Air conditioner and method of controlling the same

Abstract

An air conditioner and a method of operating the same are provided. The air conditioner may include a plurality of compressors, each of which may include a casing that stores oil therein, and an oil level detecting device that detects an oil level within the casing. Once oil levels within each of the plurality of compressors are detected, oil may be redistributed between the plurality of compressors without interrupting a normal operation of the air conditioner. Oil may be transferred from a compressor having an oil level greater than a desired amount to a compressor having an oil level less than the desired amount. If there remains a compressor that contains an insufficient amount of oil after redistributing the oil among the plurality of compressors, an oil collecting operation may be performed.

1 . An operating method for an air conditioner, the air conditioner comprising a plurality of compressors, each of which includes a casing that stores oil in an inner lower portion thereof and an oil level detecting device that detects an oil level in the casing; at least one first heat exchanger that intakes a working fluid from the plurality of compressors; at least one expansion device; at least one second heat exchanger, through which the working fluid passes after passing through the at least one first heat exchanger; a first suction pipe, through which the working fluid flows from the at least one first heat exchanger or the at least one second heat exchanger; and a plurality of second suction pipes branched from the first suction pipe and then connected to each of the compressors, the method comprising:
 detecting an oil level of each of the plurality of compressors;   distributing oil in a first compressor of the plurality of compressors containing oil over a first preset level for the first compressor toward a second compressor of the plurality of compressors containing oil lower than a second preset level for the second compressor via the first and the second suction pipes without passing through the at least one first exchanger and the at least one second heat exchanger when a number of the plurality of compressors containing oil lower than the preset level for the respective compressor is less than or equal to a predetermined number; and   performing an oil collecting operation if there exists a compressor containing oil lower than a preset level for that compressor after performing the distributing or if the number of the plurality of compressors containing oil lower than the preset level for the respective compressor is greater than the predetermined number.   
     
     
         2 . The method of  claim 1 , wherein the preset level of each of the plurality of compressors are all the same or all different. 
     
     
         3 . The method of  claim 1 , wherein the preset level of at least two of the plurality of compressors are the same or different. 
     
     
         4 . The method of  claim 1 , wherein the distributing is performed for a predetermined period of time, at predetermined time intervals, or until all of the plurality of compressors have at least the preset level for the respective compressor. 
     
     
         5 . The method of  claim 1 , wherein each of the plurality of compressors includes a first oil return pipe that connects the casing of the respective compressor to the first suction pipe, and wherein oil in the respective compressor containing oil over the preset level for the respective compressor is supplied to the first suction pipe via the first oil return pipe during the distributing. 
     
     
         6 . The method of  claim 5 , wherein the first oil return pipe connected to a compressor containing oil lower than a preset level for each compressor remains closed during the distributing. 
     
     
         7 . The method of  claim 1 , wherein the air conditioner further comprises at least one oil separator having a second oil return pipe that connects the oil separator and the first suction pipe, and wherein oil collected in the oil separator is supplied to the first suction pipe via the second oil return pipe during the distributing. 
     
     
         8 . The method of  claim 7 , wherein the at least one oil separator receives a mixture of oil and working fluid from at least one of the plurality of compressors through an oil discharge pipe. 
     
     
         9 . The method of  claim 7 , wherein the at least one oil separator stores the oil from the plurality of compressors and if the number of the plurality of compressors containing oil lower than the preset level for the respective compressor is greater than the predetermined number, the method further comprises:
 detecting an oil level of the at least one oil separator;   if the oil level of the at least one oil separator is less than a preset level for the at least one oil separator, performing the oil collecting operation; and   if the oil level of the at least one oil separator is greater than or equal to the preset level, opening a valve that allows the stored oil to flow into the compressor containing oil lower than the preset level for the respective compressor.   
     
     
         10 . The method of  claim 1 , wherein the air conditioner further comprises a plurality of oil separators, and wherein each of the plurality of compressors discharges a mixture of oil and working fluid to a respective one of the plurality of oil separators. 
     
     
         11 . The method of  claim 10 , wherein the distributing includes distributing the oil stored in the at least one oil separator toward the second compressor of the plurality of compressors containing oil lower than the second preset level for the second compressor. 
     
     
         12 . The method of  claim 1 , wherein the air conditioner further comprises a first oil return pipe that connects the casing of each compressor to the first suction pipe, and wherein oil in the respective compressor containing oil over a preset level for each compressor and the oil in the oil separator are supplied to the first suction pipe via the first and second oil return pipes during the distributing. 
     
     
         13 . The method of  claim 1 , wherein the air conditioner further comprises at least one oil reservoir that stores the oil from the plurality of compressors and if the number of the plurality of compressors containing oil lower than the preset level for the respective compressor is greater than the predetermined number, the method further comprises:
 detecting an oil level of the at least one oil reservoir;   if the oil level of the at least one reservoir is less than a preset level for the at least one oil reservoir, performing the oil collecting operation; and   if the oil level of the at least one reservoir is greater than or equal to the preset level of the at least one oil reservoir, opening a reservoir valve of the at least one reservoir as part of the distributing.   
     
     
         14 . The method of  claim 13 , wherein each of the plurality of compressors includes a first oil return pipe that connects the casing of the respective compressor to the at least one oil reservoir, and wherein oil in the respective compressor containing oil over the preset level for the respective compressor is supplied to the at least one oil reservoir via the first oil return pipe. 
     
     
         15 . The method of  claim 14 , wherein the first oil return pipe connected to the compressor containing oil lower than a preset level for each compressor remains closed during the distributing. 
     
     
         16 . The method of  claim 13 , wherein the at least one oil reservoir functions as an oil separator. 
     
     
         17 . The method of  claim 16 , wherein the oil separator receives a mixture of oil and working fluid from at least one of the plurality of compressors through an oil discharge pipe. 
     
     
         18 . An operating method for an air conditioner, the air conditioner comprising a plurality of compressors, each having an oil level detecting device, an oil transferring device that transfers oil among the plurality of compressors, and a plurality of heat exchangers and expansion devices that cooperate with the plurality of compressors, the method comprising:
 detecting an oil level of each of the plurality of compressors;   transferring oil from at least one compressor of the plurality of compressors with a relatively higher oil level to at least one compressor of the plurality of compressors with a relatively lower oil level when a number of the plurality of compressors containing oil lower than the preset level for the respective compressor is less than or equal to a predetermined number; and   performing an oil collecting operation if a number of compressors containing oil lower than a preset level for the respective compressor is greater than a predetermined number.   
     
     
         19 . The method of  claim 18 , wherein the method further comprises performing the oil collecting operation when a compressor containing oil lower than the preset level is detected after transferring the oil for a predetermined period of time. 
     
     
         20 . The method of  claim 18 , wherein the transferring comprises transferring the oil without passing through the plurality of heat exchangers and expansion devices that cooperate with the plurality of compressors. 
     
     
         21 . The method of  claim 20 , wherein the method further comprises closing an oil return pipe connected to the compressor containing oil lower than the preset level for the respective compressor during the transferring. 
     
     
         22 . An operating method for an air conditioner, the air conditioner comprising a plurality of compressors, each having an oil level detecting device, an oil transferring device that transfers oil among the plurality of compressors, and a plurality of heat exchangers and expansion devices that cooperate with the plurality of compressors, the method comprising:
 detecting an oil level of each of the plurality of compressors;   transferring oil from at least one compressor of the plurality of compressors with a relatively higher oil level to at least one compressor of the plurality of compressors with a relatively lower oil level when a number of the plurality of compressors containing oil lower than the preset level for the respective compressor is less than or equal to a predetermined number;   storing oil from at least one of the plurality of compressors during a normal operation of the air conditioner in at least one oil reservoir or at least one oil separator;   detecting an oil level of the at least one oil reservoir or the at least one oil separator when the number of compressors containing oil lower than the preset level for the respective compressor is greater than the predetermined number;   performing an oil collecting operation when the oil level of the at least one oil reservoir or the at least one oil separator is less than a preset level for the at least one oil reservoir or the at least one oil separator; and   transferring the stored oil to the at least one compressor of the plurality of compressors with the relatively lower oil level when the oil level of the at least one oil reservoir or the at least one oil separator is greater than or equal to the preset level for the at least one oil reservoir or the at least one oil separator.   
     
     
         23 . The method of  claim 22 , wherein the at least one oil reservoir or the at least one oil separator comprises at least one oil separator, and wherein the at least one oil separator receives a mixture of oil and working fluid from at least one of the plurality of compressors through an oil discharge pipe. 
     
     
         24 . The method of  claim 23 , wherein the method further comprises separating the mixture of oil and working fluid at the at least one oil separator, and storing the separated oil and transferring the separated working fluid to the plurality of heat exchangers and expansion devices that cooperate with the plurality of compressors. 
     
     
         25 . The method of  claim 23 , wherein each of the plurality of compressors includes a valve that controls a flow of the stored oil from the at least one oil separator to each respective compressor, and wherein the method further comprises opening the valve of the compressor containing oil lower than the preset level during the transferring of the stored oil. 
     
     
         26 . The method of  claim 22 , wherein the at least one oil reservoir or the at least one oil separator comprises at least one oil reservoir. 
     
     
         27 . The method of  claim 26 , wherein the at least one oil reservoir functions as an oil separator. 
     
     
         28 . The method of  claim 27 , wherein each of the plurality of compressors includes a valve that controls a flow of oil in the oil return pipe from each respective compressor to the at least one oil reservoir, and wherein the method further comprises closing the valve of the compressor containing oil lower than the preset level during the transferring. 
     
     
         29 . The method of  claim 26 , wherein each of the plurality of compressors communicates with a respective one of a plurality of oil separators. 
     
     
         30 . The method of  claim 26 , wherein the at least one oil reservoir receives oil from at least one of the plurality of compressors through a respective oil return pipe that connects the casing of each compressor to the at least one oil reservoir.