pressure in hydronic heating system

Brad White_201

as John said.

I would only add, dare I say expand upon one point. Size the expansion tanks based on system volume in gallons, not "BTU rating of the equipment". Some manufacturers still use that method but it is based on small tube copper systems. In older converted gravity systems, that tack will fail you by a factor of 2 if not 3.

Phil C

Trying to determine how much system pressure required in a 4 story building with 15 zones of closed loop baseboard radiation 400,000 btu in baseboard

John Starcher_4

One pound of pressure....

...will raise water 2.31 feet. You need to calculate the total height of elevation, from the highest point in the piping to the lowest point, and then divide by 2.31. Add in at least 3 or 4 pounds of "leftover" pressure so the top of the system will not be at zero.

You may have issues with system pressure, depending on your boiler components. Lets say you have a total 'system' height of 35'. That equates to 15.15 psi to "lift" the water that high. Adding a few psi to assure residual pressure puts you at 18 psi. This should not be a problem, as most boiler relief valves are rated at 30 psi. You need to make sure that you have a properly sized expansion tank in the system, as well.

Phil C

Thanks for the help Guys!

Phil Cullen