Flue area difference

[bsruther]

I have a third clay flue in my chimney that's never been used and I had planned on installing a stove in the basement this summer to make use of it. I was up on the roof today, checking my insert flue for creosote and figured I'd check the size of the other flue. I was disappointed to find out that it measured 3.25"X7.25".
The cross section area of a 6" flue is 28.26 sq inches. My flue is 23.5 sq inches.
The flue height is around 14'.
Is the difference in size to significant to be able to use the flue for a stove?

 

[mellow]

You can't even fit a 5.5" liner down that flue, I would say yea, to small for any wood stove, but it could be used for a dryer vent?

 

[bsruther]

I wasn't planning on putting a liner in it.

 

[fossil]

Stove manufacturers pretty much universally recommend that you run the same size flue as the collar on the stove. NFPA 211 says it's not permissable to exhaust a solid fuel-burning appliance into an existing flue with a smaller cross-sectional area than the flue collar on the appliance. It might work, but it might not draw so well. The risk is bad draft, which can be a really ugly problem. Rick

 

[Corey]

I think 14' is going to be pretty marginal on height, too. I've got 13' of 6" dia and draft is a little marginal when temps are 40+ .

 

[bsruther]

So if I did decide to use it, would a small stove give me the best chance of getting a decent draft?

 

[Chimneysweep]

So if I did decide to use it, would a small stove give me the best chance of getting a decent draft?

The cross sectional area of a 6'' flue collar is the important thing here, not so much the size of the stove.

If it were mine, I would crush out the clay tile and line w/6'' i.d. liner system, rigid if poss. flexi if nessesary.

 

[webbie]

Something like the Jotul 602 or possibly even the Black Bear (new 118)....these stoves have 5" flues (in mm) in Europe...

Basically something with a small loading door is the key. This assumes the chimney is sound. If so, I personally would have no problem with a small stove such as those mentioned.

The Morso 2B is another with a small door and small flue in the Euro model.

 

[Chimneysweep]

Something like the Jotul 602 or possibly even the Black Bear (new 118)....these stoves have 5" flues (in mm) in Europe...

Basically something with a small loading door is the key. This assumes the chimney is sound. If so, I personally would have no problem with a small stove such as those mentioned.

The Morso 2B is another with a small door and small flue in the Euro model.

The Jotuls with 5 '' collars are shipped with 5x6 increasers, this gives me the impression that the stove should be operated with the device in place.

 

[webbie]

It is very difficult to find US HT chimney in 5" sizes........which may be why adapters are included on US models.

Way back when, I sold, used and installed many a foreign stove with 4.7 or 5" pipe - some of them were actually shipped with the piping. In the early days, Jotul did not even include the adapter - you had to buy it from a secondary source.

Even the larger Jotul 118 had a 4.7" flue.......

As an example, these brand were:
Jotul
Morso
Ulefos
Waterford
Trolla
Lange
Etc.

See enclosed for a LARGE Lange model with extensive baffle - that was UL approved and had a 5" flue.

Let me state it this way so it is clear - that cross section of chimney easily has the capacity to vent a small stove and clear a small door opening of smoke.

As one other example, MANY chimney sweeps and homeowners line chimneys with 5.5" flex liner because they cannot fit a full 6". For one thing, flex cuts down the draft quite a bit - and at the same time...even if it didn't, the cross section of that 5.5" liner is about 23.7 square inches.......

Whether the chimney will draw well is a whole 'nother story not related to this cross section. You need some height and as few turns or elbows as possible and a tight installation. My guess is that your estimate of 14 feet is low - because it would seem a chimney in the basement would have to be higher than that!

Here is a link for some rough chimney capacity tables....for boilers, in this case:
http://www.engineeringtoolbox.com/chimney-area-heat-load-d_1132.html

According to that table, a 23 sq in. chimney can take 78,000 BTUs. A small stove like a 602 commonly runs at 10-20,000 BTU, and could probably max at 40-50K (you would have to TRY to do this)....at which point it would probably be glowing!

 

[Chimneysweep]

12 years in the biz and I did not know that!
Thanx! BTW does Lange have a web site? And is L.Lange the same thing?
I ask because I have a coal burning modle a cust. gave me and I can't find any info on it.

 

[bsruther]

Thanks so much for all the useful information. I'll have to absorb it tomorrow when the beer has worn off.
I haven't measured the height yet (do that tomorrow). I just assumed it was about 14' because my insert flue is 11' and it's about 3' below that. The flue pipe will come up from the stove about 2' then bend and continue to the clay flue at a 30° angle. the angled section will be about 4' long.
The clay flue is in excellent shape, it's never been used. There isn't even a hole at the bottom. I can't imagine what the flue was originally meant for. The electric water heater is in a whole nuther area and this house has never had propane or natural gas anyway. I hope there's some kind of practical way of doing this because I have 500 sf of finished basement and I'd really like to heat it with wood. I'll have to reconfigure the whole furnace room as it is, but that's no big deal.
Here's a pic of what the flue looks like from the basement.

Thanks again, this is all very helpful.

 

[gpcollen1]

Looks like someone actually had some foresight and said, let's put one more flue in while building this sucker, just in case.

 

[oconnor]

I have a Jotul Kennebec insert installed on a 5 inch flue (23 sq inches) - it does work, but it is way less than ideal, and I have 24ft or so of flue. Like Craig said, door opening seems to be the determinant - if I open both doors, I get smoke, especially if the stove and flue has cooled a bit. I will be getting mine changed out for a 6 inch soon. I would say knock out the clay tile and run 6" down - the effort will be worth it for better performance and less smoke inside.