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Condensation in the chimney

Many of you have read or responded to past posts; thanks.

My new Megasteam 513 is now running well; 13 CO2, no smoke, about 335*F at the breach. But draft is -0.05 at the breach and +0.02 over the fire.

Now it is dripping condensate down the wall and onto the floor from the chimney cleanout. At first, I thought it was just melted snow or rain (need a new cap), but it is still happening with clear skies.

I'm considering removing the baffles, to see if this will raise the temp, and improve the draft, and reduce the condensation.




  • HatterasguyHatterasguy Posts: 6,058Member
    What is the length of the vent?

    Can you check the exhaust temperature at the point where the vent enters the chimney?

    If you get a reasonable difference, consider insulating the vent to raise the chimney temp.
  • ThermalJakeThermalJake Posts: 106Member
    From the rear outlet, it rises about three feet, and then horizontally about 3 feet where it enters the chimney. The regulator is in the vertical.

    I can check the temp where it enters the chimney. I will report back.
  • icesailoricesailor Posts: 7,265Member
    Is it an outside chimney flue? Is the 335 degrees corrected or uncorrected? If it is uncorrected, it is low. Especially if it is a 3 sided outside chimney. Corrected would be 265 degrees to 275 degrees.

    If it is a 3 sided outside chimney, you need a liner to stop the condensation and ruining the chimney flue tiles.
  • ThermalJakeThermalJake Posts: 106Member
    it's about 395-400 stack temp; in a 60*F basement.
    3 sided outside flue. I always thought it merged with the fireplace flue above because of the offset, but I'm thinking maybe they remain separate.
    Also, there is no cap; that and an examination of the brickwork at the top is next.
    There have been light drip marks before, especially in rain or snow. Just not this much. I assumed that the increase was because the Megasteam was so cold in the flue that condensate was increased. But after yesterday's heavy rain, the drips were much worse. So I know that some of it must be rain.
    Obviously, I'm testing two theories at once, but I think that both may be happening. I'm going to eliminate one first, then work on the next.

  • icesailoricesailor Posts: 7,265Member
    As long as you are venting into a 3 sided outside chimney/flue, you will have condensation issues in OAT where the temperatures in the flue gas get cooled to the dew point and water vapor forms water. The acids in the flue gases will destroy the clay tiles that are supposed to be in the chimney. Someone makes insulated flue liners (Duravent?).

    You need to either drop an insulated liner down the 3 sided chimney or sidewall vent it if possible.

    When you see soot marks lower down from the top of the chimney, the clay flue tiles may already have failed. Especially if there are soot marks on the vertical joints of the bricks.
  • neilcneilc Posts: 360Member
    and if some of those joints are failed then yesterday's rain may have had additional ways in also

    CO Detector ?
  • ThermalJakeThermalJake Posts: 106Member
    upstairs tenants have one. it is silent.
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