# Pumping system / Plant Convergence issue

The following configuration of cooling loops in energyplus works with just a few of warnings which I will mention (coolingload operation control and two setpoints and HX hasoperationschememodulated control):

Now I want my pumps and chillers to have different sizes, but HeaderedPumps:ConstantSpeed gives identical pumps, so I decided to go with the following configuration with Pump:ConstantSpeed (only change):

I got plenty of these warnings, in one-day simulation, at the time that setpoint rises from 3 to 6.7:

*************  ** Warning ** HeatExchanger:FluidToFluid named HX - Iteration Limit exceeded calculating demand side loop flow rate continues.
*************  **   ~~~   **   This error occurred 29 total times;
*************  **   ~~~   **   during Warmup 0 times;
*************  **   ~~~   **   during Sizing 0 times.
*************  **   ~~~   **   Max=74.812813  Min=0.616959


It seems that when the setpoint goes from 3 to 6.7, plant has fluid in supply side with temperature lower than new setpoint (6.7). So it stops working while Heatexchanger is demanding load. I don't know if it's a bug or is something I'm doing wrong. I will be grateful for any suggestion to resolve this issue.

Update: I'm trying an EMS (python) solution like below but it doesn't work:

If demand>0 & PLR1==0 & PLR2==0:
pump1 (actuator) = ON
pump2 (actuator)= ON
pump1 flow (actuator)= max (internal variable)
pump2 flow (actuator)= max (internal variable)


The conditions are right but pumps flow does not change. I don't no why!

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