Slammer in a cabin

[Yankeesouth]

Okay.....don't beat me up too bad on this one but I have a question about throwing a slammer in an old cabin.  This is temporary....most likely till I can around to installing it correctly this summer.....10-15 weekend burns max for the life it will be installed.  I know everyone has their opinions on this topic and I also know it is not the best or even approved option now-a-days, but all that aside I have a question about performance. 

Stove to be installed is a Dutchwest 6inch vent out of the back.   The fireplace is old school with "0" damper.....just a smoke chamber.  The chimney is in great condition.....13in terracotta liner (12-15ft)....no cracks.   Can I place the stove on the hearth.....run a 2ft pipe out the back.....throw in a 90....throw in a "whatever" size pipe I need in to get me past the smoke chamber......and have a working stove? Will this work?

To make a long story short.....the open fireplace is great for looks and burns for about an hour....but without a damper it chews through the wood.   I am looking for a temporary stove install to get me through some hunting weekends for the winter.   Thoughts??

[MountainDon]

I see nobody has an opinion to express, so I'll chime in with my theory.

The stove is manufactured with a six inch diameter flue. That's a cross sectional area of about 28 square inches. The terra cotta liner is given as 13 inches. Is that circular or square? A 13" circular would have an area of about 132 sq in. A square terra cotta flue would have an area of 169 sq in.

The square flue would have an area (169 / 28 =) 6.03 times that of the stove 6 inch pipe.
A round terra cotta flue would have an area 132 / 28 = ) 4.7 times that of the 6 inch pipe.

When the smoke leaves the short section of 6 inch pipe it will hit the larger space and expand and slow right down. As it expands it will cool and slow down by a factor of 4.7 or 6. The cooling effect will also slow down the smoke even more.

I theorize that the terra cotta chimney will suffer heavy build up of creosote; there may even be condensing liquid inside the terra cotta pipe.  As well the stove will likely not have sufficient draft to keep a good fire going.

However you could try it and maybe get lucky. After all bumble bees are not supposed to be able to fly either.   

[JRR]

I agree with Don's theory.  It might be possible to insert pipe down the chimney from above to keep the exhaust velocity higher after the box.  It would take some accurate measurements, and/or perhaps a "hold off" on the bottom of the pipe;  to make sure there is still a good passageway for exhaust.  Perhaps support the pipe insert at the top of the chimney.  Stuff unbacked fiberglass around the pipe as far down as possible, again, not to interfere with hot air flow.

[MountainDon]

There are SS liners made for this. Probably expensive for temporary....

[glenn kangiser]

I think Don and JRR are correct on this also.  Note that single wall pipe will cool and collect creosote also but not as bad as the terracotta.

[MountainDon]

http://www.northlineexpress.com/chimney/chimney-pipe-stove-pipe/chimney-liner/6-inch-chimney-liner.html

[Dave Sparks]

What is the capacity of a Dutchwest stove?  I think that knowing the BTU whould help make sense of this.
For temporary, as long as you are there to monitor and deal with a big problem that could develope your plan is OK. I have seen people do really crazy things like run the flue out a window to get a 4 day drywall job done in winter.

As long as it works you are a genious. If not, it is just another reason for following the building codes. Happy turkey day everyone!

[flyingvan]

Keep in mind, smoke will go up the best chimney.  If the structure is taller and less impeded than the temporary flue you come up with, your temporary chinmney will instead act as an air intake and the smoke will go through the structure.  Your flue MUST terminate higher than the highest point of the structure.  This isn't just for fire safety.  There's actually a thermocline point in a structure you must have the chimney exceed or it simply will not draft.  The size of the chimney is important too---

"NFPA 1992 (7.5.3) states that draft hood appliances, Category I appliances and other appliances that use Type B vents must have a

chimney flue area not less than the area of the largest vent outlet plus 50% of the area of the additional flue outlet.

The following calculation works out to be the same answer as the "Rule of Thumb" sizing, i.e.: (4/22 x 3.14 = 12.56) + (3/22 x 3.14/2 = 3.53) = 16.09 / 3.14 = 5.1251/2 = 2.26 x 2 = 4.52" or 5".

The 1992 GAMA vent sizing tables for single-wall metal vent connectors attached to a tile lined masonry chimney uses Table 8. The result of those calculation using a 38,000 BTU water heater with a 3" draft hood and a 37,500 BTU boiler with a 4" draft hood connected to a 20' high chimney is to use a common flue with an area of 28 square inches or a 6" flue vs a 5" flue in the previous examples."

  I don't have a reference, but I learned a round chimney must be no less than one twelfth the diameter of the fireplace opening and a square chimney no less than one tenth.   

  There's a point of pressure equilibrium in every structure...If you have two chimneys---one is above this point, and the other is below it--say in an addition---a fire in the lower chimney could actually draft through the house up the taller chimney.  In structures with fireplaces on multiple stories, they all should terminate at the same height above the roof.  Where the flames are doeasn't matter much.  That equilibrium point is the same point in the house...

[flyingvan]

Also, while we're on the subject---I mentioned in a post that if you can place your fireplace or woodstove on the interior instead of an exterior wall, it will draft better ( and heat distribution is much better too)  The taller the chimney, the better the draft due to 'stack effect'.  (heck---they'll even draft when there's no fire) There's an exception though---if your chimney is tall enough, and it's exposed to the cold air, the smoke can cool enough to form a cold air plug in the chimney and it won't draft.  A chimney in the middle of the house will stay warm, radiating heat into the structure and back into the smoke, keeping it hot, thus less dense, and rising away.