Install a fan on interior double-wall flue pipe

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J

Joacchim

Member
Dec 3, 2018
19
Chagrin Falls, Ohio
Because of close clearances my interior stove pipe is double walled. I've been thinking about trying to exhaust the hot air between the two walls into my living space, to get a bit more heat. My thought is to put a 2" hole in the outer pipe near the ceiling but facing into the room (no clearance problems there) and then mounting a 2"muffin fan in/on the hole to pull out the air trapped inside. My double walled pipe is open at the bottom (see photo).

Couple of questions:
1. Are there bulkheads inside the double wall that would prevent air from being drawn up inside?
2. Will this have a cooling effect that would excessively reduce my stove draft?
3. What are the downsides to doing this?
4. Has anyone tried this, and if so, how did it work?

I'm new to the forum but have been burning wood for heat since around 1984. Thanks in advance! 20181203_203229.jpg
 
Last edited by a moderator:
Joacchim said:
Because of close clearances my interior stove pipe is double walled. I've been thinking about trying to exhaust the hot air between the two walls into my living space, to get a bit more heat. My thought is to put a 2" hole in the outer pipe near the ceiling but facing into the room (no clearance problems there) and then mounting a 2"muffin fan in/on the hole to pull out the air trapped inside. My double walled pipe is open at the bottom (see photo).

Couple of questions:
1. Are there bulkheads inside the double wall that would prevent air from being drawn up inside?
2. Will this have a cooling effect that would excessively reduce my stove draft?
3. What are the downsides to doing this?
4. Has anyone tried this, and if so, how did it work?

I'm new to the forum but have been burning wood for heat since around 1984. Thanks in advance!View attachment 234762
Click to expand...
That is a bad idea
 
bholler said:
That is a bad idea
Click to expand...
I'm not real serious about doing it, I was more interested in others' experience and specific reasons WHY it's a bad idea. My old stove was located so that it didn't need double wall pipe, so my thought was all I'd be doing with this idea was exposing the single wall inside - just like my old setup, but in a very limited way.
 
Joacchim said:
I'm not real serious about doing it, I was more interested in others' experience and specific reasons WHY it's a bad idea. My old stove was located so that it didn't need double wall pipe, so my thought was all I'd be doing with this idea was exposing the single wall inside - just like my old setup, but in a very limited way.
Click to expand...
You will be sucking to much heat off the pipe which could lead to poor draft and creosote problems. You would also be modifying a ul listed product which would make the vlearance reductions no longer legal and exposing the fan to temps much higher than it is intended for.
 
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Um no, just no. Tell us more about the house layout in relationship to the stove room. There may be a simpler, safer option.
 
begreen said:
Um no, just no. Tell us more about the house layout in relationship to the stove room. There may be a simpler, safer option.
Click to expand...
As I said, not too serious about doing this, but my stove is in an attached, glass-walled sunroom, about 10'×12'. It pretty much keeps the whole house heated. I was trying to think of ways to squeeze more heat out of it. My flue is no more than 15' tall, about 8' inside and about 6' triple wall stainless pipe going up through the roof eave. See photo.1543891913557-1003650875.jpg

My Central Boiler brings the house up to 66°F in the morning, (it's connected to a heat exchanger in my conventional furnace plenum). Once the Homestead gets going the furnace blower stops running.
 
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I think it’s just an old way of thinking. Using
Double wall and keeping the chimney warm makes everything safer, cleaner and work better!! Only old times with huge smoke dragons seem to want or need the heat radiation of single wall !!
 
vwmike said:
I think it’s just an old way of thinking. Using
Double wall and keeping the chimney warm makes everything safer, cleaner and work better!! Only old times with huge smoke dragons seem to want or need the heat radiation of single wall !!
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'Nuff said. Idea quashed. Thanks to all who replied.
 
Before I go, check out this (attached pdf file) outside air kit by Duravent. I'm not advertising it, just wanted to show how a reputable stovepipe manufacturer is using the double wall envelope in their stove pipe to preheat outside air for combustion. What were you guys saying about draft loss and creosote problems???
 

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  • L820_combustionaire_2011-oct.pdf
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Joacchim said:
Before I go, check out this (attached pdf file) outside air kit by Duravent. I'm not advertising it, just wanted to show how a reputable stovepipe manufacturer is using the double wall envelope in their stove pipe to preheat outside air for combustion. What were you guys saying about draft loss and creosote problems???
Click to expand...
You would have exactly the same problems i described with that system. Just because a product is available for sale doesnt mean it is a good design.
 
bholler said:
You would have exactly the same problems i described with that system. Just because a product is available for sale doesnt mean it is a good design.
Click to expand...
Yes, I haven't been a big fan of the product, though it may have its place in installations that need outside air, but are challenging.
 
Joacchim said:
1. Are there bulkheads inside the double wall that would prevent air from being drawn up inside?
Click to expand...
Yes (usually... I've heard of but have not personally seen double-walled stove pipe without these bulkheads).

Joacchim said:
2. Will this have a cooling effect that would excessively reduce my stove draft?
Click to expand...
I wouldn't say excessively, but I think it would reduce it somewhat.

Joacchim said:
3. What are the downsides to doing this?
Click to expand...
Draft issues aside, creosote buildup for sure

Joacchim said:
4. Has anyone tried this, and if so, how did it work?
Click to expand...
I have not. There are many people that have single-wall stove pipe from the firebox to the cap who otherwise burn without issue (usually with some combination of clean, hot burns with seasoned wood, straight runs, regular cleanings, that sort of thing), which is basically what you will have if you vent the heat out of that space (or install that kit you linked to). I think you'll be hard pressed to get an endorsement from this community for something that increases your chances of creosote buildup, even if you make/use some system that otherwise works fine venting that heat (for use in pre-heating the air for combustion or recovering it for yourself).
 
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