Chimney Tales and Nightmares


Active Member
Went to visit my cabin in northern Michigan last weekend, for a "wellness check". First visit since last November. The last time I was there, I was awakened by the cold at 2 in the morning. This was the last day I was to stay there before going home. The chimney for the wood burning furnace had clogged with creosote and the fire was going out. I was not prepared to sweep the chimney at 2 in the morning, so I tied a monkey wrench to some rope, climbed on the roof and dropped it down the chimney as a quick fix and left later that morning. So, I swept the chimney before I built a fire, clearing out a large quantity of creosote. The fire was burning well and all was nice and toasty until the next day when smoke started coming out of the pipe that leads from the furnace to the chimney. I was mystified by this and thought the pipe from the furnace to the chimney must be clogged, so I removed it and found that it was not clogged! Mystified, I tied my trusty monkey wrench to a rope and dropped it down the chimney and was astonished to find it clogged again, in less that one whole day!! Had to sweep the chimney again. I have owned this place for over 20 years and usually clean the chimney twice a year in spring and fall. Last year I repaired the furnace replacing the gasket that goes around the doors as they were leaking and the furnace is quite a bit more efficient using much less wood. I only burned about 10 pieces of fire wood about 30 inches long before the chimney clogged. The wood is class "A" oak and was just a little damp on the outside. I do not know why this happened, but I have some guesses.
1. The chimney has a cap to prevent water from rain and snow getting in. It only cleared the top by 6 inches and I raised it to be about 10 inches of clearance. I am thinking it was preventing a good draft through the chimney. I also think this is an unlikely cause.
2. I have not tried this yet, but I am going to open the draft at the furnace that comes into play providing air when the furnace reaches temp and the damper shuts down the air flow. Most likely cause.
3. The chimney flue had moisture in it??
Any recommendations or clues?
My first guess is that the wrench on a rope dropping down did not do a good job of cleaning the chimney, and sweeping it didn't get it all either, and a dislodged piece reclogged it.
Also, burning dry oak wood that is wet on the outside seems harmless, but it's almost as bad as green wood, the moisture turns to steam mixed with smoke, and while it doesn't have the high creosote content component that green, unseasoned wood does, smoke and water mixed is soot in the making right there.
It takes a pretty tight fitting wire brush and fiberglass rods specifically made for chimney cleaning to do a proper job, and can take a lot of sweat and ramming if its totally clogged. Not to say that you didn't do it right, but that it's just very difficult to tell when its clean, especially with a taller chimney.
I heat my whole house with woods, burning 3-4 cords a winter, and with a proper cleaning and burning dry oak wood I can get away with cleaning once a season. Add a little moisture and its several times a season. But, an 8" flue, if properly cleaned, is practically impossible to clog it in one or two days.
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Thanks for your input.
I only used the monkey wrench to see if it is clogged and to clear debris at 2 in the morning.. ;-)
The chimney has an 8 inch flue and is about 20 foot tall. Here is the brush I used to sweep the chimney. It is attached to a wire cable used to pull it through. The brush is pretty tight and I ran it through twice to sweep the chimney the first day and twice again after it clogged the second day! I just don't see how it clogged so quickly, but I suppose it is possible there could have been some debris left after the first sweep.
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