My woodstove's smoke pipe has 13 joints in it before entering the chimney, could this thin wall steel be miged or would tig be a must. Is there any other way to seal these joints? When it is very windy out I get small rings of smoke puffing out of each joint, the flue is above my peak, I have tried with /withought the rain cap and I now have a "whirlybird" on top which is suposed to aim downwind and cause a venturi to aid in draft but I am still getting the back draft. Also it only seems to happen when I have the combustion air inlet is turned down low. Thanks for any help.
I know this doesn't exactly answer the question you asked, but----
13 joints is a lot of joints for a wood heat system. If there are any bends in all that "jointery" you are loosing a lot of draft. You need at least 0.05" water column of draft for good operation and then you wouldn't see the puffing. Get a cheap draft gage and check it out. If you DO weld all that pipe together, how will you get it apart to clean it? You know, you will have to clean it from time to time because you will get creosote deposits in it. They will create a chimney fire sooner or later. Not a good thing seeing the red glow work its way up the pipe. How high is the total height above the peak? Needs to be at least
2 feet, but there can't be any downdrafts from nearby trees, buildings, etc. Maybe even need to relocate the stove to eliminate bends. One 90 degree bend costs you a lot of draft. Making that bend in 2 45's doesn't help much. If you do have a draft problem, better to install a suction fan in the pipe.
Might be a silly thought, but, do you have the pipe sections aimed in the right direction? The lower pipe should enter inside the pipe above it to help with creosote buildup and air leaks.
All these joints are in a 3' span. The pipe goes up 2' from the stove and bends 90 into the chimney but it has to offset about 6". I used 2
90 degree elbows that are each made up of 3 sections that can rotate. These are common elbows sold everywhere, the only other option are the corrigated type which will not work for me. There is an adapter to go from the 6" pipe to the 7" flue entrance. If I do weld it all together I can still take the whole unit off as one piece. Where would I go looking for a cheap draft gage. Also I should mention my house is surrounded by tall (=3D to house height) spruce trees but they are about
50-100' away in all direction. The front of the house is on the water and there are a few tall trees there. The smoke sometimes comes right down to the ground.
That's backwards as far as my experience shows, and I've seen the same woodstove set up both ways. The upper pipe should go inside the lower so that condensing smoke (liquid creosote) continues to drip down towards the stove firebox, and not out at the joints and onto the floor. With a good draft, the direction shouldn't matter to the smoke as the leaks shouldn't let smoke out but pull air into the pipe instead, so the flow of creosote determines which way the flanges go. If you need to control the smoke with the direction of the flanges, then you don't have enough draft.
As far as the original poster goes, could you put an extension on the chimney to get more height? Maybe your chimney needs a liner--a chimney too large for your stove can cause as many draft issues as one too small. Most chimney sweeps can install stainless liners in about a day, or less. Also, consider a draft damper, like the oil furnaces use. If you have enough draft except when you shut the stove way down, it will allow enough airflow to pull the smoke along without it having to go through the stove. I seem to recall it takes ten times as much air for draft to move the smoke than you actually need to burn the fuel, but I might be mis-remembering.
Are you using all the elbows to get nice vertical and horizontal runs for your flue? Consider reducing the number of joints by running the pipe at an angle instead. Most of the elbows can be adjusted to smaller angles by rotating the sections, which might allow you to use fewer elbows.
You also might have too much stove for your space--remember a woodstove is basically a space heater, not a whole house heater. If you have to turn it way down to stand being in the room, you're not getting good combustion and making too much smoke. A smaller stove might let you actually run it with enough air to burn clean and not drive you out of the room. You can only move so much heat to other rooms with fans and the like.
I've been monitoring and tweaking my wood stove for over 20 years and almost have it figured out.
The flue temperature above my stove needs to be at least 200F on a magnetic stack thermometer. This is probably the most important point. I also live where the wind can blow the smoke straight down. It won't blow back into the house if the stack is hot enough.
The stove is a copy of a good airtight Jotul but it misbehaves like yours if set for slow "cigarette burn". I arrange the wood so the incoming air has a clear path at least half way down the bottom center and the wood burns full length. It runs happily like this on three or four fist-diameter pieces of oak an hour.
There's a mirror outside showing the top of the chimney. I set the draft opening as small as possible without visible smoke, which depends on outdoor temperature, and then vary the stoking rate for more or less heat. I made a gauge like a step drill to set the draft opening consistently. Right now it's at 3mm X 20mm at the bottom and about twice that for secondary smoke-burning air above. Originally both were equal.
My stove wants at least 0.08" of draft, 0.12" is better, 0.15" when the wind comes down off Hudson's Bay. (I found a surplus Magnehelic vacuum gauge cheap) You can make a draft gauge out of a U of clear plastic tubing with colored water in it, fastened to a board. Tilt the board to rise 1 inch in 10 and the distance between the two ends of the liquid will be 10X the draft in inches of water. Once you know how hot to run the stack you don't need the draft gauge.
My wood stove was a single wall unit that left the stove and went up 30'. (about 10 meters). It was bottom pipe inside top pipe. So the top slides over the lower one in the stack up.
I never had problems with it for more than 17 years. I always cleaned it from the top - and so did my sweeper. The brush is long on extensions. Hotels and large homes have very long ones.
Now for the flow issue - two 90 degrees - that is tough on flow! I think IIRC, that is 1/4 the normal flow rate.
I might have gone stainless and with bends.
Why not an insert ?
Martin
Mart>> Might be a silly thought, but, do you have the pipe sections aimed in the
And if there does happen to be a chimney fire, that liquid creosote will be flaming liquid creosote and you really want it to stay contained.
With double-wall or triple-wall pipe, just make certain the inner pipe is oriented so liquid flowing down the chimney cannot run out.
Yup.
Sounds that way. Another possiblity might be a tight house -- negative pressure inside can cause poor draft.
Yes. My last place I put in the smallest stove cosmetically acceptable to SWMBO. It was a new house, and easy to overheat. During one of those "it's too hot in here" moments I found out the draft worked a lot better with a window cracked open just a bit.
"Phil Kangas" fired this volley in news:fntvqe$t3e $ snipped-for-privacy@aioe.org:
Well, not liquid creosote, Phil, but water mixed with creosote and other soluble combustion products, yes.
Until the pipe heats up enough, it acts just like any other condensor, and in my experience they ALL drip a little (preferably into themselves, not out) during initial fire-up.
From what I've seen on this subject of creosote dripping the problem is the 'automatic dampers' used. They allow the air intake plate to completely close off the air intake hole! This is not acceptable and is the root cause of the situation which in my opinion is very serious indeed and must be taken care of immediately. The simplest fix is with a welding rod with one end bent into a hook and you hang in on the intake hole so the plate can never close completely. None of my stoves have ever dripped 'liquid', ever. The guy with 13 joints has a real problem! phil kangas
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