My Jotul Stove smokes

[AdrienneW]

This is the first time I have had a wood stove, I have had fire places in the past and an insert, and then for the longest time central heat and air. Forgive my ignorance about wood stoves and wether or not smoking is normal.
I recently purchased a Jotul stove. I bought it at a discount store because it had some paint chips on the enamel but other wise seemed 100% perfect. We broke the stove in as the instructions stated and it has worked great. The other day I noticed a puff of smoke would poof out the front and back (top) every so often (just the vents). A friend of mine said it was because of it being windy and that I needed to open up the vents to make the inside hotter so the smoke would be pushed out. This appeared to work. Tonight however, when I had it set on "low" so it would burn all night it poofed smoke again. I checked the wind direction and it was pretty well still out side. I don't know if the chimney just caught an odd draft or not. Again I opened the vents a bit more and got it hotter and it appears to be a-ok. However, this does worry me just a tad, and I was wanting to know is this normal?
My chimney is not over the ridge of my house. And I wonder if this could be part of the problem? It is about 7 feet off of the roof, but it doesn't clear the ridge.
I don't mind an occasional poof, I just don't want my house to catch fire.

 

[jpl1nh]

You are experiencing what is called back-puffing. It happens when the oxygen supply to the fire in the firebox is not enough to be able to combust all the gasses being produced by the hot wood. The wood gasification continues to produce excess gas until it finally ignites in a mini "explosion" of combustion, the resulting pressure of which forces a puff of smoke out of every crack and crevice it can find its way through. Your friend was right to suggest increasing the air supply slightly which then provides enough oxygen to burn the gasses more steadily without them building up. It won't burn your house down but just keep adding smoke into the room, a less than desirable effect. Wind can be one of the things that causes that but often it's just plain a bit too little air for your particular stove chimney set up. If I remember correctly, your chimney should be at least 3' above your roof peak and at least 2' higher than anything within a 10' radius as well as generally being at least 14' from the exit on the stove to the top. The inside diameter or width of your flue should be within the area specified by the manufacturer. The chimney is one of those kind of after thought things for new stove users but immensely impacts the stoves performance. You can have the best stove going and with an inadequate chimney you'll be SOL. You may want to see if you can extend your chimney height to get it above the peak by 3'.

 

[begreen]

If the stove behaves better in the next couple days, it might be because it was warm outside. If not, examine the cap on your flue closely for clogging.

 

[JeffRey30747]

My understanding of the rule for chimney height is at least 3 ft higher than where it exits the roof (not the peak) and at least 2 ft higher than anything within 10 ft. I'm much higher than 3 ft from the point where it exits the roof but just a little under 2 ft higher than the roof peak which is within 10 ft (this is a 9-12 pitch roof). My Jotul Oslo sometimes has an occasional minor draft issue (some smoke when loading stove) when the weather is warm but I believe that it is a result of the cross section of the 8"x8" clay flue tile being so much greater than the 6" round flue that the stove was designed to operate with originally instead of inadequate height. Take a look at your flue to see how it meets the 3 or 2 in 10 rule.
If you don't already have a chimney cap, you might try one. If downdrafts are contributing to the backpuffing, it might help. Make sure the flue, cap and stove pipe are clean. This is both a fire hazard and an impediment to proper draft. Other than that, all I can say is keep the fire hot enough to assist draft.

Jeff

 

[cgeiger]

What everyone has written covers the majority of the probable causes for your backpuffing. Also check and see if you have a problem anytime you run any combination of bathroom fans, dryers or other items that vent inside air outside your home. This can contribute to a poor draft if your home is sealed up real tight by creating a vacuum that creates a neutral or negative draft in your chimney. Speaking of tightly sealed home - when was your home built? It's not as uncommon these days to have a newer home with ultratight insulation and sealing. Also, BeGreen is right-on regarding temps. Given the length of your flue and the height at peak issues, you will have a tough time getting a hard, steady draft if the outside air is "too warm." "Too warm" varies depending on your setup, stove, burn habits, wood, etc. but if you notice the backpuffing again be sure to note the outside air temp. One final thought - You can also try cracking a window to help - or in very tightly sealed homes you may want to consider an outside air kit (OAK) if you're stove allows for it. Both of these solutions will help release the pent up pressure by providing a way for air to flow into your home and thence into the stove and out the chimney.

 

[begreen]

How is the stove connected to the flue? Is it rear-exit or top-exit?

 

[AdrienneW]

It is connected through the back and the only time we seem to have an issue is when the wind blows pretty hard. After I wrote what I wrote last night I heard the wind throw a few really strong gusts and it did it again...then stopped when the wind died.

I will have to see if I can get the chimney height increased. That may solve my problem...who knows.

Thanks all.

 

[DAKSY]

My understanding of the rule for chimney height is at least 3 ft higher than where it exits the roof (not the peak) and at least 2 ft higher than anything within 10 ft.

You're correct, Jeff.

I'm much higher than 3 ft from the point where it exits the roof but just a little under 2 ft higher than the roof peak which is within 10 ft (this is a 9-12 pitch roof).

For a 9/12 pitch, the easy calculation is to take the top # (9) multiply it by 10 & add 24...
This will give you 114 inches out of the roof.


My Jotul Oslo sometimes has an occasional minor draft issue (some smoke when loading stove) when the weather is warm but I believe that it is a result of the cross section of the 8"x8" clay flue tile being so much greater than the 6" round flue that the stove was designed to operate with originally instead of inadequate height.

I agree with you...These damn things don't like to draft when the weather is warm...

Take a look at your flue to see how it meets the 3 or 2 in 10 rule.
If you don't already have a chimney cap, you might try one.

Chimney caps are DEFINITELY a good idea...

If downdrafts are contributing to the backpuffing, it might help.

Take a look at the relationshionship of your home to its surroundings...High trees, higher buildings or higher landscape features can also be detrimental to good draft, by causing air currents to dive down towards your chimney...

Make sure the flue, cap and stove pipe are clean. This is both a fire hazard and an impediment to proper draft. Other than that, all I can say is keep the fire hot enough to assist draft.

Again, I agree, the amount of draft required for proper smoke evacuation is a relatively small number (25 Pascals), & can be affected by many factors...
How small is 25 Pascals you ask? Well, take an 8 x 10 sheet of paper, hold it flat (like you would if you were going to write on it) & Let go of it.
It falls...Gravity makes it do so...
How much pressure underneath that piece of paper would cause it to rise from your hand if you let go?
NOT MUCH - 25 Pascals is the answer...
Try to drop that same piece of paper onto a campfire...It'll probably go up - not down..
That's why you have to open the air control fully - before you open load doors - & open the load doors slowly...or you can change the direction of that 25 Pascal flow...
That concludes Physic 101 for today!