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?

Added
Timeseries stack plot and stack plot by ascending total cooling rate is added following @aparker instruction.
Looking at the 2nd graph, I can see the fluctuation when the consequent chiller start to be operated. Is this usual? or something is causing this fluctuation?

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?

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?