Advice for improving draft in our new Jotul Oslo F-500

[Rush River]

Hello master wood burners,

I just installed our new Jotul Oslo F-500 in our 27' Yurt here in Wisconsin. I completed the 3 break-in fires this weekend, per manufacturer guidelines, and the stove kept us warm all night despite outside temps in the 20s.

I am noticing an issue however regarding adequate draft (or perhaps intake) for this otherwise awesome stove. I am unable to maintain a secondary burn, even with the primary air intake open all the way to the right for maximum intake. If I leave it in this position, the fire gradually dies down and smoke begins to rise out the chimney pipe. If I crack the ash pan door, then of course the fire starts ripping again and I can see the secondary burn in action, and no more smoke out the chimney. The Manual says to never operate the stove with ash pan door open due to risk of overfilling, so I nervously kept a close eye on my stove temp and the fire all night, but I couldn't get the stove to burn properly with it sealed all the way up and only using the primary air intake valve.

I'm not sure if the issue is my chimney height or if there is some other troubleshooting I need to do with the intake?

I first figured I would address the chimney issue. Per the manual for the F-500, it recommends a minimum of a 15-ft chimney for adequate draft.

I am using a 6" double lumin galvalume class A exterior chimney. I used DVL (double lumin) stove pipe from the stove to the chimney-the stove pipe rises about 32" from the top of the stove to a right angle, and then attaches to the galvalume (via thimble) and out the wall. The chimney height from this point was just under 12 feet to start. After noticing this draft issue, I added another 36' section of pipe. The total exterior chimney hight is now around 14.5 feet. (If i add chimney+ stove pipe height =17'ft, ie total run from top of stove to top of chimney). I lit another fire and didn't notice much difference. (see pics) Hmmm.

I'm wondering if I need to continue adding height to my chimney, or if there is some other strategy? I guess cracking the ash pan door is not the biggest deal in the world, but I don't like disregarding the manual instructions on this. I called the Jotul North America technical office and left a VM, awaiting a call back.

Any ideas or input much appreciated,

 

[kennyp2339]

Can I ask a question, with the fire going in the fire box, if you open the loading door do you get heavy smoke spillage? That would be a good indication of bad draft.
A good way to start off improving the draft is to trade out the single 90deg elbow and change to (2) 45deg elbows, this creates much less turbulence in the smoke pipe.
But I'm willing to bet, that the draft is not the issue here, I'm thinking that your wood might be to wet, the dead give away was the flames ripping once the ash door was open. Test your wood with a moisture meter, freshly split piece at or near room temp, should be 20% or lower for optimum burning.
BTW - I like the yurt, I think those things are pretty cool!

 

[Rush River]

Can I ask a question, with the fire going in the fire box, if you open the loading door do you get heavy smoke spillage? That would be a good indication of bad draft.
A good way to start off improving the draft is to trade out the single 90deg elbow and change to (2) 45deg elbows, this creates much less turbulence in the smoke pipe.
But I'm willing to bet, that the draft is not the issue here, I'm thinking that your wood might be to wet, the dead give away was the flames ripping once the ash door was open. Test your wood with a moisture meter, freshly split piece at or near room temp, should be 20% or lower for optimum burning.
BTW - I like the yurt, I think those things are pretty cool!

I would say little to no smoke spillage when I open the door, so initially I didn't think draft was the issue either. Also I was initially burning some left over pieces of untreated 2x4, and I felt like the same thing was happening, fire burning down low when I sealed up all the doors, even with the primary intake set to max. ???

 

[Zack R]

I am unable to maintain a secondary burn, even with the primary air intake open all the way to the right for maximum intake. If I leave it in this position, the fire gradually dies down and smoke begins to rise out the chimney pipe. If I crack the ash pan door, then of course the fire starts ripping again and I can see the secondary burn in action, and no more smoke out the chimney.

Any ideas or input much appreciated,

On my recently installed Jotul F55 I've had to learn how to best adjust the air control via trial and error. When the stove is fully loaded and up to temperature (500F+ stovetop) slowly close the air control in smaller increments instead of just sliding it all the way over. I've found that in my case when its about 2/3 closed there is a sweet spot where the secondary burn is running nicely, temps rise and there is no visible smoke. If I close the primary all of the way the temps drop, the flames stop (primary and secondary) and the fire starts to die down.

In contrast on my Jotul F45 it will scream up to full temp within 20min, I then close the primary all of the way and the secondaries light off in full effect with no fine tuning whatsoever.

 

[Rush River]

Even while I'm lighting the fire and getting it going with dry kindling it seems like the intake is simply inadequate to maintain secondary burn even when its wide open to the right. Is it possible that there is something that is clogging the intake in a new stove? Is there a way I can check this? I tried to review the exploded view in the manual and it didn't seem like there would be anything in the way of the intake.

Lastly, do folks think that I am likely to wreck this stove by overfiring it with the ash pan door cracked open? This seems like a simplest solution to inadequate intake, but it states all over the manual that this should NEVER be done....?

Thanks.

 

[bholler]

Even while I'm lighting the fire and getting it going with dry kindling it seems like the intake is simply inadequate to maintain secondary burn even when its wide open to the right. Is it possible that there is something that is clogging the intake in a new stove? Is there a way I can check this? I tried to review the exploded view in the manual and it didn't seem like there would be anything in the way of the intake.

Lastly, do folks think that I am likely to wreck this stove by overfiring it with the ash pan door cracked open? This seems like a simplest solution to inadequate intake, but it states all over the manual that this should NEVER be done....?

Thanks.

Yes you will without question destroy the stove running it with the ash door open. How high is the chimney top above the top of the stove?

Have you tried getting the stove up to temp with the stove door cracked open? What pipe temps are you seeing? What moisture content it your wood at? How long has it been split stacked and covered?

 

[Zack R]

Even while I'm lighting the fire and getting it going with dry kindling it seems like the intake is simply inadequate to maintain secondary burn even when its wide open to the right. Is it possible that there is something that is clogging the intake in a new stove? Is there a way I can check this? I tried to review the exploded view in the manual and it didn't seem like there would be anything in the way of the intake.

Lastly, do folks think that I am likely to wreck this stove by overfiring it with the ash pan door cracked open? This seems like a simplest solution to inadequate intake, but it states all over the manual that this should NEVER be done....?

Thanks.

The secondary burn won't really kick in when you first light the fire. You might see some flames from the secondary burn tubes but the true secondary burn is when the stove is fully up to temp and the primary air is dialed down.

There's a chance your draft isn't particularly strong so its not pulling air through the secondary system as aggressively as it could with a stronger draft. This is how I interpret what is happening on my F55, hence the need to modulate the primary air to reduce the air intake restriction enough to allow enough air for combustion.

What have the outside temperatures been recently? When it gets colder draft will improve and you will likely have better performance. I recall a few winters ago on the coldest night of the year (-30F) my stove flat out ripped no matter what the air control was set to.

 

[begreen]

Assuming that the wood is fully dried and well seasoned, then the issue is draft . The Oslo is a wonderful stove, but it will be particular about proper draft. It wants a 16ft straight-up chimney or better. For this reason, it's not the ideal yurt stove. If you are not seeing secondary burn then you are not getting good efficiency out of the stove. The short chimney pipe + two 90º turns in the flue path are effectively reducing the chimney height by about 4 ft or from the looks of it to about 11-12'. This can be improved a little on the interior by using 2 - 45º elbows and adding another full length of chimney pipe.



Also, there should be 16" of hearth on the left side of the stove for the Oslo's side loading door.

 

[Rush River]

Yes you will without question destroy the stove running it with the ash door open. How high is the chimney top above the top of the stove?

Have you tried getting the stove up to temp with the stove door cracked open? What pipe temps are you seeing? What moisture content it your wood at? How long has it been split stacked and covered?

I think stove top to chimney top is ~16 or 17 ft, including stove pipe and chimney height. after breaking in the stove at temps of 200, then 300, then 400, i let the stove run at 400-500 for an hour or two. in order to get it to this temp, i had to crack the ash door. pretty certain i wasn't overfiring at this time. if i closed it up, fire would die down, even with primary intake at max. the wood wasn't hissing at all, i don't think its wet, its red oak split ~1.5yr ago. stacked outside, not covered. i don't know the moisture content of the wood, never checked. thanks for advice.

 

[begreen]

Using the ash door for fire starting is a sure-fired way to crack the base on this stove. Don't do it.

Get some 2x4 cut-offs that are nice and dry and/or a good compressed sawdust bricks or logs. Mix them in with the wood and see if that helps it get up to temp quicker and stay at 500+ on the stovetop with obvious secondary combustion.

PS: how far are you closing down the air once the fire is burning robustly?

 

[Rush River]

Using the ash door for fire starting is a sure-fired way to crack the base on this stove. Don't do it.

Get some 2x4 cut-offs that are nice and dry and/or a good compressed sawdust bricks or logs. Mix them in with the wood and see if that helps it get up to temp quicker and stay at 500+ on the stovetop with obvious secondary combustion.

PS: how far are you closing down the air once the fire is burning robustly?

Even with the fire burning robustly, I wasn't able to close down the air intake at all. Even with max intake it seemed like my fire kept dying down over a couple minutes. i would then open the front or crack the ash door to get it roaring again. i feel like my wood was good and dry, as I was using mostly red oak but also some dry 2x4 cut offs as you suggest.

i never left the ash door wide open, but found if i only turned the handle halfway so a little air was still bleeding in through the seal, i could keep the fire hot. thanks for clarifying though why using the ash door is a bad idea with the oslo, i'm keeping that guy shut from here on out!

sounds like i should start with your advice to add more chimney height, and some 45-angles to my stove pipe... and see how it goes from there...thanks again for this advice.

 

[bholler]

Even with the fire burning robustly, I wasn't able to close down the air intake at all. Even with max intake it seemed like my fire kept dying down over a couple minutes. i would then open the front or crack the ash door to get it roaring again. i feel like my wood was good and dry, as I was using mostly red oak but also some dry 2x4 cut offs as you suggest.

i never left the ash door wide open, but found if i only turned the handle halfway so a little air was still bleeding in through the seal, i could keep the fire hot. thanks for clarifying though why using the ash door is a bad idea with the oslo, i'm keeping that guy shut from here on out!

sounds like i should start with your advice to add more chimney height, and some 45-angles to my stove pipe... and see how it goes from there...thanks again for this advice.

I think some more height and getting rid of the 90 are good. But also get a pipe thermometer and a moisture meter. They are almost required to learn how to run a stove

 

[weatherguy]

Depending on conditions and the location of your wood 1 1/2 years for oak might not get it where you need to be.

 

[Simonkenton]

The Oslo doesn't like the two 90 degree bends.

 

[begreen]

Even with the fire burning robustly, I wasn't able to close down the air intake at all. Even with max intake it seemed like my fire kept dying down over a couple minutes. i would then open the front or crack the ash door to get it roaring again. i feel like my wood was good and dry, as I was using mostly red oak but also some dry 2x4 cut offs as you suggest.

sounds like i should start with your advice to add more chimney height, and some 45-angles to my stove pipe... and see how it goes from there...thanks again for this advice.

The next time you build a fire try this trick to get the Oslo started. Take a few 2x4 cutoffs that are about 12" long and split them lengthwise to make a bunch of 12" x 2" x 2" sticks. Put 2 of those sticks about 6" apart in the stove, at right angles to the door and parallel to the sides. Then load your firewood on top of those "sleepers". The sleepers are to allow boost air to get under the wood for quicker starting. This trick really works well on shallow E/W firebox stoves. Another trick for cleaner starts that get the flue warmed up quicker is top-down burning. Here is a video illustrating the technique.

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i never left the ash door wide open, but found if i only turned the handle halfway so a little air was still bleeding in through the seal, i could keep the fire hot. thanks for clarifying though why using the ash door is a bad idea with the oslo, i'm keeping that guy shut from here on out!

Yeah, you don't want to crack the base on that stove. It's a very expensive repair.

 

[begreen]

Depending on conditions and the location of your wood 1 1/2 years for oak might not get it where you need to be.

Yes, it's hard to dry out oak in 1.5yrs unless the splits are small and conditions are right. Top covering helps, but a rainy summer does not.

The Oslo doesn't like the two 90 degree bends.

The Oslo is a great stove, strong heater and very good looking, but not ideal for a yurt. I'd say the same for the Castine. We had another yurt owner many years ago that was frustrated with their stove. They finally sold their F500 and put in an easier breathing stove. The buyer of their Oslo put it in their house and was happy with its performance and the yurt owner was delighted with the improvement after the change.

 

[JotulOwner]

The Oslo doesn't like the two 90 degree bends.

Neither does my Castine (also a Jotul). I have marginal draft with a much higher chimney than he has. Tee outs are nice for cleaning, but require more vertical pipe to get proper draft.

 

[firefighterjake]

Hello master wood burners,

I just installed our new Jotul Oslo F-500 in our 27' Yurt here in Wisconsin. I completed the 3 break-in fires this weekend, per manufacturer guidelines, and the stove kept us warm all night despite outside temps in the 20s.

I am noticing an issue however regarding adequate draft (or perhaps intake) for this otherwise awesome stove. I am unable to maintain a secondary burn, even with the primary air intake open all the way to the right for maximum intake. Well this is the most likely issue. As long as the wood is seasoned enough and the temps are high enough you should start closing the air to achieve the secondary burn and to get a longer burn. If I leave it in this position, the fire gradually dies down and smoke begins to rise out the chimney pipe. What are you seeing for stove and/or flue temps? The Oslo is like a locomotive . . . once it's up to temp you can start fiddling with the air to set it to "cruise" . . . but if the temps aren't right the fire will often die right down. Knowing the temps of the stove and/or chimney are crucial in my mind to knowing when I can shut the side door, when I can start dialing back the air, etc. If I crack the ash pan door, then of course the fire starts ripping again and I can see the secondary burn in action, and no more smoke out the chimney. I would highly suggest you not use the ash pan door . . . use the side door instead if you need more air at the start. Continuing to do so will undoubtedly result in damage as you are turning your woodstove into a forge in effect. The Manual says to never operate the stove with ash pan door open due to risk of overfilling, so I nervously kept a close eye on my stove temp and the fire all night, but I couldn't get the stove to burn properly with it sealed all the way up and only using the primary air intake valve.

I'm not sure if the issue is my chimney height or if there is some other troubleshooting I need to do with the intake? Most likely culprit could be the wood if it is not seasoned enough. Unless you oak has been cut, split and stacked for 2-3 years I would say it is the problem. Try a load of 2 x 4s and a cut pallet and see if that changes anything. That said, as others have mentioned, the Oslo is a deep breathing stove that likes a strong draft and you may be a bit on the short side.

I first figured I would address the chimney issue. Per the manual for the F-500, it recommends a minimum of a 15-ft chimney for adequate draft.

I am using a 6" double lumin galvalume class A exterior chimney. I used DVL (double lumin) stove pipe from the stove to the chimney-the stove pipe rises about 32" from the top of the stove to a right angle, and then attaches to the galvalume (via thimble) and out the wall. The chimney height from this point was just under 12 feet to start. After noticing this draft issue, I added another 36' section of pipe. The total exterior chimney hight is now around 14.5 feet. (If i add chimney+ stove pipe height =17'ft, ie total run from top of stove to top of chimney). I lit another fire and didn't notice much difference. (see pics) Hmmm.

I'm wondering if I need to continue adding height to my chimney, or if there is some other strategy? I guess cracking the ash pan door is not the biggest deal in the world, but I don't like disregarding the manual instructions on this. I called the Jotul North America technical office and left a VM, awaiting a call back.

Any ideas or input much appreciated,

 

[xman23]

Mines not fool proof until there's a 2 inch bed of coals and a hot stove box. Then I can put any thing in. Don't use the ash door. I use the side door in startup.

 

[Rush River]

Update:

Stove is working much better!

I added one 36" section of class A galvalume to my chimney, but wanted to hold off on adding 45's to my stove pipe, since I like the aesthetics right now. So after reviewing the Efficient wood stove operation video begreen posted, I adjusted my woodburning strategy, focusing on hotter cycles instead of adding a few logs at a time all night. I was able to use the side door for starts, and once I get'er up around 400-500 degrees with a big fire, I was able to seal it up and just use primary air control. I still can't turn down the primary intake too much, but for now my draft issues seem to be resolved.

Also you guys are so right, my red oak cord is still a little damp. Picked up a couple bundles of kiln dried wood, and these burnt much better. I may have to save the rest of that cord until next year and look for drier wood for now.

Really appreciate all your advice. I love this stove and am grateful that you guys were able to help me troubleshoot and get my family heated up for our first Wisconsin winter out there.

over and out...for now.

 

[begreen]

Thanks for the update. Are you seeing good secondary combustion now? If not, switch to the 45s.

With truly seasoned wood you may be ok. In the meantime start gathering 2x4 cut offs to mix in with the oak wood. Also consider buying some good quality, compressed sawdust logs or bricks to supplement the burn. And clean the flue after each cord burned.

 

[Simonkenton]

If you are still leaving the side door open, until you hit 400 to 500 degrees, you still have a big problem with that pipe.

 

[Woody Stover]

my red oak cord is still a little damp. Picked up a couple bundles of kiln dried wood, and these burnt much better. I may have to save the rest of that cord until next year and look for drier wood for now.

It's hard to find truly dry wood to buy. If you have a woodlot to work, look for small, dead-standers <8" with the bark falling off..those may be pretty dry. You can't get a good moisture reading unless the wood is at room temp, then split and tested on the fresh face.

 

[Rush River]

Yes, I am seeing good secondary combustion once the fire is established well. And to clarify, I haven't had to leave the side door open until it reaches full heat, just until it appears the fire is really going. I do think the draft could be improved further, as you guys suggest, and will consider adding 45s to the stove pipe when I get a chance, or evening increasing chimney height. I haven't noticed any spillage of smoke into the room at any point, but it still doesn't feel like it "pulls" air very aggressively.

I've got plenty of 2x4 cut offs lying around after this project, and will plan to mix those in as well to make sure I've got enough dry fuel for now. I've got several dead-standers I've been eyeing in our woods as well, I'll get started on those.

Thanks again.

 

[firefighterjake]

I love happy endings.

If you start to run short on 2 x 4s to mix in, often you can find pallets for free and mix them in. The drawbacks are the nails, time it takes to demolish the pallets and depending on how you deconstruct the pallet it may not be very stackable . . . but honestly, dead elm and pallets got me through my first year of burning less than optimal wood.