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Expansion tank p.s.i.

anziconda Member Posts: 6
   Anybody have a easy formula to calculate the CORRECT air pressure in a expansion tank for a hydronic system? Thanks.


  • Steve_210
    Steve_210 Member Posts: 646
    It should

    Be the same pressure as the water in the hydronic system when it is cold.
  • Bill Clinton_6
    Bill Clinton_6 Member Posts: 35
    How to set psi

    Sprinter is correct, but there is a trick to setting that psi.  When connected to a pressurized boiler, an expansion tank will ALWAYS have the same pressure as the boiler, unless it is higher.  To check the x-tank pressure, first note the boiler's cold pressure (adjust if needed) then relieve pressure in the boiler, then check and adjust the pressure in the xtank, then repressurize the boiler.

    The idea is that you only need the x tank to absorb the extra volume created when water is heated.  At cold, there should be no water in the tank, preserving all its volume to absorb extyra water when the heat comes on.

     Bill Clinton
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