Since the top floor is the 6th floor is it a good Idea to put at least 12psi on the system? Would not want the pump to suction to ever go beyond 0psi to a negative number. Any help would be appreciated. Primary secondary set up with boilers set at aprox. 20 psi.
Don't assume that 12 psi will be enough. While it should be, it will also depend on what other equipment is on the top floor. And the spec for your pumps. Train drivers sometimes spec strange things, including pumps.
Good one, Rich, seriously.
My father was also an engineer (hydraulic, doing among other things gantry work for NASA as a component supplier).
When he took me to work one day when I was four, I was bored out of my skull waiting for the train to show up...MAN was I disappointed!
If its in the basement, fill pressure would be 1/2 PSI per vertical foot of system elevation above the boiler, PLUS 5 PSI.
If its on top, just leave the PRV set for 12 PSI, then the pressure at the bottom will be 1/2 PSI per vertical foot of elevation BEOLOW the boiler, PLUS 12 PSI.
Most residential pumps only need 5' of NPSH to guarantee they can deliver their performance curve.