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boiler or coffee pot

Here we go,there is a 35 to 40 year old American standard hot water boiler,132,000 btu's ,boiler #GPPX5,series1BSEJ1. The problem is when it is fireing the boiler sounds like it is boiling. The pressure is at 18psi,expansion tank is good,fill valve is good and relief is not going off. The aquistat is set at 180 degrees and the water temp is operating at at or close to that. All six zones are circulating and run quiet. After the flame comes on in about two minutes the noise starts and grows with intensity until the flame shuts off. It takes only a minute or two for the noise to stop. The system circulate quite again until the demand for flame. I have checked for "mud" at the buttom,all clear. Why is the system acting this way.


  • S Davis
    S Davis Member Posts: 491

    It sounds like lime or sediment in the boiler just like can happen in a waterheater.

    S Davis

    Apex Radiant Heating
  • Aidan (UK)
    Aidan (UK) Member Posts: 290

    Probably caused by deposits of limescale or magnetite in the boiler. It's sometimes a symptom of a fault with the water make-up or a leak. Chemical cleaning will often stop it.

    Technical info here;

  • johnnyd
    johnnyd Member Posts: 51
    does a limed up water heater run less efficiently?

    I have a 7 year old NA AO Smith WH acting as dual fuel back-up to a electic boiler. Sounds like a big tea kettle, but doesn't leak and seems to have good recovery. I'm wondering about how much hot air is wasted up the flue with it limed up like this?

    I'm justifying it because it only kicks in during control periods of a few hours, but what other problems can I expect in addition to the noise? Does the lime re-distribute itself into the rest of the system. Worries about liming up the electric boiler heating elements?
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