# airtight stove?



## ahoy30 (Jun 24, 2012)

I'm trying to give someone a Garrison 2 to replace the smaller stove he has in his shop, and he asks if its airtight. Another friend has a stove(can't remember off hand what it is) that he'd been heating his house with that he wanted to sell him but got the same question. What don't I know, here?


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## BrotherBart (Jun 24, 2012)

In this ad Garrison says with the doors closed it is "airtight".

https://www.hearth.com/econtent/index.php/wiki/File:garrsion_two.pdf/


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## Don2222 (Jun 24, 2012)

Hello

Airtight was an early innovation for wood stoves to provide better heat than an open fireplace or the older open wood stoves like the Franklin Wood stove.

The theory is that open fireplaces and wood stoves are only 15 percent efficient because they pull in already warm room air to feed the fire and send it up the chimney. So engineers figured out if they kept the combustion air separate then the stove would heat all of the room air and be 70-80 percent efficient!

See pics of my old Franklin and air tight Consolidated Dutchwest and current wood pellet stove in the same location!
https://www.hearth.com/talk/threads...rs-franklin-143-433-owner.78639/#post-1001007

The pellet stove has a complete separate path for heating room air and really works great!
Here is one I have in the for sale section that I can deliver.
https://www.hearth.com/talk/threads/us-stove-5660-48-000-btu-wood-pellet-stove-1195-salem-nh.87467/


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## Don2222 (Jun 24, 2012)

BrotherBart said:


> In this ad Garrison says with the doors closed it is "airtight".
> 
> https://www.hearth.com/econtent/index.php/wiki/File:garrsion_two.pdf/


 
LOL, without gaskets it is not airtight!


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## ahoy30 (Jun 24, 2012)

BrotherBart said:


> In this ad Garrison says with the doors closed it is "airtight".
> 
> https://www.hearth.com/econtent/index.php/wiki/File:garrsion_two.pdf/


 Hey, thanks, this will help.


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## ahoy30 (Jun 24, 2012)

Don2222 said:


> Hello
> 
> Airtight was an early innovation for wood stoves to provide better heat than an open fireplace or the older open wood stoves like the Franklin Wood stove.
> 
> ...


 So basically any stove with a door is airtight?


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## Locust Post (Jun 24, 2012)

Airtight just means you have control of how much air feeds the fire. With gaskets on the doors that seals them so the only air allowed to enter the burn chamber is through the draft caps/vents.


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## ahoy30 (Jun 24, 2012)

Locust Post said:


> Airtight just means you have control of how much air feeds the fire. With gaskets on the doors that seals them so the only air allowed to enter the burn chamber is through the draft caps/vents.


 gotcha, thanks


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## Don2222 (Jun 24, 2012)

ahoy30 said:


> So basically any stove with a door is airtight?


 
NO, you need rope gaskets on the doors to be airtight! Stoves have special channels and flanges for these gaskets, so you cannot make a stove airtight that was not made that way!


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## DanCorcoran (Jun 24, 2012)

ahoy30 said:


> So basically any stove with a door is airtight?


 
Another type of "no": modern EPA-listed stoves are designed to provide secondary feed air, even with the door closed and the primary air control completely closed. This isn't a problem, it is designed that way on purpose.


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## BrotherBart (Jun 24, 2012)

Wood won't burn in anything "airtight".


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## Don2222 (Jun 24, 2012)

BrotherBart said:


> Wood won't burn in anything "airtight".


 
Yes, you need air to burn wood but where the air comes in can make a big difference. I learned that from my Wood/Coal "Airtight" stove. When burning wood I opened the combustion air intake above the wood because wood burns from top down. When I burned coal and put in the coal grates, I opened the combustion air inlet below the coal grates because coal burns from the bottom up.

So if the joints and seams in the stove are not caulked and sealed then air will come in everywhere! "Airtight" means all the joints and seams are air sealed.

As far as the Garrison 2 goes, this is from the manufacturer's comments:

"Recognizing the widespread interest
in efficient stoves that also allow
fire-watching, Garrison uses double
cast-iron doors as the focal point of
their wide- faced octagonal stoves. *The*
*doors can be closed securely for airtight*
*efficiency* or left open with the
spark guard screen in place for safely
viewing the fire."

Closing the doors was one of the 1st steps to Airtight efficiency but if the seams are not cemented with high temp caulking or equiv., then the stove is NOT truly "airtight" by today's standards!

More info on Garrison Stove Works
P.O. Box 41 2, Claremont,
New Hampshire 03743
603-542-876 1
https://www.hearth.com/econtent/index.php/wiki/Garrison_Stoves/
A very popular stove line in the time period from 1978 to 1982. The full line consisted of 3 sizes of wood stove and 1 coal unit. The first model was the Garrison I, a large steel stove with an 8” flue. This was followed by the Garrison two and three, smaller units with a 6” flue. All had rear takeoffs which allowed for easy venting into an existing masonry fireplace.
Note: Garrison also made a dual-fuel model for a short time which could burn coal as well as wood.


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## begreen (Jun 25, 2012)

What if the seams are welded?


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## Locust Post (Jun 25, 2012)

Don2222 said:


> Yes, you need air to burn wood but where the air comes in can make a big difference. I learned that from my Wood/Coal "Airtight" stove. When burning wood I opened the combustion air intake above the wood because wood burns from top down. When I burned coal and put in the coal grates, I opened the combustion air inlet below the coal grates because coal burns from the bottom up.
> 
> So if the joints and seams in the stove are not caulked and sealed then air will come in everywhere! "Airtight" means all the joints and seams are air sealed.
> 
> ...


 
I have to disagree to some extent Don. My stove and I think a lot of wood stoves especially without a grate feeds air under the wood or you could say at or through the red coals under the wood. When it reaches the back it draws upward and it is slowed and kicked back into the firebox by the baffle before it rises up the chimney. I do have air at the top that I can open which is meant to act somewhat like a secondary burn but not as efficient as the burn tubes.


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## Don2222 (Jun 25, 2012)

Locust Post said:


> I have to disagree to some extent Don. My stove and I think a lot of wood stoves especially without a grate feeds air under the wood or you could say at or through the red coals under the wood. When it reaches the back it draws upward and it is slowed and kicked back into the firebox by the baffle before it rises up the chimney. I do have air at the top that I can open which is meant to act somewhat like a secondary burn but not as efficient as the burn tubes.


 
Thanks for the input Locus Post
What I said about intake air above the wood fire was based on the 1990 design of the VC Duchwest.

Newer stoves may have a better design!

However I stand behind what I said on the definition of "Airtight"


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## Don2222 (Jun 25, 2012)

begreen said:


> What if the seams are welded?


 
As long as the seam is completely air sealed.
I believe they are spot welded to save money and then the rest of the seam is cemented.

I thought they might use high temp RTV but Vermont Castings uses a higher temp Furnace Cement.

Here is an excerpt from the Vermont Castings Resolute Acclaim Non Cat stove manual.

Repair Missing Cement in Seams
The cement in the stove seams may deteriorate over time and fall out in places. Just as with the stove doors, it is necessary to keep the seam seals in good condition. Spot-fix with furnace cement (available from your local dealer) any areas where the cement seal is visibly deteriorated. Allow 24 hours for the new cement to dry.


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## Don2222 (Jun 25, 2012)

Hello

Here is what Vermont Castings does. > http://autonopedia.org/crafts_and_technology/Woodburners/Wood_Stoves_Part1.html

*Figure 2.22 (left)-The DownDrafter (patent applied for) by Vermont Woodstove Company.*





*Figure 2.23 - Cross-section of the DownDrafter. Wood is gradually converted to charcoal as volatile substances are driven off by the heat. Slanting grates funnel the hottest coals to two choke points. Smoke must pass through the coals in order to gain access to the stovepipe, and is heated and completely burned in the process.*

Note that a downdraft stove might also be called a "coking" stove. The volatile substances are driven out of the fresh wood at the top of the firebox and pass down through the coals, where they burn completely, to provide the heat needed to continue the wood-distillation process. By the time the wood has been completely stripped of volatiles and has become charcoal, it has settled down into the zone of primary combustion to provide the fuel for coking the next charge of wood.


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## Locust Post (Jun 25, 2012)

Good here Don.........I'm on with you on the definition of airtight.


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## begreen (Jun 25, 2012)

Don2222 said:


> As long as the seam is completely air sealed.
> I believe they are spot welded to save money and then the rest of the seam is cemented.


 
I believe you are incorrect in two ways. That is, comparing cast iron construction to steel and assuming steel stove seams are spot welded.


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## begreen (Jun 25, 2012)

Don2222 said:


> Hello
> 
> Here is what Vermont Castings does. > http://autonopedia.org/crafts_and_technology/Woodburners/Wood_Stoves_Part1.html
> 
> ...


 
What stove is that exactly? Did it ever make it into production? How does this relate to on  the market VC stoves?


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## Don2222 (Jun 25, 2012)

begreen said:


> I believe you are incorrect in two ways. That is, comparing cast iron construction to steel and assuming steel stove seams are spot welded.


 
I know that the VC cast iron stoves use furnace cement for the seams.

Is the entire seam welded on the steel wood stoves? Please explain BG


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## Don2222 (Jun 25, 2012)

begreen said:


> What stove is that exactly? Did it ever make it into production? How does this relate to on the market VC stoves?


 
Not sure if their wood stoves are exactly like this but not too far off. Right?


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## begreen (Jun 25, 2012)

Don2222 said:


> Not sure if their wood stoves are exactly like this but not too far off. Right?


 
From the VC stoves there is quite a bit of difference. But they both do burn wood.


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## begreen (Jun 25, 2012)

Don2222 said:


> I know that the VC cast iron stoves use furnace cement for the seams.
> 
> Is the entire seam welded on the steel wood stoves? Please explain BG


 
Getting back to the OP's stove and off this tangent, yes if it is an exterior seam in the firebox.


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## rkshed (Jun 26, 2012)

For what its worth, I heated my small ranch with a Garrison II last winter and purchased NO oil. Ahoy, your friend will be very happy with it. Replace the door gaskets first and make sure neither of the doors is warped.If any of the bricks are cracked, Aubuchon sells them for $3.97 each.
Have fun!


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## ahoy30 (Jun 30, 2012)

Thanks, Rick, I'll tell him that.


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## Stevendoc (Oct 7, 2019)

rkshed said:


> For what its worth, I heated my small ranch with a Garrison II last winter and purchased NO oil. Ahoy, your friend will be very happy with it. Replace the door gaskets first and make sure neither of the doors is warped.If any of the bricks are cracked, Aubuchon sells them for $3.97 each.
> Have fun!


Hey I have a Garrison two as well.... Been having a lot of trouble with getting the door shut with the new gasket. I actually broke the key unfortunately trying to squeeze it shut to try and compress the rope. What size did you use??? I got 3/8 fiberglass rope not sure if it's the wrong size figured I'd ask....


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