System and method of controlling an oil flow within a refrigeration system

Abstract

A system and method of controlling an oil flow within a refrigeration system, the system including a compressor, an expansion device in flow communication with the compressor, and an electronic controller in communication with the expansion device and the compressor, wherein the electronic controller is configured to operate in an oil return mode based at least in part on an operational speed and a continuous operational run time of the compressor.

What is claimed is: 
     
         1 . A method of controlling oil flow within a compressor, the compressor operably coupled to a controller and an expansion device, the method comprising:
 (a) operating the compressor at a demand operational speed;   (b) operating the controller to determine whether the compressor has operated at a speed less than a minimal speed limit for a continuous duration of time greater than or equal to a run time limit; and   (c) operating the controller to enter an oil return mode if the compressor has operated at a speed less than the minimal speed limit for a continuous duration of time greater than or equal to the run time limit.   
     
     
         2 . The method of  claim 1 , wherein the minimal speed limit is approximately 3000 revolutions per minute. 
     
     
         3 . The method of  claim 1 , wherein the run time limit is approximately 45 minutes. 
     
     
         4 . The method of  claim 1 , wherein the oil return mode comprises:
 (i) operating the compressor at the minimal speed limit for an oil return duration of time; and   (ii) controlling the expansion device to decrease a target superheat value by an oil return target value.   
     
     
         5 . The method of  claim 4 , wherein the oil return duration of time is approximately 10 minutes. 
     
     
         6 . The method of  claim 4 , wherein the oil return target value is approximately 5 degrees Fahrenheit. 
     
     
         7 . An electronic controller comprising:
 a processor, and a memory, wherein the processor is configured to operate a program stored in memory, the program configured to:   (a) command a compressor to operate at a demand operational speed;   (b) determine whether the compressor has operated at a speed less than a minimal speed limit for a continuous duration of time greater than or equal to a run time limit; and   (c) operate in an oil return mode if the compressor has operated at a speed less than the minimal speed limit for a continuous duration of time greater than or equal to the run time limit.   
     
     
         8 . The electronic controller of  claim 7 , wherein the minimal speed limit is approximately 3000 revolutions per minute. 
     
     
         9 . The electronic controller of  claim 7 , wherein the run time limit is approximately 45 minutes. 
     
     
         10 . The electronic controller of  claim 7 , wherein to operate in an oil return mode, the program is further configured to:
 (i) command the compressor to operate at the minimal speed limit for an oil return duration of time; and   (ii) command an expansion device to operate in order to decrease a target superheat value by an oil return target value.   
     
     
         11 . The electronic controller of  claim 10 , wherein the oil return duration of time is approximately 10 minutes. 
     
     
         12 . The electronic controller of  claim 10 , wherein the oil return target value is approximately 5 degrees Fahrenheit. 
     
     
         13 . A refrigeration system comprising:
 a compressor;   an expansion device in flow communication with the compressor; and   an electronic controller in communication with the expansion device and the compressor;   wherein the electronic controller is configured to operate in an oil return mode based at least in part on an operational speed and a continuous operational run time of the compressor.   
     
     
         14 . The refrigeration system of  claim 13 , wherein to operate in an oil return mode, the electronic controller is configured to:
 (a) determine whether the operational speed is less than a minimal speed limit; and   (b) determine whether the continuous operational run time is greater than or equal to a run time limit;   
     
     
         15 . The refrigeration system of  claim 14 , wherein the minimal speed limit is approximately 3000 revolutions per minute. 
     
     
         16 . The refrigeration system of  claim 14 , wherein the run time limit is approximately 45 minutes. 
     
     
         17 . The refrigeration system of  claim 14 , wherein the electronic controller is further configured to:
 (i) command the compressor to operate at the minimal speed limit for an oil return duration of time if it is determined that the operational speed is less than the minimal speed limit and the continuous operational run time is greater than or equal to the run time limit; and   (ii) command the expansion device to operate in order to decrease a target superheat value by an oil return target value if it is determined that the operational speed is less than the minimal speed limit and the continuous operational run time is greater than or equal to the run time limit.   
     
     
         18 . The refrigeration system of  claim 17 , wherein the oil return duration of time is approximately 10 minutes. 
     
     
         19 . The refrigeration system of  claim 17 , wherein the oil return target value is approximately 5 degrees Fahrenheit.