another set-up question about D R A F T

[burr]

To keep such a valuable subject on the board, I have question on installation of my new stove. I have purchased a new Jotul F3CB and plans are to install in an extra room that used to be a patio outside of my living space. It is a room app 20x16 that is two steps down from the house with an open space of a sliding glass door to join the room to house. This addition has a simple shed roof almost flat, off of the existing 4/12 roof and has windows on each end and an exit door. Since it is two steps lower than house, all ceiling heights etc are comfortable and 8ft but no attic; simply sheetrock ceiling on the 2by10 rafters, then roofing.

Now the specifics. After constructing an 8in hearth, 60in will be dim to ceiling from top of stove (I'm doing 8" hearth to give me an even distance to ceiling for pipe lengths). Jotul requires 15ft of flue for this stove. This means 5ft inside plus 1ft 'attic' gives me only 6ft to roof surface. I do not have any of this done, just thinking. Will I actually need 9ft of chimney outside to produce proper draw ect for this set-up ? If Jotul 'requires' this set-up and I don't actually need this much, what does that mean to stove specs, ect. On this house, using common factors (3ft above peak), chimney could be way less than the height of the required 15ft.

I have not contacted Jotul except for sending purchase type information for warranty stuff. Dealer I used is not as active as one in a more usable region (middle SC) so his main concern is hot-tubs and outdoor kitchens as this stove was one of only 4 or 5 in the store and they were in the basement storage.

 

[Jotul_Dude]

I went with the "2' above" rule with my F400 install which resulted in a 13' chimney initially. It was a pain to get the stove going, smoke when opening doors, short secondary burns, etc. Added a 3' section of pipe and no more issues and stove runs better than I could have ever imagined. Granted I have another chimney 20' away and am on a hill surrounded by trees I'm sure these contributed to draft issues but if I were to install another I would always go with the manufacturers recommended height.

 

[begreen]

I had the Jotul F3cb on a 12' straight up flue system. It worked well at temps below about 45º. Above that, I would get some smoke spillage when opening the door. Our F400 was a little fussier. The large door and shallow firebox definitely meant this stove needed good draft. I had it on a new chimney 20' system but rear vented on an elbow to move it forward into the room for clearances. It worked well below 45º outside, but like our F3CB, it would spill a bit of smoke when temps were like 50º if one did not open the door very slowly.

 

[burr]

Thanks for the Jotul knowledge, it is a major investment for this ole boy that really will not demand too much out of it. That is a major reason for this choice, the beauty of this stove. Down here in SC, most of us don't use wood for primary heat but in Feb2014, we had a major storm and was without power for a while. I had a Buck28000 insert at that time and we heated and even cooked with that little insert. And this is my reasoning for a wood heat 'back-up', although I have a barnload of oak and I will look for every chance I get for using.

I did not know if Jotul may require the 15ft of flue for full coverage of stoves or if that is the design numbers for optimum use. I was hoping to start with 12ft total. Would it make a difference if the first 2 or 3 ft section out of the stove is single wall (to heat up the flue) ? Does an installation of a freestanding stove with straight up flue through the ceiling have that option or is double wall standard to the stove collar ?

 

[begreen]

If draft is weak or the wood is not fully seasoned, then the firebox won't get hot enough to support secondary combustion which is the point of modern designs. It is essential to get a good clean burn. It also puts on a nice light show when happening. Start out with the 12' flue system and try out the stove burning good dry firewood. This is what you are looking for:

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Normally single-wall and double-wall stovepipe are not mixed together. If the ceiling is 8ft then you can keep it all single-wall as long as the 18" to all combustibles is honored. If the stovepipe run is greater than 8' then it should be double-wall stovepipe. At the ceiling the flue system transitions to class A, high temp chimney pipe.