hydronic circulator system info

Tim_63

I am close to finishing the calcs on my in floor radiant system. I have a calc'd manifold head of 15 #. I need to size the expansion tank and relief valve. What is an appropriate system pressure to use: do I calc the system pressure from the head calcs (.41 x 15.....approx 7# static pressure) and go from there, or what......al of my info and calcs have come from wirsbo design manual, and Jon Siegenthaler's modern hydronic heating 2nd edition.
Thanks