second air passage to supply air from the outdoors to the indoor space. The ventilation device according to claim 1.

3. A control unit that controls a ventilation system comprising a compressor, a first heat exchanger functioning as a condenser or evaporator, a first airflow path indicating a path through which air taken in from outdoors can be discharged into an indoor space after passing through the first heat exchanger, a second heat exchanger functioning as a condenser or evaporator, a second airflow path indicating a path through which air taken in from the indoor space can be exhausted to the outdoors after passing through the second heat exchanger, and a refrigerant circuit through which the compressor, the first heat exchanger, and the second heat exchanger are connected by refrigerant piping and through which refrigerant flows, determines that the second heat exchanger is frosted while the second heat exchanger is functioning as an evaporator, and outputs a predetermined command to an actuator that controls the state of the refrigerant in the refrigerant circuit to raise the temperature of the refrigerant flowing into the second heat exchanger, causing the second heat exchanger to function as a condenser and the first heat exchanger to function as an evaporator, and also switches the airflow in the first airflow path to exhaust air from the indoor space to the outdoors. Ventilation methods.

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