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help with hydrotherm boiler noise

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Royals
Royals Member Posts: 13
in THE MAIN WALL
I have a hydrotherm model hc-125 GAS system that heats using baseboards in my home. It has been running trouble free for many years, only had to replace the circulating pump about 5 years ago. Almost every morning when it first kicks in, it makes a strange noise that last for about 5 minutes. Its like a gargle type sound, but not coming from the pump. Sounds as if it could be in the furnace itself? It gargles, pauses two or three seconds, gargles, and repeats this for 5 minutes...I tried bleeding system but there was no air in the line. The sound does go away, and all day as long as the system is still warm/hot it does not produce this sound, only when firing up from cold when heat has not kicked on for many hours. Any ideas? I'm fairly handy and not afraid to tackle this? Thank-You

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  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,002
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    Hydrotherm

    I agree: very reliable boiler.



    What is the water pressure reading?
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Royals
    Royals Member Posts: 13
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    help with hydrotherm boiler noise

    pressure is 175
  • RobbieDo
    RobbieDo Member Posts: 131
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    Pressure

    The pressure is 175??
    Rob
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,002
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    Hydrotherm

    That may be your temperature, but your pressure is normally around 12-15 psi for a 1-story house.



    We ask because you may not have enough pressure to keep the air out of your system, causing the gurgling sound.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • Royals
    Royals Member Posts: 13
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    help with hydrotherm boiler noise

    ooopps, pressure on the guage is between 10 and 20 on the guage, a  little more than half way , so i would say around 16 or 17...
  • Royals
    Royals Member Posts: 13
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    boiler noise

    Still trying to get this figured out, so early this morning when the noise first started i went to the boiler, the pressure was at 30psi when the noise was at its worst, over time after about 5 minutes the noise was gone and the pressure dropped to 20psi. Any ideas why pressure would shoot up to 30 when furnace is first firing up? is this normal?  
  • RobbieDo
    RobbieDo Member Posts: 131
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    Pressure

    So, our saying the pressure before the boiler fired was at 30psi? What is the pressure with the boiler not running? Are you pumping away from the air scoop? Do you have any pics of the system? I know, a lot of questions but that is what we need to try and diagnose since were not there. Thanks
    Rob
  • Royals
    Royals Member Posts: 13
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    boiler noise

    Those readings above are from 6am this morning from when the boiler first fired up and the noise starts....I'll get the reading tonight after the system shuts down, and then again tomorrow morning just as the system kicks on...thanks
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