6 inch to 8 inch

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wtyamamoto

New Member
Jul 17, 2006
41
Southern NH
I am installing a new stove with a 6 inch opening. The existing system has an 8 inch pipe going in to the chimney. I have checked and the current flue is properly sized for the stove.

I will need to use an adapter to go from the 6 inch for the stove to the 8 inch for the chimney.

I have seen two methods for this. One method uses the 6 to 8 adapter right off the stove with 8 inch pipes going all the way to the chimney entry. the other uses a 6 inch pipe from the stove and the adapter just at the chimney entry.

My question is, is either method better than the other or does it not make any difference?

Thank you all,
Wayne
 

suematteva

New Member
May 25, 2006
605
Rutland, VT//Southern Quebec
Wty,

We had similiar situation. went 6 inch stove to 7 inch chimmney... ran the 6 to the chimney then adapter. looks good and works good.
 

MountainStoveGuy

Minister of Fire
Jan 23, 2006
3,654
Boulder County
I agree, take the black pipe up to the 8 inch, if you have a long run of black pipe, consider installing double wall black. 8" chimney has almost twice the volume of 6". Double wall black will help keep the flue hot to help drive that big chimney. You will not get the same performance as you would with a 6" system, but it might work resonably well. If you have start up problems or back puffing problems, the first thing to look at is to change out that 8" chimney for a 6".
 

fespo

Minister of Fire
Dec 14, 2005
720
South West burbs of Chicago
Wayne, I Had same set as you do. I change to 6'' all the way -up. The best money I spent, now I know my chimmeny is safe ,new and the right size. The people before me did not put the chimmeny in right. To close the wall, no fire shields at ALL. Zip screws holding the pipe sections together. It was just a mess. If you check back to older post I asked the same question.

Espo
 

wtyamamoto

New Member
Jul 17, 2006
41
Southern NH
Thank you all for your valuable input. I think I will go with 6" to the chimney. Fespo, the chimney is was inspected and is ok, so I think I'll see how the stove operates with that size flue first and if it needs to run smaller I will reline with SS.

This is a great forum!

Wayne
 
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elkimmeg

Guest
If you are running you stove in an 8/8 clay flue you should not have to line it if the clay liners are in good condition.
The inside cross sectional area is about 48" 6" round is about 28" code will allow for an exterior flue up to 2 x larger or 56"
Both my VC intrepid cat and my resolute acclaim, are vented into separate 8/8 clay flues both draft strong
 

BrotherBart

Modestorator
Staff member
I have to ask. Is that 8" pipe lining a masonary chimney or is it a 8" metal chimney from a previously installed pre-fab fireplace?
 
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elkimmeg

Guest
Good question BB cross sectional code would kick in if the chimney has exterior exposure not above the roof line. If interior, the code allows for 3x the cross sectional area. It would be code compliant but would it draft ok? If it is an older metal prefab fire place, many of those flues were not rated for wood stove use. Most were rated to 1500 degrees very few to 1700 wood stoves require 1800 but since no 1800 is made the default becomes HT 2100. A full UL approved liner,I forgot the listing number 1477 I believe, would be required to comply with code and safety purposes or ss HT 2100 liner

There are two liner approval classifications. I will have to look it up and present the two governing classifications. The HT2100 is the higher listing than the UL 1477?. All HT 2100 are 1477 UL approved
 

wtyamamoto

New Member
Jul 17, 2006
41
Southern NH
Hello BrotherBart and elkimmeg,

The 8" pipe feeds into a masonary chimney with a flue liner that has an external dimension of about 7.5 x 12 and an internal dimension of 6.5 x 11 (I assume this is considered and 8x12).

It is a fairly large chimney as it also serves a fireplace on the 1st floor (wood stove is in basement) through a separate flue. It extends about 4 feet past the roof line.

The chimney runs through the center of the house an is not exposed to the outside in any way or even near any external wall.

I calculate the total internal area to be 71.5 square inches which in theory meets the 3x requirement for a 6" stove exit (84.78 sq in). Am I mistaken about using this calculation?

I wanted to try the stove with the existing chimney before making a decision on the expense of an SS liner.
 
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