In class Buildings.Applications.DataCenters.ChillerCooled.Examples.NonIntegratedPrimarySecondaryEconomizer, we have the results as below:

Between 1200 seconds and 1260 seconds, the primary pump is running at full speed (priPum.u[1]=1), while the chillers and the WSE are OFF (chiWSE.on[1]=false, chiWSE.on[2]=false and chiWSE.on[3]=false) and their isolation valves are closed. Thus the primary pump working pressure is at -2E11 Pa.

The cause is that in the instance chiStaCon the tWai = 60 seconds and in the instance priPumCon the tWai = 0 seconds.

We can address the issue by adding an on boolean input (from the instance plaOn.y) to the instance priPumCon and the instance CWPumCon, to avoid the pump works against the closed valves.