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Popping sound from high temp hot water boiler system.

Pat_28 Member Posts: 3

Yes, I did manually fill the heating loop to purge the majority of the air prior to closing the loop at the union. That is why I did replace the auto vents with new ones, cause I figured that there shouldn't be so much air in there still. I did not check the expantion tank pressure with the system at zero pressure. I did not think of that till last night. I believe that the system pressure should be up at around 15 psig, does that sound correct to you? It made sence to me that if the pre-charge on the expansion tank is stamped 12 psi, and there is about 13 foot head of static pressure (about 5 psi). I was thinking that I may be cavitaing in the pump impeller due to the low system pressure. Do you think that makes sence?
Thanks - Pat


  • Pat_28
    Pat_28 Member Posts: 3
    popping sound from high temp hot water system.

    I recently made a repair on a hydronic heating system zone in my home. I thought that I evacuated most of the air from the piping prior to closing up the piping. I installed new Bell and Gossett auto air vents on the boiler and figured I was done. The popping sound started coming from the boiler and I figured that maybe some of the air was not quite out of the system yet and figured that the new air vents would just take some time to evacuate the air. It has been a couple of weeks and the system is still popping. Tonight I noticed that the system pressure gage was reading low, at 4 - 5 psig, and so I checked the expantion tank to find out that the tank was only at 3.5 to 4 pound. I put about 10 psi on the expansion tank thinking that the circulator may have been cavitating. Now the system pressure is up to about 10 psi running between 130 and 160 degrees F and I am still getting the noise. Does anyone have any ideas? Thanks
  • Norm Harvey
    Norm Harvey Member Posts: 684

    You sound as if you have boiling water. I would check the guage it may not be reading properly in either field
    "We see the world as WE are, not as IT is, because it is the "I" behind the EYE that does the seeing"
  • Ed_26
    Ed_26 Member Posts: 284
    noisy boiler

    What make boiler? Do you have pump/flow problems?
  • Leo
    Leo Member Posts: 770

    Does the system have a good pressure regulator/water feed valve? Was the system manually purged, auto vents only do so much. Was the pressure checked on the expansion tank with they system at zero pressure?

  • Pat_28
    Pat_28 Member Posts: 3
    Re.: Boiler type & pump flow


    It is a Utica boiler, circa 1992, 100,000 BTU's for a 1400 sqaure log home. I was wondering if I was cavitating at the circulator due to the low (5 psi) pressure on the system. I am pretty sure it should be up at around 15 psi. I think that the flow is okay, cause it's warm upstair, on the 2nd floor (aproximatly 13 feet up). Popping (boiling) is definetly (? - I'm wrong to often to use that word too strongly) coming from either the boiler or the pump.
    Thanks - Pat
  • V8toilet_3
    V8toilet_3 Member Posts: 15

    I'm no expert on forced hot water but if the cir pump creates negative pressure than the hot water doesn't have to be 212 degrees to boil.
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