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Boiler Pressure Issue

In the attached photo, you can see a view of my boiler and plumbing system.

I've been dealing with an issue of increasing pressure in my boiler for the past few weeks. Normally, when all the valves are in the down position, the pressure increases to around 0.5-0.75 bar every night. I manually reduce the pressure by releasing water from the discharge valve.

Unfortunately, most technicians in Turkey are untrustworthy and charge exorbitant fees. So, I want to gather as much reliable information about my boiler issue before needing their services. That's why I'm turning to this forum for advice.

I've conducted several tests, and when I closed the valve on the right in the photo, I noticed that the pressure didn't increase. In my online research, I read that pressure increase issues could be due to a faulty heat exchanger, valve leakage, or expansion tank problems.

How can I determine the root cause of the problem? If the pressure doesn't increase with this valve closed, could replacing it solve my issue?

I appreciate your assistance and thank you in advance.


  • hot_rod
    hot_rod Member Posts: 21,846
    Could be the expansion tank is bad? Do you have a manual for the boiler, or look it up online. Is it a Ferroli boiler? A UK brand?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    EBEBRATT-Ed Member Posts: 15,312
    You should probably run the pressure at about 1 bar.

    There are usually 1 of three issues:

    Bad expansion tank or a loss of air charge in your expansion tank

    Leaking pressure reducing valve or make up water valve

    Or possibley a bad heat exchanger if the boiler also heats domestic hot water.

    The boiler Name and model # would help.

    Not knowing more about your boiler and your system it is hard to make any recommendations.
  • 109A_5
    109A_5 Member Posts: 1,341
    Hello @cihat,

    Not sure about your model, maybe DIVACONDENS D PLUS ?

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • Big Ed_4
    Big Ed_4 Member Posts: 2,695
    It seems to be a heat only unit . There is a pressure reducing valve in that unit . Not sure if there is an adjustment on it . It could be dirty or need of a replacement .
    I have enough experience to know , that I dont know it all
  • Jamie Hall
    Jamie Hall Member Posts: 22,912
    Does closing the white valve on the right also close off your domestic water? Or hot water? Or is that separate?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England