Differential Pressure Setting

[mackistired]

I want to install a pressure differential switch in my chilled water project. How do I get and set the pressure value? How do I know what are the values where the by pass should be fully open and fully close?
We have primary and secondary loop for this project.
Primary pump header is 50 FT H2O
Secondary pump header is 150 FT H2O

[Tesla]

HI mackistired
1st you will need to know the required pressure drop across the cooler to maintain the minimum flow. Sometimes stamped on a plate otherwise contact OEM or look up manual.
Read the instruction manual on the pressure switch. Then to set manually basically - without compressor running with pump running, and a meter across the switch terminals (or controller display) slowly close the butterfly valve on the outlet until it switches - this will be the cut out pressure. It will need adjustment (screw) and several attempts before the correct setting is found.
Bypass. There are several methods, here is the basic. With all CHWV = 100% and bypass = 0% there should be enough flo to maintain min press drop across chiller +10% (press). This should be system diff press set point. As CHVWs close the bypass opens proportionally as a range from 0% to 100%.
In writing all that the modern way is to use Siemens Mag Flo sensors to measure flow not pressure - this method is more accurate (when installed correctly) and gives better control.
Sorry I am not famillar with Ft. I hope I got that right but I'msure there is a paper on this somewhere.