Method for controlling defrost operation of a refrigeration system

Abstract

The invention relates to a method for controlling a refrigeration system by establishing a defrost period during an initial defrost period. One or more compressors of the refrigeration system are monitored to establish if the one or more compressors are running, and a parameter representative of the one or more compressors running is monitored. The monitoring establishes at least one parameter limit value representative of whether a defrost period or a non-defrost period is to be initiated. The invention also relates to a method for controlling a refrigeration system subsequent to an electrical power interruption. The invention also relates to control units for applying one or both of the methods according to the invention, and to a refrigeration system having one or more control units controlling the refrigeration system according to one or both of the methods.

What is claimed is: 
     
         1 . A method for controlling a refrigeration system, said method comprising the steps of:
 establishing a defrost period, and when one or more compressors of the refrigeration system is running, monitoring a parameter representative of the one or more compressors running,   said monitoring establishing at least one parameter limit value representative of whether a defrost period or a non-defrost period is to be initiated, and   if the parameter being monitored is above a parameter limit value, determining that a defrost period is not to be initiated subsequent to the compressor running,   if the parameter being monitored is below a parameter limit value, determining that a defrost period is to be initiated subsequent to the compressor running.   
     
     
         2 . The method according to  claim 1 , wherein the parameter limit value, when monitoring if the parameter being monitored is above a parameter limit, is the same as the parameter limit value, when monitoring if the parameter being monitored is below a parameter limit, so that no value gap is present between former and the latter parameter. 
     
     
         3 . The method according to  claim 1 , wherein the parameter limit value, when monitoring if the parameter being monitored is above a parameter limit value, is greater than the parameter limit value, when monitoring if the parameter being monitored is below a parameter limit value, so that a value gap is present between former and the latter parameter value. 
     
     
         4 . The method according to  claim 1 , wherein the at least one parameter value being representative of the compressor running being a number of compressor cycles, and
 if the number of compressor cycles is above a number limit, determining that a defrost period is not to be initiated subsequent to the compressor running, and   if the number of compressor cycles is below a number limit, determining that a defrost period is to be initiated subsequent to the compressor running.   
     
     
         5 . The method according to  claim 4 , the upper limit of compressor cycles being between 2 cycles and 100 cycles, possibly being between  2  cycles and  50  cycles, possibly being 20 cycles. 
     
     
         6 . The method according to  claim 1 , wherein the at least one parameter value being representative of the compressor running is a temperature of the compressor, and
 if the temperature of the compressor is above a temperature limit, determining that a defrost period is not to be initiated subsequent to the compressor running, and   if the number of compressor cycles is below a temperature limit, determining that a defrost period is to be initiated subsequent to the compressor running.   
     
     
         7 . The method according to  claim 1 , wherein the at lest one parameter value being representative of the compressor running is electrical power applied to the compressor, and if the electrical power applied to the compressor is above a power limit, determining that a defrost period is not to be initiated subsequent to the compressor running, and if the electrical power applied to the compressor is below a power limit, determining that a defrost period is to be initiated subsequent to the compressor running. 
     
     
         8 . A control unit for controlling a refrigeration system, said control unit capable of controlling the refrigeration system according to  claim 1 . 
     
     
         9 . A refrigeration system comprising at least one control unit, said at least one control unit being a control unit according to  claim 8 . 
     
     
         10 . The method according to  claim 2 , wherein the at least one parameter value being representative of the compressor running being a number of compressor cycles, and
 if the number of compressor cycles is above a number limit, determining that a defrost period is not to be initiated subsequent to the compressor running, and   if the number of compressor cycles is below a number limit, determining that a defrost period is to be initiated subsequent to the compressor running.   
     
     
         11 . The method according to  claim 3 , wherein the at least one parameter value being representative of the compressor running being a number of compressor cycles, and
 if the number of compressor cycles is above a number limit, determining that a defrost period is not to be initiated subsequent to the compressor running, and   if the number of compressor cycles is below a number limit, determining that a defrost period is to be initiated subsequent to the compressor running.   
     
     
         12 . The method according to  claim 2 , wherein the at least one parameter value being representative of the compressor running is a temperature of the compressor, and
 if the temperature of the compressor is above a temperature limit, determining that a defrost period is not to be initiated subsequent to the compressor running, and   if the number of compressor cycles is below a temperature limit, determining that a defrost period is to be initiated subsequent to the compressor running.   
     
     
         13 . The method according to  claim 3 , wherein the at least one parameter value being representative of the compressor running is a temperature of the compressor, and
 if the temperature of the compressor is above a temperature limit, determining that a defrost period is not to be initiated subsequent to the compressor running, and   if the number of compressor cycles is below a temperature limit, determining that a defrost period is to be initiated subsequent to the compressor running.