Lazy Draft

[Clodhopper]

I have 2 Oslos' in my house. The one that is in the dining room has great draft (almost too much sometimes) with about 24 feet of chimney including the 4 feet of double wall stovepipe to get up to the ceiling support.

The lazy one has about 15 feet of chimney including the 7 feet of dwsp going up to the cathedral ceiling support. This stove always seems to have a hard time getting going, and lately has been back puffing if I try to shut it all the way down at the wrong time. The top of this chimney is about 3 feet higher than the peak of the roof, which is about 10 feet to the west, so it should be good as far as that rule of thumb goes. Is the overall shortness of the chimney most likely the cause of my problem, and would an extra 2, maybe 3 feet make much improvement? I wouldn't want to go too much higher than that because we get a lot of wind here.
Thanks
Pete

 

[begreen]

Yes, that additional 2-3 ft can make a nice difference. The Oslo wants at least 16ft of pipe. A brace is required at 5ft above the roof penetration.

 

[Backwoods Savage]

Height can indeed make a big difference and you are seeing that firsthand. There is 9' difference in the two. If you care to check, go to the hardware and buy some cheap single wall pipe and stick it on the top. Then you can see if it makes a difference. You would not want to leave this on for long but it would allow you to see somewhat how much difference a few feet can make.

And yes, for sure in the windy area you want some bracing.

 

[Clodhopper]

Thanks for the input Begreen and Backwoods. I put another 3 foot section of chimney on this afternoon and now I have a bracing question. I have a brace that is attached to the middle of what was the top section of chimney, which left about 2 1/2 feet above the brace including the cap. With the new 3 footer on there I now have about 5 1/2 feet above the brace including the cap. Do I need to slide that brace further up the chimney, or is that adequate?
Thanks again,
Pete

 

[Hogwildz]

Standard rule is bracing every 5'.
I'd say your safe at 5'6". 6" does not justify another brace and more holes in the roof.
You can slide it up some, but probably don't need to.

 

[begreen]

There is supposed to be a brace every 5' above the roof penetration. What height was the old brace set to? How much total pipe is sticking out of the roof now?

PS: have you fired up the stove to check draft?

 

[Trilifter7]

What do you guys think about having 13' of chimney? I have 6' of single wall in a vaulted ceiling then the roof penatration then about 6' of dwsp above the roof penetration. the top of the flu is as high as the roof line but not taller than. I don't have any issues with draft now but I am burning an older non-CAT stove. I am looking at upgrading to a cat stove this spring and don't want to worry about any draft issues.

 

[Hogwildz]

YOu can try it with the set up you have, and always add to the top if needed.

 

[Clodhopper]

There is supposed to be a brace every 5' above the roof penetration. What height was the old brace set to? How much total pipe is sticking out of the roof now?

PS: have you fired up the stove to check draft?

The old brace was set at about 4 feet. Total length past the roof is about 9 feet. I do have a fire going now and the draft seems better. Still not as good as the other stove, but the pipe is still 7 feet shorter. I'll have to test drive it for a few weeks to see if it solves the puffing problem I've been having.

 

[Trilifter7]

YOu can try it with the set up you have, and always add to the top if needed.

I might try that and see how it goes. Is a 13' flu uncommon or does anyone else burn with a short flu?

 

[begreen]

The old brace was set at about 4 feet. Total length past the roof is about 9 feet. I do have a fire going now and the draft seems better. Still not as good as the other stove, but the pipe is still 7 feet shorter. I'll have to test drive it for a few weeks to see if it solves the puffing problem I've been having.

Usually the brace is adjustable. If yours has adjustable arms, raise it to the 5ft level and be happy.

 

[Hogwildz]

I might try that and see how it goes. Is a 13' flu uncommon or does anyone else burn with a short flu?

Most manufacturers spec 15' minimum, but you may be ok with 13'. If it burns good with 13', then your fine. If it has poor draft and smokes the room out when you open the door, you may want to add a couple more feet worth.

 

[dafattkidd]

Most manufacturers spec 15' minimum, but you may be ok with 13'. If it burns good with 13', then your fine. If it has poor draft and smokes the room out when you open the door, you may want to add a couple more feet worth.

Will two feet add a significant difference in draft? I am under the impression that it takes a significant length to impact draft, but I hope I'm wrong.

 

[Hogwildz]

That all depends on the set up, as each one is slightly different. 2' may put it just over the height it needs to pull the draft it needs, or 2' might still not be enough. Of course the taller the stack, the more draft you will have. At 27' here, I may at some point take 2' off, as my draft pulls plenty and then some.

 

[Trilifter7]

Thanks again Hogwildz, I will try it out and see. My draft seems to be ok with my current setup so hopefully a newer stove won't change that. I can open the door and with the bypass opened i never get smoke into the room, so that is a good sign. The only time I have an issue with smoke is sometimes on startup when its mild temps out I will get some smoke coming into the room with the top lid open. Once the stove is hot though it never seems to be an issue. I figured that was due to poor draft from low temp differentials and and cool stove.... not necissarly bc of a short stack. I would assume everyone gets that with the right conditions... or guess that would be with the wrong conditions for good burning.

 

[Hogwildz]

Thanks again Hogwildz, I will try it out and see. My draft seems to be ok with my current setup so hopefully a newer stove won't change that. I can open the door and with the bypass opened i never get smoke into the room, so that is a good sign. The only time I have an issue with smoke is sometimes on startup when its mild temps out I will get some smoke coming into the room with the top lid open. Once the stove is hot though it never seems to be an issue. I figured that was due to poor draft from low temp differentials and and cool stove.... not necissarly bc of a short stack. I would assume everyone gets that with the right conditions... or guess that would be with the wrong conditions for good burning.

Yes, at times in the shoulder seasons, I get some smoke back up (Cold starts only)due to a cold stack and more milder outside temps. Once burning 24/7 though, that issue is non-existent.

 

[ohlongarm]

I might try that and see how it goes. Is a 13' flu uncommon or does anyone else burn with a short flu?

I just make 15 feet with the King haven't noticed any problems seems to start pretty well even in warmer temps,but a little slower than cold.My run is 4.5 straight to a 45,then 2 feet horizontal then 8.5 feet straight up.

 

[Trilifter7]

I just make 15 feet with the King haven't noticed any problems seems to start pretty well even in warmer temps,but a little slower than cold.My run is 4.5 straight to a 45,then 2 feet horizontal then 8.5 feet straight up.

Good to know. I'm feeling a little better about my draft now. Never had a problem so I think i will be fine.