mixed water loop flow issues

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Hello all, We design water source heat pump systems for most of our projects. I often get unmet hours in zones because the mixed water loop flow rate goes to zero or zones get short supplied.

This often happens when a large portion of zones go into setback conditions or during shoulder seasons when energy sharing is high.

There are many hours during the year when energy is shared in the mixed water loop and the resulting load is low, but the required flow rate is high.

Can someone confirm that this is a problem? I need the flow rate to react to the call for the sum of the absolute value of connected heating and cooling loads, not the resulting load on the loop.

I use designbuilder with energyplus v9.4.

best, Greg