Patent Publication Number: US-11644208-B2

Title: Air conditioner and method for detecting incorrectly connected pipe in an air conditioner

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2020-0181160, filed in Korea on Dec. 22, 2020, in the Korean Intellectual Property Office (KIPO), the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     An air conditioner capable of detecting an incorrectly connected pipe among pipes connecting outdoor units to indoor units and a method for detecting an incorrectly connected pipe in an air conditioner are disclosed herein. 
     2. Background 
     A multi-air conditioning apparatus of an air conditioner may connect a plurality of indoor units to at least one outdoor unit through a single pipe system to control air in a plurality of indoor spaces. The indoor unit installed in each indoor space among the plurality of indoor spaces may perform a cooling operation or a heating operation. In addition, some of the plurality of indoor units may perform the cooling operation and the other indoor units may perform the heating operation. 
     The multi-air conditioning apparatus in related art may close indoor units one by one to inspect pipes when electronic expansion valves connecting the indoor units to the outdoor units are all opened. In this case, stability of the system may be obtained; however, a stabilization time period of a refrigeration cycle for the pipe inspection may be increased. In addition, the multi-air conditioning apparatus may sequentially inspect the indoor units one by one, so a lot of time may be consumed accordingly as a large number of indoor units are connected to the outdoor units. 
     In addition, when the indoor units are grouped using a binary tree method according to operation modes thereof, all indoor units may be grouped by 50% or the indoor units may be grouped through a combination thereof. This grouping method may shorten the total operation time; however, this method may consume a longer time to stabilize the refrigeration cycle than the above method according to a capacity of the connected indoor unit and a length of the pipe, and may increase a probability of incorrect detection. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein: 
         FIG.  1    is a schematic diagram of an air conditioner according to an embodiment; 
         FIG.  2    is a schematic diagram of internal components of an outdoor unit and indoor units according to an embodiment; 
         FIG.  3    is a schematic diagram of components of an outdoor unit connected to at least one indoor unit according to an embodiment; 
         FIG.  4    is a flowchart of a method for detecting an incorrectly connected pipe of an air conditioner according to an embodiment; 
         FIG.  5    is a flowchart of a method for performing pipe inspection by an outdoor unit of an air conditioner according to an embodiment; 
         FIG.  6    shows example pipe address information allocated to each indoor unit, by an outdoor unit and stored in the outdoor unit, and detection results thereof; 
         FIG.  7    shows an example of performing a group pipe inspection of an air conditioner according to an embodiment; 
         FIG.  8    shows an example of performing a group pipe inspection when an air conditioner includes seven indoor units according to an embodiment; and 
         FIG.  9    shows an example of performing a group pipe inspection when an air conditioner includes five indoor units according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments will be described with reference to accompanying drawings, such that a person having ordinary knowledge in the art to which the embodiments pertain may easily implement the technical idea. Description of well-known technology relating to the embodiments may be omitted if it unnecessarily obscures the gist. One or more embodiments are described with reference to the accompanying drawings. Same reference numerals may be used to refer to same or similar components. 
     It will be understood that, the terms “first”, “second”, and the like may be used herein to describe various components; however, these components should not be limited by these terms. These terms are only used to distinguish one component from another component. Thus, a first component may be a second component unless otherwise stated. 
     Unless otherwise stated, each component may be singular or plural through the disclosure. 
     In this document, the terms “upper,” “lower,” “on,” “under,” or the like are used such that, where a first component is arranged at “an upper portion” or “a lower portion” of a second component, the first component may be arranged in contact with the upper surface or the lower surface of the second component, or another component may be disposed between the first component and the second component. Similarly, where a first component is arranged on or under a second component, the first component may be arranged directly on or under (in contact with) the second component, or at least one other components may be disposed between the first component and the second component. 
     Further, the terms “connected,” “coupled,” or the like are used such that, where a first component is connected or coupled to a second component, the first component may be directly connected or able to be connected to the second component, or at least one additional components may be disposed between the first and second components, or the first and second components may be connected or coupled through at least one additional components. In some examples, singular expressions used in the present disclosure include plural expressions unless the context clearly indicates otherwise. In the present disclosure, terms such as “including” or “comprising” should not be construed as necessarily including all of the various components, or various steps described in the present disclosure, and terms such as “including” or “comprising” should be construed as not including some elements or some steps or further including additional elements or steps. 
     In some examples, singular expressions used in the present disclosure include plural expressions unless the context clearly indicates otherwise. In the present disclosure, terms such as “including” or “comprising” should not be construed as necessarily including all of the various components, or various steps described in the present disclosure, and terms such as “including” or “comprising” should be construed as not including some elements or some steps or further including additional elements or steps. 
     In the present disclosure, unless otherwise stated, “A and/or B” means A, B, or both. Unless otherwise stated, “C to D” means “C or more and D or less”. 
     Hereinafter, an air conditioner and a method for detecting an incorrectly connected pipe in an air conditioner according to embodiments are described. 
       FIG.  1    is a schematic diagram of an air conditioner according to an embodiment. Referring to  FIG.  1   , an air conditioner  100  according to an embodiment may include an outdoor unit  110  and a pipe address setting portion  10  configured to set a pipe address for at least one of indoor units  120  to  140 , which are connected to the outdoor unit by wire or wirelessly and through at least one pipe. 
     In this embodiment, a remote controller to wirelessly transmit the pipe address information to the at least one of indoor units  120  to  124  is described as an example of pipe address setting portion  10 . Hereinafter, the remote controller  10  is described as the pipe address setting portion  10  in drawings and the description of the disclosure. However, the pipe address setting portion  10  is not limited thereto and may be implemented as, for example, an input button or a setting button of any one of the indoor units  120  to  140 . 
     The remote controller  10  may receive data to set a pipe address for at least one of indoor units  120  to  140  from a user or a manager and wirelessly and/or wired transmit the received pipe address information to the at least one of indoor units  120  to  140 . The at least one of indoor units  120  to  140  may receive the pipe address information from the remote controller  10 , and set the pipe address information. After having the pipe address information, the indoor units may transmit the set pipe address information to the outdoor unit  110  through wired communication. However, also a wireless communication of the pipe address information to the outdoor unit may be possible or a mixed mode. 
     The outdoor unit  110  may determine whether there is an abnormality in the pipe address information received from each of the at least one of the indoor units  120  to  140  and detect incorrectly connected pipes among pipes connected to the at least one of indoor units  120  to  140 . 
     The outdoor unit  110  may perform a serial pipe inspection when a predetermined number of indoor units is connected, for example, three or less indoor units, through pipes. If a higher number than the predetermined number of indoor units is connected to the outdoor unit  110 , the outdoor unit  110  may perform a group pipe inspection, for example, when four or more indoor units are connected through pipes, a group pipe inspection may be performed. 
       FIG.  2    is a schematic diagram of internal components of an outdoor unit and an indoor unit according to an embodiment.  FIG.  3    is a schematic diagram of components of an outdoor unit connected to at least one indoor unit according to an embodiment. 
     Referring to  FIG.  2   , outdoor unit  110  according to an embodiment may include at least one of a compressor  111 , an outdoor fan  112 , expansion valves  113   a  to  113   c , a load driver  114 , a controller  115 , a temperature sensor  116 , an outdoor temperature sensor  116   a , a pipe temperature sensor  116   b , a discharge temperature sensor  116   c , a pressure sensor  117 , and a communicator  118 . However, the outdoor unit may have less components. The communicator  118  may be connected to the controller  115 . 
     Referring to  FIG.  3   , for the outdoor unit  110  according to the embodiment, a 4-way valve  310  may be connected to the compressor  111  in two directions, to an outdoor heat exchanger  320  in a first direction among remaining two directions of the 4-way valve  310 , and to a first branch  340  via a pipe (P) in a second direction among the remaining two directions of the 4-way valve  310 . 
     Referring to  FIGS.  2  and  3   , the compressor  111  may compress introduced refrigerant into high-temperature and high-pressure gas. The outdoor fan  112  may provide the compressed refrigerant with air flow (or pressure) generated based on rotation thereof. 
     The 4-way valve  310  may adjust a flow direction of refrigerant discharged from the compressor  111  in four directions (i.e., in four ways) according to an operation mode (e.g., a cooling mode or a heating mode). The first branch  340  may be connected to at least one of indoor units  120  to  140  through pipes. The first branch  340  may connect the at least one of indoor units  120  to  140  to the 4-way valve  310 . 
     An electronic expansion valve  330  may be connected to the outdoor heat exchanger  320  and may be connected to the at least one of indoor units  120  to  140  through pipes connected to a second branch  342 . The outdoor heat exchanger  320  may condense refrigerant discharged through the 4-way valve  310  or receive refrigerant compressed by the compressor  111  to exchange heat with outdoor air. 
     The at least one of expansion valves  113   a  to  113   c  may be connected to the at least one of indoor units  120  to  140  and may expand and discharge refrigerant condensed by the outdoor heat exchanger  320 . The at least one of expansion valves  113   a  to  113   c  connected to an indoor unit #1 to an indoor unit #3 are shown; however, types of the expansion valves are not limited. Expansion valve  113   d  connected to indoor unit #4, expansion valve  113   e  connected to indoor unit #5, expansion valve  113   f  connected to an indoor unit #6, expansion valve  113   g  connected to indoor unit #7, expansion valve  113   c  connected to indoor unit #8, and expansion valve  113   i  connected to indoor unit #9 may be further added. 
     The load driver  114  may control a rotational load of the outdoor fan  112 . The controller  115  may control operations of the compressor  111 , the outdoor heat exchanger  320 , and the expansion valves  113   a  to  113   c.    
     The outdoor temperature sensor  116   a  may detect an outdoor temperature. The pipe temperature sensor  116   b  may detect a temperature of the pipe through which the refrigerant flows. The discharge temperature sensor  116   c  may detect a temperature of the refrigerant discharged through the pipe. The temperature sensor  116  may convert a temperature signal detected by each of the outdoor temperature sensor  116   a , the pipe temperature sensor  116   b , and the discharge temperature sensor  116   c  into digital data and transmit the digital data to the controller  115 . 
     The pressure sensor  117  may detect a discharge pressure of the pipe. 
     The communicator  118  may communicate with the at least one of indoor units  120  to  140  by wire or wirelessly. 
     Indoor unit #1  120  may include first indoor heat exchanger (ID_Hex #1), indoor unit #2  130  may include second indoor heat exchanger (ID_Hex #2), indoor unit #3 may include third indoor heat exchanger (ID_Hex #3), and indoor unit #4 may include fourth indoor heat exchanger (ID_Hex #4). Similarly, indoor unit #9 may include ninth indoor heat exchanger (ID_Hex #9). This is exemplary and embodiments are not limited thereto. This arrangement may be applied to a plurality of indoor units. For example, this arrangement may also be applied to an 11th indoor unit or a 20th indoor unit. In this embodiment, indoor unit #1  120  may be referred to as indoor unit #1 (ID_Hex #1), indoor unit #2  130  may be referred to as indoor unit #2 (ID_Hex #2), indoor unit #3  3  may be referred to as indoor unit #3 (ID_Hex #3), and indoor unit #4 may be referred to as indoor unit #4 (ID_Hex #4). 
     Referring to  FIG.  2   , indoor unit  120 ,  130  according to an embodiment may include a communicator  121 ,  131 , at least one temperature sensor  122 ,  132 , at least one indoor temperature sensor  122   a ,  132   a , one or more pipes temperature sensors  122   b ,  132   b , a controller  123 ,  133 , a load driver  124 ,  134 , a vane  125   a ,  135   a , one or more indoor fans  125   b ,  135   b , one or more displays  126 ,  136 , and a remote receiver  127 ,  137 . Referring to  FIG.  2   , the indoor units  120  to  130  according to an embodiment may be equipped with the same components. However, they may also be different in their structure. 
     In  FIG.  2   , only internal components of indoor unit #1  120  and indoor unit #2  130  are shown. The indoor unit #3 to the indoor unit #9  140  may have the same components and the same functions as the indoor unit #1  120  and the indoor unit #2  130 . 
     The communicators  121  and  131  may communicate with the outdoor unit  110  by wire/wirelessly and transmit and receive data to and from the outdoor unit  110 . 
     Any one of the one or more temperature sensors  122  and  132  may convert temperature signals detected by the one or more indoor temperature sensors  122   a  and  132   a  and the one or more pipe temperature sensors  122   b  and  132   b  into digital data and transmit the digital data to the respective controllers  123  and  133 . The one or more indoor temperature sensors  122   a  and  132   a  may detect a temperature of an indoor space in which each indoor unit is installed. The one or more pipe temperature sensors  122   b  and  132   b  may detect a temperature of a pipe connected to each indoor unit. 
     The respective controllers  123 ,  133  of the indoor units may control operations of internal components of each indoor unit. The one or more load drivers  124  and  134  may control a rotational load of the vanes  125   a  and  135   a  and the indoor fans  125   b  and  135   b  under control of the controllers  123  and  133 . The vanes  125   a  and  135   a  and the indoor fans  125   b  and  135   b  may discharge refrigerant into the indoor space based on the rotation. 
     The displays  126  and  136  may indicate an operating state of each indoor unit. The remote receivers  127  and  137  may wirelessly receive the pipe address information from the remote controller  10 . 
     Configurations not shown in the drawings, for example, in  FIGS.  1  to  3   , and operations not described in embodiments may be the same as configurations and operations of air conditioners, which are known in the same technical field. 
       FIG.  4    is a flowchart of a method for detecting an incorrectly connected pipe of an air conditioner according to an embodiment. Referring to  FIG.  4   , for air conditioner  100  according to an embodiment, at least one of indoor units  120  to  140  may receive pipe address information from remote controller  10  and transmit the pipe address information to outdoor unit  110  (S 410 ). 
     For example, the remote controller  10  may input first pipe address information to indoor unit #1  120 , input second pipe address information to indoor unit #2  130 , input third pipe address information to indoor unit #3 (ID_Hex #3) according to an input operation by users or managers. Similarly, the remote controller  10  may input pipe address information to indoor unit #9  140 . That is, the remote controller  10  may input a ninth pipe address information to the indoor unit #9  140 . 
     Subsequently, the indoor unit #1  120  may transmit the first pipe address information to the outdoor unit  110  through communicator  121  and the indoor unit #2  130  may transmit the second pipe address information to the outdoor unit  110  through communicator  131 . Similarly, indoor unit #3 (ID_Hex #3) to indoor unit #9  140  may transmit pipe address information to the outdoor unit  110  through the communicators. 
     Subsequently, the outdoor unit  110  may set a pipe address for the at least one indoor unit based on the pipe address information received from the indoor units  120  to  140  (S 420 ). That is, the controller  115  of the outdoor unit  110  may set the pipe address for the at least one of indoor units  120  to  140  by allocating the pipe address information received from the at least one of indoor units  120  to  140  to the indoor units (e.g., ID_Hex #1 to ID_Hex #4) and storing the pipe address information to a memory thereof, as shown in  FIG.  6   . 
     Subsequently, the outdoor unit  110  may determine the pipe address information received from the at least one of indoor units  120  to  140  as normal information or abnormal information (S 430 ). That is, the controller  115  of the outdoor unit  110  may detect an error to determine whether a duplicate pipe address is allocated to the at least one of indoor units  120  to  140 . Additionally, or alternatively, the controller  115  of the outdoor unit  110  may detect whether an allocation of the pipe address to the at least one of indoor units  120  to  140  is omitted, as shown in  FIG.  6   . 
     Subsequently, the outdoor unit  110  may detect an incorrectly connected pipe among pipes connected to the at least one of indoor units  120  to  140  (S 440 ). Basically, this subsequently checking whether there is an incorrectly connected pipe among the pipes includes the checking of temperatures in some or more pipes. 
     A procedure of subsequently checking whether there is an incorrectly connected pipe among the pipes depends on how many indoor units are connected to the outdoor unit. So, depending on the number of indoor units connected to the outdoor unit, different checking procedures may be performed. 
     That is, the controller  115  of the outdoor unit  110  operates the compressor  111  and controls the electronic expansion valves  113   a  to  113   c  allocated to the at least one indoor unit to introduce refrigerant discharged from the compressor  111  into the at least one indoor unit and determines allocation of a communication address and the pipe address to the at least one indoor unit as a normal allocation or an abnormal allocation based on a temperature change of a pipe temperature sensor configured to detect a temperature of a pipe connected to each of the at least one indoor unit to detect whether pipes are incorrectly connected. In this case, the controller  115  of the outdoor unit  110  may perform a serial pipe inspection when three or less indoor units are connected through the pipes and perform a group pipe inspection when four or more indoor units are connected through the pipes. 
       FIG.  5    is a flowchart of a method for performing pipe inspection by an outdoor unit of an air conditioner according to an embodiment. Referring to  FIG.  5   , according to this embodiment, controller  115  of outdoor unit  110  may determine allocation or non-allocation of a pipe address to at least one of indoor units  120  to  140  (S 502 ). 
     The controller  115  of the outdoor unit  110  may allocate the pipe address information received from the at least one of indoor units  120  to  140  to the indoor units (e.g., ID_Hex #1 to ID_Hex #4) and store the pipe address information in a memory thereof, as shown in  FIG.  6   . 
       FIG.  6    shows example pipe address information allocated to each indoor unit, by an outdoor unit, and stored in the outdoor unit, and detection results thereof. As shown in  FIG.  6   , the controller  115  of the outdoor unit  110  may receive first pipe address information or second pipe address information from the indoor unit #1  120  and store the first pipe address information or the second pipe address information. In addition, for example, the controller  115  of the outdoor unit  110  may receive second pipe address information, the first pipe address information, or fourth pipe address information from the indoor unit #2  130 . In addition, for example, the controller  115  of the outdoor unit  110  may receive third pipe address information from the indoor unit #3 (ID_Hex #3) and store the third pipe address information. 
     When the pipe address is assigned to the at least one of indoor units  120  to  140  (corresponding to “Yes” at S 502 ), the controller  150  of the outdoor unit  110  may detect an error, such as allocation of a duplicate pipe address to the at least one of indoor units  120  to  140  and/or omission of the pipe address allocation to the at least one of indoor units  120  to  140  (S 504 ). 
     For example, as shown in  FIG.  6   , the controller  115  of the outdoor unit  110  may determine a state in which a first pipe is allocated to the indoor unit #1 (ID_Hex #1), a second pipe is allocated to the indoor unit #2 (ID_Hex #2), and a third pipe is allocated to the indoor unit #3 (ID_Hex #3) as a normal state. In addition, as shown in  FIG.  6   , the controller  115  of the outdoor unit  110  may determine a state in which pipes are cross-connected to the indoor unit #1 (ID_Hex #1) and the indoor unit #2 (ID_Hex #2), that is, the second pipe is allocated to the indoor unit #1 (ID_Hex #1) and the first pipe is allocated to the indoor unit #2 (ID_Hex #2), and the third pipe is allocated to the indoor unit #3 (ID_Hex #3) as an undetectable state. Such result might be output at the outdoor unit and/or the indoor unit to inform the user or manager of the air conditioner. 
     In addition, as shown in  FIG.  6   , the controller  115  of the outdoor unit  110  may determine a state in which the first pipe is allocated to the indoor unit #1 (ID_Hex #1), the fourth pipe is allocated to the indoor unit #2 (ID_Hex #2), and the third pipe is allocated to the indoor unit #3 (ID_Hex #3) as an error state in which allocation of a second pipe is omitted. Such a result might be output at the outdoor unit and/or the indoor unit to inform the user or manager of the air conditioner. 
     In addition, as shown in  FIG.  6   , the controller  115  of the outdoor unit  110  may determine a state in which the first pipe is allocated to the indoor unit #1 (ID_Hex #1), the first pipe is also allocated to the indoor unit #2 (ID_Hex #2), and the third pipe is allocated to the indoor unit #3 (ID_Hex #3) as a duplicate error state in which the first pipe is allocated to the indoor unit #1 (ID_Hex #1) and the indoor unit #2 (ID_Hex #2). This error may be output. 
     Subsequently, the controller  115  of the outdoor unit  110  may perform a pipe inspection in a light mode (S 506 ). The light mode is a mode in which the pipe inspection is performed when a reference value for a temperature change of an indoor heat exchanger is a value “A”. A normal mode is a mode in which a pipe inspection is performed when a reference value for a temperature change of the indoor heat exchanger is a value “B”. In this case, “A” is less than “B” (i.e., A&lt;B). So in a case of no address allocation or erroneously address allocation a normal pipe inspection is performed. 
     That is, the controller  115  of the outdoor unit  110  may set a threshold value for temperature change of each indoor heat exchanger as “A” and performs the pipe inspection in the light mode (S 508 ). Subsequently, the controller  115  of the outdoor unit  110  determines whether a predefined number, e.g. three or less indoor units are connected to the outdoor unit  110  through pipes (S 510 ), and when the predefined number, e.g. three or less indoor units are connected to the outdoor unit  110  through the pipes (corresponding to “Yes” at S 510 ), performs a serial pipe inspection (S 512 ). 
     According to this embodiment, the serial pipe inspection may be performed by sequentially detecting incorrectly connected pipes among the first pipe to the third pipe connected to the indoor unit #1 to the indoor unit #3. When the three indoor units are connected to the outdoor unit  110 , for example, the first pipe is connected to the indoor unit #1 (ID_Hex #1), the second pipe is connected to the indoor unit #2 (ID_Hex #2), and the third pipe is connected to the indoor unit #3 (ID_Hex #3), the controller  115  of the outdoor unit  110  controls electronic expansion valves  113   a  to  113   c  allocated to the indoor unit #1 to the indoor unit #3 to introduce refrigerant discharged from the compressor  111  into the indoor unit #1 to the indoor unit #3 and determines allocation of a communication address and the pipe address to the indoor unit #1 to the indoor unit #3 as normal allocation or abnormal allocation based on a temperature change of a pipe temperature sensor configured to detect a temperature of pipes connected to the indoor units to detect an incorrectly connected pipe. 
     Subsequently, the controller  115  of the outdoor unit  110  controls the compressor  111  to be operated (S 514 ) and controls electronic expansion valves  113   a  to  113   c  allocated to the indoor unit #1 to the indoor unit #3 as follows (S 516 ). For example, during a first time period (t 1 ), the controller  115  of the outdoor unit  110  opens the electronic expansion valve  113   a  connected to the indoor unit #1 (ID_Hex #1), closes the electronic expansion valve  113   b  connected to the indoor unit #2 (ID_Hex #2) and the electronic expansion valve  113   c  connected to the indoor unit #3 (ID_Hex #3), introduces refrigerant to the indoor unit #1 (ID_Hex #1) connected to the open electronic expansion valve, and determines communication address allocation and pipe address allocation to the indoor unit #1 (ID_Hex #1) as normal allocation or abnormal allocation based on a temperature change of a pipe temperature sensor of the indoor unit #1 (ID_Hex #1). 
     Subsequently, during a second time period (t 2 ), the controller  115  of the outdoor unit  110  opens the electronic expansion valve connected to the indoor unit #2 (ID_Hex #2), closes electronic expansion valves connected to the indoor unit #1 (ID_Hex #1) and the indoor unit #3 (ID_Hex #3), introduces refrigerant to the indoor unit #2 (ID_Hex #2) connected to the opened electronic expansion valve, and determines communication address allocation and pipe address allocation to the indoor unit #2 (ID_Hex #2) as normal allocation or abnormal allocation based on a temperature change of a pipe temperature sensor of the indoor unit #2 (ID_Hex #2). Subsequently, during a third time period (t 3 ), the controller  115  of the outdoor unit  110  opens the electronic expansion valve connected to the indoor unit #3 (ID_Hex #3), closes the electronic expansion valve connected to the indoor unit #1 (ID_Hex #1) and the electronic expansion valve connected to the indoor unit #2 (ID_Hex #2), introduces refrigerant into the indoor unit #3 (ID_Hex #3) connected to the opened electronic expansion valve, and determines communication address allocation and pipe address allocation to the indoor unit #3 (ID_Hex #3) as normal allocation or abnormal allocation based on a temperature change of a pipe temperature sensor of the indoor unit #3 (ID_Hex #3). 
     Based on the determination that the pipes are normally connected to the indoor units, the controller  115  of the outdoor unit  110  allocates an nth pipe to an nth indoor unit (S 518 ). For example, the controller  115  of the outdoor unit  110  allocates first pipe address information to the indoor unit #1 (ID_Hex #1), allocates the second pipe address information to the indoor unit #2 (ID_Hex #2), and allocates the third pipe address information to the indoor unit #3 (ID_Hex #3), stores and records the pipe address information in a memory thereof. 
     When the pipe address is not allocated (corresponding to “No” at S 502 ), the controller  115  of the outdoor unit  110  performs a pipe inspection in a normal mode (S 520 ). In this case, the controller  115  of the outdoor unit  110  performs the pipe inspection when a reference threshold value for the temperature change of each indoor heat exchanger is set to be “B” (S 522 ). 
     The threshold value B in the normal mode is greater than the threshold value A in the light mode (i.e., A&lt;B). That is, in the normal mode, the controller  115  of the outdoor unit  110  performs the pipe inspection for the indoor units having the greater temperature change value of the indoor heat exchanger in the normal mode than that of the indoor heat exchanger in the light mode. 
     Based on the four or more indoor units being connected to the outdoor unit  110  (corresponding to “No” at S 510 ), the controller  115  of the outdoor unit  110  performs a group pipe inspection (S 530 ), as shown in  FIG.  7   .  FIG.  7    shows an example of performing a group pipe inspection by an air conditioner according to an embodiment. 
     In the group pipe inspection, when the four or more indoor units are connected to the outdoor unit  110  through the pipes, the pipe inspection is performed for each group by grouping three indoor units into one group among the four or more indoor units. As shown in  FIG.  7   , nine indoor units are connected to the outdoor unit  110  through pipes in this embodiment. 
     For example, the controller  115  of the outdoor unit  110  groups indoor unit #1 (ID_Hex #1), indoor unit #2 (ID_Hex #2), and indoor unit #3 (ID_Hex #3) into a first group, groups indoor unit #4 (ID_Hex #4), indoor unit #5 (ID_Hex #5), and indoor unit #6 (ID_Hex #6) into a second group, and groups indoor unit #7 (ID_Hex #7), eight indoor unit (ID_Hex #8), and indoor unit #9 (ID_Hex #9) into a third group. In this case, the first pipe may be connected to the indoor unit #1 (ID_Hex #1), the second pipe may be connected to the indoor unit #2 (ID_Hex #2), the third pipe may be connected to the indoor unit #3 (ID_Hex #3), the fourth pipe may be connected to the indoor unit #4 (ID_Hex #4), the fifth pipe may be connected to the indoor unit #5 (ID_Hex #5), the sixth pipe may be connected to the indoor unit #6 (ID_Hex #6), the seventh pipe may be connected to the indoor unit #7 (ID_Hex #7), the eighth pipe may be connected to the indoor unit #8 (ID_Hex #8), and the ninth pipe may be connected to the indoor unit #9 (ID_Hex #9). 
     According to this embodiment, the group pipe inspection may be performed by detecting incorrectly connected pipes for each group when the indoor units are grouped, and subsequently detecting a pipe incorrectly connected to an nth indoor unit in each group. For example, the controller  115  may detect the incorrectly connected pipes for the first group (including the indoor unit #1 to the indoor unit #3), the second group (including the indoor unit #4 to the indoor unit #6), and the third group (including the indoor unit #7 to the indoor unit #9) and detect pipes which are incorrectly connected to the nth indoor unit, for example, first indoor units in each group (e.g., the indoor unit #1, the indoor unit #4, and the indoor unit #7) and second indoor units in each group (e.g., the indoor unit #2, the indoor unit #5, and the indoor unit #8). 
     The controller  115  of the outdoor unit  110  may detect the pipe incorrectly connected to the indoor unit #1 to the indoor unit #3 corresponding to the first group. In this case, the controller  115  controls the compressor  111  to be operated (S 532 ) and controls electronic expansion valves  113   a  to  113   c  allocated to the indoor unit #1 to the indoor unit #3 corresponding to the first group as follows (S 534 ). For example, during a first time period (t 1 ), the controller  115  opens electronic expansion valves  113   a ,  113   b , and  113   c  connected to the indoor unit #1 (ID_Hex #1), the indoor unit #2 (ID_Hex #2), and the indoor unit #3 (ID_Hex #3) belonging to the first group and closes electronic expansion valves connected to the indoor unit #4 (ID_Hex #4) to the indoor unit #9 (ID_Hex #9) belonging to the second group and the third group. In addition, the controller  115  introduces refrigerant into the indoor unit #1 (ID_Hex #1), the indoor unit #2 (ID_Hex #2), and the indoor unit #3 (ID_Hex #3) connected to opened electronic expansion valve and determines communication address allocation and pipe address allocation to the indoor unit #1 (ID_Hex #1), the indoor unit #2 (ID_Hex #2), and the indoor unit #3 (ID_Hex #3) as normal allocation or abnormal allocation based on temperature changes of pipe temperature sensors of the indoor unit #1 (ID_Hex #1), the indoor unit #2 (ID_Hex #2), and the indoor unit #3 (ID_Hex #3) to identify whether the pipes are incorrectly connected. 
     Further, the controller  115  of the outdoor unit  110  may detect incorrectly connected pipes among pipes connected to the indoor unit #4 to the indoor unit #6 corresponding to the second group. For example, during a second time period (t 2 ), the controller  115  opens electronic expansion valves  113   d ,  113   e , and  113   f  connected to the indoor unit #4 (ID_Hex #4), the indoor unit #5 (ID_Hex #5), and the indoor unit #6 (ID_Hex #6) belonging to a second group and closes electronic expansion valves connected to the indoor unit #1 (ID_Hex #1) to the indoor unit #3 (ID_Hex #3) belonging to the first group and the indoor unit #7 (ID_Hex #7) to the indoor unit #9 (ID_Hex #9) belonging to the third group. In addition, the controller  115  introduces refrigerant into the indoor unit #4 (ID_Hex #4), the indoor unit #5 (ID_Hex #5), and the indoor unit #6 (ID_Hex #6) connected to the opened electronic expansion valve, and determines allocation of a communication address and the pipe address to the indoor unit #4 (ID_Hex #4), the indoor unit #5 (ID_Hex #5), and the indoor unit #6 (ID_Hex #6) as normal allocation or abnormal allocation based on temperature changes of pipe temperature sensors of the indoor unit #4 (ID_Hex #4), the indoor unit #5 (ID_Hex #5), and the indoor unit #6 (ID_Hex #6) to identify whether the pipes are incorrectly connected. 
     Furthermore, the controller  115  of the outdoor unit  110  may detect incorrectly connected pipes among pipes connected to the indoor unit #7 to the indoor unit #9 corresponding to the third group. For example, during a third time period (t 3 ), the controller  115  opens electronic expansion valves  113   g ,  113   h , and  113   i  connected to the indoor unit #7 (ID_Hex #7), the indoor unit #8 (ID_Hex #8), and the indoor unit #9 (ID_Hex #9) belonging to the third group and closes electronic expansion valves connected to the indoor unit #1 (ID_Hex #1) to the indoor unit #6 (ID_Hex #6) belonging to the first group and the second group. In addition, the controller  115  introduces refrigerant into the indoor unit #7 (ID_Hex #7), the indoor unit #8 (ID_Hex #8), and the indoor unit #9 (ID_Hex #9) connected to the opened electronic expansion valve and determines allocation of a communication address and the pipe address to the indoor unit #7 (ID_Hex #7), the indoor unit #8 (ID_Hex #8), and the indoor unit #9 (ID_Hex #9) as normal allocation or abnormal allocation based on temperature changes of pipe temperature sensors of the indoor unit #7 (ID_Hex #7), the indoor unit #8 (ID_Hex #8), and the indoor unit #9 (ID_Hex #9). 
     In addition, the controller  115  of the outdoor unit  110  may detect a pipe incorrectly connected to first indoor units in each group. For example, the controller  115  opens electronic expansion valves connected to the indoor unit #1 (ID_Hex #1) of the first group, the indoor unit #4 (ID_Hex #4) of the second group, and the indoor unit #7 (ID_Hex #7) of the third group, which correspond to the first indoor units in each group, and closes the electronic expansion valves connected to the indoor unit #2 (ID_Hex #2), the indoor unit #3 (ID_Hex #3), the indoor unit #5 (ID_Hex #5), the indoor unit #6 (ID_Hex #6), the indoor unit #8 (ID_Hex #8), and the indoor unit #9 (ID_Hex #9) during a fourth time period (t 4 ). In addition, the controller  115  introduces refrigerant into the indoor unit #1 (ID_Hex #1), the indoor unit #4 (ID_Hex #4), and the indoor unit #7 (ID_Hex #7) connected the opened electronic expansion valve and determines allocation of a communication address and the pipe address to the indoor unit #1 (ID_Hex #1), the indoor unit #4 (ID_Hex #4), and the indoor unit #7 (ID_Hex #7) as normal allocation or abnormal allocation based on temperature changes of pipe temperature sensors of the indoor unit #1 (ID_Hex #1), the indoor unit #4 (ID_Hex #4), and the indoor unit #7 (ID_Hex #7) to identify whether the pipes are incorrectly connected. 
     Also, the controller  115  of the outdoor unit  110  may detect incorrectly connected pipes among pipes connected to second indoor units in each group. For example, the controller  115  opens electronic expansion valves connected to the indoor unit #2 (ID_Hex #2) of the first group, the indoor unit #5 (ID_Hex #5) of the second group, and the indoor unit #8 (ID_Hex #8) of the third group, which correspond to the second indoor unit in each group and closes electronic expansion valves connected to the remaining first indoor unit (ID_Hex #1), third indoor unit (ID_Hex #3), fourth indoor unit (ID_Hex #4), sixth indoor unit (ID_Hex #6), seventh indoor unit (ID_Hex #7), and ninth indoor unit (ID_Hex #9). In addition, the controller  115  introduces refrigerant into the indoor unit #2 (ID_Hex #2), the indoor unit #5 (ID_Hex #5), and the indoor unit #8 (ID_Hex #8) connected to the opened electronic expansion valve, and determines allocation of a communication address and a pipe address to the indoor unit #2 (ID_Hex #2), the indoor unit #5 (ID_Hex #5), and the indoor unit #8 (ID_Hex #8) as normal allocation or abnormal allocation based on temperature changes of pipe temperature sensors of the indoor unit #2 (ID_Hex #2), the indoor unit #5 (ID_Hex #5), and the indoor unit #8 (ID_Hex #8) to identify whether the pipes are incorrectly connected. 
     Based on the determination that the pipes are normally allocated to the indoor units, the controller  115  of the outdoor unit  110  may allocate an nth pipe to an nth indoor unit (S 518 ). 
       FIG.  8    shows an example of performing a group pipe inspection when an air conditioner includes seven indoor units according to an embodiment. Referring to  FIG.  8   , according to an embodiment, air conditioner  100  may perform the group pipe inspection by grouping three indoor units into one group when seven or more indoor units are connected to an outdoor unit  110 . 
     For example, controller  115  of the outdoor unit  110  may group indoor unit #1 (ID_Hex #1), indoor unit #2 (ID_Hex #2), and indoor unit #3 (ID_Hex #3) into a first group, group indoor unit #4 (ID_Hex #4), indoor unit #5 (ID_Hex #5), and indoor unit #6 (ID_Hex #6) into a second group, and group indoor unit #7 (ID_Hex #7) into a third group. The indoor unit #1 (ID_Hex #1) may be connected to a first pipe, the indoor unit #2 (ID_Hex #2) may be connected to a second pipe, the indoor unit #3 (ID_Hex #3) may be connected to a third pipe, the indoor unit #4 (ID_Hex #4) may be connected to a fourth pipe, the indoor unit #5 (ID_Hex #5) may be connected to the fifth pipe, the indoor unit #6 (ID_Hex #6) may be connected to the sixth pipe, and the indoor unit #7 (ID_Hex #7) may be connected to a seventh pipe. 
     The group pipe inspection for the seven indoor units may be performed by detecting incorrectly connected pipes for each group and subsequently detecting pipes incorrectly connected to an nth indoor unit in each group. For example, the controller  115  detects incorrectly connected pipes among the pipes connected to the indoor units for the first group (including the indoor unit #1 to the indoor unit #3), the second group (including the indoor unit #4 to the indoor unit #6), and the third group (including the indoor unit #7) and subsequently detects incorrectly connected pipes among the pipes connected to the nth indoor unit in each group, for example, first indoor units in each group (e.g., the indoor unit #1, the indoor unit #4, and the indoor unit #7) and second indoor units in each group (e.g., the indoor unit #2 and the indoor unit #5). 
     The controller  115  of the outdoor unit  110  detects the pipes incorrectly connected to the indoor unit #1 to the indoor unit #3 corresponding to the first group. In this case, the controller  115  controls the compressor  111  to be operated and controls the electronic expansion valves  113   a  to  113   c  allocated to the indoor unit #1 to the indoor unit #3 belonging to the first group as follows. For example, during a first time period (t 1 ), the controller  115  opens electronic expansion valves  113   a ,  113   b , and  113   c  connected to the indoor unit #1 (ID_Hex #1), the indoor unit #2 (ID_Hex #2), and the indoor unit #3 (ID_Hex #3) belonging to a first group and closes electronic expansion valves connected to the indoor unit #4 (ID_Hex #4) to the indoor unit #7 (ID_Hex #7) belonging to the remaining second group and the third group. In addition, the controller  115  introduces refrigerant into the indoor unit #1 (ID_Hex #1), the indoor unit #2 (ID_Hex #2), and the indoor unit #3 (ID_Hex #3) connected to the opened electronic expansion valve and determines allocation of a communication address and a pipe address to the indoor unit #1 (ID_Hex #1), the indoor unit #2 (ID_Hex #2), and the indoor unit #3 (ID_Hex #3) as normal allocation or abnormal allocation based on temperature change of pipe temperature sensors of the indoor unit #1 (ID_Hex #1), the indoor unit #2 (ID_Hex #2), and the indoor unit #3 (ID_Hex #3) to identify whether the pipes are incorrectly connected. 
     Subsequently, the controller  115  of the outdoor unit  110  detects pipes incorrectly connected to the indoor unit #4 to the indoor unit #6 corresponding to the second group. For example, during a second time period (t 2 ), the controller  115  opens electronic expansion valves  113   d ,  113   e  and  113   f  connected to the indoor unit #4 (ID_Hex #4), the indoor unit #5 (ID_Hex #5), and the indoor unit #6 (ID_Hex #6) belonging to a second group and closes electronic expansion valve connected to the indoor unit #1 (ID_Hex #1) to the indoor unit #3 (ID_Hex #3) belonging to the first group and the indoor unit #7 (ID_Hex #7) belonging to the third group. In addition, the controller  115  introduces refrigerant into the indoor unit #4 (ID_Hex #4), the indoor unit #5 (ID_Hex #5), and the indoor unit #6 (ID_Hex #6) connected to the opened electronic expansion valve, and determines allocation of a communication address and the pipe address to the indoor unit #4 (ID_Hex #4), the indoor unit #5 (ID_Hex #5), and the indoor unit #6 (ID_Hex #6) as normal allocation or abnormal allocation based on temperature changes of pipe temperature sensors of the indoor unit #4 (ID_Hex #4), the indoor unit #5 (ID_Hex #5), and the indoor unit #6 (ID_Hex #6) to identify whether the pipes are incorrectly connected. 
     Subsequently, the controller  115  of the outdoor unit  110  detects pipes incorrectly connected to the indoor unit #7 corresponding to the third group. For example, during a third time period (t 3 ), the controller  115  opens an electronic expansion valve  113   g  connected to the indoor unit #7 (ID_Hex #7) in the third group and closes the electronic expansion valves connected to the indoor unit #1 (ID_Hex #1) to the indoor unit #6 (ID_Hex #6) belonging to the first group and the second group. In addition, the controller  115  introduces refrigerant into the indoor unit #7 (ID_Hex #7) connected to the opened electronic expansion valve and determines allocation of a communication address and pipe address to the indoor unit #7 (ID_Hex #7) as normal allocation or abnormal allocation based on a temperature change of a pipe temperature sensor of the indoor unit #7 (ID_Hex #7) to identify whether pipe are incorrectly connected. 
     Subsequently, the controller  115  of the outdoor unit  110  may detect pipes incorrectly connected to first indoor units in each group. For example, during a fourth time period (t 4 ), the controller  115  opens electronic expansion valves connected to the indoor unit #1 (ID_Hex #1) of the first group, the indoor unit #4 (ID_Hex #4) of the second group, and the indoor unit #7 (ID_Hex #7) of the third group, which correspond to the first indoor units in each group and closes the electronic expansion valve connected to the indoor unit #2 (ID_Hex #2), the indoor unit #3 (ID_Hex #3), the indoor unit #5 (ID_Hex #5), and the indoor unit #6  6  (ID_Hex #6). In addition, the controller  115  introduces refrigerant into the indoor unit #1 (ID_Hex #1), the indoor unit #4 (ID_Hex #4), and the indoor unit #7 (ID_Hex #7) connected to the opened electronic expansion valve, and determines allocation of a communication address and the pipe address to the indoor unit #1 (ID_Hex #1), the indoor unit #4 (ID_Hex #4), and the indoor unit #7 (ID_Hex #7) as normal allocation or abnormal allocation based on temperature changes of pipe temperature sensors of the indoor unit #1 (ID_Hex #1), the indoor unit #4 (ID_Hex #4), and the indoor unit #7 (ID_Hex #7) to identify whether the pipes are incorrectly connected. 
     Subsequently, the controller  115  of the outdoor unit  110  may detect pipes incorrectly connected to second indoor units in each group. For example, during a fifth time period (t 5 ), the controller  115  opens an electronic expansion valve connected to the indoor unit #2 (ID_Hex #2) of the first group and the indoor unit #5 (ID_Hex #5) of the second group, which correspond to the second indoor unit of each group, and closes the electronic expansion valves connected to the remaining first indoor unit (ID_Hex #1), third indoor unit (ID_Hex #3), fourth indoor unit (ID_Hex #4), sixth indoor unit (ID_Hex #6), and seventh indoor unit (ID_Hex #7). In addition, the controller  115  introduces refrigerant into the indoor unit #2 (ID_Hex #2) and the indoor unit #5 (ID_Hex #5) connected to the opened electronic expansion valve and determines allocation of a communication address and the pipe address to the indoor unit #2 (ID_Hex #2) and the indoor unit #5 (ID_Hex #5) as normal allocation or abnormal allocation based on temperature changes of pipe temperature sensors of the indoor unit #2 (ID_Hex #2) and the indoor unit #5 (ID_Hex #5) to identify whether the pipes are incorrectly connected. 
     Based on the determination that the pipes are normally connected to the indoor units, the controller  115  of the outdoor unit  110  may allocate an nth pipe to an nth indoor unit. 
       FIG.  9    shows an example of performing a group pipe inspection when an air conditioner includes five indoor units according to an embodiment. Referring to  FIG.  9   , air conditioner  100  according to an embodiment may perform the group pipe inspection by grouping three indoor units into one group when five or more indoor units are connected to an outdoor nit  110  through pipes. 
     For example, controller  115  of the outdoor unit  110  may group indoor unit #1 (ID_Hex #1), indoor unit #2 (ID_Hex #2), and indoor unit #3 (ID_Hex #3) into a first group and group indoor unit #4 (ID_Hex #4) and indoor unit #5 (ID_Hex #5) into a second group. In this case, the indoor unit #1 (ID_Hex #1) may be connected to a first pipe, the indoor unit #2 (ID_Hex #2) may be connected to a second pipe, the indoor unit #3 (ID_Hex #3) may be connected to a third pipe, the indoor unit #4 (ID_Hex #4) may be connected to a fourth pipe, and the indoor unit #5 (ID_Hex #5) may be connected to a fifth pipe. 
     The group pipe detection for the five indoor units may be performed by detecting incorrectly connected pipes for each group and subsequently detecting pipes incorrectly connected to an nth indoor unit in each group. For example, the controller  115  detects the pipes incorrectly connected to the indoor unit for the first group (including the indoor unit #1 to the indoor unit #3) and the second group (including the indoor unit #4 and the indoor unit #5) and subsequently detects the pipes incorrectly connected to the nth indoor unit in each group, for example, the indoor unit #1 in each group (e.g., the indoor unit #1 and the indoor unit #4) and the indoor unit #2 in each group (e.g., the indoor unit #2 and the indoor unit #5). 
     The controller  115  of the outdoor unit  110  detects pipes incorrectly connected to the indoor unit #1 to the indoor unit #3 corresponding to the first group. In this case, the controller  115  controls compressor  111  to be operated and controls electronic expansion valves  113   a  to  113   c  allocated to the indoor unit #1 to the indoor unit #3 corresponding to the first group as follows. For example, during a first time period (t 1 ), the controller  115  opens the electronic expansion valves  113   a ,  113   b , and  113   c  connected to the indoor unit #1 (ID_Hex #1), the indoor unit #2 (ID_Hex #2), and the indoor unit #3 (ID_Hex #3) belonging to the first group and closes electronic expansion valves connected to the indoor unit #4 (ID_Hex #4) and the indoor unit #5 (ID_Hex #5) belonging to the second group. In addition, the controller  115  introduces refrigerant into the indoor unit #1 (ID_Hex #1), the indoor unit #2 (ID_Hex #2), and the indoor unit #3 (ID_Hex #3) connected to the opened electronic expansion valve and determines allocation of a communication address and the pipe address to the indoor unit #1 (ID_Hex #1), the indoor unit #2 (ID_Hex #2), and the indoor unit #3 (ID_Hex #3) as normal allocation or abnormal allocation based on temperature changes of pipe temperature sensors of the indoor unit #1 (ID_Hex #1), the indoor unit #2 (ID_Hex #2), and the indoor unit #3 (ID_Hex #3) to identify whether the pipes are incorrectly connected. 
     Subsequently, the controller  115  of the outdoor unit  110  detects pipes incorrectly connected to the indoor unit #4 and the indoor unit #5 belonging to the second group. For example, during a second time period (t 2 ), the controller  115  opens the electronic expansion valves  113   d  and  113   e  connected to the indoor unit #4 (ID_Hex #4) and the indoor unit #5 (ID_Hex #5) belonging to the second group and closes the electronic expansion valve connected to the indoor unit #1 (ID_Hex #1) to the indoor unit #3 (ID_Hex #3) belonging to the remaining first group. In addition, the controller  115  introduces refrigerant into the indoor unit #4 (ID_Hex #4) and the indoor unit #5 (ID_Hex #5) connected to the opened electronic expansion valve and determines allocation of a communication address and the pipe address to the indoor unit #4 (ID_Hex #4) and the indoor unit #5 (ID_Hex #5) as normal allocation or abnormal alocation based on temperature changes of pipe temperature sensors of the indoor unit #4 (ID_Hex #4) and the indoor unit #5 (ID_Hex #5) to identify whether the pipes are incorrectly connected. 
     Subsequently, the controller  115  of the outdoor unit  110  may detect pipes incorrectly connected to a first indoor unit in each group. For example, during a third time period (t 3 ), the controller  115  opens the electronic expansion valves connected to the indoor unit #1 (ID_Hex #1) of the first group and the indoor unit #4 (ID_Hex #4) of the second group, which correspond to the first indoor unit in each group, and closes the electronic expansion valves connected to the indoor unit #2 (ID_Hex #2), the indoor unit #3 (ID_Hex #3), and the indoor unit #5 (ID_Hex #5). In addition, the controller  115  introduces refrigerant into the indoor unit #1 (ID_Hex #1) and the indoor unit #4 (ID_Hex #4) connected to the opened electronic expansion valve determines allocation of a communication address and the pipe address to the indoor unit #1 (ID_Hex #1) and the indoor unit #4 (ID_Hex #4) as normal allocation or abnormal allocation based on temperature changes of pipe temperature sensors of the indoor unit #1 (ID_Hex #1) and the indoor unit #4 (ID_Hex #4) to identify whether the pipes are incorrectly connected. 
     Subsequently, the controller  115  of the outdoor unit  110  may detect pipes incorrectly connected to a second indoor unit in each group. For example, during a fourth time period (t 4 ), the controller  115  opens the electronic expansion valves connected to the indoor unit #2 (ID_Hex #2) of the first group and the indoor unit #5 (ID_Hex #5) of the second group, which correspond to the second indoor units in each group, and closes the electronic expansion valves connected to the remaining first indoor unit (ID_Hex #1), third indoor unit (ID_Hex #3), and fourth indoor unit (ID_Hex #4). In addition, the controller  115  introduces refrigerant into the indoor unit #2 (ID_Hex #2) and the indoor unit #5 (ID_Hex #5) connected to the opened electronic expansion valve and determines allocation of a communication address and the pipe address to the indoor unit #2 (ID_Hex #2), and the indoor unit #5 (ID_Hex #5) as normal allocation or abnormal allocation based on temperature changes of pipe temperature sensors of the indoor unit #2 (ID_Hex #2) and the indoor unit #5 (ID_Hex #5) to identify whether the pipes are incorrectly connected. Subsequently, based on the determination that the pipes are normally connected to the indoor units, the controller  115  of the outdoor unit  110  may allocate an nth pipe to an nth indoor unit. 
     According to embodiments disclosed herein, when four or more indoor units are connected to the outdoor unit, incorrectly connected pipes may be detected for each group by grouping three indoor units into one group. Further, according to embodiments disclosed herein, even if the pipe addresses are allocated by inputting pipe address data through the input means from outside, the pipe connection errors (e.g., the duplication or the omission) may be detected through the error detection according to embodiments disclosed herein. Furthermore, the pipe detection may be performed in parallel, thereby reducing detection time thereof. 
     A time period for which the incorrectly connected pipe is detected may be reduced by adjusting a temperature change reference value of the pipe of the indoor unit, compared to an operation of setting the pipe address and an address temperature based on data input by the user. The pipe inspection may be performed by changing a state of the electronic expansion valve from a closed state to an open state, thereby reducing the pipe inspection time period. 
     Embodiments disclosed herein provide an air conditioner capable of detecting incorrectly connected pipes among the pipes connecting the outdoor unit to the indoor units, and a method for detecting an incorrectly connected pipe in an air conditioner thereof. Further, embodiments disclosed herein provide an air conditioner capable of easily detecting an incorrectly connected pipe among pipes connecting an outdoor unit to indoor units and a method for detecting an incorrectly connected pipe in an air conditioner. Furthermore, embodiments disclosed herein provide an air conditioner capable of recognizing an incorrectly connected pipe among pipes and which is further able to quickly check a correctness of the connection of pipes and/or which is able to differentiate a process of checking depending on a number of indoor units connected. 
     Embodiments are not limited to what has been described. Additionally, other advantages which are not mentioned may be understood by the description and more clearly understood based on the embodiments. Further, it will be readily understood that the advantages of embodiments disclosed herein may be implemented by features defined in claims and a combination thereof. 
     An air conditioner and method according to embodiments disclosed herein should be able to only check a temperature-change portion of an indoor heat exchanger when detecting an incorrectly connected pipe among pipes connecting an outdoor unit to the indoor units, without waiting for stabilization of all cycles, thereby shortening a time period for which the incorrectly connected pipe is detected. 
     Further, the air conditioner according to embodiments disclosed herein can easily differentiate which way of checking is performed depending on the number of indoor units connected. 
     For an air conditioner according to embodiments disclosed herein, at least one indoor unit may be connected to an outdoor unit through pipes, each indoor unit may transmit pipe address information received from a remote controller to the outdoor unit, and the outdoor unit may determine whether there is an abnormality in the pipe address information received from each indoor unit, and perform a pipe inspection depending on a number of indoor units connected to the outdoor unit. The outdoor unit may perform a serial pipe inspection when predetermined number of indoor unit, for example, three or less indoor units, are connected to the outdoor unit through the pipes, and perform a group pipe inspection when more than the predetermined number of indoor units, for example, four or more indoor units, are connected to the outdoor unit through the pipes. 
     According to some embodiments, in the group pipe inspection, the outdoor unit may be configured to detect the pipe incorrectly connected to the indoor unit for each group and subsequently detect a pipe incorrectly connected to an nth indoor unit in each group. In the serial pipe inspection, the outdoor unit may be configured to sequentially detect pipes incorrectly connected to the indoor units. 
     According to some embodiments, the outdoor unit may include a compressor configured to discharge refrigerant, a 4-way valve configured to adjust a flow direction of the discharged refrigerant in four directions, a branch configured to connect the at least one indoor unit to the 4-way valve, an outdoor heat exchanger configured to heat-exchange the refrigerant with outdoor air, at least one expansion vale connected to the at least one indoor unit, and a controller configured to control an air-conditioning operation of the outdoor unit. The outdoor unit may include at least one of: a communicator configured to communicate with the indoor unit, an outdoor temperature sensor configured to detect an outdoor temperature, a pipe temperature sensor configured to detect a temperature of the pipe, a discharge temperature sensor configured to detect a temperature of the discharged refrigerant, a pressure sensor configured to detect a discharge pressure of the refrigerant, or a temperature sensor configured to convert a temperature signal detected by each temperature sensor into digital data. 
     The outdoor unit may determine whether a duplicate pipe address is allocated to the at least one indoor unit and/or allocation of the pipe address to the at least one indoor unit is omitted based on the pipe address information received from the at least one indoor unit. 
     According to embodiments disclosed herein, in the serial pipe inspection, the outdoor unit may be configured to operate the compressor and control the expansion valve allocated to each indoor unit to introduce the refrigerant discharged from the compressor into the at least one indoor unit, open an electronic expansion valve connected to an indoor unit #1 and close remaining electronic expansion valves during a first time period, open an electronic expansion valve connected to the indoor unit #2 and close remaining electronic expansion valves during a second time period, open the electronic expansion valve connected to the indoor unit #3 and close remaining electronic expansion valves during a third time period to introduce the refrigerant into the indoor unit connected to the opened electronic expansion valve, and determine whether a communication address and the pipe address are each normally allocated to the at least one indoor unit based on a temperature change of the pipe temperature sensor. The outdoor unit may be configured to perform the group pipe inspection by grouping three indoor units into one group when four or more indoor units are connected through the pipes. In the group pipe inspection, the outdoor unit may be configured to operate the compressor and control an expansion valve allocated to each indoor unit to introduce refrigerant discharged from the compressor into the at least one indoor unit, open the electronic expansion valves connected to the indoor unit #1, the indoor unit #2, and the indoor unit #3 belonging to a first group and close remaining electronic expansion valves during a first time period, open electronic expansion valves connected to an indoor unit #4, an indoor unit #5, and an indoor unit #6 belonging to a second group and close remaining electronic expansion valves during a second time period, open electronic expansion valves connected to an indoor unit #7, an indoor unit #8, and an indoor unit #9 belonging to a third group and close remaining electronic expansion valves during a third time period, open electronic expansion valves connected to the indoor unit #1, the indoor unit #4, and the indoor unit #7, which correspond to a first indoor unit in each group and close remaining electronic expansion valves during a fourth time period, open electronic expansion valves connected to the indoor unit #2, the indoor unit #5, and the indoor unit #8, which correspond to a second indoor unit in each group and close remaining electronic expansion valves during a fifth time period, introduce the refrigerant into the indoor unit connected to the opened electronic expansion valve, and determine whether the communication address and the pipe address are normally allocated to the at least one indoor unit based on a temperature change of the pipe temperature sensor. 
     According to embodiments disclosed herein, the indoor unit may include a communicator configured to communicate with the outdoor unit, a remote receiver configured to receive the pipe address information, an indoor fan configured to discharge refrigerant into an indoor space, a controller configured to control a rotational load, an indoor temperature sensor configured to detect an indoor temperature, a pipe temperature sensor configured to detect a temperature of the pipe, a temperature sensor configured to covert the temperature detected by each temperature sensor into digital data, and a display configured to indicate an operating state of each component. 
     According to embodiments disclosed herein, a method for detecting an incorrectly connected pipe of an air conditioner may include receiving, by at least one indoor unit and from at least one remote controller, pipe address information and transmitting the pipe address information to an outdoor unit, setting, by the outdoor unit, pipe address for the at least one indoor unit based on the pipe address information, determining, by the outdoor unit, the pipe address information as normal information or abnormal information, and detecting, by the outdoor unit, an incorrectly connected pipe among pipes connected to the at least one indoor unit. In this case, the outdoor unit may be configured to perform a serial pipe inspection when three or less indoor units are connected to the outdoor unit through the pipes and may perform a group pipe inspection by grouping three indoor units into one group when four or more indoor units are connected to the outdoor unit through the pipes. 
     According to embodiments disclosed herein, the air conditioner may easily set an initial address value of a system for each indoor unit using an additional remote control device. Errors such as allocation of a duplicate address or omission of an address allocation may be detected within a shorter time than before based on an address value set for the indoor unit. Correct connection to all indoor units may be easily checked by detecting whether the pipes are cross-connected to the outdoor unit and the indoor units. 
     According to embodiments disclosed herein, when the four or more indoor units are connected to the outdoor unit through the pipes, the incorrectly connected pipes may be detected by grouping three indoor units into one group. In this case, as a large number of indoor units are connected, a stabilization time period of a refrigeration cycle may be reduced, and thus, a time period for which errors are detected may be reduced. 
     As addresses are already allocated to each indoor unit, a temperature change threshold of the indoor unit may be immediately applied to the indoor unit having the allocated address based on the address. In this case, the threshold change may be less than the threshold change in other inspection method. In addition, the indoor unit identified as being in an error state may be found based on the address thereof and the threshold may vary according to the corresponding to indoor unit and may be applied to the indoor unit. 
     According to embodiments disclosed herein, a state of the electronic expansion valve (EEV) may be changed from a closed state to an open state (i.e., Close→Open), not from the open state to the closed state (i.e., Open→Close), thereby facilitating the stabilization of the refrigeration cycle. 
     In the method in the related art, about four minutes of stabilization time may be consumed per one indoor unit, that is, 36 minutes of error detection time may be consumed for nine indoor units. In embodiments disclosed herein, three indoor units are grouped into one group among the nine indoor units and identification of the addresses of all indoor units may be completed by only five detections. That is, 20 minutes of detection time may be consumed. Therefore, the error detection by grouping in embodiments disclosed herein may consume a shorter time. 
     The error detection in embodiments disclosed herein may be performed by comparing with already known information. So, the error detection may be performed by identifying only a temperature change portion of an indoor heat exchanger without waiting for stabilization of all cycles. Therefore, the error detection time may be reduced from four minutes for each indoor unit to two minutes to a time period less than four minutes for each indoor unit. 
     According to embodiments disclosed herein, when the indoor units are sequentially inspected or when the indoor units are inspected by grouping to detect a pipe incorrectly connected to the indoor unit, inspection accuracy of the incorrectly connected pipe may be improved by differently setting a criteria to determine a normal inspection combination. 
     According to embodiments disclosed herein, even when an automatic inspection is performed in a state in which the address is not allocated to each indoor unit, inspection accuracy thereof may be improved by differently setting the criteria to determine the normal inspection combination. 
     According to embodiments disclosed herein, the air conditioner and the method for detecting the incorrectly connected pipe may enable shortening the detection time period from 20 minutes to 8 to 16 minutes for five indoor units and shortening the detection time period from 36 minutes to 10 to 20 minutes for nine indoor units. 
     Further advantages, in addition to the above-mentioned advantages, are described together while describing specific matters for implementing the embodiments. 
     Embodiments have been described with reference to drawings hereinabove; however, the embodiments are not limited to the embodiments and the exemplary drawings herein, and various modifications can be made by the skilled person in the art within the scope of the technical idea. Further, even if working effects obtained based on configurations are not explicitly described in the description of embodiments, effects predictable based on the corresponding configuration have to be recognized. 
     It will be understood that when an element or layer is referred to as being “on” another element or layer, the element or layer can be directly on another element or layer or intervening elements or layers. In contrast, when an element is referred to as being “directly on” another element or layer, there are no intervening elements or layers present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that, although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. 
     Spatially relative terms, such as “lower”, “upper” and the like, may be used herein for ease of description to describe the relationship of one element or feature to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “lower” relative to other elements or features would then be oriented “upper” relative to the other elements or features. Thus, the exemplary term “lower” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Embodiments are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures). As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.