JPH10132307A - Ductless air-conditioning system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the laying cost for a duct, and prevent due condensation formed on a ceiling surface. SOLUTION: A ductless air conditioning system is adapted such that air conditioned air is supplied to a ceiling closed space formed in the ceiling of an air conditioned room, and the air conditioning air is blown out from the ceiling closed space to the air conditioned room without passage through a duct. In the ductless air conditioned system, there are provided an air mixing part 9 for forming conditioning air with mixed air of air conditioned primary supply air and return air from the air conditioned room, and a fan 2 for sending the mixed air from the mixing pat 9 into the ceiling closed space. An air supply chamber 3 is connected with the fan 2 for sending the air conditioning air from a blowoff outlet 19 into the ceiling closed space. The fan 2 is constructed as an air volume variable fan capable of altering the volume of sent air in response to a heat load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of supplying air-conditioned air to a closed space formed behind a ceiling of a room to be air-conditioned, and from there to a room through an outlet provided on the ceiling of the room to be air-conditioned without passing through a duct. To a ductless air conditioning system.

[0002]

2. Description of the Related Art In a conventional air-conditioning system, an air supply duct communicating with an air outlet is provided in a ceiling of a room or a section to be air-conditioned (hereinafter, collectively referred to as an air-conditioning room) to supply air-conditioned air. Air is supplied into the room from the outlet via an air supply duct in the ceiling. In such a duct type air conditioning system, since the duct is laid in the ceiling, it is difficult to perform the installation when the space behind the ceiling is small, and the temperature difference between the room to be air-conditioned and the room temperature is about 10 ° C. Alternatively, it is necessary to lay an air supply duct equipped with a heat insulating material behind the ceiling of the room to be air-conditioned in order to blow out the air-conditioning air consisting of warm air into the room to be air-conditioned. I couldn't.

Therefore, in order to reduce the installation cost, a ductless air-conditioning system in which the arrangement of the supply duct is partially omitted has been put to practical use. Existing ductless air conditioning systems
An air supply duct is laid up to the ceiling of the room to be air-conditioned in the same way as the duct type air conditioning system, but no air supply duct is laid below the ceiling of the room to be air-conditioned, and the closed space formed above the ceiling is used as a chamber. Air conditioning air is supplied to this closed space.

[0004]

However, when air-conditioning air is supplied to a closed space formed above the ceiling, the temperature difference between the air-conditioned air and the room temperature of the room to be air-conditioned is about 10 ° C. Drops and condenses on the ceiling surface to grow, causing water drops to drop, causing malfunctions in the room to be air-conditioned. In order to prevent dew condensation on the ceiling surface, the temperature of the supplied air-conditioning air must be set higher so as to have a temperature difference of about 6 to 7 ° C. with the room temperature of the room to be air-conditioned. If the temperature of the air-conditioning air is set higher, in order to perform air-conditioning under the same conditions as when the temperature difference is about 10 ° C., the amount of the air-conditioning air to be supplied must be increased because the temperature difference is small. In order to increase the supply amount of the air-conditioning air, it is necessary to increase the diameter of the air supply duct, and there is a problem that the enlargement of the air supply duct increases the installation cost of the duct.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a ductless air conditioning system capable of preventing dew condensation on a ceiling surface without increasing the cost of laying ducts.

[0006]

In order to achieve the above object, according to the present invention, conditioned air is supplied to a closed space formed above the ceiling of a room to be air-conditioned, and the conditioned air is supplied from the closed space to the closed space. In a ductless air-conditioning system that blows air into a room to be air-conditioned without passing through a duct, an air-mixing unit that forms the air-conditioning air by a mixture of air-conditioned primary air supply air and return air from the air-conditioning room; And a blower for sending air from the air-mixing unit into the closed space.

[0007] According to the above configuration, the cool air as the primary supply air during the cooling operation is sent to the air-mixing portion in the closed space, where it is mixed with the air from the room, and then the air is supplied to the closed space as the conditioned air. Be blown out. Thereby, the temperature difference between the conditioned air blown into the closed space and the room air is reduced, and the dew condensation on the ceiling surface of the room air is prevented. Therefore, it is possible to further lower the temperature of the primary air supply, satisfy the desired air-conditioning conditions with a low air flow, reduce the diameter of the primary air supply duct, improve workability and reduce costs. As a result, it is possible to reduce the size of the air conditioner and to put into practical use an efficient refrigeration system such as an ice heat storage system.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment,
An air supply chamber is connected to the blower, and air-conditioning air is blown into a closed space behind the ceiling from an outlet provided in the air supply chamber.

[0009] With this configuration, the air is not directly blown from the blower to the space above the ceiling, but is once supplied to the air supply chamber, and is blown out of the air supply chamber to the closed space above the ceiling. By appropriately setting the number, direction, and the like of the air outlets according to the facilities, structures, and the like, the air-conditioning air can be sent in an optimal distribution state over the entire area above the ceiling. Therefore, it is possible to distribute the amount of air blown to the room to be air-conditioned at a predetermined ratio to the peripheral portion or the central portion.

Further, in a preferred embodiment,
The air blower is a variable air volume blower capable of changing the air volume according to a heat load.

According to this configuration, the blower can discharge the maximum air volume at the time of the peak load, and the discharge amount of the blower can be reduced at the time of the partial load or the low load. At the time of heat load, the wind speed from the outlet increases and the reach becomes longer, the air flow to the perimeter zone where the heat load is large increases, and an appropriate indoor air flow distribution corresponding to the heat load is automatically obtained. Therefore, it is possible to spontaneously control the blowing of the conditioned air to the room to be air-conditioned. Further, since the fan operation power follows the fluctuation of the thermal load over time, it is possible to contribute to energy saving.

Further, in a preferred embodiment,
The primary air supply air is supplied from an air conditioner installed outside the closed space via an air supply duct communicating with the air mixing section.

With this configuration, the primary air supply air can be supplied from the air conditioner installed outside the closed space via the air supply duct. In this case, as described above, it is possible to reduce the diameter of the air supply duct, and it is possible to prevent dew condensation on the ceiling surface during the cooling operation without increasing the installation cost of the duct.

[0014] In another preferred embodiment, the primary supply air is supplied from an air conditioner installed in the closed space and connected to the air-mixing unit.

With this configuration, the primary air supply air can be supplied from the air conditioner installed in the closed space. Thereby, the air supply duct laid outside the closed space can be eliminated.

In still another preferred embodiment, the primary air supply air is supplied from an indoor unit of a building multi air conditioner installed in the closed space and connected to the air mixing section. I have.

With this configuration, it is possible to supply the primary supply air from the indoor unit of the multi air conditioner for buildings installed in the closed space. Also in this configuration, it is possible to prevent condensation on the ceiling surface during the cooling operation without increasing the installation cost of the duct, and it is possible to eliminate an air supply duct installed outside the closed space.

[0018]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory plan view of a ductless air conditioning system according to one embodiment of the present invention. FIG. 2 is a cross-sectional explanatory view showing a state behind a ceiling where a ductless air conditioning system according to one embodiment of the present invention is installed.

As shown in FIGS. 1 and 2, the ductless air-conditioning system according to the present invention includes a casing 1 as an air-mixing section for forming air-conditioned air, a fan (blower) 2 for sending out air-conditioned air from the casing 1, and a fan. 2 connected to an air supply chamber 3. The casing 1, the fan 2, and the air supply chamber 3 form a closed space 6 formed behind a ceiling 5 of a room or a section to be air-conditioned as an air-mixing fan unit (hereinafter, collectively referred to as an air-conditioned room 4). It is installed on the building interior side (see Fig. 2). That is, the ductless air conditioning system supplies the conditioned air to the closed space 6 behind the ceiling of the room 4 to be air-conditioned via the air-mixing fan unit,
The conditioned air is blown from the closed space 6 behind the ceiling to the room 4 to be air-conditioned without passing through a duct.

The casing 1 is formed in a rectangular closed box shape, and the inside is divided into two sections of an air-mixing section 8 and a fan section 9 by a current plate 7. The current plate 7 is made of, for example, a punching board or a louver provided with an infinite number of through holes 7 a, and passes through the current plate 7 from the air mixing section 8 to the fan section 9.
The air-conditioning air sucked into the fan is rectified to make the wind speed and dynamic pressure distribution uniform, thereby achieving a stable suction operation of the fan 2.
Opposite wall surfaces 1a and 1b of the casing 1 on the side of the air mixing section 8
, Openings 10 and 11 communicating with the air-mixing section 8 are opened, and a primary air supply duct 12 and a urethane duct 13 are connected to the openings 10 and 11 respectively.

The primary air supply duct 12 is connected to an air conditioner (not shown) installed outside the closed space 6 above the ceiling. The primary supply air, which is air-conditioned by the air conditioner, is supplied to the air-mixing section 8 via the primary supply duct 12. Although air-circulated air from the room to be air-conditioned is returned to the air conditioner via the return duct, illustration thereof is omitted. The primary supply air is controlled so as to adjust the inside of the room to be air-conditioned 4 to a desired air-conditioning condition.
Is set to, for example, about 10 ° C. cold air. In the case where the room 4 to be air-conditioned is heated, the air is similarly set to warm air having a predetermined temperature difference.

The urethane duct 13 is connected to a suction port 14 provided in the ceiling 5 of the room to be air-conditioned 4 and communicates the room to be air-conditioned 4 with the air-mixing section 8. The room air in the room to be air-conditioned 4 is taken into the air-mixing section 8 as return air for dew condensation prevention through the retan duct 13.

A constant air volume device 15 and a mixing accelerator 16 communicating with the primary air supply duct 12 are provided in the air mixing section 8. The constant air volume device 15 has a built-in damper (not shown) and controls the passing air volume to be constant. This damper detects a wind speed proportional to the air flow in the duct by a wind speed sensor (not shown) installed near the casing 1 of the primary air supply duct 12, and adjusts the air flow by automatic control based on the detected wind speed. The mixing accelerator 16 connected to the constant air volume device 15 has a built-in blade or louver (not shown) for adjusting the air volume and direction, and the primary supply air introduced into the air mixing section 8 from an outlet 16a thereof. And promotes mixing with the inflowing air.

In the air-mixing section 8, the air-conditioned primary supply air and the return air from the air-conditioned room 4 are mixed,
An air-fuel mixture, which is conditioned air, is formed. The temperature of the air-fuel mixture rises more than the primary air supply, and becomes about 6 to 7 ° C. at which the temperature difference from the room temperature of the room 4 to be air-conditioned does not cause condensation. The temperature and air volume of the primary air supply are controlled based on the detected temperature and humidity in accordance with a normal control method according to the indoor air conditioning conditions.

In the present invention, in addition to the indoor air-conditioning control based on the primary air supply control, a unit outlet temperature control for preventing dew condensation on the ceiling surface during the cooling operation is performed. The unit outlet temperature (condensation prevention) control detects a ceiling surface temperature or a temperature in the vicinity of the ceiling surface, and controls the blowout air amount of a variable air amount fan described later according to a difference between the ceiling surface temperature and the room temperature. It is. Therefore, when the temperature difference is large,
The air volume increases to increase the return air volume and reduce the temperature difference.

The fan 9 is provided with the fan 2. The fan 2 is a variable air volume type fan whose air volume can be changed according to a heat load or the like. The air outlet of the fan 2 communicates with the air supply chamber 3 through an opening 17 formed in the wall surface 1c of the casing 1 via a canvas joint 18 and the like.

The air supply chamber 3 is provided with a plurality (three in this example) of outlets 19 in which the blowing direction can be set. In consideration of the shape and size of the closed space 6 above the ceiling and the other facilities and structures, the air outlet 19 blows out the conditioned air to the deepest portion of the closed space 6 above the ceiling and closes the closed space 6 below the ceiling.
The number, the individual directions, the air volume ratio, and the like are set so that the air-conditioning air can be uniformly and efficiently filled in the inside and the air can be distributed optimally.

A plurality of outlets 20 are provided on the ceiling 5, and the air-conditioned air in the closed space 6 behind the ceiling is blown out from the outlets 20 to the room 4 to be air-conditioned. The installation position and the number of the air outlets 20 are appropriately selected according to the indoor conditions such as the floor area of the room 4 to be air-conditioned, the height of the ceiling 5 and the load distribution.

In the ductless air-conditioning system having the above configuration, in the cooling operation, the primary supply air supplied from the air conditioner installed outside the closed space 6 above the ceiling to the air-mixing section 8 is air-mixed. In the section 8, the air-fuel mixture is mixed with the return air from the air-conditioned room 4 to form a gas mixture having a small temperature difference from the room temperature of the air-conditioned room 4. The air-fuel mixture is blown out into the closed space 6 behind the ceiling, and further blown out from the air outlet 20 into the room 4 to be air-conditioned. Therefore, even if cold air having a large temperature difference from the room temperature of the room 4 to be air-conditioned is sent as primary air supply, the temperature difference between the closed space 6 behind the ceiling and the room does not increase,
No condensation on the ceiling.

As described above, since the low-temperature primary supply air having a large temperature difference can be used, it is possible to cope with the heat load with a small air volume. Therefore, the duct size of the primary air supply duct 12 and the size of the air conditioner can be reduced due to the decrease in the air volume, and the duct laying cost is greatly reduced.

This large temperature difference and low air volume air-conditioning system becomes possible by adopting recently popularized multi-type air conditioners for buildings with a large temperature difference between the primary air supply air and room temperature, refrigeration systems using ice storage, and the like. It is especially effective when doing so.

The fan 2 discharges the maximum air volume at the peak load. At this time, since the air-conditioning air blown out from the air outlet 20 has the maximum blowing airflow velocity together with the blowing air volume, the airflow velocity in the room to be air-conditioned 4 increases at peak load, and the sensible temperature of the occupants decreases. Therefore, at the time of cooling, the indoor set temperature of the room 4 to be air-conditioned can be increased by the amount that the perceived temperature has decreased. For this reason, the amount of heat for load processing is small, which contributes to energy saving. In addition, by increasing the air flow velocity, the air-conditioning air blow-out distance increases during heating, and it becomes easy to secure a heating area near the floor of the room 4 to be air-conditioned. Therefore, the temperature difference between the upper part and the lower part of the room 4 to be air-conditioned is eliminated, the temperature in the room becomes more uniform, and heating can be efficiently performed, contributing to energy saving. Further, during normal operation or air-conditioning operation with a small load, the amount of air blown can be automatically reduced, which contributes to energy saving.

In addition, the ductless air conditioning system of the present invention includes the air supply chamber 3 so that the air flow rate of the conditioned air and the heat load pattern of the room 4 to be air-conditioned can be matched in a zone as described below. .

That is, at the time of the peak load when the thermal load of the room 4 to be air-conditioned becomes the maximum, the fan 2 that blows out the air-fuel mixture to the air supply chamber 3 discharges the maximum air volume. When the fan 2 discharges the maximum air volume, the wind speed at the outlet 19 of the air supply chamber 3 becomes maximum. Accordingly, the reaching distance becomes longer, the air volume in the perimeter zone at the periphery of the building increases, and the air volume in the interior zone inside the building decreases. At the time of peak load, the perimeter zone has a large heat load due to outside air on the window side of the room 4 to be air-conditioned, and the interior zone has a small heat load. That is, when the fan 2 discharges the maximum air volume, a large amount of air-conditioning air is blown out to the perimeter zone where the heat load is large at the time of the peak load, and the air conditioning air is blown to the interior zone where the heat load is small as compared with the perimeter zone. The amount of air blow is reduced.

On the other hand, when the heat load of the room 4 to be air-conditioned is a partial load or a low load, the air-fuel mixture is supplied to the air supply chamber 3.
The discharge amount of the fan 2 that blows out the air is reduced. Since the discharge air volume of the fan 2 is small, the outlet 19 of the air supply chamber 3
The wind speed at the site becomes smaller and the reach distance becomes shorter. for that reason,
The air-conditioning air blown out from behind the ceiling to the air-conditioned room 4 via the air outlet 20 is in a state where the air volume in the interior zone increases and the air volume in the perimeter zone decreases. That is,
Since the discharge amount of the fan 2 is small, the blowout amount of the air-conditioning air is small in the perimeter zone where the heat load is small at the time of partial load or low load, and the interior zone where the heat load is large compared with the perimeter zone. Increases the amount of air-conditioned air blown out.

As described above, by providing the air supply chamber 3 and the fan 2 of the variable air volume type, the amount of air-conditioning air blown to the perimeter zone and the interior zone having different heat load patterns can be adjusted according to the load of each zone. It can be automatically increased or decreased automatically. Therefore, a comfortable and high-quality air-conditioning environment can be automatically obtained.

Further, in order to prevent dew condensation on the ceiling surface, the temperature of the ceiling surface or the temperature in the vicinity of the back surface of the ceiling is detected, and the air flow of the fan 2 is controlled based on the temperature difference from the room air.
When the temperature difference is large, the air flow is increased to increase the air flow in order to reduce the difference and prevent dew condensation. When the temperature difference is large as described above, it is when the heat load is large and when a large air volume is required. That is, the air volume control for preventing condensation on the ceiling surface coincides with the air volume control corresponding to the heat load. Therefore, the air volume control using the variable air volume fan 2 is automatically performed without inconsistency with the room temperature control of the primary air supply, and effective air conditioning control is realized.

FIG. 3 is an explanatory sectional view showing a state behind a ceiling where a ductless air conditioning system according to another embodiment of the present invention is installed.

In this example, the primary supply air is supplied from an air conditioner 21 installed above the ceiling. Air conditioner 2
1 is connected to a cold / hot water pipe 23 provided with a bypass electric three-way valve 22 and a drain pipe 24. Although not shown, the air conditioner 21 has an air inlet 1 for preventing dew condensation.
Separately from the air conditioning duct 4, a return duct for introducing return air from the room 4 to be air-conditioned and an outside air duct for introducing outside air are connected. The air conditioner 21 and the air mixing section 8 are connected to a canvas joint 25.
And so on.

In this way, by supplying the primary supply air from the air conditioner 21 installed in the closed space 6 above the ceiling, only the installation of the cold / hot water pipe 23 and the drain pipe 24 is sufficient, and the external air The primary air supply duct 12 laid from the conditioner to the air-mixing section 8 of the closed space 6 above the ceiling can be eliminated. Other configurations, functions and effects are the same as those of the embodiment of FIG.

FIG. 4 is an explanatory sectional view showing a state behind a ceiling where a ductless air conditioning system according to still another embodiment of the present invention is installed.

In this example, the primary supply air is supplied from an indoor unit 26 of a building multi-air conditioner (separate air conditioner) installed behind the ceiling. A refrigerant pipe 27 and a drain pipe 28 are connected to the indoor unit 26 of the separate air conditioner.
Although not shown, the indoor unit 26 of the separate air conditioner has an air conditioning target room 4 separate from the air suction port 14 for preventing dew condensation.
A return duct for introducing return air from the outside and an outside air duct for introducing outside air are connected. The indoor unit 26 of the separate air conditioner and the air mixing unit 8 are connected by a canvas joint 29 or the like.

As described above, by supplying the primary air supply air from the indoor unit 26 of the separate air conditioner installed in the closed space 6 above the ceiling, only the refrigerant pipe 27 and the drain pipe 24 need to be installed. The primary air supply duct 12 laid from the air conditioner to the air mixing section 8 of the closed space 6 above the ceiling can be eliminated. Other configurations, functions and effects are the same as those of the embodiment of FIG.

[0044]

As described above, according to the ductless air-conditioning system of the present invention, since the air-conditioning air mixing section and the blower are provided, the cool air as the primary air supply during the cooling operation is closed. After being sent to the air-mixing part in the space and mixed with the return air from the room, it is blown out to the closed space as air-conditioned air. Thereby, the temperature difference between the conditioned air blown into the closed space and the room air is reduced, and the dew condensation on the ceiling surface of the room air is prevented. For this reason, it is possible to further lower the temperature of the primary air supply, meet the desired air conditioning conditions with a low air flow, reduce the diameter of the primary air supply duct, improve workability and reduce costs. As a result, it is possible to reduce the size of the air conditioner and to commercialize an efficient refrigeration system such as an ice heat storage system.

In addition, if the air supply chamber is connected to the blower, the blower does not blow air directly from above the ceiling.
Once the air is supplied to the air supply chamber and then blown out from the outlet to the closed space behind the ceiling, the number and direction of the outlets can be adjusted appropriately according to the height and shape of the ceiling and other equipment and structures. By setting to, the air-conditioning air can be blown in an optimal distribution state over the entire area above the ceiling. Therefore, it is possible to distribute the amount of air blown to the room to be air-conditioned at a predetermined ratio to the peripheral portion or the central portion.

Also, if the blower is configured as a variable air blower capable of changing the blown amount according to the heat load,
At the time of peak load, the blower discharges the maximum air volume, and at the time of partial load or low load, the discharge amount of the blower can be reduced. As the wind speed increases, the reach becomes longer, the air flow to the perimeter zone with a large heat load increases, and an appropriate indoor air flow distribution corresponding to the heat load is automatically obtained. Therefore, it is possible to spontaneously control the blowing of the conditioned air to the room to be air-conditioned.
Further, since the fan operation power follows the fluctuation of the thermal load over time, it is possible to contribute to energy saving.

Further, if the primary supply air is supplied from an air conditioner installed outside the closed space, the primary supply air is supplied from the air conditioner installed outside the closed space through the air supply duct. Since the supply air can be supplied, the diameter of the supply air duct can be reduced as described above, and the condensation on the ceiling surface during the cooling operation can be prevented without increasing the installation cost of the duct. .

Further, if the primary supply air is supplied from an air conditioner installed in the closed space,
Since the primary air supply air can be supplied from the air conditioner installed in the closed space, the air supply duct laid outside the closed space can be eliminated.

Further, if the primary supply air is supplied from the indoor unit of the building multi air conditioner installed in the closed space, the indoor unit of the building multi air conditioner installed in the closed space is provided. Can supply the primary air supply from the roof, preventing the condensation on the ceiling surface during cooling operation without increasing the cost of laying the duct, and eliminating the duct laid outside the closed space. Can be.

[Brief description of the drawings]

FIG. 1 is an explanatory plan view of a ductless air conditioning system according to one embodiment of the present invention.

FIG. 2 is an explanatory cross-sectional view showing a state behind a ceiling where a ductless air conditioning system according to one embodiment of the present invention is installed.

FIG. 3 is an explanatory cross-sectional view showing a state behind a ceiling where a ductless air conditioning system according to another embodiment of the present invention is installed.

FIG. 4 is an explanatory sectional view showing a state behind a ceiling where a ductless air conditioning system according to still another embodiment of the present invention is installed.

[Explanation of symbols]

1: casing, 2: fan (blower), 3: air supply chamber, 4: room to be air-conditioned, 5: ceiling, 6: closed space behind ceiling,
7: straightening vane, 8: air-mixing section, 9: fan section, 12 primary air supply duct, 13: return duct, 14: air intake, 1
5: Constant air volume device, 16: Mixing accelerator, 18: Canvas joint, 19: Air outlet, 21: Air conditioner, 23: Cold and hot water piping, 24: Drain pipe, 26: Multi-air conditioner indoor unit for building, 27 : Refrigerant pipe, 28: drain pipe.

Claims (6)

[Claims] 1. A ductless air-conditioning system for supplying air-conditioned air to a closed space formed behind a ceiling of a room to be air-conditioned and blowing the air-conditioned air from the closed space to the room to be air-conditioned without passing through a duct. An air-fuel mixture unit that forms the air-conditioning air by a mixture of the primary air supply air and return air from the air-conditioned room, and a blower that sends the air-fuel mixture from the air-fuel mixture unit into the closed space. A ductless air conditioning system characterized by having. 2. The ductless air conditioning system according to claim 1, wherein an air supply chamber is connected to the blower, and air conditioning air is sent into the closed space from an outlet provided in the air supply chamber. 3. The ductless air-conditioning system according to claim 1, wherein the blower is a variable blower capable of changing a blown amount according to a heat load. 4. The air supply system according to claim 1, wherein the primary air supply air is supplied from an air conditioner installed outside the closed space via an air supply duct communicating with the air mixing section. A ductless air conditioning system according to any of the above. 5. The air conditioner according to claim 1, wherein the primary supply air is supplied from an air conditioner installed in the closed space and connected to the air mixing section. Ductless air conditioning system. 6. The air conditioner according to claim 1, wherein said primary air supply air is supplied from an indoor unit of a building multi air conditioner installed in said closed space and connected to said air mixing unit. A ductless air-conditioning system according to Crab.