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any advantage using an OAK

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by wingsfan, Jan 8, 2013.

  1. wingsfan

    wingsfan Feeling the Heat

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    I thought that the oak connection on the back of the Englander is primarily for installation in a mobile home(right or wrong)?But is there any advantages to using one in a stick built house. Our house is 5yrs old so it is pretty tight. Just wondering if you introduce cooler outside air to the stove, if it would help with burn times or not.I don't have a problem with draft or anything else, just curious.

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  2. dorkweed

    dorkweed Guest

    If you look into and around the "manifold" where the OAK connects on an Englander stove, you'll see that it's not a "sealed" unit!!!! Meaning that even if you connect an OAK, there are gaps on the front portion (behind the ash drawer) and upper sides of this manifold....................not to mention the tack welded nipple where you connect the OAK!!!

    Also, the doghouse air comes from openings near the front legs of your stove...............not the OAK. I guess what I'm saying is this...................you're always drawing some "inside" air into an Engalnder stove the way they are constructed now.
  3. MarkinNC

    MarkinNC Minister of Fire

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    If a fire uses up to 400 cubic feet per minute in a wood stove, you have the options of using the air you heat for the stove (sucking in cold air from gaps around doors etc) or from an OAK. My stove runs really great and it has an OAK. My house is 13 years old so I went with an OAK. You may find this ling interesting:

    http://www.bkinspects.com/heating-and-cooling/wood-burning-fireplaces/
  4. StihlHead

    StihlHead Guest

    Yes, the new EPA stoves with OAKs have inside air supply for the secondaries so that they cannot be damped down (and burn less efficiently). However, the majority of the air supplied to the firebox will be drawn in through the OAK if it is connected. Several people on this site have used magnets and the like to block the inside air sources to the Englanders and force more air to be drawn from the OAK. Burning 'cold air' is not an issue in my experience using OAK fitted stoves (pre and post EPA), though cold air injected into the secondary tubes may reduce the burning effectiveness. In my view OAKs draw in cold air to burn and prevents warm air from being sucked out of the house and sent up the flue. If you look at it from an efficiency perspective, why use 70-80% efficiency pre-heated air to supply the stove when you can supply cold air burning at the highest efficiency possible (100%), right inside the firebox?

    Much debate here on this site about OAK vs. no OAK. I am in the OAK camp. IMO a tight fitting newer house will benefit from an OAK and prevent back-drawing air through venting and the like, and an older loose home will also benefit from an OAK with fewer drafts and cold spots. Also while OAKs are required for all mobile and manufactured homes that are HUD certified in the US, they are also required by local and state codes for all new home construction in places like WA state.
  5. PA Fire Bug

    PA Fire Bug Feeling the Heat

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    I get easier starts and better draft in my stove with the OAK. We used the stove for a year and half without an OAK. The difference at start up is noticeable.
  6. remkel

    remkel Minister of Fire

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    I have a newer house with good insulation, however, I have one room above my garage that has some draft (I still have to improve the insulation there as I finished the room a couple years after the house was built). This being the case, I was feeling a significant draft through the house as the make up air was being drawn in through the room over the garage. I installed an OAK onto my stove and it made all the difference in the world. No more draft though the house.

    I also found that the stove drafts much more since I installed the OAK, to the point where I may have to install a damper.
  7. BobUrban

    BobUrban Minister of Fire

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    I am burning this season w/o an OAK but intend to add one next season. For the most part I am getting great results as is but you can't know what you don't know??? So my idea is after one season with it I will have a pretty good handle on this stove and it's capabilities which will allow me to better appreciate(or not) any improved differences. Also, after researching here and otherwise, I cannot see a down side so it will be a small project and something to do.
  8. bag of hammers

    bag of hammers Minister of Fire

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    My OAK install, like a bunch of other things on the to-do list, is a work in progress. I installed the outside vent hood on one nice sunny day this fall, and the duct under the pedestal was part of that build when I put it together, so I just gotta take the time to make the connections, insulate, etc.. Not in a panic as the stove runs good now with inside air, but from all I've read here and elsewhere, I've opted to give it a try. I have a propane direct vent unit (Rinnai) that keeps my place from freezing when I'm not there, and I like the idea of not using inside air for combustion. The OAK may be a big plus once we go from weekend warriors to full time residents - when other vents (stove, bath, etc.) may want to compete more with the woodstove for air. Worst case I'll have spend a couple $ and a few hours of my time with no significant benefit, but like BobUrban said, there's not really a down side.
  9. jharkin

    jharkin Minister of Fire

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    I think that 400 figure is for an open fireplace. Most of the reference Ive seen put the typical EPA stove draw at more like 30 - 50 CFM.
  10. TreeCo

    TreeCo Member

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    Which is well below the air exchange rate the room should already have to be healthy.
  11. Brewmonster

    Brewmonster Burning Hunk

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    MarkinNC said:
    If a fire uses up to 400 cubic feet per minute in a wood stove,​
    I think that 400 figure is for an open fireplace. Most of the reference Ive seen put the typical EPA stove draw at more like 30 - 50 CFM.
    That's the critical thing I've always wondered about. As TreeCo pointed out, you need to have a certain rate of air exchange even if your house is really tight and well-insulated. If we need to have more cold air coming into the house than the stove uses, what's the point of the OAK?​
    Are we confident in the figures for stove air consumption vs. air exchange?​
  12. jharkin

    jharkin Minister of Fire

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    From what Ive read (disclaimer - no professional experience) if your house is tight enough that the air consumption of the stove is a problem you probably have or should have an HRV to provide the ventilation air changes needed + OAK for the stove and any other combustion appliances like water heater, etc.

    If the house is drafty enough to provide needed ventilation without an HRV then the extra draw of the stove probably wont matter.

    To put that into numbers.. I believe the recommended minimum natural ventilation is roughly an air change every 3 hours (0.35 ACH) - Anything built tighter than that needs an HRV by code I think? To do the math on 2000ft2 house with 8ft ceilings (roughly16,000ft3)

    16,000ft3 x 0.35 ACH = 5600 CFH / 60 = 93 CFM to ventilate the entire house.

    So you could see that for a tight house the stove draw significantly increase the draftiness... but on a leaky old place like mine that probably has a couple air changes an hour (a few hundred CFM) it might not be noticed.



  13. Sprinter

    Sprinter Minister of Fire

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  14. StihlHead

    StihlHead Guest

    That site (or similar) always comes up in the OAK discussion and has been debated here may times before. I have never experienced an OAK fitted wood stove reverse flowing from the firebox in the several years I have been burning with one here, even on the rare occasion that they are over-fired or in the high winds that are fairly common here. High winds here like we had last week from the east tend to draw far more air UP the flue and I have to damp the firebox all the way down (and I still get a full flame burn). Wind direction has made no difference here.

    Not that I have a choice, I live in a HUD home.
  15. TreeCo

    TreeCo Member

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    I find it a very persuasive arguement from someone who knows quite a bit about the subject.
  16. DexterDay

    DexterDay Guest

    The secondary air needs to be heated, so it does draw internal air (minimal) and the Doghouse air is internal (preheated) and also very minimal? The Primary air is where majority of your air comes from (even when closed COMPLETELY it doesn't shut 100%) and being an EPA stove they are designed to always let some air in (not to smother).

    Mike commented on a thread not to long ago that spoke to OAK's (Englanders of course) and stated that the Primary draws more than secondary and doghouse).

    If you look inside the Primary and open and close the lever, you will see how big of an opening is left. Even when shut down 100%.

    An OAK will always help the efficiency of a stove. Using inside (warm air you already used BTU's to heat) air for 100% of your combustion and sucking all that air in through the door sills, windows, and any other leaky points of your house? Or use an OAK and draw 70% from outside and keep that Warm air you already heated inside the house?? Which in turn, keeps the windows in your room from drawing cold air in, thereby keeping the bedrooms warmer. :)

    OAK it. Especially if newer than 10 yrs. Your house is already pretty efficient being that new. Why not help it along?
    PapaDave and WidowMaker like this.
  17. RSNovi

    RSNovi Feeling the Heat

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    I recently installed a jotul c350 insert in my zero clearance fireplace. While burning I can feel a constant draft in the stove room even with the blower turned off. I think it might be from the combustion air draw.

    The zc fireplace has an OAK which I think it fed the fire through openings all around the edge of the firebox. The oak was locked closed because I used to burn gas logs. Do you think activating this oak might help with my problem? I wonder if it would feed some air to the old firebox that the insert sits in.

    I would need to pull the surround off to access the lever to open the oak.
  18. DaveGunter

    DaveGunter Member

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    +1 on an OAK in a newer tight house being a good thing. I am burning an 30nc in my insulated basement (35ft clay lined internal chimney) to heat my whole house, half of basement (500sqft) and two living space floors (1000sqft each). The 30nc was new this season, I burned until about a month ago without an OAK, and since I installed the OAK it has been easier to keep the house warm even though it has been significantly colder outside. I burn 90% white birch and 10% red maple and can only ever get about 1.5hrs of active secondaries, the stove will routinely have good coals 10 hours later on a full load usually E-W loaded. Last year with an All-Nighter Moe (huge fire box smoke dragon) I had to burn oil to keep up, I haven't burned any oil this year! The biggest differences between no OAK and OAK for me besides the house being warmer are:

    1-the stove will get up to cruising temp either from cold or a reload much quicker, sometimes on a reload in as little as 5-10 min.

    2-when closing down the air, the setting is much more sensitive, to the point where a very small touch has a big difference, this makes closing the air require more attention to get it right

    3-I am now able to completely close the primary air setting and still get good secondaries until things are coaled over, whereas before I had to leave the air about 1/8" open. This also means that I routinely open the air back up to about 1/4 (even with the ash lip) for the coaling stage which I wasn't doing before. I have to start the overnight burns earlier or make sure the wife is up later and remind her to open it up before she goes to bed.
  19. bag of hammers

    bag of hammers Minister of Fire

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    The OAK discussion is one of the most interesting and reoccurring threads I've seen in my relatively short time here on the forum. I've resurrected this same discussion myself, and as always the folks here were kind enough to bear with me, chime in and help out, even though they'd seen it a million times.

    So if it's any help here, FWIW, in addition to searching through the threads and faq's here and a visit the woodheat.org site as mentioned above, I would then check out the articles and discussions (counterpoints) from the chimneysweeponline site (Tom Oyen). Both sites are great resources IMHO, the fact that they are completely at odds on the OAK topic is really interesting (and makes you want to dig deeper). Maybe these 3 as a starting point will help set the context for the volumes of discussion taking place here and elsewhere..? Just a thought.

    http://www.woodheat.org/the-outdoor-air-myth-exposed.html
    http://www.chimneysweeponline.com/hooa.htm
    http://www.chimneysweeponline.com/hooa3.htm

    Apologies if this is a bit redundant, just my 2c on "getting grounded" on the OAK debate before diving in....
  20. StihlHead

    StihlHead Guest

    Doing this type of math (in reverse) leads me to believe that an OAK is definitely a good thing, especially in a house the size and type of mine. Adding draft in a smaller house that is already ventilated is not always a good thing. Most older houses here in the west are smaller, and one story w/o a basement. My mid-century house in California was 1200 SF. This one built in 1982 is about 1350 SF.

    The math: My house is a 24x56 ft. dubba wyde with 7.5 ft. ceilings which is a tad over 10kCF. With the higher end typical venting of a wood stove flue of 50 CFM, that is 3,000 CFH, or 0.30 ACH for this house. That alone is just under the required minimum for air changes for this house. Assuming that the house was built to have 0.35 ACH w/o the stove running, you would basically (rough order of magnitude) double the air changes w/o an OAK using a wood stove in this house.

    So you have convinced me that an OAK is a good thing here, regardless of it being required. W/o an OAK a lot of house heat here would just get sucked up the flue. It would be like removing all the weather stripping on the doors and windows and adding draft. Not desirable...
  21. semipro

    semipro Minister of Fire

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    IMO the potential advantages of using an outdoor air supply:
    • Adequate airflow and enabled flue draft and backdraft prevention in tight houses where clothes, dryers, range hoods, bath fans, gas appliances, etc. could create negative pressures.
    • Control of where air enters the house as opposed to depending upon random leakage (where leakage through insulated walls can cause moisture related problems.
    • Draft prevention and the associated loss of comfort around those random leaks
    • Ability to shut off the inlet air flow to the stove if overheating occurs (I've had to do this twice)
    • Mitigation of the "smokehouse" smell that you get from an ash filled stove during atmospheric inversions - basically isolation of the firebox from the living space.
    (begin rant) I think the term OAK is somewhat ambiguous and deserves better definition on Hearth. The stove manufacturers usually refer to the adapter that can be used to attach an outdoor air supply as an "outdoor air kit", or "OAK", Here its widely used here to describe an outdoor air supply. That's why I prefer the term "outdoor air supply" where an "open" or "open loop" system is basically a hole in the wall and a "closed" or "closed loop" system is a relatively airtight connection between the stove and the great outdoors. (rant over)
    StihlHead likes this.
  22. StihlHead

    StihlHead Guest

    Yes, I agree with your rant that an OAS would be a much better term, and I do not like using the term OAK. But OAK is the term that is used here and elsewhere.
  23. Sprinter

    Sprinter Minister of Fire

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    I had an old Earth Stove in the 80's and always wished I could plumb outside air into it. Seemed like a good idea then and still does.

    One potential criticism for OAK involves the idea that under some (pretty rare) conditions, it may not be much better than opening a window (to mitigate the negative pressure problem). Not much of a criticism IMO.

    The only legitimate concern might be that it could be possible under some wind conditions for air to get sucked into an outside intake. But even that problem can be minimized by installing the intake in a sheltered crawlspace.

    I haven't been on this forum too long, but I don't think I've seen anyone here say that they have an OAK but wish they didn't.

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