Old woodburner installation

[Blackshirt]

Hello all! Im new to the site and have found a lot of good info. I have an old Fisher stove I cleaned up and put in my house. It has a 6" hole for the pipe in the back. My fireplace has an 8" hole for the pipe. The chimney is in good shape and is approximately 6x10 3/4. Ive been hearing conflicting info on how I should hook it up. Should I...
6" pipe from stove to fireplace then use existing chimney.
6" pipe from stove to 8" pipe in fireplace then 8" pipe all the way up to top of chimney.
6" pipe from stove all the way up chimney to the top.
Can I use existing fireplace without running pipe up it?

Thanks!

 

[lango]

Patience, Grasshopper.
Someone, more qualified than me will be along.

In case they're not- I would (just ME, mind you) run 6" from stove, all the way up and out. The pipe in the chimney, ( again; if I were doing it-)would be insulated. Duravent is a manufacturer, I believe. Reason being- keeping the exhaust smoke hot enough all the way up, to prevent creosote build up.
I'm sure I probably told you something that's not up to code, or some such. That's just how I'd do it.

Good luck to you.

 

[bholler]

Hello all! Im new to the site and have found a lot of good info. I have an old Fisher stove I cleaned up and put in my house. It has a 6" hole for the pipe in the back. My fireplace has an 8" hole for the pipe. The chimney is in good shape and is approximately 6x10 3/4. Ive been hearing conflicting info on how I should hook it up. Should I...
6" pipe from stove to fireplace then use existing chimney.
6" pipe from stove to 8" pipe in fireplace then 8" pipe all the way up to top of chimney.
6" pipe from stove all the way up chimney to the top.
Can I use existing fireplace without running pipe up it?

Thanks!

Some pics of your setup would help. I am confused when you say fireplace but then talk about an 8" hole. I am not really sure what your setup is

 

[Blackshirt]

Sorry, By fireplace I meant brick wall that attaches to chimney.

 

[bholler]

Sorry, By fireplace I meant brick wall that attaches to chimney.

Ok a few things you have to check first is what condition are the clay liners in that chimney in. Is there a combustible wall behind that brick? If so how much masonry is around the crock where it passes through the wall? Is there an air space between the brick and the combustible wall?

 

[Blackshirt]

Ok a few things you have to check first is what condition are the clay liners in that chimney in. Is there a combustible wall behind that brick? If so how much masonry is around the crock where it passes through the wall? Is there an air space between the brick and the combustible wall?

The previous owners used the chimney for a pellet stove thats it. Liner looks to be in good shape. Don't know about the combustable wall but I assume drywall. I think there is masonry around most of the crock. I dont believe there is an airspace.

 

[bholler]

The previous owners used the chimney for a pellet stove thats it. Liner looks to be in good shape. Don't know about the combustable wall but I assume drywall. I think there is masonry around most of the crock. I dont believe there is an airspace.

Dry wall is combustible so is the fra ming it covers. Thinking you have masonry around the crock is not enough. That is where structure fires start. You need 12" of solid masonry between that crock a nd any conbustible materials.

As far as the air space goes you dont need it but that determines how much clearance reduction that brick gives you.

As far as condition of the liners go it is way to dirty to tell. You also need clearance between the outside of the masonry chimney structure and combustibles.

 

[Blackshirt]

Dry wall is combustible so is the fra ming it covers. Thinking you have masonry around the crock is not enough. That is where structure fires start. You need 12" of solid masonry between that crock a nd any conbustible materials.

As far as the air space goes you dont need it but that determines how much clearance reduction that brick gives you.

As far as condition of the liners go it is way to dirty to tell. You also need clearance between the outside of the masonry chimney structure and combustibles.

Should i just run 6" pipe from stove to top of chimney?

 

[bholler]

Should i just run 6" pipe from stove to top of chimney?

That wont address the wall passthrough. And unless you insulate that liner not just stove pipe it wont address the lack of clearance from the chimney either. You need a full inspection to find out exactly what you have.

 

[coaly]

The reason you get conflicting info for pipe or liner size is because it depends on other factors.
It is always best to have the same diameter pipe and flue as stove outlet all the way to the top.
Best is also an indoor chimney and insulated flue liner.
This stays hotter inside with the least amount of waste left up the chimney to keep flue gasses above the condensing point of 250* f. to the top. That is the object to keep it clean. 250* all the way to the top while smoke is present.
The larger the diameter, the more the exhaust gasses expand and cool, so the more heat you need to leave up. Below 250* will allow water vapor from combustion to condense on the flue walls allowing smoke particles to stick forming creosote.
6 inch round is 28.26 square inch area compared to 8 inch round having 50.25 and your 6 X 11 approx. 66 square inches. That gives you an idea of how much the gasses will expand, cooling the flue considerably. (It is legal to connect up to 3 X the size)

It will work with the larger existing flue but cleaning will be much more frequent and you will be running with the air open more to burn hotter wasting fuel with much more loss needed up the chimney. With a smaller stove this becomes more critical since the lower BTU output of a smaller stove may not heat the area you're trying to heat by loosing too much up the stack. You will heat 2000 sf plus with that stove with an efficient chimney. Also a efficient chimney flue allows you to install a baffle which greatly reduces smoke and makes the stove much more controllable with less temperature spikes going up the chimney.

You have a Papa Bear and without wall protection requires 36 inches of clearance to combustibles. If the bricks are full solid brick in contact with combustible material, a reduction of 33% is allowed or 24 inch clearance to rear. That affects the floor protection at front loading door where you need 18" of floor protection from stove front. The model you have was built for use on a non combustible floor such as a cement floor in basement with cement wall behind it. Your configuration against wall or fireplace opening would use a side vent to reduce hearth pad size and reduce the amount it protrudes out into the room.

As bholler mentioned be sure of the construction behind brick since 12 inches of solid cement is required around the horizontal clay liner. Many times a chimney not built to code which is unsafe for a wood stove has a pellet stove connected with the smaller inner pipe installed up through the flue.
A magnetic thermometer on the pipe surface reads 1/2 the inner actual flue gas temp. So 600 f. + flue gas temps are common at that connection to chimney flue.

If this is an exterior chimney you need 1 inch clearance from masonry to combustible and indoor chimney requires 2 inches clearance. If you don't have that, an insulated liner is required.

 

[Blackshirt]

Wow, thats a lot of info. Thank you very much!

 

[Piney]

Is this stove on a main or top floor? Do you own the house? Are you free of invasive bylaw regulation?
In similar situations I just paid for an insulated through the wall or through the ceiling, attic, roof chimney system and ignored the old Masonary chimney. Yes, inside chimneys are easier to keep warm but my through the wall one here works well and it is always -20 and often -30 through the winter and we burn 24/7 for 7 months. I do sweep it twice through the winter and am rewarded each time with a shower of minimal buildup. But it would plug eventually if ignored.
We mostly burn pine, the worst natural fuel.
Old masonary chimneys are often fire risks with real stoves though they might be able to handle a 3" pellet liner.