While I understand this concept, have been on a site where I have seen a pressure sensor installed at the ground floor, while the pumps are in the PH level (42 floors up). I couldn't get the differential pressure to vary between the supply and return. Both supply and return pressure sensors are at the Ground Floor, and the differential pressure is essentially 0 KPa. Could you clarify where the supply and return pressure sensors should be installed?

Assuming 5 PSI for each floor, that's 210 PSI head pressure to the ground floor. Both the Supply and Return read 210 PSI roughly, meaning 0 differential pressure, resulting in the VFD Pumps running at max speed.