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Boiler Making stewing or sizzling sound at 190 degrees

William
William Member Posts: 2
in THE MAIN WALL
Ao Smith copper boiler, HW100p with 2 zone loop baseboard heating system ,Bell and Gossett pump& Thrush zone valves,with aquastat heat control ,,around 18 years old ,Boiler makes a stewing or sizzling sound around 190 degrees, unit has a flow balancer and have been running with it wide open ,if balancer shut off sounds gets worse , does sound like flow problem ,and also original owners has said been like this since new. copper supply pipes being 3/4" and they flow into a 1 1/4" return which is about 4 feet returning into pump
house is 28 x 56 splt level, noise also apparent with both zones open, any help please

Comments

  • Jerry Boulanger_2
    Jerry Boulanger_2 Member Posts: 111
    Low flow in low mass boilers

    will cause the boiler to make some pretty weird noises, especially at high water temperatures. If it's possible, measure the temperature rise through the boiler when it's running. If it's more than about 15-20 degrees F, it's flow starved. You will then need to determine why and correct the problem.

    The best solution is to install a primary loop and dedicated boiler pump.
  • Murph'_4
    Murph'_4 Member Posts: 209
    could be...

    A lime or calcium build up !
  • hr
    hr Member Posts: 6,106
    Check the pressure

    run at least 15 psi, especially at 190F.

    At that age it could need a cleaner the get the HX back to good condition.

    Or a new boiler :)

    hot rod

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  • William
    William Member Posts: 2


    Jerry , primary loop, would that mean a section of pipe run only without any convectors and a extra pump? Or do you think I could split the zones I have and return them to the boiler Via 1" pipe into the exsisting 1 1/4 , One of the heating contractors at my location Suggested I move the zone valves from the return to the supply , I did that and did not help, I forgot to mention also that I had tried two flow pumps one on top of the other as instructed by another heating contractor, which did not help ,Also have installed different heat exchanger on the unit as per manufacture,which did not help, I checked the temp differece best I could from return to supply was 18 degrees close to boiler.. I really appreciate the feed back on this
  • Jerry Boulanger_2
    Jerry Boulanger_2 Member Posts: 111


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