I have a secondary loop VFD controlled with 10+ 2-way modulating valves and two 3 way valves. The VFD control is currently set to maintain a specific dp. In the winter time, the flow that this loop maintains is beyond what one chiller with a constant flow pump can provide (actual load in tons is ok for one chiller) so I'm forced to run two chillers and get a low delta T due a large amount recircing in the bypass line.
I am thinking about trying an alternate control method with the vfd secondary loop. Instead of maintaining a constant dp could I not use the actual % open of the valves? My control system would constantly be looking at the open % of each valve and attempt to drive the most open to 90% and stay there (by reducing VFD speed and total flow). If it gets above 90% then it would speed back up to maintain 90%. If another valve would open past 90% then that would become the new PV. Thoughts?