Variable flow condenser loop (EnergyPlus)

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Hi everyone. The model equips with 8 absorption chillers as 1 plant loop. Each absorption chiller is connected to a cooling tower. I want to make the condenser loop with variable flow rates.

The pumps in the condenser loop were set as variable flow pumps. But the flow rates are controlled constantly. How can i fix this?

And I am ver.8.6 user.

Thank you in advance