woodstock IS and chimney

pic of new chimney setup. it was 3' shorter last year and performance was not good from the IS. there was 9'4" of inside + outside pipe and the stove worked although i didn't use it with catalyst engaged. i had a crisis where i was sole caregiver to a family member, had my hands full, and didn't want to get in a position where i could have any type of accident.
the chimney is 8" metalbestos which i blacked out with SEM automotive trim paint. its claim to fame is neat low luster finish and good adherence to chrome and stainless steel. the black goes nicely and is more understated than if it were shiny, and won't show smoke or creosote stain the same way. the length is now 12'4" which i hope is enough. i am in new york and won't have to run the stove until later this month. the pipe is now about 6' off the roof, just under that. i put an aluminum wedge into the roof flashing which has 3 u-channels riveted in and the pipe gets some support at each evenly spaced u-channel from that point at the top of the flashing which is about 6" above the shingles. if possible it can stay that way without a roof bracket. should it need a roof bracket it will get attached to the ridge, a spot which never gives you fits and can't leak much if at all. old carpenters like me avoid problems before they start. we understand murphy's law.
first of all my wood was not 3 years old last winter, the chimney wasn't long enough, and the stove worked but did not get hot enough to cook on. it did well though with only secondary combustion and in that mode made far fewer ashes than the jotul 500 it replaced. i look forward to this winter, wood is now 2 years old and pretty dry. i don't have the 15' of stack they recommend and hope to get by as is.

 

Sorry, but this is not adding up for me. Why not install the extra 3 feet of pipe and roof support?

 

I have the same length of pipe and chimney. 12 foot. It will probably work fine when it's cold. You will really appreciate the extra length in the shoulder season when you would be struggling with good draft. The extra draft will allow you to burn lower and slower during those times. If you can get the extra few feet go for it. If not you will be ok.

 

it would be easier if the chimney was further up the roof toward the ridge. adding the extra 3' of pipe would make the cap over 9' from the shingles and extremely difficult to service. as it is right now i can put my hands on it standing on the roof. it would also look ungainly. push come to shove i will have to add the extra 3'. the roof support is no thing of beauty either.

 

if you put support right below last 3 foot piece.. the top piece you just pull off with screen clean screen. height is basically same as now.. That IS will amaze you once you use the cat! trust me!

 

thanks, lucid explanation. i'm wondering if a short, hot fire will suffice in the shoulder season and carry the house through the day. it won't be a mystery much longer as it looks like the first burn will be in about a week. the most important time for a slow burn is in the dead of winter when fuel consumption can add up. i'll keep my eye on it. maybe the stack can be lengthened another 2' if necessary for a total of 14'4".

 

So much in common with chucker , we are both carpenters, we both know Murphy and his dastardly ways and we both owned a Jotul Oslo prior to the IS. Small world.

I agree with the fellas, too bad you couldn't get that flue just a bit higher to increase your draft. Do you have a prevailing wind thats fairly regular? As Canadian border VT was saying, if you put the last section on to what you have now you can always remove it for cleaning at a manageable height and replace it when your done.

Since you didn't have entirely dry wood last season and did not use the cat much, what did your flue produce when you did your cleaning?

 

The IS really wasn't really designed for a hot quick fire. I mean you can do it but it's not it's strength.

 

+1, 100% agree

 

I didn't see the 8" part, thats a cause for concern. WS IS suggests (requires?) 6"

 

dennis

i was given to believe that people vented their IS into masonry chimneys where the tile liners have more area than 8" round pipe, and that was an acceptable setup. what is the basic problem with 8" pipe?
it wouldn't be much trouble to put a 6" liner into the pipe. would this improve things greatly?

 

tell you what i am mostly a cabinetmaker now and it would take a few weeks in the field to be an acceptable carpenter again. i love the shop work. it's an entire study setting up a shop and getting into factory science.
i cleaned the stove a few times last winter. we have a slip pipe where you can take out a screw, remove the couple sections of pipe, and then clean the stack with a couple of rods and a brush from inside the house. the wood had been cut earlier in the year and gone through the summer and then been covered. the entire winter produced about 5 gallons of creosote, certainly no more than 10.
i am looking at pipe sections now and appreciate your feedback. an 18" section would get me to 13'10" and i would still just be able to stand on the roof and remove the cap, and it would probably present an acceptable appearance, and a good chance on getting away without bracing. interesting study, this little bit.

 

It would, almost half the area...28 VS 50 sq. in.

 

I've read that a bigger pipe will really hurt draft. I ran a 1 foot chunk of 6", and a 1 foot chunk of 8" into a volume calculator. This is cubic inches of air (just for comparison).

volume of a 6 inch cylinder - Google

cubic feet of a 8" cylider - Google Search

So apparently an 8" pipe holds almost twice the cubic inches of air compared to a 6".

 

After looking at your pic again...thats 8"? Looks like 6" pipe...is it 8" OD?
That would give you 6" ID on a class A pipe, which is correct then

 

I like to use this simple formula to find area of a circle. Diameter X Diameter X .785 = area.
Then you can multiply area X height to get cylinder volume if you want that.

 

it's 8" metalbestos pipe, i guess selkirk pipe now, so it's 10" OD. it's hard to see proportion in the picture. i checked the online manual for the IS, they are okay with 8" square flue as an exterior setup, and maximum 8" round pipe, again as an exterior chimney. i don't doubt that 6" draws somewhat better. the 8" pipe got installed in the house decades ago when we had a vermont castings defiant that vented with 8" pipe. it was a big deal in those days to have an airtight stove. things have progressed.

 

5 gallons? Wow. My IS had about one cup of ash and creosote and I didn't even have perfect wood yet. This year I will though.

Run that cat!

 

This is not good, chucker.
The IS shouldn't make 5-10 cups of dust in a year in 14 feet of pipe.
you need to engage the cat...and you already know seasoning wood for 1-3 years is the key

Engaging the cat will bring the firebox temp up and make it efficient, and lower the flue temp at the same time.