Drafting problem

[wyecoyote]

Hello I'm new to this so be gentle plesae.

I have a Split Entry style house living area (3 bed, 2 bath, living room kitchen and family room upstairs and Rec room, bath, two offices down). I have a double flue chimney that I had installed two Country c210s one upstairs one downstairs. The upstairs drafts fine when I start a fire. The downstairs one does not draft on initial start and even with a good fire has difficulties. The wood I am burning is 2 to 3 year seasond and kiln dried wood. A friend of a friend owns a door/trim shop and I get the scraps. Thus I still have plenty of seasoned wood still under the deck (covered). The trim and scrap doors/frames I use to get the fires going and burn for during the day and throw a few logs on at night before bed. The downstairs one is the one I have the most problems with it billows out smoke on start up and if I shut the door all the way it will put out the fire. Anyone have any problems with this type is it because of the two levels that the smoke has to go up combinded with the small insert? I am at my wits end on this and it typically takes 20-30 minutes before the flute gets hot enough to start a draw up through the flue. Even when hot the smoke comes out when the door opens.

I have considered going to a larger insert as I find that the max burn time even with logs and the vents closed that I get maybe 3-4 hours. Would this "fix" the problem a larger insert with potentially a larger flue size? The house is also a 1970's house with basic insulation for the age so heating costs with the furnace (electric) are spendy and I prefer the wood heat.

 

[branchburner]

What are the sizes of the two flues in the chimney?

 

[LLigetfa]

The problem probably has more to do with stack effect of the house than the flue. Try opening a downstairs window a few minutes before starting the fire.

 

[ddddddden]

A bigger stove can give longer burns, courtesy of more wood in the firebox. A larger flue will not improve the draft and typically would be expected to weaken draft because it lets the smoke expand, cool, and slow down. My amateur guess is that you have 'stack effect' issues with air escaping out the top floor of your house, and you need to tighten up around the attic hatch, etc.

 

[wyecoyote]

Size of the flue is 6" for both. Stack effect I'll goggle that and see what it says. As to opening a window I usually do this just to let the smoke out when starting. Haven't tried opening one minutes prior usually just when starting up the fire to let the smoke out. I have a fan near the window to push the smoke out when it gets to bad. Don't turn the fan on until it is really smokey. Thanks for the quick replies. And the information on the larger insert.

 

[LLigetfa]

What probably happens is the house is starved for air and draws it from the downstairs flue. The more air it draws, the colder the flue gets. The colder it gets, the more air falls down it. If you feel an in-rush of air when you open a window, it confirms the air pressure deficit. Opening the window before starting the fire makes the window the better source of air, competing with and hopefully winning out over the reversed flue.

 

[learnin to burn]

You say you have 2 flues - are they right next to each other and are they the same height where they exit the roof? Are you starting the fire upstairs before downstairs?

As Outside Air Kit for 1 or both stoves will help the downstairs stove but it may not completely stop the smokey start up. Consider raising 1 of the flues a few feet.

 

[wyecoyote]

I haven't checked for an inrush of air. I'll pay more attention next time.

The flues are the same height and typically I start the upstairs one first. The downstairs one I start next.

I'll see about raising one of the flues higher and see what that does as well.

 

[oconnor]

+1 for a stack effect issue. Give the "Guide to Residential Wood Heating" a read in my signature block. It covers a lot of the questions you will have anyways, but discusses Stack Effect in a few parts.

 

[learnin to burn]

+2 on Stack effect but it is possible the upstairs stove may be causing it.

Try starting just the downstairs stove and see how it runs without the upstairs stove before making adjustments. Make sure there are no open windows upstairs or vents/dryer running as well.
If the downstairs stove runs good and no smoke enters the room on start up/reload then an OAK for the upstairs stove should cure your issue.

 

[EKLawton]

+2 on Stack effect but it is possible the upstairs stove may be causing it.

Try starting just the downstairs stove and see how it runs without the upstairs stove before making adjustments. Make sure there are no open windows upstairs or vents/dryer running as well.
If the downstairs stove runs good and no smoke enters the room on start up/reload then an OAK for the upstairs stove should cure your issue.

If that was the case wouldn't he get smoke in the house even when the stove in the basement was not being used.
not that I know, just that it would make sense.

 

[LLigetfa]

+2 on Stack effect but it is possible the upstairs stove may be causing it.

Try starting just the downstairs stove and see how it runs without the upstairs stove before making adjustments. Make sure there are no open windows upstairs or vents/dryer running as well.
If the downstairs stove runs good and no smoke enters the room on start up/reload then an OAK for the upstairs stove should cure your issue.

If that was the case wouldn't he get smoke in the house even when the stove in the basement was not being used.
not that I know, just that it would make sense.

All we know is there are two flues. If the two flues are adjacent in the same chimney, there is potential for a reversed flue to draw in smoke from the adjacent working flue. In that case, the reversing flue should be lower, not higher than the working flue.

It could be that the flue is not actually reversing but rather just stalled and not drawing. There are varying degrees of flue draft dysfunction.

 

[wyecoyote]

This morning I started the down stairs stove first. Both are inserts using the same chimney with two seperate flues side by side and at the same height. I opened the stove and no rush of air. I did open the window and got a slight rush of air into the room. I waited about 10 minutes with the window open and started up the downstairs stove. There was still a drafting problem though not nearly as bad as before. Probably half of what it used to be. Once I got the downstairs going about 20 to 30 minutes later I started the upstairs stove. This one had no problem with drafting issues. Again once the downstairs had warmed up most of the drafting issue was gone. Though if I open the door to stick more wood in it will let some smoke out not to bad.

What I notice overall is that once the downstairs is warm/hot it drafts fine. One of the primary reasons I am considering going to a larger stove so that I can keep it running throughout the day/night. Right now if I goes out (which with the size of current stove it only lasts maybe 3 to 4 hours at most). If I had a larger one that could last all night I would be ablet to stoke the fire and still have it going throughtout the night and only let it go out to clean out. As it is right now I end up having to start the fire at least once to twice a day depending upon my schedule.

The other question I have is could the tempature make a difference? The downstairs acts more like a basement with it being 5 to 15 degrees cooler than the upstairs typcally. Depending upon the time of year. Right now with the temp outside being in the 40's the lower level in the morning is close to outside temp and the upstairs is in the mid 50's in the morning after the stoves go out. Even with the stoves going the upstairs will be in the high 60's low 70's and the lower level with be in the low 60's to high 60's. Usually 5 degrees cooler with the stoves going. Even with the Furnace going it will be cooler in the lower level. I know heat rises. There is an open stairwell so the heat does go up. Which is nice in the summer the lower level stays cooler and since I spend most of the day down there it makes it easier to work.

If I read this correctly the upstairs flue should be raised a few feet to offset any reverse drafting issues?

 

[LLigetfa]

If I read this correctly the upstairs flue should be raised a few feet to offset any reverse drafting issues?

If the downstairs flue was actually reversing and not just lazy/stalled, then raising the upstairs flue slightly insures that the lower reversed flue draws only air, not smoke from the other flue. I don't think you have actual reversal. You are better off fixing the stack effect that is leaving a pressure deficit than adjust flue height. Take a smoke pencil and find the leaks upstairs that is letting warm air out and allow more makeup air in downstairs. Think of the house as a hot air balloon which works by keeping the hot air in, not the cold air out. It can and does have a big hole in the bottom but keeps the hot air inside. If the balloon had a leak at the top, it would let the hot air out.

An OAK on the upstairs insert should help. If you don't fix the pressure deficit issue, an OAK on the downstairs insert could push more smoke into the room when the door is opened and when the stove is cold, it could frost up the insert unless you include a positive shutoff.

 

[LLigetfa]

Oh, I forgot to mention... assuming the flues have liners, check that both inserts have a blockoff plate, that air is not being drawn out of the room between the flue liner and masonry.

 

[theheatelement]

That would have been my first question... he might be just emptying into a large clay tile liner

 

[LLigetfa]

That would have been my first question... he might be just emptying into a large clay tile liner

That's why you're in the biz and I'm just a wood burner.

 

[theheatelement]

Well I've learned alot on here as well... Wealth is knowledge!!

That would have been my first question... he might be just emptying into a large clay tile liner

That's why you're in the biz and I'm just a wood burner.

 

[oconnor]

+2 on Stack effect but it is possible the upstairs stove may be causing it.....

This is a bit of a truism - what causes stack effect is the buoyancy of warm air, and if the upstairs stove is lit, then yes, it is contributing to stack effect. Any heat will contribute. With stack effect can also come a flue reversal, but that is more symptom than disease - in the end, it's about what is causing a weak draft, and a reversed flue is as weak a draft as you'll get. In essence, stack effect causes a relative low pressure zone in the basement that may or may not reverse the chimney flow. If the flow has reversed, then cooling is going to set in, and opening the window will have little effect until the flow direction changes. But once flow has resumed in the right direction, that open window will alleviate the negative pressure resistance to the flue drafting.

As for flue length with adjacent flues and reverse drafting, it's as LLigetfa says, one flue longer won't stop the flue from drawing cold air, just cold smokey air.

 

[ansehnlich1]

x3, or 4, or whatever, this sounds like a stack effect...

meaning, cold air is sinking down your chimney for whatever reason, could be the draw from the upstairs unit, could be a dryer in the basement, could be a kitchen exhaust fan, could be a combination of stuff.....

like has been said, if there is no liner in the downstairs chimney, puttin' one in would help.

 

[wyecoyote]

Both have liners installed. I've cleaned them on a regular time frame about 1 to 3 months depending upon the use or just before fire season at the end of the summer. From what I have read it appears that what I have is a stack effect not a reversal effect where. I wonder if part of my overall stack effect problem might be the entry door or the replacement windows. That the old owners installed. I caulked several of the windows since there was a "draft". I'll check there and the front door as well.

Thanks for all the help I'll get the smoke pencil and do some tests around the house.

 

[LLigetfa]

I caulked several of the windows since there was a "draft".
...
Thanks for all the help I'll get the smoke pencil and do some tests around the house.

Detecting where there is cold air leaking in is easy since you feel a cold draft. Detecting where warm air is leaking out higher up is a little harder. That's where the smoke pencil comes in. Make sure there are blockoff plates too in the fireplaces. That can suck a lot of air out of a house. Check bathroom fans that might not close properly. Check attic hatches for a poor seal. In the attic, check around waste vent stacks for warm air escaping. If the roof has whirlybird vents, make sure the attic has adequate intake vents as well. whirlybirds can suck a lot of air out of a house.

If there was draft reversal, you should feel cold air roll out of the stove downstairs when you are trying to light it. You would also smell cold smoke when you open the cold stove. If it's just a pressure deficit, you would feel the inrush of air when you open a downstairs window.

Check for other consumers of air. Does the water heater and/or furnace draw room air. Is there any makeup air vents to supply the furnace room with fresh air?