Abstract:
An air conditioning system including an outdoor unit having at least one compressor, and at least one outdoor heat exchanger; a plurality of indoor units connected to the outdoor unit; a refrigerant guide unit to guide a refrigerant discharged from the at least one compressor to the indoor units through first and/or second routes; and a control unit to simultaneously control a first quantity of the refrigerant discharged from the at least one compressor to at least one of the indoor units operating in a cooling mode through the first route, and a second quantity of the refrigerant discharged from the at least one compressor to a remainder of the indoor units operating in a heating mode through the second route.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 2004-3733, filed Jan. 19, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an air conditioning system comprising a plurality of indoor units connected to an outdoor unit, in which heating and cooling operations are simultaneously performed, and a method for controlling the air conditioning system.  
         [0004]     2. Description of the Related Art  
         [0005]     Generally, an air conditioning system performs an air conditioning operation in an indoor space using a single outdoor unit and a plurality of indoor units connected to the outdoor unit. The outdoor unit includes a compressor, an outdoor heat exchanger, an outdoor fan, and a motor-operated outdoor valve. Each of the indoor units includes an indoor heat exchanger, an indoor fan, and a motor-operated indoor valve.  
         [0006]     Since a temperature which a resident can sense in an indoor space varies according to a change of seasons and surrounding environment, operating modes, such as heating and cooling modes, applied to all the indoor units are not necessarily uniform, but may, instead, be different from one another. That is, the operating modes may include a single mode, in which all the indoor units are operating in the same mode such as the heating or cooling mode, and a complex mode, in which some of the indoor units are operating in the heating mode, and the rest of the indoor units are simultaneously operating in the cooling mode. Here, the complex mode is divided into a general cooling mode, in which the majority of the indoor units are operating in the cooling mode and the remainder of the indoor units are operating in the heating mode, and a general heating mode, in which the majority of the indoor units are operating in the heating mode and the remainder of the indoor units are operating in the cooling mode.  
         [0007]     In a case in which the conventional air conditioning system starts an operation based on the general cooling mode, the refrigerant discharged from the compressor passes through the outdoor heat exchanger and is supplied to the indoor units operating in the cooling mode. Then, the refrigerant passed through the indoor units operating in the cooling mode is returned to the compressor. After the starting operation is finished, the refrigerant discharged from the compressor is divisionally supplied to the indoor units operating in the heating mode, thus allowing the air conditioning system to simultaneously operate the cooling and heating modes. Since the indoor units set in the heating mode do not perform a heating operation during the starting operation in the general cooling mode, the conventional air conditioning system is at a disadvantage because the heating operation is delayed.  
         [0008]     Operational characteristics required by the starting operation beginning under the condition in which the air conditioning system is in a stopped state, and operational characteristics required by the main operation beginning under the condition in which the air conditioning system is stabilized by the starting operation, must be considered. However, since the control applied to the starting operation and the control applied to the main operation performed after the starting operation are almost identically performed, the conventional air conditioning system has a disadvantage in that the operating efficiency is reduced. That is, the air conditioning system fluctuates extremely during the starting operation, thus being unstable and increasing the amount of time taken to stabilize the system. Further, since the conventional air conditioning system relates mainly to the cooling mode, the conventional air conditioning system has a disadvantage in that the cooling capacity is comparatively good, but the heating capacity is poor.  
       SUMMARY OF THE INVENTION  
       [0009]     Therefore, an aspect of the invention is to provide an air conditioning system in which a refrigerant discharged from compressors is supplied to indoor units operating in a heating mode during a starting operation in a general cooling mode, and a method of controlling the air conditioning system, thus rapidly performing the heating mode.  
         [0010]     Another aspect of the invention is to provide an air conditioning system in which operation is controlled in consideration of operational characteristics of a starting operation beginning in response to the system being in a stopped state, and operational characteristics of a main operation beginning in response to the system being stabilized by the starting operation, and a method of controlling the air conditioning system, thus increasing the operating efficiency of the system  
         [0011]     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.  
         [0012]     In accordance with one aspect, the present invention provides an air conditioning system comprising: an outdoor unit including at least one compressor and at least one outdoor heat exchanger; a plurality of indoor units connected to the outdoor unit; a refrigerant guide unit to guide a refrigerant discharged from the at least one compressor to the indoor units through first and/or second routes; and a control unit to simultaneously control a first quantity of the refrigerant discharged from the at least one compressor to at least one of the indoor units operating in a cooling mode through the first route, and a second quantity of the refrigerant discharged from the at least one compressor to a remainder of the indoor units operating in a heating mode through the second route  
         [0013]     The control unit may divisionally supply the refrigerant discharged from the at least one compressor through the first and second routes in a general cooling mode in which a majority of the indoor units are operating in the cooling mode and the remainder of the indoor units are operating in the heating mode.  
         [0014]     The control unit may include: indoor control units to control the indoor units; and an outdoor control unit connected to the indoor control units, wherein the outdoor control unit sets the general cooling mode in response to a total cooling capacity of the indoor units operating in the cooling mode being larger than a total heating capacity of the indoor units operating in the heating mode.  
         [0015]     The at least one outdoor heat exchanger may be installed on the first route, and an on-off valve to guide the second quantity of the refrigerant discharged from the at least one compressor to the indoor units operating in the heating mode without passing through the at least one outdoor heat exchanger may be provided on the second route.  
         [0016]     In accordance with another aspect, the present invention provides a method of controlling an air conditioning system which simultaneously performs cooling and heating operations by connecting a plurality of indoor units to an outdoor unit having at least one outdoor heat exchanger, the method comprising: setting an operating mode of the system; determining whether the set operating mode is a general cooling mode in which a majority of the indoor units are operating in a cooling mode and a remainder of the indoor units are operating in a heating mode; determining whether the system is operating in a starting mode, which results from the system starting from a stopped state, in response to the determining that the set operating mode is the general cooling mode; and supplying a first quantity of refrigerant discharged from at least one compressor to the indoor units operating in the cooling mode through a first route, and simultaneously supplying a second quantity of the refrigerant to the indoor units operating in the heating mode through a second route, in response to the determining that the system is operating in the starting mode.  
         [0017]     The general cooling mode may be set in response to a total cooling capacity of the indoor units operating in the cooling mode being larger than a total heating capacity of the indoor units operating in the heating mode.  
         [0018]     In accordance with still another aspect, the present invention provides an air conditioning system comprising: an outdoor unit including at least one compressor, at least one outdoor heat exchanger, an outdoor fan, and a motor-operated outdoor valve; a plurality of indoor units connected to the outdoor unit; a plurality of indoor heat exchangers respectively provided to the indoor units; a refrigerant guide unit to simultaneously guide a refrigerant discharged from the at least one compressor to the indoor units operating in a cooling mode through a first route and to the indoor units operating in a heating mode through a second route; and a control unit to sequentially perform a starting operation in response to the system being started from a stopped state and a main operation in response to the system being stabilized by the starting operation, and to control the at least one compressor, the outdoor fan, and the motor-operated outdoor valve according to operational characteristics of the starting and main operations.  
         [0019]     The control unit may perform the starting and main operations in response to a total cooling capacity of the indoor units operating in the cooling mode being larger than a total heating capacity of the indoor units operating in the heating mode.  
         [0020]     In accordance with yet another aspect, the present invention provides a method of controlling an air conditioning system which simultaneously performs cooling and heating operations by connecting a plurality of indoor units to an outdoor unit including at least one outdoor heat exchanger, the method comprising: setting an operating mode of the system; determining whether the set operating mode is a general cooling mode in which a majority of the indoor units are operating in a cooling mode and a remainder of the indoor units are operating in a heating mode; sequentially performing a starting operation in response to the system being started from a stopped state and a main operation in response to the system being stabilized by the starting operation; and controlling at least one compressor, an outdoor fan, and a motor-operated outdoor valve of the outdoor unit according to operational characteristics of the starting and main operations.  
         [0021]     In the starting operation, an operating capacity of the at least one compressor may be set to approximately 50-80% of a total cooling capacity of the indoor units operating in the cooling mode.  
         [0022]     In the starting operation, an opening degree of the motor-operated outdoor valve may be set according to a total cooling capacity of the indoor units operating in the cooling mode.  
         [0023]     In the starting operation, an operating capacity of the outdoor fan may be set according to a difference between a total cooling capacity of the indoor units operating in the cooling mode and a total heating capacity of the indoor units operating in the heating mode, and according to an outdoor temperature.  
         [0024]     During the sequentially performing the starting and main operation, a pressure sensed by a pressure sensor installed at an outlet of the at least one compressor may be compared to a predetermined pressure to determine whether the starting operation is terminated.  
         [0025]     In the main operation, an operating capacity of the at least one compressor may be set according to a total cooling capacity of the indoor units operating in the cooling mode.  
         [0026]     In the main operation, an opening degree of the motor-operated outdoor valve may be set according to according to a ratio of a total heating capacity of the indoor units operating in the heating mode to a total operating capacity obtained by adding a total cooling capacity of the indoor units operating in the cooling mode and the total heating capacity of the indoor units operating in the heating mode.  
         [0027]     The total heating capacity may be inversely proportional to the opening degree of the motor-operated outdoor valve.  
         [0028]     A pressure sensor to sense a pressure of refrigerant discharged from the compressors may be provided, and, in the main operation, an operating capacity of the outdoor fan may be set such that the pressure of the refrigerant sensed by the pressure sensor and supplied to the indoor units operating in the heating mode reaches a set standard pressure. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0030]      FIG. 1  is a schematic view of an air conditioning system in accordance with an embodiment of the present invention;  
         [0031]      FIG. 2  is a block diagram of the air conditioning system of  FIG. 1 ;  
         [0032]      FIG. 3  is a schematic view of the air conditioning system of  FIG. 1  in which three indoor units are operating in a cooling mode and one indoor unit is operating in a heating mode; and  
         [0033]      FIGS. 4A and 4B  are flow charts of a method of controlling the air conditioning system in accordance with the embodiment of the present invention shown in  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]     Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.  
         [0035]     The present invention relates to an air conditioning system in which a plurality of indoor units are connected to an outdoor unit.  
         [0036]     As shown in  FIG. 1 , the air conditioning system in accordance with an embodiment of the present invention comprises an outdoor unit  100 , four indoor units  200   a,    200   b,    200   c,  and  200   d,  and a directional conversion circuit  300  interposed between the outdoor unit  100  and the indoor units  200   a,    200   b,    200   c,  and  200   d  to convert the direction of a refrigerant flow.  
         [0037]     The outdoor unit  100  includes outdoor heat exchangers  101   a  and  101   b,  an outdoor fan  113 , an outdoor fan motor  114 , a motor-operated outdoor valve  102  connected to outlets of the outdoor heat exchangers  101   a  and  101   b,  an on-off valve  111  and a check valve  112  connected to the motor-operated outdoor valve  102 , capacity variable compressors  103   a  and  103   b,  a four-way valve  104 , a receiver  106 , an accumulator  107 , and an on-off valve  109  and a check valve  110  to supply a refrigerant discharged from the compressors  103   a  and  103   b  to the indoor units operating in a heating mode without passing through the outdoor heat exchangers  101   a  and  101   b.    
         [0038]     The outdoor unit  100  further includes an outdoor temperature sensor  108  to sense an outdoor temperature, and a pressure sensor  105  to sense a discharge pressure of a refrigerant discharged from the compressors  103   a  and  103   b.    
         [0039]     The indoor units  200   a,    200   b,    200   c,  and  200   d  respectively include indoor heat exchangers  201   a,    201   b,    201   c,  and  201   d,  motor-operating indoor valves  202   a,    202   b,    202   c,  and  202   d,  indoor temperature sensors  203   a,    203   b,    203   c,  and  203   d,  and pipe temperature sensors  204   a,    204   b,    204   c,  and  204   d  to sense temperatures at inlets and outlets of the indoor heat exchangers  201   a,    201   b,    201   c,  and  201   d.  The indoor units  200   a,    200   b,    200   c,  and  200   d  respectively further include indoor fans (not shown) and indoor fan motors (not shown).  
         [0040]     The directional conversion circuit  300  includes high-pressure gas valves  301   a,    301   b,    301   c,  and  301   d  respectively installed at high-pressure gas pipes (HPPs) located between the outdoor unit  100  and the indoor units  200   a,    200   b,    200   c,  and  200   d,  low-pressure gas valves  302   a,    302   b,    302   c,  and  302   d  respectively installed at low-pressure gas pipes (LPPs), and a motor-operated valve  303  installed at a common pipe (RP) to connect the outdoor unit  100  to the indoor units  200   a,    200   b,    200   c,  and  200   d.  The above high-pressure gas valves  301   a,    301   b,    301   c,  and  301   d  and low-pressure gas valves  302   a,    302   b,    302   c,  and  302   d  of the directional conversion circuit  300  are operated under the control of an outdoor control unit, which will be described later.  
         [0041]     One end of the four-way valve  104  of the outdoor unit  100  is connected to the high-pressure gas valves  301   a,    301   b,    301   c,  and  301   d  of the directional conversion circuit  300  through the high-pressure gas pipes (HPPs). Further, the accumulator  107  of the outdoor unit  100  is connected to the low-pressure gas valves  302   a,    302   b,    302   c,  and  302   d  of the directional conversion circuit  300  through the low-pressure gas pipes (LPPs).  
         [0042]     The common pipe (RP) is installed between the outdoor heat exchangers  101   a  and  101   b  of the outdoor unit  100  and the directional conversion circuit  300 , and the motor-operated outdoor valve  102  is installed in the common pipe (RP). The on-off valve  111 , connected in parallel to the motor-operated outdoor valve  102 , serves as a flow control valve.  
         [0043]     Pipes EP 1 , EP 2 , EP 3 , and EP 4  of the indoor heat exchangers  201   a,    201   b,    201   c,  and  201   d  are connected to the common pipe (RP).  
         [0044]     As shown in  FIG. 2 , the air conditioning system in accordance with the embodiment of the present invention shown in  FIG. 1  comprises an outdoor control unit  120  to control the outdoor unit  100 , first to fourth indoor control units  210   a,    210   b,    210   c,  and  210   d  to control the indoor units  200   a,    200   b,    200   c,  and  200   d,  and a connection unit  122  interposed between the outdoor control unit  120  and the first to fourth indoor control units  210   a,    210   b,    210   c,  and  210   d  to bidirectionally communicate information to operate the air conditioning system.  
         [0045]     The pressure sensor  105  and the outdoor temperature sensor  108  are connected to an input terminal of the outdoor control unit  120 .  
         [0046]     A compressor operating unit  124  to operate the compressors  103   a  and  103   b,  a four-way valve operating unit  126  to operate the four-way valve  104 , an outdoor fan operating unit  128  to operate the outdoor fan  105 , a motor-operated outdoor valve operating unit  130  to operate the motor-operated outdoor valve  102 , and an on-off valve operating unit  132  to operate the on-off valves  109  and  111  are connected to an output terminal of the outdoor control unit  120 .  
         [0047]     The first to fourth indoor control units  210   a,    210   b,    210   c,  and  210   d  respectively provide indoor temperatures sensed by the indoor temperature sensors  203   a,    203   b,    203   c,  and  203   d,  a temperature and an operating mode set by a user using a function key and a remote control unit, and information regarding capacities of the indoor heat exchangers  201   a,    201   b,    201   c,  and  201   d,  to the outdoor control unit  120 .  
         [0048]     The first to fourth indoor control units  210   a,    210   b,    210   c,  and  210   d,  in connection with the outdoor control unit  120 , respectively control the motor-operated indoor valves  202   a,    202   b,    202   c,  and  202   d  and the indoor fans (not shown).  
         [0049]      FIG. 3  illustrates the air conditioning system of  FIG. 1  in which one indoor unit (i.e., the indoor unit  200   a ) operates in a heating mode, and the remaining three indoor units (i.e., the indoor units  200   b,    200   c,  and  200   d ) operate in a cooling mode, in accordance with an embodiment of the present invention.  
         [0050]     In a general cooling mode of the air conditioning system, the outdoor control unit  120  operates the compressors  103   a  and  103   b,  opens the motor-operated outdoor valve  102  to an initial degree, and opens the on-off valve  109 . The outdoor control unit  120  opens the high-pressure gas valve  301   a  of the indoor unit  200   a  operating in the heating mode, and closes the high-pressure gas valves  301   b,    301   c,  and  301   d  of the indoor units  200   b,    200   c,  and  200   d  operating in the cooling mode. Further, the outdoor control unit  120  closes the low-pressure gas valve  302   a  of the indoor unit  200   a  operating in the heating mode, and opens the low-pressure gas valves  302   b,    302   c,  and  302   d  of the indoor units  200   b,    200   c,  and  200   d  operating in the cooling mode.  
         [0051]     A part of the refrigerant discharged from the compressors  103   a  and  103   b  passes through the on-off valve  109  and the check valve  110 , as shown by arrows represented by a solid line, and is then supplied to the indoor unit  200   a  operating in the heating mode. The other part of the refrigerant discharged from the compressors  103   a  and  103   b  passes through the outdoor heat exchangers  101   a  and  101   b  and the motor-operated outdoor valve  102 , as shown by arrows represented by a dotted line, and is then combined with the refrigerant passed through the indoor unit  200   a.  The combined refrigerant sequentially passes through the motor-operated indoor valves  202   b,    202   c,  and  202   d  and the indoor heat exchangers  201   b,    201   c,  and  201   d  of the indoor units  200   b,    200   c,  and  200   d  operating in the cooling mode, and the low-pressure gas pipes (LPPs), and is then returned to the compressors  103   a  and  103   b.  The refrigerant is circulated through the above-described cycle.  
         [0052]     In a case in which the total cooling capacity of the indoor units  200   b,    200   c,  and  200   d  operating in the cooling mode is larger than the heating capacity of the indoor unit  200   a  operating in the heating mode, the outdoor control unit  120  sets a general cooling mode, and controls the operation of the air conditioning system based on the general cooling mode. During the start operation of the general cooling mode, the refrigerant discharged from the compressors  103   a  and  103   b  is divided into two parts as shown in  FIG. 3 , thus allowing the indoor unit  200   a,  which is operating in the heating mode, to achieve rapid heating. Further, the outdoor control unit  120  sets capacities of the compressors  103   a  and  103   b  and a capacity (speed) of the outdoor fan  113  so as to satisfy characteristics of the starting of the operating mode of the air conditioning system, and controls an opening degree of the motor-operated outdoor valve  102 , thus maximizing the operating efficiency of the air conditioning system.  
         [0053]     Hereinafter, operation of the air conditioning system in accordance with the embodiment of the present invention shown in  FIG. 3  will be described in detail with reference to  FIGS. 4A and 4B .  
         [0054]     When power is applied to the air conditioning system of  FIG. 3 , the outdoor control unit  120  performs initialization ( 400 ). The initialization refers to a procedure automatically achieved according to a predetermined control program to operate the air conditioning system.  
         [0055]     After the initialization, the indoor control units  210   a,    210   b,    210   c,  and  210   d  provide operating mode signals to distinguish between heating and cooling modes set to the corresponding indoor units  200   a,    200   b,    200   c,  and  200   d,  capacities of the indoor heat exchangers  201   a,    201   b,    201   c,  and  201   d  assigned to the corresponding indoor units  200   a,    200   b,    200   c,  and  200   d,  a set temperature, and an indoor temperature to the outdoor control unit  120  through the connection unit  122 . The outdoor control unit  120  receives an outdoor temperature from the outdoor temperature sensor  108  ( 410 ).  
         [0056]     The outdoor control unit  120  calculates heating capacities (heating loads) and cooling capacities (cooling loads) based on the capacities of the indoor heat exchangers  201   a,    201   b,    201   c,  and  201   d  provided from the indoor units  200   a,    200   b,    200   c,  and  200   d.  Here, capacities of the indoor heat exchangers  201   b,    201   c,  and  201   d  of the three indoor units  200   b,    200   c,  and  200   d,  which are set to operate in the cooling mode, are summed to obtain a total cooling capacity (CQ), and a capacity of the indoor heat exchanger  201   a  of the one indoor unit  200   a,  which is set to operate in the heating mode, serves as a total heating capacity (HQ) ( 420 ).  
         [0057]     The outdoor control unit  120  determines whether the total cooling capacity (CQ) is larger than the total heating capacity (HQ) ( 430 ). In a case in which, as a result of operation  430 , it is determined that the total cooling capacity (CQ) is not larger than the total heating capacity (HQ), the operating mode of the air conditioning system is set to a corresponding one of operating modes such as a cooling mode, a heating mode, and a general heating mode in which the majority of the indoor units are operating in the heating mode and the remainder of the indoor units are operating in the cooling mode ( 431 ).  
         [0058]     In a case in which, as a result of operation  430 , it is determined that the total cooling capacity (CQ) is larger than the total heating capacity (HQ), the operating mode of the air conditioning system is set to a general cooling mode ( 440 ).  
         [0059]     The outdoor control unit  120  determines whether the general cooling mode of the air conditioning system starts ( 450 ). In a case in which, as a result of operation  450 , it is determined that the general cooling mode of the air conditioning system starts, the outdoor control unit  120  controls the four-way valve operating unit  126  to convert the route of the four-way valve  104  and the on-off valve operating unit  132  to open the on-off valve  109  such that the refrigerant flow corresponds to the general cooling mode ( 460 ).  
         [0060]     The outdoor control unit  120  controls the compressor operating unit  124  to operate the compressors  103   a  and  103   b  according to the initial operating capacity of the compressors  103   a  and  103   b.  Here, the initial operating capacity of the compressors  103   a  and  103   b  is set to approximately 50-80% of the total cooling capacity (CQ) calculated in operation  420 , thus preventing the air conditioning system from being overloaded ( 470 ).  
         [0061]     The outdoor control unit  120  controls the motor-operated outdoor valve operating unit  130  to operate the motor-operated outdoor valve  102  to an initial opening degree. Here, the initial opening degree of the motor-operated outdoor valve  102  is set by the total cooling capacity (CQ), thus preventing the air conditioning system from being overloaded ( 480 ).  
         [0062]     The outdoor control unit  120  sets the operating capacity (speed) of the outdoor fan  113  based on a difference (CQ-HQ) between the total cooling capacity (CQ) and the total heating capacity (HQ) and an outdoor temperature ( 490 ), and controls the outdoor fan operating unit  128  to operate the outdoor fan  113  based on the set operating capacity of the outdoor fan  113  ( 500 ).  
         [0063]     A part of the refrigerant discharged from the compressors  103   a  and  103   b  passes through the outdoor heat exchangers  101   a  and  101   b  and the motor-operated outdoor valve  102 , and is then supplied to the indoor units  200   b,    200   c,  and  200   d,  which are operating in the cooling mode. Simultaneously, the other part of the refrigerant discharged from the compressors  103   a  and  103   b  passes through the on-off valve  109  and the check valve  110  without passing through the outdoor heat exchangers  101   a  and  101   b,  and is then supplied to the indoor unit  200   a,  which is operating in the heating mode.  
         [0064]     During the starting operation, the pressure sensor  105  senses the pressure of the discharged refrigerant, and then supplies the sensed pressure to the outdoor control unit  120  ( 510 ). The outdoor control unit  120  compares the supplied pressure of the discharged refrigerant to a set pressure set for finishing the starting operation, and determines whether the starting operation is finished ( 520 ).  
         [0065]     In a case in which, as a result of operation  520 , it is determined that the starting operation is not finished, the operation of the air conditioning system is returned to operation  460  to perform the starting operation.  
         [0066]     In a case in which, as a result of operation  520 , it is determined that the starting operation is finished, or as a result of operation  450 , it is determined that the general cooling mode of the air conditioning system does not start, since the air conditioning system is stabilized due to the starting operation, the outdoor control unit  120  sets the operating capacity of the compressors  103   a  and  103   b.  Here, the operating capacity of the compressors  103   a  and  103   b  is set based on the total cooling capacity (CQ) ( 530 ).  
         [0067]     The outdoor control unit  120  controls the compressor operating unit  124  to operate the compressors  103   a  and  103   b  according to the set operating capacity of the compressors  103   a  and  103   b  ( 540 ).  
         [0068]     The outdoor control unit  120  sets an opening degree of the motor-operated outdoor valve  102  based on the ratio of the total heating capacity (HQ) to the total operating capacity (CQ+HQ) ( 550 ), and controls the motor-operated outdoor valve operating unit  130  to operate the motor-operated outdoor valve  102  based on the set opening degree. Here, the opening degree of the motor-operated outdoor valve  102  is set such that the larger the heating capacity of the indoor unit  200   a  operating in the heating mode is, the smaller the opening degree of the motor-operated outdoor valve  102  is, thus causing an amount of the refrigerant supplied to the indoor unit  200   a  operating in the heating mode to be increased ( 560 ).  
         [0069]     The outdoor control unit  120  sets the operating capacity of the outdoor fan  113  such that the pressure of the refrigerant discharged from the compressors  103   a  and  103   b  and supplied to the indoor unit  200   a  operating in the heating mode reaches a standard pressure ( 570 ).  
         [0070]     In order to suitably achieve the desired heating using the refrigerant supplied to the indoor unit  200   a  operating in the heating mode, it is necessary for the temperature of the refrigerant discharged from the compressors  103   a  and  103   b  to be greater than a predetermined temperature. In an embodiment of the present invention, the pressure of the discharged refrigerant sensed by the pressure sensor  105  corresponding to the temperature of the refrigerant discharged from the compressors  103   a  and  103   b  is maintained to be more than a predetermined pressure. The pressure of the refrigerant discharged from the compressors  103   a  and  103   b  varies according to the variation in the operating capacity (speed) of the outdoor fan  113 . That is, in a case in which the operating capacity of the outdoor fan  113  is increased, the heat exchanging efficiency of the outdoor heat exchangers  101   a  and  101   b  is increased, and the discharge pressure of the compressors  103   a  and  103   b  is decreased. And in a case in which the operating capacity of the outdoor fan  105  is decreased, the heat exchanging efficiency of the outdoor heat exchangers  101   a  and  101   b  is decreased, and the discharge pressure of the compressors  103   a  and  103   b  is increased.  
         [0071]     The outdoor control unit  120  controls the outdoor fan operating unit  128  to operate the outdoor fan  113  based on the set operating capacity of the outdoor fan  113  ( 580 ).  
         [0072]     The indoor control units  210   b,    210   c,  and  210   d  operating in the cooling mode receive temperatures at inlets and outlets of the indoor heat exchangers  201   b,    201   c,  and  201   d  through the pipe temperature sensors  204   b,    204   c,  and  204   d,  calculate degrees of superheat based on corresponding differences between the temperatures at the inlets and outlets, and control the opening degrees of the motor-operated indoor valves  202   b,    202   c,  and  202   d  such that the calculated degrees of superheat reach a set degree of superheat (S 590 ).  
         [0073]     The indoor control unit  210   a  operating in the heating mode fully opens the motor-operated indoor valve  202   a  ( 600 ).  
         [0074]     The outdoor control unit  120  determines whether the operation of the air conditioning system is terminated ( 610 ). In a case in which, as a result of operation  610 , it is determined that the operation of the air conditioning system is not terminated, the operating process of the air conditioning system is returned to operation  430  to continue performing the operation.  
         [0075]     In a case in which, as a result of operation  610 , it is determined that the operation of the air conditioning system is terminated, the outdoor control unit  120  stops the operations of the compressors  103   a  and  103   b,  the outdoor fan  113 , and the motor-operated outdoor valve  102 , thus stopping the operation of the air conditioning system ( 620 ).  
         [0076]     As apparent from the above description, the present invention provides an air conditioning system, in which a refrigerant discharged from compressors is supplied to indoor units, operating in a heating mode during the starting operation in a general cooling mode, and a method of controlling the air conditioning system, thus rapidly performing the heating mode. Since the compressors, an outdoor fan, and a motor-operated outdoor valve are controlled in consideration of operational characteristics required by the starting operation and operational characteristics required by the main operation in a general cooling mode, the air conditioning system is rapidly stabilized without overload during the starting operation, and operates in the general cooling mode under the condition that the system is stabilized in consideration of cooling and heating capacities, thus having good cooling and heating efficiencies.  
         [0077]     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.