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Boiler pressure issues

JOCJOC Member Posts: 4
I have a 1983 Utica 300,000BTU boiler that heats two floors and a couple of radiators in the basement.  The problem is as the boiler heats up the pressure relief valve pops at 30 psi as it should.  The contractor has changed to pressure relief valve, pump, inlet valve and expansion tank.  He feels the expansion tank is too small.  The pressure relief valve pops at around 140 degres.  The contractor put a pressure gauge above the tank so you can see what the presure reading is and it is always close to the tank.  Based on what he has done, is there any other things he should do?  If the tank is not the problem, what could be the problem?  The pump is on the return of the boiler.  If that is moved to the supply side how much would that help?  What other tricks may help? 


  • SpeyFitterSpeyFitter Member Posts: 422
    Put the odds in your favour

    And this is just happening all of a sudden and the system was fine up until recently or?

    It could be a myriad of things - the expansion tank is undersized perhaps. Also is your Pressure relief valve downstream of the pump or upstream of it? What is your pressure reducing valve (boiler feed) set at pressure wise?

    The pump will perform better if you put it on the supply side and not on the return, and have it downstream of the expansion tank & boiler feed.
    Class 'A' Gas Fitter - Certified Hydronic Systems Designer - Journeyman Plumber
  • JOCJOC Member Posts: 4
    Scott reply


    It started gradually.  The pressure relief valve is on the front of the boiler and the pump is on the bottom rear at the return.  There is no setting mechanism on the inlet valve. If it is not the tank what could be the problem?   I will talk to the contractor about moving the pump, he is coming tommrow.
  • CMadatMeCMadatMe Member Posts: 3,066
    Does This Boiler

    have a tankless coil in it? Does this only happen when a particular zone is calling? Is there a check vlv somewhere that is stuck closed? I
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • JOCJOC Member Posts: 4
    Pressure issue reply

    I do not know if the boiler has a tankles coil.  The system is not setup in zones.  When the boiler is on it heats the entire house.  The house ws built in 1903 an has the original radiators.
  • CMadatMeCMadatMe Member Posts: 3,066
    Domestic Hot Water

    What supplies your domestic hot water needs?
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • JOCJOC Member Posts: 4
    Domestic hot water

    The domestic hot water is provided by a seperate hot water heater.  The boiler temp is cool now and the psi is at 12.  In the past it may be 0, it does vary in the tank.  That does not make sense and when it gets hot the expansion tank has pressure. 
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