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Boiler PSI question

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markurl
markurl Member Posts: 9
edited December 2019 in THE MAIN WALL
Sorry for 2 postings but they are separate issues. I had a heating tech tell me that I probably have a PSI gauge issue and maybe an undersized expansion tank for my forced hot water system. The boiler PSI is reading higher than it should. I knocked on the expansion tank and it appears to have water on the top and air on the bottom. The pressure relief valve has never released any water. At a PSI as high as shown, there should be a flood in the basement. Any thoughts on this? I am concerned this work order is excessive.

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  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited December 2019
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    You can post the pictures directly. Also, you shouldn't post pricing.

    You better hope that gauge isn't working correctly.
    And get another tech.

    These are all test-able components and the word 'probably' is the sign of a non-professional. He hasn't determined the problem and he wants to replace all those parts, on a hunch?
    -Pressure-easily check-able with a stand-alone gauge, which every tech should have for troubleshooting.
    -Expansion tanks can be properly sized based on water volume in the system. Expansion tanks can also be checked to see if they lost their charge or failed.
    -Feed valve can be checked.
    -If a stand alone gauge confirms the boiler pressure, you should let it cool, drain the boiler and replace the pressure relief valve. And you should also figure out why the pressure went that high. If the gauge tells you it's under 30 psi, a tech should carefully and professionally test the prv.

    Do you have an indirect tank for domestic hot water in this system too? Or stand alone water heater?

    Could be any or a combination of a few things, but all testable.
    If you have to drain the system for anything other than the relief valve, I'd probably change the relief valve too.
    Could be air in the system too, specifically from not pumping away from the expansion tank.

    You could post more pictures of your boiler and the near boiler piping.

    There was an error rendering this rich post.

  • markurl
    markurl Member Posts: 9
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    Steve,

    I apologize on the pricing. I forgot to strip that. I attached the pictures directly and added more as you requested. Yes - there is an indirect water heater.
  • Snowmelt
    Snowmelt Member Posts: 1,416
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    you have to see if the domestic water is getting into your boiler water. that does happen when the indirect gets a pin whole leak in it. there is a way to test that also.
  • markurl
    markurl Member Posts: 9
    edited December 2019
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    @Snowmelt Do you have a link to how to test this? I believe the boiler gauge is shot as I tested the PSI of the drains and got 22PSI at the boiler drain and 15 PSI at the zone drains.
  • JUGHNE
    JUGHNE Member Posts: 11,076
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    You have valves to isolate the boiler loop from the indirect tank. If those are closed then those items would be separated.

    However, if you had a leak of house pressure going into the boiler water thru a pin hole of the internal heat exchanger in the tank, (all possible and not uncommon) then your boiler pressure would always continue to build beyond the 30 PSI opening point of the relief valve and you would know that. If that were the case, then closing the isolation valves would eliminate that cross connection.

    I would guess you need a new pressure gauge.
    You can, fortunately, valve off the expansion tank, unscrew it to relieve pressure, remove it......it should be empty after water comes out of the loose fitting. Completely removed it should have no water left and the air pressure should be set to 12-15 PSI.
    If water comes out of the air fill valve then you need a new one.

    Has this system worked well in the past?

  • markurl
    markurl Member Posts: 9
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    @JUGHNE i have only had the house for a year and have never owned a boiler before this one. The system has never been an issue. I think I will have the HVAC guy do some of the work. Is it worthwhile to replace all the parts (including expansion tank) while the system is depressurized?
  • Jamie Hall
    Jamie Hall Member Posts: 23,441
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    markurl said:

    @JUGHNE i have only had the house for a year and have never owned a boiler before this one. The system has never been an issue. I think I will have the HVAC guy do some of the work. Is it worthwhile to replace all the parts (including expansion tank) while the system is depressurized?

    Not unless they are shown to be defective. If it ain't broke, don't fix it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • retiredguy
    retiredguy Member Posts: 915
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    Those pressure/temperature gauges were Junk. I replaced them any time I could with gauges that worked.