Weak draft solutions

[WSS3]

Hey from the mountains of SW Virginia. First post from a new member.

I have a Morso Owl wood stove in a 2/12 pitch shed roof house. The single wall conector pipe indoors runs straight up about 10 feet to the roof support and a class A chimney that is proper length on the roof (48 inches) by all calculations I've seen.

The stove draft is weak enough that I get a puff of smoke when I open the door to add wood even when the stove and chimney are hot. This happens under all conditions regardless of weather. I'm a beginner at this but I know smoke indoors is bad.

I've checked the stove out by talking to Morso and doing an inspection as directed. I also used high temp caulk to seal some small leaks in the connector pipe joints. The indoor space is not depressurized. I've tried running the stove with a window open to be sure. With everything I've tried, I still have weak draft and a puff of smoke.

Is it likely that switching single wall connector pipe out for double wall will improve the draft significantly enough to resolve the backdraft problem? I've seen conversations here that double wall should be used for longer inside connector pipe runs. Does my 10 foot straight run call for double wall?

Thanks in advance for advice.

 

[DAKSY]

Your chimney may be too short...

From the Install Manual:
We recommend the length of the chimney system should be at least 16 feet (not required)
above the stove in normal domestic situations, measured from the flue collar to the top of the
chimney...

 

[Dobish]

it sounds like you might have too short of a chimney. You don't have a damper key in the chimney do you? that might also be adding to it. If you could add a section to your chimney, you might be able to determine if this was the case.

does it happen when you open the front door too?

 

[webfish]

I was thinking same thing. Chimney height. If backpuffing look at this article.

http://www.hawk.igs.net/~sunworks/backpuff.html

 

[Woody Stover]

Get 4' of cheap vent pipe you can stick up there temporarily and see if your draft improves. If so, add a 4' section of chimney. But over 5' of chimney sticking out of the roof, you will have to brace it.

 

[savageactor7]

Puff of smoke when you open the door huh...

...well try opening a window or 2 before opening the stove door. Then make some observations on the smoke. OK then open the door.

Truthfully I don't have any advice if that proves to be a smoke free work around but someone here might.

Lord knows you can't continually play window tag over your wood stove.

 

[WSS3]

it sounds like you might have too short of a chimney. You don't have a damper key in the chimney do you? that might also be adding to it. If you could add a section to your chimney, you might be able to determine if this was the case.

does it happen when you open the front door too?

Nope, no damper. And I've checked room pressure when the stove is cooking, and opened doors and windows to outdoors to make sure there's adequate combustion air. No low pressure condition indoors I'm pretty sure.

I measure about 15.5 feet of chimney from top of the fire box to the tip of the chimney (going on memory re the chimney height on the roof. I'll measure tomorrow when there's light, it's warm, and I haven't had any bourbon).

Maybe increasing the chimney height outdoors would help draft enough to solve my problem even if I am right at 16 feet? Or maybe I should try double wall indoors first?

 

[WSS3]

Get 4' of cheap vent pipe you can stick up there temporarily and see if your draft improves. If so, add a 4' section of chimney. But over 5' of chimney sticking out of the roof, you will have to brace it.

Would adding uninsulated vent pipe to the top of the stack be anything like adding insulated class A? I guess if uninsulated helped I'd know insulated would do more...

 

[Woody Stover]

Oh, I thought you only had about 10' total.
With 15', there's gotta be some other issue..

 

[schwaggly]

I can tell you what not to do. I have been burning for years and have a nice set up.
Don't get complacent. I was getting ready to burn in an insert loaded with ashes threw a bunch of crap paper ect and some milling kindling in and fired it up. 2 minutes later my room was full of smoke, first time ever. My insert is in a cold exterior chimney, we had our old drafty windows replaced, the bathroom vent fan was on close by.
3 strikes your out. I opened the windows cut the air and put out the fire. I blamed the cold chimney. After the smoke cleared I did some thinking and feel like an idiot for being so complacent