Operating Jotul F500 Oslo with 14' Stack

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caucapon

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Jan 4, 2008
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We recently acquire a nice Oslo complete with 25' of 6" stainless flexible liner for very little money, a case where the previous owner simply wanted it out fast. While we would like to install this on our living room hearth and vent through the existing fireplace, we are aware that our stack height of 14' within an exterior chimney might be fatally problematic. The only way to know, of course, is to install and attempt to fire the stove up. However, we would appreciate any comments from current Oslo owners operating with short stacks and from installers who have worked with this stove.

Previous forum threads regarding the Oslo have discussed problematic draft due to tall, not short, stacks. We suspect that our installation might cause smoke infiltration even when using only the side door. It might also prevent a consistently effective use of the stove due to poor exhaust flow even when fired at max. Extending chimney height would probably be unrealistic from our financial perspective given that the terracotta liner is 16"x7" (Extend-A-Flue not designed for such an application) and because masonry work on our stone chimney would be prohibitively expensive.

We were aware of this pitfall when the stove was purchased. We chose to make the purchase because we can almost certainly sell the stove for a valid profit. However, installation is our preference.

Any information is appreciated.
 
It will be marginal, but then so will most stoves with a short flue. Insulating the liner will definitely help. Once the stove and flue is up to temp, it should work ok though. I'd try it out. As the weather gets colder draft will improve.
 
More knowledgeable gurus will certainly chime in, but for now:

You supplied good information for comments but a exterior photo of your existing chimney or more detail on your existing chimney would also help. Example: Does your existing chimney exit at the highest point of your roof or is it downslope from the ridge somewhere in the roof?

I'm running about a 15' insulated SS interior hearth mount install with the Oslo with no problems with draft. My chimney is right at the ridge (highest point) of our roof.

From what I have read here insulating your liner (if you have enough space) helps draft and may supersede any draft problems with a minimal height chimney liner.

Shari
 
I was going to edit my post but I will just add additional thoughts here:

The reason I ask where your chimney exits is due to the 10/2 rule: Might be that you have to add to your chimney height to meet this rule and then you wouldn't have any concern about only being 14'.

Shari
 
<>Extending chimney height would probably be unrealistic from our financial perspective given that the terracotta liner is 16"x7" (Extend-A-Flue not designed for such an application) and because masonry work on our stone chimney would be prohibitively expensive.<>

There are anchor plates available which attach to your liner & will allow for the installation of one or more sections of Class A.
You may have to fabricate an extension to ensure you completely cover your (QUITE) odd sized terra cotta, & you'll need roof brace kit,
but you'll get away for a lot less than adding masonry to your chimney.
 
caucapon said:
Previous forum threads regarding the Oslo have discussed problematic draft due to tall, not short, stacks.

Not sure where you read this. The only draft problem one might experience from a tall stack would be if there were a couple of elbows involved or too wide a pipe/liner. Ours is about 20 feet straight up and operates perfectly. Best of luck and I hope it works out for you.
 
Chimney location is reasonably clean. That, at least, should not be a significant issue.
 

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Provided that chimney is 2' above the adjacent ridge line and 10' away from the ridge to the furthest right it would appear you could go with just an additional 3' of chimney and you should get the additional height your are looking for and be all set.

(neat house!)

Shari
 
You state that your clay liner is 16" by 7". If that is the case then my bet is you will surely have drafting problems. Are you measuring your chimney height from the ground up, or from the thimble up?

If I were to install in your setup and hope to have a successfully operating Oslo I would line and insulate that chimney with 6 inch pipe and run it a few feet right out the top of that chimney.
 
Let me ask a few questions:

1.) From where are you measuring the 14'? From the floor of the hearth or the stove outlet?

2.) Do you plan to top vent or rear vent?

3.) Have you purchased the cap yet?

I'm running 14' from the stove top vent to the top of the chimney on my Castine and it drafts quite well. I didn't have to extend my flue. The stove starts up fine and drafts perfectly in all weather conditions with no smoke rollout problems. I did swap out my secondary air plate for the Euro style which permits roughly 2X more air into the stove at max setting, but that was a personal preference that affords added range of adjustment.
 
I've said it before...I'll say it again. I probably have the worse chimney set up on the forum. It's an 8" exterior, two 90 bends, doesn't clear the roofline. It's about 14' tall. (and the stove has a 6" outlet) During the shoulder season, I have a slight issue getting things lit off. I compensate by using the Euro intake plate.

You're setup looks pretty good. I'm thinking with a liner, you'll be A-OK.
 
cycloxer said:
Let me ask a few questions:

1.) From where are you measuring the 14'? From the floor of the hearth or the stove outlet?

Distance is measured from stove outlet to cap top.

2.) Do you plan to top vent or rear vent?

Of necessity, this will be a rear vent.

3.) Have you purchased the cap yet?

Not as yet.


There are several additional considerations. I do have the 6" flexible stainless liner obtained with the stove. I also have a suitable length of 5.5" flexible stainless liner. I have not as yet attempted to run the 6" through my flue. I have run a light down the length of the tile passageway, and it does appear clean and straight. However, with an interior dimension of 6.25", I do suspect that slight ovalization would be required. Even a minor adjustment to the 6" liner would put it very close to the cross sectional value of the perfectly round 5.5". I am hoping that a professional installer will chime in with an opinion here. Economically, I am running in favor of the 6" because the 5.5" is still wrapped in plastic and would probably be easy enough to sell on Craigslist, etc. However, tightly controlled ovalization might be difficult and/or time consuming to achieve with possibly less than desirable results. Both ease of installation and effectiveness are critical objectives here. For me, it's all guesswork at this point.

If the 5.5" liner is used, then I also have to decide whether I want to take the chance of purchasing a quarter inch insulation kit. Again, with a 6.25" interior flue dimension, the fit will be tight. I am currently assuming, however, that there would be some very minor give to the insulation under pressure. I have also located a source for vermiculite. Of course, I could entirely forgo the insulation kit for the 5.5" or use the vermiculite in conjunction with the kit as an ultimate insulating package. Vermiculite alone would be the only option for the 6".

While I will probably wait and see, this is also the ideal time to extend the flue by some means or another. Once I cut the liner at cap level, topper installation becomes that much more complicated. However, the remarkable cost of most flue extension methods will probably deter me from this course of action unless absolutely necessary.

With a horizontal take-off, with a shorter than ideal flue, with an ultimate liner cross sectional that will be less than specified by the manufacturer, and with our being at 2150 feet above sea level (not Denver, but then not the sea level elevation of my native Jersey either), I do believe that we will be facing potential problems starting the fire, maintaining draft during reload, and with smoke roll-out. Every decision I make at this juncture will be a pain in the neck to rectify in the future. Additional dollars of significance will also be necessary with each modification. These are the reasons, of course, why I placed this issue in front of the forum. The germane experiences of people who have dealt with similar problems hopefully can offer some real guidance as decisions regarding liner, insulation, and flue extension are made.

My wife and I are retired in an extremely rural part of Virginia. There are NO resources of consequence aside from Walmart and Lowes for fifty to one hundred miles. Finding vermiculite was an act of extreme good fortune. There are no valid sources for something as simple as hi-temp silicone sealant, etc. Everything takes two to four times as long and often requires additional dollars (due to shipping if nothing else) than I was accustomed to during my sixty plus years in New Jersey. I moved this used stove from Bristol, Tn. to an elevated platform in front of my hearth by myself. Those of you who have enjoyed a similar, almost religious, experience akin to flagellation and starvation, can easily appreciate my saying that I want to move this 450 pound beast onto the stone hearth and make adjustments once and once only!!

Again, your comments are appreciated.
 
You should be able to get this stove to work. The rear vent isn't going to do you any favors, but it is not a show stopper. I would go with the 6" liner. You should be able to get it to fit in 16x7. In fact, I think that is what I have in my chimney. It depends upon the alignment of your clay tiles. Worst case you have to ovalize it a bit, but you could do that yourself with a flat board. Then I'd run a 1-2' removable extension with cap at the top of the chimney. That'll give you 15-16'. I believe the spec for the Oslo is 15'. You will have space for the vermiculite poured down either side of the liner as your tiles are 16" wide. You have all of the materials except for the top cap & extension.
 
I think you'll be fine, especially if you manage to get a liner in there. If you can score some double-wall stovepipe to connect the stove to the liner you might improve things a tad. The key is to get that chimney warm so it keeps drafting. FWIW I did an experiment with aluminum foil on my downstairs Jotul 8 (wrapped the single-wall stovepipe horizontal section & 90deg elbow with it, the foil keeps the stovepipe much hotter and therefore the flue gases much hotter, doesn't provide as much heat to the house though) and found it improved my draft ... significantly, almost to the point of overdrafting I think, so if you're truly at wit's end you can try that if all else fails. Double-walled stovepipe would be the proper (UL-listed, known to be safe) way to accomplish that tweak though. But I think you'll be fine just be sure you get a liner inside that chimney.

Another thing is technique--try the Top-Down fire, or put a torch or light some newspaper or a firestarter in the stove beforehand to prewarm the chimney, etc. Once the chimney is warm you won't have any trouble getting a fire started. The more insulated the liner the better, vermiculite sounds like a good option with the tight fitting liners. The anchor plate DAKSY mentioned is another good option as you can extend the chimney height later on with extra class A pipe.
 
I have a similar situation- running a Jotul F600CB with only a 14 1/2 foot chimney. With a 6.5x10.5" ID clay liner, the draft was too weak on days with mild outside temperatures- then I installed an insulated, ovalized 6" rigid liner, and it now performs very well. I am still learning the new stove- getting a fire fully establish takes longer than my Old Defiant, but I understand that is the nature of the new Jotuls. I just keep the side door slightly cracked till it's burning well.
 
I was also a little worried, but the Oslo has been just fine. Our setup is an external masonry chimney with a nominal 8" square clay liner, also about 14' tall. I have corner install with a top exit from the stove directly into a 90 degree elbow, and directly into a 45 degree elbow, and then into the thimble.

Much to my delight, draft has been just fine, even during shoulder season burning, even though we had lots of backpuffing problems with our prior stove.
 
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