Boiler getting overpressurized -- reaches 30 PSI and PRV releases water

Discussion in 'Boiler Forum' started by BrianW, Nov 20, 2011.

  1. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Have to know what size piping is and length of the piping. Look up square inch of the pipe x 12 x how many feet divid by 231 = gallons. That is what in the system. If your close to one size go up one size because didn't figger like what the boiler holds and if theres radiators or fan coils.
     
  2. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    The water volume of the system, and the differential between the high & low limits on the boiler controls are the relevant data for determining the expansion tank sizing, not the BTU/hr ratings.
     
  3. Shellcartels

    Shellcartels New Member

    Joined:
    Jan 5, 2021
    Location:
    Brooklyn, NY
    Thank you
     
  4. JeffreyArson

    JeffreyArson New Member

    Joined:
    Mar 16, 2021
    Location:
    New York
    There was a similar problem with the boiler, but thanks to this topic, I was able to fix everything.
     
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    The specs will likely show how much water your boiler holds...then, the rest of the equation is to estimate the volume in the pipes. What you have for convectors or radiators will vary, but if it’s essentially just a pipe rather than an old style big cast iron radiator, you estimate the total length of the pipes in the heating system, then using the volume for a round column, calculate how much water it can hold (volume of a tube = 1/2 * pi * radius squared * length. A gallon is 231 cu in, so do your length in inches, then, take the result and divide by that 231 to get gallons.
     
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