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Woodstove to chimney connection

Mike_Maines's picture

I'm installing a woodstove in my house.  The chimney is lined 8x8 tiles, but I had to cut in a new thimble and cleanout.  It had previously been used to vent a boiler.  What is the proper way to get the stove pipe into the flue?  Do I just mortar a short length of pipe into the masonry with regular mortar? 

(post #107276, reply #1 of 27)

Hi-temperature furnace cement, Mike. The stuff is a thick, gooey paste with about the same slump as, say, thinset.  Comes pre-mixed in 1-litre cans or 5-litre plastic buckets.


Dinosaur


How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....


Dinosaur

How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....

(post #107276, reply #2 of 27)

No need for sleeves or collars or thimbles?  This is in my garage, right into a concrete block chimney, no combustable walls.

(post #107276, reply #3 of 27)

No need for a thimble Mike (just a dumb carpenter), but I would sleeve it somehow-if only with the male end of a pc of similar pipe.  That will allow you to take it all out for cleaning.

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Remodeling Contractor just outside the Glass City.



http://www.quittintime.com/


 

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


(post #107276, reply #4 of 27)

But the pipe itself would stay cemented into the chimney, ay?


I must have seen a thousand woodstoves but never installed one, blind here....

(post #107276, reply #6 of 27)

The short length of pipe (the sleeve) will remain in the mortered up chimney.  The stove pipe will go into that sleeve.  You can now remove all the stove pipe for cleaning.


I've lived in several "old" houses that had a sleeve installed in the chimney.  These were in kitchens-central rooms so it is assumed they were wood stove chimney's.  Several had ember burns where the front of the stoves would be-or off to the side in the case of a cookstove.  The sleeve simply gives you a nice round (don't bend it up on install) metal lined hole to insert your pipe and remove at will.


You will probably be putting in a damper in the pipe above the stove also, no?


A Great Place for Information, Comraderie, and a Sucker Punch.


Remodeling Contractor just outside the Glass City.



http://www.quittintime.com/


 

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


(post #107276, reply #7 of 27)

Yes, I will be putting in a damper.


Thanks for the clarification.

(post #107276, reply #5 of 27)

As Calvin suggested, you can organise it so the smoke pipe from the stove to the chimney is removable for annual cleaning. You're gonna need a different brush for the flue than for the smoke pipe.


IIRYC, your chimney flue is not insulated. If that's the case, and depending on the height of the chimney, you might have some fun getting the beast started. If the column of cold air sitting in that flue is fairly tall, it won't draw till it gets going well. Couple of hints: open a door or a window before lighting it off, and start by flash-burning a few sheets of newspaper to warm up the flue.



Dinosaur


How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....


Dinosaur

How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....

(post #107276, reply #8 of 27)

Chimney flue is not insulated, but the garage is in the basement and the chimney goes through heated space before exiting the roof.  Hopefully that, and the supply of nice dry kindling and newspaper, will get the thing going without too much trouble.  Will open a door if need be as well.


Thanks for the help!

(post #107276, reply #9 of 27)

I assume you've checked the specs on woodstove chimneys for your area, especially with your insurance company? Around here, chimneys must be insulated up to 2200ºC and homologated. That doesn't include the smoke pipe, which connects the stove to the flue, but it includes all sections that pass through the structure or rise next to it.


Mostly, we're using 2"/6" pre-fab steel chimneys now to comply with that for woodstoves.



Dinosaur


How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....


Dinosaur

How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....

(post #107276, reply #10 of 27)

Checked with the insurance company, they're fine.  Didn't say anything about being homologated (that means inspected, right?).  Stove has a 5" outlet so that's what I'm using for stove pipe.  It was a second hand stove, so no documentation on it.  Woodstove is secondary (tertiary reallyl) source of heat, if that matters.  I've checked that there is at least 2" of clearance between chimney block and framing everywhere.


I can't find any specs for woodstoves in my area, which is why I asked here.

(post #107276, reply #11 of 27)

If it was me, I'd put a thimble in.
First - it's simple enough to do.
Second -you have the sleeve mentioned before
Third- I prefer the continues liner running all the way from inside the room to the chimney top.

No to say you have to just my preferred method.

(post #107276, reply #14 of 27)

Pay attention to Mike585's message above.


A 5" flue is pretty small. That smoke will be moving pretty slow thru a large flue tile - I can't remember if the chimney flue size was designated.  The saving grace is that it goes thru heated space. I'd be pretty concerned about that arrangement if the chimney was on an exterior wall.


(post #107276, reply #18 of 27)

I think what Dinosaur was talking about at first was the stovepipe to thimble connection, but you are asking about how to do the thimble itself, right?

I have always used a thimble for the horizontal section in the chimney from the outside surface of the masonry to the inner flue. You can use round clay flue section and cut it to fit, or a stainless steel, which would be easier for your situation. The SS thimble would be slightly oversized, and flared out to make it easier to insert the stove pipe when you hook up.

Position the SS thimble and grout with mortar around it with packing in drypack mortar ( drypack means do not make it too soupy - just damp enough to mix and make it set, then pack it tight, like doing shower pans. If it is too wet, it will shrink and leave cracks.

You will have cut the thimnble first to work out flush at the inner surface of the flue. If you have too big of a hole there, the dry pack grout will want to fall in as you pack it. One way to deal with that is to seat the thimble first with some high temp silicone caulk at that inside joint, or the furnace cement dino mentioned if you can get it there. Then wait a day for it to kick before packing around the thimble with mortar.

Then when you hook up the wood stove pipe to the thimble, use stove cement there as you plug it in.

I would use an 8" thimble if your hole is large enough, and do the necking down in the stovepipe connections to the 5-6"

Somebody had some mention of other details/ instructions for clearances. Did you need the basics on that too?

 

 


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(post #107276, reply #21 of 27)

I was asking for how to do the thimble itself.  It's something I've never done or seen done, and the first thing I tried didn't work.  I think the thimble might have been for a direct vent. 


Tonight at the hardware store I found the SS thimble you suggested.  6" works best with my flue, maybe the flue liner is 7"--do you measure inside or outside?  I got a reducer to go down to 5" for the stove pipe. 


The thimble fits pretty tightly into the flue liner, no more than 1/4" gaps, so I think I'll just go for the dry-pack mortar around the thimble.


Because this is in the garage, surrounded by concrete, I don't need the clearance info. 


Thanks again to everyone for the help!

(post #107276, reply #22 of 27)

Paul, what we (me and a few others) here called a thimble was the 'isolator' type of sleave that allowed air to pass around the stove pipe.  The sort that was used between floors in these old Ohio farmhouses.  I take it that isn't the same as what you are calling it?


thanks


A Great Place for Information, Comraderie, and a Sucker Punch.


Remodeling Contractor just outside the Glass City.



http://www.quittintime.com/


 

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


(post #107276, reply #24 of 27)

Yeah, a wall thimble like that is 2 or 3 walls baffled like triple wall pipe for entry through a wood framed wall or ceiling or whatever, but for the entry through the side wall of a masonry chimney into the vertical flue a single wall SS or a clay flue does the job, but it is still a thimble.

 

 


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #107276, reply #25 of 27)

Got it.

A Great Place for Information, Comraderie, and a Sucker Punch.


Remodeling Contractor just outside the Glass City.



http://www.quittintime.com/


 

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


http://www.quittintime.com/

 


(post #107276, reply #26 of 27)

http://www.vogelzang.com/Manuals/bk150eMnl.htm

Here is a pretty decent guide covering a lot of this stuff generically

 

 


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Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
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Oh Well,

We did the best we could...

(post #107276, reply #27 of 27)

Ran the stove for the first time last night--worked great!  Thanks to everyone for the help.

(post #107276, reply #12 of 27)

Check codes in your area. I'm in NY and code requires a full liner. I just had a one installed. Not cheap but I'll sleep better not worrying about a chimney fire burning the place down.

If you decide on a liner beware of cheap product. A lot of them are garbage and fail after a few years. Go with Super Flex Stainless.

My chimney guy is from your area (Sebago Lake). I'll connect you with him if you want. He's back there a lot.


Edited 10/20/2008 7:15 pm ET by mike585

(post #107276, reply #13 of 27)

I think he said he has 8x8 tiles for a liner.

then the codes would only require the thimble no?

(post #107276, reply #15 of 27)

There's a formula for flue outlet to max flue tile size. If the flue tile is over a certain size, a metal liner is supposed to be installed inside the clay tiles. I think he's OK with 5" rd going into an 8x8, but it's close. I seldom dealt with 5" flues in my woodstove days, but I do remember that an 8x12 was not acceptable for a 6" rd appliance.

(post #107276, reply #16 of 27)

2200 centigrade!!!!.Yeegads what planet do u live on?

(post #107276, reply #17 of 27)

(post #107276, reply #20 of 27)

Maybe his planet is in retrograde

;)

 

 


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #107276, reply #19 of 27)

Oh right!
Was just thinking about an unlined old chimney.
I don't have my books right here but as long as the chimney not to short, I think 8x8x is ok also.

(post #107276, reply #23 of 27)

Mike, use a standard metal thimble for your size pipe. It should extend through to the inside of the flue tile but not more. Use refractory cement and mortar it in like a pipe going through a foundation, nice and smooth. Every connection on the stove should be down hill so any water, creosote will run inside the stove pipe and not leak out of the joints. In other words the straight end goes up and the crimmped end goes down. The metal thimbles are sized so the straight end fits perfectly. Drill and use short pan heads on each connection and where it connects to the stove. Once all is attached, the pipe can't pull out of the thimble. If your thimble or stove pipe projects farther than the inside face of the flue it will act as a collection shelf for burn debris. It can cause a fire. It will also be a problem when you clean the chimney.

Beat it to fit / Paint it to match

Beat it to fit / Paint it to match