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Thread: Wood Stove Air Intake

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    Default Wood Stove Air Intake

    I have a new wood stove which seems to have plenty of air with the door cracked but with the door closed and the air intake control wide open it seems to be starving for air. My assumption is the draft is fine since the fire roars up when the dor is cracked. Has anyone had experience in using a small fan to provide some forced air flow into the air intake?

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    You won't need a fan if everything is right with the stove and flu. Double check your chimney / flu and make sure it is clean. I had the same symtoms recently and had to clean the flu pipe ( again) and also the stove we use has a shelf just under the stack and there was ash built up that had to be removed. Works great again now.

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    Depending on your stove, check to make sure that the ashes in your firebox are not clogging your intake.
    Your stove should definitely not need any help in getting air, as it was designed for volumetric efficiency.

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    Ash build up or clogged pipe would be my first guess, but green wood would cause a burn problem also, requiring more air.
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    If you can only get a draft when the door is open, and your flue is indeed blocked with creosote, BE VERY CAREFUL! You are on the verge of a chimney fire and they are scary to say the least.

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    Quote Originally Posted by saltwatertom View Post
    You won't need a fan if everything is right with the stove and flu. Double check your chimney / flu and make sure it is clean. I had the same symtoms recently and had to clean the flu pipe ( again) and also the stove we use has a shelf just under the stack and there was ash built up that had to be removed. Works great again now.
    This area mentioned is an easy miss when cleaning the stack, often you'll knock a ton of stuff down and it'll pile up on this shelf, I think all the newer stoves have this, and I think the only way to clean it really well, is from above. (sorry but that does mean removing the pipe right on the stove and cleaning it from there, pretty messy but you should be able to reach in and clear it to the stove box below then shovel out) Some have a way to remove the shelf from within and you can reach up and around and get it pretty clean.
    This accumulation on that shelf will definitely mess with the ability to move air with the door closed

    A good full exhaust stack cleaning always surprises me with the increased efficiency of air flow
    Ten Hours in that little raft off the AK peninsula, blowin' NW 60, in November.... "the Power of Life and Death is in the Tongue," and Yes, God is Good !

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    If your house is built very tight it'll cause poor draft unless a window is opened a bit.
    That's the case with my house.
    I just leave a window cracked open until I get my outdoor intake hooked up.
    "The older I get, the better I was."

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    That happened to me too. The bird screen was clogged. Woke up with a smoked up cabin coughing..not fun. Called central P&H and they diagnosed it on the phone. Ripped it out and has been great ever since.

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    Quote Originally Posted by sccron View Post
    I have a new wood stove which...
    Given the statement above, I doubt there is anything "plugged" up on a NEW stove. Is the chimney also new?

    Is the air intake on the stove functioning correctly? Being a new stove, did it ever function correctly or is this the first time using it? Could be an installation error or manufacturing defect if it has always had this problem.

    What kind of wood are you burning and how dry is it?

    You do NOT need a fan for air intake on any stove. You want the rising heat of the fire to create a draft (vacuum). Forcing air into the burn box is a bad way to try and make a wood stove work. For one thing, you will overpower all the joints in the chimney and be pushing combustion products into your living space. Very bad. Figure out what you need to create the draft.
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    how tall is your stack? good idea for it to be 12-14 feet minimum. especially with the cold temps, a cold and short chimney can tend to force cold air down into your house until you heat the chimney up and get it drafting the other way
    or perhaps your stove has a damper plate that is closed? needs to be open until the stove is good and hot.

    very common to have to crack a stove door (the ash pan door works best, if there is one) for a minute or two until the chimney heats up. especially true without well cured wood.

    as an aside providing your stove with a 3" outside air intake pipe is a very good idea, becase all that air going through the chimney has to come from somewhere.

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    Quote Originally Posted by andweav View Post
    how tall is your stack? good idea for it to be 12-14 feet minimum. especially with the cold temps, a cold and short chimney can tend to force cold air down into your house until you heat the chimney up and get it drafting the other way
    or perhaps your stove has a damper plate that is closed? needs to be open until the stove is good and hot.

    very common to have to crack a stove door (the ash pan door works best, if there is one) for a minute or two until the chimney heats up. especially true without well cured wood.

    as an aside providing your stove with a 3" outside air intake pipe is a very good idea, becase all that air going through the chimney has to come from somewhere.
    These are all good troubleshooting points,

    Sorry I missed the New Stove part of your OP, wondering what brand stove you have?
    I have a stove built by "Hearthstone," that is designed to Require an outside air source,
    as mentioned in andweav's last line.... mine has a 3in intake that is supposed to be plumbed to the outside for good air that does not pull from the house.
    As most stoves are designed to pull from the room, yours might be different.

    Do you know if that was done right when you installed it, or if yours is built that way?
    Mine has an airscoop underneath that needed to be attached to draw from the outside, (could be closed off from the shipping (?) if you missed checking on that?

    Let us know what you discover, Good Thread
    Ten Hours in that little raft off the AK peninsula, blowin' NW 60, in November.... "the Power of Life and Death is in the Tongue," and Yes, God is Good !

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    The outside air kits on stoves were for the installation in mobile homes. The Code was, you had to install (Make up air) in any mobile home or modular home.
    The problem when you do that is you are drawing in super cold air from the outside and bring it into a super heated firebox.
    What happens when hot metal gets cooled very fast? It will crack in time.

    The same problem was a code they required on a furnace. You brought in cold outside air as combustion air which was ducted to the furnace which would sweep over a heat exchanger and that would cause it to crack in a few years or so. Since then that code has been removed.

    Chances are you have a dirty chimney, the chimney is a bet too short or you have a very tight built home. If the house is 5 years or older I doubt the house is that sight.

    Hope this helps

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    sweepint, I hadn't heard about the stoves cracking over time with a cold air intake. Thanks for that info.
    My cold air intake would run about 15 ft. in the heated basement before going into the stove. Would that preheat the air enough to prevent the cracking?
    "The older I get, the better I was."

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    It's one thing to have a very hot item and give it a blast of cold air. In order to crack steel with temperature changes, it has to have a high carbon content (most wood stoves are mild steel; very low carbon). Having a continuous stream of cold air feeding into a fire box isn't the same thing at all. It's going to have fairly consistent temperatures, even though the intake area will be cooler than the stack area (which is always the case anyhow). I'd like to see some evidence of a wood stove that has cracked due to a cold air intake. Unless there were already design and structural problems with the stove, I doubt this is an issue at all. Sounds like urban legend to me.
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    yeah, I agree, that is quite the stretch to imagine cracking a stove with cold air intake.

    Factoring in the gusting nature of wind in Kodiak tho, my intake is drawn from the crawlspace beneath the house, quite a bit more stable air.
    This is a debate that rages among wood stove folks, probably not worth hacking away on here but worth reading on some websites of high end stove designers why some of them do that. It is definitely not an old school mobile home design.
    Still considered "Cutting Edge" among some stove designers.
    There's a lot to be said for not drawing the air from inside the home.
    Mine has been installed that way for quite a while, no problems, and made a huge difference when I installed the ducting to bring air in from crawlspace instead of from the room, and I do mean, a Huge Difference in the way it draws and burns. Well worth researching

    Travelers, what kind of stove are you using? and you did say "New" right, as in, could not be dirty, clogged stack, etc?
    Ten Hours in that little raft off the AK peninsula, blowin' NW 60, in November.... "the Power of Life and Death is in the Tongue," and Yes, God is Good !

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    i am with joat on this one. cracking is a non-issue because it's not a quick burst of cold air onto a hot surface. it's a steady stream of cooler air, which is continuously present from the moment the stove is lit, well before any stove parts are hot.

    good idea anyhow to run the air intake through an 'n' or a 'u' -shaped loop before entering the stove, both for a bit of pre-heat, but mostly to introduce a convective trap for cold air so it will not enter unless it's being actively drawn by the stove.

    IMO pre-heating the air is overthinking it a bit, obviously there is a bit of benefit but really not anything to worry about. I use a 6' flexible aluminum duct behind the stove, that allows for plenty of preheat.

    The outside-air intake, however, is a huge benefit. Otherwise you are most definitely getting a lot of cold-air infiltration and condensation in places that you probably don't want it.



    k-rain: regarding your drawing in air from the crawlspace, I wouldn't want to be doing that in a subarctic or colder climate, at least not with my crawlspace design. better to extend the intake pipe through the crawlspace, down below the footer and then up above grade outside the building with a screen over it. At least my crawlspace doesn't need any more cold air and while we do get howling winds here north of pamer, the chimney draft basically determines what air is coming in anyhow, so I don't think the positioning of the ait-intake changes much. A crawlspace with a boiler or furnace, and plenty of excess heat down there would be ok, but a below zero snap would make me awfully nervous about drawing air out of (and thus into)mine. I do understand the wind concerns but the stove's air valves should moderate that.

    sccron: have you troubleshooted your draft problems??

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    Quote Originally Posted by sccron View Post
    I have a new wood stove which seems to have plenty of air with the door cracked but with the door closed and the air intake control wide open it seems to be starving for air. My assumption is the draft is fine since the fire roars up when the dor is cracked. Has anyone had experience in using a small fan to provide some forced air flow into the air intake?
    "Seems" to be starving for air how? When I first light my airtight stove I leave a door cracked and the logs flame up as you'd expect. I have to leave it like this until the firebox heats up and the fire is well established. Once that's done I close the door and the dancing flames disappear. The logs just glow red with an occasional small flare ( I have a glass door). That doesn't mean the fire is being starved. it means the airtight stove is controlling the combustion rate like it's supposed to. It'll take another half hour or so before the stove is radiating good heat. These stoves aren't built for instant heat as much as for steady, long lasting, controlled heat.

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    Default intake

    If you bring the air in from the crawl space youíre preheating to some extent as compared to bringing it from the outside.
    If you look inside of most of the newer stoves out there (built in the last 10 to 12 years) you will see a square tube that runs on each side and the back of most of them. There are round tubes that run from side to side on the top of the inside of the fire box as well.
    These square and round tubs bring the air in from the bottom. You will see in time that they will crack generally in the corners do to cold air and high heat. So I can clarify what I meant on the stove cracking, I have only seen a few that cracked on the outside and that was much older stoves and they cracked at the welds or at the corner of the door face and none of that had to do with cold air. That was from overheating the stove. Most of the cracking that I am referring to is from the inside of the stove and talked about earlier in the response. Generally speaking this is not a problem even after you get a crack. We just tried to steer away from doing outside air kits there are a few models out there that required this in the installation because it took so much air from the en side of the heated house. Lopi fireplaces and some of the heat & glow fireplaces but not a lot of the woodstoves out there unless it was going into a mobile home or modular.
    I only had my head in about 15000 wood stoves over the years either cleaning or installing them in my business I had in Colorado.
    Back to the real problem, as Mr pid stated is it could be starving for air. I doubt the house is that tight.
    One easy way to check is do a draw test on the stove. Take a lit match or candle and with the door of the stove open put the flame at the face of the door frame at each corner and see what the flame is doing. It should draw the flame in 50%. Then do the same thing with cracking a window and see if there a difference.
    Second TEST is start a fire and allow it to get burning. Close the door of the stove and if you see a noticeable draw down on the flame then crack a window to see if that helps.
    If it doesnít then itís not the house it could be there in the stove or chimney. Is the stove on a pedestal?
    By the way who makes the stove?
    How high does the chimney go over the ridge of the house?
    When was the chimney cleaned last?

    Sweepint
    Wasilla, (when not overseas)
    '' Livn' The Dream ''
    26' Hewescraft Cuddy, twin 115 Yam

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