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Oslo Continues To Disappoint.....

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Nonprophet, Nov 26, 2010.

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  1. Nonprophet

    Nonprophet Minister of Fire

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    Some of you may remember my saga with our Oslo. I purchased it used last year and have always felt it was "sluggish" i.e. the hottest I've ever gotten the stove top corner thermometers was about 550-575, and that was with a roaring fire and a nearly full load of KD hardwood scraps from a cabinet maker friend.

    Last year, we had the stove in our Yurt. I had 16' of exterior 6" class A pipe topped with 4' of 6" single wall (hoping that the extended height would improve draw/heat), and then another 4' or single wall inside for a total of nearly 24' of pipe, though we did have 2 90's in that run. It worked ok, but I was always somewhat disappointed in it's performance.

    This year I moved the stove into a cabin on our property. Now I have 5' of single wall inside, and 16' of class A outside in a straight run from stove top to cap. While the performance is improved, it's still "sluggish" IMHO. For example, while I get a nice burn out of the secondaries, others here talk about increased stove-top temps after the secondaries kick in, and that never happens with our stove. At best we can maintain the existing temps as we damp down the primary air and usually we drop 50-100 degrees once the secondaries are engaged......A standard burn for us is a 3/4 to full firebox with 2-3 year seasoned wood and about 400-500 temp reading in the corners of the stove top while maintaining about 300-400 on the stove pipe surface thermometer. One thing for sure is that is seems we'll never have to worry about this stove running away from us, but still it would be nice to crank it up to 600-700 if we really needed to and I just don't ever see that happening for this stove......

    For the record, burning verified well seasoned wood, and I've checked all the air passages on the Oslo for any blockages (with a snake light and a piece of stiff wire fed through all the air channels) so we're still perplexed as to why our Oslo burning experience seems so different from others......any suggestions?

    NP

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  2. begreen

    begreen Mooderator Staff Member

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    Help me visualize the system. Does the stove top vent, up 5 ft, then a 90 elbow, short pipe to thimble and then up outside? If so, it should draft pretty well, though the single wall and 90 could be improved by using double wall pipe and a pair of 45's. One thing to check is the seal at the flue collar on the stove. There should be no air leaks. Is that cemented in? Also check the tightness of the cleanout tee cap
  3. cycloxer

    cycloxer New Member

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    How far do you damp down the primary air?
  4. Backwoods Savage

    Backwoods Savage Minister of Fire

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    What does "burning verified well seasoned wood" mean? Verified how or by whom?
  5. Green Energy

    Green Energy Feeling the Heat

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    400 - 500 F corner stove top temp is normal for me on a cold start when I shut down the primary air after 20-30 minutes and the secondaries are rolling. The center of the stove top is about 50 - 100 F hotter than the corner according to my I-R thermometer. So this is not too far off from normal performance according to the manual.

    On a reload with a healthy bed of coals, that's where I get over 600+ on my corner after ~ 30 minutes.

    It sounds like your flue system could be improved some if you want to get a greater draft as Be Green suggested. The draft is the oxygen engine that drives your stove. I have a hearth installed Oslo discharging from the rear into a T (so one 90) and then up through a insulated chimney liner ~ 24 feet. This provides plenty of draft.

    The one thing that sounds strange is that you said that your stove top temp drops when you shut down the primary air. That might happen to me when my secondaries are not strong. But with fairly dry wood (good 2 yrs of seasoned oak), not too big splits (2-4" with some 2x3" on top), and arranged not too tight so there is good air circulation, I am getting strong secondaries at ~ 30 minutes, which maintains the stove top temp until the secondaries start to fade (like 1.5 to 2 hours). I will monitor how the stove top is doing during that time to verify I am not dropping.

    It sounds like your disappointed with the heat output. If you are maintaining 400-500 F corner temp & 300-400 F flue temp you should be fine on burning clean if you have strong secondaries. Do you use a fan to increase your heat transfer to the air? I have a little cheapo fan that I point at 45 degrees to one side and it moves the air from behind the stove as well. While the stove is a great radiator, adding the forced convection does increase your heat transfer.
  6. oldspark

    oldspark Guest

    My Summit stove top temps do not climb so much after I reduce the primary air either, sure a little bit depending on the load and the flue reduces but not a major climb, so I was wondering if the climbing temps were not as dramatic as written?
  7. Green Energy

    Green Energy Feeling the Heat

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    In another thread I wrote about my temp climbing to 650 - 670 F when I reload on a healthy bed of coals. Some nights I am not letting the coals burn down, as I want to reload for the overnight burn, and go to bed. I close down my primary air as soon as I can, but the whole load gets fully involved/engulfed, due to the coal bed. So yes, I do get some very hot stove top temps after I close down the primary air, but it is limited to this type of reload. Cold starts and less healthy coal bed reloads are not so dramatic/dynamic.
  8. Mad Tom

    Mad Tom Member

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    With my Oslo I keep the control wide open until I have lots of flame, the wood is charred and my temp is no longer climbing. That can be anywhere from 450-500. I then slowly shut the control down in small increments. Depending on the wetness of the wood and the species has a lot to do with temp. I usually run it around 1/4 open or a little less. When I shut it down is when my stove top temps rise.

    500 Is in the middle of where an Oslo should run. 400 to 600. I usually run in the 500 to 550 range. Depending on the wood it will shoot up to 600 to 625. But every set up is different so you will have to play around a little. The key for me is when to shut it down and not get to a point that the stove will run away on me. I also find that not stuffing the stove full of logs helps. 3 good size logs is enough. You don,t have to stuff the whole thing full of wood. Helps if there is a bit of air space between logs.
  9. fjord

    fjord New Member

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    Oslo since 2006 for complete heating a 20'x20' cathedral ceiling cape "wing". Insulated to only R-11 in the walls since it was to be a guesthouse/workshop with no water pipes or any plumbing.
    The other stove in a 20' x 30' very well insulated add-on 'real' house with plumbing etc.. is 100% heated with a VC Encore cat from 2001.

    Ideas suggested by the Jotul techs when we had a similar problem a couple of years ago:
    Brush away as much ash as possible before opening the front door. It makes a mess if not cleaned carefully.
    Remove the "doghouse" ass'y for the air control (2 philips or hex).
    Check that the slider for primary air opens fully and closes fully. It's a simple mechanism but can get hung up in a partially closed position.
    If you see any problems with the slider opening and closing to each side, call Jotul or your dealer for a fix. There was a company 'kit' supplied back then.

    Use graphite on the slider for 'lube'.

    As with all EPA non-cat wood stoves, the primary air is severely limited. The "mommie knows best" technique : Not too much to prevent over firing, but also not too little or completely shut down for cleaner burns.

    In mid winter low teens or singles temp days, the corner thermometers will hover around +/- 600 F with the air control all the way right, or open fully, with all varieties of our firewood. Thick or thin splits; some with a little sizzle if damp from rain, some too dry. It doesn't seem to matter, the Oslo cranks out the heat when needed.

    P.S. The saying: “Chop your own wood—it will warm you twice.” is understated.
    You harvest your own firewood, it will "warm you" eight times. Nobody chops anymore, then it would be too many warms.
  10. Nonprophet

    Nonprophet Minister of Fire

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    Thanks for the help. Our old chimney had 2 90's, but in our new location it's a straight shot--no 90's, no thimble. 6' of single wall off the top of the stove into a ceiling support box, then 14' of 6" class A with a spark arrestor cap on the top.


    NP
  11. Nonprophet

    Nonprophet Minister of Fire

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    If it's from a cold start, we can't really damp down more than 50-60% or so and still keep the secondaries burning. Once I've got a nice bed of coals established, we can damp down a maximum of 75%, any less primary air than that and the secondaries don't burn and flu and stove top temps drop (250-300 flu, 300-400 stove top).

    NP
  12. Nonprophet

    Nonprophet Minister of Fire

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    It's wood cut, bucked, and split by me 2-3 years ago and stacked in the sun. MM verifies moisture content averaging 12-16%. The wood is good and dry, no problems there. Also, even with a 3/4 full load of KD hardwood, and the side door cracked, and then closed once flu temps got to 500+ and the primary air wide open, we could only get the corner stove top temps up to 575. To me, under those the conditions the stove should burn the hottest it's going to....


    NP
  13. Nonprophet

    Nonprophet Minister of Fire

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    Started from a cold start last night. 45 minutes later had flue temps of 380 or so and stove top temps of 400-425. At 60 mins flu temps at 390, stove top 450-475. Added a few more splits, charred them well, and shut down primary gradually to about 50%. Secondaries are raging. Stove top temp up to 525-530, flu temp about 340. Closed primary air down to 30% or so. Cruised at 320 flu, 480-500 stove top for a few hours, then gradually temps lowered.

    Don't get me wrong, the stove is working and it puts out heat, but it has always felt sluggish. With 20' + of pipe, outdoor temps at 25, and a load of clean dry Black Locust and Walnut it seems like I SHOULD be able to crank this stove up to 600-650 with no problem and that's just not happening.

    On the positive side, I guess I never have to worry about our Oslo running away from us, on the negative side it would be nice to rally crank this stove when temps are in the teens or lower.......


    NP
  14. ansehnlich1

    ansehnlich1 Minister of Fire

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    I'm not clear as to what type of chimney setup you have. Are you saying you have 14 feet of pipe above the roofline, uninsulated?
  15. Nonprophet

    Nonprophet Minister of Fire

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    Yes, 14' of class A metalbestos above the roof line. Single story cabin. I don't know that I'd call it "uninsulated" though......

    NP
  16. ansehnlich1

    ansehnlich1 Minister of Fire

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    Yes, I understand, it is insulated, but maybe not well enough for that length of run being exposed to the elements....I don't know, just thinking out loud here.
  17. oldspark

    oldspark Guest

    Tons of people on this forum with that much insulated pipe exposed with no problems.
  18. begreen

    begreen Mooderator Staff Member

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    One shoe does not fit all. The stove is on the cusp with marginal performance. Helping the flue gases get hotter will increase the differential between ambient and flue gas temps, thus enhancing draft. Reducing resistance will also help draft, thus the suggestion of going to double-wall pipe using a pair of 45's with a diagonal connector.
  19. fjord

    fjord New Member

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    Interesting approach: good wood, fine flue and draft, but checking the primary air control not in the picture to try ?
    Strange group.
  20. Todd

    Todd Minister of Fire

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    Yeah, I agree, maybe something wrong with the air control linkage? I don't know if it's accessible but maybe it's just not right ro something is blocking it?
  21. fjord

    fjord New Member

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    From the top:

    Ideas suggested by the Jotul techs when we had a similar problem a couple of years ago:
    Brush away as much ash as possible before opening the front door. It makes a mess if not cleaned carefully.
    Remove the “doghouse” ass’y for the air control ( 2 hex bolts in this 2006 Oslo).
    Check that the slider for primary air opens fully and closes fully. It’s a simple mechanism but can get hung up in a partially closed position.
    If you see any problems with the slider opening and closing to each side, call Jotul or your dealer for a fix. There was a company ‘kit’ supplied back then.

    Use graphite on the slider for ‘lube’.

    As with all EPA non-cat wood stoves, the primary air is severely limited. The “mommie knows best” technique : Not too much to prevent over firing, but also not too little or completely shut down for cleaner burns.

    Easy, "accessible", fast. Doable by anyone (COLD stove)
  22. begreen

    begreen Mooderator Staff Member

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    Go back to last season's thread on this stove. He's even modded the doghouse.
  23. fjord

    fjord New Member

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    Yes that's true. But this is now, not then, and this could be a solution to the lack of air....no ? So, Why not open it up ?
    "Modded" or not. "Even modded" or not, so ? So have I. So ? How many here have actually unbolted the Jotul Oslo air ass'y, looked inside, analysed the problem and solution ?

    Most stove problem solving here seems to be the hammer and nail approach: "if all you have is a hammer, everything looks like a nail". "It's the flue". No, "its the wood".

    And why "go back" last season ? Mechanicals malfunction--try the simple, first. Never dismiss anything. The intelligent approach.

    It's the flue. No, it's the wood. Flue. Wood. Flue. Wood........................................
  24. oldspark

    oldspark Guest

    Its, more like wood, flue, you, wood, flue, you, ect ect ect. :cheese:
  25. fjord

    fjord New Member

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    Sorry to get all your panties up girls. Rationale don't do no good ,huh ?
    Spellcheck can also be your friend Sparky : try "ETC".
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