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  1. #1
    Join Date
    Aug 2012
    Posts
    43

    Black Sludge Coming from chimney

    As many of you know, I had a Buderus oil boiler installed a couple weeks ago. Yesterday, I noticed a lot of blackish-green, oozy sludge dripping from the smoke pipe at the joint where it takes a right angle turn into the wall (and then up the chimney). Trying to figure out what the cause is and how to fix it.

    Here's some additional background: in the past, when we had heavy rain from the south, we occassionally got a bit of water leaking from the same joint in the smoke pipe. I assumed it was wind-driver rain that got in the chimney. It was always just clear water. No sludge or soot in it. Just a few days before my new boiler was installed, I had the chimney cleaned and a new, bigger chimney cap put on.

    For most of Monday we had rain and wind from the north due to hurrican Sandy. No problems then. In the wee hours Tuesday the rain and wind shifted to the south. It was late Tuesday morning when I discovered this puddle of black sludge on the floor, which had dripped from the smoke pipe.

    I don't know for sure whether the sludge was due to rain getting down the chimney, or possibly condensation in the chimney due to temperature or atmospheric changes. Assuming it was rain, however, I am concerned that it was such thick black ooze, whereas in the past it was just a little water.

    I had the contractor come back out and they put a baromic flue damper on, which they had not done before. They also sealed the seams of the smoke pipe with a high temp silicone, but that will just keep the ooze in the chimney, it won't really address whatever caused it in the first place.

    Any ideas what could be cauusing this heavy black ooze? Is it a sign that my boiler is not set up properlly and/or condensing in the chimney? Any other thoughts? much appreciated.

  2. #2
    Join Date
    Aug 2012
    Posts
    43
    p.s. - the sludge was very "oily" feeling.

  3. #3
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,327
    Very first thing: insist on a combustion analysis of your new boiler. Do not pass "Go", do not collect $200. Your installer needs to do this as a matter of course when commissioning a new boiler.

    Given that your chimney was cleaned prior to the boiler install, either the chimney cleaner left a bunch of debris at the bottom of the chimney after he cleaned it, which turned to sludge during your rain event, or the boiler is not firing properly and is sooting up your chimney. Get the combustion analysis done regardless, and also ask your chimney sweep if all debris was removed from the chimney prior to calling the job done.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  4. #4
    Join Date
    Aug 2012
    Posts
    43
    You may be right about the set up -- they apparently did not do any testing at the time they turned it on (that's the think with the sensor they stick in the boiler and chimney, right?). I had them test it yesterday when they came back out. I think he made some adjustments, but not sure what.

  5. #5
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,327
    If your installer used a combustion analyzer, and made some adjustments, you should request a copy of any documentation that went along with what he did yesterday. You may not understand what the readings mean, but it is always good to keep personal records on YOUR equipment, even if those records are Greek to you.

    He also should have told you if the new boiler was causing the soot and sludge or not. You need assurance the problem has been resolved. You don't want to find out via a completely sooted up boiler and furnace.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  6. #6
    Join Date
    Aug 2001
    Location
    Pavilion, NY
    Posts
    2,127
    In all likelihood the flue gas is condensing because the boiler is set up too efficiently (not enough air) and or the piping is such that the return water to to boiler is too cold for too long thus the flue gas is condensing. I would imagine the later of the 2 is your problem. This can be solved by repiping the boiler differently.
    ...

  7. #7
    Join Date
    Aug 2012
    Posts
    43
    Thanks, guys. I think the "not enough air" comment was probably dead on, as the guy who came out said I definitely needed a regulator.

    I do have a copy of the analyzer results.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,929
    Quote Originally Posted by newlyn View Post
    Thanks, guys. I think the "not enough air" comment was probably dead on, as the guy who came out said I definitely needed a regulator.

    I do have a copy of the analyzer results.
    You gonna post them?
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  9. #9
    Join Date
    Aug 2012
    Posts
    43
    Sure, will do it later tonight. Keep in mind, these are from after he made adjustments.

  10. #10
    Join Date
    Aug 2012
    Posts
    43
    Ok, here's the info from the printed ticket. Let me know what you think.

    T stack 363.7
    Co2. *11.35
    Eff 86.5
    Ex air 36.5
    Oxygen 5.8
    Co. 15 ppm
    Co airfr 21 ppm
    Inh2o draft .0044
    Ambient temp 61.9
    Instrument temp 61.3

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,929
    They're ok in general. I'd probably increase air/O2 slightly.
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  12. #12
    Join Date
    Jan 2012
    Location
    Broomall, PA
    Posts
    391
    Question...is T stack the stack temperature, or the net stack temperature? If its the stack temp, then your net stack temp is 301 degrees. Your condensing in your chimney.

  13. #13
    Join Date
    Sep 2011
    Posts
    50
    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

    You can find the rules for posting and qualifications here.

    Additional infractions may result in loss of posting privileges.
    Last edited by jpsmith1cm; 12-21-2012 at 07:07 PM. Reason: Non AOP Member

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