Ventilation equipment and ventilation method

Abstract

To suppress ideas. [Solution] The ventilation system comprises a compressor, a first heat exchanger, a first air passage that supplies air taken in from outdoors to the indoor space after passing it through the first heat exchanger, a second heat exchanger, a second air passage that exhausts air taken in from the indoor space to the outdoors after passing it through the second heat exchanger, a second ventilation unit that adjusts the amount of air that flows through the second air passage to the second heat exchanger, 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, and a control unit that detects whether a predetermined criterion indicating the possibility of frost formation on the second heat exchanger is met while the second heat exchanger is functioning as an evaporator, and if it is detected that the predetermined criterion is met, stops the compressor and controls the second ventilation unit to flow air that has passed through the second air passage to the second heat exchanger.

Description

Technical Field

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

Background Art

[0002] Conventionally, while ventilating the interior of a room using an exhaust fan and an intake fan, outdoor air that has undergone heat exchange with a refrigerant in a first heat exchanger is blown into the room, and indoor air that has undergone heat exchange with a refrigerant in a second heat exchanger is discharged outdoors. A ventilation and air-conditioning device is known (see Patent Document 1 and Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding the ventilation and air-conditioning device described in Patent Document 1, a technique has been proposed to suppress frosting on the second heat exchanger by preheating the air before it is supplied to the second heat exchanger using a preheating heater. However, various techniques for suppressing frosting can be considered.

[0005] An object of the present disclosure is to suppress frosting and continue the ventilation operation.

Means for Solving the Problems

[0006] The present disclosure is a compressor, a first heat exchanger that functions as a condenser or an evaporator, a first air flow path that supplies the air taken in from the outside to the indoor space after passing through the first heat exchanger, a second heat exchanger that functions as a condenser or an 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. A control unit that detects whether a predetermined criterion indicating the possibility of frost formation on the second heat exchanger is met while the second heat exchanger is functioning as an evaporator, and if it is detected that the predetermined criterion is met, controls the temperature of the refrigerant flowing through the second heat exchanger so that the second heat exchanger reaches a temperature at which frost does not form. To provide a ventilation system equipped with the following features.

[0007] This ventilation system suppresses frost formation by controlling the refrigerant temperature when certain criteria are met, enabling continuous ventilation operation through supplying air to the indoor space and exhausting air to the outdoors.

[0008] Regarding the ventilation system mentioned above, The control unit may detect whether the second heat exchanger meets a predetermined criterion indicating the possibility of frost formation while the second heat exchanger is functioning as an evaporator, and if it is detected that the predetermined criterion is met, it may output a signal to control an air conditioner installed in the indoor space in order to control the temperature of the refrigerant flowing through the second heat exchanger.

[0009] According to this ventilation system, the temperature of the indoor space can be adjusted by operating the air conditioner in response to the signal, and frost formation can be suppressed by controlling the temperature of the refrigerant, thereby achieving efficient frost formation suppression.

[0010] Regarding the ventilation system mentioned above, The control unit may, when the predetermined criteria are met, output a signal to the air conditioner installed in the indoor space to raise the temperature currently set on the air conditioner.

[0011] According to this ventilation system, the signal causes the air conditioner to raise the temperature of the indoor space, which in turn raises the temperature of the refrigerant and suppresses frost formation, thereby achieving efficient suppression of frost formation.

[0012] Regarding the ventilation system mentioned above, The refrigerant circuit has a bypass pipe that allows the refrigerant to flow to the second heat exchanger without passing through the first heat exchanger while the second heat exchanger is functioning as an evaporator. The control unit may also control the flow of the refrigerant compressed by the compressor to the second heat exchanger via the bypass piping when the predetermined criteria are met.

[0013] According to this ventilation system, by flowing the refrigerant to the second heat exchanger via bypass piping, the temperature of the refrigerant is increased, thereby suppressing frost formation and achieving efficient frost suppression.

[0014] Regarding the ventilation system mentioned above, Air taken from a room in the aforementioned indoor space, different from the second airflow path, passes through the second heat exchanger to the third airflow path, The system further includes a first guide mechanism that switches whether or not to guide air through the third air passage to the second heat exchanger, The control unit may also control the first guide mechanism to guide air through the third air passage to the second heat exchanger when the predetermined criteria are met.

[0015] With this ventilation system, air is guided to the second heat exchanger through the third air passage, thereby increasing the temperature of the refrigerant flowing through the second heat exchanger and suppressing frost formation, thus achieving efficient frost suppression.

[0016] Regarding the ventilation system mentioned above, The system further includes a second ventilation unit that adjusts the amount of air flowing to the second heat exchanger through the second air passage, When the control unit satisfies the predetermined criterion, it may perform control to increase the amount of air flowing through the second heat exchanger with respect to the second ventilation unit as compared to before satisfying the predetermined criterion.

[0017] According to the ventilation device, by increasing the amount of air flowing through the second heat exchanger, the temperature of the refrigerant flowing through the second heat exchanger can be increased to suppress frosting, and efficient frosting suppression can be achieved.

[0018] Regarding the above ventilation device, a plurality of the second heat exchangers, and the second ventilation unit associated with each of the second heat exchangers, and further includes: While the plurality of second heat exchangers are functioning as evaporators, when the control unit satisfies the predetermined criterion, it may perform control to increase the amount of air flowing through the second heat exchanger with respect to the second ventilation unit associated with any one of the plurality of second heat exchangers as compared to before satisfying the predetermined criterion.

[0019] According to the ventilation device, by increasing the amount of air flowing through the second heat exchanger with the second ventilation unit, the temperature of the refrigerant flowing through the second heat exchanger can be increased to suppress frosting, and efficient frosting suppression can be achieved.

[0020] Regarding the above ventilation device, When the control unit performs control to increase the amount of air with respect to the second ventilation unit associated with any one of the plurality of second heat exchangers, it may perform control to decrease the amount of air flowing through the second heat exchanger with respect to the second ventilation unit associated with the other second heat exchangers among the plurality of second heat exchangers as compared to before satisfying the predetermined criterion.

[0021] According to the ventilation device, by adjusting the total amount of air to be exhausted, the comfort of the living space can be maintained.

[0022] Regarding the above ventilation device, The system further includes a first ventilation unit that adjusts the amount of air flowing to the first heat exchanger through the first air passage, The control unit may, when it controls the second ventilation unit associated with any one of the plurality of second heat exchangers to increase the amount of air, control the first ventilation unit to increase the amount of air flowing to the first heat exchanger compared to before the predetermined standard was met, based on the amount of air increased for the second ventilation unit.

[0023] According to this ventilation system, when the air volume of the second supply unit is increased, the air volume of the first ventilation unit is also increased, and by adjusting the amount of air supplied and exhausted, the comfort of the living space can be maintained.

[0024] Regarding the ventilation system mentioned above, A first ventilation unit that adjusts the amount of air flowing to the first heat exchanger through the first air passage, The system further includes a second ventilation unit that adjusts the amount of air flowing to the second heat exchanger through the second air passage, The control unit may, when it receives a signal from an air conditioner installed in the indoor space to perform a defrosting operation while the second heat exchanger is functioning as an evaporator, deem that the predetermined criteria have been met and perform control to increase the amount of air flowing from the first ventilation unit to the first heat exchanger and to increase the amount of air flowing from the second ventilation unit to the second heat exchanger compared to before the predetermined criteria were met.

[0025] According to this ventilation system, when the air conditioner performs defrosting operation, the amount of air in the first ventilation unit and the second ventilation unit is increased, thereby suppressing the reduction in heating performance and maintaining comfort in the living space.

[0026] Regarding the ventilation system mentioned above, A bypass channel guides the air from which heat has been exchanged by the first heat exchanger to the second heat exchanger, The system further includes a second guide mechanism that switches whether or not to guide air through the bypass channel to the second heat exchanger, The control unit may also control the second guide mechanism to guide air through the bypass channel to the second heat exchanger when the predetermined criteria are met.

[0027] According to this ventilation system, by guiding air through the bypass channel to the second heat exchanger, the temperature of the refrigerant flowing through the second heat exchanger is increased, thereby suppressing frost formation and achieving efficient frost suppression.

[0028] Regarding the ventilation system mentioned above, The system further includes a second ventilation unit that adjusts the amount of air flowing to the second heat exchanger through the second air passage, The control unit may, when the predetermined criteria are met, stop the compressor and also control the second ventilation unit so that the air that has passed through the second air passage flows to the second heat exchanger.

[0029] According to this ventilation system, by stopping the compressor and then flowing air through the second heat exchanger, the temperature of the refrigerant flowing through the second heat exchanger is increased, thereby suppressing frost formation and achieving efficient frost suppression.

[0030] Regarding the ventilation system mentioned above, Multiple of the above-mentioned second heat exchangers, The system further comprises a second ventilation unit associated with each of the second heat exchangers, The refrigerant circuit further includes a first valve section for adjusting the opening of the flow path through each of the second heat exchangers, The control unit may, when the temperature information detected from the plurality of second heat exchangers meets the predetermined criteria, perform control to close the plurality of first valves corresponding to the second heat exchangers that meet the predetermined criteria in a predetermined order, and also perform control to the second ventilation unit corresponding to the second heat exchangers that meet the predetermined criteria so that the air that has passed through the second air passage flows to the second heat exchanger.

[0031] According to this ventilation system, by closing the valves in a predetermined order, the simultaneous cessation of refrigerant flow to multiple second heat exchangers is suppressed, thereby maintaining comfort in the living space.

[0032] Regarding the ventilation system mentioned above, A first ventilation unit that adjusts the amount of air flowing to the first heat exchanger through the first air passage, The system further includes a second ventilation unit that adjusts the amount of air flowing to the second heat exchanger through the second air passage, The control unit controls the first ventilation unit and the second ventilation unit so that, when the predetermined criteria are met, the amount of air exhausted to the outdoors through the second air passage is greater than the amount of air supplied to the indoor space through the first air passage.

[0033] According to this ventilation system, the amount of air flowing into the second heat exchanger increases, which raises the temperature of the refrigerant flowing through the second heat exchanger, thereby suppressing frost formation and achieving efficient frost suppression.

[0034] Regarding the ventilation system mentioned above, When the predetermined criteria are met, the control unit controls the first heat exchanger so that the temperature of the air after passing through the first heat exchanger is lower than the temperature set in the air conditioner installed in the indoor space.

[0035] This ventilation system increases the temperature of the refrigerant flowing through the second heat exchanger, thereby enabling efficient suppression of frost formation.

[0036] Regarding the ventilation system mentioned above, The system has multiple combinations of the compressor, the first heat exchanger, the second heat exchanger, the refrigerant circuit, and the second ventilation unit associated with the second heat exchanger. The control unit, when the temperature information detected from a plurality of second heat exchangers meets the predetermined criteria, controls the compressor corresponding to the second heat exchanger that meets the predetermined criteria to be stopped in a predetermined order, and controls the second ventilation unit corresponding to the second heat exchanger that meets the predetermined criteria to allow air that has passed through the second air passage to flow to the second heat exchanger.

[0037] This ventilation system helps maintain comfort in living spaces by preventing the simultaneous cessation of refrigerant supply to multiple second heat exchangers.

[0038] 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.

[0039] With this ventilation system, the first casing and the second casing are separable, which simplifies the layout and reduces the burden of installation.

[0040] Regarding the ventilation system mentioned above, The control unit, when the predetermined criteria are met, performs control to reduce the rotational speed of the compressor compared to before the predetermined criteria were met.

[0041] According to this ventilation system, by reducing the rotation speed of the compressor, the temperature of the refrigerant flowing through the second heat exchanger rises, thus enabling efficient suppression of frost formation.

[0042] 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. When the predetermined criteria are met, the control unit performs control to increase the opening degree of the second valve compared to before the predetermined criteria were met.

[0043] Regarding the ventilation system mentioned above, When the second heat exchanger functions as an evaporator, the refrigerant flow in the refrigerant circuit further includes a third valve downstream of the second heat exchanger, The control unit further controls the third valve to restrict its position compared to before the predetermined criteria were met when the second heat exchanger functions as an evaporator and the predetermined criteria are met.

[0044] Regarding the ventilation system mentioned above, A third heat exchanger that functions as a condenser or evaporator, A third air passage that exhausts the air that has exchanged heat with the refrigerant flowing through the third heat exchanger and the outdoor air to the outdoors, In addition to the compressor, the first heat exchanger, and the second heat exchanger, the refrigerant circuit includes a third heat exchanger connected by the refrigerant piping.

[0045] This disclosure is, A ventilation system comprising: a compressor during heat recovery ventilation operation; a first heat exchanger that functions as a condenser or evaporator; a first airflow path that supplies air taken in from outdoors to the indoor space after passing it through the first heat exchanger; a second heat exchanger that functions 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. An air conditioner having a third heat exchanger that functions as a condenser or evaporator, and an indoor air conditioning unit that exhausts the air that has exchanged heat with the refrigerant flowing through the third heat exchanger and the air in the indoor space back into the indoor space, A control unit that detects whether the second heat exchanger meets predetermined criteria indicating the possibility of frost formation, and, if it is detected that the predetermined criteria are met, controls the temperature of the refrigerant flowing through the second heat exchanger to a temperature at which frost formation does not occur, or controls the operation to remove frost formation from the second heat exchanger after frost formation, based on the power consumption of the ventilation device and the air conditioner required to control the temperature of the refrigerant flowing through the second heat exchanger to a temperature at which frost formation does not occur, or controls the operation to remove frost formation from the second heat exchanger after frost formation. We provide an air conditioning system equipped with the following features.

[0046] According to this air conditioning system, efficient suppression of frost formation can be achieved by controlling the temperature of the refrigerant when certain criteria are met.

[0047] This disclosure is, When controlling a ventilation system 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 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 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, the system detects whether a predetermined criterion indicating the possibility of frost formation on the second heat exchanger is met while the second heat exchanger is functioning as an evaporator, and if it is detected that the predetermined criterion is met, the system controls the temperature of the refrigerant flowing through the second heat exchanger so that the second heat exchanger reaches a temperature at which frost does not form. Provide a ventilation method.

[0048] This ventilation method allows for efficient suppression of frost formation by controlling the refrigerant temperature when certain criteria are met.

[0049] This disclosure is, The system comprises a compressor, a first heat exchanger, and a second heat exchanger connected by refrigerant piping, a refrigerant circuit through which refrigerant flows, an air supply fan that supplies outdoor air indoors through the first heat exchanger, an exhaust fan that exhausts indoor air outdoors through the second heat exchanger, and a control unit. The control unit, when the second heat exchanger is to function as an evaporator, starts the compressor and, when it determines that the low pressure of the refrigerant circuit, the evaporation temperature of the second heat exchanger, the indoor temperature, or the outdoor temperature has fallen below a first threshold for the low pressure of the refrigerant circuit, the evaporation temperature of the second heat exchanger, the indoor temperature, or the outdoor temperature, performs a first control to increase the low pressure of the refrigerant circuit. We provide ventilation systems.

[0050] According to this ventilation system, in a ventilation system equipped with a refrigerant circuit capable of recovering heat from exhaust, the compressor can be reliably operated continuously when the second heat exchanger functions as an evaporator.

[0051] Regarding the ventilation system described above, The refrigerant circuit includes a bypass pipe connecting the discharge pipe of the compressor to the second heat exchanger or a liquid pipe connected to the second heat exchanger, and a valve provided in the bypass pipe, and the control unit preferably opens the valve in the first control.

[0052] In this case, high-temperature, high-pressure gaseous refrigerant can be supplied to the second heat exchanger in the first control. This makes it possible to suppress frost formation on the second heat exchanger.

[0053] Regarding the ventilation system described above, When the control unit is open, it is preferable to close the valve if it determines that the low pressure of the refrigerant circuit, the saturation temperature of the second heat exchanger, or the intake air temperature of the exhaust fan has exceeded a second threshold for the low pressure of the refrigerant circuit, the saturation temperature of the second heat exchanger, or the intake air temperature of the second heat exchanger.

[0054] In this case, if the conditions for the second heat exchanger to function as an evaporator are met during the execution of the first control, the first control can be terminated.

[0055] Regarding the ventilation system described above, In the first control, the control unit preferably causes the second heat exchanger to draw in air at a temperature higher than the second threshold for the intake air temperature.

[0056] In this case, during the execution of the first control, air with a temperature higher than the second threshold can be introduced into the second heat exchanger. This makes it possible to suppress frost formation on the second heat exchanger.

[0057] Regarding the ventilation system described above, In the first control, it is preferable that the control unit adjusts the direction of the air supply fan's discharge so that the air blown out from the supply fan is guided to the intake side of the exhaust fan.

[0058] In this case, during the execution of the first control, air hotter than the second threshold can be introduced into the second heat exchanger.

[0059] Regarding the ventilation system described above, The system further includes an air conditioner for conditioned indoor air, and the control unit preferably drives the exhaust fan in the first control when the indoor air temperature rises above the second threshold due to the air conditioner.

[0060] In this case, during the execution of the first control, air hotter than the second threshold can be introduced into the second heat exchanger. [Brief explanation of the drawing]

[0061] [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 is a flowchart showing the frost suppression control performed by the exhaust unit of the ventilation system according to the first embodiment. [Figure 3] Figure 3 shows an example of the configuration of a ventilation system and air conditioner according to Modification 3 of the First Embodiment. [Figure 4] Figure 4 shows an example of the configuration of a ventilation system and air conditioner according to the second embodiment. [Figure 5] Figure 5 shows a refrigerant circuit according to Modification 1 of the second embodiment. [Figure 6] Figure 6 shows an example of the configuration of a ventilation system, air conditioner, and higher-level control device according to the third embodiment. [Figure 7] Figure 7 is a sequence diagram showing the flow of processing between the upper-level control device, the ventilation device, and the air conditioner when defrosting operation of the air conditioner according to the third embodiment is started. [Figure 8] Figure 8 is a sequence diagram showing the processing flow between the higher-level control device, the compressor unit, and the exhaust unit group when frost formation is possible in each of the exhaust unit groups according to the fourth embodiment. [Figure 9] Figure 9 is a diagram illustrating the arrangement of a group of devices including a higher-level control device according to the seventh 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 eighth embodiment. [Figure 11] Figure 11 shows a refrigerant circuit according to the 11th embodiment. [Figure 12] Figure 12 shows a refrigerant circuit according to a modified example of the 11th embodiment. [Figure 13] Figure 13 is a flowchart showing the processing procedure of the higher-level control device according to the 12th embodiment. [Figure 14] Figure 14 is a schematic diagram of a ventilation system according to one embodiment. [Figure 15] Figure 15 is a control block diagram of a ventilation system according to one embodiment. [Figure 16] Figure 16 is a flowchart showing the operation of a ventilation system according to one embodiment. [Figure 17]Figure 17 is a schematic diagram of the ventilation system according to the thirteenth embodiment. [Figure 18] Figure 18 is a schematic diagram of the ventilation system according to the 14th embodiment. [Figure 19] Figure 19 is a schematic diagram showing the installation of the ventilation systems according to the 14th and 15th embodiments in a building. [Figure 20] Figure 20 is a schematic diagram of the ventilation system according to the 15th embodiment. [Figure 21] Figure 21 is a schematic diagram of the ventilation system according to the 16th embodiment. [Figure 22] Figure 22 is a schematic diagram of the ventilation system according to the 17th embodiment. [Figure 23] Figure 23 is a schematic diagram of the ventilation system according to the 18th embodiment. [Modes for carrying out the invention]

[0062] The following description of the ventilation device, air conditioning system, ventilation method, and ventilation system according to this embodiment will be given with reference to the drawings. Note that the following embodiments are essentially preferred examples and are not intended to limit the scope of this disclosure, its applications, or its uses.

[0063] (First embodiment) Figure 1 is a diagram showing an example configuration of a ventilation device and air conditioner according to the first embodiment. In the example shown in Figure 1, the air conditioning system includes a ventilation device 1 and an air conditioner 2 for air conditioning an indoor space.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] The air supply passage P1 (an example of the first air passage) is a passage for supplying air taken in from outside 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 provided on the ceiling, but there are no particular restrictions on the location where the ventilation opening 92 is provided.

[0075] 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.

[0076] In this embodiment, the return air passage P2 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 P2A (an example of the second air passage) and the second return air branch passage P2B (an example of the third air passage).

[0077] The first return air branch passage (an example of a second air passage) P2A 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 having a second heat exchanger 12. The first return air branch passage P2A takes in air from a ventilation opening 91 provided in the ceiling of the living space R11. Although this embodiment describes an example where the ventilation opening 91 is located in the ceiling, it may be located in other places such as under the floor or in the wall.

[0078] The second return air branch passage (an example of a third air passage) P2B 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 P2B 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 P2A. 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 P2B can be any room in the indoor space that is different from the living room space R11.

[0079] Furthermore, an opening / closing damper 40 is provided at the tip of the second return air branch passage. The opening / closing damper 40 is normally in the closed state. The opening / closing damper 40 (an example of the first guide mechanism) can adjust the amount of air taken in from the ceiling space R12 by control via a signal line S2 from a control unit 13 provided in the exhaust unit 10.

[0080] 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.

[0081] 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, 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. The processing shown in the control units 13, 23, and 52 below may be implemented by a CPU (not shown) reading a program, or by hardware connections. The same applies to the control units and higher-level control devices shown in subsequent embodiments.

[0082] 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.

[0083] The drive motor 51 is a motor used to rotate (drive) the compressor for compressing the refrigerant.

[0084] 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.

[0085] 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.

[0086] Fan 21 functions to supply (SA) the outside air (OA) taken in to the living space R11.

[0087] The first heat exchanger 22 functions as a condenser or evaporator.

[0088] 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.

[0089] 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.

[0090] 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).

[0091] Fan 11 functions to exhaust (EA) the return air (RA) taken in from the living space R11 to the outside.

[0092] The second heat exchanger 12 functions as a condenser or evaporator.

[0093] The temperature detection unit 14 detects the indoor 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 indoor temperature to be detected includes, for example, 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).

[0094] 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.

[0095] Furthermore, the control unit 13 according to this embodiment can adjust the amount of air taken in from the ceiling space R12 by controlling the opening / closing damper 40 based on the detection result of the temperature detection unit 14.

[0096] 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 creates the possibility of the second heat exchanger 12 freezing (frost formation). Therefore, in this embodiment, control is performed to avoid freezing (frost formation) of the second heat exchanger 12, or, if frost has formed, to prevent the frost from growing. In the embodiments described later, at least one of the controls that avoid frost formation and controls that suppress frost growth if frost has formed will be referred to as frost suppression controls.

[0097] 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 meets a predetermined criterion indicating the possibility of frost formation (freezing) while the second heat exchanger 12 is functioning as an evaporator. The predetermined criterion indicating the possibility of frost formation (freezing) of the second heat exchanger 12 may be, for example, a criterion for determining whether the outdoor temperature detected by the temperature detection unit 14 is 0 degrees or lower. Furthermore, in this embodiment, the predetermined criterion is not limited to whether the outdoor temperature is 0 degrees or lower, but may also be a criterion for determining whether the outdoor temperature is the minimum operating temperature of the second heat exchanger 12.

[0098] Furthermore, the predetermined criteria do not have to be based on the ambient temperature. For example, the criterion may be whether the surface temperature of the second heat exchanger 12 is below a predetermined temperature (e.g., 0 degrees). Another example is whether the temperature of the refrigerant flowing through the second heat exchanger 12 is below a predetermined temperature (e.g., 0 degrees). In the following explanation, examples of predetermined criteria will be shown, but any criterion may be used as long as it indicates the possibility of frost (freezing) on ​​the second heat exchanger 12. For example, as shown in the embodiment described later, the criterion may be whether the low pressure of the refrigerant circuits F1, F2, F3, and F4 has fallen below a predetermined pressure threshold.

[0099] This embodiment describes an example of acquiring the ambient temperature and the surface temperature of the second heat exchanger, and determining whether the acquired temperatures meet predetermined criteria. However, this embodiment is merely an example of the information to be acquired, and the information to be acquired can be any information that allows for the determination of whether or not predetermined criteria are met. For example, in addition to the ambient temperature, the surface temperature of the second heat exchanger 12, the temperature of the refrigerant, or the pressure of the refrigerant may be acquired. Furthermore, a determination of whether or not predetermined criteria are met may be made by combining this information. The embodiments and modifications described below are also merely examples of the information to be acquired, and any information that allows for the determination of whether or not predetermined criteria are met can be used.

[0100] In this embodiment, the control unit 13 of the exhaust unit 10 determines that a predetermined criterion is met and controls the opening / closing damper 40 to guide the air present in the ceiling space R12 through the second return air branch passage P2B to the second heat exchanger 12, thereby suppressing frost formation on 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, when there is a possibility of frost formation on the second heat exchanger 12, the control unit opens the opening / closing damper 40. As a result of this control, air mixed with the warm air present in the ceiling space R12 and the air present in the living space R11 is guided to the second heat exchanger 12.

[0101] 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 suppresses frost formation on the second heat exchanger 12.

[0102] Figure 2 is a flowchart showing the frost suppression control performed by the exhaust unit 10 of the ventilation device 1 according to this embodiment.

[0103] The control unit 13 of the exhaust unit 10 obtains the ambient temperature from the temperature detection unit 14 (S1201).

[0104] The control unit 13 of the exhaust unit 10 determines, based on the acquired outside air temperature, whether or not the second heat exchanger 12 meets predetermined criteria indicating the possibility of freezing (S1202).

[0105] If the control unit 13 of the exhaust unit 10 determines that the predetermined criteria are not met (S1202: NO), it terminates without performing any further processing.

[0106] Meanwhile, if the control unit 13 of the exhaust unit 10 determines that a predetermined criterion has been met (S1202: YES), it obtains the temperature of the air in the ceiling space R12 and the temperature of the air taken in from the living space R11 from the temperature detection unit 14 (S1203).

[0107] The control unit 13 of the exhaust unit 10 determines whether the temperature of the air in the ceiling space R12 is higher than the temperature of the air in the living space R11 (S1204). If the control unit 13 determines that the temperature of the air in the ceiling space R12 is lower than or equal to the temperature of the air in the living space R11 (S1204: NO), it terminates without performing any control related to the opening / closing damper 40. If no control is performed related to the opening / closing damper 40, control to suppress frost formation, as described in the following embodiments and modifications, may be performed.

[0108] On the other hand, if the control unit 13 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 (S1204: YES), it controls the opening / closing damper 40 to open (S1205).

[0109] In this embodiment, if the processing procedure described above creates a possibility of frost formation on the second heat exchanger 12, the air in the ceiling space R12, which is warmer than the living space R11, is guided to the second heat exchanger 12.

[0110] In other words, the temperature of the air flowing into the second heat exchanger 12 increases, which in turn increases the temperature of the refrigerant flowing through the second heat exchanger 12. This reduces the possibility of frost forming on the second heat exchanger 12.

[0111] (Modification 1 of the first embodiment) In the first embodiment described above, as an example of control to increase the temperature of the air flowing through the second heat exchanger 12, a method was described in which the air in the ceiling space R12 is guided to the second heat exchanger 12 to reduce the possibility of frost formation on the second heat exchanger 12. However, the control method to increase the temperature of the air flowing through the second heat exchanger 12 is not limited to the method of guiding the air in the ceiling space R12 to the second heat exchanger 12, and other methods may be used. Therefore, in Modification 1 of the first embodiment, an example is given in which the air conditioner 2 is controlled to increase the temperature of the air (room temperature) in the living space R11.

[0112] In this modified example, the control unit 13 of the exhaust unit 10 and the control unit 71 of the outdoor unit 70 are connected by a signal line. This allows the control unit 71 of the outdoor unit 70 to output a control signal to the control unit 13 of the exhaust unit 10.

[0113] This modified example describes a configuration in which the control unit 13 of the exhaust unit 10 and the control unit 71 of the outdoor unit 70 are connected by a signal line, as one way in which information can be transmitted and received between them. However, the configuration in which information can be transmitted and received is not limited to the example in which they are connected by a signal line. Control signals may also be transmitted and received via a higher-level control device (not shown), or via a cloud or server connected via a public network.

[0114] Furthermore, the control unit 13 of the exhaust unit 10 according to this modified example detects whether or not predetermined criteria indicating the possibility of the second heat exchanger 12 freezing are met while the second heat exchanger 12 is functioning as an evaporator.

[0115] When the control unit 13 determines that a predetermined criterion is met, it outputs a control signal to the control unit 71 of the outdoor unit 70 of the air conditioner 2 to raise the temperature of the refrigerant flowing through the second heat exchanger 12, thereby increasing the temperature of the refrigerant currently set in the living space R11. In this modified example, by raising the temperature of the air in the living space R11, the temperature of the air flowing through the second heat exchanger 12 increases, which in turn increases the temperature of the refrigerant flowing through the second heat exchanger 12.

[0116] As described above, the control unit 13 in this modified example outputs a control signal to the control unit 71 to raise the temperature currently set in the living space R11, as an example of control to raise the temperature of the refrigerant flowing through the second heat exchanger 12. As a result, the room temperature in the living space R11 rises, warm air flows into the second heat exchanger 12, raising the temperature of the refrigerant flowing through the second heat exchanger 12 and suppressing frost formation on the second heat exchanger 12.

[0117] In this modified example, the control unit 71 of the outdoor unit 70 of the air conditioner 2 outputs a control signal to raise the temperature currently set in the living space R11. However, this modified example does not limit the control signal output to the control unit 71 of the outdoor unit 70 of the air conditioner 2 to a control signal that raises the temperature currently set in the living space R11; any control signal to raise the temperature of the refrigerant flowing through the second heat exchanger 12 is acceptable. For example, the control unit 13 may output a control signal to increase the airflow rate in order to circulate the air in the living space R11.

[0118] (Modification 2 of the first embodiment) The first embodiment and its modifications described above are not limiting to the use of the methods described above. Therefore, in modification 2 of the first embodiment, a method for controlling the fan 11 in order to suppress frost formation will be described.

[0119] The control unit 13 of the exhaust unit 10 in this modified example determines whether a predetermined criterion is met indicating the possibility of frost formation on the second heat exchanger 12 while the second heat exchanger 12 is functioning as an evaporator.

[0120] When the control unit 13 determines that a predetermined standard is met, it controls the fan 11 (an example of a second ventilation unit) to increase the amount of air flowing through the second heat exchanger 12 compared to before the predetermined standard was met, in order to raise the temperature of the refrigerant flowing through the second heat exchanger 12.

[0121] As described above, the control unit 13 in this modified example outputs a control signal to the fan 11 (an example of a second ventilation unit) to increase the amount of air flowing to the second heat exchanger 12 compared to before a predetermined standard is met, as an example of control to raise the temperature of the refrigerant flowing through the second heat exchanger 12. As a result, the amount of warm air flowing into the second heat exchanger 12 increases, which raises the temperature of the refrigerant and suppresses frost formation on the second heat exchanger 12.

[0122] Furthermore, if control is applied to the fan 11 to increase the amount of air flowing to the second heat exchanger 12, there is a possibility that the living space R11 will become negatively pressurized. For this reason, the control unit 13 may output a control signal to the control unit 23 of the air supply unit 20 to increase the airflow of the fan 21.

[0123] (Modification 3 of the first embodiment) The first embodiment and its modifications described above are not limiting to the use of the methods described above. Therefore, in modification 3 of the first embodiment, a method of providing a bypass passage for direct airflow between the air supply unit and the exhaust unit will be described.

[0124] Figure 3 shows an example of the configuration of a ventilation system and air conditioner according to Modification 3 of the First Embodiment. In the example shown in Figure 3, a ventilation system 1A and an air conditioner 2 are provided to provide air conditioning for an indoor space. In this modification, the same reference numerals are assigned to components similar to those in the First Embodiment, and their descriptions are omitted.

[0125] As shown in Figure 3, a bypass passage P102 is provided between the air supply unit 20 and the exhaust unit 110. The bypass passage P102 consists of a first bypass partial passage P102A on the side of the air supply unit 20 from the air supply passage P101, a third bypass partial passage P102C on the side of the exhaust unit 110 from the return air passage P103, and a second bypass partial passage P102B that connects the first bypass partial passage P102A and the third bypass partial passage P102C.

[0126] Furthermore, an opening / closing damper 140 is provided on the second bypass section flow path P102B. The opening / closing damper 140 is normally in the closed state. The opening / closing damper 140 (an example of the second guide mechanism) can guide the air heated in the supply air unit 20 directly to the exhaust unit 110 via a signal line S3 controlled by a control unit 113 provided in the exhaust unit 110.

[0127] 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 P102A and the air supply flow path P101.

[0128] The exhaust unit 110 comprises a fan 11, a second heat exchanger 12, a control unit 113, and a temperature detection unit 14. It takes in return air (RA) from the living space R11 via the return air flow path P103 and the third bypass partial flow path P102C, and exhausts it outdoors (EA).

[0129] The control unit 113 of the exhaust unit 110 in this modified example detects whether predetermined criteria indicating the possibility of frost formation on the second heat exchanger 12 are met while the second heat exchanger 12 is functioning as an evaporator.

[0130] When the control unit 13 determines that a predetermined criterion is met, it controls the opening / closing damper 140 to raise the temperature of the refrigerant flowing through the second heat exchanger 12.

[0131] As described above, the control unit 113 in this modified configuration performs control to open the on / off damper 140 to guide air to the second heat exchanger 12 through the bypass channel P102, as an example of control to raise the temperature of the refrigerant flowing through the second heat exchanger 12. This allows the air heated in the exhaust unit 110 to flow directly to the second heat exchanger 12, thereby suppressing frost formation on the second heat exchanger 12.

[0132] (Second embodiment) In the embodiments and modifications described above, an example was given in which the temperature of the refrigerant flowing through the second heat exchanger 12 is increased by adjusting the air flowing through the second heat exchanger 12. However, other methods may be used to increase the temperature of the refrigerant flowing through the second heat exchanger 12. Therefore, in this embodiment, a method of increasing the temperature of the refrigerant by controlling the refrigerant flowing through the second heat exchanger 12 will be described.

[0133] Figure 4 shows an example of the configuration of a ventilation system and air conditioner according to the second embodiment. In the example shown in Figure 4, a ventilation system 1B and an air conditioner 2 are provided to provide air conditioning for an indoor space. In this embodiment, components that are the same as those in the first embodiment are assigned the same reference numerals and their descriptions are omitted.

[0134] The control unit 52 of the compressor unit 50, the control unit 23 of the first air supply unit 220A, the control unit 23 of the second air supply unit 220B, and the control unit 213 of the exhaust unit 210 are connected by a signal line S201, indicated by a dotted line. This enables the transmission and reception of information between the control unit 52 of the compressor unit 50, the control unit 23 of the first air supply unit 220A, the control unit 23 of the second air supply unit 220B, and the control unit 213 of the exhaust unit 210.

[0135] The ventilation system 1B comprises an exhaust unit 210, a first supply unit 220A, a second supply unit 220B, a compressor unit 50, refrigerant circuits F1, F2, F3, F4, a first supply air passage P201, a second supply air passage P202, and a return air passage P203.

[0136] The first air supply channel P201 (an example of the first air supply channel) takes in air from outside, passes it through the first air supply unit 220A which has a first heat exchanger 22, and then supplies it to the living space R11 through the ventilation opening 92A.

[0137] The second air supply channel P202 (an example of the first air supply channel) takes in air from outside, passes it through the second air supply unit 220B which has the first heat exchanger 22, and then supplies it to the living space R11 through the ventilation opening 92B.

[0138] The return air passage P203 (an example of a second air passage) takes in air from the indoor space, passes it through the exhaust unit 210 which has a second heat exchanger 12, and then exhausts it outdoors.

[0139] The first air supply unit 220A and the second air supply unit 220B each include a fan 21, a first heat exchanger 22, a control unit 23, and a temperature detection unit 24, and take in outside air (OA) and supply it (SA) to the living space R11.

[0140] The exhaust unit 210 comprises a fan 11, a second heat exchanger 12, a control unit 213, and a temperature detection unit 14, and takes in return air (RA) from the living space R11 and exhausts it outdoors (EA).

[0141] The control unit 213 of the exhaust unit 210 controls the internal configuration of the exhaust unit 210. For example, the control unit 213 outputs a control signal to the control unit 52 of the compressor unit 50 according to the detection result of the temperature detection unit 14.

[0142] The process performed by the ventilation system 1B when the temperature is low will now be described. Similar to the embodiment described above, the first heat exchanger 22 of the first air supply unit 220A and the second air supply unit 220B functions as a condenser, and the second heat exchanger 12 in the exhaust unit 210 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, control is performed to suppress frost formation on the second heat exchanger 12.

[0143] Specifically, the control unit 213 of the exhaust unit 210 determines, based on the detection results from the temperature detection unit 14, whether the second heat exchanger 12 meets a predetermined criterion indicating the possibility of frost formation while the second heat exchanger 12 is functioning as an evaporator. The predetermined criterion indicating the possibility of frost formation on the second heat exchanger 12 may be, for example, a criterion for determining whether the temperature of the refrigerant detected by the temperature detection unit 14 is 0 degrees or less. Furthermore, this embodiment does not limit the predetermined criterion to a criterion based on the temperature of the refrigerant, but may also be a criterion for determining whether the pressure of the refrigerant is below a predetermined pressure.

[0144] Furthermore, the specified standards do not have to be based on the temperature or pressure of the refrigerant. For example, the standards may be based on the ambient temperature, or on the surface temperature of the second heat exchanger 12.

[0145] In this embodiment, the control unit 213 of the exhaust unit 210 determines that a predetermined criterion has been met, and outputs a control signal to the control unit 52 of the compressor unit 50 to reduce the rotational speed of the compressor compared to before the predetermined criterion was met, as a control to suppress frost formation on the second heat exchanger 12.

[0146] Then, when the control unit 52 of the compressor unit 50 receives the control signal, it outputs a control signal to the drive motor 51 that drives the compressor to reduce the rotational speed of the compressor compared to before the predetermined criteria were met. As a result, the rotational speed of the compressor decreases. Therefore, the pressure of the refrigerant flowing through the refrigerant circuits F1, F2, F3, and F4 decreases, which allows the temperature (evaporation temperature) of the refrigerant flowing through the second heat exchanger 12 to rise.

[0147] In this embodiment, the control unit 213 outputs a control signal to the control unit 52 of the compressor unit 50 to reduce the rotational speed of the compressor compared to before a predetermined standard was met, as an example of control to increase the temperature of the refrigerant flowing through the second heat exchanger 12. This suppresses frost formation on the second heat exchanger 12.

[0148] (Modification 1 of the second embodiment) In the second embodiment, an example was described in which the rotational speed of the compressor is reduced to increase the temperature (evaporation temperature) of the refrigerant flowing through the second heat exchanger 12. However, the method for increasing the temperature (evaporation temperature) of the refrigerant flowing through the second heat exchanger 12 is not limited to the method of reducing the rotational speed of the compressor. Therefore, in Modification 1, an example is described in which a bypass flow path (an example of bypass piping) is provided in the refrigerant circuit. This Modification 1 is also provided with two supply air units and one exhaust unit, similar to the second embodiment.

[0149] Figure 5 shows a refrigerant circuit according to Modification 1 of the second embodiment. In the example shown in Figure 5, the refrigerant flow is shown when the second heat exchanger 12 of the exhaust unit 310 is functioning as an evaporator. Components similar to those in the above-described embodiment are assigned the same reference numerals and their descriptions are omitted.

[0150] In the example shown in Figure 5, an air supply unit 320A, 320B, an exhaust unit 310, and a compressor unit 350 are provided.

[0151] The air supply units 320A and 320B 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.

[0152] The drive motor 25 controls the airflow of the fan 21 through control by the control unit 23.

[0153] The electric valve 26 functions as an expansion valve for reducing the pressure of the refrigerant, and switches whether or not to reduce the pressure based on control by the control unit 23. The electric valve 26 reduces the pressure when the first heat exchanger 22 is functioning as an evaporator, and does not reduce the pressure when the first heat exchanger 22 is functioning as a condenser.

[0154] The exhaust unit 310 includes a fan 11, a second heat exchanger 12, a control unit 313, a temperature detection unit 14, a drive motor 15, and an electric valve 16.

[0155] While the second heat exchanger 12 is functioning as an evaporator, the control unit 313 determines, based on the detection results from the temperature detection unit 14, whether or not predetermined criteria indicating the possibility of frost formation on the second heat exchanger 12 are met. The predetermined criteria are the same as in the second embodiment and will not be explained further.

[0156] In this modified example, the control unit 313 of the exhaust unit 310, when it determines that a predetermined criterion has been met, outputs a control signal to the control unit 352 of the compressor unit 350 to flow refrigerant through the bypass flow path F6, as a control to suppress frost formation on the second heat exchanger 12.

[0157] The drive motor 15 controls the airflow of the fan 11 through control by the control unit 313.

[0158] The electric valve 16 functions as an expansion valve for reducing the pressure of the refrigerant, and switches whether or not to reduce the pressure based on control by the control unit 313. The electric valve 16 reduces the pressure when the second heat exchanger 12 is functioning as an evaporator, and does not reduce the pressure when the second heat exchanger 12 is functioning as a condenser.

[0159] The compressor unit 350 includes a drive motor 51, a control unit 352, a compressor 53, a four-way valve 54, an electric valve 55, and a bypass electric valve 56.

[0160] The compressor 53 compresses the refrigerant flowing through the refrigerant circuit.

[0161] 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 352.

[0162] The control unit 352 controls the internal configuration of the compressor unit 350. For example, the control unit 352 controls the drive motor 51 and the four-way valve 54 shown below.

[0163] 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 F1 and F4. For example, when the second heat exchanger 12 is made to function as an evaporator based on the control of the control unit 352, the four-way valve 54 is switched to direct the refrigerant compressed by the compressor 53 to the refrigerant circuit F1.

[0164] The electric valve 55 functions as a valve that controls the opening and closing of the refrigerant circuit according to the control unit 352. When the second heat exchanger 12 functions as an evaporator, the electric valve 55 is in a closed state, preventing the flow of refrigerant.

[0165] In this modified configuration, when the second heat exchanger 12 functions as an evaporator, a bypass channel F6 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.

[0166] The bypass passage F6 is provided as a refrigerant passage that bypasses the compressor 53 and the four-way valve 54, and the refrigerant circuit F3. In other words, the bypass passage F6 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.

[0167] The bypass electric valve 56 functions as a valve for switching whether or not to allow refrigerant to flow through the bypass passage F6, according to control from the control unit 352.

[0168] Specifically, first, when the control unit 313 of the exhaust unit 310 determines that a predetermined criterion indicating the possibility of frost formation on the second heat exchanger 12 has been met, it outputs a control signal to the control unit 352 of the compressor unit 350 to flow refrigerant through the bypass flow path F6.

[0169] Then, when the control unit 352 of the compressor unit 350 receives a control signal from the control unit 313 of the exhaust unit 310 to flow refrigerant through the bypass passage F6, it controls the bypass electric valve 56 to open.

[0170] When the bypass electric valve 56 is open, the refrigerant, which has been compressed by the compressor 53 to become a high-temperature, high-pressure gas, flows into the refrigerant circuit F3 via the bypass passage F6. As a result, the temperature of the refrigerant flowing through the refrigerant circuit F3 rises. Then, the refrigerant with the increased temperature flows into the second heat exchanger 12.

[0171] In other words, in this modified configuration, if a predetermined criterion is met, the refrigerant compressed by the compressor 53 is controlled to flow to the second heat exchanger 12 via the bypass flow path F6. This suppresses frost formation on the second heat exchanger 12.

[0172] (Modification 2 of the second embodiment) Furthermore, other methods may be used to increase the temperature of the refrigerant flowing through the second heat exchanger 12. Therefore, in Modification 2 of the second embodiment, an example of controlling the electric valve 16 inside the exhaust unit 310 will be described. Note that the configuration of Modification 2 of the second embodiment is the same as the refrigerant circuit shown in Figure 5, but with the bypass flow path F6 removed.

[0173] 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.

[0174] Therefore, 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 indicating the possibility of frost formation while the second heat exchanger 12 is functioning as an evaporator. The predetermined criteria are the same as in the second embodiment and will not be explained further.

[0175] Then, when the control unit 313 determines that a predetermined criterion has been met, it performs control to suppress frost formation on the second heat exchanger 12 by increasing the opening degree of the electric valve 16 (an example of the second valve section) compared to before the predetermined criterion was met.

[0176] In other words, in this modified example, when a predetermined criterion is met, the opening of the electric valve 16 is increased to raise the temperature of the refrigerant flowing to the second heat exchanger 12. This suppresses frost formation on the second heat exchanger 12.

[0177] (Third embodiment) The embodiments and modifications described above describe an example in which a control unit within the exhaust unit determines whether or not a predetermined standard is met and performs control based on the determination result. However, the embodiments and modifications described above are not limited to a method in which the control unit within the exhaust unit performs the control. For example, a higher-level control device located above the air conditioner and ventilation device may perform the control.

[0178] Figure 6 shows an example configuration of a ventilation system, air conditioner, and higher-level control device according to the third embodiment. Components similar to those in the above-described embodiment are assigned the same reference numerals and their descriptions are omitted.

[0179] In the example shown in Figure 6, a higher-level control device 400 is provided to coordinate the ventilation system 1C and the air conditioner 2C.

[0180] The air conditioner 2C includes an outdoor unit 470 and two indoor air conditioning units 81 and 82. This embodiment does not limit the number of indoor air conditioning units to two; it may be one or three or more.

[0181] The outdoor unit 470 includes a control unit 471 along with a heat exchanger (not shown).

[0182] The control unit 471 controls the entire air conditioner 2C. The control unit 471 also transmits and receives information with the higher-level control unit 400. The control unit 471 then performs various controls in response to control signals from the higher-level control unit 400.

[0183] The ventilation system 1C comprises a first exhaust unit 410A, a second exhaust unit 410B, a first supply unit 420A, a second supply unit 420B, a compressor unit 450, refrigerant circuits F401, F402, F403, F404, a first supply air passage P401, a second supply air passage P402, a first return air passage P403, and a second return air passage P404.

[0184] The first air supply channel P401 takes in air from outside, passes it through the first air supply unit 420A which has a first heat exchanger 22, and then supplies it to the living space R11 through the ventilation opening 92A.

[0185] The second air supply channel P402 takes in air from outside, passes it through the second air supply unit 420B which has the first heat exchanger 22, and then supplies it to the living space R11 through the ventilation opening 92B.

[0186] The first return air channel P403 takes in air (return air) from the ventilation opening 91A in the indoor space, passes it through the first exhaust unit 410A which has a second heat exchanger 12, and then exhausts it to the outdoors.

[0187] The second return air channel P404 takes in air (return air) from the ventilation opening 91B in the indoor space, passes it through the second exhaust unit 410B which has a second heat exchanger 12, and then exhausts it to the outside.

[0188] Refrigerant circuits F401, F402, F403, and F404 are circuits that connect the compressor unit 450, the first heat exchanger 22 of the first supply unit 420A and the second supply unit 420B, and the second heat exchanger 12 of the first exhaust unit 410 and the second exhaust unit 410B via refrigerant piping, and allow refrigerant to flow through them.

[0189] The control unit 452 of the compressor unit 450, the control unit 423A of the first supply unit 420A, the control unit 423B of the second supply unit 420B, the control unit 413A of the first exhaust unit 410A, and the control unit 413B of the second exhaust unit 410B are connected by a signal line S401, indicated by a dotted line. This enables the transmission and reception of information between the control units 452, 423A, 423B, 413A, and 413B.

[0190] The control unit 452 of the compressor unit 450 transmits the status of the ventilation device 1C, received from the control units 423A, 423B, 413A, and 413B, to the higher-level control unit 400. This enables the higher-level control unit 400 to perform control according to the status of the ventilation device 1C.

[0191] The first air supply unit 420A comprises a fan 21, a first heat exchanger 22, a control unit 423A, 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.

[0192] The second air supply unit 420B includes a fan 21, a first heat exchanger 22, a control unit 423B, 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.

[0193] Control units 423A and 423B control the configuration within their respective air supply units. Furthermore, control units 423A and 423B transmit the detection results from the temperature detection unit 24, etc., within their respective air supply units to the control unit 452 of the compressor unit 450. The control unit 452 of the compressor unit 450 recognizes the current status from the detection results and transmits the recognition result to the higher-level control device 400. This allows the higher-level control device 400 to recognize the status of the first air supply unit 420A and the second air supply unit 420B.

[0194] The first exhaust unit 410A comprises a fan 11 (an example of a second ventilation unit), a second heat exchanger 12, a control unit 413A, and a temperature detection unit 14. It takes in return air (RA) from the ventilation opening 91A of the living space R11 and exhausts it outdoors (EA).

[0195] The second exhaust unit 410B includes a fan 11 (an example of a second ventilation unit), a second heat exchanger 12, a control unit 413B, 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).

[0196] Control units 413A and 413B control the configuration within their respective exhaust units. Furthermore, control units 413A and 413B transmit the detection results from the temperature detection unit 14, etc., within their respective exhaust units to the control unit 452 of the compressor unit 450. The control unit 452 of the compressor unit 450 recognizes the current status from the detection results and transmits the recognition result to the higher-level control device 400. This allows the higher-level control device 400 to recognize the status of the first exhaust unit 410A and the second exhaust unit 410B.

[0197] The higher-level control unit 400 performs various controls to coordinate the operation of the ventilation system 1C and the operation of the air conditioner 2C.

[0198] The higher-level control device 400 receives the status of the air conditioner 2C from the control unit 471 of the outdoor unit 470 and the status of the ventilation device 1C from the control unit 452 of the compressor unit 450. The higher-level control device 400 then performs various controls according to the status of the air conditioner 2C and the ventilation device 1C.

[0199] For example, if the higher-level control device 400 recognizes that the air conditioner 2C is performing defrosting operation based on information received from the control unit 471 of the outdoor unit 470, it performs control to improve the heating capacity of the ventilation device 1C.

[0200] In other words, when air conditioner 2C performs defrosting, air conditioner 2C 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 420A and the second supply air unit 420B is increased to compensate for the reduced function of air conditioner 2C when it performs defrosting, the temperature of the refrigerant flowing to the second heat exchanger 12 of the first exhaust unit 410A and the second exhaust unit 410B, which are connected by refrigerant circuits F401, F402, F403, and F404, will drop. In this case, the likelihood of frost formation on the second heat exchanger 12 of the first exhaust unit 410A and the second exhaust unit 410B is increased.

[0201] Therefore, when the higher-level control device 400 recognizes that the air conditioner 2C is performing defrosting operation, it increases the airflow of the ventilation device 1C to improve heating capacity and suppress the decrease in temperature within the living space R11.

[0202] Figure 7 is a sequence diagram showing the flow of processing that takes place between the upper control device 400, the ventilation device 1C, and the air conditioner 2C when the defrosting operation of the air conditioner 2C according to this embodiment is started.

[0203] First, when the control unit 471 inside the outdoor unit 470 of the air conditioner 2C starts defrosting, it sends a signal to the higher-level control device 400 indicating that defrosting will be performed (S1701).

[0204] Then, based on the received signal, the higher-level control device 400 recognizes that defrosting operation has started in the air conditioner 2C, and decides to control the airflow of the ventilation device 1C to increase in order to compensate for the decrease in function due to the defrosting operation (S1702).

[0205] The higher-level control device 400 then transmits a control signal to the control unit 452 of the compressor unit 450 instructing an increase in the airflow of the exhaust unit group (first exhaust unit 410A and second exhaust unit 410B) (S1703).

[0206] Similarly, the control unit 452 of the compressor unit 450 transmits control signals to the control units 413A and 413B of the exhaust unit group (first exhaust unit 410A and second exhaust unit 410B), respectively, instructing them to increase the airflow rate (S1704).

[0207] Based on the received control signals, the control units 413A and 413B of the exhaust unit group control the fan 11 (an example of a second ventilation unit) to increase the amount of air flowing to the second heat exchanger 12 (increase in airflow) compared to before the air conditioner 2C performed defrosting operation (S1705).

[0208] Furthermore, the higher-level control device 400 transmits a control signal to the control unit 452 of the compressor unit 450 instructing the air supply unit group (first air supply unit 420A and second air supply unit 420B) to increase the airflow rate (S1706).

[0209] Then, the control unit 452 of the compressor unit 450 transmits control signals to the control units 423A and 423B of the air supply unit group (first air supply unit 420A and second air supply unit 420B), respectively, instructing them to increase the airflow rate (S1707).

[0210] Each of the control units 423A and 423B of the air supply unit group controls the fan 21 (an example of the first ventilation unit) to increase the amount of air flowing to the first heat exchanger 22 (increase in airflow) compared to before the air conditioner 2C performed defrosting operation, based on the received control signal (S1708).

[0211] In this embodiment, the heating capacity of the ventilation device 1C is increased by increasing the supply and exhaust airflow without raising the supply air temperature of the ventilation device 1C, thereby suppressing a decrease in the room temperature of the living space R11. Furthermore, in this embodiment, by suppressing the rise in the supply air temperature of the ventilation device 1C, the possibility of frost formation on the second heat exchanger 12 due to a decrease in the evaporation temperature can be reduced.

[0212] In this embodiment, the higher-level control device 400 can increase the supply and exhaust volume of the ventilation device 1C to compensate for the reduced capacity of the air conditioner 2C due to frost formation, thereby reducing the possibility of frost formation on the second heat exchanger 12, increasing the heating capacity, and suppressing the decrease in room temperature.

[0213] The higher-level control device 400 according to this embodiment can perform various types of control in addition to the coordinated control described above.

[0214] For example, the higher-level control device 400 may, upon receiving the outside air temperature from the control unit 413A or control unit 413B of the exhaust unit group via the control unit 452 of the compressor unit 450, determine whether a predetermined criterion indicating the possibility of frost formation on the second heat exchanger 12 is met. If the higher-level control device 400 determines that the predetermined criterion is met, it may perform control to suppress frost formation on the second heat exchanger 12. As a control to suppress frost formation on the second heat exchanger 12, for example, the higher-level control device 400 may send a control signal to the control unit 471 of the outdoor unit 470 to raise the current set temperature for heating.

[0215] Furthermore, the configuration of the higher-level control device 400 shown in this embodiment may also be included as the configuration of the ventilation system. In other words, the processing performed by the higher-level control device 400 may also be considered a function of the ventilation system. The same applies to subsequent embodiments.

[0216] (Fourth embodiment) In the third embodiment, the coordinated control when the air conditioner 2C performs defrosting operation was described. However, the higher-level control device 400 performs various coordinated controls. Therefore, in the fourth embodiment, the control when there is a possibility of frost formation on the second heat exchangers 12 of the multiple exhaust units 410 will be described.

[0217] When there is a possibility of frost formation on the second heat exchangers 12 of multiple exhaust units 410, it is difficult to simultaneously suppress frost formation on the second heat exchangers 12 of multiple exhaust units 410. Therefore, the higher-level control device 400 adjusts so that it does not simultaneously suppress frost formation on the second heat exchangers 12 of multiple exhaust units 410.

[0218] In this embodiment, the frost suppression control of the ventilation device 1C is performed by increasing the amount of air flowing to the second heat exchanger 12. If the control to increase the amount of air flowing to the second heat exchanger 12 is performed simultaneously by multiple exhaust units 410A and 410B, there is a possibility that the living space R11 will become negatively pressurized.

[0219] Therefore, in this embodiment, defrost suppression control is performed by increasing the amount of air in one of the multiple exhaust units 410A and 410B, and decreasing the amount of air in the other. In other words, in this embodiment, defrost suppression operation is preferentially performed in one of the multiple exhaust units 410A and 410B. Furthermore, the higher-level control device 400 prevents the living space R11 from becoming negatively pressurized by adjusting to maintain the total amount of air being discharged.

[0220] Figure 8 is a sequence diagram showing the processing flow between the upper control unit 400, the compressor unit 450, and the exhaust unit group when there is a possibility of frost formation in each of the exhaust unit group according to this embodiment.

[0221] First, the control unit 413A of the first exhaust unit 410A obtains the ambient temperature from the temperature detection unit 14 (S1801).

[0222] The control unit 413A then notifies the control unit 452 of the compressor unit 450 of the detected outside air temperature (1802).

[0223] Furthermore, the control unit 413B of the second exhaust unit 410B obtains the ambient temperature from the temperature detection unit 14 (S1811).

[0224] The control unit 413B then notifies the control unit 452 of the compressor unit 450 of the detected outside air temperature (1812).

[0225] The control unit 452 of the compressor unit 450 determines, based on the detected ambient temperature received from the control unit 413A of the first exhaust unit 410A and the control unit 413B of the second exhaust unit 410B, whether predetermined criteria for frost formation on the second heat exchangers 12 of the first exhaust unit 410A and the second exhaust unit 410B are met (S1821). In the example shown in Figure 8, it is determined that the predetermined criteria are met for each of the second heat exchangers 12 of the first exhaust unit 410A and the second exhaust unit 410B. The predetermined criteria are the same as those described in the embodiment above, so their explanation is omitted.

[0226] The control unit 452 of the compressor unit 450 notifies the higher-level control unit 400 of the determination result indicating that frost formation is possible (S1822).

[0227] The higher-level control device 400 determines the order in which to perform frost suppression control on the first exhaust unit 410A and the second exhaust unit 410B based on the received determination result (S1831). Any method can be used to determine this order. For example, the control may be set to perform frost suppression on the unit with a higher probability of frost formation first, or it may be determined according to the priority order that has been pre-assigned to the first exhaust unit 410A and the second exhaust unit 410B. The example shown in Figure 8 is an example in which it is determined that frost suppression is performed on the first exhaust unit 410A and then on the second exhaust unit 410B.

[0228] The higher-level control device 400 transmits a signal to the control unit 452 of the compressor unit 450 indicating an instruction to increase the airflow of the first exhaust unit 410A (S1832).

[0229] Then, the control unit 452 of the compressor unit 450 transmits a signal to the control unit 413A of the first exhaust unit 410A indicating an instruction to increase the airflow rate (S1823).

[0230] As a result, the control unit 413A of the first exhaust unit 410A controls the fan 11 to increase the amount of air flowing to the second heat exchanger 12 (increase airflow) compared to before temperature detection in S1801 (S1803).

[0231] After the control described above increases the amount of air flowing to the second heat exchanger 12, the higher-level control device 400 transmits a signal to the control unit 452 of the compressor unit 450 indicating a reduction in the airflow of the second exhaust unit 410B after a predetermined time (a predetermined time for frost suppression) has elapsed (S1833).

[0232] Then, the control unit 452 of the compressor unit 450 transmits a signal to the control unit 413B of the second exhaust unit 410B indicating an instruction to reduce the airflow (S1824).

[0233] As a result, the control unit 413B of the second exhaust unit 410B controls the fan 11 to reduce the amount of air flowing to the second heat exchanger 12 (airflow reduction) compared to before temperature detection in S1811 (S1813).

[0234] In this embodiment, the total amount of air discharged is maintained by increasing the airflow of the first exhaust unit 410A and decreasing the airflow of the second exhaust unit 410B. Subsequently, the higher-level control device 400 replaces the exhaust unit that performs frost suppression.

[0235] The higher-level control device 400 transmits a signal to the control unit 452 of the compressor unit 450 indicating an instruction to reduce the airflow of the first exhaust unit 410A (S1834).

[0236] Then, the control unit 452 of the compressor unit 450 transmits a signal to the control unit 413A of the first exhaust unit 410A indicating an instruction to reduce the airflow (S1825).

[0237] As a result, the control unit 413A of the first exhaust unit 410A controls the fan 11 to reduce the amount of air flowing to the second heat exchanger 12 (airflow reduction) compared to before temperature detection in S1801 (S1804).

[0238] The higher-level control device 400 transmits a signal to the control unit 452 of the compressor unit 450 indicating an instruction to increase the airflow of the second exhaust unit 410B (S1835).

[0239] Then, the control unit 452 of the compressor unit 450 transmits a signal to the control unit 413B of the second exhaust unit 410B indicating an instruction to increase the airflow rate (S1826).

[0240] As a result, the control unit 413B of the second exhaust unit 410B controls the fan 11 to increase the amount of air flowing to the second heat exchanger 12 (increase airflow) compared to before temperature detection in S1811 (S1814).

[0241] As described above, the control unit 452 and the higher-level control device 400 of the compressor unit 450 according to this embodiment, when they determine that a predetermined criterion has been met while the multiple second heat exchangers 12 are functioning as evaporators, control the fan 11 associated with any one of the multiple second heat exchangers 12 to increase the amount of air flowing to the second heat exchanger 12 compared to before the predetermined criterion was met. As a result, the amount of (warm) air flowing to any one of the second heat exchangers 12 increases, thereby suppressing frost formation.

[0242] Furthermore, when the higher-level control device 400 controls the airflow to increase the amount of air flowing to a fan 11 associated with any one of the multiple second heat exchangers 12, it controls the airflow to the other second heat exchangers 12 fans 11 to decrease compared to before the predetermined criteria were met. This maintains the amount of air discharged from multiple exhaust unit groups, thus preventing the living space R11 from becoming negatively pressurized.

[0243] Furthermore, this embodiment can suppress frost formation on the second heat exchangers 12 of multiple exhaust units by controlling frost formation suppression for each of the multiple exhaust units in a predetermined order.

[0244] (Fifth embodiment) In the fourth embodiment, an example was described in which the amount of air discharged from multiple exhaust unit groups is adjusted to maintain that amount when controlling frost suppression. However, the method of avoiding negative pressure is not limited to adjusting the amount of air discharged from multiple exhaust unit groups to maintain that amount. Therefore, in the fifth embodiment, a case is described in which the amount of air taken in from the outside by the supply air unit group is increased when the amount of air discharged from the exhaust unit group is increased. The configuration of this embodiment is assumed to be the same as that of the fourth embodiment.

[0245] The control unit 452 of the compressor unit 450 according to this embodiment, similar to the fourth embodiment, determines whether predetermined criteria are met for frost formation on the second heat exchanger 12 of the first exhaust unit 410A and the second exhaust unit 410B, based on the temperature of the received outside air.

[0246] Then, if the control unit 452 of the compressor unit 450 determines that either the first exhaust unit 410A or the second exhaust unit 410B meets a predetermined criterion, the higher-level control device 400 instructs that exhaust unit to increase its airflow. The method of giving this instruction is the same as in the fourth embodiment and will not be explained further.

[0247] If the higher-level control device 400 determines that the first exhaust unit 410A and the second exhaust unit 410B each meet predetermined criteria, it determines the order in which frost formation suppression will be performed for the first exhaust unit 410A and the second exhaust unit 410B. The higher-level control device 400 then instructs the first exhaust unit 410A and the second exhaust unit 410B to increase the airflow according to the determined order.

[0248] In this embodiment, the higher-level control device 400, instead of issuing an instruction to decrease the airflow as shown in the fourth embodiment, instructs one or more of the first air supply unit 420A and the second air supply unit 420B to increase the airflow. The instruction to increase the airflow is given from the higher-level control device 400 to one or more of the control unit 423A of the first air supply unit 420A and the control unit 423B of the second air supply unit 420B via the control unit 452 of the compressor unit 450.

[0249] The target of the instruction to increase the airflow may be either the first air supply unit 420A or the second air supply unit 420B, or it may be either the first air supply unit 420A or the second air supply unit 420B individually. However, the higher-level control device 400 adjusts the amount of air discharged by the first exhaust unit 410A and the second exhaust unit 410B to be the same as the amount of air taken in by the first air supply unit 420A and the second air supply unit 420B.

[0250] As described above, in this embodiment, when the higher-level control device 400 controls a fan 11 associated with any 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 a predetermined standard was met, based on the increased amount of air. As a result, in this embodiment, 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.

[0251] (Sixth embodiment) The method for suppressing frost formation is not limited to the embodiments described above, and other methods may be used. In the sixth embodiment, an example of suppressing frost formation will be described in which air is flowed through the second heat exchanger 12 after stopping the operation of the compressor of the compressor unit.

[0252] The configuration of this embodiment may be any configuration, and it may also be the case where a host controller 400 as shown in FIG. 6 of the third embodiment is provided. Further, in the example shown in FIG. 6, it is assumed that two exhaust units and two air supply units are provided, but one exhaust unit and one air supply unit may be provided. Thus, the number of exhaust units and air supply units may be any number.

[0253] While the second heat exchanger 12 is functioning as an evaporator, the control unit 413A of the first exhaust unit 410A and the control unit 413B of the second exhaust unit 410B obtain the surface temperature of the second heat exchanger 12 from the temperature detection unit 14. Then, the control unit 413A and the control unit 413B of the second exhaust unit 410B transmit the detected surface temperature of the second heat exchanger 12 to the control unit 452 of the compressor unit 450.

[0254] Then, the control unit 452 of the compressor unit 450 determines whether or not a predetermined criterion indicating the possibility of the second heat exchanger 12 frosting is satisfied based on the surface temperature of the second heat exchanger 12. As a predetermined criterion indicating the possibility of the second heat exchanger 12 frosting, for example, it may be a criterion for determining whether or not the surface temperature of the second heat exchanger 12 is 0 degrees Celsius or less. Note that the predetermined criterion may be any criterion as long as it is a criterion indicating the possibility of the second heat exchanger 12 frosting. For example, the predetermined criterion may be a criterion as in the above-described embodiment, or may be a criterion based on the temperature and pressure of the refrigerant.

[0255] When the control unit 452 of the compressor unit 450 according to this embodiment determines that the predetermined criterion is satisfied, it notifies the host controller 400 of a determination result indicating that there is a possibility of the second heat exchanger 12 frosting.

[0256] Based on the determination result, the host controller 400 transmits a control signal instructing the control unit 452 of the compressor unit 450 to stop the compressor. Thereby, the control unit 452 of the compressor unit 450 performs control to stop the compressor.

[0257] Furthermore, based on the determination result, the higher-level control device 400 outputs a control signal via the control unit 452 of the compressor unit 450 to the control unit 413A of the first exhaust unit 410A and the control unit 413B of the second exhaust unit 410B, respectively, to continue the control of flowing air to the second heat exchanger 12 of the fan 11. In addition, the higher-level control device 400 may also perform control to increase the airflow rate of the fan 11, as in the fourth embodiment.

[0258] In this embodiment, by stopping the compressor inside the compressor unit 450 and flowing the air from the living space R11 to the second heat exchanger 12, the surface temperature of the second heat exchanger 12 can be increased, thereby suppressing frost formation on the second heat exchanger 12.

[0259] (Seventh Embodiment) In the sixth embodiment, an example was described in which the higher-level control device 400 controls one compressor unit 450. However, the higher-level control device 400 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 400 controls three compressor units.

[0260] Figure 9 is a diagram illustrating the arrangement of a group of devices including the higher-level control device 500 according to the seventh embodiment. The example shown in Figure 9 includes at least living spaces R501, R502, R503, restrooms R511, R512, and a pipe shaft R521.

[0261] Restrooms R511 and R512 are equipped with ventilation openings 595A and 595B, respectively.

[0262] Furthermore, the air conditioning unit 2D includes three outdoor units 571, 572, and 573, and eight indoor units 581, 582, 583, 584, 585, 586, 587, and 588. The three outdoor units 571-573 and the eight indoor units 581-588 are connected by connecting pipes (not shown).

[0263] 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.

[0264] The first ventilation system 1D_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.

[0265] 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.

[0266] 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 450A, the first air supply unit 420A, and the first exhaust unit 410A shown in Figure 6, so their explanation will be omitted.

[0267] The second ventilation system 1D_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.

[0268] 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.

[0269] 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 for the transmission and reception of information 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 450A, the first supply unit 420A, and the first exhaust unit 410A shown in Figure 6, so their explanation will be omitted.

[0270] The third ventilation system 1D_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.

[0271] 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.

[0272] Further, the third compressor unit 550C, the third air supply unit 520C, and the third exhaust unit 510C are connected by signal lines (not shown). Thereby, information can be transmitted and received between the units. In addition, the configurations within the third compressor unit 550C, the third air supply unit 520C, and the third exhaust unit 510C are the same as those of the compressor unit 450A, the first air supply unit 420A, and the first exhaust unit 410A shown in FIG. 6, and the description thereof will be omitted.

[0273] As described above, in the present embodiment, a plurality of combinations of a compressor unit, an air supply unit, an exhaust unit, and a connecting pipe are provided. The first compressor unit 550A, the second compressor unit 550B, and the third compressor unit 550C are arranged on the pipe shaft R521.

[0274] The upper control device 500 is connected to the first compressor unit 550A, the second compressor unit 550B, and the third compressor unit 550C by signal lines. Thereby, the upper control device 500 can recognize the states of the devices of the first ventilation device 1D_1 to the third ventilation device 1D_3 and perform control on each device.

[0275] With the above-described configuration, while the second heat exchangers 12 of the first exhaust unit 510A to the third exhaust unit 510C function as evaporators, the control units (not shown) of the first compressor unit 550A to the third compressor unit 550C receive the surface temperature of the second heat exchanger 12 from each of the first exhaust unit 510A to the third exhaust unit 510C.

[0276] Then, the control units of the first compressor unit 550A to the third compressor unit 550C according to the present embodiment determine whether or not a predetermined criterion indicating the possibility of frosting of the second heat exchanger 12 is satisfied based on the surface temperature of the second heat exchanger 12 while the second heat exchanger 12 functions as an evaporator. The predetermined criterion is the same as that in the above-described embodiment, and the description thereof will be omitted.

[0277] The control units of the first compressor unit 550A to the third compressor unit 550C notify the higher-level control unit 400 of the determination result indicating whether or not a predetermined standard is met.

[0278] If the higher-level control device 500 determines from the judgment result that there are multiple compressor units (for example, the first compressor unit 550A to the third compressor unit 550C) connected to the second heat exchanger 12 by connecting piping that meet predetermined criteria, it outputs control signals to the multiple compressor units (for example, the first compressor unit 550A to the third compressor unit 550C) to stop the compressors in a predetermined order, as a control to suppress frost formation on the second heat exchanger 12. This prevents multiple compressor units from stopping their compressors simultaneously. The predetermined order can be any order, such as from lowest surface temperature to highest, or it can be based on a pre-set priority order of compressor units.

[0279] Furthermore, the higher-level control device 500 maintains control over the fan 11 corresponding to the second heat exchanger 12 that meets predetermined standards, causing air from the living space R501~R503 to flow to the second heat exchanger 12. This allows the temperature of the refrigerant flowing through the second heat exchanger 12 to be increased.

[0280] In this embodiment, by performing the control described above, the flow of refrigerant to the second heat exchanger 12 is stopped while maintaining the flow of air to the second heat exchanger 12, thereby suppressing frost formation on the second heat exchanger 12.

[0281] (Eighth embodiment) In the seventh embodiment, an example was described in which the higher-level control device 500 stops multiple compressor units in a predetermined order. In contrast, the eighth embodiment describes an example in which multiple supply units and multiple exhaust units are connected to a single compressor.

[0282] Figure 10 is a diagram illustrating the arrangement of a group of devices including the higher-level control device 600 according to the eighth embodiment. Note that, among the components shown in Figure 10, components similar to those in the embodiments described above are assigned the same reference numerals, and their descriptions are omitted.

[0283] As shown in Figure 10, the compressor unit 650 is connected to the first supply unit 520A and the first exhaust unit 510A via connecting pipe F601, to the second supply unit 520B and the second exhaust unit 510B via connecting pipe F602, and to the third supply unit 520C and the third exhaust unit 510C via connecting pipe F603. This allows the refrigerant to circulate through each unit connected by connecting pipes F601, F602, and F603.

[0284] The compressor unit 650, the first supply air units 520A to the third supply air units 520C, and the first exhaust units 510A to the third exhaust units 510C are connected by signal lines (not shown), allowing information to be transmitted and received between the units. Furthermore, the higher-level control unit 500 and the compressor unit 650 are also connected by signal lines, enabling information transmission and reception between them as well.

[0285] Furthermore, the first air supply unit 520A, the second air supply unit 520B, and the third air supply unit 520C are provided with an electric valve 26 (an example of a first valve section) as shown in Figure 5. Similarly, the first exhaust unit 510A, the second exhaust unit 510B, and the third exhaust unit 510C are provided with an electric valve 16 (an example of a first valve section) as shown in Figure 5.

[0286] When the second heat exchangers 12 of the first exhaust unit 510A, the second exhaust unit 510B, and the third exhaust unit 510C function as evaporators, the electric valve 16 functions as a valve that adjusts the opening of the flow path to the second heat exchanger 12 (adjusts the refrigerant pressure). (An example of a valve)

[0287] As a result, the higher-level control device 600 can individually control the flow of refrigerant to each of the first exhaust unit 510A, the second exhaust unit 510B, and the third exhaust unit 510C by controlling the electric valve 16 to a closed state.

[0288] The control unit (not shown) of the compressor unit 650 according to this embodiment determines, based on the surface temperature of the second heat exchanger 12, whether or not predetermined criteria indicating the possibility of frost formation on 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 embodiment described above, so their explanation is omitted. The control unit 652 (not shown) of the compressor unit 650 then notifies the higher-level control unit 600 of the determination result.

[0289] In this embodiment, when the higher-level control device 600 recognizes, based on the determination result, that there are multiple second heat exchangers 12 that meet predetermined criteria, it outputs control signals to multiple exhaust units (for example, the first exhaust unit 510A to the third exhaust unit 510C) that include the second heat exchangers 12 that meet the predetermined criteria, in order to close the electric valves 16, as a control to suppress frost formation on the second heat exchangers 12. This prevents the simultaneous cessation of refrigerant flow into multiple second heat exchangers 12. The predetermined order can be any order, such as in order of lowest surface temperature, or it can be based on a preset priority order of compressor units.

[0290] Furthermore, the higher-level control device 500 maintains control over the fan 11 corresponding to the second heat exchanger 12 that meets predetermined standards, causing air from the living space R501~R503 to flow to the second heat exchanger 12.

[0291] In this embodiment, by performing the control described above, the refrigerant flowing to the second heat exchanger 12 is stopped, while the flow of air to the second heat exchanger 12 is maintained, thereby suppressing frost formation.

[0292] (Ninth embodiment) Frost formation on the second heat exchanger 12 may be suppressed using methods other than those described in the embodiments above. Therefore, in the ninth embodiment, an example of adjusting the relationship between the supply air volume and the exhaust volume will be described.

[0293] The configuration of the ninth embodiment may be any of the embodiments described above, for example, the configuration shown in Figure 6. Therefore, in this embodiment, we will describe the case in which the configuration shown in Figure 6 is provided.

[0294] Then, the control unit 452 of the compressor unit 450 according to this embodiment determines, based on the surface temperature of the second heat exchanger 12, whether or not predetermined criteria indicating the possibility of frost formation on 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 embodiment described above, so their explanation is omitted.

[0295] In this embodiment, the control unit 452 of the compressor unit 450 notifies the higher-level control unit 400 of the determination result. When the higher-level control unit 400 recognizes that there are multiple second heat exchangers 12 that meet predetermined criteria, it outputs a control signal to control fans 11 and 21 so that the total supply air volume from fans 11 (an example of a second ventilation unit) of the exhaust unit group (for example, the first exhaust unit 410A and the second exhaust unit 410B) is greater than the total exhaust air volume from fans 21 (an example of a first ventilation unit) of the supply unit group (for example, the first supply unit 420A and the second supply unit 420B). This control is intended to suppress frost formation on the second heat exchangers 12.

[0296] In this embodiment, by setting the exhaust airflow rate to be greater than the supply airflow rate, the condensation capacity of the supply air unit group is suppressed, and the evaporation temperature of the second heat exchanger 12 of the exhaust unit group is increased, thereby suppressing frost formation.

[0297] (Tenth embodiment) Frost formation on the second heat exchanger 12 may be suppressed using methods other than those described in the embodiments above. In the tenth embodiment, an example of adjusting the temperature of the air after it has passed through the first heat exchanger 22 will be described.

[0298] The configuration of the tenth embodiment may be any of the embodiments described above, for example, the configuration shown in Figure 6. Therefore, in this embodiment, we will describe the case in which the configuration shown in Figure 6 is provided.

[0299] Then, the control unit 452 of the compressor unit 450 according to this embodiment determines, based on the surface temperature of the second heat exchanger 12, whether or not predetermined criteria indicating the possibility of frost formation on 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 embodiment described above, so their explanation is omitted. The control unit 452 of the compressor unit 450 then notifies the higher-level control device 400 of the determination result.

[0300] In this embodiment, when the higher-level control device 400 recognizes that there are multiple second heat exchangers 12 that meet predetermined criteria, it outputs a control signal to the first heat exchangers of the supply air unit group (for example, the first supply air unit 420A and the second supply air unit 420B) to suppress frost formation on the second heat exchangers 12, so that the temperature of the air after passing through the first heat exchanger 22 is lower than the temperature set in the air conditioner 2C installed in the living space R11. The temperature set in the air conditioner 2C is obtained from the control unit 471 of the outdoor unit 470.

[0301] In this embodiment, the temperature of the air after passing through the first heat exchanger 22 of the air supply unit group (supply air temperature) becomes lower than the set temperature of the room. As a result, the compressor of the compressor unit 450 operates at a low rotational speed, which suppresses the decrease in the evaporation temperature of the second heat exchanger 12.

[0302] (11th embodiment) Frost formation on the second heat exchanger 12 may be suppressed using methods other than those described in the embodiments above. In the 11th embodiment, an example of adjusting the refrigerant pressure with an electric valve (an example of a third valve section) provided downstream of the exhaust unit will be described.

[0303] The configuration of the 11th embodiment may be any of the embodiments described above, for example, the configuration shown in Figure 6. Therefore, in this embodiment, we will describe the case in which the configuration shown in Figure 6 is provided.

[0304] Figure 11 is a diagram showing a refrigerant circuit according to the eleventh embodiment. In the example shown in Figure 11, the flow of refrigerant is shown when the second heat exchangers 12 of the exhaust units 410A and 410B are functioning as evaporators. Components similar to those in the embodiments described above are assigned the same reference numerals and their descriptions are omitted.

[0305] In the example shown in Figure 11, when the second heat exchangers 12 of exhaust units 410A and 410B are functioning as evaporators, electric valves 601 and 602 are provided downstream of the second heat exchangers 12 of each of the exhaust units 410A and 410B.

[0306] Then, the control unit 452 of the compressor unit 450 according to this embodiment determines, based on the surface temperature of the second heat exchanger 12, whether or not predetermined criteria indicating the possibility of frost formation on 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 embodiment described above, so their explanation is omitted. The control unit 452 of the compressor unit 450 notifies the higher-level control device 400 of the determination result.

[0307] In this embodiment, when the higher-level control device 400 recognizes that a second heat exchanger 12 that meets a predetermined criterion exists, it outputs a control signal to the control unit (control unit 413A or control unit 413B) of the exhaust unit including the second heat exchanger 12 (for example, the first exhaust unit 410A or the second exhaust unit 410B) that causes the electric valve (electric valve 601 or electric valve 602) to be throttled compared to before the predetermined criterion was met.

[0308] By reducing the opening of the expansion valve (expansion valve 161 or expansion valve 162), the pressure of the refrigerant flowing through the second heat exchanger 12 located upstream of the expansion valve (expansion valve 161 or expansion valve 162) can be increased. This increases the evaporation temperature of the refrigerant flowing through the second heat exchanger 12. Therefore, frost formation on the second heat exchanger 12 can be suppressed.

[0309] Although Figure 11 shows a bypass channel F6, in this embodiment, it may be combined with control using the bypass channel F6 as described in the above-described embodiment, or it may not be combined with it.

[0310] (Modified version of the 11th embodiment) In the 11th embodiment, an example of suppressing frost formation by using a method of restricting electric valves 601 and 602 downstream of the second heat exchanger 12 was described. In addition to the method of adjusting electric valves 601 and 602 downstream of the second heat exchanger 12, the 11th embodiment describes a case in which an exhaust unit 730 for the outdoor unit is further provided in the refrigerant circuit and the exhaust unit 730 is controlled.

[0311] Figure 12 shows a refrigerant circuit according to a modified version of the 11th embodiment. In the example shown in Figure 12, an exhaust unit 730 is further added to the refrigerant circuit shown in Figure 11. Aside from the addition of the exhaust unit 730, the configuration is the same as that of the 11th embodiment, and therefore, further explanation is omitted.

[0312] The exhaust unit 730 includes a fan 11, a third heat exchanger 732, a control unit 733, a temperature detection unit 14, a drive motor 15, and an electric valve 16.

[0313] The exhaust unit 730 functions as an outdoor unit. In other words, the exhaust unit 730 is located on a flow path (an example of a fourth air flow path) for exhausting air that has exchanged heat with the refrigerant flowing through the third heat exchanger 732 to the outside.

[0314] Then, the control unit 452 of the compressor unit 450 according to this embodiment determines, based on the surface temperature of the second heat exchanger 12, whether or not predetermined criteria indicating the possibility of frost formation on 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 embodiment described above, so their explanation is omitted. The control unit 452 of the compressor unit 450 notifies the higher-level control device 400 of the determination result.

[0315] In this embodiment, when the higher-level control device 400 recognizes the existence of a second heat exchanger 12 that meets predetermined criteria, it performs the same control as in the 11th embodiment, and also controls the third heat exchanger 732 of the exhaust unit 730 to perform heat exchange at a lower evaporation temperature compared to the second heat exchanger 12.

[0316] As shown in Figure 12, the refrigerant flow through the third heat exchanger 732 of the exhaust unit 730 is connected to the refrigerant flow through the second heat exchangers 12 of the exhaust units 410A and 410B. Therefore, by lowering the evaporation temperature of the third heat exchanger 732, the evaporation temperature of the second heat exchanger 12 can be increased. This suppresses frost formation on the second heat exchanger 12.

[0317] In the embodiments and modifications described above, a method was explained in which the processing is divided between the control unit 452 of the compressor unit 450 and the higher-level control device 500. However, the method is not limited to this method, and either the control unit 452 of the compressor unit 450 or the higher-level control device 500 may perform the determination and control of other devices. Furthermore, the method is not limited to the processing being performed by the control unit 452 of the compressor unit 450 and the higher-level control device 500. The processing of the embodiments described above may also be performed by a centrally managed server or in the cloud.

[0318] (12th embodiment) Frost formation on the second heat exchanger 12 may be suppressed using methods other than those described in the embodiments above. Therefore, in the twelfth embodiment, an example of switching the control while considering power consumption will be described.

[0319] The configuration of the 12th embodiment may be any configuration of the embodiments described above, for example, the configuration shown in Figure 6. Therefore, in this embodiment, the case with the configuration shown in Figure 6 will be described. The higher-level control device 400 performs the following control during heat recovery ventilation operation.

[0320] Then, the control unit 452 of the compressor unit 450 according to this embodiment determines, based on the surface temperature of the second heat exchanger 12, whether or not predetermined criteria indicating the possibility of frost formation on the second heat exchanger 12 are met while the second heat exchanger 12 is functioning as an evaporator. The control unit 452 of the compressor unit 450 notifies the higher-level control device 400 of the determination result.

[0321] The predetermined criteria may be determined based on the temperature of the refrigerant flowing through the second heat exchanger 12 and the pressure of the refrigerant, or they may be the same as in the embodiment described above.

[0322] In this embodiment, when the higher-level control device 400 recognizes that there are multiple second heat exchangers 12 that meet predetermined criteria, it determines whether to perform frost suppression control or to allow frost formation and perform defrosting operation after frost formation. Then, according to the determination result of the higher-level control device 400, the exhaust unit group (for example, the first exhaust unit 410A and the second exhaust unit 410B) performs frost suppression control or to allow frost formation and perform defrosting operation after frost formation.

[0323] Figure 13 is a flowchart showing the processing procedure of the higher-level control device 400 according to this embodiment.

[0324] First, the control unit 452 of the compressor unit 450 according to this embodiment receives detection results related to the second heat exchanger 12 from each of the exhaust unit group (S2101). The detection results are the temperature and pressure of the refrigerant flowing through the second heat exchanger 12.

[0325] The control unit 452 of the compressor unit 450 determines whether predetermined criteria are met based on the detection results (S2102). For example, predetermined criteria indicating the possibility of frost formation on the second heat exchanger 12 include whether the detected refrigerant (evaporation) temperature is less than a predetermined temperature t, or whether the detected refrigerant (evaporation) pressure is less than a predetermined pressure p. If it is determined that the predetermined criteria are not met (S2102: NO), the process returns to S2101. The predetermined temperature t and pressure p are values ​​determined according to the embodiment as criteria for determining whether frost formation is possible, and their explanation is omitted. This determination may be performed at predetermined time intervals (e.g., every x minutes).

[0326] If the control unit 452 of the compressor unit 450 determines that a predetermined criterion has been met (S2102: YES), it notifies the higher-level control unit 400 of the determination result.

[0327] The higher-level control device 400 then controls the temperature of the refrigerant flowing through the second heat exchanger 12 to suppress frost formation, and calculates the power consumption E1 required to maintain the current temperature of the living space R11 (S2103).

[0328] Furthermore, the higher-level control device 400 performs defrosting and calculates the power consumption E2 required to maintain the current temperature of the living space R11 (S2104).

[0329] For example, in this embodiment, the higher-level control device 500 stores in advance a power consumption calculation model that has been set in advance for calculating power consumption E1 and power consumption E2. The higher-level control device 500 then calculates the power consumption by inputting input information (for example, room temperature / outside temperature, airflow of fans 11 and 21, refrigerant pressure, compressor rotation speed, etc.: an example of the conditions of the living space) into the power consumption calculation model. Note that the method for calculating power consumption is not limited to the method using the calculation model, and other methods may be used.

[0330] Subsequently, the higher-level control device 400 determines whether the power consumption E1 is less than the power consumption E2 (S2105). If the higher-level control device 400 determines that the power consumption E1 is less than the power consumption E2 (S2105: YES), it outputs a control signal to the exhaust unit group to suppress frost formation (S2106). The method for suppressing frost formation can be any process shown in the embodiment described above, and therefore no further explanation is given. Subsequently, the higher-level control device 500 processes again starting from S2101.

[0331] Subsequently, if the higher-level control device 400 determines that the power consumption E1 is greater than or equal to (not less than) the power consumption E2 (S2105: NO), it allows frost formation on the exhaust unit group, and after determining that frost has formed based on the detection result, it outputs a control signal to execute a defrosting operation (S2107). Note that the method for performing the defrosting operation is not limited to well-known methods, and any method may be used, so the explanation is omitted.

[0332] Subsequently, the higher-level control device 400 according to this embodiment receives detection results regarding the second heat exchanger 12 from each of the exhaust unit group via the control unit 452 of the compressor unit 450 (S2108). The detection results are the temperature and pressure of the refrigerant flowing through the second heat exchanger 12.

[0333] The higher-level control device 400 determines whether the defrosting completion criteria have been met based on the detection results (S2109). For example, the defrosting completion criteria for the second heat exchanger 12 may be whether the detected refrigerant (evaporation) temperature is greater than a predetermined temperature t+α, or whether the detected refrigerant (evaporation) pressure is less than a predetermined pressure p+β. Any criteria that allows for the determination that defrosting is complete may be used as the defrosting completion criteria. The variables α and β are positive numbers determined according to the embodiment and their explanation is omitted. The device determines whether the defrosting completion criteria have been met (S2109). If it is determined that the defrosting completion criteria have not been met (S2109: NO), the process returns to S2108. This determination may be performed at predetermined time intervals (e.g., y minutes).

[0334] Meanwhile, if the higher-level control device 400 determines, based on the detection results, that the defrosting completion criteria have been met (S2109: YES), it outputs a control signal to the exhaust unit group to terminate the defrosting operation (S2110) and ends the process. After that, the higher-level control device 500 resumes processing from S2101.

[0335] The higher-level control device 500 according to this embodiment, when it determines that a predetermined criterion is met, can control the temperature of the refrigerant flowing through the second heat exchanger 12 so that it reaches a temperature at which frost does not form on the second heat exchanger 12, based on the power consumption required to control the temperature of the refrigerant flowing through the second heat exchanger 12 so that it reaches a temperature at which frost does not form on the second heat exchanger 12, and the power consumption required to operate the second heat exchanger 12 to remove frost after frost has formed on the second heat exchanger 12.

[0336] This makes it possible to suppress power consumption when suppressing or defrosting the exhaust unit group in this embodiment.

[0337] 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.

[0338] 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.

[0339] 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.

[0340] (Overview of the ventilation system) Incidentally, an air conditioning system can ventilate a room while recovering heat from the exhaust air (indoor air) into the refrigerant in the refrigerant circuit by starting the compressor, using the first heat exchanger of the supply air unit as a condenser, and using the second heat exchanger of the exhaust unit as an evaporator. In an air conditioning system, if the second heat exchanger into which the exhaust air flows is used as an evaporator, frost will form on the second heat exchanger if the temperature of the exhaust air (indoor air) is lower than a predetermined value, causing the low pressure in the refrigerant circuit to drop. In this case, it becomes difficult to keep the started compressor running continuously.

[0341] In the embodiments shown below, a ventilation system equipped with a refrigerant circuit enables reliable continuous operation of the compressor when the heat exchanger is used as an evaporator.

[0342] Figure 14 is a schematic diagram of the ventilation system of this disclosure. Figure 15 is a control block diagram of the ventilation system of this disclosure. In the following description, the ventilation system 1E according to the 13th embodiment (see Figure 17) will be referred to as the 13th ventilation system 1F, the ventilation system 1E according to the 14th embodiment (see Figures 18 and 19) will be referred to as the 14th ventilation system 1G, the ventilation system 1E according to the 15th embodiment (see Figure 20) will be referred to as the 15th ventilation system 1H, the ventilation system 1E according to the 16th embodiment (see Figure 21) will be referred to as the 16th ventilation system 1I, the ventilation system 1E according to the 17th embodiment (see Figure 22) will be referred to as the 17th ventilation system 1J, and the ventilation system 1E according to the 18th embodiment (see Figure 23) will be referred to as the 18th ventilation system 1K. In the following description, when simply referred to as "ventilation system 1E", the description refers to the configuration common to each of the 13th to 18th ventilation systems 1F to 1K.

[0343] The ventilation system 1E shown in Figure 14 is one embodiment of the ventilation device of this disclosure, and is installed in buildings such as offices and factories to provide ventilation for a target space within the building. The ventilation system 1E comprises an air supply unit 1020, an exhaust unit 1030, a compressor unit 1040, and a refrigerant circuit 1050.

[0344] As shown in Figure 14, the air supply unit 1020 comprises a first casing 1021, an air supply fan 1022, and a first heat exchanger 1023. The first casing 1021 in this embodiment is a cubic box made of a heat-insulating panel material, with an intake port 1024 and an outlet port 1025 formed on its side. The air supply fan 1022 and the first heat exchanger 1023 are arranged inside the first casing 1021. When the supply air fan 1022 is driven, the supply air unit 1020 takes in outside air (outside air OA) (hereinafter referred to as outside 1000S2, see Figures 17 and 19) into the first casing 1021, exchanges heat with the refrigerant in the first heat exchanger 1023, and then supplies the air (supply air SA) from the outlet 1025 to the indoor area (hereinafter referred to as indoor 1000S1, see Figures 17 and 19). The ventilation system 1E has a supply air passage P1001 (an example of a first air passage) for supplying the taken-in outside air OA to indoor 1000S1 from the outlet 1025 via the first casing 1021.

[0345] The first heat exchanger 1023 constitutes the refrigerant circuit 1050, which will be described later. The first heat exchanger 1023 is a cross-fin tube type or microchannel type heat exchanger and is used to exchange heat between the refrigerant flowing through the first heat exchanger 1023 and the outdoor air 1000S2 (outside air OA).

[0346] The air supply unit 1020 includes an air supply temperature sensor 1026 and an outside air temperature sensor 1027. The air supply temperature sensor 1026 is positioned in the airflow after it has passed through the first heat exchanger 1023 in the first casing 1021 and detects the temperature T1 of the air supply SA (hereinafter referred to as the discharge air temperature T1). The outside air temperature sensor 1027 is positioned in the airflow before it has passed through the first heat exchanger 1023 in the first casing 1021 and detects the temperature T2 of the outside air OA (hereinafter referred to as the outside air temperature T2).

[0347] The air supply unit 1020 includes a first heat exchanger temperature sensor 1055 and a first refrigerant temperature sensor 1056. The first heat exchanger temperature sensor 1055 detects the temperature Tb1 of the first heat exchanger 1023 (in other words, the temperature of the refrigerant inside the first heat exchanger 1023). The first refrigerant temperature sensor 1056 detects the temperature Ta2 of the refrigerant after it has passed through the first heat exchanger 1023 (at the outlet). The first heat exchanger temperature sensor 1055 may also be a pressure sensor that detects the pressure inside the first heat exchanger 1023, in which case the refrigerant temperature inside the first heat exchanger 1023 is calculated from the detected pressure value.

[0348] The exhaust unit 1030 comprises a second casing 1031, an exhaust fan 1032, and a second heat exchanger 1033. In this embodiment, the second casing 1031 is a cubic box made of a heat-insulating panel material, with an intake port 1034 and an outlet port 1035 formed on its side. The exhaust fan 1032 and the second heat exchanger 1033 are arranged inside the second casing 1031. When the exhaust fan 1032 is driven, the exhaust unit 1030 takes in indoor air 1000S1 (return air RA) into the second casing 1031, exchanges heat with the refrigerant in the second heat exchanger 1033, and then releases the air (exhaust EA) from the outlet port 1035 towards the outdoors 1000S2. The ventilation system 1E has a return air channel P1002 (an example of a second air channel) for discharging indoor air 1000S1 (return air RA) to the outdoors 1000S2 through a second casing 1031 via a discharge port 1035.

[0349] The second heat exchanger 1033 constitutes the refrigerant circuit 1050, which will be explained later. The second heat exchanger 1033 is a cross-fin tube type or microchannel type heat exchanger and is used to exchange heat between the refrigerant flowing through the second heat exchanger 1033 and the indoor air 1000S1 (return air RA).

[0350] The exhaust unit 1030 is equipped with a return air temperature sensor 1036. The return air temperature sensor 1036 is positioned in the airflow before it passes through the second heat exchanger 1033 in the second casing 1031, and detects the temperature T3 of the air flowing into the second heat exchanger 1033. In the following description, this temperature T3 will be referred to as the intake air temperature T3. In this disclosure, the intake air temperature T3 when only air taken in from indoor 1000S1 passes through the second heat exchanger 1033 is defined as the temperature of the air in indoor 1000S1. The temperature of indoor 1000S1 may be detected by a sensor (not shown) installed in indoor 1000S1.

[0351] The exhaust unit 1030 includes a second heat exchanger temperature sensor 1057 and a second refrigerant temperature sensor 1058. The second heat exchanger temperature sensor 1057 detects the temperature Tb2 of the second heat exchanger 1033 (in other words, the temperature of the refrigerant inside the second heat exchanger 1033). The second refrigerant temperature sensor 1058 detects the temperature Tb3 of the refrigerant after it has passed through the second heat exchanger 1033 (at the outlet). The second heat exchanger temperature sensor 1057 may also be a pressure sensor that detects the pressure inside the second heat exchanger 1033, in which case the refrigerant temperature inside the first heat exchanger 1023 is calculated from the detected pressure value.

[0352] The compressor unit 1040 comprises a third casing 1041, a compressor 1042, a four-way switching valve 1043, and an expansion valve 1044. Although the compressor unit 1040 in this embodiment includes a third casing 1041, the third casing 1041 may be omitted. In this case, it is preferable to house the compressor 1042 and the four-way switching valve 1043 in the first casing 1021 of the supply air unit 1020 or the second casing 1031 of the exhaust unit 1030. Although the ventilation system 1E in this embodiment houses the expansion valve 1044 in the compressor unit 1040, the expansion valve 1044 may be housed in the first casing 1021 of the supply air unit 1020 or the second casing 1031 of the exhaust unit 1030.

[0353] The compressor unit 1040 includes a low-pressure sensor 1052, a discharge pressure sensor 1053, and a discharge temperature sensor 1054. The low-pressure sensor 1052 detects the pressure PL of the refrigerant drawn into the compressor 1042. In the following description, this pressure PL will also be referred to as the low-pressure PL. The discharge pressure sensor 1053 detects the pressure PH of the refrigerant discharged from the compressor 1042. In the following description, this pressure PH will also be referred to as the high-pressure PH. The discharge temperature sensor 1054 detects the temperature Ta1 of the refrigerant discharged from the compressor 1042.

[0354] The compressor 1042 draws in low-pressure gaseous refrigerant and discharges high-pressure gaseous refrigerant. The compressor 1042 is equipped with a motor whose operating speed can be adjusted by inverter control. The compressor 1042 is a variable-capacity type (variable-capacity type) whose capacity (performance) can be changed by inverter control of the motor. However, the compressor 1042 may be a constant-capacity type. In addition, the compressor 1042 used in the ventilation system 1E of this disclosure may be configured by connecting two or more compressors in parallel.

[0355] The four-way switching valve 1043 reverses the flow of refrigerant in the refrigerant piping, switching the supply of refrigerant discharged from the compressor 1042 to either the first heat exchanger 1023 or the second heat exchanger 1033. This allows the ventilation system 1E to switch between a cooling operation mode for cooling the outside air OA (hereinafter also referred to as the first operating mode M1) and a heating operation mode for heating the outside air OA (hereinafter also referred to as the second operating mode M2). The expansion valve 1044 is an electrically operated valve capable of adjusting the flow rate and pressure of the refrigerant. In the ventilation system 1E, the opening degree of the expansion valve 1044 is controlled to adjust the pressure of the refrigerant supplied to either the first heat exchanger 1023 or the second heat exchanger 1033.

[0356] The refrigerant circuit 1050 includes a compressor 1042, a four-way switching valve 1043, an expansion valve 1044, a first heat exchanger 1023, a second heat exchanger 1033, and refrigerant piping 1051 (liquid pipe 1051L and gas pipe 1051G) connecting them. The refrigerant circuit 1050 circulates the refrigerant between the first heat exchanger 1023 and the second heat exchanger 1033.

[0357] In the ventilation system 1E with the above configuration, when the supply air unit 1020 cools and supplies outside air OA (first operating mode M1), the four-way switching valve 1043 is held in the state shown by the solid line in Figure 14. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 1042 flows into the second heat exchanger 1033 of the exhaust unit 1030 via the four-way switching valve 1043. At this time, the second heat exchanger 1033 functions as a condenser, and the refrigerant flowing through the second heat exchanger 1033 condenses and liquefies through heat exchange with the return air RA due to the operation of the exhaust fan 1032. The liquefied refrigerant is depressurized by the expansion valve 1044 and flows into the first heat exchanger 1023. At this time, the first heat exchanger 1023 functions as an evaporator, and in the first heat exchanger 1023, the refrigerant evaporates through heat exchange with the outside air OA. The outside air OA, cooled by the evaporation of the refrigerant, is supplied to the indoor unit 1000S1 as supply air SA by the supply air fan 1022. The refrigerant evaporated in the first heat exchanger 1023 returns to the compressor unit 1040 through the refrigerant piping 1051 (gas pipe 1051G), and is drawn into the compressor 1042 via the four-way switching valve 1043.

[0358] In the ventilation system 1E with the above configuration, when the supply air unit 1020 heats and supplies outside air OA (in the second operating mode M2), the four-way switching valve 1043 is held in the state shown by the dashed line in Figure 14. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 1042 passes through the four-way switching valve 1043 and flows into the first heat exchanger 1023 of the supply air unit 1020. At this time, the first heat exchanger 1023 functions as a condenser, and in the first heat exchanger 1023, the refrigerant exchanges heat with the outside air OA and condenses and liquefies. The outside air OA heated by the condensation of the refrigerant is supplied to the indoor space 1000S1 by the supply air fan 1022. The refrigerant liquefied in the first heat exchanger 1023 passes through the refrigerant piping 1051 (liquid pipe 1051L) to the compressor unit 1040, where it is reduced to a predetermined low pressure by the expansion valve 1044 and then flows into the second heat exchanger 1033. At this time, the second heat exchanger 1033 functions as an evaporator, and in the second heat exchanger 1033, the refrigerant evaporates by exchanging heat with the return air RA. The refrigerant evaporated and vaporized in the second heat exchanger 1033 is drawn into the compressor 1042 via the four-way switching valve 1043.

[0359] (Regarding the control unit) Figure 15 is a control block diagram of the ventilation system 1E. As shown in Figure 15, the ventilation system 1E has a control unit 1018. The control unit 1018 is a device that controls the operation of the ventilation system 1E and is composed of, for example, a microcomputer equipped with a processor such as a CPU and memory such as RAM and ROM. The control unit 1018 may also be implemented as hardware using an LSI, ASIC, FPGA, etc. The control unit 1018 performs predetermined functions by having the processor execute a program installed in memory.

[0360] The control unit 1018 is connected to the supply fan 1022, exhaust fan 1032, compressor 1042, four-way switching valve 1043, and expansion valve 1044. The control unit 1018 is also connected to the supply air temperature sensor 1026, outside air temperature sensor 1027, return air temperature sensor 1036, low-pressure sensor 1052, discharge pressure sensor 1053, discharge temperature sensor 1054, first heat exchanger temperature sensor 1055, first refrigerant temperature sensor 1056, second heat exchanger temperature sensor 1057, and second refrigerant temperature sensor 1058. Based on the detected values ​​of each of the sensors, the control unit 1018 controls the operation of the supply fan 1022, exhaust fan 1032, compressor 1042, four-way switching valve 1043, expansion valve 1044, and low-pressure pressure increasing means 1080.

[0361] During operation in the second operating mode M2, the control unit 1018 calculates the saturation temperature TS of the second heat exchanger 1033, which functions as an evaporator, based on the value detected by the discharge pressure sensor 1053 (high pressure PH). The control unit 1018 obtains the low pressure PL of the refrigerant circuit 1050 from the value detected by the low pressure sensor 1052. The control unit 1018 obtains the evaporation temperature TE of the second heat exchanger 1033 from the value detected by the second heat exchanger temperature sensor 1057 (temperature Tb2). Alternatively, the control unit 1018 obtains the evaporation temperature TE of the second heat exchanger 1033 from the obtained low pressure PL.

[0362] As described above, the ventilation system 1E of this disclosure has a first operating mode M1 and a second operating mode M2 ​​as user-selectable operating modes. When the user selects the first operating mode M1 and starts operating the ventilation system 1E, the control unit 1018 switches the four-way switching valve 1043 so that the first heat exchanger 1023 can be used as an evaporator and the second heat exchanger 1033 can be used as a condenser. When the user selects the second operating mode M2 ​​and starts operating the ventilation system 1E, the control unit 1018 switches the four-way switching valve 1043 so that the first heat exchanger 1023 can be used as a condenser and the second heat exchanger 1033 can be used as an evaporator. In this description, "when the user selects the second operating mode M2 ​​and starts operating the ventilation system 1E" includes cases where the switching of the four-way switching valve 1043 has already been completed and cases where the switching of the four-way switching valve 1043 has not yet been completed.

[0363] When the ventilation system 1E of this disclosure is started by selecting the second operating mode M2, the control unit 1018 may perform low-pressure rise control (first control). In the following description, the operating mode of the ventilation system 1E when the control unit 1018 performs low-pressure rise control will be referred to as low-pressure rise mode M3. When the user selects the second operating mode M2 ​​and the operation of the ventilation system 1E is started, the control unit 1018 starts the compressor 1042 and detects the low-pressure PL of the refrigerant circuit 1050 or the evaporation temperature TE of the second heat exchanger 1033. When the control unit 1018 determines that the low-pressure PL or evaporation temperature TE has fallen below the threshold set for each (referred to as the first threshold in this description), it switches the operating mode of the ventilation system 1E to low-pressure rise mode M3 and performs low-pressure rise control. Furthermore, if the control unit 1018 does not determine that the low pressure PL or evaporation temperature TE has fallen below the first threshold, it will not switch the operating mode of the ventilation system 1E to the low pressure rise mode M3 (it will not perform low pressure rise control).

[0364] In the ventilation system 1E having a refrigerant circuit 1050, when operating in the second operating mode M2, the first heat exchanger 1023 is used as a condenser and the second heat exchanger 1033 is used as an evaporator, thereby recovering the heat from the exhaust EA into the refrigerant in the refrigerant circuit 1050. In this ventilation system 1E, if the temperature of the exhaust EA becomes low, frost may form on the second heat exchanger 1033. In this case, the low pressure PL of the refrigerant circuit 1050 decreases, making it difficult to continue operating the compressor 1042. In such cases, the control unit 1018 selects the low pressure rise mode M3 to enable continuous operation of the compressor 1042. Here, "continuous operation of the compressor" means that after the compressor is started, it can continue operating without reaching a state where it cannot continue operation (has to be stopped) due to a decrease in the low pressure of the refrigerant circuit, etc.

[0365] The control unit 1018 stores a first threshold X for determining whether the conditions for operation in the second operating mode M2 ​​are met when the ventilation system 1E is started by selecting the second operating mode M2. In the ventilation system 1E of this disclosure, the first threshold X stores a pressure threshold X1, which is the first threshold X for the low pressure PL of the refrigerant circuit 1050; a refrigerant temperature threshold X2, which is the first threshold X for the evaporation temperature TE of the second heat exchanger 1033; an indoor temperature threshold X3, which is the first threshold X for the intake air temperature T3, which is the temperature of the indoor air 1000S1; and an outdoor air temperature threshold X4, which is the first threshold X for the outdoor air temperature T2, which is the temperature of the outdoor air 1000S2. In this embodiment, the control unit 1018 stores a pressure threshold X1, a refrigerant temperature threshold X2, an indoor temperature threshold X3, and an outdoor temperature threshold X4 as first thresholds X. However, in the ventilation system 1E of this disclosure, the control unit 1018 may store any one of the thresholds X1 to X4.

[0366] The control unit 1018 stores a second threshold Y for determining whether the conditions for operation in the second operating mode M2 ​​are met when the control unit 1018 is performing low-pressure rise control (in other words, when the ventilation system 1E is operating in low-pressure rise mode M3). In the ventilation system 1E of this disclosure, the second threshold Y stores a pressure threshold Y1, which is the second threshold Y for the low-pressure PL of the refrigerant circuit 1050; a saturation temperature threshold Y2, which is the second threshold Y for the saturation temperature TS of the second heat exchanger 1033; and an air temperature threshold Y3, which is the second threshold Y for the intake air temperature T3 of the second heat exchanger 1033. In this embodiment, the control unit 1018 stores a pressure threshold Y1, a saturated temperature threshold Y2, and an air temperature threshold Y3 as second thresholds Y. However, in the ventilation system 1E of this disclosure, the control unit 1018 may store at least one of the pressure threshold Y1, saturated temperature threshold Y2, or air temperature threshold Y3.

[0367] (Regarding control at the start of operation of the ventilation system) The ventilation system 1E is controlled by the control unit 1018 at the start of operation according to the flow shown in Figure 16.

[0368] As shown in Figure 16, when the ventilation system 1E is started, the control unit 1018 first determines whether or not it was started with the second operating mode M2 ​​selected (S2501). If the control unit 1018 determines in step (S2501) that it was started with the second operating mode M2 ​​selected (YES), it executes the next step (S2502). If the control unit 1018 determines in step (S2501) that it was not started with the second operating mode M2 ​​selected (NO), the control unit 1018 terminates the control at the start of operation. In step (S2502), the control unit 1018 starts the compressor 1042 and proceeds to the next step (S2503).

[0369] In step (S2503), the control unit 1018 makes a determination regarding the low pressure PL of the refrigerant circuit 1050. If, in step (S2503), the control unit 1018 determines that the low pressure PL is not below the first threshold X (pressure threshold X1) for the low pressure PL (NO), then the next step (S2504) is executed. If, in step (S2503), the control unit 1018 determines that the low pressure PL is below the first threshold X (pressure threshold X1) (YES), then the next step (S2507) is executed.

[0370] In step (S2504), the control unit 1018 makes a determination regarding the evaporation temperature TE of the second heat exchanger 1033. If, in step (S2504), the control unit 1018 determines that the evaporation temperature TE is not below the first threshold X (refrigerant temperature threshold X2) for the said evaporation temperature TE (NO), then the next step (S2505) is executed. If, in step (S2504), the control unit 1018 determines that the evaporation temperature TE is below the first threshold X (refrigerant temperature threshold X2) (YES), then the next step (S2507) is executed.

[0371] In step (S2505), the control unit 1018 makes a determination regarding the intake air temperature T3, which is the air temperature in the indoor space 1000S1. If, in step (S2505), the control unit 1018 determines that the intake air temperature T3 is not below the first threshold X (indoor temperature threshold X3) for the intake air temperature T3 (NO), then the next step (S2506) is executed. If, in step (S2505), the control unit 1018 determines that the intake air temperature T3 is below the first threshold X (indoor temperature threshold X3) (YES), then the next step (S2507) is executed.

[0372] In step (S2506), the control unit 1018 makes a determination regarding the outside air temperature T2, which is the air temperature outdoors 1000S2. If, in step (S2506), the control unit 1018 determines that the outside air temperature T2 is not below the first threshold X (outside air temperature threshold X4) for the outside air temperature T2 (NO), then the next step (S2512) is executed. If, in step (S2506), the control unit 1018 determines that the outside air temperature T2 is below the first threshold X (outside air temperature threshold X4) (YES), then the next step (S2507) is executed.

[0373] In step (S2507), the control unit 1018 performs low-pressure pressure rise control. Specifically, in step (S2507), the control unit 1018 switches the operating mode of the ventilation system 1E to low-pressure pressure rise mode M3 and operates the ventilation system 1E. When the control unit 1018 performs low-pressure pressure rise control, the ventilation system 1E uses the low-pressure pressure rise means 1080, which will be described later. After starting the execution of low-pressure pressure rise control, the control unit 1018 performs step (S2508).

[0374] In step (S2508), the control unit 1018 makes a determination regarding the low pressure PL of the refrigerant circuit 1050 while low pressure rise control is being performed. If, in step (S2508), the control unit 1018 determines that the low pressure PL does not exceed the second threshold Y (pressure threshold Y1) for that low pressure PL (NO), then step (S2509) is executed. If, in step (S2508), the control unit 1018 determines that the low pressure PL exceeds the pressure threshold Y1 (YES), then step (S2511) is executed.

[0375] In step (S2509), the control unit 1018 makes a determination regarding the saturation temperature TS of the second heat exchanger 1033. If, in step (S2509), it is determined that the saturation temperature TS does not exceed the second threshold Y (saturation temperature threshold Y2) for that saturation temperature TS (NO), then step (S2510) is executed. If, in step (S2509), it is determined that the saturation temperature TS exceeds the saturation temperature threshold Y2 (YES), then step (S2511) is executed.

[0376] In step (S2510), the control unit 1018 makes a determination regarding the intake air temperature T3 of the second heat exchanger 1033. If, in step (S2510), the control unit 1018 determines that the intake air temperature T3 does not exceed the second threshold Y (air temperature threshold Y3) for the intake air temperature T3 (NO), the process returns to step (S2508). If, in step (S2510), the control unit 1018 determines that the intake air temperature T3 exceeds the air temperature threshold Y3 (YES), the process returns to step (S2511).

[0377] In step (S2511), the control unit 1018 terminates the low-pressure rise control. After terminating the low-pressure rise control, the control unit 1018 executes step (S2512). In step (S2512), the control unit 1018 switches the operating mode of the ventilation system 1E to the second operating mode M2 ​​and starts operating the ventilation system 1E. With this, the control unit 1018 terminates the control of the operation at the start of operation (flowchart shown in Figure 16).

[0378] The judgment conditions in each step (S2508) to (S2510) are conditions for determining whether or not the compressor 1042 can be reliably operated continuously in the second operating mode M2. In other words, if any of the conditions in steps (S2508) to (S2510) are satisfied, then the conditions for reliably operating the compressor 1042 continuously in the second operating mode M2 ​​are met. The ventilation system 1E can ensure that the conditions for reliably operating the compressor 1042 continuously are met by executing low-pressure pressure rise control (first control). The ventilation system 1E can ensure that the compressor 1042 can be reliably operated continuously by starting operation in the second operating mode M2 ​​after ensuring that the conditions for reliably operating the compressor 1042 continuously are met. In this disclosure, the decision of whether or not to proceed to step (S2507) is made based on the low pressure PL in step (S2503), the evaporation temperature TE in step (S2504), the intake air temperature T3 in step (S2505), and the ambient air temperature T2 in step (S2506). However, the decision may be made based on only one of steps (S2503) to (S2506). In this disclosure, the decision of whether or not to proceed to step (S2511) is made based on the low pressure PL in step (S2508), the saturation temperature TS in step (S2509), and the intake air temperature T3 in step (S2510). However, the decision may be made based on only one of steps (S2508) to (S2510).

[0379] (Regarding detailed embodiments of the ventilation system) As shown in Figure 15, the ventilation system 1E of this disclosure includes a low-pressure pressure increasing means 1080. The first to sixth ventilation systems 1F to 1K described below have different configurations of the low-pressure pressure increasing means 1080. When the ventilation system 1E is started with the second operating mode M2 ​​selected, the low-pressure pressure increasing means 1080 is used when the low-pressure pressure increasing control described above (see Figure 16) is performed. In the following description, the same reference numerals are used for parts common to the first to sixth ventilation systems 1F to 1K, and repeated explanations of parts with the same reference numerals are omitted.

[0380] (Regarding the 13th ventilation system on the 1st floor) Figure 17 shows a 13th ventilation system 1F according to a 13th embodiment of the ventilation system 1E of the present disclosure. The 13th ventilation system 1F shown in Figure 17 comprises an air supply unit 1020, an exhaust unit 1030, and a compressor unit 1040. In the 13th ventilation system 1F, the air supply unit 1020, the exhaust unit 1030, and the compressor unit 1040 are integrated into one unit. In this embodiment, the 13th ventilation system 1F shows the air supply unit 1020, the exhaust unit 1030, and the compressor unit 1040 integrated into one unit, but in the ventilation system 1E of the present disclosure, the air supply unit 1020 (first heat exchanger 1023 and air supply fan 1022), the exhaust unit 1030 (second heat exchanger 1033 and exhaust fan 1032), and the compressor unit 1040 (compressor 1042) may be arranged separately.

[0381] The 13th ventilation system 1F can be installed, for example, outdoors in 1000S2. In the 13th ventilation system 1F shown in Figure 17, the outlet 1025 of the supply air unit 1020 and the intake 1034 of the exhaust unit 1030 are directly attached to the exterior wall surface of the building 1000B. Although this embodiment illustrates the case where the 13th ventilation system 1F is installed outdoors in 1000S2, the 13th ventilation system 1F may be installed entirely or partially indoors in 1000S1.

[0382] As shown in Figure 17, the 13th ventilation system 1F includes an air conditioner 1081, which is the first low-pressure pressure increasing means 1080. The air conditioner 1081 includes an indoor unit 1081a, an outdoor unit 1081b, and a refrigerant circuit 1081d including refrigerant piping 1081c.

[0383] (Regarding air conditioners) The air conditioner 1081 is installed in building 1000B to provide air conditioning for the air-conditioned space (indoor 1000S1). The air conditioner 1081 provides heating and cooling to the air-conditioned space by operating a vapor compression type refrigeration cycle. In this embodiment, an air conditioner 1081 that operates a vapor compression type refrigeration cycle is illustrated as an example, but the type of air conditioner used as the low-pressure pressure increasing means 1080 is not limited to this, and for example, an air conditioner that provides air conditioning for the target space by supplying chilled water and hot water from a heat source device may also be used.

[0384] The air conditioner 1081 has an indoor unit 1081a located indoors 1000S1 and an outdoor unit 1081b located outdoors 1000S2. The indoor unit 1081a and the outdoor unit 1081b are connected by refrigerant piping 1081c. The air conditioner 1081 has an air conditioning refrigerant circuit 1081d. The air conditioning refrigerant circuit 1081d includes a compressor, a four-way switching valve, an outdoor heat exchanger, an expansion valve, an indoor heat exchanger, etc. (none of which are shown). The air conditioning refrigerant circuit 1081d circulates refrigerant between the indoor unit 1081a and the outdoor unit 1081b via the refrigerant piping 1081c. The air conditioning refrigerant circuit 1081d is separated from the refrigerant circuit 1050 of the 13th ventilation system 1F and constitutes an independent circuit. The air conditioner 1081 detects the temperature indoors 1000S1.

[0385] In the 13th ventilation system 1F, the temperature of the indoor 1000S1 is increased by operating the air conditioner 1081 when low-pressure pressure rise control is performed. In the 13th ventilation system 1F, when the control unit 1018 determines that the temperature of the indoor 1000S1 detected by the air conditioner 1081 exceeds the second threshold Y (air temperature threshold Y3 for intake air temperature T3) (see Figure 15), the exhaust fan 1032 is started to operate. In the 13th ventilation system 1F, this causes the second heat exchanger 1033 to draw in air that is hotter than the air temperature threshold Y3 for intake air temperature T3. In the 13th ventilation system 1F, frost formation on the second heat exchanger 1033 is suppressed by operating the air conditioner 1081. In the 13th ventilation system 1F, the air conditioner 1081 can raise the intake air temperature T3 of the second heat exchanger 1033, which functions as an evaporator. This suppresses frost formation on the second heat exchanger 1033 and also suppresses a decrease in the low pressure PL of the refrigerant circuit 1050.

[0386] In the 13th ventilation system 1F, if the second operating mode M2 ​​is selected and the system is started, the control unit 1018 may forcibly start the air conditioner 1081. In the 13th ventilation system 1F, if the second operating mode M2 ​​is selected and the system is started, the control unit 1018 may provide the user with information prompting the user to start the air conditioner 1081, and the user may start the air conditioner 1081. If the 13th ventilation system 1F and the air conditioner 1081 are not linked, the control unit 1018 may, after providing the user with information prompting the user to start the air conditioner 1081, operate the exhaust fan 1032 after a predetermined time has elapsed to measure the intake air temperature T3, and based on the measured value, the control unit 1018 may start the air conditioner 1081. In the 13th ventilation system 1F, the control unit 1018 is configured to detect the operating status of the air conditioner 1081, and when the second operating mode M2 ​​is selected and the system is started, if the control unit 1018 detects that the air conditioner 1081 is in operation, the control unit 1018 may perform low-pressure pressure rise control.

[0387] In the 13th ventilation system 1F, when the low-pressure pressure rise control is completed, the control unit 1018 may stop the air conditioner 1081, or the control unit 1018 may continue operating the air conditioner 1081.

[0388] (Regarding Ventilation System 1G, No. 14) Figure 18 is a schematic configuration diagram of a ventilation system according to the 14th embodiment of the present disclosure. Figure 19 is a schematic configuration diagram showing the installation of the ventilation systems according to the 14th and 15th embodiments of the present disclosure in a building. The 14th ventilation system 1G shown in Figures 18 and 19 is the 14th embodiment of the ventilation system 1E of the present disclosure. The 14th ventilation system 1G differs from the 13th ventilation system 1F in that it includes a second low-pressure pressure increasing means 1082, which is a second low-pressure pressure increasing means 1080.

[0389] As shown in Figure 18, the 14th ventilation system 1G includes a second low-pressure pressure increasing means 1082. The second low-pressure pressure increasing means 1082 consists of a bypass pipe 1082a and a valve 1082b. The valve 1082b is, for example, an electric valve, a solenoid valve, etc. The bypass pipe 1082a is a pipe that bypasses the discharge pipe 45 of the compressor 1042 and the liquid pipe 1051L. The bypass pipe 1082a can supply the high-temperature, high-pressure gaseous refrigerant discharged from the compressor 1042 to the second heat exchanger 1033 via the liquid pipe 1051L. The valve 1082b can switch the flow of refrigerant in the bypass pipe 1082a. When the valve 1082b is open, gaseous refrigerant can flow through the bypass pipe 1082a, and when the valve 1082b is closed, the flow of gaseous refrigerant in the bypass pipe 1082a can be stopped.

[0390] The 14th ventilation system 1G increases the temperature of the refrigerant flowing through the second heat exchanger 1033 by opening valve 1082b and supplying gaseous refrigerant to the second heat exchanger 1033 via bypass piping 1082a, thereby suppressing frost formation on the second heat exchanger 1033. In the 14th ventilation system 1G, the second low-pressure raising means 1082 can raise the saturation temperature TS at the outlet of the second heat exchanger 1033, which functions as an evaporator, thereby suppressing frost formation on the second heat exchanger 1033 and suppressing a decrease in the low-pressure PL of the refrigerant circuit 1050.

[0391] In the 14th ventilation system 1G, the control unit 1018 terminates the low-pressure rise control by closing the valve 1082b.

[0392] (Regarding Ventilation System 1H, No. 15) Figure 20 is a schematic diagram of a ventilation system according to the 15th embodiment of the present disclosure. The 15th ventilation system 1H shown in Figures 19 and 20 is the 15th embodiment of the ventilation system 1E of the present disclosure. As shown in Figure 20, the 15th ventilation system 1H differs from the 13th and 14th ventilation systems 1F and 1G in that it includes a third low-pressure pressure increasing means 1083, which is a third low-pressure pressure increasing means 1080.

[0393] The 15th ventilation system 1H includes a third low-pressure pressure increasing means 1083. The third low-pressure pressure increasing means 1083 consists of a bypass duct 1083a and a damper 1083b. The bypass duct 1083a is formed within the third casing 1041 and connects the discharge side of the first casing 1021 with the suction side of the second casing. The bypass duct 1083a can supply a portion of the airflow (supply air SA) generated in the supply air unit 1020 to the suction side of the exhaust fan 1032 in the exhaust unit 1030. The damper 1083b includes a valve body and an opening / closing mechanism that can open and close the flow of supply air SA in the bypass duct 1083a. When damper 1083b is open, supply air SA can be circulated through bypass duct 1083a, and when damper 1083b is closed, the flow of supply air SA through bypass duct 1083a can be stopped.

[0394] In the 15th ventilation system 1H, the control unit 1018 determines that the discharge air temperature T1 detected by the supply air temperature sensor 1026 exceeds the second threshold Y (air temperature threshold Y3 for the intake air temperature T3) (see Figure 15), and opens the damper 1083b. By opening the damper 1083b, the 15th ventilation system 1H can raise the intake air temperature T3 of the second heat exchanger 1033 by supplying supply air SA to the intake side of the second heat exchanger 1033 via the bypass duct 1083a. In the 15th ventilation system 1H, the third low-pressure raising means 1083 can raise the intake air temperature T3 of the second heat exchanger 1033, which functions as an evaporator, thereby suppressing frost formation on the second heat exchanger 1033 and suppressing a decrease in the low-pressure PL of the refrigerant circuit 1050.

[0395] In the 15th ventilation system 1H, the control unit 1018 terminates the low-pressure rise control by closing the damper 1083b.

[0396] (Regarding Ventilation System 1I, No. 16) Figure 21 is a schematic diagram of a ventilation system according to the 16th embodiment of the present disclosure. The 16th ventilation system 1I shown in Figure 21 is the 16th embodiment of the ventilation system 1E of the present disclosure. As shown in Figure 21, the 16th ventilation system 1I differs from the 13th to 15th ventilation systems 1F to 1H in the configuration of the low-pressure pressure increasing means 1080. The 16th ventilation system 1I differs from the aforementioned 13th to 15th ventilation systems 1F to 1H in that the supply air unit 1020, exhaust unit 1030, and compressor unit 1040 are separated and arranged in the indoor space 1000S1. In the 16th ventilation system 1I, the supply air unit 1020, exhaust unit 1030, and compressor unit 1040 are arranged in the space above the ceiling of room R1, which is the space to be ventilated in the indoor space 1000S1 (hereinafter referred to as the space above the ceiling R2). In this embodiment, the case in which the 16th ventilation system 1I is located indoors 1000S1 is illustrated, but the 16th ventilation system 1I may be located entirely or partially outdoors 1000S2.

[0397] In the 16th ventilation system 1I, the supply air unit 1020 constitutes part of the supply air passage 1028. The supply air passage 1028 is an air passage that connects the indoor area 1000S1 and the outdoor area 1000S2. The supply air passage 1028 consists of a first supply air duct 1028a, a second supply air duct 1028b, and the supply air unit 1020. The first supply air duct 1028a connects the outdoor area 1000S2 and the supply air unit 1020. Specifically, the first supply air duct 1028a has an inlet 1028c at one end, which is connected to an opening in the exterior wall of the building 1000B and communicates with the outdoor area 1000S2. The other end of the first supply air duct 1028a is connected to the supply air unit 1020. The second air supply duct 1028b connects the air supply unit 1020 to the indoor space 1000S1. Specifically, the second air supply duct 1028b has an outlet 1028d at one end, which is connected to an opening in the ceiling of the indoor space 1000S1, thus communicating with the indoor space 1000S1. The other end of the second air supply duct 1028b is connected to the air supply unit 1020.

[0398] In the 16th ventilation system 1I, the exhaust unit 1030 constitutes part of the exhaust air passage 1038. The exhaust air passage 1038 is an air passage that connects the indoor area 1000S1 and the outdoor area 1000S2. The exhaust air passage 1038 consists of a first exhaust duct 1038a, a second exhaust duct 1038b, and the exhaust unit 1030. The first exhaust duct 1038a connects the outdoor area 1000S2 and the exhaust unit 1030. Specifically, the first exhaust duct 1038a has an exhaust port 1038c at one end, which is connected to an opening in the outer wall of the building 1000B and communicates with the outdoor area 1000S2. The other end of the first exhaust duct 1038a is connected to the exhaust unit 1030. The second exhaust duct 1038b connects the exhaust unit 1030 to the indoor unit 1000S1. Specifically, the second exhaust duct 1038b has an inlet 1038d at one end, which is connected to an opening in the ceiling of the indoor unit 1000S1, thus communicating with the indoor unit 1000S1. The other end of the second exhaust duct 1038b is connected to the exhaust unit 1030.

[0399] The 16th ventilation system 1I includes a fourth low-pressure pressure increasing means 1084. The fourth low-pressure pressure increasing means 1084 consists of a bypass duct 1084a and a damper 1084b. The bypass duct 1084a connects a second supply duct 1028b, which is connected to the discharge side of the supply air unit 1020, and a second exhaust duct 1038b, which is connected to the suction side of the exhaust unit 1030. The bypass duct 1084a can supply a portion of the airflow (supply air SA) generated in the supply air unit 1020 to the suction side of the exhaust fan 1032 in the exhaust unit 1030. The damper 1084b includes a valve body and an opening / closing mechanism that can open and close the flow of supply air SA in the bypass duct 1084a. When damper 1084b is open, supply air SA can be circulated through bypass duct 1084a, and when damper 1084b is closed, the flow of supply air SA through bypass duct 1084a can be stopped.

[0400] In the 16th ventilation system 1I, the control unit 1018 opens the damper 1084b when it determines that the discharge air temperature T1 detected by the supply air temperature sensor 1026 exceeds the second threshold Y (air temperature threshold Y3 for the intake air temperature T3). By opening the damper 1084b, the 16th ventilation system 1I can raise the intake air temperature T3 of the second heat exchanger 1033 by supplying supply air SA to the intake side of the second heat exchanger 1033 via the bypass duct 1084a. In the 16th ventilation system 1I, the fourth low-pressure raising means 1084 can raise the intake air temperature T3 of the second heat exchanger 1033, which functions as an evaporator, thereby suppressing frost formation on the second heat exchanger 1033 and suppressing a decrease in the low-pressure PL of the refrigerant circuit 1050.

[0401] In the 16th ventilation system 1I, the control unit 1018 terminates the low-pressure rise control by closing the damper 1084b.

[0402] (Regarding the 17th ventilation system 1J) Figure 22 is a schematic diagram of a ventilation system according to the 17th embodiment of the present disclosure. The 17th ventilation system 1J shown in Figure 22 is the 17th embodiment of the ventilation system 1E of the present disclosure. As shown in Figure 22, the 17th ventilation system 1J differs from the 16th ventilation system 1I in the configuration of the low-pressure pressure increasing means 1080. The 17th ventilation system 1J includes a fifth low-pressure pressure increasing means 1085, which is a fifth low-pressure pressure increasing means 1080.

[0403] The fifth low-pressure pressure increasing means 1085 consists of an intake duct 1085a, a damper 1085b, and a ceiling space temperature sensor 1085c. The intake duct 1085a is connected to the second exhaust duct 1038b and is open in the ceiling space R2, allowing air from the ceiling space R2 to be drawn into the exhaust unit 1030 by the drive of the exhaust fan 1032. In the 17th ventilation system 1J, the air from the ceiling space R2 drawn into the exhaust unit 1030 can be circulated to the second heat exchanger 1033. The damper 1085b is a valve that can open and close the airflow in the intake duct 1085a. When the damper 1085b is open, air from the ceiling space R2 can be drawn into the intake duct 1085a, and when the damper 1085b is closed, the airflow in the intake duct 1085a can be stopped.

[0404] In the 17th ventilation system 1J, the ceiling space temperature sensor 1085c is connected to the control unit 1018. The ceiling space temperature sensor 1085c can detect the temperature of the air in the ceiling space R2. In the 17th ventilation system 1J, if the control unit 1018 determines that the temperature T4 of the air in the ceiling space R2 exceeds the second threshold Y (air temperature threshold Y3 for the intake air temperature T3), it opens the damper 1085b and allows the air in the ceiling space R2 to flow to the second heat exchanger 1033 via the intake duct 1085a.

[0405] The 17th ventilation system 1J can raise the intake air temperature T3 of the second heat exchanger 1033 by opening the damper 1085b and supplying air from the ceiling space R2 to the intake side of the second heat exchanger 1033 via the intake duct 1085a. In the 17th ventilation system 1J, the 5th low-pressure raising means 1085 can raise the intake air temperature T3 of the second heat exchanger 1033, which functions as an evaporator, thereby suppressing frost formation on the second heat exchanger 1033 and suppressing a decrease in the low-pressure PL of the refrigerant circuit 1050.

[0406] In the 17th ventilation system 1J, the control unit 1018 closes the damper 1085b, thereby ending the low-pressure rise control.

[0407] (Regarding Ventilation System 1K No. 18) Figure 23 is a schematic diagram of a ventilation system according to the 18th embodiment of the present disclosure. The 18th ventilation system 1K shown in Figure 23 is the 18th embodiment of the ventilation system 1E of the present disclosure. As shown in Figure 23, the configuration of the low-pressure pressure increasing means 1080 in the 18th ventilation system 1K differs from that of the 16th and 17th ventilation systems 1I and 1J.

[0408] The 18th ventilation system 1K includes a sixth low-pressure pressure increasing means 1086, which is a sixth low-pressure pressure increasing means 1080. The sixth low-pressure pressure increasing means 1086 includes a louver 1086a configured to be rotatable around a rotation axis and a mechanism (not shown) for rotating the louver 1086a. The louver 1086a is positioned near the air outlet 1028d in the indoor space 1000S1. The louver 1086a is configured to be rotatable between a storage position 1000P1 in which the direction of air supply SA blown out from the air outlet 1028d is not changed, and an operating position 1000P2 in which the direction of air supply SA blown out from the air outlet 1028d is changed.

[0409] In the 18th ventilation system 1K, when the control unit 1018 determines that the discharge air temperature T1 detected by the supply air temperature sensor 1026 exceeds the second threshold Y (air temperature threshold Y3 for the intake air temperature T3), it rotates the louver 1086a from the stored position 1000P1 to the operating position 1000P2. In the 18th ventilation system 1K, the supply air SA discharged from the outlet 1028d hits the louver 1086a, changing its discharge direction, and flows towards the intake port 1038d. In the 18th ventilation system 1K, the intake air temperature T3 of the second heat exchanger 1033 is increased by actively drawing in the supply air SA, which is hotter than the indoor air 1000S1, from the intake port 1038d. In the 18th ventilation system 1K, the 6th low-pressure raising means 1086 can raise the intake air temperature T3 of the second heat exchanger 1033, which functions as an evaporator. This suppresses frost formation on the second heat exchanger 1033 and also suppresses a decrease in the low-pressure PL of the refrigerant circuit 1050.

[0410] In the 18th ventilation system 1K, the control unit 1018 changes the rotational position of the louver 1086a from the operating position 1000P2 to the retracted position 1000P1, thereby ending the low-pressure rise control.

[0411] [Effects of the Embodiment] (1) The ventilation system 1E shown in the above embodiment comprises a compressor 1042, a first heat exchanger 1023, a second heat exchanger 1033 connected by refrigerant piping 1051, a refrigerant circuit 1050 through which refrigerant flows, an air supply fan 1022 that supplies outdoor air 1000S2 to indoor air 1000S1 through the first heat exchanger 1023, an exhaust fan 1032 that exhausts indoor air 1000S1 to outdoor air 1000S2 through the second heat exchanger 1033, and a control unit 1018. When the control unit 1018 is using the second heat exchanger 1033 as an evaporator, it starts the compressor 1042 and performs low-pressure rise control to increase the low-pressure PL of the refrigerant circuit 1050 when it determines that the low-pressure PL of the refrigerant circuit 1050, the evaporation temperature TE of the second heat exchanger 1033, the indoor temperature 1000S1 (intake air temperature T3), or the outdoor temperature 1000S2 (outside air temperature T2) has fallen below a first threshold X for the low-pressure PL of the refrigerant circuit 1050, the evaporation temperature TE of the second heat exchanger 1033, the intake air temperature T3, or the outside air temperature T2.

[0412] According to the ventilation system 1E with this configuration, in a ventilation system equipped with a refrigerant circuit 1050 capable of recovering heat from exhaust EA, the compressor 1042 can be reliably operated continuously when the second heat exchanger 1033 functions as an evaporator.

[0413] (2) The 14th ventilation system 1G shown in the above embodiment has a refrigerant circuit 1050 which includes a bypass pipe 1082a connecting the discharge pipe 45 of the compressor 1042 to the second heat exchanger 1033 or the liquid pipe 1051L connected to the second heat exchanger 1033, and a valve 1082b provided in the bypass pipe 1082a. In the 14th ventilation system 1G, the control unit 1018 opens the valve 1082b in low-pressure pressure rise control (first control).

[0414] In this case, high-temperature, high-pressure gaseous refrigerant can be supplied to the second heat exchanger 1033 during low-pressure pressure rise control. This makes it possible to suppress frost formation on the second heat exchanger 1033.

[0415] (3) In the 14th ventilation system 1G shown in the above embodiment, when the valve 1082b is open, the control unit 1018 determines that the low pressure PL of the refrigerant circuit 1050, the saturation temperature TS of the second heat exchanger 1033, or the intake air temperature T3 of the exhaust fan 1032 exceeds the second threshold Y for the low pressure PL of the refrigerant circuit 1050, the saturation temperature TS of the second heat exchanger 1033, or the intake air temperature T3 of the second heat exchanger 1033, and closes the valve 1082b.

[0416] In this case, if the conditions for the second heat exchanger 1033 to function as an evaporator are met while the low-pressure pressure rise control is being executed, the low-pressure pressure rise control can be terminated.

[0417] (4) In each of the ventilation systems 1F, 1H~1K shown in the above embodiment, the control unit 1018 causes the second heat exchanger 1033 to draw in air at a temperature higher than the second threshold Y (air temperature threshold Y3) for the intake air temperature T3 in the low-pressure pressure rise mode M3 which performs low-pressure pressure rise control.

[0418] In this case, during the execution of low-pressure rise control, air at a temperature higher than the second threshold Y (air temperature threshold Y3) can be introduced into the second heat exchanger 1033. This makes it possible to suppress frost formation on the second heat exchanger 1033.

[0419] (5) In the 18th ventilation system 1K shown in the above embodiment, the control unit 1018 adjusts the direction of the air supply fan 1022 so that the air blown out from the supply fan 1022 is guided to the intake side of the exhaust fan 1032 in the low-pressure pressure rise mode M3, which performs low-pressure pressure rise control.

[0420] In this case, while low-pressure pressure rise control is being performed, air at a temperature higher than the second threshold Y (air temperature threshold Y3) for the intake air temperature T3 can be introduced into the second heat exchanger 1033.

[0421] (6) In the 13th ventilation system 1F shown in the above embodiment, an air conditioner 1081 is further provided to conditioned the indoor air 1000S1, and in the low-pressure pressure rise mode M3 which performs low-pressure pressure rise control, the control unit 1018 drives the exhaust fan 1032 when the air temperature of the indoor air 1000S1 rises above the second threshold Y (air temperature threshold Y3) by the air conditioner 1081.

[0422] In this case, while low-pressure pressure rise control is being performed, air at a temperature higher than the second threshold Y (air temperature threshold Y3) for the intake air temperature T3 can be introduced into the second heat exchanger 1033.

[0423] The embodiments and modifications described above illustrate methods for suppressing frost formation. 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 methods shown in other embodiments and modifications.

[0424] According to the embodiments and modifications described above, by performing the control described above, frost formation (for example, on the second heat exchanger) is suppressed, making it possible to continue ventilation operation without stopping the supply of air to the indoor space and exhaust to the outdoors. Suppression of frost formation does not mean limiting it to avoiding frost formation, but rather means controlling it so that even if frost formation occurs, the frost does not grow. In the ventilation device or ventilation system according to the embodiments and modifications, it is possible to maintain the comfort of the living space by suppressing frost formation and continuing ventilation operation.

[0425] The number of air supply units and exhaust units shown in the embodiments and modifications described above are merely examples. The number of air supply units and exhaust units can be determined according to the living space. For example, the number of air supply units may be one or more, and the number of exhaust units may also be one or more. Furthermore, the control unit shown in the embodiments and modifications described above is shown as one embodiment and may be included in any of the devices.

[0426] While 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 some or all of other embodiments.

[0427] This application claims priority based on Japanese Patent Applications No. 2021-204798 and 2021-205609, filed on 17 December 2021, and the entire contents of these Japanese Patent Applications are incorporated herein by reference. [Explanation of symbols]

[0428] 1, 1A, 1B, 1C, 1D_1, 1D_2, 1D_3 Ventilation system 2, 2C air conditioner 10, 110, 210, 310, 410A, 410B, 510A, 510B, 510C, 730 Exhaust Unit 11 Fans 12 Second heat exchanger 13, 113, 213, 313, 413A, 413B Control Unit 14 Temperature detection unit 15 Drive motor 16 Electric Valve 20, 220A, 220B, 320A, 320B, 420A, 420B, 520A, 520B, 520C Air Intake Unit 21 Fans 22 1st heat exchanger 23, 423A, 423B Control Unit 24 Temperature detection unit 25 Drive motor 26 Electric Valve 40 Opening / Closing Damper 50, 350, 450, 550A, 550B, 550C, 650 Compressor Units 51 Drive motor 52, 452 Control Unit 53 Compressor 54 Four-way valve 55 Electric Valve 56 Bypass electric valve 70, 470, 571, 572, 573 outdoor unit 71, 471 Control Unit 81, 82, 581, 582, 583, 584, 585, 586, 587, 588 Indoor air conditioning units 400, 500, 600 Higher-level control unit 601, 602 Electric Valves 732 Third heat exchanger 733 Control Unit F1, F2, F3, F4, F401, F402, F403, F404 Refrigerant Circuit F5, F501, F502, F503, F601, F602, F603 connecting piping F6 Bypass Channel P1, P101 Air Intake Channel P2, P103 Return air flow path P2A 1st return air branch P2B 2nd return air branch P102 Bypass channel P201, P401 First air supply passage P202, P402 2nd air supply flow path P203 Return air channel P403 1st return air flow path P404 2nd return air flow path 1E Ventilation System 1F Ventilation System No. 13 1G Ventilation System No. 14 1H Ventilation System No. 15 1I Ventilation System No. 16 1J Ventilation System No. 17 1K Ventilation System No. 18 1018 Control Unit 1022 Intake fan 1023 1st heat exchanger 1032 Exhaust fan 1033 Second heat exchanger 1042 Compressor 1045 Discharge piping 1050 Refrigerant Circuit 1051 Refrigerant piping 1051L liquid pipe 1080 Low-pressure pressure increasing means 1081 Air conditioner 1082a Bypass piping 1082b Valve 1000S1 Indoor 1000S2 Outdoor PL Low Pressure TE Evaporation Temperature TS saturation temperature T2 outside temperature T3 Intake air temperature X First threshold Y Second threshold Y3 Air temperature threshold (second threshold for intake air temperature) SA (Air supply) (Air blown out from the air supply fan)

Claims

1. Compressor and, A first heat exchanger that functions as a condenser or evaporator, A first airflow path supplies air taken in from outdoors to the indoor space after passing it 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, A second ventilation unit that adjusts the amount of air flowing to the second heat exchanger through the second air passage, 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. A control unit that, while the second heat exchanger is functioning as an evaporator, detects whether a predetermined criterion indicating the possibility of frost formation on the second heat exchanger is met, and if it is detected that the predetermined criterion is met, stops the compressor and controls the second ventilation unit to flow the air that has passed through the second air passage to the second heat exchanger, A ventilation system equipped with the following features.

2. When the control unit detects that the predetermined criteria are met, it controls the second ventilation unit to increase the amount of air flowing to the second heat exchanger compared to before the predetermined criteria were met. The ventilation device according to claim 1.

3. When controlling a ventilation system 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 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 through the second heat exchanger, a second ventilation unit for adjusting the amount of air flowing through the second airflow path to 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 system detects whether a predetermined criterion indicating the possibility of frost formation on the second heat exchanger is met while the second heat exchanger is functioning as an evaporator, and if it is detected that the predetermined criterion is met, the compressor is stopped and the second ventilation unit is controlled to flow air that has passed through the second airflow path to the second heat exchanger. Ventilation methods.

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