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Still have air noise in baseboards after several weeks

ryan242 Member Posts: 25
About 3-4 weeks ago I replaced the expansion tank on my boiler, couldn’t get it off so I ended up having to cut the tank from the nipple and then use a pipe wrench on it, anyhow I lost almost all my water when I did, now I can’t for the life of me get the air out of the system, it has an American air purger above the expansion tank. I have 2 zones, one with just 2 baseboards on it and the other with mostly cast iron radiators, the baseboards are so loud it wakes me up in the middle of the night. Everytime I bleed I only get water on every radiator and baseboard except the one right by the boiler, I will sometimes get a little puff of air off that one but the noise is ridiculous with this crap. Any thing I should try before saying the heck with it and just using my crappy ductless heat pumps?


  • delta T
    delta T Member Posts: 884
    That style of air separator is very common, and very commonly installed incorrectly. Somewhere in its installation instructions (which were likely thrown away immediately upon removing it from the box), it will stipulate that there be 18" of straight unobstructed pipe before the separator. In your case, it is possible to make that happen, but for the amount of headache and money, I would just replace it with a more modern 'microbubble resorber' such as a calffi discal or similar. That air separator will probably work.....eventually, but it is going to take months to scrub out all the air.
  • Alan (California Radiant) Forbes
    Your pressure looks low. Try raising it to 25 psi and then running the system. Higher pressure makes the air bubbles smaller and easier to move around.

    If that doesn't work, add a tablespoon or two of dishwashing liquid to help emancipate those sticky air bubbles.
    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
    JUGHNE Member Posts: 11,111
    An old method that may work is to heat the boiler/water up to maybe 180.
    Shut off power and let sit for 1/2 hour or so. Sometimes the air will come out at the high points and might be able to bleed.
  • ryan242
    ryan242 Member Posts: 25
    Another question here while I’m thinking of it, the return line from the radiator in the basement which is close to the boiler has a rise of pipe coming up off the main return pipe for the boiler, there is a manual air vent there now, which is about the only one I get air from when bleeding, would it be wise to put an automatic float type vent there instead? Like a taco hy vent or would that cause issues ?
  • SuperTech
    SuperTech Member Posts: 2,206
    I would leave the manual vent there. Float type air vents don't last long and can sometimes leak. Not good in a finished area. Also if they are on the return and if the boiler pressure gets low enough air can actually get pulled into the system from the air vent. 

    A microbubble resorber is the best thing you can do for the system. I would also consider moving the circulator so you are pumping away from the expansion tank and air eliminator.  Thats the best setup for keeping the system air free.
  • MikeL_2
    MikeL_2 Member Posts: 506
    That type of piping arrangement with the circulator on the return can cause automatic air vents to work in reverse, and, depending on the placement of the fill valve, it could be adding fresh water each time the circulator runs.......     
  • hot_rod
    hot_rod Member Posts: 22,498
    Very odd piping with that circulator on the relief valve port, is it pumping into or away from the boiler? And the black Taco must be pumping into the boiler? If so it is pumping at the PONPC and air removal will not be easy. Some critically placed purge valves could all ow a power purge to get rid of big air. After time that purger will eventually get some small air.

    Ideally the circulator would be just downstream of that air purger, both of them.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Bronxtech
    Bronxtech Member Posts: 18
    I didn't see where a flo valve is for main zone
    should repipe /relocate air purger and move smaller zone up to main outlet with a flo valve on both zones. The newer style air scrubbers work significantly better. Follow piping instructions, this one is wrong.
    And I believe you tapped into the built in air scrubber for your smaller zone, that should have an auto vent on top and relief valve as well. Unless they changed things around.
    Also ,bring up psi and temp. Good luck