Boiler Overflow and Auto Bleeder Issue

Discussion in 'Boiler Forum' started by velosnow, May 19, 2020.

  1. velosnow

    velosnow New Member

    Joined:
    Sep 26, 2019
    Location:
    Colorado
    You guys have been super helpful in the past and I'm back with a fresh issue in a new house. Bought a 1960's fixer last year and we have baseboard heaters coupled with a boiler. No experience with either really and have a couple questions.

    1 - In our small bathroom an air vent (at least I think that's what it is) has apparently been leaking for a long time. Finally got around to the planned demo and discovered subfloor damage so it's been doing it awhile. Question is, how do I replace it? Or can I just tighten the cap? Do I need to bleed the system if I replace it? This one might be over my head so any estimates on getting someone out is appreciated.

    2 - Our boiler has a bucket next to it that has been overflowing. Just noticed it a couple of weeks ago and assumed it just needed dumped from the winter. So I ran it outside, dumped it and put it back. Since then the boiler has maybe ran 3 hours and it already overflowed. Again, no idea what I'm really looking at. Normal? Not normal? It's about 18 years old and our home inspector said they can last a long time but indicated it's toward the end of average lifetime if memory serves.

    Thanks again!

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  2. fitter30

    fitter30 Active Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Auto air bleed just unscrews 1/8" pipe thread. System has to be drained for replacement. Might want to look at other baseboards there air bleeds you might want to change. Boiler water pressure should run 10 - 12 lbs cold. If the expansion tank bladder is bad - no air pressur or if the type of tank is just a tank it could be full of water when boiler temperature comes up pressure in the boiler will rise quickly till pressure gets to 30 lbs and relief valve will leak. Post some more pics of the bliler , pump and expansion tank.
     
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  4. velosnow

    velosnow New Member

    Joined:
    Sep 26, 2019
    Location:
    Colorado
    Thanks, I'll get back down there for some more pics tomorrow. Here is one of the tank...

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  5. fitter30

    fitter30 Active Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    That tank is a bladder style expansion tank the blue cap at the bottom is for the air charge. It's a schrader valve (tire valve). For service need a low pressure air gauge 0-50 lb or lower pressure and either air compressor or hand pump.
    With boiler off cold or under 120* depress schrader just for a second if water comes out bad tank, air charge should be same as water pressure 10-12 lbs single story house. Need pic of the pump with the relationship with the pump.
     
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    If your boiler safety pressure relief valve has been opening regularly (it normally should NOT open except in an emergency), then once you fix the reason why it had to open, you should replace it with a new one.

    Heating water expands it, so the expansion tank is critical to absorb that extra volume and keep the pressure within normal range. That tank needs to be sized properly, pre-charged properly, and not water-logged (i.e., failed) for it to work. What pressure you should have in your boiler depends somewhat on the internal controls (mine won't fire unless it is over 12-psi) and how tall the building is with regards to the piping. Pressure drops about 0.43-psi per foot...you need the top of the run to be above zero to keep it from creating a vacuum, and lowering the boiling pressure of the water in the boiler.

    FWIW, the ET normally doesn't really get all that hot, so insulating it may not gain much benefit, and it could trap moisture that could start to rust it from the outside.

    If you're lucky, you can just depressurize the heating system and pump up the old ET, but it's likely that it will need replacement. Pre-charge it to your system pressure before installation.

    I'd change that air bleeder while I had the system drained enough to open that up without water spilling everywhere.
     
  7. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    Replacing the bleeders and any leaking vents would be a good start, as well as calculating then verifying the correct system pressure and pre-charge on the expansion tank.

    Even when derated for altitude a 162K-in /132K-out boiler is likely to be RIDICULOUSLY oversized for the actual design heat load, and might even be oversized for the amount of baseboard. Most 18 year old boilers have plenty of life left in them, but if it's 4x+ oversized for the design load or crazy oversized for the radiation it might be worth retiring it early. Run a fuel-use based load calculation to get a baseline number for the "before tightening & insulating" condition of the house.

    How much baseboard total is there in the house? (If controlled as multiple zones, break it down zone by zone.)

    What is your elevation?
     
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