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I fought the OAK and the....

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by chrisasst, Dec 10, 2008.

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  1. chrisasst

    chrisasst Minister of Fire

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    OAK wins...I bought some pvc pipe and hooked up outside air to my stove. Any of you who are questioning whether or not this will improve the heat output of your stove, I am now a true believer that it does. grant it, yesterday and today has been about 15 or 20 degrees warm than the past week, but the temp that is blowing right out of the blower on my stove is about 40 degrees hotter than I tested it without the OAK.. #3 setting on my stove was blowing about 120 degrees, now it is blowing 160 degrees. I could close my damper about an inch and I actually see a little blue flame on the bottom. Also my window has not really gotten dirty either. It is amazing the difference. Now I am hoping it gets down to the teens so I can really test it.

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  2. dsnedegar3

    dsnedegar3 Member

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    What kind of stove do you have?
  3. chrisasst

    chrisasst Minister of Fire

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    I unfortunately have a Kozi 120
  4. chrisasst

    chrisasst Minister of Fire

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    well, it was 28 degrees last night. Kept my stove on #3. In the stove room temp was about 68-70. In the living room (farthest corner) it was 63. I was barely getting that on my highest setting #5 with out the outside air pipe. This is unbelievable. I feel like I should write to my stove place and thank them for letting me waste my money on all these pellets. Now all I need is some insulation and I might be ll set.
    Thanks guy for this great forum, I might only go through 4 tons instead of 6.
  5. kilarney

    kilarney New Member

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    How would an OAK increase the temperature of the air coming out of the stove? Only two ways that I can think of. 1) More oxygen in colder air provides for better combustion. 2) The air being sucked in from the room by the distribution fan is warmer. I'd be amazed if any of this would result in a 40 degree increase.

    The advantage of an OAK is that you are not taking warm inside air, using it for combustion, and blowing it outside. But this is separate from the distribution air that blows out of the stove.
  6. chrisasst

    chrisasst Minister of Fire

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    I have no idea. I didn't do anything else to the stove besides add the outside air. I wouldn't believe it either if I didn't test and do it my self.





  7. smirnov3

    smirnov3 Feeling the Heat

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    If you are using room air for your combustion blower, then that room air is being blown out of the house, and replaced with outside air

    if you are using outside air, then you aren't sucking cold air into your house


    my question is, is there any eway to get an outside air kit for an insert, or is not needed (ie your drawing air down the chimney)?
  8. dsnedegar3

    dsnedegar3 Member

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    My neighbor has an Accenta insert and uses the chimney for Outside air
  9. chrisasst

    chrisasst Minister of Fire

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    well now I don't know. I cleaned my stove the other day, first time since installing the oak, and now the stove is not running as well. So I guess it is back to the drawing board....
  10. Corie

    Corie Minister of Fire

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    FYI, PVC is not allowed for an outside air connection. Combustion air duct must be metal of minimum 26 gauge wall thickness.
  11. smirnov3

    smirnov3 Feeling the Heat

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    My insert gets its outside air from the chimney. Is it possible that the chimney is too well sealed & does not provide enough air?

    The reason I am asking is because most days, my insert can't feed more than 3 lbs/hour of pelllets (it's rated for 5)
    but when a warm front is moving in (which, I think, means the pressure increases), it consumes more pellets

    (The fire is always energetic, so the ratio of air / pellets is good)

    is this plausible?
  12. Jester

    Jester New Member

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    Most combustion fans are somewhere in the area of 240 CFM. Thats 240 CFM of air that is going up the chimney thats being replaced by outside air, through whatever nook anc cranny it can find. With mine, I did see an overall room temp difference, and a more modest stove temp difference. My flame went from an eye blinding yellow to a more orange with about the bottom 1/3 being blue. Its more like a torch now and less like a birthday candle, and Im cleaning the glass once a week now instead of daily.
  13. MCPO

    MCPO Minister of Fire

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    I`d rethink that CFM number. My bath fans are 100 CFM and have a much stronger motor and larger vent size than a pellet stove . I know it draws more air than the combustion fan in my stove does.
  14. sydney1963

    sydney1963 New Member

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    this is for an OAK not the pellet vent.
  15. Xena

    Xena Minister of Fire

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    yep, the oak is supposed to be metal not pvc.
    Most manuals mention it. Another fyi for the newbs,
    Corie I believe is employed at england stove works
    so he def. knows his stuff. ;-)
  16. chrisasst

    chrisasst Minister of Fire

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    my dealer said it was fine since it was for combustion. I see many people mention they use dryer vent hose so I guess people use various things.
  17. Xena

    Xena Minister of Fire

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    Not trying to break your cookies or anything but dealers
    don't always give accurate info. We've heard about
    it many times on this forum. In this case I'm betting your manual
    specifically says plastic pipe is not permitted for outside air.
    The dryer vent at my house is aluminum. If for no other reason,
    this post will benefit someone who wants to do it by the book.
  18. itworks

    itworks New Member

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    OK you guys have convinced me that I should use an OAK. Here's my question. I have a Harmon P68 installed in the lower level of my raised ranch. I have it vented into one of the three clay flues of my chimney with a 15 foot stainless steel flexible pipe. One of the other two flues is for the wood burning fire place on the main level. The third flue isn't being used. It would be really easy, and cheap, to hook up an OAK to the the clean out box of the third flue that's not currently used. Is that safe, and will it work?
  19. Corie

    Corie Minister of Fire

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    ASTM E 1509 requires combustion air ducts to be made of metal only with a 26 gauge wall thickness. Not breaking balls just giving you the straight info for safety sake.


    Additionally I have a very hard time believing that cold aid infiltration alone could cause that type of rise in hot air output temp. but I guess anything is possible.....
  20. Corie

    Corie Minister of Fire

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    good grief........aaaaaaand a standard comb. fan is about 80 - 100 cfm in free air for reference sake.
  21. Jester

    Jester New Member

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    Sorry Typo, I meant 140

    And for those doubting the effects on cold air and combustion, ask anyone thats involved in any kind of professional drag racing that has ever raced at New England Dragway on a warm fall afternoon, and then on the same brisk fall night, how much more power you get turning the same supercharger at the same speed. I dont know what the correlation works out to in pellet stove efficiency, but I've seen a tenth on the track.
  22. Corie

    Corie Minister of Fire

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    I'm so curious if there is any truth to this at all, I may actually conduct a test with and without outside combustion air (with combustion air temperature measure, of course) in the lab early next week.
  23. Xena

    Xena Minister of Fire

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    Jester I'm a believer because my harley always
    runs much better in the cooler weather.
  24. Devo

    Devo New Member

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    It all makes perfect sense to me. There are two reasons why the OAK would help. Without getting into the detailed physics, the more oxygen, the better the fire. Pretend you could fill up a bucket with room temperature air, which contains oxygen, and then weigh it as if you're weighing a bucket of water. If you cool down that air, it takes up less space (volume). So, you could actually put a greater amount of air (and oxygen) in the same bucket. If you weighed it, it would be heavier (greater mass although the same volume). In other words, a greater mass of oxygen for the flame. The principle is the same with air flowing thru a fixed size pipe.

    As I mentioned, there are two reasons. The second is actually related to the fan curve of the combustion air fan and the associated differential pressure that the fan is creating. Without getting into the specifics, if an outside air kit isn't installed, the combustion air fan is creating a vacuum inside the stove. The air is being supply from the inside of the house, but a cost. The fan has to overcome the resistance that the house is giving. The fan has to suck the air from all the cracks and crevices which eats up a portion of the minimal horsepower it has to begin with. Thus, the volume of air it can suck in and push out is reduced. This is actually easy to measure if you had the correct instruments. If an outside air kit is in place, the amount of fan's horsepower lost is drastically reduced, and the volume of air that the fan can push goes up. Thus, more air to the combustion chamber.

    BTW, I fabricated my own outside air kit this evening and installed it. Although I still have some details to finish up, it worked as expected.

    If you want to test your own without hooking it up to the stove, cut a hole in the wall next to the stove and insert a pipe but just thru the wall. Then, stick your hand close to the pipe while the stove is running. You'll be shocked at the airflow that the stove is pulling into the house.
  25. Corie

    Corie Minister of Fire

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    Yes, I'm aware of air density varying with temperature and how density affects mass flow rates. But if the control board of a stove isn't able to adjust fuel feed rate based on incoming air density, what difference should that additional oxygen make to the heat output of the unit? Certainly a slightly more complete combustion process, but 40 or 50 degrees difference in output temperature? I'm not saying I disagree, just that while I'm in the process of emissions testing on the new pellet unit I'm working on, I'm going to run some tests connected to outside air and disconnected and measure incoming air temperature, as well as actual output air temperature.
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