Compressor with flooded start control

Abstract

A system and method for flooded start control of a compressor having a crankcase heater are provided. A control module receives sensed data from a sensor, determines a current rate of liquid migration into the compressor, and compares the current rate with first and second predetermined thresholds. The control module operates the compressor in a flooded-start control mode, including operating the compressor according to at least one cycle with a first time period when the compressor is on and a second time period when the compressor is off. The control module operates the compressor in the flooded start control mode when the current rate is greater than the first predetermined threshold, activates the crankcase heater when the current rate is between the first and second predetermined thresholds, and operates the compressor without the flooded start control mode when the current rate is less than the second predetermined threshold.

What is claimed is: 
     
       1. A system comprising:
 a compressor for a refrigeration system, the compressor having a crankcase heater; 
 at least one sensor that generates sensed data corresponding to at least one condition of the refrigeration system; 
 a controller that receives the sensed data from the at least one sensor, determines a current rate of liquid migration into the compressor, and compares the current rate of liquid migration with a first predetermined threshold and a second predetermined threshold, the first predetermined threshold being greater than the second predetermined threshold; 
 wherein the controller operates the compressor in a flooded-start control mode, the flooded start control mode including operating the compressor according to at least one cycle including a first time period during which the compressor is on and a second time period during which the compressor is off; and 
 wherein the controller operates the compressor in the flooded start control mode in response to the current rate of liquid migration being greater than the first predetermined threshold, activates the crankcase heater in response to the current rate of liquid migration being less than the first predetermined threshold and greater than the second predetermined threshold, and operates the compressor without the flooded start control mode in response to the current rate of liquid migration being less than the second predetermined threshold. 
 
     
     
       2. The system of  claim 1  wherein the controller determines whether a locked rotor condition is present and, in response to the locked rotor condition being present, operating the compressor in the flooded start control mode with the crankcase heater activated. 
     
     
       3. A method comprising:
 generating, with at least one sensor, sensed data corresponding to at least one condition of a refrigeration system having a compressor with a crankcase heater; receiving, with a controller, sensed data from the at least one sensor; determining, with the control module, a current rate of liquid migration into the compressor; 
 comparing, with the controller, the current rate of liquid migration with a first predetermined threshold and a second predetermined threshold, the first predetermined threshold being greater than the second predetermined threshold; 
 operating, with the controller, the compressor in a flooded-start control mode, the flooded start control mode including operating the compressor according to at least one cycle including a first time period during which the compressor is on and a second time period during which the compressor is off; and 
 operating, with the controller, the compressor, in the flooded start control mode in response to the current rate of liquid migration being greater than the first predetermined threshold; 
 activating, with the controller, the crankcase heater in response to the current rate of liquid migration being less than the first predetermined threshold and greater than the second predetermined threshold; 
 operating, with the controller, the compressor without the flooded start control mode in response to the current rate of liquid migration being less than the second predetermined threshold. 
 
     
     
       4. The method of  claim 3 , further comprising determining, with the controller, whether a locked rotor condition is present and, in response to the locked rotor condition being present, operating the compressor in the flooded start control mode with the crankcase heater activated.