Making a Grandpa Bear airtight by adding a gasket

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Jeff Rohr

New Member
Jun 20, 2022
1
Black Hills, South Dakota
I have a log home with a stone fireplace on the main floor. We also have a Fisher Grandpa Bear stove in the basement. Flues from both stoves go up a common chimney. Sometimes when we have a fire burning upstairs we get the smell of smoke in the basement. I am assuming that this is caused by combustion air that is feeding the upstairs fireplace being drawn down through the flue to the basement Fisher stove and into the basement. Since the two flues exhaust into the same space above the chimney the combustion air being drawn in the stove flue pulls in smoke exiting the fireplace flue. The problem is reduced but not eliminated by keeping the door down to the basement closed, which just confirms my theory. And I of course completely close the two air intake vents on the stove doors.
I decided to try adding some gasket material in the groove of the doors to the stove to make them more airtight and thus smoke-filled combustion air will not be drawn down the stove flue to enter the basement living space. The result was that I couldn't close the doors. Judging from comments regarding Fisher stoves on this site it appears that most Fisher stoves do not have gaskets.
There are two bedrooms in the basement and when a fire is burning upstairs the smoke smell is quite annoying. Of course, building a fire in the stove eliminates the smoke coming into the basement because the stove is now drawing air in and up the chimney.
Does anyone have any suggestions?
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,513
NE Ohio
Crack a window near the FP when you are using it...you need more makeup air.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,158
central pa
I have a log home with a stone fireplace on the main floor. We also have a Fisher Grandpa Bear stove in the basement. Flues from both stoves go up a common chimney. Sometimes when we have a fire burning upstairs we get the smell of smoke in the basement. I am assuming that this is caused by combustion air that is feeding the upstairs fireplace being drawn down through the flue to the basement Fisher stove and into the basement. Since the two flues exhaust into the same space above the chimney the combustion air being drawn in the stove flue pulls in smoke exiting the fireplace flue. The problem is reduced but not eliminated by keeping the door down to the basement closed, which just confirms my theory. And I of course completely close the two air intake vents on the stove doors.
I decided to try adding some gasket material in the groove of the doors to the stove to make them more airtight and thus smoke-filled combustion air will not be drawn down the stove flue to enter the basement living space. The result was that I couldn't close the doors. Judging from comments regarding Fisher stoves on this site it appears that most Fisher stoves do not have gaskets.
There are two bedrooms in the basement and when a fire is burning upstairs the smoke smell is quite annoying. Of course, building a fire in the stove eliminates the smoke coming into the basement because the stove is now drawing air in and up the chimney.
Does anyone have any suggestions?
Check the fit of the doors. If they fit properly gasket won't change anything. Even if it does seal the doors it will just leak in elsewhere
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,513
NE Ohio
And I don't think any Fisher stoves had gaskets...I'd remove those.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,668
NE PA
Your fireplace has hot rising exhaust gases moving up the chimney which allows atmospheric air pressure to push into the fireplace opening. The indoor air that leaks up chimney as dilution air also decreases pressure in home adding to the inefficiency of the fireplace. Without an air intake near the fireplace, the higher air pressure outside has to push into the home where it can. It is using the other chimney as an air intake.

You can eliminate the problem by adding a fresh air intake close to the fireplace. This will equalize the air pressure between inside and outside. A PVC pipe through wall with an elbow pointing downward outside with an insect screen, and an elbow inside facing upward will not allow warm air inside to rise out, but when a exhaust fan or exhaust from fireplace removes air from the home, atmospheric air pressure will push into the intake pipe to equalize pressure from outside to inside. If you have a utility room downstairs with exhausting appliances, an intake on that level gives those appliances the fresh air required instead of using the chimney as an air intake as well. Clothes dryers, radon blowers, and exhaust fans are using the chimney as well.

There is no clearance between the channel iron door seal and doors of your stove for gasket material. The raised portion on back of doors makes contact in center of channel iron web, and the edges of door seal channel iron make contact on the back of doors. This 3 point contact area all the way around is considered airtight as built. You can add flat gasket only to the center of door seal channel on most stoves. To test, try a piece of cardboard in channel of iron door seal. If doors close easily, flat gasket will crush and work, but should not be necessary unless door hinge pins or hinge plate holes are worn, or hinge plates are incorrectly welded in place for the door set.

Only Fisher Stoves with glass doors use gasket material. Series III is installed in door channel, Series IV on door since the stove face has no channel iron door seal.
 
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