KR100795602B1 - Air conditioner system - Google Patents

Abstract

An air conditioner system is provided to detect a real-time temperature change generated locally to switch cooling and heating modes in accordance with changes in loads, thereby improving coziness in a room. A desired temperature is inputted to an input unit(S1). Each indoor unit of a first indoor unit group detects a temperature of a space, and each indoor unit of a second indoor unit group detects a temperature of a space(S3). The desired temperature is compared with the detected temperatures of the indoor units to obtain a cooling load or a heating load(S5). The sum of the cooling loads of each indoor unit group is compared with the sum of the heating loads of each indoor unit group by calculating the sum of cooling loads in case the temperature detected by each indoor unit is higher than the desired temperature and calculating the sum of heating loads in case the temperature detected by each indoor unit is lower than the desired temperature(S7). If the sum of the cooling loads is larger than or equal to the sum of the heating loads, a controller controls to proceed with cooling operation of indoor units of the indoor unit group of which the sum of cooling loads is calculated while stopping indoor units of the indoor group unit of which the sum of heating loads is calculated(S9). If the sum of the cooling loads is smaller than the sum of the heating loads, the controller controls to stop cooling operation of indoor units of the indoor unit group of which the sum of cooling loads is calculated while switching an outdoor unit into a heating mode to operate heating operation of indoor units of the indoor group unit of which the sum of heating loads is calculated(S10).

Description

Air Conditioner System {AIR CONDITIONER SYSTEM}

1 is a configuration diagram of a conventional air conditioner system,

2 is a block diagram of an air conditioning system according to the present invention;

3 is a control block diagram according to the present invention;

4 is a control flowchart according to a first embodiment of the present invention;

5 is a control flowchart according to a second embodiment of the present invention;

6 is a control flowchart according to a third embodiment of the present invention;

7 is a control flowchart according to a fourth embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

1: air conditioner system 20: outdoor unit

40: temperature detection unit 60: 1 indoor group

70: first indoor group 80: second indoor group

90: control unit

The present invention relates to an air conditioner system, and more particularly, to an air conditioner system having a plurality of indoor units connected to an outdoor unit and an outdoor unit, and controlling a cooling and heating mode based on a temperature detected from each indoor unit.

In general, an air conditioning system is a system configured to cool or heat a large space such as a building. The air conditioner system connects a plurality of indoor units to an outdoor unit for cooling or heating operation. For example, indoor units are installed in buildings having 10 spaces, and cooling or heating operation is performed using one outdoor unit connected to 10 indoor units installed in 10 spaces. When the above air conditioner system sets the desired temperature and proceeds with operation, the indoor unit that has reached the desired temperature stops operation and the remaining indoor unit continues to operate. Here, the space where each indoor unit is installed varies in temperature. For example, the space in the south has a faster temperature rise than the space in the north.

As shown in FIG. 1, the air conditioner system includes an outdoor unit 120 and a plurality of indoor units 150. The indoor units 150 include a first indoor unit 171, a second indoor unit 172, a third indoor unit 173, a fourth indoor unit 181, and a fifth indoor unit 182, respectively. For example, the desired temperature of each indoor unit 150 is set to 24 ° C and operated. The room where the first room 171 is installed has a room temperature of 23 ° C. so that the first room 171 continues to operate, and the room where the second room 172 is installed has a room temperature of 25 ° C. 172) is stopped. In addition, since the space where the third indoor room 173, the fourth indoor room 181, and the fifth indoor room 182 are installed are 26 ° C, 30 ° C, and 32 ° C, respectively, the third room 173 and the fourth room 181 are provided. The operation of the fifth indoor unit 182 is stopped, but in this case, cooling operation is required.

However, such an air conditioning system has a problem in that when the desired temperature is set, the heating and cooling operation can be switched only when the temperature of the space where all the indoor units are installed reaches the desired temperature. That is, as described above, the space where the third indoor room, the fourth indoor room, and the fifth indoor room are installed in the space where five indoor units are installed requires cooling, but the first indoor room does not reach the desired temperature. The heating and cooling operation cannot be switched until the temperature is reached.

Accordingly, an object of the present invention is to provide an air conditioner system that can automatically control air conditioning according to the load of a space in which a plurality of indoor units are installed.

According to the present invention, an air conditioner system includes: an outdoor unit: a plurality of indoor units connected to the outdoor unit; A plurality of temperature sensing units provided respectively to the plurality of indoor units to sense temperatures of the plurality of indoor units; And a control unit for controlling the outdoor unit to operate in one of a cooling mode and a heating mode, wherein the control unit comprises a plurality of indoor unit groups having at least one indoor unit among the plurality of indoor units, wherein the control unit comprises each of the indoor unit groups. Comparing the respective temperatures detected by the temperature sensing unit of the indoor unit with the desired temperature to calculate a comparison result, and based on the representative comparison result comparing the comparison results of the plurality of indoor unit group and the outdoor unit cooling mode and It is controlled to operate in any one of the heating modes, and the comparison result is any one of the sum of the cooling load and the sum of the heating load which is the sum of the difference between the temperature detected from the respective indoor units included in each indoor unit group and the desired temperature. It is achieved by an air conditioning system characterized by the above.

Here, the representative comparison result is preferably a comparison value of the sum of the cooling loads of any one of the plurality of indoor air groups and the sum of the other heating loads.

Preferably, the comparison result is any one of a peak of a cooling load and a peak of a heating load, which are the maximum values of a difference between a temperature sensed from at least one indoor unit of each indoor unit group and a desired temperature difference.

The representative comparison result is preferably a comparison value between peaks of one cooling load among the plurality of indoor air groups and one peak of the other heating load.

On the other hand, the control unit, if the sum of the cooling load of any one of the plurality of indoor air group and the sum of the sum of the other heating load is the same, the peak of the cooling load of any one of the plurality of indoor air group and the other peak The outdoor unit may be controlled to operate in one of the cooling mode and the heating mode based on the representative comparison result which is a comparison value of.

The comparison result is a cooling rate of [{(sum of cooling loads) / (sum of cooling loads + sum of heating loads)} × 100%] and [{(sum of heating loads) / (sum of cooling loads +) Sum of heating load)} x 100%].

The controller may control the outdoor unit to operate in one of the cooling mode and the heating mode by comparing the comparison result with a reference set value.

Here, the comparison result, which is one of the cooling rate and the heating rate, preferably has a predetermined hysteresis region.

Hereinafter, as an embodiment of the present invention, an air conditioner system having five indoor units and one outdoor unit will be described in detail with reference to the accompanying drawings.

However, prior to the description, it can be known that it can be applied to all of the air conditioner system connecting at least two indoor units to one outdoor unit.

As shown in FIG. 2 and FIG. 3, the air conditioner system 1 according to the present invention includes an outdoor unit 20, a plurality of indoor units 50 connected to the outdoor unit 20, and temperatures of the plurality of indoor units 50. Each of the plurality of temperature sensing unit 40 for detecting each of the plurality of indoor units 60 having at least one indoor unit 50 of the indoor unit 50, and the outdoor unit 20 in the cooling mode and heating mode It includes a control unit 90 for controlling to drive to any one.

One outdoor unit 20 is provided as one example of the present invention. The outdoor unit 20 preferably has a capacity that may correspond to the capacity of the plurality of indoor units 50. Inside the outdoor unit 20, a 4-way valve (not shown) for switching the air conditioner system 1 to enable cooling operation or heating operation is provided. The outdoor unit 20 is provided with a communication unit 22 that communicates with a computer 10 that can exchange information of the outdoor unit 20 with each other. In addition, the outdoor unit 20 is provided with an input unit 21 for setting a desired temperature and time.

The indoor unit 50 is provided in plural so as to be connected to the outdoor unit 20. The indoor unit 50 is an example of the present invention, and includes a first indoor 71, a second indoor 72, a third indoor 73, a fourth indoor 81, and a fifth indoor 82. However, the indoor unit 50 has at least two or more and the number may vary depending on the performance of the outdoor unit 20.

The temperature sensing unit 40 is provided corresponding to the indoor unit 50. The temperature sensing unit 40 is an example of the present invention, and corresponds to the first indoor 71, the second indoor 72, the third indoor 73, the fourth indoor 81, and the fifth indoor 82. The first temperature sensor 41, the second temperature sensor 42, the third temperature sensor 43, the fourth temperature sensor 44, and the fifth temperature sensor 45 are included. That is, the temperature sensing unit 40 is provided corresponding to the number of indoor units 50. The temperature detector 40 detects a current temperature of the space installed in each indoor unit 50. Here, the current temperature detected by the temperature detector 40 may be detected at a time interval set by the input unit 21 or at a preset time interval.

The indoor unit group 60 includes at least one of the plurality of indoor units 50. Indoor unit group 60 is an example of the present invention, the first indoor group having a first indoor (71), the second indoor (72) and the third indoor (73); And a second indoor group 80 having a fourth indoor 81 and a fifth indoor 82. Here, in the present invention, the indoor unit group 60 groups each indoor unit 50 so as to efficiently control the air conditioner system 1.

The controller 90 compares the desired temperature input through the input unit 21 with the temperature detected by the temperature sensing units 40 of the indoor units 50 to control the outdoor unit 20 by cooling operation or heating operation. , To control some of the indoor units 50 to stop. That is, the controller 90 may determine the temperature and the desired temperature detected by the first temperature detector 41, the second temperature detector 42, and the third temperature detector 43 of the first indoor group 70. The first indoor group 70 and the second indoor group by comparing the temperature detected by the fourth temperature detecting unit 44 and the fifth temperature detecting unit 45 of the second indoor group 80 with the desired temperature. Comparing the comparison result of (80), and based on the representative comparison result comparing the comparison result of the first indoor group 70 and the second indoor group 80, the outdoor unit 20 in one of the cooling mode and heating mode. Control to drive.

Detailed description of the control unit 90 will be described in detail in the control flow charts to be described later.

Hereinafter, referring to the configuration, the control flow of the air conditioner system 1 according to the present invention will be described.

Prior to the description, the control flow of the present invention is input to the desired temperature in the cooling operation during the operation of the air conditioner system (1), the control is switched to the cooling operation or heating operation by comparing the desired temperature and the current temperature in the cooling operation It shows the flow.

As shown in FIG. 4, referring to the control process of the air conditioner system 1 according to the first embodiment of the present invention, first, the desired temperature Ts is input to the input unit 21 (S1). When the desired temperature Ts is input to the input unit 21, the outdoor unit 20 is operated in the cooling mode.

After a predetermined time elapses from the start of the cooling operation, the current temperature Ti of the space in which the first indoor unit 71, the second indoor unit 72, and the third indoor unit 73 included in the first indoor group 70 is installed; The current temperature Ti of the space in which the fourth indoor 81 and the fifth indoor 82 included in the second indoor group 80 are installed is sensed (S3).

The first room 71, the second room 72, the third room 73, the fourth room 81 and the fifth room 82 of the first indoor group 70 and the second indoor group 80 The cooling load or the heating load is obtained by comparing the detected temperature Ti from the space in which the space is installed and the desired temperature Ts input from the input unit 21 (S5). Here, when the temperature (Ti)> desired temperature (Ts) detected by each indoor unit 50 of each indoor unit group 60, the sum of cooling loads [∑ (Ti-Ts)] is calculated, and each indoor unit group 60 When the temperature detected by each indoor unit 50 of Ti &lt; desired temperature (Ts), the sum of heating loads [∑ (Ts-Ti)] is calculated and the sum of the cooling loads of each indoor unit group 60 [∑ (Ti -Ts)] and the sum of the heating load [∑ (Ts-Ti)] (S7). For example, when the temperature Ti detected by each indoor unit 50 of the first indoor group 70> desired temperature Ts, the sum of cooling loads [∑ (Ti-Ts)] is calculated and the second When the temperature Ti <desired temperature Ts detected by each indoor unit 50 of the indoor unit group 80, the sum of heating loads [∑ (Ts-Ti)] is calculated and compared.

When the sum of the cooling loads is greater than or equal to the sum of the heating loads, the control unit 90 continues the cooling operation of the indoor unit 50 of the indoor unit group 60 in which the sum of the cooling loads is calculated, and the sum of the heating loads is calculated. The indoor unit 50 of the indoor unit group 60 is controlled to stop (S9). That is, when the above-described example is described, when the sum of the cooling loads of the first indoor group 70 is greater than or equal to the sum of the heating loads of the second indoor group 70, the control unit 90 is the first indoor group. The first indoor 71, second indoor 72, and third indoor 73 of 70 continue to operate in the cooling mode, and the fourth indoor 81 and the fifth indoor of the second indoor group 80 are operated. 82 is to stop.

On the other hand, when the sum of the cooling loads is less than the sum of the heating loads, the controller 90 stops the indoor unit 50 of the indoor unit group 60 in which the sum of the cooling loads is calculated, and the indoor unit group in which the sum of the heating loads is calculated. The indoor unit 50 of 60 switches the outdoor unit 20 to the heating mode to perform the heating operation (S10).

In the embodiment of FIG. 4 described above, the sum of the cooling loads and the heating loads of the indoor air group 60 is controlled to operate in the cooling mode or the heating mode, but the sum of the cooling loads and heating of the indoor air groups 60 is controlled. When the sum of the loads is minute, the sum of the squares of cooling loads [∑ (Ti-Ts) ²] and the sum of squares of heating loads [∑ (Ts-Ti) ²] can be compared.

As shown in FIG. 5, the control process of the air conditioner system 1 according to the second embodiment of the present invention will be described. First, a desired temperature Ts is input to the input unit 21 (S21). When the desired temperature Ts is input to the input unit 21, the outdoor unit 20 operates in the cooling mode.

After a predetermined time elapses from the start of the cooling operation, the current temperature Ti of the space in which the first indoor unit 71, the second indoor unit 72, and the third indoor unit 73 included in the first indoor group 70 is installed; The current temperature Ti of the space in which the fourth indoor 81 and the fifth indoor 82 included in the second indoor group 80 are installed is detected (S23).

The first room 71, the second room 72, the third room 73, the fourth room 81 and the fifth room 82 of the first indoor group 70 and the second indoor group 80 The peak of the cooling load or the peak of the heating load is obtained by comparing the temperature Ti sensed from the space where is installed with the desired temperature Ts input from the input unit 21 (S25).

The peak of the cooling load and the peak of the heating load are compared (S27). Here, the peak of the cooling load and the peak of the heating load are the maximum among the temperature difference between the temperature Ti and the desired temperature Ts detected from at least one indoor unit of each indoor unit group 60. For example, when the present temperature (Ti)> desired temperature (Ts) of the first indoor (71), the second indoor (72) and the third indoor (73) of the first indoor group 70, the cooling load is respectively In the case of 4 ° C, 7 ° C, and 2 ° C, the peak of cooling load (Max (Ti-Ts)) is 7 ° C of the second indoor unit 72, and the fourth indoors 81 and the second indoor group 80 are formed. When the heating load is 3 ° C. and 5 ° C., respectively, when the current temperature Ti of the indoor chamber 82 is the desired temperature Ts, the peak (Max (Ts-Ti)) of the heating load is 5 ° C.

When the peak of the cooling load is greater than or equal to the peak of the heating load, the control unit 90 continues the cooling operation of the indoor unit 50 of the indoor unit group 60 in which the peak of the cooling load is calculated, and the peak of the heating load is calculated. The indoor unit 50 of the indoor unit group 60 is controlled to stop (S29). That is, when the above-described example is described, when the peak of the cooling load of the second indoor unit 71 of the first indoor group 70 is greater than or equal to the peak of the heating load of the second indoor group 80, the control unit ( 90, the first indoor 71, the second indoor 72, and the third indoor 73 of the first indoor group 70 continues to operate in the cooling mode, the fourth indoor of the second indoor group 80 81 and the fifth indoor unit 82 stop.

On the other hand, when the peak of the cooling load is smaller than the peak of the heating load, the controller 90 stops the indoor unit 50 of the indoor unit group 60 in which the peak of the cooling load is calculated, and the indoor unit group in which the peak of the heating load is calculated. The indoor unit 50 of the 60 switches the outdoor unit 20 to the heating mode to perform the heating operation (S30).

In the above-described embodiment of FIG. 5, the peaks of the heating loads and the heating loads are compared with the peaks of the heating loads and the heating loads are controlled to operate in the cooling mode or the heating mode. When the comparative magnitude of the peak of the load is minute, it can be compared with the square of the peak of the cooling load [Max (Ti-Ts) ²] and the square of the peak of the heating load [Max (Ts-Ti) ²].

As shown in FIG. 6, the control process of the air conditioner system 1 according to the third embodiment of the present invention will be described. First, a desired temperature Ts is input to the input unit 21 (S51). When the desired temperature Ts is input to the input unit 21, the outdoor unit 20 operates in the cooling mode.

When the cooling operation starts and a predetermined time elapses, a current temperature Ti of a space in which each indoor unit 50 included in each indoor unit group 60 is installed is detected (S53).

The cooling load or the heating load is calculated by comparing the detected temperature Ti from the space in which the indoor units 50 included in each indoor unit group 60 are installed with the desired temperature Ts input from the input unit 21, and cooling is performed. The rate or heating rate is calculated (S55). In one embodiment of the present invention, the first room 71, the second room 72, the third room (73), the fourth room 81 of the first room group 70 and the second room group (80) And calculating a cooling load or a heating load by comparing the detected temperature Ti from the space in which the fifth indoor unit 82 is installed with the desired temperature Ts input from the input unit 21, and calculating the cooling rate or heating rate. will be. Here, the heating rate is = [{(sum of heating load) / (sum of cooling load + sum of heating load)} x 100%]. However, when the initial operation mode is the heating mode, the cooling rate = [{(sum of cooling loads) / (sum of cooling loads + sum of heating loads)} × 100%] as a comparison result.

Compare the heating rate and the set value (50%) (S57). When the heating rate is equal to or greater than the set value (50%), the control unit 90 moves the outdoor unit 20 to the heating mode so that the indoor units 50 of the indoor unit group 60 that calculate the sum of the heating loads are operated in the heating mode. After switching, the indoor units 50 included in the other indoor unit group 60 are stopped (S59).

On the other hand, when the heating rate is less than the set value (50%), the control unit 90 continues to operate in the cooling mode, the indoor unit 50 of the indoor unit group 60, the sum of the cooling load is calculated, the other indoor unit group 60 Indoor unit 50 is stopped. Here, the hysteresis section is set as shown in <Figure 1> in order to prevent frequent switching of the heating and cooling mode of the air conditioning system (1).

<Picture 1>

In <Figure 1>, cooling operation is set rate (40%) and heating operation is set rate (60%). After the heating rate is over the set value (50%) and switched to the heating mode, it is operated in the heating mode until the heating rate is not calculated below the set rate (40%), and when the heating rate is less than 40%, the cooling mode To drive.

On the contrary, when the cooling rate becomes higher than the set value (50%) when operating in the heating mode for the first time, after switching to the cooling mode, if the cooling rate is lower than the set rate (60%), the operation continues in the cooling mode and the cooling rate is set. If the rate exceeds (60%), the switch is to heating mode. The reason for setting the hysteresis section is to prevent frequent switching of heating and cooling mode based on the set value (50%). Here, of course, the hysteresis section may be arbitrarily set.

On the other hand, if the sum of the cooling loads and the sum of the heating loads is minute, the heating rate can be calculated for the square of the sum of the cooling loads and the square of the sum of the heating loads, that is, the heating rate = [{(sum of heating loads² ) / (Sum of cooling loads 2 + sum of heating loads)} × 100%].

4 to 6 described above are described based on the initial cooling operation. On the other hand, when the sum of the cooling load and the heating load is the same when operated by the first heating operation, the peak of the cooling load and the peak of the heating load are the same. The heating mode is maintained without switching to the cooling mode. Instead of comparing the heating rate and the set value (50%), the cooling rate and the set value (50%) are compared.

As shown in FIG. 7, the control process of the air conditioner system 1 according to the fourth embodiment of the present invention according to the fourth embodiment of the present invention will be described. Enter (S100). When the desired temperature Ts is input to the input unit 21, the outdoor unit 20 operates in the cooling mode or the heating mode. In this embodiment, the cooling mode is operated.

When the cooling operation starts and a predetermined time elapses, a current temperature Ti of a space in which each indoor unit 50 of each indoor unit group 60 is installed is detected (S200).

The cooling load or the heating load is obtained by comparing the temperature Ti detected from the space in which the indoor units 50 of each indoor unit group 60 are installed with the desired temperature Ts input from the input unit (S300). Here, when the temperature (Ti)> desired temperature (Ts) detected by each indoor unit 50 of each indoor unit group 60, the sum of cooling loads [∑ (Ti-Ts)] is calculated and each indoor unit group 60 When the temperature detected by each indoor unit 50 of Ti &lt; desired temperature (Ts), the sum of heating loads [∑ (Ts-Ti)] is calculated and the sum of the cooling loads of each indoor unit group 60 [∑ (Ti -Ts)] and the sum of heating loads [∑ (Ts-Ti)] compare whether the sum of cooling loads is greater than or equal to the sum of heating loads (S400).

If the sum of the cooling loads is greater than or equal to the sum of the heating loads, the sum of the cooling loads is compared with the sum of the heating loads (S600). If the sum of the cooling loads and the sum of the heating loads is not the same, the indoor unit group 60 in which the sum of the cooling loads is calculated continues to operate in the cooling mode, and the other indoor unit groups 60 are stopped (S800).

On the other hand, when the sum of the cooling load and the sum of the heating load is the same, the peak of the cooling load and the peak of the heating load are compared (S700). If the peak of the cooling load is greater than or equal to the peak of the heating load, the indoor unit group 60 in which the sum of the cooling loads is calculated continues to operate in the cooling mode, and the other indoor unit group 60 is stopped (S800). On the other hand, when the peak of the cooling load is smaller than the peak of the heating load, the indoor unit group 60 in which the sum of the cooling loads is calculated is stopped, and the indoor unit group 60 in which the sum of the heating loads is calculated is the outdoor unit to enable heating operation. Switch 20 to the heating mode (S900).

If the sum of the cooling loads is less than the sum of the heating loads in the comparison process of the sum of the cooling loads and the heating loads (S400), the indoor unit group 60 in which the sum of the cooling loads is calculated is stopped and the sum of the heating loads is calculated. The indoor unit group 60 switches the outdoor unit to the heating mode to enable heating operation (S900).

Thus, when the air conditioning system is installed in a large building, it can switch to the heating and cooling mode automatically according to the load fluctuations by detecting a real-time temperature change occurring locally, thereby improving the comfort of the occupants.

As described above, according to the present invention, when the air conditioner system is installed in a large building, it is possible to automatically switch to the heating / cooling mode according to the load fluctuation by detecting a real-time temperature change that occurs locally, and accordingly the comfort of the occupants An air conditioning system is provided that can improve the performance of the system.

Claims (9)

delete In the air conditioning system, Outdoor unit: A plurality of indoor units connected to the outdoor unit; A plurality of temperature sensing units provided respectively to the plurality of indoor units to sense temperatures of the plurality of indoor units; And a controller for controlling the outdoor unit to operate in one of a cooling mode and a heating mode. It includes a plurality of indoor unit group having at least one of the indoor unit of the plurality of indoor unit, The controller calculates a comparison result by comparing each temperature sensed by the temperature sensing unit of each indoor unit of the indoor unit group with a desired temperature, and compares the comparison results of the plurality of indoor unit groups with a representative comparison result. On the basis of the control to operate the outdoor unit in any one of the cooling mode and heating mode, The comparison result is, The air conditioner system, characterized in that any one of the sum of the cooling load and the sum of the heating load which is the sum of the difference between the temperature and the desired temperature detected from each indoor unit included in each indoor unit group. The method of claim 2, The representative comparison result is, The air conditioner system, characterized in that a comparison value of the sum of the cooling load of any one of the plurality of indoor air group and the sum of the other heating load. The method of claim 3, The comparison result is, And at least one of a peak of a cooling load and a peak of a heating load which are a maximum value of a difference between a temperature sensed from at least one indoor unit of each indoor unit group and a desired temperature difference. The method of claim 4, wherein The representative comparison result is, The air conditioner system, characterized in that the comparison value of the peak of the cooling load of any one of the plurality of indoor air groups and the peak of the other heating load. The method of claim 5, The control unit, when the sum of the cooling load of any one of the plurality of indoor air group and the sum of the sum of the other heating load is the same, And controlling the outdoor unit to operate in one of the cooling mode and the heating mode based on the representative comparison result, which is a comparison value of one of a plurality of indoor unit groups with a peak of a cooling load. Air conditioning system. The method of claim 2, The comparison result is, A cooling rate of [{(sum of cooling loads) / (sum of cooling loads + sum of heating loads)} × 100%] and [{(sum of heating loads) / (sum of heating loads + sum of heating loads) } × 100%] of the air conditioning system, characterized in that any one of the heating rate. The method of claim 7, wherein And the control unit controls the outdoor unit to operate in one of the cooling mode and the heating mode by comparing the comparison result with a reference set value. The method of claim 8, And said comparison result, which is one of said cooling rate and said heating rate, has a predetermined hysteresis region.

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