Restrictor Flue Racing, for non-EPA stove owners... have you tried this? Any recommendations from t

[JimWalshin845]

I have been thinking about this for quite some time and will be leaving for Florida in the next week or two but I may want to modify our flue when we return.

We burn a non-EPA VC Defiant stove (circa 1979) into a firepace with a 10x10"(id) flue. The stove exhaust is 8" so we barely meet the '2 x X' requirement for exhaust and flue diameter. There is a stop at the throat and at the face of the fireplace too.

Everything works great except we get at the top 4-6' of the flue a thin creosote buildup which we keep under control by adding TSP in the stove weekly. The flue is about 12' to the throat and about 1/2 of the masonry is in the adjoining garage and the last 6' has 3 sides exposed to weather. There is an adjoing flue from the oil boiler in the basement.

The creosote buildup is very minimal and stays consistantly about the depth of a fingernail but it is gooey creosote. We burn well seasoned oak, so please don't go down that path. All non-EPA stoves have some creosote buildup and I am not looking for comments as per stove replacement... unless you want to pay for the stove and installation.


I read a recent article by John Gulland about restricting the top part of the flue (restrictor plate) for run-a-way EPA stoves. He gave a good description of the pros and cons and that it may be out of compliance per EPA and may cause roll-back problems. But in our application it may work to keep hotter flue temps and avoid some creosote buildup

I have some scrap sheet metal to fabricate pipe and plate(s) to reduce the rectangle 10x10 to 8-9" round for the top 3' of the flue for the experiment and if it works out will do it correctly. We live on the 39.37Nth parallel in southern NJ so fairly mild winters.

I would like to know if others have tried this with any success and of course we are looking for suggestions.

Thank you in advance,
Jim

Addit/Edit: We burn 24/7, retired and very happy with our stove.

 

[downeast]

...will be leaving for Florida in the next week or two but I may want to modify our flue when we return.
We burn a non-EPA VC Defiant stove (circa 1979) into a firepace with a 10x10"(id) flue. The stove exhaust is 8" so we barely meet the '2 x X' requirement for exhaust and flue diameter. There is a stop at the throat and at the face of the fireplace too.
Everything works great except we get at the top 4-6' of the flue a thin creosote buildup which we keep under control by adding TSP in the stove weekly. The flue is about 12' to the throat and about 1/2 of the masonry is in the adjoining garage and the last 6' has 3 sides exposed to weather. There is an adjoing flue from the oil boiler in the basement.
The creosote buildup is very minimal and stays consistantly about the depth of a fingernail but it is gooey creosote. We burn well seasoned oak, so please don't go down that path. All non-EPA stoves have some creosote buildup and I am not looking for comments as per stove replacement... unless you want to pay for the stove and installation.
I read a recent article by John Gulland about restricting the top part of the flue (restrictor plate) for run-a-way EPA stoves. He gave a good description of the pros and cons and that it may be out of compliance per EPA and may cause roll-back problems. But in our application it may work to keep hotter flue temps and avoid some creosote buildup
I have some scrap sheet metal to fabricate pipe and plate(s) to reduce the rectangle 10x10 to 8-9" round for the top 3' of the flue for the experiment and if it works out will do it correctly. We live on the 39.37Nth parallel in southern NJ so fairly mild winters.
I would like to know if others have tried this with any success and of course we are looking for suggestions.
Thank you in advance, Jim
Addit/Edit: We burn 24/7, retired and very happy with our stove.

Same problem with an early 1980's Vermont Vermont Castings Vigilant and flue. Rather than a restrictor at the top end of the chimney, I lined the flue with 8" SS pipe down to the stove. The smoke gases cool in the mass of a square flue and fireplace throat and damper; really cooling at the top 6' for you, condensing the gases into creosote. The last 6' of restrictor may do the job, but think about doing it all the way to the stove.
The original VC Defiant was one of the finest pieces of engineering ever: thousands of them still burning. I did a partial rebuild and repair ( strange hobby I do for friends for beer) ) of a Defiant in Belfast, Maine last fall. Still in perfect shape after 25+ years with original gaskets and factory furnace cement . Do you think that today's stoves will be around in 10 years ?

 

[JimWalshin845]

Downeast,

Thanks for the advice but not enough concern for $500 in a SS liner. Again, everything works fine except for a pittance of creosote. 18 degrees out right now and the house is roasty toasty, stove dampened down all night long.

Ran across another Defiant owner this week... one of the original owners of the single back design. They are original owners and estimate there has been over 400 cords of wood run through the stove. When the stove was brand new the factory had to do a rebuild because of a defect and they re-built it once a short while back. They also told a story of a neighbor who recently traded in a their 1970's Defiant for one of them new-fangled stoves and are having terrible problems with it. Sorta makes you scratch your head and wonder why? :-S ... maybe peer-pressure or trying to keep up with them Clampetts from down south with all that Texas Tea.

Anyway, we are looking to spend about $50 bucks for the fixin which really doesn't need fixin at all.

After all I have read, here on H dot C and other boards, I doubt most stoves, inserts and z-cans will last as long as the original cast iron smoke dragon furnances that we are use to. They say they burn colder in the box and the Cat will scratch up the heat. So many complaints I see and certainly a ton of poor workmanship. Maybe we are doomed as per stoves of today to be just throw away items like cell phones and automobiles. What a pity!

Safe burns guy and keep rebuilding them cast iron dragons,
Jim

 

[swestall]

I was burning my Defiant NC with an open flue 8X12 liner and decided that I really should put a cap on top of it. (one of those wire mesh with top types) I've checked it a couple of times and it is reducing the creosote in the top part of the flue. (I was getting shiny black in the top 12"), so that would say that further restriction might just do the job: I'm interested to see the result.
I am going to line with SS next season, just for safety and ease of maintenance.

 

[johnsopi]

You could replace the stove with a new EPA stove.

 

[TMonter]

Do you think that today’s stoves will be around in 10 years ?

Neighbor's Quad 4100 is on year 7 or 8 now. He's only replaced firebrick.

 

[woodconvert]

"I would like to know if others have tried this with any success and of course we are looking for suggestions."

My situation is eerily similar to yours so do give updates.

To make sure I understand this, are talking about reducing the size only on the last 6ft??. To me it sounds like it should fix the creosote problem for the last 6 ft but i'm not sure if you'd be creating another problem for the distance prior to it. By reducing the last six feet you will increase the exhaust velocity in that distance but I believe you'd be reducing the velocity prior to the reduction. This may or may not cause problems but you would intuitively think with a slower exhaust up to the reduction that you may get more buildup but at the same time you would also retain more heat.

I'm really interested to see how this works over a period of time.

 

[JimWalshin845]

You could replace the stove with a new EPA stove.

OK John,

What time will you be delivering my new EPA stove and installing it?

 

[JimWalshin845]

I was burning my Defiant NC with an open flue 8X12 liner and decided that I really should put a cap on top of it. (one of those wire mesh with top types) .

We already have a cap and they do help keep a warmer flue temp.

 

[JimWalshin845]

"I would like to know if others have tried this with any success and of course we are looking for suggestions."

My situation is eerily similar to yours so do give updates.

To make sure I understand this, are talking about reducing the size only on the last 6ft??. To me it sounds like it should fix the creosote problem for the last 6 ft but i'm not sure if you'd be creating another problem for the distance prior to it. By reducing the last six feet you will increase the exhaust velocity in that distance but I believe you'd be reducing the velocity prior to the reduction. This may or may not cause problems but you would intuitively think with a slower exhaust up to the reduction that you may get more buildup but at the same time you would also retain more heat.

I'm really interested to see how this works over a period of time.

Actaully thinking about only reducing the last 3'. The stove exhaust is 8" so I am debating whether to reduce the top to either 8" or 9". Initially thinking about a plate at the bottom of the 3' pipe and then a plate on top, the void wrapped in kaowool or rockwool.

 

[woodconvert]

Actaully thinking about only reducing the last 3'. The stove exhaust is 8" so I am debating whether to reduce the top to either 8" or 9". Initially thinking about a plate at the bottom of the 3' pipe and then a plate on top, the void wrapped in kaowool or rockwool.

OH, I gotcha. Yeah, I would think that since there would be no actual reduction, i.e. you'd have 8" all the way up then that should work without affecting anything else. Can't hurt to try anyhow.

Just curious...with an 8x8, and if money wasn't a problem, is there double wall or tripple wall insulated that would fit inside and 8x8??. I know exactly nothing about that stuff.

 

[JimWalshin845]

Assuming you have a 6" flue exhaust on the Jotul, I think the normal double walled pipe is 9", so you would need a real big shoehorn to fit that down a 8x8" pipe.

 

[JimWalshin845]

Anyone else with any suggestions? I have had some lurkers email me, they are afraid to post due to the fact that they will be criticized for burning a smoke dragon. Funny how that happens! :coolmad: