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Disconnected OAK?

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by Tonyray, May 5, 2014.

  1. Tonyray

    Tonyray Minister of Fire

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    Has anyone ever disconnected the OAK from the're stove and seen any differences in Pellet consumption.. less? more/?
    or other operation differences? pertaining most to users who might not have really needed an Open air setup due to drafty or not well insulated house?

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  2. bob bare

    bob bare Minister of Fire

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    Well this ought to stir things up.Cold air is less efficient burning,preheated intake air becoming more commonplace.Chickenfarmer can explain it better,but cold air takes heat to burn better.However as pellet stoves are not that efficient,do not think you would see a big difference except in long term sub zero.If stoves were more efficient you would see a big difference.
  3. bob bare

    bob bare Minister of Fire

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    Sorry it is chickenman,not chickenfarmer.He builds,mods stoves.
  4. Tonyray

    Tonyray Minister of Fire

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    have read a few post where some have disconnected Oak from the back of the stove and just let it lay on the floor behind the stove...
    but the thread is closed so no input as to pellet consumption or operation differences..
    that said, with it on the floor I would assume cold outside air would be flowing thru it but being pulled into the stove but NOT as direct as when hooked up?
    either way still don;t know if this is good or bad to do this.
  5. Polar Bear

    Polar Bear Member

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    You would think if the power went out the fumes would seep out the OAK since there's no vertical draw...
  6. alternativeheat

    alternativeheat Minister of Fire

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    That depends on the exhaust arrangement according to Harman. Put in at least 4' vertical vent. I have that covered with 23 ' of vertical 4" vent ! We lost power over the winter, the flame just went to a fireplace flame till the pellets in the pot burned out. No oak, no smoke in the house.
  7. Don2222

    Don2222 Minister of Fire

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    X2, I agree 100% but I have pre-heated OAK air from the outside using Selkirk DT. There is no better more efficient solution by far!

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    Last edited: May 6, 2014
  8. stoveguy2esw

    stoveguy2esw Minister of Fire

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    one would have to look at the amount of air drawn by the stove , then think about paying to heat that air which will be used for combustion and dumped out the exhaust. I've found that houses (especially not too tight ones) which would not necessarily need and OAK for negation of pressure issues tend to be far less drafty when an OAK is installed

    most exhaust blowers are rated at up to 135CFM that's a lot of air (granted they aren't likely pulling that much but its not a trivial amount either). that air has to be replaced somehow, so if no OAK is used the air is simply going to be replaced through the nooks and crannies making the house harder IMHO to heat as this air can be drawn in through leaks farther from the stove.
    not having the time nor the ambition to study this formally I do have my OPINION that the loss of top end combustion achieved with air heated up the extra 50-70F is going to less noticeable than the heat loss generated by cold air intrusion from the negative pressure buildup from using house air.

    just my 2 cents.

    note: we at ESW feel strongly enough about it that we REQUIRE an OAK n our installation manual and to that extent we include one with every pellet stove we ship.
    UMainah, chickenman and mithesaint like this.
  9. bob bare

    bob bare Minister of Fire

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    That's why I did not touch on "to have or not",only the difference of preheated air.But if you have a stove that the intake air is not sealed(they still make them)then whenever stove is off cold air migrates into house,possibly negating any savings before.Especially true in shoulder seasons when stove may be off a few days in a row,or part of the day.Different stoves,different installs,all has to be looked at.
  10. Don2222

    Don2222 Minister of Fire

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    X2, The harman P-Series do not have any half baked OAKs. In other words, the air inlet pipe goes to a sealed burn pot with no prior opennings in the stove. Also there is a flapper valve to keep the cold air out when the stove is off! Those are important features to consider in a stove. IMHO
  11. doghouse

    doghouse Member

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    Words to live by. Thank you, Mike
  12. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Why I have always figured that 500 pound wood stove in my living room tied to a stainless liner up to the cap is a huge heat sink when it isn't burning. Not to mention the draft from the chimney since the air inlets can't even be totally closed.

    Small thing in the greater scheme of things though.
  13. railfanron

    railfanron Member

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    I just would like to add this. Without an OAK the air in a 1200 sq. ft. house is sent up the chimney in about 90 minutes of operation. I can't imagine how leaving it disconnected can actually save money.
    Ron
  14. chickenman

    chickenman Minister of Fire

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    You know you are riding my hobby horse!!
    The independent testing for certification we had done, in the full test rig room with full air movement and thermocouple control proved that we had a 10% efficiency when using a heat recovery twin flue like your Selkirk DT ( Thats the one isn't it?)
    The only downside is when starting in cold weather the cold air can make starting tricky. We use paper pellets (cat litter). Works perfect.
    Pellets are easy, try a grain fuel without the hot air intake and you quickly see the benefit. Even the Quad PS-35 works better with the hot air OAK and it is as leaky as a sieve.
    I will see you Mike and raise you one; we only sell our stoves with the double skin heat recovery flue. Buyers have no choice but to use it. The reason being if they had the option some would save the 100 bucks then complain about how it wont work properly. At the very least simple OAKs should be mandatory. Why waste the efficiency.
    That is my 2 cents worth.....
  15. moey

    moey Minister of Fire

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    What type of differential did you see in how much the air was warmed. For example if you had 5 ft of pipe and it was 0C outside what temperature was your intake air? I know there are lots of variables other then just ft of pipe. Im just curious approximately what increase in temp you saw.
  16. chickenman

    chickenman Minister of Fire

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    Yeah it is extremely variable. Our tests were done to the Aus standards with a 12' vertical flue. I cant remember exactly the variation as it was not something we were being tested for but I seem to remember that it was somewhere in the area of an increase of 20 degrees C. The real big differnce as far as efficiency goes is the reduction of air replacement as described by others above.
  17. railfanron

    railfanron Member

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    I'm wondering how much benefit you get from warm air verses cold. Warm air takes less temperature out of the combustion but cold air is denser so there is more Oxygen in it for the combustion. I bet the difference is actually very little but I really have no facts to back this up.
    Ron
  18. chickenman

    chickenman Minister of Fire

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    Hi Ron,
    We are only using multi-fuels due to the ridiculous cost of pellets out here. The fire temperature is critical in using grain to promote a healthy clinker. Without the warm air the stoves just don't work. There is no need for more oxygen infact we reduce the combustion fan speeds by over 50% on the Quad stoves. THe 35:1 air ratio you guys have to meet the exemption severely reduces the efficiency of your stoves. We have no such exemption so we reduce the combustion air flow to a sensible level hence our stoves are over 15% more efficient than yours. Pretty much the same stoves just far less heat being blown out the back. Sometimes we need to detune the stoves as we get flue condensation so we know we cannot go any cooler on the flue gas.
    So really you get a significant efficiency gain with warm combustion air you may not pick it with an lower efficiency stove but where you are running stoves to the edge of their performance for maximum efficiency the difference is stark particularly fuel consumption. I appreciate you guys have mental weather conditions compared to us but as a guide Our location has current temps (fahrenhiet) min 30, max 46. We run our 2,000sqft single storey house (very well insulated) at a constant 72. Our only heating is our stove and we burn 24lbs/24 hours.
    Now we are really pushing the envelope performance wise and your average user is not going to go to the extreme measures we do to tune their stoves but it does show you what this great form of heating is capable of. But we do use our experience to help our customers get the most out of our stoves so everyone goes better.
  19. spottedbat

    spottedbat New Member

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    What pellet stoves do not require OAK?

    Mike, i talked to you today about installing a pellet stove with the duraflex up my chimney. I was all excited and told my husband its all set- know exactly what we need blah blah. when i mentioned the OAK through the wall he was totally against it and wants a pellet stove that wont need it. ARG! i have been researching this long enough. Can you and anyone one else direct me to what brands "suggest" using one but it isnt necessary to operate with, harmon maybe? I thought i would have such a deal with the englander from amfm but now i can't have that brand because someone thinks its an eyesore. I have good airflow asw this house is not very insulated.
  20. doghouse

    doghouse Member

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    Try this: http://www.selkirkcorp.com/Selkirk/Product.aspx?id=7428
  21. spottedbat

    spottedbat New Member

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    i like the idea of selkirk direct temp but it is not for in the chimney. it would be great if we decide to go through the house wall, but that is after we run it for a year and decide its worth making a hole in the wall! Anyone have a stove that does not require having the air kit?
  22. stoveguy2esw

    stoveguy2esw Minister of Fire

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    this isn't a factor with our stoves (or most epa cert pellet stoves) 35-1 requirement does not have to be met with cert stoves so we can take it under that threshold and routinely do.
  23. chickenman

    chickenman Minister of Fire

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    That is positive then Mike. Now the rest just need to catch up.
  24. stoveguy2esw

    stoveguy2esw Minister of Fire

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    more manufacturers are doing so , the "handwriting is on the wall" has been for some time. first it was certain states such as Washington disallowing exempt units, now its being pushed on a national scale. we've been producing certified pellet stoves for at least the last 15 years and have absolutely no interest in any new designs without certifications , wouldn't be anywhere to sell them.

    IMHO this is one area where so far the industry and the government have managed to reach a modicum of symbiosis in the balance between regulation and demand. as long as progress is made in a deliberate manner which allows the industry to adjust to he changing regs we can do this. however if regulation becomes too draconian too quickly it will seriously harm the hearth industry.
    chickenman likes this.
  25. spottedbat

    spottedbat New Member

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    We were thinking of getting a pellet stove to put where our broken jotul woodstove was and run the exhaust up through the chimney with a duraflex. Since it is a single flue and would need to have an air intake tube running through something like a wall, that's quite an intrusive install and i would need to rearrange our living space and because of that air tube we are calling it quits. Also there seems to be quite a learning curve for new users, and it sounds like it takes more to run this thing than a woodstove. After many grueling hours of research we are going to pass up the pellet stove and stick to getting our woodstove refurbished. I guess our house just isn't right for the set up of a pellet stove, well at least one that wouldnt cost me thousands. Maybe in the future, especially if Selkirk makes a direct temp for a chimney not associated with a fireplace. Thanks for everyone's help in answering my questions on this very informative forum.

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