Draft with warm temps

[nate379]

I have been running my stove for about 4 months and I am starting to realize that there are certain conditions where it won't burn well because of draft conditions I think.

If it's fairly cold out I have no problems. The colder the better. Glass stays nice and clean, stove burns well.


Now when it warms up, doesn't work so well. Like today we got about 6" of snow so the air is fairly humid. I don't have much trouble getting heat out of the stove, but it seems like there isn't quite enough draft for it to burn well. The glass soots up and if I'm not careful I get smoke in the house (like if the clothes dryer is used)

Would something as simple as extended the chimney a foot or two help with this? My chimney is about 15ft now, 6ft or so sticks out past the roof, so I don't end up with a factory smoke stack if I don't need to.

 

[bogydave]

You stack sound fine.
When it's colder, you burn your stove hotter.

Mine smoked up again this week too. It was 90% clear for the month I had to burn it pretty hot.
I could see flames & or hot coals all month, about any time I looked. ("T-stat on 2.75 to 3)
Now my stat is around 2 & the glass is getting dark brown all but in the center.

I think, when burning hotter the glass is too hot to condense on the gases & they get burned up.

Maybe the wood could be dryer , but I'm having the same issues.
More so with birch than spruce, lots of oils in the birch bark, & stove temps are cooler, that may be a factor.

My burn times increased with this warm spell, burn times are well over 12 hours now. Chimney cap looks OK.
I'm loading about 1/3 less wood & still getting longer burn times. I add 2 splits (E/W close to front ) around 3 PM on a big bed of coals. Good till 11 or so when I load for the long cycle.

 

[soupy1957]

I've heard of folks who have extended their pipe for draft, but I don't know the science involved. Some places however, have "draft issues" from the get-go, and if you hadn't had problems before, then I'd think it's more about how you set the damper, than extending the chimney (imho).

I HAVE noticed days that it doesn't seem to burn the same, (heavy rain days -vs- a blue sky day, for example) but playing with my damper seems to fix the issue.

-Soupy1957

 

[Woody Stover]

if I'm not careful I get smoke in the house (like if the clothes dryer is used)

How tight is your house? If the clothes dryer is exhausting air and noticeably decreasing your draft, maybe an outside air kit would help. I'm just guessing, but it's a possibility...

 

[ecocavalier02]

the only time i get a little black in the corners is when i burn below 2. if i know im going lower i leave it on 3 for at least 20 min. to 30 then its a about hour before i bring it into the 1.5 range for a long burn. going down gradually when you want a long slow burns helps with the glass getting black. but i know bogy dave you said that the bark on the birch causes you to get some more black on the glass. my glass has stayed as clean as the day i stared the stove 3 monhs ago.

 

[My Oslo heats my home]

I burn in an Jotul Oslo and the only issues with the black soot on the glass is when I have startups, when the firebox is cold. After approx. 20- 30 mins. of burning the heat in the box increases and the film burns off. Never had any mid-burn issues with soot either. Maybe a wood issue is to blame. Wet wood, softwoods could definitely produce more soot, low firebox temps. As far as the draft is concerned, I have a 32' run to the top of the chimney, 6" liner within the brick chimney and maybe only 12" of metal exposed above the top (the cap). I have never run into draft issues until last night, it was our first issues with backdraft smoke coming into the house. I think the extreme cold had something to do with it.

 

[boatboy63]

if I'm not careful I get smoke in the house (like if the clothes dryer is used)

How tight is your house? If the clothes dryer is exhausting air and noticeably decreasing your draft, maybe an outside air kit would help. I'm just guessing, but it's a possibility...

^+1
Try opening a nearby window by 1-2" when starting and see if it helps. Also, try that when using the dryer. If smoke is coming in when your dryer is being used, it is a sign your house is too tight and not allowing enough air to enter to balance the "vacuum" created when both the stove and dryer are going. My total draft length is about 15' from stovetop to exit above roof. With this old drafty house, I never have that kind of problem.

 

[Backwoods Savage]

For sure different weather conditions will have some big effects on the draft. I've noticed more of a problem just before the snow than during it but if it warms up a lot, for sure that has an effect. Sometimes a few feet extra chimney will help. One also has to take into consideration what is around the home. Tall trees? Yes, that can and will have a big effect on the draft. Tall buildings even more so. Hills? All this has to be taken into consideration.

 

[begreen]

Agreed. Extending the flue by a foot, may not show much change. But adding 3-4 ft can make a difference, especially when the draft is marginal. For some folks this has made the difference from a stove that spills out smoke whenever the door is opened, to one that behaves pretty well. However, like Dennis mentioned, if there are mitigating factors like the flue location in relation to the roof, then it may take more height. Be sure to have a brace for every 5ft of chimney above the roof.

This article goes into more details on the effects of wind and chimney location:
http://www.woodheat.org/index.php?option=com_content&view=article&id=27&Itemid=43

 

[bogydave]

I've wondered how much barometric pressure effect burning. I know it does &
it seems to have positive effect when there is a "high" pressure area
& a negative effect when there is a Low " pressure area.

Any scientific reasons for this?

??High pressure, air is compressed more & more oxygen into the firebox.
??Low pressure, air is less dense & less oxygen.

We just went from a "high" to a "low" pressure weather front. It effects burning but why?

I know "wind" effects the draft, when the wind blows I get more draft.
Maybe the cap shape or air moving over a vertical open ended pipe has a vacuum effect.

 

[nate379]

I do have an outside air kit. When it gets like is has been (warm/humid/air pressure is weird) I just leave a window near the stove open a bit since it doesn't take much to get smoke in the house it seems.
Yes house is tight. Before I increased the intake air vent, if the dryer was running it was hard to close the front door and it would almost slam in your face when opened (standing inside). Just need to increase it more I think (working on builder with that)

As far as stove settings, I never have to run the stove at #2 to keep the house warm. Even when it was -20* a week or so ago the house was a cozy 75* with the stove at #1. Usually the knob is straight up and down though.

The wood I am burning is dry, split and corded over a year ago. When you look at the ends it's all cracked like it would be ready to split apart on it's own.

 

[Backwoods Savage]

I've wondered how much barometric pressure effect burning. I know it does &
it seems to have positive effect when there is a "high" pressure area
& a negative effect when there is a Low " pressure area.

Any scientific reasons for this?

??High pressure, air is compressed more & more oxygen into the firebox.
??Low pressure, air is less dense & less oxygen.

We just went from a "high" to a "low" pressure weather front. It effects burning but why?

I know "wind" effects the draft, when the wind blows I get more draft.
Maybe the cap shape or air moving over a vertical open ended pipe has a vacuum effect.

Dave, one more effect between the high and low pressure is that of temperature. Cooler or colder temperatures makes the air more dense. Imagine the folks who do paragliding as a good example. Colder air will give them more lift. Warm moist air is not good.