Expansion tank pressure

Pflukester

Im embarrassed to ask having been in the business for years but I need some education. When putting a new boiler into operation, what is the proper procedure for ensuring that the expansion tank pressure is correct? what is the relationship between the expansion tank pressure and setting the pressure reducing valve? Once again I have a new installation and no circulation on the third floor. Help me comrades

Paul Pollets

Exp tank pressure

The expansion tank should be charged to 12-14PSI at 0 boiler pressure. This presumes a 3 story house. You may need 16psi to reach the 3rd story, use the fast fill on the PRV to increase the pressure on purging.

MikeyB

Tank sizing

You can also type in Expansion Tank Sizing in the Site Search bar in the top right corner and search through some good info, also check out Amtrol's website

Mark Eatherton

Generally speaking...

you NEED 1/2 PSI per vertical foot of system elevation, PLUS 5 PSI to avoid air trapping at the top of the system. So, if you have 10' per story, then you are looking at roughly 25' of elevation from the top of the boiler to the top of the system (assuming radiant floor or baseboard, and boiler located in basement. If using FCU's in the attic, then add that elevation.) So, 1/2 PSI per foot = 12 PSI, PLUS 5 PSI = 17 PSI fill pressure. I usually recommend that the bladder of the tank be pressurized to the same pressure as the system fill pressure. This keeps the acceptance volume of the tank intact, otherwise you lose a portion of the acceptance factor due to the tank diaphragm being partially distended before the fluid actually starts expanding.HTHME