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clogged flue

oilwizard Member Posts: 46
Is there a clay liner or stainless? If it is just the regular clay liner and it is mostlikey a 8" or so block, then I bet the flue gases are condensing. You should have the right size liner to keep the gases hot enough. Try z-flex or some other like that.


  • antman
    antman Member Posts: 182

    I recieved a call at the end of the day today, customer had no hot water. went by on my way home, WM EG with a plus 100
    Long story short, blocked vent swith triped, reset fired, shut down, removed smoke pipe and what you see in the pix is what i saw. Well i cleaned out a 5 gal. pail of this stuff. now i didn't have my analyzer with me but i will go back tomorrow and give it a once over.

    My question, when i did the oil to gas coversion i had the chimney sweeped by a company. Is this the dried out oil that was on the lining or is it the lining of the chimney itself, I told the homeowners it needs to be cleaned again and inspected.
    Was it an improper cleaning from the start or now that they have an gas boiler it should have a sleeve installed.
    Is installing stainless linings hard to accomplish or should i leave it up to a so called chimney professional.
    this one is probably 30' (3 storys, 9' ceilings)
    Any info on specific liners that might be used?

    sorry for the flood or questions.

    Thanks, Ant

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  • Mark Hunt
    Mark Hunt Member Posts: 4,909

    Thank God for spill switches!!

    With the higher efficiencies of todays boilers we must consider what the effect of lower stack temperatures will be.

    A chimney liner would be the recommended fix here. That being said, make sure you test the draft after you install the liner AND do a "worst case depressurization" test!

    The "worst case depressurization" test is very simple. Put the building in a "winter mode" by closing all of the windows and run EVERY exhaust fan there is in the building at the same time. This will include clothes dryers, attic fans, bathroom and kitchen fans, anything that exhausts air from the building. Once you have them all running, check your draft again. You may find that the unit will not vent properly during this scenario.

    Flue gas condensation is nasty stuff as you will see in the pics I have attached. The pics show what happened to an exterior, clay lined chimney in ONE year after a fan assisted furnace was vented into it. ALL of the flue gasses were venting into the basement and were moved into the living areas via leaky return ducts and stack effect.

    It is SO important that we test these things.

    Mark H

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