Oslo performance

[senorFrog]

Rob, I quoted you from the jotul vs quad thread...

[quote author="Rob From Wisconsin" date="1179418647"]Time for me to chime-in....

As it so happens, I've owned both the 3CB & the Oslo.
Both were "pretty" stoves, but very weak on burn times.
2-4 hrs. on the 3CB and perhaps 2-5 hrs. on the Oslo.
It was rare to ever achieve an overnight burn, even w/ the Oslo.
Very disappointing.....

Rob[/quote]

I have an oslo and on a less than ideal stack setup because of the long horizonal run from stove pipe to chimney. Search on my name if you want pics. Even so, I can get decent burn times, say six hours out of it. I can def get overnight "burns" if you count hot coals and a warm 200 degree stove as part of the burn time.

I figured I could do better burn times w/better draft. That would give me better and longer secondary burn. Which I seem to only get during startup and mid burn. Toward the end of active burning I have only primary burn. BTW, I almost always leave the draft controller wide open. Never less than half open because the fire would tend to stop actively burning and just smolder. I attribute this to poor draft as well.

I was given an exhausto recently and was planning on installing this summer. I was hoping this would optimize my setup.

What do you folks think?

 

[Corie]

Can you describe the stack setup more completely? How long is this horizontal run of pipe?


I personally hate to see you have to install an exhausto fan on a woodstove unless you have exhausted all other natural draft improvement options.


Also, its hard to believe with the firebox size on the oslo that anyone was only able to get 2-5 hours of burn time with it. It just doesn't make sense from a firebox volume standpoint unless excessive draft was involved. I'm able to get 6 hours of usable heat with only 1.6 cu ft. and I know the Oslo is a quite a bit larger than that.

 

[senorFrog]

Sorry, I get way more burn time than what Rob was getting. I estimate about al least six hours of active burn.

Here are pics of my setup. Scroll down...

https://www.hearth.com/talk/threads/4008/

Please respond on this thread.

Thanks!

 

[Corie]

How tall is that masonary chimney? It looks like the house is taller than the chimney from one of the pictures. I wonder if that's reducing your draft.


Also, I wouldn't say that's an unbelievable amount of horizontal run. I've got nearly that much and an external Class A chimney and still have great draft. Plus you're using double wall stovepipe so that should keep more heat in the stack. Hrmmm.


Is the F500 one of the draft sensitive Jotuls? I don't recall it being one.

 

[senorFrog]

How tall is that masonary chimney? It looks like the house is taller than the chimney from one of the pictures. I wonder if that's reducing your draft.


Also, I wouldn't say that's an unbelievable amount of horizontal run. I've got nearly that much and an external Class A chimney and still have great draft. Plus you're using double wall stovepipe so that should keep more heat in the stack. Hrmmm.


Is the F500 one of the draft sensitive Jotuls? I don't recall it being one.

Total stack height is 15 feet. Four feet of that is the vertical stove pipe leading to horizontal run. The remaining 11 feet is chimney.

It's like 20 feet from the main house. About five feet taller than the closest pitched roof which about 13 feet away.

From what I've read, it's the F400 or castine which is very draf sensitive.

 

[Corie]

Well I guess 11 feet is quite marginal, especially with that straight horizontal run. Is adding some heigh to the chimney out of the question?


Also, did I miss what the liner dimensions of the masonary chimney were?

 

[senorFrog]

Well I guess 11 feet is quite marginal, especially with that straight horizontal run. Is adding some heigh to the chimney out of the question?


Also, did I miss what the liner dimensions of the masonary chimney were?

Masonry chimney is clay lined, 8 by 8.

Adding height is out of the question. I have a free exhuasto, so I'll install that this summer. If nothing else, this will be a good field test of an oslo on a stack with marginal draft (current) vs good draft (current plus exhuasto).

I'm just trying to predict future performance gains. I think last year it performed about 75 - 80% of ideal.

 

[Corie]

You might see an increase in control if you lined that chimney.

8x8 clay tile has a crosssectional area of 42 in^2.

A 6 inch steel liner would have a crosssectional area of 28 in^2.

That's a 66% increase in area. I know its within code, but since you have marginal height, I think a liner would be the cat's meow. Plus it would hardly cost you anything because you'd only need 11 feet of it.


I'm just saying, that's all. I just hate to see you having to use a forced draft system. I agree though, try it out see if it improves things and go from there. But for the low cost of the liner, I think it would be your best bet. Plus with an 8x8 liner, you should be able to stuff a 6 inch liner down the flue with a 1/4" of insulation to further reduce heat loss.

 

[senorFrog]

Yeh, I won't have to use it all the time as I get okay draft right now. I'd just run it at startup, windy days, very cold nights, etc. Otherwise it's just an expensive chimney cap.

PS - The inside dimension of the 8x8 is actually 6.75x6.75. My installer and elk both thought a liner wouldn't help that much in this situation. Plus the exhuasto was free.

Thanks for thinking this through with me.

 

[Rob From Wisconsin]

Rob, I quoted you from the jotul vs quad thread...

Time for me to chime-in....

As it so happens, I've owned both the 3CB & the Oslo.
Both were "pretty" stoves, but very weak on burn times.
2-4 hrs. on the 3CB and perhaps 2-5 hrs. on the Oslo.
It was rare to ever achieve an overnight burn, even w/ the Oslo.
Very disappointing.....

Rob

I have an oslo and on a less than ideal stack setup because of the long horizonal run from stove pipe to chimney. Search on my name if you want pics. Even so, I can get decent burn times, say six hours out of it. I can def get overnight "burns" if you count hot coals and a warm 200 degree stove as part of the burn time.

I figured I could do better burn times w/better draft. That would give me better and longer secondary burn. Which I seem to only get during startup and mid burn. Toward the end of active burning I have only primary burn. BTW, I almost always leave the draft controller wide open. Never less than half open because the fire would tend to stop actively burning and just smolder. I attribute this to poor draft as well.

I was given an exhausto recently and was planning on installing this summer. I was hoping this would optimize my setup.

What do you folks think?

I had many of the same flue issues that you have. My eyes weren't "opened-up" until we
pulled-out the Oslo & replaced it w/ a much less expensive steel stove. Our burn times stayed
about the same, but, considering it was a smaller stove, we got much more efficient burns with
great heat output. I guess I expect performance from a unit that I pay considerable money for.

P.S. - We have since moved & have inherited a small cast-iron stove that performs wonderfully.
So, I don't hold it against cast-iron units in general...

Rob

 

[Corie]

Hrm, I wonder if the Oslo is a problem child in general?

 

[begreen]

From what I remember MSG telling me, the Oslo is pretty flexible. The Castine is the one that likes a bit more draft. But regardless, of stove, this sounds like a sub-optimal stack.

 

[Corie]

Yeah, that I'll agree with.

 

[Mike Wilson]

Looks like you've got poor draft... line the ceramic flue and add some length to it if you can. You're getting hurt by a combination of factors... 2 bends in the run, a ceramic flue, and too short of a total chimney stack. I've got a neighbor about a mile away with an Oslo into a 18' insulated flue... just got off the phone with him after reading this thread, and he reports burn times of easily 8, and usually 10 hours. (burn time being defined by the standard "I can throw some splits onto the recently raked coals and it restarts with no effort" definition).

-- Mike

 

[titan]

I'd wager that you're poor draft is mostly due to the chimney not extending above the highest roof of your home.I had this very issue @ my first home;even though the chimney was a reasonable distance from the higher section of roof, my draft was negated as a result of that higher section's interference with normal air flow.It really doesn't take much to create a "windbreak" and mess up the natural flow of wind currents.If you absolutely can't extend that chimney,then the forced-draft fan you mentioned may be the only option.Good luck.