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Fluctuating Boiler Pressure....

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Duffman1322
Duffman1322 Member Posts: 3
in Gas Heating
Hello all. First post here looking for some help.

American Standard boiler, unsure of year but will attach pic of data plate.
Boiler has operated at 16-18 psi for the last 18 years I’ve been in my home. Last season on first startup, had an over pressure situation and blow off valve went off with pressure at 30.
Found expansion tank saturated. Replaced old tank with same model 30 tank. Boiler ran all season but pressure was all over the place. Not over pressure but ranging from 16 to creeping to 26/27 at times. Most of the time operating at 20-21 psi.
Looking for some ideas on what to look for? Other wise boiler has been flawless for years. I do an annual boiler cleaning and replaced the thermo coupler once.
Thanks for any info. Much appreciated.

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  • JUGHNE
    JUGHNE Member Posts: 11,062
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    I would first make sure the cold water fill valve, that feeds the pressure reducing valve, is off and see if pressure still changes.

    It looks like the insert coil for hot water is not in use.
    How do you heat your domestic faucet hot water?

    The air charge in the exp tank should match the operating pressure of the boiler. The factory pre-charge is usually 12 PSI.
    You can only measure it when it is disconnected from the system.
  • Duffman1322
    Duffman1322 Member Posts: 3
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    I turned valve off supplying water to pressure reducer all summer, pressure gauge did not fluctuate for months.

    I have a separate stand alone 40 gallon water heater for hot water.

    If the pre charge is 12 psi do I need to raise it to 16-18?
  • JUGHNE
    JUGHNE Member Posts: 11,062
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    Or try lowering the system pressure.
    How tall is your house?
  • Duffman1322
    Duffman1322 Member Posts: 3
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    2 story colonial.

    Only question I have with messing with the water pressure is why was the pressure fine for years only to change when the exp tank was changed?

    I could be totally wrong but it seems like adjusting the pressure ( I’m guessing at the pressure reducer?) is covering up another issue.

    Like I said earlier, pressure isnt consistent. Fluctuates, not wildly, it’s slow change day to day. One day it’ll run at 21-22 another 24-26 then 18-21. Sometimes it will remain in one range for a week without changing. Very confusing.

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