I am modelling with multiple water cooled chiller in energyplus. 
In idf file, I specified SequentialLoad for Chilled Water Distribution Scheme. However, looking at the result, it seems that multiple chiller is operating before 1 chiller get to full load as shown below graph.(x:part load ratio/y:COP) 
 
 
Does anyone know why this happen?  

 
 
 
 

