Any chimney experts available?

[gtomew]

What my problem is my aunt gave me a wood stove very nice
one not sure the make and a few day later talk got around
that I needed stack to install it.Well her neighbor had around
20 feet of ss Metalbestos very good condition he gave me free
for the taking.Well I think heck Im almost all set minus a thimble,t-cleanout.
The problem is the stove has 8" pipe and the ss pipe is 7" is there a way to
use all I have 7 to 8'' ? Also will I get smoke out or will it overheat the chimney?

 

[SKIN052]

What my problem is my aunt gave me a wood stove very nice
one not sure the make and a few day later talk got around
that I needed stack to install it.Well her neighbor had around
20 feet of ss Metalbestos very good condition he gave me free
for the taking.Well I think heck Im almost all set minus a thimble,t-cleanout.
The problem is the stove has 8" pipe and the ss pipe is 7" is there a way to
use all I have 7 to 8'' ? Also will I get smoke out or will it overheat the chimney?

You may have a hard time finding it but you should be able to get a 8" to 7" reducer. Check your local stove shop.

 

[gtomew]

Also will I get smoke out or will it overheat the chimney?

 

[SKIN052]

Reducing a flue to accommodate the stainless steel is never recommended, but doable. Smoke will depend on your draft. A strong draft will avoid smoke entering the room. Over heating the chimney will depend on the stove. If you can control the air to the stove then you should be able to control the overheat. If the draft is too strong, install a damper.


[email protected]

Ask these guys, but trust me, they will tell you not to reduce. I asked a similar question and the suggested not too. I had a couple lengths of metalbest given too me and thought I was well ahead, only to find out that it is not approved in Canada.

 

[webbie]

Do you know the wood stove model?
Can you post a pic?
What is the route to the chimney from the stove....it sounds like you are going to use a T - are you going to come right out the back of the stove to a T?

Bottom line basic answers are this.....no, you will not overheat the chimney (based on 99% of all stove models).....a 7" chimney can handle a LOT of BTUs, probably 200,000.

The concern...and not just with 7", but even with 8", is whether the stove will draft well and whether it may smoke when you load it (open the door).

If we have the stove model or pic and an idea of your chimney plan, we can shed more light on the subject.

Many of the stoves which have 8" pipe do so because they may have an option of using with the doors open and a screen. That requires a bigger flue to sweep the doors free of smoke.

 

[Renovation]

Ask these guys, but trust me, they will tell you not to reduce. I asked a similar question and they suggested not to.

Agreed. A flue manufacturer assumes enough liability without approving non-standard applications. There's little upside to that.

If the pipe is otherwise in good shape, and installed with hardware--adapters, connectors, elbows, etc.--from the same manufacturer, I see no safety risks, just performance ones.

My calculations say that the chief risks of running a stove into a flue narrower than its outlet are smoke roll out during lighting/reload, and reduced maximum output. With the stove door open, a 7" flue will have 76% the airflow of an otherwise identical 8" flue. Is that enough reduction to cause smoke roll out? Unknown. I doubt you'd see a reduction in maximum output.

HTH, and good luck!

 

[grrzoot]

Reducing a flue to accommodate the stainless steel is never recommended, but doable. Smoke will depend on your draft. A strong draft will avoid smoke entering the room. Over heating the chimney will depend on the stove. If you can control the air to the stove then you should be able to control the overheat. If the draft is too strong, install a damper.


[email protected]

Ask these guys, but trust me, they will tell you not to reduce. I asked a similar question and the suggested not too. I had a couple lengths of metalbest given too me and thought I was well ahead, only to find out that it is not approved in Canada.

Hello,

I am new to these forums, first day registered but i have come here and found much information. I wanted to help with this question. I am a CSIA certified chimney sweep with 15 years experience installing and servicing woodstoves.

I would like to point out a couple of things for you.

1.0 metalbestos is selkirks "cheap" line of chimney piping. It doesnt meet rating in canada nor does it meet HT103 standards for todays chimneys esp high efficiency wood stoves, its actually more dangerous with older stoves.
2) You should never reuse chimney pipe, unless it is brand new in the box ( and sometimes not even then) can you be sure that it is up to spec, you have no idea how the last owner treated it, weather it has been in a chimney fire, or has warpage and damage due to overheating. I personally, do not like to use selkirk pipe at all.

3.) Yes, you can reduce from 8 to 7" but you will have some issues unless you can create enough draft. depedning on your height above sea level hieght is the main factor in determining weather the draft and flow will be sufficient. By going to a smaller pipe you are increasing the draft (the rate at which the smoke moves through the pipe, and reducing the flow (the available volume oof smoke that can fit into the pipe. Under good conditions my experince is that 20-25' of height is enough to create a positive draft to pull enough air from a woodstove with an 8" flue outlet. That is assuming you are using insulated pipe inside a warm or insulated environment....
my two cents

 

[webbie]

All good point - however, Metalbestos has been sold with the HT standard for a long time.........with that name (I think).
The label on the pipe should tell you what standards, etc.

If the pipe is decades old, then.....it probably means it's time to bit the bullet and go new.

BTW, a chimney which goes out and up is not as efficient as one that goes up.....of course, that is not always possible.
But keep it in mind.

 

[BrotherBart]

Yeah from what I understand the Metalbestos with locking bands passed HT103.

 

[summit]

Do you know the wood stove model?
Can you post a pic?
What is the route to the chimney from the stove....it sounds like you are going to use a T - are you going to come right out the back of the stove to a T?

Bottom line basic answers are this.....no, you will not overheat the chimney (based on 99% of all stove models).....a 7" chimney can handle a LOT of BTUs, probably 200,000.

The concern...and not just with 7", but even with 8", is whether the stove will draft well and whether it may smoke when you load it (open the door).

If we have the stove model or pic and an idea of your chimney plan, we can shed more light on the subject.

Many of the stoves which have 8" pipe do so because they may have an option of using with the doors open and a screen. That requires a bigger flue to sweep the doors free of smoke.

+1

 

[summit]

can you find a way to come straight up off the stove rather than use the tee? If so, 8 to 7 shouldn't bother anything. Not sayin it won', but it shouldn't...