Fischer Papa Bear 8"-6" reducer???

Hooverscon

Member
Jul 21, 2017
13
Ohio
Hello guys and gals! it's been a while since my last post. I had a question regarding the best way to install a 8in to 6in reducer off of the back of a papa bear. Should I have the reducer come directly off the back side of the wood stove or should I run an 8 in elbow then to a 8-to-6" reducer? Would there be any benefit running the 8in elbow first?
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
3,900
NE PA
Papa Bear is a 6 inch stove. Are you increasing to 8 for a larger chimney? If so, use 6 inch connector pipe inside and only increase at the chimney. This is not the best configuration, and the Papa should have the same size chimney as flue outlet for the best efficiency.
Allowing exhaust gasses to expand from 6 to 8 decreases the flue gas temperature by about 1/2. Depending on chimney height, interior or exterior, can allow temperatures in the flue to drop below the 250*f. temp needed for clean operation.
 

Todd67

Minister of Fire
Jun 25, 2012
923
Northern NY
I'm thinking he might have a Grandpa Bear stove, not a Papa bear.

@Hooverscon , can you post a picture of your stove please?
 

Todd67

Minister of Fire
Jun 25, 2012
923
Northern NY
Thanks, and very nice looking Papa Bear!

I'm glad coaly understood your question, because I was reading it wrong. Refer to coaly's post above.
 
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coaly

Fisher Moderator
Staff member
Dec 22, 2007
3,900
NE PA
OK, that is a Papa Bear pictured. Does it have 6 or 8 inch outlet?
Normally they were built with 6 inch, but I have seen special built single door Papas with 8 inch.
I believe your terminology is backwards. When you have a 6 inch stove to 8 inch chimney, it is called "increaser". It goes by direction of flow. Just like water flowing through a pipe. If pipe gets larger as it goes farther from supply it increases. If it gets smaller flowing away from supply, it is reduced. So a stove goes by direction of flow from stove to chimney. I believe you're increasing from 6 inch stove outlet to a larger chimney. Correct?
 

Hooverscon

Member
Jul 21, 2017
13
Ohio
OK, that is a Papa Bear pictured. Does it have 6 or 8 inch outlet?
Normally they were built with 6 inch, but I have seen special built single door Papas with 8 inch.
I believe your terminology is backwards. When you have a 6 inch stove to 8 inch chimney, it is called "increaser". It goes by direction of flow. Just like water flowing through a pipe. If pipe gets larger as it goes farther from supply it increases. If it gets smaller flowing away from supply, it is reduced. So a stove goes by direction of flow from stove to chimney. I believe you're increasing from 6 inch stove outlet to a larger chimney. Correct?
I was unaware of a papa bear being a 6". I assumed it had an 8" chimney. That makes it much easier for me now! I'm regards to single wall pipe ( it will be installed in a barn with > 48" clearing) do you recommend stainless or a matte black finish? Does it make a difference. My buddy told me that the black pipe will rust out...
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
3,900
NE PA
Yes, single door stoves have a 6 inch outlet, double doors have 8. But there are exceptions when customers had them special built or modified themselves.
When Bob Fisher built the first steel plate stove, he made it with 6 inch outlet and covered the face of his fireplace with a steel plate and ran the 6 inch pipe into it, knowing he was building a large box (it was a Papa) with a small outlet to retain as much heat as possible. He was right, but time has proven it's best to keep the same size chimney flue all the way up to prevent creosote formation.

Black pipe will rust eventually, mostly if you burn too cool. The water vapor from combustion can condense in the pipe, leading to moisture and premature rusting. Stainless I much better, and expensive. It is also used as liner inside existing chimneys that require relining or resizing. You can get quite a few years out of black pipe, but burning coal rots them out yearly if you don't clean them, the apart, dry and store correctly. Wood ash is no where near as corrosive.

During summer with higher humidity, you have warm moist air inside and cool night air drops down the pipe at night. This allows moisture to condense on pipe, rusting more than in a temperature controlled home. The price of stainless looks good if you have to replace black pipe every two or three years!

Barns are usually much higher than 8 feet before connection to a chimney box, unless there is an existing masonry chimney being used. Depending on height of connector pipe, it may need to be double wall to prevent too much cooling before chimney.