How do I adapt my woodstove to this old chimney?

[newtimer]

I've got a woodstove with a 8" pipe opening coming out the back, and a chimney lined with 6" square clay tiles.  The chimney is about 35' tall so I think I'll have pretty good draft.  So my question is: where and how should I reduce it from 8" to 6" to have the best chance of not filling the room with smoke?

Any thoughts?

Thanks,

Ben

[newtimer]

I just went up and measured the tiles, and it turns out they're almost 7" square on the inside.  Maybe run an 8" pipe right up to them?

[Stonebrain]

Just a few hammerstrokes and the 8" pipe should fit in a 7" square,don't see any problem.

cheers,

stonebrain

[TomW]

ben;

Best advice I can offer is:

If you have to ask this question you should hire someone to do it.

This stuff can kill you done wrong. Its not neural surgery but it needs to be done properly and securely.

Burned wood my entire adult life and seen some poor installs cause loss of life and property.

Good luck with it.

Cheers.

TomW

[WindHarvester]

I agree with Tom, it can be very dangerous.

Do your homework well, or hire someone that has.

Would hate to hear you lost your life or home.

Have a wonderful safe weekend!

Lonnie

[3rd Charm]

What was the chimney used for previously? If it was used for a gas exhuast pipe, say from a hot water tank, I wouldn't use it at all for wood burning.

I would run  approved 6" insulated  pipe through the whole thing, but I don't think you have enough room, because the OD of the pipe will be 8 inches. You can use a reducer to hook the fireplace outlet to the chimney pipe.

For a woodstove 8" (ID) insulated pipe is  recommended, and depending on the pipe manufacturer, that will have up to a 10 inch outer diameter- too big to stuff inside that chimney.

I don't know if those chimney tiles lining your -what I assume is a brick chimney- is even approved for wood burning. If the Chimney ISN't a brick chimney, I seriously doubt it.  I would get someone who knows what they are doing check it out.

If it's not a proper pipe and properly insulated,you can burn your house down.

[Stonebrain]

I agree with the safe guys.

If you don't thrust the old chimney for woodburning you have to get yourself a stove with 6" outlet and run a flexible 6" stainless pipe through your chimney.

That's the way a professional installator will do it anyway.They don't thrust any chimney because they will be responsible for any failure of the chimney.

You don't need a insulated pipe for this and anyway you'll never get an insulated pipe in your chimney.

If you thrust your chimney(at your own risk),you can adapt the 8" pipe for a 7" square  without hardly reducing the passage of the exhaust gasses.Whatever you do you should never reduce the pipe to smaller sections.

cheers,

stonebrain

[dainbramaged]

"you should never reduce the pipe to smaller sections."

Why??

[Stonebrain]

If a stove has a 8" outlet it means that it needs this diameter.

If you reduce it to 6",the exhaust gasses will be slowed down too much.

The stove will malfunction,smoke,and eventually kill you with carbonmonoxyde.

cheers,

stonebrain

[nothing to lose]

As others have said, be aware of what you have!!!

If that was a chimney for an earlier burner, wood or coal, you should be fine if it's in good shape. Since you say clay tiles, I ASSUME it was a fire type chimney, I could be wrong though, but I don't see clay tiles used for much else.

As for the actaull question you asked,

"where and how should I reduce it from 8" to 6" to have the best chance of not filling the room with smoke"

It does not really matter. What matters is the chimney works well for this, and does not leak fumes into the house. From 8" to 6" itself if I could I would do right at the wood burner with a new flue ring. If your going from 8" round pipe to 6" square then as said by another, a few hammer hits and your done. Just make sure it don't have leaks.

As for filling the room with smoke, that depends on many things, not just flue size.

 Straight up and out is the best. Start adding bends and twists and you restrict flow.

6" straight up works best for me really, but I have a flat roof right there and up and out leaks bad!! I can't stop the leak with the pipe installed. So I went back to 90 over out and 90 up. It does not work as well for flow but stops the roof leaks.

Draft is maybe your main thing, and is effected by many other things. The more bends the less draft. The less heat in exhaust the less draft. Now if you have a very well sealed house also less draft.

 Something many people don't think about is other drafts!

Ok here I have a fireplace with a large flue, I have a woodburner. Guess what happens if I used both at once and do not open a window wide!!! YA, the fireplace draft will suck up the smoke from the fireplace great, BUT it also sucks smoke out the woodburner with a negative draft there. OR with a low fire in fireplace and big fire in woodburner I can suck the fumes and smoke out of the fireplace into the room.

 I can use either one anytime, or both if I open a large window wide!

 For a feastive fun thing once I did open a window wide in middle of winter and use both at once. But lack of interest in FUN stuff of family here we never use the fireplace for anything. I might as well rip it out and have that much more wall and floor space

[richhagen]

8 inch inside opening round pipe is about 50.25 square inches.  7 inch by 7 inch opening in square is 49 inches which is pretty close.  Still, you don't want this screwed up.  It is probably over a hundred people in my country who die from carbon monoxide poisoning each year.  Then you can add a few from chimney fires as well.  Rich

[TimV]

Yes use a run of 8" to get to flu. Make your transition at the chimney.

You never said what type of provision was made for original adapter from previous stove to chimney.

Usually something has been secured properly thru blocks into clay liner with masonary. Usually this is clay ring of a larger size. For example 9" . A pipe reducer/ adapter is available at most large hardware stores or stove shops to do this.

Be sure you comply with local and state fire codes. If you are not familiar with wood burning this could save your life or better yet your children.

Pipes and chimneys need a lot of periodic inspection for the number 1 enemy CREOSOTE.

Maybe you should post a picture of this chimney your trying to adapt to . Also have someone who has proper equipment to clean and check liner for cracks ....maybe last user had a fire that cracked the flue....this could be a disaster in the making but is fixable.

Better still if you need a new chimney I think best I ever came across is a an "all fuel" insulated stainless steel. expensive but by far the best way to go.

[Rob Beckers]

Hi Ben,

I went through a similar exercise last year; We had an existing wood burning fireplace with 6" rectangular tile-lined flue, and were replacing that fireplace with a high-efficiency wood burning unit (ie. the fully enclosed type). The new fireplace required 7" stainless steel flue pipe. Using the old tile flue was not allowed, despite that the surface areas of the existing flue (rectangular) and 7" pipe were just about the same. The problem was that the gases coming from the new fireplace are colder, causing more condensation, and would eat away the stone flue. Stainless was required by  code. Since the new stainless liner was going into an all-stone structure, we did not have to use the double-wall (insulated) pipe. Instead, using single-wall stainless flue sections was allowed under code. For one they are much cheaper than the double-wall stuff, but more importantly in this case it saved two inches (7" ID double-wall is 9" OD). The solution to fitting 7" pipe into a 6" opening was to take a long steel bar and break all the flue tile in the chimney channel. The tile is actually pretty easy to take out once you break it up. Taking out the tile left a (stone) chimney with plenty of space to fit the 7" stainless pipe. The new fireplace works like a charm!

-RoB-

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[newtimer]

Thanks to everyone for all the advice.  I definitely took it to heart when you said to be careful, so I got my local codes and am trying to do this by the book as much as is possible.  What I ended up doing was running the 8" up to the tile (it was last used probably 30 years ago with a coal insert, but there's no firebox so I can't do that anymore) and welding up an adapter plate to turn the round pipe into the square tile.  It's airtight and I don't feel like I lost much flow at all.  I had a chimney sweep out over the summer to look at the tile and he said it was in good shape to use.  Now I'm having him come back out tomorrow to actually sweep the chimney and take a look at what I've set up.  Also got a carbon monoxide detector and another smoke detector.  I'll hopefully have it burning tomorrow night and let you know if it drafts!

Thanks.

[3rd Charm]

You DO need insulated pipe where ever you are running through a ceiling and/or attic space. Plus code in most places calls for a certain length of insulated pipe beyond the roof line. Good luck getting insurance if you don't.

There are also codes for distances between walls and stovepipe (black pipe or stainless) indoors, as distance between walls and the fireplace itself, not to mention fire resistant flooring under the fireplace and on walls.

Pretty much ALL fireplace installations these days calls for approved insulated pipe.

I highly doubt this persons chimney would be legal. Usually oder clay chimney was made with lengths of square clay pipe, which was then bricked on the outside. These 'tiles' this person has are probably asbestos  fire guard tiles for a gas installation.

Don't forget, a chimney can get very hot, and a creosote build up occurs rapidly in uninsulated pipe, which after a period WILL burn off if you don't clean your chimney often.

 I've had a few of them, they are pretty scary. If you get one it is like a blow torch coming out of your chimney. My stainless insulated pipe turned red hot at the last foot outside, and is now a blue color, like chrome motorcycle exhaust pipes turn when they get hot near the head. The black pipe indoors that runs from my wood stove to the insulated pipe at the ceiling got a little red as well. It really roars when creosote burns, and there's nothing you can do but choke off all air and let it burn out.

No doubt it destroyed the inner insulation as well, but because that section is outside I don't worry about it.  

I clean my chimney more often now however.

Imagine what would happen if this guy got a creosote fire and that chimney has a wood frame exterior with fake brick stuck onto it!

Bye bye house, and if the insurance company didn't approve of his installation- no insurance.

I would have it checked if he doesn't know what he's doing- better safe than sorry.

[Ponderance]

I have some friends who own a chimney/ac duct cleaning company and they also install chimney flues in old broken chimneys to make them usable again. my opinion would be to maybe remove some tile to get the required 50.25 inches for the 8" flue on the stove and run an insert into the existing chimney. there's a very high possibility that the installation will fall into code requirements.  also remember that you will want to install a cap if it does not vent horizontally.

here are a couple of websites for ideas:

http://www.chimneylinerdepot.com/index.asp

http://www.oldhouseweb.com/suppliers_of/11514_Fireplace_Inserts_.shtml