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Buderus chimney condensation problems

MassMass Member Posts: 1
Hello everyone, fall 2011 I had a buderus G115 ws installed with a logamatic R 2107. I live south Boston. Last winter I noticed a significant amount of condensation / water build up inside the chimney trap. Chimeny is on the outside of the house. Contacted the contractor who installed the system. He removed 2 steel bars from the system to lower the efficiency. He said the boiler was running to hot. It did not address the issue. Had a chimney guy rebuild the chimney crown again no luck. The

Water seems excessive since I had to clean it out every 2 Weeks. Any recommendations?


  • JStarJStar Member Posts: 2,668

    Condensation is normally the result of LOW flue temperatures, or an incorrectly sized chimney, or vent connection. Do you have pictures of the boiler and chimney? How tall and what size is the chimney?
    - Joe Starosielec
    [email protected]
  • Robert O'BrienRobert O'Brien Member Posts: 2,938
    Chimney liner

    You need a stainless steel liner or alternatively you can remove the 'mustache" baffle and see if that raises stack temp enough
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • icesailoricesailor Member Posts: 7,265
    Outside Chimneys:

    I am assuming that your Buderus is Nat. Gas fired.

    I am a licensed Master Plumber in Massachusetts. From what I/we learned in our Continuing Ed in Class three for this license cycle, there are specific rules for venting into a 3 sided outside chimney. The gas permit holder is responsible for the venting. If the installer is a "Heater" and not a Licensed MA. Plumber, he should have taken the class.

    Even if you put a liner inside the flue, you probably can't make it conform. Part of the equation is the location in Massachusetts and how cold it gets. And how much chimney is exposed. The flue gasses are falling below the dew point and water is condensing in the chimney. The chimney will fail.
  • IronmanIronman Member Posts: 3,533
    edited September 2012
    Oil Fired

    That's an oil boiler, Ice. But you comments are spot on. The stack temp on that boiler is 300 - 350* depending on size and burner. It should not have been connected to an outside masonry chimney without being re-lined and insulated. The direct vent model would have been the correct choice.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • kcoppkcopp Member Posts: 2,771
    tell us...

    more about the system.... What do you have for radiation? What did it replace? Was a heatloss done? Which Model 115? Model burner....etc.
  • JackJack Member Posts: 941
    NFPA 31 lacks

    support for re-lining. We were never able to get the committee to include venting standards for re-lining. The excellent work on venting that Rick Krajewski and John Strasser did at Brookhaven in the early 90's got stuffed into Appendix E, never to see the light of day as it would raise system costs.

    I will offer a conversation I had with Rich years ago about his work. What he said was that regardless of length, height, inside/outside, etc the thing that had the most consistent positive affect on flue operation was insulating the vent connector. Products are available for this. 4" pellet vent is L-vent and the DS and DVL products from Selkirk and Duravent, respectively, are excellent as well.

    I spoke with a sweep from LI some time back who has been re-lining using App E for years and said the sizings are right on.
  • Paul PolletsPaul Pollets Member Posts: 3,022
    Vent Insulation

    A stainless steel flexible liner with insulation jacket should solve your problem...They are available from several manufacturers and usually are made from 316L SS for oil combustion. Make sure the product is UL listed.
  • rick in Alaskarick in Alaska Member Posts: 627
    edited September 2012

    My first thought was is it condensation or is there an internal leak in the boiler?What is the exhaust temperature after taking out the baffles? Is the boiler hooked up to an automatic water fill valve? Since the exhaust on this particular boiler usually runs low, and the exhaust is vented to an outside chimney, it probably is condensation, but I would definitely rule out any other potentials first.

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